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ANATOMY, 

DESCRIPTIVE  AND'SURGICAL 


BY 


HENRY   GRAY,  F.R.S., 

FELLOW  OF  THE  ROYAL  COLLEGE  OF  SURGEONS  ;    LECTURER  ON  ANATOMY  AT  ST.  GEORGE'S 
HOSPITAL  MEDICAL  SCHOOL. 


EDITED    BY 
/ 

T.  PICKERING   PICK,  F.R.C.S., 

CONSULTING  SURGEON  TO  ST.  GEORGE'S  HOSPITAL  AND  TO  THE  VICTORIA  HOSPITAL  FOR  CHILDREN: 
H.  M.   INSPECTOR  OF  ANATOMY  IN  ENGLAND  AND  WALES, 


ROBERT   HOWDEN,  M.A.,  M.B.,  CM., 

PROFESSOR  OF  ANATOMY  IN  THE  UNIVERSITY  OF  DURHAM;   EXAMINER  IN  ANATOMY  IN 

THE  UNIVERSITIES  OF  DURHAM  AND  EDINBURGH,  AND  TO  THE 

BOARD  OF   EDUCATION,  SOUTH   KENSINGTON. 


A  REVISED  AMERICAN,  FJEJOM  THE  FIFTEENTH  ENGLISH.  EDITION. 

WITH    780    ILLUSTRATIONS,   MANY   OF  WHICH   ARE   NEW. 


LEA   BROTHEES   &  CO., 

PHILADELPHIA    AND    NEW   YORK, 
1901. 


'AT 


TO 


SIR  BENJAMIN  COLLINS  BRODIE,  BART., 

F.R.S.,  D.C.L., 

SERJEANT-SURGEON  TO  THE  QUEEN, 
CORRESPONDING    MEMBER   OF   THE  INSTITUTE  OF  FRANCE, 

Ubis  Worfe  is  BeotcateO 

IN  ADMIRATION  OF 

HIS    GREAT    TALENTS 

AND  IN  REMEMBRANCE  OF 

MANY    ACTS    OF    KINDNESS    SHOWN    TO    THE   AUTHOR 

FROM  AN 

EARLY  PERIOD  OF  HIS  PROFESSIONAL  CAREER. 


PUBLISHERS'  NOTE  TO  THE  NEW  AMERICAN  EDITION. 


In  his  masterpiece  Henry  Gray  left  undying  evidence  of  his  anatomical 
knowledge  and  of  his  comprehension  of  the  best  method  of  imparting  it  to  other 
minds.  It  is  appropriate  that  a  new  and  thoroughly  revised  edition  of  such  a  work 
should  appear  in  the  opening  of  the  new  century — for  forty-five  years  it  has  easily 
held  the  front  place  among  works  on  Anatomy,  and  its  merits  are  only  brightened 
by  the  numerous  works  which  have  endeavored  to  contest  its  supremacy.  During 
that  time  it  has  had  the  benefit  of  the  careful  scrutiny  of  many  leading  anatomists 
of  the  English-speaking  race.  Anatomy  is  far  from  stationary,  either  in  its  facts 
or  in  improvements  in  the  method  of  their  presentation  ;  hence  any  work  which 
would  faithfully  reflect  the  existing  position  of  the  science  must  be  revised  at 
comparatively  frequent  intervals.  Fortunately  for  students  and  practitioners, 
Gray's  Anatomy  enjoys  a  continuous  demand  rendering  frequent  revision  pos- 
sible. 

The  splendid  illustrations  in  Gray  have  long  been  known  as  the  most  effective 
and  intelligible  presentations  of  anatomical  structures  ever  produced.  In  the 
present  revision  this  series  has  been  vastly  improved,  special  attention  having 
been  given  to  those  for  the  portion  on  General  Anatomy  and  Embryology. 

The  practical  application  of  anatomical  facts  in  medicine  and  surgery  has 
always  been  a  prominent  feature  of  the  work,  and  this  distinctive  characteristic 
has  received  especial  care. 

This  new  century  edition  is  presented  to  the  medical  public  with  the  absolute 
confidence  that  it  will  be  found  worthy  in  every  respect  to  maintain  the  exalted 
-^ioh  a  Avork  has  for  so  many  years  enjoyed  as  the  most  convenient  and 
of  its  subject. 


PREFACE  TO  THE  FIFTEENTH  ENGLISH  EDITION. 


In  this  edition  the  entire  work  has  undergone  a  careful  revision.  The 
section  on  Embryology  has  been  somewhat  amplified,  and  its  text  rendered  more 
intelligible  by  the  introduction  of  some  sixty  additional  illustrations  after  His, 
Kollmann,  Duval,  and  others.  Throughout  the  rest  of  the  work  a  considerable 
number  of  the  diagrams  have  been  redrawn  and  new  illustrations  here  and 
there   added. 

The  Editors  are  indebted  to  Dr.  R.  Bolam,  Lecturer  on  Physiology  and 
Histology,  and  to  Dr.  W.  Turnbull,  Demonstrator  of  Anatomy,  both  of  the 
University  of  Durham  College  of  Medicine,  for  their  valuable  help.  The  former 
kindly  undertook  the  revision  of  the  chapter  on  General  Anatomy  or  Histology ; 
while  the  latter  rendered  great  assistance  in  the  revision  and  proof-reading  of 
some  of  the  other  portions  of  the  work. 

It  is  hoped  that  this  edition  will  maintain  the  reputation  which  the  work  has 
for  so  many  years  enjoyed. 

7 


CONTENTS. 


DESCRIPTIVE  AND  SURGICAL  ANATOMY. 


OSTEOLOGY.— THE  SKELETON. 


"  i 


PAGE 

The  Skeleton 33 

Number  of  the  Bones 33 

Form  of  Bones 315 

The  Spixe. 

General  Characters  of  a  Vertebra     ......  34 

Characters  of  the  Cervical  Vertebrae 35 

Atlas 30 

Axis 37 

Seventh  Cervical 3!) 

Characters  of  the  Dorsal  Vertebrae 39 

Peculiar  Dorsal  Vertebras 41 

Characters  of  the  Lumbar  Vertebras 41 

Structure  of  the  Vertebrae 43 

Development  of  the  Vertebrae 43 

Atlas 44 

"  "       Axis 44 

''  "       Seventh  Cervical    ....  45 

"  "       Lumbar  Vertebrae  ....  45 

Progress  of  Ossification  in  the  Spine 45 

Sacral  and  Coccygeal  Vertebrae 45 

Sacrum 45 

Coccyx 50 

Of  the  Spine  in  General 51 

Surface  Form  of  Spine 53 

Surgical  Anatomy  of  Spine 53 

The  Skull. 

Bones  of  the  Cranium 55 

Occipital  Bone 55 

Parietal  Bones 59 

Frontal  Bone 61 

Temporal  Bones 65 

Sphenoid  Bone 72 

Ethmoid  Bone 77 

Development  of  the  Cranium 80 

The  Fontanelles 80 

Wormian  Bones ' 81 

Congenital  Fissures  and  Gaps 81 

Bones  of  the  Face  : 

Nasal  Bones 81 

Superior  Maxillary  Bones 83 

Changes  produced  in  Upper  Jaw  by  Age  .    88 

Lachrymal  Bones :    88 

Malar  Bones 89 

Palate  Bones 91 

Inferior  Turbinated  Bones 94 

Vomer 95 

Inferior  Maxillary  Bone 96 

Changes  produced  in  the  Lower  Jaw  by 

Age '.    99 

Sutures  of  the  Skull 101 

Vertex  of  the  Skull 103 

Base  of  the  Skull,  Internal  Surface 103 

Anterior  Fossa ]03 

Middle  Fossa 105 

Posterior  Fossa 106 

Base  of  Skull,  External  Surface 106 

Lateral  Region  of  the  Skull .    110 

Temporal  Fossa 110 

Mastoid  Portion Ill 

Zygomatic  Fossa Ill 


PAGE 

Spheno-niaxillary  Fossa 112 

Anterior  Region  of  the  Skull 112 

Orbits 11 3 

Nasal  Fossae 115 

Surface  Form  of  Skull 11- 

Surgical  Anatoniv  of  Skull 119 

Os  Hyoides    .    .  '. 122 

The  Thoeax. 

The  Sternum 124 

The  Ribs         128 

Peculiar  Ribs 130 

Costal  Cartilages 132 

Surface  Form  of  Chest 132 

Surgical  Anatomy  of  Chest 133 

The  L'ppee  Extremity. 

The  Shoulder  and  Pelvic  Girdles 134 

The  Clavicle 135 

Surface  Form I'M 

Surgical  Anatomv 137 

The  Scapula  ....'. 138 

Surface  Form 143 

Surgical  Anatomy 143 

The  Humerus 144 

Surface  Form 1-J!' 

Surgical  Anatomy 149 

The  Forearm    .    . 150 

The  Ulna 150 

Surface  Form 155 

The  Radius 155 

Surface  Form 157 

Surgical  Anatomv  of  Bones  of  Forearm  .  157 

The  Hand 158 

The  Carpus 158 

Bones  of  the  Upper  Row 161 

Bones  of  the  Lower  Row 163 

The  Metacarpus 165 

Peculiar  Characters  of  the  Metacarpal  Bones  .  166 

Phalanges 169 

Surface  Form  of  Bones  of  Hand     ....  169 

Surgical  Anatomy  of  Bom-  of  Hand    .    .  170 

Development  of  the  Bones  of  the  Hand.    .  170 

The  Lower  Extremity. 

Os  Innominatum 171 

Ilium 172 

Ischium 171 

Os  Pubis 176 

Development  of  the  Os  Innominatum  .    .    .    .  177 

The  Pelvis 179 

Differences  between    the    Male   and    Female 

Pelvis 182 

Surface  Form  of  Bones  of  Pelvis   .       .    .  182 

Surgical  Anatomy  of  Bones  of  Pelvis  .    .  183 

The  Femur  or  Thigh-bone 183 

Surface  Form 190 

Surgical  Anatomv 

TheLeg 191 

Patella 191 

Surface  Form 192 

Surgical  Anatomy 192 

9 


10 


CONTENTS. 


PAGE 

Tibia 192 

Surface  Form 196 

Fibula 196 

Surface  Form 198 

Surgical  Anatomy  of  Boues  of  Leg  .    .    .  198 

The  Foot 199 

Tarsus 199 

Os  Calcis 199 

Astragalus 203 

Cuboid    .    .■ 204 

Navicular 205 


Internal  Cuneiform 

Middle  "  

External         "  -ui 

Metatarsal  Bones 208 

Phalanges 210 

Development  of  the  Bones  of  the  Foot    .    .    .  211 

Construction  of  the  Foot  as  a  whole  .    .    .  211 

Surface  Form  of  Foot 213 

Surgical  Anatomy  of  Foot 213 

Sesamoid  Bones 214 


THE   ARTICULATIONS. 


Structures  composing  the  Joints 217 

Articular  Lamella  of  Bone 217 

Ligaments 217 

Synovial  Membrane 217 

Bursse 218 

Synovia 218 

Forms  of  Articulation : 

Synarthrosis 218 

Amphiarthrosis 219 

Diarthrosis 219 

Movements  of  Joints 220 

Articulations  of  the  Trunk. 

Articulations  of  the  Vertebral  Column    .    .    .  223 

"  "        Atlas  with  the  Axis    .    .  227 

"         Spine  with  the  Cranium  229 
"         Atlas  with  the  Occipital 

Bone 229 

Articulation  of  the  Axis  with  the  Occipital 

Bone 230 

Surgical  Anatomy  of  Articulations  of  the  Spine  231 

Tempero-mandibular  Articulation 231 

Surface  Form 234 

Surgical  Anatomy 234 

Articulations  of  the  Ribs  with  the  Vertebrae  : 

Costo-central 234 

Costo-transverse 236 

Articulations  of  the  Cartilages  of  the    Bibs 

with  the  Sternum  and  Eusiform  Cartilage  .  238 

Iuterchondral  Articulations 239 

Articulations  of  the   Ribs   with   their  Carti- 
lages      239 

Ligaments  of  the  Sternum 239 

Articulation  of  the  Pelvis  with  the  Spine  .    .  240 
Articulations  of  the  Pelvis  : 

Articulation  of  the  Sacrum  and  Ilium  .    .  241 
Ligament  between  the  Sacrum   and   Is- 
chium    242 

Articulation  of  the  Sacrum  and  Coccyx  .  244 

Articulation  of  the  Pubes 244 

Articulations  of  the  Upper  Extremity. 

Sterno-clavicular 245 

Surface  Form 247 

Surgical  Anatomy 247 

Acromio-clavicular 248 

Surface  Form 249 

Surgical  Anatomy 249 

Proper  Ligaments  of  the  Scapula  .    .  •    ...  249 

Shoulder-joint 251 

Surface  Form 254 

Surgical  Anatomy 254 

Elbow-joint 255 

Surface  Form 258 

Surgical  Anatomy 358 


Superior  Eadio-ulnar  Articulations 259 

Middle  Radio-ulnar  Articulation 259 

Inferior  Radio-ulnar  Articulation 260 

Surface  Form 261 

Wrist-joint 262 

Surface  Form ' .  263 

Surgical  Anatomy 263 

Articulations  of  the  Carpus 263 

"  of  the  first  row  of  Carpal  Bones  263 

of  the    second    row   of    Carpal 

Bones 264 

<:  of  the  two  rows  of  Carpal  Bones  264 

Carpo-metacarpal  Articulations 265 

of  the  Metacarpal  Bone  of  Thumb  and 

Trapezium 265 

of  the  four  inner  Metacarpal  Bones  and 

Carpus 266 

Articulations  of  the  Metacarpal  Bones  267 

Metacarpophalangeal  Articulations 267 

Surface  Form        268 

Articulations  of  the  Phalanges 268 

Articulations  of  the  Lower  Extremity. 

Hip-joint 268 

Surface  Form 272 

Surgical  Anatomy 272 

Knee-joint 274 

Surface  Form 280 

Surgical  Anatomy 280 

Superior  Tibio-fibular  Articulation 282 

Middle  Tibio-fibular  Articulation 282 

Inferior  Tibio-fibular  Articulation 282 

Articulations  between  the  Tibia  and  Fibula  .  282 

Ankle-joint 283 

Surface  Form 285 

Surgical  Anatomy 285 

Articulations  of  the  Tarsus 287 

"  of  the  Os  Calcis  and  Astragalus  287 

of  the  Os  Calcis  and  Cuboid      .  287 

"  of  the  Os  Calcis  and  Navicular  288 

Surgical  Anatomy ....  288 

of  the  Astragalus  and  Navicular  289 

"  of  the  Navicular  and  Cuneiform  289 

"  of  the  Navicular  and  Cuboid  .    .  289 

of    the    Cuneiform    with    each 

other 290 

of  the  External  Cuneiform  and 

Cuboid 290 

Tarso-metatarsal  Articulations 299 

Articulations  of  the  Metatarsal  Bones.    .    .    .  291 
Synovial  Membranes  in  Tarsal  and  Metatarsal 

Joints 291 

Metatarso-phalangeal  Articulations 292 

Articulations  of  the  Phalanges 293 

Surface  Form 293 


MUSCLES  AND  FASCIiE. 

General  Description  of  Muscle 295  I  Cranial  Region. 

Tendons 296  ,  Dissection 298 

Aponeuroses     ....    296     Occipito-fron talis 298 

"  "  Fascia        296  ,      .     ,       „     . 

Auricular  Region. 
Muscles  and  Fascia  of  the  Cranium  and       Dissection 

*ACE-  Attrahens  Auriculum 

Subdivision  into  Groups 297     Attollens  Auriculum 


CONTENTS. 


11 


PAGE 

Eetrahens  Auriculum 301 

Actions 301 

Palpebral  Region. 

Dissection 301 

Orbicularis  Palpebrarum 301 

Corrugator  Supercilii 30:2 

Tensor  Tarsi '. 302 

Actions 302 

Orbital  Region. 

Dissection 303 

Levator  Palpebrre 303 

Eectus  Superior,   Inferior.  Internal,  and  Ex- 
ternal Eecti 304 

Superior  Oblique 304 

Inferior  Oblique 305 

Actions 305 

Surgical  Anatomy 306 

Nasal  Region. 

Pyramidalis  Nasi 306 

Levator  Labii  Superioris  Alseque  Nasi  ....  306 

Dilatator  Naris,  Anterior  and  Posterior  .    .    .  306 

Compressor  Nasi 306 

Compressor  Narium  Minor 306 

Depressor  Ala?  Nasi 306 

Actions 307 

Superior  Maxillary  Region. 

Levator  Labii  Superioris  Proprius 307 

Levator  Anguli  Oris 307 

Zygomaticus,  Major  and  Minor 307 

Actions 307 

Inferior  Maxillary  Region. 

Dissection 308 

Levator  Labii  Inferioris 308 

Depressor  Labii  Inferioris 308 

Depressor  Anguli  Oris 308 

Actions 308 

Intermaxillary  Region. 

Dissection 308 

Orbicularis  Oris 308 

Buccinator 309 

Eisorius 310 

Actions 310 

Temporo-mandibular  Region. 

Masseteric  Fascia 310 

Masseter 310 

Temporal  Fascia 310 

Dissection 311 

Temporal 311 

Pterygo-mandibidar  Region. 

Dissection 312 

External  Pterygoid 312 

Internal  Pterygoid 312 

Actions 313 

Surface  Form  of  Muscles  of  Head  and  Face  .  313 

Muscles  and  Fascia  of  the  Neck. 

Subdivision  in  Groups 313 

Superficial  Region. 

Dissection 314 

Superficial  Cervical  Fascia 314 

Platysma  Myoides 314 

Surgical  Anatomy 315 

Actions 315 

Deep  Cervical  Fascia 315 

Surgical  Anatomy   .• 317 

Stern  o-mastoid 317 

Boundaries  of  the  Triangles  of  the  Neck    .    .  318 

Actions 319 

Surface  Form 319 

Surgical  Anatomy 319 

Infra-hyoid  Region. 

Dissection 319 

Sterno-hyoid     .    , •   .    .  319 


PAGE 

Sterno-thyroid 319 

Thyro-byoid 

Onio-hyoid 

Actions 

Supra-hyoid  Region. 

Dissection 301 

Digastric 321 

Stylo-liyoid 30-2 

Stylo-hyoid  Ligament 322 

Mylo-byoid    .    ., •   .    .    .    . 

Genio-hyoid :;:■_> 

Actions 303 

Lingual  Region. 

Dissection 323 

Genio-hyo-glossus 323 

Hyo-glossus 324 

Chrondro-glossus 324 

Stylo-glossus 324 

Palato-glossus 325 

Muscular  Substance  of  Tongue 325 

Superior  Lingualis 326 

Transverse  Lingualis 326 

Vertical  Lingualis 326 

Inferior  Lingualis 326 

Surgical  Anatomy 327 

Actions 327 

Pharyngeal  Region. 

Dissection 327 

Inferior  Constrictor 327 

Middle  Constrictor 328 

Superior  Constrictor 328 

Stylo-pharyngeus 329 

Actions  . 329 

Palatal  Region. 

Dissection 329 

Levator  Palati 329 

Tensor  Palati 329 

Palatine  Aponeurosis 330 

Azygos  Uvula? 330 

Palato-glossus 331 

Palato-pbaryngeus 331 

Salpingo-pharyngeus 331 

Actions 331 

Surgical  Anatomy 332 

Vertebral  Region  (Anterior). 

Eectus  Capitis  Anticus  Major 332 

Eectus  Capitis  Anticus  Minor 332 

Eectus  Capitis  Lateralis 333 

Longus  Colli 333 

Vertebral  Region   (Lateral). 

Scalenus  Anticus 334 

Scalenus  Medius 335 

Scalenus  Posticus 335 

Actions • 335 

Surface  Form  of  Muscles  of  Neck 335 

Muscles  and  Fascle  of  the  Trunk. 

Subdivision  into  Groups 336 

The  Back. 

Subdivision  into  Layers        336 

First  Layer. 

Dissection 336 

Superficial  and  Deep  Fascia? 3oi 

Trapezius jj«fi 

Ligameutuin  Nucha? 339 

Latissimus  Dorsi «39 

Second  Layer. 

Dissection •';'" 

Levator  Anguli  Scapula 340 

Ehomboideus  Minor j^1" 

Ehomboideus  Major 340 

Actions "*4" 

Third  Layer. 

Dissection 341 

Serratus  Posticus  Superior 341 


12 


CONTENTS. 


PAGE 

Serratus  Posticus  Inferior 341 

Vertebral  Aponeurosis1 341 

Lumbar  Fascia 342 

Splenius 342 

Splenitis  Capitis 342 

Splenius  Colli 342 

Actions •    •    •    •  342 

Fourth  Layer. 

Dissection 343 

Erector  Spinse * 343 

Ilio-costalis 343 

Musculus  Accessorius  ad  Ilio-costalem  ....  343 

Cervical  is  Ascendens 345 

Longissimus  Dorsi •' 345 

Trausversalis  Cervicis 345 

Trachelo-mastoid 345 

Spinalis  Dorsi 345 

Spinalis  Colli 345 

Complexus 345 

Bi  venter  Cervicis 346 

Fifth  Layer. 

Dissection 346 

Semispinalis  Dorsi  et  Colli 346 

Multifidus  Spinse 346 

Eotatores  Spinas 347 

Supraspinales 347 

Interspinals 347 

Extensor  Coccygis 347 

Intertransversales 347 

Eectus  Capitis  Posticus  Major 347 

Pectus  Capitis  Posticus  Minor 348 

Obliqaus  Capitis  Inferior 348 

Obliquus  Capitis  Superior 34S 

Suboccipital  Triangle 348 

Actions 348 

Surface  Form  of  Muscles  of  Back 349 

The  Thorax. 

Intercostal  Fascias  .    ." 350 

Intercostal  Muscles >   .    .    .  350 

External  Intercostals 350 

Internal  Intercostals 350 

Infracostales  (subcostales) 351 

Triangularis  Stern i 351 

Levatores  Costarum 352 

Diaphragm 352 

Actions 354 

Muscles  of  Inspiration  and  Expiration    .    .    .  355 

Superficial  Muscles  of  the  Abdomen. 

Dissection 356 

Superficial  Fascia 356 

External  or  Descending  Oblique 356 

External  Abdominal  Ping    .    .    . 357 

The  Intercolumnar  Fibres 358 

The  Intercolumnar  Fascia 359 

Poupart's  Ligament 359 

Gimbernat's  Ligament 359 

Triangular  Fascia 359 

Ligament  of  Cooper 359 

Internal  or  Ascending  Oblique 360 

Cremaster 361 

Trausversalis 362 

Pectus 362 

Pyramidalis 364 

Linea  Alba 365 

Lineas  Semilunares,  Lineas  Transversa?   .    .    .  365 

Actions 365 

Fascia  Trausversalis 365 

Internal  Abdominal  Ping 366 

Inguinal  Canal 366 

Surface  Form  of  Muscles  of  Abdomen     .    .    .  366 

Deep  Muscle's  of  the  Abdomen. 

Quadratus  Lumborum 367 

Actions 367 

Muscles  of  the  Pelvic  Outlet. 

Corrugator  Cutis  Ani 368 

External  Sphincter  Ani 368 


PAGE 

Internal  Sphincter  Ani 368 

Levator  Ani 369 

Coccygeus 369 

Muscles  of  the  Perinseum  in  the  Male. 

Superficial  Perineal  Fascia 370 

Transversus  Perinsei 371 

Accelerator  Urinse 371 

Erector  Penis 372 

Triangular  Ligament 373 

Compressor  Urethras 374 

Muscles  of  the  Perinseum  in  the  Female. 

Transversus  Perinsei 375 

Sphincter  Vaginas 375 

Erector  Clitoridis 375 

Triangular  Ligament 375 

Compressor  Urethrse 375 

Muscles  axd  Fascije  of  the  Upper 
Extremity. 

Subdivision  into  Groups 376 

Dissection  of  Pectoral  Region  and  Axilla    .    .  376 

Fascias  of  the  Thorax 377 

The  Shoulder. 
Anterior  Thoracic  Eegion. 

Pectoralis  Major 378 

Costo-coracoid  Membrane 378 

Pectoralis  Minor 379 

Subclavius 360 

Actions 3S1 

Lateral  Thoracic  Eegion. 

Serratus  Magnus 381 

Actions 382 

Superficial  Fascia 382 

Acromial  Eegion. 

Deep  Fascia 382 

Deltoid 382 

Actions 383 

Surgical  Anatomy 383 

Anterior  Scapular  Eegion. 

Subscapular  Fascia 383 

Subscapularis_ 383 

Actions   .    .    '. 384 

Posterior  Scapular  Eegion. 

Dissection 384 

Supraspinous  Fascia 384 

Supraspinatus 384 

Infraspinous  Fascia 384 

Infraspinatus 384 

Teres  Minor 385 

Teres  Major 386 

Actions 386 

The  Arm. 

Anterior  Humeral  Eegion. 

Dissection 386 

Deep  Fascia  of  Arm 386 

Coraco-brachialis 387 

Biceps 3i=7 

Brachialis  Anticus 368 

Actions • 388 

Posterior  Humeral  Eegion. 

Triceps 388 

Subanconeus -}^ 

Actions 389 

Surgical  Anatomy 389 

The  Forearm. 

Dissection 389 

Deep  Fascia  of  Forearm 3SD 

Anterior  Eadio-ulnar  Eegion,  Superficial  Layer.  N,^^ 

Pronator  Radii  Teres 390 

Flexor  Carpi  Radialis 391 


CONTENTS. 


15 


Superficial  Temporal  Artery.  page 

Course  and  Kelations 495 

Branches 495 

Surgical  Anatomy 496 

Internal  Maxillary  Artery. 

Course  and  Relations 496 

Branches  from  First  Portion 496 

"  "     Second  Portion 498 

"  "     Third  Portion 499 

Surgical  Anatomy  of  the  Triangles  of  the 
Neck. 

Anterior  Triangular  Space. 

Inferior  Carotid  Triangle 500 

Superior  Carotid  Triangle 500 

Submaxillary  Triangle 501 

Posterior  Triangular  Space. 

Occipital  Triangle 501 

Subclavian  Triangle 502 

Internal  Carotid  Artery. 

Cervical  Portion 502 

Petrous  Portion 503 

Cavernous  Portion      503 

Cerebral  Portion 503 

Peculiarities 504 

Surgical  Anatomy 505 

Branches 505 

Ophthalmic  Artery 505 

Cerebral  Branches  of  Internal  Carotid     .  510 

The  Blood-vessels  of  the  Brain ,    .  512 

Arteries  of  the  Upper  Extremity. 
Subclavian  Arteries. 
First  Part  of  Right  Subclavian  Artery     . 
First  Part  of  Left  Subclavian  Artery    .    . 
Second  Part  of  Subclavian  Artery    .    .    . 
Third  Part  of  Subclavian  Artery  .... 

Peculiarities 

Surface  Marking 

Surgical  Anatomy 

Branches    

Vertebral  Artery 

Basilar  Artery 

Circle  of  Willis 

Thyroid  Axis 

Inferior  Thyroid 

Suprascapular  Artery 

Transversal  is  Colli 

Internal  Mammary 

Superior  Intercostal 

The  Axilla 


Surgical  Anatomy  of  the  Axilla 


514 
516 
516 
516 
517 
518 
518 
520 
520 
522 
523 
523 
523 
524 
524 
526 
527 
527 
529 


Axillary  Artery. 

First  Portion 530 

Second  Portion 530 

Third  Portion 531 

Peculiarities      531 

Surface  Marking 531 

Surgical  Anatomy 531 

Branches .  532 

Brachial  Artery. 

Relations 533 

Bend  of  the  Elbow 534 

Peculiarities  of  Brachial  Artery 534 

Surface  Form 535 

Surgical  Anatomy 535 

Branches 536 

Radial   Artery. 

Relations 538 

Deep  Palmar  Arch 533 

Peculiarities      539 

Surface  Marking 539 

Surgical  Anatomy 539 

Branches 539 


Ulnar  Artery.  pa',e 

Relations 540 

Peculiarities  of  Ulnar  Artery 

Surface  Marking 540 

Surgical  Anatomy r,4i 

Branches 543 

Superficial  Palmar  Arch 544 

Arteries  of  the  Trunk. 

Descending  Aorta      546 

Thoracic  Aorta. 

Course  and  Relations 546 

Surgical  Anatomy 

Branches 547 

Abdominal  Aorta. 

Coui-se  and  Relations 549 

Surface  Marking 

Surgical  Anatomy 550 

Branches 550 

Coeliac  Axis 551 

Gastric  Artery      551 

Hepatic  Artery 551 

Splenic  Artery      551 

Superior  Mesenteric  Artery 553 

Inferior  Mesenteric  Artery 555 

Suprarenal  Arteries 

Renal  Arteries 556 

Spermatic  Arteries      557 

Ovarian  Arteries 557 

Phrenic  Arteries 557 

Lumbar  Arteries 

Middle  Sacral  Artery 558 

Luschka's  Gland - 


Common  Iliac  Arteries. 


Course  and  Relations 

Branches    

Peculiarities  .  .  .  . 
Surface  Marking  .  .  . 
Surgical  Anatomy   .    . 


559 
559 
559 
560 
560 


Internal  Iliac  Artery. 

Course  and  Relations 561 

Peculiarities      562 

Surgical  Anatomy 562 

Branches 563 

Vesical  Arteries 563 

Hemorrhoidal  Arteries      563 

Uterine  Arteries 563 

Vaginal  Arteries 564 

Obturator  Artery 564 

Peculiarities 565 

Internal  Pudic  Artery 565 

In  the  Male 565 

Peculiarities 

Surgical  Anatomy 

Branches 566 

In  the  Female 567 

Sciatic  Artery •'''• 

Lumbar  Artery 

Lateral  Sacral  Artery 

Gluteal  Artery 

Surface  Marking  of  Branches  of  Internal  Iliac  569 
Surgical    Anatomy  of  Branches   of  Internal 

Iliac    . 570 

External  Iliac  Artery. 

Course  and  Relations 

Surgical  Anatomy 

Deep  Epigastric  Artery 

Deep  Circumflex  Iliac  Artery  .    .    .    . 


570 
571 
572 


Arteries  of  the  Lower  Extremity. 
Femoral  Artery. 

Course  and  Relations 

Scarpa's  Triangle 

Hunter's  Canal 


572 

572 
573 


16 


CONTENTS. 


PAGE 

Common  Femoral 573 

Superficial  Femoral 574 

Peculiarities 575 

Surface  Marking 575 

Surgical  Anatomy 575 

Branches 578 

Deep  Femoral 578 

Branches 579 

Popliteal  Artery. 

Popliteal  Space 581 

Course  and  Relations 581 

Peculiarities 582 

Surface  Marking 582 

Surgical  Anatomy 582 

Branches 583 

Anterior  Tibial  Artery. 

Coarse  and  Relations 585 

Peculiarities 586 

Surface  Marking 586 

Surgical  Anatomy 586 

Branches 5S6 

Dorsalis  Pedis  Artery. 

Course  and  Relations 587 

Peculiarities 587 

Surface  Marking .' 587 

Surgical  Anatomy .    .    .  587 

Branches 588 

Posterior  Tibial  Artery. 

Course  and  Relations 588 

Peculiarities 589 

Surface  Marking 589 

Surgical  Anatomy 589 

Branches 590 

Peroneal  Artery. 

Course  and  Relations 590 

Peculiarities 590 

Plantar  Arteries 591 

Surface  Marking 592 

Surgical  Anatomy 592 

THE  VEINS. 

General  Anatomy. 

Subdivision  into   Pulmonary,  Systemic,  and 

Portal 593 

Anastomoses  of  Veins 593 

Superficial  Veins 593 

Deep  Veins,  Venae  Comites 594 

Sinuses 594 

Pulmonary  Veins 594 

Systemic  Veins 594 

Veins  of  the  Head  and  Neck. 

Frontal  Vein 595 

Facial  Vein 596 

Surgical  Anatomy 596 

Temporal  Vein 596 

Internal  Maxillary  Vein 596 

Temporo-maxillary  Vein .  597 

Posterior  Auricular  Vein 597 

Occipital  Vein 597 

Veins  of  the  Neck. 

External  Jugular  Vein 597 

Surgical  Anatomy 597 

Posterior  External  Jugular  Vein 598 

Anterior  Jugular  Vein 59H 

Internal  Jugular  Vein 598 

Lingual  Vein 598 


PAwE 

Pharyngeal  Vein 598 

Thyroid  Veins 598 

Surgical  Anatomy  of  Internal  Jugular  Vein  .  599 

Vertebral  Veins 589 

Veins  of  the  Diploe 599 

Cerebral   Veins. 

Superficial  Cerebral  Veins 600' 

Deep  Cerebral  Veins 601 

Cerebellar  Veins 60L 

Sinuses  of  the  Dura  Mater. 

Superior  Longitudinal  Sinus 602 

Inferior  Longitudinal,  Straight  Sinuses  .    .    .  602 

Lateral  Sinus 602 

Occipital  Sinuses 603 

Cavernous  Sinuses 603 

Surgical  Anatomy   .    .        604 

Circular  Sinus 604 

Superior  Petrosal  Sinus 604 

Inferior  Petrosal  Sinus 605 

Transverse  Sinuses 605 

Emissary  Veins 605 

Surgical  Anatomy 606 

Veins  of  the  Upper  Extremity  and  Thorax. 

Superficial  Veins 607 

Deep  Veins 607 

Axillary  Vein 609 

Surgical  Anatomy 609 

Subclavian  Vein 609 

Innominate  Veins 609 

Peculiarities  of 610 

Internal  Mammary  Veins 610 

Inferior  Thyroid  Veins 610 

Superior  Intercostal  Veins 611 

Superior  Vena  Cava 611 

Azygos  Veins 611 

Bronchial  Veins 611 

Spinal  Veins 612 

Veins  of  the  Lower  Extremity — Abdomen 
and  Pelvis. 

Internal  Saphenous  Vein  . 614 

External  Saphenous  Vein 614 

Popliteal  Vein 615 

Femoral  Vein 616 

External  Iliac  Vein 616 

Deep  Epigastric  Veins 616 

Deep  Circumflex  Iliac  Veins 616 

Internal  Iliac  Vein 616 

Internal  Pudic  Veins 616 

Common  Iliac  Veins 617 

Peculiarities 617 

Inferior  Vena  Cava 617 

Peculiarities 618 

Lumbar  Veins 618 

Spermatic  Veins 618 

Surgical  Anatomy 618 

Ovarian  Veins 618 

Renal  and  Suprarenal  Veins 619 

Phrenic  Veins 619 

Hepatic  Veins 619 

Portal  System  of  Veins. 

Superior  Mesenteric  Vein 619 

Splenic  Vein 619 

Inferior  Mesenteric  Vein 619 

Gastric  Veins 619 

Portal  Vein 621 

Cystic  Vein 621 

Cardiac  Veins 621 

Coronary  Sinus 622 


CONTENTS. 


17 


THE    LYMPHATICS. 


General  Anatomy.  page 

Subdivision  into  Deep  and  Superficial  ....  623 

Lymphatic  or  Conglobate  Glands 623 

Thoracic  Duct 624 

Eight  Lymphatic  Duct 625 

Lymyhatics  of  Head,  Face,  and  Neck. 

Lymphatic  Glands  of  Head 625 

Lymphatics  of  the  Head 625 

Superficial  Lymphatics  of  the  Face 626 

Deep  Lymphatics  of  tbe  Face 626 

Lymphaties  of  the  Cranium 626 

Lymphatic  Glands  of  the  Neck 627 

Superficial  Cervical  Glands 627 

Deep  Cervical  Glands 628 

Superficial  and  Deep  Cervical  Lymphatics  .  .  628 

Surgical  Anatomy 628 

Lymphatics  of  the   Upper  Extremity. 

Superficial  Lymphatic  Glands 628 

Deep  Lymphatic  Glands 628 

Axillary  Glands 628 

Surgical  Anatomy 629 

Superficial  Lymphatics  of  Upper  Extremity  .  630 

Deep  Lymphatics  of  Upper  Extremity    .    .    .  630 

Lymphatics  of  the  Lower  Extremity. 

Superficial  Inguinal  Glands 630 

Surgical  Anatomy 630 

Deep  Lymphatic  Glands 630 

Anterior  Tibial  Gland 631 

Popliteal  Glands 631 

Deep  Inguinal  Glands 631 

Gluteal  and  Ischiatic  Glands 631 

Superficial  Lymphatics  of  Lower  Extremity  631 

Internal  Group 631 

External  Group 631 

Deep  Lymphatics  of  Lower  Extremity    .    .    .  632 

Lymphatics  of  Pelvis  and  Abdomen. 

Lymphatic  Glands  of  Pelvis 632 

External  Iliac  Glands 632 

Internal  Iliac  Glands ■    ■    ■    .    .  632 

Sacral  Glands 632 

Lumbar  Glands 632 


PAGE 

Superficial  Lymphatics  of  Wall  of  Abdomen  I 

of  Gluteal  Region  .   .  632 
"          of  Scrotum  and  Peri- 
neum     633 

"  of  Penis 633 

"  of    Labia     Nymphae, 

and  Clitoris  .    .  634 

Deep  Lymphatics  of  Pelvis  and  Abdomen  .    .  634 

Lymphatics  of  Bladder i;:;i 

of  Eectum     634 

of  Uterus 634 

of  Testicle 634 

of  Kidney      634 

of  Liver 634 

Lymphatic  Glands  of  Stomach 635 

Lymphatics  of  Stomach 635 

Lymphatic  Glands  of  Spleen 635 

Lymphatics  of  Spleen G35 

Lymphatic  System  of  the  Intestine. 

Lymphatic  Glands  of  Small  Intestine  (Mesen- 
teric Glands) 635 

Lymphatic  Glands  of  Large  Intestine  ....  635 

Lymphatics  of  Small  Intestine  (Lacteals)  .    .  635 

of  Large  Intestine 635 

Lymphatics  of  Thorax. 

Lymphatic  Glands  of  Thorax         636 

Intercostal  Glands 636 

Internal  Mammary  Glands 636 

Anterior  Mediastinal  Glands 636 

Posterior  Mediastinal  Glands 636 

Superior  Lymphatics  on  Front  of  Thorax  .    .  636 

Deep  Lymphatics  of  Thorax 636 

Intercostal  Lymphatics 636 

Internal  Mammary  Lymphatics     ....  636 

Lymphatics  of  Diaphragm 636 

Bronchial  Glands 636 

Lymphatics  of  Lung 637 

Cardiac  Lymphatics 637 

Thymic  Lymphatics 637 

Thyroid  Lymphatics 637 

Lymphatics  of  CEsophagus 637 


THE  NERVOUS  SYSTEM. 


Subdivision     into     Cerebro-spinal     Centres, 

Ganglia,  and  Nerves,  etc 639 

The  Brain  and  its  Membranes. 

Membranes  of  the  Brain 639 

The  Dura  Mater. 

Structure 639 

Arteries,  Veins,  Nerves 640 

Processes  of  the  Dura  Mater \  640 

Falx  Cerebri 640 

Tentorium  Cerebelli 640 

Falx  Cerebelli 641 

Diaphragma  Selli 641 

The  Arachnoid  Membrane. 

General  Description 641 

Subdural  Space 641 

Subarachnoid  Space 641 

Cerebro-spinal  Fluid .    .    .    .  642 

Structure 642 

Glandulse  Pacchioni .  642 

The  Pia  Mater. 

General  Description  and  Structure 642 

Lymphatics  and  Nerves 643 

The  Brain. 

General  Considerations  and  Divisions  ....  643 
2 


The  Hemispheres. 

Surface  of  the  Cerebrum 643 

Longitudinal  Fissure 645 

Sylvian  Fissure 645 

Fissure  of  Rolando 646 

Parieto-occipital  Fissure 646 

Calloso-margiual  Fissure 646 

Internal  Parieto-occipital  Fissure 647 

Calcarine  Fissure 647 

Collateral  Fissure 647 

Dentate  or  Hippocampal  Fissure (>l~ 

Frontal  Lobe 648 

Parietal  Lobe 650 

Occipital  Lobe 65] 

Temporal  Lobe ,ir''-' 

Central  Lobe  or  Island  of  Reil 652 

Limbic  Lobe 652 

Olfactory  Lobe 654 

Base  of  the  Encephalon 655 

Longitudinal  Fissure 655 


655 
656 
656 
656 
656 


Corpus  Callosuni 

Lamina  Cinera 

Optic  Commissure 

Tuber  Cinereum 

Infundibulum 

Corpora  Albicantia 656 

Posterior  Perforated  Space ,,>~~ 

Pons  Varolii 657 

Crura  Cerebri 659 

Hemispheres  of  Cerebellum 


/ 


18 


CONTENTS. 


PAGE 

The  Interior  of  the  Cerebrum.   .    .    .  658 

Corpus  Callosum 659 

Lateral  Ventricles 660 

Corpus  Striatum 662 

Xucleus  Caudatus 662 

Medulla  Oblongata 656 

Optic  Tracts 657 

Xucleus  Lenticularis 662 

Internal  Capsule 663 

External  Capsule 66-4 

Claustrum 664 

Taenia  Semicircularis 664 

Fornix 664 

Anterior  Commissure 665 

Septum  Lucidum         665 

Fifth  Ventricle 666 

Hippocampus  Major 666 

Corpus  Fimbriatum 667 

Choroid  Plexus 667 

Transverse  Fissure 669 

Velum  Interpositum 669 

The  Inter-brain 669 

Third  Ventricle 670 

Middle  Commissure 671 

Posterior  Commissure 671 

Optic  Thalami 671 

Pineal  Gland 672 

The  Mid-brain 673 

Orustse 674 

Tegmentum 674 

Substantia  Xigra 675 

Corpora  Quadrigemina 675 

Corpora  Geniculata 676 

Aqueduct  of  Sylvius 676 

Subthalamic  Eegion 676 

The  Structure  of  the  Cerebrum   .    .    .  677 

White  Matter  of  the  Cerebrum 677 

Projection  Fibres 677 

Commissural  Fibres 677 

Association  Fibres 677 

Gray  Matter  of  the  Cerebi-um 678 

"       of  the  Cortex 678 

Special  Types  of  Gray  Matter      680 

The  Hind-brain 681 

Pons  Varolii 681 

Superior  Olivarv  Xucleus     . 683 

Nuclei  of  the  Fifth  Nerve .683 

Xucleus  of  the  Sixth  Xerve 683 

Nucleus  of  the  Facial  Xerve 683 

Nuclei  of  the  Auditory  Xerve 684 

Xuclei  Pontis       684 

The.  Cerebellum 684 

Lobes 684 

Upper  Surface  of  the  Cerebellum 686 

Lingula 686 

Lobulus  Centralis 686 

Culmen  Monticuli 686 

Clivus  Monticuli      6S6 

Folium  Cacuminis 686 

Under  Surface  of  the  Cerebellum 686 

Nodule  and  Flocculus 688 

Uvula  and  Amygdalae 688 

Pyramid  and  Biventral  Lobes 689 

Tuber   Valvules,    and   Posterior  Inferior 

Lobes 6S9 

Internal  Structure  of  the  Cerebellum  ....  689 

Peduncles      6S9 

Gray  Matter  of  the  Cortex 691 

Independent  Centres 693 

Weight  of  the  Cerebellum 693 

The  Medulla  Oblongata     ....  693 

Pyramids 694 

Lateral  Columns 694 

Olivary  Body 694 

Funiculus  of  Eolando 694 

Funiculus  Cuneatus 694 


PAGE- 

Funiculus  Gracilis 696 

Eestiform  Body 696 

Arciform  Fibres      696 

Fourth  Ventricle 697 

Internal  Structure  of  the  Medulla 699 

Weight  of  the  Encephalon 703 

Cerebral  Topography 705 

The  Spinal  Coed  and  its  Membeanes. 

Dissection      707 

The  Membranes  of  the  Cord.     .    .    .  707 

Dura  Mater 707 

Arachnoid      708 

Pia  Mater 709 

Ligamentum  Denticulatum 709 

The  Spinal  Cord 710 

Fissures      711 

Columns 711 

Structure 712 

Minute  Anatomy 713r- 

Neuroglia 713 

White  Substance 713 

Gray  Substance 715 

Origin  of  the  Spinal  Nerves 717 

Xerve-tracts 717 

Motor,  Efferent,  or  Descending  Tract  .    .  718 

Other  Descending  Tracts 719 

Sensory,  Afferent,  Ascending  Tract  .    .    .  719 

Other  Ascending  Tracts 719 

The  Cbanial  Xeeve. 

Enumeration 720 

Olfactory  Xerve 720 

Surgical  Anatomy 721 

Optic  Xerve 721 

Tracts 721 

Commissure 721 

Surgical  Anatomy 722 

Motor  Oculi  Xerve 722 

Surgical  Anatomy 724 

Pathetic  Xerve 725 

Surgical  Anatomy 725 

Trifacial  Xerve 725 

Gasserian  Ganglion 726 

Ophthalmic  Xerve 726 

Lachrymal  and  Frontal  Branches  ....  726 

Nasal  Branches 727 

Ophthalmic  Ganglion 729 

Superior  Maxillary  Nerve 729 

Spheno-palatine  Ganglion 732 

Inferior  Maxillary  Xerve 734 

Auriculo-temporal  Branch 735 

Lingual  Branch 735 

Inferior  Dental  Branch 736 

Otic  Ganglion 736 

Submaxillary  Ganglion 737 

Surgical  Anatomy  of  Fifth  Xerve 738 

Abducens  Xerve 738 

Eelations  of  the  Orbital  Xerves  in  the  Cavern- 
ous Sinus 739 

Eelations,  etc.,  in  the  Sphenoidal  Fissure   .    .  739 

"           in  the  Orbit 739 

Surgical  Anatomy 740 

Facial  Xerve 740 

Branches  of  Facial  Xerve 741 

Surgical  Anatomy 744 

Auditory  Xerve 745 

Surgical  Anatomy 746 

Glosso-pharyngeal  Xerve 746 

Pneumogastric  (Vagus)  Xerve 749 

Surgical  Anatomy 752 

Spinal  Accessory  Xerve 753 

Surgical  Anatomy 754 

Hypoglossal  Xerve 754 

Surgical  Anatomy 756 

The  Spinal  Xeeves. 

Boots  of  the  Spinal  Xerves 756 

Origin  of  Anterior  Eoots 756 

"        of  Posterior  Eoots 756 


CONTENTS. 


19 


Ganglia  of  the  Spinal  Nerves 757 

Posterior  Divisions  of  the  Spinal  Nerves    .    .  758 

Anterior  Divisions  of  the  Spinal  Nerves .    .    .  758 

Points  of  Emergence  of  Spinal  Nerves    .    .    .  758 

The  Cervical  Nerves. 

Eoots  of  the  Cervical  Nerves 758 

Posterior  Divisions  of  the  Cervical  Nerves     .  759 

Anterior  Divisions  of  the  Cervical  Nerves      .  760 

The  Cervical  Plexus. 

Superficial  Branches  of  the  Cervical  Plexus  .  762 

Deep  Branches  of  the  Cervical  Plexus ....  763 

The  Brachial  Plexus. 

Branches  above  the  Clavicle. 

Posterior  Thoracic 768 

Suprascapular 768 

Branches  below  the  Clavicle. 

Anterior  Thoracic 769 

Subscapular  Nerves 769 

Circumflex  Nerve .    .  769 

Musculocutaneous  Nerve 770 

Internal  Cutaneous  Nerve 770 

Lesser  Internal  Cutaneous  Nerve 771 

Median  Nerve 771 

Ulnar  Nerve 772 

Musculo-spiral  Nerve 774 

Eadial  Nerve 775 

Posterior  Interosseous  Nerve 775 

Surgical  Anatomy  of  Brachial  Plexus  ....  776 

The  Dorsal  Nerves. 

Eoots  of  the  Dorsal  Nerves 776 

Posterior  Divisions  of  the  Dorsal  Nerves    .    .  777 

Anterior  Divisions  of  the  Dorsal  Nerves     .    .  777 

First  Dorsal  Nerve 777 

Upper  Dorsal  Nerves 778 

Lower  Dorsal  Nerves 779 

Last  Dorsal  Nerve 780 

Surgical  Anatomy 780 

Thr  Lumbar  Nerves. 

Boot  of  Lumbar  Nerves 780 

Posterior  Divisions  of  Lumbar  Nerves    .    .    .  781 

Anterior  Divisions  of  Lumbar  Nerves  ....  781 

The  Lumbar  Plexus. 

Branches  of  Lumbar  Plexus 782 

Ilio-hypogastric  Nerve 782 

Uio-inguinal  Nerve 783 

Genito-crural  Nerve 783 

External  Cutaneous  Nerve 785 

Obturator  Nerve 785 

Accessory  Obturator  Nerve 786 

Anterior  Crural  Nerve 786 

Branches  of  Anterior  Crural 786 

Middle  Cutaneous 786 

Internal  Cutaneous 786 

Long  Saphenous 787 

Muscular  and  Articular  Branches  ....  787 


The  Sacral  and  Coccygeal  Nerves,  page 

Eoots  of,  origin  of 788 

Posterior  Divisions  of  Sacral  Nerves    ....    788 

Coccygeal  Nerve 789 

Anterior  Divisions  of  Sacral  Nerves     ....    789 

The  Sacral  Plexus. 

Superior  Gluteal  Nerve 

Inferior  Gluteal  Nerve 

Small  Sciatic  Nerve 

Pudic  Nerve      

Great  Sciatic  Nerve 

Internal  Popliteal  Nerve 

External  Saphenous  Nerve 

Posterior  Tibial  Nerve      

Plantar  Nerves 

External  Popliteal  or  Peroneal  Nerve  .... 

Anterior  Tibial  Nerve 

Musculo-cutaneous  Nerve 

Surgical    Anatomy   of    Lumbar    and    Sacral 
Plexus    


791 
791 
791 
793 
793 
794 
794 
794 
795 
796 
796 
796 

797 


The  Sympathetic  Nerve. 

Subdivision  of,  into  Parts 798 

Branches  of  the  Ganglia,  General  Description 

of 799 

Cervical    Portion  of   the   Gangliated 

Cord 799 

Superior  Cervical  Ganglion 799 

Carotid  Plexus 801 

Cavernous  Plexus 801 

Middle  Cervical  Ganglion 803 

Inferior  Cervical  Ganglion 803 

Thoracic  Part  of  the  Gangliated  Cord  801 

Great  Splanchnic  Nerve 804 

Lesser  Splanchnic  Nerve 804 

Smallest  Splanchnic  Nerve 804 

Lumbar    Portion    of   the    Gangliated 

Cord 805 

Pelvic    Portion    of     the    Gangliated 

Cord 805 

The  Great  Plexuses  of  the  Sympathetic. 

Cardiac  Plexuses 805 

Great  Cardiac  Plexs 806 

Superficial  Cardiac  Plexus 806 

Coronary  Plexuses 806 

Epigastric,  or  Solar  Plexus 806 

Phrenic  Plexus 808 

Suprarenal  Plexus 808 

Eenal  Plexus 808 

Spermatic  Plexus 808 

Cceliac  Plexus 808 

Superior  Mesenteric  Plexus 809 

Aortic  Plexus 809 

Inferior  Mesenteric  Plexus      809 

Hypogastric  Plexus £ 

Pelvic  Plexus £ 

Inferior  Hemorrhoidal  Plexus 809 

Vesical  Plexus      \ 

Prostatic  Plexus 809 

Vaginal  Plexus * 

Uterine  Plexus bl° 


THE   ORGANS   OF  SPECIAL  SENSE. 


The  Tongue. 

Structure  of 811 

Papillae  of 813 

Glands  of 815 

Fibrous  Septum  of 815 

Hyo-glossal  Membrane 815 

Arteries  and  Nerves  of 815 

Muscles  of 815 

Nerves  of 816 

Surgical  Anatomy 816 

The  Nose. 

■Cartilages  of 818 

Muscles  of 819 


Skin 

Mucous  Membrane 

Arteries,  Veins,  and  Nerves 

The  Xasal  Fossse. 

Outer  Wall  of 

Mucous  Membrane  of     .    .    .    •     ■ 

Superior,  Middle,  and  Inferior  Meatuses  .    . 
Arteries  and  Veins  of  Nasal  Fossse    .... 

Nerves  of  Nasal  Fossse 

Surgical  Anatomy  of  Nose  and  Nasal  Fossse 

The  Eye. 

Situation,  Form  of 

Capsule  of  Tenon 


819 
819 

819 

820 
820 

822 
823 

S23 

824 
824 


20 


CONTENTS. 


Tunics  of,  sclerotic 825 

Cornea 826 

Choroid 828 

Biliary  Body 829 

Ciliary  Muscle 830 

Iris 830 

Membrana  Pupillaris 832 

Ciliary  Muscle 832 

Retina 832 

Structure  of  Retina 833 

Structure  of  Retina  at  Yellow  Spot 838 

Arteria  Centralis  Retinae 839 

The  Humors  of  the  Eye. 

Aqueous  Humor 839 

Anterior  Chamber 839 

Posterior  Chamber 839 

Vitreous  Body 839 

Suspensory  Ligament  of  Lens 840 

Canal  of  Petit 840 

Crystalline  Lens  and  its  Capsule 840 

Changes  produced  in  the  Lens  by  Age  ....  841 

Vessels  of  the  Globe  of  the  Eye 841 

Nerves  of  the  Eyeball 841 

Surgical  Anatomy  of  Eye 841 

The  Appendages  of  the  Eye. 

Eyebrows 843 

Eyelids 843 

Eyelashes 843 

Structure  of  the  Eyelids 843 

Tarsal  Plates 843 

Meibomian  Glands 844 

Conjunctiva 845 

Carunculse  Lachrymales 845 

The  Lachrymal  Apparatus. 

Lachrymal  Gland 846 

"          Canals 846 

"          Sac 847 

Nasal  Duct 847 

Surface  Form  of  Papebral  Fissure 847 

Surgical  Anatomy ' 847 

The  Ear. 
The  External  Ear. 

Pinna,  or  Auricle 848 

Structure  of  Auricle 849 


PAGE 

Ligaments  of  the  Pinna 849 

Muscles  of  the  Pinna '  ,    •  850 

Arteries,  Veins,  and  Nerves  of  the  Pinna'  .    .  850 

Auditory  Canal 851 

Surface  Form 852 

The  Middle  Ear,  or  Tympanum. 

Cavity  of  Tympanum ,    .  852 

Roof  of  the  Tympanic  Cavity 853- 

Floor  of  the  Tympanic  Cavity 853 

Outer  Wall  of  the  Tympanic  Cavity     ....  853- 

Internal  Wall  of  the  Tympanic  Cavity    .    .    .  853 

Posterior  Wall  of  the  Tympanic  Cavity  .    .    .  854 

Anterior  Wall  of  the  Tympanic  Cavity   .    .    .  854 

Eustachian  Tube 855 

Membrana  Tympani 855 

Structure  of '  .    .  855 

Ossicles  of  the  Tympanum 85ft 

Ligaments  of  the  Ossicula 857 

Muscles  of  the  Tympanum 857 

Mucous  Membrane  of  Tympanum  ......  858- 

Arteries  of  Tympanum 858 

Veins  and  Nerves  of  Tympanum 858- 

The  Internal  Ear,  or  Labyrinth. 

Osseous  Labyrinth 859" 

Vestibule :>.-..  859- 

Semicircular  Canals: 

Superior  Semicircular  Canal    .    .    .    .    .    .  560 

Posterior  Semicircular  Canal    .    .    .    .    .    .  860 

External  Semicircular  Canal   .    .    .-■•  i.    .  860" 
Cochlea : 

Central  Axis  of,  or  Modiolus 861 

Bony  Canal  of j«    •  861 

Osseous  Lamina  Spiralis *   '.    .  862 

Membranous  Labyrinth 862 

Utricle  and  Saccule 862 

Semicircular  Canals 862 

Cochlea .  863 

Scala  Tvmpaui,  Scala  Vestibuli.   and 

Scala  Media .  863: 

Organ  of  Corti 864 

Vessels  of  the  Labyrinth .  86ft 

Auditory  Nerve 866- 

Vestibular  Nerve '    -  867 

Cochlear  Nerve ■  867 

Surgical  Anatomy 867 


THE  ORGANS  OF  DIGESTION. 


Subdivisions  of  the  Alimentary  Canal  ....  869 

The  Mouth 869 

The  Lips    . 869 

The  Cheeks 870 

The  Gums      870 

The  Teeth. 

General  Characters  of 871 

Permanent  Teeth 871 

Incisors 871 

Canine 872 

Bicuspids 872 

Molars 873 

Temporary,  or  Milk  Teeth 873 

Structure  of  the  Teeth 874 

Ivory  or  Dentine 876 

Enamel 877 

Cortical  Substance 878 

Development  of  the  Teeth 878 

of  the  Permanent  Teeth     .    .    .  881 

Eruption  of  the  Teeth 881 

The  Palate. 

Hard  Palate 883 

Soft  Palate 883 

Uvula,  Pillars  of  the  Soft  Palate 883 

Mucous  Membrane  and  Aponeurosis     ....  883 

Muscles  of  Soft  Palate 884 


The  Tonsils. 

Arteries 884 

Veins  and  Nerves  of  Tonsils 884 

The  Salivary  Glands. 
Parotid  Gland. 

Situation  and  Relations 884 

Stenson's  Duct ,...:.  885 

Surface  Form , .'    .  886 

Vessels  and  Nerves  of  Parotid  Gland   ....  886 

The  Submaxillary  Gland. 

Situation  and  Relations 886 

Wharton's  Duct 886 

Vessels  and   Nerves  of  Submaxillary  Gland  .  887 

The  Sublingual  Gland. 

Situation  and  Relations 887 

Vessels  and  Nerves  of 887 

Structure  of  Salivarv  Glands 887 

Surface  Form  of  Mouth 888- 

The  Pharynx  and  OZsophagtts. 

Situation  and  Relations 890- 

Structure  of  Pharynx 890" 

Surgical  Anatomy 891 

Relations  of  Oesophagus 891 

Structure 892- 


CONTENTS. 


21 


PAGE 

Vessels 892 

Nerves  of 893 

Surgical  Anatomy 893 


The  Abdomen. 


Boundaries 
Apertures  of 
Eegions  .    .    . 


The  Peritoneum. 


Eeflections  traced 

Lesser  Sac  of  Peritoneum 

Ligaments  formed  by  Peritoneum 

Omenta 

Lesser  Omentum 

Great  Omentum 

Gastro-splenic  Omentum 

Mesenteries 

Mesocolon,  Mesorectum,  Appendices  Epi- 
ploicee 

Eetro-peritoneal  Fossae 

The  Stomach. 

Situation 

Surfaces 

Greater  aud  Lesser  Curvatures 

Cardiac  and  Pyloric  Orifices 

Alterations  in  Position 

Pylorus ' 

Structure  of  Stomach 

Serous  Coat    

Muscular  Coat  and  Mucous  Membrane     .    .    . 

Gastric  Follicles 

Vessels  aud  Nerves  of  Stomach 

Surface  Marking 

Surgical  Anatomy 


895 
895 
895 


899 
901 
901 
901 
902 
902 
902 

903 
904 

905 
905 
906 
906 
907 
908 
908 
908 
908 
909 
910 
910 
911 


The  Small  Intestines. 
Duodenum 

First  or  Superior  Portion  .    .    . 

Second  or  Descending  Portion 

Third  or  Transverse  Portion    . 

Fourth  or  Ascending  Portion  . 
Vessels  and  Nerves  of  Duodenum  . 

Jejunum  and  Ileum 

Meckel's  Diverticulum 

Structure  of  Small  Intestines  .  .  . 
Serous  and  Muscular  Coats  .... 
Mucous  Membrane  and  Epithelium 

Valvulse  Conniventes 

Villi — their  Structure 

Simple  Follicles 

Duodenal  Glands 

Solitary  Glands 

Peyer's  Glands 

Vessels  and  Nerves 


The  Large  Intestine. 
Caecum 

Appendix  Caeci  Vermiformis    . 

Ileo-csecal  Valve  .^. 

Colon  .    .    .    ' 

Ascending 

Transverse    

Descending 

Sigmoid  Flexure 

Eectum 

Structure  of  Large  Intestine  .    .    . 

Serous  Coat       

Muscular  Coat 

Areolar  and  Mucous  Coats    .... 
Simple  Follicles 


912 
912 
912 
914 
914 
914 
914 
915 
915 
915 
915 
916 
917 
918 
918 
919 
919 
921 

922 
922 
923 
923 
923 


924 
925 
925 
925 
928 
928 
928 
928 
929 


Solitary  Glands 929 

Vessels  and  Nerves 929 

Surface  Form 930 

Surgical  Anatomy 930 

The  Liver. 

Size,  Weight,  Position  of 933 

Its  Surfaces  and  Borders 934 

Fissures. 

Longitudinal 935 

Fissure  of  Ductus  Venosus  .    .' 936 

Portal  Fissure 936 

Fissure  for  Gall-bladder 936 

Fissure  for  Inferior  Vena  Cava 93& 

Lobes. 

Eight 937 

Quadratus 937 

Spigelii 937 

Caudatus 937 

Left 937 

Ligaments. 

Falciform 937 

Lateral  and  Coronary 937 

Eound  Ligament 938 

Vessels  of  Liver 938 

Structure  of  Liver 938 

Serous  Coat 938 

Fibrous  Coat 938 

Lobules 938 

Hepatic  Cells 939 

Hepatic  Artery 940 

Portal  Vein 940 

Hepatic  Veins 940 

Biliary  Ducts 940 

Lymphatics  of  the  Liver 941 

Nerves  of  Liver 941 

Excretory  Apparatus  of  the  Liver. 

Hepatic  Duct 942 

Gall-bladder 942 

Structure 942 

Cystic  Duct 943 

Ductus  Communis  Choledochus 943 

Structure 943 

Surface  Marking  of  Liver 943 

Surgical  Anatomy 944 

The  Pancreas. 

Dissection 945 

Eelations 945 

Duct 947 

Structure 948 

Vessels  and  Nerves 948 

Surface  Marking 948 

Surgical  Anatomy 948 

The  Spleen. 

Eelations 949 

Size  and  Weight 950 

Structure  of  Serous  and  Fibrous  Coats     .    .    .  950 

Proper  Substance 951 

Splenic  Artery,  Distribution 952 

Malpighian  Bodies 952 

Capillaries  of  Spleen 953 

Veins  of  Spleen 953 

Lymphatics 953 

Nerves 954 

Surface  Marking  of  Spleen 954 

Surgical  Anatomy 954 


THE  ORGANS  OF    VOICE  AND  RESPIRATION. 


The  Larynx. 


I  Cartilage  of  Wrisberg 958 

Epiglottis 9o8 

Cartilages  of  the  Larvnx 955  |  Ligaments  of  the  Larynx 958 

Thyroid  Cartilage 955     Ligaments  Connecting  the  Thyroid  Cartilage 

Cricoid  Cartilage 956  \      with  the  Hyoid  Bone 958 

Arytenoid  Cartilages,  Cartilages  of  Santo-  Ligaments  Connecting  the  Thyroid  Cartilage 

rini 957         with  the  Cricoid 958 


22 


CONTENTS. 


PAGE 

Ligaments  Connecting  the  Arytenoid  Carti- 
lages to  the  Cricoid 959 

Ligaments  of  the  Epiglottis 959 

Superior  Aperture  of  the  Larynx 959 

Eima  Glottidis 959 

False  Vocal  Cords 960 

True  Vocal  Cords 961 

Ventricle  of  Larynx,  Sacculus  Laryngis  ."  .    .  961 

Muscles  of  Larynx 961 

Crico-thyroid 961 

Crico-arytenoideus  posticus 962 

Crico-arytenoideus  lateralis 962 

Arytenoideus 962 

Thyro-arytenoideus 962 

Muscles  of  the  Epiglottis 963 

Thyro-epiglottideus 963 

Aryteno-epiglottideus,  superior 963 

"                      inferior 963 

Actions  of  Muscles  of  Larynx 963 

Mucous  Membrane  of  Larynx 964 

Glands,  Vessels,  and  Nerves  of  Larynx  .    .    .  964 
The  Trachea. 

Relations 965 

Bronchi 966 

Structure  of  Trachea 966 

Cartilages 966 

Fibrous  Membrane 967 

Muscular  Fibres 967 

Mucous  Membrane 967 

Glands 967 

Vessels  and  Nerves 967 

Surface  Form 968 

Surgical  Anatomy  of  Laryngo-tracheal  Eegion  968 

The  Pleura. 

Reflections     .    . 969 

Vessels  and  Nerves 971 

Surgical  Anatomy 971 


The  Mediastina.  page 

Superior  Mediastinum 971 

Anterior  Mediastinum 972 

Middle  Mediastinum 972 

Posterior  Mediastinum 973 

The  Lungs 

Surfaces 973 

Borders  and  Lobes 973 

Boot  of  Lung 974 

Weight,  Color,  and  Properties  of  Substance  of 

Lung 975 

Structure  of  Lung 975 

Serous  Coat  and  Subserous  Areolar  Tissue  .    .  975 

Parenchyma  and  Lobules  of  Lung 976 

Bronchi,    Arrangement    of,    in    Substance   of 

Lung 976 

Structure  of  Smaller  Bronchial  Tubes  ....  976 

The  Air-cells 976 

Pulmonary  Artery 976 

Pulmonary  Capillaries  and  Veins 976 

Bronchial  Arteries 976 

Bronchial  Veins 977 

Lymphatics  and  Nerves  of  Lung 977 

Surface  Form  of  Lungs 977 

Surgical  Anatomy 977 

The  Thyroid  Gland. 

Surface  and  Relations 979 

Structure '.    .  980 

Vessels  and  Nerves 981 

Surgical  Anatomy 981 

The  Thymus  Gland. 

Relations 981 

Structure 982 

Vessels  and  Nerves 982 


THE   URINARY   ORGANS. 


The  Kidneys. 

Relations 985 

Dimensions,  Weight 985 

General  Structure 986 

Cortical  Substance 987 

Medullary  Substance 987 

Minute  Structure 987 

Malpigliian  Bodies 988 

Tufts 988 

Capsule 988 

Tubuli  Uriniferi,  Course 988 

Structure 990 

Renal  Blood-vessels 992 

Renal  Veins 992 

Vente  Rectee 992 

Nerves 993 

Lymphatics 993 

Surface  Form * 993 

Surgical  Anatomy 993 

The  Ureters. 

Situation 994 

Calices .  995 

Course 995 

Relations 995 

Structure 995 

Surgical  Anatomy 996 


The  Suprarenal  Capsides. 

Relations 997 

Structure 997 

Vessels  and  Nerves 998 

The  Pelvis. 

Boundaries 998 

Contents 998 

The  Bladder. 

Shape,  Position,  Relations 998 

Subdivisions 1001 

Urachus 1002 

Ligaments 1002 

Structure 1002 

Interior  of  Bladder 1003 

Vessels  and  Nerves 1004 

Surface  Form 1004 

Surgical  Anatomy 1004 

The  Male  Urethra. 

Divisions 1005 

Structure 1006 

Surgical  Anatomy 1007 

Bladder  and  Urethra  in  the  Female     ....  1007 


THE  MALE  ORGANS  OF  GENERATION. 


Prostate  Glands 1009 

Structure - 1010 

Vessels  and  Nerves 1010 

Surgical  Anatomy  ...        1011 

Cowper's  Gland 1011 

Structure 1011 

The  Penis. 

Root 1011 

Glans  Penis 1011 


Body 1012 

Structure  of  Penis 1012 

Corpora  Cavernosa 1012 

Structure        1012 

Arteries  of  the  Penis 1013 

Corpus  Spongiosum 1013 

The  Bulb 1013 

Structure  of  Corpus  Spongiosum    .......  1014 

Lymphatics  of  the  Penis 1011 


CONTENTS. 


23 


PAGE 

Nerves  of  the  Penis 1014 

Surgical  Anatomy 1014 

The  Testes  and  their  Coverings. 

Scrotum      1015 

Coverings  of  the  Testis .  1015 

Vessels  and  Nerves  of  the  Coverings  of  the 

Testis 1016 

The  Spermatic  Cord. 

Its  Composition 1016 

Relations  of,  in  Inguinal  Canal 1016 

Arteries  of  the  Cord 1016 

Veins  of  the  Cord 1016 

Lymphatics  and  Nerves  of  the  Cord     .    .    .    .1017 
Surgical  Anatomy   . 1017 

The  Testes. 

Form  and  Situation 1017 

Size  and  Weight 1018 

Coverings 1018 


Tunica  Vaginalis 1018 

Tunica  Albuginea 1018 

Mediastinum  Testis 1018 

Tunica  Vasculosa 1019 

i  Structure  of  the  Testis 1019 

Lobulus  of  the  Testis mi'.i 

Tubuli  Seminiferi 1019 

Arrangement  in  Lobuli 1019 

in  Mediastinum  Testis    ....  1019 

in  Epididymis 1019 

Spermatogenesis 1020 

Vas  Deferens,  Course,  Relations 1021 

Structure 102] 

Vas  Aberrans    . 1021 

Surgical  Anatomy 1021 

Vesiculse  Seminales. 

Form  and  Size 1022 

Relations 1022 

Structure 1022 

Ejaculatory  Ducts 1023- 


THE  FEMALE  ORGANS  OF  GENERATION. 


Mons  Veneris,  Labia  Majora 1025 

"  "         Labia  Minora 1026 

Clitoris ' 1026 

Meatus  Urinarius 1027 

Hymen,  Glands  of  Bartholin 1027 

The  Vagina. 

Relations 1028 

Structure    1028 

The  Uterus. 

Situation,  Form,  Dimensions 1028 

Fundus,  Body,  and  Cervix 1029 

Ligaments 1029 

Cavitv  of  the  Uterus 1030 

Cavitv  of  the  Cervix 1031 

Structure 1031 

Vessels  and  Nerves 1032 

Its  Form,  Size,  and  Situation  in  the  Foetus    .  1033 

"  "  "  at  Puberty    .    .  1033 

Its  Form,  Size,  etc.,  during  Menstruation   .    .  1033 


Its  Form    during  Pregnancy 1033 

after  Parturition 1033 

in  Old  Age 103a 

The  Appendages  of  the  Uterus. 
Fallopian  Tubes 1034 

Structure    1035 

Ovaries 1035 

Structure        1036- 

Graafian  Vesicles 1036 

Discharge  of  the  Ovum 1037 

Ligament  of  the  Ovary 1038 

Round  Ligaments 1038 

Vessels  and  Nerves  of  Appendages    .    .        .    .  1038 

The  Mammary  Glands. 

Situation  and  Size 1038 

Nipple 1039 

Structure  of  Mamma 1039 

Vessels  and  Nerves 1040 


THE  SURGICAL  ANATOMY  OF  HERNIA. 


INGUINAL  HEENIA. 

Coverings  of  Inguinal  Hernia. 

Dissection 1041 

Superficial  Fascia ;    .    .    .    .  1041 

Superficial  Vessels  and  Nerves 1041 

Deep  Layer  of  Superficial  Fascia 1042 

Aponeurosis  of  External  Oblique    .    .    .-.    .    .  1042 

External  Abdominal  Ring 1043 

Pillars  of  the  Ring 1043 

Intercolumnar  Fibres 1043 

"  Fascia 1043 

Poupart's  Ligament 1044 

Gimbernat's  Ligament 1044 

Triangular  Ligament 1044 

Internal  Oblique  Muscle 1045 

Cremaster 1045 

Transversalis  Muscle 1045 

Spermatic  Canal 1046 

Transversalis  Fascia 1046 

Internal  Abdominal  Ring 1047 

Subperitoneal  Areolar  Tissue 1047 

Deep  Epigastric  Artery 1047 

Peritoneum 1047 

Oblique  Inguinal  Hernia. 
Course  and  Coverings  of  Oblique  Hernia    .    .  1049 

Seat  of  Stricture      1051 

Scrotal  Hernia 1051 

Bubonocele 1051 


Congenita]  Hernia 1051 

Infantile  and  Encysted  Hernia 1051 

Hernia  into  the  Funicular  Process 1051 

Direct  Inguinal  Hernia. 
Course  and  Coverings  of  the  Hernia     ....  1052 

Seat  of  Stricture      1053 

Incomplete  Direct  Hernia in,",:; 

Comparative  Frequency  of  Oblique  and  Di- 
rect Hernia    1053 

Division  of  Stricture  in  Inguinal  Hernia    .    .  1053 

FEMORAL   HEENIA. 

Dissection 1053 

Superficial  Fascia 1053 

Cutaneous  Vessels       1054 

Internal  Saphenous  Vein 1054 

Superficial  Inguinal  Glands 1055 

Cutaneous  Nerves 1055 

Deep  Layer  of  Superficial  Fascia 1055 

Cribriform  Fascia 1055 

Fascia  Lata 1055 

Iliac  Portion 1055 

Pubic  Portion 1056 

Saphenous  Opening 1056 

( 'rural  Arch 1057 

Gimbernat's  Ligament 1058 

Femoral  Sheath 1059 

Deep  Crural  Arch 1059 

Crural  Canal 1059 


24 


CONTENTS. 


PAGE 

Femoral  or  Crural  Eing 1060 

Position  of  Parts  around  the  Eing 1060 

Septum  Crurale 1060 

Descent  of  Femoral  Hernia 1061 


PAGE 

Coverings  of  Femoral  Hernia 1061 

Varieties  of  Femoral  Hernia 1061 

Seat  of  Stricture 1061 


SURGICAL  ANATOMY  OF  THE  PERINvEUM. 


Ischio-rectal  Region. 

Dissection  of 1063 

Boundaries  of 1063 

Superficial  Fascia 1063 

Ischio-rectal  Fossa •    •    •    .    .  1064 

Position  of  Parts  contained  in 1064 

The  Perinteum  Proper  in  the  Male. 

Boundaries  and  Extent 1064 

Deep  Layer  of  Superficial  Fascia 1065 

•Course  taken  by  the  Urine  in  Eupture  of  the 

Urethra 1065 

JVEuscles  of  the  Perinseum  (Male) 1065 

Deep  Perineal  Fascia 1065 

Superficial  Layer 1066 

Deep  Layer 1066 

Parts  between  the  two  Layers 1066 

Compressor  Urethras 1067 


Cowper's  Glands 1067 

Pudic  Vessels  and  Nerves 1067 

Artery  of  the  Bulb 1067 

Position  of  the  Viscera  at  Outlet  of  Pelvis     .  1067 

Prostate  Gland "...  1068 

Surgical  Anatomy  of  Lithotomy 1068 

Parts  divided  in  the  Operation 1069 

Parts  to  be  avoided  in  the  Operation    ....  1069 
Abnormal  Course  of  Arteries  in  the  Perinseum  1069 

The  Female  Perinseum. 

Superficial  Fascia 1069 

Deep  Fascia 1069 

Compressor  Urethras 1070 

Perineal  Body 1070 

Pelvic  Fascia • 1070 

Obturator  Fascia 1071 

Eecto-vesical  Fascia :    .    .  1071 


GENERAL  ANATOMY  OR  HISTOLOGY. 


The  Animal  Cell 1073 

The  Nutritive  Fluids 1077 

Blood 1077 

Lvmph  and  Chyle 1082 

Epithelium 1082 

Connective  Tissue 1086 

The  Connective  Tissues  proper 1086 

Adipose  Tissue 1091 

Pigment 1092 

■Cartilage 1092 

White  Fibro-cartilage 1094 

Yellow  or  Eeticular,  Elastic  Cartilage      .  1094 

The  Bone 1096 

Development  of  Bone 1099 

Muscular  Tissue 1104 

Striped  Muscle  1  .    .    . .  1105 

Unstriped  Muscle 1109 

Cardiac  Muscular  Tissue 1110 

Nervous  Tissue 1111 

The  Brain      ."~- 1118 


The  Nerves 1118 

The  Sympathetic  Nerve        1120 

Origin  and  Termination  of  Nerves    .    .    .  1120 

The  Ganglia 1124 

The  Vascular  System 1126 

The  Arteries 1126 

The  Capillaries 1128 

The  Veins 1130 

The  Lymphatics 1131 

The  Lymphatic  Glands 1133 

The  Skin  and  its  Appendages 1135 

The  Nails       1139 

The  Hair 1140 

The  Sebaceous  Glands 1142 

The  Sudoriferous  Glands      1142 

Serous  Membranes      1143 

Synovial  Membranes 1145 

Mucous  Membranes    .    .    .' 1145 

Secreting  Glands 1146 


EMBRYOLOGY. 


The  Ovum 1149 

Maturation  of 1150 

Impregnation  of 1151 

Segmentation  of 1152 

Formation  of  the  Mesoblast 1154 

First  Eudiments  of  the  Embryo 1155 

Formation  of  Membranes      1160 

The  Amnion • 1160 

The  Chorion 1161 

The  Allantois .    .1162 

The  Decidua 1162 

The  Placenta 1164 

Development  of  the  Embryo 11 65 

The  Spine 1165 

The  Eibs  and  Sternum 1166 

The  Cranium  and  Face 1166 

The  Nervous  Centres 1172 

The  Nerves 1178 


The  Eye 1180 

The  Ear 1183 

The  Nose 1184 

The  Skin,  Glands,  and  Soft  Parts  .    .    .    .1186 

The  Limbs 1187 

The  Muscles 1187 

The  Blood-vascular  System      1 187 

Vitelline  Circulation 1187 

Placental  Circulation     .    .    . 1189 

The  Alimentary  Canal  and  its  Appendages    .  1198 

The  Eespiratory  Organs 1206 

The  Urinary  and  Generative  Organs    ....  1207 

Ovaries  and  Testicles 1209 

Descent  of  the  Testes 1211 

External  Organs 1212 

Chronological  Tables  of  the  Development  of 

the  Fetus 1215 


INDEX 1217 


DESCRIPTIVE  AND  SURGICAL 

ANATOMY. 


OSTEOLOGY-THE  SKELETON. 


nnHE  entire  skeleton  in  the  adult  consists  of  200  distinct  bones.     These  are — 

The  spine  or  vertebral  column  (sacrum  and  coccyx  included) 26 

Cranium 8 

Face 14 

Hyoid  bone,  sternum,  and  ribs 26 

Upper  extremities .    .  64 

Lower  extremities 62 

200 

In  this  enumeration  the  patellae  are  included  as  separate  bones,  but  the  smaller 
sesamoid  bones  and  the  ossicula  auditus  are  not  reckoned.  The  teeth  belong  to 
the    tegumentary    system. 

These  bones  are  divisible  into  four  classes :  Long,  Short,  Flat,  and  Irregular. 

The  Long  Bones  are  found  in  the  limbs,  where  they  form  a  system  of  levers, 
which  have  to  sustain  the  weight  of  the  trunk  and  to  confer  the  power  of  locomo- 
tion. A  long  bone  consists  of  a  shaft  and  two  extremities.  The  shaft  is  a  hollow 
cylinder,  contracted  and  narrowed  to  afford  greater  space  for  the  bellies  of  the 
muscles  ;  the  walls  consist  of  dense,  compact  tissue  of  great  thicknep"  in  the  middle, 
but  becoming  thinner  toward  the  extremities  ;  the  spongy  tissue  is  scanty,  and 
the  bone  is  hollowed  out  in  its  interior  to  form  the  medullary  canal.  The 
extremities  are  generally  somewhat  expanded  for  greater  convenience  of  mutual 
connection,  for  the  purposes  of  articulation,  and  to  afford  a  broad  surface  for 
muscular  attachment.  Here  the  bone  is  made  up  of  spongy  tissue  with  only  a  thin 
coating  of  compact  substance.  The  long  bones  are  not  straight,  but  curved,  the 
curve  generally  taking  place  in  two  directions,  thus  affording  greater  strength  to  the 
bone.  The  bones  belonging  to  this  class  are  the  clavicle,  humerus,  radius,  ulna, 
femur,  tibia,  fibula,  metacarpal  and  metatarsal  bones,  and  the  phalanges. 

Short  Bones. — Where  a  part  of  the  skeleton  is  intended  for  strength  and  com- 
pactness, and  its  motion  is  at  the  same  time  slight  and  limited,  it  is  divided  into  a 
number  of  small  pieces  united  together  by  ligaments,  and  the  separate  bones  are 
short  and  compressed,  such  as  the  bones  of  the  carpus  and  tarsus.  These  bones, 
in  their  structure,  are  spongy  throughout,  excepting  at  their  surface,  where  there 
is  a  thin  crust  of  compact  substance.  The  patella?  also,  together  with  the  other 
sesamoid  bones,  are  by  some  regarded  as  short  bones. 

Flat  Bones. — Where  the  principal  requirement  is  either  extensive  protection 
or  the  provision  of  broad  surfaces  for  muscular  attachment,  we  find  the  osseous 
structure  expanded  into  broad,  flat  plates,  as  is  seen  in  the  bones  of  the  skull  and 
the  shoulder-blade.  These  bones  are  composed  of  two  thin  layers  of  compact  tissue 
enclosing  between  them  a  variable  quantity  of  cancellous  tissue.  In  the  cranial 
bones  these  layers  of  compact  tissue  are  familiarly  known  as  the  tables  of  the 

3  33 


34  THE  SKELETON. 

skull ;  the  outer  one  is  thick  and  tough ;  the  inner  one  thinner,  denser,  and  more 
brittle,  and  hence  termed  the  vitreous  table.  The  intervening  cancellous  tissue 
is  called  the  diploe.  The  flat  bones  are :  the  occipital,  parietal,  frontal,  nasal, 
lachrymal,  vomer,  scapula,  os  innominatum,  sternum,  ribs,  and  patella. 

The  Irregular  or  Mixed  Bones  are  such  as,  from  their  peculiar  form,  cannot  be 
orouped  under  either  of  the  preceding  heads.  Their  structure  is  similar  to  that 
of  other  bones,  consisting  of  a  layer  of  compact  tissue  externally,  and  of  spongy 
cancellous  tissue  within.  The  irregular  bones  are :  the  vertebra?,  sacrum,  coccyx, 
temporal,  sphenoid,  ethmoid,  malar,  superior  maxillary,  inferior  maxillary,  palate, 
inferior  turbinated,  and  hyoid. 

Surfaces  of  Bones. — If  the  surface  of  any  bone  is  examined,  certain  eminences 
and  depressions  are  seen  to  which  descriptive  anatomists  have  given  the  following 
names. 

These  eminences  and  depressions  are  of  two  kinds  :  articular  and  non-articular. 
Well-marked  examples  of  articular  eminences  are  found  in  the  heads  of  the  humerus 
and  femur  and  of  articular  depressions  in  the  glenoid  cavity  of  the  scapula  and  the 
acetabulum.  Non-articular  eminences  are  designated  according  to  their  form. 
Thus,  a  broad,  rough,  uneven  elevation  is  called  a  tuberosity;  a  small,  rough 
prominence,  a  tubercle ;  a  sharp,  slender,  pointed  eminence,  a  spine ;  a  narrow, 
rough  elevation,  running  some  way  along  the  surface,  a  ridge  or  line. 

The  non-articular  depressions  are  also  of  very  variable  form,  and  are  described 
as  fossa?,  grooves,  furrows,  fissures,  notches,  etc.  These  non-articular  eminences 
and  depressions  serve  to  increase  the  extent  of  surface  for  the  attachment  of  liga- 
ments and  muscles,  and  are  usually  well  marked  in  proportion  to  the  muscularity 
of  the  subject. 

A  prominent  process  projecting  from  the  surface  of  a  bone,  which  it  has  never 
been  separate  from  or  movable  upon  is  termed  an  apophysis  (from  anbipvaiz,  an 
excrescence) ;  but  if  such  process  is  developed  as  a  separate  piece  from  the  rest  of 
the  bone,  to  which  it  is  afterward  joined,  it  is  termed  an  epiphysis  (from  In'upuoiz, 
an  accretion).  The  main  part  of  the  bone,  or  shaft,  which  is  formed  from  the 
primary  centre  of  ossification,  is  termed  the  diaphysis,  and  is  separated,  during 
growth,  from  the  epiphysis  by  a  layer  of  cartilage,  at  which  growth  in  length 
of  the  bone  takes  place. 

THE  SPINE. 

The  Spine  is  a  flexuous  and  flexible  column  formed  of  a  series  of  bones  called 

x  7 (from  vertere,  to  turn). 

■    Vertebrae   are   thirty-three    in    number,   and    have    received    the    names 
dorsal,  lumbar,  sacred,  and  coccygeal,  according  to  the  position  which 
r-_  upy;  seven  being  found  in  the  cervical  region,  twelve  in  the  dorsal,  five 

in  the  lumbar,  five  in  the  sacral,  and  four  in  the  coccygeal. 

This  number  is  sometimes  increased  by  an  additional  vertebra  in  one  region,  or 
the  number  may  be  diminished  in  one  region,  the  deficiency  being  supplied  by 
an  additional  vertebra  in  another.  These  observations  do  not  apply  to  the  cervical 
portion  of  the  spine,  the  number  of  bones  forming  which  is  seldom  increased  or 
diminished. 

The  vertebrae  in  the  upper  three  regions  of  the  spine  are  separate  throughout 
the  whole  of  life ;  but  those  found  in  the  sacral  and  coccygeal  regions  are  in  the 
adult  firmly  united,  so  as  to  form  two  bones — five  entering  into  the  formation 
of  the  upper  bone  or  sacrum,  and  four  into  the  terminal  bone  of  the  spine  or 
coccyx. 

General  Characters  of  a  Vertebra. 

Each  vertebra  consists  of  two  essential  parts — an  anterior  solid  segment  or 
body,  and  a  posterior  segment  or  arch.  The  arch  (neural)  is  formed  of  two  pedi- 
cles and  two  lamina?,  supporting  seven  processes — viz.  four  articular,  two  trans- 
verse, and  one  spinous. 

The  bodies  of  the  vertebrae  are  piled  one  upon  the  other,  forming  a  strong 


CERVICAL    VERTEBRJE.  35 

pillar  for  the  support  of  the  cranium  and  trunk  ;  the  arches  forming  a  hollow 
cylinder  behind  the  bodies  for  the  protection  of  the  spinal  cord.  The  different 
vertebra?  are  connected  together  by  means  of  the  articular  processes  and  the 
intervertebral  fibro-cartilages ;  while  the  transverse  and  spinous  processes  serve 
as  levers  for  the  attachment  of  muscles  which  move  the  different  parts  of  the 
spine.  Lastly,  between  each  pair  of  vertebra?  apertures  exist  through  which  the 
spinal  nerves  pass  from  the  cord.  Each  of  these  constituent  parts  must  now  be 
separately  examined. 

The  Body  or  Centrum  is  the  largest  part  of  a  vertebra.  Above  and  below,  it 
is  flattened;  its  upper  and  lower  surfaces  are  rough  for  the  attachment  of  the 
intervertebral  fibro-cartilages,  and  present  a  rim  around  their  circumference. 
In  front,  it  is  convex  from  side  to  side,  concave  from  above  downward.  Behind, 
it  is  flat  from  above  downward  and  slightly  concave  from  side  to  side.  Its  ante- 
rior surface  is  perforated  by  a  few  small  apertures,  for  the  passage  of  nutrient 
vessels  ;  whilst  on  the  posterior  surface  is  a  single  large,  irregular  aperture,  or 
occasionally  more  than  one,  for  the  exit  of  veins  from  the  body  of  the  vertebra — 
the  vence  basis  vertebrae. 

The  Pedicles  are  two  short,  thick  pieces  of  bone,  which  project  backward, 
one  on  each  side,  from  the  upper  part  of  the  body  of  the  vertebra,  at  the 
line  of  junction  of  its  posterior  and  lateral  surfaces.  The  concavities  above 
and  below  the  pedicles  are  the  intervertebral  notches  ;  they  are  four  in  number, 
two  on  each  side,  the  inferior  ones  being  generally  the  deeper.  When  the 
vertebra?  are  articulated  the  notches  of  each  contiguous  pair  of  bones  form  the 
intervertebral  foramina,  which  communicate  with  the  spinal  canal  and  transmit 
the  spinal  nerves  and  blood-vessels. 

The  Laminae  are  two  broad  plates  of  bone  which  complete  the  neural  arch  by 
fusing  together  in  the  middle  line  behind.  They  enclose  a  foramen,  the  spinal 
foramen,  which  serves  for  the  protection  of  the  spinal  cord ;  they  are  connected 
to  the  body  by  means  of  the  pedicles.  Their  upper  and  lower  borders  are  rough, 
for  the  attachment  of  the  ligamenta  subfiava. 

The  Spinous  Process  projects  backward  from  the  junction  of  the  two  lamina;, 
and  serves  for  the  attachment  of  muscles  and  ligaments. 

The  Articular  Processes,  four  in  number,  two  on  each  side,  spring  from  the 
junction  of  the  pedicles  with  the  lamina?.  The  two  superior  project  upward,  their 
articular  surfaces  being  directed  more  or  less  backward;  the  two  inferior  project 
downward,  their  articular  surfaces  looking  more  or  less  forward.1 

The  Transverse  Processes,  two  in  number,  project  one  at  each  side  from  the 
point  where  the  lamina  joins  the  pedicle,  between  the  superior  and  inferior 
articular  processes.     They  also  serve  for  the  attachment  of  muscles  and  ligaments. 

Character  of  the  Cervical  Vertebrae  (Fig.   1). 

The  Cervical  Vertebrae  are  smaller  than  those  in  any  other  region  of  the  spine, 
and  may  readily  be  distinguished  by  the  foramen  in  the  transverse  process,  which 
does  not  exist  in  the  transverse  process  of  either  the  dorsal  or  lumbar  vertebra?. 

The  Body  is  small,  comparatively  dense,  and  broader  from  side  to  side  than 
from  before  backward.  The  anterior  and  posterior  surfaces  are  flattened  and  of 
equal  depth ;  the  former  is  placed  on  a  lower  level  than  the  latter,  and  its  inferior 
border  is  prolonged  downward,  so  as  to  overlap  the  upper  and  fore  part  of  the 
vertebra?  below.  Its  upper  surface  is  concave  transversely,  and  presents  a  pro- 
jecting lip  on  each  side;  its  lower  surface  is  convex  from  side  to  side,  concave 
from  before  backward,  and  presents  laterally  a  shallow  concavity  which  receives 
the  corresponding  projecting  lip  of  the  adjacent  vertebra,  The  pedicles  are 
directed  outward  and  backward,  and  are  attached  to  the  body  midway  between 
the  upper  and  lower  borders,  so  that  the  superior  intervertebral  notch  is  as  deep 
as  the  inferior,  but  it  is,  at  the  same  time,  narrower.      The  lamince  are  narrow. 

1  It  may,  perhaps,  be  as  well  to  remind  the  reader  that  the  direction  of  a  surface  is  determined  by 
that  of  a  line  drawn  at  right  angles  to  it. 

{ 


36 


THE  SKELETON. 


long,  thinner  above  than  below,  and  overlap  each  other,  enclosing  the  spinal 
foramen,  Avhich  is  very  large,  and  of  a  triangular  form.  The  spinous  j^'ocess  is 
short,  and  bifid  at  the  extremity  to  afford  greater  extent  of  surface  for  the  attach- 
ment of  muscles,  the  two  divisions  being  often  of  unequal  size.  They  increase  in 
length  from  the  fourth  to  the  seventh.  The  articular  processes  are  flat,  oblique, 
and  of  an  oval  form :  the  superior  are  directed  backward  and  upward ;  the 
inferior  forward  and  downward.  The  transverse  processes  are  short,  directed 
downward,  outward,  and  forward,  bifid  at  their  extremity,  and  marked  by  a 
groove  along  their  upper  surface,  which  runs  downward  and  outward  from  the 
superior  intervertebral  notch,  and  serves  for  the  transmission  of  one  of  the  cer- 
vical nerves.  They  are  situated  in  front  of  the  articular  processes  and  on  the 
outer  side  of  the  pedicles.  The  transverse  processes  are  pierced  at  their  base  by 
a  foramen,  for  the  transmission  of  the  vertebral  artery,  vein,  and  plexus  of  nerves. 


Anterior  tubercle  of  tram- 
verse  process. 
Foramen  for  vertebral 
artery 
Posterior  tubercle  of 
transverse  process 


Transverse  process. 


^Superior  articular 
process. 
Inferior  articular  process. 


Fig.  1.— Cervical  vertebra. 

Each  process  is  formed  by  two  roots :  the  anterior  root,  sometimes  called  the 
costal  process,  arises  from  the  side  of  the  body,  and  is  the  homologue  of  the  rib 
in  the  dorsal  region  of  the  spine;  the  posterior  root  springs  from  the  junction  of 
the  pedicle  with  the  lamina,  and  corresponds  with  the  transverse  process  in  the 
dorsal  region.  It  is  by  the  junction  of  the  two  that  the  foramen  for  the  vertebral 
vessels  is  formed.  The  extremity  of  each  of  these  roots  forms  the  anterior  and 
posterior  tubercles  of  the  transverse  processes.1 

The  peculiar  vertebrae  in  the  cervical  region  are  the  first,  or  Atlas  ;  the  second, 
or  Axis  ;  and  the  seventh,  or  Vertebra  prominens.  The  great  modifications  in  the 
form  of  the  atlas  and  axis  are  designed  to  admit  of  the  nodding  and  rotatory 
movements  of  the  head. 

The  Atlas  (Fig.  2)  is  so  named  from  supporting  the  globe  of  the  head.  The 
chief  peculiarities  of  this  bone  are  that  it  has  neither  body  nor  spinous  process. 
The  body  is  detached  from  the  rest  of  the  bone,  and  forms  the  odontoid  process  of 
the  second  vertebra;  while  the  parts  corresponding  to  the  pedicles  join  in  front  to 
form  the  anterior  arch.  The  atlas  is  ring-like,  and  consists  of  an  anterior  arch, 
a  posterior  arch,  and  two  lateral  masses.  The  anterior  arch  forms  about  one-fifth 
of  the  ring:  its  anterior  surface  is  convex,  and  presents  about  its  centre  a  tubercle, 
for  the  attachment  of  the  Longus  colli  muscle ;  posteriorly  it  is  concave,  and 
marked  by  a  smooth,  oval  or  circular  facet,  for  articulation  with  the  odontoid 
process  of  the  axis.  The  upper  and  lower  borders  give  attachment  to  the  anterior 
occipito-atlantal  and  the  anterior  atlanto-axial  ligaments,  which  connect  it  with 
the  occipital  bone  above  and  the  axis  below.  The  posterior  arch  forms  about 
two-fifths  of  the  circumference  of  the   Done ;  it  terminates  behind  in  a  tubercle, 

1  The  anterior  tubercle  of  the  transverse  process  of  the  sixth  cervical  vertebra  is  of  large  size, 

and  is  sometimes  known  as  "  Chassaignac's  "  or  the  "carotid  tubercle."'    It  is  in  ^  relation  with 

the  carotid  artery,  which  lies  in  front  and  a  little  external  to  it  so  that,  as  w°  |  jinted  out  by 
Chnssaignac,  the  vessel  can  with  ease  be  compassed  against  it. 


CEB  VIC  A  L    VEB  TEBRjE. 


hich  is  the  rudiment  of  a  spinous  process,  and  gives  origin  to  the  Rectus  capitis 
osticus  mir.or.     The  diminutive  size  of  this  process  prevents  any  interference  in 
^he  movements  between  the  atlas  and  the  cranium.     The  posterior  part  of  the 
atirch  presents  above  and  behind  a  rounded  edge  for  the  attachment  of  the  posterior 
tpccipito-atlantal    ligament,   while    in    front,    immediately   behind    each   superior 
.articular  process,  is  a  groove,  sometimes  converted  into  a  foramen  by  a  delicate 
l%oiiy  spiculum  which  arches  backward  from  the  posterior  extremity  of  the  superior 
(articular  process.      These  grooves  represent  the  superior  intervertebral  notches, 
and  are  peculiar  from  being  situated  behind  the  articular  processes,  instead  of 
in  front  of  them,   as  in  the  other  vertebrae.      They  serve   for  the   transmission 
of  the  vertebral  artery,  which,  ascending  through  the  foramen  in  the  transverse 
process,   winds    round    the    lateral    mass  in  a  direction  backward    and    inward. 
They  also   transmit  the  suboccipital  (first    spinal)    nerve.       On  the  under  sur- 
face of  the  posterior  arch,  in  the  same  situation,  are  two  other  grooves,  placed 
behind  the  lateral  masses,   and  representing  the  inferior  intervertebral  notches 
of  other  vertebrae.      They  are  much  less  marked  than  the  superior.     The  lower 
border  also  gives  attachment  to  the  posterior  atlanto-axial  ligament,  which  con- 
nects it  with  the  axis.     The  lateral  masses  are  the  most  bulky  and  solid  parts  of 
the  atlas,  in  order  to  support  the  weight  of  the  head ;  they  present  two  articu- 
lating processes  above,  and  two  below.      The  two  superior  are  of  large  size,  oval, 


Tubercle 


Diagram  of  section  of  odontoid 
process. 

Diagram  of  section  of 
transverse  ligament. 

Foramen  for 
vertebral  artery. 


Groove  for  vertebral  artery 
and  1st  cervical  nerve. 


Rudimentary  spinous  process. 

Fig.  2.  — First  cervical  vertebra,  or  atlas. 

concave,  and  approach  each  other  in  front,  but  diverge  behind;  they  are  directed 
upward,  inward,  and  a  little  backward,  each  forming  a  kind  of  cup  for  the  corre- 
sponding condyle  of  the  occipital  bone,  and  are  admirably  adapted  to  the  nodding 
movements  of  the  head.  Not  infrequently  they  are  partially  subdivided  by  a 
more  or  less  deep  indentation  which  encroaches  upon  each  lateral  margin.  The 
inferior  articular  processes  are  circular  in  form,  flattened  or  slightly  concave, 
and  directed  downward  and  inward,  articulating  with  the  axis,  and  permitting 
the  rotatory  movements.  Just  below  the  inner  margin  of  each  superior  articular 
surface  is  a  small  tubercle,  for  the  attachment  of  the  transverse  ligament,  which, 
stretching  across  the  ring  of  the  atlas,  divides  it  into  two  unequal  parts;  the 
anterior  or  smaller  segment  receiving  the  odontoid  process  of  the  axis,  the  p 
rior  allowing  the  transmission  of  the  spinal  cord  and  its  membranes.  This  part 
of  the  spinal  canal  is  of  considerable  size,  to  afford  space  for  the  spinal  cord;  and 
hence  lateral  displacement  of  the  atlas  may  occur  without  compression-  of  this 
structure.  The  transverse  processes  are  of  large  size,  project  directly  outward 
and  downward  from  the  lateral  masses,  and  serve  for  the  attachment  of  special 
muscles  which  assist  in  rotating  the  head.  They  are  long,  not  bifid,  and  perfor- 
ated at  their  base  by  a  eVnal  for  the  vertebral  artery,  which  is  directed  from  below, 
upward  and  backward. 

The  Axis    (Fig.   3)   is   so  named  from  forming  the  pivot  upon  which  the  first 
vertebra,  carrying  the  head,  rotates.      The  most  distinctive  character  of  this  bone 


THE   SKELETON. 


is  the  strong,  prominent  process,  tooth-like  in  form  (hence  the  name 
■which  rises  perpendicularly  from  the  upper  surface  of  the  body, 
deeper  in  front  than  behind,  and  prolonged  downward  anteriorly  so 
the  upper  and  fore  part  of  the  next  vertebra.     It  presents  in  frc 


Odontoid  process. 


Rough  surface  for  check  ligaments: 
Articular  surface  for  transverse  ligament. 


Articular  surface  Jo. 
atlas. 


Body. 

Spinous  process.- 

~ransverse  process. 
Inferior  articular  process. 
Fig.  3.  —Second  cervical  vertebra,  or  axis. 

longitudinal  ridge,  separating  two  lateral  depressions  for  the  attachment  of  the 
Longus  colli  muscle  of  either  side.  The  odontoid  process  presents  two,  articulating 
surfaces  :  one  in  front,  of  an  oval  form,  for  articulation  with  the  atlas ;  another 
behind,  for  the  transverse  ligament — the  latter  frequently  encroaching  on  the 
sides  of  the  process.  The  apex  is  pointed,  and  gives  attachment  to  the  middle 
fasciculus  of  the  odontoid  or  check  ligaments  (dig amentum  suspensoriwni).  Below 
the  apex  the  process  is  somewhat  enlarged,  and  presents  on  either  side  a  rough 
impression  for  the  attachment  of  the  lateral  fasciculi  of  the  odontoid  or  check 
ligaments,  which  connect  it  to  the  occipital  bone ;  the  base  of  the  process,  where 
it  is  attached  to  the  body,  is  constricted,  so  as  to  prevent  displacement  from  the 

transverse  ligament,  which  binds 
Body.  it  in  this  situation  to  the  anterior 

arch  of  the  atlas.  "  Sometimes, 
however,  this  process  does  become 
displaced,  especially  in  children, 
in  whom  the  ligaments  are  more 
relaxed :  instant  death  is  the  re- 
sult of  this  accident.  The  in- 
ternal structure  of  the  odontoid 
process  is  more  compact  than  that 
of  the  body.  The  pedicles  are 
broad  and  strong,  especially  their 
anterior  extremities,  which  coa- 
lesce with  the  sides  of  the  body 
and  the  root  of  the  odontoid 
process.  The  lamina?  are  thick 
and  strong,  and  the  spinal  fora- 
men large,  but  smaller  than  that 
of  the  atlas.  The  transverse  'proc- 
esses are  very  small,  not  bifid, 
and  perforated  by  the  foramen 
for  the  vertebral  artery,  which  is 
directed  obliquely  upward  and  outward.  The  superior  articular  surfaces  are  round, 
slightly  convex,  directed  upward  and  outward,  and  are  peculiar  in  being  supported 
on  the  body,  pedicles,  and  transverse  processes.  The  inferior  articular  surfaces 
have  the  same  direction  as  those  of  the  other  cervical  vertebrae.     The  superior 


Fig.  4.- 


Spinous  process. 
■  Seventh  cervical  vertebra,  or  vertebra  prominens. 


DORSAL    VERTEBRA. 


39 


intervertebral  notches  are  very  shallow,  and  lie  behind  the^articular  processes ;  the 
inferior  in  front  of  them,  as  in  the  other  cervical  vertebrae.      The  spinous  pr> 
is  of  large  size,  very  strong,  deeply  channelled  on  its  under  surface,  and  presents 
a  bifid,  tubercular  extremity  for  the  attachment  of  muscles  which  serve  to  rotate 
the  head  upon  the  spine. 

Seventh  Cervical  (Fig.  4). — The  most  distinctive  character  of  this  vertebra 
is  the  existence  of  a  very  long  and  prominent  spinous  process;  hence  the  name 
"vertebra  prominens."  This  process  is  thick,  nearly  horizontal  in  direction,  not 
bifurcated,  and  has  attached  to  it  the  lower  end  of  the  ligamentum  nuchae.  The 
transverse  process  is  usually  of  large  size,  its  posterior  tubercles  are  large  and 
prominent,  while  the  anterior  are  small  and  faintly  marked;  its  upper  surface  has 
usually  a  shallow  groove,  and  it  seldom  presents  more  than  a  trace  of  bifurcation 
at  its  extremity.  The  foramen  in  the  transverse  process  is  sometimes  as  large  as 
in  the  other  cervical  vertebrae,  but  is  usually  smaller  on  one  or  both  sides,  and 
sometimes  wanting.  On  the  left  side  it  occasionally  gives  passage  to  the  vertebral 
artery ;  more  frequently  the  vertebral  vein  traverses  it  on  both  sides ;  but  the 
usual  arrangement  is  for  both  artery  and  vein  to  pass  in  front  of  the  transverse 
process,  and  not  through  the  foramen.  Occasionally  the  anterior  root  of  the 
transverse  process  exists  as  a  separate  bone,  and  attains  a  large  size.  It  is  then 
known  as  a  "cervical  rib." 

Characters  of  the  Dorsal  Vertebrae. 

The  Dorsal  Vertebras  are  intermediate  in  size  between  those  in  the  cervical  and 
those  in  the  lumbar  region,  and  increase  in  size  from  above  downward,  the  upper 


Superior  articular  process 


Demi-facet  for  head  of  rib. 


Facet  for  tubercle  of  rib. 


Demi-facet  for  head  of  rib. 
Inferior  articular  process. 


Fig.  5.— A  dorsal  vertebra. 


vertebrae  in  this  segment  of  the  spine  being  much  smaller  than  those  in  the  lower 
part  of  the  region.  The  dorsal  vertebrae  may  be  at  once  recognized  by  the  pres- 
ence on  the  sides  of  the  body  of  one  or  more  facets  or  half-facets  for  the  heads  of 
the  ribs. 

The  bodies  of  the  dorsal  vertebrae  resemble  those  in  the  cervical  and  lumbar 
regions  at  the  respective  ends  of  this  portion  of  the  spine ;  but  in  the  middle  of 
the  dorsal  region  their  form  is  very  characteristic,  being  heart-shaped,  and  as 
broad  in  the  antero-posterior  as  in  the  lateral  direction.  They  are  thicker  behind 
than  in  front,  flat  above  and  below,  convex  and  prominent  in  front,  deeply  concave 
behind,  slightly  constricted  in  front  and  at  the  sides,  and  marked  on  each  side, 


40 


THE   SKELETON. 


near  the  root  of  the  pedicle,  by  two  demi-facets,.  one  above,  the  other  below, 
are  covered  with  cartilage  in  the  recent  state,  and,  when  articulated  with  the 
ing  vertebrae,   form,   with   the  intervening  fibro-cartilage,   oval  surfaces 
reception  of  the  heads  of  the  corresponding  ribs.     The  •pedicles  are  directed 
ward,  and  the  inferior  intervertebral  notches  are  of  large  size,  and  deeper  tha* 
any  other  region  of  the  spine.      The  laminae,  are  broad,  thick,  and  imbricated- 
that  is  to  say,  overlapping  one  another  like  tiles  on  a  roof.     The  spinal  foramen  is 


|  An  entire  facet  above , 
\     a  demi-facet  below. 


—A  demi-facet  above. 


One  entire  facet. 


An  entire  facet, 
j  No  facet  on  transverse 
process,  which  is  ru- 
[     dimentary. 


An  entire  facet. 

C  No  facet  on  trans- 
verse process. 

\  Inferior  articular 
process,  convex 
and  turned  out- 
ward. 


Fig.  6. — Peculiar  dorsal  vertebrae. 


small,  and  of  a  circular  form.  The  spinous  processes  are  long,  triangular  on 
transverse  section,  directed  obliquely  downward,  and  terminate  in  a  tubercular 
extremity.  They  overlap  one  another  from  the  fifth  to  the  eighth,  but  are  less 
oblique  in  direction  above  and  below.  The  articular  processes  are  flat,  nearly 
vertical  in  direction,  and  project  from  the  upper  and  lower  part  of  the  pedicles ; 
the  superior  being  directed  backward  and  slightly  outward  and  upward,  the  inferior 


LUMBAR    VERTEBRA.  41 

forward  and  a  little  inward  and  downward.  The  transverse  processes  arise  from 
the  same  parts  of  the  arch  as  the  posterior  roots  of  the  transverse  processes  in 
the  neck,  and  are  situated  behind  the  articular  processes  and  pedicles ;  they  are 
thick,  strong,  and  of  great  length,  directed  obliquely  backward  and  outward, 
presenting  a  clubbed  extremity,  which  is  tipped  on  its  anterior  part  by  a  small 
concave  surface,  for  articulation  with  the  tubercle  of  a  rib.  Besides  the  articular 
facet  for  the  rib,  three  indistinct  tubercles  may  be  seen  rising  from  the  transverse 
processes,  one  at  the  upper  border,  one  at  the  lower  border,  and  one  externally. 
In  man  they  are  comparatively  of  small  size,  and  serve  only  for  the  attachment 
of  muscles.  But  in  some  animals  they  attain  considerable  magnitude,  either  for 
the  purpose  of  more  closely  connecting  the  segments  of  this  portion  of  the  spine 
or  for  muscular  and  ligamentous  attachment. 

The  peculiar  dorsal  vertebrae  are  the  first,  ninth,  tenth,  eleventh,  and  twelfth 
(Fig.  6). 

The  First  Dorsal  Vertebra  presents,  on  each  side  of  the  body,  a  single  entire 
articular  facet  for  the  head  of  the  first  rib  and  a  half  facet  for  the  upper  half  of 
the  second.  '  The  body  is  like  that  of  a  cervical  vertebra,  being  broad  trans- 
versely ;  its  upper  surface  is  concave,  and  lipped  on  each  side.  The  articular  sur- 
faces are  oblique,  and  the  spinous  process  thick,  long,  and  almost  horizontal. 

The  Ninth  Dorsal  has  no  demi-facet  below.  In  some  subjects,  however,  the 
ninth  has  two  demi-facets  on  each  side ;  when  this  occurs  the  tenth  has  only  a 
demi-facet  at  the  upper  part. 

The  Tenth.  Dorsal  has  (except  in  the  cases  just  mentioned)  an  entire  articular 
facet  on  each  side,  above,  which  is  partly  placed  on  the  outer  surface  of  the 
pedicle.     It  has  no  demi-facet  below. 

In  the  Eleventh  Dorsal  the  body  approaches  in  its  form  and  size  to  the  lumbar. 
The  articular  facets  for  the  heads  of  the  ribs,  one  on  each  side,  are  of  large  size, 
and  placed  chiefly  on  the  pedicles,  which  are  thicker  and  stronger  in  this  and  the 
next  vertebra  than  in  any  other  part  of  the  dorsal  region.  The  spinous  process 
is  short,  and  nearly  horizontal  in  direction.  The  transverse  processes  are  very 
short,  tubercular  at  their  extremities,  and  have  no  articular  facets  for  the  tubercles 
of  the  ribs. 

The  Twelfth  Dorsal  has  the  same  general  characters  as  the  eleventh,  but  may 
be  distinguished  from  it  by  the  inferior  articular  processes  being  convex  and 
turned  outward,  like  those  of  the  lumbar  vertebrae ;  by  the  general  form  of  the 
body,  laminae,  and  spinous  process,  approaching  to  that  of  the  lumbar  vertebrae ; 
and  by  the  transverse  processes  being  shorter,  and  marked  by  three  elevations,  the 
superior,  inferior,  and  external  tubercles,  which  correspond  to  the  mammilla ry, 
accessory,  and  transverse  processes  of  the  lumbar  vertebrae.  Traces  of  similar 
elevations  are  usually  to  be  found  upon  the  other  dorsal  vertebrae  (vide  ut  supra). 

Characters  of  the  Lumbar  Vertebrae. 

The  Lumbar  Vertebrae  (Fig.  7)  are  the  largest  segments  of  the  vertebral 
column,  and  can  at  once  be  distinguished  by  the  absence  of  the  foramen  in  the 
transverse  process,  the  characteristic  point  of  the  cervical  vertebrae,  and  by  the 
absence  of  any  articulating  facet  on  the  side  of  the  body,  the  distinguishing  mark 
of  the  dorsal  vertebrae. 

The  body  is  large,  and  has  a  greater  diameter  from  side  to  side  than  from  before 
backward,  slightly  thicker  in  front  than  behind,  flattened  or  slightly  concave  above 
and  below,  concave  behind,  and  deeply  constricted  in  front  and  at  the  sides, 
presenting  prominent  margins,  which  afford  a  broad  basis  for  the  support  of  the 
superincumbent  weight.  The  pedicles  are  very  strong,  'directed  backward  from 
the  upper  part  of  the  bodies ;  consequently,  the  inferior  intervertebral  notches  are 
of  considerable  depth.  The  lamina?  are  broad,  short,  and  strong,  and  the  spinal 
foramen  triangular,  larger  than  in  the  dorsal,  smaller  than  in  the  cervical,  region. 
The  spinous  processes  are  thick  and  broad,  somewhat  quadrilateral,  horizontal  in 
direction,  thicker  below  than  above,  and  terminating  by  a  rough,  uneven  border. 


42 


THE   SKELETON. 


The  superior  articular  processes  are  concave,  and  look  backward  and  inwa. 
the  inferior,  convex,  look  forward  and  outward ;  the  former  are  separated  by  c 
much  wider  interval  than  the  latter,  embracing  the  lower  articulating  processes 
of  the  vertebra  above.     The  transverse  processes  are  long,  slender,  directed  trans- 


Superior  articular  process. 


Fig.  7.— Lumbar  vertebra. 


versely  outward  in  the  upper  three  lumbar  vertebrae,  slanting  a  little  upward  in 
the  lower  two.  They  are  situated  in  front  of  the  articular  processes,  instead  of 
behind  them  as  in  the  dorsal  vertebrae,  and  are  homologous  with  the  ribs.  Of  the 
three  tubercles  noticed  in  connection  with  the  transverse  processes  of  the  twelfth 
dorsal  vertebra,  the  superior  ones  become  connected  in  this  region  with  the  back 


Inf.  articular  process. 

Mammillary  process. 
Accessory  process. 


Sup.  articular  process. 


Fig.  8. — Lumbar  vertebrae. 

part  of  the  superior  articular  processes,  and  have  received  the  name  of  mammillary 
processes  ;  the  inferior  are  represented  by  a  small  process  pointing  downward, 
situated  at  the  back  part  of  the  base  of  the  transverse  process,  and  called  the 
accessory  processes :  these  are  the  true  transverse  processes,  which  are  rudimental 
in  this  region  of  the  spine;  the  external  ones  are  the  so-called  transverse  processes, 


LUMBAR    VERTERRJE. 


43 


the  homologue  of  the  rib,  and  hence  sometimes  called  costal  processes  (Fig-  8). 
Although  in  man  these  are  comparatively  small,  in  some  animals  they  attain  con- 
siderable size,  and  serve  to  lock  the  vertebras  more  closely  together. 

The  Fifth  Lumbar  vertebra  is  characterized  by  having  the  body  much  thicker 
in  front  than  behind,  "which  accords  with  the  prominence  of  the  sacro-vertebral 
articulation ;  by  the  smaller  size  of  its  spinous  process ;  by  the  wide  interval 
between  the  inferior  articulating  processes ;  and  by  the  greater  size  and  thick- 
ness of  its  transverse  processes,  which  spring  from  the  body  as  well  as  from  the 
pedicles. 

Structure  of  the  Vertebrae. — The  body  is  composed  of  light,  spongy,  cancellous 
tissue,  having  a  thin  coating  of  compact  tissue  on  its  external  surface  perforated 
by  numerous  orifices,  some  of  large  size,  for  the  passage  of  vessels ;  its  interior 
is  traversed  by  one  or  two  large  canals,  for  the  reception  of  veins,  which  con- 
verge toward  a  single  large,  irregular  aperture  or  several  small  apertures  at  the 
posterior  part  of  the  body  of  each  bone.  The  arch  and  processes  projecting  from 
it  have,  on  the  contrary,  an  exceedingly  thick  covering  of  compact  tissue. 

Development. — Each  vertebra  is  formed  of  four  primary  centres  of  ossification 
(Fig.  9),  one  for  each  lamina  and  its  processes,  and  two  for  the  body.1'  Ossifica- 


By  If  primary  centres. 

I       ivj  \2  for  body  {8th  week), 
j&ik  \         i  m 


By  4  secondary  centres. 


lfor  each  lamina  (6th  week). 
Fig.  9.  —Development  of  a  vertebra. 

By  2  additional  plates. 


■1  for  upper  surface  ' 
of  body, 

1  for  under  surface 
of  body, 
Fig.  10. 


21  years. 


1  for  each  trans- 
verse process, 
16  years. 


2  (sometimes  1)  for  spinous  process  (16  years). 
Fig.  11. 


tion  commences  in  the  laminae  about  the  sixth  week  of  foetal  life,  in  the  situation 
where  the  transverse  processes  afterward  project,  the  ossific  granules  shooting 
backward  to  the  spine,  forward  into  the  pedicles,  and  outward  into  the  transverse 
and  articular  processes.  Ossification  in  the  body  commences  in  the  middle  of  the 
cartilage  about  the  eighth  week  by  two  closely  approximated  centres,  which  speedily 
coalesce  to  form  one  central  ossific  point.  According  to  some  authors,  ossifica- 
tion commences  in  the  lamina  only  in  the  upper  vertebrae — i.  e.,  in  the  cervical  and 
upper  dorsal.  The  first  ossific  points  in  the  lower  vertebrae  are  those  which  are  to 
form  the  body,  the  osseous  centres  for  the  laminae  appearing  at  a  subsequent  period. 
At  birth  these  three  pieces  are  perfectly  separate.  During  the  first  year  the 
laminae  become  united  behind,  the  union  taking  place  first  in  the  lumbar  region 
and  then  extending  upward  through  the  dorsal  and  lower  cervical  regions.  About 
the  third  year  the  body  is  joined  to  the  arch  on  each  side  in  such  a  manner  that 
the  body  is  formed  from  the  three  original  centres  of  ossification,  the  amount  con- 
tributed by  the  pedicles  increasing  in  extent  from  below  upward.  Thus  the 
bodies  of  the  sacral  vertebrae  are  formed  almost  entirely  from  the  central  nuclei : 
the  bodies  of  the  lumbar  are  formed  laterally  and  behind  by  the  pedicles:  in  the 
dorsal  region  the  pedicles  advance  as  far  forward  as  the  articular  depressions  for 
the  head  of  the  ribs,  forming  these   cavities  of  reception  ;  and  in  the  neck  the 

1  By  many  observers  it  is  asserted  that  the  bodies  of  the  vertebra  are  developed  from  a  single 
centre  which  speedily  becomes  bilobed,  so  as  to  give  the  appearance  of  two  nuclei  ;  but  that  there  are 
two  centres,  at  all  events  sometimes,  is  evidenced  by  the  fact  that  the  two  halves  of  the  body  of  the 
vertebra  may  remain  distinct  throughout  life  and  be  separated  by  a  fissure  through  which  a  protru- 
sion of  the  spinal  membrane  may  take  place,  constituting  an  anterior  spina  bifida. 


44 


THE  SKELETON. 


By  3  centres. 


1  for  anterior  arch  (1st  year), 

not  constant. 
1  for  each   "I  ,   *      , • ., 
lateral  mass  J     ■' 


Fig.  12.— Atlas. 


2d  year. 


6th  month. 

1  for  each  lateral  mass. 

1  for  body  (4-th  month). 

1  for  under  surface  of 

body. 


Fig.  13.— Axis. 


2  additional  centres. 


lateral  portions  of  the  bodies  are  formed  entirely  by  the  advance  of  the  pedicles. 
The  line  along  which  union  takes  place  between  the  body  and  the  neural  arch  is 
named  the  neuro-central  suture.  Before  puberty  no  other  changes  occur,  except- 
ing a  gradual  increase  in  the  growth  of  these  primary  centres  ;  the  upper  and 
under  surfaces  of  the  bodies  and  the  ends  of  the  transverse  and  spinous  processes 
being  tipped  with  cartilage,  in  which  ossific  granules  are  not  as  yet  deposited. 
At  sixteen  years  (Fig.  11)  three  secondary  centres  appear,  one  for  the  tip  of 
each  transverse  process,  and  one  for  the  extremity  of  the  spinous  process.  In 
some  of  the  lumbar  vertebrae,  especially  the  first,  second,  and  third,  a  second  ossi- 
fying centre  appears  at  the  base  of  the  spinous  process.  At  twenty-one  years  (Fig. 
10)  a  thin  circular  epiphysial  plate  of  bone  is  formed  in  the  layer  of  cartilage 

situated  on  the  upper  and  under  sur- 
faces of  the  body,  the  former  being 
the  thicker  of  the  two.  All  these 
become  joined,  and  the  bone  is  com- 
pletely formed  between  the  twenty- 
fifth  and  thirtieth  year  of  life. 

Exceptions  to  this  mode  of  de- 
velopment occur  in  the  first,  second, 
and  seventh  cervical,  and  in  the 
vertebrae  of  the  lumbar  region. 

The  Atlas  (Fig.  12).— The  num- 
ber of  centres  of  ossification  of  the 
atlas  is  very  variable.  It  may  be 
developed  from  two,  three,  four,  or 
five  centres.  The  most  frequent  ar- 
rangement is  by  three  centres.  Two 
of  these  are  destined  for  the  two 
lateral  or  neural  masses,  the  ossifica- 
tion of  which  commences  about  the 
seventh  week  near  the  articular  pro- 
cesses, and  extend  backward ;  these 
portions  of  bone  are  separated  from 
one  another  behind,  at  birth,  by  a 
narrow  interval  filled  in  with  carti- 
lage. BetAveen  the  third  and  fourth 
years  thev  unite  either  directly  or 
through  the  medium  of  a  separate  centre  developed  in  the  cartilage  in  the  middle 
line.  The  anterior  arch,  at  birth,  is  altogether  cartilaginous,  and  in  this  a  sepa- 
rate nucleus  appears  about  the  end  of  the  first  year  after  birth,  and,  extending 
laterally,  joins  the  neural  processes  in  front  of  the  pedicles.  Sometimes  there  are 
two  nuclei  developed  in  the  cartilage,  one  on  either  side  of  the  median  line,  which 
join  to  form  a  single  mass.  And  occasionally  there  is  no  separate  centre,  but  the 
anterior  arch  is  formed  by  the  gradual  extension  forward  and  ultimate  junction 
of  the  two  neural  processes. 

The  Axis  (Fig.  13)  is  developed  by  seven  centres.  The  body  and  arch  of  this 
bone  are  formed  in  the  same  manner  as  the  corresponding  parts  in  the  other  ver- 
tebrae :  one  centre  (or  two,  which  speedily  coalesce)  for  the  lower  part  of  the 
body,  and  one  for  each  lamina.  The  centres  for  the  laminae  appear  about  the 
seventh  or  eighth  week,  that  for  the  body  about  the  fourth  month.  The 
odontoid  process  consists  originally  of  an  extension  upward  of  the  cartilag- 
inous mass  in  which  the  lower  part  of  the  body  is  formed.  At  about  the 
sixth  month  of  foetal  life  two  osseous  nuclei  make  their  appearance  in  the 
base  of  this  process  :  they  are  placed  laterally,  and  join  before  birth  to  form 
a  conical  bilobed  mass  deeply  cleft  above ;  the  interval  between  the  cleft  and 
the  summit  of  the  process  is  formed  by  a  "wedge-shaped  piece  of  cartilage,  the  base 
of  the  process  being  separated  from  the  body  by  a  cartilaginous  interval,  which 


for  tubercles  on  superior  articular  process. 
Fig.  14.— Lumbar  vertebra. 


DORSAL    VERTEBRA. 


-L9 


gradually  becomes  ossified  at  its  circumference,  but  remains  cartilagin>n  between 

centre  until  advanced  age.1     Finally,  as  Humphry  has  demonstrated,  the 

the  odontoid  process  has  a  separate  nucleus,  which  appears  in  the  second  than    the 

joins  about  the  twelfth  year.     In  addition  to  these  there  is  a  secondary  < 

a  thin  epiphysial  plate  on  the  under  surface  of  the  body  of  the  bone.        ^-^ 

The  Seventh  Cervical. — The  anterior  or  costal  part  of  the  transverse  g\ 
of  the  seventh  cervical  is  developed  from  a  separate  osseous  centre  aW  abol  \ 
sixth  month  of  foetal  life,  and  joins  the  body  and  posterior  division  of  the  tr.| 
verse  process  between  the  fifth  and  sixth  years.  Sometimes  this  process  continu 
as  a  separate  piece,  and,  becoming  lengthened  outward,  constitutes  what  is  known 
as  a  cervical  rib.  This  separate  ossific  centre  for  the  costal  process  has  also  been 
found  in  the  fourth,  fifth,  and  sixth  cervical  vertebrae. 

The  Lumbar  Vertebrae  (Fig.  14)  have  two  additional  cents  s  (besides  those 
peculiar  to  the  vertebrae  generally)  for  the  mammillary  tubercles,  which  project 
from  the  back  part  of  the  superior  articular  processes.  The  tr  msverse  process  of 
the  first  lumbar  is  sometimes  developed  as  a  separate  piece,  which  may  remain 
permanently  unconnected  with  the  remaining  portion  of  the  bone,  thus  forming  a 
lumbar  rib — a  peculiarity  that  is  rarely  met  with. 

Progress  of  Ossification  in  the  Spine  generally. — Ossification  of  the  laminae  of 
the  vertebrae  commences  in  the  cervical  region  of  the  spine,  and  proceeds  gradually 
downward.  Ossification  of  the  bodies,  on  the  other  hand,  commences  a  little 
beloAv  the  centre  of  the  spinal  column  (about  the  ninth  or  tenth  dorsal  vertebra), 
and  extends  both  upward  and  downward.  Although,  however,  the  ossific  nuclei 
make  their  first  appearance  in  the  lowrer  dorsal  vertebrae,  the  lumbar  and  first 
sacral  are  those  in  which  these  nuclei  are  largest  at  birth. 

Attachment  of  Muscles. — To  the  Atlas  are  attached  nine  pairs :  the  Longus 
colli,  Rectus  capitis  anticus  minor,  Rectus  lateralis,  Obliquus  capitis  superior  and 
inferior,  Splenius  colli,  Levator  anguli  scapulae,  First  Intertransverse,  and  Rectus 
capitis  posticus  minor. 

To  the  Axis  are  attached  eleven  pairs :  the  Longus  colli.  Levator  anguli 
scapulae,  Splenius  colli,  Scalenus  medius,  Transversalis  colli,  Intertransversales, 
Obliquus  capitis  inferior,  Rectus  capitis  posticus  major,  Semispinalis  colli.  Mul- 
tifidus  spinae,  Interspinals. 

To  the  remaining  vertebrae,  generally,  are  attached  thirty-five  pairs  and  a  sin- 
gle muscle:  anteriorly,  the  Rectus  capitis  anticus  major,  Longus  colli,  Scalenus 
anticus  medius  and  posticus,  Psoas  magnus  and  parvus,  Quadratus  lumbo- 
rum,  Diaphragm,  Obliquus  abdominis  internus,  and  Transversalis  abdominis — 
posteriorly,  the  Trapezius,  Latissimus  dorsi,  Levator  anguli  scapulae,  Rhomboideus 
major  and  minor,  Serratus  posticus  superior  and  inferior,  Splenius.  Erector  spinae, 
Ilio-costalis,  Longissimus  dorsi,  Spinalis  dorsi,  Cervicalis  ascendens.  Transversalis 
colli,  Trachelo-mastoid,  Complexus,  Biventer  cervicis,  Semispinalis  dorsi  and  colli, 
Multifidus  spinae,  Rotatores  spinae,  Interspinales,  Supraspinales,  Intertransversales, 
Levatores  costarum. 

Sacral  and  Coccygeal  Vertebrae. 

The  Sacral  and  Coccygeal  Vertebrae  consist,  at  an  early  period  of  life,  of  nine 
separate  pieces,  which  are  united  in  the  adult  so  as  to  form  two  bones,  five  enter- 
ing into  the  formation  of  the  sacrum,  four  into  that  of  the  coccyx.  <  Occasionally, 
the  coccyx  consists  of  five  bones.2 

The  Sacrum  (sacer,  sacred)  is  a  large,  triangular  bone  (Fig.  15).  situated  at  the 
lower  part  of  the  vertebral  column,  and  at  the  upper  and  back  part  of  the  pelvic 
cavity,  where  it  is  inserted  like  a  wedge  between  the  two  innominate  bones :  its 
upper  part  or  base  articulating  with  the  last  lumbar  vertebrae,  its  apex  with  the 
coccyx.     The  sacrum  is  curved  upon  itself,  and  placed  very  obliquely,  its  upper 

1  See  Cunningham.  Journ.  Anat.,  vol.  xx.  p.  238. 

2  Sir  George  Humphry  describes  this  as  the  usual  composition  of  the  coccyx.—  On  the  Skeleton, 
p.  456. 


THE   SKELETON. 

44  projecting  forward,  and  forming,  with  the  last  lumbar  vertebra,  a  very 

it  angle,  called  the  'promontory  or  sacro-vertebral  angle  ;  whilst  its  central 
lateral  p&irected  backward,  so  as  to  give  increased  capacity  to  the  pelvic  cavity. 
The  line  its  for  examination  an  anterior  and  posterior  surface,  two  lateral  surfaces, 
named  tq,n  apex,  and  a  central  canal. 

ing  a  g  Anterior  Surface  is  concave  from  above  downward,  and  slightly  so  from 
undeito  sidei  In  the  middle  are  seen  four  transverse  ridges,  indicating  the  original 
beingion  of  the  bone  into  five  separate  pieces.  The  portions  of  bone  intervening 
Attween  the  ridges  correspond  to  the  bodies  of  the  vertebrae.  The  body  of  the 
lirst  segment  1$  of  large  size,  and  in  form  resembles  that  of  a  lumbar  vertebra ;  the 
succeeding  ones,  diminish  in  size  from  above  downward,  are  flattened  from  before 
backward,  and  curved  so  as  to  accommodate  themselves  to  the  form  of  the  sacrum, 
being  concave  in  Front,  convex  behind.  At  each  end  of  the  ridges  above  mentioned 
are  seen  the  anterior  sacral  foramina,  analogous  to  the  intervertebral  foramina, 


four  in  number  on  each  side,  somewhat  rounded  in  form,  diminishing  in  size 
from  above  downward,  and  directed  outward  and  forward ;  they  transmit  the 
anterior  branches  of  the  sacral  nerves  and  the  lateral  sacral  arteries.  External 
to  these  foramina  is  the  lateral  mass,  consisting  at  an  early  period  of  life  of 
separate  segments;  these  become  blended,  in  the  adult,  with  the  bodies,  with  each 
other,  and  with  the  posterior  transverse  processes.  Each  lateral  mass  is  traversed 
by  four  broad,  shallow  grooves,  which  lodge  the  anterior  sacral  nerves  as  they 
pass  outward,  the  grooves  being  separated  by  prominent  ridges  of  bone,  which  give 
attachment  to  the  slips  of  the  Pyriformis  muscle. 

If  a  vertical  section  is  made  through  the  centre  of  the  sacrum  (Fig.  16),  the 
bodies  are  seen  to  be  united  at  their  circumference  by  bone,  a  wide  interval  being 
left  centrally,  which,  in  the  recent  state,  is  filled  by  intervertebral  substance.     In 


SACRAL    AND    COCCYGEAL    VERTEBRsE. 


19 


some  bones  this  union  is  more  complete  between  the  lower  segments  than  between 
the  upper  ones. 

The  Posterior  Surface  (Fig.  17)  is  convex  and  much  narrower  than  the 
anterior.  In  the  middle  line  are  three 
or  four  tubercles,  which  represent  the 
rudimentary  spinous  processes  of  the  sac- 
ral vertebrae.  Of  these  tubercles,  the 
first  is  usually  prominent,  and  perfectly 
distinct  from  the  rest ;  the  second  and 
third  are  either  separate  or  united  into  a 
tubercular  ridge,  which  diminishes  in  size 
from  above  downward  ;  the  fourth  usually, 
and  the  fifth  always,  remaining  undevel- 
oped. External  to  the  spinous  processes 
on  each  side  are  the  lamince,  broad  and 
well  marked  in  the  first  three  pieces ; 
sometimes  the  fourth,  and  generally  the 
fifth,  are  only  partially  developed  and 
fail  to  meet  in  the  middle  line.  These 
partially  developed  laminae  are  prolonged 
downward  as  rounded  processes,  the 
sacral  cornua,  and  are  connected  to  the 
cornua  of  the  coccyx.  Between  them  the 
bony  wall  of  the  lower  end  of  the  sacral 
canal  is  imperfect,  and  is  liable  to  be 
opened  in  the  sloughing  of  bed-sores. 
External  to  the  laminae  is  a  linear  series 
of  indistinct  tubercles  representing  the 
articular  processes;  the  upper  pair  are 
large,  well  developed,  and  correspond  in 
shape  and  direction  to  the  superior  artic- 
ulating processes  of  a  lumbar  vertebra; 
the  second  and  third  are  small ;  the  fourth 
and  fifth  (usually  blended  together)  are 
situated  on  each  side  of  the  sacral"  canal 
and  assist  in  forming  the  sacral  cornua. 
External  to  the  articular  processes  are  the  four  posterior  sacral  foramina;  they 
are  smaller  in  size  and  less  regular  in  form  than  the  anterior,  and  transmit  the 
posterior  branches  of  the  sacral  nerves.  On  the  outer  side  of  the  posterior  sacral 
foramina  is  a  series  .of  tubercles,  the  rudimentary  transverse  processes  of  the  sacral 
vertebrae.  The  first  pair  of  transverse  tubercles  are  large,  very  distinct,  and 
correspond  with  each  superior  angle  of  the  bone;  t-hey  together  with  the  second 
pair,  which  are  of  small  size,  give  attachment  to  the  horizontal  part  of  the  sacro- 
iliac ligament;  the  third  give  attachment  to  the  oblique  fasciculi  of  the  posterior 
sacro-iliac  ligaments ;  and  the  fourth  and  fifth  to  the  great  sacro-sciatic  ligaments. 
The  interspace  between  the  spinous  and  transverse  processes  on  the  back  of  the 
sacrum  presents  a  wide,  shallow  concavity,  called  the  sacral  groove :  it  is 
continuous  above  with  the  vertebral  groove,  and  lodges  the  origin  of  the  Multifidus 
spinae. 

The  Lateral  Surface,  broad  above,  becomes  narrowed  into  a  thin  edge  below. 
Its  upper  half  presents  in  front  a  broad,  ear-shaped  surface  for  articulation  with 
the  ilium.  This  is  called  the  auricular  surface,  and  in  the  fresh  state  is  coated 
with  fibro-cartilage.  It  is  bounded  posteriorly  by  deep  and  uneven  impressions, 
for  the  attachment  of  the  posterior  sacro-iliac  ligaments.  The  lower  half  is  thin 
and  sharp,  and  terminates  in  a  projection  called  the  inferior  lateral  angle  ;  below 
this  angle  is  a  notch,  which  is  converted  into  a  foramen  by  articulation  with  the 
transverse  process  of  the  upper  piece  of  the  coccyx,  and  transmits  the  anterior 


Fig.  16.— Vertical  section  of  the  sacrum. 


THE  SKELETON. 


division  of  the  fifth  sacral  nerve.  This  lower,  sharp  border  gives  attachment  to 
the  greater  and  lesser  sacro-sciatic  ligaments,  and  to  some  fibres  of  the  Gluteus 
maximus  posteriorly,  and  to  the  Coccygeus  in  front. 

The  Base  of  the  sacrum,  which  is  broad  and  expanded,  is  directed  upward  and 
forward.  In  the  middle  is  seen  a  large  oval  articular  surface,  which  is  connected 
with  the  under  surface  of  the  body  of  the  last  lumbar  vertebra  by  a  fibro-carti- 
laginous  disk.  It  is  bounded  behind  by  the  large,  triangular  orifice  of  the  sacral 
canal.  The  orifice  is  formed  behind  by  the  laminae  and  spinous  process  of  _  the 
first  sacral  vertebra :  the  superior  articular  processes  project  from  it  on  each  side; 
they  are  oval,  concave,  directed  backward  and  inward,  like  the  superior  articular 
processes  of  a  lumbar  vertebra  ;  and  in  front  of  each  articular  process  is  an  inter- 
vertebral notch,  which  forms  the  lower  part  of  the  foramen  between  the  last 
lumbar  and  first  sacral  vertebra.     Lastly,  on  each  side  of  the  large  oval  articular 


Erector  spinse 


_^  Upper  half  of  fifth 
posterior  sacral  foramen. 


Fig.  17.— Sacrum,  posterior  surface. 


plate  is  a  broad  and  flat  triangular  surface  of  bone,  which  extends  outward,  sup- 
ports the  Psoas  magnus  muscle  and  lumbo-sacral  cord,  and  is  continuous  on  each 
side  with  the  iliac  fossa.  This  is  called  the  ala  of  the  sacrum,  and  gives  attach- 
ment to  a  few  of  the  fibres  of  the  Iliacus  muscle.  The  posterior  part  of  the  ala 
represents  the  transverse  process  of  the  first  sacral  segment. 

The  Apex,  directed  downward  and  slightly  forward,  presents  a  small,  oval, 
concave  surface  for  articulation  with  the  coccyx. 

The  Spinal  Canal  runs  throughout  the  greater  part  of  the  bone ;  it  is  large 
and  triangular  in  form  above,  small  and  flattened,  from  before  backward,  below. 
In  this  situation  its  posterior  wall  is  incomplete,  from  the  non-development  of  the 
laminae  and  spinous  processes.  It  lodges  the  sacral  nerves,  and  is  perforated  by 
the  anterior  and  posterior  sacral  foramina,  through  which  these  pass  out. 

Structure. — It  consists  of  much  loose,  spongy  tissue  within,  invested  externally 
by  a  thin  layer  of  compact  tissue. 


SACRAL    AND    COCCYGEAL    VERTEBRA. 


49 


Differences  in  the  Sacrum  of  the  Male  and  Female. — The  sacrum  in  the  female 
is  shorter  and  wider  than  in  the  male  ;  the  lower  half  forms  a  greater  angle  with 
the  upper,  the  upper  half  of  the  bone  being  nearly  straight,  the  lower  half  pre- 
senting the  greatest  amount  of  curvature.  The  bone  is  also  directed  more  obliquely- 
backward,  which  increases  the  size  of  the  pelvic  cavity ;  but  the  sacro-vertebral 
angle  projects  less.  In  the  male  the  curvature  is  more  evenly  distributed  over  the 
wThole  length  of  the  bone,  and  is  altogether  greater  than  in  the  female. 

Peculiarities  of  the  Sacrum. — This  bone,  in  some  cases,  consists  of  six  pieces; 
occasionally,  the  number  is  reduced  to  four.  Sometimes  the  bodies  of  the  first 
and  second  segments  are  not  joined  or  the  laminae  and  spinous  processes  have  not 
coalesced.  Occasionally  the  upper  pair  of  transverse  tubercles  are  not  joined  to 
the  rest  of  the  bone  on  one  or  both  sides  ;  and,  lastly,  the  sacral  canal  may  be  open 
for  nearly  the  lower  half  of  the  bone,  in  consequence  of  the  imperfect  development 
of  the  laminae  and  spinous  processes.  The  sacrum,  also,  varies  considerably  with 
respect  to  its  degree  of  curvature.  From  the  examination  of  a  large  number  of 
skeletons  it  would  appear  that  in  one  set  of  cases  the  anterior  surface  of  this  bone 
was  nearly  straight,  the  curvature,  which  was  very  slight,  affecting  only  its  lower 
end.  In  another  set  of  cases  the  bone  was  curved  throughout  its  whole  length, 
but  especially  toward  its  middle.  In  a  third  set  the  degree  of  curvature  was  less 
marked,  and  affected  especially  the  lower  third  of  the  bone. 

Development  (Fig.  18). — The  sacrum,  formed  by  the  union  of  five  vertebrae,  has 
thirty-five  centres  of  ossification. 

The  bodies  of  the  sacral  vertebrae  have  each  three  ossific  centres :  one  for  the 
central  part,  and  one  for  the  epiphysial  plates  on  its  upper  and  under  surface. 
Occasionally  the  primary  centres  for  the  bodies  of  the  first  and  second  piece  of  the 
sacrum  are  double. 

The  arch  of  each  sacral  vertebra  is  developed  by  two  centres,  one  for  each 
lamina.     These  unite  with  each  other  behind,  and  subsequently  join  the  body. 

The  lateral  masses  have  six  additional  centres,  two  for  each  of  the  first  three 
vertebrae.  These  centres  make  their  appearance  above  and  to  the  outer  side  of 
the  anterior  sacral  foramina  (Fig.   18),  and  are  developed  into  separate  segments 


Two  epiphysial  laminx 
for  each  lateral  surface." 


Additional  centres 
for  the  first  three  pieces.-'' 


At  birth. 


At4i 


At 
25th  year 


Fig.  18.— Development  of  the  sacrum. 


Fig.  19. 


Fig.  20. 


(Fig.  19)  ;  they  are  subsequently  blended  with  each  other,  and  with  the  bodies 
and  transverse  processes  to  form  the  lateral  mass. 

Lastly,  each  lateral  surface  of  the  sacrum  is  developed  by  two  epiphysial 
plates  (Fig.  20) :  one  for  the  auricular  surface,  and  one  for  the  remaining  part 
of  the  thin  lateral  edge  of  the  bone. 

Period  of  development. — At  about  the  eighth  or  ninth  week  of  foetal  life  ossi- 
fication of  the  central  part  of  the  bodies  of  the  first  three  vertebrae  commences. 
and  at  a  somewhat  later  period  that  of  the  last  two.  Between  the  sixth  and 
eighth  months  ossification  of  the  laminae  takes  place;  and  at  about  the  same 
period  the  centres  for  the  lateral  masses  for  the  first  three  sacral  vertebrae  make 
their  appearance.    The  period  at  which  the  arch  becomes  completed  by  the  junction 

4 


50 


THE  SKELETON. 


Cornua. 


of  the  laminae  with  the  bodies  in  front  and  with  each  other  behind  varies  in  different 
segments.  The  junction  between  the  laminae  and  the  bodies  takes  place  first  in 
the  lower  vertebrae  as  early  as  the  second  year,  but  is  not  effected  in  the  upper- 
most until  the  fifth  or  sixth  year.  About  the  sixteenth  year  the  epiphyses  for 
the  upper  and  under  surfaces  of  the  bodies  are  formed,  and  between  the  eighteenth 
and  twentieth  years  those  for  each  lateral  surface  of  the  sacrum  make  their 
appearance.  The  bodies  of  the  sacral  vertebrae  are,  during  early  life,  separated 
from  each  other  by  intervertebral  disks.  But  about  the  eighteenth  year  the  two 
lowest  segments  become  joined  together  by  ossification  extending  through  the 
disk.  This  process  gradually  extends  upward  until  all  the  segments  become 
united,  and  the  bone  is  completely  formed  from  the  twenty-fifth  to  the  thirtieth 
year  of  life. 

Articulations. — With  four  bones :  the  last  lumbar  vertebra,  coccyx,  and  the 
two  innominate  bones. 

Attachment  of  Muscles. — To  eight  pairs :  in  front,  the  Pyriformis  and  Coccyg- 
eus,  and  a  portion  of  the  Iliacus  to  the  base  of  the  bone ;  behind,  the  Gluteus 
maximus,  Latissimus  dorsi,  Multifidus  spinae,  and  Erector  spinae,  and  sometimes 
the  Extensor  coccygis. 

The  Coccyx. 

The  Coccyx  (xoxxvZ,  cuckoo),  so  called  from  having  been  compared  to  a  cuc- 
koo's beak  (Fig.  21),  is  usually  formed  of  four  small  segments  of  bone,  the  most 

rudimentary  parts  of  the  vertebral  column.  In  each 
of  the  first  three  segments  may  be  traced  a  rudi- 
mentary body,  articular  and  transverse  processes ;  the 
last  piece  (sometimes  the  third)  is  a  mere  nodule  of 
bone,  without  distinct  processes.  All  the  segments  are 
destitute  of  pedicles,  laminae,  and  spinous  processes, 
and,  consequently,  of  intervertebral  foramina  and  spinal 
canal.  The  first  segment  is  the  largest ;  it  resembles 
the  lowermost  sacral  vertebra,  and  often  exists  as  a 
separate  piece ;  the  last  three,  diminishing  in  size  from 
above  downward,  are  usually  blended  together  so  as  to 
form  a  single  bone.  The  gradual  diminution  in  the 
size  of  the  pieces  gives  this  bone  a  triangular  form,  the 
base  of  the  triangle  joining  the  end  of  the  sacrum.  It 
presents  for  examination  an  anterior  and  posterior  sur- 
face, two  borders,  a  base,  and  an  apex.  The  anterior 
surface  is  slightly  concave,  and  marked  with  three 
transverse  grooves,  indicating  the  points  of  junction  of 
the  different  pieces.  It  has  attached  to  it  the  anterior 
sacro-coccygeal  ligament  and  Levator  ani  muscle,  and 
supports  the  lower  end  of  the  rectum.  The  posterior 
surface  is  convex,  marked  by  transverse  grooves  similar 
to  those  on  the  anterior  surface ;  and  presents  on  each 
side  a  lineal  row  of  tubercles,  the  rudimentary  articular 
processes  of  the  coccygeal  vertebrae.  Of  these,  the  supe- 
rior pair  are  large,  and  are  called  the  cornua  of  the 
coccyx ;  they  project  upward,  and  articulate  with  the 
cornua  of  the  sacrum,  the  junction  between  these  two 
bones  completing  the  fifth  posterior  sacral  foramen  for  the  transmission  of  the  pos- 
terior division  of  the  fifth  sacral  nerve.  The  lateral  borders  are  thin,  and  present  a 
series  of  small  eminences,  which  represent  the  transverse  processes  of  the 
coccygeal  vertebrae..  Of  these,  the  first  on  each  side  is  the  largest,  flattened 
from  before  backward,  and  often  ascends  to  join  the  lower  part  of  the  thin 
lateral  edge  of  the  sacrum,  thus  completing  the  fifth  anterior  sacral  foramen 
for  the  transmission  of  the  anterior  division  of  the  fifth  sacral  nerve;  the  others 
diminish  in  size  from  above  downward,   and  are  often   wanting.     The  borders 


*7"oR 

Anterior  surface,. 


hi* 

'"ct'eR 

Posterior  surface. 
Fig.  21.— Coccyx. 


THE  SPINE  IN   GENERAL. 


51 


OL 


IS 


developed 
piece.  Occa- 
pieces  of  this 


of  the  coccyx  are  narrow,  and  give  attach- 
ment on  each  side  to  the  sacro-sciatic  liga- 
ments, to  the  Coccygeus  muscles  in  front  of 
the  ligaments,  and  to  the  Gluteus  maximus 
behind  them.  The  base  presents  an  oval  sur- 
face for  articulation  with  the  sacrum.  The 
apex  is  rounded,  and  has  attached  to  it  the 
tendon  of  the  external  Sphincter  muscle.  It 
is  occasionally  bifid,  and  sometimes  deflected 
to  one  or  other  side. 

Development. — The  coccyx 
by  four  centres,  one  for  each 
sionally  one  of  the  first  three 
bone  is  developed  by  two  centres,  placed  side 
by  side.  The  ossific  nuclei  make  their  ap- 
pearance in  the  following  order  :  in  the  first 
segment,  shortly  after  birth  ;  in  the  second 
piece,  at  from  five  to  ten  years ;  in  the  third, 
from  ten  to  fifteen  years ;  in  the  fourth,  from 
fifteen  to  twenty  years.  As  age  advances 
these  various  segments  become  united  with 
each  other  from  below  upward,  the  union 
between  the  first  and  second  segments  being 
frequently  delayed  until  after  the  age  of 
twenty-five  or  thirty.  At  a  late  period  of 
life,  especially  in  females,  the  coccyx  often 
becomes  joined  to  the  end  of  the  sacrum. 

Articulation. — With  the  sacrum. 

Attachment  of  Muscles. — To  four  pairs 
and  one  single  muscle  :  on  either  side,  the 
Coccygeus ;  behind,  the  Gluteus  maximus 
and  Extensor  coccygis,  when  present ;  at  the 
apex,  the  Sphincter  ani ;  and  in  front,  the 
Levator  ani. 


The   Spine  in   General. 

The  Spinal  Column,  formed  by  the  junc- 
tion of  the  vertebrae,  is  situated  in  the  median 
line,  at  the  posterior  part  of  the  trunk  ;  its 
average  length  is  about  two  feet  two  or  three  I 
inches,  measuring  along  the  curved  anterior 
surface  of  the  column.  Of  this  length  the 
cervical  part  measures  about  five,  the  dorsal 
about  eleven,  the  lumbar  about  seven  inches, 
and  the  sacrum  and  coccyx  the  remainder. 
The  female  spine  is  about  one  inch  less  than 
that  of  the  male. 

Viewed  in  front,  it  presents  two  pyramids 
joined  together  at  their  bases,  the  upper  one 
being  formed  by  all  the  vertebrae  from  the 
second  cervical  to  the  last  lumbar,  the  lower 
one  by  the  sacrum  and  coccyx.  When  ex- 
amined more  closely,  the  upper  pyramid  is 
seen  to  be  formed  of  three  smaller  pyramids. 
The   uppermost  of  these  consists  of  the  six 


1st  cervical 
or  Atlas. 


Coccyx. 
Fig.  22.— Lateral  view  of  the  spine. 


52  THE   SKELETON. 

lower  cervical  vertebrae,  its  apex  being  formed  by  the  axis  or  second  cervical,  its 
base  by  the  first  dorsal.  The  second  pyramid,  which  is  inverted,  is  formed  by 
the  four  upper  dorsal  vertebrae,  the  base  being  at  the  first  dorsal,  the  smaller  end 
at  the  fourth.  The  third  pyramid  commences  at  the  fourth  dorsal,  and  gradually 
increases  in  size  to  the  fifth  lumbar. 

Viewed  laterally  (Fig.  22),  the  spinal  column  presents  several  curves,  which 
correspond  to  the  different  regions  of  the  column,  and  are  called  cervical,  dorsal, 
lumbar,  and  pelvic.  The  cervical  curve  commences  at  the  apex  of  the  odontoid 
process,  and  terminates  at  the  middle  of  the  second  dorsal  vertebra ;  it  is  convex 
in  front,  and  is  the  least  marked  of  all  the  curves.  The  dorsal  curve,  which  is 
concave  forward,  commences  at  the  middle  of  the  second,  and  terminates  at  the 
middle  of  the  twelfth  dorsal.  Its  most  prominent  point  behind  corresponds  to 
the  spine  of  the  seventh  dorsal  vertebra.  The  lumbar  curve  commences  at  the 
middle  of  the  last  dorsal  vertebra,  and  terminates  at  the  sacro-vertebral  angle. 
It  is  convex  anteriorly ;  the  convexity  of  the  lower  three  vertebrae  being  much 
greater  than  that  of  the  upper  two.  The  pelvic  curve  commences  at  the  sacro- 
vertebral  articulation  and  terminates  at  the  point  of  the  coccyx.  It  is  concave 
anteriorly.  The  dorsal  and  pelvic  curves  are  the  primary  curves,  and  begin  to 
be  formed  at  an  early  period  of  foetal  life,  and  are  due  to  the  shape  of  the  bodies 
of  the  vertebrae.  The  cervical  and  lumbar  curves  are  compensatory  or  secondary, 
and  are  developed  after  birth  in  order  to  maintain  the  erect  position.  They  are 
due  mainly  to  the  shape  of  the  intervertebral  disks. 

The  spine  has  also  a  slight  lateral  curvature,  the  convexity  of  which  is 
directed  toAvard  the  right  side.  This  is  most  probably  produced,  as  Bichat  first 
explained,  chiefly  by  muscular  action,  most  persons  using  the  right  arm  in  prefer- 
ence to  the  left,  especially  in  making  long-continued  efforts,  when  the  body  is 
curved  to  the  right  side.  In  support  of  this. explanation  it  has  been  found  by 
Beclard  that  in  one  or  two  individuals  who  were  left-handed  the  lateral  curvature 
was  directed  to  the  left  side. 

The  movable  part  of  the  spinal  column  presents  for  examination  an  an- 
terior, a  posterior,  and  two  lateral  surfaces ;  a  base,  a  summit,  and  spinal 
canal. 

The  anterior  surface  presents  the  bodies  of  the  vertebrae  separated  in  the 
recent  state  by  the  intervertebral  disks.  The  bodies  are  broad  in  the  cervical 
region,  narrow  in  the  upper  part  of  the  dorsal,  and  broadest  in  the  lumbar  region. 
The  whole  of  this  surface  is  convex  transversely,  concave  from  above  downward  in 
the  dorsal  region,  and  convex  in  the  same  direction  in  the  cervical  and  lumbar 
regions. 

The  posterior  surface  presents  in  the  median  line  the  spinous  processes.  These 
are  short,  horizontal,  with  bifid  extremities,  in  the  cervical  region.  In  the  dorsal 
region  they  are  directed  obliquely  above,  assume  almost  a  vertical  direction  in  the 
middle,  and  are  horizontal  below,  as  are  also  the  spines  of  the  lumbar  vertebrae. 
They  are  separated  by  considerable  intervals  in  the  loins,  by  narrower  intervals 
in  the  neck,  and  are  closely  approximated  in  the  middle  of  the  dorsal  region. 
Occasionally  one  of  these  processes  deviates  a  little  from  the  median  line — a  fact 
to  be  remembered  in  practice,  as  irregularities  of  this  sort  are  attendant  also  on 
fractures  or  displacements  of  the  spine.  On  either  side  of  the  spinous  processes, 
extending  the  whole  length  of  the  column,  is  the  vertebral  groove  formed  by  the 
laminae  in  the  cervical  and  lumbar  regions,  where  it  is  shallow,  and  by  the  laminae 
and  transverse  processes  in  the  dorsal  region,  where  it  is  deep  and  broad.  In 
the  recent  state  these  grooves  lodge  the  deep  muscles  of  the  back.  External  to 
the  vertebral  grooves  are  the  articular  processes,  and  still  more  externally  the 
transverse  process.  In  the  dorsal  region  the  latter  processes  stand  backward,  on 
a  plane  considerably  posterior  to  the  same  processes  in  the  cervical  and  lumbar 
regions.  In  the  cervical  region  the  transverse  processes  are  placed  in  front  of  the 
articular  processes,  and  on  the  outer  side  of  the  pedicles,  between  the  interver- 


THE   SPINE   IN    GENERAL.  53 

tebral  foramina.  In  the  dorsal  region  they  are  posterior  to  the  pedicles,  interver- 
tebral foramina,  and  articular  processes.  In  the  lumbar  they  are  placed  also  in 
front  of  the  articular  processes,  but  behind  the  intervertebral  foramina. 

The  lateral  surfaces  are  separated  from  the  posterior  by  the  articular  processes 
in  the  cervical  and  lumbar  regions,  and  by  the  transverse  processes  in  the  dorsal. 
These  surfaces  present  in  front  the  sides  of  the  bodies  of  the  vertebrae,  marked  in 
the  dorsal  region  by  the  facets  for  articulation  with  the  heads  of  the  ribs.  More 
posteriorly  are  the  intervertebral  foramina,  formed  by  the  juxtaposition  of  the 
intervertebral  notches,  oval  in  shape,  smallest  in  the  cervical  and  upper  part  of 
the  dorsal  regions,  and  gradually  increasing  in  size  to  the  last  lumbar.  They  are 
situated  between  the  transverse  processes  in  the  neck,  and  in  front  of  them  in  the 
back  and  loins,  and  transmit  the  spinal  nerves. 

The  base  of  that  portion  of  the  vertebral  column  formed  by  the  twenty-four 
movable  vertebras  is  formed  by  the  under  surface  of  the  body  of  the  fifth  lumbar 
vertebra ;   and  the  summit  by  the  upper  surface  of  the  atlas. 

The  vertebral  or  spinal  canal  follows  the  different  curves  of  the  spine ;  it  is 
largest  in  those  regions  in  which  the  spine  enjoys  the  greatest  freedom  of  move- 
ment, as  in  the  neck  and  loins,  where  it  is  wide  and  triangular ;  and  narrow  and 
rounded  in  the  back,  where  motion  is  more  limited. 

Surface  Form.— -The  only  part  of  the  vertebral  column  which  lies  closely  under  the  skin,  and 
so  directly  influences  surface  form,  is  the  apices  of  the  spinous  processes.  These  are  always  distin- 
guishable at  the  bottom  of  a  median  furrow,  which,  more  or  less  evident,  runs  down  the  mesial 
line  of  the  back  from  the  external  occipital  protuberance  above  to  the  middle  of  the  sacrum  below. 
In  the  neck  the  fun'ow  is  broad,  and  terminates  in  a  conspicuous  projection,  which  is  caused  by 
the  spinous  process  of  the  seventh  cervical  vertebra  (vertebra  prominens).  Above  this  the 
spinous  process  of  the  sixth  cervical  vertebra  may  sometimes  be  seen  to  form  a  projection ; 
the  other  cervical  spines  are  sunken,  and .  are  not  visible,  though  the  spine  of  the  axis  can  be 
felt,  and  generally  also  the  spines  of  the  third,  fourth,  and  fifth  cervical  vertebrae.  In  the 
dorsal  region  the  furrow  is  shallow,  and  during  stooping  disappears,  and  then  the  spinous  pro- 
cesses become  more  or  less  visible.  The  markings  produced  by  these  spines  are  small  and  close 
together.  In  the  lumbar  region  the  furrow  is  deep,  and  the  situation  of  the  lumbar  spines  is 
frequently  indicated  by  little  pits  or  depressions,  especially  if  the  muscles  in  the  loins  are  well 
developed  and  the  spine  incurved.  They  are  much  larger  and  farther  apart  than  in  the  dorsal 
region.  In  the  sacral  region  the  furrow  is  shallower,  presenting  a  flattened  area  which  terminates 
below  at  the  most  prominent  part  of  the  posterior  surface  of  the  sacrum,  formed  by  the  spinous 
process  of  the  third  sacral  vertebra.  At  the  bottom  of  the  furrow  may  be  felt  the  irregular 
posterior  surface  of  the  bone.  Below  this,  in  the  deep  groove  leading  to  the  anus,  the  coccyx 
may  be  felt.  The  only  other  portions  of  the  vertebral  column  which  can  be  felt  from  the  surface 
are  the  transverse  processes  of  three  of  the  cervical  vertebrae — viz.  the  first,  the  sixth,  and  the 
seventh.  The  transverse  process  of  the  atlas  can  be  felt  as  a  rounded  nodule  of  bone  just  below 
and  in  front  of  the  apex  of  the  mastoid  process,  along  the  anterior  border  of  the  sterno-mastoid. 
The  transverse  process  of  the  sixth  cervical  vertebra  is  of  surgical  importance.  If  deep  pressure 
be  made  in  the  neck  in  the  course  of  the  carotid  artery,  opposite  the  cricoid  cartilage,  the 
prominent  anterior  tubercle  of  the  transverse  process  of  the  sixth  cervical  vertebra  can  be  felt. 
This  has  been  named  Chassaignacs  tubercle,  and  against  it  the  carotid  artery  may  be  most 
conveniently  compressed  by  the  finger.  The  transverse  process  of  the  seventh  cervical  vertebra 
can  also  often  be  felt.  Occasionally  the  anterior  root,  or  costal  process,  is  large  and  segmented 
off,  forming  a  cervical  rib. 

Surgical  Anatomy. — Occasionally  the  coalescence  of  the  lamina?  is  not  completed,  and  con- 
sequently a  cleft  is  left  in  the  arches  of  the  vertebrae,  through  which  a  protrusion  of  the  spinal 
membranes  (dura  mater  and  arachnoid),  and  sometimes  of  the  spinal  cord  itself,  takes  place, 
constituting  a  malformation  known  as  spina  bifida-  This  disease  is  most  common  in  the  lumbo- 
sacral region ;  but  it  may  occur  in  the  dorsal  or  cervical  region,  or  the  arches  throughout  the 
whole  length  of  the  canal  may  remain  unapproximated.  In  some  rare  cases,  in  consequence  of 
the  non-coalescence  of  the  two  primary  centres  from  which  the  body  is  formed,  a  similar  con- 
dition may  occur  in  front  of  the  canal,  the  bodies  of  the  vertebrae  being  found  cleft  and  the 
tumor  projecting  into  the  thorax,  abdomen,  or  pelvis,  between  the  lateral  halves  of  the  bodies 
affected. 

The  construction  of  the  spinal  column  of  a  number  of  pieces,  securely  connected  together 
and  enjoying  only  a  slight  degree  of  movement  between  any  two  individual  pieces,  though  per- 
mitting of  a  very  considerable  range  of  movement  as  a  whole,  allows  a  sufficient  degree  of 
mobility  without  any  material  diminution  of  strength.  The  many  joints  of  which  the  spine  is 
composed,  together  with  the  very  varied  movements  to  which  it  is  subjected,  render  it  liable  to 


54  THE  SKELETON. 

sprains ;  but  so  closely  are  the  individual  vertebrae  articulated  that  these  sprains  are  rarely  or 
ever  severe,  and  any  amount  of  violence  sufficiently  great  to  produce  tearing  of  the  ligaments 
would  tend  rather  to  cause  a  dislocation  or  fracture.  The  further  safety  of  the  column  and  its 
less  liability  to  injury  is  provided  for  by  its  disposition  in  curves,  instead  of  in  onestraight  line. 
For  it  is  an  elastic  column,  and  must  first  bend  before  it  breaks :  under  these  circumstances, 
being  made  up  of  three  curves,  it  represents  three  columns,  and  greater  force  is  required  to  pro- 
duce bending  of  a  short  column  than  of  a  longer  one  that  is  equal  to  it  in  breadth  and  material. 
Again,  the  safety  of  the  column  is  provided  for  by  the  interposition  of  the  intervertebral  disk 
between  the  bodies  of  the  vertebrae,  which  act  as  admirable  buffers  in  counteracting  the  effects  of 
violent  jars  or  shocks.  Fracture-dislocation  of  the  spine  may  be  caused  by  direct  or  indirect 
violence,  or  by  a  combination  of  the  two,  as  when  a  person,  falling  from  a  height,  strikes  against 
some  prominence  and  is  doubled  over  it.  The  fractures  from  indirect  violence  are  the  more  com- 
mon, and  here  the  bodies  of  the  vertebrae  are  compressed,  whilst  the  arches  are  torn  asunder  ; 
whilst  in  fractures  from  direct  violence  the  arches  are  compressed  and  the  bodies  of  the  vertebrae 
separated  from  each  other.  It  will  therefore  be  seen  that  in  both  classes  of  injury  the  spinal 
marrow  is  the  part  least  likely  to  be  injured,  and  may  escape  damage  even  where  there  has  been 
considerable  lesion  of  the  bony  framework.  For,  as  Mr.  Jacobson  states,  ' '  being  lodged  in  the 
centre  of  the  column,  it  occupies  neutral  ground  in  respect  to  forces  which  might  cause  fracture. 
For  it  is  a  law  in  mechanics  that  when  a  beam,  as  of  timber,  is  exposed  to  breakage  and  the 
force  does  not  exceed  the  limits  of  the  strength  of  the  material,  one  division  resists  compression, 
another  laceration  of  the  particles,  while  the  third,  between  the  two,  is  in  a  negative  condition."1 
Applying  this  principle  to  the  spine,  it  will  be  seen  that,  whether  the  fracture-dislocation  be  pro- 
duced by  direct  violence  or  indirect,  one  segment,  either  the  anterior  or  posterior,  will  be  exposed 
to  compression,  the  other  to  laceration,  and  the  intermediate  part,  where  the  cord  is  situated, 
will  be  in  a  neutral  state.  When  a  fracture-dislocation  is  produced  by  indirect  violence  the  dis- 
placement is  almost  always  the  same,  the  upper  segment  being  driven  forward  on  the  lower,  so 
that  the  cord  is  compressed  between  the  body  of  the  vertebra  below  and  the  arch  of  the  vertebra 
above. 

The  parts  of  the  spine  most  liable  to  be  injured  are  (1)  the  dorsi-lumbar  region,  for  this  part 
is  near  the  middle  of  the  column,  and  there  is  therefore  a  greater  amount  of  leverage,  and  more- 
over the  portion  above  is  comparatively  fixed,  and  the  vertebrae  which  form  it,  though  much 
smaller,  have  nevertheless  to  bear  almost  as  great  a  weight  as  those  below ;  (2)  the  cervico-dorsal 
region,  because  here  the  flexible  cervical  portion  of  the  spine  joins  the  more  fixed  dorsal  region ; 
and  (3)  the  atlanto-axial  region,  because  it  enjoys  an  extensive  range  of  movement,  and,  being 
near  the  skull,  is  influenced  by  violence  applied  to  the  head.  In  fracture-dislocation  it  has  been 
proposed  to  trephine  the  spine  and  remove  portions  of  the  laminae  and  spinous  processes.  The 
operation  can  only  be  of  use  when  the  paralysis  is  due  to  the  pressure  of  bone  or  the  effusion  of 
blood,  and  not  to  cases,  wdiich  are  by  far  the  most  common,  where  the  cord  is  crushed  to  a  pulp. 
And  even  in  those  cases  where  the  cord  is  compressed  by  bone  the  portion  of  displaced  bone 
which  presses  on  the  cord  is  generally  the  body  of  the  vertebra  below,  and  is  therefore  inaccess- 
ible to  operation.  The  operative  proceeding  is  one  of  great  severity,  involving  an  extensive  and 
deep  wound  and  great  risk  of  septic  meningitis,  and,  as  the  advantages  to  be  derived  from  it  are 
exceedingly  problematical  and  confined  to  a  very  few  cases,  it  is  not  often  resorted  to.  Trephin- 
ing has  also  been  resorted  to  in  some  cases  of  paraplegia  due  to  Pott's  disease  of  the  spine. 
Here  the  paralysis  is  due  to  the  pressure  of  inflammatory  products,  and  where  this  is  new  scar- 
tissue,  formed  by  the  organization  of  granulation  tissue,  its  removal  has  been  attended  with  a 
very  considerable  amount  of  success. 


THE    SKULL. 

The  Skull  is  supported  on  the  summit  of  the  vertebral  column,  and  is  of  an 
oval  shape,  wider  behind  than  in  front.  It  is  composed  of  a  series  of  flattened  or 
irregularly  shaped  bones  which,  with  one  exception  (the  lower  jaw), .are  immovably 
joined  together.  It  is  divided  into  two  parts,  the  Cranium  and  the  Face,  the 
former  of  which  constitutes  a  case  for  the  accommodation  and  protection  of  the 
brain,  while  opening  on  the  face  are  the  orifices  of  the  nose  and  mouth;  between 
the  cranium  above  and  the  face  below  the  orbital  cavities  are  situated.  The 
Cranium  (xpdvoz,  a  helmet)  is  composed  of  eight  bones — viz.,  the  occipital,  two 
parietal,  frontal,  two  temporal,  sphenoid,  and  ethmoid.  The  Face  is  composed 
of  fourteen  bones — viz.,  the  two  nasal,  two  superior  maxillary,  two  lachrymal, 
two  malar,  two  palate,  two  inferior  turbinated,  vomer,  and  inferior  maxillary. 
The  ossiculi  auditils,  the  teeth,  and  Wormian  bones  are  not  included  in  this 
enumeration. 

1  Holmes's  System  of  Surgery,  vol.  i.,  p.  529,  1883. 


THE    CRANIUM. 


55 


Occipital. 

Two  Parietal. 

Frontal. 

Uranium,  c  bones .  <   m       m  ^ 

lwo  lemporal. 


Skull,  22  fowes  < 


Face,  14  5owes 


Sphenoid. 

Ethmoid. 

Two  Nasal. 

Two  Superior  Maxillary. 

Two  Lachrymal. 

Two  Malar. 

Two  Palate. 

Two  Inferior  Turbinated. 

Vomer. 

Inferior  Maxillary. 

The  Hyoid  Bone,  situated  at  the  root  of  the  tongue  and  attached  to  the  base 
of  the  skull  by  ligaments,  has  also  to  be  considered  in  this  section. 

THE  CRANIUM. 
The  Occipital  Bone. 
The  Occipital  Bone  (ob,  caput,  against  the  head)  is  situated  at  the  back  part 


Linea 


£Cr-^N    J  SUPERIOR 

'■^'Ti£-jrj!l  CONSTRICTOR 

of  Pharynx. 


Fig.  23.— Occipital  bone.     Outer  surface. 


and  base  of  the  cranium,  is  trapezoid  in  shape  and  is  much  curved  on  itself 
(Fig.  23).  It  presents  at  its  front  and  lower  part  a  large  oval  aperture,  the 
foramen  magnum,  by  which  the  cranial  cavity  communicates  with  the  spinal  canal. 
The  portion  of  bone  behind  this  opening  is  flat  and  expanded  and  forms  the 
,;  ttr  portion  in  front  is  a  thick,  elongated  mass  of  bone,  the  basilar 
ss ;  w  either  side  of  the  foramen  are  situated  processes  bearing  the 


56  THE  SKELETON. 


condyles,  by  which  the  bone  articulates  w  \i  ji  the  atlas.  These  processes  are  known 
as  the  condylar  portions.  It  presents  for  Examination  two  surfaces,  four  borders, 
and  four  angles. 

The  external  surface  is  convex.     Mid1    .  <  -n  the  summit  of  the  bone  and 

the  posterior  margin  of  the  foramen  magmn  ominent  tubercle,  the  external 

occipital  protuberance,  and,  descending  from  far  as  the  foramen,  a  vertical 

ridge,  the  external  occipital  crest.  This  {protuberance  and  crest  give  attachment 
to  the  Ligamentum  nuchae,  and  vary  in  prominence  in  different  skulls.  Passing 
outward  from  the  occipital  protuberance  is  a  semicircular  ridge  on  each  side,  the 
superior  curved  line.  Above  this  line  there  is  often  a  second  less  distinctly  marked 
ridge,  called  the  highest  curved  line  (linea  suprema) ;  to  it  the  epicranial  aponeurosis 
is  attached.  The  bone  between  these  two  lines  is  smoother  and  denser  than  the 
rest  of  the  surface.  Running  parallel  with  these  from  the  middle  of  the  crest  is 
another  semicircular  ridge  on  each  side,  the  inferior  curved  lines.  The  surface  of 
the  bone  above  the  linea  suprema  is  rough  and  porous,  and  in  the  recent  state  is 
covered  by  the  Occipito-frontalis  muscle,  while  the  superior  and  inferior  curved 
lines,  together  with  the  surfaces  of  bone  between  and  below  them,  serve  for  the 
attachment  of  several  muscles.  The  superior  curved  line  gives  attachment  inter- 
nally to  the  Trapezius,  externally  to  the  muscular  origin  of  the  Occipito-frontalis, 
and  to  the  Sterno-cleido-mastoid  to  the  extent  shown  in  Fig.  23  ;  the  depressions 
between  the  curved  lines  to  the  Complexus  internally,  the  Splenius  capitis  and 
Obliquus  capitis  superior  externally.  The  inferior  curved  line  and  the  depressions 
below  it  afford  insertion  to  the  Rectus  capitis  posticus,  major  and  minor. 

The  foramen  magnum  is  a  large,  oval  aperture,  its  long  diameter  extending  from 
before  backward.  It  transmits  the  medulla  oblongata  and  its  membranes,  the 
spinal  accessory  nerves,  the  vertebral  arteries,  the  anterior  and  posterior  spinal 
arteries,  and  the  occipito-axial  ligaments.  Its  back  part  is  wide  for  the  transmission 
of  the  medulla,  and  the  corresponding  margin  rough  for  the  attachment  of  the  dura 
mater  enclosing  it ;  the  fore  part  is  narrower,  being  encroached  upon  by  the  con- 
dyles ;  it  has  projecting  toward  it,  from  below,  the  odontoid  process,  and  its  margins 
are  smooth  and  bevelled  internally  to  support  the  medulla  oblongata.  On  each  side 
of  the  foramen  magnum  are  the  condyles,  for  articulation  with  the  atlas^  they  are 
convex,  oval,  or  reniform  in  shape,  and  directed  downward  and  outward ;  they 
converge  in  front,  and  encroach  slightly  upon  the  anterior  segment  of  the  foramen. 
On  the  inner  border  of  each  condyle  is  a  rough  tubercle  for  the  attachment  of  the 
ligaments  (check)  which  connect  this  bone  with  the  odontoid  process  of  the  axis ; 
whilst  external  to  them  is  a  rough  tubercular  prominence,  the  transverse  or  jugular 
process,  channelled  in  front  by  a  deep  notch,  which  forms  part  of  the  jugular 
foramen  or  foramen  lacerum  posterius.  The  under  surface  of  this  process  presents 
an  eminence  Avhich  represents  the  paramastoid  process  of  some  mammals.  The 
eminence  is  occasionally  large,  and  extends  as  low  as  the  transverse  process  of  the 
atlas.  This  surface  affords  attachment  to  the  Rectus  capitis  lateralis  muscle  and 
to  the  lateral  occipito-atlantal  ligament ;  its  upper  or  cerebral^surface  presents  a 
deep  groove  which  lodges  part  of  the  lateral  sinus,  whilst  its  external  surface  is 
marked  by  a  quadrilateral  rough  facet,  covered  with  cartilage  in  the  fresh  state,  and 
articulating  with  a  similar  surface  on  the  petrous  portion  of  the  temporal  bone.  On 
the  outer  side  of  each  condyle,  near  its  fore  part,  is  a  foramen,  the  anterior  con- 
dyloid ;  it  is  directed  downward,  outward,  and  forward,  and  transmits  the  hypo- 
glossal nerve,  and  occasionally  a  meningeal  branch  of  the  ascending  pharyngeal 
artery.  This  foramen  is  sometimes  double.  Behind  each  condyle  is  a  fossa,1  some- 
times perforated  at  the  bottom  by  a  foramen,  the  posterior  condyloid,  for  the  trans- 
mission of  a  vein  to  the  lateral  sinus.  In  front  of  the  foramen  magnum  is  a  strong 
quadrilateral  plate  of  bone,  the  basilar  process,  wider  behind  than  in  front ;  its 
under  surface,  which  is  rough,  presenting  in  the  median  line  a  tubercular  ridge, 

1  This  fossa  presents  many  variations  in  size.  It  is  usually  shallow,  and  the  foramen  small  ;  occa- 
sionally wanting  on  one  or  both  sides.  Sometimes  both  fossa  and  foramen  are  large,  but  confined  to 
one  side  only  ;  more  rarely,  the  fossa  and  foramen  are  very  large  on  both  sides. 


THE    CRANIUM. 


■ji 


the  pharyngei  for  the  attachment  of  the  tendinous  raphe  and  Superior 

constrictor  of  vnx  ;  and  on  each  side  of  it  rough  depressions  for  the 

attachment  of      te  Kectus  capitis  anticus,  major  and  minor. 

The  Internal  or  Cerebral  Surface  (Fig.  24)  is  deeply  concave.  The  posterior 
part  or  tabulur  is  divided  by  a  crucial  ridge  into  four  fossae.  The  two  superior 
fossae  receive  the  occipital  lobes  of  the  cerebrum,  and  present  slight  eminences 
and  depressions  corresponding  to  their  convolutions.  The  two  inferior,  which 
receive  the  hemispheres  of  the  cerebellum,  are  larger  than  the  former,  and  com- 
paratively smooth  ;  both  are  marked  by  slight  grooves  for  the  lodgment  of  arteries. 
At  the  point  of  meeting  of  the  four  divisions  of  the  crucial  ridge  is  an  eminence, 
the  internal  occipital  protuberance.  It  nearly  corresponds  to  that  on  the  outer 
surface,  and  is  perforated  by  one  or  more  large  vascular  foramina.  From  this 
eminence  the  superior  division  of  the  crucial  ridge  runs  upward  to  the  superior 
angle  of  the  bone  ;  it  presents  a  deep  groove  for  the  superior  longitudinal  sinus, 
the  margins  of  which  give  attachment  to  the  falx  cerebri.  The  inferior  division, 
the  internal  occipital  crest,  runs  to  the  posterior  margin  of  the  foramen  magnum, 


Superior  angle. 


Lateral 
i—  Angle. 


Inferior  angle. 
Fig.  24.— Occipital  bone. 


Inner  surface 


on  the  edge  of  which  it  becomes  gradually  lost ;  this  ridge,  which  is  bifurcated 
below,  serves  for  the  attachment  of  the  falx  cerebelli.  It  is  usually  marked  by  a 
single  groove,  which  commences  at  the  back  part  of  the  foramen  magnum  and 
lodges  the  <~>or>inital  sinus.  Occasionally  the  groove  is  double  where  two  sinuses 
exist.     TL  erse  grooves  pass  outward  to  the  lateral  angles  ;  they  are  deeply 

channelled  i  lodgment  of  the  lateral  sinuses,  their  prominent  margins  afford- 


58 


THE  SKELETON. 


ing  attachment  to  the  tentorium  cerebelli.1  At  the  point  of  meeting  of  these 
grooves  is  a  depression,  the  torcular  Uerophili,2  placed  a  little  to  one  or  the  other 
side  of  the  internal  occipital  protuberance.  More  anteriorly  is  the  foramen  mag- 
num, and  on  each  side  of  it,  but  nearer  its  anterior  than  its  posterior  part,  the 
internal  openings  of  the  anterior  condyloid  foramen  ;  the  internal  openings  of  the 
posterior  condyloid  foramina  are  a  little  external  and  posterior  to  them,  protected 
by  a  small  arch  of  bone.  At  this  part  of  the  internal  surface  there  is  a  very  deep 
groove  in  which  the  posterior  condyloid  foramen,  when  it  exists,  has  its  termina- 
tion. This  groove  is  continuous,  in  the  complete  skull,  with  the  transverse  groove 
on  the  posterior  part  of  the  bone,  and  lodges  the  end  of  the  same  sinus,  the  lateral. 
In  front  of  the  foramen  magnum  is  the  basilar  process,  presenting  a  shallow 
depression,  the  basilar  groove,  which  slopes  from  behind,  upward  and  forward, 
and  supports  the  medulla  oblongata  and  part  of  the  pons  Varolii,  and  on  each  side 
of  the  basilar  process  is  a  narrow  channel,  which,  when  united  with  a  similar 
channel  on  the  petrous  portion  of  the  temporal  bone,  forms  a  groove  which  lodges 
the  inferior  petrosal  sinus. 

Angles. — The  superior  angle  is  received  into  the  interval  between  the  posterior 
superior  angles  of  the  two  parietal  bones:  it  corresponds  with  that  part  of  the 
skull  in  the  foetus  which  is  called  the  posterior  fontanelle.  The  inferior  angle  is 
represented  by  the  square-shaped  surface  of  the  basilar  process.  At  an  early 
period  of  life  a  layer  of  cartilage  separates  this  part  of  the  bone  from  the  sphenoid, 
but  in  the  adult  the  union  between  them  is  osseous.  The  lateral  angles  corre- 
spond to  the  outer  ends  of  the  transverse  grooves,  and  are  received  into  the  interval 
between  the  posterior  inferior  angles  of  the  parietal  and  the  mastoid  portion  of 
the  temporal. 

Borders. — The  superior  border  extends  on  each  side  from  the  superior  to  the 
lateral  angle,  is  deeply  serrated  for  articulation  with  the  parietal  bone,  and  forms, 
by  this  union,  the  lambdoid  suture.  The  inferior  border  extends  from  the  lateral 
to  the  inferior  angle ;  its  upper  half  is  rough,  and  articulates  with  the  mastoid  por- 
tion of  the  temporal,  forming  the  masto-occipital  suture  ;  the  inferior  half  articu- 
lates with  the  petrous  portion  of  the  temporal,  forming  the  petro-occipital  suture ; 
these  two  portions  are  separated  from  one  another  by  the  jugular  process.  In 
front  of  this  process  is  a  deep  notch,  which,  with  a  similar  one  on  the  petrous  por- 
tion of  the  temporal,  forms  the  foramen  lacerwn  posterius  or  jugular  foramen. 
This  notch  is  occasionally  subdivided  into  two  parts  by  a  small  process  of  bone, 

,  and  it  generally  presents  anjtperture 
at  its  upper  part,  the  internal  opening 
of  the  posterior  condyloid  foramen. 
Structure. — The    occipital    hone 
consists  of  two  compact  laminae,  called 
the  outer   and   inner  tables,   having 
between  them  the  diploic  tissue ;  this 
bone  is  especially  thick  at  the  ridges, 
protuberances,    condyles,    and    an- 
terior   part  of  the  basilar  process; 
while  at  the  bottom  of  the  fossae,  es- 
pecially the  inferior,  it  is  thin,  semi- 
transparent,  and  destitute  of  diploe. 
Development  (Fig.  25). — At  birth 
the   bone   consists   of  four   distinct 
parts :  a  tabular  or  expanded  portion,  which  lies  behind  the  foramen  magnum ; 
two  condylar  parts,  which  form  the  sides  of  the  foramen  ;  and  a  basilar  part,  which 
lies  in  front  of  the  foramen.    The  number  of  nuclei  for  the  tabular  part  vary.     As 

1  Usually  one  of  the  transverse  grooves  is  deeper  and  broader  than  the  other ;  occasionally,  both 
grooves  are  of  equal  depth  and  breadth,  or  both  equally  indistinct.  The  broader  of  the  two  transverse 
grooves  is  nearly  always  continuous  with  the  vertical  groove  for  the  superior  longitudinal  sinus. 

2  The  columns  of  blood  coming  in  different  directions  were  supposed  to  be  pressed  together  at  this 
point  (torcular,  a  wine-press). 


At  birth 

the  4  pieces 

separate. 


H^/or  occipital 
portion. 


1  for  each  condyloid 
portion. 


>  % 
U 


'1  for  basilar  portion.     J    rs 
Kig.  25.— Development  of  occipital  bone.    By  seven  centres. 


THE   PARIETAL    BONES. 


59 


*»""«  >«  v"£,™  j^v,^,  "i.^u  10,  i±^>.^v^i,  udduicu  in  tutr  uiicctiun  indicate 
the  figure.  The  basilar  and  two  condyloid  poitions  are  each  developed  : 
a    single    nucleus,    which    appears    a    little    later.       The    upper    portion    of 


a  rule,  there  are  four,  but  there  may  be  only  one  (Blandin)  or  as  many  as  eight 
(Meckel).  They  appear  about  the  eighth  week  of  foetal  life,  and  soon  unite" to 
form   a  single   piece,  which  is,   however,   fissured  in    the   direction    indicated  in 

from 
ipper    portion    of    the 

tabular    surface — that    is    to    say,   the    portion    above    the    transverse    fissure ia 

developed  from  membrane,  and  may  remain  separated  from  the  rest  of  the 
bone  throughout  life,  when  it  constitutes  the  interparietal  bone  :  the  rest  of  the 
bone  is  developed  from  cartilage.  At  about  the  fourth  year  the  tabular  and  the 
two  condyloid  pieces  join,  and  about  the  sixth  year  the  bone  consists  of  a  single 
piece.  At  a  later  period,  between  the  eighteenth  and  twenty-fifth  years,  the 
occipital  and  sphenoid  become  united,  forming  a  single  bone. 

Articulations. — With  six  bones :  two  parietal,  two  temporal,  sphenoid,  and  atlas. 

Attachment  of  Muscles. — To  twelve  pairs  :  to  the  superior  curved  line  are 
attached  the  Occipito-frontalis,  Trapezius,  and  Sterno-cleido-mastoid.  To  the 
space  between  the  curved  lines,  the  Complexus,1  Splenitis  capitis,  and  Obliquus 
capitis  superior ;  to  the  inferior  curved  line,  and  the  space  between  it  and  the 
foramen  magnum,  the  Rectus  capitis  posticus,  major  and  minor;  to  the  transverse 
process,  the  Rectus  capitis  lateralis  ;  and  to  the  basilar  process,  the  Rectus  capitis 
anticus,  major  and  minor,  and  Superior  constrictor  of  the  pharynx. 


Fig.  26. — Left  parietal  bone.    External  surface. 

The  Parietal  Bones. 

The  Parietal  Bones  (paries,  a  Avail)  form,  by  their  union,  the  sides  and  roof  of 
the  skull.  Each  bone  is  of  an  irregular  quadrilateral  form,  and  presents  for 
examination  two  surfaces,   four  borders,   and  four  ano-les. 

1  To  these  the  Biventer  cervicis  should  be  added,  if  it  is  regarded  as  a  separate  muscle. 


60 


THE   SKELETON. 


Surfaces. — The  external  surface  (Fig.  26)  is  convex,  smooth,  and  marked  about 
its  centre  by  an  eminence  called  the  parietal  eminence,  which  indicates  the  point 
where  ossification  commenced.  Crossing  the  middle  of  the  hone  in  an  arched 
direction  are  two  well-marked  curved  lines  or  ridges,  the  upper  and  lower  temporal 
ridges  ;  the  former  gives  attachment  to  the  temporal  fascia,  while  the  latter  indicates 
the  upper  limit  of  the  origin  of  the  temporal  muscle.  Above  these  ridges  the 
surface  of  the  bone  is  rough  and  porous,  and  covered  by  the  aponeurosis  of  the 
Occipito-frontalis  ;  between  them  the  bone  is  smoother  and  more  polished  than 
the  rest ;  below  them  the  bone  forms  part  of  the  temporal  fossa,  and  affords  attach- 
ment to  the  temporal  muscle.  At  the  back  part  of  the  superior  border,  close  to 
the  sagittal  suture,  is  a  small  foramen,,  the  parietal  foramen,  which  transmits  a 
vein  to  the  superior  longitudinal  sinus,  and  sometimes  a  small  branch  of  the 
occipital  artery.     Its  existence  is  not  constant,  and  its  size  varies  considerably. 

The  internal  surface  (Fig.  27),  concave,  presents  depressions  for  lodging  the 
convolutions  of  the  cerebrum  and  numerous  furrows  for  the  ramifications  of 
the  middle  meningeal  artery;    the  latter  runs  upward  and  backward  from  the 


Posterior 

superior 

angle. 


Posterior 

inferior 

angle. 


^.Anterior 

superior 

angle. 


§p  Anterior 
inferior 
angle. 


Fig.  27.  —Left  parietal  bone.    Internal  surface. 


anterior  inferior  angle  and  from  the  central  and  posterior  part  of  the  lower  border 
of  the  bone.  Along  the  upper  margin  is  part  of  a  shallow  groove,  which,  when 
joined  to  the  opposite  parietal,  forms  a  channel  for  the  superior  longitudinal 
sinus,  the  elevated  edges  of  which  afford  attachment  to  the  falx  cerebri.  Near 
the  groove  are  seen  several  depressions,  especially  in  the  skulls  of  old  persons ; 
they  lodge  the  Pacchionian  bodies.  The  internal  opening  of  the  parietal  foramen 
is  also  seen  when  that  aperture  exists. 

Borders. — The  superior,  the  longest  and  thickest,  is  dentated  to  articulate  with 
its  fellow  of  the  opposite  side,  forming  the  sagittal  suture.     The  inferior  is  divided 
into  three  parts  :  of  these,  the  anterior  is  thin  and  pointed,  bevelled  at  the  e 
of  the  outer  surface,  and  overlapped  by  the  tip  of  the  great  wing  of  th< 
the  middle  portion  is  arched,  bevelled  at  the  expense  of  the  ou  -< 


THE  FRONTAL    BONE.  61 

overlapped  by  the  squamous  portion  of  the  temporal ;  the  posterior  portion  is  thick 
and  serrated  for  articulation  with  the  mastoid  portion  of  the  temporal.  The 
anterior  border,  deeply  serrated,  is  bevelled  at  the  expense  of  the  outer  surface 
above  and  of  the  inner  below ;  it  articulates  with  the  frontal  bone,  forming  the 
coronal  suture.  The  posterior  border,  deeply  denticulated,  articulates  with  the 
occipital,  forming  the  lambdoid  suture. 

Angles. — The  anterior  superior  angle,  thin  and  pointed,  corresponds  with  that 
portion  of  the  skull  which  in  the  foetus  is  membranous  and  is  called  the  anterior 
fontanelle.  The  anterior  inferior  angle  is  thin  and  lengthened,  being  received  in 
the  interval  between  the  great  wing  of  the  sphenoid  and  the  frontal.  Its  inner 
surface  is  marked  by  a  deep  groove,  sometimes  a  canal,  for  the  anterior  branch  of 
the  middle  meningeal  artery.  The  posterior  superior  angle  corresponds  with  the 
junction  of  the  sagittal  and  lambdoid  sutures.  In  the  foetus  this  part  of  the  skull 
is  membranous,  and  is  called  the  posterior  fontanelle.  The  posterior  inferior  angle 
articulates  with  the  mastoid  portion  of  the  temporal  bone,  and  generally  presents 
on  its  inner  surface  a  broad,  shallow  groove  for  lodging  part  of  the  lateral  sinus. 

Development. — The  parietal  bone  is  formed  in  membrane,  being  developed  by 
one  centre,  which  corresponds  with  the  parietal  eminence,  and  makes  its  first 
appearance  about  the  seventh  or  eighth  week  of  foetal  life.  Ossification  gradually 
extends  from  the  centre  to  the  circumference  of  the  bone :  the  angles  are  conse- 
quently the  parts  last  formed,  and  it  is  in  their  situation  that  the  fontanelles  exist 
previous  to  the  completion  of  the  groAvth  of  the  bone.  Occasionally  the  parietal 
bone  is  divided  into  two  parts,  upper  and  lower,  by  an  antero-posterior  suture. 

Articulations. — With  five  bones :  the  opposite  parietal,  the  occipital,  frontal, 
temporal,  and  sphenoid. 

Attachment  of  Muscles. — One  only,  the  Temporal. 

The  Frontal  Bone. 

The  Frontal  Bone  (frons,  the  forehead)  resembles  a  cockle-shell  in  form,  and 
consists  of  two  portions — a  vertical  ox:  frontal  portion  situated  at  the  anterior  part 
of  the  cranium,  forming  the  forehead ;  and  a  horizontal  or  orbito-nasal  portion 
which  enters  into  the  formation  of  the  roof  of  the  orbits  and  nasal  fossae. 

Vertical  Portion. — External  Surface  (Fig.  28). — In  the  median  line,  traversing 
the  bone  from  the  upper  to  the  lower  part,  is  occasionally  seen  a  slightly-elevated 
ridge,  and  in  young  subjects  a  suture,  which  represents  the  line  of  union  of  the  two 
lateral  halves  of  which  the  bone  consists  at  an  early  period  of  life ;  in  the  adult 
this  suture  is  usually  obliterated  and  the  bone  forms  one  piece ;  traces  of  the 
obliterated  suture  are,  however,  generally  perceptible  at  the  lower  part.  On  either 
side  of  this  ridge,  a  little  below  the  centre  of  the  bone,  is  a  rounded  eminence,  the 
frontal  eminence.  These  eminences  vary  in  size  in  different  individuals,  and  are 
occasionally  unsymmetrical  in  the  same  subject.  They  are  especially  prominent 
in  cases  of  well-marked  cerebral  development.  The  wrhole  surface  of  the  bone 
above  this  part  is  smooth,  and  covered  by  the  aponeurosis  of  the  Occimto-frontalis 
muscle.  Below  the  frontal  eminence,  and  Separated  from  it  by  a  slight  groove  i 
the  superciliary  ridge,  broad  internally,  where  it  is  continuous  Avith  the  nasal 
eminence,  but  less  distinct  as  it  arches  outward.  These  ridges  are  caused  by  the 
projection  outward  of  the  frontal  air  sinuses,1  and  give  attachment  to  the  Orbicu- 
laris palpebrarum  and  Corrugator  supercilii.  Between  the  two  superciliary 
ridges  is  a  smooth  surface,  the  glabella  or  nasal  eminence.  Beneath  the  super- 
ciliary ridge  is  the  supraorbital  arch,  a  curved  and  prominent  margin,  which  forms 

1  Some  confusion  is  occasioned  to  students  commencing  the  study  of  anatomy  by  the  name 
"sinuses"  having  been  given  to  two  perfectly  different  kinds  of  spaces  connected  with,  the  skull. 
It  may  be  as  well,  therefore,  to  state  here,  at 'the  outset,  that  the  "sinuses"  in  the  interior  of  the 
cranium  which  produce  the  grooves  on  the  inner  surface  of  the  bones  are  venous  channels  along 
which  the  blood  runs  in  its  passage  back  from  the  brain,  while  the  "sinuses"  external  to  the  cranial 
cavity  (the  frontal,  sphenoidal,  ethmoidal,  and  maxillary)  are  hollow  spaces  in  the  bones  themselves 
which  communicate  with  the  nostrils,  and  contain  air. 


62 


THE  SKELETON. 


the  upper  boundary  of  the  orbit  and  separates  the  vertical  from  the  horizontal 
portion  of  the  bone.  The  outer  part  of  the  arch  is  sharp  and  prominent,  afford- 
ing to  the  eye,  in  that  situation,  considerable  protection  from  injury;  the  inner 
part  is  less  prominent.  At  the  junction  of  the  internal  and  middle  third  of  this 
arch  is  a  notch,  sometimes  converted  into  foramen,  and  called  the  supraorbital 
notch  or  foramen.  It  transmits  the  supraorbital  artery,  vein,  and  nerve.  A  small 
aperture  is  seen  in  the  upper  part  of  the  notch,  which  transmits  a  vein  from  the 
diploe  to  join  the. supraorbital  vein.  The  supraorbital  arch  terminates  externally 
in  the  external  angular  process  and  internally  in  the  internal  angular  process. 
The  external  angular  process  is  strong,  prominent,  and  articulates  with  the  malar 
bone;  running  upward  and  backward  from  it  are  two  well-marked  lines,  which, 
commencing  together  from  the  external  angular  process,  soon  diverge  from  each 
other  and  run  in  a  curved  direction  across  the  bone.  These  are  the  upper  and 
lower  temporal  ridges ;  the  upper  gives  attachment  to  the  temporal  fascia,  the 


Jntemal  External 

angular  process.        anguiar  process. 


Nasal  $   spine. 
Fig.  28.— Frontal  bone.    Outer  surface. 


lower  to  the  temporal  muscle.  Beneath  them  is  a  slight  concavity  that  forms  the 
anterior  part  of  the  temporal  fossa  and  gives  origin  to  the  Temporal  muscle.  The 
internal  angular  processes  are  less  marked  than  the  external,  and  articulate  with 
the  lachrymal  bones.  Between  the  internal  angular  processes  is  a  rough,  uneven 
interval,  the  nasal  notch,  which  articulates  in  the  middle  line  with  the  nasal  bone, 
and  on  either  side  with  the  nasal  process  of  the  superior  maxillary  bone.  From 
the  concavity  of  this  notch  projects  a  process,  the  nasal  process,  which  extends 
beneath  the  nasal  bones  and  nasal  processes  of  the  superior  maxillary  bones  and 
supports  the  bridge  of  the  nose.  On  the  under  surface  of  this-4s  a  long  pointed 
process,  the  nasal  spine,  and  on  either  side  a  small  grooved  surface  enters  into 
the  formation  of  the  roof  of  the  nasal  fossa.  The  nasal  spine  forms  part  of  the 
septum  of  the  nose,  articulating  in  front  with  the  nasal  bones  and  behind  with 
the  perpendicular  plate  of  the  ethmoid. 


THE   FRONTAL    BONE. 


63 


Internal  Surface  (Fig.  29). — Along  the  middle  line  is  a  vertical  groove,  the 
edges  of  which  unite  below  to  form  a  ridge,  the  frontal  crest;  the  groove  lodges 
the  superior  longitudinal  sinus,  whilst  its  margins  afford  attachment  to  the  falx 
cerebri.  The  crest  terminates  below  at  a  small  notch  which  is  converted  into  a 
foramen  by  articulation  with  the  ethmoid.  It  is  called  the  foramen  ccecnm,  and 
varies  in  size  in  different  subjects:  it  is  sometimes  partially  or  completelv 
impervious,  lodges  a  process  of  the  falx  cerebri,  and  when  open  transmits  a  vein 
from  the  lining  membrane  of  the  nose  to  the  superior  longitudinal  sinus.  On 
either  side  of  the  groove  the  bone  is  deeply  concave,  presenting  depressions 
for  the  convolutions  of  the  brain,  and  numerous  small  furrows  for  lodging  the 
ramifications  of  the  anterior  meningeal  arteries.  Several  small,  irregular  fossse 
are  seen  also  on  either  side  of  the  groove,  for  the  reception  of  the  Pacchionian 
bodies. 

Horizontal  Portion. — This  portion  of  the  bone  consists  of  two  thin  plates, 
the  orbital  plates,  which  form  the  vault  of  the  orbit,  separated  from  one 
another  by  a  median  gap,  the  ethmoidal  notch.  The  external  surface  of  each 
orbital  plate  consists  of  a  smooth,  concave,  triangular  lamina  of  bone,  marked 
vit   its   anterior   and    external    part    (immediately   beneath    the    external    angular 


«*fifflWjM%Khni 


With  superior  maxillary 

With  nasal 
With  perpendicular  plate  of  ethmoid. 

Fig.  29.— Frontal  bone.    Inner  surface 


Under  surface  of  nasal  process, 
forming  part  of  roof  of  nose. 


process)  by  a  shallow  depression,  the  lachrymal  fossa,  for  lodging  the  lachrymal 
gland;  and  at  its  anterior  and  internal  part  by  a  depression  (sometimes  a  small 
tubercle),  the  trochlear  fossa,  for  the  attachment  of  the  cartilaginous  pulley  of  the 
Superior  oblique  muscle  of  the  eye.  The  ethmoidal  notch  separates  the  two  orbital 
plates-  it  is  quadrilateral,  and  filled  up,  A\hen  the  bones  are  united,  by  the 
cribril  »nn  plate  of  the  ethmoid.  The  margins  of  this  notch  present  several  half- 
cell^  which  when  united  with  corresponding  half-cells  on  the  upper  surface  of  the 
ethmoid,  <vmplete  the  ethmoidal  cells;  two  grooves  are  also  seen  crossing  these 


64 


THE   SKELETON. 


edges  transversely ;  they  are  converted  into  canals  by  articulation  with  the  ethmoid, 
and  are  called  the  anterior  and  posterior  ethmoidal  canals :  they  open  on  the  inner 
wall  of  the  orbit.  The  anterior  one  transmits  the  nasal  nerve  and  anterior 
ethmoidal  vessels,  the  posterior  one  the  posterior  ethmoidal  vessels.  In  front  of 
the  ethmoidal  notch,  on  either  side  of  the  nasal  spine,  are  the  openings  of  the 
frontal  sinuses.  These  are  two  irregular  cavities,  which  extend  upward  and 
outward,  a  variable  distance,  between  the  two  tables  of  the  skull,  and  are 
separated  from  one  another  by  a  thin,  bony  septum,  which  is  often  displaced  to 
one  side.  They  give  rise  to  the  prominences  above  the  supraorbital  arches  called 
the  super  ciliary  ridges.  In  the  child  they  are  generally  absent,  and  they  become 
gradually  developed  as  age  advances.  These  cavities  vary  in  size  in  different 
persons,  are  larger  in  men  than  in  women,  and  are  frequently  of  unequal  size  on 
the  two  sides,  the  right  being  commonly  the  larger.  They  are  lined  by  mucous 
membrane,  and  communicate  with  the  nose  by  the  infundibulum,  and  occasionally 
with  each  other  by  apertures  in  their  septum. 

The  internal  surface  of  the  horizontal  portion  presents  the  convex  upper 
surfaces  of  the  orbital  plates,  separated  from  each  other  in  the  middle  line  by  the 
ethmoidal  notch,  and  marked  by  eminences  and  depressions  for  the  convolutions  of 
the  frontal  lobes  of  the  brain. 

Borders. — The  border  of  the  vertical  portion  is  thick,  strongly  serrated,  bevelled 
at  the  expense  of  the  internal  table  above,  where  it  rests  upon  the  parietal  bones, 
and  at  the  expense  of  the  external  table  at  each  side,  where  it  receives  the  lateral 
pressure  of  those  bones ;  this  border  is  continued  below  into  a  triangular  rough 
surface  which  articulates  with  the  great  wing  of  the  sphenoid.  The  border  of  the 
horizontal  portion  is  thin,  serrated,  and  articulates  with  the  lesser  wing  of  the 
sphenoid. 

Structure. — The  vertical  portion  and  external  angular  processes  are  very  thick, 
consisting  of  diploic  tissue  contained  between  two  compact  laminae.  The  hori- 
zontal portion  is  thin,  translucent,  and  composed  entirely  of  compact  tissue ;  hence 
the  facility  with  which  instruments  can  penetrate  the  cranium  through  this  part  of 
the  orbit. 

Development  (Fig.  30). — The  frontal  bone  is  formed  in  membrane,  being  devel- 
oped by  two  centres,  one  for  each  lateral  half,  which  make  their  appearance  about 
the  seventh  or  eighth  week,  above  the  orbital  arches.  From  this  point  ossification 
extends,  in  a  radiating  manner,  upward  into  the  forehead  and  backward  over  the 
orbit.  At  birth  the  bone  consists  of  two  pieces,  which  afterward  become  united, 
along  the  middle  line,  by  a  suture  which  runs  from  the  vertex  to  the  root  of  the 
nose.     This  suture  usually  becomes  obliterated  within  a  few  years  after  birth  ;  but 

it  occasionally  remains  throughout  life, 
constituting  the  metopie  suture.  Secondary 
centres  of  ossification  appear  for  the  nasal 
spine — one  on  either  side  at  the  internal 
angular  process  where  it  articulates  with 
the  lachrymal  bone ;  and  sometimes  there  is 
one  on  either  side  at  the  lower  end  of  the 
coronal  suture.  This  latter  centre  some- 
times remains  ununited,  and  is  known  as 
the  pterion  ossicle,  or  it  may  join  with  the 
parietal,  sphenoid,  or  temporal  bone. 

Articulations. — With  twelve  bones: 
two  parietal,  the  sphenoid,  the  ethmoid, 
two  nasal,  two  superior  maxillary,  two 
lachrymal,  and  two  malar, 
pairs  :  the  Corrugator  supercilii,  Orbicu- 
each  side. 


Fig.  30.— Frontal  bone  at  birth, 
two  lateral  halves. 


Developed  by 


Attachment  of  Muscles. — To  three 
laris  palpebrarum,   and  Temporal,  on 


THE    TEMPORAL    BONES. 


65 


The  Temporal  Bones. 

The  Temporal  Bones  (tempus,  time)  are  situated  at  the  sides  and  base  of  the 
skull,  and  present  for  examination  a  squamous,  mastoid,  and  petrous  portion. 

The  squamous  portion  (squama,  a  scale),  the  anterior  and  upper  part  of  the 
bone,  is  scale-like  in  form,  and  thin  and  translucent  in  texture  (Fig.  31).  Its  outer 
surface  is  smooth,  convex,  and  grooved  at  its  back  part  for  the  deep  temporal 
arteries ;  it  affords  attachment  to  the  Temporal  muscle  and  forms  part  of  the 
temporal  fossa.  At  its  back  part  may  be  seen  a  curved  ridge — part  of  the  temporal 
ridge;  it  serves  for  the  attachment  of  the  temporal  fascia  and  limits  the  origin  of 
the  Temporal  muscle.     The  boundary  between  the  squamous  and  mastoid  portions 


Artie,  with   ,=g»S^B- 

malar.~\       Zy9oma 


Eminentia 

articularis 


Glenoid  fossa 


DIGASTRIC. 


STYLO-GLOSSUS 


Styloid  proc. 


Auditory  proc. 

STYLO-HYOID. 


Fig.  31. — Left  temporal  bone.    Outer  surface. 

of  the  bone,  as  indicated  by  traces  of  the  original  suture,  lies  fully  half  an  inch 
below  this  ridge.  Projecting  from  the  lower  part  of  the  squamous  portion  is  a 
long,  arched  process  of  bone,  the  zygoma  or  zygomatic  process.  This  process  is 
at  first  directed  outward,  its  two  surfaces  looking  upward  and  downward ;  it  then 
appears  as  if  twisted  upon  itself,  and  runs  forward,  its  surfaces  now  looking 
inward  and  outward.  The  superior  border  of  the  process  is  long,  thin,  and  sharp, 
and  serves  for  the  attachment  of  the  temporal  fascia.  The  inferior,  short,  thick, 
and  arched,  has  attached  to  it  some  fibres  of  the  Masseter  muscle.  Its  outer 
surface  is  convex  and  subcutaneous ;  its  inner  is  concave,  and  also  affords  attach- 
ment to  the  Masseter.  The  extremity,  broad  and  deeply  serrated,  articulates 
with  the  malar  bone.  The  zygomatic  process  is  connected  to  the  temporal  bone 
by  three  divisions,  called  its  roots — an  anterior,  middle,  and  posterior.  The 
anterior,  which  is  short,  but  broad  and  strong,  is  dir^  jted  inward,  to  terminate  in 
a  rounded  eminence,  the  eminentia  articula^-  ,V  '  ,  5  eminence  forms  the  front 
boundary  of  the  glenoid  fossa,  and  '^  gJe.S,e  C,  ar<te  is  covered  with  cartilage. 
rni      middle  root  is  known  as  the  -  '  l  h,  and  is  very  prominent  in 

i  bones.     It  separates  th-   Proces?s  beinS  '*,  the  glenoid  fossa  from  the 

aal  auditory  meatus,  a*-^  m  '  mt*elJ  absent'  anencement  of  a  well-marked 
?,  the  aiaserian  fie*"he8e    ma?    be    seen  a  lar^hich  is    strongly  marked, 

5 


66 


THE   SKELETON. 


runs  from  the  upper  border  of  the  zygoma  backward  over  the  external  auditory 
meatus.  It  is  termed  the  supra-mastoid  crest,  and  forms  the  posterior  part  of  the 
lower  temporal  ridge.  At  the  junction  of  the  anterior  root  with  the  zygoma  is 
a  projection,  called  the  tubercle,  for  the  attachment  of  the  external  lateral  liga- 
ment of  the  lower  jaw ;  and  between  the  anterior  and  middle  roots  is  an  oval  depres- 
sion, forming  part  of  the  glenoid  fossa  {ykqvfj,  a  socket),  for  the  reception  of  the 
condyle  of  the  lower  jaw.  This  fossa  is  bounded,  in  front,  by  the  eminentia 
articularis ;  behind,  by  the  tympanic  plate,  which  separates  it  from  the  external 
auditory  meatus ;  it  is  divided  into  two  parts  by  a  narrow  slit,  the  Crlaserian 
fissure.  The  anterior  or  mandibular  part,  formed  by  the  squamous  portion  of 
the  bone,  is  smooth,  covered  in  the  recent  state  with  cartilage,  and  articulates 
with  the  condyle  of  the  lower  jaw.  This  part  of  the  glenoid  fossa  presents 
posteriorly  a  small  conical  eminence,  the  post-glenoid  process,  already  referred  to. 
This  process  is  the  representative  of  a  prominent  tubercle  which,  in  some  of  the 
mammalia,  descends  behind  the  condyle  of  the  jaw,  and  prevents  it  being 
displaced  backward  during  mastication  (Humphry).  The  posterior  part  of  the 
glenoid  fossa,  which  lodges  a  portion  of  the  parotid  gland,  is  formed  chiefly  by 
the  tympanic  plate,  which  constitutes  the  anterior  wall  of  the  tympanum  and 
external  auditory  meatus.  The  plate  of  bone  terminates  above  in  the  Glaserian 
fissure,  and  beloA\r  forms  a  sharp  edge,  the  vaginal  process,  which  gives  origin  to 
some  of  the  fibres  of  the  Tensor  palati  muscle.  The  Glaserian  fissure,  which 
leads  into  the  tympanum,  lodges  the  processus  gracilis  of  the  malleus,  and 
transmits  the  tympanic  branch  of  the  internal  maxillary  artery.  The  chorda 
tympani  nerve  passes  through  a  separate  canal,  parallel  to  the  Glaserian  fissure 
[canal  of  Huguier),  on  the  outer  side  of  the  Eustachian  tube,  in  the  retiring 
angle  between  the  squamous  and  petrous  portions  of  the  temporal  bone.1 


parietal 


Aquasductus  vestibuli. 

Depression  for  dura  mater. 

Meatus  auditorium  internus. 


t 

j  are 


*®jQ\  and      Great 
T^V    Eminence  for  superior  semicircular  canal, 
h  iatas  Fallopii. 

Opening  for  smaller  petrosal  nerve. 
Depression  for  Gasserian  Ganglion. 
Bristle  passed  through  carotid  canal. 


i  -  .      .    I  la^  bono     Inner  surface 

in  the  recent  staTo  three       .f.   ^ 
Thr- post-glenoid  process        Y    on  each  ^        {Y      32)  ig 
.d  mandibular  portion  oi  v     °       J  '  1 

id  terminates  at  the  commj  "1  which  lies  above  the  Eustachian 

The  posterior    root 


THE    TEMPORAL    BONES. 


67 


numerous  eminences  and  depressions  for  the  convolutions  of  the  cerebrum,  and 
two  well-marked  grooves  for  the  branches   of  the  middle  meningeal  artery. 

Borders. — The  superior  border  is  thin,  bevelled  at  the  expense  of  the  internal 
surface,  so  as  to  overlap  the  lower  border  of  the  parietal  bone,  forming  the  squam- 
ous suture.  The  anterior  inferior  border  is  thick,  serrated,  and  bevelled,  alter- 
nately at  the  expense  of  the  inner  and  outer  surfaces,  for  articulation  with  the 
great  wing  of  the  sphenoid. 

The  Mastoid  Portion  {jiaarbz,  a  nipple  or  teat)  is  situated  at  the  posterior  part  of 
the  bone ;  its  outer  surface  is  rough,  and  gives  attachment  to  the  Occipito-frontalis 
and  Retrahens  aurem  muscles.  It  is  perforated  by  numerous  foramina;  one  of 
these,  of  large  size,  situated  at  the  posterior  border  of  the  bone,  is  termed  the 
mastoid  foramen;  it  transmits  a  vein  to  the  lateral  sinus  and  a  small  artery  from 
the  occipital  to  supply  the  dura  mater.  The  position  and  size  of  this  foramen 
are  very  variable.  It  is  not  always  present;  sometimes  it  is  situated  in  the 
occipital  bone  or  in  the  suture  between  the  temporal  and  the  occipital.  The 
mastoid  portion  is  continued  below  into  a  conical  projection,  the  mastoid  process, 
the  size  and  form  of  which  vary  somewhat.  This  process  serves  for  the  attachment 
of  the  Sterno-mastoid,  Splenius  capitis,  and  Trachelo-mastoid  muscles.  On  the 
inner  side  of  the  mastoid  process  is  a  deep  groove,  the  digastric  fossa,  for  the 
attachment  of  the  Digastric  muscle ;  and,  running  parallel  with  it,  but  more  in- 
ternal, the  occipital  groove,  which  lodges  the  occipital  artery.  The  internal  surface 
of  the  mastoid  portion  presents  a  deep,  curved  groove,  the  fossa  sigmoidea,  which 
lodges  part  of  the  lateral  sinus ;  and  into  it  may  be  seen  opening  the  mastoid  fora- 


Malleus. 
Incus. 

Tensor  tympani. 
Proc.  cochlea  i- if  or  ni  is. 

Eustachian  tube. 
Carotid  canal. 


Carotid  cana, 
Fenestra  rotunda. 

aid'.  ^^SrSY^MY  /    Y7ATA     Wl  '    \ 

Aqueductus  Fallopii. 

Harrow  cells. 

Fig.  33.— Section  through  the  petrous  and  mastoid  portions  of  the  temporal  bone,  showing  the  communi- 
cation of  the  cavity  of  the  tympanum  with  the  mastoid  antrum. 

men.  The  groove  for  the  lateral  sinus  is  separated  from  the  innermost  of  the 
mastoid  air-cells  by  only  a  thin  lamina  of  bone,  and  even  this  may  be  partly 
deficient.  A  section  of  the  mastoid  process  shows  it  to  be  hollowed  out  into  a 
number  of  cellular  spaces,  communicating  Avith  each  other,  called  the  mastoid 
cells,  which  exhibit  the  greatest  possible  variety  as  to  their  size  and  number.  At 
the  upper  and  front  part  of  tb^  bone  these  cells  are  large  and  irregular,  and  con- 
tain air.  They  diminish  in  si  d  the  lower  part  of  the  bone,  those  situated 
at  the  apex  of  the  mastoid  process  being  quite  small  and  usually  containing 
marrow.  Occasionally  they  rtirely  absent,  and  the  mastoid  is  solid  through- 
out.    In    addition    to   these    may   be    seen   a  large    irregular   cavity  (Fig.  33), 


68  THE   SKELETON. 

situated  at  the  upper  and  front  part  of  the  section.  It  is  called  the  mastoid 
antrum,  and  must  be  distinguished  from  the  mastoid  cells,  though  it  communicates 
with  them.  It  is  filled  with  air,  and  is  lined  with  a  prolongation  of  the  mucous 
membrane  of  the  tympanum,  which  extends  into  it  through  an  opening,  by  which 
it  communicates  with  the  cavity  of  the  tympanum.  The  mastoid  antrum  is 
bounded  above  by  a  thin  plate  of  bone,  which  separates  it  from  the  middle  fossa 
of  the  base  of  the  skull  on  the  anterior  surface  of  the  petrous  portion  of  the 
temporal  bone  ;  below  by  the  mastoid  process ;  externally  by  the  squamous  por- 
tion of  the  bone  just  below  the  supra-mastoid  crest ;  and  internally  by  the  external 
semicircular  canal  of  the  internal  ear  which  projects  into  its  cavity.  The  opening 
by  which  it  communicates  with  the  tympanum  is  situated  at  the  superior  internal 
angle  of  the  posterior  wall  of  that  cavity,  and  opens  into  that  portion  of  the 
tympanic  cavity  which  is  known  as  the  attic  or  epityi^oanic  recess  ;  that  is  to  say, 
that  portion  of  the  tympanum  which  is  above  the  level  of  the  membrana  tympani. 
The  mastoid  cells,  like  the  other  sinuses  of  the  cranium,  are  not  developed 
until  after  puberty;  hence  the  prominence  of  this  process  in  the  adult:  the 
mastoid  antrum,  on  the  other  hand,  is  of  large  size  at  birth. 

In  consequence  of  the  communication  which  exists  between  the  tympanum  and  mastoid  cells, 
inflammation  of  the  lining  membrane  of  the  former  cavity  may  easily  travel  backward  to  that  of 
the  antrum,  leading  to  caries  and  necrosis  of  their  walis  and  the  risk  of  transference  of  the 
inflammation  to  the  lateral  sinus  or  encephalon. 

Borders. — The  superior  border  of  the  mastoid  portion  is  broad  and  rough,  its 
serrated  edge  sloping  outward,  for  articulation  with  the  posterior  inferior  angle  of 
the  parietal  bone.  The  posterior  border,  also  uneven  and  serrated,  articulates 
with  the  inferior  border  of  the  occipital  bone  between  its  lateral  angle  and  jugular 
process. 

The  Petrous  Portion  (xitpoc;,  a  stone),  so  named  from  its  extreme  density  and 
hardness,  is  a  pyramidal  process  of  bone  wedged  in  at  the  base  of  the  skull 
between  the  sphenoid  and  occipital  bones.  Its  direction  from  without  is  inward, 
forward,  and  a  little  downward.  It  presents  for  examination  a  base,  an  apex, 
three  surfaces,  and  three  borders,  and  contains,  in  its  interior,  the  essential  parts 
of  the  organ  of  hearing.  The  base  is  applied  against  the  internal  surface  of  the 
squamous  and  mastoid  portions,  its  upper  half  being  concealed ;  but  its  lower 
half  is  exposed  by  the  divergence  of  those  two  portions  of  the  bone,  which  brings 
into  view  the  oval  expanded  orifice  of  a  canal  leading  into  the  tympanum,  the 
meatus  auditorius  externus.  The  curved  tympanic  plate  forms  the  anterior  wall, 
the  floor,  and  a  part  of  the  posterior  wall  of  this  meatus,  while  the  squamous 
temporal  completes  it  above  and  behind.  The  entrance  to  the  meatus  is  bounded 
throughout  the  greater  part  of  its  circumference  by  the  auditory  process,  which  is 
the  name  applied  to  the  free  rough  margin  of  the  tympanic  plate,  and  which 
gives  attachment  to  the  cartilaginous  portion  of  the  meatus.  Superiorly  the 
entrance  to  the  meatus  is  limited  by  the  posterior  root  of  the  zygoma. 

The  apex  of  the  petrous  portion,  rough  and  uneven,  is  received  into  the 
angular  interval  between  the  posterior  border  of  the  greater  wing  of  the  sphenoid 
and  the  basilar  process  of  the  occipital ;  it  presents  the  anterior  or  internal  orifice 
of  the  carotid  canal,  and  forms  the  posterior  and  external  boundary  of  the  fora- 
men lacerum  medium. 

The  anterior  surface  of  the  petrous  portion  (Fig.  32)  forms  the  posterior  part 
of  the  middle  fossa  of  the  skull.  This  surface  is  continuous  with  the  squamous 
portion,  to  which  it  is  united  by  a  suture,  the  petrosquamous  suture,  the  remains 
of  which  are  distinct  even  at  a  late  period  of  life.  It  presents  six  points  for 
examination :  1,  an  eminence  near  the  centre,  which  indicates  the  situation  of 
the  superior  semicircular  canal ;  2,  in  front  and  a  little  to  the  outer  side  of  this 
eminence  a  depression  indicating  the  position  of  the  tympanum;  here  the  layer 
of  bone  which  separates  the  tympanum  from  the  cranial  cavity  is  extremely 
thin,   and  is  known  as  the  tegmen  tympani;    8,   a  shallow  groove,   sometimes 


THE    TEMPORAL    BONES. 


69 


Fig.  34.— Diagrammatic  view  of  the  Fundus 
of  the  internal  auditory  meatus  (Testut):  1.  Falci- 
form crest.  2,  Anterior  superior  cribriform  area. 
2'.  Internal  opening  of  the  Aquteductus  FallopiL 
3.  Vertical  crest  which  separates  the  anterior 
and  posterior  superior  cribriform  areas,  4.  Pos- 
terior superior  cribriform  area,  with  (4')  open- 
ings for  nerve-filaments.  5.  Anterior  inferior 
cribriform  area. 


form  area.  7'  Orifices  for  the  branches  of  the 
nerve  to  the  saccule.  8.  Foramen  singulare  of 
Morgagni,  with  the  anterior  portion  of  the  canal 
which  gives  passage  to  the  nerve  to  the  posterior 
semicircular  canal. 


double,  leading  outward  and  backward  to  an  oblique  opening,  the  hiatus  Fattopii, 
for  the  passage  of  the  greater  petrosal  nerve  and  the  petrosal  branch  of  the 
middle  meningeal  artery ;  4,  a  smaller 
opening,  occasionally  seen  external  to  the 
latter,  for  the  passage  of  the  smaller  pe- 
trosal nerve  ;  5,  near  the  apex  of  the  bone, 
the  termination  of  the  carotid  canal,  the 
wall  of  which  in  this  situation  is  deficient 
in  front;  6,  above  this  canal  a  shallow  de- 
pression for  the  reception  of  the  Gasserian 
ganglion. 

The  posterior  surface  forms  the  front 
part  of  the  posterior  fossa  of  the  skull,  and 
is  continuous  with  the  inner  surface  of  the 
mastoid  portion  of  the  bone.  It  presents 
three  points  for  examination :  1.  About  its 
centre,  a  large  orifice,  the  meatus  auditorius 
interims,  whose  size  varies  considerably  ;  its 
margins  are  smooth  and  rounded,  and  it 
leads  into  a  short  canal,  about  four  lines 
in  length,  which  runs  directly  outward  and 

is    closed    by    a    vertical    plate,    the    lamina  cribriform  area.    5'.  Spirally  arranged,  sieve-like 

.j  i  •    i      •        t    •  -i     -i    t  i  i  openings  for  the  nerves  to  the  cochlea.   5".  Open- 

CribrOSa,   Which    IS    divided    by   a    horizontal  ing  of  the  central  canal  of  the  cochlea.    6.  Crest 

«„„„i     *i  •„*„    -C„i    '-P  •       •    j.       i.  which  separates  the  anterior  and  posterior  infe 

Crest,    the    Crista  JalcijormiS,    mtO    tWO    Un-  rior  cribriform  areas.    7.  Posterior  inferior  cribri 

equal  portions.  Each  portion  is  subdivided 
by  a  little  vertical  crest  into  two  parts, 
named  respectively  anterior  and  poste- 
rior.     The    lower    portion    presents    three 

sets  of  foramina ;  one  group  just  below  the  posterior  part  of  the  crest,  the  area 
eribrosa  media,  consisting  of  a  number  of  small  openings  for  the  nerves  to  the 
saccule ;  below  and  posterior  to  this,  the  foramen  singidare,  or  opening  for  the 
nerve  to  the  posterior  semicircular  canal ;  in  front  and  below  the  first,  the  tractus 
spiralis  foraminosus,  consisting  of  a  number  of  small  spirally  arranged  openings 
which  terminate  in  the  canalis  centralis  cochleae  and  transmit  the  nerve  to  the 
cochlea ;  the  upper  portion,  that  above  the  crista,  presents  behind  a  series  of 
small  openings,  the  area  eribrosa  superior,  for  the  passage  of  filaments  to  the 
utricle  and  superior  and  external  semicircular  canal,  and,  in  front,  one  large 
opening,  the  commencement  of  the  aquteductus  Fallopii,  for  the  passage  of  the 
facial  nerve.  2.  Behind  the  meatus  auditorius,  a  small  slit,  almost  hidden  by  a 
thin  plate  of  bone,  leading  to  a  canal,  the  aquoeductus  vestibidi,  which  transmits 
the  ductus  endolymphaticus  together  with  a  small  artery  and  vein.  In  the  interval 
between  these  two  openings,  but  above  them,  is  an  angular  depression  which  lodges 
a  process  of  the  dura  mater,  and  transmits  a  small  vein  into  the  cancellous  tissue 
of  the  bone.  In  the  child  this  depression  is  represented  by  a  large  fossa,  the 
floccular  fossa,  which  extends  backward  as  a  blind  tunnel  under  the  superior 
semicircular  canal. 

The  inferior  or  basilar  surface  (Fig.  35)  is  rough  and  irregular,  and  forms  part 
of  the  base  of  the  skull.  Passing  from  the  apex  to  the  base,  this  surface  presents 
eleven  points  for  examination :  1,  a  rough  surface,  quadrilateral  in  form,  which 
serves  partly  for  the  attachment  of  the  Levator  palati  and  Tensor  tympani 
muscles;  2,  the  large,  circular  aperture  of  the  carotid  canal,  which  ascends  at 
first  vertically,  and  then,  making  a  bend,  runs  horizontally  forward  and  inward; 
it  transmits  the  internal  carotid  artery  and  the  carotid  plexus;  8.  the  aquoeductus 
cochlea?,  a  small,  triangular  opening,  lying  on  the  inner  side  of  the  latter,  close  to 
the  posterior  border  of  the  petrous  portion ;  it  transmits  a  vein  from  the  cochlea 
which  joins  the  internal  jugular ;  4,  behind  these  openings  a  deep  depression,  the 
jugular  fossa,) which  varies  in   depth  and  size  in  different  skulls:  it  lodges  the 


70 


THE   SKELETON. 


lateral  sinus,  and,  with  a  similar  depression  on  the  margin  of  the  jugular 

of  the  occipital  bone,  forms  the  foramen  lacerum  posterius  or  jugular  fc 

5,  a  small  foramen  for  the  passage  of  Jacobson's  nerve  (the  tympanic  bnj. 

the  glossopharyngeal) :  this  foramen  is  seen  in  front  of  the  bony  ridge  dividing 


Canals  for  Eustachian  tube  and 

TENSOR    TYMPAN1     MUSCLE. 


LEVATOR     PALAT 


Rough  quadrilateral  surface. 

Opening  of  carotid  canal. 

Canal  for  Jacobson's  nerve. 

Aquseductus  cochlese. 

Canal  for  Arnold's  nerve. 

Jugular  fossa. 

Vaginal  process. 

Styloid  process. 
Stylo-mastoid  foramen! 

Jugular  surface 

Auriadar  fissure. 


STYLO-PHARYNGEUS. 


Fig.  35.— Petrous  portion.    Inferior  surface. 


the  carotid  canal  from  the  jugular  fossa ;   6,  a  small  foramen  on  the  wall  of  the 
jugular  fossa,  for  the  entrance  of  the    auricular  branch  of  the   pneumogastric 
(Arnold's)  nerve ;   7,  behind  the  jugular  fossa  a  smooth,  square-shaped  facet,  the 
jugular  surface  ;   it  is  covered  with  cartilage  in  the  recent  state,  and  articulates 
with   the  jugular   process  of  the   occipital  bone;   8,  the  vaginal  process,  a- very 
broad,  sheath-like  plate  of  bone,  which  extends  backward  from  the  carotid  canal  and 
gives  attachment  to  part  of  the  Tensor  palati  muscle; 'this  plate  divides  behind 
into  two  laminae,  the  outer  of  which  is  continuous  Avith^the  tympanic  plate,  the 
inner  with  the  jugular  process;   9,  between  these  laminae  is  the  ninth  point  for 
examination,  the  styloid  process,  a  sharp  spine,  about  an  inch  in  length :  it  is 
directed  downward,  forward,  and  inward,  varies  in  size  and  shape.  and  sometimes 
consists    of  several    pieces    united    by  cartilage;  it  affords  attachment  to  three 
muscles,  the  Stylo-pharyngeus,  Stylo-hyoideus,  and  Stylo-glossus,  and  two  lig-' 
ments,  the  stylo-hyoid  and  stylo-maxillary;  10,  the  stylo-mastoid  foramen,  a  rat] 
large  orifice,  placed  between  the  styloid  and  mastoid  processes:  it  is  the  termfil 
tion  of  the  aquseductus  Fallopii,  and  transmits  the  facial  nerve  and  stylo-m? 
artery;  11,  the  auricular  fissure,  situated  between  the  tympanic  plate  and  m 
processes,  for  the  exit  of  the  auricular  branch  of  the  pneumogastric  nerve. 
Borders. — The  superior,  the  longest,  is  grooved  for  the  superior  petros 
and  has  attached  to  it  the  tentorium  cerebelli ;  at  its  inner  'xtremity  is  a  sen 
notch,  upon  which  the  fifth  nerve  lies.     The  postt  der  is  inte  in 

length  between  the  r  and  the  anterior.    Its  ir  If  is  marked  'oove, 

which,  when  conip  ,T  its  articulation  with  th  al,  forms  mel 


THE    TEMPORAL    BOXES. 


71 


for  the  inferior  petrosal  sinus.  Its  outer  half  presents  a  deep  excavation — the 
jugular  fossa — which,  with  a  similar  notch  on  the  occipital,  forms  the  foramen 
lacerum  posterius.  A  projecting  eminence  of  bone  occasionally  stands  out  from 
the  centre  of  the  notch,  and  divides  the  foramen  into  two  parts.  The  anterior 
border  is  divided  into  two  parts — an  outer  joined  to  the  squamous  portion  by  a 
suture,  the  remains  of  which  are  distinct ;  an  inner,  free,  articulating  with  the 
spinous  process  of  the  sphenoid.  At  the  angle  of  junction  of  the  petrous  and 
squamous  portions  are  seen  two  canals,  separated  from  one  another  by  a  thin  plate 
of  bone,  the  processus  cochleariformis ;  they  both .  lead  into  the  tympanum,  the 
upper  one  transmitting  the  Tensor  tympani  muscle,  the  lower  one  forming  the 
bony  part  of  the  Eustachian  tube. 

Structure. — The  squamous  portion  is  like  that  of  the  other  cranial  bones:  the 
mastoid  portion,  cellular;  and  the  petrous  portion,  dense  and  hard. 

Development  (Fig.  36). — The  temporal  bone  is  developed  by  ten  centres, 
exclusive  of  those  for  the  internal  ear  and  the  ossicula — viz.,  one  of  the  squamous 
portion  including  the  zygoma,  one  for  the  tympanic  plate,  six  for  the  petrous  and 
mastoid  parts,  and  two  for  the  styloid  process.  Just  before  the  close  of  foetal  life 
the  temporal  bone  consists  of  four  parts:  1.  The  squamo-zygomatic,  which  is  ossi- 
fied in  membrane  from  a  single  nucleus,  which  appears  at  its  lower  part  about  the 
second  month.  2.  The  tympanic  plate,  an  imperfect  ring,  in  the  concavity  of 
which  is  a  groove,  the  sulcus  ty?npanicus,  for  the  attachment  of  the  circumference 
of  the  tympanic  membrane.  This  is  also  ossified  from  a  single  centre,  which 
appears  about  the  third  month.  3.  The  petro-mastoid,  which  is  developed  from 
six  centres,  which  appear  about  the  fifth  or  sixth  month.  Four  of  these  are  for 
the  petrous  portion,  and  are  placed  around  the  labyrinth,  and  tAvo  for  the  mastoid 
(Vrolik).  According  to  Huxley,  the  centres  are  more  numerous,  and  are  dis- 
posed so  as  to  form  three  portions  :  (1)  including  most  of  the  labyrinth,  Avith  a  part 
of  the  petrous  and  mastoid,  he  has 
named  prootic ;  (2)  the  rest  of  the 
petrous,  the  opisthotic ;  and  (3)  the 
remainder  of  the  mastoid,  the  epiotic. 
The  petro-mastoid  is  ossified  in  carti- 
lage. 4.  The  styloid  process  is  also 
ossified  in  cartilage  from  two  centres  : 
one  for  the  base,  which  appears  before 
birth,  and  is  termed  the  tympano-hyal ; 
the  other,  comprising  the  rest  of  the 
process,  is  named  the  stylo-hyal,  and 
does  not  appear  until  after  birth. 
Shortly  before  birth  the  tympanic 
plate  joins  with  the  squamous.  The 
petrous  and  mastoid  join  with  the 
squamous  during  the  first  year,  and 
the  tympano-hyal  portion  of  the  sty- 
loid process  about  the  same  time.  The 
stylo-hyal  does  not  join  the  rest  of  the 
bone  until  after  puberty,  and  in  some 
skulls  never  becomes  united.  The 
subsequent  changes  in  this  bone  are, 
that  the  tympanic  plate  extends  outward  and  backward,  so  as  to  form  the  meatus 
auditorius.  The  extension  of  the  tympanic  plate,  however,  does  not  take  place  at 
an  equal  rate  all  round  the  circumference  of  the  ring,  but  occurs  most  rapidly 
on  its  anterior  and  posterior  portions,  and  these  outgrowths  meet  and  blend,  and 
thus,  for  a  time,  there  '  s  in  the  floor  of  the  meatus  a  foramen,  the  foramen  of 
Husclike:  this  fora  v  persist  throughout  life.     The  glenoid  cavity  is  at  first 

extremely  shallow  >ks  outward  as  well  as  downward :  it  becomes  deeper 

and  is  ultimately  <  downward.     Its  change  in  di        '    )   is  accounted  for 


l.for 

squamous 
portion, 
including 
zygoma  : 
2d  month. 


1  for  tympanic 
plate. 


6  for  petrous 

and  mastoid 

portions. 


Fig.  36 
ten  centres 


2  for  styloid  jiroeess. 

Development  of  the  temporal  bone. 


By 


72 


THE   SKELETON. 


as  follows  :  the  part  of  the  squamous  temporal  which  supports  it  lies  at  first  below 
the  level  of  the  zygoma.  As,  however,  the  base  of  the  skull  increases  in  width, 
this  lower  part  of  the  squama  is  directed  horizontally  inward  to  contribute  to 
the  middle  fossa  of  the  skull,  and  its  surfaces  therefore  come  to  look  upward  and 
downward.  The  mastoid  portion  is  at  first  quite  flat,  and  the  stylo-mastoid  fora- 
men and  rudimentary  styloid  process  lie  immediately  behind  the  entrance  to  the 
auditory  meatus.  With  the  development  of  the  air-cells  the  outer  part  of  the 
mastoid  portion  grows  downward  and  forward  to  form  the  mastoid  process,  and 
the  styloid  process  and  stylo-mastoid  foramen  now  come  to  lie  on  the  under 
surface.  The  descent  of  the  foramen  is  necessarily  accompanied  by  a  correspond- 
ing lengthening  of  the  aqueduct  of  Fallopius. 

The  downward  and  forward  growth  of  the  mastoid  process  also  pushes  for- 
ward the  tympanic  plate,  so  that  the  portion  of  it  which  formed  the  original  floor 
of  the  meatus  and  containing  the  foramen  of  Huschke  is  ultimately  found  in  the 
anterior  wall.  With  the  gradual  increase  in  size  of  the  petrous  portion  the 
floccular  fossa  or  tunnel  under  the  superior  semicircular  canal  becomes  filled  up 
and  almost  obliterated. 

Articulations. — With  five  bones — occipital,  parietal,  sphenoid,  inferior  maxil- 
lary, and  malar. 

Attachment  of  Muscles. — To  fifteen  :  to  the  squamous  portion,  the  Temporal ; 
to  the  zygoma,  the  Masseter ;  to  the  mastoid  portion,  the  Occipito-frontalis,  Sterno- 
mastoid,  Splenius  capitis,  Trachelo-mastoid,  Digastricus,  and  Retrahens  aurem ; 
to  the  styloid  process,  the  Stylo-pharyngeus,  Stylo-hyoideus,  and  Stylo-glossus ; 
and  to  the  petrous  portion,  the  Levator  palati,  Tensor  tympani,  Tensor  palati,  and 
Stapedius. 

The  Sphenoid  Bone. 

The  Sphenoid  Bone  (opfjv,  a  wedge)  is  situated  at  the  anterior  part  of  the  base 
of  the  skull,  articulating  with  all  the  other  cranial  bones,  which  it  binds  firmly  and 
solidly  together.  In  its  form  it  somewhat  resembles  a  bat  with  its  wings  extended ; 
and  is  divided  into  a  central  portion  or  body,  two  greater  and  two  lesser  wings 
extending  outward  on  each  side  of  the  body,  and  two  processes — the  pterygoid 
processes — which  project  from  it  below. 

Middle  clinoid  process. 
^Posterior  clinoid  process.  \Gr00ve  for 

olfactory,    Cci^g^ 
lract.\    Is&r.- 
M 


Foramen  opticum.. 

Foramen  lacerum  ante- 

rius  or  Sphenoidal 

fissure. 

Foramen  rotundum. 

Foramen  VesaliL 

Foramen  ovale, 

Foramen  spinosum. 


Fig.  37.— Sphenoid  bone.    Superior  surface. 


The  body  is  of  large  size,  and  hollowed  out  in  its  interior  so  as  to  form  a  mere 
shell  of  bone.  It  presents  for  examination  four  surfaces — a  superior,  an  inferior, 
an  anterior,  and  a  posterior. 

The  Superior  Surface  (Fig.   37). — In    front    is    seen   a   prominent   spine,  the 


THE   SPHENOID    BONE. 


73 


ethmoidal  spine,  for  articulation  -with  the  cribriform  plate  of  the  ethmoid;  behind 
this  a  smooth  surface  presenting,  in  the  median  line,  a  slight  longitudinal  eminence, 
with  a  depression  on  each  side  for  lodging  the  olfactory  lobes.  This  surface  is 
bounded  behind  by  a  ridge,  which  forms  the  anterior  border  of  a  narrow,  transverse 
groove,  the  optic  groove,  behind  which  lies  the  optic  commissure ;  the  ridge  terminates 
on  either  side  of  the  optic  foramen,  for  the  passage  of  the  optic  nerve  and  oph- 
thalmic artery.  Behind  the  optic  groove  is  a  small  eminence,  olive-like  in  shape, 
the  olivary  process;  and  still  more  posteriorly,  a  deep  depression,  the  pituitary 
fossa,  or  sella  turcica,  which  lodges  the  pituitary  body.  This  fossa  is  perforated 
by  numerous  foramina,  for  the  transmission  of  nutrient  vessels  into  the  substance 
of  the  bone.  It  is  bounded  in  front  by  two  small  eminences,  one  on  either  side, 
called  the  middle  clinoid  processes  {xlivq,  a  bed),  which  are  sometimes  connected 
by  a  spiculum  of  bone  to  the  anterior  clinoid  processes,  and  behind  by  a  square- 
shaped  plate  of  bone,  the  dorsum  ephippii  or  dorsum  sellce,  terminating  at  each 
superior  angle  in  a  tubercle,  the  posterior  clinoid  processes,  the  size  and  form  of 
which  vary  considerably  in  different  individuals.  These  processes  deepen  the 
pituitary  fossa,  and  serve  for  the  attachment  of  prolongations  from  the  tentorium 
cerebelli.  The  sides  of  the  dorsum  ephippii  are  notched  for  the  passage  of  the 
sixth  pair  of  nerves,  and  below  present  a  sharp  process,  the  petrosal  process,  which 
is  joined  to  the  apex  of  the  petrous  portion  of  the  temporal  bone,  forming  the  inner 
boundary  of  the  middle  lacerated  foramen.  Behind  .this  plate  the  bone  presents 
a  shallow  depression,  which  slopes  obliquely  backward,  and  is  continuous  with  the 
basilar  groove  of  the  occipital  bone ;  it  is  called  the  clivus,  and  supports  the  upper 
part  of  the  pons  Varolii.  On  either  side  of  the  body  is  a  broad  groove,  curved 
something  like  the  italic  letter  /;  it  lodges  the  internal  carotid  artery  and  the 
cavernous  sinus,  and  is  called  the  carotid  or  cavernous  groove.  Along  the  outer 
margin  of  this  groove,  at  its  posterior  part,  is  a  ridge  of  bone  in  the  angle  between 
the  body  and  greater  wing,  called  the  lingula.     The  posterior  surface,  quadrilateral 


Pterygoid  ridge 


Internal  pterygoid  plate. 
H  vmular  process. 


Fig.  38.  —  Sphenoid  bone.    Anterior  surface.1 


in  form,  is  :o  the  basilar  process  of  the  occipital  bone.     During  childhood 

these  bone      r<    •  ■  parated  by  a  layer  of  cartilage  ;  but  in  after-life  (between  the 
eighteentl  ^enty-fifth  y,ears)  th^  becomes  ossified,  ossification  commencing 

above  anc1  ling  downwa,  I  ;  and  the  two  bones  then  form  one  piece.     The 

anteri'-"  -  rface  (Fig.  38)  prest  Ire  middle  line,  a  vertical  ridge  of  bone,  the 

ire,  both  the  anterior  and  inferior  surfaces  of  the  body  of  the  sphenoid  bone  are 
;■'  eing  held  with  the  irocesses  almost  horizontal. 


74  THE  SKELETON. 

ethmoidal  crest,  which  articulates  in  front  with  the  perpendicular  plate  of  the 
ethmoid,  forming  part  of  the  septum  of  the  nose.  On  either  side  of  it  are  irregular 
openings  leading  into  the  sphenoidal  cells  or  sinuses.  These  are  two  large  irregular 
cavities  hollowed  out  of  the  interior  of  the  body  of  the  sphenoid  bone,  and  separated 
from  one  another  by  a  more  or  less  complete  perpendicular  bony  septum.  Their 
form  and  size  vary  considerably ;  they  are  seldom  symmetrical,  and  are  often 
partially  subdivided  by  irregular  osseous  laminae.  Occasionally,  they  extend  into 
the  basilar  process  of  the  occipital  nearly  as  far  as  the  foramen  magnum.  The 
septum  is  seldom  quite  vertical,  being  commonly  bent  to  one  or  the  other  side. 
These  sinuses  do  not  exist  in  children,  but  they  increase  in  size  as  age  advances. 
They  are  partially  closed,  in  front  and  below,  by  two  thin,  curved  plates  of  bone, 
the  sphenoidal  turbinated  bones,  leaving  a  round  opening  at  their  upper  parts,  by 
which  they  communicate  with  the  upper  and  back  part  of  the  nose,  and  occasionally 
with  the  posterior  ethmoidal  cells  or  sinuses.  The  lateral  margins  of  this  surface 
present  a  serrated  edge,  which  articulates  with  the  os  planum  of  the  ethmoid, 
completing  the  posterior  ethmoidal  cells ;  the  lower  margin,  also  rough  and 
serrated,  articulates  with  the  orbital  process  of  the  palate  bone,  and  the  upper 
margin  with  the  orbital  plate  of  the  frontal  bone.  The  inferior  surface  presents, 
in  the  middle  line,  a  triangular  spine,  the  rostrum,  which  is  continuous  with  the 
sphenoidal  crest  on  the  anterior  surface,  and  is  received  into  a  deep  fissure  betAveen 
the  alse  of  the  vomer.  On  each  side  may  be  seen  a  projecting  lamina  of  bone, 
which  runs  horizontally  inward  from  near  the  base  of  the  pterygoid  process  : 
these  plates,  termed  the  vaginal  processes,  articulate  with  the  edges  of  the  vomer. 
Close  to  the  root  of  the  pterygoid  process  is  a  groove,  formed  into  a  complete  canal 
when  articulated  with  the  sphenoidal  process  of  the  palate  bone ;  it  is  called  the 
ptery go-palatine  canal,  and  transmits  the  pterygo-palatine  vessels  and  pharyngeal 
nerve. 

The  Greater  Wings  are  two  strong  processes  of  bone  which  arise  from  the 
sides  of  the  body,  and  are  curved  in  a  direction  upward,  outward,  and  backward, 
being  prolonged  behind  into  a  sharp-pointed  extremity,  the  spinous  process  of  the 
sphenoid.  Each  wing  presents  three  surfaces  and  a  circumference.  The  superior 
or  cerebral  surface  (Fig.  37)  forms  part  of  the  middle  fossa  of  the  skull ;  it  is 
deeply  concave,  and  presents  eminences  and  depressions  for  the  convolutions  of  the 
brain.  At  its  anterior  and  internal  part  is  seen  a  circular  aperture,  the  foramen 
rotundum,  for  the  transmission  of  the  second  division  of  the  fifth  nerve.  Behind 
and  external  to  this  is  a  large  oval  foramen,  the  foramen  ovale,  for  the  trans- 
mission of  the  third  division  of  the  fifth  nerve,  the  small  meningeal  artery,  and 
sometimes  the  small  petrosal  nerve.1  At  the  inner  side  of  the  foramen  ovale  a 
small  aperture  may  occasionally  be  seen  opposite  the  root  of  the  pterygoid  process  ; 
it,  is  the  foramen  Vesalii,  transmitting  a  small  vein.  Lastly,  in  the  posterior  angle, 
near  to  the  spine  of  the  sphenoid,  is  a  short  canal,  sometimes  double,  the  foramen 
spftodMum ;  it  transmits  the  middle  meningeal  artery.  The  external  surface 
(Fig.  38)  is  convex,  and  divided  by  a  transverse  ridge,  the  pterygoid  ridge  or 
infratemporal  cxest,  into  two  portions.  The  superior  or  larger,  convex  from  above 
downward,  conca^^from  before  backward,  enters  into  the  formation  of  the 
temporal  fossa,  antfNrives  attachment  to  part  of  the  Temporal  muscle.  The 
inferior  portion,  smallest  in  size  and  concave,  enters  into  the  formation  of  the 
zygomatic  fossa,  and  affords  attachment  to  the  External  pterygoid  muscle.  It 
presents,  at  its  posterior  part,  a  sharp-pointed  eminence  of  bone,  the  spinous  proc- 
ess, to  which  are  connected  the  internal  lateral  ligament  of  the  lower  jaw  and  the 
Tensor  palati  muscle.  The  pterygoid  ridge,  dividing  the  temporal  and  zygomatic 
portions,  gives  attachment  to  part  of  the  External  pterygoid  muscle.  At  its  inner 
and  anterior  extremity  is  a  tria^glHar  spine  of  bone  which  serves  to  increase  the 
extent  of  origin  of  this  muscle.  The  anterior  or  orbital  surface,  smooth  and 
quadrilateral  in  form,  assists  in  forming  the  outer  wall  of  the  orbit.    It  is  bounded 

1  The  small  petrosal  nerve  sometimes  passes  through  a  special  foramen  betwef  •  +^e  foramen 
ovale  and  foramen  spinosum. 


THE   SPHENOID    BONE.  7o 

above  by  a  serrated  edge,  for  articulation  with  the  frontal  bone;  below,  bv  a 
rounded  border  which  enters  into  the  formation  of  the  spheno-maxillarv  fissure. 
Internally,  it  presents  a  sharp  border,  which  forms  the  lower  boundary  of  the 
sphenoidal  fissure,  and  has  projecting  from  about  its  centre  a  little  tubercle  of 
bone,  which  gives  origin  to  one  head  of  the  External  rectus  muscle  of  the  eve; 
and  at  its  upper  part  is  a  notch  for  the  transmission  of  a  recurrent  branch  of  the 
lachrymal  artery;  externally  it  presents  a  serrated  margin  for  articulation  with 
the  malar  bone.  One  or  two  small  foramina  may  occasionally  be  seen  for  the 
passage  of  branches  of  the  deep  temporal  arteries;  they  are  called  the  external 
orbital  foramina.  Circumference  of  the  great  tving  (Fig.  37),  commencing  from 
behind,  that  portion  of  the  circumference  from  the  body  of  the  sphenoid  to  the 
spine,  is  serrated  and  articulates  by  its  outer  half  with  the  petrous  portion  of  the 
temporal  bone,  while  the  inner  half  forms  the  anterior  boundary  of  the  foramen 
lacerum  medium,  and  presents  the  posterior  aperture  of  the  Vidian  canal  for  the 
passage  of  the  Vidian  nerve  and  artery.  In  front  of  the  spine  the  circumference 
of  the  great  wing  presents  a  serrated  edge,  bevelled  at  the  expense  of  the  inner 
table  below  and  of  the  external  above,  which  articulates  with  the  squamous  por- 
tion of  the  temporal  bone.  At  the  tip  of  the  great  wing  a  triangular  portion  is 
seen,  bevelled  at  the  expense  of  the  internal  surface,  for  articulation  with  the 
anterior  inferior  angle  of  the  parietal  bone.  Internal  to  this  is  a  triangular, 
serrated  surface,  for  articulation  with  the  frontal  bone :  this  surface  is  continuous 
internally  with  the  sharp  inner  edge  of  the  orbital  plate,  which  assists  in  the  for- 
mation of  the  sphenoidal  fissure,  and  externally  with  the  serrated  margin  for 
articulation  with  the  malar  bone. 

The  Lesser  Wings  {processes  of  Ingrassias)  are  two  thin,  triangular  plates  of 
bone  which  arise  from  the  upper  and  lateral  parts  of  the  body  of  the  sphenoid, 
and,  projecting  transversely  outward,  terminate  in  a  sharp  point  (Fig.  37).  The 
superior  surface  of  each  is  smooth,  flat,  broader  internally  than  externally,  and 
supports  part  of  the  frontal  lobe  of  the  brain.  The  inferior  surface  forms  the 
back  part  of  the  roof  of  the  orbit  and  the  upper  boundary  of  the  sphenoidal  fissure 
or  foramen  lacerum  anterius.  This  fissure  is  of  a  triangular  form,  and  leads  from 
the  cavity  of  the  cranium  into  the  orbit ;  it  is  bounded  internally  by  the  body  of 
the  sphenoid — above,  by  the  lesser  wing ;  below,  by  the  internal  margin  of  the 
orbital  surface  of  the  great  wing — and  is  converted  into  a  foramen  by  the  articu- 
lation of  this  bone  with  the  frontal.  It  transmits  the  third,  the  fourth,  the  three 
branches  of  the  ophthalmic  division  of  the  fifth,  the  sixth  nerve,  some  filaments 
from  the  cavernous  plexus  of  the  sympathetic,  the  orbital  branch  of  the  middle 
meningeal  artery,  a  recurrent  branch  from  the  lachrymal  artery  to  the  dura 
mater,  and  the  ophthalmic  vein.  The  anterior  border  of  the  lesser  wing  is  ser- 
rated for  articulation  with  the  frontal  bone ;  the  posterior,  smooth  and  rounded,  is 
received  into  the  fissure  of  Sylvius  of  the  brain.  The  inner  extremity  of  this 
border  forms  the  anterior  clinoid  process.  The  lesser  wing  is  connected  to  the 
side  of  the  body  by  two  roots,  the  upper  thin  and  flat,  the  lower  thicker,  obliquely 
directed,  and  presenting  on  its  outer  side,  near  its  junction  with  the  body,  a  small 
tubercle,  for  the  attachment  of  the  common  tendon  of  origin  of  three  of  the  muscles 
of  the  eye.  Between  the  two  roots  is  the  optic  foramen,  for  the  transmission  of 
the  optic  nerve  and  ophthalmic  artery. 

The  Pterygoid  Processes  (nreput;,  a  wing ;  elooz,  likeness),  one  on  each  side, 
descend  perpendicularly  from  the  point  where  the  body  and  greater  wing  unite 
(Fig.  39).  Each  process  consists  of  an  external  and  an  internal  plate,  which 
are  joined  together  by  their  anterior  borders  above,  but  are  separated  below, 
leaving  an  angular  cleft,  the  pterygoid  notch,  in  which  the  pterygoid  process  or 
tuberosity  of  the  palate  bone  is  received.  The  two  plates  diverge  from  each 
other  from  their  line  of  connection  in  front,  so  as  to  form  a  V-shaped  fossa,  the 
pterygoid  fossa.  The  external  pterygoid  plate  is  broad  and  thin,  turned  a  little 
outward,  and,  by  its  outer  surface,  forms  part  of  the  inner  wall  of  the  zygomatic 
fossa,  giving  attachment  to  the  External  pterygoid;   its  inner  surface  forms  part 


76 


THE  SKELETON. 


of  the  pterygoid  fossa,  and  gives  attachment  to  the  Internal  pterygoid.  The 
internal  pterygoid  plate  is  much  narrower  and  longer,  curving  outward,  at  its 
extremity,  into  a  hook-like  process  of  bone,  the  hamular  process,  around  which 
turns  the  tendon  of  the  Tensor  palati  muscle.  The  outer  surface  of  this  plate 
forms  part  of  the  pterygoid  fossa,  the  inner  surface  forming  the  outer  boundary 
of  the  posterior  aperture  of  the  nares.  On  the  posterior  surface  of  the  base  of 
the  process,  above  the  pterygoid  fossa,  is  a  small,  oval,  shallow  depression,  the 
scaphoid  fossa,  from  which  arises  the  Tensor  palati,  and  above  which  is  seen  the 


Fia.  39.— Sphenoid  bone.    Posterior  surface. 

posterior  orifice  of  the  Vidian  canal.  Below  and  to  the  inner  side  of  the  Vidian 
canal,  on  the  posterior  surface  of  the  base  of  the  internal  plate,  is  a  little  prom- 
inence, which  is  known  by  the  name  of  the  pterygoid  tubercle.  The  Superior 
constrictor  of  the  pharynx  is  attached  to  the  posterior  edge  of  the  internal 
plate.  The  anterior  surface  of  the  pterygoid  process  is  very  broad  at  its  base, 
and  forms  the  posterior  wall  of  the  sphenomaxillary  fossa.  It  supports  Meckel's 
ganglion.  It  presents,  above,  the  anterior  orifice  of  the  Vidian  canal ;  and  below, 
a  rough  margin,  which  articulates  with  the  perpendicular  plate  of  the  palate 
bone. 

The  Sphenoidal  Spongy  Bones  are  two  thin,  curved  plates  of  bones,  which  exist 
as  separate  pieces  until  puberty,  and  occasionally  are  not  joined  to  the  sphenoid 
in  the  adult.  They  are  situated  at  the  anterior  and  inferior  part  of  the  body  of 
the  sphenoid,  an  aperture  of  variable  size  being  left  in  their  anterior  wall,  through 
which  the  sphenoidal  sinuses  open  into  the  nasal  fossae.  They  are  irregular  in 
form  and  taper  to  a  point  behind,  being  broader  and  thinner  in  front.  Their 
upper  surface,  which  looks  toward  the  cavity  of  the  sinus,  is  concave ;  their  under 
surface  convex.  Each  bone  articulates  in  front  with  the  ethmoid,  externally  with 
the  palate ;  its  pointed  posterior  extremity  is  placed  above  the  vomer,  and  is 
received  between  the  root  of  the  pterygoid  process  on  the  outer  side  and  the 
rostrum  of  the  sphenoid  on  the  inner.1 

Development. — Up  to  about  the  eighth  month  of  foetal  life  the  sphenoid  bone 
consists  of  two  distinct  parts :  posterior  or  post-splienoid  part,  which  comprises 
the  pituitary  fossa,  the  greater  wings,  and  the  pterygoid  processes ;  and  an 
anterior  or  pre-sphenoid  part,  to  which  the  anterior  part  of  the  body  and  lesser 
wings  belong.  It  is  developed  by  fourteen  centres :  eight  for  the  posterior 
sphenoid  division,  and  six  for  the  anterior  sphenoid.  The  eight  centres  for  the 
posterior  sphenoid  are — one  for  each  greater  wing  and  external  pterygoid  plate, 
one  for  each  internal  pterygoid  plate,  two  for  the  posterior  part  of  the  body,  and 

1 A  small  portion  of  the  sphenoidal  turbinated  bone  sometimes  enters  into  th,e  formation  of  the 
inner  wall  of  the  orbit,  between  the  os  planum  of  the  ethmoid  in  front,  the  orbital  plate  of  the  palate 
below,  and  the  frontal  above. — Cleland,  Boy.  Soc.  Trans.,  1862. 


THE   ETHMOID    BONE.  77 

one  on  each  side  for  the  lingula.  The  six  for  the  anterior  sphenoid  are  one  for 
each  lesser  wing,  two  for  the  anterior  part  of  the  body,  and  one  for. each  sphenoidal 
turbinated  bone. 

Post-sphenoid  Division. — The  first  nuclei  to  appear  are  those  for  il 
wings  (ali- sphenoids).     They  make  their  appearance  between  the  fo) 
dum  and  foramen. ovale  about  the  eighth  week,  and  from  them  the  e: 
goid  plates  are  also  formed.      Soon  after,  the  nuclei  for  the  posterior  part  oi 
body  appear,  one  on  either  side  of  the  sella  turcica,  and  become  blended  together 
about  the  middle  of  foetal  life.     About  the  fourth  month  the  remaining  four  cen- 
tres appear,  those  for  the  internal  pterygoid  plates  being  ossified  in  membrane 
and  becoming  joined  to  the  external  pterygoid  plate  about  the  sixth  month.     The 
centres  for  the  lingulse  speedily  become  joined  to  the  rest  of  the  bone. 

one  for  each     two  for  anterior 
lesser  wing,    part  of  body. 
1      R 


/ 
/ 

one  for  each  internal,--''''  ' 

pterygoid  plate.       jng  \ 

one  for  for  ea°h  lingula.  \ 

each  great  wing  and  external  ptery- 
goid plate, 
one  for  each  Sphenoidal  turbinated  bone. 

Fig.  40.— Plan  of  the  development  of  sphenoid.    By  fourteen  centres. 

Dre-sphenoid  Division. — The  first  nuclei  to  appear  are  those  for  the  lesser 
wings  (orbito- sphenoids).  They  make  their  appearance  about  the  ninth  week,  at 
the  outer  borders  of  the  optic  foramina.  A  second  pair  of  nuclei  appear  on  the 
inner  side  of  the  foramina  shortly  after,  and,  becoming  united,  form  the  front 
part  of  the  body  of  the  bone.  The  remaining  two  centres  for  the  sphenoidal 
turbinated  bones  make  their  appearance  about  the  fifth  month.  At  birth  they 
consist  of  small  triangular  laminae,  and  it  is  not  till  the  third  year  that  they 
become  hollowed  out  and  cone-shaped.  About  the  fourth  year  they  become  fused 
with  the  lateral  masses  of  the  ethmoid,  and  hence,  from  an  embryological  point 
of  view,  may  be  regarded  as  belonging  to  the  ethmoid. 

The  pre-sphenoid  is  united  to  the  body  of  the  post-sphenoid  about  the  eighth 
month,  so  that  at  birth  the  bone  consists  of  three  pieces — viz.  the  body  in  the 
centre,  and  on  each  side  the  great  wings  with  the  pterygoid  processes.  The  lesser 
wings  become  joined  to  the  body  at  about  the  time  of  birth.  At  the  first  year 
after  birth  the  greater  wings  and  body  are  united.  From  the  tenth  to  the  twelfth 
year  the  spongy  bones  are  partially  united  to  the  sphenoid,  their  junction  being 
complete  by  the  twentieth  year.  Lastly,  the  sphenoid  joins  the  occipital  from  the 
eighteenth  to  the  twenty-fifth  year. 

Articulations. — The  sphenoid  articulates  with  all  the  bones  of  the  cranium, 
and  five  of  the  face — the  two  malar,  two  palate,  and  vomer :  the  exact  extent  of 
articulation  with  each  bone  is  shown  in  the  accompanying  figures.1 

Attachment  of  Muscles. — To  eleven  pairs  :  the  Temporal,  External  pterygoid. 
Internal  pterygoid,  Superior  constrictor,  Tensor  palati,  Levator  palpebrse,  <  >b- 
liquus  oculi  superior,  Superior  rectus,  Internal  rectus,  Inferior  rectus,  External 
rectus. 

The  Ethmoid  Bone. 

The  Ethmoid  (yjdpoz,  a  sieve)  is  an  exceedingly  light,  spongy  bone,  of  a  cubical 
form,  situated  at  the  anterior  part  of  the  base  of  th.j  cranium,  between  the  two 

1  It  also  sometimes  articulates  with  the  tuberosity  of  the  superior  maxilla. 


78 


THE  SKELETON. 


With  inferior  turbinated  bone. 

Outer  surface  of  right  lateral  mass 


Fig.  41.  — Ethmoid  bone, 
(enlarged). 


orbits,  at  the  root  of  the  nose,  and  contributing  to  form  each  of  these  cavities. 
It  consists  of  three  parts :  a  horizontal  plate,  which  forms  part  of  the  base  of 
the  cranium;  a  perpendicular  plate,  which  forms  part  of  the  septum  nasi;  and 
two  lateral  masses  of  cells. 

The  Horizontal  or  Cribriform  Plate  (Fig.  41)  forms  part  of  the  anterior  fossa 
of  the  base  of  the  skull,  and  is  received  into  the  ethmoid  notch   of  the  frontal 

bone  between  the  two  orbital 
plates.  Projecting  upward 
from  the  middle  line  of  this 
plate  is  a  thick,  smooth,  tri- 
angular process  of  bone,  the 
crista  galli,  so  called  from  its 
resemblance  to  a  cock's  comb. 
Its  base  joins  the  cribriform 
plate.  Its  posterior  border, 
long,  thin,  and  slightly  curved, 
serves  for  the  attachment  of 
the  falx  cerebri.  Its  anterior 
border,  short  and  thick,  articu- 
lates with  the  frontal  bone, 
and  presents  two  small  project- 
ing alse,  which  are  received 
into  corresponding  depressions 
in  the  frontal,  completing  the 
foramen  caecum  behind.  Its 
sides  are  smooth  and  some- 
times bulging ;  in  which  case  it  is  found  to  enclose  a  small  sinus.1  On  each  side 
of  the  crista  galli  the  cribriform  plate  is  narrow  and  deeply  grooved,  to  support 
the  bulb  of  the  olfactory  tract,  and  perforated  by  foramina  for  the  passage  of  the 
olfactory  nerves.  These  foramina  are  arranged  in  three  rows :  the  innermost, 
which  are  the  largest  and  least  numerous,  are  lost  in  grooves  on  the  upper  part 
of  the  septum ;  the  foramina  of  the  outer  row  are  continued  on  to  the  surface  of 
the  upper  spongy  bone.  The  foramina  of  the  middle  row  are  the  smallest ;  they 
perforate  the  bone  and  transmit  nerves  to  the  roof  of  the  nose.  At  the  front  part 
of  the  cribriform  plate,  on  each  side  of  the  crista  galli,  is  a  small  fissure,  which 
transmits  the  nasal  branch  of  the  ophthalmic  nerve ;  and  at  its  posterior  part  a 
a  triangular  notch,  which  receives  the  ethmoidal  spine  of  the  sphenoid. 

The  Perpendicular  Plate  (Fig.  42)  is  a  thin,  flattened  lamella  of  bone,  which 
descends  from  the  under  surface  of  the  cribriform  plate,  and  assists  in  forming 
the  septum  of  the  nose.  It  is  much  thinner  in  the  middle  than  at  the  circum- 
ference, and  is  generally  deflected  a  little  to  one  side.  Its  anterior  border  articu- 
lates with  the  nasal  spine  of  the  frontal  bone  and  crest  of  the  nasal  bones.  Its 
posterior  border,  divided  into  two  parts,  articulates  by  its  upper  half  with  the 
sphenoidal  crest  of  the  sphenoid,  by  its  lower  half  with  the  vomer.  The  inferior 
border  serves  for  the  attachment  of  the  triangular  cartilage  of  the  nose.  On  each 
side  of  the  perpendicular  plate  numerous  grooves  and  canals  are  seen,  leading  from 
foramina  on  the  cribriform  plate;  they  lodge  filaments  of  the  olfactory  nerves. 

The  Lateral  Masses  of  the  ethmoid  consist  of  a  number  of  thin-walled  cellular 
cavities,  the  ethmoidal  cells,  interposed  between  two  vertical  plates  of  bone,  the 
outer  one  of  which  forms  part  of  the  orbit,  and  the  inner  one  part  of  the  nasal 
fossa  of  the  corresponding  side.  In  the  disarticulated  bone  many  of  these 
cells  appear  to  be  broken ;  but  when  the  bones  are  articulated  they  are  closed 
in  at  every  part,  exctot  where  they  open  into  the  nasal  fossae.  The  upper 
surface  of  each  lateral  mass  presents  a  number  of  apparently  half-broken  cel- 

1  Sir  George  Humphry  states  that  the  crista  galli  is  commonly  inclined  to  one  side,  usually 
the  opposite  to  that  toward  which  the  lower  part  of  the  perpendicular  plate  is  bent. — The  Human 
Skeleton,  1858,  p.  277. 


THE   ETHMOID    BONE. 


79 


yjith  Ethmoidal 


Fig.  42. — Perpendicular  plate  of  ethmoid    (enlarged),  shown  by 
removing  the  right  lateral  mass. 


lular  spaces ;  these  are  closed  in  when  articulated  by  the  edges  of  the  eth- 
moidal notch  of  the  frontal  bone.  Crossing  this  surface  are  tA\o  grooves  on 
each  side,  converted  into  canals  by  articulation  with  the  frontal ;  they  are  the 
anterior  and  posterior  ethmoidal  canals,  and  open  on  the  inner  wall  of  the 
orbit.     The  posterior  surface  also  presents  large,  irregular  cellular  cavities,  which 

are  closed  in  by  articula- 
tion with  the  sphenoidal 
turbinated  bones  and  orbi- 
tal process  of  the  palate. 
The  cells  at  the  anterior 
surface  are  completed  by 
the  lachrymal  bone  and 
nasal  process  of  the  supe- 
rior maxillary,  and  those 
below  also  by  the  superior 
maxillary.  The  outer  sur- 
face of  each  lateral  mass 
is  formed  of  a  thin,  smooth, 
oblong  plate  of  bone,  called 
the  os  planum;  it  forms 
part  of  the  inner  Avail  of 
the  orbit,  and  articulates, 
above,  with  the  orbital 
plate  of  the  frontal ;  below. 
with  the  superior  maxil- 
lary ;  in  front,  with  the  lachrymal ;  and  behind,  with  the  sphenoid  and  orbital 
process  of  the  palate. 

From  the  inferior  part  of  each  lateral  mass,  immediately  beneath  the  os  planum, 
there  projects  downward  and  backward  an  irregular  lamina  of  bone,  called  the 
unciform  process,  from  its  hook-like  form :  it  serves  to  close  in  the  upper  part  of 
the  orifice  of  the  antrum,  and  articulates  with  the  ethmoidal  process  of  the  inferior 
turbinated  bone.     It  is  often  broken  in  disarticulating  the  bones. 

The  inner  surface  of  each  lateral  mass  forms  part  of  the  outer  wall  of  the  nasal 
fossa  of  the  corresponding  side.  It  is  formed  of  a  thin  lamella  of  bone,  which 
descends  from  the  under  surface  of  the  cribriform  plate,  and  terminates  below  in 
a  free,  convoluted  margin,  the  middle  turbinated  bone.  The  whole  of  this  sur- 
face is  rough  and  marked  above  by  numerous  grooves,  which  run  nearly  verti- 
cally downward  from  the  cribriform 
plate ;  they  lodge  branches  of  the 
olfactory  nerve,  which  are  distributed 
on  the  mucous  membrane  covering  the 
bone.  The  back  part  of  this  surface 
is  subdivided  by  a  narrow  oblique 
fissure,  the  superior  meatus  of  the 
nose,  bounded  above  by  a  thin,  curved 
plate  of  bone,  the  superior  turbinated 
bone.  By  means  of  an  orifice  at  the 
upper  part  of  this  fissure  the  posterior 
ethmoidal  cells  open  into  the  nose. 
Below,  and  in  front  of  the  superior 
meatus,  is  seen  the  convex  surface  of 
the  middle  turbinated  bone.  It  extends 
along  the  whole  length  of  the  inner  surface  of  each  lateral  mass ;  its  loAver  mar- 
gin is  free  and  thick,  and  its  concavity,  directed  outward,  assists  in  forming  the 
middle  meatus.  It  is  by  a  large  orifice  at  the  upper  and  front  part  of  the  middle 
meatus  that  the  anterior  ethmoidal  cells,  and  through  them  the  frontal  sinuses, 
communicate  with  the  nose  by  means  of  a  funnel-shaped  canal,  the  infundibulum. 


Fig.  43.  —  Ethmoid   bone.    Inner  surface    of  right 
lateral  mass  (enlarged). 


80  THE  SKELETON. 

The  cellular  cavities  of  each  lateral  mass,  thus  walled  in  by  the  os  planum  on  the 
outer  side  and  by  the  other  bones  already  mentioned,  are  divided  by  a  thin  trans- 
verse bony  partition  into  two  sets,  which  do  not  communicate  with  each  other; 
they  are  termed  the  anterior  and  posterior  ethmoidal  cells  or  sinuses.  The  former, 
more  numerous,  communicate  with  the  frontal  sinuses  above  and  the  middle 
meatus  below  by  means  of  a  long,  flexuous  canal,  the  infimdibulum  ;  the  posterior, 
less  numerous,  open  into  the  superior  meatus,  and  communicate  (occasionally) 
with  the  sphenoidal  sinuses. 

Development. — By  three  centres :  one  for  the  perpendicular  lamella,  and  one 
for  each  lateral  mass. 

The  lateral  masses  are  first  developed,  ossific  granules  making  their  appearance 
in  the  os  planum  between  the  fourth  and  fifth  months  of  foetal  life,  and  extending 
into  the  spongy  bones.  At  birth  the  bone  consists  of  the  two  lateral  masses, 
which  are  small  and  ill-developed.  During  the  first  year  after  birth  the  perpen- 
dicular plate  and  crista  galli  begin  to  ossify,  from  a  single  nucleus,  and  become 
joined  to  the  lateral  masses  about  the  beginning  of  the  second  year.  The  cribri- 
form plate  is  ossified  partly  from  the  perpendicular  plate  and  partly  from  the 
lateral  masses.  The  formation  of  the  ethmoidal  cells,  which  completes  the  bone, 
does  not  commence  until  about  the  fourth  or  fifth  year. 

Articulations. — With  fifteen  bones  :  the  sphenoid,  two  sphenoidal  turbinated,  the 
frontal,  and  eleven  of  the  face — the  two  nasal,  two  superior  maxillary,  two  lachry- 
mal, two  palate,  two  inferior  turbinated,  and  the  vomer.  No  muscles  are  attached 
to  this  bone. 

DEVELOPMENT  OF  THE  CRANIUM. 

The  early  stages  of  the  development  of  the  cranium  have  already  been  described.  Y\Te 
have  seen  that  it  is  formed  from  a  layer  of  mesoblast,  derived  from  the  protovertebral  plates 
of  the  trunk,  which  is  spread  over  the  whole  surface  of  the  rudimentary  brain.  That  por- 
tion of  this  layer  from  which  the  bones  of  the  skull  are  to  be  developed  consists  of  a  thin, 
membranous  capsule. 

Ossification  commences  in  the  roof,  and  is  preceded  by  the  deposition  of  a  membranous 
blastema  upon  the  surface  of  the  cerebral  capsule,  in  which  the  ossifying  process  extends,  the 
primitive  membranous  capsule  becoming  the  internal  periosteum,  and  being  ultimately  blended 
with  the  dura  mater.  The  ossification  of  the  bones  of  the  base  takes  place  for  the  most  part 
in  cartilage,  and  although  the  bones  of  the  vertex  of  the  skull  appear  before  those  at  the  base, 
and  make  considerable  progress  in  their  growth,  at  birth  ossification  is  more  advanced  in  the 
base,  this  portion  of  the  skull  forming  a  solid,  immovable  groundwork. 

The  Fontanelles. 

Before  birth  the  bones  at  the  vertex  and  side  of  the  skull  are  separated  from  each  other  by 
membranous  intervals  in  which  bone  is  deficient.  These  intervals  are  principally  found  at  the 
four  angles  of  the  parietal  bones.     Hence  there  are  six  fontanelles.     Their  formation  is  due  to 


Fig.  44.— Skull  at  birth,  showing  the  anterior  Fig.  45 — The  lateral  fontanelles. 

and  posterior  fontanelles. 

the  wave  of  ossification  being  circular  and  the  bones  quadrilateral ;  the  ossific  matter  first  meets 
at  the  margins  of  the  bones,  at  the  points  nearest  to  their  centres  of  ossification,  and  vacuities 


THE   NASAL    BONE.  81 

or  spaces  are  left  at  the  angles,  which  are  called  fontanelles,  so  named  from  the  pulsations  of 
the  brain,  which  are  perceptible  at  the  anterior  fontanelle,  were  likened  to  the  rising  of  water 
in  a  fountain.  The  anterior  fontanelle  is  the  largest;  it  is  lozenge-shaped,  and  corresponds  to 
the  junction  of _ the  sagittal  and  coronal  sutures;  the  posterior  fontanelle,  of  smaller  size,  is 
triangular,  and  is  situated  at  the  junction  of  the  sagittal  and  lambdoid  sutures:  the  remaining 
ones  are  situated  at  the  inferior  angles  of  each  parietal  bone.  The  latter  are  closed  soon  after 
birth ;  the  two  at  the  two  superior  angles  remain  open  longer ;  the  posterior  being  closed  in  a 
few  months  after  birth  ;  the  anterior  remaining  open  until  the  first  or  second  year.  These 
spaces  are  gradually  filled  in  by  an  extension  of  the  ossifying  process  or  by  the  development  of 
a  Wormian  bone.  Sometimes  the  anterior  fontanelle  remains  open  beyond  two  years,  and  is 
occasionally  persistent  throughout  life. 

Supernumerary  or  Wormian1  Bones. 

In  addition  to  the  constant  centres  of  ossification  of  the  skull,  additional  ones  are  occasion- 
ally found  in  the  course  of  the  sutures.  These  form  irregular,  isolated  bones,  interposed  between 
the  cranial  bones,  and  have  been  termed  Wormian  bones  or  ossa  triquetra.  They  are  most 
frequently  found  in  the  course  of  the  lambdoid  suture,  but  occasionally  also  occupy  the  situation 
of  the  fontanelles,  especially  the  posterior  and,  more  rarely,  the  anterior.  Frequently  one  is 
found  between  the  anterior  inferior  angle  of  the  parietal  bone  and  the  greater  wing  of  the 
sphenoid,  the  pterion  ossicle  (Fig.  45).  They  have  a  great  tendency  to  be  symmetrical  on  the 
two  sides  of  the  skull,  and  they  vary  much  in  size,  being  in  some  cases  not  larger  than  a  pin's 
head,  and  confined  to  the  outer  table  ;  in  other  cases  so  large  that  one  pair  of  these  bones  may 
form  the  whole  of  the  occipital  bone  above  the  superior  curved  lines,  as  described  by  Beelard 
and  Ward.  Their  number  is  generally  limited  to  two  or  three,  but  more  than  a  hundred  have 
been  found  in  the  skull  of  an  adult  hydrocephalic  skeleton.  In  their  development,  structure, 
and  mode  of  articulation  they  resemble  the  other  cranial  bones. 

Congenital  Fissures  and  Gaps. 
An  arrest  in  the  ossifying  process  may  give  rise  to  deficiencies  or  gaps;  or  to  fissures,  which 
are  of  importance  in  a  medicodegal  point  of  view,  as  they  are  liable  to  be  mistaken  for  fractures. 
The  fissures  generally  extend  from  the  margins  toward  the  centre  of  the  bone,  but  the  gaps 
may  be  found  in  the  middle  as  well  as  at  the  edges.  In  course  of  time  they  may  become  covered 
with  a  thin  lamina  of  bone. 

BONES  OF  THE  FACE. 

The  Facial  Bones  are  fourteen  in  number — viz.  the 
Two  Nasal.  Two  Palate. 

Two  Superior  Maxillary.  Two  Inferior  Turbinated. 

Two  Lachrymal.  Vomer. 

Two  Malar.  Inferior  Maxillary. 

"  Of  these,  the  upper  and  lower  jaws  are  the  fundamental  bones  for  mastication, 
and  the  others  are  accessories ;  for  the  chief  function  of  the  facial  bones  is  to 
provide  an  apparatus  for  mastication,  while  subsidiary  functions  are  to  provide  for 
the  sense-organs  (eye,  nose,  tongue)  and  a  vestibule  to  the  respiratory  and  vocal 
organs.  Hence  the  variations  in  the  shape  of  the  face  in  man  and  the  lower 
animals  depend  chiefly  on  the  question  of  the  character  of  their  food  and  their  mode 
of  obtaining  it."2 

The  Nasal  Bone. 

The  Nasal  (nasus,  the  nose)  are  two  small  oblong  bones,  varying  in  size  and 
form  in  different  individuals;  they  are  placed  side  by  side  at  the  middle  ami  upper 
part  of  the  face,  forming,  by  their  junction,  "the  bridge"  of  the  nose  (Fig.  40). 
Each  bone  presents  for  examination  two  surfaces  and  four  borders.  The  outer 
surface  is  concave  from  above  downward,  convex  from  side  to  side ;  it  is  covered 
by  the  Pyramidalis  and  Compressor  nasi  muscles,  and  gives  attachment  at  its 
upper  part  to  a  few  fibres  of  the  Occipito-frontalis  muscle  (Theile).  It  is  marked 
by  numerous  small  arterial  furrows,  and  perforated  about  its  centre  by  a  foramen, 
sometimes  double,  for  the  transmission  of  a  small  vein.  The  inner  surface  is 
concave  from   side  to  side,  convex   from   above  downward;    in  which  direction 

1  Wormius,  a  physician  in  Copenhagen,  is  said  to  have  given  the  first  detailed  description  of 
these  bones. 

2  W.  W.  Keen,  American  edition   p.  185. 

6 


82 


THE   SKELETON. 


it  is  traversed  by  a  longitudinal"  groove  (sometimes  a  canal),  for  the  passage 
of  a  branch  of  the  nasal  nerve.  The  superior  border  is  narrow,  thick,  and 
serrated,  for  articulation  with  the  nasal  notch  of  the  frontal  bone.      The  inferior 


Nasal  bone. 
Xasal  proc. — 


Lachrymal  bone. 


Orbital  surface. 
Infra-orbital 
groove. 


Infra-orbital 
foramen. 


Ant.  nasal  spine. 


Artie,  u-ith  malar. 


Maxillary 
tuberosity. 


With  frontal  bone. 


With 
'opposite  bone. 


Fig.  46.— Nasal  and  lachrymal  bone  in  situ. 

border  is  broad,  thin,  sharp,  inclined  obliquely  downward,  outward,  and  back- 
ward, and  serves  for  the  attachment  of  the  lateral  cartilage  of  the  nose.  This 
border  presents,  about  its  middle,  a  notch,  through  which  passes  the  branch  of  the 
nasal  nerve  above  referred  to,  and  is  prolonged  at  its  inner  extremity  into  a  sharp 

spine,  which,  when  articulated 
with  the  opposite  bone,  forms 
the  nasal  angle.  The  external 
border  is  serrated,  bevelled  at 
the  expense  of  the  internal  sur- 
face above  and  of  the  external 
below,  to  articulate  with  the 
nasal  process  of  the  superior 
maxillary.  The  internal  bor- 
der, thicker  above  than  below, 
articulates  with  its  fellow  of 
the  opposite  side,  and  is  pro- 
longed behind  into  a  vertical 
crest  which  forms  part  of  the 
septum  of  the  nose ;  this  crest  articulates  above  downward  with  the  nasal  spine 
of  the  frontal  above,  and  the  perpendicular  plate  of  the  ethmoid,  and  the  trian- 
gular septal  cartilage  of  the  nose. 

Development. — By  one  centre  for  each  bone,  which  appears  about  the  eighth 
week. 

Articulations. — With  four  bones  :  two  of  the  cranium,  the  frontal  and  ethmoid, 
and  two  of  the  face,  the  opposite  nasal  and  the  superior  maxillary. 

Attachment  of  Muscles. — A  few  fibres  of  the  Occipito-frontalis  muscle. 


1/ 


Outer  Surface. 
Fig.  47.— Right  nasal  bone. 


With 
frontal  spine. 

Crest. 

With 
perpendicular 
plate  of 
ethmoid. 


Groove  for  nasal  nerve. 


Liner  Surface. 

Fig.  48.— Left  nasal  bone. 


THE   SUPERIOR    MAXILLARY  BONES. 


83 


The  Superior  Maxillary  Bones  or  Maxillae. 

The  Superior  Maxillary  {maxilla,  the  jaw-bone)  are  the  most  important  bones 
of  the  face  from  a  surgical  point  of  view,  on  account  of  the  number  of  diseases  to 
which  some  of  their  parts  are  liable.  Their  careful  examination  becomes,  there- 
fore, a  matter  of  considerable  interest.  They  are  the  largest  bones  of  the  face, 
excepting  the  lower  jaw,  and  form,  by  their  union,  the  whole  of  the  upper  jaw. 
Each  bone  assists  in  the  formation  of  three  cavities,  the  roof  of  the  mouth,  the 
floor  and  outer  wall  of  the  nasal  fossae,  and  the  floor  of  the  orbit,  and  also  enters 
into  the  formation  of  two  fossae,  the  zygomatic  and  spheno-maxillary,  and  two 
fissures,  the  spheno-maxillary  and  pterygo-maxillary. 

The  bone  presents  for  examination  a  body  and  four  processes — malar,  nasal, 
alveolar,  and  palate. 

The  body  is  somewhat  cuboid,  and  is  hollowed  out  in  its  interior  to  form  a 
large  cavity,  the  antrum  of  Higlimore.  Its  surfaces  are  four — an  external  or 
facial,  a  posterior  or  zygomatic,  a  superior  or  orbital,  and  an  internal  or  nasal. 

The  external  or  facial  surface  (Fig.  49)  is  directed  forward  and  outward. 
It  presents  at  its  lower  part  a  series  of  eminences  corresponding  to  the  position 
of  the  teeth.  Just  above  those  for  the  incisor  teeth  is  a  depression,  the  incisive 
or  myrtiform  fossa,  which  gives  origin  to  the  Depressor  alae  nasi ;  and  below 
it  to  the  alveolar  border  is  attached  a  slip  of  the  Orbicularis  oris.  Above  and 
a  little  external  to  it  the  Compressor  nasi  arises.  More  external  is  another 
depression,  the  canine  fossa,  larger  and  deeper  than  the  incisive  fossa,  from  which 


Outer  Surface. 


TENDO    OOULI 


Incisive  fossa, 


Posterior  dental 
canals. 


Maxillary  tuberosity. 


Cani 


ne.    Bicuspids 


MOW 


Fig.  49.— Left  superior  maxillary  bone.    Outer  surface. 

it  is  separated  by  a  vertical  ridge,  the  canine  eminence,  corresponding  to  the 
socket  of  the  canine  tooth.  The  canine  fossa  gives  origin  to  the  Levator  anguli 
oris.  Above  the  canine  fossa  is  the  infraorbital  foramen,  the  termination  of  the 
infraorbital  canal;  it  transmits  the  infraorbital  vessels  and  nerve.  Sometimes  the 
infraorbital  canal  opens  by  two,  very  rarely  by  three,  orifices  on  the  face.  Above 
the  infraorbital  foramen  is  the  margin  of  the  orbit,  which  affords  partial  attach- 
ment to  the  Levator  labii  superioris  proprius.      To  the  sharp  margin  of  bone 


84 


THE   SKELETON. 


which  bounds  this  surface  in  front  and  separates  it  from  the  internal  surface  is 
attached  the  Dilator  naris  posterior. 

The  posterior  or  zygomatic  surface  is  convex,  directed  backward  and  outward, 
and  forms  part  of  the  zygomatic  fossa.  It  is  separated  from  the  facial  surface  by 
a  strong  ridge  of  bone,  which  extends  upward  from  the  socket  of  the  second  molar 
tooth.  It  presents  about  its  centre  several  apertures  leading  to  canals  in  the 
substance  of  the  bone ;  they  are  termed  the  posterior  dental  canals,  and  transmit 
the  posterior  dental  vessels  and  nerves.  At  the  lower  part  of  this  surface  is  a 
rounded  eminence,  the  maxillary  tuberosity,  especially  prominent  after  the  growth 
of  the  wisdom-tooth,  rough  on  its  inner  side  for  articulation  with  the  tuberosity 
of  the  palate  bone,  and  sometimes  with  the  external  pterygoid  plate.  It  gives 
attachment  to  a  few  fibres  of  origin  of  the  Internal  pterygoid  muscle.  Imme- 
diately above  this  is  a  smooth  surface,  which  forms  the  anterior  boundary  of  the 
spheno-maxillary  fossa;  it  presents  a  groove  which,  running  obliquely  downward, 
is  converted  into  a  canal  by  articulation  with  the  palate-bone,  forming  the  posterior 
palatine  canal. 

The  superior  or  orbital  surface  is  thin,  smooth,  triangular,  and  forms  part  of 
the  floor  of  the  orbit.  It  is  bounded  internally  by  an  irregular  margin  which 
in  front  presents  a  notch,  the  lachrymal  notch,  which  receives  the  lachrymal  bone ; 
in  the  middle  articulates  with  the  os  planum  of  the  ethmoid,  and  behind  with  the 
orbital  process  of  the  palate  bone  ;  bounded  externally  by  a  smooth,  rounded  edge 
which  enters  into  the  formation  of  the  spheno-maxillary  fissure,  and  which  some- 
times articulates  at  its  anterior  extremity  with  the  orbital  plate  of  the  sphenoid ; 
bounded  in  front  by  part  of  the  circumference  of  the  orbit,  which  is  continuous 
on  the  inner  side  with  the  nasal,  on  the  outer  side  with  the  malar,  process.  Along 
the  middle  line  of  the  orbital  surface  is  a  deep  groove,  the  infraorbital,  for  the 
passage  of  the  infraorbital  vessels  and  nerve.  The  groove  commences  at  the  mid- 
dle of  the  outer  border  of  this  surface,  and,  passing  forward,  terminates  in  a  canal, 
which  subdivides  into  two  branches.      One  of  the  canals,  the  infraorbital,  opens 


tfjiM-c 


Bones  partially  closing  orifice  of  antrum 
marked  in  outline. 


Ethmoid. 

Inferior  turbinated. 

Palate. 


Anterior  nasal  spine. 


Bristle  passed 
through  anterior 
palatine  canal. 


Fig.  50.— Left  superior  maxillary  bone.    Internal  surface. 


just  below  the  margin  of  the  orbit ;  the  other,  which  is  smaller,  runs  downward 
in  the  substance  of  the  anterior  wall  of  the  antrum;  it  is  called  the  anterior  dental 
canal,  and  transmits  the  anterior  dental  vessels  and  nerve  to  the  front  teeth  of 


THE   SUPERIOR    MAXILLARY  BONES.  85 

the  upper  jaw.  From  the  back  part  of  the  infraorbital  canal  a  second  small 
canal  is  sometimes  given  off,  -which  runs  down-ward  in  the  outer  wall  of  the 
antrum,  and  conveys  the  middle  dental  nerve  to  the  bicuspid  teeth.  Occasion- 
ally this  canal  is  derived  from  the  anterior  dental.  At  the  inner  and  fore  part 
of  the  orbital  surface,  just  external  to  the  lachrymal  groove  for  the  nasal  duct,  is 
a  depression  Avhich  gives  origin  to  the  Inferior  oblique  muscle  of  the  eye. 

The  internal  surface  (Fig.  50)  is  unequally  divided  into  two  parts  by  a  hori- 
zontal projection  of  bone,  the  palate  process  :  the  portion  above  the  palate  process 
forms  part  of  the  outer  wall  of  the  nasal  fossae ;  that  below  it  forms  part  of  the 
cavity  of  the  mouth.  The  superior  division  of  this  surface  presents  a  large,  irreg- 
ular opening  leading  into  the  antrum  of  Highmore.  At  the  upper  border  of  this 
aperture  are  numerous  broken  cellular  cavities,  which  in  the  articulated  skull  are 
closed  in  by  the  ethmoid  and  lachrymal  bones,  Below  the  aperture  is  a  smooth 
concavity  which  forms  part  of  the  inferior  meatus  of  the  nasal  fossae,  and  behind 
it  is  a  rough  surface  which  articulates  with  the  perpendicular  plate  of  the  palate 
bone,  traversed  by  a  groove  which,  commencing  near  the  middle  of  the  posterior 
border,  runs  obliquely  downward  and  forward,  and  forms,  when  completed  by  its 
articulation  with  the  palate  bone,  the  posterior  palatine  canal.  In  front  of  the 
opening  of  the  antrum  is  a  deep  groove,  converted  into  a  canal  by  the  lachrymal 
and  inferior  turbinated  bones.  It  is  called  the  lachrymal  groove,  and  lodges  the 
nasal  duct.  More  anteriorly  is  a  well-marked  rough  ridge,  the  inferior  turbinated 
crest,  for  articulation  with  the  inferior  turbinated  bone.  The  shallow  concavity  above 
this  ridge  forms  part  of  the  middle  meatus  of  the  nose,  while  that  below  it  forms 
part  of  the  inferior  meatus.  The  portion  of  this  surface  below  the  palate  process 
is  concave,  rough  and  uneven,  and  perforated  by  numerous  small  foramina  for  the 
passage  of  nutrient  vessels.     It  enters  into  the  formation  of  the  roof  of  the  mouth. 

The  Antrum  of  Highmore,  or  Maxillary  Sinus,  is  a  large,  pyramidal  cavity 
hollowed  out  of  the  body  of  the  maxillary  bone  :  its  apex,  directed  outward,  is 
formed  by  the  malar  process  ;  its  base,  by  the  outer  wafll  of  the  nose.  Its  walls 
are  everywhere  exceedingly  thin,  and  correspond  to  the  orbital,  facial,  and  zygo- 
matic surfaces  of  the  body  of  the  bone.  Its  inner  wall,  or  base,  presents,  in  the 
disarticulated  bone,  a  large,  irregular  aperture,  which  communicates  with  the 
nasal  fossa.  The  margins  of  this  aperture  are  thin  and  ragged,  and  the  aperture 
itself  is  much  contracted  by  its  articulation  with  the  ethmoid  above,  the  inferior 
turbinated  below,  and  the  palate  bone  behind.1  In  the  articulated  skull  this  cavity 
communicates  with  the  middle  meatus  of  the  nasal  fossae,  generally  by  two  small 
apertures  left  between  the  above-mentioned  bones.  In  the  recent  state  usually 
only  one  small  opening  exists,  near  the  upper  part  of  the  cavity,  sufficiently  large 
to  admit  the  end  of  a  probe,  the  other  being  closed  by  the  lining  membrane  of 
the  sinus. 

Crossing  the  cavity  of  the  antrum  are  often  seen  several  projecting  laminae  of 
bone,  similar  to  those  seen  in  the  sinuses  of  the  cranium  ;  and  on  its  posterior  wall 
are  the  posterior  dental  canals,  transmitting  the  posterior  dental  vessels  and  nerves 
to  the  teeth.  Projecting  into  the  floor  are  several  conical  processes,  corresponding 
to  the  roots  of  the  first  and  second  molar  teeth  ;2  in  some  cases  the  floor  is  perfo- 
rated by  the  teeth  in  this  situation. 

It  is  from  the  extreme  thinness  of  the  walls  of  this  cavity  that  we  are  enabled  to  explain 
how  a  tumor  growing  from  the  antrum  encroaches  upon  the  adjacent  parts,  pushing  up  the  floor 
of  the  orbit,  and  displacing  the  eyeball,  projecting  inward  into  the  nose,  protruding  forward  on 
to  the  cheek,  and  making  its  way  backward  into  the  zygomatic  fossa  and  downward  into  the 
mouth. 

The  Malar  Process  is  a  rough,  triangular  eminence,  situated  at  the  angle  of 

1  In  some  cases,  at  any  rate,  the  lachrymal  bone  encroaches  slightly  on  the  anterior  superior  por- 
tion of  the  opening,  and  assists  in  forming  the  inner  wall  of  the  antrum. 

2  The  number  of  teeth  whose  fangs  are  in  relation  with  the  floor  of  the  antrum  is  variable.  _  The 
antrum  "  may  extend  so  as  to  be  in  relation  to  all  the  teeth  of  the  true  maxilla,  from  the  canine  to 
the  dens  sapientice."  (See  Mr.  Salter  on  Abscess  of  the  Antrum,  in  a  System  of  Surgery,  edited  by  T. 
Holmes,  2d  ed.  vol.  iv.  p.  356.) 


86 


THE   SKELETON. 


separation  of  the  facial  from  the  zygomatic  surface.  In  front  it  is  concave,  form- 
ing part  of  the  facial  surface ;  behind  it  is  also  concave,  and  forms  part  of  the 
zygomatic  fossa ;  above  it  is  rough  and  serrated  for  articulation  with  the  malar 
bone ;  whilst  below  a  prominent  ridge  marks  the  division  between  the  facial  and 
zygomatic  surfaces.  A  small  part  of  the  Masseter  muscle  arises  from  this  process. 
The  Nasal  Process  is  a  strong,  triangular  plate  of  bone,  which  projects  upward, 
inward,  and  backward  by  the  side  of  the  nose,  forming  part  of  its  lateral  boundary. 
Its  external  surface  is  concave,  smooth,  perforated  by  numerous  foramina,  and  gives 
attachment  to  the  Levator  labii  superioris  alaeque  nasi,  the  Orbicularis  palpe- 
brarum, and  Tendo  oculi.  Its  internal  surface  forms  part  of  the  outer  wall  of 
the  nasal  fossae  :  at  its  upper  part  it  presents  a  rough,  uneven  surface,  which  ar- 
ticulates with  the  ethmoid  bone,  closing  in  the  anterior  ethmoidal  cells;  below  this 
is  a  transverse  ridge,  the  superior  turbinated  crest,  for  articulation  with  the  mid- 
dle turbinated  bone  of  the  ethmoid,  bounded  below  by  a  shallow  smooth  concavity 
which  forms  part  of  the  middle  meatus ;  below  this  again  is  the  inferior  turbinated 
crest  (already  described),  where  the  process  joins  the  body  of  the  bone.  Its  upper 
border  articulates  with  the  frontal  bone.  The  anterior  border  of  the  nasal  process 
is  thin,  directed  obliquely  downward  and  forward,  and  presents  a  serrated  edge 
for  articulation  with  the  nasal  bone  ;  its  posterior  border  is  thick,  and  hollowed 
into  a  groove,  the  lachrymal  groove,  for  the  nasal  duct :  of  the  two  margins  of  this 
groove,  the  inner  one  articulates  with  the  lachrymal  bone,  the  outer  one  forms 
part  of  the  circumference  of  the  orbit.  Just  where  the  latter  joins  the  orbital 
surface  is  a  small  tubercle,  the  lachrymal  tubercle  ;  this  serves  as  a  guide  to  the 
position  of  the  lachrymal  sac  in  the  operation  for  fistula  lachrymalis.  The 
lachrymal  groove  in  the  articulated  skull  is  converted  into  a  canal  by  the  lachrymal 
bone  and  lachrymal  process  of  the  inferior  turbinated ;  it  is  directed  downward, 
and  a  little  backward  and  outward,  is  about  the  diameter  of  a  goose-quill,  slightly 


Foramina  of  Stenson 


Anterior  palatine  canal. 


Foramen  of  Scarpa. 


Posterior  palatine  canal. 


Accessory  palatine  foramina. 

Fig.  51. — The  palate  and  alveolar  arch. 


narrower  in  the  middle  than  at   either  extremity,  and  terminates  below  in  the 
inferior  meatus.     It  lodges  the  nasal  duct. 

The  Alveolar  Process  is  the  thickest  and  most  spongy  part  of  the  bone,  broader 
behind  than  in  front,  and  excavated  into  deep  cavities  for  the  reception  of  the  teeth. 


THE   SUPERIOR    MAXILLARY  BONES. 


87 


These  cavities  are  eight  in  number,  and  vary  in  size  and  depth  according  to  the 
teeth  they  contain.  That  for  the  canine  tooth  is  the  deepest ;  those  for  the  molars 
are  the  widest,  and  subdivided  into  minor  cavities  ;  those  for  the  incisors  are  single, 
but  deep  and  narrow.  The  Buccinator  muscle  arises  from  the  outer  surface  of  this 
process,  as  far  forward  as  the  first  molar  tooth. 

The  Palate  Process,  thick  and  strong,  projects  horizontally  inward  from  the 
inner  surface  of  the  bone.  It  is  much  thicker  in  front  than  behind,  and  forms  a 
considerable  part  of  the  floor  of  the  nostril  and  the  roof  of  the  mouth. 

Its  inferior  surface  (Fig.  51)  is  concave,  rough  and  uneven,  and  forms  part  of 
the  roof  of  the  mouth.  This  surface  is  perforated  by  numerous  foramina  for  the 
passage  of  the  nutrient  vessels,  channelled  at  the  back  part  of  its  alveolar  border 
by  a  longitudinal  groove,  sometimes  a  canal,  for  the  transmission  of  the  posterior 
palatine  vessels,  and  the  anterior  and  external  palatine  nerves  from  Meckel's  gan- 
glion, and  presents  little  depressions  for  the  lodgement  of  the  palatine  glands. 
When  the  two  superior  maxillary  bones  are  articulated  together,  a  large  orifice 
may  be  seen  in  the  middle  line,  immediately  behind  the  incisor  teeth.  This  is 
the  anterior  palatine  canal  or  fossa.  On  examining  the  bottom  of  this  fossa  four 
canals  are  seen :  two  branch  off  laterally  to  the  right  and  left  nasal  fossae,  and 
two,  one  in  front  and  one  behind,  lie  in  the  middle  line.  The  former  pair  of 
these  canals  are  named  the  foramina  of  tStenson,  and  through  them  passes  the 
anterior  or  terminal  branch  of  the  descending  or  posterior  palatine  arteries, 
which  ascend  from  the  mouth  to  the  nasal  fossae.  The  canals  in  the  middle  line 
are  termed  the  foramina  of  Scarpa,  and  transmit  the  naso-palatine  nerves,  the 
left  passing  through  the  anterior,  and  the  right  through  the  posterior,  canal. 
On  the  palatal  surface  of  the  process  a  delicate  linear  suture  may  sometimes  be 
seen  extending  from  the  anterior  palatine  fossa  to  the  interval  between  the  lateral 
incisor  and  the  canine  tooth.  This  marks  out  the  intermaxillary  or  incisive  bone, 
which  in  some  animals  exists  permanently  as  a  separate  piece.  It  includes  the 
whole  thickness  of  the  alveolus,  the  corresponding  part  of  the  floor  of  the  nose, 
and  the  anterior  nasal  spine,  and  contains  the  sockets  of  the  incisor  teeth.  The 
upper  surface  is  concave  from  side  to  side,  smooth,  and  forms  part  of  the  floor  of 
the  nose.  It  presents  the  upper  orifices  of  the  foramina  of  Stenson  and  Scarpa, 
the  former  being  on  each  side  of  the  middle  line,  the  latter  being  situated  in  the 

CD  1 

intermaxillary  suture,  and  therefore  not  visible  unless 
the  two  bones  are  placed  in  apposition.  The  outer  border 
of  the  palate  process  is  incorporated  with  the  rest  of  the 
bone.  The  inner  border  is  thicker  in  front  than  behind, 
and  is  raised  above  into  a  ridge,  the  nasal  crest,  which, 
with  the  corresponding  ridge  in  the  opposite  bone,  forms 
a  groove  for  the  reception  of  the  vomer.  In  front  this 
crest  rises  to  a  considerable  height,  and  this  portion  is 
named  the  incisor  crest.  The  anterior  margin  is  bounded 
by  the  thin,  concave  border  of  the  opening  of  the  nose, 
prolonged  forward  internally  into  a  sharp  process,  form- 
ing, with  a  similar,.,  process  of  the  opposite  bone,  the 
anterior  nasal  spine.  Tbe  posterior  border  is  serrated  for 
articulation  with  the  horizontal  plate  of  the  palate  bone. 
Development. — This  bone  commences  to  ossify  at  a 
very  early  period,  and  ossification  proceeds  in  it  with 
great  rapidity,  so  that  it  is  difficult  to  ascertain  Avith 
certainty  its  precise  number  of  centres.  It  appears, 
however,  probable  that  it  is  ossified  from  four  centres, 
which  are  deposited  in.  membrane.  1.  One  which  forms 
that  portion  of  the  body  of  the  bone  which  lies  internal 
to  the  infra-orbital  canal,  including  the  floor  of  the  orbit, 
the  outer  wall  of  the  nasal  fossa,  and  the  nasal  process ;  2 
origin  to  that  portion  of  the  bone  which  lies  external  to 


j  w 

Inferior  Surface. 

Pig.  52.— Iicvelopment  of 
superior  maxillary  bont-.  At 
birth. 

A  second  which  gives 
the  infra-orbital  canal 


88  THE  SKELETON. 

and  the  malar  process ;  3.  A  third  from  which  is  developed  the  palatine  process 
posterior  to  Stenson's  canal  and  the  adjoining  part  of  the  nasal  wall;  4.  And 
a  fourth  for  the  front  part  of  the  alveolus  which  carries  the  incisor  teeth 
and  corresponds  to  the  pre-maxillary  bone  of  the  lower  animals.  These 
centres  appear  about  the  eighth  week,  and  by  the  tenth  week  the  three  first- 
named  centres  have  become  fused  together  and  the  bone  consists  of  two  por- 
tions, one  the  maxilla  proper,  and  the  other  the  pre-maxillary  portion.  The 
suture  between  these  two  portions  on  the  palate  persists  till  middle  life,  but 
is  not  to  be  seen  on  the  facial  surface.  This  is  believed  by  Callender  to  be 
due  to  the  fact  that  the  front  wall  of  the  sockets  of  the  incisive  teeth  is  not 
formed  by  the  pre-maxillary  bone,  but  by  an  outgrowth  from  the  facial  part  of  the 
superior  maxilla.  The  antrum  appears  as  a  shallow  groove  on  the  inner  surface 
of  the  bone  at  an  earlier  period  than  any  of  the  other  nasal  sinuses,  its  develop- 
ment commencing  about  the  fourth  month  of  foetal  life.  The  sockets  for  the 
teeth  are  formed  by  the  growing  downward  of  two  plates  from  the  dental  groove, 
which  subsequently  becomes  divided  by  partitions  jutting  across  from  the  one  to 
the  other. 

Articulations. — With  nine  bones  :  two  of  the  cranium,  the  frontal  and  ethmoid, 
and  seven  of  the  face — viz.  the  nasal,  malar,  lachrymal,  inferior  turbinated,  palate, 
vomer,  and  its  fellow  of  the  opposite  side.  Sometimes  it  articulates  with  the  orbital 
plate  of  the  sphenoid,  and  sometimes  with  its  external  pterygoid  plate. 

Attachment  of  Muscles. — To  twelve :  the  Orbicularis  palpebrarum,  Obliquus 
oculi  inferior,  Levator  labii  superioris  aleeque  nasi,  Levator  labii  superioris 
proprius,  Levator  anguli  oris,  Compressor  nasi,  Depressor  alse  nasi,  Dilatator 
naris  posterior,   Masseter,  Buccinator,  Internal  pterygoid,  and  Orbicularis  oris. 

CHANGES  PRODUCED  IN  THE  UPPER  JAW  BY  AGE. 

At  birth  and  during  infancy  the  diameter  of  the  bone  is  greater  in  an  antero-posterior 
than  in  a  vertical  direction.  Its  nasal  process  is  long,  its  orbital  surface  large,  and  its  tuberosity 
well  marked.  In  the  adult  the  vertical  diameter  is  the  greater,  owing  to  the  development  of 
the  alveolar  process  and  the  increase  in  size  of  the  antrum.  In  old  age  the  bone  approaches 
again  in  character  to  the  infantile  condition  :  its  height  is  diminished,  and  after  the  loss  of  the 
teeth  the  alveolar  process  is  absorbed,  and  the  lower  part  of  the  bone  contracted  and  diminished 
in  thickness. 

The  Lachrymal  Bones. 

The  Lachrymal  (lachryma,  a  tear)  are  the  smallest  and  most  fragile  bones  of 
the  face.  They  are  situated  at  the  front  part  of  the  inner  wall  of  the  orbit  (Fig. 
46).  and  resemble  somewhat  in  form,  thinness,  and  size  a  finger-nail;  hence  they 
are  termed  the  ossa  unguis.  Each  bone  presents  for  examination  two  surfaces  and 
four  borders.  The  external  or  orbital  surface  (Fig.  53)  is  divided  by  a  vertical 
ridge,  the  lachrymal  crest,  into  two  parts.  The  portion  of 
with  fronm.  bone   in   front  of    this   ridge   presents   a   smooth,    concave, 

P/j^^ljgL  \  longitudinal  groove,  the  free  margin  of  which  unites  with  the 

nasal  process  of  the  superior  maxillary  bone,  completing  the 
lachrymal  groove.  The  upper  part  of  this  groove  lodges  the 
lachrymal  sac ;  the  lower  part  lodges  the  nasal  duct.  The 
portion  of  bone  behind  the  ridge  is  smooth,  slightly  concave, 
and  forms  part  of  the  inner  wall  of  the  orbit.  The  ridge, 
with  a  part  of  the  orbital  surface  immediately  behind  it, 
affords  attachment  to  the  Tensor  tarsi  muscle :  it  terminates 
below  in  a  small,  hook-like  projection,  the  hamular  process, 
which  articulates  with  the  lachrymal,  tubercle  of  the  superior 
maxillary  bone,  and  completes  the  upper  orifice  of  the  lach- 

Fig.  53.— Left  lach-  .       •>  '  T  . l  .    ,         •"  .  -,  .    •■ 

rymai  bone.    External    rymal  groove.     It  sometimes  exists  as  a  separate  piece,  wnicn 

lagged6)    (Sllghtly   en"    is  then  called  the  lesser  lachrymal  bone.    The  internal  or  nasal 

surface    presents    a    depressed    furrow,   corresponding  to  the 

ridge   on  its  outer  surface.      The  surface  of  bone  in  front  of  this  forms  part  of 


THE   MALAR   BONES. 


89 


the  middle  meatus,  and  that  behind  it  articulates  with  the  ethmoid  bone,  fillino-  in 
the  anterior  ethmoidal  cells.  Of  the  four  borders,  the  anterior  is  the  longest,  and 
articulates  with  the  nasal  process  of  the  superior  maxillary  bone.  The  posterior, 
thin  and  uneven,  articulates  with  the  os  planum  of  the  ethmoid.  The  superior, 
the  shortest  and  thickest,  articulates  with  the  internal  angular  process  of  the 
frontal  bone.  The  inferior  is  divided  by  the  lower  edge  of  the  vertical  crest  into 
two  parts ;  the  posterior  part  articulates  with  the  orbital  plate  of  the  superior 
maxillary  bone ;  the  anterior  portion  is  prolonged  downward  into  a  pointed  pro- 
cess, which  articulates  with  the  lachrymal  process  of  the  inferior  turbinated  bone 
and  assists  in  the  formation  of  the  lachrymal  groove. 

Development. — By  a  single  centre,  which  makes  its  appearance  soon  after 
ossification  of  the  vertebrae  has  commenced. 

Articulations. — With  four  bones :  two  of  the  cranium,  the  frontal  and  ethmoid, 
and  two  of  the  face,  the  superior  maxillary  and  the  inferior  turbinated. 

Attachment  of  Muscles. — To  one  muscle,  the  Tensor  tarsi. 

The  Malar  Bones. 

The  Malar  {mala,  the  cheek)  are  two  small,  quadrangular  bones,  situated  at 
the  upper  and  outer  part  of  the  face :  they  form  the  prominence  of  the  cheek,  part 
of  the  outer  wall  and  floor  of  the  orbit,  and  part  of  the  temporal  and  zygomatic 
fossae  (Fig.  54).  Each  bone  presents  for  examination  an  external  and  an  internal 
surface ;  four  processes,  the  frontal,  orbital,  maxillary,  and  zygomatic ;  and  four 
borders.      The  external  surface  (Fig.  55)  is  smooth,   convex,  perforated  near  its 


Froni&l  s??vc.  —j^*^" 


Malar   bone 


Zygoma 
tic  proc. 


Fig.  54.— Malar  bone  in  situ. 


centre  by  one  or  two  small  apertures,  the  malar  foramina,  for  the  passage  of 
nerves  and  vessels,  covered  by  the  Orbicularis  palpebrarum  muscle,  and  affords 
attachment  to  the  Zygomaticus  major  and  minor  muscles. 

The  internal  surface  (Fig.  56),  directed  backward  and  inward,  is  concave, 
presenting  internally  a  rough,  triangular  surface,  for  articulation  with  the  supe- 
rior maxillary  bone  ;  and  externally,  a  smooth  concave  surface,  which  above  forms 
the  anterior  boundary  of  the  temporal  fossa,  and  below,  where  it  is  wider,  forms 
part  of  the  zygomatic  fossa.  This  surface  presents,  a  little  above  its  centre,  the 
aperture  of  one  or  two  malar  canals,  and  affords  attachment  to  a  portion  of  the 


90 


THE   SKELETON. 


Masseter  muscle  at  its  lower  part.  Of  the  four  processes,  the  frontal  is  thick 
and  serrated,  and  articulates  with  the  external  angular  process  of  the  frontal 
bone.  To  its  orbital  margin  is  attached  the  external  tarsal  ligament.  The 
orbital  process  is  a  thick  and  strong  plate,  which  projects  backward  from 
the  orbital  margin  of  the  bone.  Its  super  o-internal  surface,  smooth  and 
concave,  forms,  by  its  junction  with  the  orbital  surface  of  the  superior  max- 
illary bone   and  with  the  great  wing   of   the    sphenoid,   part    of  the   floor   and 


Bristles  passed 

through  temporo 

malar  canals. 


With  frontal. 


Fig.  55.— Left  malar  bone.     Outer  surface. 


Fig.  56.— Left  malar  bone.    Inner  surface. 


outer  wall  of  the  orbit.  Its  infer o-exiernal  surface,  smooth  and  convex,  forms 
part  of  the  zygomatic  and  temporal  fossae.  Its  anterior  margin  is  smooth  and 
rounded,  forming  part  of  the  circumference  of  the  orbit.  Its  superior  margin, 
rough  and  directed  horizontally,  articulates  with  the  frontal  bone  behind  the 
external  angular  process.  Its  posterior  margin  is  rough,  and  serrated  for  articu- 
lation with  the  sphenoid  ;  internally  it  is  also  serrated  for  articulation  with  the 
orbital  surface  of  the  superior  maxillary.  At  the  angle  of  junction  of  the  sphe- 
noidal and  maxillary  portions  a  short,  rounded,  non-articular  margin  is  generally 
seen ;  this  forms  the  anterior  boundary  of  the  spheno-maxillary  fissure :  occasion- 
ally, no  such  non-articular  margin  exists,  the  fissure  being  completed  by  the  direct 
junction  of  the  maxillary  and  sphenoid  bones  or  by  the  interposition  of  a  small 
Wormian  bone  in  the  angular  interval  between  them.  On  the  upper  surface  of 
the  orbital  process  are  seen  the  orifices  of  one  or  two  temporo-malar  canals ;  one 
of  these  usually  opens  on  the  posterior  surface,  the  other  (occasionally  two)  on 
the  facial  surface  :  they  transmit  filaments  (temporo-malar)  of  the  orbital  branch 
of  the  superior  maxillary  nerve.  The  maxillary  process  is  a  rough,  triangular 
surface  which  articulates  with  the  superior  maxillary  bone.  The  zygomatic  pro- 
cess, long,  narrow,  and  serrated,  articulates  with  the  zygomatic  process  of  the 
temporal  bone.  Of  the  four  borders,  the  antero-superior  or  orbital  is  smooth, 
arched,  and  forms  a  considerable  part  of  the  circumference  of  the  orbit.  The 
anteroinferior  or  maxillary  border  is  rough,  and  bevelled  at  the  expense  of  its 
inner  table,  to  articulate  with  the  superior  maxillary  bone ;  affording  attachment 
by  its  margin  to  the  Levator  labii  superioris  proprius,  just  at  its  point  of  junction 
with  the  superior  maxillary.  The  poster o-superior  or  temporal  border,  curved  like 
an  italic  letter/,  is  continuous  above  with  the  commencement  of  the  temporal 
ridge ;  below,  with  the  upper  border  of  the  zygomatic  arch :  it  affords  attachment 
to  the  temporal  fascia.  The  postero-inferior  or  zygomatic  border  is  continuous 
with  the  lower  border  of  the  zygomatic  arch,  affording  attachment  by  its  rough 
edge  to  the  Masseter  muscle. 

Development. — The  malar  bone  ossifies  generally  from  three  centres,  which 
appear  about  the  eighth  week — one  for  the  zygomatic  and  two  for  the  orbital 
portion — and  fuse  about  the  fifth  month  of  foetal  life.      The  bone  is  sometimes, 


THE   PALATE   BOXES. 


91 


after  birth,  seen  to  be  divided  by  a  horizontal  suture  into  an  upper  and   larger 
and  a  lower  and  smaller  division.      In  some  quadrumana  the  malar  bone  cons 
of  two  parts,  an  orbital  and  a  malar,  which  are  ossified  by  separate  centres. 

Articulations. — With  four  bones:   three  of  the  cranium,  frontal,  sphenoid,  and 
temporal;  and  one  of  the  face,  the  superior  maxillary. 

Attachment   of  Muscles. — To   four:    The    Levator   labii    superioris   proprius, 
Zygomaticus  major  and  minor,  and  Masseter. 


The  Palate  Bones. 

The  Palate  Bones  [palatum.,  the  palate)  are  situated  at  the  back  part  of  the 
nasal  fossae:  they  are  wedged  in  between  the  superior  maxillary  bones  and  the 

pterygoid  processes  of  the  sphenoid   (Fig.   57).     Each  bone  assists  in  the  for- 


Orbital  process. 


Spheno -palatine  for.*. 


Sphenoidal  process.^ 
Sup.  turbinated  crest. *~p 

Inf.  turbinated  crest.* 


Nasal  process. 

Sup.  turbinated,  crest. 


Inf.  turbinated  crest. 


—  A nt.  nasal  spine. 


Fig.  57. — Palate  bone  in  situ. 


mation  of  three  cavities :  the  floor  and  outer  wall  of  the  nose,  the  roof  of  the 
mouth,  and  the  floor  of  the  orbit,  and  enters  into  the  formation  of  two  fossre.  the 
spheno-maxillary  and  pterygoid;  and  one  fissure,  the  spheno-maxillary.  In 
form  the  palate  bone  somewhat  resembles  the  letter  L,  and  may  be  divided  into 
an  inferior  or  horizontal  plate  and  a  superior  or  vertical  plate. 

The  Horizontal  Plate  is  of  a  quadrilateral  form,  and  presents  two  surfaces  and 
four  borders.  The  superior  surface,  concave  from  side  to  side,  forms  the  back 
part  of  the  floor  of  the  nose.  The  inferior  surface,  slightly  concave  and  rough, 
forms  the  back  part  of  the  hard  palate.  At  its  posterior  part  may  be  seen  a 
transverse  ridge,  more  or  less  marked,  for  the  attachment  of  part  of  the  aponeu- 
rosis of  the  Tensor  palati  muscle.  At  the  outer  extremity  of  this  ridge  is  a  deep 
groove  converted  into  a  canal  by  its  articulation  with  the  tuberosity  of  the  superior 
maxillary  bone,  and  forming  the  posterior  palatine  canal.  Near  this  groove  the 
orifices  of  one  or  two  small  canals,  accessory  posterior  palatine,  may  be  seen. 
The  anterior  border  is  serrated,  bevelled  at  the  expense  of  its  inferior  surface,  and 
articulates  with  the  palate  process  of  the  superior  maxillary  bone.  The  post' 
border  is  concave,  free,  and  serves  for  the  attachment  of  the  soft  palate.  Its  inner 
extremity  is  sharp  and  pointed,  and,  when  united  with  the  opposite  bone,  forms 
a  projecting  process,  the  posterior  nasal  spine,  for  the  attachment  of  the  Azygos 
uvulae  muscle.     The  external  border  is  united  with  the  lower  part  of  the  perpen- 


92 


THE   SKELETON. 


Orbital  process. 

Orbital  surface. 


Maxillary  surface. 


Superior  meatus 
Spheno-palaline  foramen 


Maxillary 
process. 


dicular  plate  almost  at  right  angles.  The  internal  border,  the  thickest,  is  serrated 
for  articulation  with  its  fellow  of  the  opposite  side  ;  its  superior  edge  is  raised  into 
a  ridge,  which,  united  with  the  opposite  bone,  forms  a  crest  in  which  the  vomer  is 
received. 

The  Vertical  Plate  (Fig.  58)  is  thin,  of  an  oblong  form,  and  directed  upward 
and  a  little  inward.  It  presents  two  surfaces,  an  external  and  an  internal,  and 
four  borders. 

The  internal  surface  presents  at  its  lower  part  a  broad,  shallow  depression, 
which  forms  part  of  the  inferior  meatus   of  the  nose.     Immediately  above  this 

is  a  well-marked  horizontal 
ridge,  the  inferior  turbinated 
crest,  for  articulation  with  the 
inferior  turbinated  bone ; 
above  this,  a  second  broad, 
shallow  depression,  which 
forms  part  of  the  middle  mea- 
tus, surmounted  above  by  a 
horizontal  ridge  less  promi- 
nent than  the  inferior,  the 
superior  turbinated  crest,  for 
articulation  with  the  middle 
turbinated  bone.  Above  the 
superior  turbinated  crest  is  a 
narrow,  horizontal  groove, 
which  forms  part  of  the  su- 
perior meatus. 

The  external  surface  is 
rough  and  irregular  through- 
out the  greater  part  of  its 
extent,  for  articulation  with 
the  inner  surface  of  the  su- 
perior maxillary  bone,  its  upper  and  back  part  being  smooth  where  it  enters  into 
the  formation  of  the  spheno-maxillary  fossa ;  it  is  also  smooth  in  front,  where  it 
covers  the  orifice  of  the  antrum.  Toward  the  back  part  of  this  surface  is  a  deep 
groove,  converted  into  a  canal,  the  posterior 
palatine,  by  its  articulation  with  the  supe- 
rior maxillary  bone.  It  transmits  the  pos- 
terior or  descending  palatine  vessels  and 
one  of  the  descending  palatine  branches 
from  Meckel's  ganglion. 

The  anterior  border  is  thin,  irregular, 
and  presents,  opposite  the  inferior  turbi- 
nated crest,  a  pointed,  projecting  lamina, 
the  maxillary  process,  which  is  directed 
forward,  and  closes  in  the  lower  and  back 
part  of  the  opening  of  the  antrum.  The 
posterior  border  (Fig.  59)  presents  a  deep 
groove,  the  edges  of  which  are  serrated  for 
articulation  with  the  pterygoid  process  of 
the  sphenoid.  At  the  lower  part  of  this 
border  is  seen  a  pyramidal  process  of  bone, 
the  pterygoid  process  or  tuberosity  of  the 
palate,  which  is  received  into  the  angular 
interval  between  the  two  pterygoid  plates 
of  the  sphenoid  at  their  inferior  extremity. 
This  process  presents  at  its  back  part  a 
median  groove  and  two  lateral  surfaces. 


Horizontal  Plate. 

Fig.  58. — Left  palate  bone.    Internal  view.    (Enlarged.) 


Orbital  process, 
surface. 


Sphenoidal  palatine 
foramen. 

Sphenoidal  process. 
Articular  portion. 
Kon-articidar  portion. 


External  Surface. 


Posterior 
nasal  spme. 


Posterior  view. 


The  groove  is  smooth,  and  forms  part 


THE   PALATE  BONES.  93 

of  the  pterygoid  fossa,  affording  attachment  to  the  Internal  pterygoid  muscle ; 
whilst  the  lateral  surfaces  are  rough  and  uneven,  for  articulation  with  the  anterior 
border  of  each  pterygoid  plate.  A  few  fibres  of  the  Superior  constrictor  arise  from 
the  tuberosity  of  the  palate  bone.  The  base  of  this  process,  continuous  with  the 
horizontal  portion  of  the  bone,  presents  the  apertures  of  the  accessory  descending 
palatine  canals,  through  which  pass  the  two  smaller  descending  branches  of 
Meckel's  ganglion ;  whilst  its  outer  surface  is  rough  for  articulation  with  the  inner 
sui'face  of  the  body  of  the  superior  maxillary  bone. 

The  superior  border  of  the  vertical  plate  presents  two  well-marked  processes 
separated  by  an  intervening  notch  or  foramen.  The  anterior,  or  larger,  is  called 
the  orbital  process  ;  the  posterior,  the  sphenoidal. 

The  Orbital  Process,  directed  upward  and  outward,  is  placed  on  a  higher  level 
than  the  sphenoidal.  It  presents  five  surfaces,  which  enclose  a  hollow  cellular 
cavity,  and  is  connected  to  the  perpendicular  plate  by  a  narrow,  constricted  neck. 
Of  these  five  surfaces,  three  are  articular,  two  non-articular  or  free  surfaces.  The 
three  articular  are  the  anterior  or  maxillary  surface,  which  is  directed  forward, 
outward,  and  downward,  is  of  an  oblong  form,  and  rough  for  articulation  with 
the  superior  maxillary  bone.  The  posterior  or  sphenoidal  surface  is  directed 
backward,  upward,  and  inward.  It  ordinarily  presents  a  small,  open  cell,  which 
communicates  with  the  sphenoidal  cells,  and  the  margins  of  which  are  serrated 
for  articulation  with  the  vertical  part  of  the  sphenoidal  turbinated  bone.  The 
internal  or  ethmoidal  surface  is  directed  inward,  upward,  and  forward,  and 
articulates  with  the  lateral  mass  of  the  ethmoid  bone.  In  some  cases  the  cellular 
cavity  above  mentioned  opens  on  this  surface  of  the  bone ;  it  then  communicates 
with  the  posterior  ethmoidal  cells.  More  rarely  it  opens  on  both  surfaces,  and 
then  communicates  both  with  the  posterior  ethmoidal  and  the  sphenoidal  cells. 
The  non-articular  or  free  surfaces  are  the  superior  or  orbital,  directed  upward  and 
outward,  of  triangular  form,  concave,  smooth,  and  forming  the  back  part  of  the 
floor  of  the  orbit;  and  the  external  or  zygomatic  surface,  directed  outward, 
backward,  and  downward,  of  an  oblong  form,  smooth,  lying  in  the  spheno-maxil- 
lary  fossa,  and  looking  into  the  zygomatic  fossa.  The  latter  surface  is  separated 
from  the  orbital  by  a  smooth,  rounded  border,  which  enters  into  the  formation 
of  the  spheno-maxillary  fissure. 

The  Sphenoidal.  Process  of  the  palate  bone  is  a  thin,  compressed  plate,  much 
smaller  than  the  orbital,  and  directed  upward  and  inward.  It  presents  three 
surfaces  and  two  borders.  The  superior  surface,  the  smallest  of  the  three, 
articulates  with  the  under  surface  of  the  sphenoidal  turbinated  bone ;  it  presents  a 
groove,  which  contributes  to  the  formation  of  the  pterygo-palatine  canal.  The 
internal  surface  is  concave,  and  forms  part  of  the  outer  wall  of  the  nasal  fossa. 
The  external  surface  is  divided  into  an  articular  and  a  non-articular  portion :  the 
former  is  rough,  for  articulation  with  the  inner  surface  of  the  internal  pterygoid 
plate  of  the  sphenoid;  the  latter  is  smooth,  and  forms  part  of  the  spheno-maxil- 
lary fossa.  The  anterior  border  forms  the  posterior  boundary  of  the  spheno- 
palatine foramen.  The  posterior  border,  serrated  at  the  expense  of  the  outer 
table,  articulates  with  the  inner  surface  of  the  internal  pterygoid  plate. 

The  orbital  and  sphenoidal  processes  are  separated  from  one  another  by  a  deep 
notch,  which  is  converted  into  a  foramen,  the  sphenopalatine,  by  articulation 
with  the  sphenoidal  turbinated  bone.  Sometimes  the  two  processes  are  united 
above,  and  form  between  them  a  complete  foramen,  or  the  notch  is  crossed  by  one 
or  more  spiculse  of  bone,  so  as  to  form  two  or  more  foramina.  In  the  articulated 
skull  this  foramen  opens  into  the  back  part  of  the  outer  wall  of  the  superior 
meatus,  and  transmits  the  spheno-palatine  vessels  and  the  superior  nasal  and 
naso-palatine  nerves. 

Development. — From  a  single  centre,  which  makes  its  appearance  about  the 
second  month  at  the  angle  of  junction  of  the  two  plates  of  the  bone.  From  this 
point  ossification  spreads  inward  to  the  horizontal  plate,  downward  into  the 
tuberosity,  and  upward  into  the  vertical  plate.     In  the  foetus  the  horizontal  plate 


94 


THE  SKELETON. 


is  much  longer  than  the  vertical,  and  even  after  it  is  fully  ossified  the  whole  bone 
is  at  first  remarkable  for  its  shortness. 

Articulations. — With  six  bones :  the  sphenoid,  ethmoid,  superior  maxillary, 
inferior  turbinated,  vomer,  and  opposite  palate. 

Attachment  of  Muscles. — To  four :  the  Tensor  palati,  Azygos  uvulse,  Internal 
pterygoid,  and  Superior  constrictor  of  the  pharynx. 

The  Inferior  Turbinated  Bones. 

The  Inferior  Turbinated  Bones  {turbo,  a  whirl)  are  situated  one  on  each  side  of 
the  outer  wall  of  the  nasal  fossse.  Each  consists  of  a  layer  of  thin,  spongy  bone, 
curled  upon  itself  like  a  scroll — hence. its  name  "turbinated  " — and  extends  hori- 
zontally along  the  outer  wall  of  the  nasal  fossa,  immediately  below  the  orifice  of 


Lachrymal 
bone. 

\ 


Nasal  proc. 

t^Sup.  turbi- 
nated crest. 


Lachrymal 
proc. 

Inf.  turbi- 
nated crest. 


Fig.  60. — Inferior  turbinated  bone  and  Lachrymal  bone  in  situ. 

the   antrum   (Fig.  60).     Each  bone  presents  two  surfaces,  two  borders,  and  two 
extremities. 

The  internasal  surface  (Fig.  61)  is  convex,  perforated  by  uumerous  apertures, 
and  traversed  by  longitudinal  grooves  and  canals  for  the  lodgement  of  arteries  and 


Fig.  61.  —  Right  inferior  turbinated  bone, 
surface. 


Internal 


Fig.  62.  —  Right    inferior  turbinated   bone. 
External  surface. 


veins.  In  the  recent  state  it  is  covered  by  the  lining  membrane  of  the  nose.  The 
external  surface  is  concave  (Fig.  62),  and  forms  part  of  the  inferior  meatus.  Its 
upper  border  is  thin,  irregular,  and  connected  to  various  bones  along  the  outer 
wall  of  the  nose.  It  may  be  divided  into  three  portions  :  of  these,  the  anterior 
articulates  with  the  inferior  turbinated  crest  of  the  superior  maxillary  bone;  the 
posterior  with  the  inferior  turbinated  crest  of  the  palate  bone  ;  the  middle  portion 


THE     VOMER. 


95 


of  the  superior  border  presents  three  well-marked  processes,  which  vary  much  in 
their  size  and  form.  Of  these,  the  anterior  and  smallest  is  situated  at  the  junction 
of  the  anterior  fourth  with  the  posterior  three-fourths  of  the  bone  :  it  is  small  and 
pointed,  and  is  called  the  lachrymal  process  ;  it  articulates  by  its  apex  with  the 
anterior  inferior  angle  of  the  lachrymal  bone,  and  by  its  margins  with  the  groove 
on  the  back  of  the  nasal  process  of  the  superior  maxillary,  and  thus  assists  in 
forming  the  canal  for  the  nasal  duct.  At  the  junction  of  the  two  middle  fourths  of 
the  bone,  but  encroaching  on  its  posterior  fourth,  a  broad,  thin  plate,  the  ethmoidal 
process,  ascends  to  join  the  unciform  process  of  the  ethmoid ;  from  the  lower  border 
of  this  process  a  thin  lamina  of  bone  curves  downward  and  outward,  hooking 
over  the  lower  edge  of  the  orifice  of  the  antrum,  which  it  narrows  below:  it  is 
called  the  maxillary  process,  and  fixes  the  bone  firmly  to  the  outer  wall  of  the 
nasal  fossa.  The  inferior  border  is  free,  thick,  and  cellular  in  structure,  more 
especially  in  the  middle  of  the  bone.  Bone  extremities  are  more  or  less  narrow 
and  pointed,  the  posterior  being  the  more  tapering.  If  the  bone  is  held  so  that 
its  outer  concave  surface  is  directed  backward  (i.  e.,  toward  the  holder),  and  its 
superior  border,  from  which  the  lachrymal  and  ethmoidal  processes  project,  up- 
ward, the  lachrymal  process  will  be  directed  to  the  side  to  which  the  bone  belongs.1 

Development. — By  a  single  centre,  which  makes  its  appearance  about  the 
middle  of  foetal  life. 

Articulations. — With  four  bones :  one  of  the  cranium,  the  ethmoid,  and  three 
of  the  face,  the  superior  maxillary,  lachrymal,  and  palate. 

No  muscles  are  attached  to  this  bone. 

The  Vomer. 

The  Vomer  (vomer,  a  ploughshare)  is  a  single  bone,  situated  vertically  at  the 
back  part  of  the  nasal  fossae,  forming  part  of  the  septum  of  the  nose  (Fig.  63). 


Frontal  sinuses. 


Sphenoidal  sinuses. 


Perpendicular 
plate  of  eth- 
moid. 

Space  for  triangular 

cartilage  of  septum 

Vomer. 


Rostrum  of  sphenoid. 
Palate  process. 
Int.  pterygoid  plate. 


Fig.  63.— Vomer  in  situ. 


It  is  thin,  somewhat  like  a  ploughshare  in  form ;  but  it  varies  in  different  indi- 

1  If  the  lachrymal  process  is  broken  off,  as  is  often  the  case,  the  side  to  which  the  bone  belongs 
may  be  known  by  recollecting  that  the  maxillary  process  is  nearer  the  back  than  the  front  of  the  bone. 


96 


THE   SKELETON. 


With  sup.  maxitt.  bones  and  palate. 
Fig.  64.— The  vomer. 


viduals,  being  frequently  bent  to  one  or  the  other  side  ;  it  presents  for  examination 
two  surfaces  and  four  borders.  The  lateral  surfaces  are  smooth,  marked  by  small 
furrows  for  the  lodgement  of  blood-vessels,  and  by  a  groove  on  each  side,  some- 
times a  canal,  the  naso-palatine, 
which  runs  obliquely  downward 
and  forward  to  the  intermaxil- 
lary suture ;  it  transmits  the 
naso-palatine  nerve.  The  supe- 
rior border,  the  thickest,  pre- 
sents a  deep  groove,  bounded 
on  each  side  by  a  horizontal  pro- 
jecting ala  of  bone;  the  groove 
receives  the  rostrum  of  the 
sphenoid,  while  the  alae  are 
overlapped  and  retained  by  the 
vaginal  processes  which  project 
from  the  under  surface  of  the 
body  of  the  sphenoid  at  the  base 
of  the  pterygoid  processes.  At 
the  front  of  the  groove  a  fissure  is  left  for  the  transmission  of  blood-vessels  to  the 
substance  of  the  bone.  The  inferior  border,  the  longest,  is  broad  and  uneven  in 
front,  where  it  articulates  with  the  two  superior  maxillary  bones  ;  thin  and  sharp 
behind,  where  it  joins  with  the  palate  bones.  The  upper  half  of  the  anterior 
border  usually  consists  of  two  laminae  of  bone,  between  which  is  received  the 
perpendicular  plate  of  the  ethmoid ;  the  lower  half,  also  separated  into  two 
lamellae,  receives  between  them  the  lower  margin  of  the  septal  cartilage  of  the 
nose.  The  posterior  border  is  free,  concave,  and  separates  the  nasal  fossae  behind. 
It  is  thick  and  bifid  above,  thin  below. 

The  surfaces  of  the  vomer  are  covered  by  mucous  membrane,  which  is  inti- 
mately connected  with  the  periosteum,  with  the  intervention  of  very  little,  if  any, 
submucous  connective  tissue.  Hence  polypi  are  rarely  found  growing  from  this 
surface,  though  they  frequently  grow  from  the  outer  wall  of  the  nasal  fossae, 
where  the  submucous  tissue  is  abundant. 

Development. — The  vomer  at  an  early  period  consists  of  two  laminae,  separated 
by  a  very  considerable  interval,  and  enclosing  between  them  a  plate  of  cartilage, 
the  vomerine  cartilage,  which  is  prolonged  forward  to  form  the  remainder  of  the 
septum.  Ossification  commences  in  the  membrane  at  the  postero-inferior  part  of 
this  cartilage  by  two  centres,  one  on  each  side  of  the  middle  line,  which  extend 
to  form  the  two  laminae.  They  begin  to  coalesce  at  the  lower  part,  but  their 
union  is  not  complete  until  after  puberty. 

Articulations. — With  six  bones  :  two  of  the  cranium,  the  sphenoid  and  ethmoid ; 
and  four  of  the  face,  the  two  superior  maxillary  and  the  two  palate  bones ;  and 
with  the  cartilage  of  the  septum. 

The  vomer  has  no  muscles  attached  to  it. 

The  Inferior  Maxillary  Bone. 

The  Inferior  Maxillary  Bone  (the  Mandible),  the  largest  and  strongest  bone 
of  the  face,  serves  for  the  reception  of  the  lower  teeth.  It  consists  of  a  curved, 
horizontal  portion,  the  body,  and  two  perpendicular  portions,  the  rami,  which  join 
the  back  part  of  the  body  nearly  at  right  angles. 

The  Horizontal  Portion  or  Body  (Fig.  65)  is  convex  in  its  general  outline,  and 
curved  somewhat  like  a  horseshoe.  It  presents  for  examination  two  surfaces 
and  two  borders.  The  external  surface  is  convex  from  side  to  side,  concave  from 
above  downward.  In  the  median  line  is  a  vertical  ridge,  the  symphysis,  which 
extends  from  the  upper  to  the  lower  border  of  the  bone,  and  indicates  the  point  of 
junction  of  the  two  pieces  of  which  the  bone  is  composed  at  an  early  period  of  life. 


THE   INFERIOR    MAXILLARY  BONE. 


97 


The  lower  part  of  the  ridge  terminates  in  a  prominent  triangular  eminence,  the 
mental  process.  This  eminence  is  rounded  below,  and  often  presents  a  median 
depression  separating  two  processes,  the  mental  tubercles.  It  forms  the  chin,  a 
feature  peculiar  to  the  human  skull.  On  either  side  of  the  symphysis,  just  below  the 
cavities  for  the  incisor  teeth,  is  a  depression,  the  incisive  fossa,  for  the  attachment 
of  the  Levator  menti  (or  Levator  labii  inferioris) ;  more  externally  is  attached  a 
portion  of  the  Orbicularis  oris  {Accessorii  Orbicularis  inferioris),  and,  still  more 
externally,  a  foramen,  the  mental  foramen,  for  the  passage  of  the  mental  vessels 
and  nerve.  This  foramen  is  placed  just  below  the  interval  between  the  two 
bicuspid  teeth.  Running  outward  from  the  base  of  the  mental  process  on 
each  side  is  a  ridge,  the  external  oblique  line.  The  ridge  is  at  first  nearly 
horizontal,  but  afterward  inclines  upward  and  backward,  and  is  continuous 
with  the  anterior  border  of  the   ramus :   it  affords   attachment  to  the  Depressor 


Coronoid  process. 
1 


Condyle. 


Groove  for  facial  artery. 
Fig.  65.  —  Inferior  maxillary  bone.    Outer  surface.    Side  view. 

labii  inferioris  and   Depressor   anguli  oris ;    below   it   the  Platysma  myoides   is 
attached. 

The  internal  surface  (Fig.  6Q)  is  concave  from  side  to  side,  convex  from  above 
downward.  In  the  middle  line  is  an  indistinct  linear  depression,  corresponding 
to  the  symphysis  externally ;  on  either  side  of  this  depression,  just  below  its  centre, 
are  four  prominent  tubercles,  placed  in  pairs,  two  above  and  two  below ;  they  are 
called  the  genial  tubercles,  and  afford  attachment,  the  upper  pair  to  the  Genio- 
hyo-glossi,  the  lower  pair  to  the  Genio-hyoidei,  muscles.  Sometimes  the  tuber- 
cles on  each  side  are  blended  into  one ;  at  others  they  all  unite  into  an  irregular 
eminence  ;  or,  again,  nothing  but  an  irregularity  may  be  seen  on  the  surface  of  the 
bone  at  this  part.  On  either  side  of  the  genial  tubercles  is  an  oval  depression,  the 
sublingual  fossa,  for  lodging  the  sublingual  gland;  and  beneath  the  fossa  a  rough 
depression  on  each  side  which  gives  attachment  to  the  anterior  belly  of  the 
Digastric  muscle.  At  the  back  part  of  the  sublingual  fossa  the  interim!  oblique 
line  (mylo-hyoidean)  commences ;  it  is  at  first  faintly  marked,  but  becomes  more 
distinct  as  it  passes  upward  and  outward,  and  is  especially  prominent  opposite 
the  last  two  molar  teeth :  it  affords  attachment  throughout  its  whole  extent  to  the 
Mylo-hyoid  muscle ;  the  Superior  constrictor  of  the  pharynx  with  the  pterygo- 
maxillary  ligament  being  attached  above  its  posterior  extremity,  near  the  alveolar 
margin.  The  portion  of  the  bone  above  this  ridge  is  smooth,  and  covered  by  the 
mucous  membrane  of  the  mouth  ;  the  portion  below  presents  an  oblong  depression, 
the  submaxillary  fossa,  wider  behind  than  in  front,  for  the  lodgement  of  the  sub- 
maxillary gland.    The  external  oblique  line  and  the  internal  or  mylo-hyoidean  line 

7 


98 


THE   SKELETON. 


divide  the  body  of  the  bone  into  a  superior  or  alveolar  and  an  inferior  or  basilar 
portion. 

The  superior  or  alveolar  border  is  wider,  and  its  margins  thicker,  behind  than 
in  front.  It  is  hollowed  into  numerous  cavities,  for  the  reception  of  the  teeth ; 
these  cavities  are  sixteen  in  number,  and  vary  in  depth  and  size  according  to  the 
teeth  which  they  contain.  To  its  outer  side,  the  Buccinator  muscle  is  attached  as 
far  forward  as  the  first  molar  tooth.  The  inferior  border  is  rounded,  longer  than 
the  superior,  and  thicker  in  front  than  behind ;  it  presents  a  shallow  groove,  just 
where  the  body  joins  the  ramus,  over  which  the  facial  artery  turns. 


•ltV^. 


O-HYO-GLOSSUS. 


GENIO-HYOIDEUS. 


Mylo-hyoid  ridge 


Body. 


Fig.  66.  —  Inferior  maxillary  bone.    Inner  surface.    Side  view. 

The  Perpendicular  Portions,  or  Rami,  are  of  a  quadrilateral  form.  Each 
presents  for  examination  two  surfaces,  four  borders,  and  two  processes.  The 
external  surface  is  flat,  marked  with  ridges,  and  gives  attachment  throughout  nearly 
the  whole  of  its  extent  to  the  Masseter  muscle.  The  internal  surface  presents 
about  its  centre  the  oblique  aperture  of  the  inferior  dental  canal,  for  the  passage 
of  the  inferior  dental  vessels  and  nerve.  The  margin  of  this  opening  is  irregular ; 
it  presents  in  front  a  prominent  ridge,  surmounted  by  a  sharp  spine,  the  lingula, 
which  gives  attachment  to  the  internal  lateral  ligament  of  the  lower  jaw,  and  at 
its  lower  and  back  part  a  notch  leading  to  a  groove,  the  mylo-hyoidean,  which  runs 
obliquely  downward  to  the  back  part  of  the  submaxillary  fossa,  and  lodges  the 
mylo-hyoid  vessels  and  nerve.  Behind  the  groove  is  a  rough  surface,  for  the 
insertion  of  the  Internal  pterygoid  muscle.  The  inferior  dental  canal  runs  obliquely 
downward  and  forward  in  the  substance  of  the  ramus,  and  then  horizontally 
forward  in  the  body ;  it  is  here  placed  under  the  alveoli,  with  Avhich  it  communi- 
cates by  small  openings.  On  arriving  at  the  incisor  teeth,  it  turns  back  to 
communicate  with  the  mental  foramen,  giving  off  two  small  canals,  which  run 
forward,  to  be  lost  in  the  cancellous  tissue  of  the  bone  beneath  the  incisor  teeth. 
This  canal,  in  the  posterior  two-thirds 'of  the  bone,  is  situated  nearer  the  internal 
surface  of  the  jaw ;  and  in  the  anterior  third,  nearer  its  external  surface.  Its 
walls  are  composed  of  compact  tissue  at  either  extremity,  and  of  cancellous  in  the 
centre.  It  contains  the  inferior  dental  vessels  and  nerve,  from  which  branches  are 
distributed  to  the  teeth  through  small  apertures  at  the  bases  of  the  alveoli.  The 
lower  border  of  the  ramus  is  thick,  straight,  and  continuous  with  the  body  of  the 
bone.  At  Us  junction  with  the  posterior  border  is  the  angle  of  the  jaw.  which  is 
either  inverted  or  everted,  and  marked  by  rough,  oblique  ridges  on  each  side,  for 


THE   INFERIOR    MAXILLARY  BONK.  99 

the  attachment  of  the  Masseter  externally,  and  the  Internal  pterygoid  internally  : 
the  stylo-maxillary  ligament  is  attached  to  the  angle  between  these  muscles.  The 
anterior  border  is  thin  above,  thicker  below,  and  continuous  with  the  external 
oblique  line.  The  'posterior  border  is  thick,  smooth,  rounded,  and  covered  bv  the 
parotid  gland.  The  upper  border  of  the  ramus  is  thin,  and  presents  two  processes, 
separated  by  a  deep  concavity,  the  sigmoid  notch.  Of  these  processes,  the  anterior 
is  the  coronoid,  the  posterior  the  condyloid. 

The  Coronoid  Process  is  a  thin,  flattened,  triangular  eminence  of  bone,  which 
varies  in  shape  and  size  in  different  subjects,  and  serves  chiefly  for  the  attachment 
of  the  Temporal  muscle.  Its  external  surface  is  smooth,  and  affords  attachment 
to  the  Temporal  and  Masseter  muscles.  Its  internal  surface  gives  attachment  to 
the  Temporal  muscle  and  presents  the  commencement  of  a  longitudinal  ridge, 
which  is  continued  to  the  posterior  part  of  the  alveolar  process.  On  the  outer 
side  of  this  ridge  is  a  deep  groove,  continued  below  on  the  outer  side  of  the  alve- 
olar process ;  this  ridge  and  part  of  the  groove  afford  attachment,  above,  to  the 
Temporal;  below,  to  the  Buccinator  muscle. 

The  Condyloid  Process,  shorter  but  thicker  than  the  coronoid,  consists  of  two 
portions;  the  condyle,  and  the  constricted  portion  which  supports  the  condyle, 
the  neck.  The  condyle  is  of  an  oblong  form,  its  long  axis  being  transverse,  and 
set  obliquely  on  the  neck  in  such  a  manner  that  its  outer  end  is  a  little  more  for- 
ward and  a  little  higher  than  its  inner.  It  is  convex  from  before  backward  and 
from  side  to  side,  the  articular  surface  extending  farther  on  the  posterior  than  on 
the  anterior  aspect.  At  its  outer  extremity  is  a  small  tubercle  for  the  attach- 
ment of  the  external  lateral  ligament  of  the  temporo-mandibular  joint.  The 
neck  of  the  condyle  is  flattened  from  before  backward,  and  strengthened  by  ridges 
which  descend  from  the  fore  part  and  sides  of  the  condyle.  Its  lateral  margins 
are  narrow,  the  external  one  giving  attachment  to  part  of  the  external  lateral 
ligament.  Its  posterior  surface  is  convex  ;  its  anterior  is  hollowed  out  on  its 
inner  side  by  a  depression  (the  pterygoid  fossa),  for  the  attachment  of  the 
External  pterygoid  muscle. 

The  Sigmoid  Notch,  separating  the  two  processes,  is  a  deep  semilunar  depres- 
sion, crossed  by  the  masseteric  vessels  and  nerve. 

Development. — The  lower  jaw  is  developed  principally  from  membrane,  but 
partly  from  cartilage.  The  process  of  ossification  commences  early — earlier  than 
in  any  other  bone  except  the  clavicle.  The  greater  part  of  the  bone  is  formed  from 
a  centre  of  ossification  (dentary),  which  appears  between  the  fifth  and  sixth  week 
in  the  membrane  on  the  outer  surface  of  Meckel's  cartilage.  A  second  centre 
(splenial)  appears  in  the  membrane  on  the  inner  surface  of  the  cartilage,  and 
from  this  centre  the  inner  wall  of  the  sockets  of  the  teeth  is  formed ;  this  termi- 
nates above  in  the  lingula.  The  anterior  extremity  of  Meckel's  cartilage  becomes 
ossified,  forming  the  body  of  the  bone  on  each  side  of  the  symphysis.  Two  supple- 
mental patches  of  cartilage  appear  at  the  condyle  and  at  the  angle,  in  each  of 
which  a  centre  of  ossification  for  these  parts  appears ;  the  coronoid  process  is  also 
ossified  from  a  separate  centre.  At  birth  the  bone  consists  of  two  halves,  united 
by  a  fibrous  symphysis,  in  which  ossification  takes  place  during  the  first  year. 

Articulation.— With  the  glenoid  fossae  of  the  two  temporal  bones. 

Attachment  of  Muscles. — To  fifteen  pairs  :  to  its  external  surface,  commencing 
at  the  symphysis,  and  proceeding  backward:  Levator  menti,  Depressor  labii  infe- 
rioris,  Depressor  anguli  oris,  Platysma  myoides,  Buccinator,  Masseter:  a  portion 
of  the  Orbicularis  oris  (Accessorii  orbicularis  inferioris)  is  also  attached  to  this 
surface.  To  its  internal  surface,  commencing  at  the  same  point:  Genio-hyo- 
glossus,  Genio-hyoideus,  Mylo-hyoideus,  Digastric,  Superior  constrictor.  Temporal, 
Internal  pterygoid,  External  pterygoid. 

CHANGES  PRODUCED  IN  THE  LOWER  JAW  RY  AGE. 

The  changes  which  the  lower  jaw  undergoes  after  birth  relate  (1)  to  the  alterations  effected 
in  the  body  of  the  bone  by  the  first  and  second  dentitions,  the  loss  of  the  teeth  in  the  aged,  and 


100  THE   SKELETON. 

Side  View  of  the  Lower  Jaw  at  Different  Periods  of  Life. 


Fig.  67.— At  birth. 


Fig.  69. —In  the  adult. 


Fig.  70.— In  old  age. 


THE   SUTURES.  101 

the  subsequent  absorption  of  the  alveoli ;  (2)  to  the  size  and  situation  of  the  dental  canal ;  and  (3) 
to  the  angle  at  which  the  ramus  joins  with  the  body. 

At  birth  (Fig.  67)  the  bone  consists  of  lateral  halves,  united  by  fibrous  tissue.  The  body 
is  a  mere  shell  of  bone,  containing  the  sockets  of  the  two  incisor,  the  canine,  and  the  two  tem- 
porary molar  teeth,  imperfectly  partitioned  from  one  another.  The  dental  canal  is  of  large  size, 
and  runs  near  the  lower  border  of  the  bone,  the  mental  foramen  opening  beneath  the  socket  of 
the  first  molar.  The  angle  is  obtuse  (175°),  and  the  condyloid  portion  nearly  in  the  same  hori- 
zontal line  with  the  body  ;  the  neck  of  the  condyle  is  short,  and  bent  backward.  The  coronoid 
process  is  of  comparatively  large  size,  and  situated  at  right  angles  with  the  rest  of  the  bone. 

After  birth  (Fig.  68)  the  two  segments  of  the  bone  become  joined  at  the  symphysis,  from 
below  upward,  in  the  first  year ;  but  a  trace  of  separation  may  be  visible  in  the  beginning  of  the 
second  year  near  the  alveolar  margin.  The  body  becomes  elongated  in  its  whole  length,  but 
more  especially  _  behind  the  mental  foramen,  to  provide  space  for  the  three  additional  teeth 
developed  in  this  part.  The  depth  of  the  body  becomes  greater,  owing  to  increased  growth  of 
the  alveolar  part,  to  afford  room  for  the  fangs  of  the  teeth,  and  by  thickening  of  the  subdental 
portion,  which  enables  the  jaw  to  withstand  the  powerful  action  of  the  masticatory  muscles ;  but 
the  alveolar  portion  is  the  deeper  of  the  two,  and,  consequently,  the  chief  part  of  the  body  lies 
above  the  oblique  line.  The  dental  canal  after  the  second  dentition  is  situated  just  above  the 
level  of  the  mylo-hyoid  ridge,  and  the  mental  foramen  occupies  the  position  usual  to  it  in  the 
adult.  The  angle  becomes  less  obtuse,  owing  to  the  separation  of  the  jaws  by  the  teeth. 
(About  the  fourth  year  it  is  140°.) 

In  the  adult  (Fig.  69)  the  alveolar  and  basilar  portions  of  the  body  are  usually  of  equal 
depth.  The  mental  foramen  opens  midway  between  the  upper  and  lower  border  of  the  bone, 
and  the  dental  canal  runs  nearly  parallel  with  the  mylo-hyoid  line.  The  ramus  is  almost  vertical 
in  direction,  and  joins  the  body  nearly  at  right  angles. 

In  old  age  (Fig.  70)  the  bone  becomes  greatly  reduced  in  size ;  for  with  the  loss  of  the 
teeth  the  alveolar  process  is  absorbed,  and  the  basilar  part  of  the  bone  alone  remains  ;  conse- 
quently, the  chief  part  of  the  bone  is  below  the  oblique  line.  The  dental  canal,  with  the  mental 
foramen  opening  from  it,  is  close  to  the  alveolar  border.  The  rami  are  oblique  in  direction,  the 
^ngle  obtuse,  and  the  neck  of  the  condyle  more  or  less  bent  backward. 

The  Sutures. 

The  bones  of  the  cranium  and  face  are  connected  to  each  other  by  means  of 
•Sutures.  That  is,  the  articulating  surfaces  or  edges  of  the  bones  are  more  or  less 
roughened  or  uneven,  and  are  closely  adapted  to  each  other,  a  small  amount  of 
intervening  fibrous  tissue,  the  sutural  ligament,  fastening  them  together.  The 
Cranial  Sutures  may  be  divided  into  three  sets :  1.  Those  at  the  vortex  of  the 
skull.     2.  Those  at  the  side  of  the  skull.     3.  Those  at  the  base. 

The  sutures  at  the  vertex  of  the  skull  are  three :  the  sagittal,  coronal,  and 
lambdoid. 

The  Sagittal  Suture  (interparietal)  is  formed  by  the  junction  of  the  two  parietal 
■bones,  and  extends  from  the  middle  of  the  frontal  bone  backward  to  the  superior 
angle  of  the  occipital.  In  childhood,  and  occasionally  in  the  adult,  when  the  two 
halves  of  the  frontal  bone  are  not  united,  it  is  continued  forward  to  the  root  of 
the  nose.  This  suture  is  sometimes  perforated,  near  its  posterior  extremity,  by 
the  parietal  foramen;  and  in  front,  where  it  joins  the  coronal  suture,  a  space  is 
•occasionally  left  which  encloses  a  large  Wormian  bone. 

The  Coronal  Suture  (frontoparietal)  extends  transversely  across  the  vertex  of 
the  skull,  and  connects  the  frontal  with  the  parietal  bones.  It  commences  at  the 
►extremity  of  the  greater  wing  of  the  sphenoid  on  one  side,  and  terminates  at  the 
same  point  on  the  opposite  side.  The  dentations  of  the  suture  are  more  marked 
at  the  sides  than  at  the  summit,  and  are  so  constructed  that  the  frontal  rests  on 
the  parietal  above,  whilst  laterally  the  frontal  supports  the  parietal. 

The  Lambdoid  Suture  (occipitoparietal),  so  called  from  its  resemblance  to  the 
>Greek  letter  A,  connects  the  occipital  with  the  parietal  bones.  It  commences  on 
each  side  at  the  mastoid  portion  of  the  temporal  bone,  and  inclines  upward  to  the 
■  end  of  the  sagittal  suture.  The  dentations  of  this  suture  are  very  deep  and  dis- 
tinct, and  are  often  interrupted  by  several  small  Wormian  bones. 

The  sutures  at  the  side  of  the  skull  extend  from  the  external  angular  process 
>of  the  frontal  bone  to  the  lower  end  of  the  lambdoid  suture  behind.  The  anterior 
portion  is  formed  between  the  lateral  part  of  the  frontal  bone  above  and  the  malar 
.-and  great  wing  of  the    sphenoid  below,   forming   the  fronto-malar   and  fronto 


102  THE   SKELETON. 

sphenoidal  sutures.  These  sutures  can  also  be  seen  in  the  orbit,  and  form  part 
of  the  so-called  transverse  facial  suture.  The  posterior  portion  is  formed  between 
the  parietal  bone  above  and  the  great  wing  of  the  sphenoid,  the  squamous  and 
mastoid  portions  of  the  temporal  bone  below,  forming  the  sphenoparietal,  squamo- 
parietal,  and  masto-parietal  sutures. 

The  Spheno-parietal  is  very  short ;  it  is  formed  by  the  tip  of  the  great  wing  of 
the  sphenoid,  Avhich  overlaps  the  anterior  inferior  angle  of  the  parietal  bone. 

The  Squamo-parietal,  or  Squamous  Suture,  is  arched.  It  is  formed  by  the 
squamous  portion  of  the  temporal  bone  overlapping  the  middle  division  of  the 
lower  border  of  the  parietal. 

The  Masto-parietal  is  a  short  suture,  deeply  dentated,  formed  by  the  posterior 
inferior  angle  of  the  parietal  and  the  superior  border  of  the  mastoid  portion  of  the 
temporal. 

The  sutures  at  the  base  of  the  skull  are  the  basilar  in  the  centre,  and  on  each 
side  the  petro-occipital,  the  masto-occipital,  the  petro-sphenoidal,  and  the  squamo- 
sphenoidal. 

The  Basilar  Suture  is  formed  by  the  junction  of  the  basilar  surface  of  the 
occipital  bone  with  the  posterior  surface  of  the  body  of  the  sphenoid.  At  an  early 
period  of  life  a  thin  plate  of  cartilage  exists  betAveen  these  bones,  but  in  the  adult 
they  become  fused  into  one.  Between  the  outer  extremity  of  the  basilar  suture 
and  the  termination  of  the  lambdoid  an  irregular  suture  exists,  which  is  subdivided 
into  two  portions.  The  inner  portion,  formed  by  the  union  of  the  petrous  part  of 
the  temporal  with  the  occipital  bone,  is  termed  the  petro-occipital.  The  outer 
portion,  formed  by  the  junction  of  the  mastoid  part  of  the  temporal  with  the 
occipital,  is  called  the  masto-occipital.  Between  the  bones  forming  the  petro- 
occipital  suture  a  thin  plate  of  cartilage  exists ;  in  the  masto-occipital  is  occa- 
sionally found  the  opening  of  the  mastoid  foramen.  Between  the  outer  extremity 
of  the  basilar  suture  and  the  spheno-parietal  an  irregular  suture  may  be  seen, 
formed  by  the  union  of  the  sphenoid  with  the  temporal  bone.  The  inner  and 
smaller  portion  of  this  suture  is  termed  the  petro-sphenoidal ;  it  is  formed  between 
the  petrous  portion  of  the  temporal  and  the  great  wing  of  the  sphenoid :  the  outer 
portion,  of  greater  length  and  arched,  is  formed  between  the  squamous  portion  of  the 
temporal  and  the  great  wing  of  the  sphenoid ;  it  is  called  the  squamo-sphenoidal. 

The  cranial  bones  are  connected  with  those  of  the  face,  and  the  facial  bones 
with  each  other,  by  numerous  sutures,  which,  though  distinctly  marked,  have 
received  no  special  names.  The  only  remaining  suture  deserving  especial  con- 
sideration is  the  transverse.  This  extends  across  the  upper  part  of  the  face,  and 
is  formed  by  the  junction  of  the  frontal  with  the  facial  bones  :  it  extends  from  the 
external  angular  process  of  one  side  to  the  same  point  on  the  opposite  side,  and 
connects  the  frontal  with  the  malar,  the  sphenoid,  the  ethmoid,  the  lachrymal,  the 
superior  maxillary,  and  the  nasal  bones  on  each  side. 

The  sutures  remain  separate  for  a  considerable  period  after  the  complete  for- 
mation of  the  skull.  It  is  probable  that  they  serve  the  purpose  of  permitting  the 
growth  of  the  bones  at  their  margins,  while  their  peculiar  formation,  together 
with  the  interposition  of  the  sutural  ligament  between  the  bones  forming  them, 
prevents  the  dispersion  of  blows  or  jars  received  upon  the  skull.  Humphry 
remarks,  "  that,  as  a  general  rule,  the  sutures  are  first  obliterated  at  the  parts  in 
which  the  ossification  of  the  skull  was  last  completed — viz.  in  the  neighborhood 
of  the  fontanelles  ;  and  the  cranial  bones  seem  in  this  respect  to  observe  a  similar 
law  to  that  which  regulates  the  union  of  the  epiphyses  to  the  shafts  of  the  long 
bones."  The  same  author  remarks  that  the  time  of  their  disappearance  is 
extremely  variable :  they  are  sometimes  found  Avell  marked  in  skulls  edentulous 
with  age,  A\Thile  in  others  Avhich  haATe  only  just  reached  maturity  they  can  hardly 
be  traced.  The  obliteration  of  the  sutures  takes  place  sooner  on  the  inner  than 
on  the  outer  surface  of  the  skull.  The  sagittal  and  coronal  sutures  are  as  a  rule 
the  first  to  become  ossified — the  process  starting  near  the  posterior  extremity  of 
the  former  and  the  loAver  ends  of  the  latter. 


THE   BASE    OF    THE   SKULL.  103 


THE  SKULL  AS  A  WHOLE. 

The  Skull,  formed  by  the  union  of  the  several  cranial  and  facial  bones  already 
described,  Avhen  considered  as  a  Avhole  is  divisible  into  five  regions :  a  superior 
region  or  vertex,  an  inferior  region  or  base,  two  lateral  regions,  and  an  anterior 
region,  the  face. 

The  Vertex  of  the  Skull. 

The  Superior  Region,  or  Vertex,  presents  two  surfaces,  an  external  and  an 
internal. 

The  external  surface  is  bounded,  in  front,  by  the  glabella  and  supraorbital 
ridges ;  behind,  by  the  occipital  protuberance  and  superior  curved  lines  of  the 
occipital  bone ;  laterally,  by  an  imaginary  line  extending  from  the  outer  end  of 
the  superior  curved  line,  along  the  temporal  ridge,  to  the  external  angular  process 
of  the  frontal.  This  surface  includes  the  greater  part  of  the  vertical  portion  of 
the  frontal,  the  greater  part  of  the  parietal,  and  the  superior  third  of  the  occipital 
bone;  it  is  smooth,  convex,  of  an  elongated  oval  form,  crossed  transversely  by 
the  coronal  suture,  and  from  before  backward  by  the  sagittal,  Avhich  terminates 
behind  in  the  lambdoid.  The  point  of  junction  of  the  coronal  and  sagittal 
sutures  is  named  the  bregma,  and  is  represented  by  a  line  drawn  vertically 
upward  from  th.e  external  auditory  meatus,  the  head  being  in  its  normal  position. 
The  point  of  junction  of  the  sagittal  and  lambdoid  sutures  is  called  the  lambda. 
and  is  about  2|-  inches  above  the  external  occipital  protuberance.  From  before 
backward  may  be  seen  the  frontal  eminences  and  remains  of  the  suture  connect- 
ing the  two  lateral  halves  of  the  frontal  bone;  on  each  side  of  the  sagittal  suture 
are  the  parietal  foramen  and  parietal  eminence,  and  still  more  posteriorly  the 
convex  surface  of  the  occipital  bone.  In  the  neighborhood  of  the  parietal  fora- 
men the  skull  is  often  flattened,  and  the  name  of  obelion  is  sometimes  given  to 
that  point  of  the  sagittal  suture  which  lies  exactly  opposite  to  the  parietal  foramen. 

The  internal  surface  is  concave,  presents  depressions  for  the  convolutions  of  \ 
the  cerebrum,  and  numerous  furrows  for  the  lodgement  of  branches  of  the  menin- 
geal arteries.  Along  the  middle  line  of  this  surface  is  a  longitudinal  groove, 
narrow  in  front,  where  it  commences  at  the  frontal  crest,  but  broader  behind, 
where  it  lodges  the  superior  longitudinal  sinus,  and  by  its  margin  affords  attach- 
ment to  the  falx  cerebri.  On  either  side  of  it  are  several  depressions  for  the 
Pacchionian  bodies,  and  at  its  back  part  the  internal  openings  of  the  parietal 
foramina.  This  surface  is  crossed,  in  front,  by  the  coronal  suture;  from  before 
backward  by  the  sagittal ;  behind,  by  the  lambdoid. 

The  Base  of  the  Skull. 

The  Inferior  Region,  or  Base  of  the  Skull,  presents  two  surfaces — an  internal 
or  cerebral,  and  an  external  or  basilar. 

The  internal  or  cerebral  surface  (Fig.  71)  presents  three  fossae,  called  the 
anterior,  middle,  and  jjosterior  fossae  of  the  cranium. 

The  Anterior  Fossa  is  formed  by  the  orbital  plates  of  the  frontal,  the  cribri- 
form plate  of  the  ethmoid,  the  anterior  third  of  the  superior  surface  of  the  body. 
and  the  upper  surface  of  the  lesser  wings  of  the  sphenoid.  It  is  the  most  elevated 
of  the  three  fossae,  convex  externally  where  it  corresponds  to  the  roof  of  the  orbit, 
concave  in  the  median  line  in  the  situation  of  the  cribriform  plate  of  the  ethmoid. 
It  is  traversed  by  three  sutures,  the  xihmo-frontal.  e^hmo-s^hmmdal,  and  frojxLa^ 
sphenoidal,  and  lodges  the  frontal  lobe  of  the  cerebrum.  It  presenfsTm  the 
median— 1-me-,  from  before  backward,  the  commencement  of  the  groove  for  the 
superior  longitudinal  sinus  and  the  frontal  crest  for  the  attachment  of  the  falx 
cerebri ;  the  foramen  ccecum,  an  aperture  formed  between  the  frontal  bone  and  the 
crista  galli  of  the  ethmoid,  which,  if  pervious,  transmits  a  small  vein  from  the  nose 
to  the  superior  longitudinal  sinus ;  behind  the  foramen  caecum,  the  crista  galli,  the 
posterior  margin  of  which  affords  attachment  to  the  falx  cerebri ;  on  either  side  of 
the   crista  galli,   the    cribriform    plate,  which   supports   the   olfactory  bulb,  and 

J. 

- 


104 


THE    SKELETON. 


presents  three  rows  of  foramina  for  the  transmission  of  its  nervous  filaments, 
and  in  front  a  slit-like  opening  for  the  nasal  branch  of  the  onhthalmic  division 


Groove  for  superior  longitudinal  sinus. 

Grooves  for  anterior  meningeal  artery. 

Foramen  caecum. 

Crista  galli. 

Slit  for  nasal  nerve. 

Groove  for  nasal  nerve. 

Anterior  ethmoidal  foramen. 

Orifices  for  olfactory  nerves 

Posterior  ethmoidal  foramen 

Ethmoidal  spine 


Olfactory  grooves. 

Optic  foramen. 

Optic  groove. 

Olivary  process. 

Anterior  clinoid  process. 

Middle  clinoid  process. 

Posterior  clinoid  process. 

Groove  for  6th  nerve. 

Foramen  lacerum  medium. 

Orifice  of  carotid  canal. 

Depression  for  Gasserian  ganglion. 


Meatus  auditorius  interims. 

Slit  for  dura  mater. 

Superior  petrosal  groove. 

Foramen  lacerum  posterius. 

Anterior  condyloid  foramen. 

Aquseductus  vestibuli. 

Posterior  condyloid  foramen 


Mastoid  foramen 
Posterior  meningeal  grooves 


Fi ;.  71.— Base  of  the  skull.    Inner  or  cerebral  surface. 


of  the  fifth  nerve.  On  the  outer  side  of  each  olfactory  groove  are  the  internal 
openings  of  the  anterior  and  posterior  ethmoidal  foramina ;  the  former,  situated 
about  the  middle  of  the  outer  margin  of  the  olfactory  groove,  tra  ismits  the 
anterior  ethmoidal  vessels  and  the  nasal  nerve,  which  latter' runs  in  a  depression 


THE   BASE    OF    THE  SKULL.  105 

along  the  surface  of  the  ethmoid  to  the  slit-like  opening  above  mentioned ;  while 
the  posterior  ethmoidal  foramen  opens  at  the  back  part  of  this  margin  under 
cover  of  the  projecting  lamina  of  the  sphenoid,  and  transmits  the  posterior 
ethmoidal  vessels.  Farther  back  in  the  middle  line  is  the  ethmoidal  spine, 
bounded  behind  by  a  slight  elevation,  separating  two  shallow  longitudinal  grooves 
which  support  the  olfactory  lobes.  Behind  this  is  a  transverse  sharp  ridge,  run- 
ning outward  on  either  side  to  the  anterior  margin  of  the  optic  foramen,  and 
separating  the  anterior  from  the  middle  fossa  of  the  base  of  the  skull.  The 
anterior  fossa  presents,  laterally,  depressions  for  the  convolutions  of  the  brain 
and  grooves  for  the  lodgement  of  the  anterior  meningeal  arteries.     ^ 

The  Middle  Fossa,  deeper  than  the  preceding,  is  narrow  in  the  middle  line, 
but  becomes  wider  at  the  side  of  the  skull.  It  is  bounded  in  front  by  the  poste- 
rior margin  of  the  lesser  Aving  of  the  sphenoid,  the  anterior  clinoid  process,  and 
the  ridge  forming  the  anterior  margin  of  the  optic  groove  ;  behind,  by  the  superior 
border  of  the  petrous  portion  of  the  temporal  and  the  dorsum  ephippi ;  externally 
by  the  squamous  portion  of  the  temporal,  anterior  inferior  angle  of  the  parietal 
bone,  and  greater  wing  of  the  sphenoid.  It  is  traversed  by  four  sutures,  the 
squamo-parietal,   spheno-parietal,   squamo-sphenoidal,   and  petro-sphenoidal. 

In  the  middle  line,  from  before  backward,  is  the  optic  groove,  behind  which 
lies  the  optic  commissure ;  the  groove  terminates  on  each  side  in  the  optic  fora- 
men, for  the  passage  of  the  optic  nerve  and  ophthalmic  artery  ;  behind  the  optic 
groove  is  the  olivary  process,  and  laterally  the  anterior  clinoid  processes,  to  which 
are  attached  processes  of  the  tentorium  cerebelli.  Farther  back  is  the  sella 
turcica,  a  deep  depression  which  lodges  the  pituitary  gland,  bounded  in  front 
by  a  small  eminence  on  either  side,  the  middle  clinoid  process,  and  behind 
by  a  broad  square  plate  of  bone,  the  dorsum  epjhippi,  surmounted  at  each 
superior  angle  by  a  tubercle,  the  posterior  clinoid  process ;  beneath  the  latter 
process  is  a  notch,  for  the  sixth  nerve.  On  each  side  of  the  sella  turcica  is  the 
cavernous  groove :  it  is  broad,  shallow,  and  curved  somewhat  like  the  Italic 
letter/;  it  commences  behind  at  the  foramen  lacerum  medium,  and  terminates 
on  the  inner  side  of  the  anterior  clinoid  process,  and  presents  along  its  outer  mar- 
gin a  ridge  of  bone.  This  groove  lodges  the  cavernous  sinus,  the  internal  carotid 
artery,  and  the  nerves  of  the  orbit.  The  sides  of  the  middle  fossa  are  of  con- 
siderable depth;  they  present  depressions  for  the  convolutions  of  the  brain  and 
grooves  for  the  branches  of  the  middle  meningeal  artery  ;  the  latter  commence 
on  the  outer  side  of  the  foramen  spinosum,  and  consist  of  two  large  branches,  an 
anterior  and  a  posterior ;  the  former  passing  upward  and  forward  to  the  anterior 
inferior  angle  of  the  parietal  bone,  the  latter  passing  upward  and  backward. 
The  following  foramina  may  also  be  seen  from  before  backward  :  Most  anteriorly 
is  the  foramen  lacerum  antexiiu,  or  sphenoidal  fissure,  formed  above  by  the  lesser 
wing  of  the  sphenoid ;  below,  by  the  greater  wing  ;  internally,  by  the  body  of  the 
sphenoid  ;  and  sometimes  completed  externally  by  the  orbital  plate  of  the  frontal 
bone.  It  transmits  the  third,  the  fourth,  the  three  branches  of  the  ophthalmic 
division  of  the  fifth,  the  sixth  nerve,  some  filaments  from  the  cavernous  plexus  of 
the  sympathetic,  the  orbital  branch  of  the  middle  meningeal  artery,  a  recurrent 
branch  from  the  lachrymal  artery  to  the  dura  mater,  and  the  ophthalmic  vein. 
Behin_d  the  inner  extremity  of  the  sphenoidal  fissure  is  the  foramen  rotundum,  for 
the  passage  of  the  seconcl_division  of  the  fifth, or  superior  maxillary  nerve;  still 
more  posteriorly  is  seen  a  small  orifice,  the  foramen  Vesplii.  an  opening  situated 
between  the  foramen  rotundum  and  ovale,  a  little  internal  to  both  :  it  varies  in  size 
in  different  individuals,  and  is  often  absent;  when  present,  it  transmits  a  small  vein. 
It  opens  below  into  the  pterygoid  fossa,  just  at  the  outer  side  of  the  scaphoid 
depression.  Behind  and  externafto  the  latter  opening  is  ike  foramen  ovale,  which 
transmits  the  third  division  of  the  fifth  or  inferior  maxillary  nerve,  the  small 
men  tery,  and  the  small  pet    ~T*"— *H;ve.1     On  the  outer  side  of  the  foramen 

ova1  foramen  i-pinosum,  for  •  jfe  of  the  middle  meningeal  artery  ;  and 

i  gfrfiTnTiKWif  P-  74- 


/ 


106  THE   SKELETON. 

on  the  inner  side  of  the  foramen  ovale,  the  foramen  lacerum  medium.  The  lower 
part  of  this  aperture  is  filled  -with  cartilage  in  the  recent  stare.  The  Vidian 
nerve  and  a  meningeal  branch  from  the  ascending  pharyngeal  artery  pierce  this 
cartilage.  On  the  anterior  surface  of  the  petrous  portion  of  the  temporal  bone  is 
seen,  from  without  inward,  the  eminence  caused  by  the  projection  of  the  superior 
semicircular  canal ;  in  front  of  and  a  little  outside  this  is  a  depression  corresponding 
to  the  roof  of  the  tympanum  ;  the  groove  leading  to  the  hiatus  Fallopii.  for  the 
transmission  of  the  petrosal  branch  of  the  Vidian  nerve  and  the  petrosal  branch 
of  the  middle  meningeal  artery:  beneath  it.  the  smaller  groove,  for  the  passage 
of  the  lesser  petrosal  nerve;  and.  near  the  apex  of  the  bone,  the  depression  for 
the  Gasserian  ganglion  ;  and  the  orifice  of  the  carotid  canal,  for  the  passage  of 
the  internal  carotid  artery  and  carotid  plexus  of  nerves. 

The  Posterior  Fossa,  deeply  concave,  is  the  largest  of  the  three,  and  situated 
on  a  lower  level  than  either  of  the  preceding.  It  is  formed  by  the  posterior  third 
of  the  superior  surface  of  the  body  of  the  sphenoid,  by  the  occipital,  the  petrous 
and  mastoid  portions  of  the  temporal,  and  the  posterior  inferior  angle  of  the 
parietal  bone ;  it  is  crossed  by  four  sutures,  the  petro-occipital.  the  masto-occipital, 
the  masto-parietal,  and  the  basilar ;  and  lodges  the  cerebellum,  pons  Varolii,  and 
medulla  oblongata.  It  is  separated  from  the  middle  fossa  in  the  median  line  by 
the  dorsum  ephippii,  and  on  each  side  by  the  superior  border  of  the  petrous  portion 
of  the  temporal  bone.  This  border  serves  for  the  attachment  of  the  tentorium 
cerebelli,  is  groovecl_for  the  supej^3r_^ejrosal/  sinus,  and  at  its  inner  extremity 
presents  a  notch,  upon  which  rests  the  fifths  nerve.  The  circumference  of  the 
fossa  is  bounded  posteriorly  by  the  grooves  for  the  lateral  sinuses.  In  the  centre 
of  this  fossa  is  the  foramen  magnum,  bounded  on  either  side  by  a  rough  tubercle, 
which  gives  attachment  to  the  odontoidjDr  check  ligaments ;  and  a  little  above 
these  are  seen  the  internal  openings  of  the  anterior  caiTeh/loid  foramina,  through 
which  pass  the  hypoglossal  nerve  and  a  meningeal  branch  from  the  ascending 
pharyngeal  artery.  In  front  of  the  foramen  magnum  is  a  .grooved  surface,  formed 
by  the  basilar  process  of  the  occipital  bone  and  by  the  posterior  third  of  the  superior 
surface  of  the  body  of  the  sphenoid,  which  supports  the  medulla  oblongata  and 
pons  Varolii,  and  articulates  on  each  side  with  the  petrous  portion  of  the  temporal 
bone,  forming  the  petro-occipital  suture,  the  anterior  half  of  which  is  grooved  for 
the  inferior  petrosal  sinus,  the  posterior  half  being  encroached  upon  by  the  foramen 
lacerum  posterius,  ox  jugular  foramen.  This  foramen  presents  three  compartments : 
through  the  anterior  passes  the  inferior  petrosal  sinus  :  through  the  posterior,  the 
lateral  sinus  and  some  meningeal  branches  from  the  occipital  and  ascending 
pharyngeal  arteries ;  and  through  the  middle,  the  glossopharyngeal,  pneumo- 
gastric,  and  spinal  accessory  nerves.  Above  the  jugular  foramen  is  the  internal 
auditory  meatus,  for  the  facial  and  auditory  nerves  and  auditory  artery ;  behind 
and  external  to  this  is  the  slit-like  opening  leading  into  the  aquieductus  vestibuli, 
which  lodges  the  ductus  endolymphaticus :  while  between  the  two  latter,  and 
near  the  superior  border  of  the  petrous  portion,  is  a  small,  triangular  depression, 
the  remains  of  the  floccular  fossa,  which  lodges  a  process  of  the  dura  mater  and 
occasionally  transmits  a  small  vein  into  the  substance  of  the  bone.  Behind  the 
foramen  magnum  are  the  inferior  occipital  fossa?,  which  lodge  the  hemispheres  of 
the  cerebellum,  separated  from  one  another  by  the  internal  occipital  crest,  which 
serves  for  the  attachment  of  the  falx  cerebelli  and  lodges  the  occipital  sinus.  The 
posterior  fosste  are  surmounted,  above,  by  the  deep  transverse  grooves  for  the 
lodgment  of  the  lateral  sinuses.  These  channels,  in  their  passage  outward, 
groove  the  occipital  bone,  the  posterior  inferior  angle  of  the  parietal,  the  mastoid 
portion  of  the  temporal,  and  the  jugular  process  of  the  occipital,  and  terminate  at 
the  back  part  of  the  jugular  foramen.  Where  this  sinus  grooves  the  mastoid  portion 
of  the  temporal  bone  the  orifice  of  the  mastoid  foramen  may  be  seen,  and  just 
previous  to  its  termination  it  has  opening  into  it  the  posterior  condyloid  foramen. 
Neither  foramen  is  constant. 

The  External  Surface  of  the  Base  of  the  Skull  (Fig.  7:';  ??  extremely  irregular. 


THE   BASE    OF    THE   SKULL. 


107 


Fed  ate  pvoc 


Anterior  palatine  fossa. 

Transmits  left  naso-palatine  nerve. 
Transmits  (interior  palatine  vessel. 
Transmits  right  naso-palatine  nerve. 


Accessory  palatine  foramina. 
Posterior  nasal  spine. 

AZYGOS   UVULyE. 

Hamular  process. 

Sphenoid  process  of  palate. 
Ptery  go-palatine  canal. 


TENSOR    TYMPANI. 

Pharyngeal  spine  for 

SUPERIOR    CONSTRICTOR. 

Situation  of  Eustachian  tube  and 
canal  for  tensor  tympani. 

TENSOR    PALATI. 

Canal  for  Jacobson'-i  nerve. 
Aquzeductus  cochlex. 
Foramen  lacerum  posterius. 
Canal  for  Arnold's  nerve. 
Auricular  fissure. 


Fig.  72.— Base  of  the  skull.    External  surface. 


It  is  I  in  front  by  the  incisor  teeth  in  the  upper  jaw:    behind   by  the 

super  ed  lines  of  tile  occipital  bone  ;  and  laterally  by  the  alveolar  arch,  the 

lowei  of  the  mala/  bone,  the  zygoma,  and  an  imaginary  line  extending 


108  THE  SKELETON. 

from  the  zygoma  to  the  mastoid  process  and  extremity  of  the  superior  curved  line 
of  the  occiput.  It  is  formed  by  the  palate  processes  of  the  superior  maxillary  and 
palate  bones,  the  vomer,  the  pterygoid  processes,  under  surface  of  the  great  wing, 
spinous  processes  and  part  of  the  body  of  the  sphenoid,  the  under  surface  of  the 
squamous,  mastoid,  and  petrous  portions  of  the  temporal,  and  the  under  surface 
of  the  occipital  bone.  The  anterior  part  of  the  base  of  the  skull  is  raised  above 
the  level  of  the  rest  of  this  surface  (when  the  skull  is  turned  over  for  the  purpose 
of  examination),  surrounded  by  the  alveolar  process,  which  is  thicker  behind  than 
in  front,  and  excavated  by  sixteen  depressions  for  lodging  the  teeth  of  the  upper 
jaw,  the  cavities  varying  in  depth  and  size  according  to  the  teeth  they  contain. 
Immediately  behind  the  incisor  teeth  is  the  anterior  palatine  fossa.  At  the  bottom 
of  this  fossa  may  usually  be  seen  four  apertures :  two  placed  laterally,  the  foramina 
of  Stenson,  which  open  above,  one  in  the  floor  of  each  nostril,  and  transmit  the 
anterior  branch  of  the  posterior  palatine  vessels,  and  two  in  the  median  line  in 
the  intermaxillary  suture,  the  foramina  of  Scarpa,  one  in  front  of  the  other,  the 
anterior  transmitting  the  left,  and  the  posterior  (the  larger)  the  right,  naso-palatine 
nerve.  These  two  latter  canals  are  sometimes  wanting,  or  they  may  join  to  form 
a  single  one,  or  one  of  them  may  open  into  one  of  the  lateral  canals  above  referred 
to.  The  palatine  vault  is  concave,  uneven,  perforated  by  numerous  foramina, 
marked  by  depressions  for  the  palatine  glands,  and  crossed  by  a  crucial  suture, 
formed  by  the  junction  of  the  four  bones  of  which  it  is  composed.  At  the  front 
part  of  this  surface  a  delicate  linear  suture  may  frequently  be  seen,  passing  outward 
and  forward  from  the  anterior  palatine  fossa  to  the  interval  between  the  lateral  in- 
cisor and  canine  teeth,  and  marking  off  the  pre-maxillary  portion  of  the  bone.  At 
each  posterior  angle  of  the  hard  palate  is  the  posterior  -palatine  foramen,  for  the 
transmission  of  the  posterior  palatine  vessels  and  large  descending  palatine  nerve ; 
and  running  forward  and  inward  from  it  a  groove,  for  the  same  vessels  and  nerve. 
Behind  the  posterior  palatine  foramen  is  the  tuberosity  of  the  palate  bone,  perforated 
by  one  or  more  accessory  posterior  palatine  canals,  and  marked  by  the  commence- 
ment of  a  ridge,  which  runs  transversely  inward,  and  serves  for  the  attachment  of 
the  tendinous  expansion  of  the  Tensor  palati  muscle.  Projecting  backward  from 
the  centre  of  the  posterior  border  of  the  hard  palate  is  the  posterior  nasal  spine, 
for  the  attachment  of  the  Azygos  uvulae  muscle.  Behind  and  above  the  hard  palate 
is  the  posterior  aperture  of  the  nares,  divided  into  two  parts  by  the  vomer,  bounded 
above  by  the  body  of  the  sphenoid,  below  by  the  horizontal  plate  of  the  palate  bone, 
and  laterally  by  the  internal  pterygoid  plate  of  the  sphenoid.  Each  aperture 
measures  about  an  inch  in  the  vertical  and  about  half  an  inch  in  the  transverse 
direction.  At  the  base  of  the  vomer  may  be  seen  the  expanded  alae  of  this  bone, 
receiving  between  them,  on  each  side,  the  rostrum  of  the  sphenoid.  Near  the 
lateral  margins  of  the  vomer,  at  the  root  of  the  pterygoid  processes,  are  the 
pterygo-palatine  canals.  The  pterygoid  process,  which  bounds  the  posterior 
nares  on  each  side,  presents  near  its  base  the  pterygoid  or  Vidian  canal,  for  the 
Vidian  nerve  and  artery.  Each  process  consists  of  two  plates,  which  bifurcate  at 
the  extremity  to  receive  the  tuberosity  of  the  palate  bone,  and  are  separated  behind 
by  the  pterygoid  fossa,  which  lodges  the  Internal  pterygoid  muscle.  The  internal 
plate  is  long  and  narrow,  presenting  on  the  outer  side  of  its  base  the  scaphoid  fossa, 
for  the  origin  of  the  Tensor  palati  muscle,  and  at  its  extremity  the  hamular  process, 
around  AVhich  the  tendon  of  this  muscle  turns.  The  external  pterygoid  plate  is 
broad,  forms  the  inner  boundary  of  the  zygomatic  fossa,  and  affords  attachment  by 
its  outer  surface  to  the  External  pterygoid  muscle. 

Behind  the  nasal  fossae  in  the  middle  line  is  the  basilar  surface  of  the  occipital 
bone,  presenting  in  its  centre  the  pharyngeal  spine,  for  the  attachment  of  the 
Superior  constrictor  muscle  of  the  pharynx,  with  depressions  on  each  side  for 
the  insertion  of  the  Rectus  capitis  anticus  major  and  minor.  At  the  base  of  the 
external  pterygoid  plate  is  -the  foramen  ovale,  for  the  transmission  of  the  third 
division  of  the  fifth  nerve,  the  small  meningeal  artery,  and  sometimes  the  small 
petrosal  nerve ;   behind  this,  the  foramen  spinosum,  which  transmits  the  middle 


THE   BASE    OF    THE   SKULL.  109 

meningeal  artery,  and  the  prominent  spinous  process  of  the  sphenoid,  which  gives 
attachment  to  the  internal  lateral  ligament  of  the  lower  jaw  and  the  Tensor  palati 
muscle.  External  to  the  spinous  process  is  the  glenoid  fossa,  divided  into  two  parts 
by  the  Glaserian  fissure  (page  66),  the  anterior  portion  concave,  smooth,  bounded 
in  front  by  the  eminentia  articularis,  and  serving  for  the  articulation  of  the  condyle 
of  the  lower  jaw  ;  the  posterior  portion  rough,  bounded  behind  by  the  tympanic 
plate,  and  serving  for  the  reception  of  part  of  the  parotid  gland.  Emerging  from 
between  the  laminae  of  the  vaginal  process  of  the  tympanic  plate  is  the  styloid  proc- 
ess, and  at  the  base  of  this  process  is  the  stylo-mastoid  foramen,  for  the  exit  of  the 
facial  nerve  and  entrance  of  the  stylo-mastoid  artery.  External  to  the  stylo-mastoid 
foramen  is  the  auricular  fissure,  for  the  auricular  branch  of  the  pneumogastric. 
bounded  behind  by  the  mastoid  process.  Upon  the  inner  side  of  the  mastoid  proc- 
ess is  a  deep  groove,  the  digastric  fossa  ;  and  a  little  more  internally  the  occipital 
groove,  for  the  occipital  artery.  At  the  base  of  the  internal  pterygoid  plate  is  a 
large  and  somewhat  triangular  aperture,  the  foramen  lacerum  medium,  bounded  in 
front  by  the  great  wing  of  the  sphenoid,  behind  by  the  apex  of  the  petrous  portion 
of  the  temporal  bone,  and  internally  by  the  body  of  the  sphenoid  and  basilar  proc- 
ess of  the  occipital  bone :  it  presents  in  front  the  posterior  orifice  of  the  Vidian 
canal ;  behind,  the  aperture  of  the  carotid  canal.  The  basilar  surface  of  this  open- 
ing is  filled  in  the  recent  state  by  fibro-cartilaginous  substance ;  across  its  upper 
or  cerebral  aspect  passes  the  internal  carotid  artery.  External  to  this  aperture  the 
petro-splienoidal  suture  is  observed,  at  the  outer  termination  of  which  is  seen  the 
orifice  of  the  canal  for  the  Eustachian  tube  and  that  for  the  Tensor  tympani  muscle. 
Behind  this  suture  is  seen  the  under  surface  of  the  petrous  portion  of  the  temporal 
bone,  presenting,  from  within  outward,  the  quadrilateral,  rough  surface,  part  of 
which  affords  attachment  to  the  Levator  palati  and  Tensor  tympani  muscles  ;  exter- 
nal to  this  surface  the  orifices  of  the  carotid  canal  and  the  acpuseductus  cochlea?, 
the  former  transmitting  the  internal  carotid  artery  and  the  ascending  branches  of 
the  superior  cervical  ganglion  of  the  sympathetic,  the  latter  serving  for  the  passage 
of  a,  small  artery  and  vein  to  the  cochlea.  Behind  the  carotid  canal  is  a  large 
aperture,  the  jugular  foramen,  formed  in  front  by  the  petrous  portion  of  the  tem- 
poral, and  behind  by  the  occipital ;  it  is  generally  larger  on  the  right  than  on  the 
left  side,  and  is  divided  into  three  compartments  by  processes  of  dura  mater.  The 
anterior  is  for  the  passage  of  the  inferior  petrosal  sinus ;  the  posterior,  for  the 
lateral  sinus  and  some  meningeal  branches  from  the  occipital  and  ascending  phar- 
yngeal arteries ;  the  central  one,  for  the  glossopharyngeal,  pneumogastric,  and 
spinal  accessory  nerves.  On  the  ridge  of  bone  dividing  the  carotid  canal  from  the 
jugular  foramen  is  the  small  foramen  for  the  transmission  of  Jacobson's  nerve; 
and  on  the  wall  of  the  jugular  foramen,  near  the  root  of  the  styloid  process,  is  the 
small  aperture  for  the  transmission  of  Arnold's  nerve.  Behind  the  basilar  surface 
of  the  occipital  bone  is  the  foramen  magnum,  bounded  on  each  side  by  the  con- 
dyles, rough  internally  for  the  attachment  of  the  check  or  odontoid  ligaments,  and 
presenting  externally  a  rough  surface,  the  jugular  process,  Avhich  serves  for  the 
attachment  of  the  Rectus  capitis  lateralis  muscle  and  the  lateral  occipito-atlantal 
ligament.  On  either  side  of  each  condyle  anteriorly  is  the  anterior  condyloid  fossa, 
perforated  by  the  anterior  condyloid  foramen,  for  the  passage  of  the  hypoglossal 
nerve  and  a  meningeal  artery.  Behind  each  condyle  is  the  posterior  condyloid 
fossa,  perforated  on  one  or  both  sides  by  the  posterior  condyloid  foramina,  for  the 
transmission  of  a  vein  to  the  lateral  sinus.  Behind  the  foramen  magnum  is  the 
external  occipital  crest,  terminating  above  at  the  external  occipital  protuberance, 
whilst  on  each  side  are  seen  the  superior  and  inferior  curved  lines  ;  these,  as  -well 
as  the  surfaces  of  bone  between  them,  are  rough  for  the  attachment  of  the  muscles, 
which  are  enumerated  on  page  59. 


110 


THE  SKELETON. 


The  Lateral  Region  of  the  Skull. 

The  Lateral  Region  of  the  Skull  is  of  a  somewhat  triangular  form,  the  base  of 
the  triangle  being  formed  by  a  line  extending  from  the  external  angular  process 
of  the  frontal  bone  along  the  temporal  ridge  backward  to  the  outer  extremity  of 
the  superior  curved  line  of  the  occiput :  and  the  sides  by  two  lines,  the  one  drawn 
downward  and  backward  from  the  external  angular  process  of  the  frontal  bone 
to  the  angle  of  the  lower  jaw,  the  other  from  the  angle  of  the  jaw  upward  and 


0cC 


Fig.  73.— Side  view  of  the  skull.    (Cryer.; 

backward   to  the  outer  extremity  of  the  superior  curved  line.     This  region  is 
divisible  into  three  portions — temporal  fossa,  mastoid  portion,  and  zygomatic  fossa. 

The  Temporal  Fossa. 

The  Temporal  Fossa  is  bounded  above  and  behind  by  the  temporal  ridges,  which 
extend  from  the  external  angular  process  of  the  frontal  upward  and  backward 
across  the  frontal  and  parietal  bones,  curving  downward  behind  to  terminate  in  the 
posterior  root  of  the  zygomatic  process  (supra-mastoid  crest).  In  front  it  is  bounded 
by  the  frontal,  malar,  and  great  wing  of  the  sphenoid ;  externally  by  the  zygomatic 
arch  formed  conjointly  by  the  malar  and  temporal  bones;  below,  it  is  separated 
from  the  zygomatic  fossa  by  the  pterygoid  ridge,  seen  on  the  outer  surface  of  the 
great  wing  of  the  sphenoid.  This  fossa  is  formed  by  five  bones,  part  of  the  frontal, 
great  wing  of  the  sphenoid,  parietal,  squamous  portion  of  the  temporal,  and  malar 
bones,  and  is  traversed  by  six  sutures,  part  of  the  transverse  facial,  spheno-malar, 
coronal,    spheno-parietal,    squamo-parietal,    and    squamo-sphenoidal.        The    point 


THE   Z  YG  031 A  TIC  TOSS  A .  Ill 

where  the  coronal  suture  crosses  the  superior  temporal  ridge  is  sometimes  named  the 
stephanion;  and  the  region  where  the  four  bones,  the  parietal,  the  frontal,  the 
squamous,  and  the  greater  wing  of  the  sphenoid,  meet,  at  the  anterior  inferior  ancle 
of  the  parietal  bone,  is  named  the  pter  ion.  This  point  is  about  on  a  level  with  the 
external  angular  process  of  the  frontal  bone  and  about  one  and  a  half  inches  behind 
it.  This  fossa  is  deeply  concave  in  front,  convex  behind,  traversed  by  grooves  which 
lodge  branches  of  the  deep  temporal  arteries,  and  filled  by  the  Temporal  muscles. 

The  Mastoid  Portion. 

The  Mastoid  Portion  of  the  side  of  the  skull  is  bounded  in  front  by  the  tubercle 
of  the  zygoma ;  above,  by  a  line  which  runs  from  the  posterior  root  of  the  zygoma 
to  the  end  of  the  mastoid-parietal  suture  ;  behind  and  below  by  the  masto-occipital 
suture.  It  is  formed  by  the  mastoid  and  part  of  the  squamous  and  petrous  por- 
tions of  the  temporal  bone ;  its  surface  is  convex  and  rough  for  the  attachment  of 
muscles,  and  presents,  from  behind  forward,  the  mastoid  foramenj  the  mastoid  proc- 
ess, the  external  auditory  meatus  surrounded  by  the  tympanic  plate,  and,  most 
anteriorly,   the  temporo-maxillary  articulation. 

The  point  where  the  posterior  inferior  angle  of  the  parietal  meets  the  occipital 
bone  and  mastoid  portion  of  the  temporal  is  named  the  asterion. 

The  Zygomatic  Fossa. 

The  Zygomatic  Fossa  is  an  irregularly  shaped  cavity,  situated  below  and  on  the 
inner  side  of  the  zygoma  ;  bounded,  in  front,  by  the  zygomatic  surface  of  the 
superior  maxillary  bone  and  the  ridge  which  descends  from  its  malar  process ; 
behind,  by  the  posterior  border  of  the  external  pterygoid  plate  and  the  erninentia 
articularis ;  above,  by  the  pterygoid  ridge  on  the  outer  surface  of  the  great  Aving 


m 

Spheno- 

'iini.rilliiri/ 

I 

Ext.  auditor;/        y™ 

fissure.        ^«|H 

meatus.          Styloid 

process. 

Ext.        /^|t_ 

pterygoid    ,             fftn^ 

~"*  4i 

Fig.  74.— Zygomatic  foss 

i. 

of  the  sphenoid  and  the  under  part  of  the  squamous  portion  of  the  temporal : 
below,  by  the  alveolar  border  of  the  superior  maxilla ;  internally,  by  the  external 
pterygoid  plate ;  and  externally,  by  the  zygomatic  arch  and  ramus  of  the  lower 
jaw  (Fig.  74).  It  contains  the  lower  part  of  the  Temporal,  the  External  and  In- 
ternal p  muscles,  the  internal  maxillary  artery  and  vein,  and  inferior  max- 


112  THE   SKELETON. 

iliary  nerve  and  their  branches.  At  its  upper  and  inner  part  may  be  observed  two 
fissures,  the  spheno-maxillary  and  pterygo-maxillary. 

The  Spheno-maxillary  Fissure,  horizontal  in  direction,  opens  into  the  outer  and 
back  part  of  the  orbit.  It  is  formed  above  by  the  lower  border  of  the  orbital  surface 
of  the  great  wing  of  the  sphenoid ;  below,  by  the  external  border  of  the  orbital 
surface  of  the  superior  maxilla  and  a  small  part  of  the  palate  bone  ;  externally,  by 
a  small  part  of  the  malar  bone : l  internally,  it  joins  at  right  angles  with  the 
pterygo-maxillary  fissure.  This  fissure  opens  a  communication  from  the  orbit  into 
three  fossee — the  temporal,  zygomatic,  and  spheno-maxillary ;  it  transmits  the 
superior  maxillary  nerve  and  its  orbital  branch,  the  infraorbital  vessels,  and 
ascending  branches  from  the  spheno-palatine  or  Meckel's  ganglion. 

The  Pterygo-maxillary  Fissure  is  vertical,  and  descends  at  right  angles  from 
the  inner  extremity  of  the  preceding ;  it  is  a  V-shaped  interval,  formed  by 
the  divergence  of  the  superior  maxillary  bone  from  the  pterygoid  process  of  the 
sphenoid.  It  serves  to  connect  the  spheno-maxillary  fossa  with  the  zygomatic  fossa, 
and  transmits  branches  of  the  internal  maxillary  artery. 

The  Spheno-maxillary  Fossa. 

The  Spheno-maxillary  Fossa  is  a  small,  triangular  space  situated  at  the  angle  of 
junction  of  the  spheno-maxillary  and  pterygo-maxillary  fissures,  and  placed  beneath 
the  apex  of  the  orbit.  It  is  formed  above  by  the  under  surface  of  the  body  of 
the  sphenoid  and  by  the  orbital  process  of  the  palate  bone  ;  in  front,  by  the  superior 
maxillary  bone ;  behind,  by  the  anterior  surface  of  the  base  of  the  pterygoid 
process  and  lower  part  of  the  anterior  surface  of  the  great  wing  of  the  sphenoid ; 
internally,  by  the  vertical  plate  of  the  palate.  This  fossa  has  three  fissures 
terminating  in  it — the  sphenoidal,  spheno-maxillary,  and  jptery go-maxillary ;  it 
communicates  with  the  orbit  by  the  spheno-maxillary  fissure  :  with  the  nasal  fossse 
by  the  spheno-palatine  foramen,  and  with  the  zygomatic  fossa  by  the  pterygo-max- 
illary fissure.  It  also  communicates  with  the  cavity  of  the  cranium,  and  has  open- 
ing into  it  five  foramina.  Of  these,  there  are  three  on  the  posterior  wall :  the  for- 
amen rotundum  above;  below  and  internal  to  this,  the  Vidian  canal;  and  still 
more  inferiorly  and  internally,  the  ptery go-palatine  canal.  On  the  inner  wall  is 
the  spheno-palatine  foramen,  by  which  the  spheno-maxillary  communicates  with 
the  nasal  fossa ;  and  below  is  the  superior  orifice  of  the  posterior  palatine  caned, 
besides  occasionally  the  orifices  of  the  accessory  posterior  palatine  canals.  The 
fossa  contains  the  superior  maxillary  nerve  and  Meckel's  ganglion,  and  the  termi- 
nation of  the  internal  maxillary  artery. 

The  Anterior  Region  of  the  Skull. 

The  Anterior  Region  of  the  Skull,  which  forms  the  face,  is  of  an  oval  form, 
presents  an  irregular  surface,  and  is  excavated  for  the  reception  of  two  of  the 
organs  of  sense,  the  eye  and  the  nose.  It  is  bounded  above  by  the  glabella  and 
margins  of  the  orbit ;  below,  by  the  prominence  of  the  chin ;  on  each  side  by  the 
malar  bone  and  anterior  margin  of  the  ramus  of  the  jaw.  In  the  median  line  are 
seen  from  above  downward  the  glabella,  and  diverging  from  it  are  the  superciliary 
ridges,  Avhich  indicate  the  situation  of  the  frontal  sinuses  and  support  the  eyebrows. 
Beneath  the  glabella  is  the  fronto-nasal  suture,  the  mid-point  of  which  is  termed 
the  nasion,  and  below  this  is  the  arch  of  the  nose,  formed  by  the  nasal  bones,  and 
the  nasal  processes  of  the  superior  maxillary.  The  nasal  arch  is  convex  from  side 
to  side,  concave  from  above  downward,  presenting  in  the  median  line  the  inter- 
nasal  suture  formed  between  the  nasal  bones,  laterally  the  naso-maxillary  suture 
formed  between  the  nasal  bone  and  the  nasal  process  of  the  superior  maxillary 
bone.  Below  the  nose  is  seen  the  opening  of  the  anterior  nares,  which  is  heart- 
shaped,   with  the  narrow    end    upward,    and    presents    laterally  the  thin,  sharp 

1  Occasionally  the  superior  maxillary  bone  and  the  sphenoid  articulate  with  each  other  at  the 
anterior  extremity  of  this  fissure ;  the  malar  is  then  excluded  from  entering  into  its  formation. 


THE   ANTERIOR   REGION   OF    THE   SKULL.  113 

margins  serving  for  the  attachment  of  the  lateral  cartilages  of  the  nose,  and  in  the 
middle  line  below  a  prominent  process,  the  anterior  nasal  spine,  bounded  by  two 
deep  notches.  Below  this  is  the  intermaxillary  suture,  and  on  each  side  of  it  the 
incisive  fossa.  Beneath  this  fossa  are  the  alveolar  processes  of  the  upper  and 
lower  jaws,  containing  the  incisor  teeth,  and  at  the  lower  part  of  the  median  line 
the  symphysis  of  the  chin,  the  mental  process,  with  its  two  mental  tubercles, 
separated  by  a  median  groove,  and  the  incisive  fossa  of  the  lower  jaw. 

On  each  side,  proceeding  from  above  downward,  is  the  supraorbital  ridge, 
terminating  externally  in  the  external  angular  process  at  its  junction  with  the 
malar,  and  internally  in  the  internal  angular  process;  toward  the  inner  third  of 
this  ridge  is  the  supraorbital  notch  or  foramen,  for  the  passage  of  the  supraorbital 
vessels  and  nerve.  Beneath  the  supraorbital  ridge  is  the  opening  of  the  orbit, 
bounded  externally  by  the  orbital  ridge  of  the  malar  bone ;  below,  by  the  orbital 
ridge  formed  by  the  malar  and  superior  maxillary  bones  ;  internally,  by  the  nasal 
process  of  the  superior  maxillary  and  the  internal  angular  process  of  the  frontal 
bone.  On  the  outer  side  of  the  orbit  is  the  quadrilateral  anterior  surface  of  the 
malar  bone,  perforated  by  one  or  two  small  malar  foramina.  Below  the  inferior 
margin  of  the  orbit  is  the  infraorbital  foramen,  the  termination  of  the  infraorbital 
canal,  and  beneath  this  the  canine  fossa,  which  gives  attachment  to  the  Levator 
anguli  oris ;  still  lower  are  the  alveolar  processes,  containing  the  teeth  of  the  upper 
and  lower  jaws.  Beneath  the  alveolar  arch  of  the  lower  jaw  is  the  mental  foramen, 
for  the  passage  of  the  mental  vessels  and  nerve,  the  external  oblique  line,  and  at 
the  lower  border  of  the  bone,  at  the  point  of  junction  of  the  body  with  the  ramus, 
a  shallow  groove  for  the  passage  of  the  facial  artery. 

The  Orbits. 

The  Orbits  (Fig.  75)  are  two  quadrilateral  pyramidal  cavities,  situated  at  the 
upper  and  anterior  part  of  the  face,  their  bases  being  directed  forward  and 
outward,  and  their  apices  backward  and  inward,  so  that  the  axes  of  the  two.  if 
continued  backward,  would- meet  over  the  body  of  the  sphenoid  bone.  Each  orbit 
is  formed  of  seven  bones,  the  frontal,  sphenoid,  ethmoid,  superior  maxillary,  malar, 
lachrymal,  and  palate ;  but  three  of  these,  the  frontal,  ethmoid,  and  sphenoid. 
enter  into  the  formation  of  both  orbits,  so  that  the  two  cavities  are  formed  of 
eleven  bones  only.  Each  cavity  presents  for  examination  a  roof,  a  floor,  an  inner 
and  an  outer  wall,  four  angles,  a  circumference  or  base,  and  an  apex.  The  roof 
is  concave,  directed  downward  and  slightly  forward,  and  formed  in  front  by  the 
orbital  plate  of  the  frontal ;  behind  by  the  lesser  wing  of  the  sphenoid.  This 
surface  presents  internally  the  depression  for  the  cartilaginous  pulley  of  the 
Superior  oblique  muscle;  externally,  the  depression  for  the  lachrymal  gland;  and 
posteriorly,  the  suture  connecting  the  frontal  and  lesser  wing  of  the  sphenoid. 

The  floor  is  directed  upward  and  outward,  and  is  of  less  extent  than  the  roof: 
it  is  formed  chiefly  by  the  orbital  process  of  the  superior  maxillary  :  in  front,  to  a 
small  extent,  by  the  orbital  process  of  the  malar,  and  behind,  by  the  superior 
surface  of  the  orbital  process  of  the  palate.  This  surface  presents  at  its  anterior 
and  internal  part,  just  external  to  the  lachrymal  groove,  a  depression  for  the 
attachment  of  the  Inferior  oblique  muscle;  externally,  the  suture  between  the 
malar  and  superior  maxillary  bones  ;  near  its  middle,  the  infraorbital  groove  :  and 
posteriorly,  the  suture  between  the  maxillary  and  palate  bones. 

The  inner  wall  is  flattened,  nearly  vertical,  and  formed  from  before  backward 
by  the.  nasal  process  of  the  superior  maxillary,  the  lachrymal,  os  planum  of  the 
ethmoid,  and  a  small  part  of  the  body  of  the  sphenoid.  This  surface  presents 
the  lachrymal  groove  and  crest  of  the  lachrymal  bone,  and  the  sutures  connecting 
the  lachrymal  with  the  superior  maxillary,  the  ethmoid  with  the  lachrymal  in 
front,  and  the  ethmoid  Avith  the  sphenoid  behind. 

The  outer  wall  is  directed  forward  and  inward,  and  is  formed  in  front  by  the 
orbital  process  of  the  malar  bone ;    behind,  by  the  orbital  surface  of  the  greater 


114 


THE  SKELETON. 


wing  of  the  sphenoid.     On  it  are  seen  the  orifices  of  one  or  two  malar  canals,  and 
the  suture  connecting  the  sphenoid  and  malar  bones. 

Angles. — The  superior  external  angle  is  formed  by  the  junction  of  the  upper 
and  outer  walls ;  it  presents,  from  before  backward,  the  suture  connecting  the 
frontal  with  the  malar  in  front  and  with  the  great  wing  of  the  sphenoid  behind ; 
quite  posteriorly  is  the  foramen  lacerum  anterius,  or  sphenoidal  fissure,  which 
transmits  the  third,  the  fourth,  the  three  branches  of  the  ophthalmic  division  of 
the  fifth,  the  sixth  nerve,  some  filaments  from  the  cavernous  plexus  of  the  sym- 
pathetic, the  orbital  branch  of  the  middle  meningeal  artery,  a  recurrent  branch 


TENDO   OCULI 


Groove  for 
facial  artery 


Fig.  75  — Anterolateral  region  of  the  skull.    (Cryer.) 


from  the  lachrymal  artery  to  the  dura  mater,  and  the  ophthalmic  vein.  The 
superior  internal  angle  is  formed  by  the  junction  of  the  upper  and  inner  wall;  and 
presents  the  suture  connecting  the  frontal  bone  with  the  lachrymal  in  front  and 
with  the  ethmoid  behind.  The  point  of  junction  of  the  anterior  border  of  the 
lachrymal  with  the  frontal  has  been  named  the  dacryon.  This  angle  presents  two 
foramina,  the  anterior  and  posterior  ethmoidal,  the  former  transmitting  the  anterior 
ethmoidal  vessels  and  nasal  nerve,  the  latter  the  posterior  ethmoidal  vessels.  The 
inferior  external  angle,  formed  by  the  junction  of  the  outer  wall  and  floor,  presents 
the  spheno-maxillary  fissure,  which  transmits  the  superior  maxillary  nerve  and  its 
orbital  branches,  the  infraorbital  vessels,  and  the  ascending  branches  from  the 
spheno-palatine  or  Meckel's  ganglion.  The  inferior  internal  angle  is  formed  by 
the  union  of  the  lachrymal  and  os  planum  of  the  ethmoid  with  the  superior  max- 


THE   ANTERIOR    REGION   OF    THE  SKULL. 


115 


illary  and  palate  bones.  The  circumference,  or  base,  of  the  orbit,  quadrilateral 
in  form,  is  bounded  above  by  the  supraorbital  ridge ;  below,  by  the  anterior  border 
of  the  orbital  plate  of  the  malar  and  superior  maxillary  bones ;  externally,  by  the 
external  angular  process  of  the  frontal  and  malar  bones  ;  internally,  by  the  internal 
angular  process  of  the  frontal  and  the  nasal  process  of  the  superior  maxillary. 
The  circumference  is  marked  by  three  sutures,  the-fronto-maxillary  internally,  the 
fronto-malar  externally,  and  the  malo-maxillary  below ;  it  contributes  to  the  for- 
mation of  the  lachrymal  groove,  and  presents,  above,  the  supraorbital  notch  (or 
foramen),  for  the  passage  of  the  supraorbital  vessels  and  nerve.  The  apex,  situated 
at  the  back  of  the  orbit,  corresponds  to  the  optic  foramen,1  a  short,  circular  canal 
which  transmits  the  optic  nerve  and  ophthalmic  artery.  It  will  thus  be  seen  that 
there  are  nine  openings  communicating  with  each  orbit — viz.  the  optic  foramen, 
sphenoidal  fissure,  spheno-maxillary  fissure,  supraorbital  foramen,  infraorbital  canal, 
anterior  and  posterior  ethmoidal  foramina,  malar  foramina,  and  canal  for  the  nasal 
duct. 

The  Nasal  Fossae. 

The  Nasal  Fossae  are  two  large,  irregular  cavities  situated  on  either  side  of  the 
middle  line  of  the  face,  extending  from  the  base  of  the  cranium  to  the  roof  of  the 
mouth,  and  separated  from  each  other  by  a  thin  vertical  septum.  They  communi- 
cate by  two  large  apertures,  the  anterior  nares,  with  the  front  of  the  face,  and  by 
the  two  posterior  nares  with  the  naso-pharynx  behind.      These  fossae  are  much 


Roof. 

Nasal  bone. 
Nasal  spine  of  frontal  bone. 
Horizontal  plate  of  ethmoid. 
Sphenoid. 


I Probe  passed  through 

naso-lachrymal  canal. 


Bristle  passed  through 
infundibulum. 


■.  ^  \  * Lachrymal 

^J^ Ethmoid. 


Outer  Wall. 

—  Nasal  proc.  of  sup.  max. 


Unciform  process  of  ethmoid. 
Inferior  turbinated. 
Palate. 

Superior  meatus. 
Middle  meatus. 
Inferior  meatus. 


Floor. 

Anterior  nasal  spine. 
Palate  proc.  of  sup.  max. 
Palate  process  of  palate. 

Posterior  nasal  spine. 
Anterior  palatine  canal. 


Fig.  76.— Roof,  floor,  and  outer  wall  of  left  nasal  fossa. 

narrower  above  than  below,  and  in  the  middle  than  at  the  anterior  or  posterior 
openings ;  their  depth,  which  is  considerable,  is  much  greater  in  the  middle  than 
at  either  extremity.  Each  nasal  fossa  communicates  with  four  sinuses,  the  frontal 
above,  the  sphenoidal  behind,  and  the  maxillary  and  ethmoidal  on  the  outer  wall. 

1  Quain,  Testut,  and  others  give  the  apex  of  the  orbit  as  corresponding  with  the  inner  end  of  the 
sphenoidal  fissure.  It  seems  better,  however,  to  adopt  the  statement  in  the  text,  since  the  muscles 
of  the  eyeball  take  origin  around  the  optic  foramen,  and  diverge  from  it  to  the  globe  of  the  eye. 


116  THE  SKELETON. 

Each  fossa  also  communicates  with  four  cavities :  with  the  orbit  by  the  lachrymal 
groove,  with  the  mouth  by  the  anterior  palatine  can  h   the  cranium  by  the 

olfactory  foramina,  and  with  the  spheno-maxillary  foas  /  tLe  spheno-palatine 
foramen  ;  and  they  occasionally  communicate  with  eacL  her  by  an  aperture  in 
the  septum.  The  bones  entering  into  their  formation  are  fourteen  in  number : 
three  of  the  cranium,  the  frontal,  sphenoid,  and  ethmoid,  and  all  the  bones  of  the 
face,  excepting  the  malar  and  lower  jaw.  Each  cavity  is  bounded  by  a  roof,  a  floor, 
an  inner  and  an  outer  wall. 

The  upper  wall,  or  roof  (Fig.  76),  is  long,  narrow,  and  horizontal  in  its  centre, 
but  slopes  downward  at  its  anterior  and  posterior  extremities ;  it  is  formed  in  front 
by  the  nasal  bones  and  nasal  spine  of  the  frontal,  which  are  directed  downward 
and  forward ;  in  the  middle,  by  the  cribriform  plate  of  the  ethmoid,  which  is  hori- 
zontal ;  and  behind,  by  the  under  surface  of  the  body  of  the  sphenoid  and  sphe- 
noidal turbinated  bones,  the  ala  of  the  vomer  and  the  sphenoidal  process  of  the 
palate  bone,  which  are  directed  downward  and  backward.  This  surface  presents, 
from  before  backward,  the  internal  aspect  of  the  nasal  bones ;  on  their  outer  side, 
the  suture  formed  between  the  nasal  bone  and  the  nasal  process  of  the  superior 
maxillary ;  on  their  inner  side,  the  elevated  crest  which  receives  the  nasal  spine 
of  the  frontal  and  the  perpendicular  plate  of  the  ethmoid,  and  articulates  with  its 
fellow  of  the  opposite  side ;  whilst  the  surface  of  the  bones  is  perforated  by  a 
few  small  vascular  apertures,  and  presents  the  longitudinal  groove  for  the  nasal 
nerve ;  farther  back  is  the  transverse  suture,  connecting  the  frontal  with  the  nasal 
in  front,  and  the  ethmoid  behind,  the  olfactory  foramina  and  nasal  slit  on  the 
under  surface  of  the  cribriform  plate,  and  the  suture  between  it  and  the  sphenoid 
behind ;  quite  posteriorly  are  seen  the  sphenoidal  turbinated  bones,  the  orifices  of 
the  sphenoidal  sinuses,  and  the  articulation  of  the  alse  of  the  vomer  with  the  under 
surface  of  the  body  of  the  sphenoid. 

The  floor  is  flattened  from  before  backward,  concave  from  side  to  side,  and 
wider  in  the  middle  than  at  either  extremity.  It  is  formed  in  front  by  the  palate 
process  of  the  superior  maxillary ;  behind,  by  the  palate  process  of  the  palate  bone. 
This  surface  presents,  from  before  backward,  the  anterior  nasal  spine;  behind 
this,  the  upper  orifices  of  the  anterior  palatine  canal ;  internally,  the  elevated  crest 
which  articulates  with  the  vomer;  and  behind,  the  suture  between  the  palate  and 
superior  maxillary  bones,  and  the  posterior  nasal  spine. 

The  inner  wall,  or  septum  (Fig.  77),  is  a  thin  vertical  partition  which  sepa- 
rates the  nasal  fossae  from  each  other;  it  is  occasionally  perforated,  so  that  the 
fossae  communicate,  and  it  is  frequently  deflected  considerably  to  one  side.1  It 
is  formed,  in  front,  by  the  crest  of  the  nasal  bones  and  nasal  spine  of  the  frontal; 
in  the  middle,  by  the  perpendicular  plate  of  the  ethmoid ;  behind,  by  the  vomer 
and  rostrum  of  the  sphenoid ;  below,  by  the  crests  of  the  superior  maxillary  and 
palate  bones.  It  presents,  in  front,  a  large,  triangular  notch,  which  receives  the 
septal  cartilage  of  the  nose;  and  behind,  the  grooved  edge  of  the  vomer.  Its 
surface  is  marked  by  numerous  vascular  and  nervous  canals  and  the  groove  for 
the  naso-palatine  nerve,  and  is  traversed  by  sutures  connecting  the  bones  of  which 
it  is  formed. 

The  outer  wall  (Fig.  76)  is  formed,  in  front,  by  the  nasal  process  of  the 
superior  maxillary  and  lachrymal  bones ;  in  the  middle,  by  the-  ethmoid  and 
inner  surface  of  the  superior  maxillary  and  inferior  turbinated  bones ;  behind, 
by  the  vertical  plate  of  the  palate  bone  and  the  internal  pterygoid  plate  of  the 
sphenoid.  This  surface  presents  three  irregular  longitudinal  passages,  or  mea- 
tuses, termed  the  superior,  middle,  and  inferior  meatuses  of  the  nose.  The 
superior  meatus,  the  smallest  of  the  three,  is  situated  at  the  upper  and  back  part  of 
each  nasal  fossa,  occupying  the  posterior  third  of  the  outer  wall.  It  is  situated 
between  the  superior  and  middle  turbinated  bones,  and  has  opening  into  it  two 
foramina,  the  spheno-palatine  at  the  back  of  its  outer  Avail,  and  the  posterior 
ethmoidal  cells  at  the  front  part  of  the  outer  wall.     The  sphenoidal  sinus  opens 

1  See  footnote,  p.  78. 


THE   ANTERIOR    REGION    OF   THE  SKULL. 


117 


into  a  recess,  the  spheno-ethmoidal  recess,  winch  is  situated  above  and  behind  the 
superior  turbinated  bone.  The  middle  meatus  is  situated  between  the  middle  and 
inferior  turbinated  bones,  and  extends  from  the  anterior  end  of  the  inferior 
turbinated  bone  to  the  sphenopalatine  foramen  of  the  outer  wall  of  the  nasal 
fossa.  It  presents  in  front  the  orifice  of  the  infundibulum,  by  which  the  middle 
meatus  communicates  with  the  anterior  ethmoidal  cells,  and  through  these  with 
the  frontal  sinuses.      The  middle  ethmoidal  cells  also  open  into  this  meatus,  while 


Crest  of  nasal  bone. 

Nasal  spine  of 
frontal  bone. 


Space  for  triangular^ 
cartilage  of  septum 


Crest  of  palate  bone, 
■rest  of  superior  maxillary 
bone. 


Fig.  77. — Inner  wall  ot  nasal  fossae,  or  septum  of  nose. 


at  the  centre  of  the  outer  wall  is  the  orifice  of  the  antrum,  which  varies  somewhat 
as  to  its  exact  position  in  different  skulls.  The  inferior  meatus,  the  largest  of 
the  three,  is  the  space  between  the  inferior  turbinated  bone  and  the  floor  of  the 
nasal  fossa.  It  extends  along  the  entire  length  of  the  outer  wall  of  the  nose,  is 
broader  in  front  than  behind,  and  presents  anteriorly  the  lower  orifice  of  the 
canal  for  the  nasal  duct. 

The  anterior  nares  present  a  heart-shaped  or  pyriform  opening  whose  long 
axis  is  vertical  and  narrow  extremity  upward.  This  opening  in  the  recent  state 
is  much  contracted  by  the  cartilages  of  the  nose.  It  is  bounded  above  by  the 
inferior  border  of  the  nasal  bone ;  laterally  by  the  thin,  sharp  margin  which 
separates  the  facial  from  the  nasal  surface  of  the  superior  maxillary  bone ;  and 
below  by  the  same  border,  where  it  slopes  inward  to  join  its  fellow  of  the  opposite 
side  at  the  anterior  nasal  spine. 

The  posterior  nares,  or  choanse,  are  the  two  posterior  oval  openings  of  the  nasal 
fossa?,  by  which  they  communicate  with  the  upper  part  of  the  pharynx.  They  are 
situated  immediately  in  front  of  the  basilar  process,  and  are  bounded  above  by  the 
under  surface  of  the  body  of  the  sphenoid  and  alse  of  the  vomer;  below,  by  the 
posterior  border  of  the  horizontal  plate  of  the  palate  bone ;  externally,  by  the  inner 
surface  of  the  internal  pterygoid  plate ;  and  internally,  in  the  middle  line,  they 
are  separated  from  each  other  by  the  posterior  border  of  the  vomer. 


118  THE  SKELETON. 

Surface  Form. — The  various  bony  prominences  or  landmarks  which  are  to  be  easily  felt  and 
recognized  in  the  head  and  face,  and  which  afford  the  means  of  mapping  out  the  important 
structures  comprised  in  this  region,  are  as  follows : 

1.  Supraorbital  arch.  8.  Parietal  eminences. 

2.  Internal  angular  process.  9.  Temporal  ridge. 

3.  External  angular  process.  10.  Frontal  eminences. 

4.  Zygomatic  arch.  11.  Superciliary  ridges. 

5.  Mastoid  process.  12.  Nasal  bones. 

6.  External  occipital  protuberance.  13.  Lower  margin  of  orbit. 

7.  Superior  curved  line  of  occipital  bone.  14.  Lower  jaw. 

1.  The  supraorbital  arches  are  to  be  felt  throughout  their  entire  extent,  covered  by  the  eye- 
brows. They  form  the  upper  boundary  of  the  circumference  or  base  of  the  orbit,  and  separate 
the  face  from  the  forehead.  They  are  strong  and  arched,  and  terminate  internally  on  each  side 
of  the  root  of  the  nose  in  the  internal  angular  process,  which  articulates  with  the  lachrymal 
bone.  Externally  they  terminate  in  the  external  angular  process,  which  articulates  with  the 
malar  bone.  This  arched  ridge  is  sharper  and  more  defined  in  its  outer  than  in  its  inner  half, 
and  forms  an  overhanging  process  which  protects  and  shields  the  lachrymal  gland.  It  thus  pro- 
tects the  eye  in  its  most  exposed  situation  and  in  the  direction  from  which  blows  are  most  likely 
to  descend.  The  supraorbital  arch  varies  in  prominence  in  different  individuals.  It  is  more 
marked  in  the  male  than  in  the  female,  and  in  some  races  of  mankind  than  others.  In  the  less 
civilized  races,  as  the  forehead  recedes  backward,  the  supraorbital  arch  becomes  more  prominent, 
and  approaches  more  to  the  characters  of  the  monkey  tribe,  in  which  the  supraorbital  arches  are 
very  largely  developed,  and  acquire  additional  prominence  from  the  oblique  direction  of  the 
frontal  bone.  2.  The  internal  angular  process  is  scarcely  to  be  felt.  Its  position  is  indicated 
by  the  angle  formed  by  the  supraorbital  arch  with  the  nasal  process  of  the  superior  maxillary 
bone  and  the  lachrymal  bone  at  the  inner  side  of  the  orbit.  Between  the  internal  angular  pro- 
cesses of  the  two  sides  is  a  broad  surface  which  assists  in  forming  the  root  of  the  nose,  and 
immediately  above  this  a  broad,  smooth,  somewhat  triangular  surface,  the  glabella,  situated 
between  the  superciliary  ridges.  3.  The  external  angular  process  is  much  more  strongly  marked 
than  the  internal,  and  is  plainly  to  be  felt.  It  is  formed  by  the  junction  or  confluence  of  the  supra- 
orbital and  temporal  ridges,  and,  articulating  with  the  malar  bone,  it  serves  to  a  very  consider- 
able extent  to  support  the  bones  of  the  face.  In  carnivorous  animals  the  external  angular  pro- 
cess does  not  articulate  with  the  malar,  and  therefore  this  lateral  support  to  the  bones  of  the  face 
is  not  present.  4.  The  zygomatic  arch  is  plainly  to  be  felt  throughout  its  entire  length,  being 
situated  almost  immediately  under  the  skin.  It  is  formed  by  the  malar  bone  and  the  zygomatic 
pi'ocess  of  the  temporal  bone.  At  its  anterior  extremity,  where  it  is  formed  by  the  malar  bone, 
it  is  broad  and  forms  the  prominence  of  the  cheek ;  the  posterior  part  is  narrower,  and  termi- 
nates just  in  front  and  a  little  above  the  tragus  of  the  external  ear.  The  lower  border  is 
more  plainly  to  be  felt  than  the  upper,  in  consequence  of  the  dense  temporal  fascia  being 
attached  to  the  latter,  which  somewhat  obscures  its  outline.  Its  shape  differs  very  much  in  indi- 
viduals and  in  different  races  of  mankind.  In  the  most  degraded  type  of  skull — as,  for  instance, 
in  the  skull  of  the  negro  of  the  Guinea  Coast — the  malar  bones  project  forward  and  not  outward, 
and  the  zygoma  at  its  posterior  extremity  extends  farther  outward  before  it  is  twisted  on  itself  to 
be  prolonged  forward.  This  makes  the  zygomatic  arch  stand  out  in  bold  relief,  and  affords 
greater  space  for  the  Temporal  muscle.  In  skulls  which  have  a  more  pyramidal  shape,  as  in  the 
Esquimaux  or  Greenlander,  the  malar  bones  do  not  project  forward  and  downward  under  the 
eyes,  as  in  the  preceding  form,  but  take  a  direction  outward,  forming  with  the  zygoma  a  large, 
rounded  sweep  or  segment  of  a  circle.  Thus  it  happens  that  if  two  lines  are  drawn  from  the 
zygomatic  arches,  touching  the  temporal  ridges,  they  meet  above  the  top  of  the  head,  instead  of 
being  parallel,  or  nearly  so,  as  in  the  European  skull,  in  which  the  zygomatic  arches  are  not 
nearly  so  prominent.  This  gives  to  the  face  a  more  or  less  oval  type.  5.  Behind  the  ear  is  the 
mastoid  portion  of  the  temporal  bone,  plainly  to  be  felt,  and  terminating  below  in  a  nipple- 
shaped  process.  Its  anterior  border  can  be  traced  immediately  behind  the  concha,  and  its  apex 
is  on  about  a  level  with  the  lobule  of  the  ear.  It  is  rudimentary  in  infancy,  but  gradually 
develops  in  childhood,  and  is  more  marked  in  the  negro  than  in  the  European.  6.  The  external 
occipital  protuberance  is  always  plainly  to  be  felt  just  at  the  level  where  the  skin  of  the  neck 
joins  that  of  the  head.  At  this  point  the  skull  is  thick  for  the  purposes  of  safetjr,  while 
radiating  from  it  are  numerous  curved  arches  or  buttresses  of  bone  which  give  to  this  portion  of 
the  skull  further  security.  7.  Running  outward  on  either  side  from  the  external  occipital  protu- 
berance is  an  arched  ridge  of  bone,  which  can  be  more  or  less  plainly  perceived.  This  is  the 
superior  curved  line  of  the  occipital  bone,  and  gives  attachment  to  some  of  the  muscles  which 
keep  the  head  erect  on  the  spine  ;  accordingly,  we  find  it  more  developed  in  the  negro  tribes,  in 
whom  the  jaws  are  much  more  massive,  and  therefore  require  stronger  muscles  to  prevent  their 
extra  weight  carrying  the  head  forward.  Below  this  line  the  surface  of  bone  at  the  back  of  the 
head  is  obscured  by  the  overlying  muscles.  Above  it,  the  vault  of  the  cranium  is  thinly  covered 
with  soft  structures,  so  that  the  form  of  this  part  of  the  head  is  almost  exactly  that  of  the  upper 
portion  of  the  occipital,  the  parietal,  and  the  frontal  bones  themselves;  and  in  bald  persons 
even  the  lines  of  junction  of  the  bones,  especially  the  junction  of  the  occipital  and  parietal  at 
the  lambdoid  suture,_  may  be  defined  as  a  slight  depression,  caused  by  the  thickening  of  the 
borders  of  the  bones  in  this  situation.     8.  In  the  line  of  the  greatest  transverse  diameter  of  the 


SURFACE  FORM   OF   THE   SKULL.  119 

head,  on  each  side  of  the  middle  line,  are  generally  to  be  found  the  -parietal  eminences,  one  on 
each  side  of  the  middle  line,  though  sometimes  these  eminences  are  not  situated  at  the  point  of 
the  greatest  transverse   diameter,  which   is_  at   some   other   prominent   part  of  the   parietal 
region.     They  denote   the   point  where    ossification    of  the   parietal   bone   began.     They  are 
much  more  prominent  and  well-marked   in  early  life,  in  consequence  of  the  sharper  curve 
of  the  bone   at   this  period,  so   that   it    describes   the   segment   of  a  smaller  circle.     Later 
in  life,  as  the  bone  grows,  the  curve  spreads  out  and  forms  the  segment  of  a  larger  circle, 
so  that  the   eminence  becomes  less   distinguishable.      In   consequence   of  this   sharp   curve 
of  the  bone  in  early  life,   the  whole  of  the   vault  of  the   skull  has   a   squarer  shape   than 
it  has  in  later  life,  and  this  appearance  may  persist  in  some  rickety  skulls.      The  eminence 
is  more  apparent  in  the  negro's  skull  than  in  that  of  the  European.     This  is  due  to  greater  flat- 
tening of  the  temporal  fossa  in  the  former  skull  to  accommodate  the  larger  Temporal  muscle 
which  exists  in  these  races.     The  parietal  eminence  is  particularly  exposed  to  injury  from  blows 
or  falls  on  the  head,  but  fracture  is  to  a  certain  extent  prevented  by  the  shape  of  the  bone, 
which  forms  an  arch,  so  that  the  force  of  the  blow  is  diffused  over  the  bone  in  every  direction! 
9.  At  the  side  of  the  head  may  be  felt  the  temporal  ridge.     Commencing  at  the  external 
angular  process,  it  may  be  felt  as  a  curved  ridge,  passing  upward  and  then  curving  backward,  on 
the  frontal  bone,  separating  the  forehead  from  the  temporal  fossa.     It  may  then  be  traced,  pass- 
ing backward  in  a  curved  direction,  over  the  parietal  bone,  and,  though  less  marked,  still  gen- 
erally to  be  recognized.     Finally,  the  ridge  curves  downward,  and  terminates  in  the  posterior 
root  of  the  zygoma,  which  separates  the  squamous  from  the  subcutaneous  mastoid  portion  of  the 
temporal  bone.     Mr.  Victor  Horsley  has  recently  shown,  in  an  article  on  the  "Topography  of 
the  Cerebral  Cortex,"  that  the  second  temporal  ridge  (see  page  62)  can  be  made  out  on  the 
living  body.     10.  The  frontal  eminences  vary  a  good  deal  in  different  individuals,  being  con- 
siderably more  prominent  in  some  than  in  others,  and  they  are  often  not  symmetrical  on  the  two 
sides  of  the  body,  the  one  being  much  more  pronounced  than  the  other.     This  is  often  especially 
noticeable  in  the  skull  of  the  young  child  or  infant,  and  becomes  less  marked  as  age  advances. 
The  prominence  of  the  frontal  eminences  depends  more  upon  the  general  shape  of  the  whole 
bone  than  upon  the  size  of  the   protuberances   themselves.     As   the   skull   is  more    highly 
developed  in  consequence  of  increased  intellectual  capacity,  so  the  frontal  bone  becomes  more 
upright  and  the  frontal  eminences  stand  out  in  bolder  relief.     Thus  they  may  be  considered  as 
affording,  to  a  certain  extent,  an  indication  of  the  development  of  the  hemispheres  of  the  brain 
beneath,  and  of  the  mental  powers  of  the  individual.     They  are  not  so  much  exposed  to  injury 
as  the  parietal  eminences.     In  falls  forward  the  upper  extremities  are  involuntarily  thrown  out, 
and  break  the  force  of  the  fall,  and  thus  shield  the  frontal  bone  from  injury.     11.  Below  the 
frontal  eminences  on  the  forehead  are  the  superciliary  ridges,  which  denote  the  position  of  the 
frontal  sinuses,  and  vary  according  to  the  size  of  the  sinuses  in  different  individuals,  being,  as  a 
rule,  small  in  the  female,  absent  in  children,  and  sometimes  unusually  prominent  in  the  male, 
when  the  frontal  sinuses  are  largely  developed.     They  commence  on  either  side  of  the  glabella, 
and  at  first  present  a  rounded  form,  which  gradually  fades  away  at  their  outer  ends.     12.  The 
nasal  bones  form  the  prominence  of  the  nose.     They  vary  much  in  size  and  shape,  and  to  them 
is  due  the  varieties  in  the  contour  of  this  organ  and  much  of  the  character  of  the  face.     Thus, 
in  the  Mongolian  or  Ethiopian  they  are  flat,  broad  and  thick  at  their  base,  giving  to  these  tribes 
the  flattened  nose  by  which  they  are  characterized,   and  differing  very  decidedly  from  the 
Caucasian,  in  whom  the  nose,  owing  to  the  shape  of  the  nasal  bones,  is  narrow,  elevated  at  the 
bridge,  and  elongated  downward.     Below,  the  nasal  bones  are  thin  and  connected  with  the  car- 
tilages of  the  nose,  and  the  angle  or  arch  formed  by  their  union  serves  to  throw  out  the  bridge 
of  the  nose,  and  is  much  more  marked  in  some  individuals  than  others.     13.  The  lower  margin 
of  the  orbit^  formed  by  the  superior  maxillary  bone  and  the  malar  bone,  is  plainly  to  be  felt 
throughout  its  entire  length.     It  is  continuous  internally  with  the  nasal  process  of  the  superior 
maxillary  bone,  which  forms  the  inner  boundary  of  the  orbit.     At  the  point  of  junction  of  the 
lower  margin  of  the  orbit  with  the  nasal  process  is  to  be  felt  a  little  tubercle  of  bone,  which  can 
be  plainly  perceived  by  running  the  finger  along  the  bone  in  this  situation.     This  tubercle  serves 
as  a  guide  to  the  position  of  the  lachrymal  sac,  which  is  situated  above  and  behind  it,     14.  The 
outline  of  the  lowirjaw  is  to  be  felt  throughout  its  entire  length.     Just  in  front  of  the  tragus  of 
the  external  ear,  and  below  the  zygomatic  arch,  the  condyle  can  be  made  out.    When  the  mouth 
is  opened  this  prominence  of  bone  can  be  perceived  advancing  out  of  the  glenoid  fossa  on  to  the 
eminentia  articularis,  and  receding  again  when  the  mouth  is  closed.     From  the  condyle  the  pos- 
terior border  of  the  ramus  can  be  felt  extending  down  to  the  angle.    A  line  drawn  from  the  con- 
dyle to   the  angle  would  indicate  the  exact  position  of  this  border.     From  the  angle  to  the 
symphysis  of  the  chin  the  lower,  rounded  border  of  the  body  of  the  bone  is  plainly  to  be  felt. 
At  the  point  of  junction  of  the  two  halves  of  the  bone  is  a  well-marked  triangular  eminence,  the 
mental  process,  which  forms  the  prominence  of  the  chin. 

Surgical  Anatomy. — An  arrest  in  the  ossifying  process  may  give  rise  to  deficiencies  or 
gaps ;  or  to  fissures,  which  are  of  importance  in  a  medico-legal  point  of  view,  as  they  are  liable 
to_  be  mistaken  for  fractures.  The  fissures  generally  extend  from  the  margin  toward  the  centre 
of  the  bone,  but  gaps  may  be  found  in  the  middle  as  well  as  at  the  edges.  In  course  of  time 
they  may  become  covered  with  a  thin  lamina  of  bone. 

Occasionally  a  protrusion  of  the  brain  or  its  membranes  may  take  place  through  one  of  these 
gaps  in  an  imperfectly  developed  skull.  When  the  protrusion  consists  of  membranes  only,  and 
is  filled  with  cerebro-spinal  fluid,  it  is  called  a  meningocele;  when  the  protrusion  consists  of  braiD 


120  THE  SKELETON. 

as  well  as  membranes,  it  is  termed  an  encepJialocele  ;  and  when  the  protruded  brain  is  a  prolonga- 
tion from  one  of  the  ventricles,  and  is  distended  by  a  collection  of  fluid  from  an  accumulation  in 
the  ventricle,  it  is  termed  an  hydrencephalocele.  This  latter  condition  is  frequently  found  at  the 
root  of  the  nose,  where  a  protrusion  of  the  anterior  horn  of  the  lateral  ventricle  takes  place 
through  a  deficiency  of  the  fronto-nasal  suture.  These  malformations  are  usually  found  in  the 
middle  line,  and  most  frequently  at  the  back  of  the  head,  the  protrusion  taking  place  through 
the  fissures  which  separate  the  four  centres  of  ossification  from  which  the  tabular  portion  of  the 
occipital  bone  is  originally  developed  (see  page  61).  They  most  frequently  occur  through 
the  upper  part  of  the  vertical  fissure,  which  is  the  last  to  ossify,  but  not  uncommonly  through 
the  lower  part,  when  the  foramen  magnum  may  be  incomplete.  More  rarely  these  protrusions 
have  been  met  with  in  other  situations  than  those  two  above  mentioned,  both  through  normal 
fissures,  as  the  sagittal,  lambdoid,  and  other  sutures,  and  also  through  abnormal  gaps  and 
deficiencies  at  the  sides,  and  even  at  the  base  of  the  skull. 

Fractures  of  the  skull  may  be  divided  into  those  of  the  vault  and  those  of  the  base.  Frac- 
tures of  the  vault  are  usually  produced  by  direct  violence.  This  portion  of  the  skull  varies  in 
thickness  and  strength  in  different  individuals,  but,  as  a  rule,  is  sufficiently  strong  to  resist  a  very 
considerable  amount  of  violence  without  being  fractured.  This  is  due  to  several  causes :  the 
rounded  shape  of  the  head  and  its  construction  of  a  number  of  secondary  elastic  arches,  each 
made  up  of  a  single  bone ;  the  fact  that  it  consists  of  a  number  of  bones,  united,  at  all  events  in 
early  life,  by  a  sutural  ligament,  which  acts  as  a  sort  of  buffer  and  interrupts  the  continuity  of  any 
violence  applied  to  the  skull ;  the  presence  of  arches  or  ridges,  both  on  the  inside  and  outside  of 
the  skull,  which  materially  strengthen  it ;  and  the  mobility  of  the  head  upon  the  spine  which 
further  enables  it  to  withstand  violence.  The  elasticity  of  the  bones  of  the  head  is  especially 
marked  in  the  skull  of  the  child,  and  this  fact,  together  with  the  wide  separation  of  the  indi- 
vidual bones  from  each  other,  and  the  interposition  between  them  of  other  softer  structures 
renders  fracture  of  the  bones  of  the  head  a  very  uncommon  event  in  infants  and  quite  young 
children ;  as  age  advances  and  the  bones  become  joined,  fracture  is  more  common,  though  still 
less  liable  to  occur  than  in  the  adult.  Fractures  of  the  vault  may,  and  generalby  do,  involve  the 
whole  thickness  of  the  bone  ;  but  sometimes  one  table  may  be  fractured  without  any  correspond- 
ing injury  to  the  other.  Thus,  the  outer  table  of  the  skull  may  be  splintered  and  driven  into  the 
diploe,  or  in  the  frontal  or  mastoid  regions  into  the  frontal  or  mastoid  cells,  without  any  injury 
to  the  internal  table.  And  on  the  other  hand,  the  internal  table  has  been  fractured,  and  por- 
tions of  it  depressed  and  driven  inward,  without  any  fracture  of  the  outer  table.  As  a  rule,  in 
fractures  of  the  skull  the  inner  table  is  more  splintered  and  comminuted  than  the  outer, 
and  this  is  due  to  several  causes.  It  is  thinner  and  more  brittle;  the  force  of  the  violence  as  it 
passes  inward  becomes  broken  up,  and  is  more  diffused  by  the  time  it  reaches  the  inner  table  ; 
the  bone,  being  in  the  form  of  an  arch,  bends  as  a  whole  and  spreads  out,  and  thus  presses  the 
particles  together  on  the  convex  surface  of  the  arch — i.  e.  the  outer  table — and  forces  them 
asunder  on  the  concave  surface  or  inner  table  ;  and,  lastly,  there  is  nothing  firm  under  the  inner 
table  to  support  it  and  oppose  the  force.  Fractures  of  the  vault  may  be  simple  fissures  or  starred 
and  comminuted  fractures,  and  these  may  be  depressed  or  elevated.  These  latter  cases  of 
fracture  with  elevation  of  the  fractured  portion  are  uncommon,  and  can  only  be  produced  by 
direct  wound.  In  comminuted  fracture  a  portion  of  the  skull  is  broken  into  several  pieces, 
the  lines  of  fracture  radiating  from  a  centre  where  the  chief  impact  of  the  blow  was  felt ; 
if  depressed,  a  fissure  circumscribes  the  radiating  line,  enclosing  a  portion  of  skull.  If 
this  area  is  circular,  it  is  termed  a  "pond"  fracture,  and  would  in  all  probability  have  been 
caused  by  a  round  instrument,  as  a  life-preserver  or  hammer ;  if  elliptical  in  shape,  it  is 
termed  a  "  gutter  fracture,"  and  would  owe  its  shape  to  the  instrument  which  had  produced  it, 
as  a  poker. 

Fractures  of  the  base  are  most  frequently  produced  by  the  extension  of  a  fissure  from  the 
vault,  as  in  falls  on  the  head,  where  the  fissure  starts  from  the  part  of  the  vault  which  first 
struck  the  ground.  Sometimes,  however,  they  are  caused  by  direct  violence,  when  foreign 
bodies  have  been  forced  through  the  thin  roof  of  the  orbit,  through  the  cribriform  plate  of  the 
ethmoid  from  being  thrust  up  the  nose,  or  through  the  roof  of  the  pharynx.  Other  cases  of 
fracture  of  the  base  occur  from  indirect  violence,  as  in  fracture  of  the  occipital  bone  from  impac- 
tion of  the  spinal  column  against  it's  condyles  in  falls  on  the  buttocks,  knees,  or  feet,  or  in  cases 
where  the  glenoid  cavity  has  been  fractured  by  the  violent  impact  of  the  condyle  of  the  lower  jaw 
against  it  from  blows  on  the  chin. 

The  most  common  place  for  fracture  of  the  base  to  occur  is  through  the  middle  fossa,  and 
here  the  fissure  usually  takes  a  fairly  definite  course.  Starting  from  the  point  struck,  which  is 
generally  somewhere  in  the  neighborhood  of  the  parietal  eminence,  it  runs  downward  through 
the  parietal  and  squamous  portion  of  the  temporal  bone  and  across  the  petrous  portion  of  this 
bone,  frequently  traversing  and  implicating  the  internal  auditory  meatus,  to  the  middle  lacerated 
foramen.  From  this  it  may  pass  across  the  body  of  the  sphenoid,  through  the  pituitary  fossa  to 
the  middle  lacerated  foramen  of  the  other  side,  and  may  indeed  travel  round  the  whole  cranium, 
so  as  to  completely  separate  the  anterior  from  the  posterior  part.  The  course  of  the  fracture 
should  be  borne  in  mind,  as  it  explains  the  symptoms  to  which  fracture  in  this  region  may  give 
rise ;  thus,  if  the  fissure  pass  across  the  internal  auditory  meatus,  injury  to  the  facial  and 
auditory  nerves  may  result,  with  consequent  facial  paralysis  and  deafness ;  or  the  tubular  pro- 
longation of  the  arachnoid  around  these  nerves  in  the  meatus  may  be  torn,  and  thus  permit  of 
the  escape  of  the  cerebro-spinal  fluid  should  there  be  a  communication  between  the  internal  ear 


SURGICAL   ANATOMY   OF    THE   BONES    OF    THE  FACE.      Ill 

and  the  tympanum  and  the  membrana  tympani  be  ruptured,  as  is  frequently  the  case ;  again,  if 
the  fissure  passes  across  the  pituitary  fossa  and  the  muco-periosteum  covering  the  under  surface 
of  the  body  of  the  sphenoid  is  torn,  blood  will  find  its  way  into  the  pharynx  and  be  swallowed, 
and  after  a  time  vomiting  of  blood1  will  result.  Fractures  of  the  anterior  fossa,  involving  the 
bones  forming  the  roof  of  the  orbit  and  nasal  fossa,  are  generally  the  results  of  blows  on  the  fore- 
head ;  but  fracture  of  the  cribriform  plate  of  the  ethmoid  may  be  a  complication  of  fracture  of 
the  nasal  bone.  When  the  fracture  implicates  the  roof  of  the  orbit,  the  blood  finds  its  way 
into  this  cavity,  and,  travelling  forward,  appears  as  a  subconjunctival  ecchymosis.  If  the  roof 
of  the  nasal  fossa  be  fractured,  the  blood  escapes  from  the  nose.  In  rare  cases  tbere  may 
be  also  escape  of  cerebro-spinal  fluid  from  the  nose  where  the  dura  mater  and  arachnoid  have 
been  torn.  In  fractures  of  the  posterior  fossa  extravasation  of  blood  may  appear  at  the  nape  of 
the  neck. 

The  bones  of  the  skull  are  frequently  the  seat  of  nodes,  and  not  uncommonly  necrosis 
results  from  this  cause,  also  from  injury.  Necrosis  may  involve  the  entire  thickness  of  the 
skull,  but  is  usually  confined  to  the  external  table.  Necrosis  of  the  internal  table  alone  is  rarely 
met  with.     The  bones  of  the  skull  are  also  frequently  the  seat  of  sarcomatous  tumor. 

The  skull  in  rickets  is  peculiar:  the  forehead  is  high,  square,  and  projecting,  and  the 
anteroposterior  diameter  of  the  skull  is  long  in  relation  to  the  transverse  diameter.  The  bones 
of  the  face  are  small  and  ill-developed,  and  this  gives  the  appearance  of  a  larger  head  than 
actually  exists.  The  bones  of  the  head  are  often  thick,  especially  in  the  neighborhood  of  the 
sutures,  and  the  anterior  fontanelle  is  late  in  closing,  sometimes  remaining  unclosed  till  the 
fourth  year.  The  condition  of  craniotabes  has  by  some  been  also  believed  to  be  the  result 
of  rickets,  by  others  is  believed  to  be  due  to  inherited  syphilis.  In  all  probability  it  is  due 
to  both.  In  these  cases  the  bone  undergoes  atrophic  changes  in  patches,  so  that  it  becomes 
greatly  thinned  in  places,  generally  where  there  is  pressure,  as  from  the  pillow  or  nurse's  arm. 
It  is,  therefore,  usually  met  with  in  the  parietal  bone  and  verticaJ  plate  of  the  occipital  bone. 

In  congenital  syphilis  deposits  of  porous  bone  are  often  found  at  the  angles  of  the  parietal 
bones  and  two  halves  of  the  frontal  bone  which  bound  the  anterior  fontanelle.  These  deposits 
are  separated  by  the  coronal  and  sagittal  sutures,  and  give  to  the  skull  an  appearance  like  a 
"hot  cross  bun."  They  are  known  as  Parrot's  nodes,  and  such  a  skull  has  received  the  name 
of  natiform,  from  its  fancied  resemblance  to  the  buttocks. 

In  connection  with  the  bones  of  the  face  a  common  malformation  is  cleft  palate,  owing  to 
the  non-union  of  the  palatal  processes  of  the  maxillary  or  pre-oral  arch.  This  cleft  may  involve 
the  whole  or  only  a  portion  of  the  hard  palate,  and  usually  involves  the  soft  palate  also.  The 
cleft  is  in  the  middle  line,  except  it  involves  the  alveolus  in  front,  when  it  follows  the  suture 
between  the  main  portion  of  the  bone  and  the  pre-maxillary  bone.  _  Sometimes  the  cleft  runs 
on  either  side  of  the  pre-maxillary  bone,  so  that  this  bone  is  quite  isolated  from  the  maxillary 
bones  and  hangs  from  the  end  of  the  vomer.  The  malformation  is  usually  associated  with 
hare-lip,  which,  when  single,  is  almost  always  on  one  side,  corresponding  to  the  position  of  the 
suture  between  the  lateral  incisor  and  canine  tooth.  Some  few  cases  of  median  hare-lip  have 
been  described.     In  double  hare-lip  there  is  a  cleft  on  each  side  of  the  middle  line. 

The  bones  of  the  face  are  sometimes  fractured  as  the  result  of  direct  violence.  The  two 
most  commonly  broken  are  the  nasal  bone  and  the  inferior  maxilla,  and  of  these  the  latter  is  by 
far  the  most  frequently  fractured  of  all  the  bones  of  the  face.  Fracture  of  the  nasal  bone  is 
for  the  most  part  transverse,  and  takes  place  about  half  an  inch  from  the  free  margin.  The 
broken  portion  may  be  displaced  backward  or  more  generally  to  one  side  by  the  force  which 
produced  the  lesion,  as  there  are  no  muscles  here  which  can  cause  displacement.  The  malar 
bone  is  probably  never  broken  alone  ;  that  is  to  say,  unconnected  with  a  fracture  of  the  other 
bones  of  the  face.  The  zygomatic  arch  is  occasionally  fractured,  and  when  this  occurs  from 
direct  violence,  as  is  usually  the  case,  the  fragments  may  be  displaced  inward.  This  lesion  is 
often  attended  with  great  difficulty  or  even  inability  to  open  and  shut  the  mouth,  and  this  has 
been  stated  to  be  due  to  the  depressed  fragments  perforating  the  temporal  muscle,  but  would 
appear  rather  to  be  caused  by  the  injury  done  to  the  bony  origin  of  the  Masseter  muscle. 
Fractures  of  the  superior  maxilla  may  vary  much  in  degree,  from  the  chipping  off'  of  a  portion 
of  the  alveolar  arch,  a  frequent  accident  when  the  "old  key"  instrument  was  used  for  the 
extraction  of  teeth,  to  an  extensive  comminution  of  the  whole  bone  from  severe  violence,  as  the 
kick  of  a  horse.  The  most  common  situation  for  a  fracture  of  the  inferior  maxillary  bone  is  in 
the  neighborhood  of  the  canine  tooth,  as  at  this  spot  the  jaw  is  weakened  by  the  deep  socket  for 
the  fang  of  this  tooth  ;  it  is  next  most  frequently  fractured  at  the  angle  ;  then  at  the  symphysis, 
and  finally  the  neck  of  the  condyle  or  the  coronoid  process  may  be  broken.  Occasionally  a 
double  fracture  may  occur,  one  in  either  half  of  the  bone.  The  fractures  are  usually  coin  pound, 
from  laceration  of  the  mucous  membrane  covering  the  gums.  The  displacement  is  mainly  the 
result  of  the  same  violence  as  produced  the  injury,  but  may  be  further  increased  by  the  action 
of  the  muscles  passing  from  the  neighborhood  of  the  symphysis  to  the  hyoid  bone. 

The  superior  and  inferior  maxillary  bones  are  both  of  them  frequently  the  seat  of  necrosis, 
though  the  disease  affects  the  lower  much  more  frequently  than  the  upper  jaw,  probably  on 
account  of  the  greater  supply  of  blood  to  the  latter.  It  may  be  the  result  of  periostitis,  from 
tooth  irritation,  injury,  or  the  action  of  some  specific  poison,  as  syphilis,  or  from  salivation  by 
mercury ;  it  not  unfrequently  occurs  in  children  after  attacks  of  the  exanthematous  fevers,  and 
a  special  form  occurs  from  the  action  of  the  fumes  of  phosphorus  in  persons  engaged  in  the 
manufacture  of  matches. 


122  THE   SKELETON. 

Tumors  attack  the  jaw-bones  not  infrequently,  and  these  may  be  either  innocent  or  malig- 
nant: in  the  upper  jaw  cysts  may  occur  in  the  antrum,  constituting  the  so-called  dropsy  of  the 
antrum  ;  or,  again,  cysts  may  form  in  either  jaw  in  connection  with  the  teeth  :  either  cysts  con- 
nected with  the  roots  of  fully-developed  teeth,  the  "dental  cyst;"  or  cysts  connected  with 
imperfectly  developed  teeth,  the  ' '  dentigerous  cyst. ' '  Solid  innocent  tumors  include  the  fibroma, 
the  chondroma,  and  the  osteoma.  Of  malignant  tumors  there  are  two  classes,  the  sarcomata 
and  the  epithelioma.  The  sarcoma  are  of  various  kinds,  the  spindle-celled  and  round-celled,  of 
a  very  malignant  character,  and  the  myeloid  sarcoma,  principally  affecting  the  alveolar  margin  of 
the  bone.  Of  the  epitheliomata  we  find  the  squamous  variety  spreading  to  the  bone  from  the 
palate  or  gum,  and  the  cylindrical  epithelioma  originating  in  the  antrum  or  nasal  fossae. 

Both  superior  and  inferior  maxillary  bones  occasionally  require  removal  for  tumors  and  in 
some  other  conditions.  The  upper  jaw  is  removed  by  an  incision  from  the  inner  canthus  of  the 
eye,  along  the  side  of  the  nose,  round  the  ala,  and  down  the  middle  line  of  the  upper  lip.  A 
second  incision  is  carried  outward  from  the  inner  canthus  of  the  eye  along  the  lower  margin  of 
the  orbit  as  far  as  the  prominence  of  the  malar  bone.  The  flap  thus  formed  is  reflected  outward 
and  the  surface  of  the  bone  exposed.  The  connections  of  the  bone  to  the  other  bones  of  the 
face  are  then  divided  with  a  narrow  saw.  They  are  (1 )  the  junction  with  the  malar  bone,  pass- 
ing into  the  spheno-maxillary  fissure ;  (2)  the  nasal  process;  a  small  portion  of  its  upper 
extremity,  connected  with  the  nasal  bone  in  front,  the  lachrymal  bone  behind,  and  the  frontal 
bone  above,  being  left;  (3)  the  connection  with  the  bone  on  the  opposite  side  and  the  palate  in 
the  roof  of  the  mouth.  The  bone  is  now  firmly  grasped  with  lion-forceps,  and  by  means  of  a 
rocking  movement  upward  and  downward  the  remaining  attachments  of  the  orbital  plate  with 
the  ethmoid,  and  the  back  of  the  bone  with  the  palate,  broken  through.  The  soft  palate  is  first 
separated  from  the  hard  with  a  scalpel,  and  is  not  removed.  Occasionally  in  removing  the  upper 
jaw  it  will  be  found  that  the  orbital  plate  can  be  spared,  and  this  should  always  be  done  if  possi- 
ble. A  horizontal  saw-cut  is  to  be  made  just  below  the  infraorbital  foramen  and  the  bone  cut 
through  with  a  chisel  and  mallet.  Removal  of  one-half  of  the  lower  jaw  is  sometimes  required. 
If  possible,  the  section  of  the  bone  should  be  made  to  one  side  of  the  symphysis,  so  as  to  save 
the  genial  tubercles  and  the  origin  of  the  genio-hyo-glossus  muscle,  as  otherwise  the  tongue  tends 
to  fall  backward  and  may  produce  suffocation.  Having  extracted  the  central  or  preferably  the 
lateral  incisor  tooth,  a  vertical  incision  is  made  down  to  the  bone,  commencing  at  the  free  margin 
of  the  lip,  and  carried  to  the  lower  border  of  the  bone ;  it  is  then  carried  along  its  lower  border 
to  the  angle  and  up  the  posterior  margin  of  the  ramus  to  a  level  with  the  lobule  of  the  ear. 
The  flap  thus  formed  is  raised  by  separating  all  the  structures  attached  to  the  outer  surface  of 
the  bone.  The  jaw  is  now  sawn  through  at  the  point  where  the  tooth  has  been  extracted,  and 
the  knife  passed  along  the  inner  side  of  the  jaw,  separating  the  structures  attached  to  this  sur- 
face. The  jaw  is  then  grasped  by  the  surgeon  and  strongly  depressed,  so  as  to  bring  down 
the  coronoid  process  and  enable  the  operator  to  sever  the  tendon  of  the  temporal  muscle. 
The  jaw  can  be  now  further  depressed,  care  being  taken  not  to  evert  it  nor  rotate  it  outward, 
which  would  endanger  the  internal  maxillary  artery,  and  the  external  pterygoid  torn  through 
or  divided.  The  capsular  ligament  is  now  opened  in  front  and  the  lateral  ligaments  divided, 
and  the  jaw  removed  with  a  few  final  touches  of  the  knife. 

The  antrum  of  Highmore  occasionally  requires  tapping  for  suppuration.  This  may  be  done 
through  the  socket  of  a  tooth,  preferably  the  first  molar,  the  fangs  of  which  are  most  inti- 
mately connected  with  the  antrum,  or  through  the  facial  aspect  of  the  bone  above  the  alveolar 
process.  This  latter  method  does  not  perhaps  afford  such  efficient  drainage,  but  there  is  less 
chance  of  food  finding  its  way  into  the  cavity.  The  operation  may  be  performed  by  incising 
the  mucous  membrane  above  the  second  molar  tooth,  and  driving  a  trocar  or  any  sharp-pointed 
instrument  into  the  cavity. 

THE  HYOID  BONE. 

The  Hyoid  bone  is  named  from  its  resemblance  to  the  Greek  upsilon;  it  is  also 
called  the  lingual  bone,  because  it  supports  the  tongue  and  gives  attachment  to  its 
numerous  muscles.  It  is  a  bony  arch,  shaped  like  a  horseshoe,  and  consisting  of 
five  segments,  a  body,  two  greater  cornua,  and  two  lesser  cornua.  It  is  suspended 
from  the  tip  of  the  styloid  processes  of  the  temporal  bone  by  ligamentous  bands, 
the  stylo-hyoid  ligaments. 

The  Body  (basi-Jiyal)  forms  the  central  part  of  the  bone,  and  is  of  a  quadri- 
lateral form;  its  anterior  surface  (Fig.  78),  convex,  directed  forward  and  upAvard, 
is  divided  into  two  parts  by  a  vertical  ridge  which  descends  along  the  median  line, 
and  is  crossed  at  right  angles  by  a  horizontal  ridge,  so  that  this  surface  is  divided 
into  four  spaces  or  depressions.  X.t  the  point  of  meeting  of  these  two  lines  is  a 
prominent  elevation,  the  tubercle.  The  portion  above  the  horizontal  ridge  is 
directed  upward,  and  is  sometimes  described  as  the  superior  border.  The  anterior 
surface  gives  attachment  to  the  Genio-hyoid  in  the  greater  part  of  its  extent; 
above,  to   the  Genio-hyo-glossus;    below-,   to  the   Mylo-hyoid,   Sty ly -hyoid,   and 


THE  HYOID    BONE. 


123 


THYRO-HYOID 


STYLOHYOID. 


0M0-HYOID. 


GENIO-HYOID. 


STERNO-HYOID. 


MYLO-HYOID. 


Fig.  78.— Hyoid  bone.     Anterior  surface.     (Enlarged. 


aponeurosis  of  the  Digastric  (suprahyoid  aponeurosis) ;  and  between  these  to  part 
of  the  Hyo-glossus.  The  posterior  surface  is  smooth,  concave,  directed  backward 
and  downward,  and  separated  from 
the  epiglottis  by  the  thyro-hyoid 
membrane  and  by  a  quantity  of 
loose  areolar  tissue.  The  superior 
border  is  rounded,  and  gives  at- 
tachment to  the  thyro-hyoid  mem- 
brane, part  of  the  Genio-hyo-glossi 
and  Chondro-glossi  muscles.  The 
inferior  border  gives  attachment, 
in  front,  to  the  Sterno-hyoid; 
behind,  to  the  Omo-hyoid  and  to 
part  of  the  Thyro-hyoid  at  its 
junction  with  the  great  cornu. 
It  also  gives  attachment  to  the 
Levatore  glandulse  thyroideae  when 
this  muscle  is  present.  The  lat- 
eral surfaces  after  middle  life  are  joined  to  the  greater  cornua.  In  early  life  they 
are  connected  to  the  cornua  by  cartilaginous  surfaces,  and  held  together  by  liga- 
ments, and  occasionally  a  synovial  membrane  is  found  between  them. 

The  Greater  Cornua  (thyro-hyal)  project  backward  from  the  lateral  surfaces  of 
the  body ;  they  are  flattened  from  above  downward,  diminish  in  size  from  before 
backward,  and  terminate  posteriorly  in  a  tubercle  for  the  attachment  of  the  lateral 
thyro-hyoid  ligament.  The  outer  surface  gives  attachment  to  the  Hyo-glossus, 
their  upper  border  to  the  Middle  constrictor  of  the  pharynx,  their  lower  border  to 
part  of  the  Thyro-hyoid  muscle. 

The  Lesser  Cornua  (cerato-hyals)  are  two  small,  conical-shaped  eminences 
attached  by  their  bases  to  the  angles  of  junction  between  the  body  and  greater 
cornua,  and  giving  attachment  by  their  apices  to  the  stylo-hyoid  ligaments.1 
The  smaller  cornua  are  connected  to  the  body  of  the  bone  by  a  distinct  diar- 
throdial  joint,  which  usually  persists  throughout  life,  but  occasionally  becomes 
ankylosed. 

Development. — By  five  centres :  one  for  the  body,  and  one  for  each  cornu. 
Ossification  commences  in  the  body  about  the  eighth  month,  and  in  the  greater 
cornua  toward  the  end  of  fcetal  life.  Ossification  of  the  lesser  cornua  commences 
some  years  after  birth.      Sometimes  there  are  two  centres  for  the  body. 

Attachment  of  Muscles. — Sterno-hyoid,  Thyro-hyoid,  Omo-hyoid,  aponeurosis 
of  the  Digastric,  Stylo-hyoid,  Mylo-hyoid,  Genio-hyoid,  Genio-hyo-glossus,  Chon- 
dro-glossus,  Hyo-glossus,  Middle  constrictor  of  the  pharynx,  and  occasionally 
a  few  fibres  of  the  Inferior  lingualis.  It  also  gives  attachment  to  the  thyro- 
hyoidean  membrane  and  the  stylo-hyoid,  thyro-hyoid,  and  hyo-epiglottic  liga- 
ments. 

Surface  Form. — The  hyoid  bone  can  be  felt  in  the  receding  angle  below  the  chin,  and  the 
finger  can  be  carried  along  the  whole  length  of  the  bone  to  the  greater  cornu,  which  is  situated 
just  below  the  angle  of  the  jaw.  This  process  of  bone  is  best  perceived  by  making  pressure  on 
one  cornu,  and  so  pushing  the  bone  over  to  the  opposite  side,  when  the  cornu  of  this  side  will 
be  distinctly  felt  immediately  beneath  the  skin.  This  process  of  bone  is  an  important  landmark 
in  ligature  of  the  lingual  artery. 

Surgical  Anatomy. — The  hyoid  bone  is  occasionally  fractured,  generally  from  direct  vio- 
lence, as  in  the  act  of  garrotting  or  throttling.  The  great  cornu  is  the  part  of  the  bone  most  fre- 
quently broken,  but  sometimes  the  fracture  takes  place  through  the  body  of  the  bone.  In  con- 
sequence of  the  muscles  of  the  tongue  having  important  connections  with  this  bone,  there  is 
great  pain  upon  any  attempt  being  made  to  move  the  tongue,  as  in  speaking  or  swallowing. 

1  These  ligaments  in  many  animals  are  distinct  bones,  and  in  man  are  occasionally  ossified  to  a 
certain  extent. 


124  THE  SKELETON. 


THE   THORAX. 


The  Thorax,  or  Chest,  is  an  osseo-cartilaginous  cage  containing  and  protecting 
the  principal  organs  of  respiration  and  circulation.  It  is  conical  in  shape,  being 
narrow  above  and  broad  below,  flattened  from  before  backward,  and  longer  behind 
than  in  front.     It  is  somewhat  reniform  on  transverse  section. 

Boundaries. — The  posterior  surface  is  formed  by  the  twelve  dorsal  vertebrae  and 
the  posterior  part  of  the  ribs.  It  is  concave  from  above  downward,  and  presents 
on  each  side  of  the  middle  line  a  deep  groove  in  consequence  of  the  direction 
backward  and  outward  which  the  ribs  take  from  their  vertebral  extremities  to 
their  angles.  The  anterior  surface  is  flattened  or  slightly  convex,  and  inclined 
forward  from  above  downward.  It  is  formed  by  the  sternum  and  costal  cartilages. 
The  lateral  surfaces  are  convex ;  they  are  formed  by  the  ribs,  separated  from  each 
other  by  spaces,  the  intercostal  spaces.  These  are  eleven  in  number,  and  are 
occupied  by  the  intercostal  muscles. 

The  upper  opening  of  the  thorax  is  reniform  in  shape,  being  broader  from  side 
to  side  than  from  before  backward.  It  is  formed  by  the  first  dorsal  vertebra 
behind,  the  upper  margin  of  the  sternum  in  front,  and  the  first  rib  on  each  side. 
It  slopes  downward  and  forward,  so  that  the  anterior  part  of  the  ring  is  on  a 
lower  level  than  the  posterior.  The  antero-posterior  diameter  is  about  two  inches, 
and  the  transverse  about  four.  The  lower  opening  is  formed  by  the  twelfth  dorsal 
vertebra  behind,  by  the  twelfth  rib  at  the  sides,  and  in  front  by  the  cartilages  of 
the  eleventh,  tenth,  ninth,  eighth,  and  seventh  ribs,  which  ascend  on  either  side 
and  form  an  angle,  the  subcostal  angle,  from  the  apex  of  which  the  ensiform 
cartilage  projects.  It  is  wider  transversely  than  from  before  backward.  It  slopes 
obliquely  downward  and  backward,  so  that  the  cavity  of  the  thorax  is  much  deeper 
behind  than  in  front.  The  Diaphragm  closes  in  the  opening  forming  the  floor  of 
the  thorax. 

In  the  female  the  thorax  differs  as  follows  from  the  male :  1.  Its  general 
capacity  is  less.  2.  The  sternum-is  shorter.  3.  The  upper  margin  of  the  sternum 
is  on  a  level  with  the  lower  part  of  the  body  of  the  third  dorsal  vertebra,  whereas 
in  the  male  it  is  on  a  level  with  the  lower  part  of  the  body  of  the  second  dorsal 
vertebra.  4.  The  upper  ribs  are  more  movable,  and  so  allow  a  greater  enlargement 
of  the  upper  part  of  the  thorax  than  in  the  male. 

The  Sternum. 

The  Sternum  (ozepvov,  the  chest)  (Figs.  79,  80)  is  a  flat,  narrow  bone,  sit- 
uated in  the  median  line  of  the  front  of  the  chest,  and  consisting,  in  the  adult,  of 
three  portions.  It  has  been  likened  to  an  ancient  sword ;  the  upper  piece,  repre- 
serting  the  handle,  is  termed  the  manubrium  ;  the  middle  and  largest  piece,  which 
represents  the  chief  part  of  the  blade,  is  termed  the  gladiolus  ;  and  the  inferior 
piece,  which  is  likened  to  the  point  of  the  sword,  is  termed  the  ensiform  or  xiphoid 
appendix.  In  its  natural  position  its  inclination  is  oblique  from  above  downward 
and  forward.  It  is  slightly  convex  in  front,  concave  behind,  broad  above,  becoming 
narrowed  at  the  point  where  the  first  and  second  pieces  are  connected,  after  which 
it  again  widens  a  little,  and  is  pointed  at  its  extremity.  Its  average  length  in  the 
adult  is  about  seven  inches,  being  rather  longer  in  the  male  than  in  the  female. 

The  First  Piece  of  the  sternum,  or  Manubrium  (presternum),  is  of  a  somewhat 
triangular  form,  broad  and  thick  above,  narrow  below  at  its  junction  with  the 
middle  piece.  Its  anterior  surface,  convex  from  side  to  side,  concave  from  above 
downward,  is  smooth,  and  affords  attachment  on  each  side  to  the  Pectoralis  major 
and  sternal  origin  of  the  Sternp-cleido-mastoid  muscle.  In  well-mark~ed  bones  the 
ridges  limiting  the  attachment  of  these  muscles  are  very  distinct.  Its  posterior 
surface,  concave  and  smooth,  affords  attachment  on  each  side  to  the  Sterno-hyoid 
and  Sterno-thyroid  muscles.  The  superior  border,  the  thickest,  presents  at  its 
centre  the  vre-sternal  notch  ;  and  on  each  side  an  oval  articular  surface,  directed 


THE   STERNUM.  125 

upward,  backward,  and  outward,  for  articulation  with  the  sternal  end  of  the 
clavicle.  The  inferior  border  presents  an  oval,  rough  surface,  covered  in  the  recent 
state  with  a  thin  layer  of  cartilage,  for  articulation  with  the  second  portion  of  the 
bone.  The  lateral  borders  are  marked  above  by  a  depression  for  the  first  costal 
cartilage,  and  below  by  a  small  facet,  which  with  a  similar  facet  on  the  upper 
angle  of  the  middle  portion  of  the  bone,  forms  a  notch  for  the  reception  of  the 
costal  cartilage  of  the  second  rib.  These  articular  surfaces  are  separated  by  a 
narrow,   curved  edge,  which  slopes  from   above  downward  and  inward. 

The  Second  Piece  of  the  sternum,  or  Gladiolus  (meso-stemum),  considerably 
longer,  narrower,  and  thinner  than  the  first  piece,  is  broader  below  than  above. 
Its  anterior  surface  is  nearly  flat,  directed  upward  and  forward,  and  marked  by 
three  transverse  lines  which  cross  the  bone  opposite  the  third,  fourth,  and  fifth 
articular  depressions.  These  lines  are  produced  by  the  union  of  the  four  separate 
pieces  of  which  this  part  of  the  bone  consists  at  an  early  period  of  life.  At  the 
junction  of  the  third  and  fourth  pieces  is  occasionally  seen  an  orifice,  the  sternal 
foramen;  it  varies  in  size  and  form  in  different  individuals,  and  pierces  the  bone 
from  before  backward.  This  surface  affords  attachment  on  each  side  to  the 
sternal  origin  of  the  Pectoralis  major.  The  posterior  surface,  slightly  concave,  is 
also  marked  by  three  transverse  lines,  but  they  are  less  distinct  than  those  in 
front :  this  surface  affords  attachment  below,  on  each  side,  to  the  Triangularis 
sterni  muscle,  and  occasionally  presents  the  posterior  opening  of  the  sternal 
foramen.  The  superior  border  presents  an  oval  surface  for  articulation  with  the 
manubrium.  The  inferior  border  is  narrow,  and  articulates  with  the  ensiform 
appendix.  Each  lateral  border  presents,  at  each  superior  angle,  a  small  facet, 
which,  with  a  similar  facet  on  the  manubrium,  forms  a  cavity  for  the  cartilage  of 
the  second  rib ;  the  four  succeeding  angular  depressions  receive  the  cartilages  of 
the  third,  fourth,  fifth,  and  sixth  ribs ;  whilst  each  inferior  angle  presents  a  small 
facet,  which,  with  a  corresponding  one  on  the  ensiform  appendix,  forms  a  notch 
for  the  cartilage  of  the  seventh  rib.  These  articular  depressions  are  separated  by 
a  series  of  curved  interarticular  intervals,  which  diminish  in  length  from  above 
downward,  and  correspond  to  the  intercostal  spaces.  Most  of  the  cartilages 
belonging  to  the  true  ribs,  as  will  be  seen  from  the  foregoing  description,  articulate 
with  the  sternum  at  the  line  of  junction  of  two  of  its  primitive  component  seg- 
ments. This  is  well  seen  in  many  of  the  lower  animals,  where  the  separate  parts 
of  the  bone  remain  ununited  longer  than  in  man.  In  this  respect  a  striking 
analogy  exists  between  the  mode  of  connection  of  the  ribs  with  the  vertebral 
column  and  the  connection  of  the  costal  cartilages  with  the  sternum. 

The  Third  Piece  of  the  sternum,  the  Ensiform  or  Xiphoid  Appendix  (meia- 
sternum),  is  the  smallest  of  the  three ;  it  is  thin  and  elongated  in  form,  cartilagi- 
nous in  structure  in  youth,  but  more  or  less  ossified  at  its  upper  part  in  the  adult 
Its  anterior  surface  affords  attachment  to  the  chondro-xiphoid  ligament;  its 
posterior  surface,  to  some  of  the  fibres  of  the  Diaphragm  and  Triangularis  sterni 
muscles ;  its  lateral  borders,  to  the  aponeurosis  of  the  abdominal  muscles.  Above 
it  articulates  with  the  lower  end  of  the  gladiolus,  and  at  each  superior  angle 
presents  a  facet  for  the  lower  half  of  the  cartilage  of  the  seventh  rib ;  below,  by 
its  pointed  extremity  it  gives  attachment  to  the  linea  alba.  This  portion  of  the 
sternum  is  very  various  in  appearance,  being  sometimes  pointed,  broad,  and  thin, 
sometimes  bifid  or  perforated  by  a  round  hole,  occasionally  curved  or  deflected 
considerably  to  one  or  the  other  side. 

Structure. — The  bone  is  composed  of  delicate  cancellous  structure,  covered  by 
a  thin  layer  of  compact  tissue,  which  is  thickest  in  the  manubrium  between  the 
articular  facets  for  the  clavicles. 

Development. — The  cartilaginous  sternum  originally  consists  of  two  bars,  situated 
one  on  either  side  of  the  mesial  plane  and  connected  with  the  rib  cartilages  of  its 
own  side.  These  two  bars  fuse  with  each  other  along  the  middle  liue,  and  the  bone, 
including  the  ensiform  appendix,  is  developed  by  six  centres ;  one  for  the  first  piece 
or  manubrium,  four  for  the  second  piece  or  gladiolus,  and  one  for  the  ensiform 


126 


THE  SKELETON. 


STERNO-CLEIDOMASTOID 

SUBOLAVIUS. 


Fig.  79.— Sternum  and  costal  cartilages. 


Fig.  80.— Posterior  surface  of  sternum. 


THE   STERNUM. 


127 


appendix.  Up  to  the  middle  of  foetal  life  the  sternum  is  entirely  cartilaginous,  and 
when  ossification  takes  place  the  ossific  granules  are  deposited  in  the  middle  of  the 
intervals  between  the  articular  depressions  for  the  costal  cartilages,  in  the  following 
order  (Fig.  81) :  In  the  first  piece,  between  the  fifth  and  sixth  months ;  in  the 
second  and  third,  between  the  sixth  and  seventh  months ;  in  the  fourth  piece,  at 
the  ninth  month ;  in  the  fifth,  within  the  first  year  or  between  the  first  and  second 
years  after  birth;  and  in  the  ensiform  appendix,  between  the  second  and  the  seven- 
teenth or  eighteenth  years,  by  a  single  centre  which  makes  its  appearance  at  the 
upper    part    and    proceeds    gradually    downward.      To    these    may    be    added    the 


for  first  piece,  two  or  more  centres. 

for  second  piece,  usually  one. 

for  third    ~\ 
i 
for  fourth  [-  2,  placed  laterally, 

for  fifth     J 


Fig.  81.— Development  of  the  sternum  by  six 
centres.    Time  of  appearance. 


Arrest  of  development 
of  lateral  pieces,  producing 


-Sternal  fissure,  and 
Sternal  foramen. 


Fig.  82.— Time  of  union  of  sternum. 


occasional    existence^  as  described    by  Breschet,  of  two  small  episternal  centres, 
which  make  their  appearance  one  on  each  side  of  the  presternal  notch.     They  are 


1  for  1st  piece  j  5_mh  mmth  fmtal 
or  manubrium  \ 


4  for  2nd  piece 
or  gladiolus 


6-7th  month. 


9th  month. 

1st  year  after 
birth. 


1  for  ensiform  j       ^  fo  im 
cartilage       )  * 

Fig.  83.— Peculiarities  in  number  of  centres  of 
sternum. 


Rarely  unite, 
except  in  old  age. 


Between  pu1  v^y 
and  the  25th  year. 

Soon  after  puberty. 


Partly  cartilaginous  to 
advanced  life. 


Fig.  84.— Peculiarities  in  mode 
of  union  of  sternum. 


probably  vestiges  of  the  episternal  bone  of  the  monotremata  and  lizards.  It 
occasionally  happens  that  some  of  the  segments  are  formed  from  more  than  one 
centre,  the  number  and  position  of  which  vary  (Fig.  83).  Thus,  the  first  piece 
may  have  two,  three,  or  even  six  centres.  When  two  are  present,  they  are 
generally  situated  one  above  the  other,  the  upper  one  being  the  larger  ;*  the  second 
piece  has  seldom  more  than  one;  the  third,  fourth,  and  fifth  pieces  are  often  formed 
from  two  centres  placed  laterally,  the  irregular  union  of  which  will  serve  to  explain 
the  occasional  occurrence  of  the  sternal  foramen  (Fig.  84).  or  of  the  vertical  fissure 
which  occasionally  intersects  this  part  of  the  bone,  and  which  is  further  explained 
by  the  manner  in  which  the  cartilaginous  matrix,  in  which  ossification  takes  place, 
is  formed.  Union  of  the  various  centres  of  the  gladiolus  commences  about 
puberty,  from  below,  and  proceeds  upward,  so  that  by  the  age  of  twenty- 
1Sir  George  Humphry  states  that  this  is  "probably  the  more  complete  condition." 


128 


THE   SKELETON. 


Head. 


■Subcostal  groove 


five  they  are  all  united,  and  this  portion  of  bone 
consists  of  one  piece  (Fig.  82).  The  ensiform  car- 
tilage becomes  joined  to  the  gladiolus  about  forty. 
The  manubrium  is  occasionally,  but  not  invariably, 
joined  to  the  gladiolus  in  advanced  life  by  bone. 
When  this  union  takes  place,  however,  it  is  gen- 
erally only  superficial,  a  portion  of  the  centre  of 
the  sutural  cartilage  remaining  unossified. 

Articulations. — With  the  clavicles  and  seven 
costal  cartilages  on  each  side. 

Attachment  of  Muscles. — To  nine  pairs  and 
one  single  muscle:  the  Pectoralis  major,  Sterno- 
cleido-mastoid,  Sterno-hyoid,  Sterno-thyroid,  Tri- 
angularis sterni,  aponeuroses  of  the  Obliquus 
externus,  Obliquus  internus,  Transversalis,  Rectus 
muscles,  and  Diaphragm. 


\3 


/Body 

or  shaft. 


The  Ribs. 

The  Ribs  are  elastic  arches  of  bone,  which  form 
the  chief  part  of  the  thoracic  walls.  They  are 
twelve  in  number  on  each  side ;  but  this  number 
may  be  increased  by  the  development  of  a  cervical 
or  lumbar  rib,  or  may  be  diminished  to  eleven. 
The  first  seven  are  connected  behind  with  the  spine 
and  in  front  with  the  sternum,  through  the  inter- 
vention of  the  costal  cartilages  ;  they  are  called 
true  ribs.1  The  remaining  five  are  false  ribs  ;  of 
these,  the  first  three  have  their  cartilages  attached 
to  the  cartilage  of  the  rib  above :  the  last  two  are 
free  at  their  anterior  extremities ;  they  are  termed 
floating  ribs.  The  ribs  vary  in  their  direction, 
the  upper  ones  being  less  oblique  than  the 
lower.  The  extent  of  obliquity  reaches  its 
maximum  at  the  ninth  rib,  and  gradually 
decreases  from  that  rib  to  the  twelfth.  The 
ribs  are  situated  one  below  the  other  in  such 
a  manner  that  spaces  are  left  betAveen  them, 
which  are  called  intercostal  spaces.  The 
length  of  these  spaces  corresponds  to  the  length  of  the  ribs  and  their  cartilages ; 
their  breadth  is  greater  in  front  than  behind,  and  between  the  upper  than  between 
the  lower  ribs.     The  ribs  increase  in  length  from  the  first  to  the  seventh,  when 

1  Sometimes  the  eighth  rib   cartilage  articulates  with  the  sternum  ;  this  condition  occurs  more 
frequently  on  the  right  than  on  the  left  side. 


Fig.  85.— A  central  rib  of  left  side. 


THE   BIBS.  129 

they  again  diminish  to  the  twelfth.  In  breadth  they  decrease  from  above  down- 
ward ;  in  the  upper  ten  the  greatest  breadth  is  at  the  sternal  extremity. 

Common  Characters  of  the  Ribs  (Fig.  85). — A  rib  from  the  middle  of  the 
series  should  be  taken  in  order  to  study  the  common  characters  of  the  ribs. 

Each  rib  presents  two  extremities,  a  posterior  or  vertebral,  an  anterior  or  ster- 
nal, and  an  intervening  portion — the  body  or  shaft. 

The  posterior  or  vertebral  extremity  presents  for  examination  a  head.  neck. 
and  tuberosity.  The  head  (Fig.  86)  is  marked  by  a  kidney-shaped  articular  sur- 
face, divided  by  a  horizontal  ridge  into  two  facets  for  articulation  with  the  costal 
cavity  formed  by  the  junction  of  the  bodies  of  two  contiguous  dorsal  vertebrae ; 
the  upper  facet  is  small,  the  inferior  one  of  larger  size ;  the  ridge  separating  them 
serves  for  the  attachment  of  the  interarticular  ligament.  The  neck  is  that  flat- 
tened portion  of  the  rib  which  extends  outward  from  the  head ;  it  is  about  an 
inch  long,  and  is  placed  in  front  of  the  transverse  process  of  the  lower  of  the  two 
vertebrae  with  which  the  head  articulates.  Its  anterior  surface  is  flat  and  smooth, 
its  posterior  rough  for  the  attachment  of  the  middle  costo-transverse  ligament, 
and  perforated  by  numerous  foramina,  the  direction  of  which  is  less  constant  than 
those  found  on  the  inner  surface  of  the  shaft.  Of  its  two  borders  the  superior 
presents  a  rough  crest  for  the  attachment  of  the  anterior  costo-transverse  ligament ; 
its  inferior  border  is  rounded.     On  the  posterior  surface  of  the  neck,  just  where  it 

■Facet  for  body  of  upper  dorsal  vertebra. 
■Ridge  for  interarticular  ligament.    • 
■Facet  for  body" of  lower  dorsal  vertebra.' 

Articular  part  of  tuberosity. 


Non-articular  part  of  tuberosity. 
Fig.  "86.— Vertebral  extremity  of  a  rib.    External  surface. 

joins  the  shaft,  and  nearer  the  lower  than  the  upper  border,  is  an  eminence — the 
tuberosity,  or  tubercle ;  it  consists  of  an  articular  and  a  non-articular  portion. 
The  articular  portion,  the  more  internal  and  inferior  of  the  two,  presents  a  small, 
oval  surface  for  articulation  with  the  extremity  of  the  transverse  process  of  the 
lower  of  the  two  vertebrae  to  which  the  head  is  connected.  The  non-articular 
portion  is  a  rough  elevation,  which  affords  attachment  to  the  posterior  costo- 
transverse ligament.  The  tubercle  is  much  more  prominent  in  the  upper  than  in 
the  lower  ribs. 

The  shaft  is  thin  and  flat,  so  as  to  present  two  surfaces,  an  external  and  an 
internal,  and  two  borders,  a  superior  and  an  inferior.  The  external  surface  is 
convex,  smooth  and  marked  at  its  back  part,  a  little  in  front  of  the  tuberosity,  by 
a  prominent  line,  directed  obliquely  from  above  downward  and  outward ;  this 
gives  attachment  to  a  tendon  of  the  Ilio-costalis  muscle  or  of  one  of  its  accessory 
portions,  and  is  called  the  angle.  At  this  point  the  rib  is  bent  in  two  directions. 
If  the  rib  is  laid  upon  its  lower  border,  it  will  be  seen  that  the  portion  of  the  shaft 
in  front  of  the  angle  rests  upon  this  border,  while  the  portion  of  the  shaft  behind 
the  angle  is  bent  inward  and  at  the  same  time  tilted  upward.  The  interval 
between  the  angle  and  the  tuberosity  increases  gradually  from  the  second  to  the 
tenth  rib.  The  portion  of  bone  between,  these  two  parts  is  rounded,  rough,  and 
irregular,  and  serves  for  the  attachment  of  the  Longissimus  dorsi  muscle.  The 
portion  of  bone  between  the  tubercle  and  sternal  extremity  is  also  slightly  twisted 
upon  its  own  axis,  the  external  surface  looking  downward  behind  the  angle,  a  little 
upward  in  front  of  it.  This  surface  presents,  toward  its  sternal  extremity,  an 
oblique  line,  the  anterior  angle.  The  internal  surface  is  concave,  smooth,  directed 
a  little  upward  behind  the  angle,  a  little  downward  in  front  of  it.     This  surface 

9 


130  THE  SKELETON. 

is  marked  by  a  ridge  which  commences  at  the  lower  extremity  of  the  head ;  it  is 
strongly  marked  as  far  as  the  inner  side  of  the  angle,  and  gradually  becomes  lost  at 
the  junction  of  the  anterior  with  the  middle  third  of  the  bone.  The  interval 
between  it  and  the  inferior  border  presents  a  groove,  subcostal,  for  the  intercostal 
vessels  and  nerve.  At  the  back  part  of  the  bone  this  groove  belongs  to  the 
inferior  border,  but  just  in  front  of  the  angle,  where  it  is  deepest  and  broadest,  it 
corresponds  to  the  internal  surface.  The  superior  edge  of  the  groove  is  rounded ;  it 
serves  for  the  attachment  of  the  Internal  intercostal  muscle.  The  inferior  edge 
corresponds  to  the  lower  margin  of  the  rib  and  gives  attachment  to  the  External 
intercostal.  Within  the  groove  are  seen  the  orifices  of  numerous  small  foramina 
which  traverse  the  wall  of  the  shaft  obliquely  from  before  backward.  The 
superior  border,  thick  and  rounded,  is  marked  by  an  external  and  an  internal  lip, 
more  distinct  behind  than  in  front ;  they  serve  for  the  attachment  of  the  External 
and  Internal  intercostal  muscles.  The  inferior  border,  thin  and  sharp,  has  attached 
to  it  the  External  intercostal  muscle.  The  anterior  or  sternal  extremity  is  flat- 
tened, and  presents  a  porous,  oval,  concave  depression,  into  which  the  costal 
cartilage  is  received. 

Peculiar  Ribs. 

The  ribs  which  require  especial  consideration  are  five  in  number — viz.  the  first, 
second,  tenth,  eleventh  and  twelfth. 

The  first  rib  (Fig.  87)  is  one  of  the  shortest  and  the  most  curved  of  all  the  ribs  ; 
it  is  broad  and  flat,  its  surfaces  looking  upward  and  downward,  and  its  borders 
inward  and  outward.  The  head  is  of  small  size,  rounded,  and  presents  only  a 
single  articular  facet  for  articulation  with  the  body  of  the  first  dorsal  vertebra. 
The  neck  is  narrow  and  rounded.  The  tuberosity,  thick  and  prominent,  rests  on 
the  outer  border.  There  is  no  angle,  but  in  this  situation  the  rib  is  slightly  bent, 
with  the  convexity  of  the  bend  upward,  so  that  the  head  of  the  bone  is  directed 
downward.  The  upper  surface  of  the  shaft  is  marked  by  two  shallow  depressions, 
separated  by  a  small  rough  surface  for  the  attachment  of  the  Scalenus  anticus 
muscle — the  groove  in  front  of  it  transmitting  the  subclavian  vein,  that  behind  it 
the  subclavian  artery.  Between  the  groove  for  the  subclavian  artery  and  the 
tuberosity  is  a  rough  surface,  for  the  attachment  of  the  Scalenus  medius  muscle. 
The  under  surface  is  smooth,  and  destitute  of  the  groove  observed  on  the  other 
ribs.  The  outer  border  is  convex,  thick,  and  rounded,  and  at  its  posterior  part 
gives  attachment  to  the  first  serration  of  the  Serratus  magnus ;  the  inner  is  con- 
cave, thin,  and  sharp,  and  marked  about  its  centre  by  the  commencement  of  the 
rough  surface  for  the  Scalenus  anticus.  The  anterior  extremity  is  larger  and 
thicker  than  any  of  the  other  ribs. 

The  second  rib  (Fig.  88)  is  much  longer  than  the  first,  but  bears  a  very  con- 
siderable resemblance  to  it  in  the  direction  of  its  curvature.  The  non-articular 
portion  of  the  tuberosity  is  occasionally  only  slightly  marked.  The  angle  is  slight 
and  situated  close  to  the  tuberosity,  and  the  shaft  is  not  twisted,  so  that  both  ends 
touch  any  plane  surface  upon  which  it  may  be  laid ;  but  there  is  a  similar  though 
slighter  bend,  with  its  convexity  upward,  to  that  found  in  the  first  rib.  The  shaft 
is  not  horizontal,  like  that  of  the  first  rib,  its  outer  surface,  which  is  convex,  look- 
ing upward  and  a  little  outward.  It  presents,  near  the  middle,  a  rough  eminence 
for  the  attachment  of  the  second  and  third  digitations  of  the  Serratus  magnus ; 
behind  and  above  which  is  attached  the  Scalenus  posticus.  The  inner  surface, 
smooth  and  concave,  is  directed  downward  and  a  little  inward ;  it  presents  a  short 
groove  toward  its  posterior  part. 

The  tenth  rib  (Fig.  89)  has  only  a  single  articular  facet  on  its  head. 

The  eleventh  and  twelfth  ribs  (Figs.  90  and  91)  have  each  a  single  articular 
facet  on  the  head,  which  is  of  rather  large  size ;  they  have  no  neck  or  tuberosity, 
and  are  pointed  at  the  extremity.  The  eleventh  has  a  slight  angle  and  a  shallow 
groove  on  the  lower  border.  The  twelfth  has  neither,  and  is  much  shorter  than 
the  eleventh,  and  the  head  has  a  slight  inclination  downward.  Sometimes  the 
twelfth  rib  is  even  shorter  than  the  first. 


PECULIAR    RIBS. 


131 


Structure.— The  ribs  consist  of  cancellous  fissue  enclosed  in  a  thin,  compact  layer. 

Development. — Each  rib,  with  the  exception  of  the  last  two,  is  developed  by 
three  centres  :  one  for  the  shaft,  one  for  the  head,  and  one  for  the  tubercle.  The 
last  two  have  only  two  centres,  that  for  the  tubercle  being  wanting.  Ossification 
commences  in  the  shaft  of  the  ribs  at  a  very  early  period,  before  its  appearance  in 
the  vertebrae.  The  epiphysis  of  the  head,  which  is  of  slightly  angular  shape,  and 
that  for  the  tubercle,  of  a  lenticular  form,  make  their  appearance  between  the  six- 


Fig.  87 


Miglean 


Fig 


Angle 

slightly  marked 

and  close  to 

tuberosity. 


Rough ' 


Fig. 


Single  articular  facet. — 


Fig.  90. 

Single  articular  facet 


Fig.  91. 

Single  articular  facet. _J 


Figs.  87-91.— Peculiar  ribs. 

teenth  and  twentieth  years,  and  are  not  united  to  the  rest  of  the  bone  until  about 
the  twenty-fifth  year. 

Attachment  of  Muscles. —  To  nineteen:  The  Internal  and  External  intercostal.-. 
Scalenus  anticus,  Scalenus  medius,  Scalenus  posticus,  Pectoralis  minor,  Serratus 
magnus,  Obliquus  externus,  Quadratus  lumborum,  Diaphragm,  Latissimus  dorsi. 
Serratus  posticus  superior,  Serratus  posticus  inferior,  Ilio-eostalis,  Musculus  acccs- 
sorius  ad  ilio-costalem,  Longissimus  dorsi,  Cervicalis  ascendens,  Levatores  costarum, 
and  Infracostal es. 


132  THE  SKELETON. 

The  Costal  Cartilages. 

The  Costal  Cartilages  (Fig.  79,  p.  126)  are  bars  of  white,  hyaline  cartilage, 
which  serve  to  prolong  the  ribs  forward  to  the  front  of  the  chest,  and  contribute 
very  materially  to  the  elasticity  of  its  walls.  The  first  seven  are  connected  with 
the  sternum,  the  next  three  with  the  lower  border  of  the  cartilage  of  the  preceding 
rib.  The  cartilages  of  the  last  two  ribs  have  pointed  extremities,  which 
terminate  in  free  ends  in  the  walls  of  the  abdomen.  Like  the  ribs,  the  costal 
cartilages  vary  in  their  length,  breadth,  and  direction.  They  increase  in  length 
from  the  first  to  the  seventh,  then  gradually  diminish  to  the  last.  They  diminish 
in  breadth,  as  well  as  the  intervals  between  them,  from  the  first  to  the  last.  They 
are  broad  at  their  attachment  to  the  ribs,  and  taper  toward  their  sternal  extremities, 
excepting  the  first  two,  which  are  of  the  same  breadth  throughout,  and  the  sixth, 
seventh,  and  eighth,  which  are  enlarged  where  their  margins  are  in  contact.  In 
direction  they  also  vary :  the  first  descends  a  little,  the  second  is  horizontal,  the 
third  ascends  slightly,  while  all  the  rest  follow  the  course  of  the  ribs  for  a  short 
extent,  and  then  ascend  to  the  sternurn  or  preceding  cartilage.  Each  costal  carti- 
lage presents  two  surfaces,  two  borders,  and  two  extremities.  The  anterior  surface 
is  convex,  and  looks  forward  and  upward :  that  of  the  first  gives  attachment  to  the 
costo-clavicular  ligament  and  the  Subclavius  muscle ;  that  of  the  second,  third, 
fourth,  fifth,  and  sixth,  at  their  sternal  ends,  to  the  Pectoralis  major.1  The  others 
are  covered  by,  and  give  partial  attachment  to,  some  of  the  great  flat  muscles  of  the 
abdomen.  The  posterior  surface  is  concave,  and  directed  backward  and  downward, 
the  first  giving  attachment  to  the  Sterno-thyroid,  the  third  to  the  sixth  inclusive 
to  the  Triangularis  sterni,  and  the  six  or  seven  inferior  ones  to  the  Tranversalis 
muscle  and  the  Diaphragm.  Of  the  two  borders,  the  superior  is  concave,  the 
inferior  convex  :  they  afford  attachment  to  the  internal  Intercostal  muscles,  the 
upper  border  of  the  sixth  giving  attachment  to  the  Pectoralis  major  muscle. 
The  contiguous  borders  of  the  sixth,  seventh,  and  eighth,  and  sometimes  the  ninth 
and  tenth,  costal  cartilages  present  small,  smooth,  oblong-shaped  facets  at  the 
points  where  they  articulate.  Of  the  two  extremities,  the  outer  one  is  continuous 
with  the  osseous  tissue  of  the  rib  to  which  it  belongs.  The  inner  extremity  of  the 
first  is  continuous  with  the  sternum ;  the  six  succeeding  ones  have  rounded 
extremities,  which  are  received  into  shallow  concavities  on  the  lateral  margins  of 
the  sternum.  The  inner  extremities  of  the  eighth,  ninth,  and  tenth  costal  cartilages 
are  pointed,  and  are  connected  with  the  cartilage  above.  Those  of  the  eleventh  and 
twelfth  are  free  and  pointed. 

The  costal  cartilages  are  most  elastic  in  youth,  those  of  the  false  ribs  being 
more  so  than  the  true.  In  old  age  they  become  of  a  deep  yellow  color,  and  are 
prone  to  calcify. 

Attachment  of  Muscles. — To  nine :  the  Subclavius,  Sterno-thyroid,  Pectoralis 
major,  Internal  oblique,  Transversalis,  Rectus,  Diaphragm,  Triangularis  sterni,  and 
Internal  intercostals. 

Surface  Form. — The  bones  of  the  chest  are  to  a  very  considerable  extent  covered  by 
muscles,  so  that  in  the  strongly-developed  muscular  subject  they  are  for  the  most  part  con- 
cealed. In  the  emaciated  subject,  on  the  other  hand,  the  ribs,  especially  in  the  lower  and  lateral 
region,  stand  out  as  prominent  ridges  with  the  sunken,  intercostal  spaces  between  them. 

In  the  middle  line,  in  front,  the  superficial  surface  of  the  sternum  is  to  be  felt  throughout 
its  entire  length,  at  the  bottom  of  a  deep  median  furrow  situated  between  the  two  great  pectoral 
muscles  and  called  the  sternal  furrow.  These  muscles  overlap  the  anterior  surface  somewhat,  so 
that  the  whole  of  the  sternum  in  its  entire  width  is  not  subcutaneous  ;  and  this  overlap ping_  is 
greater  opposite  the  centre  of  the  bone  than  above  and  below,  so  that  the  furrow  is  wider  at  its 
upper  and  lower  parts,  but  narrower  in  the  middle.  The  centre  of  the  upper  border  of  the  ster- 
num is  visible,  constituting  the  pre-sternal  notch,  but  the  lateral  parts  of  this  border  are  obscured 
by  the  tendinous  origins  of  the  Sterno-mastoid  muscles,  which  present  themselves  as  oblique 
tendinous  cords,  which  narrow  and  deepen  the  notch.  Lower  down  on  the  subcutaneous  surface 
a  well-defined  transverse  ridge,  the  angle  of  Ludovic,  is  always  to  be  felt.  This  denotes  the  line 
of  junction  of  the  manubrium  and  body  of  the  bone,  and  is  a  useful  guide  to  the  second  costal 
cartilage,  and  thus  to  the  identity  of  any  given  rib.     The  second  rib  being  found  through  its 

1  The  first  and  seventh  also,  occasionally,  give  origin  to  the  same  muscle. 


THE    COSTAL   CARTILAGES.  133 

costal  cartilage,  it  is  easy  to  count  downward  and  find  any  other.  From  the  middle  of  the 
sternum  the  furrow  spreads  out,  and,  exposing  more  of  the  surface  of  the  hody  of  the  hone, 
terminates  helow  in  a  sudden  depression,  the  infrasternal  depression  or  pit  of  the  stomach  (scro- 
biculus  cordis),  which  corresponds  to  the  ensiform  cartilage.  This  depression  lies  between  the 
cartilages  of  the  seventh  rib,  and  in  it  the  ensiform  cartilage  may  be  felt.  The  sternum  in  its 
vertical  diameter  presents  a  general  convexity  forward,  the  most  prominent  point  of  which  is  at 
the  joint  between  the  manubrium  and  gladiolus. 

On  each  side  of  the  sternum  the  costal  cartilages  and  ribs  on  the  front  of  the  chest  are  par- 
tially obscured  by  the  great  pectoral  muscle;  through  which,  however,  they  are  to  be  felt  as 
ridges,  with  yielding  intervals  between  them,  corresponding  to  the  intercostal  spaces.  Of  these 
spaces,  the  one  between  the  second  and  third  ribs  is  the  widest,  the  next  two  somewhat  nar- 
rower, and  the  remainder,  with  the  exception  of  the  last  two,  comparatively  narrow. 

The  lower  border  of  the  Pectoralis  major  muscle  corresponds  to  the  fifth  rib,  and  below 
this,  on  the  front  of  the  chest,  the  broad,  flat  outline  of  the  ribs,  as  they  begin  to  ascend, 
and  the  more  rounded  outline  of  the  costal  cartilages,  are  often  visible.  The  lower  boundary 
of  the  front  of  the  thorax,  the  abdomino-thoracic  arch,  which  is  most  plainly  seen  by 
arching  the  body  backward,  is  formed  by  the  ensiform  cartilage  and  the  cartilages  of  the 
seventh,  eighth,  ninth,  and  tenth  ribs,  and  the  extremities  of  the  eleventh  and  twelfth  ribs  or 
their  cartilages. 

On  each  side  of  the  chest,  from  the  axilla  downward,  the  flattened  external  surfaces  of  the 
ribs  may  be  defined  in  the  form  of  oblique  ridges,  separated  by  depressions  corresponding  to  the 
intercostal  spaces.  They  are,  however,  covered  by  muscles,  which  obscure  their  outline  to  a 
certain  extent  in  the  strongly  developed.  Nevertheless,  the  ribs,  with  the  exception  of  the  first, 
can  generally  be  followed  over  the  front  and  sides  of  the  chest  without  difficulty.  _  The  first  rib, 
being  almost  completely  covered  by  the  clavicle  and  scapula,  can  only  be  distinguished  in  a  small 
portion  of  its  extent.  At  the  back  the  angles  of  the  ribs  form  a  slightly-marked  oblique  line  on 
each  side  of  and  some  distance  from  the  vertebral  spines.  This  line  diverges  somewhat  as  it 
descends,  and  external  to  it  is  a  broad,  convex  surface  caused  by  the  projection  of  the  ribs 
beyond  their  angles.  Over  this  surface,  except  where  covered  by  the  scapula,  the  individual 
ribs  can  be  distinguished. 

Surgical  Anatomy. — Malformations  of  the  sternum  present  nothing  of  surgical  importance 
beyond  the  fact  that  abscesses  of  the  mediastinum  may  sometimes  escape  through  the  sternal 
foramen.  Fractures  of  the  sternum  are  by  no  means  common,  owing,  no  doubt,  to  the  elasticity 
of  the  ribs  and  their  cartilages,  which  support  it  like  so  many  springs.  When  broken  it  is  fre- 
quently associated  with  fracture  of  the  spine,  and  may  be  caused  by  forcibly  bending  the  body 
either  backward  or  forward  until  the  chin  becomes  impacted  against  the  top  of  the  sternum.  It 
may  also  be  fractured  by  direct  violence  or  by  muscular  action.  The  fracture  usually  occurs  in 
the  upper  half  of  the  body  of  the  bone.  Dislocation  of  the  gladiolus  from  the  manubrium  also 
takes  place,  and  is  sometimes  described  as  a  fracture. 

The  bone,  being  subcutaneous,  is  frequently  the  seat  of  gummatous  tumors,  and  not  uncom- 
monly is  affected  with  caries.  Occasionally  the  bone,  and  especially  its  ensiform  appendix,  becomes 
altered  in  shape  and  driven  inward  by  the  pressure,  in  workmen,  of  tools  against  their  chest. 

The  ribs  are  frequently  broken,  though  from  their  connections  and  shape  they  are  able  to 
withstand  great  force,  yielding  under  the  injury  and  recovering  themselves  like  a  spring.  The 
middle  of  the  series  are  the  ones  most  liable  to  fracture.  The  first,  and  to  a  less  extent  the 
second,  being  protected  by  the  clavicle,  are  rarely  fractured  ;  and  the  eleventh  and  twelfth,  on 
account  of  their  loose  and  floating  condition,  enjoy  a  like  immunity.  The  fracture  generally 
occurs  from  indirect  violence,  from  forcible  compression  of  the  chest-wall,  and  the  bone  then 
gives  way  at  its  weakest  part — i.  e.  just  in  front  of  the  angle.  But  the  ribs  may  also  be  broken 
by  direct  violence,  when  the  bone  gives  way  and  is  driven  inward  at  the  point  struck,  or  they 
may  be  broken  by  muscular  action.  It  seems  probable,  however,  that  iri  these  latter  cast-.-  tin' 
bone  has  undergone  some  atrophic  changes.  Fracture  of  the  ribs  is  freqitently  complicated  with 
some  injury  to  the  viscera  contained  within  the  thorax  or  upper  part  of  the  abdominal  cavity. 
and  this  is  most  likely  to  occur  in  fractures  from  direct  violence. 

Fracture  of  the  costal  cartilages  may  also  take  place,  though  it  is  a  comparatively  rare  injury. 

The  thorax  is  frequently  found  to  be  altered  in  shape  in  certain  diseases. 

The  rickety  thorax  is  caused  chiefly  by  atmospheric  pressure.  The  balance  between  the  air 
on  the  inside  of  the  chest  and  the  outside  during  some  stage  of  respiration  is  not  equal,  the  pre- 
ponderance being  in  favor  of  the  air  outside ;  and  this,  acting  on  the  softened  ribs,  causes  them 
to  be  forced  in  at  the  junction  of  the  cartilages  with  the  bones,  which  is  the  weakest  part.  In 
consequence  of  this  the  sternum  projects  forward,  with  a  deep  depression  on  either  side  caused 
by  the  sinking  in  of  the  softened  ribs.  The  depression  is  less  on  the  left  side,  on  account  of 
the  ribs  being  supported  by  the  heart.  The  condition  is  known  as  "pigeon-breast  The 
lower  ribs,  however,  are  not  involved  in  this  deformity,  as  they  are  prevented  from  railing  in  by 
the  presence  of  the  stomach,  liver,  and  spleen.  And  when  the  liver  and  spleen  are  enlarged, 
as  they  sometimes  are  in  rickets,  the  lower  ribs  may  be  pushed  outward  :  this  causes  a  trans- 
verse constriction  just  above  the  costal  arch.  The  anterior  extremities  of  the  ribs  are  usually 
enlarged  in  rickets,  giving  rise  to  what  has  been  termed  the  ''rickety  rosary."'  The  phthisical 
chest  is  often  long  and  narrow,  flattened  from  before  backward,  and  with  great  obliquity  of  the 
ribs  and  projection  of  the  scapulae.  In  pulmonary  emphysema  the  chest  is  enlarged  in  all  its 
diameters,  and  presents  on  section  an  almost  circular  outline.     It  has  received  the  name  of  the 


134  THE  SKELETON. 

"barrel-shaped  chest."  In  severe  cases  of  lateral  curvature  of  the,  spine  the  thorax  becomes 
much  distorted.  In  consequence  of  the  rotation  of  the  bodies  of  the  vertebrae  which  takes 
place  in  this  disease  the  ribs  opposite  the  convexity  of  the  dorsal  curve  become  extremely  con- 
vex behind,  being  thrown  out  and  bulging,  and  at  the  same  time  flattened  in  front,  so  that  the 
two  ends  of  the  same  rib  are  almost  parallel.  Coincident  with  this,  the  ribs  on  the  opposite 
side,  on  the  concavity  of  the  curve,  are  sunk  and  depressed  behind  and  bulging  and  convex  in 
front.     In  addition  to  this  the  ribs  become  occasionally  welded  together  by  bony  material. 

The  ribs  are  frequently  the  seat  of  necrosis  leading  to  abscesses  and  sinuses,  which  may 
burrow  to  a  considerable  extent  over  the  wall  of  the  chest.  The  only  special  anatomical  point 
in  connection  with  these  is  that  care  must  be  taken  in  dealing  with  them  that  the  intercostal 
space  is  not  punctured  and  the  pleural  cavity  opened  or  the  intercostal  vessels  wounded,  as  the 
necrosed  portion  of  bone  is  generally  situated  on  the  internal  surface  of  the  rib. 

In  cases  of  empyema  the  chest  requires  opening  to  evacuate  the  pus.  There  is  consider- 
able difference  of  opinion  as  to  the  best  position  to  do  this.  Probably  the  best  place  in  most 
cases  will  be  found  to  be  between  the  fifth  and  sixth  ribs,  in  or  a  little  in  front  of  the  mid- 
axillary  line.  This  is  the  last  part  of  the  cavity  to  be  closed  by  the  expansion  of  the  lung ;  it 
is  not  thickly  covered  by  soft  parts ;  the  space  between  the  two  ribs  is  sufficiently  great  to  allow 
of  the  introduction  of  a  fair-sized  drainage-tube,  and  the  opening  is  in  a  dependent  position, 
when  the  patient  is  confined  to  bed,  as  he  usually  inclines  toward  the  affected  side,  so  as  to 
allow  the  sound  lung  the  freest  possible  play,  and  so  permits  of  efficient  drainage. 

THE   EXTREMITIES. 

The  extremities,  or  limbs,  are  those  long,  jointed  appendages  of  the  body 
which  are  connected  to  the  trunk  by  one  end  and  free  in  the  rest  of  their  extent. 
They  are  four  in  number :  an  upper  or  thoracic  pair,  connected  with  the  thorax 
through  the  intervention  of  the  shoulder,  and  subservient  mainly  to  prehension ; 
and  a  lower  pair,  connected  with  the  pelvis,  intended  for  support  and  locomotion. 
Both  pairs  of  limbs  are  constructed  after  one  common  type,  so  that  they  present 
•numerous  analogies,  Avhile  at  the  same  time  certain  differences  are  observed  be- 
tween the  upper  and  lower  pair,  dependent  on  the  peculiar  offices  they  have  to 
perform. 

The  bones  by  which  the  upper  and  lower  limbs  are  attached  to  the  trunk  are 
named  respectively  the  shoulder  and  pelvic  girdles,  and  they  are  constructed  on  the 
same  general  type,  though  presenting  certain  modifications  relating  to  the  different 
uses  to  which  the  upper  and  lower  limbs  are  respectively  applied.  The  shoidder 
gii'dle  is  formed  by  the  scapula  and  clavicle,  and  is  imperfect  in  front  and  behind. 
In  front,  however,  the  girdle  is  completed  by  the  upper  end  of  the  sternum,  with 
which  the  inner  extremities  of  the  clavicle  articulate.  Behind,  the  girdle  is  widely 
imperfect  and  the  scapula  is  connected  to  the  trunk  by  muscles  only.  The  pelvic 
girdle  is  formed  by  the  innominate  bones,  and  is  completed  in  front  through  the 
symphysis  pubis,  at  which  the  two  innominate  bones  articulate  with  each  other. 
It  is  imperfect  behind,  but  the  intervening  gap  is  filled  in  by  the  upper  part  of 
the  sacrum.  The  pelvic  girdle,  therefore,  presents,  with  the  sacrum,  a  complete 
ring,  comparatively  fixed,  and  presenting  an  arched  form  which  confers  upon  it  a 
solidity  manifestly  intended  for  the  support  of  the  trunk,  and  in  marked  contrast 
to  the  lightness  and  mobility  of  the  shoulder  girdle. 

With  regard  to  the  morphology  of  these  girdles,  the  blade  of  the  scapula  is 
generally  believed  to  correspond  to  the  ilium ;  but  with  regard  to  the  clavicles 
there  is  some  difference  of  opinion :  formerly  it  was  believed  that  they  corre- 
sponded to  the  ossa  pubis,  meeting  at  the  symphysis,  but  it  is  now  generally  taught 
that  the  clavicle  has  no  homologue  in  the  pelvic  girdle,  and  that  the  os  pubis  and 
ischium  are  represented  by  the  small  coracoid  process  in  man  and  most  mammals. 

THE  UPPER  EXTREMITY. 

The  bones  of  the  upper  extremity  consist  of  those  of  the  shoulder  girdle,  of 
the  arm,  the  forearm,  and  the  hand. 

THE   SHOULDER  GIRDLE. 

The  shoulder  girdle  consists  of  two  bones,  the  clavicle  and  the  scapula. 


THE    CLAVICLE.  135 

The  Clavicle. 

The  Clavicle  (clavis,  a  key),  or  collar-bone,  forms  the  anterior  portion  of  the 
shoulder  girdle.  It  is  a  long  bone,  curved  somewhat  like  the  italic  letter/,  and 
placed  nearly  horizontally  at  the  upper  and  anterior  part  of  the  thorax,  immediately 
above  the  first  rib.  It  articulates  by  its  inner  extremity  with  the  upper  border  of 
the  sternum,  and  by  its  outer  extremity  with  the  acromion  process  of  the  scapula, 
serving  to  sustain  the  upper  extremity  in  the  various  positions  Avhich  it  assumes, 
whilst  at  the  same  time  it  allows  of  great  latitude  of  motion  in  the  arm.1  It 
presents  a  double  curvature  when  looked  at  in  front,  the  convexity  being  forward 
at  the  sternal  end  and  the  concavity  at  the  scapular  end.  Its  outer  third  is  flat- 
tened from  above  downward,  and  extends,  in  the  natural  position  of  the  bone,  from 
a  point  opposite  the  coracoid  process  to  the  acromion.  Its  inner  two-thirds  are  of 
a"  prismatic  form,  and  extend  from  the  sternum  to  a  point  opposite  the  coracoid 
process  of  the  scapula. 

External  or  Flattened  Portion. — The  outer  third  is  flattened  from  above  down- 
ward, so  as  to  present  two  surfaces,  an  upper  and  a  lower;  and  two  borders, 
an  anterior  and  a  posterior.  The  upper  surface  is  flattened,  rough,  marked  by 
impressions  for  the  attachment  of  the  Deltoid  in  front  and  the  Trapezius  behind ; 
betAveen  these  two  impressions,  externally,  a  small  portion  of  the  bone  is  sub- 
cutaneous. The  under  surface  is  flattened.  At  its  posterior  border,  a  little 
external  to  the  point  where  the  prismatic  joins  with  the  flattened  portion,  is  a  rough 
eminence,  the  conoid  tubercle  ;  this,  in  the  natural  position  of  the  bone,  surmounts 
the  coracoid  process  of  the  scapula  and  gives  attachment  to  the  conoid  ligament. 
From  this  tubercle  an  oblique  line,  occasionally  a  depression,  passes  forward  and 
outward  to  near  the  outer  end  of  the  anterior  border;  it  is  called  the  oblique  line 
or  trapezoid  ridge,  and  affords  attachment  to  the  trapezoid  ligament.  The  anterior 
border  is  concave,  thin,  and  rough,  and  gives  attachment  to  the  Deltoid;  it  occa- 
sionally presents,  at  its  inner  end,  at  the  commencement  of  the  deltoid  impression, 
a  tubercle,  the  deltoid  tubercle,  which  is  sometimes  to  be  felt  in  the  living  subject. 
Tho  posterior  border  is  convex,  rough,  broader  than  the  anterior,  and  gives  attach- 
ment to  the  Trapezius. 

•  Internal  or  Prismatic  Portion. — The  prismatic  portion  forms  the  inner  two- 
thirds  of  the  bone.  It  is  curved  so  as  to  be  convex  in  front,  concave  behind,  and 
is  marked  by  three  borders,  separating  three  surfaces.  The  anterior  border  is 
continuous  with  the  anterior  margin  of  the  flat  portion.  At  its  commencement  it 
is  smooth,  and  corresponds  to  the  interval  between  the  attachment  of  the  Pectoralis 
major  and  Deltoid  muscles;  at  the  inner  half  of  the  clavicle  it  forms  the  lower 
boundary  of  an  elliptical  space  for  the  attachment  of  the  clavicular  portion  of  the 
Pectoralis  major,  and  approaches  the  posterior  border  of  the  bone.  The  superior 
border  is  continuous  with  the  posterior  margin  of  the  flat  portion,  and  separates 
the  anterior  from  the  posterior  surface.  At  its  commencement  it  is  smooth  and 
rounded,  becomes  rough  toward  the  inner  third  for  the  attachment  of  the  Sterno- 
mastoid  muscle,  and  terminates  at  the  upper  angle  of  the  sternal  extremity.  The 
posterior  or  subclavian  border  separates  the  posterior  from  the  inferior  surface,  and 
extends  from  the  conoid  tubercle  to  the  rhomboid  impression.  It  forms  the  pos- 
terior boundary  of  the  groove  for  the  Subclavius  muscle,  and  gives  attachment  to  a 
layer  of  cervical  fascia  covering  the  Omo-hyoid  muscle.  The  anterior  surface  is 
included  between  the  superior  and  anterior  borders.  It  is  directed  forward  and  a 
little  upward  at  the  sternal  end,  outward  and  still  more  upward  at  the  acromial 
extremity,  where  it  becomes  continuous  with  the  upper  surface  of  the  flat  portion. 
Externally,  it  is  smooth,  convex,  nearly  subcutaneous,  being  covered  only  by  the 

1  The  clavicle  acts  especially  as  a  fulcrum  to  enable  the  muscles  to  give  lateral  motion  to  the  arm. 
It  is  accordingly  absent  in  those  animals  vhose  fore  limbs  are  used  only  for  progression,  but  is  present 
for  the  most  part  in  those  animals  w'  ose  anterior  extremities  are  clawed  and  used  for  prehension, 
though  in  some  of  them — as,  for  instance,  in  a  large  number  of  the  carnivora— -it  is  merely  a  rudi- 
mentary bone  suspend  I  ong  the  muscles,  and  not  articulating  either  with  the  scapula  01 
sternum. 


136 


THE  SKELETON. 


Platysma ;  but,  corresponding  to  the  inner  half  of  the  bone,  it  is  divided  by  a  more 
or  less  prominent  line  into  two  parts :  a  lower  portion,  elliptical  in  form,  rough, 
and  slightly  convex,  for  the  attachment  of  the  Pectoralis  major ;  and  an  upper 
part,  which  is  rough,  for  the  attachment  of  the  Sterno-cleido-mastoid.  Between 
the  two  muscular  impressions  is  a  small  subcutaneous  interval.  The  posterior  or 
cervical  surface  is  smooth,  flat,  and  looks  backward  toward  the  root  of  the  neck. 
It  is  limited,  above,  by  the  superior  border;  below,  by  the  subclavian  border; 
internally,  by  the  margin  of  the  sternal  extremity ;  externally,  it  is  continuous 
with  the  posterior  border  of  the  flat  portion.  It  is  concave  from  within  outward, 
and  is  in  relation,  by  its  lower  part,  with  the  suprascapular  vessels.  This  surface, 
at  about  the  junction  of  the  inner  and  outer  curves,  is  also  in  close  relation  with 
the  brachial  plexus  and  subclavian  vessels.  It  gives  attachment,  near  the  sternal 
extremity,  to  part  of  the  Sterno-hyoid  muscle ;  and  presents,  at  or  near  the  middle, 
a  foramen,  directed  obliquely  outward,  which  transmits  the  chief  nutrient  artery 
of  the  bone.  Sometimes  there  are  two  foramina  on  the  posterior  surface,  or  one 
on  the  posterior,  the  other  on  the  inferior  surface.     The  inferior  or  subclavian 


Acromial  extremity. 


Sternal  extremity. 


Fig.  92.— Left  clavicle.    Superior  surface. 

surface  is  bounded,  in  front,  by  the  anterior  border ;  behind,  by  the  subclavian 
border.     It  is  narrow  internally,  but  gradually  increases  in  width  externally,  and 


Fig.  93.— Left  clavicle.    Inferior  surface. 

is  continuous  with  the  under  surface  of  the  flat  portion.  Commencing  at  the 
sternal  extremity  may  be  seen  a  small  facet  for  articulation  with  the  cartilage  A 
the  first  rib.  This  is  continuous  with  the  articular  surface  at  the  sternal  end  of 
the  bone.  External  to  this  is  a  broad,  rough  surface,  the  rhomboid  impression, 
rather  more  than  an  inch  in  length,  for  the  attachment  of  the  costo-clavicular 
(rhomboid)  ligament.  The  remaining  part  of  this  surface  is  occupied  by  i  longi- 
tudinal groove,  the  subclavian  groove,  broad  and  smooth  externally,  narrow  and 
more  uneven  internally ;  it  gives  attachment  to  the  Subclavius  muscle,  and  by  its 
margins  to  the  costo-coracoid  membrane,  which  splits  to  enclose  a  muscle;  Not 
infrequently  this  groove  is  subdivided  into  two  pa/ts  by  a  longitudinal  line,  which 
gives  attachment  to  the  intermuscular  septum  of  the  Subclavius  muscle. 

The  internal  or  sternal  extremity  of  the  clavicle  is  triangular  in  form,  directed 


THE    CLAVICLE.  137 

inward  and  a  little  downward  and  forward ;  and  presents  an  articular  facet, 
concave  from  before  backward,  convex  from  above  downward,  which  articulates 
with  the  sternum  through  the  intervention  of  an  interarticular  fibro-cartilage ;  the 
circumference  of  the  articular  surface  is  rough,  for  the  attachment  of  numerous 
ligaments.  The  posterior  border  of  this  surface  is  prolonged  backward,  so  as  to 
increase  the  size  of  the  articular  facet ;  the  upper  border  gives  attachment  to  the 
interarticular  fibro-cartilage,  and  the  lower  border  is  continuous  with  the  costal 
facet  on  the  inner  end  of  the  inferior  or  subclavian  surface,  which  articulates  with 
the  cartilage  of  the  first  rib. 

The  outer  or  acromial  extremity,  directed  outward  and  forward,  presents  a 
small,  flattened,  oval  facet,  which  looks  obliquely  downward,  for  articulation  with 
the  acromion  process  of  the  scapula.  The  circumference  of  the  articular  facet  is 
rough,  especially  above,  for  the  attachment  of  the  acromio-clavicular  ligaments. 

Peculiarities  of  the  Bone  in  the  Sexes  and  in  Individuals. — In  the  female  the 
clavicle  is  generally  shorter,  thinner,  less  curved,  and  smoother  than  in  the  male. 
In  those  persons  who  perform  considerable  manual  labor,  which  brings  into  con- 
stant action  the  muscles  connected  with  this  bone,  it  becomes  thicker  and  more 
curved,  its  ridges  for  muscular  attachment  become  prominently  marked.  The  right 
clavicle  is  generally  longer,  thicker,  and  rougher  than  the  left. 

Structure. — The  shaft,  as  well  as  the  extremities,  consists  of  cancellous  tissue, 
invested  in  a  compact  layer  much  thicker  in  the  middle  than  at  either  end.  The 
elavicle  is  highly  elastic,  by  reason  of  its  curves.  From  the  experiments  of  Mr. 
Ward  it  has  been  shown  that  it  possesses  sufficient  longitudinal  elastic  force  to 
project  its  own  weight  nearly  two  feet  on  a  level  surface  when  a  smart  blow  is 
struck  on  it;  and  sufficient  transverse  elastic  force,  opposite  the  centre  of  its 
anterior  convexity,  to  throw  its  own  weight  about  a  foot.  This  extent  of  elastic 
power  must  serve  to  moderate  very  considerably  the  effect  of  concussions  received 
upon  the  point  of  the  shoulder. 

Development. — By  two  centres :  one  for  the  shaft  and  one  for  the  sternal 
extremity.  The  centre  for  the  shaft  appears  very  early,  before  any  other  bone — 
according  to  Be'clard,  as  early  as  the  thirtieth  day.  The  centre  for  the  sternal  end 
makes  its  appearance  about  the  eighteenth  or  twentieth  year,  and  unites  with  the 
rest  of  the  bone  about  the  twenty-fifth  year. 

Articulations. — With  the  sternum,  scapula,  and  cartilage  of  the  first  rib. 

Attachment  of  Muscles. — To  six  :  the  Sterno-cleido-mastoid,  Trapezius,  Pecto- 
ralis  major,  Deltoid,  Subclavius,  and  Sterno-hyoid. 

Surface  Form. — The  clavicle  can  be  felt  throughout  its  entire  length,  even  in  persons  who 
are  very  fat.  Commencing  at  the  inner  end,  the  enlarged  sternal  extremity,  where  the  bone 
projects  above  the  upper  margin  of  the  sternum,  can  be  felt,  forming  with  the  sternum  and  the 
rounded  tendon  of  the  Sterno-mastoid  a  V-shaped  notch,  the  pre-sternal  notch.  Passing  out- 
ward, the  shaft  of  the  bone  can  be  felt  immediately  under  the  skin,  with  its  convexity  forward 
in  the  inner  two-thirds,  the  surface  partially  obscured  above  and  below  by  the  attachments  of 
the  Sterno-mastoid  and  Pectoralis  major  muscles.  In  the  outer  third  it  forms  a  gentle  curve 
backward,  and  terminates  at  the  outer  end  in  a  somewhat  enlarged  extremity  which  articulates 
with  the  acromial  process  of  the  scapula.  The  drrection  of  the  clavicle  is  almost,  if  not  quite, 
horizontal  when  the  arm  is  lying  quietly  by  the  side,  though  in  well-developed  subjects  it  may 
incline  a  little  upward  at  its  outer  end.  Its  direction  is,  however,  very  changeable  with  the 
varying  movements  of  the  shoulder-joint. 

Surgical  Anatomy.— The  clavicle  is  the  most  frequently  broken  of  any  single  bone  in  the 
body.  This  is  due  to  the  fact  that  it  is  much  exposed  to  violence,  and  is  the  onty  bony  connec- 
tion between  the  upper  limb  and  the  trunk.  The  bone,  moreover,  is  slender,  and  is  very  super- 
ficial. The  bone  may  be  broken  by  direct  or  indirect  violence  or  by  muscular  action.  The  most 
common  cause  is,  however,  from  indirect  violence,  and  the  bone  then  gives  way  at  the  junction 
of  the  outer  with  the  inner  two-thirds  of  the  bone  ;  that  is  to  say  at  the  junction  of  the  two 
curves,  for  this  is  the  weakest  part  of  the  bone.  The  fracture  is  generally  oblique,  and  the  dis- 
placement of  the  outer  fragments  is  inward,  away  from  the  surface  of  the  body ;  hence  com- 
pound fracture  of  the  clavicle  is  of  rare  occurrence.     The  inner  fragment  as  a  rule  is  little  dis- 

d.     Beneath  the  bone  the  main  vessels  of  the  upper  limb  and  the  great  nerve-cords  of  the 

fnal  plexus  lie  on  the  first  rib,  and  are  liable  to  be  wounded  in  fracture,  especially  in  fracture 
direct  violence,  when  the  force  of  the  blow  drives  the  broken  ends  inward.  Fortunately, 
ubclavius  muscle  is  interposed  between  these  structures  and  the  clavicle,  and  this  often 
its  them  from  injury. 


138 


THE  SKELETON. 


nf  a£-  clavicle  is  not  uncommonly  the  seat  of  sarcomatous  tumors,  rendering  the  oneration 
ckn'er      It  i! Ie5  25°  b°f,  »"**»&-     P*  is  a°  °Perati™  of  considSfe  diLX  and 

St-aa-io^^      *k? danger  being  the  risk  °f  «M 

The  Scapula. 

The  Scapula  (WaV?,  a  spade)  forms  the  back  part  of  the  shoulder  girdle      It 
is  a  large,  flat  bone,  triangular  in  shape,  situated  at  the  posterior  aspect  and  side  of 


Fig.  94.— Left  scapula,  anterior  surface,  or  venter. 

inLtT?'  \eUVQei\  thQ  f6C0nd  and  seventh-  or  sometimes  the  eighth  ribs  its 
parXl,W  h  tLT  "  bem§  ^^  an  inch  fr0m'  and  ™*J>  but  not  q'u  te 
Zm  aooV tht  bSoT  ?™\°Vhe  vert.eb^>  -  that  it  is  rather  closed  to 
and  three  LgS.  P'  examination  two  surfaces,  three  borders, 

The  anterior  surface,  or  venter  (Fig.  94),  presents  a  broad  concavity,  the  sub- 


THE   SCAPULA. 


139 


scapular  fossa.  It  is  marked,  in  the  inner  two-thirds,  by  several  oblique  ridges, 
which  pass  from  behind  outward  and  upward;  the  outer  third  is  smooth.  The 
oblique  ridges  give  attachment  to  the  tendinous  intersections,  and  the  surfaces 
between  them  to  the  fleshy  fibres,  of  the  Subscapularis  muscle.  The  anterior 
third  of  the  fossa,  which  is  smooth,  is  covered  by,  but  does  not  afford  attach- 
ment to,  the  fibres  of  this  muscle.  The  venter  is  separated  from  the  internal 
border  by  a  smooth,  triangular  margin  at  the  superior  and  inferior  angles, 
and   in  the  interval    between  these  by  a  narrow   edge   which   is  often  deficient. 


.ocess 


Coracoitf 


5e,  the 

ajor  being 

N  *  Twer  part  of  the 

^e  lower  part  of  the 

ied  by  the  junction  of  the 
.nded,  somewhat  inclined  out- 
Levator  anguli  scapulae  muscle. 

iV*V'^y  ^e  unwn  °f  tne  vertebral  and 

<uchment  to  the  Teres  major  and  fre- 

The  anterior  angle  is  the  thickest 

Ehe   head  of  the  scapula.     The  head 

.xiace,  the  glenoid  cavity  (ytf»y,  a  socket), 

downward,  and  its  direction  outward  and  for- 

u,oove ;  at  its  apex  is  a  slight  impression  (suprar 

Cached  the  long  tendon  of  the  Biceps  muscle.     It  is 

recent  state ;    and  its  margins,  slightly  raised,  give 

fig.  95  -ginous  structure,  the  glenoid  ligament,  by  which   its 

.  f,.  neck  of  the  scapula  is  the  slightly  depressed  surface 

This    marginal  surface  a   it  ig  mQre  distinct  on  t^e  posterior  than  on  the  anterior 

Serratus  magnus  musclebove_      Jn  the  ktter  situation  it  has  arising  from  it  a  thick 

at  its  upper  part,  wnerj  egg 

able  angle,  called  the^  gQ  ca]led  frQm  itg  fancied  resembiauce  to  a  crow's  beak 
of  the  bone  from  its  thick    curyed  ess  of  bone  which  arises  by  a  broad  base 

the  spme  and  acrom  f  the  ^^  of  ^  uk     Jt  .fl  directed  at  first  upward  and 

so  that  the  thickest  l 


140  THE   SKELETON. 

to  the  plane  of  the  glenoid  cavity,  and  must  consequently  operate  most  effectively 
on  the  head  of  the  humerus,  Avhich  is  contained  in  that  cavity. 

The  posterior  surface,  or  dorsum  (Fig.  95),  is  arched  from  above  downward, 
alternately  concave  and  convex  from  side  to  side.  It  is  subdivided  unequally  into 
two  parts  by  the  spine :  the  portion  above  the  spine  is  called  the  supraspinous 
fossa,  and  that  below  it  the  infraspinous  fossa. 

The  supraspinous  fossa,  the  smaller  of  the  two,  is  concave,  smooth,  and  broader 
at  the  vertebral  than  at  the  humeral  extremity.  It  affords  attachment  by  its  inner 
two-thirds  to  the  Supraspinatus  muscle. 

The  infraspinous  fossa  is  much  larger  than  the  preceding ;  toward  its  vertebral 
margin  a  shallow  concavity  is  seen  at  its  upper  part ;  its  centre  presents  a  promi- 
nent convexity,  whilst  toward  the  axillary  border  is  a  deep  groove  which  runs 
from  the  upper  toward  the  lower  part.  The  inner  two-thirds  of  this  surface 
affords  attachment  to  the  Infraspinatus  muscle ;  the  outer  third  is  only  covered  by 
it,  without  giving  origin  to  its  fibres.  This  surface  is  separated  from  the  axillary 
border  by  an  elevated  ridge,  which  runs  from  the  lower  part  of  the  glenoid  cavity 
downward  and  backward  to  the  posterior  border,  about  an  inch  above  the  inferior 
angle.  The  ridge  serves  for  the  attachment  of  a  strong  aponeurosis  which  sepa- 
rates the  Infraspinatus  from  the  two  Teres  muscles.  The  surface  of  bone  between 
this  line  and  the  axillary  border  is  narrow  in  the  upper  two-thirds  of  its  extent, 
and  traversed  near  its  centre  by  a  groove  for  the  passage  of  the  dorsalis  scapulae 
vessels ;  it  affords  attachment  to  the  Teres  minor.  Its  lower  third  presents  a 
broader,  somewhat  triangular  surface,  which  gives  origin  to  the  Teres  major,  and 
over  which  the  Latissimus  dorsi  glides  ;  sometimes  the  latter  muscle  takes  origin 
by  a  few  fibres  from  this  part.  The  broad  and  narrow  portions  of  bone  above 
alluded  to  are  separated  by  an  oblique  line  which  runs  from  the  axillary  border, 
downward  and  backward,  to  meet  the  elevated  ridge :  to  it  is  attached  the 
aponeurosis  separating  the  two  Teres  muscles  from  each  other. 

The   Spine  is  a  prominent  plate   of  bone  which  crosses  obliquely  the  inner 

four-fifths  of  the  dorsum  of  the  scapula  at  its  upper  part,  and  separates  the  supra- 

from  the  infraspinous  fossa :   it  commences   at  the  vertebral  border  by  a  smooth, 

-  :°Ti<?ular  surface,  over  which  the  Trapezius  glides,  separated  from  the  bone  by  a 

1    gradually  becoming  more  elevated  as  it  passes  outward,  terminates  in 

^cess,  which  overhangs  the  shoulder-joint.      The  spine  is  triangular 

above    downward,   it's    apex    corresponding    to  the  vertebral 

•  "£  h  is    directed    outward)  to  the    neck  of  the  scapula.      It 

^    ^hree  borders.     Its  superior  surface  is  concave,  assists 

^ossa,  and  affords  attachment  to  part  of  the  Supra- 

v,rface   forms  part  of  the  infraspinous  fossa,  gives 

'  muscle,  and  presents  near  its  centre  the  or^pce/- 

^f  orders,  the  anterior  is  attached  to  the  dctsinrr*- 

f  the   spine,  is  broad,  and  presents  two  lips 

c    To  the  superior  lip  is  attached  the  Trapezius 

irrh  tubercle  is  generally  seen  occupying 

insertion  of  the  middle   and  inferior 

q;hout  its  whole  length,  is  attached 

artly  covered  by  the  tendinous 

<?,  the  shortest  of  the  three,  is 

Fig.  94.-Left  scapula,  anterior  surface,  or1  S    above  with   the  under  SU1'- 

the  scapula.  The  narrow 
the  thorax,  between  the  second  and  seventh,  or  someti  from  the  glenoid  cavity, 
internal  border  or  base  being  about  an  inch  from,  ana  supra-  and  infraspinous 
parallel  with  the  spinous  processes  of  the  vertebrae,  so  that 

them  above  than  below.     It  presents  for  examination  two  sm  mit  of  the  shoulder 

and  three  angles.  ;what  triangular   or 

The  anterior  surface,  or  venter  (Fig.  94),  presents  a  broad  st  a  little  outward, 

lenoid  cavity.     Its 


\ 


THE  SCAPULA.  141 

upper  surface,  directed  upward,  backward,  and  outward,  is  convex,  rough,  and 
gives  attachment  to  some  fibres  of  the  Deltoid,  and  in  the  rest  of  its  extent  it  is 
subcutaneous.  Its  under  surface  is  smooth  and  concave.  Its  outer  border  is  thick 
and  irregular,  and  presents  three  or  four  tubercles  for  the  tendinous  origins  of  the 
Deltoid  muscle.  Its  inner  margin,  shorter  than  the  outer,  is  concave,  gives  attach- 
ment to  a  portion  of  the  Trapezius  muscle,  and  presents  about  its  centre  a  small 
oval  surface  for  articulation  with  the  acromial  end  of  the  clavicle.  Its  apex,  which 
corresponds  to  the  point  of  meeting  of  these  two  borders  in  front,  is  thin,  and  has 
attached  to  it  the  coraco-acro.mial  ligament. 

Borders. — Of  the  three  borders  of  the  scapula,  the  superior  is  the  shortest  and 
thinnest ;  it  is  concave  and  extends  from  the  superior  angle  to  the  coracoid  process. 
At  its  outer  part  is  a  deep,  semicircular  notch,  the  suprascapular,  formed  partly  by 
the  base  of  the  coracoid  process.  This  notch  is  converted  into  a  foramen  by  the 
transverse  ligament,  and  serves  for  the  passage  of  the  suprascapular  nerve.  Some- 
times this  foramen  is  entirely  surrounded  by  bone.  The  adjacent  margin  of  the 
superior  border  affords  attachment  to  the  Omo-hyoid  muscle.  The  external,  or 
axillary,  border,  is  the  thickest  of  the  three.  It  commences  above  at  the  lower 
margin  of  the  glenoid  cavity,  and  inclines  obliquely  downward  and  backward  to 
the  inferior  angle.  Immediately  below  the  glenoid  cavity  is  a  rough  impression 
(the  infraglenoid  tubercle),  about  an  inch  in  length,  which  affords  attachment  to 
the  long  head  of  the  Triceps  muscle ;  in  front  of  this  is  a  longitudinal  groove, 
which  extends  as  far  as  its  lower  third  and  affords  origin  to  part  of  the  Subscapu- 
laris  muscle.  The  inferior  third  of  this  border,  which  is  thin  and  sharp,  serves  for 
the  attachment  of  a  few  fibres  of  the  Teres  major  behind  and  of  the  Subscapularis 
in  front.  The  internal,  or  vertebral,  border,  also  named  the  base,  is  the  longest  of 
the  three,  and  extends  from  the  superior  to  the  inferior  angle  of  the  bone.  It  is 
arched,  intermediate  in  thickness  between  the  superior  and  the  external  borders, 
and  the  portion  of  it  above  the  spine  is  bent  considerably  outward,  so  as  to  form  an 
obtuse  angle  with  the  lower  part.  The  vertebral  border  presents  an  anterior  lip, 
a  posterior  lip,  and  an  intermediate  space.  The  anterior  Up  affords  attachment 
to  the  Serratus  magnus ;  the  posterior  lip,  to  the  Supraspinatus  above  the  spine, 
the  Infraspinatus  below ;  the  interval  between  the  two  lips,  to  the  Levator  anguli 
scapulae  above  the  triangular  surface  at  the  commencement  of  the  spine,  the 
Rhomboideus  minor  to  the  edge  of  that  surface ;  the  Rhomboideus  major  being 
attached  by  means  of  a  fibrous  arch  connected  above  to  the  lower  part  of  the 
triangular  surface  at  the  base  of  the  spine,  and  below  to  the  lower  part  of  the 
posterior  border. 

Angles. — Of  the  three  angles,  the  superior,  formed  by  the  junction  of  the 
superior  and  internal  borders,  is  thin,  smooth,  rounded,  somewhat  inclined  out- 
ward, and  gives  attachment  to  a  few  fibres  of  the  Levator  anguli  scapulae  muscle. 
The  inferior  angle,  thick  and  rough,  is  formed  by  the  union  of  the  vertebral  and 
axillary  borders,  its  outer  surface  affording  attachment  to  the  Teres  major  and  fre- 
quently to  a  few  fibres  of  the  Latissimus  dorsi.  The  anterior  angle  is  the  thickest 
part  of  the  bone,  and  forms  what  is  called  the  head  of  the  scapula.  The  head 
presents  a  shallow,  pyriform,  articular  surface,  the  glenoid  cavity  {ytfvy,  a  socket), 
whose  longest  diameter  is  from  above  downward,  and  its  direction  outward  and  for- 
ward. It  is  broader  below  than  above ;  at  its  apex  is  a  slight  impression  (supra- 
glenoid  tubercle),  to  which  is  attached  the  long  tendon  of  the  Biceps  muscle.  It  is 
covered  with  cartilage  in  the  recent  state;  and  its  margins,  slightly  raised,  give 
attachment  to  a  fibro-cartilaginous  structure,  the  glenoid  ligament,  by  which  its 
cavity  is  deepened.  The  neck  of  the  scapula  is  the  slightly  depressed  surface 
which  surrounds  the  head ;  it  is  more  distinct  on  the  posterior  than  on  the  anterior 
surface,  and  below  than  above.  In  the  latter  situation  it  has  arising  from  it  a  thick 
prominence,  the  coracoid  process. 

The  Coracoid  Process,  so  called  from  its  fancied  resemblauce  to  a  crow's  beak 
?,  a  cnr-  thick,  curved  process  of  bone  which  arises  by  a  broad  base 

the  uppt  f  the  neck  of  the  scapula ;  it  is  directed  at  first  upward  and 


142 


THE   SKELETON, 


inward,  then,  becoming  smallerr^t  changes  its  direction  and  passes  forward  and 
outward.  The  ascending  portion,  flattened  from  before  backward,  presents  in 
front  a  smooth,  concave  surface  over  which  passes  the  Subscapularis  muscle.  The 
horizontal  portion  is  flattened  from  above  downward,  its  upper  surface  is  convex 
and  irregular,  and  gives  attachment  to  the  Pectoralis  minor ;  its  under  surface  is 
smooth ;  its  inner  border  is  rough,  and  gives  attachment  to  the  Pectoralis  minor ; 
its  outer  border  is  also  rough  for  the  coraco-acromial  ligament,  while  the  apex  is 
embraced  by  the  conjoined  tendon  of  origin  of  the  short  head  of  the  Biceps  and 
of  the  Coraco-brachialis  and  gives  attachment  to  the  Costo-coracoid  ligament.  At 
the  inner  side  of  the  root  of  the  coracoid  process  is  a  rough  impression  for  the 
attachment  of  the  conoid  ligament ;  and  running  from  it  obliquely  forward  and 
outward  on  the  upper  surface  of  the  horizontal  portion,  an  elevated  ridge  for  the 
attachment  of  the  trapezoid  ligament. 


nferW 


Fig.  96.— Plan  of  the  development  of  the  scapula.  Bv  seven  centres.  The  epiphyses  (except  one  for  the 
coracoid  process)  appear  from  fifteen  to  seventeen  years,  and  unite  between  twenty-two  and  twenty-five  years 
of  age. 

Structure. — In  the  head,  processes,  and  all  the  thickened  parts  of  the  bone  the 
scapula  is  composed  of  cancellous  tissue,  while  in  the  rest  of  its  extent  it  is  com- 
posed of  a  thin  layer  of  dense,  compact  tissue.  The  centre  part  of  the  supra- 
spinous fossa  and  the  upper  part  of  the  infra-spinous  fossa,  but  especially  the 
former,  are  usually  so  thin  as  to  be  semitransparent ;  occasionally  the  bone  is 
found  wanting  in  this  situation,  and  the  adjacent  muscles  come  into  contact. 

Development  (Fig.  96). — By  seven  or  more  centres  :  one  for  the  body,  two  for 
the  coracoid  process,  two  for  the  acromion,  one  for  the  vertebral  border,  and  one 
for  the  inferior  angle. 

Ossification  of  the  body  of  the  scapula  commences  about  the  second  month  of 
foetal  life  by  the  formation  of  an  irregular  quadrilateral  plate  of  bone  immediately 
behind  the  glenoid  cavity.  This  plate  extends  itself  so  as  to  form  the  chief  part 
of  the  bone,  the  spine  growing  up  from  its  posterior  surface  about  the  third  month. 


THE   SCAPULA.  143 

At  birth  a  large  part  of  the  scapula  is  osseous,  but  the  glenoid  cavity,  coracoid  and 
acromion  processes,  the  posterior  border,  and  inferior  angle  are  cartilaginous. 
From  the  fifteenth  to  the  eighteenth  month  after  birth  ossification  takes  place  in  the 
middle  of  the  coracoid  process,  which  usually  becomes  joined  with  the  rest  of  the 
bone  at  the  time  when  the  other  centres  make  their  appearance.  Between  the 
fourteenth  and  twentieth  years  ossification  of  the  remaining  centres  takes  place  in 
quick  succession,  and  in  the  following  order :  first,  in  the  root  of  the  coracoid  proc- 
ess, in  the  form  of  a  broad  scale ;  secondly,  near  the  base  of  the  acromion  process ; 
thirdly,  in  the  inferior  angle  and  contiguous  part  of  the  posterior  border ;  fourthly, 
near  the  extremity  of  the  acromion  ;  fifthly,  in  the  posterior  border.  The  acromion 
process,  besides  being  formed  of  two  separate  nuclei,  has  its  base  formed  by  an 
extension  into  it  of  the  centre  of  ossification  which  belongs  to  the  spine,  the  extent 
of  which  varies  in  different  cases.  The  two  separate  nuclei  unite,  and  then  join 
with  the  extension  from  the  spine.  These  various  epiphyses  become  joined  to  the 
bone  between  the  ages  of  twenty-two  and  twenty-five  years.  Sometimes  failure  of 
union  between  the  acromion  process  and  spine  occurs,  the  junction  being  effected 
by  fibrous  tissue  or  by  an  imperfect  articulation  ;  in  some  cases  of  supposed  fracture 
of  the  acromion  with  ligamentous  union  it  is  probable  that  the  detached  segment 
was  never  united  to  the  rest  of  the  bone.  The  upper  third  of  the  glenoid  cavity 
is  usually  ossified  from  a  separate  centre  (subcoracoid)  which  makes  its  appearance 
between  the  tenth,  and  eleventh  years.  Very  often,  in  addition,  an  epiphysis 
appears  for  the  lower  part  of  the  glenoid  cavity. 

Articulations. — With  the  humerus  and  clavicle. 

Attachment  of  Muscles. — To  seventeen  :  to  the  anterior  surface,  the  Subscapu- 
laris ;  posterior  surface,  Supraspinatus,  Infraspinatus  ;  spine,  Trapezius,  Deltoid  ; 
superior  border,  Omo-hyoid ;  vertebral  border,  Serratus  magnus,  Levator  anguli 
scapulae,  Rhomboideus  minor  and  major  ;  axillary  border,  Triceps,  Teres  minor, 
Teres  major;  apex  of  glenoid  cavity,  long  head  of  the  Biceps;  coracoid  process, 
short  head  of  the  Biceps,  Coraco-brachialis,  Pectoralis  minor ;  and  to  the  inferior 
angle  occasionally  a  few  fibres  of  the  Latissimus  dorsi. 

Surface  Form. — The  only  parts  of  the  scapula  which  are  truly  subcutaneous  are  the  spine 
and  acromion  process,  but,  in  addition  to  these,  the  coracoid  process,  the  internal  or  vertebral 
border  and  inferior  angle,  and.  to  a  less  extent,  the  axillary  border,  may  be  defined.  The  acro- 
mion process  and  spine  of  the  scapula  are  easily  felt  throughout  their  entire  length,  forming, 
with  the  clavicle,  the  arch  of  the  shoulder.  The  acromion  can  be  ascertained  to  be  connected 
to  the  clavicle  at  the  acromio-clavicular  joint  by  running  the  finger  along  it,  its  position  being 
often  indicated  by  an  irregularity  or  bony  outgrowth  from  the  clavicle  close  to  the  joint.  The 
acromion  can  be  felt  forming  the  point  of  the  shoulder,  and  from  this  can  be  traced  backward 
to  join  the  spine  of  the  scapula.  The  place  of  junction  is  usually  denoted  by  a,  prominence, 
which  is  sometimes  called  the  angle.  From  here  the  spine  can  be  felt  as  a  prominent  ridge  of 
bone,  marked  on  the  surface  as  an  oblique  depression,  which  becomes  less  and  less  distinct,  and 
terminates  a  little  external  to  the  spinous  processes  of  the  vertebrae.  Its  termination  is  usually 
indicated  by  a  slight  dimple  in  the  skin  on  a  level  with  the  interval  between  the  third  and  fourth 
dorsal  spines.  Below  this  point  the  vertebral  border  of  the  scapula  may  be  traced,  running 
downward  and  outward,  and  thus  diverging  from  the  vertebral  spines,  to  the  inferior  angle  of 
the  bone,  which  can  be  recognized,  although  covered  by  the  Latissimus  dorsi  muscle.  From 
this  angle  the  axillary  border  can  usually  be  traced  through  this  thick  muscular  covering,  form- 
ing, with  the  muscles,  the  posterior  fold  of  the  axilla.  The  coracoid_  process  may  be  felt  about 
an  inch  below  the  junction  of  the  middle  and  outer  third  of  the  clavicle.  Here  it  is  covered  by 
the  anterior  border  of  the  deltoid  and  lies  a  little  to  the  outer  side  of  a  slight  depression  which 
corresponds  to  the  interval  between  the  Pectoralis  major  and  Deltoid  muscles.  When  the  arms 
are  hanging  by  the  side,  the  upper  angle  of  the  scapula  corresponds  to  the  upper  border  of  the 
second  rib  or  the  interval  between  the  first  and  second  dorsal  spines,  the  inferior  angle  to  the 
upper  border  of  the  eighth  rib  or  the  interval  between  the  seventh  and  eighth  dorsal  spines.  _ 

Surgical  Anatomy. — Fractures  of  the  body  of  the  scapula  are  rare,  owing  to  the  mobility 
of  the  bone,  the  thick  layer  of  muscles  by  which  it  is  encased  on  both  surfaces,  and  the  elas- 
ticity of  the  ribs  on  which  it  rests.  Fracture  of  the  neck  of  the  bone  is  also  uncommon.  The 
most  frequent  course  of  the  fracture  is  from  the  suprascapular  notch  to  the  infraglenoid 
tubercle,  and  it  derives  its  principal  interest  from  its  simulation  to  a  subglenoid  dislocation  of 
the  humerus.  The  diagnosis  can  be  made  by  noting  the  alteration  in  the  position  of  the 
coracoid  process.  A  fracture  of  the  neck  external  to,  and  not  including,  the  coracoid  process  is 
said  to  occur,  but  it  is  exceedingly  doubtful  whether  such  an  accident  ever  takes  place.  The 
acromion  process  is  more  frequently  broken  than  any  other  part  of  the  bone,  and  there  is  some- 


144  THE   SKELETON. 

times,  in  young  subjects,  a  separation  of  the  epiphysis.  It  is  believed  that  many  of  the  cases 
of  supposed  fracture  of  the  acromion,  with  fibrous  union,  which  have  been  found  on  post-mor- 
tem examination  are  really  cases  of  imperfectly  united  epiphysis.  Sir  Astley  Cooper  believed 
that  most  fractures  of  this  bone  united  by  fibrous  tissue,  and  the  cause  of  this  mode  of  union 
was  the  difficulty  there  was  in  keeping  the  fractured  ends  in  constant  apposition.  The  coracoid 
process  is  occasionally  broken  off,  either  from  direct  violence  or  perhaps,  rarely,  from  muscular 
action. 

Tumors  of  various  kinds  grow  from  the  scapula.  Of  the  innocent  form  of  tumors  prob- 
ably the  osteomata  are  the  most  common.  When  it  grows  from  the  venter  of  the  scapula,  as  it 
sometimes  does,  it  is  of  the  compact  variety,  such  as  usually  grows  from  membrane-formed 
bones,  as  the  bones  of  the  skull.  This  would  appear  to  afford  evidence  that  this  portion  of  the 
bone  is  formed  from  membrane,  and  not,  like  the  rest  of  the  bone,  from  cartilage.  Sarcomatous 
tumors  sometimes  grow  from  the  scapula,  and  may  necessitate  removal  of  the  bone,  with  or 
without  amputation  of  the  upper  limb.  The  bone  may  be  excised  by  a  T-shaped  incision,  and, 
the  flaps  being  reflected,  the  removal  is  commenced  from  the  posterior  or  vertebral  border,  so 
that  the  subscapular  vessels  which  lie  along  the  axillary  border  are  among  the  last  structures 
divided,  and  can  be  at  once  secured. 

THE  ARM. 

The  arm  is  that  portion  of  the  upper  extremity  which  is  situated  between  the 
shoulder  and  the  elbow.     Its  skeleton  consists  of  a  single  bone,  the  humerus. 

The  Humerus. 

The  Humerus  is  the  longest  and  largest  bone  of  the  upper  extremity ;  it  presents 
for  examination  a  shaft  and  two  extremities. 

The  Upper  Extremity  presents  a  large,  rounded  head,  joined  to  the  shaft  by  a 
constricted  portion,  called  the  neck,  and  two  other  eminences,  the  greater  and  lesser 
tuberosities  (Fig.  97). 

The  head,  nearly  hemispherical  in  form,1  is  directed  upward,  inward,  and  a 
little  backward,  and  articulates  with  the  glenoid  cavity  of  the  scapula ;  its  surface 
is  smooth  and  coated  with  cartilage  in  the  recent  state.  The  circumference  of  its 
articular  surface  is  slightly  constricted,  and  is  termed  the  anatomical  neck,  in  con- 
tradistinction to  the  constriction  which  exists  below  the  tuberosities.  The  latter 
is  called  the  surgical  neck,  from  its  often  being  the  seat  of  fracture.  It  should  be 
remembered,  however,  that  fracture  of  the  anatomical  neck  does  sometimes,  though 
rarely,  occur. 

The  anatomical  neck  is  obliquely  directed,  forming  an  obtuse  angle  with  the 
shaft.  It  is  more  distinctly  marked  in  the  lower  half  of  its  circumference  than  in 
the  upper  half,  where  it  presents  a  narrow  groove,  separating  the  head  from  the 
tuberosities.  Its  circumference  affords  attachment  to  the  capsular  ligament  and 
is  perforated  by  numerous  vascular  foramina. 

The  greater  tuberosity  is  situated  on  the  outer  side  of  the  head  and  lesser 
tuberosity.  Its  upper  surface  is  rounded  and  marked  by  three  fiat  facets,  sep- 
arated by  two  slight  ridges :  the  highest  facet  gives  attachment  to  the  tendon 
of  the  Supi'aspinatus ;  the  middle  one,  to  the  Infraspinatus ;  the  infet'ior  facet  and 
the  shaft  of  the  bone  below  it,  to  the  Teres  minor.  The  outer  surface  of  the  great 
tuberosity  is  convex,  rough,  and  continuous  with  the  outer  side  of  the  shaft. 

The  lesser  tuberosity  is  more  prominent,  although  smaller  than  the  greater :  it 
is  situated  in  front  of  the  head,  and  is  directed  inward  and  forward.  Its  summit 
presents  a  prominent  facet  for  the  insertion  of  the  tendon  of  the  Subscapularis 
muscle.  The  tuberosities  are  separated  from  one  another  by  a  deep  groove,  the 
bicipital  groove,  so  called  from  its  lodging  the  long  tendon  of  the  Biceps  muscle, 
with  which  runs  a  branch  of  the  anterior  circumflex  artery.  It  commences 
above  between  the  two  tuberosities,  passes  obliquely  downward  and  a  little 
inward,  and  terminates  at  the  junction  of  the  upper  with  the  middle  third  of 
the  bone.  It  is  deep  and  narrow  at  the  commencement,  and  becomes  shallow  and 
a  little  broader  as  it  descends.     Its  borders  are  called,  respectively,  the  anterior 

1  Though  the  head  is  nearly  hemispherical  in  form,  its  margin,  :'  Sir  G.  Humphry  has  shown, 
is  by  no  means  a  true  circle.     Its  greatest  measurement  is  fn  i  of  the  bicipital  groove  in  a 

direction  downward,  inward,  and  backward.  Hence  it  follows  that  th  greatest  elevation  of  the  arm 
can  be  obtained  by  rolling  the  articular  surface  in  this  direc  is  to  si.y,  obliquely  upward, 

outward,  and  forward. 


THE   HUMERUS. 


145 


Common  origin  of 

FLEXOR    CARPI    RADIALIS. 
PALMARIS    LONQUS. 
FLEXOR    SUBLIMIS    OIQITORUM 
FLEXOR    CARPI     ULNARIS. 


EXTENSOR    CARPI    RADIALIS 
LONQtOR. 


Common  origin  of 

EXTENSOR    CARPI    RADIALIS   BREVIS, 
COMMUNIS    DlQITORUM. 

"        MINIMI     DlQITI. 

"        CARPI     ULNARIS. 
SUPINATOR    BREVIS. 


Fig.  97.— LeJ't  humerus.    Anterior  view. 


and  posterior  bicipital  ridges,  and  form  the  upper  part  of  the  anterior  and  internal 
10 


146  THE  SKELETON. 

I 

borders  of  the  shaft  of  the  bone.  In  the  recent  state  it  is  covered  with  a  thin 
layer  of  cartilage,  lined  by  a  prolongation  of  the  synovial  membrane  of  the 
shoulder-joint,  and  receives  the  tendon  of*  insertion  of  the  Latissimus  dorsi  muscle. 

The  Shaft  of  the  humerus  is  almost  cylindrical  in  the  uppe±'  half  of  its  extent, 
prismatic  and  flattened  below,  and  presents  three  borders  ?.±d  three  surfaces  for 
examination. 

The  anterior  border  runs  from  the  front  of  the  great  tuberosity  above  to  the 
coronoid  depression  below,  separating  the  internal  from  the  external  surface.  Its 
upper  part  is  very  prominent  and  rough,  and  forms  the  outer  lip  of  the  bicipital 
groove.  It  is  sometimes  called  the  anterior  bicipital  or  pectoral  ridge,  and  serves 
for  the  attachment  of  the  tendon  of  the  Pectoralis  major.  About  its  centre  it 
forms  the  anterior  boundary  of  the  rough  deltoid  impression;  below,  it  is  smooth 
and  rounded,  aifording  attachment  to  the  Brachialis  anticus. 

The  external  border  runs  from  the  back  part  of  the  greater  tuberosity  to  the 
external  condyle,  and  separates  the  external  from  the  posterior  surface.  It  is 
rounded  and  indistinctly  marked  in  its  upper  half,  serving  for  the  attachment  of 
the  lower  part  of  the  insertion  of  the  Teres  minor,  and  below  this  of  the  external 
head  of  the  Triceps  muscle  ;  its  centre  is  traversed  by  a  broad  but  shallow,  oblique 
depression,  the  musculo-spiral  groove  ;  its  lower  part  is  marked  by  a  prominent, 
rough  margin,  a  little  curved  from  behind  forward,  the  external  mpr&cojndular^, 
ridge,  which  presents  an  anterior  lip  for  the  attachment  of  the  Sift^matorHtun^'us 
above  and  Extensor  carpi  radialis  longior  below,  a  posterior  lip  for  the  Triceps, 
and  an  intermediate  space  for  the  attachment  of  the  external  intermuscular  septum. 

The  internal  border  extends  from  the  lesser  tuberosity  to  the  internal  condyle.  Its 
upper  third  is  marked  by  a  prominent  ridge,  forming  the  posterior  lip  of  the  bicipital 
groove,  and  gives  attachment  to  the  tendon  of  the  Teres  major.  About  its  centre  is 
an  impression  for  the  attachment  of  the  Coraco-brachialis,  and  just  below  this  is  seen 
the  entrance  of  the  nutrient  canal,  directed  downward.  Sometimes  there  is  a  second 
canal,  situated  at  the  commencement  of  the  musculo-spiral  groove,  for  a  nutrient 
artery  derived  from  the  superior  profunda  branch  of  the  brachial  artery.  The 
inferior  third  of  this  border  is  raised  into  a  slight  ridge,  the  internal  supracondylar 
ridge,  which  becomes  very  prominent  below ;  it  presents  an  anterior  lip  for  the  attach- 
ment of  the  Brachialis  anticus,  a  posterior  lip  for  the  internal  head  of  the  Triceps, 
and  an  intermediate  space  for  the  attachment  of  the  internal  intermuscular  septum. 

The  external  surface  is  directed  outward  above,  where  it  is  smooth,  rounded, 
and  covered  by  the  Deltoid  muscle ;  forward  and  outward  below,  where  it  is 
slightly  concave  from  above  downward,  and  gives  origin  to  part  of  the  Brachialis 
anticus  muscle.  About  the  middle  of  this  surface  is  seen  a  rough,  triangular 
impression  for  the  insertion  of  the  Deltoid  muscle  ;  and  below  it  the  musculo-spiral 
groove,  directed  obliquely  from  behind,  forward  and  downward,  and  transmitting 
the  musculo-spiral  nerve  and  superior  profunda  artery. 

The  internal  surface,  less  extensive  than  the  external,  is  directed  inward  above, 
forward  and  inward  below ;  .  I L  its  upper  part  it  is  narrow  and  forms  the  floor  of 
the  bicipital  groove  :  to  it  is  attached  the  Latissimus  dorsi.  The  middle  part  of 
this  surface  is  slightly  rough  for  the  attachment  of  some  of  the  fibres  of  the  tendon 
of  insertion  of  the  Coraco-brachialis ;  its  lower  part  is  smooth,  concave  from  above 
downward,  and  gives  attachment  to  the  Brachialis  anticus  muscle.1 

1  A  small,  hook-shaped  process  of  bone,  the  supracondylar  process,  varying  from  ^  to  f  of  an  inch 
in  length,  is  not  infrequently  found  projecting  from  the  inner  surface  of  the  shaft  of  the  humerus  two 
inches  above  the  internal  condyle.  It  is  curved  downward,  forward,  and  inward,  and  its  pointed  ex- 
tremity is  connected  to  the  internal  border,  just  above  the  irner  condyle,  by  a  ligament  or  fibrous 
band,  which  gives  origin  to  a  portion  of  the  Pronator  radii  teres  ;  through  the  arch  completed  by  this 
fibrous  band  the  median  nerve  and  brachial  artery  pass  when  these  structures  deviate  from  their 
usual  course.  Sometimes  the  nerve  alone  is  transmitted  through  it,  or  the  nerve  maybe  accompanied 
by  the  ulnar  artery  in  cases  of  high  division  of  the  bracl  ial.  A  well-marked  groove  is  usually  found 
behind  the  process  in  which  the  nerve  and  artery  are  lod  jed.  This  space  is  analogous  to  the  supra- 
condyloid  foramen  in  many  animals,  and  probably  serves  in  them  to  protect  the  nerve  and  artery 
from  compression  during  the  contraction  of  the  muscles  .n  this  region.  A  detailed  account  of  this 
process  is  given  by  Dr.  Struthers.  in  his  Anatomical  and  Physiological  Observations,  p.  202.  An  acces- 
sory portion  of  the  Coracobrachialis  muscle  is  frequentl  r  connected  with  this  process,  according  to 
Mr.  J .  Wood  ( Journal  of  Anat.  N<     i  '    >.  47). 


THE   HUMERUS. 


147 


The  posterior  surface  (Fig.  98)  appears  some- 
what twisted,  so  that  its  upper  part  is  directed  a 
little  inward,  its  lower  part  backward  and  a  little 
outward.  Nearly  the  whole  of  this  surface  is 
covered  by  the  external  and  internal  heads  of 
the  Triceps,  the  former  of  which  is  attached  to 
its  upper  and  outer  part,  the  latter  to  its  inner 
and  back  part,  the  two  being  separated  by  the 
musculo-spiral  groove. 

The  Lower  Extremity  is  flattened  from  before 
backward,  and  curved  slightly  forward;  it  ter- 
minates below  in  a  broad,  articular  surface  which 
is  divided  into  two  parts  by  a  slight  ridge.  Pro- 
jecting on  either  side  are  the  external  and  inter- 
nal condyles.  The  articular  surface  extends  a 
little  lower  than  the  condyles,  and  is  curved 
slightly  forward,  so  as  to  occupy  the  more  ante- 
rior part  of  the  bone;  its  greatest  breadth  is 
in  the  transverse  diameter,  and  it  is  obliquely 
directed,  so  that  its  inner  extremity  occupies  a 
lower  level  than  the  outer.  The  outer  portion  of 
the  articular  surface  presents  a  smooth,  rounded 
eminence,  which  has  received  the  name  of  the 
capitellum,  or  radial  head  of  the  humerus;  it 
articulates  with  the  cup-sbaped  depression  on 
the  head  of  the  radius,  and  is  limited  to  the 
front  and  lower  part  of  the  bone,  not  extending 
as  far  back  as  the  other  portion  of  the  articular 
surface.  On  the  inner  side  of  this  eminence  is 
a  shallow  groove,  in  which  is  received  the  inner 
margin  of  the  head  of  the  radius.  Above  the 
front  part  of  the  capitellum  is  a  slight  depression, 
the  radial  fossa,  which  receives  the  anterior 
border  of  the  head  of  the  radius  when  the  fore- 
arm is  flexed.  The  inner  portion  of  the  articular 
surface,  the  trochlea,  presents  a  deep  depression 
between  two  well-marked  borders.  This  surface 
is  convex  from  before  backward,  concave  from 
side  to  side,  and  occupies  the  anterior,  lower. 
and  posterior  parts  of  the  bone.  The  external 
border,  less  prominent  than  the  internal,  corre- 
sponds to  the  interval  between  the  radius  and  the 
ulna.  The  internal  border  is  thicker,  more 
prominent,  and  consequently  of  greater  length, 
than  the  external.  The  grooved  portion  of  the 
articular  surface  fits  accurately  within  the 
greater  sigmoid  cavity  of  the  ulna :  it  is  broader 
and  deeper  on  the  posterior  than  on  the  anterior 
aspect  of  the  bone,  and  is  inclined  obliquely  from 
behind  forward  and  from  without  inward.  Above 
the  front  part  of  the  trochlear  surface  is  seen  a 
smaller  depression,  the  coronoid  fossa,  which 
receives  the  coronoid  process  of  the  ulna  during 
flexion  of  the  forearm.  Above  the  back  part  of 
the  trochlear  surface  is  a  deep,  triangular  depres- 
sion, the  olecranon  foss  t,  in  which  is  received  the 
summit  of  the  olecranon  process  in  extension  of    fig. 98,-Left 


M  3 


ft:    i 


H    i 


iressi<to± 


Jro  oh  Li 


point 


/ 


Posterior  surface. 


148 


THE  SKELETON. 


Epiphyses  of  head  and  ) 
tuberosities  Mend   at 
5th  year,   and  unite 
with   shaft    at    20th 
year. 


Unites  with  shaft  \  Cj/ 
at  18th  year.      ] 


the  forearm.     These  fossae  are  separated  from  one  another  by  a  thin,  transparent 
lamina  of  bone,  which  is  sometimes  perforated,  forming  the  supratrochlear  foramen  ; 

their  upper  margins  afford  attachment  to  the 
anterior  and  posterior  ligaments  of  the  elbow- 
joint,  and  they  are  lined,  in  the  recent  state, 
by  the  synovial  membrane  of  this  articula- 
tion. The  articular  surfaces,  in  the  recent 
state,  are  covered  with  a  thin  layer  of  car- 
tilage. The  external  condyle  {ejneondyle)  is 
a  small,  tubercular  eminence,  less  prominent 
than  the  internal,  curved  a  little  forward,  and 
giving  attachment  to  the  external  lateral  lig- 
ament of  the  elbow-joint,  and  to  a  tendon 
common  to  the  origin  of  some  of  the  ex- 
tensor and  supinator  muscles.  The  internal 
condyle  (epitrochled),  larger  and  more  prom- 
inent, and  therefore  more  liable  to  fracture, 
than  the  external,  is  directed  a  little  backward : 
it  gives  attachment  to  the  internal  lateral 
ligament,  to  the  Pronator  radii  teres,  and  to 
a  tendon  common  to  the  origin  of  some  of 
the  flexor  muscles  of  the  forearm.  The 
ulnar  nerve  runs  in  a  groove  at  the  back 
of  the  internal  condyle,  or  between  it  and 
the  olecranon  process.  These  condyles  are 
directly  continuous  above  with  the  external 
and  internal  supracondylar  ridges. 

Structure. — The  extremities  consist  of 
cancellous  tissue,  covered  with  a  thin  com- 
pact layer;  the  shaft  is  composed  of  a  cylin- 
der of  compact  tissue,  thicker  at  the  centre 
than  at  the  extremities,  and  hollowed  out 
by  a  large  medullary  canal,  which  extends  along  its  whole  length. 

Development. — By  seven,  or  occasionally  eight,  centres  (Fig.  99),  one  for  the 
shaft,  one  for  the  head,  one  for  the  tuberosities,  one  for  the  radial  head,  one  for 
the  trochlear  portion  of  the  articular  surface,  and  one  for  each  condyle.  The 
nucleus  for  the  shaft  appears  near  the  centre  of  the  bone  in  the  eighth  week,  and 
soon  extends  toward  the  extremities.  At  birth  the  humerus  is  ossified  nearly  in 
its  whole  length,  the  extremities  remaining  cartilaginous.  During  the  first  year, 
sometimes  before  birth,  ossification  commences  in  the  head  of  the  bone,  and  during 
the  third  year  the  centre  for  the  tuberosities  makes  its  appearance,  usually  by  a 
single  ossific  point,  but  sometimes,  according  to  Be'clard,  by  one  for  each  tuber- 
osity, that  for  the  lesser  being  small  and  not  appearing  until  the  fifth  year.  By  the 
sixth  year  the  centres  for  the  head  and  tuberosities  have  increased  in  size  and 
become  joined,  so  as  to  form  a  single  large  epiphysis. 

The  lower  end  of  the  humerus  is  developed  in  the  following  manner :  At  the 
end  of  the  second  year  ossification  commences  in  the  capitellum,  and  from  this 
point  extends  inward,  so  as  to  form  the  chief  part  of  the  articular  end  of  the  bone, 
the  centre  for  the  inner  part  of  the  trochlea  not  appearing  until  about  the  age  of 
twelve.  Ossification  commences  in  the  internal  condyle  about  the  fifth  year,  and 
in  the  external  one  not  until  about  the  thirteenth  or  fourteenth  year.  About  six- 
teen or  seventeen  years  the  outer  condyle  and  both  portions  of  the  articulating 
surface  (having  already  joined)  unite  with  the  shaft;  at  eighteen  years  the  inner 
condyle  becomes  'oined;  while  the  upper  epiphysis,  although  the  first  formed,  is 
not  united  until  about  the  twentieth  year. 

Articulations. — With  the  glenoid  cavity  of  the  scapula  and  with  the  ulna  and 

Ol  A 


Fig.  99.— Plan  of  the   development  of 
humerus     By  seven  centres. 


the 


radi 


THE   HUMERUS.  149 

Attachment  of  Muscles. — To  twenty-four:  to  the  greater  tuberosity,  the 
Supraspinatus,  Infraspinatus,  and  Teres  minor ;  to  the  lesser  tuberosity,  the 
Subscapularis;  to  the  anterior  bicipital  ridge,  the  Pectoralis  major;  to  the  posterior 
bicipital  ridge,  the  Teres  major;  to  the  bicipital  groove,  the  Latissimus  dorsi ;  to 
the  shaft,  the  Deltoid,  Coraco-brachialis,  Brachialis  anticus,  external  and  internal 
heads  of  the  Triceps ;  to  the  internal  condyle,  the  Pronator  radii  teres,  and  common 
tendon  of  the  Flexor  carpi  radialis,  Palmaris  longus,  Flexor  sublimis  digitorum, 
and  Flexor  carpi  ulnaris ;  to  the  external  condyloid  ridge,  the  Supinator  longus 
and  Extensor  carpi  radialis  longior ;  to  the  external  condyle,  the  common  tendon 
of  the  Extensor  carpi  radialis  brevior,  Extensor  communis  digitorum,  Extensor 
minimi  digiti,  Extensor  carpi  ulnaris,  and  Supinator  brevis ;  to  the  back  of  the 
external  condyle,  the  Anconeus. 

Surface  Form. — The  humerus  is  almost  entirely  clothed  by  the  muscles  which  surround  it, 
and  the  only  parts  of  this  bone  which  are  strictly  subcutaneous^  are  small  portions  of  the 
internal  and  external  condyles.  In  addition  to  these,  the_  tuberosities  and  a  part  of  the  head 
of  the  bone  can  be  felt  under  the  skin  and  muscles  by  which  they  are  covered.  Of  these  the 
greater  tuberosity  forms  the  most  prominent  bony  point  of  the  shoulder,  extending  beyond  the 
acromion  process  and  covered  by  the  Deltoid  muscle.  It  influences  materially  the  surface  form 
of  the  shoulder.  It  is  best  felt  while  the  arm  is  lying  loosely  by  the  side  ;  if  the  arm  be  raised, 
it  recedes  from  under  the  finger.  The  lesser  tuberosity,  directed  forward  and  inward,  is  to  be 
felt  to  the  inner  side  of  the  greater  tuberosity,  just  below  the  acromio-clavicular  joint.  Between 
the  two  tuberosities  lies  the  bicipital  groove.  This  can  be  defined  by  placing  the  finger  and 
making  firm  pressure  just  internal  to  the  greater  tuberosity  ;  then,  by  rotating  the  humerus,  the 
groove  will  be  felt  to  pass  under  the  finger  as  the  bone  is  rotated.  With  the  arm  abducted  from 
the  side,  by  pressing  deeply  in  the  axilla  the  lower  part  of  the  head  of  the  bone  is  to  be  felt. 
On  each  side  of  the  elbow-joint,  and  just  above  it,  the  internal  and  external  condyles  of  the 
bone  are  to  be  felt.  Of  these  the  internal  is  the  more  prominent,  but  the  ridge  passing  upward 
from  it,  the  internal  condyloid  ridge,  is  much  less  marked  than  the  external,  and,  as  a  rule,  is 
not  to  be  felt.  Occasionally,  however,  we  find  along  this  border  the  hook-shaped  process  men- 
tioned above.  The  external  condyle  is  most  plainly  to  be  seen  during  semiflexion  of  the  fore- 
arm, and  its  position  is  indicated  by  a  depression  between  the  attachment  of  the  adjacent 
muscles.  From  it  is  to  be  felt  a  strong  bony  ridge  running  up  the  outer  border  of  the  shaft  of 
the  bone.  This  is  the  external  supracondylar  riclge ;  it  is  concave  forward,  and  corresponds 
with  the  curved  direction  of  the  lower  extremity  of  the  humerus. 

Surgical  Anatomy. — There  are  several  points  of  surgical  interest  connected  with  the' 
humerus.  First,  as  regards  its  development.  The  upper  end,  though  the  first  to  ossify,  is  the 
last  to  join  the  shaft,  and  the  length  of  the  bone  is  mainly  due  to  growth  from  this  upper 
epiphysis.  Hence,  in  cases  of  amputation  of  the  arm  in  young  subjects  the  humerus  continues 
to  grow  considerably,  and  the  end  of  the  bone  which  immediately  after  the  operation  was  cov- 
ered with  a  thick  cushion  of  soft  tissue,  begins  to  project,  thinning  the  soft  parts  and  rendering 
the  stump  conical.  This  may  necessitate  the  removal  of  a  couple  of  inches  or  so  of  the  bone, 
and  even  after  this  operation  a  recurrence  of  the  conical  stump  may  take  place. 

There  are  several  points  of  surgical  interest  in  connection  with  fractures.  First,  as  regard 
their  causation  :  the  bone  may  be  broken  by  direct  or  indirect  violence  like  the  other  long  bones, 
but,  in  addition  to  this,  it  is  probably  more  frequently  fractured  by  muscular  action  than  any 
other  of  this  class  of  bone  in  the  body.  It  is  usually  the  shaft,  just  below  the  insertion  of  the 
Deltoid,  which  is  thus  broken.  I  have  seen  the  accident  happen  from  throwing  a  stone,  and  in 
an  apparently  healthy  adult  from  cutting  a  piece  of  hard  cake  tobacco  "  on  a  table.  In  this 
latter  case  there  was  no  disease  of  the  bone  that  could  be  discovered.  Fractures  of  the  upper 
end  may  take  place  through  the  anatomical  neck,  through  the  surgical  neck,  or  separation  of  the 
greater  tuberosity  may  occur.  Fracture  of  the  anatomical  neck  is  a  very  rare  accident :  in  fact. 
it  is  doubted  by  some  whether  it  ever  occurs.  These  fractures  are  usually  considered  to  be 
intracapsular,  but  they  are  probably  partly  within  and  partly  without  the  capsule,  as  the  lower 
part  of  the  capsule  is  inserted  some  little  distance  below  the  anatomical  neck,  while  the  upper 
part  is  attached  to  it.  They  may  be  impacted  or  non-impacted.  In  most  cases  there  is  little  or 
no  displacement  on  account  of  the  capsule,  in  whole  or  in  part,  remaining  attached  to  the  lower 
fragment.  But  occasionally  a  very  remarkable  alteration  in  position  takes  place ;  the  upper 
fragment  turns  on  its  own  axis,  so  that  the  cartilaginous  surface  of  the  bea  rests  against  the 
upper  end  of  the  lower  fragment.  When  the  fractured  end  is  entii 
surroundings,  its  vascular  supply  must  be  entirely  cut  off,  and  one  wou!<  it,  theor 

to  necrose.     But  this  must  be  exceedingly  rare,  for  Gurlt  was  unable  to  1 
cated  case  recorded.     Separation  of  the  upper  epiphysis  of  the  humeri; 
young  subject,  and  is  marked  by  a  characteristic  deformity  by  which 

recognized.  This  consists  in  the  presence  of  an  abrupt  projection  at  trie  front  of  the  joint  some 
short  distance  below  the  coracoid  process,  caused  by  the  upper  end  of  the  lower  fragment,  In 
fractures  of  the  shaft  of  the  humerus  the  lesion  may  take  place  is  any  point,  but  appears  to  be 
more  common  in  the  lower  than  in  the  upper  part  of  the  bone.  I  The  points  of  interest  in  con 


150  THE  SKELETON. 

nection  with  these  fractures  are — (1)  that  the  musculo-spiral  nerve  may  be  injured  as  it  lies  in  the 
groove  on  the  bone,  or  may  become  involved  in  the  callus  which  is  subsequently  thrown  out ; 
and  (2)  the  frequency  of  non-union.  This  is  believed  to  be  more  common  in  the  humerus  than 
in  any  other  bone,  and  various  causes  have  been  assigned  for  it.  It  would  seem  most  probably 
to  be  due  to  the  difficulty  that  there  is  in  fixing  the  shoulder-joint  and  the  upper  fragment,  and 
possibly  the  elbow-joint  and  lower  fragment  also.  Other  causes  which  have  been  assigned 
for  the  non-union  are:  (1)  that  in  attempting  passive  motion  of  the  elbow-joint  to  overcome 
any  rigidity  which  may  exist,  the  movement  does  not  take  place  at  the  articulation,  but  at  the 
seat  of  fracture  ;  or  that  the  patient,  in  consequence  of  the  rigidity  of  the  elbow,  in  attempting 
to  flex  or  extend  the  forearm  moves  the  fragment  and  not  the  joint.  (2)  The  presence  of  small 
portions  of  muscular  tissue  between  the  broken  ends.  (3)  Want  of  support  to  the  elbow,  so 
that  the  weight  of  the  arm  tends  to  drag  the  lower  fragment  away  from  the  upper.  An  import- 
ant distinction  to  make  in  fractures  of  the  lower  end  of  the  humerus  is  between  those  that 
involve  the  joint  and  those  which  do  not ;  the  former  always  serious,  as  they  may  lead  to 
impairment  of  the  utility  of  the  limb.  They  include  the  T-shaped  fracture  and  oblique  frac- 
tures which  involve  the  articular  surface.  The  fractures  which  do  not  involve  the  joint  are  the 
transverse  above  the  condyles  and  the  so-called  epitrochlear  fracture,  when  the  tip  of  the 
internal  condyle  has  broken  off,  generally  from  direct  violence. 

Under  the  head  of  separation  of  the  epiphysis  two  separate  injuries  have  been  described. 
One  where  the  whole  of  the  four  ossific  centres  which  form  the  lower  extremity  of  the  bone  are 
separated  from  the  shaft ;  and  secondly,  where  the  articular  portion  is  alone  separated,  the  two 
condyles  remaining  attached  to  the  shaft  of  the  bone.  The  epiphysial  line  between  the  shaft 
and  lower  end  runs  across  the  bone  just  above  the  tips  of  the  condyles,  a  point  to  be  borne  in 
mind  in  performing  the  operation  of  excision. 

Tumors  originating  from  the  humerus  are  of  frequent  occurrence.  A  not  uncommon  place 
for  a  chondroma  to  grow  from  is  the  shaft  of  the  bone  somewhere  in  the  neighborhood  of  the 
insertion  of  the  deltoid.     Sarcomata  frequently  grow  from  this  bone. 

THE  FOREARM. 

The  Forearm  is  that  portion  of  the  upper  extremity  which  is  situated  between 
the  elbow  and  the  wrist.  Its  skeleton  is  composed  of  two  bones,  the  ulna  and 
radius. 

The  Ulna. 

The  Ulna  (Figs.  100,  101),  so  called  from  its  forming  the  elbow  (ibXivrj),  is  a 
long  bone,  prismatic  in  form,  placed  at  the  inner  side  of  the  forearm,  parallel  with 
the  radius.  It  is  the  larger  and  longer  of  the  two  bones.  Its  upper  extremity,  of 
great  thickness  and  strength,  forms  a  large  part  of  the  articulation  of  the  elbow- 
joint  ;  it  diminishes  in  size  from  above  downward,  its  lower  extremity  being  very 
small,  and  excluded  from  the  wrist-joint  by  the  interposition  of  an  interarticular 
fibro-cartilage.     It  is  divisible  into  a  shaft  and  two  extremities. 

The  Upper  Extremity,  the  strongest  part  of  the  bone,  presents  for  examination 
two  large,  curved  processes,  the  Olecranon  process  and  the  Coronoid  process ;  and 
two  concave,  articular  cavities,  the  greater  and  lesser  sigmoid  cavities. 

The  Olecranon  Process  (coXeviq,  elbow ;  xpaviov,  head)  is  a  large,  thick,  curved 
eminence  situated  at  the  upper  and  back  part  of  the  ulna.  It  is  curved  forward 
at  the  summit  so  as  to  present  a  prominent  tip  which  is  received  into  the  olecranon 
fossa  in  extension  of  the  forearm ;  its  base  being  contracted  where  it  joins  the  shaft. 
This  is  the  narrowest  part  of  the  upper  end  of  the  ulna,  and,  consequently,  the 
most  usual  seat  of  fracture.  The  posterior  surface  of  the  olecranon,  directed  back- 
ward, is  triangular,  smooth,  subcutaneous,  and  covered  by  a  bursa.-  Its  upper 
surface  is  of  a  quadrilateral  form,  marked  behind  by  a  rough  impression  for  the 
attachment  of  the  Triceps  muscle  ;  and  in  front,  near  the  margin,  by  a  slight  trans- 
verse groove  for  the  attachment  of  part  of  the  posterior  ligament  of  the  elbow-joint. 
T+°  interior  surface  is  smooth,  concave,  covered  wdth  cartilage  in  the  recent  state, 
and  forms  the  upper  and  back  part  of  the  great  sigmoid  cavity.  The  lateral 
bcvders  present  a  continuation  of  the  same  groove  that  was  seen  on  the  margin  of 
the  superior  -  H&ce;   th<  lor   the  attachment  of  ligaments ;  viz.,  the  back 

part  of  the  i  the  posterior  ligament  externally. 

To  the  inner  border  is  I     I  a  part  of  the  Flexor  carpi  ulnaris,  while  to  the 

outer  border  is  attached  tbe  Anconeus. 


THE    ULNA, 


151 


Radius. 


xVw2 

,  wffl  « 

Occasional  origin  of  J&\   ■?•}     I    »/ 

^  s\\- 


FLEXOR    DlQITORUM 
SUBL1MIS. 


PRONATOR 
RADII    TERES 


FLEXOR     LONQUS    POL 


Radial  origin  of  flexor 

DlQITORUM    SUBLIMIS. 


Styloid  process. 

Styloid  process. 
Fig.  100.—  Borj.es  of  the  left  forearm.    Anterior  surface 


SUPINATOR    LONQUS 

Groove  for  ext.  ossis 

METACARPI     POLLICIS 
and   EXT.    BREV.    POLL 


/ 


152  THE   SKELETON. 

The  Coronoid  Process  (xopcbvy,  anything  hooked  like  a  I  beak)  is  a  trian- 

gular eminence  of  bone  which  projects  horizontally  for  rom  the  upper  and 

front  part  of  the  ulna.  Its  base  is  continuous  with  the  shaft  nd  of  considerable 
strength ;  so  much  so  that  fracture  of  it  is  an  accident  of  i  >  occurrence.  Its 
apex  is  pointed,  slightly  curved  upward,  and  received  into  the  coronoid  depression 
of  the  humerus  in  flexion  of  the  forearm.  Its  upper  surface  is  smooth,  concave, 
and  forms  the  lower  part  of  the  greater  sigmoid  cavity.  The  under  surface  is  con- 
cave, and  marked  internally  by  a  rough  impression  for  the  insertion  of  the 
Brachialis  anticus.  At  the  junction  of  this  surface  with  the  shaft  is  a  rough  emi- 
nence, the  tubercle  of  the  ulna,  for  the  attachment  of  the  oblique  ligament.  Its 
outer  surface  presents  a  narrow,  oblong,  articular  depression,  the  lesser  sigmoid 
cavity.  The  inner  surface,  by  its  prominent,  free  margin,  serves  for  the  attach- 
ment of  part  of  the  internal  lateral  ligament.  At  the  front  part  of  this  surface  is 
a  small,  rounded  eminence  for  the  attachment  of  one  head  of  the  Flexor  sublimis 
digitorum ;  behind  the  eminence,  a  depression  for  part  of  the  origin  of  the  Flexor 
profundus  digitorum ;  and,  descending  from  the  eminence,  a  ridge  which  gives 
attachment  to  one  head  of  the  Pronator  radii  teres.  Generally,  the  Flexor  longus 
pollicis  has  an  origin  from  the  lower  part  of  the  coronoid  process  by  a  rounded 
bundle  of  muscular  fibres. 

The  Greater  Sigmoid  Cavity,  so  called  from  its  resemblance  to  the  old  shape  of 
the  Greek  letter  2',  is  a  semilunar  depression  of  large  size,  formed  by  the  olecranon 
and  coronoid  processes,  and  serving  for  articulation  with  the  trochlear  surface  of 
the  humerus.  About  the  middle  of  either  lateral  border  of  this  cavity  is  a  notch 
which  contracts  it  somewhat,  and  serves  to  indicate  the  junction  of  the  two 
processes  of  which  it  is  formed.  The  cavity  is  concave  from  above  downward, 
and  divided  into  two  lateral  parts  by  a  smooth,  elevated  ridge  which  runs  from  the 
summit  of  the  olecranon  to  the  tip  of  the  coronoid  process.  Of  these  two  portions, 
the  internal  is  the  larger,  and  is  slightly  concave  transversely ;  the  external  por- 
tion is  convex  above,  slightly  concave  below.  The  articular  surface,  in  the  recent 
state,  is  covered  with  a  thin  layer  of  cartilage. 

The  Lesser  Sigmoid  Cavity  is  a  narrow,  oblong,  articular  depression,  placed  on 
the  outer  side  of  the  coronoid  process,  and  receives  the  lateral  articular  surface  of 
the  head  of  the  radius.  It  is  concave  from  before  backward,  and  its  extremities, 
which  are  prominent,  serve  for  the  attachment  of  the  orbicular  ligament.  In  the 
recent  state  it  is  covered  with  a  thin  layer  of  cartilage. 

The  Shaft,  at  its  upper  part,  is  prismatic  in  form,  and  curved  from  behind 
forward  and  from  without  inward,  so  as  to  be  convex  behind  and  externally ;  its 
central  part  is  quite  straight ;  its  lower  part  rounded,  smooth,  and  bent  a  little 
outward ;  it  tapers  gradually  from  above  downward,  and  presents  for  examination 
three  borders- and  three  surfaces. 

The  anterior  border  commences  above  at  the  prominent  inner  angle  of  the  coro- 
noid process,  and  terminates  below  in  front  of  the  styloid  process.  It  is  well  marked 
above,  smooth  and  rounded  in  the  middle  of  its  extent,  and  affords  attachment  to 
the  Flexor  profundus  digitorum :  its  lower  fourth,  marked  oif  from  the  rest  of  the 
border  by  the  commencement  of  an  oblique  ridge  on  the  anterior  surface,  serves 
for  the  attachment  of  the  Pronator  quadratus.  It  separates  the  anterior  from  the 
internal  surface. 

The  posterior  border  comment  the  apex  of  the  triangular  subcuta- 

neous surface  at  the  back  part  of  r  >n,  and  terminates  below  at  the  back 

part  of  the  styloid  process ;  it  is  well  marked  in  the  upper  three-fourths,  and 
gives  attachment  to  the  aponeurosis  com.non-  to  the  Flexor  carpi  ulnaris,  the 
Extensor  carpi  ulnaris,  and  the  Flexor  profundus  digitorum  muscles;  its  lower 
fourth  is  smooth  and  rounded.  This  bora-\t  separates  the  internal  from  the 
posterior  surface. 

The  external  or  interosseous  border  commence*'*  above  3  un;on  of  two  lines, 

which  converge  one  from  each  extremity  of  the  ffesser  sigm>  1  cL  ty,  enclosing 
between  them  a  triangular  space  for  the  attachmei       f  pa  \  Suph  ator  brevis. 


THE    ULNA. 

Ulna. 


153 


FOT  E.-.T.   CARPI    RAD.    LONGIOR. 
EXTENSOR    CARPI     RADIALIS    BRE 

EXTENSOR    LO'NGUS    POL 

FIG.  101." 


FLEXOR   SUBLIMIS    DIGITORUM 


For    EXTENSOR    CARPI    ULNAWR 
FOr    EXTENSOR    MINIMI     DIGIT). 

jh u    /extensor   indicis 

(  extensor  communis  digitorum. 

be  left  forearm.    Posterior  surface. 


154 


THE   SKELETON. 


and  terminates  below  at  the  middle  of  the  head  of  the  ulna.  Its  two  middle  fourths 
are  very  prominent ;  its  lower  fourth  is  smooth  and  rounded.  This  border  gives 
attachment  to  the  interosseous  membrane,  and  separates  the  anterior  from  the  pos- 
terior surface. 

The  anterior  surface,  much  broader  above  than  below,  is  concave  in  the  upper 
three-fourths  of  its  extent,  and  affords  attachment  to  the  Flexor  profundus  digi- 
torum ;  its  lower  fourth,  also  concave,  is  covered  by  the  Pronator  quadratus.  The 
lower  fourth  is  separated  from  the  remaining  portion  of  the  bone  by  a  prominent 
ridge,  directed  obliquely  from  above  downward  and  inward ;  this  ridge  (the  oblique 
or  Pronator  ridge)  marks  the  extent  of  attachment  of  the  Pronator  quadratus. 
At  the  junction  of  the  upper  with  the  middle  third  of  the  bone  is  the  nutrient 
canal,  directed  obliquely  upward  and  inward. 

The  posterior  surface,  directed  backward  and  outward,  is  broad  and  concave 
above,  somewhat  narrower  and  convex  in  the  middle  of  its  course,  narrow,  smooth, 
and  rounded  below.  It  presents,  above,  an  oblique  ridge,  which  runs  from  the 
posterior  extremity  of  the  lesser  sigmoid  cavity,  downward  to  the  posterior  border ; 
the  triangular  surface  above  this  ridge  receives  the  insertion  of  the  Anconeus 
muscle,  whilst  the  upper  part  of  the  ridge  itself  affords  attachment  to  the  Supinator 
brevis.  The  surface  of  bone  below  this  is  subdivided  by  a  longitudinal  ridge, 
sometimes  called  the  'perpendicular  line,  into  two  parts  :  the  internal  part  is  smooth, 
and  covered  by  the  Extensor  carpi  ulnaris  ;  the  external  portion,  wider  and  rougher, 
gives  attachment  from  above  downward  to  part  of  the  Supinator  brevis,  the  Exten- 
sor ossis  metacarpi  pollicis,  the  Extensor  longus  pollicis,  and  the  Extensor  indicis 
muscles. 

The  internal  surface  is  broad  and  concave  above,  narrow  and  convex  below. 
It  gives  attachment  by  its  upper  three-fourths  to  the  Flexor  profundus  digitorum 
muscle :  its  lower  fourth  is  subcutaneous. 

The  Lower  Extremity  of  the  ulna  is  of  small  size,  and  excluded  from  the  artic- 
ulation of  the  wrist-joint.     It  presents  for  examination  two  eminences,  the  outer 

and  larger  of  which  is  a  rounded,  articular  eminence, 
termed  the  head  of  the  ulna,  the  inner,  narrower  and 
more   projecting,    is    a    non-articular    eminence,   the 
styloid  process.     The  head  presents  an  articular  facet, 
part  of  which,  of  an  oval  or  semilunar  form,  is  directed 
downward,  and  articulates  with  the  upper  surface  of 
the  interarticular  fibro-cartilage  which  separates  it  from 
the  wrist-joint ;  the  remaining   portion,   directed  out- 
ward, is  narrow,  convex,  and  received  into  the  sigmoid 
cavity  of  the  radius.    The  styloid  process  projects  from 
the  inner  and  back  part  of  the  bone,  and  descends  a 
little  lower  than  the  head,  terminating  in  a  rounded 
summit,  which  affords  attachment  to  the  internal  lat- 
eral ligament  of  the  wrist.    The  head  is  separated  from 
the  styloid  process  by  a  depression  for  the  attachment 
of  the  triangular   interarticular  fibro-cartila^Bj 
behind,  by  a  shallow  groove   for  the  passage  o 
tendon  of  the  Extensor  carpi  ulnaris. 
Structure. — Similar  to  that  of  the  othei 
Development. — By  three  centres  :  one  for  the  g 
one  for  the  inferior  extremity,  and  one  for  tic 
ranon  (Fig.  102).      Ossification  commences  nea^  the 
middle  of  the  shaft  about  the  eighth  week,  and   -ion 
extends  through  the  greater  part  of  the  bone.      At 
birth  the  ends  are  cartilaginous.     About  the  fourti 
year  a  separate  osseous  nucleus  appears  in  the  middle 
of  the  head,  which  soon  extends  into  the  styloid  process.     About  the  tenth  year 
ossific  matter  appears  in  the  olecranon  near  its  extremity,  the  cLlef  part  of  this 


Olecranon. 

Appears  at_^^,Joins  shafl  at 

10th  year.    flpK™         16th  year_ 


Appears  at _(^^A_J°ins  shaft  at 
4th  year.     vj^V      20th  year. 

Inferior  extremity. 

Fig.  102.— Plan  of  the  develop- 
ment of  the  ulna.    By  three  centres 


THE   RADIUS.  155 

process  being  formed  from  an  extension  of  the  shaft  of  the  bone  into  it.  At 
about  the  sixteenth  year  the  upper  epiphysis  becomes  joined,  and  at  about  the 
twentieth  year  the  lower  one. 

Articulations. — With  the  humerus  and  radius. 

Attachment  of  Muscles. — To  sixteen  :  to  the  olecranon,  the  Triceps,  Anconeus, 
and  one  head  of  the  Flexor  carpi  ulnaris.  To  the  coronoid  process,  the  Brachialis 
anticus,  Pronator  radii  teres,  Flexor  sublimis  digitorum,  and  Flexor  profundus 
digitorum ;  generally  also  the  Flexor  longus  pollicis.  To  the  shaft,  the  Flexor 
profundus  digitorum,  Pronator  quadratus,  Flexor  carpi  ulnaris.  Extensor  carpi 
ulnaris,  Anconeus,  Supinator  brevis,  Extensor  ossis  metacarpi  pollicis,  Extensor 
longus  pollicis,  and  Extensor  indicis. 

Surface  Form. — The  most  prominent  part  of  the  ulna  on  the  surface  of  the  body  is  the 
olecranon  process,  which  can  always  be  felt  at  the  back  of  the  elbow-joint.  When  the  fore- 
arm is  flexed,  the  tipper  quadrilateral  surface  can  be  felt,  directed  backward  ;  during  extension 
it  recedes  into  the  olecranon  fossa,  and  the  contracting  fibres  of  the  triceps  prevent  its  being 
perceived.  At  the  back  of  the  olecranon  is  the  smooth,  triangular,  subcutaneous  surface, 
which  below  is  continuous  with  the  posterior  border  of  the  shaft  of  the  bone,  and  felt  in 
every  position  of  the  forearm.  During  extension  the  upper  border  of  the  olecranon  is  slightly 
above  the  level  of  the  internal  condyle,  and  the  process  itself  is  nearer  to  this  condyle  than 
the  outer  one.  Running  down  the  back  of  the  forearm,  from  the  apex  of  the  triangular 
surface  which  forms  the  posterior  surface  of  the  olecranon,  is  a  prominent  ridge  of  bone,  the 
posterior  border  of  the  ulna.  This  is  to  be  felt  throughout  the  entire  length  of  the  shaft  of  the 
bone,  from  the  olecranon  above  to  the  styloid  process  below.  As  it  passes  down  the  forearm  it 
pursues  a  sinuous  course  and  inclines  to  the  inner  side,  so  that,  though  it  is  situated  in  the 
middle  of  the  back  of  the  limb  above,  it  is  on  the  inner  side  of  the  wrist  at  its  termination.  It 
becomes  rounded  off  in  its  lower  third,  and  may  be  traced  below  to  the  small,  subcutaneous  sur- 
face of  the  styloid  process.  Internal  to  this  border  the  lower  fourth  of  the  inner  surface  is  to 
be  felt.  The  styloid  process  is  to  be  felt  as  a  prominent  tubercle  of  bone,  continuous  above 
with  the  posterior  subcutaneous  border  of  the  ulna,  and  terminating  below  in  a  blunt  apex, 
which  lies  a  little  internal  and  behind,  but  on  a  level  with,  the  wrist-joint.  The  styloid  process 
is  best  felt  when  the  hand  is  in  the  same  line  as  the  bones  of  the  forearm,  and  in  a  position 
midway  between  supination  and  pronation.  If  the  forearm  is  pronated  while  the  finger  is 
placed  on  the  process,  it  will  be  felt  to  recede,  and  another  prominence  of  bone  will  appear  just 
behind  and  above  it.  This  is  the  head  of  the  ulna,  which  articulates  with  the  lower  end  of  the 
radius  and  the  triangular  interarticular  fibro-cartilage,  and  now  projects  between  the  tendons  of 
the  Extensor  carpi  ulnaris  and  the  Extensor  minimi  digiti  muscles. 

The  Radius. 

The  Radius  (radius,  a  ray,  or  spoke  of  a  wTheel)  is  situated  on  the  outer  side  of 
the  forearm,  lying  side  by  side  with  the  ulna,  which  exceeds  it  in  length  and  size. 
(Figs.  100  and  101.)  Its  upper  end  is  small,  and  forms  only  a  small  part  of  the 
elbow-joint;  but  its  lower  end  is  large,  and  forms  the  chief  part  of  the  wrist.  It 
is  one  of  the  long  bones,  prismatic  in  form,  slightly  curved  longitudinally,  and,  like 
other  long  bones,  has  a  shaft  and  two  extremities. 

The  Upper  Extremity  presents  a  head,  neck,  and  tuberosity.  The  head  is  of  a 
cylindrical  form,  depressed  on  its  upper  surface  into  a  shallow  cup  which  articulates 
with  the  capitellum  or  radial  head  of  the  humerus.  In  the  recent  state  it  is  covered 
with  a  layer  of  cartilage  which  is  thinnest  at  its  centre.  Around  the  circumference 
of  the  head  is  a  smooth,  articular  surface,  broad  internally  where  it  articulates  with 
the  lesser  sigmoid  cavity  of  the  ulna  ;  narrow  in  the  rest  of  its  circumference,  where 
it  rotates  within  the  orbicular  ligament.  It  is  coated  with  cartilage  in  the  recent 
state.  The  head  is  supported  on  a  round,  smooth,  and  constricted  portion  of  bone, 
called  the  neck,  which  presents,  behind,  a  slight  ridge,  for  the  attachment  of  part 
of  the  Supinator  brevis.  Beneath  the  neck,  at  the  inner  and  front  aspect  of  the 
bone,  is  a  rough  eminence,  the  bicipital  tuberosity.  Its  surface  is  divided  into  two 
parts  by  a  vertical  line — a  posterior,  rough  portion,  for  the  insertion  of  the  tendon 
of  the  Biceps  muscle ;  and  an  anterior,  smooth  portion,  on  which  a  bursa  is 
interposed  between  the  tendon  and  the  bone. 

The  Shaft  of  the  bone  is  prismoid  in  form,  narrower  above  than  below,  and 
slightly  curved,  so  as  to  be  convex  outward.  It  presents  three  surfaces,  separated 
by  three  borders. 


156  THE   SKELETON. 

The  anterior  border  extends  from  the  lower  part  of  the  tuberosity  above  to  the 
anterior  part  of  the  base  of  the  styloid  process  below.  It  separates  the  anterior 
from  the  external  surface.  Its  upper  third  is  very  prominent ;  and  from  its 
oblique  direction,  downward  and  outward,  has  received  the  name  of  the  oblique 
line  of  the  radius.  It  gives  attachment  externally  to  the  Supinator  brevis, 
internally  to  the  Flexor  longus  pollicis,  and  between  these  to  the  Flexor  sublimis 
digitorum.  The  middle  third  of  the  anterior  border  is  indistinct  and  rounded.  Its 
lower  fourth  is  sharp,  prominent,  affords  attachment  to  the  Pronator  quadratus  and 
to  the  posterior  annular  ligament  of  the  wrist,  and  terminates  in  a  small  tubercle, 
into  which  is  inserted  the  tendon  of  the  Supinator  longus. 

The  posterior  border  commences  above  at  the  back  part  of  the  neck  of  the 
radius,  and  terminates  below  at  the  posterior  part  of  the  base  of  the  styloid  process  ; 
it  separates  the  posterior  from  the  external  surface.  It  is  indistinct  above  and  below, 
but  well  marked  in  the  middle  third  of  the  bone. 

The  internal  or  interosseous  border  commences  above  at  the  back  part  of  the 
tuberosity,  where  it  is  rounded  and  indistinct,  becomes  sharp  and  prominent  as 
it  descends,  and  at  its  lower  part  divides  into  two  ridges,  which  descend  to  the 
anterior  and  posterior  margins  of  the  sigmoid  cavity.  This  border  separates  the 
anterior  from  the  posterior  surface,  and  has  the  interosseous  membrane  attached 
to  it  throughout  the  greater  part  of  its  extent. 

The  anterior  surface  is  concave  for  its  upper  three-fourths,  and  gives  attach- 
ment to  the  Flexor  longus  pollicis  muscle  ;  it  is  broad  and  flat  for  its  lower  fourth, 
and  gives  attachment  to  the  Pronator  quadratus.  A  prominent  ridge  limits  the 
attachment  of  the  Pronator  quadratus  below,  and  between  this  and  the  inferior 
border  is  a  triangular  rough  surface  for  the  attachment  of  the  anterior  ligament  of 
the  wrist-joint.  At  the  junction  of  the  upper  and  middle  third  of  this  surface  is 
the  nutrient  foramen,  which  is  directed  obliquely  upward. 

The  posterior  surface  is  rounded,  convex,  and  smooth  in  the  upper  third  of  its 
extent,  and  covered  by  the  Supinator  brevis  muscle.  Its  middle  third  is  broad, 
slightly  concave,  and  gives  attachment  to  the  Extensor  ossis  metacarpi  pollicis 
above,  the  Extensor  brevis  pollicis  below.  Its  lower  third  is  broad,  convex,  and 
covered  by  the  tendons  of  the  muscles,  which  subsequently  run  in  the  grooves  on 
the  lower  end  of  the  bone. 

The  external  surface  is  rounded  and  convex  throughout  its  entire  extent.  Its 
upper  third  gives  attachment  to  the  Supinator  brevis  muscle.  About  its  centre  is 
seen  a  rough  ridge,  for  the  insertion  of  the  Pronator  radii  teres  muscle.  Its  lower 
part  is  narrow,  and  covered  by  the  tendons  of  the  Extensor  ossis  metacarpi  pollicis 
and  Extensor  brevis  pollicis  muscles. 

The  Lower  Extremity  of  the  radius  is  large,  of  quadrilateral  form,  and  provided 
with  two  articular  surfaces — one  at  the  extremity,  for  articulation  with  the  carpus, 
and  one  at  the  inner  side  of  the  bone,  for  articulation  with  the  ulna.  The  carpal 
articular  surface  is  of  triangular  form,  concave,  smooth,  and  divided  by  a  slight 
antero-posterior  ridge  into  two  parts.  Of  these,  the  external  is  of  a  triangular 
form,  and  articulates  with  the  scaphoid  bone ;  the  inner,  quadrilateral,  articulates 
with  the  semilunar.  The  articular  surface  for  the  ulna  is  called  the  sigmoid  cavity 
of  the  radius ;  it  is  narrow,  concave,  smooth,  and  articulates  with  the  head 
of  the  ulna.  The  circumference  of  this  end  of  the  bone  presents  three  surfaces 
— an  anterior,  external,  and  posterior.  The  anterior  surface,  rough  and  ir- 
regular, affords  attachment  to  the  anterior  ligament  of  the  wrist-joint.  The 
external  surface  is  prolonged  obliquely  downward  into  a  strong,  conical  projection, 
the  styloid  process,  which  gives  attachment  by  its  base  to  the  tendon  of  the 
Supinator  longus,  and  b}7  its  apex  to  the  external  lateral  ligament  of  the  wrist- 
joint.  The  outer  surface  of  this  process  is  marked  by  a  flat  groove,  which  runs 
obliquely  downward  and  forward,  and  gives  passage  to  the  tendons  of  the  Extensor 
ossis  metacarpi  pollicis  and  the  Extensor  brevis  pollicis.  The  posterior  surface  is 
convex,  affords  attachment  to  the  posterior  ligament  of  the  wrist,  and  is  marked  by 
three  grooves.     Proceeding  from  without  inward,  the  first  groove  is   broad  but 


THE  RADIUS. 


157 


Appears  atA 
5th  year. 


._ Unites  with  shaft 
about  puberty. 


1 

Mafi 

Is/tut 


shallow,  and  subdivided  into  two  by  a  slightly  elevated  ridge :  the  outer  of  these 
two  transmits  the  tendon  of  the  Extensor  carpi  radialis  longior,  the  inner  the 
tendon  of  the  Extensor  carpi  radialis  brevior.  The  second,  which  is  near  the 
centre  of  the  bone,  is  a  deep  but  narrow  groove,  bounded  on  its  outer  side  by  a 
sharply-defined  ridge ;  it  is  directed  obliquely  from  above,  downward  and  outward, 
and  transmits  the  tendon  of  the  Extensor  longus  pollicis.  The  third,  lying  most 
internally,  is  a  broad  groove,  for  the  passage  of  the  tendons  of  the  Extensor  indicis 
and  Extensor  communis  digitorum. 

Structure. — Similar  to  that  of  the  other  long  bones. 

Development  (Fig.  103). — By  three  centres :  one  for  the  shaft  and  one  for  each 
extremity.  That  for  the  shaft  makes  its  appearance  near  the  centre  of  the  bone, 
about  the  eighth  week  of  foetal  life.  About  the  end  of  the  second  year  ossifi- 
cation commences  in  the  lower  epiphysis,  and 
about  the  fifth  year  in  the  upper  end.  At  the 
age  of  seventeen  or  eighteen  the  upper  epiphysis 
becomes  joined  to  the  shaft,  the  lower  epiphysis 
becoming  united  about  the  twentieth  year. 

Articulation. — With  four  bones :  the  humerus, 
ulna,  scaphoid,  and  semilunar. 

Attachment  of  Muscles. — To  nine :  to  the 
tuberosity,  the  Biceps  ;  to  the  oblique  ridge, 
the  Supinator  brevis,  Flexor  sublimis  digitorum, 
and  Flexor  longus  pollicis ;  to  the  shaft  (its 
anterior  surface),  the  Flexor  longus  pollicis  and 
Pronator  quadratus  ;  (its  posterior  surface),  the 
Extensor  ossis  metacarpi  pollicis  and  Extensor 
brevis  pollicis ;  (its  outer  surface),  the  Pronator 
radii  teres ;  and  to  the  styloid  process,  the 
Supinator  longus. 

Surface  Form. — Just  below  and  a  little  in  front  of 
the  posterior  surface  of  the  external  condyle  a  part  of 
the  head  of  the  radius  may  be  felt,  covered  by  the  orbic- 
ular and  external  lateral  ligaments.  There  is  in  this  situ- 
ation a  little  dimple  in  the  skin,  which  is  most  visible 
when  the  arm  is  extended,  and  which  marks  the  posi- 
tion of  the  head  of  the  bone.  If  the  finger  is  placed  on 
this  dimple  and  the  forearm  pronated  and  supinated, 
the  head  of  the  bone  will  be  distinctly  perceived  rotating 
in  the  lesser  sigmoid  cavity.  The  upper  half  of  the 
shaft  of  the  radius  cannot  be  felt,  as  it  is  surrounded  by 
the  fleshy  bellies  of  the  muscles  arising  from  the  external  condyle.  The  lower  half  of  the  shaft 
can  be  readily  examined,  though  covered  by  tendons  and  muscles  and  not  strictly  subcutaneous. 
If  traced  downward,  the  shaft  will  be  felt 'to  terminate  in  a  lozenge-shaped,  convex  surface  on 
the  outer  side  of  the  base  of  the  styloid  process.-  This  is  the  only  subcutaneous  part  of  the  bone, 
and  from  its  lower  extremity  the  apex  of  the  styloid  process  will  be  felt  bending  inward  toward 
the  wrist.  About  the  middle  of  the  posterior  aspect  of  the  lower  extremity  of  the  bone  is  a 
well-marked  ridge,  best  perceived  when  the  hand  is  slightly  flexed  on  the  wrist.  It  forms  the 
outer  boundary  of  the  oblique  groove  on  the  posterior  surface  of  the  bone,  through  which  the 
tendon  of  the  Extensor  longus  pollicis  runs,  and  serves  to  keep  that  tendon  in  its  place. 

Surgical  Anatomy. — The  two  bones  of  the  forearm  are  more  often  broken  together  than  is 
either  the  radius  or  ulna  separately.  It  is  therefore  convenient  to  consider  the  fractures  of  these 
two  bones  together  in  the  first  instance,  and  subsequently  to  mention  the  principal  fractures 
which  take  place  in  each  bone  individually.  These  fractures  may  be  produced  by  either  direct 
or  indirect  violence,  though  more  commonly  by  direct  violence.  When  indirect  force  is  applied 
to  the  forearm  the  radius  generally  alone  gives  way,  though  both  bones  may  suffer.  The 
fracture  from  indirect  force  generally  takes  place  somewhere  about  the  middle  of  the  bones ; 
fracture  from  direct  violence  'may  occur  at  any  part,  more  often,  however,  in  the  lower  half  of 
the  bone.  The  fracture  is  usually  transverse,  but  may  be  more  or  less  oblique.  A  point  of 
interest  in  connection  with  these  fractures  is  the  tendency  that  there  is  for  the  two  bones  to  unite 
across  the  interosseous  membrane;  the  limb  should  therefore  be  put  up  in  a  position  midway 
between  supination  and  pronation,  which  is  not  only  the  most  comfortable  position,  but  also  sep- 
arates the  bones  most  widely  from  each  other,  and  therefore  diminishes  the  risk  of  the  bones 
becoming  united  across  the  interosseous  membrane.    The  splints,  anterior  and  posterior,  which  are 


Appears  at_ 
2d  year. 


Unites  with  shaft 
'  about  20th  year. 


Lower  extremity. 

Fig.  103.— Plan  of  the  development  of 
the  radius.    By  three  centres. 


158  THE  SKELETON. 

applied  in  these  cases  should  be  rather  wider  than  the  limb,  so  as  to  prevent  any  lateral  pressure 
on  the  bones.  For  in  these  cases  there  is  a  greater  liability  to  gangrene  from  the  pressure  of  the 
splints  than  in  other  parts  of  the  body.  This  is  no  doubt  due  principally  to  two  causes :  (1) 
the  flexion  of  the  forearm  compressing  to  a  certain  extent  the  brachial  artery  and  retarding  the 
flow  of  blood  to  the  limb  ;  and  (2)  the  superficial  position  of  the  two  main  arteries  of  the  forearm 
in  a  part  of  their  course,  and  their  liability  to  be  compressed  by  the  splints.  The  special 
fractures  of  the  ulna  are — (1)  Fracture  of  the  olecranon.  This  may  be  caused  by  direct  violence, 
falls  on  the  elbow  with  the  forearm  flexed,  or  by  muscular  action  by  the  sudden  contraction  of 
the  triceps.  The  most  common  place  for  the  fracture  to  occur  is  at  the  constricted  portion 
where  the  olecranon  joins  the  shaft  of  the  bone,  and  the  fracture  may  be  either  transverse  or 
oblique ;  but  any  part  may  be  broken,  even  a  thin  shell  may  be  torn  off.  Fractures  from  direct 
violence  are  occasionally  comminuted.  The  displacement  is  sometimes  very  slight,  owing  to  the 
fibrous  structures  around  the  process  not  being  torn.  (2)  Fracture  of  the  coronoid  process  some- 
times occurs  as  a  complication  of  dislocation  backward  of  the  bones  of  the  forearm,  but  it  is 
doubtful  if  it  ever  occurs  as  an  uncomplicated  injury.  (3)  Fractures  of  the  shaft  of  the  ulna 
may  occur  at  any  part,  but  usually  take  place  at  the  middle  of  the  bone  or  a  little  below  it. 
They  are  almost  always  the  result  of  direct  violence.  (4)  The  styloid  process  may  be  knocked 
off  by  direct  violence.  Fractures  of  the  radius  consist  of— ( 1 )  Fracture  of  the  head  of  the  bone ; 
this  generally  occurs  in  conjunction  with  some  other  lesion,  but  may  occur  as  an  uncomplicated 
injury.  (2)  Fracture  of  the  neck  may  also  take  place,  but  is  generally  complicated  with  other 
injury.  (3)  Fractures  of  the  shaft  of  the  radius  are  very  common,  and  may  take  place  at  any 
part  of  the  bone.  They  may  take  place  from  either  direct  or  indirect  violence.  In  fractures  of  the 
upper  third  of  the  shaft  of  the  bone,  that  is  to  say,  above  the  insertion  of  the  Pronator  radii  teres, 
the  displacement  is  very  great.  The  upper  fragment  is  strongly  supinated  by  the  Biceps  and  Supi- 
nator brevis,  and  flexed  by  the  Biceps ;  while  the  lower  fragment  is  pronated  and  drawn  toward 
the  ulna  by  the  two  pronators.  If  such  a  fracture  is  put  up  in  the  ordinary  position,  midway 
between  supination  and  pronation,  the  fracture  will  unite  with  the  upper  fragment  in  a  position 
of  supination,  and  the  lower  one  in  the  mid-position,  and  thus  considerable  impairment  of  the 
movements  of  the  hand  will  result.  The  limb  should  be  put  up  with  the  forearm  supinated.  (4) 
The  most  important  fracture  of  the  radius  is  that  of  the  lower  end  (Colles's  fracture).  The  fract- 
ure is  transverse,  and  generally  takes  place  about  an  inch  from  the  lower  extremity.  It  is  caused 
by  falls  on  the  palm  of  the  hand,  and  is  an  injury  of  advanced  life,  occurring  more  frequently  in 
the  female  than  the  male.  In  consequence  of  the  manner  in  which  the  fracture  is  caused,  the 
upper  fragment  becomes  driven  into  the  lower,  and  impaction  is  the  result ;  or  else  the  lower  frag- 
ment becomes  split  up  into  two  or  more  pieces,  so  that  no  fixation  occurs.  Separation  of  the  lower 
epiphysis  of  the  radius  may  take  place  in  the  young.  This  injury  and  Colles's  fracture  may  be 
distinguished  from  other  injuries  in  this  neighborhood — especially  dislocation,  with  which  it  is 
liable  to  be  confounded — by  observing  the  relative  positions  of  the  styloid  processes  of  the  ulna 
and  radius.  In  the  natural  condition  of  parts,  with  the  arm  hanging  by  the  side,  the  styloid  pro- 
cess of  the  radius  is  on  a  lower  level  than  that  of  the  ulna ;  that  is  to  say,  nearer  the  ground. 
After  fracture  or  separation  of  the  epiphysis  this  process  is  on  the  same  or  higher  level  than  that 
of  the  ulna,  whereas  it  would  be  unaltered  in  position  in  dislocation. 

THE  HAND. 

The  skeleton  of  the  Hand  is  subdivided  into  three  segments — the  Carpus  or 
wrist-bones ;  the  Metacarpus  or  bones  of  the  palm ;  and  the  Phalanges  or  bones 
of  the  digits. 

The  Carpus. 

The  bones  of  the  Carpus  (xaprcoz,  the  wrist),  eight  in  number,  are  arranged  in 
two  rows.  Those  of  the  upper  row,  enumerated  from  the  radial  to  the  ulnar 
side,  are  the  scaphoid,  semilunar,  cuneiform,  and  pisiform  ;  those  of  the  lower 
row,  enumerated  in  the  same  order,  are  the  trapezium,  trapezoid,  os  magnum,  and 
unciform. 

Common  Characters  of  the  Carpal  Bones. 

Each  bone  (excepting  the  pisiform)  presents  six  surfaces.  Of  these  the  anterior 
or  palmar  and  the  posterior  or  dorsal  are  rough  for  ligamentous  attachment, 
the  dorsal  surface  being  the  broader,  except  in  the  scaphoid  and  semilunar.  The 
superior  or  proximal  and  inferior  or  distal  are  articular,  the  superior  generally 
convex,  the  inferior  concave  ;  and  the  internal  and  external  are  also  articular  when 
in  contact  with  contiguous  bones,  otherwise  rough  and  tubercular.  The  structure 
in  all  is  similar,  consisting  of  cancellous  tissue  enclosed  in  a  layer  of  compact  bone. 
Each  bone  is  also  developed  from  a  single  centre  of  ossification. 


THE    CARPUS. 


159 


with 


EXTENSOR    CARP 
RADIALIS     LONGIOR, 

EXTENSOR    CARPI 
RADIALIS     BREVIOR, 


EXTENSOR  CARPI 
ULNARIS. 


Metacarpus. 


EXTENSOR    BREVIS 
POLLICIS 


ISOR    LONQUS 
OLLICIS. 


EXTENSOR    DIGITORUM 

communis  and 

EXTENSOR    1NDICIS. 


Phalanges. 
1st  Row. 


2nd  Row. 


3rd  Row. 


Fig.  104.— Bones  of  the  left  hand.    Dorsal  surface. 


160 


THE  SKELETON. 


Groove  far  tendon  of 

FLEXOR  CARPI   RADIALIS. 


FLEXOR    CARPI    ULNARIS, 


FLEXOR    BREVIS    MINIMI     DIGITI 

FLEXOR    OSSIS    METACARPI 
MINIMI    DIGITI. 


FLEXOR    OSSIS 
METACARPI    POLLICIS. 
'FLEXOR    BREVIS    POLL. 

EXTEN.   OS.   METACARP.   POLL. 
EXTENSOR    OSSIS 
METACARPI    POLLICIS. 


Metacarpus. 


FLEX.    BREVIS 

and 

ABDUCTOR 
MINIMI    DIQTI. 


Fig.  105.- Bones  of  the  left  hand.    Palmar  surface. 


THE    CARPUS. 


161 


Tuberosity 


Bones  of  the  Upper  Row. 

Scaphoid  (Fig.  106). 

For  radius. 


For  semilunar. 


For  trapezoid. 

Fig.  106.— The  left  scaphoid. 


For  os  magnum. 


The  Scaphoid  {ox&qrq,  a  boat,  slooc,  like)  is  the  largest  bone  of  the  first  row. 
It  has  received  its  name  from  its  fancied  resemblance  to  a  boat,  being  broad 
at  one  end  and  narrowed  like  a  prow  at  the  opposite.  It  is  situated  at  the 
upper  and  outer  part  of  the  carpus,  its  long  axis  being  from  above  downward, 
outward,  and  forward.  The  superior  surface  is  convex,  smooth,  of  triangular 
shape,  and  articulates  with  the  lower  end  of  the  radius.  The  inferior  surface, 
directed  downward,  outward,  and  backward,  is  smooth,  convex,  also  triangular, 
and  divided  by  a  slight  ridge  into  two  parts,  the  external  of  Avhich  articulates 
with  the  trapezium,  the  inner  writh  the  trapezoid.  The  posterior  or  dorsal  surface 
presents  a  narrow,  rough  groove  Avhich  runs  the  entire  length  of  the  bone  and 
serves  for  the  attachment  of  ligaments.  The  anterior  or  palmar  surface  is  concave 
above,  and  elevated  at  its  lower  and  outer  part  into  a  prominent  rounded  tuber- 
osity, which  projects  forward  from  the  front  of  the  carpus  and  gives  attachment  to 
the  anterior  annular  ligament  of  the  wrist  and  sometimes  a  few  fibres  of  the 
Abductor  pollicis.  The  external  surface  is  rough  and  narrow,  and  gives  attach- 
ment to  the  external  lateral  ligament  of  the  wrist.  The  internal  surface  presents 
two  articular  facets :  of  these,  the  superior  or  smaller  one  is  flattened,  of  semilunar 
form,  and  articulates  with  the  semilunar ;  the  inferior  or  larger  is  concave,  forming, 
with  the  semilunar  bone,  a  concavity  for  the  head  of  the  os  magnum. 

To  ascertain  to  which  side  the  bone  belongs,  hold  it  with  the  superior  or 
radial  convex,  articular,  surface  upward,  and  the  posterior  surface — i.  e.,  the 
narrow,  non-articular,  grooved  surface — toward  you.  The  tubercle  on  the  outer 
surface  points  to  the  side  to  Avhich  the  bone  belongs.1 

Articulations. — With  five  bones :  the  radius  above,  trapezium  and  trapezoid 
below,  os  magnum  and  semilunar  internally. 

Attachment  of  Muscles. — Occasionally  a  few  fibres  of  the  Abductor  pollicis. 

Semilunar  (Fig.  107). 

For  cuneiform.  For  radius. 


For  unciform. 

For  os  magnum. 


For 

scaphoid. 


Fig.  107.— The  left  semilunar. 


The   Semilunar  (semi,  half;    luna.  moon)  bone  may  be   distinguished   by  its 
deep  concavity  and  crescentic  outline.     It  is  situated  in  the  centre  of  the  upper 

1  In  these  directions  each  bone  is  supposed  to  be  placed  in  its  natural  position— that  is,  such  a 
position  as  it  would  occupy  when  the  arm  is  hanging  by  the  side,  the  forearm  in  a  } position  of  supi- 
nation, the  thumb  being  directed  outward,  and  the  palm  of  the  hand  looking  forward. 
11 


162  THE   SKELETON. 

row  of  the  carpus,  between  the  scaphoid  and  cuneiform.  The  superior  surface,  con- 
vex, smooth,  and  bounded  by  four  edges,  articulates  with  the  radius.  The  inferior 
surface  is  deeply  concave,  and  of  greater  extent  from  before  backward  than  trans- 
versely :  it  articulates  with  the  head  of  the  os  magnum  and  by  a  long,  narrow 
facet  (separated  by  a  ridge  from  the  general  surface)  with  the  unciform  bone. 
The  anterior  or  palmar  and  posterior  or  dorsal  surfaces  are  rough,  for  the  attach- 
ment of  ligaments,  the  former  being  the  broader  and  of  a  somewhat  rounded  form. 
The  external  surface  presents  a  narrow,  flattened,  semilunar  facet  for  articulation 
with  the  scaphoid.  The  internal  surface  is  marked  by  a  smooth,  quadrilateral 
facet,  for  articulation  with  the  cuneiform. 

Hold  it  with  the  convex  articular  surface  for  the  radius  upward,  and  the 
narrowest  non-articular  surface  toward  you.  The  semilunar  facet  for  the  scaphoid 
will  be  on  the  side  to  which  the  bone  belongs. 

Articulations. — With  five  bones  :  the  radius  above,  os  magnum  and  unciform 
below,  scaphoid  and  cuneiform  on  either  side. 

Cuneiform  (Fig.  108). 

The  Cuneiform  (cuneus,  a  wedge ;   forma,  likeness)  may  be  distinguished  by 

its  pyramidal  shape  (os  pyramidale),  and  by  its  having  an  oval,  isolated  facet  for 

articulation  with  the  pisiform  bone.     It  is  situated  at   the 

For  isiform°r  sem'lluimr'     upper  and  inner  side  of  the  carpus.     The  superior  surface 

presents   an   internal,   rough,   non-articular   portion,  and  an 

external  or  articular  portion,  which  is  convex,  smooth,  and 

articulates  with  the  triangular   interarticular   fibro-cartilage 

of  the   wrist.       The    inferior  surface,  directed   outward,  is 

For  unciform.        concave,  sinuously  curved,  and  smooth  for  articulation  with 

fig.  108.— The  left  cu-      the  unciform.     The  posterior  or  dorsal  surface  is  rough,  for 

neiform.  /  .  J  °    ' 

the  attachment  of  ligaments.  The  anterior  or  palmar  sur- 
face presents,  at  its  inner  side,  an  oval  facet,  for  articulation  with  the  pisiform ; 
and  is  rough  externally,  for  ligamentous  attachment.  The  external  surface,  the 
base  of  the  pyramid,  is  marked  by  a  flat,  quadrilateral,  smooth  facet,  for  articula- 
tion Avith  the  semilunar.  The  internal  surface,  the  summit  of  the  pyramid,  is 
pointed  and  roughened,  for  the  attachment  of  the  internal  lateral  ligament  of  the 
wrist. 

Hold  the  bone  with  the  surface  supporting  the  pisiform  facet  away  from  you, 
and  the  concavo-convex  surface  for  the  unciform  downward.  The  base  of  the 
wedge  (i.  e.,  the  broad  end  of  the  bone)  will  be  on  the  side  to  which  it  belongs. 

Articulations. — With  three  bones :  the  semilunar  externally,  the  pisiform  in 
front,  the  unciform  below ;  and  with  the  triangular,  interarticular  fibro-cartilage 
which  separates  it  from  the  lower  end  of  the  ulna. 

Pisiform  (Fig.  109). 

The  Pisiform  ( visum,  a  pea ;  forma,  likeness)  may  be  known  by  its  small  size 

and  by  its  presenting  a  single  articular  facet.     It  is  situated  on  a  plane  anterior  to 

por  the  other  bones  of  the  carpus ;    it  is  spheroidal  in  form,  with 

cuneiform.  its  long  diameter  directed  vertically.      Its  posterior  surface  is  a 

smooth,  oval  facet,   for  articulation  with   the  cuneiform.      This 

facet  approaches  the  superior,  but  not  the  inferior,  border   of 

the   bone.      The   anterior  or  palmar    surface   is    rounded    and 

rough,  and  gives  attachment  to  the  anterior    annular  ligament 

pisiform109'- The  left    an^  to  tne  Flexor    carpi  ulnaris  and  Abductor  minimi   digiti 

muscles.       The   outer  and  inner  surfaces   are   also    rough,   the 

former  being  concave,  the  latter  usually  convex. 

Hold  the  bone  with  the  posterior  surface — that  which  presents  the  articular 
facet — toward  you,  in  such  a  manner  that  the  faceted  portion  of  the  surface  is 
uppermost.     The  outer,  concave  surface  will  point  to  the  side  to  which  it  belongs. 


THE    CARPUS.  163 

Articulations. — With  one  bone,  the  cuneiform. 

Attachment  of  Muscles. — To  two:    the   Flexor   carpi   ulnaris   and   Abductor 
minimi  digiti ;  and  to  the  anterior  annular  ligament. 

Bones  of  the  Lower  Row. 
Trapezium  (Fig.  110). 
The  Trapezium  (rpdneza,  a  table)  is  of  very  irregular  form.     It  may  be  distin- 


For  trapezoid. 


Groove.  F°r  scaphoid. 

Ridge. 

^For  trapezoid. 


For  2d      \ 
metacarpal. /'<&& 

For  1st  metacarpal.  For  2d  metacarpal. 

Fig.  110.— The  left  trapezium. 

guished  by  a  deep  groove,  for  the  tendon  of  the  Flexor  carpi  radialis  muscle. 
It  is  situated  at  the  external  and  inferior  part  of  the  carpus,  between  the  scaphoid 
and  first  metacarpal  bone.  The  superior-  surface,  concave  and  smooth,  is  directed 
upward  and  inward,  and  articulates  with  the  scaphoid.  The  inferior  surface, 
directed  downward  and  inward,  is  oval,  concave  from  side  to  side,  convex  from 
before  backward,  so  as  to  form  a  saddle-shaped  surface,  for  articulation  with  the 
base  of  the  first  metacarpal  bone.  The  anterior  or  palmar  surface  is  narrow  and 
rough.  At  its  upper  part  is  a  deep  groove  running  from  above  obliquelv  down- 
ward and  inward ;  it  transmits  the  tendon  of  the  Flexor  carpi  radialis.  and  is 
bounded  externally  by  a  prominent  ridge,  the  oblique  ridge  of  the  trapezium. 
This  surface  gives  attachment  to  the  Abductor  pollicis,  Flexor  ossis  metacarpi 
pollicis,  and  Flexor  brevis  pollicis  muscles,  and  the  anterior  annular  ligament. 
The  posterior  or  dorsal  surface  is  rough.  The  external  surface  is  also  broad  and 
rough,  for  the  attachment  of  ligaments.  The  internal  surface  presents  two 
articular  facets :  the  upper  one,  large  and  concave,  articulates  with  the  trapezoid ; 
the  lower  one,  small  and  oval,  with  the  base  of  the  second  metacarpal  bone. 

Hold  the  bone  with  the  saddle-shaped  surface  downward  and  the  grooved 
surface  away  from  you.  The  prominent,  rough,  non-articular  surface  points  to  the 
side  to  which  the  bone  belongs. 

Articulations. — With  four  bones :  the  scaphoid  above,  the  trapezoid  and  second 
metacarpal  bones  internally,  the  first  metacarpal  below. 

Attachment  of  Muscles. — Abductor  pollicis,  Flexor  ossis  metacarpi  pollicis,  and 
part  of  the  Flexor  brevis  pollicis. 

Trapezoid  (Fig.  111). 

The  Trapezoid  is  the  smallest  bone  in  the  second  row.  It  may  be  known  by 
its  wedge-shaped  form,  the  broad  end  of  the  wedge  forming  the  dorsal,  the  narrow 

Anterior  surface. 
For  scaphoid.  |    For  trapezium. 


os  magnum. 
Post,  surface. 

For  2d  metacarpal. 

Fig.  111.— The  left  trapezoid. 

end  the  palmar,  surface,  and  by  its  having  four  articular  surfaces  touching  eacn 


164 


THE   SKELETON. 


other  and  separated  by  sharp  edges.  The  superior  surface,  quadrilateral  in  form, 
smooth,  and  slightly  concave,  articulates  with  the  scaphoid.  The  inferior  surface 
articulates  with  the  upper  end  of  the  second  metacarpal  bone ;  it  is  convex  from 
side  to  side,  concave  from  before  backward,  and  subdivided  by  an  elevated  ridge 
into  two  unequal  lateral  facets.  The  posterior  or  dorsal  and  anterior  or  palmar 
surfaces  are  rough,  for  the  attachment  of  ligaments,  the  former  being  the  larger 
of  the  two.  The  external  surface,  convex  and  smooth,  articulates  with  the 
trapezium.  The  internal  surface  is  eoncave  and  smooth  in  front,  for  articulation 
with  the  os  magnum ;  rough  behind,  for  the  attachment  of  an  interosseous 
ligament. 

Hold  the  bone  with  the  larger,  non-articular  surface  toward  you,  and  the 
smooth,  quadrilateral  articular  surface  upward.  The  convex,  articular  surface 
will  point  to  the  side  to  which  the  bone  belongs.1 

Articulations. — With  four  bones:  the  scaphoid  above,  second  metacarpal  bone 
below,  trapezium  externally,  os  magnum  internally. 

Os  Magnum  (Fig.  112). 

The  Os  Magnum  is  the  largest  bone  of  the  carpus,  and  occupies  the  centre  of 
the  wrist.     It  presents,  above,  a  rounded  portion  or  head,  which  is  received  into 

^For  semilunar.  For  semijunar. 

For  scaphoid. 


For 

trapezoid 


For  unciform. 


For  2d 
metacarpal. 

For  4th 
metacarpal. 
For  3d     For  4th  metacarpal, 
metacarpal. 

Fig.  112. — The  left  os  magnum. 


Ant.  surface. 


the  concavity  formed  by  the  scaphoid  and  semilunar  bones ;  a  constricted  portion 
or  neck ;  and,  below,  the  body.  The  superior  surface  is  rounded,  smooth,  and 
articulates  with  the  semilunar.  The  inferior  surface  is  divided  by  two  ridges  into 
three  facets,  for  articulation  with  the  second,  third,  and  fourth  metacarpal  bones, 
that  for  the  third  (the  middle  facet)  being  the  largest  of  the  three.  The  posterior 
or  dorsal  surface  is  broad  and  rough  ;  the  anterior  or  palmar,  narrow,  rounded, 
and  also  rough,  for  the  attachment  of  ligaments  and  a  part  of  the  Adductor 
obliquus  pollicis.  The  external  surface  articulates  with  the  trapezoid  by  a  small 
facet  at  its  anterior  inferior  angle,  behind  which  is  a  rough  depression  for  the 
attachment  of  an  interosseous  ligament.  Above  this  is  a  deep  and  rough  groove, 
which  forms  part  of  the  neck  and  serves  for  the  attachment  of  ligaments^  bounded 
superiorly  by  a  smooth,  convex  surface,  for  articulation  with  the  scaphoid.  The 
internal  surface  articulates  with  the  unciform  by  a  smooth,  concave,  oblong  facet 
which  occupies  its  posterior  and  superior  parts,  and  is  rough  in  front,  for  the 
attachment  of  an  interosseous  ligament. 

Hold  the  bone  with  the  broader,  non-articular  surface  toward  you,  and  the 
head  upward.  The  small,  articular  facet  at  the  anterior  inferior  angle  of  the 
external  surface  will  point  to  the  side  to  which  the  bone  belongs. 

Articulations. — With  seven  bones  :  the  scaphoid  and  semilunar  above ;  the 
second,  third,  and  fourth  metacarpal  below ;  the  trapezoid  on  the  radial  side ;  and 
the  unciform  on  the  ulnar  side. 

Attachment  of  Muscles. — Part  of  the  Adductor  obliquus  pollicis. 

1  Occasionally  in  a  badly  marked  bone  there  is  some  difficulty  in  ascertaining  to  which  side  the 
bone  belongs ;  the  following  method  will  sometimes  be  found  useful :  Hold  the  bone  with  its  broader, 
non-articular  surface  upward,  so  that  its  sloping  border  is  directed  toward  you.  The  border  will  slope 
to  the  side  to  which  the  bone  belongs. 


THE   METACARPUS.  165 

Unciform  (Fig.  113). 
The  Unciform  (uncus,  a  hook  ;  forma,  likeness)  may  be  readily  distinguished 

For  semilunar. 

For  os  magnum. — \ 


For  cuneiform. 


J 


For  fourth  meta 
tarsal. 

Unciform  process.  ^^*  orjij  i 

metatarsal. 

Fig.  113.— The  left  unciform. 

by  its  wedge-shaped  form  and  the  hook-like  process  that  projects  from  its  palmar 
surface.  It  is  situated  at  the  inner  and  lower  angle  of  the  carpus,  with  its  base 
downward,  resting  on  the  two  inner  metacarpal  bones,  and  its  apex  directed 
upward  and  outward.  The  superior  surface,  the  apex  of  the  Avedge,  is  narrow, 
convex,  smooth,  and  articulates  with  the  semilunar.  The  inferior  surface  articu- 
lates with  the  fourth  and  fifth  metacarpal  bones,  the  concave  surface  for  each 
being  separated  by  a  ridge  which  runs  from  before  backward.  The  posterior  or 
dorsal  surface  is  triangular  and  rough,  for  ligamentous  attachment.  The  anterior 
or  palmar  surface  presents,  at  its  lower  and  inner  side,  a  curved,  hook-like  pro- 
cess of  bone,  the  unciform  process,  directed  from  the  palmar  surface  forward  and 
outward.  It  gives  attachment  by  its  apex  to  the  annular  ligament  and  Flexor 
carpi  ulnaris ;  by  its  inner  surface  to  the  Flexor  brevis  minimi  digit!  and  the 
Flexor  ossis  metacarpi  minimi  digiti ;  and  is  grooved  on  its  outer  side,  for  the 
passage  of  the  Flexor  tendons  into  the  palm  of  the  hand.  This  is  one  of  the  four 
eminences  on  the  front  of  the  carpus  to  Avhich  the  anterior  annular  ligament  is 
attached,  the  others  being  the  pisiform  internally,  the  oblique  ridge  of  the  trape- 
zium and  the  tuberosity  of  the  scaphoid  externally.  The  internal  surface  articu- 
lates with  the  cuneiform  by  an  oblong  facet  cut  obliquely  from  above,  downward 
and  inward.  The  external  surface  articulates  with  the  os  magnum  by  its  upper 
and  posterior  part,  the  remaining  portion  being  rough,  for  the  attachment  of 
ligaments. 

Hold  the  bone  with  the  hooked  process  away  from  you,  and  the  articular  sur- 
face, divided  into  two  parts,  for  the  metacarpal  bones,  downward.  The  concavity 
of  the  process  will  be  on  the  side  to  which  the  bone  belongs. 

Articulations. — With  five  bones :  the  semilunar  above,  the  fourth  and  fifth 
metacarpal  below,  the  cuneiform  internally,  the  os  magnum  externally. 

Attachment  of  Muscles. — To  three  :  the  Flexor  brevis  minimi  digiti,  the  Flexor 
ossis  metacarpi  minimi  digiti,  the  Flexor  carpi  ulnaris. 

The  Metacarpus. 

The  Metacarpal  Bones  are  five  in  number :  they  are  long,  cylindrical  bones, 
presenting  for  examination  a  shaft  and  two  extremities. 

Common  Characters  of  the  Metacarpal  Bones. 
The  Shaft  is  prismoid  in  form  and  curved  longitudinally,  so  as  to  be  convex  in 
the  longitudinal  direction  behind,  concave  in  front.  It  presents  three  surfaces: 
two  lateral  and  one  posterior.  The  lateral  surj 'aces  are  concave,  for  the  attach- 
ment of  the  Interossei  muscles,  and  separated  from  one  another  by  a  prominent 
anterior  ridge.  The  posterior  or  dorsal  surface  presents  in  its  distal  half  a  smooth, 
triangular,  flattened  area  which  is  covered,  in  the  recent  state,  by  the  tendons  of 
the  Extensor  muscles.  This  triangular  surface  is  bounded  by  two  lines,  which 
commence  in  small  tubercles  situated  on  the  dorsal  aspect  on  either  side  of  the 


166 


THE  SKELETON. 


digital  extremity,  and,  running  backward,  converge  to  meet  together  a  little 
behind  the  centre  of  the  bone  and  form  a  ridge  which  runs  along  the  rest  of  the 
dorsal  surface  to  the  carpal  extremity.  This  ridge  separates  two  lateral,  sloping 
surfaces  for  the  attachment  of  the  Dorsal  interossei  muscles.1  To  the  tubercles 
on  the  digital  extremities  are  attached  the  lateral  ligaments  of  the  metacarpo- 
phalangeal joints. 

The  carpal  extremity,  or  "base,  is  of  a  cuboidal  form,  and  broader  behind  than 
in  front;  it  articulates  above  with  the  carpus,  and  on  each  side  with  the  adjoining 
metacarpal  bones  ;  its  dorsal  and  palmar  surfaces  are  rough,  for  the  attachment  of 
tendons  and  ligaments. 

The  digital  extremity,  or  head,  presents  an  oblong  surface,  markedly  convex 
from  before  backward,  less  so  from  side  to  side,  and  flattened  laterally ;  it  articu- 
lates with  the  proximal  phalanx  ;  it  is  broader  and  extends  farther  forward  on  the 
palmar  than  on  the  dorsal  aspect.  It  is  longer  in  the  antero-posterior  than  in  the 
transverse  diameter.  On  either  side  of  the  head  is  a  tubercle  for  the  attachment 
of  the  lateral  ligament  of  the  metacarpo-phalangeal  joint.  The  posterior  surface, 
broad  and  flat,  supports  the  Extensor  tendons ;  the  anterior  surface  is  grooved  in 
the  middle  line  for  the  passage  of  the  Flexor  tendons,  and  marked  on  each  side  by 
an  articular  eminence  continuous  with  the  terminal  articular  surface. 


Peculiar  Characters  of  the  Metacarpal  Bones. 

The  metacarpal  bone  of  the  thumb  (Fig.  114)  is  shorter  and  wider  than  the 
rest,  diverges   to   a  greater   degree   from   the   carpus,  and  its  palmar  surface   is 

directed  inward  toward  the  palm.  The  shaft  is 
flattened  and  broad  on  its  dorsal  aspect,  and  does 
not  present  the  ridge  which  is  found  on  the  other 
metacarpal  bones ;  it  is  concave  from  above  down- 
ward, on  its  palmar  surface.  The  carpal  extrem- 
ity, or  base,  presents  a  concavo-convex  surface,  for 
articulation  with  the  trapezium ;  it  has  no  lateral 
facets,  but  presents  externally  a  tubercle  for  the 
insertion  of  the  Extensor  ossis  metacarpi  pollicis. 
The  digital  extremity  is  less  convex  than  that  of 
the  other  metacarpal  bones,  broader  from  side  to 
side  than  from  before  backward.  It  presents  on 
its  palmar  aspect  two  distinct  articular  eminences 
for  the  two  sesamoid  bones  in  the  tendons  of  the 
Flexor  brevis  pollicis,  the  outer  one  being  the 
larger  of  the  two. 

The  side  to  which  this  bone  belongs  may  be 
known  by  holding  it  in  the  position  it  occupies  in  the  hand,  with  the  carpal 
extremity  upward  and  the  dorsal  surface  backward ;  the  tubercle  for  the 
Extensor  ossis  metacarpi   pollicis  will  point  to  the  side  to  which  it  belongs. 

Attachment  of  Muscles. — To  four :  the  Flexor  ossis  metacarpi  pollicis,  the 
Extensor  ossis  metacarpi  pollicis,  the  Flexor  brevis  pollicis,  and  the  First  dorsal 
interosseous. 

The  metacarpal  bone  of  the  index  finger  (Fig.  115)  is  the  longest  and  its  base 
the  largest  of  the  other  four.  Its  carpal  extremity  is  prolonged  upward  and 
inward,  forming  a  prominent  ridge.  The  dorsal  and  palmar  surfaces  of  this 
extremity  are  rough,  for  the  attachment  of  tendons  and  ligaments.  It  presents 
four  articular  facets  :  three  on  the  upper  aspect  of  the  base :  the  middle  one  of  the 
three  is  the  largest,  concave  from  side  to  side,  convex  from  before  backward,  for 
articulation  with  the  trapezoid  ;  the  external  one  is  a  small,  flat,  oval  facet,  for 
articulation  with  the  trapezium ;   the  internal  one  on  the  summit  of  the  ridge  is 

1  By  these  sloping  surfaces  the  metacarpal  bones  of  the  hand  may  be  at  once  differentiated  from 
the  metatarsal  bone  of  the  foot. 


Tub 

For  trapezium.        For  trapezium. 
Fig.  114.— The  first  metacarpal.    (Left.) 


THE   METACARPUS. 


167 


long  and  narrow,  for  articulation  with  the  os  magnum.  The  fourth  facet  is  on  the 
inner  or  ulnar  side  of  the  extremity  of  the  bone,  and  is  for  articulation  with  the 
third  metacarpal  bone. 

The  side  to  which  this  bone  belongs  is  indicated  by  the  absence  of  the  lateral 
facet  on  the  outer  (radial)  side  of  its  base,  so  that  if  the  bone  is  placed  with  its 
base  toward  the  student  and  the  palmar  surface  upward,  the  side  on  which  there 
is  no  lateral  facet  will  be  that  to  which  it  belongs. 

Attachment  of  Muscles. — To  six  :  Flexor  carpi  radialis,  Extensor  carpi  radialis 
longior,  Adductor  obliquus  pollicis,  First  and  Second  dorsal  interosseous,  and 
First  palmar  interosseous. 

The  metacarpal  bone  of  the  middle  finger  (Fig.  116)  is  a  little  smaller  than  the 
preceding :  it  presents  a  pyramidal  eminence  (the  styloid  process)  on  the  radial  side 
of  its  base  (dorsal  aspect)  which  extends  upward  behind  the  os  magnum  ;  imme- 
diately below  this,  on  the  dorsal  aspect,  is  a  rough  surface  for  the  attachment  of 


.  '""""*     "■  ■. 


For  trapezium. 
For  trapezoid. 


For  third  metacarpal. 
For  os  magnum. 


Fig.  115. — The  second  metacarpal.    (Left.) 


Styloid   For  second 
process,  metacarpal. 

For  os  magnum. 

Fig.  116.— The  third  metacarpal.     (Left.  | 


the  Extensor  carpi  radialis  brevior.  The  carpal,  articular  facet  is  concave  behind, 
flat  in  front,  and  articulates  with  the  os  magnum.  On  the  radial  side  is  a  smooth, 
concave  facet,  for  articulation  with  the  second  metacarpal  bone,  and  on  the  ulnar 
side  two  small,  oval  facets,  for  articulation  with  the  fourth  metacarpal. 

The  side  to  which  this  bone  belongs  is  easily  recognized  by  the  styloid  proc- 
ess on  the  radial  side  of  its  base.  With  the  palmar  surface  uppermost  and  the 
base  toward  the  student,  this  process  points  toward  the  side  to  which  the  bone 
belongs. 

Attachment  of  Muscles.— To  six:  Extensor  carpi  radialis  brevior.  Flexor  carpi 
radialis,  Adductor  transversus  pollicis,  Adductor  obliquus  pollicis,  and  Second  and 
Third  dorsal  interosseous. 

The  metacarpal  bone  of  the  ring  finger  (Fig.  117)  is  shorter  and  smaller  than 
the  preceding,  and  its  base  small  and  quadrilateral ;  the  carpal  surface  of  the  base 
presenting  two  facets,  a  large  one  externally,  for  articulation  with  the  unciform,  and 
a  small  one  internally,  for  the  os  magnum.  *  On  the  radial  side  are  two  oval  facets, 
for  articulation  with"' the  third  metacarpal  bone;  and  on  the  ulnar  side  a  single 
concave  facet,  for  the  fifth  metacarpal. 

If  this  bone  is  placed  with  the  base  toward  the  student  and  the  palmar  surface 


168 


THE  SKELETON. 


upward,  the  radial  side  of  the  base,  which  has  two  facets  for  articulation  with  the 
third  metacarpal  bone,  will  be  on  the  side  to  which  it  belongs.  If,  as  sometimes 
happens  in  badly  marked  bones,  one  of  these  facets  is  indistinguishable,  the  side 
may  be  known  by  selecting  the  surface  on  which  the  larger  articular  facet  is  present. 
This  facet  is  for  the  fifth  metacarpal  bone,  and  would  therefore  be  situated  on  the 
ulnar  side — that  is,  the  one  to  which  the  bone  does  not  belong. 

Attachment  of  Muscles. — To  three  :  the  Third  and  Fourth  dorsal  and  Second 
palmar  interosseous. 

The  metacarpal  bone  of  the  little  finger  (Fig.  118)  presents  on  its  base  one  facet, 
which  is  concavo-convex,  and  which  articulates  with  the  unciform  bone,  and  one 


For  third 
metacarpal.      For  os 
magnum. 


For  fift  h  meta- 
carpal 
For  unciform. 


"  ",& 


For  fourth 
metacarpal. 


Fig.  117.— The  fourth  metacarpal.    (Left.) 


For  cuneiform. 
Fig.  118.— The  fifthlmetacarpal.    (Left.) 


lateral,  articular  facet,  which  articulates  with  the  fourth  metacarpal  bone.  On  its 
ulnar  side  is  a  prominent  tubercle,  for  the  insertion  of  the  tendon  of  the  Extensor 
carpi  ulnaris.  The  dorsal  surface  of  the  shaft  is  marked  by  an  oblique  ridge  which 
extends  from  near  the  ulnar  side  of  the  upper  extremity  to  the  radial  side  of  the 
lower.  The  outer  division  of  this  surface  serves  for  the  attachment  of  the  Fourth 
dorsal  interosseous  muscle ;  the  inner  division  is  smooth  and  covered  by  the 
Extensor  tendons  of  the  little  finger. 

If  this  bone  is  placed  with  its  base  toward  the  student  and  its  palmar  surface 
upward,  the  side  of  the  head. which  has  a  lateral  facet  will  be  that  to  which  the 
bone  belongs. 

Attachment  of  Muscles. — To  five:  the  Extensor  carpi  ulnaris,  Flexor  carpi 
ulnaris,  Flexor  ossis  metacarpi  minimi  digiti,  Fourth  dorsal,  and  Third  palmar 
interosseous. 

Articulations. — Besides  the  phalangeal  articulations,  the  first  metacarpal  bone 
articulates  with  the  trapezium  ;  the  second  with  the  trapezium,  trapezoid,  os 
magnum,  and  third  metacarpal  bones  ;  the  third  with  the  os  magnum  and  second 
and  fourth  metacarpal  bones ;  the  fourth  with  the  os  magnum,  unciform,  and 
third  and  fifth  metacarpal  bones ;  and  the  fifth  Avith  the  unciform  and  fourth 
metacarpal. 

The  first  has  no  lateral  facets  on  its  carpal  extremity ;  the  second  has  no 
lateral  facet  on  its  radial  side,  but  one  on  its  ulnar  side ;  the  third  has  one  on 
its  radial  and  two  on  its  ulnar  side ;  the  fourth  has  two  on  its  radial  and  one  on 
its  ulnar  side ;   and  the  fifth  has  only  one  on  its  radial  side. 


THE   PHALANGES.  169 

The  Phalanges. 

The  Phalanges  (internodia)  are  the  bones  of  the  fingers ;  they  are  fourteen  in 
number,  three  for  each  finger,  and  two  for  the  thumb.  They  are  long  bones,  and 
present  for  examination  a  shaft  and  two  extremities.  The  shaft  tapers  from 
above  downward,  is  convex  posteriorly,  concave  in  front  from  above  downward, 
flat  from  side  to  side,  and  marked  laterally  by  rough  ridges,  which  give  attachment 
to  the  fibrous  sheaths  of  the  Flexor  tendons.  The  metacarpal  extremity,  or  base, 
in  the  first  row  presents  an  oval,  concave,  articular  surface,  broader  from  side  to 
side  than  from  before  backward;  and  the  same  extremity  in  the  other  two  rows, 
a  double  concavity,  separated  by  a  longitudinal  median  ridge,  extending  from  before 
backward.  The  digital  extremities  are  smaller  than  the  bases,  and  terminate, 
in  the  first  and  second  rows,  in  two  small,  lateral  condyles,  separated  by  a  slight 
groove ;  the  articular  surface  being  prolonged  farther  forward  on  the  palmar  than 
on  the  dorsal  surface,  especially  in  the  first  row. 

The  Ungual  Phalanges  are  convex  on  their  dorsal-,  flat  on  their  palmar,  surfaces ; 
they  are  recognized  by  their  small  size  and  by  a  roughened,  elevated  surface  of  a 
horseshoe  form  on  the  palmar  aspect  of  their  ungual  extremity,  which  serves  to 
support  the  sensitive  pulp  of  the  finger. 

Articulations. — The  first  row,  with  the  metacarpal  bones  and  the  second  row 
of  phalanges ;  the  second  row,  with  the  first  and  third ;  the  third,  with  the  second 
row. 

Attachment  of  Muscles. — To  the  base  of  the  first  phalanx  of  the  thumb,  five 
muscles  :  the  Extensor  brevis  pollicis,  Flexor  brevis  pollicis,  Abductor  pollicis, 
Adductor  transversus  and  obliquus  pollicis.  To  the  second  phalanx,  two :  the 
Flexor  longus  pollicis  and  the  Extensor  longus  pollicis.  To  the  base  of  the  first 
phalanx  of  the  index  finger,  the  First  dorsal  and  the  First  palmar  interosseous  ;  to 
that  of  the  middle  finger,  the  Second  and  Third  dorsal  interosseous ;  to  that  of 
the  ring  finger,  the  Fourth  dorsal  and  the  Second  palmar  interosseous ;  and  to  that 
of  the  little  finger,  the  Third  palmar  interosseous,  the  Flexor  brevis  minimi  digiti, 
and  Abductor  minimi  digiti.  To  the  second  phalanges,  the  Flexor  sublimis  digi- 
torum,  Extensor  communis  digitorum,  and,  in  addition,  the  Extensor  indicis  to 
the  index  finger,  the  Extensor  minimi  digiti  to  the  little  finger.  To  the  third 
phalanges,  the  Flexor  profundus  digitorum  and  Extensor  communis  digitorum. 

Surface  Form. — On  the  front  of  the  wrist  are  two  subcutaneous  eminences,  one  on  the 
radial  side,  the  larger  and  flatter,  clue  to  the  tuberosity  of  the  scaphoid  and  the  ridge  on  the 
trapezium ;  the  other,  on  the  ulnar  side,  caused  by  the  pisiform  bone.  The  tubercle  of  the 
scaphoid  is  to  be  felt  just  below  and  in  front  of  the  apex  of  the  styloid  process  of  the  radius.  It 
is  best  perceived  by  extending  the  hand  on  the  forearm.  Immediately  below  is  to  be  felt 
another  prominence,  better  marked  than  the  tubercle  ;  this  is  the  ridge  on  the  trapezium  which 
gives  attachment  to  some  of  the  short  muscles  of  the  thumb.  On  the  inner  side  of  the  front  of 
the  wrist  the  pisiform  bone  is  to  be  felt,  forming  a  small  but  prominent  projection  in  this  situa- 
tion. It  is  some  distance  below  the  styloid  process  of  the  ulna,  and  may  be  said  to  be  just  below 
the  level  of  the  styloid  process  of  the  radius.  The' rest  of  the  front  of  the  carpus  is  covered  by 
tendons  and  the  annular  ligament,  and  entirely  concealed,  with  the  exception  of  the  hooked  pro- 
cess of  the  unciform,  which  can  only  be  made  out  with  difficulty.  The  back  of  the  carpus  is 
convex  and  covered  by  the  Extensor  tendons,  so  that  none  of  the  posterior  surfaces  of  the  bones 
are  to  be  felt,  with  the  exception  of  the  cuneiform  on  the  inner  side.  Below  the  carpus  the 
dorsal  surfaces  of  the  metacarpal  bones,  except  the  fifth,  are  covered  by  tendons,  and  are  scarcely 
visible  except  in  very  thin  hands.  The  dorsal  surface  of  the  fifth  is.  however,  subcutaneous 
throughout  almost  its  whole  length,  and  is  plainly  to  be  perceived  and  felt.  In  addition  to  this, 
slightly  external  to  the  middle  line  of  the  hand,  is  a  prominence,  frequently  well  marked,  but 
occasionally  indistinct,  formed  by  the  base  of  the  metacarpal  of  the  middle  finger.  The  heads  of 
the  metacarpal  bones  are  plainly  to  be  felt  and  seen,  rounded  in  contour  and  standing  out  in  bold 
relief  under  the  skin,  when  the  fist  is  clenched.  It  should  be  borne  in  mind  that  when  the  fin- 
gers are  flexed  on  the  hand,  the  articular  surfaces  of  the  first  phalanges  glide  off  the  heads  of  the 
metacarpal  bones  on  to  their  anterior  surfaces,  so  that  the  heads  of  these  bones  form  the  prom- 
inence of  the  knuckles  and  receive  the  force  of  any  blow  which  may  be  given.  The  head  of  the 
third  metacarpal  bone  is  the  most  prominent,  and  receives  the  greater  part  of  the  shock  of  the 
blow.  This  bone  articulates  with  the  os  magnum,  so  that  the  concussion  is  carried  through  this 
bone  to  the  scaphoid  and  semilunar,  with  which  the  head  of  the  os  magnum  articulates,  and  by 
these  bones  is  transferred  to  the  radius,  along  which  it  may  be  carried  to  the  capitellum  of  the 
humerus.     The  enlarged  extremities  of  the  phalanges  are  to  be  plainly  felt :  they  form  the 


170 


THE   SKELETON. 


joints  of  the  fingers.  When  the  digits  are  bent  the  proximal  phalanges  of  the  joints  form 
prominences,  which  in  the  joint  between  the  first  and  second  phalanges  is  slightly  hollowed,  in 
accordance  with  the  grooved  shape  of  their  articular  surfaces,  whilst  at  the  last  row  the 
prominence  is  flattened  and  square-shaped.  In  the  palm  of  the  hand  the  four  inner  metacarpal 
bones  are  covered  by  muscles,  tendons,  and  the  palmar  fascia,  and  no  part  of  them  but  their 
heads  is  to  be  distinguished.  With  regard  to  the  thumb,  on  the  dorsal  aspect  the  base  of  the 
metacarpal  bone  forms  a  prominence  below  the  styloid  process  of  the  radius ;  the  shaft  is  to  be 
felt,  covered  by  tendons,  terminating  at  its  head  in  a  flattened  prominence,  in  front  of  which  can 
be  felt  the  sesamoid  bones. 

Surgical  Anatomy. — The  carpal  bones  are  little  liable  to  fracture,  except  from  extreme 
violence,  when  the  parts  are  so  comminuted  as  to  necessitate  amputation.  Occasionally  they  are 
the  seat  of  tubercular  disease.  The  metacarpal  bone  and  the  phalanges  are  not  unfrequently 
broken  from  direct  violence.  The  first  metacarpal  bone  is  the  one  most  commonly  fractured ; 
then  the  second,  the  fourth,  and  the  fifth,  the  third  being  the  one  least  frequently  broken. 
There  are  two  diseases  of  the  metacarpal  bones  and  phalanges  which  require  special  mention  on 
account  of  the  frequency  of  their  occurrence.  One  is  tubercular  dactylitis,  consisting  in  a 
deposit  of  tubercular  material  in  the  medullary  canal,  expanding  the  bone,  with  subsequent 
caseation  and  resulting  necrosis.  The  other  is  chondroma,  which  is  perhaps  more  frequently 
found  in  connection  with  the  metacarpal  bones  and  phalanges  than  with  any  other  bones. 
They  are  commonly  multiple,  and  may  spring  either  from  the  medullary  canal  or  from  the 
periosteum. 

Development  of  the  Bones  of  the  Hand. 

The  Carpal  Bones  are  each  developed  by  a  single  centre.  At  birth  they  are 
all  cartilaginous.      Ossification  proceeds  in  the  following  order  (Fig.  119):   In  the 


Carpus. 

One  centre  for  each  bone. 
All  cartilaginous  at  birth. 


Metacarpus. 

Two  centres  for  each  bone : 
One  for  shaft, 
One  for  digital  extremity, 
except  first. 


Phalanges. 

Two  centres  for  each  bone 
One  for  shaft, 
One  for  metacarpal 
extremity. 


Appears  3rd  year. 

^J^jS\Unite  20th  year. 

.Appears  8th  loeeh. 


fggg^-Appears  UthSth  year. 
|  Unite  18th-S0lh  year. 
c5  |*§i  I—  Appears  8th  week. 

Appears  UhSth  year. 
1  Unite  18th-30  year. 
'—Appears  8th  week. 


Fig.  119.— Plan  of  the  development  of  the  hand. 


os  magnum  and  unciform  an  ossific  point  appears  during  the  first  year,  the  form'u- 
preceding  the  latter  ;  in  the  cuneiform,  at  the  third  year ;  in  the  trapezium  and 
semilunar,  at  the  fifth  year,  the  former  preceding  the  latter ;  in  the  scaphoid,  at 


THE    OS  INNOMINATUM.  171 

the  sixth  year ;  in  the  trapezoid,  during  the  eighth  year ;  and  in  the  pisiform, 
about  the  twelfth  year. 

Occasionally  an  additional  bone,  the  os  centrale,  is  found  in  the  carpus,  lying 
between  the  scaphoid,  trapezoid,  and  os  magnum.  During  the  second  month  of 
foetal  life  it  is  represented  by  a  small  cartilaginous  nodule,  which,  however,  fuses 
with  the  cartilaginous  scaphoid  about  the  third  month.  Sometimes  the  styloid 
process  of  the  third  metacarpal  is  detached  and  forms  an  additional  ossicle" 

The  Metacarpal  Bones  are  each  developed  by  two  centres  :  one  for  the  shaft 
and  one  for  the  digital  extremity  for  the  four  inner  metacarpal  bones ;  one  for  the 
shaft  and  one  for  the  base  for  the  metacarpal  bone  of  the  thumb,  which  in  this 
respect  resembles  the  phalanges.1  Ossification  commences  in  the  centre  of  the 
shaft  about  the  eighth  or  ninth  week,  and  gradually  proceeds  to  either  end  of  the 
bone :  about  the  third  year  the  digital  extremities  of  the  four  inner  metacarpal 
bones  and  the  base  of  the  first  metacarpal  begin  to  ossify,  and  they  unite  about 
the  twentieth  year. 

The  Phalanges  are  each  developed  by  two  centres :  one  for  the  shaft  and  one 
for  the  base.  Ossification  commences  in  the  shaft,  in  all  three  rows,  at  about  the 
eighth  week,  and  gradually  involves  the  whole  of  the  bone  excepting  the  upper 
extremity.  Ossification  of  the  base  commences  in  the  first  row  between  the  third 
and  fourth  years,  and  a  year  later  in  those  of  the  second  and  third  rows.  The  two 
centres  become  united,  in  each  row,  between  the  eighteenth  and  tAventieth  years. 

In  the  ungual  phalanges  the  centre  for  the  shaft  appears  at  the  distal  extremity 
of  the  phalanx,  instead  of  at  the  middle  of  the  shaft,  as  is  the  case  with  the  other 
phalanges. 

THE  LOWER  EXTREMITY. 

The  bones  of  the  lower  extremity  consist  of  those  of  the  pelvic  girdle,  of  the 
thigh,  of  the  leg,  and  of  the  foot. 

The  Pelvic  Girdle. 

The  Pelvic  Girdle  consists  of  a  single  bone,  the  os  innominatum,  by  which  the 
thigh  is  connected  to  the  trunk. 

The  Os  Innominatum. 

The  Os  Innominatum  (in,  not ;  nomino,  I  name),  or  nameless  bone,  so  called  from 
bearing  no  resemblance  to  any  known  object,  is  a  large,  irregularly  shaped,  flat  bone, 
constricted  in  the  centre  and  expanded  above  and  below.  With  its  fellow  of  the 
opposite  side  it  forms  the  sides  and  anterior  wall  of  the  pelvic  cavity.  In  young 
subjects  it  consists  of  three  separate  parts,  which  meet  and  form  the  large,  cup-like 
cavity,  the  acetabulum,  situated  near  the  middle  of  the  outer  surface  of  the  bono  : 
and,  although  in  the  adult  these  have  become  united,  it  is  usual  to  describe  the 
bone  as  divisible  into  three   portions — the   ilium,  the  ischium,  and  the  os  pubis. 

The  ilium,  so  called  from  its  supporting  the  flank  (ilia),  is  the  superior,  broad, 
and  expanded  portion  which  runs  upward  from  the  acetabulum  and  forms  the 
prominence  of  the  hip. 

The  ischium  (ioyjov,  the  hip)  is  the  inferior  and  strongest  portion  of  the  bone : 
it  proceeds  downward  from  the  acetabulum,  expands  into  a  large  tuberosity,  and 
then,  curving  forward,  forms,  with  the  descending  ramus  of  the  os  pubis,  a  large 
aperture,  the  obturator  foramen. 

The  os  pubis  is  that  portion  which  extends  inward  and  downward  from  the 
acetabulum  to  articulate  in  the  middle  line  with  the  bone  of  the  opposite  side :  it 

1  Allan  Thomson  has  demonstrated  the  fact  that  the  first  metacarpal  lione  is  often  developed 
from  three  centres;  that  is  to  say,  there  is  a  separate  nucleus  for  the  distal  end,  forming  a  distinct 
epiphysis,  visible  at  the  age  of  seven  or  eight  years.  He  also  states  that  there  are  traces  of  a  proxi- 
mo! epiphysis  in  tl  '  meta — ml  bone. — Journal  of  Anatomy,  18(39. 


172 


THE   SKELETON. 


forms  the  front  of  the  pelvis,  supports  the  external  organs  of  generation,  and  has 
received  its  name  from  the  skin  over  it  being  covered  with  hair. 

The  Ilium  presents  for  examination  two  surfaces,  an  external  and  an  internal ; 
a  crest,   and  two  borders,   an  anterior  and  a  posterior. 

External  Surface  or  Dorsum  of  the  Ilium  (Fig.  120). — The  posterior  part  of  this 
surface  is  directed  backward  and  outward ;   its  front  part,  downward  and  outward. 


Anterior  superior 
spine. 


TRt 


IHo-pectineal  line 
for  Gimbernat's  ligament. 


GEMELLUS   SUPERIOR. 

/Spine  of  ischium, 


GEMELLUS    INFERIOR 


RECTUS    ABDOMINIS, 

PYRAMIDAL1S. 
ADDUCTOR  LONGUS. 


urn 


TtaW 


Fig.  120. — Right  os  innominatum.    External  surface. 


It  is  smooth,  convex  in  front,  deeply  concave  behind ;  bounded  above  by  the  crest, 
below  by  the  upper -border  of  the  acetabulum ;  in  front  and  behind  by  the  anterior 
and  posterior  borders.  This  surface  is  crossed  in  an  arched  direction  by  three 
semicircular  lines — the  superior,  middle,  and  inferior  curved  lines.  The  superior 
curved  line,  the  shortest  of  the  three,  commences  at  the  crest,  about  two  inches  in 
front  of  its  posterior  extremity  ;  it  is  at  first  distinctly  marked,  but  as  it  passes 
downward  and  backward  to  the  upper  part  of  the  great  sacro-sciatic  notch,  where 


THE    OS   INNOMINATUM. 


173 


1  „  v^rlrPfl    and  is  often  altogether  lost.     Behind  this 
it  terminates,  it  becomes  less  marked  ^and  is  g  ^   ^^ 

line  is  a  narrow  semilunar  surface,  the   uppei   P^1  ig  sm0*th  and  has  n0 

attachment  to  ^^^^^  ^T^^  longest  of  the  three, 
^^^he^r;  an  inch  b-***^ 


COMPRESSOR    URETHR/E./  -^taBq^lilB«W^rR  ANSVEBS,  ,s    pERINEI. 

Crzts  penis.  erector  pew?. 

Fig.  I21.-Kight  os  innominatum.    Internal  surface 


Near 

amen. 


i  ,  ,    iLfi   fVi+piis  medius  muscle. 

•est  is  concave,  and  affords  att ^ment  t°  tbg^  rte  &  ^  ^ 

entral  part  of  this  line  may  often  be  o&serve^  ^^  soineNVlK;  .     front    t  the 

■inferior  curved  line,  the  least  distinct^*   The  anterior  portion  is  si,  .us  ul«  u 

ch  on  the  anterior  border,  and   taking  bage  to   apex,  into  two  parts:  the 

trd,  terminates  at  the  middle  of  thftor  us;  the  inner  to  the  great  sacro- 

hone  included  between  the  middle  av,  s^divided  into  two  facets  by  an  oblique 

downward,  convex  from  before  f}jtward. .  from  the  v  per  and  outer  facet  arises 

minimus  muscle.     Beneath  the  u"         .ieriM 


( 


174  THE   SKELETON. 


part  of  the  acetabulum,  is  a  roughened  surface  (sometimes  a  depression),  to  which 
is  attached  the  reflected  tendon  of  the  Rectus  femoris  muscle. 

The  Internal  Surface  (Fig.  121)  of  the  ilium  is  bounded  above  by  the  crest ; 
below  it  is  continuous  with  the  pelvic  surface  of  the  os  pubis  and  ischium,  a  faint 
line  only  indicating  the  place  of  union  ;  and  before  and  behind  it  is  bounded  by 
the  anterior  and  posterior  borders.  It  presents  a  large,  smooth,  concave  surface, 
called  the  iliac  fossa,  or  venter  ilii,  which  lodges  the  lliacus  muscle,  and  presents 
at  its  lower  part  the  orifice  of  a  nutrient  canal ;  and  below  this  a  smooth,  rounded 
border  (the  linea  ilio-pectineci),  which  separates  the  iliac  fossa  from  that  portion  of 
the  internal  surface  which  enters  into  the  formation  of  the  true  pelvis,  and  which 
gives  attachment  to  part  of  the  Obturator  interims  muscle.  Behind  the  iliac  fossa 
is  a  rough  surface  divided  into  two  portions,  an  anterior  and  a  posterior.  The 
anterior  or  auricular  surface,  so  called  from  its  resemblance  in  shape  to  the  ear,  is 
coated  with  cartilage  in  the  recent  state,  and  articulates  with  a  surface  of  similar 
shape  on  the  side  of  the  sacrum.  The  posterior  portion  is  rough,  for  the  attach- 
ment of  the  posterior  sacro-iliac  ligaments  and  for  a  part  of  the  origin  of  the 
Erector  and  Multifidus  spinae. 

The  crest  of  the  ilium  is  convex  in  its  general  outline  and  sinuously  curved, 
being  concave  inward  in  front,  concave  outward  behind.  It  is  longer  in  the  female 
than  in  the  male,  very  thick  behind,  and  thinner  at  the  centre  than  at  the  extremi- 
frffiates  at  either  end  in  a  prominent  eminence,  the  anterior  superior 
■>•}"/■  superior  .spinous  process.  The  surface  of  the  crest  is  broad,  and 
into  an  external  lip,  an  internal  lip,  and  an  intermediate  space.  About  two 
inches  behind  the"  anterior  superior  spinous  process  there  is  a  prominent  tubercle 
on  the  outer  lip.  To  the  external  lip  is  attached  the  Tensor  fasciae  femoris, 
Obliquus  externus  abdominis,  and  Latissimus  dorsi,  and  along  its  whole  length, 
the  fascia  lata  ;  to  the  space  between  the  lips,  the  Internal  oblique  ;  to  the  internal 
lip,  the  Transversalis,  Quadratus  lumborum,  and  Erector  spinae,  the  lliacus,  and 
the  fascia  iliaca. 

The  anterior  border  of  the  ilium  is  concave.  It  presents  two  projections, 
separated  by  a  notch.  Of  these,  the  uppermost,  situated  at  the  junction  of  the 
crest  and  anterior  border,  is  called  the  anterior  superior  spinous  process  of  the  ilium, 
the  outer  border  of  which  gives  attachment  to  the  fascia  lata  and  the  origin  of 
the  Tensor  fasciae  femoris  ;  its  inner  border,  to  the  lliacus  ;  while  its  extremity 
affords  attachment  to  Poupart's  ligament  and  the  origin  of  the  Sartorius.  Beneath 
this  eminence  is  a  notch  which  gives  attachment  to  the  Sartorius  muscle,  and 
across  which  passes  the  external  cutaneous  nerve.  Below  the  notch  is  the  anterior 
inferior  spinous  process,  which  terminates  in  the  upper  lip  of  the  acetabulum  ;  it 
gives  attachment  to  the  straight  tendon  of  the  Rectus  femoris  muscle  and  the 
ilio-femoral  ligament.  On  the  inner  side  of  the  anterior  inferior  spinous  process 
is  a  broad,  shallow  groove,  over  Avhich  passes  the  Ilio-psoas  muscle.  This  groove  is 
bounded  internally  by  an  eminence,  the  ilio-pectineal,  which  marks  the  point  of 
union  of  the  ilium  and  os  pubis. 

The  posterior  border  of  the  ilium,  shorter  than  the  anterior,  also  presents  two 
projections  separated  by  a  notch,  the  posterior  superior  and  the  posterior  inferior 
spinous  processes.  The  former  corresponds  with  that  portion  of  the  inner  surface 
of  the  ilium  which  serve.'  for  the  attachment  of  the  oblique  portion  of  the  sacro- 
iliac ligaments  and  the  Multifidus  spinae ;  the  latter,  to  the  auricular  portion  which 
articulates  with  the  sacrum.  Below  the  posterior  inferior  spinous  process  is  a  deep 
notch,  the  great  sacro-sciatie.  l 

The  Ischium  forms  thp  jJ,     ;  and   back   part  of  the  os  innominatum.     It  is 

divisible  into    "VCA ,U1  ;        P1./  ;tion — the  body  ;  a  large,  rough  eminence,  on 

,  i  •  .i  ^j       .  apper -border  of  the  aceta,.  c   ,         u  j        R-  j.      -u-  x. 

i         v^-.       I r  j  mi  .  ,.        .    uberosity ;  and  a    thm   part  which  passes 

and  posterior  borders.     This  surface  is  v.  a  l  l 

semicircular  lines — the  superior,  middle,  anu  ,,  ^  , 

7  7.       ,i       i  A  xl      ',  i,  presents  three   surfaces,    external, 

curved  tine,  the  shortest  of  the  three,  comment        -i   •  <         .         ,  .  m, 

r ,      o  -.  ,     ■  ,  .,    '       .    »     ,    vnal,  internal,  and  posterior.      Ihe 

tront  of  its  posterior  extremity ;  it  is  at  first  ch. ...  ,  ,    ,        \»  -,    ,       ,, 

i  „„        q      rA  r     i         j   .     xlr  r  ,i.  the  acetabulum  formed    by  the 

doAvnward  and  backward  to  the  upper  part  of  t  J 


THE    OS  INNOMIWATUM.  175 

ischium  ;  it  is  smooth  and  concave,  and  forms  a  little  more  than  two-fifths  of 
the  acetabular  cavity  ;  its  outer  margin  is  bounded  by  a  prominent  rim  or  lip, 
the  external  border,  to  which  the  cotyloid  fibro-cartilage  is  attached.  Below  the 
acetabulum,  between  it  and  the  tuberosity,  is  a  deep  groove,  along  which  the  tendon 
of  the  Obturator  externus  muscle  runs  as  it  passes  outward  to  be  inserted  into 
the  digital  fossa  of  the  femur.  The  internal  surface  is  smooth,  concave,  and  enters 
into  the  formation  of  the  lateral  boundary  of  the  true  pelvic  cavity.  This  surface 
is  perforated  by  two  or  three  large,  vascular  foramina,  and  affords  attachment  to 
part  of  the  Obturator  internus  muscle.  The  posterior  surface  is  quadrilateral  in 
form,  broad  and  smooth.  Below,  where  it  joins  the  tuberosity,  it  presents  a  groove 
continuous  with  that  on  the  external  surface,  for  the  tendon  of  the  Obturator 
externus  muscle.  The  lower  edge  of  this  groove  is  formed  by  the  tuberosity  of  the 
ischium,  and  affords  attachment  to  the  Gemellus  inferior  muscle.  This  surface  is 
limited,  externally,  by  the  margin  of  the  acetabulum  :  behind,  by  the  posterior  bor- 
der ;  it  supports  the  Pyriformis,  the  two  Gemelli,  and  the  Obturator  internus  muscles 
in  their  passage  outward  to  the  great  trochanter.  The  external  border  forms  the 
prominent  rim  of  the  acetabulum,  and  separates  the  posterior  from  the  external 
surface.  To  it  is  attached  the  cotyloid  fibro-cartilage.  The  internal  border  is 
thin,  and  forms  the  outer  circumference  of  the  obturator  foramen.  The  posterior 
border  of  the  body  of  the  ischium  presents,  a  little  below  the  centre,  a  thin  and 
pointed,  triangular  eminence,  the  spine  of  the  ischium,  more  or  less  elongated  in 
different  subjects ;  its  external  surface  gives  attachment  to  the  Gemellus  superior, 
its  internal  surface  to  the  Coccygeus  and  Levator  ani ;  whilst  to  the  pointed 
extremity  is  connected  the  lesser  sacro-sciatic  ligament.  Above  the  spine  is  a 
notch  of  a  large  size,  the  great  sacro-sciatic,  converted  into  a  foramen  by  the 
lesser  sacro-sciatic  ligament;  it  transmits  the  Pyriformis  muscle,  the  gluteal 
vessels,  and  superior  and  inferior  gluteal  nerves ;  the  sciatic  vessels,  the  greater 
and  lesser  sciatic  nerves,  the  internal  pudic  vessels  and  nerve,  and  the  nerves  to 
the  Obturator  internus  and  Quadratus  femoris.  Of  these,  the  gluteal  vessels  and 
superior  gluteal  nerve  pass  out  above  the  Pyriformis  muscle,  the  other  structures, 
below  it.  Below  the  spine  is  a  smaller  notch,  the  lesser  sacro-sciatic  ;  it  is  smooth, 
coated  in  the  recent  state  with  cartilage,  the  surface  of  which  presents  two  or 
three  ridges  corresponding  to  the  subdivisions  of  the  tendon  of  the  Obturator 
internus,  which  winds  over  it.  It  is  converted  into  a  foramen  by  the  sacro-sciatic 
ligaments,  and  transmits  the  tendon  of  the  Obturator  internus,  the  nerve  which 
supplies  that  muscle,  and  the  internal  pudic  vessels  and  nerve. 

The  tuberosity  presents  for  examination  three  surfaces :  external,  internal, 
and  posterior.  The  external  surface  is  quadrilateral  in  shape,  and  rough  for  the 
attachment  of  muscles.  It  is  bounded  above  by  the  groove  for  the  tendon  of  the 
Obturator  externus ;  in  front  it  is  limited  by  the  posterior  margin  of  the  obtu- 
rator foramen,  and  below  it  is  continuous  with  the  ramus  of  the  bone ;  behind,  it 
is  bounded  by  a  prominent  margin  which  separates  it  from  the  posterior  surface. 
In  front  of  this  margin  the  surface  gives  attachment  to  the  Quadratus  femoris. 
and  anterior  to  this  to  some  of  the  fibres  of  origin  of  the  Obturator  externus. 
The  lower  part  of  the  surface  gives  origin  to  part  of  the  Adductor  magnus.  The 
internal  surface  forms  part  of  the  bony  wall  of  the  true  pelvis.  In  front  it  is 
limited  by  the  posterior  margin  of  the  obturator  foramen.  Behind,  it  i>  bounded 
^by  a  sharp  ridge,  for  the  attachment  of  a  falciform  prolongation  of  the  great 
sacro-sciatic  ligament;  it  sometimes  presents  a  groove  on  the  inner  side  of  this 
ridge  for  the  lodgement  of  the  internal  pudic  vessels  and  nerve  :  and.  more  ante- 
riorly, has  attached  the  Transversus  perinsei  and  Erector  penis  muscles.  The 
posterior  surface  is  divided  into  two  portions — a  lower  rough,  somewhat  triangular 
part,  and  an  upper  smooth,  quadrilateral  portion.  The  anterior  portion  is  subdivided 
by  a  prominent  vertical  ridge,  passing  from  base  to  apex,  into  two  part> :  the 
outer  s  attachment  to  the  Adductor  magnus;  tlie  inner  to  the  great  sacro- 

sciati  int.      The  upper  portion  is  subdivided  into  two  facets  by  an  oblique 

ridse  which   runs  downward  and  outward:  from  the  u   per  and  outer  facet  arises 
&  .ten  01 


176  THE  SKELETON. 

the  Semimembranosus ;    from    the    lower  and   inner,   the   Biceps  and   Scmiten- 
dinosus. 

The  ramus  is  the  thin,  flattened  part  of  the  ischium  which  ascends  from  the 
tuberosity  upward  and  inward,  and  joins  the  descending  ramus  of  the  os  pubis, 
their  point  of  junction  being  indicated  in  the  adult  by  a  rough  line.  The  outer 
surface  of  the  ramus  is  rough,  for  the  attachment  of  the  Obturator  externus 
muscle,  and  also  some  fibres  of  the  Adductor  magnus ;  its  inner  surface  forms 
part  of  the  anterior  wall  of  the  pelvis.  Its  inner  border  is  thick,  rough,  slightly 
everted,  forms  part  of  the  outlet  of  the  pelvis,  and  presents  two  ridges  and  an 
intervening  space.  The  ridges  are  continuous  with  similar  ones  on  the  descend- 
ing ramus  of  the  os  pubis :  to  the  outer  one  is  attached  the  deep  layer  of  the 
superficial  perineal  fascia,  and  to  the  inner,  the  superficial  layer  of  the  triangular 
ligament  of  the  urethra.  If  these  two  ridges  are  traced  downward,  they  will  be 
found  to  join  with  each  other  just  behind  the  point  of  origin  of  the  Transversus 
perinsei  muscle ;  here  the  two  layers  of  fascia  are  continuous  behind  the  posterior 
border  of  the  muscle.  To  the  intervening  space,  just  in  front  of  the  point  of 
junction  of  the  ridges,  is  attached  the  Transversus  perinsei  muscle,  and  in  front 
of  this  a  portion  of  the  crus  penis  vel  clitoridis  and  the  Erector  penis  vel 
clitoridis  muscle.  Its  outer  border  is  thin  and  sharp,  and  forms  part  of  the  inner 
margin  of  the  obturator  foramen. 

The  Os  Pubis  forms  the  anterior  part  of  the  os  innominatum,  and,  with  the  bone 
of  the  opposite  side,  forms  the  front  boundary  of  the  true  pelvic  cavity.  It  is 
divisible  into  a  body,  an  ascending  and  a  descending  ramus. 

The  body  is  somewhat  quadrilateral  in  sb^ape,  and  presents  for  examination 
two  surfaces  and  three  borders.  The  anterior  surface  is  rough,  directed  down- 
ward and  outward,  and  serves  for  the  attachment  of  various  muscles.  To  the 
upper  and  inner  angle,  immediately  below  the  crest,  is  attached  the  Adductor 
longus ;  lower  down,  from  without  inward,  are  attached  the  Obturator  externus, 
the  Adductor  brevis,  and  the  upper  part  of  the  Gracilis.  The  posterior  surface, 
convex  from  above  downward,  concave  from  side  to  side,  is  smooth,  and  forms 
part  of  the  anterior  wall  of  the  pelvis.  It  gives  attachment  to  the  Levator  ani, 
Obturator  internus,  a  few  muscular  fibres  prolonged  from  the  bladder,  and  the 
pubo-prostatic  ligaments.  The  upper  border  presents  for  examination  a  prominent 
tubercle,  which  projects  forward  and  is  called  the  spine  ;  to  it  are  attached  the 
outer  pillar  of  the  external  abdominal  ring  and  Poupart's  ligament.  Passing 
upward  and  outward  from  this  is  a  prominent  ridge,  forming  part  of  the  ilio- 
pectineal  line,  which  marks  the  brim  of  the  true  pelvis :  to  it  are  attached  a  por- 
tion of  the  conjoined  tendon  of  the  Internal  oblique  and  Transversalis  muscles, 
Gimbernat's  ligament,  and  the  triangular  fascia  of  the  abdomen.  Internal  to  the 
spine  of  the  os  pubis  is  the  crest,  which  extends  from  this  process  to  the  inner 
extremity  of  the  bone.  It  affords  attachment,  anteriorly,  to  the  conjoined  tendon 
of  the  Internal  oblique  and  Transversalis ;  and  posteriorly,  to  the  Rectus  and 
Pyramidalis  muscles.  The  point  of  junction  of  the  crest  with  the  inner  border 
of  the  bone  is  called  the  angle  ;  to  it,  as  well  as  to  the  symphysis,  is  attached  the 
internal  pillar  of  the  external  abdominal  ring.  The  internal  border  is  articular ; 
it  is  oval,  covered  by  eight  or  nine  transverse  ridges,  or  a  series  of  nipple-like 
processes  arranged  in  rows,  separated  by  grooves ;  they  serve  for  the  attachment 
of  a  thin  layer  of  cartilage,  placed  between  it  and  the  central  fibro-cartilage. 
The  outer  border  presents  a  sharp  margin,  which  forms  part  of  the  circumference 
of  the  obturator  foramen  and  affords  attachment  to  the  obturator  membrane. 

The  ascending  or  superior  ramus  extends  from  the  body  to  the  point  of  junc- 
tion of  the  os  pubis  with  the  ilium,  and  forms  the  upper  part  of  the  circumference 
of  the  obturator  foramen.  It  presents  for  examination  a  superior,  inferior,  and 
posterior  surface,  and  an  outer  extremity.  The  superior  surface  presents  a  con- 
tinuation of  the  ilio-pectineal  line,  already  mentioned  as  commencing  at  the  pubic 
spine.  In  front  of  this  ridge  the  surface  of  bone  is  triangular  in  form,  wider 
externally  than    internally,  o>v      xb     mA    is    covered    by  the  Pectineus    muscle. 


THE    OS   INNOMINATUM.  Ill 

The  surface  is  bounded  externally  by  a  rough  eminence,  the  ilio-peetineal,  which 
serves  to  indicate  the  point  of  junction  of  the  ilium  and  os  pubis,  and  gives 
attachment  to  the  Psoas  parvus,  when  this  muscle  is  present.  The  triangular 
surface  is  bounded  below  by  a  prominent  ridge,  the  obturator  crest,  which  extends 
from  the  cotyloid  notch  to  the  spine  of  the  os  pubis.  The  inferior  surface  forms 
the  upper  boundary  of  the  obturator  foramen,  and  presents  externally  a  broad 
and  deep  oblique  groove,  for  the  passage  of  the  obturator  vessels  and  nerve;  and 
internally  a  sharp  margin  which  forms  part  of  the  circumference  of  the  obturator 
foramen,  and  to  which  the  obturator  membrane  is  attached.  The  posterior  surface 
forms  part  of  the  anterior  boundary  of  the  true  pelvis.  It  is  smooth,  convex 
from  above  downward,  and  affords  attachment  to  some  fibres  of  the  Obturator 
internus.  The  outer  extremity,  the  thickest  part  of  the  ramus,  forms  one-fifth  of 
the  cavity  of  the  acetabulum. 

The  descending  or  inferior  ramus  of  the  os  pubis  is  thin  and  flattened.  It 
passes  outward  and  downward,  becoming  narrower  as  it  descends,  and  joins  with 
the  ramus  of  the  ischium.  Its  anterior  surface  is  rough,  for  the  attachment  of 
muscles — the  Gracilis  along  its  inner  border ;  a  portion  of  the  Obturator  externus 
where  it  enters  into  the  formation  of  the  foramen  of  that  name;  and  between 
these  two  muscles  the  Adductores  brevis  and  magnus  from  Avithin  outward.  The 
posterior  surface  is  smooth,  and  gives  attachment  to  the  Obturator  internus,  and, 
close  to  the  inner  margin,  to  the  Compressor  urethra.  The  inner  border  is  thick, 
rough,  and  everted,  especially  in  females.  It  presents  two  ridges,  separated  by 
an  intervening  space.  The  ridges  extend  downward,  and  are  continuous  with 
similar  ridges  on  the  ascending  ramus  of  the  ischium  ;  to  the  external  one  is 
attached  the  deep  layer  of  the  superficial  perineal  fascia,  and  to  the  internal  one 
the  superficial  layer  of  the  triangular  ligament  of  the  urethra.  The  outer  border 
is  thin  and  sharp,  forms  part  of  the  circumference  of  the  obturator  foramen,  and 
gives  attachment  to  the  obturator  membrane. 

The  cotyloid  cavity,  or  acetabulum,  is  a  deep,  cup-shaped,  hemispherical 
depression,  directed  downward,  outward,  and  forward ;  formed  internally  by  the 
os  pubis,  above  by  the  ilium,  behind  and  below  by  the  ischium,  a  little  less  than 
two-fifths  being  formed  by  the  ilium,  a  little  more  than  two-fifths  by  the  ischium, 
and  the  remaining  fifth  by  the  pubic  bone.  It  is  bounded  by  a  prominent,  uneven 
rim,  which  is  thick  and  strong  above,  and  serves  for  the  attachment  of  the  cotyloid 
ligament,  which  contracts  its  orifice  and  deepens  the  surface  for  articulation.  It 
presents  below  a  deep  notch,  the  cotyloid  notch,  which  is  continuous  with  a  circular 
depression,  the  fossa  acetabuli,  at  the  bottom  of  the  cavity:  this  depression  is  per- 
forated by  numerous  apertures,  lodges  a  mass  of  fat,  and  its  margins,  as  well  as 
those  of  the  notch,  serve  for  the  attachment  of  the  ligamentum  teres.  The 
notch  is  converted,  in  the  natural  state,  into  a  foramen  by  a  dense  ligamentous 
band  which  passes  across  it.  Through  this  foramen  the  nutrient  vessels  and 
nerves  enter  the  joint. 

The  obturator  or  thyroid  foramen  is  a  large  aperture  situated  between  the 
ischium  and  os  pubis.  In  the  male  it  is  large,  of  an  oval  form,  its  longest 
diameter  being  obliquely  from  before  backward  ;  in  the  female  it  is  smaller  and 
more  triangular.  It  is  bounded  by  a  thin,  uneven  margin,  to  which  a  strong 
membrane  is  attached,  and  presents,  anterior]  a  deep  groove  which  runs  from 
the  pelvis  obliquely  ii        -d   and  d  Th.  I  groove  is  converted  into   a 

foramen  by  the  obi  in  I  its   the   obturator  vessels   and 

nerve. 

Structure. — Tl  e  consists  of  much  cancellous  tissue,  especially  where  it  is 

thick,  enclosed  between  lw«  layers  of  dense,  compact  tissue.  In  the  thinner 
parts  of  the  bon  the  bottom  of  the  acetabulum  and  centre  of  the  iliac- 

fossa,  it  is  usually  isparent,  and  composed  entirely  of  compact  tissue. 

Development  (  ). — By  eight  centres:  three  primary — one  for  the  ilium, 

one  for  the  ischium,  md  one  for  the  os  pubis;  and  five  secondary— one  for  the 
crest  of  the  ilium,  one  for  the  anterior  inferior  spinous  process  (said  to  occur  more 

12 


178 


THE   SKELETON. 


frequently  in  the  male  than  the  female),  one  for  the  tuberosity  of  the  ischium,  one 
for  the  symphysis  pubis  (more  frequent  in  the  female  than  the  male),  and  one  or 
more  for  the  Y-shaped  piece  at  the  bottom  of  the  acetabulum.  These  various 
centres  appear  in  the  following  order :  First,  in  the  ilium,  at  the  lower  part  of 
the  bone,  immediately  above  the  sciatic  notch,  at  about  the  eighth  or  ninth  week  ; 
secondly,  in  the  body  of  the  ischium,  at  about  the  third  month  of  foetal  life ; 
thirdly,'  in  the  body  of  the  os  pubis,  betAveen  the  fourth  and  fifth  months.  At 
birth  the  three  primary  centres  are  quite  separate,  the  crest,  the  bottom  of  the 
acetabulum,  the  ischial  tuberosity,  and  the  rami  of  the  ischium  and  pubes  being 
still  cartilaginous.  At  about  the  seventh  or  eighth  year  the  rami  of  the  os  pubis 
and  ischium  are  almost  completely  united  by  bone.  About  the  thirteenth  or 
fourteenth  year  the  three  divisions  of  the  bone  have  extended  their  growth  into 
the  bottom  of  the  acetabulum,  being  separated  from  each  other  by  a  Y-shaped 
portion  of  cartilage,  which  now  presents  traces  of  ossification,  often  by  two  or 
more  centres.  One  of  these,  the  os  aeetabuli,  appears  about  the  age  of  twelve, 
betwTeen  the  ilium  and  os  pubis,  and  fuses  with  them  about  the  age  of  eighteen. 
It  forms  the  pubic  part  of  the  acetabulum.  The  ilium  and  ischium  then  become 
joined,  and  lastly  the  os  pubis  to  the  ischium,  through  the  intervention  of  this 
Y-shaped  portion.  At  about  the  age  of  puberty  ossification  takes  place  in  each  of 
the  remaining  portions,  and  they  become  joined  to  the  rest  of  the  bone  between 
the  twentieth  and  twenty-fifth  years.  Separate  centres  are  frequently  found  for 
the  pubic  and  ischial  spines. 

Articulations. — With  its  fellow  of  the  opposite  side,  the  sacrum,  and  femur. 


By  eight  centres 


Three  primary  {Ilium,  Ischium,  and  Os  Pubis). 
Five  Secondary. 

'  Q. 


S.  Symphysis  pubis. 


The  three  primary  centres  unite  through  Y-shaped  piece  about  puberty. 
Epiphyses  appear  about  puberty,  and  unite  about  25th  year. 

Fig.  122.— Plan  of  the  development  of  the  os  innoni.naturti. 

Attachment  of  Muscles. — To  the  ilium,  sixteen.  To  the  outer  lip  of  the  crest, 
the  Tensor  vaginae  femoris,  Obliquus  externus  abdominis,  and  Latissimus  dorsi ; 
to  the  internal  lip,  the  Iliacus,  Transversalis,  Quadratus  lumborum,  and  Erector 
spinse  ;  to  the  interspace  between  the  lips,  the  Obliquus  internus.  To  the  outer 
surface  of  the  ilium,  the  Gluteus  maximus,  Gluteus  medius,  Gluteus  minimus, 
reflected  tendon  of  the  Rectus ;  to  the  upper  part  of  the  great  sacro-sciatic  notch,  a 
portion  of  the  Pyriformis ;  to  the  internal  surface,  tjie  Iliacus :  to  that  portion  of 


THE  PELVIS. 


179 


the  internal  surface  below  the  linea  ilio-pectinea,  the  Obturator  internus  to  the 
internal  surface  of  the  posterior  superior  spine,  and  the  Multifidus  spinse  :  to  the 
anterior  border,  the  Sartorius  and  straight  tendon  of  the  Rectus.  To  the  ischium, 
thirteen.  To  the  outer  surface  of  the  ramus,  the  Obturator  externus  and  Adductor 
magnus  ;  to  the  internal  surface,  the  Obturator  internus  and  Erector  penis.  To  the 
spine,  the  Gemellus  superior,  Levator  ani,  and  Coccygeus.  To  the  tuberosity,  the 
Biceps,  Semitendinosus,  Semimembranosus,  Quadratus  femoris.  Adductor  magnus, 
Gemellus  inferior,  Transversus  perinsei,  Erector  penis.  To  the  os  pubis,  sixteen: 
Obliquus  externus,  Obliquus  internus,  Transversalis,  Rectus,  Pyramidalis,  Psoas 
parvus,  Pectineus,  Adductor  magnus,  Adductor  longus.  Adductor  brevis,  Gracilis. 
Obturator  externus  and  internus,  Levator  ani,  Compressor  urethrae,  and  occasion- 
ally a  few  fibres  of  the  Accelerator  urinae. 

The  Pelvis  (Figs.  123,  124). 

The  Pelvis,  so  called  from  its  resemblance  to  a  basin  (L.  pelvis),  is  stronger 
and  more  massively  constructed  than  either  the  cranial  or  thoracic  cavity ;  it  is  a 
bony  ring,  interposed  between  the  lower  end  of  the  spine,  which  it  supports,  and 
the  lower  extremities,  upon  which  it  rests.  It  is  composed  of  four  bones  :  the  two 
ossa  innominata,  which  bound  it  on  either  side  and  in  front,  and  the  sacrum  and 
coccyx,  which  complete  it  behind. 

The  pelvis  is  divided  by  an  oblicpie  plane  passing  through  the  prominence  of 
the  sacrum,  the  linea  ilio-pectinea,  and  the  upper  margin  of  the  symphysis  pubis 
into  the  false  and  true  pelvis. 

The  false  pelvis  is  the  expanded  portion  of  the  pelvic  cavity  which  is  situated 
above  this  plane.     It  is   bounded   on   each   side  by  the  ossa  ilii ;  in  front  it  is 


Fig.  123.— Male  pelvis  (adult 


incomplete,  presenting  a  wide  interval  between  the  spinous  processes  of  the  ilia 
on  either  side,  which  is  filled  up  in  the  recent  state  by  the  parietes  of  the  abdomen  ; 
behind,  in  the  middle  line,  is  a  deep  notch.  This  broad,  shallow  cavity  is  fitted 
to  support  the  intestines  and  to  transmit  part  of  their  weight  to  the  anterior  wall 
of  the  abdomen,  and  is,  in  fact,  really  a  portion  of  the  abdominal  cavity.  The 
term  false  pelvis  is  incorrect,  and  this  space  ought  more  properly  to  be  regarded 
as  part  of  the  hypogastric  and  iliac  regions  of  the  abdomen. 

The  true  pelvis  is  that  part  of  the  pelvic  cavity  which  is  situated  beneath  the 


180 


THE   SKELETON. 


plane.  It  is  smaller  than  the  false  pelvis,  but  its  walls  are  more  perfect.  For 
convenience  of  description  it  is  divided  into  a  superior  circumference  or  inlet,  an 
inferior  circumference  or  outlet,  and  a  cavity. 

The  superior  circumference  forms  the  brim  of  the  pelvis,  the  included  space 
being  called  the  inlet.     It  is  formed  by  the  linea  ilio-pectinea,  completed  in  front 


Fig.  124.— Female  pelvis  (adult). 

by  the  crests  of  the  pubic  bones,  and  behind  by  the  anterior  margin  of  the  base  of 
the  sacrum  and  sacro-vertebral  angle.  The  inlet  of  the  pelvis  is  somewhat  heart- 
shaped,  obtusely  pointed  in  front,  diverging  on  either  side,  and  encroached  upon 
behind  by  the  projection  forward  of  the  promontory  of  the  sacrum.  It  has  three 
principal  diameters :  antero-posterior  (sacro-pubic),  transverse,  and  oblique.  The 
antero-posterior  extends  from  the  sacro-vertebral  angle  to  the  symphysis  pubis ; 
its  average  measurement  is  four  inches  in  the  male,  four  and  three-quarters  in  the 
female.  The  transverse  extends  across  the  greatest  width  of  the  inlet,  from  the 
middle  of  the  brim  on  one  side  to  the  same  point  on  the  opposite ;  its  average 
measurement  is  four  and  a  half  in  the  male,  five  and  a  quarter  in  the  female. 
The  oblique  extends  from  the  margin  of  the  pelvis,  corresponding  to  the  ilio- 
pectineal  eminence  on  one  side,  to  the  sacro-iliac  articulation  on  the  opposite 
side ;  its  average  measurement  is  four  and  a  quarter  in  the  male  and  five  in 
the  female. 

The  cavity  of  the  true  pelvis  is  bounded  in  front  by  the  symphysis  pubis ; 
behind,  by  the  concavity  of  the  sacrum  and  coccyx,  which,  curving  forward  above 
and  below,  contracts  the  inlet  and  outlet  of  the  canal ;  and  laterally  it  is  bounded 
by  a  broad,  smooth,  quadrangular  surface  of  bone,  corresponding  to  the  inner 
surface  of  the  body  of  the  ischium  and  that  part  of  the  ilium  which  is  below 
the  ilio-pectineal  line.  The  cavity  is  shallow  in  front,  measuring  at  the  symphy- 
sis an  inch  and  a  half  in  depth,  three  inches  and  a  haft  in  the  middle,  and  four 
inches  and  a  half  posteriorly.  From  this  descripticm  it  will  be  seen  that  the 
cavity  of  the  pelvis  is  a  short,  curved  canal,  considerably  deeper  on  its  posterior 
than  on  its  anterior  wall.  This  cavity  contains,  in  the  recent  subject,  the  rectum, 
bladder,  and  part  of  the  organs  of  generation.  The  rectum  is  placed  at  the  back 
of  the  pelvis,  and  corresponds  to  the  curve  of  the  sacro-coccygeal  column  ;  the 
bladder  in  front,  behind  the  symphysis  pubis.  In  the  female  the  uterus  and 
vagina  occupy  the  interval  between  these  viscera. 

The  lower  circumference  of  the  pelvis  is  very  irregular,  and  forms  what  is 
called  the  outlet.  It  is  bounded  by  three  prominent  eminences :  one  posterior, 
formed  by  the  point  of  the  coccyx ;  and  one  on  each  side,  the  tuberosities  of  the 


THE  PELVIS.  181 

ischia.  These  eminences  are  separated  by  three  notches ;  one  in  front,  the  pubic  arch, 
formed  by  the  convergence  of  the  rami  of  the  ischia  and  pubic  bones  on  each  side. 
The  other  notches,  one  on  each  side,  are  formed  by  the  sacrum  and  coccyx  behind, 
the  ischium  in  front,  and  the  ilium  above  ;  they  are  called  the  sacro-sciatic  notches  ; 
in  the  natural  state  they  are  converted  into  foramina  by  the  lesser  and  Greater 
sacro-sciatic  ligaments.  In  the  recent  state,  when  the  ligaments  are  in  situ,  the 
outlet  of  the  pelvis  is  lozenge-shaped,  bounded  in  front  by  the  subpubic  liga- 
ment and  the  rami  of  the  os  pubis  and  ischium  ;  on  each  side  by  the  tuberosities 
of  the  ischia ;  and  behind  by  the  great  sacro-sciatic  ligaments  and  the  tip  of  the 
coccyx. 

The  diameters  of  the  outlet  of  the  pelvis  are  two,  antero-posterior  and  trans- 
verse. The  antero-posterior  extends  from  the  tip  of  the  coccyx  to  the  lower  part 
of  the  symphysis  pubis ;  its  average  measurement  is  three  and  a  quarter  inches  in 
the  male  and  five  in  the  female.  The  antero-posterior  diameter  varies  with  the 
length  of  the  coccyx,  and  is  capable  of  increase  or  diminution  on  account  of  the 
mobility  of  that  bone.  The  transverse  extends  from  the  posterior  part  of  one 
ischiatic  tuberosity  to  the  same  point  on  the  opposite  side :  the  average  measure- 
ment is  three  and  a  half  inches  in  the  male  and  four  and  three-quarters  in  the 
female.1 

Position  of  the  Pelvis. — In  the  erect  posture  the  pelvis  is  placed  obliquely  with 
regard  to  the  trunk  of  the  body :  the  bony  ring,  which  forms  the  brim  of  the  true 
pelvis,  is  placed  so  as  to  form  an  angle  of  about  60°  to  65°  with  the  ground  on 
which  we  stand.  The  pelvic  surface  of  the  symphysis  pubis  looks  upward  and 
backward,  the  concavity  of  the  sacrum  and  coccyx  downward  and  forward,  the 
base  of  the  sacrum  in  well-formed  female  bodies  being  nearly  four  inches  above 
the  upper  border  of  the  symphysis  pubis,  and  the  apex  of  the  coccyx  a  little 
more  than  half  an  inch  above  its  lower  border.  In  consequence  of  this  obliquity 
of  the  pelvis  the  line  of  gravity  of  the  head,  which  passes  through  the  middle  of 
the  odontoid  process  of  the  axis  and  through  the  points  of  junction  of  the  curves 
of  the  vertebral  column  to  the  sacro-vertebral  angle,  descends  toward  the  front 
of  the  cavity,  so  that  it  bisects  a  line  drawn  transversely  through  the  middle  of 
the  heads  of  the  thigh-bones.  And  thus  the  centre  of  gravity  of  the  head  is 
placed  immediately  over  the  heads  of  the  thigh-bones  on  which  the  trunk  is 
supported. 

Axes  of  the  Pelvis  (Fig.  125). — The  plane  of  the  inlet  of  the  true  pelvis  will 
be  represented  by  a  line  drawn  from  the  base  of  the  sacrum  to  the  upper  margin  of 
the  symphysis  pubis.  A  line' carried  at  right  angles  with  this  at  its  middle  would 
correspond  at  one  extremity  with  the  umbilicus,  and  at  the  other  with  the  middle 
of  the  coccyx :  the  axis  of  the  inlet  is  therefore  directed  downward  and  backward. 
The  axis  of  the  outlet,  produced  upward,  would  touch  the  base  of  the  sacrum, 
and  is  therefore  directed  downward  and  forward.  The  axis  of  the  cavity  is 
curved  like  the  cavity  itself:  this  curve  corresponds  to  the  concavity  of  the  sacrum 
and  coccyx,  the  extremities  being  indicated  by  the  central  points  of  the  inlet  and 
outlet.  A  knowledge  of  the  direction  of  these  axes  serves  to  explain  the  course 
of  the  foetus  in  its  passage  through  the  pelvis  during  parturition.  It  is  also 
important  to  the  surgeon,  as  indicating  the  direction  of  the  force  required  in  the 
removal  of  calculi  from  the  bladder  by  the  sub-pubic  operation,  and  as  determin- 
ing the  direction  in  which  instruments  should  be  used  in  operations  upon  the 
pelvic  viscera. 

1  The  measurements  of  the  pelvis  given  above  are,  I  believe,  fairly  accurate,  but  different  meas- 
urements are  given  by  various  authors,  no  doubt  due  in  a  great  measure  to  differences  in  the  phy- 
sique and  stature  of  the  population  from  whom  the  measurements  have  been  taken.  The  accompany- 
ing chart  has  been  formulated  to  show  the  measurements  of  the  pelvis  which  are  adopted  by  many 
obstetricians. — Ed. 

a.  p.  Obi.  Tr. 

Inlet 4  4J  5 

Cavity 4*  4£  4i 

Outlet 5  4i  4 


182 


THE  SKELETON. 


plane 


,f  outlet- 


Fig.  125. — Vertical  section  of  the  pelvis, 
with  lines  indicating  the  axis  of  the  pelvis. 


Differences  between  the  Male  and  the  Female  Pelvis. — The  female  pelvis,  looked 
at  as  a  whole,  is  distinguished  from  the  male  by  the  bones  being  more  delicate,  by 

its  width  being  greater  and  its  depth  smaller. 
The  whole  pelvis  is  less  massive,  and  its  bones 
are  lighter  and  more  slender,  and  its  muscular 
impressions  are  slightly  marked.  The  iliac  fossae 
are  shallow,  and  the  anterior  iliac  spines  Avidely 
separated ;  hence  the  greater  prominence  of  the 
hips.  The  inlet  in  the  female  is  larger  than  in 
the  male  ;  it  is  more  nearly  circular,  and  the 
sacro-vertebral  angle  projects  less  forward.  The 
cavity  is  shallower  and  wider ;  the  sacrum  is 
shorter,  wider,  and  less  curved ;  the  obturator 
foramina  are  triangular,  and  smaller  in  size  than 
in  the  male.  The  outlet  is  larger  and  the  coc- 
cyx more  movable.  The  spines  of  the  ischia 
project  less  inward.  The  tuberosities  of  the 
ischia  and  the  acetabula  are  wider  apart.  The 
pubic  arch  is  wider  and  more  rounded  than  in 
the  male,  where  it  is  an  angle  rather  than  an 
arch.  In  consequence  of  this  the  width  of  the 
fore  part  of  the  pelvic  outlet  is  much  increased 
and  the  passage  of  the  foetal  head  facilitated. 
The  size  of  the  pelvis  varies,  not  only  in  the  two  sexes,  but  also  in  different 
members  of  the  same  sex.  This  does  not  appear  to  be  influenced  in  any  way  by 
the  height  of  the  individual.  Women  of  short  stature,  as  a  rule,  have  broad  pelves. 
Occasionally  the  pelvis  is  equally  contracted  in  all  its  dimensions,  so  much  so  that 
all  its  diameters  measure  an  inch  less  than  the  average,  and  this  even  in  women 
of  average  height  and  otherwise  well  formed.  The  principal  divergences,  however, 
are  found  at  the  inlet,  and  affect  the  relation  of  the  antero-posterior  to  the  transverse 
diameter.  Thus  we  may  have  a  pelvis  the  inlet  of  which  is  elliptical  either  in  a 
transverse  or  antero-posterior  direction  ;  the  transverse  diameter  in  the  former 
and  the  antero-posterior  in  the  latter  greatly  exceeding  the  other  diameters.  Again, 
the  inlet  of  the  pelvis  in  some  instances  is  seen  to  be  almost  circular. 

The  same  differences  are  found  in  various  races.  European  women  are  said  to 
have  the  most  roomy  pelves.  That  of  the  negress  is  smaller,  circular  in  shape,  and  with 
a  narrow  pubic  arch.  The  Hottentots  and  Bushwomen  possess  the  smallest  pelves. 
In  the  foetus  and  for  several  years  after  birth  the  pelvis  is  small  in  proportion 
to  that  of  the  adult.  t  The  cavity  is  deep,  and  the  projection  of  the  sacro-vertebral 
angle  less  marked.  The  generally  accepted  opinion  that  the  female  pelvis  does 
not  acquire  its  sexual  characters  until  after  puberty  has  been  shown  by  recent 
observations1  to  be  erroneous,  the  characteristic  differences  between  the  male  and 
female  pelvis  being  distinctly  indicated  as  early  as  the  fourth  month  of  foetal  life. 

Surface  Form. — The  pelvic  bones  are  so  thickly  covered  with  muscles  that  it  is  only  at  cer- 
tain points  that  they  approach  the  surface  and  can  be  felt  through  the  skin.  In  front,  the 
anterior  superior  spinous  process  is  easily  to  be  recognized ;  a  portion  of  it  is  subcutaneous, 
and  in  thin  subjects  may  be  seen  to  stand  out  as  a  prominence  at  the  outer  extremity  of  the  fold 
of  the  groin.  In  fat  subjects  its  position  is  marked  by  an  oblique  depression  amongst  the  sur- 
rounding fat,  at  the  bottom  of  which  the  bony  process  may  be  felt.  Proceeding  upward  and 
outward  from  this  process,  the  crest  of  the  ilium  may  be  traced  throughout  its  whole  length, 
sinuously  curved.  It  is  represented,  in  muscular  subjects,  on  the  surface,  by  a  groove  or  fur- 
row, the  iliac  furroio,  caused  by  the  projection  of  fleshy  fibres  of  the  External  oblique  muscle 
of  the  abdomen  ;  the  iliac  furrow  lies  slightly  below  the  level  of  the  crest.  It  terminates  behind 
in  the  posterior  superior  spinous  process,  the  position  of  which  is  indicated  by  a  slight  depression 
on  a  level  with  the  spinous  process  of  the  second  sacral  vertebra.  Between  the  two  posterior 
superior  spinous  processes,  but  at  a  lower  level,  is  to  be  felt  the  spinous  process  of  the  third 
sacral  vertebra  (see  page  53).      Another  part  of  the  bony  pelvis  which  is  easily  accessible  to  the 

1Fehling,  Zeitschr.  fur  Geburt.  u.  Gynaek.,  Bd.  ix.  und  x.;  and  Arthur  Thomson,  Journal  of  Anatomy 
and  Physiology,  vol.  xxxiii. 


THE   FEMUR,    OR    THIGH-BONE.  183 

touch  is  the  tuberosity  of  the  ischium,  situated  beneath  the  gluteal  fold,  and,  when  the  hip  is 
flexed,  easily  to  be  felt,  as  it  is  then  to  a  great  extent  uncovered  by  muscle.  Finally,  the  spine 
of  the  os  pubis  can  always  be  readily  felt,  and  constitutes  an  important  surgical  guide,  especially 
in  connection  with  the  subject  of  hernia.  It  is  nearly  in  the  same  horizontal  line  with  the  upper 
edge  of  the  great  trochanter.  In  thin  subjects  it  is  very  apparent,  but  in  the  obese  it  is  obscured 
by  the  pubic  fat.  It  can,  however,  be  detected  by  following  up  the  tendon  of  origin  of  the 
Adductor  longus  muscle. 

Surgical  Anatomy. — There  is  arrest  of  development  in  the  bones  of  the  pelvis  in  cases 
of  extroversion  of  the  bladder ;  the  anterior  part  of  the  pelvic  girdle  being  deficient,  the  bodies 
of  the  pubic  bones  imperfectly  developed,  and  the  symphysis  absent.  The  pubic  bones  are 
separated  to  the  extent  of  from  two  to  four  inches,  the  superior  rami  shortened  and  directed 
forward,  and  the  obturator  foramen  diminished  in  size,  narrowed,  and  turned  outward.  The 
iliac  bones  are  straightened  out  more  than  normal.  The  sacrum  is  very  peculiar.  The  lateral 
curve,  instead  of  being  concave,  is  flattened  out  or  even  convex,  with  the  ilio-sacral  facets 
turned  more  outward  than  normal,  while  the  vertical  curve  is  straightened.1 

Fractures  of  the  pelvis  are  divided  into  fractures  of  the  false  pelvis  and  of  the  true  pelvis. 
Fractures  of  the  false  pelvis  vary  in  extent :  a.small  portion  of  the  crest  may  be  broken  or  one 
of  the  spinous  processes  may  be  torn  off,  and  this  may  be  the  result  of  muscular  action  ;  or  the 
bone  may  be  extensively  comminuted.  This  latter,  accident  is  the  result  of  some  crushing  vio- 
lence, and  may  be  complicated  with  fracture  of  the  true  pelvis.  These  cases  may  be  accom- 
panied by  injury  to  the  intestine  as  it  lies  in  the  hollow  of  the  bone,  or  to  the  iliac  vessels  as 
they  course  along  the  margin  of  the  true  pelvis.  Fractures  of  the  true  pelvis  generally  occur 
through  the  ascending  ramus  of  the  os  pubis  and  the  ramus  of  the  ischium,  as  this  is  the 
weakest  part  of  the  bony  ring,  and  may  be  caused  either  by  crushing  violence  applied  in  an 
antero-posterior  direction,  when  the  fracture  occurs  from  direct  force,  or  by  compression  later- 
ally, when  the  acetabula  are  pressed  together,  and  the  bone  gives  way  in  the  same  place  from 
indirect  violence.  Occasionally  the  fracture  may  be  double,  occurring  on  both  sides  of  the  body. 
It  is  in  these  cases  that  injury  to  the  contained  viscera  is  liable  to  take  place  :  the  urethra,  the 
bladder,  the  rectum,  the  vagina  in  the  female,  the  small  intestines,  and  even  the  uterus,  have 
all  been  lacerated  by  a  displaced  fragment.  Fractures  of  the  acetabulum  are  occasionally  met 
with:  either  a  portion  of  the  rim  maybe  broken  off,  or  a  fracture  may  take  place  through  the 
bottom  of  the  cavity,  and  the  head  of  the  femur  driven  inward  and  project  into  the  pelvic- 
cavity.  Separation  of  the  Y-shaped  cartilage  at  the  bottom  of  the  acetabulum  may  also  occur 
in  the  young  subject,  separating  the  bone  into  its  three  anatomical  portions. 

The  sacrum  is  occasionally,  but  rarely,  broken  by  direct  violence — i.  e.,  blows,  kicks,  or 
falls  on  the  part.  The  lesion  may  be  complicated  with  injury  to  the  nerves  of  the  sacral 
plexus,  leading  to  paralysis  and  loss  of  sensation  in  the  lower  extremity,  or  to  incontinence 
of  faeces  from  paralysis  of  the  sphincter  ani. 

The  pelvic  bones  often  undergo  important  deformity  in  rickets,  the  effect  of  which  in  the 
adult  woman  may  interfere  seriously  with  childbearing.  The  deformity  is  due  mainly  to  the 
weight  of  the  spine  and  trunk,  which  presses  on  the  sacro-vertebral  angle  and  greatly  increases 
it,  so  that  the  antero-posterior  diameter  of  the  pelvis  is  diminished.  But,  in  addition  to  this, 
the  weight  of  the  viscera  on  the  venter  ilii  causes  them  to  expand  and  the  tuberosities  of  the 
ischia  to  be  incurved.  In  osteomalacia  also  great  deformity  may  occur.  The  weight  of  the 
trunk  causes  an  increase  in  the  sacro-vertebral  angle  and  a  lessening  of  the  antero-posterior 
diameter  of  the  inlet,  and  at  the  same  time  the  pressure  of  the  acetabula  on  the  heads  of  the 
thigh-bones  causes  these  cavities,  with  the  adjacent  bone,  to  be  pushed  upward  and  backward, 
so  that  the  oblique  diameters  of  the  pelvis  are  also  diminished,  and  the  cavity  of  the  pelvis 
assumes  a  triradiate  shape,  with  the  symphysis  pubis  pushed  forward. 

THE  THIGH. 

The  Thigh  is  that  portion  of  the  lower  extremity  which  is  situated  between  the 
pelvis  and  the  knee.     It  consists  in  the  skeleton  of  a  single  bone,  the  femur. 

The  Femur,  or  Thigh-Bone. 
The  Femur  (femur,  the  thigh)  is  the  longest,2  largest,  and  strongest  bone  in 
the  skeleton,  and  almost  perfectly  cylindrical  in  the  greater  part  of  its  extent.  In 
the  erect  posture  it  is  not  vertical,  being  separated  from  its  fellow  above  by  a 
considerable  interval,  which  corresponds  to  the  entire  breadth  of  the  pelvis,  but 
inclining  gradually  downward  and  inward,  so  as  to  approach  its  fellow  toward 
its  lower  part,  for  the  purpose  of  bringing  the  knee-joint  near  the  line  of  gravity 
of  the  body.  The  degree  of  this  inclination  varies  in  different  persons,  and  is 
greater  in  the  female  than  the  male,  on  account  of  the  greater  breadth  of  the 
pelvis.  The  femur,  like  other  long  bones,  is  divisible  into  a  shaft  and  two 
extremities. 

1  Wood.     Heath's  Dictionary  of  Practical  Surgery,  i.,  426. 

2  In  a  man  six  feet  hidi  it  measures  eighteen  inches— one-fourth  of  the  whole  body. 


184 


THE  SKELETON. 


OBTURATOR   INTERNUS 
and  GEMELLI. 
PVRIFORMIS. 


' #?'/! 


v 


Shaft 


SUB-CRUREUS. 


•>S 


Fig.  12G. — Right  femur.  Anterior  surface. 


The  Upper  Extremity  presents 
for  examination  a  head,  a  neck, 
,lSe7tun°?te{eI     and  a  great  and  lesser    trochan- 
ters. 

The  head,  which  is  globular, 
and  forms  rather  more  than  a 
hemisphere,  is  directed  upward, 
inward,  and  a  little  forward,  the  greater  part 
of  its  convexity  being  above  and  in  front.  Its 
surface  is  smooth,  coated  with  cartilage  in  the 
recent  state,  except  at  a  little  behind  and  below 
its  centre,  where  is  an  ovoid  depression,  for  the 
attachment  for  the  ligamentum  teres.  The  neck 
is  a  flattened  pyramidal  process  of  bone  which 
connects  the  head  with  the  shaft.  It  varies  in 
length  and  obliquity  at  various  periods  of  life 
and  under  different  circumstances.  The  angle 
is  widest  in  infancy,  and  becomes  lessened 
during  growth,  so  that  at  puberty  it  forms  a 
gentle  curve  from  the  axis  of  the  shaft.  In 
the  adult  it  forms  an  angle  of  about  130°  with 
the  shaft,  but  varies  in  inverse  proportion  to 
the  development  of  the  pelvis  and  the  stature. 
In  consequence  of  the  prominence  of  the  hips 
and  widening  of  the  pelvis  in  the  female,  the 
neck  of  the  thigh-bone  forms  more  nearly  a 
right  angle  with  the  shaft  than  it  does  in  man. 
It  has  been  stated  that  the  angle  diminishes  in 
old  age  and  the  direction  of  the  neck  becomes 
horizontal,  but  this  statement  is  founded- on 
insufficient  evidence.  Sir  George  Humphry 
states  that  the  angle  decreases  during  the 
period  of  growth,  but  after  full  growth  has  been 
attained  it  does  not  usually  undergo  any  change, 
even  in  old  age.  He  further  states  that  the 
angle  varies  considerably  in  different  persons 
of  the  same  age.  It  is  smaller  in  short  than  in 
long  bones,  and  when  the  pelvis  is  wide.1  The 
neck  is  flattened  from  before  backward,  con- 
tracted in  the  middle,  and  broader  at  its  outer 
extremity,  where  it  is  connected  with  the  shaft, 
than  at  its  summit,  where  it  is  attached  to  the 
head.  The  vertical  diameter  of  the  outer  half 
is  increased  by  the  thickening  of  the  lower  edge, 
which  slopes  downward  to  join  the  shaft  at  the 
lesser  trochanter,  so  that  the  outer  half  of  the 
neck  is  flattened  from  before  backward,  and  its 
vertical  diameter  measures  one-third  more  than 
the  antero-posterior.  The  inner  half  is  smaller 
and  of  a  more  circular  shape.  The  anterior 
surface  of  the  neck  is  perforated  by  numerous 
vascular  foramina.  The  posterior  surface  is 
smooth,  and  is  broader  and  more  concave  than 
the  anterior ;  it  gives  attachment  to  the  pos- 
terior part  of  the  capsular  ligament  of  the 
hip-joint,  about  half  an  inch  above  the  posterior 
1  Journal  of  Anatomy  and  Physiology. 


THE   FEMUR,    OB    THIGH-BONE.  185 

intertrochanteric  line.  The  superior  border  is  short  and  thick,  and  terminates 
externally  at  the  great  trochanter ;  its  surface  is  perforated  by  large  foramina. 
The  inferior  border,  long  and  narrow,  curves  a  little  backward,  to  terminate  at 
the  lesser  trochanter. 

The  Trochanters  (zpoydto,  to  run  or  roll)  are  prominent  processes  of  bone 
which  afford  leverage  to  the  muscles  which  rotate  the  thigh  on  its  axis.  They 
are  two  in  number,  the  great  and  the  lesser. 

The  Great  Trochanter  is  a  large,  irregular,  quadrilateral  eminence,  situated  at 
the  outer  side  of  the  neck,  at  its  junction  with  the  upper  part  of  the  shaft.  It  is 
directed  a  little  outward  and  backward,  and  in  the  adult  is  about  three-quarters 
of  an  inch  lower  than  the  head.  It  presents  for  examination  two  surfaces  and  four 
borders.  The  external  surface,  quadrilateral  in  form,  is  broad,  rough,  convex,  and 
marked  by  a  prominent  diagonal  impression,  which  extends  from  the  posterior 
superior  to  the  anterior  inferior  angle,  and  serves  for  the  attachment  of  the  tendon 
of  the  Gluteus  medius.  Above  the  impression  is  a  triangular  surface,  sometimes 
rough  for  part  of  the  tendon  of  the  same  muscle,  sometimes  smooth  for  the  inter- 
position of  a  bursa  between  that  tendon  and  the  bone.  Below  and  behind  the 
diagonal  line  is  a  smooth,  triangular  surface,  over  which  the  tendon  of  the  Gluteus 
maximus  muscle  plays,  a  bursa  being  interposed.  The  internal  surface  is  of  much 
less  extent  than  the  external,  and  presents  at  its  base  a  deep  depression,  the  digitcd 
or  trochanteric  fossa,  for  the  attachment  of  the  tendon  of  the  Obturator  externus 
muscle ;  above  and  in  front  of  this  an  impression  for  the  attachment  of  the 
Obturator  internus  and  Gemelli.  The  superior  border  is  free ;  it  is  thick  and 
irregular,  and  marked  near  the  centre  by  an  impression  for  the  attachment  of 
the  Pyriformis.  The  inferior  border  corresponds  to  the  point  of  junction  of 
the  base  of  the  trochanter  with  the  outer  surface  of  the  shaft;  it  is  marked  by  a 
rough,  prominent,  slightly  curved  ridge,  which  gives  attachment  to  the  upper 
part  of  the  Yastus  externus  muscle.  The  anterior  border  is  prominent,  somewhat 
irregular,  as  well  as  the  surface  of  bone  immediately  beloAV  it ;  it  affords  attach- 
ment at  its  outer  part  to  the  Gluteus  minimus.  The  posterior  border  is  very 
prominent,  and  appears  as  a  free,  rounded  edge,  which  forms  the  back  part  of  the 
digital  fossa. 

The  Lesser  Trochanter  is  a  conical  eminence  which  varies  in  size  in  different 
subjects;  it  projects  from  the  lower  and  back  part  of  the  base  of  the  neck.  Its 
base  is  triangular,  and  connected  with  the  adjacent  parts  of  the  bone  by  three 
well-marked  borders :  two  of  these  are  above — the  internal  continuous  with  the 
lower  border  of  the  neck,  the  external  with  the  posterior  intertrochanteric  line — 
while  the  inferior  border  is  continuous  with  the  middle  division  of  the  linea 
aspera.  Its  summit,  which  is  directed  inward  and  backward,  is  rough,  and 
gives  insertion  to  the  tendon  of  the  Ilio-psoas.  The  Iliacus  is  also  inserted  into 
the  shaft  below  the  lesser  trochanter  between  the  Vastus  internus  in  front  and  the 
Pectineus  behind. 

A  av ell-marked  prominence  of  variable  size,  which  projects  from  the  upper  and 
front  part  of  the  neck  at  its  junction  with  the  great  trochanter,  is  called  the  tubercle 
of  the  femur ;  it  is  the  point  of  meeting  of  five  muscles:  the  Gluteus  minimus 
externally,  the  Vastus  externus  below,  and  the  tendon  of  the  Obturator  internus 
and  Gemelli  above.  Running  obliquely  downward  and  inward  from  the  tubercle  is 
the  spiral  line  of  the  femur,  or  anterior  intertrochanteric  line  ;  it  winds  round  the 
inner  side  of  the  shaft,  below  the  lesser  trochanter,  and  terminates  in  the  linea 
aspera,  about  two  inches  below  this  eminence.  Its  upper  half  is  rough,  and  affords 
attachment  to  the  ilio-femoral  ligament  of  the  hip-joint :  its  lower  half  is  less 
prominent,  and  gives  attachment  to  the  upper  part  of  the  Vastus  internus.  Run- 
ning obliquely  downward  and  inward  from  the  summit  of  the  great  trochanter  on 
the  posterior  surface  of  the  neck  is  a  very  prominent,  well-marked  ridge,  the  pos- 
terior intertrochanteric  line.  Its  upper  half  forms  the  posterior  border  of  the  great 
trochanter,  and  its  lower  half  runs"  downward  and  inward  to  the  upper  and  back 
part  of  the  lesser  trochanter.       A  slight  ridge  sometimes  commences  about  the 


186 


THE  SKELETON. 


tyOfl 


OBTURATOR    EXTERNUS. 


mm 


ti  \ 


11/ 


•K- 


R 
/_-# 


\4 


w 


Popliteal  Space. 


middle  of  the  posterior  intertro- 
chanteric line,  and  passes  vertically 
downward  for  about  two  inches 
along  the  back  part  of  the  shaft : 
it  is  called  the  linea  quadrati,  and 
gives  attachment  to  the  Quadratus 
femoris  and  a  few  fibres  of  the  Ad- 
ductor magnus  muscles.1 

The  Shaft,  almost  cylindrical  in 
form,  is  a  little  broader  above  than 
in  the  centre,  and  somewhat  flat- 
tened below,  from  before  backward. 
It  is  slightly  arched,  so  as  to  be 
convex  in  front  and  concave  be- 
hind, where  it  is  strengthened  by 
a  prominent' longitudinal  ridge,  the 
linea  aspera.  It  presents  for  ex- 
amination three  borders,  separating 
three  surfaces.  Of  the  three  bor- 
ders, one,  the  linea  aspera,  is  pos- 
terior ;  the  other  two  are  placed 
laterally. 

The  linea  aspera  (Fig-  127)  is 
a  prominent  longitudinal  ridge  or 
crest,  on  the  middle  third  of  the 
bone,  presenting  an  external  lip, 
an  internal  lip,  and  a  rough  inter- 
mediate space.  Above,  this  crest 
is  prolonged  by  three  ridges.  The 
most  external  one  is  very  rough, 
and  is  continued  almost  vertically 
upward  to  the  base  of  the  great 
trochanter.  It  is  sometimes  termed 
the  gluteal  ridge,  and  gives  attach- 
ment to  part  of  the  Gluteus  maxi- 
mus  muscle  ;  its  upper  part  is  often 
elongated  into  a  roughened  crest, 
on  which  is  a  more  or  less  well- 
marked,  rounded  tubercle,  a  rudi- 
mental  third  trochanter.  The  mid- 
dle ridge,  the  least  distinct,  is 
continued  to  the  base  of  the  tro- 
chanter minor,  and  the  internal 
one  is  lost  above  in  the  spiral  line 
of  the  femur.  Below,  the  linea 
aspera  is  prolonged  by  two  ridges, 
which  enclose  between  them  a  tri- 
angular space,  the  popliteal  surface, 
upon  which  rests  the  popliteal  ar- 
tery. Of  these  two  ridges,  the  outer 
{^Groove/or  tendon  of  one  js  the  more  prominent,  and  de- 


■r„ 


POPL1TEUS. 


'<.A 


^ 


w 


EEC-1 


.an1 


<v/7 


Fig.  127. — Right  femur.    Posterior  surface. 


1  Generally  there  is  merely  a  slight 
thickening  about  the  centre  of  the  inter- 
trochanteric line,  marking  the  point  of 
attachment  of  the  Quadratus  femoris.  This 
is  termed  by  some  anatomists  the  tubercle 
of  the  Quadratus. 


\       THE   FEMUR,    OB    THIGH-BONE.  187 

scends  to  the  summit  of  the  outer  condyle.  The  inner  one  is  less  marked,  especially 
at  its  upper  part,  where  it  is  crossed  by  the  femoral  artery.  It  terminates,  below, 
at  the  summit  of  the  internal  condyle,  in  a  small  tubercle,  the  Adductor  tubercle, 
which  affords  attachment  to  the  tendon  of  the  Adductor  magnus. 

To  the  inner  lip  of  the  linea  aspera  and  its  inner  prolongation  above  and 
below  is  attached  the  Vastus  internus,  and  to  the  outer  lip  and  its  outer  prolonga- 
tion above  is  attached  the  Vastus  externus.  The  Adductor  magnus  is  attached 
to  the  linea  aspera,  to  its  outer  prolongation  above  and  its  inner  prolongation 
below.  Between  the  Vastus  externus  and  the  Adductor  magnus  are  attached  two 
muscles — viz.  the  Gluteus  maximus  above,  and  the  short  head  of  the  Biceps 
below.  Between  the  Adductor  magnus  and  the  Vastus  internus  four  muscles  are 
attached :  the  Iliacus  and  Pectineus  above,  the  Adductor  brevis  and  Adductor 
longus  below.  The  linea  aspera  is  perforated  a  little  below  its  centre  by  the 
nutrient  canal,  which  is  directed  obliquely  upward. 

The  tivo  lateral  borders  of  the  femur  are  only  slightly  marked,  the  outer  one 
extending  from  the  anterior  inferior  angle  of  the  great  trochanter  to  the  anterior 
extremity  of  the  external  condyle  ;  the  inner  one  from  the  spiral  line,  at  a  point 
opposite  the  trochanter  minor,  to  the  anterior  extremity  of  the  internal  condyle. 
The  internal  border  marks  the  limit  of  attachment  of  the  Crureus  muscle  internally. 

The  anterior  surface  includes  that  portion  of  the  shaft  which  is  situated 
between  the  two  lateral  borders.  It  is  smooth,  convex,  broader  above  and 
below  than  in  the  centre,  slightly  twisted,  so  that  its  upper  part  is  directed 
forward  and  a  little  outward,  its  lower  part  forward  and  a  little  inward. 
To  the  upper  three-fourths  of  this  surface  the  Crureus  is  attached ;  the  lower 
fourth  is  separated  from  the  muscle  by  the  intervention  of  the  synovial 
membrane  of  the  knee-joint  and  a  bursa,  and  affords  attachment  to  the 
Subcrureus  to  a  small  extent.  The  external  surface  includes  the  portion 
of  bone  between  the  external  border  and  the  outer  lip  of  the  linea  aspera :  it  is 
continuous  above  with  the  outer  surface  of  the  great  trochanter,  below  with  the 
outer  surface  of  the  external  condyle ;  to  its  upper  three-fourths  is  attached  the 
outer  portion  of  the  Crureus  muscle.  The  internal  surface  includes  the  portion  of 
bone  between  the  internal  border  and  the  inner  lip  of  the  linea  aspera ;  it  is 
continuous  above  with  the  lower  border  of  the  neck,  below  with  the  inner  side  of 
the  internal  condyle  :  it  is  covered  by  the  Vastus  externus  muscle. 

The  Lower  Extremity,  larger  than  the  upper,  is  of  a  cuboid  form,  flattened  from 
before  backward,  and  divided  into  two  large  eminences,  the  condyles  (xovdukot;, 
a  knuckle),  by  an  interval  which  presents  a  smooth  depression  in  front  called  the 
trochlea,  and  a  notch  of  considerable  size  behind — the  inter  condyloid  notch.  The 
external  condyle  is  the  more  prominent  anteriorly,  and  is  the  broader  both  in  the 
antero-posterior  and  transverse  diameters.  The  internal  condyle  is  the  narrower, 
longer,  and  more  prominent  inferiorly.  This  difference  in  the  length  of  the  two 
condyles  is  only  observed  when  the  bone  is  perpendicular,  and  depends  upon  the 
obliquity  of  the  thigh-bones,  in  consequence  of  their  separation  above  at  the 
articulation  with  the  pelvis.  If  the  femur  is  held  obliquely,  the  surfaces  of  the 
two  condyles  will  be  seen  to  be  nearly  horizontal.  The  two  condyles  are  directly 
continuous  in  front,  and  form  a  smooth  trochlear  surface,  which  articulates  with 
the  patella.  It  presents  a  median  groove,  which  extends  downward  and  back- 
ward to  the  interconclyloid  notch;  and  two  lateral  convexities,  of  which  the 
external  is  the  broader,  more  prominent,  and  prolonged  farther  upward  upon  the 
front  of  the  outer  condyle.  The  external  border  of  this  articular  surface  is  also 
more  prominent,  and  ascends  higher  than  the  internal  one.  The  intercondyloid 
notch  lodges  the  crucial  ligaments ;  it  is  bounded  laterally  by  the  opposed  surfaces 
of  the  two  condyles,  and  in  front  by  the  lower  end  of  the  shaft. 

Outer  Condyle. — The  outer  surface  of  the  external  condyle  presents,  a  little 
behind  its  centre,  an  eminence,  the  outer  tuberosity  ;  it  is  less  prominent  than  the 
inner  tuberosity,  and  gives  attachment  to  the  external  lateral  ligaments  of  the 
knee.     Immediately  beneath  it  is  a  groove   which   commences  at  a  depression  a 


188 


THE  SKELETON. 


little  behind  the  centre  of  the  lower  border  of  this  surface :  the  front  part  of  this 
depression  gives  origin  to  the  Popliteus  muscle,  the  tendon  of  which  is  lodged  in 
the  groove  during  flexion  of  the  knee.  The  groove  is  smooth,  covered  with  carti- 
lage in  the  recent  state,  and  runs  upward  and  backward  to  the  posterior  extremity 
of  the  condyle.  The  inner  surface  of  the  outer  condyle  forms  one  of  the  lateral 
boundaries  of  the  inter  condyloid  notch,  and  gives  attachment,  by  its  posterior  part, 
to  the  anterior  crucial  ligament.  The  inferior  surface  is  convex,  smooth,  and  broader 
than  that  of  the  internal  condyle.  The  posterior  extremity  is  convex  and  smooth  : 
just  above  and  to  the  outer  side  of  the  articular  surface  is  a  depression  for  the  tendon 
of  the  outer  head  of  the  Gastrocnemius,  above  which  is  the  origin  of  the  Plantaris. 

Inner  Condyle. — The  inner  surface  of  the  inner  condyle  presents  a  convex  emi- 
nence, the  inner  tuberosity,  rough  for  the  attachment  of  the  internal  lateral  liga- 
ment. The  outer  side  of  the  inner  condyle  forms  one  of  the  lateral  boundaries 
of  the  intercondyloid  notch,  and  gives  attachment,  by  its  anterior  part,  to  the 
posterior  crucial  ligament.  Its  inferior  or  articular  surface  is  convex,  and 
presents  a  less  extensive  surface  than  the  external  condyle.  Just  above  the  articular 
surface  of  the  condyle,  behind,  is  a  depression  for  the  tendon  of  origin  of  the  inner 
head  of  the  Gastrocnemius. 

Structure. — The  shaft  of  the  femur  is  a  cylinder  of  compact  tissue,  hollowed 
by  a  large  medullary  canal.  The  cylinder  is  of  great  thickness  and  density  in  the 
middle  third  of  the  shaft,  where  the  bone  is  narrowest  and  the  medullary  canal 
well  formed;  but  above  and  below  this  the  cylinder  gradually  becomes  thinner, 
owing  to  a  separation  of  the  layers  of  the  bone  into  cancelli,  which  project  into  the 
medullary  canal  and  finally  obliterate  it,  so  that  the  upper  and  lower  ends  of  the 
shaft,  and  the  articular  extremities  more  especially,  consist  of  cancellated  tissue 
invested  by  a  thin,   compact  layer. 

The  arrangement  of  the  cancelli  in  the  ends  of  the  femur  is  remarkable.  In 
the  upper  end  they  are  arranged  in  two  sets.  One,  starting  from  the  top  of  the  head, 
the  upper  surface  of  the  neck,  and  the  great  trochanter,  converge  to  the  inner 
circumference  of  the  shaft  (Fig.  128) ;  these  are  placed  in  the  direction  of  greatest 
pressure,  and  serve  to  support  the  vertical  weight  of  the  body.  The  second  set 
are  planes  of  lamella  intersecting  the  former  nearly  at  right  angles,  and  are  situ- 
ated in  the  line  of  the  greatest  jS^^^Grwt  trochanter. 
tension — that  is  to  say,  along  the 
lines  in  which  the  muscles  and 
ligaments  exert  their  traction. 
In  the  head  of  the  bone  these 


Digital  fossa. 


Fig.  128.— Diagram  showing  the  arrange- 
ment of  the  cancelli  of  the  neck  of  the  femur. 


Lesser 
[JSt'.-U  trochanter. 


Tig.  129.— Calcar  femorale. 


THE   FEMUR,    OB    THIGH-BONE. 


189 


planes  are  arranged  in  a  curved  form,  in  order  to  strengthen  the  bone  when  exposed 
to  pressure  in  all  directions.  In  the  midst  of  the  cancellous  tissue  of  the  neck  is 
a  vertical  plane  of  compact  bone,  the  femoral  spur  (calcar  femorale)  which  com- 
mences at  the  point  where  the  neck  joins  the  shaft  midway  between  the  lesser 
trochanter  and  the  internal  border  of  the  shaft  of  the  bone,  and  extends  in  the 
direction  of  the  digital  fossa  (Fig.  129).  This  materially  strengthens  this  portion 
of  the  bone.  Another  point  in  connection  with  the  structure  of  the  neck  of  the 
femur  requires  mention,  especially  on  account  of  its  influence  on  the  production  of 
fracture  in  this  situation.  It  will  be  noticed  that  a  considerable  portion  of  the 
great  trochanter  lies  behind  the  level  of  the  posterior  surface  of  the  neck  ;  and  if  a 
section  be  made  through  the  trochanter  at  this  level,  it  will  be  seen  that  the 
posterior  wall  of  the  neck  is  prolonged  into  the  trochanter.  This  prolongation  is 
termed  by  Bigelow  the  "  true  neck,"  1  and  forms  a  thin,  dense  plate  of  bone,  which 
passes  beneath  the  posterior  intertrochanteric  ridge  toward  the  outer  surface  of 
the  bone. 

In  the  lower  end  the  cancelli  spring  on  all  sides  from  the  inner  surface  of 
the  cylinder,  and  descend  in  a  perpendicular  direction  to  the  articular  surface,  the 
cancelli  being  strongest  and  having  a  more  accurately  perpendicular  course  above 
the  condyles.  In  addition  to  this,  however,  horizontal  planes  of  cancellous  tissue 
are  to  be  seen,  so  that  the  spongy  tissue  in  this  situation  presents  an  appearance  of 
being  mapped  out  into  a  series  of  rectangular  areas. 

Articulations. — With  three  bones  :  the  os  innominatum,  tibia,  and  patella. 

Development  (Fig.  130). — The  femur  is  developed  bj five  centres:  one  for  the 
shaft,  one  for  each  extremity,  and  one  for  each  trochanter.  Of  all  the  long  bones, 
except  the  clavicle,  it  is  the  first  to  show  traces  of  ossification :  this  commences  in 
the  shaft,  at  about  the  seventh  week  of  foetal  life,  the  centres  of  ossification  in  the 
epiphyses  appearing  in  the  following 
order :  First,  in  the  lower  end  of 
the  bone,  at  the  ninth  month  of  foetal 
life2  (from  this  the  condyles  and 
tuberosities  are  formed)  ;  in  the  head 
at  the  end  of  the  first  year  after 
birth  ;  in  the  great  trochanter,  during 
the  fourth  year ;  and  in  the  lesser 
trochanter,  between  the  thirteenth 
and  fourteenth.  The  order  in  which 
the  epiphyses  are  joined  to  the  shaft 
is  the  reverse  of  that  of  their  appear- 
ance :  their  junction  does  not  com- 
mence until  after  puberty,  the  lesser 
trochanter  being  first  joined,  then 
the  great,  then  the  head,  and,  lastly, 
the  inferior  extremity  (the  first  in 
which  ossification  commenced),  which 
is  not  united  until  the  twentieth 
year. 

Attachment  of  Muscles. — To 
twenty-three.  To  the  great  tro- 
chanter :  the  Gluteus  medius,  Gluteus 
minimus,  Pyriformis,  Obturator  inter- 
nus,  Obturator  externus,  Gemellus 
superior,  Gemellus  inferior,  and 
Quadratus  femoris.  To  the  lesser 
trochanter :  the  Psoas  magnus  and 
the  Iliacus  below  it.     To  the  shaft : 

1  Biqelow  on  the  Hip,  p.  121.  ,      .       ,    .       .  .    .       .,         ,      j 

2  This  is  said  to  be  the  only  epiphysis  in  which  ossification  begins  before  birth  ;  though  accord- 
ing to  some  observers,  the  centre  for  the  upper  epiphysis  of  the  tibia  also  appears  betore  birth. 


Appears   at    4th 
year ;  joins  shaft  \> 
about  18th  year.  ^ 


Appears  at  end 
of  1st  year  ; 

joins  shaft  about 
18th  year. 


Appears  13th-14th  year ; 
joins  shaft  about  18th 
year. 


Fig.  130. 
five  centres. 


Appears  at Mf  m Joins  shaft  "I  : 

9th  month^         !  ,   -^f      year. 
( foetal). 

Lower  extremity. 
Plan  of  the  development  of  the  femur.    By 


190  THE  SKELETON. 

the  Vastus  externus,  Gluteus  maximus,  short  head  of  the  Biceps,  Vastus  internus, 
Adductor  magnus,  Pectineus,  Adductor  brevis.  Adductor  longus,  Crureus,  and 
Subcrureus.      To  the  condyles :  the  Gastrocnemius,  Plantaris,  and  Popliteus. 

Surface  Form. — The  femur  is  covered  with  muscles,  so  that  in  fairly  muscular  subjects  the 
shaft  is  not  to  be  detected  through  its  fleshy  covering,  and  the  only  parts  accessible  to  the  touch 
are  the  outer  surface  of  the  great  trochanter  and  the  lower  expanded  end  of  the  bone.  The 
external  surface  of  the  great  trochanter  is  to  be  felt,  especially  in  certain  positions  of  the  limb.  Its 
position  is  generally  indicated  by  a  depression,  owing  to  the  thickness  of  the  Gluteus  medius  and 
minimus,  which  project  above  it.  When,  however,  the  thigh  is  flexed,  and  especially  if 
crossed  over  the  opposite  one,  the  trochanter  produces  a  blunt  eminence  on  the  surface.  The 
upper  border  is  about  on  a  line  with  the  spine  of  the  os  pubis,  and  its  exact  level  is  indicated  by 
a  line  drawn  from  the  anterior  superior  spinous  process  of  the  ilium,  oyer  the  outer  side  of  the 
hip,  to  the  most  prominent  point  of  the  tuberosity  of  the  ischium.  This  is  known  as  Nelaton's 
line.  The  outer  and  inner  condyles  of  the  lower  extremity  are  easily  to  be  felt.  _  The  outer  one 
is  more  subcutaneous  than  the  inner  one,  and  readily  felt.  The  tuberosity  on  it  is  comparatively 
little  developed,  but  can  be  more  or  less  easily  recognized.  The  inner  condyle  is  more  thickly 
covered,  and  this  gives  a  general  convex  outline  to  this  part,  especially  when  the  knee  is 
flexed.  The  tuberosity  on  it  is  easily  felt,  and  at  the  upper  part  of  the  condyle  the  sharp 
tubercle  for  the  insertion  of  the  tendon  of  the  Adductor  magnus  can  be  recognized  without 
difficulty.  When  the  knee  is  flexed,  and  the  patella  situated  in  the  interval  between  the  con- 
dyles and  the  upper  end  of  the  tibia,  a  part  of  the  trochlear  surface  of  the  femur  can  be  made 
out  above  the  patella. 

Surgical  "Anatomy. — There  are  one  or  two  points  about  the  ossification  of  the  femur 
bearing  on  practice  to  which  allusion  must  be  made.  It  has  been  stated  above  that  the 
lower  end  of  the  femur  is  the  only  epiphysis  in  which  ossification  has  commenced  at  the  time  of 
birth.  The  presence  of  this  ossific  centre  is,  therefore,  a  proof,  in  newly-born  children  found 
dead,  that  the  child  has  arrived  at  the  full  period  of  utero-gestation,  and  is  always  relied  upon  in 
medico-legal  investigations.  The  position  of  the  epiphysial  line  should  be  carefully  noted.  It 
is  on  a  level  with  the  adductor  tubercle,  and  the  epiphysis  does  not,  therefore,  form  the  whole 
of  the  cartilage-clad  portion  of  the  lower  end  of  the  bone.  It  is  essential  to  bear  this  point  in 
mind  in  performing  excision  of  the  knee,  since  growth  in  length  of  the  femur  takes  place  chiefly 
from  the  lower  epiphysis,  and  any  interference  with  the  epiphysial  cartilage  in  a  young  child 
would  involve  such  ultimate  shortening  of  the  limb,  from  want,  of  growth,  as  to  render  it 
almost  useless.  Separation  of  the  lower  epiphysis  may  take  place  up  to  the  age  of  twenty,  at 
which  time  it  becomes  completely  joined  to  the  shaft  of  the  bone  ;  but,  as  a  matter  of  fact,  few 
cases  occur  after  the  age  of  sixteen  or  seventeen.  The  epiphysis  of  the  head  of  the  femur  is  of 
interest  principally  on  account  of  its  being  the  seat  of  origin  of  a  large  number  of  cases  of 
tuberculous  disease  of  the  hip-joint.  The  disease  commences  in  the  majority  of  cases  in  the 
highly  vascular  and  growing  tissue  in  the  neighborhood  of  the  epiphysis,  and  from  here  extends 
into  the  joint. 

Fractures  of  the  femur  are  divided,  like  those  of  the  other  long  bones,  into  fractures  of  the 
upper  end ;  of  the  shaft ;  and  of  the  lower  end.  The  fractures  of  the  upper  end  may  be 
classified  into  (1)  fracture  of  the  neck;  (2)  fracture  at  the  junction  of  the  neck  with  the  great 
trochanter;  (3)  fracture  of  the  great  trochanter;  and  (4)  separation  of  the  epiphysis,  either 
of  the  head  or  of  the  great  trochanter.  The  first  of  these,  fracture  of  the  neck,  is  usually 
termed  intracapsular  fracture,  but  this  is  scarcely  a  correct  designation,  as,  owing  to  the  attach- 
ment of  the  capsular  ligament,  the  fracture  may  be  partly  within  and  partly  without  the  cap- 
sule, when  the  fracture  occurs  at  the  lower  part  of  the  neck.  It  generally  occurs  in  old  people, 
principally  women,  and  usually  from  a  very  slight  degree  of  indirect  violence.  Probably 
the  main  cause  of  the  fracture  taking  place  in  old  people  is  in  consequence  of  the  degenerative 
changes  which  the  bone  has  undergone.  Merkel  believes  that  it  is  mainly  due  to  the  absorp- 
tion of  the  calcar  femorale.  These  fractures  are  occasionally  impacted.  As  a  rule  they  unite  by 
fibrous  tissue,  and  frequently  no  union  takes  place,  and  the  surfaces  of  the  fracture  become 
smooth  and  eburnated. 

Fractures  at  the  junction  of  the  neck  with  the  great  trochanter  are  usually  termed  extra- 
capsular, but  this  designation  is  also  incorrect,  as  the  fracture  is  partly  within  the  capsule, 
owing  to  its  attachment  in  front  to  the  anterior  intertrochanteric  line,  which  is  situated  below 
the  line  of  fracture.  These  fractures  are  produced  by  direct  violence  to  the  great  trochanter,  as 
from  a  blow  or  fall  laterally  on  the  hip.  From  the  manner  in  which  the  accident  is  caused,  the 
neck  of  the  bone  is  driven  into  the  trochanter,  where  it  may  remain  impacted,  or  the  trochanter 
may  be  split  up  into  two  or  more  fragments,  and  thus  no  fixation  takes  place. 

Fractures  of  the  great  trochanter  may  be  either  "oblique  fracture  through  the  trochanter 
major,  without  implicating  the  neck  of  the  bone"  (Astley  Cooper),  or  separation  of  the  great 
trochanter.  Most  of  the  recorded  cases  of  this  latter  injury  occurred  in  young  persons,  and  were 
probably  cases  of  separation  of  the  epiphysis  of  the  great  trochanter.  Separation  of  the  epiphysis 
of  the  head  of  the  femur  has  been  said  to  occur,  but  has  probably  never  been  verified  by  post- 
mortem examination. 

Fractures  of  the  shaft  may  occur  at  any  part,  but  the  most  usual  situation  is  at  or  near  the 
centre  of  the  bone.     They  may  be  caused  by  direct  or  indirect  violence  or  by  muscular  action. 


THE   PATELLA. 


191 


Fractures  of  the  upper  third  of  the  shaft  are  almost  always  the  result  of  indirect  violence, 
whilst  those  of  the  lower  third  are  the  result,  for  the  most  part,  of  direct  violence.  En  the 
middle  third  fractures  occur  from  both  forms  of  injury  in  about  equal  proportions.  Fractures 
of  the  shaft  are  generally  oblique,  but  they  may  be  transverse,  longitudinal,  or  spiral.  The 
transverse  fracture  occurs  most  frequently  in  children.  The  fractures  of  the  lower  end  of  the 
femur  include  transverse  fracture  above  the  condyles,  the  most  common  ;  and  this  may  be  com- 
plicated by  a  vertical  fracture  between  the  condyles,  constituting  the  T-shaped  fracture.  In 
these  cases  the  popliteal  artery  is  in  danger  of  being  wounded.  Oblique  fracture,  separating 
either  the  internal  or  external  condjde,  and  a  longitudinal  incomplete  fracture  between  the  con- 
dyles, may  also  take  place. 

The  femur  as  well  as  the  other  bones  of  the  leg  are  frequently  the  seat  of  acute  necrosi-  in 
young  children.  This  is  no  doubt  due  to  their  greater  exposure  to  injury,  which  is  often  the 
exciting  cause  of  this  disease.  Tumors  not  unfrequently  are  found  growing  from  the  femur  : 
the  most  common  forms  being  sarcoma,  which  may  grow  either  from  the  periosteum  or  from  the 
medullary  tissue  within  the  interior  of  the  bone ;  and  exostosis,  which  is  commonly  found 
originating  in  the  neighborhood  of  the  epiphysial  cartilage  of  the  lower  end. 

THE  LEG. 

The  skeleton  of  the  Leg  consists  of  three  bones  :  the  Patella,  a  large  sesamoid 
bone,  placed  in  front  of  the  knee  :  the  Tibia ;  and  the  Fibula. 

The  Patella  (Figs.  131,  132). 

The  Patella  (patella,  a  small  pan)  is  a  flat,  triangular  bone,  situated  at  the 
anterior  part  of  the  knee-joint.  It  is  usually  regarded  as  a  sesamoid  bone, 
developed  in  the  tendon  of'  the 
Quadriceps  extensor.  It  resem- 
bles these  bones  (1)  in  its  being 
developed  in  a  tendon  ;  (2)  in 
its  centre  of  ossification  pre- 
senting a  knotty  or  tuberculated 
outline ;  (3)  in  its  structure 
being  composed  mainly  of  dense 
cancellous  tissue,  as  in  the  other 
sesamoid  bones.  It  serves  to 
protect  the  front  of  the  joint, 
and  increases  the  leverage  of 
the  Quadriceps  extensor  by 
making  it  act  at  a  greater  angle 
three  borders,  and  an  apex. 

The  anterior  surface  is  convex,  perforated  by  small  apertures,  for  the  passage 
of  nutrient  vessels,  and  marked  by  numerous  rough,  longitudinal  striae.  This 
surface  is  covered,  in  the  recent  state,  by  an  expansion  from  the  tendon  of  the 
Quadriceps  extensor,  which  is  continuous  below  with  the  superficial  fibres  of  the 
ligamentum  patellae.  It  is  separated  from  the  integument  by  a  bursa.  The 
posterior  surface  presents  a  smooth,  oval-shaped,  articular  surface,  covered  with 
cartilage  in  the  recent  state,  and  divided  into  two  facets  by  a  vertical  ridge,  which 
descends  from  the  superior  border  toAvard  the  inferior  angle  of  the  bone.  The 
ridge  corresponds  to  the  groove  on  the  trochlear  surface  of  the  femur,  and  the  two 
facets  to  the  articular  surfaces  of  the  two  condyles  ;  the  outer  facet,  for  articulation 
with  the  outer  condyle,  being  the  broader  and'  deeper.  This  character  serv< 
indicate  the  side  to  which  the  bone  belongs.  Below  the  articular  surface  is  a 
rough,  convex,  non-articular  depression,  the  lower  half  of  which  gives  attachment 
to  the  ligamentum  patellae,  the  upper  half  being  separated  from  the  head  of  the 
tibia  by  adipose  tissue. 

The  superior  border  is  thick,  and  sloped  from  behind,  downward  and  forward  : 
it  gives  attachment  to  that  portion  of  the  Quadriceps  extensor  which  is  derived 
from  the  Rectus  and  Crureus  muscles.  The  lateral  borders  are  thinner,  converging 
below.  They  give  attachment  to  that  portion  of  the  Quadriceps  extensor  derived 
from  the  external  and  internal  Vasti  muscles. 

The  apex  is  pointed,  and  gives  attachment  to  the  ligamentum  patellae. 


"^, 


Fig.  131.— Right  patella, 
terior  surface. 


An- 


FlG.   13J.— Ki^ht  patella. 
Posterior  surface. 


It  presents  an  anterior  and  a  posterior  surface. 


192  THE  SKELETON. 

Structure. — It  consists  of  a  nearly  uniform  dense  cancellous  tissue  covered 
by  a  thin  compact  lamina.  The  cancelli  immediately  beneath  the  anterior  surface 
are  arranged  parallel  with  it.  In  the  rest  of  the  bone  they  radiate  from  the 
posterior  articular  surface    toward  the  other  parts  of  the  bone. 

Development. — By  a  single  centre,  which  makes  its  appearance,  according  to 
Beclard,  about  the  third  year.  In  two  instances  I  have  seen  this  bone  cartilagi- 
nous throughout,  at  a  much  later  period  (six  years).  More  rarely,  the  bone  is 
developed  by  two  centres,  placed  side  by  side.  Ossification  is  completed  about  the 
age  of  puberty. 

Articulations. — With  the  two  condyles  of  the  femur. 

Attachment  of  Muscles. — To  four :  the  Rectus,  Crureus,  Vastus  internus,  and 
Vastus  externus.  These  muscles,  joined  at  their  insertion,  constitute  the  Quadriceps 
extensor  cruris. 

Surface  Form. — The  external  surface  of  the  patella  can  be  seen  and  felt  in  front  of  the 
knee.  In  the  extended  position  of  the  limb  the  internal  border  is  a  little  more  prominent  than 
the  outer,  and  if  the  Quadriceps  extensor  is  relaxed,  the  bone  can  be  moved  from  side  to  side 
and  appears  to  be  loosely  fixed.  If  the  joint  is  flexed,  the  patella  recedes  into  the  hollow 
between  the  condyles  of  the  femur  and  the  upper  end  of  the  tibia,  and  becomes  firmly  fixed 
against  the  femur. 

Surgical  Anatomy. — The  main  surgical  interest  about  the  patella  is  in  connection  with 
fractures  ;  which  are  of  common  occurrence.  They  may  be  produced  by  muscular  action  ;  that 
is  to  say,  by  violent  contraction  of  the  Quadriceps  extensor  while  the  limb  is  in  a  position  of 
semi-flexion,  so  that  the  bone  is  snapped  across  the  cond3*les ;  or  by  direct  violence,  such  as 
falls  on  the  knee.  In  the  former  class  of  cases  the  fracture  is  transverse  ;  in  the  latter  it  may 
be  oblique,  longitudinal,  stellate,  or  the  bone  variously  comminuted.  The  principal  interest  in 
these  cases  attaches  to  their  treatment.  Owing  to  the  wide  separation  of  the  fragments,  and 
the  difficulty  there  is  in  maintaining  them  in  apposition,  union  takes  place  by  fibrous  tissue, 
and  this  may  subsequently  stretch,  producing  wide  separation  of  the  fragments  and  permanent 
lameness.  Various  plans,  including  opening  the  joint  and  suturing  the  fragments,  have  been 
advocated  for  overcoming  this  difficulty. 

In  the  larger  number  of  cases  of  fracture  of  the  patella  the  knee-joint  is  involved,  the  car- 
tilage which  covers  its  posterior  surface  being  also  torn.  In  some  cases  of  fracture  from  direct 
violence,  however,  this  need,  not  necessarily  happen,  the  lesion  involving  only  the  superficial 
part  of  the  bone ;  and,  as  Morris  has  pointed  out,  it  is  an  anatomical  possibility,  in  complete 
fracture,  if  the  lesion  involve  only  the  lower  and  non-articular  part  of  the  bone,  for  it  to  take 
place  without  injury  to  the  synovial  membrane. 

The  Tibia  (Figs.  133,  134). 

The  Tibia  (tibia,  a  flute  or  pipe)  is  situated  at  the  front  and  inner  side  of  the 
leg,  and,  excepting  the  femur,  is  the  longest  and  largest  bone  in  the  skeleton.  It 
is  prismoid  in  form,  expanded  above,  where  it  enters  into  the  knee-joint,  more 
slightly  enlarged  below.  In  the  male  its  direction  is  vertical  and  parallel  with 
the  bone  of  the  opposite  side ;  but  in  the  female  it  has  a  slightly  oblique  direction 
downward  and  outward,  to  compensate  for  the  oblique  direction  of  the  femur 
inward.     It  presents  for  examination  a  shaft  and  two  extremities. 

The  Upper  Extremity,  or  Head,  is  large,  and  expanded  on  each  side  into  two 
lateral  eminences,  the  tuberosities.  Superiorly,  the  tuberosities  present  two  smooth, 
concave  surfaces,  which  articulate  with  the  condyles  of  the  femur  ;  the  internal, 
articular  surface  is  longer,  deeper,  and  narrower  than  the  external,  oval  from 
before  backward,  to  articulate  with  the  internal  condyle ;  the  external  one 
is  broader  and  more  circular,  concave  from  side  to  side,  but  slightly  convex  from 
before  backward,  especially  at  its  posterior  part,  where  it  is  prolonged  on  to  the 
posterior  surface  for  a  short  distance,  to  articulate  with  the  external  condyle. 
Between  the  two  articular  surfaces,  and  nearer  the  posterior  than  the  anterior 
aspect  of  the  bone,  is  an  eminence,  the  spinous  process  of  the  tibia,  surmounted 
by  a  prominent  tubercle  on  each  side,  on  to  the  lateral  aspect  of  which  the  facets 
just  described  are  prolonged;  in  front  and  behind  the  spinous  process  is  a  rough 
depression  for  the  attachment  of  the  anterior  and  posterior  crucial  ligaments 
and  the  semilunar  fibro-cartilages.  The  anterior  surfaces  of  the  tuberosities  are 
continuous  with  one  another,  forming  a  single  large  surface,  which  is  somewhat 


THE    TIBIA. 


193 


flattened :  it  is  triangular,  broad 
above,  and  perforated  by  large  vas- 
cular foramina ;  narrow  below, 
where  it  terminates  in  a  prominent 
oblong  elevation  of  large  size,  the 
tubercle  of  the  tibia ;  the  lower 
half  of  this  tubercle  is  rough,  for 
the  attachment  of  the  ligamentum 
patellae  ;  the  upper  half  presents  a 
smooth  facet  supporting,  in  the 
recent  state,  a  bursa  which  sep- 
arates the  ligament  from  the  bone. 
Posteriorly  the  tuberosities  are 
separated  from  each  other  by  a 
shallow  depression,  the  popliteal 
notch,  which  gives  attachment  to 
part  of  the  posterior  crucial  liga- 
ment and  part  of  the  posterior 
ligament  of  the  knee-joint.  The 
inner  tuberosity  presents  poste- 
riorly a  deep  transverse  groove, 
for  the  insertion  of  one  of  the 
fasciculi  of  the  tendon  of  the 
Semi-membranosus.  Its  lateral 
surface  is  convex,  rough,  and 
prominent :  it  gives  attachment  to 
the  internal  lateral  ligament.  The 
outer  tuberosity  presents  posteriorly 
a  flat  articular  facet,  nearly  circu- 
lar in  form,  directed  downward, 
backward,  and  outward,  for  articu- 
lation with  the  fibula  Its  lateral 
surface  is  convex  and  rough,  more 
prominent  in  front  than  the  in- 
ternal :  it  presents  a  prominent 
rough  eminence,  situated  on  a  level 
with  the  upper  border  of  the  tuber- 
cle of  the  tibia  at  the  junction  of 
its  anterior  and  outer  surfaces,  for 
the  attachment  of  the  ilio-tibial 
band.  Just  below  this  the  Ex- 
tensor longus  digitorum  and  a  slip 
from  the  Biceps  are  attached. 

The  Shaft  of  the  tibia  is  of  a 
triangular  prismoid  form,  broad 
above,  gradually  decreasing  in  size 
to  its  most  slender  part,  at  the 
commencement  of  its  lower  fourth, 
where  fracture  most  frequently 
occurs ;  it  then  enlarges  again 
toward  its  lower  extremity.  It 
presents  for  examination  three 
borders  and  three  surfaces. 

The  anterior  border    '         nost 
prominent  of  the  three 
the  crest  of  the  tibia,  6> 
lar  language,  the  shin  ; 

13 


Head 
Styloid  process 


EXTERNAL 
LATERAL 
LIGAMENT. 


Fibula 


External  malleolus. 
Fig.  133.— Bones  of  the  right  les 


Internal  malleolus. 


Anterior  surface. 


is  c<£!   id 
in  poj  li- 
cences above  at  the  tubercle,  and  terminates  below 


194 


THE   SKELETON. 


i-  .li£w^Y" 'Styloid  process. 


Fibula^ 


Pig.  134. — Bones  of  the  right  leg.    Posterior  surface. 

ticus,   Extensor  proprius  hallucis,  Extensor 

The  posterior  surface  (Fig.  134)  presents 

the  oblique  line  of  the  tibia,  which  extends 


at  the  anterior  margin  of  the  inner 
malleolus.  This  border  is  very 
prominent  in  the  upper  two-thirds 
of  its  extent,  smooth  and  rounded 
below.  It  presents  a  very  flexuous 
course,  being  usually  curved  out- 
ward above  and  inward  below ;  it 
gives  attachment  to  the  deep  fascia 
of  the  leg. 

The  internal  border  is  smooth 
and  rounded  above  and  below,  but 
more  prominent  in  the  centre ;  it 
commences  at  the  back  part  of  the 
inner  tuberosity,  and  terminates  at 
the  posterior  border  of  the  internal 
malleolus ;  its  upper  part  gives  at- 
tachment to  the  internal  lateral  liga- 
ment of  the  knee  to  the  extent  of 
about  two  inches,  and  to  some  fibres 
of  the  Popliteus  muscle ;  its  middle 
third  to  some  fibres  of  the  Soleus  and 
Flexor  longus  digitorum  muscles. 

The  external  border,  or  inter- 
osseous ridge,  is  thin  and  prominent, 
especially  its  central  part,  and  gives 
attachment  to  the  interosseous  mem- 
brane ;  it  commences  above  in  front 
of  the  fibular  articular  facet,  and 
bifurcates  below,  to  form  the  bounda- 
ries of  a  triangular  rough  surface,  for 
the  attachment  of  the  interosseous 
ligament  connecting  the  tibia  and 
fibula. 

The  internal  surface  is  smooth, 
convex,  and  broader  above  than 
below ;  its  upper  third,  directed  for- 
ward and  inward,  is  covered  by  the 
aponeurosis  derived  from  the  tendon 
of  the  Sartorius,  and  by  the  tendons 
of  the  Gracilis  and  Semitendinosus, 
all  of  which  are  inserted  nearly  as 
far  forward  as  the  anterior  border; 
in  the  rest  of  its  extent  it  is  sub- 
cutaneous. 

The  external  surface  is  narrower 
than  the  internal ;  its  upper  two- 
thirds  presents  a  shallow  groove  for 
the  attachment  of  the  Tibialis  an- 
ticus  muscle ;  its  lower  third  is 
smooth,  convex,  curves  gradually 
forward  to  the  anterior  aspect  of 
the  bone,  and  is  covered  from 
within  outward  by  the  tendons  of 
the  following  muscles  :  Tibialis  an- 
longus  digitorum. 

,  at  its  upper  part,  a  prominent  ridge, 
from  the  back  part  of  the  articular 


THE    TIBIA. 


195 


facet  for  the  fibula  obliquely  downward,  to  the  internal  border,  at  the  junction  of  its 
upper  and  middle  thirds.  It  marks  the  lower  limit  for  the  insertion  of  the  Popliteus 
muscle,  and  serves  for  the  attachment  of  the  popliteal  fascia  and  part  of  the  Soleus, 
Flexor  longus  digitorum,  and  Tibialis  posticus  muscles  ;  the  triangular  concave  sur- 
face, above  and  to  the  inner  side  of  this  line,  gives  attachment  to  the  Popliteus 
muscle.  The  middle  third  of  the  posterior  surface  is  divided  by  a  vertical  ridge 
into  two  lateral  halves  :  the  ridge  is  well  marked  at  its  commencement  at  the 
oblique  line,  but  becomes  gradually  indistinct  below;  the  inner  and  broader  half 
gives  attachment  to  the  Flexor  longus  digitorum,  the  outer  and  narrower  to  part  of 
the  Tibialis  posticus.  The  remaining  part  of  the  bone  presents  a  smooth  surface 
covered  by  the  Tibialis  posticus,  Flexor  longus  digitorum,  and  Flexor  longus  hal- 
lucis  muscles.  Immediately  below  the  oblique  line  is  the  medullary  foramen,  which 
is  large  and  directed  obliquely  downward. 

The  Lower  Extremity,  much  smaller  than  the  upper,  presents  five  surfaces ;  it  is 
prolonged  dowmvard,  on  its  inner  side,  to  a  strong  process,  the  internal  malleolus. 
The  inferior  surface  of  the  bone  is  quadrilateral,  and  smooth  for  articulation  with  the 
astragalus.  This  surface  is  concave  from  before  backward,  and  broader  in  front  than 
behind.  It  is  traversed  from  before  backward  by  a  slight  elevation,  separating  two 
lateral  depressions.  It  is  narrow  internally,  where  the  articular  surface  becomes  con- 
tinuous with  that  on  the  inner  malleolus.  The  anterior  surface  of  the  lower  extrem- 
ity is  smooth  and  rounded  above,  and  covered  by  the  tendons  of  the  Extensor 
muscles  of  the  toes  ;  its  lower  margin  presents  a  rough  transverse  depression,  for 
the  attachment  of  the  anterior  ligament  of  the  ankle-joint;  the  posterior  surface 
presents  a  superficial  groove  directed  obliquely  downward  and  inward,  continuous 
with  a  similar  groove  on  the  posterior  surface  of  the  astragalus,  and  serving  for  the 
passage  of  the  tendon  of  the  Flexor  longus  hallucis  ;  the  external  surface  presents  a 
triangular  rough  depression  for  the  attachment  of  the  inferior  interosseous  ligament, 
connecting  it  with  the  fibula ;  the  lower  part  of  this  depression  is  smooth,  covered 
with  cartilage  in  the  recent  state,  and 
articulates  with  the  fibula.  This  surface 
is  bounded  by  two  prominent  borders,  con- 
tinuous above  with  the  interosseous  ridge ; 
they  afford  attachment  to  the  anterior  and 
posterior  inferior  tibio-fibiflar  ligaments. 
The  internal  surface  of  the  lower  extrem- 
ity is  prolonged  downward  to  form  a  strong 
pyramidal  process,  flattened  from  without 
inward — the  internal  malleolus.  The  inner 
surface  of  this  process  is  convex  and  sub- 
cutaneous ;  its  outer  surface  is  smooth  and 
slightly  concave,  and  articulates  with  the 
astragalus  ;  its  anterior  border  is  rough, 
for  the  attachment,  of  the  anterior  fibres 
of  the  internal  lateral  or  Deltoid  ligament ; 
its  posterior  border  presents  a  broad  and 
deep  groove,  directed  obliquely  downward 
and  inward,  which  is  occasionally  double  : 
this  groove  transmits  the  tendons  of  the 
Tibialis  posticus  and  Flexor  longus  digi- 
torum muscles.  The  summit  of  the  in- 
ternal malleolus  is  marked  by  a  rough 
depression  behind,  for  the  attachment  of 
the  internal  lateral  ligament  of  the  ankle- 
joint. 

Structure. — Like  that  of  the  other  long  bones.  At  the  junction  of  the  middle 
and  lower  third,  where  the  bone  is  smallest,  the  wall  of  the  shaft  is  thicker  than 
in  other  parts,  in  order  to  compensate  for  the  smallness  of  the  calibre  of  the  bone. 


Upper  extremity. 


Appears  at 
birth. 


Appears  at  2nd_ 
year. 


Joins  shaft  about 
20th  year. 


Joins  shaft  about 

lSllt  year. 


T.ou-er  extremity. 

Fig.  135.— Plan  of  the  development  of  the  tibia. 
By  three  centres. 


196  THE   SKELETON. 

Development. — By  three  centres  (Fig.  135) :  one  for  the  shaft,  and  one  for 
each  extremity.  Ossification  commences  in  the  centre  of  the  shaft  about  the 
seventh  week,  and  gradually  extends  toward  either  extremity.  The  centre  for 
the  upper  epiphysis  appears"  before  or  shortly  after  birth  ;  it  is  flattened  in  form, 
and  has  a  thin,  tongue-shaped  process  in  front  which  forms  the  tubercle.  That 
for  the  lower  epiphysis  appears  in  the  second  year.  The  lower  epiphysis  joins 
the  shaft  at  about  the  eighteenth,  and  the  upper  one  about  the  twentieth,  year. 
Two  additional  centres  occasionally  exist — one  for  the  tongue-shaped  process  of  the 
upper  epiphysis,  which  forms  the  tubercle,  and  one  for  the  inner  malleolus. 

Articulations. — With  three  bones  :  the  femur,  fibula,  and  astragalus. 

Attachment  of  Muscles. — To  twelve:  to  the  inner  tuberosity,  the  Semimem- 
branosus :  to  the  outer  tuberosity,  the  Tibialis  anticus  and  Extensor  longus  digi- 
torum  and  Biceps ;  to  the  shaft,  its  internal  surface,  the  Sartorius,  Gracilis,  and 
Semitendinosus ;  to  its  external  surface,  the  Tibialis  anticus ;  to  its  posterior  sur- 
face, the  Popliteus,  Soleus,  Flexor  longus  digitorum,  and  Tibialis  posticus ;  to  the 
tubercle,  the  ligamentum  patellae,  by  which  the  Quadriceps  extensor  muscle  is 
inserted  into  the  tibia.  In  addition  to  these  muscles,  the  Tensor  fasciae  femoris  is 
inserted  indirectly  into  the  tibia,  through  the  ilio-tibial  band,  and  the  Peroneus 
longus  occasionally  derives  a  few  fibres  of  origin  from  the  outer  tuberosity. 

Surface  Form. — A  considerable  portion  of  the  tibia  is  subcutaneous  and  easily  to  be  felt. 
At  the  upper  extremity  the  tuberosities  are  to  be  recognized  just  below  the  knee.  The  internal 
one  is  broad  and  smooth,  and  merges  into  the  subcutaneous  surface  of  the  shaft  below.  The 
external  one  is  narrower  and  more  prominent,  and  on  it,  about  midway  between  the  apex  of  the 
patella  and  the  head  of  the  fibula,  may  be  felt  a  prominent  tubercle  for  the  insertion  of  the  ilio- 
tibial  band.  In  front  of  the  upper  end  of  the  bone,  between  the  tuberosities,  is  the  tubercle  of 
the  tibia,  forming  an  oval  eminence  which  is  continuous  below  with  the  anterior  border  or  crest 
of  the  bone.  This  border  can  be  felt,  forming  the  prominence  of  the  shin,  in  the  upper  two- 
thirds  of  its  extent  as  a  sharp  and  flexuous  ridge,  curved  outward  above  and  inward  below.  In 
the  lower  third  of  the  leg  the  border  disappears,  and  the  bone  is  concealed  by  the  tendons  of 
the  muscles  on  the  front  of  the  leg.  Internal  to  the  anterior  border  is  to  be  felt  the  broad 
internal  surface  of  the  tibia,  slightly  encroached  upon  by  the  muscles  in  front  and  behind.  It 
commences  above  at  the  wide  expanded  inner  tuberosity,  and  terminates  below  at  the  internal 
malleolus.  The  internal  ^malleolus  is  a  broad  prominence  situated  on  a  higher  level  and  some- 
what farther  forward  than  the  external  malleolus.  It  overhangs  the  inner  border  of  the  arch 
of  the  foot.  Its  anterior  border  is  nearly  straight ;  its  posterior  border  presents  a  sharp  edge, 
which  forms  the  inner  margin  of  the  groove  for  the  tendon  of  the  Tibialis  posticus  muscle. 

The  Fibula  (Figs.  133,  134). 

The  Fibula  {fibula,  a  clasp)  is  situated  at  the  outer  side  of  the  leg.  It  is  the 
.  smaller  of  the  two  bones,  and,  in  proportion  to  its  length,  the  most  slender  of  all 
the  long  bones  ;  it  is  placed  on  the  outer  side  of  the  tibia,  with  which  it  is  con- 
nected above  and  below.  Its  upper  extremity  is  small,  placed  toward  the  back  of 
the  head  of  the  tibia  and  below  the  level  of  the  knee-joint,  and  excluded  from  its 
formation ;  the  lower  extremity  inclines  a  little  forward,  so  as  to  be  on  a  plane 
anterior  to  that  of  the  upper  end,  projects  below  the  tibia,  and  forms  the  outer 
ankle.     It  presents  for  examination  a  shaft  and  two  extremities. 

The  Upper  Extremity,  or  Head,  is  of  an  irregular  quadrate  form,  presenting 
above  a  flattened  articular  facet,  directed  upward,  forward,  and  inward,  for  artic- 
ulation with  a  corresponding  facet  on  the  external  tuberosity  of  the  tibia.  On 
the  outer  side  is  a  thick  and  rough  prominence,  continued  behind  into  a  pointed 
eminence,  the  styloid  process,  which  projects  upward  from  the  posterior  part  of 
the  head.  The  prominence  gives  attachment  to  the  tendon  of  the  Biceps  muscle 
and  to  the  long  external  lateral  ligament  of  the  knee,  the  ligament  dividing  the 
tendon  into  two  parts.  The  summit  of  the  styloid  process  gives  attachment  to  the 
short  external  lateral  ligament.  The  remaining  part  of  the  circumference  of  the 
head  is  rough,  for  the  attachment  of  muscles  and  ligaments.  It  presents  in  front  a 
tubercle  for  the  origin  of  the  upper  and  anterior  part  of  the  Peroneus  longus,  and 
the  adjacent  surface  gives  attachment  to  the  anterior  superior  tibio-fibular  ligament ; 
and'  behind,  another  tubercle  for  the  attachment  of  the  posterior  superior  tibio- 
fibular ligament  and  the  upper  fibres  of  the  Soleus  muscle. 


THE   FIBULA.  197 

The  shaft  presents  four  borders — the  antero-external,  the  antero-internal,  the 
postero-external,  and  the  postero-internal ;  and  four  surfaces — anterior,  posterior, 
internal,  and  external. 

The  antero-external  border  commences  above  in  front  of  the  head,  runs  verti- 
cally downward  to  a  little  below  the  middle  of  the  bone,  and  then,  curving  some- 
what outward,  bifurcates  so  as  to  embrace  the  triangular  subcutaneous  surface 
immediately  above  the  outer  surface  of  the  external  malleolus.  This  border  gives 
attachment  to  an  intermuscular  septum,  which  separates  the  extensor  muscles  on 
the  anterior  surface  of  the  leg  from  the  Peroneus  longus  and  brevis  muscles  on  the 
outer  surface. 

The  antero-internal  border,  or  interosseous  ridge,  is  situated  close  to  the  inner 
side  of  the  preceding,  and  runs  nearly  parallel  with  it  in  the  upper  third  of  its 
extent;  but  diverges  from  it  so  as  to  include  a  broader  space  in  the  lower  two-thirds. 
It  commences  above,  just  beneath  the  head  of  the  bone  (sometimes  it  is  quite 
indistinct  for  about  an  inch  below  the  head),  and  terminates  below  at  the  apex  of 
a  rough  triangular  surface  immediately  above  the  articular  facet  of  the  external 
malleolus.  It  serves  for  the  attachment  of  the  interosseous  membrane,  which  sepa- 
rates the  extensor  muscles  in  front  from  the  flexor  muscles  behind. 

The  postero-external  border  is  prominent ;  it  commences  above  at  the  base 
of  the  styloid  process,  and  terminates  below  in  the  posterior  border  of  the  outer 
malleolus.  It  is  directed  outward  above,  backward  in  the  middle  of  its  course, 
backward  and  a  little  inward  below,  and  gives  attachment  to  an  aponeurosis  which 
separates  the  Peronei  muscles  on  the  outer  surface  of  the  shaft  from  the  flexor 
muscles  on  its  posterior  surface. 

The  postero-internal  border,  sometimes  called  the  oblique  line,  commences  above 
at  the  inner  side  of  the  head,  and  terminates  by  becoming  continuous  with  the 
antero-internal  border  or  interosseous  ridge  at  the  lower  fourth  of  the  bone.  It  is 
well  marked  and  prominent  at  the  upper  and  middle  parts  of  the  bone.  It  gives 
attachment  to  an  aponeurosis  which  separates  the  Tibialis  posticus  from  the  Soleus 
above  and  the  Flexor  longus  hallucis  below. 

The  anterior  surface  is  the  interval  between  the  antero-external  and  antero- 
internal  borders.  It  is  extremely  narrow  and  flat  in  the  upper  third  of  its  extent ; 
broader  and  grooved  longitudinally  in  its  lower  third  ;  it  serves  for  the  attachment 
of  three  muscles,  the  Extensor  longus  digitorum,  Peroneus  tertius,  and  Extensor 
proprius  hallucis. 

The  external  surface  is  the  space  between  the  antero-external  and  postero- 
external borders.  It  is  much  broader  than  the  preceding,  and  often  deeply  grooved, 
is  directed  outward  in  the  upper  two-thirds  of  its  course,  backward  in  the  lower 
third,  where  it  is  continuous  with  the  posterior  border  of  the  external  malleolus. 
This  surface  is  completely  occupied  by  the  Peroneus  longus  and  brevis  muscles. 

The  internal  surface  is  the  interval  included  between  the  antero-internal  and 
the  postero-internal  borders.  It  is  directed  inward,  and  is  grooved  for  the  attach- 
ment of  the  Tibialis  posticus  muscle. 

The  posterior  surface  is  the  space  included  between  the  postero-external  and 
the  postero-internal  borders;  it  is  continuous  below  with  the  rough  triangular 
surface  above  the  articular  facet  of  the  outer  malleolus;  it  is  directed  backward 
above,  backward  and  inward  at  its  middle,  directly  inward  below.  Its  upper 
third  is  rough,  for  the  attachment  of  the  Soleus  muscle  ;  its  lower  part  presents 
a  triangular  rough  surface,  connected  to  the  tibia  by  a  strong  interosseous  ligament, 
and  between  these  two  points  the  entire  surface  is  covered  by  the  fibres  of  origin 
of  the  Flexor  longus  hallucis  muscle.  At  about  the  middle  of  this  surface  is  the 
nutrient  foramen,  Avhich  is  directed  downward. 

The  Lower  Extremity,  or  external  malleolus,  is  of  a  pyramidal  form,  somewhat 
flattened  from  without  inward,  and  is  longer,  and  descends  lower  than  the  internal 
malleolus.  Ics  external  surface  is  convex,  subcutaneous,  and  continuous  with  the 
triangular  (also  subcutaneous)  surface  on  the  outer  side  of  the  shaft.  The  internal 
surface  presents  in  front  a  smooth  triangular  facet,  broader  above  than  below,  and 


198 


THE   SKELETON. 


shaft,  and  one   for 
the  eighth  week  of 


convex  from  above  downward,  which  articulates  with  a  corresponding  surface  on 
the  outer  side  of  the  astragalus.  Behind  and  beneath  the  articular  surface  is  a 
rough  depression  which  gives  attachment  to  the  posterior  fasciculus  of  the  external 
lateral  ligament  of  the  ankle.  The  anterior  border  is  thick  and  rough,  and  marked 
below  by  a  depression  for  the  attachment  of  the  anterior  fasciculus  of  the  external 
lateral  ligament.  The  posterior  border  is  broad  and  marked  by  a  shallow  groove, 
for  the  passage  of  the  tendons  of  the  Peroneas  longus  and  brevis  muscles.  The 
summit  is  rounded,  and  gives  attachment  to  the  middle  fasciculus  of  the  external 
lateral  ligament. 

In  order  to  distinguish  the  side  to  which  the  bone  belongs,  hold  it  with  the 
lower  extremity  downward  and  the  broad  groove  for  the  Peronei  tendons  back- 
ward— i.  e.  toward  the  holder :  the  triangular  subcutaneous  surface  will  then  be 
directed  to  the  side  to  which  the  bone  belongs. 

Articulations. — With  two  bones  :  the  tibia  and  astragalus. 
Development. — By  three  centres  (Fig.  136) :  one  for  the 
each  extremity.  Ossification  commences  in  the  shaft  about 
foetal  life,  a  little  later  than  in  the  tibia,  and  extends  gradually  toward  the 
extremities.  At  birth  both  ends  are  cartilaginous.  Ossification  commences  in 
the  lower  end  in  the  second  year,  and  in  the  upper  one  about  the  fourth  year. 
The  lower  epiphysis,  the  first  in  which  ossification  commences,  becomes  united  to 
the  shaft  about  the  twentieth  year;  the  upper  epiphysis  joins  about  the  twenty- 
fifth  year.  Ossification  appearing  first  in  the  lower  epiphysis  is  contrary  to  the 
rule  which  prevails  with  regard  to  the  commencement  of  ossification  in  epiphyses 
- — viz.  that  that  epiphysis  toward  which  the  nutrient  artery  is  directed  commences 
to  ossify  last ;  but  it  follows  the  rule  which  prevails  with  regard  to  the  union  of 
epiphyses,  by  uniting  first. 

Attachment  of  Muscles. — To  nine  :    to  the  head, 
Upper  extremity.  the    Biceps,    Soleus,   and    Peroneus    longus ;  to    the 

shaft,  its  anterior  surface,  the  Extensor  longus  digi- 
torum,  Peroneus  tertius,  and  Extensor  proprius 
hallucis  ;  to  the  internal  surface,  the  Tibialis  pos- 
ticus ;  to  the  posterior  surface,  the  Soleus  and  Flexor 
longus  hallucis  ;  to  the  external  surface,  the  Peroneus 
longus  and  brevis. 

Surface  Form. — The  only  parts  of  the  fibula  which  are 
to  be  felt  are  the  head  and  the  lower  part  of  the  external  sur- 
face of  the  shaft  and  the  external  malleolus.  The  head  is  to 
be  seen  and  felt  behind  and  to  the  outer  side  of  the  outer 
tuberosity  of  the  tibia.  It  presents  a  small,  prominent 
triangular  eminence  slightly  above  the  level  of  the  tubercle 
of*  the  tibia.  The  external  malleolus  presents  a  narrow  elon- 
gated prominence,  situated  on  a  plane  posterior  to  the  internal 
malleolus  and  reaching  to  a  lower  level.  From  it  may  be 
traced  the  lower  third  or  half  of  the  external  surface  of  the 
shaft  of  the  bone  in  the  interval  between  the  Peroneus  tertius 
in  front  and  the  other  two  Peronei  tendons  behind. 

Surgical  Anatomy. — In  fractures  of  the  bones  of  the 

leg  both  bones  are  usually  fractured,  but  each  bone  may  be 

broken  separately,  the  fibula  more  frequently  than  the  tibia. 

Fracture  of  both  bones  may  be  caused  either  by  direct  or  indirect 

Appears  atJ^kMUyiites  about        violence.     When  it  occurs  from  indirect  force,  the  fracture  in 

2nd  year.     \^)  20th  year.  the  tibia  is  at  the  junction  of  the  middle  and  lower  third  of 

the  bone.  Many  causes  conduce  to  render  this  the  weakest 
part  of  the  bone.  The  fracture  of  the  fibula  is  usually  at 
rather  a  higher  level.  These  fractures  present  great  variety, 
both  as  regards  their  direction  and  condition.  They  may  be 
oblique,  transverse,  longitudinal,  or  spiral.  When  oblique, 
they  are  usually  the  result  of  indirect  violence,  and  the  direction  of  the  fracture  is  from  behind, 
downward,  forward,  and  inward  in  many  cases,  but  may  be  downward  and  outward  or  downward 
and  backward.  When  transverse,  the  fracture  is  often  at  the  upper  part  of  the  bone,  and  is  the 
result  of  direct  violence.  The  spiral  fracture  usually  commences  as  a  vertical  fissure,  involving 
the  ankle-joint,  and  is  associated  with  fracture  of  the  fibula  higher  up.  It  is  the  result  of  torsion, 
from  twisting  of  the  body  whilst  the  foot  is  fixed. 


Appears  about    , 
^th  year. 


Unites  about 
25th  year. 


Lower  extremity. 

Fig.  136.— Plan  of  the  develop 
ment  of  the  fibula.  By  three  centres 


THE    TARSUS:    THE    CALCANEUM.  199 

Fractures  of  the  tibia  alone  are  almost  always  the  result  of  direct  violence,  except  where  the 
malleolus  is  broken  off  by  twists  of  the  foot.  Fractures  of  the  fibula  alone  may  arise  from 
indirect  or  direct  force,  those  of  the  lower  end  being  usually  the  result  of  the  former,  and  those 
higher  up  being  caused  by  a  direct  blow  on  the  part. 

The  tibia  and  fibula,  like  the  femur,  are  frequently  the  seat  of  acute  necrosis.  Chronic 
abscess  is  more  frequently  met  with  in  the  cancellous  tissue  of  the  head  and  lower  end  of  the 
tibia  than  in  any  other  bone  of  the  body.  The  abscess  is  of  small  size,  very  chronic,  and  prob- 
ably the  result  of  tuberculous  osteitis  in  the  highly  vascular  growing  tissue  at  the  end  of  the 
shaft  near  the  epiphyseal  cartilage  in  the  young  subject. 

The  tibia  is  the  bone  which  is  most  frequently  and  most  extensively  distorted  in  rickets.  Ir 
gives  way  at  the  junction  of  the  middle  and  lower  third,  its  weakest  part,  and  presents  a  curve 
forward  and  outward. 

THE  FOOT  (Figs.  137,  138). 

The  skeleton  of  the  Foot  consists  of  three  divisions :  the  Tarsus,  Metatarsus, 
and  Phalanges. 

The  Tarsus. 

The  bones  of  the  Tarsus  are  seven  in  number :  viz.,  the  calcaneuru  or  os  calcis, 
astragalus,  cuboid,  navicular,  internal,  middle,  and  external  cuneiform  bones. 

The  Calcaneum  (Fig.  139). 

The  Calcaneum,  or  Os  Calcis  (calx,  the  heel),  is  the  largest  and  strongest  of  the 
tarsal  bones.  It  is  irregularly  cuboidal  in  form,  having  its  long  axis  directed 
forward  and  outward.  It  is  situated  at  the  lower  and  back  part  of  the  foot, 
serving  to  transmit  the  weight  of  the  body  to  the  ground,  and  forming  a  stronc 
lever  for  the  muscles  of  the  calf.  It  presents  for  examination  six  surfaces : 
superior,  inferior,   external,  internal,   anterior,  and  posterior. 

The  superior  surface  is  formed  behind  by  the  upper  aspect  of  that  part  of  the 
os  calcis  which  projects  backward  to  form  the  heel.  It  varies  in  length  in  differ- 
ent individuals ;  is  convex  from  side  to  side,  concave  from  before  backward,  and 
corresponds  above  to  a  mass  of  adipose  substance  placed  in  front  of  the  tendo 
Achillis.  In  the  middle  of  the  superior  surface  are  two  (sometimes  three)  articular 
facets,  separated  by  a  broad  shallow  groove,  Avhich  is  directed  obliquely  forward 
and  outward,  and  is  rough  for  the  attachment  of  the  interosseous  ligament 
connecting  the  astragalus  and  os  calcis.  Of  the  two  articular  surfaces,  the  external 
is  the  larger,  and  situated  on  the  body  of  the  bone :  it  is  of  an  oblong  form,  wider 
behind  than  in  front,  and  convex  from  before  backward.  The  internal  articular 
surface  is  supported  on  a  projecting  process  of  bone,  called  the  lesser  process  of 
the  calcaneum  (sustentaculum  tali) ;  it  is  also  oblong,  concave  longitudinally,  and 
sometimes  subdivided  into  two  parts,  which  differ  in  size  and  shape.  More 
anteriorly  is  seen  the  upper  surface  of  the  greater  process,  marked  by  a  rough 
depression  for  the  attachment  of  numerous  ligaments,  and  a  tubercle  for  the  origin 
of  the  Extensor  brevis  digitorum  muscle. 

The  inferior  surface  is  narrow,  rough,  uneven,  wider  behind  than  in  front 
and  convex  from  side  to  side ;  it  is  bounded  posteriorly  by  two  tubercles  separated 
by  a  rough  depression ;  the  external,  small,  prominent,  and  rounded,  gives  attach- 
ment to  part  of  the  Abductor  minimi  cligiti :  the  internal,  broader  and  larger,  for 
the  support  of  the  heel,  gives  attachment,  by  its  prominent  inner  margin,  to  the 
Abductor  hallucis,  and  in  front  to  the  Flexor  brevis  digitorum  muscles  and  plantar 
fascia;  the  depression  between  the  tubercles  gives  attachment  to  the  Abductor 
minimi  digiti.  'The  rough  surface  in  front  of  the  tubercles  gives  attachment  to  the 
long  plantar  ligament  and  to  the  outer  head  of  the  Flexor  accessorius  muscle  : 
while  to  a  prominent  tubercle  nearer  the  anterior  part  of  this  surface,  as  well  as 
to  a  transverse  groove  in  front  of  it,  is  attached  the  short  plantar  ligament. 

The  external  surface  is  broad,  flat,  and  almost  subcutaneous ;  it  presents  near 
its  centre  a  tubercle,  for  the  attachment  of  the  middle  fasciculus  of  the  external 
lateral  ligament.     At  its  upper  and  anterior  part  this  surface  gives  attachment  to 


200 


THE   SKELETON. 


Groove  for  peroneus  lonqus. 
Groove  for  peroneus  brevis.' — 


PERONEUS  TERTIUS 
PERONEUS  BREVIS. 


Groove  for  tendon  of 

FLEXOR    LONGUS    HALLUOlS. 


Tarsus, 


Metatarsus. 


Innermost  tendon  of 

EXTENSOR    BREVIS    DIGITORUM 


Phalanges. 


EXTENSOR    LONGUS    HALLUCIS 


Fig.  137.-Bones  of  the  right  foot.    Dorsal  surface. 


THE    TARSUS:    THE    CALCANEUM. 


201 


ACCESSORIES 


VIS    HALLUCIS 


TIBIALIS    ANT 


FLEXOR  BREVIS 
O'ld  ABDUCTOR 
MINJMI     DIGITI. 


FLEXOR    BREVIS    DIGlTORUM. 


FLEXOR     LONGUS    DIGlTORUM 


Fig.  138.— Bones  of  the  right  foot.    Plantar  surface. 


202 


THE   SKELETON. 


the  external  calcaneo-astragaloid  ligament ;  and  in  front  of  the  tubercle  it  presents 
a  narrow  surface  marked  by  two  oblique  grooves,  separated  by  an  elevated  ridge 
which  varies  much  in  size  in  different  bones  ;  it  is  named  the  peroneal  tubercle,  and 
gives  attachment  to  a  fibrous  process  from  the  external  annular  ligament.  The 
superior  groove  transmits  the  tendon  of  the  Peroneus  brevis ;  the  inferior,  the 
tendon  of  the  Peroneus  longus. 

The  internal  surface  is  deeply  concave ;  it  is  directed  obliquely  downward  and  for- 
ward, and.  serves  for  the  transmission  of  the  plantar  vessels  and  nerves  into  the  sole  of 
the  foot;  it  affords  attachment  to  part  of  the  Flexor  accessorius  muscle.  At  its  upper 
and  fore  part  it  presents  an  eminence  of  bone,  the  lesser  process  or  sustentaculum 
tali,  which  projects  horizontally  inward,  and  to  it  a  slip  of  the  tendon  of  the 
Tibialis   posticus   is   attached.     This  process  is   concave  above,  and  supports  the 


Peroneal  tubercle. 
Groove  for 
Peroneus  brevis. 


Groove  for 
Peroneus  longus.  Tubercle  for  ext.  lat.  lig. 


For  tendo 
A  chillis. 


For  astragalus. 


Sustentaculum         For  cuboid, 
tali. 

Groove  for  Flex, 
long,  hallucis. 

Fig.  139.— The  left  os  calcis.    a.  Posteroexternal  view.    b.  Antero-internal  view. 


anterior  articular  surface  of  the  astragalus ;  below,  it  is  grooved  for  the  tendon  of 
the  Flexor  longus  hallucis.  Its  free  margin  is  rough,  for  the  attachment  of  part  of 
the  internal  lateral  ligament  of  the  ankle-joint. 

The  anterior  surface,  of  a  somewhat  triangular  form,  articulates  with  the 
cuboid.  It  is  concave  from  above  downward  and  outward,  and  convex  in  the 
opposite  direction.  Its  inner  border  gives  attachment  to  the  inferior  calcaneo- 
navicular ligament. 

The  posterior  surface  is  rough,  prominent,  convex,  and  wider  below  than  above. 
Its  lower  part  is  rongh,  for  the  attachment  of  the  tendo  Achillis  and  the  tendon  of 
the  Plantaris  muscle ;  its  upper  part  is  smooth,  and  is  covered  by  a  bursa  which 
separates  the  tendons  from  the  bone. 

Articulations. — With  two  bones :  the  astragalus  and  cuboid. 

Attachment  of  Muscles. — To  eight :  part  of  the  Tibialis  posticus,   the  tendo 


THE    TARSUS:    THE   ASTRAGALUS. 


203 


Achillis,  Plantaris,  Abductor  hallucis,  Abductor  minimi  digiti,  Flexor  brevis  digi- 
torum,  Flexor  accessorius,  and  Extensor  brevis  digitorum. 

The  Astragalus  (Fig.  140). 
The  Astragalus  (darpdyaAoz,  a  die)  is  the  largest  of  the  tarsal  bones,  next  to 


For 

navicular.     Neck. 


Sup.  surface 
for  tibia. 


For  inner 
malleolus. 

For  navicular. 


For  ezt, 
malleolus 


Groove  for 
Flex.  long.  hall. 


Fur  inferior 
calc.  navic.  lig. 


os  calcis. 
Fig.  140  —The  left  astragalus,    a.  Superior  and  external  view.    b.  Inferior  and  internal  view. 

the  os  calcis.  It  occupies  the  middle  and  upper  part  of  the  tarsus,  supporting  the 
tibia  above,  articulating  with  the  malleoli  on  either  side,  resting  below  upon  the 
os  calcis,  and  joined  in  front  to  the  navicular.  This  bone  may  easily  be  recognized 
by  its  large  rounded  head,  by  the  broad  articular  facet  on  its  upper  convex  surface, 
or  by  the  two  articular  facets  separated  by  a  deep  groove  on  its  under  concave 
surface.     It  presents  six  surfaces  for  examination. 

The  superior  surface  presents,  behind,  a  broad  smooth  trochlear  surface  for 
articulation  with  the  tibia.  The  trochlea  is  broader  in  front  than  behind,  convex 
from  before  backward,  slightly  concave  from  side  to  side  ;  in  front  of  it  is  the  upper 
surface  of  the  neck  of  the  astragalus,  rough  for  the  attachment  of  ligaments. 
The  inferior  surface  presents  two  articular  facets  separated  by  a  deep  groove. 
The  groove  runs  obliquely  forward  and  outward,  becoming  gradually  broader 
and  deeper  in  front :  it  corresponds  with  a  similar  groove  upon  the  upper  surface 
of  the  os  calcis,  and  forms,  when  articulated  with  that  bone,  a  canal,  filled  up  in 
the  recent  state  by  the  interosseous  calcaneo-astragaloid  ligament.  Of  the  two 
articular  facets,  the  posterior  is  the  larger,  of  an  oblong  form  and  deeply  concave 
from  side  to  side ;  the  anterior  is  shorter  and  narrower,  of  an  elongated  oval  form, 
convex  longitudinally,  and  often  subdivided  into  two  by  an  elevated  ridge ;  of 
these,  the  posterior  articulates  with  the  lesser  process  of  the  os  calcis ;  the  anterior, 
with  the  upper  surface  of  the  inferior  calcaneonavicular  ligament.  The  internal 
surface  presents  at  its  upper  part  a  pear-shaped  articular  facet  for  the  inner  malleo- 
lus, continuous  above  with  the  trochlear  surface ;  below  the  articular  surface  is  a 
rough  depression,  for  the  attachment  of  the  deep  portion  of  the  internal  lateral 
ligament.  The  external  surface  presents  a  large  triangular  facet,  concave  from 
above  downward  for  articulation  with  the  external  malleolus  ;  it  is  continuous  above 
with  the  trochlear  surface ;  and  in  front  of  it  is  a  rough  depression  for  the  attach- 
ment of  the  anterior  fasciculus  of  the  external  lateral  ligament  of  the  ankle-joint. 
The  anterior  surface,  convex  and  rounded,  forms  the  head  of  the  astragalus  ;  it  is 
smooth,  of  an  oval  form,  and  directed  obliquely  inward  and  downward  :  it  articu- 
lates with  the  navicular.  On  its  under  and  inner  surface  is  a  small  facet,  continu- 
ous in  front  with  the  articular  surface  of  the  head,  and  behind  with  the  smaller 
facet  for  the  os  calcis.  This  rests  on  the  inferior  calcaneonavicular  ligament,  being 
separated  from  it  by  the  synovial  membrane,  which  is  prolonged  from  the  anterior 
calcaneo-astragaloid  joint  to  the  astragalo-navicular  joint.     The  head  is  surrounded 


204 


THE  SKELETON. 


by  a  constricted  portion,  the  neck  of  the  astragalus.  The  posterior  surface  is 
narrow,  and  traversed  by  a  groove,  which  runs  obliquely  downward  and  inward, 
and  transmits  the  tendon  of  the  Flexor  longus  hallucis,  external  to  which  is  a 
prominent  tubercle,  to  which  the  posterior  fasciculus  of  the  external  lateral  liga- 
ment is  attached.  This  tubercle  is  sometimes  separated  from  the  rest  of  the 
astragalus,  and  is  then  known  as  the  os  trigonum.  To  the  inner  side  of  the  groove 
is  a  second,  but  less  marked,  tubercle. 

To  ascertain  to  which  foot  the  bone  belongs,  hold  it  with  the  broad  articular 
surface  upward,  and  the  rounded  head  forward;  the  lateral  triangular  articular 
surface  for  the  external  malleolus  will  then  point  to  the  side  to  which  the  bone 
belongs. 

Articulations. — With  four  bones :  tibia,  fibula,  os  calcis,  and  navicular. 

The  Cuboid  (Fig.  141). 

The  Cuboid  (xuftoz,  a  cube ;  eldoc,  like)  bone  is  placed  on  the  outer  side  of  the 
foot,  in  front  of  the  os  calcis,  and  behind  the  fourth  and  fifth  metatarsal  bones.     It 

For  fourth 
metatarsal. 


Occasional  facet ■■     Jg 
for  navicular. 


B    rf 


/    % 
Groove  for 
Peroneus  longus.    For  os  calcis. 
■  fifth  metatarsal. 
Fig.  141.— The  left  cuboid,    a.  Antero-mternal  view.    b.  Postero-external  view. 

is  of  a  pyramidal  shape,  its  base  being  directed  inward,  its  apex  outward.  It  may 
be  distinguished  from  the  other  tarsal  bones  by  the  existence  of  a  deep  groove  on 
its  under  surface,  for  the  tendon  of  the  Peroneus  longus  muscle.  It  presents  for 
examination  six  surfaces :   three  articular  and  three  non-articular. 

The  non-articular  surfaces  are  the  superior,  inferior,  and  external.  The 
superior  or  dorsal  surface,  directed  upward  and  outward,  is  rough,  for  the  attach- 
ment of  numerous  ligaments.  The  inferior  or  plantar  surface  presents  in  front  a 
deep  groove,  which  runs  obliquely  from  without,  forward  and  inward  ;  it  lodges 
the  tendon  of  the  Peroneus  longus,  and  is  bounded  behind  by  a  prominent  ridge, 
to  which  is  attached  the  long  calcaneo-cuboid  ligament.  The  ridge  terminates 
externally  in  an  eminence,  the  tuberosity  of  the  cuboid,  the  surface  of  which 
presents  a  convex  facet,  for  articulation  with  the  sesamoid  bone  of  the  tendon 
contained  in  the  groove.  The  surface  of  bone  behind  the  groove  is  rough,  for  the 
attachment  of  the  short  plantar  ligament,  a  few  fibres  of  the  Flexor  brevis  hallucis, 
and  a  fasciculus  from  the  tendon  of  the  Tibialis  posticus.  The  external  surface, 
the  smallest  and  narrowest  of  the  three,  presents  a  deep  notch  formed  by  the 
commencement  of  the  peroneal  groove. 

The  articular  surfaces  are  the  posterior,  anterior,  and  internal.  The  posterior 
surface  is  smooth,  triangular,  and  concavo-convex,  for  articulation  with  the 
anterior  surface  of  the  os  calcis.  The  anterior,  of  smaller  size,  but  also  irregu- 
larly triangular,  is  divided  by  a  vertical  ridge  into  two  facets :  the  inner  one, 
quadrilateral  in  form,  articulates  with  the  fourth  metatarsal  bone ;  the  outer  one, 
larger  and  more  triangular,  articulates  Avith  the  fifth  metatarsal.  The  internal 
surface  is  broad,  rough,  irregularly  quadrilateral,  presenting  at  its  middle  and 
upper  part  a  smooth  oval  facet,  for  articulation  with  the  external  cuneiform  bone ; 
and  behind  this  (occasionally)  a  smaller  facet,  for  articulation  with  the  navic- 
ular ;  it  is  rough  in  the  rest  of  its  extent,  for  the  attachment  of  strong  interosseous 
ligaments. 


THE    CUNEIFORM  BOXES. 


205 


To  ascertain  to  which  foot  the  bone  belongs,  hold  it  so  that  its  under  surface, 
marked  by  the  peroneal  groove,  looks  downward,  and  the  large  concavo-convex 
articular  surface  backward  toward  the  holder :  the  narrow  non-articular  surface, 
marked  by  the  commencement  of  the  peroneal  groove,  will  point  "to  the  side  to 
which  the  bone  belongs. 

Articulations. — With  four  bones :  the  os  calcis,  external  cuneiform,  and  the 
fourth  and  fifth  metatarsal  bones ;  occasionally  with  the  navicular. 

Attachment  of  Muscles. — Part  of  the  Flexor  brevis  hallucis  and  a  slip  from 
the  tendon  of  the  Tibialis  posticus. 


The  Navicular  (Fig.  142). 
The  Navicular  or  Scaphoid  bone  is  situated  at   the  inner  side  of  the  tarsus, 


For  int. 
cuneiform. 


For  mid.  cuneiform. 


For  ext. 
cuneiform. 


For  cuboid 

(occasional) 


Fig.  142.— The  left  navicula 


For  astragalus. 
a.  Antero-external  view.     b.  Posterointernal  view. 


between  the  astragalus  behind  and  the  three  cuneiform  bones  in  front.  It 
may  be  distinguished  by  its  form,  being  concave  behind,  convex  and  subdivided 
into  three  facets  in  front. 

The  anterior  surface,  of  an  oblong  form,  is  convex  from  side  to  side,  and  sub- 
divided by  two  ridges  into  three  facets,  for  articulation  with  the  three  cuneiform 
bones.  The  posterior  surface  is  oval,  concave,  broader  externally  than  internally, 
and  articulates  with  the  rounded  head  of  the  astragalus.  The  superior  surface  is 
convex  from  side  to  side,  and  rough  for  the  attachment  of  ligaments.  The 
inferior'is  irregular,  and  also  rough  for  the  attachment  of  ligaments.  The  interna? 
surface  presents  a  rounded  tubercular  eminence,  the  tuberosity  of  the  navicular, 
the  lower  part  of  which  projects,  and  gives  attachment  to  part  of  the  tendon  of 
the  Tibialis  posticus.  The  external  surface  is  rough  and  irregular,  for  the 
attachment  of  ligamentous  fibres,  and  occasionally  presents  a  small  facet  for 
articulation  with  the  cuboid  bone. 

To  ascertain  to  which  foot  the  bone  belongs,  hold  it  with  the  concave  articular 
surface  backward,  and  the  convex  dorsal  surface  upward ;  the  external  surface — 
i.  e.  the  surface  opposite  the  tubercle — will  point  to  the  side  to  which  the  bone 
belongs. 

Articulations. — With  four  bones  :  astragalus  and  three  cuneiform  ;  occasionally 
also  with  the  cuboid. 

Attachment  of  Muscles. — Part  of  the  Tibialis  posticus. 

The  Cuneiform  Bones. 
The  Cuneiform  Bones  have  received  their  name  from  their  wedge-like  shape 
(cuneus,  a  wedge;  forma,  likeness).  They  form,  with  the  cuboid,  the  anterior 
row  of  the  tarsus,  being  placed  between  the  navicular  behind,  the  three  innermost 
metatarsal  bones  in  front,  and  the  cuboid  externally.  They  are  called  the  first, 
second,  and  third,  counting  from  the  inner  to  the  outer  side  of  the  foot,  and, 
from  their  position,  internal,  middle,  and  external. 


206 


THE   SKELETON, 


The  Internal  Cuneiform  (Fig.  143). 
The  Internal  Cuneiform  is  the  largest  of  the  three.     It  is  situated  at  the  inner 
For  first  For  second     For  middle   side  of  the  foot,  between  the  navicular 


metatarsal. 


metatarsal.       cuneiform. 


For  tendon  of 
Tibialis  ant. 


For  navicular. 


Fig.  143.— The  left  internal  cuneiform 
internal  view.     b.  Posteroexternal  view. 


Antero- 


behind  and  the  base  of  the  first  meta- 
tarsal in  front.  It  may  be  distin- 
guished from  the  other  two  by  its  large 
size,  and  by  its  not  presenting  such  a 
distinct  wedge-like  form.  Without 
the  others  it  may  be  known  by  the 
large,  kidney-shaped  anterior  articu- 
lating surface  and  by  the  prominence 
on  the  inferior  or  plantar  surface  for 
the  attachment  of  the  Tibialis  posti- 
cus. It  presents  for  examination  six 
surfaces. 

The  internal  surface  is  subcuta- 
neous, and  forms  part  of  the  inner  bor- 
der of  the  foot ;  it  is  broad,  quadrilateral,  and  presents  at  its  anterior  inferior  angle  a 
smoot  oval  facet,  into  which  the  tendon  of  the  Tibialis  anticus  is  partially  inserted  ; 
in  the  rest  of  its  extent  it  is  rough,  for  the  attachment  of  ligaments.  The  external 
surface  is  concave,  presenting,  along  its  superior  and  posterior  borders,  a  narrow 
reversed  L-shaped  surface  for  articulation  with  the  middle  cuneiform  behind,  and 
second  metatarsal  bone  in  front ;  in  the  rest  of  its  extent  it  is  rough  for  the 
attachment  of  ligaments  and  part  of  the  tendon  of  the  Peroneus  longus.  The 
anterior  surface,  kidney-shaped,  much  larger  than  the  posterior,  articulates  with 
the  metatarsal  bone  of  the  great  toe.  The  'posterior  surface  is  triangular,  concave, 
and  articulates  with  the  innermost  and  largest  of  the  three  facets  on  the  anterior 
surface  of  the  navicular.  The  inferior  or  plantar  surface  is  rough,  and  presents  a 
prominent  tuberosity  at  its  back  part  for  the  attachment  of  part  of  the  tendon  of 
the  Tibialis  posticus.  It  also  gives  attachment  in  front  to  part  of  the  tendon  of  the 
the  Tibialis  anticus.  The  superior  surface  is  the  narrows-pointed  end  of  the  wedge, 
which  is  directed  upward  and  outward ;  it  is  rough  for  the  attachment  of  ligaments. 
To  ascertain  to  which  side  the  bone  belongs,  hold  it  so  that  its  superior  narrow 
edge  looks  upward,  and  the  long,  kidney-shaped,  articular  surface  forward ;  the 
external  surface,  marked  by  its  vertical  and  horizontal  articular  facets,  will  point 
to  the  side  to  which  it  belongs. 

Articulations. — With  four  bones :  navicular,  middle  cuneiform,  first  and  second 
metatarsal  bones. 

Attachment   of   Muscles. — To  three :    the  Tibialis  anticus  and  posticus,   and 
Peroneus  longus. 

The  Middle  Cuneiform  (Fig.  144). 
The  Middle  Cuneiform,  the  smallest  of  the  three,  is  of  very  regular  wedge-like 

form,  the  broad  extremity  being  placed 
upward,  the  narrow  end  downward.  It  is 
situated  between  the  other  two  bones  of 
the  same  name,  and  articulates  with  the 
navicular  behind  and  the  second  meta- 
tarsal in  front.  It  is  smaller  than  the 
external  cuneiform  bone,  from  which  it 
may  be  further  distinguished  by  the  L- 
shaped  articular  facet,  Avhich  runs  round 
the  upper  and  back  part  of  its  inner 
surface. 

The  anterior  surface,  triangular  in  form 
and  narrower  than  the  posterior,  articulates  with  the  base  of  the  second  meta- 
tarsal bone.    The  posterior  surface,  also  triangular,  articulates  with  the  navicular. 


For  int.  cuneiform 


For  navicular. 


For  ext.  cuneiform. 


Fig.  144  — The  left  middle  cuneiform,  a.  Antero- 
internal  view.    b.  Postero-external  view. 


THE    CUNEIFORM  BONES. 


207 


The  internal  surface  presents  a  reversed  L-shaped  articular  facet,  running  alono- 
the  superior  and  posterior  borders,  for  articulation  with  the  internal  cuneiform, 
and  is  rough  in  the  rest  of  its  extent  for  the  attachment  of  ligaments.  The 
external  surface  presents  posteriorly  a  smooth  facet  for  articulation  with  the 
external  cuneiform  hone.  The  superior  surface  forms  the  base  of  the  wedge;  it 
is  quadrilateral,  broader  behind  than  in  front,  and  rough  for  the  attachment  of 
ligaments.  The  inferior  surface,  pointed  and  tubercular,  is  also  rough  for  liga- 
mentous attachment  and  for  the  insertion  of  a  slip  from  the  tendon  of  the  Tibialis 
posticus. 

To  ascertain  to  which  foot  the  bone  belongs,  hold  its  superior  or  dorsal  surface 
upward,  the  broadest  edge  being  toward  the  holder:  the  smooth  facet  (limited 
to  the  posterior  border)  will  then  point  to  the  side  to  which  it  belongs. 

Articulations. — With  four  bones :  navicular,  internal  and  external  cuneiform, 
and  second  metatarsal  bone. 

Attachment  of  Muscles. — A  slip  from  the  tendon  of  the  Tibialis  posticus  is 
attached  to  this  bone. 


For  cuboid. 


For  third 
second  metatarsal. metatarsal. 


Fig.  145. — The  left  external  cuneiform, 
nal  view.     B.  Antero-extemal  view. 


Postero-inter- 


The  External  Cuneiform  (Fig.  145). 
The  External  Cuneiform,  intermediate  in  size  between  the  two  preceding,  is 
of  a  very  regular  wedge-like  form,  the  broad  extremity  being  placed  upward^the 
narrow  end  downward.     It  occupies 
the  centre  of  the  front  row  of  the  For  n™jcular- 

.  I  tor  mid.  cuneiform. 

tarsus,  between  the  middle  cunei- 
form internally,  the  cuboid  exter- 
nally, the  navicular  behind,  and 
the  third  metatarsal  in  front.  It 
is  distinguished  from  the  internal 
cuneiform  bone  by  its  more  regular 
wedge-like  shape  and  by  the  absence 
of  the  kidney-shaped  articular  sur- 
face :  from  the  middle  cuneiform, 
by  the  absence  of  the  reversed  L- 
shaped  facet,  and  by  the  two  articular  facets  which  are  present  on  both  its  inner 
and  outer  surfaces.     It  has  six  surfaces  for  examination. 

The  anterior  surface,  triangular  in  form,  articulates  with  the  third  metatarsal 
bone.  The  posterior  surface  articulates  with  the  most  external  facet  of  the 
navicular,  and  is  rough  below  for  the  attachment  of  ligamentous  fibres.  The 
internal  surface  presents  two  articular  facets,  separated  by  a  rough  depression  ; 
the  anterior  one,  sometimes  divided  into  two,  articulates  with  the  outer  side  of  the 
base  of  the  second  metatarsal  bone ;  the  posterior  one  skirts  the  posterior  border 
and  articulates  with  the  middle  cuneiform  ;  the  rough  depression  between  the  two 
gives  attachment  to  an  interosseous  ligament.  The  external  surface  also  presents 
two  articular  facets,  separated  by  a  rough  non-articular  surface ;  the  anterior  facet, 
situated  at  the  superior  angle  of  the  bone,  is  small,  and  articulates  with  the  inner 
side  of  the  base  of  the  fourth  metatarsal;  the  posterior  and  larger  one  articulates 
with  the  cuboid ;  the  rough,  non-articular  surface  serves  for  the  attachment  of  an 
interosseous  ligament.  The  three  facets  for  articulation  with  the  three  metatarsal 
bones  are  continuous  with  one  another,  and  covered  by  a  prolongation  of  the  same 
cartilage ;  the  facets  for  articulation  with  the  middle  cuneiform  and  navicular  are 
also  continuous,  but  that  for  articulation  with  the  cuboid  is  usually  separate.  The 
superior  or  dorsal  surface  is  of  an  oblong  scpuare  form,  its  posterior  external  angle 
being  prolonged  backward.  The  inferior  or  plantar  surface  is  an  obtuse  rounded 
margin,  and  serves  for  the  attachment  of  part  of  the  tendon  of  the  Tibialis  posticus, 
part  of  the  Flexor  brevis  hallucis,  and  ligaments. 

To  ascertain  to  which  side  the  bone  belongs,  hold  it  with  the  broad  dorsal 


208 


THE  SKELETON. 


surface  upward,  the  prolonged  edge  backward ;  the  separate  articular  facet  for  the 
cuboid  will  point  to  ihe  proper  side. 

Articulations. — With  six  bones  :  the  navicular,  middle  cuneiform,  cuboid,  and 
second,  third,  and  fourth  metatarsal  bones. 

Attachment  of  Muscles. — To  two :  part  of  the  Tibialis  posticus,  and  Flexor 
brevis  hallucis. 

The  number  of  tarsal  bones  may  be  reduced  owing  to  congenital  ankylosis, 
which  may  occur  between  the  os  calcis  and  cuboid,  the  os  calcis  and  navicular,  the 
os  calcis  and  astragalus,  or  the  astragalus  and  navicular. 


The  Metatarsal  Bones. 

The  Metatarsal  Bones  are  five  in  number,  and  are  numbered  one  to  five,  in 
accordance  with  their  position  from  within  outward;  they  are  long  bones,  and 
present  for  examination  a  shaft  and  two  extremities. 

Common  Characters. — The  shaft  is  prismoid  in  form,  tapers  gradually  from  the 
tarsal  to  the  phalangeal  extremity,  and  is  slightly  curved  longitudinally,  so  as  to 
be  concave  below,  slightly  convex  above.  The  posterior  extremity,  or  base,  is 
wedge-shaped,  articulating  by  its  terminal  surface  with  the  tarsal  bones,  and  by 
its  lateral  surfaces  with  the  contiguous  metatarsal  bones,  its  dorsal  and  plantar 
surfaces  being  rough  for  the  attachment  of  ligaments.  The  anterior  extremity, 
or  head,  presents  a  terminal  rounded  articular  surface,  oblong  from  above 
downward,  and  extending  farther  backward  below  than  above.  Its  sides  are 
flattened  and  present  a  depression,  surmounted  by  a  tubercle,  for  ligamentous 
attachment.  Its  under  surface  is  grooved  in  the  middle  line  for  the  passage 
of  the  Flexor  tendon,  and  marked  on  each  side  by  an  articular  eminence 
continuous  with  the  terminal  articular  surface. 

Peculiar  Characters. — The  First 
(Fig.  146)  is  remarkable  for  its 
great  thickness,  but  is  the  shortest 


of  all  the  metatarsal  bones.  The 
shaft  is  strong  and  of  well-marked 
prismoid  form.  The  posterior  ex- 
tremity presents,  as  a  rule,  no  lateral 
articular  facet,  but  occasionally  on 
the  outer  side  there  is  an  oval  facet 
by  which  it  articulates  with  the 
second  metatarsal  bones.  Its  ter- 
minal articular  surface  is  of  large 
size,  kidney-shaped;  its  circumfer- 
ence is  grooved,  for  the  tarso-meta- 
tarsal  ligaments,  and  internallv 
gives  attachment  to  part  of  the 
tendon  of  the  Tibialis  anticus :  its 
inferior  angle  presents  a  rough 
oval  prominence  for  the  insertion 
of  the  tendon  of  the  Peroneus 
longus.     The  head  is  of  large  size  ; 

on  its  plantar  surface  are  two  grooved  facets,  over  which  glide  sesamoid  bones ; 

the  facets  are  separated  by  a  smooth  elevated  ridge. 

This  bone  is  known  by  the  single  kidney-shaped  articular  surface  on  its  base, 

the  deeply  grooved  appearance  of  the  plantar  surface  of  its  head,  and  its  great 

thickness  relatively  to  its  length.     When  it  is  placed  in  its  natural  position,  the 

concave  border  of  the  kidney-shaped  articular  surface  on  its  base  points  to  the 

side  to  which  the  bone  belongs. 

Attachment  of  Muscles. — To  three:  part  of  the  Tibialis  anticus,  the  Peroneus 

longus,  and  the  First  dorsal  interosseous. 


For  internal  cuneiform. 


Occasional  facet  for 
second  metatarsal. 


Fig.  146.— The  first  metatarsal.    (Left.) 


THE  METATARSAL  BONES. 


209 


The  Second  (Fig.  147)  is  the  longest  and  largest  of  the  remaining  metatarsal 
bones,  being  prolonged  backward  into  the  recess  formed  between  the  three  cunei- 
form bones.  Its  tarsal  extremity  is  broad  above,  narrow  and  rough  below.  It 
presents  four  articular  surfaces :  one  behind,  of  a  triangular  form,  for  articulation 
with  the  middle  cuneiform;  one  at  the  upper  part  of  its  internal  lateral  surface, 
for  articulation  with  the  internal  cuneiform :  and  two  on  its  external  lateral  sur- 
face— an  upper  and  a  lower,  separated  by  a  rough  non-articular  interval.  Each  of 
these  articular  surfaces  is  divided  by  a  vertical  ridge  into  two  facets,  thus  making 
four  facets;  the  two  anterior  of  these  articulate  with  the  third  metatarsal;  the 
two  posterior  (sometimes  continuous)  with  the  external  cuneiform.     In  addition 


fc,  »j 


Occasional 
facet  for  first 
metatarsal. 
For  middle  cuneiform. 


For  external 
cuneiform. 


Fig.  147. — The  second  metatarsal.    (Left.) 


/  For  second  metatarsal.  For  fourth 

For  middle  cuneiform.  metatarsal. 

Fig.  148.— The  third  metatarsal.    (Left.) 


to  these  articular  surfaces  there  is  occasionally  a  fifth  when  this  bone  articulates 
with  the  first  metatarsal  bone.  It  is  oval  in  shape,  and  is  situated  on  the  inner 
side  of  the  shaft  near  the  base. 

The  facets  on  the  tarsal  extremity  of  the  second  metatarsal  bone  serve  at 
once  to  distinguish  it  from  the  rest,  and  to  indicate  the  foot  to  which  it  belongs; 
there  being  one  facet  at  the  upper  angle  of  the  internal  surface,  and  two  facets, 
each  subdivided  into  two  parts,  on  the  external  surface,  pointing  to  the  side  to 
which  the  bone  belongs.  The  fact  that  the  two  posterior  subdivisions  of  these 
external  facets  sometimes  run  into  one  should  not  be  forgotten. 

Attachment  of  Muscles. — To  four  :  the  Adductor  obliquus  hallucis,  First  and 
Second  dorsal  interosseous,  and  a  slip  from  the  tendon  of  the  Tibialis  posticus ; 
occasionally  also  a  slip  from  the  Peroneus  longus. 

The  Third  (Fig.  148)  articulates  behind,  by  means  of  a  triangular  smooth 
surface,  with  the  external  cuneiform  ;  on  its  inner  side,  by  two  facets,  with  the 
second  metatarsal;  and  on  its  outer  side,  by  a  single  facet,  with  the  fourth  meta- 
tarsal. The  latter  facet  is  of  circular  form  and  situated  at  the  upper  angle  of 
the  base. 

The  third  metatarsal  is  known  by  its  having  at  its  tarsal  end  two  undivided 
facets  on  the  inner  side,  and  a  single  facet  on  the  outer.  This  distinguishes  it 
from  the  second  metatarsal,  in  which  the  two  facets,  found  on  one  side  of  its 
tarsal  end,  are  each  subdivided  into  two.  The  single  facet  (when  the  bone  is  put 
in  its  natural  position)  is  on  the  side  to  which  the  bone  belongs. 

14 


210 


THE  SKELETON. 


Attachment  of  Muscles. — To  five :  Adductor  obliquus  hallucis,  Second  and. 
Third  dorsal,  and  First  plantar  interosseous,  and  a  slip  from  the  tendon  of  the 
Tibialis  posticus. 

The  Fourth  (Fig.  149)  is  smaller  in  size  than  the  preceding ;  its  tarsal 
extremity  presents  a  terminal  quadrilateral  surface,  for  articulation  with  the 
cuboid ;  a  smooth  facet  on  the  inner  side,  divided  by  a  ridge  into  an  anterior 
portion  for  articulation  with  the  third  metatarsal,  and  a  posterior  portion  for 
articulation  with  the  external  cuneiform  ;  on  the  outer  side  a  single  facet,  for 
articulation  with  the  fifth  metatarsal. 

The  fourth  metatarsal  is  known  by  its  having  a  single  facet  on  either  side  of 
the  tarsal  extremity,  that  on  the  inner  side  being  divided  into  two  parts.  If  this- 
subdivision  be  not  recognizable,  the  fact  that  its  tarsal  end  is  bent  somewhat  out- 
ward will  indicate  the  side  to  which  it  belongs. 

Attachment  of  Muscles. — To  five :  Adductor  obliquus  hallucis,  Third  and 
Fourth  dorsal,  and  Second  plantar  interosseous,  and  a  slip  from  the  tendon  of  the 
Tibialis  posticus. 


For  cuboid 
For  ext.  cuneiform. 


For  fifth 
metatarsal. 


Tuberosity. 


Fig.  149.— The  fourth  metatarsal.    (Left.) 


For  fourth 
metatarsal.     \ 
For  cuboid. 

Fig.  150.— The  fifth  metatarsal.    (Left.) 


The  Fifth  (Fig.  150)  is  recognized  by  the  tubercular  eminence  on  the  outer 
side  of  its  base.  It  articulates  behind,  by  a  triangular  surface  cut  obliquely 
from  without  inward,  with  the  cuboid,  and  internally  with  the  fourth  metatarsal. 

The  projection  on  the  outer  side  of  this  bone  at  its  tarsal  end  at  once  dis- 
tinguishes it  from  the  others,  and  points  to  the  side  to  which  it  belongs. 

Attachment  of  Muscles. — To  six :  the  Peroneus  brevis,  Peroneus  tertius, 
Flexor  brevis  minimi  digiti,  Adductor  transversus  hallucis,  Fourth  dorsal,  and 
Third  plantar. 

Articulations. — Each  bone  articulates  with  the  tarsal  bones  by  one  extremity, 
and  by  the  other  with  the  first  row  of  phalanges.  The  number  of  tarsal  bones 
with  which  each  metatarsal  articulates  is  one  for  the  first,  three  for  the  second, 
one  for  the  third,  two  for  the  fourth,  and  one  for  the  fifth. 


The  Phalanges. 

The  Phalanges  of  the  foot,  both  in  number  and  general  arrangement,  resemble 
those  in  the  hand ;  there  being  two  in  the  great  toe  and  three  in  each  of  the  other 
toes. 


CONSTRUCTION   OF    THE   FOOT  AS  A    WHOLE.  211 

The  phalanges  of  the  first  row  resemble  closely  those  of  the  hand.  The  shaft 
is  compressed  from  side  to  side,  convex  above,  concave  below.  The  posterior 
extremity  is  concave ;  and  the  anterior  extremity  presents  a  trochlear  surface,  for 
articulation  with  the  second  phalanges. 

The  phalanges  of  the  second  row  are  remarkably  small  and  short,  but  rather 
broader  than  those  of  the  first  row. 

The  ungual  phalanges  in  form  resemble  those  of  the  fingers  ;  but  they  are 
smaller,  flattened  from  above  downward,  presenting  a  broad  base  for  articulation 
with  the  second  row,  and  an  expanded  extremity  for  the  support  of  the  nail  and 
end  of  the  toe. 

Articulation. — The  first  row,  with  the  metatarsal  bones  behind  and  second 
phalanges  in  front ;  the  second  row  of  the  four  outer  toes,  with  the  first  and  third 
phalanges  ;  of  the  great  toe,  with  the  first  phalanx ;  the  third  row  of  the  four 
outer  toes,  with  the  second  phalanges. 

Attachment  of  Muscles. — To  the  first  phalanges.  Great  toe,  five  muscles : 
innermost  tendon  of  Extensor  brevis  digitorum,  Abductor  hallucis,  Adductor 
obliquus  hallucis,  Flexor  brevis  hallucis,  Adductor  transversus  hallucis.  Second 
toe,  three  muscles:  First  and  Second  dorsal  interosseous  and  First  lumbrical. 
Third  toe,  three  muscles  :  Third  dorsal  and  First  plantar  interosseous  and  Second 
lumbrical.  Fourth  toe,  three  muscles  :  Fourth  dorsal  and  Second  plantar  inter- 
osseous and  Third  lumbrical.  Fifth  toe,  four  muscles  :  Flexor  brevis  minimi 
digiti,  Abductor  minimi  digiti,  and  Third  plantar  interosseous,  and  Fourth 
lumbrical. — Second  phalanges.  Great  toe ;  Extensor  longus  hallucis,  Flexor 
longus  hallucis.  Other  toes ;  Flexor  brevis  digitorum,  one  slip  of  the  common 
tendon  of  the  Extensor  longus  and  brevis  digitorum.1 — Third  phalanges  :  two  slips 
from  the  common  tendon  of  the  Extensor  longus  and  Extensor  brevis  digitorum, 
and  the  Flexor  longus  digitorum. 

Development  of  the  Foot  (Fig.  151). 

The  Tarsal  bones  are  each  developed  by  a  single  centre,  excepting  the  os  calcis, 
which  has  an  epiphysis  for  its  posterior  extremity.  The  centres  make  their  appear- 
ance in  the  following  order :  os  calcis,  at  the  sixth  month  of  foetal  life ;  astragalus, 
about  the  seventh  month ;  cuboid,  at  the  ninth  month ;  external  cuneiform, 
during  the  first  year ;  internal  cuneiform  in  the  third  year ;  middle  cuneiform  and 
navicular  in  the  fourth  year.  The  epiphysis  for  the  posterior  tuberosity  of 
the  os  calcis  appears  at  the  tenth  year,  and  unites  with  the  rest  of  the  bone  soon 
after  puberty. 

The  Metatarsal  bones  are  each  developed  by  tivo  centres :  one  for  the  shaft 
and  one  for  the  digital  extremity  in  the  four  outer  metatarsal ;  one  for  the  shaft 
and  one  for  the  base  in  the  metatarsal  bone  of  the  great  toe.2  Ossification 
commences  in  the  centre  of  the  shaft  about  the  ninth  week,  and  extends  toward 
either  extremity.  The  centre  in  the  proximal  end  of  the  first  metatarsal  bone 
appears  about  the  third  year,  the  centre  in  the  distal  end  of  the  other  bones 
between  the  fifth  and  eighth  years;  they  become  joined  between  the  eighteenth  and 
twentieth  years. 

The  Phalanges  are  developed  by  two  centres  for  each  bone :  one  for  the  shaft 
and  one  for  the  metatarsal  extremity.  The  centre  for  the  shaft  appears  about  the 
tenth  week,  that  for  the  epiphysis  between  the  fourth  and  tenth  years ;  they  join 
the  shaft  about  the  eighteenth  year. 

Construction  of  the  Foot  as  a  Whole. 

The  foot  is  constructed  on  the  same  principles  as  the  hand,  but  modified  to  form 
a  firm  basis  of  support  for  the  rest  of  the  body  when  in  the   erect   position.     It 

1  Except  the  second  phalanx  of  the  fifth  toe,  which  receives  no  slip  from  the  Extensor  brevis 
digitorum. 

2  As  was  noted  in  the  first  metacarpal  bone,  so  in  the  first  metatarsal,  there  is  often  to  be  observed 
a  tendency  to  the  formation  of  a  second  epiphysis  in  the  distal  extremity.     (See  footnote,  p.  171.) 


212 


THE  SKELETON. 


is  more  solidly  constructed,  and  its  component  parts  are  less  movable  on  each  other 
than  in  the  hand.  This  is  especially  the  case  Avith  the  great  toe,  which  has  to 
assist  in  supporting  the  body,  and  is  therefore  constructed  with  greater  solidity ;  it 
lies  parallel  with  the  other  toes,  and  has  a  very  limited  degree  of  mobility,  whereas 
the  thumb,  which  is  occupied  in  numerous  and  varied  movements,  is  constructed 
in  such  a  manner  as  to  permit  of  great  mobility.  Its  metacarpal  bone  is  directed 
away  from  the  others,  so  as  to  form  an  acute  angle  with  the  second,  and  it  enjoys 
a  considerable  range  of  motion  at  its  articulation  with  the  carpus.  The  foot  is 
placed  at  right  angles  to  the  leg — a  position  which  is  almost  peculiar  to  man,  and 
has  relation  to  the  erect  position  which  he  maintains.  In  order  to  allow  of  its 
supporting  the  weight  of  the  whole  body  in  this  position  with  the  least  expenditure 
of  material,  it  is  constructed  in  the  form  of  an  arch.  This  arch  is  not,  however, 
made  up  of  two  equal  limbs.  The  hinder  one,  which  is  made  up  of  the  os  calcis 
and  the  posterior  part  of  the  astragalus,  is  about  half  the  length  of  the  anterior 
limb,  and  measures  about  three  inches.      The  anterior  limb  consists  of  the  rest  of 


y  sis. 


.Appears  10th  year  ; 

unites  after  puberty. 


Tarsus. 

One  centre  for  each,  hone, 
except  os  calcis. 


Metatarsus. 

Two  centres  for  each  bone 
One  for  shaft, 
One  for  digital  extremity 
except  1st. 

Appears  7th  week, 

Unite  18th-20th  year. 

Appears  3rd  year,     'mad) 

Appears  4-th  year. 
Unite  17-18th  year. 
Phalanges.    Appears  2nd~4th  month 
Two  centres  for  each  bone : 
One  for  shaft, 

One  for  metatarsal       Appears  6th-7th  year. 
extremity.  Unite  27th-18lh  year 


Appears  5th  year. 
Unite  18th-20  year. 


-Appears  7th  week. 


(  .l£=3S 


^3 


Appears  2nd~4th  monthr^J^t  J»  f 

Appears  6th  year.-^^,  s  (W 

Unite  17th-  18th  year.-{  „  ~ 
Appeai-s  7th  week.  — <»J>  Jj 

Fig.  151.— Plan  of  the  development  of  the  foot. 

the  tarsal  and  the  metatarsal  bones,  and  measures  about  seven  inches.  It  may  be 
said  to  consist  of  two  parts,  an  inner  segment  made  up  of  the  head  of  the  astragalus, 
the  navicular,  the  three  cuneiform,  and  the  three  inner  metatarsal  bones ;  and  an 
outer  segment  composed  of  the  os  calcis,  the  cuboid,  and  the  two  outer  metatarsal 
bones.  The  summit  of  the  arch  is  at  the  superior  articular  surface  of  the  astragalus ; 
and  its  two  extremities — that  is  to  say,  the  two  piers  on  which  the  arch  rests  in 
standing — are  the  tubercles  on  the  under  surface  of  the  os  calcis  posteriorly,  and 


SURGICAL    ANATOMY   OF    THE   FOOT.  213 

the  heads  of  the  metatarsal  bones  anteriorly.  The  weakest  part  of  the  arch  is  the 
joint  between  the  astragalus  and  scaphoid,  and  here  it  is  more  liable  to  yield  in 
those  who  are  overweighted,  and  in  those  in  whom  the  ligaments  which  complete 
and  preserve  the  arch  are  relaxed.  This  weak  point  in  the  arch  is  braced  on  its 
concave  surface  by  the  inferior  calcaneonavicular  ligament,  which  is  more  elastic 
than  most  other  ligaments,  and  thus  allows  the  arch  to  yield  from  jars  or  shocks 
applied  to  the  anterior  portion  of  the  foot  and  quickly  restores  it  to  its  pristine  con- 
dition. This  ligament  is  supported  internally  by  blending  with  the  Deltoid  ligament, 
and  inferiorly  by  the  tendon  of  the  Tibialis  posticus  muscle,  which  is  spread  out 
into  a  fan-shaped  insertion,  and  prevents  undue  tension  of  the  ligament  or  such  an 
amount  of  stretching  as  would  permanently  elongate  it. 

In  addition  to  this  longitudinal  arch  the  foot  presents  a  transverse  arch,  at  the 
anterior  part  of  the  tarsus  and  hinder  part  of  the  metatarsus.  This,  however,  can 
scarcely  be  described  as  a  true  arch,  but  presents  more  the  character  of  a  half-dome. 
The  inner  border  of  the  central  portion  of  the  longitudinal  arch  is  elevated  from 
the  ground,  and  from  this  point  the  bones  arch  over  to  the  outer  border,  which  is 
in  contact  with  the  ground,  and,  assisted  by  the  longitudinal  arch,  produce  a  sort  of 
rounded  niche  on  the  inner  side  of  the  foot,  which  gives  the  appearance  of  a 
transverse  as  well  as  a  longitudinal  arch. 

The  line  of  the  foot,  from  the  point  of  the  heel  to  the  toes,  is  not  quite  straight, 
but  is  directed  a  little  outward,  so  that  the  inner  border  is  a  little  convex  and  the 
outer  border  concave.  This  disposition  of  the  bones  becomes  more  marked  when 
the  longitudinal  arch  of  the  foot  is  lost,  as  in  the  disease  known  under  the  name 
of  "flat-foot." 

Surface  Form. — On  the  dorsum  of  the  foot  the  individual  bones  are  not  to  be  distinguished 
with  the  exception  of  the  head  of  the  astragalus,  which  forms  a  rounded  projection  in  front  of 
the  ankle-joint  when  the  foot  is  forcibly  extended.  The  whole  surface  forms  a  smooth  convex 
outline,  the  summit  of  which  is  the  ridge  formed  by  the  head  of  the  astragalus,  the  navicular, 
the  middle  cuneiform,  and  the  second  metatarsal  bones ;  from  this  it  gradually  inclines  outward 
and  more  rapidly  inward.  On  the  inner  side  of  the  foot,  the  internal  tuberosity  of  the  os  calcis 
and  the  ridge  separating  the  inner  from  the  posterior  surface  of  the  bone  may  be  felt  most  pos- 
teriorly. In  front  of  this,  and  below  the  internal  malleolus,  may  be  felt  the  projection  of  the 
sustentaculum  tali.  Passing  forward  is  the  well-marked  tuberosity  of  the  navicular  bone,  situ- 
ated about  an  inch  or  an  inch  and  a  quarter  in  front  of  the  internal  malleolus.  Further  toward 
the  front,  the  ridge  formed  by  the  base  of  the  first  metatarsal  bone  can  be  obscurely  felt,  and 
from  this  the  shaft  of  the  bone  can  be  traced  to  the  expanded  head  articulating  -with  the  base 
of  the  first  phalanx  of  the  great  toe.  Immediately  beneath  the  base  of  this  phalanx,  the 
internal  sesamoid  bone  is  to  be  felt.  Lastly,  the  expanded  ends  of  the  bones  forming  the  last 
joint  of  the  great  toe  are  to  be  felt.  On  the  outer  side  of  the  foot  the  most  posterior  bony 
point  is  the  outer  tuberosity  of  the  os  calcis,  with  the  ridge  separating  the  posterior  from  the 
outer  surface  of  the  bone.  In  front  of  this  the  greater  part  of  the  external  surface  of  the  os 
calcis  is  subcutaneous ;  on  it,  below  and  in  front  of  the  external  malleolus,  may  be  felt  the  pero- 
neal ridge,  when  this  process  is  present.  Farther  forward,  the  base  of  the  fifth  metatarsal  bone 
forms  a  prominent  and  well-defined  landmark,  and  in  front  of  this  the  shaft  of  the  bone,  with 
its  expanded  head,  and  the  base  of  the  first  phalanx  may  be  defined.  The  sole  of  the  foot  is 
almost  entirely  covered  by  soft  parts,  so  that  but  few  bony  parts  are  to  be  made  out,  and  these 
somewhat  obscurely.  The  hinder  part  of  the  under  surface  of  the  os  calcis  and  the  heads  of  the 
metatarsal  bones,  with  the  exception  of  the  first,  which  is  concealed  by  the  sesamoid  bones, 
may  be  recognized. 

Surgical  Anatomy. — Considering  the  injuries  to  which  the  foot  is  subjected,  it  is  surpris- 
ing how  seldom  the  tarsal  bones  are  fractured.  This  is  no  doubt  due  to  the  fact  that  the  tarsus 
is  composed  of  a  number  of  bones,  articulated  by  a  considerable  extent  of  surface  and  joined 
together  by  very  strong  ligaments,  which  serve  to  break  the  force  of  violence  applied  to  this 
part  of  the  body.  When  fracture  does  occur,  these  bones,  being  composed  for  the  most  part 
of  a  soft  cancellous  structure,  covered  only  by  a  thin  shell  of  compact  tissue,  are  often  extensively 
comminuted,  especially  as  most  of  the  fractures  are  produced  by  direct  violence.  And  having 
only  a  very  scanty  amount  of  soft  parts  over  them,  the  fractures  are  very  often  compound,  and 
amputation  is  frequently  necessary. 

When  fracture  occurs  in  the  anterior  group  of  tarsal  bones,  it  is  almost  invariably  the  result 
of  direct  violence  ;  but  fractures  of  the  posterior  group,  that  is,  of  the  calcaneum  and  astrag- 
alus, are  most  frequently  produced  by  falls  from,  a  height  on  to  the  feet ;  though  fracture  of 
the  os  calcis  may  be  caused  by  direct  violence  or  by  muscular  action.  The  posterior  part  of  the 
bone,  that  is,  the  part  behind  the  articular  surfaces,  is  almost  always  the  seat  of  the  fracture, 
though  some  few  cases  of  fracture  of  the  sustentaculum  tali  and  of  vertical  fracture  between 
the  two  articulating  facets  have  been  recorded.     The  neck  of  the  astragalus,  being  the  weakest 


214  THE  SKELETON. 

part  of  the  bone,  is  most  frequently  fractured,  though  fractures  may  occur  in  any  part  and 
almost  in  any  direction,  either  associated  or  not  with  fracture  of  other  bones. 

In  cases  of  club-foot,  especially  in  congenital  cases,  the  bones  of  the  tarsus  become  altered 
in  shape  and  size,  and  displaced  from  their  proper  positions.  This  is  especially  the  case  in  con- 
genital equino-varus,  in  which  the  astragalus,  particularly  about  the  head,  becomes  twisted  and 
atrophied,  and  a  similar  condition  may  be  present  in  the  other  bones,  more  especially  the  navic- 
ular. The  tarsal  bones  are  peculiarly  liable  to  become  the  seat  of  tuberculous  caries  from  com- 
paratively trivial  injuries.  There  are  several  reasons  to  account  for  this.  They  are  composed 
of  a  delicate  cancellated  structure,  surrounded  by  intricate  synovial  membranes.  They  are  situ- 
ated at  the  farthest  point  from  the  central  organ  of  the  circulation  and  exposed  to  vicissitudes 
of  temperature ;  and,  moreover,  on  their  dorsal  surface  are  thinly  clad  with  soft  parts  which 
have  but  a  scanty  blood-supply.  And  finally,  after  slight  injuries,  they  are  not  maintained  in  a 
condition  of  rest  to  the  same  extent  as  similar  injuries  in  some  other  parts  of  the  body.  Caries 
of  the  calcaneum  or  astragalus  may  remain  limited  to  the  one  bone  for  a  long  period,  but  when 
one  of  the  other  bones  is  affected,  the  remainder  frequently  become  involved,  in  consequence 
of  the  disease  spreading  through  the  large  and  complicated  synovial  membrane  which  is  more 
or  less  common  to  these  bones. 

Amputation  of  the  whole  or  a  part  of  the  foot  is  frequently  required  either  for  injury  or 
disease.  The  principal  amputations  areas  follow:  (1)  Syme's  :  amputation  at  the  ankle-joint 
by  a  heel-flap,  with  removal  of  the  malleoli  and  sometimes  a  thin  slice  from  the  lower  end  of 
the  tibia.  (2)  Roux's:  amputation  at  the  ankle-joint  by  a  large  internal  flap.  (3)  Pirogoff's 
amputation :  removal  of  the  whole  of  the  tarsal  bones,  except  the  posterior  part  of  the  os  calcis 
and  a  thin  slice  from  the  tibia  and  fibula  including  the  two  malleoli.  The  sawn  surface  of  the 
os  calcis  is  then  turned  up  and  united  to  the  similar  surface  of  the  tibia.  (4)  Subastragaloid 
amputation  :  removal  of  the  foot  below  the  astragalus  through  the  joint  between  it  and  the  os 
calcis.  This  operation  has  been  modified  by  Hancock,  who  leaves  the  posterior  third  of  the  os 
calcis  and  turns  it  up  against  the  denuded  surface  of  the  astragalus.  This  latter  operation  is  of 
doubtful  utility  and  is  rarely  performed.  (5)  Chopart's  or  medio-tarsal :  removal  of  the  ante- 
rior part  of  the  foot  with  all  the  tarsal  bones  except  the  os  calcis  and  astragalus ;  disarticula- 
tion being  effected  through  the  joints  between  the  astragalo-scaphoid  and  calcaneo-cuboid  in 
joints.  (6)  Lisfranc's :  amputation  of  the  anterior  part  of  the  foot  through  the  tarso-metatarsal 
joints.  This  has  been  modified  by  Hey,  who  disarticulated  through  the  joints  of  the  four  outer 
metatarsal  bones  with  the  tarsus,  and  sawed  off  the  projecting  internal  cuneiform  ;  and  by  Skey, 
who  sawed  off  the  base  of  the  second  metatarsal  bone  and  disarticulated  the  others. 

The  bones  of  the  tarsus  occasionally  require  removal  individually.  This  is  especially  the 
case  with  the  astragalus  and  os  calcis  for  disease  limited  to  the  one  bone,  or  again  the  astragalus 
may  require  excision  in  cases  of  subastragaloid  dislocation,  or,  as  recommended  by  Mr.  Lund, 
in  cases  of  inveterate  talipes.  The  cuboid  has  been  removedfor  the  same  reason  by  Mr.  Solly. 
But  both  these  two  latter  operations  have  fallen  very  much  into  disuse,  and  have  been  super- 
seded by  resection  of  a  wedge-shaped  piece  of  bone  from  the  outer  side  of  the  tarsus.  Finally, 
Mickulicz  and  Watson  have  devised  operations  for  the  removal  of  more  extensive  portions  of 
the  tarsus.  Mikulicz's  operation  consists  in  the  removal  of  the  os  calcis  and  astragalus,  along 
with  the  articular  surfaces  of  the  tibia  and  fibula,  and  also  of  the  scaphoid  and  cuboid.  The 
remaining  portion  of  the  tarsus  is  then  brought  into  contact  with  the  sawn  surfaces  of  the  tibia 
and  fibula,  and  fixed  there.  The  result  is  a  position  of  the  shortened  foot  resembling  talipes 
equinus.  Watson's  operation  is  adapted  to  those  cases  where  the  disease  is  confined  to  the 
anterior  tarsal  bones.  By  two  lateral  incisions  he  saws  through  the  bases  of  the  metatarsal 
bones  in  front  and  opens  up  the  joints  between  the  scaphoid  and  astragalus,  and  the  cuboid  and 
os  calcis,  and  removes  the  intervening  bones. 

The  metatarsal  bones  and  phalanges  are  nearly  always  broken  by  direct  violence,  and  in  the 
majority  of  cases  the  injury  is  the  result  of  severe  crushing  accidents,  necessitating  amputation. 
The  metatarsal  bones,  and  especially  that  of  the  great  toe,  are  frequently  diseased,  either  in 
tubercular  subjects  or  in  perforating  ulcer  of  the  foot. 

Sesamoid  Bones. 

These  are  small  rounded  masses,  cartilaginous  in  early  life,  osseous  in  the  adult, 
which  are  developed  in  those  tendons  which  exert  a  great  amount  of  pressure  upon 
the  parts  over  which  they  glide.  It  is  said  that  they  are  more  commonly  found,  in 
the  male  than  in  the  female,  and  in  persons  of  an  active  muscular  habit  than  in 
those  who  are  weak  and  debilitated.  They  are  invested  throughout  their  whole 
surface  by  the  fibrous  tissue  of  the  tendon  in  which  they  are  found,  excepting  upon 
that  side  which  lies  in  contact  with  the  part  over  which  they  play,  where  they 
present  a  free  articular  facet.  They  may  be  divided  into  two  kinds :  those  which 
glide  over  the  articular  surfaces  of  joints,  and  those  which  play  over  the  cartilag- 
inous facets  found  on  the  surfaces  of  certain  bones. 


SESAMOID   BONES.  215 

The  sesamoid  bones  of  the  joints  in  the  upper  extremity,  are  two  on  the  palmar 
surface  of  the  metacarpo-phalangeal  joint  in  the  thumb,  developed  in  the  tendons 
of  the  Flexor  brevis  pollicis ;  occasionally  one  or  two  opposite  the  metacarpo- 
phalangeal articulations  of  the  fore  and  little  fingers ;  and,  still  more  rarely,  one 
opposite  the  same  joints  of  the  third  and  fourth  fingers.  In  the  lower  extremity, 
the  patella,  which  is  developed  in  the  tendon  of  the  Quadriceps  extensor ;  two  small 
sesamoid  bones,  found  in  the  tendons  of  the  Flexor  brevis  hallucis,  opposite  the 
metatarso-phalangeal  joint  of  the  great  toe ;  and  occasionally  one  in  the  metatarso- 
phalangeal joint  of  the  second  toe,  the  little  toe,  and,  still  more  rarely,  the  third 
and  fourth  toes. 

Those  found  in  the  tendons  which  glide  over  certain  bones  occupy  the  following 
situations :  one  sometimes  found  in  the  tendon  of  the  Biceps  cubiti,  opposite  the 
tuberosity  of  the  radius  :  one  in  the  tendon  of  the  Peroneus  longus,  where  it  glides 
through  the  groove  in  the  cuboid  bone ;  one  appears  late  in  life  in  the  tendon  of  the 
Tibialis  anticus,  opposite  the  smooth  facet  of  the  internal  cuneiform  bone ;  one  is 
found  in  the  tendon  of  the  Tibialis  posticus,  opposite  the  inner  side  of  the  head  of  the 
astragalus ;  one  in  the  outer  head  of  the  Gastrocnemius,  behind  the  outer  condyle 
of  the  femur;  and  one  in  the  conjoined  tendon  of  the  Psoas  and  Iliacus,  where  it 
glides  over  the  os  pubis.  Sesamoid  bones  are  found  occasionally  in  the  tendon  of 
the  Gluteus  maximus,  as  it  passes  over  the  great  trochanter,  and  in  the  tendons 
which  wind  round  the  inner  and  outer  malleoli. 


THE  ARTICULATIONS. 


THE  various  bones  of  which  the  Skeleton  consists  are  connected  together  at 
different  parts  of  their  surfaces,  and  such  a  connection  is  designated  by  the 
name  of  Joint  or  Articulation.  If  the  joint  is  immovable,  as  between  the  cranial  and 
most  of  the  facial  bones,  the  adjacent  margins  of  the  bones  are  applied  in  almost 
close  contact,  a  thin  layer  of  fibrous  membrane,  the  sutural  ligament,  and,  at  the 
base  of  the  skull,  in  certain  situations,  a  thin  layer  of  cartilage,  being  interposed. 
Where  slight  movement  is  required,  combined  with  great  strength,  the  osseous  sur- 
faces are  united  by  tough  and  elastic  fibro-cartilages,  as  in  the  joints  between  the 
vertebral  bodies  and  interpubic  articulations ;  but  in  the  movable  joints  the  bones 
forming  the  articulation  are  generally  expanded  for  greater  convenience  of  mutual 
connection,  covered  by  cartilage,  held  together  by  strong  bands  or  capsules  of 
fibrous  tissue  called  ligaments,  and  partially  lined  by  a  membrane,  the  synovial 
membrane,  which  secretes  a  fluid  to  lubricate  the  various  parts  of  which  the  joint 
is  formed;  so  that  the  structures  which  enter  into  the  formation  of  a  joint  are 
bone,  cartilage,  fibro-cartilage,  ligament,  and  synovial  membrane. 

Bone  constitutes  the  fundamental  element  of  all  the  joints.  In  the  long  bones 
the  extremities  are  the  parts  which  form  the  articulations ;  they  are  generally 
somewhat  enlarged,  consisting  of  spongy  cancellous  tissue,  with  a  thin  coating  of 
compact  substance.  In  the  flat  bones  the  articulations  usually  take  place  at  the 
edges,  and,  in  the  short  bones  at  various  parts  of  their  surface.  The  layer  of 
compact  bone  which  forms  the  articular  surface,  and  to  which  the  cartilage  is 
attached,  is  called  the  articular  lamella.  It  is  of  a  white  color,  extremely  dense, 
and  varies  in  thickness.  Its  structure  differs  from  ordinary  bone-tissue  in  this 
respect,  that  it  contains  no  Haversian  canals,  and  its  lacunae  are  much  larger  than 
in  ordinary  bone  and  have  no  canaliculi.  The  vessels  of  the  cancellous  tissue,  as 
they  approach  the  articular  lamella,  turn  back  in  loops,  and  do  not  perforate  it ; 
this  layer  is  consequently  more  dense  and  firmer  than  ordinary  bone,  and  is  evi- 
dently designed  to  form  a  firm  and  unyielding  support  for  the  articular  cartilage. 

The  cartilage,  which  covers  the  articular  surfaces  of  bone,  and  is  called  the- 
articular,  will  be  found  described,  with  the  other  varieties  of  cartilage,  in  the  section 
on  General  Anatomy. 

Ligaments  consist  of  bands  of  various  forms,  serving  to  connect  together  the 
articular  extremities  of  bones,  and  composed  mainly  of  bundles  of  ivhite  fibrous 
tissue  placed  parallel  with,  or  closely  interlaced  with,  one  another,  and  presenting 
a  white,  shining,  silvery  aspect.  A  ligament  is  pliant  and  flexible,  so  as  to  allow 
of  the  most  perfect  freedom  of  movement,  but  strong,  tough,  and  inextensile,  so 
as  not  readily  to  yield  under  the  most  severely  applied  force  ;  it  is  consequently 
well  adapted  to  serve  as  the  connecting  medium  between  the  bones.  Some  liga- 
ments consist  entirely  of  yellow  elastic  tissue,  as  the  ligamenta  subflava,  which 
connect  together  the  adjacent  arches  of  the  vertebrae  and  the  ligamentum  nuchae 
in  the  lower  animals.  In  these  cases  it  will  be  observed  that  the  elasticity  of  the 
ligament  is  intended  to  act  as  a  substitute  for  muscular  power. 

Synovial  membrane  is  a  thin,  delicate  membrane  of  connective  tissue,  with 
branched  connective-tissue  corpuscles.  Its  secretion  is  thick,  viscid,  and  glairy, 
like  the  Avhite  of  egg,  and  is  hence  termed  synovia.  The  synovial  membranes 
found  in  the  body  admit  of  subdivision  into  three  kinds — articular,  bursal,  and 
vaginal. 

The  articular  synovial  membranes  are  found  in  all  the  freely  movable  joints. 
In  the  foetus  this  membrane  is  said,  by  Toynbee,  to  be  continued  over  the  surface 

217 


218  THE  ARTICULATIONS. 

of  the  cartilages ;  but  in  the  adult  it  is  wanting,  excepting  at  their  circumference, 
upon  which  it  encroaches  for  a  short  distance,  and  to  which  it  is  firmly  attached ; 
it  then  invests  the  inner  surface  of  the  capsular  or  other  ligaments  enclosing  the 
joint,  and  is  reflected  over  the  surface  of  any  tendons  passing  through  its  cavity,  as 
the  tendon  of  the  Popliteus  in  the  knee  and  the  tendon  of  the  Biceps  in  the 
shoulder.  Hence  the  articular  synovial  membrane  may  be  regarded  as  a  short 
wide  tube,  attached  by  its  open  ends  to  the  margins  of  the  articular  cartilages,  and 
covering  the  inner  surface  of  the  various  ligaments  which  connect  the  articular 
surfaces,  so  that  along  with  the  cartilages  it  completely  encloses  the  joint-cavity. 
In  some  of  the  joints  the  synovial  membrane  is  thrown  into  folds,  which  pass 
across  the  cavity.  They  are  called  synovial  ligaments,  and  are  especially  distinct 
in  the  knee.  In  other  joints  there  are  flattened  folds,  subdivided  at  their  margins 
into  fringe-like  processes,  the  vessels  of  which  have  a  convoluted  arrangement. 
These  latter  generally  project  from  the  synovial  membrane  near  the  margin  of  the 
cartilage  and  lie  flat  upon  its  surface.  They  consist  of  connective  tissue  covered 
with  endothelium,  and  contain  fat-cells  in  variable  quantities,  and,  more  rarely, 
isolated  cartilage-cells.  The  larger  folds  often  contain  considerable  quantities  of 
fat.  They  were  described  by  Clopton  Havers  as  mucilaginous  glands,  and  as  the 
source  of  the  synovial  secretion.  Under  certain  diseased  conditions  similar  pro- 
cesses are  found  covering  the  entire  surface  of  the  synovial  membrane,  forming  a 
mass  of  pedunculated  fibro-fatty  growths  which  project  into  the  joint.  Similar 
structures  are  also  found  in  some  of  the  bursal  and  vaginal  synovial  membranes. 

The  bursal  synovial  membranes  are  found  interposed  between  surfaces  which 
move  upon  each  other,  producing  friction,  as  in  the  gliding  of  a  tendon  or  of  the 
integument  over  projecting  bony  surfaces.  They  admit  of  subdivision  into  two 
kinds,  the  bursas  mucosas  and  the  bursas  synovice.  The  bursas  mucosas  are  large, 
simple,  or  irregular  cavities  in  the  subcutaneous  areolar  tissue,  enclosing  a  clear 
viscid  fluid.  They  are  found  in  various  situations,  as  between  the  integument  and 
the  front  of  the  patella,  over  the  olecranon,  the  malleoli,  and  other  prominent  parts. 
The  bursas  synovias  are  found  interposed  between  muscles  or  tendons  as  they  play 
over  projecting  bony  surfaces,  as  between  the  Glutei  muscles  and  the  surface  of 
the  great  trochanter.  They  consist  of  a  thin  wall  of  connective  tissue,  partially 
covered  by  patches  of  cells,  and  contain  a  viscid  fluid.  Where  one  of  these  exists 
in  the  neighborhood  of  a  joint,  it  may  communicate  with  its  cavity,  as  in  the  case 
of  the  bursa  between  the  tendon  of  the  Psoas  and  Iliacus  and  the  capsular  ligament 
of  the  hip,  or  the  one  interposed  between  the  under  surface  of  the  Subscapularis 
and  the  neck  of  the  scapula. 

The  vaginal  synovial  membranes  {synovial  sheaths)  serve  to  facilitate  the  gliding 
of  tendons  in  the  osseo-fibrous  canals  through  which  they  pass.  The  membrane  is 
here  arranged  in  the  form  of  a  sheath,  one  layer  of  which  adheres  to  the  wall  of 
the  canal,  and  the  other  is  reflected  upon  the  surface  of  the  contained  tendon,  the 
space  between  the  two  free  surfaces  of  the  membrane  containing  synovia.  These 
sheaths  are  chiefly  found  surrounding  the  tendons  of  the  flexor  and  extensor 
muscles  of  the  fingers  and  toes  as  they  pass  through  the  osseo-fibrous  canals  in  the 
hand  or  foot. 

Synovia  is  a  transparent,  yellowish-white  or  slightly  reddish  fluid,  viscid  like 
the  white  of  egg,  having  an  alkaline  reaction  and  slightly  saline  taste.  It  consists, 
according  to  Frerichs,  in  the  ox,  of  94.85  water,  0.56  mucus  and  epithelium,  0.07 
fat,  3.51  albumen  and  extractive  matter,  and  0.99  salts. 

The  articulations  are  divided  into  three  classes :  synarthrosis,  or  immovable  ; 
amphiar  thro  sis,  or  mixed;  and  diarthrosis,  or  movable  joints. 

1.  Synarthrosis.    Immovable  Articulations. 

Synarthrosis  includes  all  those  articulations  in  which  the  surfaces  of  the  bones 
are  in  almost  direct  contact,  fastened  together  by  an  intervening  mass  of  connective 
tissue,  and  in  Avhich  there  is  no  appreciable  motion,  as  the  joints  between  the  bones 


CLASSIFICATION   OF  JOINTS.  219 

of  the  cranium  and  face,  excepting  those  of  the  lower  jaw.  The  varieties  of  synar- 
throsis are  four  in  number  :   Sutura,  Schindylesis,  Gomphosis,  and  Synchondrosis. 

Sutura  (a  seam)  is  that  form  of  articulation  where  the  contiguous  margins  of 
flat  bones  are  united  by  a  thin  layer  of  fibrous  tissue.  It  is  met  with  only  in  the 
skull.  Where  the  articulating  surfaces  are  connected  by  a  series  of  processes  and 
indentations  interlocked  together,  it  is  termed  sutura  vera,  of  which  there  are 
three  varieties :  sutura  dentata,  serrata,  and  limbosa.  The  surfaces  of  the  bones 
are  not  in  direct  contact,  being  separated  by  a  layer  of  membrane  continuous 
externally  with  the  pericranium,  internally  with  the  dura  mater.  The  sutura 
dentata  (dens,  a  tooth)  is  so  called  from  the  tooth-like  form  of  the  projecting 
articular  processes,  as  in  the  suture  between  the  parietal  bones.  In  the  sutura 
serrata  (serra,  a  saw)  the  edges  of  the  two  bones  forming  the  articulation  are 
serrated  like  the  teeth  of  a  fine  saw,  as  between  the  two  portions  of  the  frontal 
bone.  In  the  sutura  limbosa  (limbus,  a  selvage),  besides  the  dentated  processes, 
there  is  a  certain  degree  of  bevelling  of  the  articular  surfaces,  so  that  the  bones 
overlap  one  another,  as  in  the  suture  between  the  parietal  and  frontal  bones. 
When  the  articulation  is  formed  by  roughened  surfaces  placed  in  apposition  with 
■one  another,  it  is  termed  the  false  suture  {sutura  notha),  of  which  there  are  two 
kinds :  the  sutura  squamosa  {squama,  a  scale),  formed  by  the  overlapping  of  two 
•contiguous  bones  by  broad  bevelled  margins,  as  in  the  squamo-parietal  (squamous) 
suture;  and  the-  sutura  harmonia  {apjuouia,  a  joining  together),  where  there  is 
simple  apposition  of  two  contiguous  rough  bony  surfaces,  as  in  the  articulation 
between  the  two  superior  maxillary  bones  or  of  the  horizontal  plates  of  the  palate 
bones. 

Schindylesis  {oyivftb'kqouz,  a  fissure)  is  that  form  of  articulation  in  which  a  thin 
plate  of  bone  is  received  into  a  cleft  or  fissure  formed  by  the  separation  of  two 
laminae  in  another  bone,  as  in  the  articulation  of  the  rostrum  of  the  sphenoid  and 
perpendicular  plate  of  the  ethmoid  with  the  vomer,  or  in  the  reception  of  the  latter 
in  the  fissure  between  the  superior  maxillary  and  palate  bones. 

G-omphosis  {ybfupoQ,  a  nail)  is  an  articulation  formed  by  the  insertion  of  a 
conical  process  into  a  socket,  as  a  nail  is  driven  into  a  board ;  this  is  not  illustrated 
by  any  articulation  between  bones,  properly  so  called,  but  is  seen  in  the  articulation 
of  the  teeth  with  the  alveoli  of  the  maxillary  bones. 

Synchondrosis. — Where  the  connecting  medium  is  cartilage  the  joint  is  termed 
a  synchondrosis.  This  is  a  temporary  form  of  joint,  for  the  cartilage  becomes  con- 
verted into  bone  before  adult  life.  Such  a  joint  is  found  between  the  epiphyses 
and  shafts  of  long  bones. 

2.  Amphiarthrosis.     Mixed  Articulations. 

In  this  form  of  articulation  the  contiguous  osseous  surfaces  are  either  connected 
together  by  broad  flattened  disks  of  fibro-cartilage,  of  a  more  or  less  com- 
plex structure,  which  adhere  to  the  end  of  each  bone,  as  in  the  articulation  be- 
tween the  bodies  of  the  vertebras  and  the  pubic  symphyses.  This  is  termed 
Symphysis.  Or,  secondly,  the  bony  surfaces  are  united  by  an  interosseous  liga- 
ment, as  in  the  inferior  tibio-fibular  articulation.  To  this  the  term  Syndesmosis 
is  applied. 

3.  Diarthrosis.    Movable  Articulations. 

This  form  of  articulation  includes  the  greater  number  of  the  joints  in  the  body, 
mobility  being  their  distinguishing  character.  They  are  formed  by  the  approxi- 
mation of  two  contiguous  bony  surfaces  covered  with  cartilage,  connected  by 
ligaments  and  lined  by  synovial  membrane.  The  varieties  of  joints  in  this  class 
have  been  determined  by  the  kind  of  motion  permitted  in  each.  There  are  two 
varieties  in  which  the  movement  is  uniaxial ;  that  is  to  say,  all  movements  take 
place  around  one  axis.  In  one  form,  the  Ginglymus,  this  axis  is,  practically 
speaking,  transverse ;  in  the  other,  the  trochoid  or  pivot-joint,  it  is  longitudinal. 
There  are  two  varieties  where  the  movement  is  biaxial,  or  around  two  horizontal 


220  THE  ARTICULATIONS. 

axes  at  right  angles  to  each  other  or  at  any  intervening  axis  between  the  two. 
These  are  the  condyloid  and  saddle-joint.  There  is  one  form  of  joint  where  the 
movement  is  polyaxial,  the  enarthrosis  or  ball-and-socket  joint.  And  finally  there 
are  the  Arthrodia  or  Gliding  joints. 

Ginglymus  or  Hinge-joint  (yiyylujjLOQ,  a  hinge). — In  this  form  of  joint  the 
articular  surfaces  are  moulded  to  each  other  in  such  a  manner  as  to  permit  motion 
only  in  one  plane,  forward  and  backward ;  the  extent  of  motion  at  the  same  time 
being  considerable.  The  direction  which  the  distal  bone  takes  in  this  motion  is 
never  in  the  same  plane  as  that  of  the  axis  of  the  proximal  bone,  but  there  is 
always  a  certain  amount  of  alteration  from  the  straight  line  during  flexion.  The 
articular  surfaces  are  connected  together  by  strong  lateral  ligaments,  which  form 
their  chief  bond  of  union.  The  most  perfect  forms  of  ginglymus  are  the  inter- 
phalangeal  joints  and  the  joint  between  the  humerus  and  ulna ;  the  knee  and  ankle 
are  less  perfect,  as  they  allow  a  slight  degree  of  rotation  or  lateral  movement  in 
certain  positions  of  the  limb. 

Trochoides  (pivot-joint). — Where  the  movement  is  limited  to  rotation,  the  joint 
is  formed  by  a  pivot-like  process  turning  within  a  ring,  or  the  ring  on  the  pivot,  the 
ring  being  formed  partly  of  bone,  partly  of  ligament.  In  the  superior  radio-ulnar 
articulation  the  ring  is  formed  partly  by  the  lesser  sigmoid  cavity  of  the  ulna ;  in 
the  rest  of  its  extent,  by  the  orbicular  ligament ;  here  the  head  of  the  radius 
rotates  within  the  ring.  In  the  articulation  of  the  odontoid  process  of  the  axis 
with  the  atlas  the  ring  is  formed  in  front  by  the  anterior  arch  of  the  atlas  ;  behind, 
by  the  transverse  ligament ;  here  the  ring  rotates  round  the  odontoid  process. 

Condyloid  Articulations. — In  this  form  of  joint  an  ovoid  articular  head,  or 
condyle,  is  received  into  an  elliptical  cavity  in  such  a  manner  as  to  permit  of 
flexion  and  extension,  adduction  and  abduction  and  circumduction,  but  no  axial 
rotation.  The  articular  surfaces  are  connected  together  by  anterior,  posterior,  and 
lateral  ligaments.     An  example  of  this  form  of  joint  is  found  in  the  wrist. 

Articulations  by  Reciprocal  Reception  (saddle-joint). — In  this  variety  the 
articular  surfaces  are  concavo-convex  ;  that  is  to  say,  they  are  inversely  convex  in 
one  direction  and  concave  in  the  other.  The  movements  are  the  same  as  in  the 
preceding  form  ;•  that  is  to  say,  there  is  flexion,  extension,  adduction,  abduction, 
and  circumduction,  but  no  axial  rotation.  The  articular  surfaces  are  connected  by 
a  capsular  ligament.  The  best  example  of  this  form  of  joint  is  the  carpo-meta- 
carpal  joint  of  the  thumb. 

Enarthrosis  is  that  form  of  joint  in  which  the  distal  bone  is  capable  of  motion 
around  an  indefinite  number  of  axes  which  have  one  common  centre.  It  is  formed 
by  the  reception  of  a  globular  head  into  a  deep  cup-like  cavity  (hence  the  name 
"ball-and-socket"),  the  parts  being  kept  in  apposition  by  a  capsular  ligament 
strengthened  by  accessory  ligamentous  bands.  Examples  of  this  form  of  articulation 
are  found  in  the  hip  and  shoulder. 

Arthrodia  is  that  form  of  joint  which  admits  of  a  gliding  movement;  it  is 
formed  by  the  approximation  of  plane  surfaces  or  one  slightly  concave,  the  other 
slightly  convex,  the  amount  of  motion  between  them  being  limited  by  the 
ligaments,  or  osseous  processes,  surrounding  the  articulation ;  as  in  the  articular 
processes  of  the  vertebrae,  the  carpal  joints,  except  that  of  the  os  magnum  with  the 
scaphoid  and  semilunar  bones,  and  the  tarsal  joints  with  the  exception  of  the  joint 
between  the  astragalus  and  the  navicular. 

On  the  next  page,  in  a  tabular  form,  are  the  names,  distinctive  characters,  and 
examples  of  the  different  kinds  of  articulations. 

The  Kinds  of  Movement  admitted  in  Joints. 

The  movements  admissible  in  joints  may  be  divided  into  four  kinds  :  gliding, 
angular  movement,  circumduction,  and  rotation.  These  movements  are  often, 
however,  more  or  less  combined  in  the  various  joints,  so  as  to  produce  an  infinite 
variety,  and  it  is  seldom  that  we  find  only  one  kind  of  motion  in  any  particular  joint. 


CLASSIFICATION    OF  JOINTS. 


221 


Synarthrosis,  or 
Immovable  Joint. 
Surfaces  separated 
by  fibrous  mem- 
brane or  by  line 
of  cartilage,  with- 
out any  interven- 


ing 


synovia 
cavity,     and     im- 
movably   con- 
nected  with   each 
other. 

As  in  joints  of 
cranium  and  face 
(except  lower 
jaw). 


Amphiar  thro  sis, 
Mixed  Articula- 
tion. 


Sutura      vera 
(true),     articulate   * 
by   indented   bor 
ders. 


Sutura.  Ar- 
ticulation by 
processes  and  < 
indentations 
interlocked  to- 
gether. 


Dentata,  having 
tooth-like  processes. 

As  in  interparietal 
suture. 

Serrata,  having  ser- 
rated edges  like  the 
teeth  of  a  saw. 

As  in  interfronial 
suture. 

Limbosa,  having 
bevelled  margins  and 
dentated  processes. 

As  in  fronto-parie- 
tal  suture. 

Squamosa,  formed 
by  thin  bevelled  mar- 
gins, overlapping  each 
other. 

As  in  squamo-parie- 


Diarthrosis, 
Movable   Joint. 


Sutura      notha 
(false),     articulate  {   tal  suture 
^  by  rough  surfaces.         Harmonia, formedby 
the  apposition  of  con- 
tiguous rough  surfaces. 
As    in    intermaxil- 
^  lary  suture. 

Schindylesis. — Articulation  formed  by  the  reception  of  a 
thin  plate  of  one  bone  into  a  fissure  of  another. 

As  in  articulation  of  rostrum  of  sphenoid  with  vomer. 
G-omphosis. — Articulation    formed  by  the  insertion  of   a 
^_  conical  process  into  a  socket :  the  teeth. 

r  Symphysis. — Surfaces  connected  by  fibro-cartilage,  not 
I  separated  by  synovial  membrane,  and  having  limited  motion. 
\  As  in  joints  between  bodies  of  vertebrae. 

Syndesmosis. — Surfaces  united  by  an  interosseous  ligament. 
I  As  in  the  inferior  tibio-fibular  articulation. 

G-inglymus. — Hinge-joint;  motion  limited  to  two  directions, 
forward  and  backward.  Articular  surfaces  fitted  together 
so  as  to  permit  of  movement  in  one  plane.  As  in  the  inter- 
phalangeal  joints  and  the  joint  between  the  humerus  and  the 
ulna. 

Trochoides,  or  Pivot-joint. — Articulation  by  a  pivot  process 
turning  within  a  ring  or  ring  around  a  pivot.  As  in  superior 
radio-ulnar  articulation  and  atlanto-axial  joint. 

Condyloid. — Ovoid  head  received  into  elliptical  cavity. 
Movements  in  every  direction  except  axial  rotation.  As  the 
wrist-joint. 

Reciprocal  Reception  (saddle-joint). — Articular  surfaces 
inversely  convex  in  one  direction  and  concave  in  the  other. 
Movement  in  every  direction  except  axial  rotation.  As  in  the 
carpo-metacarpal  joint  of  the  thumb. 

Enarthrosis.— Ball-and-socket  joint;  capable  of  motion  in 
all  directions.  Articulations  by  a  globular  head  received  into 
a  cup-like  cavity.     As  in  hip-  and  shoulder-joints. 

Arthrodia. — Gliding  joint ;  articulations  by  plane  surfaces, 
which  glide  upon  each  other.     As  in  carpal  and  tarsal  articu- 
l  lations. 


222  THE  ARTICULATIONS 

G-liding  movement  is  the  most  simple  kind  of  motion  that  can  take  place  in  a 
joint,  one  surface  gliding  or  moving  over  another  without  any  angular  or  rotatory 
movement.  It  is  common  to  all  movable  joints,  but  in  some,  as  in  the  articu- 
lations of  the  carpus  and  tarsus,  it  is  the  only  motion  permitted.  This  movement 
is  not  confined  to  plane  surfaces,  but  may  exist  between  any  two  contiguous 
surfaces,  of  whatever  form,  limited  by  the  ligaments  which  enclose  the  articu- 
lation. 

Angular  movement  occurs  only  between  the  long  bones,  and  by  it  the  angle 
between  the  two  bones  is  increased  or  diminished.  It  may  take  place  in  four 
directions :  forward  and  backward,  constituting  flexion  and  extension,  or  inward 
and  outward,  from  the  mesial  line  of  the  body  (or  in  the  fingers  and  toes  from 
the  middle  line  of  the  hand  or  foot),  constituting  adduction  and  abduction.  The 
strictly  ginglymoid  or  hinge-joints  admit  of  flexion  and  extension  only.  Abduction 
and  adduction,  combined  with  flexion  and  extension,  are  met  with  in  the  more 
movable  joints;  as  in  the  hip,  shoulder,  and  metacarpal  joint  of  the  thumb,  and 
partially  in  the  wrist. 

Circumduction  is  that  limited  degree  of  motion  which  takes  place  between  the 
head  of  a  bone  and  its  articular  cavity,  whilst  the  extremity  and  sides  of  the  limb 
are  made  to  circumscribe  a  conical  space,  the  base  of  which  corresponds  with  the 
inferior  extremity  of  the  limb,  the  apex  with  the  articular  cavity ;  this  kind  of 
motion  is  best  seen  in  the  shoulder-  and  hip-joints. 

Rotation  is  the  movement  of  a  bone  upon  an  axis,  which  is  the  axis  of  the  pivot 
on  which  the  bone  turns,  as  in  the  articulation  between  the  atlas  and  axis,  when 
the  odontoid  process  serves  as  a  pivot  around  which  the  atlas  turns ;  or  else  is  the 
axis  of  a  pivot-like  process  which  turns  within  a  ring,  as  in  the  rotation  of  the 
radius  upon  the  humerus. 

Ligamentous  Action  of  Muscles. — The  movements  of  the  different  joints  of  a 
limb  are  combined  by  means  of  the  long  muscles  which  pass  over  more  than  one 
joint,  and  which,  when  relaxed  and  stretched  to  their  greatest  extent,  act  as 
elastic  ligaments  in  restraining  certain  movements  of  one  joint,  except  when 
combined  with  corresponding  movements  of  the  other,  these  latter  movements 
being  usually  in  the  opposite  direction.  Thus  the  shortness  of  the  hamstring 
muscles  prevents  complete  flexion  of  the  hip,  unless  the  knee-joint  is  also  flexed, 
so  as  to  bring  their  attachments  nearer  together.  The  uses  of  this  arrangement 
are  threefold :  1.  It  co-ordinates  the  kinds  of  movement  which  are  the  most 
habitual  and  necessary,  and  enables  them  to  be  performed  with  the  least  expendi- 
ture of  power.  "  Thus  in  the  usual  gesture  of  the  arms,  whether  in  grasping  or 
rejecting,  the  shoulder  and  the  elbow  are  flexed  simultaneously,  and  simultaneously 
extended,"  in  consequence  of  the  passage  of  the  Biceps  and  Triceps  cubiti  over  both 
joints.  2.  It  enables  the  short  muscles  which  pass  over  only  one  joint  to  act  upon 
more  than  one.  "  Thus,  if  the  Rectus  femoris  remain  tonically  of  such  length 
that,  when  stretched  over  the  extended  hip,  it  compels  extension  of  the  knee,  then 
the  Gluteus  maximus  becomes  not  only  an  extensor  of  the  hip,  but  an  extensor 
of  the  knee  as  well."  3.  It  provides  the  joints  with  ligaments  which,  while  they 
are  of  very  great  power  in  resisting  movements  to  an  extent  incompatible  with  the 
mechanism  of  the  joint,  at  the  same  time  spontaneously  yield  when  necessary. 
"  Taxed  beyond  its  strength,  a  ligament  will  be  ruptured,  whereas  a  contracted 
muscle  is  easily  relaxed;  also,  if  neighboring  joints  be  united  by  ligaments,  the 
amount  of  flexion  or  extension  of  each  must  remain  in  constant  proportion  to  that 
of  the  other ;  while,  if  the  union  be  by  muscles,  the  separation  of  the  points  of  attach- 
ment of  those  muscles  may  vary  considerably  in  different  varieties  of  movement, 
the  muscles  adapting  themselves  tonically  to  the  length  required."  The  quotations 
are  from  a  very  interesting  paper  by  Dr.  Cleland  in  the  Journal  of  Anatomy  and 
Physiology,  No.  1,  1866,  p.  85;  by  whom  I  believe  this  important  fact  in  the 
mechanism  of  joints  was  first  clearly  pointed  out,  though  it  has  been  independently 
observed  afterward  by  other  anatomists.  Dr.  W.  W.  Keen  points  out  how 
important  it  is  "  that  the  surgeon  should  remember  this  ligamentous  action  of 


OF    THE    VERTEBRAL    COLUMN.  223 

muscles  in  making  passive  motion — for  instance,  at  the  wrist  after  Colles's  fracture. 
If  the  fingers  be  extended,  the  wrist  can  be  flexed  to  a  right  angle.  If,  however, 
they  be  first  flexed,  as  in  "  making  a  fist,"  flexion  at  the  wrist  is  quickly  limited  to 
from  forty  to  fifty  degrees  in  different  persons,  and  is  very  painful  beyond  that 
point.  Hence  passive  motion  here  should  be  made  with  the  fingers  extended. 
In  the  leg,  when  flexing  the  hip,  the  knee  should  be  flexed."  Dr.  Keen  further 
points  out  that  "  a  beautiful  illustration  of  this  is  seen  in  the  perching  of  birds, 
whose  toes  are  forced  to  clasp  the  perch  by  just  such  a  passive  ligamentous 
action  so  soon  as  they  stoop.  Hence  they  can  go  to  sleep  and  not  fall  off  the 
perch." 

The  articulations  may  be  arranged  into  those  of  the  trunk,  those  of  the  upper 
extremity,  and  those  of  the  lower  extremity. 


ARTICULATIONS   OF   THE   TRUNK. 

These  may  be  divided  into  the  following  groups,  viz. : 

VII.   Of  the  cartilages  of  the  ribs  with 
the  sternum  and  with  each  other. 
VIII.   Of  the  sternum. 
IX.   Of  the  vertebral  column  with  the 

pelvis. 
X.   Of  the  pelvis. 


I.  Of  the  vertebral  column 

II.  Of  the  atlas  with  the  axis. 

III.  Of  the  atlas  with  the  occipital  bone. 

IV.  Of  the  axis  with  the  occipital  bone. 
V.  Of  the  lower. jaw. 

VI.  Of  the  ribs  with  the  vertebrae. 


I.    Articulations  of  the  Vertebral  Column. 

The  different  segments  of  the  spine  are  connected  together  by  ligaments,  which 
may  be  divided  into  five  sets :  1.  Those  connecting  the  bodies  of  the  vertebrae. 
2.  Those  connecting  the  lamina?..  3.  Those  connecting  the  articular  processes. 
4.   Those  connecting  the  spinous  processes.     5.   Those  of  the  transverse  processes. 

The  articulations  of  the  bodies  of  the  vertebrae  with  each  other  form  a  series  of 
amphiarthrodial  joints ;  those  between  the  articular  processes  form  a  series  of 
arthrodial  joints. 

1.    The  Ligaments  of  the  Body. 

Anterior  Common  Ligament.  Posterior  Common  Ligament. 

Intervertebral  Substance. 

The  Anterior  Common  Ligament  (Figs.  152,  153,  160,  164)  is  a  broad  and 
strong  band  of  fibres  which  extends  along  the  anterior  surface  of  the  bodies  of  the 
vertebrae  from  the  axis  to  the  sacrum.  It  is  broader  below  than  above,  thicker 
in  the  dorsal  than  in  the  cervical  or  lumbar  regions,  and  somewhat  thicker 
opposite  the  front  of  the  body  of  each  vertebra  than  opposite  the  interver- 
tebral substance.  It  is  attached,  above,  to  the  Ixody  of  the  axis  by  a  pointed 
process,  where  it  is  continuous  with  the  anterior  atlanto-axial  ligament,  and  is 
connected  with  the  tendon  of  insertion  of  the  Longus  colli  muscle,  and  extends 
down  as  far  as  the  upper  bone  of  the  sacrum.  It  consists  of  dense  longitudinal 
fibres,  which  are  intimately  adherent  to  the  intervertebral  substance  and  the 
prominent  margins  of  the  vertebrae,  but  less  closely  to  the  middle  of  the  bodies. 
In  the  latter  situation  the  fibres  are  exceedingly  thick,  and  serve  to  fill  up  the 
concavities  on  their  front  surface  and  to  make  the  anterior  surface  of  the  spine 
more  even.  This  ligament  is  composed  of  several  layers  of  fibres,  -which  vary  in 
length,  but  are  closely  interlaced  with  each  other.  The  most  superficial  or  longest 
fibres  extend  between  four  or  five  vertebrae.  A  second  subjacent  set  extend 
between  two  or  three  vertebrae,  whilst  a  third  set,  the  shortest  and  deepest,  extend 
from  one  vertebra  to  the  next.  At  the  side  of  the  bodies  the  ligament  consists  of 
a  few  short  fibres,  which  pass  from  one  vertebra  to  the  next,  separated  from  the 
median  portion  by  large  oval  apertures  for  the  passage  of  vessels. 

The  Posterior  Common  Ligament  (Figs.  152, 156)  is  situated  within  the  spinal 


224 


THE   ARTICULATIONS 


canal,  and  extends  along  the  posterior  surface  of  the  bodies  of  the  vertebrae  from 
the  body  of  the  axis  above,  where  it  is  continuous  with  the  occipito-axial  ligament, 
to  the  sacrum  below.  It  is  broader  above  than  below,  and  thicker  in  the  dorsal 
than  in  the  cervical  or  lumbar  regions.  In  the  situation  of  the  intervertebral 
substance  and  contiguous  margins  of  the  vertebrae,  Avhere  the  ligament  is  more 
intimately  adherent,  it  is  broad,  and  presents  a  series  of  dentations  with  inter- 
vening concave  margins :  but  it  is  narrow  and  thick  over  the  centre  of  the  bodies, 
from  which  it  is  separated  by  the  vence  basis  vertebra?.  This  ligament  is  composed 
of  smooth,  shining,  longitudinal  fibres,  denser  and  more  compact  than  those  of  the 
anterior  ligament,  and  composed  of  a  superficial  layer  occupying  the  interval 
between  three  or  four  vertebrae,  and  of  a  deeper  layer  which  extends  between 
one  vertebra  and  the  next  adjacent  to  it.     It  is  separated  from  the  dura  mater  of 


ANTERIOR 
COMMON     LIGAMENT. 


POSTERIOR 

CO  MMON 
LIGAMENT. 


Fig.  152. — Vertical  section  of  two  vertebra  and  their  ligaments,  from  the  lumbar  region. 

the  spinal  cord  by  some   loose   connective  tissue  which  is  very  liable  to  serous 
infiltration. 

The  Intervertebral  Substance  (Figs.  152,  161)  is  a  lenticular  disk  of  composite 
structure  interposed  between  the  adjacent  surfaces  of  the  bodies  of  the  vertebrae 
from  the  axis  to  the  sacrum,  and  forming  the  chief  bond  of  connection  between 
those  bones.  These  disks  vary  in  shape,  size,  and  thickness  in  different  parts  of 
the  spine.  In  shape  they  accurately  correspond  with  the  surfaces  of  the  bodies 
between  which  they  are  placed,  being  oval  in  the  cervical  and  lumbar  regions,  and 
circular  in  the  dorsal.  Their  size  is  greatest  in  the  lumbar  region.  In  thickness 
they  vary  not  only  in  the  different  regions  of  the  spine,  but  in  different  parts  of 
the  same  disk  :  thus,  they  are  thicker  in  front  than  behind  in  the  cervical  and 
lumbar  regions,  while  they  are  uniformly  thick  in  the  dorsal  region.  The  inter- 
vertebral disks  form  about  one-fourth  of  the  spinal  column,  exclusive  of  the  first 
two  vertebrae ;  they  are  not  equally  distributed,  however,  between  the  various 
bones ;  the  dorsal  portion  of  the  spine  having,  in  proportion  to  its  length,  a  much 
smaller  quantity  than  in  the  cervical  and  lumbar  regions,  which  necessarily  gives 
to  the  latter  parts  greater  pliancy  and  freedom  of  movement.  The  intervertebral  disk- 
are  adherent,  by  their  surfaces,  to  a  thin  layer  of  hyaline  cartilage  which  covers  the 
upper  and  under  surfaces  of  the  bodies  of  the  vertebrae,  and  in  which,  in  early  life. 
the  epiphyseal  plate  develops,  and  by  their  circumference  are  closely  connected  in 


OF    THE    VERTEBRAL    COLUMN.  225 

front  to  the  anterior,  and  behind  to  the  posterior  common  ligament ;  whilst  in  the 
dorsal  region  they  are  connected  laterally,  by  means  of  the  interarticular  ligament, 
to  the  heads  of  those  ribs  which  articulate  with  two  vertebrae  ;  they,  consequently, 
form  part  of  the  articular  cavities  in  which  the  heads  of  these  bones  are  received. 
Structure  of  the  Intervertebral  Substance. — The  intervertebral  substance  is 
composed,  at  its  circumference,  of  laminae  of  fibrous  tissue  and  fibro-cartilage ; 
and,  at  its  centre,  of  a  soft,  pulpy,  highly  elastic  substance,  of  a  yellowish  color, 
which  rises  up  considerably  above  the  surrounding  level  when  the  disk  is  divided 
horizontally.  This  pulpy  substance,  which  is  especially  well  developed  in  the 
lumbar  region,  is  the  remains  of  the  chorda  dorsalis,  and,  according  to  Luschka, 
contains  a  small  synovial  cavity  in  its  centre.  The  laminae  are  arranged  concen- 
trically one  within  the  other,  the  outermost  consisting  of  ordinary  fibrous  tissue, 
but  the  others  and  more  numerous  consisting  of  white  fibro-cartilage.  These 
plates  are  not  quite  vertical  in  their  direction,  those  near  the  circumference  being 
curved  outward  and  closely  approximated ;  whilst  those  nearest  the  centre  curve 
in  the  opposite  direction,  and  are  somewhat  more  widely  separated.  The  fibres  of 
which  each  plate  is  composed  are  directed,  for  the  most  part,  obliquely  from  above 
downward,  the  fibres  of  adjacent  plates  passing  in  opposite  directions  and  varying 
in  every  layer  ;  so  that  the  fibres  of  one  layer  are  directed  across  those  of  another, 
like  the  limbs  of  the  letter  X.  This  laminar  arrangement  belongs  to  about  the 
outer  half  of  each  disk.  The  pulpy  substance  presents  no  concentric  arrangement, 
and  consists  of  a  fine  fibrous  matrix,  containing  angular  cells,  united  to  form  a 
reticular  structure. 

2.  Ligaments  connecting  the  Laminae. 
Ligamenta  Subflava. 

The  Ligamenta  Subflava  (Fig.  152)  are  interposed  between  the  laminae  of  the 
vertebrae,  from  the  axis  to  the  sacrum.  They  are  most  distinct  when  seen  from 
the  interior  of  the  spinal  canal ;  when  viewed  from  the  outer  surface  they  appear 
short,  being  overlapped  by  the  laminae.  Each  ligament  consists  of  two  lateral 
portions,  which  commence  on  each  side  at  the  root  of  either  articular  process,  and 
pass  backward  to  the  point  where  the  laminae  converge  to  form  the  spinous 
process,  where  their  margins  are  in  contact  and  to  a  certain  extent  united ;  slight 
intervals  being  left  for  the  passage  of  small  vessels.  These  ligaments  consist  of 
yellow  elastic  tissue,  the  fibres  of  which,  almost  perpendicular  in  direction,  are 
attached  to  the  anterior  surface  of  the  laminae  above,  some  distance  from  its 
inferior  margin,  and  to  the  posterior  surface,  as  well  as  to  the  margin  of  the 
lamina  below.  In  the  cervical  region  they  are  thin  in  texture,  but  very  broad  and 
long  ;  they  become  thicker  in  the  dorsal  region,  and  in  the  lumbar  acquire  very 
considerable  thickness.  Their  highly  elastic  property  serves  to  preserve  the 
upright  posture  and  to  assist  in  resuming  it  after  the  spine  has  been  flexed. 
These  ligaments  do  not  exist  between  the  occiput  and  atlas  or  between  the  atlas 
and  axis. 

3.  Ligaments  connecting  the  Articular  Processes. 
Capsular. 

The  Capsular  Ligaments  (Fig.  154)  are  thin  and  loose  ligamentous  sacs,  attached 
to  the  contiguous  margins  of  the  articulating  processes  of  each  vertebra  through 
the  greater  part  of  their  circumference,  and  completed  internally  by  the  ligamenta 
subflava.  They  are  longer  and  looser  in  the  cervical  than  in  the  dorsal  or  lumbar 
regions.  The  capsular  ligaments  are  lined  on  their  inner  surface  by  synovial 
membrane. 

4.  Ligaments  connecting  the  Spinous  Processes. 
Supraspinous.  Interspinous. 

The  Supraspinous  Ligament  (Fig.  152)  is  a  strong  fibrous  cord,  which  connects 

15 


226  THE  ARTICULATIONS 

together  the  apices  of  the  spinous  processes  from  the  seventh  cervical  to  the  spinous 
processes  of  the  sacrum.  It  is  thicker  and  broader  in  the  lumbar  than  in  the  dorsal 
region,  and  intimately  blended,  in  both  situations,  with  the  neighboring  aponeu- 
rosis. The  most  superficial  fibres  of  this  ligament  connect  three  or  four  vertebras ; 
those  deeper-seated  pass  between  two  or  three  vertebras  ;  whilst  the  deepest  connect 
the  contiguous  extremities  of  neighboring  vertebras.  It  is  continued  upward  to 
the  external  occipital  protuberance,  as  the  ligamentum  nuchas,  which,  in  the 
human  subject,  is  thin  and  forms  merely  an  intermuscular  septum. 

The  Interspinous  Ligaments  (Fig.  152),  thin  and  membranous,  are  interposed 
between  the  spinous  processes.  Each  ligament  extends  from  the  root  to  the 
summit  of  each  spinous  process  and  connects  together  their  adjacent  margins. 
They  meet  the  ligamenta  subflava  in  front  and  the  supi'a-spinous  ligament  behind. 
They  are  narrow  and  elongated  in  the  dorsal  region  ;  broader,  quadrilateral  in 
form,  and  thicker  in  the  lumbar  region ;  and  only  slightly  developed  in  the  neck. 

5.  Ligaments  connecting  the  Transverse  Processes. 
Intertransverse. 

The  Intertransverse  Ligaments  consist  of  bundles  of  fibres  interposed 
between  the  transverse  processes.  In  the  cervical  region  they  consist  of  a  few 
irregular,  scattered  fibres  ;  in  the  dorsal,  they  are  rounded  cords  intimately  con- 
nected with  the  deep  muscles  of  the  back  ;  in  the  lumbar  region  they  are  thin  and 
membranous. 

Actions. — The  movements  permitted  in  the  spinal  column  are,  Flexion,  Exten- 
sion, Lateral  Movement,  Circumduction,  and  Rotation. 

In  Flexion,  or  movement  of  the  spine  forward,  the  anterior  common  ligament 
is  relaxed,  and  the  intervertebral  substances  are  compressed  in  front,  while  the 
posterior  common  ligament,  the  ligamenta  subflava,  and  the  inter-  and  supra- 
spinous ligaments  are  stretched,  as  well  as  the  posterior  fibres  of  the  intervertebral 
disks.  The  interspaces  between  the  laminas  are  widened,  and  the  inferior  articular 
processes  of  the  vertebras  above  glide  upward  upon  the  articular  processes  of  the 
vertebras  below.     Flexion  is  the  most  extensive  of  all  the  movements  of  the  spine. 

In  Extension,  or  movement  of  the  spine  backward,  an  exactly  opposite  dis- 
position of  the  parts  takes  place.  This  movement  is  not  extensive,  being  limited  by 
the  anterior  common  ligament  and  by  the  approximation  of  the  spinous  processes. 

Flexion  and  extension  are  free  in  the  lower  part  of  the  lumbar  region  between 
the  third  and  fourth  and  fourth  and  fifth  lumbar  vertebras  ;  above  the  third 
they  are  much  diminished,  and  reach  their  minimum  in  the  middle  and  upper 
part  of  the  back.  They  increase  again  in  the  neck,  the  capability  of  motion 
backward  from  the  upright  position  being  in  this  region  greater  than  that  of  the 
motion  forward,  whereas  in  the  lumbar  region  the  reverse  is  the  case. 

In  Lateral  Movement,  the  sides  of  the  intervertebral  disks  are  compressed,  the 
extent  of  motion  being  limited  by  the  resistance  offered  by  the  surrounding  liga- 
ments and  by  the  approximation  of  the  transverse  processes.  This  movement  may 
take  place  in  any  part  of  the  spine,  but  is  most  free  in  the  neck  and  loins. 

Circumduction  is  very  limited,  and  is  produced  merely  by  a  succession  of  the 
preceding  movements. 

Rotation  is  produced  by  the  twisting  of  the  intervertebral  substances  ;  this, 
although  only  slight  between  any  two  vertebras,  produces  a  considerable  extent  of 
movement  when  it  takes  place  in  the  whole  length  of  the  spine,  the  front  of  the 
upper  part  of  the  column  being  turned  to  one  or  the  other  side.  This  movement 
takes  place  only  to  a  slight  extent  in  the  neck,  but  is  freer  in  the  upper  part  of 
the  dorsal  region,  and  is  altogether  absent  in  the  lumbar  region. 

It  is  thus  seen  that  the  cervical  region  enjoys  the  greatest  extent  of  each 
variety  of  movement,  flexion  and  extension  especially  being  very  free.  In  the 
dorsal  region  the  three  movements  of  flexion,  extension,  and  circumduction  are 
permitted  only  to  a  slight  extent,  while  rotation  is  very  free  in  the  upper  part  and 


OF    THE  ATLAS    WITH   THE   AXIS.  227 

ceases  below.  In  the  lumbar  region  there  is  free  flexion,  extension,  and  lateral 
movement,  but  no  rotation. 

As  Sir  George  Humphry  has  pointed  out,  the  movements  permitted  are  mainly 
due  to  the  shape  and  position  of  the  articulating  processes.  In  the  loins  the 
inferior  articulating  processes  are  turned  outward  and  embraced  by  the  superior ; 
this  renders  rotation  in  this  region  of  the  spine  impossible,  while  there  is  nothing 
to  prevent  a  sliding  upward  and  downward  of  the  surfaces  on  each  other,  so  as  to 
allow  of  flexion  and  extension.  In  the  dorsal  region,  on  the  other  hand,  the 
articulating  processes,  by  their  direction  and  mutual  adaptation,  especially  at  the 
upper  part  of  the  series,  permit  of  rotation,  but  prevent  extension  and  flexion, 
while  in  the  cervical  region  the  greater  obliquity  and  lateral  slant  of  the  articular 
processes  allow  not  only  flexion  and  extension,  but  also  rotation. 

The  principal  muscles  Avhich  produce  flexion  are  the  Sterno-mastoid,  Rectus 
capitis  anticus  major,  and  Longus  colli ;  the  Scaleni ;  the  abdominal  muscles  and 
the  Psoas  magnus.  Extension  is  produced  by  the  fourth  layer  of  the  muscles  of 
the  back,  assisted  in  the  neck  by  the  Splenius,  Semispinalis  dorsi  et  colli,  and 
the  Multifidus  spinse.  Lateral  motion  is  produced  by  the  fourth  layer  of  the 
muscles  of  the  back,  by  the  Splenius  and  the  Scaleni,  the  muscles  of  one  side  only 
acting ;  and  rotation  by  the  action  of  the  following  muscles  of  one  side  only — viz. 
the  Sterno-mastoid,  the  Rectus  capitis  anticus  major,  the  Scaleni,  the  Multifidus 
epinge,  the  Complexus,  and  the  abdominal  muscles. 

II.  Articulation  of  the  Atlas  with  the  Axis. 

The  articulation  of  the  Atlas  with  the  Axis  is  of  a  complicated  nature,  comprising 
no  fewer  than  four  distinct  joints.  There  is  a  pivot  articulation  between  the  odontoid 
process  of  the  axis  and  the  ring  formed  between  the  anterior  arch  of  the  atlas  and 
the  transverse  ligament  (see  Fig.  155).  Here  there  are  two  joints:  one  in  front 
between  the  posterior  surface  of  the  anterior  arch  of  the  atlas  and  the  front  of  the 
odontoid  process  (the  atlanto-odontoid  joint  of  Cruveilhier) ;  the  other  between  the 
anterior  surface  of  the  transverse  ligament  and  the  back  of  the  process  (the 
syndesmo-odontoid  joint).  Between  the  articular  processes  of  the  two  bones 
there  is  a  double  arthrodia  or  gliding  joint.  The  ligaments  which  connect  these 
bones  are  the 

Anterior  Atlanto-axial.  Transverse. 

Posterior  Atlanto-axial.  Two  Capsular. 

The  Anterior  Atlanto-axial  Ligament  (Fig.  153)  is  a  strong,  membranous  layer, 
attached,  above,  to  the  lower  border  of  the  anterior  arch  of  the  atlas ;  below,  to  the 
base  of  the  odontoid  process  and  to  the  front  of  the  body  of  the  axis.  It  is  strength- 
ened in  the  middle  line  by  a  rounded  cord,  which  is  attached,  above,  to  the  tubercle 
on  the  anterior  arch  of  the  atlas,  and  below  to  the  body  of  the  axis,  being  a  con- 
tinuation upward  of  the  anterior  common  ligament  of  the  spine.  These  ligaments 
are  in  relation,  in  front,  with  the  Recti  antici  majores. 

The  Posterior  Atlanto-axial  Ligament  (Fig.  154)  is  a  broad  and  thin  membra- 
nous layer,  attached,  above,  to  the  lower  border  of  the  posterior  arch  of  the  atlas ; 
below,  to  the  upper  edge  of  the  laminae  of  the  axis.  This  ligament  supplies  the 
place  of  the  ligamenta  subflava,  and  is  in  relation,  behind,  with  the  Inferior  oblique 
muscles. 

The  Transverse  Ligament !  (Figs.  155,  156)  is  a  thick,  strong  band,  which  arches 
across  the  ring  of  the  atlas,  and  serves  to  retain  the  odontoid  process  in  firm  con- 
nection with  its  anterior  arch.  This  ligament  is  flattened  from  before  backward, 
broader  and  thicker  in  the  middle  than  at  either  extremity,  and  firmly  attached  on 

1  It  has  been  found  necessary  to  describe  the  transverse  ligament  with  tliose  of  tbe  atlas  and  axis  : 
but  the  student  must  remember  that  it  is  really  a  portion  of  the  mechanism  by  which  the  movements 
of  the  head  on  the  spine  are  regulated ;  so  that  the  connections  between  the  atlas  and  axis  ought 
always  to  be  studied  together  with  tliose  between  the  latter  bones  and  the  skull. 


228 


THE   ARTICULATIONS. 


each  side  to  a  small  tubercle  on  the  inner  surface  of  the  lateral  mass  of  the  atlas. 
As  it  crosses  the  odontoid  process,  a  small  fasciculus  is  derived  from  its  upper,  and 
another  from  its  lower,  border  ;  the  former  passing  upward,  to  be  inserted  into  the 
basilar  process  of  the  occipital  bone ;  the  latter,  downward,  to  be  attached  to  the 
posterior  surface  of  the  body  of  the  axis  ;  hence,  the  whole  ligament  has  received 
the  name  of  cruciform.  The  transverse  ligament  divides  the  ring  of  the  atlas 
into  two  unequal  parts :  of  these,  the  posterior  and  larger  serves  for  the 
transmission  of  the  cord  and  its  membranes  and  the  spinal  accessory  nerves ; 
the  anterior  and  smaller  contains  the  odontoid  process.  Since  the  space  between 
the  anterior  arch  of  the  atlas  and  the  transverse  ligament  is  smaller  at  the  lower 


\Sj\         OOOIPITO-         f    CAPSULAR    LIGA- 
MENT and 
synovial  mem- 
brane. 


ATLANTO- 
AXIAL,        (capsular  ligament 
and  synovial 
membrane. 


Fig.  153. — Occipito-atlantal  and  atlantoaxial  ligaments.    Front  view. 


part  than  the  upper  (because  the  transverse  ligament  embraces  firmly  the  narrow 
neck  of  the  odontoid  process),  this  process  is  retained  in  firm  connection  with 
the  atlas  after  all  the  other  ligaments  have  been  divided. 

The  Capsular  Ligaments  are  two  thin  and  loose  capsules,  connecting  the  lateral 
masses  of  the  atlas  with  the  superior  articular  surfaces  of  the  axis,  the  fibres  being 
strengthened  at  the  posterior  and  inner  part  of  the  articulation  by  an  accessory 
ligament,  which  is  attached  below  to  the  body  of  the  axis  near  the  base  of  the 
odontoid  process. 

There  are  four  Synovial  Membranes  in  this  articulation :  one  lining  the  inner 
surface  of  each  of  the  capsular  ligaments ;  one  between  the  anterior  surface  of  the 
odontoid  process  and  the  anterior  arch  of  the  atlas,  the  atlanto -odontoid  joint ; 
and  one  between  the  posterior  surface  of  the  odontoid  process  and  the  transverse 
ligament,  the  syndesmo-odontoid  joint.  The  latter  often  communicates  with 
those  between  the  condyles  of  the  occipital  bone  and  the  articular  surfaces  of  the 
atlas. 

Actions. — This  joint  allows  the  rotation  of  the  atlas  (and,  with  it,  of  the  cra- 
nium) upon  the  axis,  the  extent  of  rotation  being  limited  by  the  odontoid  liga- 
ments. 

The  principal  muscles  by  which  this  action  is  produced  are  the  Sten^o-mastoid. 
and  Complexus  of  one  side,  acting  with  the  Rectus  capitis  anticus  major,,  Splonius, 
Trachelo-mastoid,  Rectus  capitis  posticus  major,  and  Inferior  oblique  of  the  other 
side. 


OF    THE   ATLAS    WITH   THE    OCCIPITAL    BONE. 


229 


ARTICULATIONS  OF  THE  SPINE  WITH  THE  CRANIUM. 

The  ligaments  connecting  the  spine  with  the  cranium  may  be  divided  into  two 
sets — those  connecting  the  occipital  bone  with  the  atlas,  and  those  connecting  the 
occipital  bone  with  the  axis. 

III.  Articulation  of  the  Atlas  with  the  Occipital  Bone. 

This  articulation  is  a  double  condyloid  joint.     Its  ligaments  are  the 

Anterior  Occipito-atlantal.  Two  Lateral  Occipito-atlantal. 

Posterior  Occipito-atlantal.  Two  Capsular. 

The  Anterior  Occipito-atlantal  Ligament  (Fig.  153)  is  a  broad  membranous 
layer,   composed    of    densely  woven    fibres,  which    passes    between    the    anterior 


Arch  for  passage  of 
vertebral  artery 
and  1st  cervical 


Fig.  154.— Occipito-atlantal  and  atlanto-axial  ligaments.    Posterior  view. 

margin  of  the  foramen  magnum  above,  and  the  whole  length  of  the  upper  border 
of  the  anterior  arch  of  the  atlas  below.  Laterally,  it  is  continuous  with  the 
capsular  ligaments.  In  the  middle  line  in  front  it  is  strengthened  by  a  strong, 
narrow,  rounded  cord,  which  is  attached,  above,  to  the  basilar  process  of  the 
occiput,  and,  below,  to  the  tubercle  on  the  anterior  arch  of  the  atlas.  This  liga- 
ment is  in  relation,  in  front,  with  the  Recti  antici  minores :  behind,  with  the 
odontoid  ligaments. 

The  Posterior  Occipito-atlantal  Ligament  (Fig.  154)  is  a  very  broad  but  thin 
membranous  lamina  intimately  blended  with  the  dura  mater.  It  is  connected, 
above,  to  the  posterior  margin  of  the  foramen  magnum  ;  below,  to  the  upper  border 
of  the  posterior  arch  of  the  atlas.  This  ligament  is  incomplete  at  each  side,  and 
forms,  with  the  superior  intervertebral  notch,  an  opening  for  the  passage  of  the 
vertebral  artery  and  suboccipital  nerve.  The  fibrous  band  which  arches  over  the 
artery  and  nerve  sometimes  becomes  ossified.  It  is  in  relation,  behind,  with  the 
Recti  pos.ici  minores  and  Obliqui  superiores ;  in  front,  with  the  dura  mater  of  the 
spinal  caaal,  to  which  it  is  intimately  adherent. 

The  Lateral  Ligaments  are  strong  fibrous  bands,  directed  obliquely  upward  and 


230 


THE   ARTICULATIONS. 


inward,  attached  above  to  the  jugular  process  of  the  occipital  bone ;  below,  to  the 
base  of  the  transverse  process  of  the  atlas. 

The  Capsular  Ligaments  surround  the  condyles  of  the  occipital  bone,  and  con- 
nect them  with  the  articular  processes  of  the  atlas  ;  they  consist  of  thin  and  loose 
capsules,  which  enclose  the  synovial  membrane  of  the  articulation. 

Synovial  Membranes. — There  are  two  synovial  membranes  in  this  articulation, 
one  lining  the  inner  surface  of  each  of  the  capsular  ligaments.  These  occasionally 
communicate  with  that  between  the  posterior  surface  of  the  odontoid  process  and 
the  transverse  ligament. 

Actions. — The  movements  permitted  in  this  joint  are  flexion  and  extension, 
which  give  rise  to  the  ordinary  forward  and  backward  nodding  of  the  head,  besides 


Fig.  155.— Articulation  between  odontoid  process  and  atlas. 

slight  lateral  motion  to  one  or  the  other  side.  When  either  of  these  actions  is 
carried  beyond  a  slight  extent,  the  whole  of  the  cervical  portion  of  the  spine  assists 
in  its  production.  Flexion  is  mainly  produced  by  the  action  of  the  Rectus  capitis 
anticus  major  et  minor  and  the  Stern o-mastoid  muscles  ;  extension  by  the  Rectus 
capitis  posticus  major  et  minor,  the  Superior  oblique,  the  Complexus,  Splenius, 
and  upper  fibres  of  the  Trapezius.  The  Recti  laterales  are  concerned  in  the  lat- 
eral movement,  assisted  by  the  Trapezius,  Splenius,  Complexus,  and  the  Sterno- 
mastoid  of  the  same  side,  all  acting  together.  According  to  Cruveilhier,  there  is  a 
slight  motion  of  rotation  in  this  joint. 


IV.   Articulation  of  the  Axis  with  the  Occipital  Bone. 

Occipito-axial.  Three  Odontoid. 

To  expose  these  ligaments  the  spinal  canal  should  be  laid  open  by  removing 
the  posterior  arch  of  the  atlas,  the  laminre  and  spinal  process  of  the  axis,  and  the 
portion  of  the  occipital  bone  behind  the  foramen  magnum,  as  seen  in  Fig.  156. 

The  Occipito-axial  Ligament  [apparatus  ligamentosus  colli)  is  situated  within 
the  spinal  canal.  It  is  a  broad,  strong  band,  which  covers  the  odontoid  process 
and  its  ligaments,  and  appears  to  be  a  prolongation  upward  of  the  posterior  common 
ligament  of  the  spine.  It  is  attached,  below,  to  the  posterior  surface  of  the  body 
of  the  axis,  and,  becoming  expanded  as  it  ascends,  is  inserted  into  the  basilar 
groove  of  the  occipital  bone,  in  front  of  the  foramen  magnum,  where  it  becomes 
blended  with  the  dura  mater  of  the  skull. 

Relations. — By  its  anterior  surface  with  the  transverse  ligament ;  by  its  posterior 
surface  with  the  dura  mater. 

The  Odontoid  or  Check  Ligaments  {alar  ligaments)  are  strong,  rounded,  fibrous 
cords,  which  arise  one  on  either  side  of  the  upper  part  of  the  odontoid  process,  and, 
passing  obliquely  upward  and  outward,  are  inserted  into  the  rough  depress"  u  is  on 
the  inner  side  of  the  condyles  of  the  occipital  bone.  In  the  triangular  interval  left 
between  these  ligaments  another  strong  fibrous  cord  (ligamentum  susp  ,  or 


ARTICULATION    OF    THE   LOWER    JAW. 


231 


middle  odontoid  ligament)  may  be  seen,  "which  passes  almost  perpendicularly  from 
the  apex  of  the  odontoid  process  to  the  anterior  margin  of  the  foramen  magnum, 
being  intimately  blended  with  the  deep  portion  of  the  anterior  occipito-atlantal 
ligament  and  upper  fasciculus  of  the  transverse  ligament  of  the  atlas. 

Actions. — The  odontoid  ligaments  serve  to  limit  the  extent  to  which  rotation 


The  vertical  portion  of 

ODONTOID     LIGAMENTS. 


CAPSULAR     LIGAMENT 

and  synovial 
membrane. 


CAPSULAR    LIGAMENT 

and  synovial 
membrane. 


Fig.  156.— Occipito-axial  and  atlantoaxial  ligaments.    Posterior  view,  obtained  by  removing  the  arches  of 
the  vertebras  and  the  posterior  part  of  the  skull. 

of  the  cranium  may  be  carried ;  hence   they    have    received  the  name  of  check 
ligaments. 

In  addition  to  these  ligaments,  which  connect  the  atlas  and  axis  to  the  skull, 
the  ligamentum  nuchae  must  be  regarded  as  one  of  the  ligaments  by  which  the 
spine  is  connected  with  the  cranium.     It  is  described  on  a  subsequent  page. 

Surgical  Anatomy. — The  ligaments  which  unite  the  component  parts  of  the  vertebrae 
together  are  so  strong,  and  these  bones  are  so  interlocked  by  the  arrangement  of  their 
articulating  processes,  that  dislocation  is  very  uncommon,  and,  indeed,  unless  accompanied  by 
fracture,  rarely  occurs,  except  in  the  upper  part  of  the  neck.  Dislocation  of  the  occiput  from 
the  atlas  has  only  been  recorded  in  one  or  two  cases;  but  dislocation  of  the  atlas  from  the  axis, 
with  rupture  of  the  transverse  ligament,  is  much  more  common :  it  is  the  mode  in  which 
death  is  produced  in  many  cases  of  execution  by  hanging.  In  the  lower  part  of  the  neck- 
that  is,  below  the  third  cervical  vertebra— dislocation  unattended  by  fracture  occasionally  takes 
place. 

V.   Articulation  of  the  Lower  Jaw  (Temporomandibular). 

This  is  a  ginglymo-arthrodial  joint:  the  parts  entering  into  its  formation  on 
each  side  are,  above,  the  anterior  part  of  the  glenoid  cavity  of  the_  temporal  bone 
and  the  eminentia  articularis  ;  and,  below,  the  condyle  of  the  lower  jaw.  The  liga- 
ments are  the  following : 

External  Lateral.  Stylo-mandibular. 

Internal  Lateral.  Capsular. 

Interarticular  Fibro-cartilage. 

The  External  Lateral  Ligament  (Fig.  157)  is  a  short,  thin,  and  narrow 
fasciculus,  attached,  above,  to  the  outer  surface  of  the  zygoma  and  to  the 
tubercle  on  its  lower  border ;  below,  to  the  outer  surface  and  posterior  border  of 
the  neck  of  the  lower  jaw.      It  is  broader  above  than  below;  its  fibres  are  placed 


232 


THE  ARTICULATIONS. 


parallel  with  one  another,  and  directed  obliquely  downward  and  backward.     Ex- 
ternally, it  is  covered  by  the  parotid  gland  and  by  the  integument.     Internally, 


Fig.  157.— Temporomandibular  articulation.    External  view. 

it  is  in  relation  with  the  capsular  ligament,  of  which  it  is  an  accessory  band,  and 

not  separable  from  it. 

The  Internal  Lateral  Ligament  (Spheno-mandibular)  (Fig.  158)  is  a  flat,  thin. 

band  which  is  attached  above  to  the  spinous  process  of  the  sphenoid  bone,  and, 

becoming  broader  as  it  descends,  is 
inserted  into  the  lingula  and  margin 
of  the  dental  foramen.  Its  outer 
surface  is  in  relation,  above,  with 
the  External  pterygoid  muscle ; 
lower  down  it  is  separated  from 
the  neck  of  the  condyle  by  the  in- 
ternal maxillary  artery ;  and  still 
more  inferiorly,  the  inferior  dental 
vessels  and  nerve  separate  it  from 
the  ramus  of  the  jaw.  The  inner 
surface  is  in  relation  with  the  In- 
ternal pterygoid.  It  is  really 
the  fibrous  covering  of  a  part  of 
Meckel's  cartilage. 

The  Stylo  -mandibular  Ligament 
is  a  specialized  band  of  the  cervi- 
cal fascia,  which  extends  from  near 
the  apex  of  the  styloid  process  of 
the  temporal  bone  to  the  angle  and 
posterior  border  of  the  ramus  of 
the  lower  jaw,  between  the  Masse- 
ter  and  Internal  pterygoid  muscles. 

This  ligament  separates  the  parotid  from  the  submaxillary  gland,  and  has  attached 

to  its  inner  side  part  of  the  fibres  of  origin  of  the  Stylo-glossus  muscle.     Although 


Fig.  158.—  Temporo-mandibular  articulation.    Internal  view. 


ARTICULATION    OF    THE   LOWER    JAW. 


233 


Fig.  159. — Vertical  section  of  temporo-mandibular 
articulation. 


usually  classed  among  the  ligaments  of  the  jaw,  it  can  be  considered  only  as  an 
accessory  to  the  articulation. 

The  Capsular  Ligament  forms  a  thin  and  loose  capsule,  attached  above  to  the 
circumference  of  the  glenoid  cavity  and  the  articular  surface  immediately  in  front ; 
below,  to  the  neck  of  the  condyle  of  the  lower  jaw.  It  consists  of  a  few  thin  scat- 
tered fibres,  and  can  hardly  be  considered  as  a  distinct  ligament ;  it  is  thickest  at 
the  back  part  of  the  articulation.1 

The  Interarticular  Fibro- cartilage  (Fig.  159)  is  a  thin  plate  of  an  oval  form, 
placed  horizontally  between  the  condyle  of  the  jaw  and  the  glenoid  cavity.  Its 
upper  surface  is  concavo-convex  from 
before  backward,  and  a  little  convex 
transversely,  to  accommodate  itself  to 
the  form  of  the  glenoid  cavity.  Its 
under  surface,  where  it  is  in  contact 
with  the  condyle,  is  concave.  Its  cir- 
cumference is  connected  to  the  cap- 
sular ligament,  and  in  front  to  the 
tendon  of  the  External  pterygoid 
muscle.  It  is  thicker  at  its  circum- 
ference, especially  behind,  than  at  its 
centre.  The  fibres  of  which  it  is  com- 
posed have  a  concentric  arrangement, 
more  apparent  at  the  circumference 
than  at  the  centre.  Its  surfaces  are 
smooth.  It  divides  the  joint  into 
two   cavities,    each   of  which   is   furnished  with   a   separate  synovial    membrane. 

The  Synovial  Membranes,  two  in  number,  are  placed,  one  above,  and  the  other 
below,  the  fibro-cartilage.  The  upper  one,  the  larger  and  looser  of  the  two,  is  con- 
tinued from  the  margin  of  the  cartilage  covering  the  glenoid  cavity  and  eminentia 
articularis  on  to  the  upper  surface  of  the  fibro-cartilage.  The  lower  one  passes  from 
the  under  surface  of  the  fibro-cartilage  to  the  neck  of  the  condyle  of  the  jaw.  being 
prolonged  downward  a  little  farther  behind  than  in  front.  The  interarticular  cartilage 
is  sometimes  perforated  in  its  centre ;  the  two  synovial  sacs  then  communicate  with 
each  other. 

The  nerves  of  this  joint  are  derived  from  the  auriculo-temporal  and  masseteric 
branches  of  the  inferior  maxillary.  The  arteries  are  derived  from  the  temporal 
branch  of  the  external  carotid. 

Actions. — The  movements  permitted  in  this  articulation  are  very  extensive. 
Thus,  the  jaw  may  be  depressed  or  elevated,  or  it  may  be  carried  forward  or  back- 
ward. It  must  be  borne  in  mind  that  there  are  two  distinct  joints  in  this  articu- 
lation— that  is  to  say,  one  between  the  condyle  of  the  jaw  and  the  interarticular 
fibro-cartilage,  and  another  between  the  fibro-cartilage  and  the  glenoid  fossa  :  when 
the  jaw  is  depressed,  as  in  opening  the  mouth,  the  movements  which  take  place  in 
these  two  joints  are  not  the  same.  In  the  lower  compartment,  that  between  the 
condyle  and  the  fibro-cartilage,  the  movement  is  of  a  ginglymoid  or  hinge-like 
character,  the  condyle  rotating  on  a  transverse  axis  on  the  fibro-cartilage ;  while  in 
the  upper  compartment  the  movement  is  of  a  gliding  character,  the  nbro-cartilage, 
together  with  the  condyle,  gliding  forward  on  to  the  eminentia  articularis.  These 
two  movements  take  place  simultaneously — the  condyle  and  fibro-cartilage  move 
forward  on  the  eminence,  and  at  the  same  time  the  condyle  revolves  on  the  fibro- 
cartilage.  In  the  opposite  movement  .of  shutting  the  mouth  the  reverse  action  takes 
place;  the  fibro-cartilage  glides  back,  carrying  the  condyle  with  it.  and  tins  at  the 
same  time  revolves  back  to  its  former  position.  When  the  jaw  is  carried  horizon- 
tally forward,  as  in  protruding  the  lower  incisors  in  front  of  the  upper,  the  move- 

*Sir  G.  Humphry  describes  the  internal  portion  of  the  capsular  ligament  separately  as  the  short 
internal  lateral  ligament  ■  and  it  certainly  seems  as  deserving  of  a  separate  description  as  the  external 
lateral  ligament  is. 


234  THE  ARTICULATIONS 

ment  takes  place  principally  in  the  upper  compartment  of  the  joint:  the  fibro- 
cartilage,  carrying  with  it  the  condyle,  glides  forward  on  the  glenoid  fossa.  This 
is  because  this  movement  is  mainly  effected  by  the  External  pterygoid  muscles, 
which  are  inserted  into  both  condyle  and  interarticular  fibro-cartilage.  The  grind- 
ing or  chewing  movement  is  produced  by  the  alternate  movement  of  one  condyle, 
with  its  fibro-cartilage,  forward  and  backward,  while  the  other  condyle  moves 
simultaneously  in  the  opposite  direction ;  at  the  same  time  the  condyle  undergoes  a 
vertical  rotation  on  its  own  axis  on  the  fibro-cartilage  in  the  lower  compartment. 
One  condyle  advances  and  rotates,  the  other  condyle  recedes  and  rotates,  in  alter- 
nate succession. 

The  lower  jaw  is  depressed  by  its  own  weight,  assisted  by  the  Platysma,  the 
Digastric,  the  Mylo-hyoid,  and  the  Genio-hyoid.  It  is  elevated  by  the  anterior 
part  of  the  Temporal,  Masseter,  and  Internal  pterygoid.  It  is  drawn  forward  by 
the  simultaneous  action  of  the  External  pterygoid  and  the  superficial  fibres  of  the 
Masseter ;  and  it  is  drawn  bachiuard  by  the  deep  fibres  of  the  Masseter  and  the 
posterior  fibres  of  the  Temporal  muscle.  The  grinding  movement  is  caused  by  the 
alternate  action  of  the  two  External  pterygoids. 

Surface  Form. — The  temporo-mandibular  articulation  is  quite  superficial,  situated  below  the 
base  of  the  zygoma,  in  front  of  the  tragus  and  external  auditory  meatus,  and  behind  the  poste- 
rior border  of  the  upper  part  of  the  Masseter  muscle.  Its  exact  position  can  be  at  once  ascer- 
tained by  feeling  for  the  condyle  of  the  jaw,  the  working  of  which  can  be  distinctly  felt  in  the 
movements  of  the  lower  jaw  in  opening  and  shutting  the  mouth.  When  the  mouth  is  opened 
wide,  the  condyle  advances  out  of  the  glenoid  fossa  on  to  the  eminentia  articularis,  and  a  depres- 
sion is  felt  in  the  situation  of  the  joint. 

Surgical  Anatomy. — The  lower  jaw  is  dislocated  only  in  one  direction — viz.  forward.  The 
accident  is  caused  by  violence  or  muscular  action.  When  the  mouth  is  open,  the  condyle  is 
situated  on  the  eminentia  articularis,  and  any  sudden  violence,  or  even  a  sudden  muscular  spasm, 
as  during  a  convulsive  yawn,  may  displace  the  condyle  forward  into  the  zygomatic  fossa.  The 
displacement  may  be  unilateral  or  bilateral,  according  as  one  or  both  of  the  condyles  are  dis- 
placed.    The  latter  of  the  two  is  the  more  common. 

Sir  Astley  Cooper  described  a  condition  which  he  termed  "subluxation."  It  occurs 
principally  in  delicate  women,  and  is  believed  by  some  to  be  due  to  the  relaxation  of  the  liga- 
ments, permitting  too  free  movement  of  the  bone,  and  possibly  some  displacement  of  the  fibro- 
cartilage.  Others  have  believed  that  it  is  due  to  gouty  or  rheumatic  changes  in  the  joint.  In 
close  relation  to  the  condyle  of  the  jaw  is  the  external  auditory  meatus  and  the  tympanum  ;  any 
force,  therefore,  applied  to  the  bone  is  liable  to  be  attended  with  damage  to  these  parts,  or 
inflammation  in  the  joint  may  extend  to  the  ear,  or  on  the  other  hand  inflammation  of  the  middle 
ear  may  involve  the  articulation  and  cause  its  destruction,  thus  leading  to  ankylosis  of  the  joint. 
In  children,  arthritis  of  this  joint  may  follow  the  exanthemata,  and  in  adults  it  occurs  as  the 
result  of  some  constitutional  conditions,  as  rheumatism  or  gout.  The  temporo-mandibular 
joint  is  also  occasionally  the  seat  of  osteo-arthritis,  leading  to  great  suffering  during  efforts  of 
mastication.  A  peculiar  affection  sometimes  attacks  the  neck  and  condyle  of  the  lower  jaw, 
consisting  in  hypertrophy  and  elongation  of  these  parts  and  consequent  protrusion  of  the  chin 
to  the  opposite  side. 

VI.    Articulations  of  the  Ribs  with  the  Vertebra. 

The  articulations  of  the  ribs  with  the  vertebral  column  may  be  divided  into 
two  sets :  1.  Those  which  connect  the  heads  of  the  ribs  with  the  bodies  of  the 
vertebrae,  costo-central.  2.  Those  which  connect  the  necks  and  tubercles  of  the 
ribs  with  the  transverse  processes,  costo-transverse. 

1.    Articulations  between  the  Heads  of  the  Ribs  and  the  Bodies 
of  the  Vertebrae  (Fig.  160). 

These  constitute  a  series  of  arthrodial  joints,  formed  by  the  articulation  of  the 
heads  of  the  ribs  with  the  cavities  on  the  contiguous  margins  of  the  bodies  of  the 
dorsal  vertebrae  and  the  intervertebral  substance  between  them,  except  in  the  case 
of  the  first,  tenth,  eleventh,  and  twelfth  ribs,  where  the  cavity  is  formed  by  a  single 
vertebra.      The  bones  are  connected  bv  the  following;  ligaments : 

Anterior  Costo-vertebral  or  Stellate. 
Capsular.  Interarticular. 

The  Anterior  Costo-vertebral  or  Stellate  Ligament  connects  the  anterior  prat  of 


OF    THE   BIBS    WITH    THE    VEBTEBBJE. 


235 


the  head  of  each  rib  with  the  sides  of  the  bodies  of  two  vertebrae  and  the  interver- 
tebral disk  between  them.  It  consists  of  three  flat  bundles  of  ligamentous  fibres, 
which  are  attached  to  the  anterior  part  of  the  head  of  the  rib,  just  beyond  the 
articular  surface.  The  superior  fibres  pass  upward  to  be  connected  with  the  body 
of  the  vertebra  above ;  the  inferior  one  descends  to  the  body  of  the  vertebra 
below ;  and  the  middle  one,  the  smallest  and  least  distinct,  passes  horizontally 
inward,  to  be  attached  to  the  intervertebral  substance. 

Relations. — In  front,  with  the  thoracic  ganglia  of  the  sympathetic,  the  pleura, 
and,  on  the  right  side,  with  the  vena  azygos  major;  behind,  with  the  interarticular 
ligament  and  synovial  membranes. 

In  the  first  rib,  which  articulates  with  a  single  vertebra,  this  ligament  does 
not  present  a  distinct  division  into  three  fasciculi ;  its  fibres,  however,  radiate, 
and  are  attached  to  the  body  of  the  last  cervical  vertebra,  as  well  as  to  the  body  of 
the  vertebra  with  which  the  rib  articulates.  In  the  tenth,  eleventh,  and  twelfth 
ribs  also,  which  likewise  articulate  with  a  single  vertebra,  the  division  does  not 
exist ;  but  the  fibres  of  the  ligament  in  each  case  radiate  and  are  connected  with 
the  vertebra  above,  as  well  as  that  with  which  the  ribs  articulate. 

The  Capsular  Ligament  is  a  thin  and  loose  ligamentous  bag,  which  surrounds 
the  joint  between  the  head  of  the  rib  and  the  articular  cavity  formed  by  the 
intervertebral  disk  and  the 
adjacent  vertebra.  It  is 
very  thin,  firmly  connected 
with  the  anterior  ligament, 
and  most  distinct  at  the 
upper  and  lower  parts  of 
the  articulation.  Behind, 
some  of  its  fibres  pass 
through  the  intervertebral 
foramen  to  the  back  of  the 
intervertebral  disk.  This 
is  the  analogue  of  the  liga- 
mentum  coiijugale  of  some 
mammals,  which  unites  the 
heads  of  opposite  ribs  across 
the  back  of  the  interverte- 
bral disk. 

The  Interarticular  Liga- 
ment is  situated  in  the 
interior  of  the  joint.  It 
consists  of  a  short  band  of 
fibres,  flattened  from  above 
downward,  attached  by  one 
extremity  to  the  sharp 
crest   which   separates    the 

two  articular  facets  on  the  head  of  the  rib,  and  by  the  other  to  the  intervertebral 
disk.  It  divides  the  joint  into  two  cavities,  which  have  no  communication  with 
each  other.  In  the  first,  tenth,  eleventh,  and  twelfth  ribs  the  interarticular  liga- 
ment does  not  exist ;   consequently  there  is  but  one  synovial  membrane. 

The  Synovial  Membrane. — There  are  two  synovial  membranes  in  each  of  the 
articulations  in  which  there  is  an  interarticular  ligament,  one  on  each  side  oi  this 
structure. 

2.  Articulations  of  the  Necks  and  Tubercles  of  the  Ribs  with 

the  Transverse  Processes  (Fig.  161). 
The  articular  portion  of  the  tubercle  of  the  rib  and  adjacent  transverse  process 
form  an  arthrodial  joint. 

In  the  eleventh  and  twelfth  ribs  this  articulation  is  wanting. 


pper synov 
cavity.  j 

INTERARTICULAR    LIGAMEN 

Lower  synovial  cavity. 

Fig.  160.— Costovertebral  and  costotransverse  articulations, 
rior  view. 


236 


THE   ARTICULATIONS 


The  ligaments  connecting  these  parts  are  the — 

Anterior  Costo-transverse. 

Middle  Costo-transverse  (Interosseous). 

Posterior  Costo-transverse. 

Capsular. 

The  Anterior  Costo-transverse  Ligament  {superior  or  long)  consists  of  two  sets 
of  fibres  :  the  one  (anterior)  is  attached  below  to  the  sharp  crest  on  the  upper 
border  of  the  neck  of  each  rib,  and  passes  obliquely  upward  and  outward  to  the 
lower  border  of  the  transverse  process  immediately  above;  the  other  (jiosterior)  is 
attached  below  to  the  neck  of  the  rib,  and  passes  upward  and  inward  to  the  base 
of  the  transverse  process  and  outer  border  of  the  lower  articular  process  of  the 
vertebra  above.  This  ligament  is  in  relation,  in  front,  with  the  intercostal  vessels 
and  nerves;  behind,  with  the  Longissimus  dorsi.  Its  internal  border  is  thickened 
and  free,  and  bounds  an  aperture  through  which  pass  the  posterior  branches  of  the 
intercostal  vessels  and  nerves.  Its  external  border  is  continuous  with  a  thin 
aponeurosis  which  covers  the  External   intercostal  muscle. 

The  first  rib  has  no  anterior  costo-transverse  ligament. 

The  Middle  Costo-transverse  or  Interosseous  Ligament  consists  of  short  but 
strong  fibres  which  pass  between  the  rough  surface  on  the  posterior  part  of  the 
neck  of  each  rib  and  the  anterior  surface  of  the  adjacent  transverse  process.     In 


ANTERIOR    COSTO-TRANSVERSE 
LIGAMENT    DIVIDED. 


MIDDLE    COSTO-TRANSVERSE 

Or    INTEROSSEOUS 
POSTERIOR    COSTO- 
TRANSVERSE   LIGAMENT 


Fig.  161.— Costo-transverse  articulation.    Seen  from  above. 

order  fully  to  expose  this  ligament,  a  horizontal  section  should  be  made  across  the 
transverse  process  and  corresponding  part  of  the  rib  ;  or  the  rib  may  be  forcibly 
separated  from  the  transverse  process  and  its  fibres  put  on  the  stretch. 

In  the  eleventh  and  tivelfth  ribs  this  ligament  is  quite  rudimentary  or 
wanting. 

The  Posterior  Costo-transverse  Ligament  is  a  short  but  thick  and  strong  fascic- 
ulus which  passes  obliquely  from  the  summit  of  the  transverse  process  to  the 
rough  non-articular  portion  of  the  tubercle  of  the  rib.  This  ligament  is  shorter 
and  more  oblique  in  the  upper  than  in  the  lower  ribs.  Those  corresponding  to 
the  superior  ribs  ascend,  while  those  of  the  inferior  ribs  descend  slightly. 

In  the  eleventh  and  tivelfth  ribs  this  ligament  is  wanting. 


OF   THE   RIBS    WITH    THE    VERTEBRAE. 


237 


The  Capsular  Ligament  is  a  thin,  membranous  sac  attached  to  the  circumference 
of  the  articular  surfaces,  and  enclosing  a  small  synovial  membrane. 

In  the  eleventh  and  twelfth  ribs  this  ligament  is  absent. 

Actions. — The  heads  of  the  ribs  are  so  closely  connected  to  the  bodies  of  the 
vertebrae  by  the  stellate  and  interarticular  ligaments,  and  the  necks  and  tubercles 
of  the  ribs  to  the  transverse  processes,  that  only  a  slight  sliding  movement  of 
the  articular  surfaces  on  each  other  can  take  place  in  these  articulations.  The 
result  of  this  gliding  movement  with  respect  to  the  six  upper  ribs  consists  in  an 
elevation  of  the  front  and  middle  portion  of  the  rib,  the  hinder  part  being  pre- 
vented from  performing  any  upward  movement  by  its  close  connection  with  the 
spine.  In  this  gliding  movement  the  rib  rotates  on  an  axis  corresponding  with  a 
line  drawn  through  the  two  articulations,  Costo-central  and  Costo-transverse,  which 
the  rib  forms  with  the  spine.  With  respect  to  the  seventh,  eighth,  ninth,  and  tenth 
ribs,  each  one,  besides  rotating  in  a  similar  manner  to  the  upper  six,  also  rotates 
on  an  axis  corresponding  with  a  line  drawn  from  the  head  of  the  rib  to  the 
sternum.  By  the  first  movement — that  of  rotation  of  the  rib  on  an  axis  corre- 
sponding with  a  line  drawn  through  the  two  articulations  which  this  bone  forms 
with  the  spine — an  elevation  of  the  anterior  part  of  the  rib  takes  place,  and 
a  consequent  enlargement  of  the 
antero-posterior  diameter  of  the 
chest.  None  of  .  the  ribs  lie  in 
a  truly  horizontal  plane ;  they  are 
all  directed  more  or  less  obliquely, 
so  that  their  anterior  extremities 
lie  on  a  lower  level  than  their  pos- 
terior, and  this  obliquity  increases 
from  the  first  to  the  seventh,  and 
then  again  decreases.  If  we  ex- 
amine any  one  rib — say,  that  in 
which  there  is  the  greatest  obliq- 
uity— we  shall  see  that  it  is  ob- 
vious that  as  its  sternal  extremity 
is  carried  upward,  it  must  also  be 
thrown  forward ;  so  that  the  rib 
may  be  regarded  as  a  radius  mov- 
ing on  the  vertebral  joint  as  a  cen- 
tre, and  causing  the  sternal  attach- 
ment to  describe  an  arc  of  a  circle 
in  the  vertical  plane  of  the  body. 
Since  all  the  ribs  are  oblique  and 
connected  in  front  to  the  sternum 
by  the  elastic  costal  cartilages,  they 
must  have  a  tendency  to  thrust  the 
sternum  forward,  and  so  increase 
the  antero-posterior  diameter  of 
the  chest.  By  the  second  move- 
ment— that  of  the  rotation  of  the 
rib  on  an  axis  corresponding  with 
a  line  drawn  from  the  head  of  the 
rib   to  the  sternum — an  elevation 

of    the    middle    portion    of    the    rib  Fig.  162  —  Diagrams  showing  the  axis 

;    l  l  i  ,i  ribs  in  the  movements  of  respiration.    The  one  axis  of  rota- 

takes    place,    and    consequently    an     Son  corresponds  with  a  line  clrawn  through  the  two  articu- 

inerease  in   the  transverse  diameter     lations  which  the  rib  forms  with  the  spine  (a,  b), and  the 
mnedse  in  me  iidnsveise  uidLueiei      Qther  wUh  a  ]ine  drawn  from  the  head  of  the  rib  to  the 

Of  the  chest.       For  the  ribs   not  only    sternum  (a,  b).    (From  Kirke's  Handbook  of  Physiology.) 

slant   downward   and   forward  from 

their  vertebral  attachment,  but  they  are  also  oblique  in  relation  to  their  transverse 

plane — that  is  to  say,  their  middle  is  on  a  lower  level  than  either  their  vertebral  or 


238  THE  ARTICULATIONS 

sternal  extremities.  It  results  from  this  that  when  the  ribs  are  raised,  the  centre 
portion  is  thrust  outward,  somewhat  after  the  fashion  in  which  the  handle  of  a 
bucket  is  thrust  away  from  the  side  when  raised  to  a  horizontal  position,  and 
the  lateral  diameter  of  the  chest  is  increased  (see  Fig.  162).  The  mobility  of 
the  different  ribs  varies  very  much.  The  first  rib  is  more  fixed  than  the  others, 
on  account  of  the  weight  of  the  upper  extremity  and  the  strain  of  the  ribs  beneath  ; 
but  on  the  freshly  dissected  thorax  it  moves  as  freely  as  the  others.  From  the 
same  causes  the  movement  of  the  second  rib  is  also  not  very  extensive.  In  the 
other  ribs  this  mobility  increases  successively  down  to  the  last  two,  which  are  very 
movable.     The  ribs  are  generally  more  movable  in  the  female  than  in  the  male. 

VII.  Articulation  of  the  Cartilages  of  the  Ribs  with  the  Sternum, 

etc.  (Fig.  163). 

The  articulations  of  the  cartilages  of  the  true  ribs  with  the  sternum  are  arthro- 
dial  joints,  with  the  exception  of  the  first,  in  which  the  cartilage  is  almost  always 
directly  united  with  the  sternum,  and  which  must  therefore  be  regarded  as  a 
synarthrodial  articulation.      The  ligaments  connecting  them  are — 

Anterior  Chondro-sternal.  Interarticular  Chondro-sternal. 

Posterior  Chondro-sternal.  Anterior  Chondro-xiphoid. 

Capsular.  Posterior  Chondro-xiphoid. 

The  Anterior  Chondro-sternal  Ligament  is  a  broad  and  thin  membranous  band 
that  radiates  from  the  front  of  the  inner  extremity  of  the  cartilages  of  the  true 
ribs  to  the  anterior  surface  of  the  sternum.  It  is  composed  of  fasciculi  which  pass 
in  different  directions.  The  superior  fasciculi  ascend  obliquely,  the  inferior  pass 
obliquely  downward,  and  the  middle  fasciculi  horizontally.  The  superficial  fibres 
of  this  ligament  are  the  longest :  they  intermingle  with  the  fibres  of  the  ligaments 
above  and  below  them,  with  those  of  the  opposite  side,  and  with  the  tendinous 
fibres  of  origin  of  the  Pectoralis  major,  forming  a  thick  fibrous  membrane  which 
covers  the  surface  of  the  sternum.  This  is  more  distinct  at  the  lower  than  at  the 
upper  part. 

The  Posterior  Chondro-sternal  Ligament,  less  thick  and  distinct  than  the 
anterior,  is  composed  of  fibres  which  radiate  from  the  posterior  surface  of  the 
sternal  end  of  the  cartilages  of  the  true  ribs  to  the  posterior  surface  of  the  sternum, 
becoming  blended  with  the  periosteum. 

The  Capsular  Ligament  surrounds  the  joints  formed  between  the  cartilages 
of  the  true  ribs  and  the  sternum.  It  is  very  thin,  intimately  blended  Avith  the 
anterior  and  posterior  ligaments,  and  strengthened  at  the  upper  and  lower  part  of 
the  articulation  by  a  few  fibres  which  pass  from  the  cartilage  to  the  side  of  the 
sternum.     These  ligaments  protect  the  synovial  membranes. 

The  Interarticular  Chondro-sternal  Ligaments. — These  are  only  found  between 
the  second  and  third  costal  cartilages  and  the  sternum.  The  cartilage  of  the 
second  rib  is  connected  with  the  sternum  by  means  of  an  interarticular  ligament 
attached  by  one  extremity  to  the  cartilage  of  the  second  rib,  and  by  the  other 
extremity  to  the  cartilage  which  unites  the  first  and  second  pieces  of  the  sternum. 
This  articulation  is  provided  with  two  synovial  membranes.  The  cartilage  of  the 
third  rib  is  connected  with  the  sternum  by  means  of  an  interarticular  ligament 
which  is  attached  by  one  extremity  to  the  cartilage  of  the  third  rib,  and  by  the 
other  extremity  to  the  point  of  junction  of  the  second  and  third  pieces  of  the 
sternum.     This  articulation  is  provided  with  two  synovial  membranes. 

The  Anterior  Chondro-xiphoid. — This  is  a  band  of  ligamentous  fibres  which 
connects  the  anterior  surface  of  the  seventh  costal  cartilage,  and  occasionally  also 
that  of  the  sixth,  to  the  anterior  surface  of  the  ensiform  appendix.  It  varies  in 
length  and  breadth  in  different  subjects. 

The  Posterior  Chondro-xiphoid  is  a  similar  band  of  fibres  on  the  internal  or 
posterior  surface,  though  less  thick  and  distinct. 


OF   THE  STERNUM.  239 

Synovial  Membranes. — There  is  no  synovial  membrane  between  the  first  costal 
cartilage  and  the  sternum,  as  this  cartilage  is  directly  continuous  with  the  sternum. 
There  are  two  synovial  membranes,  both  in  the  articulation  of  the  second  and  third 
costal  cartilages  to  the  sternum.  There  is  generally  one  synovial  membrane  in  each 
of  the  joints  between  the  fourth,  fifth,  sixth,  and  seventh  costal  cartilages  to  the 
sternum;  but  it  is  sometimes  absent  in  the  sixth  and  seventh  chondro-sternal 
joints.  Thus  there  are  eight  synovial  cavities  on  each  side  in  the  articulations 
between  the  costal  cartilages  of  the  true  ribs  and  the  sternum.  After  middle  life 
the  articular  surfaces  lose  their  polish,  become  roughened,  and  the  svnovial 
membranes  appear  to  be  wanting.  In  old  age  the  articulations  do  not  exist,  the 
cartilages  of  most  of  the  ribs  becoming  continuous  Avith  the  sternum. 

Actions. — The  movements  which  are  permitted  in  the  chondro-sternal  articu- 
lations are  limited  to  elevation  and  depression,  and  these  only  to  a  slight  extent. 

Articulations  of  the  Cartilages  of  the  Ribs  with  each  other 
(Interchondral)  (Fig.   163). 

The  contiguous  borders  of  the  sixth,  seventh,  and  eighth,  and  sometimes  the 
ninth  and  tenth,  costal  cartilages  articulate  with  each  other  by  small,  smooth, 
oblong-shaped  facets.  Each  articulation  is  enclosed  in  a  thin  capsular  ligament 
lined  by  synovial  membrane,  and  strengthened  externally  and  internally  by  liga- 
mentous fibres  (interchondral  ligaments)  which  pass  from  one  cartilage  to  the 
other.  Sometimes  the  fifth  costal  cartilage,  more  rarely  that  of  the  ninth,  articu- 
lates, by  its  lower  border,  with  the  adjoining  cartilage  by  a  small  oval  facet;  more 
frequently  they  are  connected  together  by  a  few  ligamentous  fibres.  Occasionally 
the  articular  surfaces  above  mentioned  are  wanting. 

Articulations  of  the  Ribs  with  their  Cartilages  (Costo-chondral) 

(Fig.  163). 

The  outer  extremity  of  each  costal  cartilage  is  received  into  a  depression  in  the 
sternal  end  of  the  ribs,  and  the  two  are  held  together  by  the  periosteum. 

VIII.  Articulations  of  the  Sternum. 

The  first  piece  of  the  sternum  is  united  to  the  second  either  by  an  amphi- 
arthrodial  joint — a  single  piece  of  true  fibro-cartilage  uniting  the  segments — or 
by  a  diarthrodial  joint,  in  which  each  bone  is  clothed  with  a  distinct  lamina  of 
cartilage,  adherent  on  one  side,  free  and  lined  with  synovial  membrane  on  the 
other.  In  the  latter  case  the  cartilage  covering  the  gladiolus  is  continued  without 
interruption  on  to  the  cartilages  of  the  second  ribs.  Mr.  Rivington  has  found  the 
diarthrodial  form  of  joint  in  about  one-third  of  the  specimens  examined  by  him  ; 
Mr.  Maisonneuve  more  frequently.  It  appears  to  be  rare  in  childhood,  and  is 
formed,  in  Mr.  Rivington's  opinion,  from  the  amphiarthrodial  form  by  absorption. 
The  diarthrodial  joint  seems  to  have  no  tendency  to  ossify  at  any  age,  while  the 
amphiarthrodial  is  more  liable  to  do  so,  and  has  been  found  ossified  as  early  as 
thirty-four  years  of  age.     The  two  segments  are  further  connected  by  an 

Anterior  Intersternal  Ligament. 
Posterior  Intersternal  Ligament. 

The  Anterior  Intersternal  Ligament  consists  of  a  layer  of  fibres,  having  a 
longitudinal  direction;  it  blends  with  the  fibres  of  the  anterior  chondro-sternal 
ligaments  on  both  sides,  and  with  the  tendinous  fibres  of  origin  of  the  Pectoralis 
major.     This  ligament  is  rough,  irregular,  and  much  thicker  below  than  above*. 

The  Posterior  Intersternal  Ligament  is  disposed  in  a  somewhat  similar 
manner  on  the  posterior  surface  of  the  articulation. 


240 


THE   ARTICULATIONS 


IX.  Articulation  of  the  Vertebral  Column  with  the  Pelvis. 

The  ligaments  connecting  the  last  lumbar  vertebra  with  the  sacrum  are  similar 
to  those  which  connect  the  segments  of  the  spine  with  each  other — viz. :  1.  The 

The  synovial  cavities  exposed  by 
a  vertical  section  of  the  sternum  and  cartilages* 

Cartilage  continous  with 
sternum. 


INTERARTICULAR    LIGAMENT  (Mi 

two  synovial  membranes. 


Single  synovial 
membrane. 


Fig.  163.— Chondro-sternal,  chondro-xiphoid,  and  interchondral  articulations.    Anterior  view. 


continuation  downward  of  the  anterior  and  posterior  common  ligaments.  2.  The 
intervertebral  substance  connecting  the  flattened  oval  surfaces  of  the  two  bones 
and  forming  an  amphiarthrodial  joint.  3.  Ligamenta  subflava,  connecting  the 
arch  of  the  last  lumbar  vertebra  with  the  posterior  border  of  the  sacral  canal. 
4.  Capsular  ligaments  connecting  the  articulating  processes  and  forming  a  double 
arthrodia.    5.  Inter-  and  supraspinous  ligaments. 

The  two  proper  ligaments  connecting  the  pelvis  with  the  spine  are  the  lumbo- 
sacral and  ilio-lumbar. 

The  Lumbo-sacral  Ligament  (Fig.  164)  is  a  short,  thick,  triangular  fasciculus, 
which  is  connected  above  to  the  lower  and  front  part  of  the  transverse  process 


OF    THE   PELVIS. 


241 


of  the  last  lumbar  vertebra,  passes  obliquely  outward,  and  is  attached  below  to 

the  lateral  surface  of  the  base  of  the  sacrum,  becoming  blended  with  the  anterior 

sacro-iliac  ligament.    This  ligament  is  in  relation,  in  front,  with  the  Psoas  muscle. 

The  Ilio-lumbar  Ligament  (Fig.   164)  passes  horizontally  outward  from  the 


Aperture  of  communication 

with 
Bursa  oj  psoas  and  iliacus. 


9*  ft 

'  Femur. 

Fig.  164— Articulations  of  pelvis  and  hip.    Anterior  view. 

apex  of  the  transverse  process  of  the  last  lumbar  vertebra  to  the  crest  of  the  ilium 
immediately  in  front  of  the  sacro-iliac  articulation.  It  is  of  a  triangular  form, 
thick  and  narrow  internally,  broad  and  thinner  externally.  It  is  in  relation,  in 
front,  with  the  Psoas  muscle ;  behind,  with  the  muscles  occupying  the  vertebral 
groove ;  above,  with  the  Quadratus  lumborum. 

X.  Articulations  of  the  Pelvis. 

The  ligaments  connecting  the  bones  of  the  pelvis  with  each  other  may  be 
divided  into  four  groups :  1.  Those  connecting  the  sacrum  and  ilium.  2.  Those 
passing  between  the  sacrum  and  ischium.  3.  Those  connecting  the  sacrum  and 
coccyx.     4.  Those  between  the  two  pubic  bones. 

1.    Articulations  of  the  Sacrum  and  Ilium. 

The  sacro-iliac  articulation  is  an  amphiarthrodial  joint,  formed  between  the 
lateral  surfaces  of  the  sacrum  and  ilium.  The  anterior  or  auricular  portion  of  each 
articular  surface  is  covered  with  a  thin  plate  of  cartilage,  thicker  on  the  sacrum 
than  on  the  ilium.  These  are  in  close  contact  with  each  other,  and  to  a  certain 
extent  united  together  by  irregular  patches  of  softer  fibro-cartilage,  and  at  their 
upper  and  posterior  part  by  fine  fibres  of  interosseous  fibrous  tissue.  In  a  con- 
siderable part  of  their  extent,  especially  in  advanced  life,  they  are  not  connected 
together,  but  are  separated  by  a  space  containing  a  synovial-like  fluid,  and  hence 
the  joint  presents  the  characters  of  a  diarthrosis. 

The  ligaments  connecting  these  surfaces  are  the  anterior  and  posterior  sacro-iliac. 

16 


242 


THE   ARTICULATIONS 


The  Anterior  Sacro-iliac  Ligament  (Fig.  164)  consists  of  numerous  thin  hands 
which  connect  the  anterior  surfaces  of  the  sacrum  and  ilium. 

The  Posterior  Sacro-iliac  (Fig.  165)  is  a  strong  interosseous  ligament,  situated 
in  a  deep  depression  between  the  sacrum  and  ilium  behind,  and  forming  the  chief 
bond  of  connection  between  those  bones.  It  consists  of  numerous  strong  fasciculi 
which  pass  between  the  bones  in  various  directions.  Three  of  these  are  of  large 
size :  the  two  superior,  nearly  horizontal  in  direction,  arise  from  the  first  and 
second  transverse  tubercles  on  the  posterior  surface  of  the  sacrum,  and  are  inserted 
into  the  rough,  uneven  surface  at  the  posterior  part  of  the  inner  surface  of  the 
ilium.  The  third  fasciculus,  oblique  in  direction,  is  attached  by  one  extremity  to 
the  third  transverse  tubercle  on  the  posterior  surface  of  the  sacrum,  and  by  the 
other  to  the  posterior  superior  spine  of  the  ilium ;  it  is  sometimes  called  the 
oblique  sacro-iliac  ligament. 

The  position  of  the  sacro-iliac  joint  is  indicated  by  the  posterior  superior  spine  of  the  ilium. 
This  process  is  immediately  behind  the  centre  of  the  articulation. 

2.  Ligaments  passing  between  the  Sacrum  and  Ischium  (Fig.  165). 

The  Great  Sacro-sciatic  (Posterior). 
The  Lesser  Sacro-sciatic  (Anterior). 

The  Great  or  Posterior  Sacro-sciatic  Ligament  is  situated  at  the  lower  and 
back   part   of  the  pelvis.     It  is  flat,    and   triangular  in   form ;   narrower  in   the 


Fig.  165.— Articulations  of  pelvis  and  hip.    Posterior  view 

middle  than  at  the  extremities  ;  attached  by  its  broad  base  to  the  posterior  inferior 
spine  of  the  ilium,  to  the  fourth  and  fifth  transverse  tubercles  of  the  sacrum,  and 
to  the  lower  part  of  the  lateral  margin  of  that  ]  aid  the  coccyx.     Passing 

obliquely  downward,  outward,  and  forward,  it  becomes  narrow  and  thick,  and 
at  its  insertion  into  the  inner  margin  of  the  tuberosity  of  the  ischium  it  increases 


OF    THE   PELVIS. 


243 


in  breadth,  and  is  prolonged  forward  along  the  inner  margin  of  the  ramus,  forming 
what  is  known  as  the  falciform  ligament.  The  free  concave  edge  of  this  prolonga- 
tion has  attached  to  it  the  obturator  fascia,  with  which  it  forms  a  kind  of  groove, 
protecting  the  internal  pudic  vessels  and  nerve.  One  of  its  surfaces  is  turned 
toward  the  perinseum,  the  other  toward  the  Obturator  internus  muscle. 

The  posterior  surface  of  this  ligament  gives  origin,  by  its  whole  extent,  to  fibres 
of  the  Gluteus  maximus.  Its  anterior  surface  is  united  to  the  lesser  sacro-sciatic 
ligament.  Its  external  border  forms,  above,  the  posterior  boundary  of  the  oreat 
sacro-sciatic  foramen,  and,  below,  the  posterior  boundary  of  the  lesser  sacro-sciatic 
foramen.  Its  lower  border  forms  part  of  the  boundary  of  the  perinaeum.  It  is 
pierced  by  the  coccygeal  branch  of  the  sciatic  artery  and  coccygeal  nerve. 

The  Lesser  or  Anterior  Sacro-sciatic  Ligament,  much  shorter  and  smaller 
than  the  preceding,  is  thin,  triangular  in  form,  attached  by  its  apex  to  the  spine 
of  the  ischium,  and  internally,  by  its  broad  base,  to  the  lateral  margin  of  the 
sacrum  and  coccyx,  anterior  to  the  attachment  of  the  great  sacro-sciatic  ligament, 
with  which  its  fibres  are  intermingled. 

It  is  in  relation,  anteriorly,  with  the  Coccygeus  muscle ;  posteriorly,  it  is  covered 
by  the  great  sacro-sciatic  ligament  and  crossed  by  the  internal  pudic  vessels  and 
nerve.  Its  superior  border  forms  the  lower  boundary  of  the  great  sacro-sciatic 
foramen ;  its  inferior  border,  part  of  the  lesser  sacro-sciatic  foramen. 

These  two  ligaments  convert  the  sacro-sciatic  notches  into  foramina.  The 
superior  or  great  sacro-sciatic  foramen  is  bounded,  in  front  and  above,  by  the 


POUPART'S 
LIGAMENT 


Obturator 
membrane 


ANT.   SACRO-ILIAC 
LIGAMENT. 


GREAT    SACRO- 
SCIATIC    LIGA- 
MENT. 


LESSER  SACRO- 
SCIATIC  LIGA- 
MENT. 


GREAT    SACRO- 
SCIATIC    LIGA- 
MENT. 


Fig.  166.— Side  view  of  pelvis,  showing  the  great  and  lesser  sacro-sciatic  ligaments. 

posterior  border  of  the  os  innominatum  ;  behind,  by  the  great  sacro-sciatic  ligament : 
and  below,  by  the  lesser  sacro-sciatic  ligament.  It  is  partially  filled  up,  in  the 
recent  state,  by  the  Pyriformis  muscle,  which  passes  through  it.  Above  this  muscle 
the  gluteal  vessels  and  superior  gluteal  nerve  emerge  from  the  pelvis,  and,  below 
it,  the  sciatic  vessels  and  nerves,  the  internal  pudic  vessels  and  nerve,  the  inferior 
gluteal  nerve,  and  the  nerves  to  the  obturator  internus  and  quadratus  femoris.  The 
inferior  or  lesser  sacro-sciatic  foramen  is  bounded,  in  front,  by  the  tuber  ischii ; 
above,  by  the  spine  and  lesser  sacro-sciatic  ligament ;  behind,  by  the  greater  sacro- 


244  THE   ARTICULATIONS. 

sciatic  ligament.     It  transmits  the  tendon  of  the  Obturator  internus  muscle,  its 
nerve,  and  the  internal  pudic  vessels  and  nerve. 


3.  Articulation  of  the  Sacrum  and  Coccyx. 

This  articulation  is  an  amphiarthrodial  joint,  formed  between  the  oval  surface 
at  the  apex  of  the  sacrum  and.  the  base  of  the  coccyx.  It  is  analogous  to  the 
joints  between  the  bodies  of  the  vertebrae,  and  is  connected  by  similar  ligaments. 
They  are  the 

Anterior  Sacro-coccygeal.  Lateral  Sacro-coccygeal. 

Posterior  Sacro-coccygeal.  Interposed  Fibro-cartilage. 

Interarticular. 

The  Anterior  Sacro-coccygeal  Ligament  consists  of  a  few  irregular  fibres  which 
descend  from  the  anterior  surface  of  the  sacrum  to  the  front  of  the  coccyx,  becom- 
ing blended  with  the  periosteum. 

The  Posterior  Sacro-coccygeal  Ligament  is  a  flat  band  of  a  pearly  tint,  which 
arises  from  the  margin  of  the  lower  orifice  of  the  sacral  canal,  and  descends  to  be 
inserted  into  the  posterior  surface  of  the  coccyx.  This  ligament  completes  the 
lower  and  back  part  of  the  sacral  canal.  Its  superficial  fibres  are  much  longer 
than  the  more  deeply  seated.  This  ligament  is  in  relation,  behind,  with  the 
Gluteus  maximus. 

The  Lateral  Sacro-coccygeal  Ligaments  connect  the  transverse  processes  of  the 
coccyx  to  the  lower  lateral  angles  of  the  sacrum. 

A  Fibro-cartilage  is  interposed  between  the  contiguous  surfaces  of  the  sacrum 
and  coccyx ;  it  diifers  from  that  interposed  between  the  bodies  of  the  vertebrae  in 
being  thinner,  and  its  central  part  firmer  in  texture.  It  is  somewhat  thicker  in 
front  and  behind  than  at  the  sides.  Occasionally,  a  synovial  membrane  is  found 
when  the  coccyx  is  freely  movable,  which  is  more  especially  the  case  during 
pregnancy. 

The  Interarticular  Ligaments  are  thin  bands  of  ligamentous  tissue  which 
connect  the  cornua  of  the  two  bones  together. 

The  different  segments  of  the  coccyx  are  connected  together  by  an  extension 
downward  of  the  anterior  and  posterior  sacro-coccygeal  ligaments,  a  thin  annular 
disk  of  fibro-cartilage  being  interposed  between  each  of  the  bones.  In  the  adult 
male  all  the  pieces  become  ossified,  but  in  the  female  this  does  not  commonly  occur 
until  a  later  period  of  life.  The  separate  segments  of  the  coccyx  are  first  united, 
and  at  a  more  advanced  age  the  joint  between  the  sacrum  and  coccyx  is  ob- 
literated. 

Actions. — The  movements  which  take  place  between  the  sacrum  and  coccyx, 
and  between  the  different  pieces  of  the  latter  bone,  are  forward  and  backward ; 
they  are  very  limited.     Their  extent  increases  during  pregnancy. 


4.  Articulation  of  the  Ossa  Pubis  (Symphysis  Pubis)  (Fig.  167). 

The  articulation  between  the  pubic  bones  is  an  amphiarthrodial  joint,  formed 
by  the  junction  of  the  two  oval  articular  surfaces  of  the  ossa  pubis.  The  ligaments 
of  this  articulation  are  the 

Anterior  Pubic.  Posterior  Pubic. 

Superior  Pubic.  Subpubic. 

Interpubic  Disk. 


STEBNO- CLA  VICULAB    ABTICULA  TION. 


245 


The  Anterior  Pubic  Ligament  consists  of  several  superimposed  layers  which 
pass  across  the  front  of  the  articulation.  The  superficial  fibres  pass  obliquely 
from  one  bone  to  the  other,  decussating 

and  forming  an  interlacement  with  the  Il!l"Ulie  cartil 

fibres  of  the  aponeurosis  of  the   Ex- 
ternal oblique  and  the  tendon  of  the  Intermediate^ro-airHlage. 
Rectus  muscles.     The  deep  fibres  pass 
transversely  across  the  symphysis,  and 
are  blended  with  the  fibro-cartilage. 

The  Posterior  Pubic  Ligament  con- 
sists of  a  few  thin,  scattered  fibres 
which  unite  the  two  pubic  bones  pos- 
teriorly. 

The  Superior  Pubic  Ligament  is  a 
band  of  fibres  which  connects  together 
the  two  pubic  bones  superiorly. 

The  Subpubic  Ligament  is  a  thick, 
triangular  arch  of  ligamentous  fibres, 
connecting  together  the  two  pubic 
bones  below  and  forming  the  upper 
boundary  of  the  pubic  arch.  Above, 
it    is   blended   with  the  interarticular 

fibro-cartilage  ;  laterally  it  is  united  with  the  descending  rami  of  the  os  pubis. 
Its  fibres  are  closely  connected  and  have  an  arched  direction. 

The  Interpubic  Disk  consists  of  a  disk  of  cartilage  and  fibro-cartilage  con- 
necting the  surfaces  of  the  pubic  bones  in  front.  Each  of  the  two  surfaces  is 
covered  by  a  thin  layer  of  hyaline  cartilage  which  is  firmly  connected  to  the  bone 
by  a  series  of  nipple-like  processes  which  accurately  fit  within  corresponding  depres- 
sions on  the  osseous  surfaces.  These  opposed  cartilaginous  surfaces  are  connected 
together  by  an  intermediate  stratum  of  fibrous  tissue  and  fibro-cartilage  which 
varies  in  thickness  in  different  subjects.  It  often  contains  a  cavity  in  its  centre, 
probably  formed  by  the  softening  and  absorption  of  the  fibro-cartilage,  since  it 
rarely  appears  before  the  tenth  year  of  life,  and  is  not  lined  by  synovial  membrane. 
It  is  larger  in  the  female  than  in  the  male,  but  it  is  very  questionable  whether  it 
enlarges,  as  was  formerly  supposed,  during  pregnancy.  It  is  most  frequently 
limited  to  the  upper  and  back  part  of  the  joint,  but  it  occasionally  reaches  to  the 
front,  and  may  extend  the  entire  length  of  the  cartilage.  This  cavity  may  be 
easily  demonstrated  by  making  a  vertical  section  of  the  symphysis  pubis  near  its 
posterior  surface  (Fig.  167). 

The  Obturator  Ligament  is  more  properly  regarded  as  analogous  to  the 
muscular  fasciae,  with  which  it  will  be  described. 


Fig.  167.— Vertical  section  of  the  symphysis  pubis. 
Made  near  its  posterior  surface. 


ARTICULATIONS  OF  THE  UPPER  EXTREMITY. 

The  articulations  of  the  upper  extremity  may  be  arranged  in  the  following 
groups:  I.  Sterno-clavicular  articulation.  II.  Acromio-clavicular  articulation. 
III.  Ligaments  of  the  Scapula.  IV.  Shoulder-joint.  V.  Elbow-joint.  VI. 
Radio-ulnar  articulations.  VII.  Wrist-joint.  VIII.  Articulations  of  the  Carpal 
Bones.  IX.  Carpo-metacarpal  articulations.  X.  Metacarpophalangeal  articula- 
tions.    XI.  Articulations  of  the  Phalanges. 

I.  Sterno-clavicular  Articulation  (Fig.  168). 
The  Sterno-clavicular  is  regarded  by  most  anatomists  as  an  arthrodial  joint, 
but  Cruveilhier  considers  it  to  be  an  articulation  by  reciprocal  reception.  Probably 
the  former  opinion  is  the  correct  one,  the  varied  movement  which  the  joint 
enjoys  being  due  to  the  interposition  of  an  interarticular  fibro-cartilage  between 
the  joint  surfaces.      The  parts  entering  into  its  formation  are  the  sternal  end  of  the 


246 


THE  ARTICULATIONS. 


clavicle,  the  upper   and  lateral  part  of  the  first   piece  of   the  sternum,  and  the 
cartilage  of  the  first  rib.     The  articular  surface  of  the  clavicle  is  much  larger  than 


Fig.  168. — Sternoclavicular  articulation.    Anterior  view. 

that  of  the  sternum,  and  invested  with  a  layer  of  cartilage  1  which  is  considerably 
thicker  than  that  on  the  latter  bone.     The  ligaments  of  this  joint  are  the 


Capsular. 

Anterior  Sterno-clavicular. 

Posterior  Sterno-clavicular. 


Interclavicular. 
Costo-clavicular  (rhomboid). 
Interarticular  Fibro-cartilasre. 


The  Capsular  Ligament  completely  surrounds  the  articulation,  consisting  of 
fibres  of  varying  degrees  of  thickness  and  strength.  Those  in  front  and  behind 
are  of  considerable  thickness,  and  form  the  anterior  and  posterior  sterno-clavicu- 
lar ligaments ;  but  those  above  and  below,  especially  in  the  latter  situation,  are 
thin  and  scanty,  and  partake  more  of  the  character  of  connective  tissue  than  true 
fibrous  tissue. 

The  Anterior  Sterno-clavicular  Ligament  is  a  broad  band  of  fibres  which 
covers  the  anterior  surface  of  the  articulation,  being  attached,  above,  to  the  upper 
and  front  part  of  the  inner  extremity  of  the  clavicle,  and,  passing  obliquely 
downward  and  inward,  is  attached,  below,  to  the  upper  and  front  part  of  the  first 
piece  of  the  sternum.  This  ligament  is  covered,  in  front,  by  the  sternal  portion  of 
the  Sterno-cleido-mastoid  and  the  integument ;  behind,  it  is  in  relation  with  the 
interarticular  fibro-cartilage  and  the  two  synovial  membranes. 

The  Posterior  Sterno-clavicular  Ligament  is  a  similar  band  of  fibres  which 
covers  the  posterior  surface  of  the  articulation,  being  attached,  above,  to  the  upper 
and  back  part  of  the  inner  extremity  of  the  clavicle,  and,  passing  obliquely 
downward  and  inward,  is  attached,  below,  to  the  upper  and  back  part  of  the  first 
piece  of  the  sternum.  It  is  in  relation,  in  front,  with  the  interarticular  fibro- 
cartilage  and  s}rnovial  membranes  ;  behind,  with  the  Sterno-hyoid  and  Sterno- 
thyroid muscles. 

The  Interclavicular  Ligament  is  a  flattened  band  which  varies  considerably 
in  form  and  size  in  different  individuals  ;  it  passes  in  a  curved  direction  from  the 
upper  part  of  the  inner  extremity  of  one  clavicle  to  the  other,  and  is  also 
attached  to  the  upper  margin  of  the  sternum.  It  is  in  relation,  in  front,  with 
the  integument ;  behind,  with  the  Sterno-thyroid  muscles. 

The  Costo-clavicular  Ligament  (rhomboid)  is  short,  flat,  and  strong :  it  is  of 
a  rhomboid  form,  attached,  below,  to  the  upper  and  inner  part  of  the  cartilage  of 
the  first  rib  :  it  ascends  obliquely  backward  and  outward,  and  is  attached,  above, 

1  According  to  Bruch,  the  sternal  end  of  the  clavicle  is  covered  by  a  tissue  which  is  rather 
fibrous  than  cartilaginous  in  structure. 


STERNO-CLAVICULAR    ARTICULATIONS.  247 

to  the  rhomboid  depression  on  the  under  surface  of  the  clavicle.  It  is  in  relation, 
in  front,  with  the  tendon  of  origin  of  the  Subclavius ;  behind,  with  the  subclavian 
vein. 

The  Interarticular  Fibro-cartilage  is  a  flat  and  nearly  circular  disk,  interposed 
between  the  articulating  surfaces  of  the  sternum  and  clavicle.  It  is  attached, 
above,  to  the  upper  and  posterior  border  of  the  articular  surface  of  the  clavicle ; 
below,  to  the  cartilage  of  the  first  rib,  at  its  junction  with  the  sternum;  and  by 
its  circumference,  to  the  anterior  and  posterior  sterno-clavicular  and  interclavicular 
ligaments.  It  is  thicker  at  the  circumference,  especially  its  upper  and  back  part, 
than  at  its  centre  or  below.  It  divides  the  joint  into  two  cavities,  each  of  which  is 
furnished  with  a  separate  synovial  membrane. 

Of  the  two  Synovial  Membranes  found  in  this  articulation,  one  is  reflected 
from  the  sternal  end  of  the  clavicle  over  the  adjacent  surface  of  the  fibro-cartilage 
and  cartilage  of  the  first  rib  ;  the  other  is  placed  between  the  articular  surface  of 
the  sternum  and  adjacent  surface  of  the  fibro-cartilage  ;  the  latter  is  the  larger  of 
the  two. 

Actions. — This  articulation  is  the  centre  of  the  movements  of  the  shoulder,  and 
admits  of  a  limited  amount  of  motion  in  nearly  every  direction — upward,  down- 
ward, backward,  forward — as  well  as  circumduction.  When  these  movements 
take  place  in  the  joint,  the  clavicle  in  its  motion  carries  the  scapula  with  it,  this 
bone  gliding  on  the  outer  surface  of  the  chest.  This  joint  therefore  forms  the 
centre  from  which  all  movements  of  the  supporting  arch  of  the  shoulder  originate, 
and  is  the  only  point  of  articulation  of  this  part  of  the  skeleton  with  the  trunk. 
"  The  movements  attendant  on  elevation  and  depression  of  the  shoulder  take  place 
between  the  clavicle  and  the  interarticular  fibro-cartilage,  the  bone  rotating  upon 
the  ligament  on  an  axis  drawn  from  before  backward  through  its  own  articular 
facet.  When  the  shoulder  is  moved  forward  and  backward,  the  clavicle,  with 
the  interarticular  fibro-cartilage,  rolls  to  and  fro  on  the  articular  surface  of  the 
sternum,  revolving,  with  a  sliding  movement,  round  an  axis  drawn  nearly  vertically 
through  the  sternum.  In  the  circumduction  of  the  shoulder,  which  is  compounded 
of  these  two  movements,  the  clavicle  revolves  upon  the  interarticular  fibro-cartilage, 
and  the  latter,  with  the  clavicle,  rolls  upon  the  sternum."  l  Elevation  of  the  clavicle 
is  principally  limited  by  the  costo-clavicular  ligament ;  depression,  by  the  inter- 
clavicular. The  muscles  which  raise  the  clavicle,  as  in  shrugging  the  shoulders, 
are  the  upper  fibres  of  the  Trapezius,  the  Levator  anguli  scapulae,  the  clavicular 
liead  of  the  Sterno-mastoid,  assisted  to  a  certain  extent  by  the  two  Rhomboids, 
which  pull  the  vertebral  border  of  the  Scapula  backward  and  upward,  and  so 
raise  the  clavicle.  The  depression  of  the  clavicle  is  principally  effected  by 
gravity,  assisted  by  the  Subclavius,  Pectoralis  minor,  and  lower  fibres  of  the 
Trapezius.  It  is  drawn  backward  by  the  Rhomboids  and  the  middle  and  lower 
fibres  of  the  Trapezius, :  ml  forward  by  the  Serratus  magnus  and  Pectoralis  minor. 

Surface  Form.— The  position  of  the  sterno-clavicular  joint  maybe  easily  ascertained  by  feel- 
ing the  enlarged  sternal  end  of  the  collar-bone  just  external  to  the  long,  cord-like,  sternal  origin 
of  the  Sterno-mastoid  muscle.  If  this  muscle  is  relaxed  by  bending  the  head  forward,  a  depres- 
sion just  internal  to  the  end  of  the  clavicle,  and  between  it  and  the  sternum,  can  be  felt,  indica- 
ting the  exact  position  of  the  joint,  which  is  subcutaneous.  When  the  arm  hangs  by  the  side, 
the  cavity  of  the  joint  is  V-shaped.  If  the  arm  is  raised,  the  bones  become  more  closely  approx- 
imated, and  the  cavity  becomes  a  mere  slit. 

Surgical  Anatomy. — The  strength  of  this  joint  mainly  depends  upon  its  ligaments,  and 
it  is  to  this,  and  to  the  fact  that  the  force  of  the  blow  is  generally  transmitted  along  the 
long  axis  of  the  clavicle,  that  dislocation  rarely  occurs,  and  that  the  bone  is  generally  broken 
rather  than  displaced.  When  dislocation  does  occur,  the  course  which  the  displaced  bone  takes 
depends  more  upon  the  direction  in  which  the  violence  is  applied  than  upon  the  anatomical 
construction  of  the  joint;  it  may  be  either  forward,  backward,  or  upward.  The  chief  point 
worthy  of  note,  as  regards  the  construction  of  the  joint,  in  regard  to  dislocations,  is  the  fact 
that,  owing  to  the 'shape  of  the  articular  surfaces  being  so  little  adapted  to  each  other,  and 
that  the  strength  of  the  joint  mainly  depends  upon  the  ligaments,  the  displacement  when 
reduced  is  very  liable  to  recur,  and  hence  it  is  extremely  difficult  to  keep  the  end  of  the  bone  in  its 
proper  place. 

1  Humphry,  On  the  Human  Skeleton,  p.  402. 


248 


THE   ARTICULATIONS. 


II.  Acromio- clavicular  Articulation  (Fig.  169). 


The  Acromioclavicular  is  an  arthrodial  joint  formed  between  the  outer 
extremity  of  the  clavicle  and  the  inner  margin  of  the  acromion  process  of  the- 
scapula.     Its  ligaments  are  the 

f  Trapezoid 
Coraco-clavicular-<       and 
(  Conoid. 


Superior  Acromioclavicular. 
Inferior  Acromioclavicular. 
Interarticular  Fibro  -cartilage. 


The  Superior  Acromioclavicular  Ligament  is  a  quadrilateral  band  which 
covers  the  superior  part  of  the  articulation,  extending  between  the  upper  part  of 
the  outer  end  of  the  clavicle  and  the  adjoining  part  of  the  upper  surface  of  the 
acromion.  It  is  composed  of  parallel  fibres  which  interlace  with  the  aponeurosis 
of  the  Trapezius  and  Deltoid  muscles ;  below,  it  is  in  contact  with  the  inter- 
articular fibrocartilage  (when  it  exists)  and  the  synovial  membranes. 

The  Inferior  Acromioclavicular  Ligament,  somewhat  thinner  than  the  pre- 
ceding, covers  the  under  part  of  the  articulation,  and  is  attached  to  the  adjoining 
surfaces  of  the  two  bones.  It  is  in  relation,  above,  with  the  synovial  membranes, 
and  in  rare  cases  with  the  interarticular  fibrocartilage ;  below,  with  the  tendon. 


Fig.  169.— The  left  shoulder-joint,  scapuloclavicular  articulations,  and  proper  ligaments  of  scapula. 

of  the  Supraspinatus.  These  two  ligaments  are  continuous  with  each  other  in> 
front  and  behind,  and  form  a  complete  capsule  round  the  joint. 

The  Interarticular  Fibrocartilage  is  frequently  absent  in  this  articulation. 
When  it  exists  it  generally  only  partially  separates  the  articular  surfaces,  and 
occupies  the  upper  part  of  the  articulation.  More  rarely  it  completely  separates 
the  joint  into  two  cavities. 

The   Synovial  Membrane. — There  is  usually  only  one  synovial  membrane  in. 


PROPER    LIGAMENTS    OF    THE   SCAPULA.  249 

this  articulation,  but  when  a  complete  interarticular  fibro-cartilage  exists  there  are 
two  synovial  membranes. 

The  Coraco-clavicular  Ligament  serves  to  connect  the  clavicle  with  the  coracoid 
process  of  the  scapula.  It  does  not  properly  belong  to  this  articulation,  but  as  it 
forms  a  most  efficient  means  in  retaining  the  clavicle  in  contact  with  the  acromial 
process,  it  is  usually  described  with  it.  It  consists  of  two  fasciculi,  called  the 
trapezoid  and  conoid  ligaments. 

The  Trapezoid  Ligament,  the  anterior  and  external  fasciculus,  is  broad,  thin, 
and  quadrilateral ;  it  is  placed  obliquely  between  the  coracoid  process  and  the 
clavicle.  It  is  attached,  below,  to  the  upper  surface  of  the  coracoid  process ; 
above,  to  the  oblique  line  on  the  under  surface  of  the  clavicle.  Its  anterior  border 
is  free ;  its  posterior  border  is  joined  with  the  conoid  ligament,  the  two  forming 
by  their  junction  a  projecting  angle. 

The  Conoid  Ligament,  the  posterior  and  internal  fasciculus,  is  a  dense  band  of 
fibres,  conical  in  form,  the  base  being  directed  upward,  the  summit  downward. 
It  is  attached  by  its  apex  to  a  rough  impression  at  the  base  of  the  coracoid  process, 
internal  to  the  preceding ;  above,  by  its  expanded  base,  to  the  conoid  tubercle  on 
the  under  surface  of  the  clavicle,  and  to  a  line  proceeding  internally  from  it  for 
half  an  inch.  These  ligaments  are  in  relation,  in  front,  with  the  Subclavius  and 
Deltoid  ;  behind,  with  the  Trapezius.  They  serve  to  limit  rotation  of  the  scapula, 
the  Trapezoid  limiting  rotation  forward,  and  the  Conoid  backward. 

Actions. — The  movements  of  this  articulation  are  of  two  kinds  :  1.  A  gliding 
motion  of  the  articular  end  of  the  clavicle  on  the  acromion.  2.  Rotation  of  the 
scapula  forward  and  backward  upon  the  clavicle,  the  extent  of  this  rotation  being 
limited  by  the  two  portions  of  the  coraco-clavicular  ligament. 

The  acromio-clavicular  joint  has  important  functions  in  the  movements  of  the 
upper  extremity.  It  has  been  well  pointed  out  by  Sir  George  Humphry  that  if  there 
had  been  no  joint  between  the  clavicle  and  scapula  the  circular  movement  of  the 
scapula  on  the  ribs,  (as  in  throwing  both  shoulders  backward  or  forward)  would 
have  been  attended  with  a  greater  alteration  in  the  direction  of  the  shoulder  than  is 
consistent  with  the  free  use  of  the  arm  in  such  position,  and  it  would  have  been 
impossible  to  give  a  blow  straight  forward  with  the  full  force  of  the  arm  ;  that  is  to 
say,  with  the  combined  force  of  the  scapula,  arm,  and  forearm.  "  This  joint,"  as 
he  happily  says,  "is  so  adjusted  as  to  enable  either  bone  to  turn  in  a  hinge-like 
manner  upon  a  vertical  axis  drawn  through  the  other,  and  it  permits  the  surfaces 
of  the  scapula,  like  the  baskets  in  a  roundabout  swing,  to  look  the  same  way  in 
every  position  or  nearly  so."  Again,  when  the  whole  arch  formed  by  the  clavicle 
and  scapula  rises  and  falls  (in  elevation  or  depression  of  the  shoulders),  the  joint 
between  these  two  bones  enables^  the  scapula  still  to  maintain  its  lower  part  in 
contact  with  the  ribs. 

Surface  Form. — The  position  of  the  acromio-clavicular  joint  can  generally  be  ascertained  by 
the  slightly  enlarged  extremity  of  the  outer  end  of  the  clavicle,  which  causes  it  to  project  above 
the  level  of  the  acromion  process  of  the  scapula.  Sometimes  this  enlargement  is  so  considerable 
as  to  form  a  rounded  eminence,  which  is  easily  to  be  felt.  The  joint  lies  in  the  plane  of  a  ver- 
tical line  passing  up  the  middle  of  the  front  of  the  arm. 

Surgical  Anatomy.— Owing  to  the  slanting  shape  of  the  articular  surfaces  of  this  joint, 
dislocation  generally  occurs  downward ;  that  is  to  say,  the  acromion  process  of  the  scapula  is 
dislocated  under  the  outer  end  of  the  clavicle;  but  dislocations  in  the  opposite  direction  have 
been  described.  The  displacement  is  often  incomplete,  on  account  of  the  strong  coraco-elaviculai 
ligaments,  which  remain  untorn.  The  same  difficulty  exists,  as  in  the  sterno-clavicular  disloca- 
tion, in  maintaining  the  ends  of  the  bone  in  position  after  reduction. 

III.  Proper  Ligaments  of  the  Scapula  (Fig.  169). 

The  proper  ligaments  of  the  scapula  are  the 

Coraco-acromial.  Transverse. 

The  Coraco-acromial  Ligament  is  a  strong  triangular  band,  extending  between 
the  coracoid  and  acromial  processes.      It  is  attached,  by  its  apex,  to  the  summit 


250 


THE   ARTICULATIONS. 


of  the  acromion  just  in  front  of  the  articular  surface  for  the  clavicle,  and  by  its 
broad  base  to  the  whole  length  of  the  outer  border  of  the  coracoid  process.  Its 
posterior  fibres  are  directed  inward,  its  anterior  fibres  forward  and  inward.  This 
ligament  completes  the  vault  formed  by  the  coracoid  and  acromion  processes  for 
the  protection  of  the  head  of  the  humerus.  It  is  in  relation,  above,  with  the 
clavicle  and  under  surface  of  the  Deltoid;  below,  with  the  tendon  of  the  Supra- 
spinatus  muscle,  a  bursa  being  interposed.  Its  outer  border  is  continuous  with 
a  dense  lamina  that  passes  beneath  the  Deltoid  upon  the  tendons  of  the  Supra- 
and  Infraspinatus  muscles.  This  ligament  is  sometimes  described  as  consisting 
■of  two  marginal  bands  and  a  thinner  intervening  portion,  the  two  bands  being 
attached  respectively  to  the  apex  and  base  of  the  coracoid  process,  and  joining 
together  at  their  attachment  into  the  acromion  process.  When  the  Pectoralis 
minor  is  inserted,  as  sometimes  is  the  case,  into  the  capsule  of  the  shoulder-joint 
instead  of  into  the  coracoid  process,  it  passes  between  these  two  bands,  and  the 
intervening  portion  is  then  deficient. 

The  Transverse  or  Coracoid  {suprascapular)  Ligament  converts  the  suprascapu- 
lar notch  into  a  foramen.  It  is  a  thin  and  flat  fasciculus,  narrower  at  the  middle 
than  at  the  extremities,  attached  by  one  end  to  the  base  of  the  coracoid  process, 
a,nd  by  the  other  to  the  inner  extremity  of  the  scapular  notch.  The  supra- 
scapular nerve  passes  through  the  foramen ;  the  suprascapular  vessels  pass  over 
the  ligament. 

An  additional  ligament  (the  spino-glenoid)  is  sometimes  found  on  the  scapula, 
stretching  from  the  outer  border  of  the  spine  to  the  margin  of  the  glenoid 
cavit}r.  When  present,  it  forms  an  arch  under  which  the  suprascapular  vessels 
and  nerve  pass  as  they  enter  the  infraspinous  fossa. 


BICEPS. 
CORACO-ACROMIAL    \      GLENOID    LIGAMENT. 

LIGAMENT. 
DELTOID. 


DELTOID.      SUPRA-SPINATUS. 


TERES    MAJ 


UB- 

SCAPULA- 

RIS. 

TRICEPS. 


SUB- 
SCAPULARIS. 


teres  major.      Circumflex  vessels.  Circumflex  vessels. 

Fig.  170.— Vertical  sections  through  the  shoulder-joint,  the  arm  being  vertical  and  horizontal.    (After  Henle.) 


Movements  of  Scapula. — The  scapula  is  capable  of  being  moved  upward  and 
downward,  forward  and  backward,  or,  by  a  combination  of  these  movements,  cir- 
cumducted on  the  wall  of  the  chest.  The  muscles  which  raise  the  scapula  are  the 
upper  fibres  of  the  Trapezius,  the  Levator  anguli  scapulse,  and  the  two  Rhom- 
boids ;  those  which  depress  it  are  the  lowrer  fibres  of  the  Trapezius,  the  Pectoralis 
minor,  and,  through  the  clavicle,  the  Subclavius.  The  scapula  is  drawn  backward 
by  the  Rhomboids  and  the  middle  and  lower  fibres  of  the  Trapezius,  and  forward 
by  the  Serratus  magnus  and  Pectoralis  minor,  assisted,  when  the  arm  is  fixed,  by 
the  Pectoralis  major.  The  mobility  of  the  scapula  is  very  considerable,  and 
greatly  assists  the  movements  of  the  arm  at  the  shoulder-joint.  Thus,  in  raising 
the  arm  from  the  side  the  Deltoid  and  Supraspinatus  can   only  lift  it  to  a  right 


THE  SHOULDER- JOINT.  251 

angle  with  the  trunk,  the  further  elevation  of  the  limb  being  effected  by  the 
"Trapezius  and  Serratus  magnus  moving-  the  scapula  on  the  wall  of  the  chest. 
This  mobility  is  of  special  importance  in  ankylosis  of  the  shoulder-joint,  the 
movements  of  this  bone  compensating  to  a  very  great  extent  for  the  immobility 
of  the  joint. 

IV.  Shoulder-joint  (Fig.  169). 

The  Shoulder  is  an  enarthrodial  or  ball-and-socket  joint.  The  bones  entering 
into  its  formation  are  the  large  globular  head  of  the  humerus,  which  is  received 
into  the  shallow  glenoid  cavity  of  the  scapula — an  arrangement  which  permits  of 
very  considerable  movement,  whilst  the  joint  itself  is  protected  against  displacement 
by  the  tendons  which  surround  it  and  by  atmospheric  pressure.  The  ligaments  do 
not  maintain  the  joint  surfaces  in  apposition,  because  when  they  alone  remain  the 
humerus  can  be  separated  to  a  considerable  extent  from  the  glenoid  cavity  ;  their 
use,  therefore,  is  to  limit  the  amount  of  movement.  Above,  the  joint  is  protected 
by  an  arched  vault,  formed  by  the  under  surface  of  the  coracoid  and  acromion 
processes,  and  the  coraco-acromial  ligament.  The  articular  surfaces  are  covered  by 
a  layer  of  cartilage  :  that  on  the  head  of  the  humerus  is  thicker  at  the  centre  than 
at  the  circumference,  the  reverse  being  the  case  in  the  glenoid  cavity.  The  liga- 
ments of  the  shoulder  are  the 

Capsular.  Transverse  humeral. 

Coraco-humeral.  Glenoid.1 

The  Capsular  Ligament  completely  encircles  the  articulation,  being  attached, 
above,  to  the  circumference_of  the  glenoid  cavity  beyond  the  glenoid  ligament; 
below,  to  the  anatomical  neck  of  the  humerus,  approaching  nearer  to  the  articular 
cartilage  above  than  in  the  rest  of  its  extent.  It  is  thicker  above  and  below  than 
elsewhere,  and  is  remarkably  loose  and  lax,  and  much  larger  and  longer  than  is 
necessary  to  keep  the  bones" in  contact,  allowing  them  to  be  separated  from  each 
•other  more  than  an  inch — an  evident  provision  for  that  extreme  freedom  of  move- 
ment which  is  peculiar  to  this  articulation.  Its^superficial  surface  is  strengthened, 
above,  by  the  Supraspinatus  ;  below,  by  the  long  head  of  the  Triceps  ;  behind,  by 
the  tendons  of  the  Infraspinatus  and  Teres  minor ;  and  in  front,  by  the  tendon  of 
the  Subscapularis.  The  capsujar_jig^rment  usually  presents  three  openings ;  one 
anteriorly,  below  the  coracoid  process,  establishes  a  communication  between  the 
synovial  membrane  of  the  joint  and  a  bursa  beneath  the  tendon  of  the  Subscapu- 
laris muscle.  The  second,  which  is  not  constant,  is  at  the  posterior  part,  where  a 
communication  sometimes  exists  between  the  joint  and  a  bursal  sac  belonging  to 
the  Infraspinatus  muscle.  The  third  is  seen  between  the  two  tuberosities,  for  the 
passage  of  the  long  tendon  of  the  Biceps  muscle. 

The  Coraco-humeral  is  a  broad  band  which  strengthens  the  upper  part  of  the 
•capsular  ligament.  It  arises  from  the  outer  border  of  the  coracoid  process,  and 
passes  obliquely  downward  and  outward  to  the  front  of  the  great  tuberosity  of  the 
humerus,  being  DleirdM"'with  the  tendon  of  the  Supraspinatus  muscle.  This  liga- 
ment is  ^intimately  united  to  the  capsular  in  the  greater  part  of  its  extent. 

Supplemental  Bands  of  the  Capsular  Ligament. — In  addition  to  the  coraco- 
humeral  ligament,  the  capsular  ligament  is  strengthened  by  supplemental  bands  in 
the  interior  of  the  joint.  One  of  these  bands  is  situated  on  the  inner  side  of  the 
joint,  and  passes  from  the  inner  edge  of  the  glenoid  cavity  to  the  lower  part  of  the 
lesser  tuberosity  of  the  humerus.  This  is  sometimes  known  as  Flood*  ligament, 
and  is  supposed  to  correspond  with  the  ligamentum  teres  of  the  hip-joint.  A 
second  of  these  bands  is  situated  at  the  lower  part  of  the  joint,  and  passes  from  the 
under  edge  of  the  glenoid  cavity  to  the  under  part  of  the  neck  of  the  humerus,  and 
is  known  as  Schlemms  ligament.  A  third,  called  the  gleno-humeral  ligament,  is 
situated  at  the  upper  part  of  the  joint,  and  projects  into  its  interior,  so  that  it  can 

1  The  long  tendon  of  origin  of  the  Biceps  muscle  also  acts  as  one  of  the  ligaments  of  this  joint. 
See  the  observations  on  p.  222  on  the  function  of  the  muscles  passing  over  more  than  one  joint. 


252  THE   ARTICULATIONS. 

be  seen  only  when  the  capsule  is  opened.  It  is  attached  above  to  the  apex  of  the' 
glenoid  cavity,  close  to  the  root  of  the  coracoid  process,  and,  passing  downward 
along  the  inner  edge  of  the  tendon  of  the  Biceps,  is  attached  below  to  the  lesser 
tuberosity  of  the  humerus,  where  it  forms  the  inner  boundary  of  the  upper  part  of 
the  bicipital  groove.  It  is  a  thin,  ribbon-like  band,  occasionally  quite  free  from 
the  capsule. 

The  Transverse  Humeral  Ligament. — This  is  a  broad  band  of  fibrous  tissue 
passing  from  the  lesser  to  the  greater  tuberosity  of  the  humerus,  and  always. 
limited  to  that  portion  of  the  bone  which  lies  above  the  epiphyseal  line.  It  con- 
verts the  bicipital  groove  into  an  osseo-aponeurotic  canal,  and  is  the  analogue  of 
the  strong  process  of  bone  which  connects  the  summits  of  the  two  tuberosities  in 
the  musk  ox. 

The  Glenoid  Ligament  is  a  fibro-cartilaginous  rim,  attached  round  the  margin 
of  the  glenoid  cavity.  It  is  triangular  on  section,  the  thickest  portion  being  fixed 
to  the  circumference  of  the  cavity,  the  free  edge  being  thin  and  sharp.  It  is 
continuous  above  with  the  long  tendon  of  the  Biceps  muscle,  which  bifurcates  at 
the  upper  part  of  the  cavity  into  two  fasciculi,  and  becomes  continuous  with  the 
fibrous  tissue  of  the  glenoid  ligament.  This  ligament  deepens  the  cavity  for 
articulation,  and  protects  the  edges  of  the  bone.  It  is  lined  by  the  synovial 
membrane. 

The  Synovial  Membrane  is  reflected  from  the  margin  of  the  glenoid  cavity  over 
the  fibro-cartilaginous  rim  surrounding  it :  it  is  then  reflected  over  the  internal 
surface  of  the  capsular  ligament,  covers  the  lower  part  and  sides  of  the  anatomical 
neck  of  the  humerus  as  far  as  the  cartilage  covering  the  head  of  the  bone.  The 
long  tendon  of  the  Biceps  muscle  which  passes  through  the  capsular  ligament  is- 
enclosed  in  a  tubular  sheath  of  synovial  membrane,  which  is  reflected  upon  it  at 
the  point  where  it  perforates  the  capsule,  and  is  continued  around  it  as  far  as  the 
summit  of  the  glenoid  cavity.  The  tendon  of  the  Biceps  is  thus  enabled  to 
traverse  the  articulation,  but  it  is  not  contained  in  the  interior  of  the  synovial 
cavity.  The  synovial  membrane  communicates  with  a  large  bursal  sac  beneath 
the  tendon  of  the  Subscapularis  by  an  opening  at  the  inner  side  of  the  capsular 
ligament ;  it  also  occasionally  communicates  with  another  bursal  sac,  beneath  the 
tendon  of  the  Infraspinatus,  through  an  orifice  at  its  posterior  part.  A  third 
bursal  sac,  which  does  not  communicate  with  the  joint,  is  placed  between  the  under 
surface  of  the  Deltoid  and  the  outer  surface  of  the  capsule. 

The  Muscles  in  relation  with  the  joint  are,  above,  the  Supraspinatus ;  below, 
the  long  head  of  the  Triceps ;  in  front,  the  Subscapularis ;  behind,  the  Infra- 
spinatus and  Teres  minor ;  within,  the  long  tendon  of  the  Biceps.  The  Deltoid  is 
placed  most  externally,  and  covers  the  articulation  on  its  outer  side,  as  well  as  in 
front  and  behind. 

The  Arteries  supplying  the  joint  are  articular  branches  of  the  anterior  and 
posterior  circumflex,  and  suprascapular. 

The  Nerves  are  derived  from  the  circumflex  and  suprascapular. 

Actions. — The  shoulder-joint  is  capable  of  movement  in  every  direction,  forward, 
backward,  abduction,  adduction,  circumduction,  and  rotation.  The  humerus  is 
drawn  forward  by  the  Pectoralis  major,  anterior  fibres  of  the  Deltoid,  Coraco- 
brachialis,  and  by  the  Biceps  when  the  forearm  is  flexed ;  backward,  by  the  Latis- 
simus  clorsi,  Teres  major,  posterior  fibres  of  the  Deltoid,  and  by  the  Triceps  when 
the  forearm  is  extended ;  it  is  abducted  (elevated)  by  the  Deltoid  and  Supraspinatus  ;. 
it  is  adducted  (depressed)  by  the  Subscapularis,  Pectoralis  major,  Latissimus  dorsi, 
and  Teres  major  ;  it  is  rotated  outward  by  the  Infraspinatus  and  Teres  minor; 
and  it  is  rotated  inward  by  the  Subscapularis,  Latissimus  dorsi,  Teres  major,  and 
Pectoralis  major. 

The  most  striking  peculiarities  in  this  joint  are  :  1.  The  large  size  of  the  head 
of  the  humerus  in  comparison  with  the  depth  of  the  glenoid  cavity,  even  when 
supplemented  by  the  glenoid  ligament.     2.   The  looseness  of  the  capsule  of  the 


THE   SHO  ULDEB-JOINT. 


253 


joint.     3.   The  intimate  connection  of  the  capsule  with  the  muscles  attached  to  the 
head  of  the  humerus.     4.   The  peculiar  relation  of  the  biceps  tendon  to  the  joint. 

It  is  in  consequence  of  the  relative  size  of  the  two  articular  surfaces  that  the 
joint  enjoys  such  free  movement  in  every  possible  direction.  When  these  movements 
of  the  arm  are  arrested  in  the  shoulder-joint  by  the  contact  of  the  bony  surfaces 
and  by  the  tension  of  the  corresponding  fibres  of  the  capsule,  together  with  that  of 
the  muscles  acting  as  accessory  ligaments,  they  can  be  carried  considerably  farther 
by  the  movements  of  the  scapula,  involving,  of  course,  motion  at  the  acromio-  and 
sterno-clavicular  joints.  These  joints  are  therefore  to  be  regarded  as  accessory 
structures  to  the  shoulder-joint.1  The  extent  of  these  movements  of  the  scapula  is 
very  considerable,  especially  in  extreme  elevation  of  the  arm,  which  movement  is 
best  accomplished  when  the  arm  is  thrown  somewhat  forward  and  outward,  because 
the  margin  of  the  head  of  the  humerus  is  by  no  means  a  true  circle ;  its  greatest 
diameter  is  from  the  bicipital  groove  downward,  inward,  and  backward,  and  the 
greatest  elevation  of  the  arm  can  be  obtained  by  rolling  its  articular  surface  in  the 
direction  of  the  measurement.  The  great  width  of  the  central  portion  of  the 
humeral  head  also  allows  of  very  free  horizontal  movement  when  the  arm  is 
raised  to  a  right  angle,  in  which  movement  the  arch  formed  by  the  acromion,  the 
coracoid  process,  and  the  coraco-acromial  ligament  constitutes  a  sort  of  supple- 
mental articular  cavity  for  the  head  of  the  bone. 

The  looseness  of  the  capsule  is  so  great  that  the  arm  will  fall  about  an  inch 
from  the  scapula  when  the  muscles  are  dissected  from  the  capsular  ligament  and 
an  opening  made  in  it  to  remove  the  atmospheric  pressure.  The  movements  of 
the  joint,  therefore,  are  not  regulated  by  the  capsule  so  much  as  by  the  surrounding 
muscles  and  by  the  pressure  of  the  atmosphere — an  arrangement  which  "  renders 
the  movements  of  the  joint  much  more  easy  than  they  would  otherwise  have  been, 
and  permits  a  swinging,  pendulum-like  vibration  of  the  limb  when  the  muscles 
are  at  rest  "  (Humphry).  The  fact,  also,  that  in  all  ordinary  positions  of  the  joint 
the  capsule  is  not  put  on  the  stretch  enables  the  arm  to  move  freely  in  all  direc- 
tions. Extreme  iy  •-^ments  are  checked  by  the  tension  of  appropriate  portions  of 
the  capsule,  as  ife  ,_"•>  I  l\£,  yl:e  interlocking  of  the  bones.  Thus  it  is  said  that 
"  abduction  is  r  |!  §f|>.(','/  lj  ■.|||.  ||ontact  of  the  great  tuberosity  with  the  upper  edge  of 
the  glenoid  cijjf 
(Beaunis  et  3VG'|-i 


the  shoulder-  \thl 
fitting,  in  d 
humerus 

Cath 
head,  th< 
a  short 
scapula 
upward 
during  t 
extent — 
the  secon5 
chiefly  in 

Theintf**' 
converts  thes 
and  it  is  regai\ 
of  the  capsule  v 
driven  between  1 

The  peculiar  I 


i),pM4  by  the  tension  of  the  coraco-humeral  ligament " 

and2  maintains  that  the  limitations  of  movement  at 

le  structure  of  the  joint  itself,  the  glenoid  ligament 

~-i  the  elevated  arm,  into  the  anatomical  neck  of  the 

that  in  abducting  the  arm  and  raising  it  above  the 
[ughout  the  whole  movement  with  the  exception  of 
g  and  at  the  end ;  that  the  humerus  moves  on  the 
lging  to  the  horizontal  position,  but  also  in  passing 
vertical  above ;  that  the  clavicle  moves  not  only 
movement  but  in  the  first  as  well,  though  to  a  less 
lavicle  are  concerned  in  the  first  stage  as  well  as  in 

erus  is  partly  involved  in  the  second  as  well   as 


endons  of  the  four  short  muscles  with  the  capsule 
tic  and  spontaneously  acting  ligaments  of  the  joint, 
ntended  to  prevent  the  folds  into  which  all  portions 
fall  in  the  varying  positions  of  the  joint  from  being 
e  pressure  of  the  atmosphere, 
i  Biceps  tendon  to  the  shoulder-joint  appear  to  sub- 
first  place,  by  its  connection  with  both  the  shoulder 
zes  the  action  of  the  two  joints,  and  acts  as  an 
elastic  ligament  in  I  in  the  manner  previously  adverted  to.4     Next,  it 

strengthens  the  iippe*  °f  tne  C(r>e  articular  cavity,  and  prevents  the  head  of  the 
1  See  p.  249.  2  Journal   °n    eaC    ,     d  Physiology,  vol.  xviii.,  1884.  3  Ibid.  *Seep.  222. 


serve  various  purpoint> showing 
and  elbow  the  mu, 


254  THE   ARTICULATIONS. 

humerus  from  being  pressed  up  against  the  acromion  process,  when  the  Deltoid! 
contracts,  instead  of  forming  the  centre  of  motion  in  the  glenoid  cavity.  By  its 
passage  along  the  bicipital  groove  it  assists  in  rendering  the  head  of  the  humerus, 
steady  in  the  various  movements  of  the  arm.  When  the  arm  is  raised  from  the 
side  it  assists  the  Supra-  and  Infraspinatus  in  rotating  the  head  of  the  humerus  in 
the  glenoid  cavity.  It  also  holds  the  head  of  the  bone  firmly  in  contact  with  th& 
glenoid  cavity,  and  prevents  its  slipping  over  its  lower  edge,  or  being  displaced  by 
the  action  of  the  Latissimus  dorsi  and  Pectoralis  major,  as  in  climbing  and  many 
other  movements. 

Surface  Form. — The  direction  and  position  of  the  shoulder-joint  may  be  indicated  by  a  line 
drawn  from  the  middle  of  the  coraco-acromial  ligament,  in  a  curved  direction,  with  its  con- 
vexity inward,  to  the  innermost  part  of  that  portion  of  the  head  of  the  humerus  which  can  be 
felt  in  the  axilla  when  the  arm  is  forcibly  abducted  from  the  side.  When  the  arm  hangs  by  the 
side,  not  more  than  one-third  of  the  head  of  the  bone  is  in  contact  with  the  glenoid  cavity,  and 
three-quarters  of  its  circumference  is  in  front  of  a  vertical  line  drawn  from  the  anterior  border  of 
the  acromion  process. 

Surgical  Anatomy. — Owing  to  the  construction  of  the  shoulder-joint  and  the  freedom  of 
movement  which  it  enjoys,  as  well  as  in  consequence  of  its  exposed  situation,  it  is  more  frequently 
dislocated  than  any  other  joint  in  the  body.  Dislocation  occurs  when  the  arm  is  abducted,  and 
when,  therefore,  the  head  of  the  humerus  presses  against  the  lower  and  front  part  of  the  cap- 
sule, which  is  the  thinnest  and  least  supported  part  of  the  ligament.  The  rent  in  the  capsule 
almost  invariably  takes  place  in  this  situation,  and  through  it  the  head  of  the  bone  escapes,  so 
that  the  dislocation  in  most  instances  is  primarily  subglenoid.  The  head  of  the  bone  does  not 
usually  remain  in  this  situation,  but  generally  assumes  some  other  position,  which  varies  accord- 
ing to  the  direction  and  amount  of  force  producing  the  dislocation  and  the  relative  strength  of 
the  muscles  in  front  and  behind  the  joint.  In  consequence  of  the  muscles  at  the  back  being- 
stronger  than  those  in  front,  and  especially  on  account  of  the  long  head  of  the  Triceps  pre- 
venting the  bone  passing  backward,  dislocation  forward  is  much  more  common  than  back- 
ward. The  most  frequent  position  which  the  head  of  the  humerus  ultimately  assumes  is  on  the 
front  of  the  neck  of  the  scapula,  beneath  the  coracoid  process,  and  hence  named  subcora- 
coid  dislocation.  Occasionally,  in  consequence  probably  of  a  greater  amount  of  force  being 
brought  to  bear  un  the  limb,  the  head  is  driven  farther  inward,  and  rests  on  the  upper  part  of 
the  front  of  the  chest,  beneath  the  clavicle  (subclavicular).  Sometimes  it  remains  in  the  position 
in  which  it  was  primarily  displaced,  resting  o~J°  -  ^'Uary  border  g£ai  scapula  (subglenoid), 
and  rarely  it  passes  backward  and  remains  well  as  by  %A  ^?e  inner  sideath  the  spine  (sub- 
spinous). m  -becked  by  the  Aother  bursal  s.     ,    .  , 

The  shoulder-joint  is  sometimes  the  set vJtv  9^,,„r  i+c  nno+or;nr  «s,  both  acute  and 
chronic,  which  attack  joints,  though  pe%0"{'  ^? UC^0E  ltS  P°ste"°*  Pints  of  equal  size 
and  importance.  Acute  synovitis  may  r.  .  Cilaiaj.  Clel .it,  is  placed  betwmiaj  or  may  fol- 
low secondarily  on  the  so-called  acute  eJomt  are  due  to  tj'apsule.  th  effusion  into- 
the  joint,  and  when  this  occurs  the  different  positions  o>ve,  the  Supraspinal'  of  the  joint 
rounded.  Special  projections  may  o<  'carmlaris  •  behind uar  nganient. 
Thus  a  swelling  may  appear  just  in  f>/- 3  t  .  ,  '  r  '.  '  "  m'ty,  from  effu- 
sion into  the  bursa  beneath  the  Sul  ,  nas  Panted  out  if  the  Biceps._  Iheis  sometimes. 
bilobed  may  be  seen  in  the  interval  scaPu^a  rotates  thrown  its  outer  side,  as  s,  from  effu- 
sion into  the  diverticulum,  which  rpaoe  at  the  beo-jnnin  tne  biceps. 
The  effusion  into  the  synovial  meruot  only  from  the  ha  J  branches  of  the  ant* the  asilla> 
where  a  soft,  elastic,  fluctuating  s as  it  aTvl™~     1          , 

Tubercular  arthritis  not  unf.      T  aPPr<>acnes  the  o  total  de 

structipn  of  the  articulation ,_  wh  .    SeC(ina  half  of  the 
necessitate  excision.     This  joint  k?-  e->  the  scapula  and  c 


1  suprascapular.  ation  may 

lent  in  every  direction.-t  of  osteo- 


arthritis, and  may  also  be'  affected ;    and  that  the  hur^d  rotation.      The  h^'  when  ifc 
becomes  the  seat  ot  Charcot  s  disease  ffrst 

Excision  of  the  shoulder-joint  • 
cular  form)  which  have  gone  on  to  dmate  union  of  the  i 
fractures,  particularly  those  arising  ie  muscles  into  ela«? 
injury  to  the  head  of  the  bone ;  in  somded  as  being-  ah 

r>ain  •    anrl  nossihlv  in  somp  fpw  rasps  of         i  i      ,        o       ' 


pain  ;  and  possibly  in  some  few  cases  of'    .^  "^"S  tt  so  1     Lt/  ^^'  "\"  " 
operation  is  best  performed  by  making  a°uld ^alternately  ^oralis  major, 
ment  down  the  arm  for  about  three  inchesie  bones  by  ^infraspinatus  s 
of  the  Biceps,  which  may  be  either  divideoelations  of  th<issimus   dorsi/1  ■-  as  to  whether  it 

muscles  attached 
t         of  the  bone  can 


fibres  of  the  Deltoily  tlie  tuber_ 
flexed  ;  backward,  hslocations  and 
eltoid,  and  by  the  rbeen  extensive 
the  Deltoid  and  gf^^J  mrgj£ 

o-acromial  liga- 
nfraspinatus  at.    ..  aud  the  tendon 


is  implicated  in  the  disease  or  not.     The  caoses       j     ,-, 

to  the  greater  and  lesser  tuberosities  of      i  '  ,  fc ,     -,     m,      i     hesd  of  the  bone  can 

then  be  thrust  out  of  the  wound  and  sa  e  narmomj :  1-  ine  ta^jT0W  saw  ;n  s{tu  anc| 
subsequently  removed.  The  section  should  fill  positions!  the  glenoic  ,e  articular  surface, 
so  as  to_  leave  the  bone  as  long  as  possiblcr  part  of  th looseness  4  f,Hn  ^e  examined,  and 
gouged  if  carious. 

of  Anatomy  a 


THE   ELBOW-JOINT. 


255 


V.  Elbow-joint  (Figs.  171,  172). 

The  Elbow  is  a  ginglymus  or  hinge-joint.  The  bones  entering  into  its  forma- 
tion are  the  trochlear  of  the  humerus,  which  is  received  into  the  greater  sigmoid 
cavity  of  the  ulna,  and  admits  of  the  movements  peculiar  to  this  joint — viz. 
flexion  and  extension  ;  whilst  the  lesser,  or  radial,  head  of  the  humerus  articulates 
with  the  cup-shaped  depression  on  the  head  of  the  radius  ;  the  circumference  of  the 
head  of  the  radius  articulates  with  the  lesser  sigmoid  cavity  of  the  ulna,  allowing  of 
the  movement  of  rotation  of  the  radius  on  the  ulna,  the  chief  action  of  the  supe- 
rior radio-ulnar  articulation.  The  articular  surfaces  are  covered  with  a  thin  layer 
of  cartilage,  and  connected  together  by  a  capsular  ligament  of  unequal  thickness, 
being  especially  thickened  on  its  two  sides  and,  to  a  less  extent,  in  front  and 
behind.  These  thickened  portions  are  usually  described  as  distinct  ligaments 
under  the  following  names : 


Anterior. 
Posterior. 


Internal  Lateral. 
External  Lateral. 


The  orbicular   ligament   of  the  upper  radio-ulnar   articulation  must  also  be 
reckoned  among  the  ligaments  of  the  elbow. 

The  Anterior   Ligament  (Fig.  171)  is  a  broad  and  thin  fibrous  layer  which 
covers  the  anterior  surface  of  the  joint.     It  is  attached  to  the  front  of  the  internal 

condyle  and  to  the  front  of  the 
humerus  immediately  above  the 
coronoid  and  radial  fossse  ;  below, 


Fig.  171.— Left  elbow-joint,  showing  anterior 
and  internal  ligaments. 


Fig.  172.— Left    elbow-joint,  showing   poste- 
rior and  external  ligaments. 


to  the  anterior  surface  of  the  coronoid  process  of   the  ulna  and  orbicular  liga- 
ment, being  continuous   on  each  side  with  the  lateral  ligaments.     Its  superficial 


256  THE   ARTICULATIONS. 

fibres  pass  obliquely  from  the  inner  condyle  of  the  humerus  outward  to  the 
orbicular  ligament.  The  middle  fibres,  vertical  in  direction,  pass  from  the  upper 
part  of  the  coronoid  depression  and  become  partly  blended  with  the  preceding,  but 
mainly  inserted  into  the  anterior  surface  of  the  coronoid  process.  The  deep  or 
transverse  set  intersects  these  at  right  angles.  This  ligament  is  in  relation,  in 
front,  with  the  Brachialis  anticus,  except  at  its  outermost  part ;  behind,  with  the 
synovial  membrane. 

The  Posterior  Ligament  (Fig.  172)  is  a  thin  and  loose  membranous  fold,  attached, 
above,  to  the  lower  end  of  the  humerus,  above  and  at  the  sides  of  the  olecranon 
fossa ;  below,  to  the  groove  on  the  upper  and  outer  surfaces  of  the  olecranon.  The 
superficial  or  transverse  fibres  pass  between  the  adjacent  margins  of  the  olecranon 
fossa.  The  deeper  portion  consists  of  vertical  fibres,  some  of  which,  thin  and 
weak,  pass  from  the  upper  part  of  the  olecranon  fossa  to  the  margin  of  the  ole- 
cranon ;  others,  thicker  and  stronger,  pass  from  the  back  of  the  capitellum  of  the 
humerus  to  the  posterior  border  of  the  lesser  sigmoid  cavity  of  the  ulna.  This 
ligament  is  in  relation,  behind,  with  the  tendon  of  the  Triceps  and  the  Anconeus ; 
in  front,  with  the  synovial  membrane. 

The  Internal  Lateral  Ligament  (Fig.  171)  is  a  thick  triangular  band  consisting 
of  two  portions,  an  anterior  and  posterior,  united  by  a  thinner  intermediate  por- 
tion. The  anterior  -portion,  directed  obliquely  forward,  is  attached,  above,  by  its 
apex,  to  the  front  part  of  the  internal  condyle  of  the  humerus ;  and,  below,  by  its 
broad  base,  to  the  inner  margin  of  the  coronoid  process.  The  posterior  -portion, 
also  of  triangular  form,  is  attached,  above,  by  its  apex,  to  the  lower  and  back 
part  of  the  internal  condyle ;  below,  to  the  inner  margin  of  the  olecranon. 
Between  these  two  bands  a  few  intermediate  fibres  descend  from  the  internal  con- 
dyle to  blend  with  a  transverse  band  of  ligamentous  tissue  which  bridges  across 
the  notch  between  the  olecranon  and  coronoid  processes.  This  ligament  is  in 
relation,  internally,  with  the  Triceps  and  Flexor  carpi  ulnaris  muscles  and  the 
ulnar  nerve,  and  gives  origin  to  part  of  the  Flexor  sublimis  digitorum. 

The  External  Lateral  Ligament  (Fig.  172)  is  a  short  and  narrow  fibrous  band 
less  distinct  than  the  internal,  attached,  above,  to  a  depression  below  the  external 
condyle  of  the  humerus ;  below,  to  the  orbicular  ligament,  some  of  its  most  pos- 
terior fibres  passing  over  that  ligament,  to  be  inserted  into  the  outer  margin  of  the 
ulna.  This  ligament  is  intimately  blended  with  the  tendon  of  origin  of  the 
Supinator  brevis  muscle. 

The  Synovial  Membrane  is  very  extensive.  It  covers  the  margin  of  the 
articular  surface  of  the  humerus,  and  lines  the  coronoid  and  olecranon  fossae  on 
that  bone ;  from  these  points  it  is  reflected  over  the  anterior,  posterior,  and 
lateral  ligaments,  and  forms  a  pouch  between  the  lesser  sigmoid  cavity,  the 
internal  surface  of  the  orbicular  ligament,  and  the  circumference  of  the  head  of 
the  radius.  Projecting  into  the  cavity  is  a  crescentic  fold  of  synovial  membrane, 
between  the  radius  and  ulna,  suggesting  the  division  of  the  joint  into  two  :  one  the 
humero-radial,  the  other  the  humero-ulnar. 

Between  the  capsular  ligament  and  the  synovial  membrane  are  three  masses 
of  fat ;  one,  the  largest,  above  the  olecranon  fossa,  which  is  pressed  into  the  fossa  by 
the  triceps  during  flexion ;  a  second,  over  the  coronoid  fossa ;  and  a  third,  over 
the  radial  fossa.     These  are  pressed  into  their  respective  fossae  during  extension. 

The  Muscles  in  relation  with  the  joint  are,  in  front,  the  Brachialis  anticus; 
"behind,  the  Triceps  and  Anconeus;  externally,  the  Supinator  brevis  and  the 
common  tendon  of  origin  of  the  Extensor  muscles ;  internally,  the  common 
tendon  of  origin  of  the  Flexor  muscles,  and  the  Flexor  carpi  ulnaris,  with  the 
ulnar  nerve  (Fig.  173). 

The  Arteries  supplying  the  joint  are  derived  from  the  anastomosis  between  the 
superior  profunda,  inferior  profunda,  and  anastomotica  magna  arteries,  branches  of 
the  brachial,  with  the  anterior,  posterior,  and  interosseous  recurrent  branches  of 
the  ulnar  and  the  recurrent  branch  of  the  radial.  These  vessels  form  a  complete 
chain  of  inosculation  around  the  joint. 


THE  ELBOW-JOINT. 


257 


The  Nerves  are  derived  from  the  ulnar  as  it  passes  between  the  internal  condyle 
and  the  olecranon  ;  a  filament  from  the  musculo-cutaneous  (Riidinger),  and  two 
from  the  median  (Macalister). 

Actions. — The  elbow-joint  comprises  three  different  portions — viz.,  the  joint 
between  the  ulna  and  humerus,  that  between  the  head  of  the  radius  and  the 
humerus,  and  the  superior  radio-ulnar 
articulation,  described  below.  All  these 
articular  surfaces  are  invested  by  a  com- 
mon synovial  membrane,  and  the  move- 
ments of  the  whole  joint  should  be  studied 
together.  The  combination  of  the  move- 
ments  of  flexion  and  extension  of  the 
forearm  with  those  of  pronation  and  supi- 
nation of  the  hand,  which  is  ensured  by 
the  two  being  performed  at  the  same  joint, 
is  essential  to  the  accuracy  of  the  various 
minute  movements  of  the  hand. 

The  portion  of  the  joint  between  the 
ulna  and  humerus  is  a  simple  hinge-joint, 
and  allows  of  movements  of  flexion  and 
extension  only.  Owing  to  the  obliquity 
of  the  trochlear  surface  of  the  humerus, 
this  movement  does  not  take  place  in  a 
straight  line ;  so  that  when  the  forearm  is 
■extended  and  supinated  the  axis  of  the 
arm  and  forearm  is  not  in  the  same  line, 
but  the  one  portion  of  the  limb  forms  an 
angle  with  the  others,  and  the  hand,  with 
the  forearm,  is  directed  outward.  During 
flexion,  on  the  other  hand,  the  forearm 
and  the  hand  tend  to  approach  the  middle 
line  of  the  body,  and  thus  enable  the  hand 
to  be  easily  carried  to  the  face.  The  shape 
of  the  articular  surface  of  the  humerus, 
with  its  prominences  and  depressions  accurately  adapted  to  the  opposing  surfaces 
of  the  olecranon,  prevents  any  lateral  movement.  Flexion  is  produced  by  the 
action  of  the  Biceps  and  Brachialis  anticus,  assisted  by  the  muscles  arising  from 
the  internal  condyle  of  the  humerus  and  the  Supinator  longus ;  extension,  by  the 
Triceps  and  Anconeus,  assisted  by  the  extensors  of  the  wrist  and  by  the  Extensor 
communis  digitorum  and  Extensor  minimi  digiti. 

The  joint  between  the  head  of  the  radius  and  the  capitellum  or  radial  head  of 
the  humerus  is  an  arthrodial  joint.  The  bony  surfaces  would  of  themselves  con- 
stitute an  enarthrosis,  and  allow  of  movement  in  all  directions  were  it  not  for  the 
orbicular  ligament  by  which  the  head  of  the  radius  is  bound  down  firmly  to  the 
.sigmoid  cavity  of  the  ulna,  and  which  prevents  any  separation  of  the  two  bones 
laterally.  It  is  to  the  same  ligament  that  the  head  of  the  radius  owes  its  security 
from  dislocation,  which  would  otherwise  constantly  occur  as  a  consequence  of  the 
shallowness  of  the  cup-like  surface  on  the  head  of  the  radius.  In  fact,  but  for 
this  ligament  the  tendon  of  the  biceps  would  be  liable  to  pull  the  head  of  the 
radius  out  of  the  joint.1  In  complete  extension  the  head  of  the  radius  glides  so 
far  back  on  the  outer  condyle  that  its  edge  is  plainly  felt  at  the  back  of  the 
articulation.  Flexion  and  extension  of  the  elbow-joint  are  limited  by  the 
tension  of  the  structures  on  the  front  and  back  of  the  joint,  the  limitation  of 
flexion  being  also  aided  by  the  soft  structures  of  the  arm  and  forearm  coming  in 
■contact. 

In  combination  with  any  position  of  flexion  or  extension  the  head  of  the  radius 

1  Humphry,  op.  cit.,  p.  419. 
17 


Fig.  173. — Sagittal  section  of  the  right  elbow- 
joint,  taken  somewhat  obliquely  and  seen  from  the 
radial  aspect.    (After  Braune.) 


258  THE  ARTICULATIONS. 

can  be  rotated  in  the  upper  radio-ulnar  joint,  carrying  the  hand  with  it.  The- 
hand  is  directly  articulated  to  the  lower  surface  of  the  radius  only,  and  the  concave 
or  sigmoid  surface  on  the  lower  end  of  the  radius  travels  round  the  lower  end  of 
the  ulna.  The  latter  bone  is  excluded  from  the  wrist-joint  (as  will  be  seen  in  the 
sequel)  by  the  interarticular  fibro-cartilage.  Thus,  rotation  of  the  head  of  the 
radius  round  an  axis  which  passes  through  the  centre  of  the  radial  head  of  the 
humerus  imparts  circular  movement  to  the  hand  through  a  very  considerable  arc. 

Surface  Form. — If  the  forearm  be  slightly  flexed  on  the  arm,  a  curved  crease  or  fold  with 
its  convexity  downward  niay  be  seen  running  across  the  front  of  the  elbow,  extending  from  one 
condyle  to  the  other.  The  centre  of  this  fold  is  some  slight  distance  above  the  line  of  the  joint. 
The  position  of  the  radio-humeral  portion  of  the  joint  can  be  at  once  ascertained  by  feeling  for  a 
slight  groove  or  depression  between  the  head  of  the  radius  and  the  capitellum  of  the  humerus  at 
the  back  of  the  articulation. 

Surgical  Anatomy. — From  the  great  breadth  of  the  joint,  and  the  manner  in  which  the 
articular  surfaces  are  interlocked,  and  also  on  account  of  the  strong  lateral  ligaments  and  the 
support  which  the  joint  derives  from  the  mass  of  muscles  attached  to  each  condyle  of  the 
humerus,  lateral  displacement  of  the  bones  is  very  uncommon,  whereas  antero-posterior  disloca- 
tion, on  account  of  the  shortness  of  the  antero-posterior  diameter,  the  weakness  of  the  anterior 
and  posterior  ligaments,  and  the  want  of  support  of  muscles,  much  more  frequently  takes  place, 
dislocation  backward  taking  place  when  the  forearm  is  in  a  position  of  extension,  and  forward 
when  in  a  position  of  flexion.  For,  in  the  former  position,  that  of  extension,  the  coronoid  pro- 
cess is  not  interlocked  into  the  coronoid  fossa,  and  loses  its  grip  to  a  certain  extent,  whereas  the 
olecranon  process  is  in  the  olecranon  fossa,  and  entirely  prevents  displacement  forward.  On 
the  other  hand,  during  flexion,  the  coronoid  process  is  in  the  coronoid  fossa,  and  prevents- 
dislocation  backward,  while  the  olecranon  loses  its  grip  and  is  not  so  eflicient,  as  during  exten- 
sion, in  preventing  a  forward  displacement.  When  lateral  dislocation  does  take  place,  it  is  gen- 
erally incomplete. 

Dislocation  of  the  elbow-joint  is  of  common  occurrence  in  children,  far  more  common 
than  dislocation  of  any  other  articulation,  for,  as  a  rule,  fracture  of  a  bone  more  frequently 
takes  place,  under  the  application  of  any  severe  violence,  in  young  persons  than  dislocation.  In 
lesions  of  this  joint  there  is  ften  very  great  difficulty  in  ascertaining  the  exact  nature  of  the 
injury. 

The  elbow-joint  is  occasionally  the  seat  of  acute  synovitis.  The  synovial  membrane  then 
becomes  distended  with  fluid,  the  bulging  showing  itself  principally  around  the  olecranon  pro- 
cess ;  that  is  to  say,  on  its  inner  and  outer  sides  and  above,  in  consequence  of  the  laxness  of  the 
posterior  ligament.  Occasionally  a  well-marked,  triangular  projection  may  be  seen  on  the  outer 
side  of  the  olecranon,  from  bulging  of  the  synovial  membrane  beneath  the  Anconeus  muscle. 
Again,  there  is  often  some  swelling  just  above  the  head  of  the  radius,  in  the  line  of  the  radio- 
humeral  joint,  There  is  generally  not  much  swelling  at  the  front  of  the  joint,  though  sometimes 
deep-seated  fulness  beneath  the  Brachialis  anticus  may  be  noted.  When  suppuration  occurs  the 
abscess  usually  points  at  one  or  other  border  of  the  Triceps  muscle ;  occasionally  the  pus- 
discharges  itself  in  front,  near  the  insertion  of  the  Brachialis  anticus  muscle.  Chronic  synovitis, 
usually  of  tubercular  origin,  is  of  common  occurrence  in  the  elbow-joint :  under  these  circum- 
stances the  forearm  tends  to  assume  the  position  of  semi-flexion  which  is  that  of  greatest  ease 
and  relaxation  of  ligaments.  It  should  be  borne  in  mind  that  should  ankylosis  occur  in  this  or 
the  extended  position,  the  limb  will  not  be  nearly  so  useful  as  if  ankylosed  in  a  position  of  rather 
less  than  a  right  angle.  Loose  cartilages  are  sometimes  met  with  in  the  elbow-joint,  not  so- 
commonly,  however,  as  in  the  knee ;  nor  do  they,  as  a  rule,  give  rise  to  such  urgent  sjmiptoms, 
and  rai'ely  require  operative  interference.  The  elbow-joint  is  also  sometimes  affected  with 
osteo-arthritis,  but  this  affection  is  less  common  in  this  articulation  than  in  some  other  of  the 
larger  joints. 

Excision  of  the  elbow  is  principally  required  for  three  conditions :  viz.  tubercular  arthritis, 
injury  and  its  results,  and  faulty  ankylosis ;  but  may  be  necessary  for  some  other  rarer  condi- 
tions, such  as  disorganizing  arthritis  after  pyasmia,  unreduced  dislocations,  and  osteo-arthritis. 
The  results  of  the  operation  are,  as  a  rule,  more  favorable  than  those  of  excision  of  any  other 
joint,  and  it  is  one,  therefore,  that  the  surgeon  should  never  hesitate  to  perform,  especially  in 
the  first  three  of  the  conditions  mentioned  above.  The  operation  is  best  performed  by  a  single 
vertical  incision  down  the  back  of  the  joint,  a  transverse  incision,  over  the  outer  condyle,  being 
added  if  the  parts  are  much  thickened  and  fixed.  A  straight  incision  is  made  about  four 
inches  long,  the  mid-point  of  which  is  on  a  level  with  and  a  little  to  the  inner  side  of  the  tip  of 
the  olecranon.  This  incision  is  made  down  to  the  bone,  through  the  substance  of  the  Triceps 
muscle.  The  operator  with  the  point  of  his  knife,  and  guarding  the  soft  parts  with  his  thumb- 
nail, separates  them  from  the  bone.  In  doing  this  there  are  two  structures  which  he  should 
carefully  avoid :  the  ulnar  nerve,  which  lies  parallel  to  his  incision,  but  a  little  internal,  as 
it  courses  down  between  the  internal  condyle  and  the  olecranon  process,  and  the  prolongation  of 
the  Triceps  into  the  deep  fascia  of  the  forearm  over  the  Anconeus  muscle.  Having  cleared  the 
bones  and  divided  the  lateral  and  posterior  ligaments,  the  forearm  is  strongly  flexed  and  the 
ends  of  the  bone  turned  out  and  sawn  off.     The  section  of  the  humerus  should  be  through 


RADIO-ULNAR   ARTICULATIONS.  259 

the  base  of  the  condyles,  that  of  the  ulna  and  radius  should  be  just  below  the  level  of  the 
lesser  sigmoid  cavity  of  the  ulna  and  the  neck  of  the  radius.  In  this  operation  the  object  is 
to  obtain  such  union  as  shall  allow  free  motion  of  the  bones  of  the  forearm ;  and,  therefore, 
passive  motion  must  be  commenced  early,  that  is  to  say,  about  the  tenth  day. 

VI.  Radio-ulnar  Articulations. 

The  articulation  of  the  radius  with  the  ulna  is  effected  by  ligaments  which 
connect  together  both  extremities  as  well  as  the  shafts  of  these  bones.  They  may, 
consequently,  be  subdivided  into  three  sets :  1,  the  superior  radio-ulnar,  which  is 
a  portion  of  the  elbow-joint;  2,  the  middle  radio-ulnar;  and,  3,  the  inferior  radio- 
ulnar articulations. 

1.  Superior  Radio-ulnar  Articulation. 

This  articulation  is  a  trochoid  or  pivot-joint.  The  bones  entering  into  its 
formation  are  the  inner  side  of  the  circumference  of  the  head  of  the  radius  rotating 
within  the  lesser  sigmoid  cavity  of  the  ulna.  Its  only  ligament  is  the  annular  or 
orbicular. 

The  Orbicular  Ligament  (Fig.  172)  is  a  strong,  flat  band  of  ligamentous  fibres, 
Avhich  surrounds  the  head  of  the  radius,  and  retains  it  in  firm  connection  wTith  the 
lesser  sigmoid  cavity  of  the  ulna.  It  forms  about  four-fifths  of  an  osseo-fibrous  ring, 
attached  by  each  end  to  the  extremities  of  the  lesser  sigmoid  cavity,  and  is  smaller 
at  the  lower  part  of  its  circumference  than  above,  by  which  means  the  head  of  the 
radius  is  more  securely  held  in  its  position.  Its  outer  surface,  is  strengthened 
by  the  external  lateral  ligament  of  the  elbow,  and  affords  origin  to  part  of  the 
Supinator  brevis  muscle.  Its  inner  surface  is  smooth,  and  lined  by  synovial 
membrane.  The  synovial  membrane  is  continuous  with  that  which  lines  the 
elbow-joint. 

Actions. — The  movement  which  takes  place  in  this  articulation  is  limited  to 
rotation  of  the  head  of  the  radius  within  the  orbicular  ligament,  and  upon  the 
lesser  sigmoid  cavity  of  the  ulna,  rotation  forward  being  called  pronation;  rotation 
backward,  supination.  Supination  is  performed  by  the  Biceps  and  Supinator 
brevis,  assisted  to  a  slight  extent  by  the  Extensor  muscles  of  the  thumb  and,  in 
certain  positions,  by  the  Supinator  longus.  Pronation  is  performed  by  the  Pro- 
nator radii  teres  and  the  Pronator  quadratus,  assisted,  in  some  positions,  by  the 
Supinator  longus. 

Surface  Form.— The  position  of  the  superior  radio-ulnar  joint  is  marked  on  the  surface  of 
the  body  by  the  little  dimple  on  the  back  of  the  elbow  which  indicates  the  position  of  the  head 
of  the  radius. 

Surgical  Anatomy. — Dislocation  of  the  head  of  the  radius  alone  is  not  an  uncommon 
accident,  and  occurs  most  frequently  in  young  persons  from  falls  on  the  hand  when  the  forearm 
is  extended  and  supinated,  the  head  of  the  bone  being  displaced  forward.  It  is  attended  by 
rupture  of  the  orbicular  ligament.  Occasionally  a  peculiar  injury,  which  is  supposed  to  be  a 
subluxation,  occurs  in  young  children  in  lifting  them  from  the  ground  by  the  hand  or  forearm. 
It  is  believed  that  the  head  of  the  radius  is  displaced  downward  in  the  orbicular  ligament,  the 
upper  border  of  which  becomes  folded  over  the  head  of  the  radius,  between  it  and  the  capitel- 
lum  of  the  humerus. 

2.    Middle  Radio-ulnar  Union. 

The  interval  between  the  shafts  of  the  radius  and  ulna  is  occupied  by  two 
ligaments. 

Oblique.  Interosseous. 

The  Oblique  or  Round  Ligament  (Fig.  171)  is  a  small,  flattened  fibrous  band 
which  extends  obliquely  downward  and  outward  from  the  tubercle  of  the  ulna  at 
the  base  of  the  coronoid  process  to  the  radius  a  little  below  the  bicipital  tuberosity. 
Its  fibres  run  in  the  opposite  direction  to  those  of  the  interosseous  ligament,  and 
it  appears  to  be  placed  as  a  substitute  for  it  in  the  upper  part  of  the  interosseous 
interval.     This  ligament  is  sometimes  wanting. 


260  THE  ARTICULATIONS. 

The  Interosseous  Membrane  is  a  broad  and  thin  plane  of  fibrous  tissue  descending 
obliquely  downward  and  inward,  from  the  interosseous  ridge  on  the  radius  to  that 


Inferior  radio-ulnar 
articulation. 


Carpal  articulations. 


Carpo-metacarpal 
^i^articulatiom. 


Fig.  174-Ligaments  of  wrist  and  hand.    Anterior  view. 


on  the  ulna.  It  is  deficient  above,  commencing  about  an  inch  beneath  the  tubercle 
of  the  radius;  is  broader  in  the  middle  than  at  either  extremity;  and  presents  an 
oval  aperture  just  above  its  lower  margin  for  the  passage  of  the  anterior  mter- 
olseous  vessels  to  the  back  of  the  forearm.  This  ligament  serves  to  connect  the 
bones  anc  to  increase  the  extent  of  surface  for  the  attachment  of  the  deep  muscles 
Between  its  upper  border  and  the  oblique  ligament  an  interval  exists  through 
Wh  ch  the  pos  eVior  interosseous  vessels  pass.  Two  or  three  fibrous  bands  are 
occasionally  found  on  the  posterior  surface  of  this  membrane  which  descend 
Suely  from  the  ulna  toward  the  radius,  and  which  have  consequently ^a  diree- 
tncontrarT  to  that  of  the  other  fibres.  It  is  in  relation,  in  j rant  by  its  upper 
thieeTu  A  with  the  Flexor  longus  pollicis  on  the  outer  side  and  with  the 
Flexor  profundus  digitorum  on  the  inner,  lying  upon  the  interval  between .which 
are  the  anterior  interosseous  vessels  and  nerve;  by  its  lower  fourth,  with  the 
pTontor  iadratus;  iekincl,  *Jh  the  Supinator  brevis,  E^or  ««s  me acarpi 
nollicis  Extensor  brevis  pollicis,  Extensor  longus  pollicis  Extensor  mdicis ,  and 
near  The  wrist,  with  the  anterior  interosseous  artery  and  posterior  interosseous 

H6TV6 

3    Inferior  Radio-ulnar  Articulation. 

This  is  a  pivot-joint,  formed  by  the  head  of  the  ulna  received  into  the ^sigmoid 

cavity  at  the  inner  side  of  the  lower  end  of  the  radius.    The  articular  surfaces  are 

covered  by  a  thin  layer  of  cartilage,  and  connected  together  by  the  following  iig- 

aments :  _  .      t>    v      i   „« 

Anterior  Radio-ulnar.  Posterior  Radio-ulnai. 

Interarticular  Fibro-cartilage. 

The  Anterior  Radio-ulnar  Ligament  (Fig.  174)  fa   a  narrow  band  of  fibres 

extending  from  the  anterior  margin  of  the  sigmoid  cavity  of  the  radms  to  the 

^^t^£K«*  175)  extends  between  similar  points 

OT  &I££i52l£££r^lYT)   is  triangular  in  shape,   and  fa 


RADIO-  ULNA R  ARTICULA TIONS. 


261 


placed  transversely  beneath  the  head  of  the  ulna,  binding  the  lower  end  of  this 
bone  and  the  radius  firmly  together.  Its  periphery  is  thicker  than  its  centre,  which 
is  thin  and  occasionally  perforated.  It  is  attached  by  its  apex  to  a  depression 
which  separates  the  styloid  process  of  the  ulna  from  the  head  of  that  bone ;  and 
by  its  base,  which  is  thin,  to  the  prominent  edge  of  the  radius,  which  separates  the 
sigmoid  cavity  from  the  carpal  articulating  surface.  Its  margins  are  united  to  the 
ligaments  of  the  wrist-joint.  Its  upper  surface,  smooth  and  concave,  articulates 
with  the  head  of  the  ulna,  forming  an  arthrodial  joint;  its  under  surface,  also 
concave  and  smooth,  forms  part  of  the  wrist-joint  and  articulates  with  the  cuneiform 
and  inner  part  of  the  semilunar  bone.  Both  surfaces  are  lined  by  a  synovial 
membrane — the  upper  surface,  by  one  peculiar  to  the  radio-ulnar  articulation  ;  the 
under  surface,  by  the  synovial  membrane  of  the  wrist. 


Inferior  rcdio-ulnar 

articulation 


Wrist-joint 
Carpal  articulations 


Carpo-metacarpal 

articulations 


Fig.  175. — Ligaments  of  wrist  and  hand.    Posterior  view. 

The  Synovial  Membrane  (Fig.  177)  of  this  articulation  has  been  called,  from 
its  extreme  looseness,  the  membrana  sacciformis  ;  it  extends  horizontally  inward 
between  the  head  of  the  ulna  and  the  interarticular  fibro-cartilage,  and  upward 
between  the  radius  and  the  ulna,  forming  here  a  very  loose  cul-de-sac.  The  quan- 
tity of  synovia  which  it  contains  is  usually  considerable. 

Actions. — The  movement  in  the  inferior  radio-ulnar  articulation  is  just  the 
reverse  of  that  in  the  superior  radio-ulnar  joint.  It  consists  of  a  movement  of 
rotation  of  the  lower  end  of  the  radius  round  an  axis  which  corresponds  to  the 
centre  of  the  head  of  the  ulna.  When  the  radius  rotates  forward,  pronation  of  the 
forearm  and  hand  is  the  result ;  and  when  backward,  supination.  It  will  thus  be 
seen  that  in  pronation  and  supination  of  the  forearm  and  hand  the  radius  describes 
a  segment  of  a  cone,  the  axis  of  which  extends  from  the  centre  of  the  head  of 
the  radius  to  the  middle  of  the  head  of  the  ulna.  In  this  movement,  however, 
the  ulna  is  not  quite  stationary,  but  rotates  a  little  in  the  opposite  direction. 
So  that  it  also  describes  the  segment  of  a  cone,  though  of  smaller  size  than  that 
described  by  the  radius.  The  movement  which  causes  this  alteration  in  the  posi- 
tion of  the  head  of  the  ulna  takes  place  principally  at  the  shoulder-joint  by  a  rota- 
tion of  the  humerus,  but  possibly  also  to  a  slight  extent  at  the  elbow-joint.1 

Surface  Form. — The  position  of  the  inferior  radio-ulnar  joint  may  be  ascertained  by 
feeling  for  a  slight  groove  at  the  back  of  the  wrist,  between  the  prominent  head  of  the 
ulna  and  the  lower  end  of  the  radius,  when  the  forearm  is  in  a  state  of  almost  complete  prona- 
tion. 

1  See  Jowrn,  of  Anat.  and  Phys.,  vol.  xix.,  parts  ii.,  iii.,  and  iv. 


262 


THE   ARTICULATIONS 


VII.  Radio-carpal  or  Wrist-joint. 

The  Wrist  is  a  condyloid  articulation.     The  parts  entering  into  its  formation 

are  the  lower  end  of  the  radius  and  under  surface 
of  the  interarticular  fibro-cartilage,  which  form 
together  the  receiving  cavity,  and  the  scap1  oid, 
semilunar,  and  cuneiform  bones,  which  form  the 
condyle.  The  articular  surface  of  the  radius  and 
the  under  surface  of  the  inter-articular  fibro-car- 
tilage are  the  receiving  cavity,  forming  together 
a  transversely  elliptical  concave  surface.  The 
articular  surfaces  of  the  scaphoid,  semilunar,  and 
cuneiform  bones  form  together  a  smooth,  convex 
surface,  the  condyle,  which  is  received  into  the 
concavity  above  mentioned.  All  the  bony  sur- 
faces of  the  articulation  are  covered  with  cartilage, 
and  connected  together  by  a  capsule,  which  is 
divided  into  the  following  ligaments : 

External  Lateral.  Anterior. 

Internal  Lateral.  Posterior. 


The  External  Lateral  Ligament  {radio-carpal) 
(Fig.  174)  extends  from  the  summit  of  the  styloid 
process  of  the  radius  to  the  outer  side  of  the 
scaphoid,  some  of  its  fibres  being  prolonged  to  the 
trapezium  and  annular  ligament. 

The  Internal  Lateral  Ligament  (idno-carpal)  is 
a  rounded  cord,  attached,  above,  to  the  extremity 
of  the  styloid  process  of  the  ulna,  and  dividing 
below  into  two  fasciculi,  which  are  attached,  one 
to  the  inner  side  of  the  cuneiform  bone,  the  other 
to  the  pisiform  bone  and  annular  ligament. 

The  Anterior  Ligament  is  a  broad  membranous 
band,  attached,  above,  to  the  anterior  margin  of 
the  lower  end  of  the  radius,  its  styloid  process  and 
the  ulna :  its  fibres  pass  downward  and  inward  to 
be  inserted  into  the  palmar  surface  of  the  scaphoid, 
semilunar,  and  cuneiform  bones,  some  of  the  fibres 
being  continued  to  the  os  magnum.  In  addition 
to  this  broad  membrane,  there  is  a  distinct 
rounded  fasciculus,  superficial  to  the  rest,  which 
passes  from  the  base  of  the  styloid  process  of  the 
ulna  to  the  semilunar  and  cuneiform  bones.  This 
ligament  is  perforated  by  numerous  apertures  for  the  passage  of  vessels,  and  is 
in  relation,  in  front,  with  the  tendons  of  the  Flexor  profundus  digitorum  and 
Flexor  longus  pollicis;  behind,  with  the  synovial  membrane  of  the  wrist-joint. 

The  Posterior  Ligament  (Fig.  175),  less  thick  and  strong  than  the  anterior,  is 
attached,  above,  to  the  posterior  border  of  the  loAver  end  of  the  radius  ;  its  fibres 
pass  obliquely  downward  and  inward,  to  be  attached  to  the  dorsal  surface  of  the 
scaphoid,  semilunar,  and  cuneiform  bones,  being  continuous  with  those  of  the 
dorsal  carpal  ligaments.  This  ligament  is  in  relation,  behind,  with  the  extensor 
tendons  of  the  fingers ;  in  front,  with  the  synovial  membrane  of  the  wrist. 

The  Synovial  Membrane  (Fig.  177)  lines  the  inner  surface  of  the  ligaments 
above  described,  extending  from  the  lower  end  of  the  radius  and  interarticular 
fibro-cartilage  above  to  the  articular  surfaces  of  the  carpal  bones  below.  It  is 
loose  and  lax,  and  presents  numerous  folds,  especially  behind. 

Relations. — The  wrist-joint  is  covered  in  front  by  the  flexor  and  behind  by  the 
extensor  tendons  ;  it  is  also  in  relation  with  the  radial  and  ulnar  arteries. 


Fig.  176.— Longitudinal  section  of  the 
right  forearm,  hand,  and  third  finger, 
viewed  from  the  ulnar  aspect.  (After 
Braune.) 


OF    THE    CARPUS.  263 

The  Arteries  supplying  the  joint  are  the  anterior  and  posterior  carpal  branches 
of  the  radial  and  ulnar,  the  anterior  and  posterior  interosseous,  and  some  ascending 
branches  from  the  deep  palmar  arch. 

The  Nei'ves    are  derived  from  the  ulnar  and  posterior  interosseous. 

Actions. — The  movements  permitted  in  this  joint  are  flexion,  extension,  abduc- 
tion, adduction,  and  circumduction.  Its  actions  will  be  further  studied  with  those 
of  the  carpus,  with  which  they  are  combined. 

Surface  Form. — The  line  of  the  radio-carpal  joint  is  on  a  level  with  the  apex  of  the  styloid 
process  of  the  ulna. 

Surgical  Anatomy. — The  wrist-joint  is  rarely  dislocated,  its  strength  depending  mainly 
upon  the  numerous  strong  tendons  which  surround  the  articulation.  Its  security  is  further  pro- 
vided for  by  the  number  of  small  bones  of  which  the  carpus  is  made  up,  and  which  are  united 
by  very  strong  ligaments.  The  slight  movement  which  takes  place  between  the  several  bones 
serves  to  break  the  jars  that  result  from  falls  or  blows  on  the  hand.  Dislocation  backward, 
which  is  the  more  common,  simulates  to  a  considerable  extent  Colles'  fracture  of  the  radius,  and 
is  liable  to  be  mistaken  for  it.  The  diagnosis  can  be  easily  made  out  by  observing  the 
relative  position  of  the  styloid  processes  of  the  radius  and  the  ulna.  In  the  natural  condition  the 
styloid  process  of  the  radius  is  on  a  lower  level — i.  e.  nearer  the  ground — when  the  arm  hangs  by 
the  side,  than  that  of  the  ulna,  and  the  same  would  be  the  case  in  dislocation.  In  Colles'  frac- 
ture, on  the  other  hand,  the  styloid  process  of  the  radius  is  on  the  same,  or  even  a  higher  level 
than  that  of  the  ulna. 

The  wrist-joint  is  occasionally  the  seat  of  acute  synovitis,  the  result  of  traumatism  or  arising 
in  the  rheumatic  or  pyaemic  state.  When  the  synovial  sac  is  distended  with  fluid,  the  swelling 
is  greatest  on  the  dorsal  aspect  of  the  wrist,  showing  a  general  fulness,  with  some  bulging  between 
the  tendons.  The  inflammation  is  prone  to  extend  to  the  intercarpal  joints  and  to  attack  also 
the  sheaths  of  the  tendons  in  the  neighborhood.  Chronic  inflammation  of  the  wrist  is  generally 
tubercular,  and  often  leads  to  similar  disease  in  the  synovial  sheaths  of  adjacent  tendons  and  of 
the  intercarpal  joints.  The  disease,  therefore,  when  progressive,  often  leads  to  necrosis  of  the 
carpal  bones,  and  the  result  is  often  unsatisfactory. 

VIII.  Articulations  of  the  Carpus. 

These  articulations  may  be  subdivided  into  three  sets: 

1.  The  Articulations  of  the  First  Row  of  Carpal  Bones. 

2.  The  Articulations  of  the  Second  Row  of  Carpal  Bones 

3.  The  Articulations  of  the  Two  Rows  with  each  other. 

1.  Articulations  of  the  First  Row  of  Carpal  Bones. 

These  are  arthrodial  joints.  The  ligaments  connecting  the  scaphoid,  semilunar, 
and  cuneiform  bones  are — 

Dorsal.  Palmar. 

Two  Interosseous. 

The  Dorsal  Ligaments  are  placed  transversely  behind  the  bones  of  the  first 
row  ;  they  connect  the  scaphoid  and  semilunar  and  the  semilunar  and  cuneiform. 

The  Palmar  Ligaments  connect  the  scaphoid  and  semilunar  and  the  semilunar 
and  cuneiform  bones  ;  they  are  less  strong  than  the  dorsal,  and  placed  very  deeply 
below  the  anterior  ligament  of  the  wrist. 

The  Interosseous  Ligaments  (Fig.  177)  are  two  narrow  bundles  of  fibrous 
tissue  connecting  the  semilunar  bone  on  one  side  with  the  scaphoid,  and  on  the 
other  with  the  cuneiform.  They  are  on  a  level  with  the  superior  surfaces  of  these 
bones,  and  close  the  upper  part  of  the  spaces  between  them.  Their  upper  surfaces 
are  smooth,  and  form  with  the  bones  the  convex  articular  surfaces  of  the  wrist- 
joint. 

The  ligaments  connecting  the  pisiform  bone  are — 

Capsular.  Tavo  Palmar  ligaments. 

The  Capsular  Ligament  is  a  thin  membrane  which  connects  the  pisiform  bone 
to  the  cuneiform.     It  is  lined  with  a  separate  synovial  membrane. 

The  two  Palmar  Ligaments  are  two  strong  fibrous  bands  which  connect  the 


264  THE  ARTICULATIONS. 

pisiform  to  the  unciform,  the  jwso-uncinate,  and  to  the  base  of  the  fifth  metacarpal 
bone,  the  piso-metacarpal  ligament  (Fig.  174). 

2.  Articulations  of  the  Second  Row  of  Carpal  Bones. 

These  are  also  arthrodial  joints.  The  articular  surfaces  are  covered  with  carti- 
lage, and  connected  by  the  following  ligaments : 

Dorsal.  Palmar. 

Three  Interosseous. 

The  Dorsal  Ligaments  extend  transversely  from  one  bone  to  another  on  the 
dorsal  surface,  connecting  the  trapezium  with  the  trapezoid,  the  trapezoid  with 
the  os  magnum,   and  the  os  magnum  with  the  unciform. 

The  Palmar  Ligaments  have  a  similar  arrangement  on  the  palmar  surface. 

The  three  Interosseous  Ligaments,  much  thicker  than  those  of  the  first  rowy 
are  placed  one  between  the  os  magnum  and  the  unciform,  a  second  between  the 
os  magnum  and  the  trapezoid,  and  a  third  between  the  trapezium  and  trapezoid. 
The  first  of  these  is  much   the  strongest,  and  the  third  is  sometimes  wanting. 

3.  Articulations  of  the  Two  Rows  of  Carpal  Bones  with  each  Other. 

The  joint  betAveen  the  scaphoid,  semilunar,  and  cuneiform,  and  the  second  row 
of  the  carpus,  or  the  mid-carpal  joint,  is  made  up  of  three  distinct  portions ;  in  the 
centre  the  head  of  the  os  magnum  and  the  superior  surface  of  the  unciform 
articulate  with  the  deep,  cup-shaped  cavity  formed  by  the  scaphoid  and  semilunar 
bones,  and  constitute  a  sort  of  ball-and-socket  joint.  On  the  outer  side  the 
trapezium  and  trapezoid  articulate  with  the  scaphoid,  and  on  the  inner  side  the 
unciform  articulates  with  the  cuneiform,   forming  gliding  joints. 

The  ligaments  are — 

Anterior  or  Palmar.  External  Lateral. 

Posterior  or  Dorsal.  Internal  Lateral. 

The  Anterior  or  Palmar  Ligaments  consist  of  short  fibres,  which  pass,  for  the 
most  part,  from  the  palmar  surface  of  the  bones  of  the  first  row  to  the  front  of  the 
os  magnum. 

The  Posterior  or  Dorsal  Ligaments  consist  of  short,  irregular  bundles  of  fibres 
passing  between  the  bones  of  the  first  and  second  row  on  the  dorsal  surface  of  the 
carpus. 

The  Lateral  Ligaments  are  very  short:  they  are  placed,  one  on  the  radial,  the 
other  on  the  ulnar  side  of  the  carpus ;  the  former,  the  stronger  and  more  distinct, 
connecting  the  scaphoid  and  trapezium  bones,  the  latter  the  cuneiform  and  unciform  ; 
they  are  continuous  with  the  lateral  ligaments  of  the  wrist-joint.  In  addition  to 
these  ligaments,  a  slender  interosseous  band  sometimes  connects  the  os  magnum 
and  the  scaphoid. 

The  Synovial  Membrane  of  the  Carpus  is  very  extensive :  it  passes  from  the 
under  surface  of  the  scaphoid,  semilunar,  and  cuneiform  bones  to  the  upper  surface 
of  the  bones  of  the  second  row,  sending  upward  two  prolongations — between  the 
scaphoid  and  semilunar  and  the  semilunar  and  cuneiform  ;  sending  downward 
three  prolongations  between  the  four  bones  of  the  second  row,  which  are  further 
continued  onward  into  the  carpo-metacarpal  joints  of  the  four  inner  metacarpal 
bones,  and  also  for  a  short  distance  between  the  metacarpal  bones.  There  is  a 
separate  synovial  membrane  between  the  pisiform  and  cuneiform  bones. 

Actions. — The  articulation  of  the  hand  and  wrist,  considered  as  a  whole,  is 
divided  into  three  parts  :  (1)  the  radius  and  the  interarticular  fibro-cartilage ; 
(2)  the  meniscus,  formed  by  the  scaphoid,  semilunar,  and  cuneiform,  the  pisiform 
bone  having  no  essential  part  in  the  movements  of  the  hand ;  (3)  the  hand  proper, 
the  metacarpal  bones  with  the  four  carpal  bones  on  which  they  are  supported — viz. 
the  trapezium,  trapezoid,  os  magnum,  and  unciform.     These  three  elements  form 


CARPOMETACARPAL    ARTICULATIONS.  265 

two  joints :  (1)  the  superior  (wrist-joint  proper),  between  the  meniscus  and  bones 
of  the  forearm ;  (2)  the  inferior,  between  the  hand  and  meniscus  (transverse  or 
mid-carpal  joint). 

(1)  The  articulation  between  the  forearm  and  carpus  is  a  true  condyloid  artic- 
ulation, and  therefore  all  movements  but  rotation  are  permitted.  Flexion  and 
extension  are  the  most  free,  and  of  these  a  greater  amount  of  extension  than  flexion 
is  permitted  on  account  of  the  articulating  surfaces  extending  farther  on  the  dorsal 
than  on  the  palmar  aspect  of  the  carpal  bones.  In  this  movement  the  carpal 
bones  rotate  on  a  transverse  axis  drawn  between  the  tips  of  the  styloid  processes 
of  the  radius  and  ulna.  A  certain  amount  of  adduction  (or  ulnar  flexion)  and 
abduction  (or  radial  flexion)  is  also  permitted.  Of  these  the  former  is  considerablv 
greater  in  extent  than  the  latter.  In  this  movement  the  carpus  revolves  upon  an 
antero-posterior  axis  drawn  through  the  centre  of  the  wrist.  Finally,  circumduction 
is  permitted  by  the  consecutive  movements  of  adduction,  extension,  abduction,  and 
flexion,  with  intermediate  movements  between  them.  There  is  no  rotation,  but 
this  is  provided  for  by  the  supination  and  pronation  of  the  radius  on  the  ulna. 
The  movement  of  flexion  is  performed  by  the  Flexor  carpi  radialis,  the  Flexor 
carpi  ulnaris,  and  the  Palmaris  longus ;  extension,  by  the  Extensor  carpi  radialis 
longior  et  brevior  and  the  Extensor  carpi  ulnaris  ;  adduction  (ulnar  flexion),  by  the 
Flexor  carpi  ulnaris  and  the  Extensor  carpi  ulnaris  ;  and  abduction  (radial  flexion), 
by  the  Extensors  of  the  thumb  and  the  Extensor  carpi  radialis  longior  et  brevior 
and  the  Flexor  carpi  radialis. 

(2)  The  chief  movements  permitted  in  the  transverse  or  mid-carpal  joint  are 
flexion  and  extension  and  a  slight  amount  of  rotation.  In  flexion  and  extension, 
which  is  the  movement  most  freely  enjoyed,  the  trapezium  and  trapezoid  on  the 
radial  side  and  the  unciform  on  the  ulnar  side  glide  forward  and  backward  on  the 
scaphoid  and  cuneiform  respectively,  while  the  head  of  the  os  magnum  and  the 
superior  surface  of  the  unciform  rotate  in  the  cup-shaped  cavity  of  the  scaphoid 
and  semilunar.  Flexion  at  this  ioint  is  freer  than  extension.  A  verv  trifling 
amount  of  rotation  is  also  permitted,  the  head  of  the  os  magnum  rotating  round  a 
vertical  axis  drawn  through  its  own  centre,  while  at  the  same  time  a  slight  gliding; 
movement  takes  place  in  the  lateral  portions  of  the  joint. 

IX.  Carpo-metacarpal  Articulations. 

1.  Articulation  op  the  Metacarpal  Bone  of  the  Thumb  with  the 

Trapezium. 

This  is  a  joint  of  reciprocal  reception,  and  enjoys  great  freedom  of  movement, 
on  account  of  the  configuration  of  its  articular  surfaces,  which  are  saddle-shaped, 
so  that,  on  section,  each  bone  appears  to  be  received  into  a  cavity  in  the  other, 
according  to  the  direction  in  which  they  are  cut.  The  joint  is  surrounded  by  a 
capsular  ligament. 

The  Capsular  Ligament  is  thick,  but  loose,  and  passes  from  the  circumference 
of  the  upper  extremity  of  the  metacarpal  bone  to  the  rough  edge  bounding  the 
articular  surface  of  the  trapezium ;  it  is  thickest  externally  and  behind,  and  lined 
by  a  separate  synovial  membrane. 

Movements. — In  the  articulation  of  the  metacarpal  bone  of  the  thumb  -with  the 
trapezium  the  movements  permitted  are  flexion,  extension,  adduction,  abduction, 
and  circumduction.  When  the  joint  is  flexed  the  metacarpal  bone  is  brought  in 
front  of  the  palm  and  the  thumb  is  gradually  turned  to  the  fingers.  It  is  by  this 
peculiar  movement  that  the  tip  of  the  thumb  is  opposed  to  the  other  digits ;  for 
by  slightly  flexing  the  fingers  the  palmar  surface  of  the  thumb  can  be  brought  in 
contact  with  their  palmar  surfaces  one  after  another. 


266 


THE   ARTICULATIONS. 


2.  Articulations  of  the  Metacarpal  Bones  of  the  Four  Inner 
Fingers  with  the  Carpus. 

The  joints  formed  between  the  carpus  and  four  inner  metacarpal  bones  are 
arthrodial  joints.      The  ligaments  are — 

Dorsal.  Palmar. 

Interosseous.  - 

The  Dorsal  Ligaments,  the  strongest  and  most  distinct,  connect  the  carpal  and 

metacarpal  bones  on  their  dorsal  surface.      The  second  metacarpal  bone  receives 

two  fasciculi — one  from  the  trapezium,  the  other  from  the  trapezoid ;  the  third 

metacarpal  receives  two — one  from  the  trapezoid  and  one  from  the  os  magnum ; 

the  fourth  two — one  from  the  os 
magnum  and  one  from  the  unciform  ; 
the  fifth  receives  a  single  fasciculus 
from  the  unciform  bone,  which  is 
continuous  with  a  similar  ligament 
on  the  palmar  surface,  forming  an 
incomplete  capsule. 

The  Palmar  Ligaments  have  a 
somewhat  similar  arrangement  on  the 
palmar  surface,  with  the  exception 
of  the  third  metacarpal,  which  has 
three  ligaments — an  external  one 
from  the  trapezium,  situated  above 
the  sheath  of  the  tendon  of  the 
Flexor  carpi  radialis ;  a  middle  one, 
from  the  os  magnum ;  and  an  inter- 
nal one,  from  the  unciform. 

The  Interosseous  Ligaments  con- 
sist of  short,  thick  fibres,  which  are 
limited  to  one  part  of  the  carpo- 
metacarpal articulation ;  they  con- 
nect the  contiguous  inferior  angles 
of  the  os  magnum  and  unciform  with 
the  adjacent  surfaces  of  the  third 
and  fourth  metacarpal  bones. 

The  Synovial  Membrane  is  a  con- 
tinuation  of  that  between  the  two 
rows  of  carpal  bones.      Occasionally,  the   articulation   of  the  unciform   with  the 
fourth  and  fifth  metacarpal  bones  has  a  separate  synovial  membrane. 

The  synovial  membranes  of  the  wrist  and  carpus  (Fig.  177)  are  thus  seen  to 
be  five  in  number.  The  first,  the  membrana  sacciformis,  passes  from  the  lower 
end  of  the  ulna  to  the  sigmoid  cavity  of  the  radius,  and  lines  the  upper  surface 
of  the  interarticular  fibro-cartilage.  The  second  passes  from  the  lower  end  of 
the  radius  and  interarticular  fibro-cartilage  above  to  the  bones  of  the  first  row 
below.  The  third,  the  most  extensive,  passes  between  the  contiguous  margins  of 
the  two  rows  of  carpal  bones — between  the  bones  of  the  second  row  to  the  carpal 
extremities  of  the  four  inner  metacarpal  bones.  The  fourth,  from  the  margin  of 
the  trapezium  to  the  metacarpal  bone  of  the  thumb.  The  fifth,  between  the 
adjacent  margins  of  the  cuneiform  and  pisiform    bones. 

Actions. — The  movement  permitted  in  the  carpo-metacarpal  artieuh  of  the 

four  inner  fingers  is  limited  to  a  slight  gliding  of  the  articular  surfaces  upon  each 
other,  the  extent  of  which  varies  in  the  different  joints.  Thus  the  articulation  of 
the  metacarpal  bone  of  the  little  finger  is  most  movable,  then  that  of  the  ring 
finger.  The  metacarpal  bones  of  the  index  and  middle  fingers  are  almost 
immovable. 


Fig.  177.— Vertical  section  through  the  articulations  at 
the  wrist,  showing  the  five  synovial  membranes. 


META CABPO-PHALANGEAL    ARTICULA  TIONS. 


267 


•TgjJ  Metacarpophalangeal 
articulation. 


LATERAL    LIGAMENT 


3.  Articulations  of  the  Metacarpal  Bones  with  each  other. 

The  carpal  extremities  of  the  four  inner  metacarpal  bones  articulate  with 
one  another  at  each  side  by  small  surfaces  covered  with  cartilages,  and  connected 
together  by  dorsal,  palmar,  and  interosseous  ligaments. 

The  Dorsal  and  Palmar  Ligaments  pass  transversely  from  one  bone  to  another 
•on  the  dorsal  and  palmar  surfaces.  The  Interosseous  Ligaments  pass  between 
their  contiguous  surfaces,  jnst  beneath  their  lateral  articular  facets. 

The  Synovial  Membrane  between  the  lateral  facets  is  a  reflection  from  that 
■between  the  two  rows  of  carpal  bones. 

The  Transverse  Metacarpal  Ligaments  (Fig.  178)  is  a  narrow  fibrous  band  which 
passes  transversely  across  the  anterior  surfaces  of  the  digital  extremities  of  the  four 
inner  metacarpal  bones,  connecting 
them  together.  It  is  blended  an- 
teriorly with  the  anterior  (glenoid) 
ligament  of  the  metacarpal-phalan- 
geal articulations.  To  its  posterior 
border  is  connected  the  fascia  which 
■covers  the  Interossei  "muscles.  Its 
anterior  surface  is  concave  where  the 
flexor  tendons  pass  over  it.  Behind 
it  the  tendons  of  the  Interossei 
muscles  pass  to  their  insertion. 

X.  Metacarpophalangeal  Articu- 
lations (Fig.  178). 

These  articulations  are  of  the 
■condyloid  kind,  formed  by  the  re- 
ception of  the  rounded  head  of  the 
metacarpal  bone  into  a  shallow  cavity 
in  the  extremity  of  the  first  phalanx. 
The  ligaments  are — 
Anterior. 
Two  Lateral. 

The  Anterior  Ligaments  {Glenoid 
Ligaments  of  Cruveilhier)  are  thick, 
dense,  fibrous  structures,  placed  on 
the  palmar  surface  of  the  joints  in 
the  intervals  between  the  lateral 
ligaments,  to  which  they  are  con- 
nected ;  they  are  loosely  united  to 
the  metacarpal  bone,  but  very  firmly 
to  the  base  of  the  first  phalanges. 
Their  palmar  surface  is  intimately 
Wended  with  the  transverse  metacar- 
pal ligament,  and  presents  a  groove  for 
the  passage  of  the  flexor  tendons,  the 
sheath  surrounding  which  is  connected  to  each  side  of  the  groove.  By  their  deep 
surface  they  form  part  of  the  articular  surface  for  the  head  of  the  metacarpal  bone, 
and  are  lined  by  a  synovial  membrane. 

The  Lateral  Ligaments  are  strong,  rounded  cords  placed  one  on  each  side  of 
the  joint,  each  being  attached  by  one  extremity  to  the  posterior  tubercle  on  the 
side  of  the  head  of  the  metacarpal  bone,  and  by  the  other  to  the  contiguous 
extremity  of  the  phalanx. 

Actions. — The  movements  which  occur  in  these  joints  are  flexion,  extension, 
adduction,  abduction,  and  circumduction  ;  the  lateral  movements  are  very  limited. 


Phalangeal 
articulations. 


Fig.  178.— Articulations  of  the  phalanges. 


268  THE   ARTICULATIONS. 

Surface  Form. — The  prominences  of  the  knuckles  do  not  correspond  to  the  position  of  the 
joints  either  of  the  metacarpo-phalangeal  or  interphalangeal  articulations.  These  prominences 
are  invariably  formed  by  the  distal  ends  of  the  proximal  bone  of  each  joint,  and  the  line  indi- 
cating the  position  of  the  joint  must  be  sought  considerably  in  front  of  the  middle  of  the  knuckle. 
The  usual  rule  for  finding  these  joints  is  to  flex  the  distal  phalanx  on  the  proximal  one  to  a  right- 
angle  ;  the  position  of  the  joint  is  then  indicated  by  an  imaginary  fine  drawn  along  the  middle  of 
the  lateral  aspect  of  the  proximal  phalanx. 

XI.  Articulations  of  the  Phalanges. 

These  are  ginglymus  joints.     The  ligaments  are — 

Anterior.  Two  Lateral. 

The  arrangement  of  these  ligaments  is  similar  to  those  in  the  metacarpo- 
phalangeal articulations ;  the  extensor  tendon  supplies  the  place  of  a  posterior 
ligament. 

Actions. — The  only  movements  permitted  in  the  phalangeal  joints  are  flexion 
and  extension  ;  these  movements  are  more  extensive  between  the  first  and  second 
phalanges  than  between  the  second  and  third.  The  movement  of  flexion  is  very- 
considerable,  but  extension  is  limited  by  the  anterior  and  lateral  ligaments. 

ARTICULATIONS  OF   THE  LOWER  EXTREMITY. 

The  articulations  of  the  Lower  Extremity  comprise  the  following  groups  : 
I.  The  hip-joint.  II.  The  knee-joint.  III.  The  articulations  between  the  tibia 
and  fibula.  IV.  The  ankle-joint.  V.  The  articulations  of  the  tarsus.  VI.  The 
tarso-metatarsal  articulations.  VII.  Articulations  of  the  metatarsal  bones  with 
each  other.  VIII.  The  metatarso-phalangeal  articulations.  IX.  The  articu- 
lations of  the  phalanges. 

I.  Hip-joint  (Fig.  179). 

This  articulation  is  an  enarthrodial  or  ball-and-socket  joint,  formed  by  the 
reception  of  the  head  of  the  femur  into  the  cup-shaped  cavity  of  the  acetabulum. 
The  articulating  surfaces  are  covered  with  cartilage,  that  on  the  head  of  the  femur 
being  thicker  at  the  centre  than  at  the  circumference,  and  covering  the  entire 
surface,  with  the  exception  of  a  depression  just  belowr  its  centre  for  the  ligamen- 
tum  teres ;  that  covering  the  acetabulum  is  much  thinner  at  the  centre  than  at 
the  circumference.  It  forms  an  incomplete  cartilaginous  ring  of  a  horseshoe 
shape,  being  deficient  below,  where  there  is  a  circular  depression,  which  is  occu- 
pied in  the  recent  state  by  a  mass  of  fat  covered  by  synovial  membrane.  The 
ligaments  of  the  joints  are  the 

Capsular.  •  Teres. 

Ilio-femoral.  Cotyloid. 

Transverse. 

The  Capsular  Ligament  is  a  strong,  dense,  ligamentous  capsule,  embracing  the 
margin  of  the  acetabulum  above  and  surrounding  the  neck  of  the  femur  below. 
Its  upper  circumference  is  attached  to  the  acetabulum,  above  and  behind,  two  or 
three  lines  external  to  the  cotyloid  ligament ;  but  in  front  it  is  attached  to  the 
outer  margin  of  this  ligament,  and  opposite  to  the  notch  wThere  the  margin  of  this 
cavity  is  deficient,  it  is  connected  to  the  transverse  ligament,  and  by  a  few  fibres 
to  the  edge  of  the  obturator  foramen.  Its  lower  circumference  surrounds  the  neck 
of  the  femur,  being  attached,  in  front,  to  the  spiral  or  anterior  intertrochanteric 
line  ;  above,  to  the  base  of  the  neck ;  behind,  to  the  neck  of  the  bone,  about  half 
an  inch  above  the  posterior  intertrochanteric  line.  From  this  insertion  the  fibres 
are  reflected  upward  over  the  neck  of  the  femur,  forming  a  sort  of  tubular  sheath 
(the  cervical  reflection),  which  blends  with  the  periosteum  and  can  be  traced  as  far 
as  the  articular  cartilage.  On  the  surface  of  the  neck  of  the  femur  some  of  these 
reflected  fibres  are  raised  into  longitudinal  folds,  termed  retinacula.  It  is  much 
thicker  at  the  upper  and   fore  part  of  the  joint,  where  the  greatest  amount  of 


THE   HIP-JOINT. 


269 


resistance  is  required,  than  below  and  internally,  where  it  is  thin,  loose,  and 
lono-er  than  in  any  other  part.  It  consists  of  two  sets  of  fibres,  circular  and 
longitudinal.  The  circular  fibres  {zona  orbicularis)  are  most  abundant  at  the  lower 
and  back  part  of  the  capsule,  and  form  a  sling  or  collar  around  the  neck  of  the 
femur.  Anteriorly  they  blend  with  the  deep  surface  of  the  ilio-femoral  ligament, 
and  through  its  medium  reach  the  anterior  inferior  spine  of  the  ilium.  The 
longitudinal  fibres  are  greatest  in  amount  at  the  upper  and  front  part  of  the  cap- 


Fig.  179.— Left  hip-joint  laid  open. 

-sule.  where  they  form  distinct  bands  or  accessory  ligaments,  of  which  the  most 
important  is  the  ilio-femoral.  The  other  accessory  bands  are  known  as  the  pubo- 
fe>noral,  passing  from  the  ilio-pectineal  eminence  to  the  front  of  the  capsule ;  and 
ischio-capsular,  passing  from  the  ischium,  just  below  the  acetabulum,  to  blend 
with  the  circular  fibres  at  the  lower  part  of  the  joint.  The  external  surface 
(Fig.  164,  page  241)  is  rough,  covered  by  numerous  muscles,  and  separated  in 
front  from  the  Psoas  and  Iliacus  by  a  synovial  bursa,  which  not  infrequently 
communicates,  by  a  circular  aperture,  with  the  cavity  of  the  joint.  It  differs  from 
the  capsular  ligament  of  the  shoulder  in  being  much  less  loose  and  lax.  and  in  not 
being  perforated  for  the  passage  of  a  tendon. 

The  Ilio-femoral  Ligament  (Figs.  164  and  180)  is  an  accessory  band  of  fibres 
extending  obliquely  across  the  front  of  the  joint;  it  is  intimately  connected  with 
the  capsular  ligament,  and  serves  to  strengthen  it  in  this  situation.  It  is  attached, 
above,  to  the  lower  part  of  the  anterior  inferior  spine  of  the  ilium;  and.  diverging 
below,  forms  two  bands,  of  which  one  passes  downward  to  be  inserted  into  the 
lower  part  of  the  anterior  intertrochanteric  line;  the  other  passes  downward  and 
outward  to  be  inserted  into  the  upper  part  of  the  same  line  and  adjacent  part  of  the 
neck  of  the  femur.  Between  the  two  bands  is  a  thinner  part  of  the  capsule. 
Sometimes  there  is  no  division,  but  the  ligament  spreads  out  into  a  flat,  triangular 
band,  which  is  attached  below  into  the  whole  length  of  the  anterior  intertrochan- 
teric line.      This  ligament  is  frequently  called  the  Y-shaped  ligament  of  Bigelow; 


270 


THE   ARTICULATIONS. 


and  the  outer  or  upper  of  the  two  bands  is  sometimes  described  as  a  separate  liga- 
ment, under  the  name  of  the  ilio-trochanteric  ligament. 

The  Ligamentum  Teres  is  a  triangular  band  implanted  by  its  apex  into  the 
depression  a  little  behind  and  below  the  centre  of  the  head  of  the  femur,  and 
by  its  broad  base  into  the  margins  of  the  cotyloid  notch,  becoming  blended  'with 
the  transverse  ligament.  It  is  formed  of  connective  tissue,  surrounded  by  a  tubular 
sheath  of  synovial  membrane.  Sometimes  only  the  synovial  fold  exists,  or  the 
ligament  may  be  altogether  absent.     The  ligament  is  made  tense  when  the  hip  is. 

semiflexed,  and  the  limb  then  adducted  and. 
rotated  outward;  it  is,  on  the  other  hand, 
relaxed  when  the  limb  is  abducted.  It  has,, 
however,  but  little  influence  as  a  ligament, 
though  it  may  to  a  certain  extent  limit  move- 
ment, and  would  appear  to  be  merely  a  modi- 


^^ciC^ 

Xliga- 

/   \  MENTUIW! 

TERES. 

obturator/ 

MEMBRANE. 

^\ 

Jj 

Fig.  180.— Hip-joint,  showing  the  ilio-femoral 
ligament.    (After  Bigelow.) 


Fig.  181.— Vertical  section  through  hip-joint.    (Henle.J- 


fication  of  the  folds  which  in  other  joints  fringe  the  margins  of  reflection  of 
synovial  membranes  (see  page  218). 

The  Cotyloid  Ligament  is  a  fibro-cartilaginous  rim  attached  to  the  margin  of 
the  acetabulum,  the  cavity  of  which  deepens ;  at  the  same  time  it  protects  the- 
edges  of  the  bone  and  fills  up  the  inequalities  on  its  surface.  It  bridges  over  the 
notch  as  the  transverse  ligament,  and  thus  forms  a  complete  circle,  which  closely^ 
surrounds  the  head  of  the  femur,  and  assists  in  holding  it  in  its  place,  acting  as  a 
sort  of  valve.  It  is  prismoid  on  section,  its  base  being  attached  to  the  mar- 
gin of  the  acetabulum,  and  its  opposite  edge  being  free  and  sharp ;  whilst  its- 
two  surfaces  are  invested  by  synovial  membrane,  the  external  one  being  in 
contact  with  the  capsular  ligament,  the  internal  one  being  inclined  inward,  so 
as  to  narrow  the  acetabulum  and  embrace  the  cartilaginous  surface  of  the  head  of 
the  femur.  It  is  much  thicker  above  and  behind  than  below  and  in  front,  and 
consists  of  close,  compact  fibres,  which  arise  from  different  points  of  the  circum- 
ference of  the  acetabulum  and  interlace  with  each  other  at  very  acute  angles. 

The  Transverse  Ligament  is  in  reality  a  portion  of  the  cotyloid  ligament, 
though  differing  from  it  in  having  no  cartilage-cells  amongst  its  fibres.  It  con- 
sists of  strong,  flattened  fibres,  which  cross  the  notch  at  the  lower  part  of  the 
acetabulum  and  convert  it  into  a  foramen.  Thus  an  interval  is  left  beneath  the- 
ligament  for  the  passage  of  nutrient  vessels  to  the  joint. 


THE  HIP-JOINT. 


271 


The  Synovial  Membrane  is  very  extensive.  Commencing  at  the  margin  of  the 
cartilaginous  surface  of  the  head  of  the  femur,  it  covers  all  that  portion  of  the 
neck  which  is  contained  within  the  joint;  from  the  neck  it  is  reflected  on  the 
internal  surface  of  the  capsular  ligament,  covers  both  surfaces  of  the  cotyloid  liga- 
ment and  the  mass  of  fat  contained  in  the  depression  at  the  bottom  of  the  acetab- 


Bursa 


Isch.  caps,  ligament. 


RECT.    FEM. 


Ileo-fem.  ligament 


Pub.  fern,  ligament 


Fig.  182.— Relation  of  muscles  to  hip-joint.    (Henle.) 


ulum,  and  is  prolonged  in  the  form  of  a  tubular  sheath  around  the  ligamentum 
teres,  as  far  as  the  head  of  the  femur.  It  sometimes  communicates  through  a 
hole  in  the  capsular  ligament  between  the  inner  band  of  the  Y-shaped  ligament 
and  the  pubo-femoral  ligament  with  a  bursa  situated  on  the  under  surface  of  the 
Ilio-psoas  muscle. 

The  muscles  in  relation  with  the  joint  are,  in  front,  the  Psoas  and  Iliacus, 
separated  from  the  capsular  ligament  by  a  synovial  bursa ;  above,  the  reflected 
head  of  the  Rectus  and  Gluteus  minimus,  the  latter  being  closely  adherent  to  the 
capsule ;  internally,  the  Obturator  externus  and  Pectineus  ;  behind,  the  Pyriformis, 
Gemellus  superior,  Obturator  internus,  Gemellus  inferior,  Obturator  externus,  and 
Quadratus  femoris  (Fig.  182). 

The  arteries  supplying  the  joint  are  derived  from  the  obturator,  sciatic,  internal 
circumflex,  and  gluteal. 

The  nerves  are  articular  branches  from  the  sacral  plexus,  great  sciatic,  obtu- 
rator, accessory  obturator,  and  a  filament  from  the  branch  of  the  anterior  crural 
supplying  the  Rectus. 

Actions. — The  movements  of  the  hip  are  very  extensive,  and  consist  of 
flexion,  extension,  adduction,  abduction,  circumduction,  and  rotation. 

The  hip-joint  presents  a  very  striking  contrast  to  the  shoulder-joint  in  the 
much  more  complete  mechanical  arrangements  for  its  security  and  for  the  limita- 
tion of  its  movements.  In  the  shoulder,  as  we  have  seen,  the  head  of  the 
humerus  is  not  adapted  at  all  in  size  to  the  glenoid  cavity,  and  is  hardly  re- 
strained in  any  of  its  ordinary  movements  by  the  capsular  ligament.  In  the  hip- 
joint,  on  the  contrary,  the  head  of  the  femur  is  closely  fitted  to  the  acetabulum 


272  THE   ARTICULATIONS. 

for  a  distance  extending  over  nearly  half  a  sphere,  and  at  the  margin  of  the  bony 
cup  it  is  still  more  closely  embraced  by  the  cotyloid  ligament,  so  that  the  head 
of  the  femur  is  held  in  its  place  by  that  ligament  even  when  the  fibres  of  the  cap- 
sule have  been  quite  divided  (Humphry).  The  anterior  portion  of  the  capsule, 
•described  as  the  ilio-femoral  ligament,  is  the  strongest  of  all  the  ligaments  in  the 
body,  and  is  put  on  the  stretch  by  any  attempt  to  extend  the  femur  beyond  a 
straight  line  with  the  trunk.  That  is  to  say,  this  ligament  is  the  chief  agent  in 
maintaining  the  erect  position  without  muscular  fatigue ;  for  a  vertical  line  passing 
through  the  centre  of  gravity  of  the  trunk  falls  behind  the  centres  of  rotation  in 
the  hip-joints,  and  therefore  the  pelvis  tends  to  fall  backward,  but  is  prevented  by 
the  tension  of  the  ilio-femoral  and  capsular  ligaments.  The  security  of  the  joint 
may  be  also  provided  for  by  the  two  bones  being  directly  united  through  the  liga- 
mentum  teres ;  but  it  is  doubtful  whether  this  so-called  ligament  can  have  much 
influence  upon  the  mechanism  of  the  joint.  Flexion  of  the  hip-joint  is  arrested 
by  the  soft  parts  of  the  thigh  and  abdomen  being  brought  into  contact  when  the 
leg  is  flexed  on  the  thigh  ;  and  by  the  action  of  the  hamstring  muscles  when  the 
leg  is  extended ; l  extension,  by  the  tension  of  the  ilio-femoral  ligament  and  front 
of  the  capsule ;  adduction,  by  the  thighs  coming  into  contact ;  abduction,  with 
flexion  by  the  outer  band  of  the  ilio-femoral  ligament,  the  outer  part  of  the  capsu- 
lar ligament ;  abduction,  by  the  inner  band  of  the  ilio-femoral  ligament  and  the 
pubo-femoral  band;  rotation  outward,  by  the  outer  band  of  the  ilio-femoral  liga- 
ment ;  and  rotation  inward,  by  the  ischio- capsular  ligament  and  the  hinder  part  of 
the  capsule.  The  muscles  which  flex  the  femur  on  the  pelvis  are  the  Psoas,  Iliacus, 
Rectus,  Sartorius,  Pectineus,  Adductor  longus  and  brevis,  and  the  anterior  fibres 
of  the  Gluteus  medius  and  minimus.  Extension  is  mainly  performed  by  the 
Gluteus  maximus,  assisted  by  the  hamstring  muscles.  The  thigh  is  adducted  by 
the  Adductor  magnus,  longus,  and  brevis,  the  Pectineus,  the  Gracilis,  and  lower 
part  of  the  Gluteus  maximus,  and  abducted  by -the  Gluteus  medius  and  minimus 
and  upper  part  of  the  Gluteus  maximus.  The  muscles  which  rotate  the  thigh 
inward  are  the  anterior  fibres  of  the  Gluteus  medius,  the  Gluteus  minimus,  and  the 
Tensor  fasciae  femoris ;  while  those  which  rotate  it  outward  are  the  posterior  fibres 
of  the  Gluteus  medius,  the  Pyriformis,  Obturator  externus  and  internus.  Gemellus 
superior  and  inferior,  Quadratus  femoris,  Iliacus,  Gluteus  maximus,  the  three 
Adductors,   the  Pectineus,  and  the  Sartorius. 

Surface  Form. — A  line  drawn  from  the  anterior  superior  spinous  process  of  the  ilium  to 
the  most  prominent  part  of  the  tuberosity  of  the  ischium  (Nekton's  line)  runs  through  the 
■centre  of  the  acetabulum,  and  would,  therefore,  indicate  the  level  of  the  hip-joint ;  or,  in  other 
words,  the  upper  border  of  the  great  trochanter,  which  lies  on  Nekton's  line,  is  on  a  level  with 
the  centre  of  the  hip-joint. 

Surgical  Anatomy. — In  dislocation  of  the  hip  "  the  head  of  the  thigh-bone  may  rest  at 
any  point  around  its  socket"  (Bryant) ;  but  whatever  position  the  head  ultimately  assumes,  the 
primary  displacement  is  generally  downward  and  inward,  the  capsule  giving  way  at  its  weakest — 
that  is,  its  lower  and  inner — part.  The  situation  that  the  head  of  the  bone  subsequently  assumes 
is  determined  by  the  degree  of  flexion  or  extension,  and  of  outward  or  inward  rotation  of 
the  thigh  at  the  moment  of  luxation,  influenced,  no  doubt,  by  the  ilio-femoral  ligament,  which 
is  not  easily  ruptured.  When,  for  instance,  the  head  is  forced  backward,  this  ligament  forms  a 
■fixed  axis,  round  which  the  head  of  the  bone  rotates,  and  is  thus  driven  on  to  the  dorsum  of  the 
ilium.  The  ilio-femoral  ligament  also  influences  the  position  of  the  thigh  in  the  various  disloca- 
tions :  in  the  dislocations  backward  it  is  tense,  and  produces  inversion  of  the  limb ;  in  the 
dislocation  on  to  the  pubes  it  is  relaxed,  and  therefore  allows  the  external  rotators  to  evert  the 
thigh ;  while  in  the  thyroid  dislocation  it  is  tense  and  produces  flexion.  The  muscles  inserted 
into  the  upper  part  of  the  femur,  with  the  exception  of  the  Obturator  internus,  have  very  little 
direct  influence  in  determining  the  position  of  the  bone.  But  Bigelow  has  endeavored  to  show 
that  the  Obturator  internus  is  the  principal  agent  in  determining  whether,  in  the  backward 
dislocations,  the  head  of  the  bone  shall  be  ultimately  lodged  on  the  dorsum  of  the  ilium  or  in 
or  near  the  sciatic  notch.  In  both  dislocations  the  head  passes,  in  the  first  instance,  in  the 
same  direction ;  but,  as  Bigelow  asserts,  in  the  displacement  on  to  the  dorsum,  the  head  of  the 
bone  travels  up  behind  the  acetabulum,  in  front  of  the  muscle  ;  while  in  the  dislocation  into  the 

1  The  hip-joint  cannot  be  completely  flexed,  in  most  persons,  without  at  the  same  time  flexing 
the  knee,  on  account  of  the  shortness  of  the  hamstring  muscles. — Cleland,  Journ.  of  Anat.  and  Phis., 
No.  1,  Old  Series,  p.  87. 


THE   HIP-JOINT.  273 

sciatic  notch,  the  head  passes  behind  the  muscle,  and  is  therefore  prevented  from  reaching  the 
dorsum,  in  consequence  of  the  tendon  of  the  muscle  arching  over  the  neck  of  the  bone,  and  so 
remains  in  the  neighborhood  of  the  sciatic  notch.  Bigelow,  therefore,  distinguishes  these  two 
forms  of  dislocation  by  describing  them  as  dislocations  backward,  "  above  and  below,"  the  Ob- 
turator internus. 

The  ilio-femoral  ligament  is  rarely  torn  in  dislocations  of  the  hip,  and  this  fact  is  taken 
advantage  of  by  the  surgeon  in  reducing  these  dislocations  by  manipulation.  It  is  made  to  act 
as  a  fulcrum  to  a  lever,  of  which  the  long  arm  is  the  shaft  of  the  femur,  and  the  short  arm  the 
neck  of  the  bone. 

The  hip-joint  is  rarely  the  seat  of  acute  synovitis  from  injury,  on  account  of  its  deep 
position  and  its  thick  covering  of  soft  parts.  Acute  inflammation  may,  and  does,  frequently 
occur  as  the  result  of  constitutional  conditions,  as  rheumatism,  pyaemia,  etc.  When,  in  these 
cases,  effusion  takes  place,  and  the  joint  becomes  distended  with  fluid,  the  swelling  is  not  very 
easy  to  detect  on  account  of  the  thickness  of  the  capsule  and  the  depth  of  the  articulation.  It 
is  principally  to  be  found  on  the  front  of  the  joint,  just  internal  to  the  ilio-femoral  ligament ; 
or  behind,  at  the  lower  and  back  part.  In  these  two  places  the  capsule  is  thinner  than 
elsewhere.  Disease  of  the  hip-joint  is  much  more  frequently  of  a  chronic  character  and  is 
usually  of  a  tubercular  origin.  It  begins  either  in  the  bones  or  in  the  synovial  membrane, 
more  frequently  in  the  former,  and  probably,  in  most  cases,  at  the  growing,  highly  vascular 
tissue  in  the  neighborhood  of  the  epiphysial  cartilage.  In  this  respect  it  differs  very  materially 
from  tubercular  arthritis  of  the  knee,  where  the  disease  usually  commences  in  the  synovial 
membrane.  The  reasons  why  the  disease  so  frequently  begins  in  this  situation  are  twofold : 
first,  this  part  being  the  centre  of  rapid  growth,  its  nutrition  is  unstable  and  apt  to  pass  into 
inflammatory  action ;  and,  secondly,  great  strain  is  thrown  upon  it,  from  the  frequency  of  falls 
and  blows  upon  the  hip,  which  causes  crushing  of  the  epiphyseal  cartilage  or  the  cancellous 
tissue  in  its  neighborhood,  with  the  results  likely  to  follow  such  an  injury.  In  addition  to  these, 
the  depth  of  the  joint  protects  it  from  the  causes  of  synovitis. 

In  chronic  hip-disease  the  affected  limb  assumes  an  altered  position,  the  cause  of  which  it 
is  important  to  understand.  In  the  early  stage  of  a  typical  case  the  limb  is  flexed,  abducted, 
and  rotated  outward.  In  this  position  all  the  ligaments  of  the  joint  are  relaxed  :  the  front  of 
the  capsule  by  flexion ;  the  outer  band  of  the  ilio-femoral  ligament  by  abduction ;  and  the 
inner  band  of  this  ligament  and  the  back  of  the  capsule  by  rotation  outward.  It  is,  therefore, 
the  position  of  the  greatest  ease.  The  condition  is  not  quite  obvious  at  first  upon  examining  a 
patient.  If  the  patient  is  laid  in  the  supine  position,  the  affected  limb  will  be  found  to  be 
extended  and  parallel  with  the  other.  But  it  will  be  found  that  the  pelvis  is  tilted  downward 
on  the  diseased  side  and  the  limb  apparently  longer  than  its  fellow,  and  that  the  lumbar 
spine  is  arched  forward  (lordosis).  If  now  the  thigh  is  abducted  and  flexed,  the  tilting  down- 
ward and  the  arching  forward  of  the  pelvis  disappears.  The  condition  is  thus  explained.  A 
limb  which  is  flexed  and  abducted  is  obviously  useless  for  progression,  and,  in  order  to  over- 
come the  difficulty,  the  patient  depresses  the  affected  side  of  his  pelvis  in  order  to  produce 
parallelism  of  his  limbs,  and  at  the  same  time  rotates  his  pelvis  on  its  transverse  horizontal  axis, 
so  as  to  direct  the  limb  downward  instead  of  forward.  In  the  latter  stages  of  the  disease  the 
limb  becomes  flexed  and  abducted  and  inverted.  This  position  probably  depends  upon  muscular 
action,  at  all  events  as  regards  the  adduction.  The  Adductor  muscles  are  supplied  by  the 
obturator  nerve,  which  also  largely  supplies  the  joint.  These  muscles  are  therefore  thrown  into 
reflex  action  by  the  irritation  of  the  peripheral  terminations  of  this  nerve  in  the  inflamed  artic- 
ulation. Osteo-arthritis  is  not  uncommon  in  the  hip-joint,  and  it  is  said  to  be  more  common  in 
the  male  than  in  the  female,  in  whom  the  knee-joint  is  more  frequently  affected.  It  is  a  disease 
of  middle  age  or  more  advanced  period  of  life. 

Congenital  dislocation  is  more  commonly  met  with  in  the  hip-joint  than  in  any  other  articula- 
tion. The  displacement  usually  takes  place  on  to  the  dorsum  ilii.  It  gives  rise  to  extreme 
lordosis,  and  a  waddling  gait  is  noticed  as  soon  as  the  child  commences  to  walk. 

Excision  of  the  hip  may  be  required  for  disease  or  for  injury,  especially  gunshot.  It  may 
be  performed  either  by  an  anterior  incision  or  a  posterior  one.  The  former  one  entails  less 
interference  with  important  structures,  especially  muscles,  than  the  posterior  one,  but  permits 
of  less  efficient  drainage.  In  these  days,  however,  when  the  surgeon  aims  at  securing 
healing  of  his  wound  without  suppuration,  this  second  desideratum  is  not  of  so  much  import- 
ance. In  the  operation  in  front  the  surgeon  makes  an  incision  three  to  four  inches  in  length, 
starting  immediately  below  and  external  to  the  anterior  superior  spinous  process  of  the  ilium, 
downward  and  inward  between  the  Sartorius  and  Tensor  fasciae  femoris,  to  the  neck  of  the 
bone,  dividing  the  capsule  at  its  upper  part.  A  narrow- bladed  saw  now  divides  the  neck  of  the 
femur,  and  the  head  of  the  bone  is  extracted  with  sequestrum  forceps.  All  diseased  tissue  is 
carefully  removed  with  a  sharp  spoon  or  scissors,  and  the  cavity  thoroughly  flushed  out  with  a 
hot  antiseptic  fluid. 

The  posterior  method  consists  in  making  an  incision  three  or  four  inches  long,  commencing 
midway  between  the  top  of  the  great  trochanter  and  the  anterior  superior  spine,  and  ending 
over  the  shaft,  just  below  the  trochanter.  The  muscles  are  detached  from  the  great  trochanter, 
and  the  capsule  opened  freely.  The  head  and  neck  are  freed  from  the  soft  parts  and  the  bone 
sawn  through  just  below  the  top  of  the  trochanter  with  a  narrow  saw.  The  head  of  the  bone  is 
then  levered  out  of  the  acetabulum.  In  both  operations,  if  the  acetabulum  is  eroded,  it  must  be 
freely  gouged. 


274  THE  ARTICULATIONS. 

II.  Knee-joint. 

The  knee-joint  was  formerly  described  as  a  ginglymus  or  hinge-joint,  but  is 
really  of  a  much  more  complicated  character:  It  must  be  regarded  as  consist- 
ing of  three  articulations  in  one :  one  between  each  condyle  of  the  femur  and  the 
corresponding  tuberosity  of  the  tibia,  which  are  condyloid  joints,  and  one  between 
the  patella  and  the  femur,  which  is  partly  arthrodial,  but  not  completely  so,  since 
the  articular  surfaces  are  not  mutually  adapted  to  each  other,  so  that  the  movement 
is  not  a  simple  gliding  one.  This  view  of  the  construction  of  the  knee-joint  receives 
confirmation  from  the  study  of  the  articulation  in  some  of  the  lower  mammals, 
where  three  synovial  membranes  are  sometimes  found,  corresponding  to  these  three 
subdivisions,  either  entirely  distinct  or  only  connected  together  by  small  communi- 
cations. This  view  is  further  rendered  probable  by  the  existence  of  the  two  crucial 
ligaments  within  the  joint,  which  must  be  regarded  as  the  external  and  internal 
lateral  ligaments  of  the  inner  and  outer  joints  respectively.  The  existence  of 
the  ligamentum  mucosum  would  further  indicate  a  tendency  to  separation  of  the 
synovial  cavity  into  two  minor  sacs,  one  corresponding  to  each  joint. 

The  bones  entering  into  the  formation  of  the  knee-joint  are  the  condyles  of  the 
femur  above,  the  head  of  the  tibia  below,  and  the  patella  in  front.  The  bones  are 
connected  together  by  ligaments,  some  of  which  are  placed  on  the  exterior  of  the 
joint,  while  others  occupy  its  interior. 

External  Ligaments.  Interior  Ligaments. 

Anterior,  or  Ligamentum  Anterior,  or  External  Crucial. 

Patellae.  Posterior,  or  Internal  Crucial. 

Posterior,  or  Ligamentum  Two  Semilunar  Fibro-cartilages. 

Posticum  Winslowii.  Transverse. 

Internal  Lateral.  Coronary. 

Two  External  Lateral.  Ligamentum  mucosum.  \  Processes    of    Syn- 

Capsular.  Ligamenta  alaria.  J       ovial  Membrane. 

The  Anterior  Ligament,  or  Ligamentum  Patellae  (Fig.  183),  is  the  central 
portion  of  the  common  tendon  of  the  Extensor  muscles  of  the  thigh  which  is 
continued  from  the  patella  to  the  tubercle  of  the  tibia,  supplying  the  place  of  an 
anterior  ligament.  It  is  a  strong,  flat,  ligamentous  band  about  three  inches  in 
length,  attached,  above,  to  the  apex  of  the  patella  and  the  rough  depression  on  its 
posterior  surface ;  below,  to  the  lower  part  of  the  tubercle  of  the  tibia,  its  superficial 
fibres  being  continuous  over  the  front  of  the  patella  with  those  of  the  tendon  of  the 
Quadriceps  extensor.  The  lateral  portions  of  the  tendon  of  the  Extensor  muscles 
pass  down  on  either  side  of  the  patella,  attached  to  the  borders  of  this  bone  and  its 
ligament,  to  be  inserted  into  the  upper  extremity  of  the  tibia  on  each  side  of  the 
tubercle  ;  externally,  these  portions  merge  into  the  capsular  ligament.  They  are 
termed  lateral  patellar  ligaments.  The  posterior  surface  of  the  ligamentum  patellae 
can  usually  be  easily  separated  from  the  front  of  the  capsular  ligament. 

The  Posterior  Ligament  (Ligamentum  Posticum  Winslowii)  (Fig.  184)  is  a  broad, 
flat,  fibrous  band,  formed  of  fasciculi  separated  from  one  another  by  apertures  for 
the  passage  of  vessels  and  nerves.  It  is  attached,  above,  to  the  upper  margin  of  the 
intercondyloid  notch  of  the  femur,  and  below,  to  the  posterior  margin  of  the  head 
of  the  tibia.  Superficial  to  the  main  part  of  the  ligament  is  a  strong  fasciculus 
derived  from  the  tendon  of  the  Semimembranosus,  and  passing  from  the  back 
part  of  the  inner  tuberosity  of  the  tibia  obliquely  upward  and  outward  to  the 
back  part  of  the  outer  condyle  of  the  femur.  The  posterior  ligament  forms 
part  of  the  floor  of  the  popliteal  space,   and  the  popliteal  artery  rests  upon  it. 

The  Internal  Lateral  Ligament  is  a  broad,  flat,  membranous  band,  thicker 
behind  than  in  front,  and  situated  nearer  to  the  back  than  the  front  of  the  joint. 
It  is  attached,  above,  to  the  inner  tuberosity  of  the  femur ;  below,  to  the  inner 
tuberosity  and  inner  surface  of  the  shaft  of  the  tibia  to  the  extent  of  about  two 
inches.     It  is  crossed,  at  its  lower  part,  by  the  tendons  of  the  Sartorius,  Gracilis. 


THE   KNEE-JOINT. 


275 


and  Semitendinosus  muscles,  a  synovial  bursa  being  interposed.  Its  deep  surface 
covers  the  anterior  portion  of  the  tendon  of  the  Semimembranosus,  with  which  it 
is  connected  by  a  few  fibres,  the  synovial  membrane  of  the  joint,  and  the  inferior 
internal  articular  vessels  and  nerve;  it  is  intimately  adherent  to  the  internal  semi- 
lunar fibro-cartilae;e. 


Fig.  183. — Right  knee-joint.    Anterior  view. 


Fig.  184. — Right  knee-joint.    Posterior  view. 


The  Long  External  Lateral  Ligament  is  a  strong,  rounded,  fibrous  cord  situated 
nearer  to  the  back  than  the  front  of  the  joint.  It  is  attached,  above,  to  the  back 
part  of  the  outer  tuberosity  of  the  femur ;  below,  to  the  outer  part  of  the  head  of 
the  fibula.  Its  outer  surface  is  covered  by  the  tendon  of  the  Biceps,  which  divides 
at  its  insertion  into  two  parts,  separated  by  the  ligament.  The  ligament  has, 
passing  beneath  it,  the  tendon  of  the  Popliteus  muscle  and  the  inferior  external 
articular  vessels  and  nerve. 

The  Short  External  Lateral  Ligament  is  an  accessory  bundle  of  fibres  placed 
behind  and  parallel  with  the  preceding,  attached,  above,  to  the  lower  and  back 
part  of  the  outer  tuberosity  of  the  femur ;  below,  to  the  summit  of  the  styloid 
process  of  the  fibula.  This  ligament  is  intimately  connected  with  the  capsular 
ligament,  and  has,  passing  beneath  it,  the  tendon  of  the  Popliteus  muscle  and  the 
inferior  external  articular  vessels  and  nerve. 

The  Capsular  Ligament  consists  of  an  exceedingly  thin  but  strong,  fibrous 
membrane  which  fills  in  the  intervals  left  between  the  stronger  bands  above 
described,  and  is  inseparably  connected  with  them.  In  front  it  blends  with  and 
forms  part  of  the  lateral  patellar  ligaments  and  fills  in  the  interval  between  the 
anterior  and  lateral  ligaments  of  the  joint,  with  which  latter  structures  it  is  closely 
connected.  Behind,  it  is  formed  chiefly  of  vertical  fibres,  which  arise  above  from 
the  condyles  and  intercondyloid  notch  of  the  femur,  and  is  connected  below  with 
the  back   part  of  the  head  of  the  tibia,  being  closely  united  with  the  origins  of 


276 


THE   ARTICULATIONS. 


Femur. 


the  Gastrocnemius,  Plantaris,  and  Popliteus  muscles.     It  passes  in  front  of,  but  is 
inseparably  connected  with,  the  posterior  ligament. 

The  Crucial  are  two  interosseous  ligaments   of  considerable  strength  situated 

in  the  interior  of  the  joint,  nearer  its  posterior 
than  its  anterior  part.  They  are  called  crucial 
because  they  cross  each  other  somewhat  like 
the  lines  of  the  letter  X  ;  and  have  received 
the  names  anterior  and  jjosterior,  from  the 
position  of  their  attachment  to  the  tibia. 

The  Anterior,  or  External  Crucial  Liga- 
ment (Fig.  185),  is  attached  to  the  depres- 
sion in  front  of  the  spine  of  the  tibia,  being 
blended  with  the  anterior  extremity  of  the 
external  semilunar  fibro-cartilage,  and,  pass- 
ing obliquely  upward,  backward,  and  out- 
Avard,  is  inserted  into  the  inner  and  back 
part  of  the  outer  condyle  of  the  femur. 

The  Posterior,  or  Internal  Crucial  Liga- 
ment, is  stronger,  but  shorter  and  less  ob- 
lique in  its  direction,  than  the  anterior.  It 
is  attached  to  the  back  part  of  the  depres- 
sion behind  the  spine  of  the  tibia,  to  the 
popliteal  notch,  and  to  the  posterior  extrem- 
ity of  the  external  semilunar  fibro-cartilage ; 
and  passes  upward,  forward,  and  inward,  to 
be  inserted  into  the  outer  and  fore  part  of  the 
inner  condyle  of  the  femur.  It  is  in  relation, 
in  front,  with  the  anterior  crucial  ligament ; 
behind,  with  the  capsular  ligament. 

The  Semilunar  Fibre-cartilages  (Fig.  186) 
are  two  crescentic  lamellae  which  serve  to 
deepen  the  surface  of  the  head  of  the 
tibia,  for  articulation  Avith  the  condyles  of 
the  femur.  The  circumference  of  each  cartilage  is  thick,  convex,  and  attached  to 
the  inside  of  the  capsule  of    the  knee  ;    the  inner  border  is  thin,  concave  and 

free.  Their  upper  surfaces 
are  concave,  and  in  relation 
Avith  the  condyles  of  the 
femur ;  their  loAATer  surfaces 
are  flat,  and  rest  upon  the 
head  of  the  tibia.  Each  car- 
tilage covers  nearly  the  outer 
tAvo-thirds  of  the  correspond- 
ing articular  surface  of  the 
tibia,  leaving  the  inner  third 
uncovered  ;  both  surfaces  are 
smooth  and  invested  by  syno- 
vial membrane. 

The  Internal  Semilunar 
Fibro-cartilage  is  nearly  sem- 
icircular in  form,  a  little 
elongated  from  before  back- 
ward, and  broader  behind  than  in  front ;  its  anterior  extremity,  thin  and  pointed, 
is  attached  to  a  depression  on  the  anterior  margin  of  the  head  of  the  tibia,  in 
front  of  the  anterior  crucial  ligament ;  its  posterior  extremity  is  attached  to  the 
depression  behind  the  spine,  betAveen  the  attachments  of  the  external  semilunar 
fibro-cartilage  and  the  posterior  crucial  ligaments. 


Fig.  185. — Right  knee-joint 
nal  ligaments. 


Showing  inter- 


FiG.  186.— Head  of  tibia,  with  semilunar  cartilages,  etc.    Seen  from 
above.    Right  side. 


THE  KNEE-JOINT. 


277 


The  External  Semilunar  Fibro-cartilage  forms  nearly  an  entire  circle,  covering 
a  larger  portion  of  the  articular  surface  than  the  internal  one.  It  is  grooved  on 
its  outer  side  for  the  tendon 
of  the  Popliteus  muscle.  Its 
extremities,  at  their  insertion, 
are  interposed  between  the 
two  extremities  of  the  inter- 
nal semilunar  fibro-cartilage ; 
the  anterior  extremity  being 
attached  in  front  of  the  spine 
of  the  tibia  to  the  outer  side 
of,  and  behind,  the  anterior 
crucial  ligament,  with  which 
it  blends ;  the  posterior  ex- 
tremity being  attached  behind 
the  spine  of  the  tibia,  in  front 
of  the  posterior  extremity  of 
the  internal  semilunar  fibro- 
cartilage.  Just  before  its  in- 
sertion  posteriorly  it  gives  off 
a  strong  fasciculus,  the  liga- 
ment of  Wrisberg,  which  passes 
obliquely  upward  and  outward, 
to  be  inserted  into  the  inner 
condyle  of  the  femur,  close  to 
the  attachment  of  the  poste- 
rior crucial  ligament.  Occa- 
sionally a  small  fasciculus  is 
given  off  which  passes  forward 
to  be  inserted  into  the  back 
part  of  the  anterior  crucial  lig- 
ament. The  external  semi- 
lunar fibro-cartilage  gives  off 
from  its  anterior  convex  mar- 
gin a  fasciculus  which  forms 
the  transverse  ligament. 

The  Transverse  Ligament 
is  a  band  of  fibres  Avhich 
passes  transversely  from  the 
anterior  convex  margin  of  the  external  semilunar  fibro-cartilage  to  the  anterior 
convex  margin  of  the  internal  semilunar  fibro-cartilage ;  its  thickness  varies 
considerably  in  different  subjects,  and  it  is  sometimes  absent  altogether. 

The  Coronary  Ligaments  are  merely  portions  of  the  capsular  ligament,  which 
connect  the  circumference  of  each  of  the  semilunar  fibro-cartilages  with  the 
margin  of  the  head  of  the  tibia. 

The  Synovial  Membrane  of  the  knee-joint  is  the  largest  and  most  extensive  in 
the  body.  Commencing  at  the  upper  border  of  the  patella,  it  forms  a  short  cul-de- 
sac  beneath  the  Quadriceps  extensor  tendon  of  the  thigh,  on  the  lower  part  of  the 
front  of  the  shaft  of  the  femar  :  this  communicates  with  a  synovial  bursa  inter- 
posed between  the  tendon  and  the  front  of  the  femur  by  an  orifice  of  variable  size. 
On  each  side  of  the  patella  the  synovial  membrane  extends  beneath  the  aponeurosis 
of  the  Vasti  muscles,  and  more'  especially  beneath  that  of  the  Vastus  internus. 
Below  the  patella  it  is  separated  from  the  anterior  ligament  by  the  anterior  part 
of  the  capsule  and  a  considerable  quantity  of  adipose  tissue.  In  this  situation  it 
sends  off  a  trianf  ular  prolongation,  containing  a  few  ligamentous  fibres,  which 
extends  from  the  anterior  part  of  the  joint  below  the  patella  to  the  front  of  the 
intercondyloid  notch.     This  fold  has  been  termed  the  Ugamentum  mucosum.     It 


Fig.  187.— Longitudinal  section  through  the  middle  of  the  right 
knee-joint.    (After  Braune.) 


278  THE  ARTICULATIONS. 

also  sends  off  two  fringe-like  folds,  called  the  ligamenta  alaria,  which  extend  from 
the  sides  of  the  ligamentum  mucosum,  upward  and  laterally  between  the  patella 
and  femur.  On  either  side  of  the  joint  it  passes  downward  from  the  femur,  lining 
the  capsule  to  its  point  of  attachment  to  the  semilunar  cartilages  ;  it  may  then  be 
traced  over  the  upper  surfaces  of  these  cartilages  to  their  free  borders,  and  from 
thence  along  their  under  surfaces  to  the  tibia.  At  the  back  part  of  the  external 
one  it  forms  a  cul-de-sac  between  the  groove  on  its  surface  and  the  tendon  of  the 
Popliteus ;  it  surrounds  the  crucial  ligaments  and  lines  the  inner  surface  of  the 
ligaments  which  enclose  the  joint.  The  pouch  of  synovial  membrane  between 
the  Extensor  tendon  and  front  of  the  femur  is  supported,  during  the  movements 
of  the  knee,  by  a  small  muscle,  the  Subcrureus,  which  is  inserted  into  the  upper 
part  of  the  capsular  ligament. 

The  folds  of  synovial  membrane  and  the  fatty  processes  contained  in  them  act, 
as  it  seems,  mainly  as  padding  to  fill  up  interspaces  and  obviate  concussions. 
Sometimes  the  bursa  beneath  the  Quadriceps  extensor  is  completely  shut  off  from 
the  rest  of  the  synovial  cavity,  thus  forming  a  closed  sac  between  the  Quadriceps 
and  the  lower  part  of  the  front  of  the  femur,  or  it  may  communicate  with  the 
synovial  cavity  by  a  minute  aperture. 

The  bursae  about  the  knee-joint  are  the  following: 

In  front  there  are  three  bursae :  one  is  interposed  between  the  patella  and  the 
skin ;  another,  of  small  size,  between  the  upper  part  of  the  tuberosity  of  the  tibia 
and  the  ligamentum  patellae  ;  and  a  third  between  the  lower  part  of  the  tuberosity 
of  the  tibia  and  the  skin.  On  the  outer  side  there  are  four  bursas  :  (1)  one  beneath 
the  outer  head  of  the  Gastrocnemius  (which  sometimes  communicates  with  the 
joint) ;  (2)  one  above  the  external  lateral  ligament  between  it  and  the  tendon  of 
the  Biceps ;  (3)  one  beneath  the  external  lateral  ligament  between  it  and  the  ten- 
don of  the  Popliteus  (this  is  sometimes  only  an  expansion  from  the  next  bursa)  ; 
(4)  one  beneath  the  tendon  of  the  Popliteus  between  it  and  the  condyle  of  the  femur, 
which  is  almost  always  an  extension  from  the  synovial  membrane. 

On  the  inner  side  there  are  five  bursae  :  (1)  one  beneath  the  inner  head  of  the 
Gastrocnemius,  which  sends  a  prolongation  between  the  tendons  of  the  Gastro- 
cnemius and  Semimembranosus :  this  bursa  often  communicates  with  the  joint ; 
(2)  one  above  the  internal  lateral  ligament  between  it  and  the  tendons  of  the 
Sartorius,  Gracilis,  and  Semitendinosus ;  (3)  one  beneath  the  internal  lateral 
ligament  between  it  and  the  tendon  of  the  Semimembranosus :  this  is  sometimes 
only  an  expansion  from  the  next  bursa ;  (4)  one  beneath  the  tendon  of  the  Semi- 
membranosus, between  it  and  the  head  of  the  tibia ;  (5)  sometimes  there  is  a  bursa 
between  the  tendons  of  the  Semimembranosus  and  of  the  Semitendinosus. 

Structures  around  the  Joint. — In  front  and  at  the  sides,  the  Quadriceps  exten- 
sor ;  on  the  outer  side,  the  tendons  of  the  Biceps  and  the  Popliteus  and  the 
external  popliteal  nerve ;  on  the  inner  side,  the  Sartorius,  Gracilis,  Semitendinosus, 
and  Semimembranosus  ;  behind,  an  expansion  from  the  tendon  of  the,  Semimembra- 
nosus, the  popliteal  vessels,  and  the  internal  popliteal  nerve,  Popliteus,  Plantaris, 
and  inner  and  outer  heads  of  the  Gastrocnemius,  some  lymphatic  glands,  and 
fat. 

The  Arteries  supplying  the  joint  are  derived  from  the  anastomotica  magna 
branch  of  the  femoral,  articular  branches  of  the  popliteal,  anterior  and  posterior 
recurrent  branches  of  the  anterior  tibial,  and  descending  branch  from  the  external 
circumflex  of  the  Profunda. 

The  Nerves  are  derived  from  the  obturator,  anterior  crural,  and  external  and 
internal  popliteal. 

Actions. — The  knee-joint  permits  of  movements  of  flexion  and  extension,  and, 
in  certain  positions,  of  slight  rotation  inward  and  outward.  The  movement  of 
flexion  and  extension  does  not,  however,  take  place  in  a  simple,  hinge-like  man- 
ner, as  in  other  joints,  but  is  a  complicated  movement,  consisting  of  a  certain 
amount  of  gliding  and  rotation  ;  so  that  the  same  part  of  one  articular  surface  is 
not  always  applied  to  the  same  part  of  the  other  articular  surface,  and  the   axis 


THE   KNEE-JOINT.  279 

of  motion  is   not  a  fixed  one.     If  the  joint  is  examined  while  in  a  condition  of 

extreme  flexion,  the  posterior  part  of  the  articular  surfaces 

of  the  tibia  will  be  found  to  be  in  contact  with  the  posterior 

rounded  extremities  of  the  condyles  of  the  femur  ;   and  if 

a   simple   hinge-like  movement    were  to   take  place,   the 

axis,  round  which   the   revolving  movement   of  the   tibia 

occurs,  would  be  in  the  back  part  of  the  condyle.     If  the 

leg  is  now  brought  forward  into  a  position  of  semiflexion, 

the  upper  surface  of  the  tibia  will  be  seen   to  glide  over 

the  condyles  of  the  femur,  so  that  the  middle  part  of  the 

articular  facets  are  in  contact,  and  the  axis  of  rotation  ^SiH?' 

must  therefore  have  shifted  forward  to  nearer  the  centre  FlG    188__ view   of  the 

of   the  condyles.     If  the  leg    is    now   brought    into    the     posterior  surface  of  the  Pa- 

,     ,  J .    .  ...     „     °-  ,.  ,.  -P  ,  ■.       tella,  showing    diagrammat- 

extended  position,  a  still  further  gliding  takes  place  and     icaUy  the  areas  of  contact 
a  further  shifting  forward  of  the  axis  of  rotation.     This     positions  of  theVnee. ' 
is  not,  however,  a  simple  movement,  but  is  accompanied 

by  a  certain  amount  of  rotation  outward  round  a  vertical  axis  drawn  through  the 
centre  of  the  head  of  the  tibia.  This  rotation  is  due  to  the  greater  length  of  the 
internal  condyle,  and  to  the  fact  that  the  anterior  portion  of  its  articular  surface 
is  inclined  obliquely  outward.  In  consequence  of  this  it  will  be  seen  that  toward 
the  close  of  the  movement  of  extension — that  is  to  say,  just  before  complete 
extension  is  effected — the  tibia  glides  obliquely  upward  and  outward  over  this 
oblique  surface  on  the  inner  condyle,  and  the  leg  is  therefore  necessarily  rotated 
outward.  In  flexion  of  the  joint  the  converse  of  these  movements  takes  place: 
the  tibia  glides  backward  round  the  end  of  the  femur,  and  at  the  com- 
mencement of  the*  movement  the  tibia  is  directed  downward  and  inward  along 
the  oblique  curve  of  the  inner  condyle,  thus  causing  an  inward  rotation  to 
the  leg. 

During,  flexion  and  extension  the  patella  moves  on  the  lower  end  of  the  femur, 
but  this  movement  is  not  a  simple  gliding  one ;  for  if  the  articular  surface  of  this 
bone  is  examined,  it  will  be  found  to  present  on  each  side  of  the  central  vertical 
ridge  two  less  marked  transverse  ridges,  which  divide  the  surface,  except  a  small 
portion  along  the  inner  border,  which  is  cut  off  by  a  slight  vertical  ridge  into 
six  facets  (see  Fig.  188),  and  therefore  does  not  present  a  uniform  curved  sur- 
face, as  would  be  the  case  if  a  simple  gliding  movement  took  place.  These  six 
facets — three  on  each  side  of  the  median  vertical  ridge — correspond  to  and  denote 
the  parts  of  the  bone  respectively  in  contact  with  the  condyles  of  the  femur  during 
flexion,  semiflexion,  and  extension.  In  flexion  only  the  upper  facets  on  the  patella 
are  in  contact  Avith  the  condyles  of  the  femur ;  the  lower  two-thirds  of  the  bone 
rests  upon  the  mass  of  fat  which  occupies  the  space  between  the  femur  and  tibia. 
In  the  semiflexed  position  of  the  joint  the  middle  facets  on  the  patella  rest  upon 
the  most  prominent  portion  of  the  condyles,  and  thus  afford  greater  leverage  to 
the  Quadriceps  by  increasing  its  distance  from  the  centre  of  motion.  In  complete 
extension  the  patella  is  drawn  up,  so  that  only  the  loAver  facets  are  in  contact  with 
the  articular  surfaces  of  the  condyles.  The  narrow  strip  along  the  inner  border 
is  in  contact  with  the  outer  aspect  of  the  internal  condyle  when  the  leg  is  fully  flexed 
at  the  knee-joint.  As  in  the  elbow,  so  it  is  in  the  knee — the  axis  of  rotation  in 
flexion  and  extension  is  not  precisely  at  right  angles  to  the  axis  of  the  bone,  but 
during  flexion  there  is  a  certain  amount  of  alteration  of  plane :  so  that,  whereas  in 
flexion  the  femur  and  tibia  are  in  the  same  plane,  in  extension  the  one  bone  forms 
an  anode  of  about  ten  degrees  with  the  other.  There  is.  however,  this  difference 
between  the  two  extremities :  that  in  the  upper,  during  extension,  the  humeri  are 
parallel  and  the  bones  of  the  forearm  diverge ;  in  the  lower,  the  femora  converge 
below  and  the  tibia  are  parallel. 

In  addition  to  the  slight  rotation  during  flexion  and  extension,  the  tibia  eniovs 

•  •  •     •  f»        1 

an  independent  rotation  on  the  condyles  of  the  femur  in  certain  positions  of  the 
joint.     This  movement  takes  place  between  the  interarticular  fibro-cartilages  and 


280  THE  ARTICULATIONS. 

the  tibia,  whereas  the  movement  of  flexion  and  extension  takes  place  between  the 
interarticular  fibro-cartilages  and  the  femur.  So  that  the  knee  may  be  said  to 
consist  of  two  joints,  separated  by  the  fibro-cartilages  :  an  upper  (menisco-femoral), 
in  which  flexion  and  extension  take  place ;  and  a  lower  (menisco-tibial),  allowing 
of  a  certain  amount  of  rotation.  This  latter  movement  can  only  take  place  in  the 
semiflexed  position  of  the  limb,  when  all  the  ligaments  are  relaxed. 

During  flexion  the  ligamentum  patellae  is  put  upon  the  stretch,  as  is  also 
the  posterior  crucial  ligament  in  extreme  flexion.  The  other  ligaments  are  all 
relaxed  by  flexion  of  the  joint,  though  the  relaxation  of  the  anterior  crucial  ligament 
is  very  trifling.  Flexion  is  only  checked  during  life  by  the  contact  of  the  leg  with 
the  thigh.  In  the  act  of  extending  the  leg  upon  the  thigh  the  ligamentum  patellae  is 
tightened  by  the  Quadriceps  extensor;  but  when  the  leg  is  fully  extended,  as  in  the 
erect  posture,  the  ligament  becomes  relaxed,  so  as  to  allow  free  lateral  movement  to 
the  patella,  which  then  rests  on  the  front  of  the  lower  end  of  the  femur.  The  other 
ligaments,  with  the  exception  of  the  posterior  crucial,  which  is  partly  relaxed,  are  all 
on  the  stretch.  When  the  limb  has  been  brought  into  a  straight  line,  extension  is 
checked  mainly  by  the  tension  of  all  the  ligaments  except  the  posterior  crucial  and 
ligamentum  patellae.  The  movements  of  rotation  of  which  the  knee  is  capable  are 
permitted  in  the  semiflexed  condition  by  the  partial  relaxation  of  both  crucial  liga- 
ments, as  well  as  the  lateral  ligaments.  Rotation  inward  appears  to  be  limited  by 
the  tension  of  the  anterior  crucial  ligament,  and  by  the  interlocking  of  the  two  liga- 
ments ;  but  rotation  outward  does  not  appear  to  be  checked  by  either  crucial 
ligament,  since  they  uncross  during  the  execution  of  this  movement,  but  by  the 
lateral  ligaments,  especially  the  internal.  The  main  function  of  the  crucial  liga- 
ments is  to  act  as  a  direct  bond  of  union  between  the  tibia  and  femur,  preventing 
the  former  bone  from  being  carried  too  far  backward  or  forward.  Thus  the 
anterior  crucial  ligament  prevents  the  tibia  being  carried  too  far  forward  by  the 
extensor  tendons,  and  the  posterior  crucial  checks  too  great  movement  backward 
by  the  flexors.  They  also  assist  the  lateral  ligaments  in  resisting  ,any  lateral 
bending  of  the  joint.  The  interarticular  cartilages  are  intended,  as  it  seems, 
to  adapt  the  surface  of  the  tibia  to  the  shape  of  the  femur  to  a  certain  extent, 
so  as  to  fill  up  the  intervals  which  would  otherwise  be  left  in  the  varying 
positions  of  the  joint,  and  to  interrupt  the  jars  which  would  be  so  frequently 
transmitted  up  the  limb  in  jumping  or  falls  on  the  feet ;  also  to  permit  of  the 
two  varieties  of  motion,  flexion  and  extension,  and  rotation,  as  explained  above. 
The  patella  is  a  great  defence  to  the  knee-joint  from  any  injury  inflicted  in  front, 
and  it  distributes  upon  a  large  and  tolerably  even  surface  during  kneeling  the 
pressure  which  would  otherwise  fall  upon  the  prominent  ridges  of  the  condyles ;  it 
also  affords  leverage  to  the  Quadriceps  extensor  muscle  to  act  upon  the  tibia ;  and 
Mr.  Ward  has  pointed  out  '  how  this  leverage  varies  in  the  various  positions  of  the 
joint,  so  that  the  action  of  the  muscles  produces  velocity  at  the  expense  of  force  in 
the  commencement  of  extension,  and,  on  the  contrary,  at  the  close  of  extension 
tends  to  diminish  velocity,  and  therefore  the  shock  to  the  ligaments  at  the  moment 
tension  of  the  structures  takes  place. 

Extension  of  the  leg  on  the  thigh  is  performed  by  the  Quadriceps  extensor ; 
flexion  by  the  hamstring  muscles,  assisted  by  the  Gracilis  and  Sartorius,  and, 
indirectly,  by  the  Gastrocnemius,  Popliteus,  and  Plantaris ;  rotation  outward,  by 
the  Biceps ;  and  rotation  inward  by  the  Popliteus,  Semitendinosus,  and,  to  a 
slight  extent,  the  Semimembranosus,  the  Sartorius,   and  the  Gracilis. 

Surface  Form. — The  interval  between  the  two  bones  entering  into  the  formation  of  the 
knee-joint  can  always  easily  be  felt.  If  the  limb  is  extended,  it  is  situated  on  a  slightly  higher  level 
than  the  apex  of  the  patella;  but  if  the  limb  is  slightly  flexed, a  knife  carried  horizontally  back- 
ward immediately  below  the  apex  of  the  patella  would  pass  directly  into  the  joint.  When  the 
knee-joint  is  distended  with  fluid,  the  outline  of  the  synovial  membrane  at  the  front  of  the  knee 
may  be  fairlv  well  mapped  out. 

Surgical  Anatomy- -From  a  consideration  of  the  construction  of  the  knee-joint  it  would 
at  first  ear  to  be  one  of  the  least  secure  of  any  of  the  joints  in  the  body.     It  is  formed 

1  Human  Osteology,  p.  405. 


THE  KNEE-JOINT.  281 

between  the  two  longest  bones,  and  therefore  the  amount  of  leverage  which  can  be  brought  to 
bear  upon  it  is  very  considerable  ;  the  articular  surfaces  are  but  ill  adapted  to  each  other,  and 
the  range  and  variety  of  motion  which  it  enjoys  is  great.  All  these  circumstances  tend  to  render 
the  articulation  very  insecure  ;  but,  nevertheless,  on  account  of  the  very  powerful  ligaments 
which  bind  the  bones  together,  the  joint  is  one  of  the  strongest  in  the  body,  and  dislocation 
from  traumatism  is  of  very  rare  occurrence.  When,  on  the  other  hand,  the  ligaments  have 
been  softened  or  destroyed  by  disease,  partial  displacement  is  very  liable  to  "occur,  and  is 
frequently  brought  about  by  the  mere  action  of  the  muscles  displacing  the  articular  surfaces 
from  each  other.  The  tibia  may  be  dislocated  in  any  direction  from  the  femur — forward,  back- 
ward, inward,  or  outward  ;  or  a  combination  of  two  of  these  dislocations  may  occur — that  is,  the 
tibia  may  be  dislocated  forward  and  laterally,  or  backward  and  laterally ;  and  any  of  these  dis- 
locations may  be  complete  or  incomplete.  As  a  rule,  however,  the  antero-posterior  dislocations 
are  complete,  the  lateral  ones  incomplete. 

One  or  other  of  the  semilunar  cartilages  may  become  displaced  and  nipped  between  the 
femur  and  tibia.  The  accident  is  produced  by  a  twist  of  the  leg  when  the  knee  is  flexed,  and  is 
accompanied  by  a  sudden  pain  and  fixation  of  the  knee  in  a  flexed  position.  The  cartilage  may 
be  displaced  either  inward  or  outward :  that  is  to  say,  either  inward  toward  the  tibial  spine,  so 
that  the  cartilage  becomes  lodged  in  the  intercondyloid  notch  ;  or  outward,  so  that  the  cartilage 
projects  beyond  the  margin  of  the  two  articular  surfaces.  Acute  synovitis,  the  result  of 
traumatism  or  exposure  to  cold,  is  very  common  in  the  knee,  on  account  of  its  superficial  posi- 
tion. When  distended  with  fluid,  the  swelling  shows  itself  above  and  at  the  sides  of  the  patella, 
reaching  about  an  inch  or  more  above  the  trochlear  surface  of  the  femur,  and  extending  a  little 
higher  under  the  Vastus  internus  than  the  Vastus  externus.  Occasionally  the  swelling  may 
extend  two  inches  or  more.  At  the  sides  of  the  patella  the  swelling  extends  lower  at  the"  inner 
side  than  it  does  on  the  outer  side.  The  lower  level  of  the  synovial  membrane  is  just  above  the 
level  of  the  upper  part  of  the  head  of  the  fibula.  In  the  middle  line  it  covers  the  upper  third 
of  the  ligamentum  patellae,  being  separated  from  it,  however,  by  the  capsule  and  a  pad  of  fat. 
Chronic  synovitis  principally  shows  itself  in  the  form  of  pulpy  degeneration  of  the  synovial 
membrane,  leading  to  tubercular  arthritis.  The  reasons  why  tubercular  disease  of  the  knee 
usually  commences  in  the  synovial  membrane  appear  to  be  the  complex  and  extensive  nature  of 
this  sac;  the  extensive  vascular  supply  to  it;  and  the  fact  that  injuries  are  generally  diffused 
and  applied  to  the  front  of  the  joint  rather  than  to  the  ends  of  the  bones.  Syphilitic  disease 
not  unfrequently  attacks  the  knee-joint.  In  the  hereditary  form  of  the  disease  it  is  usually 
symmetrical,  attacking  both  joints,  which  become  filled  with  synovial  effusion,  and  is  very 
intractable  and  difficult  of  cure.  In  the  tertiary  form  of  the  disease  gummatous  infiltration  of 
the  synovial  membrane  may  take  place.  The  knee  is  one  of  the  joints  most  commonly  affected 
with  osteo-arthritis,  and  is  said  to  be  more  frequently  the  seat  of  this  disease  in  women  than  in 
men.  The  occurrence  of  the  so-called  loose  cartilage  is  almost  confined  to  the  knee,  though  they 
are  occasionally  met  with  in  the  elbow,  and,  rarely,  in  some  other  joints.  Many  of  them  occur 
in  cases  of  osteo-arthritis,  in  which  calcareous  or  cartilaginous  material  is  formed  in  one  of  the 
synovial  fringes  and  constitutes  the  foreign  body,  and  may  or  may  not  become  detached,  in  the 
former  case  only  meriting  the  usual  term,  "loose"  cartilage.  In  other  cases  they  have  their 
origin  in  the  exudation  of  inflammatory  lymph,  and  possibly,  in  some  rare  instances,  a  portion 
of  the  articular  cartilage  or  one  of  the  semilunar  cartilages  becomes  detached  and  constitutes  the 
foreign  body. 

Genu  valgum,  or  knock-knee,  is  a  common  deformity  of  childhood,  in  which,  owing  to 
changes  in  and  about  the  joint,  the  angle  between  the  outer  border  of  the  tibia  and  femur  is 
diminished,  so  that  as  the  patient  stands  the  two  internal  condyles  of  the  femora  are  in  contact, 
but  the  two  internal  malleoli  of  the  tibiae  are  more  or  less  widely  separated  from  each  other. 
When,  however,  the  knees  are  flexed  to  a  right  angle,  the  two  legs  are  practically  parallel  with 
each  other.  At  the  commencement  of  the  disease  there  is  a  yielding  of  the  internal  lateral  liga- 
ment and  other  fibrous  structures  on  the  inner  side  of  the  joint ;  as  a  result  of  this  there  is  a 
constant  undue  pressure  of  the  outer  tuberosity  of  the  tibia  against  the  outer  condyle  of  the 
femur.  This  extra  pressure  causes  arrest  of  growth  and,  possibly,  wasting  of  the  outer  con- 
dyle, and  a  consequent  tendency  for  the  tibia  to  become  separated  from  the  internal  condyle. 
To  prevent  this  the  internal  condyle  becomes  depressed ;  probably,  as  was  first  pointed  out  by 
Mikulicz,  by  an  increased  growth  of  the  lower  end  of  the  diaphysis  on  its  inner  side,  so  that  the 
line  of  the  epiphysis  becomes  oblique  instead  of  transverse  to  the  axis  of  the  bone,  with  a  direc- 
tion downward  and  inward. 

Excision  of  the  knee-joint  is  most  frequently  required  for  tubercular  disease  of  this  articula- 
tion, but  is  also  practised  in  cases  of  disorganization  of  the  knee  after  rheumatic  fever,  pyaemia, 
etc.,  in  osteo-arthritis,  and  in  ankylosis.  It  is  also  occasionally  called  for  in  cases  of  injury,  gun- 
shot or  otherwise.  The  operation  is  best  performed  either  by  a  horseshoe  incision,  starting  from 
one  condyle,  descending  as  low  as  the  tubercle  of  the  tibia,  where  it  crosses  the  leg,  and  is  then 
carried  upward  to  the  other  condyle ;  or  by  a  transverse  incision  across  the  patella.  In  this 
latter  incision  the  patella  is  either  removed  or  sawn  across,  and  the  halves  subsequently  sutured 
together.  The  bones  having  been  cleared,  and  in  those  cases  where  the  operation  is  performed 
for  tubercular  disease  all  pulpy  tissue  having  been  carefully  removed,  the  section  of  the  femur 
is  first  made.  This  should  never  include,  in  children,  more  than,  at  the  most,  two-thirds 
of  the  articular  surface,  otherwise  the  epiphyseal  cartilage  will  be  involved,  with  disastrous  results 
as  regards  the  growth  of  the  limb.     Afterward  a  thin  slice  should  be  removed  from  the  upper 


282  THE  ARTICULATIONS. 

end  of  the  tibia,  not  more  than  half  an  inch.  If  any  diseased  tissue  still  appears  to  he  left  iir 
the  bones,  it  should  be  removed  with  the  gouge  rather  than  that  a  further  section  of  the  bones 
should  be  made. 

III.   Articulations  between  the  Tibia  and  Fibula. 

The  articulations  between  the  tibia  and  fibula  are  effected  by  ligaments  which 
connect  both  extremities,  as  well  as  the  shafts  of  the  bones.  They  may,  con- 
sequently, be  subdivided  into  three  sets :  1.  The  Superior  Tibio-fibular  articula- 
tion. 2.  The  Middle  Tibio-fibular  ligament  or  interosseous  membrane.  3.  The 
Inferior  Tibio-fibular  articulation. 

1.  Superior  Tibio-fibular  Articulation. 

This  articulation  is  an  arthrodial  joint.  The  contiguous  surfaces  of  the  bones 
present  two  flat,  oval  facets  covered  with  cartilage,  and  connected  together  by  the 
following  ligaments: 

Capsular. 

Anterior  Superior  Tibio-fibular. 

Posterior  Superior  Tibio-fibular. 

The  Capsular  Ligament  consists  of  a  membranous  bag  which  surrounds  the 
articulation,  being  attached  around  the  margins  of  the  articular  facets  on  the  tibia 
and  fibula,  and  is  much  thicker  in  front  than  behind. 

The  Anterior  Superior  Ligament  (Fig.  185)  consists  of  two  or  three  broad  and 
flat  bands  which  pass  obliquely  upward  and  inward  from  the  front  of  the  head  of 
the  fibula  to  the  front  of  the  outer  tuberosity  of  the  tibia. 

The  Posterior  Superior  Ligament  (Fig.  184)  is  a  single  thick  and  broad  band 
which  passes  upward  and  inward  from  the  back  part  of  the  head  of  the  fibula  to 
the  back  part  of  the  outer  tuberosity  of  the  tibia.  It  is  covered  by  the  tendon  of 
the  Popliteus  muscle. 

A  Synovial  Membrane  lines  this  articulation,  which  at  its  upper  and  back  part 
is  occasionally  continuous  with  that  of  the  knee-joint. 

2.    Middle  Tibio-fibular  Ligament  or  Interosseous  Membrane. 

An  interosseous  membrane  extends  between  the  contiguous  margins  of  the 
tibia  and  fibula,  and  separates  the  muscles  on  the  front  from  those  on  the  back  of 
the  leg.  It  consists  of  a  thin,  aponeurotic  lamina  composed  of  oblique  fibres 
which  for  the  most  part  pass  downward  and  outward  between  the  interosseous  ridges 
on  the  two  bones ;  some  few  fibres,  however,  pass  in  the  opposite  direction,  down- 
ward and  inward.  It  is  broader  above  than  below.  Its  upper  margin  does  not 
quite  reach  the  superior  tibio-fibular  joint,  but  presents  a  free  concave  border,  above 
which  is  a  large,  oval  aperture  for  the  passage  of  the  anterior  tibial  vessels  forward 
to  the  anterior  aspect  of  the  leg.  At  its  lower  part  is  an  opening  for  the  passage 
of  the  anterior  peroneal  vessels.  It  is  continuous  below  with  the  inferior  inter- 
osseous ligament,  and  is  perforated  in  numerous  parts  for  the  passage  of  small  vessels. 
It  is  in  relation,  in  front,  with  the  Tibialis  anticus,  Extensor  longus  digitorum, 
Extensor  proprius  hallucis,  Peroneus  tertius,  and  the  anterior  tibial  vessels  and 
nerve;  behind,  with  the  Tibialis  posticus  and  Flexor  longus  hallucis. 

3.  Inferior  Tibio-fibular  Articulation. 

This  articulation  is  formed  by  the  rough,  convex  surface  of  the  inner  side  of 
the  lower  end  of  the  fibula,  connected  with  a  concave  rough  surface  on  the  outer 
side  of  the  tibia.  Below,  to  the  extent  of  about  two  lines,  these  surfaces  are 
smooth,  and  covered  with  cartilage,  which  is  continuous  Avith  that  of  the  ankle- 
joint.     The  ligaments  of  this  joint  are — 

Anterior  Inferior  Tibio-fibular.  Transverse  or  Inferior. 

Posterior  Inferior  Tibio-fibular.  Inferior  Interosseous. 


THE   ANKLE-JOINT. 


283 


The  Anterior  Inferior  Ligament  (Fig.  190)  is  a  flat,  triangular  band  of  fibres, 
broader  below  than  above,  which  extends  obliquely  downward  and  outward 
between  the  adjacent  margins  of  the  tibia  and  fibula,  on  the  front  aspect  of  the 
articulation.  It  is  in  relation,  in  front,  with  the  Peroneus  tertius,  the  aponeurosis 
of  the  leg,  and  the  integument;  behind,  with  the  inferior  interosseous  ligament; 
and  lies  in  contact  with  the  cartilage  covering  the  astragalus. 

The  Posterior  Inferior  Ligament,  smaller  than  the  preceding,  is  disposed  in  a 
similar  manner  on  the  posterior  surface  of  the  articulation. 

The  Transverse  Ligament  or  Inferior  Ligament  lies  under  cover  of  the  posterior 
ligament,  and  is  a  strong,  thick  band  of  yellowish  fibres  which  passes  transversely 
across  the  back  of  the  joint,  from  the  external  malleolus  to  the  posterior  border  of 
the  articular  surface  of  the  tibia,  almost  as  far  as  its  malleolar  process.  This  liga- 
ment projects  below  the  margin  of  the  bones,  and  forms  part  of  the  articulating 
surface  for  the  astragalus. 

The  Inferior  Interosseous  Ligament  consists  of  numerous  short,  strong,  fibrous 
bands  which  pass  between  the  contiguous  rough  surfaces  of  the  tibia  and  fibula, 
and  constitute  the  chief  bond  of  union  between  the  bones.  This  ligament  is  con- 
tinuous above  with  the  interosseous  membrane. 

The  Synovial  Membrane  lining  the  articular  surface  is  derived  from  that  of  the 
ankle-joint. 

Actions. — The  movement  permitted  in  these  articulations  is  limited  to  a  very 
slight  gliding  of  the  articular  surfaces  one  upon  another. 

IV.  Ankle-joint. 

The  Ankle  is  a  ginglymus    or  hinge-joint.     The  bones  entering  into  its  forma- 
tion are  the  lower  extremity  of  the  tibia  and  its  malleolus  and  the  external  mal- 
leolus of  the  fibula,  which  forms  a  mortise  to  receive  the  upper  convex  surface  of 
the  astragalus  and  its  two  lateral  facets.     The  bony  surfaces  are  covered  with  carti- 


Tarso-  metata  rsal 
articulations, 


Fjg.  189.— Ankle-joint :  tarsal  and  tarsometatarsal  articulations.    Internal  view.     Right  side. 


lage  and  connected  together  by  a  capsule,  which  in  places  forms  thickened  bands 
constituting  the  following  ligaments : 


Anterior. 
Posterior. 


Internal  Lateral. 
External  Lateral. 


284 


THE   ARTICULATIONS. 


The  Anterior  Ligament  (Fig.  189)  is  a  broad,  thin,  membranous  layer,  attached, 
above,  to  the  anterior  margin  of  the  lower  extremity  of  the  tibia ;  below,  to  the 
margin  of  the  astragalus,  in  front  of  its  articular  surface.  It  is  in  relation,  in  front, 
with  the  Extensor  tendons  of  the  toes,  with  the  tendons  of  the  Tibialis  anticus  and 
Peroneus  tertius,  and  the  anterior  tibial  vessels  and  nerve;  behind,  it  lies  in  con- 
tact with  the  synovial  membrane. 

The  Posterior  Ligament  is  very  thin,  and  consists  principally  of  transverse 
fibres.  It  is  attached,  above,  to  the  margin  of  the  articular  surface  of  the  tibia, 
blending  with  the  transverse  tibio-fibular  ligament ;  below,  to  the  astragalus,  behind 
its  superior  articular  facet.  Externally,  where  a  somewhat  thickened  band  of 
transverse  fibres  is  attached  to  the  hollow  on  the  inner  surface  of  the  external 
malleolus,  it  is  thicker  than  internally. 

The  Internal  Lateral  or  Deltoid  Ligament  is  a  strong,  flat,  triangular  band,, 
attached,  above,  to  the  apex  and  anterior  and  posterior  borders  of  the  inner  mal- 
leolus. The  most  anterior  fibres  pass  forward  to  be  inserted  into  the  navicular 
bone  and  the  inferior  calcaneonavicular  ligament;  the  middle  descend  almost 
perpendicularly  to  be  inserted  into  the  sustentaculum  tali  of  the  os  calcis  ;  and  the 
posterior  fibres  pass  backward  and  outward  to  be  attached  to  the  inner  side  of  the 
astragalus.  This  ligament  is  covered  by  the  tendons  of  the  Tibialis  posticus  and 
Flexor  longus  digitorum  muscles. 


Inferior  tibio-fibular  articulation. 


Ankle-joint. 

Tarsal  articulations. 


Fig.  190.— Ankle-joint :  tarsal  and  tarsometatarsal  articulations.    External  view.    Right  side. 


The  External  Lateral  Ligament  (Fig.  190)  consists  of  three  distinctly  special- 
ized fasciculi  of  the  capsule,  taking  different  directions  and  separated  by  distinct 
intervals ;  for  which  reason  it  is  described  by  some  anatomists  as  three  distinct 
ligaments.1 

The  anterior  fasciculus  (anterior  astragalo-fibular),  the  shortest  of  the.  three, 
passes  from  the  anterior  margin  of  the  external  malleolus  forward  and  inward  to 
the  astragalus,  in  front  of  its  external  articular  facet. 

The  posterior  fasciculus  (posterior  astragalo-fibular),  the  most  d(  eated, 

passes  inward  f  T      depression  at  the  inner  and  back  part  of  the  exter::  1  mal- 

leolus to  a  pre  .Vibercle  on  the  posterior  surface  of  the  astragalu  .  ■  fib 

are  almost  horizontal  in  direction. 

1  Humphry,  On  the  Skeleton,  p.  559. 


res 


THE  ANKLE-JOINT.  285 

The  middle  fasciculus  (calcaneo-fibular),  the  longest  of  the  three,  is  a  narrow, 
rounded  cord  passing  from  the  apex  of  the  external  malleolus  downward  and  slightly 
backward  to  a  tubercle  on  the  outer  surface  of  the  os  calcis.  It  is  covered  by  the 
tendons  of  the  Peroneus  longus  and  brevis. 

The  Synovial  Membrane  invests  the  inner  surface  of  the  ligaments,  and  sends 
a  duplicature  upward  between  the  lower  extremities  of  the  tibia  and  fibula  for  a 
short  distance. 

Eelations. — The  tendons,  vessels,  and  nerves  in  connection  with  the  joint  are, 
in  front,  from  within  outward,  the  Tibialis  anticus,  Extensor  proprius  hallucis, 
anterior  tibial  vessels,  anterior  tibial  nerve,  Extensor  longus  digitorum,  and  Pero- 
neus tertius ;  behind,  from  within  outward,  the  Tibialis  posticus,  Flexor  longus 
digitorum,  posterior  tibial  vessels,  posterior  tibial  nerve,  Flexor  longus  hallucis ; 
and,  in  the  groove  behind  the  external  malleolus,  the  tendons  of  the  Peroneus 
longus  and  brevis. 

The  Arteries  supplying  the  joint  are  derived  from  the  malleolar  branches  of 
the  anterior  tibial  and  the  peroneal. 

The  Nerves  are  derived  from  the  anterior  and  posterior  tibial. 

Actions. — The  movements  of  the  joint  are  those  of  flexion  and  extension. 
Flexion  consists  in  the  approximation  of  the  dorsum  of  the  foot  to  the  front  of  the 
leg,  while  in  extension  the  heel  is  drawn  up  and  the  toes  pointed  downward.  The 
malleoli  tightly  embrace  the  astragalus  in  all  positions  of  the  joint,  so  that  any 
slight  degree  of  lateral  movement  which  may  exist  is  simply  due  to  stretching 
of  the  inferior  tibio-fibular  ligaments  and  slight  bending  of  the  shaft  of  the 
fibula.  Of  the  ligaments,  the  internal,  or  deltoid,  is  of  very  great  power — so 
much  so  that  it  usually  resists  a  force  which  fractures  the  process  of  bone  to  which 
it  is  attached.  Its  middle  portion,  together  with  the  middle  fasciculus  of  the 
external  lateral  ligament,  binds  the  bones  of  the  leg  firmly  to  the  foot  and  resists 
displacement  in  every  direction.  Its  anterior  and  posterior  fibres  limit  extension 
and  flexion  of  the  foot  respectively,  and  the  anterior  fibres  also  limit  abduction. 
The  posterior  portion  of  the  external  lateral  ligament  assists  the  middle  portion  in 
resisting  the  displacement  of  the  foot  backward,  and  deepens  the  cavity  for  the 
reception  of  the  astragalus.  The  anterior  fasciculus  is  a  security  against  the  dis- 
placement of  the  foot  forward,  and  limits  extension  of  the  joint.  The  movements 
of  inversion  and  eversion  of  the  foot,  together  with  the  minute  changes  in  form  by 
which  it  is  applied  to  the  ground  or  takes  hold  of  an  object  in  climbing,  etc.,  are 
mainly  effected  in  the  tarsal  joints,  the  one  which  enjoys  the  greatest  amount  of 
motion  being  that  betAveen  the  astragalus  and  os  calcis  behind  and  the  navicular 
and  cuboid  in  front.  This  is  often  called  the  transverse  or  medio-tar sal  joint,  and 
it  can,  with  the  subordinate  joints  of  the  tarsus,  replace  the  ankle-joint  in  a  great 
measure  when  the  latter  has  become  ankylosed. 

Extension  of  the  tarsal  bones  upon  the  tibia  and  fibula  is  produced  by  the 
Gastrocnemius,  Soleus,  Plantaris,  Tibialis  posticus,  Peroneus  longus  and  brevis, 
Flexor  longus  digitorum,  and  Flexor  longus  hallucis ;  flexion,  by  the  Tibialis  anti- 
cus, Peroneus  tertius,  Extensor  longus  digitorum,  and  Extensor  proprius  hallucis  ;l 
inversion,  in  the  extended  position,  is  produced  by  the  Tibialis  anticus  and  posti- 
cus ;  and  eversion  by  the  Peronei. 

Surface  Form. — The  line  of  the  ankle-joint  may  be  indicated  by  a  transverse  line  drawn 
across  the  front  of  the  lower  part  of  the  leg,  about  half  an  inch  above  the  level  of  the  tip  of  the 
internal  malleolus. 

Surgical  Anatomy. — Displacement  of  the  trochlear  surface  of  the  astragalus  from  the 
tibio-fibular  mortise  is  not  of  common  occurrence,  as  the  ankle-joint  is  a  very  strong  and  powerful 
articulation,  and  great  force  is  required  to  produce  it.  Nevertheless,  dislocation  does  occasionally 
occur,  both  in  an  antero-posterior  and  a  lateral  direction.  In  the  latter,  which  is  the  most  com- 
mon, fracture  is  a  necessary  accompaniment  of  the  injury.  The  d'  Wation  in  these  cases  is 
somewhat  peculiar,  and  is  not  a  displacement  in  a  horizontally  later.,    uirection,  such  as  usually 

1  The  student  must  bear  in  mind  that  the  Extensor  longus  digitorum  and  Extensor  proprius  hal- 
lucis are  extensors  of  the  toes,  but  flexors  of  the  ankle,  and  that  the  Flexor  longus  digitorum  and  Flexor 
longus  hallucis  are  flexors  of  the  toes,  but  extensors  of  the  ankle. 


286 


THE   ABTICULATIONS 


occurs  in  lateral  dislocations  of  ginglymoid  joints,  but  the  astragalus  undergoes  a  partial  rotation 
round  an  anteroposterior  axis  drawn  through  its  own  centre,  so  that  the  superior  surface,  instead 
of  being  directed  upward,  is  inclined  more  or  less  inward  or  outward  according  to  the  variety  of 
the  displacement. 

The  ankle-joint  is  more  frequently  sprained  than  any  joint  in  the  body,  and  this  may  lead 
to  acute  synovitis.  In  these  cases,  when  the  synovial  sac  is  distended  with  fluid,  the  bulging 
appears  principally  in  the  front  of  the  joint,  beneath  the  anterior  tendons,  and  on  either  side, 
between  the  Tibialis  anticus  and  the  internal  lateral  ligament  on  the  inner  side,  and  between  the 
Peroneus  tertius  and  the  external  lateral  ligament  on  the  outer  side.  In  addition  to  this,  bulging 
frequently  occurs  posteriorly,  and  a  fluctuating  swelling  may  be  detected  on  either  side  of  the 
tendo  Achillis. 

Chronic  synovitis  may  result  from  frequent  sprains,  and  when  once  this  joint  has  been 
sprained  it  is  more  liable  to  a  recurrence  of  the  injury  than  it  was  before  ;  or  it  may  be  tuber- 


Fig.  191.— Section  of  the  right  foot  near  its  inner  border,  dividing  the  tibia,  astragalus,  navicular,  internal 
cuneiform,  and  first  metatarsal  bone,  and  the  first  phalanx  of  the  great  toe.    (After  Braune.) 

cular  in  its  origin,  the  disease  usually  commencing  in  the  astragalus  and  extending  to  the  joint, 
though  it  may  commence  as  a  synovitis  the  result  probably  of  some  slight  strain  in  a  tubercular 
subject. 

Excision  of  the  ankle-joint  is  not  often  performed  for  two  reasons.  In  the  first  place, 
disease  of  the  articulation  for  which  this  operation  is  indicated  is  frequently  associated  with 
disease  of  the  tarsal  bones,  which  prevents  its  performance;  and,  secondly,  the  foot  after 
excision  is  frequently  of  very  little  use  ;  far  less,  in  fact,  than  after  a  Symes's  amputation,  which 
is  often,  therefore,  a  preferable  operation  in  these  cases.  Excision  may,  however,  be  attempted 
in  cases  of  tubercular  arthritis,  in  a  young  and  otherwise  healthy  subject,  where  the  disease  is 
limited  to  the  bones  forming  the  joint.  It  may  also  be  required  after  injury  where  the  vessels 
and  nerves  have  not  been  damaged  and  the  patient  is  young  and  free  from  visceral  disease. 
The  excision  is  best  performed  by  two  lateral  incisions.  One  commencing  two  and  a  half  inches 
above  the  external  malleolus,  carried  down  the  posterior  border  of  the  fibula,  round  the  end  of 
the  bone,  and  then  forward  and  downward  as  far  as  the  calcaneo-cuboid  joint,  midway  between 
the  tip  of  the  external  malleolus  and  the  tuberosity  on  the  fifth  metatarsal  bone.  Through  this 
incision  the  fibula  is  cleared,  the  external  lateral  ligament  is  divided,  and  the  bone  sawn  through 
about  half  an  inch  Above  the  level  of  the  ankle-joint  and  removed.  A  similar  curved  incision  is 
now  made  on  the  inner  side  of  the  foot,  commencing  two  and  a  half  inches  above  the  lower  end 
ot  the  tibia,  carried  down  the  posterior  border  of  the  bone,  round  the  internal  malleolus,  and 
forward  and  downward  to  the  tuberosity  of  the  navicular  bone.  Through  this  incision  the  tibia 
is  cleared  in  front  and  behind,  the  internal  lateral,  the  anterior  and  posterior  ligaments  divided, 
and  the  end  of  the  tibia  protruded  through  the  wound  by  displacing  the  foot  outward,  and  sawn 
off  sufficiently  high  to  secure  a  healthy  section  of  bone.  The  articular  surfaceof  the  astragalus 
is  now  to  be  sawn  off  or  the  whole  bone  removed.  In  cases  where  the  operation  is  performed 
for  tubercular  arthritis  the  latter  course  is  probably  preferable,  as  the  injury  done  by  the  saw  is 
frequently  the  starting  point  of  fresh  caries  ;  and  after  removal  of  the  whole  bone  the  shortening 
is  not  appreciably  increased,  and  the  result  as  regards  union  appears  to  be  as  good  as  when  two 
sawn  surfaces  of  bone  are  brought  into  apposition. 


OF   THE    TARSUS.  287 

V.  Articulations  of  the  Tarsus. 

1.   Articulations  of  the  Os  Calcis  and  Astragalus. 

The  articulations  between  the  os  calcis  and  astragalus  are  two  in  number — 
anterior  and  posterior.  They  are  arthrodial  joints.  The  bones  are  connected 
together  by  four  ligaments : 

External  Calcaneo-astragaloid.  Posterior  Calcaneo-astragaloid. 

Internal  Calcaneo-astragaloid.  Interosseous. 

The  External  Calcaneo-astragaloid  Ligament  (Fig.  190)  is  a  short,  strong, 
fasciculus  passing  from  the  outer  surface  of  the  astragalus,  immediately  beneath 
its  external  malleolar  facet,  to  the  outer  surface  of  the  os  calcis.  It  is  placed  in 
front  of  the  middle  fasciculus  of  the  external  lateral  ligament  of  the  ankle-joint, 
with  the  fibres  of  which  it  is  parallel. 

The  Internal  Calcaneo-astragaloid  Ligament  is  a  band  of  fibres  connecting  the 
internal  tubercle  of  the  back  of  the  astragalus  with  the  back  of  the  sustentaculum 
tali.     Its  fibres  blend  with  those  of  the  inferior  calcaneonavicular  ligament. 

The  Posterior  Calcaneo-astragaloid  Ligament  (Fig.  189)  connects  the  external 
tubercle  of  the  astragalus  with  the  upper  and  inner  part  of  the  os  calcis ;  it  is  a 
short  band,  the  fibres  of  which  radiate  from  their  narrow  attachment  to  the 
astragalus. 

The  Interosseous  Ligament  forms  the  chief  bond  of  union  between  the  bones. 
It  consists  of  numerous  vertical  and  oblique  fibres  attached  by  one  extremity  to  the 
groove  between  the  articulating  facets  on  the  under  surface  of  the  astragalus ;  by 
the  other  to  a  corresponding  depression  on.  the  upper  surface  of  the  os  calcis.  It 
is  very  thick  and  strong,  being  at  least  an  inch  in  breadth  from  side  to  side,  and 
serves  to  unite  the  os  calcis  and  astragalus  solidly  together. 

The  Synovial  Membranes  (Fig.  193)  are  two  in  number :  one  for  the  posterior 
calcaneo-astragaloid  articulation ;  a  second  for  the  anterior  calcaneo-astragaloid 
joint.  The  latter  synovial  membrane  is  continued  forward  between  the  contiguous 
.surfaces  of  the  astragalus  and  navicular  bones. 

Actions. — The  movements  permitted  between  the  astragalus  and  os  calcis  are 
limited  to  a  gliding  of  the  one  bone  on  the  other  in  a  direction  from  before  back- 
ward, and  from  side  to  side. 

2.  Articulations  of  the  Os  Calcis  with  the  Cuboid. 
The  ligaments  connecting  the  os  calcis  with  the  cuboid  are  four  in  number : 

ta        i  j  Superior  Calcaneo-cuboid. 

\  Internal  Calcaneo-cuboid  (Interosseous). 


pi  j  Long  Calcaneo-cuboid. 

\  Short  Calcaneo-cuboid. 


The  Superior  Calcaneo-cuboid  Ligament  (Fig.  190)  is  a  thin  and  narrow  fasciculus 
which  passes  between  the  contiguous  surfaces  of  the  os  calcis  and  cuboid  on  the 
dorsal  surface  of  the  joint. 

The  Internal  Calcaneo-cuboid  (Interosseous)  Ligament  (Fig.  190)  is  a  short 
but  thick  and  strong  band  of  fibres  arising  from  the  os  calcis,  in  the  deep  hollow 
which  intervenes  between  it  and  the  astragalus,  and  closely  blended,  at  its  origin, 
with  the  superior  calcaneonavicular  ligament.  It  is  inserted  into  the  inner  side  of 
the  cuboid  bone.  This  ligament  forms  one  of  the  chief  bonds  of  union  between 
the  first  and  second  rows  of  the  tarsus. 

The  Long  Calcaneo-cuboid  (Long  Plantar)  Ligament  (Fig.  192),  the  more  super- 
ficial of  the  two  plantar  ligaments,  is  the  longest  of  all  the  ligaments  of  the  tarsus  : 
it  is  attached  to  the  under  surface  of  the  os  calcis,  from  near  the  tuberosities,  as  far 
forward  as  the  anterior  tubercle ;  its  fibres  pass  forward  to  be  attached  to  the 
ridge  on  the  under  surface  of  the  cuboid  bone,  the  more  superficial  fibres  being 


288 


THE   ARTICULATIONS 


continued  onward  to  the  bases  of  the  second,  third,  and  fourth  metatarsal  bones. 
This  ligament  crosses  the  groove  on  the  under  surface  of  the  cuboid  bone,  convert- 
ing it  into  a  canal  for  the  passage  of  the  tendon  of  the  Peroneus  longus. 

The  Short  Calcaneo-cuboid  (Short  Plantar)  Ligament  lies  nearer  to  the  bones 
than  the  preceding,  from  which  it  is  separated  by  a  little  areolar  tissue.  It  is 
exceedingly  broad,  about  an  inch  in  length,  and  extends  from  the  tubercle  and  the 
depression  in  front  of  it,  on  the  fore  part  of  the  under  surface  of  the  os  calcis,  to 
the  inferior  surface  of  the  cuboid  bone  behind  the  peroneal  groove. 

Synovial  Membrane. — The  synovial  membrane  in  this  joint  is  distinct.  It 
lines  the  inner  surface  of  the  ligaments. 

Actions. — The  movements  permitted  between  the  os  calcis  and  cuboid  are 
limited  to  a  slight  gliding  upon  each  other. 

3.  The  Ligaments  connecting  the  Os  Calcis  and  Navicular. 

Though  these  two  bones  do  not  directly  articulate,  they  are  connected  together 
by  two  ligaments  : 

Superior  or  External  Calcaneonavicular. 
Inferior  or  Internal  Calcaneonavicular. 

The  Superior  or  External  Calcaneonavicular  (Fig.  190)  arises,  as  already  men- 
tioned, with  the  internal  calcaneo-cuboid  in  the 
deep  hollow  between  the  astragalus  and  os 
calcis ;  it  passes  forward  from  the  upper  surface 
of  the  anterior  extremity  of  the  os  calcis  to  the 
outer  side  of  the  navicular  bone.  These  two 
ligaments  resemble  the  letter  Y,  being  blended 
together  behind,  but  separated  in  front. 

The  Inferior  or  Internal  Calcaneonavicular 
(Fig.  192)  is  by  far  the  larger  and  stronger  of 
the  two  ligaments  between  these  bones ;  it  is 
a  broad  and  thick  band  of  fibres,  which  passes 
forward  and  inward  from  the  anterior  margin 
of  the  sustentaculum  tali  of  the  os  calcis  to  the 
under  surface  of  the  navicular  bone.  This 
ligament  not  only  serves  to  connect  the  os 
calcis  and  navicular,  but  supports  the  head  of 
the  astragalus,  forming  part  of  the  articular 
cavity  in  which  it  is  received.  The  upper 
surface  presents  a  nbro-cartilaginous  facet, 
lined  by  the  synovial  membrane  continued 
from  the  anterior  calcaneo-astragaloid  articu- 
lation, upon  which  a  portion  of  the  head  of 
the  astragalus  rests.  Its  under  surface  is  in 
contact  with  the  tendon  of  the  Tibialis  posticus 
muscle ; 1  its  inner  border  is  blended  with  the 
fore  part  of  the  Deltoid  ligament,  thus  com- 
pleting the  socket  for  the  head  of  the  astragalus. 

Surgical  Anatomy. — The  inferior  calcaneonav- 
icular ligament,  by  supporting  the  head  of  the  astrag- 
alus, is  principally  concerned  in  maintaining  the  arch 
of  the  foot,  and  when  it  yields,  the  head  of  the  astrag- 
alus is  pressed  downward,  inward,  and  forward  by  the 
weight  of  the  body,  and  the  foot  becomes  flattened, 
expanded,  and  turned  outward,  constituting  the  dis- 
ease known  as  flat-foot.     This  ligament  contains  a  considerable  amount  of  elastic  fibre,  so  as  to 

1  Mr.  Hancock  describes  an  extension  of  this  ligament  upward  on  the  inner  side  of  the  foot* 
which  completes  the  socket  of  the  joint  in  that  direction  (Lancet,  1866  vol.  i.,  p.  618). 


Fi<s.  192.— Ligaments  of  the  plantar  surface 
of  the  foot. 


OF    THE    TABS  US.  289 

give  elasticity  to  the  arch  and  spring  to  the  foot;  hence  it  is  sometimes  called  the  "spring" 
ligament.  It  is  supported,  on  its  under  surface,  by  the  tendon  of  the  Tibialis  posticus,  'which 
spreads  out  at  its  insertion  into  a  number  of  fasciculi  which  are  attached  to  most  of  the  tarsal 
and  metatarsal  bones ;  this  prevents  undue  stretching  of  the  ligament  and  is  a  protection  against 
the  occurrence  of  flat-foot. 

4.   Articulation  of  the  Astragalus  with  the  Navicular  Bone. 

The  articulation  between  the  astragalus  and  navicular  is  an  arthrodial  joint : 
the  rounded  head  of  the  astragalus  being  received  into  the  concavity  formed  by 
the  posterior  surface  of  the  navicular,  the  anterior  articulating  surface  of  the 
calcaneum,  and  the  upper  surface  of  the  inferior  calcaneonavicular  ligament, 
which  fills  up  the  triangular  interval  between  these  bones.  The  only  ligament  of 
this  joint  is  the  superior  astragalo-navicular.  It  is  a  broad  band,  which  passes 
obliquely  forward  from  the  neck  of  the  astragalus  to  the  superior  surface  of  the 
navicular  bone.  It  is  thin,  and  weak  in  texture,  and  covered  by  the  Extensor  ten- 
dons.    The  inferior  calcaneonavicular  supplies  the  place  of  an  inferior  ligament. 

The  Synovial  Membrane  which  lines  the  joint  is  continued  forward  from  the 
anterior  calcaneo-astragaloid  articulation. 

Actions. — This  articulation  permits  of  considerable  mobility,  but  its  feebleness 
is  such  as  to  allow  occasionally  of  dislocation  of  the  other  bones  of  the  tarsus 
from  the  astragalus. 

The  transverse  tarsal  or  medio-tarsal  joint  is  formed  by  the  articulation  of  the 
os  calcis  with  the  cuboid,  and  by  the  articulation  of  the  astragalus  with  the  nav- 
icular. The  movement  which  takes  place  in  this  joint  is  more  extensive  than  that 
in  the  other  tarsal  joints,  and  consists  of  a  sort  of  rotation  by  means  of  which  the 
sole  of  the  foot  may  be  slightly  flexed  and  extended  or  carried  inward  (inverted) 
and  outward  (everted). 

5.  The  Articulation  of  the  Navicular  with  the  Cuneiform  Bones. 
The  navicular  is  connected  to  the  three  cuneiform  bones  by 
Dorsal  and  Plantar  ligaments. 

The  Dorsal  Ligaments  are  small,  longitudinal  bands  of  fibrous  tissue  arranged 
as  three  bundles,  one  to  each  of  the  cuneiform  bones.  That  bundle  of  fibres 
which  connects  the  navicular  with  the  internal  cuneiform  is  continued  round  the 
inner  side  of  the  articulation  to  be  continuous  with  the  plantar  ligament  which 
connects  these  two  bones. 

The  Plantar  Ligaments  have  a  similar  arrangement  to  those  on  the  dorsum. 
They  are  strengthened  by  processes  given  off  from  the  tendon  of  the  Tibialis  posticus. 

Actions. — The  movements  permitted  between  the  navicular  and  cuneiform 
bones  are  limited  to  a  slight  gliding  upon  each  other. 

The  Synovial  Membrane  of  these  joints  is  part  of  the  great  tarsal  synovial 
membrane. 

6.  The  Articulation  of  the  Navicular   with  the  Cuboid. 

The  navicular  bone  is  connected  with  the  cuboid  by 

Dorsal,  Plantar,  and  Interosseous  ligaments. 

The  Dorsal  Ligament  consists  of  a  band  of  fibrous  tissue  which  passes  obliquely 
forward  and  outward  from  the  navicular  to  the  cuboid  bone. 

The  Plantar  Ligament  consists  of  a  band  of  fibrous  tissue  which  passes  nearly 
transversely  between  these  two  bones. 

The  Interosseous  Ligament  consists  of  strong  transverse  fibres  which  pass 
between  the  rough  non-articular  portions  of  the  lateral  surfaces  of  these  two 
bones. 

Actions. — The  movements  permitted  between  the  navicular  and  cuboid  bones 
are  limited  to  a  slight  gliding  upon  each  other. 

The  Synovial  Membrane  of  this  joint  is  part  of  the  great  tarsal  synovial 
membrane. 

19 


290  THE   ARTICULATIONS. 

7.  The  Articulation  of  the  Cuneiform  Bones  with  each  other. 

These  bones  are  connected  together  by 

Dorsal,  Plantar,  and  Interosseous  ligaments. 

The  Dorsal  Ligaments  consist  of  two  bands  of  fibrous  tissue  which  pass  trans- 
versely, one  connecting  the  internal  with  the  middle  cuneiform,  and  the  other 
connecting   the  middle  with  the  external  cuneiform. 

The  Plantar  Ligaments  have  a  similar  arrangement  to  those  on  the  dorsum. 
They  are  strengthened  by  the  processes  given  off  from  the  tendon  of  the  Tibialis 
posticus. 

The  Interosseous  Ligaments  consist  of  strong  transverse  fibres  Avhich  pass 
between  the  rough  non-articular  portions  of  the  lateral  surfaces  of  the  adjacent 
cuneiform  bones. 

The  Synovial  Membrane  of  these  joints  is  part  of  the  great  tarsal  synovial 
membrane. 

Actions. — The  movements  permitted  between  the  cuneiform  bones  are  limited 
to  a  slight  gliding  upon  each  other. 

8.  The  Articulation  of  the  External  Cuneiform  Bone  with  the  Cuboid. 

These  bones  are  connected  together  by 

Dorsal,  Plantar,  and  Interosseous  ligaments. 

The  Dorsal  Ligament  consists  of  a  band  of  fibrous  tissue  which  passes  trans- 
versely between  these  two  bones. 

The  Plantar  Ligament  has  a  similar  arrangement.  It  is  strengthened  by  a 
process  given  off  from  the   tendon   of  the    Tibialis  posticus. 

The  Interosseous  Ligament  consists  of  strong  transverse  fibres  which  pass 
between  the  rough  non-articular  portions  of  the  lateral  surfaces  of  the  adjacent 
sides  of  these  two  bones. 

The  Synovial  Membrane  of  this  joint  is  part  of  the  great  tarsal  synovial 
membrane. 

Actions. — The  movements  permitted  between  the  external  cuneiform  and  cuboid 
are  limited  to  a  slight  gliding  upon  each  other. 

Nerve-supply. — All  the  joints  of  the  tarsus  are  supplied  by  the  anterior  tibial 
nerve. 

Surgical  Anatomy. — In  spite  of  the  great  strength  of  the  ligaments  which  connect  the 
tarsal  bones  together,  dislocation  at  some  of  the  tarsal  joints  does  occasionally  occur ;  though,  on 
account  of  the  spongy  character  of  the  bones,  they  are  more  frequently  broken  than  dislocated, 
as  the  result  of  violence.  When  dislocation  does  occur,  it  is  most  commonly  in  connection  with 
the  astragalus ;  for  not  only  may  this  bone  be  dislocated  from  the  tibia  and  fibula  at  the  ankle- 
joint,  but  the  other  bones  may  be  dislocated  from  it,  the  trochlear  surface  of  the  bone  remaining 
in  situ  in  the  tibio-fibular  mortise.  This  constitutes  what  is  known  as  the  subastragaloid 
dislocation.  Or,  again,  the  astragalus  may  be  dislocated  from  all  its  connections — from  the 
tibia  and  fibula  above,  the  os  calcis  below,  and  the  navicular  in  front — and  may  even  undergo  a 
rotation,  either  on  a  vertical  or  horizontal  axis.  In  the  former  case  the  long  axis  of  the  bone 
becoming  directed  across  the  joint,  so  that  the  head  faces  the  articular  surface  on  one  or 
other  malleolus ;  or,  in  the  latter,  the  lateral  surfaces  becoming  directed  upward  and  down- 
ward, so  that  the  trochlear  surface  faces  to  one  or  the  other  side.  Finally,  dislocation  may 
occur  at  the  medio-tarsal  joint,  the  anterior  tarsal  bones  being  luxated  from  the  astragalus  and 
calcaneum.  The  other  tarsal  bones  are  also,  occasionally,  though  rarely,  dislocated  from  their 
connections. 

VI.   Tarso -metatarsal  Articulations. 

These  are  arthrodial  joints.  The  bones  entering  into  their  formation  are  four 
tarsal  bones — viz.  the  internal,  middle,  and  external  cuneiform  and  the  cuboid — 
which  articulate  Avith  the  metatarsal  bones  of  the  five  toes.  The  metatarsal  bone 
of  the  great  toe  articulates  with  the  internal  cuneiform  ;  that  of  the  second  is 
deeply  wedged  in  between  the  internal  and  external  cuneiform,  resting  against  the 
middle  cuneiform,  and  being  the  most  strongly  articulated  of  all  the  metatarsal 
bones ;  the  third  metatarsal  articulates  with  the  extremity  of  the  external  cunei- 


TABSO-METATABSAL    ARTICULATIONS.  291 

form ;  the  fourth  with  the  cuboid  and  external  cuneiform ;  and  the  fifth,  with  the 
cuboid.  The  articular  surfaces  are  covered  with  cartilage,  lined  by  synovial 
membrane,  and  connected  together  by  the  following  ligaments : 

Dorsal.  Plantar.  Interosseous. 

The  Dorsal  Ligaments  consist  of  strong,  flat,  fibrous  bands,  which  connect  the 
tarsal  with  the  metatarsal  bones.  The  first  metatarsal  is  connected  to  the  internal 
cuneiform  by  a  single  broad,  thin,  fibrous  band ;  the  second  has  three  dorsal 
ligaments,  one  from  each  cuneiform  bone ;  the  third  has  one  from  the  external 
cuneiform ;  the  fourth  has  two,  one  from  the  external  cuneiform  and  one  from  the 
cuboid ;  and  the  fifth,  one  from  the  cuboid. 

The  Plantar  Ligaments  consist  of  longitudinal  and  oblique  fibrous  bands 
connecting  the  tarsal  and  metatarsal  bones,  but  disposed  with  less  regularity 
than  on  the  dorsal  surface.  Those  for  the  first  and  second  metatarsal  are  the  most 
strongly  marked ;  the  second  and  third  metatarsal  receive  strong  fibrous  bands 
which  pass  obliquely  across  from  the  internal  cuneiform ;  the  plantar  ligaments 
of  the  fourth  and  fifth  metatarsal  consist  of  a  few  scanty  fibres  derived  from  the 
cuboid. 

The  Interosseous  Ligaments  are  three  in  number — internal,  middle,  and  external. 
The  internal  one  is  the  strongest  of  the  three,  and  passes  from  the  outer  extremity 
of  the  internal  cuneiform  to  the  adjacent  angle  of  the  second  metatarsal.  The 
middle  one,  less  strong  than  the  preceding,  connects  the  external  cuneiform  with 
the  adjacent  angle  of  the  second  metatarsal.  The  external  interosseous  ligament 
connects  the  outer  angle  of  the  external  cuneiform  with  the  adjacent  side  of  the 
third  metatarsal. 

The  Synovial  Membrane  between  the  internal  cuneiform  bone  and  the  first 
metatarsal  bone  is  a  distinct  sac.  The  synovial  membrane  between  the  middle  and 
external  cuneiform  behind,  and  the  second  and  third  metatarsal  bones  in  front,  is 
part  of  the  great  tarsal  synovial  membrane.  Two  prolongations  are  sent  forward 
from  it — one  between  the  adjacent  sides  of  the  second  and  third  metatarsal  bones, 
and  one  between  the  third  and  fourth  metatarsal  bones.  The  synovial  membrane 
between  the  cuboid  and  the  fourth  and  fifth  metatarsal  bones  is  a  distinct  sac.  From 
it  a  prolongation  is  sent  forward  between  the  fourth  and  fifth  metatarsal  bones. 

Actions. — The  movements  permitted  between  the  tarsal  and  metatarsal  bones 
are  limited  to  a  slight  gliding  upon  each  other. 

VII.   Articulations  of  the  Metatarsal  Bones  with  Each  Other. 

The  base  of  the  first  metatarsal  bone  is  not  connected  with  the  second  meta- 
tarsal bone  by  any  ligaments ;  in  this  respect  it  resembles  the  thumb. 

The  bases  of  the  four  outer  metatarsal  bones  are  connected  together  by  dorsal, 
plantar,  and  interosseous  ligaments. 

The  Dorsal  Ligaments  consist  of  bands  of  fibrous  tissue  which  pass  transversely 
between  the  adjacent  metatarsal  bones. 

The  Plantar  Ligaments  have  a  similar  arrangement  to  those  on  the  dorsum. 

The  Interosseous  Ligaments  consist  of  strong  transverse  fibres  which  pass  between 
the  rough  non-articular  portions  of  the  lateral  surfaces. 

The  Synovial  Membrane  between  the  second  and  third  and  the  third  and  fourth 
metatarsal  bones  is  part  of  the  great  tarsal  synovial  membrane. 

The  synovial  membrane  between  the  fourth  and  fifth  metatarsal  bones  is  a 
prolongation  of  the  synovial  membrane  of  the  cubo-metatarsal  joint. 

Actions. — The  movement  permitted  in  the  tarsal  ends  of  the  metatarsal  bones 
is  limited  to  a  slight  gliding  of  the  articular  surfaces  upon  one  another. 

The  Synovial  Membranes  in  the  Tarsal  and  Metatarsal  Joints. 

The  Synovial  Membranes  (Fig.  193)  found  in  the  articulations  of  the  tarsus 
and  metatarsus   are   six  in  number :    one  for  the  posterior  calcaneo-astragaloid 


292 


THE   ARTICULATIONS 


articulation ;  a  second  for  the  anterior  calcaneo-astragaloid  and  astragalo-navicular 
articulations ;  a  third  for  the  calcaneo-cuboid  articulation  ;  and  a  fourth  for  the 
articulations  of  the  navicular  with  the  three  cuneiform,  the  three  cuneiform  with 
each  other,  the  external  cuneiform  with  the  cuboid,  and  the  middle  and  external 
cuneiform  with  the  bases  of  the  second  and  third  metatarsal  bones,  and  the  lateral 
surfaces  of  the  second,  third,  and  fourth  metatarsal  bones  with  each  other  ;  a  fifth 
for  the  internal  cuneiform  with  the  metatarsal  bone  of  the  great  toe ;  and  a  sixth 
for  the  articulation  of  the  cuboid  with  the  fourth  and  fifth  metatarsal  bones.  A 
small  synovial  membrane  is  sometimes  found  between  the  contiguous  surfaces  of  the 
navicular  and  cuboid  bones. 

Nerve-supply. — The  nerves  supplying  the  tarso-metatarsal  joints  are  derived 
from  the  anterior  tibial. 

The  digital  extremities  of  all  the  metatarsal  bones  are  connected  together  by 
the    transverse  metatarsal  ligament. 

The  Transverse  Metatarsal  Ligament  is  a  narrow  fibrous  band  which  passes 
transversely  across  the  anterior  extremities  of  all  the  metatarsal  bones,  connecting 


Pig.  193.— Oblique  section  of  the  articulations  of  the  tarsus  and  metatarsus.  Showing  the  six  synovial 
membranes. 

them  together.  It  is  blended  anteriorly  Avith  the  plantar  (glenoid)  ligament  of 
the  metatarso-phalangeal  articulations.  To  its  posterior  border  is  connected  the 
fascia  covering  the  Interossei  muscles.  Its  inferior  surface  is  concave  where  the 
Flexor  tendons  pass  over  it.  Above  it  the  tendons  of  the  Interossei  muscles  pass 
to  their  insertion.  It  differs  from  the  transverse  metacarpal  ligament  in  that  it 
connects  the  metatarsal  bone  of  the  great  toe  with  the  rest  of  the  metatarsal  bones. 

VIII.   Metatarso-phalangeal  Articulations. 

The  metatarso-phalangeal  articulations  are  of  the  condyloid  kind,  formed  by  the 
reception  of  the  rounded  head  of  the  metatarsal  bone  into  a  superficial  cavity  in  the 
extremity  of  the  first  phalanx. 

The  ligaments  are — 

Plantar.  Two  Lateral. 

The  Plantar  Ligaments  (Glenoid  ligaments  of  Cruveilhier)  are  thick,  dense, 
fibrous  structures.  Each  is  placed  on  the  plantar  surface  of  the  joint  in  the 
interval  between  the  lateral  ligaments,  to  which  they  are  connected ;  they  are 
loosely  united  to  the  metatarsal  bone,  but  very  firmly  to  the  base  of  the  first 
phalanges.  Their  plantar  surface  is  intimately  blended  with  the  transverse  meta- 
tarsal ligament,  and  presents  a  groove  for  the  passage  of  the  Flexor  tendons,  the 
sheath  surrounding  which  is  connected  to  each  side  of  the  groove.     By  their  deep 


OF    THE   PHALANGES.  293 

surface  they  form  part  of  the  articular  surface  for  the  head  of  the  metatarsal  bone, 
and  are  lined  by  a  synovial  membrane. 

The  Lateral  Ligaments  are  strong,  rounded  cords,  placed  one  on  each  side  of  the 
joint,  each  being  attached,  by  one  extremity,  to  the  posterior  tubercle  on  the  side  of 
the  head  of  the  metatarsal  bone  ;  and,  by  the  other,  to  the  contiguous  extremity  of 
the  phalanx. 

The  Posterior  Ligament  is  supplied  by  the  extensor  tendon  placed  over  the  back 
of  the  joint. 

Actions. — The  movements  permitted  in  the  metatarso-phalangeal  articulations 
are  flexion,  extension,  abduction,  and  adduction. 

IX.   Articulations  of  the  Phalanges. 

The  articulations  of  the  phalanges  are  ginglymus  joints. 

The  ligaments  are — 

Plantar.  Two  Lateral. 

The  arrangement  of  these  ligaments  is  similar  to  those  in  the  metatarso- 
phalangeal articulations ;  the  extensor  tendon  supplies  the  place  of  a  posterior 
ligament. 

Actions. — The  only  movements  permitted  in  the  phalangeal  joints  are  flexion 
and  extension ;  these  movements  are  more  extensive  between  the  first  and  second 
phalanges  than  between  the  second  and  third.  The  movement  of  flexion  is  very 
considerable,  but  extension  is  limited  by  the  plantar  and  lateral  ligaments. 

Surface  Form. — The  principal  joints  which  it  is  necessary  to  distinguish,  with  regard  to  the 
surgery  of  the  foot,  are  the  medio-tarsal  and  the  tarso-metatarsal  joints.  The  joint  between  the 
astragalus  and  the  navicular  is  best  found  by  means  of  the  tubercle  of  the  navicular  bone,  for 
the  line  of  the  joint  is  immediately  behind  this  process.  If  the  foot  is  grasped  and  forcibly 
extended,  a  rounded  prominence,  the  head  of  the  astragalus,  will  appear  on  the  inner  side  of 
the  dorsum  in  front  of  the  ankle-joint,  and  if  a  knife  is  carried  downward,  just  in  front  of  this 
prominence  and  behind  the  line  of  the  navicular  tubercle,  it  will  enter  the  astragalo-navicular 
joint.  The  calcaneo-cuboid  joint  is  situated  midway  between  the  external  malleolus  and  the 
prominent  end  of  the  fifth  metatarsal  bone.  The  plane  of  the  joint  is  in  the  same  line  as  that 
of  the  astragalo-navicular.  The  position  of  the  joint  between  the  fifth  metatarsal  bone  and  the 
cuboid  is  easily  found  by  the  projection  of  the  fifth  metatarsal  bone,  which  is  the  guide  to  it. 
The  direction  of  the  line  of  the  joint  is  very  oblique,  so  that,  if  continued  onward,  it  would 
pass  through  the  head  of  the  first  metatarsal  bone.  The  joint  between  the  fourth  metatarsal 
bone  and  the  cuboid  and  external  cuneiform  is  the  direct  continuation  inward  of  the  previous 
joint,  but  its  plane  is  less  oblique  ;  it  would  be  represented  by  a  line  drawn  from  the  outer  side 
of  the  articulation  to  the  middle  of  the  first  metatarsal  bone.  The  plane  of  the  joint  between 
the  third  metatarsal  bone  and  the  external  cuneiform  is  almost  transverse.  It  would  be  repre- 
sented by  a  line  drawn  from  the  outer  side  of  the  joint  to  the  base  of  the  first  metatarsal  bone. 
The  tarso-metatarsal  articulation  of  the  great  toe  corresponds  to  a  groove  which  can  be  felt  by 
making  firm  pressure  on  the  inner  side  of  the  foot  one  inch  in  front  of  the  tubercle  on  the 
navicular  bone  ;  and  the  joint  between  the  second  metatarsal  bone  and  the  middle  cuneiform  is 
to  be  found  on  the  dorsum  of  the  foot,  half  an  inch  behind  the  level  of  the  tarso-metatarsal 
joint  of  the  great  toe.  The  line  of  the  joints  between  the  metatarsal  bones  and  the  first 
phalanges  is  about  an  inch  behind  the  webs  of  the  corresponding  toes. 


THE  MUSCLES  AND  FASCLE.1 


THE  Muscles  are  connected  with  the  bones,  cartilages,  ligaments,  and  skin, 
either  directly  or  through  the  intervention  of  fibrous  structures  called  tendons 
or  aponeuroses.  Where  a  muscle  is  attached  to  bone  or  cartilage,  the  fibres  ter- 
minate in  blunt  extremities  upon  the  periosteum  or  perichondrium,  and  do  not 
come  into  direct  relation  with  the  osseous  or  cartilaginous  tissue.  Where  muscles 
are  connected  with  the  skin,  they  either  lie  as  a  flattened  layer  beneath  it,  or  are 
connected  with  its  areolar  tissue  by  larger  or  smaller  bundles  of  fibres,  as  in  the 
muscles  of  the  face. 

The  muscles  vary  extremely  in  their  form.  In  the  limbs,  they  are  of  consid- 
erable length,  especially  the  more  superficial  ones,  the  deep  ones  being  generally 
broad  ;  they  surround  the  bones  and  form  an  important  protection  to  the  various 
joints.  In  the  trunk  they  are  broad,  flattened,  and  expanded,  forming  the  parietes 
of  the  cavities  which  they  enclose ;  hence  the  reason  of  the  terms,  long,  broad, 
short,  etc.,  used  in  the  description   of  a  muscle. 

There  is  a  considerable  variation  in  the  arrangement  of  the  fibres  of  certain 
muscles  with  reference  to  the  tendons  to  which  they  are  attached.  In  some,  the 
fibres  are  parallel  and  run  directly  from  their  origin  to  their  insertion ;  these  are 
quadrilateral  muscles,  such  as  the  Thyro-hyoid.  A  modification  of  these  is  found 
in  the  fusiform  muscles,  in  which  the  fibres  are  not  quite  parallel,  but  slightly 
curved,  so  that  the  muscle  tapers  at  each  end ;  in  their  action,  however,  they 
resemble  the  quadrilateral  muscles.  Secondly,  in  other  muscles  the  fibres  are 
convergent ;  arising  by  a  broad  origin,  they  converge  to  a  narrow  or  pointed 
insertion.  This  arrangement  of  fibres  is  found  in  the  triangular  muscles — e.  g.  the 
Temporal.  In  some  muscles,  which  otherwise  would  belong  to  the  quadrilateral 
or  triangular  type,  the  origin  and  insertion  are  not  in  the  same  plane,  but  the  plane 
of  the  line  of  origin  intersects  that  of  their  insertion  ;  such  is  the  case  in  the 
Pectineus  muscle.  Thirdly,  in  some  muscles  the  fibres  are  oblique  and  converge, 
like  the  plumes  of  a  pen,  to  one  side  of  a  tendon,  which  runs  the  entire  length  of 
the  muscle.  Such  a  muscle  is  rhomboidal  or  penniform,  as  the  Peronei.  A 
modification  of  these  rhomboidal  muscles  is  found  in  those  cases  where  oblique  fibres 
converge  to  both  sides  of  a  central  tendon  which  runs  clown  the  middle  of  the 
muscle  ;  these  are  called  bipenniform,  and  an  example  is  afforded  in  the  Rectus 
femoris.  Finally,  we  have  muscles  in  which  the  fibres  are  arranged  in  curved 
bundles  in  one  or  more  planes,  as  in  the  Sphincter  muscles.  The  arrangement  of 
the  muscular  fibres  is  of  considerable  importance  in  respect  to  their  relative 
strength  and  range  of  movement.  Those  muscles  where  the  fibres  are  long  and 
few  in  number  have  great  range,  but  diminished  strength ;  where,  on  the  other 
hand,  the  fibres  are  short  and  more  numerous,  there  is  great  power,  but  lessened 
range. 

Muscles  differ  much  in  size :  the  Gastrocnemius  forms  the  chief  bulk  of  the 
back  of  the  leg,  and  the  fibres  of  the  Sartorius  are  nearly  two  feet  in  length,  whilst 

1  The  Muscles  and  Fascia?  are  described  conjointly,  in  order  that  the  student  may  consider  the 
arrangement  of  the  latter  in  his  dissection  of  the  former.  It  is  rare  for  the  student  of  anatomy  in  this 
country  to  have  the  opportunity  of  dissecting  the  fascia?  separately ;  and  it  is  for  this  reason,  as  well 
as  from  the  close  connection  that  exists  between  the  muscles  and  their  investing  sheaths,  that  they  are 
considered  together.  Some  general  observations  are  first  made  on  the  anatomy  of  the  muscles  and 
fascia?,  the  special  description  being  given  in  connection  with  the  different  regions. 

295 


296  THE   MUSCLES   AND    FASCIA. 

the  Stapedius,  a  small  muscle  of  the  internal  ear,  weighs  about  a  grain,  and  its- 
fibres  are  not  more  than  two  lines  in  length. 

The  names  applied  to  the  various  muscles  have  been  derived— 1,  from  their 
situation,  as  the  Tibialis,  Radialis,  Ulnaris,  Peroneus ;  2,  from  their  direction,  as 
the  Rectus  abdominis,  Obliqui  capitis,  Transversalis ;  3,  from  their  uses,  as  Flexors, 
Extensors,  Abductors,  etc. ;  4,  from  their  shape,  as  the  Deltoid,  Trapezius,  Rhom- 
boideus;  5,  from  the  number  of  their  divisions,  as  the  Biceps,  the  Triceps;  6, 
from  their'  points  of  attachment,  as  the  Sterno-cleido-mastoid,  Sterno-hyoid, 
Sterno-thyroid.  .  . 

In  the  description  of  a  muscle  the  term  origin  is  meant  to  imply  its  more  nxea 
or  central  attachment,  and  the  term  insertion,  the  movable  point  to  which  the 
force  of  the  muscle  is  directed ;  but  the  origin  is  absolutely  fixed  in  only  a  very 
small  number  of  muscles,  such  as  those  of  the  face,  which  are  attached  by  one 
extremity  to  the  bone  and  by  the  other  to  the  movable  integument;  in  the  greater 
number  the  muscle  can  be  made  to  act  from  either  extremity. 

In  the  dissection  of  the  muscles  the  student  should  pay  especial  attention  to 
the  exact  origin,  insertion,  and  actions  of  each,  and  its  more  important  relations 
with  surrounding  parts.  An  accurate  knowledge  of  the  points  of  attachment  of 
the  muscles  is  of  great  importance  in  the  determination  of  their  action.  By  a 
knowledge  of  the  action  of  the  muscles  the  surgeon  is  able  to  explain  the  causes 
of  displacement  in  various  forms  of  fracture  and  the  causes  which  produce 
distortion  in  various  deformities,  and,  consequently,  to  adopt  appropriate  treat- 
ment in  each  case.  The  relations,  also,  of  some  of  the  muscles,  especially  those  in 
immediate  apposition  with  the  larger  blood-vessels,  and  the  surface-markings  they 
produce,  should  be  especially  remembered,  as  they  form  useful  guides  in  the 
application  of  a  ligature  to  those  vessels.  ' 

Tendons  are  white,  glistening,  fibrous  cords,  varying  in  length  and  thickness, 
sometimes  round,  sometimes  flattened,  of  considerable  strength,  and  devoid  of 
elasticity.  They  consist  almost  entirely  of  white  fibrous  tissue,  the  fibrik  of 
which  have  an  undulating  course  parallel  with  each  other  and  are  firmly  united 
together.  They  are  very  sparingly  supplied  with  blood-vessels,  the  smaller 
tendons  presenting  in  their  interior  not  a  trace  of  them.  Nerves  also  are  not 
present  in  the  smaller  tendons,  but  the  larger  ones,  as  the  tendo  Achillis,  receive 
nerves  which  accompany  the  nutrient  vessels.  The  tendons  consist  principally  of 
a  substance  which  yields  gelatin. 

Aponeuroses  are  flattened  or  ribbon-shaped  tendons,  of  a  pearly-white  color, 
iridescent,  glistening,  and  similar  in  structure  to  the  tendons.  They  are  destitute 
of  nerves,  and  the  thicker  ones  only  sparingly  supplied  with  blood-vessels. 

The  tendons  and  aponeuroses  are  connected,  on  the  one  hand,  with  the  muscles, 
and,  on  the  other  hand,  with  the  movable  structures,  as  the  bones,  cartilages, 
ligaments,  fibrous  membranes  (for  instance,  the  sclerotic).  Where  the  muscular 
fibres  are  in  a  direct  line  with  those  of  the  tendon  or  aponeurosis,  the  two 
are  directly  continuous,  the  muscular  fibre  being  distinguishable  from  that 
of  the  tendon  only  by  its  striation.  But  where  the  muscular  fibre  joins  the 
tendon  or  aponeurosis  at  an  oblique  angle  the  former  terminates,  according 
to  Kolliker,  in  rounded  extremities,  which  are  received  into  corresponding  depres- 
sions on  the  surface  of  the  latter,  the  connective  tissue  between  the  fibres 
beina  continuous  with  that  of  the  tendon.  The  latter  mode  of  attachment 
occurs  in  all  the  penniform  and  bipenniform  muscles,  and  in  those  muscles 
the  tendons  of  which  commence  in  a  membranous  form,  as  the  Gastrocnemius 

and  Soleus.  .  „ 

The  fascise  {fascia,  a  bandage)  are  fibro-areolar  or  aponeurotic  laminae  ot 
variable  thickness  and  strength,  found  in  all  regions  of  the  body,  investing  the 
softer  and  more  delicate  organs.  The  fasciae  have  been  subdivided,  from  the 
situation  in  which  they  are  found,  into  two  groups,  superficial  and  deep. 

The  superficial  fascia  is  found  immediately  beneath  the  integument  over  almost 
the  entire  surface  of  the  body.     It  connects  the  skin  with  the  deep  or  aponeurotic 


MUSCLES   AND    FASCJjE    OF    THE    CRANIUM  AND    FACE.     297 

fascia,  and  consists  of  fibro-areolar  tissue,  containing  in  its  meshes  pellicles  of  fat 
in  varying  quantity.  In  the  eyelids  and  scrotum,  where  adipose  tissue  is  rarely 
deposited,  this  tissue  is  very  liable  to  serous  infiltration.  The  superficial  fascia 
varies  in  thickness  in  different  parts  of  the  body:  in  the  groin  it  is  so  thick  as  to 
be  capable  of  being  subdivided  in  several  laminae.  Beneath  the  fatty  layer  of 
the  superficial  fascia,  which  is  immediately  subcutaneous,  there  is  generally  another 
layer  of*  the  same  structure,  comparatively  devoid  of  adipose  tissue,  in  which  the 
trunks  of  the  subcutaneous  vessels  and  nerves  are  found,  as  the  superficial  epigas- 
tric vessels  in  the  abdominal  region,  the  radial  and  ulnar  veins  in  the  forearm, 
the  saphenous  veins  in  the  leg  and  thigh,  and  the  superficial  lymphatic  glands; 
certain  cutaneous  muscles  also  are  situated  in  the  superficial  fascia,  as  the 
Platysma  myoides  in  the  neck,  and  the  Orbicularis  palpebrarum  around  the  eye- 
lids. This  fascia  is  most  distinct  at  the  lower  part  of  the  abdomen,  the  scrotum, 
perinaeum,  and  extremities ;  is  very  thin  in  those  regions  where  muscular  fibres 
are  inserted  into  the  integument,  as  on  the  side  of  the  neck,  the  face,  and  around 
the  margin  of  the  anus.  It  is  very  dense  in  the  scalp,  in  the  palms  of  the  hands 
and  soles  of  the  feet,  forming  a  fibro-fatty  layer  which  binds  the  integument 
firmly  to  the  subjacent  structure. 

The  superficial  fascia  connects  the  skin  to  the  subjacent  parts,  facilitates  the 
movement  of  the  skin,  serves  as  a  soft  medium  for  the  passage  of  vessels  and  nerves 
to  the  integument,  and  retains  the  warmth  of  the  body,  since  the  fat  contained  in 
its  areolae  is  a  bad  conductor  of  heat. 

The  deep  fascia  is  a  dense,  inelastic,  unyielding  fibrous  membrane,  forming 
sheaths  for  the  muscles  and  affording  them  broad  surfaces  for  attachment.  It 
consists  of  shining  tendinous  fibres,  placed  parallel  with  one  another,  and  connected 
together  by  other  fibres  disposed  in  a  rectilinear  manner.  It  is  usually  exposed  on 
the  removal  of  the  superficial  fascia,  forming  a  strong  investment,  which  not  only 
binds  down  collectively  the  muscles  in  each  region,  but  gives  a  separate  sheath  to 
each,  as  well  as  to  the  vessels  and  nerves.  The  fasciae  are  thick  in  unprotected 
situations,  as  on  the  outer  side  of  a  limb,  and  thinner  on  the  inner  side.  The  deep 
fasciae  assist  the  muscles  in  their  action  by  the  degree  of  tension  and  pressure  they 
make  upon  their  surface ;  and  in  certain  situations  this  is  increased  and  regulated 
by  muscular  action ;  as,  for  instance,  by  the  Tensor  fasciae  femoris  and  Gluteus 
maximus  in  the  thigh,  by  the  Biceps  in  the  upper  and  lower  extremities,  and 
Palmaris  longus  in  the  hand.  In  the  limbs  the  fasciae  not  only  invest  the  entire 
limb,  but  give  oif  septa  which  separate  the  various  muscles,  and  are  attached 
beneath  to  the  periosteum :  these  prolongations  of  fasciae  are  usually  spoken  of  as 
intermuscular  septa. 

The  Muscles  and  Fasciae  may  be  arranged,  according  to  the  general  division 
of  the  body,  into  those  of  the  cranium,  face,  and  neck  ;  those  of  the  trunk  ;  those  of 
the  upper  extremity ;  and  those  of  the  lower  extremity. 

MUSCLES  AND  FASCIAE   OF   THE   CRANIUM  AND  FACE. 

The  muscles  of  the  Cranium  and  Face  consist  of  ten  groups,  arranged  according 
to  the  region  in  which  they  are  situated : 

1.  Cranial  Region.     ^  6.   Maxillary  Region.  " 

2.  Auricular  Region'.  7.   Mandibular  Region. 

3.  Palpebral  Region.^  8.   Intermaxillary  Region. 

4.  Orbital  Region.  9.   Temporo-mandibular  Region. 

5.  Nasal  Region.     -""  10.  Pterygomandibular  Region. 

The  muscles  contained  in  each  of  these  groups  are  the  following: 
1.    Cranial  Region.  2.  Auricular  Region. 

Occipito-frontalis.  Attrahens  auriculam. 

Attollens  auriculam. 
Retrahens  auriculam. 


298 


THE   MUSCLES  AND    FASCIA. 


3.  Palpebral  Region. 

Orbicularis  palpebrarum. 
Corrugator  supercilii. 
Tensor  tarsi. 

4.  Orbital  Region. 

Levator  palpebrse. 
Rectus  superior. 
Rectus  inferior. 
Rectus  internus. 
Rectus  externus. 
Obliquus  superior. 
Obliquus  inferior. 

5.  Nasal  Region. 

Pyramidalis  nasi. 

Levator  labii  superioris  alseque  nasi. 

Dilatator  naris  posterior. 

Dilatator  naris  anterior. 

Compressor  nasi. 

Compressor  narium  minor. 

Depressor  alae  nasi. 


6.  Maxillary  Region. 
Levator  labii  superioris. 
Levator  anguli  oris. 
Zygomaticus  major. 
Zygomaticus  minor. 

7.  Mandibular  Region. 

Levator  labii  inferioris. 
Depressor  labii  inferioris. 
Depressor  anguli  oris. 

8.  Intermaxillary  Region. 

Buccinator. 
Risorius. 
Orbicularis  oris. 

9.  Temporo-mancUbular  Region. 

Masseter. 
Temporal. 

10.  Pterygo-mandibular  Region. 

Pterygoideus  externus. 
Pterygoideus  internus. 


1.  Cranial  Region— Occipito-frontalis. 

Dissection  (Fig.  194). — The  head  being  shaved,  and  a  block  placed  beneath  the  back  of 
the  neck,  make  a  vertical  incision  through  the  skin  from  before  backward,  commencing 
at  the  root  of  the  nose  in  front,  and  terminating  behind  at  the  occipital  protuberance ;  make 


Dissection  of  scalp. 


2,  3,  of  auricular  region. 


4,  5,  6,  of  face. 


7,  8,  of  neck. 


Fig.  194.— Dissection  of  the  head,  face,  and  neck. 

a  second  incision  in  a  horizontal  direction  along  the  forehead  and  round  the  side  of  the 
head,  from  the  anterior  to  the  posterior  extremity  of  the  preceding.  Raise_  the  skin  in  front, 
from  the  subjacent  muscle,  from  below  upward ;  this  must  be  done  with  extreme  care, 
removing  the  integument  from  the  outer  surface  of  the  vessels  and  the  nerves  which  lie 
immediately  beneath  the  skin. 

The  Skin  of  the  Scalp. — This  is  thicker  than  in  any  other  part  of  the  body.    It 
is  intimately  adherent  to  the  superficial  fascia.     The  hair-follicles  are  very  closely 


CRANIAL    REGION. 


299 


set  together,  and  extend  throughout  the  whole  thickness  of  the  skin.     It  also  con- 
tains a  number  of  sebaceous  glands. 

The  superficial  fascia  in  the  cranial  region  is  a  firm,  dense,  fibro-fatty  layer 
intimately  adherent  to  the  integument,  and  to  the  Occipito-frontalis  and  its  tendi- 


CORRUQATOH    SUPERCILI 


DILATATOR    NARIS    ANTERIOR. 

PILATATOR    NARIS    POSTERIOR. 

COMPRESSOR    NARIUM     MINOR. 

DEPRESSOR    AL/E    NASI. 


Fig.  195—  Muscles  of  the  head,  face,  and  neck. 

nous  aponeurosis ;  it  is  continuous,  behind,  with  the  superficial  fascia  at  the  back 
part  of  the  neck ;  and,  laterally,  is  continued  over  the  temporal  fascia.  It  con- 
tains between  its  layers  the  superficial  vessels  and  nerves  and  much  granular  fat. 
1  he  Occipito-frontalis  (Fig.  195)  is  a  broad  musculo-fibrous  layer,  which  covers 
the  whole  of  one  side  of  the  vertex  of  the  skull,  from  the  occiput  to  the  eyebrow. 
it  consists  of  two  muscular  slips,  separated  by  an  intervening  tendinous  aponeurosis. ' 
The  occipital  portion  (sometimes  called  the  occipitalis  muscle)  is  thin,  .juadri- 
lateraHn  form,  and  about  an  inch  and  a  half  in  length  ;  it  arises  from  the  outer 
two-thirds  of  the  superior  curved  line  of  the  occipital  bone,  ami  from  the  mastoid 
portion  of  the  temporal.     Its  fibres  of  origin  are  tendinous,  but  they  soon  become 


300  THE   MUSCLES   AND    FASCIAE. 

muscular,  and  ascend  in  a  parallel  direction  to  terminate  in  a  tendinous  aponeu- 
rosis. The  frontal  portion  (sometimes  called  the  frontalis  muscle)  is  thin,  of  a 
quadrilateral  form,  and  intimately  adherent  to  the  superficial  fascia.  It  is  broader, 
its  fibres  are  longer,  and  their  structure  paler  than  the  occipital  portion.  Its  internal 
fibres  are  continuous  with  those  of  the  Pyramidalis  nasi.  Its  middle  fibres  become 
blended  with  the  Corrugator  supercilii  and  Orbicularis  palpebrarum ;  and  the 
outer  fibres  are  also  blended  with  the  latter  muscle  over  the  external  angular  pro- 
cess. According  to  Theile,  the  innermost  fibres  are  attached  to  the  nasal  bones, 
the  outer  to  the  external  angular  process  of  the  frontal  bone.  From  these 
attachments  the  fibres  are  directed  upward,  and  join  the  aponeurosis  below  the 
coronal  suture.  The  inner  margins  of  the  frontal  portions  of  the  two  muscles  are 
joined  together  for  some  distance  above  the  root  of  the  nose ;  but  between  the 
occipital  portions  there  is  a  considerable,  though  variable,  interval,  which  is  occupied 
by  the  aponeurosis. 

The  aponeurosis  covers  the  upper  part  of  the  vertex  of  the  skull,  being 
continuous  across  the  middle  line  with  the  aponeurosis  of  the  opposite  muscle. 
Behind,  it  is  attached,  in  the  interval  between  the  occipital  origins,  to  the  occipital 
protuberance  and  highest  curved  lines  of  the  occipital  bone;  in  front,  it  forms  a 
short  and  narrow  prolongation  between  the  frontal  portions ;  and  on  each  side  it 
has  connected  with  it  the  Attollens  and  Attrahens  auriculam  muscles ;  in  this 
situation  it  loses  its  aponeurotic  character,  and  is  continued  over  the  temporal 
fascia  to  the  zygoma  as  a  layer  of  laminated  areolar  tissue.  This  aponeurosis 
is  closely  connected  to  the  integument  by  the  firm,  dense,  fibro-fatty  layer 
which  forms  the  superficial  fascia ;  it  is  connected  with  the  pericranium  by 
loose  cellular  tissue,  which  allows  of  a  considerable  degree  of  movement  of  the 
integument. 

Nerves. — The  frontal  portion  of  the  Occipito-frontalis  is  supplied  by  the 
facial  nerve ;  its  occipital  portion  by  the  posterior  auricular  branch  of  the  facial. 

Actions. — The  frontal  portion  of  the  muscle  raises  the  eyebrows  and  the  skin 
over  the  root  of  the  nose,  and  at  the  same  time  draws  the  scalp  forward,  throwing 
the  integument  of  the  forehead  into  transverse  wrinkles.  The  posterior  portion 
draws  the  scalp  backward.  By  bringing  alternately  into  action  the  frontal  and 
occipital  portions  the  entire  scalp  may  be  moved  forward  and  backward.  In  the 
ordinary  action  of  the  muscles,  the  eyebrows  are  elevated,  and  at  the  same  time 
the  aponeurosis  is  fixed  by  the  posterior  portion,  thus  giving  to  the  face  the 
expression  of  surprise :  if  the  action  is  more  exaggerated,  the  eyebrows  are  still 
further  raised,  and  the  skin  of  the  forehead  thrown  into  transverse  wrinkles,  as  in 
the  expression  of  fright  or  horror. 

2.  Auricular  Region  (Fig.  195). 

Attrahens  auriculam.  Attollens  auriculam. 

Retrahens  auriculam. 

These  three  small  muscles  are  placed  immediately  beneath  the  skin  around 

the  external  ear.     In  man,  in  whom  the  external  ear  is  almost  immovable,  they 

are  rudimentary.     They  are  the   analogues  of  large   and   important  muscles   in 

some  of  the  mammalia. 

Dissection. — This  requires  considerable  care,  and  should  be  performed  in  the  following 
manner :  To  expose  the  Attollens  auriculam,  draw  the  pinna,  or  broad  part  of  the  ear,  downward, 
when  a  tense  band  will  be  felt  beneath  the  skin,  passing  from  the  side  of  the  head  to  the 
upper  part  of  the  concha ;  by  dividing  the  skin  over  this  band  in  a  direction  from  below 
upward,  and  then  reflecting  it  on  each  side,  the  muscle  is  exposed.  To  bring  into  view  the 
Attrahens  auriculam,  draw  the  helix  backward  by  means  of  a  hook,  when  the  muscle  will  be 
made  tense,  and  may  be  exposed  in  a  similar  manner  to  the  preceding.  To  expose  the  Retra- 
hens auriculam,  draw  the  pinna  forward,  when  the  muscle,  being  made  tense,  may  be  felt  beneath 
the  skin  at  its  insertion  into  the  back  part  of  the  concha,  and  may  be  exposed  in  the  same 
manner  as  the  other  muscles. 

The  Attrahens  auriculam  (Auricularis  anterior),  the  smallest  of  the  three,  is 
thin,  fan-shaped,  and  its  fibres  pale  and  indistinct:  they  arise  from  the  lateral 


PALPEBRAL    REGION.  301 

edge  of  the  aponeurosis  of  the  Occipito-frontalis,  and  converge  to  be  inserted 
into  a  projection  on  the  front  of  the  helix. 

Relations. — Superficially,  with  the  skin  ;  deeply,  with  the  areolar  tissue  derived 
from  the  aponeurosis  of  the  Occipito-frontalis,  beneath  which  are  the  temporal 
artery  and  vein  and  the  temporal  fascia. 

The  Attollens  auriculam  (Aurieularis  superior),  the  largest  of  the  three,  is 
thin  and  fan-shaped  :  its  fibres  arise  from  the  aponeurosis  of  the  Occipito-frontalis 
and  converge  to  be  inserted  by  a  thin,  flattened  tendon  into  the  upper  part  of  the 
cranial  surface  of  the  pinna. 

Relations. — Superficially,  with  the  integument;  deeply,  with  the  areolar  tissue 
derived  from  the  aponeurosis  of  the  Occipito-frontalis,  beneath  which  is  the  tem- 
poral fascia. 

The  Retrahens  auriculam  (Auricularis  posterior)  consists  of  two  or  three  fleshy 
fasciculi,  which  arise  from  the  mastoid  portion  of  the  temporal  bone  by  short 
aponeurotic  fibres.  They  are  inserted  into  the  lower  part  of  the  cranial  surface 
of  the  concha. 

Relations. — Superficially,  with  the  integument ;  deeply,  with  the  mastoid  portion 
of  the  temporal  bone  and  the  posterior  auricular  artery  and  nerve. 

Nerves. — The  Attrahens  and  Attollens  auriculam  are  supplied  by  the  temporal 
branch  of  the  facial ;  the  Retrahens  auriculam  is  supplied  by  the  posterior  auricu- 
lar branch  of  the  same  nerve. 

Actions. — In  man,  these  muscles  possess  very  little  action :  the  Attrahens  auric- 
ulam draws  the  ear  forward  and  upward;  the  Attollens  auriculam  slightly  raises 
it;  and  the  Retrahens  auriculam  draws  it  backward. 

3.  Palpebral  Region  (Fig.  195). 

Orbicularis  palpebrarum.  Levator  palpebrse. 

Corrugator  supercilii.  Tensor  tarsi. 

Dissection  (Fig.  194). — In  order  to  expose  the  muscles  of  the  face,  continue  the  longi- 
tudinal incision  made  in  the  dissection  of  the  Occipito-frontalis  down  the  median  line  of  the 
face  to  the  tip  of  the  nose,  and  from  this  point  onward  to  the  upper  lip ;  and  carry  another 
incision  along  the  margin  of  the  lip  to  the  angle  of  the  mouth,  and  transversely  across  the  face 
to  the  angle  of  the  jaw.  Then  make  an  incision  in  front  of  the  external  ear,  from  the  angle  of 
the  jaw  upward,  to  join  the  transverse  incision  made  in  exposing  the  Occipito-frontalis. 
These  incisions  include  a  square-shaped  flap,  which  should  be  removed  in  the  direction  marked 
in  the  figure,  with  care,  as  the  muscles  at  some  points  are  intimately  adherent  to  the 
integument. 

The  Orbicularis  palpebrarum  is  a  sphincter  muscle,  which  surrounds  the  cir- 
cumference of  the  orbit  and  eyelids.  It  arises  from  the  internal  angular  process 
of  the  frontal  bone,  from  the  nasal  process  of  the  superior  maxillary  bone  in  front 
of  the  lachrymal  groove  for  the  nasal  duct,  and  from  the  anterior  surface  and 
borders  of  a  short  tendon,  the  tendo  oculi,  or  internal  tarsal  ligament,  placed  at  the 
inner  angle  of  the  orbit.  From  this  origin  the  fibres  are  directed  outward,  forming 
a  broad,  thin,  and  flat  layer,  which  covers  the  eyelids,  surrounds  the  circumference 
of  the  orbit,  and  spreads  out  over  the  temple  and  downward  on  the  cheek.  The 
palpebral  portion  (ciliaris)  of  the  Orbicularis  is  thin  and  pale;  it  arises  from  the 
bifurcation  of  the  tendo  palpebrarum,  and  forms  a  series  of  concentric  curves,  which 
are  on  the  outer  side  of  the  eyelids  inserted  into  the  external  tarsal  ligament.  The 
orbital  portion  (orbicularis  latus)  is  thicker  and  of  a  reddish  color:  its  fibres  are 
well  developed,  and  form  complete  ellipses.  The  upper  fibres  of  this  portion  blend 
with  the  Occipito-frontalis  and  Corrugator  supercilii. 

Relations. — By  its  superficial  surface,  with  the  integument.  By  its  deep  surface, 
above,  with  the  Occipito-frontalis  and  Corrugator  supercilii,  with  which  it  is  inti- 
mately blended,  and  with  the  supra-orbital  vessels  and  nerve ;  below,  it  covers  the 
lachrymal  sac,  and  the  origin  of  the  Levator  labii  superioris  alseque  nasi,  the  Leva- 
tor labii  superioris,  and  the  Zygomaticus  minor  muscles.  Internally,  it  is  occa- 
sionally blended  with  the  Pyramidalis  nasi.     Externally,  it  lies  on  the  temporal 


302 


THE   MUSCLES   AKD    FASCIJE. 


HORNER'S    MUSCLE. 


ORBICULARIS 
PALPEBRARUM. 


fascia.      On  the  eyelids  it  is  separated  from  the  conjunctiva  by  the  Levator  palpe- 
bral the  tarsal  ligaments,  the  tarsal  plates,  and  the  Meibomian  glands. 

The  tendo  oculi  (internal  tarsal  ligament)  is  a  short  tendon,  about  two  lines  in 
length  and  one  in  breadth,  attached  to  the  nasal  process  of  the  superior  maxillary 
bone  in  front  of  the  lachrymal  groove.  Crossing  the  lachrymal  sac,  it  divides  into 
two  parts,  each  division  being  attached  to  the  inner  extremity  of  the  corresponding 
tarsal  plate.  As  the  tendon  crosses  the  lachrymal  sac.  a  strong  aponeurotic  lamina  is 
o-iven  off  from  the  posterior  surface,  which  expands  over  the  sac,  and  is  attached  to  the 
ridge  on  the  lachrymal  bone.  This  is  the  reflected  aponeurosis  of  the  tendo  oculi. 
The  external  tarsal  ligament  is  a  much  weaker  structure  than  the  tendo  oculi. 
It  is  attached  to  the  margin  of  the  frontal  process  of  the  malar  bone,  and  passes 
inward  to  the  outer  commissure  of  the  eyelids  :  it  connects  together  the  outer 
extremities  of  the  two  tarsal  cartilages. 

Use  of  Tendo  oculi. — Besides  giving  attachment  to  part  of  the  Orbicularis  palpe- 
brarum and  to  the  tarsal  plates,  it  serves  to  suck  the  tears  into  the  lachrymal  sac. 
by  its  attachment  to  the  sac.  Thus,  each  time  the  eyelids  are  closed,  the  tendo 
oculi  becomes  tightened,  through  the  action  of  the  Orbicularis,  and  draws  the  wall 
of  the  lachrymal  sac  outward  and  forward,  so  that  a  vacuum  is  made  in  the  sac,  and 
the  tears  are  sucked  along  the  lachrymal  canals  into  it. 

The  Corrugator  supercilii  is  a  small,  narrow,  pyramidal  muscle,  placed  at  the 
inner  extremity  of  the  eyebrow,   beneath   the  Occipito-frontalis  and  Orbicularis 

palpebrarum  muscles.  It  arises  from 
the  inner  extremity  of  the  supercil- 
iary ridge,  from  whence  its  fibres 
pass  upward  and  outward,  and,  pass- 
ing between  the  palpebral  and  orbital 
portions  of  the  Orbicularis  palpebra- 
rum, are  inserted  into  the  deep  surface 
of  the  skin,  opposite  the  middle  of 
the  orbital  arch. 

Relations. — By  its  anterior  sur- 
face with  the  Occipito-frontalis  and 
Orbicularis  palpebrarum  muscles : 
by  its  posterior  surface,  with  the 
frontal  bone  and  supratrochlear 
nerve. 

The  Levator  palpebral  will  be 
described  with  the  muscles  of  the 
orbital  region. 

The  Tensor  tarsi  (Horner's 
muscle)  (Fig.  196)  is  a  small  thin 
muscle  about  three  lines  in  breadth 
and  six  in  length,  situated  at  the 
inner  side  of  the  orbit,  behind  the 
tendo  oculi.  It  arises  from  the  crest 
and  adjacent  part  of  the  orbital  sur- 
face of  the  lachrymal  bone,  and. 
passing  across  the  lachrymal  sac,  divides  into  two  slips,  which  cover  the  lachrymal 
canals  and  are  inserted  into  the  tarsal  plates  internal  to  the  puncta  lachrymalia. 
Its  fibres  appear  to  be  continuous  with  those  of  the  palpebral  portion  of  the 
Orbicularis  palpebrarum  ;  it  is  occasionally  very  indistinct. 

Nerves. — The  Orbicularis  palpebrarum.  Corrugator  supercilii,  and  Tensor  tarsi 
are  supplied  by  the  facial  nerve.  Recent  investigations  tend  to  show  that  the 
Orbieukms  palpebrarum,  Corrugator  supercilii.  and  frontal  part  of  the  Occipito- 
frontalis  are  in  reality  supplied  by  fibres  of  the  third  nerve,  which  descend  through 
the  pons  varolii  to  join  the  facial  nerve. 

Actions. — The  Orbicularis  palpebrarum  is  the  sphincter  muscle  of  the  eyelids 


PUNCTA 

LACH  RY- 

MALI  A. 


LAB. 

.  AL/E- 
:    NASI. 


Fig.  196.— Horner's  muscle.    (From  a  preparation  in  the 
Museum  of  the  Royal  College  of  Surgeons  of  England. .1 


THE    ORBITAL    REGION. 


303 


The  palpebral  portion  acts  involuntarily,  closing  the  lids  gently,  as  in  sleep  or  in 
blinking;  the  orbicular  portion  is  subject  to  the  will.  When  the  entire  muscle  is 
brought  into  action,  the  skin  of  the  forehead,  temple,  and  cheek  is  drawn  inward 
toward  the  inner  angle  of  the  orbit,  and  the  eyelids  are  firmly  closed  as  in  photophobia. 
When  the  skin  of  the  forehead,  temple,  and  cheek  is  thus  drawn  inward  by  the 
action  of  the  muscle  it  is  thrown  into  folds,  especially  radiating  from  the  outer 
angle  of  the  eyelids,  which  give  rise  in  old  age  to  the  so-called  "  crow's  feet."  The 
Levator  palpebrse  is  the  direct  antagonist  of  this  muscle  ;  it  raises  the  upper  eyelid 
and  exposes  the  globe.  The  Corrugator  supercilii  draws  the  eyebrow  downward 
and  inward,  producing  the  vertical  wrinkles  of  the  forehead.  It  is  the  "  frowning  " 
muscle,  and  may  be  regarded  as  the  principal  agent  in  the  expression  of  suffering. 
The  Tensor  tarsi  draws  the  eyelids  and  the  extremities  of  the  lachrymal  canals 
inward  and  compresses  them  against  the  surface  of  the  globe  of*  the  eye ;  thus 
placing  them  in  the  most  favorable  situation  for  receiving  the  tears.  It  serves, 
also,  to  compress  the  lachrymal  sac. 

4.  Orbital  Region  (Fig.  197). 

Levator  palpebrge  superioris.  Rectus  interims. 

Rectus  superior.  Rectus  externus. 

Rectus  inferior.  Obliquus  oculi  superior. 

Obliquus  oculi  inferior. 

Dissection. — To  open  the  cavity  of  the  orbit,  remove  the  skull-cap  and  brain ;  then  saw 
through  the  frontal  bone  at  the  inner  extremity  of  the  supraorbital  ridge,  and   externally  at  its 


Fig.  197.— Muscles  of  the  right  orbit. 

junction  with  the  malar.  Break  in  pieces  the  thin  roof  of  the  orbit  by  a  few  slight  blows 
of  the  hammer,  and  take  it  away;  drive  forward  the  superciliary  portion  of  the  frontal  bone  by 
a  smart  stroke,  but  do  not  remove  it,  as  that  would  destroy  the  pulley  of  the  Obliquus 
superior.  When  the  fragments  are  cleared  away,  the  periosteum  of  the  orbit  will  be  exposed ; 
this  being  removed,  together  with  the  fat  which  fills  the  cavity  of  the  orbit,  the  several  muscles 
of  this  region  can  be  examined.  The  dissection  will  be  facilitated  by  distending  the  globe 
of  the  eye.  In  order  to  effect  this,  puncture  the  optic  nerve  near  the  eyeball  with  a  curved 
needle,  and  push  the  needle  onward  into  the  globe ;  insert  the  point  of  a  blowpipe  through 
this  aperture,  and  force  a  little  air  into  the  cavity  of  the  eyeball ;  then  apply  a  ligature  round 
the  nerve  so  as  to  prevent  the  air  escaping.  The  globe  being  now  drawn  forward,  the  muscles 
will  be  put  upon  the  stretch. 

The  Levator  palpebrae  superioris  is  thin,  flat,  and  triangular  in  shape.  It 
arises  from  the  under  surface  of  the  lesser  Aving  of  the  sphenoid,  above  and  in 
front  of  the  optic  foramen,  from  which  it  is  separated  by  the  origin  of  the  Superior 
rectus.     At  its  origin   it  is  narrow  and  tendinous,  but  soon  becomes  broad  and 


304 


THE   MUSCLES   AND    FASCIA. 


fleshy,  and  finally  terminates  in  a  wide  aponeurosis,  which  is  inserted  into  the 
upper  margin  of  the  superior  tarsal  plate.  From  this  aponeurosis  a  thin  expan- 
sion is  continued  onward,  passing  between  the  fibres  of  the  Orbicularis  to  be 
inserted  into  the  skin  of  the  lid,  and  some  deeper  fibres  blend  with  an  expansion 
from  the  sheath  of  the  Superior  rectus  muscle,  and  are  with  it  prolonged  into  the 
conjunctiva. 

Relations. — By  its  upper  surface,  with  the  frontal  nerve  and  supraorbital 
artery,  the  periosteum  of  the  orbit  and  lachrymal  gland ;  and,  in  the  lid,  with  the 
inner  surface  of  the  tarsal  ligament ;  by  its  under  surface,  with  the  Superior 
rectus,  and,  in  the  lid,  with  the  conjunctiva.  A  small  branch  of  the  third  nerve 
enters  its  under  surface. 

The  Superior  rectus,  the  thinnest  and  narrowest  of  the  four  Recti,  arises 
from  the  upper  margin  of  the  optic  foramen  beneath  the  Levator  palpebnB,  and 
from  the  fibrous  sheath  of  the  optic  nerve ;  and  is  inserted  by  a  tendinous  ex- 
pansion into  the  sclerotic  coat,  about  three  or  four  lines  from  the  margin  of 
the  cornea. 

Relations. — By  its  upper  surface,  with  the  Levator  palpebrae  ;  by  its  under  sur- 
face, with  the  optic  nerve,  the  ophthalmic  artery,  the  nasal  nerve,  and  the  branch 
of  the  third  nerve  which  supplies  it ;  and,  in  front,  with  the  tendon  of  the  Superior 
oblique  and  the  globe  of  the  eye. 

The  Inferior  and  Internal  Recti  arise  by  a  common  tendon  (the  ligament  of 
Zinn),1  which  is  attached  round  the  circumference  of  the  optic  foramen,  except  at 
its  upper  and  outer  part.  The  External  rectus  has  two  heads :  the  upper  one 
arises  from  the  outer  margin  of  the  optic  foramen  immediately  beneath  the  Superior 
rectus ;  the  lower  head,  partly  from  the  ligament  of  Zinn  and  partly  from  a  small 

pointed  process  of  bone  on  the  lower  margin  of 
the  sphenoidal  fissure.  Each  muscle  passes 
forward  in  the  position  implied  by  its  name,  to 
be  inserted  by  a  tendinous  expansion  (the 
tunica  albuginea)  into  the  sclerotic  coat,  about 
three  or  four  lines  from  the  margin  of  the 
cornea.  Between  the  two  heajls— of  the  Ex- 
ternal rectus  is  a  narrow  interval,  through 
which  passes  the  third,  the  nasal  branch  of  the 
ophthalmic^  division  of  the  fifth  and  sixth 
nerves,  and  the  ophthalmic  vein.  Although 
nearly  all  of  these  muscles  present  a  common 
origin  and  are  inserted  in  a  similar  manner 
into  the  sclerotic^coat,  there  are  certain  differ- 
ences to  be  observed  in  them  as  regards  their  length  and  breadth.  The  Internal 
rectus  is  the  broadest,  the  External  is  the  longest,  and  the  Superior  is  the  thinnest 
and  narrowest. 

The  Superior  oblique  is  a  fusiform  muscle  placed  at  the  upper  and  inner  side  of 
the  orbit,  internal  to  the  Levator  palpebrse.  It  arises  about  a  line  above  the  inner 
margin  of  the  optic  foramen,  and,  passing  forward  to  the  inner  angle  of  the  orbit, 
terminates  in  a  rounded  tendon,  which  plays  in  a  ring  or  pulley  formed  by  cartil- 
aginous tissue  attached  to  a  depression  beneath  the  internal  angular  process  of  the 
frontal  bone,  the  contiguous  surfaces  of  the  tendon  and  ring  being  lined  by  a 
delicate  synovial  membrane  and  enclosed  in  a  thin  fibrous  investment.  The 
tendon  is  reflected  backward,  outward,  and  downward  beneath  the  Superior  rectus 
to  the  outer  part  of  the  globe  of  the  eye,  and  is  inserted  into  the  sclerotic  coat, 

1  The  ligament  of  Zinn  ought,  perhaps  more  appropriately,  to  be  termed  the  aponeurosis  or  tendon 
of  Zinn.  Mr.  C.  B.  Lockwood  has  described  a  somewhat  similar  structure  on  the  under  surface  of  the 
Superior  rectus  muscle,  which  is  attached  to  the  lesser  wing  of  the  sphenoid,  forming  the  upper  and 
outer  margin  of  the  optic  foramen.  This  superior  tendon  gives  origin  to  the  Superior  rectus,  the 
superior  head  of  the  External  rectus,  and  the  upper  part  of  the  Internal  rectus.  {Journal  of  Anatomy 
and  Physiology,  vol.  xx.  part  i.  p.  1.) 


Rectus  superior, 

Levator 
■palpebral  superior. 


Obliquus  superior 


Rectus  inferior. 


Fig.  198.— The  relative  position  and  attach 
ment  of  the  muscles  of  the  left  eyeball. 


rC 


THE    ORBITAL    REGION.  *X  305 

behind  the  equator  of  the  eyeball,  the  insertion  of  the  muscle  lying  between  the 
Superior  and  External  recti. 

Relations. — By  its  upper  surface,  with  the  periosteum  covering  the  roof  of  the 
orbit  and  the  fourth  nerve:  the  tendon,  where  it  lies  on  the  globe  of  the  eye,  is 
covered  by  the  Superior  rectus ;  by  its  under  surface,  with  the  nasal  nerve, 
ethmoidal  arteries,  and  the  upper  border  of  the  internal  rectus. 

The  Inferior  oblique  is  a  thin,  narrow  muscle  placed  near  the  anterior  margin 
of  the  orbit.  It  arises  from  a  depression  on  the  orbital  plate  of  the  superior 
maxillary  bone,  external  to  the  lachrymal  groove.  Passing  outward,  backward, 
and  upward  between  the  Inferior  rectus  and  the  floor  of  the  orbit,  and  then 
between  the  eyeball  and  the  External  rectus,  it  is  inserted  into  the  outer  part  of 
the  sclerotic  coat  between  the  Superior  and  External  recti,  near  to,  but  somewhat 
behind,  the  tendon  of  insertion  of  the  Superior  oblique. 

Relations. — By  its  ocular  surface,  with  the  globe  of  the  eye  and  with  the  Inferior 
rectus  ;  by  its  orbital  surface,  with  the  periosteum  covering  the  floor  of  the  orbit, 
and  with  the  External  rectus.  Its  borders  look  forward  and  backward ;  the 
posterior  one  receives  a  branch  of  the  third  nerve. 

Nerves. — The  Levator  palpebrse,  Inferior  oblique,  and  all  the  Recti  excepting 
the  External,  are  suppliecTtrylhe  thirdjoerve  pthe  Superior_oblique,  by  the  fourth  ; 
the  External  rectus,  by  the  sixth. 

Actions. — The  Levator  palpebrse  raises  the  upper  eyelid,  and  is  the  direct 
antagonist  of  the  Orbicularis  palpebrarum.  The  four  Recti  muscles  are  attached 
in  such  a  manner  to  the  globe  of  the  eye  that,  acting  singly,  they  will  turn  it 
either  upward,  downward,  inward,  or  outward,  as  expressed  by  their  names. 
The  movement  produced  by  the  Superior  or  Inferior  rectus  is  not  quite  a  simple 
one,  for,  inasmuch  as  they  pass  obliquely  outward  and  forward  to  the  eyeball,  the 
elevation  or  depression  of  the"  cornea  mu&t  be  accompanied  by-a  certain  deviation 
inward,  with  a  slight  amount  of  rotation,  which,  however,  is  corrected  by  the 
Oblique  muscles,  the  Inferior  oblique  correcting  the  deviation  inward  of  the 
Superior  rectus,  and  the  Superior  oblique  that  of  the  Inferior  rectus.  The  con- 
traction of  the  External  and  Internal  recti,  on  the  other  hand,  produces  a  purely 
horizontal  movement.  If  any  two  contiguous  recti  of  one  e}re  act  together,  they 
carry  the  globe  of  the  eye  in  the  diagonal  of  these  directions — viz.  upward  and 
inward,  upward  and  outward,  downward  and  inward,  or  downward  and  outward. 
The  movement  of  circumduction,  as  in  looking  round  a  room,  is  performed  by 
the  alternate  action  of  the  four  Recti.  The  Oblique  muscles  rotate  the  eyeball 
on  its  antero-posterior  axis,  this  kind  of  movement  being  required  for  the  correct 
viewing  of  an  object  when  the  head  is  moved  laterally,  as  from  shoulder  to 
shoulder,  in  order  that  the  picture  may  fall  in  all  respects  on  the  same  part  of  the 
retina  of  each  eye.1 

Fascise  of  the  Orbit. — The  connective  tissue  of  the  orbit  is  in  various  places  con- 
densed into  thin  membranous  layers,  which  may  be  conveniently  described  as  (1)  the 
orbital  fascia;  (2)  the  sheath  of  the  muscles;   and  (3)  the  covering  of  the  eyeball. 

(1)  The  orbital  fascia.  This  forms  the  periosteum  of  the  orbit.  It  is  loosely 
connected  to  the  bones,  from  which  it  can  be  readily  separated.  Behind,  it  is 
connected  /with  the  dura  mater  by  processes  which  pass  through  the  optic  foramen 
and  sphenoidal  fissure,  and  with  the  sheath  of  the  optic  nerve.  In  front  it  is 
connected  with  the  periosteum  at  the  margin  of  the  orbit,  and  sends  oif  a  process 
which  assists  in  forming  the  palpebral  fascia.  From  its  internal  surface  two 
processes  are  given  off — one  to  enclose  the  lachrymal  gland,  the  other  to  hold  the 
pulley  of  the  Superior  oblique  muscle  in  position. 

(2)  The  sheaths  of  the  muscles  give  off  expansions  to  the  margins  of  the  orbit 
which  limit  the  action  of  the  muscles. 

1  "  On  the  Oblique  Muscles  of  the  Eye  in  Man  and  Vertebrate  Animals,"  by  John  Struthers,  M.  D.r 
in  Anatomical  and  Physiological  Observations.  For  a  fuller  account  of  tbe  various  co-ordinate  actions 
of  the  muscles  of  a  single  eye  and  of  both  eyes  than  our  space  allows,  the  reader  may  be  referred  to 
Dr.  M.  Foster's  Text-book  of  Physiology. 

20  -  ± 


306  THE   MUSCLES    AND    FASCIAE. 

(3)  The  fascia  covering  the  eyeball — Tenon's  capsule — will  be  described  in 
the  sequel. 

Surgical  Anatomy. — The  position  and  exact  point  of  insertion  of  the  tendons  of  the 
Internal  and  External  recti  muscles  into  the  globe  should  be  carefully  examined  from  the  front  of 
the  eyeball,  as  the  surgeon  is  often  required  to  divide  the  one  or  the  other  muscle  for  the  cure 
of  strabismus.  In  convergent  strabismus,  which  is  the  more  common  form  of  the  disease,  the 
eye  is  turned  inward,  requiring  the  division  of  the  Internal  rectus.  In  the  divergent  form, 
which  is  more  rare,  the  eye  is  turned  outward,  the  External  rectus  being  especially  implicated. 
The  deformity  produced  in  either  case  is  to  be  remedied  by  division  of  one  or  the  other  muscle. 
The  operation  is  thus  performed  :  The  lids  are  to  be  well  separated  ;  the  eyeball  being  rotated 
outward  or  inward,  the  conjunctiva  should  be  raised  by  a  pair  of  forceps  and  divided  immediately 
beneath  the  lower  border  of  the  tendon  of  the  muscle  to  be  divided,  a  little  behind  its  insertion 
into  the  sclerotic ;  the  submucous  areolar  tissue  is  then  divided,  and  into  the  small  aperture 
thus  made  a  blunt  hook  is  passed  upward  between  the  muscle  and  the  globe,  and  the  tendon  of 
the  muscle  and  conjunctiva  covering  it  divided  by  a  pair  of  blunt-pointed  scissors.  Or  the 
tendon  may  be  divided  by  a  subconjunctival  incision,  one  blade  of  the  scissors  being  passed 
upward  between  the  tendon  and  the  conjunctiva,  and  the  other  between  the  tendon  and  the 
sclerotic.  The  student,  when  dissecting  these  muscles,  should  remove  on  one  side  of  the  subject 
the  conjunctiva  from  the  front  of  the  eye,  in  order  to  see  more  accurately  the  position  of  the 
tendons,  while  on  the  opposite  side  the  operation  may  be  performed. 

5.  Nasal  Region  (Fig.  195). 

Pyramidalis  nasi.  Dilatator  naris  anterior. 

Levator  labii  superioris  alaeque  nasi.  Compressor  nasi. 

Dilatator  naris  posterior.  Compressor  narium  minor. 

Depressor  alee  nasi. 

The  Pyramidalis  nasi  is  a  small  pyramidal  slip  placed  over  the  nasal  bone.  Its 
origin  is  by  tendinous  fibres  from  the  fascia  covering  the  lower  part  of  the  nasal 
bone  and  upper  part  of  the  cartilage,  where  it  blends  with  the  Compressor  nasi, 
and  it  is  inserted  into  the  skin  over  the  lower  part  of*  the  forehead  between  the 
two  eyebrows,  its  fibres  decussating  with  those  of  the  Occipito-frontalis. 

Relations. — By  its  upper  surface,  with  the  skin  ;  by  its  under  surface,  with  the 
frontal  and  nasal  bones. 

The  Levator  labii  superioris  alseque  nasi  is  a  thin  triangular  muscle  placed 
by  the  side  of  the  nose,  and  extending  between  the  inner  margin  of  the  orbit  and 
upper  lip.  It  arises  by  a  pointed  extremity  from  the  upper  part  of  the  nasal 
process  of  the  superior  maxillary  bone,  and,  passing  obliquely  downward  and 
outward,  divides  into  two  slips,  one  of  which  is  inserted  into  the  cartilage  of  the 
ala  of  the  nose ;  the  other  is  prolonged  into  the  upper  lip,  becoming  blended  with 
the  Orbicularis  oris  and  Levator  labii  superioris  proprius. 

Relations. — In  front,  with  the  integument,  and  with  a  small  part  of  the 
Orbicularis  palpebrarum  above. 

The  Dilatator  naris  posterior  is  a  small  muscle  which  is  placed  partly  beneath 
the  elevator  of  the  nose  and  lip.  It  arises  from  the  margin  of  the  nasal  notch  of 
the  superior  maxilla  and  from  the  sesamoid  cartilages,  and  is  inserted  into  the 
skin  near  the  margin  of   the  nostril. 

The  Dilatator  naris  anterior  is  a  thin  delicate  fasciculus  passing  from  the 
cartilage  of  the  ala  of  the  nose  to  the  integument  near  its  margin.  This  muscle  is 
situated  in  front  of  the  preceding. 

The  Compressor  nasi  is  a  small,  thin,  triangular  muscle  arising  by  its  apex 
from  the  superior  maxillary  bone,  above  and  a  little  external  to  the  incisive  fossa ; 
its  fibres  proceed  upward  and  inward,  expanding  into  a  thin  aponeurosis  which 
is  attached  to  the  fibro-cartilage  of  the  nose  and  is  continuous  on  the  bridge  of 
the  nose  with  that  of  the  muscle  of  the  opposite  side  and  with  the  aponeurosis  of 
the  Pyramidalis  nasi. 

The  Compressor  narium  minor  is  a  small  muscle  attached  by  one  end  to  the  alar 
cartilage,  and  by  the  other  to  the  integument  at  the  end  of  the  nose. 

The  Depressor  alae  nasi  is  a  short  radiated  muscle  arising  from  the  incisive 
fossa  of  the  superior  maxilla ;  its  fibres  ascend  to  be  inserted  into  the  septum  and 


THE   SUPERIOR    M AXILLARY  REGION.  307 

back  part  of  the  ala  of  the  nose.  This  muscle  lies  between  the  mucous  membrane 
and  muscular  structure  of  the  lip. 

Nerves. — All  the  muscles  of  this  group  are  supplied  by  the  facial  nerve. 

Actions. — The  Pyramidalis  nasi  draws  down  the  inner  angle  of  the  eyebrows 
and  produces  transverse  wrinkles  over  the  bridge  of  the  nose.  The  Levator  labii 
superioris  alaeque  nasi  draws  upward  the  upper  lip  and  ala  of  the  nose :  its  most 
important  action  is  upon  the  nose,  which  it  dilates  to  a  considerable  extent.  The 
action  of  this  muscle  produces  a  marked  influence  over  the  countenance,  and  it  is 
the  principal  agent  in  the  expression  of  contempt  aud  disdain.  The  two  Dilatatores 
nasi  enlarge  the  aperture  of  the  nose.  Their  action  in  ordinary  breathing  is  to 
resist  the  tendency  of  the  nostrils  to  close  from  atmospheric  pressure,  but  in 
difficult  breathing  they  may  be  noticed  to  be  in  violent  action,  as  well  as  in  some 
emotions,  as  anger.  The  Depressor  alse  nasi  is  a  direct  antagonist  of  the  other 
muscles  of  the  nose,  drawing  the  ala  of  the  nose  downward,  and  thereby  constrict- 
ing the  aperture  of  the  nares.  The  Compressor  nasi  depresses  the  cartilaginous 
part  of  the  nose  and  compresses  the  alse  together. 

6.  Superior  Maxillary  Region  (Fig.  195). 

Levator  labii  superioris.  Zygomaticus  major. 

Levator  anguli  oris.  Zygomaticus  minor. 

The  Levator  labii  superioris  (proprius)  is  a  thin  muscle  of  a  quadrilateral  form. 
It  arises  from  the  lower  margin  of  the  orbit  immediately  above  the  infraorbital 
foramen,  some  of  its  fibres  being  attached  to  the  superior  maxilla,  others  to  the 
malar  bone ;  its  fibres  converge  to  be  inserted  into  the  muscular  substance  of  the 
upper  lip. 

Relations. — By  its  superficial  surface  above,  with  the  lower  segment  of  the 
Orbicularis  palpebrarum ;  below,  it  is  subcutaneous.  By  its  deep  surface  it 
conceals  the  origin  of  the  Compressor  nasi  and  Levator  anguli  oris  muscles, 
and  the  infraorbital  vessels  and  nerve,  as  they  escape  from  the  infraorbital 
foramen. 

The  Levator  anguli  oris  arises  from  the  canine  fossa  immediately  below  the 
infraorbital  foramen  ;  its  fibres  incline  doAvnward  and  a  little  outward,  to  be 
inserted  into  the  angle  of  the  mouth,  intermingling  with  those  of  the  Zygomaticus 
major,  the  Depressor  anguli  oris,  and  the  Orbicularis. 

Relations. — By  its  superficial  surface,  with  the  Levator  labii  superioris  and 
the  infraorbital  vessels  and  nerves ;  by  its  deep  surface,  with  the  superior  maxilla, 
the  Buccinator,  and  the  mucous  membrane. 

The  Zygomaticus  major  is  a  slender  fasciculus  which  arises  from  the  malar 
bone,  in  front  of  the  zygomatic  suture,  and,  descending  obliquely  downward  and 
inward,  is  inserted  into  the  angle  of  the  mouth,  where  it  blends  with  the  fibres  of 
the  Levator  anguli  oris,  the  Orbicularis  oris,  and  the  Depressor  anguli  oris. 

Relations. — By  its  superficial  surface,  with  the  subcutaneous  adipose  tissue ; 
by  its  deep  surface,  with  the  Masseter  and  Buccinator  muscles  and  the  facial  artery 
and  vein. 

The  Zygomaticus  minor  arises  from  the  malar  bone  immediately  behind  the 
maxillary  suture,  and,  passing  downward  and  inward,  is  continuous  with  the 
Orbicularis  oris  at  the  outer  margin  of  the  Levator  labii  superioris.  It  lies  in 
front  of  the  preceding. 

Relations. — By  its  superficial  surface,  with  the  integument  and  the  Orbicularis 
palpebrarum  above ;  by  its  deep  surface,  with  the  Masseter,  Buccinator,  and 
Levator  anguli  oris,  and  the  facial  artery  and  vein. 

Nerves. — This  group  of  muscles  is  supplied  b,y  the  facial  nerve. 

Actions. — The  Levator  labii  superioris  is  the  proper  elevator  of  the  upper  lip, 
carrying  it  at  the  same  time  a  little  forward.  It  assists  in  forming  the  naso-labial 
ridge,  which  passes  from  the  side  of  the  nose  to  the  upper  lip  and  gives  to  the  face 
an  expression  of  sadness.     The  Levator  anguli  oris  raises  the  angle  of  the  mouth. 


308  THE   MUSCLES   AND    FASCIjE. 

and  assists  the  Levator  labii  superioris  in  producing  the  naso-labial  ridge.  The 
Zygoniaticus  major  draws  the  angle  of  the  mouth  backward  and  upward,  as  in 
laughing ;  whilst  the  Zygoniaticus  minor,  being  inserted  into  the  outer  part  of  the 
upper  lip  and  not  "into  the  angle  of  the  mouth,  draws  it  backward,  upward,  and 
outward,  and  thus  gives  to  the  face  an  expression  of  sadness. 

7.  Inferior  Maxillary  Region  (Fig.  195). 

Levator  labii  inferioris  (Levator  menti). 
Depressor  labii  inferioris  (Quadratus  menti). 
Depressor  anguli  oris  (Triangularis  menti). 

Dissection. — The  muscles  in  this  region  may  be  dissected  by  making  a  vertical  incision 
through  the  integument  from  the  margin  of  the  lower  lip  to  the  chin :  a  second  incision  should 
then  be  carried  along  the  margin  of  the  lower  jaw  as  far  as  the  angle,  and  the  integument  care- 
fully removed  in  the  direction  shown  in  Fig.  194. 

The  Levator  labii  inferioris  (Levator  menti)  is  to  be  dissected  by  everting  the 
lower  lip  and  raising  the  mucous  membrane.  It  is  a  small  conical  fasciculus  placed 
on  the  side  of  the  frsenum  of  the  lower  lip.  It  arises  from  the  incisive  fossa, 
external  to  the  symphysis  of  the  lower  jaw;  its  fibres  descend  to  be  inserted  into 
the  integument  of  the  chin. 

Relation. — On  its  inner  surface,  with  the  mucous  membrane ;  in  the  median 
line,  it  is  blended  with  the  muscle  of  the  opposite  side;  and  on  its  outer  side,  with 
the  Depressor  labii  inferioris. 

The  Depressor  labii  inferioris  (Quadratus  menti)  is  a  small  quadrilateral 
muscle.  It  arises  from  the  external  oblique  line  of  the  lower  jaw,  between  the 
symphysis  and  mental  foramen,  and  passes  obliquely  upward  and  inward,  to  be 
inserted  into  the  integument  of  the  lower  lip,  its  fibres  blending  with  the  Orbicularis 
oris  and  with  those  of  its  fellow  of  the  opposite  side.  It  is  continuous  with  the 
fibres  of  the  Platysma  at  its  origin.  This  muscle  contains  much  yellow  fat  inter- 
mingled with  its  fibres. 

Relations. — By  its  superficial  surface,  with  part  of  the  Depressor  anguli  oris 
and  with  the  integument,  to  which  it  is  closely  connected ;  by  its  deep  surface, 
with  the  mental  vessels  and  nerves,  the  mucous  membrane  of  the  lower  lip,  the 
labial  glands,   and  the  Levator  menti,    with  which  it  is  intimately  united. 

The  Depressor  anguli  oris  (Triangularis  menti)  is  triangular  in  shape,  arising, 
by  its  broad  base,  from  the  external  oblique  line  of  the  lower  jaw,  from  whence  its 
fibres  pass  upward,  to  be  inserted,  by  a  narrow  fasciculus,  into  the  angle  of  the 
mouth.  It  is  continuous  with  the  Platysma  at  its  origin  and  with  the  Orbicu- 
laris oris  and  Risorius  at  its  insertion,  and  some  of  its  fibres  are  directly  continuous 
with  those  of  the  Levator  anguli  oris. 

Relations. — By  its  superficial  surface,  with  the  integument ;  by  its  deep  surface, 
with  the  Depressor  labii  inferioris  and  Buccinator. 

Nerves. — This  group  of  muscles  is  supplied  by  the  facial  nerve. 

Actions. — The  Levator  labii  inferioris  raises  the  lower  lip  and  protrudes  it 
forward,  and  at  the  same  time  wrinkles  the  integument  of  the  chin,  expressing 
doubt  or  disdain.  The  Depressor  labii  inferioris  draws  the  lower  lip  directly 
downward  and  a  little  outward,  as  in  the  expression  of  irony.  The  Depressor 
anguli  oris  depresses  the  angle  of  the  mouth,  being  the  antagonist  to  the  Levator 
anguli  oris  and  Zygomaticus  major;  acting  with  these  muscles,  it  will  draw  the 
angle  of  the  mouth  directly  backward. 

8.  Intermaxillary  Region. 

Orbicularis  oris.  Buccinator.  Risorius. 

Dissection. — The  dissection  of  these  muscles  may  be  considerably  facilitated  by  filling  the 
cavity  of  the  mouth  with  tow,  so  as  to  distend  the  cheeks  and  lips ;  the  mouth  should  then  be 
closed  by  a  few  stitches  and  the  integument  carefully  removed  from  the  surface. 

The  Orbicularis  oris  (Fig.  195)  is  not  a  sphincter  muscle,  like  the  Orbicularis 


THE   INTERMAXILLARY  REGION.  «'J09 

palpebrarum,  but  consists  of  numerous  strata  of  muscular  fibres,  having  different 
directions,  which  surround  the  orifice  of  the  mouth.  These  fibres  are  partially 
derived  from  the  other  facial  muscles  which  are  inserted  into  the  lips,  and  are 
partly  fibres  proper  to  the  lips  themselves.  Of  the  former,  a  considerable  number 
are  derived  from  the  Buccinator  and  form  the  deeper  stratum  of  the  Orbicularis. 
Some  of  them — namely,  those  near  the  middle  of  the  muscle — decussate  at  the  angle  « 
of  the  mouth,  those  arising  from  the  upper  jaw  passing  to  the  lower  lip,  and  those 
from  the  lower  jaw  to  the  upper  lip.  Other  fibres  of  the  muscle,  situated  at  its 
upper  and  lower  part,  pass  across  the  lips  from  side  to 'side  without  decussation. 
Superficial  to  this  stratum  is  a  second,  formed  by  the  Levator  and  Depressor 
anguli  oris,  which  cross  each  other  at  the  angle  of  the  mouth,  those  from  the 
Depressor  passing  to  the  upper  lip,  and  those  from  the  Levator  to  the  lower  lip, 
along  which  they  run  to  be  inserted  into  the  skin  near  the  median  line.  In 
addition  to  these  there  are  fibres  from  the  other  muscles  inserted  into  the  lips — the 
Levator  labii  superioris,  the  Levator  labii  superioris  alseque  nasi,  the  Zygomatici, 
and  the  Depressor  labii  inferioris ;  these  intermingle  with  the  transverse  fibres 
above  described,  and  have  principally  an  oblique  direction.  The  proper  fibres  of 
the  lips  are  oblique,  and  pass  from  the  under  surface  of  the  skin  to  the  mucous 
membrane  through  the  thickness  of  the  lip.  And  in  addition  to  these  are  fibres 
by  which  the  muscle  is  connected  directly  with  the  maxillary  bones  and  the  sep- 
tum of  the  nose.  These  consist,  in  the  upper  lip,  of  four  bands,  two  of  which 
(Musculus  incisivus  superior)  arise  from  the  alveolar  border  of  the  superior 
maxilla,  opposite  the  lateral  incisor  tooth,  and,  arching  outward  on  each  side, 
are  continuous  at  the  angles  of  the  mouth  with  the  other  muscles  inserted  into 
this  part.  The  two  remaining  muscular  slips,  called  the  Naso-labialis,  connect 
the  upper  lip  to  the  back  of  the  septum  of  the  nose :  as  they  descend  from  the 
septum  an  interval  is  left  between  them.  It  is  this  interval  which  forms  the 
depression  seen  on  the  surface  of  the  skin  beneath  the  septum  of  the  nose.  The 
additional  fibres  for  the  lower  segment  {Musculus  incisivus  inferior)  arise  from 
the  inferior  maxilla,  externally  to  the  Levator  labii  inferioris,  and  arch  outward 
to  the  angles  of  the  mouth,  to  join  the  Buccinator  and  the  other  muscles  attached 
to  this  part. 

Eelations. — By  its  superficial  surface,  with  the  integument,  to  which  it  is 
closely  connected ;  by  its  deep  surface,  with  the  buccal  mucous  membrane,  the 
labial  glands,  and  coronary  vessels ;  by  its  outer  circumference  it  is  blended  with 
the  numerous  muscles  which  converge  to  the  mouth  from  various  parts  of  the  face. 
Its  inner  circumference  is  free,  and  covered  by  the  mucous  membrane. 

The  Buccinator  (Fig.  208)  is  a  broad,  thin  muscle,  quadrilateral  in  form, 
which  occupies  the  interval  between  the  jaws  at  the  side  of  the  face.  It  arises 
from  the  outer  surface  of  the  alveolar  processes  of  the  upper  and  lower  jaws, 
corresponding  to  the  three  molar  teeth,  and,  behind,  from  the  anterior  border  of 
the  pterygo-maxillary  ligament.  The  fibres  converge  toward  the  angle  of  the 
mouth,  where  the  central  fibres  intersect  each  other,  those  from  below  being 
continuous  with  the  upper  segment  of  the  Orbicularis  oris,  and  those  from  above 
with  the  inferior  segment ;  the  highest  and  lowest  fibres  continue  forward  uninter- 
ruptedly into  the  corresponding  segment  of  the  lip,  without  decussation. 

Relations. — By  its  superficial  surface,  behind,  with  a  large  mass  of  fat,  which 
separates  it  from  the  ramus  of  the  lower  jaw,  the  Masseter,  and  a  small  portion  of 
the  Temporal  muscle ;  anteriorly,  with  the  Zygomatici,  Risorius,  Levator  anguli 
oris,  Depressor  anguli  oris,  and  Stenson's  duct,  which  pierces  it  opposite  the 
second  molar  tooth  of  the  upper  jaw  ;  the  facial  artery  and  vein  cross  it  from  below 
upward ;  it  is  also  crossed  by  the  branches  of  the  facial  and  buccal  nerves ;  by 
its  internal  surface,  with  the  buccal  glands  and  mucous  membrane  of  the  mouth. 

The  pterygo-maxillary  ligament  separates  the  Buccinator  muscle  from  the 
Superior  constrictor  of  the  pharynx.  It  is  a  tendinous  band,  attached  by  one 
extremity  to  the  apex  of  the  internal  pterygoid  plate,  and  by  the  other  to  the 
posterior  extremity  of  the  internal  oblique  line  of  the  lower  jaw.    Its  inner  surface 


310  THE   MUSCLES   AND    FASCIAE. 

corresponds  to  the  cavity  of  the  mouth,  and  is  lined  by  mucous  membrane.  Its 
outer  surface  is  separated  from  the  ramus  of  the  jaw  by  a  quantity  of  adipose 
tissue.  Its  posterior  border  gives  attachment  to  the  Superior  constrictor  of  the 
pharynx ;  its  anterior  border,  to  the  fibres  of  the  Buccinator  (see  Fig.  208). 

The  Risorius  (Santorini)  (Fig.  195)  consists  of  a  narrow  bundle  of  fibres  which 
arises  in  the  fascia  over  the  Masseter  muscle,  and,  passing  horizontally  forward, 
is  inserted  into  the  skin  at  the  angle  of  the  mouth.  It  is  placed  superficial  to 
the  Platysma,  and  is  broadest  at  its  outer  extremity.  This  muscle  varies  much 
in  its  size  and  form. 

Nerves. — The  muscles  in  this  group  are  all  supplied  by  the  facial  nerve.  The 
buccal  branch  of  the  inferior  maxillary  nerve  pierces  the  Buccinator  muscle,  and 
by  some  anatomists  is  regarded  as  partly  supplying  this  muscle.  Probably  it 
merely  pierces  it  on  its  Avay  to  the  mucous  membrane  of  the  cheek. 

Actions. — The  Orbicularis  oris  in  its  ordinary  action  produces  the  direct 
closure  of  the  lips ;  by  its  deep  fibres,  assisted  by  the  oblique  ones,  it  closely 
applies  the  lips  to  the  alveolar  arch.  '  The  superficial  part,  consisting  principally 
of  the  decussating  fibres,  brings  the  lips  together  and  also  protrudes  them  for- 
ward. The  Buccinators  contract  and  compress  the  cheeks,  so  that,  during  the 
process  of  mastication,  the  food  is  kept  under  the  immediate  pressure  of  the  teeth. 
When  the  cheeks  have  been  previously  distended  with  air,  the  Buccinator  muscles 
expel  it  from  between  the  lips,  as  in  blowing  a  trumpet.  Hence  the  name 
(buccina,  a  trumpet).  The  Risorius  retracts  the  angles  of  the  mouth,  and  pro- 
duces the  unpleasant  expression  which  is  sometimes  seen  in  tetanus,  and  is  known 
as  "risus  sardonicus." 

9.  Temporo-mandibular  Region. 

Masseter.  Temporal. 

Masseteric  Fascia. — Covering  the  Masseter  muscle,  and  firmly  connected  with 
it,  is  a  strong  layer  of  fascia  derived  from  the  deep  cervical  fascia.  Above,  this 
fascia  is  attached  to  the  lower  border  of  the  zygoma,  and,  behind,  it  covers  the 
parotid  gland,  constituting  the  parotid  fascia. 

The  Masseter  is  exposed  by  the  removal  of  this  fascia  (Fig.  195) ;  it  is  a  short, 
thick  muscle,  somewhat  quadrilateral  in  form,  consisting  of  two  portions,  super- 
ficial and  deep.  The  superficial  portion,  the  larger,  arises  by  a  thick,  tendinous 
aponeurosis  from  the  malar  process  of  the  superior  maxilla,  and  from  the  anterior 
two-thirds  of  the  lower  border  of  the  zygomatic  arch :  its  fibres  pass  downward 
..and  backward,  to  be  inserted  into  the  angle  and  lower  half  of  the  outer  surface 
of  the  ramus  of  the  jaw.  The  deep  portion  is  much  smaller  and  more  muscular 
in  texture ;  it  arises  from  the  posterior  third  of  the  lower  border  and  the  whole  of 
the  inner  surface  of  the  zygomatic  arch ;  its  fibres  pass  downward  and  forward, 
to  be  inserted  into  the  upper  half  of  the  ramus  and  outer  surface  of  the  coronoid 
process  of  the  jaw.  The  deep  portion  of  the  muscle  is  partly  concealed,  in  front 
by  the  superficial  portion ;  behind,  it  is  covered  by  the  parotid  gland.  The  fibres 
of  the  two  portions  are  united  at  their  insertion. 

Relations. — By  its  superficial  surface,  with  the  Zygomatici,  the  parotid  gland 
and  Socia  parotidis,  and  Stenson's  duct ;  the  branches  of  the  facial  nerve  and  the 
transverse  facial  vessels,  which  cross  it ;  the  masseteric  fascia ;  the  Risorius, 
Santorini,  Platysma  myoides,  and  the  integument ;  by  its  deep  surface,  with  the 
Temporal  muscle  at  its  insertion,  the  ramus  of  the  jaw,  the  Buccinator  and  the 
long  buccal  nerve,  from  which  it  is  separated  by  a  mass  of  fat.  The  masseteric 
nerve  and  artery  enter  in  on  its  under  surface.  Its  posterior  margin  is  over- 
lapped by  the  parotid  gland.  Its  anterior  margin  projects  over  the  Buccinator 
muscle,  and  the  facial  vein  lies  on  it  below. 

The  temporal  fascia  is  seen,  at  this  stage  of  the  dissection,  covering  in  the 
Temporal  muscle.  It  is  a  strong,  fibrous  investment,  covered,  on  its  outer  surface, 
by  the  Attrahens  and  Attollens  auriculam  muscles,  the  aponeurosis  of  the  Occipito- 


THE    TEMPORO-MANDIBVLAR    REGION. 


311 


frontalis,  and  by  part  of  the  Orbicularis  palpebrarum.  The  temporal  vessels  and 
the  auriculo-temporal  nerve  cross  it  from  below  upward.  Above,  it  is  a  single 
layer,  attached  to  the  entire  extent  of  the  upper  temporal  ridge ;  but  below,  where 
it  is  attached  to  the  zygoma,  it  consists  of  two  layers,  one  of  which  is  inserted  into 
the  outer,  and  the  other  into  the  inner,  border  of  the  zygomatic  arch.  A  small 
quantity  of  fat,  the  orbital  branch  of  the  temporal  artery,  and  a  filament  from  the 
orbital,  or  temporo-malar,  branch  of  the  superior  maxillary  nerve,  are  contained 
between  these  two  layers.  It  affords  attachment  by  its  inner  surface  to  the 
superficial  fibres  of  the  Temporal   muscle. 

Dissection. — In  order  to  expose  the  Temporal  muscle,  remove  the  temporal  fascia,  which 
may  be  effected  by  separating  it  at  its  attachment  along  the  upper  border  of  the  zygoma,  and 
dissecting  it  upward  from  the  surface  of  the  muscle.  The  zygomatic  arch  should  then 
be  divided  in  front  at  its  junction  with  the  malar  bone,  and  behind  near  the  external  auditory 
meatus,  and  drawn  downward  with  the  Masseter,  which  should  be  detached  from  its  inser- 
tion into  the  ramus  and  angle  of  the  jaw.  The  whole  extent  of  the  Temporal  muscle  is  then 
exposed. 

The  Temporal  (Fig.  199)  is  a  broad,  radiating  muscle  situated  at  the  side  of  the 
head  and  occupying  the  entire  extent  of  the  temporal  fossa.  It  arises  from  the 
whole  of  the  temporal  fossa  except  that  portion  of  it  that  is  formed  by  the  malar 
bone.  Its  attachment  extends  from  the  external  angular  process  of  the  frontal  in 
front  to  the  mastoid  portion  of  the  temporal  behind,  and  from  the  curved  line  on 
the  frontal  and  parietal  bones  above  to  the  pterygoid  ridge  on  the  great  wing  of 
the  sphenoid  below.  It  is  also  attached  to  the  inner  surface  of  the  temporal  fascia. 
Its  fibres  converge  as  they  descend,  and  terminate  in  an  aponeurosis,  the  fibres  of 


Fig.  199. — The  Temporal  muscle,  the  zygoma  and  Masseter  having  been  removed. 

which,  radiated  at  its  commencement,  converge  into  a  thick  and  fiat  tendon,  which 
is  inserted  into  the  inner  surface,  apex,  and  anterior  border  of  the  coronoid  process 
of  the  jaw,  nearly  as  far  forward  as  the  last  molar  tooth. 

Relations. — By  its  superficial  surface,  with  the  integument,  the  Attrahens  and 
Attollens  auriculam  muscles,  the  temporal  vessels  and  nerves,  the  aponeurosis  of 
the  Occipito-frontalis,  the  temporal  fascia,  the  zygoma,  and  Masseter:  by  its 
deep  surface,  with  the  temporal  fossa,  the  External  pterygoid  and  part  of  the 
Buccinator  muscles,  the  internal  maxillary  artery,  its  deep  temporal  branches, 
and  the  deep  temporal  nerves.     Behind  the  tendon  are  the  masseteric  vessels  and 


312 


THE  MUSCLES   AND    FASCIAE. 


nerve,  and  in  front  of  it  the  buccal  vessels  and  nerve.     Its  anterior  border  is 
separated  from  the  malar  bone  by  a  mass  of  fat. 

Nerves. — -Both  muscles  are  supplied  by  the  inferior  maxillary  nerve. 

10.  Ptery  go  -mandibular  Region  (Fig.  200). 
External  Pterygoid.  Internal  Pterygoid. 

Dissection. — The  Temporal  muscle  having  been  examined,  saw  through  the  base  of  the 
coronoid  process,  and  draw  it  upward,  together  with  the  Temporal  muscle,  which  should  be 
detached  from  the  surface  of  the  temporal  fossa.  Divide  the  ramus  of  the  jaw  just  below  the 
condyle,  and  also,  by  a  transverse  incision  extending  across  the  middle,  just  above  the  dental 
foramen ;  remove  the  fragment,  and  the  Pterygoid  muscles  will  be  exposed. 

The  External  Pterygoid  is  a  short,  thick  muscle,  somewhat  conical  in  form, 
which  extends  almost  horizontally  between  the  zygomatic  fossa  and  the  condyle  of 
the  jaw.  It  arises  by  two  heads,  separated  by  a  slight  interval :  the  upper  arises 
from  the  inferior  surface  of  the  greater  wing  of  the  sphenoid  and  from  the  ptery- 
goid ridge,  which  separates  the  zygomatic  from  the  temporal  fossa ;  the  lotver 
from  the  outer  surface  of  the  external  pterygoid  plate.  Its  fibres  pass  horizon- 
tally backward  and  outward,  to  be  inserted  into  a  depression  in  front  of  the  neck 
of  the  condyle  of  the  lower  jaw  and  into  the  corresponding  part  of  the  inter- 
articular  fibro-cartilage. 

Relations. — By  its  external  surface,  with  the  ramus  of  the  lower  jaw,  the 
internal  maxillary  artery,  which  crosses  it,1  the  tendon  of  the  Temporal  muscle, 
and  the  Masseter ;  by  its  internal  surface  it  rests  against  the  upper  part  of  the 
Internal  pterygoid,  the  internal  lateral  ligament,  the  middle  meningeal  artery, 


Fig.  200.— The  Pterygoid  muscles,  the  zygomatic  arch  and  a  portion  of  the  ramus  of  the  jaw  having  been 
removed. 

and  inferior  maxillary  nerve  ;  by  its  upper  harder  it  is  in  relation  with  the  temporal 
and  masseteric  branches  of  the  inferior  maxillary  nerve ;  by  its  lower  border  it  is 
in  relation  with  the  inferior  dental  and  gustatory  nerves.  Through  the  interval 
between  the  two  portions  of  the  muscle,  the  buccal  nerve  emerges  and  the  internal 
maxillary  artery  passes,  Avhen  the  trunk  of  this  vessel  lies  on  the  muscle  (see 
Fig.  200). 

The  Internal  Pterygoid   is  a  thick,  quadrilateral   muscle,   and   resembles  the 
Masseter  in  form.     It  arises  from  the  pterygoid  fossa,  being  attached  to  the  inner 
1  This  is  the  usual  relation,  hut  in  many  cases  the  artery  will  be  found  below  the  muscle. 


THE  MUSCLES  AND   FASCIAE    OF   THE  NECK.  313 

surface  of  the  external  pterygoid  plate  and  to  the  grooved  surface  of  the  tuber- 
osity of  the  palate  bone,  and  by  a  second  slip  from  the  outer  surface  of  the 
tuberosities  of  the  palate  and  superior  maxillary  bones  ;  its  fibres  pass  downward, 
outward,  and  backward,  to  be  inserted,  by  a  strong,  tendinous  lamina,  into  the 
lower  and  back  part  of  the  inner  side  of  the  ramus  and  angle  of  the  lower  jaw. 
as  high  as  the  dental  foramen. 

Eelations. — By  its  external  surface,  with  the  ramus  of  the  lower  jaw,  from 
which  it  is  separated,  at  its  upper  part,  by  the  External  pterygoid,  the  internal 
lateral  ligament,  the  internal  maxillary  artery,  the  dental  vessels  and  nerves,  and 
the  lingual  nerve,  and  a  process  of  the  parotid  gland.  By  its  internal  surface, 
with  the  Tensor  palati,  being  separated  from  the  Superior  constrictor  of  the 
pharynx  by  a  cellular  interval. 

Nerves. — These  muscles  are  supplied  by  the  inferior  maxillary  nerve. 

Actions. — The  Temporal  and  Masseter  and  Internal  pterygoid  raise  the  lower 
jaw  against  the  upper  with  great  force.  The  superficial  portion  of  the  Masseter 
assists  the  External  pterygoid  in  drawing  the  lower  jaw  forward  upon  the  upper, 
the  jaw  being  drawn  back  again  by  the  deep  fibres  of  the  Masseter  and  posterior 
fibres  of  the  Temporal.  The  External  pterygoid  muscles  are  the  direct  agents  in 
the  trituration  of  the  food,  drawing  the  lower  jaw  directly  forward,  so  as  to  make 
the  lower  teeth  project  beyond  the  upper.  If  the  muscle  of  one  side  acts,  the 
corresponding  side  of  the  jaw  is  drawn  forward,  and,  the  other  condyle  remaining 
fixed,  the  symphysis  deviates  to  the  opposite  side.  The  alternation  of  these 
movements  on  the  two  sides  produces  trituration. 

Surface  Form. — The  outline  of  the  muscles  of  the  head  and  face  cannot  be  traced  on  the 
surface  of  the  body,  except  in  the  case  of  two  of  the  masticatory  muscles.  Those  of  the  head 
are  thin,  so  that  the  outline  of  the  bone  is  perceptible  beneath  them.  Those  in  the  face  are 
small,  covered  by  soft  skin,  and  often  by  a  considerable  layer  of  fat,  so  that  their  outline  is  con- 
cealed, but  they  serve  to  round  off  and  smooth  prominent  borders  and  to  fill  up  what  would  be 
otherwise  unsightly  angular  depressions.  Thus,  the  Orbicularis  palpebrarum  rounds  off  the 
prominent  margin  of  the  orbit,  and  the  Pyramidalis  nasi  fills  in  the  sharp  depression  beneath 
the  glabella,  and  thus  softens  and  tones  down  the  abrupt  depression  which  is  seen  on  the 
unclothed  bone.  In  like  manner,  the  labial  muscles,  converging  to  the  lips  and  assisted  by  the 
superimposed  fat,  fill  in  the  sunken  hollow  of  the  lower  part  of  the  face.  Although  the  muscles 
of  the  face  are  usually  described  as  arising  from  the  bones  and  inserted  into  the  nose,  lips,  and 
corners  of  the  mouth,  they  have  fibres  inserted  into  the  skin  of  the  face  along  their  whole 
extent,  so  that  almost  every  point  of  the  skin  of  the  face  has  its  muscular  fibre  to  move  it ; 
hence  it  is  that  when  in  action  the  facial  muscles  produce  alterations  in  the  skin-surface, 
giving  rise  to  the  formation  of  various  folds  or  wrinkles,  or  otherwise  altering  the  relative 
position  of  parts,  so  as  to  produce  the  varied  expressions  with  which  the  face  is  endowed ; 
hence  these  muscles  are  termed  the  "muscles  of  expression."  The  only  two  muscles  in  this 
region  which  greatly  influence  surface  form  are  the  Masseter  and  the  Temporal.  The  Masseter 
is  a  quadrilateral  muscle,  which  imparts  fulness  to  the  hinder  part  of  the  cheek.  When  the 
muscle  is  firmly  contracted,  as  when  the  teeth  are  clenched,  its  outline  is  plainly  visible ; 
the  anterior  border  forms  a  prominent  vertical  ridge,  behind  which  is  a  considerable  fulness, 
especially  marked  at  the  lower  part  of  the  muscle ;  this  fulness  is  entirely  lost  when  the 
mouth  is  opened  and  the  muscle  no  longer  in  a  state  of  contraction.  The  Temporal  muscle 
is  fan-shaped,  and  fills  the  Temporal  fossa,  substituting  for  it  a  somewhat  convex  form, 
the  anterior  part  of  which,  on  account  of  the  absence  of  hair  over  the  temple,  is  more 
marked  than  the  posterior,  and  stands  out  in  strong  relief  when  the  muscle  is  in  a  state  of  con- 
traction. 

MUSCLES  AND  FASCIiE   OF   THE  NECK. 

The  muscles  of  the  neck  may  be  arranged  into  groups  corresponding  with  the 
region  in  which  they  are  situated. 

These  groups  are  nine  in  number : 

1.  Superficial  cervical  region.  5.  Muscles  of  the  Pharynx. 

2.  Depressors  of  the  Os  Hyoides  6.  Muscles  of  the  Soft  Palate. 

and  Larynx.  7.  Muscles  of  the  Anterior  Arer- 

3.  Elevators  of  the  Os  Hyoides  tebral  Region. 

and  Larynx.  8.  Muscles  of  the  Lateral  Ver- 

4.  Muscles  of  the  Tongue.  tebral  Region. 

9.  Muscles  of  the  Larynx. 


314 


THE   MUSCLES   AND    FASCIA. 


The  muscles  contained  in  each  of  these  groups  are  the  following : 


1.  Superficial  Region. 

Platysma  myoides. 
Sterno-cleido-mastoid. 


Infra-hyoid  Region. 

2.  Depressors  of  the  Os  hyoides  and 
Larynx. 

Sterno-hyoid. 
Sterno-thyroid. 
Thyro-hyoid. 
Omo-hyoid. 

Supra-hyoid  Region. 

3.  Elevators  of  the  Os  hyoides  and 

Larynx. 

Digastric. 
Stylo-hyoid. 
Mylo-hyoid. 
Genio-hyoid. 

Lingual  Region. 

4.  Muscles  of  the  Tongue. 

Genio-hyo-glossus. 

Hyo-glossus. 

Chondro-glossus. 

Stylo-glossus. 

Palato-glossus. 


5.  Muscles  of  the  Pharynx. 
Inferior  constrictor. 
Middle  constrictor. 
Superior  constrictor. 
Stylo-pharyngeus. 
Palato-pharyngeus. 

6.  Muscles  of  the  Soft  Palate. 
Levator  palati. 

Tensor  palati. 
Azygos  uvulae. 
Palato-glossus. 
Palato-pharyngeus. 
Salpingo-pharyngeus. 

7.  Muscles  of  the  Anterior   Vertebral 

Region. 
Rectus  capitis  anticus  major. 
Rectus  capitis  anticus  minor. 
Rectus  capitis  lateralis. 
Longus  colli. 

8.  Muscles  of  the  Lateral  Vertebral 

Region. 

Scalenus  anticus. 
Scalenus  medius. 
Scalenus  posticus. 

9.  Muscles  of  the  Larynx. 
Included  in  the  description  of 

the  Larynx. 


1.  Superficial  Cervical  Region. 

Platysma  myoides.  Sterno-cleido-mastoid. 

Dissection. — A  block  having  been  placed  at  the  back  of  the  neck,  and  the  face  turned  to 
the  side  opposite  that  to  be  dissected,  so  as  to  place  the  parts  upon  the  stretch,  make  two  trans- 
verse incisions :  one  from  the  chin,  along  the  margin  of  the  lower  jaw,  to  the  mastoid  process, 
and  the  other  along  the  upper  border  of  the  clavicle.  Connect  these  by  an  oblique  incision 
made  in  the  course  of  the  Sterno-mastoid  muscle,  from  the  mastoid  process  to  the  sternum ;  the 
two  flaps  of  integument  having  been  removed  in  the  direction  shown  in  Fig.  194,  the  superficial 
fascia  will  be  exposed. 

The  Superficial  Cervical  Fascia  is  a  thin,  aponeurotic  lamina  which  is  hardly 
demonstrable  as  a  separate  membrane.  Beneath  it  is  found  the  Platysma  myoides 
muscle. 

The  Platysma  myoides  (Fig.  195)  is  a  broad,  thin  plane  of  muscular  fibres 
placed  immediately  beneath  the  superficial  fascia  on  each  side  of  the  neck.  It 
arises  by  thin,  fibrous  bands  from  the  fascia  covering  the  upper  part  of  the  Pectoral 
and  Deltoid  muscles ;  its  fibres  pass  over  the  clavicle  and  proceed  obliquely 
upward  and  inward  along  the  side  of  the  neck.  The  anterior  fibres  interlace, 
below  and  behind  the  symphysis  menti,  with  the  fibres  of  the  muscle  of  the 
opposite  side ;  the  posterior  fibres  pass  over  the  lower  jaw,  some  of  them  being 
attached  to  the  bone  below  the  external  oblique  line,  others  passing  on  to  be 
inserted  into  the  skin  and  subcutaneous  tissue  of  the  lower  part  of  the  face, 
many  of  these  fibres  blending  with  the  muscles  about  the  angle  and  lower  part 
of  the  mouth.  Sometimes  fibres  can  be  traced  to  the  Zygomatic  muscles  or  to 
the  margin  of  the  Orbicularis  oris.  Beneath  the  Platysma  the  external  jugular 
vein  may  be  seen  descending  from  the  angle  of  the  jaw  to  the  clavicle. 


THE  SUPERFICIAL    CERVICAL    REGION.  315 

Surgical  Anatomy. — It  is  essential  to  remember  the  direction  of  the  fibres  of  the  Platysma 
in  connection  with  the  operation  of  bleeding  from  the  external  jugular  vein ;  for  if  the  point 
of  the  lancet  is  introduced  in  the  direction  of  the  muscular  fibres,  the  orifice  made  will  be 
filled  up  by  the  contraction  of  the  muscle,  and  blood  will  not  flow  ;  but  if  the  incision  is  made 
across  the  course  of  the  fibres,  they  will  retract  and  expose  the  orifice  in  the  vein,  and  so  allow 
the  flow  of  blood. 

Relations. — By  its  external  surface,  with  the  integument,  to  which  it  is  united 
more  closely  below  than  above;  by  its  internal  surface,  with  the  Pectoralis 
major  and  Deltoid,  and  with  the  clavicle.  In  the  neck,  with  the  external  and 
anterior  jugular  veins,  the  deep  cervical  fascia,  the  superficial  branches  of  the 
cervical  plexus,  the  Sterno-mastoid,  Sterno-hyoid,  Omo-hyoid,  and  Digastric 
muscles ;  behind  the  Sterno-mastoid  muscle  it  covers  in  the  posterior  triangle  of 
the  neck.  On  the  face  it  is  in  relation  with  the  parotid  gland,  the  facial  artery 
and  vein,  and  the  Masseter  and  Buccinator  muscles. 

Action. — The  Platysma  myoides  produces  a  slight  wrinkling  of  the  surface  of 
the  skin  of  the  neck,  in  an  oblique  direction,  when  the  entire  muscle  is  brought 
into  action.  Its  anterior  portion,  the  thickest  part  of  the  muscle,  depresses  the 
lower  jaw;  it  also  serves  to  draAv  down  the  lower  lip  and  angle  of  the  mouth  on 
each  side,  being  one  of  the  chief  agents  in  the  expression  of  melancholy. 

The  Deep  cervical  fascia  lies  under  cover  of  the  Platysma  myoides  muscle  and 
constitutes  a  complete  investment  for  the  neck.  It  also  forms  a  sheath  for  the 
carotid  vessels,  and,  in  addition,  is  prolonged  deeply  in  the  shape  of  certain  proc- 
esses or  lamellae,  which  come  into  close  relation  with  the  structures  situated  in 
front  of  the  vertebral  column. 

The  investing  portion  of  the  fascia  is  attached  behind  to  the  ligamentum 
nuchas  and  to  the  spine  of  the  seventh  cervical  vertebra.  Along  this  line  it  splits 
to  enclose  the  Trapezius  muscle,  at  the  anterior  border  of  which  the  two  enclosing 
lamellae  unite  and  form  a  strong  membrane,  which  extends  forward  so  as  to  roof 
in  the  posterior  triangle  of  the  neck.  Along  the  hinder  edge  of  the  Sterno-mastoid 
this  membrane  again  divides  to  enclose  this  muscle,  at  the  anterior  edge  of  which 
it  once  more  forms  a  single  lamella,  which  roofs  in  the  anterior  triangle  of  the  neck, 
and,  reaching  forward  to  the  middle  line,  is  continuous  with  the  corresponding 
part  from  the  opposite  side  of  the  neck.  In  the  middle  line  of  the  neck  it  is 
attached  to  the  symphysis  menti  and  body   of  the  hyoid  bone. 

Above,  the  fascia  is  attached  to  the  superior  curved  line  of  the  occiput,  to  the 
mastoid  process  of  the  temporal,  and  to  the  whole  length  of  the  body  of  the  jaw. 
Opposite  the  angle  of  the  jaw  the  fascia  is  very  strong,  and  binds  the  anterior 
edge  of  the  Sterno-mastoid  firmly  to  that  bone.  Between  the  jaw  and  the  mastoid 
process  it  ensheaths  the  parotid  gland — the  layer  which  covers  the  gland  extending 
upward  under  the  name  of  the  parotid  fascia  to  be  fixed  to  the  zygomatic  arch. 
From  the  layer  which  passes  under  the  parotid  a  strong  band,  the  stylo-mandibular 
ligament,  reaches  from  the  styloid  process  to  the  angle  of  the  jaw. 

Below,  the  fascia  is  attached  to  the  acromion  process,  the  clavicle,  and  manu- 
brium sterni.  Some  little  distance  above  the  last,  however,  it  splits  into  two 
layers,  superficial  and  deep.  The  former  is  attached  to  the  anterior  border  of  the 
manubrium,  the  latter  to  its  posterior  border  and  to  the  interclavicular  ligament. 
Between  these  two  layers  is  a  slit-like  interval,  the  suprasternal  space,  or  space  of 
Burns.  It  contains  a  small  quantity  of  areolar  tissue,  and  sometimes  a  lymphatic 
gland;  the  lower  portions  of  the  anterior  jugular  veins  and  their  transverse 
connecting  branch;  and  also  the  sternal  heads  of  the   Sterno-mastoid  muscles. 

The  fascia  which  lines  the  deep  aspect  of  the  Sterno-mastoid  gives  off  certain 
important  processes,  viz.  :  (1)  A  process  to  envelop  the  tendon  of  the  Omo-hyoid, 
and  bind  it  down  to  the  sternum  and  first  costal  cartilage.  (2)  A  strong  sheath, 
the  carotid  sheath,  for  the  large  vessels  of  the  neck,  enclosed  within  which  are  the 
carotid  artery,  internal  jugular  vein,  the  vagus,  and  descendens  hypoglossi  nerves. 
(3)  The  prevertebral  fascia,  which  extends  inward  behind  the  carotid  vessels, 
where  it  assists  in  forming  their  sheath,  and  passes  in  front  of  the  prevertebral 
muscles.    It  thus  forms  the  posterior  limit  of  a  fibrous  compartment  which  contains 


316 


THE   MUSCLES   AND    FASCIAE. 


the  larynx  and  trachea,  the  thyroid  gland,  and  the  pharynx  and  oesophagus.  The 
prevertebral  fascia  is  fixed  above  to  the  base  of  the  skull,  while  below  it  is  con- 
tinued mto  the  thorax  in  front  of  the  Longus  colli  muscles.  Parallel  to  the  carotid 
vessels  and  along  their  inner  aspect  it  gives  off  a  thin  lamina,  the  buccopharyn- 
geal fascia,  which  closely  invests  the  constrictor  muscles  of  the  pharynx,  and  is 
continued  forward  from  the  Superior  constrictor  on  to  the  Buccinator.'  It  is 
attached  to  the  prevertebral  layer  by  loose  connective  tissue  only,  and  thus  an 
easily  distended  space,  the  retropharyngeal  space,  is  found  between  them.  This 
space  is  limited  above  by  the  base  of  the  skull,  while  below  it  extends  behind  the 


OMO-HYOID. 

Thyroid  body. 


Common  carotid  artery. , 
Internal  jugidar  vein.* 


STERNO-MASTOID 


Pneumogas 
trie  nerve. 


■Anterior  jugular  vein. 

STERNO-HYOID. 
-STER  NO-THYROID. 


_  Trachea. 


jj§~  (Esophagus. 

-LONGUS    COLLI. 

-6th  cervical. 
-Vertebral  vessels. 


SPLENIUS 
COLLI.      J 

1 

LEVATOR    ")  V 

ANGULI      > * 

SCAPUUE 


TRAPEZIUS 


SEMI-SPINALIS   COLLI. 


-•COMPLEXUS. 


-J--SPLENIUS    CAPITIS. 


Fig.  201,-Section  of  the  neck  at  about  the  level  of  the  sixth  cervical  vertebra.    Showing  the  arrangement  of 

the  deep  cervical  fascia.  s  «"iu0emeiit  oi 

oesophagus  into  the  thorax,  where  it  is  continued  into  the  posterior  mediastinum, 
llie  prevertebral  fascia  is  prolonged  downward  and  outward  behind  the  carotid 
vessels  and  in  front  of  the   Scaleni  muscles,  and  forms  a   sheath  for  the  brachial 

S?t£  T  Ymn  rSelS-i?  the  rSteri°r  trianSle  0f  the  neck'  and>  continued 
under  the  clavicle  as  the  axillary  sheath,  is  attached  to  the  deep  surface  of  the 

betw^nT1  meirblT-  InT?ateiy  ab°Ve  the  Clavicle  an  areolar  sPa<*  exists 
!jt  th*  mvesting  >ver  and  the  sheath  of  the  subclavian  vessels,  and  in  it  are 
found  the  lower  part  of  the  external  jugular  vein,  the  descending  clavicular  nerves, 
tne  suprascapular  and  transversalis  colli   vessels,   and  the  posterior  belly  of  the 


THE   SUPERFICIAL    CERVICAL    REGION.  317 

Omohyoid  muscle.  This  space  extends  downward  behind  the  clavicle,  and  is 
limited  below  by  the  fusion  of  the  costo-coracoid  membrane  with  the  anterior  wall 
of  the  axillary  sheath.  (4)  The  pre-tracheal  fascia,  Avhich  extends  inward  in  front 
of  the  carotid  vessels,  and  assists  in  forming  the  carotid  sheath.  It  is  further 
continued  behind  the  depressor  muscles  of  the  hyoid  bone,  and,  after  enveloping 
the  thyroid  body,  is  prolonged  in  front  of  the  trachea  to  meet  the  corresponding 
layer  of  the  opposite  side.  Above,  it  is  fixed  to  the  hyoid  bone,  while  below  it  is 
carried  downward  in  front  of  the  trachea  and  large  vessels  at  the  root  of  the  neck, 
and  ultimately  blends  with  the  fibrous  pericardium. 

Surgical  Anatomy. — The  cervical  fascia  is  of  considerable  importance  from  a  surgical 
point  of  view.  As  will  be  seen  from  the  foregoing  description,  it  may  be  divided  into  three 
layers:  (J)  A  superficial  layer;  (2)  a  layer  passing  in  front  of  the  trachea,  and  forming  with 
the  superficial  layer  a  sheath  for  the  depressors  of  the  hyoid  bone;  (3)  a  prevertebral  layer 
passing  in  front  of  the  bodies  of  the  cervical  vertebrae,  and  forming  with  the  second  layer 
a  space  in  which  are  contained  the  trachea,  oesophagus,  etc.  The  superficial  layer  forms  a  com- 
plete investment  for  the  neck.  It  is  attached  behind  to  the  ligamentum  nuchas  and  the  spine 
of  the  seventh  cervical  vertebra  ;  above  it  is  attached  to  the  external  occipital  protuberance,  to 
the  superior  curved  line  of  the  occiput,  to  the  mastoid  process,  to  the  zygoma  and  the  lower 
jaw ;  below  it  is  attached  to  the  manubrium  sterni,  the  clavicle,  the  acromion  process,  and  the 
spine  of  the  scapula  ;  in  front  it  blends  with  the  fascia  of  the  opposite  side.  This  layer  would 
oppose  the  extension  of  abscesses  or  new  growths  toward  the  surface,  and  pus  forming  beneath 
it  would  have  a  tendency  to  extend  laterally.  If  it  is  in  the  posterior  triangle,  it  might  extend 
backward  under  the  Trapezius,  forward  under  the  Sterno-mastoid,  or  downward  under  the 
clavicle  for  some  distance,  until  stopped  by  the  junction  of  the  cervical  fascia  to  the  Costo- 
coracoid  membrane.  If  the  pus  is  contained  in  the  anterior  triangle,  it  might  find  its  way  into 
the  anterior  mediastinum,  being  situated  in  front  of  the  layer  of  fascia  which  passes  down  into 
the  thorax  to  become  continuous  with  the  pericardium ;  but  owing  to  the  lesser  density  and 
thickness  of  the  fascia  in  this  situation  it  more  frequently  finds  its  way  through  it  and  points 
above  the  sternum.  The  second  layer  of  fascia  is  connected  above  with  the  hyoid  bone.  It 
passes  down  beneath  the  depressors  and  in  front  of  the  thyroid  body  and  trachea  to  become 
continuous  with  the  fibrous  layer  of  the  pericardium.  Laterally  it  invests  the  great  vessels  of 
the  neck  and  is  connected  with  the  superficial  layer  beneath  the  Sterno-mastoid.  Pus  forming 
beneath  this  layer  would  in  all  probability  find  its  way  into  the  posterior  mediastinum.  The 
third  layer  (the  prevertebral  fascia)  is  connected  above  to  the  base  of  the  skull.  Pus  forming 
beneath  this  layer,  in  cases,  for  instance,  of  caries  of  the  bodies  of  the  cervical  vertebrae,  might 
extend  toward  the  posterior  and  lateral  part  of  the  neck  and  point  in  this  situation,  or  might 
perforate  this  layer  of  fascia  and  the  pharyngeal  fascia  and  point  into  the  pharynx  (retro- 
pharyngeal abscess] . 

In  cases  of  cut  throat  the  cervical  fascia  is  of  considerable  importance.  When  the  wound 
involves  only  the  superficial  layer  the  injury  is  usually  trivial,  the  only  special  danger  being 
injury  to  the  external  jugular  vein,  and  the  only  special  complication  being  diffuse  cellulitis. 
But  where  the  second  of  the  two  layers  has  been  opened  up,  important  structures  may  have 
been  injured,  which  may  lead  to  serious  results. 

It  may  be  worth  while  mentioning  that  in  Burns' s  space  is  contained  the  sternal  head  of 
origin  of  the  Sterno-mastoid  muscle,  so  that  this  space  is  opened  in  division  of  this  tendon. 
The  anterior  jugular  vein  is  also  contained  in  the  same  space. 

The  Sterno-mastoid  or  Sterno-cleido-mastoid  (Fig.  202)  is  a  large,  thick  muscle, 
which  passes  obliquely  across  the  side  of  the  neck,  being  enclosed  between  the  two 
layers  of  the  deep  cervical  fascia.  It  is  thick  and  narrow  at  its  central  part,  but  is 
broader  and  thinner  at  each  extremity.  It  arises,  by  two  heads,  from  the  sternum 
and  clavicle.  The  sternal  portion  is  a  rounded  fasciculus,  tendinous  in  front,  fleshy 
behind,  which  arises  from  the  upper  and  anterior  part  of  the  first  piece  of 
the  sternum,  and  is  directed  upward,  outward,  and  backward.  The  clavicular 
portion  arises  from  the  inner  third  uf  the  superior  border  and  anterior  surface  of 
the  clavicle,  being  composed  of  fleshy  and  aponeurotic  fibres  ;  it  is  directed  almost 
vertically  upward.  These  two  portions  are  separated  from  one  another,  at  their 
origin,  by  a  triangular  cellular  interval,  but  become  gradually  blended,  below  the 
middle  of  the  neck,  into  a  thick,  rounded  muscle,  which  is  inserted,  by  a  strong 
tendon,  into  the  outer  surface  of  the  mastoid  process,  from  its  apex  to  its  superior 
border,  and  by  a  thin  aponeurosis  into  the  outer  half  of  the  superior  curved  line 
of  the  occipital  bone.  The  Sterno-mastoid  varies  much  in  its  extent  of  attach- 
ment to  the  clavicle :  in  one  case  the  clavicular  may  be  as  narrow  as  the  sternal 
portion  ;  in  another,  as  much  as  three  inches  in  breadth.     When  the  clavicular 


318 


THE  MUSCLES  %ND    FASCIA. 


origin  is  broad,  it  is  occasionally  subdivided  into  numerous  slips  separated  by 
narrow  intervals.  More  rarely,  the  corresponding  margins  of  the  Sterno-mastoid 
and  Trapezius  have  been  found  in  contact.  In  the  application  of  a  ligature  to  the 
third  part  of  the  subclavian  artery  it  will  be  necessary,  where  the  muscles  come 
close  together,  to  divide  a  portion  of  one  or  of  both. 

This  muscle  divides  the  quadrilateral  space  at  the  side  of  the  neck  into  two 
triangles,  an  anterior  and  a  posterior.  The  boundaries  of  the  anterior  triangle 
are,  in  front,  the  median  line  of  the  neck  ;  above,  the  lower  border  of  the  body  of 
the  jaw,  and  an  imaginary  line  drawn  from  the  angle  of  the  jaw  to  the  mastoid 


Fig.  202.— Muscles  of  the  neck  and  boundaries  of  the  triangles. 

process  ;  behind,  the  anterior  border  of  the  Sterno-mastoid  muscle.  The  apex  of 
the  triangle  is  at  the  upper  border  of  the  sternum.  The  boundaries  of  the 
'posterior  triangle  are,  in  front,  the  posterior  border  of  the  Sterno-mastoid ;  below, 
the  middle  third  of  the  clavicle ;  behind,  the  anterior  margin  of  the  Trapezius.1 
The  apex  corresponds  with  the  meeting  of  the  Sterno-mastoid  and  Trapezius  on 
the  occipital  bone. 

Relations. — By  its  superficial  surface,  with  the  integument  and  Platysma, 
from  which  it  is  separated  by  the  external  jugular  vein,  the  superficial  branches 
of  the  cervical  plexus,  and  the  anterior  layer  of  the  deep  cervical  fascia.  By  its 
deep  surface  it  is  in  relation  with  the  Sterno-clavicular  articulation  ;  a  process  of 
the  deep  cervical  fascia ;  the  Sterno-hyoid,  Sterno-thyroid.  Omo-hyoid,  posterior 
belly  of  the  Digastric,  Levator  anguli  scapulae,  Splenius  and  Scaleni  muscles ; 
common  carotid  artery,  internal  and  anterior  jugular  veins,  commencement  of  the 
internal  and  external  carotid  arteries,  the  occipital,  subclavian,  transversalis  colli, 
and  suprascapular  arteries  and  veins  ;  the  phrenic,  pneumogastric,  hypoglossal, 
descendens  and  communicans  hypoglossi  nerves ;  the  spinal  accessory  nerve,  which 

1  The  anatomy  of  these  triangles  will  be  more  exactly  described  with  that  of  the  vessels  of  the 
neck. 


THE   INFBA-HYOID    REGION.  319 

pierces   its   upper  third ;    the   cervical   plexus,  parts   of  the  thyroid  and  parotid 

glands,  and  deep  lymphatic  glands. 

Nerves. — The  Platysrna  uiyoides  is  supplied  by  the  facial  nerve ;  the  Sterno- 

cleido-mastoid,  by  the  spinal  accessory  and  deep  branches  of  the  cervical  plexus- 
Actions. — When    only   one    Sterno-mastoid   muscle    acts,   it    draws    the    head 

toward  the  shoulder  of  the  same  side,  assisted  by  the  Splenius  and  the  Obliquus 

capitis  inferior  of  the  opposite  side.     At  the  same  time  it  rotates  the  head  so  as  to 

carry  the  face  toward  the  opposite  side.     If  the  head  is  fixed,  the  two  muscles 

assist  in  elevating  the  thorax  in  forced  inspiration. 

Surface  Form. — The  anterior  edge  of  the  muscle  forms  a  very  prominent  ridge  beneath 
the  skin,  which  it  is  important  to  notice,  as  it  forms  a  guide  to  the  surgeon  in  making  the  neces- 
sary incisions  for  ligature  of  the  common  carotid  artery  and  for  oesophagotomy. 

Surgical  Anatomy. — The  relations  of  the  sternal  and  clavicular  parts  of  the  Sterno-mastoid 
should  be  carefully  examined,  as  the  surgeon  is  sometimes  required  to  divide  one  or  both  por- 
tions of  the  muscles  in  wry-neck.  One  variety  of  this  distortion  is  produced  by  spasmodic  con- 
traction or  rigidity  of  the  Sterno-mastoid  ;  the  head  being  carried  down  toward  the  shoulder  of 
the  same  side,  and  the  face  turned  to  the  opposite  side  and  fixed  in  that  position.  When  there 
is  permanent  shortening,  subcutaneous  division  of  the  muscle  is  resorted  to  by  some  surgeons. 
This  is  performed  by  introducing  a  tenotomy  knife  beneath  it,  close  to  its  origin,  and  dividing 
it  from  behind  forward  whilst  the  muscle  is  put  well  upon  the  stretch.  There  is  seldom  any 
difficulty  in  dividing  the  sternal  portion  by  making  a  puncture  on  the  inner  side  of  the  tendon, 
and  then  pushing  a  blunt  tenotome  behind  it,  and  cutting  forward.  In  dividing  the  clavicular 
portion  care  must  be  taken  to  avoid  wounding  the  external  jugular  vein,  which  runs  parallel 
with  the  posterior  border  of  the  muscle  in  this  situation,  or  the  anterior  jugular  vein,  which 
crosses  beneath  it.  If  the  external  jugular  vein  lies  near  the  muscle,  it  is  safer  to  make  the 
first  puncture  at  the  outer  side  of  the  tendon,  and  introduce  a  blunt  tenotome  from  without 
inward.  Many  surgeons  prefer  dividing  the  muscle  by  the  open  method.  An  incision  is  made 
over  either  origin  of  the  muscle,  the  tendon  is  exposed,  a  director  is  passed  underneath  it, 
and  it  is  then  divided.  With  care  and  attention  to  asepsis  this  plan  of  treatment  is  devoid  of 
risk,  and  in  this  way  the  accidental  division  of  the  vessels  can  be  avoided.  Some  of  the  fibres 
of  the  Sterno-mastoid  muscle  are  occasionally  torn  during  birth,  especially  in  breech  presenta- 
tions ;  this  is  accompanied  by  hemorrhage  and  formation  of  a  swelling  within  the  substance  of 
the  muscle.  This  by  some  is  believed  to  be  one  of  the  Causes  of  wry-neck,  the  scar  tissue 
which  is  formed  contracting  and  shortening  the  muscle. 

2.  Infra-hyoid  Region  (Figs.  202,  203). 

Depressors  of  the  Os  Hyoides  and  Larynx. 

Sterno-hyoid.  Thyro-hyoid. 

Sterno-thyroid.  Omo-hyoid. 

Dissection. — The  muscles  in  this  region  may  be  exposed  by  removing  the  deep  fascia  from 
the  front  of  the  neck.  In  order  to  see  the  entire  extent  of  the  Omo-hyoid  it  is  necessary  to 
divide  the  Sterno-mastoid  at  its  centre,  and  turn  its  ends  aside,  and  to  detach  the  Trapezius 
from  the  clavicle  and  scapula.  This,  however,  should  not  be  clone  until  the  Trapezius  has  been 
dissected. 

The  Sterno-hyoid  is  a  thin,  narrow,  ribbon-like  muscle,  which  arises  from  the 
inner  extremity  of-  the  clavicle,  the  posterior  sterno-clavicular  ligament,  and  the 
upper  and  posterior  part  of  the  first  piece  of  the  sternum  ;  passing  upward  and 
inward,  it  is  inserted,  by  short,  tendinous  fibres,  into  the  lower  border  of  the  body 
of  the  os  hyoides.  This  muscle  is  separated,  below,  from  its  fellow  by  a  consider- 
able interval ;  but  the  two  muscles  come  into  contact  with  one  another  in  the 
middle  of  their  course,  and  from  this  upward  lie  side  by  side.--  It  sometimes 
presents,  immediately  above  its  origin,  a  transverse  tendinous  intersection,  like 
those  in  the  Rectus  abdominis. 

Relations. — By  its  superficial  surface,  below,  with  the  sternum,  the  sternal  end 
of  the  clavicle,  and  the  Sterno-mastoid  ;  and  above,  with  the  Platysrna  and  deep 
cervical  fascia ;  by  its  deep  surface,  with  the  Sterno-thyroid,  Crico-thyroid,  and 
Thyro-hyoid  muscles,  the  thyroid  gland,  the  superior  thyroid  vessels,  the  thyroid 
cartilage,  the  crico-thyroid  and  thyro-hyoid  membranes. 

The  Sterno-thyroid  is  situated  beneath  the  preceding  muscle,  but  is  shorter  and 
wider  than  it.     It  arises  from  the  posterior  surface  of  the  first  bone  of  the  sternum, 


320 


THE   MUSCLES   AND    FASCIA. 


below  the  origin  of  the  Sterno-hyoid,  and  from  the  edge  of  the  cartilage  of  the 
first  rib,  occasionally  of  the  second  rib  also,  and  is  inserted  into  the  oblique 
line  on  the  side  of  the  ala  of  the  thyroid  cartilage.  This  muscle  is  in  close  contact 
with  its  fellow  at  the  lower  part  of  the  neck,  and  is  occasionally  traversed  by  a 
transverse  or  oblique  tendinous  intersection,  like  those  in  the  Rectus  abdominis. 

Relations. — By  its  anterior  surface,  with  the  Sterno-hyoid,  Omo-hyoid,  and 
Sterno-mastoid ;  by  its  posterior  surface,  from  below  upward,  with  the  trachea, 
vena  innominata,  common  carotid  (and  on  the  right  side  the  arteria  innominata), 
the  thyroid  gland  and  its  vessels,  and  the  lower  part  of  the  larynx  and  pharynx. 
The  inferior  thyroid  vein  lies  along  its  inner  border,  a  relation  which  it  is 
important  to  remember  in  the  operation  of  tracheotomy.  On  the  left  side  the  deep 
surface  of  the  muscle  is  in  relation  to  the  oesophagus. 

The  Thyro-hyoid  is  a  small,  quadrilateral  muscle  appearing  like  a  continuation 
of  the  Sterno-thyroid.  It  arises  from  the  oblique  line  on  the  side  of  the  thyroid 
cartilage,  and  passes  vertically  upward  to  be  inserted  into  the  lower  border  of  the 
body  and  greater  cornu  of  the  hyoid  bone. 

Relations. — By  its  external  surface,  with  the  Sterno-hyoid  and  Omo-hyoid 
muscles  ;  by  its  internal  surface,  with  the  thyroid  cartilage,  the  thyro-hyoid 
membrane,   and  the  superior  laryngeal  vessels  and  nerve. 

The  Omo-hyoid  passes  across  the  side  of  the  neck,  from  the  scapula  to  the 

Symphysis 
of  jaw. 


Sternum. 
Fig.  203.— Muscles  of  the  neck.    Anterior  view. 


hyoid  bone.  It  consists  of  two  fleshy  bellies,  united  by  a  central  tendon.  It 
arises  from  the  upper  border  of  the  scapula,  and  occasionally  from  the  transverse 
ligament  which  crosses  the  suprascapular  notch,  its  extent  of  attachment  to  the 
scapula  varying  from  a  few  lines  to  an  inch.  From  this  origin  the  posterior  belly 
forms  a  flat,  narrow  fasciculus,  which  inclines  forward  and  slightly  upward  across 
the  lower  part  of  the  neck,  behind  the  Sterno-mastoid  muscle,  where  it  becomes 
tendinous ;  it  then  changes  its  direction,  forming  an  obtuse  angle,  and  terminates 
in  the  anterior  belly,  which  passes  almost  vertically  upward,  close  to  the  outer 
border  of  the  Sterno-hyoid,  to  be  inserted  into  the  lower  border  of  the  body  of  the 


THE   SUPRA-HYOID    REGION.  321 

os  hyoides,  just  external  to  the  insertion  of  the  Sterno-hyoid.  The  central  tendo.n 
of  this  muscle,  which  varies  much  in  length  and  form,  is  held  in  position  byal 
process  of  the  deep  cervical  fascia,  which  includes  it  in  a  sheath.  This  procesa 
is  prolonged  down,  to  be  attached  to  the  clavicle  and  first  rib.  It  is  by  this  means 
that  the  angular  form  of  the  muscle  is  maintained. 

This  muscle  subdivides  each  of  the  two  large  triangles  at  the  side  of  the  neck 
into  two  smaller  triangles ;  the  two  posterior  ones  being  the  posterior  superior  or 
occipital,  and  the  posterior  inferior  or  subclavian  ;  the  two  anterior,  the  anterior 
superior  or  superior  carotid,  and  the  anterior  inferior  or  inferior  carotid  triangle*. 

Relations. — By  its  superficial  surface,  Avith  the  Trapezius,  the  Sterno-mastoid, 
deep  cervical  fascia,  Platysma,  and  integument ;  by  its  deep  surface,  with  the 
Scaleni  muscles,  phrenic  nerve,  lower  cervical  nerves,  which  go  to  form  the  brachial 
plexus,  the  suprascapular  vessels  and  nerve,  sheath  of  the  common  carotid  artery 
and  internal  jugular  vein,  the  Sterno-thyroid  and  Thyro-hyoid  muscles. 

Nerves. — The  Thyro-hyoid  is  supplied  by  the  hypoglossal ;  the  other  muscles 
of  this  group  by  branches  from  the  loop  of  communication  between  the  descendens 
and  communicans  hypoglossi. 

Actions. — These  muscles  depress  the  larynx  and  hyoid  bone,  after  they  have 
been  drawn  up  with  the  pharynx  in  the  act  of  deglutition.  The  Omo-hyoid 
muscles  not  only  depress  the  hyoid  bone,  but  carry  it  backward  and  to  one  or  the 
other  side.  It  is  concerned  especially  in  prolonged  inspiratory  efforts ;  for  by 
tensing  the  lower  part  of  the  cervical  fascia  it  lessens  the  inward  suction  of  the  soft 
parts,  which  would  otherwise  compress  the  great  vessels  and  the  apices  of  the  lungs. 
The  Thyro-hyoid  may  act  as  an  elevator  of  the  thyroid  cartilage  when  the  hyoid 
bone  ascends,  drawing  upward  the  thyroid  cartilage,  behind  the  os  hyoides.  The 
Sterno-thyroid  acts  as  a  depressor  of  the  thyroid  cartilage. 

3.  Supra-hyoid  Region  (Figs.  202,  203). 

Elevators  of  the  Os  Hyoides — Depressors  of  the  Lower  Jaw. 

Digastric.  Mylo-hyoid. 

Stylo-hyoid.  Genio-hyoid. 

Dissection. — To  dissect  these  muscles  a  block  should  be  placed  beneath  the  back  of  the 
neck,  and  the  head  drawn  backward  and  retained  in  that  position.  On  the  removal  of  the  deep 
fascia  the  muscles  are  at  once  exposed. 

The  Digastric  consists  of  two  fleshy  bellies  united  by  an  intermediate,  rounded 
tendon.  It  is  a  small  muscle,  situated  below  the  side  of  the  body  of  the  lower 
jaw,  and  extending,  in  a  curved  form,  from  the  side  of  the  head  to  the  symphysis 
of  the  jaw.  The  posterior  belly,  longer  than  the  anterior,  arises  from  the  digastric 
groove  on  the  inner  side  of  the  mastoid  process  of  the  temporal  bone,  and  passes 
downward,  forward,  and  inward.  The  anterior  belly  arises  from  a  depression 
on  the  inner  side  of  the  lower  border  of  the  jaw,  close  to  the  s}'mphysis,  and 
passes  downward  and  backward.  The  two  bellies  terminate  in  the  central 
tendon  which  perforates  the  Stylo-hyoid,  and  is  held  in  connection  with  the  side 
of  the  body  and  the  greater  cornu  of  the  hyoid  bone  by  a  fibrous  loop,  lined  by  a 
synovial  membrane.  A  broad  aponeurotic  layer  is  given  off  from  the  tendon  of 
the  Digastric  on  each  side,  which  is  attached  to  the  body  and  great  cornu  of  the 
hyoid  bone :  this  is  termed  the  supra-hyoid  aponeurosis.  It  forms  a  strong  layer 
of  fascia  between  the  anterior  portion  of  the  two  muscles,  and  a  firm  investment 
for  the  other  muscles  of  the  supra-hyoid  region  which  lie  deeper. 

The  Digastric  muscle  divides  the  anterior  superior  triangle  of  the  neck  into 
two  smaller  triangles ;  the  upper,  or  submaxillary,  being  bounded,  above,  by  the 
lower  border  of  the  body  of  the  jaAV,  and  a  line  drawn  from  its  angle  to  the 
mastoid  process ;  below,  by  the  posterior  belly  of  the  Digastric  and  the  Stylo- 
hyoid muscles  ;  in  front,  by  the  middle  line  of  the  neck  and  the  anterior  belly  of  the 
Digastric,  the  lower  or  superior  carotid  triangle  being  bounded  above  by  the  poste- 
rior belly  of  the  Digastric,  behind  by  the  Sterno-mastoid,  below  by  the  Omo-hyoid. 

21 


322  THE  MUSCLES  AND    FASCIA. 

b  Relations. — By  its  superficial  surface  with  the  mastoid  process,  the  Platysma7 
frerno-niastoid,  part  of  the  Splenitis,  Trachelo-mastoid,  and  Stylo-hyoid  muscles, 
lid  the  parotid  gland.  By  its  deep  surface,  the  anterior  belly  lies  on  the  Mylo- 
nyoid ;  the  posterior  belly  on  the  Stylo-glossus,  Stylo-pharyngeus,  and  Hyo-glossus 
muscles,  the  external  carotid  artery  and  its  occipital,  lingual,  facial,  and  ascending 
pharyngeal  branches,  the  internal  carotid  artery,  internal  jugular  vein,  and  hypo- 
glossal nerve. 

The  Stylo-hyoid  is  a  small,  slender  muscle,  lying  in  front  of,  and  above,  the 
posterior  belly  of  the  Digastric.  It  arises  from  the  back  and  outer  surface  of  the 
styloid  process,  near  the  base ;  and,  passing  downward  and  forward,  is  inserted  into 
the  body  of  the  hyoid  bone,  just  at  its  junction  with  the  greater  cornu,  and  imme- 
diately above  the  Omo-hyoid.  This  muscle  is  perforated,  near  its  insertion,  by  the 
tendon  of  the  Digastric. 

Relations. — By  its  superficial  surface  above  with  the  parotid  gland  and  deep 
cervical  fascia;  below  it  is  superficial,  being  situated  immediately  beneath  the  deep 
cervical  fascia.  By  its  deep  surface,  with  the  posterior  belly  of  the  Digastric,  the 
external  carotid  artery,  with  its  lingual  and  facial  branches,  the  Hyo-glossus 
muscle,  and  the  hypoglossal  nerve. 

The  Stylo-hyoid  Ligament. — In  connection  with  the  Stylo-hyoid  muscle  may  be 
described  a  ligamentous  band,  the  Stylo-hyoid  ligament.  It  is  a  fibrous  cord,  often 
containing  a  little  cartilage  in  its  centre,  which  continues  the  styloid  process  down 
to  the  hyoid  bone,  being  attached  to  the  tip  of  the  former  and  the  small  cornu  of 
the  latter.  It  is  often  more  or  less  ossified,  and  in  many  animals  forms  a  distinct 
bone,  the  epihyal. 

The  anterior  belly  of  the  Digastric  should  be  removed,  in  order  to  expose  the  next  muscle. 

The  Mylo-hyoid  is  a  flat,  triangular  muscle,  situated  immediately  beneath  the 
anterior  belly  of  the  Digastric,  and  forming,  with  its  fellow  of  the  opposite  side,  a 
muscular  floor  for  the  cavity  of  the  mouth.  It  arises  from  the  whole  length  of  the 
mylo-hyoid  ridge  of  the  lower  jaw,  extending  from  the  symphysis  in  front  to  the 
last  molar  tooth  behind.  The  posterior  fibres  pass  inward  and  slightly  downward, 
to  be  inserted  into  the  body  of  the  os  hyoides.  The  middle  and  anterior  fibres  are 
inserted  into  a  median  fibrous  raphe-,  extending  from  the  symphysis  of  the  lower 
jaw  to  the  hyoid  bone,  where  they  join  at  an  angle  with  the  fibres  of  the  opposite 
muscle.  The  median  raphe"  is  sometimes  wanting ;  the  muscular  fibres  of  the  two 
sides  are  then  directly  continuous  with  one  another. 

Relations. — By  its  cutaneous  or  under  surface,  with  the  Platysma,  the  anterior 
belly  of  the  Digastric,  the  supra-hyoid  aponeurosis,  the  submaxillary  gland,  sub- 
mental vessels,  and  mylo-hyoid  vessels  and  nerve;  by  its  deep  or  superior  surface, 
with  the  Genio-hyoid,  part  of  the  Hyo-glossus  and  Stylo-glossus  muscles,  the  hypo- 
glossal and  lingual  nerves,  the  submaxillary  ganglion,  the  sublingual  gland,  the 
deep  portion  of  the  submaxillary  gland,  and  Wharton's  duct ;  the  sublingual  and 
ranine  vessels,  and  the  buccal  mucous  membrane. 

Dissection. — The  Mylo-hyoid  should  now  be  removed,  in  order  to  expose  the  muscles  which 
lie  beneath  ;  this  is  effected  by  reflecting  it  from  its  attachments  to  the  hyoid  bone  and  jaw,  and 
separating  it  by  a  vertical  incision  from  its  fellow  of  the  opposite  side. 

The  Genio-hyoid  is  a  narrow,  slender  muscle,  situated  immediately  beneath 1  the 
inner  border  of  the  preceding.  It  arises  from  the  inferior  genial  tubercle  on  the 
inner  side  of  the  symjmysis  of  the  jaAv,  and  passes  downward  and  backward,  to 
be  inserted  into  the  anterior  surface  of  the  body  of  the  os  hyoicles.  This  muscle 
lies  in  close  contact  with  its  fellow  of  the  opposite  side,  and  increases  slightly  in 
breadth  as  it  descends. 

Relations. — It  is  covered  by  the  Mylo-hyoid,  and  lies  along  the  lower  border 
of  the  Genio-hyo-glossus. 

Nerves. — The  Digastric  is  supplied  :  its  anterior  belly,  by  the  mylo-hyoid  branch 

1  This  refers  to  the  depth  of  the  muscles  from  the  skin  in  the  order  of  dissection.  In  the  erect 
position  of  the  body  each  of  these  muscles  lies  above  the  preceding. 


THE   LINGUAL    REGION. 


323 


of  the  inferior  dental;  its  posterior  belly,  by  the  facial;  the  Stylo-hyoid,  by  tb'n 
facial ;  the  Mylo-hyoid,  by  the  mylo-hyoid  branch  of  the  inferior  dentaf ;  the  Gen^al 
hyoid,  by  the  hypoglossal.  pon 

Actions. — This  group  of  muscles  performs  two  very  important  actions.      T  .s^e 
raise  the  hyoid  bone,  and  with  it  the  base  of  the  tongue,  during  the  act  of  de^lis  in 
tion ;  or,  when  the  hyoid  bone  is  fixed  by  its  depressors  and  those  of  the  laP0SSUS 
they  depress  the  lower  jaw.     During  the  first  act  of  deglutition,  when  the 
is  being  driven  from  the  mouth  into  the  pharynx,  the  hyoid  bone,  and  with  i^rotid 
tongue,  is  carried  upward  and  forward  by  the  anterior  belly  of  the  Digastric,  the 
Mylo-hyoid,  and  Genio-hyoid  muscles.     In  the  second  act,  when  the  mass  is  pass- 
ing through  the  pharynx,  the  direct  elevation  of  the  hyoid  bone  takes  place  by 
the  combined  action  of  all  the  muscles ;  and  after  the  food  has  passed  the  hyoid 
bone  is  carried  upward  and  backward  by  the  posterior  belly  of  the  Digastric  and 
Stylo-hyoid  muscles,  which  assist  in  preventing  the  return  of  the  morsel  into  the 
mouth. 

4.  Lingual  Region. 

Genio-hyo-glossus.  Stylo-glossus. 

Hyo-glossus.  Palato-glossus. 

Chondro-glossus. 

Dissection. — After  completing  the  dissection  of  the  preceding  muscles,  saw  through  the 
lower  jaw  just  external  to  the  symphysis.  _  Then  draw  the  tongue  forward,  and  attach  it,  by  a 
stitch,  to  the  nose ;  when  its  muscles,  which  are  thus  put  on  the  stretch,  may  be  examined. 

The  Genio-hyo-glossus  has  received  its  name  from  its  triple  attachment  to  the 
jaw,  hyoid  bone,  and  tongue,  but  it  would  be  better  named  the   Genio-glossus, 


Fig.  204.— Muscles  of  the  tongue.    Left  side. 

since  its  attachment  to  the  hyoid  bone  is  very  slight  or  altogether  absent.     It  is  a 
flat,  triangular  muscle,  placed  vertically  on  either  side  of  the  middle  line,  its  apex 


324 


THE  MUSCLES  AND    FASCIAE. 


•orresponding  with  its  point  of  attachment  to  the  lower  jaw,  its  base  with  its 

p  sertion  into  the  tongue  and  hyoid  bone.      It  arises  by  a  short  tendon  from  the 

nd  oerjor  genial  tubercle  on  the  inner  side  of  the  symphysis  of  the  jaw,  immediately 

nyoiCye  tne  Genio-hyoid  ;  from  this  point  the  muscle  spreads  out  in  a  fan-like  form, 

muscLv  0f  the  inferior  fibres  passing  downward,  to  be  attached  by  a  thin  aponeurosis 

pharyithe  upper  part  of  the  body  of  the  hyoid  bone,  a  few  fibres  passing  between 

glossal  lyo-glossus  and  Chondro-glossus  to  blend  with  the  Constrictor  muscles  of  the 

^hynx ;  the  middle  fibres  passing  backward,  and  the  superior  ones  upward  and 

forward,  to  enter  the  whole  length  of  the  under  surface  of  the  tongue,  from  the 

base  to  the  apex.      The  two  muscles  lie  on  either  side  of  the  median  plane;  behind, 

they  are  quite  distinct  from  each  other,  and  are  separated  at  their  insertion  into 

the  under  surface  of  the  tongue  by  a  tendinous  raphe*,  which  extends  through  the 

middle  of  the  organ ;  in  front,  the  two  muscles  are  more  or  less  blended :  distinct 

fasciculi  are  to  be  seen  passing  off  from  one  muscle,  crossing  the  middle  line, 

and  intersecting  with  bundles  of  fibres  derived  from  the  muscle  on  the  other  side 

(Fig.  205). 

Relations. — By  its  internal  surface  it  is  in  contact  with  its  fellow  of  the  opposite 
side;  by  its  external  surface,  with  the  Inferior  lingualis,  the  Hyo-glossus,  the  lin- 
gual artery  and  hypoglossal  nerve,  the  lingual  nerve,  and  sublingual  gland ;  by 

its  upper  border,  with  the  mucous  membrane  of 
the  floor  of  the  mouth  (fraenum  linguae) ;  by  its 
lower  border,  with  the  Genio-hyoid. 

The  Hyo-glossus  is  a  thin,  flat,  quadrilateral 
muscle  which  arises  from  the  side  of  the  body 
and  whole  length  of  the  greater  cornu  of  the 
hyoid  bone,  and  passes  almost  vertically  upward 
to  enter  the  side  of  the  tongue,  between  the 
Stylo-glossus  and  Lingualis.  Those  fibres  of 
this  muscle  wThich  arise  from  the  body  are 
directed  upward  and  backward,  overlapping 
those  arising  from  the  greater  cornu,  wThich  are 
directed  upward  and  forward. 

Relations. — By  its  external  surface,  with  the 
Digastric,  the  Stylo-hyoid,  Stylo-glossus,  and 
jVTylo-hyoid  muscles,  the  submaxillary  ganglion, 
the  lingual  and  hypoglossal  nerves,  Wharton's 
duct,  the  ranine  vein,  the  sublingual  gland,  and 
the  deep  portion  of  the  submaxillary  gland. 
By  its  deep  surface,  with  the  Stylo-hyoid  liga- 
ment, the  Genio-hvo-glossus.  Lingualis,  and 
Middle  constrictor,  the  lingual  vessels,  and  the 
glosso-pharyngeal  nerve. 

The  Chondro-glossus  is  a  distinct  muscular 

slip,  though  it  is  sometimes  described  as  a  part 

of  the  Hvo-glossus,  from  which,  however,  it  is 

separated  by  the  fibres  of  the  Genio-hyo-glossus, 

which  pass  to  the  side  of  the  pharynx.     It  is 

about  three-quarters  to  an  inch  in  length,  and 

arises  from  the  inner  side  and  base  of  the  lesser 

cornu  and  contiguous  portion  of  the  body  of  the 

hyoid  bone,  and  passes  directly  upward  to  blend  with  the  intrinsic  muscular  fibres 

of  the  tongue,  between  the  Hyo-glossus  and  Genio-hyo-glossus.     A  small  slip  of 

muscular  fibre  is  occasionally  found,   arising  from  the  cartilago    triticia   in  the 

thyro-hyoid  ligament,  and  passing  upward  and  forward  to  enter  the  tongue  with 

the  hindermost  fibres  of  the  Hyo-glossus. 

The  Stylo-glossus,  the  shortest  and  smallest  of  the  three  styloid  muscles,  arises 
from  the  anterior  and  outer  side  of  the  styloid  process,  near  its  apex,  and  from  the 


CHONDRO-GLOSSUS. 

Fig.  205.— Muscles  of  the  tongue  from  be- 
low. (From,  a  preparation  in  the  Museum  of 
the  Royal  College  of  Surgeons  of  England.) 


THE   LINGUAL    REGION. 


325 


stylomandibular  ligament,  to  which  its  fibres,  in  most  cases,  are  attached  by  a  thin 

aponeurosis.     Passing  downward  and  forward  between  the  internal  and  external 

irotid  arteries,  and  becoming  nearly  horizontal  in  its  direction,  it  divides  upon 

v  side  of  the  tongue  into  two  portions  :   one  longitudinal,  which  enters  the  side 

&ie  tongue  near  its  dorsal  surface,  blending  with  the  fibres  of  the  Lingualis  in 

v    of  the  Hyo-glossus ;    the   other   oblique,    which   overlaps  the  Hyo-glossus 

me  and  decussates  with  its  fibres. 

Relations. — By  its  external  surface,  from  above  downward,  with  the  parotid 
j and,  the  Internal  pterygoid  muscle,  the  lingual  nerve,  and  the  mucous  membrane 
of  the  mouth ;  by  its  internal  surface,  with  the  tonsil,  the  Superior  constrictor, 
and  the  Hyo-glossus  muscle. 

The  Palato-glossus,  or  Constrictor  isthmi  faucium,  although  it  is  one  of  the 
muscles  of  the  tongue,  serving  to  draw  its  base  upward  during  the  act  of  degluti- 
tion, is  more  nearly  associated  with  the  soft  palate,  both  in  its  situation  and  func- 
tion;  it  will  consequently  be  described  with  that  group  of  muscles. 

Nerves. — The  Palato-glossus  is  probably  innervated  by  the  spinal  accessory  nerve, 
through  the  pharyngeal  plexus ;  the  remaining  muscles  of  this  group,  by  the  hypo- 
glossal. 

Muscular  Substance  of  Tongue. — The  muscular  fibres  of  the  tongue  run  in  vari- 
ous directions.  These  fibres  are  divided  into  two  sets — Extrinsic  and  Intrinsic. 
"The  extrinsic  muscles  of  the  tongue  are  those  which  have  their  origin  external, 
and  only  their  terminal  fibres  contained  in  the  substance  of  the  organ.  They  are  : 
the  Stylo-glossus,  the  Hyo-glossus,  the  Palato-glossus,  the  Genio-hyo-glossus,  and 
part  of  the  Superior  constrictor  of  the  pharynx  (Pharyngeo-glossus).  The  intrinsic 
are  those  which  are  contained  entirely  within  the  tongue,  and  form  the  greater 
part  of  its  muscular  structure. 

The  tongue  consists  of  symmetrical  halves 
separated  from  each  other  in  the  middle  line  by 
a  fibrous  septum.  Each  half  is  composed  of 
muscular  fibres  arranged  in  various  directions, 
containing  much  interposed  fat,  and  supplied  by 
vessels  and  nerves. 

/ 


(M^^j^JvwnnhAAAArirwnn 


S— h 


CUT    EDGE    OF   SUPERIOR    LINGUALIS. 

Fig.  206. — Muscles  on  the  dorsum  of  the 


Fig.  207.— Coronal  section  of  tongue.  Showing  intrinsic 
muscles.  (Altered  from  Krause.)  a,  lingual  artery;  b,  Inferior 
lingualis,  cut  through ;  c,  fibres  of  Hyo-glos.sus  ;  d,  oblique  fibres 
of  Stylo-glossus;  e,  insertion  of  Transverse  lingualis:  /,  Supe- 
rior lingualis  ;  (i,  papillae  to  tongue  :  1>,  vertical  fibres  <.f  Oenio- 
nyo-glossus  intersecting  Transverse  lingualis  ;  i,  septum. 


tongue. 


To  demonstrate  the  various  fibres  of  the  tongue,  the  organ  should  be  sub- 
jected to   prolonged  boiling,  in  order  to  soften  the  connective  tissue;  the  dis- 


326  THE   MUSCLES  AND    FASCIA. 

section  may  then  be  commenced  from  the  dorsum  (Fig.  206).  Immediately 
beneath  the  mucous  membrane  is  a  submucous,  fibrous  layer,  into  which  the 
muscular  fibres  which  terminate  on  the  surface  of  the  tongue  are  inserted.  Upon 
removing*;  this,  with  the  mucous  membrane,  the  first  stratum  of  muscular  fibres  is 
exposed.  This  belongs  to  the  group  of  intrinsic  muscles,  and  has  been  named  the 
Superior  lingualis  (m.  longitudinalis  superior).  It  consists  of  a  thin  layer  of 
oblique  and  longitudinal  fibres  which  arise  from  the  submucous  fibrous  layer,  close 
to  the  Epiglottis,  and  from  the  fibrous  septum,  and  pass  forward  and  outward  to 
the  edges  of  the  tongue.  Between  its  fibres  pass  some  vertical  fibres  derived  from 
the  Genio-hyo-glossus  and  from  the  vertical  intrinsic  muscle,  which  will  be  described 
later  on.  Beneath  this  layer  is  the  second  stratum  of  muscular  fibres,  derived  prin- 
cipally from  the  extrinsic  muscles.  In  front  it  is  formed  by  the  fibres  derived  from 
the  Stylo-glossus,  running  along  the  side  of  the  tongue,  and  sending  one  set  of  fibres 
over  the  dorsum  which  runs  obliquely  forward  and  inward  to  the  middle  line,  and 
another  set  of  fibres,  seen  at  a  later  period  of  the  dissection,  on  to  the  under  surface 
of  the  sides  of  the  anterior  part  of  the  tongue,  which  run  forward  and  inward, 
between  the  fibres  of  the  Hyo-glossus,  to  the  middle  line.  Behind  this  layer  of 
fibres,  derived  from  the  Stylo-glossus,  are  fibres  derived  from  the  Hyo-glossus, 
assisted  by  some  few  fibres  of  the  Palato-glossus.  The  Hyo-glossus,  entering  the 
side  of  the  under  surface  of  the  tongue,  between  the  Stylo-glossus  and  Inferior  lin- 
gualis,  passes  round  its  margin  and  spreads  out  into  a  layer  on  the  dorsum,  which 
occupies  the  middle  third  of  the  organ,  and  runs  almost  transversely  inward  to  the 
septum.  It  is  reinforced  by  some  fibres  from  the  Palato-glossus ;  other  fibres  of  this 
muscle  pass  more  deeply  and  intermingle  with  the  next  layer.  The  posterior  part 
of  the  second  layer  of  the  muscular  fibres  of  the  tongue  is  derived  from  those 
fibres  of  the  Hyo-glossus  which  arise  from  the  lesser  cornu  of  the  hyoid  bone,  and 
are  here  described  as  a  separate  muscle — the  Chondro-glossus.  The  fibres  of  this 
muscle  are  arranged  in  a  fan-shaped  manner,  and  spread  out  over  the  posterior 
third  of  the  tongue.  Beneath  this  layer  is  the  great  mass  of  the  intrinsic  muscles 
of  the  tongue,  intersected  at  right  angles  by  the  terminal  fibres  of  one  of  the 
extrinsic  muscles — the  Genio-hyo-glossus.  This  portion  of  the  tongue  is  paler 
in  color  and  softer  in  texture  than  that  already  described,  and  is  sometimes 
designated  the  medullary  portion  in  contradistinction  to  the  firmer  superficial  part, 
which  is  termed  the  cortical  portion.  It  consists  largely  of  transverse  fibres,  the 
Transverse  lingualis  (m.  transversus  linguce),  and  of  vertical  fibres,  the  Vertical 
lingualis  (m.  vertioulis  linguce).  The  Transverse  lingualis  forms  the  largest  portion 
of  the  third  layer  of  muscular  fibres  of  the  tongue.  The  fibres  arise  from  the 
median  septum,  and  pass  outward  to  be  inserted  into  the  submucous  fibrous  layer 
at  the  sides  of  the  tongue.  Intermingled  with  these  transverse  intrinsic  fibres  are 
transverse  extrinsic  fibres  derived  from  the  Palato-glossus  and  the  Superior  con- 
strictor of  the  pharynx.  These  transverse  extrinsic  fibres,  however,  run  in  the 
opposite  direction,  passing  inward  toward  the  septum.  Intersecting  the  transverse 
fibres  are  a  large  number  of  vertical  fibres  derived  partly  from  the  Genio-hyo- 
glossus  and  partly  from  intrinsic  fibres,  the  Vertical  lingualis.  The  fibres  derived 
from  the  Genio-hyo-glossus  enter  the  under  surface  of  the  tongue  on  each  side  of 
the  median  septum  from  base  to  apex.  They  ascend  in  a  radiating  manner  to  the 
dorsum,  being  inserted  into  the  submucous  fibrous  layer  covering  the  tongue  on 
each  side  of  the  middle  line.  The  Vertical  lingualis  is  found  only  at  the  borders 
of  the  fore  part  of  the  tongue,  external  to  the  fibres  of  the  Genio-hyo-glossus. 
Its  fibres  extend  from  the  upper  to  the  under  surface  of  the  organ,  decussating 
with  the  fibres  of  the  other  muscles,  and  especially  with  the  Transverse  lingualis. 
The  fourth  layer  of  muscular  fibres  of  the  tongue  consists  partly  of  extrinsic  fibres 
derived  from  the  Stylo-glossus,  and  partly  of  intrinsic  fibres,  the  Inferior  lingualis 
(m.  longitudinalis  inferior).  At  the  sides  of  the  under  surface  of  the  organ  are 
some  fibres  derived  from  the  Stylo-glossus,  which,  as  it  runs  forward  at  the  side  of 
the  tongue,  gives  off  fibres  which,  passing  forward  and  inward  between  the  fibres 
of  the  Hyo-glossus,  form  an  inferior  oblique  stratum  which  joins  in  front  with  the 


THE  PHARYNGEAL    REGION.  327 

anterior  fibres  of  the  Inferior  lingualis.  The  Inferior  lingualis  is  a  longitudinal 
band,  situated  on  the  under  surface  of  the  tongue,  and  extending  from  the  base  to 
the  apex  of  the  organ.  Behind,  some  of  its  fibres  are  connected  with  the  body  of 
the  hyoid  bone.  It  lies  between  the  Hyo-glossus  and  the  Genio-hyo-glossus,  and 
in  front  of  the  Hyo-glossus  it  gets  into  relation  with  the  Stylo-glossus,  with  the 
fibres  of  which  it  blends.  It  is  in  relation  by  its  under  surface  with  the  ranine 
artery. 

Surgical  Anatomy. — The  fibrous  septum  which  exists  between  the  two  halves  of  the 
tongue  is  very  complete,  so  that  the  anastomosis  between  the  two  lingual  arteries  is  not  very 
tree,  a  fact  often  illustrated  by  injecting  one-half  of  the  tongue  with  colored  size,  while  the  other 
half  is  left  uninjected  or  is  injected  with  size  of  a  different  color. 

This  is  a  point  of  considerable  importance  in  connection  with  removal  of  one-half  of  the 
tongue  for  cancer,  an  operation  which  is  now  frequently  resorted  to  when  the  disease  is  strictly 
confined  to  one  side  of  the  tongue.  If  the  mucous  membrane  is  divided  longitudinally  exactly 
in  the  middle  line,  the  tongue  can  be  split  into  halves  along  the  median  raphe  without  any 
appreciable  haemorrhage,  and  the  diseased  half  can  then  be  removed. 

Actions. — The  movements  of  the  tongue,  although  numerous  and  complicated, 
may  be  understood  by  carefully  considering  the  direction  of  the  fibres  of  its 
muscles.  The  G-enio-hyo-glossi  muscles,  by  means  of  their  posterior  fibres,  draw 
the  base  of  the  tongue  forward,  so  as  to  protrude  the  apex  from  the  mouth.  The 
anterior  fibres  draw  the  tongue  back  into  the  mouth.  The  whole  length  of  these 
two  muscles,  acting  along  the  middle  line  of  the  tongue,  draw  it  downward,  so  as  to 
make  it  concave  from  side  to  side,  forming  a  channel  along  which  fluids  may  pass 
toward  the  pharynx,  as  in  sucking.  The  Hyo-glossi  muscles  depress  the  tongue 
and  draw  down  its  sides,  so  as  to  render  it  convex  from  side  to  side.  The  Stylo- 
glossi muscles  draw  the  tongue  upward  and  backward.  The  Palato-glossi  muscles 
draw  the  base  of  the  tongue  upward.  With  regard  to  the  intrinsic  muscles,  both 
the  Superior  and  Inferior  linguales  tend  to  shorten  the  tongue,  but  the  former,  in 
addition,  turn  the  tip  and  sides  upward  so  as  to  render  the  dorsum  concave,  while 
the  latter  pull  the  tip  downward  and  cause  the  dorsum  to  become  convex.  The 
Transverse  lingualis  narrows  and  elongates  the  tongue,  and  the  Vertical  lingualis 
flattens  and  broadens  it.  The  complex  arrangement  of  the  muscular  fibres  of 
the  ton-gue,  and  the  various  directions  in  which  they  run,  give  to  this  organ  the 
power  of  assuming  the  various  forms  necessary  for  the  enunciation  of  the  different 
consonantal  sounds ;  and  Dr.  Macalister  states  that  "  there  is  reason  to  believe 
that  the  musculature  of  the  tongue  varies  in  different  races  owing  to  the  hereditary 
practice  and  habitual  use  of  certain  motions  required  for  enunciating  the  several 
vernacular  languages." 

5.  Pharyngeal  Region. 

Inferior  constrictor.  Superior  constrictor. 

Middle  constrictor.  Stylo-pharyngeus. 

Palato-pharyngeus.       1       /c,  ,■      \ 

a  i   •  -\  Y      (See  next  section.) 

balpmgo-pharyngeus.  j       v  7 

Dissection  (Fig.  208). — In  order  to  examine  the  muscles  of  the  pharynx,  cut  through  the 
trachea  and  oesophagus  just  above  the  sternum,  and  draw  them  upward  by  dividing  the  loose 
areolar  tissue  connecting  the  pharynx  with  the  front  of  the  vertebral  column.  The  parts  being 
drawn  well  forward,  apply  the  edge  of  the  saw  immediately  behind  the  styloid  processes,  and 
saw  the  base  of  the  skull  through  from  below  upward.  The  pharynx  and  mouth  should  then 
be  stuffed  with  tow,  in  order  to  distend  its  cavity  and  render  the  muscles  tense  and  easier  of 
dissection. 

The  Inferior  constrictor,  the  most  superficial  and  thickest  of  the  three  con- 
strictors, arises  from  the  sides  of  the  cricoid  and  thyroid  cartilages.  To  the 
cricoid  cartilage  it  is  attached  in  the  interval  between  the  Crico-thyroid  muscle 
in  front  and  the  articular  facet  for  the  thyroid  cartilage  behind.  To  the  thyroid 
cartilage  it  is  attached  to  the  oblique  line  on  the  side  of  the  great  ala,  the 
cartilaginous  surface  behind  it,  nearly  as  far  as  its  posterior  border,  and  to  the 
inferior  cornu.  From  these  attachments  the  fibres  spread  backward  and  inward, 
to  be  inserted  into  the  fibrous  raphe  in  the  posterior  median  line  of  the  pharynx. 


328 


THE   MUSCLES   AND    FASCIJE. 


The  inferior  fibres  are  horizontal,  and  continuous  -with  the  fibres  of  the  oesophagus : 
the  rest  ascend,  increasing  in  obliquity,  and  overlap  the  Middle  constrictor. 

Relations. — It  is  covered  by  a  thin  membrane  which  surrounds  the  entire 
pharynx  (bucco-pharyngeal  fascia).      Behind,  it  is  in  relation  with  the  vertebral 

column  and  the  prevertebral  fascia  and 
muscles  ;  laterally,  with  the  thyroid  gland, 
the  common  carotid  artery,  and  the 
Sterno-thyroid  muscle :  by  its  internal 
surface,  with  the  Middle  constrictor,  the 
Stvlo-pharvngeus,  Palato-pharvngeus.  the 
fibrous  coat  and  mucous  membrane  of  the 
pharynx.  The  internal  laryngeal  nerve 
and  the  laryngeal  branch  of  the  Superior 
Thyroid  artery  pass  near  the  upper  bor- 
der, and  the  inferior,  or  recurrent  laryn- 
geal nerve,  and  the  laryngeal  branch  of 
the  Inferior  Thyroid  artery,  beneath  the 
lower  border  of  this  muscle,  previous  to 
their  entering  the  larynx. 

The  Middle  constrictor  is  a  flattened, 
fan-shaped  muscle,  smaller  than  the  pre- 
ceding. It  arises  from  the  whole  length 
of  the  upper  border  of  the  greater  cornu 
of  the  hyoid  bone,  from  the  lesser  cornu, 
and  from  the  stylo-hyoid  ligament.  The 
fibres  diverge  from  their  origin,  the  lower 
ones  descending  beneath  the  Inferior  con- 
strictor, the  middle  fibres  passing  trans- 
versely, and  the  upper  fibres  ascending 
and  overlapping  the  Superior  constrictor. 
The  muscle  is  inserted  into  the  posterior 
median  fibrous  raphe',  blending  in  the  mid- 
dle line  with  the  one  of  the  opposite  side. 
Relations. — This  muscle  is  separated  from  the  Superior  constrictor  by  the 
glosso-pharyngeal  nerve  and  the  Stylo-pharyngeus  muscle  and  Stylo-hyoid  liga- 
ment;  and  from  the  Inferior  constrictor  by  the  superior  laryngeal  nerve.  Behind, 
it  lies  on  the  vertebral  column,  the  Longus  colli,  and  the  Rectus  capitis  anticus 
major.  On  each  side  it  is  in  relation  with  the  carotid  vessels,  the  pharyngeal 
plexus,  and  some  lymphatic  glands.  Near  its  origin  it  is  covered  by  the  Hyo- 
glossus,  from  which  it  is  separated  by  the  lingual  vessels.  It  lies  upon  the 
Superior  constrictor,  the  Stylo-pharyngeus,  the  Palato-pharyngeus.  the  fibrous 
coat,  and  the  mucous  membrane  of  the  pharynx. 

The  Superior  Constrictor  is  a  quadrilateral  muscle,  thinner  and  paler  than  the 
other  constrictors,  and  situated  at  the  upper  part  of  the  pharynx.  It  arises  from 
the  lower  third  of  the  posterior  margin  of  the  internal  pterygoid  plate  and  its 
hamular  process,  from  the  contiguous  portion  of  the  palate  bone  and  the  reflected 
tendon  of  the  Tensor. palati  muscle,  from  the  pterygo-maxiliary  ligament,  from  the 
alveolar  process  above  the  posterior  extremity  of  the  mylo-hyoid  ridge,  and  by  a 
few  fibres  from  the  side  of  the  tongue.  From  these  points  the  fibres  curve  back- 
ward, to  be  inserted  into  the  median  raphe,  being  also  prolonged  by  means  of  a 
fibrous  aponeurosis  to  the  pharyngeal  spine  on  the  basilar  process  of  the  occipital 
bone.  The  superior  fibres  arch  beneath  the  Levator  palati  and  the  Eustachian 
tube,  the  interval  between  the  upper  border  of  the  muscle  and  the  basilar  process 
being  deficient  in  muscular  fibres  and  closed  by  the  pharyngeal  aponeurosis.  This 
interval  is  known  as  the  sinus  of  Morgagni. 

Relations. — By  its  outer  surface,  with  the  prevertebral  fascia  and  muscles, 
the  vertebral  column,  the  internal  carotid  and  ascending  pharyngeal  arteries,  the 


Fig.  208.— Muscles  of  the  pharynx.    External  view. 


THE   PALATAL    REGION.  329 

internal  jugular  vein  and  pharyngeal  venous  plexus,  the  glossopharyngeal,  pneu- 
mogastric,  spinal  accessory,  hypoglossal,  lingual,  and  sympathetic  nerves,  the 
Middle  constrictor  and  Internal  pterygoid  muscles,  the  Styloid  process,  the  Stylo- 
hyoid ligament,  and  the  Stylo-pharyngeus.  By  its  internal  surface,  with  the 
Palato-pharyngeus,  the  tonsil,  the  fibrous  coat  and  mucous  membrane  of  the 
pharynx. 

The  Stylo-pharyngeus  is  a  long,  slender  muscle,  round  above,  broad  and  thin 
below.  It  arises  from  the  inner  side  of  the  base  of  the  styloid  process,  passes 
downward  along  the  side  of  the  pharynx  between  the  Superior  and  Middle 
constrictors,  and  spreads  out  beneath  the  mucous  membrane,  where  some  of  its 
fibres  are  lost  in  the  Constrictor  muscles ;  and  others,  joining  with  the  Palato- 
pharyngeus,  are  inserted  into  the  posterior  border  of  the  thyroid  cartilage.  The 
glosso-pharyngeal  nerve  runs  on  the  outer  side  of  this  muscle,  and  crosses  over  it 
in  passing  forward  to  the  tongue. 

Relations. — Externally,  with  the  Stylo-glossus  muscle,  the  parotid  gland,  the 
■external  carotid  artery,  and  the  Middle  constrictor ;  internally,  with  the  internal 
carotid,  the  internal  jugular  vein,  the  Superior  constrictor,  Palato-pharyngeus,  and 
mucous  membrane. 

Nerves. — The  Constrictors  are  supplied  by  branches  from  the  pharyngeal 
plexus,  the  Stylo-pharyngeus  by  the  glosso-pharyngeal  nerve,  and  the  Inferior 
■constrictor  by  an  additional  branch  from  the  external  laryngeal  nerve  and  by  the 
recurrent  laryngeal. 

Actions. — When  deglutition  is  about  to  be  performed,  the  pharynx  is  drawn 
upward  and  dilated  in  different  directions,  to  receive  the  morsel  propelled  into  it 
from  the  mouth.  The  Stylo-pharyngei,  which  are  much  farther  removed  from 
one  another  at  their  origin  than  at  their  insertion,  draw  the  sides  of  the  pharynx 
upward  and  outward,  and  so  increase  its  transverse  diameter,  its  breadth  in  the 
antero-posterior  direction  being  increased  by  the  larynx  and  tongue  being  carried 
forward  in  their  ascent.  As  soon  as  the  morsel  is  received  in  the  pharynx,  the 
Elevator  muscles  relax,  the  bag  descends,  and  the  Constrictors  contract  upon 
the  morsel,  and  convey  it  gradually  downward  into  the  oesophagus.  Besides 
its  action  in  deglutition,  the  pharynx  also  exerts  an  important  influence  in  the 
modulation  of  the  voice,  especially  in  the  production  of  the  higher  tones. 

6.  Palatal  Region. 

Levator  palati.  Palato-glossus. 

Tensor  palati.  Palato-pharyngeus. 

Azygos  uvulae.  Salpingo-pharyngeus. 

Dissection  (Fig.  209). — Lay  open  the  pharynx  from  behind  by  a  vertical  incision  extending 
from  its  upper  to  its  lower  part,  and  partially  divide  the  occipital  attachment  by  a  transverse 
incision  on  each  side  of  the  vertical  one  ;  the  posterior  surface  of  the  soft  palate  is  then  exposed. 
Having  fixed  the  uvula  so  as  to  make  it  tense,  the  mucous  membrane  and  glands  should  be  care- 
fully removed  from  the  posterior  surface  of  the  soft  palate,  and  the  muscles  of  this  part  are  at 
once  exposed. 

The  Levator  palati  is  a  long,  thick,  rounded  muscle,  placed  on  the  outer  side 
of  the  posterior  nares.  It  arises  from  the  under  surface  of  the  apex  of  the  petrous 
portion  of  the  temporal  bone,  and  from  the  inner  surface  of  the  cartilaginous  por- 
tion of  the  Eusatchian  tube ;  after  passing  into  the  pharynx,  above  the  upper  con- 
cave margin  of  the  Superior  constrictor,  it  passes  obliquely  downward  and  inward, 
its  fibres  spreading  out  in  the  soft  palate  as  far  as  the  middle  line,  where  they 
blend  with  those  of  the  opposite  side. 

Relations. — Externally,  with  the  Tensor  palati  and  Superior  constrictor  and 
Eustachian  tube ;  internally,  with  the  mucous  membrane  of  the  pharynx  ;  pos- 
teriorly, with  the  posterior  fasciculus  of  the  Palato-pharyngeus,  the  Azygos  uvulae, 
and  the  mucous  lining  of  the  soft  palate. 

The  Circumflexus  or  Tensor  palati  is  a  broad,  thin,  ribbon-like  muscle,  placed 
on  the  outer  side  of  the  Levator  palati,  and  consisting  of  a  vertical  and  a  horizontal 


330 


THE   MUSCLES   AND    FASCIA. 


portion.  The  vertical  portion  arises  by  a  flat  lamella  from  the  scaphoid  fossa  at 
the  base  of  the  internal  pterygoid  plate ;  from  the  spine  of  the  sphenoid  and  the 
outer  side  of  the  cartilaginous  portion  of  the  Eustachian  tube :  descending  verti- 
cally between  the  internal  pterygoid  plate  and  the  inner  surface  of  the  Internal 
pterygoid  muscle,  it  terminates  in  a  tendon,  which  winds  round  the  hamular  proc- 
ess, being  retained  in  this  situation  by  some  of  the  fibres  of  origin  of  the  Internal 
pterygoid  muscle.  Between  the  hamular  process  and  the  tendon  is  a  small  bursa. 
The  tendon  or  horizontal  portion  then  passes  horizontally  inward,  and  is  inserted 
into  a  broad  aponeurosis,  the  palatine,  aponeurosis,  and  into  the  transverse  ridge 
on  the  horizontal  portion  of  the  palate  bone. 


Fig.  209.— Muscles  of  the  soft  palate,  the  pharynx  being  laid  open  from  behind. 

Relations. — Externally,  with  the  Internal  pterygoid ;  internally,  with  the 
Levator  palati,  from  which  it  is  separated  by  the  Eustachian  tube  and  Superior 
constrictor,  and  with  the  internal  pterygoid  plate.  In  the  soft  palate  its  tendon 
and  the  palatine  aponeurosis  are  anterior  to  those  of  the  Levator  palati,  being  cov- 
ered by  the  Palato-glossus  and  the  mucous  membrane. 

Palatine  Aponeurosis.— Attached  to  the  posterior  border  of  the  hard  palate  is 
a  thin,  firm,  fibrous  lamella  which  supports  the  muscles  and  gives  -strength  to  the 
soft  palate.  It  is  thicker  above  than  below,  where  it  becomes  very  thin  and 
difficult  to  define.     Laterally,  it  is  continuous  with  the  pharyngeal  aponeurosis. 

The  Azygos  uvulse  is  not  a  single  muscle,  as  would  be  inferred  from  its  name, 
but  a  pair  of  narrow  cylindrical  fleshy  fasciculi  placed  on  either  side  of  the  median 
line  of  the  soft  palate.  Each  muscle  arises  from  the  posterior  nasal  spine  of  the 
palate  bone  and  from  the  contiguous  tendinous  aponeurosis  of  the  soft  palate,  and 
descends  to  be  inserted  into  the  uvula. 


THE   PALATAL    REGLON.  331 

Relations. — Anteriorly,  with  the  tendinous  expansion  of  the  Levatores  palati  ; 
behind,  with  the  posterior  fasciculus  of  the  Palato-pharyngeus  and  the  mucous 
membrane. 

The  two  next  muscles  are  exposed  by  removing  the  mucous  membrane  from  the  pillars  of 
the  fauces  throughout  nearly  their  whole  extent. 

The  Palato-glossus  (Constrictor  isthmi  faucium)  is  a  small  fleshy  fasciculus, 
narrower  in  the  middle  than  at  either  extremity,  forming,  with  the  mucous 
membrane  covering  its  surface,  the  anterior  pillar  of  the  soft  palate.  It  arises 
from  the  anterior  surface  of  the  soft  palate  on  each  side  of  the  uvula,  and,  passing 
downward,  forward,  and  outward  in  front  of  the  tonsil,  is  inserted  into  the  side 
of  the  tongue,  some  of  its  fibres  spreading  over  the  dorsum,  and  others  passing 
deeply  into  the  substance  of  the  organ  to  intermingle  with  the  Transversus  linguae. 
In  the  soft  palate  the  fibres  of  this  muscle  are  continuous  with  those  of  the  muscle 
of  the  opposite  side. 

The  Palato-pharyngeus  is  a  long,  fleshy  fasciculus,  narrower  in  the  middle  than 
at  either  extremity,  forming,  with  the  mucous  membrane  covering  its  surface,  the 
posterior  pillar  of  the  soft  palate.  It  is  separated  from  the  Palato-glossus  by  an 
angular  interval,  in  which  the  tonsil  is  lodged.  It  arises  from  the  soft  palate  by 
an  expanded  fasciculus,  which  is  divided  into  two  parts  by  the  Levator  palati  and 
Azygos  uvulae.  The  posterior  fasciculus  lies  in  contact  with  the  mucous  membrane, 
and  also  joins  with  the  corresponding  muscle  in  the  middle  line ;  the  anterior 
fasciculus,  the  thicker,  lies  in  the  soft  palate  between  the  Levator  and  Tensor,  and 
joins  in  the  middle  line  the  corresponding  part  of  the  opposite  muscle.  Passing 
outward  and  downward  behind  the  tonsil,  the  Palato-pharyngeus  joins  the  Stylo- 
pharyngeus,  and  is  inserted  with  that  muscle  into  the  posterior  border  of  the 
thyroid  cartilage,  some  of  its  fibres  being  lost  on  the  side  of  the  pharynx,  and 
others  passing  across  the  middle  line  posteriorly  to  decussate  with  the  muscle  of 
the  opposite  side. 

Relations. — In  the  soft  palate  its  'posterior  surface  is  covered  by  mucous 
membrane,  from  which  it  is  separated  by  a  layer  of  palatine  glands.  By  its 
anterior  surface  it  is  in  relation  with  the  Tensor  palati.  Where  it  forms  the 
posterior  pillar  of  the  fauces  it  is  covered  by  mucous  membrane,  excepting  on 
its  outer  surface.  In  the  pharynx  it  lies  between  the  mucous  membrane  and  the 
Constrictor  muscles. 

The  Salpingo-pharyngeus. — This  muscle  arises  from  the  inferior  part  of  the 
Eustachian  tube  near  its  orifice ;  it  passes  downward  and  blends  with  the  posterior 
fasciculus  of  the  Palato-pharyngeus. 

In  a  dissection  of  the  soft  palate  from  its  posterior  or  nasal  surface  to  its  anterior 
or  oral  surface,  the  muscles  would  be  exposed  in  the  following  order :  viz.  the 
posterior  fasciculus  of  the  Palato-pharyngeus,  covered  over  by  the  mucous  membrane 
reflected  from  the  floor  of  the  nasal  fossae  ;  the  Azygos  uvulae  ;  the  Levator  palati ; 
the  anterior  fasciculus  of  the  Palato-pharyngeus ;  the  aponeurosis  of  the  Tensor 
palati,  and  the  Palato-glossus  covered  over  by  a  reflection  from  the  oral  mucous 
membrane. 

Nerves. — The  Tensor  palati  is  supplied  by  a  branch  from  the  otic  ganglion ; 
the  remaining  muscles  of  this  group  are  in  all  probability  supplied  by  the  internal 
branch  of  the  spinal  accessory,  whose  fibres  are  distributed  along  with  certain 
branches  of  the  pneumogastric  through  the  pharyngeal  plexus.1  It  is  possible, 
however,  that  the  Levator  palati  may  be  supplied  by  the  facial  through  the 
Petrosal  branch  of  the  Vidian. 

Actions. — During  the  first  stage  of  deglutition  the  morsel  of  food  is  driven 
back  into  the  fauces  by  the  pressure  of  the  tongue  against  the  hard  palate,  the 
base  of  the  tongue  being,  at  the  same  time,  retracted,  and  the  larynx  raised  with 
the  pharynx,  and  carried  forward  under  it.  During  the  second  stage  the  entrance 
to  the  larynx  is  closed,  not,  as  was  formerly  supposed,  by  the  folding  backward 
1  Journal  of  Anatomy  and  Physiology,  vol.  xxiii.,  p.  523. 


332  THE   MUSCLES   AND    FASCIA. 

of  the  epiglottis  over  it,  but,  as  Anderson  Stuart  has  shown,  by  the  drawing 
forward  of  the  arytenoid  cartilages  toward  the  cushion  of  the  epiglottis — a  move- 
ment produced  by  the  contraction  of  the  external  thyro-arytenoid,  the  arytenoid, 
and  aryteno-epiglottidean  muscles. 

The  morsel  of  food  after  leaving  the  tongue  passes  on  to  the  posterior  or 
laryngeal  surface  of  the  epiglottis,  and  glides  along  this  for  a  certain  distance  ;J 
then  the  Palato-glossi  muscles,  the  constrictors  of  the  fauces,  contract  behind  the 
food  ;  the  soft  palate  is  slightly  raised  by  the  Levator  palati,  and  made  tense  by 
the  Tensor  palati ;  and  the  Palato-pharyngei,  by  their  contraction,  pull  the  pharynx 
upward  over  the  morsel  of  food,  and  at  the  same  time  come  nearly  together,  the 
uvula  filling  up  the  slight  interval  between  them.  By  these  means  the  food  is 
prevented  passing  into  the  upper  part  of  the  pharynx  or  the  posterior  nares ;  at 
the  same  time  the  latter  muscles  form  an  inclined  plane,  directed  obliquely  down- 
ward and  backward,  along  the  under  surface  of  which  the  morsel  descends  into 
the  lower  part  of  the  pharynx.  The  Salpingo-pharyngeus  raises  the  upper  and 
lateral  part  of  the  pharynx — i.  e.  that  part  which  is  above  the  point  where  the 
Stylo-pharyngeus  is  attached  to  the  pharynx. 

Surgical  Anatomy. — The  muscles  of  the  soft  palate  should  be  carefully  dissected,  the  rela- 
tions they  bear  to  the  surrounding  parts  especially  examined,  and  their  action  attentively  studied 
upon  the  dead  subject,  as  the  surgeon  is  required  to  divide  one  or  more  of  these  muscles  in  the 
operation  of  staphylorraphy.  Sir  W.  Fergusson  was  the  first  to  show  that  in  the  congenital 
deficiency  called  cleft  palate  the  edges  of  the  fissure  are  forcibly  separated  by  the  action  of  the 
Levatores  palati  and  Palato-pharyngei  muscles,  producing  very  considerable  impediment  to  the 
healing  process  after  the  performance  of  the  operation  for  uniting  their  margins  by  adhesion  ;  he, 
consequently,  recommended  the  division  of  these  muscles  as  one  of  the  most  important  steps  in 
the  operation.  This  he  effected  by  an  incision  made  with  a  curved  knife  introduced  behind  the 
soft  palate.  The  incision  is  to  be  halfway  between  the  hamular  process  and  Eustachian  tube, 
and  perpendicular  to  a  fine  drawn  between  them.  This  incision  perfectly  accomplishes  the 
division  of  the  Levator  palati.  The  Palato-pharyngeus  may  be  divided  by  cutting  across  the 
posterior  pillar  of  the  soft  palate,  just  below  the  tonsil,  with  a  pair  of  blunt-pointed  curved 
scissors ;  and  the  anterior  pillar  may  be  divided  also.  To  divide  the  Levator  palati  the  plan 
recommended  by  Mr.  Pollock  is  to  be  greatly  preferred.  The  soft  palate  being  put  upon  the 
Stretch,  a  double-edged  knife  is  passed  through  it  just  on  the  inner  side  of  the  hamular  process 
and  above  the  line  of  the  Levator  palati.  The  handle  being  now  alternately  raised  and 
depressed,  a  sweeping  cut  is  made  along  the  posterior  surface  of  the  soft  palate,  and  the  knife 
withdrawn,  leaving  only  a  small  opening  in  the  mucous  membrane  on  the  anterior  surface.  If 
this  operation  is  performed  on  the  dead  body  and  the  parts  afterward  dissected,  the  Levator 
palati  will  be  found  completely  divided.  In  the  present  day,  however,  this  division  of  the 
muscles,  as  part  of  the  operation  of  staphylorraphy,  is  not  so  much  insisted  upon.  All  tension 
is  prevented  by  making  longitudinal  incisions  on  either  side,  parallel  to  the  cleft  and  just 
internal  to  the  hamular  process,  in  such  a  position  as  to  avoid  the  posterior  palatine  artery. 

7.  Anterior  Vertebral  Region. 

Rectus  capitis  anticus  major.  Rectus  capitis  lateralis. 

Rectus  capitis  anticus  minor.  Longus  colli. 

The  Rectus  capitis  anticus  major  (Fig.  210),  broad  and  thick  above,  narrow 
below,  appears  like  a  continuation  upward  of  the  Scalenus  anticus.  It  arises  by 
four  tendinous  slips  from  the  anterior  tubercles  of  the  transverse  processes  of  the 
third,  fourth,  fifth,  and  sixth  cervical  vertebrae,  and  ascends,  converging  toward 
its  fellow  of  the  opposite  side,  to  be  inserted  into  the  basilar  process  of  the  occip- 
ital bone. 

Relations. — By  its  anterior  surface,  with  the  pharynx,  the  sympathetic  nerve, 
and  the  sheath  enclosing  the  internal  and  common  carotid  artery,  internal  jugular 
vein,  and  pneumogastric  nerve ;  by  its  posterior  surface,  with  the  Longus  colli,  the 
Rectus  capitis  anticus  minor,  and  the  upper  cervical  vertebrae. 

The  Rectus  capitis  anticus  minor  is  a  short,  flat  muscle,  situated  immediately 
behind  the  upper  part  of  the  preceding.  It  arises  from  the  anterior  surface  of  the 
lateral  mass  of  the  atlas  and  from  the  root  of  its  transverse  process,  and,  passing 

1  Walton  (quoted  by  A.  Stuart)  maintains  that  the  epiglottis  is  not  essential  to  the  deglutition  even 
of  liquids. 


THE   LATERAL    VERTEBRAL    REGLON. 


333 


obliquely  upward  and  inward,  is  inserted  into  the  basilar  process  immediately 
behind  the  preceding  muscle. 

Relations. — By  its  anterior  surface,  with  the  Rectus  capitis  anticus  major;  by 
its  posterior  surface,  with  the  front  of  the  occipito-atlantal  articulation. 

The  Rectus  capitis  lateralis  is  a  short,  flat  muscle,  which  arises  from  the  upper 
surface  of  the  transverse  process  of  the  atlas,  and  is  inserted  into  the  under  surface 
of  the  jugular  process  of  the  occipital  bone. 

Relations. — By  its  anterior  surface,  with  the  internal  jugular  vein;  by  its^os- 
terior  surface,  with  the  vertebral  artery.  On  its  outer  side  lies  the  occipital  artery ; 
on  its  inner  side,  the  suboccipital  nerve. 


Fig.  210.— The  prevertebral  muscles. 

The  Longus  colli  is  a  long,  flat  muscle,  situated  on  the  anterior  surface  of  the 
spine,  between  the  atlas  and  the  third  dorsal  vertebra.  It  is  broad  in  the  middle, 
narrow  and  pointed  at  each  extremity,  and  consists  of  three  portions :  a  superior 
oblique,  an  inferior  oblique,  and  a  vertical  portion.  The  superior  oblique  portion 
arises  from  the  anterior  tubercles  of  the  transverse  processes  of  the  third,  fourth, 
and  fifth  cervical  vertebrae,  and,  ascending  obliquely  inward,  is  inserted  by  a  nar- 
row tendon  into  the  tubercle  on  the  anterior  arch  of  the  atlas.  The  inferior 
oblique  portion,  the  smallest  part  of  the  muscle,  arises  from  the  front  of  the  bodies 
of  the  first  two  or  three  dorsal  vertebrae,  and,  ascending  obliquely  outward,  is 
inserted  into  the  anterior  tubercles  of  the  transverse  processes  of  the  fifth  and 
sixth  cervical  vertebrae.  The  vertical  portion  lies  directly  on  the  front  of  the  spine ; 
it  arises,  below,  from  the  front  of  the  bodies  of  the  upper  three  dorsal  and  lower 
three  cervical  vertebrae,  and  is  inserted  above  into  the  front  of  the  bodies  of  the 
second,  third,  and  fourth  cervical  vertebrae  above. 


33*4 


THE   MUSCLES  AND    FASCIJE. 


Relations. — By  its  anterior  surface,  "with  the  prevertebral  fascia,  the  pharynx, 
the  oesophagus,  sympathetic  nerve,  the  sheath  of  the  great  vessels  of  the  neck, 
the  inferior  thyroid  artery,  and  recurrent  laryngeal  nerve ;  by  its  posterior  sur- 
face, with  the  cervical  and  dorsal  portions  of  the  spine.  Its  inner  border  is 
separated  from  the  opposite  muscle  by  a  considerable  interval  below,  but  they 
approach  each  other  above. 

8.  Lateral  Vertebral  Region. 

Scalenus  anticus.  Scalenus  meclius. 

Scalenus  posticus. 

The  Scalenus  anticus  is  a  conical-shaped  muscle,  situated  deeply  at  the  side  of 
the  neck,  behind  the  Sterno-mastoid.    It  arises  from  the  anterior  tubercles  of  the 

STYLO-GLOSSUS.- 
STYLO- HYOI,D. 

OBLIQUUS    CAPITIS    SUPERIOR. 


ERNO-HYOID. 


Fig.  211. 
England.) 


-Muscles  of  the  neck.    (From  a  preparation  in  the  Museum  of  the  Royal  College  of  Surgeons  of 


transverse  processes  of  the  third,  fourth,  fifth,  and  sixth   cervical  vertebras,  and, 
descending  almost  vertically,  is  inserted  by  a  narrow,  flat  tendon  into  the  Scalene 


THE   LATERAL     VERTEBRAL    REGION.  335 

tubercle  on  the  inner  border  and  upper  surface  of  the  first  rib.  The  lower  part 
of  this  muscle  separates  the  subclavian  artery  and  vein,  the  latter  being  in  front, 
and  the  former,  with  the  brachial  plexus,  behind. 

Relations. — In  front,  with  the  clavicle,  the  Subclavius,  Sterno-mastoid,  and 
Omo-hyoid  muscles,  the  transversalis  colli,  the  suprascapular  and  ascending  cer- 
vical arteries,  the  subclavian  vein,  and  the  phrenic  nerve  ;  by  its  posterior  surface, 
with  the  Scalenus  medius,  pleura,  the  subclavian  artery,  and  brachial  plexus  of 
nerves.  It  is  separated  from  the  Longus  colli,  on  the  inner  side,  by  the  vertebral 
artery.  On  the  anterior  tubercles  of  the  transverse  processes  of  the  cervical  ver- 
tebras, between  the  attachments  of  the  Scalenus  anticus  and  Longus  colli,  lies  the 
Ascending  cervical  branch  of  the  inferior  thyroid  artery. 

The  Scalenus  medius,  the  largest  and  longest  of  the  three  Scaleni,  arises  from 
the  posterior  tubercles  of  the  transverse  processes  of  the  lower  six  cervical  vertebras, 
and,  descending  along  the  side  of  the  vertebral  column,  is  inserted  by  a  broad 
attachment  into  the  upper  surface  of  the  first  rib,  behind  the  groove  for  the  sub- 
clavian artery,  as  far  back  as  the  tubercle.  It  is  separated  from  the  Scalenus 
anticus  by  a  subclavian  artery  below  and  the  cervical  nerves  above.  The  pos- 
terior thoracic,  or  nerve  of  Bell,  is  formed  in  the  substance  of  the  Scalenus  medius 
and  emerges  from  it.      The  nerve  to  the  Rhomboids  also  pierces  it. 

Relations. — By  its  anterior  surface,  with  the  Sterno-mastoid ;  it  is  crossed  by 
the  clavicle,  the  Omo-hyoid  muscle,  subclavian  artery,  and  the  cervical  nerves.  To 
its  outer  side  is  the  Levator  anguli  scapulas  and  the  Scalenus  posticus  muscle. 

The  Scalenus  posticus,  the  smallest  of  the  three  Scaleni,  arises,  by  two  or  three 
separate  tendons,  from  the  posterior  tubercles  of  the  transverse  processes  of  the 
lower  two  or  three  cervical  vertebras,  and,  diminishing  as  it  descends,  is  inserted 
by  a  thin  tendon  into  the  outer  surface  of  the  second  rib,  behind  the  attachment  of 
the  Serratus  magnus.  This  is  the  most  deeply  placed  of  the  three  Scaleni,  and  is 
occasionally  blended  with  the  Scalenus  medius. 

Nerves. — The  Rectus  capitis  anticus  major  and  minor  and  the  Rectus  lateralis 
are  supplied  by  the  first  cervical  nerve,  and  from  the  loop  formed  between  it  and 
the  second  ;  the  Longus  colli  and  Scaleni,  by  branches  from  the  anterior  divisions 
of  the  lower  cervical  nerves  (fifth,  sixth,  seventh,  and  eighth)  before  they  form  the 
brachial  plexus.  The  Scalenus  medius  also  receives  a  filament  from  the  deep 
external  branches  of  the  cervical  plexus. 

Actions. — The  Rectus  anticus  major  and  minor  are  the  direct  antagonists  of  the 
muscles  at  the  back  of  the  neck,  serving  to  restore  the  head  to  its  natural  position 
after  it  has  been  drawn  backward.  These  muscles  also  serve  to  flex  the  head,  and, 
from  their  obliquity,  rotate  it,  so  as  to  turn  the  face  to  one  or  the  other  side.  The 
Longus  colli  flexes  and  slightly  rotates  the  cervical  portion  of  the  spine.  The 
Scaleni  muscles,  when  they  take  their  fixed  point  from  above,  elevate  the  first  and 
second  ribs,  and  are,  therefore,  inspiratory  muscles.  When  they  take  their  fixed 
point  from  below,  they  bend  the  spinal  column  to  one  or  the  other  side.  If  the 
muscles  of  both  sides  act,  lateral  movement  is  prevented,  but  the  spine  is  slightly 
flexed.     The  Rectus  lateralis,  acting  on  one  side,  bends  the  head  laterally. 

Surface  Form. — The  muscles  in  the  neck,  with  the  exception  of  the  Platysma  myoides.  are 
invested  by  the  deep  cervical  fascia,  which  softens  down  their  form,  and  is  of  considerable 
importance  in  connection  with  deep  cervical  abscesses  and  tumors,  modifying  the  direction  of 
their  growth  and  causing  them  to  extend  laterally  instead  of  toward  the  surface.  The  Platysma 
myoides  does  not  influence  surface  form  except  it  is  in  action,  when  it  produces  wrinkling  of  the 
skin  of  the  neck,  which  is  thrown  into  oblique  ridges  parallel  with  the  fasciculi  of  the  muscle. 
Sometimes  this  contraction  takes  place  suddenly  and  repeatedly  as  a  sort  of  spasmodic  twitching, 
the  result  of  a  nervous  habit.  The  Stemo-cMdo-mastoid  is  the  most  important  muscle  of  tfic 
neck  as  regards  its  surface  form.  If  the  muscle  is  put  into  action  by  drawing  the  chin  down- 
ward and  to  the  opposite  shoulder,  its  surface  form  will  be  plainly  outlined.  The  sternal  origin 
will  stand  out  as  a  sharply-defined  ridge,  while  the  clavicular  origin  will  present  a  flatter  and  not 
so  prominent  an  outline.  The  fleshy  middle  portion  will  appear  as  an  oblique  roll  or  elevation, 
with  a  thick  rounded  anterior  border  gradually  becoming  less  marked  above.  On  the  opposite 
side — i.  e.  on  the  side  to  which  the  head  is  turned— the  outline  is  lost,  its  place  being  occupied 
by  an  oblique  groove  in  the  integument.     When  the  muscle  is  at  rest  its  anterior  border  is  still 


336 


THE   MUSCLES  AND    FASCIA 


visible,  forming  an  oblique  rounded  ridge,  terminating  below  in  tbe  sharp  outline  of  the  sternal 
head.  The  posterior  border  of  the  muscle  does  not  show  above  the  clavicular  head.  The 
anterior  border  is  defined  by  drawing  a  line  from  the  tip  of  the  mastoid  process  to  the  sterno- 
clavicular joint.  It  is  an  important  surface-marking  in  the  operation  of  ligature  of  the  common 
carotid  artery  and  some  other  operations.  Between  the  sternal  and  clavicular  heads  is  a  slight 
depression,  most  marked  when  the  muscle  is  in  action.  This  is  bounded  below  by  the  prominent 
sternal  extremity  of  the  clavicle.  Between  the  sternal  origins  of  the  two  muscles  is  a  V-shaped 
space,  the  suprasternal  notch,  more  pronounced  below,  and  becoming  toned  down  above,  where 
the  Sterno-hyoid  and  Sterno-thyroid  muscles,  lying  upon  the  trachea,  become  more  prominent. 
Above  the  hyoid  bone,  in  the  middle  line,  the  anterior  belly  of  the  Digastric  to  a  certain  extent 
influences  surface  form.  It  corresponds  to  a  line  drawn  from  the  symphysis  of  the  lower  jaw  to 
the  side  of  the  body  of  the  hyoid  bone,  and  renders  this  part  of  the  hyo-mental  region  convex. 
In  the  posterior  triangle  of  the  neck,  the  posterior  belly  of  the  Omo-hyoid,  when  in  action,  forms- 
a  conspicuous  object,  especially  in  thin  necks,  presenting  a  cord-like  form  running  across  this- 
region,  almost  parallel  with,  and  a  little  above,  the  clavicle. 


MUSCLES  AND    FASCL®  OF    THE  TRUNK. 

The  muscles  of  the  Trunk  may  be  arranged  in  four  groups,  corresponding 
with  the  region  in  which  they  are  situated. 


I. 
II. 


The  Back. 
The  Thorax. 


III. 
IV. 


The  Abdomen. 
The  Perinseum. 


I.  MUSCLES  OF  THE  BACK. 

The  muscles  of  the  Back  are  very  numerous,  and  may  be  subdivided  into  five 
layers : 

First  Layer.  Longissimus  dorsi. 

Trapezius.  SPinalis  dorsi- 

Latissimus  dorsi. 

Cervical  Region. 

Second  Layer.  Cervicalis  ascendens. 

Transversalis  cervicis. 
Levator  anguli  scapula.  Trachelo-mastoid. 

Rhomboideus  minor.  Complexus. 

Rhomboideus  major.  Bi venter  cervicis. 

Spinalis  colli. 
Third  Layer. 


Serratus  posticus  superior. 
Serratus  posticus  inferior. 
Splenius  capitis. 
Splenius  colli. 

Fourth  Layer. 

Sacral  and  Lumbar  Regions. 
Erector  spinse. 

Dorsal  Region. 

Ilio-costalis. 

Musculus  accessorius  ad  ilio-cos      ^m. 


First  Layer. 


.rapezms. 


Fifth  Layer. 

Semispinalis  dorsi. 
Semispinalis  colli. 
Multifidus  spinse. 
Rotatores  spinse. 
Supraspinales. 
Interspinales. 
Extensor  coccygis. 
Intertransversales. 
Rectus  capitis  posticus  major. 
Rectus  capitis  posticus  minor. 
Obliquus  capitis  inferior. 
Obliquus  capitis  superior. 


Latissimus  dorsi. 


Dissection  (Fig.  212). — Placf  the  'xidy  in  a  prory  position,  with  the  arms  extended 
over  the  sides  of  the  table,  and  the  chesi  and  abdemen  .-supported  by  several  blocks,  so  as- 
to  render  the  muscles  tense.  Then  make  an  incision  along  the  middle  line  of  the  back  from  the 
occipital  protuberance  to  the  coccyx.     Make  a  transverse  incision  from  the  upper  end  of  this  to 


OF    THE   BACK. 


337 


the  mastoid  process,  and  a  third  incision  from  its  lower  end,  along  the  crest  of  the  ilium  to 
about  its  middle.  This  large  intervening  space  should,  for  convenience  of  dissection,  be  sub- 
divided by  a  fourth  incision,  extending  obliquely  from 
the  spinous  process  of  the  last  dorsal  vertebra,  upward 
and  outward,  to  the  acromion  process.  This  incision  cor- 
responds with  the  lower  border  of  the  Trapezius  muscle. 
The  flaps  of  integument  are  then  to  be  removed  in  the 
direction  shown  in  the  figure. 

The  superficial  fascia  is  exposed  upon  re- 
moving the  skin  from  the  back.  It  forms  a 
layer .  of  considerable  thickness  and  strength, 
in  which  a  quantity  of  granular  pinkish  fat  is 
contained.  It  is  continuous  with  the  super- 
ficial fascia  in  other  parts  of  the  body.  The 
deep  fascia  is  a  dense  fibrous  layer  attached  to 
the  occipital  bone,  the  spines  of  the  vertebrae, 
the  crest  of  the  ilium,  and  the  spine  of  the 
scapula.  It  covers  over  the  superficial  muscles, 
forming  sheaths  for  them,  and  in  the  neck 
forms  the  posterior  part  of  the  deep  cervical 
fascia ;  in  the  thorax  it  is  continuous  with  the 
deep  fascia  of  the  axilla  and  chest,  and  in  the 
abdomen  with  that  covering  the  abdominal 
muscles. 

The  Trapezius  (Fig.  213)  is  a  broad,  flat, 
triangular  muscle,  placed  immediately  beneath 
the  skin  and  fascia,  and  covering  the  upper  and 
back  part  of  the  neck  and  shoulders.  It  arises 
from  the  external  occipital  protulierance  anxTthe 
inner  third  of  the  superior  curved  line  of  the 
occipital  bone ;  from  the  ligamentum  nuchae, 
the  spinous  process  of  the  seventh  cervical,  and  those  of  all  the  dorsal  vertebrae ; 
and  from  the  corresponding  portion  of  the  supraspinous  ligament.  From  this 
origin  the  superior  fibres  proceed  downward  and  outward,  the  inferior  ones 
upward  and  outward,  and  the  middle  fibres  horizontally,  and  are  inserted, 
the  superior  ones  into  the  outer  third  of  the  posterior  border  of  the  clavicle ; 
the  middle  fibres  into  the  inner  margin  of  the  acromion  process,  and  into  the 
superior  lip  of  the  posterior  border  or  crest  of  the  spine  of  the  scapula;  the 
inferior  fibres  converge  near  the  scapula,  and  terminate  in  a  triangular  apo- 
neurosis, which  glides  over  a  smooth  surface  at  the  inner  extremity  of  the 
spine,  to  be  inserted  into  a  tubercle  at  the  outer  part  of  this  smooth  surface. 
The  Trapezius  is  fleshy  in  the  greater  part  of  its  extent,  but  tendinous  at  its  origin 
and  insertion.  At  its  occipital  origin  it  is  connected  to  the  bone  by  a  thin  fibrous 
lamina,  firmly  adherent  to  the  skin,  and  wanting  the  lustrous,  shining  appearance 
of  aponeuroses.  At  its  origin  from  the  spines  of  the  vertebrae  it  is  connected  to 
the  bones  by  means  of  a  broad  semi-elliptical  aponeurosis,  which  occupies  the 
space  between  the  sixth  cervical  and  the  third  dorsal  vertebrae,  and  forms,  with 
the  aponeurosis  of  the  opposite  muscle,  a  tendinous  ellipse.  The  rest  of  the  muscle 
arises  by  numerous  short  tendinous  fibres.  If  the  Trapezius  is  dissected  on  both 
sides,  the  two  muscles  resemble  a  trapezium  or  diamond-shaped  quadrangle ;  two 
angles  corresponding  to  the  shoulders ;  a  third  to  the  occipital  protuberance ; 
and  the  fourth  to  the  spinous  process  of  the  last  dorsal  vertebra. 

The  clavicular  insertion  of  this  muscle  varies  as  to  the  extent  of  its  attach- 
ment ;  it  sometimes  advances  as  far  as  the  middle  of  the  clavicle,  and  may  even 
become  blended  with  the  posterior  edge  of  the  Sterno-mastoid  or  overlai^  it.  This 
should  be  borne  in  mind  in  the  operation  for  tying  the  third  part  of  the  subclavian 
artery. 

22 


Fig.  212.— Dissection  of  the  muscles  of 
the  back. 


338 


THE   3IUSCLES   AND    FASCIjE 


Fig.  213— Muscles  of  the  back.    On  the  left  side  is  exposed  the  firs,-  layer;  on  the  right  side,  the  second 
layer  and  part  of  the  third. 

Relations. — By  its  superficial  surface,  with   the  integument;  by  its  deep  sur- 
face, in  the  neck,  with  the  Complexus,  Splenius,  Lex  ator  anguli  scapulae,  and 


OF   THE   BACK.  339 

Ehomboideus  minor;  in  the  back,  with  the  Rhomboideus  major,  Snpraspinatus, 
Infraspinatus,  and  Vertebral  aponeurosis  (which  separates  it  from  the  prolongations 
-of  the  Erector  spinae),  and  the  Latissimus  dorsi.  The  spinal  accessory  nerve  and 
the  superficial  cervical  artery  and  branches  from  the  third  and  fourth  cervical 
nerves  pass  beneath  the  anterior  border  of  this  muscle.  The  anterior  margin  of 
its  cervical  portion  forms  the  posterior  boundary  of  the  posterior  triangle  of  the 
neck,  the  other  boundaries  being  the  Sterno-mastoid  in  front  and  the  clavicle 
below. 

The  Ligamentum  nuchse  (Fig.  213)  is  a  fibrous  membrane,  which,  in  the  neck, 
represents  the  supraspinous  and  interspinous  ligaments  of  the  lower  vertebrae. 
It  extends  from  the  external  occipital  protuberance  to  the  spinous  process  of  the 
seventh  cervical  vertebra.  From  its  anterior  border  a  fibrous  lamina  is  given  off, 
which  is  attached  to  the  external  occipital  crest,  the  posterior  tubercle  of  the 
atlas,  and  the  spinous  process  of  each  of  the  cervical  vertebrae,  so  as  to  form  a 
septum  between  the  muscles  on  each  side  of  the  neck.  In  man  it  is  merely  the 
rudiment  of  an  important  elastic  ligament,  which,  in  some  of  the  lower  animals, 
serves  to  sustain  the  weight  of  the  head. 

The  Latissimus  dorsi  is  a  broad  flat  muscle  which  covers  the  lumbar  and  the 
lower  half  of  the  dorsal  regions,  and  is  gradually  contracted  into  a  narrow  fasci- 
culus at  its  insertion  into  the  humerus.  It  arises  by  tendinous  fibres  from  the 
spinous  processes  of  the  six  inferior  dorsal  vertebrae  and  from  the  posterior  layer 
of  the  lumbar  fascia  (see  page  342),  by  which  it  is  attached  to  the  spines  of  the 
lumbar  and  sacral  vertebrae  and  to  the  supraspinous  ligament.  It  also  arises 
from  the  external  lip  of  the  crest  of  the  ilium,  behind  the  origin  of  the  External 
oblique,  and  by  fleshy  digitations  from  the  three  or  four  lower  ribs,  Avhicb  are 
interposed  between  similar  processes  of  the  External  oblique  muscle  (Fig.  218, 
page  358).  From  this  extensive  origin  the  fibres  pass  in  different  directions,  the 
upper  ones  horizontally,  the  middle  obliquely  upward,  and  the  lower  verticallv 
upward,  so  as  to  converge  and  form  a  thick  fasciculus,  which  crosses  the  inferior 
angle  of  the  scapula,  and  occasionally  receives  a  few  fibres  from  it.  The  muscle 
then  curves  around  the  lower  border  of  the  Teres  major,  and  is  twisted  upon  itself, 
so  that  the  superior  fibres  become  at  first  posterior  and  then  inferior,  and  the 
vertical  fibres  at  first  anterior  and  then  superior.  It  then  terminates  in  a  short 
quadrilateral  tendon,  about  three  inches  in  length,  which,  passing  in  front  of  the 
tendon  of  the  Teres  major,  is  inserted  into  the  bottom  of  the  bicipital  groove  of 
the  humerus,  its  insertion  extending  higher  on  the  humerus  than  that  of  the 
tendon  of  the  Pectoralis  major.  The  lower  border  of  the  tendon  of  this  muscle  is 
united  with  that  of  the  Teres  major,  the  surfaces  of  the  two  being  separated  by  a 
bursa ;  another  bursa  is  sometimes  interposed  between  the  muscle  and  the  inferior 
angle  of  the  scapula.  This  muscle  at  its  insertion  gives  off  an  expansion  to  the 
deep  fascia  of  the  arm. 

A  muscular  slip,  axillary  arch,  varying  from  3  to  4  inches  in  length,  and  from  i  to  J  of  an 
inch  in  breadth,  occasionally  arises  from  the  upper  edge  of  the  Latissimus  dorsi  about  the  mid- 
dle of  the  posterior  fold  of  the  axilla,  and  crosses  the  axilla  in  front  of  the  axillary  vessels  and  nerves, 
to  join  the  under  surface  of  the  tendon  of  the  Pectoralis  major,  the  Coraco-brachialis,  or  the 
fascia  over  the  Biceps.  The  position  of  this  abnormal  slip  is  a  point  of  interest  in  its  relation 
to  the  axillary  artery,  as  it  crosses  the  vessel  just  above  the  spot  usually  selected  for  the 
application  of  a  ligature,  and  may  mislead  the  surgeon  during  the  operation.  It  maybe  easily 
recognized  by  the  transverse  direction  of  its  fibres.  Dr.  Struther  found  it.  in  8  out  of  105 
subjects,  occurring  seven  times  on  both  sides. 

There  is  usually  a  fibrous  slip  which  passes  from  the  lower  border  of  the  tendon  of  the 
Latissimus  dorsi,  near  its  insertion,  to  the  long  head  of  the  Triceps.  This  is  occasionally 
muscular,  and  is  the  representative  of  the  Dorso-ejntrochlearis  muscle  of  apes. 

Eelations. — Its  superficial  surface  is  subcutaneous,  excepting  at  its  upper  part, 
where  it  is  covered  by  the  Trapezius,  and  at  its  insertion,  where  its  tendon  is 
crossed  by  the  axillary  vessels  and  the  brachial  plexus  of  nerves.  By  its  deep 
surface  it  is  in  relation  with  the  Lumbar  fascia,  the  Serratus  posticus  inferior, 
the  lower  external  intercostal  muscles  and  ribs,  inferior  angle  of  the  scapula, 
Rhomboideus    major,    Infraspinatus,    and   Teres    major.       Its    outer    margin    is 


340  THE  MUSCLES   AND    FASCIJE 

separated  below  from  the  External  oblique  by  a  small  triangular  interval,  the 
triangle  of  Petit ;  and  another  triangular  interval  exists  between  its  upper 
border  and  the  margin  of  the  Trapezius,  in  which  the  Rhomboideus  major  muscle 
is  exposed. 

Nerves. — The  Trapezius  is  supplied  by  the  spinal  accessory,  and  by  branches 
from  the  anterior  divisions  of  the  third  and  fourth  cervical  nerves  :  the  Latissimus 
dorsi,  by  the  middle  or  long  subscapular  nerve. 

Second  Layer. 

Levator  anguli  scapulae.  Rhomboideus  minor. 

Rhomboideus  major. 

Dissection. — The  Trapezius  must  be  removed,  in  order  to  expose  the  next  layer ;  to  effect 
this,  detach  the  muscle  from  its  attachment  to  the  clavicle  and  spine  of  the  scapula,  and  turn 
it  back  toward  the  spine. 

The  Levator  anguli  scapulae  is  situated  at  the  back  part  and  side  of  the  neck. 
It  arises  by  tendinous  slips  from  the  transverse  process  of  the  atlas,  and  from  the 
posterior  tubercles  of  the  transverse  process  of  the  second,  third,  and  fourth 
cervical  vertebrae ;  these,  becoming  fleshy,  are  united  so  as  to  form  a  flat  muscle, 
which,  passing  downward  and  backward,  is  inserted  into  the  posterior  border  of 
the  scapula,  between  the  superior  angle  and  the  triangular  smooth  surface  at  the 
root  of  the  spine. 

Relations. — By  its  superficial  surface,  with  the  integument,  Trapezius,  and 
Sterno-mastoid ;  by  its  deep  surface,  with  the  Splenius  colli,  Transversalis 
cervicis,  Cervicalis  ascendens,  and  Serratus  posticus  superior  muscles,  and  with 
the  posterior  scapular  artery  and  the  nerve  to  the  Rhomboids. 

The  Rhomboideus  minor  arises  from  the  ligamentum  nuchae  and  spinous 
processes  of  the  seventh  cervical  and  first  dorsal  vertebrae.  Passing  downward 
and  outward,  it  is  inserted  into  the  margin  of  the  triangular  smooth  surface  at  the 
root  of  the  spine  of  the  scapula.  This  small  muscle  is  usually  separated  from  the 
Rhomboideus  major  by  a  slight  cellular  interval. 

Relations. — By  its  superficial  (posterior)  surface,  with  the  Trapezius ;  by  its 
deep  surface,  with  the  same  structures  as  the  Rhomboideus  major. 

The  Rhomboideus  major  is  situated  immediately  below  the  preceding,  the 
adjacent  margins  of  the  two  being  occasionally  united.  It  arises  by  tendinous 
fibres  from  the  spinous  processes  of  the  four  or  five  upper  dorsal  vertebrae  and  the 
supraspinous  ligament,  and  is  inserted  into  a  narrow  tendinous  arch  attached 
above  to  the  lower  part  of  the  triangular  surface  at  the  root  of  the  spine ;  below, 
to  the  inferior  angle,  the  arch  being  connected  to  the  border  of  the  scapula  by  a 
thin  membrane.  When  the  arch  extends,  as  it  occasionally  does,  but  a  short 
distance,  the  muscular  fibres  are  inserted  into  the  scapula  itself. 

Relations. — By  its  superficial  (posterior)  surface,  with  the  Latissimus  dorsi ;  by 
its  deep  (anterior)  surface,  with  the  Serratus  posticus  superior,  posterior  scapular 
artery,  the  vertebral  aponeurosis  which  separates  it  from  the  prolongations  from 
the  Erector  spinas,  the  Intercostal  muscles,  and  ribs. 

Nerves. — The  Rhomboid  muscles  are  supplied  by  branches  from  the  anterior- 
division  of  the  fifth  cervical  nerve ;  the  Levator  anguli  scapulae,  by  the  anterior 
division  of  the  third  and  fourth  cervical  nerves,  and  frequently  by  a  branch  from 
the  nerve  to  the  Rhomboids. 

Actions. — The  movements  effected  by  the  preceding  muscles  are  numerous,  as 
may  be  conceived  from  their  extensive  attachment.  The  whole  of  the  Trapezius 
when  in  action  retracts  the  scapula  and  braces  back  the  shoulder;  if  the  head  is 
fixed,  the  upper  part  of  the  Trapezius  will  elevate  the  point  of  the  shoulder,  as  in 
supporting  weights ;  Avhen  the  lower  fibres  re.  brought  into  action,  they  assist  in 
depressing  the  bone.  The  middle  and  lower  ibres  of  the  muscle  rotate  the  scap- 
ula, causing  elevation  of  the  acromion  process      If  the  shoulders  are  fixed,  both 


OF    THE   BACK.  341 

Trapezii,  acting  together,  will  draw  the  head  directly  backward ;  or  if  only  one 
acts,  the  head  is  drawn  to  the  corresponding  side. 

The  Latissimus  dorsi,  when  it  acts  upon  the  humerus,  depresses  it,  draws  it  back- 
ward, adducts,  and  at  the  same  time  rotates  it  inward.  It  is  the  muscle  which  is 
principally  employed  in  giving  a  downward  blow,  as  in  felling  a  tree  or  in  sabre 
practice.  If  the  arm  is  fixed,  the  muscle  may  act  in  various  ways  upon  the  trunk  ; 
thus,  it  may  raise  the  lower  ribs  and  assist  in  forcible  inspiration  ;  or,  if  both  arms 
are  fixed,  the  two  muscles  may  assist  the  Abdominal  and  great  Pectoral  muscles  in 
suspending  and  drawing  the  whole  trunk  forward,  as  in  climbing  or  walking  on 
crutches. 

The  Levator  anguli  scapulce  raises  the  superior  angle  of  the  scapula,  assisting 
the  Trapezius  in  bearing  weights  or  in  shrugging  the  shoulders.  If  the  shoulder 
be  fixed,  the  Levator  anguli  scapulae  inclines  the  neck  to  the  corresponding  side 
and  rotates  it  in  the  same  direction.  The  Rhomboid  muscles  carry  the  inferior 
angle  backward  and  upward,  thus  producing  a  slight  rotation  of  the  scapula  upon 
the  side  of  the  chest,  the  Rhomboideus  major  acting  especially  on  the  lower  angle 
of  the  scapula  through  the  tendinous  arch  by  which  it  is  inserted.  The  Rhomboid 
muscles,  acting  together  with  the  middle  and  inferior  fibres  of  the  Trapezius,  will 
draw  the  scapula  directly  backward  toward  the  spine. 

Third  Layer. 

Serratus  posticus  superior.  Serratus  posticus  inferior. 

o   i     •       f  Splenius  capitis. 
bplenms<  Qr!     ■  jr 

1  (  bplenms  colli. 

Dissection. — To  bring  into  view  the  third  layer  of  muscles,  remove  the  whole  of  the  second, 
together  with  the  Latissimus  dorsi,  by  cutting  through  the  Levator  anguli  scapulae  and  Rhom- 
boid muscles  near  their  origin,  and  reflecting  them  downward,  and  by  dividing  the  Latissimus 
dorsi  in  the  middle  by  a  vertical  incision  carried  from  its  upper  to  its  lower  part,  and  reflecting 
the  two  halves  of  the  muscle. 

The  Serratus  posticus  superior  is  a  thin,  flat,  quadrilateral  muscle  situated  at 
the  upper  and  back  part  of  the  thorax.  It  arises  by  a  thin  and  broad  aponeurosis 
from  the  ligamentum  nuchae,  and  from  the  spinous  processes  of  the  last  cervical 
.and  two  or  three  upper  dorsal  vertebrae  and  from  the  supraspinous  ligament. 
Inclining  downward  and  outward,  it  becomes  muscular,  and  is  inserted,  by  four 
fleshy  digitations  into  the  upper  borders  of  the  second,  third,  fourth,  and  fifth  ribs, 
a  little  beyond  their  angles. 

Relations. — By  its  superficial  surface,  with  the  Trapezius,  Rhomboidei,  and 
Levator  anguli  scapulae ;  by  its  deep  surface,  with  the  Splenius  and  the  vertebral 
aponeurosis,  which  separates  it  from  the  prolongations  of  the  Erector  spinae, 
and  with  the  Intercostal  muscles  and  ribs. 

The  Serratus  posticus  inferior  is  situated  at  the  junction  of  the  dorsal  and  lumbar 
regions ;  it  is  of  an  irregularly  quadrilateral  form,  broader  than  the  preceding, 
and  separated  from  it  by  a  considerable  interval.  It  arises  by  a  thin  aponeurosis 
from  the  spinous  processes  of  the  last  two  dorsal  and  two  or  three  upper  lumbar 
vertebrae,  and  from  the  supraspinous  ligaments.  Passing  obliquely  upward 
and  outward,  it  becomes  fleshy,  and  divides  into  four  flat  digitations,  which  are 
inserted  into  the  lower  borders  of  the  four  lower  ribs,  a  little  beyond  their  angles. 
The  thin  aponeurosis  of  origin  is  intimately  blended  with  the  lumbar  fascia. 

Relations. — By  its  superficial  surface,  with  the  Latissimus  dorsi.  By  its  deep 
surface,  with  the  Erector  spinae,  ribs,  and  Intercostal  muscles.  Its  upper  margin 
is  continuous  with  the  vertebral  aponeurosis. 

The  Vertebral  aponeurosis  is  a  thin,  fibrous  lamina,  extending  along  the  whole 
length  of  the  back  part  of  the  thoracic  region,  serving  to  bind  down  the  long 
Extensor  muscles  of  the  back  which  support  the  spine  and  head,  and  separate  them 
from  those  muscles  which  connect  the  spine  to  the  upper  extremity.  It  consists  of 
longitudinal  and  transverse  fibres  blended  together,  forming  a  thin  lamella,  which 
is  attached  in  the  median  line  to  the  spinous  processes  of  the  dorsal  vertebrae ;  ex- 


\ 


342  THE   MUSCLES  AND    FASCIAE 

ternally,  to  the  angles  of  the  ribs ;  and  below,  to  the  upper  border  of  the  Serratus: 
posticus  inferior  and  a  portion  of  the  lumbar  fascia,  which  gives  origin  to  the  Latis- 
simus  dorsi ;  above,  it  passes  beneath  the  Serratus  posticus  superior  and  the  Sple- 
nius, and  blends  with  the  deep  fascia  of  the  neck. 

The  Lumbar  fascia  or  aponeurosis  (Fig.  213),  which  may  be  regarded  as  the  pos- 
terior aponeurosis  of  the  Trans versalis  abdominis  muscle,  consists  of  three  laminae, 
which  are  attached  as  follows :  the  posterior  layer,  to  the  spiner  of  the  lumbar  and 
sacral  vertebrae  and  their  supraspinous  ligaments ;  the  middle,  to  the  tips  of  the 
transverse  processes  of  the  lumbar  vertebrae  and  their  intertransverse  ligaments;  the 
anterior,  to  the  roots  of  the  lumbar  transverse  processes.  The  posterior  layer  is- 
continued  above  as  the  vertebral  aponeurosis,  while  inferiorily  it  is  fixed  to  the 
outer  lip  of  the  iliac  crest.  With  this  layer  are  blended  the  aponeurotic  origin 
of  the  Serratus  posticus  inferior  and  part  of  that  of  the  Latissimus  dorsi.  The 
middle  layer  is  attached  above  to  the  last  rib,  and  below  to  the  iliac  crest;  the  an- 
terior layer  is  fixed  below  to  the  ilio-lumbar  ligament  and  iliac  crest ;  while  above 
it  is  thickened  to  form  the  external  arcuate  ligament  of  the  diaphragm,  and  stretches 
from  the  tip  of  the  last  rib  to  the  transverse  process  of  the  first  or  second  lumbar 
vertebra.  These  three  layers,  together  with  the  vertebral  column,  enclose  two- 
spaces,  the  posterior  of  which  is  occupied  by  the  Erector  spinas  muscle,  and  the 
anterior  by  the  Quadratus  lumborum. 

Now  detach  the  Serratus  posticus  superior  from  its  origin,  and  turn  it  outward,  when  the 
Splenius  muscle  will  be  brought  into  view. 

The  Splenius  is  situated  at  the  back  of  the  neck  and  upper  part  of  the  dorsal 
region.  At  its  origin  it  is  a  single  muscle,  narrow,  and  pointed  in  form  ;  but  it 
soon  becomes  broader,  and  divides  into  two  portions,  which  have  separate  inser- 
tions. It  arises,  by  tendinous  fibres,  from  the  lower  half  of  the  ligamentum  nuchas, 
from  the  spinous  processes  of  the  last  cervical  and  of  the  six  upper  dorsal  vertebrae, 
and  from  the  supraspinous  ligament.  From  this  origin  the  fleshy  fibres  proceed 
obliquely  upward  and  outward,  forming  a  broad  fiat  muscle,  which  divides  as  it 
ascends  into  two  portions,  the  Splenius  capitis  and  Splenius  colli. 

The  Splenius  capitis  is  inserted  into  the  mastoid  process  of  the  temporal  bone, 
and  into  the  rough  surface  on  the  occipital  bone  just  beneath  the  superior  curved 
line. 

The  Splenius  colli  is  inserted,  by  tendinous  fasciculi,  into  the  posterior  tubercles 
of  the  transverse  processes  of  the  two  or  three  upper  cervical  vertebras. 

The  Splenius  is  separated  from  its  fellow  of  the  opposite  side  by  a  triangular 
interval,  in  which  is  seen  the  Complexus. 

Relations. — By  its  superficial  surface,  with  the  Trapezius,  from  which  it  is 
separated  below  by  the  Rhomboidei  and  the  Serratus  posticus  superior.  It  is 
covered  at  its  insertion  by  the  Sterno-mastoid,  and  at  the  lower  and  back  part  of 
the  neck  by  the  Levator  anguli  scapulae ;  by  its  deep  surface,  with  the  Spinalis 
dorsi,  Longissimus  dorsi,  Semispinalis  colli,  Complexus,  Trachelo-mastoid,  and 
Transversalis  cervicis. 

Nerves. — The  Splenius  is  supplied  from  the  external  branches  of  the  posterior 
divisions  of  the  cervical  nerves ;  the  Serratus  posticus  superior  is  supplied  by  the 
external  branches  of  the  posterior  divisions  of  the  upper  dorsal  nerves  ;  the  Serratus 
posticus  inferior  by  the  external  branches  of  the  posterior  divisions  of  the  lower 
dorsal  nerves. 

Actions. — The  Serrati  are  respiratory  muscles.  The  Serratus  posticus  supe- 
rior elevates  the  ribs ;  it  is  therefore  an  inspiratory  muscle ;  Avhile  the  Serratus 
inferior  draws  the  lower  ribs  downward  and  backward,  and  thus  elongates  the 
thorax.  It  also  fixes  the  lower  ribs,  thus  aiding  the  downward  action  of  the 
diaphragm  and  resisting  the  tendency  which  it  has  to  draw  the  lower  ribs  upward 
and  forward.  It  must  therefore  be  regarded  as  a  muscle  of  inspiration.  This  muscle 
is  also  probably  a  tensor  of  the  vertebral  aponeurosis.  The  Splenii  muscles  of  the 
two  sides,  acting  together,  draw  the  head  directly  backward,  assisting  the  Trapezius. 


i 


OF    THE   BACK.  343 

and  Complexus ;  acting  separately,  they  draw  the  head  to  one  or  the  other  side, 
and  slightly  rotate  it,  turning  the  face  to  the  same  side.  They  also  assist  in  sup- 
porting the  head  in  the  erect  position. 

Fourth  Layer. 
I.  Erector  spinas. 
a.    Outer   Column.  b.  Middle   Column. 

Ilio-costalis.  Longissimus  dorsi. 

Musculus  accessorius.  Transversalis  cervicis. 

Cervicalis  ascendens.  Trachelo-mastoid. 

c.  Inner   Column. 
Spinalis  dorsi. 

II.   Complexus. 

Dissection. — To  expose  the  muscles  of  the  fourth  layer,  remove  entirely  the  Serrati  and  the 
vertebral  and  lumbar  fasciae.  Then  detach  the  Splenius  by  separating  its  attachment  to  the 
spinous  processes  and  reflecting  it  outward. 

The  Erector  spinse  (Fig.  214)  and  its  prolongations  in  the  dorsal  and  cervical 
regions  fill  up  the  vertebral  groove  on  each  side  of  the  spine.  It  is  covered  in 
the  lumbar  region  by  the  lumbar  fascia ;  in  the  dorsal  region,  by  the  Serrati 
muscles  and  the  vertebral  aponeurosis ;  and  in  the  cervical  region,  by  a  layer  of 
cervical  fascia  continued  beneath  the  Trapezius  and  the  Splenius.  This  large 
muscular  and  tendinous  mass  varies  in  size  and  structure  at  different  parts  of  the 
spine.  In  the  sacral  region  the  Erector  spinse  is  narrow  and  pointed,  and  its  origin 
chiefly  tendinous  in  structure.  In  the  lumbar  region  the  muscle  becomes  enlarged, 
and  forms  a  large  fleshy  mass.  In  the  dorsal  region  it  subdivides  into  two  parts, 
which  gradually  diminish  in  size  as  they  ascend  to  be  inserted  into  the  vertebrae 
and  ribs. 

The  Erector  spines  arises  from  the  anterior  surface  of  a  very  broad  and  thick 
tendon,  which  is  attached,  internally,  to  the  spines  of  the  sacrum,  to  the  spinous 
processes  of  the  lumbar  and  the  eleventh  and  twelfth  dorsal  vertebrae,  and  the  su- 
praspinous ligament ;  externally,  to  the  back  part  of  the  inner  lip  of  the  crest  of 
the  ilium,  and  to  the  series  of  eminences  on  the  posterior  part  of  the  sacrum,  which 
represents  the  transverse  processes,  where  it  blends  with  the  great  sacro-sciatic  and 
posterior  sacro-iliac  ligaments.  Some  of  its  fibres  are  continuous  with  the  fibres 
of  origin  of  the  Gluteus  maximus.  The  muscular  fibres  form  a  single  large  fleshy 
mass,  bounded  in  front  by  the  transverse  processes  of  the  lumbar  vertebrae  and  by 
the  middle  lamella  of  the  lumbar  fascia.  Opposite  the  last  rib  it  divides  into  two 
parts,  the  Ilio-costalis  and  the  Longissimus  dorsi ;  the  Spinalis  dorsi  is  given  off 
from  the  latter  in  the  upper  dorsal  region. 

The  Ilio-costalis  (Sacro-lumbalis),  the  external  portion  of  the  Erector  spinas,  is 
inserted,  generally,  by  six  or  seven  flattened  tendons  into  the  inferior  borders  of 
the  angles  of  the  six  or  seven  lower  ribs.  The  number  of  the  tendons  of  this  muscle 
is,  however,  very  variable,  and  therefore  the  number  of  ribs  into  which  it  is  in- 
serted. Frequently  it  is  found  to  possess  nine  or  ten  tendons,  and  sometimes  as 
many  tendons  as  there  are  ribs,  and  is  then  inserted  into  the  angles  of  all  the  ribs. 
If  this  muscle  is  reflected  outward,  it  will  be  seen  to  be  reinforced  by  a  scries  of 
muscular  slips  which  arise  from  the  angles  of  the  ribs ;  by  means  of  these  the  Ilio- 
costalis  is  continued  upward  to  the  upper  ribs  and  cervical  portion  of  the  spine. 
The  accessory  portions  form  two  additional  muscles,  the  Musculus  accessorius  and 
the  Cervicalis  ascendens. 

The  Musculus  accessorius  ad  ilio-costalem  arises,  by  separate  flattened  tendons, 
from  the  upper  borders  of  the  angles  of  the  six  lower  ribs  :  these  become  muscular, 
and  are  finally  inserted,  by  separate  tendons,  into  the  upper  borders  of  the  angles 


344 


THE   MUSCLES   AND    FASCIA 

Occipital  bone. 


MULTIFIDUS   S 


First  dorsal  vertebra. — 


First  lumbar  vertebr 


First  sacral  verteb 


Fig.  214. — Muscles  of  the  back.    Deep  layers. 

of  the  six  upper  ribs  and  into  the  back  of  the  transverse  process  of  the  seventh 
cervical  vertebra. 


OF    THE  BACK.  345 

The  Cervicalis  ascendens J  is  the  continuation  of  the  Accessorius  upward  into 
the  neck  ;  it  is  situated  on  the  inner  side  of  the  tendons  of  the  Accessorius,  arising 
from  the  angles  of  the  four  or  five  upper  ribs,  and  is  inserted  by  a  series  of  slender 
tendons  into  the  posterior  tubercles  of  the  transverse  processes  of  the  fourth,  fifth, 
and  sixth  cervical  vertebrae. 

The  Longissimus  dorsi  is  the  middle  and  largest  portion  of  the  Erector  spina. 
In  the  lumbar  region,  where  it  is  as  yet  blended  with  the  Ilio-costalis,  some  of  the 
fibres  are  attached  to  the  whole  length  of  the  posterior  surface  of  the  transver.-e 
processes  and  the  accessory  processes  of  the  lumbar  vertebrae,  and  to  the  middle 
layer  of  the  lumbar  fascia.  In  the  dorsal  region,  the  Longissimus  dorsi  is  inserted, 
by  long  thin  tendons,  into  the  tips  of  the  transverse  processes  of  all  the  dorsal  ver- 
tebrae, and  into  from  seven  to  eleven  of  the  lower  ribs  between  their  tubercles  and 
angles.  This  muscle  is  continued  upward  to  the  cranium  and  cervical  portion  of 
the  spine  by  means  of  two  additional  muscles,  the  Transversalis  cervicis  and  Trach- 
elo-mastoid. 

The  Transversalis  cervicis  or  colli,  placed  on  the  inner  side  of  the  Longissimus 
dorsi,  arises  by  long  thin  tendons  from  the  summits  of  the  transverse  processes  of 
the  six  upper  dorsal  vertebrae,  and  is  inserted  by  similar  tendons  into  the  posterior 
tubercles  of  the  transverse  processes  of  the  cervical  vertebrae,  from  the  second  to  the 
sixth  inclusive. 

The  Trachelo-mastoid  lies  on  the  inner  side  of  the  preceding,  between  it  and 
the  Complexus  muscle.  It  arises,  by  tendons,  from  the  transverse  processes  of 
the  five  or  six  upper  dorsal  vertebrae,  and  the  articular  processes  of  the  three  or 
four  lower  cervical.  The  fibres  form  a  small  muscle,  which  ascends  to  be  inserted 
into  the  posterior  margin  of  the  mastoid  process,  beneath  the  Splenius  and 
Sterno-mastoid  muscles.  This  small  muscle  is  almost  always  crossed  by  a 
tendinous  intersection  near  its  insertion  into  the  mastoid  process.2 

The  Spinalis  dorsi  connects  the  spinous  processes  of  the  upper  lumbar  and  the 
dorsal  vertebrae  together  by  a  series  of  muscular  and  tendinous  slips  which  are 
intimately  blended  with  the  Longissimus  dorsi.  It  is  situated  at  the  inner  side  of 
the  Longissimus  dorsi,  arising,  by  three  or  four  tendons,  from  the  spinous  pro- 
cesses of  the  first  two  lumbar  and  the  last  two  dorsal  vertebrae :  these,  uniting, 
form  a  small  muscle,  which  is  inserted,  by  separate  tendons,  into  the  spinous  pro- 
cesses of  the  dorsal  vertebrae,  the  number  varying  from  four  to  eight.  It  is 
intimately  united  with  the  Semispinalis  dorsi,  which  lies  beneath  it. 

The  Spinalis  colli  is  a  small  muscle,  connecting  together  the  spinous  processes 
of  the  cervical  vertebrae,  and  analogous  to  the  Spinalis  dorsi  in  the  dorsal  region. 
It  varies  considerably  in  its  size  and  in  its  extent  of  attachment  to  the  vertebrae, 
not  only  in  different  bodies,  but  on  the  two  sides  of  the  same  body.  It  usually 
arises  by  fleshy  or  tendinous  slips,  varying  from  two  to  four  in  number,  from  the 
spinous  processes  of  the  fifth,  sixth,  and  seventh  cervical  vertebrae,  and  occasionally 
from  the  first  and  second  dorsal,  and  is  inserted  into  the  spinous  process  of  the 
axis,  and  occasionally  into  the  spinous  processes  of  the  two  vertebrae  below  it. 
This  muscle  was  found  absent  in  five  cases  out  of  twenty-four. 

Relations. — The  Erector  spinae  and  its  prolongations  are  bound  down  to  the 
vertebrae  and  ribs  in  the  lumbar  and  dorsal  regions  by  the  lumbar  fascia  and  the 
vertebral  aponeurosis.  The  inner  part  of  these  muscles  covers  the  muscles  of  the 
fifth  layer.  In  the  neck  they  are  in  relation,  by  their  superficial  sxirface,  with  the 
Trapezius  and  Splenius  ;  by  their  deep  surface,  with  the  Semispinalis  dorsi  et  colli 
and  the  Recti  and  Obliqui. 

The  Complexus  is  a  broad  thick  muscle,  situated  at  the  upper  and  back  part  of 
the  neck,  beneath  the   Splenius,  and  internal  to   the  Transversalis   cervicis    and 

1  This  muscle  is  sometimes  called  "Cervicalis  descendens."  The  student  should  remember  that 
these  long  muscles  take  their  fixed  point  from  above  or  from  below,  according  to  circumstances. 

2  These  two  muscles  (Transversalis  cervicis  and  Trachelo-mastoid)  are  sometimes  described  as 
one,  having  a  common  origin,  but  dividing  above  at  their  insertion.  The  Trachelo-mastoid  is  then 
termed  the  Transversalis  capitis. 


346  THE  IfUSCLES  AND   FASCIAE 

Trachelo-mastoid.  It  arises,  by  a  series  of  tendons,  from  the  tips  of  the  transverse 
processes  of  the  upper  six  or  seven  dorsal  and  the  last  cervical  vertebrae,  and  from 
the  articular  processes  of  the  three  cervical  above  this.  The  tendons,  uniting,  form 
a  broad  muscle,  which  passes  obliquely  upward  and  inward,  and  is  inserted  into 
the  innermost  depression  between  the  two  curved  lines  of  the  occipital  bone.  This 
muscle,  about  its  middle,  is  traversed  by  a  transverse  tendinous  intersection.  The 
Biv enter  eervicis  is  a  small  fasciculus,  situated  on  the  inner  side  of  the  preceding, 
and  in  the  majority  of  cases  blended  with  it ;  it  has  received  its  name  from  having 
a  tendon  intervening  between  two  fleshy  bellies.  It  is  sometimes  described  as  a 
part  of  the  Complexus.  It  arises  by  from  two  to  four  tendinous  slips,  from  the 
transverse  processes  of  as  many  of  the  upper  dorsal  vertebrae,  and  is  inserted,  on 
the  inner  side  of  the  Complexus,  into  the  superior  curved  line  of  the  occipital  bone. 
Relations. — The  Complexus  is  covered  by  the  Splenius  and  the  Trapezius. 
It  lies  on  the  Rectus  capitis  posticus  major  and  minor,  the  Obliquus  capitis 
superior  and  inferior,  and  on  the  Semispinalis  colli,  from  which  it  is  separated  by 
the  profunda  eervicis  artery,  the  princeps  eervicis  artery,  and  branches  of  the 
posterior  primary  divisions  of  the  cervical  nerves.  The  Biventer  eervicis  is 
separated  from  its  fellow  of  the  opposite  side  by  the  ligamentum  nuchae. 

Fifth  Layer. 

Semispinalis  dorsi.  Extensor  coccygis. 

Semispinalis  colli.  Intertransversales. 

Multifidus  spinae.  Rectus  capitis  posticus  major. 

Rotatores  spinae.  Rectus  capitis  posticus  minor. 

Supraspinales.  Obliquus  capitis  inferior. 

Interspinales.  Obliquus  capitis  superior. 

Dissection. — Remove  the  muscles  of  the  preceding  layer  by  dividing  and  turning  aside  the 
Complexus ;  then  detach  the  Spinalis  and  Longissimus  dorsi  from  their  attachments,  divide  the 
Erector  spina?  at  its  connection  below  to  the  sacral  and  lumbar  spines,  and  turn  it  outward. 
The  muscles  filling  up  the  interval  between  the  spinous  and  transverse  processes  are  then 
exposed. 

The  Semispinalis  dorsi  (Fig.  214)  consists  of  thin,  narrow,  fleshy  fasciculi 
interposed  between  tendons  of  considerable  length.  It  arises  by  a  series  of  small 
tendons  from  the  transverse  processes  of  the  lower  dorsal  vertebrae,  from  the 
tenth  or  eleventh  to  the  fifth  or  sixth ;  and  is  inserted,  by  five  or  six  tendons, 
into  the  spinous  processes  of  the  upper  four  dorsal  and  lower  two  cervical  vertebrae. 

The  Semispinalis  colli,  thicker  than  the  preceding,  arises  by  a  series  of  tendinous 
and  fleshy  fibres  from  the  transverse  processes  of  the  upper  five  or  six  dorsal  vertebrae, 
and  is  inserted  into  the  spinous  processes  of  four  cervical  vertebrae,  from  the  axis  to  the 
fifth  cervical.  The  fasciculus  connected  with  the  axis  is  the  largest,  and  chiefly 
muscular  in  structure. 

Relations. — By  their  superficial  surface,  from  below  upward,  with  the  Spinalis 
dorsi,  Longissimus  dorsi,  Splenius,  Complexus,  the  profunda  eervicis  artery,  the 
princeps  eervicis  artery,  and  the  internal  branches  of  the  posterior  divisions  of 
the  first,  second,  and  third  cervical  nerves ;  by  their  deep  surface,  with  the  Mul- 
tifidus spinae. 

The  Multifidus  spinae  consists  of  a  number  of  fleshy  and  tendinous  fasciculi 
which  fill  up  the  groove  on  either  side  of  the  spinous  processes  of  the  vertebrae, 
from  the  sacrum  to  the  axis.  In  the  sacral  region  these  fasciculi  arise  from  the 
back  of  the  sacrum,  as  low  as  the  fourth  sacral  foramen,  and  from  the  aponeurosis 
of  origin  of  the  Erector  spinae  ;  from  the  inner  surface  of  the  posterior  superior  spine 
of  the  ilium  and  posterior  sacro-iliac  ligaments  ;  in  the  lumbar  regions,  from  the  ar- 
ticular processes ;  in  the  dorsal  region,  from  the  transverse  processes  ;  and  in  the 
cervical  region,  from  the  articular  processes  of  the  three  or  four  lower  vertebrae. 
Each  fasciculus,  passing  obliquely  upward  and  inward,  is  inserted  into  the  whole 
length  of  the  spinous  process  of  one  of  the  vertebrae  above.  These  fasciculi 
vary  in  length  :  the  most  superficial,  the  longest,  pass  from  one  vertebra  to  the 


OF    THE  BACK.  347 

third  or  fourth  above ;   those  next  in  order  pass  from  one  vertebra  to  the  second  or 
third  above ;  whilst  the  deepest  connect  two  contiguous  vertebrae. 

Relations. — By  its  superficial  surface,  with  the  Longissirnus  dorsi,  Spinalis 
dorsi,  Semispinalis  dorsi,  and  Semispinalis  colli ;  by  its  deep  surface,  with  the 
laminae  and  spinous  processes  of  the  vertebrae,  and  with  the  Rotatores  spinae  in 
the  dorsal  region. 

The  Rotatores  spinas  are  found  only  in  the  dorsal  region  of  the  spine,  beneath 
the  Multifidus  spinae ;  they  are  eleven  in  number  on  each  side.  Each  muscle 
is  small  and  somewhat  quadrilateral  in  form  ;  it  arises  from  the  upper  and  back 
part  of  the  transverse  process,  and  is  inserted  into  the  lower  border  and  outer 
surface  of  the  lamina  of  the  vertebra  above,  the  fibres  extending  as  far  inward  as 
the  root  of  the  spinous  process.  The  first  is  found  between  the  first  and  second 
dorsal ;  the  last,  between  the  eleventh  and  twelfth.  Sometimes  the  number  of 
these  muscles  is  diminished  by  the  absence  of  one  or  more  from  the  upper  or  lower 
end. 

The  Supraspinales  consist  of  a  series  of  fleshy  bands  which  lie  on  the  spinous 
processes  in  the  cervical  region  of  the  spine. 

The  Interspinals  are  short  muscular  fasciculi,  placed  in  pairs  between  the 
spinous  processes  of  the  contiguous  vertebrae,  one  on  each  side  of  the  interspinous 
ligament.  In  the  cervical  region  they  are  most  distinct,  and  consist  of  six  pairs, 
the  first  being  situated  between  the  axis  and  third  vertebra,  and  the  last  between 
the  last  cervical  and  the  first  dorsal.  They  are  small  narrow  bundles,  attached, 
above  and  below,  to  the  apices  of  the  spinous  processes.  In  the  dorsal  region 
they  are  found  between  the  first  and  second  vertebrae,  and  occasionally  betwe«n 
the  second  and  third ;  and  below,  between  the  eleventh  and  twelfth.  Id  the, 
lumbar  region  there  are  four  pairs  of  these  muscles  in  the  intervals  between  the 
five  lumbar  vertebrae.  There  is  also  occasionally  one  in  the  interspinous  space, 
between  the  last  dorsal  and  first  lumbar,  and  between  the  fifth  lumbar  and  the 
sacrum. 

The  Extensor  coccygis  is  a  slender  muscular  fasciculus,  occasionally  present, 
which  extends  over  the  lower  part  of  the  posterior  surface  of  the  sacrum  and 
coccyx.  It  arises  by  tendinous  fibres  from  the  last  bone  of  the  sacrum  or  first 
piece  of  the  coccyx,  and  passes  downward  to  be  inserted  into  the  lower  part  of 
the  coccyx.  It  is  a  rudiment  of  the  Extensor  muscle  of  the  caudal  vertebrae  of 
the  lower  animals. 

The  Intertransversales  are  small  muscles  placed  between  the  transverse  proc- 
esses of  the  vertebrae.  In  the  cervical  region  they  are  most  developed,  consisting 
of  rounded  muscular  and  tendinous  fasciculi,  which  are  placed  in  pairs,  passing 
between  the  anterior  and  the  posterior  tubercles  of  the  transverse  processes  of  two 
contiguous  vertebrae,  separated  from  one  another  by  the  anterior  division  of  the 
cervical  nerve,  which  lies  in  the  groove  between  them.  In  this  region  there  are 
seven  pairs  of  these  muscles,  the  first  pair  being  between  the  atlas  and  axis,  and 
the  last  pair  between  the  seventh  cervical  and  first  dorsal  vertebrae.  In  the  dorsal 
region  they  are  least  developed,  consisting  chiefly  of  rounded  tendinous  cords  in  the 
intertransverse  spaces  of  the  upper  dorsal  vertebrae;  but  between  the  transverse 
processes  of  the  lower  three  dorsal  vertebrae,  and  between  the  transverse  processes 
of  the  last  dorsal  and  the  first  lumbar,  they  are  muscular  in  structure.  In  the  lum- 
bar region  they  are  arranged  in  pairs,  on  either  side  of  the  spine,  one  set  occupy- 
ing the  entire  interspace  between  the  transverse  processes  of  the  lumbar  vertebrae, 
the  intertransversales  laterales  ;  the  other  set,  intertransversales  mediales,  passing 
from  the  accessory  process  of  one  vertebra  to  the  mammillary  process  of  the  next. 

The  Rectus  capitis  posticus  major  arises  by  a  pointed  tendinous  origin  from  the 
spinous  process  of  the  axis,  and,  becoming  broader  as  it  ascends,  is  inserted  into 
the  inferior  curved  line  of  the  occipital  bone  and  the  surface  of  bone  immediately 
below  it.  As  the  muscles  of  the  two  sides  pass  upward  and  outward,  they  leave 
between  them  a  triangular  space,  in  which  are  seen  the  Recti  capitis  postici 
minores  muscles. 


348  THE   MUSCLES   AND    FASCIAE 

Relations. — By  its  superficial  surface,  with  the  Complexus,  and,  at  its  inser- 
tion, with  the  Superior  oblique  ;  by  its  deep  surface,  with  part  of  the  Rectus  capitis 
posticus  minor,  the  posterior  arch  of  the  atlas,  the  posterior  occipito-atlantal  liga- 
ment, and  part  of  the  occipital  bone. 

The  Rectus  capitis  posticus  minor,  the  smallest  of  the  four  muscles  in  this 
region,  is  of  a  triangular  shape  ;  it  arises  by  a  narrow  pointed  tendon  from  the 
tubercle  on  the  posterior  arch  of  the  atlas,  and,  becoming  broader  as  it  ascends,  is 
inserted  into  the  rough  surface  beneath  the  inferior  curved  line,  nearly  as  far  as 
the  foramen  magnum,  nearer  to  the  middle  line  than  the  preceding. 

Relations. — By  its  superficial  surface,  with  the  Complexus  and  the  Rectus 
capitis  posticus  major;  by  its  deep  surface,  with  the  posterior  occipito-atlantal 
ligament. 

The  Obliquus  capitis  inferior,  the  larger  of  the  two  Oblique  muscles,  arises 
from  the  apex  of  the  spinous  process  of  the  axis,  and  passes  outward  and  slightly  up- 
ward, to  be  inserted  into  the  lower  and  back  part  of  the  transverse  process  of  the  atlas. 

Relations. — By  its  superficial  surface,  with  the  Complexus  and  with  the  pos- 
terior division  of  the  second  cervical  nerve,  which  crosses  it ;  by  its  deep  surface, 
with  the  vertebral  artery  and  posterior  atlanto-axial  ligament. 

The  Obliquus  capitis  superior,  narrow  below,  wide  and  expanded  above,  arises 
by  tendinous  fibres  from  the  upper  surface  of  the  transverse  process  of  the  atlas, 
joining  with  the  insertion  of  the  preceding,  and,  passing  obliquely  upward  and 
inward,  is  inserted  into  the  occipital  bone,  between  the  two  curved  lines,  external 
to  the  Complexus. 

Relations. — By  its  superficial  surface,  with  the  Complexus  and  Trachelo-mastoid 
and  occipital  artery.    By  its  deep  surface,v?\th  the  posterior  occipito-atlantal  ligament. 

The  Suboccipital  Triangle. — Between  the  two  oblique  muscles  and  the  Rectus 
capitis  posticus  major  a  triangular  interval  exists,  the  suboccipital  triangle.  This 
triangle  is  bounded,  above  and  internally,  by  the  Rectus  capitis  posticus  major; 
above  and  externally,  by  the  Obliquus  capitis  superior  ;  below  and  externally,  by 
the  Obliquus  capitis  inferior.  It  is  covered  in  by  a  layer  of  dense  fibro-fatty  tissue, 
situated  beneath  the  Complexus  muscle.  The  floor  is  formed  by  the  posterior  oc- 
cipito-atlantal ligament  and  the  posterior  arch  of  the  atlas.  It  contains  the  verte- 
bral artery,  as  it  runs  in  a  deep  groove  on  the  upper  surface  of  the  pos- 
terior arch   of  the   atlas,  and   the   posterior  division   of  the  suboccipital  nerve. 

Nerves. — The  third,  fourth,  and  fifth  layers  of  the  muscles  of  the  back  are 
supplied  by  the  posterior  primary   divisions  of  the  spinal  nerves. 

Actions. — When  both  the  Spinales  dorsi  contract,  they  extend  the  dorsal 
region  of  the  spine ;  when  only  one  muscle  contracts,  it  helps  to  bend  the  dorsal 
portion  of  the  spine  to  one  side.  The  Erector  spinas,  comprising  the  Ilio-costalis 
and  the  Longissimus  dorsi  with  their  accessory  muscles,  serves,  as  its  name  implies, 
to  maintain  the  spine  in  the  erect  posture ;  it  also  serves  to  bend  the  trunk  back- 
ward when  it  is  required  to  counterbalance  the  influence  of  any  weight  at  the 
front  of  the  body,  as,  for  instance,  when  a  heavy  weight  is  suspended  from  the 
neck,  or  when  there  is  any  great  abdominal  distension,  as  in  pregnancy  or  dropsy  ; 
the  peculiar  gait  under  such  circumstances  depends  upon  the  spine  being  drawn 
backward  by  the  counterbalancing  action  of  the  Erector  spina?  muscles.  The 
muscles  which  form  the  continuation  of  the  Erector  spinas  upward  steady  the 
head  and  neck,  and  fix  them  in  the  upright  position.  If  the  Ilio-costalis  and 
Longissimus  dorsi  of  one  side  act,  they  serve  to  draw  down  the  chest  and  spine  to 
the  corresponding  side.  The  Cervicales  ascendens,  taking  their  fixed  points  from 
the  cervical  vertebras,  elevate  those  ribs  to  which  they  are  attached;  taking  their  fixed 
points  from  the  ribs,  both  muscles  help  to  extend  the  neck  ;  while  one  muscle 
bends  the  neck  to  its  own  side.  The  Transversalis  cervicis,  when  both  muscles  act, 
taking  their  fixed  point  from  below,  bend  the  neck  backward.  The  Trachelo- 
mastoid,  when  both  muscles  act,  taking  their  fixed  point  from  below,  bend  the  head 
backward ;  while,  if  only  one  muscle  acts,  the  face  is  turned  to  the  side  on  which 
the' muscle  is  acting,  and  then  the  head  is  bent  to  the  shoulder.      The  two  Recti 


OF    THE   BACK.  349 

muscles  draw  the  head  backward.  The  Rectus  capitis  posticus  major,  owing  to 
its  obliquity,  rotates  the  cranium,  with  the  atlas,  round  the  odontoid  process, 
turning  the  face  to  the  same  side.  The  Multifidus  spinee  acts  successively  upon  the 
different  parts  of  the  spine ;  thus,  the  sacrum  furnishes  a  fixed  point  from  which 
the  fasciculi  of  this  muscle  act  upon  the  lumbar  region ;  these  then  become  the 
fixed  points  for  the  fasciculi  moving  the  dorsal  region,  and  so  on  throughout  the 
entire  length  of  the  spine ;  it  is  by  the  successive  contraction  and  relaxation  of 
the  separate  fasciculi  of  this  and  other  muscles  that  the  spine  preserves  the  erect 
posture  without  the  fatigue  that  would  necessarily  have  been  produced  had  this 
position  been  maintained  by  the  action  of  a  single  muscle.  The  Multifidus  spina-', 
besides  preserving  the  erect  position  of  the  spine,  serves  to  rotate  it,  so  that  the 
front  of  the  trunk  is  turned  to  the  side  opposite  to  that  from  which  the  muscle 
acts,  this  muscle  being  assisted  in  its  action  by  the  Obliquus  externus  abdominis. 
The  Complexi  draw  the  head  directly  backward  :  if  one  muscle  acts,  it  draws 
the  head  to  one  side,  and  rotates  it  so  that  the  face  is  turned  to  the  opposite 
side.  The  Superior  oblique  draws  the  head  backward,  and,  from  the  obliquitv 
in  the  direction  of  its  fibres,  will  slightly  rotate  the  cranium,  turning  the  face  to 
the  opposite  side.  The  Obliquus  capitis  inferior  rotates  the  atlas,  and  with  it  the 
cranium,  round  the  odontoid  process,  turning  the  face  to  the  same  side.  The 
Semispinals,  when  the  muscles  of  the  two  sides  act  together,  help  to  extend  the 
spine  ;  when  the  muscles  of  one  side  only  act,  they  rotate  the  dorsal  and  cervical 
parts  of  the  spine,  turning  the  body  to  the  opposite  side.  The  Supraspinales  and 
Interspmales  by  approximating  the  spinous  processes  help  to  extend  the  spine. 
The  Intertransversales  approximate  the  transverse  processes,  and  help  to  bend  the 
spine  to  one  side.  The  Rotatores  spinse  assist  the  Multifidus  spinas  to  rotate  the 
spine,  so  that  the  front  of  the  trunk  is  turned  to  the  side  opposite  to  that  from 
which  the  muscle  acts. 

,.„.  Surface  Forms.— The  surface  forms  produced  by  the  muscles  of  the  back  are  numerous  and 
difiicult  to  analyze  unless  they  are  considered  in  systematic  order.     The  most  superficial  layer, 
consisting  of  large  strata  of  muscular  substance,  influences  to  a  certain  extent  the  surface  form' 
and  at  the  same  time  reveals  the  forms  of  the  layers  beneath.     The  Trapezius  at  the  upper  pare 
ot  the  back,  and  in  the  neck,  covers  over  and  softens  down  the  outline  of  the  underlying  muscles 
Its  anterior  border  forms  the  posterior  boundary  of  the  posterior  triangle  of  the  neck  °  It  forms 
a  slight  undulating  ridge  which  passes  downward   and  forward  from  the  occiput  to  the  junction 
oUhe  middle  and  outer  third  of  the  clavicle.     The  tendinous  ellipse  formed  bv  a  part  of  the 
origin  of  the  two  muscles  at  the  back  of  the  neck  is  always  to  be  seen  as  an*oval  depression 
more  marked  when  the  muscle  is  in  action.     A  slight  dimple  on  the  skin  opposite  the  interval 
between  the  spinous  processes  of  the  third  and  fourth  dorsal  vertebra?  marks  the  triangular 
aponeurosis  by  which  the  inferior  fibres  are  inserted  into  the  root  of  the  spine  of  the  scapula 
brom  this  point  the  inferior  border  of  the  muscle  may  be  traced  as  an  undulating  ridge  to  the 
spinous  process  of  the  twelfth  dorsal  vertebra.     In  like  manner,  the  Latissimus  dorsi  softens 
down  and  modulates  the  underlying  structures  at  the  lower  part  of  the  back  and  lower  part  of 
the  side  of  the  chest.     In  this  way  it  modulates  the  outline  of  the  Erector  spina?  ;  of  the  Serratus 
posticus  inferior,  which  is  sometimes  to  be  discerned  through  it,  and  is  sometimes  entirely 
obscured  by  it ;  of  part  of  the  Serratus  magnus  and  Superior  oblique,  which  it  covers  ;  and  of 
the  convex  oblique  ridges  formed  by  the  ribs  with  the  intervening  intercostal  spaces.     The 
anterior  border  of  the  muscle  is  the  only  part  which  gives  a  distinct  surface  form.     This  border 
may  be  traced,  when  the  muscle  is  in  action,  as  a  rounded  edge,  starting  from  the  crest  of  the 
ilium,  and  passing  obliquely  forward  and  upward  to  the  posterior  border  of  the  axilla,  where  it 
■combines  with  the  Teres  major  in  forming  a  thick  rounded  fold,  the  posterior  boundary  of  the 
axillary  space.     The  muscles  in  the  second  layer  influence  to  a  very  considerable  extent  the  surface 
form  of  the  back  of  the  neck  and  upper  part  of  the  trunk.     The  Levator  anguli  scapuloz  reveals 
itself  as  a  prominent  divergent  line,  running  downward  and  outward,  from  the  transverse  pro- 
cesses of  the  upper  cervical  vertebrae  to  the  angle  of  the  scapula,  covered  over  and  toned  down 
by  the  overlying  Trapezius.     The  Rlimnboidei  produce,  when  in  action,  a  vertical  eminence 
between  the  vertebral  border  of  the  scapula  and  the  spinal  furrow,  varying  in  intensity  according 
to  the  condition  of  contraction  or  relaxation  of  the  Trapezius  muscle,  by  which  they  are  for  the 
most  part  covered.    The  lowermost  part  of  the  Rhomboideus  major  is  uncovered  by  the  Trapezius, 
and  forms  on  the  surface  an  oblique  ridge  running  upward  anil  inward  from  the  inferior  angle 
}f  the  scapula.     Of  the  muscles  of  the  third  layer  of  the  back,  the  Serratus  posticus  superior 
ioes  not  in  any  way  influence  surface  form.     The   Serratus  posticus  inferior,  when  in  strong 
iction^  may  occasionally  be  revealed  as  an  elevation  beneath  the  Latissimus  dorsi.     The  Splenii 
py  their  divergence  serve  to  broaden  out  the  upper  part  of  the  back  of  the  neck  and  produoe  a 


350  THE   MUSCLES  AND    EASCIJE 

local  fulness  in  this  situation,  but  do  not  otherwise  influence  surface  form.  _  Beneath  all  these 
muscles  those  of  the  fourth  layer — the  Erector  spince  and  its  continuations — influence  the  surface 
form  in  a  decided  manner.  In  the  loins,  the  Erector  spinas,  bound  down  by  the  lumbar  fascia, 
forms  a  rounded  vertical  eminence,  which  determines  the  depth  of  the  spinal  furrow,  and  which 
below  tapers  to  a  point  on  the  posterior  surface  of  the  sacrum  and  becomes  lost  there.  In  the 
back  it  forms  a  flattened  plane  which  gradually  becomes  lost.  In  the  neck  the  only  part  of  this 
group  of  muscles  which  influences  surface  form  is  the  Trachelo-mastoid,  which  produces  a  short 
convergent  line  across  the  upper  part  of  the  posterior  triangle  of  the  neck,  appearing  from 
under  cover  of  the  posterior  border  of  the  Sterno-mastoid  and  being  lost  below  beneath  the 
Trapezius. 

2.  MUSCLES  AND  FASCLE  OF  THE  THORAX. 

The  muscles  belonging  exclusively  to  this  region  are  few  in  number.     They  are  the 
Intercostales  externi.  Triangularis  sterni. 

Intercostales  interni.  Levatores  costarum. 

Infracostales.  Diaphragm. 

Intercostal  Fasciae. — A  thin  but  firm  layer  of  fascia  covers  the  outer  surface  of 
the  External  intercostal  and  the  inner  surface  of  the  Internal  intercostal  muscles  ; 
and  a  third  layer,  the  middle  intercostal  fascia,  more  delicate,  is  interposed  between 
the  two  planes  of  muscular  fibres.  These  are  the  intercostal  fasciae  ;  they  are  best 
marked  in  those  situations  where  the  muscular  fibres  are  deficient,  as  between  the 
External  intercostal  muscles  and  sternum,  in  front,  and  between  the  Internal 
intercostals  and  spine,  behind. 

The  Intercostal  muscles  (Fig.  230)  are  two  thin  planes  of  muscular  and  tendinous 
fibres,  placed  one  over  the  other,  filling  up  the  intercostal  spaces,  and  being  directed 
obliquely  between  the  margins  of  the  adjacent  ribs.  They  have  received  the  name 
"  external  "  and  "  internal  "  from  the  position  they  bear  to  one  another.  The 
tendinous  fibres  are  longer  and  more  numerous  than  the  muscular ;  hence  the  walls 
of  the  intercostal  spaces  possess  very  considerable  strength,  to  which  the  crossing  of 
the  muscular  fibres  materially  contributes. 

The  External  Intercostals  are  eleven  in  number  on  each  side.  They  extend 
from  the  tubercles  of  the  ribs,  behind,  to  the  commencement  of  the  cartilages  of 
the  ribs,  in  front,  where  they  terminate  in  a  thin  membrane,  the  anterior  inter- 
costal membrane,  wThich  is  continued  forward  to  the  sternum.  They  arise  from  the 
lower  border  of  each  rib,  and  are  inserted  into  the  upper  border  of  the  rib  below. 
In  the  two  lowTest  spaces  they  extend  to  the  end  of  the  cartilages,  and  in  the  upper 
two  or  three  spaces  they  do  not  quite  extend  to  the  ends  of  the  ribs.  Their  fibres 
are  directed  obliquely  downward  and  forward,  in  a  similar  direction  with  those  of 
the  External  oblique  muscle  of  the  abdomen.  They  are  thicker  than  the  Internal 
intercostals. 

Relations. — By  their  outer  surface,  with  the  muscles  which  immediately  invest 
the  chest — viz.  the  Pectoralis  major  and  minor,  Serratus  magnus,  and  Rhomboideus 
major,  Serratus  posticus  superior  and  inferior,  Scalenus  posticus,  Uio-costalis, 
Longissimus  dorsi,  Cervicalis  ascendens,  Trans versalis  cervicis,  Levatores  costarum, 
Obliquus  externus  abdominis,  and  the  Latissimus  dorsi;  by  their  internal  surface, 
with  the  middle  intercostal  fascia,  which  separates  them  from  the  intercostal  vessels 
and  nerve  and  the  Internal  intercostal  muscles,  and,  behind,  from  the  pleura. 

The  Internal  intercostals  are  also  eleven  in  number  on  each  side.  They  com- 
mence anteriorly  at  the  sternum,  in  the  interspaces  between  the  cartilages  of  the 
true  ribs,  and  from  the  anterior  extremities  of  the  cartilages  of  the  false  ribs,  and 
extend  backward  as  far  as  the  angles  of  the  ribs,  whence  they  are  continued  to  the 
vertebral  column  by  a  thin  aponeurosis,  the  posterior  intercostal  membrane.  They 
arise  from  the  ridge  on  the  inner  surface  of  each  rib,  as  well  as  from  the  corre- 
sponding costal  cartilage,  and  are  inserted  into  the  upper  border  of  the  rib  below. 
Their  fibres  are  directed  obliquely  downward  and  backward,  passing  in  the  oppo- 
site direction  to  the  fibres  of  the  External  intercostal  muscle. 

Relations. — By  their  external  surface,  with  the  intercostal  vessels  and  nerves 
and  the  External  intercostal  muscles  ;   near  the  sternum,  with  the  anterior  inter- 


OF     rHE    THORAX. 


351 


costal  membrane  and  the  Pectoralis  major.  By  their  internal  surface,  with  the 
pleura  costalis,   Triangularis  sterni,  and  Diaphragm. 

The  Infracostales  (subcostales)  consist  of  muscular  and  aponeurotic  fasciculi, 
which  vary  in  number  and  length :  they  are  placed  on  the  inner  surface  of  the  ribs, 
where  the  Internal  intercostal  muscles  cease ;  they  arise  from  the  inner  surface  of 
one  rib,  and  are  inserted  into  the  inner  surface  of  the  first,  second,  or  third  rib 
below.  Their  direction  is  most  usually  oblique,  like  the  Internal  intercostals. 
They  are  most  frequent  between  the  lower  ribs. 

The  Triangularis  sterni  (Fig.  215)  is  a  thin  plane  of  muscular  and  tendinous 
fibres,  situated  upon  the  inner  wall  of  the  front  of  the  chest.  It  arises  from  the 
lower  third  of  the  posterior  surface  of  the  sternum,  from  the  posterior  surface  of 
Ihe  ensiform  cartilage,  and  from  the  sternal  ends  of  the  costal  cartilages  of  the-  three 


STERNO-MASTOID 


SUBCLAVIUS. 


SUBCLAVIUS. 


jayyi     Internal  mam- 
fell        mary  artery. 


TRIANGULARIS 
STERNI. 


TRANSVERSALIS    ABDOMINIS. 


!Fig.  215.— Posterior  surface  of  sternum  and  costal  cartilages,  showing  Triangularis  sterni  muscle.    (From  a 
preparation  in  the  Museum  of  the  Royal  College  of  Surgeons  of  England.) 


or  four  lower  true  ribs.  Its  fibres  diverge  upward  and  outward,  to  be  inserted  by 
digitations  into  the  lower  border  and  inner  surfaces  of  the  costal  cartilages  of  the 
second,  third,  fourth,  fifth,  and  sixth  ribs.  The  lowest  fibres  of  this  muscle  are 
horizontal  in  their  direction,  and  are  continuous  with  those  of  the  Transversal  is : 
those  which  succeed  are  oblique,  whilst  the  superior  fibres  are  almost  vertical.  This 
muscle  varies  much  in  its  attachment,  not  only  in  different  bodies,  but  on  opposite 
sides  of  the  same  body. 

Relations. — In  front,  with  the  sternum,   ensiform  cartilage,  costal  cartilages. 


352  THE   MUSCLES   AJYO    EASCIJEJ 


Internal   intercostal    muscles,   and    internal    mammary  vessels ;    behind,   with  the 
pleura,  pericardium,  and  anterior  mediastinum. 

The  Levatores  Costarum  (Fig.  214),  twelve  in  number  on  each  side,  are  small 
tendinous  and  fleshy  bundles  which  arise  from  the  extremities  of  the  transverse 
processes  of  the  seventh  cervical  and  eleven  upper  dorsal  vertebrae,  and,  passing 
obliquely  downward  and  outward,  are  inserted  into  the  upper  border  of  the  rib 
below  them,  between  the  tubercle  and  the  angle.  The  Inferior  levatores  divide 
into  two  fasciculi,  one  of  which  is  inserted  as  above  described ;  the  other  fasciculus 
passes  down  to  the  second  rib  below  its  origin ;  thus,  each  of  the  lower  ribs  re- 
ceives fibres  from  the  transverse  processes  of  two  vertebrae. 

Nerves. — The  muscles  of  this  group  are  supplied  by  the  intercostal  nerves. 

The  Diaphragm  (dcd<ppayjua,  a  partition  wall)  (Fig.  216)  is  a  thin,  musculo- 
fibrous  septum,  consisting  of  muscular  fibres  externally,  which  arise  from  the  cir- 
cumference of  the  thoracic  cavity  and  pass  upward  and  inward  to  converge  to  a 
central  tendon.  It  is  placed  obliquely  at  the  junction  of  the  upper  with  the  middle 
third  of  the  trunk,  and,  separating  the  thorax  from  the  abdomen,  forming  the  floor 
of  the  former  cavity  and  the  roof  of  the  latter.  It  is  elliptical,  its  longest  diameter 
being  from  side  to  side,  somewhat  fan-shaped,  the  broad  elliptical  portion  being 
horizontal,  the  narrow  part,  the  crura,  which  represents  the  handle  of  the  fan, 
vertical,  and  joined  at  right  angles  to  the  former.  It  is  from  this  circumstance 
that  some  anatomists  describe  it  as  consisting  of  two  portions,  the  upper  or  great 
muscle  of  the  Diaphragm,  and  the  lower  or  lesser  muscle.  It  arises  from  the  whole 
of  the  internal  circumference  of  the  thorax,  being  attached,  in  front,  by  fleshy 
fibres  to  the  ensiform  cartilage  ;  on  either  side,  to  the  inner  surface  of  the  cartilages 
and  bony  portions  of  the  six  or  seven  inferior  ribs,  interdigitating  with  the  Trans- 
versalis ;  and  behind,  to  two  aponeurotic  arches,  named  the  ligamentum  arcuatum 
externum  et  internum,  and  by  the  crura,  to  the  lumbar  vertebras.  The  fibres  from 
these  sources  vary  in  length :  those  arising  from  the  ensiform  appendix  are  very 
short  and  occasionally  aponeurotic  ;  those  from  the  ligamenta  arcuata,  and  more 
especially  those  from  the  cartilages  of  the  ribs  at  the  side  of  the  chest,  are  longer, 
describe  well-marked  curves  as  they  ascend,  and  finally  converge  to  be  inserted 
into  the  circumference  of  the  central  tendon.  Between  the  sides  of  the  muscular 
slip  from  the  ensiform  appendix  and  the  cartilages  of  the  adjoining  ribs  the  fibres 
of  the  Diaphragm  are  deficient,  the  interval  being  filled  by  areolar  tissue,  covered 
on  the  thoracic  side  by  the  pleurae  ;  on  the  abdominal,  by  the  peritoneum.  This  is, 
consequently,  a  weak  point,  and  a  portion  of  the  contents  of  the  abdomen  may 
protrude  into  the  chest,  forming  phrenic  or  diaphragmatic  hernia,  or  a  collection 
of  pus  in  the  mediastinum  may  descend  through  it,  so  as  to  point  at  the  epigas- 
trium. A  triangular  gap  is  sometimes  seen  between  the  fibres  springing  from  the 
internal  and  those  arising  from  the  external  arcuate  ligament.  When  it  exists,  the 
kidney  is  separated  from  the  pleura  only  by  fatty  and  areolar  tissue. 

The  ligamentum  arcuatum  internum  is  a  tendinous  arch,  thrown  across  the 
upper  part  of  the  Psoas  magnus  muscle,  on  each  side  of  the  spine.  It  is  connected, 
by  one  end,  to  the  outer  side  of  the  body  of  the  first  or  second  lumbar  vertebra, 
being  continuous  with  the  outer  side  of  the  tendon  of  the  corresponding  crus ;  and, 
by  the  other  end,  to  the  front  of  the  transverse  process  of  the  first,  and  sometimes 
also  to  that  of  the  second,  lumbar  vertebra." 

The  ligamentum  arcuatum  externum  is  the  thickened  upper  margin  of  the 
anterior  lamella  of  the  lumbar  fascia ;  it  arches  across  the  upper  part  of  the  Quad- 
ratus  lumborum,  being  attached,  by  one  extremity,  to  the  front  of  the  transverse 
process  of  the  first  lumbar  vertebra,  and,  by  the  other,  to  the  apex  and  lower 
margin  of  the  last  rib. 

The  Crura. — The  Diaphragm  is  connected  to  the  spine  by  two  crura  or  pillars, 
which  are  situated  on  the  bodies  of  the  lumbar  vertebras,  on  each  side  of  the  aorta. 
The  crura,  at  their  origin,  are  tendinous  in  structure ;  the  right  crus,  larger  and 
longer  than  the  left,  arising  from  the  anterior  surface  of  the  bodies  and  inter- 
vertebral substances  of  the  three  or  four  upper  lumbar  vertebrae ;  the  left,  from 


OF   THE    THORAX. 


353 


the  two  upper ;  both  blending  with  the  anterior  common  ligament  of  the  spine. 
These  tendinous  portions  of  the  crura  pass  forward  and  inward,  and  gradually 
converge  to  meet  in  the  middle  line,  forming  an  arch,  beneath  which  passes  the 
aorta,  vena  azygos  major,  and  thoracic  duct.  From  this  tendinous  arch  muscular 
fibres  arise,  Avhich  diverge,  the  outermost  portion  being  directed  upward  and 
outward  to  the  central  tendon ;  the  innermost  decussating  in  front  of  the  aorta, 
and  then  diverging,  so  as  to  surround  the  oesophagus  before  ending  in  the  central 
tendon.  The  fibres  derived  from  the  right  crus  are  the  most  numerous  and  pass 
in  front  of  those  derived  from  the  left. 

The   Central  or   Cordiform   Tendon  of  the  Diaphragm   is   a  thin  but  strong 
tendinous  aponeurosis,  situated  at  the  centre  of  the  vault  formed  by  the  muscle, 


^Worm  CaX^L. 


Fig.  216.— The  Diaphragm.    Under  surface 


immediately  below  the  pericardium,  with  which  it  is  partly  blended.  It  is  shaped 
somewhat  efoil  leaf,  consisting  of  three  divisions,  or  leaflets,  separated 

from  one  ;  >y  slight  indentations.      The  right  leaflet  is  the  largest ;  the 

middle  one  d  toward  the  ensiform  cartilage,  the  next  in  size ;  and  the 

left,  the  smallest.  In  structure,  the  tendon  is  composed  of  several  planes  of 
fibres  whic  intersect  one  another  at  various  angles,  and  unite  into  straight  or 
curved  bun  11   3— an  arrangement  which  affords  it  additional  strength. 

The  (9/  onnected  with   the  Diaphragm   are   three  large   and   several 

smaller  ape  tares.  The  former  are  the  aortic,  the  oesophageal,  and  the  opening 
for  the  ven 

The  ao\  ing  is  the  lowest  and   the  most  posterior  of  the  three  large 

1/apertures  d  with   this  muscle,  being  at   the  level  of  the  first  lumbar 

vertebra.  uated  slightly  to  the  left  of  the  middle   line,  immediately  in 

front  of  th  of  the  vertebras ;  and  is,  therefore,  behind  the  Diaphragm,  not 

23 


354  THE   MUSCLES  AND    FASCIAE 

in  it.  It  is  an  osseo-aponeurotic  aperture,  formed  by  a  tendinous  arch  thrown 
across  the  front  of  the  bodies  of  the  vertebrae,  from  the  crus  on  one  side  to  that 
on  the  other,  and  transmits  the  aorta,  vena  azygos  major,  and  thoracic  duct. 
Sometimes  the  vena  azygos  major  is  transmitted  upward  through  the  right  crus. 
Occasionally  some  tendinous  fibres  are  prolonged  across  the  bodies  of  the  ver- 
tebrae from  the  inner  part  of  the  lower  end  of  tbe  crura,  passing  behind  the  aorta, 
and  thus  converting  the  opening  into  a  fibrous  ring. 

The  oesophageal  opening  is  situated  at  the  level  of  the  tenth  dorsal  vertebra ; 
it  is  elliptical  in  form,  muscular  in  structure,  and,  formed  by  the  decussating  fibres 
of  the  two  crura,  is  placed  above,  and,  at  the  same  time,  anterior,  and  a  little  to 
the  left  of  the  preceding.  It  transmits  the  oesophagus  and  pneumogastric  nerves 
and  some  small  oesophageal  arteries.  The  anterior  margin  of  this  aperture  is 
occasionally  tendinous,  being  formed  by  the  margin  of  the  central  tendon. 

The  opening  for  the  vena  cava  {foramen  quadratum)  is  the  highest,  about  on 
the  level  of  the  disc  between  the  eighth  and  ninth  dorsal  vertebrae ;  it  is  quadri- 
lateral in  form,  tendinous  in  structure,  and  placed  at  the  junction  of  the  right 
and  middle  leaflets  of  the  central  tendon,  its  margins  being  adherent  to  the  wall 
of  the  inferior  vena  cava. 

The  right  crus  transmits  the  greater  and  lesser  splanchnic  nerves  of  the  right 
side ;  the  left  crus  transmits  the  greater  and  lesser  splanchnic  nerves  of  the  left 
side,  and  the  vena  azygos  minor.  The  gangliated  cords  of  the  sympathetic 
usually  enter  the  abdominal  cavity  by  passing  behind  the  internal  arcuate 
ligaments. 

The  Serous  Membranes  in  relation  with  the  Diaphragm  are  four  in  number: 
three  lining  its  upper  or  thoracic  surface ;  one,  its  abdominal.  The  three  serous 
membranes  on  its  upper  surface  are  the  pleura  on  either  side  and  the  serous  layer 
of  the  pericardium,  which  covers  the  middle  portion  of  the  tendinous  centre.  The 
serous  membrane  covering  its  under  surface  is  a  portion  of  the  general  peritoneal 
membrane  of  the  abdominal  cavity. 

The  Diaphragm  is  arched,  being  convex  toward  the  chest  and  concave  to  the 
abdomen.  The  right  portion  forms  a  complete  arch  from  before  backward,  being 
accurately  moulded  over  the  convex  surface  of  the  liver,  and  having  resting  upon 
it  the  concave  base  of  the  right  lung.  The  left  portion  is  arched  from  before  back- 
ward in  a  similar  manner ;  but  the  arch  is  narrower  in  front,  being  encroached  upon 
by  the  pericardium,  and  lower  than  the  right,  at  its  summit,  by  about  three-quarters 
of  an  inch.  It  supports  the  base  of  the  left  lung,  and  covers  the  great  end  of  the 
stomach,  the  spleen,  and  left  kidney.  At  its  circumference  the  Diaphragm  is 
higher  in  the  mesial  line  of  the  body  than  at  either  side ;  but  in  the  middle  of  the 
thorax  the  central  portion,  which  supports  the  heart,  is  on  a  lower  level  than  the 
two  lateral  portions. 

Nerves. — The  Diaphragm  is  supplied  by  the  phrenic  nerves  and  lower  inter- 
costal nerves  and  phrenic  plexus  of  the  sympathetic. 

Actions. — The  Intercostals  are  the  chief  agents  in  the  movement  of  the  ribs 
in  ordinary  respiration.  When  the  first  rib  is  elevated  and  fixed  by  the  Scaleni,  the 
External  intercostals  raise  the  other  ribs,  especially  their  fore  part,  and  so  increase 
the  capacity  of  the  chest  from  before  backward ;  at  the  same  time  they  evert  their 
lower  borders,  and  so  enlarge  the  thoracic  cavity  transversely.  The  Internal 
intercostals,  at  the  side  of  the  thorax,  depress  the  ribs  and  invert  their  lower 
borders,  and  so  diminish  the  thoracic  cavity  ;  but  at  the  fore  part  of  the  chest  these 
muscles  assist  the  External  intercostals  in  raising  the  cartilages.1     The  Levatores 

1  The  view  of  the  action  of  the  Intercostal  muscles  given  in  the  text  is  that  which  is  taught  by 
Hutchinson  (Cycl.  of  Anal,  and  Phys.,  art.  "  Thorax"),  and  is  usually  adopted  in  our  schools.  It  is, 
however,  much  disputed.  Hamberger  believed  that  the  External  intercostals  act  as  elevators  of  the 
ribs,  or  muscles  of  inspiration,  while  the  Internal  act  in  expiration.  Haller  taught  that  both  sets  of 
muscles  act  in  common — viz.  as  muscles  of  inspiration — and  this  view  is  adopted  by  many  of  the  besta . 
anatomists  of  the  Continent,  and  appears  supported  by  many  observations  made  on  the  human  subject  r 
under  various  conditions  of  disease,  and  on  living  animals  after  the  muscles  have  been  exposed  under 
chloroform.     The  reader  may  consult  an  interesting  paper  by  Dr.  Cleland  in  the  Journal  of  Anat.  and 


OF   THE   THORAX.  355 

costarum  assist  the  External  intercostals  in  raising  the  ribs.  The  Triangularis, 
sterni  draws  down  the  costal  cartilages  ;   it  is  therefore  an  expiratory  muscle.    n 

The  Diaphragm  is  the  principal  muscle  of  inspiration.  When  in  a  conditi<e(j 
of  rest  the  muscle  presents  a  domed  surface,  concave  toward  the  abdomen  ;  a  he 
consists  of  a  circumferential  muscular  and  a  central  tendinous  part.  Wh)ra 
the  muscular  fibres  contract,  they  become  less  arched,  or  nearly  straight,  a.-n. 
thus  cause  the  central  tendon  to  descend,  and  in  consequence  the  level  of  th  • 
chest-wall  is  lowered,  the  vertical  diameter  of  the  chest  being  proportionally 
increased.  In  this  descent  the  different  parts  of  the  tendon  move  unequally. 
The  left  leaflet  descends  to  the  greatest  extent ;  the  right  to  a  less  extent,  on 
account  of  the  liver ;  and  the  central  leaflet  the  least,  because  of  its  connection  to 
the  pericardium.  In  descending  the  diaphragm  presses  on  the  abdominal  viscera, 
and  so  to  a  certain  extent  causes  a  projection  of  the  abdominal  wall ;  but  in  conse- 
quence of  these  viscera  not  yielding  completely,  the  central  tendon  becomes  a  fixed 
point,  and  enables  the  circumferential  muscular  fibres  to  act  from  it,  and  so  elevate 
the  lower  ribs  and  expand  the  lower  part  of  the  thoracic  cavity ;  and  Duchenne 
has  shown  that  the  Diaphragm  has  the  power  of  elevating  the  ribs,  to  which  it 
is  attached,  by  its  contraction,  if  the  abdominal  viscera  are  in  situ,  but  that  if  these 
organs  are  removed,  this  power  is  lost.  When  at  the  end  of  inspiration  the  Dia- 
phragm relaxes,  the  thoracic  walls  return  to  their  natural  position  in  consequence 
of  their  elastic  reaction  and  of  the  elasticity  and  weight  of  the  displaced  viscera.1 

In  all  expulsive  acts  the  Diaphragm  is  called  into  action,  to  give  additional 
power  to  each  expulsive  effort.  Thus,  before  sneezing,  coughing,  laughing,  and 
crying,  before  vomiting,  previous  to  the  expulsion  of  the  urine  and  faeces,  or  of 
the  foetus  from  the  womb,  a  deep  inspiration  takes  place. 

The  height  of  the  Diaphragm  is  constantly  varying  during  respiration,  the 
muscle  being  carried  upward  or  downward  from  the  average  level ;  its  height  also 
varies  according  to  the  degree  of  distension  of  the  stomach  and  intestines,  and  the 
size  of  the  liver.  After  a  forced  expiration,  the  right  arch  is  on  a  level,  in  front, 
with  the  fourth  costal  cartilage  ;  at  the  side,  with  the  fifth,  sixth,  and  seventh 
ribs  ;  and  behind,  with  the  eighth  rib,  the  left  arch  being  usually  from  one  to  two 
ribs'  breadth  below  the  level  of  the  right  one.  In  a  forced  inspiration,  it  descends 
from  one  to  two  inches ;  its  slope  would  then  be  represented  by  a  line  drawn  from 
the  ensiform  cartilage  toward  the  tenth  rib. 

Muscles  of  Inspiration  and  Expiration. — The  muscles  which  assist  the  action 
of  the  Diaphragm  in  ordinary  tranquil  inspiration  are  the  Intercostals  and  the 
Levatores  costarum,  as  above  stated,  and  the  Scaleni.  When  the  need  for  more 
forcible  action  exists,  the  shoulders  and  the  base  of  the  scapula  are  fixed,  and  then 
the  powerful  muscles  of  forced  inspiration  come  into  play ;  the  chief  of  these  are 
the  Trapezius,  the  Pectoralis  minor,  the  Serratus  posticus  superior  and  inferior, 
and  the  Rhomboidei.  The  lower  fibres  of  the  Serratus  magnus  may  possibly  assist 
slightly  in  dilating  the  chest  by  raising  and  everting  the  ribs.  The  Sterno- 
mastoid  also,  when  the  head  is  fixed,  assists  in  forced  inspiration  by  drawing  up 
the  sternum  and  by  fixing  the  clavicle,  and  thus  affording  a  fixed  point  for  the 
action  of  the  muscles  of  the  chest.  The  Ilio-costalis  and  Quadratus  lumborum 
assist  in  forced  inspiration  by  fixing  the  last  rib  (see .  page  367). 

The  ordinary  action  of  expiration  is  hardly  effected  by  muscular  force,  but 
results  from  a  return  of  the  walls  of  the  thorax  to  a  condition  of  rest,  owing  to 
their  own  elasticity  and  to  that  of  the  lungs.     Forced   expiratory  actions  are 

Phys.  No.  II.,  May,  1867,  p.  209,  "On  the  ITutehinsonian  Theory  of  the  Action  of  the  Intercostal 
Muscles,"  who  refers  also  to  Henle,  Lusphka,  Budge,  and  Baumler,  Observations  on  the  Action  of  the 
Intercostal  Muscles,  Erlangen.  1860.  <  In  New  Syd.  SocSs  Year-Bookfor  1861 ,  p.  69.)  Dr.  W.  W.  Keen  has 
come  to  the  conclusion,  from  experiments  made  upon  a  criminal  executed  by  hanging,  that  the  Exter- 
nal intercostals  are  muscles  of  expiration,  as  they  pulled  the  ribs  down,  while  the  Internal  intercostals 
pulled  the  ribs  up  and  are  n  usdfcs  of  inspiration  (  Trans.  Cull.  PIu/s.  Philadelphia,  Third  Series,  vol.  i., 
1875,  p.  97). 

1  For  a  detailed  description  of  the  general  relations  of  the  Diaphragm,  and  its  action,  refer  to 
Dr.  Sibson's  Medical  Anatomy.    \ 


356 


THE   MUSCLES   AND    FASCIAE 


performed  mainly  by  the  flat  muscles  (Obliqui  and  Transversalis)  of  the  abdomen, 
aL«isted  also  by  the  Rectus.  Other  muscles  of  forced  expiration  are  the  Internal 
°,n  ercostals  and  Triangularis  sterni  (as  above  mentioned). 

801  o  V  J 


Oci 

teb 


3.    MUSCLES  OF  THE  ABDOMEN. 


The  muscles  of  the  abdomen  may  be  divided  into  two  groups :   1.  The  super- 
cial  muscles  of  the  abdomen ;  2.  The  deep  muscles  of  the  abdomen. 


1.  Superficial  Muscles. 

The  Muscles  in  this  region  are,  the 
Obliquus  Externus. 
Obliquus  Interims. 

Pvramidalis. 


Transversalis. 
Rectus. 


5.   Dis- 
section of\ 
inguinal 
hernia. 


Dissection  (Fig.  217). — To  dissect  the  abdominal 
muscles,  make  a  vertical  incision  from  the  ensiform  car- 
tilage to  the  symphysis  pubis  ;  a  second  incision  from  the 
umbilicus  obliquely  upward  and  outward  to  the  outer  sur- 
face of  the  chest,  as  high  as  the  lower  border  of  the  fifth 
or  sixth  rib ;  and  a  third',  commencing  midway  between 
the  umbilicus  and  pubes,  transversely  outward  to  the  ante- 
rior superior  iliac  spine,  and  along  the  crest  of  the  ilium 
as  far  as  its  posterior  third.  Then  reflect  the  three  flaps 
included  between  these  incisions  from  within  outward,  in 
the  lines  of  direction  of  the  muscular  fibres.  If  necessary, 
the  abdominal  muscles  may  be  made  tense  by  inflating  the 
peritoneal  cavity  through  the  umbilicus. 

The  Superficial  fascia  of  the  abdomen  consists, 
over  the  greater  part  of  the  abdominal  wall,  of  a 
single  layer  of  fascia,  which  contains  a  variable 
amount  of  fat ;  but  as  this  layer  approaches  the 
groin  it  is  easily  divisible  into  two  layers,  be- 
tween which  are  found  the  superficial  vessels  and 
nerves  and  the  superficial  inguinal  lymphatic 
glands.  The  superficial  layer  (fascia  of  Camper) 
is  thick,  areolar  in  texture,  containing  adipose 
tissue  in  its  meshes,  the  quantity  of  which  varies 
in  different  subjects.  Below  it  passes  over  Pou- 
part's  ligament,  and  is  continuous  with  the  outer 
layer  of  the  superficial  fascia  of  the  thigh.  In  the  male  this  fascia  is  continued 
over  the  penis  and  outer  surface  of  the  cord  to  the  scrotum,  where  it  helps  to  form 
the  dartos.  As  it  passes  to  the  scrotum  it  changes  its  character,  becoming  thin, 
destitute  of  adipose  tissue,  and  of  a  pale  reddish  color,  and  in  the  scrotum  it 
acquires  some  involuntary  muscular  fibres.  From  the  scrotum  it  may  be  traced 
backward  to  be  continuous  with  the  superficial  fascia  of  the  perineum.  In  the 
female  this  fascia  is  continued  into  the  labia  majora.  The  deeper  layer  (fascia  of 
Scarpa)  is  thinner  and  more  membranous  in  character  than  the  superficial  layer. 
In  the  middle  line  it  is  intimately  adherent  to  the  linea  alba  and  to  the  symphysis 
pubis,  and  is  prolonged  on  to  the  dorsum  of  the  penis,  forming  the  suspensory 
ligament ;  above,  it  is  continuous  with  the  superficial  fascia  over  the  rest  of  the 
trunk  ;  below,  it  blends  with  the  fascia  lata  of  the  thigh  a  little  below  Poupart's 
ligament;  and  below  and  internally  it  is  continued  over  the  penis  and  spermatic 
cord  to  the  scrotum,  where  it  helps  to  form  the  dartos.  From  the  scrotum  it  may 
be  traced  backward  to  be  continuous  with  the  deep  layer  of  the  superficial  fascia 
of  the  perinseum.      In  the  female  it  is  continued  into  the  labia  majora. 

The  External  or  Descending  Oblique  muscle  (Fig.  218)  is  situated  on  the  side 
and  fore  part  of  the  abdomen ;  being  the  largest  and  the  most  superficial  of  the 
three  flat  muscles  in  this  region.  It  is  broad,  thin,  and  irregularly  quadrilateral, 
its  muscular  portion  occupying  the  side,  its  aponeurosis  the  anterior  wall,  of  the 


Fig.  217.— Dissection  of  abdomen! 


\ 


OF    THE   ABDOMEN.  357 

abdomen.  It  arises,  by  eight  fleshy  digitations,  from  the  external  surface  and 
lower  borders  of  the  eight  inferior  ribs ;  these  digitations  are  arranged  in  an 
oblique  line  running  downward  and  backward ;  the  upper  ones  being  attached 
close  to  the  cartilages  of  the  corresponding  ribs  ;  the  lowest,  to  the  apex  of  the 
cartilage  of  the  last  rib ;  the  intermediate  ones,  to  the  ribs  at  some  distance  from 
their  cartilages.  The  five  superior  serrations  increase  in  size  from  above  down- 
ward, and  are  received  between  corresponding  processes  of  the  Serratus  magnus ; 
the  three  lower  ones  diminish  in  size  from  above  downward,  receiving  between 
them  corresponding  processes  from  the  Latissimus  dorsi.  From  these  attachments, 
the  fleshy  fibres  proceed  in  various  directions.  Those  from  the  lowest  ribs  pass 
nearly  vertically  downward,  to  be  inserted  into  the  anterior  half  of  the  outer  lip 
of  the  crest  of  the  ilium  ;  the  middle  and-upper  fibres,  directed  downward  and  for- 
ward, terminate  in  an  aponeurosis,  opposite  a  line  drawn  from  the  prominence  of 
the  ninth  costal  cartilage  to  the  anterior  superior  spinous  process  of  the  ilium. 

The  Aponeurosis  of  the  External  Oblique  is  a  thin,  but  strong  .  bi^nows 
aponeurosis,  the  fibres  of  which  are  directed  obliquely  downward  and  inward.  It 
is  joined  with  that  of  the  opposite  muscle  along  the  median,'' line,  covers  the 
whole  of  the  front  of  the  abdomen;  above,  it  is  connected  wit'a  the  lower  border 
of  the  Pectoralis  major  ;  below,  its  fibres  are  closely,  aggregated  together,  and 
extend  obliquely  across  from  the  anterior  superior  spine  of  the  ilium  to  the  spine 
of  the  os  pubis  and  the  linea  ilio-pectinea.  In  the  median  line  it  interlaces  with 
the  aponeurosis  of  the  opposite  muscle,  forming  the  lint1  a  alba,  which  extends  from 
the  ensiform  cartilage  to  the  symphysis  pubis. 

That  portion  of  the  aponeurosis  which  extends  /oetwgen  the  anterior  superior 
spine  of  the  ilium  and  the  spine  of  is  ajtrr *$  JtiniL,  folded  inwardne 

and  continuous  below  with  the  fascia  Is    •■>  it  is^n31e. 

portion  which  is  reflected   from  P<  ■■■[■  **£he  lower  border  of  the  aponeurosis  of 

along  the  pectineal  line  is  called  G-imberna.ji  from  the  anterior  superior  spine  of 
ment  of  the  latter  to  the  ik^11-1  |A  line,  latter  point  it  is  reflected  outward  to  be 
behind  the  inner  pillar  of  \\Mvm^  to  me  li  half  an  inch,  forming  Gimbernat's  liga- 
ancl  form  a  thin,  trianguh.v  ''<■*  ir  layer,  ^downward  toward  the  thigh,  where  it  is 
the  abdomen.  half  is  rounded  and  oblique  in  direction. 

In  the  aponeurosis  of  t i0  External  oblhhment  to  the  os  pubis,  is  more  horizontal 
os  pubis,  is  a  triangular  owning,  the  exteroiic  cord, 
tion  of  the  fibres  of  the  aponeurosis  in  thisuded  between  the  crural    arch  and  the 

Relations. — By  its  externa^  surface,  wwhich  descend  from  the  abdomen  into  the 
epigastric  and  circumflex  (liac  vessels,  and  a  a  subsequent  page. 
surface,  with  the  Internal  oblique,  the  lo\the  aponeurosis  of  the  External  oblique 
Intercostal  muscles,  the  C  ^master,  the  spenvard  from  the  spine  of  the  os  pubis  to  be 
ment  in  the  female.  Its  posterior  border,  erat  half  an  inch  in  length,  larger  in  the 
of  the  ilium,  is  flesny  tb-JUghout  and  free  in  direction  in  the  erect  posture,  and  of 
Latissimus  dorsi,  thous'^r'genera%  a  trianpvard.  Its  base,  or  outer  margin,  is  con- 
muscles  near  the  cr<?-'t  of  the  ilium,  in  wet  with  the  crural  sheath,  forming  the 
oblique.  This  trian^J  Petit' s  triangle,  r.apex  corresponds  to  the  spine  of  the  os 
External  oblique,  bfhinhby  the  Latissimus  o  the  pectineal  line,  and  is  continuous 
while  its  floai  is  1  ■  Jn  <*■  DY  the  Internal  obli   Its  anterior  margin  is  continuous  with 

The  fol:  iVii  °Jj*the  aponeurosis  oied  upward  and  downward, 

to  be  further  descKbel :  v;z.,  the  external  ah  is  a  layer  of  tendinous  fibres  of  a 
and  fascif.,  Pojparts  hgiment,  Gimbernat', apex  to  the  pectineal  line,  where  it  is 
of  the  ah  .onie.r  t  passes  inward  beneath  the  spermatic 

The  Exten.1'''1  Abdominal  Ring. — Just  ab)ed  fascia,  lying  behind  the  inner  pillar 
of  the  os  pu;is  an  interval  is  seen  in  the  ;  of  the  conjoined  tendon,  and  interlaces 
called  the  JEx •  ernal  Abdor^inal  Ring.     The  nea  alba. 

what  trian<Tuh11    m  form,  ^nd  corresponds    ligamentous  band,  which  was  first  de- 
aponeurosis.       'Jt    usually  measures    from    lupward  and  backward  from  the  base  of 
transversely  a^out  half   an  inch.     It  is  boal  line,  to  which  it  is  attached.     It  i 
pubis ;  above  '  Dy  a  series  o."  curved  fibres,  ty  the  pectineal  aponeurosis,  and  by ,. 

,:       \ 
\ 


358 


THE  MUSCLES  AND    FASCIAE 


the  upper  angle  of  the  ring,  so  as  to  increase  its  strength ;  and  on  each  side,  by 
the  margins  of  the  opening  in  the  aponeurosis,  which  are  called  the  columns  or 
pillars  of  the  ring. 

The  external  pillar,  which  is  at  the  same  time  inferior  from  the  obliquity  of  its 
direction,  is  the  stronger:  it  is  formed  by  that  portion  of  Poupart's  ligament 
which  is  inserted  into  the  spine  of  the  os  pubis ;  it  is  curved  so  as  to  form  a  kind 
of  groove,  upon  which  the  spermatic  cord  rests.      The  internal  or  superior  pillar 


Fig.  217.— Dissection  of  abdomen! 


s.  Dis-j,     KJ  ,   /  \  ove 

section  of\\    \  '•'«  <*  /  \ 

inguinal  ]\  \  '  \  smg!e    * 

hernia.         /A  \a)  amount 

groin 

tween  wj 

nerves 

glands 

is   thick! 

tissue  i 

in  diifer 

part's  li 
layer  of  the  superficial  fascia  of  the  tl 
over  the  penis  and  outer  surface  of  the  c 
the  dartos.     As  it  passes  to  the  scrotu 
destitute  of  adipose  tissue,  and  of  a  p^js 
acquires  some  involuntary  muscular  fibJ§i 
backward  to  be  continuous  with  the  si~ 
female  this  fascia  is  continued  into  the  9 
Scarpa)  is  thinner  and  more  membrane 
In  the  middle  line  it  is  intimately  adhei 
pubis,  and  is  prolonged  on  to  the  do::xternal  oblique  muscle. 
ligament;  above,  it  is  continuous  with 
trunk  ;  below    it  blends  with  the  fasciatached  tQ  the  froDt 
ligament;  and  below  and  internally  it 
cord  to  the  scrotum,  where  it  helps  to 
be  traced  backward  to  be  continuous  "v 


trunK ;   oeiow    it  blends  with  the    asciatached  t    the  f      t  of  ^       «  • 

^m.en^.and_bel0W  ^nd  ^nially  itfflite  side,  that  of  the  right  ^1™  ^ 


cord  to  the  scrotum,  where  it  helps  to  1 

.  to  be  continuous  v.„  ^aaaarrOL  +^  +v,„  ,M1,mof;f         ,  . 

of  the  perinseur  In  the  female  it  is  PassaSf  l?  the  ;Peim^  c ,C01f  in  the  male, 
ml  P^ri^u™'  l*  me  *!mal®  ?  1S  it  is  much  larger  in  men  tb  in/jn  ,,,ompn  ' 
The  External  or  Descending  Obhgueatic  cord   and\,nce  thi       -^£™*>™ 

and  fore  part  of  the  abdomen;  being  rt     irer  "equency 

three  fiat  muscles  in  this  region.     It  j3ries  of  curyed   [,ndinouj 

its  muscular  portion  occupying  the  si  I 


hich  arch 


OF    THE  ABDOMEN.  359 

across  the  lower  part  of  the  aponeurosis  of  the  External  oblique.  Thev  have 
received  their  name  from  stretching  across  between  the  two  pillars  of  the  external 
ring,  describing  a  curve  with  the  convexity  downward.  They  are  much  thicker 
and  stronger  at  the  outer  margin  of  the  external  ring,  where  they  are  connected 
to  the  outer  third  of  Poupart's  ligament,  than  internally,  where  they  are  inserted 
into  the  linea  alba.  They  are  more  strongly  developed  in  the  male  than  in  the 
female.  The  intercolumnar  fibres  increase  the  strength  of  the  lower  part  of  the 
aponeurosis,  and  prevent  the  divergence  of  the  pillars  from  one  another. 

These  intercolumnar  fibres  as  they  pass  across  the  external  abdominal  ring  are 
themselves  connected  together  by  delicate  fibrous  tissue,  thus  forming  a  fascia, 
which  as  it  is  attached  to  the  pillars  of  the  ring  covers  it  in,  and  is  called  the 
intercolumnar  fascia.  This  intercolumnar  fascia  is  continued  down  as  a  tubular 
prolongation  around  the  outer  surface  of  the  cord  and  testis,  and  encloses  them  in 
a  distinct  sheath  ;  hence  it  is  also  called  the  external  spermatic  fascia. 

The  sac  of  an  inguinal  hernia,  in  passing  through  the  external  abdominal  ring,  receives  an 
investment  from  the  intercolumnar  fascia. 

If  the  finger  is  introduced  a  short  distance  into  the  external  abdominal  ring 
and  the  limb  is  then  extended  and  rotated  outward,  the  aponeurosis  of  the 
External  oblique,  together  with  the  iliac  portion  of  the  fascia  lata,  will  be  felt  to 
become  tense,  and  the  external  ring  much  contracted ;  if  the  limb  is  on  the  con- 
trary flexed  upon  the  pelvis  and  rotated  inward,  this  aponeurosis  will  become  lax 
and  the  external  abdominal  ring  sufficiently  enlarged  to  admit  the  finger  with 
comparative  ease :  hence  the  patient  should  always  be  put  in  the  latter  position 
when  the  taxis  is  applied  for  the  reduction  of  an  inguinal  hernia  in  order  that  the 
abdominal  walls  may  be  relaxed  as  much  as  possible. 

Poupart's  ligament,  or  the  crural  arch,  is  the  lower  border  of  the  aponeurosis  of 
the  External  oblique  muscle,  and  extends  from  the  anterior  superior  spine  of 
the  ilium  to  the  pubic  spine.  From  this  latter  point  it  is  reflected  outward  to  be 
attached  to  the  pectineal  line  for  about  half  an  inch,  forming  Gimbernat's  lio-a- 
ment.  Its  general  direction  is  curved  downward  toward  the  thigh,  where  it  is 
continuous  with  the  fascia  lata.  Its  outer  half  is  rounded  and  oblique  in  direction. 
Its  inner  half  gradually  widens  at  its  attachment  to  the  os  pubis,  is  more  horizontal 
in  direction,  and  lies  beneath  the  spermatic  cord. 

Nearly  the  whole  of  the  space  included  between  the  crural  arch  and  the 
innominate  bone  is  filled  in  by  the  parts  which  descend  from  the  abdomen  into  the 
thigh.     These  will  be  referred  to  again  on  a  subsequent  page. 

Gimbernat's  ligament  is  that  part  of  the  aponeurosis  of  the  External  oblique 
muscle  which  is  reflected  upward  and  outward  from  the  spine  of  the  os  pubis  to  be 
inserted  into  the  pectineal  line.  It  is  about  half  an  inch  in  length,  larger  in  the 
male  than  in  the  female,  almost  horizontal  in  direction  in  the  erect  posture,  and  of 
a  triangular  form  with  the  base  directed  outward.  Its  base,  or  outer  margin,  is  con- 
cave, thin,  and  sharp,  and  lies  in  contact  with  the  crural  sheath,  forming  the 
inner  boundary  of  the  femoral  ring.  Its  apex  corresponds  to  the  spine  of  the  os 
pubis.  Its  posterior  margin  is  attached  to  the  pectineal  line,  and  is  continuous 
with  the  pubic  portion  of  the  fascia  lata.  Its  anterior  margin  is  continuous  with 
Poupart's  ligament.      Its  surfaces  are  directed  upward  and  downward. 

The  triangular  fascia  of  the  abdomen  is  a  layer  of  tendinous  fibres  of  a 
triangular  shape,  which  is  attached  by  its  apex  to  the  pectineal  line,  where  it  is 
continuous  with  Gimbernat's  ligament.  It  passes  inward  beneath  the  spermatic 
cord,  and  expands  into  a  somewhat  fan-shaped  fascia,  lying  behind  the  inner  pillar 
of  the  external  abdominal  ring,  and  in  front  of  the  conjoined  tendon,  and  interlaces 
with  the  ligament  "r\-,  *t  piss^:.,|e  at  the  line;1,  alba. 

Ligament  of  C  eati'i  this  rnus(Jerstrong  ligamentous  band,  which  was  first  de- 
scribed by  Sir  A\  e  ttesticle  and  Joixtends  upward  and  backward  from  the  base  of 
Gimbernat's  ligjthe  .  "\  emaster  svrrolpectineal  line,  to  which  it  is  attached.     It  i 
strengthened  bj  Palis,  by  the  pectineal  aponeurosis,  and  by ... 


360 


THE   MUSCLES  AND    FASCIAE 


lateral  expansion  from  the  lower  attachment  of  the  linea  alba  (adminiculum  linese 
albse). 

Dissection. — Detach  the  External  oblique  by  dividing  it  across,  just  in  front  of  its  attach- 
ment to  the  ribs,  as  far  as  its  posterior  border,  and  separate  it  below  from  the  crest  of  the  ilium 
as  far  as  the  anterior  superior  spine ;  then  separate  the  muscle  carefulty  from  the  Internal 
oblique,  which  lies  beneath,  and  turn  it  toward  the  opposite  side. 

The  Internal  or  Ascending  oblique  muscle  (Fig.  219),  thinner  and  smaller 
than  the  preceding,  beneath  which  it  lies,  is  of  an  irregularly  quadrilateral  form, 


Conjoined  tendon. 


CREMASTER. 


Fig.  219.— The  internal  oblique  muscle. 

and  situated  at  the  side  and  fore  part  of  the  abdomen.  It  arises,  by  fleshy  fibres, 
from  the  outer  half  of  Poupart's  ligament,  being  attached  to  the  groove  on  its 
upper  surface ;  from  the  anterior  two-thirds  of  the  middle  lip  of  the  crest  of  the 
ilium,  and  from  the  posterior  lamella  of  the  lumbar  fascia.  From  this  origin  the 
fibres  diverge :  those  from  Poupart's  ligament,  few  in  number  and  paler  in  color 
than  the  rest,  arch  downward  and  inward  across  the  spermatic  cord  in  the  male  and 
the  round  ligament  in  the  female,  and,  becoming  tendinous,  are  inserted,  conjointly 
with  those  of  the  Transversalis,  into  the  crest  of  the  os  pubis  and  pectineal  line,  to  the 
extent  of  half  an  inch,  forming  what  is  known  as  the  conioined  tendon  of  the  In- 
ternal oblique  and  Transversalis ;  thnse  from  the,-'  L1  '.I'"—1  *  of  the  iliac  origin 
are  horizontal  in  their  direction,  and,  becoming         -P-,  ,-,  -i  he  lower  fourth  of 

tn/i    linno       onm  llnnovio       vxooc?      ir»     tv/m^  f      nf   f  lin      T?n/     ' 


.the  linea  semilunaris,  pass  in  front  of  the  Re 
tjnea  alba ;  those  which  arise  from  the  middle 
j£Se   ilium   pass  obliquely  upward  and   inwar* 


fineaalba;  those  which  arise  from  the  middle,  ■,  I    J:        t 

/  curved   jsndmou^  n 


%&nserted  into  the 

rom  the  crest  of 

an    aponeurosis 


OF    THE   ABDOMEN.  361 

which  divides  at  the  outer  horde  •  of  the  Rectus  muscle  into  two  lamellae,  which  are 
continued  forward,  in  front  and  behind  this  muscle,  to  the  linea  alba,  the  posterior 
lamella  being  also  connected  to  the  cartilages  of  the  seventh,  eighth,  and  ninth 
ribs  ;  the  most  posterior  fibres  pass  almost  vertically  upward,  to  be  inserted  into 
the  lower  borders  of  the  cartilages  of  the  three  lower  ribs,  being  continuous  with 
the  Internal  intercostal  muscles. 

The  conjoined  tendon  of  the  Internal  oblique  and  Transversalis  is  inserted  into 
the  crest  of  the  os  pubis  and  pectineal  line,  immediately  behind  the  external  ab- 
dominal ring,  serving  to  protect  what  would  otherwise  be  a  weak  point  in  the  ab- 
dominal Avail.  Sometimes  this  tendon  is  insufficient  to  resist  the  pressure  from 
within,  and  is  carried  forward  in  front  of  the  protrusion  through  the  external  ring, 
forming  one  of  the  coverings  of  direct  inguinal  hernia  ;  or  the  hernia  forces  its  way 
through  the  fibres  of  the  conjoined  tendon.  The  conjoined  tendon  is  sometimes 
divided  into  an  outer  and  an  inner  portion — the  former  being  termed  the  ligament 
of  Hesselbach  ;  the  latter,  the  ligament  of  Henle. 

The  aponeurosis  of  the  Internal  oblique  is  continued  forward  to  the  middle 
line  of  the  abdomen,  where  it  joins  with  the  aponeurosis  of  the  opposite  muscle  at 
the  linea  alba,  and  extends  from  the  margin  of  the  thorax  to  the  os  pubis.  At  the 
outer  margin  of  the  Rectus  muscle  this  aponeurosis,  for  the  upper  three-fourths  of 
its  extent,  divides  into  two  lamellae,  which  pass,  one  in  front  ami  tlvj  other  behind 
the  muscle,  enclosing  it  in  a  kind  of  sheath,  and  reuniting  on  its  inner  border  at 
the  linea  alba;  the  anterior  layer  is  blended  with  the  aponeurosis  of  the  External 
oblique  muscle  ;  the  posterior  layer  with  that  of  tie  Transversalis.  Along  the 
lower  fourth  the  aponeurosis  passes  altogether  in.  front  of  the  Rectus  without  any 
separation.  Where  the  aponeurosis  ceases  to  Split,  ana  passes  altogether  in  front 
of  the  Rectus  muscle,  a  deficiency  is  left  iBr-^he  sheath  of  the  muscle  behind  ;  this 
is  marked  above  by  a  sharp  lunated  Eaargih  having  its  concavity  downward. 
This  is  known  as  the  semilunar  fold  of' Douglas. 

Relations. — By  its  external  sup-face',  with  the  External  oblique,  Latissimus 
dorsi,  spermatic  cord,  and  t  tern'ai  ring;  by  its  internal  surface,  with  the  Trans- 
versalis muscle,  the  lover  intercostal  vessels  and  nerves,  the  ilio-hypogastric  and 
the  ilio-inguinal  nerves.  -JN  ear  Poupart's  ligament  it  lies  on  the  fascia  trans- 
versalis, internal  ring,  and-  spermatic  cord.  Its  lower  border  forms  the  upper 
boundary  of  the  inguinal  Cjanal. 

The  Cremaster  muscle  is  a  thin,  muscular  layer,  composed  of  a  number  of 
fasciculi  which  arise  fj/om  the  inner  part  of  Poupart's  ligament,  where  its  fibres 
are  continuous  with  those  of  the  Internal  oblique  and  also  occasionally  with 
the  Transversalis.  fit  passes  along  the  outer  side  of  the  spermatic  cord,  descends 
with  it  through  the  axternal  abdominal  ring  upon  the  front  and  sides  of  the  cord, 
and  forms  a  series  of  /loops  which  differ  in  thickness  and  length  in  different  subjects. 
Those  at  the  upper  jpart  of  the  cord  are  exceedingly  short,  but  they  become  in 
succession  longer  any]  longer,  the  longest  reaching  down  as  low  as  the  testicle. 
where  a  few  are  inserted  into  the  tunica  vaginalis.  These  loops  are  united 
together  by  areolar  tissue,  and  form  a  thin  covering  over  the  cord  and  testis,  the 
fascia  cremasterica.  The  fibres  ascend  along  the  inner  side  of  the  cord,  and  are 
inserted  by  a  small  ;  minted  tendon  into  the  crest  of  the  os  pubis  and  front  of  the 
sheath  of  the  Re-  b. 

It  will  be  observe  d  that  the  origin  and  insertion  of  the  Cremaster  is  precisely 
similar  to  that  <  f  the  lower  fibres  of  the  Internal  oblique.  This  fact  affords  an  easy 
explanation  of  thej  er  in   which   the  testicle  and  cord    are  invested  by  this 

muscle.  At  an  eaflj  Moil  of  fetal  life  the  testis  is  placed  at  the  lower  and  back 
part  of  the  abdon  met  cavity,  but  during  its  descent  toward  the  scrotum,  which 
takes  place  before  '  iHuh,  it  passes  leneath  the  arched  fibres  of  the  Internal  oblique. 
In  its  passage  beneatm  this  muscle  some  fibres  are  derived  from  its  lower  part 
which  accompany  t  e  ttestick  and  jord  into  the  scrotum.  It  occasionally  happens 
that  the  loops  of  the  C|  emaster  surround  the  cord,  some  lying  behind  as  well  as  in 


362  THE  MUSCLES  AND  FASCIA 

front.  It  is  probable  that  under  these  circumstances  the  testis,  in  its  descent, 
passed  through  instead  of  beneath  the  fibres  of  the  Internal  oblique. 

In  the  descent  of  an  oblique  inguinal  hernia,  which  takes  the  same  course  as 
the  spermatic  cord,  the  Cremaster  muscle  forms  one  of  its  coverings.  This  muscle 
becomes  largely  developed  in  cases  of  hydrocele  and  large  old  scrotal  hernia. 
The  Cremaster  muscle  is  found  only  in  the  male,  but  almost  constantly  in  the  fe- 
male a  few  muscular  fibres  may  be  seen  on  the  surface  of  the  round  ligament, 
Avhich  correspond  to  this  muscle,  and  in  cases  of  oblique  inguinal  hernia  in 
the  female  a  considerable  amount  of  muscular  fibre  may  be  found  covering 
the  sac. 

Dissection. — Detach  the  Internal  oblique  in  order  to  expose  the  Transversalis  beneath.  This 
may  be  effected  by  dividing  the  muscle,  above,  at  its  attachment  to  the  ribs ;  below,  at  its  con- 
nection with  Poupart's  ligament  and  the  crest  of  the  ilium ;  and  behind,  by  a  vertical  incision 
extending  from  the  last  rib  to  the  crest  of  the  ilium.  The  muscle  should  previously  be  made 
tense  by  drawing  upon  it  with  the  fingers  of  the  left  hand,  and  if  its  division  is  carefully  effected, 
the  cellular  interval  between  it  and  the  Transversalis,  as  well  as  the  direction  of  the  fibres  of  the 
latter  muscle,  will  afford  a  clear  guide  to  their  separation  ;  along  the  crest  of  the  ilium  the  cir- 
cuiiiflex  iliac  vessels  are  interposed  between  them,  and  form  an  important  guide  in  separating 
them.     The  muscle  should  then  be  thrown  inward  toward  the  linea  alba. 

Th  „•  Tra.nsversalis  muscle  (Fig.  220),  so  called  from  the  direction  of  its  fibres, 
.  >st  internal  iiat  muscle  of  the  abdomen,  being  placed  immediately  beneath 
tht  ernal  (  lique.  It  arises  by  fleshy  fibres  from  the  outer  third  of  Poupart's 
ligament;  from  the  inner  Jit>  of  the  crest  of  the  ilium  for  its  anterior  three-fourths  ; 
from  the  inner  surface  of  the  cartilages  of  the  six  lower  ribs,  interdigitating  with 
the  Diaphragm;  and  from  the  lurnbar  fescia,  which  may  be  regarded  as  the  pos- 
terior aponeurosis  of  the  muscle.  (See  page  o42.)  The  muscle  terminates  in  front 
in  a  broad  aponeurosis,  the  lower  fibre-  eh  curve  downward  and  inward,  and 

are  inserted,  together  with  those  of  the  It  rnal  oblique,  into  the  lower  part  of  the 
linea  alba,  the  crest  of  the  os  pubis  and  pectineal  line  forming  what  is  known  as 
the  conjoined  tendon  of  the  Internal  oblique  a,  versalis.      Throughout  the 

rest,  of  its  extent  the  aponeurosis  passes  horizontally  in  ■  ard,  and  is  inserted  into 
the  linea  alba,  its  upper  three-fourths  passing  behind. tht  Rectus  muscle,  blending 
with  the  posterior  lamella  of  the  Internal  oblique  ;\ts  lower  fourth  passing  in 
front  of  the  Rectus. 

Relations. — By  its  external  surface,  with  the  Internal!  oblique,  the  lower  inter- 
costal nerves,  and  the  inner  surface  of  the  cartilages  of  tn'O  lower  ribs  ;  by  its  in- 
ternal surface,  with  the  fascia  transversalis,  which  separated  it  from  the  periton- 
eum.    Its  lower  border  forms  the  upper  boundary  of  the  ingl'inal  canal. 

Dissection. — To  expose  the  Rectus  muscle,  open  its  sheath  I  (,al  incision  extending 

from  the  margin  of  the  thorax  to  the  os  pubis,  and  then  reflect  the  two  [1  rtions  from  the  surface 
of  the  muscle,  which  is  easily  done,   excepting  at  the  lineae  tran  p  where  so  close  an 

adhesion  exists  that  the  greatest  care  is  requisite  in  separating  them.  low  raise  the  outer  edge 
of  the  muscle,  in  order  to  examine  the  posterior  layer  of  the  sheath.  By  dividing  the  muscle  in 
the  centre,  and  turning  its  lower  part  downward,  the  point  t  here  the  posterior  wall  of  the 
sheath  terminates  in  a  thin  curved  margin  will  be  seen. 

The  Rectus  abdominis  is  a  long  flat  muscle,  which  extepds  along  the  whole 
length  of  the  front  of  the  abdomen,  being  separated  from  its  fellow  of  the  opposite 
side  by  the  linea  alba.  It  is  much  broader,  but  thinner,  al'ove  than  below,  and 
arises  by  two  tendons,  the  external  or  larger  beiijtg  attached  I  -  the  crest  of  the  os 
pubis,  the  internal,  smaller  portion  interlacing  with  its  felldwi '  >f  the  opposite  side, 
and  being  connected  with  the  ligaments  covering  the  front  of,  fhe  symphysis  pubis. 
The  fibres  ascend,  and  the  muscle  is  inserted  "<iy  three  por  rions  of  unequal  size 
into  the  cartilages  of  the  fifth,  sixth,  and  seveith  ribs.  T  upper  portion,  at- 
tached principally  to  the  cartilage  of  the  fifth  rib,  usually  br>:  l)me  fibres  of  inser- 
tion into  the  anterior  extremity  of  the  rib   itself.      Sot,  -  are  occasionally 

,   connected  writh  th^  costo-xiphoid  ligaments  anil  side   of  1  '  e  ensiform   cartilage. 

U        The  Rectus  muscle  is  traversed  by  tendinoiB  intersect' ions,  three  in  number. 

its 


OF    THE   ABDOMEN. 


363 


which  have  received  the  name  of  linece  transversa.  One  of  these  is  usually 
situated  opposite  the  umbilicus,  and  two  above  that  point;  of  the  latter,  one 
corresponds  to  the  extremity  of  the  ensiform  cartilage,  and  the  other  to  the 
interval  between  the  ensiform  cartilage  and  the  umbilicus.  These  intersections 
pass  transversely  or  obliquely  across  the  muscle  in  a  zigzag  course ;  they  rarely 
extend  completely  through  its  substance,   sometimes    pass  only  halfway  across 


IAnea  alba 


Fig.  220. — The  Transversalis,  Rectus,  and  Pyramidalis  muscles. 

it,  and  are  intimately  adherent  in  front  to  the  sheath  in  which  the  muscle  is 
enclosed.  Sometimes  one  or  two  additional  lines  may  be  seen,  one  usually  below 
the  umbilicus ;  the  position  of  the  other,  when  it  exists,  is  variable.  These 
additional  lines  are  for  the  most  part  incomplete. 

The  Rectus  is  enclosed  in  a  sheath  (Fig.  221)  formed  by  the  aponeu"  oses  of  the 
Oblique  and  Transversalis  muscles,  which  are  arranged  in  the  following  manner. 
When  the  aponeurosis  of  the  Internal  oblique  arrives  at  the  outer  margin  of  the 
Rectus,  it  divides  into  two  lamellae,  one  of  which  passes  in  front  of  the  Rectus. 


364 


THE  MUSCLES  AND    FASCIJE 


blending  with  the  aponeurosis  of  the  External  oblique ;  the  other,  behind  it, 
blending  with  the  aponeurosis  of  the  Transversalis  ;  and  these,  joining  again  at  its 
inner  border,  are  inserted  into  the  linea  alba.  This  arrangement  of  the  aponeuroses 
exists  along  the  upper  three-fourths  of  the  muscle :  at  the  commencement  of  the 
lower  fourth,  the  posterior  wall  of  the  sheath  terminates  in  a  thin  curved  margin, 
the  semilunar  fold  of  Douglas,  the  concavity  of  which  looks  downward  toward 
the  pubes ;  the  aponeuroses  of  all  three  muscles  passing  in  front  of  the  Rectus 
without  any  separation.  The  extremities  of  the  fold  of  Douglas  descend  as  pillars 
to  the  os  pubis.  The  inner  pillar  is  attached  to  the  symphysis  pubis ;  the  outer 
pillar,  which  is  named  by  Braune  the  ligament  of  Hesselbach,  passes  downward  as 
a  distinct  band  on  the  inner  side  of  the  internal  abdominal  ring,  and  there  its 
fibres  divide  into  two  sets,  internal  and  external ;  the  internal  fibres  are  attached 
to  the  ascending  ramus  of  the  os  pubis  and  the  pectineal  fascia ;  the  external  ones 
pass  to  the  Psoas  fascia,  to  the  deep  surface  of  Poupart's  ligament,  and  to  the 
tendon  of  the  Transversalis  on  the  outer  side  of  the  ring.  The  Rectus  muscle,  in 
the  situation  where  its  sheath  is  deficient,  is  separated  from  the  peritoneum  by  the 
transversalis  fascia. 


Fig.  221. — A  transverse  section  of  the  abdomen  in  the  lumbar  region. 


The  Pyramidalis  is  a  small  muscle,  triangular  in  shape,  placed  at  the  lower 
part  of  the  abdomen,  in  front  of  the  Rectus,  and  contained  in  the  same  sheath 
with  that  muscle.  It  arises  by  tendinous  fibres  from  the  front  of  the  os  pubis 
and  the  anterior  pubic  ligament ;  the  fleshy  portion  of  the  muscle  passes  upward, 
diminishing  in  size  as  it  ascends,  and  terminates  by  a  pointed  extremity,  which  is 
inserted  into  the  linea  alba,  midway  between  the  umbilicus  and  the  os  pubis.  This 
muscle  is  sometimes  found  wanting  on  one  or  both  sides ;  the  lower  end  of  the 
Rectus  then  becomes  proportionately  increased  in  size.  Occasionally  it  has  been 
found  double  on  one  side,  or  the  muscles  of  the  two  sides  are  of  unequal  size. 
Sometimes  its  length  exceeds  what  is  stated  above. 

Besides  the  Rectus  and  Pyramidalis  muscles,  the  sheath  of  the  Rectus  contains 
the  superior  and  deep  epigastric  arteries,  the  terminations  of  the  lumbar  arteries 
and  of  the  lower  intercostal  arteries  and  nerves. 

Nerves. — The  abdominal  muscles  are  supplied  by  the  lower  intercostal  nerves. 
The  Transversalis  and  Internal  oblique  also  receive  filaments  from  the  hypogastric 
branch  of  the  ilio-hypogastric  and  sometimes  from  the  ilio-inguinal.  The  Cremaster 
is  supplied  by  the  genital  branch  of  the  Genito-crural. 

In  the  description  of  the  abdominal  muscles  mention  has  frequently  been  made 
of  the  linea  alba,  linese  semilunares,  and  linese  transversa: ;  when  the  dissection  of 
the  muscles  is  completed  these  structures  should  be  examined. 


J 


OF    THE   ABDOMEN.  365 

The  linea  alba  is  a  tendinous  raphe'  seen  along  the  middle  line  of  the  abdomen, 
extending  from  the  ensiform  cartilage  to  the  symphysis  pubis,  to  which  it  is 
attached.  It  is  placed  between  the  inner  borders  of  the  Recti  muscles,  and  is 
formed  by  the  blending  of  the  aponeuroses  of  the  Obliqui  and  Transversales  muscles. 
It  is  narrow  below,  corresponding  to  the  narrow  interval  existing  between  the 
Recti ;  but  broader  above,  as  these  muscles  diverge  from  one  another  in  their 
ascent,  becoming  of  considerable  breadth  after  great  distension  of  the  abdomen  from 
pregnancy  or  ascites.  It  presents  numerous  apertures  for-  the  passage  of  vessels 
and  nerves  :  the  largest  of  these  is  the  umbilicus,  which  in  the  foetus  transmits  the 
umbilical  vessels,  but  in  the  adult  is  obliterated,  the  cicatrix  being  stronger  than 
the  neighboring  parts ;  hence  umbilical  hernia  occurs  in  the  adult  near  the 
umbilicus,  whilst  in  the  foetus  it  occurs  at  the  umbilicus.  The  linea  alba  is  in 
relation,  in  front,  with  the  integument,  to  which  it  is  adherent,  especially  at  the 
umbilicus  ;  behind,  it  is  separated  from  the  peritoneum  by  the  transversalis  fascia  ; 
and  below,  by  the  urachus,  and  the  bladder  when  that  organ  is  distended. 

The  linese  semilunares  are  two  curved  tendinous  lines  placed  one  on  each  side 
of  the  liftea-albQi.-  Each  corresponds  with  the  outer  border  of  the  Rectus  muscle, 
extends  from  the  cartilage  of  the  ninth  rib  to  the  pubic  spine,  and  is  formed  by 
the  aponeurosis  of  the  Internal  oblique  at  its  point  of  division  to  enclose  the 
Rectus,  where  it  is  reinforced  in  front  by  the  External  oblique  and  behind  by  the 
Transversalis. 

The  lineae  transversa  are  narrow  transverse  lines  which  intersect  the  Recti  mus- 
cles, as  already  mentioned ;  they  connect  the  linese  semilunares  with  the  linea  alba. 

Actions. — The  abdominal  muscles  perform  a  threefold  action : 

When  the  pelvis  and  thorax  are  fixed,  they  compress  the  abdominal  viscera,  by 
constricting  the  cavity  of  the  abdomen,  in  which  action  they  are  materially  assisted 
by  the  descent  of  the  diaphragm.  By  these  means  the  foetus  is  expelled  from  the 
uterus,  the  faeces  from  the  rectum,  the  urine  from  the  bladder,  and  the  contents  of 
the  stomach  in  vomiting. 

If  the  pelvis  and  spine  are  fixed,  these  muscles  compress  the  lower  part  of  the 
thorax,  materially  assisting  expiration*  If  the  pelvis  alone  is  fixed,  the  thorax  is 
bent  directly  forward  when  the  muscles  of  both  sides  act,  or  to  either  side  when 
those  of  the  two  sides  act  alternately,  rotation  of  the  trunk  at  the  same  time  taking 
place  to  the  opposite  side. 

If  the  thorax  is  fixed,  these  muscles,  acting  together,  draw  the  pelvis  upward, 
as  in  climbing ;  or,  acting  singly,  they  draw  the  pelvis  upward,  and  bend  the 
vertebral  column  to  one  side  or  the  other.  The  Recti  muscles,  acting  from  below, 
depress  the  thorax,  and  consequently  flex  the  vertebral  column ;  Avhen  acting  from 
above,  they  flex  the  pelvis  upon  the  vertebral  column.  The  Pyramidales  are 
tensors  of  the  linea  alba. 

The  fascia  transversalis  is  a  thin  aponeurotic  membrane  which  lies  between  the 
inner  surface  of  the  Transversalis  muscle  and  the  extra-peritoneal  fat.  It  forms, 
part  of  the  general  layer  of  fascia  which  lines  the  interior  of  the  abdominal  and 
pelvic  cavities,  and  is  directly  continuous  with  the  iliac  and  pelvic  fasciae.  In  the 
inguinal  region  the  transversalis  fascia  is  thick  and  dense  in  structure,  and  joined 
by  fibres  from  the  aponeurosis  of  the  Transversalis  muscle,  but  it  becomes  thin 
and  cellular  as  it  ascends  to  the  Diaphragm,  and  blends  with  the  fascia  covering 
this  muscle.  In  front,  it  unites,  across  the  middle  line  with  the  fascia  on  the 
opposite  side  of  the  body,  and  behind  it  becomes  lost  in  the  fat  which  covers  the 
posterior  surfaces  of  the  kidneys.  Below,  it  has  the  following  attachments : 
posteriorly,  it  is  connected  to  the  whole  length  of  the  crest  of  the  ilium,  between 
the  attachments  of  the  Transversalis  and  Iliacus  muscles ;  between  the  anterior 
superior  spine  of  the  ilium  and  the  femoral  vessels  it  is  connected  to  the  posterior 
margin  of  Poupart's  ligament,  and  is  there  continuous  with  the  iliac  fascia. 
Internal  to  the  femoral  vessels  it  is  thin  and  attached  to  the  os  pubis  and  pectineal 
line,  behind  the  conjoined  tendon,  with  which  it  is  united;  and,  corresponding  to 
the  point  where  the  femoral  vessels  pass  into  the  thigh,  this  fascia  descends  in 


366  THE  MUSCLES  AND   FASCIJE 

front  of  them,  forming  the  anterior  wall  of  the  crural  sheath.  Beneath  Poupart's 
ligament  it  is  strengthened  by  a  band  of  fibrous  tissue,  which  is  only  loosely  con- 
nected to  Pjupart's  ligament,  and  is  specialized  as  the  deep  crural  arch.  The 
spermatic  cord  in  the  male  and  the  round  ligament  in  the  female  pass  through  this 
fascia ;  the  point  where  they  pass  through  is  called  the  internal  abdominal  ring. 
This  opening  is  not  visible  externally,  owing  to  a  prolongation  of  the  transversalis 
fascia  on  these  structures,  forming  the  infundibuliform  fascia. 

The  internal  or  deep  abdominal  ring  is  situated  in  the  transversalis  fascia, 
midway  between  the  anterior  superior  spine  of  the  ilium  and  the  symphysis  pubis, 
and  about  half  an  inch  above  Poupart's  ligament.  It  is  of  an  oval  form,  the 
extremities  of  the  oval  directed  upward  and  downward,  varies  in  size  in  different 
subjects,  and  is  much  larger  in  the  male  than  in  the  female.  It  is  bounded,  above 
and  externally,  by  the  arched  fibres  of  the  Transversalis  ;  below  and  internally,  by 
the  deep  epigastric  vessels.  It  transmits  the  spermatic  cord  in  the  male  and  the 
round  ligament  in  the  female.  From  its  circumference  a  thin  funnel-shaped 
membrane,  the  infundibuliform  fascia,  is  continued  round  the  cord  and  testis, 
enclosing  them  in  a  distinct  pouch. 

When  the  sac  of  an  oblique  inguinal  hernia  passes  through  the  internal  or  deep  abdominal 
ring,  the  infundibuliform  process  of  the  transversalis  fascia  forms  one  of  its  coverings. 

•  The  inguinal  or  spermatic  canal  contains  the  spermatic  cord  in  the  male  and 
the  round  ligament  in  the  female.  It  is  an  oblique  canal  about  an  inch  and  a  half 
in  length,  directed  downward  and  inward,  and  placed  parallel  to  and  a  little  above 
Poupart's  ligament.  It  commences  above  at  the  internal  or  deep  abdominal  ring, 
which  is  the  point  where  the  cord  enters  the  spermatic  canal,  and  terminates  below 
at  the  external  ring.  It  is  bounded  in  front  by  the  integument  and  superficial 
fascia,  by  the  aponeurosis  of  the  External  oblique  throughout  its  whole  length,  and 
by  the  Internal  oblique  for  its  outer  third  ;  behind,  by  the  triangular  fascia,  the 
conjoined  tendon  of  the  Internal  oblique  and  Transversalis,  transversalis  fascia, 
and  the  subperitoneal  fat  and  peritoneum  ;  above,  by  the  arched  fibres  of  the 
Internal  oblique  and  Transversalis ;  below,  by  Gimbernat's  ligament,  and  by  the 
union  of  the  fascia  transversalis  with  Poupart's  ligament.  The  deep  epigastric 
artery  passes  upward  and  inward  behind  the  canal  lying  close  to  the  inner  side  of 
the  internal  abdominal  ring.  The  interval  between  this  artery  and  the  outer  edge 
of  the  Rectus  is  named  Hesselbach's  triangle,  the  base  of  which  is  formed  by 
Poupart's  ligament.  \ 

That  form  of  protrusion  in  which  the  intestine  follows  the  course  of  the  spermatic  cord 
along  the  spermatic  canal  is  called  oblique  inguinal  hernia. 

The  Deep  Crural  Arch. — Curving  over  the  vessels,  just  at  the  point  where  they 
become  femoral,  on  the  abdominal  side  of  Poupart's  ligament  and  loosely  connected 
with  it,  is  a  thickened  band  of  fibres  called  the  deep  crural  arch.  It  is  apparently 
a  thickening  of  the  fascia  transversalis,  joining  externally  to  the  centre  of 
Poupart's  ligament,  and  arching  across  the  front  of  the  crural  sheath  to  be  inserted 
by  a  broad  attachment  into  the  spine  of  the  os  pubis  and  ilio-pectineal  line,  behind 
the  conjoined  tendon.  In  some  subjects  this  structure  is  not  very  prominently 
marked,  and  not  infrequently  it  is  altogether  wanting. 

Surface  Form. — The  only  two  muscles  of  this  group  which  have  any  considerable  influ- 
ence on  surface  form  are  the  External  oblique  and  Rectus  muscles  of  the  abdomen.  With 
regard  to  the  External  oblique,  the  upper  digitations  of  its  origin  from  the  ribs  are  well  marked, 
intermingled  with  the  serrations  of  the  Serratus  magnus ;  the  lower  digitations  are  not  visible, 
being  covered  by  the  thick  border  of  the  Latissimus  dorsi.  Its  attachment  to  the.crest  of  the 
ilium,  in  conjunction  with  the  Internal  oblique,  forms  a  thick  oblique  roll,  which  determines  the 
iliac  furrow.  Sometimes  on  the  front  of  the  lateral  region  of  the  abdomen  an  undulating  out- 
line marks  the  spot  where  the  muscular  fibres  terminate  and  the  aponeurosis  commences.  The 
outer  border  of  the  Rectus  is  defined  by  the  linea  semilunaris,  which  may  be  exactly  defined  by 
putting  the  muscle  into  action.  It  corresponds  with  a  curved  line,  with  its  convexity  outward, 
drawn  from  the  end  of  the  cartilage  of  the  ninth  rib  to  the  spine  of  the  os  pubis,  so  that 
the  centre  of  the  line,  at  or  near  the  umbilicus,  is  three  inches  [from  the  median  line.     The 


OF   THE  PELVIC   OUTLET.  367 

inner  border  of  the  Rectus  corresponds  to  the  linea  alba,  marked  on  the  surface  of  the  body  by 
a  groove,  the  abdominal  furrow,  which  extends  from  the  infrasternal  fossa  to,  or  to  a  little  below, 
the  umbilicus,  where  it  gradually  becomes  lost.  The  surface  of  the  Rectus  presents  three  trans- 
verse furrows,  the  linem  transversa'.  The  upper  two  of  these,  one  opposite  or  a  little  below  the 
tip  of  the  ensiform  cartilage,  and  another,  midway  between  this  point  and  the  umbilicus,  are 
usually  well  marked  ;  the  third,  opposite  the  umbilicus,  is  not  so  distinct.  The  umbilicus,  situ- 
ated in  the  linea  alba,  varies  very  much  in  position  as  regards  its  height.  It  is  always  situated 
above  a  zone  drawn  round  the  body  opposite  the  highest  point  of  the  crest  of  the  ilium,  gene- 
rally being  about  three-quarters  of  an  inch  to  an  inch  above  this  line.  It  generally  corresponds, 
therefore,  to  the  fibro-cartilage  between  the  third  and  fourth  lumbar  vertebrae. 

2.  Deep  Muscles  of  the  Abdomen. 

Psoas  magnus.  Iliacus. 

Psoas  parvus.  Quadratus  lumborum. 

The  Psoas  magnus,  the  Psoas  parvus,  and  the  Iliacus  muscles,  with  the  fascia 
covering  them,  Avill  be  described  with  the  Muscles  of  the  Lower  Extremity. 

The  Fascia  covering  the  Quadratus  Lumborum. — This  is  the  most  anterior  of  the 
three  layers  of  the  lumbar  fascia.  It  is  a  thin  layer  of  fascia,  which,  passing  over 
the  anterior  surface  of  the  Quadratus  lumborum,  is  attached,  internally,  to  the 
bases  of  the  transverse  processes  of  the  lumbar  vertebrae ;  below,  to  the  ilio-lum- 
bar  ligament ;  and  above,  to  the  apex  and  lower  border  of  the  last  rib. 

The  portion  of  this  fascia  which  extends  from  the  transverse  process  of  the 
first  lumbar  vertebra  to  the  apex  and  lower  border  of  the  last  rib  constitutes  the 
ligamentum  arcuatum  externum. 

The  Quadratus  lumborum  (Fig.  214,  page  344)  is  situated  in  the  lumbar  region. 
It  is  irregularly  quadrilateral  in  shape,  and  broader  below  than  above.  It  arises 
by  aponeurotic  fibres  from  the  ilio-lumbar  ligament  and  the  adjacent  portion  of  the 
crest  of  the  ilium  for  about  two  inches,  and  is  inserted  into  the  lower  border  of 
the  last  rib  for  about  half  its  length,  and  by  four  small  tendons,  into  the  apices 
of  the  transverse  processes  of  the  four  upper  lumbar  vertebras.  Occasionally  a 
second  portion  of  this  muscle  is  found  situated  in  front  of  the  preceding.  This 
arises  from  the  upper  borders  of  the  transverse  processes  of  three  or  four  of  the 
lower  lumbar  vertebrae,  and  is  inserted  into  the  loAver  margin  of  the  last  rib.  The 
Quadratus  lumborum  is  contained  in  a  sheath  formed  by  the  anterior  and  middle 
lamellae  of  the  lumbar  fasciae. 

Relations. — Its  anterior  surface  (or  rather  the  fascia  which  covers  its  anterior 
surface)  is  in  relation  with  the  colon,  the  kidney,  the  Psoas  muscle,  and  the 
Diaphra||^  Between  the  fascia  and  the  muscle  are  the  last  dorsal,  ilio-hypogas- 
tric,  and  ilio-inguinal  nerves.  Its  posterior  surface  is  in  relation  with  the  middle 
lamella  of  the^mibar  fascia,  which  separates  it  from  the  Erector  spinae.  The 
Quadratus  luml^um  extends,  however,  beyond  the,  outer  border  of  the  Erector 
spinas. 

Nerve-supply. — The  anterior  branches  of  the  last  dorsal  and  first  lumbar 
nerves ;  sometimes  also  a  branch  from  the  second  lumbar  nerve. 

Actions. — The  Quadratus  lumborum  draws  down  the  last  rib,  and  acts  as  a 
muscle  of  inspiration  by  helping  to  fix  the  origin  of  the  Diaphragm.  If  the 
thorax  and  spine  are  fixed,  it  may  act  upon  the  pelvis,  raising  it  toward  its  own 
side  when  only  one  muscle  is  put  in  action;  and  when  both  muscles  act  together, 
either  from  below  or  above,  thev  flex  the  trunk. 


cvf^pj 


SCLES  OF  THE  PELVIC  OUTLET. 

The  muscles  of  this  region  are  situated  at  the  pelvic  outlet  in  the  ischio-rectal 
region  and  the  perinaeum.      They  include  the  following: 
I.  Muscles  of  the  ischio-rectal  region. 
II.   Muscles  of  the  perinaeum  :  a.   In  the  Male ;  B.   In  the  Female. 


368 


THE  MUSCLES  AND   FASCIA 


I.  Muscles  of  the  Ischio-rectal  Region. 

Corrugator  cutis  ani.  Internal  sphincter  ani. 

mi. 

Coccygeus. 


External  sphincter  ani. 


Levator  ani. 


The  Corrugator  Cutis  Ani. — Around  the  anus  is  a  thin  stratum  of  involuntary 
muscular  fibre,  which  radiates  from  the  orifice.  Internally,  the  fibres  fade  off 
into  the  submucous  tissue,  while  externally  they  blend  with  the  true  skin.  By 
its  contraction  it  raises  the  skin  into  ridges  around  the  margin  of  the  anus. 

The  External  sphincter  ani  is  a  thin,  flat  plane  of  muscular  fibres,  elliptical  in 
shape  and  intimately  adherent  to  the  integument  surrounding  the  margin  of  the 
anus.  It  measures  about  three  or  four  inches  in  length  from  its  anterior  to  its 
posterior  extremity,  being  about  an  inch  in  breadth  opposite  the  anus.  It  arises 
from  the  tip  and  back  of  the  coccyx  by  a  narrow  tendinous  band,  and  from  the 
superficial  fascia  in  front  of  that  bone;  and  is  inserted  into  the  central  tendinous 
point  of  the  perinseum,  joining  with  the  Transversus  perinsei,  the  Levator  ani, 
and  the  Accelerator  urime.  Like  other  sphincter  muscles,  it  consists  of  two 
planes  of  muscular  fibre,  which  surround  the  margin  of  the  anus  and  join  in  a 
commissure  in  front  and  behind,  some  fibres  crossing  from  side  to  side  in  front 
and  behind  the  anus. 


PECTINEUS. 


ADDUCTOR 

LONGUS. 
GRACILIS 


Epididymis. 


Ampulla. 

Ampulla  of  vasa 
deferens. 


Testicle. 

Ascending  ramus 

ISCHIUM. 

Internal  pudic 
vessels  and  nerve 


Fig.  222.— Side  view  of  pelvis,  showing  Levator  ani.    (From  a  preparation  in  the  Museum  of  the  Royal 
College  of  Surgeons.) 

Nerve-supply. — A  branch  from  the  anterior  division  of  the  fourth  sacral  and 
the  inferior  hemorrhoidal  branch  of  the  internal  pudic. 

Actions. — The  action  of  this  muscle  is  peculiar:  1.  It  is,  like  other  muscles, 
always  in  a  state  of  tonic  contraction,  and  having  no  antagonistic  muscle,  it  keeps 
the  anal  orifice  closed.  2.  It  can  be  put  into  a  condition  of  greater  contraction 
under  the  influence  of  the  will,  so  as  to  occlude  more  firmly  the  anal  aperture  in 
expiratory  efforts  unconnected  with  defecation.  3.  Taking  its  fixed  point  at 
the  coccyx,  it  helps  to  fix  the  central  point  of  the  perinseum,  so  that  the  Accele- 
rator urinse  may  act  from  this  fixed  point. 

The  Internal   sphincter   ani  is  a  muscular   ring   which  surrounds    the    lower 


OF   THE   PERINJEUM.  369 

extremity  of  the  rectum  for  about  an  inch,  its  inferior  border  being  contiguous 
to,  but  quite  separate  from,  the  External  sphincter.  This  muscle  is  about  two 
lines  in  thickness,  and  is  formed  by, an  aggregation  of  the  involuntary  circular 
fibres  of  the  intestine.  It  is  paler  in  color  and  less  coarse  in  texture  than  the 
External  sphincter. 

Actions. — Its  action  is  entirely  involuntary.  It  helps  the  External  sphincter 
to  occlude  the  anal  aperture. 

The  Levator  ani  (Fig.  222)  is  a  broad,  thin  muscle,  situated  on  each  side  of 
the  pelvis.  It  is  attached  to  the  inner  surface  of  the  sides  of  the  true  pelvis,  and 
descending,  unites  with  its  fellow  of  the  opposite  side  to  form  the  floor  of  the 
pelvic  cavity.  It  supports  the  viscera  in  this  cavity  and  surrounds  the  various 
structures  which  pass  through  it.  It  arises,  in  front,  from  the  posterior  surface 
of  the  body  of  the  os  pubis  on  the  outer  side  of  the  symphysis ;  posteriorly,  from 
the  inner  surface  of  the  spine  of  the  ischium ;  and  between  these  two  points,  from 
the  angle  of  division  between  the  obturator  and  recto-vesical  layers  of  the  pelvic 
fascia  at  their  under  part.  The  fibres  pass  downward  to  the  middle  line  of  the 
floor  of  the  pelvis,  and  are  inserted,  the  most  posterior  into  the  sides  of  the  apex 
of  the  coccyx  ;  those  placed  more'anteriorly  unite  with  the"  muscles  of  the  opposite 
side  in  a  median  fibrous  raphe,  which  extends'  between  the  coccyx  and  the  margin 
of  the  anus.  The  middle  fibres,  which  form  the  larger  portion  of  the  muscle,  are 
inserted  into  the  side  of  the  rectum,  blending  with  the  fibres  of  the  Sphincter 
muscles ;  lastly,  the  anterior  fibres,  the  longest,  descend  upon  the  side  of  the 
prostate  gland  to  unite  beneath  it  with  the  muscle  of  the  opposite  side,  blending 
with  the  fibres  of  the  External  sphincter  and  Transversus  perinsei  muscles  at  the 
central  tendinous  point  of  the'  perinasum. 

The  anterior  portion  is  occasionally  separated  from  the  rest  of  the  muscle  by 
connective  tissue.  From  this  circumstance,  as  well  as  from  its  peculiar  relation 
with  the  prostate  gland,  descending  by  its  side,  and  surrounding  it  as  in  a  sling, 
it  has  been  described  by  Santorini  and  others  as  a  distinct  muscle,  under  the  name 
of  Levator  prostatse.  In  the  female,  the  anterior  fibres  of  the  Levator  ani  descend 
upon  the  side  of  the  vagina. 

Relations. — By  its  inner  or  pelvic  surface,  with  the  recto-vesical  fascia,  which 
separates  it  from  the  viscera  of  the  pelvis  and  from  the  peritoneum.  By  its  outer 
or  perineal  surface,  it  forms  the  inner  boundary  of  the  ischio-rectal  fossa,  and  is 
covered  by  a  thin  layer  of  fascia,  the  ischio-rectal  or  anal  fascia,  given  off  from  the 
obturator  fascia.  Its  posterior  border  is  free  and  separated  from  the  Coccygeus 
muscle  by  a  cellular  interspace.  Its  anterior  border  is  separated  from  the  muscle 
of  the  opposite  side  by  a  triangular  space,  through  which  the  urethra,  and  in  the 
female  the  vagina,  passes   from  the  pelvis. 

Nerve-supply. — A  branch  from  the  anterior  division  of  the  fourth  sacral  nerve 
and  a  branch  from  the  pudic  nerve,  which  is  sometimes  derived  from  the  perineal, 
sometimes  from  the  inferior  hemorrhoidal  division. 

Actions. — This  muscle  supports  the  lower  end  of  the  rectum  and  vagina,  and 
also  the  bladder  during  the  efforts  of  expulsion.  It  elevates  and  inverts  the  lower 
end  of  the  rectum  after  it  has  been  protruded  and  everted  during  the  expulsion  of 
the  faeces.     It  is  also  a  muscle  of  forced  expiration. 

The  Coccygeus  is  situated  behind  and  parallel  with  the  preceding.  It  is  a  tri- 
angular plane  of  muscular  and  tendinous  fibres,  arising,  by  its  apex,  from  the 
spine  of  the  ischium  and  lesser  sacro-sciatic  ligament,  and  inserted,  by  its  base, 
into  the  margin  of  the  coccyx  and  into  the  side  of  the  lower  piece  of  the  sacrum. 
It  assists  the  Levator  ani  and  Pyriformis  in  closing  in  the  back  part  of  the  outlet 
of  the  pelvis. 

Relations. — By  iu;  inner  or  pelvic  surface,  with  the  rectum.  By  its  external 
surface,  with  the  lesser  ^cro-sciatic  ligament.  The  loioer  border  is  in  relation 
with  the  posterior  border  of  the  Levator  ani,  but  separated  from  it  by  a  cellular 
interval  :  its  upper  border  is  in  relation  with  the  lower  border  of  the  Pyriformis, 
but  separated  from  it  by  the  sciatic  and  internal  pudic  vessels  and  nerve. 
24 


370 


THE  MUSCLES   AND    FASCIjE. 


Nerve-supply. — A  branch  from  the  fourth  and  fifth  sacral  nerves. 
Action.  —The  Coccygei  muscles  raise  and  support  the  coccyx,  after  it  has  been 
pressed  backward  during  defecation  or  parturition. 

II.  A.  Muscles  and  Fasciae  of  the  Perinseum  in  the  Male. 


Trans  versus  perinsei. 
Accelerator  urinse. 


Erector  penis. 
Compressor  urethras. 


Superficial  Fascia. — The  superficial  fascia  of  the  perinseum  consists  of  two 
layers,  superficial  and  deep,  as  in  other  regions  of  the  body. 

The  superficial  layer  is  thick,  loose,  areolar  in  texture,  and  contains  much 
adipose  tissue  in  its  meshes,  the  amount  of  which  varies  in  diiferent  subjects.  In 
front,  it  is  continuous  with  the  dartos  of  the  scrotum ;  behind,  it  is  continuous 
with  the  subcutaneous  areolar  tissue  surrounding  the  anus  ;  and,  on  either  side, 
with  the  same  fascia  on  the  inner  side  of  the  thighs.  This  layer  should  be  care- 
fully removed  after  it  has  been   examined,  when  the   deep  layer  will  be  exposed. 

The  deep  layer  of  superficial  fascia  (Fascia  of  Colles)  is  thin,  aponeurotic  in 
structure,  and  of  considerable  strength,  serving  to  bind  down  the  muscles  of  the 
root  of  the  penis.  It  is  continuous,  in  front,  with  the  dartos  of  the  scrotum;  on 
either  side  it  is  firmly  attached  to  the  margins  of  the  rami  of  the  os  pubis  and 
ischium,  external  to  the  crus  penis,  and  as  far  back  as  the  tuberosity  of  the  isch- 
ium;   posteriorly,  it  curves  down  behind  the  Transversus  perinsei  muscles  to  join 


Fig.  223.— The  perinseum.    The  integument  and  superficial  layer  of  superficial  fascia  reflected. 

the  lower  margin  of  the  triangular  ligament.  This  fascia  not  only  covers  the 
muscles  in  this  region,  but  sends  upward  a  vertical  septum  from  its  deep  surface, 
which  separates  the  back  part  of  the  subjacent  space  into  two,  the  septum  being 
incomplete  in  front. 

The  Central  Tendinous  Point  of  the  Perinseum. — Thr  is  a  fibrous  point  in  the 
middle  line  of  the  perinseum,  between  the  urethra  and  the  rectum,  being  about 
half  an  inch  in  front  of  the  anus.  At  this  pome  four  muscles  converge  and  are 
attached:  viz.,  the  External  sphincter  ani,  the  Accelerator  urinse,  and  the  two 


/ 


OF   THE   PERINsEUM. 


Ml 


Transversus  perineei ;  so  that  by  the  contraction  of  these  muscles,  which  extend  in 
opposite  directions,  it  serves  as  a  fixed  point  of  support. 

The  Transversus  perinaei  is  a  narrow  muscular  slip,  which  passes  more  or  less 
transversely  across  the  back  part  of  the  perineal  space.  It  arises  by  a  small  tendon 
from  the  inner  and  fore  part  of  the  tuberosity  of  the  ischium,  and,  passing  inward, 
is  inserted  into  the  central  tendinous  point  of  the  perimeum,  joining  in  this  situation 


V^RECTUS 

ABDOMINIS. 


Fig.  224.— The  muscles  attached  to  the  front  of  the  pelvis.  (From  a  preparation  in  the  Museum  of  the  Royal 
College  of  Surgeons  of  England.) 

with  the  muscle  of  the  opposite  side,  the  External  sphincter  ani  behind,  and  the 
Accelerator  urinse  in  front. 

Nerve-supply. — The  perineal  branch  of  the  internal  pudic. 

Actions. — By  their,  contraction  they  serve  to  fix  the  central  tendinous  point  of 
the  perinseum. 

The  Accelerator  urinse  (Ejaculator  seminis,  or  Bidbo-cavernosus)  is  placed  in 
the  middle  line  of  the  perinseum,  immediately  in  front  of  the  anus.  It  consists  of 
two  symmetrical  halves,  united  along  the  median  line  by  a  tendinous  raphe.  It 
arises  from  the  central  tendon  of  the  perinneum,  and  from  the  median  raphe*  in 
front.     From  this  point  its  fibres  diverge  like  the  plumes  of  a  pen ;  the  most 


372 


THE   MUSCLES   AND    FASCIAE 


posterior  form  a  thin  layer,  which  is  lost  on  the  anterior  surface  of  the  triangular 
ligament;  the  middle  fibres  encircle  the  bulb  and  adjacent  parts  of  the  corpus 
spongiosum,  and  join  with  the  fibres  of  the  opposite  side,  on  the  upper  part  of  the 
corpus  spongiosum,  in  a  strong  aponeurosis  ;  the  anterior  fibres,  the  longest  and 
most  distinct,  spread  out  over  the  sides  of  the  corpus  cavernosum,  to  be  inserted 
partly  into  that  body,  anterior  to  the  Erector  penis,  occasionally  extending  to  the 
os  pubis ;  partly  terminating  in  a  tendinous  expansion,  which  covers  the  dorsal 
vessels  of  the  penis.  The  latter  fibres  are  best  seen  by  dividing  the  muscle 
longitudinally,  and  dissecting  it  outward  from  the  surface  of  the  urethra. 

Action. — This  muscle  serves  to  empty  the  canal  of  the  urethra,  after  the 
bladder  has  expelled  its  contents  ;  during  the  greater  part  of  the  act  of  micturition 
its  fibres  are  relaxed,  and  it  only  comes  into  action  at  the  end  of  the  process.  The 
middle  fibres   are  supposed,  by  Krause,  to   assist  in  the  erection  of  the  corpus 


GREAT  SACRO- 
SCIATIC    LIGAMENT. 


Superficial  perineal  artery. 
—Superficial  perineal  nerve. 
Internal  pudic  nerve. 
Internal  pudic  artery. 


Fig.  225.— The  superficial  muscles  and  vessels  of  the  perinseuru. 


spongiosum,  by  compressing  the  erectile  tissue  of  the  bulb.  The  anterior  fibres, 
according  to  Tyrrel,  also  contribute  to  the  erection  of  the  penis,  as  they  are  inserted 
into,  and  continuous  with,  the  fascia  of  the  penis,  compressing  the  dorsal  vein 
during  the  contraction  of  the  muscle. 

The  Erector  penis  (Ischio-cavernous)  covers  part  of  the  crus  penis.  It  is  an 
elongated  muscle,  broader  in  the  middle  than  at  either  extremity,  and  situated  on 
either  side  of  the  lateral  boundary  of  the  perinseum.  It  arises  by  tendinous  and 
fleshy  fibres  from  the  inner  surface  of  the  tuberosity  of  the  ischium,  behind  the 
crus  penis,  from  the  surface  of  the  crus,  and  from  the  adjacent  portion  of  the 
ramus  of  the  ischium.  From  these  points  fleshy  fibres  succeed,  which  end  in  an 
aponeurosis  which  is  inserted  into  the  sides  and  under  surface  of  the  crus  penis. 

Nerve-supply. — The  perineal  branch  of  the  internal  pudic. 

Actions. — It  compresses  the  crus  penis  and  retards  the  return  of  the  blood 
through  the  veins,  and  thus  serves  to  maintain  the  organ  erect. 

Between  the  muscles  just  examined  a  triangular  space  exists,  bounded 
internally  by  the  Accelerator  urinas,  externally  by  the  Erector  penis,  and  behind 


OF    THE   PERINEUM. 


373 


by  the  Transversus  perinsei.  The  floor  of  this  space  is  formed  by  the  triangular 
ligament  of  the  urethra  (deep  perineal  fascia),  and  running  from  behind  forward 
in  it  are  the  superficial  perineal  vessels  and  nerves,  the  long  pudendal  nerve ;  the 
transverse  perineal  artery  coursing  along  the  posterior  boundary  of  the  space  on 
the  Transversus  perinsei  muscle. 

The  Triangular  Ligament  {Deep  perineal  fascia)  is  stretched  almost  horizontal^ 
across  the  pubic  arch,  so  as  to  close  in  the  front  part  of  the  outlet  of  the  pelvis. 
It  consists  of  two  dense  membranous  laminse.  which  are  united  along  their 
posterior  borders,  but  are  separated  in  front  by  intervening  structures.  The 
superficial  of  these  two  layers,  the  inferior  layer  of  the  triangular  ligament,  is 
triangular  in  shape,  about  an  inch  and  a  half  in  depth.  Its  apex  is  directed 
forward,  and  is  separated  from  the  subpubic  ligament  by  an  oval  openino-  for  the 
transmission  of  the  dorsal  vein  of  the  penis.  Its  lateral  margins  are  attached  on 
each  side  to  the  rami  of  the  ischium  and  os  pubis,  above  the  crura  penis.  Its  base 
is  directed  toward  the  rectum,  and  connected  to  the  central  tendinous  point  of  the 
peringeum.  It  is  continuous  with  the  deep  layer  of  the  superficial  fascia  behind 
the  Transversus  perinsei  muscle,  and  with  a  thin  fascia  which  covers  the  cutaneous 
surface  of  the  Levator  ani  muscle  {anal  or  ischio-rectal  fascia). 


'Anterior  layer  of 

deep  perineal  fascia  removed, 

showing 

^COMPRESSOR    URETHR/E. 

^Internal  pudic  artery. 
— -Artery  of  the  bulb. 
Cowper's  gland. 


Fig.  226.— Triangular  ligament  or  deep  perineal  fascia.    On  the  left  side  the  superficial  laver  has  been 
removed. 


This  layer  of  the  triangular  ligament  is  perforated,  about  an  inch  below  the 
symphysis  pubis,  by  the  urethra,  the  aperture  for  which  is  circular  in  form  and 
about  three  or  four  lines  in  diameter ;  by  the  arteries  to  the  bulb  and  the  ducts  of 
Cowper's  glands  close  to  the  urethral  orifice ;  by  the  arteries  to  the  corpora  caver- 
nosa— one  on  each  side,  close  to  the  pubic  arch  and  about  halfway  along  the 
attached  margin  of  the  ligament ;  by  the  dorsal  arteries  and  nerves  of  the  penis 
near  the  apex  of  the  ligament.  Its  base  is  also  perforated  by  the  superficial 
perineal  vessels  and  nerves,  while  between  its  apex  and  the  subpubic  ligament  the 
dorsal  vein  of  the  penis  passes  upward  into  the  pelvis. 

If  this  superficial  or  inferior  layer  of  the  triangular  ligament  is  detached  on 
either  side,  the  following  structures  will  be  seen  between  it  and  the  deeper  layer : 
the  dorsal  vein  of  the  penis ;    the  membranous  portion  of  the  urethra,   and  the 


374 


THE   MUSCLES   AND   FASCIAE 


Compressor  urethrce  muscle ;  Cowper's  glands  and  their  ducts ;  the  pudic  vessels 
and  dorsal  nerve  of  the  penis ;  the  artery  and  nerve  of  the  bulb,  and  a  plexus  of 
veins. 

The  deep  layer  of  the  ligament  (superior  layer  of  the  triangular  ligament)  is 
derived  from  the  obturator  fascia  and  stretches  across  the  pubic  arch.  If  the 
obturator  fascia  is  traced  inward  after  covering  the  Obturator  internus  muscle, 
it  will  be  found  to  be  attached  by  some  of  its  deeper  or  anterior  fibres  to  the  inner 
margin  of  the  ischio-pubic  ramus,  while  its  superficial  or  posterior  fibres  pass  over 
this  attachment  to  become  the  superior  layer  of  the  triangular  ligament.  Behind, 
this  layer  of  the  fascia  is  continuous  with  the  inferior  layer  and  with  the  fascia  of 
Colles,  and  in  front  it  is  separated  from  the  apex  of  the  prostate  gland  through  the 
intervention  of  a  prolongation  of  the  recto-vesical  fascia.  It  is  pierced  by  the 
urethra,  or  rather  consists  of  two  halves  which  are  separated  in  the  middle  line  by 
the  urethra  passing  between  them. 


TRANSVERSUS 

PERI  N/EI. 


TUBER    ISCHII. 


Fig.  227.— Muscles  of  the  female  perineeum. 


The  Compressor  urethrse  (Constrictor  urethrce)  surrounds  the  whole  length  of 
the  membranous  portion  of  the  urethra,  and  is  contained  between  the  two  layers 
of  the  triangular  ligament.  It  arises,  by  aponeurotic  fibres,  from  the  junction  of 
the  rami  of  the  os  pubis  and  ischium,  to  the  extent  of  half  or  three-quarters  of  an 
inch  :  each  segment  of  the  muscle  passes  inward,  and  divides  into  two  fasciculi, 
which  surround  the  urethra  from  the  prostate  gland  behind  to  the  bulbous  por- 
tion of  the  urethra  in  front ;  and  unite,  at  the  upper  and  lower  surfaces  of  this 
tube,  with  the  muscle  of  the  opposite  side  by  means  of  a  tendinous  raphe\ 

Nerve-supply. — The  perineal  branch  of  the  internal  pudic. 

Actions. — The  muscles  of  both  sides  act  together  as  a  sphincter,  compressing 
the  membranous  portion  of  the  urethra.  During  the  transmission  of  fluids  they, 
like  the  Acceleratores  urinse,  are  relaxed,  and  come  into  action  only  at  the  end  of 
the  process,  to  eject  the  last  drops  of  the  fluid. 


OF    THE   PERINEUM.  375 

II.  B.  Muscles  of  the  Perinaeum  in  the  Female  (Fig.  227). 

Transversus  perinaei.  Erector  clitoridis. 

Sphincter  vaginae.  Compressor  urethrae. 

The  Transversus  perinaei  in  the  female  is  a  narrow  muscular  slip,,  which  passes 
more  or  less  transversely  across  the  back  part  of  the  perineal  space.  It  arises  by 
a  small  tendon  from  the  inner  and  fore  part  of  the  tuberosity  of  the  ischium,  and. 
passing  inward,  is  inserted  into  the  central  point  of  the  perinaeum,  joining  in  this 
situation  with  the  muscle  of  the  opposite  side,  the  External  sphincter  ani  behind, 
and  the  Sphincter  vaginae  in  front. 

Nerve-supply. — The  perineal  branch  of  the  internal  pudic. 

Actions. — By  their  contraction  they  serve  to  fix  the  central  tendinous  point  of 
the  perinaeum. 

The  Sphincter  vaginas  surrounds  the  orifice  of  the  vagina,  and  is  analogous 
to  the  Accelerator  urinae  in  the  male.  It  is  attached  posteriorly  to  the  central 
tendinous  point  of  the  perinaeum,  where  it  blends  with  the  External  sphincter  ani. 
Its  fibres  pass  forward  on  each  side  of  the  vagina,  to  be  inserted  into  the  corpora 
cavernosa  of  \)n%  clitoris,  a  fasciculus  crossing  over  the  body  of  the  organ  so  as  to 
compress  the  dorsal  vein. 

Nerve-supply. — The  perineal  branch  of  the  internal  pudic. 

Actions. — It  diminishes  the  orifice  of  the  vagina.  The  anterior  fibres  contribute 
to  the  erection  of.  the  clitoris,  as  they  are  inserted  into  and  are  continuous  with  the 
fascia  of  the  clitoris ;  compressing  the  dorsal  vein  during  the  contraction  of  the 
muscle. 

The  Erector  clitoridis  resembles  the  Erector  penis  in  the  male,  but  is  smaller  than 
it.  It  covers  the  unattached  part  of  the  crus  clitoridis.  It  is  an  elongated  muscle, 
broader  at  the  middle  than  at  either  extremity,  and  situated  on  either  side  of  the 
lateral  boundary  of  the  perinaeum.  It  arises  by  tendinous  and  fleshy  fibres  from 
the  inner  surface  of  the  tuberosity  of  the  ischium,  behind  the  crus  clitoridis  from 
the  surface  of  the  crus,  and  from  the  adjacent  portion  of  the  ramus  of  the  ischium. 
From  these  points  fleshy  fibres  succeed,  which  end  in  an  aponeurosis,  which  is 
inserted  into  the  sides  and  under  surface  of  the  crus  clitoridis. 

Nerve-supply. — The  perineal  branch  of  the  internal  pudic. 

Actions. — It  compresses  the  crus  clitoridis  and  retards  the  return  of  blood 
through  the  veins,  and  thus  serves  to  maintain  the  organ  erect. 

The  triangular  ligament  (deep  perineal  fascia)  in  the  female  is  not  so  strong  as 
in  the  male.  It  is  attached  to  the  pubic  arch,  its  apex  being  connected  with  the 
subpubic  ligament.  It  is  divided  in  the  middle  line  by  the  aperture  of  the  vagina, 
with  the  external  coat  of  which  it  becomes  blended,  and  in  front  of  this  is  perfor- 
ated by  the  urethra.  Its  posterior  border  is  continuous,  as  in  the  male,  with  the 
deep  layer  of  the  superficial  fascia  around  the  Transversus  perinaei  muscle. 

Like  the  triangular  ligament  in  the  male,  it  consists  of  two  layers,  between 
which  are  to  be  found  the  following  structures  :  the  dorsal  vein  of  the  clitoris, 
a  portion  of  the  urethra  and  the  Compressor  urethrae  muscle,  the  glands  of  Bar- 
tholin and  their  ducts  ;  the  pudic  vessels  and  the  dorsal  nerve  of  the  clitoris  ;  the 
arteries  of  the  bulbi  vestibuli,  and  a  plexus  of  veins. 

The  Compressor  urethrae  {Constrictor  urethra?)  arises  on  each  side  from  the 
margin  of  the  descending  ramus  of  the  os  pubis.  The  fibres,  passing  inward, 
divide  into  two  sets :  those  of  the  fore  part  of  the  muscle  are  directed  across  the 
subpubic  arch  in  front  of  the  urethra  to  blend  with  the  muscular  fibres  of  the 
opposite  side ;  while  those  of  the  hinder  and  larger  part  pass  inward  to  blend  with 
the  wall  of  the  vagina  behind  the  urethra. 

Nerve-supply. — The  perineal  branch  of  the  internal  pudic. 


376  THE  MUSCLES  AND    FASCIJE 

MUSCLES  AND  FASCLE  OF  THE  UPPER  EXTREMITY. 

The  Muscles  of  the  Upper  Extremity  are  divisible  into  groups,  corresponding 
with  the  different  regions  of  the  limb. 


I.  Of  the  Thoracic  Region. 
1.  Anterior   Thoracic  Region. 

Pectoralis  major.     Pectoralis  minor. 
Subclavius. 

2.  Lateral  Thoracic  Region. 
Serratus  magnus. 

II.  Of  the  Shoulder  and  Arm. 

3.  Acromial  Region. 
Deltoid.  _ 

4.  Anterior  Scapular  Region. 

Subscapulars. 

5.  Posterior  Scapular  Region. 

Supraspinatus.  Teres  minor. 

Infraspinatus.  Teres  major. 

6.  Anterior  Humeral  Region. 

Coraco-brachialis.  Biceps. 

Brachialis  anticus. 

7.  Posterior  Humeral  Region. 
Triceps'.  Subanconeus. 


III.  Of  the  Forearm. 

Anterior  Radio-  Ulnar  Region. 
Pronator  radii  teres. 
Flexor  carpi  radialis. 
<   Palmaris  longus. 
|  Flexor  carpi  ulnaris. 
^  Flexor  sublimis  digitorum. 
f  Flexor  profundus  digitorum. 
<(  Flexor  longus  pollicis. 
^  Pronator  quadratus. 


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9.  Radial  Region. 

Supinator  longus. 

Extensor  carpi  radialis  longior. 

Extensor  carpi  radialis  brevior. 

10.  Posterior  Radio-  Ulnar  Region. 

C Extensor  communis  digitorum. 
j  Extensor  minimi  digiti. 
j  Extensor  carpi  ulnaris. 
I  Anconeus. 

f  Supinator  brevis. 
|  Extensor  ossis  metacarpi pollicis. 
<(  Extensor  brevis  pollicis. 
|  Extensor  longus  pollicis. 
t^ Extensor  indicis. 

IV.  Of  the  Hand. 

11.  Radial  Region. 

Abductor  pollicis. 

Flexor  ossis  metacarpi  pollicis 

(Opponens  pollicis). 
Flexor  brevis  pollicis. 
Adductor  obliquus  pollicis. 
Adductor  trans  versus  pollicis. 

12.  Ulnar  Region. 

Palmaris  brevis. 
Abductor  minimi  digiti. 
Flexor  brevis  minimi  digiti. 
Flexor  ossis  metacarpi  minimi  digiti 
(Opponens  minimi  digiti). 

13.  Middle  Palmar  Region. 

Lumbricales. 
Interossei  palmares. 
Interossei  dorsales. 


Dissection  of  Pectoral  Region  and  Axilla  (Fig.  228). — The  arm  being  drawn  away 
from  the  side  nearly  at  right  angles  with  the  trunk  and  rotated  outward,  make  a  vertical  in- 
cision through  the  integument  in  the  median  line  of  the  chest,  from  the  upper  to  the  lower  part 
of  the  sternum ;  a  second  incision  along  the  lower  border  of  the  Pectoral  muscle,  from  the  ensi- 
form  cartilage  to  the  inner  side  of  the  axilla:  a  third,  from  the  sternum  along  the  clavicle,  as 
far  as  its  centre ;  and  a  fourth,  from  the  middle  of  the  clavicle  obliquely  downward,  along  the 
interspace  between  the  Pectoral  and  Deltoid  muscles,  as  low  as  the  fold  of  the  armpit.  The  flap 
of  integument  is  then  to  be  dissected  off  in  the  direction  indicated  in  the  figure,  hut  not  entirely 
removed,  as  it  should  be  replaced  on  completing  the  dissection.  If  a  transverse  incision  is  now 
made  from  the  lower  end  of  the  sternum  to  the  side  of  the  chest,  as  far  as  the  posterior  fold  of 
the  armpit,  and  the  integument  reflected  outward,  the  axillary  space  will  be  more  completely 
exposed. 


OF   THE    THORACIC  REGION.  377 

I.  Muscles  and  Fasciae  of  the  Thoracic  Region. 

1.  Anterior   Thoracic  Region. 

Pectoralis  major.  Pectoralis  minor. 

Subclavius. 

The  superficial  fascia  of  the  thoracic  region  is  a  loose  cellulo-fibrous  layer 
enclosing  masses  of  fat  in  its  spaces.  It  is  continuous  with  the  superficial  fascia  of 
the  neck  and  upper  extremity  above,  and  of  the  abdomen  below.  Opposite  the 
mamma  it  divides  into  two  layers,  one  of  which  passes  in  front,  the  other  behind, 
that  gland ;  and  from  both  of  these  layers  numerous  septa  pass  into  its  substance, 
supporting  its  various  lobes  :  from  the  anterior  layer  fibrous  processes  pass  forward 
to  the  integument  and  nipple.  These  processes  were  called  by  Sir  A.  Cooper  the 
ligamenta  suspensoria,  from  the  support  they  afford  to  the  gland  in  this  situation. 

The  deep  fascia  of  the  thoracic  region  is  a  thin  aponeurotic  lamina,  covering 
the  surface  of  the   great  Pectoral  muscle,   and   sending  numerous  prolongations 


1.  Dissection  of 
Pectoral  Region 
and  Axilla. 


8.  Dissection  of 
Shoulder  and  Arm. 


2.  Bend  of  Elbow. 


4-.  Forearm. 


5.  Palm  of  Hand. 


Fig.  228. — Dissection  of  upper  extremity. 

between  its  fasciculi :  it  is  attached,  in  the  middle  line,  to  the  front  of  the  ster- 
num, and  above  to  the  clavicle  ;  externally  and  below  it  becomes  continuous  with 
the  fascia  over  the  shoulder,  axilla,  and  thorax.  It  is  very  thin  over  the  upper 
part  of  the  muscle,  thicker  in  the  interval  between  the  Pectoralis  major  and  Latis- 
simus  dorsi,  where  it  closes  in  the  axillary  space,  and  divides  at  the  outer  margin 
of  the  latter  muscle  into  two  layers,  one  of  which  passes  in  front  and  the  other  be- 
hind it;  these  proceed  as  far  as  the  spinous  processes  of  the  dorsal  vertebrae,  to 
which  they  are  attached.  As  the  fasci  leaves  the  lower  edge  of  the  Pectoralis 
major  to  pass  across  the  floor  of  the  axilla  it  .-ends  a  layer  upward  under  cover  of 
the  muscle  :  this  lamina  splits  to  envelop  the  Pectoralis  minor,  at  the  upper  edge  of 
which  it  becomes  continuous  with  the  CO!  I  >-coracoid  membrane.  The  hollow  of  the 
armpit,  seen  when  the  arm  is  abducted,    >  mainly  produced  by  the  traction  of  this 


378  THE  MUSCLES  AND    FASCIAE 

fascia  on  the  axillary  floor,  and  hence  it  is  sometimes  named  the  suspensory  liga- 
ment of  the  axilla.  At  the  lower  part  of  the  thoracic  region  this  fascia  is  well  de- 
veloped, and  is  continuous  with  the  fibrous  sheath  of  the  Recti  muscles. 

The  Pectoralis  major  (Fig.  229)  is  a  broad,  thick,  triangular  muscle,  situated 
at  the  upper  and  fore  part  of  the  chest,  in  front  of  the  axilla.  It  arises  from  the 
anterior  surface  of  the  sternal  half  of  the  clavicle ;  from  half  the  breadth  of  the 
anterior  surface  of  the  sternum,  as  low  down  as  the  attachment  of  the  cartilage 
of  the  sixth  or  seventh  rib ;  this  portion  of  its  origin  consists  of  aponeurotic 
fibres,  which  intersect  with  those  of  the  opposite  muscle  ;  it  also  arises  from  the 
cartilages  of  all  the  true  ribs,  with  the  exception,  frequently,  of  the  first  or  of  the 
seventh,  or  both  ;  and  from  the  aponeurosis  of  the  External  oblique  muscle  of  the 
abdomen.  The  fibres  from  this  extensive  origin  converge  toward  its  insertion, 
giving  to  the  muscle  a  radiated  appearance.  Those  fibres  which  arise  from  the 
clavicle  pass  obliquely  outward  and  downward,  and  are  usually  separated  from  the 
rest  by  a  cellular  interval :  those  from  the  lower  part  of  the  sternum,  and  the 
cartilages  of  the  lower  true  ribs,  pass  upward  and  outward,  whilst  the  middle 
fibres  pass  horizontally.  They  all  terminate  in  a  flat  tendon,  about  two  inches 
broad,  which  is  inserted  into  the  outer  bicipital  ridge  of  the  humerus.  This 
tendon  consists  of  two  laminae,  placed  one  in  front  of  the  other,  and  usually 
blended  together  below.  The  anterior,  the  thicker,  receives  the  clavicular  and 
upper  half  of  the  sternal  portion  of  the  muscle  :  and.  its  fibres  are  inserted  in  the 
same  order  as  that  in  which  they  arise ;  that  is  to  say,  the  outermost  fibres  of 
origin  from  the  clavicle  are  inserted  at  the  uppermost  part  of  the  tendon  ;  the 
upper  fibres  of  origin  from  the  sternum  pass  down  to  the  lowermost  part  of  this 
anterior  lamina  of  the  tendon  and  extend  as  low  as  the  tendon  of  the  Deltoid  and 
join  with  it.  The  posterior  lamina  of  the  tendon  receives  the  attachment  of  the 
lower  half  of  the  sternal  portion  and  the  deeper  part  of  the  muscle  from  the  costal 
cartilages.  These  deep  fibres,  and  particularly  those  from  the  lower  costal  carti- 
lages, ascend  the  higher,  turning  backward  successively  behind  the  superficial  and 
upper  ones,  so  that  the  tendon  appears  to  be  twisted.  The  posterior  lamina 
reaches  higher  on  the  humerus  than  the  anterior  one,  and  from  it  an  expansion  is 
given  off  which  covers  the  bicipital  groove  and  blends  with  the  capsule  of  the 
shoulder-joint.  From  the  deepest  fibres  of  this  lamina  at  its  insertion  an  expan- 
sion is  given  off  which  lines  the  bicipital  groove  of  the  humerus,  while  from  the 
lower  border  of  the  tendon  a  third  expansion  passes  downward  to  the  fascia  of  the 
arm. 

Relations. — By  its  anterior  surface,  with  the  integument,  the  superficial  fascia, 
the  Platysma,  some  of  the  branches  of  the  descending  cervical  nerves,  the  mammary 
gland,  and  the  deep  fascia  ;  by  its  posterior  surface :  its  thoracic  portion,  with  the 
sternum,  the  ribs  and  costal  cartilages,  the  costo-coracoid  membrane,  the  Subclavius, 
Pectoralis  minor,  Serratus  magnus,  and  the  Intercostals  ;  its  axillary  portion  forms 
the  anterior  wall  of  the  axillary  space,  and  covers  the  axillary  vessels  and  nerves, 
the  Biceps  and  Coraco-brachialis  muscles.  Its  upper  border  lies  parallel  with  the 
Deltoid,  from  which  it  is  separated  by  a  slight  interspace  in  which  lie  the  cephalic 
vein  and  humeral  branch  of  the  acromial  thoracic  artery.  Its  lower  border  forms 
the  anterior  margin  of  the  axilla,  being  at  first  separated  from  the  Latissimus  dorsi 
by  a  considerable  interval ;  but  both  muscles  gradually  converge  toward  the  outer 
part  of  the  space. 

Dissection. — Detach  the  Pectoralis  major  by  dividing  the  muscle  along  its  attachment  to  the 
clavicle,  and  by  making  a  vertical  incision  through  its  substance  a  little  external  to  its  line  of 
attachment  to  the  sternum  and  costal  cartilages.  The  muscle  should  then  be  reflected  outward, 
and  its  tendon  carefully  examined.  The  Pectoralis  minor  is  now  exposed,  and  immediately 
above  it,  in  the  interval  between  its  upper  border  and  the  clavicle,  a  strong  fascia,  the  costo- 
coracoid  membrane. 

The  costo-coracoid  membrane  is  a  strong  fascia,  situated  under  cover  of  the 
clavicular  portion  of  the  Pectoralis  major  muscle.  It  occupies  the  interval  between 
the  Pectoralis  minor  and  Subclavius  muscles,  and  protects  the  axillary  vessels  and 


OF    THE    THORACIC   REGION. 


379 


nerves.  Traced  upward,  it  splits  to  enclose  the  Subclavius  muscle,  and  its  two 
layers  are  attached  to  the  clavicle,  one  in  front  of  and  the  other  behind  the  muscle ; 
the  latter  layer  fuses  with  the  deep  cervical  fascia  and  with  the  sheath  of  the 
axillary  vessels.     Internally,  it  blends  with  the  fascia  covering  the  first  two  inter- 


Fig.  229.— Muscles  of  the  chest  and  front  of  the  arm.    Superficial  view. 

costal  spaces,  and  is  attached  also  to  the  first  rib  internal  to  the  origin  of  the  Sub- 
clavius muscle.  Externally  it  is  very  thick  and  dense,  and  is  attached  to  the  cora- 
coid  process.  The  portion  extending  from  its  attachment  to  the  first  rib  to  the 
coracoid  process  is  often  whiter  and  denser  than  the  rest ;  this  is  sometimes  called 
the  costo-coracoid  ligament.  Below,  it  is  thin,  and  at  the  upper  border  of  the  Pec- 
toralis  minor  it  splits  into  two  layers  to  invest  the  muscle  ;  from  the  lower  border  of 
the  Pectoralis  minor  it  is  continued  downward  to  join  the  axillary  fascia,  and  out- 
ward to  join  the  fascia  over  the  short  head  of  the  Biceps.  The  costo-coracoid  mem- 
brane is  pierced  by  the  cephalic  vein,  the  acromial  thoracic  artery  and  vein,  super- 
ior thoracic  artery,  and  anterior  thoracic  nerves. 

The  Pectoralis  minor  (Fig.  230)  is   a  thin,  flat,  triangular  muscle,  situated  at 
the  upper  part  of  the  thorax,  beneath  the  Pectoralis  major.     It  arises  by  three 


380 


THE  MUSCLES   AND    FASCIAE 


tendinous  digitations  from  the  upper  margin  and  outer  surface  of  the  third,  fourth, 
and  fifth  ribs,  near  their  cartilages,  and  from  the  aponeurosis  covering  the  Inter- 
costal muscles ;  the  fibres  pass  upward  and  outward,  and  converge  to  form  a  flat 
tendon,  which  is  inserted  into  the  inner  border  and  upper  surface  of  the  coracoid 
process  of  the  scapula. 

Relations. — By  its  anterior  surface,  with  the  Pectoralis  major  and  the  thoracic 


Fig.  230.— Muscles  of  the  chest  and  front  of  the  arm,  with  the  boundaries  of  the  axilla. 

branches  of  the  acromial  thoracic  artery.  By  its  posterior  surface,  with  the 
ribs,  Intercostal  muscles,  Serratus  magnus,  the  axillary  space,  and  the  axillary 
vessels  and  brachial  plexus  of  nerves.  Its  upper  border  is  separated  from  the 
clavicle  by  a  triangular  interval,  broad  internally,  narrow  externally,  which  is 
occupied  by  the  costo-coracoid  membrane.  In  this  space  is  the  first  part  of  the 
axillary  vessels  and  nerves.  Running  parallel  to  the  lower  border  of  the  muscle  is 
the  long  thoracic  artery. 

The  costo-coracoid  membrane  should  now  be  removed,  when  the  Subclavius  muscle  will 
be  seen. 

The  Subclavius  is  a  small  triangular  muscle,  placed  in  the  interval  between  the 
clavicle  and  the  first  rib.  It  arises  by  a  short,  thick  tendon  from  the  first  rib  and 
its  cartilage  at  their  j  unction,  in  front  of  the  rhomboid  ligament;  the  fleshy  fibres 
proceed  obliquely  upward  and  outward,  to  be  inserted  into  a  deep  groove  on  the 
under  surface  of  the  clavicle. 

Relations. — By  its  upper  surface,  with  the  clavicle.  By  its  deep  surface  it  is 
separated  from  the  first  rib  by  the  subclavian  vessels  and  brachial  plexus  of  nerves. 
Its  anterior  surface  is  separated  from  the  Pectoralis  major  by  the  costo-coracoid 


THE  LATERAL    THORACIC   REGION. 


381 


Slip  Of  SERRATUS 

Magnus  to  first  rib 


Spine  of 

scapula. 


membrane,  which,  with  the  clavicle,  forms  an  osseo-fibrous  sheath   in  which  the 
muscle  is  enclosed. 

If  the  costal  attachment  of  the  Pectoralis  minor  is  divided  across,  and  the  muscle  reflected 
outward,  the  axillary  vessels  and  nerves  are  brought  fully  into  view,  and  should  be  examined. 

Nerves. — The  Pectoral  muscles  are  supplied  by  the  anterior  thoracic  nerves ; 
the  Pectoralis  major  through  these  nerves  re- 
ceives filaments  from  all  the  spinal  nerves 
entering  into  the  formation  of  the  brachial 
plexus;  the  Pectoralis  minor  receives  its 
fibres  from  the  eighth  cervical  and  first  dorsal 
nerves.  The  Subclavius  is  supplied  by  a 
filament  from  the  fifth  cervical  nerve. 

Actions. — If  the  arm  has  been  raised  by 
the  Deltoid,  the  Pectoralis  major  will,  con- 
jointly with  the  Latissimus  dorsi  and  Teres 
major,  depress  it  to  the  side  of  the  chest. 
If  acting  alone,  it  adducts  and  draws  for- 
ward the  arm,  bringing  it  across  the  front 
of  the  chest,  and  at  the  same  time  rotates 
it  inward.  The  Pectoralis  minor  depresses 
the  point  of  the  shoulder,  drawing  the  scap- 
ula downward  arid  inward  to  the  thorax,  and 
throwing  the  inferior  angle  backward.  The 
Subclavius  depresses  the  shoulder,  drawing 
the  clavicle  downward  and  forward.  When 
the  arms  are  fixed,  all  three  muscles  act  upon 
the  ribs,  drawing  them  upward  and  expand- 
ing the  chest,  and  thus  becoming  very  im- 
portant agents  in  forced  inspiration.  Asth- 
matic patients  always  assume  an  attitude 
which  fixes  the  shoulders,  so  that  all  these 
"muscles  may  be  brought  into  action  to  assist 
in  dilating  the  cavity  of  the  chest. 


2.  Lateral  Thoracic  Region. 

Serratus  mao-nus. 


EXTERNAL 


Eighth  rib. 


Fig.  231.— Serratus  magnus.    (From  a  prepara- 
tion in  the  Museum  of  the  Royal  College  of  Sur- 


The  Serratus  magnus  (Fig.  231)  is  a  thin,  ge0ns  of  England 
irregularly  quadrilateral  muscle,  situated  be- 
tween the  ribs  and  the  scapula  at  the  upper  and  lateral  part  of  the  chest.  It 
arises  by  nine  digitations  or  slips  from  the  outer  surface  and  upper  border  of  the 
eight  upper  ribs  (the  second  rib  giving  origin  to  two  slips),  and  from  the  aponeurosis 
covering  the  corresponding  intercostal  muscles.  From  this  extensive  attachment 
the  fibres  pass  backward,  closely  applied  to  the  chest-wall,  and  reach  the  verte- 
bral border  of  the  scapula,  and  are  inserted  into  its  ventral  aspect  in  the  following 
manner.  The  upper  two  digitations — i.  e.,  the  one  from  the  first  rib  and  the  higher, 
of  the  two  from  the  second  rib — converge  to  be  inserted  into  a  triangular  area  on 
the  ventral  aspect  of  the  superior  angle.  The  next  two  digitations  spread  out  to 
form  a  thin  triangular  sheet,  the  base  of  which  is  directed  backward  and  is  inserted 
into  nearly  the  whole  length  of  the  ventral  aspect  of  the  vertebral  border.  The 
lower  five  digitations  converge,  as  they  pass  backward  from  the  ribs,  to  form  a  fan- 
shaped  structure,  the  apex  of  which  is  inserted,  partly  by  muscular  and  partly  by 
tendinous  fibres,  into  a  triangular  impression  on  the  ventral  aspect  of  the  inferior 
angle.  The  lower  four  slips  interdigitate  at  their  origin  with  the  upper  five  slips 
of  the  External  oblique  muscle  of  the  abdomen. 


382  •  THE   MUSCLES   AND    FASCIAE. 

Relations. — This  muscle  is  partly  covered,  in  front,  by  the  Pectoral  muscles ; 
behind,  by  the  Subscapularis.  The  axillary  vessels  and  nerves  lie  upon  its  upper 
part,  while  its  deep  surface  rests  upon  the  ribs  and  intercostal  muscles. 

Nerve. — The  Serratus  magnus  is  supplied  by  the  posterior  thoracic  nerve,  which 
is  derived  from  the  fifth,  sixth,  and  generally  the  seventh  cervical  nerves. 

Actions. — The  Serratus  magnus,  as  a  whole,  carries  the  scapula  forward,  and  at 
the  same  time  raises  the  vertebral  border  of  the  bone.  It  is  therefore  concerned 
in  the  action  of  pushing.  Its  lower  and  stronger  fibres  move  forward  the  lower 
angle  and  assist  the  Trapezius  in  rotating  the  bone  round  an  axis  through  its  centre, 
and  thus  assists  this  muscle  in  raising  the  acromion  and  supporting  weights  upon 
the  shoulder.  It  is  also  an  assistant  to  the  Deltoid  in  raising  the  arm,  inasmuch  as 
during  the  action  of  this  latter  muscle  it  fixes  the  scapula  and  so  steadies  the  glen- 
oid cavity  on  which  the  head  of  the  humerus  rotates.  After  the  Deltoid  has  raised 
the  arm  to  a  right  angle  with  the  trunk,  the  Serratus  magnus  and  the  Trapezius, 
by  rotating  the  scapula,  raise  the  arm  into  an  almost  vertical  position.  It  is  pos- 
sible that  when  the  shoulders  are  fixed  the  lower  fibres  of  the  Serratus  magnus  may 
assist  in  raising  and  everting  the  ribs ;  but  it  is  not  the  important  inspiratory  mus- 
cle which  it  was  formerly  believed  to  be. 

Surgical  Anatomy. — When  the  muscle  is  paralyzed,  the  vertebral  border,  and  especially 
the  lower  angle  of  the  scapula,  leaves  the  ribs  and  stands  out  prominently  on  the  surface,  giving 
a  peculiar  "winged  "  appearance  to  the  back.  The  patient  is  unable  to  raise  the  arm,  and  an 
attempt  to  do  so  is  followed  by  a  further  projection  of  the  lower  angle  of  the  scapula  from  the 
back  of  the  thorax. 

Dissection. — After  completing  the  dissection  of  the  axilla,  if  the  muscles  of  the  back  have 
been  dissected,  the  upper  extremity  should  be  separated<  from  the  trunk.  Saw  through  the 
clavicle  at  its  centre,  and  then  cut  through  the  muscles  which  connect  the  scapula  and  arm  with 
the  trunk,  viz.  :  the  Pectoralis  minor  in  front.  Serratus  magnus  at  the  side,  and  the  Levator 
anguli  scapulas,  the  Rhomboids,  Trapezius,  and  Latissimus  dorsi  behind.  These  muscles  should 
be  cleaned  and  traced  to  their  respective  insertions.  Then  make  an  incision  through  the  integu- 
ment, commencing  at  the  outer  third  of  the  clavicle,  and  extending  along  the  margin  of  that 
bone,  the  acromion  process,  and  spine  of  the  scapula ;  the  integument  should  be  dissected  from 
above  downward  and  outward,  when  the  fascia  covering  the  Deltoid  is  exposed  (Fig.  228,  No.  3). 

II.  MUSCLES  AND  FASCIA  OF  THE  SHOULDER  AND  ARM 

The  superficial  fascia  of  the  upper  extremity  is  a  thin  cellulo-fibrous  layer, 
containing  the  superficial  veins  and  lymphatics,  and  the  cutaneous  nerves.  It  is 
most  distinct  in  front  of  the  elboAv,  and  contains  very  large  superficial  veins~~and 
nerves ;  in  the  hand  it  is  hardly  demonstrable,  the  integument  being  closely 
adherent  to  the  deep  fascia  by  dense  fibrous,  bands.  Small  subcutaneous  bursae  are 
found  in  this  fascia  over  the  acromion,  the  olecranon,  and  the  knuckles.  The 
deep  fascia  of  the  upper  extremity  comprises  the  aponeurosis  of  the  shoulder, 
arm,  and  forearm,  the  anterior  and  posterior  annular  ligaments  of  the  carpus,  and 
the  palmar  fascia.  These  will  be  considered  in  the  description  of  the  muscles  of 
the  several  regions. 

3.  Acromial  Region. 

Deltoid. 

The  deep  fascia  covering  the  Deltoid  (deltoid  aponeurosis)  is  a  fibrous  layer 
which  covers  the  outer  surface  of  the  muscle,  thick  and  strong  behind,  where  it 
is  continuous  with  the  infraspinatus  fascia,  thinner  over  the  rest  of  its  extent. 
It  sends  doAvn  numerous  prolongations  between  the  fasciculi  of  the  muscle. 
In  front,  it  is  continuous  with  the  fascia  covering  the  great  Pectoral  muscle ; 
behind,  with  that  covering  the  Infraspinatus ;  above,  it  is  attached  to  the  clavicle, 
the  acromion,  and  spine  of  the  scapula  ;  below,  it  is  continuous  with  the  deep  fascia 
of  the  arm. 

The  Deltoid  (Fig.  229)  is  a  large,  thick,  triangular  muscle,  which  gives  the 
rounded  outline  to  the  shoulder,  and  has  received  its  name  from  its  resemblance  to 
the  Greek  letter  A  reversed.  It  surrounds  the  shoulder-joint  in  the  greater  part 
of  its  extent,  covering  it  on  its  outer  side,  and  in  front  and  behind.     It  arises  from 


THE   ANTERIOR    SCAPULAR    REGION.  383 

the  outer  third  of  the  anterior  border  and  upper  surface  of  the  clavicle ;  from  the 
outer  margin  and  upper  surface  of  the  acromion  process,  and  from  the  lower  lip  of 
the  posterior  border  of  the  spine  of  the  scapula,  as  far  back  as  ihe  triangular  surface 
at  its  inner  end.  From  this  extensive  origin  the  fibres  converge  toward  their  inser- 
tion, the  middle  passing  vertically,  the  anterior  obliquely,  backward,  the  posterior 
obliquely  forward  ;  they  unite  to  form  a  thick  tendon,  which  is  inserted  into  a 
rough  triangular  prominence  on  the  middle  of  the  outer  side  of  the  shaft  of  the 
humerus.  At  its  insertion  the  muscle  gives  off  an  expansion  to  the  deep  fascia  of 
the  arm.  This  muscle  is  remarkably  coarse  in  texture,  and  the  arrangement  of 
its  muscular  fibres  is  somewhat  peculiar ;  the  central  portion  of  the  muscle — that 
is  to  say,  the  part  arising  from  the  acromion  process — consists  of  oblique  fibres, 
which  arise  in  a  bipenniform  manner  from  the  sides  of  tendinous  intersections, 
generally  four  in  number,  which  are  attached  above  to  the  acromion  process  and 
pass  downward  parallel  to  one  another  in  the  substance  of  the  muscle.  The 
oblique  muscular  fibres  thus  formed  are  inserted  into  similar  tendinous  intersec- 
tions, generally  three  in  number,  which  pass  upward  from  the  insertion  of  the 
muscle  into  the  humerus  and  alternate  with  the  descending  septa.  The  portions 
of  the  muscle  which  arise  from  the  clavicle  and  spine  of  the  scapula  are  not 
arranged  in  this  manner,  but  pass  from  their  origin  above,  to  be  inserted  into  the 
margins  of  the  inferior  tendon. 

Relations. — By  its  superficial  surface,  with  the  integument,  the  superficial  and 
deep  fasciae,  Platysma,  and  supra-acromial  nerves.  Its  deep  surface  is  separated 
from  the  head  of  the  humerus  by  a  large  sacculated  synovial  bursa,  and  covers  the 
coracoid  process,  coraco-acromial  ligament,  Pectoralis  minor,  Coraco-brachialis, 
both  heads  of  the  Biceps,  the  tendon  of  the  Pectoralis  major,  the  insertions 
of  the  Supraspinatus,  Infraspinatus,  and  Teres  minor,  the  scapular  and 
external  heads  of  the  Triceps,  the  circumflex  vessels  and  nerve,  and  the  humerus. 
Its  anterior  border  is  separated  at  its  upper  part  from  the  Pectoralis  major  by 
a  cellular  interspace,  which  lodges  the  cephalic  vein  and  humeral  branch  of  the 
acromial  thoracic  artery :  lower  down  the  two  muscles  are  in  close  contact.  Its 
posterior  border  rests  on  the  Infraspinatus  and  Triceps  muscles. 

Nerves. — The  Deltoid  is  supplied  by  the  fifth  and  sixth  cervical  through  the 
circumflex  nerve. 

Actions. — The  Deltoid  raises  the  arm  directly  from  the  side,  so  as  to  bring  it 
at  right  angles  with  the  trunk.  Its  anterior  fibres,  assisted  by  the  Pectoralis 
major,  draw  the  arm  forward;  and  its  posterior  fibres,  aided  by  the  Teres  major 
and  Latissimus  dorsi,  draw  it  backward. 

Surgical  Anatomy. — The  Deltoid  is  very  liable  to  atrophy,  and  when  in  this  condition 
simulates  dislocation  of  the  shoulder-joint,  as  there  is  flattening  of  the  shoulder  and  apparent 
prominence  of  the  acromion  process ;  upon  examination,  however,  it  will  be  found  that  the 
relative  position  of  the  great  tuberosity  of  the  humerus  to  the  acromion  and  coracoid  process  is 
unchanged.  Atrophy  of  the  Deltoid  may  be  due  to  disuse  or  loss  of  trophic  influence,  either 
from  injury  to  the  circumflex  nerve  or  cord  lesions,  as  in  infantile  paralysis.  _ 

Dissection. — Divide  the  Deltoid  across,  near  its  upper  part,  by  an  incision  carried  along  the 
margin  of  the  clavicle,  the  acromion  process  and  spine  of  the  scapula,  and  reflect  it  downward, 
when  the  structures  under  cover  of  it  will  be  seen. 

4.  Anterior  Scapular  Region. 

Subscapulars. 

The  subscapular  fascia  is  a  thin  membrane  attached  to  the  entire  circumference 
of  the  subscapular  fossa,  and  affording  attachment  by  its  inner  surface  to  some  of 
the  fibres  of  the.  Subscapularis  muscle :  when  this  is  removed,  the  Subscapulars 
muscle  is  exposed. 

The  Subscapularis  (Fig.  230)  is  a  large  triangular  muscle  which  fills  up  the 
subscapular  fossa,  arising  from  its  internal  two-thirds,  with  the  exception  of  a 
narrow  margin  along  the  posterior  border,  and  the  surfaces  at  the  superior  and 
inferior  angles  which  afford  attachment  to  the  Serratus  magnus :  it  also  arises  from 


384  THE  MUSCLES  AND   FASCIAE. 

the  lower  two-thirds  of  the  groove  on  the  axillary  border  of  the  bone.  Some  fibres 
arise  from  tendinous  laminae,  which  intersect  the  muscle,  and  are  attached  to  ridges 
on  the  bone ;  and  others  from  an  aponeurosis,  which  separates  the  muscle  from  the 
Teres  major  and  the  long  head  of  the  Triceps.  The  fibres  pass  outward,  and, 
gradually  converging,  terminate  in  a  tendon,  which  is  inserted  into  the  lesser 
tuberosity  of  the  humerus.  Those  fibres  which  arise  from  the  axillary  border  of  the 
scapula  are  inserted  into  the  neck  of  the  humerus  to  the  extent  of  an  inch  below 
the  tuberosity.  The  tendon  of  the  muscle  is  in  close  contact  with  the  anterior  part 
of  the  capsular  ligament  of  the  shoulder-joint,  and  glides  over  a  large  bursa,  which 
separates  it  from  the  base  of  the  coracoid  process.  This  bursa  communicates  with 
the  cavity  of  the  joint  by  an  aperture  in  the  capsular  ligament. 

Relations. — Its  anterior  surface  forms  a  considerable  part  of  the  posterior  Avail 
of  the  axilla,  and  is  in  relation  with  the  Serratus  magnus,  Coraco-brachialis,  and 
Biceps,  the  axillary  vessels  and  brachial  plexus  of  nerves,  and  the  subscapular 
vessels  and  nerves.  By  its  posterior  surface,  with  the  scapula  and  the  capsular 
ligament  of  the  shoulder-joint.  Its  lower  border  is  contiguous  with  the  Teres 
major  and  Latissimus  dorsi. 

Nerves. — It  is  supplied  by  the  fifth  and  sixth  cervical  nerves  through  the  upper 
and  lower  subscapular  nerves. 

Actions. — The  Subscapularis  rotates  the  head  of  the  humerus  inward;  when 
the  arm  is  raised,  it  draws  the  humerus  forward  and  downward.  It  is  a  powerful 
defence  to  the  front  of  the  shoulder-joint,  preventing  displacement  of  the  head  of 
the  bone. 

5.  Posterior  Scapular  Reg-ion  (Fig.  232). 

Supraspinatus.  Teres  minor. 

Infraspinatus.  Teres  major. 

Dissection. — To  expose  these  muscles,  and  to  examine  their  mode  of  insertion  into  the 
humerus,  detach  the  Deltoid  and  Trapezius  from  their  attachment  to  the  spine  of  the  scapula 
and  acromion  process.  Remove  the  clavicle  by  dividing  the  ligaments  connecting  it  with  the 
coracoid  process,  and  separate  it  at  its  articulation  with  the  scapula :  divide  the  acromion  process 
near  its  root  with  a  saw.  The  fragments  being  removed,  the  tendons  of  the  posterior  Scapular 
muscles  will  be  fully  exposed,  and  can  be  examined.  A  block  should  be  placed  beneath  the 
shoulder-joint,  so  as  to  make  the  muscles  tense. 

The  Supraspinous  fascia  is  a  thick  and  dense  membranous  layer,  which  com- 
pletes the  osseo-fibrous  case  in  which  the  Supraspinatus  muscle  is  contained, 
aifording  attachment,  by  its  inner  surface,  to  some  of  the  fibres  of  the  muscle.  It 
is  thick  internally,  but  thinner  externally  under  the  coraco-acromial  ligament. 
When  this  fascia  is  removed,  the   Supraspinatus  muscle  is  exposed. 

The  Supraspinatus  muscle  occupies  the  whole  of  the  supraspinous  fossa,  arising 
from  its  internal  two-thirds  and  from  the  strong  fascia  which  covers  its  sur- 
face. The  muscular  fibres  converge  to  a  tendon  which  passes  across  the  upper 
part  of  the  capsular  ligament  of  the  shoulder-joint,  to  which  it  is  intimately 
adherent,  and  is  inserted  into  the  highest  of  the  three  facets  on  the  great 
tuberosity  of  the  humerus. 

Relations. — By  its  upper  surface,  with  the  Trapezius,  the  clavicle,  the  acromion, 
the  coraco-acromial  ligament,  and  the  Deltoid ;  by  its  under  surface,  with  the 
scapula,  the  suprascapular  vessels  and  nerve,  and  upper  part  of  the  shoulder-joint. 

The  Infraspinous  fascia  is  a  dense  fibrous  membrane,  covering  in  the  Infra- 
spinatus muscle  and  attached  to  the  circumference  of  the  infraspinous  fossa  ;  it 
affords  attachment,  by  its  inner  surface,  to  some  fibres  of  that  muscle.  At  the  point 
where  the  Infraspinatus  commences  to  be  cohered  by  the  Deltoid,  this  fascia  divides 
into  two  layers :  one   layer  passes  ove  deltoid  muscle,  helping  to  form  the 

Deltoid  fascia  already  described ;  the  othei  passes  beneath  the  Deltoid  to  the 
shoulder-joint. 

The  infraspinatus  is  a  thick,  triangula.  1e,  which  occupies  the  chief  part 

of  the  infraspinous  fossa,  arising  by  fleshy  fibres  from  its  internal  two-thirds,  and 


THE   POSTERIOR   SCAPULAR    REGION. 


385 


by  tendinous  fibres  from  the  ridges  on  its  surface :  it  also  arises  from  a  strong 
fascia  which  covers  it  externally,  and  separates  it  from  the  Teres  major  and  minor. 
The  fibres  converge  to  a  tendon  which  glides  over  the  external  border  of  the 
spine  of  the  scapula,  and,  passing. across  the  posterior  part  of  the  capsular  ligament 
of  the  shoulder-joint,  is  inserted  into  the  middle  facet  on  the  great  tuberosity  of 
the  humerus.  The  tendon  of  this  muscle  is  occasionally  separated  from  the  spine 
of  the  scapula  by  a  synovial  bursa  which  communicates  with  the  synovial  cavity 
of  the  shoulder-joint. 

Relations. — By  its  posterior  surface,  with  the  Deltoid,  the  Trapezius,  Latissimus 
dorsi,  and  the  integument ;  by  its  anterior  surface,  with  the  scapula,  from  which 


Pig.  232.— Muscles  on  the  dorsum  of  the  Scapula  and  the  Triceps. 

it  is  separated  by  the  suprascapular  and  dorsalis  scapulae  vessels,  and  with  the 
capsular  ligament  of  the  shoulder-joint.  Its  lower  border  is  in  contact  with  the 
Teres  minor,  occasionally  united  with  it,  and  with  the  Teres  major. 

The  Teres  minor  is  a  narrow,  elongated  muscle,  which  arises  from  the  dorsal  sur- 
face of  the  axillary  border  of  the  scapula  for  the  upper  two-thirds  of  its  extent, 
and  from  two  aponeurotic  laminae,  one  of  which  separates  this  muscle  from  the 
Infraspinatus,  the  other  from  the  Teres  major;  its  fibres  pass  obliquely  upward 
and  outward,  and  terminate  in  a  tendon  which  is  inserted  into  the  lowest  of  the 
three  facets  on  the  great  tuberosity  of  the  humerus,  and,  by  fleshy  fibres,  into  the 
humerus  immediately  below  it.  The  tendon  of  this  muscle  passes  across  the 
posterior  part  of  the  capsular  ligament  of  the  shoulder-joint. 

Relations. —  By  its  posterior  surface,  with  the  Deltoid  and  the  integument; 
by  its  anterior  surface,  with  the  scapula  and  dorsal  branch  of  the  subscapular 
artery,  the  long  head  of  the  Triceps,  and  the  shoulder-joint;  by  its  upper  border, 
with  the  Infraspinatus  ;  by  its  lower  border,  with  the  Teres  major,  from  which  it 
is  separated  anteriorly  by  the  long  head  of  the  Triceps. 

25 


386  THE  ES   AND   FASCIA. 

The  Teres  major  is  a  thic1    '  i  lewhat  flattened  muscle,  which  arises  from  the 

oval  surface  on  the  dorsal  aspe  he  inferior  angle  of  the  scapula,  and  from  the 

fibrous  septa  interposed  be1  and  the  Teres  minor  and  Infraspinatus ;  the 

fibres  are  directed  upward  and  outward,  and  terminate  in  a  flat  tendon,  about  two 
inches  in  length,  which  is  inserted  into  the  inner  bicipital  ridge  of  the  humerus. 
The  tendon  of  this  muscle,  a^t  its  insertion  into  the  humerus,  lies  behind  that  of  the 
Latissimus  dorsi,  from  which  it  is  separated  by  a  synovial  bursa,  the  two  tendons 
being,  however,  united  along  their  lower  borders  for  a  short  distance. 

Relations. — By  its  posterior  surface,  with  the  Latissimus  dorsi  below,  and  the 
long  head  of  the  Triceps  above.  By  its  anterior  surface,  with  the  Subscapularis, 
Latissimus  dorsi,  Coraco-brachialis,  short  head  of  the  Biceps,  the  axillary  vessels, 
and  brachial  plexus  of  nerves.  Its  upper  border  is  at  first  in  relation  with  the 
Teres  minor,  from  which  it  is  afterward  separated  by  the  long  head  of  the  Triceps. 
Its  lower  border  forms,  in  conjunction  with  the  Latissimus  dorsi,  part  of  the 
posterior  boundary  of  the  axilla.  The  Latissimus  dorsi  at  first  covers  the  origin 
of  the  Teres  major,  then  wraps  itself  obliquely  round  its  lower  border,  so  that  its 
tendon  ultimately  comes  to  lie  in  front  of  that  of  the  Teres  major. 

Nerves. — The  Supra-  and  Infra-spin atus  muscles  are  supplied  by  the  fifth  and 
sixth  cervical  nerves  through  the  suprascapular  nerve ;  the  Teres  minor,  by  the 
fifth  cervical,  through  the  circumflex;  and  the  Teres  major,  by  the  fifth  and  sixth 
cervical,  through  the  lower  subscapular. 

Actions. — The  Supraspinatus  assists  the  Deltoid  in  raising  the  arm  from  the 
side,  and  fixes  the  head  of  the  humerus  in  the  glenoid  cavity.  The  Infraspinatus 
and  Teres  minor  rotate  the  head  of  the  humerus  outward :  when  the  arm  is  raised,, 
they  assist  in  retaining  it  in  that  position  and  carrying  it  backward.  One  of  the 
most  important  uses  of  these  three  muscles  is  the  great  protection  they  afford  to 
the  shoulder-joint,  the  Supraspinatus  supporting  it  above,  and  preventing  displace- 
ment of  the  head  of  the  humerus  upward,  while  the  Infraspinatus  and  Teres  minor 
protect  it  behind,  and  prevent  dislocation  backward.  The  Teres  major  assists  the 
Latissimus  dorsi  in  drawing  the  humerus  downward  and  backward,  when  pre- 
viously raised,  and  rotating  it  inward ;  when  the  arm  is  fixed,  it  may  assist  the 
Pectoral  and  Latissimus  dorsi  muscles  in  drawing  the  trunk  forward. 

THE  ARM. 

6.  Anterior  Humeral  Region  (Fig.  230). 

Coraco-brachialis.  Biceps.  Brachialis  anticus. 

Dissection. — The  arm  being  placed  on  the  table,  with  the  front  surface  uppermost,  make 
a  vertical  incision  through  the  integument  along  the  middle  line,  from  the  outer  extremity  of 
the  anterior  fold  of  the  axilla  to  about  two  inches  below  the  elbow-joint,  where  it  should  be 
joined  by  a  transverse  incision,  extending  from  the  inner  to  the  outer  side  of  the  forearm  ;  the 
two  flaps  being  reflected  on  either  side,  the  fascia  should  be  examined  (Fig.  228). 

The  deep  fascia  of  the  arm  is  continuous  with  that  covering  the  Deltoid  and 
the  great  Pectoral  muscles,  by  means  of  which  it  is  attached,  above,  to  the 
clavicle,  acromion,  and  spine  of  the  scapula ;  it  forms  a  thin,  loose,  membranous 
sheath  investing  the  muscles  of  the  arm,  sending  down  septa  between  them,  and 
composed  of  fibres  disposed  in  a  circular  or  spiral  direction,  and  connected  together 
by  vertical  and  oblique  fibres.  It  differs  in  thickness  at  different  parts,  being  thin 
over  the  Biceps,  but  thicker  where  it  covers  the  Triceps,  and  over  the  condyles  of 
the  humerus  ;  it  is  strengthened  by  fibrous  aponeuroses,  derived  from  the  Pectoralis 
major  and  Latissimus  dorsi  on  the  inner  side,  and  from  the  Deltoid  externally. 
On  either  side  it  gives  off  a  strong  intermuscular  septum,  which  is  attached  to  the 
supracondylar  ridge  and  condyle  of  the  humerus.  These  septa  serve  to  separate  the 
muscles  of  the  anterior  from  those  of  the  posterior  brachial  region.  The  external 
intermuscular  septum  extends  from  the  lower  part  of  the  anterior  bicipital  ridge, 
along  the  external  supracondylar  ridge,  to  the  outer  condyle ;  it  is  blended  with  the 
tendon  of  the  Deltoid,  gives  attachment  to  the  Triceps  behind,  to  the  Brachialis 
anticus,   Supinator  longus,  and  Extensor  carpi  radialis  longior,  in  front,  and  is 


THE   ANTERIOR    HUMERAL    REGION.  387 

perforated  by  the  musculo-spiral  nerve  and  superior  profunda  artery.  The  internal 
intermuscular  septum,  thicker  than  the  preceding,  extends  from  the  lower  part  of  the 
posterior  lip  of  the  bicipital  groove  below  the  Teres  major,  along  the  internal  supra- 
condylar ridge  to  the  inner  condyle ;  it  is  blended  with  the  tendon  of  the  Coraco- 
brachialis,  and  affords  attachment  to  the  Triceps  behind,  and  the  Brachialis  anticus 
•  in  front.  It  is  perforated  by  the  ulnar  nerve  and  the  inferior  profunda  and  anasto- 
motic arteries.  At  the  elbow  the  deep  fascia  is  attached  to  all  the  prominent 
points  round  the  joint — viz.  the  condyles  of  the  humerus  and  the  olecranon  process 
of  the  ulna — and  is  continuous  with  the  deep  fascia  of  the  forearm.  Just  below  the 
middle  of  the  arm,  on  its  inner  side,  in  front  of  the  internal  intermuscular  septum, 
is  an  oval  opening  in  the  deep  fascia  which  transmits  the  basilic  vein  and  some 
lymphatic  vessels.  On  the  removal  of  this  fascia  the  muscles,  vessels,  and  nerves 
of  the  anterior  humeral  region  are  exposed. 

The  Coraco-brachialis,  the  smallest  of  the  three  muscles  in  this  region,  is  sit- 
uated at  the  upper  and  inner  part  of  the  arm.  It  arises  by  fleshy  fibres  from 
the  apex  of  the  coracoid  process,  in  common  with  the  short  head  of  the  Biceps, 
and  from  the  intermuscular  septum  between  the  two  muscles ;  the  fibres  pass 
downward,  backward,  and  a  little  outward,  to  be  inserted  by  means  of  a  flat  ten- 
don into  an  impression  at  the  middle  of  the  inner  surface  and  internal  border  of 
the  shaft  of  the  humerus  between  the  origins  of  the  Triceps  and  Brachialis 
anticus.  It  is  perforated  by  the  musculo-cutaneous  nerve.  The  inner  border  of 
the  muscle  forms  a  guide  to  the  position  of  the  brachial  artery  in  tying  the  vessel 
in  the  upper  part  of  its  course. 

Relations. — By  its  anterior  surface,  with  the  Pectoralis  major  above,  and  at 
its  insertion  with  the  brachial  vessels  and  median  nerve  which  cross  it ;  by  its 
posterior  surface,  with  the  tendons  of  the  Subscapulars,  Latissimus  dorsi,  and 
Teres  major,  the  inner  head  of  the  Triceps,  the  humerus,  and  the  anterior  circum- 
flex vessels ;  by  its  inner  border,  with  the  brachial  artery,  and  the  median  and 
musculo-cutaneous  nerves ;  by  its  outer  border,  with  the  short  head  of  the  Biceps 
and  Brachialis  anticus. 

The  Biceps  (Biceps  flexor  cubiti)  is  a  long  fusiform  muscle,  occuping  the  whole 
of  the  anterior  surface  of  the  arm,  and  divided  above  into  two  portions  or  heads, 
from  which  circumstance  it  has  received  its  name.  The  short  head  arises  by  a 
thick  flattened  tendon  from  the  apex  of  the  coracoid  process,  in  common  with  the 
Coraco-brachialis.  The  long  head  arises  from  the  upper  margin  of  the  glenoid 
cavity,  and  is  continuous  with  the  glenoid  ligament.  This  tendon  arches  over 
the  head  of  the  humerus,  being  enclosed  in  a  special  sheath  of  the  synovial  mem- 
brane of  the  shoulder-joint;  it  then  passes  through  an  opening  in  the  capsular 
ligament  at  its  attachment  to  the  humerus,  and  descends  in  the  bicipital  groove, 
in  which  it  is  retained  by  a  fibrous  prolongation  from  the  tendon  of  the  Pectoralis 
major.  Each  tendon  is  succeeded  by  an  elongated  muscular  belly,  and  the  two 
bellies,  although  closely  applied  to  each  other,  can  readily  be  separated  until 
within  about  three  inches  of  the  elbow-joint.  Here  they  end  in  a  flattened  ten- 
don, which  is  inserted  into  the  back  part  of  the  tuberosity  of  the  radius,  a 
synovial  bursa  being  interposed  between  the  tendon  and  the  front  of  the  tuber- 
osity. As  the  tendon  of  the  muscle  approaches  the  radius  it  becomes  twisted 
upon  itself,  so  that  its  anterior  surface  becomes  external  and  is  applied  to  the 
tuberosity  of  the  radius  at  its  insertion:  opposite  the  bend  of  the  elbow  the  ten- 
don gives  off,  from  its  inner  side,  a  broad  aponeurosis,  the  bicipital  fascia  (semi- 
lunar fascia),  which  passes  obliquely  downward  and  inward  across  the  brachial 
artery,  and  is  continuous  with  the  deep  fascia  of  the  forearm  (Fig.  229).  The 
inner  border  of  this  muscle  forms  a  guide  to  the  position  of  the  vessel  in  tying 
the  brachial  artery  in  the  middle  of  the  arm.1 

1 A  third  head  to  the  Biceps  is  occasionally  found  (Theile  says  as  often  as  once  in  eight  or  nine 
subjects),  arising  at  the  upper  and  inner  part  of  the  Brachialis  anticus,  with  the  fibres  of  which  it 
is  continuous,  and  inserted  into  the  bicipital  fascia  and  inner  side  of  the  tendon  of  the  Biceps.  In 
most  cases  this  additional  slip  passes  behind  the  brachial  artery  in  its  course  down  the  arm.  Occa- 
sionally the  third  head  consists  of  two  slips  which  pass  down,  one  in  front,  the  other  behind  the  artery, 
concealing  the  vessel  in  the  lower  half  of  the  arm. 


388  THE  MUSCLES  AND   FASCIJE. 

Relations. — Its  anterior  surface  is  overlapped  above  by  the  Pectoralis  major 
and  Deltoid ;  in  the  rest  of  its  extent  it  is  covered  by  the  superficial  and  deep 
fasciae  and  the  integument.  Its  posterior  surface  rests  above  on  the  shoulder- 
joint  and  upper  part  of  the  humerus;  below  it  rests  on  the  Brachialis  anticus, 
with  the  musculo-cutaneous  nerve  intervening  between  the  two,  and  on  the 
Supinator  brevis.  Its  inner  border  is  in  relation  with  the  Coraco-brachialis,  and 
overlaps  the  brachial  vessels  and  median  nerve ;  its  outer  border,  with  the  Deltoid 
and  Supinator  longus. 

The  Brachialis  anticus  is  a  broad  muscle,  which  covers  the  elbow-joint  and 
the  lower  half  of  the  front  of  the  humerus.  It  is  somewhat  compressed  from 
before  backward,  and  is  broader  in  the  middle  than  at  either  extremity.  It  arises 
from  the  lower  half  of  the  outer  and  inner  surfaces  of  the  shaft  of  the  humerus, 
and  commences  above  at  the  insertion  of  the  Deltoid,  which  it  embraces  by  two 
angular  processes.  Its  origin  extends  below,  to  within  an  inch  of  the  margin  of 
the  articular  surface,  and  is  limited  on  each  side  by  the  external  and  internal 
borders  of  the  shaft  of  the  humerus.  It  also  arises  from  the  intermuscular  septa 
on  each  side,  but  more  extensively  from  the  inner  than  the  outer,  from  which  it  is 
separated  below  by  the  Supinator  longus  and  Extensor  carpi  radialis  longior.  Its 
fibres  converge  to  a  thick  tendon,  which  is  inserted  into  a  rough  depression  on  the 
anterior  surface  of  the  coronoid  process  of  the  ulna,  being  received  into  an  inter- 
val between  two  fleshy  slips  of  the  Flexor  profundus  digitorum. 

Relations. — By  its  anterior  surface,  with  the  Biceps,  the  brachial  vessels, 
musculo-cutaneous,  and  median  nerves;  by  its, posterior  surface,  with  the  humerus 
and  front  of  the  elbow-joint;  by  its  inner  border,  with  the  Triceps,  ulnar  nerve, 
and  Pronator  radii  teres,  from  which  it  is  separated  by  the  intermuscular  septum; 
by  its  outer  border,  with  the  musculo-spiral  nerve,  radial  recurrent  artery,  the 
Supinator  longus,  and  Extensor  carpi  radialis  longior. 

Nerves. — The  muscles  of  this  group  are  supplied  by  the  musculo-cutaneous 
nerve.  The  Brachialis  anticus  usually  receives  an  additional  filament  from  the 
musculo-spiral.  The  Coraco-brachialis  receives  its  supply  primarily  from  the 
seventh  cervical,  the  Biceps  and  Brachialis  anticus  from  the  fifth  and  sixth 
cervical  nerves. 

Actions. — The  Coraco-brachialis  draws  the  humerus  forward  and  inward,  and 
at  the  same  time  assists  in  elevating  it  toward  the  scapula.  The  Biceps  is  a 
flexor  of  the  forearm ;  it  is  also  a  powerful  supinator,  and  serves  to  render  tense 
the  deep  fascia  of  the  forearm  by  means  of  the  broad  aponeurosis  given  off  from 
its  tendon.  The  Brachialis  anticus  is  a  flexor  of  the  forearm,  and  forms  an 
important  defence  to  the  elbow-joint.  When  the  forearm  is  fixed,  the  Biceps 
and  Brachialis  anticus  flex  the  arm  upon  the  forearm,  as  is  seen  in  efforts  of 
climbing. 

7.  Posterior  Humeral  Region. 

Triceps.  Subanconeus. 

The  Triceps  (Triceps  extensor  cubiti)  (Fig.  232)  is  situated  on  the  back  of  the 
arm,  extending  the  entire  length  of  the  posterior  surface  of  the  humerus.  It  is  of 
large  size,  and  divided  above  into  three  parts ;  hence  its  name.  These  three 
portions  have  been  named  (1)  the  middle,  scapular,  or  long  head ;  (2)  the  external, 
or  long  humeral ;  and  (3)  the  internal,  or  short  humeral  head. 

The  middle  or  scapular  head  arises,  by  a  flattened  tendon,  from  a  rough 
triangular  depression  on  the  scapula,  immediately  below  the  glenoid  cavity,  being 
blended  at  its  upper  part  with  the  capsular  ligament ;  the  muscular  fibres  pass 
downward  between  the  two  other  portions  of  the  muscle,  and  join  with  them  in 
the  common  tendon  of  insertion. 

The  external  head  arises  from  the  posterior  surface  of  the  shaft  of  the  humerus, 
between  the  insertion  of  the  Teres  minor  and  the  upper  part  of  the  musculo-spiral 
groove ;  from  the  external  border  of  the  humerus  and  the  external  intermuscular 


THE   POSTERIOR    HUMERAL    REGION.  389 

septtim:  the  fibres  from  this  origin  converge  toward  the  common  tendon  of 
insertion. 

The  internal  head  arises  from  the  posterior  surface  of  the  shaft  of  the  humerus, 
below  the  groove  for  the  musculo-spiral  nerve;  commencing  above,  narrow  and 
pointed,  below  the  insertion  of  the  Teres  major,  and  extending  to  within  an  inch 
of  the  trochlear  surface :  it  also  arises  from  the  internal  border  of  the  humerus, 
and  from  the  back  of  the  whole  length  of  the  internal  and  lower  part  of  the 
external  intermuscular  septa.  The  fibres  of  this  portion  of  the  muscle  are 
directed,  some  downward  to  the  olecranon,  whilst  others  converge  to  the  common 
tendon  of  insertion. 

The  common  tendon  of  the  Triceps  commences  about  the  middle  of  the  back  part 
of  the  muscle  :  it  consists  of  two  aponeurotic  laminae,  one  of  which  is  subcutaneous 
and  covers  the  posterior  surface  of  the  muscle  for  the  lower  half  of  its  extent ;  the 
other  is  more  deeply  seated  in  the  substance  of  the  muscle  :  after  receiving  the 
attachment  of  the  muscular  fibres,  they  join  together  above  the  elbow,  and  are 
inserted,  for  the  most  part,  into  the  back  part  of  the  upper  surface  of  the  olecranon 
process  ;  a  band  of  fibres  is,  however,  continued  downward,  on  the  outer  side, 
over  the  Anconeus,  to  blend  with  the  deep  fascia  of  the  forearm.  A  small  bursa, 
occasionally  multilocular,  is  situated  on  the  front  part  of  this  surface,  beneath  the 
tendon. 

The  long  head  of  the  Triceps  descends  between  the  Teres  minor  and  Teres 
major,  dividing  the  triangular  space  between  these  two  muscles  and  the  humerus 
into  two  smaller  spaces,  one  triangular,  the  other  quadrangular  (Fig.  232).  The 
triangular  space  contains  the  dorsalis  scapulae  vessels ;  it  is  bounded  by  the  Teres 
minor  above,  the  Teres  major  below,  and  the  scapular  head  of  the  Triceps 
externally :  the  quadrangular  space  transmits  the  posterior  circumflex  vessels 
and  the  circumflex  nerve ;  it  is  bounded  by  the  Teres  minor  above,  the  Teres 
major  below,  the  scapular  head  of  the  Triceps  internally,  and  the  humerus  exter- 
nally. 

Relations. — By  its  -posterior  surface,  with  the  Deltoid  above :  in  the  rest  of  its 
extent  it  is  subcutaneous ;  by  its  anterior  surface,  with  the  humerus,  musculo- 
spiral  nerve,  superior  profunda  vessels,  and  back  part  of  the  elbow-joint.  Its 
middle  or  long  head  is  in  relation,  behind,  with  the  Deltoid  and  Teres  minor ;  in 
front,   with  the  Subscapulars,   Latissimus  dorsi,  and  Teres  major. 

The  Subanconeus  is  a  name  given  to  a  few  fibres  from  the  under  surface  of  the 
lower  part  of  the  Triceps  muscle,  which  are  inserted  into  the  posterior  ligament 
of  the  elbow-joint.  By  some  authors  it  is  regarded  as  the  analogue  of  the  Sub- 
crureus  in  the  lower  limb,  but  it  is  not  a  separate  muscle. 

Nerves. — The  Triceps  is  supplied  by  the  seventh  and  eighth  cervical  nerves 
through  the  musculo-spiral  nerve. 

Actions. — The  Triceps  is  the  great  extensor  muscle  of  the  forearm,  serving, 
when  the  forearm  is  flexed,  to  extend  the  elbow-joint.  It  is  the  direct  antagonist 
of  the  Biceps  and  Brachialis  anticus.  When  the  arm  is  extended  the  long  head 
of  the  muscle  may  assist  the  Teres  major  and  Latissimus  dorsi  in  drawing  the 
humerus  backward  and  in  adducting  it  to  the  thorax.  The  long  head  of  the 
Triceps  protects  the  under  part  of  the  shoulder-joint,  and  prevents  displacement 
of  the  head  of  the  humerus  downward  and  backward.  The  Subanconeus  draws 
up  the  posterior  ligament  during  extension  of  the  forearm. 

Surgical  Anatomy. — The  existence  of  the  band  of  fibres  from  the  Triceps  to  the  fascia  of 
the  forearm  is  of  importance  in  excision  of  the  elbow,  and  should  always  be  carefully  preserved 
from  injury  by  the  operator,  as  by  means  of  these  fibres  the  patient  is  enabled  to  extend  the 
forearm,  a  movement  which  would  otherwise  mainly  be  accomplished  by  gravity ;  that  is  to  say. 
allowing  the  forearm  to  drop  from  its  own  weight. 

III.  MUSCLES  AND  FASCLE  OF  THE  FOREARM. 

Dissection.— To  dissect  the  forearm,  place  the  limb  in  the  position  indicated  in  Fig.  228 ; 
make  a  vertical  incision  along  the  middle  line  from  the  elbow  to  the  wrist,  and  a  transverse 
incision  at  the  extremity  of  this ;  the  superficial  structures  being  removed,  the  deep  fascia  of 
the  forearm  is  exposed. 


390  THE   MUSCLES   AND    FASCIA. 

The  deep  fascia  of  the  forearm,  continuous  above  with  that  enclosing  the  arm, 
is  a  dense,  highly  glistening  aponeurotic  investment,  which  forms  a  general  sheath 
enclosing  the  muscles  in  this  region  ;  it  is  attached,  behind,  to  the  olecranon  and 
posterior  border  of  the  ulna,  and  gives  off  from  its  inner  surface  numerous  inter- 
muscular septa,  which  enclose  each  muscle  separately.  Below,  it  is  continuous  in 
front  with  the  anterior  annular  ligament,  and  forms  a  sheath  for  the  tendon  of  the 
Palmaris  longus  muscle,  which  passes  over  the  annular  ligament  to  be  inserted 
into  the  palmar  fascia.  Behind,  near  the  wrist-joint,  it  becomes  much  thickened 
by  the  addition  of  many  transverse  fibres,  and  forms  the  posterior  annular  liga- 
ment. It  consists  of  circular  and  oblique  fibres,  connected  together  by  numerous 
vertical  fibres.  It  is  much  thicker  on  the  dorsal  than  on  the  palmar  surface,  and 
at  the  lower  than  at  the  upper  part  of  the  forearm,  and  is  strengthened  above  by 
tendinous  fibres  derived  from  the  Brachialis  anticus  and  Biceps  in  front,  and  from 
the  Triceps  behind.  Its  deep  surface  gives  origin  to  muscular  fibres,  especially 
at  the  upper  part  of  the  inner  and  outer  sides  of  the  forearm,  and  forms  the 
boundaries  of  a  series  of  conical-shaped  cavities,  in  which  the  muscles  are 
contained.  Besides  the  vertical  septa  separating  each  muscle,  transverse  septa  are 
given  off  both  on  the  anterior  and  posterior  surfaces  of  the  forearm,  separating  the 
deep  from  the  superficial  layer  of  muscles.  Numerous  apertures  exist  in  the  fascia 
for  the  passage  of  vessels  and  nerves ;  one  of  these,  of  large  size,  situated  at  the 
front  of  the  elbow,  serves  for  the  passage  of  a  communicating  branch  between  the 
superficial  and  deep  veins. 

The  muscles  of  the  forearm  may  be  subdivided  into  groups  corresponding  to 
the  region  they  occupy.  One  group  occupies  the  inner  and  anterior  aspect  of  the 
forearm,  and  comprises  the  Flexor  and  Pronator  muscles.  Another  group  occupies 
its  outer  side,  and  a  third  its  posterior  aspect.  The  two  latter  groups  include  all 
the  Extensor  and  Supinator  muscles. 

8.  Anterior  Radio-ulnar  Region. 

The  muscles  in  this  region  are  divided  for  convenience  of  description  into  two 
groups  or  layers,  superficial  and  deep. 

Superficial  Layer. 

Pronator  radii  teres.  Flexor  carpi  ulnaris. 

Flexor  carpi  radialis.  Flexor  sublimis  digitorum. 

Palmaris  longus. 

These  muscles  take  origin  from  the  internal  condyle  of  the  humerus  by  a 
common   tendon. 

The  Pronator  radii  teres  arises  by  two  heads.  One,  the  larger  and  more 
superficial,  arises  from  the  humerus,  immediately  above  the  internal  condyle,  and 
from  the  tendon  common  to  the  origin  of  the  other  muscles  ;  also  from  the  fascia 
of  the  forearm  and  intermuscular  septum  between  it  and  the  Flexor  carpi  radialis. 
The  other  head  is  a  thin  fasciculus  which  arises  from  the  inner  side  of  the 
coronoid  process  of  the  ulna,  joining  the  preceding  at  an  acute  angle.  Between 
the  two  heads  the  median  nerve  enters  the  forearm.  The  muscle  passes  obliquely 
across  the  forearm  from  the  inner  to  the  outer  side,  and  terminates  in  a  flat  tendon, 
which  turns  over  the  outer  margin  of  the  radius,  and  is  inserted  into  a  rough  im- 
pression at  the  middle  of  the  outer  surface  of  the  shaft  of  that  bone. 

Relations. — By  its  anterior  surface,  throughout  the  greater  part  of  its  extent, 
with  the  deep  fascia ;  at  its  insertion  it  is  crossed  by  the  radial  vessels  and  nerve, 
and  covered  by  the  Supinator  longus  ;  by  its  posterior  surface,  with  the  Brachialis 
anticus,  Flexor  sublimis  digitorum,  the  median  nerve,  and  ulnar  artery,  the  small 
or  deep  head  being  interposed  between  the  two  latter  structures.  Its  outer  border 
forms  the  inner  boundary  of  a  triangular  space  in  which  are  placed  the  brachial 
artery,  median  nerve,  and  tendon  of  the  Biceps  muscle.  ^Jts  inner  border  is  in 
contact  with  the  Flexor  carpi  radialis. 


THE  FOREARM. 


391 


Surgical  Anatomy. — This  muscle,  when  suddenly  brought  into  very  active  use,  as  in  the 
game  of  lawn  tennis,  is  apt  to  be  strained,  producing  slight  swelling,  tenderness,  and  pain  on 
putting  the  muscle  into  action.     This  is  known  as  "lawn-tennis  arm." 

The  Flexor  carpi  radialis  lies  on  the  inner  side  of  the  preceding  muscle.  It 
arises  from  the  internal  condyle  by  the  common  tendon,  from  the  fascia  of  the  fore- 
arm, and  from  the  intermuscular  septa  between  it  and  the  Pronator  radii  teres,  on 
the  outside,  the  Palmaris  longus  internally,  and  the  Flexor  sublimis  cligitorum 
beneath.  Slender  and  aponeurotic  in  structure  at  its  commencement,  it  increases 
in  size,  and  terminates  in  a  tendon  which  forms 
rather  more  than  the  lower  half  of  its  length. 
This  tendon  passes  through  a  canal  on  the  outer 
side  of  the  annular  ligament,  runs  through  a 
groove  in  the  os  trapezium  (which  is  converted 
into  a  canal  by  a  fibrous  sheath,  and  lined  by  a 
synovial  membrane),  and  is  inserted  into  the  base./ 
of  the  metacarpal  bone  of  the  index  finger,  and 
by  a  slip  into  the  base  of  the  metacarpal  bone  of 
the  middle  finger.  The  radial  artery  lies  between 
the  tendon  of  this  muscle  and  the  Supinator 
longus,  and  may  easily  be  tied  in  this  situation. 

Relations. — By  its  superficial  surface,  with 
the  deep  fascia  and  the  integument ;  by  its  deep 
surface,  with  the  Flexor  sublimis  digitorum, 
Flexor  longus  pollicis,  and  wrist-joint;  by  its 
outer  border,  with  the  Pronator  radii  teres  and 
the  radial  vessels ;  by  its  inner  border,  with  the 
palmaris  longus  above  and  the  median  nerve  below. 

The  Palmaris  longus  is  a  slender,  fusiform 
muscle  lying  on  the  inner  side  of  the  pre- 
ceding. It  arises  from  the  inner  condyle  of  the 
humerus  by  the  common  tendon,  from  the  deep 
fascia,  and  the  intermuscular  septa  between  it  and 
the  adjacent  muscles.  It  terminates  in  a  slender 
flattened  tendon,  which  passes  over  the  upper  part 
of  the  annular  ligament,  to  end  in  the  central  part 
of  the  palmar  fascia  and  lower  part  of  the  annu- 
lar ligament,  frequently  sending  a  tendinous  slip 
to  the  short  muscles  of  the  thumb.  This  muscle 
is  often  absent,  and  is  subject  to  very  considerable 
variations :  it  may  be  tendinous  above  and  muscu- 
lar below  ;  or  it  may  be  muscular  in  the  centre,  with 
a  tendon  above  and  below  ;  or  it  may  present  two 
muscular  bundles  with  a  central  tendon  ;  or  finally 
it  may  consist  simply  of  a  mere  tendinous  band. 

Relations. — By  its  superficial  surface,  wTith  the 
deep  fascia.  By  its  deep  surface,  with  the  Flexor 
sublimis  digitorum.  Internally,  with  the  Flexor 
carpi  ulnaris.  Externally,  with  the  Flexor  carpi 
radialis.  The  median  nerve  lies  close  to  the  tendon, 
just  above  the  wrist,  on  its  inner  and  posterior  side. 

The  Flexor  carpi  ulnaris  lies  along  the  ulnar 
side  of  the  forearm.  It  arises  by  two  heads,  con- 
nected by  a  tendinous  arch,  beneath  which  pass 
the  ulnar  nerve  and  posterior  ulnar  recurrent 
artery.  One  head  arises  from  the  inner  condyle  of  the  humerus  by  the  com- 
mon tendon  ;  the  other  from  the  inner  margin  of  the  olecranon  and  from  the 
upper  two-thirds  of  the  posterior  border  of  the  ulna  by  an  aponeurosis,  common 


Fig.  233  —Front  of  the  left  forearm. 
Superficial  muscles. 


392  THE   MUSCLES  AND    FASCIJE. 

to  it  and  the  Extensor  carpi  ulnaris  and  Flexor  profundus  digitorum ;  and  from 
the  intermuscular  septum  between  it  and  the  Flexor  sublimis  digitorum.  The 
fibres  terminate  in  a  tendon  which  occupies  the  anterior  part  of  the  lower  half  of 
the  muscle,  and  is  inserted  into  the  pisiform  bone,  and  is  prolonged  from  this  to 
the  fifth  metacarpal  and  unciform  bones,  by  the  piso-metacarpal  and  piso-uncinate 
ligaments  :  it  is  also  attached  by  a  few  fibres  to  the  annular  ligament.  The  ulnar 
artery  lies  on  the  outer  side  of  the  tendon  of  this  muscle,  in  the  lower,  two-thirds  of 
the  forearm,  the  tendon  forming  a  guide  in  tying  the  vessel  in  this  situation. 

Relations. — By  its  superficial  surface,  with  the  deep  fascia,  with  which  it  is 
intimately  connected  for  a  considerable  extent ;  by  its  deep  surface,  with  the  Flexor 
sublimis  digitorum,  the  Flexor  profundus  digitorum,  the  Pronator  quadratus,  and 
the  ulnar  vessels  and  nerve ;  by  its  outer  or  radial  border,  with  the  Palmaris 
longus  above  and  the  ulnar  vessels  and  nerve  below. 

The  Flexor  sublimis  digitorum  (perforatus)  is  placed  beneath  the  preceding 
muscles,  which  therefore  must  be  removed  in  order  to  bring  its  attachment  into 
view.  It  is  the  largest  of  the  muscles  of  the  superficial  layer,  and  arises  by  three 
heads.  One  head  arises  from  the  internal  condyle  of  the  humerus  by  the  common 
tendon,  from  the  internal  lateral  ligament  of  the  elbow-joint,  and  from  the  inter- 
muscular septum  common  to  it  and  the  preceding  muscles.  The  second  head  arises 
from  the  inner  side  of  the  coronoid  process  of  the  ulna,  above  the  ulnar  origin  of 
the  Pronator  radii  teres  (Fig.  100,  p.  151).  The  third  head  arises  from  the  oblique 
line  of  the  radius,  extending  from  the  tubercle  to  the  insertion  of  the  Pronator 
radii  teres.  The  fibres  pass  vertically  downward,  forming  a  broad  and  thick  muscle, 
which  speedily  divides  into  two  planes  of  muscular  fibres,  superficial  and  deep :  the 
superficial  plane  divides  into  two  parts  which  end  in  tendons  for  the  middle  and 
ring  fingers ;  the  deep  plane  also  divides  into  two  parts,  which  end  in  tendons  for 
the  index  and  little  fingers,  but  previously  to  having  done  so,  it  gives  oiF  a  mus- 
cular slip,  which  joins  that  part  of  the  superficial  plane  which  is  intended  for  the 
ring  finger.  As  the  four  tendons  thus  formed  pass  beneath  the  annular  ligament 
into  the  palm  of  the  hand,  they  are  arranged  in  pairs,  the  superficial  pair  corres- 
ponding to  the  middle  and  ring  fingers,  the  deep  pair  to  the  index  and  little  fingers. 
The  tendons  diverge  from  one  another  as  they  pass  onward.  Opposite  the  bases  of 
the  first  phalanges  each  tendon  divides  into  two  slips,  to  allow  of  the  passage  of 
the  corresponding  tendon  of  the  Flexor  profundus  digitorum  ;  the  two  portions  of 
the  tendon  then  unite  and  form  a  grooved  channel  for  the  reception  of  the  accom- 
panying deep  flexor  tendon.  Finally  they  subdivide  a  second  time,  to  be  inserted 
into  the  sides  of  the  second  phalanges  about  their  middle.  After  leaving  the  palm, 
these  tendons,  accompanied  by  the  deep  flexor  tendons,  lie  in  osseo-aponeurotic 
canals  (Fig.  234).  These  canals  are  formed  by  strong  fibrous  bands,  which  arch 
across  the  tendons,  and  are  attached  on  each  side  to  the  margins  of  the  phalanges. 
Opposite  the  middle  of  the  proximal  and  second  phalanges  the  sheath  is  very 
strong,  and  the  fibres  pass  transversely  ;  but  opposite  the  joints  it  is  much  thinner, 
and  the  fibres  pass  obliquely.  Each  sheath  is  lined  by  a  synovial  membrane, 
which  is  reflected  on  the  contained  tendons. 

Relations. — In  the  forearm,  by  its  superficial  surface,  with  the  deep  fascia  and 
all  the  preceding  superficial  muscles ;  by  its  deep  surface,  with  the  Flexor  profundus 
digitorum,  Flexor  longus  pollicis,  the  ulnar  vessels  and  nerve,  and  the  median 
nerve.  In  the  hand  its  tendons  are  in  relation,  in  front,  with  the  palmar  fascia, 
superficial  palmar  arch,  and  the  branches  of  the  median  nerve ;  behind,  with  the 
tendons  of  the  deep  Flexor  and  the  Lumbricales. 

Deep  Layer. 

Flexor  profundus  digitorum.  Flexor  longus  pollicis. 

Pronator  quadratus. 

Dissection. — Divide  each  of  the  superficial  muscles  at  its  centre,  and  turn  either  end  aside; 
the  deep  layer  of  muscles,  together  with  the  median  nerve  and  ulnar  vessels,  will  then  be 
exposed. 


THE   ANTERIOR    BRACHIAL    REGION. 


393 


The  Fler.or  profundus  digitorum 
(perforans)  (Fig.  234)  is  situated  on 
the  ulnar  side  of  the  forearm,  im- 
mediately beneath  the  superficial 
Flexors.  It  arises  from  the  upper 
three-fourths  of  the  anterior  and 
inner  surfaces  of  the  shaft  of  the 
ulna,  embracing  the  insertion  of  the 
Brachialis  anticus  above,  and  extend- 
ing, below,  to  within  a  short  distance 
of  the  Pronator  quadratus.  It  also 
arises  from  a  depression  on  the  inner 
side  of  the  coronoid  process ;  by  an 
aponeurosis  from  the  upper  three- 
fourths  of  the  posterior  border  of  the 
ulna,  in  common  with  the  Flexor  and 
Extensor  carpi  ulnaris;  and  from  the 
ulnar  half  of  the  interosseous  mem- 
brane. The  fibres  form  a  fleshy  belly 
of  considerable  size,  which  divides 
into  four  tendons :  these  pass  under 
the  annular  ligament  beneath  the 
tendons  of  the  Flexor  sublimis  digi- 
torum. Opposite  the  first  phalanges 
the  tendons  pass  through  the  openings 
in  the  two  slips  of  the  tendons  of  the 
Flexor  sublimis  digitorum,  and  are 
finally  inserted  into  the  bases  of  the 
last  phalanges.  The  portion  of  the 
muscle  for  the  index  finger  is  usually 
distinct  throughout,  but  the  tendons 
for  the  three  inner  fingers  are  con- 
nected together  by  cellular  tissue  and 
tendinous  slips  as  far  as  the  palm  of 
the  hand.  The  tendons  of  this  muscle 
and  those  of  the  Flexor  sublimis  digi- 
torum, whilst  contained  in  the  osseo- 
aponeurotic  canals  of  the  fingers,  are 
invested  in  a  synovial  sheath,  and  are 
connected  to  each  other  and  to  the 
phalanges  by  slender  tendinous  fila- 
ments, called  vincula  accessoria  ten- 
dinwn.  One  of  these  connects  the 
deep  tendon  to  the  bone  before  it 
passes  through  the  superficial  tendon  ; 
a  second  connects  the  two  tendons 
together,  after  the  deep  tendons  have 
passed  through  ;  and  a  third  connects 
the  deep  tendon  to  the  head  of  the 
second  phalanx.  This  last  consists 
largely  of  yellow  elastic  tissue,  and 
may  assist  in  drawing  down  the  ten- 
don after  flexion  of  the  finger.1 

Four  small  muscles,  the  Lumbri- 
cales,  are  conn  acted  with  the  tendons 
of  the  Flexor  profundus  in  the  palm. 
They  will  be  described  with  the  mus- 
cles in  that  region. 


Fig.  234.— Front  of  the  left  forearm.    Deep  muscles. 
1  Marshall,  Brit,  a, id  For.  Med.-Chir.  Rev.,  1853. 


394  THE   MUSCLES  AND    FASCIjE. 

Relations. — By  its  superficial  surface,  in  the  forearm,  with  the  Flexor  sublimis 
dioitorum,  the  Flexor  carpi  ulnaris,  the  ulnar  vessels  and  nerve,  and  the  median 
nerve;  and  in  the  hand,  with  the  tendons  of  the  superficial  Flexor;  by  its  deep 
surface,  in  the  forearm,  with  the  ulna,  the  interosseous  membrane,  the  Pronator 
quadratus ;  and  in  the  hand,  with  the  interossei,  Adductor  pollicis,  and  deep 
palmar  arch  ;  by  its  ulnar  border,  with  the  Flexor  carpi  ulnaris  ;  by  its  radial 
border,  with  the  Flexor  longus  pollicis,  the  anterior  interosseous  vessels  and  nerve 
being  interposed. 

The  Flexor  longus  pollicis  is  situated  on  the  radial  side  of  the  forearm,  lying 
on  the  same  plane  as  the  preceding.  It  arises  from  the  grooved  anterior  surface 
of  the  shaft  of  the  radius,  commencing  above,  immediately  below  the  tuberosity 
and  oblique  line,  and  extending  below  to  within  a  short  distance  of  the  Pronator 
quadratus.  It  also  arises  from  the  adjacent  part  of  the  interosseous  membrane, 
and  generally  by  a  fleshy  slip  from  the  inner  border  of  the  coronoid  process  or  from 
the  internal  condyle  of  the  humerus.  The  fibres  pass  downward,  and  terminate  in 
a  flattened  tendon  which  passes  beneath  the  annular  ligament,  is  then  lodged 
in  the  interspace  between  the  outer  head  of  the  Flexor  brevis  pollicis  and  the 
Adductor  obliquus  pollicis,  and,  entering  an  osseo-aponeurotic  canal  similar  to 
those  for  the  other  flexor  tendons,  is  inserted  into  the  base  of  the  last  phalanx 
of  the  thumb. 

Relations. — By  its  superficial  surface,  with  the  Flexor  sublimis  digitorum, 
Flexor  carpi  radialis,  Supinator  longus,  and  radial  vessels  ;  by  its  deep  surface, 
with  the  radius,  interosseous  membrane,  and  Pronator  quadratus ;  by  its  ulnar 
border,  with  the  Flexor  profundus  digitorum,  from  which  it  is  separated  by  the 
anterior  interosseous  vessels  and  nerve. 

The  Pronator  quadratus  is  a  small,  flat,  quadrilateral  muscle,  extending  trans- 
versely across  the  front  of  the  radius  and  ulna,  above  their  carpal  extremities.  It 
arises  from  the  oblique  or  pronator  ridge  on  the  lower  part  of  the  anterior  surface 
of  the  shaft  of  the  ulna ;  from  the  lower  fourth  of  the  anterior  surface  and  the 
anterior  border  of  the  ulna ;  and  from  a  strong  aponeurosis  which  covers  the  inner 
third  of  the  muscle.  The  fibres  pass  outward  and  slightly  downward,  to  be 
inserted  into  the  lower  fourth  of  the  anterior  surface  and  anterior  border  of  the 
shaft  of  the  radius. 

Relations. — By  its  superficial  surface,  with  the  Flexor  profundus  digitorum, 
the  Flexor  longus  pollicis,  Flexor  carpi  radialis,  and  the  radial  ssels;  by  its 
deep  surface,  with  the  radius,  ulna,  and  interosseous  membrane. 

Nerves. — All  the  muscles  of  the  superficial  layer  are  sup  the  median 

nerve,  excepting  the  Flexor  carpi  ulnaris,  which  is  supplied  ulnar.      The 

Pronator  radii  teres  and  the  Flexor  carpi  radialis  derive  th  ty  primarily 

from  the  sixth  cervical;  the  Palmaris  longus  from  the  eighth  . ! ;  the  Flexor 

sublimis  digitorum  from  the  seventh  and  eighth  cervical  and  real,  and  the 

Flexor  carpi  ulnaris  from  the  eighth  cervical  and  first  dorsal  Of  the  deep 

layer,  the  Flexor  profundus  digitorum  is  supplied  by  the  eigh  ial  and  first 

dorsal  through  the  ulnar  and  anterior  interosseous  branch  o  modian.     The 

remaining  two  muscles,  Flexor  longus   pollicis  and  Pronator  is,  are  also 

supplied  by  the  eighth  cervical  and  first  dorsal  through  the  a  interosseous 

branch  of  the  median. 

Actions. — These  muscles  act  upon  the  forearm,  the  wrist.  hand.     The 

Pronator  radii  teres  helps  to  rotate  the  radius  upon  the  ulna,  g  the  hand 

prone :    Avhen    the    radius    is    fixed  it  assists  the    other    mus  :1<  lexing  the 

forearm.     The    Flexor    carpi    radialis   is   one  of  the  flexors  o  /ist;  when 

acting    alone  it  flexes   the   wrist,    inclining  it  to   the   radial  B  ■  t  can   also 

assist  in  pronating  the  forearm  and  hand,  and,  by  continuing  1,  to  bend 

the  elbow\     The  Flexor  carpi  ulnaris  is  one  of  the  flexors  of  ist :  when 

acting  alone  it  flexes  the  wrist,  inclining  it  to  the  ulnar  side,  a  ontinuing 

to  contract,  it  bends  the  elbow.     The  Palmaris  longus  is  a  tei  he  palmar 

fascia.     It  also   assists  in  flexing  the  wrist  and  elbow.     The  sublimis 


THE   RADIAL    REGION. 


395 


digitorum  flexes  first  the  middle  and 
then  the  approximal  phalanx.  It 
assists  in  flexing  the  wrist  and  elbow. 
The  Flexor  profundus  digitorum  is  one 
of  the  flexors  of  the  phalanges.  After 
the  Flexor  sublimis  has  bent  the  second 
phalanx,  the  Flexor  profundus  flexes 
the  terminal  one,  but  it  cannot  do  so 
until  after  the  contraction  of  the  super- 
ficial muscle.  It  also  assists  in  flexing 
the  wrist.  The  Flexor  longus  pollicis 
is  a  flexor  of  the  phalanges  of  the 
thumb.  When  the  thumb  is  fixed  it 
also  assists  in  flexing  the  wrist.  The 
Pronator  quadratus  helps  to  rotate  the 
radius  upon  the  ulna,  rendering  the 
hand  prone. 

9.  Radial  Region  (Fig.  235). 

Supinator  longus. 

Extensor  carpi  radialis  longior. 

Extensor  carpi  radialis  brevior. 

Dissection. — Divide  the  integument  in 
the  same  manner  as  in  the  dissection  of  the 
anterior  brachial  region,  and,  after  having 
examined  the  cutaneous  vessels  and  nerves 
and  deep  fascia,  remove  all  those  structures. 
The  muscles  will  then  be  exposed.  The  re- 
moval of  the  fascia  will  be  considerably 
facilitated  by  detaching  it  from  below  up- 
ward. Great  care  should  be  taken  to  avoid 
cutting  across  the  tendons  of  the  muscles  of 
the  thumb,  which  cross  obliquely  the  larger 
tendons  running  down  the  back  of  the  radius. 

The  Supinator  longus  (brachio- 
radialis)  is  the  most  superficial  muscle 
on  the  radial  side  of  the  forearm  ;  it  is 
fleshy  for  the  upper  two-thirds  of  its 
extent,  tendinous  below.  It  arises  from 
the  upper  two-thirds  of  the  external 
supracondylar  ridge  of  the  humerus, 
and  from  the  external  intermuscular 
septum,  being  limited  above  by  the 
musculo-spiral  groove.  The  fibres  ter- 
minate above  the  middle  of  .the  fore- 
arm in  a  flat  tendon,  which  is  inserted 
into  the  outer  side  of  the  base  of  the 
styloid  process  of  the  radius. 

Relations. — By  its  superficial  sur- 
face, with  the  integument  and  fascia 
for  the  greater  part  of  its  extent ; 
near  its  insertion  it  is  crossed  by  the 
Extensor  ossis  metacarpi  pollicis  and 
the  Extensor  brevis  pollicis ;  by  its 
deep  surface,  with  the  humerus,  the 
Extensor  carpi  radialis  longior  and 
brevior,  the  insertion  of  the  Pronator 


radii  teres,  and  the  Supinator  brevis ;    riciaimuscies 


Fig.  235— Posterior  surface  of  the  forearm.    Super- 


396  THE  MUSCLES   AND    FASCIAE. 

by  its  inner  border,  above  the  elbow,  with  the  Brachialis  anticus,  the  musculo- 
spiral  nerve,  and  radial  recurrent  artery  ;  and  in  the  forearm  with  the  radial 
vessels  and  nerve. 

The  Extensor  carpi  radialis  longior  is  placed  partly  beneath  the  preceding 
muscle.  It  arises  from  the  lower  third  of  the  external  supracondylar  ridge  of 
the  humerus,  and  from  the  external  intermuscular  septum  by  a  few  fibres  from 
the  common  tendon  of  origin  of  the  Extensor  muscles  of  the  forearm.  The 
fibres  terminate  at  the  upper  third  of  the  forearm  in  a  flat  tendon,  which  runs 
along  the  outer  border  of  the  radius,  beneath  the  extensor  tendons  of  the  thumb ; 
it  then  passes  through  a  groove  common  to  it  and  the  Extensor  carpi  radialis 
brevior,  immediately  behind  the  styloid  process,  and  is  inserted  into  the  base  of 
the  metacarpal  bone  of  the  index  finger,  on  its  radial  side. 

Relations. — By  its  superficial  surface,  with  the  Supinator  longus  and  fascia 
of  the  forearm ;  its  outer  side  is  crossed  obliquely  by  the  extensor  tendons  of  the 
thumb  ;  by  its  deep  surface,  with  the  elbow-joint,  the  Extensor  carpi  radialis 
brevior,  and  back  part  of  the  wrist. 

The  Extensor  carpi  radialis  brevior  is  shorter,  as  its  name  implies,  and  thicker 
than  the  preceding  muscle,  beneath  which  it  is  placed.  It  arises  from  the 
external  condyle  of  the  humerus  by  a  tendon  common  to  it  and  the  three 
following  muscles;  from  the  external  lateral  ligament  of  the  elbow-joint,  from 
a  strong  aponeurosis  which  covers  its  surface,  and  from  the  intermuscular 
septa  between  it  and  the  adjacent  muscles.  The  fibres  terminate  about  the 
middle  of  the  forearm  in  a  fiat  tendon  which  is  closely  connected  with  that  of 
the  preceding  muscle,  and  accompanies  it  to  the  wrist,  lying  in  the  same  groove 
on  the  posterior  surface  of  the  radius  ;  it  passes  beneath  the  extensor  tendons  of 
the  thumb,  then  beneath  the  annular  ligament,  and,  diverging  somewhat  from  its 
fellow,  is  inserted  into  the  base  of  the  metacarpal  bone  of  the  middle  finger,  on 
its  radial  side. 

The  tendons  of  the  two  preceding  muscles  pass  through  the  same  compartment 
of  the  annular  ligament,  and  are  lubricated  by  a  single  synovial  membrane,  but  are 
separated  from  each  other  by  a  small  vertical  ridge  of  bone  as  they  lie  in  the 
groove  at  the>  back  of  the  radius. 

Relations. — By  its  superficial  surface,  with  the  Extensor  carpi  radialis  longior, 
and  with  the  Extensor  muscles  of  the  thumb  which  cross  it ;  by  its  deep  surface, 
with  the  Supinator  brevis,  tendon  of  the  Pronator  radii  teres,  radius,  and  wrist- 
joint;  by  its  ulnar  border,  with  the  Extensor  communis  digitorum. 

10.  Posterior  Radio-ulnar  Region  (Fig.  235). 

The  muscles  in  this  region  are  divided  for  purposes  of  description  into  two 
groups  or  layers,  superficial  and  deep. 

Superficial   Layer. 

Extensor  communis  digitorum.  Extensor  carpi  ulnaris. 

Extensor  minimi  digiti.  Anconeus. 

The  Extensor  communis  digitorum  is  situated  at  the  back  part  of  the  forearm. 
It  arises  from  the  external  condyle  of  the  humerus  by  the  common  tendon,  from 
the  deep  fascia,  and  the  intermuscular  septa  between  it  and  the  adjacent  muscles. 
Just  below  the  middle  of  the  forearm  it  divides  into  three  fleshy  masses,  from 
which  tendons  proceed;  these  pass,  together  with  the  Extensor  indicis,  through 
a  separate  compartment  of  the  annular  ligament,  lubricated  by  a  synovial  mem- 
brane. The  tendons  then  diverge,  the  innermost  one  dividing  into  two;  and  all, 
after  passing  across  the  back  of  the  hand,  are  inserted  into  the  second  and  third 
phalanges  of  the  fingers  in  the  following  manner :  the  outermost  tendon,  accom- 
panied by  the  Extensor  indicis,  goes  to  the  index  finger ;  the  second  tendon  is 
sometimes  connected  to  the  first  by  a  thin  transverse  band,  and  receives  a  slip 
from  the  third  tendon ;   it  goes  to   the  middle  finger;   the  third  tendon  gives  off 


THE  POSTERIOR    RADIO-ULNAR   REGION.  397 

the  slip  to  the  second,  and  receives  a  very  considerable  part  of  the  fourth  tendon; 
the  fourth,  or  innermost  tendon,  divides  into  two  parts :  one  goes  to  join  the 
third  tendon,  the  other,  reinforced  by  the  Extensor  minimi  digiti,  goes  to  the 
little  finger.  Each  tendon  opposite  the  metacarpophalangeal  articulation  becomes 
narrow  and  thickened,  and  gives  off  a  thin  fasciculus  upon  each  side  of  the  joint, 
which  blends  with  the  lateral  ligaments  and  serves  as  the  posterior  ligament ; 
after  having  passed  the  joint  it  spreads  out  into  a  broad  aponeurosis,  which  covers 
the  whole  of  the  dorsal  surface  of  the  first  phalanx,  being  reinforced,  in  this 
situation,  by  the  tendons  of  the  Interossei  and  Lumbricales.  Opposite  the  first 
phalangeal  joint  this  aponeurosis  divides  into  three  slips,  a  middle  and  two 
lateral:  the  former  is  inserted  into  the  base  of  the  second  phalanx;  and  the  two 
lateral,  which  are  continued  onward  along  the  sides  of  the  second  phalanx,  unite 
by  their  contiguous  margins,  and  are  inserted  into  the  dorsal  surface  of  the  last 
phalanx.  As  the  tendons  cross  the  phalangeal  joints  they  furnish  them  with 
posterior  ligaments. 

Relations. — By  its  superficial  surface,  with  the  fascia  of  the  forearm  and  hand, 
the  posterior  annular  ligament,  and  integument ;  by  its  deep  surface,  with  the 
Supinator  brevis,  the  Extensor  muscles  of  the  thumb  and  index  finger,  the 
posterior  interosseous  vessels  and  nerve,  the  wrist-joint,  carpus,  metacarpus,  and 
phalanges  ;  by  its  radial  border,  with  the  Extensor  carpi  radialis  brevior ;  by  its 
ulnar  border,  with  the  Extensor  minimi  digiti  and  Extensor  carpi  ulnaris. 

The  Extensor  minimi  digiti  is  a  slender  muscle  placed  on  the  inner  side  of 
the  Extensor  communis,  with  which  it  is  generally  connected.  It  ai^ises  from  the 
common  tendon  by  a  thin,  tendinous  slip,  and  from  the  intermuscular  septa 
between  it  and  the  adjacent  muscles.  Its  tendon  runs  through  a  separate 
compartment  in  the  annular  ligament  behind  the  inferior  radio-ulnar  joint,  then 
divides  into  two  as  it  crosses  the  hand,  the  outermost  division  being  joined  by  the 
slip  from  the  innermost  tendon  of  the  common  extensor.  The  two  slips  thus  formed 
spread  into  a  broad  aponeurosis,  which  after  receiving  a  slip  from  the  Abductor 
minimi  digiti  is  inserted  into  the  second  and  third  phalanges.  The  tendon  is 
situated  on  the  ulnar  side  of,  and  somewhat  more  superficial  than,  the  common 
extensor. 

The  Extensor  carpi  ulnaris  is  the  most  superficial  muscle  on  the  ulnar  side  of 
the  forearm.  It  arises  from  the  external  condyle  of  the  humerus  by  the  common 
tendon ;  by  an  aponeurosis  from  the  posterior  border  of  the  ulna  in  common 
with  the  Flexor  carpi  ulnaris  and  the  Flexor  profundus  digitorum ;  and  from  the 
deep  fascia  of  the  forearm.  This  muscle  terminates  in  a  tendon  which  runs  through 
a  groove  behind  the  styloid  process  of  the  ulna,  passes  through  a  separate  compart- 
ment in  the  annular  ligament,  and  is  inserted  into  the  prominent  tubercle  on  the 
ulnar  side  of  the  base  of  the  metacarpal  bone  of  the  little  finger. 

Relations. — By  its  superficial  surface,  with  the  deep  fascia  of  the  forearm  ;  by 
its  deep  surface,  with  the  ulna  and  the  muscles  of  the  deep  layer. 

The  Anconeus  is  a  small  triangular  muscle  placed  behind  and  below  the  elbow- 
joint,  and  appears  to  be  a  continuation  of  the  external  portion  of  the  Triceps.  It 
arises  by  a  separate  tendon  from  the  back  part  of  the  outer  condyle  of  the  humerus, 
and  is  inserted  into  the  side  of  the  olecranon  and  upper  fourth  of  the  posterior 
surface  of  the  shaft  of  the  ulna ;  its  fibres  diverge  from  their  origin,  the  upper 
ones  being  directed  transversely,  the  lower  obliquely  inward. 

Relations. — By  its  superficial  surface,  with  a  strong  fascia  derived  from  the 
Triceps  ;  by  its  deep  surface,  with  the  elbow-joint,  the  orbicular  ligament,  the 
ulna,  and  a  small  portion  of  the  Supinator  brevis. 

Deep  Layer  (Fig.  237). 

Supinator  brevis.  Extensor  brevis  pollicis. 

Extensor  ossis  metacarpi  pollicis.  Extensor  longus  pollicis. 

Extensor  indicis. 


398 


THE  MUSCLES  AND    FASCIAE. 


The  Supinator  brevis  (Fig.  236)  is  a  broad  muscle,  of 

curved  round  the  upper  third  of  the  radius.     It  cons  its 

muscular  fibres,   between  which  lies 

the  posterior  interosseous  nerve.   The 

two    planes   arise   in    common:    the 

superficial  one  by  tendinous,  and  the 

deeper  by  muscular,  fibres  from  the  » 

external    condyle    of  the  humerus; 

from    the  external   lateral   ligament 

of  the  elbow-joint  and  the  orbicular 
ligament  of  the  radius;  from,  the 
ndge  on  the  ulna,  which  runs  ob- 
liquely downward  from  the  posterior 
extremity  of  the  lesser  sigmoid  cav- 
ity;  from  the  triangular  depression 
m  front  of  it :  and  from  a  tendinous 
expansion  which  covers  the  sur- 
face of  the  muscle.  The  superficial 
fibres  surround  the  upper  part   of 


Int, 

Condyle. 


hollow  cylindrical  form, 
of  two  distinct  planes  of 


Olecranon, 


Coronoid 

proc 
Head  of 

radius 


TENDON    OF 
BICEPS. 


Surgeons  of  EnSd  )  &  R°yal  ColIe?e  of 


Fig.  237,-Posterior  surface  of  the  forearm,    neep  muscles. 


Ae  radius,  and  are  inserted  into  the  ,  7  ~ ™Mre*™-  *•.— 
»d  te  the  oblique  line  efthe  radlus  T]  "*%  °f  the  WciPital  tuberosity 
Pronator  radii  teres.  The  uD„er  fiW,  f  IT  j*"™  aS  the  inserti°"  "{  the 
fasciculus,  which  encircles  theP1neck  of  ^h        Vdeepf  pkne  fo™  a   sling.like 

tne  neck  of  .he  radms  above  the  tuberosity  aid  is 


THE   POSTERIOR    RADIO-ULNAR    REGION.  399 

attached  to  the  back  part  of  its  inner  surface  :  the  greater  part  of  this  portion  of 
the  muscle  is  inserted  into  the  posterior  and  external  surface  of  the  shaft,  midway 
between  the  oblique  line  and  the  head  of  the  bone.  Between  the  insertion  of  the 
two  planes  the  posterior  interosseous  nerve  lies  on  the  shaft  of  the  bone. 

Relations. — By  its  superficial  surface,  with  the  superficial  Extensor  and 
Supinator  muscles,  and  the  radial  vessels  and  nerve ;  by  its  deep  surface,  with  the 
elbow-joint,  the  interosseous  membrane,  and  the  radius. 

The  Extensor  ossis  metacarpi  pollicis  is  the  most  external  and  the  largest  of 
the  deep  extensor  muscles :  it  lies  immediately  below  the  Supinator  brevis,  with 
which  it  is  sometimes  united.  It  arises  from  the  outer  part  of  the  posterior  surface 
of  the  shaft  of  the  ulna  below  the  insertion  of  the  Anconeus,  from  the  interosseous 
membrane,  and  from  the  middle  third  of  the  posterior  surface  of  the  shaft  of  the 
radius.  Passing  obliquely  downward  and  outward,  it  terminates  in  a  tendon  "which 
runs  through  a  groove  on  the  outer  side  of  the  styloid  process  of  the  radius,  accom- 
panied by  the  tendon  of  the  Extensor  brevis  pollicis,  and  is  inserted  into  the  base 
of  the  metacarpal  bone  of  the  thumb.  It  occasionally  gives  off  two  slips  near  its 
insertion — one  to  the  Trapezium,  and  the  other  to  blend  with  the  origin  of  the 
Abductor  pollicis. 

Relations. — By  its  superficial  surface,  with  the  Extensor  communis  digitorum, 
Extensor  minimi  digiti,  and  fascia  of  the  forearm,  and  with  the  branches  of  the 
posterior  interosseous  artery  and  nerve  which  cross  it ;  by  its  deep  surface,  with 
the  ulna,  interosseous  membrane,  radius,  the  tendons  of  the  Extensor  carpi  radialis 
longior  and  brevior,  which  it  crosses  obliquely,  and,  at  the  outer  side  of  the  wrist, 
with  the  radial  vessels ;  by  its  upper  border,  with  the  Supinator  brevis ;  by  its 
lower  border,  with  the  Extensor  brevis  pollicis. 

The  Extensor  brevis  pollicis  {Extensor  primi  internodii  pollicis),  the  smallest 
muscle  of  this  group,  lies  on  the  inner  side  of  the  preceding.  It  arises  from  the  pos- 
terior surface  of  the  shaft  of  the  radius,  below  the  Extensor  ossis  metacarpi  pollicis, 
and  from  the  interosseous  membrane.  Its  direction  is  similar  to  that  of  the 
Extensor  ossis  metacarpi  pollicis,  its  tendon  passing  through  the  same  groove  on 
the  outer  side  of  the  styloid  process,  to  be  inserted  into  the  base  of  the  first  phalanx 
of  the  thumb. 

Relations. — The  same  as  those  of  the  Extensor  ossis  metacarpi  pollicis. 

The  Extensor  longus  pollicis  {Extensor  secundi  internodii  pollicis)  is  much  larger 
than  the  preceding  muscle,  the  origin  of  which  it  partly  covers  in.  It  arises  from 
the  outer  part  of  the  posterior  surface  of  the  shaft  of  the  ulna,  below  the  origin  of 
the  Extensor  ossis  metacai'pi  pollicis,  and  from  the  interosseous  membrane.  It 
terminates  in  a  tendon  which  passes  through  a  separate  compartment  in  the  annular 
ligament,  lying  in  a  narrow,  oblique  groove  at  the  back  part  of  the  lower  end  of  the 
radius.  It  then  crosses  obliquely  the  tendons  of  the  Extensor  carpi  radialis  lon- 
gior and  brevior,  being  separated  from  the  other  extensor  tendons  of  the  thumb  by 
a  triangular  interval,  in  which  the  radial  artery  is  found,  and .  is  finally  inserted 
into  the  base  of  the  last  phalanx  of  the  thumb. 

Relations. — By  its  superficial  surj ?ace,  with  the  same  parts  as  the  Extensor  ossis 
metacarpi  pollicis ;  by  its  deep  surface,  with  the  ulna,  interosseous  membrane,  the 
posterior  interosseous  nerve,  radius,  the  wrist,  the  radial  vessels,  and  metacarpal 
bone  of  the  thumb. 

The  Extensor  indicis  is  a  narrow,  elongated  muscle  placed  on  the  inner  side  of, 
and  parallel  with,  the  preceding.  It  arises  from  the  posterior  surface  of  the  shaft 
of  the  ulna,  below  the  origin  of  the  Extensor  longus  pollicis  and  from  the  inter- 
osseous membrane.  Its  tendon  passes  with  the  Extensor  communis  digitorum 
through  the  same  canal  in  the  annular  ligament,  and  subsequently  joins  the  tendon 
of  the  Extensor  communis  which  belongs  to  the  index  finger,  opposite  the  lower 
end  of  the  corresponding  metacarpal  bone,  lying  to  the  ulnar  side  of  the  tendon 
from  the  common  Extensor. 

Relations. — The  relations  are  similar  to  those  of  the  preceding  muscles. 

Nerves. — The  Supinator  longus  is  supplied  by  the  sixth,  the  Extensor  carpi 


400  THE   MUSCLES   AND    FASCIA. 

radialis  longior  by  the  sixth  and  seventh,  and  the  Anconeus  by  the  seventh  and 
eighth  cervical  nerves,  all  through  the  musculo-spiral  nerve ;  the  remaining  muscles 
of  the  radial  and  posterior  brachial  region  are  supplied  through  the  posterior 
interosseous  nerve,  the  Supinator  brevis  being  supplied  by  the  sixth  cervical,  the 
Extensor  carpi  radialis  brevior  by  the  sixth  and  seventh  cervical,  and  all  the  other 
muscles  by  the  seventh  cervical. 

Actions. — The  muscles  of  the  radial  and  posterior  brachial  regions,  which 
comprise  all  the  extensor  and  supinator  muscles,  act  upon  the  forearm,  wrist,  and 
hand ;  they  are  the  direct  antagonists  of  the  pronator  and  flexor  muscles.  The 
Anconeus  assists  the  Triceps  in  extending  the  forearm.  The  chief  action  of  the 
Supinator  longus  is  that  of  a  flexor  of  the  elbow-joint,  but  in  addition  to  this  it 
may  act  both  as  a  supinator  or  a  pronator  ;  that  is  to  say,  if  the  forearm  is  forcibly 
pronated  it  will  act  as  a  supinator,  and  bring  the  bones  into  a  position  midAvay 
between  supination  and  pronation ;  and,  vice  versa,  if  the  arm  is  forcibly  supinated, 
it  will  act  as  a  pronator,  and  bring  the  bones  into  the  same  position,  midway 
between  supination  and  pronation.  The  action  of  the  muscle  is  therefore  to  throw 
the  forearm  and  hand  into  the  position  they  naturally  occupy  when  placed  across 
the  chest.  The  Supinator  brevis  is  a  supinator  ;  that  is  to  say,  when  the  radius 
has  been  carried  across  the  ulna  in  pronation  and  the  back  of  the  hand  is  directed 
forward,  this  muscle  carries  the  radius  back  again  to  its  normal  position  on  the 
outer  side  of  the  ulna,  and  the  palm  of  the  hand  is  again  directed  forward.  The 
Extensor  carpi  radialis  longior  extends  the  wrist  and  abducts  the  hand.  It  may 
also  assist  in  bending  the  elbow-joint;  at  all  events,  it  serves  to  fix  or  steady  this 
articulation.  The  Extensor  carpi  radialis  brevior  assists  the  Extensor  carpi  radi- 
alis longior  in  extending  the  wrist,  and  may  also  act  slightly  as  an  abductor  of  the 
hand.  The  Extensor  carpi  ulnaris  helps  to  extend  the  hand,  but  when  acting 
alone  inclines  it  toward  the  ulnar  side  ;  by  its  continued  action  it  extends  the 
elbow-joint.  The  Extensor  communis  digitorum  extends  the  phalanges,  then  the 
wrist,  and  finally  the  elboAV.  It  acts  principally  on  the  proximal  phalanges,  the 
middle  and  terminal  phalanges  being  extended  by  the  Interossei  and  Lumbri- 
cales.  It  has  also  a  tendency  to  separate  the  fingers  as  it  extends  them.  The 
Extensor  minimi  digiti  extends  similarly  the  little  finger,  and  by  its  continued 
action  it  assists  in  extending  the  wrist.  It  is  owing  to  this  muscle  that  the  little 
finger  can  be  extended  or  pointed  whilst  the  others  are  flexed.  The  chief  action  of 
the  Extensor  ossis  metacarpi  pollicis  is  to  carry  the  thumb  outward  and  backward 
from  the  palm  of  the  hand,  and  hence  it  has  been  called  the  abductor  pollicis  lon- 
gus. By  its  continued  action  it  helps  to  extend  and  abduct  the  wrist.  The 
Extensor  brevis  pollicis  extends  the  proximal  phalanx  of  the  thumb.  By  its 
continued  action  it  helps  to  extend  and  abduct  the  wrist.  The  Extensor  longus 
pollicis  extends  the  terminal  phalanx  of  the  thumb.  By  its  continued  action  it 
helps  to  extend  and  abduct  the  wrist.  The  Extensor  indicis  extends  the  index 
finger,  and  by  its  continued  action  assists  in  extending  the  wrist.  It  is  owing 
to  this  muscle  that  the  index  finger  can  be  extended  or  pointed  while  the  others 
are  flexed. 

Surgical  Anatomy. — The  tendons  of  the  Extensor  muscles  of  the  thumb  are  liable  to 
become  strained  and  their  sheaths  inflamed  after  excessive  exercise,  producing  a  sausage-shaped 
swelling  along  the  course  of  the  tendon,  and  giving  a  peculiar  creaking  sensation  to  the  finger 
when  the  muscle  acts.  In  consequence  of  its  often  being  caused  by  such  movements  as  wringing 
clothes,  it  is  known  as  "washerwoman's  sprain." 

IV.  MUSCLES  AND  FASCLE    OF  THE  HAND. 

The  Muscles  of  the  Hand  are  subdivided  into  three  groups :  1.  Those  of  the 
thumb,  which  occupy  the  radial  side  and  produce  the  thenar  eminence ;  2.  Those 
of  the  little  finger,  which  occupy  the  ulnar  side  and  give  rise  to  the  hynothenar 
eminence ;  3.  Those  in  the  middle  of  the  palm  and  within  the  interosseous 
spaces. 


THE   HAND. 


401 


Dissection  (Fig.  228). — Make  a  transverse  incision  across  the  front  of  the  wrist,  and  a 
second  across  the  heads  of  the  metacarpal  bones :  connect  the  two  by  a  vertical  incision  in  the 
middle  line,  and  continue  it  through  the  cen- 
tre of  the  middle  finger.  The  anterior  and 
posterior  annular  ligaments  and  the  palmar 
fascia  should  then  be  dissected. 


1.QNO,     FLEX^C^Qp 


The  Anterior  Annular  Ligament  is 
a  strong,  fibrous  band  which  arches 
over  the  carpus,  converting  the  deep 
groove  on  the  front  of  the  carpal 
bones  into  a  canal,  beneath  which 
pass  the  flexor  tendons  of  the  fingers. 
It  is  attached,  internally,  to  the  pisi- 
form bone  and  the  hook  of  the  unci- 
form bone,  and  externally  to  the 
tuberosity  of  the  scaphoid  and  to  the 
inner  part  of  the  anterior  surface  and 
the  ridge  on  the  trapezium.  It  is 
continuous,     above,     with    the    deep  ' 

fascia  of  the  forearm,  of  which  it  may  be  regarded  as  a  thickened  portion,#  and, 
below,  with  the  palmar  fascia.  It  is  crossed  by  the  ulnar  vessels  and  nerve  and 
the  cutaneous  branches  of  the  median  and  ulnar  nerves.  At  its  outer  extremity 
is  the  tendon  of  the  Flexor  carpi  radialis,  which  lies  in  the  groove  on  the  trapezium 
between  the  attachments  of  the  annular  ligament  to  the  bone.  It  has  inserted  into 
its  anterior  surface  a  part  of  the  tendon  of  the  Palmaris  longus  and  part  of  the 
tendon  of  the   Flexor  carpi   ulnaris,   and  has  arising  from  it,   below,   the   small 


Sfc-  'NT.  pOlA" 


Fig.  238.— Transverse  section  through  the  wrist,  show- 
ing the  annular  ligaments  and  the  canals  for  the  passage 
of  the  tendons. 


ANNULAR    LIGAMENT 
FLEXOR    LONGUS    POLLICIS 
FLEXOR    CARPI    RADIALIS 
MUSCLES    OF   THUMB 


Median  nerve. 
Ulnar  vessels. 

LMARIS    BREVIS. 


1st  Metacarpal 


EXT.    PRIM 

INTERNOD. 

POLL. 

EXT.    SEC. 

INTERNOD. 

POLL. 

Trapezium! 

Radial  vessels. 

EXT.    CARP.    RAD.    LO 

Trapezoid. 

EXTENSOR    CARPI     RADIAL!! 
BREVIOR. 


MUSCLES    OF 
LITTLE 
INGER. 


EXT.    CARPI 
ULNARIS. 


EXTENSOR 
MINIMI 
DIGITI. 


EXTENSOR 
COMMUNIS 
DIGITORUM. 


EXTENSOR    INDICIS. 

Os  magnum. 


Fig.  239. — Transverse  section  through  the  carpus,  showing  the  relative  positions  of  the  tendons,  vessels,  and 
nerves.    (Henle.) 

muscles  of  the  thumb  and  little  finger.  Beneath  it  pass  the  lendons  of  the  Flexor 
sublimis  and  profundus  digitorum,  the  Flexor  longus  pollicis,  and  the  median 
nerve. 

The  Synovial  Membranes  of  the  Flexor  Tendons  at  the  Wrist. — There  are  two 
synovial  membranes  which  enclose  all  the  tendons  as  they  pass  beneath  this  lig- 
ament— one  for  the  Flexor  sublimis  and  profundus  digitorum,  the  other  for  the 
Flexor  longus  pollicis.  They  extend  up  into  the  forearm  for  about  an  inch  above 
the  annular  ligament,  and  downward  about  halfway  along  the  metacarpal  bone, 
where  they  terminate  in  a  blind  diverticulum  around  each  pair  of  tendons,  with  the 
exception  of  that  of  the  thumb  and  those  of  the  little  finger — in  these  two  digits 
the  diverticulum  is  continued  on,  and  communicates  with  the  synovial  sheath  of  the 
tendons   in   the  fingers.     In   the  other  three  fingers  the  synovial  sheath   of  the 

26 


402 


THE   MUSCLES   AND    FASCIJE. 


tendons  begins  as  a  blind  pouch  without  communication  with  the  large  synovial 
sac  (Fig.  240). 

Surgical  Anatomy. — This  arrangement  of  the  synovial  sheaths  explains  the  fact  that 
thecal  abscess  in  the  thumb  and  little  finger  is  liable  to  be  followed  by  abscesses  in  the  forearm, 
from  extension  of  the  inflammation  along  the  continuous  synovial  sheaths.  Ganglion  is  apt  to 
occur  in  this  situation,  constituting  "compound  palmar  ganglion"  ;  it  presents  an  hour-glass 
outline,  with  a  swelling  in  front  of  the  wrist  and  in  the  palm  of  the  hand,  and  a  constriction 
corresponding  to  the  annular  ligament  between  the  two.  The  fluid  can  be  forced  from  the  one 
swelling  to  the  other  under  the  ligament. 

The  Posterior  Annular  Ligament  is  a  strong  fibrous  band  extending  obliquely 
downward  and  inward  across  the  back  of  the  wrist,  and  consisting  of  the  deep 
fascia  of  the  back  of  the  forearm,  strengthened  by  the  addition  of  some  transverse 
fibres.      It   binds   down   the   extensor   tendons    in    their  passage   to   the   fingers, 

being  attached,  internally,  to  the  styloid 
process  of  the  ulna,  the  cuneiform  and 
pisiform  bones ;  externally,  to  the  margin 
of  the  radius ;  and,  in  its  passage  across 
the  wrist,  to  the  elevated  ridges  on  the 
posterior  surface  of  the  radius.  It  pre- 
sents six  compartments  for  the  passage 
of  tendons,  each  of  which  is  lined  by  a 
separate  synovial  membrane.  These  are, 
from  without  inward — 1.  On  the  outer 
side  of  the  styloid  process,  for  the  ten- 
dons of  the  Extensor  ossis  metacarpi 
and  Extensor  brevis  pollicis  ;  2.  Behind 
the  styloid  process,  for  the  tendons  of 
the  Extensor  carpi  radialis  longior  and 
brevior;  3.  About  the  middle  of  the 
posterior  surface  of  the  radius,  for  the 
tendon  of  the  Extensor  longus  pollicis ; 
4.  To  the  inner  side  of  the  latter,  for  the 
tendons  of  the  Extensor  communis  digi- 
torum  and  Extensor  indicis ;  5.  Oppo- 
site the  interval  between  the  radius  and 
ulna,  for  the    Extensor   minimi    digiti ; 

Fig.  240.— Diagram  showing  the  arrangement  of  the    6.   Grooving  the  back  of  the  ulna,  for  the 
synovial  sheaths  of  the  palm  and  fingers.  tendon     of    ^    Extengor    carpi    ulnaris. 

The  synovial  membranes  lining  these  sheaths  are  usually  very  extensive,  reach- 
ing from  above  the  annular  ligament,  down  upon  the  tendons  for  a  variable 
distance  on  the  back  of  the  hand. 

The  deep  palmar  fascia  (Fig.  241)  forms  a  common  sheath  which  invests  the 
muscles  of  the  hand.     It  consists  of  a  central  and  two  lateral  portions. 

The  central  portion  occupies  the  middle  of  the  palm,  is  triangular  in  shape,  of 
great  strength  and  thickness,  and  binds  down  the  tendons  and  protects  the  ves- 
sels and  nerves  in  this  situation.  It  is  narrow  above,  where  it  is  attached  to  the 
lower  margin  of  the  annular  ligament,  and  receives  the  expanded  tendon  of 
the  Palmaris  longus  muscle.  Below7,  it  is  broad  and  expanded,  and  divides 
into  four  slips  for  the  four  fingers.  Each  slip  gives  off  superficial  fibres, 
which  are  inserted  into  the  skin  of  the  palm  and  finger,  those  to  the 
palm  joining  the  skin  at  the  furrow  corresponding  to  the  metacarpo-phalangeal  ar- 
ticulation, and  those  to  the  fingers  passing  into  the  skin  at  the  transverse  fold  at 
the  base  of  the  fingers.  The  deeper  part  of  each  slip  subdivides  into  two  proc- 
esses, which  are  inserted  into  the  lateral  margins  of  the  anterior  (glenoid)  liga- 
ment of  the  metacarpo-phalangeal  joint.  From  the  sides  of  these  processes 
offsets  are  sent  backward,  to  be  attached  to  the  borders  of  the  lateral  surfaces  of 


THE   HAND. 


403 


the  metacarpal  bones  at  their  distal  extremities.  By  this  arrangement  short 
channels  are  formed  on  the  front  of  the  lower  ends  of  the  metacarpal  bones, 
through  which  the  flexor  tendons  pass.  Dr.  W.  W.  Keen  describes  a  fifth  slip  as 
frequently  found  passing  to  the  thumb.  The  intervals  left  in  the  fascia  between 
the  four  fibrous  slips  transmit  the  digital  vessels  and  nerves  and  the  tendons  of 
the  Lumbricales.  At  the  points  of  division  of  the  palmar  fascia  into  the  slips 
above  mentioned  numerous  strong,  transverse  fibres  bind  the  separate  processes 
together.  The  palmar  fascia  is  intimately  adherent  to  the  integument  by  dense 
fibro-areolar  tissue,  forming  the  superficial  palmar  fascia,  and  gives  origin  by  its 
inner  margin   to  the  Palmaris  brevis :   it  covers  the  superficial  palmar  arch,  the 


Digital  ar 
Digital  tier 


Fig.  o4i._Palmar  fascia.    (From  a  preparation  in  the  Museum  of  the  Royal  College  of  surgeons  of 
England.) 

tendons  of  the  flexor  muscles,  and  the  branches  of  the  median  and  ulnar  nerves, 
and  on  each  side  it  gives  off  a  vertical  septum,  which  is  continuous  with  the 
interosseous  aponeurosis  and  separates  the  lateral  from  the  middle  palmar  group 

ot  iyiiiscIgs. 

The  lateral  portions  of  the  palmar  fascia  are  thin,  fibrous  layers,  which  cover, 
on  the  radial  side,  the  muscles  of  the  ball  of  the  thumb,  and,  on  the  ulnar  side,  the 
muscles  of  the  little  finger ;  they  are  continuous  with  the  dorsal  fascia,  and  in  the 
palm  with  the  central  portion  of  the  palmar  fascia. 


404  THE   MUSCLES   AND    FASCIAE. 

The  Superficial  Transverse  Ligament  of  the  Fingers  is  a  thin,  fibrous  band 
which  stretches  across  the  roots  of  the  four  fingers,  and  is  closely  attached  to  the 
skin  of  the  clefts,  and  internally  to  the  fifth  metacarpal  bone,  forming  a  sort  of 
rudimentary  web.  Beneath  it  the  digital  vessels  and  nerves  pass  onward  to  their 
destination. 

Surgical  Anatomy.— The  palmar  fascia  is  liable  to  undergo  contraction,  producing  a  very 
inconvenient  deformity  known  as  "  Dupuytren's  contraction."  The  ring  and  little  fingers  are 
most  frequently  implicated,  but  the  middle,  the  index,  and  the  thumb  may  be  involved.  The 
proximal  phalanx  is  drawn  down  and  cannot  be  straightened,  and  the  two  distal  phalanges 
become  similarly  flexed  as  the  disease  advances. 

2.  Radial  Region  (Figs.  242,  243). 

Abductor  pollicis.  Flexor  brevis  pollicis. 

Opponens  (Flexor  ossis  metacarpi)  pollicis.        Abductor  obliquus  pollicis. 
Adductor  transversus  pollicis. 

The  Abductor  pollicis  is  a  thin,  flat  muscle,  placed  immediately  beneath  the 
integument.  It  arises  from  the  annular  ligament,  the  tuberosity  of  the  scaphoid, 
and  the  ridge  of  the  trapezium,  frequently  by  two  distinct  slips ;  and,  passing  out- 
ward and  downward,  is  inserted  by  a  thin,  flat  tendon  into  the  radial  side  of  the 
base  of  the  first  phalanx  of  the  thumb,  sending  a  slip  to  join  the  tendon  of  the  Ex- 
tensor longus  pollicis. 

Relations. — By  its  superficial  surface,  with  the  palmar  fascia  and  superficialis 
volse  artery,  which  frequently  perforates  it.  By  its  deep  surface,  with  the  Op- 
ponens pollicis,  from  wThich  it  is  separated  by  a  thin  aponeurosis.  Its  inner  border 
is  separated  from  the  Flexor  brevis  pollicis  by  a  narrow  cellular  interval. 

The  Opponens  pollicis  [Flexor  ossis  metacarpi  pollicis)  is  a  small,  triangular 
muscle,  placed  beneath  the  preceding.  It  arises  from  the  palmar  surface  of  the 
ridge  on  the  trapezium  and  from  the  annular  ligament,  passes  downward  and  out- 
ward, and  is  inserted  into  the  whole  length  of  the  metacarpal  bone  of  the  thumb  on 
its  radial  side. 

Relations. — By  its  sujierficial  surface,  with  the  Abductor  and  Flexor  brevis 
pollicis.  By  its  deep  surface,  with  the  trapezio-metacarpal  articulation.  By  its 
inner  border,  with  the  Adductor  obliquus  pollicis. 

The  Flexor  brevis  pollicis  consists  of  two  portions,  outer  and  inner.  The  outer 
and  more  superficial  portion  arises  from  the  outer  two-thirds  of  the  lower  border  of 
the  annular  ligament,  and  passes  along  the  outer  side  of  the  tendon  of  the  Flexor 
longus  pollicis  ;  and,  becoming  tendinous,  has  a  sesamoid  bone  developed  in  its 
tendon,  and  is  inserted  into  the  outer  side  of  the  base  of  the  first  phalanx  of  the 
thumb.  The  inner  and  deeper  portion  of  the  muscle  is  very  small,  and  arises  from 
the  ulnar  side  of  the  first  metacarpal  bone  beneath  the  Adductor  obliquus  pollicis, 
and  is  inserted  into  the  inner  side  of  the  base  of  the  first  phalanx  with  this  muscle. 

Relations. — By  its  superficial  surface,  with  the  palmar  fascia.  By  its  deep 
surface,  with  the  tendon  of  the  Flexor  longus  pollicis.  By  its  external  surface, 
with  the  Opponens  pollicis.     Behind,  with  the  Adductor  obliquus  pollicis. 

The  Adductor  obliquus  pollicis  arises  by  several  slips  from  the  os  magnum,  the 
bases  of  the  second  and  third  metacarpal  bones,  the  anterior  carpal  ligaments,  and 
the  sheath  of  the  tendon  of  the  Flexor  carpi  radialis.  From  this  origin  the  greater 
number  of  fibres  pass  obliquely  downward  and  converge  to  a  tendon,  which, 
uniting  with  the  tendons  of  the  deeper  portion  of  the  Flexor  brevis  pollicis  and 
the  Adductor  transversus,  is  inserted  into  the  inner  side  of  the  base  of  the  first 
phalanx  of  the  thumb,  a  sesamoid  bone  being  developed  in  the  tendon  of  insertion. 
A  considerable  fasciculus,  however,  passes  more  obliquely  outward  beneath  the 
tendon  of  the  long  flexor  to  join  the  superficial  portion  of  the  short  flexor  arid  the 
Abductor  pollicis.1 

1  This  muscle  was  formerly  descr'bed  as  the  deep  portion  of  the  Flexor  brevis  pollicis. 


THE   RADIAL    REGION. 


405 


Relations. — By  its  superficial  surface,  with  the  Flexor  longus  pollicis  and  the 
•outer  head  of  the  Flexor  brevis  pollicis.  Its  deep  surface  is  in  relation  with  the 
deep  palmar  arch,  which  passes  between  the  two  adductors. 

The  Adductor  transversus  pollicis  (Fig.  242)  is  the  most  deeply  seated  of  this 
group  of  muscles.  It  is  of  a  triangular  form,  arising,  by  its  broad  base,  from  the 
lower  two-thirds  of  the  metacarpal  bone  of  the  middle  finger  on  its  palmar  surface ; 
the  fibres,  proceeding  outward,  converge,  to  be  inserted,  with  the  inner  part  of 
the  Flexor  brevis  pollicis,  and  the  Adductor  obliquus  pollicis,  into  the  ulnar  side 
of  the  base  of  the  first  phalanx  of  the  thumb.  From  the  common  tendon  of  inser- 
tion a  slip  is  prolonged  to  the  Extensor  longus  pollicis. 

Relations. — By  its  superficial  surface,  with  the  Adductor  obliquus  pollicis, 
the  tendons  of  the  Flexor  profundus,  and  the  Lumbricales.  Its  deep  surface 
covers  the  first  two  interosseous  spaces,  from  which  it  is  separated  by  a  strong 
aponeurosis. 

Three  of  these  muscles  of  the  thumb,  the  Abductor,  the  Adductor  transversus, 
and  the  Flexor  brevis  pollicis,  at  their  insertions  give  off  fibrous  expansions  which 


EXTENSOR    LONGUS 
POLLICIS. 

First  metacarpal 
bone. 


OPPONENS    POLLICIS 


Fig.  242.— Muscles  of  thumb.    (From  a  preparation  iu  the  Museum  of  the  Royal  College  of  Surgeons  01 
England.) 

join  the  tendon  of  the  Extensor  longus  pollicis.  This  permits  of  flexion  of  the 
proximal  phalanx  and  extension  of  the  terminal  phalanx  at  the  same  time.  These 
■expansions,  originally  figured  by  Albinus,  have  been  more  recently  described  by 
M.  Duchenne  {Physiologic  des  Mouvements). 

Nerves. — The  Abductor,  Opponens,  and  outer  head  of  the  Flexor  brevis  pollicis 
are  supplied  by  the  sixth  cervical  through  the  median  nerve;  the  inner  head  of  the 
Flexor  brevis,  and  the  Adductors,  by  the  eighth   cervical  through  the  ulnar  nerve. 

Actions. — The  actions  of  the  muscles  of  the  thumb  are  almost  sufficiently  indi- 
cated by  their  names.  This  segment  of  the  hand  is  provided  with  three  extensors 
— an  extensor  of  the  metacarpal  bone,  an  extensor  of  the  first,  and  an  extensor  of 
the  second  phalanx  ;  these  occupy  the  dorsal  surface  of  the  forearm  and  hand. 


406  THE  MUSCLES  A,  CTjE. 

There  are  also  three  flexors  on  the  palmar  pinface — a  flexor  of  the  metacarpal 
bone,  a  flexor  of  the  proximal,  and  a  flexor  of  inal  phalanx;  there  is  also 

an  Abductor  and  two  Adductors.  The  Abductor  pollicis  moves  the  metacarpal 
bone  of  the  thumb  outward;  that  is,  away  from  t 1 1 - ■  index  finger.  The  Flexor 
ossis  metacarpi  pollicis  flexes  the  metacarpal  bon< — ik;u  is,  draws  it  inward  over 
the  palm — and  at  the  same  time  rotates  the  bone,  so  as  to  turn  the  ball  of  the 
thumb   toward  the    fingers,   thus    producing    the  mo\  t  of  opposition.     The 

Flexor  brevis  pollicis  flexes  and  adducts  the  proxim  anx  of  the  thumb.     The 

Adductores  pollicis  move  the  metacarpal  bone  of  the  thumb  inward;  that  is,  to- 
ward the  index  finger.  These  muscles  give  to  the  t  -  mb  its  extensive  range  of 
motion.  It  will  be  noticed,  however,  that  in  consequence  of  the  position  of  the 
first  metacarpal  bone,  these  movements  differ  from  the  corresponding  movements  of 
the  metacarpal  bones  of  the  other  fingers.  Thus  extension  of  the  thumb  more 
nearly  corresponds  to  the  motion  of  abduction  in  the  other  fingers,  and  flexion  to 
adduction. 

12.  Ulnar  Region  (Fig.  243). 

Palmaris  brevis. 

Abductor  minimi  digiti.  Flexor  brevis  minimi  digiti. 

Opponens  (Flexor  ossis  metacarpi)  minimi  digiti. 

The  Palmaris  brevis  is  a  thin  quadrilateral  muscle  placed  beneath  the  integu- 
ment on  the  ulnar  side  of  the  hand.  It  arises  by  tendinous  fasciculi  from  the 
annular  ligament  and  palmar  fascia  ;  the  fleshy  fibres  pass  inward,  to  be  inserted 
into  the  skin  on  the  inner  border  of  the  palm  of  the  hand. 

Relations. — By  its  superficial  surface,  with  the  integument,  to  which  it  is 
intimately  adherent,  especially  by  its  inner  extremity ;  by  its  deep  surface,  with 
the  inner  portion  of  the  palmar  fascia,  which  separates  it  from  the  ulnar  vessels 
and  nerve,  and  from  the  muscles  of  the  ulnar  side  of  the  hand. 

The  Abductor  minimi  digiti  is  situated  on  the  ulnar  border  of  the  palm  of  the 
hand.  It  arises  from  the  pisiform  bone  and  from  the  tendon  of  the  Flexor  carpi 
ulnaris,  and  terminates  in  a  flat  tendon,  which  divides  into  two  slips ;  one  is 
inserted  into  the  ulnar  side  of  the  base  of  the  first  phalanx  of  the  little  finger. 
The  other  slip  is  inserted  into  the  ulnar  border  of  the  aponeurosis  of  the  Extensor 
minimi  digiti. 

Relations. — By  its  superficial  surface,  with  the  inner  portion  of  the  palmar 
fascia  and  the  Palmaris  brevis ;  by  its  deep  surface,  with  the  Flexor  ossis  meta- 
carpi minimi  digiti ;  by  its  outer  border,  with  the  Flexor  brevis  minimi  digiti. 

The  Flexor  brevis  minimi  digiti  lies  on  the  same  plane  as  the  preceding  muscle, 
on  its  radial  side:  It  arises  from  the  convex  aspect  of  the  hook  of  the  unciform 
bone  and  anterior  surface  of  the  annular  ligament,  and  is  inserted  into  the  inner 
side  of  the  base  of  the  first  phalanx  of  the  little  finger.  It  is  separated  from  the 
Abductor  at  its  origin  by  the  deep  branches  of  the  ulnar  artery  and  nerve.  This 
muscle  is  sometimes  wanting  ;   the  Abductor  is  then,  usually,  of  large  size. 

Relations. — By  its  superficial  surface,  with  the  internal  portion  of  the  palmar 
fascia  and  the  Palmaris  brevis ;  by  its  deep  surface,  with  the  Opponens.  The 
deep  branch  of  the  ulnar  artery  and  the  corresponding  branch  of  the  ulnar  nerve 
pass  between  the  Abductor  and  Flexor  brevis  minimi  digiti  muscles. 

The  Opponens  (Flexor  ossis  metacarpi)  minimi  digiti  (Fig.  234)  is  of  a  triangular 
form,  and  placed  immediately  beneath  the  preceding  muscles.  It  arises  from  the 
convexity  of  the  hook  of  the  unciform  bone  and  contiguous  portion  of  the  annular 
ligament ;  its  fibres  pass  downward  and  inward,  to  be  inserted  into  the  whole 
length  of  the  metacarpal  bone  of  the  little  finger,   along  its  ulnar  margin. 

Relations. — By  its  superfi  al  surface,  with  the  Flexor  brevis  and  Abductor 
minimi  digiti;  by  its  deep  %m  ~ :e,  with  the  Interossei  muscles  in  the  fourth 
metacarpal  space,  the  inetaci  >ne,  and  the  Flexor  tendons  of  the  little  finger. 


THE    ULNAR    REGION. 


407 


Nerves. — All   the  muscles  of  this  group  are  supplied  by  the  eighth  cervical 
nerve  through  the  ulnar  nerve. 


Fig.  243.— Muscles  of  the  left  hand.    Palmar  surface. 

Actions.— The  Abductor  minimi  digiti  abducts  the  little  finger  from  the  middle 
line  of  the  hand.  It  corresponds  to  a  dorsal  interosseous  muscle.  It  also  assists 
in  flexing  the  proximal  phalanx.  The  Flexor  brevis  minimi  digiti  abducts  the 
little  finger  from  the  middle  line  of  the  hand.  It  also  assists  m  Hexing  the 
proximal  phalanx.  The  Opponens  minimi  digiti  draws  forward  the  fitrh  meta- 
carpal bone,  so  as  to  deepen  the  hollow  of  the  palm.  The  Palmans  brevis  corrugates 
the  skin  on  the  inner  side  of  the  palm  of  the  hand. 


408  THE   MUSCLES   AND    FASCIA. 

13.  Middle  Palmar  Region. 

Lumbricales.  Interossei  dorsales. 

Interossei  palmares. 

The  Lumbricales  (Fig.  243)  are  four  small  fleshy  fasciculi,  accessories  to  the 
deep  Flexor  muscle.  They  arise  from  the  tendons  of  the  deep  Flexor :  the  first  and 
second,  from  the  radial  side  and  palmar  surface  of  the  tendons  of  the  index  and 
middle  Angers  respectively  ;  the  third,  from  the  contiguous  sides  of  the  tendons  of 
the  middle  and  ring  fingers ;  and  the  fourth,  from  the  contiguous  sides  of  the 
tendons  of  the  ring  and  little  fingers.  They  pass  to  the  radial  side  of  the  corre- 
sponding fingers,  and  opposite  the  metacarpo-phalangeal  articulation  each  tendon  is 
inserted  into  the  tendinous  expansion  of  the  Extensor  communis  digitorum, 
covering  the  dorsal  aspect  of  each  finger. 

The  Interossei  muscles  (Figs.  244,  245)  are  so  named  from  occupying  the 
intervals  between  the  metacarpal  bones,  and  are  divided  into  two  sets,  a  dorsal 
and  palmar. 

The  Dorsal  interossei  are  four  in  number,  larger  than  the  palmar,  and  occupy 
the  intervals  between  the.  metacarpal  bones.  They  are  bipenniform  muscles,  aris- 
ing by  two  heads  from  the  adjacent  sides  of  the  metacarpal  bones,  but  more  exten- 
sively from  the  metacarpal  bone  of  the  finger  into  which  the  muscle  is  inserted. 
They  are  inserted  into  the  bases  of  the  first  phalanges  and  into  the  aponeurosis  of 
the  common  Extensor  tendon.  Between  the  double  origin  of  each  of  these  mus- 
cles is  a  narrow  triangular  interval,  through  the  first  of  which  passes  the  radial 
artery  ;  through  the  other  three  passes  a  perforating  branch  from  the  deep  palmar 
arch. 

The  First  dorsal  interosseous  muscle,  or  Abductor  indicis,  is  larger  than  the 
others.  It  is  flat,  triangular  in  form,  and  arises  by  two  heads,  separated  by  a 
fibrous  arch,  for  the  passage  of  the  radial  artery  from  the  dorsum  to  the  palm  of 
the  hand.  The  outer  head  arises  from  the  upper  half  of  the  ulnar  border  of  the 
first  metacarpal  bone ;  the  inner  head,  from  almost  the  entire  length  of  the  radial 
border  of  the  second  metacarpal  bone ;  the  tendon  is  inserted  into  the  radial  side 
of  the  index  finger.  The  second  and  third  dorsal  interossei  are  inserted  into  the 
middle  finger,  the  former  into  its  radial,  the  latter  into  its  ulnar  side.  The  fourth 
is  inserted  into  the  ulnar  side  of  the  ring  finger. 

The  Palmar  interossei,  three  in  number,  are  smaller  than  the  Dorsal,  and  placed 
upon  the  palmar  surface  of  the  metacarpal  bones,  rather  than  between  them. 
They  arise  from  the  entire  length  of  the  metacarpal  bone  of  one  finger,  and  are 
inserted  into  the  side  of  the  base  of  the  first  phalanx  and  aponeurotic  expansion 
of  the  common  extensor  tendon  of  the  same  finger. 

The  first  arises  from  the  ulnar  side  of  the  second  metacarpal  bone,  and  is 
inserted  into  the  same  side  of  the  first  phalanx  of  the  index  finger.  The  second 
arises  from  the  radial  side  of  the  fourth  metacarpal  bone,  and  is  inserted  into  the 
same  side  of  the  ring  finger.  The  third  arises  from  the  radial  side  of  the  fifth 
metacarpal  bone,  and  is  inserted  into  the  same  side  of  the  little  finger.  From  this 
account  it  may  be  seen  that  each  finger  is  provided  with  two  Interossei  muscles, 
with  the  exception  of  the  little  finger,  in  which  the  Abductor  muscle  takes  the  place 
of  one  of  the  pair. 

Nerves. — The  two  outer  Lumbricales  are  supplied  by  the  sixth  cervical  nerve, 
through  the  third  and  fourth  digital  branches  of  the  median  nerve :  the  two 
inner  Lumbricales  and  all  the  Interossei  are  supplied  by  the  eighth  cervical 
nerve,  through  the  deep  palmar  branch  of  the  ulnar  nerve.  Brooks  states  that 
the  third  lumbrical  received  a  twig  from  the  median  in  twelve  out  of  twenty-one 
cases. 

Actions.--  -The  Palmar  interossei  muscles  adduct  the  fingers  to  an  .aginary 
line  drawn  ]  aally  through  the  centre  of  the  middle  finger;  and  the  Dorsal 

interossei  abduct  the  fingers  from  that  line.     In  addition  to  this,  tin  Interossei,  in 


SURFACE   FORM   OF    THE    UPPER    EXTREMITY. 


409 


conjunction  with  the  Lumbricales,  flex  the  first  phalanges  at  the  metacarpophalan- 
geal joints,  and  extend  the  second  and  third  phalanges  in  consequence  of  their 
insertion  into  the  expansion  of  the  extensor  tendons.  The  Extensor  communis 
digitorum  is  believed  to  act  almost  entirely  on  the  first  phalanges. 

SURFACE  FORM  OF  THE  UPPER  EXTREMITY. 

The  Pectoralis  major  largely  influences  surface  form  and  conceals  a  considerable  part  of  the 
thoracic  wall  in  front.  Its  sternal  origin  presents  a  festooned  border  which  bounds  and  deter- 
mines the  width  of  the  sternal  furrow.  Its  clavicular  origin  is  somewhat  depressed  and  flattened, 
and  between  the  two  portions  of  the  muscle  is  often  an  oblique  depression  which  differentiates 
the  one  from  the  other.  The  outer  margin  of  the  muscle  is  generally  well  marked  above,  and 
bounds  the  infraclavicular  fossa,  a  triangular  interval  which  separates  the  Pectoralis  major  from 
the  Deltoid.  It  gradually  becomes  less  marked  as  it  approaches  the  tendon  of  insertion,  and 
becomes  more  closely  blended  with  the  Deltoid  muscle.  The  lower  border  of  the  Pectoralis 
major  forms  the  rounded  anterior  axillary  fold,  and  corresponds  with  the  direction  of  the  fifth 
rib.  The  Pectoralis  minor  influences  surface  form.  When  the  arm  is  raised  its  lowest  slip  of 
origin  produces  a  local  fulness  just  below  the  border  of  the  anterior  fold  of  the  axilla,  and  so 
serves  to  break  the  sharp  line  of  the  lower  border  of  the  Pectoralis  major  muscle,  which  is 
produced  when  the  arm  is  in  this  position.  The  origin  of  the  Serratus  magnus  produces  a  very 
characteristic  surface  marking.  When  the  arm  is  raised  from  the  side  in  a  well-developed 
subject,  the  five  or  six  lower  serrations  are  plainly  discernible,  forming  a  zigzag  line,  caused  by 
the  series  of  digitations,  which  diminish  in  size  from  above  downward,  and  have  their  apices 
arranged  in  the  form  of  a  curve.  When  the  arm  is  lying  by  the  side,  the  first  serration  to 
appear,  at  the  lower  margin  of  the  Pectoralis  major,  is  the  one  attached  to  the  fifth  rib.  The 
Deltoid,  with  the  prominence  of  the  upper  extremity  of  the  humerus,  produces  the  rounded 
outline  of  the  shoulder.  It  is  rounder  and  fuller  in  front  than  behind,  where  it  presents  a 
somewhat  flattened  form.  Its  anterior  border,  above,  presents  a  rounded,  slightly  curved 
eminence,  which  bounds  externally  the  infraclavicular  fossa ;  below,  it  is  closely  united  with  the 


Fig.  244.— The  Dorsal  interossei  of  left  hand. 


Fig.  245 —The  Palmar  interossei  of  left  hand. 


Pectoralis  major.  Its  posterior  border  is  thin,  flattened,  and  scarcely  marked  above  ;  below,  it 
is  thicker  and  more  prominent.  When  the  muscle  is.  in  action,  the  middle  portion  becomes 
irregular,  presenting  alternate  longitudinal  elevations  and  depressions,  the  elevations  correspond- 
ing to  the  fleshy  portions,  the  depressions  to  the  tendinous  intersections  of  the  muscle,  lhe 
insertion  of  the  Deltoid  is  marked  by  a  depression  on  the  outer  side  of  the  middle  of  the  arm. 
Of  the  scapular  muscles,  the  only  one  which  materially  influences  surface  form  is  the  Teres 
major,  which  assists  the  Latissimus  dorsi  in  forming  the  thick,  rounded  told  of  the  posterior 
boundary  of  the  axilla.  When  the  arm  is  raised,  the  Coraco-brachiahs  reveals  itself  as  a  long, 
narrow  elevation  which  emerges  from  under  cover  of  the  anterior  fold  of  the  axilla  and  runs 
downward,  internal  to  the  shaft  of  the  humerus.     When  the  arm  is  hanging  by  the  side,  its 


410  THE   MUSCLES    AND    FASCIAE. 

front  and  inner  part  presents  the  prominence  of  the  Biceps,  bounded  on  either  side  by  an  inter- 
muscular depression.  This  muscle  determines  the  contour  of  the  front  of  the  arm,  and  extends 
from  the  anterior  margin  of  the  axilla  to  the  bend  of  the  elbow.  Its  upper  tendons  are  con- 
cealed by  the  Pectoralis  major  and  the  Deltoid,  and  its  lower  tendon  sinks  into  the  space  at  the 
bend  of  the  elbow.  When  the  muscle  is  in  a  state  of  complete  contraction — that  is  to  say, 
when  the  forearm  has  been  flexed  and  supinated — it  presents  a  rounded  convex  form,  bulged 
out  laterally,  and  its  length  is  diminished.  On  each  side  of  the  Biceps,  at  the  lower  part  of 
the  arm,  the  Brachialis  anticus  is  discernible.  On  the  outer  side  it  forms  a  narrow  eminence 
which  extends  some  distance  up  the  arm  along  the  border  of  the  Biceps.  On  the  inner  side  it 
shows  itself  only  as  a  little  fulness  just  above  the  elbow.  On  the  back  of  the  arm  the  long  head 
of  the  Triceps  may  be  seen  as  a  longitudinal  eminence  emerging  from  under  cover  of  the  Deltoid, 
and  gradually  merging  into  the  longitudinal  flattened  plane  of  the  tendon  of  the  muscle  on  the 
lower  part  of  the  back  of  the  arm.  The  tendon  of  insertion  of  the  muscle  extends  about  half- 
way up  the  back  of  the  arm,  where  it  forms  an  elongated  flattened  plane  when  the  muscle  is  in 
action.  Under  similar  conditions  the  surface  forms  produced  by  the  three  heads  of  the  muscle 
are  well  seen.  On  the  anterior  aspect  of  the  elbow  are  to  be  seen  two  muscular  elevations, 
one  on  each  side,  separated  above  and  converging  below  so  as  to  form  a  triangular  space. 
Of  these,  the  inner  elevation,  consisting  of  the  flexors  and  pronator,  forms  the  prominence 
along  the  inner  side  and  front  of  the  forearm.  It  is  a  fusiform  mass,  pointed  above  at  the 
internal  condyle  and  gradually  tapering  off  below.  The  Pronator  radii  teres,  the  innermost 
muscle  of  the  group,  forms  the  boundary  of  the  triangular  space  at  the  bend  of  the  elbow.  It 
is  shorter,  less  prominent,  and  more  oblique  than  the  outer  boundary.  The  most  prominent 
part  of  the  eminence  is  produced  by  the  Flexor  carpi  radialis,  the  muscle  next  in  order  on  the 
inner  side  of  the  preceding  one.  It  forms  a  rounded  prominence  above,  and  can  be  traced 
downward  to  its  tendon,  which  can  be  felt  lying  on  the  front  of  the  wrist,  nearer  to  the  radial 
than  to  the  ulnar  border,  and  to  the  inner  side  of  the  radial  artery.  The  Pahnaris  longus 
presents  no  surface  marking  above,  but  below  is  the  most  prominent  tendon  on  the  front  of  the 
wrist,  standing  out,  when  the  muscle  is  in  action,  as  a  sharp,  tense  cord  beneath  the  skin.  The 
Flexor  sublimis  digitorum  does  not  directly  influence  surface  form.  The  position  of  its  four 
tendons  on  the  front  of  the  lower  part  of  the  forearm  is  indicated  by  an  elongated  depression 
between  the  tendons  of  the  Palmaris  longus  and  the  Flexor  carpi  ulnaris.  The  Flexor  carpi 
ulnaris  occupies  a  small  part  of  the  posterior  surface  of  the  forearm,  and  is  separated  from  the 
extensor  and  supinator  group,  which  occupies  the  greater  part  of  this  surface,  by  the  ulnar 
furrow,  produced  by  the  subcutaneous  posterior  border  of  the  ulna.  Its  tendon  can  be  perceived 
along  the  ulnar  border  of  the  front  of  the  forearm,  and  is  most  marked  when  the  hand  is  flexed 
and  adducted.  The  deep  muscles  of  the  front  of  the  forearm  have  no  direct  influence  on  surface 
form.  The  external  group  of  muscles  of  the  forearm,  consisting  of  the  extensors  and  supi- 
nators, occupy  the  outer  and  a  considerable  portion  of  the  posterior  surface  of  this  region.  It 
has  a  fusiform  outline,  which  is  altogether  on  a  higher  level  than  the  pronato-flexor  group.  Its 
apex  emerges  from  between  the  Triceps  and  Brachialis  anticus  muscles  some  distance  above  the 
elbow-joint,  and  acquires  its  greatest  breadth  opposite  the  external  condyle,  and  thence  grad- 
ually shades  off  into  a  flattened  surface.  About  the  middle  of  the  forearm  it  divides  into  two 
longitudinal  eminences  which  diverge  from  each  other,  leaving  a  triangular  interval  between  them. 
The  outer  of  these  two  groups  of  muscles  consists  of  the  Supinator  longus  and  the  Extensor 
carpi  radialis  longior  et  brevior,  which  form  a  longitudinal  eminence  descending  from  the  exter- 
nal condylar  ridge  in  the  direction  of  the  styloid  process  of  the  radius.  The  other  and  more 
posterior  group  consists  of  the  Extensor  communis  digitorum.  the  Extensor  minimi  digiti,  and 
the  Extensor  carpi  ulnaris.  It  commences  above  as  a  tapering  form  at  the  external  condyle  of 
the  humerus,  and  is  separated  behind  at  its  upper  part  from  the  Anconeus  by  a  well-marked 
furrow,  and  below,  from  the  pronato-flexor  mass,  by  the  ulnar  furrow.  In  the  triangular  inter- 
val left  between  these  two  groups  the  extensors  of  the  thumb  and  index  finger  are  seen.  The 
only  two  muscles  of  this  region  which  require  special  mention  as  independently  influencing 
surface  form  are  the  Supinator  longus  and  the  Anconeus.  The  inner  border  of  the  Supinator 
longus  forms  the  outer  boundary  of  the  triangular  space  at  the  bend  of  the  elbow.  It  com- 
mences as  a  rounded  border  above  the  condyle,  and  is  longer,  less  oblique,  and  more  prominent 
than  the  inner  boundary.  Lower  down,  the  muscle  forms  a  full  fleshy  mass  on  the  outer  side  of 
the  upper  part  of  the  forearm,  and  below  tapers  into  a  tendon,  which  may  be  traced  down  to 
the  styloid  process  of  the  radius.  The  Anconeus  presents  a  well-marked  and  characteristic 
surface  form  in  the  shape  of  a  triangular,  slightly  elevated  surface,  immediately  external  to  the 
subcutaneous  posterior  surface  of  the  olecranon,  and  differentiated  from  the  common  extensor 
group  by  a  well-marked  oblique  longitudinal  depression.  The  upper  angle  of  the  triangle  corre- 
sponds to  the  external  condyle,  and  is  marked  by  a  depression  or  dimple  in  this  situation.  In 
the  interval  caused  by  the  divergence  from  each  other  of  the  two  groups  of  muscles  into 
which  the  extensor  and  supinator  group  is  divided  at  the  lower  part  of  the  forearm  an  oblique 
elongated  eminence  is  seen,  caused  by  the  emergence  of  two  of  the  extensors  of  the  thumb 
from  their  deep  origin  at  the  back  of  the  forearm.  This  eminence,  full  above  and  becoming 
flattened  out  and  partially  subdivided  below,  runs  downward  and  outward  over  the  back 
and  outer  surface  of  the  radius  to  the  outer  side  of  the  wrist-joint,  where  it  forms  a  ridge, 
especially  marked  when  the  thumb  is  extended,  which  passes  onward  to  the  posterior  aspect  of 
the  thumb.  The  tendons  of  most  of  the  extensor  muscles  are  to  be  seen  and  felt  at  the  level 
of  the  wrist-joint,     Most  externally  are  the  tendons  of  the  Extensor  ossis  metacarpi  poilicis  and 


SURGICAL    ANATOMY   OF    THE    UPPER    EXTREMITY.        411 

the  Extensor  brevis  pollieis,  forming  a  vertical  ridge  over  the  outer  side  of  the  joint  from  the 
styloid  process  of  the  radius  to  the  thumb.  Internal  to  this  is  the  oblique  ridge  produced  by 
the  tendon  of  the  Extensor  longus  pollieis,  very  noticeable  when  the  muscle  is  in  action.  The 
Extensor  carpi  radialis  longior  is  scarcely  to  be  felt,  but  the  Extensor  carpi  radialis  brevior  can 
be  distinctly  perceived  as  a  vertical  ridge  emerging  from  under  the  inner  border  of  the  tendon 
of  the  Extensor  longus  pollieis,  when  the  hand  is  forcibly  extended  at  the  wrist.  Internal  to 
this,  again,  can  be  felt  the  tendons  of  the  Extensor  indicis,  Extensor  communis  digitorum,  and 
Extensor  minimi  digiti ;  the  latter  tendon  being  separated  from  those  of  the  common  extensor 
by  a  slight  furrow.  The  muscles  of  the  hand  are  principally  concerned,  as  far  as  regards  sur- 
face-form, in  producing  the  thenar  and  hypothenar  eminences,  and  individually  are  not  to  be 
distinguished,  on  the  surface,  from  each  other.  The  Adductor  transversus  pollieis  is,  however, 
an  exception  to  this ;  its  anterior  border  gives  rise  to  a  ridge  across  the  web  of  skin  connecting 
the  thumb  to  the  rest  of  the  hand.  The  thenar  eminence  is  much  larger  and  rounder  than  the 
hypothenar  one,  which  presents  a  longer  and  narrower  eminence  along  the  ulnar  side  of  the 
hand.  When  the  Palmaris  brevis  is  in  action  it  produces  a  wrinkling  of  the  skin  over  the  hypo- 
thenar eminence,  and  a  deep  dimple  on  the  ulnar  border  of  the  hand.  The  anterior  extremities 
of  the  Lumbrical  muscles  help  to  produce  the  soft  eminences  just  behind  the  clefts  of  the  fingers, 
separated  from  each  other  by  depressions  corresponding  to  the  flexor  tendons  in  their  sheaths. 
Between  the  thenar  and  hypothenar  eminences,  at  the  wrist-joint,  is  a  slight  groove  or  depression, 
widening  out  as  it  approaches  the  fingers;  beneath  this  we  have  the  strong  central  part  of  the 
palmar  fascia.  Here  we  have  some  furrows,  which  are  pretty  constant  in  their  arrangement, 
and  bear  some  resemblance  to  the  letter  M .  One  of  these  furrows  passes  obliquely  outward 
from  the  groove  between  the  thenar  and  hypothenar  regions  near  the  wrist  to  the  head  of  the 
metacarpal  bone  of  the  index  finger.  A  second  passes  inward,  with  a  slight  inclination  upward, 
from  the  termination  of  the  first  to  the  ulnar  side  of  the  hand.  A  third  runs  nearly  parallel 
with  the  second  and  about  three-quarters  of  an  inch  below  it.  Lastly,  crossing  these  two  latter 
furrows,  is  an  oblique  furrow  parallel  with  the  first.  The  skin  of  the  palm  of  the  hand  differs 
considerably  from  that  of  the  forearm.  At  the  wrist  it  suddenly  becomes  hard  and  dense,  and 
covered  with  a  thick  layer  of  cuticle.  The  skin  in  the  thenar  region  presents  these  characteris- 
tics less  than  elsewhere.  In  spite  of  this  hardness  and  density,  the  skin  of  the  palm  is  exceed- 
ingly sensitive  and  very  vascular.  It  is  destitute  of  hair,  and  no  sebaceous  follicles  have  been 
found  in  this  region.  Over  the  fingers  the  skin  again  becomes  thinner,  especially  at  the  flexures 
of  the  joints,  and  over  the  terminal  phalanges  it  is  thrown  into  numerous  ridges  in  consequence 
of  the  arrangement  of  the  papillae  in  it.  These  ridges  form,  in  different  individuals,  dis- 
tinctive and  permanent  patterns,  which  may  be  used  for  purposes  of  identification.  The  super- 
ficial fascia  in  the  palm  is  made  up  of  dense  fibro-fatty  tissue.  This  tissue  binds  down  the  skin 
so  firmly  to  the  deep  palmar  fascia  that  very  little  movement  is  permitted  between  the  two. 
On  the  back  of  the  hand  the  Dorsal  interossei  produce  elongated  swellings  between  the  meta- 
carpal bones.  The  first  dorsal  interosseous  (Abductor  indicis),  when  the  thumb  is  closely  ad- 
ducted  to  the  hand,  forms  a  prominent  fusiform  bulging ;  the  other  interossei  are  not  so- 
marked. 


SURGICAL  ANATOMY  OF  THE  UPPER  EXTREMITY. 

The  student,  having  completed  the  dissection  of  the  muscles  of  the  upper  extremity,  should 
consider  the  effects  likely  to  be  produced  by  the  action  of  the  various  muscles  in  fracture  of  the 
bones. 

In  considering  the  actions  of  the  various  muscles  upon  fractures  of  the  upper  extremity,  the 
most  common  forms  of  injmy  have  been  selected  both  for  illustration  and  description. 

Fracture  of  the  middle  of  the  clavicle  (Fig.  246)  is  always  attended  with  considerable  dis- 
placement;  the  inner  end  of  the  outer  fragment  is  displaced  inward  and  backward,  while  the 
outer  end  of  the  same  fragment  is  rotated  forward.  The  whole  outer  fragment  is  somewhat  de- 
pressed. 

The  displacement  is  produced  as  follows  :  inward,  by  the  muscles  passing  from  the  chest  to 
the  outer  fragment  of  the  clavicle,  to  the  scapula,  and  to  the  humerus,  viz..  the  Subclavius  and 
the  Pectoralis  minor,  and,  to  a  less  extent,  the  Pectoralis  major  and  the  Latissimus  dorsi :  back- 
ward, in  consequence  of  the  rotation  of  the  outer  fragment.  The  Serratus  magnus  causes  the 
scapula  to  rotate  on  the  wall  of  the  chest ;  this  carries  the  acromion  and  outer  end  of  the  outer 
fragment  of  the  clavicle  forward  and  causes  the  piece  of  bone  to  rotate  round  a  vertical  axis 
through  its  centre,  and  so  carries  the  inner  end  of  the  outer  portion  backward.  The  depression 
of  the  whole  outer  fragment  is  produced  by  the  weight  of  the  arm  and  by  the  contraction  of  the 
Deltoid.  The  outer  end  of  the  inner  fragment  appears  to  be  elevated,  the  skin  being  drawn 
tensely  over  it ;  this  is  owing  to  the  depression  of  the  outer  fragment,  as  the  inner  fragment  is 
usually  kept  fixed  by  the  costo-clavicular  ligament  and  by  the  antagonism  between  the  Sterno- 
mastoid  and  Pectoralis  major  muscles.  But  it  may  be  raised  by  an  unusually  strong  Sterno-mas- 
toid,  or  by  the  inner  end  of  the  outer  fragment  getting  below  and  behind  it.  The  causes  <>f  dis- 
placement, having  been  ascertained,  it  is  easy  to  apply  the  appropriate  treatment.  The  outer 
fragment  is  to  be  drawn  outward,  and,  together  with  the  scapula,  raised  upward  to  a  level  with 
the  inner  fragment,  and  retained  in  that  position. 


412 


THE   MUSCLES   AND    FASCIAE. 


Fig.  246.— Fracture  of  the  middle  of  the 
clavicle. 


In  fracture  of  the  acromial  end  of  the  clavicle.,  between  the  conoid  and  trapezoid  ligaments, 
only  slight  displacement  occurs,  as  these  ligaments,  from  their  oblique  insertion,  serve  to  hold 

both  portions  of  the  bone  in  apposition.  Fracture,  also, 
of  the  sternal  end,  internal  to  the  costo-clavicular  liga- 
ment, is  attended  with  only  slight  displacement,  this 
ligament  serving  to  retain  the  fragments  in  close  appo- 
sition. 

Fracture  of  the  acromion  process  usually  arises  from 
violence  applied  to  the  upper  and  outer  part  of  the 
shoulder  ;  it  is  generally  known  by  the  rotundity  of  the 
shoulder  being  lost,  from  the  Deltoid  drawing  the  frac- 
tured portion  downward  and  forward ;  and  the  displace- 
ment may  easily  be  discovered  by  tracing  the  margin  of 
the  clavicle  outward,  when  the  fragment  will  be  found 
resting  on  the  front  and  upper  part  of  the  head  of  the 
humerus.  In  order  to  relax  the  anterior  and  outer 
fibres  of  the  Deltoid  (the  opposing  muscle),  the  arm 
should  be  drawn  forward  across  the  chest  and  the  elbow 
well  raised,  so  that  the  head  of  the  bone  may  press  the 
acromion  process  upward  and  retain  it  in  its  position. 

Fracture  of  the  coracoid  process  is  an  extremery  rare 
accident,  and  is  usually  caused  by  a  sharp  blow  on  the 
point  of  the  shoulder.  Displacement  is  here  produced 
by  the  combined  actions  of  the  Pectoralis  minor,  short 
head  of  the  Biceps,  and  Coraco-brachialis,  the  former 
muscle  drawing  the  fragment  inward,  and  the  latter 
directly  downward,  the  amount  of  displacement  being 
limited  by  the  connection  of  this  process  to  the  acromion 
by  means  of  the  coraco-acromial  ligament.  In  many 
cases  there  appears  to  have  been  little  or  no  displace- 
ment, from  the  fact  that  the  coraco-clavicular  ligament 
has  remained  intact,  and  has  kept  the  separated  fragment  from  displacement.  In  order  to  re- 
lax these  muscles  and  replace  the  fragments  in  close  apposition,  the  forearm  should  be  flexed  so 
as  to  relax  the  Biceps,  and  the  arm  drawn  forward  and  inward  across  the  chest,  so  as  to  relax 
the  Coraco-brachialis  ;  the  humerus  should  then  be  pushed  upward  against  the  coraco-acromial 
ligament,  and  the  arm  retained  in  that  position. 

Fracture  of  the  surgical  neck  of  the  humerus  (Fig.  247)  is  very  common,  is  attended  with 
considerable  displacement,  and  its  appearances  correspond  somewhat  with  those  of  dislocation 
of  the  head  of  the  humerus  into  the  axilla.  The  upper  fragment  is  slightly  elevated  under  the 
coraco-acromial  ligament  by  the  muscles  attached  to  the  greater  and  lesser  tuberosities ;  the 
lower  fragment  is  drawn  inward  by  the  Pectoralis  major,  Latissimus  dorsi,  and  Teres  major ;  and 
the  humerus  is  thrown  obliquely  outward  from  the  side  by  the  Deltoid,  and  occasionally  elevated 
so  as  to  cause  the  upper  end  of  the  lower  fragment  to  project  beneath  and  in  front  of  the  cora- 
coid process.  The  deformity  is  reduced  by  fixing  the  shoulder, 
and  drawing  the  arm  outward  and  downward.  To  counteract 
the  opposing  muscles,  and  to  keep  the  fragments  in  position,  a 
small  conical-shaped  pad  should  be  placed  in  the  axilla,  and  the 
arm  bandaged  to  the  side  by  a  broad  roller  passed  round  the 
chest,  in  such  a  manner  that  the  elbow  is  carried  slightly  for- 
ward, so  as  to  throw  the  upper  end  of  the  lower  fragment 
backward  and  outward  toward  the  head  of  the  bone.  The 
whole  is  then  covered  with  a  carefully  moulded  gutta-percha  or 
poroplastic  shoulder  cap. 

In  fracture  of  the  shaft  of  the  humerus  below  the  insertion 
of  the  Pectoralis  major,  Latissimus  dorsi,  and  Teres  major,  and 
above  the  insertion  of  the  Deltoid,  there  is  also  considerable 
deformity,  the  upper  fragment  being  drawn  inward  by  the 
first-mentioned  muscles,  and  the  lower  fragment  upward  and 
outward  by  the  Deltoid,  producing  shortening  of  the  limb  and 
a  considerable  prominence  at  the  seat  of  fracture,  from  the 
fractured  ends  of  the  bone  riding  over  one  another,  especially 
if  the  fracture  takes  place  in  an  oblique  direction.  The  frag- 
ments may  be  brought  into  apposition  by  extension  from  the 
Fig.  247.— Fracture  of  the  surgical  elbow,  and  retained  in  that  position  by  adopting  the  same 
neck  of  the  humerus.  means  as  in  the  preceding  injury. 

In  fractures  of  the  shaft  of  the  humerus  immediately  below 
the  insertion  of  the  Deltoid,  the  amount  of  deformity  depends  greatly  upon  the  direction  of  the 
fracture.  If  it  occurs  in  a  transverse  direction,  only  slight  displacement  takes  place,  the  upper 
fragment  being  drawn  a  little  forward ;  but  in  oblique  fracture  the  combined  actions  of  the 
Biceps  and  Brachialis  anticus  muscles  in  front  and  the  Triceps  behind  draw  upward  the  lower 
fragment,  causing  it  to  glide  over  the  upper  fragment,  either  backward  or  forward,  accord- 


SURGICAL    ANATOMY   OF    THE    UPPER    EXTREMITY. 


413 


ing  to  the  direction  of  the  fracture.  Simple  extension  reduces  the  deformity,  and  the 
application  of  a  shoulder  cap  and  splints  to  the  arm  will  retain  the  fragments  in  apposition. 
Care  should  be  taken  not  to  raise  the  elbow,  but  the  forearm  and  hand  may  be  supported  in  a 
sling. 

Fracture  of  the  humerus  (Fig.  24S)  immediately  above  the  condyles  deserves  very  attentive 
consideration,  as  the  general  appearances  correspond  somewhat  with  those  produced  by  sep- 
aration of  the  epiphysis  of  the  humerus,  and  with  those  of  dislocation  of  the  radius  and  ulna 
backward.  If  the  direction  of  the  fracture  is  oblique  from  above,  downward  and  forward,  the 
lower  fragment  is  drawn  upward  by  the  Brachialis  anticus  and  Biceps  in  front  and  the  Triceps 
behind ;  and  at  the  same  time  is  drawn  backward  behind  the  upper  fragment  of  the  Triceps. 
This  injury  may  be  diagnosed  from  dislocation  by  the  increased  mobility  in  fracture,  the  exist- 
ence of  crepitus,  and  the  fact  of  the  deformity  being  remedied  by  extension,  on  the  discontin- 
uance of  which  it  is  reproduced.  The  age  of  the  patient  is  of  importance  in  distinguishing  this 
form  of  injury  from  separation  of  the  epiphysis.  If  fracture  occurs  in  the  opposite  direction  to 
that  shown  in  Fig.  248,  the  lower  fragment  is  drawn  upward  and  forward,  causing  a  consider- 
able prominence  in  front,  and  the  upper  fragment  projects  backward  beneath  the  tendon  of  the 
Triceps  muscle. 

Fracture  of  the  olecranon  process  (Fig.  249)  is  a  frequent  accident.  The  detached  fragment 
is  displaced  upward,  by  the  action  of  the  Triceps  muscle,  from  half  an  inch  to  two  inches ;  the 


Fig.  248.— Fracture  of  the  humerus  above 
the  condyles. 


Fig.  249. — Fracture  of  the  olecranon. 


prominence  of  the  elbow  is  consequently  lost,  and  a  deep  hollow  is  felt  at  the  back  part  of  the 
joint,  which  is  much  increased  on  flexing  the  limb.  The  patient  at  the  same  time  loses,  more 
or  less,  the  power  of  extending  the  forearm.  The  treatment  consists  in  relaxing  the  Triceps  by 
extending  the  limb,  and  retaining  it  in  the  extended  position  by  means  of  a  long  straight  splint 
applied  to  the  front  of  the  arm  ;  the  fragments  are  thus  brought  into  close  apposition,  and  may 
be  further  approximated  by  drawing  down  the  upper  fragment.  Union  is  generally  liga- 
mentous. 

Fracture  of  the  neclt,  of  the  radius  is  an  exceedingly  rare  accident,  and  is  generally  caused 
by  direct  violence.  Its  diagnosis  is  somewhat  obscure,  on  account  of  the  slight  deformity  visible, 
the  injured  part  being  surrounded  by  a  large  number  of  muscles ;  but  the  movements  of  prona- 
tion and  supination  are  entirely  lost.  The  upper  fragment  is  drawn  outward  by  the  Supinator 
brevis,  its  extent  of  displacement  being  limited  by  the  attachment  of  the  orbicular  ligament. 
The  lower  fragment  is  drawn  forward  and  slightly  upward  by  the  Biceps,  and  inward  by  the 
Pronator  radii  teres,  its  displacement  forward  and  upward  being  counteracted  _  in  some  degree 
by  the  Supinator  brevis.  The  treatment  essentially  consists  in  relaxing  the  Biceps.  Supinator 
brevis,  and  Pronator  radii  teres  muscles  by  flexing  the  forearm,  and  placing  it  in  a  position  mid- 
way between  pronation  and  supination,  extension  having  been  previously  made  so  as  to  bring 
the  parts  in  apposition. 

In  fracture  of  the  radius  below  the  insertion  of  the  Biceps,  but  above  the  insertion  of  the 
Pronator  radii  teres,  the  upper  fragment  is  strongly  supinated  by  the  Biceps  and  Supinator 
brevis,  and  at  the  same  time  drawnforward  and  flexed  by  the  Biceps;  the  lower  fragment  is 
pronated  and  drawn  inward  toward  the  ulna  by  the  pronators.  Thus  there  is  extreme  dis- 
placement with  very  little  deformity.     In  treating  such  a  fracture  the  arm  must  be  put  up  in 


414 


THE   MUSCLES  AND    FASCIA. 


Fig.  250.— Fracture  of  the  shaft  of  the  radius. 


a  position  of  supination,  otherwise  union  will  take  place  with  great  impairment  of  the  move- 
ments of  the  hand.     In  fractures  of  the  radius  below  the  insertion  of  the  Pronator  radii  teres 

(Fig.  250),  the  upper  fragment  is  drawn  up- 
ward by  the  Biceps  and  inward  by  the  Pro- 
nator radii  teres,  holding  a  position  midway 
between  pronation  and  supination,  and  a  de- 
gree of  fulness  in  the  upper  half  of  the  fore- 
arm is  thus  produced :  the  lower  fragment  is 
drawn  downward  and  inward  toward  the  ulna 
by  the  Pronator  quadratus.  and  thrown  into  a 
state  of  pronation  by  the  same  muscle  ;  at  the 
same  time,  the  Supinator  longus.  by  elevating 
the  styloid  process,  into  which  it  is  inserted, 
will  serve  to  depress  the  upper  end  of  the 
lower  fragment  still  more  toward  the  ulna. 
In  order  to  relax  the  opposing  muscles  the 
forearm  should  be  bent,  and  the  limb  placed  in  a  position  midway  between  pronation  and 
supination ;  the  fracture  is  then  easily  reduced  by  extension  from  the  wrist  and  elbow :  well- 
padded  splints  should  be  applied  on  both  sides  of  the  forearm  from  the  elbow  to  the  wrist ; 
the  hand  being  allowed  to  fall,  will,  by  its  own  weight,  counteract  the  action  of  the  Pronator 
quadratus  and  Supinator  longus,  and  elevate  the  lower  fragment  to  the  level  of  the  upper 
one. 

In  fracture  of  the  shaft  of  the  ulna  the  upper  fragment  retains  its  usual  position,  but  the 
lower  fragment  is  drawn  outward  toward  the  radius  Toy  the  Pronator  quadratus.  producing  a 
well-marked  depression  at  the  seat  of  fracture  and  some  fulness  on  the  dorsal  and  palmar  sur- 
faces of  the  forearm.  The  fracture  is  easily  reduced  by  extension  from  the  wrist  and  forearm. 
The  forearm  should  be  flexed,  and  placed  in  a  position  midway  between  pronation  and  supina- 
tion, and  well-padded  splints  applied  from  the  elbow  to  the  ends  of  the  fingers. 

In  fracture  of  the  shafts  of  the  radius  and  ulna  together  the  lower  fragments  are  drawn 
upward,  sometimes  forward,  sometimes  backward,  according  to  the  direction  of  the  fracture,  by 
the  combined  actions  of  the  Flexor  and  Extensor  muscles,  producing  a  degree  of  fulness  on  the 
dorsal  or  palmar  surface  of  the  forearm  ;  at  the  same  time  the  two  fragments  are  drawn  into 
contact  by  the  Pronator  quadratus,  the  radius  being  in  a  state  of  pronation :  the  upper  frag- 
ment of  the  radius  is  drawn  upward  and  inward  by  the  Biceps  and  Pronator  radii  teres  to  a 
higher  level  than  the  ulna ;  the  upper  portion  of  the  ulna  is  slightly  elevated  by  the  Brachialis 
anticus.  The  fracture  may  be  reduced  by  extension  from  the  wrist  and  elbow,  and  the  forearm 
should  be  placed  in  the  same  position  as  in  fracture  of  the  ulna. 

In  fracture  of  the  lower  end  of  the  radius  (Fig.  251 )  the  displacement  which  is  produced 
is-very  considerable,  and  bears  some  resemblance  to  dislocation  of  the  carpus  backward,  from 
which  it  should  be  carefully  distinguished.  The  lower  fragment  is  displaced  backward  and 
upward,  but  this  displacement  is  probably  due  to  the  force  of  the  blow  driving  the  portion  of 
the  bone  into  this  position  and  not  to  any  muscular  influence.  The  upper  fragment  projects 
forward,  often  lacerating  the  substance  of  the  Pronator  quadratus,  and  is  drawn  by  this  muscle 
into  close  contact  with  the  lower  end  of  the  ulna,  causing  a  projection  on  the  anterior  surface  of 


Fig.  251. — Fracture  of  the  lower  end  of  the  radius. 


the  forearm,  immediately  above  the  carpus,  from  the  flexor  tendons  being  thrust  forward.  This 
fracture  may  be  distinguished  from  dislocation  by  the  deformity  being  removed  on  making  suf- 
ficient extension,  when  crepitus  may  be  occasionally  detected ;  at  the  same  time,  on  extension 
being  discontinued,  the  parts  immediately  resume  their  deformed  appearance  (see  also  page 
128).  The  age  of  the  patient  will  also  assist  in  determining  whether  the  injury  is  fracture  or 
separation  of  the  epiphysis.  The  treatment  consists  in  flexing  the  forearm,  and  making  power- 
ful extension  from  the  wrist  and  elbow,  depressing  at  the  same  time  the  radial  side  of  the  hand, 
and  retaining  the  parts  in  that  position  by  well-padded  pistol-shaped  splints. 


THE   ILIAC   BEG  ION. 


415 


MUSCLES  AND  FASCLE  OF  THE  LOWER  EXTREMITY. 

The  Muscles  of  the  Lower  Extremity  are  subdivided  into  groups  correspond- 
ing with  the  different  regions  of  the  limb. 

I.  Iliac  Region. 

Psoas  magnus. 
Psoas  parvus,  i 
Iliacus. 

II.  Thigh.  ^ 

1.  Anterior  Femoral  Region. 

Tensor  fasciae  femoris. 
Sartorius. 
C  Rectus. 
■Quadriceps  J  Vastus  externus. 
extensor     j  Vastus  internus. 
(^  Crureus. 
Subcrureus. 

2.  Internal  Femoral  Region. 

Gracilis. 
Pectineus. 
Adductor  longus. 
Adductor  brevis. 
Adductor  magnus. 

3.    Gluteal  Region. 

Gluteus  maximus. 
Gluteus  medius. 
Gluteus  minimus. 
Pyriformis. 
Obturator  internus. 
Gemellus  superior.    . 
Gemellus  inferior. 
Quadratus  femoris. 
Obturator  externus. 

4.  Posterior  Femoral 
Region. 
Biceps. 

Semitendinosus. 
Semimembranosus. 

III.  Leg. 

5.   Anterior  Tibio-fibular 
Region. 

Tibialis  anticus. 


Extensor  proprius  hallucis. 
Extensor  longus  digitorum. 
Peroneus  tertius. 

6.  Posterior  Tibio-fibular  Region. 
Superficial  Layer. 

Gastrocnemius. 

Soleus. 

Plantaris. 

Deep  Layer. 

Popliteus. 

Flexor  longus  hallucis. 
Flexor  longus  digitorum. 
Tibialis  posticus. 

7.  Fibular  Region. 

Peroneus  longus. 
Peroneus  brevis. 

IV.  Foot. 

8.  Dorsal  Region. 
Extensor  brevis  digitorum. 

9.  Plantar  Region. 

First  Layer. 

Abductor  hallucis. 
Flexor  brevis  digitorum. 
Abductor  minimi  digiti. 

Second  Layer. 

Flexor  accessorius. 
Lumbricales. 

Third  Layer. 

Flexor  brevis  hallucis. 
Adductor  obliquus  hallucis. 
Flexor  brevis  minimi  digiti. 
Adductor  transversus  hallucis. 

Fourth  Layer. 
The  Interossei. 


I.  MUSCLES  AND  FASCLE  OF  THE  ILIAC  REGION. 

Psoas  magnus.  Psoas  parvus.  Iliacus. 

Dissection. — No  detailed  description  is  required  for  the  dissection  of  these  muscles.  On 
the  removal  of  the  viscera  from  the  abdomen  they  are  exposed,  covered  by  the  peritoneum  and 
a  thin  layer  of  fascia,  the  iliac  fascia. 

The  iliac  fascia1  is  the  aponeurotic  layer  which  lines  the  back  part  of  the 
abdominal  cavity,  and  covers  the  Psoas  and  Iliacus  muscles  throughout  their  whole 
xThe  student  must  not  confound  this  fascia  with  the  iliac  portion  of  the  fascia  lata  (see  p.  420). 


416  THE   MUSCLES   AND    FASCIJE. 

extent.  It  is  thin  above,  and  becomes  gradually  thicker  below  as  it  approaches  the 
crural  arch. 

The  i  covering  the  Psoas  is  attached,  above,  to  the  ligamentum  arcuatum 

internun  ternally,  by  a  series  of  arched  processes  to   the  intervertebral  sub- 

stances Eftnd  i  .eminent  margins  of  the  bodies  of  the  vertebrae,  and  to  the  upper  part 
of  the  sacrum,  the  intervals  so  left,  opposite  the  constricted  portions  of  the  bodies, 
transmitting  the  lumbar  arteries  and  veins  and  filaments  of  the  sympathetic  cord. 
Externally,  above  the  crest  of  the  ilium,  this  portion  of  the  iliac  fascia  is  continu- 
ous with  the  anterior  lamella  of  the  lumbar  fascia  (see  page  842),  but  below  the 
crest  of  the  ilium  it  is  continuous  with  the  fascia  covering  the  Iliacus. 

The  portion  investing  the  Iliacus  is  connected  externally  to  the  whole  length 
of  the  inner  border  of  the  crest  of  the  ilium,  and  internally  to  the  brim  of  the  true 
pelvis,  where  it  is  continuous  with  the  periosteum  ;  and  at  the  ilio-pectineal  emi- 
nence it  receives  the  tendon  of  insertion  of  the  Psoas  parvus,  when  that  muscle 
exists.  External  to  the  femoral  vessels,  this  fascia  is  intimately  connected  to  the 
posterior  margin  of  Poupart's  ligament,  and  is  continuous  with  the  fascia  transver- 
salis.  Immediately  to  the  outer  side  of  the  femoral  vessels  the  fascia  iliaca  is  pro- 
longed backward  and  inward  from  Poupart's  ligament  as  a  band,  the  ilio-pectineal 
ligament,  which  is  attached  to  the  ilio-pectineal  eminence.  This  ligament  divides 
the  space  between  Poupart's  ligament  and  the  innominate  bone  into  two  parts,  the 
inner  of  which  transmits  the  femoral  vessels,  the  outer  the  ilio-psoas  and  the  anterior 
crural  nerve  (Fig.  166).  Internal  to  the  vessels  the  iliac  fascia  is  attached  to  the 
ilio-pectineal  line  behind  the  conjoined  tendon,  where  it  is  again  continuous  with  the 
transversalis  fascia ;  and,  corresponding  to  the  point  where  the  femoral  vessels  pass 
into  the  thigh,  this  fascia  descends  behind  them,  forming  the  posterior  wall  of  the 
femoral  sheath.  This  portion  of  the  iliac  fascia  which  passes  behind  the  femoral 
vessels  is  also  attached  to  the  ilio-pectineal  line  beyond  the  limits  of  the  attach- 
ment of  the  conjoined  tendon;  at  this  part  it  is  continuous  with  the  pubic  portion 
of  the  fascia  lata  of  the  thigh.  The  external  iliac  vessels  lie  in  front  of  the  iliac 
fascia,  but  all  the  branches  of  the  lumbar  plexus  behind  it ;  it  is  separated  from 
the  peritoneum  by  a  quantity  of  loose  areolar  tissue. 

The  Psoas  magnus  (Fig.  253)  is  a  long  fusiform  muscle  placed  on  the  side  of 
the  lumbar  region  of  the  spine  and  margin  of  the  pelvis.  It  arises  from  the  front 
of  the  bases  and  lower  borders  of  the  transverse  processes  of  the  lumbar  vertebrae 
by  five  fleshy  slips ;  also  from  the  sides  of  the  bodies  and  the  corresponding  inter- 
vertebral substances  of  the  last  dorsal  and  all  the  lumbar  vertebrae.  The  muscle 
is  connected  to  the  bodies  of  the  vertebrae  by  five  slips ;  each  slip  is  attached  to 
the  upper  and  lower  margins  of  two  vertebrae,  and  to  the  intervertebral  substance 
between  them,  the  slips  themselves  being  connected  by  the  tendinous  arches  which 
extend  across  the  constricted  part  of  the  bodies,  and  beneath  which  pass  the  lumbar 
arteries  and  veins  and  filaments  of  the  sympathetic  cord.  These  tendinous  arches 
also  give  origin  to  muscular  fibres,  and  protect  the  blood-vessels  and  nerves  from 
pressure  during  the  action  of  the  muscle.  The  first  slip  is  attached  to  the  con- 
tiguous margins  of  the  last  dxtfaal—ajnd  first^  lumbar  vertebrae ;  the  last  to  the 
contiguous  margins  of  the  fourth  and  fifth  lumbar  vertebrae,  and  to  the  interver- 
tebral substance.  From  these  points  the  muscle  passes  down  across  the  brim  of 
the  pelvis,  and,  diminishing  gradually  in  size,  passes  beneath  Poupart's  ligament, 
and  terminates  in  a  tendon  which,  after  receiving  nearly  the  whole  of  the  fibres  of 
the  Iliacus,  is  inserted  into  the  lesser  trochanter  of  the  femur. 

Relations. — In  the  lumbar  region  :  by  its  anterior  surface,  which  is  placed 
behind  the  peritoneum,  with  the  iliac  fascia,  the  ligamentum  arcuatum  internum, 
the  kidney,  Psoas  parvus,  renal  vessels,  ureter,  spermatic  vessels,  genito-crural 
nerve,  and  the  colon  ;  by  its  posterior  surface,  with  the  transverse  prqeesses  of  the 
lumbar  vertebrae  and  the  Quadratus  lumborum,  from  which  it  is  separated  by  the 
anterior  lamella  of  the  lumbar  fascia.  The  lumbar  plexus  is  situated  in  the 
posterior  part  of  the  substance  of  the  muscle.  By  its  inner  side  the  muscle  is  in 
relation  with  the  bodies  of  the  lumbar  vertebrae,  the  lumbar  arteries,  the  ganglia 


THE   ILIAC   REGION.  417 

of  the  sympathetic  nerve,  and  their  branches  of  communication  with  the  spinal 
nerves  ;  the  lumbar  glands ;  the  vena  cava  inferior  on  the  right  and  the  aorta  on 
the  left  side,  and  along  the  brim  of  the  pelvis  with  the  external  iliac  artery.  In 
the  thigh  it  is  in  relation,  in  front,  with  the  fascia  lata ;  behind,  with  the  capsular 
ligament  of  the  hip,  from  which  it  is  separated  by  a  synovial  bursa,  which 
frequently  communicates  with  the  cavity  of  the  joint  through  an  opening  of 
variable  size ;  by  its  inner  border,  with  the  Pectineus  and  internal  circumflex 
artery,  and  also  with  the  femoral  artery,  which  slightly  overlaps  it :  by  its  outer 
border,  with  the  anterior  crural  nerve  and  Iliacus  muscle. 

The  Psoas  parvus  is  a  long  slender  muscle  placed  in  front  of  threrPsoas  magnus. 
It  arises  from  the  sides  of  the  bodies  of  the  last  dorsal  and  first  lumbar  vertebrae 
and  from  the  intervertabrarhmbstance  between  them.  "It  forms  a  sruarbflat  muscular 
bundle,  which  terminates  in  a  long  flat  tendon  inserted  into  the  ilio-pectineal 
eminence,  and,  by  its  outer  border,  into  the  iliac  fascia.  This  muscle  is  often 
absent,   and,  according  to  Cruveilhier,   sometimes  double. 

Relations. — It  is  covered  by  the  peritoneum,  and,  at  its  origin,  by  the  ligamentum 
arcuatum  internum ;  it  rests  on  the  Psoas  magnus. 

The  Iliacus  is  a  flat,  triangular  muscle  which  fills  up  the  whole  of  the  iliac 
fossa.  It  arises  from  the  upper  two-thirds  of  this  fossa  and  from  the  inner  margin 
of  the  crest  of  the  ilium ;  behind,  from  the  ilio-lumbar  ligament  and  base  of  the 
sacrum  ;  in  front,  from  the  anterior  superior  and  anterior  inferior  spinous  processes 
of  the  ilium,  from  the  notch  between  them,  and  by  a  few  fibres  from  the  capsule 
of  the  hip-joint.  The  fibres  converge  to  be  inserted  into  the  outer  side  of  the 
tendon  of  the  Psoas,  some  of  them  being  prolonged  on  to  the  shaft  of  the  femur 
for  about  an  inch  below  and  in  front  of  the  lesser  trochanter.1 

Relations. —  Within  the  abdomen  :  by  its  anterior  surface,  with  the  iliac  fascia, 
which  separates  the  muscle  from  the  peritoneum,  and  with  the  external  cutaneous 
nerve;  on  the  right  side,  with  the  caecum  ;  on  the  left  side,  with  the  sigmoid  flexure 
of  the  colon;  by  its  posterior  surface,  with  the  iliac  fossa;  by  its  inner  border, 
with  the  Psoas  magnus  and  anterior  crural  nerve.  In  the  thigh,  it  is  in  relation, 
by  its  anterior  surface,  with  the  fascia  lata,  Rectus,  Sartorius,  and  profunda  femoris 
artery;  behind,  with  the  capsule  of  the  hip-joint,  a  synovial  bursa  common  to  it 
and  the  Psoas  magnus  being  interposed. 

Nerves. — The  Psoas  magnus  is  supplied  by  the  anterior  branches  of  the  second 
and  third  lumbar  nerves  ;  the  Psoas  parvus,  when  it  exists,  is  supplied  by  the 
anterior  branch  of  the  first  lumbar  nerve ;  and  the  Iliacus  by  the  anterior 
branches  of  the  second  and  third  lumbar  nerves  through  the  anterior  crural. 

Actions.— The  Psoas  and  Iliacus  muscles,  acting  from  above,  flex  the  thigh 
upon  the  pelvis.  Acting  from  below,  the  femur  being  fixed,  the  muscles  of  both 
sides  bend  the  lumbar  portion  of  the  spine  and  pelvis  forward.  They  also  serve  to 
maintain  the  erect  position,  by  supporting  the  spine  and  pelvis  upon  the  femur, 
and  assist  in  raising  the  trunk  when  the  body  is  in  the  recumbent  posture. 

The  Psoas  parvus  is  a  tensor  of  the  iliac  fascia. 

Surgical  Anatomy.— In  the  iliac  fascia  there  is  no  definite  septum  between  the  portions  of 
fascia  covering  the  Psoas  and  Iliacus  respectively,  and  the  fascia  is  only  connected  to  the  subja- 
cent muscles  by  a  quantity  of  loose  connective  tissue.  When  abscess  forms  beneath  this  fascia, 
as  it  is  very  apt  to  do,  the  matter  is  contained  in  an  osseo-fibrous  cavity  which  is  closed  on  all 
sides  within  the  abdomen,  and  is  open  only  at  its  lower  part,  where  the  fascia  is  prolonged  over 
the  muscle  into  the  thigh. 

Abscess  within  the  sheath  of  the  Psoas  muscle  {Psoas  abscess)  is  generally  due  to  tubercular 
caries  of  the  bodies  of  the  lower  dorsal  and  lumbar  vertebra3.  When  the  disease  is  in  the  dorsal 
region,  the  matter  tracts  down  the  posterior  mediastinum,  in  front  of  the  bodies  of  the  vertebrae, 
and,  passing  beneath  the  ligamentum  arcuatum  internum,  enters  the  sheath  of  the  Psoas  muscle, 
down  which  it  passes  as  far  as  the  pelvic  brim  ;  it  then  gets  beneath  the  iliac  portion  of  the  fascia 
and  fills  up  the  iliac  fossa.  In  consequence  of  the  attachment  of  the  fascia  to  the  pelvic  brim,  it 
rarely  finds   its  way  into  the  pelvis,  but  passes   by  a  narrow  opening  under  Poupart's  ligament 

1  The  Psoas  and  Iliacus  are  sometimes  regarded  as  a  single  muscle,  the  llio-psoas,  having  two  heads 
of  origin  and  a  single  insertion. 
27 


418  THE  MUSCLES   AND    FASCIuE. 

into  the  thigh,  to  the  outer  side  of  the  femoral  vessels.  It  thus  follows  that  a  Psoas  abscess  may 
be  described  as  consisting  of  four  parts :  (1)  a  somewhat  narrow  channel  at  its  upper  part,  in  the 
Psoas  sheath  ;  (2)  a  dilated  sac  in  the  iliac  fossa  ;  (3)  a  constricted  neck  under  Poupart's  liga- 
ment ;  and  (4)  a  dilated  sac  in  the  upper  part  of  the  thigh.  When  the  lumbar  vertebrae  are 
the  seat  of  the  disease,  the  matter  finds  its  way  directly  into  the  substance  of  the  muscle.  The 
muscular  fibres  are  destroyed,  and  the  nervous  cords  contained  in  the  abscess  are  isolated  and 
exposed  in  its  interior ;  the  femoral  vessels  which  lie  in  front  of  the  fascia  remain  intact,  and  the 
peritoneum  seldom  becomes  implicated.  All  Psoas  abscesses  do  not,  however,  pursue  this 
course  :  the  matter  may  leave  the  muscle  above  the  crest  of  the  ilium,  and,  tracking  backward, 
may  point  in  the  loin  [lumbar  abscess) ;  or  it  may  point  above  Poupart's  ligament  in  the  inguinal 
region ;  or  it  may  follow  the  course  of  the  iliac  vessels  into  the  pelvis,  and,  passing  through  the 
great  sacro-sciatic  notch,  discharge  itself  on  the  back  of  the  thigh ;  or  it  may  open  into  the 
bladder  or  find  its  way  into  the  perinseum. 

II.  MUSCLES  AND  FASCLffi  OF  THE  THIGH. 

1.  Anterior  Femoral  Region. 

J  Rectus. 
Tensor  fasciae  femoris.  Quadriceps!  Vastus  externus. 


Sartorius.  extensor 


Subcrureus. 


Vastus  internus. 
Crureus. 


Dissection. — To  expose  the  muscles  and  fasciae  in  this  region,  make  an  incision  along 
Poupart's  ligament,  from  the  anterior  superior  spine  of  the  ilium  to  the  spine  of  the  os  pubis ; 
a  vertical  incision  from  the  centre  of  this,  along  the  middle  of  the  thigh  to  below  the  knee-joint; 
and  a  transverse  incision  from  the  inner  to  the  outer  side  of  the  leg,  at  the  lower  end  of  the  ver- 
tical incision.  The  flaps  of  integument  having  been  removed,  the  superficial  and  deep  fasciae 
should  be  examined.  The  more  advanced  student  should  commence  the  study  of  this  region  by 
an  examination  of  the  anatomy  of  femoral  hernia  and  Scarpa's  triangle,  the  incisions  for  the 
dissection  of  which  are  marked  out  in  the  figure  252. 

The  superficial  fascia  forms  a  continuous  layer  over  the  whole  of  the  thigh, 
consisting  of  areolar  tissue,  containing  in  its  meshes  much  fat,  and  capable  of 
being  separated  into  two  or  more  layers,  between  which  are  found  the  superficial 
vessels  and  nerves.  It  varies  in  thickness  in  different  parts  of  the  limb :  in  the 
groin  it  is  thick,  and  the  two  layers  are  separated  from  one  another  by  the  super- 
ficial inguinal  lymphatic  glands,  the  internal  saphenous  vein,  and  several  smaller 
vessels.  One  of  these  two  layers,  the  superficial,  is  continuous  above  with  the 
superficial  fascia  of  the  abdomen.  The  deep  layer  of  the  superficial  fascia  is  a 
very  thin,  fibrous  layer,  best  marked  on  the  inner  side  of  the  long  saphenous  vein 
and  below  Poupart's  ligament.  It  is  placed  beneath  the  subcutaneous  vessels  and 
nerves  and  upon  the  surface  of  the  fascia  lata.  It  is  intimately  adherent  to  the 
fascia  lata  a  little  beloAV  Poupart's  ligament.  It  covers  the  saphenous  opening  in 
the  fascia  lata,  being  closely  united  to  its  circumference,  and  is  connected  to  the 
sheath  of  the  femoral  vessels,  corresponding  to  its  under  surface.  The  portion  of 
fascia  covering  this  aperture  is  perforated  by  the  internal  saphenous  vein  and  by 
numerous  blood-  and  lymphatic  vessels  ;  hence  it  has  been  termed  the  cribriform 
fascia,  the  openings  for  these  vessels  having  been  likened  to  the  holes  in  a  sieve. 
The  cribriform  fascia  adheres  closely  both  to  the  superficial  fascia  and  to  the  fascia 
lata,  so  that  it  is  described  by  some  anatomists  as  part  of  the  fascia  lata,  but  is 
usually  considered  (as  in  this  work)  as  belonging  to  the  superficial  fascia.  It  is  not 
until  the  cribriform  fascia  has  been  cleared  away  that  the  saphenous  opening  is 
seen,  so  that  this  opening  does  not  in  ordinary  cases  exist  naturally,  but  is  the 
result  of  dissection.  Mr.  Callender,  however,  speaks  of  cases  in  which,  probably 
as  the  result  of  pressure  from  enlarged  inguinal  lymphatic  glands,  the  fascia  has 
become  atrophied,  and  a  saphenous  opening  exists  independent  of  dissection.  A 
femoral  hernia  in  passing  through  the  saphenous  opening  receives  the  cribriform 
fascia  as  one  of  its  coverings.  A  large  subcutaneous  bursa  is  found  in  the  super- 
ficial fascia  over  the  patella. 

The  deep  fascia  of  the  thigh  is  exposed  on  the  removal  of  tie  8U]  u'ficial  fascia, 


THE   ANTERIOR    FEMORAL    REGION. 


419 


/ 1.  Dissection   of 
\  femoral  hernia, 

and     Scarpa's 

triangle. 


2.  Front  of  thigh. 


3  1 3.  Front  of  leg. 


and  is  named,  from  its  great  extent,  the  fascia  lata  ;  it  forms  a  uniform  invest- 
ment for  the  whole  of  this  region  of  the  limb,  but  varies  in  thickness  in  different 
parts ;  thus,  it  is  thicker  in  the  upper  and  outer  part  of  the  thigh,  where  it  receives 
a  fibrous  expansion  from  the  Gluteus  maximus 
muscle,  and  the  Tensor  fascipe  femoris  is  in- 
serted between  its  layers :  it  is  very  thin 
behind,  and  at  the  upper  and  inner  part  where 
it  covers  the  Adductor  muscles,  and  again  be- 
comes stronger  around  the  knee,  receiving  fibrous 
expansions  from  the  tendon  of  the  Biceps  ex- 
ternally, and  from  the  Sartorius  internally, 
and  Quadriceps  extensor  cruris  in  front.  The 
fascia  lata  is  attached,  above  and  behind,  to 
the  back  of  the  sacrum  and  coccyx ;  exter- 
nally, to  the  crest  of  the  ilium ;  in  front,  to 
Poupart's  ligament  and  to  the  body  of  the  os 
pubis ;  and  internally,  to  the  descending  ramus 
of  the  os  pubis,  to  the  ramus  and  tuberosity  of 
the  ischium,  and  to  the  lower  border  of  the 
great  sacro-sciatic  ligament.  From  its  attach- 
ment to  the  crest  of  the  ilium  it  passes  down 
over  the  Gluteus  niedius  muscle  to  the  upper 
border  of  the  Gluteus  maximus,  where  it  splits 
into  two  layers,  one  passing  superficial  to  and 
the  other  beneath  this  muscle.  At  the  lower 
border  of  the  muscle  the  two  layers  reunite. 
Externally  the  fascia  lata  receives  the  greater 
part  of  the  tendon  of  insertion  of  the  Gluteus 
maximus,  and  becomes  proportionately  thick- 
ened. The  portion  of  the  fascia  lata  arising 
from  the  front  part  of  the  crest  of  the  ilium, 
corresponding  to  the  origin  of  the  Tensor 
fasciae  femoris,  passes  down  the  outer  side 
of  the  thigh  as  two  layers,  one  superficial  to 
and  the  other  beneath  this  muscle ;  these  at 
its  lower  end  become  blended  together  into  a 
thick  and  strong  band,  having;  first  received  the 
insertion  of  the  muscle.     This  band  is  continued 

downward,  under  the  name  of  the  ilio-tibial  band,  to  be  inserted  into  the  external 
tuberosity  of  the  tibia.  Below,  the  fascia  lata  is  attached  to  all  the  prominent 
points  around  the  knee-joint — viz.,  the  condyles  of  the  femur,  tuberosities  of  the 
tibia,  and  head  of  the  fibula.  On  each  side  of  the  patella  it  is  strengthened  by 
transverse  fibres  given  off  from  the  lower  part  of  the  Yasti  muscles,  which  are 
attached  to  and  support  this  bone.  Of  these  the  outer  is  the  stronger,  and  is  con- 
tinuous with  the  ilio-tibial  band.  From  the  inner  surface  of  the  fascia  lata  are 
given  off  two  strong  intermuscular  septa,  which  are  attached  to  the  whole  length 
of  the  linea  aspera  and  its  prolongations  above  and  below :  the  external  and 
stronger  one,  which  extends  from  the  insertion  of  the  Gluteus  maximus  to  the 
outer  condyle,  separates  the  Vastus  externus  in  front  from  the  short  head  of  the 
Biceps  behind,  and  gives  partial  origin  to  these  muscles  ;  the  inner  one,  the  thinner 
of  the  two,  separates  the  Vastus  internus  from  the  Adductor  and  Pectineus  mus- 
cles. Besides  these  there  are  numerous  smaller  septa,  separating  the  individual 
muscles  and  enclosing  each  in  a  distinct  sheath.  At  the  upper  and  inner  part  of 
the  thigh,  a  little  below  Poupart's  ligament,  a  large  oval-shaped  aperture  is  observed 
after  the  superficial  fascia  has  been  cleared  off:  it  transmits  the  internal  saphenous 
vein  and  othe  n'   r  vessels,  and  is  termed  the  saphenous  opening.     In  order  more 

correctly  to  consider  tl.e  mode  of  formation  of  this  aperture,  the  fascia  lata  in  this 


4-  Dorsum  of  foot. 


Fig.  252. — Dissection  of  lower  extremity. 
Front  view. 


420 


THE   MUSCLES  AND    FASCIJE. 


part  of  the  thigh  is  described  as  consisting  of 
two  portions — an  iliac  portion  and  a  pubic 
portion. 

The  iliac  portion  is  all  that  part,  of  the 
fascia  lata  on  the  outer  side  of  the  saphenous 
opening.  It  is  attached,  externally,  to  the 
crest  of  the  ilium  and  its  anterior  superior 
spine,  to  the  whole  length  of  Poupart's  liga- 
ment as  far  internally  as  the  spine  of  the  os 
pubis,  and  to  the  pectineal  line  in  conjunction 
with  Gimbernat's  ligament.  From  the  spine 
of  the  os  pubis  it  is  reflected  downward  and 
outward,  forming  an  arched  margin,  the  falci- 
form process  or  boundary  (superior  comu)  of 
the  saphenous  opening ;  this  margin  overlies 
and  is  adherent  to  the  anterior  layer  of  the 
sheath  of  the  femoral  vessels :  to  its  edge  is 
attached  the  cribriform  fascia ;  and,  below,  it 
is  continuous  with  the  pubic  portion  of  the 
fascia  lata. 

The  pubic  portion  is  situated  at  the  inner 
side  of  the  saphenous  opening :  at  the  lower  J 
margin  of  this  aperture  it  is  continuous  with 
the  iliac  portion ;  traced  upward,  it  covers  the 
surface  of  the  Pectineus,  Adductor  longus,  and 
Gracilis  muscles,  and,  passing  behind  the  sheath 
of  the  femoral  vessels,  to  which  it  is  closely 
united,  is  continuous  with  the  sheath  of  the 
Psoas  and  Iliacus  muscles,  and  is  attached  above 
to  the  ilio-pectineal  line,  where  it  becomes 
continuous  with  the  iliac  fascia.  From  this 
description  it  may  be  observed  that  the  iliac 
portion  of  the  fascia  lata  passes  in  front  of  the 
femoral  vessels,  and  the  pubic  portion  behind 
them,  so  that  an  apparent  aperture  exists  be- 
tween the  two,  through  which  the  internal 
saphenous  joins  the  femoral  vein.1 

The  fascia  should  now  be  removed  from  the  sur- 
face of  the  muscles.  This  may  be  effected  by  pinch- 
ing it  up  between  the  forceps,  dividing  it,  and  sepa- 
rating it  from  each  muscle  in  the  course  of  its  fibres. 

The  Tensor  fasciae  femoris  arises  from  the 
anterior  part  of  the  outer  lip  of  the  crest  of 
the  ilium,  and  from  the  outer  surface  of  the  an- 
terior superior  spinous  process,  and  part  of  the 
outer  border  of  the  notch  below  it,  between  the 
Gluteus  medius  and  Sartorius,  and  from  the 
surface  of  the  fascia  covering  the  Gluteus 
medius.  It  is  inserted  between  two  layers  of 
the  fascia  lata,  about  one-fourth  down  the  outer 
side  of  the  thigh.  From  the  point,  of  insertion 
the  fascia  is  continued  downward  to  the  ex- 
ternal tuberosity  of  the  tibia  as  a  thickened 
band,  the  ilio-tibial  band. 

1  These  parts  will  be  again  more  particularly  de- 
femoral  region.  scribed  with  the  anatomy  of  Hernia. 


X 


THE  ANTERIOR    FEMORAL    REGION.  421 

Relations. — By  its  superficial  surface,  with  the  fascia  lata  and  the  integument ; 
by  its  deep  surface,  with  the  Gluteus  medius,  Rectus  femoris,  Vastus  externus, 
and  the  ascending  branches  of  the  external  circumflex  artery;  by  its  anterior 
border,  with  the  Sartorius,  from  which  it  is  separated  below  by  a  triangular  space, 
in  which  is  seen  the  Rectus  femoris ;  by  its  posterior  border,  with  the  Gluteus 
medius. 

The  Sartorius,  the  longest  muscle  in  the  body,  is  flat,  narrow,  and  ribbon-like ; 
it  arises  by  tendinous  fibres  from  the  anterior  superior  spinous  process  of  the 
ilium  and  the  upper  half  of  the  notch  below  it,  passes  obliquely  across  the  upper 
and  anterior  part  of  the  thigh,  from  the  outer  to  the  inner  side  of  the  limb,  then 
descends  vertically,  as  far  as  the  inner  side  of  the  knee,  passing  behind  the  inner 
condyle  of  the  femur,  and  terminates  in  a  tendon  which,  curving  obliquely 
forward,  expands  into  a  broad  aponeurosis,  inserted,  in  front  of  the  Gracilis  and 
Semitendinosus,  into  the  upper  part  of  the  inner  surface  of  the  shaft  of  the  tibia, 
nearly  as  far  forward  as  the  crest.  The  upper  part  of  the  tendon  is  curved  back- 
ward over  the  upper  edge  of  the  tendon  of  the  Gracilis  so  as  to  be  inserted  behind 
it.  An  offset  is  derived  from  the  upper  margin  of  this  aponeurosis,  which  blends 
with  the  fibrous  capsule  of  the  knee-joint,  and  another,  given  off  from  its  lower 
border,  blends  with  the  fascia  on  the  inner  side  of  the  leg. 

The  relations  of  this  muscle  to  the  femoral  artery  should  be  carefully  examined, 
as  it  constitutes  the  chief  guide  in  tying  the  vessel.  In  the  upper  third  of  the 
thigh  it  forms  the  outer  side  of  a  triangular  space,  Scarpa's  triangle,  the  inner 
side  of  which  is  formed  by  the  inner  border  of  the  Adductor  longus,  and  the  base, 
turned  upward,  by  Poupart's  ligament ;  the  femoral  artery  passes  perpendicularly 
through  the  middle  of  this  space  from  its  base  to  its  apex.  In  the  middle  third  of 
the  thigh  the  femoral  artery  lies  first  along  the  inner  border,  and  then  behind  the 
Sartorius. 

Relations. — By  its  superficial  surface,  with  the  fascia  lata  and  integument ; 
by  its  deep  surface,  with  the  Rectus,  Iliacus,  Vastus  internus,  anterior  crural 
nerve,  sheath  of  the  femoral  vessels,  Adductor  longus,  Adductor  magnus,  Gracilis, 
Semitendinosus,  long  saphenous  nerve,  and  internal  lateral  ligament  of  the  knee- 
joint. 

The  Quadriceps  extensor  includes  the  four  remaining  muscles  on  the  front  of 
the  thigh.  It  is  the  great  Extensor  muscle  of  the  leg,  forming  a  large  fleshy 
mass  which  covers  the  front  and  sides  of  the  femur,  being  united  below  into  a 
single  tendon,  attached  to  the  patella,  and  above  subdivided  into  separate  por- 
tions, which  have  received  distinct  names.  Of  these,  one  occupying  the  middle 
of  the  thigh,  connected  above  with  the  ilium,  is  called  the  Rectus  femoris,  from  its 
straight  course.  The  other  divisions  lie  in  immediate  connection  with  the  shaft 
of  the  femur,  which  they  cover  from  the  trochanters  to  the  condyles.  The  portion 
on  the  outer  side  of  the  femur  is  termed  the  Vastus  externus  ;  that  covering  the 
inner  side,  the  Vastus  interims ;  and  that  covering  the  front  of  the  femur,  the 
Orureus. 

The  Rectus  femoris  is  situated  in  the  middle  of  the  anterior  region  of  the 
thigh  ;  it  is  fusiform  in  shape,  and  its  superficial  fibres  are  arranged  in  a  bipenni- 
form  manner,  the  deep  fibres  running  straight  down  to  the  deep  aponeurosis.  It 
arises  by  two  tendons:  one,  the  anterior  or  straight,  from  the  anterior  inferior 
spinous  process  of  the  ilium  ;  the  other,  the  posterior  or  reflected  tendon,  from  a 
groove  above  the  brim  of  the  acetabulum  ;  the  two  unite  at  an  acute  angle  and 
spread  into  an  aponeurosis,  which  is  prolonged  downward  on  the  anterior  surface 
of  the  muscle  and  from  which  the  muscular  fibres  arise.1  The  muscle  terminates 
in  a  broad  and  thick  aponeurosis,  which  occupies  the  lower  two-thirds  of  its  pos- 

1  Mr.  W.  E.  Williams,  in  an  interesting-  paper  in  the  Journ.  of  Anat.  and  Phys.,  vol.  xiii.  p.  204, 
points  out  that  the  reflected  tendc-i  Is  the  real  origin  of  the  muscle,  and  is  alone _  present 
in   early  foetal   life.     The   direct   te  lerely  an  accessory  band  of  condensed   fascia.     The 

paper  will  well   repay  perusal,  thoug  e  particulars    I  think   the   description   in   the  text 

more  generally  accurate. — Ed. 


/  J 


422  THE  MUSCLES  AND   FASCIJE. 

terior    surface,    and,    gradually    becoming    narrowed    into    a   flattened    tendon,   is 
inserted  into  the  patella  in  common   with  the  Vasti  and  Crureus. 

Relations. — By  its  superficial  surface,  with  the  anterior  fibres  of  the  Gluteus 
minimus,  the  Tensor  fasciae  femoris,  the  Sartorius,  and  the  Iliacus ;  by  its  lower 
three-fourths,  with  the  fascia  lata.  By  its  posterior  surface,  with  the  hip-joint, 
the  external  circumflex  vessels,  branches  of  the  anterior  crural  nerve,  and  the 
Crureus  and  Vasti  muscles. 

The  Vastus  externus  is  the  largest  part  of  the  Quadriceps  extensor.  It  arises 
by  a  broad  aponeurosis,  which  is  attached  to  the  upper  half  of  the  anterior  inter- 
trochanteric line,  to  the  anterior  and  inferior  borders  of  the  root  of  the  great 
trochanter,  to  the  outer  lip  of  the  gluteal  ridge,  and  to  the  upper  half  of  the  outer 
lip  of  the  linea  aspera :  this  aponeurosis  covers  the  upper  three-fourths  of  the 
muscle,  and  from  its  inner  surface  many  fibres  take  origin.  A  few  additional 
fibres  arise  from  the  tendon  of  the  Gluteus  maximus,  and  from  the  external  inter- 
muscular septum  between  the  Vastus  externus  and  short  head  of  the  Biceps.  The 
fibres  form  a  large  fleshy  mass,  which  is  attached  to  a  strong  aponeurosis,  placed 
on  the  under  surface  of  the  muscle  at  its  lower  part :  this  becomes  contracted  and 
thickened  into  a  flat  tendon,  which  is  inserted  into  the  outer  border  of  the  patella, 
blending  with  the  great  Extensor  tendon,  and  giving  an  expansion  to  the  capsule 
of  the  knee-joint. 

Relations. — By  its  superficial  surface,  with  the  Rectus,  the  Tensor  fasciae 
femoris,  the  fascia  lata,  and  the  tendon  of  the  Gluteus  maximus,  from  which  it  is 
separated  by  a  synovial  bursa.  By  its  deep  surface,  with  the  Crureus,  some  large 
branches  of  the  external  circumflex  artery  and  anterior  crural  nerve  being  inter- 
posed. 

The  Vastus  internus  and  Crureus  appear  to  be  inseparably  united,  but  when 
the  Rectus  femoris  has  been  reflected,  a  narrow  interval  will  be  observed  extending 
upward  from  the  inner  border  of  the  patella  between  the  two  muscles.  Here  they 
can  be  separated,  and  the  separation  should  be  continued  upward  as  far  as  the 
lower  part  of  the  anterior  intertrochanteric  line,  where,  however,  the  two  muscles 
are  frequently  continuous. 

The  Vastus  internus  arises  from  the  lower  half  of  the  anterior  intertrochanteric 
line,  the  spiral  line,  the  inner  lip  of  the  linea  aspera,  the  upper  part  of  the  internal 
supra-condylar  line,  and  the  tendon  of  the  Adductor  magnus  and  internal  inter- 
muscular septum.  Its  fibres  are  directed  downward  and  forward,  and  are  chiefly 
attached  to  an  aponeurosis  which  lies  on  the  deep  surface  of  the  muscle  and  is 
inserted  into  the  inner  border  of  the  patella  and  the  Quadriceps  extensor  tendon, 
an  expansion  being  sent  to  the  capsule  of  the  knee-joint. 

The  Crureus  arises  from  the  front  and  outer  aspect  of  the  shaft  of  the  femur  in 
its  upper  two-thirds  and  from  the  lower  part  of  the  external  intermuscular  septum. 
Its  fibres  end  in  a  superficial  aponeurosis,  which  forms  the  deep  part  of  the  Quad- 
riceps extensor  tendon. 

Relations. — The  inner  edge  of  the  Crureus  is  in  contact  with  the  anterior  edge 
of  the  Vastus  internus,  but  when  separated  from  each  other,  as  directed  above,  the 
latter  muscle  is  seen  merely  to  overlap  the  inner  aspect  of  the  femoral  shaft  without 
taking  any  fibres  of  origin  from  it.  The  Vastus  internus  is  partly  covered  by  the 
Rectus  and  Sartorius,  but  where  these  separate  near  the  knee  it  becomes  superficial, 
and  produces  a  well-marked  prominence  above  the  inner  aspect  of  the  knee.  In 
the  middle  third  of  the  thigh  it  forms  the  outer  wall  of  Hunter's  canal,  which 
contains  the  femoral  vessels  and  the  long  saphenous  nerve — the  roof  of  the  canal 
being  formed  by  a  strong  fascia  which  extends  from  the  Vastus  internus  to  the  Ad- 
ductores  longus  and  magnus.  The  Crurei  is  almost  completely  hidden  by  the 
Rectus  femoris  and  Vastus  externus.  The  deep  surface  of  the  two  muscles  is  in 
relation  to  the  femur  and  Subcrureus  muscle.  A  synovial  bursa  is  situated  between 
the  femur  and  the  portion  of  the  Quadriceps  extensor  tendon  above  the  patella  ;  in 
the  adult  it  communicates  with  the  synovial  cavity  of  the  knee-joint. 

The  tendons  of  the  different  portions  of  the  Quadriceps  extensor  unite  at  the 


THE   INTERNAL    FEMORAL    REGION.  423 

lower  part  of  the  thigh,  so  as  to  form  a  single  strong  tendon,  which  is  inserted  into 
the  upper  part  of  the  patella,  some  few  fibres  passing  over  it  to  blend  with  the 
Ligamentum  patellae.  More  properly,  the  patella  may  be  regarded  as  a  sesamoid 
bone,  developed  in  the  tendon  of  the  Quadriceps  ;  and  the  Ligamentum  patellae, 
which  is  continued  from  the  lower  part  of  the  patella  to  the  tuberosity  of  the  tibia, 
as  the  proper  tendon  of  insertion  of  the  muscle.  A  synovial  bursa,  the  post-patel- 
lar  bursa,  is  interposed  between  the  tendon  and  the  upper  part  of  the  tuberosity  of 
the  tibia ;  and  another,  the  pre-patellar  bursa,  is  placed  over  the  patella  itself. 
This  latter  bursa  often  becomes  enlarged,   constituting  "  house-maid's  knee." 

The  Subcrureus  is  a  small  muscle,  usually  distinct  from  the  Crureus,  but  occa- 
sionally blended  with  it,  which  arises  from  the  anterior  surface  of  the  lower  part  of 
the  shaft  of  the  femur,  and  is  inserted  into  the  upper  part  of  the  cul-de-sac  of  the 
capsular  ligament  which  projects  upward  beneath  the  Quadriceps  for  a  variable 
distance.     It  sometimes  consists  of  several  separate  muscular  bundles. 

Nerves. — The  Tensor  fasciae  femoris  is  supplied  by  the  fourth  and  fifth  lumbar 
and  first  sacral  nerves  through  the  superior  gluteal  nerve ;  the  other  muscles  of 
this  region,  by  the  second,  third,  and  fourth  lumbar  nerves,  through  branches  of 
the  anterior  crural. 

Actions. — The  Tensor  fasciae  femoris  is  a  tensor  of  the  fascia  lata ;  continuing 
its  action,  the  oblique  direction  of  its  fibres  enables  it  to  abduct  and  to  rotate  the 
thigh  inward.  In  the  erect  posture,  acting  from  below,  it  will  serve  to  steady  the 
pelvis  upon  the  head  of  the  femur,  and  by  means  of  the  ilio-tibial  band  it  steadies 
the  condyles  of  the  femur  on  the  articular  surfaces  of  the  tibia,  and  assists  the 
Gluteus  maximus  in  supporting  the  knee  in  the  extended  position.  The  Sartorius 
flexes  the  leg  upon  the  thigh,  and,  continuing  to  act,  flexes  the  thigh  upon  the 
pelvis  ;  it  next  rotates  the  thigh  outward.  It  was  formerly  supposed  to  adduct  the 
thigh,  so  as  to  cross  one  leg  over  the  other,  and  hence  received  its  name  of  Sartorius, 
or  tailor's  muscle  (sartor,  a  tailor),  because  it  was  supposed  to  assist  in  crossing  the 
legs  in  the  squatting  position.  When  the  knee  is  bent  the  Sartorius  assists  the 
Semitendinosus,  Semimembranosus,  and  Popliteus  in  rotating  the  tibia  inward. 
.  Taking  its  fixed  point  from  the  leg,  it  flexes  the  pelvis  upon  the  thigh,  and,  if  one 
muscle  acts,  assists  in  rotating  the  pelvis.  The  Quadriceps  extensor  extends  the 
leg  upon  the  thigh.  The  Rectus  muscle  assists  the  Psoas  and  Iliacus  in  supporting 
the  pelvis  and  trunk  upon  the  femur.  It  also  assists  in  flexing  the  thigh  on  the 
pelvis,  or  if  the  thigh  is  fixed  it  will  flex  the  pelvis.  The  Vastus  internus  draws 
the  patella  inward  as  well  as  upward. 

Surgical  Anatomy. — A  few  fibres  of  the  Rectus  muscle  are  liable  to  be  ruptured  from 
severe  strain.  This  accident  is  especially  liable  to  occur  during  the  games  of  football  and  cricket, 
and  is  sometimes  known  as  "  cricket  thigh.  "  The  patient  experiences  a  sudden  pain  in  the  part, 
as  if  he  had  been  struck,  and  the  Rectus  muscle  stands  out  and  is  felt  to  be  tense  and  rigid.  The 
accident  is  often  followed  by  considerable  swelling  from  inflammatory  effusion.  Occasionally  the 
Quadriceps  extensor  may  be  torn  away  from  its  insertion  into  the  patella,  or  the  tendon  of  the 
patella  may  be  ruptured  about  an  inch  above  the  bone.  This  accident  is  caused  in  the  same 
manner  as  fracture  of  the  patella  by  muscular  action  is  produced — viz.  by  a  violent  muscular 
effort  to  prevent  falling  whilst  the  knee  is  in  a  position  of  semiflexion.  A  distinct  gap  can  be 
felt  above  the  patella,  and,  owing  to  the  retraction  of  the  muscular  fibres,  union  may  fail  to  take 
place. 

2.  Internal  Femoral  Region. 

/  Gracilis.  Adductor  longus. 

Pectineus.  Adductor  brevis. 

Adductor  magnus. 

Dissection. — These  muscles  are  at  once  exposed  by  removing  the  fascia  from  the  fore  part 
and  inner  side  of  the  thigh.  The  limb  should  be  abducted,  so  as  to  render  the  muscles  tense 
and  easier  of  dissection. 

The  Gracilis  (Figs.  253,  256)  is  the  most  superficial  muscle  on  the  inner  side 
of  the  thigh.  It  is  thin  and  flattened,  broad  above,  narrowing  and  tapering  below. 
It  arises  by  a  thin  aponeurosis  from  the  lower  half  of  the  marr  in  of  the  symphysis 
and  the  anterior  half  of  the  pubic  arch.      The  fibres  pass  vertically  downward,  and 


424 


THE  MUSCLES  AND    FASCIJE. 


terminate  in  a  rounded  tendon  which  passes  behind  the  internal  condyle  of  the 
femur,  and,  curving  round  the  inner  tuberosity  of  the  tibia,  becomes  flattened,  and 

is  inserted  into  the  upper  part  of  the  inner 
surface  of  the  shaft  of  the  tibia,  below  the 
tuberosity.  A  few  of  the  fibres  of  the  lower 
part  of  the  tendon  are  prolonged  into  the 
deep  fascia  of  the  leg.  The  tendon  of  this 
muscle  is  situated  immediately  above  that 
of  the  Semitenclinosus,  and  its  upper  edge  is 
overlapped  by  the  tendon  of  the  Sartorius, 
with  which  it  is  in  part  blended.  As  it 
passes  across  the  internal  lateral  ligament 
of  the  knee-joint  it  is  separated  from  it 
by  a  synovial  bursa  common  to  it  and  the 
Semitendinosus  muscle. 

Relations. — By  its  superficial  surface, 
with  the  fascia  lata  and  the  Sartorius  be- 
low :  the  internal  saphenous  vein  crosses  it 
obliquely  near  its  lower  part,  lying  super- 
ficial to  the  fascia  lata  ;  the  internal  saph- 
enous nerve  emerges  between  its  tendon  and 
that  of  the  Sartorius ;  by  its  deep  surface, 
with  the  Adductor  brevis  and  the  Adductor 
magnus  and  the  internal  lateral  ligament  of 
the  knee-joint. 

The  Pectineus  (Fig.  253)  is  a  flat,  quad- 
rangular muscle,  situated  at  the  anterior  part 
of  the  upper  and  inner  aspect  of  the  thigh. 
It  arises  from  the  linea  ilio-pectinea,  and  to 
a  slight  extent  from  the  surface  of  the  bone 
in  front  of  it  between  the  pectineal  eminence 
and  spine  of  the  os  pubis,  and  from  the 
fascia  covering  the  anterior  surface  of  the 
muscle  ;  the  fibres  pass  downward,  backward, 
and  outward,  to  be  inserted  into  a  rough  line 
leading  from  the  lesser  trochanter  to  the 
linea  aspera. 

Relations. — By  its  anterior  surface,  with 
the  pubic  portion  of  the  fascia  lata,  which 
separates  it  from  the  femoral  vessels  and 
internal  saphenous  vein ;  by  its  posterior 
surface,  with  the  capsular  ligament  of  the 
hip-joint,  the  Adductor  brevis  and  Obturator 
externus  muscles,  the  obturator  vessels  and 
nerve  being  interposed  ;  by  its  outer  border, 
with  the  Psoas,  a  cellular  interval  separating 
them,  through  which  pass  the  internal  cir- 
cumflex vessels ;  by  its  inner  border,  with 
the  margin  of  the  Adductor  longus. 

The   Adductor    longus,  the   most  super- 
ficial of  the  three  Adductors,  is  a  flat  trian- 
gular   muscle    lying  on  the    same  plane  as 
the  Pectineus.     It  arises,  by  a  flat  narrow 
-Deep  muscles  of  the  internal  femoral    tendon,  from  the  front  of  the  os  pubis,   at 

the  angle  of  junction  of  the  crest  with  the 
symphysis ;  and  soon  expands  into  a  broad  fleshy  belly,  which,  passing  down- 
ward,   backward,   and    outward,    is    inserted    by    an    aponeurosis,   into    the    linea 


THE   INTERNAL    FEMORAL    REGION.  425 

aspera,  between  the  Vastus  interims  and   the  Adductor  raagnus,   with  both  of 
which  it  is  usually  blended. 

Relations. — By  its  anterior  surface,  with  the  fascia  lata,  the  Sartorius.  and. 
near  its  insertion,  with  the  femoral  artery  and  vein;  by  its  posterior  surface,  with 
the  Adductor  brevis  and  magnus.  the  anterior  branches  of  the  obturator  nerve. 
and  with  the  profunda  artery  and  vein  near  its  insertion  ;  by  its  outer  border,  with 
the  Pectineus ;  by  its  inner  border,  with  the  Gracilis. 

The  Pectineus  and  Adductor  longus  should  now  be  divided  near  their  origin,  and  turned 
downward,  when  the  Adductor  brevis  and  Obturator  externus  will  be  exposed. 

The  Adductor  brevis  is  situated  immediately  behind  the  two  preceding  muscles. 
It  is  somewhat  triangular  in  form,  and  arises  by  a  narrow  origin  from  the  outer 
surface  of  the  body  and  descending  ramus  of  the  os  pubis,  between  the  Gracilis 
and  Obturator  externus.  Its  fibres,  passing  backward,  outward,  and  downward, 
are  inserted,  by  an  aponeurosis,  into  the  lower  part  of  the  line  leading  from  the 
lesser  trochanter  to  the  linea  aspera  and  the  upper  part  of  the  same  line,  imme- 
diately behind  the  Pectineus  and  upper  part  of  the  Adductor  longus. 

Relations. — By  its  anterior  surface,  with  the  Pectineus,  Adductor  longus,  pro- 
funda femoris  artery,  and  anterior  branches  of  the  obturator  nerve ;  by  its  pos- 
terior surface,  with  the  Adductor  magnus  and  posterior  branch  of  the  obturator 
nerve  ;  by  its  outer  border,  with  the  internal  circumflex  artery,  the  Obturator  exter- 
nus, and  conjoined  tendon  of  the  Psoas  and  Iliacus ;  by  its  inner  border,  with  the 
Gracilis  and  Adductor  magnus.  This  muscle  is  pierced,  near  its  insertion,  by  the 
second  or  first  and  second  perforating  branches  of  the  profunda  femoris  artery. 

The  Adductor  brevis  should  now  be  cut  away  near  its  origin,  and  turned  outward,  when 
the  entire  extent  of  the  Adductor  magnus  will  be  exposed. 

The  Adductor  magnus  is  a  large  triangular  muscle  forming  a  septum  between 
the  muscles  on  the  inner  and  those  on  the  back  of  the  thigh.  It  arises  from  a 
small  part  of  the  descending  ramus  of  the  os  pubis,  from  the  ramus  of  the  is- 
chium, and  from  the  outer  margin  of  the  inferior  part  of  the  tuberosity 
of  the  ischium.  Those  fibres  which  arise  from  the  ramus  of  the  os  pubis 
are  very  short,  horizontal  in  direction,  and  are  inserted  into  the  rough  line 
leading  from  the  great  trochanter  to  the  linea  aspera,  internal  to  the  Gluteus 
maximus;  those  from  the  ramus  of  the  ischium  are  directed  downward  and 
outward  with  different  degrees  of  obliquity,  to  be  inserted,  by  means  of  a  broad 
aponeurosis,  into  the  linea  aspera  and  the  upper  part  of  its  internal  prolonga- 
tion below.  The  internal  portion  of  the  muscle,  consisting  principally  of  those 
fibres  wdiich  arise  from  the  tuberosity  of  the  ischium,  forms  a  thick  fleshy  mass 
consisting  of  coarse  bundles  which  descend  almost  vertically,  and  terminate  about 
the  lower  third  of  the  thigh  in  a  rounded  tendon.  Avhich  is  inserted  into  the 
Adductor  tubercle  on  the  inner  condyle  of  the  femur,  being  connected  by  a  fibrous 
expansion  to  the  line  leading  upward  from  the  tubercle  to  the  linea  aspera. 
Between  the  two  portions  of  the  muscle  an  interval  is  left,  tendinous  in  front, 
fleshy  behind,  for  the  passage  of  the  femoral  vessels  into  the  popliteal  space.  The 
external  portion  of  the  muscle  at  its  attachment  to  the  femur  presents  three  or  four 
osseo-aponeurotic  openings,  formed  by  tendinous  arches  attached  to  the  bone,  from 
wrhich  muscular  fibres  arise.  The  three  superior  of  these  apertures  are  for  the 
three  perforating  arteries,  and  the  fourth,  when  it  exists,  for  the  terminal  branch 
of  the  profunda. 

Relations.-r-By   its   anterior   surface,    with   the    Pectineus.   Adductor    brevis. 
Adductor  longus,  and  the  femoral  and  profunda  vessels  and  obturator  nerve :  by 
its  posterior  surface,  with  the  great  sciatic  nerve,  the  Gluteus  maximus  71 
Semitenclinosus,  and  Semimembranosus.      By  its  superior  or  shortest  7  '*     . 
parallel  with  the  Quadratus  femoris,  the  internal  circumflex  ar*    ,  "       .  ,       ,     l    ; 
them;    by  its   internal  or  longest  border,  with  the  Grae::\.  1  V      '1    r 

lata ;  by  its  external  or  attached  border  it  is  inserted  in 
Adductor  brevis  and  Adductor  longus,  which  separate  it 


426  THE   MUSCLES  AND    FASCIAE. 

and  in  front  of  the  Gluteus  maximus  and  short  head  of  the  Biceps,  which  separate 
it  from  the  Vastus  externus. 

Nerves. — The  three  Adductor  muscles  and  the  Gracilis  are  supplied  by  the 
third  and  fourth  lumbar  nerves  through  the  obturator  nerve  ;  the  Adductor  mag- 
nus  receiving  an  additional  branch  from  the  sacral  plexus  through  the  great 
sciatic.  The  Pectineus  is  supplied  by  the  second,  third,  and  fourth  lumbar  nerves 
through  the  anterior  crural,  and  by  the  accessory  obturator,  from  the  third  lumbar, 
when  it  exists.     Occasionally  it  receives  a  branch  from  the  obturator  nerve.1 

Actions. — The  Pectineus  and  three  Adductors  adduct  the  thigh  powerfully : 
they  are  especially  used  in  horse  exercise,  the  flanks  of  the  horse  being  grasped 
between  the  knees  by  the  actions  of  these  muscles.  In  consequence  of  the  obliquity 
of  their  insertion  into  the  linea  aspera  they  rotate  the  thigh  outward,  assisting 
the  external  Rotators,  and  when  the  limb  has  been  abducted  they  draAv  it  inward, 
carrying  the  thigh  across  that  of  the  opposite  side.  The  Pectineus  and  Adductor 
brevis  and  longus  assist  the  Psoas  and  Iliacus  in  flexing  the  thigh  upon  the  pelvis. 
In  progression,  also,  all  these  muscles  assist  in  drawing  forward  the  hinder  limb. 
The  Gracilis  assists  the  Sartorius  in  flexing  the  leg  and  rotating  it  inward ;  it  is 
also  an  adductor  of  the  thigh.  If  the  lower  extremities  are  fixed,  these  muscles 
may  take  their  fixed  point  from  below  and  act  upon  the  pelvis,  serving  to  maintain 
the  body  in  an  erect  posture,  or,  if  their  action  is  continued,  to  flex  the  pelvis 
forward  upon  the  femur. 

Surgical  Anatomy. — The  Adductor  longus  is  liable  to  be  severely  strained  in  those 
who  ride  much  on  horseback,  or  its  tendon  to  be  ruptured  by  suddenly  gripping  the  saddle. 
And,  occasionally,  especially  in  cavalry  soldiers,  the  tendon  may  become  ossified,  constituting  the 
"rider's  bone." 

THE  HIP. 

3.  Gluteal  Region. 

Gluteus  maximus.  Obturator  internus. 

Gluteus  medius.  Gemellus  superior. 

Gluteus  minimus.  -Gemellus  inferior. 

Pyriformis.  Quadratus  femoris. 

Obturator  externus. 

Dissection  (Fig.  255). — The  subject  should  be  turned  on  its  face,  a  block  placed  beneath 
the  pelvis  to  make  the  buttocks  tense,  and  the  limbs  allowed  to  hang  over  the  end  of  the  table, 
with  the  foot  inverted  and  the  thigh  abducted.  Make  an  incision  through  the  integument  along 
the  crest  of  the  ilium  to  the  middle  of  the  sacrum,  and  thence  downward  to  the  tip  of  the  coccyx, 
and  carry  a  second  incision  from  that  point  obliquely  downward  and  outward  to  the  outer  side 
of  the  thigh,  tour  inches  below  the  great  trochanter.  The  portion^  of  integument  included 
between  these  incisions  is  to  be  removed  in  the  direction  shown  in  the  figure. 

The  Gluteus  maximus  (Fig.  256),  the  most  superficial  muscle  in  the  gluteal 
region,  is  a  very  broad  and  thick,  fleshy  mass  of  a  quadrilateral  shape,  which 
forms  the  prominence  of  the  nates.  Its  large  size  is  one  of  the  most  characteristic 
points  in  the  muscular  system  in  man,  connected  as  it  is  with  the  power  he  has  of 
maintaining  the  trunk  in  the  erect  posture.  In  structure  the  muscle  is  remarkably 
coarse,  being  made  up  of  muscular  fasciculi  lying  parallel  with  one  another,  and 
collected  together  into  large  bundles,  separated  by  deep  cellular  intervals.  It 
arises  from  the  superior  curved  line,  of  the  ilium  and  the  portion  of  bone,  including 
,ne  crest,  immediately  above  and  behind  it ;  from  the  posterior  surface  of  the  lower 
part  of  the  sacrum,  the  side  of  the  coccyx,  the  aponeurosis  of  the  Erector  spinae 
muscle,  the  great  sacro-sciatic  ligament,  and  the  fascia  covering  the  Gluteus  medius. 
"*1"i  fibres  are  directed  obliquely  downward  and  outward;  those  forming  the  upper 
^portion  of  the  muscle,  together  with  the  superficial  fibres  of  the  lower 

Fig.  254.  -Deep  muscK. describes  the  Pectineus  as  consisting  of  two  incompletely  separated  strata,  of 

region.  '-i.tum,  which  is  constant,  is  supplied  by  the  anterior  crural  nerve,  or  in 

urator,  with  which  it  is  intimately  related;    while  the  inner  or  ven- 

symphysis  ;     and   SOOn   eupplied  by  the  obturator  nerve.—  Journal  of  Anatomy  and  Physiology, 

ward,    backward,  and    o 


'IE    GLUTEAL    REGION.  429 

iter,  behind,  but  oftei>;  partly  blended  Avith,  the  tendon  of  the  Obturator  inter- 
Porti  and  Gemelli  muscles 

ano-  Relations. — By  its  ant\  rior  surface,  within  the  pelvis,  with  the  Rectum  (espe- 
fiDrt,lly  on  the  left  side),  the  i-acral  plexus  of  nerves,  and  the  branches  of  the  internal 
sert^g  vessels;  external  to  tile  pelvis,  with  the  posterior  surface  of  the  ischium  and 
troc')sular  ligament  of  the  hip-joint;  by  its  posterior  surface,  within  the  pelvis,  with 
tus  (s  sacrum,  and  external  to  it,  with  the  Gluteus  maximus  ;  by  its  upper  border, 

;h  the  Gluteus  medius,  from  which  it  is  separated  by  the  gluteal  vessels  and 
latio)erior  gluteal  nerve ;  by  its  lower  border,  with  the  Gemellus  superior  and 
slze>ccygeus,  the  sciatic  vessels  and  nerves,  the  internal  pudic  vessels  and  nerve,  and 
fr°m3cular  branches  from  the  sacral  plexus,  passing  from  the  pelvis  in  the  interval 
wantween  ^ne  two  muscles. 

ischiirphg  Obturator  membrane  (Fig.  166)  is  a  thin  layer  of  interlacing  fibres  which 
of  th^es  £ne  obturator  foramen.     It  is   attached,   externally,  to  the  margin  of  the 

■^imen ;  internally,  to  the  posterior  surface  of  the  ischio-pubic  ramus,  below  and 
a  thi)rnai  t0  the  margin  of  the  foramen.  It  is  occasionally  incomplete,  and  presents 
cutants  upper  and  outer  part  a  small  canal,  which  is  bounded  below  by  a  thickened 
abov<d  0f  fibres,  for  the  passage  of  the  obturator  vessels  and  nerve.  Both  obturator 
and  3Cles  are  connected  with  this  membrane. 

•  Dissection.— The  next  muscle,  as  well  as  the  origin  of  the  Pyriformis,  can  only  be  seen 

interin  ^ne  pe}vis  is  divided  and  the  viscera  removed, 
the  is 

Bicep^he  Obturator  internus,  like  the  preceding  muscle,  is  •situated  partly  within  the 

Adduty  °f  the  pelvis,  and  partly  at  the  back  of  the  hip-joint.     It  arises  from  the 

of  th(ir  surface  of  the  anterior  and  external  wall  of  the  pelvis,  where  it  surrounds 

of  the§rea^er  Par^  °f  the  obturator  foramen,  being  attached  to  the  descending  ramus 

and  tlne  os  Pubis  and  the  ramus  of  the  ischium,  and  at  the  side  to  the  inner  surface 

pudic  ie  innominate  bone  below  and  behind  the  pelvic  brim,  reaching  from  the  upper 

from  t  °f  the  great  sacro-sciatic  foramen  above  and  behind  to  the  thyroid  foramen 

low  thw  anc^  in  front.     It  also  arises  from  the  inner  surface  of  the  obturator  mem- 

and  tFe  except  at  its  posterior  part,  from  the  tendinous  arch  which  completes  the 

cumfk'l  for  the  passage  of  the  obturator  vessels  and  nerve  and  to  a  slight  extent  from 

musch obturator  layer  of  the  pelvic  fascia,  which   covers   it.     The  fibres   converge 

with  t^ty'  anc^  are  directed  backward  and  downward,  and  terminate  in  four  or  five 

lower  inous  bands,  which  are  found  on  its  deep  surface ;  these  bands  are  reflected  at 

2;ht  angle  over  the  inner  surface   of  the  tuberosity  of  the  ischium,  which  is 

Difved  for  their  reception ;  the  groove  is  covered  with  cartilage,  and  lined  by  a 

i  '.'"S'vial  bursa.     The  muscle  leaves  the  pelvis  by  the  lesser  sacro-sciatic  foramen  ; 

,  '\   the  tendinous  bands  unite  into  a  single  flattened  tendon,  which  passes  horizon- 

r    outward,  and,  after  receiving  the  attachment  of  the  Gemelli,  is  inserted  into 

Jird;  I'ore  part  of  the  inner  surface  of  the  great  trochanter  in  front  of  the  Obturator 
ff\  ?  -nus.     A   synovial    bursa,   narrow    and   elongated   in   form,   is   usually  found 
een    the    tendon  of  this    muscle   and   the   capsular  ligament  of  the  hip:    it 
Tbionally  communicates  with  the  bursa  between  the  tendon  and  the  tuberosity 
surfacie  ischium,  the  two  forming  a  single  sac. 

interi(in  order  to  display  the  peculiar  appearances  presented  by  the  tendon  of  this  muscle,  it 
arises  be  divided  near  its  insertion  and  reflected  inward. 

>  lelations. —  Within  the  pelvis  this  muscle  is  in  relation,  by  its  anterior  surface, 

■  ,      fi  the  obturator  membrane  and  inner  surface  of  the  anterior  wall  of  the  pelvis ; 

;s  posterior  surface,  with  the  pelvic  and  obturator  fascire,  which  separate  it 

the  Levator  ani ;  and  it  is  crossed  by  the  internal  pudic  vessels  and  nerve. 

surface  forms  the  outer  boundary  of  the  ischio-rectal  fossa.     External  to  the 
its  l  ns  •  i 

_  is  it  is  covered  by  the  Gluteus  maximus,  crossed  by  the  great  sciatic  nerve, 

„,         rests  on  the  beck  p-"110  f  tb'V""  joint.     As  the  tendon  of  the  Obturator 

+L-ensonus  emerges  from  £    #ien  l"e  fen\ur  f.^-men  it  is  overlapped  bv  the  two 

■?™elli,  while ,  nearer ne  pelvis  forward  if  it  has  nsg   [n   &Qnt   of  it   aml   form   a 

g  b>e  in  which  the  'on  the  head  of  the  femur' 
Pynfc 


430  THE   MUSCLES   AND    FASC1LE.. 


The  G-emelli  are  two  small  muscular  fasciculi,  accessaries  to  the  tendon  of  the 
Obturator  internus,  which  is  received  into  a  groove  between  them.  They  are  called 
superior  and  inferior.  I 

The  Gemellus  superior,  the  smaller  of  the  two,  arises  from  the  outer  surface 
of  the  spine  of  the  ischium,  and,  passing  horizontally  outward,  becomes  blended 
with  the  upper  part  of  the  tendon  of  the  Obturator  internus,  and  is  inserted  with 
it  into  the  inner  surface  of  the  great  trochanter.  This  muscle  is  sometimes 
wanting. 

Relations. — By  its  superficial  surface,  with  the  Gluteus  maximus  and  the 
sciatic  vessels  and  nerves  ;  by  its  deep  surface,  with  the  capsule  of  the  hip-joint; 
by  its  upper  border,  with  the  lower  margin  of  the  Pyriformis  ;  by  its  lower  border, 
with  the  tendon  of  the  Obturator  internus. 

The  Gemellus  inferior  arises  from  the  upper  part  of  the  tuberosity  of  the 
ischium,  where  it  forms  the  lower  edge  of  the  groove  for  the  Obturator  internus 
tendon,  and,  passing  horizontally  outward,  is  blended  with  the  lower  part  of  the 
tendon  of  the  Obturator  internus,  and  is  inserted  with  it  into  the  inner  surface  of 
the  great  trochanter. 

Relations. — By  its  superficial  surface,  with  the  Gluteus  maximus  and  the 
sciatic  vessels  and  nerves ;  by  its  deep  surface,  with  the  capsular  ligament  of  the 
hip-joint;  by  its  upper  border,  with  the  tendon  of  the  Obturator  internus  ;  by  its 
lower  border,  with  the  tendon  of  the  Obturator  externus  and  Quadratus  femoris. 

The  Quadratus  femoris  is  a  short,  flat  muscle,  quadrilateral  in  shape  (hence 
its  name),  situated  between  the  Gemellus  inferior  and  the  upper  margin  of  the 
Adductor  magnus.  It  arises  from  the  upper  part  of  the  external  lip  of  the  tuber- 
osity of  the  ischium,  and,  proceeding  horizontally  outward,  is  inserted  into  the 
upper  part  of  the  linea  quadrata ;  that  is,  the  line  which  crosses  the  posterior  inter- 
trochanteric line.  A  synovial  bursa  is  often  found  between  the  under  surface  of 
this  muscle  and  the  lesser  trochanter,  which  it  covers. 

Relations. — By  its  posterior  surface,  with  the  Gluteus  maximus  and  the  sciatic 
vessels  and  nerves ;  by  its  anterior  surface,  with  the  tendon  of  the  Obturator 
externus  and  trochanter  minor  and  with  the  capsule  of  the  hip-joint ;  by  its 
upper  border,  with  the  Gemellus  inferior.  Its  lower  border  is  separated  from  the 
Adductor  magnus  by  the  terminal  branches  of  the  internal  circumflex  vessels. 

Dissection. — In  order  to  expose  the  next  muscle  (the  Obturator  externus),  it  is  necessary 
to  remove  the  Psoas,  Iliacus,  Pectineus,  and  Adductor  brevis  and  longus  muscles  from  the  front 
and  inner  side  of  the  thigh,  and  the  Gluteus  maximus  and  Quadratus  femoris  from  the  back 
part.  Its  dissection  should,  consequently,  be  postponed  until  the  muscles  of  the  anterior  and 
internal  femoral  regions  have  been  explained. 

The  Obturator  externus  (Fig.  257)  is  a  flat,  triangular  muscle,  which  covers  the 
outer  surface  of  the  anterior  wall  of  the  pelvis.  It  arises  from  the  margin  of 
bone  immediately  around  the  inner  side  of  the  obturator  foramen,  viz.,  from  the 
body  and  ramus  of  the  os  pubis  and  the  ramus  of  the  ischium;  it  also  arises 
from  the  inner  two-thirds  of  the  outer  surface  of  the  obturator  membrane,  and 
from  the  tendinous  arch  which  completes  the  canal  for  the  passage  of  the  obtu- 
rator vessels  and  nerves.  The  fibres  from  the  pubic  arch  extend  on  to  the 
inner  surface  of  the  bone,  from  which  they  obtain  a  narrow  origin  between  the 
margin  of  the  foramen  and  the  attachment  of  the  membrane.  The  fibres  con- 
verging pass  backward,  outward,  and  upward,  and  terminate  in  a  tendon  which 
runs  across  the  back  part  of  the  hip-joint,  and  is  inserted  into  the  digital  fossa  of 
the  femur. 

Relations. — By  its  anterior  surface,  with  the  Psoas,  Iliacus,  Pectineus,  Adductor 

magnus,  and  Adductor  brevis  ;  and  more  externally,  with  the  neck  of  the  femur 

and  capsule  of  the  hip-joint.     The   obturator    artery  and  vein  lie  between   this 

muscle  and  the  obturator  membrane ;  thfM„-  nerficV'    •  art  of  the  obturator  nerve 

,  -.6  «»  consisting    t  two  iric  .  • 

lies  above  the  muscle,  and  the  dees  constant,  is  supplied  by  the  sPy  ^s  posterior  surface, 
with  the  obturator  membrane  a^11  which  it  is  intimately  related; 

Nerves.— The  Gluteus  m-d  by  the  obturator  nerve—Jo™*  o/i,imbar  and  first  and 


THE    GLUTEAL    REGION. 


431 


second  sacral  nerves  through  the  inferior  gluteal  nerve  from  the  sacral  plexus ; 
the  Gluteus  meclius  and  minimus,  by  the  fourth  and  fifth  lumbar  and  first  sacral 
nerves  through  the  superior  gluteal ;  the  Pyriformis  is  supplied  by  the  first  and 
second  sacral  nerves;  the  Gemellus  inferior  and  Quadratus  femoris  by  the  last 
lumbar  and  first  sacral  nerve ;  the  Gemellus  superior  and  Obturator  internus  by 
the  fifth  lumbar  and  first  and  second  sacral  nerves,  and  the  Obturator  externus  bv 
the  second,  third,  and  fourth  lumbar  nerves  through  the  obturator. 


Anterior  division  of 
obturator  nerve. 


Anterior  inferior 
iliac  sjnne. 


Capsular  liga- 
ment partly 
cut  away. 


Posterior  division 
of  obturator 
nerve. 

Internal  circum- 
flex artery. 


Fig.  257.— Obturator  externus  muscle.    (From  a  preparation  in  the  Museum  of  the  Royal  College  of  Surgeons  of 

England.) 

Actions. — The  Gluteus  maximus,  when  it  takes  its  fixed  point  from  the  pelvis, 
extends  the  femur  and  brings  the  bent  thigh  into  a  line  with  the  body.  Taking 
its  fixed  point  from  below,  it  acts  upon  the  pelvis,  supporting  it  and  the  whole 
trunk  upon  the  head  of  the  femur,  which  is  especially  obvious  in  standing  on  one 
leg.  Its  most  powerful  action  is  to  cause  the  body  to  regain  the  erect  position 
after  stooping  by  drawing  the  pelvis  backward,  being  assisted  in  this  action  by 
the  Biceps,  Semitendinosus,  and  Semimembranosus.  The  Gluteus  maximus  is  a 
tensor  of  the  fascia  lata,  and  by  its  connection  with  the  ilio-tibial  band  it  steadies 
the  femur  on  the  articular  surface  of  the  tibia  during  standing,  when  the  extensor 
muscles  are  relaxed.  The  lower  part  of  the  muscle  also  acts  as  an  adductor  and 
external  rotator  of  the  limb.  The  Gluteus  medius  and  minimus  abduct  the 
thigh  when  the  limb  is  extended,  and  are  principally  called  into  action  in 
supporting  the.  body  on  one  limb,  in  conjunction  with  the  Tensor  fasciae  femoris. 
Their  anterior  fibres,  by  drawing  the  great  trochanter  forward,  rotate  the  thigh 
inward,  in  which  action  they  are  also  assisted  by  the  Tensor  fascire  femoris.  The 
remaining  muscles  are  powerful  rotators  of  the  thigh  outward.  In  the  sitting 
posture,  when  the  thigh  is  flexed  upon  the  pelvis,  their  action  as  rotator  ceases,  and 
they  become  abductors,  with  the  exception  of  the  Obturator  externus,  which  still 
rotates  the  femur  outward.  When  the  femur  is  fixed,  the  Pyriformis  and  Obturator 
muscles  serve  to  draw  the  pelvis  forward  if  it  has  been  inclined  backward,  and 
assist  in  steadying  it  upon  the  head  of  the  femur. 


432  THE   MUSCLES   AND    FASCIAE. 

4.  Posterior  Femoral  Region. 

Biceps.  Semitendinosus.  Semimembranosus. 

(Hamstring  muscles.) 

Dissection  (Fig.  255). — Make  a  vertical  incision  along  the  middle  of  the  back  of  the  thigh, 
from  the  lower  fold  of  the  nates  to  about  three  inches  below  the  back  of  the  knee-joint,  and 
there  connect  it  with  a  transverse  incision,  carried  from  the  inner  to  the  outer  side  of  the  leg. 
Make  a  third  incision  transversely  at  the  junction  of  the  middle  with  the  lower  third  of  the 
thigh.  The  integument  having  been  removed  from  the  back  of  the  knee,  and  the  boundaries 
of  the  popliteal  space  examined,  the  removal  of  the  integument  from  the  remaining  part  of 
the  thigh  should  be  continued,  when  the  fascia  and  muscles  of  this  region  will  be  exposed. 

The  Biceps  (Biceps  flexor  cruris)  is  a  large  muscle,  of  considerable  length, 
situated  on  the  posterior  and  outer  aspect  of -the  thigh  (Fig.  256).  It  arises  by 
two  heads.  One,  the  long  head,  arises  from  the  lower  and  inner  impression  on 
the  back  part  of  the  tuberosity  of  the  ischium,  by  a  tendon  common  to  it  and  the 
Semitendinosus,  and  from  the  lower  part  of  the  great  sacro-sciatic  ligament.  The 
femoral,  or  short  head,  arises  from  the  outer  lip  of  the  linea  aspera,  between  the 
Adductor  magnus  and  Vastus  externus,  extending  up  almost  as  high  as  the 
insertion  of  the  Gluteus  maximus ;  from  the  outer  prolongation  of  the  linea  aspera 
to  within  two  inches  of  the  outer  condyle ;  and  from  the  external  intermuscular 
septum.  The  fibres  of  the  long  head  form  a  fusiform  belly,  which,  passing 
obliquely  downward  and  a  little  outward,  terminates  in  an  aponeurosis  which 
covers  the  posterior  surface  of  the  muscle,  and  receives  the  fibres  of  the  short 
head  :  this  aponeurosis  becomes  gradually  contracted  into  a  tendon,  which  is 
inserted  into  the  outer  side  of  the  head  of  the  fibula,  and  by  a  small  slip  into  the 
lateral  surface  of  the  external  tuberosity  of  the  tibia.  At  its  insertion  the  tendon 
divides  into  two  portions,  which  embrace  the  long  external  lateral  ligament  of 
the  knee-joint.  From  the  posterior  border  of  the  tendon  a  thin  expansion  is 
given  off  to  the  fascia  of  the  leg.  The  tendon  of  this  muscle  forms  the  outer 
hamstring. 

Relations. — By  its  superficial  surface,  with  the  Gluteus  maximus  and  the 
small  sciatic  nerve,  the  fascia  lata,  and  integument.  By  its  deep  surface,  with 
the  Semimembranosus,  Adductor  magnus,  and  Vastus  externus,  the  great  sciatic 
nerve,  and,  near  its  insertion,  with  the  external  head  of  the  Gastrocnemius, 
Plantaris,  the  superior  external  articular  artery,  and  the  external  popliteal  nerve. 

The  Semitendinosus,  remarkable  for  the  great  length  of  its  tendon,  is  situated 
at  the  posterior  and  inner  aspect  of  the  thigh.  It  arises  from  the  lower  and  inner 
impression  on  the  tuberosity  of  the  ischium  by  a  tendon  common  to  it  and  the  long 
head  of  the  Biceps;  it  also  arises  from  an  aponeurosis  which  connects  the  adjacent 
surfaces  of  the  two  muscles  to  the  extent  of  about  three  inches  after  their  origin. 
It  forms  a  fusiform  muscle,  which,  passing  downward  and  inward,  terminates  a 
little  below  the  middle  of  the  thigh  in  a  long  round  tendon  which  lies  along  the 
inner  side  of  the  popliteal  space,  then  curves  around  the  inner  tuberosity  of  the 
tibia,  and  is  inserted  into  the  upper  part  of  the  inner  surface  of  the  shaft  of  that 
bone  nearly  as  far  forward  as  its  anterior  border.  At  its  insertion  it  gives  off  from 
its  lower  border  a  prolongation  to  the  deep  fascia  of  the  leg.  This  tendon  lies 
behind  the  tendon  of  the  Sartorius,  and  below  that  of  the  Gracilis,  to  which  it  is 
united.     A  tendinous  intersection  is  usually  observed  about  the  middle  of  the  muscle. 

Relations. — By  its  superficial  surface,  with  the  Gluteus  maximus  and  fascia 
lata ;  by  its  deep  surface,  with  the  Semimembranosus,  Adductor  magnus,  inner 
head  of  the  Gastrocnemius,  and  internal  lateral  ligament  of  the  knee-joint,  the 
last  being  separated  from  the  tendon  by  a  bursa. 

The  Semimembranosus,  so  called  from  its  membranous  tendon  of  origin,  is  sit- 
uated at  the  back  part  and  inner  side  of  the  thigh.  It  arises  by  a  thick  tendon 
from  the  upper  and  outer  impression  on  the  back  part  of  the  tuberosity  of  the 
ischium,  above  and  to  the  outer  side  of  the  Biceps  and  Semitendinosus,  and  is  inserted 
into  the  groove  on  the  inner  and  back  part  of  the  inner  tuberosity  of  the  tibia,  be- 


THE   POSTERIOR    FEMORAL    REGION. 


433 


neath  the  internal  lateral  ligament.  The  tendon  of 
the  muscle  at  its  origin  expands  ir.to  an  aponeurosis 
which  covers  the  upper  part  of  its  anterior  surface : 
from  this  aponeurosis  muscular  fibres  arise,  and  con- 
verge to  another  aponeurosis,  which  covers  the  lower 
part  of  its  posterior  surface  and  contracts  into  the 
tendon  of  insertion.  The  tendon  of  the  muscle  at 
its  insertion  gives  off  certain  fibrous  expansions  ;  one 
of  these,  of  considerable  size,  passes  upward  and 
outward  to  be  inserted  into  the  back  part  of  the 
outer  condyle  of  the  femur,  forming  part  of  the  pos- 
terior ligament  of  the  knee-joint ;  a  second  is  con- 
tinued downward  to  the  fascia  which  covers  the 
Popliteus  muscle.  The  tendon  also  sends  a  few 
fibres  to  join  the  internal  lateral  ligament  of  the 
joint. 

The  tendons  of  the  two  preceding  muscles,  with 
that  of  the  Gracilis,  form  the  inner  hamstring. 

Relations. — By  its  superficial  surface,  with  the 
Gluteus  maximus,  Semitendinosus,  Biceps,  and  fas- 
cia lata ;  by  its  deep  surface,  with  the  origin  of  the 
Quadratus  femoris,  popliteal  vessels,  Adductor  mag- 
nus,  and  inner  head  of  the  Gastrocnemius,  from 
which  it  is  separated  by  a  synovial  bursa ;  by  its 
inner  border,  with  the  Gracilis ;  by  its  outer  border, 
with  the  great  sciatic  nerve,  and  its  internal  popliteal 
branch. 

Nerves. — The  muscles  of  this  region  are  supplied 
by  the  first,  second,  and  third  sacral  nerves  through 
the  great  sciatic  nerve. 

Actions. — The  hamstring  muscles  flex  the  leg 
upon  the  thigh.  When  the  knee  is  semiflexed, 
the  Biceps,  in  consequence  of  its  oblique  direc- 
tion downward  and  outward,  rotates  the  leg  slightly 
outward ;  and  the  Semitendinous,  and  to  a  slight 
extent  the  Semimembranosus,  rotate  the  leg  inward, 
assisting  the  Popliteus.  Taking  their  fixed  point 
from  below,  these  muscles  serve  to  support  the  pelvis 
upon  the  head  of  the  femur  and  to  draw  the  trunk 
directly  backward,  as  in  raising  it  from  the  stooping 
position  or  in  feats irdJ'aceength,  when  the  body  is 
thrown  backward  iits  Jisororm  of  an  arch.  When 
the  leg  is  extendeofoctjidoie  thigh,  they  limit  the 
amount  of  flexion  itoiihe  3  trunk  on  the  lower 
limbs.  i&  j-  li§ 

ibl  do 

Surgical  Anatonrjtiui!  ■.  tendons  of  these  muscles 
occasionally  require  subcP^jl  wus  division  in  some  forms  of 
spurious  ankylosis  of  t\\  LaIe-joint  dependent  upon  per- 
manent contraction  and  I  y  of  the  Flexor  muscles,  or 
from  stiffening  of  the  lner  8ntous  and  other  tissues  sur- 
rounding the  joint,  the  resnk  of  disease.  This  is  effected  by 
putting  the  tendon  upon  the  stretch,  and  inserting  a  nar- 
row, sharp-poin  between  it  and  the  skin  :  the  cut- 
ting edge  being  sd  toward  the  tendon,  it  should  be 
divided,  taking  .  ■•  that  the  wound  in  the  skin  is  not 
at  the  same  tin  d.  The  relation  of  the  external 
popliteal  nerve  to  the  tendon  of  the  Biceps  must  always  be 
borne  in  mind  in  di  his  tendon. 
28  1 


leg. 


Fig.  258.— Muscles  of  the  front  of  the 


434  THE   MUSCLES  AND    FASCIsE. 

III.  MUSCLES  AND  FASCLE,  OF  THE  LEG. 

These  may  be  divided  into  three  groups  :  those  on  the  anterior,  those  on  the 
posterior,  and  those  on  the  outer  side  of  the  leg. 

5.  Anterior  Tibio-fibular  Region. 

Tibialis  anticus.  Extensor  longus  digitorum. 

Extensor  proprius  hallucis.1  Peroneus  tertius. 

Dissection  (Fig.  252). — The  knee  should  be  bent,  a  block  placed  beneath  it,  and  the  foot 
kept  in  an  extended  position ;  then  make  an  incision  through  the  integument  in  the  middle 
line  of  the  leg  to  the  ankle,  and  continue  it  along  the  dorsum  of  the  foot  to  the  toes.  Make  a 
second  incision  transversely  across  the  ankle,  and  a  third  in  the  same  direction  across  the  bases 
of  the  toes ;  remove  the  flaps  of  integument  included  between  these  incisions  in  order  to  examine 
the  deep  fascia  of  the  leg. 

The  Deep  Fascia  of  the  Leg  forms  a  complete  investment  to  the  muscles, 
but  is  not  continued  over  the  subcutaneous  surfaces  of  the  bones.  It  is  con- 
tinuous above  with  the  fascia  lata,  receiving  an  expansion  from  the  tendon 
of  the  Biceps  on  the  outer  side,  and  from  the  tendons  of  the  Sartorius,  Gracilis, 
and  Semitendinosus  on  the  inner  side  ;  in  front  it  blends  with  the  periosteum 
covering  the  subcutaneous  surface  of  the  tibia,  and  with  that  covering  the  head 
and  external  malleolus  of  the  fibula  ;  below  it  is  continuous  with  the  annular 
ligaments  of  the  ankle.  It  is  thick  and  dense  in  the  upper  and  anterior  part 
of  the  leg,  and  gives  attachment,  by  its  deep  surface,  to  the  Tibialis  anticus 
and  Extensor  longus  digitorum  muscles,  but  thinner  behind,  where  it  covers 
the  Gastrocnemius  and  Soleus  muscles.  Over  the  popliteal  space  it  is  much 
strengthened  by  transverse  fibres  which  stretch  across  from  the  inner  to  the  outer 
hamstring  muscles,  and  it  is  here  perforated  by  the  external  saphenous  vein.  Its 
deep  surface  gives  off,  on  the  outer  side  of  the  leg,  two  strong  intermuscular  septa 
which  enclose  the  Peronei  muscles,  and  separate  them  from  the  muscles  on  the  an- 
terior and  posterior  tibial  regions  and  several  smaller  and  more  slender  processes 
which  enclose  the  individual  muscles  in  each  region  ;  at  the  same  time  a  broad 
transverse  intermuscular  septum,  called  the  deep  transverse  fascia  of  the  leg,  inter- 
venes between  the  superficial  and  deep  muscles  :n  the  posterior  tibio-fibular  region. 

Remove  the  fascia  by  dividing  it  in  the  same  direction  as  the  integument,  excepting  oppo- 
site the  ankle,  where  it  should  be  left  entire.  Commence  th-e  removal  of  the  fascia  from  below, 
opposite  the  tendons,  and  detach  it  in  the  line  of  direction  of  the  muscular  fibres. 

The  Tibialis  anticus  is  situated  on  the  outer  side  of  the  tibia ;  it  is  thick  and 
fleshy  at  its  upper  part,  tendinous  below.  It  arises  from  the  outer  tuberosity  and 
upper  two-thirds  of  the  external  surface  of  the  shaft  of  the  tibia;  from  the  adjoin- 
ing part  of  the  interosseous  membrane  ;  from  the  deep  surlnu^  of  the  fascia ;  and 
from  the  intermuscular  septum  between  it  and  the  Exte»(loniOI1gUS  digitorum: 
the  fibres  pass  vertically  downward,  and  terminate  in  a  teip  ini  which  is  apparent 
on  the  anterior  surface  of  the  muscle  at  the  lower  third  of  1  .rfaqeg.  After  passing 
through  the  innermost  compartment  of  the  anterior  annulai  1Ils^ament,  it  is  inserted 
into  the  inner  and  under  surface  of  the  internal  cuneiform ie  Ine  and  base  of  the 


metatarsal  bone  of  the  great  toe.  jhe 

Relations. — By  its  anterior  surface,  with  the  fascia  ancjt  t'ith  the  annular  liga- 
ment; by  its  posterior  surface,  with  the  interosseous  membpeiie,  tibia,  ankle-joint, 
and  inner  side  of  the  tarsus:  this  surface  also  overlaps  th    interior  tibial  vessels 

1  There  is  no  such  word  as  "  Hallux, -eis."  It  is  the  result  of  some  ignorant  blunder,  copied 
until  it  has  become  established  by  usage  ;  it  has  been  thought  better,  therefore,  to  retain  it.  Accord- 
ing to  Lewis  and  Short  the  word  is  Allex,  masculine  ;  genitive,  Al/LICiSf  the  great  toe,  and  the  cor- 
rect rendering  would  be  Extensor  proprius  allicis.  It  is  a  rare  word,  and}  is  sometimes  spelt,  but  not 
so  correctly,  ''  Hallex."  It  is  used  by  Plautus,  in  t lie  "  Pcenulus"  V.,  y.  31,  of  a  little  man,  as  we 
might  say  "  a  hop-o'-my-thumb."  "  Tunc  hie  am  u  tor  audes  esse,  allez  vil'i"  (To  think  of  you  daring 
to  make  up  to  her,  you  hop-o'-my-thumb  !  i.  The  word  "  alex,"  sometimes  spelt  "  allex,"  a  fish 
sauce,  is  probably  a  different  word  altogether.      Jt  is  used  by  Horace  and  Pliny. 


THE   ANTERIOR    TIBIO-FIBULAR    BEGIOX.  435 

and  nerve  in  the  upper  part  of  the  leg.  By  its  inner  surface,  with  the  tibia;  by 
its  outer  surface,  with  the  Extensor  longus  cligitorum  and  Extensor  proprius  hal- 
lucis,  and  the  anterior  tibial  vessels  and  nerve. 

The  Extensor  proprius  hallucis  is  a  thin,  elongated,  and  flattened  muscle  situ- 
ated between  the  Tibialis  anticus  and  Extensor  longus  digitorum.  It  arises  from 
the  anterior  surface  of  the  fibula  for  about  the  middle  two-fourths  of  its  extent,  its 
origin  being  internal  to  that  of  the  Extensor  longus  digitorum ;  it  also  arises  from 
the  interosseous  membrane  to  a  similar  extent.  The  fibres  pass  downward,  and 
terminate  in  a  tendon  which  occupies  the  anterior  border  of  the  muscle,  passes 
through  a  distinct  compartment  in  the  lower  portion  of  the  annular  ligament, 
crosses  the  anterior  tibial  vessels  near  the  bend  of  the  ankle,  and  is  inserted  into 
the  base  of  the  last  phalanx  of  the  great  toe.  Opposite  the  metatarso-phalangeal 
articulation  the  tendon  gives  off  a  thin  prolongation  on  each  side,  which  covers  the 
surface  of  the  joint.  It  usually  sends  an  expansion  from  the  inner  side  of  the 
tendon,  to  be  inserted  into  the  base  of  the  first  phalanx. 

Relations. — By  its  anterior  surface,  with  the  fascia  and  the  anterior  annular  liga- 
ment; by  its  posterior  surface,  with  the  interosseous  membrane,  fibula,  tibia,  and 
ankle-joint ;  by  its  outer  side,  with  the  Extensor  longus  digitorum  above,  the  dorsalis 
pedis  vessels,  anterior  tibial  nerve,  and  Extensor  brevis  digitorum  below ;  by  its 
inner  side,  with  the  Tibialis  anticus  and  the  anterior  tibial  vessels  above.  The 
muscle  is  external  to  the  anterior  tibial  vessels  in  the  upper  part  of  the  leg  ;  but 
in  the  lower  third  its  tendon  crosses  over  them,  so  that  it  lies  internal  to  them  on 
the  dorsum  of  the  foot. 

The  Extensor  longus  digitorum  is  an  elongated,  flattened,  penniform  muscle 
situated  the  most  externally  of  all  the  muscles  on  the  fore  part  of  the  leg.  It 
arises  from  the  outer  tuberosity  of  the  tibia  ;  from  the  upper  three-fourths  of 
the  anterior  surface  of  the  shaft  of  the  fibula ;  from  the  interosseous  membrane ; 
from  the  deep  surface  of  the  fascia ;  and  from  the  intermuscular  septa  between  it 
and  the  Tibialis  anticus  on  the  inner  and  the  Peronei  on  the  outer  side.  The 
tendon  enters  a  canal  in  the  annular  ligament  with  the  Peroneus  tertius,  and  divides 
into  four  slips,  which  run  across  the  dorsum  of  the  foot  and  are  inserted  into  the 
second  and  third  phalanges  of  the  four  lesser  toes.  The  mode  in  which  the  tendons 
are  inserted  is  the  following  :  The  three  inner  tendons  opposite  the  metatarso- 
phalangeal articulation  are  joined,  on  their  outer  side,  by  a  tendon  of  the  Extensor 
brevis  digitorum.  They  all  receive  a  fibrous  expansion  from  the  Interossei  and 
Lumbricales,  and  then  spread  out  into  a  broad  aponeurosis,  which  covers  the  dorsal 
surface  of  the  first  phalanx  :  this  aponeurosis,  at  the  articulation  of  the  first  with 
the  second  phalanx,  divides  into  three  slips — a  middle  one,  which  is  inserted  into 
the  base  of  the  second  phalanx,  and  two  lateral  slips,  which,  after  uniting  on  the 
dorsal  surface  of  the  second  phalanx,  are  continued  onward,  to  be  inserted  into 
the  base  of  the  third. 

Relations. — By  its  anterior  surface,  with  the  fascia  and  the  annular  ligament ; 
by  its  posterior  surface,  with  the  fibula,  interosseous  membrane,  ankle-joint,  and 
Extensor  brevis  digitorum ;  by  its  inner  side,  with  the  Tibialis  anticus,  Extensor 
proprius  hallucis,  and  anterior  tibial  vessels  and  nerve ;  by  its  outer  side,  with  the 
Peroneus  longus  and  brevis. 

The  Peroneus  tertius  is  a  part  of  the  Extensor  longus  digitorum,  and  might 
he  described  as  its  fifth  tendon.  The  fibres  belonging  to  this  tendon  arise  from 
the  lower  fourth  of  the  anterior  surface  of  the  fibula,  from  the  lower  part  of  the 
interosseous  membrane,  and  from  an  intermuscular  septum  between  it  and  the 
Peroneus  brevis.  The  tendon,  after  passing  through  the  same  canal  in  the 
annular  ligament  as  the  Extensor  longus  digitorum,  is  inserted  into  the  dorsal 
surface  of  the  base  of  the  metatarsal  bone  of  the  little  toe.  This  muscle  is  some- 
times wanting. 

Nerves. — These  muscles  are  supplied  by  the  fourth  and  fifth  lumbar  and  first 
sacral  nerves  through  the  anterior  tibial  nerve. 

Actions. — The  Tibialis  anticus  and  Peroneus  tertius  are  the  direct  flexors  of  the 


436  THE  MUSCLES  AND  E^.JJE. 

foot  at  the  ankle-joint;  the  former  muscle,  when  acting  in  conjunction  with  the 
Tibialis  posticus,  raises  the  inner  border  of  thp  foot  (i.  e.,  inverts  the  foot);  and 
the  latter,  acting  with  the  Peroneus  brevis  and  longus,  draws  the  outer  border  of 
the  foot  upward  and  the  sole  outward  (i.  e.,  everts  the  foot).  The  Extensor  longus 
digitorum  and  Extensor  proprius  hallucis  extend  the  phalanges  of  the  toes,  and, 
continuing  their  action,  flex  the  foot  upon  the  leg.  Taking  their  fixed  point  from 
below,  in  the  erect  posture,  all  these  muscles  serve  to  fix  the  bones  of  the  leg  in  the 
perpendicular  position,  and  give  increased  strength  to  the  ankle-joint. 

6.  Posterior  Tibio -fibular  Region. 

Dissection  (Fig.  255). — Make  a  vertical  incision  along  the  middle  line  of  the  back  of  the 
leg,  from  the  lower  part  of  the  popliteal  space  to  the  heel,  connecting  it  below  by  a  transverse 
incision  extending  between  the  two  malleoli ;  the  flaps  of  integument  being  removed,  the  fascia 
and  muscles  should  be  examined. 

The  muscles  in  this  region  of  the  leg  are  subdivided  into  two  layers — super- 
ficial and  deep.  The  superficial  layer  constitutes  a  powerful  muscular  mass, 
forming  the  calf  of  the  leg.  Their  large  size  is  one  of  the  most  characteristic 
features  of  the  muscular  apparatus  in  man,  and  bears  a  direct  connection  with  his 
ordinary  attitude  and  mode  of  progression. 

Superficial  Layer. 
Gastrocnemius.  Soleus.  Plantaris. 

The  Gastrocnemius  is  the  most  superficial  muscle,  and  forms  the  greater  part 
of  the  calf.  It  arises  by  two  heads,  which  are  connected  to  the  condyles  of  the  femur 
by  two  strong  flat  tendons.  The  inner  and  larger  head  arises  from  a  depression  at 
the  upper  and  back  part  of  the  inner  condyle  and  from  the  adjacent  part  of  the 
femur.  The  outer  head  arises  from  an  impression  on  the  outer  side  of  the  external 
condyle  and  from  the  posterior  surface  of  the  femur  immediately  above  the  condyle. 
Both  heads,  also,  arise  by  a  few  tendinous  and  fleshy  fibres  from  the  ridges  which 
are  continued  upward  from  the  condyles  to  the  linea  aspera.  Each  tendon  spreads 
out  into  an  aponeurosis,  which  covers  the  posterior  surface  of  that  portion  of  the 
muscle  to  which  it  belongs  •  the  muscular  fibres  of  the  inner  head  being  thicker  and 
extending  lower  than  those  of  the  outer.  From  the  anterior  surface  of  these  tendi- 
nous expansions  muscular  fibres  are  given  off.  The  fibres  in  the  median  line,  which 
correspond  to  the  accessory  portions  of  the  muscle  derived  from  the  bifurcations  of 
the  linea  aspera,  unite  at  an  angle  upon  a  median  tendinous  raphe  below :  the 
remaining  fibres  converge  to  an  aponeurosis  which  covers  the  anterior  surface  of 
the  muscle,  and  this,  gradually  contracting,  unites  with  the  tendon  of  the  Soleus, 
and  forms  with  it  the  tendo  Achillis. 

Relations. — By  its  superfiical  surface,  with  the  fascia  of  the  leg,  which  separates 
it  from  the  external  saphenous  vein  and  nerve  ;  by  its  deep  surface,  with  the  pos- 
terior ligament  of  the  knee-joint,  the  Popliteus,  Soleus,  Plantaris,  popliteal  vessels, 
and  internal  popliteal  nerve.  The  tendon  of  the  inner  head  corresponds  with  the 
back  part  of  the  inner  condyle,  from  which  it  is  separated  by  a  synovial  bursa, 
which,  in  some  cases,  communicates  with  the  cavity  of  the  knee-joint.  The  ten- 
don of  the  outer  head  contains  a  sesamoid  fibro-cartilage  (rarely  osseous)  where  it 
plays  over  the  corresponding  outer  condyle ;  and  one  is  occasionally  found  in  the 
tendon  of  the  inner  head. 

The  Gastrocnemius  should  be  divided  across,  just  below  its  origin,  and  turned  downward, 
in  order  to  expose  the  next  two  muscles. 

The  Soleus  is  a  broad  flat  muscle  situated  immediately  beneath  the  Gastroc- 
nemius. It  has  received  its  name  from  its  resemblance  in  shape  to  a  sole-fish.  It 
arises  by  tendinous  fibres  from  the  back  part  of  the  head  of  the  fibula  and  from 
the  upper  third  of  the  posterior  surface  of  its  shaft ;  from  the  oblique  line  of  the 


THE   POSTERIOR    TIBIO-FIBULAR    REGION. 


437 


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O'CBN  E 

Wo 


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tibia  and  from  the  middle  third  of  its  internal  border ;  some  fibres  also  arise  from 
a  tendinous  arch  placed  between  the  tibial  and  fibular  origins  of  the  muscle,  be- 
neath which  the  popliteal  vessels  and  internal 
popliteal  nerve  pass.  The  fibres  pass  back- 
ward to  an  aponeurosis  which  covers  the  pos- 
terior surface  of  the  muscle,  and  this,  gradually 
becoming  thicker  and  narrower,  joins  with  the 
tendon  of  the  Gastrocnemius,  and  forms  with 
it  the  tendo  Achillis. 

Relations. — By  its  superficial  surface, 
with  the  Gastrocnemius  and  Plantaris ;  by 
its  deep  surface,  with  the  Flexor  longus 
digitorum,  Flexor  longus  hallucis,  Tibialis 
posticus,  and  posterior  tibial  vessels  and 
nerve,  from  which  it  is  separated  by  the 
transverse  intermuscular  septum  or  deep 
transverse  fascia  of  the  leg. 

The  Tendo  Achillis,  the  common  tendon 
of  the  Gastrocnemius  and  Soleus,1  is  the 
thickest  and  strongest  tendon  in  the  body. 
It  is  about  six  inches  in  length,  and  com- 
mences about  the  middle  of  the  leg,  but  re- 
ceives fleshy  fibres  on  its  anterior  surface 
nearly  to  its  lower  end.  Gradually  becoming 
contracted  below,  it  is  inserted  into  the  lower 
part  of  the  posterior  surface  of  the  os  calcis, 
a  synovial  bursa  being  interposed  between 
the  tendon  and  the  upper  part  of  this  surface. 
The  tendon  spreads  out  somewhat  at  its  lower 
end,  so  that  its  narrowest  part  is  usually  about 
an  inch  and  a  half  above  its  insertion.  The 
tendon  is  covered  by  the  fascia  and  the  in- 
tegument, and  is  separated  from  the  deep 
muscles  and  vessels  by  a  considerable  interval 
filled  up  with  areolar  and  adipose  tissue. 
Along  its  outer  side,  but  superficial  to  it,  is 
the  external  saphenous  vein. 

The  Plantaris  is  an  extremely  diminutive 
muscle  placed  between  the  Gastrocnemius 
and  Soleus,  and  remarkable  for  its  long  and 
delicate  tendon.  It  arises  from  the  lower 
part  of  the  outer  prolongation  of  the  linea 
aspera  and  from  the  posterior  ligament  of  the 
knee-joint.  It  forms  a  small  fusiform  belly, 
about  three  or  four  inches  in  length,  termi- 
nating in  a  long  slender  tendon  which  crosses 
obliquely  between  the  two  muscles  of  the  calf, 
and,  running  along  the  inner  border  of  the 
tendo  Achillis,  is  inserted  with  it  into  the 
posterior  part  of  the  os  calcis.  This  muscle 
is  occasionally  double,  and  is  sometimes  want- 
ing. Occasionally,  its  tendon  is  lost  in  the 
fascia  of  the  lesr. 


iC 


Tendons  of 

5NEUS    LONGUS 
nd    BREVIS. 


Ca7c/s'\ 


Fig.  259.— Muscles  of  the  back  of  the  leg. 
Superficial  layer. 


internal  annular  ligament  or  in  the 

Nerves. — The  Gastrocnemius  is  supplied  by  the  first  and  second  sacral  nerves. 

1  These  two  muscles  with  a  common  tendon  are  by  some  anatomists  classed  together  as  one  muscle, 
the  Triceps  surce,  the  two  heads  of  origin  of  the  Gastrocnemius  and  the  Soleus  constituting  the  three 
heads  of  the  Triceps,  and  the  tendo  Achillis  the  single  tendon  of  insertion. 


438  THE   MUSCLES  AND    FASCi^E. 

and  the  Plantaris  by  the  fourth  and  fifth  lumbar  and  first  sacral  nerves  through  the 
internal  popliteal.  The  Soleus  is  supplied  by  the  fifth  lumbar  and  first  and  second 
sacral  nerves  through  the  internal  popliteal  and  posterior  tibial. 

Actions. — The  muscles  of  the  calf  are  the  chief  extensors  of  the  foot  at  the 
ankle-joint.  They  possess  considerable  power,  and  are  constantly  called  into  use  in 
standing,  walking,  dancing,  and  leaping  ;  hence  the  large  size  they  usually  present. 
In  walking  these  muscles  draw  powerfully  upon  the  os  calcis,  raising  the  heel,  and 
with  it  the  entire  body,  from  the  ground ;  the  body  being  thus  supported  on  the 
raised  foot,  the  opposite  limb  can  be  carried  forward.  In  standing,  the  Soleus, 
taking  its  fixed  point  from  below,  steadies  the  leg  upon  the  foot,  and  prevents  the 
body  from  falling  forward,  to  which  there  is  a  constant  tendency  from  the  superin- 
cumbent weight.  The  Gastrocnemius,  acting  from  below,  serves  to  flex  the  femur 
upon  the  tibia,  assisted  by  the  Popliteus.  The  Plantaris  is  the  rudiment  of  a  large 
muscle  which  exists  in  some  of  the  lower  animals  and  is  continued  over  the  os  cal- 
cis to  be  inserted  into  the  plantar  fascia.  In  man  it  is  an  accessory  to  the  Gastroc- 
nemius, extending  the  ankle  if  the  foot  is  free,  or  bending  the  knee  if  the  foot  is 
fixed.  Possibly,  acting  from  below,  by  its  attachment  to  the  posterior  ligament 
of  the  knee-joint,  it  may  pull  that  ligament  backward  during  flexion,  and  so  pro- 
tect it  from  being  compressed  between  the  two  articular  surfaces. 

Deep  Layer  (Fig.  260). 

Popliteus.  Flexor  longus  digitorum. 

Flexor  longus  hallucis.  Tibialis  posticus. 

Dissection. — Detach  the  Soleus  from  its  attachment  to  the  fibula  and  tibia,  and  turn  ifc 
downward,  when  the  deep  layer  of  muscles  is  exposed,  covered  by  the  deep  transverse  fascia  of 
the  leg. 

The  Deep  Transverse  Fascia  of  the  leg  is  a  transversely  placed,  intermuscular 
septum,  between  the  superficial  and  deep  muscles  in  the  posterior  tibio-fibular  region. 
On  either  side  it  is  connected  to  the  margins  of  the  tibia  and  fibula.  Above,  where 
it  covers  the  Popliteus,  it  is  thick  and  dense,  and  receives  an  expansion  from  the 
tendon  of  the  Semimembranosus ;  it  is  thinner  in  the  middle  of  the  leg,  but  below, 
where  it  covers  the  tendons  passing  behind  the  malleoli,  it  is  thickened  and  con- 
tinuous with  the  internal  annular  ligament. 

This  fascia  should  now  be  removed,  commencing  from  below  opposite  the  tendons,  and 
detaching  it  from  the  muscles  in  the  direction  of  their  fibres. 

The  Popliteus  is  a  thin,  flat,  triangular  muscle,  which  forms  part  of  the  floor  of 
the  popliteal  space.  It  arises  by  a  strong  tendon,  about  an  inchjn  length,  from  a 
deep  depression  on  the  outer  side  of  the  external  condyle  of  the  femur,  and  from 
the  posterior  ligament  of  the  knee-joint,  and  is  inserted  into  the  inner  two-thirds  of 
the  triangular  surface  above  the  oblique  line  on  the  posterior  surface  of  the  shaft  of 
the  tibia,  and  into  the  tendinous  expansion  covering  the  surface  of  the  muscle. 
The  tendon  of  the  muscle  is  covered  by  that  of  the  Biceps  and  by  the  external  lat- 
eral ligament  of  the  knee-joint ;  it  grooves  the  posterior  border  of  the  external  semi- 
lunar fibro-cartilage,  and  is  invested  by  the  synovial  membrane  of  the  knee-joint. 

Relations. — By  its  superficial  surface,  with  the  fascia  covering  it,  which  separates 
it  from  the  Gastrocnemius,  Plantaris,  popliteal  vessels,  and  internal  popliteal  nerve ;. 
by  its  deep  surface,  with  the  knee-joint  and  back  of  the  tibia. 

The  Flexor  Jongus  hallucis  is  situated  on  the  fibular  side  of  the  leg,  and  is  the 
most  superficial  and  largest  of  the  three  next  muscles.  It  arises  from  the  lower 
two-thirds  of  the  posterior  surface  of  the  shaft  of  the  fibula,  with  the  exception  of 
an  inch  at  its  lowest  part ;  from  the  lower  part  of  the  interosseous  membrane ; 
from  an  intermuscular  septum  between  it  and  the  Peronei,  externally ;  and  from 
the  fascia  covering  the  Tibialis  posticus  internally.  The  fibres  pass  obliquely 
downward  and  backward,  and  terminate  in  a  tendon  Avhich  occupies  nearly  the 
whole  length  of  the  posterior  surface  of  the  muscle.  This  tendon  occnpies  a  groove 
on  the  posterior  surface  of  the  lower  end  of  the  tibia ;  it  then  lies  in  a  second  groove 


THE   POSTERIOR    TIBIO-FIBULAR    REGION. 


439 


is 


W 


/.! 


on  the  posterior  surface  <of  the  astragalus,  and  finally  in  a  third  groove,  beneath  the 
sustentaculum  tali  of  the  os.,calcis,  and  passes  into  the  sole  of  the  foot,  where 
it  runs  forward  between  the  two  heads  of  the  Flexor  brevis  hallucis,  and 
inserted  into  the  base  of  the  last  phalanx  of  the  great 
toe.  The  grooves  in  the  astragalus  and  os  calcis,  which 
contain  the  tendon  of  the  muscle,  are  converted  by  tendi- 
nous fibres  into  distinct  canals  lined  by  synovial  membrane ; 
and  as  the  tendon  crosses  the  sole  of  the  foot,  it  is  con- 
nected to  the  common  flexor  by  a  tendinous  slip. 

Relations. — By  its  superficial  surface,  with  the  Soleus 
and  tendo  Achillis,  from  which  it  is  separated  by  the  deep 
transverse  fascia ;  by  its  deep  surface,  with  the  fibula, 
Tibialis  posticus,  the  peroneal  vessels,  the  lower  part  of 
the  interosseous  membrane,  and  the  ankle-joint;  by  its 
outer  border,  with  the  Peronei ;  by  its  inner  border,  with 
the  Tibialis  posticus  and  posterior  tibial  vessels  and  nerve. 
In  the  sole  of  the  foot  it  lies  above  the  Abductor  hallucis 
and  Flexor  long-us  digitorum. 

The  Flexor  longus  digitorum  (perforans)  is  situated  on 
the  tibial  side  of  the  leg.  At  its  origin  it  is  thin  and 
pointed,  but  gradually  increases  in  size  as  it  descends. 
It  arises  from  the  posterior  surface  of  the  shaft  of  the  tibia, 
immediately  below  the  oblique  line  to  within  three  inches 
of  its  extremity,  internal  to  the  tibial  origin  of  the  Tibialis 
posticus ;  some  fibres  also  arise  from  the  fascia  covering 
the  Tibialis  posticus.  The  fibres  terminate  in  a  tendon 
which  runs  nearly  the  whole  length  of  the  posterior  sur- 
face of  the  muscle.  This  tendon  passes  behind  the  internal 
malleolus  in  a  groove,  common  to  it  and  the  Tibialis  pos- 
ticus, but  separated  from  the  latter  by  a  fibrous  septum, 
each  tendon  being  contained  in  a  special  sheath  lined  by 
a  separate  synovial  membrane.  It  then  passes  obliquely 
forward  and  outward,  superficial  to  the  internal  lateral 
ligament  into  the  sole  of  the  foot  (Fig.  262),  where,  cross- 
ing superficially  to  the  tendon  of  the  Flexor  longus  hal- 
lucis,1 to  which  it  is  connected  by  a  strong  tendinous  slip, 
it  becomes  expanded,  is  joined  by  the  Flexor  accessorius, 
and  finally  divides  into  four  tendons  which  are  inserted 
into  the  bases  of  the  last  phalanges  of  the  four  lesser  toes, 
each  tendon  passing  through  a  fissure  in  the  tendon  of  the 
Flexor  brevis  digitorum  opposite  the  base  of  the  first 
phalanges. 

Relations. — In  the  leg :  by  its  superficial  surface, 
with  the  posterior  tibial  vessels  and  nerve,  and  the  deep 
transverse  fascia,  which  separates  it  from  the  Soleus 
muscle ;  by  its  deep  surface,  with  the  Tibia  and  Tibialis 
posticus.  In  the  foot  it  is  covered  by  the  Abductor 
hallucis  and  Flexor  brevis  digitorum,  and  crosses  superfi- 
cial to  the  Flexor  longus  hallucis. 

The  Tibialis  posticus  lies  between  the  two  preceding 
muscles,  and  is  the  most  deeply  seated  of  all  the  muscles 
in  the  leg.  It  commences  above  by  two  pointed  processes, 
separated  by  an  angular  interval,  through  which  the  an- 
terior tibial  vessels  pass  forward  to  the  front  of  the  leg.  It  arises  from  the  whole  of 
the  posterior  surface  of  the  interosseous  membrane,  excepting  its  lowest  part,  from 
the  outer  portion  of  the  posterior  surface  of  the  shaft  of  the  tibia,  between  the 

1  That  is,  in  the  order  of  dissection  of  the  sole  of  the  foot. 


Fir,.  260.— Muscles  of  the 
back  of  the  leg.    Deep  layer. 


440  THE  MUSCLES  AND   FASCIA. 

commencement  of  the  oblique  line  above,  and  the  junction  of  the  middle  and  lower 
third  of  the  shaft  below ;  and  from  the  upper  two-thirds  of  the  internal  surface  of 
the  fibula ;  some  fibres  also  arise  from  the  deep  transverse  fascia  and  from  the 
intermuscular  septa,  separating  it  from  the  adjacent  muscles  on  each  side.  This 
muscle,  in  the  lower  fourth  of  the  leg,  passes  in  front  of  the  Flexor  longus 
digitoram,  and  terminates  in  a  tendon  which  passes  through  a  groove  behind 
the  inner  malleolus  with  the  tendon  of  that  muscle,  but  enclosed  in  a  separate 
sheath ;  it  then  passes  through  another  sheath,  over  the  internal  lateral  liga- 
ment into  the  foot,  and  then  beneath  the  inferior  calcaneonavicular  ligament, 
and  is  inserted  into  the  tuberosity  of  the  navicular  and  internal  cuneiform  bones. 
The  tendon  of  this  muscle  contains  a  sesamoid  fibro-cartilage  as  it  passes  over  the 
navicular  bone,  and  gives  off  fibrous  expansions,  one  of  which  passes  backward  to 
the  sustentaculum  tali  of  the  os  calcis,  others  outward  to  the  middle  and  external 
cuneiform  and  cuboid,  and  some  forward  to  the  bases  of  the  second,  third,  and 
fourth  metatarsal  bones  (Fig.  263). 

Relations. — By  its  superficial  surface,  with  the  Soleus,  from  which  it  is 
separated  by  the  deep  transverse  fascia,  the  Flexor  longus  digitorum,  the  posterior 
tibial  vessels  and  nerve,  and  the  peroneal  vessels ;  by  its  deep  surface,  with  the 
interosseous  ligament,  the  tibia,  fibula,  and  ankle-joint. 

Nerves. — The  Popliteus  is  supplied  by  the  fourth  and  fifth  lumbar  and  first  sacral 
nerves,  through  the  internal  popliteal ;  the  Flexor  longus  digitorum  and  Tibialis 
posticus  by  the  fifth  lumbar  and  first  sacral ;  and  the  Flexor  longus  hallucis  by  the 
fifth  lumbar  and  first  and  second  sacral  nerves  through  the  posterior  tibial. 

Actions. — The  Popliteus  assists  in  flexing  the  leg  upon  the  thigh  ;  when  the  leg 
is  flexed,  it  will  rotate  the  tibia  inward.  It  is  especially  called  into  action  at  the 
commencement  of  the  act  of  bending  the  knee,  inasmuch  as  it  produces  a  slight 
inward  rotation  of  the  tibia,  which  is  essential  in  the  early  stage  of  this  movement. 
The  Tibialis  posticus  is  a  direct  extensor  of  the  foot  at  the  ankle-joint;  acting  in 
conjunction  with  the  Tibialis  anticus,  it  turns  the  sole  of  the  foot  inward  (i.  e., 
inverts  the  foot),  antagonizing  the  Peronei,  which  turn  it  outward  (evert  it).  In 
the  sole  of  the  foot  the  tendon  of  the  Tibialis  posticus  lies  directly  below  the  inferior 
calcaneo-scaphoid  ligament,  and  is  therefore  an  important  factor  in  maintaining  the 
arch  of  the  foot.  The  Flexor  longus  digitorum  and  Flexor  longus  hallucis  are  the 
direct  flexors  of  the  phalanges,  and,  continuing  their  action,  extend  the  foot  upon 
the  leg ;  they  assist  the  Gastrocnemius  and  Soleus  in  extending  the  foot,  as  in  the 
act  of  walking  or  in  standing  on  tiptoe. 

In  consequence  of  the  oblique  direction  of  the  tendon  of  the  long  flexor  the 
toes  would  be  drawn  inward  were  it  not  for  the  Flexor  accessorius  muscle,  which 
is  inserted  into  the  outer  side  of  its  tendon  and  draws  it  to  the  middle  line  of  the 
foot  during  its  action.  Taking  their  fixed  point  from  the  foot,  these  muscles  serve 
to  maintain  the  upright  posture  by  steadying  the  tibia  and  fibula  perpendicularly 
upon  the  ankle-joint.  They  also  serve  to  raise  these  bones  from  the  oblique  posi- 
tion they  assume  in  the  stooping  posture. 

7.  Fibular  Region. 

Peroneus  longus.  Peroneus  brevis. 

Dissection.— The  muscles  are  readily  exposed  by  removing  the  fascia  covering  their  surface, 
from  below  upward,  in  the  line  of  direction  of  their  fibres. 

The  Peroneus  longus  is  situated  at  the  upper  part  of  the  outer  side  of  the  leg, 
and  is  the  more  superficial  of  the  two  muscles.  It  arises  from  the  head  and  upper 
two-thirds  of  the  outer  surface  of  the  shaft  of  the  fibula,  from  the  deep  surface  of 
the  fascia,  and  from  the  intermuscular  septa  between  it  and  the  muscles  on  the 
front,  and  those  on  the  back  of  the  leg,  occasionally  also  by  a  few  fibres  from  the 
outer  tuberosity  of  the  tibia.  Between  its  attachment  to  the  head  and  to  the 
shaft  of  the  fibula  there  is  a  small  interval  of  bone  from  which  no  muscular  fibres 
arise ;  through  this  gap  the  external  popliteal  nerve  passes  beneath  the  muscle. 


THE  FIBULAR   REGION.  441 

It  terminates  in  a  long  tendon,  which  passes  behind  the  outer  malleolus,  in  a 
groove  common  to  it  and  the  tendon  of  the  Peroneus  brevis,  behind  which  it  lies, 
the  groove  being  converted  into  a  canal  by  a  fibrous  band,  and  the  tendons 
invested  by  a  common  synovial  membrane ;  it  is  then  reflected  obliquely  forward 
across  the  outer  side  of  the  os  calcis,  below  its  peroneal  tubercle,  being  contained 
in  a  separate  fibrous  sheath,  lined  by  a  prolongation  of  the  synovial  membrane 
which  lines  the  groove  behind  the  malleolus.  Having  reached  the  outer  side  of 
the  cuboid  bone,  it  runs  in  a  groove  on  the  under  surface  of  that  bone,  which  is 
converted  into  a  canal  by  the  long  calcaneo-cuboid  ligament,  and  is  lined  by  a 
synovial  membrane:  the  tendon  then  crosses  the  sole  of  the  foot  obliquely, 
and  is  inserted  into  the  outer  side  of  the  base  of  the  metatarsal  bone  of  the 
great  toe  and  the  internal  cuneiform  bone.  Occasionally  it  sends  a  slip  to 
the  base  of  the  second  metatarsal  bone.  The  tendon  changes  its  direction  at 
two  points:  first,  behind  the  external  malleolus;  secondly,  on  the  outer  side 
of  the  cuboid  bone ;  in  both  of  these  situations  the  tendon  is  thickened,  and 
in  the  latter  a  sesamoid  fibro-cartilage,  or  sometimes  a  bone,  is  usually  developed 
in  its  substance. 

Relations. — By  its  superficial  surface,  with  the  fascia  and  integument ;  by  its 
deep  surface,  with  the  fibula,  external  popliteal  nerve,  the  Peroneus  brevis,  os 
calcis,  and  cuboid  bone ;  by  its  anterior  border,  with  an  intermuscular  septum, 
which  intervenes  between  it  and  the  Extensor  longus  digitorum  ;  by  its  posterior 
border,  with  an  intermuscular  septum,  which  separates  it  from  the  Soleus  above 
and  the  Flexor  longus  hallucis  below. 

The  Peroneus  brevis  lies  beneath  the  Peroneus  longus,  and  is  shorter  and 
smaller  than  it.  It  arises  from  the  lower  two-thirds  of  the  external  surface  of 
the  shaft  of  the  fibula,  internal  to  the  Peroneus  longus,  and  from  the  intermuscular 
septa  separating  it  from  the  adjacent  muscles  on  the  front  and  back  part  of  the 
leg.  The  fibres  pass  vertically  downward,  and  terminate  in  a  tendon  which  runs 
in  front  of  that  of  the  preceding  muscle  through  the  same  groove,  behind  the 
external  malleolus,  being  contained  in  the  same  fibrous  sheath  and  lubricated  by 
the  same  synovial  membrane.  It  then  passes  through  a  separate  sheath  on  the 
outer  side  of  the  os  calcis,  above  that  for  the  tendon  of  the  Peroneus  longus,  the 
two  tendons  being  here  separated  by  the  peroneal  tubercle,  and  is  finally  inserted 
into  the  tuberosity  at  the  base  of  the  metatarsal  bone  of  the  little  toe,  on  its 
outer  side. 

Relations. — By  its  superficial  surface,  with  the  Peroneus  longus  and  the  fascia 
of  the  leg  and  foot ;  by  its  deep*  surface,  with  the  fibula  and  outer  side  of  the 
os  calcis. 

Nerves. — The  Peroneus  longus  and  brevis  are  supplied  by  the  fourth  and  fifth 
lumbar  and  first  sacral  nerves  through  the  musculo-cutaneous  branch  of  the 
external  popliteal  nerve. 

Actions. — The  Peroneus  longus  and  brevis  extend  the  foot  upon  the  leg,  in 
conjunction  with  the  Tibialis  posticus,  antagonizing  the  Tibialis  anticus  and 
Peroneus  tertius,  which  are  flexors  of  the  foot.  The  Peroneus  longus  also  everts 
the  sole  of  the  foot;  hence  the  extreme  eversion  occasionally  observed  in  fracture 
of  the  lower  end  of  the  fibula,  where  that  bone  offers  no  resistance  to  the  action 
of  this  muscle.  From  the  oblique  direction  of  the  Peroneus  longus  tendon  across 
the  sole  of  the  foot  it  is  an  important  agent  in  the  maintenance  of  the  transverse 
arch  of  the  foot.  Taking  their  fixed  point  below,  the  Peronei  serve  to  steady  the 
leg  upon  the  foot.  This  is  especially  the  case  in  standing  upon  one  leg,  when 
the  tendency  of  the  superincumbent  weight  is  to  throw  the  leg  inward  :  the 
Peroneus  longus  overcomes  this  tendency  by  drawing  on  the  outer  side  of  the 
leg,  and  thus  maintains  the  perpendicular  direction  of  the  limb. 

.  Surgical  Anatomy. — The  student  should  now  consider  the  position  of  the  tendons  of  the 
various  muscles  of  the  leg,  their  relation  with  the  ankle-joint  and  surrounding  blood-vessels,  and 
especially  their  action  upon  the  foot,  as  their  rigidity  and  contraction  give  rise  to  one  or  other  of 
the  kinds  of  deformity  known  as  club-foot.     The  most  simple  and  common  deformity,  and  one 


442  THE  MUSCLES  AND    FASCIA 

that  is  rarely,  if  ever,  congenital,  is  the  talipes  equinus,  the  heel  being  raised  by  rigidity  and  con- 
traction of  the  Gastrocnemius  muscle,  and  the  patient  walking  upon  the  ball  of  the  foot.  In  the 
talipes  varus  the  foot  is  forcibly  adducted  and  the  inner  side  of  the  sole  raised,  sometimes  to  a 
right  angle  with  the  ground,  by  the  action  of  the  Tibialis  anticus  and  posticus.  In  the  talipes 
valgus  the  outer  edge  of  the  foot  is  raised  by  the  Peronei  muscles,  and  the  patient  walks  on  the 
inner  ankle.  In  the  talipes  calcaneus  the  toes  are  raised  by  the  extensor  muscles,  the  heel  is 
depressed,  and  the  patient  walks  upon  it.  Other  varieties  of  deformity  are  met  with,  as  the 
talipes  equino-varus,  equino-valgus,  and  calcaneo-valgus,  whose  names  sufficiently  indicate  their 
nature.  Of  these,  the  talipes  equino-varus  is  the  most  common  congenital  form  :  the  heel  is 
raised  by  the  tendo  x\chillis,  the  inner  border  of  the  foot  drawn  upward  by  the  Tibialis  anticus, 
the  anterior  two-thirds  twisted  inward  by  the  Tibialis  posticus,  and  the  arch  increased  by  the 
contraction  of  the  plantar  fascia,  so  that  the  patient  walks  on  the  middle  of  the  outer  border  of 
the  foot.  Each  of  these  deformities  may  sometimes  be  successfully  relieved  by  division  of  the 
opposing  tendons  and  fascia  :  by  this  means  the  foot  regains  its  proper  position,  and  the  tendons 
heal  by  the  organization  of  lymph  thrown  out  between  the  divided  ends.  The  operation  is 
easily  performed  by  putting  the  contracted  tendon  upon  the  stretch,  and  dividing  it  by  means 
of  a  narrow,  sharp-pointed  knife  inserted  beneath  it. 

Rupture  of  a  few  of  the  fibres  of  the  Gastrocnemius  or  rupture  of  the  Plantaris  tendon  not 
uncommonly  occurs,  especially  in  men  somewhat  advanced  in  life,  from  some  sudden  exertion, 
and  frequently  occurs  during  the  game  of  lawn  tennis,  and  is  hence  known  as  "lawn-tennis  leg." 
The  accident  is  accompanied  by  a  sudden  pain,  and  produces  a  sensation  as  if  the  individual  had 
been  struck  a  violent  blow  on  the  part.  The  tendo  Achillis  is  also  sometimes  raptured.  It  is 
stated  that  John  Hunter  ruptured  his  tendo  Achillis  whilst  dancing  at  the  age  of  forty. 

IV.  MUSCLES  AND  FASCLE  OF  THE  FOOT. 

The  fibrous  bands,  or  thickened  portions  of  the  fascia  of  the  leg,  which  bind  down  the 
tendons  in  front  of  and  behind  the  ankle  in  their  passage  to  the  foot  should  now  be  examined  ; 
they  are  termed  the  annular  ligaments,  and  are  three  in  number — anterior,  internal,  and 
external. 

The  Anterior  Annular  Ligament  consists  of  a  superior  or  transverse  portion,  which 
binds  down  the  Extensor  tendons  as  they  descend  on  the  front  of  the  tibia  and 
fibula ;  and  an  inferior  or  Y-shaped  portion,  Avhich  retains  them  in  connection  with 
the  tarsus,  the  two  portions  being  connected  by  a  thin  intervening  layer  of  fascia. 
The  transverse  portion  is  attached  externally  to  the  lower  end  of  the  fibula  and  in- 
ternally to  the  tibia  ;  above  it  is  continuous  with  the  fascia  of  the  leg ;  it  contains 
only  one  synovial  sheath,  for  the  tendon  of  the  Tibialis  anticus ;  the  other  tendons 
and  the  anterior  tibial  vessels  and  nerve  passing  beneath  it,  but  without  any  dis- 
tinct synovial  sheath.  The  Y-shaped  portion  is  placed  in  front  of  the  ankle-joint, 
the  stem  of  the  Y  being  attached  externally  to  the  upper  surface  of  the  os  calcis,  in 
front  of  the  depression  for  the  interosseous  ligament ;  it  is  directed  inward,  as  a 
double  layer,  one  lamina  passing  in  front,  and  the  other  behind,  the  tendons  of  the 
Peroneus  tertius  and  Extensor  longus  digitorum.  At  the  inner  border  of  the  latter 
tendon  these  two  layers  join  together,  forming  a  sort  of  loop  or  sheath  in  which  the 
tendons  are  enclosed,  surrounded  by  a  synovial  membrane.  From  the  inner  ex- 
tremity of  this  loop  the  two  limbs  of  the  Y  diverge  :  one  passes  upward  and  inward, 
to  be  attached  to  the  internal  malleolus,  passing  over  the  Extensor  proprius  hallucis 
and  the  vessels  and  nerves,  but  enclosing  the  Tibialis  anticus  and  its  synovial  sheath 
by  a  splitting  of  its  fibres.  The  other  limb  extends  downward  and  inward  to  be 
attached  to  the  inner  border  of  the  plantar  fascia,  and  passes  over  the  tendons  of 
the  Extensor  proprius  hallucis  and  Tibialis  anticus  and  also  the  vessels  and  nerves. 
These  two  tendons  are  contained  in  separate  synovial  sheaths  situated  beneath  the 
ligament. 

The  Internal  Annular  Ligament  is  a  strong  fibrous  band  which  extends  from 
the  inner  malleolus  above  to  the  internal  marg-in  of  the  os  calcis  below,  converting 
a  series  of  grooves  in  this  situation  into  canals  for  the  passage  of  the  tendons  of 
the  Flexor  muscles  and  vessels  into  the  sole  of  the  foot.  It  is  continuous  by  its 
upper  border  with  the  deep  fascia  of  the  leg,  and  by  its  lower  border  with  the 
plantar  fascia  and  the  fibres  of  origin  of  the  Abductor  hallucis  muscle.  The  four 
canals  which  it  forms  transmit,  from  within  outward,  first,  the  tendon  of  the  Tibi- 
alis posticus ;  second,  the  tendon  of  the  Flexor  longus  digitorum ;  third,  the  pos- 


OF    THE  FOOT.  443 

terior  tibial  vessels  and  nerve,  which  run  through  a  broad  space  beneath  the  liga- 
ment ;  lastly,  in  a  canal  formed  partly  by  the  astragalus,  the  tendon  of  the 
Flexor  longus  hallucis.  The  canals  for  the  tendons  are  lined  by  a  separate  synovial 
membrane. 

The  External  Annular  Ligament  extends  from  the  extremity  of  the  outer  mal- 
leolus to  the  outer  surface  of  the  os  calcis  :  it  binds  down  the  tendons  of  the  Pero- 
neus  longus  and  brevis  muscles  in  their  passage  beneath  the  outer  ankle.  The  two 
tendons  are  enclosed  in  one  synovial  sac. 

Dissection  of  the  Sole  of  the  Foot. — The  foot  should  be  placed  on  a  high  block  with  the 
sole  uppermost,  and  firmly  secured  in  that  position.  Carry  an  incision  round  the  heel  and  along 
the  inner  and  outer  borders  of  the  foot  to  the  great  and  little  toes.  This  incision  should  divide 
the  integument  and  thick  layer  of  granular  fat  beneath  until  the  fascia  is  visible  ;  the  skin  and 
fat  should  then  be  removed  from  the  fascia  in  a  direction  from  behind  forward,  as  seen  in  Fig.. 
255. 

The  Plantar  Fascia,  the  densest  of  all  the  fibrous  membranes,  is  of  great  strength, 
and  consists  of  pearly-white  glistening  fibres,  disposed,  for  the  most  part,  longi- 
tudinally :  it  is  divided  into  a  central  and  two  lateral  portions. 

The  central  'portion,  the  thickest,  is  narrow  behind  and  attached  to  the  inner 
tubercle  of  the  os  calcis,  posterior  to  the  origin  of  the  Flexor  brevis  digitorum,  and, 
becoming  broader  and  thinner  in  front,  divides  near  the  heads  of  the  metatarsal 
bones  into  five  processes,  one  for  each  of  the  toes.  Each  of  these  processes  divides- 
opposite  the  metatarso-phalangeal  articulation  into  two  strata,  superficial  and  deep. 
The  superficial  stratum  is  inserted  into  the  skin  of  the  transverse  sulcus  which 
divides  the  toes  from  the  sole.  The  deeper  stratum  divides  into  two  slips  which 
embrace  the  sides  of  the  flexor  tendons  of  the  toes,  and  blend  with  the  sheaths  of 
the  tendons,  and  laterally  with  the  transverse  metatarsal  ligament,  thus  forming  a 
series  of  arches  through  which  the  tendons  of  the  short  and  long  flexors  pass  to 
the  toes.  The  intervals  left  between  the  five  processes  allow  the  digital  vessels  and 
nerves  and  the  tendons  of  the  Lumbricales  muscles  to  become  superficial.  At  the 
point  of  division  of  the  fascia  into  processes  and  slips  numerous  transverse  fibres 
are  superadded,  which  serve  to  increase  the  strength  of  the  fascia  at  this  part  by 
binding  the  processes  together  and  connecting  them  with  the  integument.  The 
central  portion  of  the  plantar  fascia  is  continuous  with  the  lateral  portions  at  each 
side,  and  sends  upward  into  the  foot,  at  their  point  of  junction,  tAvo  strong  vertical 
intermuscular  septa,  broader  in  front  than  behind,  which  separate  the  middle  from 
the  external  and  internal  plantar  group  of  muscles  ;  from  these,  again,  thinner 
transverse  septa  are  derived,  which  separate  the  various  layers  of  muscles  in  this 
region.  The  upper  surface  of  this  fascia  gives  attachment  behind  to  the  Flexor 
brevis  digitorum  muscle. 

The  lateral  portions  of  the  plantar  fascia  are  thinner  than  the  central  piece,,  and 
cover  the  sides  of  the  foot. 

The  outer  portion  covers  the  under  surface  of  the  Abductor  minimi  digiti ;  it  is 
thick  behind,  thin  in  front,  and  extends  from  the  os  calcis,  forward,  to  the  base  of 
the  fifth  metatarsal  bone,  into  the  outer  side  of  which  it  is  attached  ;  it  is  con- 
tinuous internally  with  the  middle  portion  of  the  plantar  fascia,  and  externally 
with  the  dorsal  fascia. 

The  inner  portion  is  very  thin,  and  covers  the  Abductor  hallucis  muscle  ;  it  is 
attached  behind  to  the  interna]  annular  ligament,  and  is  continuous  around  the 
side  of  the  foot  with  the  dorsal  fascia,  and  externally  with  the  middle  portion  of 
the  plantar  fascia. 

8.  Dorsal  Region. 

Extensor  brevis  digitorum. 
The  Fascia  on  the  dorsum  of  the  foot  is  a  thin  membranous  layer  continuous 
above  with  the  anterior  margin  of  the   annular  ligament ;  it   becomes  gradually 
lost  opposite  the  heads  of  the  metatarsal  bones,  and  on  each  side  blends  with  the 


444  THE   MUSCLES   AND    FASCIJE 

lateral  portions  of  the  plantar  fascia ;  it  forms  a  sheath  for  the  tendons  placed  on 
the  dorsum  of  the  foot.  On  the  removal  of  this  fascia  the  muscles  and  tendons  of 
the  dorsal  region  of  the  foot  are  exposed. 

The  Extensor  brevis  digitorum  (Fig.  258)  is  a  broad  thin  muscle  which  arises 
from  the  fore  part  of  the  upper  and  outer  surfaces  of  the  os  calcis,  in  front  of  the 
groove  for  the  Peroneus  brevis,  from  the  external  calcaneo-astragaloid  ligament, 
and  from  the  common  limb  of  the  Y-shaped  portion  of  the  anterior  annular  ligament. 
It  passes  obliquely  across  the  dorsum  of  the  foot,  and  terminates  in  four  tendons. 
The  innermost,  which  is  the  largest,  is  inserted  into  the  dorsal  surface  of  the  base 
of  the  first  phalanx  of  the  great  toe,  crossing  the  Dorsalis  pedis  artery  ;  the  other 
three,  into  the  outer  sides  of  the  long  extensor  tendons  of  the  second,  third,  and 
fourth  toes. 

Relations. — By  its  superficial  surface,  with  the  fascia  of  the  foot,  the  tendons 
of  the  Extensor  longus  digitorum  and  Peroneus  tertius ;  by  its  deep  surface,  with 
the  tarsal  and  metatarsal  arteries  and  bones  and  the  Dorsal  interossei  muscles. 

Nerves. — It  is  supplied  by  the  anterior  tibial  nerve. 

Actions. — The  Extensor  brevis  digitorum  is  an  accessory  to  the  long  Extensor, 
extending  the  phalanges  of  the  four  inner  toes,  but  acting  only  on  the  first  phalanx 
of  the  great  toe.  The  obliquity  of  its  direction  counteracts  the  oblique  movement 
given  to  the  toes  by  the  long  Extensor,  so  that,  both  muscles  acting  together,  the 
toes  are  evenly  extended. 


9.  Plantar  Region. 

The  muscles  in  the  plantar  region  of  the  foot  may  be  divided  into  three  groups, 
in  a  similar  manner  to  those  in  the  hand.  Those  of  the  internal  plantar  region 
are  connected  with  the  great  toe,  and  correspond  with  those  of  the  thumb  ;  those 
of  the  external  plantar  region  are  connected  with  the  little  toe,  and  correspond 
with  those  of  the  little  finger  ;  and  those  of  the  middle  plantar  region  are  con- 
nected with  the  tendons  intervening  between  the  two  former  groups.  But  in  order 
to  facilitate  the  dissection  of  these  muscles  it  will  be  found  more  convenient  to 
divide  them  into  four  layers,  as  they  present  themselves,  in  the  order  in  which 
they  are  successively  exposed. 

First  Layer. 

Abductor  hallucis.  Flexor  brevis  digitorum. 

Abductor  minimi  digiti. 

Dissection. — Remove  the  fascia  on  the  inner  and  outer  sides  of  the  foot,  commencing  in 
front  over  the  tendons  and  proceeding  backward.  The  central  portion  should  be  divided  trans- 
versely in  the  middle  of  the  foot,  and  the  two  flaps  dissected  forward  and  backward. 

The  Abductor  hallucis  lies  along  the  inner  border  of  the  foot.  It  arises  from 
the  inner  tubercle  on  the  under  surface  of  the  Os  calcis ;  from  the  internal  annular 
ligament ;  from  the  plantar  fascia ;  and  from  the  intermuscular  septum  between  it 
and  the  Flexor  brevis  digitorum.  The  fibres  terminate  in  a  tendon  which  is 
inserted,  together  with  the  innermost  tendon  of  the  Flexor  brevis  hallucis,  into 
the  inner  side  of  the  base  of  the  first  phalanx  of  the  great  toe. 

Relations. — By  its  superficial  surface,  with  the  plantar7  fascia ;  by  its  deep  sur- 
face, with  the  Flexor  brevis  hallucis,  the^  Flexor  £,ccessorius,  and  the  tendons  of 
the  Flexor  longus  digitorum  and  Flexor  longus  hallucis,  the  Tibialis  anticus  and 
posticus,  the  plantar  vessels  and  nerves.  Its  outer  border  is  in  relation  to  the 
Flexor  brevis  digitorum. 

The  Flexor  brevis  digitorum  (perforatus)  lies  in  the  middle  of  the  sole 
of  the  foot,  immediately  beneath 1  the  plantar  fascia,  with  which  it  is  firmly 
united.       It    arises    by    a    narrow    tendinous    process,    from    the    inner    tubercle 

1  That  is,  in  order  of  dissection  of  the  sole  of  the  foot. 


OF    THE   FOOT. 


445 


of  the  os  calcis,  from  the  central  part  of  the  plantar  fascia,  and  from  the 
intermuscular  septa  between  it  and  the  adjacent  muscles.  It  passes  forward, 
and  divides  into  four  tendons,  one  for  each 
of  the  four  outer  toes.  Opposite  the  bases 
of  the  first  phalanges  each  tendon  divides 
into  two  slips,  to  allow  of  the  passage  of 
the  corresponding  tendon  of  the  Flexor  longus 
digitorum;  the  two  portions  of  the  tendon 
then  unite  and  form  a  grooved  channel  for 
the  reception  of  the  accompanying  long  flexor 
tendon.  Finally,  they  divide  a  second  time, 
to  be  inserted  into  the  sides  of  the  second 
phalanges  about  their  middle.  The  mode  of 
division  of  the  tendons  of  the  Flexor  brevis 
digitorum  and  their  insertion  into  the  pha- 
langes is  analogous  to  the  Flexor  sublimis  digi- 
torum in  the  hand. 

Relations. — By  its  superficial  surface,  with 
the  plantar  fascia;  by  its  deep  surface,  with 
the  Flexor  accessorius,  the  Lumbricales,  the 
tendons  of  the  Flexor  longus  digitorum,  and 
the  external  plantar  vessels  and  nerve,  from 
which  it  is  separated  by  a  thin  layer  of  fascia. 
The  outer  and  inner  borders  are  separated  from 
the  adjacent  muscles  by  means  of  vertical  pro- 
longations of  the  plantar  fascia. 

Fibrous  Sheaths  of  the  Flexor  Tendons. — 
These  are  not  so  well  marked  as  in  the  fingers. 
The  flexor  tendons  of  the  toes  as  they  run 
along  the  phalanges  are  retained  against  the 
bones  by  a  fibrous  sheath,  forming  osseo-apo- 
neurotic  canals.  These  sheaths  are  formed 
by  strong  fibrous  bands  which  arch  across  the 
tendons  and  are  attached  on  each  side  to  the 
margins  of  the  phalanges.  Opposite  the 
middle  of  the  proximal  and  second  phalanges 
the  sheath  is  very  strong,  and  the  fibres  pass 
transversely,  but  opposite  the  joints  it  is  much 
thinner,  and  the  fibres  pass  oblnNely.  Each 
sheath  is  lined  by  a  synovial  membrane  which 
is  reflected  on  the  contained  tendon. 

The  Abductor  minimi  digiti  lies  along  the 
outer  border  of  the  foot.  It  arises,  by  a  very  broad  origin,  from  the  outer  tubercle 
of  the  os  calcis,  from  the  under  surface  of  the  os  calcis  between  the  two  tubercles, 
from  the  fore  part  of  the  inner  tubercle,  from  the  plantar  fascia  and  the  intermus- 
cular septum,  between  it  and  the  Flexor  brevis  digitorum.  Its  tendon,  after  glid- 
ing over  a  smooth  facet  on  the  under  surface  of  the  base  of  the  fifth  metatarsal 
bone,  is  inserted  with  the  short  Flexor  of  the  little  toe  into  the  outer  side  of  the 
base  of  the  first  phalanx  of  this  toe. 

Relations. — By  its  superficial  surface,  with  the  plantar  fascia;  by  its  deep  sur- 
face, with  the  Flexor  accessorius,  the  Flexor  brevis  minimi  digiti,  the  long  plantar 
ligament,  and  the  tendon  of  the  Peroneus  longus.  On  its  inner  side  are  the 
external  plantar  vessels  and  nerve,  and  it  is  separated  from  the  Flexor  brevis 
digitorum  by  a  vertical  septum  of  fascia. 

Dissection.— The  muscles  of  the  superficial  layer  should  be  divided  at  their  origin  by  insert- 
ing the  knife  beneath  each,  and  cutting  obliquely  backward,  so  as  to  detach  them  from  the 
bone ;  they  should  then  be  drawn  forward,  in  order  to  expose  the  second  layer,  but  not  cut 


Fig.  261. — Muscles  of  the  sole  of  the  foot. 
First  Layer. 


\ 


446 


THE   MUSCLES  AND    FASCIJE 


away  at  their  insertion.  The  two  layers  are  separated  by  a  thin  membrane,  the  deep  plantar 
fascia,  on  the  removal  of  which  is  seen  the  tendon  of  the  Flexor  longus  digitorum,  the  Flexor 
accessorius,  the  tendon  of  the  Flexor  longus  hallucis,  and  the  Lumbricales.     The  long  flexor 

tendons  diverge  from  each  other  at  an  acute  angle  ; 
the  Flexor  longus  hallucis  runs  along  the  inner 
side  of  the  foot,  on  a  plane  superior  to  that  of  the 
Flexor  longus  digitorum,  the  direction  of  which  is 
obliquely  outward. 

Second  Layer. 
Flexor  accessorius.  Lumbricales. 

The  Flexor  accessorius  arises  by  two 
heads,  which  are  separated  from  each  other 
by  the  long  plantar  ligament:  the  inner  or 
larger,  which  is  muscular,  being  attached 
to  the  inner  concave  surface  of  the  os  calcis 
below  the  groove  which  lodges  the  tendon 
of  the  Flexor  longus  hallucis  ;  the  outer 
head,  flat  and  tendinous,  to  the  outer  surface 
of  the  os  calcis,  in  front  of  its  lesser  tubercle, 
and  to  the  long  plantar  ligament ;  the  two 
portions  join  at  an  acute  angle,  and  are 
inserted  into  the  outer  margin  and  upper 
and  under  surfaces  of  the  tendon  of  the 
Flexor  longus  digitorum,  forming  a  kind  of 
groove  in  which  the  tendon  is  lodged.1 

Relations. — By  its  superficial  surface, 
with  the  muscles  of  the  superficial  layer, 
from  which  it  is  separated  by  the  external 
plantar  vessels  and  nerves ;  by  its  deep 
surface,  with  the  os  calcis  and  long 
calcaneo-cuboid  ligament. 

The  Lumbricales  are  four  small  muscles 
accessory  to  the  tendons  of  the  Flexor 
longus  digitorum :  they  arise  from  the 
tendons  of  the  long  Flexor,  as  far  back  as 
their  angle  of  division,  each  arising  from 
two  tendons,  except  the  internal  one. 
Each  muscle  terminates  in  a  tendon, 
which  passes  forward  on  the  inner  side 
of  the  four  lesser  toes,  and  is  inserted  into 
the  expansion  of  the  long  Extensor  tendon 
on  the  dorsum  of  the  first  phalanx  of  the 
corresponding  toe. 

Dissection. — The  flexor  tendons  should  be  divided  at  the  back  part  of  the  foot,  and  the 
Flexor  accessorius  at  its  origin,  and  drawn  forward,  in  order  to  expose  the  third  layer. 

Third  Layer. 

Flexor  brevis  hallucis. 
Adductor  obliquus  hallucis. 
Flexor  brevis  minimi  digiti. 
Adductor  transversus  hallucis. 

The  Flexor  brevis  hallucis  arises,  by  a  pointed  tendinous  process,  from  the 
inner  part  of  the  under  surface  of  the  cuboid  bone,  from  the  contiguous  portion  of 
the  external  cuneiform,  and  from  the  prolongation  of  the  tendon  of  the  Tibialis 

1  According  to  Turner,  the  fibres  of  the  Flexor  accessorius  end  in  aponeurotic  bands,  which  con- 
tribute slips  to  the  second,  third,  and  fourth  digits. 


Fig.  262.— Muscles  of    the  sole   of    the 
Second  layer. 


foot. 


OF    THE   FOOT. 


447 


posticus,  which  is  attached  to  that  bone.  The  muscle  divides,  in  front,  into 
two  portions,  which  are  inserted  into  the  inner  and  outer  sides  of  the  base  of  the 
first  phalanx  of  the  great  toe,  a  sesamoid  bone  being  developed  in  each  tendon 
at  its  insertion.  The  inner  portion  of  this 
muscle  is  blended  with  the  Abductor 
hallucis  previous  to  its  insertion,  the 
outer  with  the  Adductor  obliquus  hallu- 
cis, and  the  tendon  of  the  Flexor 
longus  hallucis  lies  in  a  groove  between 
them. 

Relations. — By  its  superficial  surface, 
with  the  Abductor  hallucis  and  the  ten- 
don of  the  Flexor  longus  hallucis ;  by  its 
deep  surface,  with  the  tendon  of  the  Per- 
oneus longus  and  metatarsal  bone  of  the 
great  toe ;  by  its  inner  border,  with  the 
Abductor  hallucis ;  by  its  outer  border, 
with  the  Adductor  obliquus  hallucis. 

The  Adductor  obliquus  hallucis  is  a 
large,  thick,  fleshy  mass  passing  obliquely 
across  the  foot  and  occupying  the  hollow 
space  between  the.  four  inner  metatarsal 
bones.  It  arises  from  the  tarsal  extrem- 
ities of  the  second,  third  and  fourth  met- 
atarsal bones,  and  from  the  sheath  of  the 
tendon  of  the  Peroneus  longus,  and  is 
inserted,  together  with  the  outer  portion 
of  the  Flexor  brevis  hallucis,  into  the 
outer  side  of  the  base  of  the  first  phalanx 
of  the  great  toe. 

The  small  muscles  of  the  great  toe, 
the  Abductor,  Flexor  brevis,  Adductor 
obliquus,  and  Adductor  transversus,  like 
the  similar  muscles  of  the  thumb,  give 
•off  fibrous  expansions,  at  their  inser- 
tions, to  blend  with  the  long  Extensor 
tendon. 

The  Flexor  brevis  minimi  digiti  lies 
■on  the  metatarsal  bone  of  the  little  toe, 
and  much  resembles  one  of  the  Interossei. 
It  arises  from  the  base  of  the  metatarsal 
bone  of  the  little  toe,  and  from  the  sheath 
•of  the  Peroneus  longus ;  its  tendon  is 
inserted  into  the  base  of  the  first  phalanx  of  the  little  toe  on  its  outer  side. 
Occasionally  some  of  the  deeper  fibres  of  the  muscle  are  inserted  into  the  outer  part 
of  the  distal  half  of  the  fifth  metatarsal  bone;  these  are  described  by  some  as  a 
distinct  muscle,  the  Opponens  minimi  digiti. 

Relations. — By  its  superficial  surface,  with  the  plantar  fascia  and  tendon  of 
the  Abductor  minimi  digiti ;   by  its  deep  surface,  with  the  fifth  metatarsal  bone. 

The  Adductor  transversus  hallucis  ( Transversus  pedis)  is  a  narrow,  flat,  muscular 
fasciculus,  stretched  transversely  across  the  heads  of  the  metatarsal  bones,  between 
them  and  the  flexor  tendons.  It  arises  from  the  inferior  metatarso-phalangea] 
ligaments  of  the  three  outer  toes,  sometimes  only  from  the  third  and  fourth  and 
from  the  transverse  ligament  of  the  metatarsus  ;  and  is  inserted  into  the  outer  side 
of  the  first  phalanx  of  the  great  toe,  its  fibres  being  blended  with  the  tendon  of 
insertion  of  the  Adductor  obliquus  hallucis. 

Relations. — By  its  superficial  surface,  with  the  tendons  of  the  long  and  short 
Flexors  and  Lumbricales ;  by  its  deep  surface,  with  the  Interossei. 


Fig.  263.— Muscles  of  the  sole  of  the  foot.    Third 
layer. 


448 


THE  MUSCLES  AND    FASCIA. 


Fourth  Layer. 
The  Interossei. 

The  Interossei  muscles  in  the  foot  are  similar  to  those  in  the  hand,  with  this 
exception,  that  they  are  grouped  around  the  middle  line  of  the  second  toe,  instead 
of  the  middle  line  of  the  third  finger,  as  in  the  hand.  They  are  seven  in  number, 
and  consist  of  two  groups,  dorsal  and  plantar. 

The  Dorsal  interossei,  four  in  number,  are  situated  between  the  metatarsal 
bones.  They  are  bipenniform  muscles,  arising  by  two  heads  from  the  adjacent 
sides  of  the  metatarsal  bones,  between  which  they  are  placed  ;  their  tendons  are 
inserted  into  the  bases  of  the  first  phalanges,  and  into  the  aponeurosis  of  the 
common  extensor  tendon.     In  the  angular  interval  left  between  the  heads  of 


Fig.  264.— The  Dorsal  interossei.    Left  foot. 


Fig.  265.— The  Plantar  interossei.    Left  foot. 


each  muscle  at  its  posterior  extremity  the  perforating  arteries  pass  to  the 
dorsum  of  the  foot,  except  in  the  First  interosseous  muscle,  where  the  interval 
allows  the  passage  of  the  communicating  branch  of  the  dorsalis  pedis  artery. 
The  First  dorsal  interosseous  muscle  is  inserted  into  the  inner  side  of  the  second 
toe ;  the  other  three  are  inserted  into  the  outer  sides  of  the  second,  third,  and 
fourth  toes. 

The  Plantar  interossei,  three  in  number,  lie  beneath,  rather  than  between,  the 
metatarsal  bones.  They  are  single  muscles,  and  are  each  connected  with  but  one 
metatarsal  bone.  They  arise  from  the  base  and  inner  sides  of  the  shaft  of  the 
third,  fourth,  and  fifth  metatarsal  bones,  and  are  inserted  into  the  inner  sides  of 
the  bases  of  the  first  phalanges  of  the  same  toes,  and  into  the  aponeurosis  of  the 
common  extensor  tendon. 

Nerves. — The  Flexor  brevis  digitorum,  the  Flexor  brevis  and  Abductor  hallucis, 
and  the  innermost  Lumbrical  *  are  supplied  by  the  internal  plantar  nerve.     All 

1  Formerly  the  two  inner  Lumbricales  were  described  as  being  supplied  by  the  internal  plantar 
nerve.  Brooks,  however  (Journal  of  Anatomy,  vol.  xxi.,  p.  575),  in  ten  dissections  found  that  in 
nine  of  them  only  the  inner  Lumbrical  obtained  its  nerve  supply  from  this  source.  In  the- 
tenth  instance  the  first  and  second  Lumbricales  were  supplied  by  both  external  and  internal 
plantar. 


SURFACE   F0R3I    OF    THE   LOWER    EXTREMITY.  449 

the  other  muscles  in  the  sole  of  the  foot  by  the  external  plantar.  The  first  dorsal 
interosseous  muscle  frequently  receives  an  extra  filament  from  the  internal  branch 
of  the  anterior  tibial  nerve  on  the  dorsum  of  the  foot,  and  the  second  dorsal 
interosseous  a  twig  from  the  external  branch  of  the  same  nerve. 

Actions. — All  the  muscles  of  the  foot  act  upon  the  toes,  and  for  purposes  of 
description  as  regards  their  action  may  be  grouped  as  Abductors,  Adductors, 
Flexors,  or  Extensors.  The  Abductors  are  the  Dorsal  interossei,  the  Abductor 
hallucis,  and  the  Abductor  minimi  digiti.  The  Dorsal  interossei  are  abductors 
from  an  imaginary  line  passing  through  the  axis  of  the  second  toe,  so  that  the 
first  muscle  draws  the  second  toe  inward,  toward  the  great  toe ;  the  second 
muscle  draws  the  same  toe,  outward ;  the  third  draws  the  third  toe,  and  the 
fourth  draws  the  fourth  toe,  in  the  same  direction.  Like  the  interossei  in  the 
hand,  they  also  flex  the  proximal  phalanges  and  extend  the  two  terminal  pha- 
langes. The  Abductor  hallucis  abducts  the  great  toe  from  the  others,  and  also 
flexes  the  proximal  phalanx  of  this  toe.  And  in  the  same  way  the  action  of  the 
Abductor  minimi  digiti  is  twofold — as  an  abductor  of  this  toe  from  the  others, 
and  also  as  a  flexor  of  the  proximal  phalanx.  The  Adductors  are  the  Plantar 
interossei,  the  Adductor  obliquus  hallucis,  and  the  Adductor  transversus  hallucis. 
The  plantar  interosseous  muscles  adduct  the  third,  fourth,  and  fifth  toes  toward 
the  imaginary  line  passing  through  the  second  toe,  and  by  means  of  their  inser- 
tion into  the  aponeurosis  of  the  extensor  tendon  they  flex  the  proximal  phalanges 
and  extend  the  tAvo  terminal  phalanges.  The  Adductor  obliquus  hallucis  is 
chiefly  concerned  in  adducting  the  great  toe  toward  the  second  one,  but  also 
assists  in  flexing  this  toe.  The  Adductor  transversus  hallucis  approximates  all 
the  toes,  and  thus  increases  the  curve  of  the  transverse  arch  of  the  metatarsus. 
The  Flexors  are  the  Flexor  brevis  digitorum,  the  Flexor  accessorius,  the  Flexor 
brevis  hallucis,  the  Flexor  brevis  minimi  digiti,  and  the  Lumbricales.  The 
Flexor  brevis  digitorum  flexes  the  second  phalanges  upon  the  first,  and,  con- 
tinuing its  action,  may  flex  the  first  phalanges  also  and  bring  the  toes  together. 
The  Flexor  accessorius  assists  the  Long  flexor  of  the  toes,  and  converts  the 
oblique  pull  of  the  tendons  of  that  muscle  into  a  direct  backward  pull  upon  the 
toes.  The  Flexor  brevis  minimi  digiti  flexes  the  little  toe  and  draws  its  meta- 
tarsal bone  downward  and  inward.  The  Lumbricales,  like  the  corresponding 
muscles  in  the  hand,  assist  in  flexing  the  proximal  phalanx,  and  by  their  inser- 
tion into  the  long  Extensor  tendon  aid  in  straightening  the  two  terminal  pha- 
langes. The  only  muscle  in  the  Extensor  group  is  the  Extensor  brevis  digi- 
torum. It  extends  the  first  phalanx  of  the  great  toe,  and  assists  the  long  Exten- 
sor in  extending  the  next  three  toes,  and  at  the  same  time  gives  to  the  toes  an 
outward  direction  when  they  are  extended. 

Surface  Form. — Of  the  muscles  of  the  thigh,  those  of  the  iliac  region  have  no  influence 
on  surface  form,  while  those  of  the  anterior  femoral  region,  being  to  a  great  extent  superficial, 
largely  contribute  to  the  surface  form  of  this  part  of  the  body.  The  Tensor  fascice  femoris 
produces  a  broad  elevation  immediately  below  the  anterior  portion  of  the  crest  of  the  ilium  and 
behind  the  anterior  superior  spinous  process.  From  its  lower  border  a  longitudinal  groove, 
corresponding  to  the  ilio-tibial  band,  may  be  seen  running  down  the  outer  side  of  the  thigh  to 
the  outer  side  of  the  knee-joint.  The  Sartorius  muscle,  when  it  is  brought  into  action  by 
flexing  the  leg  on  the  thigh  and  the  thigh  on  the  pelvis,  and  rotating  the  thigh  outward, 
presents  a  well-marked  surface  form.  At  its  upper  part,  where  it  constitutes  the  outer 
boundary  of  Scarpa's  triangle,  it  forms  a  prominent  oblique  ridge,  which  becomes  changed  into 
a  flattened  plane  below,  and  this  gradually  merges  in  a  general  fulness  on  the  inner  side  of  the 
knee-joint.  When  the  Sartorius  is  not  in  action,  a  depression  exists  between  the  Extensor 
quadriceps  and  the  Adductor  muscles,  running  obliquely  downward  and  inward  from  the  apex 
of  Scarpa's  triangle  to  the  inner  side  of  the  knee,  which  corresponds  to  this  muscle.  In  the 
depressed  angle  formed  by  the  divergence  of  the  Sartorius  and  Tensor  fasciae  femoris  muscles, 
just  below  the  anterior  superior  spinous  process  of  the  ilium,  the  Rectus  femoris  mutch  appears, 
and,  below  this,  determines  to  a  great  extent  the  convex  form  of  the  front  of  the  thigh. 
In  a  well- developed  subject  the  borders  of  the  muscle,  when  in  action,  are  clearly  to  be  defined. 
The  Vastus  externus  forms  a  long  flattened  plane  on  the  outer  side  of  the  thigh,  traversed  by 
the  longitudinal  groove  formed  by  the  ilio-tibial  band.  The  Vastus  interims,  on  the  inner  side 
of  the  lower  half  of  the  thigh,  gives  rise  to  a  considerable  prominence,  which  increases  toward 
29 


450  THE   MUSCLES  AND    FASCIAE. 

the  knee  and  terminates  somewhat  abruptly  in  this  situation  with  a  full,  curved  outline.  The 
Crureus  and  Subcrureus  are  completely  hidden,  and  do  not  directly  influence  surface  form.  The 
Adductor  muscles,  constituting  the  internal  femoral  group,  are  not  to  be  individually  distin- 
guished from  each  other,  with  the  exception  of  the  upper  tendon  of  the  Adductor  longus  and 
the  lower  tendon  of  the  Adductor  magnus.  The  upper  tendon  of  the  Adductor  longus,  when 
the  muscle  is  in  action,  stands  out  as  a  prominent  ridge,  which  runs  obliquely  downward  and 
outward  from  the  neighborhood  of  the  pubic  spine,  and  forms  the  inner  boundary  of  a  flattened 
triangular  space  on  the  upper  part  of  the  front  of  the  thigh,  known  as  Scarpa's  triangle.  The 
lower  tendon  of  the  Adductor  magnus  can  be  distinctly  felt  as  a  short  ridge  extending  down  to 
the  Adductor  tubercle  on  the  internal  condyle,  between  the  Sartorius  and  Vastus  internus. 
The  Adductor  group  of  muscles  fills  in  the  triangular  space  at  the  upper  part  of  the  thigh, 
formed  between  the  oblique  femur  and  the  pelvic  wall,  and  to  them  is  due  the  contour  of  the 
inner  border  of  the  thigh,  the  Gracilis  largely  contributing  to  the  smoothness  of  the  outline. 
These  muscles  are  not  marked  off  on  the  surface  from  those  of  the  posterior  femoral  region  by 
any  intermuscular  marking ;  but  on  the  outer  side  of  the  thigh  these  latter  muscles  are  defined 
from  the  Vastus  externus  by  a  distinct  marking,  corresponding  to  the  external  intermuscular 
septum.  The  Gluteus  maximus  and  a  part  of  the  Gluteus  medius  are  the  only  muscles  of  the 
buttock  which  influence  surface  form.  The  other  part  of  the  Gluteus  medius,  the  Gluteus 
minimus,  and  the  External  rotators  are  completely  hidden.  The  Gluteus  maximus  forms  the 
full  rounded  outline  of  the  buttock ;  it  is  more  prominent  behind,  compressed  in  front,  and 
terminates  at  its  tendinous  insertion  in  a  depression  immediately  behind  the  great  trochanter. 
Its  lower  border  does  not  correspond  to  the  gluteal  fold,  but  is  much  more  oblique,  being 
marked  by  a  line  drawn  from  the  side  of  the  coccyx  to  the  junction  of  the  upper  with  the  lower 
two-thirds  of  the  thigh  on  the  outer  side.  From  beneath  the  lower  margin  of  this  muscle  the 
hamstring  muscles  appear,  at  first  narrow  and  not  well  marked,  but  as  they  descend  becoming 
more  prominent  and  widened  out,  and  eventually  dividing  into  two  well-marked  ridges,  which 
constitute  the  upper  boundaries  of  the  popliteal  space,  and  are  formed  by  the  tendons  of  the 
inner  and  outer  hamstring  muscles  respectively.  In  the  upper  part  of  the  thigh  these  muscles  are 
not  to  be  individually  distinguished  from  each  other,  but  lower  down  the  separation  between  the 
Semitenclinosus  and  Semimembranosus  is  denoted  by  a  slight  intermuscular  marking.  The 
external  hamstring  tendon  formed  by  the  Biceps  is  seen  as  a  thick  cord  running  down  to 
the  head  of  the  fibula.  The  inner  hamstring  tendons  comprise  the  Semitendinosus,  the 
Semimembranosus,  and  the  Gracilis.  The  Semitendinosus  is  the  most  internal  of  these,  and 
can  be  felt,  in  certain  positions  of  the  limb,  as  a  sharp  cord ;  the  Semimembranosus  is 
thick,  and  the  Gracilis  is  situated  a  little  farther  forward  than  the  other  two.  All  the 
muscles  on  the  front  of  the  leg  appear  to  a  certain  extent  somewhere  on  the  sur- 
face, but  the  form  of  this  region  is  mainly  dependent  upon  the  Tibialis  anticus  and  the 
Extensor  longus  digitorum.  The  Tibialis  anticus  is  well  marked,  and  presents  a  fusiform 
enlargement  at  the  outer  side  of  the  tibia,  and  projects  beyond  the  crest  of  the  shin-bone. 
From  the  muscular  mass  its  tendon  may  be  traced  downward,  standing  out  boldly,  when  the 
muscle  is  in  action,  on  the  front  of  the  tibia  and  ankle-joint,  and  coursing  down  to  its  insertion 
along  the  inner  border  of  the  foot.  A  well-marked  groove  separates  this  muscle  externally 
from  the  Extensor  longus  digitorum,  which  fills  up  the  rest  of  the  space  between  the  upper 
part  of  the  shaft  of  the  tibia  and  fibula.  It  does  not  present  so  bold  an  outline  as  the  Tibialis 
anticus,  and  its  tendon  below,  diverging  from  the  tendon  of  the  Tibialis  anticus,  forms  with  the 
latter  a  sort  of  plane,  in  which  may  be  seen  the  tendon  of  the  Extensor  proprius  hallucis.  A 
groove  on  the  outer  side  of  the  Extensor  longus  digitorum,  seen  most  plainly  when  the  muscle 
is  in  action,  separates  the  tendon  from  a  slight  eminence  corresponding  to  the  Peroneus  tertius. 
The  fleshy  fibres  of  the  Peroneus  longus  are  strongly  marked  at  the  upper  part  of  the  outer 
side  of  the  leg,  especially  when  the  muscle  is  in  action.  It  forms  a  bold  swelling, 
separated  by  furrows  from  the  Extensor  longus  digitorum  in  front  and  the  Soleus 
behind.  Below,  the  fleshy  fibres  terminate  abruptly  in  a  tendon  which  overlaps 
the  more  flattened  form  of  the  Peroneus  brevis.  At  the  external  malleolus  the  ten- 
don of  the  Peroneus  brevis  is  more  marked  than  that  of  the  Peroneus  longus. 
On  the  dorsum  of  the  foot  the  tendons  of  the  Extensor  muscles,  emerging  from 
beneath  the  anterior  annular  ligament,  spread  out  and  can  be  distinguished  in  the  following 
order:  The  most  internal  and  largest  is  the  Tibialis  anticus,  then  the  Extensor  proprius  hallucis: 
next  comes  the  Extensor  longus  digitorum,  dividing  into  four  tendons  to  the  four  outer  toes ;  and 
lastly,  most  externally,  is  the  Peroneus  tertius.  The  flattened  form  of  the  dorsum  of  the  foot  is 
relieved  by  the  rounded  outline  of  the  fleshy  belly  of  the  Extensor  brevis  digitorum,  which  forms  a 
soft  fulness  on  the  outer  side  of  the  tarsus  in  front  of  the  external  malleolus,  and  by  the  Dorsal 
interossei,  which  bulge  between  the  metatarsal  bones.  At  the  back  of  the  knee  is  the  popliteal 
space,  bounded  above  by  the  tendons  ofVhe  hamstring  muscle ;  below,  by  the  two  heads  of  the 
Gastrocnemius.  Below  this  space  is  the  prominent  fleshy  mass  of  the  calf  of  the  leg,  produced 
by  the  Gastrocnemius  and  Soleus.  When  these  muscles  are  in  action,  as  in  standing  on  tiptoe, 
the  borders  of  the  Gastrocnemius  are  well  defined,  presenting  two  curved  lines,  which  converge 
to  the  tendon  of  insertion.  Of  these  borders,  the  inner  is  more  prominent  than  the  outer. 
The  fleshy  mass  of  the  calf  terminates  somewhat  abruptly  below  in  the  tendo  Achillis,  which 
stands  out  prominently  on  the  lower  part  of  the  back  of  the  leg.  It  presents  a  somewhat 
tapering  form  in  the  upper  three-fourths  of  its  extent,  but  widens  out  slightly  below.  When 
the  muscles  of  the  calf  are  in  action,  the  lateral  portions  of  the  Soleus  may  be  seen,  forming 


SURGICAL    ANATOMY    OF    THE   LOWER    EXTREMITY.       451 

curved  eminences,  of  which  the  outer  is  the  longer,  on  either  side  of  the  Gastrocnemius. 
Behind  the  inner  border  of  the  lower  part  of  the  shaft  of  the  tibia  a  well-marked  ridge,  pro- 
duced by  the  tendon  of  the  Tibialis  posticus,  is  visible  when  this  muscle  is  in  a  state  of  con- 
traction. 

On  the  sole  of  the  foot  the  superficial  layer  of  muscles  influences  surface  form  :  the  Abductor 
minimi  digiti  most  markedly.  This  muscle  forms  a  narrow  rounded  elevation  along  the  outer 
border  of  the  foot,  while  the  Abductor  hallueis  does  the  same,  though  to  a  less  extent,  on  the 
inner  side.  The  Flexor  brevis  dlgltorum,  bound  down  by  the  plantar  fascia,  is  not  very  appa- 
rent ;  it  produces  a  flattened  form,  covered  by  the  thickened  skin  of  the  sole,  which  is  here 
thrown  into  numerous  wrinkles. 


SURGICAL  ANATOMY  OF  THE  LOWER  EXTREMITY. 


The  student  should  now  consider  the  effects  produced  by  the  action  of  the  various  muscles 
in  fractures  of  the  bones  of  the  lower  extremity.     The  more 
common  forms  of  fractures  are  selected  for  illustration  and  de- 
scription. 

In  fracture  of  the  neck  of  the  femur  internal  to  the  capsular 
ligament  (Fig.  266)  the  characteristic  marks  are  slight  shorten- 
ing of  the  limb  and  eversion  of  the  foot,  neither  of  which 
symptoms  occurs,  however,  in  some  cases  until  some  time  after 


PYRIFORMIS. 
GEMELLUS    SUPERIOR. 
OBTURATOR    INTERNUS. 
GEMELLUS    INFERIOR. 
OBTURATOR    EXTERNUS. 
QUADRATUS    FEMORIS. 


Pig.  266.- 
ligament. 


-Fracture  of  the  neck  of  the  femur  within  the  capsular 


Fig.  267. — Fracture  of  the  femur 
below  the  trochanters. 


the  injury.  The  eversion  is  caused  by  the  weight  of  the  limb  rotating  it  outward.  The  short- 
ening is  produced  by  the  action  of  the  Glutei,  and  by  the  Rectus  femoris  in  front  and  the 
Biceps,  Semitendinosus,  and  Semimembranosus  behind. 

In  fracture  of  the  femur  just  below  the  trochanters  (Fig.  267),  the  upper  fragment,  the 
portion  chiefly  displaced,  is  tilted  forward  almost  at  right  angles  with  the  pelvis  by  the  combined 
action  of  the  Psoas  and  Iliacus,  and,  at  the  same  time,  everted  and  drawn  outward  by  the 
External  rotator  and  Glutei  muscles,  causing  a  marked  prominence  at  the  upper  and  outer  side 
o£  the  thigh,  and  much  pain  from  the  bruising  and  laceration  of  the  muscles.  The  limb  is 
shortened,  in  consequence  of  the  lower  fragment  being  drawn  upward  by  the  Rectus  in  front. 
and  the  Biceps.  Semimembranosus,  and  Semitendinosus  behind,  and  is  at  the  same  time 
everted.  This  fracture  may  be  reduced  in  two  different  methods :  either  by  direct  relaxation 
of  all  the  opposing  muscles,  to  effect  which  the  limb  should  be  put  up  in  such  a  manner  that 
the  thigh  is  flexed  on  the  pelvis  and  the  leg  on  the  thigh ;  or  by  overcoming  the  contraction  of 
the  muscles  by  continued  extension,  which  may  be  effected  by  means  of  the  long  splint. 

Oblique  fracture  of  the  femur  immediately  above  the  condyles  (Fig.  268)  is  a  formidable 


452 


THE   BLOOD-VASCULAR    SYSTEM. 


injury,  and  attended  with  considerable  displacement.  On  examination  of  the  limb  the  lower 
fragment  may  be  felt  deep  in  the  popliteal  space,  being  drawn  backward  by  the  Gastrocnemius 
and  Plantaris  muscles,  and  upward  by  the  Hamstring  and  Rectus 
muscles.  The  pointed  end  of  the  upper  fragment  is  drawn 
inward  by  the  Pectineus  and  Adductor  muscles,  and  tilted  for- 
ward by  the  Psoas  and  Iliacus,  piercing  the  Rectus  muscle  and 
occasionally  the  integument.  Relaxation  of  these  muscles  and 
direct  approximation  of  the  broken  fragments  are  effected  by 
placing  the  limb  on  a  double  inclined  plane.  The  greatest  care 
is  requisite  in  keeping  the  pointed  extremity  of  the  upper  frag- 
ment in  proper  position  ;  otherwise,  after  union  of  the  fracture, 
the  power  of  extension  of  the  limb  is  partially  destroyed,  from 
the  Rectus  muscle  being  held  down  by  the  fractured  end  of  the 


Fig.  268— Fracture  of  the 
femur  above  the  condyles. 


Fig.  269.— Fracture 
of  the  patella. 


Fig.  270.— Oblique  fracture  of 
the  shaft  of  the  tibia. 


bone,  and  from  the  patella,  when  elevated,  being  drawn  upward  against  the  projecting  fragment. 
In  fracture  of  the  patella  (Fig.  269)  the  fragments  are  separated  by  the  effusion  which 


Fig.  271.— Fracture  of  the  fibula  with  dislocation  of  the  foot  outward—"  Pott's  fracture. 


takes  place  into  the  joint,  and  possibly  by  the  action  of  the  Quadriceps  extensor ;  the  extent  of 
separation  of  the  two  fragments  depending  upon  the  degree  of  laceration  of  the  ligamentous 
structures  around  the  bone. 


SURGICAL    ANATOMY   OF    THE   LOWER    EXTREMITY.        453 

_  In  oblique  fracture  of  the  shaft  of  the  tibia  (Fig.  270),  if  the  fracture  has  taken  place 
obliquely  from  above,  downward  and  forward,  the  fragments  ride  over  one  another,  the  lower 
fragments  being  drawn  backward  and  upward  by  the  powerful  action  of  the  muscles  of  the 
calf;  the  pointed  extremity  of  the  upper  fragment  projects  forward  immediately  beneath  the 
integument,  often  protruding  through  it  and  rendering  the  fracture  a  compound  one.  If 
the  direction  of  the  fracture  is  the  reverse  of  that  shown  in  the  figure,  the  pointed  extremity  of 
the  lower  fragment  projects  forward,  riding  upon  the  lower  end  of  the  upper  one.  By  bending 
the  knee,  which  relaxes  the  opposing  muscles,  and  making  extension  from  the  ankle  and  counter- 
extension  at  the  knee,  the  fragments  may  be  brought  into  apposition.  It  is  often  necessary, 
however,  in  compound  fracture,  to  remove  a  portion  of  the  projecting  bone  with  the  saw  before 
complete  adaptation  can  be  effected. 

Fracture  of  the  fibula  with  dixit, cat  ion  of  the  foot  out  intra1.  (Fig.  271  J,  commonly  known  as 
':  Pott's  fracture,"  is  one  of  the  most  frequent  injuries  of  the  ankle-joint.  The  fibula  is  frac- 
tured about  three  inches  above  the  ankle ;  in  addition  to  this  the  internal  malleolus  is  broken 
off,  or  the  deltoid  ligament  torn  through,  and  the  end  of  the  tibia  displaced  from  the  correspond- 
ing surface  of  the  astragalus.  The  foot  is  markedly  everted,  and  the  sharp  edge  of  the  upper 
end  of  the  fractured  malleolus  presses  strongly  against  the  skin  ;  at  the  same  time,  the  heel  is 
drawn  up  by  the  muscles  of  the  calf.  This  injury  can  generally  be  reduced  by  flexing  the  leg  at 
right  angles  with  the  thigh,  which  relaxes  all  the  opposing  muscles,  and  by  making  extension 
from  the  ankle  and  counter-extension  at  the  knee. 


THE  BLOOD-VASCULAR  SYSTEM. 


THE  blood-vascular  system  comprises  the  heart  and  blood-vessels  with  their 
contained  fluid,  the  blood.  The  composition  of  the  blood  and  the  minute 
anatomy  of  the  blood-vessels  will  be  considered  in  the  section  on  Histology. 

The  Heart  is  the  central  organ  of  the  entire  system,  and  consists  of  a  hollow 
muscle ;  by  its  contraction  the  blood  is  pumped  to  all  parts  of  the  body  through 
a  complicated  series  of  tubes,  termed  arteries.  The  arteries  undergo  enormous 
ramification  in  their  course  throughout  the  body,  and  end  in  very  minute  vessels, 
called  arterioles,  which  in  their  turn  open  into  a  close-meshed  network  of  micro- 
scopic vessels,  termed  capillaries.  After  the  blood  has  passed  through  the 
capillaries  it  is  collected  into  a  series  of  larger  vessels,  called  veins,  by  which  it  is 
again  returned  to  the  heart.  The  passage  of  the  blood  through  the  heart  and 
blood-vessels  constitutes  what  is  termed  the  circulation  of  the  blood,  of  which  the 
following  is  an  outline. 

The  human  heart  is  divided  by  a  septum  into  two  halves,  right  and  left,  each 
half  being  further  constricted  into  two  cavities,  the  upper  of  the  two  being  termed 
the  auricle  and  the  lower  the  ventricle.  The  heart  therefore  consists  of  four 
chambers  or  cavities,  two  forming  the  right  half,  the  right  auricle  and  right 
ventricle,  and  two  the  left  half,  the  left  auricle  and  left  ventricle.  The  right 
half  of  the  heart  contains  venous  or  impure  blood  ;  the  left,  arterial  or  pure  blood. 
From  the  cavity  of  the  left  ventricle  the  pure  blood  is  carried  into  a  large  artery, 
the'  aorta,  through  the  numerous  branches  of  which  it  is  distributed  to  all  parts 
of  the  body,  with  the  exception  of  the  lungs.  In  its  passage  through  the  capil- 
laries of  the  body  the  blood  gives  up  to  the  tissues  the  materials  necessary  for 
their  growth  and  nourishment,  and  at  the  same  time  receives  from  the  tissues  the 
waste  products  resulting  from  their  metabolism,  and  in  doing  so  becomes  changed 
from  arterial  or  pure  blood  into  venous  or  impure  blood,  which  is  collected  by  the 
veins  and  through  them  returned  to  the  right  auricle  of  the  heart.  From  this 
cavity  the  impure  blood  passes  into  the  right  ventricle,  from  which  it  is  conveyed 
through  the  pulmonary  arteries  to  the  lungs.  In  the  capillaries  of  the  lungs  it 
again  becomes  arterialized,  and  is  then  carried  to  the  left  auricle  by  the  pulmonary 
veins.  From  this  cavity  it  passes  into  that  of  the  left  ventricle,  from  which  the 
cycle  once  more  begins. 

The  course  of  the  blood  from  the  left  ventricle  through  the  body  generally  to 
the  right  side  of  the  heart  constitutes  the  greater  or  systemic  circulation,  while  its 
passage  from  the  right  ventricle  through  the  lungs  to  the  left  side  of  the  heart  is 
termed  the  lesser  or  pulmonary  circulation. 

It  is  necessary,  however,  to  state  that  the  blood  which  circulates  through  the 
spleen,  pancreas,  stomach,  small  intestine,  and  the  greater  part  of  the  large  intes- 
tine is  not  returned  directly  from  these  organs  to  the  heart,  but  is  collected  into 
a  large  vein,  termed  the  portal  vein,  by  which  it  is  carried  to  the  liver.  In  the 
liver  this  vein  divides,  after  the  manner  of  an  artery,  and  ultimately  ends  in 
capillary  vessels,  from  which  the  rootlets  of  a  series  of  veins,  called  the  hepatic 
veins,  arise ;  these  carry  the  blood  into  the  inferior  vena  cava,  which  conveys  it 
to  the  right  auricle. 

From  this  it  will  be  seen  that  the  blood  contained  in  the  portal  vein  passes 
through  two  sets  of  capillary  vessels  :  (1)  those  in  the  spleen,  pancreas,  stomach, 
etc.,  and  (2)  those  in  the  liver. 

455 


456 


THE  BLOOD-VASCULAR    SYSTEM. 


Pulmonary  Capillaries 


Speaking  generally,  the  arteries  may  be  said  to  contain  pure,  and  the  veins 
impure,  blood.  This  is  true  of  the  systemic,  but  not  of  the  pulmonary,  vessels, 
since  it  has  been  seen  that  the  impure  blood  is  conveyed  from  the  heart  to  the 

lungs  by  the  pulmonary  arteries,  and  the 
pure  blood  returned  from  the  lungs  to  the 
heart  by  the  pulmonary  veins.  Arteries, 
therefore,  must  be  defined  as  vessels  which 
convey  blood  from  the  heart,  and  veins  as 
vessels  which  return  blood  to  the  heart. 

The  heart  and  lungs  are  contained 
within  the  cavity  of  the  thorax,  the  walls 
of  which  afford  them  protection.  The 
heart  lies  between  the  two  lungs,  and  is 
there  enclosed  within  a  membranous  bag, 
the  pericardium,  while  each  lung  is  in- 
vested by  a  serous  membrane,  the  pleura. 
The  skeleton  of  the  thorax  and  the  shape 
and  boundaries  of  the  cavity  will  be  de- 
scribed in  the  section  on  General  Anatomy. 
The  Cavity  of  the  Thorax. — The  capa- 
city of  the  cavity  of  the  thorax  does  not 
correspond  with  its  apparent  size  exter- 
nally, because  (1)  the  space  enclosed  by 
the  lower  ribs  is  occupied  by  some  of  the 
abdominal  viscera ;  and  (2)  the  cavity  ex- 
tends above  the  first  rib  into  the  neck. 
The  size  of  the  cavity  of  the  thorax  is 
constantly  varying  during  life  with  the 
movements  of  the  ribs  and  Diaphragm, 
and  with  the  degree  of  distention  of  the 
abdominal  viscera.  From  the  collapsed 
state  of  the  lungs,  as  seen  when  the  thorax 
is  opened,  in  the  dead  body,  it  would 
appear  as  if  the  viscera  only  partly  filled 
the  cavity  of  the  thorax,  but  during  life 
there  is  no  vacant  space,  that  which  is 
seen  after  death  being  filled  up  by  the 
expanded  lungs. 

The  Upper  Opening  of  the  Thorax. — The 
parts  which  pass  through  the  upper  opening 
of  the  thorax  are,  from  before  backward  in  or  near  the  middle  line,  the  Sterno- 
hyoid and  Sterno-thyroid  muscles,  the  remains  of  the  thymus  gland,  the  trachea, 
oesophagus,  thoracic  duct,  the  inferior  thyroid  veins,  and  the  Longus  colli  muscle 
of  each  side ;  at  the  sides,  the  innominate  artery,  the  left  common  carotid  and  left 
subclavian  arteries,  the  internal  mammary  and  superior  intercostal  arteries,  the 
right  and  left  innominate  veins,  the  pneumogastric,  cardiac,  phrenic,  and  sympa- 
thetic nerves,  the  anterior  branch  of  the  first  dorsal  nerve,  and  the  recurrent 
laryngeal  nerve  of  the  left  side.  The  apex  of  each  lung,  covered  by  the  pleura, 
also  projects  through  this  aperture,  a  little  above  the  margin  of  the  first  rib. 

The  Lower  Opening  of  the  Thorax  is  wider  transversely  than  from  before  back- 
ward. It  slopes  obliquely  downward  and  backward,  so  that  the  cavity  of  the 
thorax  is  much  deeper  behind  than  in  front.  The  Diaphragm  (see  page  325)  closes 
in  the  opening,  forming  the  floor  of  the  thorax.  The  floor  is  flatter  at  the  centre 
than  at  the  sides,  and  is  higher  on  the  right  side  than  on  the  left,  corresponding  in 
the  dead  body  to  the  upper  border  of  the  fifth  costal  cartilage  on  the  former,  and 
to  the  corresponding  part  of  the  sixth  costal  cartilage  on  the  latter.  From  the 
highest  point  on  each  side  the  floor  slopes  suddenly  downward  to  the  attachment 


Fig.  272.— Diagram  to  show  the  course  of  the 
circulation  of  the  blood. 


THE   PERICARDIUM. 


457 


of  the  Diaphragm  to  the  ribs ;  this  is  more  marked  behind  than  in  front,  so  that 
only  a  narrow  space  is  left  between  it  and  the  wall  of  the  thorax. 

THE  PERICARDIUM. 

The  Pericardium  (Figs.- 273,  274)  is  a  conical  membranous  sac  in  which  the 
heart  and  the  commencement  of  the  great  vessels  are  contained.  It  is  placed 
behind  the  sternum  and  the  cartilages  of  the  third,  fourth,  fifth,  sixth,  and  seventh 
ribs  of  the  left  side,  in  the  interval  between  the  pleurae. 


Right  common 
carotid  artery. 
Inferior  thyroid 
vein. 
Left  innomi- 
nate vein. 
Right  innomi- 
nate vein. 

Superior  vena 
cava. 


Right  pulmo- 
nary veins. 


Right  sub-  Left  common 

fclavian  art.  carotid  art. 


Fig.  273.— I  ,  from  in  front.    The  sac  has  been  distended  with  plaster.    (From  a  preparation  in 

the  Museum  01  I  College  of  Surgeons  of  England.) 

Its  ape  is  lirected  upward,  and  surrounds  the  great  vessels"  about  two  inches 
above  thei  origin  from  the  base  of  the  heart.  Its  base  is  attached  to  the  central 
tendon  and  to  the  left  part  of  the  adjoining  muscular  structure  of  the  Diaphragm. 
In  front  it  is  separated  from  the  sternum  by  the  remains  of  the  thymus  gland 
above  and  a  little  loose  areolar  tissue  below,  and  is  covered  by  the  margins  of  the 
lungs,  especially  the  left.  Behind,  it  rests  upon  the  bronchi,  the  oesophagus,  and 
the  descending  aorta.  Laterally,  it  is  covered  by  the  pleurae,  and  is  in  relation  to 
the  inner  surface  of  the  lungs;  the  phrenic  nerve  with  its  accompanying  vessels 
descends  be1    een  the  pericardium  and  pleura  on  either  side. 


458 


THE   BLOOD-VASCULAR   SYSTEM. 


Structure  of  the  Pericardium. — The  pericardium  is  a  fibre-serous  membrane, 
and  consists,  therefore,  of  two  layers,  an  external  fibrous  and  an  internal  serous. 

The  fibrous  layer  is  a  strong,  dense  membrane.  Above,  it  surrounds  the  great 
vessels  arising  from  the  base  of  the  heart,  on  which  it  is  continued  in  the  form 
of  tubular  prolongations  which  are  gradually  lost  upon  their  external  coat,  the 
strongest  being  that  which  encloses  the  aorta.  The  pericardium  may  be  traced 
over  these  vessels,  to  become  continuous  with  the  deep  layer  of  the  cervical  fascia. 
In  front  the  pericardium  is  connected  to  the  posterior  surface  of  the  sternum  by 
two  fibrous  bands,  the  superior  and  inferior  ster?w-pericardiac  ligaments,  the  upper 


Right  subclavian  artery. 


Left  subclavian  artery 
Right  pulmonary  artery. 


Fig.  274.— Pericardium,  from  behind.    (From  the  same  preparation  as  the  preceding  figure.) 

passing  to  the  manubrium,  and  the  lower  to  the  ensiform  cartilage.  On  each  side 
of  the  ascending  aorta  it  sends  upward  a  diverticulum :  the  one  on  the  left  side, 
somewhat  conical  in  shape,  passes  upward  and  outward,  between  the  arch  of  the 
aorta  and  the  pulmonary  artery,  as  far  as  the  ductus  arteriosus,  where  it  termi- 
nates in  a  crecal  extremity,  which  is  attached  by  loose  connective  tissue  to  the 
obliterated  duct  (Fig.  278).  The  one  on  the  right  side  passes  upward  and  to  the 
right,  between  the  ascending  aorta  and  vena  cava  superior,  and  also  terminates  in 
a  csecal  extremity.  Below,  the  fibrous  layer  is  attached  to  the  central  tendon  of 
the  Diaphragm,  and  on  the  left  side  to  its  muscular  fibres. 

The  vessels  receiving  fibrous  prolongations  from  this  membrane  are  the  aorta, 
the  superior  vena  cava,  the  right  and  left  pulmonary  arteries,  and  the  four  pulmo- 


THE   PERICARDIUM. 


459 


nary  veins.     As  the  inferior  vena  cava  enters  the  pericardium  through  the  central 
tendon  of  the  Diaphragm,  it  receives  no  covering  from  the  fibrous  layer. 

The  serous  layer  invests  the  heart,  and  is  then  reflected  on  the  inner  surface 
of  the  pericardium.  It  consists,  therefore,  of  a  visceral  and  parietal  portion.  The 
former  invests  the  surface  of  the  heart,  and  the  commencement  of  the  great  vessels. 
to  the  extent  of  an  inch  and  a  half  from  their  origin ;  from  these  it  is  reflected 
upon  the  inner  surface  of  the  fibrous  layer,  lining,  below,  the  upper  surface  of  the 
central  tendon  of  the  Diaphragm.  The  serous  membrane  encloses  the  aorta  and 
pulmonary  artery  in  a  single  tube,  so  that  a  passage,  termed  the  transverse  sinus 
of  the  pericardium,  exists  between  these  vessels  in  front  and  the  auricles  behind. 


Fig.  275.— Front  view  of  the  thorax.  The  ribs  and  sternum  are  represented  in  relation  to  the  lungs,  heart, 
and  other  internal  organs.  1.  Pulmonary  orifice.  2.  Aortic  orifice.  3.  Left  auriculo-ventricular  orifice.  4.  Right 
auriculo-ventricular  orifice. 

The  membrane  only  partially  covers  the  superior  vena  cava  and  the  four  pulmonary 
veins,  and  scarcely  covers  the  inferior  cava,  as  this  vessel  enters  the  heart  almost 
directly  after  it  has  passed  through  the  Diaphragm.  Its  inner  surface  is  smooth 
and  glistening,  and  secretes  a  serous  fluid,  which  serves  to  facilitate  the  movements 
of  the  heart. 

Arteries  of  the  Pericardium. — These  are  derived  from  the  internal  mammary 
and  its  musculo-phrenic  branch,  and  from  the  descending  thoracic  aorta. 

Nerves  of  the  Pericardium. — These  are  branches  from  the  vagus,  the  phrenic, 
and  the  sympathetic. 

The  Vestigial  Fold  of  the  Pericardium.— BeUveen  the  left  pulmonary  artery  and 
subjacent  pulmonary  vein  is  a  triangular  fold  of  the  serous  pericardium  ;  it  is  known 


4.  460  THE  BLOOD- VASCULAR   SYSTEM. 

as  the  vestigial  fold  of  Marshall.  It  is  formed  by  the  duplicative  of  the  serous 
layer  over  the  remnant  of  the  lower  part  of  the  left  superior  cava  (duct  of  Cuvier), 
which,  after  birth,  becomes  obliterated,  and  remains  as  a  fibrous  band  stretching 
from  the  left  superior  intercostal  vein  to  the  left  auricle,  where  it  is  continuous  with 
a  small  vein,  the  oblique  vein  of  Marshall,  which  opens  into  the  coronary  sinus. 

Surgical  Anatomy.- — Paracentesis  of  the  pericardium  is  sometimes  required  in  cases  of 
effusion  into  its  cavity.  The  operation  is  best  performed  in  the  fifth  intercostal  space,  one  inch 
to  the  left  of  the  sternum.  The  operation  has  been  performed,  however,  in  the  fourth,  sixth, 
and  seventh  spaces,  and  also  on  the  right  side  of  the  sternum.  Porter  considers  that  by  ' '  reason 
of  the  uncertain  and  varying  relations  of  the  pleura,  and  also  of  the  anterior  position  of  the 
heart,  whenever  the  pericardial  sac  is  distended  with  fluid,  aspiration  of  the  pericardium  is  a 
much  more  dangerous  procedure  than  open  incision  when  done  by  skilled  hands."  He  recom- 
mends that  the  operation  should  be  done  by  resecting  the  fifth  costal  cartilage  on  the  left  side. 
By  this  means  the  surgeon  avoids  opening  the  pleural  cavity,  and  secures  continuous  and  free 
drainage,  if  the  case  is  one  of  purulent  pericarditis. 

THE   HEART. 

The  Heart  is  a  hollow  muscular  organ  of  a  conical  form,  placed  between  the 
lungs,  and  enclosed  in  the  cavity  of  the  pericardium. 

Position. — The  heart  is  placed  obliquely  in  the  chest :  the  broad  attached  end, 
or  base,  is  directed  upward,  backward,  and  to  the  right,  and  corresponds  with  the 
dorsal  vertebrae,  from  the  fifth  to  the  eighth  inclusive ;  the  apex  is  directed  down- 
ward, forward,  and  to  the  left,  and  corresponds  to  the  space  between  the  cartilages 
of  the  fifth  and  sixth  ribs,  three-quarters  of  an  inch  to  the  inner  side,  and  an  inch 
and  a  half  below  the  left  nipple,  or  about  three  and  a  half  inches  from  the  middle 
line  of  the  sternum.  The  heart  is  placed  behind  the  lower  two-thirds  of  the 
sternum,  and  projects  farther  into  the  left  than  into  the  right  half  of  the  cavity 
of  the  chest,  extending  from  the  median  line  about  three  inches  in  the  former  direc- 
tion, and  only  one  and  a  half  in  the  latter  ;  about  one-third  of  the  heart  lies  to  the 
right  and  two-thirds  to  the  left  of  the  mesial  plane.  The  anterior  surface  of  the 
heart  is  round  and  convex,  directed  upward  and  forward,  and  formed  chiefly  by  the 
right  auricle  and  ventricle,  together  with  a  small  part  of  the  left  ventricle.  Its 
posterior  surface,  which  looks  downward  rather  than  backward,  is  flattened  and 
rests  upon  the  Diaphragm,  and  is  formed  chiefly  by  the  left  ventricle.  The  right 
or  lower  border  is  long,  thin,  and  sharp  ;  the  left  or  upper  border  short,  but  thick 
and  round. 

Size. — The  heart,  in  the  adult,  measures  five  inches  in  length,  three  inches  and 
a  half  in  breadth  in  the  broadest  part,  and  two  inches  and  a  half  in  thickness. 
The  prevalent  weight,  in  the  male,  varies  from  tejuto  twelve-ounces ;  in  the  female, 
from  eight  to  ten  :  its  proportions  to  the  body  being  as  1  to  169  in  males ;  1  to  149 
in  females.  The  heart  continues  increasing  in  weight,  and  also  in  length,  breadth, 
and  thickness,  up  to  an  advanced  period  of  life :  this  increase  is  more  marked  in 
men  than  in  women. 

Component  Parts. — As  has  already  been  stated  (page  455),  the  heart  is  sub- 
divided by  a  muscular  septum  into  two  lateral  halves,  which  are  named  respectively 
right  and  left ;  and  a  transverse  constriction  subdivides  each  half  of  the  organ  into 
two  cavities,  the  upper  cavity  on  each  side  being  called  the  auricle,  the  lower  the 
ventricle.  The  course  of  the  blood  through  the  heart  cavities  and  blood-vessels 
has  already  been  described  (page  455). 

The  division  of  the  heart  into  four  cavities  is  indicated  by  grooves  upon  its 
surface.  The  groove  separating  the  auricles  from  the  ventricles  is  called  the 
auriculo-ventricular  groove.  It  is  deficient,  in  front,  where  it  is  crossed  by  the 
root  of  the  pulmonary  artery.  It  contains  the  trunks  of  the  nutrient  vessels  of 
the  heart.  The  auricular  portion  occupies  the  base  of  the  heart,  and  is  subdivided 
into  two  cavities  by  a  median  septum.  The  two  ventricles  are  also  separated  into 
a  right  'and  left  by  two  furrows,  the  interventricular  grooves,  which  are  situated 
one  on  the  anterior,  the  other  on  the  posterior,  surface ;  these  extend  from  the  base 
of  the  ventricular  portion  to  near  the  apex  of  the  organ ;  the  former  being  situatec 


THE   HEART. 


461 


nearer  to  the  left  border  of  the  heart,  and  the  latter  to  the  right.  It  follows,  there- 
fore, that  the  right  ventricle  forms  the  greater  portion  of  the  anterior  surface  of 
the  heart,   and  the  left  ventricle  more  of  its  posterior  surface. 

Each  of  these  cavities  should  now  be  separately  examined. 

The  Right  Auricle  is  a  little  larger  than  the  left,  its  -walls  somewhat  thinner, 
measuring  about  one  line ;  and  its  cavity  is  capable  of  containing  about  two  ounces. 
It  consists  of  two  parts :  a  principal  cavity,  the  sinus  venosus,  or  atrium,  situated 
posteriorly,  and  an  anterior,  smaller  portion,  the  appendix  auriculce. 


Bristle  passed  throng 
right  auriculo-ventricular  opening. 

Fig.  276.— The  right  auricle  and  ventricle  laid  open,  the  anterior  walls  of  both  being  removed. 


The  sinus  is  the  large  quadrangular  cavity,  placed  between  the  two  vense 
cavse ;  its  walls  are  extremely  thin  ;  it  is  connected  below  with  the  right  ventricle, 
and  internally  Avith  the  left  auricle,  being  free  in  the  rest  of  its  extent. 

The  appendix  auricula?,  so  called  from  its  fancied  resemblance  to  a  dog's  ear, 
is  a  small  conical  muscular  pouch,  the  margins  of  which  present  a  dentated  edge. 
It  projects  from  the  sinus  forward  and  to  the  left  side,  overlapping  the  root  of  the 
aorta. 

To  examine  the  interior  of  the  right  auricle,  an  incision  should  be  made  along  its  right 
border,  from  the  entrance  of  the  superior  vena  cava  to  that  of  the  inferior.  A  second  cut'8  t0 
be  made  from  the  centre  of  this  first  incision  to  the  tip  of  the  auricular  appendix,  and  the  flaps 
raised. 

The  internal  surface  of  the  right  auricle  is  smooth,  except  in  the  appen- 
dix and  adjacent  part  of  the  anterior  wall  of  the  sinus  venosus,  where  the  mus- 
cular wall  is  thrown  into  parallel  ridges  resembling  the  teeth  of  a  comb  and 
hence  named  the  musculi  pectinati.  These  end  behind  on  a  vertical  smooth 
ridge,  the  crista  terminalis  of  His,  the  position  of  which  is  indicated  on  the  sur- 
face of  the  distended  auricle  by  a  furrow,  the  sulcus  terminalis  (His)  \  this  rep- 
resents the  line  of  fusion  of  the  sinus  venosus  of  the  embryo  with  the  primitive 
auricle  proper. 


462  THE   BLOOD-VASCULAR    SYSTEM. 

It  presents  the  following  parts  for  examination : 

Superior  cava. 

Inferior  cava.  , -,-,  ,  . 

Openings  {    Coronarv  sinus.  Valves  i  ^achian. 

Foramina  Thebesii.  I  Coronary. 

Auriculo-ventricular. 

Fossa  ovalis. 

Annulus  ovalis. 

Tuberculum  Loweri. 

Musculi  pectinati. 

The  superior  vena  cava  returns  the  blood  from  the  upper  half  of  the  body,  and 
opens  into  the  upper  and  back  part  of  the  auricle,  the  direction  of  its  orifice  being 
downward  and  forward. 

The  inferior  vena  cava,  larger  than  the  superior,  returns  the  blood  from  the 
lower  half  of  the  body,  and  opens  into  the  lowest  part  of  the  auricle  near  the 
septum,  the  direction  of  its  orifice  being  upward  and  inward.  The  direction  of 
a  current  of  blood  through  the  superior  vena  cava  would  consequently  be  toward 
the  auriculo-ventricular  orifice,  whilst  the  direction  of  the  blood  through  the 
inferior  cava  would  be  toward  the  auricular  septum.  This  is  the  normal  direction 
of  the  two  currents  in  foetal  life. 

The  coronary  sinus  opens  into  the  auricle,  between  the  inferior  vena  cava  and 
the  auriculo-ventricular  opening.  It  returns  the  blood  from  the  substance 
of  the  heart,  and  is  protected  by  a  semicircular  fold  of  the  lining  membrane 
of  the  auricle,  the  coronary  valve  {valve  of  Thebesius).  The  sinus,  before  enter- 
ing the  auricle,  is  considerably  dilated — nearly  to  the  size  of  the  end  of  the  little 
finger.  Its  wall  is  partly  muscular,  and  at  its  junction  with  the  great  coronary 
vein  is  somewhat  constricted  and  furnished  with  a  valve  consisting  of  two  unequal 
segments. 

The  foramini  Thebesii  are  numerous  minute  apertures,  the  mouths  of  small 
veins  (venas  cordis  minima?)*  which  open  on  various  parts  of  the  inner  surface  of 
the  auricle.  They  return  the  blood  directly  from  the  muscular  substance  of  the 
heart.  Some  of  these  foramina  are  minute  depressions  in  the  walls  of  the  heart, 
presenting  a  closed  extremity. 

The  auriculo-ventricular  opening  is  the  large  oval  aperture  of  communication 
between  the  auricle  and  the  ventricle,  to  be  presently  described. 

The  Eustachian  valve  is  situated  between  the  anterior  margin  of  the  inferior 
vena  cava  and  the  auriculo-ventricular  orifice.  It  is  semilunar  in  form,  its  convex 
margin  being  attached  to  the  Avail  of  the  vein ;  its  concave  margin,  wyhich  is  free, 
terminating  in  two  cornua,  of  which  the  left  is  attached  to  the  anterior  edge  of 
the  annulus  ovalis,  the  right  being  lost  on  the  wall  of  the  auricle.  The  valve  is 
formed  by  a  duplicature  of  the  lining  membrane  of  the  auricle  containing  a  few 
muscular  fibres. 

In  the  foetus  this  valve  is  of  large  size,  and  serves  to  direct  the  blood  from  the 
inferior  vena  cava,  through  the  foramen  ovale,  into  the  left  auricle. 

In  the  adult  it  is  occasionally  persistent,  and  may  assist  in  preventing  the 
reflux  of  blood  into  the  inferior  vena  cava ;  more  commonly  it  is  small,  and  its 
free  margin  presents  a  cribriform  or  filamentous  appearance ;  occasionally  it  is 
altogether  wanting. 

The  coronary  valve  (valve  of  Thebesius)  is  a  semicircular  fold  of  the  lining 
membrane  of  the  auricle,  protecting  the  orifice  of  the  coronary  sinus.  It  prevents 
the  regurgitation  of  blood  into  the  sinus  during  the  contraction  of  the  auricle. 
This  valve  is  occasionally  double. 

The  fossa  ovalis  is  an  oval  depression  corresponding  to  the  situation  of  the 
foramen  ovale  in  the  foetus.  It  is  situated  at  the  lower  nart  of  the  septum  auricu- 
larum,  above  and  to  the  left  of  the  orifice  of  the  inferio:  vena  cava. 

The  annulus  ovalis  is  the  prominent  oval  margin  o?  the  foramen  ovale.     It  is 


THE   HEART.  463 

most  distinct  above  and  at  the  sides ;  below,  it  is  deficient.  A  small  slit-like 
valvular  opening  is  occasionally  found,  at  the  upper  margin  of  the  fossa  ovalis, 
which  leads  upward  beneath  the  annulus  into  the  left  auricle,  and  is  the  remains 
of  the  aperture  between  the  two  auricles  in  the  foetus. 

The  tubereulum  Loweri  is  a  small  projection  on  the  right  wall  of  the  auricle, 
between  the  two  venae  cavae.  It  is  most  distinct  in  the  hearts  of  quadrupeds ;  in 
man  it  is  scarcely  visible.  It  was  supposed  by  Lower  to  direct  the  blood  from  the 
superior  cava  toward  the  auriculo-ventricular  opening. 

*\^  The  Right  Ventricle  is  triangular  in  form,  and  extends  from  the  right  auricle  to 
near  the  apex  of  the  heart.  Its  anterior  or  upper  surface  is  rounded  and  convex, 
and  forms  the  larger  part  of  the  front  of  the  heart.  Its  under  surface  is  flattened, 
rests  upon  the  Diaphragm,  and  forms  only  a  small  part  of  the  back  of  the  heart. 
Its  posterior  wall  is  formed  by  the  partition  between  the  two  ventricles,  the  septum 
ventriculorum,  so  that  a  transverse  section  of  the  cavity  presents  a  semilunar  outline. 
The  surface  of  the  septum  is  convex  and  bulges  into  the  cavity  of  the  right  ventricle. 
Its  upper  and  inner  angle  is  prolonged  into  a  conical  pouch,  the  infundibulum,  or 
conies  arteriosus,  from  which  the  pulmonary  artery  arises.  The  walls  of  the  right 
ventricle  are  thinner  than  those  of  the  left,  the  proportion  between  them  being  as 
1  to  3.  The  wall  is  thickest  at  the  base,  and  gradually  becomes  thinner  toward 
the  apex.  The  cavity  equals  in  size  that  of  the  left  ventricle,  and  is  capable  of 
containing  about  three  fluidounces.1 

To  examine  the  interior  of  the  right  ventricle,  its  anterior  wall  should  he  turned  downward 
and  to  the  right  in  the  form  of  a  triangular  flap.  This  is  accomplished  by  making  two  incisions : 
(1)  from  the  pulmonary  artery  to  the  apex  of  the  ventricle  parallel  to,  but  a  little  to  the  right 
of,  the  anterior  interventricular  furrow ;  (2)  another,  starting  from  the  upper  extremity  of  the 
first  and  carried  outward  parallel  to,  but  a  little  below,  the  auriculo-ventricular  furrow,  care 
being  taken  not  to  injure  the  auriculo-ventricular  valve. 

The  following  parts  present  themselves  for  examination : 

p,       .        f  Auriculo-ventricular. 
*  \  Opening  of  the  pulmonary  artery. 

Valves  j  Tricuspid. 
(_  {semilunar. 

And  a  muscular  and  tendinous  apparatus  connected  with  the  tricuspid  valve : 
Colunmae  carnese.  Chordae  tendineae. 

The  auriculo-ventricular  orifice  is  the  large  oval  aperture  of  communication 
between  the  auricle  and  ventricle.  It  is  situated  at  the  base  of  the  ventricle,  near 
the  right  border  of  the  heart.  It  is  about  an  inch  and  a  half  in  diameter,2  oval 
from  side  to  side,  surrounded  by  a  fibrous  ring,  covered  by  the  lining  membrane  of 
the  heart;  it  is  considerably  larger  than  the  corresponding  aperture  on  the  left  side, 
being  sufficient  to  admit  the  ends  of  four  fingers.    It  is  guarded  by  the  tricuspid  valve. 

The  opening  of  the  pulmonary  artery  is  circular  in  form,  and  situated  at  the 
summit  of  the  conus  arteriosus,  close  to  the  septum  ventriculorum.     It  is  pla~    jlX 
above  and  on  the  left  side  of  the  auriculo-ventricular  opening,  upon  the  pvoncimo 
aspect  of  the  heart.     Its  orifice  is  guarded  by  the  pulmonary  semilunar  v 

The  tricuspid  valve  consists  of  three  segments  of  a  triangular  or  a  right  side  ; 
shape,  formed  by  a  duplicature  of  the  lining  membrane  of  the  heart, 
by  a  layer  of  fibrous  tissue,  which  contains,  according  to  Kiirschr  seen   *  lunated 

which  is  turned 

^Morrant  Baker  says  that  "taking  the  mean  of  various  estimates,  it  may  byj^t  auricle 
ventricle  is  able  to  contain  four  to, .six  ounces  of  blood"  (Kirke's  Physiology,  10''° 

2  In  the  Patholoqical  Transactions,  vol.  vi.,  p.  119,  Dr.  Peacock  has  given  f  little  to  the  left  of  the 
upon  the  weight     I  d  dimensions  of  the  heart  in  health  and  disease.     He  str(.    an(j  carrv  it  up  from 
investigatior       .        in  the  healthv  adult  heart,  the  right  auriculo-ventriculi  ,'  '    +•  ,."'     '.lir.  n,„.;,,nln 
circumterenr  lines,  or  4f|  inches :  the  left  auriculo-ventricular  apf   * 

ence  of  44.3  f  inches ;  "the  pulmonic  orifice  of  40  lines,  or  3if  inc 

of  35.5  lines  ches;  but  the  dimensions  of  the  orifices  r'sliape  than  the  ricllt  ventricle, 

proportion."  ar  Vert"re  haViDg  a  ^^  °f  fl'°m  4°val  or  nearlv  circular  outline.    It 

<i  heart,  and  a  considerable  part  of 


464  THE  BLOOD-VASCULAR   SYSTEM. 

muscular  fibres.  These  segments  are  connected  by  their  bases  to  the  fibrous  ring 
surrounding  the  auriculo-ventricular  orifice,  and  by  their  sides  with  one  another,  so 
as  to  form  a  continuous  annular  membrane,  which  is  attached  round  the  margin  of 
the  auriculo-ventricular  opening,  their  free  margins  and  ventricular  surfaces  aifording 
attachment  to  a  number  of  delicate  tendinous  cords,  the  chordce  tendinece.  The 
largest  and  most  movable  segment  is  placed  toward  the  left  side  of  the  auriculo- 
ventricular  opening,  interposed  between  that  opening  and  the  infundibulum ;  hence 
it  is  called  the  left  or  infundibular  cusp.  Another  segment  corresponds  to  the 
right  part  of  the  front  of  the  ventricle,  the  right  or  marginal  cusp ;  and  a  third  to 
its  posterior  wall,  the  posterior  or  septal  cusp.  The  central  part  of  each  segment 
is  thick  and  strong:  the  lateral  margins  are  thin  and  translucent.  The  chordae 
tendineae  are  connected  with  the  adjacent  margins  of  the  principal  segments  of  the 
valve,  and  are  further  attached  to  each  segment  in  the  following  manner  :  1.  Three 
or  four  reach  the  attached  margin  of  each  segment,  where  they  are  continuous  with 
the  auriculo-ventricular  tendinous  ring.  2.  Others,  four  to  six  in  number,  are 
attached  to  the  central  thickened  part  of  each  segment.  3.  The  most  numerous 
and  finest  are  connected  with  the  marginal  portion  of  each  segment. 

The  columnoz  carnem  are  the  rounded  muscular  columns  which  project  from 
nearly  the  whole  of  the  inner  surface  of  the  ventricle,  excepting  near  the  opening 
of  the  pulmonary  artery,  where  the  wall  is  smooth.  They  may  be  classified,  accord- 
ing to  their  mode  of  connection  with  the  ventricle,  into  three  sets.  The  first  set 
merely  form  prominent  ridges  on  the  inner  surface  of  the  ventricle,  being  attached 
by  their  entire  length  on  one  side,  as  well  as  by  their  extremities.  The  second  set 
are  attached  by  their  two  extremities,  but  are  free  in  the  rest  of  their  extent;  while 
the  third  set  (musculi  papillares)  are  attached  by  one  extremity  to  the  wall  of  the 
heart,  the  opposite  extremity  giving  attachment  to  the  clxordoz  tendineo?.  There 
are  twopapillary  muscles,  anterior  and  posterior:  of  these,  the  anterior  is  the  larger; 
its  chordae  tendineae  are  connected  with  the  right  and  left  segments  of  the  valve. 
The  posterior  is  not  always  single,  but  sometimes  consists  of  two  or  three  muscular 
columns ;  its  chordae  tendineae  are  connected  with  the  posterior  and  the  right  seg- 
ments. In  addition  to  these,  some  few  chordae  may  be  seen  springing  directly  from 
the  ventricular  septum,  or  from  small  eminences  on  it,  and  passing  to  the  left  and 
posterior  segments.  A  fleshy  band,  well  marked  in  the  ox  and  some  other  animals, 
is  frequently  seen  passing  from  the  base  of  the  anterior  papillary  muscle  to  the 
interventricular  septum.  From  its  attachments  it  may  assist  in  preventing  over- 
distention  of  the  auricle,  and  so  has  been  named  the  moderator  band. 

The  right  auriculo-ventricular  orifice  allows  the  blood  to  pass  freely  from  the 
right  auricle  into  the  right  ventricle,  and  it  will  be  noted  that  the  surface  of  the 
tricuspid  valve  next  the  blood-current  is  quite  smooth.  When  the  right  ventricle 
contracts  to  force  the  blood  into  the  pulmonary  artery,  the  segments  of  the  tricuspid 
valve  come  together  and  close  the  auriculo-ventricular  opening,  and  so  prevent  the 
blood  from  passing  bac^:  into  the  auricle.  The  papillary  muscles  and  chordae  ten- 
^dineae  moor  the  segments  of  the  valve,  and  prevent  their  being  forced  through  into 

7$uricle  by  the  weight  of  blood  behind  them, 
inferior  \  semilunar  valves,  three  in  number,1  guard  the  orifice  of  the  pulmonary 
In  the^^J  consist  of  three  semicircular  folds,  two  anterior  (right  and  left)  and 
reflux  of  blc?£'  f°rmed  by  a  duplicature  of  the  lining  membrane,  strengthened  by 
free  margin  pi     ^hey  are  attached,   by  their  convex  margins,  to  the  wall  of  the 
altogether  wantiiunction  Wltn   tne   ventricle,    the   straight   border  being  free,   and 
The  coronary  m  tne  lunien  of  the  vessel.      The  free  margin  of  each  is  some- 
membrane  of  the  autne  rest  °^  tne  valye>  is  strengthened  by  a  bundle  of  tendinous 
the  regurgitation  of'  a^  *ts  middle,  a  small  projecting  thickened  nodule,  called  cor- 
This  valve  is  occasioonsistm§  °^  bundles  of  interlacing  connective-tissue  fibres  with 
The  fossa  ovalis  i_tissue  cells  and  some  few  elastic  fibres.     From  this  nodule 

foramen  ovale  in  the  foetus.     iVes  have  been  found  to  be  two  in  number  instead  of  three  (Dr. 
larum,  above  and  to  the  left  of  tistern  Med,  and  Surg.  Journ.,  Julyv  1873),  and  the  same  variety 
The  annulus  ovalis  is  the  pronfemilunar  valves* 


THE   HEART.  465 

tendinous  fibres  radiate  through  the  valve  to  its  attached  margin,  and  these  fibres 
form  a  constituent  part  of  its  substance  throughout  its  whole  extent,  excepting  two 
narrow  lunated  portions,  the  lunulas,  placed  one  on  each  side  of  the  nodule  im- 
mediately adjoining  the  free  margin ;  here  the  valve  is  thin,  and  formed  merely  by 
the  lining  membrane.  During  the  passage  of  the  blood  along  the  pulmonary  artery 
these  valves  are  opened,  and  the  course  of  the  blood  along  the  tube  is  uninter- 
rupted ;  but  during  the  ventricular  diastole,  when  the  current  of  blood  along  the 
pulmonary  artery  is  checked  and  partly  thrown  back  by  its  elastic  walls,  these 
valves  become  immediately  expanded,  and  effectually  close  the  entrance  of  the 
tube.  When  the  valves  are  closed,  the  lunated  portions  of  each  are  brought  into 
contact  with  one  another  by  their  opposed  surfaces,  the  three  corpora  Arantii  fill- 
ing up  the  small  triangular  space  that  would  be  otherwise  left  by  the  approxima- 
tion of  the  three  semilunar  valves. 

Between  the  semilunar  valves  and  the  commencement  of  the  pulmonary  artery 
are  three  pouches  or  dilatations,  one  behind  each  valve.  These  are  the  pulmonary 
sinuses  (sinuses  of  Valsalva).  Similar  sinuses  exist  between  the  semilunar  valves 
and  the  commencement  of  the  aorta ;  they  are  larger  than  the  pulmonary  sinuses. 
The  blood,  in  its  regurgitation  toward  the  heart,  finds  its  way  into  these  sinuses, 
and  so  shuts  down  the  valve-flaps. 

In  order  to  examine  the  interior  of  the  left  auricle,  make  an  incision  on  the  posterior  surface 
of  the  auricle  from  the  pulmonary  veins  on  one  side  to  those  on  the  other,  the  incision  being 
carried  a  little  way  into  the  vessels.  Make  another  incision  from  the  middle  of  the  horizontal 
one  to  the  appendix. 

The  Left  Auricle  is  rather  smaller  than  the  right ;  its  walls  thicker,  measuring 
about  one  line  and  a  half;  it  consists,  like  the  right,  of  two  parts,  a  principal  cavity, 
or  sinus,  and  an  appendix  auriculas. 

The  sinus  is  cuboidal  in  form,  and  concealed  in  front  by  the  pulmonary  artery 
and  aorta :  internally,  it  is  separated  from  the  right  auricle  by  the  septum  auricu- 
larum  ;  behind,  it  receives  on  each  side  two  pulmonary  veins,  being  free  in  the  rest 
of  its  extent. 

The  ap>pendix  auriculas  is  somewhat  constricted  at  its  junction  with  the  auricle; 
it  is  longer,  narrower,  and  more  curved  than  that  of  the  right  side,  and  its  margins 
are  more  deeply  indented,  presenting  a  kind  of  foliated  appearance.  Its  direction 
is  forward  and  toward  the  right  side,  overlapping  the  root  of  the  pulmonary  artery. 

Within  the  auricle  the  following  parts  present  themselves  for  examination : 

The  openings  of  the  four  pulmonary  veins. 
Auriculo-ventricular  opening. 
Musculi  pectinati. 

The  pulmonary  veins,  four  in  number,  open,  two  into  the  right,  and  two  into 
the  left  side  of  the  auricle.  The  two  left  veins  frequently  terminate  by  a  common 
opening.     They  are  not  provided  with  valves. 

The  auriculo-ventricular  opening  is  the  large  oval  aperture  of  communication 
between  the  auricle  and  ventricle.  It  is  rather  smaller  than  the  corresponding 
opening  on  the  opposite  side  (see  note,  page  463). 

The  musculi  pectinati  are  fewer  in  number  and  smaller  than  on  the  right  side  ; 
they  are  confined  to  the  inner  surface  of  the  appendix. 

On  the  inner  surface  of  the  septum  auricularum  may  be  seen  a  lunated 
impression  bounded  below  by  a  crescentic  ridge  the  concavity  of  which  is  turned 
upward.      The  depression  is  just  above  the  fossa  ovalis  in  the  right  auricle. 

To  examine  the  interior  of  the  left  ventricle,  make  an  incision  a  little  to  the  left  of  the 
anterior  interventricular  groove  from  the  base  to  the  apex  of  the  heart,  and  carry  it  up  from 
thence,  a  little  to  the  left  of  the  posterior  interventricular  groove,  nearly  as  far  as  the  auriculo- 
ventricular  groove. 

The  Left  Ventricle  is  longer  and  more  conical  in  shape  than  the  right  ventricle, 
and  on  transverse  section  its  cavity  presents  an  oval  or  nearly  circular  outline.  It 
forms  a  small  part  of  the  anterior  surface  of  the  heart,  and  a  considerable  part  of 

30 


466 


THE   BLOOD-VASCULAR    SYSTEM. 


its  posterior  surface.  It  also  forms  the  apex  of  the  heart  by  its  projection  beyond 
the  right  ventricle.  Its  walls  are  much  thicker  than  those  of  the  right  side,  the 
proportion  being  as  3  to  1.  They  are  thickest  opposite  the  widest  part  of  the 
ventricle,  becoming  gradually  thinner  toward  the  base,  and  also  toward  the  apex, 
which  is  the  thinnest  part. 

The  following  parts  present  themselves  for  examination  : 


r,       ■         ( Auriculo- ventricular. 
Openings  |  Aortic 

Chordae  tendinese. 


T7  ,        f  Mitral. 
Valves  <  a      ., 

[  bemnunar. 

Columnae  earner. 


The  auriculo -ventricular  opening  is  placed  below  and  to  the  left  of  the  aortic 
orifice.     It  is  a  little  smaller  than  the  corresponding  aperture  of  the  opposite  side, 


Bristle  passed  through  left 
auriculo-ventricular  opening. 


Passed  through  aortic  opening. 


Fig.  277.— The  left  auricle  and  ventricle  laid  open,  the  posterior  walls  of  both  being  removed. 

admitting  only  two  fingers ;  but,  like  it,  is  broader  in  the  transverse  than  in  the 
antero-posterior  diameter.  It  is  surrounded  by  a  dense  fibrous  ring,  covered  by 
the  lining  membrane  of  the  heart,   and  guarded  by  the  mitral  valves. 

The  aortic  opening  is  a  circular  aperture,  in  front  and  to  the  right  side  of  the 
auriculo-ventricular,  from  which  it  is  separated  by  one  of  the  segments  of  the 
mitral  valve.  Its  orifice  is  guarded  by  the  semilunar  valves.  The  portion  of  the 
ventricle  immediately  below  the  aortic  orifice  is  often  termed  the  aortic  vestibule 
of  Sibson.  It  possesses  fibrous  instead  of  muscular  walls,  and  so  does  not  collapse 
during  the  ventricular  diastole ;  it  thus  gives  space  for  the  segments  of  the  aortic 
valve  during  its  closure. 

The  mitral  valve  is  attached  to  the  circumference  of  the  auriculo-ventricular 
orifice  in  the  same  way  that  the  tricuspid  valve  is  on  the  opposite  side.  It  is 
formed  by  a  duplicature  of  the  lining  membrane,  strengthened  by  fibrous  tissue, 
and  contains  a  few  muscular  fibres.  It  is  larger  in  size,  thicker,  and  altogether 
stronger  than  the  tricuspid,  and  consists  of  two  segments  of  unequal  size.  The 
larger  segment  is  placed  in  front  and  to  the  right  between  the  auriculo-ventricular 


THE   HEART. 


467 


and  aortic  orifices,  the  smaller  to  the  left  and  behind  the  opening,  close  to  the 
wall  of  the  ventricle.  Two  smaller  segments  are  usually  found  at  the  angles  of 
1  unction  of  the  larger.  The  mitral  valve-flaps  are  furnished  with  chordae  ten- 
dineae,  the  mode  of  attachment  of  which  is  precisely  similar  to  those  on  the  right 
side ;  but  they  are  thicker,  stronger,  and  less  numerous. 

The  semilunar  valves  surround  the  orifice  of  the  aorta ;  two  are  posterior 
(right  and  left)  and  one  anterior :  they  are  similar  in  structure  and  in  their  mode 
of  attachment  to  those  of  the  pulmonary  artery.  They  are,  however,  larger, 
thicker,  and  stronger  than  those  of  the  right  side ;  the  lunulae  are  more  distinct, 
and  the  corpora  Arantii  larger  and  more  prominent.  Opposite  each  segment  the 
wall  of  the  aorta  presents  a  slight  dilatation  or  bulging  (sinus  of  Valsalva).  They 
are  larger  than  those  at  the  commencement  of  the  pulmonary  artery. 


Pulmonary 
artery. 


Fig.  278.— Section  of  the  heart,  showing  the  interventricular  septum. 

The  columnar  cameo*,  admit  of  a  subdivision  into  three  sets,  like  those  upon 
the  right  side ;  but  they  are  smaller,  more  numerous,  and  present  a  dense  inter- 
lacement, especially  at  the  apex,  and  upon  the  posterior  Avail.  Those  attached  by 
one  extremity  only,  the  musculi  papillares,  are  two  in  number,  being  connected 
one  to  the  anterior,  the  other  to  the  posterior  wall ;  they  are  of  large  size,  and  ter- 
minate by  free  rounded  extremities,  from  which  the  chordae  tendineae  arise. 

The  septum  between  the  two  ventricles  is  thick,  especially  below  (Fig.  278). 
At  its  upper  part  it  suddenly  tapers  off  and  becomes  destitute  of  muscular  fibres, 
consisting  only  of  fibrous  tissue,  covered  by  two  layers  of  endocardium  ;  and  on 
the  right  side" also  covered,  during  diastole,  by  one  of  the  flaps  of  the  tricuspid 
valve.  This  upper  portion  is  termed  the  membranous  part  of  the  septum,  and  is 
continued  upward  and  forms  the  septum  between  the  aortic  vestibule  and  the  right 


468  THE  BLOOD-VASCULAR   SYSTEM. 

auricle.  It  is  derived  from  the  lower  part  of  the  aortic  septum  of  the  foetus,  and 
an  abnormal  communication  may  exist  at  this  part,  owing  to  defective  development 
of  this  septum. 

The  Endocardium  is  a  thin  membrane  which  lines  the  internal  surface  of  the 
heart ;  it  assists  in  forming  the  valves  by  its  reduplications,  and  is  continuous  with 
the  lining  membrane  of  the  great  blood-vessels.  It  is  a  smooth,  transparent 
membrane,  giving  to  the  inner  surface  of  the  heart  its  glistening  appearance.  It 
is  more  opaque  on  the  left  than  on  the  right  side  of  the  heart,  thicker  in  the 
auricles  than  in  the  ventricles,  and  thickest  in  the  left  auricle.  It  is  thin  on  the 
musculi  pectinati  and  on  the  columns  carnese,  but  thicker  on  the  smooth  part  of 
the  auricular  and  ventricular  walls  and  on  the  tips  of  the  musculi  papillares. 

Structure. — The  heart  consists  of  muscular  fibres,  and  of  fibrous  rings  which 
serve  for  their,  attachment.  It  is  closely  covered  by 'the  visceral  layer  of  the 
serous  pericardium  (epicardiwn),  and  its  cavities  are  lined  by  the  endocardium. 
Between  these  two  membranes  is  the  muscular  wall  of  the  heart,  the  myocardium. 

The  fibrous  rings  surround  the  auriculo-ventricular  and  arterial  orifices ;  they  are 
stronger  upon  the  left  than  on  the  right  side  of  the  heart.  The  auriculo-ventricular 
rinss  serve  for  the  attachment  of  the  muscular  fibres  of  the  auricles  and  ventricles, 
and  also  for  the  mitral  and  tricuspid  valves ;  the  ring  on  the  left  side  is  closely 
connected  by  its  right  margin  with  the  aortic  arterial  ring.  Between  these  and 
the  right  auriculo-ventricular  ring  is  a  mass  of  fibrous  tissue,  and  in  some  of  the 
larger  animals,  as  the  ox  and  elephant,  a  nodule  of  bone,  the  os  cordis. 

The  fibrous  rings  surrounding  the  arterial  orifices  serve  for  the  attachment  of 
the  great  vessels  and  semilunar  valves.  Each  ring  receives,  by  its  ventricular 
margin,  the  attachment  of  the  muscular  fibres  of  the  ventricles ;  its  opposite  margin 
presents  three  deep  semicircular  notches,  within  which  the  middle  coat  of  the 
artery  (which  presents  three  convex  semicircular  segments)  is  firmly  fixed,  the 
attachment  of  the  artery  to  its  fibrous  ring  being  strengthened  by  the  thin  cellular 
coat  and  serous  membrane  externally  and  by  the  endocardium  within.  It  is 
opposite  the  margins  of  these  semicircular  notches,  in  the  arterial  rings,  that  the 
endocardium  by  its  reduplication,  forms  the  semilunar  valves,  the  fibrous  structure 
of  the  ring  being  continued  into  each  of  the  segments  of  the  valve  at  this  part. 
The  middle  coat  of  the  artery  in  this  situation  is  thin,  and  the  sides  of  the  vessel 
are  dilated  to  form  the  sinuses  of  Valsalva. 

The  muscxdar  structure  of  the  heart  consists  of  bands  of  fibres  which  present 
an  exceedingly  intricate  interlacement.  They  are  of  a  deep  red  color  and  marked 
with  transverse  striae. 

The  muscular  fibres  of  the  heart  admit  of  a  subdivision  into  two  groups,  those  of 
the  auricles  and  those  of  the  ventricles,  which  are  quite  independent  of  one  another. 

Fibres  of  the  Auricles. — These  are  disposed  in  two  layers — a  superficial  layer 
common  to  both  cavities,  and  a  deep  layer  proper  to  each.  The  superficial  fibres 
are  more  distinct  on  the  anterior  surface  of  the  auricles,  across  the  bases  of  which 
they  run  in  a  transverse  direction,  forming  a  thin,  but  incomplete  layer.  Some  of 
these  fibres  pass  into  the  septum  auricularum.  The  interned  or  deep  fibres  proper 
to  each  auricle  consist  of  two  sets,  looped  and  annular  fibres.  The  looped  fibres 
pass  upward  over  each  auricle,  being  attached  by  two  extremities  to  the  corre- 
sponding auriculo-ventricular  rings  in  front  and  behind.  The  annular  fibres 
surround  the  whole  extent  of  the  appendices  auricularum,  and  are  continued  upon 
the  walls  of  the  vense  cavse  and  coronary  sinus  on  the  right  side,  and  upon  the 
pulmonary  veins  on  the  left  side,  at  their  connection  with  the  heart.  In  the 
appendices  they  interlace  with  the  longitudinal  fibres. 

Fibres  of  the  Ventricles. — These  are  arranged  in  an  exceedingly  complex  man- 
ner, and  the  accounts  given  by  various  anatomists  differ  considerably.  This  is  prob- 
ably due  partly  to  the  fact  that  the  various  layers  of  muscular  fibres  of  which  the 
heart  is  said  to  be  composed  are  not  independent,  but  their  fibres  are  interlaced 
to  a  considerable  extent,  and  therefore  any  separation  into  layers  must  be  to  a 
great  extent  artificial ;  and  also  partly  to  the  fact,  pointed  out  by  Henle,  that 


THE   HEART.  ^469 

there  are  varieties  in  the  arrangement  due  to  individual  differences.  If  the 
epicardium  and  the  subjacent  fat  are  removed  from  a  heart  which  has  been  subjected 
to  prolonged  boiling,  so  as  to  dissolve  the  connective  tissues,  the  superficial  fibres 
of  the  ventricles  will  be  exposed.  They  will  be  seen  to  commence  at  the  base  of 
the  heart,  where  they  are  attached  to  the  tendinous  rings  around  the  orifices,  and 
to  pass  obliquely  downward  toward  the  apex,  with  a  direction  from  right  to  left. 
At  the  apex  the  fibres  turn  suddenly  inward  into  the  interior  of  the  ventricle, 
forming  what  is  called  the  vortex.  On  the  back  of  the  heart  it  will  be  seen  that 
the  fibres  pass  continuously  from  one  ventricle  to  the  other  over  the  interventricular 
groove ;  and  the  same  thing  will  be  noticed  on  the  front  of  the  heart  at  the  upper 
and  lower  end  of  the  anterior  interventricular  groove,  but  in  the  middle  portion 
of  this  groove  the  fibres  passing  from  one  ventricle  to  the  other  are  interrupted 
by  fibres  emerging  from  the  septum  along  the  groove ;  many  of  the  superficial 
fibres  pass  in  also  at  this  groove  to  the  septum.  The  vortex  is  produced,  as  stated 
above,  by  the  sudden  turning  inward  of  the  superficial  fibres  in  a  peculiar  spiral 
manner  into  the  interior  of  the  ventricle.  Those  fibres  which  descended  on  the 
posterior  surface  of  the  heart  enter  the  left  ventricle  at  the  vortex,  and,  ascending, 
form  the  posterior  part  of  the  inner  layer  of  muscular  fibres  lining  this  cavity  and 
the  right  (posterior)  musculus  papillaris ;  those  fibres  which  descend  on  the  front 
of  the  heart  to  reach  the  apex  also  pass,  at  the  vortex,  into  the  interior  of  the 
ventricle,  where  they  form  the  remainder  of  the  innermost  layer  of  the  ventricle 
and  the  left  (anterior)  musculus  papillaris.  The  fibres  forming  the  inner  layer  of 
the  wall  of  the  ventricle  ascend  to  be  attached  to  the  fibrous  rings  around  the 
orifices. 

By  dissection  these  superficial  fibres  may  be  removed  as  a  thin  stratum,  and  it 
will  then  be  found  that  the  ventricles  are  made  up  of  oblique  fibres  superimposed  in 
layers  one  on  the  top  of  another,  and  assuming  gradually  a  less  oblique  direction  as 
they  pass  to  the  middle  of  the  thickness  of  the  ventricular  wall,  so  that  in  the  centre 
of  the  wall  the  fibres  are  transverse.  Internal  to  this  central  transverse  layer  the 
fibres  become  oblique  again,  but  in  the  opposite  direction  to  the  external  ones.  This 
division  into  distinct  layers  is,  however,  to  a  great  extent  artificial,  as  the  fibres 
pass  across  from  one  layer  to  another,  and  have  therefore  to  be  divided  in  the 
dissection,  and  the  change  in  the  direction  of  the  fibres  is  very  gradual.  These 
oblique  fibres  commence  above  at  the  fibrous  rings  at  the  base  of  the  heart,  and, 
descending  toward  the  apex,  they  enter  the  septum  near  its  lower  end.  In  the 
septum  the  fibres  which  form  the  left  ventricle  may  be  traced  in  three  directions: 
1.  Some  pass  upAvard  to  be  attached  to  the  central  mass  of  fibrous  tissue.  2.  Others 
pass  through  the  septum  to  become  continuous  with  the  fibres  of  the  right  ventricle. 
3.  The  remainder  pass  through  the  septum  to  encircle  the  ventricle  as  annular 
fibres.  Of  the  fibres  of  the  right  ventricle,  some  on  entering  the  septum  pass 
upward  to  be  attached  to  the  central  mass  of  fibrous  tissue;  some,  entering  the 
septum  from  behind,  pass  forward  to  become  continuous  with  the  fibres  on  the 
anterior  surface  of  the  left  ventricle ;  and  others,  entering  in  front,  pass  backward 
to  join  the  fibres  on  the  posterior  wall  of  the  left  ventricle.  The  septum  therefore 
consists  of  three  varieties  of  fibres — viz.,  annular  fibres,  special  to  the  left  ventricle  ; 
ascending  fibres,  derived  from  both  ventricles  and  ascending  through  the  septum 
to  the  central  fibro-cartilage  ;  and  decussating  fibres,  derived  from  the  anterior  wall 
of  one  ventricle  and  passing  to  the  posterior  wall  of  the  other  ventricle,  or  from 
the  posterior  wall  of  the  right  ventricle  and  passing  to  the  anterior  wall  of  the  left. 
In  addition  to  these  fibres  there  are  a  considerable  number  which  appear  to  encircle 
both  ventricles  and  which  pass  across  the  septum  without  turning  into  it. 

Vessels  and  Nerves. — The  arteries  supplying  the  heart  are  the  right  and  left 
coronary  from  the  aorta. 

The  veins  accompany  the  arteries,  and  terminate  in  the  right  auricle.  They  are, 
the  anterior  or  great,  posterior,  left  and  anterior  cardiac  veins,  the  right  or  small, 
and  the  left  or  great,  coronary  sinuses  and  the  venae  Thebesii  (vence  cordis  minimce). 

The  lymphatics  terminate  in  the  thoracic  and  right  lymphatic  ducts. 


470.  THE   BLOOD-VASCULAR   SYSTEM. 

The  nerves  are  derived  from  the  cardiac  plexuses,  which  are  formed  partly  from 
the  cranial  nerves  and  partly  from  the  sympathetic.  They  are  freely  distributed 
both  on  the  surface  and  in  the  substance  of  the  heart,  the  separate  filaments  being 
furnished  with  small  ganglia. 

Surface  Form. — In  order  to  show  the  extent  of  the  heart  in  relation  to  the  front  of  the 
chest,  draw  a  line  from  the  lower  border  of  the  second  left  costal  cartilage,  one  inch  from  the 
sternum,  to  the  upper  border  of  the  third  right  costal  cartilage,  half  an  inch  from  the  sternum. 
This  represents  the  base-line  or  upper  limit  of  the  organ.  Take  a  point  an  inch  and  a  half 
below  and  three-quarters  of  an  inch  internal  to  the  left  nipple — that  is,  about  three  and  a  half 
inches  to  the  left  of  the  median  line  of  the  body.  This  represents  the  apex  of  the  heart. 
Draw  a  line  from  this  apex-point,  with  a  slight  convexity  downward,  to  the  junction  of  the 
seventh  right  costal  cartilage  to  the  sternum.  This  represents  the  lower  limit  of  the  heart. 
Join  the  right  extremity  of  the  first  line — that  is,  the  base-line — with  the  right  extremity  of 
this  line — that  is,  to  the  seventh  right  chondro-sternal  joint — with  a  slight  curve  outward,  so 
that  it  projects  about  an  inch  and  a  half  from  the  middle  line  of  the  sternum.  Lastly,  join  the 
left  extremity  of  the  base-line  and  the  apex-point  by  a  line  curved  slightly  to  the  left. 

The  position  of  the  various  orifices  is  as  follows :  viz.  the  pulmonary  orifice  is  situated  in 
the  upper  angle  formed  by  the  articulation  of  the  third  left  costal  cartilage  with  the  sternum  ; 
the  aortic  orifice  is  a  little  below  and  internal  to  this,  behind  the  left  border  of  the  sternum, 
close  to  the  articulation  of  the  third  left  costal  cartilage  to  this  bone.  The  left  auriculo-ventric- 
ular  opening  is  behind  the  sternum,  rather  to  the  left  of  the  median  line,  and  opposite  the 
fourth  costal  cartilages.  The  right  auriculo- ventricular  opening  is  a  little  lower,  opposite  the 
fourth  interspace  and  in  the  middle  line  of  the  body  (Fig.  275). 

A  portion  of  the  area  of  the  heart  thus  mapped  out  is  uncovered  by  lung,  and  therefore 
gives  a  dull  note  on  percussion ;  the  remainder,  being  overlapped  by  the  lung,  gives  a  more  or 
less  resonant  note.  The  former  is  known  as  the  area  of  superficial  cardiac  dulness ;  the  latter 
as  the  area  of  deep  cardiac  dulness.  The  area  of  superficial  cardiac  dulness  is  included  between 
a  line  drawn  from  the  centre  of  the  sternum,  on  a  level  with  the  fourth  costal  cartilages,  to  the 
apex  of  the  heart  and  a  line  drawn  from  the  same  point  down  the  lower  third  of  the  middle  line 
of  the  sternum.  Below,  this  area  merges  into  the  dulness  which  corresponds  to  the  liver.  Dr. 
Latham  lays  down  the  following  rule  as  a  sufficient  practical  guide  for  the  definition  of  the  por- 
tion of  the  heart  which  is  uncovered  by  lung  or  pleura :  "  Make  a  circle  of  two  inches  in  diam- 
eter round  a  point  midway  between  the  nipple  and  the  end  of  the  sternum." 

Surgical  Anatomy. — Wounds  of  the  heart  are  often  immediately  fatal,  but  not  necessarily 
so.  They  may  be  non-penetrating,  when  death  may  occur  from  hemorrhage,  :f  one  of  the 
coronary  vessels  has  been  wounded,  or  subsequently  from  pericarditis ;  or,  on  the  )ther  hand, 
the  patient  may  recover.  Even  a  penetrating  wound  is  not  necessarily  fatal,  if  the  wound  is 
a  small  one.  A  flap  comprising  the  whole  thickness  of  the  thoracic  wall  may  be  made,  the 
cavity  of  the  pericardium  opened,  and  the  wound  in  the  heart  sutured.  This  has  been  done 
successfully. 

Peculiarities  in  the  Vascular  System  of  the  Foetus. 

The  chief  peculiarities  in  the  heart  of  the  foetus  are  the  direct  communication 
between  the  two  auricles  through  the  foramen  ovale  and  the  large  size  of  the 
Eustachian  valve.  There  are  also  several  minor  peculiarities.  Thus,  the  position 
of  the  heart  is  vertical  until  the  fourth  month,  when  it  commences  to  assume  an 
oblique  direction.  Its  size  is  also  very  considerable  as  compared  with  the  body,  the 
proportion  at  the  second  month  being  1  to  50 ;  at  birth  it  is  as  1  to  120 ;  whilst 
in  the  adult  the  average  is  about  1  to  160.  At  an  early  period  of  foetal  life  the 
auricular  portion  of  the  heart  is  larger  than  the  ventricular,  the  right  auricle  being 
more  capacious  than  the  left ;  but  toward  birth  the  ventricular  portion  becomes 
the  larger.  The  thickness  of  both  ventricles  is  at  first  about  equal,  but  toward 
birth  the  left  becomes  much  the  thicker  of  the  two. 

The  foramen  ovale  is  situated  at  the  lower  and  back  part  of  the  septum  auricu- 
larum,  forming  a  communication  between  the  auricles.  It  remains  as  a  free  oval 
opening  until  the  middle  period  of  foetal  life.  About  this  period  a  fold  grows  up 
from  the  posterior  wall  of  the  auricle  to  the  left  of  the  foramen  ovale,  and  advances 
over  the  opening  so  as  to  form  a  sort  of  valve,  which  allows  the  blood  to  pass  only 
from  the  right  to  the  left  auricle,  and  not  in  the  opposite  direction. 

The  Eustachian  valve  is  directed  upward  on  the  left  side  of  the  opening  of  the 
inferior  vena  cava,  and  serves  to  direct  the  blood  from  this  vessel  through  the 
foramen  ovale  into  the  left  auricle. 

The  peculiarities  in  the  arterial  sj^stem  of  the  foetus  are  the  communication 
between  the  pulmonary  artery  and  the  descending  aorta  by  means  of  the  ductus 


THE   HEART.  471 

arteriosus,  and  the  communication  between  the  internal  iliac  arteries  and  the 
placenta  by  means  of  the  umbilical  arteries. 

The  ductus  arteriosus  is  a  short  tube,  about  half  an  inch  in  length  at  birth,  and 
of  the  diameter  of  a  goosequill.  In  the  early  condition  it  forms  the  continuation  of 
the  pulmonary  artery,  and  opens  into  the  descending  aorta  just  below  the  orio-in 
of  the  left  subclavian  artery,  and  so  conducts  the  chief  part  of  the  blood  from  the 
right  ventricle  into  this  vessel.  When  the  branches  of  the  pulmonary  artery  have 
become  larger  relatively  to  the  ductus  arteriosus,  the  latter  is  chiefly  connected 
to  the  left  pulmonary  artery ;  and  the  fibrous  cord,  Avhich  is  all  that  remains 
of  the  ductus  arteriosus  in  later  life,  will  be  found  to  be  attached  to  the  root  of 
that  vessel. 

The  umbilical  or  hypogastric  arteries  arise  from  the  internal  iliacs,  in  addition 
to  the  branches  given  off  from  those  vessels  in  the  adult.  Ascending  along  the 
sides  of  the  bladder  to  its  apex,  they  pass  out  of  the  abdomen  at  the  umbilicus 
and  are  continued  along  the  umbilical  cord  to  the  placenta,  coiling  round  the 
umbilical  vein.  They  carry  to  the  placenta  the  blood  which  has  circulated  in 
the  system  of  the  foetus. 

The  peculiarity  in  the  venous  system  of  the  foetus  is  the  communication 
established  between  the  placenta  and  the  liver  and  portal  vein  through  the 
umbilical  vein,  and  the  inferior  vena  cava  through  the  ductus  venosus. 


Fcstal  Circulation. 

The  blood  destined  for  the  nutrition  of  the  foetus  is  returned  from  the  placenta 
to  the  foetus  by  the  umbilical  vein.  This  vein  enters  the  abdomen  at  the  umbilicus, 
and  passes  upward  along  the  free  margin  of  the  suspensory  ligament  of  the  liver 
to  the  under  surface  of  that  organ,  where  it  gives  off  two  or  three  branches  to  the 
left  lobe,  one  of  which  is  of  large  size,  and  others  to  the  lobus  quadratus  and 
lobulus  Spigelii.  At  the  transverse  fissure  it  divides  into  two  branches  :  of  these, 
the  larger  is  joined  by  the  portal  vein  and  enters  the  right  lobe  ;  the  smaller 
branch  continues  outward,  under  the  name  of  the  ductus  venosus,  and  joins 
the  left  hepatic  vein  at  the  point  of  junction  of  that  vessel  with  the  inferior 
vena  cava.  The  blood,  therefore,  which  traverses  the  umbilical  vein  reaches 
the  inferior  vena  cava  in  three  different  ways :  the  greater  quantity  circulates 
through  the  liver  with  the  portal  venous  blood  before  entering,  the  vena  cava 
by  the  hepatic  veins ;  some  enters  the  liver  directly,  and  is  also  returned  to  the 
inferior  cava  by  the  hepatic  veins ;  the  smaller  quantity  passes  directly  into  the 
vena  cava  by  the  junction  of  the  ductus  venosus  with  the  left  hepatic  vein. 

In  the  inferior  cava  the  blood  carried  by  the  ductus  venosus  and  hepatic  veins 
becomes  mixed  with  that  returning  from  the  lower  extremities  and  wall  of  the 
abdomen.  It  enters  the  right  auricle,  and,  guided  by  the  Eustachian  valve,  passes 
through  the  foramen  ovale  into  the  left  auricle,  where  it  becomes  mixed  with  a 
small  quantity  of  blood  returned  from  the  lungs  by  the  pulmonary  veins.  From 
the  left  auricle  it  passes  into  the  left  ventricle,  and  from  the  left  ventricle  into 
the  aorta,  by  means  of  which  it  is  distributed  almost  entirely  to  the  head  and 
upper  extremities,  a  small  quantity  being  probably  carried  into  the  descending 
aorta.  From  the  head  ami  upper  extremities  the  blood  is  returned  by  the 
tributaries  of  the  superior  vena  cava  to  the  right  auricle,  where  it  becomes  mixed 
with  a  small  portion  of  the  blood  from  the  inferior  cava,  From  the  right  auricle 
it  descends  over  the  Eustachian  valve  into  the  right  ventricle,  and  from  the  right 
ventricle  passes  into  the  pulmonary  artery.  The  lungs  of  the  foetus  being 
inactive,  only  a  small  quantity  of  the  blood  of  the  pulmonary  artery  is  distributed 
to  them  by  the  right  and  left  pulmonary  arteries,  and  is  returned  by  the  pulmonary 
Veins  to  the  left  auricle ;  the  greater  part  passes  through  the  ductus  arteriosus 
into  the  commencement  of  the  descending  aorta,  where  it  becomes  mixed  with  a 
small  quantity  of  blood  transmitted  by  the  left  ventricle  into  the  aorta.     Through 


472 


THE   BLOOD-VASCULAR  SYSTEM. 


this  vessel  it  descends  to  supply  the  lower  extremities  and  viscera  of  the  abdo- 
men and  pelvis,  the  chief  portion  being,  however,  conveyed  by  the  umbilical 
arteries  to  the  placenta.  . 

From  the  preceding  account  of  the  circulation  of  the  blood  m  the  Icetus  it  will 

\\q  S6GI1 

1.  That  the  placenta  serves  the  purposes  of  nutrition  and  excretion,  receiving 


Ductus  arteriosus. 


Internal  iliac  artery. 


Fig.  279.-Plan  of  the  foetal  circulation.    In  this  plan  the  figured  arrows  represent  the  kind  of  Wood  as 

well  as  the  direction  which  it  takes  in  the  vessels.  Thus,  arterial  blood  is  figured  ~%>- -> ,  venous  bloo 

•^ > ;  mixed  (arterial  and  venous)  blood,  ^> >. 

the  impure  blood  from  the  foetus,  and  returning  it  charged  with  additional  nutri- 

tive  material.  . 

2.  That  nearly  the  whole  of  the  blood  of  the  umbilical  vein  traverses  the  liver 


THE   HEART.  473 

before  entering  the  inferior  .cava ;  hence  the  large  size  of  this  organ,  especially  at 
an  early  period  of  foetal  life. 

3.  That  the  right  auricle  is  the  point  of  meeting  of  a  double  current,  the 
blood  in  the  inferior  cava  being  guided  by  the  Eustachian  valve  into  the  left 
auricle,  whilst  that  in  the  superior  cava  descends  into  the  right  ventricle.  At  an 
early  period  of  foetal  life  it  is  highly  probable  that  the  two  streams  are  quite  dis- 
tinct, for  the  inferior  cava  opens  almost  directly  into  the  left  auricle,  and  the 
Eustachian  valve  would  exclude  the  current  along  the  vein  from  entering  the 
right  ventricle.  At  a  later  period,  as  the  separation  between  the  two  auricles 
becomes  more  distinct,  it  seems  probable  that  some  mixture  of  the  two  streams 
must  take  place. 

4.  The  pure  blood  carried  from  the  placenta  to  the  foetus  by  the  umbilical 
vein,  mixed  with  the  blood  from  the  portal  vein  and  inferior  cava,  passes  almost 
directly  to  the  arch  of  the  aorta,  and  is  distributed  by  the  branches  of  that  vessel 
to  the  head  and  upper  extremities ;  hence  the  large  size  and  perfect  development 
of  those  parts  at  birth. 

5.  The  blood  contained  in  the  descending  aorta,  chiefly  derived  from  that 
which  has  already  circulated  through  the  head  and  upper  limbs,  together  with  a 
small  quantity  from  the  left  ventricle,  is  distributed  to  the  lower  extremities ; 
hence  the  small  size  and  imperfect  development  of  these  parts  at  birth. 

Changes  in  the  Vascular  System  at  Birth. 

At  birth,  when  respiration  is  established,  an  increased  amount  of  blood 
from  the  pulmonary  artery  passes  through  the  lungs,  which  now  perform  their 
office  as  respiratory  organs,  and  at  the  same  time  the  placental  circulation 
is  cut  off.  The  foramen  ovale  becomes  gradually  closed  by  about  the  tenth 
day  after  birth ;  the  valvular  fold  above  mentioned  becomes  adherent  to  the 
margins  of  the  foramen  for  the  greater  part  of  its  circumference,  but  above 
a  slit-like  opening  is  left  between  the  two  auricles  which  sometimes -remains  per- 
sistent. 

The  ductus  arteriosus  begins  to  contract  immediately  after  respiration  is  estab- 
lished, becomes  completely  closed  from  the  fourth  to  the  tenth  day,  and  ultimately 
degenerates  into  an  impervious  cord  which  serves  to  connect  the  left  pulmonary 
artery  to  the  descending  aorta. 

Of  the  umbilical  or  hypogastric  arteries,  the  portion  continued  on  to  the 
bladder  from  the  trunk  of  the  corresponding  internal  iliac  remains  pervious 
as  the  superior  vesical  artery,  and  the  part  extending  from  the  side  of  the  bladder 
to  the  umbilicus  becomes  obliterated  between  the  second  and  fifth  clays  after  birth, 
and  projects  as  a  fibrous  cord  toward  the  abdominal  cavity,  carrying  on  it  a  fold 
of  peritoneum  and  separating  two  of  the  fossae  of  the  peritoneum  spoken  of  in  the 
section  on  the  surgical  anatomy  of  direct  inguinal  hernia. 

The  umbilical  vein  and  ductus  venosus  become  completely  obliterated  between 
the  second  and  fifth  days  after  birth,  and  ultimately  dwindle  to  fibrous  cords,  the 
former  becoming  the  round  ligament  of  the  liver,  the  latter  the  fibrous  cord,  which 
in  the  adult  may  be  traced  along  the  fissure  of  the  ductus  venosus. 


THE  ARTERIES. 

The  Arteries  are  cylindrical  tubular  vessels  Avhich  serve  to  convey  blood  from 
both  ventricles  of  the  heart  to  every  part  of  the  body.  These  vessels  were  named 
arteries  (drjp,  air ;  rypelv,  to  contain)  from  the  belief  entertained  by  the  ancients 
that  they  contained  air.  To  Galen  is  due  the  honor  of  refuting  this  opinion ;  he 
showed  that  these  vessels,  though  for  the  most  part  empty  after  death,  contain  blood 
in  the  living  body. 

The  distribution  of  the  systemic  arteries  is  like  a  highly  ramified  tree,  the 
common  trunk  of  which,  formed  by  the  aorta,  commences  at  the  left  ventricle  of 
the  heart,  the  smallest  ramifications  corresponding  to  the  circumference  of 
the  body  and  the  contained  organs.  The  arteries  are  found  in  nearly  every 
part  of  the  body,  with  the  exception  of  the  hairs,  nails,  epidermis,  cartilages, 
and  cornea  ;  and  the  larger  trunks  usually  occupy  the  most  protected  situa- 
tions, running,  in  the  limbs,  along  the  flexor  side,  where  they  are  less  exposed 
to  injury. 

There  is  considerable  variation  in  the  mode  of  division  of  the  arteries  :  occa- 
sionally a  short  trunk  subdivides  into  several  branches  at  the  same  point,  as  we 
observe  in  the  coeliac  and  thyroid  axes ;  or  the  vessel  may  give  off  several  branches 
in  succession,  and  still  continue  as  the  main  trunk,  as  is  seen  in  the  arteries  of 
the  limbs ;  but  the  usual  division  is  dichotomous ;  as,  for  instance,  the  aorta 
dividing  into  the  two  common  iliacs,  and  the  common  carotid  into  the  external 
and  internal. 

The  branches  of  arteries  arise  at  very  variable  angles :  some,  as  the  superior 
intercostal  arteries  from  the  aorta,  arise  at  an  obtuse  angle :  others,  as  the  lumbar 
arteries,  at  a  right  angle  ;  or,  as  the  spermatic,  at  an  acute  angle.  An  artery  from 
which  a  branch  is  given  off  is  smaller  in  size,  but  retains  a  uniform  diameter  until 
a  second  branch  is  derived  from  it.  A  branch  of  an  artery  is  smaller  than  the 
trunk  from  which  it  arises ;  but  if  an  artery  divides  into  two  branches,  the  com- 
bined area  of  the  two  vessels  is,  in  nearly  every  instance,  someAvhat  greater  than 
that  of  the  trunk ;  and  the  combined  area  of  all  the  arterial  branches  greatly 
exceeds  the  area  of  the  aorta;  so  that  the  arteries  collectively  may  be  regarded 
as  a  cone,  the  apex  of  which  corresponds  to  the  aorta,  the  base  to  the  capillary 
system. 

The  arteries,  in  their  distribution,  communicate  with  one  another,  forming 
what  is  called  an  anastomosis  (avd,  between ;  ar6fia1  mouth),  or  inosculation ; 
and  this  communication  is  very  free  between  the  large  as  well  as  between  the 
smaller  branches.  The  anastomosis  between  trunks  of  equal  size  is  found  where 
great  activity  of  the  circulation  is  requisite,  as  in  the  brain ;  here  the  two 
vertebral  arteries  unite  to  form  the  basilar,  and  the  two  internal  carotid  arteries 
are  connected  by  a  short  communicating  trunk ;  it  is  also  found  in  the  abdo- 
men, the  intestinal  arteries  having  very  ample  anastomoses  between  their  larger 
branches.  In  the  limbs  the  anastomoses  are  most  numerous  and  of  largest 
size  around  the  joints,  the  branches  of  an  artery  above  inosculating  with  branches 
from  the  vessels  below ;  these  anastomoses  are  of  considerable  interest  to  the 
surgeon,  as  it  is  by  their  enlargement  that  a  collateral  circulation  is  established 
after  the  application  of  a  ligature  to  an  artery  for  the  cure  of  aneurism.  The 
smaller  branches  of  arteries  anastomose  more  frequently  than  the  larger,  and 
between  the  smallest  twigs  these  inosculations  become  so  numerous  as  to  constitute 
a  close  network  that  pervades  nearly  every  tissue  of  the  body. 

Throughout  the  body  generally  the  larger  arterial  branches  pursue  a  perfectly 
straight  course,  but  in  certain  situations  they  are  tortuous ;  thus,  the  facial  artery 
in  its  course  over  the  face,  and  the  arteries  of  the  lips,  are  extremely  tortuous  in 
their   course,  to  accommodate  themselves  to  the  movements  of  the  parts.      The 

474 

r 


THE   ARTERIES.  475 

uterine  arteries  are  also  tortuous,  to  accommodate  themselves  to  the  increase  of 
size  which  the  organ  undergoes  during  pregnancy.  Again,  the  internal  carotid 
and  vertebral  arteries,  previous  to  their  entering  the  cavity  of  the  skull,  describe 
a  series  of  curves,  which  are  evidently  intended  to  diminish  the  velocity  of  the 
current  of  blood  by  increasing  the  extent  of  surface  over  which  it  moves  and 
adding  to  the  amount  of  impediment  which  is  produced  by  friction. 

The  arteries  are  dense  in  structure,  of  considerable  strength,  highly  elastic, 
and,  when  divided,  they  preserve,  although  empty,  their  cylindrical  form. 

The  minute  structure  of  these  vessels  has  been  described  in  the  chapter  on 
General  Anatomy. 

In  the  description  of  the  arteries  we  shall  first  consider  the  efferent  trunk  of 
the  pulmonic  circulation,  the  pulmonary  artery,  and  then  the  efferent  trunk  of  the 
systemic  circulation,  the  aorta  and  its  branches. 

PULMONARY  ARTERY  (Fig.  280). 

The  Pulmonary  Artery  conveys  the  venous  blood  from  the  right  side  of  the 
heart  to  the  lungs.  It  is  a  short,  wide  vessel,  about  2  inches  in  length  and  1^- 
inches  (30  mm.)  in  diameter,  arising  from  the  left  side  of  the  base  (conus  arterio- 
sus) of  the  right  ventricle,  in  front  of  the  aorta.  It  extends  obliquely  upward 
and  backward,  passing  at  first  in  front  of  and  then  to  the  left  of  the  ascending 
aorta,  as  far  as  the  under  surface  of  the  arch,  where  it  divides,  about  on  a  level 
with  the  intervertebral  substance  between  the  fifth  and  sixth  dorsal  vertebrae, 
into  two  branches  of  nearly  equal  size,  the  right  and  left  pulmonary  arteries. 

Relations. — The  whole  of  this  vessel  is  contained,  together  with  the  ascending 
aorta,  in  the  pericardium.  It  is  enclosed  with  the  aorta  in  a  single  tube  of  the 
serous  pericardium,  which  is  continued  upward  upon  them  from  the  base  of  the 
heart  and  connects  them  together.  The  fibrous  layer  of  the  pericardium  becomes 
gradually  lost  upon  the  external  coat  of  its  two  branches.  In  front,  the  pulmonary 
artery  is  separated  from  the  anterior  extremity  of  the  second  left  intercostal  space 
by  the  pleura  and  left  lung,  in  addition  to  the  pericardium ;  it  rests  at  first  upon 
the  ascending  aorta,  and  higher  up  lies  in  front  of  the  left  auricle  on  a  plane 
posterior  to  the  ascending  aorta.  On  each  side  of  its  origin  is  the  appendix  of 
the  corresponding  auricle  and  a  coronary  artery,  the  left  coronary  artery  passing, 
in  the  first  part  of  its  course,  behind  the  vessel. 

The  right  pulmonary  artery,  longer  and  larger  than  the  left,  runs  horizontally 
outward,  behind  the  ascending  aorta  and  superior  vena  cava,  to  the  root  of  the  right 
lung,  where  it  divides  into  two  branches,  of  which  the  lower  and  larger  supplies 
the  middle  and  lower  lobes  ;  the  upper  and  smaller  is  distributed  to  the  upper  lobe. 

The  left  pulmonary  artery,  shorter  and  somewhat  smaller  than  the  right, 
passes  horizontally  in  front  of  the  descending  aorta  and  left  bronchus  to  the  root 
of  the  left  lung,  where  it  divides  into  two  branches  for  the  two  lobes. 

The  root  of  the  left  pulmonary  artery  is  connected  to  the  under  surface  of  the 
arch  of  the  aorta  by  a  short  fibrous  cord,  the  ligamentum  arteriosum;  this  is  the 
remains  of  a  vessel  peculiar  to  foetal  life,  the  ductus  arteriosus. 

The  terminal  branches  of  the  pulmonary  artery  will  be  described  with  the 
anatomy  of  the  lung. 

TEE  AORTA. 

The  aorta  (dopry,  arteria  magna)  is  the  main  trunk  of  a  series  of  vessels  which 
convey  the  oxygenated  blood  to  the  tissues  of  the  body  for  their  nutrition.  This 
vessel  commences  at  the  upper  part  of  the  left  ventricle,  where  it  is  about  one  and 
one-eighth  inches  in  diameter,  a^nd,  after  ascending  for  a  short  distance,  arches 
backward  and  to  the  left  side,  over  the  root  of  the  left  lung,  then  descends  within 
the  thorax  on  the  left  side  of  the  vertebral  column,  passes  through  the  aortic  open- 
ing in  the  Diaphragm,  and,  entering  the  abdominal  cavity,  terminates,  considerably 
diminished  in  size  (about  seven-tenths  of  an  inch  in  diameter),  opposite  the  lower 
border  of  the  fourth  lumbar  vertebra,  where  it  divides  into  the  right  and  left 
common  iliac  arteries.     Hence  it  is  divided   into  the  ascending  aorta,  the  arch  of 


476 


THE  BLOOD-VASCULAR   SYSTEM. 


the  aorta,  and  the  descending  aorta,  which  last  is  again  divided  into  thoracic  aorta 
and  abdominal  aorta,  from  the  position  of  these  parts. 

THE  ASCENDING  AORTA. 

The  ascending  aorta  is  about  two  inches  in  length.  It  commences  at  the  upper 
part  of  the  left  ventricle,  on  a  level  with  the  lower  border  of  the  third  costal  carti- 
lage, behind  the  left  half  of  the  sternum ;  it  passes  obliquely  upward,  forward,  and 
to  the  right,  in  the  direction  of  the  heart's  axis,  as  high  as  the  upper  border  of  the 


Right  vagus. 
Recurrent  laryngeal. 


Left  vagus. 
Left  phrenic. 


Fig.  280. — The  arch  of  the  aorta  and  its  branches. 

second  right  costal  cartilage,  describing  a  slight  curve  in  its  course,  and  being  situ- 
ated, when  distended,  about  a  quarter  of  an  inch  behind  the  posterior  surface  of  the 
sternum.  A  little  above  its  commencement  it  is  somewhat  enlarged,  and  presents 
three  small  dilatations,  called  the  sinuses  of  Valsalva,  opposite  to  which  are  attached 
the  three  semilunar  valves,  which  serve  the  purpose  of  preventing  any  regurgitation 
of  blood  into  the  cavity  of  the  ventricle.  These  valves  are  placed  one  in  front  and 
two  behind.  At  the  union  of  the  ascending  with  the  transverse  part  of  the  aorta 
the  calibre  of  the  vessel  is  increased,  owing  to  a  bulging  outward  of  its  right  wall. 
This  dilatation  is  termed  the  great  sinus  of  the  aorta.     A  section  of  the  aorta 


THE    CORONARY  ARTERIES.  477 

opposite  this  part  has  a  somewhat  oval  figure ;  but  below  the  attachment  of  the 
valves  it  is  circular.  This  portion  of  the  aorta  is  contained  in  the  cavity  of  the 
pericardium,  and,  together  with  the  pulmonary  artery,  is  invested  in  a  tube  of 
serous  membrane,  continued  on  to  them  from  the  surface  of  the  heart. 

Relations. — The  ascending  aorta  is  covered  at  its  commencement  by  the  trunk 
of  the  pulmonary  artery  and  the  right  auricular  appendix,  and,  higher  up,  is 
separated  from  the  sternum  by  the  pericardium,  the  right  pleura,  and  anterior 
margin  of  right  lung,  some  loose  areolar  tissue,  and  the  remains  of  the  thymus 
gland;  behind,  it  rests  upon  the  right  pulmonary  artery  and  left  auricle.  On  the 
right  side  it  is  in  relation  with  the  superior  vena  cava  and  right  auricle  ;  on  the 
left  side,  with  the  pulmonary  artery. 

Plan  of  the  Relations  of  the  Ascending  Aorta. 

In  front. 
Pulmonary  artery. 
Right  auricular  appendix. 
Pericardium. 
Right  pleura  and  lung. 
Remains  of  thymus  gland. 

Right  side.  s^~    "V.  Left  side, 

Superior  vena  cava.  /  \  Pulmonary  artery. 

Right  auricle. 


Behind, 
Right  pulmonary  artery. 
Left  auricle. 

Branches  of  the  Ascending  Aorta. 

The  only  branches  of  the  ascending  aorta  are  the  coronary  arteries.  They 
supply  the  heart,  and  are  two  in  number,  right  and  left,  arising  near  the  com- 
mencement of  the  aorta,  immediately  above  the  free  margin  of  the  semilunar 
valves. 

THE  CORONARY  ARTERIES. 

The  Right  Coronary  Artery,  about  the  size  of  a  crow's  quill,  arises  from  the 
anterior  sinus  of  Valsalva.  It  passes  forward  between  the  pulmonary  artery  and 
the  right  auricular  appendix,  then  runs  obliquely  to  the  right  side,  in  the  groove 
between  the  right  auricle  and  ventricle,  and,  curving  around  the  right  border  of 
the  heart,  runs  along  its  posterior  surface  as  far  as  the  posterior  interventricular 
groove,  where  its  divides  into  two  branches,  one  of  which  (transverse)  continues 
onward  in  the  groove  between  the  left  auricle  and  ventricle,  and  anastomoses  with 
the  left  coronary ;  the  other  (descending)  courses  along  the  posterior  interven- 
tricular furrow,  supplying  branches  to  both  ventricles  and  to  the  septum,  and 
anastomosing  at  the  apex  of  the  heart  Avith  the  descending  branches  of  the  left 
coronary. 

This  vessel  sends  a  large  branch  {marginal)  along  the  thin  margin  of  the  right 
ventricle  to  the  apex,  which  in  its  course  gives  off  numerous  small  branches  to 
the  anterior  and  posterior  surfaces  of  the  ventricle.  It  also  gives  off  a  branch 
(infundibular)  which  ramifies  over  the  front  part  of  the  conus  arteriosus  of  the  right 
ventricle. 

The  Left  Coronary,  larger  than  the  former,  ai'ises  from  the  left  posterior  sinus  of 
Valsalva ;  it  passes  forward  between  the  pulmonaiy  artery  and  the  left  auricular 
appendix,  and  divides  into  two  branches.  Of  these,  one  (transverse)  passes  trans- 
versely outward  in  the  left  auriculo-ventricular  groove,  and  winds  around  the  left 
border  of  the  heart  to  its  posterior  surface,  where  it  anastomoses  with  the  trans- 

\ 


478' 


THE   BLOOD-VASCULAR    SYSTEM. 


verse  branch  of  the  right  coronary  ;  the  other  {descending)  passes  along  the  anterior 
interventricular  groove  to  the  apex  of  the  heart,  where  it  anastomoses  with  the  de- 
scending branches  of  the  right  coronary.  The  left  coronary  supplies  the  left 
auricle  and  its  appendix,  gives  branches  to  both  ventricles,  and  numerous  small 
branches  to  the  pulmonary  artery  and  commencement  of  the  aorta.1 

Peculiarities. — These  vessels  occasionally  arise  by  a  common  trunk,  or  their  number  may 
be  increased  to  three,  the  additional  branch  being  of  small  size.  More  rarely  there  are  two 
additional  branches. 

THE  ARCH  OF  THE  AORTA. 

The  arch,  or  transverse  aorta,  commences  at  the  upper  border  of  the  second 
chondro-sternal  articulation  of  the  right  side,  and  passes  at  first  upward  and  back- 
ward and  from  right  to  left,  and  then  from  before  backward,  to  the  left  side  of  the 
lower  border  of  the  fourth  dorsal  vertebra  behind.  Its  upper  border  is  usually 
about  an  inch  below  the  upper  margin  of  the  sternum. 

Between  the  origin  of  the  left  subclavian  artery  and  the  attachment  of  the 
ductus  arteriosus  the  lumen  of  the  foetal  aorta  is  considerably  narrowed,  forming 
what  is  termed  the  aortic  isthmus,  while  immediately  beyond  the  ductus  arte- 
riosus the  vessel  presents  a  fusiform  dilatation  which  His  has  named  the  aortic 
spindle — the  point  of  junction  of  the  two  parts  being  marked  in  the  concavity 
of  the  arch  by  an  indentation  or  angle.  These  conditions  persist,  to  some  extent, 
in  the  adult,  where  His  found  that  the  average  diameter  of  the  spindle  exceeded 
that  of  the  isthmus  by  3  mm.  (about  one-eighth  of  an  inch). 

Relations. — Its  anterior  surface  is  covered  by  the  pleurae  and  lungs  and  the 
remains  of  the  thymus  gland,  and  crossed  toward  the  left  side  by  the  left  pneumo- 
gastric  and  phrenic  nerves  and  superficial  cardiac  branches  of  the  left  sympathetic 
and  vagus,  and  by  the  left  superior  intercostal  vein.  Its  posterior  surface  lies  on 
the  trachea,  just  above  its  bifurcation,  on  the  great,  or  deep,  cardiac  plexus,  the 
oesophagus,  thoracic  duct,  and  left  recurrent  laryngeal  nerve.  Its  upper  border  is 
in  relation  with  the  left  innominate  vein,  and  from  its  upper  part  are  given  off  the 
innominate,  left  common  carotid  and  left  subclavian  arteries.  Its  lower  border  is 
in  relation  with  the  bifurcation  of  the  pulmonary  artery,  the  remains  of  the  ductus 
arteriosus,  which  is  connected  with  the  left  division  of  that  vessel,  and  the  super- 
ficial cardiac  plexus  ;  the  left  recurrent  laryngeal  nerve  winds  round  it  from 
before  backward,  whilst  the  left  bronchus  passes  below  it. 


Plan  of  the  Relations  of  the  Arch  of  the  Aorta. 

Above. 
Left  innominate  vein. 
Innominate  artery. 
Left  carotid. 
Left  subclavian. 


In  From. 
Pleurae  and  lungs. 
Remains  of  thymus  gland. 
Left  pneumogastric  nerve. 
Left  phrenic  nerve. 
Superficial  cardiac  nerves. 
Left  superior  intercostal  vein. 


Behind. 
Trachea. 

Deep  cardiac  plexus. 
(Esophagus. 
Thoracic  duct. 
Left  recurrent  nerve. 


Belotv. 


Bifurcation  of  pulmonary  artery. 
Remains  of  ductus  arteriosus. 
Superficial  cardiac  plexus. 
Left  recurrent  nerve. 
Left  bronchus. 

1  According  to  Dr.  Samuel  West,  there  is  a  very  free  and  complete  anastomosis  between  the  two 
coronary  arteries  (Lancet,  June  2,  1883,  p.  945).  This,  however,  is  not  the  view  generally  held  by 
anatomists,  for,  with  the  exception  of  the  anastomosis  mentioned  above  in  the  auriculo-ventricular  and 
interventricular  grooves,  it  is  believed  that  the  two  arteries  only  communicate  by  very  small  vessels 
in  the  substance  of  the  heart. 


/ 


THE   ARCH   OF    THE   AORTA. 


479 


Peculiarities. — The  height  to  which  the  aorta  rises  in  the  chest  is  usually  about  an  inch 
below  the  upper  border  of  the  sternum ;  but  it  may  ascend  nearly  to  the  top  of  that  bone. 
Occasionally  it  is  found  an  inch  and  a  half,  more  rarely  two  or  even  three  inches,  below  this 
point. 

In  Direction. — Sometimes  the  aorta  arches  over  the  root  of  the  right  instead  of  the  left 
lung,  as  in  birds,  and  passes  down  on  the  right  side  of  the  spine.  In  such  cases  all  of  the 
viscera  of  the  thoracic  and  abdominal  cavities  are  transposed.  Less  frequently,  the  aorta,  after 
arching  over  the  root  of  the  right  lung,  is  directed  to  its  usual  position  on  the  left  side  of  the 
spine,  this  peculiarity  not  being  accompanied  by  any  transposition  of  the  viscera. 

In  Conformation. — The  aorta  occasionally  divides,  as  in  some  quadrupeds,  into  an  ascend- 
ing and  descending  trunk,  the  former  of  which  is  directed  vertically  upward,  and  subdivides 
into  three  branches,  to  supply  the  head  and  upper  extremities.  Sometimes  the  aorta  subdivides 
soon  after  its  origin  into  two  branches,  which  soon  reunite.  In  one  of  these  cases  the  oesophagus 
and  trachea  were  found  to  pass  through  the  interval  left  by  their  division  ;  this  is  the  normal 
condition  of  the  vessel  in  the  reptilia. 

Surgical  Anatomy. — Of  all  the  vessels  of  the  arterial  system,  the  aorta,  and  more  espe- 
cially its  arch,  is  most  frequently  the  seat  of  disease  ;  hence  it  is  important  to  consider  some  of 
the  consequences  that  may  ensue  from  aneurism  of  this  part. 

It  will  be  remembered  that  the  ascending  aorta  is  contained  in  the  pericardium,  just  behind 
the  sternum,  being  crossed  at  its  commencement  by  the  pulmonary  artery  and  right  auricular 
appendix,  and  having  the  right  pulmonary  artery  behind,  the  vena  cava  on  the  right  side,  and 
the  pulmonary  artery  and  left  auricle  on  the  left  side. 

Aneurism  of  the  ascending  aorta,  in  the  situation  of  the  sinuses  of  Valsalva,  in  the  great 
majority  of  cases,  affects  the  anterior  sinus  ;  this  is  mainly  owing  to  the  fact  that  the  regurgita- 


Le.ft  subclavian 
artery. 

Left  common 
carotid  artery. 


Bight  pulmonary 
vein. 

Eight  pulmonary 
vein.  /. 


Vena  asygos 
major. 


Inferior  thyroid 
rein. 

Right  innomi- 
nate vein. 

Right  subclavian  artery.     Right  common   carotid  artery. 

Fig.  282.— Relation  of  great  vessels  at  base  of  heart,  seen  from  above.    (From  a  preparation  in  the  Museum 
of  the  Eoyal  College  of  Surgeons  of  England.) 


tion  of  blood  upon  the  sinuses  takes  place  chiefly  on  the  anterior  aspect  of  the  vessel.  As  the 
aneurismal  sac  enlarges  it  may  compress  any  or  all  of  the  structures  in  immediate  proximity  with 
it,  but  chiefly  projects  toward  the  right  anterior  side,  and,  consequently,  interferes  mainly  with 
those  structures  that  have  a  corresponding  relation  with  the  vessel.  In  the  majority  of  cases  it 
bursts  into  the  cavity  of  the  pericardium,  the  patient  suddenly  drops  down  dead,  and,  upon  a 
post-mortem  examination,  the  pericardial  sac  is  found  full  of  blood;  or  it  may  compress  the 
right  auricle,  or  the  pulmonary  artery  and  adjoining  part  of  the  right  ventricle,  and  open  into 
one  or  the  other  of  these  parts,  or  may  press  upon  the  superior  vena  cava. 

Aneurism  of  the  ascending  aorta,  originating  above  the  sinuses,  most  frequently  implicates 
the  right  anterior  wall  of  the  vessel,  where,  as  has  been  explained,  there  exists  a  normal  dilata- 
tion, the  great  sinus  of  the  aorta;  this  is  probably  mainly  owing  to  the  blood  being  impelled 
against  this  part,  The  direction  of  the  aneurism  is  also  chiefly  toward  the  right  of  the  median 
line.  If  it  attains  a  large  size  and  projects  forward,  it  may  absorb  the  sternum  and  the  cartilages 
of  the  ribs,  usually  on  the  right  side,  and  appear  as  a  pulsating  tumor  on  the  front  of  the  chest, 
just  below  the  manubrium  ;  or  it  may  burst  into  the  pericardium,  or  may  compress  or  open  into 
the  right  lung,  the  trachea,  bronchi,  or  oesophagus. 


480  THE  BLOOD-VASCULAR   SYSTEM. 

Kegarding  the  transverse  aorta,  the  student  is  reminded  that  the  vessel  lies  on  the  trachea, 
.  the  oesophagus,  and  thoracic  duct ;  that  the  recurrent  laryngeal  nerve  winds  around  it ;  and  that 
from  its  upper  part  are  given  off  three  large  trunks,  which  supply  the  head,  neck,  and  upper 
extremities.  Now,  an  aneurismal  tumor,  taking  origin  from  the  posterior  part  of  the  vessel, 
its  most  usual  site,  may  press  upon  the  trachea,  impede  the  breathing,  or  produce  cough, 
haemoptysis,  or  stridulous  breathing,  or  it  may  ultimately  burst  into  that  tube,  producing  fatal 
hemorrhage.  Again,  its  pressure  on  the  laryngeal  nerves  may  give  rise  to  sj'mptoms  which 
so  accurately  resemble  those  of  laryngitis  that  the  operation  of  tracheotomy  has  in  some  cases 
been  resorted  to,  from  the  supposition  that  disease  existed  in  the  larynx ;  or  it  may  press  upon 
the  thoracic  duct  and  destroy  life  by  inanition  ;  or  it  ma}'  involve  the  oesophagus,  producing 
dysphagia;  or  may  burst  into  the  oesophagus,  when  fatal  haemorrhage  will  occur.  Again,  the 
innominate  artery,  or  the  subclavian,  or  left  carotid,  may  be  so  obstructed  by  clots  as  to  produce 
a  weakness,  or  even  a  disappearance,  of  the  pulse  in  one  or  the  other  wrist  or  in  the  left  tem- 
poral artery ;  or  the  tumor  may  present  itself  at  or  above  the  manubrium,  generally  either  in  the 
median  line  or  to  the  right  of  the  sternum,  and  may  simulate  an  aneurism  of  one  of  the  arteries 
of  the  neck. 

Branches  of  the  Arch  of  the  Aorta  (Figs.  280,  281). 

The  branches  given  off  from  the  arch  of  the  aorta  are  three  in  number  :  the 
innominate  artery,  the  left  common  carotid,  and  the  left  subclavian. 

Peculiarities.— Position  of  the  Branches. — The  branches,  instead  of  arising  from  the  high- 
est part  of  the  arch  (their  usual  position),  may  be  moved  more  to  the  right,  arising  from  the 
commencement  of  the  transverse  or  upper  part  of  the  ascending  portion  :  or  the  distance  from 
one  another  at  their  origin  may  be  increased  or  diminished,  the  most  frequent  change  in  this 
respect  being  the  approximation  of  the  left  carotid  toward  the  innominate  artery. 

The  Number  of  the  primary  branches  may  be  reduced  to  a  single  vessel,  or  more  commonly 
two :  the  left  carotid  arising  from  the  innominate  artery,  or  (more  rarely)  the  carotid  and  sub- 
clavian arteries  of  the  left  side  arising  from  a  left  innominate  artery.  But  the  number  may  be 
increased  to  four,  from  the  right  carotid  and  subclavian  arteries  arising  directly  from  the  aorta, 
the  innominate  being  absent.  In  most  of  these  latter  cases  the  right  subclavian  has  been  found 
to  arise  from  the  left  end  of  the  arch;  in  other  cases  it  was  the  second  or  third  branch  given  off 
instead  of  the  first.  Another  common  form  in  which  there  are  four  primary  branches  is  that 
in  which  the  left  vertebral  artery  arises  from  the  a*eh  of  the  aorta  between  the  left  carotid  and 
subclavian  arteries.  Lastly,  the  number  of  trunks  from  the  arch  may  be  increased  to  five 
or  six;  in  these  instances,  the  external  and  internal  carotids  arise  separately  from  the  arch,  the 
common  carotid  being  absent  on  one  or  both  sides.  In  some  cases,  where  six  branches  have 
been  found,  it  has  been  due  to  a  separate  origin  of  the  vertebral  on  both  sides. 

Number  Usual,  Arrangement  Different. — When  the  aorta  arches  over  to  the  right  side, 
the  three  branches  have  an  arrangement  the  reverse  of  what  is  usual,  the  innominate  supplying 
the  left  side,  and  the  carotid  and  subclavian  (which  arise  separately)  the  right  side.  In  other 
cases,  where  the  aorta  takes  its  usual  course,  the  two  carotids  may  be  joined  in  a  common  trunk, 
and  the  subclavians  arise  separately  from  the  arch,  the  right  subclavian  generally  arising  from 
the  left  end  of  the  arch.1 

In  some  instances  other  arteries  are  found  to  arise  from  the  arch  of  the  aorta.  Of  these 
the  most  common  are  the  bronchial,  one  or  both,  and  the  thyroidea  ima ;  but  the  internal 
mammary  and  the  inferior  thyroid  have  been  seen  to  arise  from  this  vessel. 

INNOMINATE  ARTERY. 

The  innominate  artery  (brachio-cephalic)  is  the  largest;  branch  given  off  from 
the  arch  of  the  aorta.  It  arises,  on  a  level  with  the  upper  border  of  the  second 
right  costal  cartilage,  from  the  commencement  of  the  arch  of  the  aorta  in  front 
of  the  left  Carotid,  and,  ascending  obliquely  to  the  upper  border  of  the  right 
sterno-clavicular  articulation,  divides  into  the  right  common  carotid  and  right 
subclavian  arteries.  This  vessel  varies  from  an  inch  and  a  half  to  two  inches  in 
length. 

Relations. — In  front,  it  is  separated  from  the  first  piece  of  the  sternum  by  the 
Sterno-hyoid  and  Sterno-thyroid  muscles,  the  remains  of  the  thymus  gland,  the 
left  innominate  and  right  inferior  thyroid  veins  which  cross  its  root,  and  some- 
times the  inferior  cervical  cardiac  branch  of  the  right  pneumogastric.  Behind,  it 
lies  upon  the  trachea,  which  it  crosses  obliquely.  On  the  right  side  is  the  right 
innominate  vein,  right  pneumogastric  nerve,  and  the  pleura ;  and  on  the  left  side, 

1  The  anomalies  of  the  aorta  and  its  branches  are  minutely  described  by  Krause  in  Henle's 
Anatomy  (Brunswick,  1868),  vol.  iii.,  p.  203  et  seq. 


THE    INNOMINATE   ARTERY.  481 

he  remains  of  the  thymus  gland,  the  origin  of  the  left  carotid  artery,  the  left 
inferior  thyroid  vein,  and  the  trachea. 

Branches. — The  innominate  usually  gives  off  no  branches,  hut  occasionally  a 
mall  branch,  the  thyroidea  ima,  is  given  off  from  this  vessel.  It  also  sometimes 
;ives  off  a  thymic  or  bronchial  branch.  The  Thyroidea  ima  ascends  in  front  of 
he  trachea  to  the  lower  part  of  the -thyroid  body,  which  it  supplies.  It  varies 
;reatly  in  size,  and  appears  to  compensate  for  deficiency  or  absence  of  one  of  the 
ther  thyroid  vessels.  It  occasionally  is  found  to  arise  from  the  right  common 
arotid  or  from  the  aorta,  the  subclavian,   or  internal  mammary  vessels. 

Plan  of  the  Relations  of  the  Innominate  Artery. 

In  front. 
Sternum. 

Sterno-hyoid  and  Sternothyroid  muscles. 
Remains  of  thymus  gland. 
Left  innominate  and  right  inferior  thyroid  veins. 
Inferior  cervical  cardiac  branch  from  right  pneumogastric  nerve, 

Right  side.  /  \  Left  side. 

Right  innominate  vein.  f    innominate    \  Remains  of  thymus. 

Right  pneumogastric  nerve.  \      Artery-      J  Left  carotid. 

Pleura.  V  /  Left  inferior  thyroid  vein. 

\^.     ^  Trachea. 

Behind. 
Trachea. 

Peculiarities  in  Point  of  Division. — When  the  bifurcation  of  the  innominate  artery  varies 
rom  the  point  above  mentioned,  it  sometimes  ascends  a  considerable  distance  above  the  sternal 
nd  of  the  clavicle  ;  less  frequently  it  divides  below  it.  In  the  former  class  of  cases  its  length 
lay  exceed  two  inches,  and  in  the  latter  be  reduced  to  an  inch  or  less.  These  are  points  of  con- 
iderable  interest  for  the  surgeon  to  remember  in  connection  with  the  operation  of  tying  this  vessel. 

Position. — When  the  aorta  arches  over  to  the  right  side,  the  innominate  is  directed  to  the 
ift  side  of  the  neck  instead  of  the  right. 

Collateral  Circulation. — Allan  Burns  demonstrated,  on  the  dead  subject,  the  possibility  of 
tie  establishment  of  the  collateral  circulation  after  ligature  of  the  innominate  artery,  by  tying 
nd  dividing  that  artery,  after  which,  he  says,  "Even  coarse  injection,  impelled  into  the  aorta, 
assing  freely  by  the  anastomosing  branches  into  the  arteries  of  the  right  arm,  filling  them  and 
11  the  vessels  of  the  head  completely"  {Surgical  Anatomy  of  the  Head  and  Neck,  p.  62). 
'he  branches  by  which  this  circulation  would  be  carried  on  are  very  numerous ;  thus,  all  the 
ommunications  across  the  middle  line  between  the  branches  of  the  carotid  arteries  of  opposite 
ides  would  be  available  for  the  supply  of  blood  to  the  right  side  of  the  head  and  neck ;  while 
he  anastomosis  between  the  superior  intercostal  of  the  subclavian  and  the  first  aortic  intercostal 
see  infra  on  the  collateral  circulation  after  obliteration  of  the  thoracic  aorta)  would  bring  the 
lood,  by  a  free  and  direct  course,  into  the  right  subclavian :  the  numerous  connections,  also, 
letween  the  intercostal  arteries  and  the  branches  of  the  axillary  and  internal  mammary  arteries 
rould,  doubtless,  assist  in  the  supply  of  blood  to  the  right  arm,  while  the  deep  epigastric,  from 
he  external  iliac,  would,  by  means  of  its  anastomosis  with  the  internal  mammary,  compensate 
or  any  deficiency  in  the  vascularity  of  the  wall  of  the  chest. 

Surgical  Anatomy. — Although  the  operation  of  tying  the  innominate  artery  has  been 
lerformed  by  several  surgeons  for  aneurism  of  the  right  subclavian  extending  inward  as  far  as 
he  Scalenus,  in  only  five  instances,  according  to  Mr.  Jacobson,  has  the  patient  survived. 
Pott's  patient,  however,  on  whom  the  operation  was  first  performed,  lived  nearly  four  weeks, 
nd  Graefe's  more  than  two  months.  The  chief  danger  of  the  operation  appears  to  be  the  fre- 
luency  of  secondary  hemorrhage  ;  but  in  the  present  day,  with  the  practice  of  aseptic  surgery 
-nd  our  greater  knowledge  of  the  use  of  the  ligature,  more  favorable  results  may  be  anticipated. 
)ther  causes  of  death  after  operation  are  pleurisy,  pericarditis,  and  suppurative  cellulitis.  The 
nain  obstacles  to  the  operation  are.  as  the  student  will  perceive  from  his  dissection  of  this 
ressel,  the  deep  situation  of  the  artery  behind  and  beneath  the  sternum,  and  the  number  of 
mportant  structures  which  surround  it  in  every  part. 

In  order  to  apply  a  ligature  to  this  vessel,  the  patient  is  to  be  placed  upon  his  back,  with  the 
borax  slightly  raised,  the  head  bent  a  little  backward,  and  the  shoulder  on  the  side  of  the  aneu- 
'ism  strongly  depressed,  so  as  to  draw  out  the  artery  from  behind  the  sternum  into  the  neck, 
in  incision  three  or  more  inches  long  is  then  made  along  the  anterior  border  of  the  Sterno-mas- 
;oid  muscle,  terminating  at  the  sternal  end  of  the  clavicle.  From  this  point  a  second  incision  is 
carried  about  the  same  length  along  the  upper  border  of  the  clavicle.  The  skin  is  then  dissected 
back,  and  the  Platysma  divided  on  a  director :  the  sternal  end  of  the  Sterno-mastoid  is  now 
brought  into  view,  and,  a  director  being  passed  beneath  it  and  close  to  its  under  surface,  so  as  to 
avoid  any  small  vessels,  it  is  to  be  divided  ;  in  like  manner  the  clavicular  origin  is  to  be  divided 
31 

.  I 


482 


THE  BLOOD-VASCULAR    SYSTEM. 


throughout  the  whole  or  greater  part  of  its  attachment.  By  pressing  aside^  any  loose  cellular 
tissue  or  vessels  that  may  now  appear  the  Sterno-hyoid  and  Sterno-thyroid  muscles  will  be 
exposed,  and  must  be  divided,  a  director  being  previously  passed  beneath  them.  The  inferior 
thyroid  veins  may  come  into  view,  and  must  be  carefully  drawn,  either  upward  or  downward,  by 
means  of  a  blunt  hook,  or  tied  with  double  ligatures  and  divided.  After  tearing  through  a 
strong  fibro-cellular  lamina,  the  right  carotid  is  brought  into  view,  and,  being  traced  downward, 
the  arteria  innominata  is  arrived  at.  The  left  innominate  vein  should  now  be  depressed ;  the 
right  innominate  vein,  the  internal  jugular  vein,  and  the  pneumogastric  nerve  drawn  to  the  right 
side  ;  and  a  curved  aneurism  needle  may  then  be  passed  around  the  vessel,  close  to  its  surface, 
and  in  a  direction  from  below  upward  and  inward,  care  being  taken  to  avoid  the  right  pleural 
sac.  the  trachea,  and  cardiac  nerves.  The  ligature  should  be  applied  to  the  artery  as  high  as 
•possible,  in  order  to  allow  room  between  it  and  the  aorta  for  the  formation  of  the  coagulum. 
The  importance  of  avoiding  the  thyroid  plexus  of  veins  during  the  primary  steps  of  the  opera- 
tion, and  the  pleural  sac  whilst  including  the  vessel  in  the  ligature,  should  be  most  carefully  borne 
in  mind.  After  the  artery  has  been  secured,  the  common  carotid  should  be  tied  about  half  an 
inch  above  its  origin,  and  also  the  thyroidea  ima  if  the  vessel  is  of  any  size.  The  several 
muscles  are  united  by  buried  sutures. 

ARTERIES  OF  THE  HEAD  AND  NECK. 

The  artery  which  supplies  the  head  and  neck  is  the  Common  Carotid :  it  ascends 
in  the  neck  and  divides  into  two  branches :  the  External  Carotid,  supplying  the 
superficial  parts  of  the  head  and  face  and  the  greater  part  of  the  neck  ;  and  the 
Internal  Carotid,  supplying  to  a  great  extent  the  parts  within  the  cranial  cavity. 


The  Common  Carotid  Arteries. 

The  common  carotid  arteries,  although  occupying  a  nearly  similar  position  in 
the  neck,  differ  in  position,  and,  consequently,  in  their  relation  at  their  origin. 
The  right  carotid  arises  from  the  innominate  artery,  behind  the  right  sterno- 
clavicular articulation  ;  the  left  from  the  highest  part  of  the  arch  of  the  aorta. 
The  left  carotid  is,  consequently,  longer,  and  at  its  origin  is  contained  within  the 
thorax.  The  course  and  relations  of  that  portion  of  the  left  carotid  which  inter- 
venes between  the  arch  of  the  aorta  and  the  left  sterno-clavicular  articulation  will 
first  be  described  (see  Fig.  280). 

The  left  carotid  within  the  thorax  ascends  obliquely  outward  from  the  arch  of 
the  aorta  to  the  root  of  the  neck.  In  front,  it  is  separated  from  the  first  piece  of 
the  sternum  by  the  Sterno-hyoid  and  Sterno-thyroid  muscles,  the  left  innominate 
vein,  and  the  remains  of  the  thymus  gland ;  behind,  it  lies  on  the  trachea,  oesoph- 
agus, and  thoracic  duct.  Internally,  it  is  in  relation  with  the  innominate 
artery,  inferior  thyroid  veins  and  remains  of  thymus  gland ;  externally,  with  the 
left  pneumogastric  nerve,  left  pleura,  and  lung.  The  left  subclavian  artery  is 
posterior  and  slightly  external  to  it. 

Plan  of  the  Relations  of  the  Left  Common  Carotid. 
Thoracic  Portion. 

In  front. 
Sternum. 

Sterno-hyoid  and  Sterno-thyroid  muscles. 
Left  innominate  vein. 
Remains  of  thymus  gland. 


Internally. 

Innominate  artery. 
Inferior  thyroid  veins. 
Remains  of  thymus  gland. 


Externally. 

Left  pneumogastric  nerve. 
Left  pleura  and  lung. 
Left  subclavian  artery. 


Behind. 

Trachea. 

(Esophagus. 

Thoracic  duct. 

Left  subclavian  artery. 


THE    COMMON   CAROTID    ARTERIES. 


483 


In  the  neck  the  two  common  carotids  resemble  each  other  so  closely  that  one 
lescription  will  apply  to  both.  Each  vessel  passes  obliquely  upward  from  behind 
She  sterno-clavicular  articulation  to  a  level  with  the  upper  border  of  the  'thyroid 
cartilage,  opposite  the  fourth  cervical  vertebra,  where  it  divides  into  the  external 


Fig.  283.— Surgical  anatomy  of  the  arteries  of  the  neck,  showing  the  carotid  and  subclavian  arteries. 

and  internal  carotid;  these  names  being  derived  from  the  distribution  of  the 
arteries  to  the  external  parts  of  the  head  and  face  and  to  the  internal  parts  of  the 
cranium  and  orbit  respectively. 

At  the  lower  part  of  the  neck  the  two  common  carotid  arteries  are  separated 
from  each  other  by  a  small  interval,  which  contains  the  trachea;  but  at  the  upper 
part,  the  thyroid  body,  the  larynx  and  pharynx  project  forward  between  the 
two  vessels,  and  give  the  appearance  of  their  being  placed  farther  back  in  this 
situation.     The  common  carotid  artery  i  i  aed  in  a  sheath  derived  from  the 

deep  cervical  fascia,  which  also  encloses  the  internal  jugular  vein  and  pneumo- 
gastric  nerve,  the  vein  lying  on  the  oute.  sid  -  of  t  be  artery,  and  the  nerve  between 


484  THE   BLOOD-  VASCULAR   SJSTE1 

the  artery  and  vein,  on  a  plane  posterior  to  both.  On  opening  the  sheath  these 
three  structures  are  seen  to  be  separated  from  one  another,  each  being  enclosed  in 
a  separate  fibrous  investment. 

Relations. — At  the  lower  part  of  the  neck  the  common  carotid  artery  is  very 
deeply  seated,  being  covered  by  the  integument,  superficial  fascia,  Platysma,  and 
deep  cervical  fascia,  the  Sterno-mastoid,  Sterno-hyoid,  and  Sterno-thyroid  muscles, 
and  by  the  Omo-hyoid,  opposite  the  cricoid  cartilage  ;  but  in  the  upper  part  of  its 
course,  near  its  termination,  it  is  more  superficial,  being  covered  merely  by  the 
integument,  the  superficial  fascia,  Platysma,  deep  cervical  fascia,  and  inner  margin 
of  the  Sterno-mastoid,  and,  when  the  latter  is  drawn  backward,  it  is  seen  to  be 
contained  in  a  triangular  space,  bounded  behind  by  the  Sterno-mastoid,  above  by 
the  posterior  belly  of  the  Digastric,  and  below  by  the  anterior  belly  of  the  Omo- 
hyoid. This  part  of  the  artery  is  crossed  obliquely,  from  within  outward,  by  the 
sterno-rntostoid  artery;  it  is  crossed  also  by  the  superior  and  middle  thyroid  veins, 
which  terminate  in  the  internal  jugular;  and,  descending  on  its  sheath  in  front,  is 
seen  the  descendens  hypoglossi  nerve,  this  filament  being  joined  by  one  or  two 
branches  from  the  cervical  nerves,  which  cross  the  vessel  from  without  inward. 
Sometimes  the  descendens  hypoglossi  is  contained  within  the  sheath.  The  middle 
thyroid  vein  crosses  the  artery  about  its  middle,  and  the  anterior  jugular  vein  below; 
the  latter,  however,  is  separated  from  the  artery  by  the  Sterno-hyoid  and  Sterno- 
thyroid muscles.  Behind,  the  artery  is  separated  from  the  transverse  processes  of 
the  vertebrae  by  the  Longus  colli  and  Rectus  capitis  anticus  major,  the  sympathetic 
nerve  being  interposed  between  it  and  the  muscles.  The  recurrent  laryngeal  nerve 
and  inferior  thyroid  artery  cross  behind  the  vessel  at  its  lower  part.  Internally,  it 
is  in  relation  with  the  trachea  and  thyroid  gland,  the  later  overlapping  it,  the  inferior 
thyroid  artery  and  recurrent  laryngeal  nerve  being  interposed  :  higher  up,  with  the 
larynx  and  pharynx.  On  its  outer  side  are  placed  the  internal  jugular  vein  and 
pneumogastric  nerve. 

At  thf  lower  part  of  the  neck  the  internal  jugular  vein  on  the  right  side  diverges 
from  the  artery.tbut  on  the  left  side  it  approaches  it,  and  often  overlaps  its  lower 
part.  This  isv*an  important  fact  to  bear  in  mind  during  the  performance  of  any 
operation  on  the  lower  part  of  the  left  common  carotid  artery. 

Plan  of  the  Relations  of  the  Common  Carotid  Artery. 

i  In  front. 

Integument  and  superficial  fascia.  Omo-hyoid. 

Deep  ceHncal  fascia.  Des^jdens  and  Communicans  hypoglossi 
Platysm^    '          .-■"  IW^es. 

Stfe'OTio-nJasljbid.    •  Sterno-mastoid  artery. 

Sterfai- hyoifl.  Superior  and  middle  thyroid  veins. 

Stenw-thyfiid.  Anterior  jugular  vein. 

If*  Ttiify 

ExteniaMy:  Internally. 

Internal  jugular  vein.  /^       ""X  Trachea. 

Pneumogastric  nerve.  /  \  Thyroid  gland. 

Recurrent  laryngeal  nerve. 

Inferior  thyroid  artery. 

Larynx. 

Pharynx. 
Behind. 
Longus  colli.  Sympathetic  nerve. 

Rectus  capitis  anticus  major.  Inferior  thyroid  artery. 

Recurrent  laryngeal  nerve. 

Peculiarities  as  to  Origin.— The  right  common  carotid  may  arise  above  or  below  the  upper 
border  of  the  sterno-clavicular  articulation.  This  variation  occurs  in  one  out  of  about  eight 
cases  and  a  half,  and  the  origin  is  more  frequently  below  than  above ;  or  the  artery  may  arise 
as  a  separate  branch  from  the  arch  of  the  aorta  or  in  conjunction  with  the  left  carotid.  The 
left  common  carotid  varies  more  frequently  in  its  origin  than  the  right.  In  the  majority  of 
abnormal  cases  it  arises  with  the  innominate  artery,  or,  if  the  innominate  artery  is  absent,  the  j 
two  carotids  arise  usually  by  a  single  trunk.  It  rarely  joins  with  the  left  subclavian,  except  in 
cases  of  transposition  of  the  arch. 


THE    COMMON   CAROTID    ARTERIES.  485 

Peculiarities  as  to  Point  of  Division.— The  most  important  peculiarities  of  this  vessel,  in 
a  surgical  point  of  view,  relate  to  its  place  of  division  in  the  neck.  In  the  majority  of  abnormal 
cases  this  occurs  higher  than  usual,  the  artery  dividing  into  two  branches  opposite  the  hyoid 
bone,  or  even  higher ;  more  rarely  it  occurs  below,  opposite  the  middle  of  the  larynx  or  the 
lower  border  of  the  cricoid  cartilage ;  and  one  case  is  related  by  Morgagni  where  the  common 
carotid,  only  an  inch  and  a  half  in  length,  divided  at  the  root  of  the  neck.  Very  rarely  the 
common  carotid  ascends  in  the  neck  without  any  subdivision,  the  internal  carotid  being  wanting ; 
and  in  a  few  cases  the  common  carotid  has  been  found  to  be  absent,  the  external  and  internal 
carotids  arising  directly  from  the  arch  of  the  aorta.  This  peculiarity  existed  on  both  sides  in 
some  instances,  on  one  side  in  others. 

Occasional  Branches. — The  common  carotid  usually  gives  off  no  branch  previous  to  its 
bifurcation ;  but  it  occasionally  gives  origin  to  the  superior  thyroid  or  its  laryngeal  branch,  the 
ascending  pharyngeal,  the  inferior  thyroid,  or,  more  rarely,  the  vertebral  artery. 

Surface  Marking. — The  carotid  arteries  are  covered  throughout  their  entire  extent  by  the 
Sterno-mastoid  muscle,  but  their  course  does  not  correspond  to  the  anterior  border  of  the  muscle, 
which  passes  in  a  somewhat  curved  direction  from  the  mastoid  process  to  the  sterno-clavicular 
joint.  The  course  of  the  artery  is  indicated  more  exactly  by  a  line  drawn  from  the  sternal  end 
of  the  clavicle  below,  to  a  point  midway  between  the  angle  of  the  jaw  and  the  mastoid  process 
above.  That  portion  of  the  line  below  the  level  of  the  upper  border  of  the  thyroid  cartilage 
would  represent  the  course  of  the  vessel. 

Surgical  Anatomy. — The  operation  of  tying  the  common  carotid  artery  may  be  necessary 
in  a  case  of  wound  of  that  vessel  or  its  branches,  in  aneurism,  or  in  a  case  of  pulsating  tumor  of 
the  orbit  or  skull.  If  the  wound  involves  the  trunk  of  the  common  carotid,  it  will  be  necessary 
to  tie  the  artery  above  and  below  the  wounded  part.  But  in  cases  of  aneurism,  or  where  one  of 
the  branches  of  the  common  carotid  is  wounded  in  an  inaccessible  situation,  it  may  be  judged 
necessary  to  tie  the  trunk.  In  such  cases  the  whole  of  the  artery  is  accessible,  and  any  part  may 
be  tied  except  close  to  either  end.  When  the  case  is  such  as  to  allow  of  a  choice  being  made, 
the  lower  part  of  the  carotid  should  never  be  selected  as  the  spot  upon  which  to  place  a  ligature, 
for  not  only  is  the  artery  in  this  situation  placed  very  deeply  in  the  neck,  but  it  is  covered 
by  three  layers  of  muscles,  and,  on  the  left  side,  the  internal  jugular  vein,  in  the  great  majority 
of  cases,  passes  obliquely  in  front  of  it.  Neither  should  the  upper  end  be  selected,  for  here  the 
superior  thyroid  vein  and  its  tributaries  would  give  rise  to  very  considerable  difficulty  in  the 
application  of  a  ligature.  The  point  most  favorable  for  the  operation  is  that  part  of  the  vessel 
which  is  at  the  level  of  the  cricoid  cartilage.  It  occasionally  happens  that  the  carotid 
artery  bifurcates  below  its  usual  position :  if  the  artery  be  exposed  at  its  point  of  bifurcation, 
both  divisions  of  the  vessel  should  be  tied  near  their  origin,  in  preference  to  tying  the  trunk 
of  the  artery  near  its  termination  ;  and  if,  in  consequence  of  the  entire  absence  of  the  common 
carotid  or  from  its  early  division,  two  arteries,  the  external  and  internal  carotids,  are  met  with, 
the  ligature  should  be  placed  on  that  vessel  which  is  found  on  compression  to  be  connected  with 
the  disease. 

In  this  operation  the  direction  of  the  vessel  and  .the  inner  margin  of  the  Sterno-mastoid  are 
the  chief  guides  to  its  performance.  The  patient  should  be  placed  on  his  back  with  the  head 
thrown  back  and  turned  slightly  to  the  opposite  side :  an  incision  is  to  be  made,  three  inches 
long,  in  the  direction  of  the  anterior  border  of  the  Sterno-mastoid,  so  that  the  centre  corresponds 
to  the  level  of  the  cricoid  cartilage :  after  dividing  the  integument,  superficial  fascia,  and 
Platysma,  the  deep  fascia  must  be  cut  through  on  a  director,  so  as  to  avoid  wounding 
numerous  small  veins  that  are  usually  found  beneath.  The  head  may  now  be  brought  forward 
so  as  to  relax  the  parts  somewhat,  and  the  margins  of  the  wound  held  asunder  by  retractors. 
The  descendens  hypoglossi  nerve  may  now  be  exposed,  and  must  be  avoided,  and,  the  sheath  of 
the  vessel  having  been  raised  by  forceps,  is  to  be  opened  to  a  small  extent  over  the  artery  at  its 
inner  side.  The  internal  jugular  vein  may  present  itself  alternately  distended  and  relaxed  ;  this 
should  be  compressed  both  above  and  below,  and  drawn  outward,  in  order  to  facilitate  the  opera- 
tion. The  aneurism  needle  is  passed  from  the  outside,  care  being  taken  to  keep  the  needle  in 
close  contact  with  the  artery,  and  thus  avoid  the  risk  of  injuring  the  internal  jugidar  vein  or 
including  the  vagus  nerve.  Before  the  ligature  is  tied  it  should  be  ascertained  that  nothing  but 
the  artery  is  included  in  it. 

Ligature  of  the  Common  Carotid  at  the  Lower  Part  of  the  Neck.— This  operation  is 
sometimes  required  in  cases  of  aneurism  of  the  upper  part  of  the  carotid,  especially  if  the  sac  is 
of  large  size.  It  is  best  performed  by  dividing  the  sternal  origin  of  the  Sterno-mastoid  muscle, 
but  may  be  done  in  some  cases,  if  the  aneurism  is  not  of  very  large  size,  by  an  incision 
along  the  anterior  border  of  the  Sterno-mastoid,  extending  down  to  the  sterno-clavicular  articula- 
tion^ and  by  then  retracting  the  muscle.  The  easiest  and  best  plan,  however,  is  to  make  an 
incision  two  or  three  inches  long  down  the  lower  part  of  the  anterior  border  of  the  Sterno- 
niastoid  muscle  to  the  sterno-clavicular  joint,  and  a  second  incision,  starting  from  the  termination 
of  the  first,  along  the  upper  border  of  the  clavicle  for  about  two  u  his  incision  is  made 

through  the  superficial  and  deep  fascia,  and  the  sternal  origin  oft]  exposed.     This  is  to 

be  divided  on  a  director,  and  turned  up,  with  the  superficu         uotures   as  a  triangular  flap. 
Some  loose  connective  tissue  is  to  be  divided  or  torn  thro  cr  border  of  the 

Sterno-hyoid  muscle  exposed.     In  doing  this  care  must  b  i  wound  the  anterior 

jugular  vein,  which  crosses  the  muscle  to  reach  the  ext  r  subclavian  vein.     The 

Sterno-hyoid,  and  with  it  the  Sterno-thyroid.  are  to  be  drawn  inward  by  means  of  a  retractor, 


486  THE   BLOOD-VASCULAR    SYSTEM, 

and  the  slieath  of  the  vessel  is  exposed.  This  must  be  opened  with  great  care  on  its  inner 
or  tracheal  side,  so  as  to  avoid  the  internal  jugular  vein.  This  is  especially  necessary  on 
the  left  side,  where  the  artery  is  commonly  overlapped  by  the  vein.  On  the  right  side  there  is 
usually  an  interval  between  the  artery  and  the  vein,  and  not  the  same  risk  of  wounding  the 
latter. 

The  common  carotid  artery,  being  a  long  vessel  without  any  branches,  is  particularly  suitable 
for  the  performance  of  Brasdor's  operation  for  the  cure  of  an  aneurism  of  the  lower  part  of  the 
vessel.  Brasdor's  procedure  consists  in  ligaturing  the  artery  on  the  distal  side  of  the  aneurism, 
and  in  the  case  of  the  common  carotid  there  are  no  branches  given  oft'  from  the  vessel  between 
the  aneurism  and  the  site  of  the  ligature ;  hence  the  flow  of  blood  through  the  sac  of  the 
aneurism  is  diminished  and  cure  takes  place  in  the  usual  way,  by  the  deposit  of  laminated  fibrin. 

Collateral  Circulation. — After  ligature  of  the  common  carotid  the  collateral  circulation 
can  be  perfectly  established,  by  the  free  communication  which  exists  between  the  carotid  arteries 
of  opposite  sides,  both  without  and  within  the  cranium,  and  by  enlargement  of  the  branches  of 
the  subclavian  artery  on  the  side  corresponding  to  that  on  which  the  vessel  hasbeen  tied — the 
chief  communication  outside  the  skull  taking  place  between  the  superior  and  inferior  thyroid 
arteries,  and  the  profunda  cervicis  and  arteria  princeps  cervicis  of  the  occipital';  the  vertebral 
taking  the  place  of  the  internal  carotid  within  the  cranium. 

Sir  A.  Cooper  had  an  opportunity  of  dissecting,  thirteen  years  after  the  operation,  the  case 
in  which  he  first  successfully  tied  the  common  carotid  (the  second  case  in  which  he  performed 
the  operation).1  The  injection,  however,  does  not  seem  to  have  been  a  successful  one.  It 
showed  merely  that  the  arteries  at  the  base  of  the  brain  (circle  of  Willis)  were  much  enlarged  on 
the  side  of  the  tied  artery,  and  that  the  anastomosis  between  the  branches  of  the  external  carotid 
on  the  affected  side  and  those  of  the  same  artery  on  the  sound  side  was  free,  so  that  the  external 
carotid  was  pervious  throughout, 

The  External  Carotid  Artery. 

The  external  carotid  artery  (Fig.  283)  commences  opposite  the  upper  border  of 
the  thyroid  cartilage,  and,  taking  a  slightly  curved  course,  passes  upward  and  for- 
ward, and  then  inclines  backward  to  the  space  between  the  neck  of  the  condyle 
of  the  lower  jaw  and  the  external  meatus,  where  it  divides  into  the  temporal  and 
internal  maxillary  arteries.  It  rapidly  diminishes  in  size  in  its  course  up  the  neck, 
owing  to  the  number  and  large  size  of  the  branches  given  off  from  it.  In  the 
child  it  is  somewhat  smaller  than  the  internal  carotid,  but  in  .the  adult  the  two 
vessels  are  of  nearly  equal  size.  At  its  commencement  this  artery  is  more  super- 
ficial, and  placed  nearer  the  middle  line  than  the  internal  carotid,  and  is  contained 
in  the  triangular  space  bounded  by  the  Sterno-mastoid  behind,  the  Omo-hyoid 
below,  and  the  posterior  belly  of  the  Digastric  and  Stylo-hyoid  above. 

Relations. — It  is  covered  by  the  skin,  superficial  fascia,  Platysma,  deep  fascia, 
and  anterior  margin  of  the  Sterno-mastoid,  crossed  by  the  hypoglossal  nerve,  and 
by  the  lingual  and  facial  veins ;  it  is  afterward  crossed  by  the  Digastric  and 
Stylo-hyoid  muscles,  and  higher  up  passes  deeply  into  the  substance  of  the  parotid 
gland,  where  it  lies  beneath  the  facial  nerve  and  the  junction  of  the  temporal  and 
internal  maxillary  veins.  Internally  is  the  hyoid  bone,  wall  of  the  pharynx,  the 
superior  laryngeal  nerve,  and  the  ramus  of  the. jaw,  from  which  it  is  separated  by 
a  portion  of  the  parotid  gland.  Externally,  in  the  lower  part  of  its  course,  is  the 
internal  carotid  artery.  Behind  it,  near  its  origin,  is  the  superior  laryngeal  nerve ; 
and  higher  up,  it  is  separated  from  the  internal  carotid  by  the  Stylo-glossus  and 
Stylo-pharyngeus  muscles,  the  glosso-pharyngeal  nerve,  and  part  of  the  parotid 
gland. 

Plan  of  the  Relations  of  the  External  Carotid. 

In  front. 
Skin,  superficial  fascia. 
Platysma  and  deep  fascia. 
Anterior  border  of  Sterno-mastoid. 
Hypoglossal  nerve. 
Lingual  and  facial  veins. 
Digastric  and  Stylo-hyoid  muscles. 
Parotid  gland  with  facial  nerve  and  temporo-maxillary  vein  in  its 
substance. 

1  Guy's  Hospital  Reports,  i.,  56. 


THE  EXTERNAL    CAROTCD   ARTERY.  4S7 

Internally.  /^/^/^^\ 

Hyoid  bone.  l/y/y/        \  n  n 

Pharynx.  Y^TTT^     '  Externally. 

Superior  laryngeal  nerve.  v  '9*fotld-    y  Internal  carotid  artery. 

Parotid  gland.  V  / 

Ramus  of  jaw.  ^ -^ 

Behind. 
Superior  laryngeal  nerve. 
Stylo-glossus. 
Stylo-pharyngeus. 
Grlosso-pharyngeal  nerve. 
Parotid  gland. 

Surface  Marking. — The  position  of  the  external  carotid  artery  may  be  marked  out  with 
sufficient  accuracy  by  a  line  drawn  from  the  front  of  the  meatus  of  the  external  ear  to  the  side 
of  the  cricoid  cartilage,  slightly  arching  the  line  forward. 

Surgical  Anatomy. — The  application  of  a  ligature  to  the  external  carotid  may  be  required 
in  case  of  wounds  of  this  vessel,  or  of  its  branches  when  these  cannot  be  tied,  and  in  some  cases 
of  pulsating  tumor  of  the  scalp  or  face.  The  operation  has  not  received  the  attention  which  it 
deserves,  owing  to  the  fear  which  surgeons  have  entertained  of  secondary  haemorrhage,  on 
account  of  the  number  of  branches  given  off  from  the  vessel.  This  fear,  however,  has  been 
shown  by  Mr.  Cripps  not  to  be  well  founded.1  To  tie  this  vessel  near  its  origin,  below  the  point 
where  it  is  crossed  by  the  Digastric,  an  incision  about  three  inches  in  length  should  be  made 
along  the  margin  of  the  Sterno-mastoid,  from  the  angle  of  the  jaw  to  the  upper  border  of  the 
thyroid  cartilage.  The  ligature  should  be  applied  between  the  lingual  and  superior  thyroid 
branches.  To  tie  the  vessel  above  the  Digastric,  between  it  and  the  parotid  gland,  an  incision 
should  be  made,  from  the  lobe  of  the  ear  to  the  great  cornu  of  the  os  hyoides,  dividing  succes- 
sively the  skin,  Platysma,  and  fascia.  By  drawing  the  Sterno-mastoid  outward,  and  the  posterior 
belly  of  the  Digastric  and  Stylo-hyoid  muscles  downward,  and  separating  them  from  the  parotid 
gland,  the  vessel  will  be  exposed,  and  a  ligature  may  be  applied  to  it.  The  circulation  is  at  once 
re-established  by  the  free  communication  between  most  of  the  large  branches  of  the  artery 
(facial,  lingual,  superior  thyroid,  occipital)  and  the  corresponding  arteries  of  the  opposite  side, 
and  by  the  anastomosis  of  its  branches  with  those  of  the  internal  carotid,  and  of  the  occipital 
with  the  branches  of  the  subclavian,  etc. 

Branches. — The  external  carotid  artery  gives  off  eight  branches,  which,  for 
convenience  of  description,  may  be  divided  into  four  sets.  (See  Fig.  284,  Plan  of 
the  Branches). 

Anterior.  Posterior.  Ascending.  Terminal. 

Superior  Thyroid.  Occipital.  Ascending  Pha-  Superficial  Temporal. 

Lingual.  Posterior  Auricular,     ryngeal.  Internal  Maxillary. 
Facial. 

The  student  is  here  reminded  that  many  variations  are  met  with  in  the 
number,  origin,  and  course  of  these  branches  in  different  subjects;  but  the  above 
arrangement  is  that  which  is  found  in  the  great  majority  of  cases. 

The  Superior  Thyroid  Artery  (Figs.  283  and  288)  is  the  first  branch  given  off 
from  the  external  carotid,  being  derived  from  that  vessel  just  below  the  great 
cornu  of  the  hyoid  bone.  At  its  commencement  it  is  quite  superficial,  being 
covered  by  the  integument,  fascia,  and  Platysma,  and  is  contained  in  the 
triangular  space  bounded  by  the  Sterno-mastoid,  Digastric,  and  Omo-hyoicl  muscles. 
After  running  upward  and  inward  for  a  short  distance,  it  curves  downward 
and  forward,  in  an  arched  and  tortuous  manner,  to  the  upper  part  of  the  thyroid 
gland,  passing  beneath  the  Omo-hyoid,  Sterno-hyoid,  and  Sterno-thyroid  muscles, 
and  supplying  them.  It  distributes  numerous  branches  to  the  upper  part  of  the 
giand,  anastomosing  with  its  fellow  of  the  opposite  side  and  with  the  inferior  thyroid 
arteries.  The  branches  supplying  the  gland  are  genei'ally  three  in  number :  one, 
the  largest,  supplies  principally  the  anterior  surface  of  the  gland ;  it  courses  along 
the  inner  border  of  the  lobe  as  far  as  the  upper  border  of  the  isthmus,  and  then 
passes  in  the  substance  of  the  isthmus  to  the  middle  line  of  the  neck,  where  it 
anastomoses  with  the  corresponding  artery  of  the  opposite  side :  a  second  branch 
courses  along  the  external  border  of  the  lobe,  and  supplies  this  portion  of  the  gland, 
and  the  third  passes  to  the  posterior  surface,  the  upper  part  of  which  it  supplies. 

1  Med.-Chir.  Tranr,.,  lxi.,  229. 


488  THE  BLOOD-VASCULAR    SYSTEM. 

Besides  the  arteries  distributed  to  the  muscles  by  which  it  is  covered  and  to  the 
substance  of  the  gland,  the  branches  of  the  superior  thyroid  are  the  following : 

Hyoid.  Superior  laryngeal. 

Superficial  descending  branch  (Sterno-mastoid).      Crico-thyroid. 

The  hyoid  (infra-hyoid)  is  a  small  branch  which  runs  along  the  lower  border 
of  the  os  hyoides  beneath  the  Thyro-hyoid  muscle ;  after  supplying  the  muscles 
connected  to  that  bone,  it  forms  an  arch,  by  anastomosing  with  the  vessel  of  the 
opposite  side. 

The  superficial  descending  or  Sterno-mastoid  branch  runs  downward  and  outwar 
across  the  sheath  of  the  common  carotid  artery,  and  supplies  the  Sterno-mastoid 
and  neighboring  muscles  and  integument.     There  is  frequently  a  separate  branch 
from  the  external  carotid  distributed  to  the  Sterno-mastoid  muscle. 

The  superior  laryngeal,  larger  than  either  of  the  preceding,  accompanies  the 
internal  laryngeal  nerve,  beneath  the  Thyro-hyoid  muscle :  it  pierces  the  thyro- 
hyoid membrane,  and  supplies  the  muscles,  mucous  membrane,  and  glands  of  the 
larynx,  anastomosing  with  the  branch  from  the  opposite  side. 

The  crico-thyroid  is  a  small  branch  which  runs  transversely  across  the  crico- 
thyroid membrane,  communicating  with  the  artery  of  the  opposite  side. 

Surgical  Anatomy. — The  superior  thyroid,  or  one  of  its  branches,  is  often  divided  in 
cases  of  cut  throat,  giving  rise  to  considerable  hemorrhage.  In  such  cases  the  artery  should  be 
secured,  the  wound  being  enlarged  for  that  purpose,  if  necessary.  The  operation  may  be  easily 
performed,  the  position  of  the  artery  being  very  superficial,  and  the  only  structures  of  importance 
covering  it  being  a  few  small  veins.  The  operation  of  tying  the  superior  thyroid  artery  in 
bronchocele  has  been  performed  in  numerous  instances  with  partial  or  temporary  success.  When, 
however,  the  collateral  circulation  between  this  vessel  and  the  artery  of  the  opposite  side,  and 
the  inferior  thyroid,  is  completely  re-established,  the  tumor  usually  regains  its  former  size,  and 
hence  the  operation  has  been  given  up,  especially  as  better  results  are  obtained  by  other  means. 
Both  thyroid  arteries  on  the  same  side,  and  indeed  all  the  four  thyroid  arteries,  have  been  tied 
in  enlarged  thyroid. 

The  position  of  the  superficial  descending  branch  is  of  importance  in  connection  with  the 
operation  of  ligation  of  the  common  carotid  artery.  It  crosses  and  lies  on  the  sheath  of  this 
vessel,  and  may  chance  to  be  wounded  in  opening  the  sheath.  The  position  of  the  crico-thyroid 
branch  should  be  remembered,  as  it  may  prove  the  source  of  troublesome  hemorrhage  during 
the  operation  of  laryngotomy. 

The  Lingual  Artery  (Fig.  288)  arises  from  the  external  carotid  between  the 
superior  thyroid  and  facial ;  it  first  runs  obliquely  upward  and  inward  to  the  great 
coimu  of  the  hyoid  bone ;  it  then  curves  downward  and  forward,  forming  a  loop 
which  is  crossed  by  the  hypoglossal  nerve,  and,  passing  beneath  the  Digastric  and 
Stylo-hyoid  muscles,  it  runs  horizontally  forward,  beneath  the  Hyo-glossus,  and 
finally,  ascending  almost  perpendicularly  to  the  tongue,  turns  forward  on  its  under 
surface  as  far  as  the  tip,  under  the  name  of  the  ranine  artery. 

Relations. — Its  first,  or  oblique,  portion  is  superficial,  being  contained  in  the 
same  triangular  space  as  the  superior  thyroid  artery,  resting  upon  the  middle  con- 
strictor of  the  pharynx,  and  covered  by  the  Platysma  and  fascia  of  the  neck.  Its 
second,  or  curved,  portion  also  lies  upon  the  middle  constrictor,  being  covered  at 
first  by  the  tendon  of  the  Digastric  and  the  Stylo-hyoid  muscle,  and  afterward  by 
the  Hyo-glossus,  the  latter  muscle  separating  it  from  the  hypoglossal  nerve.  Its 
third,  or  horizontal,  portion  lies  between  the  Hyo-glossus  and  Genio-hyo-glossus 
muscles.  The  fourth,  or  terminal,  part,  under  the  name  of  the  ranine,  runs  along 
the  under  surface  of  the  tongue  to  its  tip  :  it  is  very  superficial,  being  covered 
only  by  the  mucous  membrane,  and  rests  on  the  Lingualis  on  the  outer  side  of 
the  Genio-hyo-glossus.  The  hypoglossal  nerve  crosses  the  lingual  artery,  and  then 
becomes  separated  from  it,  in  the  second  part  of  its  course,  by  the  Hyo-glossus 
muscle. 

The  branches  of  the  lingual  artery  are — the 

Hyoid.  Sublingual. 

Dorsalis  Linguae.  Ranine. 


BRANCHES    OF    THE   EXTERNAL    CAROTID.  489 

The  hyoid  branch  (supra-hyoid)  runs  along  the  upper  border  of  the  hyoid  bone, 
supplying  the  muscles  attached  to  it  and  anastomosing  with  its  fellow  of  the 
opposite  side. 

The  dorsalis  lingua  (Fig.  288)  arises  from  the  lingual  artery  beneath  the  Hyo- 
glossus  muscle  (which,  in  the  figure,  has  been  partly  cut  away,  to  show  the 
vessel) ;  it  ascends  to  the  dorsum  of  the  tongue,  and  supplies  the  mucous  mem- 
brane, the  tonsil,  soft  palate,  and  epiglottis,  anastomosing  with  its  fellow  from 
the  opposite  side.  This  artery  is  frequently  represented  by  two  or  three  small 
branches. 

The  sublingual,  which  may  be  described  as  a  branch  of  bifurcation  of  the 
lingual  artery,  arises  at  the  anterior  margin  of  the  Hyo-glossus  muscle,  and 
runs  forward  between  the  Genio-hyo-glossus  and  the  sublingual  gland.  It 
supplies  the  substance  of  the  gland,  giving  branches  to  the  Mylo-hyoid  and 
neighboring  muscles,  the  mucous  membrane  of  the  mouth  and  gums.  One 
branch  runs  behind  the  alveolar  process  of  the  lower  jaw  in  the  substance  of  the 
gum  to  anastomose  Avith  a  similar  artery  from  the  other  side. 

The  ranine  may  be  regarded  as  the  other  branch  of  bifurcation,  or,  as  is  more 
usual,  as  the  continuation  of  the  lingual  artery  ;  it  runs  along  the  under  surface 
of  the  tongue,  resting  on  the  Inferior  lingualis,  and  covered  by  the  mucous 
membrane  of  the  mouth ;  it  lies  on  the  outer  side  of  the  Genio-hyo-glossus, 
accompanied  by  the  lingual  nerve.  On  arriving  at  the  tip  of  the  tongue  it  has 
been  said  to  anastomose  with  the  artery  of  the  opposite  side,  but  this  is  denied 
by  Hyrtl.     These  vessels  in  the  mouth  are  placed  one  on  each  side  of  the  frgenum. 

Surgical  Anatomy. — The  lingual  artery  may  be  divided  near  its  origin  in  cases  of  cut 
throat,  a  complication  that  not  unfrequently  happens  in  this  class  of  wounds ;  or  severe 
haemorrhage  which  cannot  be  restrained  by  ordinary  means  may  ensue  from  a  wound  or  deep 
ulcer  of  the  tongue.  In  the  former  case  the  primary  wound  may  be  enlarged  if  necessary,  and 
the  bleeding  vessels  secured.  In  the  latter  case  it  has  been  suggested  that  the  lingual  artery 
should  be  tied  near  its  origin.  Ligature  of  the  lingual  artery  is  also  occasionally  practised,  as  a 
palliative  measure,  in  cases  of  cancer  of  the  tongue,  in  order  to  check  the  progress  of  the 
disease  by  starving  the  growth,  and  it  is  sometimes  tied  as  a  preliminary  measure  to  removal  of 
the  tongue.  The  operation  is  a  difficult  one,  on  account  of  the  depth  of  the  artery,  the  number 
of  important  parts  by  which  it  is  surrounded,  the  loose  and  yielding  nature  of  the  parts  upon 
which  it  is  supported,  and  its  occasional  irregularity  of  origin.  An  incision  is  to  be  made  in 
a  curved  direction  from  a  finger's  breadth  external  to  the  symphysis  of  the  jaw  downward  to  the 
cornu  of  the  hyoid  bone,  and  then  upward  to  near  the  angle  of  the  jaw.  Care  must  be  taken 
not  to  carry  this  incision  too  far  backward,  for  fear  of  endangering  the  facial  vein.  In  the  first 
incision  the  skin,  superficial  fascia,  and  Platysma  will  be  divided,  and  the  deep  fascia  exposed. 
This  is  then  to  be  incised  and  the  submaxillary  gland  exposed  and  pulled  upward  by  retractors. 
A  triangular  space  is  now  exposed,  bounded  internally  by  the  posterior  border  of  the  Mylo- 
hyoid muscle:  below  and  externally,  by  the  tendon  of  the  Digastric;  and  above,  by  the  hypo- 
glossal nerve.  The  floor  of  the  space  is  formed  by  the  Hyo-glossus  muscle,  beneath  which  the 
artery  lies.  The  fibres  of  this  muscle  are  now  to  be  cut  through  horizontally  and  the  vessel 
exposed,  care  being  taken,  while  near  the  vessel,  not  to  open  the  pharynx. 

Troublesome  haemorrhage  may  occur  in  the  division  of  the  frsenum  in  children  if  the  ranine 
artery,  which  lies  on  each  side  of  it,  is  wounded.  The  student  should  remember  that  the  opera- 
tion is  always  to  be  performed  with  a  pair  of  blunt-pointed  scissors,  and  the  mucous  membrane 
only  is  to  be  divided  by  a  very  superficial  cut,  which  cannot  endanger  any  vessel.  The  scissors, 
also,  should  be  directed  away  from  the  tongue.  Any  further  liberation  of  the  tongue  which  may 
be  necessary  can  be  effected  by  tearing. 

The  Facial  Artery  (Fig.  285)  arises  a  little  above  the  lingual,  and  passes 
obliquely  upward,  beneath  the  Digastric  and  Stylo-hyoid  muscles,  and  frequently 
beneath  the  hypoglossal  nerve ;  it  now  runs  forward  under  cover  of  the  body  of 
the  lower  jaw,  lodged  in  a  groove  on  the  posterior  surface  of  the  submaxillary 
gland ;  this  may  be  called  the  cervical  part  of  the  artery.  It  then  curves  upward 
over  the  body  of  the  jaw  at  the  anterior  inferior  angle  of  the  Masseter  muscle ; 
passes  forward  and  upward  across  the  cheek  to  the  angle  of  the  mouth,  then  up- 
ward along  the  side  of  the  nose,  and  terminates  at  the  inner  canthus  of  the  eye, 
under  the  name  of  the  angular  artery.  This  vessel,  both  in  the  neck  and  on  the 
face,  is  remarkably  tortious :  in  the  former  situation,  to  accommodate  itself  to  the 
movements  of  the  pharynx  in  deglutition,  and  in  the  latter  to  the  movements  of 
the  jaw  and  the  lips  and  cheeks. 


490 


THE   BLOOD-VASCULAR    SYSTEM. 


Relations. — In  the  neck  its  origin  is  superficial,  being  covered  by  the  integu- 
ment, Platysma,  and  fascia ;  it  then  passes  beneath  the  Digastric  and  Stylo-hyoid 
muscles  and  part  of  the  submaxillary  gland.  It  lies  upon  the  middle  constrictor 
of  the  pharynx,  and  is  separated  from  the  Stylo-glossus  and  Hyo-glossus  muscles 
by  a  portion  of  the  submaxillary  gland.  On  the  face,  where  it  passes  over  the 
body  of  the  lower  jaw,  it  is  comparatively  superficial,  lying  immediate^  beneath 
the  Platysma.  In  this  situation  its  pulsation  may  be  distinctly  felt,  and  compres- 
sion of  the  vessel  against  the  bone  can  be  effectually  made.     In  its  course  over  the 


teria  septi  nasi, 
uperior  coronary. 


Inferior  coronary. 
Inferior  labial. 


Fig.  285.— The  arteries  of  the  face  and  scalp.1 


face  it  is  covered  by  the  integument,  the  fat  of  the  cheek,  and,  near  the  angle  of  the 
mouth,  by  the  Platysma,  Risorius,  and  Zygomatici  muscles.  It  rests  on  the  Buc- 
cinator, the  Levator  anguli  oris,  and  the  Levator  labii  superioris  (sometimes  pierc- 
ing or  else  passing  under  this  last  muscle).  The  facial  vein  lies  to  the  outer  side 
of  the  artery,  and  takes  a  more  direct  course  across  the  face,  where  it  is  separated 
from  the  artery  by  a  considerable  interval.  In  the  neck  it  lies  superficial  to  the 
artery.  ^ he  branches  of  the  facial  nerve  cross  the  artery,  and  the  infra-orbital 
nerve  lies  beneath  it. 

The  branches  of  this  vessel  may  be  divided  into  two  sets :  those  given  off  below 
the  jaw  (cervical),  and  those  on  the  face  (facial). 

1  The  muscular  tissue  of  the  lips  must  be  supposed  to  have  been  cut  away,  in  order  to  show  the 
course  of  the  coronary  arteries. 


BRANCHES    OF    THE   EXTERNAL    CAROTID.  491 

Cervical  Branches.  Facial  Branches. 

Inferior  or  Ascending  Palatine.  Muscular. 

Tonsillar.  Inferior  Labial. 

Submaxillary.  Inferior  Coronary. 

Submental.  Superior  Coronary. 

Muscular.  Lateral  Nasal. 

Angular. 

The  inferior  or  ascending  palatine  (Fig.  289)  passes  up  between  the  Stylo- 
glossus and  Stylo-pharyngeus  to  the  outer  side  of  the  pharynx,  along  -which  it  is 
continued  between  the  Superior  constrictor  and  the  Internal  pterygoid  to  near  the 
base  of  the  skull.  It  supplies  the  neighboring  muscles,  the  tonsil,  and  Eustachian 
tube,  and  divides,  near  the  Levator  palati,  into  two  branches :  one  follows  the 
course  of  the  Levator  palati,  and,  winding  over  the  upper  border  of  the  Superior 
constrictor,  supplies  the  soft  palate  and  the  palatine  glands,  anastomosing  with  its 
fellow  of  the  opposite  side  and  with  the  posterior  palatine  branch  of  the  internal 
maxillary  artery  ;  the  other  pierces  the  Superior  constrictor  and  supplies  the  tonsil, 
anastomosing  with  the  tonsillar  and  ascending  pharyngeal  arteries. 

The  tonsillar  branch  (Fig.  289)  passes  up  between  the  Internal  pterygoid  and 
Stylo-glossus,  and  then  ascends  along  the  side  of  the  pharynx,  perforating  the 
Superior  constrictor,  to  ramify  in  the  substance  of  the  tonsil  and  root  of  the 
tongue. 

The  submaxillary  or  glandular  branches  consist  of  three  or  four  large  vessels, 
which  supply  the  submaxillary  gland,  some  being  prolonged  to  the  neighboring 
muscles,   lymphatic  glands,   and  integument. 

The  submental,  the  largest  of  the  cervical  branches,  is  given  off  from  the  facial 
artery  just  as  that  vessel  quits  the  submaxillary  gland  :  it  runs  forward  upon  the 
Mylo-hyoid  muscle,  just  below  the  body  of  the  jaw  and  beneath  the  Digastric; 
after  supplying  the  surrounding  muscles,  and  anastomosing  with  the  sublingual 
artery  by  branches  which  perforate  the  Mylo-hyoid  muscle,  it  arrives  at  the  sym- 
physis of  the  chin,  where  it  turns  over  the  border  of  the  jaw  and  divides  into  a 
superficial  and  a  deep  branch  ;  the  former  passes  between  the  integument  and 
Depressor  labii  inferioris,  supplies  both,  and  anastomoses  with  the  inferior  labial. 
The  deep  branch  passes  between  the  latter  muscle  and  the  bone,  supplies  the  lip, 
and  anastomoses  with  the  inferior  labial  and  mental  arteries. 

The  muscular  branches  are  distributed  to  the  Internal  pterygoid  and  Stylo-hyoid 
in  the  neck,  and  to  the  Masseter  and  Buccinator  on  the  face. 

The  inferior  labial  passes  beneath  the  Depressor  anguli  oris,  to  supply  the 
muscles  and  integument  of  the  lower  lip,  anastomosing  with  the  inferior  coronary 
and  submental  branches  of  the  facial,  and  with  the  mental  branch  of  the  inferior 
dental  artery. 

The  inferior  coronary  is  derived  from  the  facial  artery,  near  the  angle  of  the 
mouth :  it  passes  upward  and  inward  beneath  the  depressor  anguli  oris,  and,  pen- 
etrating the  Orbicularis  oris  muscle,  runs  in  a  tortuous  course  along  the  edge  of 
the  lower  lip  between  this  muscle  and  the  mucous  membrane,  inosculating  with 
the  artery  of  the  opposite  side.  This  artery  supplies  the  labial  glands,  the  mucous 
membrane,  and  muscles  of  the  lower  lip,  and  anastomoses  with  the  inferior  labial 
and  the  mental  branch  of  the  inferior  dental  artery. 

The  superior  coronary  is  larger  and  more  tortuous  in  its  course  than  the  pre- 
ceding. It  follows  the  same  course  along  the  edge  of  the  upper  lip,  lying  between 
the  mucous  membrane  and  the  Orbicularis  oris,  and  anastomoses  with  the  artery 
of  the  opposite  side.  It  supplies  the  textures  of  the  upper  lip,  and  gives  off  in  its 
course  two  or  three  vessels  which  ascend  to  the  nose.  One,  named  the  inferior 
artery  of  the  septum,  ramifies  on  the  septum  of  the  nares  as  far  as  the  point  of  the 
nose  ;  another,  the  artery  of  the  ala,  supplies  the  ala  of  the  nose. 

The  lateralis  nasi  is  derived  from  the  facial,  as  that  vessel  is  ascending  along 
the  side  of  the  nose ;   it  supplies  the   ala   and  dorsum  of  the  nose,  anastomosing 


492 


THE   BLOOD-VASCULAR    SYSTEM. 


with  its  fellow,  the   nasal  branch   of  the    ophthalmic,  the   inferior  artery  of  the 
septum,  the  artery  of  the  ala,    and   the  infra-orbital. 

The  angular  artery  is  the  termination  of  the  trunk  of  the  facial ;  it  ascends  to 
the  inner  angle  of  the  orbit,  imbedded  in  the  fibres  of  the  Levator  labii  superioris 
alseque  nasi,  and  accompanied  by  a  large  vein,  the  angular  ;  it  distributes  some 
branches  on  the  cheek  which  anastomose  with  the  infra-orbital,  and  after  supplying 
the  lachrymal  sac  and  Orbicularis  palpebrarum  muscle,  terminates  by  anastomos- 
ing with  the  nasal  branch  of  the  ophthalmic  artery. 

Internal  jugular  vein 
Occipital  artery 


Internal  maxil- 
lary artery. 

\    Facial 
nerve. 


Lingual 
nerve. 
Inferior  dental 
nerve. 

Mylo-hyoid 
nerve. 


SUPERIOR    OBLIQUE 
MUSCLE. 


Vertebral  artery 


INFERIOR     OBLIQUE 
MUSCLE. 

Pneumogastric 
nerve. 


Hypo-glossal 
nerve. 
Internal  carotid 


STERNO-MASTOID 
MUSCLE. 


Superior  thyroid 
artery. 
External  carotid 
artery. 


Fig.  286.— The  occipital  artery  and  its  relations.    (From  a  dissection  by  Mr.  Gerald  S.  Hughes.) 


The  anastomoses  of  the  facial  artery  are  very  numerous,  not  only  with  the 
vessel  of  the  opposite  side,  but,  in  the  neck,  with  the  sublingual  branch  of  the 
lingual ;  with  the  ascending  pharyngeal ;  with  the  posterior  palatine,  a  branch  of 
the  internal  maxillary,  by  its  inferior  or  ascending  palatine  and  tonsillar  branches  ; 
on  the  face,  with  the  mental  branch  of  the  inferior  dental  as  it  emerges  from  the  mental 


BRANCHES    OF    THE   EXTERNAL    CAROTID.  493 

foramen,  with  the  transverse  facial,  a  branch  of  the  temporal ;  with  the  infra-orbital, 
a  branch  of  the  internal  maxillary,  and  with  the  nasal  branch  of  the  ophthalmic. 

Peculiarities. — The  facial  artery  not  unfrequently  arises  by  a  common  trunk  with  the 
lingual.  This  vessel  is  also  subject  to  some  variations  in  its  size  and  in  the  extent  to  which  it 
supplies  the  face.  It  occasionally  terminates  as  the  submental,  and  not  unfrequently  supplies 
the  face  only  as  high  as  the  angle  of  the  mouth  or  nose.  The  deficiency  is  then  supplied  by 
enlargement  of  one  of  the  neighboring  arteries. 

Surgical  Anatomy. — The  passage  of  the  facial  artery  over  the  body  of  the  jaw  would 
appear  to  afford  a  favorable  position  for  the  application  of  pressure  in  case  of  haemorrhage 
from  the  lips,  the  result  either  of  an  accidental  wound  or  during  an  operation ;  but  its  applica- 
tion is  useless,  except  for  a  very  short  time,  on  account  of  the  free  communication  of  this 
vessel  with  its  fellow  and  with  numerous  branches  from  different  sources.  In  a  wound  involv- 
ing the  lip  it  is  better  to  seize  the  part  between  the  fingers,  and  evert  it,  when  the  bleeding 
vessel  may  be  atonce  secured  with  pressure -forceps.  In  order  to  prevent  haemorrhage  in  cases 
of  removal  of  diseased  growths  from  the  part,  the  lip  should  be  compressed  on  each  side 
between  the  fingers  and  thumb  or  by  a  pair  of  specially  devised  clamp-forceps,  whilst  the  surgeon 
excises  the  diseased  part.  In  order  to  stop  haemorrhage  where  the  lip  has  been  divided  in  an 
operation,  it  is  necessary,  in  uniting  the  edges  of  the  wound,  to  pass  the  sutures  through  the 
cut  edges,  almost  as  deep  as  its  mucous  surface  ;  by  these  means  not  only  are  the  cut  surfaces 
mox*e  neatly  and  securely  adapted  to  each  other,  but  the  possibility  of  haemorrhage  is  prevented 
by  including  in  the  suture  the  divided  artery.  If  the  suture  is,  on  the  contrary,  passed  through 
merely  the  cutaneous  portion  of  the  wound,  haemorrhage  occurs  into  the  cavity  of  the  mouth. 
The  student  should,  lastly,  observe  the  relation  of  the  angular  artery  to  the  lachrymal  sac,  and 
it  will  be  seen  that,  as  the  vessel  passes  up  along  the  inner  margin  of  the  orbit,  it  ascends  on 
its  nasal  side.  In  operating  for  fistula  lachrymalis  the  sac  should  always  be  opened  on  its  outer 
side,  in  order  that  this  vessel  may  be  avoided. 

The  Occipital  Artery  (Figs.  285,  286)  arises  from  the  posterior  part  of  the  ex- 
ternal carotid,  opposite  the  facial,  near  the  lower  margin  of  the  Digastric  muscle.  At 
its  origin  it  is  covered  by  the  posterior  belly  of  the  Digastric  and  Stylo-hyoid  muscles, 
and  the  hypoglossal  nerve  winds  around  it  from  behind  forward ;  higher  up,  it 
passes  across  the  internal  carotid  artery,  the  internal  jugular  vein,  and  the  pneumo- 
gastric  and  spinal  accessory  nerves ;  it  then  ascends  to  the  interval  between  the 
transverse  process  of  the  atlas  and  the  mastoid  process  of  the  temporal  bone,  and 
passes  horizontally  backward,  grooving  the  surface  of  the  latter  bone,  being  covered 
by  the  Sterno-mastoid,  Splenius,  Trachelo-mastoid,  and  Digastric  muscles,  and 
resting  upon  the  Rectus  lateralis,  the  Superior  oblique,  and  Complexus  muscles ; 
it  then  changes  its  course  and  passes  vertically  upward,  pierces  the  fascia  which 
connects  the  cranial  attachment  of  the  Trapezius  with  the  Sterno-mastoid,  and 
ascends  in  a  tortuous  course  over  the  occiput,  as  high  as  the  vertex,  where  it 
divides  into  numerous  branches.  It  is  accompanied  in  the  latter  part  of  its  course 
by  the  great  occipital,  and  occasionally  by  a  cutaneous  filament  from  the  suboccip- 
ital nerve. 

The  branches  given  off  from  this  vessel  are — 

Muscular.  Auricular. 

Sterno-mastoid.  Meningeal. 

Arteria  Princeps  Cervicis. 

The  muscular  branches  supply  the  Digastric,  Stylo-hyoid,  Splenius,  and 
Trachelo-mastoid  muscles. 

The  sterno-mastoid  is  a  large  and  constant  branch,  generally  arising  from  the 
artery  close  to  its  commencement,  but  sometimes  springing  directly  from  the 
external  carotid.  It  first  passes  downward  and  backward  over  the  hypoglossal 
nerve,  and  enters  the  substance  of  the  muscle  in  company  with  the  spinal  acces- 
sory nerve. 

The  auricular  branch  supplies  the  back  part  of  the  concha.  It  frequently 
gives  off  a  branch,  which  enters  the  skull  through  the  mastoid  foramen  and  sup- 
plies the  dura  mater,  the  diploe,  and  the  mastoid  cells. 

The  meningeal  branch  ascends  with  the  internal  jugular  vein,  and  enters  the 
skull  through  the  foramen  lacerum  posterius,  to  supply  the  dura  mater  in  the  pos- 
terior fossa. 

The  arteria  princeps  cervicis  (Fig.  289),  the  largest  branch  of  the  occipital, 
descends  along  the  back  part  of  the  neck  and  divides  into  a  superficial  and  a  deep 


494  THE   BLOOD-VASCULAR    SYSTEM. 

portion.  The  former  runs  beneath  the  Splenius,  giving  off  branches  which  per- 
forate that  muscle  to  supply  the  Trapezius,  which  anastomose  with  the  superficial 
cervical  artery,  a  branch  of  the  transversalis  colli :  the  latter  passes  beneath  the 
Complexus  between  it  and  the  Semispinalis  colli,  and  anastomoses  with  branches 
from  the  vertebral  and  with  the  deep  cervical  artery,  a  branch  of  the  superior 
intercostal.  The  anastomosis  between  these  vessels  serves  mainly  to  establish  the 
collateral  circulation  after  ligation  of  the  carotid  or  subclavian  artery. 

The  cranial  branches  of  the  occipital  artery  are  distributed  upon  the  occiput ; 
they  are  very  tortuous,  and  lie  between  the  integument  and  Occipito-frontalis, 
anastomosing  with  the  artery  of  the  opposite  side,  the  posterior  auricular  and 
temporal  arteries.  They  supply  the  back  part  of  the  Occipito-frontalis  muscle, 
the  integument,   and  pericranium. 

The  Posterior  Auricular  Artery  (Fig.  285)  is  a  small  vessel  which  arises  from 
the  external  carotid,  above  the  Digastric  and  Stylo-hyoid  muscles,  opposite  the 
apex  of  the  styloid  process.  It  ascends,  under  cover  of  the  parotid  gland,  on  the 
styloid  process  of  the  temporal  bone,  to  the  groove  between  the  cartilage  of  the  ear 
and  the  mastoid  process,  immediately  above  which  it  divides  into  its  two  terminal 
branches,  the  auricular  and  mastoid.  Just  before  arriving  at  the  mastoid  process, 
this  artery  is  crossed  by  the  portio  dura,  and  has  beneath  it  the  spinal  accessory 
nerve. 

Besides  several  small  branches  to  the  Digastric,  Stylo-hyoid,  and  Sterno-mas- 
toid  muscles  and  to  the  parotid  gland,  this  vessel  gives  off  three  branches  : 

Stylo-mastoid.  Auricular.  Mastoid. 

The  stylo-mastoid  branch  enters  the  stylo-mastoid  foramen,  and  supplies  the 
tympanum,  mastoid  cells,  and  semicircular  canals.  In  the  young  subject  a  branch 
from  this  vessel  forms,  with  the  tympanic  branch  from  the  internal  maxillary,  a 
vascular  circle,  which  surrounds  the  membrana  tympani,  and  from  which  delicate 
vessels  ramify  on  that  membrane.  It  anastomoses  with  the  petrosal  branch  of  the 
middle  meningeal  artery  by  a  twig  which  enters  the  hiatus  Fallopii. 

The  auricular  branch,  one  of  the  terminal  branches,  ascends  behind  the  ear. 
beneath  the  Retrahens  auriculam  muscle,  and  is  distributed  to  the  back  part  of 
the  cartilage  of  the  ear,  upon  which  it  ramifies  minutely,  some  branches  curving 
round  the  margin  of  the  fibro-cartilage,  others  perforating  it,  to  supply  its  anterior 
surface.  It  anastomoses  with  the  posterior  branch  of  the  superficial  temporal  and 
also  with  its  anterior  auricular  branches. 

The  mastoid  branch  passes  backward,  over  the  Sterno-mastoid  muscle,  to  the 
scalp  above  and  behind  the  ear.  It  supplies  the  posterior  belly  of  the  Occipito-fron- 
talis muscle  and  the  scalp  in  this  situation.    It  anastomoses  with  the  occipital  artery. 

The  Ascending  Pharyngeal  Artery  (Fig.  289),  the  smallest  branch  of  the 
external  carotid,  is  a  long,  slender  vessel,  deeply  seated  in  the  neck,  beneath,  the 
other  branches  of  the  external  carotid  and  the  Stylo-pharyngeus  muscle.  It  arises 
from  the  back  part  of  the  external  carotid,  near  the  commencement  of  that  vessel, 
and  ascends  vertically  between  the  internal  carotid  and  the  side  of  the  pharynx,  to 
the  under  surface  of  the  base  of  the  skull,  lying  on  the  Rectus  capitis  anticus  major. 
Its  branches  may  be  subdivided  into  four  sets : 

Prevertebral.  Pharyngeal.  Tympanic.  Meningeal. 

The  prevertebral  branches  are  numerous  small  vessels  which  supply  the  Recti 
capitis  antici  and  Longus  colli  muscles,  the  sympathetic,  hypoglossal,  and  pneu- 
mogastric  nerves,  and  the  lymphatic  glands,  anastomosing  with  the  ascending 
cervical  artery. 

The  pharyngeal  branches  are  three  or  four  in  number.  Two  of  these  descend 
to  supply  the  middle  and  inferior  Constrictors  and  the  Stylo-pharyngeus,  ramifying 
in  their  substance  and  in  the  mucous  membrane  lining  them.  The  largest  of  the 
pharyngeal  branches  passes  inward,  running  upon  the  Superior  constrictor,  and 
sends   ramifications   to   the   soft  palate   and   tonsil,  which  take  the  place  of  the 


BRANCHES    OF    THE   EXTERNAL    CAROTID.  495 

ascending  palatine  branch  of  the  facial  artery  when  that  vessel  is  of  small  size. 
A  twig  from  this  branch  supplies  the  Eustachian  tube. 

The  tympanic  branch  is  a  small  artery  which  passes  through  a  minute  foramen 
in  the  petrous  portion  of  the  temporal  bone,  in  company  with  the  tympanic  branch 
of  the  Grlosso-pharyngeal  nerve  to  supply  the  inner  wall  of  the  tympanum  and 
anastomose  with  the  other  tympanic  arteries. 

The  meningeal  branches  consist  of  several  small  vessels,  which  pass  through 
foramina  in  the  base  of  the  skull,  to  supply  the  dura  mater.  One,  the  posterior 
meningeal,  enters  the  cranium  through  the  foramen  lacerum  posterius ;  a  second 
passes  through  the  foramen  lacerum  medium  ;  and  occasionally  a  third  through  the 
anterior  condyloid  foramen.     They  are  all  distributed  to  the  dura  mater. 

Surgical  Anatomy.— The  ascending  pharyngeal  artery  has  been  wounded  from  the  throat, 
as  in  the  case  in  which  the  stem  of  a  tobacco-pipe  was  driven  into  the  vessel,  causing  fatal 
hemorrhage. 

The  Superficial  Temporal  Artery  (Fig.  285),  the  smaller  of  the  two  terminal 
branches  of  the  external  carotid,  appears,  from  its  direction,  to  be  the  continuation 
of  that  vessel.  It  commences  in  the  substance  of  the  parotid  gland,  in  the  inter- 
space between  the  neck  of  the  lower  jaw  and  the  external  auditory  meatus,  crosses 
over  the  posterior  root  of  the  zygoma,  passes  beneath  the  Attrahens  auriculam 
muscle,  lying  on  the  temporal  fascia,  and  divides,  about  two  inches  above  the 
zygomatic  arch,  into  two  branches,  an  anterior  and  a  posterior. 

The  anterior  temporal  runs  tortuously  upward  and  forward  to  the  forehead, 
supplying  the  muscles,  integument,  and  pericranium  in  this  region,  and  anasto- 
moses with  the  supra-orbital  and  frontal  arteries. 

The  posterior  temporal,  larger  than  the  anterior,  curves  upward  and  backward 
along  the  side  of  the  head,  lying  superficial  to  the  temporal  fascia,  and  inosculates 
with  its  fellow  of  the  opposite  side,  and  with  the  posterior  auricular  and  occipital 
arteries. 

The  superficial  temporal  artery,  as  it  crosses  the  zygoma,  is  covered  by  the 
Attrahens  auriculam  muscle,  and  by  a  dense  fascia  given  off  from  the  parotid 
gland  :  it  is  crossed  by  the  temporo-facial  division  of  the  facial  nerve  and  one  or 
two  veins,  and  is  accompanied  by  the  auriculo-temporal  nerve,  which  lies  behind 
it.  Besides  some  twigs  to  the  parotid  gland,  the  articulation  of  the  jaw.  and  the 
Masseter  muscle,  its  branches  are,  the 

Transverse  Facial.  Middle  Temporal. 

Anterior  Auricular. 

The  transverse  facial  is  given  off  from  the  temporal  before  that  vessel  quits 
the  parotid  gland ;  running  forward  through  its  substance,  it  passes  transversely 
across  the  face,  between  Stenson's  duct  and  the  lower  border  of  the  zygoma,  and 
divides  on  the  side  of  the  face  into  numerous  branches,  which  supply  the  parotid 
gland,  the  Masseter  muscle,  and  the  integument,  anastomosing  with  the  facial, 
masseteric,  and  infra-orbital  arteries.  This  vessel  rests  on  the  Masseter,  and  is 
accompanied  by  one  or  two  branches  of  the  facial  nerve.  It  is  sometimes  a  branch 
of  the  external  carotid. 

The  middle  temporal  artery  arises  immediately  above  the  zygomatic  arch,  and, 
perforating  the  temporal  fascia,  gives  branches  to  the  Temporal  muscle,  anasto- 
mosing with  the  deep  temporal  branches  of  the  internal  maxillary.  It  occasion- 
ally gives  off  an  orbital  branch,  which  runs  along  the  upper  border  of  the  zygoma, 
between  the  two  layers  of  the  temporal  fascia,  to  the  outer  angle  of  the  orbit.  This 
branch,  which  may  ai'  s  directly  from  the  superficial  temporal  artery,  supplies  the 
Orbicularis  palpebral'!  nastomoses  with  the  lachrymal  and  palpebral  branches 

of  the  ophthalmic  art 

The  anterior  auricular  branches  are  distributed  to  the  anterior  portion  of  the 
pinna,  the  lobule,  an  the  external  meatus,  anastomosing  with  branches  of 

the  posterior  auricular. 


496  THE   BLOOD-VASCULAR    SYSTEM. 

Surgical  Anatomy. — Formerly  the  operation  of  arteriotoniy  was  performed  upon  this 
vessel  in  cases  of  inflammation  of  the  eye  or  brain,  but  now  the  operation  is  probably  never 
performed.  If  the  student  will  consider  the  relations  of  the  trunk  of  the  vessel  as  it  crosses 
the  zygomatic  arch,  with  the  surrounding  structures,  he  will  observe  that  it  is  covered  by  a 
thick  and  dense  fascia,  crossed  by  one  of  the  main  divisions  of  the  facial  nerve  and  one  or 
two  veins,  and  accompanied  by  the  auriculo-temporal  nerve.  Bleeding  should  not  be  performed 
in  this  situation,  as  much  difficulty  may  arise  from  the  dense  fascia  over  the  vessel  preventing  a 
free  flow  of  blood,  and  considerable  pressure  is  requisite  afterward  to  arrest  the  hemorrhage. 
Again,  a  varicose  aneurism  may  be  formed  by  the  accidental  opening  of  one  of  the  veins  in 
front  of  the  artery ;  or  severe  neuralgic  pain  may  arise  from  the  operation  implicating  one  of 
the  nervous  filaments  in  the  neighborhood.  The  anterior  branch,  on  the  contrary,  is  sub- 
cutaneous, is  a  large  vessel,  and  is  readily  compressed  ;  it  is  consequently  more  suitable  for  the 
operation. 

The  Internal  Maxillary  (Fig.  287),  the  larger  of  the  two  terminal  branches  of 
the  external  carotid,  arises  from  that  vessel  opposite  the  neck  of  the  condyle  of  the 
lower  jaw,  and  is  at  first  embedded  in  the  substance  of  the  parotid  gland  ;  it  passes 
inward  between  the  ramus  of  the  jaw  and  the  internal  lateral  ligament,  and  then 
upon  the  outer  surface  of  the  External  pterygoid  muscle  to  the  spheno-maxillary 
fossa,  to  supply  the  deep  structures  of  the  face.  For  convenience  of  description  it 
is  divided  into  three  portions :  a  maxillary,  a  pterygoid,  and  a  spheno-maxillary. 

In  the  first  part  of  its  course  (maxillary  portion)  the  artery  passes  horizontally 
forward  and  inward,  between  the  ramus  of  the  jaw  and  the  internal  lateral  ligament. 
The  artery  here  lies  parallel  to  and  a  little  below  the  auriculo-temporal  nerve ;  it 
crosses  the  inferior  dental  nerve,  and  lies  along  the  lower  border  of  the  External 
pterygoid  muscle. 

In  the  second  part  of  its  course  (pterygoid  portion)  it  runs  obliquely  forward 
and  upward  upon  the  outer  surface  of  the  External  pterygoid  muscle,  being 
covered  by  the  ramus  of  the  lower  jaw  and  lower  part  of  the  Temporal  muscle; 
or  it  may  pass  on  the  inner  surface  of  the  External  pterygoid  muscle  to  reach  the 
interval  between  its  two  heads,  between  which  it  passes  to  reach  the  spheno- 
maxillary fossa. 

In  the  third  part  of  its  course  (spheno-maxillary  portion)  it  approaches  the 
superior  maxillary  bone,  and  enters  the  spheno-maxillary  fossa  in  the.  interval 
between  the  two  heads  of  the  External  pterygoid,  where  it  lies  in  relation  with 
Meckel's  ganglion,  and  gives  off  its  terminal  branches. 

The  branches  of  this  vessel  may  be  divided  into  three  groups,  corresponding 
with  its  three  divisions. 

Branches  of  the  First  or  Maxillary  Portion  (Fig.  288). 

Tympanic  (anterior).  Small  meningeal. 

Deep  auricular.  Inferior  dental. 

Middle  meningeal. 

The  tympanic  branch  passes  upward  behind  the  articulation  of  the  lower  jaw, 
enters  the  tympanum  through  the  Grlaserian  fissure,  and  ramifies  upon  the  mem- 
brana  tympani,  forming  a  vascular  circle  around  the  membrane  with  the  stylo- 
mastoid artery,  and  anastomosing  with  the  Vidian  and  the  tympanic  branch  from 
the  internal  carotid. 

The  deep  auricular  branch  often  arises  in  common  with  the  preceding.  It 
passes  upward  in  the  substance  of  the  parotid  gland,  behind  the  temporo-max- 
illary  articulation,  pierces  the  cartilaginous  or  bony  wall  of  the  external  audi- 
tory meatus,  and  supplies  its  cuticular  lining  and  the  outer  surface  of  the 
membrana  tympani. 

The  middle  meningeal  is  the  largest  of  the  branches  which  supply  the  dura 
mater.  It  arises  from  the  internal  maxillary,  between  the  internal  lateral  liga- 
ment and  the  neck  of  the  jaw,  and  passes  vertically  upward  between  the  two 
roots  of  the  auriculo-temporal  nerve  to  the  foramen  spinosum  of  the  sphenoid 
bone.  On  entering  the  cranium  it  divides  into  two  branches,  anterior  and  poste- 
rior.     The  anterior  branch,  the  larger,  crosses  the  great  ala  of  the  sphenoid,  and 


BRANCHES    OF    THE   EXTERNAL    CAROTID. 


497 


reaches  the  groove,  or  canal,  in  the  anterior  inferior  angle  of  the  parietal  bone : 
it  then  divides  into  branches  which  spread  out  between  the  dura  mater  and  internal 
surface  of  the  cranium,  some  passing  upward  over  the  parietal  bone  as  far  as  the 
vertex,  and  others  backward  to  the  occipital  bone.  The  posterior  branch  crosses 
the  squamous  portion  of  the  temporal,  and  on  the  inner  surface  of  the  parietal 


Incisor. 


Fig.  287.— The  internal  maxillary  artery  and  its  branches. 


~Pterygo-palatine, 


\  ^Vidian 

Descending  Palatine 


Small  Meningeal 
Middle  Meningeal 
Tympanie 


Fig.  288.— Plan  of  the  branches. 


bone  divides  into  branches  which  supply  the  posterior  part  of  the  dura  mater  and 
cranium.  The  branches  of  this  vessel  are  distributed  partly  to  the  dura  mater, 
but  chiefly  to  the  bones ;  they  anastomose  with  the  arteries  of  the  opposite  side, 
and  with  the  anterior  and  posterior  meningeal. 

The  middle  meningeal  on  entering  the  cranium  gives  oft  the  following  collat- 
eral branches  :  1.  Numerous  small  vessels  to  the  Gasserian  ganglion,  and  to  the 
dura  mater  in  this  situation.  2.  A  branch  (petrosal  branch),  which  enters  the 
hiatus  Fallopii,  supplies  the  facial  nerve,  and  anastomoses  with  the  stylo-mastoid 
branch  of  the  posterior  auricular  artery.  3.  A  minute  tympanic  branch,  which 
runs  in  the  canal  for  the  Tensor  tympani  muscle,  and  supplies  this  muscle  and  the 
lining  membrane  of  the  canal.  4.  Orbital  branches,  which  pass  through  the 
sphenoidal  fissure,  or  through  separate  canals  in  the  great  wing  of  the  sphenoid  to 
anastomose  with  the  lachrymal  or  other  branches  of  the  ophthalmic  artery.  5. 
Temporal  or  anastomotic  branches,  which  pass  through  foramina  in  the  great  wing 
of  the  sphenoid,  and  anastomose  in  the  temporal  fossa  with  the  deep  temporal 
arteries. 


498  THE   BLOOD-VASCULAR    SYSTEM. 

Surgical  Anatomy. — The  middle  meningeal  is  an  artery  of  considerable  surgical  import- 
ance, as  it  may  be  injured  in  fractures  of  the  temporal  region  of  the  skull,  and  the  injury  may 
be  followed  by  considerable  haemorrhage  between  the  bone  and  dura  mater,  which  may  cause 
compression  of  the  brain  and  require  the  operation  of  trephining  for  its  relief.  This  artery 
crosses  the  anterior  inferior  angle  of  the  parietal  bone  at  a  point  1  £  inches  behind  the  external 
angular  process  of  the  frontal  bone,  and  If  inches  above  the  zygoma.  From  this  point  the  ante- 
rior branch  passes  upward  and  slightly  backward  to  the  sagittal  suture,  lying  about  J  inch  to 
f  inch  behind  the  coronal  suture.  The  posterior  branch  passes  upward  and  backward  over  the 
squamous  portion  of  the  temporal  bone.  In  order  to  expose  the  artery  as  it  lies  in  the  canal  in 
the  parietal  bone,  a  semilunar  incision,  with  its  convexity  upward,  should  be  made,  commencing 
an  inch  behind  the  external  angular  process,  and  carried  backward  for  2  inches.  The  structures 
cut  through  are  :  (I)  skin  ;  (2)  superficial  fascia,  with  branches  of  the  superficial  temporal  vessels 
and  nerves;  (3)  the  fascia  continued  down  from  the  aponeurosis  of  the  Occipito-frontalis ;  (4) 
the  two  layers  of  the  temporal  fascia ;  (5)  the  temporal  muscle ;  (6)  the  deep  temporal  vessels  ; 
(7)  the  pericranium ;  and  (8)  the  bone. 

The  small  meningeal  is  sometimes  derived  from  the  preceding.  It  enters  the 
skull  through  the  foramen  ovale,  and  supplies  the  Gasserian  ganglion  and  dura 
mater. 

The  inferior  dental  descends  with  the  inferior  dental  nerve  to  the  foramen  on 
the  inner  side  of  the  ramus  of  the  jaw.  It  runs  along  the  dental  canal  in  the  sub- 
stance of  the  bone,  accompanied  by  the  nerve,  and  opposite  the  first  bicuspid  tooth 
divides  into  two  branches,  incisor  and  mental ;  the  former  is  continued  forward 
beneath  the  incisor  teeth  as  far  as  the  symphysis,  where  it  anastomoses  with  the 
artery  of  the  opposite  side  ;  the  mental  branch  escapes  with  the  nerve  at  the  mental 
foramen,  supplies  the  structures  composing  the  chin,  and  anastomoses  with  the  sub- 
mental inferior  labial  and  inferior  coronary  arteries.  Near  its  origin  the  inferior 
dental  artery  gives  off  a  lingual  branch,  which  descends  with  the  lingual  (gustatory) 
nerve  and  supplies  the  mucous  membrane  of  the  mouth.  As  the  inferior  dental 
artery  enters  the  foramen  it  gives  off  a  mylo-hyo.id  branch,  which  runs  in  the  mylo- 
hyoid groove,  and  ramifies  on  the  under  surface  of  the  Mylo-hyoid  muscle.  The 
dental  and  incisor  arteries  during  their  course  through  the  substance  of  the  bone 
give  oiF  a  few  twigs  which  are  lost  in  the  cancellous  tissue,  and  a  series  of  branches 
which  correspond  in  number  to  the  roots  of  the  teeth  :  these  enter  the  minute 
apertures  at  the  extremities  of  the  fangs  and  supply  the  pulp  of  the  teeth. 


Branches  of  the  Second  or  Pterygoid  Portion. 

Deep  Temporal.  Masseteric. 

Pterygoid.  Buccal. 

These  branches  are  distributed,  as  their  names  imply,  to  the  muscles  in  the 
maxillary  region. 

The  deep  temporal  branches,  two  in  number,  anterior  and  posterior,  each  occupy 
that  part  of  the  temporal  fossa  indicated  by  its  name.  Ascending  between  the 
Temporal  muscle  and  pericranium,  they  supply  that  muscle  and  anastomose  with 
the  middle  temporal  artery,  the  anterior  branch  communicating  with  the  lachrymal 
through  small  branches  which  perforate  the  malar  bone  and  great  wing  of  the 
sphenoid. 

The  pterygoid  branches,  irregular  in  their  number  and  origin,  supply  the 
Pterygoid  muscles. 

The  masseteric  is  a  small  branch  which  passes  outward,  above  the  sigmoid 
notch  of  the  lower  jaw,  to  the  deep  surface  of  the  Masseter.  It  supplies  that 
muscle,  and  anastomoses  with  the  masseteric  branches  of  the  facial  and  with  the 
transverse  facial  artery. 

The  buccal  is  a  small  branch  which  runs  obliquely  forward  between  the  Internal 
pterygoid  and  the  ramus  of  the  jaw,  to  the  outer  surface  of  the  Buccinator,  to 
which  i-t  is  distributed,  anastomosing  with  branches  of  the  facial  artery. 


B1E  TCHE8    OF    THE   EXTERNAL    CAROTID.  499 


BRANCHECtfflF    THE    THIRD    OR    SPHENO-MAXILLARY    PORTION. 

Alveolar.  ,  Vidian. 

Infra-orbital.  Pterygopalatine. 

Posterior  or  Descending  Palatine.  Naso-  or  Spheno-palatine. 

The  alveolar  or  posterior  dental  uranch.  is  given  off  from  the  internal  maxillary 
by  a  common  branch  with  the  infra-orbital,  and  just  as  the  trunk  of  the  vessel  is 
passing  into  the  spheno-maxillary  fossa.  Descending  upon  the  tuberosity  of  the 
superior  maxillary  bone,  it  divides  into  numerous  branches,  some  of  which  enter 
the  posterior  dental  canals,  to  supply  the  molar  and  bicuspid  teeth  and  the  lining 
of  the  antrum,  and  others  are  continued  forward  on  the  alveolar  process  to  supply 
the  gums. 

The  infra-orbital  appears,  from  its  direction,  to  be  the  continuation  of  the  trunk 
of  the  internal  maxillary.  It  arises  from  that  vessel  by  a  common  trunk  with  the 
preceding  branch,  and  runs  along  the  infra-orbital  canal  with  the  superior  maxil- 
lary nerve,  emerging  upon  the  face  at  the  infra-orbital  foramen,  beneath  the  Levator 
labii  superioris.  Whilst  contained  in  the  canal,  it  gives  oif  branches  which  ascend 
into  the  orbit,  and  assist  in  supplying  the  Inferior  rectus  and  Inferior  oblique 
muscles  and  the  lachrymal  gland.  Other  branches  {anterior  dental)  descend 
through  the  anterior  dental  canals  in  the  bone,  to  supply  the  mucous  membrane  of 
the  antrum  and  the  front  teeth  of  the  upper  jaw.  On  the  face,  some  branches  pass 
upward  to  the  inner  angle  of  the  orbit  and  the  lachrymal  sac,  anastomosing  with 
the  angular  branch  of  the  facial  artery  ;  other  branches  pass  inward  toward  the 
nose,  anastomosing  with  the  nasal  branch  of  the  ophthalmic ;  and  other  branches 
descend  beneath  the  Levator  labii  superioris,  and  anastomose  with  the  transverse 
facial  and  buccal  arteries. 

The  four  remaining  branches  arise  from  that  portion  of  the  internal  maxillary 
which  is  contained  in  the  spheno-maxillary  fossa. 

The  descending  palatine  descends  through  the  posterior  palatine  canal  with  the 
anterior  palatine  branch  of  Meckel's  ganglion,  and,  emerging  from  the  posterior 
palatine  foramen,  runs  forward  in  a  groove  on  the  inner  side  of  the  alveolar  border 
of  the  hard  palate  to  the  anterior  palatine  canal,  where  the  terminal  branch  of  the 
artery  passes  upward  through  the  foramen  of  Stenson  to  anastomose  with  the  naso- 
palatine artery.  Its  branches  are  distributed  to  the  gums,  the  mucous  membrane  of 
the  hard  palate,  and  the  palatine  glands.  Whilst  it  is  contained  in  the  palatine 
canal  it  gives  off  branches  which  descend  in  the  accessory  palatine  canals  to  supply 
the  soft  palate  and  tonsil,  anastomosing  with  the  ascending  palatine  artery. 

Surgical  Anatomy. — The  position  of  the  descending  palatine  artery  on  the  hard  palate 
should  be  borne  in  mind  in  performing  an  operation  for  the  closure  of  a  cleft  in  the  hard  palate, 
as  it  is  in  danger  of  being  wounded,  and  may  give  rise  to  formidable  hemorrhage.  In  one  case 
in  which  jt  was  wounded  it  was  necessary  to  plug  the  posterior  palatine  canal  in  order  to  arrest 
the  bleeding. 

The  Vidian  branch  passes  backward  along  the  Vidian  canal  with  the  Vidian 
nerve.  It  is  distributed  to  the  upper  part  of  the  pharynx  and  Eustachian  tube, 
sending  a  small  branch  into  the  tympanum,  which  anastomoses  with  the  other 
tympanic  arteries. 

The  pterygo-palatine  is  a  very  small  branch,  which  passes  backward  through 
the  pterygo-palatine  canal  with  the  pharyngeal  nerve,  and  is  distributed  to  the 
upper  part  of  the  pharynx  and  Eustachian  tube. 

The  spheno-palatine  passes  through  the  spheno-palatine  foramen  into  the 
cavity  of  the  nose,  at  the  back  part  of  the  superior  meatus,  and  divides  into 
two  branches  :  one  internal,  the  niso-palatine  or  artery  of  the  septum,  passes 
obliquely  downward  and  forward  along  the  septum  nasi,  supplies  the  mucous 
membrane,  and  anastomoses  in  front  with/  the  terminal  branch  of  the  descending 
palatine.  The  external  branches,  two  /Or  three  in  number,  supply  the  mucous 
membrane  covering  the  lateral  wall  of'/.ie  nose,  the  antrum,  and  the  ethmoid  and 
sphenoid  cells. 


Uf 


i 


500  THE   BLOOD- VASCULAR   SYSTfflf 

SURGICAL  ANATOMY  OF  THE  TRIANGLES  •  it  THE  NECK. 

The  student  having  considered  the  relative  anatomy  of  the  large  arteries  of  the 
neck  and  their  branches,  and  the  relations  they  bear  to  the  veins  and  nerves,  should 
now  examine  these  structures  collectively,  as  they  present  themselves  in  certain 
regions  of  the  neck,  in  each  of  which  important  operations  are  constantly  being 
performed. 

The  side  of  the  neck  presents  a  somewhat  quadrilateral  outline,  limited,  above, 
by  the  lower  border  of  the  body  of  the  jaw,  and  an  imaginary  line  extending  from 
the  angle  of  the  jaw  to  the  mastoid  process  ;  below,  by  the  prominent  upper  border 
of  the  clavicle  ;  in  front,  by  the  median  line  of  the  neck ;  behind,  by  the  anterior 
margin  of  the  Trapezius  muscle.  This  space  is  subdivided  into  two  large  triangles 
by  the  Sterno-mastoid  muscle,  which  passes  obliquely  across  the  neck,  from  the 
sternum  and  clavicle  below  to  the  mastoid  process  above.  The  triangular  space 
in  front  of  this  muscle  is  called  the  anterior  triangle  ;  and  that  behind  it,  the 
posterior  triangle. 

Anterior  Triangle  of  the  Neck. 

The  anterior  triangle  is  bounded,  in  front,  by  a  line  extending  from  the  chin 
to  the  sternum ;  behind,  by  the  anterior  margin  of  the  Sterno-mastoid ;  its  base, 
directed  upward,  is  formed  by  the  lower  border  of  the  body  of  the  jaw  and  a  line 
extending  from  the  angle  of  the  jaw  to  the  mastoid  process ;  its  apex  is  below,  at 
the  sternum.  This  space  is  subdivided  into  three  smaller  triangles  by  the  Digastric 
muscle  above  and  the  anterior  belly  of  the  Omo-hyoid  below.  These  smaller 
triangles  are  named,  from  below  upward,  the  inferior  carotid,  the  superior  carotid, 
and  the  submaxillary  triangle. 

The  Inferior  Carotid  Triangle  is  bounded,  in  front,  by  the  median  line  of  the 
neck  ;  behind,  by  the  anterior  margin  of  the  Sterno-mastoid ;  above,  by  the  anterior 
belly  of  the  Omo-hyoid ;  and  is  covered  by  the  integument,  superficial  fascia, 
Platysma,  and  deep  fascia,  ramifying  between  which  are  some  of  the  descending 
branches  of  the  superficial  cervical  plexus.  Beneath  these  superficial  structures 
are  the  Sterno-hyoid  and  Sterno-thyroid  muscles,  which,  together  with  the  anter- 
ior margin  of  the  Sterno-mastoid,  conceal  the  lower  part  of  the' common  carotid 
artery.1 

This  vessel  is  enclosed  within  its  sheath,  together  with  the  internal  jugular 
vein  and  pneumogastric  nerve :  the  vein  lying  on  the  outer  side  of  the  artery  on 
the  right  side  of  the  neck,  but  overlapping  it  below  on  the  left  side  ;  the  nerve 
lying  between  the  artery  and  vein,  on  a  plane  posterior  to  both.  In  front  of  the 
sheath  are  a  few  filaments  descending  from  the  loop  of  communication  between  the 
descendens  and  communicans  hypoglossi ;  behind  the  sheath  are  seen  the  inferior 
thyroid  artery,  the  recurrent  laryngeal  nerve,  and  the  sympathetic  nerve ;  and  on 
its  inner  side,  the  trachea,  the  thyroid  gland — much  more  prominent  in  the  female 
than  in  the  male — and  the  lower  part  of  the  larynx.  By  cutting  into  the  upper 
part  of  this  space  and  slightly  displacing  the  Sterno-mastoid  muscle  the  common 
carotid  artery  may  be  tied  below  the  Omo-hyoid  muscle. 

The  Superior  Carotid  Triangle  is  bounded,  behind,  by  the  Sterno-mastoid ; 
below,  by  the  anterior  belly  of  the  (  mo-hyoid ;  and  above,  by  the  Posterior  belly 
of  the  Digastric  muscle.  It  is  covered  by  the  integument,  superficial  fascia, 
Platysma,  and  deep  fascia,  ramifying  between  which  are  branches  of  the  facial 
and  superficial  cervical  nerves.  Its  flo>.r  is  formed  by  parts  of  the  Thyro-hyoid^ 
Hyo-glossus,  and  the  inferior  and  middle  Constrictor  muscles  of  the  pharynx. 
This  space,  when  dissected,  is  seen  to  cont  in  the  upper  part  of  the  common  carotid 

1  Therefore  the  common  carotid  artery  and  ntei  aal  jugular  vein  are  not,  strictly  speaking,  con- 
tained in  this  triangle,  since  they  are  covert' 1  by  the  ^terno-mastoid  muscle;  that  is  to  say,  lie  behind 
the  anterior  border  of  that  muscle,  which  forms  ^e  posterior  border  of  the  triangle.     But  as  they  lie 


very  close  to  the  structures  which  are  really  co^tauied  in  the  triangle,  and  whose  position  it  is 
essential  to  remember  in  operating  on  tbl6  pi»rt  01  th:  artery,  it  has  seemed  expedient  to  study  the 
relations  of  all  these  parts  together. 


U,  \ 


\ 

THE  POSTERIOR    7JRIA.NGLE    OE    THE   NECK.  501 

artery,  which  bifurcates  opposite  the  upper  border  of  the  thyrokl  cartilage  into  the 
external  and  internal  carotid.  Th<s«>  vessels  are  occasionally  somewhat  concealed 
from  view  by  the  anterior  margin  of  the  Sterno-mastoid  muscle,  which  overlaps 
them.  The  external  and  internal  carotids  lie  side  by  side,  the  external  being  the 
more  anterior  of  the  two.  The  following  branches  of  the  external  carotid  are 
also  met  with  in  this  space:  the  superior  thyroid,  running  forward  and  downward  ; 
the  lingual,  directly  forward ;  the  facial,  forward  and  upward ;  the  occipital,  back- 
ward ;  and  the  ascending  pharyngeal  directly  upward  on  the  inner  side  of  the 
internal  carotid.  The  veins  met  with  are:  the  internal  jugular,  which  lies  on  the 
outer  side  of  the  common  and  internal  carotid  arteries,  and  veins  corresponding  to 
the  above-mentioned  branches  of  the  external  carotid— viz.,  the  superior  thyroid, 
the  lingual,  facial,  ascending  pharyngeal,  and  sometimes  the  occipital,  all  of 
which  accompany  their  corresponding  arteries  and  terminate  in  the  internal  jugula; 
The  nerves  in  this  space  are  the  following :  In  front  of  the  sheath  of  the  co 
carotid  is  the  descendens  hypoglossi.  The  hypoglossal  nerve  crosses  b 
internal  and  external  carotids  above,  curving  round  the  occipital  artery 
origin.  Within  the  sheath,  between  the  artery  and  vein,  and  behind  both 
"pneumogastric  nerve ;  behind  the  sheath,  the  sympathetic.  On  the  oute 
the  vessels  the  spinal  accessory  nerve  runs  for  a  short  distance  before^ 
the  Sterno-mastoid  muscle;  and  on  the  inner  side  of  the  external  carotid,  just 
below  the  hyoid  bone,  may  be  seen  the  internal  laryngeal  nerve ;  and,  still  more 
inferiorly,  the  external  laryngeal  nerve.  The  upper  part  of  the  larynx  and  lower 
part  of  the  pharynx  are  also  found  in  the  front  part  of  this  space. 

The  Submaxillary  Triangle^eorresponds  to  the  part  of  the  neck   immediately 
beneath  the  body  of  the  jaw.      It  is  bounded,  above,  by  the  lower  border  of  the 
body  of  the  jaw  and  a  line  drawn  from  its  angle  to  the  mastoid  process ;  below, 
by  the  posterior  belly  of  the  Digastric   and  Stylo-hyoid  muscles  ;  in  front,  by  the 
anterior  belly  of  the  Digastric.    It  is  covered  by  the  integument,  superficial  fascia, 
Platysma,  and  deep  fascia,  ramifying  between  which  are  branches  of  the  facial  and 
ascending  filaments  of  the  superficial  cervical  nerves.     Its  floor  is  formed  by  the 
Mylo-hyoid  and  Hyo-glossus  muscles.      This  space  contains,  in  front,  the  subm? 
illary  gland,  superficial  to  which  is  the  facial  vein,  while  imbedded  in  it 
facial  artery  and  its  glandular  branches ;   beneath  this  gland,  on  the  surf? 
Mylo-hyoid  muscle,  are  the  submental  artery  and  the  mylo-hyoid  artenjnal  in  the 
The  posterior  part  of  this  triangle  is  separated  from  the  anterior  pape   then  curves 
maxillary  ligament :  it  contains  the  external  carotid  artery;. _»j^Cer  the  cavity  of 
the  substance  of  the  parotid,  gland :  this  vessel  hss.     In  this  canal  the  artery  lies 
to,  the  internal  carotid,  being  crossed  by  +1  from  the  latter  cavity  it  is  separated 
course  the  posterior  auricular,  temporal,. m  in  the  young  subject,  and  often  ab- 
deeply  are  the  internal  carotid,  the  m4  is  separated  from  the  G-asserian  ganglion 
nerve,  separated  from  the  externals  the  floor  of  the  fossa  for  the  ganglion  and  the 
geus  muscles  and  the  glosso-phar  the  canal.      Frequently  this  bony  plate  is  more 

ganglion  is   separated  from  the  artery  by  fibrous 

rated  from  the  bony  wall  of  the  carotid  canal  by  a 

.Postertc]  js  surrounded  by  filaments  of  the  carotid  plexus, 

The  posterior  triangle   ismch  of  the  suPerio'r  cervical  ganglion  of  the  sympa- 
behind,   by  the  anterior  mft.    ,       ',  .,  .  -    .'.  _  . 

middle  third  of  the  clavi  mternal  carotid  artery  m  this  part  of  its  course  is 
about  an  inch  above  the  r'  of  th*  dura  ^  mater  forming  the  cavernous  sinus,  but 
divides  it  unequally  mto'fne  °{  ^e  !mu?-  X*  f  ^t  ascends  to  the  posterior 
triangle  '  torwarc*   "J  tne  sic*e  of  the  body  of  the  sphenoid  bone, 

Th      Occipital,    the  K°n  the  ^ner  sj.de  °f  the  anter^or  <***<*&  P^ess,  and 
tormmg  the  roof  of  the  sinus.     In  this  part  of  its  course 

1  Th.  remark  will  nts  °f  the  sympathetic  nerve,  and  has  in  relation  with  it 

Th  numerated  ase. 

11  'ic\for.m  paying  perforated  the  dura  mater,  on  the  inner  side  of  the 

i  ose  relation  to      ,       V    L  .  .  .. 

ions  on  this  gla>  tlae  internal  carotid  passes  between  the  second  and  third 


502  THE  BLOOD-VASCULAR  SYSTEM. 

front,  by  the  Sterno-mastoid ;  behind,  by  the  Trapezius;  below,  by  the  Omo- 
hyoid. Its  floor  is  formed  from  above  downward  by  the  Splenitis,  Levator  anguli 
scapulae,  and  the  middle  and  posterior  Scaleni  muscles.  It  is  covered  by  the 
integument,  the^Platysma  below,  the  superficial  and  deep  fasciae  ;  the  spinal  acces- 
sory nerve  is  directed  obliquely  across  the  space  from  the  Sterno-mastoid, 
which  it  pierces,  to  the  under  surface  of  the  Trapezius :  below,  the  descending 
branches  of  the  cervical  plexus  and  the  transversalis  colli  artery  and  vein  cross 
the  space.  A  chain  of  lymphatic  glands  is  also  found  running  along  the  pos- 
terior border  of  the  Sterno-mastoid,  from  the  mastoid  process  to  the  root  of  the 
neck. 

The  Subclavian,  the  smaller  of  the  two  posterior  triangles,  is  bounded,  above, 
by  the  posterior  belly  of  the  Omo-hyoid  ;  below,  by  the  clavicle,  its  base,  directed 
forward,  being  formed  by  the  Sterno-mastoid.     The  size  of  the  subclavian  trian- 
gle varies  according  to  the  extent  of  attachment  of  the  clavicular  portion  of  the 
Sterno-mastoid  and  Trapezius  muscles,  and  also  according  to  the  height  at  which 
tLe  Omo-hyoid  crosses  the  neck  above  the  clavicle.     Its  height  also  varies  much 
according  to  the  position  of  the  arm,  being  much  diminished  by  raising  the  limb, 
on  account  of  the  ascent  of  the  clavicle,  and  increased  by  drawing  the  arm  down- 
Avard,  when  that  bone  is  depressed.     This  space  is  covered  by  the  integument, 
the  Platysma,   the   superficial    and   deep   fascise,   and   crossed  by  the   descending 
branches  of  the  cervical  plexus.      Just  above  the  level  of  the  clavicle  the  third 
portion  of  the  subclavian  artery  curves  outward  and  downward  from  the  outer 
margin  of  the  Scalenus  anticus,  across  the  first  rib,  to  the  axilla.     Sometimes  this 
vessel  rises  as  high  as  an  inch  and  a  half  above  the  clavicle,  or  to  any  point  inter- 
mediate between  this  and  its  usual  level.      Occasionally  it  passes  in  front  of  the 
Scalenus  anticus  or  pierces  the  fibres  of  that  muscle.     The  subclavian  vein  lies 
behind  the  clavicle,  and  is  usually  not  seen  in  this  space ;   but  it  occasionally  rises 
as  high  up  as  the  artery,  and  has  even  been  seen  to  pass  with  that  vessel  behind 
the  Scalenus  anticus.     The  brachial  plexus  of  nerves  lies  above  the  artery,  and 
*'n    close    contact    with    it.       Passing    transversely    behind    the    clavicle    are    the 
br^rascapular  vessels,  and  traversing  its  upper  angle  in  the  same  direction,  the 
arethe'salis  colli  artery  and  vein.     The  external  jugular  vein  runs  vertically 
ior  margl  behind  the  posterior  border  of  the  Sterno-mastoid,  to  terminate  in  the 
artery.1        'ein  >  it  receives  the  transverse  cervical  and  suprascapular  veins,  which 
This  vesseivm  a  plexus  in  front  of  the  artery,  and  a  small  vein  which  crosses 
vein  and  pneumonitis  cephalic.      The  small  nerve  to  the  Subclayius  muscle  also 
the  right  side  of  °the  neck,  but  (Addle.     A  lymphatic  glandTTs  also  found  in  the 
lying  between  the  artery  and  vein,  ofc  rib  with  the  first  digitation  of  the  Serratus 
sheath  are  a  few  filaments  descending  fix 
descendens  and  communicans  hypoglossi ;    fc+id  Artery. 
thyroid  artery,  the  recurrent  laryngeal  nerve,  a^rior         .  of  the  brai]^  the 
its  inner  side,  the  trachea,  the  thyroid  gland— muP()rehead  and  nQge      Itg  gize  in 
than  in  the  male— and  the  lower  part  of  the  laryi-hou  h  in  the  cMld  it  ig  la 
part  of  this  space  and  slightly  displacing  the  Stenof  curvatures  that  it  preSente 
carotid  artery  may  be  tied  below  the  Omo-hyoid  m         or  twQ  flexm.eg  near  the 
The   Superior   Carotid   Triangle   is  bounded,   beh  ^  ^^  and  &{        ^  gide 
below,  by  the  anterior  belly  of  the  C  mo-hyoid  ;  and      curyature  wnich  Resembles 
of  the   Digastric   muscle.     It  is  covered   by  the ;  int  babl    diminish  the 

Platysma,  and  deep  fascia,  ramifying  between  which    ^  of  Fsurfiw/over  which  it 
and  superficial  cervical  nerves.     Its  floe r  is  tormed  by^  from  frictjon 

Hvo-fflossus,  and  the  inferior  and  middle   Constrictor ,  .  ,  .      , 

ujfu  giussua,  auu  me  1  it  may  be  conveniently 

This  space,  when  dissected,  is  seen  to  cont  un  the  upper  £   &^  cerebral. 

1  Therefore  the  common  carotid  artery  and  'nteiaal  jugular  vein  commences  at  the  bifur- 


cations of  all  these  parts  together. 


THE   INTERNAL    CAROTID    ARTERY.  503 

carotid  triangle,  and  lying  on  the  same  level  as  the  external  carotid,  but  behind 
that  artery  overlapped  by  the  Sterno-mastoid  and  covered  by  the  deep  fascia, 
Platysma,  and  integument :  it  then  passes  beneath  the  parotid  gland,  being  crossed 
by  the  hypoglossal  nerve,  the  Digastric  and  Stylorhyoid  muscles,  and  the  occipital 
and  posterior  auricular  arteries.  Higher  up.^it  is  separated  from  the  external 
carotid  by  the  Stylo-glossus  and  Stylo-pharyngeus  muscles,  the  glossopharyngeal 
nerve,  and  pharyngeal  branch  of  the  pneumogastric.  It  is  in  relation,  behind,  with 
the  Rectus  capitis  anticus  major,  the  superior  cervical  ganglion  of  the  sympathetic, 
and  superior  laryngeal  nerve ;  externally,  with  the  internal  jugular  vein  and  pneu- 
mogastric nerve,  the  nerve  lying  on  a  plane  posterior  to  the  artery  ;  internally, 
with  the  pharynx,  tonsil,  the  superior  laryngeal  nerve,  and  ascending  pharyngeal 
artery.  At  the  base  of  the  skull  the  glosso-pharyngeal,  vagus,  spinal  accessory, 
and  hypoglossal  nerves  lie  between  the  artery  and  the  internal  jugular  vein. 

Plan  of  the  Relations  of  the   Internal   Carotid  Artery  in  the  Neck. 

In  front. 

Skin,  superficial  anil  deep  fasciae. 

Platysma.        <-        ~j 

Sterno-mastoid.    .    ' 

Occipital  and  posterior  auricular  arteries. 

Hypoglossal  nerve. 

Parotid  gland. 

Stylo-glossus  and  Stylo-pharyngeus  muscles. 

Grlosso-pharyngeal  nerve. 

Pharyngeal  branch  of  the  pneumogastric. 

/  ""X  Internally. 

Externally.  /    x  .  \ 

f      CaS      |  Pharynx. 

Internal  jugular  vein.  I       Artery.  Superior  laryngeal  nerve. 

Pneumogastric  nerve.  \  /  Ascending  pharyngeal  artery. 

X^^^  Tonsil. 

Behind. 
Rectus  capitis  anticus  major. 
Sympathetic. 
Superior  laryngeal  nerve. 

Petrous  Portion. — When  the  internal  carotid  artery  enters  the  canal  in  the 
petrous  portion  of  the  temporal  bone,  it  first  ascends  a  short  distance,  then  curves 
forward  and  inward,  and  again  ascends  as  it  leaves  the  canal  to  enter  the  cavity  of 
the  skull  between  the  lingula  and  petrosal  process.  In  this  canal  the  artery  lies 
at  first  in  front  of  the  cochlea  and  tympanum  ;  from  the  latter  cavity  it  is  separated 
by  a  thin,  bony  lamella,  which  is  cribriform  in  the  young  subject,  and  often  ab- 
sorbed in  old  age.  Farther  forward  it  is  separated  from  the  Grasserian  ganglion 
by  a  thin  plate  of  bone,  which  forms  the  floor  of  the  fossa  for  the  ganglion  and  the 
roof  of  the  horizontal  portion  of  the  canal.  Frequently  this  bony  plate  is  more 
or  less  deficient,  and  then  the  ganglion  is  separated  from  the  artery  by  fibrous 
membrane.  The  artery  is  separated  from  the  bony  wall  of  the  carotid  canal  by  a 
prolongation  of  dura  mater,  and  is  surrounded  by  filaments  of  the  carotid  plexus, 
derived  from  the  ascending  branch  of  the  superior  cervical  ganglion  of  the  sympa- 
thetic, and  a  number  of  small  veins. 

Cavernous  Portion. — The  internal  carotid  artery  in  this  part  of  its  course  is 
situated  between  the  layers  of  the  dura  mater  forming  the  cavernous  sinus,  but 
covered  by  the  lining  membrane  of  the  sinus.  It  at  first  ascends  to  the  posterior 
clinoid  process,  then  passes  forward  by  the  side  of  the  body  of  the  sphenoid  bone, 
and  again  curves  upward  on  the  inner  side  of  the  anterior  clinoid  process,  and 
perforates  the  dura  mater,  forming  the  roof  of  the  sinus.  In  this  part  of  its  course 
it  is  surrounded  by  filaments  of  the  sympathetic  nerve,  and  has  in  relation  with  it 
externally  the  sixth  nerve. 

Cerebral  Portion. — Having  perforated  the  dura  mater,  on  the  inner  side  of  the 
anterior  clinoid  process,  the  internal  carotid  passes  between  the  second  and  third 


504 


THE   BLOOD-VASCULAR    SYSTEM. 


cranial  nerves  to  the  anterior  perforated  spot  at  the  inner  extremity  of  the  fissure 
of  Sylvius,  where  it  gives  off  its  terminal  or  cerebral  branches.  This  portion 
of  the  artery  has  the  optic  nerve  on  its  inner  side,  and  the  third  nerve  externally. 

Peculiarities —The  length  of  the  internal  carotid  varies  according  to  the  length  of  the 
neck,  and  also  according  to  the  point  of  bifurcation  of  the  common  carotid.     Its  origin  some- 


lst  Aortic  lWeTC' 


Fig.  289.— The  internal  carotid  and  vertebral  arteries.    Right  side. 

times  takes  place  from  the  arch  of  the  aorta ;  in  such  rare  instances  this  vessel  has  been  found 
to  be  placed  nearer  the  middle  line  of  the  neck  than  the  external  carotid  as  far  upwaid aa  the 
larynx,  when  the  latter  vessel  crossed  the  internal  carotid.  The  course  of  the  vessel,  instead  of 
being  straight,  may  be  very  tortuous.  A  few  instances  are  recorded  in  which  this  vessel  was 
altogether  absent-  in  one  of  these  the  common  carotid  passed  up  the  neck  and  gave  off  the 
usual  branches  of  the  external  carotid,  the  cranial  portion  of  the  internal  carotid  being  replaced 
by  Two  branches  of  the  internal  maxillary,  which  entered  the  skull  through  the  foramen  rotundum 
and  ovale  and  joined  to  form  a  single  vessel. 


THE  INTERNAL    CAROTID    ARTERY.  505 

Surgical  Anatomy. — The  cervical  part  of  the  internal  carotid  is  very  rarely  wounded. 
Mr.  Cripps,  in  an  interesting  paper  in  the  Medico-  Ghirurgical  Transactions,  compares  the  rare- 
ness of  a  wound  of  the  internal  carotid  with  one  of  the  external  or  its  branches.  It  is,  however, 
sometimes  injured  by  a  stab  or  gunshot  wound  in  the  neck,  or  even  occasionally  by  a  stab  from 
within  the  mouth,  as  when  a  person  receives  a  thrust  from  the  end  of  a.pai-asol  or  falls  down 
with  a  tobacco-pipe  in  his  mouth.  The  relation  of  the  internal  carotid  with  the  tonsil  should  be 
especially  remembered,  as  instances  have  occurred  in  which  the  artery  has  been  wounded  during 
the  operation  of  scarifying  the  tonsil,  and  fatal  haemorrhage  has  supervened.  The  indications 
for  ligature  are  wounds,  when  the  vessel  should  be  exposed  by  a  careful  dissection  and  tied 
above  and  below  the  bleeding  point;  and  aneurism,  which  if  non-traumatic  may  be  treated  by 
ligature  of  the  common  carotid,  but  if  traumatic  in  origin  by  exposing  the  sac  and  tying  the 
vessel  above  and  below.  The  incision  for  ligature  of  the  cervical  portion  of  the  internal  carotid 
should  be  made  along  the  anterior  border  of  the  Sterno-mastoid,  from  the  angle  of  the  jaw  to 
the  upper  border  of  the  thyroid  cartilage.  The  superficial  structures  being  divided  and  the 
Sterno-mastoid  defined  and  drawn  outward,  the  cellular  tissue  must  be  carefully  separated  and 
the  posterior  belly  of  the  Digastric  and  hypoglossal  nerve  sought  for  as  guides  to  the  vessel. 
When  the  artery  is  found  the  external  carotid  should  be  drawn  inward  and  the  Digastric  muscles 
upward,  and  the  aneurism  needle  passed  from  without  inward. 

The  branches  given  off  from  the  internal  carotid  are — 

From  the  Petrous  portion     .     Tympanic  (internal  or  deep). 

(  Arterige  Receptaculi. 
From  the  Cavernous  portion    <  Anterior  Meningeal. 

(  Ophthalmic. 

f  Anterior  Cerebral. 

xr        ±1     n      t     7        .•  I  Middle  Cerebral. 

From  the  Cerebral  portion       <  ^  „  .     , . 

r  Jrostenor  Communicating. 

(^Anterior  Choroid. 

The  cervical  portion  of  the  internal  carotid  gives  off  no  branches. 

The  tympanic  is  a  small  branch  which  enters  the  cavity  of  the  tympanum 
through  a  minute  foramen  in  the  carotid  canal,  and  anastomoses  with  the  tympanic 
branch  of  the  internal  maxillary,  and  with  the  stylo-mastoid  artery. 

The  arterise  receptaculi  are  numerous  small  vessels,  derived  from  the  internal 
carotid  in  the  cavernous  sinus ;  they  supply  the  pituitary  body,  the  Gasserian 
ganglion,  and  the  walls  of  the  cavernous  and  inferior  petrosal  sinuses.  Some  of 
these  branches  anastomose  with  branches  of  the  middle  meningeal. 

The  anterior  meningeal  is  a  small  branch  which  passes  over  the  lesser  wing  of 
the  sphenoid  to  supply  the  dura  mater  of  the  anterior  fossa ;  it  anastomoses  with 
the  meningeal  branch  from  the  posterior  ethmoidal  artery. 

The  Ophthalmic  Artery  arises  from  the  internal  carotid,  just  as  that  vessel 
is  emerging  from  the  cavernous  sinus,  on  the  inner  side  of  the  anterior  clinoid 
process,  and  enters  the  orbit  through  the  optic  foramen,  below  and  on  the  outer 
side  of  the  optic  nerve.  It  then  passes  over  the  nerve  to  the  inner  wall  of  the 
orbit,  and  thence  horizontally  forward,  beneath  the  lower  border  of  the  Superior 
oblique  muscle,  to  a  point  behind  the  internal  angular  process  of  the  frontal  bone, 
where  it  divides  into  two  terminal  branches,  the  frontal  and  nasal.  As  the  artery 
crosses  the  optic  nerve  it  is  accompanied  by  the  nasal  nerve,  and  is  separated  from 
the  frontal  nerve  by  the  Rectus  superior  and  Levator  palpebrce  superioris  muscles. 

Branches. — The  branches  of  this  vessel  may  be  divided  into  an  orbital  group, 
which  are  distributed  to  the  orbit  .and  surrounding  parts,  and  an  ocular  group, 
which  supply  the  muscles  and  globe  of  the  eye : 

Orbital  Group.  Ocular  Group. 

Lachrymal.  Short  Ciliary. 

Supra-orbital.  Long  Ciliary. 

PobI  thmoidal.  Anterior  Ciliary. 

Ant<  i  hmoidal.  Arteria  Centralis  Retinae. 

I  lpebral.  Muscular. 

F 


506 


THE   BLOOD-VASCULAR    SYSTEM. 


The  lachrymal  is  one  of  the  largest  branches  derived  from  the  ophthalmic, 
arising  close  to  the  optic  foramen  ;  not  infrequently  it  is  given  off  from  the  artery 
before  it  enters  the  orbit.  It  accompanies  the  lachrymal  nerve  along  the  upper 
border  of  the  External  rectus  muscle,  and  is  distributed  to  the  lachrymal  gland. 
Its  terminal  branches,  escaping  from  the  gland,  are  distributed  to  the  eyelids  and 
conjunctiva:  of  those  supplying  the  eyelids,  two  are  of  considerable  size  and  are 
named   the  external  palpebral ;  they  run  inward   in   the  upper   and  lower  lids 


Nasal.        Palpebral. 


Supra-orbital. 


Anterior  ethmoidal. 


Posterior  ethmoidal. 


Temporal  branches 
of  lachrymal. 


Muscular. 


Ophthalmic. 


Internal  carotid. 


Fig.  290.— The  ophthalmic  artery  and  its  branches,  the  roof  of  the  orbit  having  been  removed. 


respectively,  and  anastomose  with  the  internal  palpebral  arteries,  forming  an 
arterial  circle  in  this  situation.  The  lachrymal  artery  gives  off  one  or  two  malar 
branches,  one  of  which  passes  through  a  foramen  in  the  malar  bone,  to  reach  the 
temporal  fossa,  and  anastomoses  with  the  deep  temporal  arteries  ;  the  other  appears 
on  the  cheek  through  the  malar  foramen,  and  anastomoses  with  the  transverse 
facial.  A  branch  is  also  sent  backward  through  the  sphenoidal  fissure  to  the  dura 
mater,  which  anastomoses  with  a  branch  of  the  middle  meningeal  artery. 

Peculiarities.— The  lachrymal  artery  is  sometimes  derived  from  one  of  the  anterior  branches 
of  the  middle  meningeal  artery. 

The  supra-orbital  artery  arises  from  the  ophthalmic  as  that  vessel  is  crossing 
over  the  optic  nerve.  Ascending  so  as  to  arise  above  all  the  muscles  of  the  orbit, 
it  passes  forward,  with  the  supra-orbital  nerve,  between  the  periosteum  and 
Levator  palpebrae ;  and,  passing  through  the  supra-orbital  foramen,  divides  into  a 
superficial  and  deep  branch,  which  supply  the  integument,  the  muscles,  and  the 
pericranium  of  the  forehead,  anastomosing  with  the  frontal,  the  anterior  branch 
of  the  temporal,  and  the  artery  of  the  opposite  side.  This  artery  in  the  orbit 
supplies  the  Superior  rectus  and  the  Levator  palpebrse,  and  sends  a  branch 
inward,  across  the  pulley  of  the  Superior  oblique  muscle,  to  supply  the  parts  at  the 
inner  canthus.  At  the  supra-orbital  foramen  it  frequently  transmits  a  branch  to 
the  diploe. 

The   ethmoidal  branches   are   two   in   number — posterior  and  anterior.      The 


BRANCHES    OF    THE  INTERNAL    CAROTID. 


507 


former,  which  is  the  smaller,  passes  through  the  posterior  ethmoidal  foramen, 
supplies  the  posterior  ethmoidal  cells,  and,  entering  the  cranium,  gives  off  a 
meningeal  branch,  which  supplies  the  adjacent  dura  mater,  and  nasal  branches 
which  descend  into  the  nose  through  apertures  in  the  cribriform  plate,  anasto- 
mosing with  branches  of  the  spheno-palatine.  The  anterior  ethmoidal  artery 
accompanies  the  nasal  nerve  through  the  anterior  ethmoidal  foramen,  supplies  the 


Fig.  291.— The  arter 
removed. 


ise  of  the  brain.    The  right  half  of  the  cerebellum  and  pons  have  been 


N.B. — It  will  b  hat  in  the  illustration  the  two  anterior  cerebral  arteries  have  been 

drawn  at  a  consiclera  ce  from  each  other :  this  makes  the  anterior  communicating  artery 

appear  very  much  loi  it  really  is. 


508 


THE  BLOOD-VASCULAR   SYSTEM. 


anterior  ethmoidal  cells  and  frontal  sinuses,  and,  entering  the  cranium,  gives  off 
a  meningeal  branch,  which  supplies  the  adjacent  dura  mater  and  nasal  branches, 
which  descend  into  the  nose,  through  the  slit  by  the  side  of  the  crista  galli,  and, 
running  along  the  groove  on  the  under  surface  of  the  nasal  bone,  supply  the  skin 
of  the  nose. 

The  palpebral  arteries,  two  in  number,  superior  and  inferior,  arise  from  the 
ophthalmic,  opposite  the  pulley  of  the  Superior  oblique  muscle ;  they  leave  the 
orbit  to  encircle  the  eyelids  near  their  free  margin,  forming  a  superior  and  an 
inferior  arch,  which  lie  between  the  Orbicularis  muscle  and  tarsal  plates ;  the 
superior  palpebral  inosculating  at  the  outer  angle  of  the  orbit  with  the  orbital 
branch  of  the  temporal  artery,  and  with  the  upper  of  the  two  external  palpebral 
branches  from  the  lachrymal  artery^ — the  inferior  palpebral  inosculating,  at  the 
outer  angle  of  the  orbit,  with  the  lower  of  the  two  external  palpebral  branches 
from  the  lachrymal  and  with  the  transverse  facial  arteries,  and  at  the  inner  side 
of  the  lid  with  a  branch  from  the  angular  artery.  From  this  last  anastomosis  a 
branch  passes  to  the  nasal  duct,  ramifying  in  its  mucous  membrane,  as  far  as  the 
inferior  meatus. 


Fissure  of 
Rolando 


Middle 
Occipital 
Fissii.re^/'/-*  X 

o^  I 

Fig.  292.— Vascular  area  of  the  upper  surface  of  the  cerebrum.  (After  Duret.)  I.  The  part  supplied  by  the 
external  and  inferior  frontal  artery.  II.  The  part  supplied  by  the  ascending  frontal.  III.  The  part  supplied  < 
by  the  ascending  parietal.    IV.  The  part  supplied  by  the  parieto-sphenoidal  artery. 


The  frontal  artery,  one  of  the  terminal  branches  of  the  ophthalmic,  passes  from 
the  orbit  at  its  inner  angle,  and,  ascending  on  the  forehead,  supplies  the  integument, 
muscles,  and  pericranium,  anastomosing  with  the  supraorbital  artery  and  with  the 
artery  of  the  opposite  side. 

The  nasal  artery,  the  other  terminal  branch  of  the  ophthalmic,  emerges  from 
the  orbit  above  the  tendo  oculi,  and,  after  giving  a  branch  to  the  upper  part  of 
the  lachrymal  sac,  divides  into  two  branches,  one  of  which  crosses  the  root  of 
the  nose,  the  transverse  nasal,  and   anastomoses  with   the  angular   artery ;    the 


BRANCHES    OF    THE   INTERNAL    CAROTID. 


509 


other,  the  dorsalis  nasi,  runs  along  the  dorsum  of  the  nose,  supplies  its  outer 
surface,  and  anastomoses  with  the  artery  of  the  opposite  side  and  with  the  lateral 
nasal  branch  of  the  facial. 

The  ciliary  arteries  are  divisible  into  three  groups,  the  short,  long,  and 
anterior.  The  short  ciliary  arteries,  from  six  to  twelve  in  number,  arise  from  the 
ophthalmic  or  some  of  its  branches ;  they  surround  the  optic  nerve  as  they  pass 
forward  to  the  posterior  part  of  the  eyeball,  pierce  the  sclerotic  coat  around  the 
entrance  of  the  nerve,  and  supply  the  choroid  coat  and  ciliary  processes.  The 
long  ciliary  arteries,  two  in  number,  pierce  the  posterior  part  of  the  sclerotic  at 
some  little  distance  from  the  optic  nerve,  and  run  forward,  along  each  side  of 
the  eyeball,  between  the  sclerotic  and  choroid,  to  the  ciliary  muscle,  where  they 
divide  into  two  branches ;  these  form  an  arterial  circle,  the  circulus  major,  around 
the  circumference  of  the  iris,  from  which  numerous  radiating  branches  pass 
forward,  in  its  substance,  to  its  free  margin,  where  they  form  a  second  arterial 
circle,  the  circulus  minor,  around  its  pupillary  margin.  The  anterior  ciliary 
arteries  are  derived  from  the  muscular   branches  ;   they  pass  to  the  front  of  the 


Fissure  of  Rolando 


Fig.  293.— Vascular  area  of  the  internal  surface  of  the  cerebrum.  (After  Duret.)  I.  The  part  supplied  by  the 
anterior  and  internal  frontal.  II.  The  part  supplied  by  the  middle  and  internal  frontal.  III.  The  partsup- 
plied  by  the  posterior  and  internal  frontal.  IV.  The  part  supplied  by  the  posterior  temporal :  and  V.  The  part 
supplied  by  the  occipital,  both  terminal  branches  of  the  posterior  cerebral. 


eyeball  in  company  with  the  tendons  of  the  Recti  muscles,  form  a  vascular  zone 
beneath  the  conjunctiva,  and  then  pierce  the  sclerotic  a  short  distance  from  the 
cornea  and  terminate  in  the  circulus  major  of  the  iris. 

The  arteria  centralis  retinae  is  the  first  and  one  of  the  smallest  branches  of 
the  ophthalmic  artery.  It  runs  for  a  short  distance  within  the  dural  sheath  of 
the  nerve,  but  about  half  an  inch  behind  the  eyeball  it  pierces  the  optic  nerve 
obliquely,  and  runs  forward  in  the  centre  of  its  substance,  and  enters  the  globe 
of  the  eye  through  the  porus  opticus.  Its  mode  of  distribution  will  be  described 
in  the  account  of  the  anatomy  of  the  eye. 

The  muscular  branches,  two  in  number,  superior  and  inferior,  frequently  spring 
from  a  common  trunk.  The  superior,  the  smaller,  often  wanting,  supplies  the 
Levator  palpebne,  Superior  rectus,  and  Superior  oblique.  The  inferior,  more 
constant  in  its  existence,  passes  forward,  between  the  optic  nerve  and  Inferior 
rectus,  and  is  distributed  to  the  External,  Internal,  and  Inferior  recti,  and  Inferior 
oblique.  This  vessel  gives  off  most  of  the  anterior  ciliary  arteries.  Additional 
muscular  branches  are  given  off  from  the  lachrymal  and  supra-orbital  arteries  or 
from  the  ophthalmic  itself. 


510 


THE   BLOOD-VASCULAR   SYSTEM. 


The  anterior  cerebral  arises  froni  the  internal  carotid  at  the  inner  extremity 
of  the  fissure  of  Sylvius.  It  passes  forward  and  inward  across  the  anterior  perfo- 
rated space,  above  the  optic  nerve,  to  the  corurnencenient  of  the  great  longitudinal 
fissure.  Here  it  conies  into  close  relationship  with  the  artery  of  the  opposite  side, 
and  the  two  vessels  are  connected  together  by  a  short  anastomosing  trunk,  about 
two  lines  in  length,  the  anterior  communicating  artery.  From  this  point  the  two 
vessels  run  side  by  side  in  the  longitudinal  fissure,  curve  round  the  genu  of  the 
corpus  callosum,  and,  turning  backward,  continue  along  its  upper  surface  to  its 
posterior  part,  where  they  terminate  by  anastomosing  with  the  posterior  cerebral 
arteries.     In  their  course  they  give  off  the  following  branches : 

Antero-median  o-anodionic.  Anterior  internal  frontal. 

Inferior  internal  frontal.  Middle  internal  frontal. 

Posterior  internal  frontal. 

The  antero-median  ganglionic  is  a  group  of  small  arteries  which  arise  at  the 
commencement  of  the  anterior  cerebral  artery  ;  they  pierce  the  anterior  perforated 
space  and  lamina  cinerea,  and  supply  the  head  of  the  caudate  nucleus. 


Fig.  294. — Vascular  area  of  the  inferior  surface  of  the  cerebrum.  (After  Duret.)  I.  The  part  supplied  by 
the  anterior  temporal  artery.  II.  The  part  supplied  by  the  posterior  temporal  artery.  III.  The  part  supplied 
by  the  occipital  artery. 


The  inferior  internal  frontal,  two  or  three  in  number,  are  distributed  to  the 
orbital  surface  of  the  frontal  lobe,  where  they  supply  the  olfactory  lobe,  gyrus 
rectus,  and  internal  orbital  convolution. 

The  anterior  internal  frontal  brandies  supply  a  part  of  the  marginal  convolu- 
tion, and  send  branches  over  the  edge  of  the  hemisphere  to  the  superior  and 
middle  frontal  convolutions  and  upper  part  of  the  ascending  frontal  convolution. 
The  middle  internal  frontal  branches  supply  the  corpus  callosum,  the  convolution 
of  the  corpus  callosum,  the  inner  surface  of  the  first  frontal  convolution,  and  the 


BRANCHES    OF    THE   INTERNAL    CAROTID.  511 

upper  part  of  the  ascending  frontal  convolution.  The  posterior  internal  frontal 
branches  supply  the  lob  us  quadratus  and  adjacent  outer  surface  of  the  hemisphere. 

The  anterior  communicating  artery  is  a  short  branch,  about  two  lines  in 
length,  but  of  moderate  size,  connecting  together  the  two  anterior  cerebral 
arteries  across  the  longitudinal  fissure.  Sometimes  this  vessel  is  wanting,  the 
two  arteries  joining  together  to  form  a  single  trunk,  which  afterward  divides.  Or 
the  vessel  may  be  wholly  or  partially  divided  into  two  ;  .frequently  it  is  longer  and 
smaller  than  usual.  It  gives  off  some  of  the  antero-median  ganglionic- group  of 
vessels,  which  are,  however,  principally  derived  from  the  anterior  cerebral. 

The  middle  cerebral  artery  (Fig.  295),  the  largest  branch  of  the  internal  carotid, 
passes  obliquely  outward  along  the  fissure  of  Sylvius,  and  opposite  the  island  of 
Reil  divides  into  its  terminal  branches.  The  branches  of  the  middle  cerebral 
artery  are — 

Antero-lateral  ganglionic.  Ascending  frontal. 

Inferior  external  frontal.  Ascending  parietal. 

Parieto-temporal. 

The  antero-lateral  ganglionic  branches  are  a  group  of  small  arteries  which 
arise  at  the  commencement  of  the  middle  cerebral  artery  ;  they  pierce  the  anterior 
perforated  space  and  supply  the  greater  part  of  the  caudate  nucleus,  the  lenticular 
nucleus,  the  internal  capsule,  and  a  part  of  the  optic  thalamus.  One  artery  of  this 
group  is  of  larger  size  than  the  rest,  and  is  of  special  importance,  as  being  the 
artery  in  the  brain  most  frequently  ruptured ;  it  has  been  termed  by  Charcot  the 
" artery  of  cerebral  hemorrhage."  It  passes  up  between  the  lenticular  nucleus 
and  the  external  capsule,  and  ultimately  ends  in  the  caudate  nucleus.  The 
inferior  external  frontal  supplies  the  third  or  inferior  frontal  convolution  (Broca's 
convolution)  and  the  outer  part  of  the  orbital  surface  of  the  frontal  lobe.  The 
ascending  frontal  supplies  the  ascending  frontal  convolution.  The  ascending 
'parietal  supplies  the  ascending  parietal  convolution  and  the  lower  part  of  the 
superior  parietal  convolution.  The  parieto-teinporal  supplies  the  supra-marginal, 
the  superior,  and  part  of  the  middle  temporal  convolutions,  and  the  angular  gyrus. 

The  posterior  communicating  artery  arises  from  the  back  part  of  the  internal 
carotid,  runs  directly  backward,  and  anastomoses  with  the  posterior  cerebral,  a 


FISSURE  OF 
ROLANDO. 


Per  for 
Branches 

Middle  Cerebral 
Artery. 


Fig.  295.— The  distribution  of  the  middle  cerebral  artery.    (After  Charcot.) 

branch  of  the  basilar.  This  artery  varies  considerably  in  size,  being  sometimes 
3mall,  and  occasionally  so  large  that  the  posterior  cerebral  may  be  considered  as 
arising  from  the  internal   carotid  rather  than   from  the  basilar!     It  is   frequently 


512 


THE   BLOOD-VASCULAR    SYSTEM. 


larger  on  one  side  than  on  the  other  side.  From  the  posterior  half  of  this  vessel 
are  given  off  a  number  of  small  branches,  the  postero-median  ganglionic  branches, 
which,  with  similar  vessels  from  the  posterior  cerebral,  pierce  the  posterior  perfo- 
rated space  and  supply  the  internal  surfaces  of  the  optic  thalami  and  the  walls  of 
the  third  ventricle. 

The  anterior  choroid  is  a  small  but  constant  branch  which  arises  from  the 
back  part  of  the  internal  carotid,  near  the  posterior  communicating  artery. 
Passing  backward  and  outward  between  the  temporal  lobe  and  the  crus  cerebri,  it 
enters  the  descending  horn  of  the  lateral  ventricle  through  the  transverse  fissure 
and  ends  in  the  choroid  plexus.  It  is  distributed  to  the  hippocampus  major,  corpus 
fimbriatum,  velum  interpositum,  and  choroid  plexus. 

The  Blood-vessels  of  the  Brain. 

Recent  investigations  have  tended  to  show  that  the  mode  of  distribution  of 
the  vessels  of  the  brain  has  an  important  bearing  upon  a  considerable  number  of 
the  anatomical  lesions  of  which  this  part  of  the  nervous  system  may  be  the  seat ; 
it  therefore  becomes  important  to  consider  a  little  more  in  detail  the  way  in  which 
the  cerebral  vessels  are  distributed. 

The  cerebral  arteries  are  derived  from  the  internal  carotid  and  the  vertebral, 
which  at  the  base  of  the  brain  form  a  remarkable  anastomosis  known  as  the  circle 
of  Willis.  It  is  formed  in  front  by  the  anterior  cerebral  arteries,  branches  of  the 
internal  carotid,  which  are  connected  together  by  the  anterior  communicating ; 
behind  by  the  two  posterior  cerebrals,  branches  of  the  basilar  which  are  connected 
on  each  side  with  the  internal  carotid  by  the  posterior  communicating  (Fig.  291, 
p.  507).  The  parts  of  the  brain  included  within  this  arterial  circle  are  the  lamina 
cinerea,  the  commissure  of  the  optic  nerves,  the  infundibulum,  the  tuber  cinereum, 
the  corpora  albicantia,  and  the  posterior  perforated  space. 


Anterior  cerebral  artery. 


llnternafcar^tid  artery. 


Middle  cerebral  artery. 
I  \ 


ebral  artery. 


^ 


Fig.  296.— Diagram  of  the  arterial  circulation  at  the  base  of  the  brain.  (After  Charcot.)  I.  Antero-median 
group  of  ganglionic  branches.  II.  Postero-median  group.  III.  Right  and  left  antero-lateral  group.  IV.  Right 
and  left  postero-lateral  group.    The  dotted  line  shows  the  limit  of  the  ganglionic  circle. 

From  the  circle  of  Willis  arise  the  three  trunks  which  together  supply  each 
cerebral  hemisphere.  From  its  anterior  part  proceed  the  two  anterior  cerebrals 
from  its  antero-lateral  part  the  middle  cerebrals,  and  from  its  posterior  part  the 


THE  BLOOD-VESSELS    OF    THE   BRAIN. 


513 


posterior  cerebrals.  Each  of  these  principal  arteries  gives  origin  to  two  very 
different  systems  of  secondary  vessels.  One  of  these  systems  has  been  named  the 
centrcd^anglimiic  system,  and  the  vessels  belonging  to  it  supply  the  central  ganglia 
of  the  brain ;  the  other  has  been  named  the  cortical  arterial  system,  and  its  vessels 
ramify  in  the  pia  mater  and  supply  the  cortex  and  subjacent  medullary  matter. 
These  two  systems,  though  they  have  a  common  origin,  do  not  communicate  at  any 
point  of  their  peripheral  distribution,  and  are  entirely  independent  of  each  other. 
Though  some  of  the  arteries  of  the  cortical  system  approach,  at  their  terminations, 
the  regions  supplied  by  the  central  ganglionic  system,  no  communication  between 
the  two  sets  of  vessels  takes  place,  and  there  is  between  the  parts  supplied  by 
the  two  systems  a  borderland  of  diminished  nutritive  activity,  where,  it  is  said, 
softening  is  especially  liable  to  occur  in  the  brains  of  old  people. 

The  Central  Ganglionic  System. — All  the  vessels  belonging  to  this  system  are 
given  off  from  the  circle  of  Willis  or  from  the  vessels  immediately  after  their  origin 


Fig.  297.— Distribution  of  the  cortical  arteries.  (After  Charcot.)  1.  Medullary  arteries.  1'.  Group  of  medullary 
arteries  in  the  sulcus  between  two  adjacent  convolutions.  1".  Arteries  situated  among  the  short  associa- 
tion fibres.  2,  2.  Cortical  arteries,  o.  Capillary  network  with  fairly  wide  meshes,  situated  beneath  the  pia 
mater,  b.  Network  with  more  compact,  polygonal  meshes,  situated  in  the  cortex,  c.  Transitional  network  with 
wider  meshes,    d.  Capillary  network  in  the  white  matter. 

from  it,  so  that  if  a  circle  is  drawn  at  a  distance  of  about  an  inch  from  the  circle 
of  Willis,  it  will  include  the  origin  of  all  the  arteries  belonging  to  this  system  (Fig. 
296).  The  vessels  of  this  system  form  six  principal  groups  :  (I.)  the  antero-median 
group,  derived  from  the  anterior  cerebrals  and  anterior  communicating ;  (II.)  the 
poster  o-median  group,  from  the  posterior  cerebrals  and  posterior  communicating ; 
(III.)  the  right  and  left  antero-lateral  group,  from  the  middle  cerebrals :  and  (IV.) 
the  right  and  left  postero-lateral  group,  from  the  posterior  cerebrals,  after  they  have 
wound  round  the  crura  cerebri.  The  vessels  belonging  to  this  system  are  larger 
than  those  of  the  cortical  system,  and  are  what  Cohnheim  has  termed  "  terminal  " 
arteries  ;  that  is  to  say,  vessels  which  from  their  origin  to  their  termination  neither 
supply  nor  receive  any  anastomotic  branch,  so  that  by  one  of  the  small  vessels 
only  a  limited  area  of  the  central  ganglia  can  be  injected;  and  the  injection  cannot 
be  driven  beyond  the  area  the  part  supplied  by  the  particular  vessel  which  is  the 
subject  of  the  experiment. 

The  Cortical  Artexial  System. — The  vessels  forming  this  system  are  the  terminal 
branches  of  the  an^     ior,  middle,  and  posterior  cerebral  arteries,  described  above. 
33 


514  THE   BLOOD-  VASCULAR    SYSTEM. 

These  vessels  divide  and  ramify  in  the  substance  of  the  pia  mater,  and  give  oft" 
nutrient  arteries  which  penetrate  the  cortex  perpendicularly.  These  nutrient  vessels 
are  divisible  into  two  classes — the  long  and  short.  The  long — or,  as  they  are  some- 
times called,  the  medullary — arteries  pass  through  the  gray  matter  to  penetrate  the 
centrum  ovale  to  the  depth  of  about  an  inch  and  a  half,  without  intercommunica- 
ting otherwise  than  by  very  fine  capillaries,  and  thus  constitute  so  many  independ- 
ent small  systems.  The  short  vessels  are  confined  to  the  cortex,  where  they  form 
with  the  long  vessels  a  compact  network  in  the  middle  zone  of  the  gray  matter,  the 
outer  and  inner  zones  being  sparingly  supplied  with  blood  (Fig.  297).  The  vessels 
of  the  cortical  arterial  system  are  not  so  strictly  "terminal"  as  those  of  the 
central  ganglionic  system,  but  they  approach  this  type  very  closely,  so  that  injec- 
tion of  one  area  from  the  vessel  of  another  area,  though  it  may  be  possible,  is 
frequently  very  difficult,  and  is  only  effected  through  vessels  of  small  calibre.  As 
a  result  of  this,  obstruction  of  one  of  the  main  branches  or  its  divisions  may  have 
the  effect  of  producing  softening  in  a  very  limited  area  of  the  cortex.1 

ARTERIES  OF   THE  UPPER  EXTREMITY. 

The  artery  which  supplies  the  upper  extremity  continues  as  a  single  trunk 
from  its  commencement  down  to  the  elbow,  but  different  portions  of  it  have 
received  different  names  according  to  the  region  through  which  it  passes.  That 
part  of  the  vessel  which  extends  from  its  origin  to  the  outer  border  of  the  first 
rib  is  termed  the  subclavian ;  beyond  this  point  to  the  lower  border  of  the  axilla 
it  is  termed  the  axillary ;  and  from  the  lower  margin  of  the  axillary  space  to  the 
bend  of  the  elbow  it  is  termed  brachial ;  here  the  single  trunk  terminates  by 
dividing  into  two  branches,  the  radial  and  ulnar — an  arrangement  precisely  similar 
to  what  occurs  in  the  lower  limb. 

THE  SUBCLAVIAN  ARTERIES  (Fig.  298). 

The  subclavian  artery  on  the  right  side  arises  from  the  innominate  artery 
opposite  the  right  sterno-clavicular  articulation  ;  on  the  left  side  it  arises  from  the 
arch  of  the  aorta.  It  follows,  therefore,  that  these  two  vessels  must,  in  the  first 
part  of  their  course,  differ  in  their  length,  their  direction,  and  their  relation  with 
neighboring  parts. 

In  order  to  facilitate  the  description  of  these  vessels,  more  especially  from  a 
surgical  point  of  view,  each  subclavian  artery  has  been  divided  into  three  parts. 
The  first  portion,  on  the  right  side,  passes  upward  and  outward  from  the  origin 
of  the  vessel  to  the  inner  border  of  the  Scalenus  anticus.  On  the  left  side  it  ascends 
nearly  vertically,  to  gain  the  inner  border  of  that  muscle.  The  second  part  passes 
outward,  behind  the  Scalenus  anticus ;  and  the  third  part  passes  from  the  outer 
margin  of  that  muscle,  beneath  the  clavicle,  to  the  outer  border  of  the  first  rib, 
where  it  becomes  the  axillary  artery.  The  first  portion  of  these  two  vessels 
differs  so  much  in  its  course  and  in  its  relation  with  neighboring  parts  that  it 
will  be  described  separately.  The  second  and  third  parts  are  alike  on  the  two 
sides. 

First  Part  op  the  Right  Subclavian  Artery  (Figs.  280,  283,  298). 

The  right  subclavian  artery  arises  from  the  arteria  innominata,  opposite  the 
upper  part  of  the  right  sterno-clavicular  articulation,  and  passes  upward  and  out- 
ward to  the  inner  margin  of  the  Scalenus  anticus  muscle.  In  this  part  of  its 
course  it  ascends  a  little  above  the  clavicle,  the  extent  to  which  it  does  so  varying 
in  different  cases.  It  is  covered,  in  front,  by  the  integument,  superficial  fascia, 
Platysma,   deep  fascia,  the   clavicular  origin  of  the   Sterno-mastoid,  the   Sterno- 

1  The  student  who  desires  further  information  on  this  subject  is  referred  to  Charcot's  Localization 
of  Cerebral  and  Spinal  Diseases,  p.  42  et  seq.,  whence  the  facts  above  given  have  been  principally 
derived. 


THE   SUBCLAVIAN  ARTERIES. 


515 


hyoid,  and  Sternothyroid  muscles,  and  another  layer  of  the  deep  fascia.  It  is 
crossed  by  the  internal  jugular  and  vertebral  veins,  and  by  the  pneumogastric 
and  the  cardiac  branches  of  the  sympathetic.  A  loop  of  the  sympathetic  nerve 
itself  also  crosses  the  artery,  forming  a  ring  around  the  vessels.  The  anterior 
jugular  vein  passes  outward  in  front  of  the  artery  but  is  not  in  contact  with  it, 
being  separated  from  it  by  the  Sterno-hyoid  and  Sterno-thyroid  muscles.  Below 
and  behind  the  artery  is  the  pleura,  which  separates  it  from  the  apex  of  the  lung ; 
behind  is  the  cord  of  the  sympathetic  nerve ;  the  recurrent  laryngeal  nerve  winds 
round  the  lower  and  back  part  of  the  vessel. 


Phrenic  nerve.      Vertebral  artery. 


Inferior  thyroid  artery. 


Supra-scapular 
artery. 
Supra-  \      S^W 

scapular\  ^\ 


neumo- 
(jastric 
nerve. 


Subclavian 

artery. 
External  jugu- 
lar vein. 
Right  innomi- 
nate vein. 
Innomi- 
\nate  artery. 


'  Profunda  artery. 

■ Musculo-spiral  nerve. 

Fig.  298. — The  subclavian  artery,  showing  its  relations.    (From  a  preparation  in  the  Museum  of  the  Royal 
College  of  Surgeons  of  England.) 


Plan 


of  Relations  of  First  Portion  of 

In  front. 
Skin,  superficial  fascia. 
Platysma,  deep  fascia, 


*Y« 


the  Right  Subclav  jc1  tnf 

e  takes  place,  in  some  cases|J.  °^s.-^ 
o  frequently,  in  the  cavity  of  £  vJc-qJ  *   l  _.., 
,-ate  trunk  from  the  arch  of  thf©  ^e      a«e/*ao 
Clavicular  origin  of  Sterno-masto"'  even  the  last  branch  derived  fr(f  sCa]  * i2'eiijc       6j 
Sterno-hyoid  and  Sterno-ttewddrely  the  second  or  third.     When  jy  •     e^e  lrj        ^-, 
Anterior  jugular,  Interns  the  innominate  artery;  when  the  seconf  ,ji}]edja  f  .ck\  1( 
Pneumogastric  and  cardihe  right  carotid  ;  and  when  the  last  bra /'e^        Ce{Y  t0  n 
Loop  from  the  sympath  upper  or  back  part,  and  passes  obhqueFW0,       ■*#</  tj      Je 


516  THE  BLOOD-VASCULAR    SYSTEM. 


Beneath. 
Pleura. 
Recurrent  laryngeal  nerve. 

Behind. 
Recurrent  laryngeal  nerve. 
Sympathetic. 
Pleura  and  apex  of  lung. 

First  Part  of  the  Left  Subclavian  Artery  (Fig.  280). 

The  left  subclavian  artery  arises  from  the  end  of  the  arch  of  the  aorta, 
opposite  the  fourth  dorsal  vertebra,  and  ascends  nearly  vertically  to  the  inner 
margin  of  the  Scalenus  anticus  muscle.  This  part  of  the  vessel  is,  therefore, 
longer  than  the  right,  situated  deeply  in  the  cavity  of  the  chest,  and  directed 
nearly  vertically  upward,  instead  of  arching  outward  like  the  vessel  of  the 
opposite  side. 

It  is  in  relation,  in  front,  with  the  pneumogastric,  cardiac,  and  phrenic  nerves, 
which  lie  parallel  with  it,  the  left  carotid  artery,  left  internal  jugular  and  vertebral 
veins,  and  the  commencement  of  the  left  innominate  vein,  and  is  covered  by  the 
Sterno-thyroid,  Sterno-hyoid,  and  Sterno-mastoid  muscles ;  behind,  it  is  in  relation 
with  the  oesophagus,  thoracic  duct,  inferior  cervical  ganglion  of  the  sympathetic, 
and  Longus  colli ;  higher  up,  however,  the  oesophagus  and  thoracic  duct  lie  to  its 
right  side ;  the  latter  ultimately  arching  over  the  vessel  to  join  the  angle  of  union 
between  the  subclavian  and  internal  jugular  veins.  To  its  inner  side  are  the 
oesophagus,  trachea,  and  thoracic  duct ;   to  its  outer  side,  the  left  pleura  and  lung. 

Plan  of  Relations  of  First  Portion  of  Left  Subclavian  Artery. 

In  front. 
^Pneumogastric,  cardiac,  and  phrenic  nerves. 
Left  carotid  artery. 
Thoracic  duct. 

Left  internal  jugular,  vertebral,  and  innominate  veins. 
Sterno-thyroid,  Sterno-hyoid,  and  Sterno-mastoid  muscles. 


Inner  side.  /  \^ 

-Lracnea.  Subclavian 

(Esophagus.  I       Artery.       /  Pleura  and  left  lung. 

Thoracic  duct.  V  / 

Behind. 
(Esophagus  and  thoracic  duct. 
Inferior  cervical  ganglion  of  sympathetic. 
Longus  colli. 

Second  and  Third  Parts  of  the  Subclavian  Artery  (Figs.  283,  298). 

The  Second  Portion  of  the  Subclavian  Artery  lies  behind  the  Scalenus  anticus 
muscle;  it  is  very  short,  and  forms  the  highest  part  of  the  arch  described  by  that 
vessel.  irigl* 

RelP-"t  °f  tuT+  is  covered,  in  front,  by  the  skin,  superficial  fascia,  Platysma, 
deep  cltne  inner  margin  of  U,st0id,  and  the  Scalenus  anticus  muscle.  On  the 
right  siclascends  a  little  above  the  crated  from  the  second  part  of  the  artery  by  thej 
Anterioif1*  cases.  It  is  covered,  zVhe  left  side  the  nerve  crosses  the  first  part  off 
the  arteri  deep  fascia,  the  claviculai.W  ^f  the  muscle.  Behind,  it  is  in  relation! 
with  theudent  who  desires  further  information  on  t  Above,  with  the  brachial  plexus  of  I 
nerves.  H  Spinal  Diseases,  p.  42  et  seq.,  whence  ilavian  vein  lies  below  and  in  front  of| 
the  artery,  3  anticus. 


THE  SUBCLAVIAN  ARTERIES.  517 


Plan  of  Relations  of  Second  Portion  of  Subclavian  Artery. 

In  front. 
Skin  and  superficial  fascia. 
Platysma  and  deep  cervical  fascia. 
Sterno-mastoid. 
Phrenic  nerve.  --•- 
Scalenus  anticus. 
Subclavian  vein. 

Above.  I     Subclavian    \  Below. 

I  ■        Artery.         j 

Brachial  plexus.  \     Portion.     /  Pleura. 

Behind. 
Pleura  and  Middle  Scalenus. 

The  Third  Portion  of  the  Subclavian  Artery  passes  downward  and  outward 
from  the  outer  margin  of  the  Scalenus  anticus  to  the  outer  border  of  the  first  rib, 
where  it  becomes  the  axillary  artery.  This  portion  of  the  vessel  is  the  most 
superficial,  and  is  contained  in  a  subclavian  triangle  (see  page  502). 

Relations. — It  is  covered,  in  front,  by  the  skin,  the  superficial  fascia,  the 
Platysma,  the  descending  clavicular  branches  of  the  cervical  plexus,  and  the  deep 
cervical  fascia ;  by  the  clavicle,  the  Subclavius  muscle,  and  the  suprascapular 
artery  and  vein,  and  the  transverse  cervical  vein ;  the  nerve  to  the  Subclavius 
muscle  passes  vertically  downward  in  front  of  the  artery.  The  external  jugular 
vein  crosses  it  at  its  inner  side,  and  receives  the  suprascapular  and  transverse 
cervical  veins,  which  frequently  form  a  plexus  in  front  of  it.  The  subclavian 
vien  is  below  and  in  front  of  the  artery,  lying  close  behind  the  clavicle.  Behind, 
it  lies  on  the  Middle  scalene  muscle  and  the  lowest  cord  of  the  brachial  plexus, 
formed  by  the  union  of  the  last  cervical  and  first  dorsal  nerves.  Above  it,  and 
to  its  outer  side,  is  the  brachial  plexus  and  Omo-hyoid  muscle.  Below,  it  rests  on 
the  upper  surface  of  the  first  rib. 

Plan  of  Relations  of  Third  Portion  of  Subclavian  Artery. 

In  front. 
Skin  and  superficial  fascia. 
Platysma  and  deep  cervical  fascia. 

Descending  branches  of  cervical  plexus.     Nerve  to  Subclavius  muscle. 
Subclavius  muscle,  suprascapular  artery,  and  vein. 
The  external  jugular  and  transverse  cervical  veins. 
The  clavicle. 

Above.  I   Su^a0Ilan    \  Below. 


Brachial  plexus.  \     portion.     /  First  rib. 

Omo-hyoid. 


Behind. 

Scalenus  medius. 

Lower  cord  of  brachial  plexus. 

Peculiarities. — The  subclavian  arteries  vary  in  their  origin,  their  course,  and  the  height  to 
which  they  rise  in  the  neck. 

The  origin  of  the  right  subclavian  from  the  innominate  takes  place,  in  some  cases,  above  the 
sterno-clavicular  articulation,  and  occasionally,  but  less  frequently,  in  the  cavity  of  the  thorax, 
below  that  joint.  Or  the  artery  may  arise  as  a  separate  trunk  from  the  arch  of  the  aorta.  In 
such  cases  it  may  be  either  the  first,  second,  third,  or  even  the  last  branch  derived  from  that  ves- 
sel ;  in  the  majority  of  cases  it  is  the  first  or  last,  rarely  the  second  or  third.  When  it  is  the  first 
branch,  it  occupies  the  ordinary  position  of  the  innominate  artery ;  when  the  second  or  third,  it 
gains  its  usual  position  by  passing  behind  the  right  carotid  ;  and  when  the  last  branch,  it  arises 
from  the  left  extremity  of  the  arch,  at  its  upper  or  back  part,  and  passes  obliquely  toward  the 


A 


518  THE   BLOOD-VASCULAR   SYSTEM. 

right  side,  usually  behind  the  trachea,  oesophagus,  and  right  carotid,  sometimes  between  the 
oesophagus  and  trachea  to  the  upper  border  of  the  first  rib,  whence  it  follows  its  ordinary  course. 
In  very  rare  instances  this  vessel  arises  from  the  thoracic  aorta,  as  low  down  as  the  fourth  dor- 
sal vertebra.  Occasionally  it  perforates  the  anterior  Scalenus  ;  more  rarely  it  passes  in  front  of 
that  muscle.  Sometimes  the  subclavian  vein  passes  with  the  artery  behind  the  Anterior  Scalene. 
The  artery  may  ascend  as  high  as  an  inch  and  a  half  above  the  clavicle  or  any  intermediate 
point  between  this  and  the  upper  border  of  the  bone,  the  right  subclavian  usually  ascending 
higher  than  the  left. 

The  left  subclavian  is  occasionally  joined  at  its  origin  with  the  left  carotid. 

Surface  Marking. — The  course  of  the  subclavian  artery  in  the  neck  may  be  mapped  out 
by  describing  a  curve,  with  its  convexity  upward  at  the  base  of  the  posterior  triangle.  The  inner 
end  of  this  curve  corresponds  to  the  sterno-clavicular  joint,  the  outer  end  to  the  centre  of  the 
lower  border  of  the  clavicle.  The  curve  is  to  be  drawn  with  such  an  amount  of  convexity  that 
its  mid-point  reaches  half  an  inch  above  the  upper  border  of  the  clavicle.  The  left  subclavian 
artery  is  more  deeply  placed  than  the  right  in  the  first  part  of  its  course,  and,  as  a  rule,  does  not 
reach  quite  as  high  a  level  in  the  neck.  It  should  be  borne  in  mind  that  the  posterior  border  of 
the  Sterno-mastoid  muscle  corresponds  to  the  outer  border  of  the  Scalenus  anticus,  so  that  the 
third  portion  of  the  artery,  that  part  most  accessible  for  operation,  lies  immediately  external  to 
the  posterior  border  of  the  Sterno-mastoid. 

Surgical  Anatomy. — The  relations  of  the  subclavian  arteries  of  the  two  sides  having  been 
examined,  the  student  should  direct  his  attention  to  a  consideration  of  the  best  position  in  which 
compression  of  the  vessel  may  be  effected,  or  in  what  situation  a  ligature  may  be  best  applied  in 
cases  of  aneurism  or  wound. 

Compression  of  the  subclavian  artery  is  required  in  cases  of  operations  about  the  shoul- 
der, in  the  axilla,  or  at  the  upper  part  of  the  arm  ;  and  the  student  will  observe  that  there  is 
only  one  situation  in  which  it  can  be  effectually  applied— viz.  where  the  artery  passes  across  the 
upper  surface  of  the  first  rib.  In  order  to  compress  the  vessel  in  this  situation,  the  shoulder 
should  be  depressed,  and  the  surgeon,  grasping  the  side  of  the  neck,  should  press  with  his 
thumb  in  the  angle  formed  by  the  posterior  border  of  the  Sterno-mastoid  with  the  upper  border 
of  the  clavicle,  downward,  backward,  and  inward  against  the  rib  ;  if  from  any  cause  the  shoulder 
cannot  be  sufficiently  depressed,  pressure  may  be  made  from  before  backward,  so  as  to  compress 
the  artery  against  the  middle  Scalenus  and  transverse  process  of  the  seventh  cervical  vertebra. 
In  appropriate  cases,  a  preliminary  incision  may  be  made  through  the  cervical  fascia,  and  the 
finger  may  be  pressed  down  directly  upon  the  artery. 

Ligature  of  the  subclavian  artery  may  be  required  in  cases  of  wounds  or  of  aneurism  in 
the  axilla,  or  in  cases  of  aneurism  on  the  cardiac  side  of  the  point  of  ligature  ;  and  the  third  part 
of  the  artery  is  that  which  is  most  favorable  for  an  operation,  on  account  of  its  being  compara- 
tively superficial  andmost  remote  from  the  origin  of  the  large  branches.  In  those  cases  where 
the  clavicle  is  not  _  displaced,  this  operation  may  be  performed  with  comparative  facility ;  but 
where  the  clavicle  is  pushed  up  by  a  large  aneurismal  tumor  in  the  axilla  the  artery  is  placed  at 
a  great  depth  from  the  surface,  which  materially  increases  the  difficulty  of  the  operation. 
Under  these  circumstances  it  becomes  a  matter  of  importance  to  consider  the  height  to  which 
this  vessel  reaches  above  the  bone.  Tn  ordinary  cases  its  arch  is  about  half  an  inch  above  the 
clavicle,  occasionally  as  high  as  an  inch  and  a  half,  and  sometimes  so  low  as  to  be  on  a  level  with 
its  upper  border.  If  the  clavicle  is  displaced,  these  variations  will  necessarily  make  the  opera- 
tion more  or  less  difficult  according  as  the  vessel  is  more  or  less  accessible. 

The  chief  points  in  the  operation  of  tying  the  third  portion  of  the  subclavian  artery  are  as 
follows  :  The  patient  being  placed  on  a  table  in  the  supine  position,  with  the  head  drawn  over  to 
the  opposite  side  and  the  shoulder  depressed  as  much  as  possible,  the  integument  should  be 
drawn  downward  over  the  clavicle,  and  an  incision  made  through  it,  upon  that  bone,  from  the 
anterior  border  of  the  Trapezius  to  the  posterior  border  of  the  Sterno-mastoid,  to  which  may  be 
added  a  short  vertical  incision  meeting  the  inner. end  of  the  preceding.  The  object  in  drawing 
the  skin  downward  is  to  avoid  any  risk  of  wounding  the  external  jugular  vein,  for  as  it  perforates 
the  deep  fascia  above  the  clavicle,  it  cannot  be  drawn  downward  with  the  skin.  The  soft  parts 
should  now  be  allowed  to  glide  up,  and  the  cervical  fascia  should  be  divided  upon  a  director, 
and  if  the  interval  between  the  Trapezius  and  Sterno-mastoid  muscles  be  insufficient  for  the  per- 
formance of  the  operation,  a  portion  of  one  or  both  may  be  divided.  The  external  jugular  vein 
will  now  be  seen  toward  the  inner  side  of  the  wound  :  this  and  the  suprascapular  and  transverse 
cervical  veins,  which  terminate  in  it,  should  be  held  aside.  If  the  external  jugular  vein  is  at  all 
in  the  way  and  exposed  to  injury,  it  should  be  tied  in  two  places  and  divided.  The  suprascapu- 
lar artery  should  be  avoided,  and  the  Omo-hyoid  muscle  held  aside  if  necessary.  In  the  space 
beneath  this  muscle  careful  search  must  be  made  for  the  vessel :  a  deep  layer  of  fascia  and  some 
connective  tissue  having  been  divided  carefully,  the  outer  margin  of  the  Scalenus  anticus  muscle 
must  be  felt  for,  and,  the  finger  being  guided  by  it  to  the  first  rib,  the  pulsation  of  the  subcla- 
vian artery  will  be  felt  as  it  passes  over  the  rib.  The  sheath  of  the  vessels  having  been  opened, 
the  aneurism  needle  may  then  be  passed  around  the  artery  from  above  downward  and  inward,  so 
as  to  avoid  including  any  of  the  branches  of  the  brachial  plexus.  If  the  clavicle  is  so  raised  by 
the  tumor  that  the  application  of  the  ligature  cannot  be  effected  in  this  situation,  the  artery  may 
be  tied  above  the  first  rib,  or  even  behind  the  Scalenus  anticus  muscle :  the  difficulties  of  the 
operation  in  such  a  case  will  be  materially  increased,  on  account  of  the  greater  depth  of  the  artery 
and  the  alteration  in  position  of  the  surrounding  parts. 


; 


BRANCHES    OF   THE   SUBCLAVIAN  ARTERY.  519 

The  second  part  of  the  subclavian  artery,  from  being  that  portion  which  rises  highest  in 
the  neck,  has  been  considered  favorable  for  the  application  of  the  ligature  when  it  is  difficult  to 
tie  the  artery  in  the  third  part  of  its  course.  There  are,  however,  many  objections  to  the  ope- 
ration in  this  situation.  It  is  necessary  to  divide  the  Scalenus  anticus  muscle,  upon  which  lies 
the  phrenic  nerve,  and  at  the  inner  side  of  which  is  situated  the  internal  jugular  vein  ;  and  a 
wound  of  either  of  these  structures  might  lead  to  the  most  dangerous  consequences.  Again, 
the  artery  is  in  contact,  below,  with  the  pleura,  which  must  also  be  avoided ;  and,  lastly,  the 
proximity  of  so  many  of  its  large  branches  arising  internal  to  this  point  must  be  a  still  further 
objection  to  the  operation.  In  cases,  however,  where  the  sac  of  an  axillary  aneurism  encroaches 
on  the  neck,  it  may  be  necessary  to  divide  the  outer  half  or  two-thirds  of  the  Scalenus  anticus 
muscle,  so  as  to  place  the  ligature  on  the  vessel  at  a  greater  distance  from  the  sac.  The  opera- 
tion is  performed  exactly  in  the  same  way  as  ligature  of  the  third  portion,  until  the  Scalenus 
anticus  is  exposed,  when  it  is  to  be  divided  on  a  director  (never  to  a  greater  extent  than  its  outer 
two-thirds),  and  it  immediately  retracts.  The  operation  is  therefore  merely  an  extension  of  liga- 
ture of  the  third  portion  of  the  vessel. 

In  those  cases  of  aneurism  of  the  axillary  or  subclavian  artery  which  encroach  upon  the 
outer  portion  of  the  Scalenus  muscle  to  such  an  extent  that  a  ligature  cannot  be  applied  in  that 
situation,  it  may  be  deemed  advisable,  as  a  last  resource,  to  tie  the  first  portion  of  the  subcla- 
vian artery.  On  the  left  side  this  operation  is  almost  impracticable ;  the  great  depth  of  the 
artery  from  the  surface,  its  intimate  relation  with  the  pleura,  and  its  close  proximity  to  the 
thoracic  duct  and  to  so  many  important  veins  and  nerves,  present  a  series  of  difficulties  which  it 
is  next  to  impossible  to  overcome.1  On  the  right  side  the  operation  is  practicable,  and  has  been 
performed,  though  never  with  success.  The  main  objection  to  the  operation  in  this  situation  is 
the  smallness  of  the  interval  which  usually  exists  between  the  commencement  of  the  vessel  and 
the  origin  of  the  nearest  branch.  The  operation  may  be  performed  in  the  following  manner : 
The  patient  being  placed  on  the  table  in  the  supine  position  with  the  neck  extended,  an  incision 
should  be  made  along  the  upper  border  of  the  inner  part  of  the  clavicle,  and  a  second  along 
the  inner  border  of  the  Sterno-mastoid,  meeting  the  former  at  an  angle.  The  attachment  of 
both  heads  of  the  Sterno-mastoid  must  be  divided  on  a  director  and  turned  outward ;  a  few 
small  arteries  and  veins,  and  occasionally  the  anterior  jugular,  must  be  avoided,  or,  if  necessary, 
ligatured  in  two  places  and  divided,  and  the  Sterno-hyoid  and  Sterno-thyroid  muscles  divided  in 
the  same  manner  as  the  preceding  muscle.  After  tearing  through  the  deep  fascia  with  the  finger- 
nail, the  internal  jugular  vein  will  be  seen  crossing  the  subclavian  artery  ;  this  should  be  pressed 
aside  and  the  artery  secured  by  passing  the  needle  from  below  upward,  by  which  the  pleura  is 
more  effectually  avoided.  The  exact  position  of  the  vagus  nerve,  the  recurrent  laryngeal,  the 
phrenic  and  sympathetic  nerves  should  be  remembered,  and  the  ligature  should  be  applied  near 
the  origin  of  the  vertebral,  in  order  to  afford  as  much  room  as  possible  for  the  formation  of  a 
coagulum  between  the  ligature  and  the  origin  of  the  vessel.  It  should  be  remembered  that  the 
right  subclavian  artery  is  occasionally  deeply  placed  in  the  first  part  of  its  course  when  it  arises 
from  the  left  side  of  the  aortic  arch,  and  passes  in  such  cases  behind  the  oesophagus  or  between 
it  and  the  trachea. 

Collateral  Circulation.— After  ligature  of  the  third  part  of  the  subclavian  artery  the  col- 
lateral circulation  is  mainly  established  by  three  sets  of  vessels,  thus  described  in  a  dissection : 

"  1.  A  posterior  set,  consisting  of  the  suprascapular  and  posterior  scapular  branches  of  the 
subclavian,  anastomosing  with  the  subscapular  from  the  axillary. 

"  2.  An  internal  set  produced  by  the  connection  of  the  internal  mammary  on  the  one  hand, 
with  the  superior  and  long  thoracic  arteries,  and  the  branches  from  the  subscapular  on  the 
other. 

"3.  A  middle  or  axillary  set,  which  consisted  of  a  number  of  small  vessels  derived  from 
branches  of  the  subclavian,  above,  and,  passing  through  the  axilla,  terminated  either  in  the 
main  trunk  or  some  of  the  branches  of  the  axillary  below.  This  last  set  presented  most  con- 
spicuously the  peculiar  character  of  newly-formed  or,  rather,  dilated  arteries,  being  excessively 
tortuous,  and  forming  a  complete  plexus. 

"  The  chief  agent  in  the  restoration  of  the  axillary  artery  below  the  tumor  was  the  sub- 
scapular artery,  which  communicated  most  freely  with  the  internal  mammary,  suprascapular, 
and  posterior  scapular  branches  of  the  subclavian,  from  all  of  which  it  received  so  great  an 
influx  of  blood  as  to  dilate  it  to  three  times  its  natural  size."  2 

When  a  ligature  is  applied  to  the  first  part  of  the  subclavian  artery,  the  collateral  circula- 
tion is  carried  on  by — 1,  the  anastomosis  between  the  superior  and  inferior  thyroid  ;  2,  the  anas- 
tomosis of  the  two  vertebrals ;  3,  the  anastomosis  of  the  internal  mammary  with  the  deep 
epigastric  and  the  aortic  intercostals ;  4,  the  superior  intercostal  anastomosing  with  the  aortic 
intercostals ;  5,  the  profunda  cervicis  anastomosing  with  the  princeps  cervicis ;  6,  the  scapular 
branches  of  the  thyroid  axis  anastomosing  with  the  branches  of  the  axillary ;  and  7,  the  thoracic 
branches  of  the  axillary  anastomosing  with  the  aortic  intercostals. 

1  The  operation  was,  however,  performed  in  New  York  by  Dr.  J.  K.  Rodgers,  and  the  case  is 
related  in  A  System  of  Surgery,  edited  by  T.  Holmes,  2d  ed.,  vol.  iii.,  pp.  620,  etc 

2  Guy's  Hospital  ,  <  i.,  1836:  case  of  axillary  aneurism,  in  which  Mr.  Aston  Key  had 
tied  the  subclavian  ar    >                   mter  edge  of  the  Scalenus  muscle  twelve  years  previously. 


520 


THE   BLOOD-VASCULAR    SYSTEM. 


Branches. — The  branches  given  off  from  the  subclavian  artery  are 


Vertebral. 
Internal  mammary. 


Thyroid  axis. 
Superior  intercostal. 


Fig.  299. — Plan  of  the  branches  of  the  right 
subclavian  artery. 


On  the  left  side  all  four  branches  generally  arise  from  the  first  portion  of  the 
vessel;    but  on   the   right   side,  the  superior  intercostal   usually   arises  from    the 

second  portion  of  the  vessel.  On  both 
sides  of  the  body  the  first  three  branches 
arise  close  together  at  the  inner  margin 
of  the  Scalenus  anticus ;  in  the  majority 
of  cases,  a  free  interval  of  from  half  an 
inch  to  an  inch  exists  between  the  com- 
mencement of  the  artery  and  the  origin  of 
the  nearest  branch  ;  in  a  samller  number  of 
cases,  an  interval  of  more  than  an  inch  ex- 
ists, but  it  never  exceeds  an  inch  and  three- 
quarters.  In  a  very  few  instances,  the 
interval  has  been  found  to  be  less  than  half 
an  inch.  The  vertebral  artery  arises  from 
the  upper  and  posterior  part  of  the  artery, 
the  internal  mammary  from  the  lower  part 
of  the  artery  ;  the  thyroid  axis  from  in  front, 
.and  the  superior  intercostal  from  behind. 
The  Vertebral  Artery  (Fig.  289)  i^  generally  the  first  and  largest  branch  of 
the  subclavian ;  it  arises  from  the  upper  and  back  part  of  the  first  portion  of  the 
vessel,  and,  passing  upward,  enters  tine  foramen  in  the  transverse  process  of  the 
sixth  cervical  vertebra,1  and  ascends  through  the  foramina  in  the  transverse 
processes  of  all  the  vertebrae  above  this.  Above  the  upper  border  of  the  axis  it  in- 
clines outward  and  upward  to  the  foramen  in  the  transverse  process  of  the  atlas, 
through  which  it  passes ;  it  then  winds  backward  behind  its  articular  process,  runs 
in  a  deep  groove  on  the  upper  surface  of  the  posterior  arch  of  this  bone,  and,  pass- 
ing beneath  the  posterior  occipito-atlantal  ligament,  pierces  the  dura  mater  and 
arachnoid,  and  enters  the  skull  through  the  foramen  magnum.  It  then  passes  for- 
ward and  upward,  inclining  from  the  lateral  aspect  to  the  front  of  the  medulla 
oblongata.  It  unites  in  the  middle  line  with  the  vessel  of  the  opposite  side  at  the 
lower  border  of  the  pons  Varolii  to  form  the  basilar  artery. 

Relations. — At  its  origin,  it  is  situated  behind  the  internal  jugular  and  vertebral 
veins,  and  is  crossed  by  the  inferior  thyroid  artery  :  it  lies  between  the  Longus 
colli  and  Scalenus  anticus  muscles,  having  the  thoracic  duct  in  front  of  it  on  the 
left  side.  It  rests  on  the  transverse  process  of  the  seventh  cervical  vertebra  and 
the  sympathetic  nerve.  Within  the  foramina  formed  by  the  transverse  processes  of 
the  vertebrae  it  is  accompanied  by  a  plexus  of  nerves  from  the  inferior  cervical 
ganglion  of  the  sympathetic,  and  is  surrounded  by  a  dense  plexus  of  veins  which 
unite  to  form  the  vertebral  vein  at  the  lower  part  of  the  neck.  It  is  situated  in 
front  of  the  cervical  nerves,  as  they  issue  from  the  intervertebral  foramina.  While 
winding  round  the  articular  process  of  the  atlas,  it  is  contained  in  a  triangular 
space  {suboccipital  triangle)  formed  by  the  Rectus  capitis  posticus  major,  the 
Superior  and  Inferior  oblique  muscles  ;  and  at  this  point  is  covered  by  the  Com- 
plexus  muscle.  The  suboccipital  nerve  here  lies  betw'een  the  artery  and  the  bone. 
Within  the  skull,  as  it  winds  round  the  medulla  oblongata,  it  is  placed  between  the 
hypoglossal  nerve  and  the  anterior  root  of  the  suboccipital  nerve,  beneath  the  first 
digitation  of  the  ligamentum  denticulatum,  and  finally  ascends  between  the  basilar 
process  of  the  occipital  bone  and  the  anterior  surface  of  the  medulla  oblongata. 

1  The  vertebral  artery  sometimes  enters  the  foramen  in  the  transverse  process  of  the  fifth  ver- 
tebra. Dr.  Smyth,  who  tied  this  artery  in  the  living  subject,  found  it,  in  one  of  his  dissections,  pass- 
ing into  the  foramen  in  the  seventh  vertebra. 


BRANCHES    OF    THE   SUBCLAVIAN  ARTERY.  521 

Branches. — These  may  be  divided  into  two  sets — those  given  off  in  the  neck 
and  those  within  the  cranium. 

Cervical  Branches.  Cranial  Branches. 

Lateral  Spinal.  Posterior  Meningeal. 

Muscular.  Anterior  Spinal. 

Posterior  Spinal. 

Posterior  Inferior  Cerebellar. 

Bulbar. 

The  lateral  spinal  branches  enter  the  spinal  canal  through  the  intervertebral 
foramina  and  divide  into  two  branches.  Of  these,  one  passes  along  the  roots  of 
the  nerves  to  supply  the  spinal  cord  and  its  membranes,  anastomosing  with  the 
other  arteries  of  the  spinal  cord ;  the  other  divides  into  an  ascending  and  a 
descending;  branch,  which  unite  with  similar  branches  from  the  arterv  above  and 
below,  so  that  two  lateral  anastomotic  chains  are  formed  on  the  posterior  surface 
of  the  bodies  of  the  vertebrae  near  the  attachment  of  the  pedicles.  From  these 
anastomotic  chains  branches  are  given  off  to  supply  the  periosteum  and  the  bodies 
of  the  vertebrae,  and  to  communicate  with  similar  branches  from  the  opposite  side  ; 
from  these  latter  small  branches  are  given  off  which  join  similar  branches  above 
and  below,  so  that  a  central  anastomotic  chain  is  formed  on  the  posterior  surface 
of  the  bodies  of  the  vertebrae. 

Muscular  branches  are  given  off  to  the  deep  muscles  of  the  neck,  where  the 
vertebral  artery  curves  round  the  articular  process  of  the  atlas.  They  anastomose 
with  the  occipital  and  with  the  ascending  and  deep  cervical  arteries. 

The  posterior  meningeal  are  one  or  two  small  branches  given  off  from  the 
vertebral  opposite  the  foramen  magnum.  They  ramify  between  the  bone  and  dura 
mater  in  the  cerebellar  fossae,  and  supply  the  falx  cerebelli. 

The  anterior  spinal  is  a  small  branch  which  arises  near  the  termination  of  the 
vertebral,  and,  descending  in  front  of  the  medulla  oblongata,  unites  with  its  fellow 
of  the  opposite  side  at  about  the  level  of  the  foramen  magnum.  One  of  these  ves- 
sels is  usually  larger  than  the  other,  but  occasionally  they  are  about  equal  in  size. 
The  single  trunk  thus  formed  descends  on  the  front  of  the  spinal  cord,  and  is  rein- 
forced by  a  succession  of  small  branches  wrhich  enter  the  spinal  canal  through  the 
intervertebral  foramina  ;  these  branches  are  derived  from  the  vertebral  and  ascend- 
ing cervical  of  the  inferior  thyroid  in  the  ne.ck  ;  from  the  intercostal  in  the  dorsal 
region ;  and  from  the  lumbar,  ilio-lumbar,  and  lateral  sacral  arteries  in  the  lower 
part  of  the  spine.  They  unite,  by  means  of  ascending  and  descending  branches,  to 
form  a  single  anterior  median  artery,  which  extends  as  far  as  the  lower  part  of  the 
spinal  cord.  This  vessel  is  placed  in  the  pia  mater  along  the  anterior  median 
fissure ;  it  supplies  that  membrane  and  the  substance  of  the  cord,  and  sends  off 
branches  at  its  lower  part  to  be  distributed  to  the  cauda  equina,  and  ends  on  the 
central  fibrous  prolongation  of  the  cord. 

The  posterior  spinal  arises  from  the  vertebral  at  the  side  of  the  medulla 
oblongata :  passing  backAvard  to  the  posterior  aspect  of  the  spinal  cord,  it  descends 
on  each  side,  lying  behind  the  posterior  roots  of  the  spinal  nerves,  and  is 
reinforced  by  a  succession  of  small  branches  which  enter  the  spinal  canal  through 
the  intervertebral  foramina,  and  by  which  it  is  continued  to  the  lower  part  of  the 
cord  and  to  the  cauda  equina.  Branches  from  these  vessels  form  a  free  anasto- 
mosis round  the  posterior  roots  of  the  spinal  nerves,  and  communicate,  by  means 
of  very  tortuous  transverse  branches,  with  the  vessel  of  the  opposite  side.  At  its 
commencement  it  gives  off  an  ascending  branch,  which  terminates  on  the  side  of 
the  fourth  ventricle. 

The  posterior  inferior  cerebellar  artery  (Fig.  291),  the  largest  branch  of  the 
vertebral,  winds  backward  round  the  upper  part  of  the  medulla  oblongata,  passing 
between  the  origin  of  Lhe  pneumogastric  and  spinal  accessory  nerves,  over  the 
restiform  body  to  the  under  surface  of  the  cerebellum,  where  it  divides  into  two 


522  THE  BLOOD-VASCULAR   SYSTEM. 

branches — an  internal  one,  which  is  continued  backward  to  the  notch  between 
the  two  hemispheres  of  the  cerebellum ;  and  an  external  one,  which  supplies  the 
under  surface  of  the  cerebellum  as  far  as  its  outer  border,  where  it  anastomoses 
with  the  anterior  inferior  cerebellar  and  the  superior  cerebellar  branches  of  the 
basilar  artery.  Branches  from  this  artery  supply  the  choroid  plexus  of  the  fourth 
ventricle. 

The  bulbar  arteries  comprise  several  minute  vessels  which  spring  from  the 
vertebral  and  its  branches  and  are  distributed  to  the  medulla  oblongata. 

Surgical  Anatomy. — The  vertebral  artery  has  been  tied  in  several  instances:  1,  for 
wounds  or  traumatic  aneurism  ;  2,  after  ligation  of  the  innominate,  either  at  the  same  time  to 
prevent  hemorrhage,  or  later  on  to  arrest  bleeding  where  it  has  occurred  at  the  seat  of  ligature  ; 
and  3.  in  epilepsy.  In  these  latter  cases  the  treatment  has  been  recommended  by  Dr. 
Alexander,  of  Liverpool,  in  the  hope  that  by  diminishing  the  supply  of  blood  to  the  posterior 
part  of  the  brain  and  the  spinal  cord  a  diminution  or  cessation  of  the  epileptic  fits  would  result. 
But.  on  account  of  the  uncertainty  as  to  what  cases,  if  any,  derived  benefit  from  the  operation, 
it  has  now  been  abandoned.  The  operation  of  ligation  of  the  vertebral  is  performed  by  making 
an  incision  along  the  posterior  border  of  the  Sterno-mastoid  muscle,  just  above  the  clavicle. 
The  muscle  is  pulled  to  the  inner  side,  and  the  anterior  tubercle  of  the  transverse  process  of  the 
sixth  cervical  vertebra  sought  for.  A  deep  layer  of  fascia  being  now  divided,  the  interval  be- 
tween the  Scalenus  anticus  and  the  Longus  colli  just  below  their  attachment  to  the  tubercle  is 
defined,  and  the  artery  and  vein  found  in  the  interspace.  The  vein  is  to  be  drawn  to  the 
outer  side,  and  the  aneurism  needle  passed  from  without  inward.  Drs.  Eamskill  and  Bright 
have  pointed  out  that  severe  pain  at  the  back  of  the  head  may  be  symptomatic  of  disease 
of  the  vertebral  artery  just  before  it  enters  the  skull.  This  is  explained  by  the  close  connec- 
tion of  the  artery  with  the  suboccipital  nerve  in  the  groove  on  the  posterior  arch  of  the  atlas. 
Disease  of  the  same  artery  has  been  also  said  to  affect  speech,  from  pressure  on  the  hypo- 
glossal where  it  is  in  relation  with  the  vessel,  leading  to  paralysis  of  the  muscles  of  the 
tongue. 

The  Basilar  Artery  (Fig.  291),  so  named  from  its  position  at  the  base  of  the 
skull,  is  a  single  trunk  formed  by  the  junction  of  the  two  vertebral  arteries  ;  it  ex- 
tends from  the  posterior  to  the  anterior  border  of  the  pons  Varolii,  lying  in  its 
median  groove,  under  cover  of  the  arachnoid.  It  ends  by  dividing  into  the  two 
posterior  cerebral  arteries.     Its  branches  are,  on  each  side,  the  following  : 

Transverse.  Superior  Cerebellar. 

Anterior  Inferior  Cerebellar.  Posterior  Cerebral. 

The  transverse  branches  supply  the  pons  Varolii  and  adjacent  parts  of  the  brain  ; 
one  branch,  the  internal  auditory,  accompanies  the  auditory  nerve  into  the  in- 
ternal auditory  meatus. 

The  anterior  inferior  cerebellar  artery  passes  backward  across  the  crus  cerebelli, 
to  be  distributed  to  the  anterior  border  of  the  under  surface  of  the  cerebellum, 
anastomosing  with  the  posterior  inferior  cerebellar  branch  of  the  vertebral. 

The  superior  cerebellar  arteries  arise  near  the  termination  of  the  basilar.  They 
pass  outward,  immediately  behind  the  third  nerves,  which  separate  them  from  the 
posterior  cerebral,  wind  round  the  crura  cerebri,  close  to  the  fourth  nerve,  and, 
arriving  at  the  upper  surface  of  the  cerebellum,  divide  into  branches  which  ramify 
in  the  pia  mater  and,  reaching  the  circumference  of  the  cerebellum,  anastomose 
with  the  branches  of  the  inferior  cerebellar  arteries.  Several  branches  are  given 
to  the  pineal  gland,  the  valve  of  Vieussens,  and  the  velum  interpositum. 

The  posterior  cerebral  arteries,  the  two  terminal  branches  of  the  basilar,  are 
larger  than  the  preceding,  from  which  they  are  separated  near  their  origin  by 
the  third  nerves.  Passing  outward,  parallel  to  the  superior  cerebellar  artery,  and 
receiving  the  posterior  communicating  from  the  internal  carotid,  they  wind  round 
the  crura  cerebri,  and  pass  to  the  under  surface  of  the  occipital  lobes  of  the  cere- 
brum, and  break  up  into  branches  for  the  supply  of  the  temporal  and  occipital 
lobes.      The  branches  of  the  posterior  cerebral  artery  are  : 

Postero-meclian  ganglionic.  f  Anterior  temporal. 

Posterior  choroid.  Three  terminal.  -    Posterior  temporal. 

Postero-latei'al  ganglionic.  (^  Occipital. 


BRANCHES    OF    THE   SUBCLAVIAN  ARTERY.  525 

The  postero-median  ganglionic  branches  (Fig.  296)  are  a  group  of  smaerve    gca. 
which  arise  at  the  commencement  of  the  posterior  cerebral  artery  ;  these,  sometimes 
lar  branches  from  the   posterior   communicating,   pierce   the  posterior  trapezius 
space,  and  supply  the  internal  surfaces  of  the  optic  thalami  and  the  wal 
third  ventricle.      The  posterior  choroid  enters  the  interior  of  the  brain  bei. 
splenium  of  the  corpus   callosum,  and   supplies   the  velum   interpositum   i 
choroid    plexus.       The  postero-lateral  ganglionic  branches  are  a   group   ot 
arteries  which  arise  from  the  posterior  cerebral  artery,  after  it  has  turned  rounu 
crus   cerebri  ;  they  supply    a   considerable  portion  of  the    optic   thalamus. 
terminal  branches  are  distributed  as  follows  :   the  first  {anterior  temporal)  to 
uncinate  gyrus ;  the  second  [posterior  temporal)  to  the  external  occipital  and  i 
third  temporal   convolutions ;    and  the  third  (occipital)    to   the  inner   and   outt 
surfaces  of  the  occipital  lobe. 

v?  Circle  of  Willis. — The  remarkable  anastomosis  which  exists  between  the 
branches  of  the  internal  carotid  and  vertebral  arteries  at  the  base  of  the  brain 
constitutes  the  circle  of  Willis.  It  is  formed,  in  front,  by  the  anterior  cerebral 
arteries,  branches  of  the  internal  carotid,  which  are  connected  together  by  the 
anterior  communicating ;  behind,  by  the  two  posterior  cerebrals,  branches  of  the 
basilar,  which  are  connected  on  each  side  with  the  internal  carotid  by  the  pos- 
terior communicating  arteries  (Fig.  291).  It  is  by  this  anastomosis  that  the  cere- 
bral circulation  is  equalized,  and  provision  made  for  effectually  carrying  it  on  if 
one  or  more  of  the  branches  are  obliterated.  The  parts  of  the  brain  included 
within  this  arterial  circle  are — the  lamina  cinerea,  the  commissure  of  the  optic 
nerves,  the  infundibulum,  the  tuber  cinereum,  the  corpora  albicantia,  and  the 
posterior  perforated  space. 

The  Thyroid  Axis  (Fig.  283)  is  a  short  thick  trunk  which  arises  from  the  fore 
part  of  the  first  portion  of  the  subclavian  artery,  close  to  the  inner  border  of  the 
Scalenus  anticus  muscle,  and  divides,  almost  immediately  after  its  origin,  into 
three  branches — the  inferior  thyroid,   suprascapular,  and  transversalis  colli. 

The  Inferior  thyroid  artery  passes  upward,  in  front  of  the  vertebral  i  artery  and 
Longus  colli  muscle ;  then  turns  inward  behind  the  sheath  of  the  common  carotid 
artery  and  internal  jugular  vein,  and  also  behind  the  sympathetic  nerve,  the  middle 
cervical  ganglion  resting  upon  the  vessel,  and,  reaching  the  lower  border  of  the 
lateral  lobe  of  the  thyroid  gland,  it  divides  into  two  branches,  which  supply  the 
posterior  and  under  part  of  the  organ,  and  anastomose  in  its  substance  with  the  supe- 
rior thyroid  and  with  the  corresponding  artery  of  the  opposite  side.  The  recurrent 
laryngeal  nerve  passes  upward,  generally  behind  but  occasionally  in  front  of  the 
artery.      Its  branches  are  :   the 

Inferior  Laryngeal.  (Esophageal. 

Tracheal.  Ascending  Cervical. 

Muscular. 

The  inferior  laryngeal  branch  ascends  upon  the  trachea  to  the  back  part  of  the 
larynx,  in  company  with  the  recurrent  laryngeal  nerve,  and  supplies  the  muscles 
and  mucous  membrane  of  this  part,  anastomosing  with  the  branch  from  the  oppo- 
site side  and  with  the  laryngeal  branch  from  the  superior  thyroid  artery. 

The  tracheal  branches  are  distributed  upon  the  trachea,  anastomosing  below 
with  the  bronchial  arteries. 

The  oesophageal  branches  are  distributed  to  the  oesophagus,  and  anastomose 
with  the  oesophageal  branches  of  the  aorta. 

The  ascending  cervical  is  a  small  branch  which  arises  from  the  inferior  thyroid 
just  where  that  vessel  is  passing  behind  the  common  carotid  artery,  and  runs  up 
on  the  anterior  tubercles  of  the  transverse  processes  of  the  cervical  vertebrae  in 
the  interval  between  the  Scalenus  anticus  and  Rectus  capitis  anticus  major.  It 
gives  branches  to  the  muscles  of  the  neck,  which  anastomose  with  branches  of  the 
vertebral,  and  sends  one  or  two  branches  into  the  spinal  canal  through  the  inter- 
vertebral foramina  to  be  distributed  to  the  spinal  cord  and  its  membranes,  and  to 


526  THE   BLOOD-VASCULAR    SYSTEM. 

The  posterior  scapular  passes  beneath  the  Levator  anguli  scapulae  to  the  supe- 
rior angle  of  the  scapula,  and  then  descends  along  the  posterior  border  of  that  bone 
as  far  as  the  inferior  angle.  In  its  course  it  is  covered  by  the  Rhomboid  muscles, 
supplying  them  and  the  Latissimus  dorsi  and  Trapezius,  and  anastomosing  with  the 
suprascapular  and  subscapular  arteries,  and  with  the  posterior  branches  of  some  of 
the  intercostal  arteries. 

Peculiarities. — The  superficial  cervical  frequently  arises  as  a  separate  branch  from  the 
thyroid  axis ;  and  the  posterior  scapular,  from  the  third,  more  rarely  from  the  second,  part  of 
the  subclavian. 

The  Internal  mammary  (Fig.  301)  arises  from  the  under  surface  of  the  first 
portion  of  the  subclavian  artery,  opposite  the  thyroid  axis.  It  passes  downward 
and  inward  behind  the  costal  cartilage  of  the  first  rib  to  the  inner  surface  of  the 
anterior  wall  of  the  chest,  resting  against  the  costal  cartilages  about  half  an  inch 
from  the  margin  of  the  sternum  ;  and,  at  the  interval  between  the  sixth  and  seventh 
cartilages,  divides  into  two  branches,  the  musculo-phrenic  and  superior  epigastric. 

Relations. — At  its  origin  it  is  covered  by  the  internal  jugular  and  subclavian 
veins,  and  as  it  enters  the  thorax  is  crossed  from  without  inward  by  the  phrenic 
nerve,  and  then  passes  forward  close  to  the  outer  side  of  the  innominate  vein.  In 
the  upper  part  of  the  thorax  it  lies  behind  the  costal  cartilages  and  Internal  inter- 
costal muscles,  and  is  crossed  by  the  terminations  of  the  upper  six  intercostal  nerves. 
At  first  it  lies  upon  the  pleura,  but  at  the  lower  part  of  the  thorax  the  Triangularis 
sterni  separates  the  artery  from  this  membrane.  It  has  two  venae  comites  ;  these 
unite  into  a  single  vein,  which  joins  the  innominate  vein  of  its  own  side. 

The  branches  of  the  internal  mammary  are — 

Comes  Nervi  Phrenici  (Superior  Phrenic).  Anterior  Intercostal. 

Mediastinal.  Perforating. 

Pericardiac.  Musculo-phrenic. 

Sternal.  Superior  Epigastric. 

The  comes  nervi  phrenici  (superior  phrenic),  is  a  long  slender  branch  which 
accompanies  the  phrenic  nerve,  between  the  pleura  and  pericardium,  to  the 
Diaphragm,  to  which  it  is  distributed,  anastomosing  with  the  other  phrenic 
arteries  from  the  internal  mammary  and  abdominal  aorta. 

The  mediastinal  branches  are  small  vessels  which  are  distributed  to  the  areolar 
tissue  and  lymphatic  glands  in  the  anterior  mediastinum  and  the  remains  of  the 
thymus  gland. 

The  pericardiac  branches  supply  the  upper  part  of  the  anterior  surface  of  the 
pericardium,  the  lower  part  receiving  branches  from  the  musculo-phrenic  artery. 

The  sternal  branches  are  distributed  to  the  Triangularis  sterni  and  to  the 
posterior  surface  of  the  sternum. 

The  mediastinal,  pericardiac,  and  sternal  branches,  together  with  some  twigs 
from  the  comes  nervi  phrenici,  anastomose  with  branches  from  the  intercostal  and 
bronchial  arteries,  and  form  a  minute  plexus  beneath  the  pleura,  which  has  been 
named  by  Turner  the  subpleural  mediastinal  plexus. 

The  anterior  intercostal  arteries  supply  the  five  or  six  upper  intercostal  spaces. 
The  branch  corresponding  to  each  space  soon  divides  into  two,  or  the  two 
branches  may  come  off  separately  from  the  parent  trunk.  The  small  vessels  pass 
outward  in  the  intercostal  spaces,  one  lying  near  the  lower  margin  of  the  rib 
above,  and  the  other  near  the  upper  margin  of  the  rib  below,  and  anastomose 
with  the  intercostal  arteries  from  the  aorta.  They  are  at  first  situated  between 
the  pleura  and  the  Internal  intercostal  muscles,  and  then  between  the  Internal 
and  External  intercostal  muscles.  They  supply  the  Intercostal  muscles,  and,  by 
branches  which  perforate  the  External  intercostal  muscle,  the  Pectoral  muscles 
and  the  mammary  gland. 

The  perforating  arteries  correspond  to  the  five  or  six  upper  intercostal  spaces. 
They  arise  from  the  internal  mammary,  pass  forward  through  the  intercostal 
spaces,  and,  curving  outward,  supply  the  Pectoralis  major  and  the   integument. 


SURGICAL    ANATOMY   OF    THE  AXILLA.  527 

Those  which  correspond  to  the  second,  third,  and  fourth  spaces  are  distributed  to 
the  mammary  gland.     In  females,  during  lactation,  these  branches  are  of  large  size. 

The  musculo-phrenic  artery  is  directed  obliquely  downward  and  outward, 
behind  the  cartilages  of  the  false  ribs,  perforating  the  Diaphragm  at  the  eighth  or 
ninth  rib,  and  terminating,  considerably  reduced  in  size,  opposite  the  last  inter- 
costal space.  It  gives  off  anterior  intercostal  arteries  to  each  of  the  intercostal 
spaces  across  which  it  passes ;  these  diminish  in  size  as  the  spaces  decrease  in 
length,  and  are  distributed  in  a  manner  precisely  similar  to  the  anterior  intercostals 
from  the  internal  mammary.  The  musculo-phrenic  also  gives  branches  to  the 
lower  part  of  the  pericardium,  and  others  which  run  backward  to  the  Diaphragm 
and  downward  to  the  abdominal  muscles. 

The  superior  epigastric  continues  in  the  original  direction  of  the  internal 
mammary  ;  it  descends  through  the  cellular  interval  between  the  costal  and  sternal 
attachments  of  the  Diaphragm,  and  enters  the  sheath  of  the  Rectus  abdominis 
muscle,  at  first  lying  behind  the  muscle,  and  then  perforating  it  and  supplying  it, 
and  anastomosing  with  the  deep  epigastric  artery  from  the  external  iliac.  Some 
vessels  perforate  the  sheath  of  the  Rectus,  and  supply  the  muscles  of  the  abdomen 
and  the  integument,  and  a  small  branch,  which  passes  inward  upon  the  side  of  the 
ensiform  appendix,  anastomoses  in  front  of  that  cartilage  with  the  artery  of  the 
opposite  side.  It  also  gives  some  twigs  to  the  Diaphragm,  while  from  the  artery 
of  the  right  side  small  branches  extend  into  the  falciform  ligament  of  the  liver  and 
anastomose  with  the  hepatic  artery. 

Surgical  Anatomy. — The  course  of  the  internal  mammary  artery  may  be  denned  by  draw- 
ing a  line  across  the  six  upper  intercostal  spaces  half  an  inch  from  and  parallel  with  the  sternum. 
The  position  of  the  vessel  must  be  remembered,  as  it  is  liable  to  be  wounded  in  stabs  of  the 
chest- wall.     It  is  most  easily  reached  by  a  transverse  incision  in  the  second  intercostal  space. 

The  Superior  Intercostal  (Fig.  289)  arises  from  the  upper  and  back  part  of  the 
subclavian  artery,  behind  the  Anterior  scalenus  muscle  on  the  right  side,  and  to 
the  inner  side  of  that  muscle  on  the  left  side.  Passing  backward,  it  gives  off  the 
deep  cervical  branch,  and  then  descends  behind  the  pleura  in  front  of  the  necks  of 
the  first  two  ribs,  and  inosculates  with  the  first  aortic  intercostal.  As  it  crosses  the 
neck  of  the  first  rib  it  lies  to  the  inner  side  of  the  anterior  division  of  the  first 

I  dorsal  nerve  and  to  the  outer  side  of  the  first  thoracic  ganglion  of  the  sympathetic. 
In  the  first  intercostal  space  it  gives  off  a  branch  which  is  distributed  in  a  manner 

;  similar  to  the  distribution  of  the  aortic  intercostals.      The  branch  for  the  second 

1  intercostal  space  usually  joins  with  one  from  the  highest  aortic  intercostal.  Each 
intercostal  gives  off  a  branch  to  the  posterior  spinal  muscles,  and  a  small  one  which 

;  passes  through  the  corresponding  intervertebral  foramen  to  the  spinal  cord  and  its 
membranes. 

The  deep  cervical  branch  [profunda  cervicis)  arises,  in  most  cases,  from  the 

!  superior  intercostal,  and  is  analogous  to  the  posterior  branch  of  an  aortic  inter- 
costal artery  ;  occasionally  it  arises  as  a  separate  branch  from  the  subclavian  artery. 
Passing  backward,  above  the  eighth  cervical  nerve  and  between  the  transverse 
process  of  the  seventh  cervical  vertebra  and  the  first  rib,  it  runs  up  the  back  part 
of  the  neck,  between  the  Oomplexus  and  Semispinalis  colli  muscles,  as  high  as  the 

I  axis,  supplying  these  and  adjacent  muscles,  and  anastomosing  with  the  deep  branch 
of  the  arteria  princeps  cervicis  of  the  occipital,  and  with  branches  which  pass  out- 
ward from  the  vertebral.     It  gives  off  a  special  branch  which  enters  the  spinal 
I  canal  through  the  intervertebral  foramen  between  the  seventh  cervical  and  first 
|  dorsal  vertebrae. 

SURGICAL  ANATOMY   OF  THE  AXILLA. 

The  Axilla  is  a  pyramidal  space,  situated  between  the  upper  and  lateral  part 
of  the  chest  and  the  inner  side  of  the  arm. 

Boundaries. — Its  apex,  which  is  directed  upward  toward  the  root  of  the  neck, 
corresponds  to  the  interval  between  the  first  rib,  the  upper  edge  of  the  scapula, 


528 


THE   BLOOD-VASCULAR   SYSTEM. 


and  the  clavicle,  through  which  the  axillary  vessels  and  nerves  pass.  The  base, 
directed  downward/ is  formed  by  the  integument  and  a  thick  layer  of  fascia,  the 
axillary  fascia,  extending  between  the  lower  border  of  the  Pectoralis  major  in  front 
and  the  lower  border  of  the  Latissimus  dorsi  behind ;  it  is  broad  internally  at  the 
chest,  but  narrow  and  pointed  externally  at  the  arm.  The  anterior  boundary  is 
formed  by  the  Pectoralis  major  and  minor  muscles,  the  former  covering  the  whole 
of  the  anterior  wall  of  the  axilla,  the  latter  covering  only  its  central  part.  The 
space  between  the  inner  border  of  the  Pectoralis  minor  and  the  clavicle  is  occupied 
by  the  costo-coracoid  membrane.  The  posterior  boundary,  which  extends  some- 
what lower  than  the  anterior,  is  formed  by  the  Subscapulars  above,  the  Teres 
major  and  Latissimus  dorsi  below.  On  the  inner  side  are  the  first  four  ribs  with 
their  corresponding  Intercostal  muscles,  and  part  of  the  Serratus  magnus.  On  the 
outer  side,  where  the  anterior  and  posterior  boundaries  converge,  the  space  is  nar- 
row, and  bounded  by  the  humerus,  the  Coraco-brachialis  and  Biceps  muscles. 

Contents. — This  space  contains  the  axillary  vessels  and  brachial  plexus  of 
nerves,  with  their  branches,  some  branches  of  the  intercostal  nerves,  and  a  large 
number  of  lymphatic  glands,  all  connected  together  by  a  quantity  of  fat  and  loose 
areolar  tissue. 

Their  Position. — The  axillary  artery  and  vein,  with  the  brachial  plexus  of 
nerves,  extend  obliquely  along  the  outer  boundary  of  the  axillary  space,  from  its 
apex  to  its  base,  and  are  placed  much  nearer  the  anterior  than  the  posterior  wall, 
the  vein  lying  to  the  inner  or  thoracic  side  of  the  artery  and  partially  concealing 
it.  At  the  fore  part  of  the  axillary  space,  in  contact  with  the  Pectoral  muscles, 
are  the  thoracic  branches  of  the  axillary  artery,  and  along  the  anterior  margin 


Anterior 
circumflex 


Fig.  302.— The  axillary  artery  and  its  branches. 


are  the  thoracic  branches  of  the  axillary  artery,  and  along  the  lower  ma 
Pectoralis  minor  the  long  thoracic  artery  extends  to  the  side  of  the  che; 
back  part,  in  contact  with  the  lower  margin  of  the  Subscapularis  mus* 
subscapular  vessels  and  nerves ;  winding  around  the  outer  border  of  thi 


THE   AXILLARY  ARTERY.  529 

the  dorsalis  scapulae  artery  and  veins  ;  and,  close  to  the  neck  of  the  humerus,  the 
posterior  circumflex  vessels  and  the  circumflex  nerve  are  seen  curving  backward  to 
the  shoulder. 

Along  the  inner  or  thoracic  side  no  vessel  of  any  importance  exists,  the  upper 
part  of  the  space  being  crossed  merely  by  a  few  small  branches  from  the  superior 
thoracic  artery.  There  are  some  important  nerves,  however,  in  this  situation — 
viz.  the  posterior  thoracic  or  external  respiratory  nerve,  descending  on  the  sur- 
face of  the  Serratus  magnus,  to  which  it  is  distributed ;  and  perforating  the  upper 
and  anterior  part  of  this  wall,  the  intercosto-humeral  nerve  or  nerves,  passing 
across  the  axilla  to  the  inner  side  of  the  arm. 

The  cavity  of  the  axilla  is  filled  by  a  quantity  of  loose  areolar  tissue  and  a  large 
number  of  small  arteries  and  veins,  all  of  which  are,  however,  of  inconsiderable 
size,  and  numerous  lymphatic  glands,  the  position  and  arrangement  of  which  are 
described  on  a  subsequent  page. 

Surgical  Anatomy. — The  axilla  is  a  space  of  considerable  surgical  importance.  It  trans- 
mits the  large  vessels  and  nerves  to  the  upper  extremity,  and  these  may  be  the  seat  of  injury  or 
disease :  it  contains  numerous  lymphatic  glands  which  may  require  removalwhen  diseased  ;  in  it 
is  a  quantity  of  loose  connective  and  adipose  tissue  which  may  be  readily  infiltrated  with  blood 
or  inflammatory  exudation,  and  it  may  be  the  seat  of  rapidly-growing  tumors.  Moreover,  it  is 
covered  at  its  base  by  thin  skin,  largely  supplied  with  sebaceous  and  sweat  glands,  which  is  fre- 
quently the  seat  of  small  cutaneous  abscesses  and  boils,  and  of  eruptions  due  to  irritation.  _ 

In  suppuration  in  the  axilla  the  arrangement  of  the  fasciae  plays  a  very  important  part  in  the 
direction  which  the  pus  takes.  As  described  on  page  379,  the  costo-coracoid  membrane,  after 
covering  in  the  space  between  the  clavicle  and  the  upper  border  of  the  Pectoralis  minor,  splits 
to  enclose  this  muscle,  and,  reblending  at  its  lower  border,  becomes  incorporated  with  the  axillary 
fascia  at  the  anterior  fold  of  the  axilla.  This  is  known  as  the  clavi-pectoral  fascia.  Suppura- 
tion may  take  place  either  superficial  to  or  beneath  this  layer  of  fascia ;  that  is,  either  between 
the  Pectorals  or  below  the  Pectoralis  minor :  in  the  former  case,  it  would  point  either  at  the  ante- 
rior border  of  the  axillary  fold  or  in  the  groove  between  the  Deltoid  and  the  Pectoralis  major ; 
in  the  latter,  the  pus  would  have  a  tendency  to  surround  the  vessels  and  nerves  and  ascend  into 
the  neck,  that  being  the  direction  in  which  there  is  least  resistance.  Its  progress  toward  the 
skin  is  prevented  by  the  axillary  fascia;  its  progress  backward,  by  the  Serratus  magnus  ;  forward, 
by  the  clavi-pectoral  fascia  ;  inward,  by  the  wall  of  the  thorax  ;  and  outward,  by  the  upper  limb. 
The  pus  in  these  cases,  after  extending  into  the  neck,  has  been  known  to  spread  through  the 
superior  opening  of  the  thorax  into  the  mediastinum. 

In  opening  an  axillary  abscess  the  knife  should  be  entered  in  the  floor  of  the  axilla,  midway 
between  the  anterior  and  posterior  margins  and  near  the  thoracic  side  of  the  space.  It  is  well 
to  use  a  director  and  dressing  forceps  after  an  incision  has  been  made  through  the  skin  and 
fascia  in  the  manner  directed  by  the  late  Mr.  Hilton. 

The  student  should  attentively  consider  the  relation  of  the  vessels  and  nerves  in  the  several 
parts  of  the  axilla,  for  it  is  the  almost  universal  plan,  in  the  present  day,  to  remove  the  glands 
from  the  axilla  in  operating  for  cancer  of  the  breast.  In  performing  such  an  operation  it  will  be 
necessary  to  proceed  with  much  cau^;°  \:  '\e  direction  of  the  outer  wall  and  apex  of  the  space, 
as  here  the  axillary  vessels  will  be  llirS  1r  of  being  wounded.  Toward  the  posterior  wall  it 
will  be  necessary  to  avoid  the  subscap2noe  dorsalis  scapulae,  and  posterior  circumflex  vessels. 
Along  the  anterior  wall  it  will  be  necessary  to  avoid  the  thoracic  branches.  In  clearing  out  the 
axilla  the  axillary  vein  should  be  first  defined  and  cleared  by  the  fingers  and  an  elevator  up  to 
the  apex  of  the  axilla,  the  Pectoralis  major  being  pulled  up  by  an  assistant  with  a  retractor. 
When  the  apex  of  the  space  is  reached,  all  fat  and  glands  must  be  carefully  removed  and  the 
whole  axilla  cleared  by  separating  the  tissues  along  the  inner  and  posterior  walls,  so  that  when 
the  proceeding  is  completed,  the  axilla  is  cleared  of  all  its  contents  except  the  main  vessels  and 
nerves. 

THE   AXILLARY  ARTERY. 

The  Axillary  Artery,  the  continuation  of  the  subclavian,  commences  at  the 
outer  border  of  the  first  rib,  and  terminates  at  the  lower  border  of  the  tendon  of 
the  Teres  major  muscle,  where  it  takes  the  name  of  brachial.  Its  direction  varies 
with  the  position  of  the  limb :  when  the  arm  lies  by  the  side  of  the  chest,  the 
vessel  forms  a  gentle  curve,  the  convexity  being  upward  and  outward ;  when  it  is 
directed  at  right  angles  with  the  trunk,  the  vessel  is  nearly  straight ;  and  when 
it  is  elevated  still  higher,  the  artery  describes  a  curve  the  concavity  of  which  is 
directed  upward.  At  its  commencement  the  artery  is  very  deeply  situated,  but 
near  its  termination  is  superficial,  being  covered  only  by  the  skin  and  fascia.  The 
description  of  the  relations  of  this  vessel  is  facilitated  by  its  division  into  three 
34 

L 


530 


THE  BLOOD- VASCULAR    SYSTEM. 


portions,  the  first  portion  being  that  above  the  Pectoralis  minor ;   the  second  por- 
tion, behind ;  and  the  third  below,  that  muscle. 

The  first  portion  of  the  axillary  artery  is  in  relation,  in  front,  with  the  clavic- 
ular portion  of  the  Pectoralis  major,  the  costo-coracoid  membrane,  the  external 
anterior  thoracic  nerve,  and  the  acromio-thoracic  and  cephalic  veins  ;  behind,  with 
the  first  intercostal  space,  the  corresponding  Intercostal  muscle,  the  second  and  a 
portion  of  the  third  digitations  of  the  Serratus  magnus,  and  the  posterior  thoracic 
and  internal  anterior  thoracic  nerves ;  on  its  outer  side,  with  the  brachial  plexus, 
from  which  it  is  separated  by  a  little  cellular  interval ;  on  its  inner  or  thoracic  side, 
with  the  axillary  vein,  which  overlaps  the  artery. 

Relations  of  the  First  Portion  of  the  Axillary  Artery. 

In  front. 
Pectoralis  major. 
Costo-coracoid  membrane. 
External  anterior  thoracic  nerve. 
Acromio-thoracic  and  Cephalic  veins. 


Outer  side. 
Brachial  plexus. 


Inner  side. 
Axillary  vein. 


Behind. 
First  Intercostal  space  and  Intercostal  muscle. 
Second  and  third  digitations  of  Serratus  magnus. 
Posterior  thoracic  and  Internal  anterior  thoracic  nerves. 

The  second  portion  of  the  axillary  artery  lies  behind  the  Pectoralis  minor.  It 
is  covered,  in  front,  by  the  Pectoralis  major  and  minor  muscles;  behind,  it  is 
separated  from  the  Subscapularis  by  a  cellular  interval ;  on  the  inner  side  is  the 
axillary  vein,  separated  from  the  artery  by  the  inner  cord  of  the  plexus  and  the 
internal  anterior  thoracic  nerve.  The  brachial  plexus  of  nerves  surrounds  the 
artery  on  three  sides,  and  separates  it  from  direct  contact  with  the  vein  and  adjacent 
muscles.  -/ 


Relations  of  the  Second  Portion  of  the  Axillary  Artery. 

In  front. 
Pectoralis  major  Slllftbr. 


Outer  side. 
Outer  cord  of  plexus. 


Inner  side. 

Axillary  vein. 

Inner  cord  of  plexus. 

Internal  anterior  thoracic  nerve. 


Behind. 
Subscapularis. 
Posterior  cord  of  plexus. 

The  third  portion  of  the  axillary  artery  lies  below  the  Pectoralis  minor.  It  is 
in  relation,  in  front,  with  the  lower  part  of  the  Pectoralis  major  above,  being 
covered  only  by  the  integument  and  fascia  below,  where  it  is  crossed  by  the  inner 
head  of  the  median  nerve ;  behind,  with  the  lower  part  of  the  Subscapularis  and 
the  tendons  of  the  Latissimus  clorsi  and  Teres  major;  on  it&-outer  side,  with  the 
Coraco-brachialis ;  on  its  inner  or  thoracic  side,  with  the  axillary  vein.  The  nerves 
of  the  brachial  plexus  bear  the  following  relation  to  the  artery  in  this  part  of  its 
course :  on  the  outer  side  is  the  median  nerve,  and  the  musculocutaneous  for  a 
short  distance;  on  the  inner  side,  the  ulnar  (between  the  vein  ami  artery)  and 
lesser  internal  cutaneous  nerves  (to  the  inner  side  of  the  vein)  :   in  front,  is  the 


THE   AXILLARY  ARTERY.  531 

internal  cutaneous  nerve,  and  behind,  the  musculo-spiral  and  circumflex,  the  latter 
extending  only  to  the  lower  border  of  the  Subscapulars  muscle. 

Relations  of  the  Third  Portion  of  the  Axillary  Artery. 

In  front. 
Integument  and  fascia. 
Pectoralis  major. 
Inner  head  of  median  nerve. 
,  Internal  cutaneous  nerve. 

Outer  side.  f                 \                                Inner  side. 

Coraco-brachialis.  f       Art^y?      )  Ulnar  nerve. 

Median  nerve.  I  Third  portion.  J  Axillary  vein. 

Musculo-cutaneous  nerve.  \                 J  Lesser  internal  cutaneous  nerve. 

Behind. 
Subscapulars. 

Tendons  of  Latissimus  dorsi  and  Teres  major. 
Musculo-spiral  and  circumflex  nerves. 

Peculiarities. — The  axillary  artery,  in  about  one  case  out  of  every  ten,  gives  off  a  large 
branch,  which  forms  either  one  of  the  arteries  of  the  forearm  or  a  large  muscular  trunk.  In  the 
first  set  of  cases  this  artery  is  most  frequently  the  radial  (1  in  33),  sometimes  the  ulnar  (1  in  72), 
and,  very  rarely,  the  interosseous  (1  in  506).  In  the  second  set  of  cases  the  trunk  has  been 
found  to  give  origin  to  the  subscapular,  circumflex,  and  profunda  arteries  of  the  arm.  Some- 
times only  one  of  the  ■  circumflex,  or  one  of  the  profunda  arteries,  arose  from  the  trunk.  In' 
these  cases  the  brachial  plexus  surrounded  the  trunk  of  the  branches  and  not  the  main  vessel. 

Surface  Marking. — The  course  of  the  axillary  artery  may  be  marked  out  by  raising  the 
arm  to  a  right  angle  and  drawing  a  line  from  the  middle  of  the  clavicle  to  the  point  where  the 
tendon  of  the  Pectoralis  major  crosses  the  prominence  caused  by  the  Coraco-brachialis  as  it 
emerges  from  under  cover  of  the  anterior  fold  of  the  axilla.  The  third  portion  of  the  artery  can 
be  felt  pulsating  beneath  the  skin  and  fascia,  at  the  junction  of  the  anterior  with  the  middle 
third  of  the  space  between  the  anterior  and  posterior  folds  of  the  axilla,  close  to  the  inner  border 
of  the  Coraco-brachialis. 

Surgical  Anatomy. — The  student,  having  carefully  examined  the  relations  of  the  axillary 
artery  in  its  various  parts,  should  now  consider  in  what  situation  compression  of  this  vessel 
may  be  most  easily  effected,  and  the  best  position  for  the  application  of  a  ligature  to  it  when 
necessary. 

Compression  of  the  vessel  may  be  required  in  the  removal  of  tumors  or  in  amputation  of 
the  upper  part  of  the  arm ;  and  the  only  situation  in  which  this  can  be  effectually  made  is  in  the 
lower  part  of  its  course ;  by  pressing  on  it  in  this  situation  from  within  outward  against  the 
humerus  the  circulation  may  be  effectually  arrested. 

The  axillary  artery  is  perhaps  more  frequently  lacerated  than  any  other  artery  in  the  body, 
with  the  exception  of  the  popliteal,  by  violent  movements  of  the  upper  extremity,  especially  in 
those  cases  where  its  coats  are  diseased.  It  has  occasionally  been  ruptured  in  attempts  to  reduce 
old  dislocations  of  the  shoulder-joint.  This  lesion  is  most  likely  to  occur  during  the  preliminary 
breaking  down  of  adhesions,  in  consequence  of  the  artery  having  become  fixed  to  the  capsule 
of  the  joint.  Aneurism  of  the  axillary  artery  is  of  frequent  occurrence,  a  large  percentage  of 
the  cases  being  traumatic  in  their  origin,  due  to  the  violence  to  which  it  is  exposed  in  the  varied, 
extensive,  and  often  violent  movement  of  the  limb. 

The  application  of  a  ligature  to  the  axillary  artery  may  be  required  in  cases  of 
aneurism  of  the  upper  part  of  the  brachial  or  as  a  distal  operation  for  aneurism  of  the  sub- 
clavian ;  and  there  are  only  two  situations  in  which  it  can  be  secured — viz.  in  the  first  and  in  the 
third  parts  of  its  course  ;  for  the  axillary  artery  at  its  central  part  is  so  deepfy  seated,  and,  at  the 
same  time,  so  closely  surrounded  with  large  nervous  trunks,  that  the  application  of  a  ligature  to 
it  in  that  situation  would  be  almost  impracticable. 

In  the  third  part  of  its  course  the  operation  is  most  simple,  and  may  be  performed  in  the 
following  manner:  The  patient  being  placed  on  a  bed  and  the  arm  separated  from  the  side,  with 
the  hand  supinated,  an  incision  is  made  through  the  integument  forming  the  floor  of  the  axilla 
about  two  inches  in  length,  a  little  nearer  to  the  anterior  than  the  posterior  fold  of  the  axilla. 
After  carefully  dissecting  through  the  areolar  tissue  and  fascia,  the  median  nerve  and  axillary 
vein  are  exposed  ;  the  former  having  been  displaced  to  the  outer  and  the  latter  to  the  inner  side 
of  the  arm,  the  elbow  being  at  the  same  time  bent,  so  as  to  relax  the  structures  and  facilitate 
their  separation,  the  ligature  may  be  passed  round  the  artery  from  the  ulnai-  to  the  radial  side. 

This  portion  of  the  artery  is  occasionally  crossed  by  a  muscidar  slip,  the  axillary  arch,  derived 
from  the  Latissimus  dorsi,  which  may  mislead  the  surgeon  during  an  operation.  The  occasional 
existence  of  this  muscular  fasciculus  was  spoken  of  in  the  description  of  the  muscles.  It  may 
easily  be  recognized  by  the  transverse  direction  of  its  fibres. 

/ 


532  THE   BLOOD-VASCULAR   SYSTEM. 

The  first  portion  of  the  axillary  artery  may  be  tied  in  cases  of  aneurism  encroaching  so  far 
upward  that  a  ligature  cannot  he  applied  in  the  lower  part  of  its  course.  Notwithstanding  that 
this  operation  has  been  performed  in  some  few  cases,  and  with  success,  its  performance  is 
attended  with  much  difficulty  and  danger.  The  student  will  remark  that  in  this  situation  it 
would  be  necessary  to  divide  a  thick  muscle,  and,  after  incising  the  costo-coracoid  membrane, 
the  artery  would  be  exposed  at  the  bottom  of  a  more  or  less  deep  space,  with  the  cephalic  and 
axillary  veins  in  such  relation  with  it  as  must  render  the  application  of  a  ligature  to  this  part 
of  the  vessel  particularly  hazardous.  Under  such  circumstances  it  is  an  easier,  and  at  the 
same  time  more  advisable,  operation  to  tie  the  subclavian  artery  in  the  third  part  of  its  course. 

The  vessel  can  be  best  secured  by  a  curved  incision  with  the  convexity  downward  from  a 
point  half  an  inch  external  to  the  Sterno-clavicular  joint  to  a  point  half  an  hich  internal  to  the 
coracoid  process.  The  limb  is  to  be  well  abducted  and  the  head  inclined  to  the  opposite  side, 
and  this  incision  carried  through  the  superficial  structures,  care  being  taken  of  the  cephalic  vein 
at  the  outer  angle  of  the  incision.  The  clavicular  origin  of  the  Pectoralis  major  is  then  divided 
in  the  whole  extent  of  the  wound.  The  arm  is  now  to  be  brought  to  the  side,  and  the  upper 
edge  of  the  Pectoralis  minor  defined  and  drawn  downward.  The  costo-coracoid  membrane  is  to 
be  carefully  divided  on  a  director  close  to  the  coracoid  process,  and  the  axillary  sheath  exposed  ; 
this  is  to  be  opened  with  especial  care  on  account  of  the  vein  overlapping  the  artery.  The 
needle  should  be  passed  from  below,  so  as  to  avoid  wounding  the  vein. 

In  a  case  of  wound  of  the  vessel  the  general  practice  of  cutting  down  upon,  and  tying  it 
above  and  below  the  wounded  point  should  be  adopted  in  all  cases. 

Collateral  Circulation  after  Ligature  of  the  Axillary  Artery. — If  the  artery  be  tied 
above  the  origin  of  the  acromial  thoracic,  the  collateral  circulation  will  be  carried  on  by  the  same 
branches  as  after  the  ligature  of  the  subclavian ;  if  at  a  lower  point,  between  the  acromial 
thoracic  and  subscapular  arteries,  the  latter  vessel,  by  its  free  anastomoses  with  the  other 
scapular  arteries,  branches  of  the  subclavian,  will  become  the  chief  agent  in  carrying  on  the  cir- 
culation, to  which  the  long  thoracic,  if  it  be  below  the  ligature,  will  materially  contribute  by  its 
anastomoses  with  the  intercostal  and  internal  mammary  arteries.  If  the  point  included  in  the 
ligature  be  below  the  origin  of  the  subscapular  artery,  it  will  most  probably  also  be  below  the 
origins  of  the  two  circumflex  arteries.  The  chief  agents  in  restoring  the  circulation  will  then  be 
the  subscapular  and  the  two  circumflex  arteries  anastomosing  with  the  superior  profunda  from 
the  brachial,  which  will  be  afterward  referred  to  as  performing  the  same  office  after  ligation  of 
the  brachial.  The  cases  in  which  the  operation  has  been  performed  are  few  in  number,  and  no 
published  account  of  dissections  of  the  collateral  circulation  appears  to  exist. 

Branches  of  the  Axillary  Artery. 
The  branches  of  the  axillary  artery  are — 

xt         £    j^—^rf  Superior  Thoracic.  ^  7        ,  f  Long  Thoracic. 

Jerom  nr#t  parti    A  •  1  mi,        •  ±rom  second  part  <    A1   &m, 

-^___.     L         |  Acromial  Ihoracic.  r        \ ~Alar--±  horacte. 

(  Subscapular. 
<  Posterior  Circ 
I  Anterior  Circumflex. 


From  third  part  <  Posterior  Circumflex. 


The  superior  thoracic  is  a  small  artery  which  arises  from  the  axillary  sepa- 
rately or  by  a  common  trunk  with  the  acromial  thoracic.  Running  forward  and 
inward  along  the  upper  border  of  the  Pectoralis  minor,  it  passes  between  it  and  the 
Pectoralis  major  to  the  side  of  the  chest.  It  supplies  these  muscles  and  the  parietes 
of  the  thorax,  anastomosing  with  the  internal  mammary  and  intercostal  arteries. 

The  acromial  thoracic  is  a  short  trunk  which  arises  from  the  fore  part  of  the 
axillary  artery,  its  origin  being  generally  overlapped  by  the  upper  edge  of  the 
Pectoralis  minor.  Projecting  forward  to  the  upper  border  of  the  Pectoralis  minor, 
it  divides  into  three  sets  of  branches — thoracic,  acromial,  and  descending.  The 
thoracic  branches,  two  or  three  in  number,  are  distributed  to  the  Serratus  magnus 
and  Pectoral  muscles,  anastomosing  with  the  intercostal  branches  of  the  internal 
mammary.  The  acromial  branches  are  directed  outward  toward  the  acromion, 
supplying  the  Deltoid  muscle,  and  anastomosing,  on  the  surface  of  the  acromion, 
with  the  suprascapular  and  posterior  circumflex  arteries.  The  descending  or 
humeral  branch  passes  in  the  space  between  the  Pectoralis  major  and  Deltoid  in 
the  same  groove  as  the  cephalic  vein,  and  supplies  both  muscles.  The  artery  also 
gives  off"  a  very  small  branch,  the  clavicular,  which  passes  upward  to  the  Sub- 
clavius  muscle. 

The  long  thoracic  passes  downward  and  inward  along  the  lower  border  of  the 
Pectoralis   minor  to  the  side  of  the   chest,  supplying  the   Serratus  magnus,  the 


THE   BRACHIAL    ARTERY.  533 

Pectoral  muscles,  and  mammary  gland,  and  sending  branches  across  the  axilla  to 
the  axillary  glands  and  Subscapulars ;  it  anastomoses  with  the  internal  mammary 
and  intercostal  arteries. 

The  alar  thoracic  is  a  small  branch  which  supplies  the  glands  and  areolar  tissue 
of  the  axilla.  Its  place  is  frequently  supplied  by  branches  from  some  of  the  other 
thoracic  arteries. 

The  subscapular,  the  largest  branch  of  the  axillary  artery,  arises  opposite  the 
lower  border  of  the  Subscapularis  muscle,  and  passes  downward  and  backward 
along  its  lower  margin  to  the  inferior  angle  of  the  scapula,  where  it  anastomoses 
with  the  long  thoracic  and  intercostal  arteries  and  with  the  posterior  scapular,  a 
branch  of  the  transversalis  colli,  from  the  thyroid  axis  of  the  subclavian.  About 
an  inch  and  a  half  from  its  origin  it  gives  off  a  large  branch,  the  dorsalis  scapulce, 
and  terminates  by  supplying  branches  to  the  muscles  in  the  neighborhood. 

The  dorsalis  scapulae  is  given  off  from  the  subscapular  about  an  inch  and  a  half 
from  its  origin,  and  is  generally  larger  than  the  continuation  of  the  vessel.  It 
curves  round  the  axillary  border  of  the  scapula,  leaving  the  axilla  through  the 
space  between  the  Teres  minor  above,  the  Teres  major  below,  and  the  long  head 
of  the  Triceps  externally  (Fig.  300),  and  enters  the  infraspinous  fossa  by  passing 
under  cover  of  the  Teres  minor,  where  it  anastomoses  with  the  posterior  scapular 
and  suprascapular  arteries.  In  its  course  it  gives  off  two  sets  of  branches :  one 
enters  the  subscapular  fossa  beneath  the  Subscapularis,  which  it  supplies,  anasto- 
mosing with  the  posterior  scapular  and  suprascapular  arteries ;  the  other  is  con- 
tinued along  the  axillary  border  of  the  scapula,  between  the  Teres  major  and 
minor,  and,  at  the  dorsal  surface  of  the  inferior  angle  of  the  bone,  anastomoses 
with  the  posterior  scapular.  In  addition  to  these,  small  branches  are  distributed 
to  the  back  part  of  the  Deltoid  muscle  and  the  long  head  of  the  Triceps,  anasto- 
mosing with  an  ascending  branch  of  the  superior  profunda  of  the  brachial. 

The  circumflex  arteries  wind  round  the  neck  of  the  humerus.  The  posterior 
circumflex  (Fig.  300),  the  larger  of  the  two,  arises  from  the  back  part  of  the  axillary 
opposite  the  lower  border  of  the  Subscapularis  muscle,  and,  passing  backward  with 
the  circumflex  veins  and  nerve  through  the  quadrangular  space  bounded  by  the 
Teres  major  and  minor,  the  scapular  head  of  the  Triceps  and  the  humerus,  winds 
round  the  neck  of  that  bone  and  is  distributed  to  the  Deltoid  muscle  and  shoulder- 
joint,  anastomosing  with  the  anterior  circumflex  and  acromial  thoracic  arteries,  and 
with  the  superior  profunda  branch  of  the  brachial  artery.  The  anterior  circumflex 
Figs.  300,  302),  considerably  smaller  than  the  preceding,  arises  nearly  opposite 
that  vessel  from  the  outer  side  of  the  axillary  artery.  It  passes  horizontally  out- 
ward beneath  the  Coraco-brachialis  and  short  head  of  the  Biceps,  lying  upon  the 
fore  part  of  the  neck  of  the  humerus,  and,  on  reaching  the  bicipital  groove,  gives 
off  an  ascending  branch  which  passes  upward  along  the  groove  to  supply  the  head 
of  the  bone  and  the  shoulder-joint.  The  trunk  of  the  vessel  is  then  continued  out- 
ward beneath  the  Deltoid,  which  it  supplies,  and  anastomoses  with  the  posterior 
circumflex  artery. 

THE  BRACHIAL  ARTERY  (Fig.  303). 

The  Brachial  Artery  commences  at  the  lower  margin  of  the  tendon  of  the  Teres 
major,  and,  passing  down  the  inner  and  anterior  aspect  of  the  arm,  terminates  about 
half  an  inch  below  the  bend  of  the  elbow,  where  it  divides  into  the  radial  and 
ulnar  arteries.  At  first  the  brachial  artery  lies  internal  to  the  humerus  ;  but  as  it 
passes  down  the  arm  it  gradually  gets  in  front  of  the  bone,  and  at  the  bend  of  the 
elbow  it  lies  midway  between  the  two  condyles. 

Relations. — This  artery  is  superficial  throughout  its  entire  extent,  being  covered, 
in  front,  by  the  integument,  the  superficial  and  deep  fasciae ;  the  bicipital  fascia 
separates  it  opposite  the  elbow  from  the  median  basilic  vein ;  the  median  nerve 
crosses  it  at  its  middle;  behind,  it  is  separated  from  the  long  head  of  the  Triceps 
by  the  musculo-spiral  nerve  and  superior  profunda  artery.     It  then  lies  upon  the 


534  THE  BLOOD-  VASCULAR   SYSTEM. 

inner  head  of  the  Triceps,  next  upon  the  insertion  of  the  Coraco-brachialis,  and 
lastly  on  the  Brachialis  anticus ;  by  its  outer  side,  it  is  in  relation  with  the  com- 
mencement of  the  median  nerve  and  the  Coraco-brachialis  and  Biceps  muscles, 
which  overlap  the  artery  to  a  considerable  extent;  by  its  inner  side,  its  upper 
half  is  in  relation  with  the  internal  cutaneous  and  ulnar  nerves,  its  lower  half  with 
the  median  nerve.  The  basilic  vein  lies  on  the  inner  side  of  the  artery,  but  is  sepa- 
rated from  it  in  the  lower  part  of  the  arm  by  the  deep  fascia.  It  is  accompanied  by 
two  venae  comites,  which  lie  in  close  contact  with  the  artery,  being  connected 
together  at  intervals  by  short  transverse  communicating  branches. 

Plan  of  the  Relations  of  the  Beachial  Artery. 

In  front. 

Integument  and  fasciae. 
Bicipital  fascia,  median  basilic  vein. 
Median  nerve. 
k  Overlapped  by  Coraco-brachialis  and  Biceps. 

Jid  /^~~^ 

Outer  side.  /  \  Inner  side. 


Median  nerve  (above).                  If    Artery.  Internal  cutaneous  and  Ulnar  nerves. 

Coraco-brachialis.                          \\  //        Median  nerve  (below). 

Biceps.  \\, „//         Basilic  vein. 

Behind. 

Triceps  (long  and  inner  heads).  ^ 
Musculo-spiral  nerve.  \^ 

Superior  profunda  artery.     \/ 
Coraco-brachialis.  ■ 

Brachialis  anticus. 

SURGICAL  ANATOMY  OF  THE  BEND  OF  THE  ELBOW. 

At  the  bend  of  the  elbow  the  brachial  artery  sinks  deeply  into  a  triangular 
interval,  the  base  of  which  is  directed  upward,  and  may  be  represented  by  a  line 
connecting  the  two  condyles  of  the  humerus ;  the  sides  are  bounded,  externally,  by 
the  inner  edge  of  the  Supinator  longus  ;  internally,  by  the  outer  margin  of  the 
Pronator  radii  teres ;  its  floor  is  formed  by  the  Brachialis  anticus  and  Supinator 
brevis.  This  space  contains  the  brachial  artery  with  its  accompanying  veins,  the 
radial  and  ulnar  arteries,  the  median  and  musculo-spiral  nerves,  and  the  tendon  of 
the  Biceps.  The  brachial  artery  occupies  the  middle  line  of  this  space,  and 
divides  opposite  the  neck  of  the  radius  into  the  radial  and  ulnar  arteries ;  it  is 
covered,  in  front,  by  the  integument,  the  superficial  fascia,  and  the  median  basilic 
vein,  the  vein  being  separated  from  direct  contact  with  the  artery  by  the  bicipital 
fascia.  Behind,  it  lies  on  the  Brachialis  anticus,  which  separates  it  from  the 
elbow-joint.  The  median  nerve  lies  on  the  inner  side  of  the  artery,  close  to  it 
above,  but  separated  from  it  below  by  the  coronoid  origin  of  the  Pronator  radii 
teres.  The  tendon  of  the  Biceps  lies  to  the  outer  side  of  the  space,  and  the  mus- 
culo-spiral nerve  still  more  externally,  situated  upon  the  Supinator  brevis  and 
partly  concealed  by  the  Supinator  longus. 

Peculiarities  of  the  Brachial  Artery  as  regards  its  Course. — The  brachial  artery,  ac- 
companied by  the  median  nerve,  may  leave  the  inner  border  of  the  Biceps  and  descend  toward 
the  inner  condyle  of  the  humerus,  where  it  usually  curves  round  a  prominence  of  bone,  the 
supra-condylar  process,  from  which  a  fibrous  arch  is  usually  thrown  over  the  artery;  it  then 
inclines  outward,  beneath  or  through  the  substance  of  the  Pronator  radii  teres  muscle,  to  the 
bend  of  the  elbow.  The  variation  bears  considerable  analogy  to  the  normal  condition  of  the 
artery  in  some  of  the  carnivora :  it  has  been  referred  to  in  the  description  of  the  humerus 
(page  146). 

As  regards  its  Division. — Occasionally,  the  artery  is  divided  for  a  short  distance  at  its 
upper  part  into  two  trunks,  which  are  united  above  and  below.  A  similar  peculiarity  occurs 
in  the  main  vessel  of  the  lower  limb. 


BRANCHES    OF    THE   BRACHIAL    ARTERY. 


535 


The  point  of  bifurcation  may  be  above  or  below  the  usual  point,  the  former  condition  being 
by  far  the  more  frequent,     Out  of  481  examinations  recorded  by  Mr.  Quain,  some  made  on  the 
right  and  some  on  the  left  side  of  the  body,  in  386  the  artery  bifurcated  in  its  normal  position. 
In  one  case  only  was  the  place  of  division  lower 
than  usual,  being  two  or  three  inches  below  the 
elbow-joint,     "  In  94  cases  out  of  481,  or  about 
1  in  5$,  there  were  two  arteries  instead  of  one 
in  some  part  or  in  the  whole  of  the  arm." 

There  appears,  however,  to  be  no  corre- 
spondence between  the  arteries  of  the  two  arms 
with  respect  to  their  irregular  division  ;  for  in 
61  bodies  it  occurred  on  one  side  only  in  43 ; 
on  both  sides,  in  different  positions,  in  13 ;  on 
both  sides,  in  the  same  position,  in  5. 

The  point  of  bifurcation  takes  place  at 
different  parts  of  the  arm,  being  most  fre- 
quent in  the  upper  part,  less  so  in  the  lower 
part,  and  least  so  in  the  middle,  the  most 
usual  point  for  the  application  of  a  ligature ; 
under  any  of  these  circumstances  two  large 
arteries  would  be  found  in  the  arm  instead  of 
one.  The  most  frequent  (in  three  out  of  four) 
of  these  peculiarities  is  the  high  division  of 
the  radial.  That  artery  often  arises  from  the 
inner  side  of  the  brachial,  and  runs  parallel 
with  the  main  trunk  to  the  elbow,  where  it 
crosses  it,  lying  beneath  the  fascia ;  or  it  may 
perforate  the  fascia  and  pass  over  the  artery 
immediately  beneath  the  integument. 

The  ulnar  sometimes  arises  from  the 
brachial  high  up,  and  accompanies  that  ves- 
sel to  the  lower  part  of  the  arm,  and  descends 
toward  the  inner  condyle.  In  the  forearm  it 
generally  lies  beneath  the  deep  fascia,  super- 
ficial to  the  flexor  muscles ;  occasionally  be- 
tween the  integument  and  deep  fascia,  and 
very  rarely  beneath  the  flexor  muscles. 

The  interosseous  artery  sometimes  arises 
from  the  upper  part  of  the  brachial  or  axil- 
lary ;  as  it  passes  down  the  arm  it  lies  behind 
the  main  trunk,  and  at  the  bend  of  the  elbow 
regains  its  usual  position. 

In  some  cases  of  high  division  of  the 
radial  the  remaining  trunk  (ulnar  interosseous) 
occasionally  passes,  together  with  the  median 
nerve,  along  the  inner  margin  of  the  arm  to 
the  inner  condyle,  and  then  passing  from 
within  outward,  beneath  or  through  the  Pro- 
nator radii  teres,  regains  its  usual  position  at 
the  bend  of  the  elbow. 

Occasionally  the  two  arteries  representing 
the  brachial  are  connected  at  the  bend  of  the 
elbow  by  a  short  transverse  branch,  and  are 
even  sometimes  reunited. 

Sometimes,  long  slender  vessels,  vasa  aber- 
rantia,  connect  the  brachial  or  axillary  arteries  with  one  of  the  arteries  of  the  forearm  or  a 
branch  from  them.     These  vessels  usually  join  the  radial. 

Varieties  in  Muscular  Relations.1— The  brachial  artery  is  occasionally  concealed  in  some 
part  of  its  course  by  muscular  or  tendinous  slips  derived  from  the  Coraco-brachialis,  Biceps, 
Brachials  anticus,  and  Pronator  radii  teres  muscles. 

Surface  Marking. — The  direction  of  the  brachial  artery  is  marked  by  a  line  drawn  along 
the  inner  edge  of  the  Biceps  from  the  insertion  of  the  Teres  major  muscle  to  the  point  midway 
between  the  condyles  of  the  humerus. 

Surgical  Anatomy.— Compression  of  the  brachial  artery  is  required  in  cases  of  amputation 
and  some  other  operations  in  the  arm  and  forearm  ;  and  it  will  be  observed  that  it  maybe  effected 
in  almost  any  part  of  the  course  of  the  artery.  If  pressure  is  made  in  the  upper  part  of  the 
limb,  it  should  be  directed  from  within  outward ;  and  if  in  the  lower  part,  from  before  backward, 
as  the  artery  lies  on  the  inner  side  of  the  humerus  above  and  in  front  below.  The  most  favor- 
able situation  is  abc  ut  the  middle  of  the  arm,  where  it  lies  on  the  tendon  of  the  Coraco-brachialis 
on  the  inner  flat  side  of  the  humerus. 

1  See  Struther's  Anatomical  and  Physiological  Observations. 


Fig.  303.— The  brachial  artery. 


536  THE  BLOOD-VASCULAR    SYSTEM. 

The  application  of  a  ligature  to  the  brachial  artery  may  be  required  in  case  of  wound  of 
the  vessel  and  in  some  cases  of  wound  of  the  palmar  arch.  It  is  also  sometimes  necessary  in 
cases  of  aneurism  of  the  brachial,  the  radial,  ulnar,  or  interosseous  arteries.  The  artery  may 
be  'secured  in  any  part  of  its  course.  The  chief  guides  in  determining  its  position  are  the  sur- 
face markings  produced  by  the  inner  margin  of  the  Coraco-braehialis  and  Biceps,  the  known 
course  of  the  vessel,  and  its  pulsation,  which  should  be  carefully  felt  for  before  any  operation  is 
performed,  as  the  vessel  occasionally  deviates  from  its  usual  position  in  the  arm.  In  whatever 
situation  the  operation  is  performed,  great  care  is  necessary,  on  account  of  the  extreme  thinness 
of  the  parts  covering  the  artery  and  the  intimate  connection  which  the  vessel  has  throughout  its 
whole  course  with  important  nerves  and  veins.  Sometimes  a  thin  layer  of  muscular  fibre  is 
met  with  concealing  the  artery ;  if  such  is  the  case,  it  must  be  cut  across  in  order  to  expose  the 
vessel. 

In  the  upper  third  of  the  arm  the  artery  may  be  exposed  in  the  following  manner :  The 
patient  being  placed  supine  upon  a  table,  the  affected  limb  should  be  raised  from  the  side  and 
the  hand  supinated.  An  incision  about  two  inches  in  length  should  be  made  on  the  inner 
side  of  the  Coraco-braehialis  muscle,  and  the  subjacent  fascia  cautiously  divided,  so  as  to  avoid 
wounding  the  internal  cutaneous  nerve  or  basilic  vein,  which  sometimes  runs  on  the  surface  of 
the  artery  as  high  as  the  axilla.  The  fascia  having  been  divided,  it  should  be  remembered  that 
the  ulnar  and  internal  cutaneous  nerves  lie  on  the  inner  side  of  the  artery,  the  median  on  the 
outer  side,  the  latter  nerve  being  occasionally  superficial  to  the  artery  in  this  situation,  and  that 
the  venae  comites  are  also  in  relation  with  the  vessel,  one  on  either  side.  These  being  carefully 
separated,  the  aneurism  needle  should  be  passed  round  the  artery  from  the  inner  to  the  outer 
side. 

If  two  arteries  are  present  in  the  arm  in  consequence  of  a  high  division,  they  are  usually 
placed  side  by  side :  and  if  they  are  exposed  in  an  operation,  the  surgeon  should  endeavor  to 
ascertain,  by  alternately  pressing  on  each  vessel,  which  of  the  two  communicates  with  the  wound 
or  aneurism,  when  a  ligature  may  be  applied  accordingly ;  or  if  pulsation  or  haemorrhage  ceases 
only  when  both  vessels  are  compressed,  both  vessels  may  be  tied,  as  it  may  be  concluded  that 
the  two  communicate  above  the  seat  of  disease  or  are  reunited. 

_  It  should  also  be  remembered  that  two  arteries  may  be  present  in  the  arm  in  a  case  of  high 
division,  and  that  one  of  these  may  be  found  along  the  inner  intermuscular  septum,  in  a  line 
toward  the  inner  condyle  of  the  humerus,  or  in  the  usual  position  of  the  brachial,  but  deeply 
placed  beneath  the  common  trunk :  a  knowledge  of  these  facts  will  suggest  the  precautions 
necessary  in  every  case,  and  indicate  the  measures  to  be  adopted  when  anomalies  are  met 
with. 

In  the  middle  of  the  arm  the  brachial  artery  may  be  exposed  by  making  an  incision  along 
the  inner  margin  of  the  Biceps  muscle.  The  forearm  being  bent  so  as  to  relax  the  muscle,  it 
should  be  drawn  slightly  aside,  and,  the  fascia  being  carefully  divided,  the  median  nerve  will  be 
exposed  lying  upon  the  artery  (sometimes  beneath) ;  this  being  drawn  inward  and  the  muscle 
outward,  the  artery  should  be  separated  from  its  accompanying  veins  and  secured.  In  this 
situation  the  inferior  profunda  may  be  mistaken  for  the  main  trunk,  especially  if  enlarged,  from 
the  collateral  circulation  having  become  established ;  this  may  be  avoided  by  directing  the  incis- 
ion externally  toward  the  Biceps,  rather  than  inward  or  backward  toward  the  Triceps. 

The  lower  part  of  the  brachial  artery  is  of  interest  in  a  surgical  point  of  view,  on  account 
of  the  relation  which  it  bears  to  the  veins  most  commonly  opened  in  venesection.  Of  these 
vessels,  the  median  basilic  is  the  largest  and  most  prominent,  and,  consequently,  the  one  usually 
selected  for  the  operation.  It  should  be  remembered  that  this  vein  runs  parallel  with  the 
brachial  artery,  from  which  it  is  separated  by  the  bicipital  fascia,  and  that  care  should  be  taken 
in  opening  the  vein  not  to  carry  the  incision. too  deeply,  so  as  to  endanger  the  artery. 

Collateral  Circulation. — After  the  application  of  a  ligature  to  the  brachial  artery  in  the 
upper  third  of  the  arm,  the  circulation  is  carried  on  by  branches  from  the  circumflex  and 
subscapular  arteries,  anastomosing  with  ascending  branches  from  the  superior  profunda.  If  the 
brachial  is  tied  below  the  origin  of  the  profunda  arteries,  the  circulation  is  maintained  by  the 
branches  of  the  profundae,  anastomosing  with  the  recurrent  radial,  ulnar,  and  interosseous 
arteries.  In  two  cases  described  by  Mr.  South,1  in  which  the  brachial  artery  had  been  tied  some 
time  previously,  in  one  '"  a  long  portion  of  the  artery  had  been  obliterated,  and  sets  of  vessels 
are  descending  on  either  side  from  above  the  obliteration,  to  be  received  into  others  which  ascend 
in  a  similar  manner  from  below  it.  In  the  other  the  obliteration  is  less  extensive,  and  a  single 
curved  artery  about  as  big  as  a  crow-quill  passes  from  the  upper  to  the  lower  open  part  of  the 
artery. ' ' 

The  branches  of  the  brachial  artery  are — the 

Superior  Profunda.  Inferior  Profunda. 

Nutrient.  Anastomotica  Magna. 

Muscular. 

1  Chelius's  Surgery,  vol.  ii.  p.  254.  See  also  White's  engraving,  referred  to  by  Mr.  South,  of  the 
anastomosing  branches  after  ligature  of  the  brachial,  in  White's  Cases  inlSurgen,.  Porta  also  gives  a 
case  (with  drawings)  of  the  circulation  after  ligature  of  both  brachial  and  radial  (Alterazioni 
Patoligiche  delle  Arterie). 


BRANCHES    OF   THE   BRACHIAL    ARTERY.  537 

The  superior  profunda  arises  from  the  inner  and  back  part  of  the  brachial,  just 
below  the  lower  border  of  the  Teres  major,  and  passes  backward  to  the  interval 
between  the  outer  and  inner  heads  of  the  Triceps  muscle,  accompanied  by  the 
musculo-spiral  nerve ;  it  winds  around  the  back  part  of  the  shaft  of  the  humerus 
in  the  spiral  groove,  between  the  outer  head  of  the  Triceps  and  the  bone,  to  the 
outer  side  of  the  humerus,  where  it  reaches  the  external  intermuscular  septum  and 
divides  into  two  terminal  branches.  One  of  these  pierces  the  external  intermus- 
cular septum,  and  descends,  in  company  with  the  musculo-spiral  nerve,  to  the  space 
between  the  Brachialis  anticus  and  Supinator  longus,  where  it  anastomoses  with  the 
recurrent  branch  of  the  radial  artery ;  while  the  other,  much  the  larger  of  the  two, 
descends  along  the  back  of  the  external  intermuscular  septum  to  the  back  of  the 
elbow-joint,  where  it  anastomoses  with  the  posterior  interosseous  recurrent,  and  across 
the  back  of  the  humerus  with  the  posterior  ulnar  recurrent,  the  anastomotica  macrna, 
and  inferior  profunda  (Fig.  306).  The  superior  profunda  supplies  the  Triceps  muscle 
and  gives  off  a  nutrient  artery  which  enters  the  bone  at  the  upper  end  of  the  musculo- 
spiral  groove.  Near  its  commencement  it  sends  off  a  branch  which  passes  upward 
between  the  external  and  long  heads  of  the  Triceps  muscle  to  anastomose  with  the 
posterior  circumflex  artery,  and,  while  in  the  groove,  a  small  branch  which  accom- 
panies a  branch  of  the  musculo-spiral  nerve  through  the  substance  of  the  Triceps 
muscle  and  ends  in  the  Anconeus  below  the  outer  condyle  of  the  humerus. 

The  nutrient  artery  of  the  shaft  of  the  humerus  arises  from  the  brachial,  about 
the  middle  of  the  arm.  Passing  downward  it  enters  the  nutrient  canal  of  that 
bone  near  the  insertion  of  the  Coraco-brachialis  muscle. 

The  inferior  profunda,  of  small  size,  arises  from  the  brachial,  a  little  below  the 
middle  of  the  arm ;  piercing  the  internal  intermuscular  septum,  it  descends  on  the 
surface  of  the  inner  head  of  the  Triceps  muscle  to  the  space  between  the  inner 
condyle  and  olecranon,  accompanied  by  the  ulnar  nerve,  and  terminates  by  anasto- 
mosing with  the  posterior  ulnar  recurrent  and  anastomotica  magna.  It  sometimes 
supplies  a  branch  to  the  front  of  the  internal  condyle,  which  anastomoses  with  the 
anterior  ulnar  recurrent. 

The  anastomotica  magna  arises  from  the  brachial  about  two  inches  above  the 
elbow-joint.  It  passes  transversely  inward  upon  the  Brachialis  anticus,  and,  piercing 
the  internal  intermuscular  septum,  winds  round  the  back  part  of  the  humerus 
between  the  Triceps  and  the  bone,  forming  an  arch  above  the  olecranon  fossa  by  its 
junction  with  the  posterior  articular  branch  of  the  superior  profunda.  As  this  vessel 
lies  on  the  Brachialis  anticus,  branches  ascend  to  join  the  inferior  profunda,  and 
others  descend  in  front  of  the  inner  condyle  to  anastomose  with  the  anterior  ulnar 
recurrent.  Behind  the  internal  condyle  an  offset  is  given  off  which  anastomoses 
with  the  inferior  profunda  and  posterior  ulnar  recurrent  arteries  and  supplies  the 
Triceps. 

The  muscular  are  three  or  four  large  branches,  which  are  distributed  to  the 
muscles  in  the  course  of  the  artery.  They  supply  the  Coraco-brachialis,  Biceps, 
and  Brachialis  anticus  muscles. 

The  Anastomosis  around  the  Elbow-joint  (Fig.  306). — The  vessels  engaged  in 
this  anastomosis  may  be  conveniently  divided  into  those  situated  in  front  and 
behind  the  internal  and  external  condyles.     The  branches  anastomo^W-  >'-  ^-     j 
of  the  internal  condyle  are  the  anastomotica  magna,  the  anterior  ^}\    \Jp 
and  the  anterior  terminal  branch  of  the  inferior  profunda.   Thosp     p| 
condyle  are  the   anastomotica  magna,   the    posterior    ulna' 
posterior  terminal  branch  of  the  inferior  profunda.    The  Wdiai  arteries.   Deep  view. 
front  of  the  external  condyle  are  the  radial  recurrer- 

branch  of  the  superior  profunda.  Those  faorwartt  upon  the  Interossei  muscles, 
more  properly  described  as  being  situaterigers  with  the  digital  branches  ol  the 
olecranon)  are  the  anastomotica  ma"r 

terminal  branch  of  the  superioiches  arise  from  the  concavity  of  the  deep  palmar 
mosis  above  the  olecranon,  fonront  of  the  wrist,  supplying  the  carpal  articulations 
anastomotica  magna  and  posteiterior  carpal  arch. 


538 


THE   BLOOD-VASCULAR   SYSTEM. 


From  this  description  it  will  be  observed  that  the  anastomotica  magna  is  the 
vessel  most  engaged,  the  only  part  of  the  anastomosis  in  which  it  is  not  employed 
being  that  in  front  of  the  external  condyle. 

Radial  Artery  (Fig.  304). 

The  Radial  Artery  appears,  from  its  direction,  to  be  the  continuation  of  the 
brachial,  but  in  size  it  is  smaller  than  the  ulnar.  It  commences  at  the  bifurcation 
of  the  brachial,  just  below  the  bend  of  the  elbow,  and  passes  along  the  radial  side 
of  the  forearm  to  the  wrist ;  it  then  winds  backward,  round  the  outer  side  of  the 
carpus,  beneath  the  extensor  tendons  of  the  thumb,  to  the  upper  end  of  the  space 
between  the  metacarpal  bones  of  the  thumb  and  index  finger,  and,  finally,  passes 
forward,  between  the  two  heads  of  the  First  dorsal  interosseous  muscle,  into  the 
palm  of  the  hand,  where  it  crosses  the  metacarpal  bones  to  the  ulnar  border  of  the 
hand,  to  form  the  deep  palmar  arch.  At  its  termination  it  inosculates  with  the 
deep  branch  of  the  ulnar  artery.  The  relations  of  this  vessel  may  thus  be  con- 
veniently divided  into  three  parts — viz.,  in  the  forearm,  at  the  back  of  the  wrist, 
and  in  the  hand. 

Relations. — In  the  forearm  this  vessel  extends  from  opposite  the  neck  of  the 
radius  to  the  fore  part  of  the  styloid  process,  being  placed  to  the  inner  side  of  the 
shaft  of  the  bone  above  and  in  front  of  it  below.  It  is  overlapped  in  the  upper 
part  of  its  course  by  the  fleshy  belly  of  the  Supinator  longus  muscle ;  throughout 
the  rest  of  its  course  it  is  superficial,  being  covered  by  the  integument,  the  super- 
ficial and  deep  fascise.  In  its  course  downward  it  lies  upon  the  tendon  of  the 
Biceps,  the  Supinator  brevis,  the  Pronator  radii  teres,  the  radial  origin  of  the  Flexor 
sublimis  digitorum,  the  Flexor  longus  pollicis,  the  Pronator  quadratus,  and  the 
lower  extremity  of  the  radius.  In  the  upper  third  of  its  course  it  lies  between 
the  Supinator  longus  and  the  Pronator  radii  teres  ;  in  its  lower  two-thirds,  between 
the  tendons  of  the  Supinator  longus  and  the  Flexor  carpi  radialis.  The  radial 
nerve  lies  close  to  the  outer  side  of  the  artery  in  the  middle  third  of  its  course, 
and  some  filaments  of  the  musculo-cutaneous  nerve,  after  piercing  the  deep  fascia, 
run  along  the  lower  part  of  the  artery  as  it  winds  round  the  wrist.  The  vessel  is 
accompanied  by  vense  comites  throughout  its  whole  course. 


Plan  of  the  Relations  of  the  Radial  Artery  in  the  Forearm. 

In  front. 
Skin,  superficial  and  deep  fasciae. 
Supinator  longus. 


Inner  side. 
Pronator  radii  teres.  - 
Flexor  carpi  radialis. 


are  ucBbcin.u^5 

in  a  similar  mannt. 

curved  artery  about  . 

artery. 

The  branches  of  tht 


Outer  side. 
Supinator  longus. 
Radial  nerve  (middle  third). 


Superior  Pro. 
Nutrient. 


Behind. 
Tendon  of  Biceps. 
Supinator  brevis. 
Pronator  radii  teres. 
Flexcr  sublimis  digitorum. 
Flexor  longus  pollicis. 
Pronator  quadratus. 
Radius. 


-be   outer  side  of  the  carpus  from  the  styloid 
Muse  lies  upon   the  external  lateral  ligament, 

,TT, .   ;r';um,  being   covered  by  the  extensor 

1  Chelius's  Surgery,  vol.  ii.  p.  254.  See  also  White's  en^,©       f  .,  /•   ,  ■, 

anastomosing  branches  after  ligature  of  the  brachial,  in  Whiteiaments  <*  tne  laOial  nen  e,  ana 

case   (with  drawings)   of   the  circulation  after  ligature  of   bend   a  falament  of   the  musculo- 

Patoligiche  delle  Arterie). 


THE   RADIAL    ARTERY. 


539 


In  the  hand  it  passes  from  the  upper  end  of  the  first  interosseous  space, 
between  the  heads  of  the  Abductor  indicis  or  First  dorsal  interosseous  muscle, 
transversely  across  the  palm,  to  the  base  of  the  metacarpal  bone  of  the  little 
fino-er,  where  it  inosculates  with  the  communicating  branch  from  the  ulnar  artery, 
forming  the  deep  palmar  arch.  It  lies  upon  the  carpal  extremities  of  the  metacarpal 
bones  and  the  Interossei  muscles,  being  covered  by  the  Adductor  obliquus  pollicis, 
the  flexor  tendons  of  the  fingers,  the  Lumbricales,  the  Opponens,  and  Flexor 
brevis  minimi  digiti.  Alongside  of  it  is  the  deep  branch  of  the  ulnar  nerve,  but 
running  in  the  opposite  direction ;  that  is  to  say,  from  within  outward. 

Peculiarities. — The  origin  of  the  radial  artery,  according  to  Quain,  is,  in  nearly  one  ease 
in  eight,  higher  than  usual ;  more  frequently  arising  from  the  axillary  or  upper  part  of  the 
brachial  than  from  the  lower  part  of  this  vessel.  The  variations  in  the  position  of  this  vessel 
in  the  arm  and  at  the  bend  of  the  elbow  have  been  already  mentioned.  In  the  forearm  it 
deviates  less  frequently  from  its  position  than  the  ulnar.  It  has  been  found  lying  over  the  fascia 
instead  of  beneath  it.  It  has  also  been  observed  on  the  surface  of  the  Supinator  longus,  instead 
of  under  its  inner  border ;  and  in  turning  round  the  wrist  it  has  been  seen  lying  over,  instead  of 
beneath,  the  extensor  tendons  of  the  thumb. 

Surface  Marking. — The  position  of  the  radial  artery  in  the  forearm  is  represented  by  a 
line  drawn  from  the  outer  border  of  the  tendon  of  the  Biceps  in  the  centre  of  the  hollow  in  front 
of  the  elbow-joint  with  a  straight  course  to  the  inner  side  of  the  fore  part  of  the  styloid  process 
of  the  radius. 

Surgical  Anatomy  .—The  radial  artery  is  much  exposed  to  injury  in  its  lower  third,  and  is 
frequently  wounded  by  the  hand  being  driven  through  a  pane  of  glass,  by  the  slipping  of  a 
knife  or  chisel  held  in  the  other  hand,  and  such-like  accidents.  The  injury  is  often  followed  by 
a  traumatic  aneurism,  for  which  the  old  operation  of  laying  open  the  sac  and  securing  the  vessel 
above  and  below  is  required. 

The  operation  of  tying  the  radial  artery  is  required  in  cases  of  wounds  either  of  its  trunk  or 
of  some  of  its  branches,  or  for  aneurism  ;  and  it  will  be  observed  that  the  vessel  may  be  exposed 
in  any  part  of  its  course  through  the  forearm  without  the  division  of  any  muscular  fibres.  The 
operation  in  the  middle  or  inferior  third  of  the  forearm  is  easily  performed,  but  in  the  upper 
third,  near  the  elbow,  it  is  attended  with  some  difficulty,  from  the  greater  depth  of  the  vessel 
and  from  its  being  overlapped  by  the  Supinator  longus  muscle. 

To  tie  the  artery  in  the  upper  third  an  incision  three  inches  in  length  should  be  made 
through  the  integument,  in  a  line  drawn  from  the  centre  of  the  bend  of  the  elbow  to  the  front 
of  the  styloid  process  of  the  radius,  avoiding  the  branches  of  the  median  vein ;  the  fascia  of 
the  arm  being  divided  and  the  Supinator  longus  drawn  a  little  outward,  the  artery  will  be 
exposed.  The  venae  comites  should  be  carefully  separated  from  the  vessel,  and  the  ligature 
passed  from  the  radial  to  the  ulnar  side. 

In  the  middle  third  of  the  forearm  the  artery  may  be  exposed  by  making  an  incision  of 
JKSJAsz'  iength  on  the  inner  margin  of  the  Supinator  longus.  In  this  situation  the  radial  nerve 
lies  in  close  relation  with  the  outer  side  of  the  artery,  and  should,  as  well  as  the  veins,  be  care- 
fully avoided.  \ 

In  the  lower  third  the  artery  is  easily  secured  by  dividing  the  integument  and  fascia  in  the 
interval  between  the  tendons  of  the  Supinator  longus  and  Flexor  carpi  radialis  muscles. 

The  branches  of  the  radial  artery  may  be  divided  into  three  groups,  corre- 
sponding with  the  three  regions  in  which  the  vessel  is  situated. 

f  Radial  Ren-      pi       .-  /  d£Nti^&mk&\*%  mal. 

Muscular,  "ng  branch 
•{    a  „* : r  arch. 


In  the 

Forearm. 


Anterior 


[  SuperfieeifV 
v       x         ard    ir 


three  in 


veen  the  heads 
orsal  interossei 
:  with  the  dorsal 


">SSeOUS    three  Or  Fig-  305.— Ulnar  and  radial  arteries.    Deep  view. 

The  radial  recurren  from'  the  con. 

betwee  inches  ojmar  arcn  ;   they  run  forward  upon   the  Interossei  muscles, 

and  tl?  en  fheti,e  clefts  of   the   fingers   with    the   digital   branches   of   the 

muscle  be  elbow 

superi  ofunda.            ent  branches  arise  from  the  concavity  of   the  deep  palmar 

The  muscular  branchy  jn  front  0f  ^e  wrist,  supplying  the  carpal  articulations 

the  fc ;  ..rm.                           •>  ~nterior  carpal  arch. 


540 


THE   BLOOD-VASCULAR    SYSTEM. 


Radial  recurrent. 


The  anterior  carpal  is  a  small  vessel  which  arises  from  the  radial  artery  near  the 
lower  border  of  the  Pronator  quadratus,  and,  running  inward  in  front  of  the  radius, 

anastomoses  with  the  anterior  carpal 
branch  of  the  ulnar  artery.  In  this 
way  an  arterial  anastomosis,  anterior 
carpal  arch,  is  formed  in  front  of  the 
wrist;  it  is  joined  by  branches  from 
the  anterior  interosseous  above,  and 
by  recurrent  branches  from  the  deep 
palmar  arch  below,  and  gives  off 
branches  which  descend  to  supply 
the  articulations  of  the  wrist  and 
carpus. 

The  superficialis  volse  arises  from 
the  radial  artery,  just  where  this 
vessel  is  about  to  wind  round  the 
wrist.  Running  forward,  it  passes 
between,  occasionally  over,  the  mus- 
cles of  the  thumb,  which  it  supplies, 
and  sometimes  anastomoses  with  the 
palmar  portion  of  the  ulnar  artery, 
completing  the  superficial  palmar 
arch.  This  vessel  varies  consider- 
ably in  size  :  usually  it  is  very  small, 
and  terminates  in  the  muscles  of  the 
thumb  ;  sometimes  it  is  as  large  as 
the  continuation  of  the  radial. 

The  posterior  carpal  is   a  small 
vessel  which   arises  from  the  radial 
artery  beneath  the  extensor  tendons 
of  the  thumb  ;    crossing  the  carpus 
transversely  to  the  inner  border  of 
the  hand,  it    anastomoses   with    the 
posterior  carpal  branch  of  the  ulnar, 
forming  the  posterior    carpal   arch, 
which  is  joined   by  the  termination 
of  the  anterior    interosseous  artery. 
From  this  arch  are  given  off  descend- 
ing branches,  the  dorsal  interosseous 
arteries  for  the  third  and  fourth  in- 
terosseous spaces,  which  run  forward 
*ahird  and  Fourth  dorsal  in- 
uscles,    and     divide    into 
al  branches  which  supply 
t   sides    of   the   middle, 
:tle  fingers  respectively, 
ag     with      the      digital 
"he    superficial    palmar 
eir  origin  they  anasto- 
e    perforating  branches 
p  palmar  arch, 
^e  outer  side  of  the  acarpal  (first  dorsal  inter- 
Musc  lies  upon   the  exte)  °rises  beneath  the  ex- 

,..„„,„,     wl .,  ;"um,  being  cois  of  the  thumb,  some- 

1  Chelius  s  Surqery,  vol.  u.  p.  254.  See  also   White  s  en. ,,,  °       ,    ,,  ,      .  9 

anastomosing  branches'after  ligature  of  the  brachial,  in  Whit^ments  0      the     posterior      Carpal , 

case   (with  drawings)   of   the  circulation  after  ligature  of   bend   a  is  muscle,  it  communicates, : 

Patoligiche  delle  Arterie).  m  the  deep  palmar  arch ;  and 


Superficialis  volse. 


erf  stew. 
Pronator  radii  teres. 
Flexor  carpi  radialis 


in  a  similar  mamit-. 
curved  artery  about 
artery. 

The  branches  of  th<. 


Raa 


Superior 
Nutrient. 


Behind. 
Tendon  of  Biceps. 
Supinator  brevis. 
Pronator  radii  teres. 
Flexor  sublimis  digitorum. 
Flexor  longus  pollicis. 
Pronator  quadratus. 
Radius. 


BRANCHES    OF    THE   RADIAL    ARTERY. 


543 


Anastomotica 
magna. 


Anterior  ulnar 
recurrent. 

Posterior  ulnar 
recurrent. 


in  front  it  divides  into  two  dorsal  digital  branches,  which  supply  the  adjoiiL,6 
sides  of  the  index  and  middle  fingers,  inosculating  with  the  digital  branch  of  tlu 
superficial  palmar  arch. 

The  dorsales  pollicis  are  two  vessels  which   run  along  the  sides  of  the  dorsal 
aspect    of  the  thumb.      They  arise 
separately,  or  occasionally  by  a  com- 
mon trunk,  near  the  base  of  the  first 
metacarpal  bone. 

The  dorsalis  indicis,  also  a  small 
branch,  runs  along  the  radial  side  of 
the  back  of  the  index  finger,  send- 
ing; a  few  branches  to  the  Abductor 
indicis. 

The  princeps  pollicis  arises  from 
the  radial  just  as  it  turns  inward  to 
the  deep  part  of  the  hand  ;  it  de- 
scends between  the  Abductor  indicis 
and  Adductor  obliquus  pollicis,  then 
between  the  Adductor  transversus 
pollicis  and  Adductor  obliquus  pol- 
licis, along  the  ulnar  side  of  the 
metacarpal  bone  of  the  thumb,  to 
the  base  of  the  first  phalanx,  where 
it  divides  into  two  branches,  which 
run  along  the  sides  of  the  palmar 
aspect  of  the  thumb,  and  form  an 
arch  on  the  palmar  surface  of  the 
last  phalanx,  from  which  branches 
are  distributed  to  the  integument 
and  pulp  of  the  thumb. 

The  radialis  indicis  arises  close 
to  the  preceding,  descends  between 
the  Abductor  indicis  and  Adductor 
transversus  pollicis,  and  runs  along 
the  radial  side  of  the  index  finger 
to  its  extremity,  where  it  anastomoses 
with  the  collateral  digital  artery 
from  the  superficial  palmar  arch. 
At  the  lower  border  of  the  Adductor 
transversus  pollicis  this  vessel  anas- 
tomoses with  the  princeps  pollicis, 
and  gives  a  communicating  branch 
to  the  superficial  palmar  arch. 

The  perforating  arteries,  three  in 
number,  pass  backward  from  the 
deep  palmar  arch  between  the  heads 
of  the  last  three  Dorsal  interossei 
muscles,  to  inosculate  with  the  dorsal 
interosseous  arteries. 

The  palmar  interosseous,  three  or 
four  in  number,  arise  from  the  con- 

of  the  deep  palmar  arch  ;   they  run  forward  upon   the  Interossei  muscles, 

I    anastomose   at  the  clefts  of  the  fingers   with    the   digital   branches   of  the 
rficial  arch. 

The  palmar  recurrent  branches  arise  from  the  concavity  of  the  deep  palmar 
arch.      They  pass  upward  in  front  of  the  wrist,  supplying  the  carpal  articulations 
ud  anastomosing  with  the  anterior  carpal  arch. 


Muscular. 


Anterior  carpal 
Superficialis  volse 


Anterior  carpal. 


Deep  branch  of 
ulnar. 


Fig.  305.— Ulnar  and  radial  arteries.    Deep  view. 


544 


THE   BLOOD-VASCULAR    SYSTEM. 


joins  the  posterior  carpal  branch  of  the  ulnar  artery.      This  artery  gives  off,  near 
its  origin,  the  interosseous  recurrent  branch. 

The  interosseous  recurrent  artery  is  a  large  vessel  which  ascends  to  the  interval 

between    the    external   condyle 


Descending  branch  from 
superior  profunda. 


Anastomotica 
magna. 


Posterior  ulnar 
recurrent. 


and  olecranon,  on  or  through  the 
fibres  of  the  Supinator  brevis, 
but  beneath  the  Anconeus,  anas- 
tomosing with  a  branch  from  the 
superior  profunda,  and  with  the 
posterior  ulnar  recurrent  and 
anastomotica  magna. 

The  muscular  "branches  are 
distributed  to  the  muscles  along 
the  ulnar  side  of  the  forearm. 

The  anterior  carpal  is  a  small 
vessel  which  crosses  the  front 
of  the  carpus  beneath  the  ten- 
dons of  the  Flexor  profundus, 
and  inosculates  with  a  corre- 
sponding branch  of  the  radial 
Posterior  interosseous,    artery. 

The  posterior  carpal  arises 
immediately  above  the  pisiform 
bone,  and  winds  backward  be- 
neath the  tendon  of  the  Flexor 
carpi  ulnaris :  it  passes  across 
the  dorsal  surface  of  the  carpus 
beneath  the  extensor  tendons, 
anastomosing  with  a  correspond- 
ing branch  of  the  radial  artery, 
and  forming  the  posterior  carpal 
arch.  Immediately  after  its 
origin  it  gives  off  a  small  branch 
which  runs  along  the  ulnar  side 
of  the  metacarpal  bone  of  the 
little  finger,  forming  one  of  the 
metacarpal  arteries,  and  sup- 
plies the  ulnar  side  of  the  dorsal 
surface  of  the  little  finger. 

The  branch  to  the  deep  pal- 
mar arch  (deep  or  communicating 
branch)  (Fig.  305)  passes  deeply 
inward  between  the  Abductor 
minimi  digiti  and  Flexor'brevis 
minimi  digiti,  near  their  Origins; 
it  anastomoses  with  the  termina- 
tion of  the  radial  'artery,  com- 
pleting the  deep  palmar  arch. 

The  continuation  of  the 
trunk  of  the  ulnar  artery  in  the 
hand  forms  the  greater  part  of 
the  superficial  palmar  arch. 

The  Superficial  Palmar  Arch  (Fig.  304). 

The  Superficial  Palmar  Arch  is  formed  by  the  ulnar  artery  in  the  hand,  and  is 
completed  on  the  outer  side  by  this  vessel  anastomosing  with  a  branch  from  the 
radialis  indicis,  though  sometimes  the  arch  is  completed  by  the  ulnp-r  anastomosing 


Posterior  carpal 
(ulnar). 


Termination  of  an- 
terior interosseous. 


Posterior  carpal 
(radial). 

Radial. 

Dorsalis  pollicis. 
Dorsalis  indicis. 


Fig.  306.— Arteries  of  the  back  of  the  forearm  and  hand 


THE   SUPERFICIAL    PALMAR    ARCH.  545 

with  the  superficial  volse  or  princeps  pollicis  of  the  radial  artery.  The  arch  passes 
across  the  palm,  describing  a  curve,  with  its  convexity  forward,  to  the  space 
between  the  ball  of  the  thumb  and  the  index  finger,  where  the  above-mentioned 
anastomosis  takes  place. 

Relations. — The  superficial  palmar  arch  is  covered  by  the  skin,  the  Palmaris 
brevis,  and  the  palmar  fascia.  It  lies  upon  the  annular  ligament,  the  Flexor  brevis 
of  the  little  finger,  the  tendons  of  the  superficial  flexor  of  the  fingers,  and  the 
divisions  of  the  median  and  ulnar  nerve.5. 


Plan  of  the  Relations  of  the  Superficial  Palmar  Arch. 

In  front. 
Skin. 

Palmaris  brevis. 
Palmar  fascia. 


Behind. 
Annular  ligament. 
Flexor  brevis  of  little  finger. 
Superficial  flexor  tendons. 
Divisions  of  median  and  ulnar  nerves. 

Branches  of  the  Superficial  Palmar  Arch. 

Digital. 

The  digital  branches  (Fig.  304),  four  in  number,  are  given  off  from  the  con- 
vexity of  the  superficial  palmar  arch.  They  supply  the  ulnar  side  of  the  little 
finger  and  the  adjoining  sides  of  the  little,  ring,  middle,  and  index  fingers,  the 
radial  side  of  the  index  finger  and  thumb  being  supplied  from  the  radial  artery. 
The  digital  arteries  at  first  lie  superficial  to  the  flexor  tendons,  but  as  they  pass 
forward  with  the  digital  nerves  to  the  clefts  between  the  fingers  they  lie  between 
them,  and  are  there  joined  by  the  interosseous  branches  from  the  deep  palmar 
arch.  The  digital  arteries  on  the  sides  of  the  fingers  lie  beneath  the  digital 
nerves ;  and  about  the  middle  of  the  last  phalanx  the  two  branches  for  each 
finger  form  an  arch,  from  the  convexity  of  which  branches  pass  to  supply  the 
pulp  of  the  finger. 

Surface  Marking. — The  superficial  palmar  arch  is  represented  by  a  curved  line,  starting 
from  the  outer  side  of  the  pisiform  bone  and  carried  downward  as  far  as  the  middle  third  of 
the  palm,  and  then  curved  outward  on  a  level  with  the  upper  end  of  the  cleft  between  the 
thumb  and  index  finger. 

The  deep  palmar  arch  is  situated  about  half  an  inch  nearer  to  the  carpus. 

Surgical  Anatomy. — Wounds  of  the  palmar  arches  are  of  special  interest,  and  are  always 
difficult  to  deal  with.  When  the  superficial  arch  is  wounded  it  is  generally  possible,  by  enlarging 
the  wound  if  necessary,  to  secure  the  vessel  and  tie  it ;  or  in  cases  where  it  is  found  impossible 
to  encircle  the  vessel  with  a  ligature,  a  pair  of  Wells's  artery  clips  may  be  applied  and  left  on  for 
twenty-four  or  forty-eight  hours.  Wounds  of  the  deep  arch  are  not  so  easily  dealt  with.  It  may 
be  possible  to  secure  the  vessel  by  forcipressure  forceps,  which  may  be  left  on  ;  or,  failing  this, 
the  wound  may  be  carefully  plugged  with  gauze  and  an  outside  dressing  carefully  bandaged  on. 
The  plug  should  be  allowed  to  remain  untouched  for  three  or  four  days.  In  wounds  of  the  deep 
palmar  arch  a  ligature  may  be  applied  to  the  bleeding  points  from  the  dorsum  of  the  hand  by 
resection  of  the  upper  part  of  the  third  metacarpal  bone.  It  is  useless  in  these  cases  to  ligate 
one  of  the  arteries  of  the  forearm  alone,  and  indeed  simultaneous  ligation  of  both  radial  and 
ulnar  arteries  above  the  wrist  is  often  unsuccessful,  on  account  of  the  anastomosis  carried  on  by 
the  carpal  arches.  Therefore,  upon  the  failure  of  pressure  to  arrest  hemorrhage,  it  is  expedient 
to  apply  a  ligature  to  the  brachial  artery. 
35 

i     / 


546  THE   BLOOD-VASCULAR   SYSTEM. 

ARTERIES  OF  THE  TUUNK. 
THE  DESCENDING  AORTA. 


The  Descending  Aorta  is  divided  into  two  portions,  the  thoracic  and  abdominal, 
in  correspondence  with  the  two  great  cavities  of  the  trunk  in  which  it  is  situated. 

THE  THORACIC  AORTA. 

The  Thoracic  Aorta  commences  at  the  lower  border  of  the  fourth  dorsal  verte 
bra,  on  the  left  side,  and  terminates  at  the  aortic  opening  in  the  Diaphragm,  in  front 
of  the  lower  border  of  the  last  dorsal  vertebra.  At  its  commencement  it  is  situatec 
on  the  left  side  of  the  spine ;  it  approaches  the  median  line  as  it  descends,  and  at 
its  termination  lies  directly  in  front  of  the  column.  The  direction  of  this  vessel 
being  influenced  by  the  spine,  upon  which  it  rests,  it  describes  a  curve  which  is 
concave  forward  in  the  dorsal  region.  As  the  branches  given  off  from  it  are  small, 
the  diminution  in  the  size  of  the  vessel  is  inconsiderable.  It  is  contained  in  the 
back  part  of  the  posterior  mediastinum. 

Relations. — It  is  in  relation,  in  front,  from  above  downward,  with  the  root  of 
the  left  lung,  the  pericardium,  the  oesophagus,  and  the  Diaphragm :  behind,  with 
the  vertebral  column  and  the  vena  azygos  minor ;  on  the  right  side,  with  the  vena 
azygos  major  and  thoracic  duct;  on  the  left  side,  with  the  left  pleura  and  lung. 
The  oesophagus,  with  its  accompanying  nerves,  lies  on  the  right  side  of  the  aorta 
above  ;  but  at  the  lower  part  of  the  thorax  it  gets  in  front  of  the  aorta,  and  close 
to  the  Diaphragm  is  situated  to  its  left  side. 

Plan  of  the  Relations  of  the  Thoracic  Aorta. 

In  front. 

Root  of  left  lung. 
Pericardium. 

(Esophagus. 
Diaphragm. 

Right  side.  f  \                             Left  side. 

(Esophagus  (above).  (  Thoracic     \  Pleura. 

Vena  azygos  major.  \  Aorta"      J  Left  lung. 

Thoracic  duct.  V  /  (Esophagus  (below). 

Behind. 
Vertebral  column. 
Superior  and  inferior  azygos  minor  veins. 

The  aorta  is  occasionally  found  to  be  obliterated  at  a  particular  spot — viz. ,  at  the  junction  of 
the  arch  with  the  thoracic  aorta,  just  below  the  ductus  arteriosus.  Whether  this  is  the  result  of 
disease  or  of  congenital  malformation  is  immaterial  to  our  present  purpose  ;  it  affords  an  interest- 
ing opportunity  of  observing  the  resources  of  the  collateral  circulation.  The  course  of  the  anas- 
tomosing vessels,  by  which  the  blood  is  brought  from  the  upper  to  the  lower  part  of  the  artery, 
will  be  found  well  described  in  an  account  of  two  cases  in  the  Pathological  Transactions,  vols.  viii. 
and  x.  In  the  former  (p.  162)  Mr.  Sydney  Jones  thus  sums  up  the  detailed  description  of  the 
anastomosing  vessels  :  "The  principal  communications  by  which  the  circulation  was  carried  on, 
were — Firstly,  the  internal  mammary,  anastomosing  with  the  intercostal  arteries,  with  the  phrenic 
of  the  abdominal  aorta  by  means  of  the  musculo-phrenic  and  comes  nervi  phrenici,  and  largely 
with  the  deep  epigastric.  Secondly,  the  superior  intercostal,  anastomosing  anteriorly  by  means 
of  a  large  branch  with  the  first  aortic  intercostal,  and  posteriorly  with  the  posterior  branch  of  the 
same  artery.  Thirdly,  the  inferior  thyroid,  by  means  of  a  branch  about  the  size  of  an  ordinary 
radial,  formed  a  communication  with  the  first  aortic  intercostal.  Fourthly,  the  transversalis  colli, 
by  means  of  very  large  communications  with  the  posterior  branches  of  the  intercostals.  Fifthly, 
the  branches  (of  the  subclavian  and  axillary)  going  to  the  side  of  the  chest  were  large,  and 
anastomosed  freely  with  the  lateral  branches  of  the  intercostals."  In  the  second  case  also  (vol. 
x.  p.  97)  Mr.  Wood  describes  the  anastomoses  in  a  somewhat  similar  manner,  adding  the  remark 
that  "  the  blood  which  was  brought  into  the  aorta  through  the  anastomoses  of  the  intercostal 
arteries  appeared  to  be  expended  principally  in  supplying  the  abdomen  and  pelvis,  while  the  sup 
ply  to  the  lower  extremities  had  passed  through  the  internal  mammary  and  epigastrics. " 


BRANCHES    OF    THE    THORACIC  AORTA.  547 

Surgical  Anatomy. — The  student  should  now  consider  the  effects  likely  to  be  produced  by 
aneurism  of  the  thoracic  aorta,  a  disease  of  common  occurrence.  When  we  consider  the  great 
depth  of  the  vessel  from  the  surface  and  the  number  of  important  structures  which  surround  it 
on  every  side,  it  may  easily  be  conceived  what  a  variety  of  obscure  symptoms  may  arise  from  dis- 
ease of  this  part  of  the  arterial  system,  and  how  they  may  be  liable  to  be  mistaken  for  those  of 
other  affections.  Aneurism  of  the  thoracic  aorta  most  usually  extends  backward  along  the  left 
side  of  the  spine,  producing  absorption  of  the  bodies  of  the  vertebra?,  with  curvature  of  tKe urai. . 
whilst  the  irritation  or  pressure  on  the  cord  will  give  rise  to  pain,  either  in  the  cheit,'  back,  or 
loins,  with  radiating  pain  in  the  left  upper  intercostal  spaces,  from  pressure  or  the  intercostal 
nerves ;  at  the  same  time  the  tumor  may  project  backward  on  each  side  of  the  spine,  beneath  the 
integument,  as  a  pulsating  swelling,  simulating  abscess  connected  witb  d*seased  bone,  or  it  may 
displace  the  oesophagus  and  compress  the  lung  on  one  or  the  otb  ""■  ie.  If  the  tumor  extend 
forward,  it  may  press  upon  and  displace  the  heart,  giving  rise, f  palpitation  and  other  symptoms 
of  disease  of  that  organ  ;  or  it  may  displace,  or  even  com"  v7s,  the  oesophagus,  causing  pain  and 
difficulty  of  swallowing,  as  in  stricture  of  that  tube  ;  anc  ultimately  even  open  into  it  by  ulcera- 
tion, producing  fatal  haemorrhage.  If  the  disease  ext  mds  to  the  right  side,  it  may  press  upon 
the  thoracic  duct ;  or  it  may  burst  into  the  pleural  cavity  or  into  the  trachea  or  lung  ;  and  lastly, 
it  may  open  into  the  posterior  mediastinum. 

Branches  of  the  Thoracic  Aorta. 

Pericardiac.  (Esophageal. 

Bronchial.  Posterior  Mediastinal. 

Intercostal. 

The  pericardiac  are  a  few  small  vessels,  irregular  in  their  origin,  distributed  to 
the  pericardium. 

The  bronchial  arteries  are  the  nutrient  vessels  of  the  lungs,  and  vary  in  num- 
ber, size,  and  origin.  That  of  the  right  side  arises  from  the  first  aortic  intercostal, 
or  by  a  common  trunk  with  the  left  bronchial  from  the  front  of  the  thoracic  aorta. 
Those  of  the  left  side,  usually  two  in  number,  arise  from  the  thoracic  aorta,  one  a 
little  lower  than  the  other.  Each  vessel  is  directed  to  the  back  part  of  the  corre- 
sponding bronchus  along  which  it  runs,  dividing  and  subdividing  along  the  bron- 
chial tube,  supplying  them,  the  cellular  tissue  of  the  lungs,  the  bronchial  glands, 
and  the  oesophagus. 

The  oesophageal  arteries,  usually  four  or  five  in  number,  arise  from  the  front 
of  the  aorta,  and  pass  obliquely  downward  to  the  oesophagus,  forming  a  chain  of 
anastomoses  along  that  tube,  anastomosing  with  the  oesophageal  branches  of  the 
inferior  thyroid  arteries  above,  and  with  ascending  branches  from  the  phrenic  and 
gastric  arteries  below. 

The  posterior  mediastinal  arteries  are  numerous  small  vessels  wThich  supply  the 
glands  and  loose  areolar  tissue  in  the  mediastinum. 

The  Intercostal  arteries  arise  from  the  back  of  the  aorta.  They  are  usually 
nine  in  number  on  each  side,  the  two  superior  intercostal  spaces  being  supplied 
by  the  superior  intercostal,  a  branch  of  the  subclavian.  The  second  space  usually 
receives  a  considerable  branch  from  the  first  aortic  intercostal,  which  joins  with 
the  branch  from  the  superior  intercostal  of  the  subclavian.  The  branch  which 
runs  along  the  lower  border  of  the  last  rib  is  named  the  subcostal  artery.  The 
right  intercostals  are  longer  than  the  left,  on  account  of  the  position  of  the  aorta 
on  the  left  side  of  the  spine  :  they  pass  outward,  across  the  bodies  of  the  vertebrae, 
to  the  intercostal  spaces,  being  covered  by  the  pleura,  the  oesophagus,  thoracic 
duct,  sympathetic  nerve,  and  the  vena  azygos  major ;  the  left,  passing  outward, 
are  crossed  by  the  sympathetic ;  the  upper  two  are  also  crossed  by  the  superior 
intercostal  vein,  the  lower  by  the  azygos  minor  veins.  In  each  intercostal  space 
the  artery  passes  outward,  at  first  lying  upon  the  External  intercostal  muscle, 
covered  in  front  by  the  pleura  and  a  thin  fascia.  It  then  passes  between  the  two 
layers  of  Intercostal  muscles,  and,  having  ascended  obliquely  to  the  lower  border 
of  the  rib  above  it,  is  continued  forward  in  the  groove  on  its  lower  border  and 
anastomoses  with  the  anterior  intercostal  branches  of  the  internal  mammary. 
The  first  aortic  intercoste1-,^1^.  Gnoses  with  the  superior  intercostal,  and  tbe  last 
three  pass  between  the  %S     '  %    -cles,  inosculating  with  the  epigastric  in  front 


548 


THE  BLOOD-VASCULAR    SYSTEM. 


^and  with  the  phrenic  and  lumbar  arteries.     Each  intercostal  artery  is  accompanied 

I  vein  and  nerve,  the  former  being  above,  and  the  latter  below,  except  in  the 

c  intercostal  spaces,  where  the  nerve  is  at  first  above  the  artery.     The  arteries 

rotected  from  pressure  during  the  action  of  the  Intercostal  muscles  by  fibrous 

olies  thrown  across,  and  attached  by  each  extremity  to  the  bone.     The  lower 

c^asC^Stal  arteries  are  continued  anteriorly  from  the  intercostal  spaces  into  the 


Fig.  307. — The  abdominal  aorta  and  i:s  branches. 

abdominal  wall,  except  the  subcostal,  which  lies  throughout  its  whole  course  in  the 
abdominal  wall,  since  it  is  placed  below  the  last  nb.h  They  pass  behind  the  costal 
cartilages  between  the  internal  oblique  and  Traisversalis  muscle  to  the  sheath  of 
the  Rectus,  whero  they  anastomose  with  the  internal  mammary  and  the  deep 
epigastric  arteries.  Behind,  the  subcostal  artery  anastomoses  with  the  first 
lumbar  artery. 

Each  intercostal  artery  gives  off  the  following  branches : 

Posterior  or  dorsal  branch.    a    m^f  ^  Spinal. 
Collateral  r 


THE  ABDOMINAL    AORTA.  549 

The  posterior  or  dorsal  branch  of  each  intercostal  artery  passes  backward  to  the 
inner  side  of  the  anterior  costo-transverse  ligament,  and  divides  into  an  external  and 
internal  branch,  which  are  distributed  to  the  muscles  and  integument  of  the  back. 

The  spinal  branch,  which  enters  the  spinal  canal  through  the  intervertebral 
foramen,  is  distributed  to  the  spinal  cord  and  its  membranes,  and  to  the  bodies  of 
the  vertebne  in  the  same  manner  as  the  lateral  spinal  branches  from  the  vertebral. 

The  collateral  intercostal  branch  comes  off  from  the  intercostal  artery  near  the 
angle  of  the  rib,  and  descends  to  the  upper  border  of  the  rib  below,  along  which  it 
courses  to  anastomose  with  the  anterior  intercostal  branch  of  the  internal  mammary. 

Surgical  Anatomy. — The  position  of  the  intercostal  vessels  should  be  borne  in  mind 
in  performing  the  operation  of  paracentesis  thoracis.  The  puncture  should  never  be  made 
nearer  the  middle  line  posteriorly  than  the  angle  of  the  rib,  as  the  artery  crosses  the  space 
internal  to  this  point.  In  the  lateral  portion  of  the  chest,  where  the  puncture  is  usually 
made,  the  artery  lies  at  the  upper  part  of  the  intercostal  space,  and  therefore  the  puncture 
should  be  made  just  above  the  upper  border  of  the  rib  forming  the  lower  boundary  of  the 
space. 

THE  ABDOMINAL  AORTA    (Fig.  307). 

The  Abdominal  Aorta  commences  at  the  aortic  opening  of  the  Diaphragm,  in 
front  of  the  lower  border  of  the  body  of  the  last  dorsal  vertebra,  and,  descending 
a  little  to  the  left  side  of  the  vertebral  column,  terminates  on  the  body  of  the 
fourth  lumbar  vertebra,  commonly  a  little  to  the  left  of  the  middle  line,1  where  it 
divides  into  the  two  common  iliac  arteries.  It  diminishes  rapidly  in  size,  in  con- 
sequence of 'the  many  large  branches  which  it  gives  off.  As  it  lies  upon  the  bodies 
of  the  vertebras,  the  curve  which  it  describes  is  convex  forward,  the  greatest  con- 
vexity corresponding  to  the  third  lumbar  vertebra,  which  is  a  little  above  and  to 
the  left  side  of  the  umbilicus. 

Relations. — It  is  covered,  in  front,  by  the  lesser  omentum  and  stomach,  behind 
which  are  the  branches  of  the  cceliac  axis  and  the  solar  plexus ;  below  these,  by 
the  splenic  vein,  the  pancreas,  the  left  renal  vein,  the  transverse  portion  of  the 
duodenum,  the  mesentery,  and  aortic  plexus.  Behind,  it  is  separated  from  the 
lumbar  vertebras  and  intervening  discs  by  the  anterior  common  ligament  and  left 
lumbar  veins.  On  the  right  side  it  is  in  relation  with  the  inferior  vena  cava  (the 
right  crus  of  the  Diaphragm  being  interposed  above),  the  vena  azygos  major, 
thoracic  duct,  and  right  semilunar  ganglion  ;  on  the  left  side,  with  the  sympathetic 
nerve  and  left  semilunar  ganglion. 

Plan  of  the  Relations  of  the  Abdominal  Aorta. 

In  front. 

Lesser  omentum  and  stomach. 
Branches  of  the  cceliac  axis  and  solar  plexus. 
Splenic  vein. 
Pancreas. 
Left  renal  vein. 
Transverse  duodenum. 
Mesentery. 
Aortic  plexus. 
Right  side. 

Right  crus  of  Diaphragm.  /  \  Left  side. 

Inferior  vena  cava.  f     Abdominal    \  G  im^„.i    .•    „„„- 

-it  ■  Aorta  sympathetic  nerve. 

Vena   azygos  major.  Tifr.lm.ilm.™- «•!•* 

Inoracic  duct. 
Right  semilunar  ganglion. 

Behind. 

Left  lumbar  veins. 
Vertebral  column. 

1  Lord  Lister,  having  accurately  examined  30  bodies  in  order  to  ascertain  the  exact  point  of 
termination  of  this  vessel,  found  it  "either  absolutely,  or  almost  absolutely,  mesial  in  15,  while  in 
13  it  deviated  more  or  less  to  the  left,  and  in  2  was  slightly  to  the  right"  (System  of  Surgery,  edited 
by  T.  Holmes,  2d  ed.,  vol.  v.,  p.  652). 


Left  semilunar  ganglion. 


550  THE  BLOOD-VASCULAR   SYSTEM. 

Surface  Marking.— In  order  to  map  out  the  abdominal  aorta  on  the  surface  of  the  abdomen, 
a  line  must  be  drawn  from  the  middle  line  of  the  body,  on  a  level  with  the  distal  extremity  of 
the  seventh  costal  cartilage,  downward  and  slightly  to  the  left,  so  that  it  just  skirts  the  umbilicus, 
to  a,  zone  drawn  round  the  body  opposite  the  highest  point  of  the  crest  of  the  ilium.  This 
point  is  generally  half  an  inch  below  and  to  the  left  of  the  umbilicus,  but  as  the  position  of  this 
structure  varies  with  the  obesity  of  the  individual,  it  is  not  a  reliable  landmark  as  to  the  situation 
of  the  bifurcation  of  the  aorta. 

Surgical  Anatomy. — Aneurisms  of  the  abdominal  aorta  near  the  coeliac  axis  communicate 
in  nearly  equal  proportion  with  the  anterior  and  posterior  parts  of  the  artery. 

When  an  aneurisnial  sac  is  connected  with  the  back  part  of  the  abdominal  aorta,  it  usually 
produces  absorption  of  the  bodies  of  the  vertebras,  and  forms  a  pulsating  tumor  that  presents 
itself  in  the  left  hypochondriac  or  epigastric  regions,  and  is  accompanied  by  symptoms  of  dis- 
turbance in  the  alimentary  canal.  Pain  is  invariably  present,  and  is  usually  of  two  kinds — a 
fixed  and  constant  pain  in  the  back,  caused  by  the  tumor  pressing  on  or  displacing  the  branches 
of  the  solar  plexus  and  splanchnic  nerves  ;  and  a  sharp  lancinating  pain,  radiating  along  those 
branches  of  the  lumbar  nerves  which  are  pressed  on  by  the  tumor ;  hence  the  pain  in  the  loins, 
the  testes,  the  hypogastrium,  and  in  the  lower  limb  (usually  of  the  left  side).  This  form  of 
aneurism  usually  bursts  into  the  peritoneal  cavity  or  behind  the  peritoneum  in  the  left  hypo- 
chondriac region ;  or  it  may  form  a  large  aneurismal  sac,  extending  down  as  low  as  Poupart's 
ligament ;  haemorrhage  in  these  cases  being  generally  very  extensive,  but  slowly  produced,  and 
not  rapidly  fatal. 

When  an  aneurismal  sac  is  connected  with  the  front  of  the  aorta  near  the  coeliac  axis,  it 
forms  a  pulsating  tumor  in  the  left  _  hypochondriac  or  epigastric  regions,  usually  attended  with 
symptoms  of  disturbance _  of  the  alimentary  canal,  as  sickness,  dyspepsia,  or  constipation,  and 
accompanied  by  pain,  which  is  constant,  but  nearly  always  fixed  in  the  loins,  epigastrium,  or 
some  part  of  the  abdomen ;  the  radiating  pain  being  rare,  as  the  lumbar  nerves  are  seldom 
implicated.  This  form  of  aneurism  may  burst  into  the  peritoneal  cavity  or  behind  the  peritoneum, 
between  the  layers  of  the  mesentery,  or,  more  rarely,  into  the  duodenum ;  it  rarely  extends  back- 
ward so  as  to  affect  the  spine. 

The  abdominal  aorta  has  been  tied  several  times,  and  although  none  of  the  patients  perma- 
nently recovered,  still,  as  one  of  them  lived  as  long  as  ten  days,  the  possibility  of  the  re- 
establishment  of  the  circulation  may  be  considered  to  be  proved.  In  the  lower  animals  this 
artery  has  been  often  successfully  tied.  The  vessel  may  be  reached  in  several  ways.  In  the 
original  operation,  performed  by  Sir  A.  Cooper,  an  incision  was  made  in  the  linea  alba,  the 
peritoneum  opened  in  front,  the  finger  carried  down  amongst  the  intestines  toward  the  spine,  the 
peritoneum  again  opened  behind  by  scratching  through  the  mesentery,  and  the  vessel  thus  reached. 
Or  either  of  the  operations  described  below  for  securing  the  common  iliac  artery  may,  by  extend- 
ing the  dissection  a  sufficient  distance  upward,  be  made  use  of  to  expose  the  aorta.  The  chief 
difficulty  in  the  dead  subject  consists  in  isolating  the  artery  in  consequence  of  its  great  depth  ;  but 
in  the  living  subject  the  embarrassment  resulting  from  the  proximity  of  the  aneurismal  tumor,  and 
the  great  probability  of  disease  in  the  vessel  itself,  add  to  the  clangers  and  difficulties  of  this  for- 
midable operation  so  greatly  that  it  is  very  doubtful  whether  it  ought  ever  to  be  performed. 

The  collateral  circulation  would  be  carried  on  by  the  anastomosis  between  the  internal 
mammary  and  the  deep  epigastric  ;  by  the  free  communication  between  the  superior  and  inferior 
mesenteries  if  the  ligature  were  placed  above  the  latter  vessel ;  or  by  the  anastomosis  between 
the  inferior  mesenteric  and  the  internal  pudic  when  (as  is  more  common)  the  point  of  ligature  is 
below  the _  origin  of  the  inferior  mesenteric;  and  possibly  by  the  anastomoses  of  the  lumbar 
arteries  with  the  branches  of  the  internal  iliac. 

The  circulation  through  the  abdominal  aorta  may  be  commanded,  in  thin  persons,  by  firm 
pressure  with  the  fingers.  A  tourniquet  has  been  invented  for  this  purpose  which  is  sometimes 
used  in  amputation  at  the  hip-joint  and  some  other  operations. 

Branches  of  the  Abdominal  Aorta. 
Phrenic.  Superior  Mesenteric.  Ovarian  in  female. 

('  Gastric.  Suprarenal.  Inferior  Mesenteric. 

Coeliac  Axis.  <  Hepatic.  Renal.  Lumbar. 

(  Splenic.  Spermatic  in  male.  Sacra  Media. 

The  branches  may  be  divided  into  two  sets  :  1.  Those  supplying  the  viscera. 
2.   Those  distributed  to  the  walls  of  the  abdomen. 

Visceral  Branches.  Renal. 

{Gastric.  Spermatic  or  Ovarian. 
Hepatic. 
Splenic.  Parietal  Branches. 

Superior  Mesenteric.  Phrenic. 

Inferior  Mesenteric.  Lumbar. 

Suprarenal.  Sacra  Media. 


THE    CCELIAC  AXIS. 


551 


J  !    The  Cceliac  Axis  (Fig.  308). 

ry  raise  the  liver,  draw  down  the  stomacl 
intum. 

The  Coeliac  Axis  is  a  short  thick  trunk,  about  half  an  inch  in  length,  which 


To  expose  this  artery  raise  the  liver,  draw  down  the  stomach,  and  then  tear  through  the 
layers  of  the  lesser  omentum. 


Cystic  at 


Fig.  308.— The  coeliac  axis  and  its  branches,  the  liver  having  been  raised  and  the  lesser  omentum  removed. 

arises  from  the  aorta,  close  to  the  margin  of  the  opening  in  the  Diaphragm,  and, 
passing  nearly  horizontally  forward  (in  the  erect  posture),  divides  into  three  large 
branches,  the  gastric,  hepatic,  and  splenic,  occasionally  giving  off  one  of  the 
phrenic  arteries. 

Relations. — It  is  covered  by  the  lesser  omentum.  On  the  right  side  it  is  in 
relation  with  the  right  semilunar  ganglion  and  the  lobus  Spigelii ;  on  the  left  side, 
with  the  left  semilunar  ganglion  and  cardiac  end  of  the  stomach.  Below,  it  rests 
upon  the  upper  border  of  the  pancreas. 

The  Gastric  or  Coronary  Artery,  the  smallest  of  the  three  branches  of  the 
coeliac  axis,  passes  upward  and  to  the  left  side,  to  the  cardiac  orifice  of  the  stomach, 
distributing  branches  to  the  oesophagus  which  anastomose  with  the  aortic  oesopha- 
geal arteries ;  others  supply  the  cardiac  end  of  the  stomach,  inosculating  with 
branches  of  the  splenic  artery ;  it  then  passes  from  left  to  right,  along  the  lesser 
curvature  of  the  stomach  to  the  pylorus,  lying  se  between  the  layers  of 

the  lesser  omentum,  and  giving  branches  to  bot  of  the  organ  :  at  its  ter- 

mination it  anastomoses  with  the  pyloric  brand,  p  .   >patic. 

The  Hepatic  Artery  in  the  adult  is  interna  size  between  the  gastric 

and  splenic  ;  in  the  foetus  it  is  the  largest  of  the  t  iches  of  the  coeliac  axis. 

It  is  first  directed  forward  and  to  the  right,  to  t  largin  of  the  pyloric  end 


A 


552 


THE   BLOOD-VASCULAR   SYSTEM. 


of  the  stomach,  forming  the  lower  boundary  of  the  foramen  of  Winslow.  It  then 
passes  upward  between  the  layers  of  the  lesser  omentum,  and  in  front  of  the  fora- 
men of  Winslow,  to  the  transverse  fissure  of  the  liver,  where  it  divides  into  two 
branches,  right  and  left,  which  supply  the  corresponding  lobes  of  that  organ, 
accompanying  the  ramifications  of  the  vena  portge  and  hepatic  duct.  The  hepatic 
artery,  in  its  course  along  the  right  border  of  the  lesser  omentum,  is  in  relation 
with  the  ductus  communis  choledochus  and  portal  veins,  the  duct  lying  to  the 
right  of  the  artery  and  the  vena  portse  behind. 
Its  branches  are — the 


f  Gastro-epiploica  Dextra. 

\  Pancreatico-duodenalis  Superior. 


Pyloric. 
Gastro-duodenalis 

Cystic. 

The  pyloric  branch  arises  from  the  hepatic,  above  the  pylorus,  descends  to  the 
pyloric  end  of  the  stomach,  and  passes  from  right  to  left  along  its  lesser  curvature, 


Great 


Fig.  309.— The  cceliac  axis  and  its  branches,  the  stomach  having  been  raised  and  the  transverse  meso-colon 
removed  (semi-diagrammatic). 

supplying  it  with  branches  and  inosculating  with  the  gastric  branches  of  the  coro- 
nary artery. 

The  gastro-duodenalis  (Fig.  309)  is  a  short  but  large  branch,  which  descends, 
near  the  pylorus,  behinjLJiLeLjLraL^iaiion  of  the  duodenum,  an'id  divides  at  the 
lower  border  of  this  viscus  into  two  branches,  the  gastro-epiploica  dextra  and  the 
panoreatico-duodenalis  superior.  Previous  to  its  division,  it  gives  qfif  two  or  three 
small  inferior  pyloric  branches  to  the  pyloric  end  of  the  stomach  ari  ^  pancreas. 


/ 


THE   SUPERIOR    MESENTERIC  ARTERY.  553 

The  gastro-epiploica  dextra  runs  from  right  to  left  along  the  greater  curvature 
of  the  stomach,  between  the  layers  of  the  great  omentum,  anastomosing  about  the 
middle  of  the  lower  border  of  the  stomach  with  the  gastro-epiploica  sinistra  from 
the  splenic  artery.  This  vessel  gives  off  numerous  branches,  some  of  which  ascend 
to  supply  both  surfaces  of  the  stomach,  whilst  others  descend  to  supply  the  great 
omentum. 

The  pancreatico-duodenalis  superior  descends  between  the  contiguous  margins 
of  the  duodenum  and  pancreas.  It  supplies  both  these  organs,  and  anastomoses 
with  the  inferior  pancreatico-duodenal  branch  of  the  superior  mesenteric  artery 
and  with  the  pancreatic  branches  of  the  splenic. 

The  cystic  artery  (Fig.  308),  usually  a  branch  of  the  right  hepatic,  passes 
upward  and  forward  along  the  neck  of  the  gall-bladder,  and  dWides  into  two 
branches,  one  of  which  ramifies  on  its  free  surface,  the  other  between  it  and  the 
substance  of  the  liver. 

The  Splenic  Artery,  in  the  adult,  is  the  largest  of  the  three  branches  of  the 
coeliac  axis,  and  is  remarkable  for  the  extreme  tortuosity  of  its  course.  It  passes 
horizontally  to  the  left  side,  behind  the  peritoneum  and  along  the  upper  border  of 
the  pancreas,  accompanied  by  the  splenic  vein,  which  lies  below  it,  and  on  arriving 
near  the  spleen  divides  into  branches,  some  of  which  enter  the  hilum  of  that  organ 
to  be  distributed  to  its  structure,  whilst  others  are  distributed  to  the  pancreas  and 
great  end  of  the  stomach.     Its  branches  are — the 

Pancreaticse  Parvge.  Gastric  (Vasa  Brevia). 

Pancreatica  Magna.  Gastro-epiploica  Sinistra. 

The  pancreatic  are  numerous  small  branches  derived  from  the  splenic  as  it 
runs  behind  the  upper  border  of  the  pancreas,  supplying  its  middle  and  left  parts. 
One  of  these,  larger  than  the  rest,  is  given  off  from  the  splenic  near  the  left 
extremity  of  the  pancreas ;  it  runs  from  left  to  right  near  the  posterior  surface  of 
the  gland,  following  the  course  of  the  pancreatic  duct,  and  is  called  the  pancreatica 
magna.  These  vessels  anastomose  with  the  pancreatic  branches  of  the  pancreatico- 
duodenal arteries,  derived  from  the  hepatic  on  the  one  hand  and  superior  mesenteric 
on  the  other. 

The  gastric  (vasa  brevia)  consists  of  from  five  to  seven  small  branches,  which 
arise  either  from  the  termination  of  the  splenic  artery  or  from  its  terminal  branches, 
and,  passing  from  left  to  right,  between  the  layers  of  the  gastro-splenic  omentum, 
are  distributed  to  the  great  curvature  of  the  stomach,  anastomosing  with  branches 
of  the  gastric  and  gastro-epiploica  sinistra  arteries. 

The  gastro-epiploica  sinistra,  the  largest  branch  of  the  splenic,  runs  from  left 
to  right  along  the  great  curvature  of  the  stomach,  between  the  layers  of  the  great 
omentum,  and  anastomoses  with  the  gastro-epiploica  dextra.  In  its  course  it 
distributes  several  branches  to  the  stomach,  which  ascend  upon  both  surfaces ; 
others  descend  to  supply  the  omentum. 

The  Superior  Mesenteric  Artery  (Fig.  310). 

In  order  to  expose  this  vessel  raise  the  great  omentum  and  transverse  colon,  draw  down  the 
small  intestines,  and  cut  through  the  peritoneum  where  the  transverse  meso-colon  and  mesen- 
tery join:  the  artery  will  then  be  exposed  just  as  it  issues  from  beneath  the  lower  border  of  the 
pancreas. 

The  Superior  Mesenteric  Artery  supplies  the  whole  length  of  the  small  intestine, 
except  the  first  part  of  the  duodenum ;  it  also  supplies  the  caecum,  ascending 
and  transverse  colon  ;  it  is  a  vessel  of  large  size,  arising  from  the  fore  part  of  the 
aorta  about  !  I      of  an  inch  below  the  coeliac  axis  ;  being  covered  at  its  origin 

by  the  splen  nd  pancreas.      It  passes  forward,  between   the  pancreas  and 

transverse  portion  '  the  duodenum,  crosses  in  front  of  this  portion  of  the  intes- 
tine, and  d(  itween  the  layers  of  the  mesentery  to  the  right  iliac  fossa, 
where,  consh' .  iminished  in  size,  it  anastomoses  with  one  of  its  own  branches 
— viz.,  ileo-i  its  course  it  forms  an  arch,  the  convexity  of  which  is  directed 


554 


THE   BLOOD-VASCULAR   SYSTEM. 


forward  and.  downward  to  the  left  side,  the  concavity  backward  and  upward  to  the 
right.  It  is  accompanied  by  the  superior  mesenteric  vein,  and  is  surrounded 
by  the  superior  mesenteric  plexus   of    nerves.      Its  branches  are — the 


Inferior  Pancreatico-duodenal. 
Vasa  Intestini  Tenuis. 

Colica  Media. 


Ileo-colic. 
Colica  Dextra. 


t  ■- —  ■ "    ,**"■■■•■  <,; 

Fig.  310.— The  superior  mesenteric  artery  and  its  branches. 

The  inferior  pancreatico-duodenal  is  given  oif  from  the  superior  mesenteric,  or 
from  its  first  intestinal  branch  behind  the  pancreas.  It  courses  to  the  right  be- 
tween the  head  of  the  pancreas  and  duodenum,  and  then  ascends  to  anastomose 
with  the  superior  pancreatico-duodenal  artery.  It  distributes  branches  to  the  head 
of  the  pancreas  and  to  the  transverse  and  descending  portions  of  the  duodenum. 

The  vasa  intestini  tenuis  arise  from  the  convex  side  of  the  superior  mesenteric 
artery.  They  are  usually  from  twelve  to  fifteen  in  number,  and  are  distributed  to 
the  jejunum  and  ileum.  They  run  parallel  with  one  another  between  the  layers 
of  the  mesentery,  each  vessel  dividing  into  two  branches,  which  unite  with  a  sim- 
ilar branch  on  each  side,  forming  a  series  of  arches  the  convexities-  of  which  are 
directed  toward  the  intestine.  From  this  first  set  of  arches  branches  arise, 
which  again  unite  with  similar  branches  from  either  side,  and  thus  a  second  series 
of  arches  is  formed ;  and  from  these  latter,  a  third,  and  a  fourth,  or  even  fifth, 
series  of  arches  is  constituted,  diminishing  in  size  the  nearer  they  approach  the 


THE  INFERIOR   MESENTERIC  ARTERY.  555 

intestine.  From  the  terminal  arches  numerous  small  straight  vessels  arise  which 
encircle  the  intestine,  upon  which  they  are  distributed,  ramifying  between  its 
coats.  Throughout  their  course  small  branches  are  given  off  to  the  glands  and 
other  structures  between  the  layers  of  the  mesentery. 

The  ileo-colic  artery  is  the  lowest  branch  given  off  from  the  concavity  of  the 
superior  mesenteric  artery.  It  descends  between  the  layers  of  the  mesentery  to 
the  right  iliac  fossa,  where  it  divides  into  two  branches.  Of  these,  the  inferior 
division  inosculates  with  the  termination  of  the  superior  mesenteric  artery,  forming 
with  it  an  arch,  from  the  convexity  of  which  branches  proceed  to  supply  the  termi- 
nation of  the  ileum,  the  caecum  and  appendix  cseci,  and  the  ileo-csecal  valve.  The 
superior  division  inosculates  with  the  colica  dextra  and  supplies  the  commence- 
ment of  the  colon. 

The  colica  dextra  arises  from  about  the  middle  of  the  concavity  of  the  superior 
mesenteric  artery,  and,  passsyag  behind  the  peritoneum  to  the  middle  of  the 
ascending  colon,  divides  into  two  branches — a  descending  branch,  which  inoscu- 
lates with  the  ileo-colic ;  and  the  ascending  branch,  which  anastomoses  with  the 
colica  media.  These  branches  form  arches,  from  the  convexity  of  which  vessels 
are  distributed  to  the  ascending  colon.  The  branches  of  this  vessel  are  covered 
with  peritoneum  only  on  their  anterior  aspect. 

The  colica  media  arises  from  the  upper  part  of  the  concavity  of  the  superior 
mesenteric,  and,  passing  forward  between  the  layers  of  the  transverse  meso-colon, 
divides  into  two  branches,  the  one  on  the  right  side  inosculating  with  the  colica 
dextra ;  that  on  the  left  side,  with  the  colica  sinistra,  a  branch  of  the  inferior 
mesenteric.  From  the  arches  formed  by  their  inosculation  branches  are  distrib- 
uted to  the  transverse  colon.  The  branches  of  this  vessel  lie  between  two  layers 
of  the  transverse  meso-colon. 

The  Inferior  Mesenteric  Artery  (Fig.  311). 

In  order  to  expose  this  vessel  draw  the  small  intestines  and  mesentery  over  to  the  right 
side  of  the  abdomen,  raise  the  transverse  colon  toward  the  thorax,  and  divide  the  peritoneum 
covering  the  front  side  of  the  aorta. 

The  Inferior  Mesenteric  Artery  supplies  the  descending  and  sigmoid  flexure  of 
the  colon  and  the  greater  part  of  the  rectum.  It  is  smaller  than  the  superior 
mesenteric,  and  arises  from  the  left  side  of  the  aorta,  between  one  and  two 
inches  above  its  division  into  the  common  iliacs.  It  passes  downward  to  the  left 
iliac  fossa,  and  then  descends,  between  the  layers  of  the  meso-rectum,  into  the 
pelvis,  under  the  name  of  the  superior  hemorrhoidal  artery.  It  lies  at  first  in  close 
relation  with  the  left  side  of  the  aorta,  and  then  passes  as  the  superior  hemor- 
rhoidal in  front  of  the  left  common  iliac  artery.     Its  branches  are — the 

Colica  Sinistra.  Sigmoid. 

»  Superior  Hgemorrhoidal. 

The  colica  sinistra  passes  behind  the  peritoneum,  in  front  of  the  left  kidney, 
to  reach  the  descending  colon,  and  divides  into  two  branches — an  ascending 
branch,  which  inosculates  with  the  colica  media;  and  a  descending  branch,  which 
anastomoses  with  the  sigmoid  artery.  From  the  arches  formed  by  these  inoscu- 
lations branches  are  distributed  to  the  descending  colon. 

The  sigmoid  artery  runs  obliquely  downward  across  the  Psoas  muscle  to  the 
sigmoid  flexure  of  the  colon,  and  divides  into  branches  which  supply  that  part  of 
the  intestine,  anastomosing  above  with  the  colica  sinistra,  and  below  with  the 
superior  haemorrhoidal  artery.  This  vessel  is  sometimes  replaced  by  three  or  four 
sm^11  1    anches. 

mperior  haemorrhoidal  artery,  the  continuation  of  the  inferior  mesenteric, 

into  the  pelvis  between  the  layers  of  the  meso-rectum,  crossing,  in  its 

c<  e  ureter  and  left  common  iliac  vessels.     It  divides  into  two  branches, 

apfhj  end  one  on  each  side  of  the  rectum,  and  about  five  inches  from  the  anus 

bi  to  several  small  branches,  which  pierce  the  muscular  coat  of  the  bowel 


556 


THE   BLOOD-VASCULAR    SYSTEM. 


and  run  downward,  as  straight  vessels,  placed  at  regular  intervals  from  each  other 
in  the  wall  of  the  gut  between  its  muscular  and  mucous  coat,  to  the  level  of  the 
internal  sphincter ;  here  they  form  a  series  of  loops  around  the  lower  end  of  the 
rectum,  and  communicate  with  the  middle  hsemorrhoidal  arteries,  branches  of  the 
internal  iliac,  with  the  inferior  hemorrhoidal  branches  of  the  internal  pudic. 


Middle  hsemorrhoidal 
Inferior  hsemorrhoidal 


Fig.  311. — The  inferior  mesenteric  and  its  branches. 


The  Suprarenal  Arteries  (Fig.  307). 

The  suprarenal  arteries  are  two  small  vessels  which  arise,  one  on  each  side  of 
the  aorta,  opposite  the  superior  mesenteric  artery.  They  pass  obliquely  upward 
and  outward,  over  the  crura  of  the  Diaphragm,  to  the  under  surface  of  the  supra- 
renal capsules,  to  which  they  are  distributed,  anastomosing  with  capsular  branches 
from  the  phrenic  and  renal  arteries.  In  the  adult  these  arteries  are  of  small  size  ; 
in  the  foetus  they  are  as  large  as  the  renal  arteries. 

The  Renal  Arteries  (Fig.  307), 

The  renal  arteries  are  two  large  trunks  which  arise  from  the  sides  of  the  aorta 
immediately  below  the  superior  mesenteric  artery.  Each  is  directed  outward 
across  the  crus  of  the  Diaphragm,  so  as  to  form  nearly  a  right  angle  with  the 
aorta.  The  right  is  longer  than  the  left,  on  account  of  the  position  of  the  aorta ; 
it  passes  behind  the  inferior  vena  cava.      The  left  is  somewhat  higher  than  the 


THE   PHRENIC  ARTERIES.  557 

rio-ht.  Before  reaching  the  hilum  of  the  kidney,  each  artery  divides  into  four  or 
five  branches  ;  the  greater  number  of  which  generally  lie  between  the  renal  vein 
and  ureter,  the  vein  being  in  front,  the  ureter  behind.  Each  vessel  gives  off  some 
small  branches  to  the  suprarenal  capsule,  the  ureter,  and  the  surrounding  cellular 
tissue  and  muscles.  Frequently  there  is  a  second  renal  artery,  which  is  given  off 
from  the  abdominal  aorta  either  above  or  below  the  renal  artery  proper,  the  former 
being  the  more  common  position.  Instead  of  entering  the  kidney  at  the  hilum, 
these  accessory  renal  arteries  usually  pierce  the  upper  or  lower  part  of  the  gland. 

The  Spermatic  Arteries. 

The  spermatic  arteries  are  distributed  to  the  testes.  They  are  two  slender 
vessels  of  considerable  length,  which  arise  from  the  front  of  the  aorta  a  little  below 
the  renal  arteries.     Each  artery  passes  obliquely  outward  and  downward  behind 

;  the  peritoneum,  resting  on  the  Psoas  muscle,  the  right  spermatic  lying  in  front  of 
the  inferior  vena  cava,  the  left  behind  the  sigmoid  flexure  of  the  colon.     It  then 

;  crosses  obliquely  over  the  ureter  and  the  lower  part  of  the  external  iliac  artery  to 
reach  the  internal  abdominal  ring,  through  which  it  passes,  and  accompanies  the 
other  constituents  of  the  spermatic  cord  along  the  inguinal  canal  to  the  scrotum, 
where  it  becomes  tortuous,  and  divides  into  several  branches,  two  or  three  of 

;  which  accompany  the  vas  deferens  and  supply  the  epididymis,  anastomosing  with 

i  the  artery  of  the  vas  deferens ;  others  pierce  the  back  part  of  the  tunica  albuginea, 
and  supply  the  substance  of  the  testis. 

The  Ovarian  Arteries. 

The  ovarian  arteries  (Fig.  313)  are  the  corresponding  arteries  in  the  female  to 
i  the  spermatic  in  the  male.  They  supply  the  ovaries,  are  shorter  than  the  sper- 
matic, and  do  not  pass  out  of  the  abdominal  cavity.  The  origin  and  course  of  the 
first  part  of  the  artery  are  the  same  as  the  spermatic  in  the  male,  but  on  arriving 
I  at  the  margin  of  the  pelvis  the  ovarian  artery  passes  inward,  between  the  two 
layers  of  the  broad  ligament  of  the  uterus,  to  be  distributed  to  the  ovary.  One 
or  two  small  branches  supply  the  Fallopian  tube ;  another  passes  on  to  the  side 
of  the  uterus  and  anastomoses  with  the  uterine  arteries.  Other  offsets  are  con- 
tinued along  the  round  ligament  through  the  inguinal  canal,  to  the  integument  of 
the  labium  and  groin. 

At  an  early  period  of  foetal  life,  when  the  testes  or  ovaries  lie  by  the  side  of 
the  spine  below  the  kidneys,  the  spermatic  or  ovarian  arteries  are  short ;  but  as 
these  organs  descend  from  the  abdomen  into  the  scrotum  or  pelvis,  the  arteries 
become  gradually  lengthened. 

The  Phrenic  Arteries. 

The  phrenic  arteries  are  two  small  vessels  which  present  much  variety  in 
their  origin.  They  may  arise  separately  from  the  front  of  the  aorta,  immediately 
above  the  coeliac  axis,  or  by  a  common  trunk,  which  may  spring  either  from  the 
aorta  or  from  the  coeliac  axis.  Sometimes  one  is  derived  from  the  aorta,  and  the 
other  from  one  of  the  renal  arteries.  In  only  one  out  of  thirty-six  cases  examined 
did  these  arteries  arise  as  two  separate  vessels  from  the  aorta.  They  diverge  from 
one  another  across  the  crura  of  the  Diaphragm,  and  then  pass  obliquely  upward 
and  outward  upon  its  under  surface.  The  left  phrenic  passes  behind  the  oesoph- 
agus and  runs  forward  on  the  left  side  of  the  oesophageal  opening.  The  right 
phrenic  passes  behind  the  inferior  vena  cava,  and  ascends  along  the  right  side  of 
the  aperture  for  transmitting  that  vein.  Near  the  back  part  of  the  central  tendon 
each  vessel  divides  into  two  branches.  The  internal  branch  runs  forward  to  the 
front  of  the  thorax,  supplying  the  Diaphragm  and  anastomosing  with  its  fellow  of 


558  THE  BLOOD-VASCULAR   SYSTEM. 

the  opposite  side,  and  with  the  musculophrenic  and  comes  nervi  phrenici,  branches 
of  the  internal  mammary.  The  external  branch  passes  toward  the  side  of  the 
thorax  and  inosculates  with  the  intercostal  arteries.  The  internal  branch  of  the 
right  phrenic  gives  off  a  few  vessels  to  the  inferior  vena  cava,  and  the  left  one 
some  branches  to  the  oesophagus.  Each  vessel  also  sends  capsular  branches  to 
the  suprarenal  capsule  of  its  own  side.  The  spleen  on  the  left  side  and  the  liver 
on  the  right  also  receive  a  few  branches  from  these  vessels. 

The  Lumbar  Arteries. 

The  lumbar  arteries  are  analogous  to  the  intercostal.  They  are  usually  four 
in  number  on  each  side,  and  arise  from  the  back  part  of  the  aorta,  nearly  at  right 
angles  with  that  vessel.  They  pass  outward  and  backward,  around  the  sides  of 
the  body  of  the  lumbar  vertebra,  behind  the  sympathetic  nerve  and  the  Psoas 
magnus  muscle,  those  on  the  right  side  being  covered  by  the  inferior  vena  cava, 
and  the  two  upper  ones  on  each  side  by  the  crura  of  the  Diaphragm.  In  the 
interval  between  the  transverse  processes  of  the  vertebrae  each  artery  divides  into 
a  dorsal  and  an  abdominal  branch. 

The  dorsal  branch  gives  off,  immediately  after  its  origin,  a  spinal  branch,  which 
enters  the  spinal  canal ;  it  then  continues  its  course  backward  between  the  trans- 
verse processes,  and  is  distributed  to  the  muscles  and  integument  of  the  back, 
anastomosing  with  the  similar  branches  of  the  adjacent  lumbar  arteries  and  with 
the  posterior  branches  of  the  intercostal  arteries. 

The  spinal  branch  enters  the  spinal  canal  through  the  intervertebral  foramen, 
to  be  distributed  to  the  spinal  cord  and  its  membranes  and  to  the  bodies  of  the 
vertebrae  in  the  same  manner  as  the  lateral  spinal  branches  from  the  vertebra 
(see  page  521). 

The  abdominal  branches  pass  outward,  having  a  variable  relation  to  tin 
Quadratus  lumborum  muscle.  Most  frequently  the  first  branch  passes  in  fron 
of  the  muscle  and  the  others  behind  it ;  sometimes  the  order  is  reversed  and  th< 
lowest  branch  passes  in  front  of  the  muscle.  At  the  outer  border  of  the  Quadratus 
they  are  continued  between  the  abdominal  muscles,  anastomose  with  branches  of 
the  epigastric  and  internal  mammary  in  front,  the  intercostals  above,  and  those  of 
the  ilio-lumbar  and  circumflex  iliac  below. 

The  Middle  Sacral  Artery. 

The  Middle  Sacral  Artery  is  a  small  vessel,  which  arises  from  the  back  part  of 
the  aorta  just  at  its  bifurcation.  It  descends  upon  the  last  lumbar  vertebra,  am 
along  the  middle  line  of  the  front  of  the  sacrum,  to  the  upper  part  of  the  coccyx 
where  it  anastomoses  with  the  lateral  sacral  arteries,  and  terminates  in  a  minut< 
branch,  which  runs  down  to  the  situation  of  the  body  immediately  to  be  described  a 
"Luschka's  gland."  From  it  branches  arise  which  run  through  the  meso-rectuu 
to  supply  the  posterior  surface  of  the  rectum.  Other  branches  are  given  off  01 
each  side,  which  anastomose  with  the  lateral  sacral  arteries,  and  send  off  small  offset 
which  enter  the  anterior  sacral  foramina. 

The  artery  is  the  representative  of  the  caudal  prolongation  of  the  aorta  o: 
animals,  and  its  lateral  branches  correspond  to  the  intercostal  and  lumbar  arterie 
in  the  dorsal  and  lumbar  regions. 

Coccygeal  Gland,  or  Luschka's  Gland. — Lying  near  the  tip  of  the  coccyx  in 
small  tendinous  interval  formed  by  the  union  of  the  Levator  ani  muscles  of  eac 
side,  and  just  above  the  coccygeal  attachment  of  the  Sphincter  ani,  is  a  smal 
conglobate  body  about  as  large  as  a  lentil  or  a  pea,  first  described  by  Luschka. 
and  named  by  him  the  coccygeal  gland.  Its  most  obvious  connections  are  with  th 
arteries  of  the  part. 

Structure. — It  consists  of  a  congeries  of  small  arteries  with  little  aneurisms 
dilatations  derived  from  the  middle  sacral  and  freely  communicating  with  eac 

1  Der  Hirnanhang  und  die  Steissdriise  des  Memchen,  Berlin,  1860 ;  Anatomie  des  Menschen,  Tiibingej 
1864,  vol.  ii.  pt.  2,  p.  187. 


THE    COMMON  ILIAC  ARTERIES. 


559 


other.  These  vessels  are  enclosed  in  one  or  more  layers  of  polyhedral  granular  cells, 
and  the  whole  structure  is  invested  in  a  capsule  of  connective  tissue  which  sends 
in  trabeculse,  dividing  the  interior  into  a  number  of  spaces  in  which  the  vessels 
and  cells  are '  contained.  Nerves  pass  into  this  little  body  from  the  sympathetic, 
but  their  mode  of  termination  is  unknown.  Macalister  believes  the  glomerulus  of 
vessels  "  consists  of  the  condensed  and  convoluted  metameric  dorsal  arteries  of  the 
caudal  segments  imbedded  in  tissue  which  is  possibly  a  small  persisting  fragment 
of  the  neurenteric  canal." 

THE  COMMON  ILIAC  ARTERIES. 

The  abdominal  aorta  divides  into  the  two  common  iliac  arteries.  The  bifurca- 
tion usually  takes  place  on  the  left  side  of  the  body  of  the  fourth  lumbar  vertebra. 
The  common  iliac  arteries  are  about  two  inches  in  length  ;  diverging  from  the 
termination  of  the  aorta,  they  pass  downward  and  outward  to  the  margin  of  the 
pelvis,  and  divide  opposite  the  intervertebral  substance,  between  the  last  lumbar 
vertebra  and  the  sacrum,  into  two  branches,  the  external  and  internal  iliac  arteries, 
the  former  supplying  the  lower  extremity ;  the  latter,  the  viscera  and  parietes  of 

the  pelvis. 

The  right  common  iliac  is  somewhat  longer  than  the  left,  and  passes  more 
obliquely  across  the  body  of  the  last  lumbar  vertebra.  In  front  of  it  are  the 
peritoneum,  the  small  intestines,  branches  of  the  sympathetic  nerve,  and,  at  its 
point  of  division,  the  ureter.  Behind,  it  is  separated  from  the  fourth  and  fifth 
lumbar  vertebree,  with  the  intervening  intervertebral  disc,  by  the  two  common 
iliac  veins.  On  its  outer  side,  it  is  in  relation  with  the  inferior  vena  cava  and 
the  right  common  iliac  vein,  above,  and  the  Psoas  magnus  muscle  below. 

The  left  common  iliac  is  in  relation,  in  front,  with  the  peritoneum,  branches 
of  the  sympathetic  nerve,  and  the  superior  hemorrhoidal  artery ;  and  is  crossed 
at  its  point  of  bifurcation  by  the  ureter.  It  rests  on  the  bodies  of  the  fourth  and 
fifth  lumbar  vertebrae,  with  the  intervening  intervertebral  disc.  The  left  common 
iliac  vein  lies  partly  on  the  inner  side,  and  partly  beneath  the  artery ;  on  its 
outer  side,  the  artery  is  in  relation  with  the  Psoas  magnus  muscle. 


Plan  of  the  Relations  of  the  Common  Iliac  Arteries. 


In  front. 
Peritoneum. 
Small  intestines. 
Sympathetic  nerves. 
Ureter. 


Outer  side. 

Vena  cava. 
Right  common 

iliac  vein. 
Psoas  muscle. 


Behind. 
Fourth  and  fifth  lumbar  vertebrae. 
Right  and  left  common  iliac  veins. 


Inner  side. 

Left  common 
iliac  vein. 


In  front. 
Peritoneum. 
Sympathetic  nerves. 
Superior  haeniorrhoidal  artery. 
Ureter. 

Outer  side. 

Psoas  magnus 
muscle. 


Behind. 

Fourth  and  fifth  lumbar  vertebrae. 
Left  common  iliac  vein. 


Branches. — The  common  iliac  arteries  give  off  small  branches  to  the  peritoneum 
Psoas  magnus,  ureters,  and  the  surrounding  cellular  tissue,  and  occasionally  give 
origin  to  the  ilio-lumbar  or  renal  arteries. 

Peculiarities.— The  point  of  origin  varies  according  to  the  bifurcation  of  the  aorta.  In 
three-fourths  of  a  large  number  of  cases  the  aorta  bifurcated  either  upon  the  fourth  lumbar 
vertebra  or  upon  the  intervertebral  disk  between  it  and  the  fifth,  the  bifurcation  being,  in  one 
case  out  of  nine  below,  and  in  one  out  of  eleven  above,  this  point,  In  ten  out  of  every  thirteen 
cases  the  vessel  bifurcated  within  half  an  inch  above  or  below  the  level  of  the  crest  ot  the  ilium 
more  frequently  below  than  above.  #  . 

The  point  of  division  is  subject  to  great  variety.  In  two-thirds  ot  a  large  number  ot  cases 
it  was  between  the  last  lumbar  vertebra  and  the  upper  border  of  the  sacrum  being  above  that 


560  THE   BLOOD-VASCULAR    SYSTEM. 

point  in  one  case  out  of  eight ;  and  below  it  in  one  case  out  of  six.     The  left  common  iliac 
artery  divides  lower  down  more  frequently  than  the  right. 

The  relative  length,  also,  of  the  two  common  iliac  arteries  varies.  The  right  common  iliac 
was  the  longer  in  sixty-three  cases,  the  left  in  fifty-two,  whilst  they  were  both  equal  in  fifty- 
three.  The  length  of  the  arteries  varied  in  five-sevenths  of  the  cases  examined  from  an  inch 
and  a  half  to  three  inches  ;  in  about  half  of  the  remaining  cases  the  artery  was  longer  and  in 
the  other  half  shorter,  the  minimum  length  being  less  than  half  an  inch,  the  maximum  four 
and  a  half  inches.  In  two  instances  the  right  common  iliac  has  been  found  wanting,  the 
external  and  internal  iliacs  arising  directly  from  the  aorta. 

Surface  Marking.— Draw  a  zone  round  the  body  opposite  the  highest  part  of  the  crest 
of  the  ilium  ;  in  this  line  take  a  point  half  an  inch  to  the  left  of  the  middle  line.  From  this 
draw  two  lines  to  points  midway  between  the  anterior  superior  spines  of  the  ilium  and  the 
symphysis  pubis.  These  two  diverging  lines  will  represent  the  course  of  the  common  and 
external  iliac  arteries.  Draw  a  second  zone  round  the  body  corresponding  to  the  level  of  the 
anterior  superior  spines  of  the  ilium  :  the  portion  of  the  diverging  lines  between  the  two  zones 
will  represent  the  course  of  the  common  iliac  artery;  the  portion  below  the  lower  zone,  that  of 
the  external  iliac  artery. 

Surgical  Anatomy. — The  application  of  a  ligature  to  the  common  iliac  artery  may  be 
required  on  account  of  aneurism  or  haemorrhage  implicating  the  external  or  internal  iliacs. 
Now  that  the  surgeon  no  longer  dreads  opening  the  peritoneal  cavity,  there  can  be  no  question 
that  the  easiest  and  best  method  of  tying  the  artery  is  by  a  transperitoneal  route.  The  abdomen 
is  opened  by  an  incision  in  either  the  semilunar  line  or  the  linea  alba ;  the  intestines  are  drawn 
to  one  side  and  the  peritoneum  covering  the  artery  divided.  The  sheath  is  then  opened,  and 
the  needle  passed  from  within  outward.  On  the  right  side  great  care  must  be  exercised  in 
passing  the  needle,  since  both  the  common  iliac  veins  lie  behind  the  artery.  After  the  vessel 
has  been  tied  the  incision  in  the  peritoneum  over  the  artery  should  be  sutured.  Formerly  there 
were  two  different  methods  by  which  the  common  iliac  artery  was  tied,  without  opening  the 
peritoneal  cavity  :  1,  an  anterior  or  iliac  incision,  by  which  the  vessel  is  approached  more  directly 
from  the  front ;  and  2,  a  posterior  abdominal  or  lumbar  incision,  by  which  the  vessel  is  reached 
from  behind.  If  the  surgeon  select  the  iliac  region,  a  curved  incision,  from  five  to  eight  inches 
in  length  according  to  the  amount  of  fat,  is  made,  commencing  just  outside  the  middle  of 
Poupart's  ligament  and  a  finger's  breadth  above  it,  and  carried  outward  toward  the  anterior 
superior  iliac  spine,  then  upward  toward  the  ribs,  and  finally  curving  inward  toward  the 
umbilicus.  The  abdominal  muscles  and  transversalis  fascia  are  divided,  and  the  peritoneum 
raised  upward  and  inward  until  the  Psoas  is  reached.  The  artery  will  be  found  on  the  inner 
side  of  this  muscle,  and  is  to  be  cleared  with  a  director,  especial  care  being  taken  on  the  right 
side,  as  here  the  common  iliac  veins  lie  behind  the  artery.  The  aneurism  needle  is  to  be  passed 
from  within  outward.  ButMf  the  aneurismal  tumor  should  extend  high  up  in  the  abdomen,  along 
the  external  iliac,  it  is  better  to  select  the  posterior  or  lumbar,  by  making  an  incision  partly  in 
the  abdomen,  partly  in  the  loin.  The  incision  is  commenced  at  the  anterior  extremity  of  the 
last  rib,  proceeding  directly  downward  to  the  ilium ;  it  is  then  curved  forward  along  the  crest  of 
the  ilium  and  a  little  above  it  to  the  anterior  superior  spine  of  that  bone.  The  abdominal  mus- 
cles having  been  cautiously  divided  in  succession,  the  transversalis  fascia  must  be  carefully  cut 
through,  and  the  peritoneum,  together  with  the  ureter,  separated  from  the  artery  and  pushed 
aside  ;  the  sacro-iliac  articulation  must  then  be  felt  for,  and  upon  it  the  vessel  will  be  felt  pulsat- 
ing, and  may  be  fully  exposed  in  close  connection  with  its  accompanying  vein.  On  the  right 
side  both  common  iliac  veins,  as  well  the  inferior  vena  cava,  are  in  close  connection  with  the 
artery,  and  must  be  carefully  avoided.  On  the  left  side  the  vein  usually  lies  on  the  inner  side 
and  behind  the  artery  ;  but  it  occasionally  happens  that  the  two  common  iliac  veins  are  joined  on 
the  left  instead  of  the  right  side,  which  would  add  much  to  the  difficulty  of  an  operation  in  such 
a  case.  The  common  iliac  artery  may  be  so  short  that  danger  may  be  apprehended  from  second- 
ary haemorrhage  if  a  ligature  is  applied  to  it.  It  would  be  preferable,  in  such  a  case,  to  tie  both 
the  external  and  internal  iliacs  near  their  origin. 

Collateral  Circulation. — The  principal  agents  in  carrying  on  the  collateral  circulation  after 
the  application  of  a  ligature  to  the  common  iliac  are — the  anastomoses  of  the  haemorrhoidal 
branches  of  the  internal  iliac  with  the  superior  haemorrhoidal  from  the  inferior  mesenteric ;  the 
anastomoses  of  the  uterine  and  ovarian  arteries  and  of  the  vesical  arteries  of  opposite  sides  ;  of 
the  lateral  sacral  with  the  middle  sacral  artery  ;  of  the  epigastric  with  the  internal  mammary, 
inferior  intercostal  and  lumbar  arteries ;  of  the  circumflex  iliac  with  the  lumbar  arteries  ;  of  the 
ilio-lumbar  with  the  last  lumbar  artery ;  of  the  obturator  artery,  by  means  of  its  pubic  branch, 
with  the  vessel  of  the  opposite  side  and  with  the  deep  epigastric.^  _ 

Compression  of  the  Common  Iliac  Arteries. — The  common  iliac  arteries  are  most  effi- 
ciently compressed  by  Davy's  lever.  The  instrument  consists  of  a  gum-elastic  tube  about  two 
feet  long,  in  which  fits  a  round  wooden  "  lever  "  considerably  longer  than  the  tube.  A  small 
quantity  of  olive  oil  having  been  injected  into  the  rectum,  the  gum-elastic  tube,  softened  in  hot 
water,  is  passed  into  the  bowel  sufficiently  far  to  permit  its  pressing  upon  the  common  iliac  artery 
as  it  lies  in  the  groove  between  the  last  lumbar  vertebra  and  the  Psoas  muscle.  The  wooden 
lever  is  then  inserted  into  the  tube,  and  the  projecting  end  carried  toward  the  opposite  thigh 
and  raised,  when  it  acts  as  a  lever  of  the  first  order,  the  anus  being  the  fulcrum.     In  cases 


THE  INTERNAL    ILIAC  ARTERY. 


561 


where  the  meso-rectum  is  abnormally  short  it  may  be  impossible,  without  unjustifiable  force,  to 
compress  the  artery  on  the  right  side. 

Internal  Iliac  Artery  (Fig.  312). 

The  internal  iliac  artery  supplies  the  walls  and  viscera  of  the  pelvis,  the 
generative  organs,  and  inner  side  of  the  thigh.  It  is  a  short  thick  vessel, 
smaller    in    the    adult  than   the   external   iliac,    and   about   an   inch   and   a   half 


Fig.  312.— Arteries  of  the  pelvis. 

in  length.  It  arises  at  the  point  of  bifurcation  of  the  common  iliac,  and, 
passing  downward  to  the  upper  margin  of  the  great  sacro-sciatic  foramen,  divides 
into  two  large  trunks,  an  anterior  and  posterior ;  from  its  anterior  division 
a  partially  obliterated  cord,  the  hypogastric  artery,  extends  forward  to  the 
bladder. 

Relations. — In  front,  with  the  ureter,  which  separates  it  from  the  peri- 
toneum. Behind,  with  the  internal  iliac  vein,  the  lumbo-sacral  cord,  and 
Pyriformis  muscle.  By  its  outer  side,  near  its  origin,  with  the  Psoas  magnus 
muscle. 


36 


562  1HE  BLOOD-VASCULAR   SYSTEM. 

Plan  of  the  Relations  of  the  Internal  Iliac  Artery. 

In  front. 

Peritoneum. 
Ureter. 

Outer  side. 
Psoas  magnus. 


Behind. 

Internal  iliac  vein. 
Lumbo-sacral  cord. 
Pyriformis  muscle. 

In  the  foetus  the  internal  iliac  artery  (hypogastric)  is  twice  as  large  as  the 
external  iliac,  and  appears  to  be  the  continuation  of  the  common  iliac.  Instead 
of  dipping  into  the  pelvis,  it  passes  forward  to  the  bladder,  and  ascends  along 
the  sides  of  that  viscus  to  its  summit,  to  which  it  gives  branches ;  it  then  passes 
upward  along  the  back  part  of  the  anterior  wall  of  the  abdomen  to  the  umbilicus, 
converging  toward  its  fellow  of  the  opposite  side.  Having  passed  through  the 
umbilical  opening,  the  two  arteries  twine  round  the  umbilical  vein,  forming  with 
it  the  umbilical  cord,  and  ultimately  ramify  in  the  placenta.  The  portion  of  the 
vessel  within  the  abdomen  is  called  the  hypogastric  artery,  and  that  external  to 
that  cavity,  the  umbilical  artery. 

At  birth,  when  the  placental  circulation  ceases,  the  upper  portion  of  the 
hypogastric  artery,  extending  from  the  summit  of  the  bladder  to  the  umbilicus, 
contracts,  and  ultimately  dwindles  to  a  solid  fibrous  cord ;  but  the  lower  portion, 
extending  from  its  origin  (in  what  is  now  the  internal  iliac  artery)  for  about  an 
inch  and  a  half  to  the  wall  of  the  bladder,  and  thence  to  the  summit  of  that  organ, 
is  not  totally  impervious,  though  it  becomes  considerably  reduced  in  size,  and 
serves  to  convey  blood  to  the  bladder  under  the  name  of  the  superior  vesical 
artery. 

Peculiarities  as  regards  Length. — In  two-thirds  of  a  large  number  of  cases  the  length  of 
the  internal  iliac  varied  between  an  inch  and  an  inch  and  a  half;  in  the  remaining  third  it 
was  more  frequently  longer  than  shorter,  the  maximum  length  being  three  inches,  the  minimum 
half  an  inch. 

The  lengths  of  the  common  and  internal  iliac  arteries  bear  an  inverse  proportion  to 
each  other,  the  internal  iliac  artery  being  long  when  the  common  iliac  is  short,  and  vice 
versa. 

As  regards  its  Place  of  Division. — The  place  of  division  of  the  internal  iliac  varies 
between  the  upper  margin  of  the  sacrum  and  the  upper  border  of  the  sacro-sciatic  for- 
amen. 

The  arteries  of  the  two  sides  in  a  series  of  cases  often  differed  in  length,  but  neither  seemed 
constantly  to  exceed  the  other. 

Surgical  Anatomy. — The  application  of  a  ligature  to  the  internal  iliac  artery  may  be 
required  in  cases  of  aneurism  or  hgemorrhage  affecting  one  of  its  branches.  The  vessel  may  be 
secured  by  making  an  incision  through  the  abdominal  parietes  in  the  iliac  region  in  a  direction 
and  to  an  extent  similar  to  that  for  securing  the  common  iliac  ;  the  transversalis  fascia  having 
been  cautiously  divided,  and  the  peritoneum  pushed  inward  from  the  iliac  fossa  toward  the 
pelvis,  the  finger  may  feel  the  pulsation  of  the  external  iliac  at  the  bottom  of  the  wound,  and  by 
tracing  this  vessel  upward  the  internal  iliac  is  arrived  at,  opposite  the  sacro-iliac  articulation.  It 
should  be  remembered  that  the  vein  lies  behind  and  on  the  right  side,  a  little  external  to 
the  artery,  and  in  close  contact  with  it ;  the  ureter  and  peritoneum,  which  lie  in  front,  aiust  also 
be  avoided.  The  degree  of  facility  in  applying  a  ligature  to  this  vessel  will  mainly  defend  upon 
its  length.  It  has  been  seen  that  in  the  great  majority  of  the  cases  examined  the  irtery  was 
short,  varying  from  an  inch  to  an  inch  and  a  half;  in  these  cases  the  artery  is  deepl  seated  in 
the  pelvis;  when,  on  the  contrary,  the  vessel  is  longer,  it  is  found  partly  above  that  cavity.  If 
the  artery  is  very  short,  as  occasionally  happens,  it  would  be  preferable  to  apply  a  lirature  to  the 
common  iliac  or  upon  the  external  and  internal  iliacs  at  their  origin. 

Probably  a  better  method  of  tying  the  internal  iliac  artery  is  by  an  abdomina1  section  in  the 
median  line  and  reaching  the  vessel  through  the  peritoneal  cavity.  This  nan  has  been 
advocated  by  Dennis  of  New  York  on  the  following  grounds  :  (1)  It  no  way  incr  ases  the  danger 
of  the  operation  ;  (2)  it  prevents  a  series  of  accidents  which  have  occurred  durng  ligature  of  the 
artery  by  the  older  methods ;  (3)  it  enables  the  surgeon  to  ascertain  the  exactextent  of  disease 


THE   INTERNAL    ILIAC  ARTERY.  563 

in  the  main  arterial  trunk,  and  select  his  spot  for  the  application  of  the  ligature ;  and  (4)  it 
occupies  much  less  time._ 

Collateral  Circulation. — In  Professor  Owen's  dissection  of  a  case  in  which  the  internal 
iliac  artery  had  been  tied  by  Stevens  ten  years  before  death  for  aneurism  of  the  sciatic  artery, 
the  internal  iliac  was  found  impervious  for  about  an  inch  above  the  point  where  the  ligature  had 
been  applied,  but  the  obliteration  did  not  extend  to  the  origin  of  the  external  iliac,  as  the  ilio- 
lumbar artery  arose  just  above  this  point.  Below  the  point  of  obliteration  the  artery  resumed 
its  natural  diameter,  and  continued  so  for  half  an  inch,  the  obturator,  lateral  sacral,  and  gluteal 
arising  in  succession  from  the  latter  portion.  The  obturator  artery  was  entirely  obliterated. 
The  lateral  sacral  artery  was  as  large  as  a  crow's  quill,  and  had  a  very  free  anastomosis  with  the 
artery  of  the  opposite  side  and  with  the  middle  sacral  artery.  The  sciatic  artery  was  entirely 
obliterated  as  far  as  its  point  of  connection  with  the  aneurismal  tumor,  but  on  the  distal  side  of 
the  sac  it  was  continued  down  along  the  back  of  the  thigh  nearly  as  large  in  size  as  the  femoral, 
being  pervious  about  an  inch  below  the  sac  by  receiving  an  anastomosing  vessel  from  the  pro- 
funda.1 The  circulation  was  carried  on  by  the  anastomoses  of  the  uterine  and  ovarian  arteries; 
of  the  opposite  vesical  arteries ;  of  the  haemorrhoidal  branches  of  the  internal  iliac  with 
those  from  the  inferior  mesenteric ;  of  the  obturator  artery,  by  means  of  its  pubic  branch, 
with  the  vessel  of  the  opposite  side  and  with  the  epigastric  and  internal  circumflex ;  of  the 
circumflex  and  perforating  branches  of  the  profunda  femoris  with  the  sciatic ;  of  the  gluteal 
with  the  posterior  branches  of  the  sacral  arteries;  of  the  ilio-lumbar  with  the  last  lumbar;  of 
the  lateral  sacral  with  the  middle  sacral ;  and  of  the  circumflex  iliac  with  the  ilio-lumbar  and 
gluteal. 

Branches  of  the  Internal  Iliac. 

From  the  Anterior  Trunk.  From  the  Posterior  Trunk. 

Superior  Vesical.  Ilio-lumbar. 

Middle  Vesical.  Lateral  Sacral. 

Inferior  Vesical.  Gluteal. 

Middle  Hemorrhoidal. 

Obturator. 

Internal  Pudic. 

Sciatic. 

T    n       7    f  Uterine. 

In  female  <  ir     .     , 

J  \  Vaginal. 

The  superior  vesical  is  that  part  of  the  foetal  hypogastric  artery  which  remains 
pervious  after  birth.  It  extends  to  the  side  of  the  bladder,  distributing  numerous 
branches  to  the  apex  and  body  of  the  organ.  From  one  of  these  a  slender  vessel 
is  derived  which  accompanies  the  vas  deferens  in  its  course  to  the  testis,  where  it 
anastomoses  with  the  spermatic  artery.  This  is  the  artery  of  the  vas  deferens. 
Other  branches  supply  the  ureter. 

The  middle  vesical,  usually  a  branch  of  the  superior,  is  distributed  to  the  base 
of  the  bladder  and  under  surface  of  the  vesiculas  seminales. 

The  inferior  vesical  arises  from  the  anterior  division  of  the  internal  iliac, 
frequently  in  common  with  the  middle  haemorrhoidal,  and  is  distributed  to  the 
base  of  the  bladder,  the  prostate  gland,  and  vesiculge  seminales.  The  branches 
distributed  to  the  prostate  communicate  with  the  corresponding  vessel  of  the 
opposite  side. 

The  middle  haemorrhoidal  artery  usually  arises  together  with  the  preceding 
vessel.  It  supplies  the  anus  and  parts  outside  the  rectum,  anastomosing  wTith  the 
other  hemorrhoidal  arteries. 

The  uterine  artery  (Fig.  313)  passes  inward  from  the  anterior  trunk  of  the 
internal  iliac  to  the  neck  of  the  uterus.  Ascending  in  a  tortuous  course  on  the 
side  of  this  viscus,  between  the  layers  of  the  broad  ligament,  it  distributes  branches 
to  its  substance,  anastomosing,  near  its  termination,  with  a  branch  from  the  ovarian 
artery.  It  gives  off  branches  to  the  cervix  uteri  {cervical),  and  branches  which 
descend  on  the  vagina,  and,  joining  with  branches  from  the  vaginal  arteries,  form 
a  median  longitudinal  vessel  both  in  front  and  behind ;  these  descend  on  the  ante- 
rior and  posterior  surfaces  of  the  vagina,  and  are  named  the  azygos  arteries  of  the 
va^na. 

1  Medico-Chirurgical  Trans.,  vol.  xvi. 


564 


THE   BLOOD-VASCULAR   SYSTEM. 


The  vaginal  artery  is  analogous  to  the  inferior  vesical  in  the  male ;  it  descends 
upon  the  vagina,  supplying  its  mucous  membrane,  and  sending  branches  to  the 
neck  of  the  bladder  and  contiguous  part  of  the  rectum.  It  assists  in  forming  the 
azygos  arteries  of  the  vagina. 


Branches  to  tube. 


Branches  to  fundus. 
V 


Vaginal  arteries. 
Fig.  313. — The  arteries  of  the  internal  organs  of  generation  of  the  female,  seen  from  behind.    (After  Hyrtl.) 

The  Obturator  Artery  usually  arises  from  the  anterior  trunk  of  the  internal 
iliac ;  frequently  from  the  posterior.  It  passes  forward,  below  the  brim  of  the 
pelvis,  to  the  upper  part  of  the  obturator  foramen,  and,  escaping  from  the  pelvic 
cavity  through  a  short  canal  formed  by  a  groove  on  the  under  surface  of  the 
ascendino-  ramus  of  the  os  pubis  and  the  arched  border  of  the  obturator  membrane, 
it  divides  into  an  internal  and  external  branch.  In  the  pelvic  cavity  this  vessel 
lies  upon  the  pelvic  fascia,  beneath  the  peritoneum,  and  a  little  below  the  obtu- 
rator nerve. 

Branches. —  Within  the  pelvis,  the  obturator  artery  gives  off  an  iliac  branch  to 
the  iliac  fossa,  which  supplies  the  bone  and  the  Iliacus  muscle,  and  anastomoses 
with  the  ilio-lumbar  artery ;  a  vesical  branch,  which  runs  backward  to  supply  the 
bladder ;  and  a  pubic  branch,  which  is  given  off  from  the  vessel  just  before  it 
leaves  the  pelvic  cavity.  This  branch  ascends  upon  the  back  of  the  os  pubis, 
communicating  with  offsets  from  the  deep  epigastric  artery  and  with  the  corre- 
sponding vessel  of  the  opposite  side.  It  is  placed  on  the  inner  side  of  the  femoral 
ring.  External  to  the  pelvis,  the  obturator  artery  divides  into  an  internal  and  an 
external  branch,  which  are  deeply  situated  beneath  the  Obturator  externus  muscle. 

The  internal  branch  curves  downward  along  the  inner  margin  of  the  obturator 
foramen,  lying  beneath  the  Obturator  externus  muscle ;  it  distributes  branches  to 
the  Obturator  externus,  Pectineus,  Adductors,  and  Gracilis,  and  anastomoses  with 
the  external  branch  and  with  the  internal  circumflex  artery. 

The  external  branch  curves  round  the  outer  margin  of  the  foramen,  also  lying 
beneath  the  Obturator  externus  muscle,  to  the  space  between  the  Gemellus  inferior 
and  Quadratus  femoris,  where  it  divides  into  two  branches  :  one,  the  smaller,  courses 
inward  around  the  lower  margin  of  the  foramen  and  anastomoses  with  the  internal 
branch  and  with  the  internal  circumflex  ;  the  other  inclines  outward  in  the  groove 


BRANCHES    OF   THE  INTERNAL   ILIAC.  565 

below  the  acetabulum,  and  supplies  the  muscles  attached  to  the  tuberosity  of  the 
ischium  and  anastomoses  with  the  sciatic  artery.  It  sends  a  branch  to  the  hip- 
joint  through  the  cotyloid  notch,  which  ramifies  on  the  round  ligament  as  far  as 
the  head  of  the  femur. 

Peculiarities. — In  two  out  of  every  three  cases  the  obturator  arises  from  the  internal  iliac  ; 
in  one  case  in  three  and  a  half  from  the  epigastric ;  and  in  about  one  in  seventy-two  cases  by 
two  roots  from  both  vessels.  It  arises  in  about  the  same  proportion  from  the  external  iliac 
artery.  The  origin  of  the  obturator  from  the  epigastric  is  not  commonly  found  on  both  sides 
of  the  same  body. 

When  the  obturator  artery  arises  at  the  front  of  the  pelvis  from  the  epigastric,  it  descends 
almost  vertically  to  the  upper  part  of  the  obturator  foramen.  The  artery  in  this  course  usually 
lies  in  contact  with  the  external  iliac  vein  and  on  the  outer  side  of  the  femoral  ring  (Fig.  314,  a)  ; 
in  such  cases  it  would  not  be  endangered  in  the  operation  for  femoral  hernia.  Occasionally, 
however,  it  curves  inward  along  the  free  margin  of  Grimbernat's  ligament  (Fig.  314,  b),  and 


Fig.  314.— Variations  in  origin  and  course  of  obturator  artery. 

under  such  circumstances  would  almost  completely  encircle  the  neck  of  a  hernial  sac  (supposing 
a  hernia  to  exist  in  such  a  case),  and  would  be  in  great  danger  of  being  wounded  if  an  operation 
was  performed. 

The  internal  pudic  is  the  smaller  of  the  two  terminal  branches  of  the  anterior 
trunk  of  the  internal  iliac,  and  supplies  the  external  organs  of  generation. 
Though  the  course  of  the  artery  is  the  same  in  the  two  sexes,  the  vessel  is  much 
smaller  in  the  female  than  in  the  male,  and  the .  distribution  of  its  branches 
somewhat  different.  The  description  of  its  arrangement  in  the  male  will  first  be 
given,  and  subsequently  the  differences  which  it  presents  in  the  female  will  be 
mentioned. 

The  Internal  Pudic  Artery  in  the  Male  passes  downward  and  outward  to  the 
lower  border  of  the  great  sacro-sciatic  foramen,  and  emerges  from  the  pelvis 
between  the  Pyriformis  and  Coccygeus  muscles  :  it  then  crosses  the  spine  of  the 
ischium  and  re-enters  the  pelvis  through  the  lesser  sacro-sciatic  foramen.  The 
artery  now  crosses  the  Obturator  interims  muscle  along  the  outer  wall  of  the  ischio- 
rectal fossa,  being  situated  about  an  incfc  and  a  half  above  the  lower  margin  of  the 
ischial  tuberosity.  It  is  here  contained  in  a  sheath  of  the  obturator  fascia,  and 
gradually  approaches  the  margin  of  the  ramus  of  the  ischium,  along  which  it  passes 
forward  and  upward,  pierces  the  base  of  the  superficial5"  layer  of  the  triangular 
ligament  of  the  urethra,  and  runs  forward  along  the  inner  margin  of  the  ramus  of 
the  os  pubis,  and  divides  into  its  two  terminal  branches,  the  dorsal  artery  of  the 
penis  and  the  artery  of  the  corpus  cavernosum. 

Relations. — In  the  first  part  of  its  course,  within  the  pelvis,  it  lies  in  front  of 
the  Pyriformis  muscle  and  sacral  plexus  of  nerves,  and  the  sciatic  artery,  and 
on  the  outer  side  of  the  rectum  (on  the  left  side).  As  it  crosses  the  spine  of 
the  ischium  it  is  covered  by  the  Gluteus  maximus  and  overlapped  by  the  great 
sacro-sciatic  ligament.  Here  the  obturator  nerve  lies  to  the  inner  side  and  the 
nerve  to  the  Obturator  internus  to  the  outer  side  of  the  vessel.  In  the  pelvis  it 
lies  on  the  outer  side  of  the  ischio-rectal  fossa,  upon  the  surface  of  the  Obturator 
internus  muscle,  contained  in  a  fibrous  canal  (canal  of  Alcock)  formed  by  the 
splitting  of  the  obturator  fascia.  It  is  accompanied  by  the  pudic  veins  and  the 
pudic  nerve. 


566 


THE   BLOOD-  VASCULAR    SYSTEM. 


Deep 

circumflex 
iliac 


Ileo-lumbar 


Peculiarities. — The  internal  pudie  is  sometimes  smaller  than  usual,  or  fails  to  give  off  one 
or  two  of  its  usual  branches ;  in  such  cases  the  deficiency  is  supplied  by  branches  derived  from  j 
an  additional  vessel,  the  accessory  pudic,  which  generally  arises  from  the  internal  pudic  artery 

before  its  exit  from  the  great  ( 
sacro-sciatic  foramen.  It 
passes  forward  along  the  J 
lower  part  of  the  bladder  { 
and  across  the  side  of  the 
prostate  gland  to  the  root 
of  the  penis,  where  it  per- 
forates the  triangular  liga- 
ment and  gives  off  the 
branches  usually  derived 
from  the  pudic  artery.  The 
deficiency  most  frequently 
met  with  is  that  in  which 
the  internal  pudic  ends  as 
the  artery  of  the  bulb,  the 
artery  of  the  corpus  cav- 
ernosum  and  arteria  dorsalis 
penis  being  derived  from 
the  accessory  pudic.  Or  the 
pudic  may  terminate  as  the 
superficial  perineal,  the  ar- 1 
tery  of  the  bulb  being  de- 
rived, with  the  other  two 
branches,  from  the  acces- 
sory vessel.  Occasionally 
the  accessory  pudic  artery 
is  derived  from  one  of  the 
other  branches  of  the  in- 
ternal iliac,  most  frequently 
the  inferior  vesical  or  the 
obturator. 

Surgical  Anatomy  — 
The  relation  of  the  acces- 
sory pudic  to  the  prostate 
gland  and  urethra  is  of  the 
greatest  interest  in  a  surgi- 
cal point  of  view,  as  this 
vessel  is  in  danger  of  being 
wounded  in  the  lateral 
operation  of  lithotomy.  The 
student  should  also  study 
the  position  of  the  inter- 
nal pudic  artery  and  its 
branches,  when  running  a 
normal  course  with  regard 
to  the  same  operation.  The 
superficial  and  the  trans- 
verse perineal  arteries  are, 
of  necessity,  divided  in  this 
operation,  but  the  hemorrhage  from  these  vessels  is  seldom  excessive;  should  a  ligature  be 
required,  it  can  readily  be  applied  on  account  of  their  superficial  position.  The  artery  of  the 
bulb  may  be  divided  if  the  incision  be  carried  too  far  forward,  and  injury  of  this  vessel  may  be 
attended  with  serious  or  even  fatal  consequences.  The  main  trunk  of  the  internal  pudic  artery 
may  be  wounded  if  the  incision  be  carried  too  far  outward  ;  but,  being  bound  down  by  the  strong 
obturator  fascia  and  under  cover  of  the  ramus  of  the  ischium,  the  accident  is  not  very  likely  to 
occur  unless  the  vessel  runs  an  anomalous  course. 

Branches. — The  branches  of  the  internal  pudic  artery  are — 

Muscular.  Transverse  Perineal. 

Inferior  Hemorrhoidal.  Artery  of  the  Bulb. 

Superficial  Perineal.  Artery  of  the  Corpus  Cavernosuon- 

Dorsal  Artery  of  the  Penis. 

The  muscular  branches  consist  of  two  sets — one  given  off  in  the  pelvis,  tbe 
other  as  the  vessel  crosses  the  ischial  spine.  The  former  are  several  small  offsets 
which  supply  the  Levator  ani,  the  Obturator  internus,  the  Pyriformis,  and  tbe 


epigastric 


Obturat 


Int.  pudic 


Inf.  hemorrhoidal 


Dorsal  artery 
Artery  of  corp.  cav 


Perineal 
Fig.  315.— The  internal  pudic  artery  and  its  branches  in  the  male.  (Gegenbaur.) 


BRANCHES    OF    THE   INTERNAL    ILIAC. 


.69 


Coccygeus  muscles.     The  branches  given  off  outside  the  pelvis  are  distribute  t0 
the  adjacent  part  of  the  Gluteus  maximus  and  External  rotator  muscles.     T 
anastomose  with  branches  of  the  sciatic  artery.  aj 

The  inferior  hemorrhoidal  are  two  or  three  small  arteries  which  arise  from  the  in 
ternal  pudic  as  it  passes  above  the  tuberosity  of  the  ischium.      Crossing  the  ischio- 
rectal fossa,  they  are  distributed  to  the  muscles  and  integument  of  the  anal  region. 

The  superficial  perineal  artery  supplies  the  scrotum  and  muscles  and  integu- 
ment of  the  perinseum.  It  arises  from  the  internal  pudic  in  front  of  the  preceding 
branches,  and  turns  upward,  crossing  either  over  or  under  the  Transversus  perinsei 
muscle,  and  runs  forward,  parallel  to  the  pubic  arch,  in  the  interspace  between  the 
Accelerator  urinse  and  Erector  penis  muscles,  both  of  which  it  supplies,  and  is 
finally  distributed  to  the  skin  and  dartos  of  the  scrotum.  In  its  passage  through 
the  perinseum  it  lies  beneath  the  superficial  perineal  fascia. 

The  transverse  perineal  is  a  small  branch  which  arises  either  from  the  internal 
pudic  or  from  the  superficial  perineal  artery  as  it  crosses  the  Transversus  perinsei 
muscle.  It  runs  transversely  inward  along  the  cutaneous  surface  of  the  Trans- 
versus perinsei  muscle,  Avhich  it  supplies,  as  well  as  the  structures  between  the  anus 
and  bulb  of  the  urethra,  and  anastomoses  with  the  one  of  the  opposite  side. 

The  artery  of  the  bulb  is  a  large  but  very  short  vessel  which  arises  from  the 
internal  pudic  between  the  two  layers  of  the  triangular  ligament,  and,  passing 
nearly  transversely  inward,  between  the  fibres  of  the  Compressor  urethras  muscle, 
it  pierces  the  bulb  of  the  urethra,  in  which  it  ramifies.  It  gives  off  a  small  branch 
which  descends  to  supply  Cowper's  gland. 

Surgical  Anatomy. — This  artery  is  of  considerable  importance  in  a  surgical  point  of  view, 
as  it  is  in  danger  of  being  wounded  in  the  lateral  operation  of  lithotomy — an  accident  usually 
attended  in  the  adult  with  alarming  hemorrhage.  The  vessel  is  sometimes  very  small,  occasion- 
ally wanting,  or  even  double.  It  sometimes  arises  from  the  internal  pudic  earlier  than  usual, 
and  crosses  the  perinseum  to  reach  the  back  part  of  the  bulb.  In  such  a  case  the  vessel  could 
hardly  fail  to  be  wounded  in  the  performance  of  the  lateral  operation  of  lithotomy.  If,  on  the 
contrary,  it  should  arise  from  an  accessory  pudic,  it  lies  more  forward  than  usual  and  is  out  of 
danger  in  the  operation. 

The  artery  of  the  corpus  cavernosum,  one  of  the  terminal  branches  of  the 
internal  pudic,  arises  from  that  vessel  while  it  is  situated  between  the  two  layers 
of  the  triangular  ligament ;  it  pierces  the  superficial  layer,  and,  entering  the  crus 
penis  obliquely,  it  runs  forward  in  the  centre  of  the  corpus  cavernosum,  to  which 
its  branches  are  distributed. 

The  dorsal  artery  of  the  penis  ascends  between  the  crus  and  pubic  symphysis, 
and,  piercing  the  triangular  ligament,  passes  between  the  two  layers  of  the  sus- 
pensory ligament  of  the  penis,  and  runs  forward  on  the  dorsum  of  the  penis  to  the 
glans,  where  it  divides  into  two  branches,  which  supply  the  glans  and  prepuce. 
On  the  dorsum  of  the  penis  it  lies  immediately  beneath  the  integument,  parallel 
with  the  dorsal  vein  and  the  corresponding  artery  of  the  opposite  side.  It  supplies 
the  integument  and  fibrous  sheath  of  the  corpus  cavernosum,  sending  branches 
through  the  sheath  to  anastomose  with   the  preceding  vessel. 

The  Internal  Pudic  Artery  in  the  Female  is  smaller  than  in  the  male.  Its  origin 
and  course  are  similar,  and  there  is  considerable  analogy  in  the  distribution  of  its 
branches.  The  superficial  perineal  artery  supplies  the  labia  pudendi ;  the  artery 
of  the  bulb  supplies  the  bulbi  vestibuli  and  the  erectile  tissue  of  the  vagina ;  the 
artery  of  the  corpus  cavernosum  supplies  the  cavernous  body  of  the  clitoris ;  and 
the  arteria  dorsalis  clitoridis  supplies  the  dorsum  of  that  organ,  and  terminates 
in  the  glans  and  in  the  membranous  fold  corresponding  to  the  prepuce  of  the 
male. 

The  Sciatic  Artery  (Fig.  316),  the  larger  of  the  two  terminal  branches  of  the 
anterior  trunk  of  the  internal  iliac,  is  distributed  to  the  muscles  at  the  back  of  the 
pelvis.  It  passes  down  to  the  lower  part  of  the  great  sacro-sciatic  foramen  behind 
the  internal  pudic  artery,  resting  on  the  sacral  plexus  of  nerves  and  Pyriformis 


56( 


THE   BLOOD-VASCULAR    SYSTEM. 


or 
an 


Termination 
of  internal 
circumflex. 


;cle,  and  escapes  from  the  pelvis  through  this  foramen  between  the  Pyriformis 
Coccygeus.     It  then  descends  in  the  interval  between  the  trochanter  major  and 

tuberosity  of  the  ischium,  ac- 
companied by  the  sciatic  nerves, 
and  covered  by  the  Gluteus 
maximus,  and  is  continued  down 
the  back  of  the  thigh  supplying 
the  skin,  and  anastomosing  with 
branches  of  the  perforating  arte- 
ries. 

Within  the  pelvis  it  distrib- 
utes branches  to  the  Pyriformis, 
Coccygeus,    and    Levator    ani 
muscles ;     some    hemorrhoidal 
branches,     which     supply     the 
rectum,   and    occasionally  take 
the  place  of  the  middle  hemor- 
rhoidal    artery;     and     vesical 
branches  to  the  base  and  neck 
of  the  bladder,  vesicule  semi- 
nales,  and  prostate  gland.     Ex- 
ternal to  the  pelvis  it  gives  off 
the  following  branches : 
Coccygeal. 
Inferior  Gluteal. 
Comes  Nervi  Ischiadici. 
Muscular. 
Anastomotic. 
Articular. 

The  coccygeal  branch  runs 
inward,  pierces  the  great  sacro- 
sciatic  ligament,  and  supplies 
the  Gluteus  maximus,  the  in- 
tegument, and  other  structures 
on  the  back  of  the  coccyx. 

The  inferior  gluteal  branches, 
three  or  four  in  number,  supply 
the  Gluteus  maximus  muscle, 
anastomosing  with  the  gluteal 
artery  in  the  substance  of  the 
muscle. 

The  comes  nervi  ischiadici 
is  a  long,  slender  vessel  which 
accompanies  the  great  sciatic 
nerve  for  a  short  distance ;  it 
then  penetrates  it  and  runs  in 
its  substance  to  the  lower  part 
of  the  thigh. 

The  muscular  branches  supply  the  Gluteus  maximus,  anastomosing  with  the 
gluteal  artery  in  the  substance  of  the  muscle :  the  external  rotators,  anastomosing 
with  the  internal  pudic  artery ;  and  the  muscles  attached  to  the  tuberosity  of  the 
ischium,  anastomosing  with  the  external  branch  of  the  obturator  and  the  internal 
circumflex  arteries. 

The  anastomotic  artery  is  directed  downward  across  the  external  rotators,  and 
assists  in  forming  the  so-called  crucial  anastomosis  by  anastomosing  with  the 
superior  perforating  and  the  internal  and  external  circumflex. 


Superior  internal 
articular. 


ior  muscular. 


Fig.  316. — The  arteries    of  the   gluteal  and  posterior  femoral 
regions. 


BRANCHES    OF    THE   INTERNAL    ILIAC.  569 

The  articular  branch,  generally  derived  from  the  anastomotic,  is  distributed  to 
the  capsule  of  the  hip-joint. 

The  Ilio-lumbar  Artery,  given  off  from  the  posterior  trunk  of  the  internal 
iliac,  turns  upward  and  outward  between  the  obturator  nerve  and  lumbo-sacral 
cord,  to  the  inner  margin  of  the  Psoas  muscle,  behind  which  it  divides  into  a  lum- 
bar and  an  iliac  branch. 

The  lumbar  branch  supplies  the  Psoas  and  Quadratus  lumborum  muscles, 
anastomosing  with  the  last  lumbar  artery,  and  sends  a  small  spinal  branch  through 
the  intervertebral  foramen,  between  the  last  lumbar  vertebra  and  the  sacrum,  into 
the  spinal  canal,  to  supply  the  cauda  equina. 

The  iliac  branch  descends  to  supply  the  Iliacus  muscle ;  some  offsets,  running 
between  the  muscle  and  the  bone,  anastomose  with  the  iliac  branch  of  the 
obturator ;  one  of  these  enters  an  oblique  canal  to  supply  the  cliploe,  whilst  others 
run  along  the  crest  of  the  ilium,  distributing  branches  to  the  Gluteal  and  Abdom- 
inal muscles,  and  anastomose  in  their  course  with  the  gluteal,  circumflex  iliac, 
and  external  circumflex  arteries. 

The  Lateral  Sacral  Arteries  (Fig.  312)  are  usually  two  in  number  on  each  side, 
superior  and  inferior. 

The  superior,  which  is  of  large  size,  passes  inward,  and,  after  anastomosing 
with  branches  from  the  middle  sacral,  enters  the  first  or  second  anterior  sacral 
foramen,  is  distributed  to  the  contents  of  the  sacral  canal,  and,  escaping  by  the 
corresponding  posterior  sacral  foramen,  supplies  the  skin  and  muscles  on  the 
dorsum  of  the  sacrum,  anastomosing  with  the  gluteal. 

The  inferior  passes  obliquely  across  the  front  of  the  Pyriformis  muscle  and 
sacral  nerves  to  the  inner  side  of  the  anterior  sacral  foramina,  descends  on  the 
front  of  the  sacrum,  and  anastomoses  over  the  coccyx  with  the  sacra  media  and 
opposite  lateral  sacral  arteries.  In  its  course  it  gives  off  branches  which  enter 
the  anterior  sacral  foramina  ;  these,  after  supplying  the  contents  of  the  sacral  canal, 
escape  by  the  posterior  sacral  foramina,  and  are  distributed  to  the  muscles  and  skin 
on  the  dorsal  surface  of  the  sacrum,  anastomosing  with  the  gluteal. 

The  Gluteal  Artery  is  the  largest  branch  of  the  internal  iliac,  and  appears  to 
be  the  continuation  of  the  posterior  division  of  that  vessel.  It  is  a  short,  thick 
trunk,  which  passes  out  of  the  pelvis  above  the  upper  border  of  the  Pyriformis 
muscle,  and  immediately  divides  into  a  superficial  and  deep  branch.  Within  the 
pelvis  it  gives  off  a  few  muscular  branches  to  the  Iliacus,  Pyriformis,  and  Obtu- 
rator internus,  and,  just  previous  to  quitting  that  cavity,  a  nutrient  artery,  which 
enters  the  ilium. 

The  superficial  branch  passes  beneath  the  Gluteus  maximus  and  divides  into 
numerous  branches,  some  of  which  supply  that  muscle,  whilst  o'thevs  perforate  its 
tendinous  origin,  and  supply  the  integument  covering  the  posterior  surface  of  the 
sacrum,  anastomosing  with  the  posterior  branches  of  the  sacral  arteries. 

The  deep  branch  runs  between  the  Gluteus  medius  and  minimus,  and  sub- 
divides into  two.  Of  these,  the  superior  division,  continuing  the  original  course 
of  the  vessel,  passes  along  the  upper  border  of  the  Gluteus  minimus  to  the 
anterior  superior  spine  of  the  ilium,  anastomosing  with  the  circumflex  iliac  and 
ascending  branches  of  the  external  circumflex  artery.  The  inferior  division 
crosses  the  Gluteus  minimus  obliquely  to  the  trochanter  major,  distributing 
branches  to  the  Glutei  muscles7  and  inosculates  with  the  external  circumflex 
artery.     Some  branches  pierce  the  Gluteus  minimus  to  supply  the  hip-joint. 

Surface  Mark;"  ~  T\  position  of  the  three  main  branches  of  the  internal  iliac,  the 
sciatic,  internal  puc  teal,  which  may  occasionally  be  the  object  of  surgical  interference, 
is  indicated  on  the  :he  following  way :  A  line  is  to  be  drawn  from  the  posterior  supe- 
rior iliac  spine  to  i  or  superior  angie  of  the  great  trochanter,  with  the  limb  slightly 
flexed  and  rotated  i  ie  point  of  emergence  of  the  gluteal  artery  from  the  upper  part  of 
the  sciatic  notch  w  nd  with  the  junction  of  the  upper  with  the  middle  third  of  this 
line.  A  second  lin  i  Irawn  from  the  same  point  to  the  outer  part  of  the  tuberosity  of 
the  ischium  ;  the  ji  of  the  lower  frith  the  middle  third  marks  the  point  of  emergence  of 
the  sciatic  and  pudi  rom  the  great  sciatic  notch. 


570  THE  BLOOD-VASCULAR   SYSTEM. 

Surgical  Anatomy. — Any  of  these  three  vessels  may  require  ligating  for  a  wound  or  for 
aneurism,  which  is  generally  traumatic.  The  gluteal  arteiy  is  ligated  by  turning  the  patient 
two-thirds  over  on  his  face  and  making  an  incision  from  the  posterior  superior  spine  of  the  ilium 
to  the  upper  and  posterior  angle  of  the  great  trochanter.  This  must  expose  the  Gluteus  maxi- 
mus  muscle,  and  its  fibres  are  to  be  separated  through  the  whole  thickness  of  the  muscle  and 
pulled  apart  with  retractors.  The  contiguous  margins  of  the  Gluteus  medius  and  Pyriformis 
are  now  to  be  separated  from  each  other,  and  the  artery  will  be  exposed  emerging  from  the 
sciatic  notch.  In  ligation  of  the  sciatic  artery,  the  incision  should  be  made  parallel  with  that 
for  ligation  of  the  gluteal,  but  one  inch  and  a  half  lower  down.  After  the  fibres  of  the  Gluteus 
maximus  have  been  separated,  the  vessel  is  to  be  sought  for  at  the  lower  border  of  the  Pyri- 
formis ;  the  great  sciatic  nerve,  which  lies  just  above  it,  forming  the  chief  guide  to  the  artery. 

The  External  Iliac  Artery  (Fig.  312). 

The  external  iliac  artery  is  larger  in  the  adult  than  the  internal  iliac,  and 
passes  obliquely  downward  and  outward  along  the  inner  border  of  the  Psoas 
muscle,  from  the  bifurcation  of  the  common  iliac  to  Poupart's  ligament,  where  it 
enters  the  thigh  and  becomes  the  femoral  artery. 

Relations. — In  front,  with  the  peritoneum,  subperitoneal  areolar  tissue,  the  ter- 
mination of  the  ileum  on  the  right  side,  and  the  sigmoid  flexure  on  the  left,  and  a  thin 
layer  of  fascia  derived  from  the  iliac  fascia,  which  surrounds  the  artery  and  vein. 
At  its  origin  it  is  occasionally  crossed  by  the  ureter.  The  spermatic  vessels  descend 
for  some  distance  upon  it  near  its  termination,  and  it  is  crossed  in  this  situation  by 
the  genital  branch  of  the  genito-crural  nerve  and  the  deep  circumflex  iliac  vein ; 
the  vas  deferens  curves  down  along  its  inner  side.  Behind,  it  is  in  relation  with 
the  external  iliac  vein,  which,  at  Poupart's  ligament,  lies  at  its  inner  side ;  on  the 
left  side  the  vein  is  altogether  internal  to  the  artery.  Externally,  it  rests  against 
the  Psoas  muscle,  from  which  it  is  separated  by  the  iliac  fascia.  The  artery  rests 
upon  this  muscle,  near  Poupart's  ligament.  Numerous  lymphatic  vessels  and 
glands  are  found  lying  on  the  front  and  inner  side  of  the  vessel. 

Plan   of   the   Relations    of   the   External   Iliac   Artery. 

In  front. 
Peritoneum,  intestines,  and  fascia. 
Near  f  kyraphati0  vessels  and  glands. 

Pounart's      J  SPe™iatic  vessels. 
Litranient       I  Gtamto-crural  nerve  (genital  branch). 
g  '       [  Deep  circumflex  iliac  vein. 

Outer  side.  I  \  Inner  side. 

Psoas  magnus.  1       ilia™*      )  External  iliac  vein  and  vas  deferens 

Iliac  fascia.  V  J  near  Poupart's  ligament. 

Behind. 
External  iliac  vein. 
Psoas  magnus. 

Surface  Marking. — The  surface  line  indicating  the  course  of  the  external  iliac  artery  has 
been  already  given  (see  page  560). 

Surgical  Anatomy. — The  application  of  a  ligature  to  the  external  iliac  may  be  required  in 
cases  of  aneurism  of  the  femoral  artery  or  for  a  wound  of  the  artery.  This  vessel  may  be 
secured  in  any  part  of  its  course,  excepting  near  its  upper  end,  which  is  to  be  avoided  on 
account  of  the  proximity  of  the  great  stream  of  blood  in  the  internal  iliac,  and  near  its  lower 
end,  which  should  also  be  avoided,  on  account  of  the  proximity  of  the  deep  epigastric  and  cir- 
cumflex iliac  vessels.  The  patient  having  been  placed  in  the  supine  position,  an  incision  should 
be  made,  commencing  below  at  a  point  about  three-quarters  of  an  inch  above  Poupart's  liga- 
ment, and  a  little  external  to  its  middle,  and  running  upward  and  outward,  parallel  to  Poupart's 
ligament,  to  a  point  one  inch  internal  and  one  inch  above  the  anterior  superior  spine  of  the 
ilium.  When  the  artery  is  deeply  seated,  more  room  will  be  required,  and  may  be  obtained  by 
curving  the  incision  from  the  point  last  named  inward  toward  the  umbilicus  for  a  short  distance. 
Another  mode  of  heating  the  vessel  is  the  plan  advocated  by  Sir  Astley  Cooper,  by  making 
an  incision  close  to  Poupart's  ligament  from  about  hal^  an  inch  outside  of  the  external  abdomi- 
nal ring  to  one  inch  internal  to  the  anterior  superior  spine  of  the  ilium.     This  incision,  being 


THE  EXTERNAL    ILIAC  ARTERY.  571 

made  in  the  course  of  the  fibres  of  the  aponeurosis  of  the  external  oblique,  is  less  likely  to  be 
followed  by  a  ventral  hernia,  but  there  is  danger  of  wounding  the  epigastric  artery,  and  only 
the  lower  end  of  the  vessel  can  be  ligated.  Abernethy,  who  first  tied  this  artery,  made  his 
incision  in  the  course  of  the  vessel.  The  abdominal  muscles  and  transversalis  fascia  having 
been  cautiously  divided,  the  peritoneum  should  be  separated  from  the  iliac  fossa  and  raised 
toward  the  pelvis ;  and  on  introducing  the  finger  to  the  bottom  of  the  wound,  the  artery  may  be 
felt  pulsating  along  the  inner  border  of  the  Psoas  muscle.  The  external  iliac  vein  is  generally 
found  on  the  inner  side  of  the  artery,  and  must  be  cautiously  separated  from  it  by  the  finger- 
nail or  handle  of  the  knife,  and  the  aneurism  needle  should  be  introduced  on  the  inner  side, 
between  the  artery  and  the  vein. 

Ligation  of  the  external  iliac  artery  has  recently  been  performed  by  a  transperitoneal 
method.  An  incision  four  inches  in  length  is  made  in  the  semilunar  line,  commencing  about  an 
inch  below  the  umbilicus  and  carried  through  the  abdominal  wall  into  the  peritoneal  cavity. 
The  intestines  are  then  pushed  upward  and  held  out  of  the  way  by  a  broad  abdominal  retractor, 
and  an  incision  made  through  the  peritoneum  at  the  margin  of  the  pelvis  in  the  course  of  the 
artery,  and  the  vessel  secured  in  any  part  of  its  course  which  may  seem  desirable  to  the  opera- 
tor. The  advantages  of  this  operation  appear  to  be  that  if  it  is  found  necessary,  the  common 
iliac  artery  can  be  ligated  instead  of  the  external  iliac  without  extension  or  modification  of  the 
incision  ;  and  secondly,  that  the  vessel  can  be  ligated  without  in  any  way  interfering  with  the 
coverings  of  the  sac.  Possibly  a  disadvantage  may  exist  in  the  greater  risk  of  hernia  after  this 
method. 

Collateral  Circulation. — The  principal  anastomoses  in  carrying  on  the  collateral  circulation, 
after  the  application  of  a  ligature  to  the  external  iliac,  are — the  ilio-lumbar  with  the  circumflex 
iliac ;  the  gluteal  with  the  external  circumflex  ;  the  obturator  with  the  internal  circumflex  ;  the 
sciatic  with  the  superior  perforating  and  circumflex  branches  of  the  profunda  artery ;  and  the 
internal  pudic  with  the  external  pudic.  When  the  obturator  arises  from  the  epigastric,  it  is 
supplied  with  blood  by  branches,  either  from  the  internal  iliac,  the  lateral  sacral,  or  the  inter- 
nal pudic.  The  epigastric  receives  its  supply  from  the  internal  mammary  and  inferior 
intercostal  arteries,  and  from  the  internal  iliac  by  the  anastomoses  of  its  branches  with  the 
obturator. 

In  the  dissection  of  a  limb  eighteen  years  after  the  successful  ligature  of  the  external  iliac 
artery  by  Sir  A.  Cooper,  which  is  to  be  found  in  Guy's  Hospital  Reports,  vol.  i.  p.  50,  the 
anastomosing  branches  are  described  in  three  sets:  An  anterior  set. — 1,  a  very  large  branch 
from  the  ilio-lumbar  artery  to  the  circumflex  iliac ;  2,  another  branch  from  the  ilio-lumbar, 
joined  by  one  from  the  obturator,  and  breaking  up  into  numerous  tortuous  branches  to  anastomose 
with  the  external  circumflex ;  3,  two  other  branches  from  the  obturator,  which  passed  over  the 
brim  of  the  pelvis,  communicated  with  the  epigastric,  and  then  broke  up  into  a  plexus  to  anas- 
tomose with  the  internal  circumflex.  An  internal  set. — Branches  given  off  from  the  obturator, 
after  quitting  the  pelvis,  which  ramified  among  the  adductor  muscles  on  the  inner  side  of  the 
hip-joint,  and  joined  most  freely  with  branches  of  the  internal  circumflex.  A  posterior  set. — 
1,  three  large  branches  from  the  gluteal  to  the  external  circumflex  ;  2,  several  branches  from  the 
sciatic  around  the  great  sciatic  notch  to  the  internal  and  external  circumflex,  and  the  perforating 
branches  of  the  profunda. 

Branches. — Besides  several  small  branches  to  the  Psoas  muscle  and  the  neigh- 
boring lymphatic  glands,  the  external  iliac  gives  off  two  branches  of  considerable 
size — the 

Deep  Epigastric  and  Deep  Circumflex  Iliac. 

The  Deep  Epigastric  Artery  arises  from  the  external  iliac  a  few  lines  above 
Poupart's  ligament.  It  at  first  descends  to  reach  this  ligament,  and  .then  ascends 
obliquely  along  the  inner  margin  of  the  internal  abdominal  ring,  lying  between 
the  transversalis  fascia  and  peritoneum,  and,  continuing  its  course  upward,  it 
pierces  the  transversalis  fascia,  and,  passing  over  the  semilunar  fold  of  Douglas, 
enters  the  sheath  of  the  Rectus  muscle.  It  then  ascends  on  the  posterior  surface 
of  the  muscle,  and  finally  divides  into  numerous  branches,  which  anastomose, 
above  the  umbilicus,  with  the  superior  epigastric  branch  of  the  internal  mammary 
and  with  the  inferior  intercostal  arteries  (Fig.  301).  The  deep  epigastric  artery 
bears  a  very  important  relation  to  the  internal  abdominal  ring  as  it  passes  obliquely 
upward  and  inward  from  its  origin  from  the  external  iliac.  In  this  part  of  its 
course  it  lies  along  the  lower  and  inner  margin  of  the  ring  and  beneath  the  com- 
mencement of  the  spermatic  cord.  As  it  passes  to  the  inner  side  of  the  internal 
abdominal  ring  it  is  crossed  by  the  vas  deferens  in  the  male  and  the  round  ligament 
in  the  female. 

Branches. — The  branches  of  this  vessel  are  the  following  :  The  cremasteric, 
which  accompanies  the  spermatic    cord,    and   supplies  the   Cremaster  muscle  and 


572  THE   BLOOD-VASCULAR    SYSTEM. 

other  coverings  of  the  cord,  anastomosing  with  the  spermatic  artery ;  a  pubic 
branch,  which  runs  along  Poupart's  ligament,  and  then  descends  behind  the  os 
pubis  to  the  inner  side  of  the  femoral  ring,  and  anastomoses  with  oifsets  from  the 
obturator  artery ;  muscular  branches,  some  of  which  are  distributed  to  the  abdom- 
inal muscles  and  peritoneum,  anastomosing  with  the  lumbar  and  circumflex  iliac 
arteries;  others  perforate  the  tendon  of  the  External  oblique,  and  supply  the 
integument,  anastomosing  with  branches  of  the  superficial  epigastric. 

Peculiarities. — The  origin  of  the  epigastric  may  take  place  from  any  part  of  the  external 
iliac  between  Poupart's  ligament  and  two  inches  and  a  half  above  it,  or  it  may  arise  below  tin's 
ligament,  from  the  common  femoral  or  from  the  deep  femoral. 

Union  with  Branches. — It  frequently  arises  from  the  external  iliac  by  a  common  trunk 
with  the  obturator.  Sometimes  the  epigastric  arises  from  the  obturator,  the  latter  vessel  being 
furnished  by  the  internal  iliac,  or  the  epigastric  may  be  formed  of  two  branches,  one  derived 
from  the  external  iliac,  the  other  from  the  internal  iliac. 

Surgical  Anatomy.— The  deep  epigastric  artery  follows  a  line  drawn  from  the  middle  of 
Poupart's  ligament  toward  the  umbilicus  ;  but  shortly  after  this  line  crosses  the  linea  semilunaris 
the  direction  changes,  and  the  course  of  the  vessel  is  directly  upward  in  the  line  of  junction  of 
the  inner  third  with  the  outer  two-thirds  of  the  Rectus  muscle.  It  has  important  surgical 
relations,  in  addition  to  the  fact  that  it  is  one  of  the  principal  means,  through  its  anastomosis 
with  the  internal  mammary,  in  establishing  the  collateral  circulation  after  ligature  of  either  the 
common  or  external  iliac  arteries.  It  lies  close  to  the  internal  abdominal  ring,  and  is  therefore 
internal  to  an  oblique  inguinal  hernia,  but  external  to  a  direct  inguinal  hernia,  as  it  emerges 
from  the  abdomen.  It  forms  the  outer  boundary  of  Hesselbach's  triangle.  It  is  in  close  rela- 
tionship with  the  spermatic  cord,  which  lies  in  front  of  it  in  the  inguinal  canal,  separated  only 
by  the  transversalis  fascia.     The  vas  deferens  hooks  round  its  outer  side. 

The  Deep  Circumflex  Iliac  Artery  arises  from  the  outer  side  of  the  external 
iliac  nearly  opposite  the  epigastric  artery.  It  ascends  obliquely  outward  behind 
Poupart's  ligament,  contained  in  a  fibrous  sheath  formed  by  the  junction  of  the 
transversalis  and  iliac  fasciae,  to  the  anterior  superior  spinous  process  of  the  ilium. 
It  then  runs  along  the  inner  surface  of  the  crest  of  the  ilium  to  about  its  middle, 
where  it  pierces  the  Transversalis,  and  runs  backward  between  that  muscle  and 
the  Internal  oblique,  to  anastomose  with  the  ilio-lumbar  and  gluteal  arteries. 
Opposite  the  anterior  superior  spine  of  the  ilium  it  gives  off  a  large  branch,  which 
ascends  between  the  Internal  oblique  and  Transversalis  muscles,  supplying  them, 
and  anastomosing  with  the  lumbar  and  epigastric  arteries. 

ARTERIES  OF  THE  LOWER  EXTREMITY. 

The  artery  which  supplies  the  greater  part  of  the  lower  extremity  is  the  direct 
continuation  of  the  external  iliac.  It  continues  as  a  single  trunk  from  Poupart's 
ligament  to  the  lower  border  of  the  Popliteus  muscle,  and  here  divides  into  two 
branches,  the  anterior  and  posterior  tibial,  an  arrangement  exactly  similar  to  what 
occurs  in  the  upper  limb.  For  convenience  of  description,  the  upper  part  of  the 
main  trunk  is  named  femoral,  the  lower  part,  popliteal. 

The  Femoral  Artery  (Fig.  317). 

The  femoral  artery  commences  immediately  behind  Poupart's  ligament,  midway 
between  the  anterior  superior  spine  of  the  ilium  and  the  symphysis  pubis,  and,  pass- 
ing down  the  fore  part  and  inner  side  of  the  thigh,  terminates  at  the  opening  in  the 
Adductor  magnus,  at  the  junction  of  the  middle  with  the  lower  third  of  the  thigh, 
where  it  becomes  the  popliteal  artery.  The  vessel,  at  the  upper  part  of  the  thigh, 
lies  in  front  of  the  hip-joint,  just  on  a  line  with  the  innermost  part  of  the  head  of 
the  femur  ;  in  the  lower  part  of  its  course  it  is  in  close  relation  with  the  inner  side 
of  the  shaft  of  the  bone,  and  between  these  two  parts  the  vessel  is  some  distance 
from  the  bone.  In  the  upper  third  of  the  thigh  it  is  contained  in  a  triangular  space 
called  Scarpa's  triangle.  In  the  middle  third  of  the  thigh  it  is  contained  in  an 
aponeurotic  canal  called  Hunter 's  canal. 

Scarpa's  Triangle. — Scarpa's  triangle  corresponds  to  the  depression  seen 
immediately  below  the  fold  of  the  groin.  It  is  a  triangular  space,  the  apex  of 
which  is  directed  downward,  and  the  sides  formed  externally  by  the  Sartorius. 
internally  by  the  inner  margin  of  the  Adductor  longus,  and  above  by  Poupart's 


THE  FEMORAL    ARTERY. 


573 


ligament.  The  floor  of  the  space  is  formed  from  without  inward  by  the  Iliacus, 
Psoas,  Pectineus  (in  some  cases  a  small  part  of  the  Adductor  brevis),  and  the  Ad- 
ductor longus  muscles ;  and  it  is  divided  into  two  nearly  equal  parts  by  the 
femoral  vessels,  which  extend  from  the  middle  of  its  base  to  its  apex,  the  artery 
giving  off  in  this  situation  its  cutaneous  and  profunda  branches,  the  vein  receiving 
the  deep  femoral  and  internal  saphenous.  On  the  outer  side  of  the  femoral  artery 
is  the  anterior  crural  nerve  divid- 
ing into  its  branches.  Besides  the 
vessels  and  nerves,  this  space  con- 
tains some  fat  and  lymphatics. 

Hunter's  Canal. — This  is  the 
aponeurotic  space  in  the  middle 
third  of  the  thigh,  extending  from 
the  apex  of  Scarpa's  triangle  to  the 
femoral  opening  in  the  Adductor 
magnus  muscle.  It  is  bounded, 
externally,  by  the  Vastus  internus  ; 
internally  by  the  Adductors  longus 
and  magnus  muscles;  and  covered 
in  by  a  strong  aponeurosis  which 
extends  transversely  from  the  Vas- 
tus internus  across  the  femoral 
vessels  to  the  Adductor  longus 
and  magnus ;  lying  on  which 
aponeurosis  is  the  Sartorius  mus- 
cle. It  contains  the  femoral  artery 
and  vein  enclosed  in  their  own 
sheath  of  areolar  tissue,  the  vein 
being  behind  and  oir"ithe  outer 
side  of  the  artery,  and  the  internal 
or  long  saphenous  nerve  lying  at 
first  on  the  outer  side  and  then  in 
front  of  the  vessels. 

For  convenience  of  description, 
and  also  in  reference  to  its  surgical 
anatomy,  the  femoral  artery  is  di- 
vided into  a  short  trunk,  about  an 
inch  and  a  half  or  two  inches  n 
which    is   known    as  the 
femoral  artery,  while  i 
der  of  the  vessel    is 
superficial  femora^ 


f- 


it  from   the 

funda    feme 

given  off  fron™ 

oral  at  its  terming 

by  its  derivati 

trunk,     murks 

ment    of    the  ficial    femoral 

artery. 

The  common  femoral  artery  is 
very  superfi  |.  being  covered 
by  and      superficial! 


(pro- 
branch 
i  mon  fern- 
and  which, 
the  parent 
commence- 


otum. 


Long  saphenous 
nerve. 

Anastomotica 
magna. 


Superior  exter 
articular. 


Inferior  WKtei 
articular. 


Anterior  tibial 
recurrent. 


Anastomotica 
magna. 
flffjfj — Superior  internah.- 
articular.lS[ng 

<.  arise  from 
I  I    jfunda  fernoris, 
'fpb.  of  a  firm  eoagu- 
/,  and  rarely  between 
id  appear,  then,  that 
111  is  between  four  and 
situation,  an  incision 
rie  vessel,  the  patient  lying 
Fig.  317.— The  ^  am]  rotated  outward.     A 
y  to  join  the  internal  saphe- 


faseia^jfj  Ifcjal  inguinal  lymphatic  glands,  the  iliac  per  cautiously  divided  and  the 

and  rius^SMigation  downward  ol  the  Trans versalis  fasciaexpose  fully  the  sheath  of 
ri°ri  Ligation  of  ie  sheath  of  the  vessels.  It  has  in  front  of -formed  for  elephantiasis  of 
cnjieg  and  acute  of  the  genito-cruraljnerve,  the  superficial  circus  vol.  ii.,  p.  37). 


/ 


574 


THE  BLOOD-VASCULAR   SYSTEM. 


occasionally  the  superficial  epigastric  vein.  It  rests  on  the  inner  margin  of  the 
Psoas  muscle,  which  separates  it  from  the  capsular  ligament  of  the  hip-joint,  and 
a  little  lower  on  the  Pectineus  muscle  ;  and  crossing  behind  it  is  the  branch  to  the 
Pectineus  from  the  anterior  crural  nerve.  Separating  the  artery  from  the  Pec 
tineus  muscles  in  the  pubic  portion  of  the  fascia  lata  and  the  prolongation  from  the 
fascia  covering  the  Iliacus  muscle,  which  forms  the  posterior  layer  of  the  sheath 
of  the  vessels.  The  anterior  crural  nerve  lies  about  half  an  inch  to  the  outer 
side  of  the  common  femoral  artery,  being  separated  from  the  artery  by  a  small 
part  of  the  Psoas  muscle.  To  the  inner  side  of  the  artery  is  the  femoral  vein, 
between  the  margins  of  the  Pectineus  and  Psoas  muscles.  The  two  vessels  are 
enclosed  in  a  strong  fibrous  sheath  formed  by  the  proper  sheath  of  the  vessels, 
strengthened  by  the  fascia  lata  (see  page  419) ;  the  artery  and  vein  are  separated, 
however,  from  one  another  by  a  thin  fibrous  partition. 

Plan  of  Relations  of  the  Common  Femoral  Artery. 

In  front. 
Skin  and  superficial  fascia. 
Superficial  inguinal  glands.    ->. — 
Iliac  portion  of  fascia  lata. 
Prolongation  of  trans versalis  fascia. 
Crural  branch  of  genito-crural  nerve, 
Superficial  circumflex  iliac  vein. 
'V  Superficial  epigastric  vein. 


: 


Inner  side. 
Femoral  vein. 


Outer  side. 

Small  part  of  Psoas  muscle, 
separating  the  artery  from  the 
anterior  crural  nerve. 


cation 


Behind. 
fascia  covering  Iliacus  muscle. 
P  fascia  lata. 


Ps 


The  superficial  femoral  artb<y  '.rperficial  where  it  lies  in  Scarpa's  tri- 
angle. Here  it  is  covered  by  the  ,  pvrficial  and  deep  fascia,  and  crossed 
by  the  internal  cutaneous  branch  l  or  crural  nerve.  In  Hunter's  canal 
it  is  more  deeply  seated,  being  co\  red  b\    he  integument,  the  superficial  and 


ng  of  Hunter's  canal.     The 

%  .vyithout  inward.     Behind,  the 

sirNand  the  profunda  artery  and 

>wer  down  on  the  Adduc- 

{ter  side  is  the  long  saphe- 

stus  internus  muscle, 

i  ,iV  side  is  the  Adductor 


deep  fascia,   the   Sa^torius  and   aponeurotic 

internal  saphenous  /ierve   crosses   the  a. 

artery  lies  at  its  Hpper  part  on   the  fern 

vein,  which  separate  it  from  the  Pectineus  rrvm  ■ 

tor  longus  and  Adductor  magnus  muscles.      JjH 

nous  nerve  and  /the  nerve  to  the   Vastus  inte-mi 
•     '-"d,  at  its  lower  part,   the  femoral   vein.      To;  i 
Add  ot   .ahove  and  the  Adductor  magnus    andiSa 

where  it  becom^ 

lies  in  front  of  tnF  Relations  of  the"  Superficial  Femq:  rtery 

the  femur  ;  in  the  .  In  front. 

of  the  shaft  of  the  b.         Skin,  superficial  and  deep  fajscise. 

from  the  bone.      In  the    Internal  cutaneous  nerve,     j 

,,    ,    a  ,        .  oartonus. 

called  Scarpa  s  triangle  Aponeurotic  covering  of  Hjinter's  canal, 
aponeurotic  canal  called  Jnternal  saphenous  nerve.    I 

Scarpa's    Triangle. — \  > \ 

immediately  below  the  f  / '       .  .  .  \  0uter  s  .  , 

i  •    i      •       -. .  -,     ,  „„  /     Superficial     \  T  -.  Hit   apex 

which  is  directed  dowrus-  Femoral  Long  saphenoii       s  J, 

internally  by  the  iane  f»  I    "^  J\  $S&2S  £  Poupart 

^^_-^^  Femoral  vein  i 


i  //> 

THE   FEMORAL    ARTERY.  575 

Behind. 

Femoral  vein. 
Profunda  artery  and  vein. 
Pectineus  muscle. 
Adductor  longus. 
Adductor  magnus. 

The  femoral  vein,  at  Poupart's  ligament,  lies  close  to  the  inner  side  of  the 
I  artery,  separated  from  it  by  a  thin  fibrous  partition ;  but  lower  down  it  is  behind 
it,  and  then  to  its  outer  side. 

The  internal  saphenous  nerve  is  situated  on  the  outer  side  of  the  artery,  in  the 
middle  third  of  the  thigh,  beneath  the  aponeurotic  covering  of  Hunter's  canal,  but 
not  usually  within  the  sheath  of  the  vessels.  The  internal  cutaneous  nerve  passes 
obliquely  across  the  upper  part  of  the  sheath  of  the  femoral  artery. 

Peculiarities.— Double  Femoral  reunited.— Several  cases  are  recorded  in  which  the  femoral 
artery  divided  into  two  trunks  below  the  origin  of  the  profunda,  and  became  reunited  near  the 
opening  in  the  Adductor  magnus  so  as  to  form  a  single  popliteal  artery.  One  of  them  occurred 
in  a  patient  operated  upon  for  popliteal  aneurism. 

Change  of  Position. — A  few  cases  have  been  recorded  in  which  the  femoral  artery  was 
situated  at  the  back  of  the  thigh,  the  vessel  being  continuous  above  with  the  internal  iliac, 
escaping  from  the  pelvis  through  the  great  sacro-sciatic  foramen,  and  accompanying  the  great 
sciatic  nerve  to  the  popliteal  space,  where  its  division  occurred  in  the  usual  manner.  The 
external  iliac  in  these  cases  was  small,  and  terminated  in  the  profunda. 

Position  of  the  Vein. — The  femoral  vein  is  occasionally  placed  along  the  inner  side  of  the 
artery,  throughout  the  entire  extent  of  Scarpa's  triangle,  or  it  may  be  slit  so  that  a  large  vein  is 
placed  on  each  side  of  the  artery  for  a  greater  or  less  extent. 

Origin  of  the  Profunda. — This  vessel  occasionally  arises  from  the  inner  side,  and,  more 
rarely,  from  the  back  of  the  common  trunk  ;  but  the  more  important  peculiarity,  in  a  surgical 
point  of  view,  is  that  which  relates  to  the  height  at  which  the  vessel  arises  from  the  femoral.  In 
three-fourths  of  a  large  number  of  cases  it  arose  between  one  or  two  inches  below  Poupart's 
ligament ;  in  a  few  cases  the  distance  was  less  than  an  inch  ;  more  rarely,  opposite  the  ligament ; 
and  in  one  case,  above  Poupart's  ligament,  from  the  external  iliac.  Occasionally,  the  distance 
between  the  origin  of  the  vessel  and  Poupart's  ligament  exceeds  two  inches,  and  in  one  case  it 
was  found  to  be  as  much  as  four  inches. 

Surface  Marking. — The  upper  two-thirds  of  a  line  drawn  from  a  point  midway  between 
the  anterior  superior  spine  of  the  ilium  and  the  symphysis  pubis  to  the  prominent  tuberosity  on 
the  inner  condyle  of  the  femur,  with  the  thigh  abducted  and  rotated  outward,  will  indicate  the 
course  of  the  femoral  artery. 

Surgical  Anatomy. —  Compression  of  the  femoral  artery,  which  is  constantly  requisite  in 
amputations  and  other  operations  on  the  lower  limb,  and  also  for  the  cure  of  popliteal  aneurisms, 
is  most  effectually  made  immediately  below  Poupart's  ligament.  In  this  situation  the  artery  is 
very  superficial,  and  is  merely  separated  from  the  ascending  ramus  of  the  os  pubis  by  the  Psoas 
muscle  ;  so  that  the  surgeon,  by  means  of  his  thumb  or  a  compressor,  may  effectually  control  the 
circulation  through  it.  This  vessel  may  also  be  compressed  in  the  middle  third  of  the  thigh  by 
placing  a  compress  over  the  artery,  beneath  the  tourniquet,  and  directing  the  pressure  from 
within  outward,  so  as  to  compress  the  vessel  against  the  inner  side  of  the  shaft  of  the  femur. 

The  application  of  a  ligature  to  the  femoral  artery  may  be  required  in  the  cases  of 
wound  or  aneurism  of  the  arteries  of  the  leg,  of  the  popliteal  o^femoral ; x  and  the  vessel  may 
be  exposed  and  tied  in  any  part  of  its  course.  The  great  depth  of  this  vessel  at  its  lower  part, 
its  close  connection  with  important  structures,  and  the  density  of  its  sheath  render  the  opera- 
tion in  this  situation  one  of  much  greater  difficulty  than  the  application  of  a  ligature  at  its  upper 
part,  where  it  is  more  superficial. 

Ligature  of  the  common  femoral  artery  is  usually  considered  unsafe,  on  account  of  the  con- 
nection of  large  branches  with  it — viz.  the  deep  epigastric  and  the  deep  circumflex  iliac  arising 
just  above  Poupart's  ligament ;  on  account  of  the  number  of  small  branches  which  arise  from 
it  in  its  short  course  ;  and  on  account  of  the  uncertainty  of  the  origin  of  the  profunda  femoris, 
which,  if  it  arise  high  up,  would  be  too  close  to  the  ligature  for  the  formation  of  a  firm  coagu- 
lum.  The  profunda  sometimes  arises  higher  than  the  point  above  mentioned,  and  rarely  between 
two  or  three  inches  (in  one  case  four)  below  Poupart's  ligament.  It  would  appear,  then,  that 
the  most  favorable  situation  for  the  application  of  a  ligature  to  the  femoral  is  between  four  and 
five  inches  from  its  point  of  origin.  In  order  to  expose  the  artery  in  this  situation,  an  incision 
between  three  and  four  inches  long  should  be  made  in  the  course  of  the  vessel,  the  patient  lying 
in  the  recumbent  position,  with  the  limb  slightly  flexed  and  abducted,  and  rotated  outward.  A 
large  vein  is  frequently  met  with,  passing  in  the  course  of  the  artery  to  join  the  internal  saphe- 
nous vein ;  this  must  be  avoided,  and,  the  fascia  lata  having  been  cautiously  divided  and  the 
Sartorius  exposed,  that  muscle  must  be  drawn  outward  in  order  to  expose  fully  the  sheath  of 

1  Ligation  of  the  femoral  artery  has  been  also  recommended  and  performed  for  elephantiasis  of 
the  leg  and  acute  inflammation  of  the  knee-joint  (Maunder,  Clin.  Soc.  Trans.,  vol.  ii.,  p.  37). 


576  THE  BLOOD-VASCULAR  SYSTEM. 

the  vessels.  The  finger  being  introduced  into  the  wound  and  the  pulsation  of  the  artery  felt, 
the  sheath  should  be  opened  on  the  outer  side  of  the  vessel  to  a  sufficient  extent  to  allow  of  the 
introduction  of  the  ligature,  but  no  farther ;  otherwise  the  nutrition  of  the  coats  of  the  vessel 
may  be  interfered  with,  or  muscular  branches  which  arise  from  the  vessel  at  irregular  intervals 
may  be  divided.  In  this  part  of  the  operation  the  long  saphenous  nerve  and  the  nerve  to  the 
Vastus  internus,  which  is  in  close  relation  with  the  sheath,  should  be  avoided.  The  aneurism 
needle  must  be  carefully  introduced  and  kept  close  to  the  artery,  to  avoid  the  femoral  vein, 
which  lies  behind  the  vessel  in  this  part  of  its  course. 

To  expose  the  artery  in  Hunter's  canal,  an  incision  should  be  made  through  the  integument, 
between  three  and  four  inches  in  length,  a  finger's  breadth  internal  to  the  line  of  the  artery,  in 
the  middle  of  the  thigh — i.  e.,  midway  between  the  groin  and  the  knee.  The  fascia  lata  having 
been  divided,  and  the  outer  border  of  the  Sartorius  muscle  exposed,  it  should  be  drawn  inward, 
when  the  strong  fascia  which  is  stretched  across  from  the  Adductors  to  the  Vastus  internus  will 
be  exposed,  and  must  be  freely  divided ;  the  sheath  of  the  vessels  is  now  seen,  and  must  be 
opened,  and  the  artery  secured  by  passing  the  aneurism  needle  between  the  vein  and  artery  in 
the  direction  from  without  inward.  The  femoral  vein  in  this  situation  lies  on  the  outer  side  of 
the  artery,  the  long  saphenous  nerve  on  its  anterior  and  outer  side. 

It  has  been  seen  that  the  femoral  artery  occasionally  divides  into  two  trunks  below  the  origin 
of  the  profunda.  If  in  the  operation  for  tying  the  femoral  two  vessels  are  met  with,  the  surgeon 
should  alternately  compress  each',  in  order  to  ascertain  which  vessel  is  connected  with  the 
aneurismal  tumor  or  with  the  bleeding  from  the  wound,  and  that  one  only  should  be  tied  which 
controls  the  pulsation  or  haemorrhage.  If,  however,  it  is  necessary  to  compress  both  vessels 
before  the  circulation  in  the  tumor  is  controlled,  both  should  be  tied,  as  it  would  be  probable  that 
they  became  reunited,  as  in  the  instances  referred  to  above. 

In  wounds  of  the  femoral  artery  the  question  of  the  mode  of  treatment  is  of  considerable 
importance.  If  the  wound  in  the  superficial  structures  is  a  large  one,  the  injured  vessel  must 
be  exposed  and  tied;  but  if  the  wound  is  a  punctured  one  and  the  bleeding  has  ceased,  the 
question  will  arise  whether  to  cut  down  upon  the  artery  or  to  trust  to  pressure.  Mr.  Cripps  \ 
advises  that  if  the  wound  is  in  the  "upper  part  of  the  thigh — that  is  to  say,  in  a  position  where 
the  femoral  artery  is  comparatively  superficial — the  surgeon  may  enlarge  the  opening  with  a 
good  prospect  of  finding  the  wounded  vessel  without  an  extensive  or  prolonged  operation.  If 
the  wound  be  in  the  lower  half  of  the  thigh,  owing  to  the  greater  depth  of  the  artery  and  the 
possibility  of  its  being  the  popliteal  that  is  wounded,  the  search  is  rendered  a  far  more  severe 
and  hazardous  operation,  and  it  should  not  be  undertaken  until  a  thorough  trial  of  pressure  has 
proved  ineffectual. 

Great  care  and  attention  are  necessary  for  the  successful  application  of  pressure.  The  limb 
should  be  carefully  bandaged  from  the  foot  upward  to  the  wound,  which  is  not  covered,  and  then 
ouward  to  the  groin.  The  wound  is  then  dusted  with  iodoform  or  boracic  powder  and  a  conical 
pad  applied  over  the  wound.  Rollers  the  thickness  of  the  index  finger  are  then  placed  along 
the  course  of  the  vessel  above  and  below  the  wound,  and  the  whole  carefully  bandaged  to  a  back 
splint  with  a  foot-piece. 

Collateral  Circulation. — When  the  common  femoral  is  tied  the  main  channels  for  carrying 
on  the  circulation  are  the  anastomoses  of  the  gluteal  and  circumflex  iliac  arteries  above  with  the 
external  circumflex  below ;  of  the  obturator  and  sciatic  above  with  the  internal  circumflex  below ; 
and  of  the  comes  nervi  ischiadici  with  the  arteries  in  the  ham. 

The  principal  agents  in  carrying  on  the  collateral  circulation  after  ligature  of  the  superficial 
femoral  artery  are,  according  to  Sir  A.  Cooper,  as  follows  : 

"  The  arteria  profunda  formed  the  new  channel  for  the  blood."  "The  first  artery  sent  off 
passed  down  close  to  the  back  of  the  thigh-bone,  and  entered  the  two  superior  articular  branches 
of  the  popliteal  artery. ' ' 

"The  second  new  large  vessel,  arising  from  the  profunda  at  the  same  part  with  the  former, 
passed  down  by  the  inner  side  of  the  Biceps  muscle  to  a  branch  of  the  popliteal  which  was  dis- 
tributed to  the  Gastrocnemius  muscle ;  whilst  a  third  artery,  dividing  into  several  branches, 
passed  down  with  the  sciatic  nerve  behind  the  knee-joint,  and  some  of  its  branches  united  them- 
selves with  the  inferior  articular  arteries  of  the  popliteal,  with  some  recurrent  branches  of  those 
arteries,  with  arteries  passing  to  the  Gastrocnemii,  and,  lastly,  with  the  origin  of  the  anterior 
and  posterior  tibial  arteries. " 

"It  appears,  then,  that  it  is  those  branches  of  the  profunda  which  accompany  the  sciatic 
nerve  that  are  the  principal  supporters  of  the  new  circulation."  2 

In  Porta' s  work3  (tab.  xii.,  xiii. )  is  a  good  representation  of  the  collateral  circulation  after 
the  ligature  of  the  femoral  artery.  The  patient  had  survived  the  operation  three  years.  The 
lower  part  of  the  artery  is  at  least  as  large  as  the  upper  ;  about  two  inches  of  the  vessel  appear 
to  have  been  obliterated.  The  external  and  internal  circumflex  arteries  are  seen  anastomosing 
by  a  great  number  of  branches  with  the  lower  branches  of  the  femoral  (muscular  and  anasto- 
motica  magna)  and  with  the  articular  branches  of  the  popliteal.  _  The  branches  from  the 
external  circumflex  are  extremely  large  and  numerous.  One  very  distinct  anastomosis  can  be 
traced  between  this  artery  on  the  outside  and  the  anastomotica  magna  on  the  inside  through  the 
intervention  of  the  superior  external  articular  artery,  with  which  they  both  anastomose  ;    and 

1  Heath's  Dictionary  of  Practical  Surgery,  vol.  i.  p.  525. 

s  Med.-Chir.  Trans.,  vol.  ii.  1811.  3A  oatologiche  delle  Arleriq,. 


THE   FEMORAL    ARTERY. 


577 


blood  reaches  even  the  anterior  tibial  recurrent  from  the  external  circumflex  by  means  of 
anastomosis  with  the  same  external  articular  artery.  The  perforating  branches  of  the  profunda 
are  also  seen  bringing  blood  round  the  obliterated  portion  of  the  artery  into  long  branches 
(muscular)  which  have  been  given  off  just  below  that  portion.  The  termination  of  the  profunda 
itself  anastomoses  most  freely  with  the  superior  external  articular.  A  long  branch  of  anasto- 
mosis is  also  traced  down  from  the  internal  iliac  by  means  of  the  comes  nervi  ischiadici  of  the 
sciatic,  which  anastomoses  on  the  popliteal  nerves  with  branches  from  the  popliteal  and  posterior 
tibial  arteries.  In  this  case  the  anastomosis  had  been  too  free,  since  the  pulsation  and  growth 
of  the  aneurism  recurred,  and  the  patient  died  after  ligature  of  the  external  iliac. 

There  is  an  interesting  preparation  in  the  Museum  of  the  Royal  College  of  Surgeons  of  a 
limb  on  which  John  Hunter  had  tied  the  femoral  artery  fifty  years  before  the  patient's  death. 
The  whole  of  the  superficial  femoral  and  popliteal  artery  seems  to  have  been  obliterated.     The 


External  iliac  artery. 

Deep  epigastric  artery. 
Spermatic  cord. 


Superior 

circumflex 

iliac  artery. 

Common  femoral.  - 


Profunda 
femoris.  \ 

External  cir-_ 
cumflex. 


Fig.  318.— Femoral  artery  and  its  branches.    (From  a  preparation  in  the  Museum  of  the  Royal  College  of 
Surgeons  of  England.) 


anastomosis  by  means  <>f  the  comes  nervi  ischiadici,  which  is  shown  in  Porta's  plate,  is  dis- 
tinctly seen:  the  ei  ircumflex  and  the  termination  of  the  profunda  artery  seem  to 
have  been  the  chiei  la  of  anastomoses;  but  the  injection  has  not  been  a  very  success- 
ful one. 


578  THE  BLOOD-VASCULAR    SYSTEM. 

Branches. — The  branches  of  the  femoral  artery  are — the 

Superficial  Epigastric.  (  External  Circumflex. 

Superficial  Circumflex  Iliac.  Profunda  <  Internal  Circumflex. 

Superficial  External  Pudic.  (_  Three  Perforating. 

Deep  External  Pudic.  Muscular. 

Anastomotica  Magna. 

The  superficial  epigastric  arises  from  the  femoral  about  half  an  inch  below  Pou- 
part's  ligament,  and,  passing  through  the  saphenous  opening  in  the  fascia  lata, 
ascends  on  the  abdomen,  in  the  superficial  fascia  covering  the  External  oblique 
muscle,  nearly  as  high  as  the  umbilicus.  It  distributes  branches  to  the  superficial 
inguinal  glands,  the  superficial  fascia,  and  the  integument,  anastomosing  with 
branches  of  the  deep  epigastric. 

The  superficial  circumflex  iliac,  the  smallest  of  the  cutaneous  branches,  arises 
close  to  the  preceding,  and,  piercing  the  fascia  lata,  runs  outward,  parallel  with 
Poupart's  ligament,  as  far  as  the  crest  of  the  ilium,  dividing  into  branches  which 
supply  the  integument  of  the  groin,  the  superficial  fascia,  and  the  superficial  ingui- 
nal lymphatic  glands,  anastomosing  with  the  deep  circumflex  iliac  and  with  the 
gluteal  and  external  circumflex  arteries. 

The  superficial  external  pudic  (superior)  arises  from  the  inner  side  of  the  femoral 
artery,  close  to  the  preceding  vessels,  and,  after  passing  through  the  saphenous  opening, 
courses  inward,  across  the  spermatic  cord  or  round  ligament,  to  be  distributed  to  the 
integument  on  the  lower  part  of  the  abdomen,  the  penis  and  scrotum  in  the  male, 
and  the  labium  in  the  female,  anastomosing  with  branches  of  the  internal  pudic. 

The  deep  external  pudic  (inferior),  more  deeply  seated  than  the  preceding,  passes 
inward  across  the  Pectineus  and  Adductor  longus  muscles,  covered  by  the  fascia 
lata,  which  it  pierces  at  the  inner  border  of  the  thigh,  its  branches  being  distrib- 
uted, in  the  male,  to  the  integument  of  the  scrotum  and  perinseum ;  and  in  the 
female  to  the  labium,  anastomosing  with  branches  of  the  superficial  perineal  artery. 

The  Profunda  Femoris  (deep  femoral  artery)  (Fig.  318)  nearly  equals  the  size  of 
the  superficial  femoral.  It  arises  from  the  outer  and  back  part  of  the  femoral 
artery,  from  one  to  two  inches  below  Poupart's  ligament.  It  at  first  lies  on  the 
outer  side  of  the  superficial  femoral,  and  then  passes  behind  it  and  the  femoral 
vein  to  the  inner  side  of  the  femur,  and,  passing  downward  beneath  the  Adductor 
longus,  terminates  at  the  lower  third  of  the  thigh  in  a  small  branch  which  pierces 
the  Adductor  magnus  (and  from  this  circumstance  is  sometimes  called  the  fourth 
perforating  artery),  and  is  distributed  to  the  flexor  muscles  on  the  back  of  the 
thigh,  anastomosing  with  branches  of  the  popliteal  and  inferior  perforating  arteries. 

Relations. — Behind,  it  lies  first  upon  the  Iliacus,  and  then  on  the  Pectineus, 
Adductor  brevis,  and  Adductor  magnus  muscles.  In  front,  it  is  separated  from 
the  superficial  femoral  artery,  above  by  the  femoral  and  profunda  veins,  and  below 
by  the  Adductor  longus.  On  its  outer  side  the  origin  of  the  Vastus  internus  sepa- 
rates it  from  the  femur. 

Plan  of  the  Relations  of  the  Profunda  Artery. 

In  front. 
Superficial  femoral  artery. 
Femoral  and  Profunda  veins. 
Adductor  longus. 

Outer  side. 
Vastus  internus. 


Behind. 
Iliacus. 
Pectineus. 
Adductor  brevis. 
Adductor  magnus. 


BRANCHES    OF    THE   FEMORAL    ARTERY.  579 

The  profunda  gives  off  the  following  named  branches : 

External  circumflex.          Internal  circumflex.  Four  perforating. 

The  External  Circumflex  Artery  supplies  the  muscles  on  the  front  of  the  thigh. 
It  arises  from  the  outer  side  of  the  profunda,  passes  horizontally  outward,  between 
the  divisions  of  the  anterior  crural  nerve  and  behind  the  Sartorius  and  Rectus 
muscles,  and  divides  into  three  sets  of  branches — ascending,  transverse,  and  de- 
scending. 

The  ascending  branches  pass  upward,  beneath  the  Tensor  fasciae  femoris  muscle, 
to  the  outer  side  of  the  hip,  anastomosing  with  the  terminal  branches  of  the  gluteal 
and  deep  circumflex  iliac  arteries. 

The  descending  branches,  three  or  four  in  number,  pass  downward,  behind  the 
Rectus,  upon  the  Vasti  muscles,  to  which  they  are  distributed,  one  or  two  passing 
beneath  the  Vastus  externus  as  far  as  the  knee,  anastomosing  with  the  superior 
articular  branches  of  the  popliteal  artery.  These  are  accompanied  by  the  branch 
of  the  anterior  crural  nerve  to  the  Vastus  externus. 

The  transverse  branch,  the  smallest,  passes  outward  over  the  Crureus,  pierces 
the  Vastus  externus,  and  winds  round  the  femur  to  its  back  part,  just  below  the 
great  trochanter,  anastomosing  at  the  back  of  the  thigh  with  the  internal  circum- 
flex, sciatic,  and  superior  perforating  arteries. 

The  Internal  Circumflex  Artery,  smaller  than  the  external,  arises  from  the  inner 
and  back  part  of  the  profunda,  and  winds  round  the  inner  side  of  the  femur,  be- 
tween the  Pectineus  and  Psoas  muscles.  On  reaching  the  upper  border  of  the  Ad- 
ductor brevis  it  gives  off  two  branches,  one  of  which  passes  inward  to  be  distrib- 
uted to  the  Adductor  muscles,  the  Gracilis,  and  Obturator  externus,  anastomosing 
with  the  obturator  artery ;  the  other  descends,  and  passes  beneath  the  Adductor 
brevis,  to  supply  it  and  the  great  Adductor  ;  while  the  continuation  of  the  vessel 
passes  backward  and  divides  into  an  ascending  and  a  transvei'se  branch  (Fig.  257). 
The  ascending  branch  passes  obliquely  upward  upon  the  tendon  of  the  Obturator 
externus  and  under  cover  of  the  Quadratus  femoris  toward  the  digital  fossa,  where 
it  anastomoses  with  twigs  from  the  gluteal  and  sciatic  arteries.  The  transverse 
branch,  larger  than  the  ascending,  appears  between  the  Quadratus  femoris  and 
upper  border  of  the  Adductor  magnus,  anastomosing  with  the  sciatic,  external  cir- 
cumflex, and  superior  perforating  arteries  ("the  crucial  anastomosis').  Opposite 
the  hip-joint,  the  artery  gives  off  an  articular  vessel,  which  enters  the  joint  beneath 
the  transverse  ligament ;  and,  after  supplying  the  adipose  tissue,  passes  along  the 
round  ligament  to  the  head  of  the  bone. 

The  perforating  arteries  (Fig.  316),  usually  four  in  number,  are  so  called  from 
their  perforating  the  tendon  of  the  Adductor  magnus  muscle  to  reach  the  back  of 
the  thigh.  They  pass  backward  close  to.  the  linea  aspera  of  the  femur,  under  cover 
of  small  tendinous  arches  in  the  Adductor  magnus.  The  first  is  given  off  above 
the  Adductor  brevis,  the  second  in  front  of  that  muscle,  and  the  third  immediately 
below  it. 

The  first  perforating  artery  passes  backward  between  the  Pectineus  and  Ad- 
ductor brevis  (sometimes  perforates  the  latter) ;  it  then  pierces  the  Adductor  mag- 
nus close  to  the  linea  aspera.  It  gives  off  branches  which  supply  the  Adductor 
brevis,  the  Adductor  magnus,  the  Biceps,  and  Gluteus  maximus  muscles,  and  anas- 
tomoses with  the  sciatic,"internal  and  external  circumflex,  and  middle  perforating 
arteries. 

The  second  perforating  artery,  larger  than  the  first,  pierces  the  tendons  of  the 
Adductor  brevis  and  Adductor  magnus  muscles,  and  divides  into  ascending  and 
descending  branches,  which  supply  the  flexor  muscles  of  the  thigh,  anastomosing 
with  the  first  and  third  perforating.  The  second  artery  frequently  arises  in  com- 
mon with  the  first.  The  nutrient  artery  of  the  femur  is  usually  given  off  from  this 
branch. 

The  third  perforating  artery  is  given  off  below  the  Adductor  brevis ;  it  pierces 
the  Adductor  magnus,  and  divides  into  branches  which  supply  the  flexor  muscles 


580 


THE  BLOOD-VASCULAR   SYSTEM. 


of  the  thigh ;  anastomosing  above  with  the  higher  perforating  arteries,  and  below 
with  the  terminal   branches  of  the  profunda  and  the  muscular  branches  of  the 

popliteal. 

The  fourth  perforating  artery  is  represented  by  the  termination  oi  the  profunda 

femoris  artery. 


Long 

saphenous 

nerve. 


—Femoral 
artery. 


Fig.  319.— Side  view  of  the  popliteal  artery.    (From  a  preparation  in  the  Museum  of  the  Royal  College  of 
Surgeons  of  England.) 

Muscular  branches  are  given  off  from  the  superficial  femoral  throughout  its 
entire  course.  They  vary  from  two  to  seven  in  number,  and  supply  chiefly  the 
Sartorius  and  Vastus  internus. 

The  anastomotica  magna  (Fig.  319)  arises  from  the  femoral  artery  just  before 
it  passes  through  the  tendinous  opening  in  the  Adductor  magnus  muscle,  and 
immediately  divides  into  a  superficial  and  deep  branch. 

The  superficial  branch  pierces  the  aponeurotic  covering  of  Hunter's  canal,  and 


THE  POPLITEAL    ARTERY.  581 

accompanies  the  long  saphenous  nerve  to  the  inner  side  of  the  thigh.  It  passes 
between  the  Sartorius  and  Gracilis  muscles,  and,  piercing  the  fascia  lata,  is  distrib- 
uted to  the  integument  of  the  upper  and  inner  part  of  the  leg,  anastomosing  with 
the  inferior  internal  articular. 

The  deep  branch  descends  in  the  substance  of  the  Vastus  internus,  lying  in 
front  of  the  tendon  of  the  Adductor  magnus,  to  the  inner  side  of  the  knee,  where  it 
anastomoses  with  the  superior  internal  articular  artery  and  anterior  recurrent 
branch  of  the  anterior  tibial.  A  branch  from  this  vessel  crosses  outward  above 
the  articular  surface  of  the  femur,  forming  an  anastomotic  arch  with  the  superior 
external  articular  artery,  and  supplies  branches  to  the  knee-joint. 

Popliteal  Artery. 

The  popliteal  artery  commences  at  the  termination  of  the  femoral  at  the 
opening  in  the  Adductor  magnus,  and,  passing  obliquely  downward  and  outward 
behind  the  knee-joint  to  the  lower  border  of  the  Popliteus  muscle,  divides  into 
the  anterior  and  posterior  tibial  arteries.  A  portion  of  the  artery  lies  in  the 
popliteal  space  ;  but  above  and  below,  to  a  considerable  extent,  it  is  covered  by 
the  muscles  which  form  the  boundaries  of  the  space,  and  is  therefore  beyond  the 
confines  of  the  hollow. 

THE  POPLITEAL  SPACE  (Fig.  320). 

Dissection. — A  vertical  incision  about  eight  inches  in  length  should  be  made  along  the 
back  part  of  the  knee-joint,  connected  above  and  below  by  a  transverse  incision  from  the  inner 
to  the  outer  side  of  the  limb.  The  flaps  of  integument  included  between  these  incisions  should 
be  reflected  in  the  direction  shown  in  Fig.  255,  page  427. 

Boundaries. — The  popliteal  space,  or  the  ham,  is  a  lozenge-shaped  space, 
widest  at  the  back  part  of  the  knee-joint,  and  deepest  above  the  articular  end  of 
the  femur.  It  is  bounded  externally,  above  the  joint,  by  the  Biceps,  and,  below 
the  joint,  by  the  Plantaris  and  external  head  of  the  Gastrocnemius.  Internally, 
above  the  joint,  by  the  Semimembranosus,  Semitendinosus,  Gracilis,  and  Sartorius  ; 
below  the  joint,  by  the  inner  head  of  the  Gastrocnemius. 

Above,  it  is  limited  by  the  apposition  of  the  inner  and  outer  hamstring 
muscles;  below,  by  the  junction  of  the  two  heads  of  the  Gastrocnemius. 
The  floor  is  formed,  by  the  lower  part  of  the  posterior  surface  of  the  shaft  of 
the  femur,  the  posterior  ligament  of  the  knee-joint,  the  upper  end  of  the  tibia, 
and  the  fascia  covering  the  Popliteus  muscle,  and  the  space  is  covered  in  by  the 
fascia  lata. 

Contents. — It  contains  the  popliteal  vessels  and  their  branches,  together  with 
the  termination  of  the  external  saphenous  vein,  the  internal  and  external  popliteal 
nerves  and  some  of  their  branches,  the  lower  extremity  of  the  small  sciatic  nerve, 
the  articular  branch  from  the  obturator  nerve,  a  few  small  lymphatic  glands,  and 
a  considerable  quantity  of  loose  adipose  tissue. 

Position  of  Contained  Parts. — The  internal  popliteal  nerve  descends  in  the 
middle  line  of  the  space,  lying  superficial  and  crossing  the  artery  from  without 
inward.  The  external  popliteal  nerve  descends  on  the  outer  side  of  the  upper 
part  of  the  space,  lying  close  to  the  tendon  of  the  Biceps  muscle.  More  deeply 
at  the  bottom  of  the  space  are  the  popliteal  vessels,  the  vein  lying  superficial  to 
the  artery,  to  which  it  is  closely  united  by  dense  areolar  tissue :  it  is  a  thick- 
walled  vessel,  and  lies  at  first  to  the  outer  side  of  the  artery,  and  then  crosses 
it  to  gain  the  inner  side  below  ;  sometimes  the  vein  is  double,  the  artery  lying 
between  the  two  venre  comites,  which  are  usually  connected  by  short  transverse 
branches.  More  deeply,  and,  at  its  upper  part,  close  to  the  surface  of  the  bone, 
is  the  popliteal  artery,  and  passing  off  from  it  at  right  angles  are  its  articular 
branches.  The  articular  branch  from  the  obturator  nerve  descends  upon  the 
popliteal  artery  to  supply  the  knee,  and  occasionally  there  is  found  deep  in  the 
space  an  articular  filament  from  the  great  sciatic  nerve.     The  popliteal  lymphatic 


582 


THE  BLOOD-VASCULAR    SYSTEM. 


glands,  four  or  five  in  number,  are  found  surrounding  the  artery ;  one  usually 
lies  superficial  to  the  vessel ;  another  is  situated  between  it  and  the  bone,  and  the 
rest  are  placed  on  either  side  of  it. 

The  Popliteal  Artery,  in  its  course  downward  from  the  aperture  in  the  Adductor 
magnus  to  the  lower  border  of  the  Popliteus  muscle,  rests  first  on  the  inner  surface 
of  the  femur,  and  is  then  separated  by  a  little  fat  from  the  hollowed  popliteal 
surface  of  the  bone ;  in  the  middle  of  its  course  it  rests  on  the  posterior  ligament 
of  the  knee-joint,  and  below  on  the  fascia  covering  the  Popliteus  muscle.  Super- 
ficially, it  is  covered  above  by  the  Semimembranosus  ;  in  the  middle  of  its  course, 
by  a  quantity  of  fat,  which  separates  it  from  the  deep  fascia  and  integument ;  and 
below  it  is  overlapped  by  the  Gastrocnemius,  Plantaris,  and  Soleus  muscles,  the 
popliteal  vein,  and  the  internal  popliteal  nerve.  The  popliteal  vein,  which  is 
intimately  attached  to  the  artery,  lies  superficial  and  external  to  it  above ;  it  then 
crosses  it  and  lies  to  its  inner  side.  The  internal  popliteal  nerve  is  still  more 
superficial  and  external  above,  but  below  the  joint  it  crosses  the  artery  and  lies 
on  its  inner  side.  Laterally,  the  artery  is  bounded  by  the  muscles  which  are 
situated  on  either  side  of  the  popliteal  space. 


Plan  of  Relations  of  Popliteal  Artery. 

In  front. 
Femur. 

Ligamenturu  posticum. 
Popliteus. 


Line)'  side. 
Semimembranosus. 
Internal  condyle. 
Gastrocnemius  (inner  head). 


Popliteal 
Artery. 


Outer  side. 
Biceps. 

Outer  condyle. 
Gastrocnemius  (outer  head). 
Plantaris. 


Behind. 
Semimembranosus. 
Fascia. 

Popliteal  vein. 
Internal  popliteal  nerve. 
Gastrocnemius. 
Plantaris. 
Soleus. 

Peculiarities  in  Point  of  Division.— Occasionally  the  popliteal  artery  divides  prematurely 
into  its  terminal  branches ;  this  unusual  division  occurs  most  frequently  opposite  the  knee-joint. 
The  anterior  tibial  under  these  circumstances  may  pass  in  front  of  the  Popliteus  muscle. 

Unusual  Branches. — The  artery  sometimes  divides  into  the  anterior  tibial  and  peroneal, 
the  posterior  tibial  being  wanting  or  very  small.  Occasionally  the  popliteal  is  found  to  divide 
into  three  branches,  the  anterior  and  posterior  tibial  and  peroneal. 

Surface  Marking.— The  course  of  the  upper  part  of  the  popliteal  artery  is  indicated  by 
a  line  drawn  from  the  outer  border  of  the  Semimembranosus  muscle  at  the  junction  of  the 
middle  and  lower  third  of  the  thigh  obliquely  downward  to  the  middle  of  the  popliteal  space, 
exactly  behind  the  knee-joint.  From  this  point  it  passes  vertically  downward  to  the  level  of  a 
line  drawn  through  the  lower  part  of  the  tubercle  of  the  tibia. 

Surgical  Anatomy. — The  popliteal  artery  is  not  infrequently  the  seat  of  injury.  It  may  be 
torn  by  direct  violence,  as  by  the  passage  of  a  cart-wheel  over  the  knee  or  by  hyper-extension  of 
the  knee ;  and  in  the  dead  body,  at  all  events,  the  middle  and  internal  coats  may  be  ruptured  by 
extreme  flexion.  It  may  also  be  lacerated  by  fracture  of  the  lower  part  of  the  shaft  of  the 
femur  or  by  antero-posterior  dislocation  of  the  knee-joint.  It  has  been  torn  in  breaking  down 
adhesions  in  cases  of  fibrous  ankylosis  of  the  knee,  and  is  in  danger  of  being  wounded,  and  in 
fact  has  been  wounded,  in  performing  Macewen's  operation  of  osteotomy  of  the  lower  end  of  the 
femur  for  genu  valgum.  In  addition,  Spencer  records  a  case  in  which  the  popliteal  artery  was 
wounded  from  in  front  by  a  stab  just  below  the  knee,  the  knife  passing  through  the  interosseous 
space.  The  popliteal  artery  is  more  frequently  the  seat  of  aneurism  than  is  any  other  artery 
in  the  body,  with  the  exception  of  the  thoracic  aorta.  This  is  due  no  doubt,  in  a  great 
measure  to  the  amount  of  movement  to  which  it  is  subjected,  and  to  the  fact  that  it  is  supported 
by  loose  and  lax  tissue  only,  and  not  by  muscles,  as  is  the  case  with  most  arteries. 

Ligature  of  the  popliteal  artery  is  required  in  cases  of  wound  of  that  vessel,  but  for  aneurism 
of  the  posterior  tibial  it  is  preferable  to  tie  the  superficial  femoral.  The  popliteal  may  be  tied 
in  the  upper  or  lower  part  of  its  course ;  but  in  the  middle  of  the  ham  the  operation  is  attended 


BRANCHES    OF    THE   POPLITEAL    ARTERY.  583 

with  considerable  difficulty,  from  the  great  depth  of  the  artery  and  from  the  extreme  degree  of 
tension  of  the  lateral  boundaries  of  the  space. 

In  order  to  expose  the  vessel  in  the  upper  part  of  its  course,  the  patient  should  be  placed 
in  the  supine  position,  with  the  knee  flexed  and  the  thigh  rotated  outward,  so  that  it  rests  on 
its  outer  surface ;  an  incision  three  inches  in  length,  beginning  at  the  junction  of  the  middle 
and  lower  third  of  the  thigh,  is  to  be  made  parallel  to  and  immediately  behind  the  tendon  of 
the  Adductor  magnus,  and  the  skin,  superficial  and  deep  fascise  divided.  J  The  tendon  of  the 
muscle  is  thus  exposed,  and  is  to  be  drawn  forward  and  the  hamstring  tendtons  backward.  A 
quantity  of  fatty  tissue  will  now  be  opened  up,  in  which  the  artery  will  be  fe!^ pulsating.  This 
is  to  be  separated  with  the  point  of  a  director  until  the  artery  is  exposed.  The  vein  and  nerve 
will  not  be  seen,  as  they  lie  to  the  outer  side  of  the  artery.  The  sheath  is  to  be  opened  and 
the  aneurism  needle  passed  from  before  backward,  keeping  its  point  close  to  the  artery  for  fear 
of  injuring  the  vein.  The  only  structure  to  avoid  is  the  long  saphenous  vein  in  the  superficial 
incision.  The  upper  part  of  the  popliteal  artery  may  also  be  tied  by  an  incision  on  the  back  of 
the  limb,  along  the  outer  margin  of  the  Semimembranosus,  but  the  operation  is  a  more  difficult 
one,  as  the  internal  popliteal  nerve  and  the  popliteal  vein  are  first  exposed,  and  great  care  has 
to  be  exercised  in  separating  them  from  the  artery. 

To  expose  the  vessel  in  the  lower  part  of  its  course,  where  the  artery  lies  between  the  two 
heads  of  the  Gastrocnemius,  the  patient  should  be  placed  in  the  prone  position  with  the  limb 
extended.  An  incision  should  then  be  made  through  the  integument  in  the  middle  line,  com- 
mencing opposite  the  bend  of  the  knee-joint,  care  being  taken  to  avoid  the  external  saphenous 
vein  and  nerve.  After  dividing  the  deep  fascia  and  separating  some  dense  cellular  membrane, 
the  artery,  vein,  and  nerve  will  be  exposed,  descending  between  the  two  heads  of  the  Gastrocne- 
mius. Some  muscular  branches  of  the  popliteal  should  be  avoided  if  possible,  or,  if  divided, 
tied  immediately.  The  leg  being  now  flexed,  in  order  the  more  effectually  to  separate  the  two 
heads  of  the  Gastrocnemius,  the  nerve  should  be  drawn  inward  and  the  vein  outward,  and  the 
aneurism  needle  passed  between  the  artery  and  vein  from  without  inward. 

Branches. — The  branches  of  the  popliteal  artery  are — the 

M         -,      j  Superior.  Superior  External  Articular. 

Muscular  |  Inferior  or  gural>  Azygos  Articular. 

Cutaneous.  Inferior  Internal  Articular. 

Superior  Internal  Articular.  Inferior  External  Articular. 

The  superior  muscular  branches,  two  or  three  in  number,  arise  from  the  upper 
part  of  the  popliteal  artery,  and  are  distributed  to  the  lower  part  of  the  Adductor 
magnus  and  flexor  muscles  of  the  thigh,  anastomosing  with  the  fourth  perforating 
branch  of  the  profunda. 

The  inferior  muscular  (sural)  are  two  large  branches  which  are  distributed  to 
the  two  heads  of  the  Gastrocnemius  and  to  the  Plantaris  muscle.  They  arise  from 
the  popliteal  artery  opposite  the  knee-joint. 

The  cutaneous  branches  arise  separately  from  the  popliteal  artery  or  from 
some  of  its  branches ;  they  descend  between  the  two  heads  of  the  Gastrocnemius 
muscle,  and,  piercing  the  deep  fascia,  are  distributed  to  the  integument  of  the 
calf.      One  branch  usually  accompanies  the  short,  or  external,  saphenous  vein. 

The  superior  articular  arteries,  two  in  number,  arise  one  on  each  side  of  the 
popliteal,  and  wind  round  the  femur  immediately  above  its  condyles  to  the  front 
of  the  knee-joint.  The  internal  branch  winds  inward  beneath  the  hamstring 
muscles,  to  which  it  supplies  branches,  above  the  inner  head  of  the  Gastrocnemius, 
and,  passing  beneath  the  tendon  of  the  Adductor  magnus,  divides  into  two 
branches,  one  of  which  supplies  the  Vastus  internus,  inosculating  with  the  anasto- 
motica  magna  and  inferior  internal  articular ;  the  other  ramifies  close  to  the 
surface  of  the  femur,  supplying  it  and  the  knee-joint,  and  anastomosing  with  the 
superior  external  articular  artery.  This  branch  is  frequently  of  small  size,  a 
condition  which  is  associated  with  an  increase  in  the  size  of  the  anastomotica 
magna.     The  external  branch  pas  the  outer  condyle,  beneath  the  tendon 

of  the  Biceps,  and  divides  into  a  superficial  and  deep  branch :  the  superficial 
branch  supplies  the  Vastus  exteri  us,  and  anastomoses  with  the  descending  branch 
of  the  external  circumflex  and  the  inferior  external  articular  arteries  ;  the  deep 
branch  supplies  the  lower  part  oJ  the  fem  ir  and  knee-joint,  and  forms  an  anasto- 
motic arch  across  the  bone  with  motica  magna  and  the  inferior  internal 
articular  arteries. 


584  THE  BLOOD-VASCULAR   SYSTEM. 

The  azygos  articular  is  a  small  branch  arising  from  the  popliteal  artery  oppo- 


■  Sural  arteries. 


Im 


-Anterior  peroneal. 


M 


Fig.  320.— The  popliteal,  posterior  tibial,  and 
peroneal  arteries. 


Inferior 
external 

articular 


Inferior  internal 
articular. 


Communicating. 


Fig.  321.— Surgical  anatomy  of  the  anterior  tibial 
and  dorsalis  pedis  arteries. 


site  the  bend  of  the  knee-joint.     It  pierces  the  posterior  ligament,  and  supplies  the 
ligaments  and  synovial  membrane  in  the  interior  of  the  articulation. 


THE  ANTERIOR    TIBIAL    ARTERY.  585 

The  inferior  articular  arteries,  two  in  number,  arise  from  the  popliteal  beneath 
the  Gastrocnemius,  and  wind  round  the  head  of  the  tibia  below  the  joint.  The 
internal  one  first  descends  along  the  upper  margin  of  the  Popliteus  muscle,  to  which 
it  gives  branches ;  it  then  passes  below  the  inner  tuberosity,  beneath  the  internal 
lateral  ligament,  at  the  anterior  border  of  which  it  ascends  to  the  front  and  inner 
side  of  the  joint,  to  supply  the  head  of  the  tibia  and  the  articulation  of  the  knee, 
anastomosing  with  the  inferior  external  articular  and  superior  internal  articular 
arteries.  The  external  one  passes  outward  above  the  head  of  the  fibula,  to  the 
front  of  the  knee-joint,  passing  in  its  course  beneath  the  outer  head  of  the  Gastroc- 
nemius, the  external  lateral  ligament,  and  the  tendon  of  the  Biceps  muscle,  and 
divides  into  branches  which  anastomose  with  the  inferior  internal  articular  artery, 
the  superior  external  articular  artery,  and  the  anterior  recurrent  branch  of  the 
anterior  tibial. 

Circumpatellar  Anastomosis. — Around  and  above  the  patella,  and  on  the  con- 
tiguous ends  of  the  femur  and  tibia,  is  a  large  network  of  vessels,  forming  a 
superficial  and  deep  plexus.  The  superficial  plexus  is  situated  between  the  fascia 
and  skin  round  about  the  patella ;  the  deep  plexus,  which  forms  a  close  network 
of  vessels,  lies  on  the  surface  of  the  lower  end  of  the  femur  and  upper  end  of  the 
tibia  around  their  articular  surfaces,  and  sends  numerous  offsets  into  the  interior  of 
the  joint.  The  arteries  from  which  this  plexus  is  formed  are  the  two  internal  and 
two  external  articular  branches  of  the  popliteal,  the  anastomotica  magna,  the 
terminal  branch  of  the  profunda,  the  descending  branch  from  the  external  circum- 
flex, and  the  anterior  recurrent  branch  of  the  anterior  tibial. 


The  Anterior  Tibial  Artery  (Fig.  321). 

The  anterior  tibial  artery  commences  at  the  bifurcation  of  the  popliteal  at  the 
lower  border  of  the  Popliteus  muscle,  passes  forward  between  the  two  heads  of  the 
Tibialis  postiqus,  and  through  the  large  oval" aperture  above  the  upper  border  of 
the  interosseous  membrane  to  the  deep  part  of  the  front  of  the  leg  :  it  here  lies 
close  to  the  inner  side  of  the  neck  of  the  fibula  ;  it  then  descends  on  the  anterior 
surface  of  the  interosseous  membrane,  gradually  approaching  the  tibia  ;  and  at  the 
lower  part  of  the  leg  lies  on  this  bone,  and  then  on  the  anterior  ligament  of  the 
ankle  to  the  bend  of  the  ankle-joint,  where  it  lies  more  superficially,  and  becomes 
the  dorsalis  pedis. 

Relations. — In  the  upper  two-thirds  of  its  extent  it  rests  upon  the  interosseous 
membrane,  to  which  it  is  connected  by  delicate  fibrous  arches  thrown  across  it ; 
in  the  lower  third,  upon  the  front  of  the  tibia  and  the  anterior  ligament  of  the 
ankle-joint.  In  the  upper  third  of  its  course  it  lies  between  the  Tibialis  anticus 
and  Extensor  longus  digitorum ;  in  the  middle  third,  between  the  Tibialis  anticus 
and  Extensor  proprius  hallucis.  At  the  bend  of  the  ankle  it  is  crossed  by  the 
tendon  of  the  Extensor  proprius  hallucis,  and  lies  between  it  and  the  innermost 
tendon  of  the  Extensor  longus  digitorum.  It  is  covered,  in  the  upper  two-thirds 
of  its  course,  by  the  muscles  which  lie  on  either  side  of  it  and  by  the  deep  fascia ; 
in  the  lower  third,  by  the  integument,  anterior  annular  ligament,  and  fascia. 

The  anterior  tibial  artery  is  accompanied  by  two  veins  (veme  comites),  which 
lie  one  on  each  side  of  the  artery;  the  anterior  tibial  nerve,  coursing  round  the 
outer  side  of  the  neck  of  the  fibula,  comes  into  relation  with  the  outer  side  of  the 
artery  shortly  after  it  has  passed  through  the  opening  in  the  interosseous  mem- 
brane ;  about  the  middle  of  the  leg  it  is  placed  superficial  to  it;  at  the  lower  part 
of  the  artery  the  nerve  is  generally  again  on  the  outer  side. 


586  THE   BLOOD-VASCULAR    SYSTEM. 

Plan  of  the  Relations  of  the  Anterior  Tibial  Artery. 

In  front. 
Integument,  superficial  and  deep  fasciae. 
Anterior  tibial  nerve. 

Tibialis  anticus  (overlaps  it  in  the  upper  part  of  the  leg). 
Extensor  longus  digitorum  }  i        i      •,    Y  i  j.i   \ 
Extensor  proprms  hallucis  |  (°verlaP  lt  &**&?)• 
Anterior  annular  ligament. 

Inner  side.  ^  ^\  Outer  side. 

Tibialis  anticus.  /    Anterior    \  Anterior  tibial  nerve. 

Extensor  proprius  hallucis  Tibia"      )  Extensor  longus  digitorum. 

(crosses  it  at  its  lower  V  I  Extensor  proprius  hallucis. 

part).  \.  / 

Behind. 
Interosseous  membrane. 
Tibia. 
Anterior  ligament  of  ankle-joint. 

Peculiarities  in  Size— This  vessel  may  be  diminished  in  size,  may  be  deficient  to  a  greater 
or  less  extent,  or  may  be  entirely  wanting,  its  place  being  supplied  by  perforating  branches  from 
the  posterior  tibial  or  by  the  anterior  division  of  the  peroneal  artery. 

Course. — The  artery  occasionally  deviates  in  its  course  toward  the  fibular  side  of  the  leg, 
regaining  its  usual  position  beneath  the  annular  ligament  at  the  front  of  the  ankle.  In  two 
instances  the  vessel  has  been  found  to  approach  the  surface  in  the  middle  of  the  leg,  being 
covered  merely  by  the  integument  and  fascia  below  that  point. 

Surface  Marking. — Draw  a  line  from  the  inner  side  of  the  head  of  the  fibula  to  mid- 
way between  the  two  malleoli.  In  this  line  take  a  point  one  inch  and  a  quarter  below  the 
head  of  the  fibula,  and  the  portion  of  the  line  below  this  point  will  mark  the  course  of  the 
artery. 

Surgical  Anatomy. — The  anterior  tibial  artery  may  be  tied  in  the  upper  or  lower  part  of 
the  leg.  In  the  upper  part  the  operation  is  attended  with  great  difficulty,  on  account  of  the 
depth  of  the  vessel  from  the  surface.  An  incision,  about  four  inches  in  length,  should  be  made 
through  the  integument,  midway  between  the  spine  of  the  tibia  and  the  outer  margin  of  the 
fibula,  and  the  deep  fascia  exposed.  The  wound  must  now  be  carefully  dried,  its  edges  retracted, 
and  the  white  line  separating  the  Tibialis  anticus  from  the  Extensor  longus  digitorum  sought 
for.  When  this  has  been  clearly  defined,  the  deep  fascia  is  to  be  divided  in  this  line,  and  the 
Tibialis  anticus  separated  from  adjacent  muscles  with  the  handle  of  the  scalpel  or  a  director  until 
the  interosseous  membrane  is  reached.  The  foot  is  to  be  flexed  in  order  to  relax  the  muscles,  and 
upon  drawing  them  apart,  the  artery  will  be  found  lying  on  the  interosseous  membrane  with  the 
nerve  on  its  outer  side  or  on  the  top  of  the  artery.  The  nerve  should  be  drawn  outward,  and 
the  venaa  comites  separated  from  the  artery  and  the  needle  passed  around  it. 

To  tie  the  vessel  in  the  lower  third  of  the  leg  above  the  ankle-joint  an  incision  about  three 
inches  in  length  should  be  made  through  the  integument  between  the  tendons  of  the  Tibialis 
anticus  and  Extensor  proprius  hallucis  muscles,  the  deep  fascia  being  divided  to  the  same  extent. 
The  tendon  on  either  side  should  be  held  aside,  when  the  vessel  will  be  seen  lying  upon  the 
tibia,  with  the  nerve  on  the  outer  side  and  one  of  the  venae  comites  on  either  side. 

The  branches  of  the  anterior  tibial  artery  are — the 

Posterior  Recurrent  Tibial.  Muscular. 

Superior  Fibular.  Internal  Malleolar. 

Anterior  Recurrent  Tibial.  External  Malleolar. 

The  posterior  recurrent  tibial  is  not  a  constant  branch,  and  is  given  off  from 
the  anterior  tibial  before  that  vessel  passes  through  the  interosseous  space.  It 
ascends  beneath  the  Popliteus  muscle,  which  it  supplies,  and  anastomoses  with  the 
lower  articular  branches  of  the  popliteal  artery,  giving  off  an  offset  to  the 
superior  tibio-fibular  joint. 

The  superior  fibular  is  sometimes  given  off  from  the  anterior  tibial,  sometimes 
from  the  posterior  tibial.  It  passes  outward,  round  the  neck  of  the  fibula,  through 
the  Soleus,  which  it  supplies,  and  ends  in  the  substance  of  the  Peroneus  longus 
muscle. 

The  anterior  recurrent  tibial  branch  arises  from  the  anterior  tibial  as  soon  as 
that  vessel  has  passed  through  the  interosseous  space ;  it  ascends  in  the  Tibialis 
anticus  muscle,  and  ramifies  on  the  front  and  sides  of  the  knee-joint,  anastomos- 


THE   DOBS  A  LIS  PEDIS  ARTERY.  587 

ing  with  the  articular  branches  of  the  popliteal  and  with  the  anastomotica  magna, 
assisting  in  the  formation  of  the  circumpatellar  plexus. 

The  muscular  branches  are  numerous ;  they  are  distributed  to  the  muscles 
which  lie  on  each  side  of  the  vessel,  some  piercing  the  deep  fascia  to  supply  the 
integument,  others  passing  through  the  interosseous  membrane,  and  anastomosing 
with  branches  of  the  posterior  tibial  and  peroneal  arteries. 

The  malleolar  arteries  supply  the  ankle-joint.  The  internal  arises  about  two 
inches  above  the  articulation,  and  passes  beneath  the  tendons  of  the  Extensor 
proprius  hallucis  and  Tibialis  anticus  to  the  inner  ankle,  upon  which  it  ramifies, 
anastomosing  with  branches  of  the  posterior  tibial  and  internal  plantar  arteries 
and  with  the  internal  calcanean  from  the  posterior  tibial.  The  external  passes 
beneath  the  tendons  of  the  Extensor  longus  digitorum  and  Peroneus  tertius,  and 
supplies  the  outer  ankle,  anastomosing  with  the  anterior  peroneal  artery  and  with 
ascending  branches  from  the  tarsal  branch  of  the  dorsalis  pedis. 

The  Dorsalis  Pedis  Artery  (Fig.  321). 

The  dorsalis  pedis,  the  continuation  of  the  anterior  tibial,  passes  forward  from 
the  bend  of  the  ankle  along  the  tibial  side  of  the  foot  to  the  back  part  of  the  first 
intermetatarsal  space,  where  it  divides  into  two  branches,  the  dorsalis  hallucis,  and 
co  mmunica  ting . 

Relations. — This  vessel,  in  its  course  forward,  rests  upon  the  astragalus,  navic- 
ular, and  middle  cuneiform  bones  and  the  ligaments  connecting  them,  being  cov- 
ered by  the  integument  and  fascia,  anterior  annular  ligament,  and  crossed  near 
its  termination  by  the  innermost  tendon  of  the  Extensor  brevis  digitorum.  On 
its  tibial  side  is  the  tendon  of  the  Extensor  proprius  hallucis ;  on  its  jibidar  side, 
the  innermost  tendon  of  the  Extensor  longus  digitorum,  and  the  termination  of  the 
anterior  tibial  nerve.      It  is  accompanied  by  two  veins. 

Plan  of  the  Relations  of  the  Dorsalis  Pedis  Artery. 

In  front. 

Integument  and  fascia. 

Anterior  annular  ligament. 

Innermost  tendon  of  Extensor  brevis  digitorum. 


Tibial  side. 


Fibular  side. 


"Extensor  nrnnrins  h  ^dis.  Extensor  longus  digitorum. 

Extensor  proprius  nallucis.  \  /  Anterior  tibial  nerve. 


Behind. 

Astragalus. 
Navicular. 
Middle  cuneiform, 
and  their  ligaments. 

Peculiarities  in  Size. — The  dorsal  artery  of  the  foot  may  be  larger  than  usual,  to  compen- 
sate for  a  deficient  plantar  artery ;  or  it  may  be  deficient  in  its  terminal  branches  to  the  toes, 
which  are  then  derived  from  the  internal  plantar ;  or  its  place  may  be  supplied  altogether  by  a 
large  anterior  peroneal  artery. 

Position. — This  artery  frequently  curves  outward,  lying  external  to  the  line  between  the 

•  of  the  ankle  and  the  back  part  of  the  first  interosseous  space. 
Surface  Marking. — The  dorsalis  pedis  artery  is  indicated  on  the  surface  of  the  dorsum  of 
the  foot  by  a  line  drawn  from  the  centre  of  the  space  between  the  two  malleoli  to  the  back  of  the 
first  intermetatarsal  space. 

Srrgical  Anatomy. — This  artery  may  be  tied,  by  making  an  incision  through  the  integu- 
ment letween  two  and  three  inches  in  length,  on  the  fibular  side  of  the  tendon  of  the  Extensor 
!>ropri  is  hallucis,  in  the  interval  between  it  and  the  inner  border  of  the  short  Extensor  muscle. 
The  iu  vision  should  not  extend  farther  forward  than  the  back  part  of  the  first  intermetatarsal 


588  THE  BLOOD-VASCULAR    SYSTEM. 

space,  as  the  artery  divides  in  that  situation.    The  deep  fascia  being  divided  to  the  same  extent, 
the  artery  will  be  exposed,  the  nerve  lying  upon  its  outer  side. 

Branches. — The  branches  of  the  dorsalis  pedis  are — the 

Tarsal.  Dorsalis  Hallucis. 

Metatarsal — Interosseous.  Communicating. 

The  tarsal  artery  arises  from  the  dorsalis  pedis,  as  that  vessel  crosses  the  navic- 
ular bone ;  it  passes  in  an  arched  direction  outward,  lying  upon  the  tarsal  bones, 
and  covered  by  the  Extensor  brevis  digitorum ;  it  supplies  that  muscle  and  the 
articulations  of  the  tarsus,  and  anastomoses  with  branches  from  the  metatarsal, 
external  malleolar,  peroneal,  and  external  plantar  arteries. 

The  metatarsal  arises  a  little  anterior  to  the  preceding ;  it  passes  outward  to 
the  outer  part  of  the  foot,  over  the  bases  of  the  metatarsal  bones,  beneath  the  ten- 
dons of  the  short  Extensor,  its  direction  being  influenced  by  its  point  of  origin ; 
and  it  anastomoses  with  the  tarsal  and  external  plantar  arteries.  This  vessel 
gives  off  three  branches,  the  interosseous  arteries,  which  pass  forward  upon  the 
three  outer  Dorsal  interossei  muscles,  and,  in  the  clefts  between  the  toes,  divide 
into  two  dorsal  collateral  branches  for  the  adjoining  toes.  At  the  back  part  of 
each  interosseous  space  these  vessels  receive  the  posterior  perforating  branches 
from  the  plantar  arch,  and  at  the  fore  part  of  each  interosseous  space  they  are 
joined  by  the  anterior  perforating  branches  from  the  digital  arteries.  The  outer- 
most interosseous  artery  gives  off  a  branch  which  supplies  the  outer  side  of  the 
little  toe. 

The  dorsalis  hallucis  {first  dorsal  interosseous)  runs  forward  along  the  outer 
border  of  the  first  metatarsal  bone,  and  at  the  cleft  between  the  first  and  second 
toes  divides  into  two  branches,  one  of  which  passes  inward,  beneath  the  tendon  of 
the  Extensor  proprius  hallucis,  and  is  distributed  to  the  inner  border  of  the  great 
toe ;  the  outer  branch  bifurcates,  to  supply  the  adjoining  sides  of  the  great  and 
second  toes. 

The  communicating  artery  dips  down  into  the  sole  of  the  foot,  between  the  two 
heads  of  the  First  dorsal  interosseous  muscle,  and  inosculates  with  the  termination 
of  the  external  plantar  artery,  to  complete  the  plantar  arch.  It  here  gives  off  its 
plantar  digital  branch,  which  is  named  the  arteria  magna  hallucis.  This  artery 
passes  forward  along  the  first  interosseous  space,  and,  after  sending  a  branch  alon^ 
the  inner  side  of  the  great  toe,  bifurcates  for  the  supply  of  the  adjacent  sides  of  the 
great  and  second  toes. 

The  Posterior  Tibial  Artery. 

The  posterior  tibial  is  an  artery  of  large  size,  which  extends  obliquely  down- 
ward from  the  lower  border  of  the  Popliteus  muscle,  along  the  tibial  side  of  the 
leg,  to  the  fossa  between  the  inner  ankle  and  the  heel,  where  it  divides  beneath 
the  origin  of  the  Abductor  hallucis,  on  a  level  with  a  line  drawn  from  the  point  of 
the  internal  malleolus  to  the  centre  of  the  convexity  of  the  heel,  into  the  internal 
and  external  plantar  arteries.  At  its  origin  it  lies  opposite  the  interval  between 
the  tibia  and  fibula ;  as  it  descends,  it  approaches  the  inner  side  of  the  leg,  lying 
behind  the  tibia,  and,  in  the  lower  part  of  its  course,  is  situated  midway  between 
the  inner  malleolus  and  the  tuberosity  of  the  os  calcis. 

Relations. — It  lies  successively  upon  the  Tibialis  posticus,  the  Flexor  longus 
digitorum,  the  tibia,  and  the  back  part  of  the  ankle-joint.  It  is  covered  by  the 
deep  transverse  fascia,  which  separates  it  above  from  the  Gastrocnemius  and 
Soleus  muscles :  at  its  termination  it  is  covered  by  the  Abductor  hallucis  muscle. 
In  the  lower  third,  where  it  is  more  superficial,  it  is  covered  only  by  the  integ- 
ument and  fascia,  and  runs  parallel  with  the  inner  border  of  the  tendo  Achillis. 
It  is  accompanied  by  two  veins  and  by  the  posterior  tibial  nerve,  which  lies  at 
first  to  the  inner  side  of  the  artery,  but  soon  crosses  it,  and  is,  in  the  greater  part 
of  its  course,  on  its  outer  side. 


THE  POSTERIOR    TIBIAL    ARTERY.  589 

Plan  of  the  Relations  of  the  Posterior  Tibial  Artery. 

In  front. 
Tibialis  posticus. 
Flexor  longus  digitorum. 
Tibia. 
Ankle-joint. 

Inner  side,  [  \  Outer  side. 

Posterior  tibial  nerve,  ?Tibi™r  Posterior  tibial  nerve, 

upper  tbird.  V  I  lower  two-thirds. 

Behind. 
Integument  and  fascia. 
Gastrocnemius. 
Soleus. 

Deep  transverse  fascia. 
Posterior  tibial  nerve. 
Abductor  hallucis. 

f  Behind  the  Inner  ankle  the  tendons  and  blood-vessels  are  arranged,  under 
ver  of  the  internal  annular  ligament,  in  the  following  order,  from  within  out- 
ward :  First,  the  tendons  of  the  Tibialis  posticus  and  Flexor  longus  digitorum, 
lying  in  the  same  groove,  behind  the  inner  malleolus,  the  former  being  the  most 
internal.  External  to  these  is  the  posterior  tibial  artery,  having  a  vein  on  either 
side :  and,  still  more  externally,  the  posterior  tibial  nerve.  About  half  an  inch 
nearer  the  heel  is  the  tendon  of  the  Flexor  longus  hallucis. 

Peculiarities  in  Size. — The  posterior  tibial  is  not  unfrequently  smaller  than  usual,  or 
absent,  its  place  being  supplied  by  a  large  peroneal  artery  which  passes  inward  at  the  lower  end 
of  the  tibia,  and  either  joins  the  small  tibial  artery  or  continues  aloneto  the  sole  of  the  foot. 

Surface  Marking. — The  course  of  the  posterior  tibial  artery  is  indicated  by  a  line  drawn 
from  a  point  one  inch  below  the  centre  of  the  popliteal  space  to  midway  between  the  tip  of  the 
internal  malleolus  and  the  centre  of  the  convexity  of  the  heel. 

Surgical  Anatomy. — The  application  of  a  ligature  to  the  posterior  tibial  may  be  required 
in  cases  of  wound  of  the  sole  of  the  foot  attended  with  great  haemorrhage,  when  the  vessel 
should  be  tied  at  the  inner  ankle.  In  cases  of  wound  of  the  posterior  tibial  it  will  be  necessary 
to  enlarge  the  opening  so  as  to  expose  the  vessel  at  the  wounded  point,  excepting  where  the 
vessel  is  injured  by  a  punctured  wound  from  the  front  of  the  leg.  In  cases  of  aneurism  from 
wound  of  the  artery  low  down,  the  vessel  should  be  tied  in  the  middle  of  the  leg.  But  in 
aneurism  of  the  posterior  tibial  high  up  it  would  be  better  to  tie  the  femoral  artery. 

To  tie  the  posterior  tibial  artery  at  the  ankle,  a  semilunar  incision,  convex  backward,  should 
be  made  through  the  integument,  about  two  inches  and  a  half  in  length,  midway  between  the 
heel  and  inner  ankle  or  a  little  nearer  the  latter.  The  subcutaneous  cellular  tissue  having  been 
divided,  a  strong  and  dense  fascia,  the  internal  annular  ligament,  is  exposed.  This  ligament  is 
continuous  above  with  the  deep  fascia  of  the  leg,  covers  the  vessels  and  nerves,  and  is  intimately 
adherent  to  the  sheaths  of  the  tendons.  This  having  been  cautiously  divided  upon  a  director, 
the  sheath  of  the  vessels  is  exposed,  and,  being  opened,  the  artery  is  seen  with  one  of  the  venae 
comites  on  each  side.  The  aneurism  needle  should  be  passed  round  the  vessel  from  the  heel 
toward  the  ankle,  in  order  to  avoid  the  posterior  tibial  nerve,  care  being  at  the  same  time  taken 
not  to  include  the  venae  comites. 

The  vessel  may  also  be  tied  in  the  lower  third  of  the  leg  by  making  an  incision,  about  three 
inches  in  length,  parallel  with  the  inner  margin  of  the  tendo  Achillis.  The  internal  saphenous 
vein  being  carefully  avoided,  the  two  layers  of  fascia  must  be  divided  upon  a  director,  when  the 
artery  is  exposed  along  the  outer  margin  of  the  Flexor  longus  digitorum,  with  one  of  its  venae 
comites  on  either  side  and  the  nerve  lying  external  to  it, 

To  tie  the  posterior  tibial  in  the  middle  of  the  leg  is  a  very  difficult  operation,  on  account  of 
the  great  depth  of  the  vessel  from  the  surface.  The  patient  being  placed  in  the  recumbent  posi- 
turn^tlie  injured  limb  should  rest  on  its  outer  side,  the  knee  being  partially  bent  and  the  foot 
extended,  so  as  to  relax  the  muscles  of  the  calf.  An  incision  about  four  inches  in  length  should 
then  be  made  through  the  integument  a  finger's  breadth  behind  the  inner  margin  of  the  tibia, 
taking  care  to  avoid  1  iternal  saphenous  vein.  The  deep  fascia  having  been  divided,  the 
margin  of  the  Gra  cnemius  is  exposed,  and  must  be  drawn  aside,  and  the  tibial  attachment  ot 
the  Soleus  dividi  or  being  previously  passed  beneath  it.  _  The  artery  may  now   be 

felt  pulsating  be  h<    deep  fascia  about  an  inch  from  the  margin  of  the  tibia.      1  he  fascia 

having  been divi<  ie  limb  placed  in  such  a  position  as  to  relax  the  muscles  ot  the 

calf  as  much  as  I  lie  veins  should  be  separated  from  the  artery,  and  the   aneurism 

needle  passed  ro  ssel  from  without  inward,  so  as  to  avoid  wounding  the   posterior 

tibial  nerve. 


590  THE  BLOOD-VASCULAR   SYSTEM. 

The  branches  of  the  posterior  tibial  artery  are — the 

Peroneal.  Nutrient. 

Muscular.  Communicating. 

Internal  Calcanean. 

The  Peroneal  Artery  lies,  deeply  seated,  along  the  back  part  of  the  fibular  side 
of  the  leg.  It  arises  from  the  posterior  tibial  about  an  inch  below  the  lower 
border  of  the  Popliteus  muscle,  passes  obliquely  outward  to  the  fibula,  and  then 
descends  along  the  inner  border  of  that  bone,  contained  in  a  fibrous  canal  between 
the  Tibialis  posticus  and  the  Flexor  longus  hallucis,  or  in  the  substance  of  the 
latter  muscle  to  the  lower  third  of  the  leg,  where  it  gives  off  the  anterior  -peroneal. 
It  then  passes  across  the  articulation  between  the  tibia  and  fibula  to  the  outer  side 
of  the  os  calcis,  where  it  gives  off  its  terminal  branches,  the  external  calcanean. 

Relations. — This  vessel  rests  at  first  upon  the  Tibialis  posticus,  and  then,  for 
the  greater  part  of  its  course,  in  a  fibrous  canal  betAveen  the  origins  of  the  Flexor 
longus  hallucis  and  Tibialis  posticus,  covered  or  surrounded  by  the  fibres  of  the 
Flexor  longus  hallucis.  It  is  covered,  in  the  upper  part  of  its  course,  by  the  Soleus 
and  deep  transverse  fascia ;  below,  by  the.  Flexor  longus  hallucis. 

Plan  of  the  Relations  of  the  Peroneal  Artery. 

In  front. 

Tibialis  posticus. 
Flexor  longus  hallucis. 

Outer  side.  j  \  Inner  side. 

Fibula.  (      Artery*       ]  Flexor  longus  hallucis. 

Flexor  longus  hallucis. 

Behind. 

Soleus. 

Deep  transverse  fascia. 

Flexor  longus  hallucis. 

Peculiarities  in  Origin. — The  peroneal  artery  may  arise  three  inches  below  the  Popliteus, 
or  from  the  posterior  tibial  high  up,  or  even  from  the  popliteal. 

Its  size  is  more  frequently  increased  than  diminished ;  and  then  it  either  reinforces  the 
posterior  tibial  by  its  junction  with  it,  or  altogether  takes  the  place  of  the  posterior  tibial  in  the 
lower  part  of  the  leg  and  foot,  the  latter  vessel  only  existing  as  a  short  muscular  branch.  In 
those  rare  cases  where  the  peroneal  artery  is  smaller  than  usual  a  branch  from  the  posterior 
tibial  supplies  its  place,  and  a  branch  from  the  anterior  tibial  compensates  for  the  diminished 
anterior  peroneal  artery.     In  one  case  the  peroneal  artery  has  been  found  entirely  wanting. 

The  anterior  peroneal  is  sometimes  enlarged,  and  takes  the  place  of  the  dorsal  artery  of  the 
foot. 

The  branches  of  the  peroneal  are — the 

Muscular.  Communicating. 

Nutrient.  Posterior  Peroneal. 

Anterior  Peroneal.  External  Calcanean. 

Muscular  Branches. — The  peroneal  artery  in  its  course  gives  off  branches  to 
the  Soleus,  Tibialis  posticus,  Flexor  longus  hallucis,  and  Peronei  muscles. 

The  nutrient  artery  supplies  the  fibula. 

The  Anterior  peroneal  pierces  the  interosseous  membrane,  about  two  inches 
above  the  outer  malleolus,  to  reach  the  fore  part  of  the  leg,  and,  passing  down 
beneath  the  Peroneus  tertius  to  the  outer  ankle,  ramifies  on  the  front  and  outer 
side  of  the  tarsus,  anastomosing  with  the  external  malleolar  and  tarsal  arteries. 

The  communicating  is  given  off  from  the  peroneal  about  an  inch  from  its  lower 
end,  and,  passing  inward,  joins  the  communicating  branch  of  the  posterior  tibial. 

The  Posterior  peroneal  passes  down  behind  the  outer  ankle  to  the  back  of  the 
external  malleolus,  to  terminate  in  branches  which  ramify  on  the  outer  surface 
and  back  of  the  os  calcis. 


THE   PLANTAR    ARTERIES. 


591 


The  External  calcanean  are  the  terminal  branches  of  the  peroneal  artery  ;  they 
pass  to  the  outer  side  of  the  heel,  and  communicate  with  the  external  malleolar, 
and,  on  the  back  of  the  heel,  with  the  internal  calcanean  arteries. 

The  nutrient  artery  of  the  tibia  arises  from  the  posterior  tibial  near  its  origin, 
and,  after  supplying  a  few  muscular  branches,  enters  the  nutrient  canal  of  that 
bone,  which  it  traverses  obliquely  from  above  downward.  This  is  the  largest 
nutrient  artery  of  bone  in  the  body. 

The  muscular  branches  of  the  posterior  tibial  are  distributed  to  the  Soleus  and 
deep  muscles  along  the  back  of  the  leg. 

The  communicating  branch,  to  join  a  similar  branch  of  the  peroneal,  runs  trans- 
versely across  the  back  of  the  tibia,  about  two  inches  above  its  lower  end,  passing 
beneath  the  Flexor  longus  hallucis. 

The  internal  calcanean  are  several  large  arteries  which  arise  from  the  posterior 


Communicating 

branch  of 
dorsalis  pedis. 
Its  digital 
branches. 


Fig.  322.— The  plantar  arteries.    Superficial  view. 


Fig.  323.— The  plantar  arteries.    Deep  view. 


tibial  just  before  its  division :  they  are  distributed  to  the  fat  and  integument 
behind  the  tendo  Achillis  and  about  the  heel,  and  to  the  muscles  on  the  inner  side 
of  the  sole,  anastomosing  with  the  peroneal  and  internal  malleolar,  and,  on  the  back 
of  the  heel,  with  the  external  calcanean  arteries. 

The  Internal  Plantar  Artery  (Figs.  322,  323),  much  smaller  than  the  external, 
passes  forward  along  the  inner  side  of  the  foot.  It  is  at  first  situated  above1  the 
Abductor  hallucis,  and  then  between  it  and  the  Flexor  brevis  digitoruru,  both  of 
which  it  supplies.  At  the  base  of  the  first  metatarsal  bone,  where  it  has  become 
much  diminished  in  size,  it  passes  along  the  inner  border  of  the  great  toe,  inoscu- 
lating with  its  digital  branch.  Small  superficial  digital  branches  accompany  the 
digital  branches  of  the  internal  plantar  nerve  and  join  the  plantar  digital  arteries 
of  the  three  inner  spaces. 

The  External  Plantar  Artery,  much  larger  than  the  internal,  passes  obliquely 
outward  and  forward  to  the  base  of  the  fifth  metatarsal  bone.  It  then  turns 
obliquely   inward    to    the  interval    between    the    bases    of  the   first   and   second 


1  This  refers  to  the  erect  position  of  the  body 
is  deeper  than  the  muscle. 


In  the  ordinary  position  for  dissection  the  artery 


592  THE  BLOOD-VASCULAR    SYSTEM. 

metatarsal  bones,  where  it  anastomoses  with  the  communicating  branch  from  the 
dorsalis  pedis  artery,  thus  completing  the  plantar  arch.  As  this  artery  passes 
outward,  it  is  first  placed  between  the  os  calcis  and  Abductor  hallucis,  and  then 
between  the  Flexor  brevis  digitorum  and  Flexor  accessorius,  and  as  it  passes 
forward  to  the  base  of  the  little  toe,  it  lies  more  superficially  between  the  Flexor 
brevis  digitorum  and  Abductor  minimi  digiti,  covered  by  the  deep  fascia  and 
integument.  The  remaining  portion  of  the  vessel  is  deeply  situated :  it  extends 
from  the  base  of  the  metatarsal  bone  of  the  little  toe  to  the  back  part  of  the 
first  interosseous  space,  and  forms  the  plantar  arch ;  it  is  convex  forward,  lies 
upon  the  Interossei  muscles  opposite  the  tarsal  ends  of  the  metatarsal  bones,  and 
is  covered  by  the  Adductor  obliquus  hallucis,  the  flexor  tendons  of  the  toes,  and 
the  Lumbricales. 

Surface  Marking. — The  course  of  the  internal  plantar  artery  is  represented  by  a  line 
drawn  from  the  mid-point  between  the  tip  of  the  internal  malleolus  and  the  centre  of  the  con- 
vexity of  the  heel  to  the  middle  of  the  under  surface  of  the  great  toe ;  the  external  plantar  by 
a  line  from  the  same  point  to  within  a  finger's  breadth  of  the  tuberosity  of  the  fifth  metatarsal 
bone.  The  plantar  arch  is  indicated  by  a  line  drawn  from  this  point ;  i.  e.  a  finger's  breadth 
internal  to  the  tuberosity  of  the  fifth  metatarsal  bone  transversely  across  the  foot  to  the  back  of 
the  first  interosseous  space. 

Surgical  Anatomy. — Wounds  of  the  plantar  arch  are  always  serious,  on  account  of  the 
depth  of  the  vessel  and  the  important  structures  which  must  be  interfered  with  in  an  attempt 
to  ligate  it.  They  must  be  treated  on  similar  lines  to  those  of  wounds  of  the  palmar  arches 
(see  page  545).  Delorme  has  shown  that  it  may  be  ligated  from  the  dorsum  of  the  foot  in 
almost  any  part  of  its  course  by  removing  a  portion  of  one  of  the  three  middle  metatarsal  bones. 

Branches. — The  plantar  arch,  besides  distributing  numerous  branches  to  the 
muscles,  integument,  and  fasciae  in  the  sole,  gives  off  the  following  branches : 

Posterior  Perforating.  Digital — Anterior  Perforating. 

The  Posterior  Perforating  are  three  small  branches  which  ascend  through  the 
back  part  of  the  three  outer  interosseous  spaces,  between  the  heads  of  the  Dorsal 
interossei  muscles,  and  anastomose  with  the  interosseous  branches  from  the  meta- 
tarsal artery. 

The  Digital  Branches  are  four  in  number,  and  supply  the  three  outer  toes  and 
half  the  second  toe.  The  first  passes  outward  from  the  outer  side  of  the  plantar 
arch,  and  is  distributed  to  the  outer  side  of  the  little  toe,  passing  in  its  course 
beneath  the  Abductor  and  short  Flexor  muscles.  The  second,  third,  and  fourth 
run  forward  along  the  interosseous  spaces,  and  on  arriving  at  the  clefts  between 
the  toes  divide  into  collateral  branches,  which  supply  the  adjacent  sides  of  the 
three  outer  toes  and  the  outer  side  of  the  second.  At  the  bifurcation  of  the  toes 
each  digital  artery  sends  upward,  through  the  fore  part  of  the  corresponding 
interosseous  space,  a  small  branch,  which  inosculates  with  the  interosseous  branches 
of  the  metatarsal  artery.     These  are  the  anterior  perforating  branches. 

From  the  arrangement  already  described  of  the  distribution  of  the  vessels  to 
the  toes  it  will  be  seen  that  both  sides  of  the  three  outer  toes  and  the  outer  side 
of  the  second  toe  are  supplied  by  branches  from  the  plantar  arch ;  both  sides  of 
the  great  toe  and  the  inner  side  of  the  second  are  supplied  by  the  communicating 
branch  of  the  dorsalis  pedis. 


THE  VEINS. 

The  Veins  are  the  vessels  which  serve  to  return  the  blood  from  the  capillaries 
of  the  different  parts  of  the  body  to  the  heart.  They  consist  of  two  distinct  sets 
of  vessels,  the  pulmonary  and  systemic. 

The  Pulmonary  Veins  are  concerned  in  the  circulation  in  the  lungs.  Unlike 
other  vessels  of  this  kind,  they  contain  arterial  blood,  which  they  return  from  the 
lungs  to  the  left  auricle  of  the  heart. 

The  Systemic  Veins  are  concerned  in  the  general  circulation ;  they  return  the 
venous  blood  from  the  body  generally  to  the  right  auricle  of  the  heart. 

The  Portal  Vein,  an  appendage  to  the  systemic  venous  system,  is  confined  to 
the  abdominal  cavity,  returning  the  venous  blood  from  the  viscera  of  digestion, 
and  carrying  it  to  the  liver  by  a  single  trunk  of  large  size,  the  vena  porta*.  This 
vessel  ramifies  in  the  substance  of  the  liver  and  breaks  up  into  a  minute  network 
of  capillaries.  These  capillaries  then  re-collect  to  form  the  hepatic  veins,  by  which 
the  blood  is  conveyed  to  the  inferior  vena  cava. 

The  veins,  like  the  arteries,  are  found  in  nearly  every  tissue  of  the  body. 
They  commence  by  minute  plexuses  which  receive  the  blood  from  the  capillaries. 
The  branches  which  have  their  commencement  in  these  plexuses  unite  together 
into  trunks,  and  these,  in  their  passage  toward  the  heart,  constantly  increase  in 
size  as  they  receive  tributaries  or  join  other  veins.  The  veins  are  larger  and 
altogether  more  numerous  than  the  arteries  ;  hence  the  entire  capacity  of  the 
venous 'System  is  much  greater  than  that  of  the  arterial,  the  pulmonary  veins 
excepted,  which  only  slightly  exceed  in  capacity  the  pulmonary  arteries.  From 
the  combined  area  of  the  smaller  venous  branches  being  greater  than  the  main 
trunks,  it  results  that  the  venous  system  represents  a  cone,  the  summit  of  which 
corresponds  to  the  heart,  its  base  to  the  circumference  of  the  body.  In  form  the 
veins  are  perfectly  cylindrical,  like  the  arteries,  their  walls  being  collapsed  when 
empty,  and  the  uniformity  of  their  surface  being  interrupted  at  intervals  by  slight 
constrictions,  which  indicate  the  existence  of  valves  in  their  interior.  They 
usually  retain,  however,  the  same  calibre  as  long  as  they  receive  no  bi'anches. 

The  veins  communicate  very  freely  with  one  another,  especially  in  certain 
regions  of  the  body,  and  this  communication  exists  between  the  larger  trunks  as 
well  as  between  the  smaller  branches.  Thus,  in  the  cavity  of  the  cranium  and 
between  the  veins  of  the  neck,  where  obstruction  would  be  attended  with  immi- 
nent danger  to  the  cerebral  venous  system,  we  find  that  the  sinuses  and  larger 
veins  have  large  and  very  frequent  anastomoses.  The  same  free  -communication 
exists  between  the  veins  throughout  the  whole  extent  of  the  spinal  canal,  and 
between  the  veins  composing  the  various  venous  plexuses  in  the  abdomen  and  pel- 
vis, as  the  spermatic,  uterine,  vesical,  and  prostatic. 

Veins  have  thinner  Avails  than  arteries,  the  difference  in  thickness  being  due  to 
the  small  amount  of  elastic  and  muscular  tissues  which  the  veins  contain.  The 
superficial  veins  usually  have  thicker  coats  than  the  deep  veins,  and  the  veins  of 
the  lower  limb  are  thicker  than  those  of  the  upper. 

The  minute  structure  of  these  vessels  will  be  described  in  the  section  on 
General  Anatomy. 

The  systemic  veins  are  subdivided  into  three  sets  :  superficial,  deep,  and  sinuses. 

The  Superficial  or  Cutaneous  Veins  are  found  between  the  layers  of  the  super- 
ficial fascia,  immediately  beneath  the  integument;  they  return  the  blood  from 
these  structures,  and  communicate  with  the  deep  veins  by  perforating  the  deep 
fascia. 

38  593 


594  THE   BLOOD-VASCULAR   SYSTEM. 

The  Deep  Veins  accompany  the  arteries,  and  are  usually  enclosed  in  the  same 
sheath  with  those  vessels.  With  the  smaller  arteries — as  the  radial,  ulnar,  brachial, 
tibial,  peroneal — they  exist  generally  in  pairs,  one  lying  on  each  side  of  the  ves- 
sel, and  are  called  venae,  eomites.  The  larger  arteries — as  the  axillary,  subclavian, 
popliteal,  and  femoral — have  usually  only  one  accompanying  vein.  In  certain 
organs  of  the  body,  however,  the  deep  veins  do  not  accompany  the  arteries ;  for 
instance,  the  veins  in  the  skull  and  spinal  canal,  the  hepatic  veins  in  the  liver,  and 
the  larger  veins  returning  blood  from  the  osseous  tissue. 

Sinuses  are  venous  channels  which,  in  their  structure  and  mode  of  distribution, 
differ  altogether  from  the  veins.  They  are  found  only  in  the  interior  of  the  skull, 
and  consist  of  channels  formed  by  a  separation  of  the  two  layers  of  the  dura  mater, 
their  outer  coat  consisting  of  fibrous  tissue,  their  inner  of  an  endothelial  layer 
continuous  with  the  lining  membrane  of  the  veins. 

THE   PULMONARY   VEINS. 

The  Pulmonary  Veins  return  the  arterial  blood  from  the  lungs  to  the  left 
auricle  of  the  heart.  They  are  four  in  number,  two  for  each  lung.  The  pulmo- 
nary differ  from  other  veins  in  several  respects  :  1.  They  carry  arterial  instead  of 
venous  blood.  2.  They  are  destitute  of  valves.  3.  They  are  only  slightly  larger 
than  the  arteries  they  accompany.  4.  They  accompany  those  vessels  singly. 
They  commence  in  a  capillary  network  upon  the  walls  of  the  air-cells,  where 
they  are  continuous  with  the  capillary  ramifications  of  the  pulmonary  artery,  and, 
uniting  together,  form  one  vessel  for  each  lobule.  These  vessels,  uniting  suc- 
cessively, form  a  single  trunk  for  each  lobe,  three  for  the  right  and  two  for  the 
left  lung.  The  vein  from  the  middle  lobe  of  the  right  lung  generally  unites  with 
that  from  the  upper  lobe,  forming  two  trunks  on  each  side,  which  open  separately 
into  the  left  auricle.  Occasionally  they  remain  separate ;  there  are  then  three 
veins  on  the  right  side.  Not  unfrequently  the  two  left  pulmonary  veins  termi- 
nate by  a  common  opening. 

Within  the  lung,  the  branches  of  the  pulmonary  artery  are  infront,  the  veins 
behind,  and  the  bronchi  between  the  two. 

At  the  root  of  the  lung*  the  veins  are  infront,  the  artery  in  the  middle,  and 
the  bronchus  behind. 

Within  the  pericardium,  their  anterior  surface  is  invested  by  the  serous  layer 
of  this  membrane.  The  right  pulmonary  veins  pass  behind  the  right  auricle  and 
ascending  aorta  and  superior  vena  cava  ;  the  left  pass  in  front  of  the  thoracic 
aorta  with  the  left  pulmonary  artery. 

THE    SYSTEMIC   VEINS. 

The  systemic  veins  may  be  arranged  into  three  groups :  1.  Those  of  the  head 
and  neck,  upper  extremity,  and  thorax,  which  terminate  in  the  superior  vena  cava. 
2.  Those  of  the  lower  extremity,  abdomen,  and  pelvis,  which  terminate  in  the  infe- 
rior vena  cava.  3.  The  cardiac  veins,  which  open  directly  into  the  right  auricle 
of  the  heart. 

VEINS  OF  THE  HEAD  AND  NECK. 

The  veins  of  the  head  and  neck  may  be  subdivided  into  three  groups :  1.  The 
veins  of  the  exterior  of  the  head  and  face.  2.  The  veins  of  the  neck.  3.  The 
veins  of  the  diploe  and  interior  of  the  cranium. 

Veins  of  the  Exterior  of  the  Head  and  Face. 

The  veins  of  the  exterior  of  the  head  and  face  are — the 
Frontal.  Temporal. 

Supra-orbital.  Internal  Maxillary. 

Angular.  Temporo-maxillary. 

Facial.  Posterior  Auricular. 

Occipital. 


VEINS    OF   THE   EXTERIOR    OF    THE   HEAD    AND    FACE,     595 

The  frontal  vein  commences  on  the  anterior  part  of  the  skull  by  a  venous 
plexus  which  communicates  with  the  anterior  tributaries  of  the  temporal  vein. 
The  veins  converge  to  form  a  single  trunk,  which  runs  downward  near  the 
middle  line  of  the  forehead  parallel  with  the  vein  of  the  opposite  side,  and  unites 
with  it  at  the  root  of  the  nose  by  a  transverse  branch  called  the  nasal  arch. 
Occasionally  the  frontal  veins  join  to  form  a  single  trunk,  which  bifurcates  at  the 


FrontaL 
Communicating 
branch  with 

hthalmic  vein. 
Angular. 


Fig.  324.— Veins  of  the  head  and  neck. 

root  of  the  nose  into  the  two  angular  veins.  At  the  root  of  the  nose  the  veins 
diverge  and  join  the  supra-orbital  vein,  at  the  inner  angle  of  the  orbit,  to  form 
the  angular  vein. 

The  supra-orbital  vein  commences  on  the  forehead,  communicating  with  the 
anterior  temporal  vein,  and  runs  downward  and  inward,  superficial  to  the 
Occipito-frontalis  muscle,  receiving  tributaries  from  the  neighboring  structures, 
and  joins  the  frontal  vein  at  the  inner  angle  of  the  orbit  to  form  the  angular 
vein. 

The  angular  vein,  formed  by  the  junction  of  the  frontal  and  supra-orbital 
veins,  runs  obliquely  downward  and  outward  on  the  side  of  the  root  of  the  nose, 
and  receives  the  veins  of  the  ala  nasi  on  its  inner  side  and  the  superior  palpebral 
veins  on  its  outer  side ;  it  moreover  communicates  with  the  ophthalmic  vein,  thus 


596  THE   BLOOD-VASCULAR    SYSTEM. 

establishing  an  important  anastomosis  between  this  vessel  and  the  cavernous  sinus. 
Some  small  veins  from  the  dorsum  of  the  nose  terminate  in  the  nasal  arch. 

The  Facial  Vein  commences  at  the  side  of  the  root  of  the  nose,  being  a  direct 
continuation  of  the  angular  vein.  It  lies  behind  and  follows  a  less  tortuous 
course  than  the  facial  artery.  It  passes  obliquely  downward  and  outward, 
beneath  the  Zygomaticus  major  and  minor  muscles,  descends  along  the  anterior 
border  of  the  Masseter,  crosses  over  the  body  of  the  lower  jaw,  with  the  facial 
artery,  and,  passing  obliquely  outward  and  backward,  beneath  the  Platysma 
and  cervical  fascia,  unites  with  the  anterior  division  of  the  temporo-m axillary  vein, 
to  form  a  trunk  of  large  size  {common  facial  vein),  which  enters  the  internal 
jugular.  From  near  its  termination  a  comniunicatin«;  branch  often  runs  down  the 
anterior  border  of  the  Sterno-mastoid  to  join  the  lower  part  of  the  anterior  jugular. 

Tributaries. — The  facial  vein  receives,  near  .the  angle  of  the  mouth,  communi- 
cating tributaries  of  considerable  size  (the  deep  facial  or  anterior  internal  maxil- 
lary vein)  from  the  pterygoid  plexus.  It  is  also  joined  by  the  inferior  palpebral, 
the  superior  and  inferior  labial  veins,  the  buccal  veins  from  the  cheek,  and  the 
masseteric  veins.  Below  the  jaw  it  receives  the  submental ;  the  inferior  palatine, 
which  returns  the  blood  from  the  plexus  around  the  tonsil  and  soft  palate ;  the 
submaxillary  vein,  which  commences  in  the  submaxillary  gland  ;  and,  generally, 
the  ranine  vein. 

Surgical  Anatomy. — There  are  some  points  about  the  facial  vein  which  render  it  of  great 
importance  in  surgery.  It  is  not  so  flaccid  as  are  most  superficial  veins,  and,  in  consequence  of 
this,  remains  more  patent  when  divided.  It  has,  moreover,  no  valves.  It  communicates  freely 
with  the  intracranial  circulation,  not  only  at  its  commencement  by  its  tributaries,  the  angular 
and  supra-orbital  veins,  communicating  with  the  ophthalmic  vein,  a  tributary  of  the  cavernous 
sinus,  but  also  by  its  deep  branch,  which  communicates  through  the  pterygoid  plexus  with  the 
cavernous  sinus  by  branches  which  pass  through  the  foramen  ovale  and  foramen  lacerum 
medium  (see  page  606).  These  facts  have  an  important  bearing  upon  the_  surgery  of  some 
diseases  of  the  face,  for  on  account  of  its  patency  the  facial  vein  favors  septic  absorption,  and 
therefore  any  phlegmonous  inflammation  of  the  face  following  a  poisoned  woundis  liable  to  set 
up  thrombosis  in  the  facial  vein,  and  detached  portions  of  the  clot  may  give  rise  to  purulent 
foci  in  other  parts  of  the  body.  And  on  account  of  its  communications  with  the  cerebral  sinuses 
these  thrombi  are  apt  to  extend  upward  into  them  and  so  induce  a  false  issue. 

The  Temporal  Vein  commences  by  a  minute  plexus  on  the  side  and  vertex  of 
the  skull,  which  communicates  with  the  frontal  and  supra-orbital  veins  in  front, 
the  corresponding  vein  of  the  opposite  side,  and  the  posterior  auricular  and 
occipital  veins  behind.  From  this  network  anterior  and  posterior  branches  are 
formed  Avhich  unite  above  the  zygoma,  forming  the  trunk  of  the  vein.  This 
trunk  is  joined  in  this  situation  by  a  large  vein,  the  middle  temporal,  which 
receives  the  blood  from  the  substance  of  the  Temporal  muscle  and  pierces  the 
fascia  at  the  upper  border  of  the  zygoma.  The  temporal  vein  then  descends 
between  the  external  auditory  meatus  and  the  condyle  of  the  jaw,  enters  the  sub- 
stance of  the  parotid  gland,  and  unites  with  the  internal  maxillary  vein  to  form 
the  temporo-maxillary   vein. 

Tributaries. — The  temporal  vein  receives  in  its  course  some  parotid  veins,  an 
articular  branch  from  the  articulation  of  the  jaw,  anterior  auricular  veins  from 
the  external  ear,  and  a  vein  of  large  size,  the  transverse  facial,  from  the  side  of 
the  face.  The  middle  temporal  vein,  previous  to  its  junction  with  the  temporal 
vein,  receives  a  branch,  the  orbital  vein,  which  is  formed  by  some  external  palpe- 
bral branches,  and  passes  backward  between  the  layers  of  the  temporal  fascia. 

The  Internal  Maxillary  Vein  is  a  vessel  of  considerable  size,  receiving  branches 
which  correspond  with  those  of  the  internal  maxillary  artery.  Thus  it  receives 
the  middle  meningeal  veins,  the  deep  temporal,  the  pterygoid,  masseteric,  buccal, 
alveolar,  some  palatine  veins,  and  the  inferior  dental.  These  branches  form  a 
large  plexus,  the  pterygoid,  which  is  placed  between  the  Temporal  and  External 
pterygoid  and  partly  between  the  Pterygoid  muscles.  This  plexus  communicates 
very  freely  with  the  facial  vein  and  with  the  cavernous  sinus  by  branches  through 
the  foramen  Vesalii,  foramen  ovale,  and  foramen  lacerum  medium,  at  the  base  of 


THE    VEINS    OF    THE  NECK.  597 

the  skull.  The  trunk  of  the  vein  fchen  passes  backward  behind  the  neck  of  the 
lower  jaw,  and  unites  with  the  vein,  forming  the  temporo-maxillary  vein. 

The  Temporo-maxillary  "Vein,  formed  by  the  union  of  the  temporal  and 
internal  maxillary  veins,  descends  in  the  substance  of  the  parotid  gland  on  the 
outer  surface  of  the  external  carotid  artery,  between  the  ramus  of  the  jaw  and 
the   Sterno-mastoid   muscle,    a  les    into  two   branches,  an  anterior,  which 

passes  inward  to  join  the  facial  vein,  and  a  posterior,  which  is  joined  by  the  poste- 
rior auricular  vein  and  becomes  the  external  jugular. 

The  Posterior  Auricular  Vein  commences  upon  the  side  of  the  head  by  a  plexus 
which  communicates  with  the  tributaries  of  the  temporal  and  occipital  veins. 
The  vein  descends  behind  the  external  ear  and  joins  the  posterior  division  of  the 
temporo-maxillary  vein,  forming  the  external  jugular.  This  vessel  receives  the 
stylo-mastoid  vein  and  some  tributaries  from  the  back  part  of  the  external  ear. 

The  Occipital  Veins  commence  at  the  back  part  of  the  vertex  of  the  skull  by 
a  plexus  in  a  similar  manner  to  the  other  veins.  These  unite  and  form  one  or 
two  veins,  which  follow  the  course  of  the  occipital  artery,  passing  deeply  beneath 
the  muscles  of  the  back  part  of  the  neck,  and  terminate  in  the  internal  jugular, 
occasionally  in  the  external  jugular  vein.  aI  these  veins  pass  across  the  mastoid 
portion  of  the  temporal  bone,  one  of  them  receives  the  mastoid  vein,  which  thus 
establishes  a  communication  with  the  lateral  sinus. 

The  Veins  of  the  Neck. 

The  veins  of  the  neck,  which  return  the  blood  from  the  head  and  face,  are — the 

External  Jugular.  Anterior  Jugular. 

Posterior  External  Jugular.  Internal  Jugular. 

Vertebral. 

The  External  Jugular  Vein  receives  the  greater  part  of  the  blood  from  the 
exterior  of  the  cranium  and  ^deep  parts  of  the  face,  being  formed  by  the  junction  of 
the  posterior  division  of  the  temporo-maxillary  and  posterior  auricular  veins.  It 
commences  in  the  substance  of  the  parotid  gland,  on  a  level  with  the  angle  of  the 
lower  jaw,  and  runs  perpendicularly  down  the  neck  in  the  direction  of  a  line 
drawn  from  the  angle  of  the  jaw  to  the  middle  of  the  clavicle.  In  its  course  it 
crosses  the  Sterno-mastoid  muscle,  and  runs  parallel  with  its  posterior  border  as 
far  as  its  attachment  to  the  clavicle,  where  it  perforates  the  deep  fascia,  and 
terminates  in  the  subclavian  vein,  on  the  outer  side  of  or  in  front  of  the  Scalenus 
anticus  muscle.  In  the  neck  it  is  separated  from  the  Sterno-mastoid  by  the  invest- 
ing layer  of  the  deep  cervical  fascia,  and  is  covered  by  the  Platysma,  the  superficial 
fascia,  and  the  integument.  This  vein  is  crossed  about  its  middle  by  the  super- 
ficialis  colli  nerve,  and  its  upper  half  is  accompanied  by  the  auricularis  magnus 
nerve.  The  external  jugular  vein  varies  in  size,  bearing  an  inverse  proportion  to 
that  of  the  other  veins  of  the  neck  ;  it  is  occasionally  double.  It  is  provided  with 
two  pairs  of  valves,  the  lower  pair  being  placed  at  its  entrance  into  the  subclavian 
vein,  the  upper  pair  in  most  cases  about  an  inch  and  a  half  above  the  clavicle. 
The  portion  of  vein  between  the  two  sets  of  valves  is  often  dilated,  and  is  termed 
the  sinus.  These  valves  do  not  prevent  the  regurgitation  of  the  blood  or  the 
passage  of  injection  from  below  upward.1 

Surgical  Anatomy.— Venesection  used  formerly  to  be  performed  on  the  external  jugular 
vein,  but  is  now  probably  never  resorted  to.  The  anatomical  point  to  be  remembered  m  per- 
forming this  operation  is  to  cut  across  the  fibres  of  the  Platysma  myoides  in  opening  the  vein, 
so  that  bv  their  contraction  they  will  expose  the  orifice  in  the  vein  and  so  allow  the  flow  ot 

1.1,.-  ] 

Tribiuaries. — T  reives  the  occipital  occasionally,  the  posterior  external 

id   near  ation,  the  suprascapular  and  transverse  cervical  veins. 

ident  may  refer  to  an  interesting  paper  by  Dr.  Strutters,  "  On  Jugular  Venesection   in 
A  ,  atomically  and  -imentally  considered,  including  the  Demonstration  of    Valves  in 

tl  "he  Neck  "  in    hi   Edinburgh  Medical  Journal  for  November,  1856. 


598  THE  BLOOD-VASCULAR   SYSTEM. 

It  communicates  with  the  anterior  jugular,  and,  in  the  substance  of  the  parotid, 
receives  a  large  branch  of  communication  from  the  internal  jugular. 

The  Posterior  External  Jugular  Vein  commences  in  the  occipital  region,  and 
returns  the  blood  from  the  integument  and  superficial  muscles  in  the  upper  and 
back  part  of  the  neck,  lying  between  the  Splenius  and  Trapezius  muscles.  It  runs 
down  the  back  part  of  the  neck,  and  opens  into  the  external  jugular  just  below 
the  middle  of  its  course. 

The  Anterior  Jugular  Vein  commences  near  the  hyoid  bone  from  the  con- 
vergence of  several  superficial  veins  from  the  submaxillary  region.  It  passes 
down  between  the  median  line  and  the  anterior  border  of  the  Sterno-mastoid, 
and  at  the  lower  part  of  the  neck  passes  beneath  that  muscle  to  open  into  the 
termination  of  the  external  jugular  or  into  the  subclavian  vein  (Fig.  331).  This 
vein  varies  considerably  in  size,  bearing  almost  always  an  inverse  proportion  to  the 
external  jugular.  Most  frequently  there  are  two  anterior  jugulars,  a  right  and 
left,  but  occasionally  only  one.  This  vein  receives  some  laryngeal  veins,  and 
occasionally  a  small  thyroid  vein.  Just  above  the  sternum  the  two  anterior 
jugular  veins  communicate  by  a  transverse  trunk,  which  receives  tributaries  from 
the  inferior  thyroid  veins.  It  also  communicates  with  the  internal  jugular.  There 
are  no  valves  in  this  vein. 

The  Internal  Jugular  Vein  collects  the  blood  from  the  interior  of  the  cranium, 
from  the  superficial  parts  of  the  face,  and  from  the  neck.  It  commences  just 
external  to  the  jugular  foramen,  at  the  base  of  the  skull,  being  formed  by  the 
coalescence  of  the  lateral  and  inferior  petrosal  sinuses  (Fig.  329).  At  its  origin  it 
is  somewhat  dilated,  and  this  dilatation  is  called  the  sinus,  or  gulf,  of  the  internal 
jugular  vein.  It  runs  down  the  side  of  the  neck  in  a  vertical  direction,  lying  at 
first  on  the  outer  side  of  the  internal  carotid,  and  then  on  the  outer  side  of  the 
common  carotid,  and  at  the  root  of  the  neck  unites  with  the  subclavian  vein  to 
form  the  innominate  vein.  The  internal  jugular  vein,  at  its  commencement,  lies 
upon  the  Rectus  capitis  lateralis,  and  behind  the  internal  carotid  artery  and  the 
nerves  passing  through  the  jugular  foramen  ;  lower  down,  the  vein  and  artery  lie 
upon  the  same  plane,  the  glosso-pharyngeal  and  hypoglossal  nerves  passing  forward 
between  them  ;  the  pneumogastric  descends  between  and  behind  them  in  the  same 
sheath,  and  the  spinal  accessory  passes  obliquely  outward,  behind  or  in  front  of, 
the  vein.  At  the  root  of  the  neck  the  vein  of  the  right  side  is  placed  at  a  little 
distance  from  the  artery ;  on  the  left  side  it  usually  lies  over  the  artery  at  its 
lower  part.  The  right  internal  jugular  vein  crosses  the  first  part  of  the  subclavian 
artery.  The  vein  is  of  considerable  size,  but  varies  in  different  individuals,  the 
left  one  being  usually  the  smaller.  It  is  provided  with  a  pair  of  valves,  which 
are  placed  at  its  point  of  termination  or  from  half  to  three-quarters  of  an  inch 
above  it. 

Tributaries. — This  vein  receives  in  its  course  the  facial,  lingual,  pharyngeal, 
superior  and  middle  thyroid  veins,  and  sometimes  the  occipital.  At  its  point  of 
junction  with  the  common  facial  vein  it  becomes  greatly  increased  in  size. 

The  lingual  veins  commence  on  the  dorsum,  sides,  and  under  surface  of  the 
tongue,  and,  passing  backward,  following  the  course  of  the  lingual  artery  and  its 
branches,  terminate  in  the  internal  jugular.  Sometimes  the  ranine  vein,  which  is 
a  branch  of  considerable  size  commencing  below  the  tip  of  the  tongue,  joins  the 
lingual.  Generally,  however,  it  passes  backward,  crosses  the  Hyo-glossus  muscle 
in  company  with  the  hypoglossal  nerve,  and  joins  the  facial. 

The  pharyngeal  vein  commences  in  a  minute  plexus,  the  pharyngeal,  at  the 
back  part  and  sides  of  the  pharynx,  and,  after  receiving  meningeal  tributaries 
and  the  Vidian  and  spheno-palatine  veins,  terminates  in  the  internal  jugular.  It 
occasionally  opens  into  the  facial,  lingual,  or  superior  thyroid  vein. 

The  superior  thyroid  vein  commences  in  the  substance  and  on  the  surface  of 
the  thyroid  gland  by  tributaries  corresponding  with  the  branches  of  the  superior 
thyroid  artery,  and  terminates  in  the  upper  part  of  the  internal  jugular  vein.  It 
receives  the  superior  laryngeal  and  crico-thyroid  veins. 


THE    VEINS    OF    THE   DIPLOE.  599 

The  middle  thyroid  vein  collects  the  blood  from  the  lower  part  of  the  lateral 
lobe  of  the  Lb  -oid  gland,  and,  being  joined  by  some  veins  from  the  larynx  and 
trache       ermi nates  in  the  lower  part  of  the  internal  jugular  vein. 

The  facial    nd  occipital  veins  have  been  described  above. 

?  ;cal  Aiatomy. — The  internal  jugular  vein  occasionally  requires  ligature  in  cases  of 
septic  thrombosis  of  the  lateral  sinus  from  suppuration  in  the  middle  ear,  in  order  to  prevent 
septic  emboli  being  carried  into  the  general  circulation.  This  operation  has  been  performed 
recently  in  several  cases,  with  the  most  satisfactory  results.  The  cases  are  generally  those  of 
chronic  disease  of  the  middle  ear,  with  discharge  of  pus  which  perhaps  has  existed  for  many 
years.  The  patient  is  seized  with  acute  septic  inflammation,  spreading  to  the  mastoid  cells, 
and  consequent  on  this,  septic  thrombosis  of  the  lateral  sinus  extending  to  the  internal  jugular 
vein.  Such  cases  are  always  extremely  grave,  for  there  is  a  danger  of  a  portion  of  the  septic 
clot  being  detached  and  causing  septic  embolism  in  the  thoracic  viscera.  If  the  condition  is 
suspected,  the  sinus  should  be  at  once  explored  by  trephining  at  a  point  an  inch  behind  the 
centre  of  the  external  auditory  meatus  and  a  quarter  of  an  inch  above  Reid's  base  line.  The 
condition  of  the  sinus  is  then  investigated,  and  if  it  is  found  to  be  thrombosed,  the  surgeon 
should  at  once  proceed  to  ligate  the  internal  jugular  vein,  by  an  incision  along  the  anterior 
border  of  the  sterno-mastoid,  the  centre  of  which  is  on  a  level  with  the  greater  cornu  of  the 
hyoid  bone.  The  vein  should  be  ligated  in  two  places  and  divided  between.  After  the  vessel 
has  been  secured  and  divided,  the  lateral  sinus  is  to  be  thoroughly  cleared  out,  and  by  removing 
the  ligature  from  the  upper  end  of  the  divided  vein,  all  septic  clots  removed  by  syringing  from 
the  sinus  through  the  vein.  If  hemorrhage  occurs  from  the  distal  end  of  the  sinus,  it  can  be 
arrested  by  careful  plugging  with  antiseptic  gauze. 

The  Vertebral  Vein  commences  in  the  occipital  region  by  numerous  small 
tributaries  from  the  deep  muscles  at  the  upper  and  back  part  of  the  neck  ;  these 
pass  outward  and  enter  the  foramen  in  the  transverse  process  of  the  atlas,  and 
descend,  forming  a  dense  plexus  around  the  vertebral  artery  in  the  canal  formed 
by  the  foramina  in  the  transverse  processes  of  the  cervical  vertebrae.  This 
plexus  unites  at  the  lower  part  of  the  neck  into  two  main  trunks,  one  of  which 
emerges  from  the  foramen  in  the  transverse  process  of  the  sixth  cervical  vertebra, 
and  the  other  through  that  of  the  seventh,  and,  uniting,  form  a  single  vessel, 
which  terminates  at  the  root  of  the  neck  in  the  back  part  of  the  innominate  vein 
near  its  origin,  its  mouth  being  guarded  by  a  pair  of  valves.  On  the  right  side 
it  crosses  the  first  part  of  the  subclavian  artery. 

Tributaries. — The  vertebral  vein  receives  in  its  course  a  vein  from  the  inside 
of  the  skull  through  the  posterior  condyloid  foramen ;  muscular  veins  from  the 
muscles  in  the  prevertebral  region ;  dorsi-spinal  veins,  from  the  back  part  of  the 
cervical  portion  of  the  spine ;  meningo-rachidian  veins,  from  the  interior  of  the 
spinal  canal ;  the  anterior  and  posterior  vertebral  veins ;  and  close  to  its  termina- 
tion it  is  joined  by  a  small  vein  from  the  first  intercostal  space  which  accompanies 
the  superior  intercostal  artery. 

The  anterior  vertebral  vein  commences  in  a  plexus  around  the  transverse  pro- 
cesses of  the  upper  cervical  vertebrae,  descends  in  company  with  the  ascending 
cervical  artery  between  the  Scalenus  anticus  and  Rectus  capitis  anticus  major 
muscles,  and  opens  into  the  vertebral  vein  just  before  its  termination. 

The  posterior  vertebral  vein  (the  deep  cervical)  accompanies  the  profunda  cer- 
vicis  artery,  lying  between  the  Complexus  and  Semispinalis  colli.  It  commences 
in  the  suboccipital  region  by  communicating  branches  from  the  occipital  vein  and 
tributaries  from  the  deep  muscles  at  the  back  of  the  neck.  It  receives  tribu- 
taries from  the  plexuses  around  the  spinous  processes  of  the  cervical  vertebrae,  and 
terminates  in  the  lower  end  of  the  vertebral  vein. 

The  Veins  of  the  Diploe. 

The  diploe  of  the  cranial  bones  is  channelled  in  the  adult  by  a  number  of 
tortuous  canals,  which  are  lined  by  a  more  or  less  complete  layer  of  compact 
tissi 

The  veins  they  contain  are  large  and  capacious,  their  walls  being  thin,  and 
form  nly  of  endothelium  resting  upon  a  layer  of  elastic  tissue,  and  they  pre- 
sent at  irregular  intervals   pouch-like  dilatations,  or  culs-de-sac,  which  serve  as 


600 


THE    BLOOD-VASCULAR   SYSTEM. 


reservoirs  for  the  blood.     These  are  the  veins  of  the  diploe' ;  they  can  only  be 
displayed  by  removing  the  outer  table  of  the  skull. 

In  adult  life,  as  long  as  the  cranial  bones  are  distinct  and  separable,  these 
veins  are  confined  to  the  particular  bones ;  but  in  old  age,  -when  the  sutures  are 
united,  they  communicate  with  each  other  and  increase  in  size.  These  vessels 
communicate,  in  the  interior  of  the  cranium,  with  the  meningeal  veins  and  with 
the  sinuses  of  the  dura  mater,  and  on  the  exterior  of  the  skull  with  the  veins  of 
the  pericranium.  They  are  divided  into  the  frontal,  which  opens  into  the  supra- 
orbital vein  by  an  aperture  in  the  supra-orbital  notch  ;  the  anterior  temporal, 
which  is  confined  chiefly  to  the  frontal  bone,  and  opens  into  one  of  the  deep 
temporal  veins,  after  escaping  by  an  aperture  in  the  great  wing  of  the  sphenoid  ; 


Fig.  325.— Veins  of  the  Diploe  as  displayed  by  the  removal  of  the  outer  table  of  the  skull. 


the  posterior  temporal,  which  is  confined  to  the  parietal  bone,  and  terminates  in 
the  lateral  sinus  by  an  aperture  at  the  posterior  inferior  angle  of  the  parietal 
bone  ;  and  the  occipital,  the  largest  of  the  four,  which  is  confined  to  the  occipital 
bone,  and  opens  either  into  the  occipital  vein  or  internally  into  the  lateral  sinus 
or  torcular  Herophili. 

The  Cerebral  Veins. 

The  Cerebral  Veins  are  remarkable  for  the  extreme  thinness  of  their  coats  in 
consequence  of  the  muscular  tissue  in  them  being  wanting,  and  for  the  absence 
of  valves.  They  may  be  divided  into  two  sets :  the  superficial,  which  are  placed 
on  the  surface,  and  the  deep  veins,  which  occupy  the  interior  of  the  organ. 

The  Superficial  Cerebral  Veins  ramify  upon  the  surface  of  the  brain,  being 
lodged  in  the  sulci  between  the  convolutions,  a  few  running;  across  the  convolu- 
tions.  They  receive  branches  from  the  substance  of  the  brain  and  terminate  in 
the  sinuses.  They  are  named,  from  the  position  they  occupy,  superior,  median, 
and  inferior  cerebral  veins. 

The  Superior  Cerebral  Veins,  eight  to  twelve  in  number  on  each  side,  return 
the  blood  from  the  convolutions  on  the  superior  surface  of  the  hemisphere;  they 
pass  forward  and  inward  toward  the  great  longitudinal  fissure,  where  they  receive 
the  median  cerebral  veins  ;  near  their  termination  they  become  invested  with  a 
tubular  sheath  of  the  arachnoid  membrane,  and  open  into  the  superior  longitudi- 
nal sinus  in  the  opposite  direction  to  the  course  of  the  current  of  the  blood. 

The  Median  Cerebral  Veins  return  the  blood  from  the  convolutions  of  the  mesial 


THE  SINUSES    OF    THE   DUB  A    MATER.  601 

surface  of  the  corresponding  hemisphere;    they  open  into  the  superior. cerebral 
veins,  or  occasionally  into  the  inferior  longitudinal  sinus. 

The  Inferior  Cerebral  Veins  ramify  on  the  lower  part  of  the,  outer  and  on 
the  under  surface  of  the  cerebral  hemisphere.  Some,  collecting  tributaries  from 
the  under  surface  of  the  anterior  lobes  of  the  brain,  terminate  in  the  cavernous 
sinus.  One  vein  of  large  size,  the  middle  cerebral  vein,  commences  on  the  under 
surface  of  the  temporal  lobe,  and,  running  along  the  fissure  of  Sylvius,  opens 
into  the  cavernous  sinus.  Another  large  vein,  the  great  anastomotic  vein  of  Tro- 
lard,  commences  on  the  parietal  lobe,  runs  along  the  horizontal  limb  of  the  fissure 
of  Sylvius,  and  opens  into  the  anterior  part  of  the  cavernous  sinus  under  the  lesser 
wino-  of  the  sphenoid.  Others  commence  on  the  under  surface  of  the  base  of  the 
brain,  and  unite  to  form  from  three  to  five  veins,  which  open  into  the  superior 
petrosal  and  lateral  sinuses  from  before  backward. 

The  Deep  Cerebral,  or  Ventricular  Veins  (vena?  Galeni),  are  two  in  number. 
They  are  formed  by  the  union  of  two  veins,  the  vena  corporis  striati,  and  the 
choroid  vein,  on  either  side.  They  run  backward,  parallel  with  one  another, 
between  the  layers  of  the  velum  interpositum,  and  pass  out  of  the  brain  at 
the  great  transverse  fissure,  between  the  posterior  extremity,  or  splenium,  of  the 
corpus  callosum  and  the  tubercula  quadrigemina,  to  enter  the  straight  sinus.  The 
two  veins  usually  unite  to  form  one,  the  vena  magna  Galeni,  before  opening  into 
the  straight  sinus,  just  before  their  union  they  receive  the  basilar  vein. 

The  vena  corporis  striati  commences  in  the  groove  between. the  corpus  striatum 
and  thalamus  opticus,  receives  numerous  veins  from  both  of  these  parts,  and  unites 
behind  the  anterior  pillar  of  the  fornix  with  the  choroid  vein  to  form  one  of  the 
vense  Galeni. 

The  choroid  vein  runs  along  the  whole  length  of  the  outer  border  of  the  choroid 
plexus,  receiving  veins  from  the  hippocampus  major,  the  fornix  and  corpus  callosum, 
and  unites,  at  the  anterior  extremity  of  the  choroid  plexus,  with  the  vein  of  the 
corpus  striatum. 

The  Basilar  vein  commences  at  the  anterior  perforated  space  at  the  base  of  the 
brain  by  the  union  of  a  small  anterior  cerebral  vein,  which  courses  backward 
between  the  anterior  lobes  of  the  cerebrum,  with  the  deep  Sylvian  vein,  which 
descends  through  the  lower  part  of  the  Sylvian  fissure.  It  passes  backward  round 
the  crus  cerebri,  receiving  the  inferior  striate  vein  from  the  corpus  striatum,  inter- 
peduncular veins  from  the  interpeduncular  space,  ventricular  veins  from  the  middle 
cornu  of  the  lateral  ventricles,  and  tributaries  from  the  uncinate  convolution,  and 
enters  the  vein  of  Galen  just  before  its  junction  with  the  vein  of  the  opposite  side. 

The  Cerebellar  veins  occupy  the  surface  of  the  cerebellum,  and  are  disposed 
in  three  sets,  superior,  inferior,  and  lateral.  The  superior  pass  partly  forward 
and  inward,  across  the  superior  vermiform  process,  to  terminate  in  the  straight 
sinus  and  the  venae  Galeni,  partly  outward  to  the  lateral  and  superior  petrosal 
sinuses.  The  inferior  cerebellar  veins,-  of  large  size,  terminate  in  the  lateral, 
superior  petrosal,  and  occipital  sinuses. 

The  perivascular  lymphatics  alluded  to  in  the  section  on  General  Anatomy  are  especially 
found  in  connection  with  the  vessels  of  the  brain.  These  vessels  are  enclosed  in  a  sheath, 
which  acts  as  a  lymphatic  channel,  through  which  the  lymph  is  carried  to  the  subarachnoid 
and  subdural  spaces,  from  which  it  is  returned  into  the  general  circulation. 

The  Sinuses  of  the  Dura  Mater. 

The  sinuses  of  the  dura  mater  are  venous  channels,  analogous  to  the  veins,  their 
outer  coat  being  formed  by  the  dura  mater  ;  their  inner,  by  a  continuation  of  the 
lining  membrane  of  the  veins.  They  are  fourteen  in  number,  and  are  divided  into 
two  sets  :  1,  those  situated  at  the  upper  and  back  part  of  the  skull ;  2,  those  at 
the  base  of  the  skull.     The  former  are — the 

Superior  Longitudinal  Sinus.  Straight  Sinus. 

Inferior  Longitudinal  Sinus.  Lateral  Sinuses. 

Occipital  Sinus. 


602  THE   BLOOD-VASCULAR   SYSTEM. 

The  Superior  Longitudinal  Sinus  occupies  the  attached  margin  of  the  falx 
cerebri.  Commencing  at  the  foramen  caecum,  through  which,  in  the  child,  it  con- 
stantly communicates  by  a  small  branch  with  the  veins  of  the  nasal  fossae,  it  runs 
from  before  backward,  grooving  the  inner  surface  of  the  frontal,  the  adjacent 
margins  of  the  two  parietal,  and  the  superior  division  of  the  crucial  ridge  of  the 
occipital  bone,  and  terminates  by  opening  into  the  torcular  Herophili.  The  sinus 
is  triangular  in  form,  narrow  in  front,  and  gradually  increases  in  size  as  it  passes 
backward.  On  examining  its  inner  surface  it  presents  the  internal  openings  of  the 
superior  cerebral  veins,  which  run,  for  the  most  part,  from  behind  forward,  and 
open  chiefly  at  the  back  part  of  the  sinus,  their  orifices  being  concealed  by  fibrous 
folds  ;  numerous  fibrous  bands  (chorda?  Willisii)  are  also  seen,  extending  transversely 
across  the  inferior  angle  of  the  sinus:  and,  lastly,  some  small,  white,  projecting 
bodies,  the  glandula?  Pacchioni.  This  sinus  receives  the  superior  cerebral  veins, 
numerous  veins  from  the  diploe  and  dura  mater,  and,  at  the  posterior  extremity 
of  the  sagittal  suture,  veins  from  the  pericranium,  which  pass  through  the  parietal 
foramina. 

The  torcular  Heroi^hili,  or  confluence  of  the  sinuses,  is  the  dilated  extremity  of 
the  superior  longitudinal  sinus.  It  is  of  irregular  form,  and  is  lodged  on  one  side 
(generally  the  right)  of  the  internal  occipital  protuberance.  From  it  the  lateral 
sinus  of  the  side  to  which  it  is  deflected  is  derived.  It  receives  also  the  blood  from 
the  occipital  sinus. 

The  Inferior  Longitudinal  Sinus,  more  correctly  described  as  the  inferior  longi- 
tudinal vein,  is  contained  in  the  posterior  part  of  the  free  margin  of  the  falx 
cerebri.  It  is  of  a  cylindrical  form,  increases  in  size  as  it  passes  backward,  and 
terminates  in  the  straight  sinus.  It  receives  several  veins  from  the  falx  cerebri, 
and  occasionally  a  few  from  the  mesial  surface  of  the  hemispheres. 

The  Straight  Sinus  is  situated  at  the  line  of  junction  of  the  falx  cerebri  with 
the  tentorium.  It  is  triangular  in  form,  increases  in  size  as  it  proceeds  backward, 
and  runs  obliquely  downward  and  backward  from  the  termination  of  the  inferior 
longitudinal  sinus  to  the  lateral  sinus  of  the  opposite  side  to  that  into  which  the 
superior  longitudinal  sinus  is  prolonged.     It  communicates  by  a  cross  branch 


Torcular  herophili 


Foramen  csecum. 


IS 


Fig.  326.— Vertical  section  of  the  skull,  showing  the  sinuses  of  the  dura  mater. 


with  the  torcular  Herophili.  Beside  the  inferior  longitudinal  sinus,  it  receives 
the  venae  Galeni  and  the  superior  cerebellar  veins.  A  few  transverse  bands  cross 
its  interior. 

The  Lateral  Sinuses  are  of  large  size,  and  are  situated  in  the  attached  margin 
of  the  tentorium  cerebelli.    They  commence  at  the  internal  occipital  protuberance, 


THE  SINUSES    OF    THE   DURA    MATER. 


603 


one,  generally  the  right,  being  the  direct  continuation  of  the  superior  longi- 
tudinal sinus,  the  other  of  the  straight  sinus.  They  pass  outward  and  forward, 
describing  a  slight  curve  with  its  convexity  upward,  to  the  base  of  the  petrous 
portion  of  the  temporal  bone,  then  curve  downward  and  inward  on  each  side 
to  reach  the  jugular  foramen,  where  they  terminate  in  the  internal  jugular 
vein.  Each  sinus  rests,  in  its  course,  upon  the  inner  surface  of  the  occipital, 
the  posterior  inferior  angle  of  the  parietal,  the  mastoid  portion  of  the  temporal, 
and  on  the  occipital  again  just  before  its  termination.  These  sinuses  are  frequently 
of  unequal  size,  that  formed  by  the  superior  longitudinal  sinus  being  the  larger,  and 
they  increase  in  size  as  they  proceed  from  behind  forward.  The  horizontal  portion 
is  of  a  triangular  form,  the  curved  portion  semicylindrical.  Their  inner  surface  is 
smooth,  and  not  crossed  by  the  fibrous  bands  found  in  the  other  sinuses. 
These  sinuses  receive  the  blood  from  the  superior  petrosal  sinuses  at  the 
base  of  the  petrous  portion  of  the  temporal  bone,  and  they  unite  with  the 
inferior  petrosal  sinus,  just  external  to  the  jugular  foramen,  to  form  the  internal 
jugular  vein  (Fig.  329).  They  communicate  with  the  veins  of  the  pericranium 
by  means  of  the  mastoid  and  posterior  condyloid  veins,  and  they  receive  some  of 
the  inferior  cerebral  and  inferior  cerebellar  veins  and  some  veins  from  the  diploe. 
The  petrosquamous  sinus,  when  present,  runs  backward  along  the  junction  of 
the  petrous  and  squamous-temporal,  and  opens  into  the  lateral  sinus. 

The  Occipital  is  the  smallest  of  the  cranial  sinuses.  It  is  generally  single,  but 
occasionally  there  are  two.  It  is  situated  in  the  attached  margin  of  the  falx  cere- 
belli.  It  commences  by  several  small  veins  around  the  margin  of  the  foramen 
magnum,  one  of  which  joins  the  termination  of  the  lateral  sinus  ;  it  communicates 
with  the  posterior  spinal  veins  and  terminates  in  the  torcular  Herophili. 

The  sinuses  at  the  base  of  the  skull  are — the 

Cavernous  sinuses.  ^  Superior  Petrosal  sinuses. 

Circular  sinus.  s  Inferior  Petrosal  sinuses.  ^ 

Transverse  sinus,      is 

The  Cavernous  Sinuses  are  named  from  their  presenting  a  reticulated  structure, 
due  to  their  being  traversed  by  numerous  interlacing  filaments.  They  are  two  in 
number,  of  irregular  form,  larger  behind  than  in  front,  and  are  placed  one  on  each  side 


Dura  mater  lining' 
pituitary  fossa 


Sixth  nerve. 


'Lining  membrane  of  sinus. 
'Third  nerve. 


Internal  carotid 


Fourth  nerve. 

First  division  of  fifth  nerve. 


Fig.  327.— Plan  showing  the  relative  position  of  the  structures  in  the  right  cavernous  sinus,  viewed  from 
behind. 

of  the  sella  turcica,  extending  from  the  sphenoidal  fissure  to  the  apex  of  the  petrous 
portion  of  the  temporal  bone ;  they  receive  anteriorly  the  ophthalmic  vein  through 
the  sphenoidal  fissure,  and  open  behind  into  the  petrosal  sinuses.  On  the  inner 
wall  of  each  sinus  is  found  the  internal  carotid  artery,  accompanied  by  filaments  of 
the  carotid  plexus  and  by  the  sixth  nerve ;  and  on  its  outer  wall,  the  third,  fourth, 
and  ophthalmic  division  of  the  fifth  nerve.  These  parts  are  separated  from  the 
blood  flowing  along  the  sinus  by  the  lining  membrane,  which  is  continuous  with  the 
inner  coat  of  the  veins.  The  cavernous  sinuses  receive  some  of  the  cerebral  veins, 
and  also  a  small  sinus,  the  sjjheno-parietal,  which  extends  inward  on  the  under 
aspect  of  the  lesser  wing  of  the  sphenoid ;  they  communicate  with  the  lateral 
sinuses  by  means  of  the  superior  and  inferior  petrosal  sinuses,  and  with  the  facial 
vein  through  the  ophthalmic  vein.  They  also  communicate  with  each  other  by 
means  of  the  circular  sinus. 


604 


THE   BLOOD-VASCULAR   SYSTEM. 


Surgical  Anatomy. — An  arteriovenous  communication  may  be  established  between  the 
cavernous  sinus  and  the  carotid  artery,  as  it  lies  in  it,  giving  rise  to  a  pulsating  tumor  in  the 
orbit.  These  communications  may  be  the  result  of  injury,  such  as  a  bullet  wound,  a  stab,  or  a 
blow  or  fall  sufficiently  severe  to  cause  a  fracture  of  the  base  of  the  skull  in  this  situation,  or 
they  may  occur  idiopathically  from  the  rupture  of  an  aneurism  or  a  diseased  condition  of  the 
internal  carotid  artery.  The  disease  begins  with  sudden  noise  and  pain  in  the  head,  followed  by 
exophthalmos,  swelling,  and  congestion  of  the  lids  and  conjunctivse.  and  development  of  a 
pulsating  tumor  at  the  margin  of  the  orbit,  with  thrill  and  the  characteristic  bruit ;  accompany- 
ing these  symptoms  there  niay  be  impairment  of  sight,  paralysis  of  the  iris  and  orbital  muscles, 
and  pain  of  varying  intensity.  In  some  cases  the  opposite  orbit  becomes  affected  by  the  pas- 
sage of  the  arterial  blood  into  the  opposite  sinus  by  means  of  the  circular  sinus.  Or  the  arterial 
blood  may  find  its  way  through  the  emissary  veins  (see  page  605)  into  the  pterygoid  plexus,  and 
thence  into  the  veins  of  the  face.  Pulsating  tumors  of  the  orbit  may  also  be  due  to  traumatic 
aneurism  of  one  of  the  orbital  arteries,  and  symptoms  resembling  those  of  pulsating  tumor  may 
be  produced  by  pressure  on  the  ophthalmic  vein,  as  it  enters  the  sinus,  by  an  aneurism  of  the 
internal  carotid  artery. 

The  Ophthalmic  Veins  are  two  in  number,  superior  and  inferior. 

The  superior  ophthalmic  vein  connects  the  angular  vein  at  the  inner  angle  of 
the  orbit  with  the  cavernous  sinus ;  it  pursues  the  same  course  as  the  ophthalmic 
artery,  and  receives  tributaries  corresponding  to  the  branches  derived  from  that 
vessel.  Forming  a  short  single  trunk,  it  passes  through  the  inner  extremity  of 
the  sphenoidal  fissure,  and  terminates  in  the  cavernous  sinus. 


Opening  of  mastoid 
vein. 


1  Torcular  Herophili. 
Fig.  328.— The  sinuses  at  the  base  of  the  skull. 

The  inferior  ophthalmic  vein  receives  the  veins  from  the  floor  of  the  orbit,  and 
either  passes  out  of  the  orbit  through  the  spheno-maxillary  fissure  to  join  the 
pterygoid  plexus  of  veins,  or  else,  passing  backward  through  the  sphenoidal 
fissure,  it  enters  the  cavernous  sinus,  either  by  a  separate  opening,  or,  more 
frequently,  in  common  with  the  superior  ophthalmic  vein. 

The  Circular  sinus  is  formed  by  two  transverse  vessels,  the  anterior  and  posterior 
intercavernous  sinuses,  which  connect  together  the  two  cavernous  sinuses ;  the  one 
passing  in  front  and  the  other  behind  the  pituitary  body,  and  thus  forming  with  the 
cavernous  sinuses  a  venous  circle  around  that  body.  The  anterior  one  is  usually 
the  larger  of  the  two,  and  one  or  other  is  occasionally  found  to  be  absent. 

The  Superior  petrosal  sinus  is  situated  along  the  superior  border  of  the  petrous 
portion  of  the  temporal  bone,   in  the  front  part  of  the  attached    margin  of  the 


THE  SINUSES    OF    THE   DURA    MATER. 


605 


tentorium.  It  is  small  and  narrow,  and  connects  together  the  cavernous  and 
lateral  sinuses  at  each  side.  It  receives  some  cerebellar  and  inferior  cerebral  veins, 
and  veins  from  the  tympanic  cavity. 

The  Inferior  petrosal  sinus  is  situated  in  the  groove  formed  by  the  junction  of 
the  posterior  border  of  the  petrous  portion  of  the  temporal  with  the  basilar  process 
of  the  occipital.  It  commences  in  front  at  the  termination  of  the  cavernous  sinus, 
and  behind  joins  the  lateral  sinus  after  it  has  passed  through  the  jugular  foramen  ; 
the  junction  of  these  two  sinuses  forming  the  commencement  of  the  internal  jugu- 
lar vein.  The  inferior  petrosal  sinus  receives  the  veins  from  the  internal  ear  and 
also  veins  from  the  medulla,  pons,  and  under  surface  of  the  cerebellum. 

The  junction  of  the  two  sinuses  takes  place  at  the  lower  border  of.  or  just 
external  to,  the  jugular  foramen.  The  exact  relation  of  the  parts  to  one  another 
in  the  foramen  is  as  follows:  The  inferior  petrosal  sinus  is  in  front,  with  the 
meningeal  branch  of  the  ascending  pharyngeal  artery,  and  is  directed  obliquely 
downward  and  backward ;  the  lateral  sinus  is  situated  at  the  back  part  of  the  fora- 


Inferior 

petrosal  sinus 


Optic  nerve 
Int.  carotid  mien/ 

Motor  ocuti  nerve 


Dorsum  sellw 


9th,  10th,  and  11th 
cranial  nerves 


Lateral  sinus 
Pig.  329. — Relation  of  nerves  to  sinuses  in  jugular  foramen.    (Henle.) 

men  with  a  meningeal  branch  of  the  occipital  artery,  and  between  the  two  are 
the  glosso-pharyngeal,  pneumogastric,  and  spinal  accessory  nerves.  These  three 
sets  of  structures  are  divided  from  each  other  by  two  processes  of  fibrous  tissue. 
The  junction  of  the  sinuses  takes  place  superficial  to  the  nerves,  so  that  these  latter 
lie  a  little  internal  to  the  venous  channels  in  the  foramen  (see  Fig.  829).  These 
sinuses  are  semicylindrical  in  form. 

The  Transverse  Sinus,  or  basilar  sinus,  consists  of  several  interlacing  veins 
between  the  layers  of  the  dura  mater  over  the  basilar  process  of  the  occipital  bone, 
which  serve  to  connect  the  two  inferior  petrosal  sinuses.  With  them  the  anterior 
spinal  veins  communicate. 

Emissary  Veins. — The  emissary  veins  are  vessels  which  pass  through  apertures 


606 


THE   BLOOD-VASCULAR   SYSTEM. 


in  the  cranial  wall  and  establish  communications  between  the  sinuses  inside  the 
skull  and  the  veins  external  to  it.      Some  of  these  are  always  present,  others  only 

occasionally  so.  They  vary  much  in  size 
in  different  individuals.  The  principal 
emissary  veins  are  the  following:  1.  A 
vein,  almost  always  present,  which  passes 
through  the  mastoid  foramen  and  con- 
nects the  lateral  sinus  with  the  posterior 
auricular  or  with  an  occipital  vein.  2.  A 
vein  which  passes  through  the  parietal 
foramen  and  connects  the  superior  longi- 
tudinal sinus  with  the  veins  of  the  scalp. 
3.  A  plexus  of  minute  veins  which  pass 
through  the  anterior  condyloid  foramen 
and  connect  the  occipital  sinus  with  the 
vertebral  vein  and  deep  veins  of  the 
neck.  4.  An  inconstant  vein  which 
passes  through  the  posterior  condyloid 
foramen  and  connects  the  lateral  sinus 
with  the  deep  veins  of  the  neck.  5.  One 
or  two  veins  of  considerable  size  which 
pass  through  the  foramen  ovale  and  con- 
nect the  cavernous  sinus  with  the  ptery- 
goid and  pharyngeal  plexuses.  6.  Two 
or  three  small  veins  which  pass  through 
the  foramen  lacerum  medium  and  connect 
the  cavernous  sinus  with  the  pterygoid 
and  pharyngeal  plexuses.  7.  There  is 
sometimes  a  small  vein  passing  through 
the  foramen  of  Vesalius  connecting  the 
same  parts.  8.  A  plexus  of  veins  pass- 
ing through  the  carotid  canal  and  con- 
necting the  cavernous  sinus  with  the  in- 
ternal jugular  vein. 

Surgical  Anatomy.— These  emissary 
veins  are  of  great  importance  in  surgery.  In 
addition  to  them  there  are,  however,  other  com- 
munications between  the  intra-  and  extra-cra- 
nial circulation,  as,  for  instance,  the  communi- 
cation of  the  angular  and  supra-orbital  veins 
with  the  ophthalmic  vein  at  the  inner  angle  of 
the  orbit  (page  595),  and  the  communication 
of  the  veins  of  the  scalp  with  the  diploic  veins 
(page  599).  Through  these  communications 
inflammatory  processes  commencing  on  the  out- 
side of  the  skull  may  travel  inward,  leading  to 
osteo-phlebitis  of  the  diploe  and  inflammation 
of  the  membranes  of  the  brain.  To  this  in 
former  clays  was  to  be  attributed  one  of  the 
principal  dangers  of  scalp  wounds  and  other 
injuries  of  the  scalp. 

By  means  of  these  emissary  veins  blood 
may  be  abstracted  almost  directly  from  the  intra- 
cranial circulation.  For  instance,  leeches  applied 
behind  the  ear  abstract  blood  almost  directly 
from  the  lateral  sinus  by  means  of  the  vein 
passing  through  the  mastoid  foramen.  Again, 
epistaxis  in  children  will  frequently  relieve  severe 
Fig.  330.— The  superficial  veins  of  the  upper  extremity,    headache,  the  blood  which  flows  from  the  nose 

being  derived  from  the  longitudinal  sinus  by 
means  of  the  vein  which  passes  through  the  foramen  caecum,  which  is  another  communication 
between  the  intracranial  and  extracranial  circulation  which  is  constantly  found  in  children. 


Median  cephalic 

External 
cutaneous  nerve. 


C  Internal 
-j  cutaneous 
(_    nerve. 
Median 
basilic. 


VEINS    OF   THE    UPPER    EXTREMPPY  AND    THORAX.        607 
VEINS  OF  THE  UPPER  EXTREMITY  AND  THORAX. 

The  veins  of  the  Upper  Extremity  are  divided  into  two  sets,  superficial  and  deep. 

The  Superficial  Veins  are  placed  immediately  beneath  the  integument  between 
the  two  layers  of  superficial  fascia. 

The  Deep  Veins  accompany  the  arteries,  and  constitute  the  venae  comites  of 
those  vessels. 

Both  sets  of  vessels  are  provided  with  valves,  which  are  more  numerous  in  the 
deep  than  in  the  superficial. 

The  superficial  veins  of  the  upper  extremity  are — the 

Superficial  veins  of  the  Hand.  Median. 

Anterior  Ulnar.  Median  Cephalic. 

Posterior  Ulnar.  Median  Basilic. 

Common  Ulnar.  Basilic. 

Radial.  Cephalic. 

The  Superficial  Veins  of  the  Hand  and  Fingers  are  principally  situated  on  the 
dorsal  surface,  and  form  two  plexuses,  an  inner  and  outer,  on  the  back  of  the 
hand.  The  inner  plexus  is  formed  by  the  veins  from  the  little  finger  (vena  salva- 
tella),  the  ring  finger,  and  the  ulnar  side  of  the  middle  finger  ;  from  it  the  anterior 
and  posterior  ulnar  veins  are  derived.  The  outer  plexus  is  formed  by  veins  from 
the  thumb,  the  index  finger,  and  radial  side  of  the  middle  finger ;  from  it  the 
radial  vein  is  derived.  These  two  plexuses  communicate  on  the  back  of  the  hand, 
forming  the  superficial  arch  of  veins  in  this  situation.  The  superficial  veins  from 
the  palm  of  the  hand  form  a  plexus  in  front  of  the  wrist,  from  which  the  median 
vein  is  derived. 

The  Anterior  Ulnar  Vein  commences  on  the  anterior  surface  of  the  ulnar  side 
of  the  hand  and  wrist,  and  ascends  along  the  anterior  surface  of  the  ulnar  side  of 
the  forearm  to  the  bend  of  the  elbow,  where  it  joins  with  the  posterior  ulnar  vein 
to  form  the  common  ulnar.  Occasionally  it  opens  separately  into  the  median 
basilic  vein.  It  communicates  with  branches  of  the  median  vein  in  front  and 
with  the  posterior  ulnar  behind. 

The  Posterior  Ulnar  Vein  commences  on  the  posterior  surface  of  the  ulnar  side 
of  the  wrist.  It  runs  on  the  posterior  surface  of  the  ulnar  side  of  the  forearm, 
and  just  below  the  elbow  unites  with  the  anterior  ulnar  vein  to  form  the  common 
ulnar,  or  else  joins  the  median  basilic  to  form  the  basilic.  It  communicates  with 
the  deep  veins  of  the  palm  by  a  branch  which  emerges  from  beneath  the  Abductor 
minimi  digiti  muscle. 

The  Common  Ulnar  is  a  short  trunk  which  is  not  constant.  When  it  exists  it 
is  formed  by  the  junction  of  the  two  preceding  veins,  and,  passing  upward  and 
outward,  joins  the  median  basilic  to  form  the  basilic  vein.  When  it  does  not 
exist  the  anterior  and  posterior  ulnar  veins  open  separately  into  the  median 
basilic  vein. 

The  Radial  Vein  commences  from  the  dorsal  surface  of  the  wrist,  communi- 
cating Avith  the  deep  veins  of  the  palm  by  a  branch  which  passes  through  the 
first  interosseous  space.  It  forms  a  large  vessel,  which  ascends  along  the  radial 
side  of  the  forearm  and  receives  numerous  veins  from  both  its  surfaces.  At 
the  bend  of  the  elbow  it  unites  with  the  median  cephalic  to  form  the  cephalic 
vein. 

The  Median  Vein  ascends  on  the  front  of  the  forearm,  and  communicates  with 
the  anterior  ulnar  and  radial  veins.  At  the  bend  of  the  elbow  it  receives  a  branch 
of  communication  from  the  deep  veins,  and  divides  into  two  branches,  the  median 
cephalic  and  median  basilic,  which  diverge  from  each  other  as  they  ascend. 

The  Median  Cephalic,  usually  the  smaller  of  the  two,  passes  outward  in  the 
groove  between  the  Supinator  longus  and  Biceps  muscles,  and  joins  with  the 
radial  to  form  the  cephalic  vein.  The  branches  of  the  external  cutaneous  nerve 
pass  beneath  this  vessel. 


608  THE  BLOOD- VASCULAR   SYSTEM. 

The  Median  Basilic  Vein  passes  obliquely  inward,  in  the  groove  between  the! 
Biceps  and  Pronator  radii  teres,  and  joins  the  common  ulnar  to  form  the  basilic; 
This  vein  passes  in  front  of  the  brachial  artery,  from  which  it  is  separated  by  a; 
fibrous  expansion  (the  bicipital  fascia)  which  is  given  off  from  the  tendon  of  the' 
Biceps  to  the  fascia  covering  the  Flexor  muscles  of  the  forearm.  Filaments  of 
the  internal  cutaneous  nerve  pass  in  front  as  well  as  behind  this  vessel.1 

Venesection  is  usually  performed  at  the  bend  of  the  elbow,  and  as  a  matter  of  practice  the 
largest  vein  in  this  situation  is  commonly  selected.  This  is  usually  the  median  basilic,  and  there 
are  anatomical  advantages  and  disadvantages  in  selecting  this  vein.  The  advantages  are,  that 
in  addition  to  its  being  the  largest,  and  therefore  yielding  a  greater  supply  of  blood,  it  is  the 
least  movable  and  can  be  easily  steadied  on  the  bicipital  fascia  on  which  it  rests.  The  disadvan- 
tages are,  that  it  is  in  close  relationship  with  the  brachial  artery,  separated  only  by  the  bicipital 
fascia ;  and  formerly,  when  venesection  was  frequently  practised,  arterio-venous  aneurism  was 
no  uncommon  result  of  this  practice.  Another  disadvantage  is,  that  the  median  basilic  is 
crossed  by  some  of  the  branches  of  the  internal  cutaneous  nerve,  and  these  may  be  divided  in 
the  operation,  giving  rise  to  "  traumatic  neuralgia  of  extreme  intensity  "  (Tillaux). 

The  Basilic  Vein  is  of  considerable  size,  formed  by  the  coalescence  of  the  common 
ulnar  vein  with  the  median  basilic.  It  passes  upward  along  the  inner  side  of  the 
Biceps  muscle,  pierces  the  deep  fascia  a  little  below  the  middle  of  the  arm,  and,  ascend- 
ing in  the  course  of  the  brachial  artery  to  the  lower  border  of  the  tendons  of  the  Latis- 
simus  dorsi  and  Teres  major  muscles,  it  is  continued  onward  as  the  axillary  vein. 

The  Cephalic  Vein  courses  along  the  outer  border  of  the  Biceps  muscle,  lying 
in  the  same  groove  with  the  upper  external  cutaneous  branch  of  the  musculo-spiral 
nerve,  to  the  upper  third  of  the  arm ;  it  then  passes  in  the  interval  between  the 
Pectoralis  major  and  Deltoid  muscles,  lying  in  the  same  groove  with  the  descending 
or  humeral  branch  of  the  acromial-thoracic  artery.  It  pierces  the  costo-coracoid 
membrane,  and  crossing  the  axillary  artery,  it  terminates  in  the  axillary  vein  just 
below  the  clavicle.  This  vein  is  occasionally  connected  with  the  external  jugular 
or  subclavian  by  a  branch  which  passes  from  it  upward  in  front  of  the  clavicle. 

The  Deep  Veins  of  the  Upper  Extremity  follow  the  course  of  the  arteries, 
forming  their  venae  comites.  They  are  generally  two  in  number,  one  lying  on 
each  side  of  the  corresponding  artery,  and  they  are  connected  at  intervals  by 
short  transverse  branches. 

There  are  two  digital  veins  accompanying  each  artery  along  the  sides  of  the 
fingers :  these,  uniting  at  their  base,  pass  along  the  interosseous  spaces  in  the 
palm,  and  terminate  in  the  two  venae  comites  which  accompany  the  superficial 
palmar  arch.  Branches  from  these  vessels  on  the  radial  side  of  the  hand  accom- 
pany the  superficialis  volae,  and  on  the  ulnar  side  terminate  in  the  deep  ulnar 
veins.  The  deep  ulnar  veins,  as  they  pass  in  front  of  the  wrist,  communicate  with 
the  interosseous  and  superficial  veins,  and  at  the  elbow  unite  with  the  deep  radial 
veins  to  form  the  venae  comites  of  the  brachial  artery. 

The  Interosseous  Veins  accompany  the  anterior  and  posterior  interosseous 
arteries.  The  anterior  interosseous  veins  commence  in  front  of  the  wrist,  where 
they  communicate  with  the  deep  radial  and  ulnar  veins  ;  at  the  upper  part  of  the 
forearm  they  receive  the  posterior  interosseous  veins,  and  terminate  in  the  venae 
comites  of  the  ulnar  artery. 

The  Deep  Palmar  Veins  accompany  the  deep  palmar  arch,  being  formed  by 
tributaries  which  accompany  the  ramifications  of  that  vessel.  They  communicate 
with  the  deep  ulnar  veins  at  the  inner  side  of  the  hand,  and  on  the  outer  side 
terminate  in  the  venae  comites  of  the  radial  artery.  At  the  wrist  they  receive  a 
dorsal  and  a  palmar  tributary  from  the  thumb,  and  unite  with  the  deep  radial 
veins.  Accompanying  the  radial  artery,  these  vessels  terminate  in  the  venae 
comites  of  the  brachial  artery. 

1  Cruveilhier  says :  "  Numerous  varieties  are  observed  in  the  disposition  of  the  veins  of  the 
elbow ;  sometimes  the  common  median  vein  is  wanting ;  but  in  those  cases  its  two  branches  are  fur- 
nished by  the  radial  vein,  and  the  cephalic  is  almost  always  in  a  rudimentary  condition.  In  other 
cases  only  two  veins  are  found  at  the  bend  of  the  elbow,  the  radial  and  ulnar,  wk  ich  are  continuous, 
without  any  demarcation,  with  the  cephalic  and  basilic." 


THE   INNOMINATE    VEINS. 

611 

The  Brachial  Veins  are  placed  one  on  each  side  of  the  brachial  artery,  rec. 
tributaries  corresponding  with  the  branches  given  off  from    that  vessel ;    at  ^ends 
lower  margin  of  the  Subscapularis,  they  join  the  axillary  vein.  ^d 

These  deep  veins  have  numerous  anastomoses,  not  only  with  each  other,  but 
also  with  the  superficial  veins. 

The  Axillary  Vein  is  of  large  size,  and  is  the  continuation  upward  of  the 
basilic  vein.  It  commences  at  the  lower  border  of  the  tendons  of  the  Teres  major 
and  Latissimus  dorsi,  increases  in  size  as  it  ascends,  by  receiving  tributaries  cor- 
responding with  the  branches  of  the  axillary  artery,  and  terminates  immediately 
beneath  the  clavicle  at  the  outer  border  of  the  first  rib,  where  it  becomes  the  sub- 
clavian vein.  This  vessel  is  covered  in  front  by  the  Pectoral  muscles  and  costo- 
coracoid  membrane,  and  lies  on  the  thoracic  side  of  the  axillary  artery,  which  it 
partially  overlaps.  Near  its  termination  it  receives  the  cephalic  vein.  This  vein  is 
provided  with  a  pair  of  valves  opposite  the  lower  border  of  the  Subscapularis  muscle ; 
valves  are  also  found  at  the  termination  of  the  cephalic  and  subscapular  veins. 

Surgical  Anatomy.— There  are  several  points  of  surgical  interest  in  connection  with  the 
axillary  vein.  Being  more  superficial,  larger,  and  slightly  overlapping  the  axillary  artery,  it  is 
more  liable  to  be  wounded  in  the  operation  of  extirpation  of  the  axillary  glands,  especially  as 
these  glands,  when  diseased,  are  apt  to  become  adherent  to  the  vessel.  When  wounded  there 
is  always  a  danger  of  air  being  drawn  into  its  interior,  and  death  resulting.  This  is  due  not  only 
to  the  fact  that  it  is  near-the  thorax,  and  therefore  liable  to  be  influenced  by  the  respiratory 
movements,  but  also  because  it  is  adherent  by  its  anterior  surface  to  the  costo-coracoid  membrane, 
and  therefore  if  wounded  is  likely  to  remain  patulous  and  favor  the  chance  of  air  being  sucked 
in.  This  adhesion  of  the  vein  to  the  fascia  prevents  its  collapsing,  and  therefore  favors  the 
furious  bleeding  which  takes  place  in  these  cases. 

To  avoid  wounding  the  axillary  vein  in  the  extirpation  of  glands  from  the  axilla,  no  sharp 
cutting  instruments  should  be  used  after  the  axillary  cavity  has  been  freely  exposed,  and  care 
should  be  taken  to  use  no  undue  force  in  isolating  the  glands.  Should  the  vein  be  so  embedded 
in  the  malignant  deposit  that  the  latter  cannot  be  removed  without  taking  away  a  part  of  the 
vein,  this  must  be  done,  the  vessel  having  been  first  ligated  above  and  below. 

The  Subclavian  Vein,  the  continuation  of  the  axillary,  extends  from  the  outer 
border  of  the  first  rib  to  the  inner  end  of  the  clavicle,  where  it  unites  with  the 
internal  jugular  to  form  the  innominate  vein.  It  is  in  relation,  in  front,  with  the 
clavicle  and  Subclavius  muscle ;  behind  and  above,  with  the  subclavian  artery, 
from  which  it  is  separated  internally  by  the  Scalenus  anticus  muscle  and  phrenic 
nerve.  Below,  it  rests  in  a  depression  on  the  first  rib  and  upon  the  pleura. 
Above,  it  is  covered  by  the  cervical  fascia  and  integument. 

The  subclavian  vein  occasionally  rises  in  the  neck  to  a  level  Avith  the  third  part 
of  the  subclavian  artery,  and  in  two  instances  has  been  seen  passing  with  this  vessel 
behind  the  Scalenus  anticus.  This  vessel  is  usually  provided  with  valves  about 
an  inch  from  its  termination  in  the  innominate,  just  external  to  the  entrance  of  the 
external  jugular  vein. 

Tributaries. — It  receives  the  external  and  anterior  jugular  veins  and  a  small 
branch  from  the  cephalic,  outside  the  Scalenus,  and  on  the  inner  side  of  that 
muscle  the  internal  jugular  vein.  At  the  angle  of  junction  with  the  internal 
jugular  the  left  subclavian  vein  receives  the  thoracic  duct,  while  the  right  sub- 
clavian vein  receives  the  right  lymphatic  duct. 

The  Innominate  or  Brachiocephalic  Veins  (Fig.  331)  are  two  large  trunks, 
placed  one  on  each  side  of  the  root  of  the  neck,  and  formed  by  the  union  of  the 
internal  jugular  and  subclavian  veins  of  the  corresponding  side. 

The  Right  Innominate  Vein  is  a  short  vessel,  an  inch  in  length,  which  com- 
mences at  the  inner  end  of  the  clavicle,  and,  passing  almost  vertically  downward, 
joins  with  the  left  innominate  vein  just  below  the  cartilage  of  the  first  rib,  close  to 
the  right  border  of  the  sternum,  to  form  the  superior  vena  cava.  It  lies  superficial 
and  external  to  the  innominate  artery ;  on  its  right  side  is  the  phrenic  nerve,  and 
the  pleura  is  here  interposed  between  it  and  the  apex  of  the  lung.  This  vein,  at 
the  angle  of  junction  of  the  internal  jugular  with  the  subclavian,  receives  the 
right  vertebral  vein,  and,  lower  down,  the  right  internal  mammary,  right  inferior 
thyroid,  and  sometimes  the  right  superior  intercostal  veins. 

39 


608 


THE   BLOOD-VASCULAR    SYSTEM. 


—.Anterior  jugular. 


Superior  thyroid 
Middle  thyroid. (, 

4 


Mediastinal 

and 
pericardiac. 


External  jugular. 


X\  Left  Innominate  Vein,  about  two  and  a  half  inches  in  length,  and  larger 
Bi£  the  right,  passes  from  left  to  right  across  the  upper  and  front  part  of  the  chest, 

at  the  same  time  inclining 
downward,  to  unite  with  its 
fellow  of  the  opposite  side, 
forming  the  superior  vena 
cava.  It  is  in  relation,  in 
front,  with  the  first  piece 
of  the  sternum,  from  which 
it  is  separated  by  the  Sterno- 
hyoid and  Sterno-thyroid 
muscles,  the  thymus  gland 
or  its  remains,  and  some 
loose  areolar  tissue.  Be- 
hind, it  lies  across  the  roots 
of  the  three  large  arteries 
arising  from  the  arch  of  the 
aorta.  This  vessel  is  joined 
by  the  left  vertebral,  left 
internal  mammary,  left  in- 
ferior thyroid,  and  the  left 
superior  intercostal  veins, 
and  occasionally  some  thy- 
mic and  pericardiac  veins. 
There  are  no  valves  in  the 
innominate  veins. 

Peculiarities. — Sometimes 
the  innominate  veins  open  sep- 
irately  into  the  right  auricle  ;  in 
such  cases,  the  right  vein  takes 
the  ordinary  course  of  the  supe- 
rior vena  cava ;  but  the  left  vein 
— left  superior  vena  cava,  as  it 
is  termed — after  communicating 
by  a  small  branch  with  the  right 
one,  passes  in  front  of  the  root 
of  the  left  lung,  and,  turning  to 
the  back  of  the  heart,  receives 
the  cardiac  veins,  and  termin- 
ates in  the  back  of  the  right 
auricle.  This  occasional  con- 
dition in  the  adult  is  due  to  the 
persistence  of  the  early  foetal 
condition,  and  is  the  normal 
state  of  things  in  birds  and 
some  mammalia. 

The  internal  mammary 
veins,  two  in  number  to 
each  artery,  follow  the 
course  of  that  vessel,  and 
receive  branches  corre- 
sponding with  those  derived 
from  it.  The  twTo  veins  of 
each  side  unite  into  a  single 
trunk,  which  terminates  in 
the  innominate  vein. 

The  inferior  thyroid 
veins,  twro,  frequently  three 
or  four,  in  number,  arise  in  the  venous  plexus  on  the  thyroid  body,  communicating 
with  the  middle  and  superior  thyroid  veins.      They  form  a  plexus  in  front  of  the 


Fig.  331.— The  venae  cavee  and  azygos  veins,  with  their  formative 
branches . 


THE    VENA    CAVA.  611 

trachea,  behind  the  Sterno-thyroid  muscles.  From  this  plexus  a  left  vein  descends 
and  joins  the  left  innominate  trunk,  and  a  right  vein  passes  obliquely  down-ward 
and  outward  across  the  innominate  artery  to  open  into  the  right  innominate  vein, 
just  at  its  junction  with  the  superior  vena  cava.  These  veins  receive  oesophageal, 
tracheal,  and  inferior  laryngeal  veins,  and  are  provided  with  valves  at  their  termi- 
nation in  the  innominate  veins. 

The  Superior  intercostal  veins  (right  and  left)  drain  the  blood  from  two  or  three 
intercostal  spaces  below  the  first.  The  right  vein  passes  downward  and  inward  and 
opens  into  the  vena  azygos  major ;  the  left  runs  across  the  transverse  aorta  and 
opens  into  the  left  innominate  vein.  It  usually  receives  the  left  bronchial  and 
left  superior  phrenic  vein,  and  communicates  below  with  the  vena  azygos  minor 
superior.  The  highest  intercostal  vein,  i.  e.,  from  the  first  space,  opens  directly  into 
the  corresponding  vertebral  or  innominate  vein. 

The  Superior  Vena  Cava  receives  the  blood  which  is  conveyed  to  the  heart  from 
the  whole  of  the  upper  half  of  the  body.  It  is  a  short  trunk,  varying  from  two 
inches  and  a  half  to  three  inches  in  length,  formed  by  the  junction  of  the  two 
innominate  veins.  It  commences  immediately  below  the  cartilage  of  the  first  rib 
close  to  the  sternum  on  the  right  side,  and,  descending  vertically,  enters  the  peri- 
cardium about  an  inch  and  a  half  above  the  heart,  and  terminates  in  the  upper  part 
of  the  right  auricle  opposite  the  upper  border  of  the  third  right  costal  cartilage.  In 
its  course  it  describes  a  slight  curve,  the  convexity  of  which  is  turned  to  the  right 
side. 

Relations. — In  front,  with  the  pericardium  and  process  of  cervical  fascia  which 
is  continuous  with  it :  this  separates  it  from  the  thymus  gland  and  from  the  ster- 
num ;  behind,  with  the  root  of  the  right  lung ;  on  its  right  side,  with  the  phrenic 
nerve  and  right  pleura  ;  on  its  left  side,  with  the  commencement  of  the  innominate 
artery  and  ascending  part  of  the  aorta.  The  portion  contained  within  the  peri- 
cardium is  covered  by  the  serous  layer  of  that  membrane  in  its  anterior  three- 
fourths.  It  receives  the  vena  azygos  major  just  before  it  enters  the  pericardium, 
and  several  small  veins  from  the  pericardium  and  parts  in  the  mediastinum.  The 
superior  vena  cava  has  no  valves. 

The  Azygos  Veins  connect  together  the  superior  and  inferior  venae  cavse,  taking 
the  place  of  those  vessels  in  that  part  of  the  chest  occupied  by  the  heart. 

The  larger,  or  right  azygos  vein  (vena  azygos  major),  commences  opposite  the 
first  or  second  lumbar  vertebra  by  a  branch  from  the  right  lumbar  veins  (the 
ascending  lumbal');  sometimes  by  a  branch  from  the  right  renal  vein  or  from  the 
inferior  vena  cava.  It  enters  the  thorax  through  the  aortic  opening  in  the  Dia- 
phragm, and  passes  along  the  right  side  of  the  vertebral  column  to  the  fourth  dorsal 
vertebra,  where  it  arches  forward  over  the  root  of  the  right  lung,  and  terminates 
in  the  superior  vena  cava  just  before  that  vessel  enters  the  pericardium.  Whilst 
passing  through  the  aortic  opening  of  the  Diaphragm  it  lies  with  the  thoracic 
duct  on  the  right  side  of  the  aorta,  and  in  the  thorax  it  lies  upon  the  intercostal 
arteries  on  the  right  side  of  the  aorta  and  thoracic  duct,  and  is  partly  covered  by 
pleura. 

Tributaries. — It  receives  the  lower  ten  intercostal  veins  of  the  right  side,  the 
upper  two  or  three  of  these  opening  first  of  all  into  the  right  superior  intercostal 
vein.  It  receives  the  azygos  minor  veins,  several  oesophageal,  mediastinal,  and 
pericardial  veins ;  near  its  termination,  the  right  bronchial  vein  ;  and  generally 
the  right  superior  intercostal  vein.  A  few  imperfect  valves  are  found  in  this  vein ; 
but  its  tributaries  are  provided  with  complete  valves. 

The  intercostal  veins  on  the  left  side,  below  the  three  upper  intercostal  spaces, 
usually  form  two  trunks,  named  the  left  lower  and  the  left  upper  azygos  veins. 

The  left  lower,  or  smaller  azygos  vein  (vena  azygos  minor),  commences  in  the 
lumbar  region  by  a  branch  from  one  of  the  lumbar  veins  (ascending  lumbar)  or 
from  the  left  renal.  It  passes  into  the  thorax  through  the  left  crus  of  the  Dia- 
phragm, and,  ascending  on  the  left  side  of  the  spine  as  high  as  the  ninth  dorsal 
vertebra,  passes  across  the  column,  behind  the  aorta  and  thoracic  duct,  to  terminate 


612 


THE   BLOOD-VASCULAB    SYSTEM. 


in  the  right  azygos  vein.     It  receives  the  four  or  five  lower  intercostal  veins  of  the 
left  side,  and  some  oesophageal  and  mediastinal  veins. 

The  left  upper  azygos  vein  varies  inversely  with  the  size  of  the  left  superior 
intercostal.  It  receives  veins  from  the  intercostal  spaces  between  the  left  superior 
intercostal  vein  and  highest  tributary  of  the  left  lower  azygos.  They  are  usually 
three  or  four  in  number,  and  join  to  form  a  trunk  which  ends  in  the  right  azygos 
vein  or  in  the  left  lower  azygos.  It  sometimes  receives  the  left  bronchial  vein. 
When  this  vein  is  small  or  altogether  wanting,  the  left  superior  intercostal  vein 
will  extend  as  low  as  the  fifth  or  six  intercostal  space. 

Surgical  Anatomy.— In  obstruction  of  the  inferior  vena  cava  the  azygos  veins  are  one  of 
the  principal  means  by  which  the  venous  circulation  is  carried  on,  connecting  as  they  do  the  superior 
and  inferior  venae  cavae,  and  communicating  with  the  common  iliac  veins  by  the  ascending  lumbar 
veins,  and  with  many  of  the  tributaries  of  the  inferior  vena  cava. 

The  bronchial  veins  return  the  blood  from  the  substance  of  the  lungs ;  that  of 
the  right  side  opens  into  the  vena  azygos  major  near  its  termination ;  that  of  the 
left  side,  into  the  left  superior  intercostal  vein  or  left  upper  azygos  vein. 

THE  SPINAL  VEINS. 

The  numerous  venous  plexuses  placed  upon  and  within  the  spine  may  be 
arranged  into  four  sets  : 

1.  Those  placed  on  the  exterior  of  the  spinal  column  (the  dorsi-spinal  veins). 

2.  Those  situated  in  the  interior  of  the  spinal  canal,  between  the  vertebrae  and 
the  theca  vertebralis  (meningo-rachidian  veins). 

3.  The  veins  of  the  bodies  of  the  vertebrae  (yenee  basis  vertebrarum). 

4.  The  veins  of  the  spinal  cord  (medulli-spinal). 

1.  The  Dorsi-spinal  Veins   commence  by  small  branches  which  receive  their 


The  dorsi-spinal  veins. 


Fig.  332.— Transverse  section  of  a  dorsal  vertebra,  showing  the  spinal  veins. 


blood  from  the  integument  of  the  back  of  the  spine  and  from  the  muscles  in  the 
vertebral  grooves.  They  form  a  complicated  network,  which  surrounds  the  spinous 
processes,  the  laminae,  and  the  transverse  and  articular  processes  of  all  the  ver- 
tebrae. At  the  bases  of  the  transverse  processes  they  communicate,  by  means  of 
ascending  and  descending  branches,  with  the  veins  surrounding  the  contiguous 
vertebrae,  and  they  join  with  the  veins  in  the  spinal  canal  by  branches  which 
perforate  the  ligamenta  subflava.  Other  branches  pass  obliquely  forward, 
between  the  transverse  processes,  and  communicate  with  the  intraspinal  veins 
through  the  intervertebral  foramina.      They  terminate  by  joining  the  vertebral 


THE  SPINAL    VEINS. 


613 


veins  in  the  neck,  the  intercostal  veins  in  the  thorax,  and  the  lumbar  and  sacral 
veins  in  the  loins  and  pelvis. 

2.  The  Meningo-rachidian  Veins. — The  principal  veins  contained  in  the  spinal 
canal  are  situated  between  the  theca  vertebralis  and  the  vertebrae.  They  consist 
of  two  longitudinal  plexuses,  one  of  which  runs  along  the  posterior  surface  of  the 
bodies  of  the  vertebrae  {anterior  longitudinal  spinal  veins).  The  other  plexus 
{posterior  longitudinal  spinal  veins)  is  placed  on  the  inner  or  anterior  surface  of 
the  laminae  of  the  vertebrae. 

The  Anterior  Longitudinal  Spinal  Veins  consist  of  two  large,  tortuous  veins 
which  extend  along  the  whole  length  of  the  vertebral  column,  from  the  foramen 
magnum,  where  they  communicate  by  a  venous  ring  around  that  opening,  to  the 
base  of  the  coccyx,  being  placed  one  on  each  side  of  the  posterior  surface  of  the 
bodies  of  the  vertebrae  along  the  margin  of  the  posterior  common  ligament. 
These  veins  communicate  together  opposite  each  vertebra  by  transverse  trunks 
which  pass  beneath  the  ligament,  and  receive  the  large  vence  basis  vertebrarum 
from  the  interior  of  the  body  of  each  vertebra.  The  anterior  longitudinal  spinal 
veins  are  least  developed  in  the  cervical  and  sacral  regions.      They  are  not  of 


Fig.  333.— Vertical  section  of  two  dorsal  vertebra,  showing  the  spinal  veins. 

uniform  size  throughout,  being  alternately  enlarged  and  constricted.  At  the 
intervertebral  foramina  they  communicate  with  the  dorsi-spinal  veins,  and  with 
the  vertebral  veins  in  the  neck,  with  the  intercostal  veins  in  the  dorsal  region, 
and  with  the  lumbar  and  sacral  veins  in  the  corresponding  regions. 

The  Posterior  Longitudinal  Spinal  Veins,  smaller  than  the  anterior,  are 
situated  one  on  each  side,  between  the  inner  surface  of  the  laminae  and  the  theca 
vertebralis.  They  communicate  (like  the  anterior)  opposite  each  vertebra  by 
transverse  trunks,  and  with  the  anterior  longitudinal  veins  by  lateral  transverse 
branches  which  pass  from  behind  forward.  These  veins,  by  branches  which  per- 
forate the  ligamenta  subflava,  join  with  the  dorsi-spinal  veins.  From  them 
branches  are  given  off  which  pass  through  the  intervertebral  foramina  and  join 
the  vertebral,  intercostal,  lumbar,   and  sacral  veins. 

3.  The  Veins  of  the  Bodies  of  the  Vertebrae  (vena?  basis  vertebraruni)  emerge 
from  the  foramina  on  their  posterior  surface,  and  join  the  transverse  trunk  con- 
necting the  anterior  longitudinal  spinal  veins.  They  are  contained  in  large,  tor- 
tuous channels  in  the  substance  of  the  bones,  similar  in  every  respect  to  those 
found  in  the  diploe  of  the  cranial  bones.  These  canals  lie  parallel  to  the  upper 
and  lower  surface  of  the  bones.  They  commence  by  small  openings  on  the  front 
and  sides  of  the  bodies  of  the  vertebrae,  through  which  communicating  branches 
from  the  veins  external  to  the  bone  pass  into  its  substance,  and  converge  to  the 
principal  canal,  which  is  sometimes  double  toward  its  posterior  part,  and  open 
into  the  corresponding  transverse  branch  uniting  the  anterior  longitudinal  veins. 
They  become  greatly  developed  in  advanced  age. 

4.  The  Veins  of  the  Spinal  Cord  (medulU-spinal)  consist  of  a  minute,  tortuous, 


614  THE  BLOOD-VASCULAR   SYSTEM. 

venous  plexus  which  covers  the  entire  surface  of  the  cord,  being  situated  between 
the  pia  mater  and  arachnoid.  These  vessels  emerge  chiefly  from  the  median 
furrows,  and  are  largest  in  the  lumbar  region.  Near  the  base  of  the  skull  they 
unite  and  form  two  or  three  small  trunks,  which  communicate  with  the  vertebral 
veins,  and  then  terminate  in  the  inferior  cerebellar  veins  or  in  the  inferior  petro- 
sal sinuses.  Each  of  the  spinal  nerves  is  accompanied  by  a  branch  as  far  as  the 
intervertebral  foramina,  where  it  joins  the  other  veins  from  the  spinal  canal. 
There  are  no  valves  in  the  spinal  veins. 

VEINS  OF  THE  LOWER  EXTREMITY,  ABDOMEN,  AND  PELVIS. 

The  Veins  of  the  Lower  Extremity  are  subdivided,  like  those  of  the  upper, 
into  two  sets,  superficial  and  deep,  the  superficial  veins  being  placed  beneath  the 
integument,  between  the  two  layers  of  superficial  fascia,  the  deep  veins  accom- 
panying the  arteries  and  forming  the  venae  comites  of  those  vessels.  Both  sets 
of  veins  are  provided  Avith  valves,  which  are  more  numerous  in  the  deep  than  in 
the  superficial  set.  These  valves  are  also  more  numerous  in  the  lower  than  in 
the  upper  limb. 

The  Superficial  Veins  of  the  Lower  Extremity  are  the  internal  or  long  saphen- 
ous and  the  external  or  short  saphenous. 

On  the  dorsum  of  the  foot  is  a  venous  arch  situated  in  the  superficial  struc- 
tures over  the  anterior  extremities  of  the  metatarsal  bones.  It  has  its  convexity 
directed  forward,  and  receives  digital  tributaries  from  the  upper  surface  of  the 
toes ;  at  its  concavity  it  is  joined  by  numerous  small  veins  which  form  a  plexus 
on  the  dorsum  of  the  foot.  The  arch  terminates  internally  in  the  long  saphenous, 
externally  in  a  short  saphenous  vein. 

The  internal  or  long  saphenous  vein  (Fig.  334)  commences  at  the  inner  side  of 
the  arch  on  the  dorsum  of  the  foot ;  it  ascends  in  front  of  the  inner  malleolus 
and  along  the  inner  side  of  the  leg,  behind  the  inner  margin  of  the  tibia,  accom- 
panied by  the  internal  saphenous  nerve.  At  the  knee  it  passes  backward  behind 
the  inner  condyle  of  the  femur,  ascends  along  the  inside  of  the  thigh,  and,  pass- 
ing through  the  saphenous  opening  in  the  fascia  lata,  terminates  in  the  femoral 
vein  about  an  inch  and  a  half  below  Poupart's  ligament.  This  vein  receives  in 
its  course  cutaneous  tributaries  from  the  leg  and  thigh,  and  at  the  saphenous 
opening  the  superficial  epigastric,  superficial  circumflex  iliac,  and  external  pudic 
veins.  The  veins  from  the  inner  and  back  part  of  the  thigh  frequently  unite  to 
form  a  large  vessel,  which  enters  the  main  trunk  near  the  saphenous  opening ; 
and  sometimes  those  on  the  outer  side  of  the  thigh  join  to  form  another  large 
vessel ;  so  that  occasionally  three  large  veins  are  seen  converging  from  different 
parts  of  the  thigh  toward  the  saphenous  opening.  The  internal  saphenous  vein 
communicates  in  the  foot  with  the  internal  plantar  vein  ;  in  the  leg,  with  the 
posterior  tibial  veins  by  branches  which  perforate  the  tibial  origin  of  the  Soleus 
muscle,  and  also  with  the  anterior  tibial  veins ;  at  the  knee,  with  the  articular 
veins  ;  in  the  thigh,  with  the  femoral  vein  by  one  or  more  bi-anches.  The  valves 
in  this  vein  vary  from  two  to  six  in  number  ;  they  are  more  numerous  in  the 
thigh  than  in  the  lea;. 

The  external  or  short  saphenous  vein  (Fig.  335)  commences  at  the  outer  side 
of  the  arch  on  the  dorsum  of  the  foot ;  it  ascends  behind  the  outer  malleolus, 
and  along  the  outer  border  of  the  tendo  Achillis,  across  which  it  passes  at  an 
acute  angle  to  reach  the  middle  line  of  the  posterior  aspect  of  the  leg.  Passing 
directly  upward,  it  perforates  the  deep  fascia  in  the  lower  part  of  the  popliteal 
space,  and  terminates  in  the  popliteal  vein,  between  the  heads  of  the  Gastro- 
cnemius muscle.1     It  receives  numerous  large  tributaries  from  the  back  part  of 

1  Mr.  Gay  calls  attention  to  the  fact  that  the  external  saphenous  vein  often  (he  says  invariably) 
penetrates  the  fasciaat  or  about  the  point  where  the  tendon  of  the  Gastrocnemius  commences,  and  runs 
below  the  fascia  in  the  rest  of  its  course,  or  sometimes  among  the  muscular  fibres,  to  join  the  popliteal 
vein.  ( See  Gay  on  Varicose  Disease  of  the  Lower  Extremities,  p.  24,  where  there  is  also  a  careful  and 
elaborate  description  of  the  branches  of  the  saphena  veins.) 


VEINS    OF    THE   LOWER    EXTREMITY. 


615 


the  leg,   and   communicates   with  the  deep  veins  on  the  dorsum  of  the  foot  and 
behind  the   outer  malleolus.     Before   it  perforates   the  deep  fascia  it  gives  off 

a     communicating     branch,     which 
\  passes  upward   and  inward  to  join 

)  the  internal  saphenous  vein.     This 

I: \>vV\X\  vein     nas    a    variable    number    of 

valves,  from  three  to  nine  (Gay), 
one  of  which  is  always  found  near 
its  termination  in  the  popliteal 
vein.  The  external  saphenous 
nerve   lies   close   beside    this   vein. 


/ 


I?  ■ " 


y^\ 


Surgical  Anatomy.— The  saphena 
veins  are  of  considerable  surgical  import- 
ance, since  a  varicose  condition  of  these 
vessels  is  more  frequently  met  with  than 
of  those  in  other  parts  of  the  body,  except 
perhaps  the  spermatic  and  hemorrhoidal 
veins.  The  course  of  the  internal 
saphenous  is  in  front  of  the  tip  of  the 
malleolus,  over  the  subcutaneous  surface 
of  the  lower  end  of  the  tibia,  and  then 
along  the  internal  border  of  this  bone 
to  the  back  part  of  the  internal  condyle  of 
the  femur,  whence  it  follows  the  course 
of  the  Sartorius  muscle,  and  is  represented 
on  the  surface  by  a  line  drawn  from  the 
posterior  border  of  the  Sartorius  on  a 
level  with  the  internal  condyle  to  the 
saphenous  opening.  The  short  saphenous 
lies  behind  the  external  malleolus,  and 
from  this  follows  the  middle  line  of  the 
calf  to  just  below  the  ham.  It  is  not 
generally  so  apparent  beneath  the  skin  as 
the  internal  saphenous.  Both  these  veins 
in  the  leg  are  accompanied  by  nerves,  the 
internal  saphenous  being  joined  by  its 
companion  nerve  just  below  the  level  of 
the  knee-joint.  No  doubt  much  of  the 
pain  of  varicose  veins  in  the  leg  is  due  to 
this  fact.  On  the  Continent  the  internal 
saphenous  vein  as  it  rests  on  the  tibia 
just  above  the  malleolus  is  sometimes 
selected   for  venesection. 


f 


Fig.  335.— External 
or  short  saphenous 
vein. 


m 


The    Deep    Veins   of  the   Lower 
Extremity  accompany  the  arteries  and  their  branches, 
and  are  called  the  vena?  comites  of  those  vessels. 

The  external  and  internal  plantar  veins  unite  to  form 
the  posterior  tibial.  They  accompany  the  posterior 
tibial  artery  and  are  joined  by  the  peroneal  veins. 

The  anterior  tibial  veins  are  formed  bv  a  con- 
tinuation upward  of  the  venae  comites  of  the  dorsalis 
pedis  artery.  They  pass  between  the  tibia  and  fibula, 
through  the  large  oval  aperture  above  the  interosse- 
ous membrane,  and  form,  by  their  junction  with  the 
posterior  tibial,  the  popliteal  vein. 

The  valves  in  the  deep  veins  are  very  numerous. 

The  Popliteal  Vein  is  formed  by  the  i unction  of  the 

jig.  334 — The  internal  or  Ion?  •■  e    .\  .       •  i  .       •  .-■,•    i 

saphenous  vein  and  its  branches,    venae  comites  ot  the  anterior  and  posterior  tibial  ves- 
sels;   it    ascends   through  the   popliteal    space    to    the 
tendinous  aperture  in  the  Adductor  magnus,  where  it  becomes  the  femoral  vein. 
In  the  lower  part  of  its  course  it  is  placed  internal  to  the  artery;  between  the 


616  THE  BLOOD-VASCULAR    SYSTEM. 

heads  of  the  Gastrocnemius  it  is  superficial  to  that  vessel ;  but  above  the  knee- 
joint  it  is  close  to  its  outer  side.  It  receives  the  sural  veins  from  the  Gastro- 
cnemius muscle,  the  articular  veins,  and  the  external  saphenous.  The  valves  in 
this  vein  are  usually  four  in  number. 

The  Femoral  Vein  accompanies  the  femoral  artery  through  the  upper  two- 
thirds  of  the  thigh.  In  the  lower  part  of  its  course  it  lies  external  to  the  artery  ; 
higher  up  it  is  behind  it ;  and  at  Poupart's  ligament  it  lies  to  its  inner  side  and 
on  the  same  plane.  It  receives  numerous  muscular  tributaries,  and  about  an  inch 
and  a  half  below  Poupart's  ligament  it  is  joined  by  the  profunda  femoris ;  near  its 
termination  it  is  joined  by  the  internal  saphenous  vein.  The  valves  in  this  vein 
are  four  or  five  in  number. 

The  External  Iliac  Vein  commences  at  the  termination  of  the  femoral,  beneath 
the  crural  arch,  and,  passing  upward  along  the  brim  of  the  pelvis,  terminates 
opposite  the  sacro-iliac  synchondrosis  by  uniting  with  the  internal  iliac  to  form 
the  common  iliac  vein.  On  the  right  side  it  lies  at  first  along  the  inner  side  of 
the  external  iliac  artery,  but  as  it  passes  upward  gradually  inclines  behind  it. 
On  the  left  side  it  lies  altogether  on  the  inner  side  of  the  artery.  It  receives, 
immediately  above  Poupart's  ligament,  the  deep  epigastric  and  deep  circumflex 
iliac  veins  and  a  small  pubic  vein,  corresponding  to  the  pubic  branch  of  the 
obturator  artery.  According  to  Friedreich,  it  frequently  contains  one,  and  some- 
times two  valves. 

The  Deep  Epigastric  Veins. — Two  veins  accompany  the  deep  epigastric  artery ; 
they  usually  unite  into  a  single  trunk  before  their  termination  in  the  external 
iliac  vein. 

The  Deep  Circumflex  Iliac  Veins. — Two  veins  accompany  the  deep  circumflex 
iliac  artery.  These  unite  into  a  single  trunk  which  crosses  the  external  iliac 
artery  just  above  Poupart's  ligament  and  terminates  in  the  external  iliac 
vein. 

The  Internal  Iliac  Vein  is  formed  by  the  venae  comites  of  the  branches  of  the 
internal  iliac  artery,  the  umbilical  arteries  of  the  foetus  excepted.  It  receives  the 
blood  from  the  exterior  of  the  pelvis  by  the  gluteal,  sciatic,  internal  pudic,  and 
obturator  veins,  and  from  the  organs  in  the  cavity  of  the  pelvis  by  the  hemor- 
rhoidal and  vesico-prostatic  plexuses  in  the  male,  and  the  uterine  and  vaginal 
plexuses  in  the  female.  The  vessels  forming  these  plexuses  are  remarkable  for 
their  large  size,  their  frequent  anastomoses,  and  the  number  of  valves  which  they 
contain.  The  internal  iliac  vein  lies  at  first  on  the  inner  side,  and  then  behind  the 
internal  iliac  artery,  and  terminates  opposite  the  sacro-iliac  articulation  by  uniting 
with  the  external  iliac  to  form  the  common  iliac  vein.      This  vessel  has  no  valves. 

The  internal  pudic  veins  (yence,  comites)  have  the  same  course  as  the  internal 
pudic  artery.  They  receive  tributaries  corresponding  to  the  branches  of  the 
artery,  except  the  tributary  corresponding  to  the  dorsal  artery  of  the  penis;  that 
is,  the  dorsal  vein  of  the  penis,  which  opens  into  the  prostatic  plexus. 

The  hemorrhoidal  plexus  surrounds  the  lower  end  of  the  rectum,  being  formed 
by  the  superior  hsemorrhoidal  veins,  tributaries  of  the  inferior  mesenteric.  It 
commences  as  a  series  of  dilated  pouches,  about  twelve  in  number,  which  are 
arranged  circularly  at  the  verge  of  the  anus  and  are  connected  by  transverse 
branches.  From  these  pouches  veins,  about  six  in  number,  pass  upward  in  a 
straight  direction  in  the  submucous  tissue  for  about  three  inches ;  they  then  pierce 
the  muscular  coat  and  become  arranged  in  a  circular  manner  at  right  angles  to  the 
long  axis  of  the  gut,  and  eventually  unite  to  form  the  superior  hsemorrhoidal  vein. 

Surgical  Anatomy. — The  veins  of  this  plexus  are  apt  to  become  dilated  and  varicose,  and 
form  piles.  This  is  due  to  several  anatomical  reasons :  the  vessels  are  contained  in  very  loose, 
lax  connective  tissue,  so  that  they  get  less  support  from  .surrounding  structures  than  most  other 
veins,  and  are  less  capable  of  resisting  increased  blood  pressure :  the  condition  is  favored  by 
gravitation,  being  influenced  by  the  erect  posture,  either  sitting  or  standing,  and  by  the  fact 
that  the  superior  hjemorrhoidal  and  portal  veins  have  no  valves :  the  veins  pass  through  mus- 
cular tissue  and  are  liable  to  be  compressed  by  its  contraction,  especially  during  the  act  of 
■defecation :  they  are  affected  by  every  form  of  portal  obstruction. 


VEINS    OF    THE   LOWER    EXTREMITY.  617 

The  vesico-prostatic  plexus  surrounds  the  neck  and  base  of  the  bladder  and 
prostate  gland.  It  communicates  with  the  hemorrhoidal  plexus  behind,  and 
receives  the  dorsal  vein  of  the  penis,  which  enters  the  pelvis  beneath  the  subpubic 
ligament.  This  plexus  is  supported  upon  the  sides  of  the  bladder  by  a  reflection 
of  the  pelvic  fascia.  The  veins  composing  it  are  very  liable  to  become  varicose, 
and  often  contain  hard,  earthy  concretions,  called  phleboliths. 

Surgical  Anatomy. — This  plexus  is  wounded  in  the  lateral  operation  of  lithotomy,  and  it  is 
through  it  that  septic  matter  finds  its  way  into  the  general  circulation  after  this  operation. 

The  dorsal  vein  of  the  penis  is  a  vessel  of  large  size  which  returns  the  blood 
from  the  body  of  that  organ.  At  first  it  consists  of  two  branches,  which  are 
contained  in  the  groove  on  the  dorsum  of  the  penis,  and  it  receives  veins  from  the 
glans  penis,  the  corpus  spongiosum,  and  numerous  superficial  veins ;  these  unite 
into  a  single  trunk,  which  passes  between  the  two  parts  of  the  suspensory  ligament 
of  the  penis,  and  through  an  aperture  below  the  subpubic  ligament,  and  divides 
into  two  branches,  which  enter  the  prostatic  plexus. 

The  vaginal  plexus  surrounds  the  vagina,  being  especially  developed  at  the 
orifice  of  the  canal ;  it  communicates  with  the  vesical  plexus  in  front,  and  with  the 
heemorrhoidal  plexus  behind. 

The  uterine  plexus  is  situated  along  the  sides  and  superior  angles  of  the  uterus, 
between  the  layers  of  the  broad  ligament,  receiving,  during  pregnancy,  large 
venous  canals  (the  uterine  sinuses)  from  the  substance  of  the  placenta.  The  veins 
composing  this  plexus  anastomose  frequently  with  each  other  and  with  the  ovarian 
veins.     They  are  not  tortuous  like  the  arteries. 

The  Common  Iliac  Veins  are  formed  by  the  union  of  the  external  and  internal 
iliac  veins  in  front  of  the  sacro-iliac  articulation :  passing  obliquely  upward 
toward  the  right  side,  they  terminate  upon  the  intervertebral  substance  between 
the  fourth  and  fifth  lumbar  vertebrae,  where  the  veins  of  the  two  sides  unite  at  an 
acute  angle  to  form  the  inferior  vena  cava.  The  right  common  iliac  is  shorter 
than  the  left,  nearly  vertical  in  its  direction,  and  ascends  behind  and  then  to  the 
outer  side  of  its  corresponding  artery.  The  left  common  iliac,  longer  and  more 
oblique  in  its  course,  is  at  first  situated  on  the  inner  side  of  the  corresponding 
artery,  and  then  behind  the  right  common  iliac.  Each  common  iliac  receives  the 
ilio-lumbar,  and  sometimes  the  lateral  sacral,  veins.  The  left  receives,  in  addition, 
the  middle  sacral  vein.     No  valves  are  found  in  these  veins. 

The  middle  sacral  veins  accompany  the  corresponding  artery  along  the  front 
of  the  sacrum,  and  join  to  form  a  single  vein  which  terminates  in  the  left  common 
iliac  vein ;  occasionally  in  the  angle  of  junction  of  the  two  iliac  veins. 

Peculiarities. — The  left  common  iliac  vein,  instead  of  joining  with  the  right  in  its  usual 
position,  occasionally  ascends  on  the  left  side  of  the  aorta  as  high  as  the  kidney,  where,  after 
receiving  the  left  renal  vein,  it  crosses  over  the  aorta,  and  then  joins  with  the  right  vein  to  form 
the  vena  cava.  In  these  cases  the  two  common  iliacs  are  connected  by  a  small  communicating 
branch  at.  the  spot  where  they  are  usually  united.1 

The  Inferior  Vena  Cava  returns  to  the  heart  the  blood  from  all  the  parts  below 
the  Diaphragm.  It  is  formed  by  the  junction  of  the  two  common  iliac  veins  on 
the  right  side  of  the  fifth  lumbar  vertebra.  It  passes  upward  along  the  front  of 
the  spine  on  the  right  side  of  the  aorta,  and,  having  reached  the  under  surface  of 
the  liver,  is  contained  in  a  groove  on  its  posterior  surface.  It  then  perforates  the 
central  tendon  of  the  Diaphragm,  enters  the  pericardium,  where  it  is  covered  for  a 
very  short  distance  by  its  serous  layer,  and  terminates  in  the  lower  and  back  part 
of  the  right  auricle.  At  its  termination  in  the  auricle  it  is  provided  with  a  valve, 
the  Eustachian,  which  is  of  large  size  during  foetal  life. 

Relations. — In  front,  from  below  upward,  with  the  mesentery,  right  spermatic 
artery,  transverse  portion  of  the   duodenum,  the  pancreas,  portal  vein,   and  the 

1  See  two  cases  which  have  been  described  by  Mr.  "Walsham  in  the  St.  Bartholomcv'  s  Hospital 
Reports,  vols.  xvi.  and  xvii.  e 


618  THE   BLOOD-VASCULAR   SYSTEM. 

posterior  surface  of  the  liver,  which  partly  and  occasionally  completely  surrounds 
it ;  behind,  with  the  vertebral  column,  the  right  crus  of  the  Diaphragm,  the  right 
renal  and  lumbar  arteries,  right  semilunar  ganglion ;  on  the  left  side,  with  the 
aorta. 

Peculiarities. — In  Position. — This  vessel  is  sometimes  placed  on  the  left  side  of  the  aorta, 
as  high  as  the  left  renal  veins,  after  receiving  which  it  crosses  over  to  its  usual  position  on  the 
right  side ;  or  it  may  be  placed  altogether  on  the  left  side  of  the  aorta,  as  far  upward  as  its  ter- 
mination in  the  heart :  in  such  cases  the  abdominal  and  thoracic  viscera,  together  with  the  great 
vessels,  are  all  transposed. 

Point  of  Termination. — Occasionally  the  inferior  vena  cava  joins  the  right  azygos  vein, 
which  is  then  of  large  size.  In  such  cases  the  superior  cava  receives  the  whole  of  the  blood 
from  the  body  before  transmitting  it  to  the  right  auricle,  except  the  blood  from  the  hepatic  veins, 
which  passes  directly  into  the  right  auricle. 

Tributaries. — It  receives  in  its  course  the  following!;  veins : 

Lumbar.  Suprarenal. 

Right  Spermatic.  Phrenic. 

Renal.  Hepatic. 

The  lumbar  veins,  four  in  number  on  each  side,  collect  the  blood  by  dorsal 
tributaries  from  the  muscles  and  integument  of  the  loins  and  by  abdominal  tribu- 
taries from  the  Avails  of  the  abdomen,  where  they  communicate  with  the  epigastric 
veins.  At  the  spine  they  receive  veins  from  the  spinal  plexuses,  and  then  pass 
forward,  round  the  sides  of  the  bodies  of  the  vertebrae  beneath  the  Psoas  magnus, 
and  teirninate  at  the  back  part  of  the  inferior  cava.  The  left  lumbar  veins  are 
longer  than  the  right,  and  pass  behind  the  aorta.  The  lumbar  veins  are  connected 
together  by  a  longitudinal  vein  which  passes  in  front  of  the  transverse  processes  of  the 
lumbar  vertebrae,  and  is  called  the  ascending  lumbar.  It  forms  the  most  frequent 
origin  of  the  corresponding  vena  azygos,  and  serves  to  connect  the  common  iliac, 
ilio-lumbar,  lumbar,  and  azygos  veins  of  the  corresponding  side  of  the  body. 

The  spermatic  veins  emerge  from  the  back  of  the  testis,  and  receive  tributaries 
from  the  epididymis  ;  they  unite  and  form  a  convoluted  plexus  called  the  spermatic 
plexus  (plexus  pampiniformis),  which  forms  the  chief  mass  of  the  cord  :  the  vessels 
composing  this  plexus  are  very  numerous,  and  ascend  along  the  cord  in  front  of 
the  vas  deferens  ;  below  the  external  abdominal  ring  they  unite  to  form  three  or 
four  veins,  which  pass  along  the  inguinal  canal,  and,  entering  the  abdomen  through 
the  internal  abdominal  ring,  coalesce  to  form  two  veins,  which  ascend  on  the  Psoas 
muscle  behind  the  peritoneum,  lying  one  on  each  side  of  the  spermatic  artery,  and 
unite  to  form  a  single  vein,  which  opens  on  the  right  side  into  the  inferior  vena 
cava  at  an  acute  angle ;  on  the  left  side  into  the  left  renal  vein  at  a  right  angle. 
The  spermatic  veins  are  provided  with  valves.1  The  left  spermatic  vein  passes 
behind  the  sigmoid  flexure  of  the  colon,  and  is  thus  exposed  to  pressure  from  the 
contents  of  that  bowel. 

Surgical  Anatomy. — The  spermatic  veins  are  very  frequently  varicose,  constituting  the 
disease  known  as  varicocele.  Though  it  is  quite  possible  that  the  originating  cause  of  this 
affection  may  be  a  congenital  abnormality  either  in  the  size  or  number  of  the  veins  of  the 
pampiniform  plexus,  still  it  must  be  admitted  that  there  are  many  anatomical  reasons  why  these 
veins  should  become  varicose— viz.  the  imperfect  support  afforded  to  them  by  the  loose  tissue  of 
the  scrotum  ;  their  great  length  ;  their  vertical  course  ;  their  dependent  position  ;  their  plexiform 
arrangement  in  the  scrotum,  with  their  termination  in  one  small  vein  in  the  abdomen  ;  their  few 
and  imperfect  valves;  and  the  fact  that  they  maybe  subjected  to  pressure  in  their  passage 
through  the  abdominal  wall. 

The  ovarian  veins  are  analogous  to  the  spermatic  in  the  male  ;  they  ^orm  a 
plexus  near  the  ovary  and  in  the  broad  ligament  and  Fallopian  tube,  communi- 
cating with  the  uterine  plexus.  They  terminate  in  the  same  way  as  the  spermatic 
veins  in  the  male.  Valves  are  occasionally  found  in  these  veins.  These  vessels, 
like  the  uterine  veins,  become  much  enlarged  during  pregnancy. 

1  Kivington  has  pointed  out  that  a  valve  is  usually  found  at  the  orifices  of  both  the  right  and 
left  spermatic  veins.  When  no  valves  exist  at  the  opening  of  the  left  spermatic  vein  into  the  left 
renal  vein,  valves  are  generally  present  in  the  left  renal  vein  within  a  quarter  of  an  inch  from 
the  orifice  of  the  spermatic  vein  (Journal  of  Anatomy  and  Physiology,  vol.  vii.  p.  163). 


THE   PORTAL    SYSTEM    OF    VEINS.  619 

The  renal  veins  are  of  large  size,  and  placed  in  front  of  the  renal  arteries.1 
The  left  is  longer  than  the  right,  and  passes  in  front  of  the  aorta,  just  below  the 
origin  of  the  superior  mesenteric  artery.  It  receives  the  left  spermatic,  the  left 
inferior  phrenic,  and,  generally,  the  left  suprarenal  veins.  It  opens  into  the  vena 
cava  a  little  higher  than  the  right. 

The  suprarenal  veins  are  two  in  number :  that  on  the  right  side  terminates  in 
the  vena  cava ;  that  on  the  left  side,  in  the  left  renal  or  phrenic  vein. 

The  phrenic  veins  follow  the  course  of  the  phrenic  arteries.  The  tivo  superior, 
of  small  size,  accompany  the  phrenic  nerve  and  comes  nervi  phrenici  artery,  and 
join  the  internal  mammary.  The  two  inferior  phrenic  veins  follow  the  course  of 
the  phrenic  arteries,  and  terminate,  the  right  in  the  inferior  vena  cava,  the  left  in 
the  left  renal  vein. 

The  hepatic  veins  commence  in  the  substance  of  the  liver,  in  the  capillary 
terminations  of  the  portal  vein  and  hepatic  artery  :  these  tributaries,  gradually 
uniting,  usually  form  three  large  veins,  which  converge  toward  the  posterior 
surface  of  the  liver  and  open  into  the  inferior  vena  cava,  wThilst  that  vessel  is 
situated  in  the  groove  at  the  back  part  of  this  organ.  Of  these  three  veins,  one 
from  the  right,  and  another  from  the  left  lobe,  open  obliquely  into  the  inferior 
vena  cava,  that  from  the  middle  of  the  organ  and  lobulus  Spigelii  having  a  straight 
course.  The  hepatic  veins  run  singly,  and  are  in  direct  contact  with  the  hepatic 
tissue.     They  are  destitute  of  valves. 

The  Portal  System  of  Veins. 

The  portal  venous  system  is  composed  of  four  large  veins  which  collect  the 
venous  blood  from  the  viscera  of  digestion  (stomach,  intestine,  and  pancreas)  and 
from  the  spleen.  The  trunk  formed  by  their  union  (vena  portce)  enters  the  liver 
and  ramifies  throughout  its  substance  after  the  manner  of  an  artery  and  ends 
in  capillaries,  from  which  the  blood  is  collected  into  the  hepatic  veins,  which 
terminate  in  the  inferior  vena  cava.  The  branches  in  this  vein  are  in  all  cases 
single,  and  destitute  of  valves. 

The  veins  forming  the  portal  system  are :  the 

Superior  mesenteric.  Inferior  mesenteric. 

Splenic.  Gastric. 

Cystic. 

The  superior  mesenteric  vein  returns  the  blood  from  the  small  intestines  and 
from  the  caecum  and  ascending  and  transverse  portions  of  the  colon,  correspond- 
ing with  the  distribution  of  the  branches  of  the  superior  mesenteric  artery.  The 
large  trunk  formed  by  the  union  of  these  branches  ascends  along  the  right  side 
and  in  front  of  the  corresponding  artery,  passes  in  front  of  the  transverse  por- 
tion of  the  duodenum,  and  unites,  behind  the  upper  border  of  the  pancreas,  with 
the  splenic  vein  to  form  the  vena  portge.     It  receives  the  right  gastro-epiploic  vein. 

The  splenic  vein  commences  by  five  or  six  large  branches  which  return  the 
blood  from  the  substance  of  the  spleen.  These,  uniting,  form  a  single  vessel,  which 
passes  from  left  to  right,  grooving  the  upper  and  back  part  of  the  pancreas  below 
the  artery,  and  terminates  at  its  greater  end  by  uniting  at  a  right  angle  with  the 
superior  mesenteric  to  form  the  vena  portse.  The  splenic  vein  is  of  large  size,  and 
not  tortuous  like  the  artery.  It  receives  the  vasa  brevia  from  the  left  extremity  of 
the  stomach,  the  left  gastro-epiploic  vein,  pancreatic  branches  from  the  pancreas, 
the  pancreatico-duodenal  vein,  and  the  inferior  mesenteric  vein. 

The  inferior  mesenteric  vein  returns  the  blood  from  the  rectum,  sigmoid  flexure, 
and  descending  colon,  corresponding  with  the  ramifications  of  the  branches  of 
the  inferior  mesenteric  artery.  It  lies  to  the  left  of  the  artery,  and  ascends  be- 
neath the  peritoneum  in  the  lumbar  region  ;  it  passes  behind  the  transverse  portion 

1  The  student  may  observe  that  all  veins  above  the  Diaphragm,  which  do  not  lie  on  the  same 
plane  as  the  arteries  which  they  accompany,  lie  in  front  of  them,  and  that  all  veins  below  the 
Diaphragm,  which  do  not  lie  on  the  same  plane  as  the  arteries  which  they  accompany,  lie  behind 
them,  except  the  renal  and  profunda  femoris  vein. 


620 


THE   BLOOD-VASCULAR   SYSTEM. 


of  the  duodenum  and  pancreas,  and  terminates  in  the  splenic  vein.  Its  hemor- 
rhoidal branches  inosculate  with  those  of  the  internal  iliac,  and  thus  establish  a 
communication  between  the  portal  and  the  general  venous  system.1 

The  gastric  veins  are  two  in  number :  one,  a  small  vein,  corresponds  to  the 
pyloric  branch  of  the  hepatic  artery  ;  the  other,  considerably  larger,  corresponds 
to  the  gastric  artery.     The  former  {pyloric,  Walsham)  runs  along  the  lesser  cur- 


Fig.  336.— Portal  vein  and  its  branches. 

Note. — In  this  diagram  the  right  gastro-epiploic  vein  opens  into  the  splenic  vein  ;  generally 
it  empties  itself  into  the  superior  mesenteric,  close  to  its  termination. 

vature  of  the  stomach  toward  the  pyloric  end,  receives  branches  from  the  pylorus 
and  duodenum,  and  ends  in  the  vena  portse.  The  latter  {coronary,  Walsham) 
begins  near  the  pylorus,  runs  along  the  lesser  curvature  of  the  stomach  toward  the 

1  Besides  this  anastomosis  between  the  portal  vein  and  the  branches  of  the  vena  cava,  other 
anastomoses  between  the  portal  and  systemic  veins  are  formed  by  the  communication  between  the 
gastric  veins  and  the  oesophageal  veins,  which  empty  themselves  into  the  vena  azygos  minor  ;  between 
the  left  renal  vein  Snd  the  veins  of  the  intestines,  especially  of  the  colon  and  duodenum ;  between  the 
veins  of  the  round  ligament  of  the  liver  and  the  portal  veins  ;  and  between  the  superficial  branches 
of  the  portal  veins  of  the  liver  and  the  phrenic  veins,  as  pointed  out  by  Mr.  Kiernan.  (See  Physio- 
logical Anatomy,  by  Todd  and  Bowman,  1859,  vol.  ii.  p.  348.) 


THE    CARDIAC    VEINS.  621 

oesophageal  opening,  and  then  passes  across  the  front  of  the  spine  from  left  to  right 
to  end  in  the  vena  portse,  at  a  point  a  little  above  the  junction  of  the  pyloric  vein. 

The  Portal  Vein  is  formed  by  the  junction  of  the  superior  mesenteric  and 
splenic  veins,  their  union  taking  place  in  front  of  the  vena  cava  and  behind  the 
upper  border  of  the  head  of  the  pancreas.  Passing  upward  through  the  right 
border  of  the  lesser  omentum  to  the  under  surface  of  the  liver,  it  enters  the  trans- 
verse fissure,  where  it  is  somewhat  enlarged,  forming  the  sinus  of  the  portal  vein, 
and  divides  into  two  branches  which  accompany  the  ramifications  of  the  hepatic 
artery  and  hepatic  duct  throughout  the  substance  of  the  liver.  Of  these  two 
branches,  the  right  is  the  larger,  but  the  shorter,  of  the  two.  The  portal  vein  is 
about  three  or  four  inches  in  length,  and,  whilst  contained  in  the  lesser  omentum, 
lies  behind  and  between  the  common  bile  duct  and  the  hepatic  artery,  the  former 
being  to  the  right,  the  latter  to  the  left.  These  structures  are  accompanied  by 
filaments  of  the  hepatic  plexus  of  nerves  and  numerous  lymphatics,  surrounded  by 
a  quantity  of  loose  areolar  tissue  {capsule  of  Grlisson),  and  placed  between  the 
layers  of  the  lesser  omentum. 

The  Cystic  Vein.^-The  vena  portge  generally  receives  the  cystic  vein,  although 
it  sometimes  terminates  in  the  right  branch  of  the  vena  portse. 

The  portal  vein  divides,  in  the  substance  of  the  liver,  like  an  artery,  and  its 
minute  ramifications  end  in  capillaries,  from  which  the  blood  is  carried  to  the 
inferior  vena  cava  by  the  hepatic  veins  ;  these  veins  also  collect  the  blood  which 
has  been  brought  to  the  liver  by  the  hepatic  artery.  It  will  therefore  be  seen 
that  the  blood  which  is  carried  to  the  liver  by  the  portal  vein  passes  through  two 
sets  of  capillary  vessels,  viz.  :  (1)  the  capillaries  in  the  stomach,  intestine,  pancreas, 
and  spleen,  and  (2)  the  capillaries  of  the  portal  vein  in  the  liver. 

THE  CARDIAC  VEINS. 

The  veins  which  return  the  blood  from  the  substance  of  the  heart  are :  the 

Great  cardiac  vein.  Anterior  cardiac  veins. 

Posterior  cardiac  vein.  Right  or  small  coronary  vein. 

Left  cardiac  veins.  Coronary  sinus. 

Vense  Thebesii. 

The  Great  Cardiac  Vein  (sometimes  called  the  Coronary  vein)  is  a  vessel  of 
considerable  size,  which  commences  at  the  apex  of  the  heart,  and  ascends  along 
the  anterior  interventricular  groove  to  the  base  of  the  ventricles.  It  then  curves 
to  the  left  side,  around  the  auriculo-ventricular  groove,  between  the  left  auricle  and 
ventricle,  to  the  back  part  of  the  heart,  and  opens  into  the  left  extremity  of  the 
coronary  sinus,  its  aperture  being  guarded  by  two  valves.  It  receives,  in  its  course, 
tributaries  from  both  ventricles,  but  especially  the  left,  and  also  from  the  left 
auricle  ;  one  of  these,  ascending  along  the  thick  margin  of  the  left  ventricle,  is  of 
considerable  size.     The  vessels  joining  it  are  provided  with  valves. 

The  Posterior  Cardiac  Vein  (sometimes  called  the  Middle  cardiac  vein)  commences 
by  small  tributaries,  at  the  apex  of  the  heart,  communicating  with  those  of  the 
preceding.  It  ascends  along  the  posterior  interventricular  groove  to  the  base  of  the 
heart,  and  terminates  in  the  coronary  sinus,  its  orifice  being  guarded  by  a  valve. 
It  receives  the  veins  from  the  posterior  surface  of  both  ventricles. 

The  Left  Cardiac  Veins  are  three  or  four  small  vessels,  which  collect  the  blood 
from  the  posterior  surface  of  the  left  ventricle,  and  open  into  the  lower  border  of 
the  coronary  sinus. 

The  Anterior  Cardiac  Veins  are  three  or  four  small  vessels,  which  collect  the 
blood  from  the  anterior  surface  of  the  right  ventricle.  One  of  these  (the  vein  of 
G-alen),  larger  than  the  rest,  runs  along  the  right  border  of  the  heart.  They  open 
separately  into  the  lower  part  of  the  right  auricle. 

The  Right  or  Small  Coronary  Vein  runs  along  the  groove  between  the  right 
auricle  and  ventricle,  to  open  into  the  right  extremity  of  the  coronary  sinus.  It 
receives  blood  from  the  back  part  of  the  right  auricle  and  ventricle. 


622  THE  BLOOD-VASCULAR    SYSTEM. 

The  Coronary  Sinus  is  that  portion  of  the  anterior  or  great  cardiac  vein  which 
is  situated  in  the  posterior  part  of  the  left  auriculo-ventricular  groove.  It  is  about 
an  inch  in  length,  presents  a  considerable  dilatation,  and  is  covered  by  the  muscular 
fibres  of  the  left  auricle.  It  receives  the  veins  enumerated  above,  and  an  oblique 
vein  from  the  back  part  of  the  left  auricle,  the  remnant  of  the  obliterated  left 
Cuvierian  duct  of  the  foetus,  described  by  Mr.  Marshall.  The  great  coronary 
sinus  terminates  in  the  right  auricle,  between  the  inferior  vena  cava  and  the 
auriculo-ventricular  aperture,  its  orifice  being  guarded  by  a  semilunar  fold  of  the 
lining  membrane  of  the  heart,  the  Thebesian  valve.  All  the  veins  joining  this 
vessel,  excepting  the  oblique  vein  above  mentioned,  are  provided  with  valves. 

The  Vense  Thebesii  (vence  cordis  minima?)  are  numerous  minute  veins,  which 
return  the  blood  directly  from  the  muscular  substance,  without  entering  the  venous 
current.  They  open  by  minute  orifices  (foramina  Thebesii)  on  the  inner  surface 
of  the  right  auricle. 


THE  LYMPHATIC  SYSTEM. 


THE  Lymphatic  System  includes  not  only  the  lymphatic  vessels  and  the  glands 
through  which  they  pass,  but  also  the  lacteal  or  chyliferous  vessels.  The 
lacteals  are  the  lymphatic  vessels  of  the  small  intestine,  and  differ  in  no  respect 
from  the  lymphatics  generally,  excepting  that  they  contain  a  milk-white  fluid,  the 
chyle,  during  the  process  of  digestion,  and  convey  it  into  the  blood  through  the 
thoracic  duct. 

The  lymphatics  have  derived  their  name  from  the  appearance  of  the  fluid  con- 
tained in  their  interior  (lympha,  water).  They  are  also  called  absorbents,  from  the 
property  they  possess  of  absorbing  certain  materials  from  the  tissues  and  conveying 
them  into  the  circulation. 

The  lymphatics  are  exceedingly  delicate  vessels,  the  coats  of  which  are  so 
transparent  that  the  fluid  they  contain  is  readily  seen  through  them.  They  retain 
a  nearly  uniform  size,  being  interrupted  at  intervals  by  constrictions,  which  give 
them  a  knotted  or  beaded  appearance.  These  constrictions  are  due  to  the  pres- 
ence of  valves  in  their  interior.  Lymphatics  have  been  found  in  nearly  every 
texture  and  organ  of  the  body  which  contain  blood-vessels.  Such  non-vascular 
structures  as  cartilage,  the  nails,  cuticle,  and  hair  have  none,  but  with  these 
exceptions  it  is  probable  that  eventually  all  parts  will  be  found  to  be  permeated 
by  these  vessels. 

The  lymphatics  are  arranged  into  a  superficial  and  deep  set.  The  superficial 
lymphatics,  on  the  surface  of  the  body,  are  placed  immediately  beneath  the  integ- 
ument, accompanying  the  superficial  veins  ;  they  join  the  deep  lymphatics  in  cer- 
tain situations  by  perforating  the  deep  fascia.  In  the  interior  of  the  body  they 
lie  in  the  submucous  areolar  tissue  throughout  the  whole  length  of  the  gastro- 
pulmonary  and  genito-urinary  tracts,  and  in  the  subserous  tissue  in  the  cranial, 
thoracic,  and  abdominal  cavities.  The  method  of  their  origin  will  be  described 
later,  along  with  the  other  details  of  their  minute  anatomy.  Here  it  will  be 
sufficient  to  say  that  a  plexiform  network  of  minute  lymphatics  may  be  found 
interspersed  among  the  proper  elements  and  blood-vessels  of  the  several  tissues, 
the  vessels  composing  which,  as  well  as  the  meshes  between  them,  are  much  larger 
than  those  of  the  capillary  plexus.  From  these  networks  small  vessels  emerge, 
which  pass  either  to  a  neighboring  gland  or  to  join  some  larger  lymphatic  trunk. 
The  deep  lymphatics,  fewer  in  number  and  larger  than  the  superficial,  accompany 
the  deep  blood-vessels.  Their  mode  of  origin  is  probably  similar  to  that  of  the 
superficial  vessels.  The  lymphatics  of  any  part  or  organ  exceed  the  veins  in 
number,  but  in  size  they  are  much  smaller.  Their  anastomoses  also,  especially 
those  of  the  large  trunks,  are  more  frequent,  and  are  effected  by  vessels  equal  in 
diameter  to  those  which  they  connect,  the  continuous  trunks  retaining  the  same 
diameter. 

The  lymphatic  or  absorbent  glands,  named  also  conglobate  glands,  are  small, 
solid,  glandular  bodies  situated  in  the  course  of  the  lymphatic  and  lacteal  ves- 
sels. In  size  they  vary  from  a  hemp-seed  to  an  almond,  and  their  color,  on  sec- 
tion, is  of  a  pinkish-gray  tint,  excepting  the  bronchial  glands,  which  in  the  adult 
are  mottled  with  black  Each  gland  has  a  layer  or  capsule  of  cellular  tissue 
investing  it,  from  ilongations  dip  into  its  substance,  forming  partitions. 

The  lymphatic  an  «.   vessels  pass  through  these  bodies  in  their  passage  to 

the  thoracic  and  tic  ducts.     A  lymphatic   or  lacteal  vessel,   previous  to 

623 


624 


THE   LYMPHATIC  SYSTEM 


Right 
lymphatic  lrm^ 
duct. 


entering  a  gland,  divides  into  several  small  branches,  which  are  named  afferent 
vessels.     As  they  enter  their  external  coat  becomes  continuous  with  the  capsule  of 

the  gland,  and  the  vessels,  much 
thinned,  and  consisting  only  of 
their  internal  or  endothelial  coat, 
pass  into  the  gland,  and  branch 
out  upon  and  in  the  tissue  of  the 
capsule,  these  branches  opening 
into  the  lymph-sinuses  of  the 
gland.  From  these  sinuses  fine 
branches  proceed  to  form  a  plex- 
us, the  vessels  of  which  unite  to 
form  a  single  efferent  vessel,  which, 
on  emerging  from  the  gland,  is 
again  invested  with  an  external 
coat.  (Further  details  on  the  mi- 
nute anatomy  of  the  lymphatic  ves- 
sels and  glands  will  be  found  in  the 
section   on  General  Anatomy.) 

THE  THORACIC  DUCT. 
The  thoracic  duct  (Fig.  337) 
conveys  the  great  mass  of  lymph 
and  chyle  into  the  blood.  It  is  the 
common  trunk  of  all  the  lymphatic 
vessels  of  the  body,  excepting  those 
of  the  right  side  of  the  head,  neck, 
and  thorax,  and  right  upper  ex- 
tremity, the  right  lung,  right  side 
of  the  heart,  and  the  convex  sur- 
face of  the  liver.  It  varies  in 
length  from  fifteen  to  eighteen 
inches  in  the  adult,  and  extends 
from  the  second  lumbar  vertebra 
to  the  root  of  the  neck.  It  com- 
mences in  the  abdomen  by  a  trian- 
gular dilatation,  the  receptaculum 
chyli  (reservoir  or  cistern  of  Pec- 
quet), which  is  situated  upon  the 
front  of  the  body  of  the  second 
lumbar  vertebra,  to  the  right  side 
and  behind  the  aorta,  by  the  side 
of  the  right  crus  of  the  Diaphragm. 
It  ascends  into  the  thorax  through 
the  aortic  opening  in  the  Dia- 
phragm,  lying  to  the  right  "of  the 
aorta,  and  is  placed  in  the  pos- 
terior mediastinum  in  front  of  the 
vertebral  column,  lying  between 
the  aorta  and  vena  azygos  major. 
Opposite  the  fourth  dorsal  ver- 
tebra it  inclines  toward  the  left 
side,  and  ascends  behind  the  arch  of  the  aorta  on  the  left  side  of  the 
oesophagus,  and  behind  the  first  portion  of  the  left  subclavian  artery,  to  the 
upper  orifice  of  the  thorax.  Opposite  the  seventh  cervical  vertebra  it  turns 
outward  and  then  curves  downward  over  the  subclavian  artery  and  in  front  of 
the  Scalenus  anticus  muscle,  so  as  to  form  an  arch,  and  terminates  in   the  left 


Fig.  337.— The  thoracic  and  right  lymphatic  duct. 


OF    THE   HEAD,  FACE,  AND    NECK.  625 

subclavian  vein  at  its  angle  of  junction  with  the  left  internal  jugular  vein.  The 
thoracic  duct,  at  its  commencement,  is  about  equal  in  size  to  the  diameter  of  a 
goosequill,  diminishes  considerably  in  its  calibre  in  the  middle  of  the  thorax,  and 
is  ao-ain  dilated  just  before  its  termination.  It  is  generally  flexuous  in  its  course, 
and  constricted  at  intervals  so  as  to  present  a  varicose  appearance.  The  thoracic 
duct  not  unfrequently  divides  in  the  middle  of  its  course  into  two  branches  of 
unequal  size,  which  soon  reunite,  or  into  several  branches,  which  form  a  plexiform 
interlacement.  It  occasionally  divides,  at  its  upper  part,  into  two  branches,  of 
which  the  one  on  the  left  side  terminates  in  the  usual  manner,  while  that. on  the 
right  opens  into  the  right  subclavian  vein,  in  connection  with  the  right  lymphatic 
duct.  The  thoracic  duct  has  numerous  valves  throughout  its  whole  course,  but 
they  are  more  numerous  in  the  upper  than  in  the  lower  part :  at  its  termination  it 
is  provided  with  a  pair  of  valves,  the  free  borders  of  which  are  turned  toward  the 
vein,  so  as  to  prevent  the  passage  of  venous  blood  into  the  duct. 

Tributaries. — The  thoracic  duct,  at  its  commencement,  receives  four  or  five 
large  trunks  from  the  abdominal  lymphatic  glands,  and  also  the  trunk  of  the 
lacteal  vessels.  Within  the  thorax  it  is  joined  by  the  lymphatic  vessels  from  the 
left  half  of  the  Avail  of  the  thoracic  cavity,  the  lymphatics  from  the  sternal  and 
intercostal  glands,  those  of  the  left  lung,  left  side  of  the  heart,  trachea,  and 
oesophagus;  and,  just  before  its  termination,  it  receives  the  lymphatics  of  the  left 
side  of  the  head  and  neck  and  left  upper  extremity. 

Structure. — The  thoracic  duct  is  composed  of  three  coats,  which  differ  in  some 
respects  from  those  of  the  lymphatic  vessels.  The  internal  coat  consists  of  a  single 
layer  of  flattened  lanceolate-shaped  endothelial  cells  with  serrated  borders ;  of  a 
subendothelial  layer,  similar  to  that  found  in  the  arteries ;  and  an  elastic  fibrous 
coat,  the  fibres  of  which  run  in  a  longitudinal  direction.  The  middle  coat  con- 
sists of  a  longitudinal  layer  of  white  connective  tissue  with  elastic  fibres,  external 
to  which  are  several  laminae  of  muscular  tissue,  the  fibres  of  which  are  for  the 
most  part  disposed  transversely,  but  some  are  oblique  or  longitudinal  and  inter- 
mixed with  elastic  fibres.  The  external  coat  is  composed  of  areolar  tissue,  with 
elastic  fibres  and  isolated  fasciculi  of  muscular  fibres. 

The  Eight  Lymphatic  Duct  is  a  short  trunk,  about  half  an  inch  in  length  and 
a  line  or  a  line  and  a  half  in  diameter.  It  terminates  in  the  right  subclavian  vein 
at  its  angle  of  junction  with  the  right  internal  jugular  vein.  Its  orifice  is  guarded 
by  two  semilunar  valves,  which  prevent  the  passage  of  venous  blood  into  the  duct. 

Tributaries. — It  receives  the  lymph  from  the  right  side  of  the  head  and  neck, 
the  right  upper  extremity,  the  right  side  of  the  thorax,  the  right  lung  and  right 
side  of  the  heart,  and  from  part  of  the  convex  surface  of  the  liver. 

LYMPHATICS  OF  THE  HEAD,  FACE,  AND  NECK. 

The  Lymphatic  Glands  of  the  Head  (Fig.  338)  are  arranged  in  the  following 
groups  :  (1)  The  occipital,  one  or  two  in  number,  placed  at  the  back  of  the  head,  close 
to  the  occipital  artery.  (2)  The  posterior  auricular  or  mastoid,  usually  two  in  num- 
ber, situated  on  the  insertion  of  the  Sterno-mastoid  to  the  mastoid  process.  Both 
these  sets  of  glands  are  affected  in  cutaneous  eruptions  and  other  diseases  of  the  scalp. 
(3)  The  parotid  or  pre- auricular,  some  of  which  are  superficial  to,  and  others  are 
imbedded  in,  the  substance  of  the  parotid  gland.  (4)  The  buccal,  one  or  more, 
placed  on  the  surface  of  the  Buccinator  muscle.  (5)  The  internal  maxillary,  be- 
neath the  ramus  of  the  jaw.  (6)  The  lingual,  two  or  three  in  number,  lying  on 
the  Hyo-glossus  and  Grenio-hyo-glossus.  (7)  The  retro-pl Laryngeal,  lying  one  on 
each  side  of  the  middle  line  in  front  of  the  Rectus  capitis  anticus  major. 

The  lymphatic  vessels  of  the  scalp  are  divided  into  an  anterior  and  &  posterior 
set,  which  follow  the  course  of  the  temporal  and  occipital  vessels.  The  tem- 
poral accompany  the  temporal  artery  in  front  of  the  ear,  to  the  parotid 
lymphatic  glands,  from  which  they  proceed  to  the  lymphatic  glands  of  the 
neck.      The    occipital   follow    the    course    of    the    occipital    artery,    descend    to 

40 


626 


THE   LYMPHATIC  SYSTEM 


the  occipital  and  posterior  auricular  lymphatic  glands,  and  finally  join  the  cervi- 
cal glands. 

The  Lymphatic  Vessels  of  the  Face  are  divided  into  two  sets,  superficial  and 
deep. 

The  superficial  lymphatic  vessels  of  the  face  are  more  numerous  than  those  of 
the  head,  and  commence  over  its  entire  surface.  Those  from  the  frontal  region 
accompany  the  frontal  vessels  ;  they  then  pass  obliquely  across  the  face,  running 


Fig.  338.— The  superficial  lymphatics  and  glands  of  the  head,  face,  and  neck. 

with  the  facial  vein,  pass  through  the  buccal  glands  on  the  surface  of  the  Bucci- 
nator muscle,  and  join  the  submaxillary  lymphatic  glands.  The  latter  receive  the 
lymphatic  vessels  from  the  lips,  and  are  often  found  enlarged  in  cases  of  malignant 
disease  of  those  parts. 

The  lymphatic  vessels  of  the  cranium  consist  of  two  sets,  the  meningeal  anc 
cerebral.  The  meningeal  lymphatics  accompany  the  meningeal  vessels,  escape 
through  foramina  at  the  base  of  the  skull,  and  join  the  deep  cervical  lymphatic 
glands.  The  cerebral  lymphatics  are  described  by  Eshmann  as  being  situatec 
between  the  arachnoid  and  pia  mater,  as  well  as  in  the  choroid  plexuses  of  the 
lateral  ventricles  ;  they  accompany  the  trunks  of  the  carotid  and  vertebral  arteries, 
and  probably  pass  through  foramina  at  the  base  of  the  skull  to  terminate  in  the 
deep  cervical  glands.  They  have  not  at  present  been  demonstrated  in  the  dura 
mater  or  in  the  substance  of  the  brain. 

The  lymphatics  of  the  orbit  and  of  the  temporal  and  zygomatic  fossse  run  with 


OF    THE   NECK. 


62" 


the  branches  of  the  internal  maxillary  artery  to  the  maxillary  glands,  and  after- 
ward to  the  deep  cervical.  '■ 

The  lymphatics  of  the  nose  can  he  injected  from  the  subdural  and  subarachnoid 
spaces.  They  terminate  in  the  retropharyngeal  and  supra-hyoid  glands  lhe 
lymphatics  of  the  tongue  chiefly  accompany  the  ranme  vein  first  to  the  lingual 
glands  and  from  these  to  the  deep  cervical.  Those  from  the  anterior  part  of  the 
tongue  and  floor  of  the  mouth  pierce  the  Mylohyoid  muscles  and  so  reach  the 
submaxillary  glands.  From  the  upper  part  of  the  pharynx  the  lymphatics  pass 
to  the  retropharyngeal  glands;  from  the  lower  part,  to  the  deep  cervical  glands 
From   the  larynx   two  sets  of  vessels   arise :   an   upper,  piercing  the   thyro-hyoiu 


Fig.  339.— The  deep  lymphatics  and  glands  of  the  neck  and  thorax. 


membrane  and  joining  the  superior  set  of  deep  glands ;  and  a  lower  perforating 
the  crico-thyroid  membrane  to  join  the  lower  set  of  deep  cervical  glands  ine 
lymphatics  of  the  thyroid  body  accompany  the  superior  and  inferior  thyroid  arte- 
ries, and  open  partly  into  the  upper  and  partly  into  the  lower  set  of  deep  cervical 

S  anThe  Lymphatic  Glands  of  the  Neck  are  divided  into  two  sets,  superficial  and 

ee%\e  superficial  cervical  glands  may  be  arranged  in  three  sets :  (1)  The 
submaxillary,  eight  to  ten  in  number,  situated  beneath  the  body  of  the  lo*ei 
jaw  in  the  submaxillary  triangle;  (2)  suprahyoid,  one  or  two  in  number,  situated 


628  THE   LYMPHATIC  SYSTEM 

in  the  middle  line  of  the  neck,  between  the  anterior  bellies  of  the  two  digastric 
muscles ;  and  (3)  cervical,  placed  in  the  course  of  the  external  jugular  vein  be- 
tween the  Platysma  and  deep  fascia.  They  are  most  numerous  at  the  root  of  the 
neck,  in  the  triangular  interval  between  the  clavicle,  the  Sterno-mastoid,  and  the 
Trapezius,  where  they  are  continuous  with  the  axillary  glands.  A  few  small  glands 
are  also  found  on  the  front  and  sides  of  the  larynx. 

The  deep  cervical  glands  (Fig.  339)  are  numerous  and  of  large  size ;  they  form 
a  chain  along  the  sheath  of  the  carotid  artery  and  internal  jugular  vein,  lying  by 
the  side  of  the  pharynx,  oesophagus,  and  trachea,  and  extending  from  the  base  of 
the  skull  to  the  thorax,  where  they  communicate  with  the  lymphatic  glands  in  that 
cavity.  They  are  subdivided  into  two  sets :  an  upper,  ten  to  twenty  in  number. 
situated  about  the  bifurcation  of  the  common  carotid  and  along  the  upper  part 
of  the  internal  jugular  vein  ;  and  a  lower,  ten  to  fifteen  in  number,  clustered  around 
the  lower  part  of  the  internal  jugular  vein,  and  extending  outward  into  the  supra- 
clavicular fossa,  where  they  are  continuous  with  the  axillary  glands.  Internally, 
this  set  is  continuous  with  the  mediastinal  glands. 

The  superficial  and  deep  cervical  lymphatic  vessels  are  a  continuation  of  those 
already  described  on  the  cranium  and  face.  After  traversing  the  glands  in  those 
regions,  they  pass  through  the  chain  of  glands  which  lie  along  the  sheath  of  the 
carotid  vessels,  being  joined  by  the  lymphatics  from  the  pharynx,  oesophagus, 
larynx,  trachea,  and  thyroid  gland.  At  the  lower  part  of  the  neck,  after  receiving 
some  lymphatics  from  the  thorax,  they  unite  into  a  single  trunk,  which  terminates, 
on  the  left  side,  in  the  thoracic  duct ;  on  the  right  side,  in  the  right  lymphatic 
duct. 

Surgical  Anatomy. — The  cervical  glands  are  very  frequently  the  seat  of  tuberculous 
disease.  This  condition  is  most  usually  set  up  by  some  lesion  in  those  parts  from  which  they 
receive  their  lymph.  This  excites  some  inflammation,  which  subsequently  takes  on  a  tuberculous 
character.  It  is  very  desirable,  therefore,  for  the  surgeon,  in  dealing  with  these  cases,  to  possess 
a  knowledge  of  the  relation  of  the  respective  groups  of  glands  to  the  periphery.  The  following 
table  is  extracted  from  Mr.  Treves' s  work  on  Scrofula  audits  Gland  Diseases : 

Scalp. — Posterior  part  =  suboccipital  and  mastoid  glands.  Frontal  and  parietal  portions  = 
parotid  glands. 

Lymphatic  vessels  from  the  scalp  also  enter  the  superficial  cervical  set  of  glands. 

Skin  of  face  and  neck  —  submaxillary,  parotid,  and  superficial  cervical  glands. 

External  ear  =  superficial  cervical  glands. 

Lower  lip  =  submaxillary  and  suprahyoid  glands. 

Buccal  cavity  =  submaxillary  and  upper  set  of  deep  cervical  glands. 

Gums  of  lower  jaw  =  submaxillary  glands. 

Tongue.- — Anterior  portion  =  suprahyoid  and  submaxillary  glands.  Posterior  portion  = 
upper  set  of  deep  cervical  glands. 

Tonsils  and  palate  =  upper  set  of  deep  cervical  glands. 

Pharynx. — Upper  part  =  parotid  and  retro- pharyngeal  glands.  Lower  part  =  upper  set  of 
deep  cervical  glands. 

Larynx,  orbit,  and  roof  of  mouth  =  upper  set  of  deep  cervical  glands. 

Nasal  fossa?  =  retro-pharyngeal  glands,  upper  set  of  deep  cervical  glands.  Some  lymphatic 
vessels  from  posterior  part  of  the  fossae  enter  the  parotid  glands. 

LYMPHATICS  OF  THE  UPPER  EXTREMITY. 

The  Lymphatic  Glands  of  the  Upper  Extremity  (Fig.  340)  are  divided  into  two 
sets,  superficial  and  deep. 

The  superficial  lymphatic  glands  are  few  and  of  small  size.  There  are  occa- 
sionally two  or  three  in  front  of  the  elbow,  and  one  or  two  above  the  internal 
condyle  of  the  humerus,  near  the  basilic  vein,  while  one  or  two  may  be  found  lying 
beside  the  cephalic  vein  between  the  Pectpralis  major  and  Deltoid  muscles. 

The  deep  lymphatic  glands  are  few  in  number,  and  are  subdivided  into 
those  in  the  forearm,  the  arm,  and  the  axilla.  In  the  forearm  a  few  small 
ones  are  occasionally  found  in  the  course  of  the  radial  and  ulnar  vessels.  In  the 
arm  there  is  a  chain  of  small  glands  along  the  inner  side  of  the  brachial  artery. 
One,  sometimes  two,  fairly  constant  glands  are  situated  a  little  above  and  in  front 
of  the  inner  condyle  of  the  humerus.      In  the  axilla  they  are  of  large  size,  and 


OF   THE    UPPER   EXTREMITY. 


629 


,      -  -u  a  .uir,  af  these  elands  surrounds  the  axillary 

usually  ten  or  twelve  in  number.     A  chain  o      ^se  g  the  lymphatic 

vessels,  imbedded  in  a  quantity  of  ^ose  aieola    Us sue    tn e  ^     ^ 

vessels  from  the  arm;  others  are  dispersed  m .the  ^al  ^        ^         the  lower 


Axillary  glands 


Fig.  340.-The  superficial  lymphatics  and  glands  of  the  upper  extremity 


Two  o,  three  subclavian  or  .f^^^t^^  S£ 

on  the  lefl  >  opening  into  the  thoracic  duct.  _ 


630  THE    LYMPHATIC  SYSTEM 

front  and  side  of  tbe  abdomen,  or  the  band,  forearm,  and  arm,  tbe  axillary  glands  are  liable  to 
be  found  enlarged. 

The  lymphatic  vessels  of  the  upper  extremity  are  divided  into  two  sets,  super 
ficial  and  deep. 

The  superficial  lymphatic  vessels  of  the  upper  extremity  commence  on  the  fin 
gers,  two  vessels  running  along  either  side  of  each  finger,  one  on  the  palmar  anc 
the  other  on  the  dorsal  surface.  Those  on  the  palmar  surface  form  an  arch  in  the 
palm  of  the  hand,  from  which  are  derived  two  sets  of  vessels,  which  pass  up  the 
forearm,  taking  the  course  of  the  subcutaneous  veins.  The  lymphatics  from  the 
dorsal  surface  of  the  fingers  form  a  plexus  on  the  back  of  the  hand,  and,  winding 
around  the  inner  and  outer  borders  of  the  forearm,  unite  with  those  in  front.  Those 
from  the  inner  border  of  the  hand  accompany  the  ulnar  veins  along  the  inner  side 
of  the  forearm  to  the  bend  of  the  elbow,  where  they  are  joined  by  some  lymphatics 
from  the  outer  side  of  the  forearm  :  they  then  follow  the  course  of  the  basilic  vein 
communicate  Avith  the  glands  immediately  above  the  elbow,  and  terminate  in  the 
axillary  glands,  joining  with  the  deep  lymphatics.  The  superficial  lymphatics  from 
the  outer  and  back  part  of  the  hand  accompany  the  radial  veins  to  the  bend  of  the 
elbow.  They  are  less  numerous  than  the  preceding.  At  the  bend  of  the  elbow 
the  greater  number  join  the  basilic  group  ;  the  rest  ascend  with  the  cephalic  vein 
on  the  outer  side  of  the  arm,  some  crossing  the  upper  part  of  the  Biceps  obliquely, 
to  terminate  in  the  axillary  glands,  whilst  one  or  two  accompany  the  cephalic  vein 
in  the  cellular  interval  between  the  Pectoralis  major  and  Deltoid,  and  enter  the 
subclavian  lymphatic  glands. 

The  deep  lymphatic  vessels  of  the  upper  extremity  accompany  the  deep  blood- 
vessels. In  the  forearm  they  consist  of  four  sets,  corresponding  with  the  radial 
ulnar,  and  interosseous  arteries  ;  they  pass  through  the  glands  occasionally  founc 
in  the  course  of  those  vessels,  and  communicate  at  intervals  with  the  superficial 
lymphatics.  In  their  course  upward  some  of  them  pass  through  the  glands  which 
lie  upon  the  brachial  artery ;  they  then  enter  the  axillary  and  subclavian  glands, 
and  at  the  root  of  the  neck  terminate  on  the  left  side  in  the  thoracic  duct,  and  on 
the  right  side  in  the  right  lymphatic  duct. 

LYMPHATICS  OF  THE  LOWER  EXTREMITY. 

The  Lymphatic  Glands  of  the  Lower  Extremity  are  divided  into  two  sets,  super- 
ficial and  deep.  The  superficial  are  confined  to  the  inguinal  region,  forming  the 
superficial  inguinal  lymphatic  glands. 

The  superficial  inguinal  lymphatic  glands,  placed  immediately  beneath  the 
integument,  are  of  large  size,  and  vary  from  eight  to  ten  in  number.  They  are 
divisible  into  two  groups  :  an  upper  oblique  set,  disposed  irregularly  along  Pou- 
part's  ligament,  which  receive  the  lymphatic  vessels  from  the  integument  of  the 
scrotum,  penis,  parietes  of  the  abdomen,  perineal  and  gluteal  regions,  and  the 
mucous  membrane  of  the  urethra ;  and  an  inferior  vertical  set,  two  to  five  in  num- 
ber, which  surround  the  saphenous  opening  in  the  fascia  lata,  a  few  being  some- 
times continued  along  the  saphenous  vein  to  a  variable  extent.  This  latter  group 
receives  the  superficial  lymphatic  vessels  from  the  lower  extremity.  Leaf1  figures 
some  of  the  efferent  vessels  from  these  glands  as  terminating  directly  in  the  veins 
of  this  region. 

Surgical  Anatomy. — These  glands  frequently  become  enlarged  in  diseases  implicating  the 
parts  from  which  their  lymphatics  originate.  Thus  in  malignant  or  syphilitic  affections  of  the 
prepuce  and  penis,  or  of  the  labia  majora  in  the  female,  in  cancer  scroti,  in  abscess  in  the  peri- 
nseum,  or  in  any  other  diseases  affecting  the  integument  and  superficial  structures  in  those  parts, 
or  the  subumbiiical  part  of  the  abdominal  wall  or  the  gluteal  region,  the  upper  chain  of  glands 
is  almost  invariably  enlarged,  the  lower  chain  being  implicated  in  diseases  affecting  the  lower 
limb. 

The  deep  lymphatic  glands  are  the  anterior  tibial,  popliteal,  deep  inguinal, 
gluteal,   and  ischiatic. 

1  The  Surgical  Anatomy  of  the  Lymphatic  Glands,  1898. 


OF    THE   LOWER    EXTREMITY. 


631 


Superficial 
inguinal 
glands. 


mm 

mil 


The  anterior  tibial  gland  is  not  con- 
stant in  its  existence.  It  is  generally 
found  by  the  side  of  the  anterior  tibial 
artery,  upon  the  interosseous  mem- 
brane at  the  upper  part  of  the  leg.  Occa- 
sionally, two  glands  are  found  in  this 
situation. 

The  popliteal  glands,  four  or  five  in 
number,  are  of  small  size ;  they  surround 
the  popliteal  vessels,  imbedded  in  the  cel- 
lular tissue  and  fat  of  the  popliteal  space. 

The  deep  inguinal  glands  are  placed 
beneath  the  deep  fascia  around  the  femoral 
artery  and  vein.  They  are  of  small  size, 
and  communicate  with  the  superficial 
inguinal  glands  through  the  saphenous 
opening. 

The   gluteal  and  ischiatic  glands  are  ^3s  :i\\aY\\M1?k 

placed,  the  former  above,  the  latter  below, 

the   Pyriformis   muscle,    resting  on   their  ^i^^/ftljCPW  pf 

corresponding  vessels  as  they  pass  through 
the  great  sacro-sciatic  foramen. 

The  Lymphatic  Vessels  of  the  Lower 
Extremity,  like  the  veins,  may  be  divided 
into  two  sets,  supterjieial  and  deep. 

The  superficial  lymphatic  vessels  are 
placed  beneath  the  integument  in  the 
superficial  fascia,  and  are  divisible  into 
two  groups :  an  internal  group,  which  fol- 
low the  course  of  the  internal  saphenous 
vein ;  and  an  external  group,  which  ac- 
company the  external  saphenous.  The 
internal  group,  the  larger,  commence  on 
the  inner  side  and  dorsum  of  the  foot; 
they  pass,  some  in  front  and  some  behind, 
the  inner  ankle,  run  up  the  leg  with  the 
internal  saphenous  vein,  pass  with  it  be- 
hind the  inner  condyle  of  the  femur,  and 
accompany  it  to  the  groin,  where  they  ter- 
minate in  the  group  of  superficial  inguinal 
lymphatic  glands  which  surround  the 
saphenous  opening.  Some  of  the  efferent 
vessels  from  these  glands  pierce  the  cribri- 
form fascia  and  sheath  of  the  femoral  ves- 
sels, and  terminate  in  a  lymphatic  gland 
contained  in  the  femoral  canal,  thus  estab- 
lishing a  communication  between  the  lym- 
phatics of  the  lower  extremity  and  those 
of  the  trunk  ;  others  pierce  the  fascia  lata 
and  join  the  deep  inguinal  glands.  The 
external  group  arise  from  the  outer  side 
of  the  foot,  ascend  in  front  of  the  leg, 
and,  just  below  the  knee,  cross  the  tibia 
from  without  inward,  to  join  the  lym- 
phatics on  the  inner  side  of  the  thigh. 
Others   commence    on    the    outer   side  of 

.-,       c     i.  i     !_•     j    xi.  11      i  Fig.  341.— The  superficial  lymphatics  a 

tne  loot,  pass  behind  the  outer  malleolus,    0f  the  lower  extremity. 


.V\ 


nd  glands 


632  THE  LYMPHATIC  SYSTEM 

and  accompany  the  external  saphenous  vein  along  the  back  of  the  leg,  where  they 
enter  the  popliteal  glands. 

The  deep  lymphatic  vessels  of  the  lower  extremity  are  few  in  number  and 
accompany  the  deep  blood-vessels.  In  the  leg  they  consist  of  three  sets,  the 
anterior  tibial,  peroneal,  and  posterior  tibial,  which  accompany  the  corresponding 
blood-vessels,  two  or  three  to  each  artery ;  they  ascend  with  the  blood-vessels  and 
enter  the  lymphatic  glands  in  the  popliteal  space ;  the  efferent  vessels  from  these 
glands  accompany  the  femoral  vein  and  join  the  deep  inguinal  glands ;  from  these, 
the  vessels  pass  beneath  Pouparts  ligament  and  communicate  with  the  chain  of 
glands  surrounding  the  external  iliac  vessels. 

The  deep  lymphatic  vessels  of  the  gluteal  and  ischiatic  regions  follow  the 
course  of  the  blood-vessels,'  and  join  the# gluteal  and  ischiatic  glands  at  the  great 
sacro-sciatic  foramen. 

LYMPHATICS   OF   THE   PELVIS   AND  ABDOMEN. 

The  Lymphatic  Glands  in  the  Pelvis  are  the  external  iliac,  the  internal  iliac, 
and  the  sacral.     Those  of  the  abdomen  are  the  lumbar  and  cceliac  glands. 

The  external  iliac  glands  form  an  uninterrupted  chain  round  the  external  iliac 
vessels,  three  being  placed  round  the  commencement  of  the  vessels  just  behind  the 
crural  arch.  They  communicate  below  with  the  deep  inguinal  lymphatic  glands, 
and  above  with  the  lumbar  glands. 

The  internal  iliac  glands  surround  the  internal  iliac  vessels ;  they  receive  the 
lymphatic  vessels  corresponding  to  the  branches  of  the  internal  iliac  artery,  and 
communicate  with  the  lumbar  glands. 

The  sacral  glands  occupy  the  sides  of  the  anterior  surface  of  the  sacrum,  some 
being  situated  in  the  meso-rectal  fold.  These  and  the  internal  iliac  glands  are 
affected  in  malignant  disease  of  the  bladder,  rectum,  or  uterus. 

The  lumbar  glands  are  very  numerous ;  they  are  situated  on  the  front  of  the 
lumbar  vertebrae,  surrounding  the  common  iliac  vessels,  the  aorta,  and  vena  cava ; 
they  receive  the  lymphatic  vessels  from  the  lower  extremities  and  pelvis,  as  well  as 
from  the  testes  and  some  of  the  abdominal  viscera  :  the  efferent  vessels  from  these 
glands  unite  into  a  few  large  trunks,  which,  with  the  lacteals,  form  the  commence- 
ment of  the  thoracic  duct.  In  addition  to  these  there  are  a  few  small  lateral  lum- 
bar glands  which  lie  between  the  transverse  processes  of  the  vertebrae,  behind  the 
Psoas  muscle,  and  receive  lymphatics  from  the  back.  In  some  cases  of  malignant 
disease  these  glands  become  enormously  enlarged,  completely  surrounding  the  aorta 
and  vena  cava,  and  occasionally  greatly  contracting  the  calibre  of  those  vessels. 
In  all  cases  of  malignant  disease  of  the  testes  and  in  malignant  disease  of  the  lower 
limb,  before  any  operation  is  attempted,  careful  examination  of  the  abdomen  should 
be  made,  in  order  to  ascertain  if  any  enlargement  exists ;  and  if  any  should  be 
detected,  all  operative  measures  should  be  avoided  as  fruitless. 

The  Cceliac  (Hands,  nearly  twenty  in  number,  surround  the  cceliac  axis  and  lie 
in  front  of  the  aorta  near  the  origin  of  that  vessel.  They  receive  the  lymphatic 
vessels  from  a  large  part  of  the  liver,  from  the  spleen,  pancreas,  and  stomach. 
Their  efferent  vessels  join  the  lacteals  from  the  intestine  and  open  into  the 
receptaculum  chyli. 

The  Lymphatic  Vessels  of  the  Abdomen  and  Pelvis  may  be  divided  into  two  sets, 
superficial  and  deep. 

The  superficial  lymphatic  vessels  of  the  walls  of  the  abdomen  and  pelvis  follow 
the  course  of  the  superficial  blood-vessels.  Those  derived  from  the  integument 
of  the  lower  part  of  the  abdomen  below  the  umbilicus  follow  the  course  of  the 
superficial  epigastric  vessels  and  converge  to  the  superior  group  of  the  superficial 
inguinal  glands',  a  deeper  set  accompany  the  deep  epigastric  vessels,  and  commu- 
nicate with  the  external  iliac  glands.  The  superficial  lymphatics  from  the  sides 
of  the  lumbar  part  of  the  abdominal  Avail  wind  round  the  crest  of  the  ilium, 
accompanying  the  superficial  circumflex  iliac  vessels,  to  join  the  superior  group 


OF    THE   PELVIS   AND    ABDOMEN. 


633 


of  the  superficial  inguinal  glands ;  the  greater  number,  however,  run  back- 
ward along  with  the  ilio-lumbar  and  lumbar  vessels,  to  join  the  lateral  lumbar 
glands. 

The  superficial  lymphatic  vessels  of  the  gluteal  region  turn  horizontally  round 
the  outer  side  of  the  nates,  and  join  the  superficial  inguinal  glands. 

The  superficial  lymphatic  vessels  of  the  scrotum  and  perinaeum  follow  the  course 
of  the  external  pudic  vessels,  and  terminate  in  the  superficial  inguinal  glands. 


Lumbar 
glands. 


Sacral  glands. 


iliac  glands, 


External 
iliac  glands 


Deep 
inguinal 
glands.  ) 
// 


Deep  lymphatics  of  penis. 


Fig.  342.— The  deep  lymphatic  vessels  and  glands  of  the  abdomen  and  pelvis. 

The  superfh  ial  lymphatic  vessels  of  the  penis  occupy  the  sides  and  dorsum  of 
the  organ,  the  iving  the  lymphatics  from  the  skin  covering  the  glans 

penis ;  they  all       .  to  the  upper  chain  of  the  superficial  inguinal  glans.     The 

deep  lymphatic     ess  the  penis  follow  the  course  of  the  internal  pudic  vessels, 

and  join  the  intei  rial        c  glands. 


634  THE   LYMPHATIC  SYSTEM 

In  the  female  the  lymphatic  vessels  of  the  mucous  membrane  of  the  labia, 
nymphge,  and  clitoris  terminate  in  the  upper  chain  of  the  inguinal  glands. 

The  deep  lymphatic  vessels  of  the  abdomen  and  pelvis  take  the  course  of  the 
principal  blood-vessels,  Those  of  the  parietes  of  the  pelvis,  which  accompany 
the  gluteal,  ischiatic,  and  obturator  vessels,  follow  the  course  of  the  internal  iliac 
artery,  and  ultimately  join  the  lumbar  lymphatics. 

The  efferent  vessels  from  the  inguinal  glands  enter  the  pelvis  beneath  Poupart's 
ligament,  where  they  lie  in  close  relation  with  the  femoral  vein ;  they  then  pass 
through  the  chain  of  glands  surrounding  the  external  iliac  vessels,  and  finally  ter- 
minate in  the  lumbar  glands.  They  receive  the  deep  epigastric  and  circumflex 
iliac  lymphatics. 

The  lymphatic  vessels  of  the  bladder  arise  from  the  entire  surface  of  the 
organ ; 1  the  greater  number  run  beneath  the  peritoneum  on  its  posterior  surface, 
and,  after  passing  through  the  lymphatic  glands  in  that  situation,  join  with  the 
lymphatics  from  the  prostate  and  vesiculse  seminales,  and  enter  the  internal  iliac 
glands. 

The  lymphatic  vessels  of  the  rectum  are  of  large  size ;  after  passing  through 
some  small  glands  that  lie  upon  its  outer  wall  and  in  the  meso-rectum  they  pass  to 
the  sacral  glands. 

The  lymphatic  vessels  of  the  uterus  consist  of  two  sets,  superficial  and  deep, 
the  former  being  placed  beneath  the  peritoneum,  the  latter  in  the  substance  of  the 
organ.  The  lymphatics  of  the  cervix  uteri,  together  with  those  from  the  greater 
part  of  the  vagina,  enter  the  internal  iliac  and  sacral  glands;  those  from  the  body 
and  fundus  of  the  uterus  pass  outward  in  the  broad  ligaments,  and.  being  joined 
by  the  lymphatics  from  the  ovaries,  broad  ligaments,  and  Fallopian  tubes, 
ascend  with  the  ovarian  vessels  to  open  into  the  lumbar  glands ;  the  lymphatics 
from  the  lower  part  of  the  vagina  join  those  of  the  external  genitals  and  pass  to 
the  superficial  inguinal  glands.  In  the  unimpregnated  uterus  they  are  small,  but 
during  gestation  they  become  very  greatly  enlarged. 

The  lymphatic  vessels  of  the  testicle  consist  of  two  sets,  superficial  and  deep :  the 
former  commence  on  the  surface  of  the  tunica  vaginalis,  the  latter  in  the  epididy- 
mis and  body  of  the  testis.  They  form  several  large  trunks  which  ascend  with 
the  spermatic  cord,  and,  accompanying  the  spermatic  vessels  into  the  abdomen, 
terminate  into  the  lumbar  glands;  hence  the  enlargement  of  these  glands  in 
malignant  disease  of  the  testis. 

The  lymphatic  vessels  of  the  kidney  arise  on  the  surface,  and  also  in  the  inte- 
rior of  the  organ ;  they  join  at  the  hilum,  and,  after  receiving  the  lymphatic  vessels 
from  the  ureter  and  suprarenal  capsules,  open  into  the  lumbar  glands. 

The  lymphatic  vessels  of  the  liver  are  divisible  into  two  sets,  superficial  and  deep. 
The  former  arise  in  the  subperitoneal  areolar  tissue  over  the  entire  surface  of  the 
organ.  Those  on  the  convex  surface  may  be  divided  into  four  groups :  1.  Those 
which  pass  from  behind  forward,  consisting  of  three  or  four  branches,  which 
ascend  in  the  falciform  ligament  and  unite  to  form  a  single  trunk,  which  passes  up 
between  the  fibres  of  the  Diaphragm,  behind  the  ensiform  cartilage,  to  enter  the 
anterior  mediastinal  glands,  and  finally  ascends  to  the  root  of  the  neck,  to  ter- 
minate in  the  right  lymphatic  duct.  2.  Another  group,  which  also  incline  from 
behind  forward,  are  reflected  over  the  anterior  margin  of  the  liver  to  its  under 
surface,  and  from  thence  pass  along  the  longitudinal  fissure  to  the  glands  in  the 
gastro-hepatic  omentum.  3.  A  third  group  incline  outward  to  the  right  lateral 
ligament,  and,  uniting  into  one  or  two  large  trunks,  pierce  the  Diaphragm,  and 
run  along  its  upper  surface  to  enter  the  anterior  mediastinal  glands,  or,  instead 
of  entering  the  thorax,  turn  inward  across  the  crus  of  the  Diaphragm  and  open 
into  the  commencement  of  the  thoracic  duct.  4.  The  fourth  group  incline  out- 
ward from  the  surface  of  the  left  lobe  of  the  liver  to  the  left  lateral  ligament, 
pierce  the  Diaphragm,  and,  passing  forward,  terminate  in  the  glands  in  the  ante- 
rior mediastinum. 

1  Curnow  states  that  they  are  confined  to  the  base  of  the  organ. 


OF    THE   INTESTINES.  635 

The  superficial  lymphatics  on  the  under  surface  of  the  liver  are  divided  into 
three  sets  :   1.  Those  on  the  right  side  of  the  gall-bladder  enter  the  lumbar  glands. 

2.  Those  surrounding  the  gall-bladder  form  a  remarkable  plexus ;  they  accom- 
pany the  hepatic  vessels,  and  open  into  the  glands  in  the  gastro-hepatic  omentum. 

3.  those  on  the  left  of  the  gall-bladder  pass  to  the  oesophageal  glands  and  to  the 
glands  which  are  situated  along  the  lesser  curvature  of  the  stomach. 

The  deep  lymphatics  accompany  the  branches  of  the  portal  vein  and  the  hepatic 
artery  and  duct  through  the  substance  of  the  liver ;  passing  out  at  the  transverse 
fissure,  they  enter  the  lymphatic  glands  along  the  lesser  curvature  of  the  stomach 
and  behind  the  pancreas,  or  join  with  one  of  the  lacteal  vessels  previous  to  its 
termination  in  the  thoracic  duct. 

The  lymphatic  glands  of  the  stomach  are  of  small  size ;  they  are  placed  along 
the  upper  part  of  the  lesser   and  toward  the  pyloric  end  of  the  greater  curvature. 

The  lymphatic  vessels  of  the  stomach  consist  of  two  sets,  superficial  and  deep  ; 
the  former  originating  in  the  subserous,  and  the  latter  in  the  submucous  coat. 
They  follow  the  course  of  the  blood-vessels,  and  may  consequently  be  arranged 
into  three  groups.  The  first  group  accompany  the  gastric  vessels  along  the  lesser 
curvature  to  the  cardiac  orifice,  receiving  branches  from  both  surfaces  of  the 
orcran,  and  pass  to  the  coeliac  glands.  The  second  group  pass  from  the  great 
end  of  the  stomach,  accompanying  the  vasa  brevia,  and  enter  the  splenic 
lymphatic  glands.  The  third  group  run  along  the  greater  curvature  with  the 
right  gastro-epiploic  vessels  toward  the  pylorus,  and,  receiving  the  lymphatics 
from  the  upper  part  of  the  duodenum,  terminate  in  the  coeliac  glands. 

The  lymphatic  glands  of  the  spleen  occupy  the  hilum.  Its  lymphatic  vessels 
consist  of  two  sets,  superficial  and  deep ;  the  former  are  placed  beneath  its 
peritoneal  covering,  the  latter  in  the  substance  of  the  organ ;  they  accompany  the 
blood-vessels,  passing  through  a  series  of  small  glands,  and,  after  receiving  the 
lymphatics  from  the  pancreas,  ultimately  pass  into  the  coeliac  glands. 

The  lymphatics  of  the  pancreas  also  enter  the  coeliac  glands. 

THE  LYMPHATIC  SYSTEM  OF  THE  INTESTINES. 

The  lymphatic  glands  of  the  small  intestine  are  placed  between  the  layers  of 
the  mesentery,  occupying  the  meshes  formed  by  the  superior  mesenteric  vessels, 
and  hence  called  mesenteric  glands.  They  vary  in  number  from  a  hundred  to  a 
hundred  and  fifty,  and  in  size  from  that  of  a  pea  to  that  of  a  small  almond.1 
These  glands  are  most  numerous  and  largest  above,  the  glands  of  the  jejunum, 
being  more  numerous  than  those  of  the  ileum.  This  latter  group  becomes  enlarged 
and  infiltrated  with  deposit  in  cases  of  fever  accompanied  with  ulceration  of  the 
intestines. 

The  lymphatic  glands  of  the  large  intestine  are  much  less  numerous  than  the 
mesenteric  glands ;  they  are  situated  along  the  vascular  arches  formed  by  the 
arteries  previous  to  their  distribution,  and  even  sometimes  upon  the  intestine 
itself.  They  are  fewest  in  number  along  the  transverse  colon,  where  they  form 
an  uninterrupted  chain  with  the  mesenteric  glands. 

The  lymphatic  vessels  of  the  small  intestine  are  called  lacteals,  from  the  milk- 
white  fluid  they  usually  contain :  they  consist  of  two  sets,  superficial  and  deep, 
the  former  lie  between  the  layers  of  the  muscular  coat  and  between  the  muscular 
and  peritoneal  coats,  taking  a  longitudinal  course  along  the  outer  side  of  the 
intestine  ;  the  latter  occupy  the  submucous  tissue,  and  course  transversely  round 
the  intestine,  accompanied  by  the  branches  of  the  mesenteric  vessels ;  they  pass 
between  the  layers  of  the  mesentery,  enter  the  mesenteric  glands,  and  finally 
unite  to  form  two  or  three  large  trunks  which  terminate  separately  in  the  receptac- 
ulum  chyli ;  frequently,  however,  they  first  unite  to  form  a  single  large  trunk, 
termed  the  intestinal  lymphatic  trunk. 

The  lymphatic  vessels  of  the  large  intestine  consist  of  two  sets  :  those  of  the 
1  Leaf  (op.  cit.)  says  it  is  very  common  to  find  not  more  than  forty  or  fifty. 


636  THE   LYMPHATIC  SYSTEM 

caecum,  ascending  and  transverse  colon,  which,  after  passing  through  their  proper 
glands,  enter  the  mesenteric  glands  ;  and  those  of  the  descending  colon,  sigmoid 
flexure,  and  rectum,  which  pass  to  the  lumbar  glands. 


THE  LYMPHATICS  OF  THE  THORAX. 

The  Lymphatic  Glands  of  the  Thoracic  Wall  are  the  intercostal,  internal  mam- 
mary, anterior  mediastinal,  and  posterior  mediastinal. 

The  intercostal  glands  are  small,  and  situated  on  each  side  of  the  spine,  near 
the  costo-vertebral  articulations ;  they  vary  from  one  to  three  in  each  space. 

The  sternal  or  internal  mammary  glands  are  placed  at  the  anterior  extremity 
of  each  intercostal  space,  by  the  side  of  the  internal  mammary  vessels. 

The  anterior  mediastinal  glands  are  placed  in  the  loose  areolar  tissue  of  the 
anterior  mediastinum,  some  lying  upon  the  Diaphragm  in  front  of  the  pericardium, 
and  others  round  the  great  vessels  at  the  base  of  the  heart. 

The  posterior  mediastinal  glands  are  situated  in  the  areolar  tissue  in  the  poste- 
rior mediastinum,  forming  a  continuous  chain  by  the  side  of  the  aorta  and  oesoph- 
agus ;  they  communicate  on  each  side  with  the  intercostal,  below  Avith  the  lumbar, 
and  above  with  the  deep  cervical  glands. 

The  Superficial  Lymphatic  Vessels  of  the  Front  of  the  Thorax  run  across  the 
great  Pectoral  muscle,  and  those  on  the  back  part  of  this  cavity  lie  upon  the 
Trapezius  and  Latissimus  dorsi ;  they  all  converge  to  the  axillary  glands.  The 
lymphatics  from  the  greater  part  of  the  mammary  gland  pass  outward  to  the 
lower  border  of  the  Pectoralis  major  muscle,  where  they  enter  a  chain  of  small 
glands  situated  in  the  axillary  space  along  the  lower  border  of  its  anterior 
boundary.  Some  few  lymphatics  from  the  inner  side  of  the  mammary  gland  pass 
through  the  intercostal  spaces  to  reach  the  anterior  mediastinal  glands. 

The  Deep  Lymphatic  Vessels  of  the  Thoracic  "Wall  are  the  intercostal,  internal 
mammary,  and  diaphragmatic. 

The  intercostal  lymphatic  vessels  follow  the  course  of  the  intercostal  vessels, 
receiving  lymphatics  from  the  intercostal  muscles  and  pleura  ;  they  pass  backward 
to  the  spine,  and  unite  with  lymphatics  from  the  back  part  of  the  thorax  and  spinal 
canal.  After  traversing  the  intercostal  glands,  they  pass  down  the  spine  and 
terminate  in  the  thoracic  duct. 

The  internal  mammary  lymphatic  vessels  follow  the  course  of  the  internal 
mammary  vessels;  they  commence  in  the  muscles  of  the  abdomen  above  the 
umbilicus,  communicating  with  the  epigastric  lymphatics,  ascend  between  the 
fibres  of  the  Diaphragm  at  its  attachment  to  the  ensiform  appendix,  and  in  their 
course  behind  the  costal  cartilages  are  joined  by  the  intercostal  lymphatics;  they 
terminate  on  the  right  side  in  the  right  lymphatic  duct,  on  the  left  side  in  the 
thoracic   duct. 

The  lymphatic  vessels  of  the  Diaphragm  follow  the  course  of  their  correspond- 
ing vessels,  and  terminate,  some  in  front  in  the  anterior  mediastinal  and  internal 
mammary  glands,  some  behind,  in  the  intercostal  and  posterior  mediastinal  lymph- 
atics. 

The  Lymphatic  G-lands  of  the  Viscera  of  the  Thorax  are  the  bronchial 
glands. 

The  bronchial  glands  are  situated  round  the  bifurcation  of  the  trachea  and 
roots  of  the  lungs.  They  are  ten  or  twelve  in  number,  the  largest  being  placed 
opposite  the  bifurcation  of  the  trachea,  the  smallest  round  the  bronchi  and  their 
primary  divisions  for  some  little  distance  within  the  substance  of  the  lungs.  In 
infancy  they  present  the  same  appearance  as  lymphatic  glands  in  other  situations ; 
in  the  adult  they  assume  a  brownish  tinge,  and  in  old  age  a  deep  black  color. 
Occasionally  they  become  sufficiently  enlarged  to  compress  and  narrow  the  canal 
of  the  bronchi,  and  they  are  often  the  seat  of  tuberculous  deposits. 

The  superior  mediastinal  or  cardiac  glands  lie  in  front  of  the  transverse  aorta 


OF   THE    THORAX.  637 

and  left  innominate  vein  ;  this  group  consists  of  numerous  large  glands.  They 
receive  the  lymph  from  the  pericardium,  heart,  and  thymus  gland. 

The  lymphatic  vessels  of  the  lung  consist  of  two  sets,  superficial  and  deep  : 
the  former  are  placed  beneath  the  pleura,  forming  a  minute  plexus  which  covers 
the  outer  surface  of  the  lung ;  the  latter  accompany  the  blood-vessels  and  run  along 
the  bronchi :  they  both  terminate  at  the  root  of  the  lungs  in  the  bronchial  glands. 
The  efferent  vessels  from  these  glands,  two  or  three  in  number,  ascend  upon  the 
trachea  to  the  root  of  the  neck,  traverse  the  tracheal  and  oesophageal  glands,  and 
terminate  on  the  left  side  in  the  thoracic  duct  and  on  the  right  side  in  the  right 
lymphatic  duct. 

The  cardiac  lymphatic  vessels  consist  of  two  sets,  superficial  and  deep  :  the 
former  arise  in  the  subserous  areolar  tissue  of  the  surface,  and  the  latter  in  the 
deeper  tissues  of  the  heart.  They  follow  the  course  of  the  coronary  vessels  :  those 
of  the  right  side  unite  into  a  trunk  at  the  root  of  the  aorta,  which,  ascending  across 
the  arch  of  that  vessel,  communicates  with  one  or  more  of  the  cardiac  glands,  and 
passes  backward  to  the  trachea,  upon  which  it  ascends,  to  terminate  at  the  root  of 
the  neck  in  the  right  lymphatic  duct.  Those  of  the  left  side  unite  into  a  single 
vessel  at  the  base  of  the  heart,  which,  passing  along  the  pulmonary  artery  and 
traversing  some  glands  at  the  root  of  the  aorta,  ascends  on  the  trachea  to  terminate 
in  the  thoracic  duct. 

The  thymic  lymphatic  vessels  arise  from  the  under  surface  of  the  thymus  gland, 
and  enter  the  superior  mediastinal  glands,  from  which  they  emerge  as  two  vessels : 
these  terminate,  one  on  each  side,  in  the  corresponding  internal  jugular  vein. 

The  lymphatic  vessels  of  the  oesophagus  form  a  plexus  round  that  tube,  traverse 
the  glands  in  the  posterior  mediastinum,  and,  after  communicating  with  the 
pulmonary  lymphatic  vessels  near  the  roots  of  the  lungs,  terminate  in  the  thoracic 
duct. 


THE  NERVOUS  SYSTEM. 


THE  Nervous  System  is  composed  ■  1.  Of  a  series  of  large  centres  of  nerve- 
matter,  called,  collectively,  the  cerebrospinal  centres  or  cerebrospinal  axis. 
2.  Of  smaller  centres,  termed  ganglia.  3.  Of  nerves  connected  either  with  the 
cerebro-spinal  axis  or  the  ganglia.  And  4.  Of  certain  modifications  of  the  periph- 
eral terminations  of  the  nerves  forming  the  organs  of  the  external  senses. 

The  Cerebro-spinal  axis  consists  of  the  brain  or  encephalon  and  the  spinal 
cord,  which  are  contained  within  the  skull  and  spinal  canal.  The  brain  and  its 
membranes  will  be  first  considered,  and  then  the  spinal  cord  and  its  coverings. 

THE   MEMBRANES   OF   THE   BRAIN. 

Dissection. — To  examine  the  brain  with  its  membranes,  the  skull-cap  must  be  removed. 
In  order  to  effect  this,  saw  through  the  external  table,  the  section  commencing,  in  front,  about 
an  inch  above  the  margin  of  the  orbit,  and  extending,  behind,  to  a  little  above  the  level  with 
the  occipital  protuberance.  Then  break  the  internal  table  with  the  chisel  and  hammer,  to  avoid 
injuring  the  investing  membranes  or  brain  ;  loosen  and  forcibly  detach  the  skull-cap,  when  the 
dura  mater  will  be  exposed.  The  adhesion  between  the  bone  and  the  dura  mater  is  very 
intimate,  and  much  more  so  in  the  young  subject  than  in  the  adult. 

The  membranes  of  the  brain  are  :  the  dura  mater,  arachnoid  membrane,  and 
pia  mater. 

The  Dura  Mater. 

The  Dura  Mater  is  a  thick  and  dense  inelastic  fibrous  membrane  which  lines 
the  interior  of  the  skull.  Its  outer  surface  is  rough  and  fibrillated,  and  adheres 
closely  to  the  inner  surface  of  the  bones,  forming  their  internal  periosteum,  this 
adhesion  being  most  marked  opposite  the  sutures  and  at  the  base  of  the  skull. 
Its  inner  surface  is  smooth  and  lined  by  a  layer  of  endothelium.  It  sends  four 
processes  inward,  into  the  cavity  of  the  skull,  for  the  support  and  protection  of 
the  different  parts  of  the  brain,  and  is  prolonged  to  the  outer  surface  of  the  skull 
through  the  various  foramina  which  exist  at  the  base,  and  thus  becomes  contin- 
uous with  the  pericranium  ;  its  fibrous  layer  forms  sheaths  for  the  nerves  which 
pass  through  these  apertures.  At  the  base  of  the  skull  it  sends  a  fibrous  prolon- 
gation into  the  foramen  csecum ;  it  sends  a  series  of  tubular  prolongations  round 
the  filaments  of  the  olfactory  nerves  as  they  pass  through  the  cribriform  plate, 
and  also  round  the  nasal  nerve  as  it  passes  through  the  nasal  slit ;  a  prolongation 
is  also  continued  through  the  sphenoidal  fissure  into  the  orbit,  and  another  is  con- 
tinued into  the  same  cavity  through  the  optic  foramen,  forming  a  sheath  for  the 
optic  nerve,  which  is  continued  as  far  as  the  eyeball.  In  the  posterior  fossa  it 
sends  a  process  into  the  internal  auditory  meatus,  ensheathing  the  facial  and 
auditory  nerves;  another  through  the  jugular  foramen,  forming  a  sheath  for  the 
structures  which  pass  through  this  opening ;  and  a  third  through  the  anterior 
condyloid  foramen.  Around  the  margin  of  the  foramen  magnum  it  is  closely 
adherent  to  the  bone,  and  is  continuous  with  the  dura  mater  lining  the  spinal 
canal.  In  certain  situations,  as  already  mentioned  (page  594),  the  fibrous  layers 
of  this  membrane  separate,  to  form  sinuses  for  the  passage  of  venous  blood. 
Upon  the  outer  surface  of  the  dura  mater,  in  the  situation  of  the  longitudinal 
sinus,  may  be  seen  numerous  small  whitish   bodies,   the  glandule  Pacchioni. 

Structure. — The  dura  mater  consists  of  white  fibrous  tissue  with  connective- 
tissue  cells  and  elastic  fibres  arranged  in  flattened  laminre  which  are  imperfectly 
separated  by  lacunar  spaces  and  blood-vessels  into  two  layers,  endosteal  and 
meningeal.      The  endosteal  layer  is  the  internal  periosteum  for  the  cranial  bones, 

639 


640  THE  NERVOUS  SYSTEM. 

and  contains  the  blood-vessels  for  their  supply.  At  the  margin  of  the  foramen 
magnum  it  becomes  continuous  with  the  periosteum  lining  the  spinal  canal.  The 
meningeal  or  supporting  layer  is  lined  on  its  inner  surface  by  a  layer  of  nucleated 
endothelium,  similar  to  that  found  on  serous  membranes  :  these  cells  were  formerly 
regarded  as  belonging  to  the  arachnoid  membrane.  By  its  reduplication  the 
meningeal  layer  forms  the  falx  cerebri,  the  tentorium  and  falx  cerebelli,  and  the 
diaphragma  sellae.  The  two  layers  are  connected  by  fibres  which  intersect  each 
other  obliquely. 

Its  arteries  are  very  numerous,  but  are  chiefly  distributed  to  the  bones.  Those 
found  in  the  anterior  fossa  are  the  anterior  meningeal  branches  of  the  anterior  and 
posterior  ethmoidal  and  internal  carotid,  and  a  branch  from  the  middle  meningeal. 
In  the  middle  fossa  are  the  middle  and  small  meningeal  branches  of  the  internal 
maxillary,  a  branch  from  the  ascending  pharyngeal,  which  enters  the  skull  through 
the  foramen  lacerum  medium  basis  cranii,  branches  from  the  internal  carotid,  and 
a  recurrent  branch  from  the  lachrymal.  In  the  posterior  fossa  are  meningeal 
branches  from  the  occipital,  one  of  which  enters  the  skull  through  the  jugular 
foramen,  and  the  other  through  the  mastoid  foramen ;  the  posterior  meningeal, 
from  the  vertebral ;  occasionally  meningeal  branches  from  the  ascending  pharyngeal, 
which  enter  the  skull,  one  at  the  jugular  foramen,  the  other  at  the  anterior 
condyloid  foramen,  and  a  branch  from  the  middle  meningeal. 

The  veins,  which  return  the  blood  from  the  dura  mater,  and  partly  from  the 
bones,  anastomose  with  the  diploic  veins.  These  vessels  terminate  in  the  various 
sinuses,  with  the  exception  of  two  which  accompany  the  middle  meningeal  artery, 
and  pass  out  of  the  skull  at  the  foramen  spinosum  to  join  the  internal  maxillary 
vein ;  above  they  communicate  with  the  superior  longitudinal  sinus.  Many  of 
the  meningeal  veins  do  not  open  directly  into  the  sinuses,  but  indirectly  through 
a  series  of  ampullae  termed  venous  lacunae.  These  are  found  on  each  side  of  the 
superior  longitudinal  sinus,  especially  near  its  middle  portion,  and  are  often 
invaginated  by  Pacchionian  bodies ;  they  also  exist  near  the  lateral  and  straight 
sinuses.  They  communicate  with  the  underlying  cei-ebral  veins,  and  also  with 
the  diploic  and  emissary  veins. 

The  nerves  of  the  dura  mater  are  filaments  from  the  Gasserian  ganglion,  from 
the  ophthalmic,  superior  maxillary,  inferior  maxillary,  vagus,  and  hypoglossal 
nerves,  and  from  the  sympathetic. 

Processes  of  the  Dura  Mater. — The  processes  of  the  dura  mater,  sent  inward 
into  the  cavity  of  the  skull,  are  four  in  number :  the  falx  cerebri,  the  tentorium 
cerebelli,  the  falx  cerebelli,  and  the  diaphragma  sellse. 

The  falx  cerebri,  so  named  from  its  sickle-like  form,  is  a  strong  arched  process 
of  the  dura  mater,  which  descends  vertically  in  the  longitudinal  fissure  between 
the  two  hemispheres  of  the  brain.  It  is  narrow  in  front,  where  it  is  attached  to 
the  crista  galli  of  the  ethmoid  bone,  and  broad  behind,  where  it  is  connected  with 
the  upper  surface  of  the  tentorium.  Its  upper  margin  is  convex,  and  attached  to 
the  inner  surface  of  the  skull,  in  the  middle  line,  as  far  back  as  the  internal  occip- 
ital protuberance ;  it  contains  the  superior  longitudinal  sinus.  Its  lower  margin 
is  free,  concave,  and  presents  a  sharp  curved  edge,  which  contains  the  inferior 
longitudinal  sinus. 

The  tentorium  cerebelli  is  an  arched  lamina  of  dura  mater,  elevated  in  the 
middle  and  inclining  downward  toward  the  circumference.  It  covers  the  upper 
surface  of  the  cerebellum,  arid  supports  the  occipital  lobes  of  the  brain,  and 
prevents  them  pressing  upon  the  cerebellum.  It  is  attached,  behind,  by  its  convex 
border  to  the  transverse  ridges  upon  the  inner  surface  of  the  occipital  bone,  and 
there  encloses  the  lateral  sinuses  ;  in  front,  to  the  superior  margin  of  the  petrous 
portion  of  the  temporal  bone  on  either  side,  enclosing  the  superior  petrosal 
sinuses ;  and  at  the  apex  of  this  bone  the  free  or  internal  border  and  the  attached 
or  external  border  meet,  and,  crossing  one  another,  are  continued  forward,  to 
be  attached  to  the  anterior  and  posterior  clinoid  processes  respectively.  Along 
the  middle  line  of  its  upper  surface  the  posterior  border  of  the  falx  cerebri  is 


THE   MEMBRANES    OF    THE  BRAIN.  641 

attached,  the  straight  sinus  being  placed  at  their  point  of  junction.  Its  anterior 
border  is  free  and  concave,  and  bounds  a  large  oval  opening  for  the  transmission 
of  the  crura  cerebri. 

Thefalx  cerebelli  is  a  small  triangular  process  of  dura  mater  received  into  the 
indentation  between  the  two  lateral  lobes  of  the  cerebellum  behind.  Its  base  is 
attached,  above,  to  the  under  and  back  part  of  the  tentorium  ;  its  posterior  margin, 
to  the  lower  division  of  the  vertical  crest  on  the  inner  surface  of  the  occipital 
bone.  As  it  descends  it  sometimes  divides  into  two  smaller  folds,  which  are  lost 
on  the  sides  of  the  foramen  magnum. 

The  diaphragma  settee  is  a  horizontal  process  formed  by  a  reduplication  of  the 
meningeal  layer  of  the  dura  mater.  It  forms  a  small  circular  fold,  which  con- 
stitutes a  roof  for  the  sella  turcica.  This  almost  completely  covers  the  pituitary 
body,  presenting  merely  a  small  central  opening  for  the  infundibulum  to  pass 
through. 

The  Arachnoid  Membrane. 

The  arachnoid  {ap&yyq  eldoq,  like  a  spider's  web),  so  named  for  its  extreme 
thinness,  is  a  delicate  membrane  which  envelops  the  brain,  lying  between  the  pia 
mater  internally  and  the  dura  mater  externally ;  from  this  latter  membrane  it  is 
separated  by  a  space,  the  subdural  space. 

It  invests  the  brain  loosely,  being  separated  from  direct  contact  with  the 
cerebral  substance  by  the  pia  mater,  and  a  quantity  of  loose  areolar  tissue,  the 
subarachnoidean.  On  the  upper  surface  of  the  cerebrum  the  arachnoid  is  thin  and 
transparent,  and  may  be  easily  demonstrated  by  injecting  a  stream  of  air  beneath 
it  by  means  of  a  blowpipe ;  it  passes  over  the  convolutions  without  dipping  down 
into  the  sulci  between  them.  At  the  base  of  the  brain  the  arachnoid  is  thicker, 
and  slightly  opaque  toward  the  central  part ;  it  covers  the  anterior  lobes,  and 
extends  across  between  the  two  temporal  lobes  so  as  to  leave  a  considerable 
interval  between  it  and  the  brain,  the  anterior  subarachnoidean  space  (Cisterna 
pontis) ;  it  is  in  contact  with  the  pons  and  under  surface  of  the  cerebellum ;  but 
between  the  hemispheres  of  the  cerebellum  and  the  medulla  oblongata  another  con- 
siderable interval  is  left  between  it  and  the  brain,  called  the  posterior  subarach- 
noidean space  (Cisterna  magna).  These  two  spaces  communicate  together  across 
the  crura  cerebelli.  Other  smaller  cisternse  are  found  in  various  positions  ;  and  all 
communicate  freely  with  one  another.  The  arachnoid  membrane  surrounds  the 
nerves  which  arise  from  the  brain,  and  encloses  them  in  loose  sheaths  as  far  as 
their  point  of  exit  from  the  skull. 

The  subarachnoid  space  is  the  interval  between  the  arachnoid  and  pia  mater. 
It  is  not,  properly  speaking,  a  space,  for  it  is  occupied  everywhere  by  a  spongy 
tissue  consisting  of  trabecule  of  delicate  connective  tissue,  which  pass  from  the  pia 
mater  to  the  arachnoid,  and  in  the  meshes  of  which  the  subarachnoid  fluid  is  con- 
tained. This  so-called  space  is  small  on  the  surface  of  the  hemispheres  ;  but  at 
the  base  of  the  brain  the  subarachnoid  tissue  is  less  abundant  and  its  meshes 
larger,  where  it  forms  the  Cisternse  pontis  et  magna  mentioned  above.  In  addition 
to  these  two  large  spaces,  a  third  is  formed  on  the  upper  surface  of  the  corpus  cal- 
losum,  for  the  arachnoid  stretches  across  from  one  cerebral  hemisphere  to  the  other 
immediately  beneath  the  free  border  of  the  falx  cerebri,  and  thus  leaves  a  space  in 
which  the  anterior  cerebral  arteries  are  contained.  Another  space  is  found  in  the 
fissure  of  Sylvius,  for  the  arachnoid  stretches  across  from  the  anterior  to  the  middle 
lobe  of  the  brain,  without  dipping  down  to  the  bottom  of  the  fissure,  and  in  this 
space  the  middle  cerebral  artery  ramifies.  The  subarachnoid  space  communi- 
cates with  the  general  ventricular  cavity  of  the  brain  by  means  of  three  openings  : 
one  of  these  is  in  the  middle  line  at  the  inferior  boundary  of  the  fourth  ventricle, 
where  an  opening  in  the  pia-matral  covering  of  this  cavity,  the  foramen  of  Magen- 
die,  exists  and  permits  the  passage  of  fluid  from  the  one  space  to  the  other.  The 
other  two  communications  are  at  the  extremities  of  the  lateral  recesses  of  the  fourth 
ventricle,  behind  the  upper  roots  of  the  glosso-pharyngeal  nerves  ;  they  are  named 
41 


642  THE  NERVOUS  SYSTEM. 

the  foramina  of  Key  and  Retzius.  It  is  stated  by  Merkel  that  the  lateral  ven- 
tricles also  communicate  with  the  subarachnoid  space  at  the  apices  of  their  descend- 
ing horns. 

The  subdural  space  also  contains  fluid ;  this  is,  however,  small  in  quantity 
compared  with  the  cerebro-spinal  fluid  and  is  probably  of  the  nature  of  lymph. 

The  cerebrospinal  fluid  fills  up  the  subarachnoid  space.  It  is  a  clear,  limpid 
fluid,  having  a  saltish  taste  and  a  slightly  alkaline  reaction.  According  to 
Lassaigne,  it  consists  of  98.5  parts  of  water,  the  remaining  1.5  per  cent,  being 
solid  matters,  animal  and  saline.  It  varies  in  quantity,  being  most  abundant  in 
old  persons,  and  is  quickly  reproduced.  Its  chief  use  is  probably  to  afford 
mechanical  protection  to  the  nervous  centres,  and  to  prevent  the  effects  of 
concussions  communicated  from  without. 

Structure. — The  arachnoid  consists  of  bundles  of  white  fibrous  and  elastic 
tissue  intimately  blended  together.  Its  outer  surface  is  covered  with  a  layer  of 
endothelium.  Vessels  of  considerable  size,  but  few  in  number,  and,  according  to 
Bochdalek,  a  rich  plexus  of  nerves  derived  from  the  motor  division  of  the  fifth, 
the  facial,  and  the  spinal  accessory  nerves,  are  found  in  the  arachnoid. 

Glandulae  Pacchioni  or  Arachnoid  Villi. 

The  glandulae  Pacchioni  are  numerous  small  whitish  granulations  usually  col- 
lected into  clusters  of  variable  size,  which  are  found  in  the  following  situations : 
1.  Upon  the  outer  surface  of  the  dura  mater,  in  the  vicinity  of  the  superior  longi- 
tudinal sinus,  being  received  into  little  depressions  on  the  inner  surface  of  the 
calvarium.  2.  On  the  inner  surface  of  the  dura  mater.  3.  In  the  superior 
longitudinal  sinus.     4.   On  the  pia  mater,  near  the  margin  of  the  hemispheres. 

These  bodies  are  not  glandular  in  structure,  but  simply  enlarged  normal  villi 
of  the  arachnoid.  In  their  growth  they  appear  to  perforate  the  dura  mater,  and 
when  of  large  size  they  cause  absorption  of  the  bone,  and  come  to  be  lodged  in 
pits  or  depressions  on  the  inner  table  of  the  skull.  Their  manner  of  growth  is  as 
follows  :  at  an  early  period  they  project  through  minute  holes  in  the  inner  layer  of 
the  dura  mater,  which  open  into  large  venous  spaces  situated  in  the  tissues  of  the 
membrane,  on  either  side  of  the  longitudinal  sinus  and  communicating  with  it. 
In  their  onward  growth  the  villi  push  the  outer  layer  of  the  dura  mater  before 
them,  and  this  forms  over  them  a  delicate  membranous  sheath.  In  structure  they 
consist  of  spongy  trabecular  tissue,  covered  over  by  a  membrane,  which  is  continu- 
ous with  the  arachnoid.  The  space  between  these  two  coverings,  derived  from  the 
ilura  mater  and  arachnoid  respectively,  corresponds  to  and  is  continuous  with  the 
subdural  space.  The  spongy  tissue  of  which  they  are  composed  is  continuous 
with  the  trabecular  tissue  of  the  subarachnoid  space;  so  that  fluid  injected  into 
the  subarachnoid  space  finds  its  way  into  the  Pacchionian  bodies ;  and  through 
their  coverings  filters  into  the  superior  longitudinal  sinus.  They  are  supposed  to  be 
the  means  by  which  excess  of  cerebro-spinal  fluid  is  got  rid  of,  when  its  quantity 
is  increased  above  normal. 

These  bodies  are  not  found  in  infancy,  and  very  rarely  until  the  third  year. 
They  are  usually  found  after  the  seventh  year ;  and  from  this  period  they  increase 
in  number  as  age  advances.     Occasionally  they  are  wanting. 

The  Pia  Mater. 

The  pia  mater  is  a  vascular  membrane,  and  derives  its  blood  from  the  internal 
carotid  and  vertebral  arteries.  It  consists  of  a  minute  plexus  of  blood-vessels,  held 
together  by  an  extremely  fine  areolar  tissue.  It  invests  the  entire  surface  of  the 
brain,  dipping  down  between  the  convolutions  and  laminae,  and  is  prolonged  into  the 
interior,  forming  the  velum  interpositum  and  choroid  plexuses  of  the  lateral  and  fourth 
ventricles.  Upon  the  surfaces  of  the  hemispheres,  where  it  covers  the  gray  matter  of 
the  convolutions,  it  is  very  vascular,  and  gives  off  from  its  inner  surface  a  multitude 
of  minute  vessels,  which  extend  perpendicularly  for  some  distance  into  the  cerebral 


HEMISPHERES    OF    THE  BRAIN.  643 

substance.  At  the  base  of  the  brain,  in  the  situation  of  the  anterior  and  posterior 
perforated  spaces,  a  number  of  long  straight  vessels  are  given  off,  which  pass 
through  the  white  matter  to  reach  the  gray  substance  in  the  interior.  On  the 
cerebellum  the  membrane  is  more  delicate,  and  the  vessels  from  its  inner  surface 
!  are  shorter.  The  pia  mater  of  the  spinal  cord  is  thicker,  firmer,  and  less  vascular 
than  that  of  the  brain,  and  as  it  is  traced  upward  over  the  medulla  it  is  seen  to 
preserve  these  characters.  At  the  upper  border  of  the  medulla  it  is  prolonged 
over  the  lower  half  of  the  fourth  ventricle,  forming  a  covering  for  it  (tela  choroidea 
inferior)  before  it  is  reflected  on  to  the  under  surface  of  the  cerebellum. 

According  to  Fohmann  and  Arnold,  this  membrane  contains  numerous  lym- 
phatic vessels.  Its  nerves  are  derived  from  the  sympathetic,  and  also  from  the 
third,  fifth,  sixth,  facial,  glosso-pharyngeal,  pneumogastric,  and  spinal  accessory. 
They  accompany  the  branches  of  the  arteries. 

THE   BRAIN. 

GENERAL  CONSIDERATIONS  AND  DIVISIONS. 

The  encephalon  or  brain  is  that  portion  of  the  cerebro-spinal  axis  which  is  con- 
tained in  the  cavity  of  the  cranium.  For  purposes  of  description  it  may  be 
divided  into  five  parts,  as  follows  :  (1)  the  two  cerebral  hemispheres ;  (2)  the 
inter-brain ;  (3)  the  mid-brain  ;  (4)  the  pons  Varolii  and  cerebellum  ;  and  (5)  the 
medulla  oblongata.  If  the  student  Avill  refer  to  the  section  on  the  Development  of 
the  Brain  he  will  find  that  these  five  portions  correspond  fairly  accurately  to  the 
five  secondary  cerebral  vesicles,  of  which  the  brain  at  an  early  period  of  embry- 
onal life  consisted :  the  prosencephalon,  or  first  vesicle,  by  means  of  a  protrusion 
from  its  front  part  on  either  side,  forms  the  cerebral  hemispheres  and  the  lateral 
ventricles ;  the  remainder  of  the  prosencephalon,  together  with  the  second  vesicle, 
the  thalamencephalon,  form  the  inter-brain  and  third  ventricle ;  the  third  vesicle, 
the  mesencephalon,  forms  the  mid-brain,  or  that  portion  which  connects  the  inter- 
brain  and  hemispheres  above  with  the  pons  Varolii  below,  and  the  cavity  of  the 
vesicle  forms  the  aqueduct  of  Sylvius,  or  iter  a  tertio  ad  quartum  ventriculum  ;  the 
fourth  vesicle,  the  epencephalon,  becomes  the  future  pons  Varolii  and  cerebellum, 
and  its  cavity  forms  the  upper  half  of  the  fourth  ventricle ;  and,  finally,  the  fifth 
vesicle,  the  melencephalon,  develops  into  the  medulla  oblongata,  and  its  cavity 
forms  the  lower  half  of  the  fourth  ventricle.  It  will  thus  be  seen  that  the  five 
divisions  of  the  encephalon  mentioned  above  correspond  to  the  five  secondary  cere- 
bral vesicles,  with  the  exception  of  the  first  two,  which  together  form  the  cerebral 
hemispheres  and  the  inter-brain.  In  consequence  of  this  these  two  portions  of 
the  brain  are  sometimes  grouped  together  as  the  cerebrum. 

I.  The  Hemispheres  of  the  Brain. 

General  Considerations. — The  two  hemispheres  constitute  the  largest  portion  of 
the  encephalon,  and,  together  with  the  parts  derived  from  the  thalamencephalon, 
form  what  is  called  by  some  writers  the  fore-brain.  They  occupy  the  whole  of  the 
vault  of  the  skull,  and  consist  of  a  central  cavity,  in  either  hemisphere,  surrounded 
by  exceedingly  thick  and  convoluted  walls  of  nervous  tissue.  The  under  surface 
or  base  of  the  cerebrum  is  of  an  irregular  form,  resting  in  front  on  the  anterior 
and  middle  fossae  of  the  skull  and  behind  upon  the  tentorium  cerebelli.  The 
upper  surface  is  of  an  ovoid  form,  broader  behind  than  in  front,  convex  in  general 
outline,  and  divided  into  two  lateral  halves  or  hemispheres,  right  and  left,  by  the 
great  longitudinal  fissure,  which  extends  throughout  the  entire  length  of  the  cere- 
brum in  the  middle  line,  reaching  down  to  the  base  of  the  brain  in  front  and 
behind,  but  interrupted  in  the  middle  by  a  broad  transverse  commissure  of  white 
matter,  the  corpus  caUosum,  which  connects  the  two  hemispheres  together. 

The  Surface  of  the  Cerebrum. — Each  hemisphere  presents  an  outer  convex  sur- 
face, filling  the  concavity  of  the  corresponding  half  of  the  vault  of  the  cranium  ; 


644 


THE   NERVOUS  SYSTEM. 


an  inner,  flattened  surface,  which  is  vertical  and  directed  toward  the  correspond- 
ing surface  of  the  opposite  hemisphere  (the  two  forming  the  sides  of  the  longitu- 
dinal fissure)  ;  and  an  under  surface  or  base,  of  an  irregular  form,  which  rests  in 
front  on  the  anterior  and  middle  fossae  of  the  base  of  the  skull,  and  behind  upon 
the  tentorium  cerebelli.  The  hemispheres  are  composed  of  an  outer  stratum  of 
gray  matter,  called  the  cortical  substance.  It  is  thrown  into  a  number  of  creases 
or  infoldings,  which  are  termed  fissures  and  sulci,  and  these  separate  the  surface 
into  a  number  of  irregular  eminences,  named  convolutions  or  gyri. 

The  infoldings  or  creases  are  of  two  kinds,  fissures  and  sulci.  The  fissures  are 
of  large  size,  and  appear  early  in  foetal  life  ;  they  are  few  in  number,  nearly  con- 
stant in  their  arrangement,  and  are  produced  by  infoldings  of  the  entire  thickness 


NFERIOR 

FRONTAL 

CONV. 


Fissure  of 
Rolando. 


/-v         - —   I,  —-       Parieto-oceipital 
Oq  fissure. 

fiG.  343. — Upper  surface  of  the  brain,  the  arachnoid  having  been  removed. 

of  the  wall  of  the  prosencephalon,  producing  corresponding  elevations  in  the  inte- 
rior of  the  ventricle,  and  hence  are  termed  complete  fissures.     They  comprise  (a 
the  hippocampal,  or  dentate  fissure  ;  (b)  the  anterior  part  of  the  calcarine  fissure 
(e)  the  collateral  fissure.     The  sulci  are  more  numerous  ;  they  are  superficial  de 
pressions  of  the  gray  matter,  which  is  folded  inward  and   only  indents  the  centra 
white  substance.      They  produce  no  corresponding  elevations  in  the  interior  of  the 
ventricle,  and  are  therefore  spoken  of  as  incomplete  fissures.     They  are  fairly  con 
stant  in  their  arrangement,  and  have  received  names  indicative  of  their  position 
and  direction,  but  at  the  same  time  vary,  within  certain  limits,  in  different  indi 
viduals.     They  are  similar,  without  being  absolutely  identical,  on  the  two  sides  ol 
the  brain.     It  therefore  follows  that  the  gyri  or  convolutions  which  lie  between 
these  sulci  are  fairly  constant  in  their  general  arrangement. 


HEMISPHERES    OF    THE   BRAIN. 


645 


The  number  and  extent  of  the  convolutions,  as  well  as  the  depth  of  the  inter- 
vening sulci,  appear  to  bear  a  close  relation  to  the  intellectual  power  of  the  individ- 
ual, as  is  shown  in  their  increasing  complexity  of  arrangement  as  one  ascends  from 
the  lowest  mammalia  up  to  man,  where  they  present  a  most  complex  arrangement. 
Again,  in  the  child,  at  birth,  before  the  intellectual  faculties  are  exercised,  the 
convolutions  are  simpler,  and  the  sulci  between  them  shallower,  than  in  the  adult. 
In  old  age,  when  the  mental  faculties  have  diminished  in  activity,  they  become 
less  prominently  marked.  By  their  arrangement  the  convolutions  are  adapted  to 
increase  the  amount  of  gray  matter  without  occupying  much  additional  space,  while 
they  also  afford  a  greater  extent  of  surface  for  the  termination  of  white  fibres  in 
gray  matter. 

It  will  be  convenient,  in  the  first  instance,  to  describe  the  fissure  which  sepa- 
rates the  two  hemispheres  from  each  other,  and  those  which  divide  each  hemisphere 
into  its  larger  divisions. 

The  Longitudinal  Fissure  (Fig.  348). — This  great  fissure  separates  the  cerebrum 
into  two  hemispheres,  and  reaches  from  the  front  to  the  back  of  the  organ  :  it  contains 
a  vertical  process  of  the  dura  mater,  the  falx  cerebri  (page  640).  In  front  and  be- 
hind it  extends  from  the  top  to  the  bottom  of  the  cerebrum,  and  completely  sepa- 


JParieto- 
occipital 
Fissure 


Fig.  344.— Fissures  and  lobes  on  the  external  surface  of  the  cerebral  hemispheres. 

rates  the  two  hemispheres,  but  its  middle  portion  only  separates  the  hemispheres 
for  about  half  their  vertical  extent,  the  floor  of  this  part  of  the  fissure  being 
formed  by  the  great  central  white  commissure,  the  corpus  callosum,  which  connects 
the  two  hemispheres  together. 

The  remaining  fissures  are  situated  in  one  or  other  of  the  two  hemispheres,  with 
the  exception  of  the  transverse  fissure,  one-half  of  which  is  contained  in  each 
hemisphere. 

Sylvian  Fissure  (Fig.  344). — This  fissure  is  a  well-marked  cleft  on  the  base  and 
side  of  the  hemisphere.  Starting  at  the  base  of  the  brain  in  a  depression,  the 
vallecula  Sylvii,  in  which  is  situated  the  anterior  perforated  space,  it  passes  out- 
ward to  the  external  surface  of  the  hemisphere.     It  here  gives  off  a  short  anterior 


646  THE  NERVOUS  SYSTEM. 

limb,  which  passes  forward,  and  a  short  ascending  limb,  which  passes  upward  into 
the  inferior  frontal  convolution.  It  is  then  continued  backward  as  the  horizontal 
limb,  which  terminates  by  an  upward  inflexion  in  the  parietal  lobe.  It  occupies 
the  middle  third  of  the  lateral  surface  of  the  hemisphere. 

The  Fissure  of  Rolando  is  situated  about  the  middle  of  the  outer  surface  of  the 
hemisphere,  and,  coursing  obliquely  downward  and  forward,  divides  the  surface 
of  the  hemisphere  into  approximately  equal  parts.  It  commences  at  or  near  the 
longitudinal  fissure,  a  little  behind  its  mid-point,  and  runs  sinuously  downward 
and  forward,  to  terminate  a  little  above  the  horizontal  limb  of  the  fissure  of 
Sylvius,  and  about  half  an  inch  behind  the  ascending  limb  of  the  same  fissure. 
It  forms  two  chief  curves :  the  upper  or  superior  genu  is  concave  forward  and 
upward,  while  the  lower  or  inferior  genu  has  its  concavity  directed  backward. 

The  parieto-occipital  fissure  is  only  seen  to  a  slight  extent  on  the  outer  surface 
of  the  hemisphere,  being  situated  for  the  most  part  on  its  mesial  aspect.  The 
portion  on  the  outer  surface  is  called  the  external  parieto-occipital  fissure,  to  dis- 
tinguish it  from  the  part  continued  on  to  the  internal  surface,  which  is  termed  the 
internal  parieto-occipital  fissure.  The  external  parieto-occipital  fissure  commences 
about  midway  between  the  posterior  extremity  or  occipital  pole  of  the  brain  and 
the  fissure  of  Rolando,  and  runs  downward  and  outward  for  about  an  inch. 

These  three  fissures  divide  the  external  surface  of  the  hemisphere  into  four 
lobes:  the  frontal,  the  parietal,  the  occipital,  and  the  temporal.  To  these  must  be 
added  (1)  the  central  lobe,  or  island  of  Reil,  which  is  situated  deeply  in  the  Sylvian 
fissure,  and  (2)  the  olfactory  lobe,  which  is  found  at  the  base  of  the  brain  and  was 
formerly  described  under  the  name  of  the  olfactory  nerve. 

The  Lobes  on  the  External  Surface. — The  lobes  on  the  external  surface  have 
received  their  names  from  the  bones  of  the  skull  with  which  they  are  most  nearly 
in  relation,  but  it  must  be  borne  in  mind  that  they  do  not  correspond  in  shape  or 
limit  with  the  bone  after  which  they  are  named.  The  division  is,  moreover,  to 
certain  extent  artificial,  as  will  be  seen  from  the  following  description.  If  a  line 
is  drawn  in  continuation  of  the  external  parieto-occipital  fissure  downward  and 
outward  to  the  lower  border  of  the  hemisphere,  it  will  impinge  on  a  slight  notch, 
the  pre-occipital  notch,  and  if  a  second  line  is  prolonged  backward  from  the  hori- 
zontal part  of  the  fissure  of  Sylvius  to  join  the  first,  the  division  of  the  outer  surface 
of  the  hemisphere  into  four  lobes  will  be  accomplished  (Fig.  344).  The  portion  in 
front  of  the  fissure  of  Rolando  is  the  frontal  lobe ;  that  behind  the  fissure  of 
Rolando  and  above  the  fissure  of  Sylvius  is  the  parietal  lobe ;  the  portion  behind 
the  parieto-occipital  fissure  and  its  continuation  is  the  occipital  lobe ;  and  the  part 
below  the  fissure  of  Sylvius  and  in  front  of  the  occipital  lobe  is  the  temporal  lobe. 

The  Fissures  and  Lobes  of  the  Mesial  and  Tentorial  Surfaces. — The  mesial  sur- 
face of  the  cerebrum  can  only  be  fully  viewed  by  dividing  the  corpus  callosum  and 
the  structures  beneath  it  longitudinally  in  the  middle  line ;  in  order  to  expose  the 
tentorial  surface,  the  pons  Varolii,  cerebellum,  and  medulla  must  be  removed,  by 
division  of  the  cms  cerebri  on  either  side.  When  this  has  been  done,  a  section 
such  as  is  represented  in  Fig.  345  will  be  shown.  The  parts  in  the  centre,  below 
the  corpus  callosum,  belong  to  the  interior  of  the  brain,  and  will  be  disregarded 
for  the  present,  while  the  lobes  and  fissures  of  the  remaining  portion  of  the  hemi- 
sphere are  considered.  The  fissures  are  five  in  number,  in  addition  to  a  small  part 
of  the  fissure  of  Sylvius,  the  commencement  of  which  is  seen,  separating  the 
frontal  and  temporal  lobes.  These  fissures  are  named  the  calloso-marginal,  the 
internal  .parieto-occipital,  the  calcarine,  the  collateral,  and  the  dentate  or  hippo- 
campal. 

The  calloso-marginal  fissure  commences  below  the  anterior  extremity  of  the 
corpus  callosum  ;  it  at  first  runs  forward  and  upward,  parallel  with  the  rostrum  of 
the  corpus  callosum,  and,  winding  round  in  front  of  the  genu  of  that  body,  it  con- 
tinues from  before  backward,  between  the  upper  margin  of  the  hemisphere  and 
the  convolution  of  the  corpus  callosum,  to  about  midway  between  the  anterior 
and  posterior  extremities  of  the  brain,  where  it  ascends  to  reach  the  upper  margin 


HEMISPHERES    OF    THE   BRAIN. 


647 


of  the  hemisphere,  a  short  distance  behind  the  superior  extremity  of  the  fissure 
of  Rolando. 

The  internal  parieto-occipital  extends  in  an  oblique  direction  downward  and 
forward  to  join  the  calcarine  fissure,  on  a  level  with  the  hinder  end  of  the  corpus 
callosum. 

The  calcarine  fissure  commences,  usually  by  two  branches,  close  to  the  posterior 
extremity  of  the  hemisphere.  These  soon  unite,  and  the  fissure  runs  nearly  hori- 
zontally forward,  and  is  joined  by  the  parieto-occipital  fissure,  and  continues  as 
far  as  the  posterior  extremity  of  the  corpus  callosum,  a  little  below  the  level  of 
which  it  terminates.  Its  anterior  part  causes  the  prominence  in  the  interior  cf 
the  brain,  known  as  the  hippocampus  minor  or  calcar  avis. 


Fig.  345.— Fissures  and  lobes  on  the  internal  surface  of  the  cerebral  hemispheres. 


The  collateral  fissure  is  situated  on  the  tentorial  surface,  below  and  external 
to  the  preceding,  being  separated  from  it  by  the  sub-collateral  or  uncinate  gyrus. 
It  runs  forward,  from  the  posterior  extremity  of  the  brain,  nearly  as  far  as  the  tip 
of  the  temporal  lobe.  It  lies  below  the  posterior  and  descending  horns  of  the 
lateral  ventricle,  and  its  middle  part  causes  the  prominence  in  the  interior  of  the 
brain,  known  as  the  eminentia  collateralis. 

The  dentate  or  hippocampal  fissure  commences  immediately  behind  the  posterior 
extremity  of  the  corpus  callosum,  and  runs  forward  to  terminate  at  the  recurved 
part  of  the  hippocampal  gyrus.  It  causes  the  prominence  of  the  hippocampus 
major  in  the  descending  horn  of  the  lateral  ventricle.  In  addition  to  these  fissures, 
which  are  constant,  there  is  frequently  an  irregular  broken  fissure,  which  appears 
to  be  a  continuation  backward  of  the  posterior  part  of  the  calloso-marginal  fissure, 
before  it  ascends  to  reach  the  upper  edge  of  the  hemisphere.  This  has  been 
termed  the  post-limbic  fissure.  ■  These  fissures  map  off  portions  of  the  internal  and 
tentorial  surfaces  of  the  hemispheres,  which  form  parts  of  the  lobes  found  on  the 
external  surface.  That  portion  which  lies  in  front  and  above  the  calloso-marginal 
fissure  belongs  almost  entirely  to  the  frontal  lobe ;  its  posterior  extremity,  which 
extends  for  a  short  distance  behind  the  upper  end  of  the  fissure  of  Rolando,  forms 
a  small  part  of  the  obe  ;  that  portion  which  lies  above  the  internal  parieto- 

occipital fissure  ami  behind  the  calloso-marginal  fissure  forms  a  part  of  the  parietal 
lobe;  that  betwee  the  ]  ••  'ieto-occipital  fissure  above  and  the  calcarine  fissure 
below  is  a  portion  of  sipital  lobe ;  and  all  the  region  below  the  calcarine 


648 


THE  NERVOUS  SYSTEM. 


fissure  behind  and  the  collateral  fissure  in  front  belongs  to  the  temporal  lobe  The 
remainder  of  the  mesial  and  tentorial  surfaces  of  the  hemisphere  constitute  what 
Rroca  termed  the  limbic  lobe,  which  is  subsequently  referred  to  (page  652). 

The  surface  of  the  hemisphere  has  thus  been  divided  into  its  different  parts 
viz.:  the  frontal,  the  parietal,  the  occipital,  the  temporal,  the  limbic  the 
olfactory  lobes,  and  the  island  of  Reil.  Each  of  these  lobes  is  further  subdivided 
into  convolutions  or  gyri  by  smaller  fissures,  which,  though  less  constant  in  their 
arrangement  than  the  fissures  already  described,  have  a  fairly  definite  course. 

1.  The  Frontal  Lobe.— On  its  external  surface  the  frontal  lobe  presents  three 
sulci,  which  divide  it  into  four  convolutions  (Fig.  346).  The  precentral  sulcus 
runs    upward  through   this  lobe,   parallel  to   the  lower  half  of  the  fissure  of 

End  of  calloso- 
marginal  fissure. 


Parieto- 
occipital 
fissure. 


Ascending  fissure 
of  Sylvius. 

Fissure 
of  Sylvius 


Fig.  346. — Convolutions  and  sulci  on  the  external  surface  of  the  cerebral  hemisphere. 


Rolando.  It  is  frequently  broken  or  interrupted  by  annectant  gyri.  It  limits 
a  convolution,  which  lies  between  it  and  the  fissure  of  Rolando,  and  which  is 
called  the  ascending  frontal  convolution.  From  it  two  sulci,  the  superior  and 
inferior  frontal,  run  forward  and  downward,  and  divide  the  remainder  of  the 
outer  surface  of  the  lobe  into  three  parallel  principal  convolutions,  named  respec- 
tively the  superior,  middle,  and  inferior  frontal  convolutions. 

The  ascending  frontal  convolution  is  a  simple  convolution,  bounded  in  front  by 
the  precentral  sulcus,  behind  by  the  fissure  of  Rolando,  and  extending  from  the 
upper  margin  of  the  hemisphere  above  to  a  little  behind  the  bifurcation  of  the 
fissure  of  Sylvius  below. 

The  superior  frontal  convolution  is  situated  between  the  margin  of  the  longi- 
tudinal fissure  and  the  superior  frontal  sulcus.  It  extends  above  on  to  the  inner 
aspect  of  the  hemisphere,  forming  the  greater  part  of  the  marginal  convolution, 
and  in  front  on  to  the  orbital  surface,  forming  the  internal  orbital  convolution. 
It  is  usually  more  or  less  completely  subdivided  into  two  by  an  antero-posterior 


HEMISPHERES    OF    THE   BRAIN. 


649 


sulcus,  the  sulcus  frontalis  mesialis  of  Cunningham,  which,  however,  is  frequently 
interrupted  and  broken  into  several  parts  by  bridging  convolutions. 

The  middle  frontal  convolution  is  situated  between  the  superior  and  inferior 
frontal  sulci,  and  extends  from  the  precentral  sulcus  on  to  the  orbital  surface  of 
the  lobe,  where  it  forms  the  anterior  orbital  convolution.  The  middle  frontal 
convolution  is  frequently  subdivided  into  two  by  a  sagittally  directed  sulcus,  the 
sulcus  frontalis  medius  of  Eberstaller. 

The  inferior  frontal  convolution  is  situated  below  the  inferior  frontal  sulcus, 
and  extends  forward  from  the  lower  part  of  the  precentral  sulcus,  on  to  the  under 
surface  of  the  lobe,  where  it  forms  the  posterior  orbital  convolution.  The  inferior 
frontal  convolution  is  subdivided  by  the  anterior  and  ascending  limbs  of  the 
fissure  of  Sylvius  into  three  parts,  viz. :  (1)  anterior  or  pars  orbitalis,  below  the 


GYRUS 
RECTUS 


ANTERIOR 

PERFORATED 

SPACE 


Fig.  347.— Convolutions  and  sulci  on  the  under  surface  of  the  anterior  lobe. 


anterior  limb  of  the  fissure;  (2)  middle  or  pars  triangularis  ('-' cap "  of  Broca), 
between  the  two  limbs ;  and  (3)  posterior  or  pars  basalis,  behind  the  ascending 
limb. 

The  left  inferior  frontal  convolution  is,  as  a  rule,  more  highly  developed  than 
the  right,  and  is  named  the  convolution  of  Broca,  from  the  fact  that  in  1861 
Broca  discovered  that  it  was  the  centre  for  language. 

The  under  surface  of  the  frontal  lobe  rests  on  the  orbital  plate  of  the  frontal 
bone,  and  is  sometimes  named  the  orbital  lobe  (Fig.  347).  It  is  divided  into  three 
convolutions  by  a  well-marked  sulcus,  the  orbital  or  tri-radiate  sulcus.  These  are 
named,  from  thei  isition,  the  internal,  anterior,  and  posterior  orbital 'convolutions, 
and  are  the  conti  respectively  of  the  superior,  middle,  and  inferior  frontal 

convolutions  of  the  external  surface.  The  internal  orbital  convolution  presents  a 
well-marked  ante  or  groove  or  sulcus,  the  olfactory  sulcus,  for  the  olfactory 


650 


THE  NERVOUS  SYSTEM. 


tract ;  and  the  portion  internal  to  this  is  named  the  gyrus  rectus,  and  is  continuous 
with  the  marginal  gyrus,  presently  to  be  described.  The  mesial  or  internal  surface 
of  the  frontal  lobe  is  occupied  by  a  single  curved  convolution,  which  from  its  situa- 
tion is  termed  the  marginal  gyrus  (Fig.  348).  It  commences  in  front  of  the  ante- 
rior perforated  space,  runs  along  the  margin  of  the  longitudinal  fissure  on  the 
mesial  surface  of  the  orbital  lobe,  where  it  is  continuous  with  the  internal  orbital 
convolution ;  it  then  ascends,  and  runs  backward  to  the  point  where  the  calloso- 
marginal  fissure  turns  upward  to  reach  the  superior  border  of  the  hemisphere. 
An  oval  portion  at  the  posterior  part  of  this  convolution  is  sometimes  marked  off 
by  a  vertical  fissure,  and  is  distinguished  as  the  'paracentral  gyrus,  because  it  is 
continuous  with  the  convolutions  in  front  and  behind  the  central  fissure  or  fissure 
of  Rolando. 

2.  The  Parietal  Lobe. — On  its  external  surface  the  parietal  lobe  presents  for 
examination  two  sulci  and  three  convolutions. 


Fig.  348.— Convolutions  and  sulci  on  the  internal  surface  of  cerebral  hemispheres. 


The  intra-parietal  sulcus  commences  close  to  the  horizontal  limb  of  the  fissure 
of  Sylvius,  about  midway  between  the  fissure  of  Rolando  and  the  upturned  ex- 
tremity of  the  fissure  of  Sylvius.  It  first  runs  upward  parallel  to  and  behind  the 
lower  half  of  the  fissure  of  Rolando,  and  then  turns  backward,  extending  nearly 
to  the  termination  of  the  external  parietooccipital  fissure,  where  it  sometimes 
becomes  continuous  with  the  superior  occipital  sulcus.  The  ascending  portion  of 
this  sulcus  separates  off  a  convolution,  the  ascending  parietal,  which  lies  between 
it  and  the  fissure  of  Rolando,  while  the  horizontal  portion  divides  the  remainder 
of  the  external  surface  of  the  parietal  lobe  into  two  other  convolutions,  the  superior 
and  inferior  parietal. 

The  post-central  sulcus  is  a  slightly  marked  groove,  which  is  sometimes  a  branch 
of  the  intra-parietal  sulcus,  being  given  off  where  the  ascending  portion  of  this 
sulcus  turns  backward.  It  lies  parallel  to  and  behind  the  upper  part  of  the  fissure 
of  Rolando,  and  separates  the  ascending  from  the  superior  parietal  convolution.1 

1  Professor  Cunningham  describes  these  two  sulci,  the  intra-parietal  and  post-central,  somewhat 
differently.  He  regards  them  as  both  belonging  to  the  intra-parietal  sulcus,  which  he  divides  into 
three  parts :  the  ascending  portion  of  the  intra-parietal,  as  described  above,  he  terms  the  ramus 
verticalis  inferior ;  the  horizontal  portion  as  the  ramus  horizontalis ;  while  the  post-central  sulcus  he 
denominates  the  ramus  verticalis  superior.  He  states  tbat  considerable  variability  is  exhibited  in  the 
relation  to  each  other  of  these  different  parts  of  the  intra-parietal  sulcus,  but  that  the  one  in  which 
the  three  parts  of  the  sulcus  are  confluent  is  by  far  the  most  constant  condition.     Sometimes,  however, 


HEMISPHERES    OF    THE   BRAIN.  651 

The  ascending  parietal  convolution  is  bounded  in  front  by  the  fissure  of 
Rolando,  behind  by  the  ascending  portion  of  the  intra-parietal  sulcus  and  by  the 
post-central  sulcus.  It  extends  from  the  great  longitudinal  fissure  above  to  the 
horizontal  limb  of  the  fissure  of  Sylvius  below.  It  lies  parallel  with  the  ascending 
frontal  convolution,  with  which  it  is  connected  below,  and  also,  sometimes,  above 
the  termination  of  the  fissure  of  Rolando. 

The  superior  parietal  convolution  is  bounded  in  front  by  the  post-central 
sulcus,  which  lies  between  it  and  the  previous  convolution,  but  with  which  it  is 
usually  connected  above  the  upper  extremity  of  the  sulcus ;  behind,  it  is  bounded 
by  the  external  pari eto- occipital  fissure,  below  the  termination  of  which  it  is 
joined  to  the  occipital  lobe  by  a  narrow  convolution,  the  first  annectant  gyrus ; 
below,  it  is  separated  from  the  inferior  parietal  convolution  by  the  horizontal 
portion  of  the  intra-parietal  sulcus ;  and  above,  it  is  continuous  on  the  inner 
surface  of  the  hemisphere  with  the  quadrate  lobe. 

The  inferior  parietal  convolution  is  that  portion  of  the  parietal  lobe  which  is 
situated  between  the  ascending  portion  of  the  intra-parietal  sulcus  in  front,  the 
horizontal  portion  of  the  same  sulcus  above,  the  horizontal  limb  of  the  fissure  of 
Sylvius  below,  and  the  posterior  boundary  of  the  parietal  lobe  behind.  It  is 
divided  into  two  convolutions  by  an  indistinct  groove.  One,  the  supra-marginal, 
lies  behind  the  ascending  part  of  the  intra-parietal  sulcus  and  above  the  horizontal 
limb  of  the  fissure  of  Sylvius,  over  the  extremity  of  which  it  arches.  It  is  con- 
nected in  front  with  the  ascending  parietal  convolution  below  the  intra-parietal 
sulcus,  and  behind  with  the  superior  temporal  convolution  round  the  posterior 
extremity  of  the  fissure  of  Sylvius.  The  other,  the  angular,  is  united  anteriorly 
with  the  foregoing,  while  posteriorly  it  is  continuous  with  the  middle  temporal 
convolution  by  a  process  which  curves  round  the  superior  temporal  or  parallel 
sulcus.     It  is  connected  with  the  occipital  lobe  by  the  second  annectant  gyrus. 

The  internal  or  mesial  surface  of  the  parietal  lobe  is  continuous  with  the 
external  surface  over  the  upper  edge  of  the  hemisphere.  It  is  of  small  size,  and 
forms  one  square-shaped  convolution,  which  from  its  shape  is  termed  the  quadrate 
lobe.     From  its  situation  above  the  cuneate  lobe  it  is  sometimes  named  precuneus. 

3.  The  Occipital  Lobe. — The  occipital  lobe  is  divided  on  its  external  surface 
into  three  convolutions  by  two  indistinct  sulci,  the  superior  and  middle  occipital 
sulci.  They  are  directed  backward  across  the  lobe,  being  frequently  small  and 
ill  marked ;  the  superior  is  sometimes  continuous  with  the  horizontal  portion  of 
the  intra-parietal  sulcus. 

The  superior  occipital  convolution  is  situated  above  the  superior  sulcus,  and  is 
connected  to  the  superior  parietal  convolution  by  the^rs^  annectant  gyrus. 

The  middle  occipital  convolution  is  situated  between  the  superior  and  middle 
occipital  sulci,  and  is  connected  to  the  angular  convolution  by  the  second  annectant 
gyrus,  and  to  the  middle  temporal  convolution  by  the  third  annectant  gyrus. 

The  inferior  occipital  convolution  is  situated  below  the  middle  occipital  sulcus, 
and  is  sometimes  separated  from  the  external  occipito-temporal  convolution  on 
the  under  surface  of  the  hemisphere  by  an  inconstant  sulcus,  the  inferior  occipital 
sulcus.  It  is  connected  to  the  inferior  temporal  convolution  by  the  fourth  annec- 
tant gyrus. 

The  internal  or  mesial  surface  of  the  occipital  lobe  presents  a  triangular  con- 
volution, which  is  known  as  the  cuneus  or  cuneate  lobule.  It  is  situated  between 
the  internal  parieto-occipital  and  calcarine  fissures,  which,  as  already  mentioned, 
meet  some  distance  behind  the  posterior  extremity  of  the  corpus  callosum. 

the  three  parts  of  the  sulcus  may  be  separate,  or  the  ramus  horizontalis  confluent  with  the  ramus 
verticalis  inferior,  the  ramus  verticalis  superior  remaining  separate ;  or,  again,  the  vertical  limbs  may 
be  confluent  and  the  horizontal  limb  separate;  or,  finally,  the  ramus  horizontalis  may  be  joined  to 
the  lower  end  of  the  ramus  verticalis  superior,  while  the  lower  vertical  ramus  is  separate.  The  pro- 
longation of  the  intra-parietal  sulcus  into  the  occipital  lobe,  which  sometimes  exists,  he  calls  the 
ramus  occipitalis.  In  the  majority  of  cases,  however,  the  occipital  ramus  is  separated  from  the  main 
portion  of  the  intra-parietal  sulcus  by  a  superficial  or  deep  bridging  convolution.  (Journal  of  Anatomy 
and  Physiology,  vol.  xxiv.,  part  ii.,  p.  135.) 


652  THE  NERVOUS  SYSTEM. 

4.  The  temporal  lobe,  sometimes  called  the  temporo-sphenoidal  lobe,  presents 
an  outer  and  an  inferior  surface.  The  outer  surface  is  subdivided  by  two  fissures, 
named  respectively  the  first  and  second  temporal  sulci.  The  first  temporal  sulcus 
is  well  marked,  and  runs  from  before  backward  through  the  temporal  lobe 
parallel  with,  but  some  little  distance  below,  the  horizontal  limb  of  the  fissure  of 
Sylvius,  and  hence  is  often  termed  the  parallel  sulcus.  The  second  temporal  sulcus 
takes  the  same  direction  as  the  first,  but  is  situated  at  a  lower  level,  and  is  often 
interrupted  by  one  or  more  bridging  convolutions.  These  two  sulci  subdivide  this 
surface  of  the  temporal  lobe  into  three  convolutions.  The  first  or  superior  tem- 
poral convolution  is  situated  between  the  horizontal  limb  of  the  fissure  of  Sylvius 
and  the  first  temporal  sulcus,  and  is  continuous  behind  with  the  supra-marginal 
convolution.  The  second  or  middle  temporal  convolution  lies  between  the  first 
and  second  temporal  sulci,  and  is  continued  behind  into  the  angular  and  middle 
occipital  convolutions.  The  third  or  inferior  temporal  convolution  is  placed  below 
the  second  temporal  sulcus  :  it  is  connected  posteriorly  with  the  inferior  occipital 
convolution,  and  is  also  prolonged  on  to  the  under  or  tentorial  surface  of  the 
temporal  lobe,  where  it  is  limited  internally  by  the  third  temporal  sulcus,  about 
to  be  described. 

The  inferior  or  tentorial  surface  presents  two  fissures,  viz.  :  the  third  temporal 
sulcus  and  the  collateral  fissure — the  latter  of  which  has  already  been  described 
(page  647).  The  third  temporal  sulcus  extends  from  near  the  occipital  pole 
behind,  to  near  the  anterior  extremity  of  the  temporal  lobe  in  front,  but  is,  how- 
ever, frequently  subdivided  by  bridging  gyri.  The  convolutions  on  the  inferior 
surface  are  (1)  the  fourth  temporal  or  subcollateral  convolution  (sometimes  called 
the  external  occipitotemporal),  situated  between  the  third  temporal  sulcus  and  the 
collateral  fissure ;  and  (2)  the  subcalcarine  convolution  or  lingual  lobule,  lying 
between  the  calcarine  fissure  above  and  the  posterior  part  of  the  collateral  fissure 
below  and  continuous  in  front  with  the  hippocampal  convolution,  the  latter  forming 
part  of  the  limbic  lobe.1 

The  central  lobe  or  island  of  Reil  (Fig.  349)  lies  deeply  in  the  Sylvian  fissure, 
and  can  only  be  seen  when  the  lips  of  that  fissure  are  widely  separated,  since  it  is 
overlapped  and  hidden  by  the  convolutions  which  bound  the  fissure.  These 
convolutions  are  termed  the  opercula  of  the  insula  ;  they  are  separated  from  each 
other  by  the  three  limbs  of  the  Sylvian  fissure,  and  named  the  orbital,  frontal, 
fronto-parietal,  and  temporal  opercula.  It  is  almost  surrounded  by  a  deep 
limiting  sulcus,  which  separates  it  from  the  frontal,  parietal,  and  temporal  lobes. 
When  the  opercula  have  been  removed,  the  insula  presents  the  form  of  a  triangular 
eminence ;  its  apex  is  directed  downward  and  inward  toward  the  anterior 
perforated  space,  and  is  continuous  in  front  with  the  posterior  orbital  convolution 
and  behind  with  the  hippocampal  convolution.  It  is  divided  into  a  pre-central 
and  a  post-central  lobe  by  the  sulcus  centralis,  which  runs  backward  and  upward 
from  the  apex  of  the  insula.  The  pre-central  lobe  is  further  subdivided  by 
shallow  sulci  into  three  or  four  short  convolutions,  the  gyri  breves,  while  the 
post-central  lobe  is  named  the  gyrus  longus  and  is  often  bifurcated  at  its  upper 
extremity.  The  gray  matter  of  the  insula  is  continuous  with  that  of  the  different 
opercula,  while  its  mesial  surface  corresponds  with  the  lenticular  nucleus  of  the 
corpus  striatum. 

Limbic  Lobe. — The  term  limbic  lobe  (grande  lobe  limbique)  was  introduced 
by  Broca  in  1878,  and  under  it  he  included  two  convolutions,  viz.,  the  callosal 
and  hippocampal,  which  together  arch  round  the  corpus  callosum  and  the 
hippocampal  fissure.  These  he  separated  on  the  morphological  ground  that 
they  are  well   developed   in    animals  possessing  a  keen  sense  of  smell    (osmatie 

1  It  will  be  seen  from  this  description  that  the  tentorial  surface  of  the  occipital  lobe  is  regarded 
as  forming  part  of  the  same  surface  as  the  temporal  lobe.  The  boundary  between  the 
occipital  and  temporal  lobes  on  the  tentorial  surface  is  purely  artificial,. and  if  represented  by  a 
line  drawn  upward  and  inward  from  the  pre-occipital  notch,  would  cut  both  the  subcollateral  and 
subcalcarine  gyri. 


HEMISPHERES    OF    THE   BRAIN. 


653 


animals),  such  as  the  clog  and  fox.  To  the  lobe  thus  denned  the  following  parts 
must  be  added,  viz.  :  the  laminae  of  the  septum  lucidum,  together  with  the 
fornix  and  its  fimbriae,  which  may  be  regarded  as  forming  an  inner  or  deep  arch  ; 
the  peduncles  and  longitudinal  striae  of  the  corpus  callosum,  together  with  the 
gyrus  dentatus,  which  form  a  middle  arch,  while  the  outer  arch  is  constituted  by 
the  callosal  and  hippocampal  convolutions :  the  first  two  arches  are  separated 
from  each  other  by  the  corpus  callosum. 

Convolutions  of  the  Limbic  Lobe. — (1)  The  callosal  convolution,  gyrus  forni- 
catus,  or  gyrus  cinguli  is  an  arch-shaped  convolution,  lying  in  close  relation  to 
the  superficial  surface  of  the  corpus  callosum,  from  which  it  is  separated  by  a  slit- 
like fissure,  the  callosal  fissure.  It  commences  below  the  rostrum  of  the  corpus 
callosum,  curves  round  in  front  of  the  genu,  extends  along  the  upper  surface  of 
the  body,  and  finally  turns  downward  behind  the  splenium,  where  it  is  connected 
by  a  narrow  isthmus  with  the  gyrus  hippocampi.  It  is  separated  from  the 
marginal  convolution  by  the  calloso-marginal  sulcus,  from  the  quadrate  lobe  by 
the  post-limbic  sulcus,  and  from  the  subcalcarine  convolution  by  the  calcarine 
fissure. 

(2)  The  hippocampal  convolution  (gyrus  hippocampi)  is  bounded  above  by  the 
hippocampal  or  dentate  fissure,  and  below  by  the  anterior  part  of  the  collateral 


Fig.  349.— The  Island  of  Reil.    Left  side.    The  overlapping  parts  of  the  hemisphere  have  been  removed. 
(Dalton.)    1,  2,  3,  gyri  breves  ;  4,  5,  gyrus  longus,  bifurcated  at  its  upper  extremity. 

fissure.  Behind,  it  is  continuous  superiorly,  through  the  isthmus,  with  the  callosal 
convolution,  and  inferiorly  with  the  subcalcarine  or  lingual  convolution.  Its 
anterior  extremity  is  recurved  in  the  form  of  a  hook,  and  is  named  the  uncus. 
Running  in  the  substance  of  the  callosal  and  hippocampal  convolutions,  and  con- 
necting them  together,  is  a  tract  of  arched  fibre?,  named  the  cingulum.  The  outer 
root  of  the  olfactory  tract  passes  into  the  anterior  extremity  of  the  hippocampal 
convolution,  and  the  inner  root  into  the  commencement  of  the  callosal  convolution, 
so  that  these  two  convolutions,  with  the  addition  of  the  olfactory  tract,  present  a 
racquet-like  appearance — the  olfactory  tract  constituting  the  handle  and  the  two 
convolutions  the  circumference  of  the  blade. 

(3)  The  dentate  convolution  (formerly  named  the  dentate  fascia)  is  situated  above 
the  gyrus  hippocampi,  from  which  it  is  separated  by  the  hippocampal  or  dentate 
fissure.  It  is  covered  by  the  fimbria,  and  is  a  narrow,  elongated  convolution,  the 
free  surface  of  which  presents  a  notched  or  toothed  appearance,  hence  its  name. 
Posteriorly  it  is  prolonged  as  a  delicate  lamina,  the  fasciola  cinerea,  around  the 
splenium  of  the  corpus  callosum,  and  becomes  continuous  on  the  upper  surface 
of  that  body  with  its  mesial  and  lateral  longitudinal  striae.  Anteriorly  it  is  pro- 
longed into  the  notch  produced  by  the  recurving  of  the  uncus,  where  it  forms  a 
sharp  curve;  from  here  it  can  be  traced  as  a  delicate  band  (band  of  Giacomini) 
over  the  uncus,  on  the  outer  surface  of  which  it  is  lost. 


654 


THE   NERVOUS  SYSTEM. 


The  remaining  structures  which  contribute  to  the  formation  of  the  limbic  lobe 
will  be  subsequently  described. 

The  olfactory  lobe  is  situated  on  the  under  surface  of  the  frontal  lobe.  It  is 
rudimentary  in  man  and  some  other  mammals,  but  in  vertebrates  generally  it  is 
well  developed,  and  consists  of  a  distinct  extension  of  the  cerebral  hemisphere, 
enclosing  a  portion  of  the  anterior  horn  of  the  lateral  ventricle.  In  man  it  is  long 
and  slender,  and  may  be  described  as  consisting  of  two  parts,  the  anterior  and 
posterior  olfactory  lobules. 

The  anterior  olfactory  lobule  is  made  up  of:  (1)  the  olfactory  bulb ;  (2)  the 
olfactory  tract ;  (3)  the  trigonum  olfactorium  ;  and  (4)  the  area  of  Broca. 


Frontal  lobe. 


Temporo- 

sphenoidal 

lobe. 


Occipital 
lobe. 


Fig.  350.— Base  of  the  brain. 


(1)  The  olfactory  bulb  is  an  oval  mass  of  a  reddish-gray  color,  which  rests  on 
the  cribriform  plate  of  the  ethmoid  bone,  and  forms  the  anterior  expanded  extrem- 
ity of  the  olfactory  tract.  Its  under  surface  receives  the  olfactory  nerves,  which 
pass  upward  through  the  cribriform  plate  from  the  olfactory  region  of  the  nose. 
Its  minute  structure  will  be  subsequently  described. 

(2)  The  olfactory  tract  is  a  band  of  white  matter,  triangular  on  section,  the 
apex  being  directed  upward.  It  lies  in  the  olfactory  sulcus  on  the  under  surface 
of  the  frontal  lobe.  Traced  backward,  it  is  seen  to  divide  into  two  roots,  an  outer 
and  an  inner.  The  outer  root  passes  across  the  outer  part  of  the  anterior  perforated 
space  to  the  nucleus  amygdalae  and  the  anterior  part  of  the  gyrus  hippocampi. 
The  inner  root  turns  sharply  inward,  and  ends  partly  in  Broca's  area  and  partly  in 


r 


HEMISPHERES    OF    THE  BRAIN.  655 

the  callosal  convolution  ;  in  other  words,  the  inner  root  is  continuous  with  one 
extremity  and  the  outer  root  with  the  other  extremity  of  the  limhic  lobe. 

(3)  The  trigonum  olfactorium  is  situated  between  the  diverging  roots  of  the 
olfactory  tract,  and  is  sometimes  described  at  the  middle  or  gray  root  of  the  tract. 
It  is  part  of  an  area  of  gray  matter,  which  forms  the  base  of  the  anterior  olfactory 
lobule ;  another  portion  of  it  is  termed  (4)  the  area  of  Broca  ;  and  a  third  portion, 
of  no  special  significance,  is  situated  external  to  the  outer  root  of  the  olfactory 
tract.  This  area  of  gray  matter  is  bounded  internally  and  posteriorly  by  a  fissure 
(fissura  prima)  which  separates  it  from  the  peduncle  of  the  corpus  callosum  and 
from  the  posterior  olfactory  lobule.  The  area  of  Broca  is  continuous  with  the 
gyrus  fornicatus. 

The  posterior  olfactory  lobule  or  anterior  perforated  space  is  marked  off  from 
the  anterior  lobule  by  the  fissura  prima,  and  is  situated  at  the  commencement  of 
the  fissure  of  Sylvius.  Internally,  it  is  bounded  by  the  peduncle  of  the  corpus 
callosum,  and  is  continuous  with  the  lamina  cinerea.  Posteriorly  it  is  bounded 
by  the  optic  tract,  and  it  is  partially  concealed  by  the  temporal  lobe  which  overlaps 
it.  It  has  received  the  name  of  anterior  perforated  space  from  its  being  perforated 
by  numerous  openings,  which  transmit  blood-vessels  to  the  interior  of  the  brain, 
and  it  corresponds  to  the  under  surface  of  the  lenticular  nucleus  and  part  of  the 
claustrum. 

Under  Surface  or  Base  of  the  Encephalon  (Fig.  350). — Having  considered  the 
surface  of  the  hemispheres,  the  student  should  direct  his  attention  to  the  base  of 
the  brain,  before  commencing  the  study  of  the  component  parts  which  make  up 
the  two  hemispheres. 

The  base  of  the  brain  presents  for  examination  the  under  surfaces  of  the 
frontal  and  temporal  lobes ;  the  structures  contained  in  the  interpeduncular  space, 
with  the  crura  cerebri  or  cerebral  peduncles ;  the  under  surfaces  of  the  pons 
Varolii,  cerebellum,  and  medulla  oblongata ;  and  the  superficial  origins  of  the 
cranial  nerves. 

The  various  objects  exposed  to  view  (with  the  exception  of  the  origins  of  the 
cranial  nerves,  which  will  be  considered  in  another  section)  in  the  middle  line  and 
on  either  side  of  the  middle  line,  are  here  arranged  in  the  order  they  are  met  with 
from  before  backward. 

In  the.  Middle  Line.  On  Each  Side  of  the  Middle  Line. 

Longitudinal  fissure.  Frontal  lobe. 

Rostrum  and  peduncles  of  Olfactory  lobe. 

corpus  callosum.  Fissure  of  Sylvius. 

Lamina  cinerea.  Optic  tracts. 

Optic  commissure.  Crus  cerebri. 

Tuber  cinereum.  Temporal  lobe. 

Infundibulum.  Hemisphere  of  cerebellum. 

Pituitary  body. 
Corpora  albicantia. 
Posterior  perforated  space. 
Pons  Varolii. 
Medulla  oblongata. 

The  longitudinal  fissure  partially  separates  the  two  hemispheres  from  each 
other.  It  divides  completely  the  anterior  portions  of  the  two  frontal  lobes :  and 
on  raising  the  cerebellum  and  pons,  it  will  be  seen  to  separate  completely  the  two 
occipital  lobes :  of  these  two  portions  of  the  longitudinal  fissure,  that  which 
separates  the  occipital  lobes  is  the  longer.  The  intermediate  part  of  the  fissure 
is  filled  up  by  the  great  transverse  band  of  white  matter,  the  corpus  callosum. 
In  the  fissure  between  the  two  frontal  lobes  the  anterior  cerebral  arteries  ascend 
on  the  corpus  callosum. 

The  corpus  callosum  terminates  at  the  base  of  the  brain  by  a  concave  margin, 


656  THE  NERVOUS  SYSTEM. 

which  is  connected  with  the  tuber  cinereum  through  the  intervention  of  a  thin 
layer  of  gray  substance,  the  lamina  cinerea.  This  may  be  exposed  by  gently 
raising  and  drawing  back  the  optic  commissure.  A  white  band  may  be  observed 
on  each  side,  passing  backward  from  the  under  surface  of  the  corpus  callosum, 
across  the  posterior  margin  of  the  anterior  perforated  space  to  the  hippocampal 
gyrus,  where  each  meets  the  corresponding  outer  root  of  the  olfactory  tract :  these 
bands  are  called  the  peduncles  of  the  corpus  callosum.  They  may  be  traced 
upward  around  the  genu  to  become  continuous  with  the  strice  longitudinales  on  its 
upper  surface.  Laterally,  this  portion  of  the  corpus  callosum  extends  into  the 
frontal  lobe. 

The  lamina  cinerea  is  a  thin  layer  of  gray  substance,  extending  backward  from 
the  termination  of  the  corpus  callosum  above  the  optic  commissure  to  the  tuber 
cinereum;  it  is  continuous  on  each  side  with  the  gray  matter  of  the  anterior  per- 
forated space,  and  forms  the  anterior  part  of  the  inferior  boundary  of  the  third! 
ventricle. 

The  optic  commissure  is  situated  in  the  middle  line,  immediately  in  front  of  the! 
tuber  cinereum  and  below  the  lamina  cinerea ;  that  is  to  say,  the  commissure  isj 
superficial  to  the  lamina  in  the  order  of  dissection  when  the  base  is  uppermost.  It  I 
is  the  point  of  junction  between  the  two  optic  tracts,  and  will  be  described  with! 
the  cranial  nerves.  .  Immediately  behind  the  diverging  optic  tracts,  and  betweenl' 
them  and  the  peduncles  of  the  cerebrum  {crura  cerebri),  is  a  lozenge-shaped 
interval,  the  interpeduncular  space,  which  is  bounded  behind  by  the  pons  Varolii,  i 
and  in  which  are  found  the  following  parts:  the  tuber  cinereum,  infundibulum, 
pituitary  body,  corpora  albicantia,   and   the  posterior  perforated  space. 

The  tuber  cinereum  is  an  eminence  of  gray  matter,  situated  between  the  optic 
tracts,  and  extending  from  the  corpora  albicantia  to  the  optic  commissure,  to  whichl 
it  is  attached ;  it  is  connected  with  the  surrounding  parts  of  the  cerebrum,  forms 
part  of  the  floor  of  the  third  ventricle,  and  is  continuous  with  the  gray  substance 
in  that  cavity.  From  the  middle  of  its  under  surface  a  conical  tubular  process  of  I 
gray  matter,  about  two  lines  in  length,  is  continued  downward  and  forward  to  bel 
attached  to  the  posterior  lobe  of  the  pituitary  body.  This  is  the  infundibulum, 
and  its  canal,  which  is  funnel-shaped,  communicates  with  the  third  ventricle. 

The  pituitary  body  (hypophysis  cerebri)  is  a  small,  reddish-gray,  vascular  mass,  • 
weighing  from  five  to  ten  grains,  and  of  an  oval  form,  situated  in  the  sella  turcica,} 
where  it  is  retained  by  a  process  of  dura  mater,  named  the  diaphragma  sellae.j 
This  process  covers  in  the  sella  turcica,  and  has  a  small  hole  in  its  centre  through; 
which  the  infundibulum  passes. 

Structure. — The  pituitary   body   is  very   vascular,  and   consists   of  two  lobes,  ; 
separated  from  one   another  by  a  fibrous    lamina.      Of  these,  the  anterior  is  the! 
larger,  of  an  oblong  form,  and   somewhat    concave   behind,  where   it  receives  thel 
posterior  lobe,  which  is  round.      The  two    lobes  differ  both   in  development  and 
structure.     The  anterior  lobe,  of  a  dark,   reddish-brown  color,  is  developed  from1 
the  epiblast  of  the  buccal  cavity,  and  resembles  to  a  considerable  extent,  in  micro-r 
scopic  structure,  the  thyroid   body.     It   consists  of  a  number  of  isolated  vesicles| 
and  slightly  convoluted  tubules,  lined  by  epithelium  and  united  together  by  a  very! 
vascular  connective  tissue.      The  epithelium  is  columnar  and  occasionally  ciliated.! 
The  alveoli  sometimes    contain   a  colloid   material,  similar   to  that  found  in  thel 
thyroid  body,  and  their  walls  are  surrounded  by  a  close  network  of  lymphatic  andj 
capillary  blood-vessels.      The  posterior  lobe  is  developed  as  an  outgrowth  from  thel 
embryonic   brain,  and    during   foetal   life   contains   a   cavity  which   communicates^ 
through  the  infundibulum  with  the  cavity  of  the  third  ventricle.      In  the  adult  iti 
becomes  firmer   and   more  solid,  and  consists  of  a  sponge-like   connective  tissue 
arranged  in  the  form  of  reticulating  bundles,  between  which  are  branched  cells, f 
some  of  them  containing  pigment.     In  the  lower  animals  the  two  lobes  are  quite y 
distinct,  and  it  is  only  in  the  mammalia  that  they  become  fused  together. 

The  corpora  albicantia  or  mammillaria  are  two  small,  round,  white  masses,}" 
each   about  the  size  of  a  pea,  placed  side  by  side  immediately  behind  the  tuber 


HEMISPHERES    OF    THE   BRAIN. 


657 


cinereum,  and  connected  with  each  other  across  the  mesial  plane.  They  are 
mainly  formed  by  the  anterior  crura  of  the  fornix,  which,  after  descending  to  the 
base  of  the  brain,  are  twisted  upon  themselves  to  form  loops,  and  constitute  the 
white  covering  of  the  corpora  albicantia.  A  second  fasciculus,  the  bundle  of 
Vicq  d'Azyr,  converges  from  the  optic  thalamus,  and  enters  the  anterior  part  of 
each  body  on  its  dorso-mesial  surface.  They  are  composed  externally  of  white 
substance,  and  internally  of  gray  matter ;  the  nerve-cells  of  the  gray  matter  are 
arranged  in  two  sets,  inner  and  outer,  the  cells  of  the  former  set  being  the  smaller. 
They  are  also  connected  to  the  tegmentum  by  a  small  bundle  of  fibres,  the  peduncle 
of  the  mammillary  body.  At  an  early  period  of  foetal  life  they  are  blended 
together  into  one  large  mass,  but  become  separated  about  the  seventh  month.  In 
most  vertebrates  there  is  only  one  median  corpus  albicans. 

The  posterior  perforated  space  (pons  Tarini)  corresponds  to  a  whitish-gray 
fossa  placed  between  the  corpora  albicantia  in  front,  the  pons  Varolii  behind,  and 
the  crus  cerebri  on  either  side.  It  forms  the  posterior  part  of  the  floor  of  the 
third  ventricle,  and  is  perforated  by  numerous  small  orifices  for  the  passage  of 
the  postero-median  ganglionic  branches  of  the  posterior  cerebral  and  posterior 
communicating  arteries. 


Gray  matter 
White  matter. 


Ventricle  of 
corpus  callosum. 


Corpus  callosum. 


Hippocampus 
major. 


Pneumogastric 
nerve. 


Fig.  351.— Transverse  vertical  section  of  the  brain,  through  the  fore  part  of  the  foramen  magnum,  looked 
at  from  the  front.    (After  Hirschfleld  and  Leveille.) 

The  pons  Varolii  is  situated  immediately  behind  the  two  crura  of  the  cerebrum. 
It  consists  of  a  broad  band  of  white  fibres,  which  pass  transversely  from  one  cere- 
bellar hemisphere  to  the  other ;  the  band  becoming  narrower  as  it  enters  the  cere- 
bellum. In  the  middle  line' on  its  under  surface  a  narrow  groove  runs  from  before 
backward  and  accommodates  the  basilar  artery. 

The  medulla  oblongata  emerges  from  the  posterior  border  of  the  pons  Varolii ; 
it  is  pyramidal  in  form,  and  is  continuous  below  with  the  cervical  portion  of  the 
spinal  cord.  It  is  marked  on  its  ventral  surface  by  a  median  fissure,  continuous 
below  with  the  anterior  median  fissure  of  the  cord,  and  on  either  side  by  secondary 
fissures  and  columns,  which  will  be  described  in  the  sequel. 

The  Frontal  Lobe. — The  under  surface  of  the  frontal  lobe,  sometimes  named 
the  orbital  lobe,  is  seen  on  the  anterior  part  of  the  base  of  the  brain  on  either  side 
of  the  median  line.      It  has  already  been  described  (page  649). 
42 


658 


THE  NERVOUS  SYSTEM. 


The  fissure  of  Sylvius  at  the  base  of  the  brain  separates  the  frontal  from  the 
temporal  lobe,  and  lodges  the  middle  cerebral  artery.  It  has  also  been  described 
(page  645). 

The  optic  tracts  are  well-marked  flattened  bands  of  fibres,  which  run  obliquely 
across  the  eras  cerebri  on  either  side,  and  unite  anteriorly  to  form  the  optic  com- 
missure.     They  will  be  described  in  connection  with  the  cranial  nerves. 

The  crura  cerebri  (peduncles  of  the  cerebrum)  are  two  thick  cylindrical  bundles 
of  white  matter,  which  appear  in  front  of  the  anterior  border  of  the  pons,  and 
diverge  as  they  pass  forward  and  outward  to  enter  the  under  surface  of  each  hemi- 
sphere. Each  eras  is  about  three-quarters  of  an  inch  in  length,  and  is  about  the 
same  in  breadth  anteriorly,  but  somewhat  less  posteriorly.  They  are  marked  upon 
their  surface  with  longitudinal  striae,  and  each  is  crossed,  just  before  entering 
the  hemisphere,  by  the  fourth  nerve  and  the  optic  tract,  the  latter  of  which  is 
adherent  by  its  upper  surface  to  the  peduncle. 


Fig.  352.— Section  of  the  brain.    Made  on  a  level  with  the  corpus  callosum. 

The  Temporal  Lobe. — The  under  surface  of  the  temporal  lobe  is  visible  at  the 
base  of  the  brain,  on  either  side  of  the  crura  and  the  structures  contained  in  the 
interpeduncular  space.  It  is  separated  anteriorly  from  the  frontal  lobe  by 
the  fissure  of  Sylvius,  and  behind  is  limited  by  the  anterior  border  of  the  lateral 
hemispheres  of  the  cerebellum.  The  fissures  and  lobes  on  its  surface  have  already 
been  described  (page  652). 

The  hemispheres  of  the  cerebellum  are  situated  on  either  side  of  the  middle 
line,  and  cover  the  occipital  lobes  of  the  cerebrum,  when  viewed  from  the  base. 
The  cerebellum  differs  much  in  appearance  from  the  rest  of  the  encephalon,  being 


INTERIOR    OF    THE    CEREBRUM.  659 

of  a  darker  color,  while  its  convolutions  are  smaller  and  narrower,  and  arranged 
like  the  leaves  of  a  book,  and  hence  called  folia. 

General  Arrangement  of  the  Parts  Composing  the  Cerebrum. — Each  hemisphere, 
as  already  stated,  consists  of  a  central  cavity,  the  lateral  ventricle,  surrounded  by 
thick  and  convoluted  walls  of  nervous  tissue. 

Interior  of  the  Cerebrum. — If  the  upper  part  of  either  hemisphere  is  removed 
with  a  knife,  about  half  an  inch  above  the  level  of  the  corpus  callosum,  its  internal 
white  matter  will  be  exposed.  It  is  an  oval-shaped  centre,  of  white  substance, 
surrounded  on  all  sides  by  a  narrow  convoluted  margin  of  gray  matter,  which 
presents  an  equal  thickness  in  nearly  every  part.  This  white  central  mass  has 
been  called  the  centrum  ovale  minus.  Its  surface  is  studded  with  numerous 
minute  red  dots  (puncta  vasculosa),  produced  by  the  escape  of  blood  from  divided 
blood-vessels.  In  inflammation  or  great  congestion  of  the  brain  these  are  very 
numerous  and  of  a  dark  color.  If  the  remaining  portion  of  one  hemisphere  is 
slightly  separated  from  the  other,  a  broad  band  of  white  substance  will  be  observed, 
connecting  them  at  the  bottom  of  the  longitudinal  fissure ;  this  is  the  corpus 
callosum.  The  margins  of  the  hemispheres  which  overlap  this  portion  of  the  brain 
are  called  the  labii  cerebri.  Each  labium  is  part  of  the  callosal  convolution 
already  described ;  and  the  space  between  it  and  the  upper  surface  of  the  corpus 
callosum  is  termed  the  callosal  fissure  (Fig.  348).  The  hemispheres  should  now 
be  sliced  off  to  a  level  with  the  upper  surface  of  the  corpus  callosum,  when  the 
white  substance  of  that  structure  will  be  seen  connecting  the  two  hemispheres. 
The  large  expanse  of  medullary  matter  now  exposed,  surrounded  by  the  con- 
voluted margin  of  gray  substance,  is  called  the  centrum  ovale  majus  of  Vieussens 
(Fig.  352). 

The  Corpus  Callosum. — The  corpus  callosum  is  a  thick  stratum  of  transversely 
directed  nerve-fibres,  by  which  probably  almost  every  part  of  one  hemisphere  is 
connected  with  the  corresponding  part  of  the  other  hemisphere.  The  fibres  of 
this  body,  when  they  pass  from  it  into  the  hemispheres  radiate  in  various  direc- 
tions, to  terminate  in  the  gray  matter  of  the  periphery.  It  thus  connects  the  two 
hemispheres  of  the  brain,  forming  their  great  transverse  commissure,  and  at  the 
same  time  roofs  in  the  lateral  ventricles.  The  best  conception  of  its  size  and 
form  is  obtained  by  making  an  anterior  posterior  vertical  section  through  the 
centre  of  the  brain  (Fig.  353).  It  is  then  seen  to  be  a  long,  thick,  irregularly 
flattened  arch  ;  in  front  taking  a  sharp  bend,  the  genu,  and  dipping  downward 
and  backward  to  the  base  of  the  brain  by  a  reflected  portion,  the  rostrum,  which 
is  connected  with  the  lamina  cinerea  ;  behind  it  terminates  by  a  rounded  end, 
which  is  folded  over  and  is  named  the  splenium.  It  is  about  four  inches  in  length, 
and  extends  to  within  an  inch  and  a  half  of  the  anterior,  and  two  inches  and  a 
half  of  the  posterior  extremity  of  the  cerebrum.  It  is  somewhat  broader  behind 
than  in  front,  and  is  thicker  at  either  end  than  in  its  central  part,  being  thickest 
behind.  The  reflected  anterior  portion  of  the  corpus  callosum  is  called  the  beak  or 
rostrum  ;  it  becomes  gradually  thinner  as  it  descends,  and  is  attached  by  its  lateral 
margins  to  the  frontal  lobes.  At  its  termination,  in  addition  to  joining  the  lamina 
cinerea,  the  corpus  callosum  gives  off  two  bands  of  white  substance,  the  peduncles 
of  the  corpus  callosum,  already  described  (page  656). 

Posteriorly,  the  corpus  callosum  forms  a  thick  rounded  fold,  called  the  splenium 
or  pad,  which  is  free  for  a  little  distance  as  it  curves  forward,  and  is  then  contin- 
uous by  its  under  surface  with  the  fornix.  The  splenium  overlaps  the  mesencepha- 
lon, but  is  separated  from  it  by  the  pia  mater,  which  is  prolonged  forward  to  form 
the  velum  interpositum.  On  its  upper  surface,  the  structure  of  the  corpus  callo- 
sum is  very  apparent,  being  collected  into  coarse  transverse  bundles.  Along  the 
middle  line  is  a  longitudinal  depression,  the  so-called  raphe,  bounded  laterally  by 
two  or  more  slightly  elevated  longitudinal  bands,  called  the  stride  longitudinales  or 
nerves  of  Lancisi ;  and,  still  more  externally,  other  longitudinal  striae  are  seen. 
beneath  the  callosal  convolutions.  These  are  the  strios  long  itudin  ales  laterales.  or 
toznia  tectos.     On  each  side  of  the  middle  line  the  under  surface  of  the  corpus  cal- 


660 


THE  NERVOUS  SYSTEM. 


losum  forms  the  roof  of  the  lateral  ventricles,  while  in  the  mesial  plane  it  is  con- 
tinuous behind  with  the  fornix,  being  separated  from  it  in  front  by  the  septum 
lucidum,  which  forms  a  vertical  partition  between  the  two  ventricles.  On  each  side 
the  fibres  of  the  corpus  callosum  extend  into  the  substance  of  the  hemispheres,  con- 
necting them  together.  The  greater  thickness  of  the  two  extremities  of  this  com- 
missure is  explained  by  the  fact  that  the  fibres  from  the  anterior  and  posterior  parts 
of  each  hemisphere  cannot  pass  directly  across,  but  have  to  take  a  curved  direction. 


Fig.  353.— Vertical  median  section  of  the  encephalon,  showing  the  parts  in  the  middle  line. 


1.  Convolution  of  the  corpus  callosum.    Above  it 

is  the  calloso-marginal  fissure. 

2.  Fissure  of  Rolando. 

3.  The  parietooccipital  fissure. 

4.  4,  point  to  the  calcarine  fissure,  which  is  just 

above  the  numbers.  Between  2  and  3  are  the 
convolutions  of  the  quadrate  lobe.  Between  3 
and  4  is  the  cuneate  lobe. 

5.  The  corpus  callosum. 

6.  The  septum  lucidum. 

7.  The  fornix. 

8.  Anterior  crus  of  the   fornix,  descending  to  the 

base  of  the  brain,  and  turning  on  itself  to  form 
the  corpus  albicans.  The  bundle  of  Vicq 
d'Azyr  is  indicated  by  a  dotted  line. 

9.  The  optic  thalamus.    Behind  the  anterior  crus 


of  the  fornix  a  shaded  part  indicates  the  fora- 
men of  Monro ;  in  front  of  the  number  an 
oval  mark  shows  the  position  of  the  gray  or 
middle  commissure. 

10.  The  velum  interpositum. 

11.  The  pineal  gland. 

12.  The  corpora  quadrigemina. 

13.  The  crus  cerebri. 

14.  The  valve  of   Vieussens    (to  the  right  of  the 

number). 

15.  The  pons  Varolii. 

16.  The  third  nerve. 

17.  The  pituitary  body. 

18.  The  optic  nerve. 

19  points  to  the  anterior  commissure,  indicated  by 
the  oval  outline  behind  the  number. 


The  part  of  the  corpus  callosum  which  curves  forward  on  each  side  from  the  genu 
into  the  frontal  lobe  and  covers  the  front  part  of  the  anterior  cornu  of  the  lateral 
ventricle  is  called  the  forceps  anterior  or  minor.  The  part  which  curves  backward 
from  each  side  of  the  splenium  into  the  occipital  lobe  is  known  as  the  forceps  pos- 
terior or  major.  Between  these  two  parts  on  each  side  is  the  main  body  of  the 
fibres,  which  extend  laterally  into  the  temporal  lobe  and  cover  in  the  body  of  the 
lateral  ventricle.      These  are  known  as  the  tapetum  or  mat. 

An  incision  should  now  be  made  through  the  corpus  callosum,  on  either  side  of  the  raphe, 
when  two  large  irregular  cavities  will  be  exposed,  which  extend  through  a  great  part  of  the 
length  of  each  hemisphere.     These  are  the  lateral  ventricles. 

The  Lateral  Ventricles  (Fig.  354). — The  lateral  ventricles,  two  in  number,  right 
and  left,  are  irregular  cavities  situated  in  the  lower  and  inner  parts  of  the  cerebral 


INTERIOR    OF    THE    CEREBRUM. 


661 


hemisphere,  one  on  either  side  of  the  middle  line.  They  are  separated  from  each 
other  by  a  mesial  vertical  partition,  the  septum  lueidum,  but  communicate  with 
the  third  ventricle  and  indirectly  wJ(th  each  other  through  the  foramen  of  Monro. 
They  are  lined  by  a  thin,  diaphanous  membrane,  the  ependyma,  which  is  covered 
by  ciliated  epithelium,  and  are  moistened  by  a  serous  fluid,  which,  even  in  health, 
may  be  secreted  in  considerable  amount.  Each  lateral  ventricle  consists  of  a  cen- 
tral cavity  or  body,  and  three  prolongations  from  it,  termed  cornua.  The  anterior 
•cornu  curves  forward  and  outward  into  the  frontal  lobe;  the  posterior  backward 
and  inward  into  the  occipital  lobe ;  and  the  middle  descends  into  the  temporal 
lobe. 

The  central  cavity  or  body  of  the  lateral  ventricle  is  situated  in  the  lower  part 
of  the  parietal  lobe.     It  is  an  irregularly  curved  cavity,  triangular  in  shape  on 


Fig.  354. — The  lateral  ventricles  of  the  brain. 

transverse  section,  and  presents  a  roof,  a  floor,  and  an  inner  wall.  Its  roof  is 
formed  by  the  under  surface  of  the  corpus  callosum  ;  its  inner  wall  is  the  septum 
lueidum,  which  separates  it  from  the  opposite  ventricle  and  connects  the  under 
surface  of  the  corpus  callosum  with  the  fornix  ;  its  floor  is  formed  by  the  following 
parts,  enumerated  in  their  order  of  position,  from  before  backward :  the  caudate 
nucleus  of  the  corpus  striatum,  tcenia  semicircularis,  optic  thalamus,  choroid  plexus, 
one-half  of  the  fornix  and  its  posterior  pillar. 

The  anterior  cornu  passes  forward  and  outward,  with  a  slight  inclination  down- 
ward, from  the  foramen  of  Monro  into  the  frontal  lobe,  curving  round  the  anterior 
extremity  of  the  caudate  nucleus.  It  is  bounded  above  by  the  corpus  callosum. 
and  below  by  the  upper  surface  of  its  reflected  portion,  the  rostrum.  It  is  bounded 
internally  by  the  anterior  portion  of  the  septum  lueidum,  and  externally  by  the 


662  THE  NERVOUS  SYSTEM. 

head  of  the  caudate  nucleus  of  the  corpus  striatum.  Its  apex  reaches  the  poste- 
rior surface  of  the  genu  of  the  corpus  callosum. 

The  posterior  cornu  curves  backward  into,  the  substance  of  the  occipital  lobe, 
its  direction  being  backward  and  outward,  and  then  inward ;  its  concavity  is  there- 
fore directed  inward.  Its  roof  is  formed  by  the  fibres  of  the  corpus  callosum 
passing  to  the  temporal  and  occipital  lobes.  On  its  inner  wall  is  seen  a  longi- 
tudinal eminence,  which  is  in  an  involution  of  the  ventricular  wall  produced  by  the 
calcarine  sulcus ;  this  is  called  the  hippocampus  minor,  or  calcar  avis.  Just  above 
this  the  forceps  major  of  the  corpus  callosum,  sweeping  round  to  enter  the  occipital 
lobe,  causes  another  projection," which  is  known  as  the  bulb  of  the  posterior  horn. 
The  hippocampus  minor  and  bulb  of  the  posterior  horn  are  extremely  variable  in 
their  degree  of  development,  being  in  some  cases  ill  defined,  while  in  others  they 
are  unusually  prominent. 

Between  the  middle  and  posterior  cornu  is  a  triangular  area,  called  the  trigo- 
num  ventriculi  (see  Descending  Horn). 

The  middle  or  descending  cornu,  the  largest  of  the  three,  traverses  the  temporal 
lobe  of  the  brain,  forming  in  its  course  a  remarkable  curve  round  the  back  of  the 
optic  thalamus.  It  passes  at  first  backward,  outward,  and  downward,  and  then 
curves  round  the  eras  cerebri,  forward  and  inward,  to  within  an  inch  of  the  apex 
of  the  temporal  lobe,  its  direction  being  fairly  well  indicated  on  the  surface  of  the 
brain  by  that  of  the  parallel  sulcus.  Its  upper  boundary,  or  roof,  is  formed  chiefly 
by  the  under  surface  of  the  tapetum  of  the  corpus  callosum,  but  the  tail  of  the 
nucleus  caudatus  of  the  corpus  striatum  and  the  taenia  semicircularis  are  also 
prolonged  into  it,  and  extend  forward  in  the  roof  of  the  descending  horn  to  its 
extremity,  where  they  end  in  a  mass  of  gray  matter,  the  amygdaloid  nucleus  : 
this  nucleus  is  merely  a  localized  thickening  of  the  adjacent  gray  cortex.  Its 
loAver  boundary,  or  floor,  presents  for  examination  the  following  parts :  the  hippo- 
campus major,  pes  hippocampi,  eminentia  collateralis  or  pes  accessorius,  corpus 
fimbriatum,  prolonged  from  the  posterior  pillar  of  the  fornix,  and  the  choroid 
plexus.  Along  the  mesial  aspect  of  the  descending  cornu  there  is  a  cleft-like 
opening,  which  is  the  lower  part  of  the  transverse  fissure,  through  which  the 
choroid  plexus  of  the  pia  mater  is  invaginated  into  the  ventricle,  but  covered  by 
the  ependyma,  which  is  pushed  in  before  it. 

The  corpus  striatum  has  received  its  name  from  the  striped  appearance  which 
its  section  presents,  in  consequence  of  diverging  white  fibres  being  mixed  with  the 
gray  matter  which  forms  the  greater  part  of  its  substance.  The  larger  portion  of 
this  body  is  embedded  in  the  white  substance  of  the  hemisphere,  and  is  therefore 
external  to  the  ventricle.  It  is  termed  the  extra-ventricular  portion  or  the  nucleus 
lenticularis ;  a  part,  however,  is  visible  in  the  ventricle  and  its  anterior  cornu : 
this  is  the  intra-ventricular  portion,  or  the  nucleus  caudatus. 

The  nucleus  caudatus  (Fig.  355)  is  a  pear-shaped,  highly  arched  mass  of  gray 
matter ;  its  broad  extremity  is  directed  forward  into  the  fore  part  of  the  body  and 
anterior  cornu  of  the  lateral  ventricle ;  its  narrow  end  is  directed  outward  and 
backward  on  the  outer  side  of  the  optic  thalamus ;  it  is  continued  downward  into 
the  roof  of  the  descending  cornu,  where  it  terminates  in  the  nucleus  amygdala?,  a 
collection  of  gray  matter  in  the  apex  of  the  temporal  lobe.  It  is  covered  by  the 
lining  of  the  ventricle,  and  crossed  by  some  veins  of  considerable  size.  It  is 
separated  from  the  extra-ventricular  portion,  in  the  greater  part  of  its  extent,  by  a 
lamina  of  white  matter,  which  is  called  the  internal  capsule,  but  the  two  portions 
of  the  corpus  striatum  are  united  in  front. 

The  nucleus  lenticularis,  or  extra-ventricular  portion  of  the  corpus  striatum,  is 
only  seen  in  sections  of  the  hemisphere.  When  divided  horizontally,  it  presents, 
to  some  extent,  the  appearance  of  a  biconvex  lens,  while  a  vertical  transverse 
section  of  it  gives  a  somewhat  triangular  outline.  It  does  not  extend  as  far  forward 
or  backward  as  the  nucleus  caudatus.  It  is  bounded  externally  by  a  lamina  of  white 
matter  called  the  external  capsule,  on  the  outer  surface  of  which  is  a  thin  layer  of 
gray  matter  termed  the  claustrum.     The  claustrum  presents  ridges  and  furrows  on 


INTERIOR    OF   THE    CEREBRUM. 


663 


its  outer  surface,  corresponding  to  the  convolutions  and  sulci  of  the  island  of  Reil, 
from  which  it  is  separated  by  a  thin  white  lamina. 

Upon  making  aPtransve/se  vertical  section  through  the  middle  of  the  nucleus 
lenticular!*™  is°seen  to  present  two  white  lines,  parallel  with  its  ateral  border 
Lhich TvTde  it  up  into  three  zones,  of  which  the  outer  and  largest  is  of  a  reddish 
To  01   and  is  knowPn  as  the  putamen,  while  the  two  inner  are  paler  and  of  a  yellowish 

int  'and  are  termed  the  globus  pallidu,     All   three   zones  are  marked  by  fin 
radiating  white  fibres,  which  are  most  distinct  in  the  putamen       The  gray  matter 

?  he corpus  Striatum  is  traversed  by  nerve-fibres  some  of  which  are  beheved ^o 
originate  in  it.  The  cells  are  multipolar,  both  large  and  small,  those  of  the 
lenticular  nucleus  containing  yellow  pigment. 


Fig  355  -Middle  part  of  a  horizontal  section  through  the  cerehrum  at  the  level  of  the  dotted  line  in  the 
small  figure  of  one  hemisphere.    (From  Ellis,  after  Dalton.) 

The  internal  capsule  is  formed  by  fibres  of  the  crusta  of  the  crus  cerebri, 
supplemented  by  fibres  derived  from  the  corpus  striatum  and  OP11^1^™ 
each  side.  In  horizontal  section  (Fig.  355)  it  is  seen  to  be  somewhat  abrupt^ 
curved,  with  its  convexity  inward  ;  the  prominence  of  the  curve  is  ^™£»* 
and  projects  between  the  caudate  nucleus  and  the  optic  thalamus.  The  portion  in 
front  of  the  genu  is  termed  the  anterior  limb,  and  separates  the  lenticular  from  the 
caudate  nucleus  ;  the  portion  behind  the  genu  is  the  posterior  hmb,  and  separates 
the  lenticular  nucleus  from  the  optic  thalamus.  The  internal  capsule  is  con  p0 -sed 
largely  of  fibres  :h,  derived  from  the  crusta  of  the  crus  cerebri,  are  continued 

through  it  to  the  cortex  of  the  cerebral  hemispheres,  the  fib  res  of 1 ^anterior 
limb  passing  to  he  frontal  region  ;  those  from  the  genu  and  the  "f*«ri«tofO-&i^ 
of  the  posterio    limb  pass  to  the  Rolandic  area  of  the  cortex,  while  those  in  the 


664  THE  NERVOUS  SYSTEM. 

hindermost  third  of  the  same  limb  pass  to  the  temporo-occipital  region.  In 
addition  to  these,  there  are  fibres  which  terminate  in  the  corpus  striatum  and  the 
optic  thalamus ;  and  other  fibres  derived  from  the  gray  matter  of  these  two  bodies, 
from  the  subthalamic  region,1  and  from  the  hemisphere  of  the  opposite  side 
through  the  corpus  callosum,  which  pass  through  the  internal  capsule  to  the 
cerebral  cortex. 

The  external  capsule  is  a  lamina  of  white  matter,  situated  on  the  outer  side  of 
the  lenticular  nucleus,  between  it  and  the  claustrum,  and  is  continuous  with  the 
internal  capsule  below  and  behind  the  lenticular  nucleus.  It  is  made  up  of  fibres 
derived  partly  from  the  anterior  white  commissure  and  partly  from  the  sub- 
thalamic region. 

The  claustrum  is  a  thin  layer  of  gray  matter,  situated  on  the  outer  surface  of 
the  external  capsule.  On  transverse  section  it  is  seen  to  be  triangular,  with  its 
apex  directed  upward  and  its  base  downward.  Its  inner  surface,  which  is  con- 
tiguous to  the  outer  capsule,  is  smooth,  but  its  outer  surface  presents  ridges  and 
furrows  which  correspond  with  the  convolutions  and  sulci  of  the  island  of  Reil, 
with  which  it  is  in  close  relationship.  The  claustrum  is  regarded  as  a  detached 
portion  of  the  gray  matter  of  the  island  of  Reil,  from  which  it  is  separated  by  a 
layer  of  white  fibres,  the  capsula  extrema  or  band  of  Baillarger.  Its  cells  are  small 
and  spindle-shaped,  and  contain  yellow  pigment ;  they  are  similar  to  those  found 
in  the  deepest  layer  of  the  cortex. 

The  taenia  semicircularis  is  a  narrow,  whitish  band  of  medullary  substance, 
situated  in  the  depression  between  the  caudate  nucleus  and  the  optic  thalamus. 
Anteriorly  its  fibres  are  partly  continued  into  the  anterior  pillar  of  the  fornix  ; 
some,  however,  pass  over  the  anterior  commissure  to  the  gray  matter  between  the 
caudate  nucleus  and  septum  lucidum,  while  others  penetrate  the  caudate  nucleus. 
Posteriorly  it  is  continued  into  the  roof  of  the  middle  or  descending  horn  of  the 
lateral  ventricle,  at  the  extremity  of  which  it  enters  the  nucleus  amygdalce, 
an  oval  mass  of  gray  matter,  situated  in  the  roof  of  the  lower  extremity  of  the 
descending  horn.  Like  the  corpus  striatum,  it  is  formed  by  a  localized  thicken- 
ing of  the  gray  matter  of  the  cortex  cerebri.  Superficial  to  it  is  a  large  vein, 
vena  corporis  striati,  which  receives  numerous  small  veins  from  the  surface  of 
the  corpus  striatum  and  optic  thalamus  ;  it  runs  forward  and  passes  through  the 
foramen  of  Monro  to  join  the  corresponding  vena  Galeni.  On  the  surface  of 
the  vein  of  the  corpus  striatum  is  a  narrow  band  of  white  fibres,  named  the 
lamina  cornea. 

The  remains  of  the  corpus  callosum  should  now  be  removed  in  order  to  expose  the  fornix. 

The  fornix  (Figs.  353,  354)  is  a  longitudinal,  arch-shaped  lamella  of  white 
matter,  situated  beneath  the  corpus  callosum,  with  which  it  is  continuous  behind, 
but  separated  in  front  by  the  septum  lucidum.  It  may  be  described  as  consisting 
of  two  symmetrical  halves,  one  for  either  hemisphere.  The  two  portions  are  not 
united  to  each  other  in  front  and  behind,  but  their  central  parts  are  joined  together 
in  the  middle  line.  The  two  anterior,  separated  parts  are  called  the  anterior 
pillars  {columnm  fornicis)  ;  the  intermediate  united  portions  constitute  the  body 
of  the  fornix  ;  and  the  posterior  parts,  which  are  also  separated  from  each  other, 
are  called  the  posterior  pillars  {crura  fornicis). 

The  body  of  the  fornix  is  triangular,  narrow  in  front,  broad  behind.  Its 
upper  surface  is  connected,  in  the  median  line,  to  the  septum  lucidum  in  front,  and 
the  corpus  callosum  behind ;  laterally  this  surface  forms  part  of  the  floor  of  each 
lateral  ventricle.  Its  under  surface  rests  upon  the  velum  interpositum,  which 
separates  it  from  the  third  ventricle  and  the  inner  portion  of  the  upper  surface 
of  the  optic  thalami.  Its  outer  edge,  on  each  side,  is  free,  and  is  connected  with 
the  choroid  plexuses. 

The  anterior  pillars  arch  downward  toward  the  base  of  the  brain,  separated 

1  The  subthalamic  region  is  the  mass  upon  which  the  optic  thalamus  rests,  and  is  an  extension 
forward  of  the  tegmentum  of  the  mesencephalon  (see  page  674). 


INTERIOR    OF    THE    CEREBRUM.  665 

from  each  other  by  a  narrow  interval.  They  are  composed  of  white  fibres,  which 
descend  through  the  gray  matter  in  the  lateral  wall  of  the  third  ventricle,  and 
are  placed  immediately  behind  the  anterior  commissure.  At  the  base  of  the  brain, 
each  pillar  becomes  twisted  upon  itself  to  form  a  loop,  somewhat  resembling  the 
figure  of  8.  The  lowest  part  of  the  loop  constitutes  the  white  matter  of  the  cor- 
responding corpus  albicans,  from  which  the  fibres  can  apparently  be  traced  upward 
and  backward,  as  the  bundle  of  Vicq  d'Azyr,  into  the  substance  of  the  corre- 
sponding optic  thalamus  (Fig.  353).  It  must  be  stated,  bowever,  that  there  is 
probably  no  direct  continuity  between  this  bundle  and  the  anterior  pillar  of  the 
fornix — the  latter  possibly  ending  in  the  gray  matter  of  the  corpus  albicans.  The 
anterior  crura  of  the  fornix  are  joined  in  their  course  by  the  peduncles  of  the  pineal 
gland  and  the  superficial  fibres  of  the  taenia  semicircularis,  and  receive  fibres  from 
the  septum  lucidum.  Zuckerkandl  describes  an  olfactory  fasciculus,  which  becomes 
detached  from  the  main  portion  of  the  anterior  pillar  of  the  fornix,  and  passes 
downward,  in  front  of  the  anterior  commissure,  to  the  base  of  the  brain,  where  it 
divides  into  two  bundles,  one  joining  the  inner  root  of  tbe  olfactory  tract;  the 
other,  the  peduncle  of  the  corpus  callosum,  and  through  it  reaching  the  hippo- 
campal  convolution. 

Between  the  anterior  pillars  of  the  fornix  and  the  anterior  extremity  of  the 
optic  thalamus,  an  oval  aperture  is  seen  on  each  side ;  this  is  the  foramen  of  Monro 
(Fig.  359).  The  two  openings  descend  toward  the  middle  line,  and  lead  into  the 
upper  part  of  the  third  ventricle.  Through  this  foramen  the  lateral  ventricles 
communicate  with  the  third  ventricle,  and  consequently  with  each  other ;  through 
it  also  the  two  choroid  plexuses  become  joined  with  each  other  across  the  middle 
line.  The  boundaries  of  the  opening  are,  above  and  in  front,  the  anterior  pillars 
of  the  fornix  ;  behind,  the  anterior  extremity  of  the  optic  thalamus. 

The  posterior  pillars  are  the  backward  prolongations  of  the  two  halves  of  the 
body  of  the  fornix.  They  are  flattened  bands,  and,  at  their  commencement,  are 
intimately  connected  by  their  upper  surfaces  with  the  corpus  callosum.  Diverging 
from  one  another,  each  curves  round  the  posterior  extremity  of  the  optic  thalamus, 
and  then  passes  downward  and  forward  into  the  descending  horn  of  the  lateral 
ventricle.  Here  it  lies  along  the  concavity  of  the  hippocampus  major,  on  the  sur- 
face of  which  some  of  its  fibres  are  spread  out,  while  the  remainder  are  continued, 
as  the  corpus  fimbriatum  or  tamia  hippocampi,  into  the  hook  or  uncus  of  the  hip- 
pocampal  convolution.  Upon  examining  the  under  surface  of  the  fornix,  between 
its  diverging  posterior  pillars,  a  triangular  portion  of  the  under  surface  of  the  cor- 
pus callosum  may  be  seen.  On  it  are  a  number  of  curved  or  oblique  lines  passing 
between  the  two  pillars  of  the  fornix.  This  portion  has  been  termed  the  lyra, 
from  the  fancied  resemblance  it  bears  to  a  harp. 

The  anterior  commissure  is  a  bundle  of  white  fibres,  placed  in  front  of  the 
anterior  pillars  of  the  fornix,  and  appears  to  connect  together  the  corpora  striata. 
On  transverse  section  it  is  seen  to  be  oval  in  shape,  its  long  diameter  being  vertical 
in  direction  and  measuring  about  onerfifth  of  an  inch.  Its  fibres  can  be  traced 
backward  and  downward  through  the  globus  pallidus  and  below  the  putamen  on 
each  side  into  the  substance  of  the  temporal  lobe.  It  serves  in  this  way  to  con- 
nect the  two  temporal  lobes,  but  it  also  contains  fibres  from  the  olfactory  tract  of 
the  opposite  side,  the  decussation  of  which  in  the  anterior  commissure  may  serve 
to  explain  the  condition  of  crossed  anosmia,  e.g.,  where  there  is  a  lesion  in  one 
temporal  lobe  with  a  loss  of  smell  in  the  olfactory  area  of  the  opposite  side  of 
the  nose. 

The  septum  lucidum  is  a  thin,  double,  vertically  placed  partition,  which  forms 
the  internal  boundary  of  the  body  and  anterior  horn  of  the  lateral  ventricle.  It 
consists  of  two  distinct  laminse,  separated  in  part  of  their  extent  by  a  narrow  chink 
or  interval,  called  the  fifth  ventricle.  It  is  a  thin,  semitransparent  septum,  at- 
tached, above,  to  the  under  surface  of  the  corpus  callosum  ;  below,  to  the  anterior 
part  of  the  fornix  behind,  and  the  reflected  portion  of  the  corpus  callosum  in  front. 
It  is  triangular  in  form,  broad  in  front  and  narrow  behind  ;  its  inferior  angle  cor- 


866 


THE   NERVOUS  SYSTEM. 


responds  with  the  upper  part  of  the  anterior  commissure.  The  outer  surface  of 
each  lamina  is  directed  toward  the  lateral  ventricle,  and  is  covered  by  the  ependyma 
of  that  cavity,  while  its  mesial  surface  bounds  the  cavity  of  the  fifth  ventricle. 

Fifth  Ventricle. — The  fifth  ventricle  was  originally  a  part  of  the  great  longi- 
tudinal fissure,  which  has  become  shut  off  by  the  union  of  the  hemispheres  in  the 
formation  of  the  corpus  callosum  above  and  the  fornix  below.  Each  half  of  th( 
septum  is  therefore  formed  by  the  median  wall  of  the  hemisphere,  and  consists  of 
an  internal  layer  of  gray  matter,  derived  from  the  gray  matter  of  the  cortex,  an( 
an  external  layer  of  white  substance  continuous  with  the  white  matter  of  the  cere 
bral  hemispheres.  The  fifth  ventricle  differs  from  the  other  ventricles  of  the  brain 
inasmuch  as  it  is  not  developed  from  the  cavity  of  the  cerebral  vesicles,  it  is  no 
lined  by  ciliated  epithelium  but  by  altered  pia  mater,  and  it  does  not  communicate 
with  the  general  ventricular  cavity  ;  further,  the  fluid  it  contains  is  of  the  nature 
of  lymph. 

The  structures  on  the  floor  of  the  descending  horn  of  the  lateral  ventricle  wil 
now  be  described. 

The  hippocampus  major,  or   cornu  Ammonis  (Fig.  356),  is   a  white   eminence 
about  two  inches  in  length,  of  a  curved  elongated  form,  extending  throughout  the 


Eminentia 
collateralis.  J 

Hippocampus  ] 
major.         J 

Gray  matter  ~\ 

of  the         r 

hippocampus.  J 


f  Fascia 
\  dentata. 

Uncinate 

convolution. 

Uncinate 

process. 


Fig.  356.— Transverse  section  of  the  middle  horn  of  the  lateral  ventricle.    (From  a  drawing  by  Mr.  F.  A 
Barton.) 

entire  length  of  the  floor  of  the  descending  horn  of  the  lateral  ventricle.     At  it 
lower    extremity    it    becomes    enlarged,    and    presenting    two    or   three    roundec 
elevations   with    intervening    depressions,    it    resembles    the  paw    of    an    animal 
and  is  called  the  pes  hippocampi.     If  a  transverse  section  is  made  through  the 
hippocampus  major,  it  will  be  seen  that  this  eminence  is  produced  by  the  folding 
of  the  cortex  of  the  brain  to  form  the  dentate  (hippocampal)  sulcus.      To  the  oute 
side  and  parallel  with  the  hippocampus  major  an  elongated  eminence,  the  eminentia 
collateralis,  is  frequently  recognized.     It  corresponds  with  the  middle  part  of  the 
collateral  fissure,  and  its  size  depends  on  the  direction  and  depth  of  this  fissure 
The  main  mass  of  the  hippocampus  major  consists  of  gray  matter,  but  on  its  ven 
tricular  surface  is  a  thin  layer  of  white  matter,  knoAvn  as  the  alveus,  which  is  con 
tinuous  with  the  corpus  fimbriatum  of  the  fornix  and  is  covered  by  the  ependyma 
of  the   ventricle.       Dr.   J.    G.    Macarthy,   of  McGrill   University,   Montreal,    ha 
shown x  that,  if  the  alveus  and  superficial  strata  of  gray  matter  be  reflected  from 
the   surface  of  the  hippocampus   by  an  incision  carried  along  its  convexity,  the 
"core  "  of  the  hippocampus,  as  he  terms  it,  presents  in  many  cases  a  corrugated  or 
crimped  appearance. 

1  Journal  of  Anat.  and  Phys.,  vol.  xxiii.,  1899. 


INTERIOR    OF    THE    CEREBRUM. 


667 


The  corpus  fimbriatum  or  fimbria  {taenia  hippocampi)  has  already  been  men- 
tioned as  a  part  of  the  posterior  pillar  of  the  fornix.  It  consists  of  a  narrow  white 
band,  which  is  placed  immediately  below  the  choroid  plexus,  and  is  attached  by  its 
deep 'surface  to  the  white  matter  (alveus)  of  the  hippocampus  major  as  it  courses 
throuo-h  the  descending  cornu  of  the  lateral  ventricle.  It  can  be  traced  as  far  as 
the  uncus  or  hook  of  the  hippocampal  gyrus.  Its  inner  margin  is  free,  and  rests 
upon  the  dentate  convolution,  from  which  it  is  separated  by  a  slit-like  fissure,  the 
fimbrio-dentate  fissure.  Its  outer  margin  is  attenuated  and  irregular,  and  forms 
the  line  along  which  the  ependyma  is  reflected  over  the  choroid  plexus  as  the 
latter  is  invao-inated  through  the  inferior  part  of  the  transverse  fissure.  When  the 
choroid  plexus  is  pulled  away  it  carries  the  ependyma  with  it,  and  the  descending 
horn  opens  on  to  the  surface  of  the  brain  through  the  transverse  fissure.  If  now 
the  inner  border  of  the  corpus  fimbriatum  be  raised,  a  notched  band  of  gray 
matter,  the  gyrus  dentatus,  will  be  exposed;  this  has  already  been  described  as 
forming  part  of  the  limbic  lobe  (page  653). 


Fornix 

Optic  thalamus 
Corpora  quadrigemina 


Fig.  357.— Diagram  showing  the  mode  of  formation  of  the  velum  interpositum. 

The  choroid  plexus  is  a  highly  vascular,  fringe-like  structure,  which  is  situated 
partly  in  the  body  and  partly  in  the  descending  cornu  of  the  lateral  ventricle.  It 
will  be  desirable  to  consider  these  two  portions  separately,  in  order  to  get  a  just 
conception  of  how  they  are  formed. 

The  portion  in  the  body  of  the  ventricle  is  the  vascular,  fringed  border  of  a 
triangular  fold  of  pia  mater,  the   velum  interpositum,  which  lies  on   the  under 
surface  of  the  fornix  and  forms  the  roof  of  the  third  ventricle.     It  will  be  remem- 
bered that  the  developing  brain  vesicles  are  covered  by  pia  mater.     As  the  pro- 
longation from  the  first  vesicle,  which  is  to  form  the  cerebral  hemispheres,  increases 
in  size,  it  grows  backward  and  downward  and  covers  the  other  vesicles,  with  the 
result  that  the  pia  mater  covering  the  hemisphere  comes  in  contact  with  that  cover- 
ing the  upper  surface  of  the  second  vesicle   (Fig.   357).1     A  portion  of  the  two 
layers  which  are  in  contact  forms  the  velum  interpositum.    Immediately  above  is  the 
body  of  the  fornix,  which  is  formed  by  the  fusion  of  the  cerebral  hemisphere-  ' 
the  middle  line  and  below  is  the  cavity  of  the  second  vesicle  (the  third  ver' 
with  the  optic  thalamus  on  either  side  (Fig.   359).     Just  beyond  the 
border  of  the  fornix,  between  it  and  the  tenia  semicircularis,  is  a  T 

1  In  the  diagram  the  two  layers  are  represented  as  being  separated  from  each 
of  clearness. 


668 


THE   NERVOUS   SYSTEM. 


first  cerebral  vesicle,  which  is  not  developed  into  nervous  matter  but  is  made  up 
only  of  ependyma  covered  by  pia  mater.  The  vessels  of  this  portion  of  the  highly 
vascular  pia  mater  become  dilated  and  prolonged,  and  grow  into  the  ventricle, 
pushing  the  ependyma  before  them,  and  forming  an  irregular  congeries  of  vessels, 
apparently  encroaching  on  the  cavity  of  the  lateral  ventricle,  but  in  reality  being 
external  to  it,  because  they  are  separated  from  it  by  the  lining  membrane  of  the 
cavity,  the  ependyma.  This  vascular  structure  is  the  choroid  plexus  of  the 
body  of  the  ventricle. 

The  part  of  the  choroid  plexus  seen  in  the  descending  cornu  is  formed  in 
exactly  the  same  way,  viz.,  by  an  ingrowth  of  the  vessels  of  the  pia  mater  into  the 
cavity,  pushing  the  ependyma  before  it,  at  a  part  of  the  wall  of  the  horn  where 


Fig.  358.— The  fornix,  velum  interpositum,  and  middle  or  descending  cornu  of  the  lateral  ventricle. 

there  is  a  similar  absence  of  nervous  tissue  and  where  it  consists  simply  of  pia 
mater  and  ependyma  in  close  contact.  This  portion  lies  between  the  corpus  fim- 
briatum  in  the  floor  and  the  taenia  semicircularis  in  the  roof  of  the  descending 
horn.  This  area,  destitute  of  nervous  matter,  is  continuous  with  the  area  in  the 
body  of  the  ventricle,  from  which  the  choroid  plexus  of  this  region  originated,  and 
in  it  the  vessels  of  its  pia  mater  increase,  and.  invaginating  the  ependyma,  appear 
in  the  descending  horn  as  its  choroid  plexus.  In  the  body  of  the  ventricle  the 
choroid  plexus  is  really  the  vascular  fringed  margin  of  the  velum ;  beyond  the  pos- 
terior margin  of  the  velum  the  plexus  of  the  descending  horn  is  continuous  with 
Alie  pia  mater  on  the  surface  of  the  gyrus  hippocampi;  the  two  portions  of  the 
a  are,  howeyer,  directly  continuous  with  each  other.  The  gap  or  cleft 
which  the  invagination  of  the  pia  mater  takes  place  is  called  the  trans- 


THE  INTER-BRAIN.  669 

In  front,  the  choroid  plexus  of  the  lateral  ventricle  is  small  and  tapering,  and 
communicates  with  that  of  the  opposite  side  through  the  foramen  of  Monro.  In 
structure  it  consists  of  minute  and  highly  vascular  villous  processes,  containing 
an  afferent  and  efferent  vessel,  and  covered  by  a  single,  layer  of  flattened  epithelium, 
the  cells  of  which  often  contain  a  yellowish  fat  molecule.  The  anterior  choroidal 
artery  is  derived  from  the  internal  carotid,  and  enters  the  ventricle  at  the  extremity 
of  the  descending  cornu,  and,  after  ramifying  in  the  plexus,  sends  branches  into 
the  adjacent  parts  of  the  brain.  The  posterior  choroidal  arteries,  one  or  two  in 
number,  are  derived  from  the  posterior  cerebral  artery,  and  reach  the  plexus  by 
passing  forward  under  the  splenium  of  the  corpus  callosum.  The  veins  of  the 
choroid  plexus  unite  to  form  a  prominent  vein,  which  courses  from  behind  forward 
to  the  foramen  of  Monro,  and  joins  with  the  vein  of  the  corpus  striatum  to  form 
the  corresponding  vein  of  Galen. 

The  transverse  fissure  is  not  a  real  fissure  or  cleft,  because  it  is  filled  by  the 
invagination  of  the  pia  mater,  forming  the  velum  interpositum  and  the  choroid 
plexuses,  covered  by  the  lining  of  the  ventricular  cavities.  If  this  involution 
of  pia  mater  is  pulled  out,  the  ventricular  lining  will  necessarily  be  torn  away  with 
it,  and  a  cleft-like  space  will  be  left  on  either  side,  extending  from  the  foramen  of 
Monro  to  the  bottom  of  the  descending  horn  of  the  lateral  ventricle.  The  upper 
part  of  this  cleft,  that  is  to  say,  the  part  nearest  the  foramen  of  Monro,  is  between 
the  lateral  border  of  the  body  of  the  fornix  and  the  optic  thalamus  ;  below  this, 
at  the  commencement  of  the  middle  horn,  it  is  between  the  commencing  corpus 
fimbriatum  of  the  fornix  and  the  pulvinar  of  the  optic  thalamus  ;  and  lower  still, 
in  the  descending  horn,  between  the  corpus  fimbriatum  on  the  floor  and  the  taenia 
semicircularis  in  the  roof  of  the  cornu.  Posteriorly  the  transverse  fissure  opens 
between  the  splenium  of  the  corpus  callosum  above,  and  the  corpora  quadrigemina 
and  pineal  gland  below.  Through  the  fissure  the  vense  Galeni  emerge  to  join  the 
straight  sinus. 

The  velum  interpositum  or  tela  choroidea  superior  (Fig.  358)  is  a  vascular  mem- 
brane, and  is  a  prolongation  of  the  pia  mater  into  the  interior  of  the  brain  through 
the  middle  part  of  the  transverse  fissure.  It  is  of  a  triangular  form,  and  separates 
the  under  surface  of  the  body  and  posterior  pillars  of  the  fornix  from  the  cavity  of 
the  third  venti'icle.  Laterally  it  covers  the  inner  part  of  the  upper  surface  of  the 
optic  thalamus.  Its  posterior  border  or  base  lies  beneath  the  splenium  of  the  corpus 
callosum  above,  and  the  optic  thalamus,  the  corpora  quadrigemina,  and  pineal  body 
below.  Its  anterior  extremity,  or  apex,  ends  just  behind  the  anterior  pillars  of  the 
fornix,  where  it  is  connected  with  the  anterior  extremities  of  the  choroid  plexuses, 
which  are  here  united  through  the  foramen  of  Monro,  and  are  then  prolonged  back- 
ward on  the  under  surface  of  the  velum  as  the  choroid  plexuses  of  the  third  ventricle  ; 
in  front,  these  plexuses  of  the  third  ventricle  lie  close  to  the  middle  line,  but  diverge 
from  each  other  behind.  The  lateral  margins  of  the  velum  interpositum  form  the 
choroid  plexuses  of  the  lateral  ventricles.  It  is  supplied  by  the  anterior  and  pos- 
terior choroidal  arteries,  already  described.  The  veins  of  the  velum  interpositum, 
the  vence  Gfaleni,  two  in  number,  run  between  its  layers,  each  being  formed  by  the 
union  of  the  vein  of  the  corpus  striatum  with  the  choroid  vein.  The  venre  Galeni 
unite  posteriorly  into  a  single  trunk,  the  vena  magna  Galeni,  which  terminates  in 
the  straight  sinus  (Fig.  326). 

II.  The  Inter-brain. 

The  inter-brain  (thalamencephalon)  is  the  region  of  the  third  ventricle,  and 
comprises  the  parts  developed  from  the  second  cerebral  vesicle,  together  with  that 
portion  of  the  first  vesicle  which  is  not  concerned  in  the  formation  of  the  cerebral 
hemispheres. 

The  inter-brain  is  connected  above  and  in  front  with  the  cerebral  hemispheres ; 
behind,  with  the  mid-brain  or  mesencephalon.  On  its  upper  surface  it  is  entirely 
concealed  from  view,  as  it  is  covered  by  those  portions  of  the  internal  surfaces  of 


670 


THE    NERVOUS  SYSTEM. 


the  cerebral  hemispheres  which  have  fused  together  to  form  the  corpus  callosum 
and  the  fornix,  and  is  separated  from  the  latter  by  the  two  layers  of  pia  mater 
which  form  the  velum  interpositum.  Inferiorly  it  reaches  the  base  of  the  brain, 
forming  the  structures  contained  in  the  interpeduncular  space. 

The  third  ventricle  is  the  cavity  of  the  inter-brain  (Fig.  359).  It  is  a  narrow 
median  crevice  between  the  two  optic  thalami,  which  constitute  the  side  walls  of  the 
inter-brain.  Its  roof  is  formed  by  the  velum  interpositum,  from  which  are  sus- 
pended the  choroid  plexuses  of  the  third  ventricle.  Its  floor,  somewhat  oblique  in 
its  direction,  is  formed,  from  before  backward,  by  the  tuber  cinereum,  with  its 
infundibulum  and  pituitary  body  ;  the  corpora  albicantia  ;  the  posterior  perforated 
space;  and  the  tegmenta  of  the  crura  cerebri.  Its  sides  are  formed  by  the  optic 
thalami,  and  are  limited  above  by  a  delicate  band  of  white  fibres,  the  stria  pinealis, 


Fig.  359.— The  third  and  fourth  ventricles.    An  arrow  has  been  placed  in  the  position  of  the  foramen  of  Monro. 

which  runs  along  the  junction  of  the  mesial  and  upper  surfaces  of  the  optic  thala- 
mus to  join  the  anterior  pillars  of  the  fornix.  Its  sides  are  somewhat  convex,  so 
that  in  the  middle  of  the  ventricle  the  two  lateral  walls  are  almost  in  contact,  and 
are  here  united  across  the  middle  line  by  a  band  of  gray  nervous  matter,  the  middle, 
gray,  or  soft  commissure.  The  ventricle  is  bounded  in  front  by  the  anterior  pillars 
of  the  fornix  and  the  lamina  cinerea  ;  behind  by  the  pineal  gland,  the  posterior 
commissure,  and  the  upper  end  of  the  iter  a  tertio  ad  quartum  ventriculum.  The 
cavity  is  much  deeper  in  front  than  behind,  and  presents  a  recess  at  its  anterior 
part,  which  lies  over  the  optic  commissure  and  is  therefore  termed  the  optic  recess. 
Behind  and  below  this  is  the  conical  depression  of  the  infundibulum,  passing  down- 
ward and  forward  to  the  pituitary  body.     At  its  posterior  extremity  the  cavity 


THE   INTER-BRAIN.  671 

forms  another  and  smaller  recess,  which  extends  into  the  stalk  of  the  pineal  gland, 
and  is  termed  the  'pineal  recess.  At  its  upper  and  anterior  part,  immediately  be- 
hind the  anterior  pillars  of  the  fornix  and  in  front  of  the  optic  thalamus,  is  an 
opening,  the  foramen  of  Monro,  by  which  this  ventricle  communicates  with  the 
lateral  ventricle  on  either  side.  The  roof  of  the  cavity  is  limited  in  front  and 
behind  by  transverse  bands  of  white  matter,  known  respectively  as  the  anterior 
and  posterior  commissures.  The  former  has  already  been  described  in  connection 
with  the  corpus  striatum  (page  665). 

The  middle  or  soft  commissure  consists  almost  entirely  of  gray  matter.  It 
connects  the  two  optic  thalami,  and  is  continuous  with  the  gray  matter  lining  the 
anterior  part  of  the  third  ventricle.  It  is  frequently  broken  in  examining  the 
brain,  and  might  then  be  supposed  to  be  wanting ;  it  is  sometimes  double. 

The  posterior  commissure  is  a  rounded  band  of  white  fibres,  which  stretches 
across  from  one  optic  thalamus  to  the  other,  overlying  the  upper  end  of  the 
aqueduct  of  Sylvius,  or  iter  a  tertio  ad  qUartum  ventriculum.  It  is  usually 
described  as  belonging  to  the  inter-brain,  but  would  appear  to  belong  in  part  to 
the  mid-brain,  since  some  of  its  fibres  are  commissural  and  connect  the  anterior 
corpora  quadrigemina  to  the  fillet  of  the  opposite  side  (see  below).  In  addition 
there  are  other  decussating  fibres,  which  come  from  the  tegmentum  of  the  crus 
cerebri  on  one  side  and  decussate  with  those  of  the  opposite  side  in  the  posterior 
commissure,  and  passing  through  the  optic  thalamus  reach  the  cerebral  hemispheres. 
Fibres  have  also  been  described  as  taking  their  origin  in  the  pineal  body  and 
ganglion  habenulse,  and  passing  across  to  the  posterior  longitudinal  bundle  and 
oculomotor  nucleus  of  the  opposite  side ;  these  fibres  occupy  the  ventral  part  of 
the  commissure,  and  receive  their  myelin  sheath  before  those  in  its  dorsal  part. 
But  to  a  certain  extent  the  posterior  commissure  belongs  to  the  inter-brain,  since 
it  contains  fibres  which  serve  as  commissural  fibres  between  the  two  optic  thalami. 

The  optic  thalami  are  two  large  oblong  masses,  situated  on  either  side  of  the 
third  ventricle,  and  lying  between  the  diverging  portions  of  the  corpora  striata. 
They  are  composed  mainly  of  gray  matter,  but  their  free  surfaces  are  coated  with 
a  thin  layer  of  white  nervous  tissue.  They  present  outer  and  under  surfaces, 
which  are  not  free,  but  are  blended  with  contiguous  parts  of  the  brain,  and  upper, 
inner,  and  posterior  surfaces,  which  are  free.  The  anterior  extremity  is  narrow, 
and  forms  the  posterior  boundary  of  the  foramen  of  Monro.  The  outer  surface 
is  in  contact  with  the  posterior  limb  of  the  internal  capsule,  which  separates  it 
from  the  lenticular  nucleus.  The  inferior  surface  rests  upon  and  is  continuous 
with  the  tegmentum  of  the  crus  cerebri.  Its  upper  surface  is  free,  and  is  separated 
from  the  caudate  nucleus  by  a  furrow  which  lodges  the  lamina  cornea,  the  vein  of 
the  corpus  striatum,  and  the  taenia  semicircularis.  It  is  divided  into  an  outer  and 
an  inner  part  by  a  groove  which  runs  from  behind,  forward  and  inward.  The 
outer  part  forms  a  portion  of  the  floor  of  the  lateral  ventricle,  and  is  covered  by 
the  ependyma  of  that  cavity ;  it  terminates  in  front  in  a  tubercle,  the  anterior 
tubercle  of  the  optic  thalamus.  The  inner  part  is  covered  by  the  velum  inter- 
positum,  which  separates  it  from  the  fornix,  and  is  excluded  from  both  the  lateral 
and  third  ventricles  by  the  reflection  of  the  lining  of  these  cavities,  and  is  there- 
fore destitute  of  an  ependymal  covering. 

The  internal  surface  forms  the  lateral  wall  of  the  third  ventricle,  and  running 
along  its  upper  border  is  the  peduncle  of  the  pineal  gland,  from  which  the 
ependyma  of  the  third  ventricle  is  reflected  on  to  the  under  surface  of  the  velum 
interpositum.  The  posterior  surface  projects  beyond  the  level  of  the  corpora 
quadrigemina,  and  forms  a  well-marked  rounded  prominence,  the  posterior  tubercle 
or  pulvinar.  The  pulvinar  is  continued  externally  into  a  second  eminence,  the 
external  geniculate  body,  which  is  placed  above  and  to  the  outer  side  of  the  internal 
geniculate  body,  and  from  which  it  is  separated  by  the  superior  brachium,  one  of 
the  roots  of  the  optic  tract. 

The  optic  thalamus  is  formed  chiefly  of  gray  matter,  which  is  arranged  in  two 
masses,  the   outer  and   inner  nuclei,  and  these  are  partially  separated  from  each 


672  THE  NERVOUS  SYSTEM. 

other  by  an  S-shaped  vertical  lamina  of  white  matter,  called  the  internal  medullary 
lamina.  This  is  named  internal  in  contradistinction  to  a  second  or  external  medullary 
lamina  of  white  matter,  which  coats  the  outer  surface  of  the  optic  thalamus  and 
connects  it  with  the  internal  capsule.  The  inner  nucleus  is  connected  with  the 
corresponding  nucleus  of  the  opposite  side  through  the  middle  commissure  of  the 
third  ventricle.  The  external  nucleus,  which  is  the  larger  of  the  two,  extends 
backward  into  the  pulvinar.  The  gray  matter  of  the  optic  thalamus  contains 
large  multipolar  and  fusiform  cells,  and  is  traversed  in  every  direction  by  numerous 
nerve-fibres. 

The  optic  thalamus  is  intimately  connected  with  the  following  structures : 

1.  It  constitutes  a  relay  for  the  greater  number  of  the  fibres  of  the  tegmentum 
of  the  crus  cerebri. 

2.  The  pulvinar  receives  many  of  the  fibres  of  the  optic  tract. 

3.  It  is  connected  with  the  cerebral  cortex,  (a)  through  the  anterior  stalk  of 
the  optic  thalamus,  which  passes  from  the  anterior  extremity  of  the  thalamus 
through  the  anterior  limb  of  the  internal  capsule  to  the  frontal  lobe ;  (b)  through 
the  posterior  stalk  or  optic  radiations,  consisting  of  fibres  which  take  their  origin 
in  the  pulvinar  and  are  transmitted  through  the  extreme  posterior  part  of  the 
internal  capsule  to  the  occipital  lobe ;  (c)  through  the  inferior  stalk  or  ansa 
peduncularis,  made  up  of  fibres  which  leave  the  inferior  surface  of  the  thalamus 
and  end  in  the  temporal  lobe ;  (d)  through  fibres  which  pass  from  the  external 
surface  of  the  thalamus  to  the  parietal  lobe. 

4.  With  the  corpus  striatum.  The  fibres  destined  for  the  caudate  nucleus  leave 
the  external  surface  ;  those  for  the  lenticular  nucleus,  the  inferior  aspect  of  the 
thalamus. 

5.  With  the  corpus  albicans  through  the  bundle  of  Vicq  d'Azyr. 

In  connection  with  the  optic  thalamus  two  small  nuclei  of  gray  matter  require 
consideration  :  (1)  One  of  these,  the  anterior  nucleus,  is  situated  in  the  anterior 
tubercle  of  the  optic  thalamus.  This  nucleus  receives  the  fibres  (bundle  of  Vicq 
d'Azyr)  which  take  origin  in  the  cells  of  the  corpus  albicans  (see  page  657). 
Though  this  bundle  of  fibres  appears  to  be  the  direct  continuation  of  the  anterior 
pillar  of  the  fornix  through  the  corpus  albicans  to  the  optic  thalamus,  it  is  be- 
lieved to  have  no  histological  continuity  with  it.  The  fibres  of  the  anterior 
pillar  of  the  fornix  form  synapses  in  the  corpus  albicans  around  the  cells  which 
give  origin  to  the  bundle  of  Vicq  d'Azyr,  and  thus  an  indirect  communication 
only  is  established  between  the  fornix  and  the  optic  thalamus.  (2)  The  second 
gray  nucleus  lies  in  a  depressed  space,  the  trigonum  habenulce,  situated  between  the 
pulvinar  and  the  posterior  part  of  the  peduncle  of  the  pineal  gland.  It  is  termed 
the  ganglion  of  the  habenula.  It  receives  fibres  from  the  peduncles  of  the  pineal 
body,  and  sends  off  others  which  pass  to  a  small  collection  of  gray  matter, 
situated  between  the  diverging  crura  cerebri,  and  named  the  ganglion  inter- 
pedunculare. 

The  pineal  gland  {epiphysis  cerebri),  so  named  from  its  peculiar  shape  (pinus, 
a  fir-cone),  is  a  small  reddish  gray  body,  conical  in  shape  (hence  its  synonym, 
conariuni),  placed  immediately  above  and  behind  the  posterior  commissure  and 
between  the  anterior  corpora  quadrigemina,  on  which  it  rests.  It  is  covered  by  the 
velum  interpositum,  which  intervenes  between  it  and  the  splenium  of  the  corpus 
callosum.  It  is  an  upgrowth  from  the  second  cerebral  vesicle  (hence  the  name 
epiphysis),  and  is  at  first  hollow,  but  soon  becomes  solid  and  loses  its  connection 
with  the  ventricular  cavity.  It  is  retained  in  its  position  by  a  duplicative  of  pia 
mater,  derived  from  the  under  surface  of  the  velum  interpositum,  which  almost 
completely  invests  it.  The  pineal  gland  is  about  four  lines  in  length  and  from 
two  to  three  in  width  at  its  base,  and  is  said  to  be  larger  in  the  child  than  in  the 
adult,  and  in  the  female  than  in  the  male.  It  is  attached  on  either  side  by  a 
flattened  stalk  of  white  matter,  the  pedunculus  conarii.  This  stalk  consists  of  two 
laminae,  upper  and  lower,  separated  by  a  little  recess,  the  pineal  recess  (see  page 
671).      The  lower  lamina  is  prolonged  into  the  posterior  commissure.     The  upper 


THE  MID-BRAIN.  673 

divides  into  two  strands,  the  peduncles  of  the  pineal  gland,  or  stria?  pinealis  ;  these 
extend  on  either  side  along  the  optic  thalamus  at  the  junction  of  its  mesial  and 
upper  surfaces  (see  page  671)  to  the  anterior  pillars  of  the  fornix,  with  which  they 
blend.  The  two  stalks  join  together  at  their  posterior  extremity,  in  front  of  the 
pineal  gland,  forming  a  sort  of  festoon,  and  the  base  of  the  gland  is  connected  to 
their  posterior  margin  at  the  point  of  junction. 

Structure. — The  pineal  gland  consists  of  a  number  of  follicles,  lined  by  epithe- 
lium, and  connected  together  by  ingrowths  of  connective  tissue.  The  follicles  con- 
tain a  transparent  viscid  fluid  and  a  quantity  of  sabulous  matter  named  acervulus 
cerebri,  composed  of  phosphate  and  carbonate  of  lime,  phosphate  of  magnesia  and 
ammonia,  with  a  little  animal  matter.  These  concretions  are  almost  constant  in 
their  existence,  and  are  present  at  all  periods  of  life.  They  are  found  upon  the 
surface  of  the  pineal  body  and  occasionally  upon  its  peduncles. 

Morphologically  the  pineal  gland  is  regarded  as  the  homologue  of  the  structure 
termed  the  pineal  eye  of  the  lizards.  In  these  reptiles  the  epiphysis  cerebri  is 
attached  by  an  elongated  stalk  and  projects  through  the  parietal  foramen.  Its 
extremity  lies  immediately  under  the  epidermis,  and  on  microscopic  examination 
presents,  in  a  rudimentary  fashion,  structures  similar  to  those  found  in  the  eyeball. 

III.  The  Mid-Brain. 

The  mid-brain,  or  mesencephalon,  is  the  constricted  portion  of  the  brain  which 
connects  the  pons  Varolii  with  the  inter-brain  and  hemispheres,  and  hence  it  is 
frequently  called  the  isthmus  cerebri.  It  is  developed  from  the  third  cerebral 
vesicle,  the  cavity  of  which  becomes  the  aqueduct  of  Sylvius.  It  comprises  the 
crura  cerebri,  the  corpora  quadrigemina,  the  geniculate  bodies,  and  the  Sylvian 
aqueduct.  Its  direction  is  from  before  backward  and  downward.  In  front  and 
above  it  is  continuous  with  the  inter-brain  ;  below,  with  the  pons.  Its  two  surfaces 
are  ventral  and  dorsal.  They  are  free,  but  concealed :  the  ventral  surface  by  the 
apices  of  the  temporal  lobes  which  overlap  it ;  the  dorsal,  by  the  overhanging  cere- 
bral hemispheres.  The  ventral  surface  when  exposed  by  drawing  aside  the 
temporal  lobes,  is  seen  to  consist  of  two  cylindrical  bundles  of  white  matter  which 
emerge  from  the  pons  and  diverge   as  they 

pass  forward  and  outward  to  enter  the  inner  Aqueduct^T™1™' 

and  under  part  of  either  hemisphere.  They 
are  the  crura  cerebri  or  cerebral  peduncles, 
and  between  them  is  a  triangular  area, 
already  described  as  part  of  the  interpe- 
duncular space  (see  page  6bo) ;  near  the  point 
of  divergence  of  the  crura  the  roots  of  the 
third  nerve  are  seen  to  emerge  in  several 
bundles  from  a  groove,  the  sulcus  oculo- 
motor his.     The  dorsal  surface  is   not  visible 

..-,  -iii  ,■  c      i  it  Interpeduncular  snace. 

until  a  considerable  portion  ot    the  cerebral  .*      ,  ,       .„ ,_    . 

■.         .      ,  i      ,i  i    •  Fig.  360.— Transverse  section  of  the  mid-brain. 

hemispheres  and  other  overlying  structures 

have  been  removed.  It  then  presents  four  rounded  eminences  placed  in  pairs,  two 
in  front  and  two  behind,  and  separated  from  one  another  by  a  crucial  depression. 
These  are  termed  the  corpora  or  tubercula  quadrigemina.  The  ventral  and  dorsal 
surfaces  meet  on  the  side  of  the  mid-brain,  and  are  separated  from  each  other  bv  a 
furrow,  the  lateral  groove,  which  runs  from  below  upward  and  forward  (Fig.  359). 
If  across  section  be  made  through  the  mesencephalon  (Fig.  360)  it  will  be  seen 
that  each  lateral  half  is  divided  into  two  unequal  portions  by  a  lamina  of  deeply 
pigmented  gray  matter,  named  the  substantia  nigra  :  of  these  the  postero-superior 
portion  is  named  the  tegmentum,  and  the  anteroinferior  the  crusta  or  pes.  The 
substantia,  nigra  is  curved  on  section  with  its  concavity  upward,  and  extends  from 
the  lateral  groove  externally  to  the  oculomotor  sulcus  internally.  The  two  crustse 
are  quite  separate  from  one  another,  but  the  two  halves  of  the  tegmentum  are  joined 

43 


674  THE  NERVOUS  SYSTEM. 

to  each  other  in  the  mesial  plane  by  a  prolongation  forward  of  the  raphe  or  median 
septum  of  the  pons.  Laterally  the  tegmenta  are  free,  but  dorsally  they  blend 
with  the  corpora  quadrigemina. 

Crustse. — The  crustae,  which  are  two  in  number,  separated  by  the  interpeduncu- 
lar space,  are  semilunar  in  section,  and  consist  of  longitudinal  bundles  of  white 
fibres,  which  may  be  divided  into  three  principal  sets :  (1)  Those  occupying  the 
outer  third  of  the  crusta  are  believed  to  arise  from  the  cells  of  the  nuclei  pontis, 
gray  nuclei  in  the  pons  Varolii,  and  pass  through  the  posterior  part  of  the 
internal  capsule  to  the  cerebral  cortex  of  the  occipital  and  temporal  lobes.  (2)  The 
fibres  occupying  the  middle  third  of  the  crusta  take  their  origin  in  the  cells  of 
the  Rolandic  area  of  the  cortex,  and,  converging  to  the  internal  capsule,  pass  down 
through  its  genu  and  through  the  anterior  two-thirds  of  its  posterior  limb  to  the 
crusta,  from  which  they  are  prolonged  through  the  pons  into  the  anterior  pyramid 
of  the  medulla  oblongata.  (3)  The  origin,  from  below,  of  the  fibres  occupying  the 
inner  third  of  the  crusta  is  uncertain,  though  by  some  they  are  believed  to  arise  in 
the  crusta  itself,  from  the  cells  of  the  locus  niger.  Above,  they  pass  through  the 
anterior  part  of  the  internal  capsule  to  the  cerebral  cortex  of  the  frontal  lobe.  In 
addition  to  these  three  sets  of  longitudinal  fibres,  a  well-marked  bundle,  defined 
by  having  an  oblique  direction,  must  be  noted.  This  is  named  the  mesial  fillet. 
It  arises  from  the  fillet  (see  below),  and  at  the  lower  part  of  the  crusta  is  situated 
at  its  mesial  border  ;  as  it  ascends  it  courses  obliquely  outward  to  reach  the  lateral 
border  of  the  middle  group  of  fibres  (pyramidal  tract)  and  becomes  lost  in  the 
subthalamic  region. 

The  tegmentum,  or  that  portion  of  the  mid-brain  which  is  superior  to  the  sub- 
stantia nigra,  consists  of  longitudinally  directed  strands  of  white  fibres,  which  are 
separated  from  each  other  by  transversely  arched  fibres.  There  is  also  a  consider- 
able quantity  of  gray  matter.  It  thus  forms  a  peculiar  reticulated  structure,  which 
has  been  named  formatio  reticularis,  and  is  similar  to  a  like  structure  in  the  pons 
and  medulla,  with  which  it  is  continuous.  In  some  parts  of  the  tegmentum  the 
longitudinal  fibres  are  arranged  in  fairly  well-defined  tracts,  which  are  as  follows : 
1.  The  posterior  longitudinal  bundle,  which  is  composed  of  large  nerve-fibres,  and 
lies  on  either  side  of  the  median  line,  just  beloAv  the  aqueduct.  These  fibres  are 
continued  upward  from  the  anterior  column  of  the  cord,  in  which  they  probably 
form  short  longitudinal  commissures  between  its  different  segments.  They  pass 
through  the  pyramid  of  the  medulla,  then  form  the  posterior  longitudinal  bundle 
of  the  pons,  and  enter  the  tegmentum  ;  here  they  give  off  fibres  to  the  nuclei  of  the 
third  and  fourth  cranial  nerves.  At  the  front  of  the  mid-brain  some  of  the  fibres 
of  the  posterior  longitudinal  bundle  enter  the  posterior  commissure  and  there 
decussate  (see  page  671)  ;  others  pass  upward  to  the  subthalamic  region.  2.  Fibres 
from  the  superior  cerebellar  peduncle.  These  lie  on  either  side  of  the  middle  line 
of  the  tegmentum,  and,  as  they  pass  through  it,  decussate  with  each  other,  so  that 
the  fibres  of  one  half  of  the  cerebellum  pass  to  the  opposite  half  of  the  cerebrum. 
Having  crossed  to  the  opposite  side,  the  bundle  of  fibres  passes  upward  and  for- 
ward, enclosing  a  mass  of  gray  matter,  the  red  nucleus,  or  nucleus  of  the  tegmen- 
tum, from  which  it  probably  receives  fibres,  and  eventually  passes  into  the  optic 
thalamus.  3.  The  fillet.  This  takes  its  chief  origin  in  the  medulla,  and  passes 
through  the  pons  to  the  mid-brain,  as  will  be  described  in  the  sequel.  It  forms  a 
considerable  bundle  of  longitudinal  fibres  in  the  ventral  part  of  the  tegmentum,  and 
divides  into  three  parts — the  upper,  mesial,  and  lower  fillet.  The  upper  fillet 
passes  to  the  upper  pair  of  corpora  quadrigemina  and  the  occipital  region  of  the 
cerebral  hemisphere.  The  mesial  fillet  has  already  been  alluded  to  in  the  descrip- 
tion of  the  crusta.  After  separating  from  the  rest  of  the  fillet  its  fibres  assume  an 
oblique  direction,  and  are  eventually  lost  in  the  subthalamic  region.  The  loiver 
fillet,  also  called  lemniscus,  is  situated  in  the  ventral  part  of  the  tegmentum, 
through  which  it  passes  obliquely  and  emerges  at  its  side,  and  after  crossing  the 
superior  peduncle  of  the  cerebellum,  passes  to  the  inferior  quadrigeminal  bodies. 
It  is  reinforced  by  some  fibres  from  the  superior  medullary  velum.     4.  Fibres  from 


THE   MID-BBAIN.  675 

the  olivary  nucleus,  which  pass  in  a  longitudinal  direction  through  the  reticular 
formation  of  the  tegmentum  and  are  continued  onward  into  the  internal  capsule. 

The  red  nucleus  or  nucleus  of  the  tegmentum,  is  a  tract  of  gray  matter  situated 
on  either  side  of  the  middle  line,  and  is  composed  of  numerous  large  cells,  which 
are  deeply  pigmented.  It  is  pierced  by  the  fibres  of  the  third  nerve,  and  pro- 
longed above  into  the  posterior  part  of  the  subthalamic  region. 

The  Substantia  Nigra. — This,  as  already  stated,  is  a  layer  of  deeply  pigmented 
gray  matter,  which  separates  the  crusta  from  the  tegmentum.  It  is  thicker  inter- 
nally than  externally,  where  it  is  partially  divided  up  by  the  mesial  fillet  passing 
from  the  tegmentum  to  the  crusta.  It  is  traversed  at  its  inner  part  by  some 
of  the  fibres  of  origin  of  the  third  cranial  nerve.  The  cells  are  small  and  mul- 
tipolar, and  are  characterized  by  containing  a  large  amount  of  dark  pigment 
granules. 

The  corpora  or  tubercula  quadrigemina  are  four  rounded  eminences  placed  in 
pairs,  two  in  front  and  two  behind,  and  separated  from  one  another  by  a  crucial 
depression.  They  are  situated  on  the  dorsal  surface  of  the  mid-brain,  immediately 
behind  the  third  ventricle  and  posterior  commissure,  and  beneath  the  splenium  of 
the  corpus  callosum.  The  anterior  or  upper  pair,  sometimes  called  the  nates,  are 
the  larger.  They  are  oval,  their  long  diameter  being  directed  forward  and  out- 
ward, and  are  of  a  gray  color.  The  posterior  or  lower  pair,  called  the  testes,  are 
hemispherical  in  form,  and  lighter  in  color  than  the  preceding.  From  the  outer 
side  of  each  of  these  eminences,  a  prominent  white  band,  termed  bracMum,  is  con- 
tinued forward  and  outward.  Those  from  the  nates  (brachia  anteriora)  pass 
obliquely  outward  between  the  pulvinar  and  the  inner  geniculate  bodies  into  the 
external  geniculate  bodies.  Those  from  the  testes  [brachia  posteriora)  lose  them- 
selves beneath  an  oval  prominence  on  either  side  of  the  corpora  quadrigemina, 
called  the  internal  geniculate  body.  The  corpora  quadrigemina  are  larger  in  the 
lower  animals,  than  in  man.  In  fishes,  reptiles,  and  birds  they  are  hollow,  and 
only  two  in  number  [corpora  bigeminal)  ;  they  represent  the  anterior  quadrigeminals 
of  mammals.  In  these  lower  animals  the  corpora  bigemina  are  frequently  termed 
the  optic  lobes,  because  of  their  connection  with  the  optic  tracts.  In  the  mammalia 
they  are  four  in  number,  and  solid.  In  the  human  foetus  all  four  bodies  are 
differentiated  by  the  fifth  month,  and  form  at  this  time  a  considerable  proportion 
of  the  brain. 

The  corpora  quadrigemina  are  composed  of  white  matter  externally,  and  gray 
matter  within.  The  posterior  pair  consist  almost  entirely  of  gray  matter,  covered 
over  by  a  very  thin  stratum  of  white  substance.  Beneath  the  gray  matter  is  a 
thin  layer  of  white  fibres,  forming  a  part  of  the  lower  fillet.  This  separates 
the  gray  matter  of  the  posterior  corpora  quadrigemina  from  the  central  gray 
matter  of  the  aqueduct.  The  anterior  pair  are  covered  superficially  by  a  thin 
stratum  of  white  matter,  the  stratum  zonale,  the  fibres  of  which  are  fine  and 
arranged  transversely.  Beneath  this  is  the  stratum  cinereum,  a  layer  of  gray 
matter  which  resembles  a  cup,  semilunar  in  shape,  thicker  in  the  centre,  and 
thinning  off  toward  the  margins,  and  consisting  of  numerous  multipolar  cells,  for 
the  most  part  of  small  size,  embedded  in  a  fine  network  of  nerve-fibres.  Below 
this  again  is  the  stratum  opticum,  or  upper  gray-white  layer,  characterized  by  the 
large  amount  of  fine  nerve-fibres  which  intersect  the  gray  matter.  These  fibres 
vary  in  size  in  different  parts  of  the  layer,  but  have  for  the  most  part  a  longitudinal 
direction.  The  nerve-cells  between  the  fibres  are  larger,  and  send  their  axis- 
cylinder  processes  into  the  next  stratum.  Finally  there  is  the  stratum  lemnisri, 
or  deep  gray-white  layer,  which  separates  the  rest  of  the  body  from  the  gray  matter 
around  the  aqueduct.  It  consists  of  fibres  partly  derived  from  the  upper  fillet 
and  partly  from  the  cells  of  the  preceding  layer.  Interspersed  among  these  fibres 
are  nerve-cells  of  large  size. 

In  close  relationship  with  the  corpora  quadrigemina  are  the  superior  peduncles 
of  the  cerebellum.  They  emerge  from  the  upper  and  mesial  part  of  the  hemi- 
spheres of  the  cerebellum,  and  run  upward  and  forward  to  the  corpora  quadri- 


676  THE   NERVOUS  SYSTEM. 

gemma,  with  which  they  come  in  close  contact.  They  then  pass  under  these 
bodies,  through  the  tegmentum  {vide  supra),  and  enter  the  optic  thalamus. 

The  corpora  geniculata  are  two  small,  oblong  masses  on  each  side,  situated 
behind  and  beneath  the  posterior  end  of  the  optic  thalamus,  and  named,  from  their 
position,  corpus  geniculatum  externum  and  internum.  These  two  bodies  are  sepa- 
rated from  each  other  by  the  brachium  anterius  of  the  anterior  quadrigeminal  body. 
It  is  convenient  and  customary  to  describe  these  two  bodies  together,  but  the 
student  should  bear  in  mind  that  the  corpus  geniculatum  externum  belongs  in 
reality  to  the  optic  thalamus ;  the  corpus  geniculatum  internum  alone  being  a  part 
of  the  mid-brain.  The  external  geniculate  body  is  of  a  dark  color,  and  presents  a 
laminated  arrangement,  consisting  of  alternate  layers  of  gray  and  white  matter. 
Its  cells  are  large,  multipolar,  and  pigmented  ;  their  processes  are  intimately  related 
with  the  visual  area  in  the  cerebral  cortex  of  the  occipital  region.  It  is  believed 
that  the  intercellular  gray  matter  of  these  bodies  is  composed,  to  a  considerable 
extent,  of  the  terminations  of  the  optic  nerve,  which  form  synapses  around  the  cells. 
The  internal  geniculate  body  is  smaller  in  size,  lighter  in  color,  and  does  not  pre- 
sent a  laminated  arrangement.  It  receives  the  posterior  brachium  from  the  inferior 
quadrigeminal  body,  and  some  of  the  fibres  of  the  optic  tract  appear  to  enter  it. 
The  internal  geniculate  bodies  are  connected  with  each  other  through  the  optic 
commissure  by  a  band  of  fibres  named  Gruddens  commissure  (see  page  721).  The 
anterior  quadrigeminal  body,  the  pulvinar,  and  the  external  geniculate  body  are 
intimately  concerned  with  vision.  They  constitute  the  lower  cerebral  centre  for 
the  optic  nerve-fibres  which  end  in  them.  Extirpation  of  the  eyes  in  newly  born 
animals  entails  an  arrest  of  their  development,  but  has  no  effect  on  the  poste- 
rior quadrigeminal  body  or  the  internal  geniculate  body.  These  latter  also  are 
well  developed  in  the  mole,  where  the  superior  quadrigeminal  body  is  rudi- 
mentary. 

The  Aqueduct  of  Sylvius,  or  Iter  a  Tertio  ad  Quartum  Ventriculum. — This  is  a 
narrow  canal,  about  half  an  inch  in  length,  situated  between  the  corpora  quadri- 
gemina  and  the  tegmentum,  and  connecting  the  third  with  the  fourth  ventricle. 
Its  shape  on  transverse  section  varies,  being  T-shaped  below,  triangular  above,  and 
oval  about  the  middle  of  its  course.  It  is  lined  by  columnar  ciliated  epithelium, 
and  surrounded  by  a  layer  of  gray  matter,  called  the  central  gray  matter  of  the 
aqueduct,  which  is  continuous  with  the  gray  matter  of  the  third  and  fourth  ven- 
tricles. This  gray  matter  is  separated  above  from  that  of  the  corpora  quadri- 
gemina  by  the  stratum  lemnisci ;  below  it,  is  the  posterior  longitudinal  bundle  and 
the  fonnatio  reticularis  of  the  tegmentum.  The  central  gray  matter  is  more 
abundant  below  the  canal  than  above  it.  Here  are  certain  defined  group  of 
cells,  which  are  connected  with  the  roots  of  the  third,  fourth,  and  fifth  cranial 
nerves. 

Subthalamic  Region. — One  other  structure,  to  which  allusion  has  already  been 
made,  requires  mention  in  this  connection ;  it  is  the  subthalamic  region.  It  is  a 
prolongation  forward  of  the  tegmentum  of  the  crus  cerebri,  which  becomes  con- 
tinuous with  the  lower  surface  of  the  optic  thalamus.  Toward  the  anterior  part 
of  the  crus  cerebri  the  tegmentum  becomes  thinned  out,  and  is  blended  with  the 
superjacent  portion  of  the  optic  thalamus.  To  this  region,  the  name  subthalamic 
tegmental  region  has  been  given.  In  front  it  is  lost  at  the  base  of  the  brain  in 
the  gray  matter  of  the  anterior  perforated  space,  and  is  continuous  with  the  gray 
matter  of  the  floor  of  the  third  ventricle.  The  subthalamic  tegmental  region  con- 
tains a  forward  prolongation  of  the  red  nucleus,  and  consists  from  above  downward 
of  three  layers :  (1)  stratum  dorsale,  which  is  directly  applied  to  the  under  surface 
of  the  optic  thalamus,  and  consists  of  fine  longitudinal  fibres ;  (2)  zona  incerta,  a 
continuation  forward  of  the  formatio  reticularis  of  the  tegmentum  ;  and  (3)  the 
corpus  subthalamicum,  a  mass  of  gray  matter  which  on  section  presents  a  lenticular 
shape,  and  lies  immediately  above  the  substantia  nigra. 


STRUCTURE    OF    THE    CEREBRUM.  677 

STRUCTURE  OF  THE  CEREBRUM. 

The  cerebrum,  like  the  other  parts  of  the  great  nerve  centre,  is  composed  of 
gray  and  white  matter.  In  order  to  give  some  general  idea  of  its  construction,  at 
all  events  in  part,  it  may  be  compared,  for  the  sake  of  illustration,  to  a  tree,  the 
trunk  of  which  divides  into  two  main  divisions,  and  these  break  up  into  smaller 
branches,  which  finally  end  in  twigs,  to  which  are  attached  the  leaves,  forming  an 
investment  to  the  branches  and  covering  the  whole  tree.  The  trunk  is  represented 
by  the  medulla  oblongata  as  it  passes  through  the  foramen  magnum  ;  the  two  main 
divisions  by  the  crura  cerebri,  which  break  up  into  smaller  branches  ;  these  diverge 
from  each  other,  dividing  and  subdividing,  until  they  reach  the  surface  of  the 
hemispheres,  where  they  terminate  in  single  nerve-fibres,  which  are  continuous  with 
the  basal  axial  cylinder  processes  of  the  nerve-cells,  the  representatives  of  the 
leaves.  These  cells  are  arranged  on  the  surface,  resembling  a  cap,  covering  the 
hemispheres,  and  constitute  the  cerebral  cortex.  But  here  the  analogy  ends,  for 
in  the  cerebrum  there  are,  in  addition  to  this  cortex,  other  masses  of  gray  matter 
situated  in  the  middle  of  the  brain  ;  and  other  white  fibres  besides  the  diverging 
ones  that  have  been  mentioned,  and  which  serve  either  to  connect  the  two  cerebral 
hemispheres,  or  to  unite  different  structures  in  the  same  hemisphere. 

The  white  matter  of  the  cerebrum  consists  of  medullated  fibres,  varying  in  size 
and  arranged  in  bundles,  separated  by  neuroglia.  They  may  be  divided  into  three 
distinct  systems,  according  to  the  course  they  take.  1.  Projection  or  peduncular 
fibres,  which  connect  the  hemisphere  with  the  medulla  oblongata  and  cord.  2. 
Transverse  or  commissural  fibres,  which  unite  together  the  two  hemispheres.  3. 
Association  fibres,  which  connect  different  structures  in  the  same  hemisphere. 
These  are,  in  many  instances,  collateral  branches  of  the  projection  fibres,  but 
others  are  the  axons  of  independent  cells. 

1.  The  projection  or  peduncular  fibres  consist  of  fibres  which  pass  either  to  or 
from'  the  cord.  They  form  the  longitudinal  fibres  of  the  pons,  and  at  its  upper 
border  divide  into  two  main  groups,  which,  diverging  from  each  other,  constitute 
the  crura  cerebri  or  cerebral  peduncles.  In  the  crura  cerebri,  as  has  been  before 
described,  the  diverging  fibres  are  arranged  in  two  strata,  which  are  separated  by 
the  substantia  nigra ;  the  ventral  or  superficial  stratum  forming  the  crusta  of  these 
bodies,  and  the  dorsal  or  deeper  stratum,  the  tegmentum.  The  fibres  derived 
from  these  two  sources  take  a  different  course,  and  will  have  to  be  separately 
considered. 

The  fibres  of  the  crusta  are  derived  from  the  pyramid  of  the  medulla,  and  are 
continued  upward  through  the  pons  :  they  are  reinforced  in  their  passage  through 
the  crus  by  accessory  fibres,  derived  from  the  central  gray  nucleus  around  the 
Sylvian  aqueduct  and  from  the  substantia  nigra.  When  they  emerge  from  the 
crus,  most  of  the  fibres  pass  through  the  internal  capsule,  and  when  they  leave  it, 
spread  out  forward,  upward,  and  backward,  forming  a  series  of  radiating  fibres, 
the  corona  radiata,  which  proceed  to  the  cortex.  As  the  fibres  pass  through  the 
internal  capsule  they  give  off  branches  to  the  optic  thalamus  and  to  the  caudate 
and  lenticular  nuclei  of  the  striate  body,  and  other  fibres,  derived  especially  from 
the  first  of  these  ganglia,  form  a  part  of  the  corona  radiata,  and  pass  to  the  cortex 
of  the  cerebral  hemispheres.  The  fibres  of  the  tegmentum  are  continuous  with 
those  longitudinal  fibres  of  the  pons  which  are  derived  from  the  nucleus  gracilis 
and  nucleus  cuneatus,  and  from  the  formatio  reticularis  of  the  medulla.  They  are 
reinforced  by  fibres  from  the  corpora  quadrigemina  and  the  corpora  geniculata.  and 
from  the  superior  peduncle  of  the  cerebellum.  Some  of  the  fibres  are  continued 
directly  to  the  cerebral  cortex,  but  the  majority  pass  to  the  subthalamic  region, 
and  either  end  there  or  in  the  substance  of  the  optic  thalamus — the  connection 
with  the  cortex  being  effected  by  means  of  fibres  which  arise  in  the  optic  thalamus. 
They  spread  out  to  form  part  of  the  corona  radiata,  and  are  distributed  especially 
to  the  cortex  of  the  temporal  and  occipital  lobes. 

2.  The  transverse  or  commissural  fibres  connect  the  two  hemispheres.      They 


678  THE   NERVOUS  SYSTEM. 

include :  (a)  the  transverse  fibres  of  the  corpus  callosum  ;  (b)  the  anterior  com- 
missure ;  (<?)  the  posterior  commissure,  and  have  already  been  described. 

3.  Association  Fibres. — These  connect  different  structures  in  the  same  hemi- 
sphere, and  are  of  two  kinds:  (1)  Those  which  unite  adjacent  convolutions,  short 
association  fibres  ;  (2)  those  which  pass  between  more  distant  parts  in  the  same 
hemisphere,  long  association  fibres. 

The  short  association  fibres  are  situated  immediately  beneath  the  gray  sub- 
stance of  the  cortex  of  the  hemispheres,  and  connect  together  adjacent  con- 
volutions. 

The  long  association  fibres  include  the  following :  (a)  the  uncinate  fasciculus ; 
(b)  the  cingulum ;  (c)  the  superior  longitudinal  fasciculus  ;  (d)  the  inferior  longi- 
tudinal fasciculus ;  (e)  the  perpendicular  fasciculus  ;   and  (/)  the  fornix. 

(a)  The  uncinate  fasciculus  passes  across  the  bottom  of  the  Sylvian  fissure, 
and  connects  the  convolutions  of  the  frontal  lobe  with  the  anterior  end  of  the 
temporal  lobe. 

(b)  The  cingulum  is  a  band  of  white  matter  which  encircles  the  hemisphere  in 
an  antero-posterior  direction,  lying  in  the  substance  of  the  convolution  of  the 
corpus  callosum.  Commencing  in  front  at  the  anterior  perforated  space,  it  passes 
forward  and  upward  parallel  Avith  the  rostrum,  winds  round  the  genu,  runs  in 
the  convolution  from  before  backward,  immediately  above  the  corpus  callosum, 
turns  round  its  posterior  extremity,  and  passes  into  the  hippocampus  major,  through 
which  it  courses  to  its  anterior  extremity. 

(c)  The  superior  longitudinal  fasciculus  runs  along  the  convex  surface  of  the 
hemisphere,  and  connects  the  frontal  and  occipital  and  the  frontal  and  temporal 
lobes. 

(d)  The  inferior  longitudinal  fasciculus  is  a  collection  of  fibres  which  connects 
the  temporal  and  occipital  lobes,  running  along  the  outer  wall  of  the  descending 
and  posterior  cornua  of  the  lateral  ventricle. 

(e)  The  perpendicular  fascicidus  runs  vertically  through  the  front  part  of 
the  occipital  lobe,  and  connects  the  inferior  parietal  lobule  with  the  fourth  temporal 
convolution. 

(/)  The  fornix  connects  the  hippocampal  convolution  with  the  corpus  albicans, 
and,  by  means  of  the  bundle  of  Vicq  d'Azyr,  with  the  optic  thalamus  (see  page 
672).  Through  the  fibres  of  the  lyra  it  probably  also  unites  the  opposite  hippo- 
campal convolutions. 

The  gray  matter  of  the  cerebrum  is  disposed  in  two  great  groups :  (1)  The  gray 
matter  of  the  cerebral  cortex.  (2)  The  gray  matter  of  the  basal  ganglia,  the 
nucleus  caudatus  and  the  nucleus  lenticularis  of  the  corpus  striatum  ;  the  claustrum 
and  the  amygdaloid  nucleus.  They  are,  with  the  exception  of  the  amygdaloid 
nucleus,  situated  to  the  inner  side  of  the  island  of  Reil.  and  form  with  this  convo- 
lution the  oldest  part  of  the  hemisphere,  for  they  are  the  first  parts  of  the  enceph- 
alon  to  be  differentiated  in  the  development  of  the  individual.  They  are  simply 
semi-detached  local  thickenings  of  the  gray  cortex.  The  optic  thalamus  is  not 
reckoned  as  a  basal  ganglion,  but  as  belonging  to  the  thalamencephalon. 

GRAY  MATTER  OF  THE  CORTEX. 

On  examining  a  section  through  one  of  the  convolutions  of  the  Rolandic  area 
w;th  a  lens,  it  is  seen  to  consist  of  alternating  white  and  gray  layers  thus  disposed 
from  the  surface  inward :  (1)  a  thin  layer  of  white  substance ;  (2)  a  layer  of  gray 
substance ;  (3)  a  second  layer  of  white  substance  (outer  band  of  Baillarger  or 
band  of  Gennari) ;  (4)  a  second  gray  layer;  (5)  a  third  white  layer  (inner  band  of 
Baillarger)  ;  (6)  a  third  gray  layer,  which  rests  on  the  medullary  substance  of  the 
convolution. 

The  cortex  is  made  up  of  nerve-cells  which  vary  in  size  and  shape,  and  of  nerve- 
fibres,  which  are  either  medullated  or  naked  axis-cylinders,  embedded  in  a  matrix 
of  neuroglia. 


GRAY  MATTER    OF    THE    CORTEX. 


679 


Molecular  layer 


Layer  of  small 
pyramidal  cells. 


Layer  of  large 
pyramidal  cells. 


Nerve-cells. — According  to  Cajal,  whose  description  is  now  generally  accepted, 
the  nerve-cells  are  arranged  in  four  layers,  named  from  the  surface  inward  as 
follows  :  (1)  the  molecular  layer  ;  (2)  the  layer  of  small  pyramidal  cells ;  (3)  the 
layer  of  large  pyramidal  cells ;  (4)  the  layer  of  polymorphous  cells. 

The  Molecular  Layer. — In  this  layer  the  cells  are  polygonal,  triangular,  or  fusi- 
form in  shape.  Each  polygonal  cell  gives  off  some  four  or  five  dendrites,  while 
its  axon  may  arise  directly  from  the  cell  or  from  one  of  its  dendrites.  The  axons 
and  dendrites  of  these  cells  ramify  in  the  molecular  layer.  Each  triangular  cell 
gives  off  two  or  three  dendrites,  from  one  of  which  the  axon  arises,  the  dendrites 
and  the  axon  ramifying  in  the  mole- 
cular layer.  The  fusiform  cells  are 
placed  with  their  long  axes  parallel  to 
the  surface  and  are  mostly  bipolar, 
each  pole  being  prolonged  into  a 
dendrite,  which  runs  horizontally  for 
some  distance  and  furnishes  ascending 
branches.  Their  axons,  two  or  three 
in  number,  arise  from  the  dendrites, 
and,  like  them,  take  a  horizontal  course, 
giving  off  numerous  ascending  collat- 
erals. The  distribution  of  the  axons 
and  dendrites  of  all  three  sets  of  cells 
is  limited  to  the  molecular  layer. 

The  Layer  of  Small  and  the  Layer 
of  Large  Pyramidal  Cells. — The  cells 
in  these  two  layers  may  be  studied 
together,  since,  with  the  exception  of 
the  difference  in  size  and  the  more 
superficial  position  of  the  smaller  cells, 
they  resemble  each  other.  The  body 
of  each  cell  is  pyramidal  in  shape,  its 
base  being  directed  to  the  deeper  parts 
and  its  apex  toward  the  surface.  It 
contains  granular  pigment,  and  stains 
deeply  with  ordinary  reagents.  The 
nucleus  is  nucleolated,  of  large  size, 
and  round  or  oval  in  shape.  The  base 
of  the  cell  gives  off  the  axis-cylinder, 
and  this  passes  into  the  central  white 
substance,  giving  off  collaterals  in  its 
course,  and  is  distributed  as  a  projec- 
tion, commissural,  or  association  fibre. 
Both  the  apical  and  basal  parts  of  the 

cell  give  off  dendrites.  The  apical  dendrite  is  directed  toward  the  surface,  and 
ends  in  the  molecular  layer  by  dividing  into  numerous  branches,  all  of  which  may 
be  seen,  when  prepared  by  the  silver  or  methylene-blue  method,  to  be  studied  with 
projecting  bristle-like  processes.  The  larger  pyramidal  cells,  especially  in  the 
Rolandic  area,  may  exceed  50  fx  in  length  and  40  p.  in  breadth,  and  are  termed 
giant  cells. 

Layer  of  Polymorphous  Cells. — The  cells  in  this  layer,  as  their  name  implies, 
are  very  irregular  in  contour,  the  commonest  varieties  being  of  a  spindle,  star, 
oval,  or  triangular  shape.  Their  dendrites  are  directed  outward,  toward,  but  do 
not  reach,  the  molecular  layer ;  their  axons  pass  into  the  subjacent  white  matter. 

There  are  two  other  kinds  of  cells  in  the  cerebral  cortex,  but  their  axons  pass 
in  a  direction  opposite  to  that  of  the  pyramidal  and  polymorphous  cells,  among 
which  they  lie.  They  are :  (a)  the  cells  of  Golgi,  the  axons  of  which  do  not 
become  medullated,  but  divide  immediately  after  their  origin  into  a  large  number 


Polymorphous 
layer. 


White  medullary 
substance. 


Fig.  361.— The  four  layers  of  cells  in  the  cerebral  cor- 
tex.   (After  Cajal.)    Modified  from  Testut. 


680  THE  NERVOUS  SYSTEM. 

of  branches,  which  are  directed  toward  the  surface  of  the  cortex  ;  (b)  the  cells  of 
Martinotti,  which  are  chiefly  found  in  the  polymorphous  layer.  Their  dendrites 
are  short,  and  may  have  an  ascending  or  descending  course,  while  their  axons  pass 
out  into  the  molecular  layer  and  form  an  extensive  horizontal  arborization. 

Nerve-fibres. — These  fill  up  a  large  part  of  the  intervals  between  the  cells,  and 
may  be  medullated  or  non-medullated — the  latter  comprising  the  axons  of  the 
smallest  pyramidal  cells  and  the  cells  of  Golgi.  In  their  direction  the  fibres  may 
be  either  transverse  (tangential  or  horizontal)  or  vertical  (radial).  The  transverse 
fibres  run  parallel  to  the  surface  of  the  hemisphere,  intersecting  the  vertical  fibres 
at  a  right  angle.  They  consist  of  several  strata,  of  which  the  following  are  the 
most  important :  (1)  a  stratum  of  white  fibres  covering  the  superficial  aspect  of 
the  molecular  layer ;  (2)  the  external  band  of  Baillarger,  or  band  of  Gennari, 
Avhich  runs  through  the  layer  of  large  pyramidal  cells  ;  (3)  the  internal  band  of 
Baillarger,  which  intervenes  between  the  layer  of  large  pyramidal  cells  and  the 
polymorphous  layer.  According  to  Cajal,  the  transverse  fibres  consist  of  (a)  the 
collaterals  of  the  pyramidal  and  polymorphous  cells  and  of  the  cells  of  Martinotti ; 
(b)  the  arborizations  of  the  axons  of  Golgi's  cells;  (c)  the  collaterals  and  terminal 
arborizations  of  the  projection,  commissural,  or  association  fibres.  The  vertical 
fibres. — Some  of  these,  viz.,  the  axons  of  the  pyramidal  and  polymorphous  cells, 
are  directed  toward  the  central  white  matter,  while  others,  the  terminations  of  the 
commissural,  projection,  or  association  fibres,  pass  outward  to  end  in  the  cortex. 
The  axons  of  the  cells  of  Martinotti  are  also  ascending  fibres. 

In  certain  parts  of  the  cortex  this  typical  structure  is  departed  from.  The 
chief  of  these  regions  are:  (1)  the  occipital  lobe,  (2)  the  hippocampus  major,  (3) 
the  dentate  convolution,  and  (4)  the  olfactory  bulb. 

Special  Types  of  Gray  Matter. 

1.  In  the  cuneus  and  the  calcarine  fissure  of  the  occipital  lobe,  Cajal  has 
recently  described  as  many  as  nine  layers.  Here  the  inner  band  of  Baillarger  is 
absent ;  the  outer  band  of  Baillarger  (band  of  Gennari)  is,  on  the  other  hand,  of 
considerable  thickness.  If  a  section  be  examined  microscopically,  an  additional 
layer  is  seen  to  be  interpolated  between  the  molecular  layer  and  the  layer  of  small 
pyramidal  cells.  This  extra  layer  consists  of  two  or  three  strata  of  fusiform  cells, 
the  long  axes  of  which  are  at  right  angles  to  the  surface.  Each  cell  gives  off  two 
dendrites,  external  and  internal,  from  the  latter  of  which  the  axon  arises  and 
passes  into  the  white  central  substance.  In  the  layer  of  small  pyramidal  cells, 
fusiform  cells,  identical  with  the  above,  are  seen,  as  well  as  ovoid  or  star-like  cells 
with  ascending  axons  (cells  of  Martinotti).  This  area  of  the  cortex  forms  the 
visual  centre,  and  it  has  been  shown  by  Dr.  J.  S.  Bolton1  that  in  old  standing 
cases  of  optic  atrophy  the  thickness  of  Gennari's  band  is  reduced  by  nearly 
50  per  cent. 

2.  In  the  hippocampus  major  the  molecular  layer  is  very  thick  and  contains  a 
large  number  of  Golgi  cells.  It  has  been  divided  into  three  strata  :  (a)  S.  con- 
volutum  or  S.  granulosum,  containing  many  tangential  fibres ;  (b)  S.  lacunosum, 
presenting  numerous  lymphatic  or  vascular  spaces  ;  (c)  S.  radiatum,  exhibiting  a 
rich  plexus  of  fibrils.  The  two  layers  of  pyramidal  cells  are  condensed  into  one, 
and  the  cells  are  mostly  of  large  size.  The  axons  of  the  cells  in  the  polymorphous 
layer  may  run  in  an  ascending,  descending,  or  horizontal  direction.  Between  the 
polymorphous  layer  and  the  ventricular  ependyma  is  the  white  substance  of  the 
alveus. 

3.  In  the  rudimentary  dentate  convolution  the  molecular  layer  contains  some 
pyramidal  cells,  while  the  layer  of  pyramidal  cells  is  almost  entirely  represented 
by  small  ovoid  cells. 

4.  The  Olfactory  Bulb. — In  many  of  the  lower  animals  this  contains  a  cavity 
which  communicates   through   the  holloAv  olfactory   stalk  with  the  cavity   of  the 

1  Phil.  Trans,  of  Royal  Society,  Series  B,  vol.  cxciii,  p.  165. 


THE  HIND-BRAIN.  681 

lateral  ventricle.  In  man  the  original  cavity  is  filled  up  by  neuroglia  and  its 
wall  becomes  thickened,  but  much  more  so  on  its  ventral  than  on  its  dorsal  aspect. 
Its  dorsal  part  contains  a  small  amount  of  gray  and  white  matter,  but  it  is  scanty 
and  ill  defined.  A  section  through  the  ventral  part  shows  it  to  consist  of  the 
following  layers  from  without  inward.  (1)  A  layer  of  olfactory  nerve-fibres,  which 
are  the  non-medullated  axons  prolonged  from  the  olfactory  cells  of  the  nose,  and 
which  reach  the  bulb  by  passing  through  the  cribriform  plate  of  the  ethmoid  bone. 
At  first  they  cover  the  bulb,  and  then  penetrate  it  to  end  by  forming  synapses 
with  the  dendrons  of  the  mitral  cells,  presently  to  be  described.  (2)  Glomerular 
layer. — This  contains  numerous  spheroidal  reticulated  enlargements,  termed 
glomeruli,  which  are  produced  by  the  branching  and  arborization  of  the  processes 
of  the  olfactory  nerve-fibres  with  the  descending  dendrite  of  the  mitral  cells.  (3) 
Molecular  layer. — This  is  formed  of  a  matrix  of  neuroglia,  embedded  in  which  are 
the  mitral  cells.  These  cells  are  pyramidal  in  shape,  and  the  basal  part  of  each 
gives  off  a  thick  dendron  Avhich  descends  into  the  glomerular  layer,  where  it 
arborizes  as  indicated  above,  and  others  which  interlace  with  similar  dendrites  of 
neighboring  mitral  cells.  The  axons  pass  through  the  next  layer  into  the  white 
matter  of  the  bulb,  from  which,  after  becoming  bent  on  themselves  at  a  right 
angle,  they  are  continued  into  the  olfactory  tract.  (4)  Nerve-fibre  layer. — This 
lies  next  the  central  core  of  neuroglia,  and  its  fibres  consist  of  the  axons  or  affer- 
ent processes  of  the  mitral  cells  which  are  passing  to  the  brain ;  some  efferent 
fibres  are,  however,  also  present,  and  terminate  in  the  molecular  layer,  but  nothing 
is  known  as  to  their  exact  origin. 

IV.  The  Hind-Brain. 

The  hind-brain,  or  epencephalon,  comprises  those  parts  which  are  developed  from 
the  fourth  cerebral  vesicle ;  namely,  the  pons,  the  cerebellum,  and  the  upper  half 
of  the  fourth  ventricle. 

PONS  VAROLII. 

The  pons  Varolii  {tuber  annulare)  is  the  bond  of  union  of  the  various  segments 
of  the  encephalon,  connecting  the  cerebrum  above,  the  medulla  oblongata  below, 
and  the  cerebellum  behind.  It  is  situated  above  the  medulla  oblongata,  below 
the  crura  cerebri,  and  between  the  hemispheres  of  the  cerebellum.  It  is  about  an 
inch  in  length  and  in  thickness,  and  about  an  inch  and  a  half  in  width.  It  pre- 
sents four  surfaces :  superior,  which  is  attached,  by  direct  continuation  of  fibres,  to 
the  mid-brain  ;  inferior,  which  is  continuous  with  the  medulla  oblongata  ;  while 
the  anterior  or  ventral  and  the  posterior  or  dorsal  surfaces  are  free. 

The  anterior  or  ventral  surface  is  very  prominent,  markedly  convex  from  side 
to  side,  and  less  so  from  before  backward.  It  consists  of  transverse  white  fibres, 
which  arch  like  a  bridge  across  the  middle  line,  and  on  either  side  are  gathered 
together  into  a  compact  mass,  forming  the  middle  peduncle  of  the  cerebellum. 
Above  and  below  it  presents  a  well-defined  border ;  below,  its  transverse  fibres 
slightly  overlap  the  pyramidal  bodies  of  the  medulla,  which  disappear  into  its  sub- 
stance ;  above,  the  transverse  fibres  slightly  overlap  the  crura  cerebri  which  emerge 
from  it.  This  surface  rests  upon  the  clivus  of  the  sphenoid  bone,  and  presents  in 
the  middle  line  a  longitudinal  groove,  wider  in  front  than  behind,  in  which  rests 
the  basilar  artery. 

The  posterior  or  dorsal  surface  of  the  pons  is  free,  but  is  concealed  from  view 
by  the  cerebellum.  It  forms  the  upper  part  of  the  floor  of  the  fourth  ventricle, 
and  will  be  described  with  this  cavity. 

Structure. — Transverse  sections  of  the  pons  Varolii  show  that  it  consists  of  two 
parts,  which  differ  in  appearance  and  structure  from  each  other :  the  anterior  or 
ventral  portion  consists  for  the  most  part  of  fibres  arranged  in  transverse  and 
longitudinal  bundles  with  a  small  amount  of  gray  matter ;  the  posterior  or  dorsal 
portion  is  a  continuation  of  the  reticular  formation  of  the  medulla,  and  is  called 


682 


THE   NERVOUS  SYSTEM. 


the  tegmental  portion,  as  most  of  its  constituents  are  continued  into  the  tegmentum 
of  the  crus  cerebri. 

The  anterior  or  ventral  part  consists  of  three  layers  of  fibres :  1.  superficial 
transverse  fibres ;  2.  longitudinal  fibres ;  3.  deep  transverse  fibres.  These  three 
layers  are  not,  however,  completely  differentiated  from  each  other,  for  some 
transverse  fibres  may  be  seen  between  the  bundles  of  the  longitudinal  fibres 
(Fig.  362). 

1.  The  superficial  transverse  fibres,  consisting  of  a  rather  thick  layer  on  the 
ventral  surface  of  the  pons,  cross  the  middle  line,  and  proceeding  laterally  are 
collected  into  a  large  rounded  bundle  of  fibres  on  each  side.  This  bundle,  with 
the  addition. of  some  transverse  fibres  from  the  deeper  part  of  the  pons,  forms  the 
middle  peduncle  of  the  cerebellum  of  the  corresponding  side. 

2.  The  longitudinal  fibres  enter  the  pons  below  as  a  single  mass,  which  forms 
the  continuation  upward  of  the  fibres  of  the  pyramids  of  the  medulla ;  as  thev 
ascend  they  become  broken  up  into  bundles  by  some  of  the  transverse  fibres,  and 


Fig.  362. — Superficial  dissection  of  the  medulla  oblongata  and  pons.    (Ellis.) 

are  continued  into  the  crusta  of  the  mid-brain.  They  lie  on  either  side  of  the 
middle  line,  and  cause  a  bulging  of  the  superficial  transverse  fibres  on  the  ventral 
surface  of  the  pons,  with  a  longitudinal  mesial  groove  between  them.  This  is  the 
groove,  mentioned  above,  in  which  the  basilar  artery  is  received.  As  the  fibres 
ascend  they  are  increased  in  number,  being  reinforced  by  others  derived  from  the 
nerve-cells  in  the  deep  transverse  strata. 

3.  The  deep  transverse  fibres  form  a  thicker  layer  than  the  superficial  set,  and 
there  is  much  gray  matter  between  them.  The  fibres  pass  from  the  middle  line, 
where  they  interlace  with  those  from  the  opposite  side,  and,  coursing  to  the  lateral 
borders  of  the  pons,  they,  for  the  most  part,  curve  dorsally,  and  assist  the  super- 
ficial transverse  fibres  in  forming  the  middle  peduncle  of  the  cerebellum.  Some 
of  the  fibres  join  the  nerve-cells  which  are  situated  in  the  gray  matter  of  this 
layer,  and  in  addition  nerve-fibres  derived  from  others  of  these  cells  pass  off  to 
join  the  longitudinal  fibres  (see  above). 


THE   HIND-BRAIN.  683 

The  tegmental  or  dorsal  portion  of  the  pons  is  chiefly  constituted  by  a  con- 
tinuation upward  of  the  reticular  formation  and  gray  matter  of  the  medulla.  It 
is  subdivided  into  lateral  halves  by  a  median  raphe"  continuous  with  that  of  the 
medulla,  but  this  does  not  extend  into  the  ventral  half  of  the  pons,  being  here 
obliterated  by  the  transverse  fibres. 

The  dorsal  portion  of  the  pons,  like  the  ventral,  contains  both  transverse  and 
longitudinal  fibres.  The  transverse  fibres  are  collected  into  a  distinct  bundle, 
which,  from  its  shape,  is  sometimes  termed  the  trapezium  or  corpus  trapezoides. 
It  consists  of  fibres  which  proceed  laterally  to  become  connected  with  the  cells  of 
the  accessory  auditory  nucleus.  The  longitudinal  fibres,  which  are  continuous 
with  those  of  the  medulla,  are  mostly  collected  into  two  bundles  on  either  side. 
One  of  these  lies  between  the  corpus  trapezoides  and  the  formatio  reticularis  of 
the  pons,  and  is  a  continuation  upward  of  the  sensory  tracts ;  it  is  termed  the 
fillet.  The  other  bundle  is  situated  more  dorsally,  near  the  floor  of  the  fourth 
ventricle;  it  is  the  posterior  longitudinal  bundle,  and  contains  both  ascending  and 
descending  fibres.  Other  longitudinal  fibres,  which  are  more  diffusely  distributed, 
arise  from  the  cells  of  the  gray  matter  of  the  pons  itself.  The  greater  part  of  the 
dorsal  portion  of  the  pons  is,  as  stated  above,  a  continuation  upward  of  the 
formatio  reticularis  of  the  medulla,  and,  like  it,  presents,  on  transverse  section, 
viewed  under  a  moderate  magnifying  power,  a  reticular  appearance.  In  addition 
to  the  gray  matter,  which  presents  a  number  of  small  reticularly  arranged  masses, 
with  nerve-cells,  there  are  some  important  collections  of  nerve-cells  which  require 
mention. 

1.  The  superior  olivary  nucleus  is  a  small  isolated  collection  of  gray  matter, 
situated  on  the  dorsal  surface  of  the  outer  part  of  the  trapezium.  In  structure  it 
resembles  the  inferior  olivary  nucleus  of  the  medulla,  presently  to  be  described, 
and  is  situated  immediately  above  it.  The  nerve-fibres  derived  from  its  cells  pass 
into  the  trapezium,  and,  as  stated  above,  cross  the  middle  line  and  enter  the  acces- 
sory auditory  nucleus  of  the  other  side.  The  other  collections  of  nerve-cells  in  the 
formatio  reticularis  of  the  pons  are  nuclei  from  which  some  of  the  cranial  nerves 
arise. 

2.  Nuclei  of  the  Fifth  Nerve. — The  nuclei  of  the  fifth  nerve  in  the  pons  are  two 
in  number :  one  for  the  motor  root  and  the  other  for  the  sensory.  The  motor 
nucleus  is  situated  in  the  higher  portion  of  the  pons,  close  under  the  dorsal  surface 
and  along  the  line  of  the  lateral  margin  of  the  fourth  ventricle.  The  sensory 
nucleus  lies  external  to  the  motor  one,  beneath  the  superior  peduncle  of  the  cere- 
bellum, which  forms  the  lateral  boundary -of  the  upper  half  of  the  fourth  ventricle. 
Some  of  the  fibres  from  these  nuclei  pass  to  the  raphe  of  the  pons,  and  thence 
probably  to  the  higher  parts  of  the  brain  ;  the  rest  form  the  nerve-roots  of  the 
motor  and  sensory  parts  of  the  fifth  nerve  respectively.  They  pass  through  the 
pons  to  emerge  on  its  ventral  surface  at  its  lateral  and  constricted  portion,  nearer 
its  superior  than  its  inferior  margin.  It  must  be  mentioned  that  the  whole  of  the 
roots  of  the  fifth  nerve  are  not  formed  from  these  nuclei.  The  sensory  root  is 
partly  formed  by  a  long  tract  of  fibres,  known  as  the  ascending  root,  which  can 
be  traced  through  the  pons  and  medulla  to  the  upper  part  of  the  spinal  cord.  The 
motor  root,  in  like  manner,  is  partly  formed  by  a  long  tract  of  fibres,  which  passes 
downward  from  the  gray  matter  in  the  floor  of  the  Sylvian  aqueduct  and  which  is 
termed  the  descending  root. 

3.  The  nucleus  of  the  sixth  nerve  is  situated  beneath  the  floor  of  the  fourth 
ventricle,  on  either  side  of  the  middle  line.  It  lies  close  to  the  root  of  the  facial 
nerve,  immedia:  „y  to  be  described,  being  a  little  external  to  and  beneath  it,  and 
corresponds  to  pper  half  of  the  fasciculus  teres  of  the  floor  of  the  fourth 
ventricle  (Fig.  I  '1).  The  fibres  pass  through  the  substance  of  the  pons,  and 
emerge  at  the  lower  margin  of  this  structure,  between  it  and  the  upper  end  of 
the  medulla. 

4.  The  nucleus  of  the  facial  nerve  is  of  elongated  form,  and  is  situated  deeply 
in  the  reticular  formation  below  the  floor  of   the  fourth  ventricle  and  dorsal  to 


684  THE  NERVOUS  SYSTEM. 

the  superior  olivary  nucleus.  The  roots  of  the  nerve  derived  from  it  pursue  a 
remarkably  tortuous  course  in  the  substance  of  the  pons.  At  first  they  pass  back- 
ward and  inward  till  they  reach  the  floor  of  the  fourth  ventricle,  close  to  the 
median  groove,  where  they  are  collected  into  a  rounded  bundle.  This  passes  up- 
ward and  forward,  producing  an  elevation  [fasciculus  teres)  in  the  floor  of  the  ven- 
tricle, and  then  takes  a  sharp  bend  and  arches  outward  through  the  substance  of 
the  pons  to  emerge  at  its  lower  border  in  the  interval  between  the  olivary  and 
restiform  bodies  of  the  medulla. 

5.  The  nuclei  of  the  auditory  nerve  are  two  in  number,  dorsal  and  ventral.  The 
dorsal  nucleus  is  principally  situated  in  the  medulla,  but  is  prolonged  upward  into 
the  pons,  where  it  lies  beneath  the  upper  half  of  the  floor  of  the  fourth  ventricle. 
The  ventral  or  accessory  nucleus  is  also  partly  contained  in  the  medulla  and  partly 
in  the  pons.  In  the  medulla  it  is  situated  on  the  antero-external  surface  of  the 
restiform  body,  lying  between  the  vestibular  and  cochlear  divisions  of  the  auditory 
nerve,  the  latter  being  to  its  outer  side.  In  the  pons  it  is  seen  to  lie  beyond  the 
boundary  of  the  fourth  ventricle  on  the  outer  and  ventral  aspect  of  the  restiform 
body.  A  third  nucleus  {nucleus  of  Deiters)  is  sometimes  termed  the  outer  nucleus 
of  the  auditory  nerve.  It  is  situated  below  the  outer  angle  of  the  fourth  ventricle, 
and  contains  multipolar  nerve-cells  of  large  size.  The  root  of  the  auditory  nerve 
consists  of  two  portions,  lateral  and  mesial,  which  pass,  one  to  the  outer  and  the 
other  to  the  inner  side  of  the  restiform  body,  those  from  the  lateral  part  arising 
mainly  from  the  ventral  nucleus,  those  from  the  mesial  part  arising  from  the  dorsal 
auditory  nucleus.  They  emerge  at  the  lower  border  of  the  pons,  in  the  groove 
between  the  olivary  and  restiform  bodies. 

The  Nuclei  Pontis. — In  addition  to  these  nuclei  of  gray  matter,  which  have 
been  described  as  being  situated  in  the  tegmental  or  dorsal  portion  of  the  pons, 
there  are  small  masses  of  gray  matter,  as  mentioned  above,  in  the  anterior  or  ven- 
tral portion.  These  are  known  as  the  nuclei  pontis,  and  consist  of  small  multipolar 
nerve-cells,  scattered  between  the  bundles  of  transverse  fibres. 

THE  CEREBELLUM. 

The  Cerebellum  is  contained  in  the  inferior  occipital  fossae,  and  is  situated 
beneath  the  occipital  lobes  of  the  cerebrum,  from  which  it  is  separated  by  the  ten- 
torium cerebelli.  In  form,  it  is  oblong  and  flattened  from  above  downward,  its 
great  diameter  being  from  side  to  side.  It  measures  from  three  and  a  half  to  four 
inches  transversely,  two  to  two  and  a  half  inches  from  before  backward,  and  is 
about  two  inches  thick  in  the  centre,  and  about  six  lines  at  the  circumference.  It 
consists  of  gray  and  white  matter :  the  former,  darker  than  that  of  the  cerebrum, 
occupies  the  surface  ;  the  latter,  the  interior.  The  surface  of  the  cerebellum  is  not 
convoluted  like  that  of  the  cerebrum,  but  is  traversed  by  numerous  curved  furrows 
or  sulci,  which  vary  in  depth  at  different  parts,  and  separate  the  laminae  of  which 
it  is  composed. 

Lobes  of  the  Cerebellum. — The  cerebellum  consists  of  three  parts  or  lobes,  a 
median  and  two  lateral.  They  are  all  continuous  with  each  other,  and  are  substan- 
tially the  same  in  structure.  The  median  portion  is  called  the  worm  or  vermiform 
process,  from  the  annulated  appearance  which  it  presents,  owing  to  transverse 
ridges  and  furrows  upon  it.  On  the  upper  surface  of  the  cerebellum,  the  worm  is 
only  slightly  elevated  above  the  level  of  the  lateral  portions,  but  on  the  under  sur- 
face it  is  sunk  almost  out  of  sight  in  a  deep  depression,  which  is  called  the  val- 
lecula. The  lateral  parts  are  called  hemispheres  ;  they  attain  a  considerable  size, 
overlapping  and  obscuring  the  inferior  part  of  the  worm.  Below  and  behind  they 
are  separated  by  a  deep  notch  {posterior  cerebellar  notch,  incisura  marsupialis), 
and  in  front  by  a  broader,  shallower  notch  {anterior  cerebellar  notch,  incisura  semi- 
lunaris). The  anterior  notch  lies  close  to  the  pons  and  upper  part  of  the  medulla, 
and  its  upper  edge  encircles  the  posterior  corpora  quadrigemina.  The  posterior 
notch  is  free,  and  contains,  in  the  recent  state,  the  upper  part  of  the  falx  cerebelli. 


THE   HIND-BRAIN. 


685 


The  sides  of  the  notches  are  formed  by  the  margins  of  the  hemispheres,  while  the 
bottom  of  the  notches  is  formed  by  the  anterior  and  posterior  extremities  of  the 
worm  respectively.  The  cerebellum  is  characterized  by  its  laminated  or  foliated 
aDpearance;  it  is  everywhere  marked  by  deep,  transverse,  somewhat  curved  fis- 
sures, which  lie  close  together,  and  extend  for  a  considerable  depth  into  the  sub- 
stance of  the  cerebellum,  dividing  it  into  a  series  of  layers  or  leaves.  Upon  making 
sections  across  the  laminae  it  will  be  seen  that  the  folia,  though  differing  in  appear- 
ance from  the  convolutions  of  the  cerebrum,  are  homologous  with  them,  inasmuch 
as  they  consist  of  a  central  white  substance,  with  a  covering  or  cortex  of  gray 
matter. 

The  largest  and  deepest  fissure  is  the  great  horizontal  fissure.  It  commences 
in  front  at  the  pons,  and  passes  horizontally  round  the  free  margin  of  the  hemi- 
sphere to  the  middle  line  behind,  and  divides  the  cerebellum  into  an  upper  and 


Ala  lobuli  centralis.      Post-central 
Lobulus  centralis.  \  fissure. 


Great 

horizontal 

fissure. 


Pre-clival  fissure. 

Post-clival  fissure. 


Fig.  363.— Upper  surface  of  the  cerebellum.    (Schiifer.) 


lower  portion.  Several  secondary  but  deep  fissures  separate  the  cerebellum  into 
lobes,  and  these  are  further  subdivided  by  shallower  sulci,  which  separate  the  indi- 
vidual folia  or  laminse  from  each  other. 

The  cerebellum  is  connected  to  the  cerebrum,  pons,  and  medulla  by  three  pairs 
of  peduncles  ;  which  will  be  described  in  the  sequel ;  a  superior  pair,  connect  it 
with  the  cerebrum ;  a  middle  pair,  with  the  pons ;  and  an  inferior  pair,  with  the 
medulla. 

Upper  Surface  of  Cerebellum  (Fig.  363). — The  superior  surface  of  the  cerebel- 
lum is  somewhat  elevated  in  the  middle  line  and  sloped  toward  its  circumference, 
its  hemispheres  being  connected  together  by  an  elevated  median  portion  or  lobe, 
the  superior  worm  or  superior  vermiform  process.  The  surface  is  traversed  by  four 
curved  fissures,  which  are  named  from  their  situation,  in  front  or  behind  two  promi- 
nent lobes  of  the  worm,  the  central  lobe  and  the  clivus,  (1)  the  pre-central  fissure, 

(2)  the  post-central  fissure,  (3)  the  pre-clival  fissure,  and  (4)  the  post-clival  fissure. 
These  four  fissures  divide  the  entire  upper  surface  of  the  cerebellum  into  five  lobes, 
but  the  portion  of  the  lobe  in  the  worm  has  received  a  different  name  from  that  in 
the  hemisphere,  though  the  two  are  continuous  with  each  other.  The  five  lobes  in 
the  worm  are  named  from  before  backward  :  (1)  the  lingula,  (2)  the  lobulus  centralis. 

(3)  the  cubnen  monticuli,  (4)  the  clivus  monticuli,  and  (5)  the  folium  eaeuminis. 
The  five  lobes  in  the  hemispheres  are  named  from  before  backward :  (1)  the  frcenu- 
lum,  (2)  the  ala  lobuli  centralis,  (3)  anterior  crescentic,  (4)  posterior  erescentic,  and 
(5)  posterior  superior.  The  arrangement  of  these  fissures  and  lobules  will  be  under- 
stood by  reference  to  the  accompanying  schematic  arrangement,  in  which  the  lob- 
ules are  named  in  order  from  before  backward  with  the  fissures  which  separate 
them  : 


686  THE   NERVOUS  SYSTEM. 

UPPER  SURFACE  OF  THE  CEREBELLUM. 

Worm.  Hemisphere. 

Lingula.  Frenulum. 

Pre-central  fissure. 
Lobulus  centralis.  Ala  lobuli  centralis. 

Post-central  fissure. 
Culmen  monticuli.  Anterior  crescentic  lobe. 

Pre-clival  fissure. 
Clivus  monticuli.  Posterior  crescentic  lobe. 

Post-clival  fissure. 
Folium  cacuminis.  Posterior  superior  lobe. 

The  lingula  is  a  tongue-shaped  process  of  the  cerebellum,  which  lies  in  front  of 
the  lobulus  centralis  and  is  partially  or  completely  concealed  by  it.  It  is  in  rela- 
tion, in  front,  with  the  valve  of  Vieussens,  on  the  dorsal  surface  of  which  it  rests 
and  with  which  it  is  connected  ;  its  white  matter  being  continuous  with  that  of  the 
valve.  At  either  side  the  lingula  gradually  shades  off,  and  is  prolonged  only  for  a 
short  distance  into  the  hemispheres,  where  it  forms  the  frsenulum.  This  does  not 
stretch  beyond  the  superior  peduncle  of  the  cerebellum  over  which  it  lies. 

The  Lobulus  Centralis. — The  lobulus  centralis  is  a  small  square  lobe,  situated  in 
the  anterior  notch.  It  overlaps  the  lingula  and  is  in  turn  partially  concealed  by 
the  culmen  monticuli.  Laterally  the  lobulus  centralis  extends  along  the  upper 
and  anterior  part  of  each  hemisphere,  where  it  forms  a  wing-like  prolongation,  the 
ala  lobuli  centralis. 

The  culmen  monticuli  is  much  larger  than  the  two  lobes  just  described,  and  con- 
stitutes, with  the  succeeding  lobe,  the  clivus,  the  bulk  of  the  upper  worm.  In  front 
it  partially  overlaps  and  obscures  the  lobulus  centralis,  and  behind  it  is  separated 
from  the  clivus  by  the  pre-clival  fissure.  It  forms  the  most  prominent  part  of  the 
upper  worm,  and  is  marked  on  its  surface  by  three  or  four  secondary  fissures, 
dividing  it  up  into  smaller  lobules.  Laterally  it  is  continuous  with  the  anterior 
crescentic  lobe  of  the  hemispheres,  which  is  distinctly  differentiated  from  the  poste- 
rior crescentic  lobe  by  the  pre-clival  fissure,  though  the  two  were  formerly  classed 
together  as  the  quadrate  lobe  of  the  lateral  hemisphere. 

The  clivus  monticuli  is  of  considerable  size,  and,  as  stated  above,  forms  with  the 
cnlmen  the  major  part  of  the  superior  worm.  It  consists  of  a  group  of  laminse, 
which  in  front  are  separated  from  the  culmen  by  the  pre-clival  fissure  and  behind 
appear  to  be  almost  continuous  with  the  folium  cacuminis,  especially  in  the  median 
line ;  but  it  will  be  found,  on  careful  examination,  to  be  separated  from  it  by  a 
well-defined  fissure,  the  post-clival  fissure.  Laterally  this  lobe  is  continued  into 
the  hemispheres  as  the  posterior  crescentic  lobe,  which  is  somewhat  semilunar  in 
shape,  and,  with  the  anterior  crescentic  lobe,  constitutes  the  greater  part  of  the 
upper  surface  of  the  hemispheres. 

The  folium  cacuminis  is  a  short  and  narrow,  concealed  band  at  the  posterior 
extremity  of  the  worm,  consisting  apparently  of  a  single  folium,  but  in  reality 
marked  on  its  upper  and  under  surfaces  by  secondary  fissui'es.  Laterally  it 
expands  in  either  hemisphere  into  a  considerable  lobe,  which  is  semilunar  in  shape, 
and  is  situated  at  the  postero-superior  part  of  the  hemisphere  and  bounded  below 
by  the  great  horizontal  fissure.  It  is  named  the  posterior  superior  lobe  and  occupies 
the  posterior  third  of  the  upper  surface  of  the  hemisphere,  forming  its  rounded 
postero-lateral  border. 

The  Under  Surface  of  the  Cerebellum  (Fig.  364)  presents  in  the  middle  line  the 
inferior  worm,  buried  in  the  vallecula,  and  separated  from  the  hemispheres  by 


THE   HIND-BRAIN. 


687 


latera*  grooves.  Here,  as  on  the  upper  surface,  there  are  deep  fissures,  dividing  it 
into  separate  segments  or  lobes,  but  the  arrangement  is  more  complicated,  and  the 
relation  of  the  segments  of  the  worm  to  those  of  the  hemisphere  is  less  clearly 
marked.     The  fissures  are  three  in  number,  but  are  not  so  regularly  disposed  as 


Post-  nodular  fissure. 


Flocculus. 


Pre- 
pyramidal 
fissure 


Great 

horizontal 

fissure. 


Post 
pyramided 

fissure. 


Fig.  364.— Under  surface  of  the  cerebellum.    (Schafer.) 


those  on  the  upper  surface  (Fig.  365).  They  are  named,  from  their  relation  to  the 
pyramid  and  nodule,  two  of  the  lobes  on  the  under  surface  of  the  worm,  (1)  post- 
nodular,  (2)  pre-pyramidal,  and  (3)  post-pyramidal  fissures.  The  part  of  the  worm 
in  front  of  the  post-nodular  fissure  is  termed  the  nodule,  and  the  lobule  in  the  hemi- 
sphere corresponding  with  this  is  the  flocculus.     The  next  lobe  is  situated  between 


Fig.  365.— Diagram  showing  fissures  on  under  surface  of  the  cerebellum  :  F.,  flocculus ;  N.,  nodule  :  U,  uvula ; 
Py.,  pyramid;  Am.,  amygdala;  Bivent.,  biventral  lobe. 

the  post-nodular  and  pre-pyramidal  fissures.  In  the  vermiform  process  it  is  known 
as  the  uvula,  and  its  lateral  expansion  in  the  hemisphere  is  named  the  amygdala 
or  tonsil.  The  lobule  of  the  worm  between  the  pre-  and  post-pyramidal  fissures 
is  the  pyramid,  and  its  corresponding  part  in  the  hemisphere  is  the  biventral  or 
digastric  lobe.  Finally,  behind  the  post-pyramidal  fissure  in  the  worm  is  a  small 
lobe,  the  tuber  valvulce  or  tuber  posticum  :  this,  in  the  hemispheres,  expands  into  a 
large  lobe,  which  occupies  at  least  two-thirds  of  the  inferior  surface  of  the  cerebel- 
lum,  and  is  subdivided  into  two  by  a  secondary  fissure,  named   the  post-gracile 


688  THE  NERVOUS  SYSTEM. 

fissure.  The  anterior  of  the  two  subdivisions  is  named  the  slender  lobe ;  and  the 
posterior,  the  inferior  semilunar  or  posterior  inferior  lobe.  These  fissures  and  lobes 
are  here  arranged,  from  before  backward,  in  a  schematic  form : 

UNDER  SURFACE  OF  THE  CEREBELLUM. 

Worm.  Hemisphere. 

Nodule.  Flocculus. 

Post-nodular  fissure. 

Uvula.  Amygdala. 

Pre-pyramidal  fissure. 

Pyramid.  Biventral  lobe. 

Post-pyramidal  fissure. 

(  Slender  lobe. 
Tuber  valvulse.  <  Post-gracile  fissure. 

( Inferior  semilunar  lobe. 

The  chief  fissures  of  the  under  surface,  as  stated  above,  are  three  in  number, 
and  are  not  so  regularly  disposed  as  on  the  upper  surface.  (1)  The  post-nodular 
fissure  in  the  worm  courses  transversely  across  it,  separating  the  nodule  in  front 
from  the  uvula  behind.  When  it  reaches  the  hemispheres  it  passes  in  front  of  the 
amygdala,  and  then  crosses  between  the  flocculus  in  front  and  the  biventral  lobe 
behind,  and  joins  the  anterior  end  of  the  great  horizontal  fissure.  (2)  The  pre- 
pyramidal  fissure  crosses  the  worm  between  the  uvula  in  front  and  the  pyramid 
behind,  then  curves  laterally  behind  the  amygdala,  and  passes  forward  along  the 
outer  border  of  this  lobe,  between  it  and  the  biventral  lobe,  to  join  the  post-nodular 
sulcus.  (3)  The  post-pyramidal  fissure  passes  across  the  worm  behind  the  pyramid 
and  in  front  of  the  tuber  valvulae,  and  in  the  hemispheres  courses  behind  the 
amygdala  and  biventral  lobes,  and  then  along  the  outer  border  of  the  biventral 
lobe  to  the  post-nodular  sulcus.  It  cuts  off  at  least  two-thirds  of  the  inferior 
surface  of  the  hemisphere.  From  it  a  secondary  sulcus  springs,  and  coursing 
forward  and  outward  divides  this  surface  into  two  parts  and  falls  into  the  great 
horizontal  fissure.      This  sulcus  is  termed  the  post-gracile  fissure. 

THE  LOBES  OF  THE  INFERIOR  SURFACE  OF  THE  CEREBELLUM. 

The  Nodule  and  Flocculus. — The  nodule  is  a  distinct  prominence,  forming  the 
anterior  extremity  of  the  inferior  Avorm.  It  projects  into  the  roof  of  the  fourth 
ventricle,  and  can  only  be  distinctly  seen  after  the  cerebellum  has  been  separated 
from  the  medulla  and  pons.  On  each  side  of  the  nodule  is  a  thin  layer  of  white 
substance,  named  the  inferior  medullary  velum.  It  is  semilunar  in  form,  its 
convex  border  being  continuous  with  the  Avhite  substance  of  the  cerebellum  ;  it 
extends  on  either  side  as  far  as  the  flocculus,  which  it  connects  with  the  nodule. 
The  flocculus  is  a  prominent,  irregular  lobule,  situated  just  in  front  of  the  biventral 
lobe,  between  it  and  the  middle  peduncle  of  the  cerebellum.  It  is  subdivided  into 
a  few  small  laminae,  and  is  connected  to  the  inferior  medullary  velum  by  its  central 
white  core. 

The  Uvula  and  Amygdalae. — The  uvula  occupies  a  considerable  portion  of  the 
inferior  worm  ;  it  is  separated  on  either  side  from  the  amygdala  by  a  deep  groove, 
the  sulcus  vallecida?,  at  the  bottom  of  which  it  is  connected  to  the  amygdala  by 
a  commissure  of  gray  matter,  indented  on  its  surface,  and  called  the  furrowed  band. 
It  is  marked  on  its  surface  by  three  or  four  transverse  fissures.  The  amygdalae, 
or  tonsils,  are  rounded  masses,  situated  in  the  lateral  hemispheres.  Each  lies  in 
a  deep  fossa  between  the  uvula  and  the  biventral  lobe ;  this  fossa  is  known  by  the 
name  of  the  bird's  nest  (nidis  avis). 


THE  HIND-BRAIN.  689 

The  Pyramid  and  Biventral  Lobes. — The  pyramid  is  a  conical  projection,  forming 
the  largest  prominence  of  the  lower  worm.  It  is  separated  from  the  hemispheres 
by  the  sulcus  vallecula,  across  which  it  is  connected  to  the  biventral  lobe  by  an 
indistinct  band  of  gray  matter,  analogous  to  the  furrowed  band  already  described. 
The  biventral  lobe  is  triangular  in  shape,  with  the  apex  pointing  inward  and 
backward  to  become  joined  by  the  connecting  band  to  the  pyramid.  The  external 
border  is  separated  from  the  slender  lobe  by  the  post-pyramidal  fissure.  The  base  is 
directed  forward,  and  is  on  a  line  with  the  anterior  border  of  the  amygdala,  and  is 
separated  from  the  flocculus  by  the  post-nodular  fissure. 

The  Tuber  Valvulae  or  Tuber  Posticum,  and  Posterior  Inferior  Lobes. — The  tuber 
valvulae  is  the  posterior  division  of  the  inferior  worm.  It  is  of  small  size,  and 
laterally  spreads  out  into  the  large  posterior  inferior  lobes  of  the  hemispheres. 
These  lobes,  which,  as  stated  above,  comprise  at  least  two-thirds  of  the  inferior 
surface  of  the  hemisphere,  are  divided  into  two  by  the  post-gracile  fissure.  The 
anterior  lobe  is  named  the  slender  lobe,  and  the  posterior,  the  inferior  semilunar 
lobe.  Both  these  lobes  show  a  tendency  to  subdivision  into  two ;  that  of  the 
slender  lobe  is  well  marked,  and  its  subdivisions  are  sometimes  described  as 
distinct  lobes  and  named  the  anterior  and  posterior  slender  lobes,  the  fissure 
between  them  being  termed  the  intra-gracile  fissure. 

INTERNAL  STRUCTURE  OF  THE  CEREBELLUM. 

The  cerebellum  consists  of  white  and  gray  matter. 

The  White  Matter. — If  a  sagittal  section  (Fig.  366)  is  made  through  either 
hemisphere  of  the  cerebellum,  the  interior  will  be  found  to  consist  of  a  central 
stem  of  white  matter,  which  contains  in  its  interior  a  gray  mass,  the  corpus  den- 
tatum.  From  the  surface  of  this  central  stem  a  series  of  plates  of  medullary 
matter  are  detached,  which,  covered  with  gray  matter,  form  the  laminae.  In 
consequence  of  the  main  branches  from  the  central  stem  dividing  and  subdividing, 
the  section  presents  a  characteristic  appearance,  which  is  named  the  arbor  vitce. 
If  a  vertical  section  is  made  in  the  median  plane  of  the  cerebellum  it  will  be  found 
that  the  central  stem  divides  into  two  main  branches,  which,  from  their  direction, 
may  be  named  respectively  the  vertical  and  the  horizontal  branch.  The  vertical 
branch  passes  upward  to  the  culmen,  where  it  subdivides  freely,  some  of  its  ramifi- 
cations passing  forward  and  upward  to  the  central  lobe.  The  horizontal  branch 
passes  backward  to  the  folium  cacuminis,  considerably  diminished  in  size  in 
consequence  of  having  given  off  large  secondary  branches :  one,  from  its  upper 
surface,  ascends  to  the  clivus ;  the  others  descend,  and  enter  the  lobes  in  the 
inferior  vermiform  process,  the  tuber  valvules,  the  pyramid,  the  uvula,  and  the 
nodule.  It  is  not  necessary  to  describe  in  detail  the  various  divisions  of  the  white 
matter,  as  they  correspond  to  the  lobes  on  the  surface. 

The  white  matter  of  the  cerebellum  includes  two  varieties  of  nerve  matter : 
(1)  the  peduncular  fibres,  which  are  directly  continuous  with  those  of  the  pedun- 
cles of  the  cerebellum ;  (2)  the  fibres  proper  (fibrce  prop-ice)  of  the  cerebellum 
itself. 

The  Peduncles  of  the  Cerebellum. — From  the  anterior  part  of  each  hemisphere 
arise  three  large  processes  or  peduncles — superior,  middle,  and  inferior — by  which 
the  cerebellum  is  connected  with  the  rest  of  the  encephalon. 

The  superior  peduncles  form  the  upper  lateral  boundaries  of  the  floor  of  the 
fourth  ventricle.  As  they  extend  forward  and  upward  they  converge  on  the 
dorsal  aspect  of  the  ventricle,  and  thus  assist  to  roof  it  in.  They  may  be 
traced  as  far  as  the  corpora  quadrigemina,  under  which  they  pass.  They  enter 
the  upper  and  mesial  part  of  the  medullary  substance  of  the  hemispheres,  beneath 
the  ala  lobuli  centralis  and  the  fraenulum,  and  pass  to  a  great  extent  into  the 
interior  of  the  corpus  dentatum,  though  some  of  their  fibres  wind  round  it  arm 
reach  the  gray  cortical  matter,  especially  of  the  inferior  surface. 

The  fibres  of  the  superior  peduncles  mainly  emerge  from  the  hilum  of  the  corpus 

44 


690 


THE   NERVOUS  SYSTEM. 


dentaturu ;  others  come  from  the  cortex  and  probably  also  from  the  smaller  nuclei 
in  the  central  white  substance.  The  majority  of  the  fibres  decussate  with  those 
of  the  opposite  peduncle  below  the  corpora  quadrigemina,  and  pass  to  the  red 
nucleus  of  the  tegmentum,  from  which  a  relay  is  prolonged  through  the  optic 
thalamus  to  the /cerebral  cortex.  Fibres  also  connect  the  spinal  cord  with  the 
cerebellum  through  its  superior  peduncles ;  these  are  chiefly  derived  from  the 
antero-lateral  ascending  cerebellar  tract  of  Growers. 

The  Valve  of  Vieussens  or  Superior  Medullary  Velum. — Stretched  across  from 
one  superior  peduncle  to  the  other  is  a  thin,  transparent  lamina  of  white  matter, 
the  valve  of  Vieussens  ;  on  to  the  dorsal  surface  of  its  lower  half  the  folia  of  the 
lingula  are  prolonged.  It  forms  with  the  superior  peduncles  the  roof  of  the  upper 
part  of  the  fourth  ventricle,  and  is  continuous  with  the  central  white  stem  of  the 
cerebellum.  It  is  narrow  above,  where  it  passes  beneath  the  corpora  quadri- 
gemina, and  broader  below,  at  its  connection  with  the  white  substance  of  the 
superior  worm  of  the  cerebellum.  A  slight  elevated  ridge  descends  upon  the  upper 
part  of  the  valve  from  between  the  lower  corpora  quadrigemina,  and  on  either  side 
of  this  may  be  seen  the  fourth  nerve. 


Anterior 
crescentic  lobe. 


Ala  lobuli  centralis. 


Lingula. 


Superior  peduncles 
of  cerebellum. 


Great 
horizontal    ^ 
fissure,  °e' 


Slender  lobe 


Amygdala. 


Nodule.     Fourth  ventricle. 


Fig.  366. — Sagittal  section  of  the  cerebellum,  near  the  point  of  junction  of  the  worm  with  the  hemisphere. 
(Schafer.) 

The  middle  peduncles  are  the  largest  of  the  three  pairs.  They  consist  of  a 
mass  of  curved  fibres,  which,  as  already  described,  comprises  most  of  the  trans- 
verse fibres  of  the  pons.  They  enter  the  cerebellum  between  the  margins  of  the 
great  horizontal  fissure  at  the  anterior  notch,  and  the  fibres  spread  out  in  all 
directions  :  some  passing  to  the  upper  part,  and  some  to  the  lower  part  of  the  hemi- 
sphere, while  others  pass  to  its  middle  region.  Of  the  fibres  contained  in  the 
middle  peduncles  many  are  commissural  between  the  two  hemispheres  of  the  cere- 
bellum ;  others  apparently  end  in  the  grav  matter ;  others  have  been  described  as 
giving  fibres  to  the  posterior  longitudinal  bundle,  and  through  it  to  the  nuclei  of 
the  third,  fourth,  and  six  nerves.  Cajal  describes  still  another  set,  which  have 
their  origin  in  the  gray  reticular  formation  of  the  pons,  and  which  pass  partly  into 
the  peduncle  of  the  same  side  and  partly  into  that  of  the  opposite  side. 

The  inferior  peduncles  connect  the  cerebellum  with  the  medulla  oblongata.  As 
the  restiform  bodies  of  the  latter,  they  will  be  described  in  the  sequel.  They  pass 
upward  and  outward,  forming  part  of  the  lateral  wall  of  the  fourth  ventricle,  and 


THE   HIND-BRAIN. 


691 


enter  the  cerebellum  beneath  the  middle  peduncle ;  passing  upward  they  end  in 
the  gray  cortex  of  the  upper  surface  of  the  hemisphere,  some  being  prolonged  into 
the  white  matter  of  the  superior  vermiform  process.  The  following  are  the  chief 
sets  of  fibres  in  the  inferior  peduncles :  (1)  from  the  direct  cerebellar  tract  of  the 
spinal  cord ;  (2)  from  the  gracile  and  cuneate  nuclei  (crossed  and  uncrossed  fibres) ; 
(3)  from  the  opposite  olivary  body  of  the  medulla ;  (4)  fibres  to  the  nuclei  of  the 
fifth,  eighth,  ninth,  and  tenth  nerves ;  (5)  descending  cerebellar  fibres  which  pass 
down  the  restiform  body  and  anterolateral  column  of  the  cord  to  terminate  around 
the  cells  in  the  anterior  horn  of  the  cord. 

The  fibrae  propria  of  the  cerebellum  are  of  two  kinds  :  (1)  commissural  fibres, 
which  cross  the  middle  line  to  connect  the  opposite  halves  of  the  cerebellum,  some 
at  the  anterior  part,  and  others  at  the  posterior  part  of  the  vermiform  process ;  (2) 
arcuate  or  association  fibres,  which  connect  adjacent  laminae  with  each  other. 

The  gray  matter  of  the  cerebellum  is  found  in  two  situations :  (1)  on  the 
surface,   forming  the  cortex  ;  (2)  as  independent  masses  in  the  interior. 

1.  The  gray  matter  of  the  cortex  presents  a  characteristic  foliated  appearance, 
due  to  the  series  of  laminae  which  are  given  off  from  the  central  white  matter ;  these 
in  their  turn  give  off  secondary  laminae,  which  are  covered  with  gray  matter.    This 


Fig.  367. — Diagrammatic  representation  of  the  cells  of  the  cerebellum, 
ogy.")    A,  molecular  layer  ;  B,  nuclear  layer  ;  C,  white  matter. 


Punctated 

molecular 

layer. 


(Modified  from  Foster's  "  Physiol- 


arrangement  gives  to  the  cut  surface  of  the  organ  a  foliated  appearance  (Fig.  366). 
Externally,  the  cortex  is  covered  by  pia  mater;  internally,  is  the  medullary  centre, 
consisting  mainly  of  nerve-fibres.       » 

Microscopic  Appearance  of  the  Cortex. — The  cortex  presents  a  remarkable 
structure,  consisting  of  two  distinct  layers,  viz.,  an  external  gray  molecular  layer, 
and  an  internal,  rust-colored,  granular  layer.  Between  the  two  layers  is  an  incom- 
plete stratum  of  the  characteristic  cells  of  the  cerebellum,  the  corpuscles  of 
Purkinje. 

The  external  gray  or  molecular  layer  (Figs.  367,  368)  consists  of  fibres  and  cells. 
The  nerve-fibres  are  delicate  fibrillae,  and  are  derived  from  the  following  sources : 
(a)  the  dendrites  and  axon  collaterals  of  Purkinje's  cells;  (6)  fibres  from  cells  in 
the  granular  layer  ;  (c)  fibres  from  the  central  white  substance  of  the  cerebellum  ; 
(d)  fibres  derived  from  cells  in  the  molecular  layer  itself.  In  addition  to  these  are 
other  fibres,  which  have  a  vertical  direction.  These  are  the  processes  of  large 
glia-cells,  situated  in  the  granular  layer.  They  pass  outward  to  the  periphery  of 
the  gray  matter,  where  they  expand  into  little  conical  enlargements,  which  form 


692 


THE  NERVOUS  SYSTEM. 


a  sort  of  limiting  membrane  beneath  the  pia  mater,  analogous  to  the  membrana 
limitans  interna  in  the  retina,  formed  by  the  fibres  of  Miiller. 

The  cells  of  the  molecular  layer  are  small,  and  are  arranged  in  two  strata,  an. 
outer  and  an  inner.  They  all  possess  branching  axis-cylinder  processes ;  those  of 
the  inner  layer  run  for  some  distance  horizontally,  i.  e.,  parallel  with  the  surface  of 
the  folia,  giving  oif  at  intervals  collaterals,  which  pass  in  a  vertical  direction 
toward  the  cell-bodies  of  Purkinje's  coi*puscles,  around  which  they  become  enlarged, 
and  ramify  like  a  basket.  Hence  these  cells  of  the  inner  layer  are  named  basket- 
cells. 

The  corpuscles  of  Purhinje  (Fig.  368)  are  flask-shaped  cells,  situated  at  the 
junction  of  the  molecular  and  granular  layers,  their  bases  resting  against  the  latter.. 


External  gray  or 
cellular  layer. 


Corpuscles  of  Purkinje. 


—  White  substance. 

Fig.  368.— Vertical  section  through  the  gray  matter  of  the  human  cerebellum.    Magnified  about  100  diam- 
eters.   (Klein  and  Noble  Smith.) 

From  the  bottom  of  the  flask  the  axis-cylinder  process  arises ;  this  passes  through 
the  granular  layer,  and,  becoming  medullated,  is  continued  as  a  nerve-fibre  in  the 
medullary  substance  beneath.  This  axon  gives  off  fine  collaterals  as  it  passes 
through  the  granular  layer,  some  of  which  run  back  into  the  molecular  layer. 
From  the  neck  of  the  flask  numerous  dendrites  are  given  off,  which  branch  in  an 
antler-like  manner  in  the  molecular  layer  and  terminate  in  free  extremities. 

The  internal  rust-colored  or  granular  layer  (Fig.  368)  is  characterized  by  con- 
taining numerous  small  nerve-cells  or  granules  of  a  reddish-brown  color,  together 
with  many  nerve-fibrils.     Most  of  the  cells  are  nearly  spherical  and  provided  with 


THE   MEDULLA    OBLONGATA.  693 

:short  dendrites,  which  spread  out  in  a  spider-like  manner  in  the  granular  layer. 
Their  axons  pass  outward  into  the  molecular  layer,  and,  bifurcating  at  right  angles, 
Tun  horizontally  for  some  distance.  In  the  outer  part  of  the  granular  layer  are 
also  to  be  observed  some  larger  cells,  of  the  type  termed  Golgi  cells  (Fig.  367). 
Their  axons  undergo  frequent  division  as  soon  as  they  leave  the  nerve-cells,  and 
pass  into  the  granular  layer,  while  their  dendrites  ramify  chiefly  in  the  molecular 
layer. 

Finally,  in  the  gray  matter  of  the  cerebellar  cortex  fibres  are  to  be  seen  which 
come  from  the  white  centre  and  penetrate  the  cortex.  The  cell  origin  of  these 
fibres  is  unknown,  though  it  is  believed  that  it  is  probably  in  the  gray  matter  of 
the  spinal  cord.  Some  of  these  fibres  end  in  the  granular  layer,  by  dividing  into 
numerous  branches,  on  which  are  to  be  seen  peculiar  moss-like  appendages  ;  hence 
they  have  been  termed  by  Ramon  y  Cajal  the  "  moss  fibres"  ;  they  form  an  arbor- 
escence  around  the  cells  of  the  granular  layer.  Other  fibres  derived  from  the 
medullary  centre  can  be  traced  into  the  molecular  layer,  where  their  branches 
cling  around  the  dendrites  of  Purkinje's  cells,  and  hence  they  have  been  named 
the  clinging  or  tendril  fibres. 

2.  The  independent  centres  of  gray  matter  in  the  cerebellum  are  four  in  number 
on  each  side  :  one  is  of  large  size,  and  is  known  as  the  corpus  dentatum  ;  the  other 
three,  much  smaller,  are  situated  near  the  middle  of  the  cerebellum,  and  are  known 
as  the  nucleus  emboliformis,  nucleus  globosus,  and  nucleus  fastigii. 

The  corpics  dentatum  or  ganglion  of  the  cerebellum  is  situated  a  little  to  the 
inner  side  of  the  centre  of  the  stem  of  the  white  matter  of  the  hemisphere.  It 
consists  of  an  irregularly  folded  lamina  of  a  grayish-yellow  color,  containing  white 
fibres,  and  presenting  on  its  antero-internal  aspect  an  opening,  the  hilum,  from 
which  most  of  the  fibres  of  the  superior  cerebellar  peduncle  emerge. 

The  nucleus  emboliformis  is  a  mass  of  gray  matter  placed  immediately  to  the 
inner  side  of  the  corpus  dentatum,  and  partly  covering  its  hilum.  The  nucleus 
globosus  is  an  elongated  mass  of  gray  matter,  directed  antero-posteriorly,  and 
placed  to  the  inner  side  of  the  preceding.  The  nucleus  fastigii  is  somewhat  larger 
than  the  other  two,  and  is  situated  close  to  the  middle  line  at  the  anterior  end  of 
the  superior  vermiform  process,  and  immediately  over  the  roof  of  the  fourth  ven- 
tricle, from  which  it  is  separated  by  a  thin  layer  of  white  matter.  It  is  known  as 
the  roof  nucleus  of  Stilling. 

Weight  of  the  Cerebellum. — Its  average  weight  in  the  male  is  about  5  oz.,  4  drs. 
It  attains  its  maximum  weight  between  the  twenty-fifth  and  fortieth  years,  its 
increase  in  weight  after  the  fourteenth  year  being  relatively  greater  in  the  female 
than  in  the  male.  The  proportion  between  the  cerebellum  and  cerebrum  is,  in  the 
male,  as  1  to  8-^-,  and  in  the  female  as  1  to  8.  In  the  infant  the  cerebellum  is 
proportionately  much  smaller  than  in  the  adult,  the  relation  between  it  and  the  cere- 
brum being,  according  to  Chaussier,  between  1  to  13,  and  1  to  26  ;  by  Cruveilhier 
the  proportion  was  found  to  be  1  to  20. 

V.  The  Medulla  Oblongata  (Fig.  370). 

The  medulla  oblongata'  or  metencephalon,  known  also  as  the  spinal  bulb,  is 
the  lowest  division  of  the  encephalon,  and  is  continuous  with  the  spinal  cord. 
It  is  developed  from  the  fifth  cerebral  vesicle,  the  cavity  of  which  forms  the  lower 
half  of  the  fourth  ventricle.  It  extends  from  the  lower  margin  of  the  pons  Varolii 
to  a  plane  passing  transversely  just  below  the  decussation  of  the  pyramids,  at  which 
level  the  spinal  cord  commences.  This  plane  corresponds  to  the  lower  margin  of 
the  foramen  magnum.  The  upper  limit  of  the  medulla  is  marked  off  from  the  pons 
Varolii  on  its  ventral  aspect  by  the  abrupt  lower  margin  of  the  latter. 

The  medulla  oblongata  is  directed  from  above  obliquely  downward  and  back- 
ward ;  its  ventral  surface  rests  on  the  basilar  groove  of  the  occipital  bone,  while 
its  dorsal  surface  is  received  into  the  fossa  between  the  hemispheres  of  the  cere- 
bellum, and  forms  the  lower  part  of  the  floor  of  the  fourth  ventricle.     It  is  pyramidal 


694 


THE   NERVOUS  SYSTEM. 


Middle 
peduncle  of 
cerebellum. 


Fig.    369.— Medulla    oblongata    and    pons 
Varolii.    Anterior  surface. 


in  shape,  its  broad  extremity  directed  upward,  its  lower  end  being  narrow  at  its 
point  of  connection  with  the  cord.  It  measures  an  inch  in  length,  three-quarters 
of  an  inch  in  breadth  at  its  wi.dest  part,  and  half  an  inch  in  thickness.  Its  surface 
is  marked,  in  the  median  line,  in  front  and  behind,  by  an  anterior  and  a  posterior 

median  fissure,  which  are  continuous  with 
similar  fissures  on  the  anterior  and  posterior 
surfaces  of  the  cord.  The  anterior  fissure 
contains  a  fold  of  pia  mater,  and  terminates 
just  below  the  pons  in  a  cul-de-sac,  the. fora- 
men eoscum  of  Vicq  d'Azyr.  It  is  inter- 
rupted at  its  lower  part  by  some  bundles  of 
fibres,  which  cross  obliquely  from  one  side 
to  the  other,  forming  the  decussation  of  the 
pyramids.  The  posterior  is  a  deep  but  nar- 
row fissure,  continued  upward  to  about  the 
middle  of  the  medulla,  where  it  expands  into- 
the  fourth  ventricle. 

These  two  fissures  divide  the  medulla  into 
two  symmetrical  halves,  each  half  presenting 
elongated  eminences,  which  are  continuous 
with  the  columns  of  the  cord.  By  taking" 
the  lines  along  which  some  of  the  cranial 
nerves  emerge  from  the  medulla,  as  land- 
marks, the  surface  of  this  portion  of  the 
nervous  system  may  be  divided  into  three  columns,  in  the  same  way  as  the  spinal 
cord  is  divided  into  three  columns  by  the  lines  corresponding  to  the  points  of  exit  of 
the  anterior  and  posterior  roots  of  the  spinal  nerves.  The  anterior  column  com- 
prises that  portion  which  is  situated  between  the  anterior  median  fissure  and  the 
fibres  of  origin  of  the  hypoglossal  nerve  :  this  column  is  called  the  pyramid.  The 
lateral  column  comprises  that  portion  which  is  situated  between  the  fibres  of  origin 
of  the  hypoglossal  nerve  and  the  fibres  of  origin  of  the  glosso-pharyngeal,  pneu- 
mogastric,  and  spinal  accessory  nerves.  In  the  lower  part  of  the  medulla  this 
column  is  single,  and  is  called  the  lateral  tract ;  but  in  the  upper  part  an  oval- 
shaped  body  comes  forward  between  it  and  the  pyramid,  and  pushes  aside  the 
lateral  tract.  This  is  called  the  olivary  body.  The  posterior  column  comprises 
that  portion  which  is  situated  between  the  fibres  of  the  origin  of  the  glosso-pharyn- 
geal, pneumogastric,  and  spinal  accessory  nerves  and  the  posterior  median  fissure. 
It  is  marked  by  slight  furrows  dividing  it  into  smaller  columns,  and  these  in  the- 
lower  part  of  the  medulla  are  named,  from  without  inward,  the  funiculus  of 
Rolando,  the  funiculus  cuneatus,  and  the  funiculus  gracilis  ;  in  the  upper  part 
of  the  medulla,  the  funiculus  of  Rolando  and  the  funiculus  cuneatus  appear 
to  become  fused  together,  forming  a  single  bodv,  called  the  restiform  body 
(Fig.  370). 

The  pyramids  are  two  pyramidal  bundles  of  white  matter,  placed  one  on  either 
side  of  the  anterior  median  fissure,  and  separated  from  the  olivary  body  by  a  slight 
depression,  from  which  the  roots  of  the  hypoglossal  nerve  emerge.  At  the  lower 
border  of  the  pons  these  bodies  are  somewhat  constricted  and  are  here  crossed 
by  a  band  of  arched  fibres,  the  ponticidus  of  Arnold ;  below  this  they  become 
enlarged,  and  then  taper  as  they  descend  to  their  lower  extremity.  The  fibres  of 
which  these  pyramids  are  composed  may  be  arranged  in  two  bundles :  an  outer, 
continuous  below  with  the  direct  pyramidal  tract  of  the  anterior  column  of  the 
same  side  of  the  spinal  cord,  and  an  inner,  continuous  with  the  crossed  pyramidal 
tract  of  the  lateral  column  of  the  opposite  side  of  the  cord.  As  will  be  subse- 
quently mentioned,  the  direct  pyramidal  tract  in  the  cord  lies  next  to  the  anterior 
median  fissure,  but  as  the  crossed  pyramidal  tract  of  the  cord  ascends  to  the 
medulla  it  decussates  with  its  fellow  of  the  opposite  side  across  the  anterior  median 
fissure,  and  so  displaces  la ter^l^hje_dirxxit- pyramidal  tract,  and  ascends,  after  decus- 


THE   MEDULLA     OBLONGATA. 


695 


Restiform  body. 

Clava. 

Cuneate  tubercle. 


sation,  through  the  medulla  to  its  inner  or  mesial  side.      This  decussation  is  usually 

spoken  of  as  the  decussation  of  the 'pyramids,  but  it  must  be  borne  in  mind  that  it  is 

only  a  portion  of  the  fibres  of  the  pyramid  which 

decussate ;  namely,  those  derived  from  the  crossed 

pyramidal  tract  of  the  cord ;  the  outermost  fibres, 

derived  from  the  anterior  column  of  the  cord, 

do  not  decussate.     Each  pyramid    enters    the 

substance  of  the  pons  in  one  bundle,  and  may 

be  traced  through  it,   after    breaking  up  into 

several  smaller  fasciculi,  into  the  corresponding 

crus  cerebri. 

The  lateral  column,  in  the  lower  part  of  the 
medulla,  is  of  the  same  width  as  the  lateral 
column  of  the  cord,  and  appears  on  the  surface 
to  be  a  direct  continuation  of  it.  As  a  matter 
of  fact  it  is  only  a  part  of  the  lateral  column  of 
the  spinal  cord  which  is  continued  upward  into 
this  column;  for  the  crossed  pyramidal  tract 
passes  into  the  pyramid  of  the  opposite  side, 
and  the  direct  cerebellar  tract  of  the  lateral 
column  of  the  cord  passes  into  the  restiform 
body.  The  rest  of  the  lateral  column  of  the 
cord,  that  is  to  say,  the  antero-lateral  ground 
bundle  and  the  antero-lateral  cerebellar  tract, 
can  be  traced  upward  into  this  area.  In  the 
upper  part  of  the  medulla,  the  lateral  tract, 
on  account  of  the  interpolation  of  the  olivary 
body,  becomes  almost  concealed  by  this  body. 

The  olivary  body  is  a  prominent  oval  mass, 
situated  on  the  outer  side  of  the  pyramid,  from 
which  it  is  separated  by  a  slight  groove,  along 
which  the  fibres  of  the  hypoglossal  nerve 
emerge.  It  is  separated  externally  from  the 
restiform  body  by  a  longitudinal,  narrow  band  of  fibres,  prolonged  upward  from 
the  lateral  tract,  and  by  a  groove,  from  which  the  glosso-pharyngeal,  pneumo- 
gastric,  and  spinal  accessory  nerves  arise.  It  is  equal  in  breadth  to  the  pyramid; 
it  is  broader  above  than  below,  and  is  about  half  an  inch  in  length,  being  separated 
above  from  the  pons  Varolii  by  a  slight  depression,  in  which  a  band  of  arched 
fibres  is  sometimes  to  be  seen.  Numerous  white  fibres  {superficial  arciform  fibres) 
are  seen  winding  across  the  lower  half  of  the  pyramid  and  the  olivary  body  to 
enter  the  restiform  body. 

The  funiculus  of  Rolando  is  a  longitudinal  prominence  on  the  outer  side  of  the 
lateral  tract.  It  begins  at  the  lower  end  of  the  medulla  by  a  tapering  extremity, 
and  has,  apparently,  no  corresponding  column  in  the  cord.  It  gradually  enlarges 
as  it  ascends,  and  forms,  at  a  level  with  the  lower  border  of  the  olivary  body,  a 
considerable  prominence,  known  as  the  tubercle  of  Rolando.  This  is  caused  by 
the  substantia  gelatinosa  of  Rolando  of  the  cord  gradually  finding  its  way  to  the 
surface,  so  as  to  form  a  prominence  there.  About  half  an  inch  below  the  pons  the 
funiculus  of  Rolando  appears  to  blend  with  the  funiculus  cuneatus.  In  front,  it  is 
separated  from  the  lateral  tract  by  a  distinct  groove,  the  continuation  upward  of 
the  postero-lateral  groove  of  the  cord ;  behind,  the  separation  from  the  funiculus 
cuneatus  is  much  less  distinct. 

The  funiculus  cuneatus  is  the  direct  continuation  upward  of  the  postero-lateral 
column  (tract  of  Burdach)  of  the  cord.  It  is  situated  between  the  funiculus  of 
Rolando  and  the  funiculus  gracilis.  It  enlarges  as  it  ascends,  and  forms,  opposite 
the  lower  extremity  of  the  fourth  ventricle,  a  slight  eminence  or  enlargement,  the 


^!S& 


.1  fea 


Fig.  370.— Posterior  surface  of  the  me- 
dulla oblongata. 


696  THE  NERVOUS  SYSTEM. 

cuneate  tubercle,  which  is  best  marked  in  children.  Above  this  point  it  disappears 
from  the  surface. 

The  funiculus  gracilis  is  the  direct  continuation  upward  of  the  postero-median 
column  of  the  cord  (tract  of  Groll).  It  is  a  narrow  white  band,  placed  parallel  to 
and  along  the  side  of  the  posterior  median  fissure.  It  is  separated  from  the 
funiculus  cuneatus  by  a  slight  groove,  continuous  with  that  on  the  surface  of  the 
cord,  which  marks  off  the  postero-median  column.  At  first  the  funiculi  of  the 
two  sides  lie  in  close  contact  on  either  side  of  the  posterior  median  fissure.  Oppo- 
site the  apex  of  the  fourth  ventricle  each  presents  an  enlargement,  the  clava ; 
they  then  diverge  and  form  the  lateral  boundaries  of  the  lower  part  of  the  fourth 
ventricle,  and  gradually  tapering  off  become  no  longer  traceable. 

The  Restiform  Body. — The  upper  part  of  the  posterior  area  of  the  medulla  is 
occupied  by  the  restiform  body.  It  appears,  at  first  sight,  as  if  this  body  were  the 
direct  continuation  upward  of  the  funiculus  cuneatus  and  the  funiculus  of  Rolando, 
and  it  was  formerly  described  as  such.  This,  however,  is  not  so,  for  the  restiform 
body  is  largely  formed  by  a  set  of  fibres,  the  •external  arcuate  fibres,  which  issue 
from  the  anterior  median  fissure  and  will  presently  be  described.  '  They  pass 
laterally  over  the  pyramid  and  olive,  and  assist  in  forming  the  restiform  body. 
There  is  also  a  narrow  strand  of  fibres,  derived  from  the  lateral  column  of  the 
cord,  the  direct  cerebellar  tract,  which  joins  the  above-mentioned  arcuate  fibres. 
These  two  sets  of  fibres,  reinforced  by  the  internal  arcuate  fibres  from  the  opposite 
side  of  the  medulla,  form  the  restiform  body. 

The  restiform  bodies  are  the  largest  prominences  of  the  medulla,  and  are 
placed  between  the  lateral  tracts  in  front  and  the  funiculus  cuneatus  behind,  from 
both  of  which  they  are  separated  by  slight  grooves.  As  they  ascend  they  diverge 
from  each  other,  assist  in  forming  the  lower  part  of  the  lateral  boundaries  of  the 
fourth  ventricle,  and  then  enter  the  corresponding  hemisphere  of  the  cerebellum, 
forming  its  inferior  peduncles. 

The  posterior  surface  of  the  medulla  oblongata  forms  part  of  the  floor  of  the 
fourth  ventricle.  This  portion  is  of  a  triangular  form,  bounded  on  each  side  by 
the  diverging  funiculi  graciles  and  cuneati  and  restiform  bodies.  The  divergence 
of  these  two  funiculi  and  of  the  restiform  bodies,  together  with  the  opening  out 
of  the  posterior  fissure  and  central  canal  of  the  spinal  cord,  displays  in  the  floor  of 
the  ventricle  the  gray  matter  of  the  medulla,  which  is  continuous  below  with  the 
gray  matter  of  the  cord.  In  the  middle  line  is  seen  a  longitudinal  furrow,  Avhich 
divides  this  part  of  the  ventricle  into  right  and  left  halves,  and  is  continuous 
below  with  the  central  canal  of  the  cord. 

The  arciform  or  arcuate  fibres,  Avhich  have  been  mentioned  as  forming  part  of 
the  restiform  body,  are  found  in  the  upper  half  of  the  medulla,  crossing  its  surface 
and  also  traversing  its  substance.  They  are  divided  for  purposes  of  description 
into  two  sets — external  and  internal.  The  external  or  superficial  arciform  fibres 
..have  already  been  alluded  to  as  crossing  the  pyramid  and  olivary  body  on  each 
side.  They  emerge  from  the  anterior  median  fissure,  and  if  traced  into  it  are 
found  to  enter  the  raphe'  and  cross  to  the  opposite  side,  after  which  their  further 
course  is  a  matter  of  some  doubt.  After  emerging  from  the  anterior  median 
fissure  they  cross  the  pyramid  and  olivary  body,  often  concealing  from  view  the 
upper  part  of  the  cuneate  and  Rolandic  funiculi,  and  enter  the  restiform  body. 
As  they  cross  the  olivary  body  they  are  reinforced  by  some  of  the  internal  arciform 
fibres,  which  come  to  the  surface  on  the  inner  side  of,  or  through,  this  structure. 
The  internal  arciform  fibres  are  described  with  the  microscopic  anatomy  of  the 
medulla. 

It  is  advisable,  at  this  stage,  to  take  up  the  consideration  of  the  cavity  of  the 
fourth  ventricle,  an  acquaintance  with  which  will  render  the  description  of  the 
internal  structure  of  the  medulla  oblongata  more  intelligible. 


THE  MEDULLA    0BL0NGA1A.  697 

The  Fourth  Ventricle  (Fig.  371). 

The  fourth  ventricle  is  lozenge-  or  diamond-shaped ;  that  is  to  say,  it  is  com- 
posed of  two  triangles,  with  their  bases  in  contact.  The  sides  of  the  lower  triangle 
are  formed  by  the  divergence  of  the  funiculi  graciles,  funiculi  cuneati,  and  resti- 
form  bodies  of  the  medulla  on  either  side.  As  these  columns  pass  upward  in  the 
medulla  they  turn  outward  from  the  median  line,  and,  diverging  from  each  other, 
form  the  lateral  boundaries  of  the  lower  half  of  the  fourth  ventricle.  In  like 
manner  the  sides  of  the  upper  triangle  are  formed  by  the  convergence  of  the 
superior  peduncles  of  the  cerebellum^  These  peduncles  are  separated  below  by  a 
somewhat  wide  interval,  but  as  they  pass  upward  and  forward  toward  the 
corpora  quadrigemina.  they  gradually  converge  and  ultimately  come  into  contact 
with  each  others  This  cavity  is  therefore  bounded  laterally  by  the  superior 
peduncles  of  the  cerebellum  in  its  upper  half,  and  by  the  funiculi  graciles,  the 
funiculi  cuneati,  and  the  restiform  bodies  in  its  lower  half.  It  presents  four 
angles.  The  upper  angle  reaches  as  high  as  the  upper  border  of  the'pon>s,  and 
corresponds  with  the  lower  opening  of  the  aqueduct  of  Sylvius,  by  which  this 
ventricle  communicates  with  the  third  ventricle^  The  lower  angle  is  on  a  level 
with  the  lower  border  of  the  olivary  body,  and  is  continuous  with  the  central 
canal  of  the  spinal  cord.  From  the  resemblance  that  it  bears  to  the  point  of  a 
writing  pen  it  has  been  named  the  calamus  scriptorius.  Its  lateral  angles  extend 
for  some  distance  between  the  medulla  and  the  cerebellum,  each  forming  a  pointed 
lateral  recess. 

The  roof  of  the    fourth  ventricle    is    formed    from   above    downward  by  the 
following    structures :    a   part  of  the   superior  peduncles  of  the   cerebellum,  the 
superior  medullary  velum\  the  inferior  medullary  velumi,  the  tela  choroidea  inferior,  j^  ' 
the  obex,  and  the  ligula. 

The  superior  peduncles  of  the  cerebellum,  when  they  emerge  from  the  medullary 
substance  of  its  hemispheres,  pass  upward  and  forward,  forming  the  lateral 
boundaries  of  the  upper  half  of  the  fourth  ventricle,  but,  converging  as  they 
approach  the  corpora  quadrigemina,  the  mesial  portions  of  the  peduncles  form  a 
part  of  the  roof  of  the  cavity,  in  consequence  of  the  ventricle  extending  to  a 
slight  extent  underneath  the  peduncles. 

The  Superior  Medullary  Velum  (Valve  of  Vieussens). — In  the  angular  interval 
left  between  the  two  superior  peduncles  is  a  thin  lamina  of  white  matter,  con- 
tinuous with  the  white  centre  of  the  cerebellum,  which  bridges  across  from  one 
peduncle  to  the  other,  and  so  completes  the  roof  of  the  superior  part  of  the 
ventricle.  \  This  is  the  superior  medullary  velum,  or  valve  of  Vieussens.  Its  dorsal 
surface  is  covered  by  the  folia  of  the  lingula,  already  described  (page  686). 

The  inferior  medullary  velum  is  a  thin  layer  of  white  substance,  prolonged 
from  the  white  centre  of  the  medulla  on  either  side  of  the  nodule,  which  assists  in 
forming  a  part  of  the  roof  of  the  fourth  ventricle,  stretching  over  it  toward  its 
lateral  angles.  It  is  continuous  with  the  white  substance  of  the  cerebellum  by 
its  convex  edge,  while  its  thin  concave  margin  is  apparently  free.  In  reality, 
however,  it  is  continuous  with  the  epithelium  of  the  ventricle,  which  is  prolonged 
downward  from  the  velum  to  the  edge  of  the  ligula. 

The  tela  choroidea  inferior  is  a  layer  of  pia  mater,  which  covers  in  the  lower 
part  of  the  fourth  ventricle  below  the  inferior  medullary  velum.  Superiorly 
it  is  reflected  on  to  the  under  surface  of  the  cei-ebellum,  while  inferiorly  it  is 
continued  on  to  the  restiform  bodies  and  lower  part  of  the  medulla.  This  part  of 
the  roof  of  the  ventricle  contains  no  nervous  matter,  but  consists  merely  of  the 
ventricular  epithelium  covered  by  pia  mater.  The  tela  choroidea  inferior,  like  the 
superior,  really  consists  of  two  layers,  which  become  more  or  less  adherent,  viz., 
that  covering  the  under  surface  of  the  cerebellum  and  that  covering  the  epithelium. 
It  also  possesses  a  pair  of  choroid  plexuses,  which  project  into  the  ven- 
tricular cavity  invaginating  before  them  the  epithelial  lining.  Each  plexus  con- 
sists of  a  vertical  portion  which  extends   forward,  near  the  middle  line,  from  the 


698 


THE   NERVOUS   SYSTEM. 


foramen  of  Majendie,  and  of  a  transverse  part,  which  passes  outward  into  the  lateral 
recess  of  the  ventricle  as  far  as  the  foramina  of  Key  and  Retzius.  The  two 
plexuses  present  the  form  of  a  T,  the  vertical  limb  of  which  is,  however,  double, 
|(  .  The  tela  does  not  form  a  complete  membrane,  for  in  it  there  are  three 
openings,  one  in  the  middle  line  at  the  inferior  angle  of  the  ventricle,  just 
above  the  position  of  the  opening  of  the  central  canal  of  the  cord  ;  this  is  the  fora- 
men of  Majendie  :  the  other  two  are  at  the  extremities  of  the  lateral  recesses  of  the 
ventricle,  and  are  named  the  foramina  of  Key  and  Retzius  (see  page  642). 
Through  these  foramina  the  ventricles  of  the  brain  communicate  with  the 
subarachnoid  space. 

The  obex  is  a  thin  triangular  lamina  of  gray  matter,  continuous  below  with  the 
anterior  gray  commissure  of  the  cord,  which  fills  in  the  angle  between  the  two 
diverging  funiculi  graciles  for  a  short  distance. 

The  ligula  (tosnice)  are  narrow  bands  of  white  matter,  which  project  from  the 
internal  border  of  the  funiculi  graciles.     They  at  first  run  upward  and  forward, 


Locus  cseruleus. 
Fovea  superior. 


Trigonum  Jvypoglossi, 


Ala  cinerea.—A 


Corpora  quadrigemina. 

Processus  e  cerebello  ad  testes. 
Valve  of  Vieussens. 

Eminentia  teres. 

Conductor  sonorus. 
-Strise  acusticse. 

Trigonum  acustici. 
Clava. 

Tuberculum  cuneatum. 
Lateral  column. 


Fig.  371.— Floor  of  the  fourth  ventricle.    Diagrammatic. 

ana  then  turn  outward  over  the  restiform  bodies,  as  far  as  the  latera  recesses  of  the 
ventricle.  Their  inner  borders  are  continuous  with  the  epithelial  roof  of  the 
ventricle. 

The  floor  of  the  fourth  ventricle  (Fig.  371)  is  rhomboidal  in  shape,  and  is 
traversed  by  a  vertical  median  fissure,  the  sulcus  Jongitudinalis  medianus.  At  its 
widest  part,  opposite  the  level  of  the  lateral  recesses,  it  is  marked  by  some  trans- 
verse white  lines,  the  strice  medullaris  or  strice  acusticos.  These  consist  of  white 
fibres,  which  emerge  from  the  longitudinal  sulcus,  and  pass  outward  across  the  floor 
of  the  ventricle. 

These  striae  divide  the  floor  of  the  ventricle  into  two  triangles,  inferior  and 
superior.  The  inferior  triangle,  or  lower  half  of  the  floor,  presents  above  an 
angular  groove,  the  fovea  inferior,  the  apex  of  which  is  at  the  striae,  while  the  two 
limbs  diverge  below,  and  form  the  sides  of  a  triangular,  dark  area,  termed  the  ala 
cinerea,  which  becomes  elevated  into  a  prominence  below  (eminentia  cinerea). 
This  area  corresponds  with  the  nuclei  of  the  vagus  and  glossopharyn- 
geal nerves,  and  is  therefore  termed  the  trigonum  vagi.  A  second  triangular  area 
lies  between  the  inner  limb  of  the  fovea  and  the  median  sulcus  ;  its  base  is  directed 


THE  MEDULLA    OBLONGATA.  699 

upward,  and  limited  by  the  striae  medullaris.  It  is  termed  the  trigonum 
hypoglos-si,  because  it  corresponds  in  position  to  the  tract  of  nerve-cells  from  -which 
the  hypoglossal  nerve  takes  origin.  A  third  triangular  area  to  the  outer  side  of 
the  fovea  inferior,  is  named  the  trigonum  acustici.  It  lies  between  the  groove 
forming  the  outer  boundary  of  the  fovea  inferior  and  the  lateral  wall  of  the  ventricle, 
and,  like  the  trigonum  hypoglossi,  has  its  base  directed  upward.  Here  it  is  con- 
tinuous with  a  prominence,  the  tuberculum  acusticum,  which  extends  into  the  ante- 
rior part  of  the  floor  of  the  ventricle. 

The  superior  triangle,  or  upper  half  of  the  floor  of  the  fourth  ventricle,  i.  e.,  the 
part  above  the  striae  medullaris,  presents  in  the  middle  line  the  continuation  of 
the  median  longitudinal  sulcus.  On  either  side  of  this  is  a  spindle-shaped  longi- 
tudinal eminence,  prominent  in  its  centre,  but  less  so  above  and  below.  This  is 
the  eminentia  teres,  and  is  produced  by  an  underlying  bundle  of  white  fibres,  the 
funiculus  teres,  formed,  in  part  at  all  events,  by  the  fibres  of  the  facial  nerve. 
Immediately  above  and  to  the  outer  side  of  the  eminentia  teres  is  an  angular  de- 
pression, the  fovea  superior  ;  this  is  sometimes  crossed  by  a  whitish  band  of  fibres, 
the  conductor  sonorus,  which  is  connected  below  with  the  striae  medullaris.  Above 
the  fovea  is  a  bluish  depressed  area,  the  locus  cceruleus.  Its  color  is  due  to  some 
pigmented  nerve-cells,  showing  through  the  white  covering  of  the  floor.  These  pig- 
mented cells  are  named  the  substantia  ferruginosa,  and  in  them  one  of  the  roots  of 
the  fifth  nerve  terminates. 

The  lining  membrane  of  the  fourth  ventricle  is  continuous  above  with  that  of 
the  third,  through  the  aqueduct  of  Sylvius,  and  below  with  that  of  the  central 
canal  of  the  spinal  cord.  The  cavity  of  the  ventricle  communicates  below  with  the 
subarachnoidean  space  by  means  of  the  foramen  of  Majendie  and  the  foramina  of 
Key  and  Retzius,  already  described. 


Internal  Structure  of  the  Medulla  Oblongata  (Fig.  372). 

If  the  cranial  nerves  emerging  from  the  medulla  are  traced  into  its  substance, 
it  will  be  seen  that  they  divide  each  half  into  three  wedge-shaped  areas,  Avhich  are 
named  the  anterior,  lateral,  and  posterior  areas  of  the  medulla,  and  each  of  which 
corresponds  to  one  of  the  subdivisions  already  described  on  the  surface  of  this  por- 
tion of  the  encephalon. 

The  anterior  area  comprises  that  portion  which  is  situated  between  the  anterior 
median  fissure  and  the  fibres  of  origin  of  the  hypoglossal  nerve.  On  the  surface 
of  the  medulla  this  area  corresponds  to  the  pyramid. 

The  lateral  area  is  situated  between  the  fibres  of  origin  of  the  hypoglossal  nerve 
on  the  one  hand,  and  the  fibres  of  the  glosso-pharyngeal,  pneumogastric,  and  spinal 
accessory  nerves  on  the  other.  On  the  surface  of  the  medulla,  in  its  lower  part, 
this  area  is  single,  and  is  called  the  lateral  tract ;  but  in  the  upper  part  an  oval- 
shaped  body,  the  olivary  body,  comes  forward  between  it  and  the  pyramid,  pushing 
aside  the  lateral  tract. 

The  posterior  area  comprises  that  portion  which  is  situated  between  the  fibres 
of  origin  of  the  glosso-pharyngeal,  pneumogastric,  and  spinal  accessory  nerves,  and 
the  posterior  median  fissure.  On  the  surface  of  the  medulla  this  area  is  marked 
by  slight  furrows,  splitting  it  up  into  smaller  columns ;  those  in  the  lower  part  of 
the  medulla  are  named,  from  without  inward,  the  funiculus  of  Rolando,  the  funic- 
ulus cuneatus,  and  the  funiculus  gracilis ;  in  the  upper  part  of  the  medulla  they 
are  replaced  by  the  restiform  body.  Finally,  the  halves  of  the  medulla  are  sepa- 
rated from  each  other  by  a  median  septum  or  raphe'. 

Each  of  these  three  areas  is  made  up  of  gray  and  white  matter,  the  former 
"being  derived  for  the  most  part  from  that  of  the  cord.  In  like  manner  the  white 
matter  is  partly  made  up  of  longitudinal  fibres  continuous  with  those  of  the  cord, 
and  partly  of  transverse  fibres  which  intersect  them. 

In  order  to  understand  the  internal  structure  of  the  medulla,  it  is  necessary  to 


700 


THE  NERVOUS  SYSTEM. 


describe  the  appearances  as  they  are  seen  in  the  upper  and  lower  portions  of  the 
medulla,  since  they  differ  considerably  in  these  two  parts. 

The  Lower  Part  of  the  Medulla. — The  first  change  in  the  internal  structure  is 
caused  by  the  passage  of  the  fibres  of  the  crossed  pyramidal  tract  obliquely 
through  the  gray  matter  of  the  anterior  horn.  As  stated  above,  the  pyramid  is 
composed  of  fibres  derived  from  the  direct  pyramidal  tract  of  the  anterior  column 
of  the  cord  of  the  same  side,  and  from  the  crossed  pyramidal  tract  of  the  lateral 
column  of  the  opposite  half  of  the  cord.  Those  fibres  which  are  derived  from  the 
direct  pyramidal  tract  and  which  in  the  cord  lie  close  to  the  median  fissure  are  in 
the  medulla  placed  to  the  outer  side  of  the  pyramid,  being  pushed  aside,  as  it 
wTere,  by  the  interpolation  of  the  fibres  derived  from  the  crossed  pyramidal  tract, 
which  are  much  more  numerous.  The  crossed  pyramidal  fibres  ascend  from  the 
lateral  column  of  the  spinal  cord,  and,  passing  through  the  anterior  gray  cornu 
and  across  the  middle  line,  form  the  inner  part  of  the  pyramid.  In  consequence 
of  this  passage  of  white  fibres  through  its  substance  the  anterior  gray  cornu  is 


Nucleus  of  funiculus  teres. 


Nucleus  ambig. 

Baphe. — 
Formatio  reticularis-. — 


Continuation  of  antero- 
lateral ground-bundle 


Accessory  olivary  nuclei 


Vagus  nuclei 
Hypoglossal 


Ligula. 


Funiculus  Solitarius. 
Nucleus  gracilis. 

^Nucleus  cuneatus. 


Qorpus  restiforme. 

Nucleus  of  Rolando 

Ascending  root  of 
fifth  nerve. 


Vagus  root. 

""Arciform  fibres. 
"^Nucleus  lateralis. 


Olivary  nucleus. 


Hypoglossal  nerve. 
Nucleus  of  ext.  arc.  fibres. 
"External  arciform  fibres. 
Anterior  median  fissure. 

Fig.  372.— Section  of  the  medulla  oblongata  at  about  the  middle  of  the  olivary  body.    (Schwalbe.) 

broken  up  into  a  coarse  network,  while  one  portion  of  it,  the  caput  cornu,  is 
entirely  separated  from  the  rest ;  only  the  base  of  the  cornu  remains  intact,  close 
to  the  ventro-lateral  aspect  of  the  central  canal.  The  caput  cornu,  thus  separated, 
is  displaced  laterally,  and  comes  to  lie  close  to  the  caput  cornu  posterioris,  which 
has  also  shifted  its  position.  In  consequence  of  this  breaking  up  of  the  greater 
part  of  the  anterior  gray  cornu  by  white  fibres  a  coarse  network  is  formed  in  the 
anterior  and  lateral  areas  of  the  medulla,  which  is  named  the  formatio  reticu- 
laris. 

The  posterior  cornu  also  undergoes  somewhat  similar  changes.  It  becomes 
subdivided  by  the  passage  through  it  of  the  sensory  fibres  of  the  columns  of  Goll 
and  Burdach.  These  pass  across  to  the  opposite  anterior  area  of  the  medulla, 
where  they  are  seen  to  lie  immediately  on  the  dorsal  aspect  of  the  pyramids.  In 
their  passage  through  the  posterior  horns  of  gray  matter  the  latter  become  sub- 
divided, in  a  manner  somewhat  similar  to  what  has  been  seen  to  occur  in  the 
anterior  horns.     This  crossing  of  the  sensory  fibres  is  termed  the  superior  py 'ram- 


THE   MEDULLA    OBLONGATA.  701 

idol  or  sensory  decussation.  The  caput  cornu  is  displaced  outward,  so  as  almost  to 
reach  the  surface,  where  it  forms  a  projection,  the  funiculus  Rolando,  which 
enlarges  above  into  a  distinct  prominence,  the  tubercle  of  Rolando.  Above  the 
level  of  the  tubercle  of  Rolando  the  caput  cornu  is  separated  from  the  surface  by 
a  band  of  fibres,  termed  the  ascending  root  of  the  fifth  nerve,  and  by  the  external 
arcuate  fibres.  The  neck  of  the  cornu  becomes  broken  up  into  a  reticular  forma- 
tion by  the  decussation  of  the  columns  of  Goll  and  Burdach,  and  by  this  means 
the  caput  is  separated  from  the  rest  of  the  gray  matter.  The  base  of  the  cornu 
increases  in  size,  and,  as  the  central  canal  expands  into  the  fourth  ventricle, 
becomes  pushed  outward,  and  portions  of  it  extend  into  the  funiculi  graciles  and 
cuneati,  and  produce  externally  the  eminences  of  the  clava  and  cuneate  tubercle. 
A  third  portion  of  the  base  becomes  separated  from  the  rest,  and  is  placed  outside 
the  nucleus  of  the  funiculus  cuneatus.  This  is  called  the  accessory  cuneate  nucleus, 
and  is  supposed  to  be  a  continuation  upward  of  Clarke's  vesicular  column  of  the 
cord. 

The  Upper  Part  of  the  Medulla. — The  upper  part  of  the  medulla  comprises  the 
portion  which  enters  into  the  formation  of  the  floor  of  the  fourth  ventricle,  where, 
in  fact,  the  upper  end  of  the  central  canal  has  opened  out  into  this  cavity.  In 
this  region  the  formatio  reticularis  is  confined  chiefly  to  the  anterior  and  lateral 
areas.  In  the  ventral  portion  of  the  posterior  area  there  is  only  a  small  amount 
of  reticular  formation,  but  in  addition  to  this  there  are  individual  masses  of  cells 
scattered  among  the  longitudinal  fibres. 

The  formatio  reticularis  is  situated  in  the  medulla,  behind  the  pyramid  and 
olivary  body,  extending  laterally  as  far  as  the  restiform  bodies,  and  dorsally  to 
within  a  short  distance  of  the  floor  of  the  fourth  ventricle.  It  presents  a  peculiar 
reticulated  appearance,  from  which  it  derives  its  name,  and  which  is  due  to  the 
intersection  of  bundles  of  fibres  running  at  right  angles  to  each  other,  some  being 
longitudinal,  others  transverse.  The  formatio  reticularis  presents  a  different 
appearance  in  the  anterior  area  from  what  it  does  in  the  lateral  area.  In  the 
former  there  is  almost  an  entire  absence  of  nerve-cells  in  the  reticulated  network, 
and  hence  it  is  known  as  the  formatio  reticularis  alba ;  whereas,  in  the  lateral 
area,  the  nerve-cells  are  numerous,  and,  as  a  consequence,  this  part  is  known  as 
the  formatio  reticularis  grisea.  In  the  substance  of  the  formatio  reticularis  is  a 
small  nucleus  of  gray  matter.  It  is  situated  near  the  dorsal  aspect  of  the  hilum 
of  the  olivary  nucleus,  and  has  been  named  the  inferior  central  nucleus.  The 
fibres  of  the  formatio  reticularis  are  longitudinal  and  transverse.  In  the  anterior 
area  the  longitudinal  fibres  may  be  arranged  in  two  well-defined  sets :  (1)  one  set 
lies  immediately  behind  the  pyramid,  and  is  named  the  fillet  or  lemniscus.  The 
fibres  of  the  fillet  are  chiefly  derived  from  the  cells  of  the  gracile  and  cuneate 
nuclei,  and  may  therefore  be  regarded  as  relay  fibres  of  the  columns  of  Goll  and 
Burdach  of  the  spinal  cord,  which  terminate  in  synapses  around  the  cells  of  the 
gracile  and  cuneate  nuclei.  They  are  prolonged  inward  and  forward  across  the 
middle  line  forming  the  superior  pyramidal  or  sensory  decussation  (decussation  of 
the  fillet) ;  (2)  the  other  set  is  continued  from  the  antero-lateral  ground  bundle 
of  the  cord,  and  a  portion  of  these  fibres  forms  the  posterior  longitudinal 
bundle  already  referred  to  (page  695).  Both  these  sets  of  fibres  are  continued 
upward  into  the  pons  and  mid-brain.  The  longitudinal  fibres  of  the  reticular 
formation  in  the  lateral  area  are  not  arranged  in  distinct  bundles.  They 
are  derived  from  the  lateral  column  of  the  cord,  after  the  crossed  pyramidal 
tract  has  passed  over  to  the  opposite  side.  The  longitudinal  fibres  of  the  posterior 
area  are  merely  indeterminate  fibres  of  the  formatio  reticularis,  with  the  exception 
of  two  distinct  bundles,  which  may  be  regarded  as  ascending  roots  of  the  fifth  and 
vago-glosso-pharyngeal  nerves;  the  latter  is  termed  the  funiculus  solitarius. 

The  transverse  fibres  of  the  reticular  formation  are  the  arched  or  arcuate  fibres. 
The  external  arcif or m  fibres  have  already  been  described.  The  internal  arciform 
fibres  are  more  numerous  than  the  superficial  set ;  they  traverse  nearly  the  whole 
area  of  the  upper  half  of  the  medulla,  except  the  pyramid.     They  pass  from   the 


702  THE  NERVOUS  SYSTEM. 

raphe"  ;  some  become  superficial  and  join  the  external  arciform  fibres,  while  others 
remain  deep  and  pass  to  the  olivary  body,  the  restiform  body,  and  to  the  nuclei  of 
the  funiculus  cuneatus  and  funiculus  gracilis. 

Independent  Nuclei. — In  the  upper  part  of  the  medulla  are  several  independent 
nuclei  of  gray  matter,  which  may  be  divided  into  two  sets :  (1)  those  which  are 
traceable  from  the  gray  matter  of  the  spinal  cord ;  and  (2)  those  which  are  not 
represented  in  the  cord.  The  former  are  the  hypoglossal  nucleus,  the  nucleus  of 
the  funiculus  teres,  and  those  of  the  auditory,  glosso-pharyngeal,  vagus,  and  spinal 
accessory  nerves.  The  latter  are  the  nucleus  of  the  olivary  body  and  the  acces- 
sory olivary  nuclei.  In  addition  to  these,  small  collections  of  gray  matter  are  to 
be  found  in  the  median  septum  or  raphe". 

The  Hypoglossal  Nucleus. — The  base  of  the  anterior  horn,  which  in  the  lower 
part  of  the  medulla  was  situated  on  the  ventro-lateral  aspect  of  the  central  canal, 
now  approaches  the  floor  of  the  ventricle,  where  it  lies  close  to  the  median  sulcus 
under  the  funiculus  teres.  In  it  is  a  column  of  large  nerve-cells,  from  which  the 
roots  of  the  hypoglossal  nerve  are  derived.  It  is  accordingly  designated  the 
hypoglossal  nucleus. 

The  Auditory  Nuclei. — Toward  the  upper  part  of  the  medulla,  a  considerable 
tract  of  gray  matter  may  be  found  lying  immediately  beneath  that  portion  of  tin 
floor  of  the  fourth  ventricle  which  is  known  as  the  trigonum  acustici.  This  is  the 
dorsal  or  inner  auditory  nucleus,  and  it  lies  just  external  to  the  vago-glosso- 
pharyngeal  nucleus.  In  addition  to  this,  there  is  a  small  collection  of  nerve-cells 
on  the  ventral  surface  of  the  restiform  body,  between  the  two  roots  of  the  auditory 
nerve,  which  is  known  as  the  accessory  or  ventral  auditory  nucleus.  On  the  outer 
side  of  the  "restiform  body  is  a  mass  of  cells  associated  Avith  the  cochlear  root  of  the 
auditory  nerve.  This  mass  is  termed  the  lateral  acoustic  tubercle  or  ganglion 
radicis  cochlearis. 

Nuclei  of  the  Glosso-pharyngeal  and  Vagus  Nerves. — These  are  two  in  number, 
principal  and  accessory.  The  principal  nucleus  of  the  two  nerves  lies  beneath  that 
portion  of  the  floor  of  the  fourth  ventricle,  which  is  known  as  the  ala  cinerea  and 
fovea  inferior.  They  form  an  oblong  mass  of  gray  matter,  above  the  nucleus  of 
the  spinal  accessory  and  lateral  to  the  hypoglossal  nucleus.  The  accessory  nuclei 
are  situated  in  the  reticular  formation  of  the  posterior  area,  some  distance  from  the 
floor  of  the  fourth  ventricle.  They  consist  of  a  pear-shaped  mass  of  cells,  which 
is  connected  with  the  rest  of  the  gray  matter  by  a  sort  of  stalk  or  peduncle,  and 
was  formerly  known  as  the  nucleus  anibiguus. 

Nucleus  of  the  Spinal  Accessory  Nerve. — This  nucleus  consists  of  a  group  of 
cells,  which  is  situated  partly  in  the  lower  part  of  the  medulla  at  the  base  of  the 
posterior  horn  and  close  to  the  central  canal.  It  extends  upward,  lying  beneath 
the  lower  part  of  the  floor  of  the  fourth  ventricle  and  on  the  outer  side  of  the 
hypoglossal  nucleus. 

The  Nucleus  of  the  Olivary  Body. — When  the  olivary  body  is  cut  across,  it  is 
seen  to  be  covered  externally  by  white  fibres,  and  internally  to  consist  of  a  gray 
layer.  This  gray  layer  is  the  nucleus  of  the  olivary  body,  or,  as  it  is  sometimes 
called,  the  corpus  dentatum  of  the  olive.  It  is  composed  of  a  thin,  wavy  lamina, 
which  is  arranged  in  the  form  of  a  hollow  capsule,  open  at  its  upper  and  inner  part, 
and  presenting  a  zigzag  or  dentated  outline.  Microscopically  examined,  the 
olivary  nucleus  is  seen  to  consist  of  small  rounded  yellowish  nerve-cells  embedded 
in  a  matrix  of  neuroglia  and  fine  nerve-fibres.  White  fibres,  which  can  be  traced 
from  the  raphe",  and  are  probably  derived  from  the  opposite  olive,  enter  the 
interior  of  the  capsule  by  the  aperture  at  its  upper  or  inner  part,  constituting  the 
olivary  peduncle. 

The  fibres  of  the  olivary  peduncle  as  they  enter  the  body  diverge,  and  some 
are  lost  in  the  gray  matter  of  the  olivary  nucleus ;  others  pass  through  it,  and 
of  these  some  turn  backward  to  join  the  restiform  body,  and  pass  to  the  cerebellum 
as  internal  arcuate  fibres ;  while  others  pierce  the  white  matter  of  the  olivary  body 
and,  reaching  the  surface,  are  continued  to  the  restiform  body  as  external  arcuate 


THE   MEDULLA    OBLONGATA. 


703 


fibres.  The  fibres  of  the  olivary  peduncle  connect  the  olivary  nucleus  with  the 
cerebral  hemisphere  of  the  same  side.  The  nucleus  is  also  connected  to  the  anterior 
horn  of  the  same  side  of  the  cord ;  and  with  the  opposite  cerebellar  hemisphere 
through  the  internal  arcuate  fibres.  Removal  of  one  cerebellar  hemisphere  is 
followed  by  atrophy  of  the  opposite  olivary  nucleus. 

Accessory  Olivary  Nuclei. — Two  small  isolated  masses  of  gray  matter  are  to  be 
found,  one  on  the  mesial  and  the  other  on  the  dorsal  aspect  of  the  corpus  denta- 
tum.  These  are  the  mesial  and  lateral  accessory  olivary  nuclei.  They  are  con- 
nected with  the  restiform  body  by  some  of  the  internal  arcuate  fibres.  The  fibres 
of  the  hypoglossal  nerve,  as  they  traverse  the  bulb,  pass  between  the  mesial 
accessory  nucleus  and  the  chief  olivary  nucleus. 

The  Raphe. — The  raphe*  is  situated  in  the  middle  line  of  the  medulla,  above  the 
decussation  of  the  pyramids.  It  consists  of  nerve-fibres  intermingled  with  nerve- 
cells.  The  fibres  have  different  directions,  which  can  only  be  seen  in  suitable 
microscopic  sections,  thus :  1.  Some  are  antero-posterior ;  these  in  front  are  con- 
tinuous with  the  superficial  arciform  fibres.  2.  Some  are  longitudinal ;  these  are 
derived  from  the  arciform  fibres,  which  on  entering  the  raphe  change  their  direction 
and  become  longitudinal.  3.  Some  are  oblique ;  these  are  continuous  with  the 
deep  arciform  fibres  which  pass  from  the  raphe*. 

The  nerve-cells  of  the  raphe  are  multipolar  ;  some  are  connected  with  the 
antero-posterior  fibres,  others  with  the  superficial  arcuate  fibres. 


Fig.  373.— Side  view  of  the  brain  of  man,  showing  the  localization  of  various  functions.    (After  Ferrier.) 

I.  Centre  for  movements  of  opposite  leg  and  foot.  2,  3,  4.  Centres  for  complex  movements  of  the  arms  and  legs, 
as  in  swimming.  5.  Extension  forward  of  the  arm  and  hand.  6.  Supination  of  the  hand  and  flexion  of  the 
forearm.    7,  8.  Elevators  and  depressors  of  the  angle  of  the  mouth.    9,  10.  Movements  of  the  lips  and  tongue. 

II.  Retraction  of  the  angle  of  the  mouth.  12.  Movements  of  the  eves.  13,  13'.  Vision.  14.  Hearing,  a.b.c.d. 
Movements  of  the  wrists  and  fingers. 


Weight  of  the  Encephalon. — The  average  weight  of  the  brain  in  the  adult  male 
is  49|  oz.,  or  a  little  more  than  3  lbs.  avoirdupois ;  that  of  the  female  44  oz. ;  the 
average  difference  between  the  two  being  from  5  to  6  oz.  The  prevailing  weight 
of  the  brain  in  the  male  ranges  between  46  oz.  and  53  oz..  and  in  the  female 
between  41  oz.  and  47  oz.  In  the  male  the  maximum  weight  out  of  278  cases  was 
65  oz.,  and  the  minimum  weight  34  oz.     The  maximum  weight  of  the  adult  female 


704 


THE  NERVOUS  SYSTEM. 


brain,  out  of  191  cases,  was  56  oz.,  and  the  minimum  weight  31  oz.  According  to 
Luschka,  the  average  weight  of  a  man's  brain  is  1424  grammes  (about  45  oz.), 
of  a  woman's  1272  grammes  (about  41  oz.),  and,  according  to  Krause,  1570 
grammes  (about  48J  oz.)  for  the  male,  and  1350  (about  43  oz.)  for  the  female.  It 
appears  that  the  weight  of  the  brain  increases  rapidly  up  to  the  seventh  year,  more 
slowly  to  between  sixteen  and  twenty,  and  still  more  slowly  to  between  thirty  and 
forty,  when  it  reaches  its  maximum.  Beyond  this  period,  as  age  advances  and  the 
mental  faculties  decline,  the  brain  diminishes  slowly  in  weight,  about  an  ounce 
for  each  subsequent  decennial  period.     These  results  apply  alike  to  both  sexes. 


Fig.  374. — Top  view  of  the  brain  of  man,  showing  the  localization  of  various  functions.    (After  Ferrier.) 

I.  Centre  for  movements  of  opposite  leg  and  foot.  2,  3,  4.  Centres  for  complex  movements  of  the  arms  and  legs, 
as  in  swimming.  5.  Extension  forward  of  the  arm  and  hand.  6.  Supination  of  the  hand  and  flexion  of  the 
forearm.    7,  8.  Elevators  and  depressors  of  the  angle  of  the  mouth.    9, 10.  Movements  of  the  lips  and  tongue. 

II.  Retraction  of  the  angle  of  the  mouth.  12.  Movements  of  the  eyes.  13, 13'.  Vision.  14.  Hearing,  a,  b,  c,  d. 
Movements  o'  the  wrists  and  fingers. 

The  size  of  the  brain  was  tormerly  said  to  bear  a  general  relation  to  the  intel- 
lectual capacity  of  the  individual.  Cuvier's  brain  weighed  rather  more  than  64  oz., 
that  of  the  late  Dr.  Abercrombie  63  oz.,  and  that  of  Dupuytren  62|  oz.  On  the 
other  hand,  the  brain  of  an  idiot  seldom  weighs  more  than  23  oz.  But  these  facts 
are  by  no  means  conclusive,  and  it  is  Avell  known  that  these  weights  have  been 
equalled  by  the  brains  of  persons  who  never  displayed  any  remarkable  intellect. 
Dr.  Haldennan  of  Cincinnati  has  recorded  the  case  of  a  mulatto,  aged  forty-five, 
whose  brain  weighed  68f  oz. ;  he  had  been  a  slave,  and  was  never  regarded  as 
particularly  intelligent ;  he  was  illiterate,  but  is  said  to  have  been  reserved,  medi- 
tative, and  economical.  Dr.  Ensor,  district  medical  officer  at  Port  Elizabeth, 
reports  that  the  brain  of  Carey,  the  Irish  informer,  weighed  61  oz.     M.  Nikiforoff 


THE   BRAIN  AND    ITS   MEMBRANES. 


705 


has  published  an  article  on  the  subject  of  the  weight  of  brains  in  the  Novosti. 
According  to  him,  the  weight  of  the  brain  has  no  influence  whatever  on  the 
mental  faculties.  It  ought  to  be  remembered  that  the  significance  of  the  weight 
of  the  brain  should  depend  upon  the  proportion  it  bears  to  the  dimensions  of  the 
whole  body  and  to  the  age  of  the  individual.  It  is  equally  important  to  know 
what  was  the  cause  of  death,  for  long  illness  or  old  age  exhausts  the  brain.  To 
define  the  real  degree  of  development  of  the  brain  it  is  therefore  necessary  to 
have  a  knowledge  of  the  condition  of  the  whole  body,  and,  as  this  is  usually 
lacking,  the  mere  record  of  weight  possesses  little  significance. 

The  human  brain  is  heavier  than  that  of  all  the  lower  animals,  excepting  the 
elephant  and  whale.  The  brain  of  the  former  weighs  from  eight  to  ten  pounds ; 
and  that  of  a  whale,  in  a  specimen  seventy-five  feet  long,  weighed  rather  more 
than  five  pounds. 


Fig.  375.— Drawing  to  illustrate  cranio-cerebral  topography.   (Taken  from  a  cast  in  the  Museum  of  the  Royal 
College  of  Surgeons  of  England,  prepared  by  Professor  Cunningham.) 

Cerebral  Localization  and  Topography. — Physiological  and  pathological  research  have 
now  gone  far  to  prove  that  the  surface  of  the  brain  may  be  mapped  out  into  series  of  definite 
areas,  each  one  of  which  is  intimately  connected  with  some  well-defined  function.  And  this  is 
especially  true  with  regard  to  the  convolutions  on  either  side  of  the  fissure  of  Rolando,  which 
are  believed  by  most  physiologists  of  the  present  day  to  be  concerned  in  motion,  those  grouped 
around  the  fissure  being  associated  with  movements  of  the  extremities  of  the  opposite  side  of 
the  body,  and  those  around  the  lower  end  of  the  fissure  being  related  to  movements  of  the 
mouth  and  tongue. 

This  is  not  the  place,  nor  can  space  be  given,  to  describe  these  localities.  But  the  two 
accompanying  cuts  from  Ferrier  (Figs.  373,  374)  have  been  introduced,  and  will  serve  to  indi- 
cate the  position  of  the  more  important  areas. 

The  relation  of  the  principal  fissures  and  convolutions  of  the  cerebrum  to  the  outer  sur- 
face of  the  scalp  has  been  the  subject  of  much  investigation,  and  many  systems  have  been 
45 


706 


THE   NERVOUS  SYSTEM. 


devised  by  which  one  may  localize  these  parts  from  an  examination  of  the  external  surface  of 
the  head. 

These  plans  can  only  be  regarded  as  approximately  correct  for  several  reasons  :  in  the  first 
place,  because  the  relations  of  the  convolutions  and  sulci  to  the  surface  are  found  to  be  very 
variable  in  different  individuals ;  secondly,  because  the  surface  area  of  the  scalp  is  greater  than 
the  surface  area  of  the  brain,  so  that  lines  drawn  on  the  one  cannot  correspond  exactly  to  sulci 
or  convolutions  on  the  other ;  and  thirdly,  because  the  sulci  and  convolutions  in  two  individuals 
are  never  precisely  alike.  Nevertheless,  the  principal  fissures  and  convolutions  can  be  mapped 
out  with  sufficient  accuracy  for  all  practical  purposes,  so  that  any  particular  convolution  can  be 
generally  exposed  by  removing  with  the  trephine  a  certain  portion  of  the  skull's  area. 

The  various  landmarks  on  the  outside  of  the  skull,  which  can  be  easily  felt,  and  which  serve 
as  indications  of  the  position  of  the  parts  beneath,  have  been  already  referred  to  (see  page  222), 
and  the  relation  of  the  fissures  and  convolutions  to  these  landmarks  is  as  follows : 

Longitudinal  Fissure. — This  corresponds  to  a  line  drawn  from  the  glabella  at  the  root  of 
the  nose  to  the  external  occipital  protuberance. 

The  Fissure  of  Sylvius. — The  position  of  the  fissure  of  Sylvius  and  its  horizontal  limb  is 
marked  by  a  line  starting  from  a  point  one  inch  and  a  quarter  horizontally  behind  the  external 
angular  process  of  the  frontal  bone  to  a  point  three-quarters  of  an  inch  below  the  most  promi- 
nent point  of  the  parietal  eminence.  The  first  three-quarters  of  an  inch  will  represent  the  main 
fissux*e,  the  remainder  the  horizontal  limb.  The  bifurcation  of  the  fissure  is,  therefore,  two 
inches  behind  and  about  a  quarter  of  an  inch  above  the  level  of  the  external  angular  process. 
The  ascending  limb  of  the  fissure  passes  upward  from  this  point  parallel  to,  and  immediately 
behind,  the  coronal  suture. 

Fissure  of  Rolando. — To  find  the  upper  end  of  the  fissure  of  Rolando,  a  measurement 
should  be  taken  from  the  glabella  to  the  external  occipital  protuberance.  The  position  of  the 
top  of  the  sulcus  will  be,  measuring  from  in  front,  55.6  per  cent,  of  the  whole  distance  from  the 
glabella  to  the  external  occipital  protuberance.  Professor  Thane  adopts  a  somewhat  simpler 
method.  He  divides  the  distance  from  the  glabella  to  the  external  occipital  protuberance  over 
the  top  of  the  head  into  two  equal  parts,  and,  having  thus  defined  the  middle  point  of  the  ver- 
tex, he  takes  half  an  inch  behind  it  as  the  top  of  the  sulcus.  This  is  not  quite  so  accurate  as 
the' former  method,  but  it  is  sufficiently  so  for  all  practical  purposes,  and  on  account  of  its  sim- 
plicity is  very  generally  adopted.    From  this  point  the  fissure  runs  downward  and  forward  for  3| 


Fig.  376.— Relations  of  the  principal  fissures  and  convolutions  of  the  cerebrum  to  the  outer  surface  of  the 
scalp.    (Reid.) 

inches,  its  axis  making  an  angle  of  67°  with  the  middle  line.  Cunningham  states  that  this  angle 
more  nearly  averages  71.5°.  In  order  to  mark  this  groove,  two  strips  of  metal  may  be  employed 
— one,  the  shorter,  being  fixed  to  the  middle  of  the  other  at  theangle  mentioned.  _  If  the  longer 
strip  is  now  placed  along  the  sagittal  suture  so  that  the  junction  of  the  two_  strips  is  over  the 
point  corresponding  to  the  top  of  the  furrow,  the  shorter,  oblique  strip  will  indicate  the  direction 


THE  SPINAL    CORD    AND    ITS   MEMBRANES.  707 

and  3|  inches  will  mark  the  length  of  the  furrow.  Dr.  Wilson  has  devised  an  instrument,  called 
a  cyrtometer,  which  combines  the  scale  of  measurements  for  localizing  the  fissure  with  data  for 
representing  its  length  and  direction.1  Professor  Thane  gives  the  lower  end  of  the  furrow  as 
"close  to  the  posterior  limb,  and  about  half  an  inch  behind  the  bifurcation  of  the  fissure  of 
Sylvius. "  So  that,  according  to  this  anatomist,  a  line  drawn  from  a  point  half  an  inch  behind 
the  mid-point  between  the  glabella  and  external  occipital  protuberance  to  this  spot  would  mark 
out  the  fissure  of  Rolando.  Dr.  Reid  adopts  a  different  method  (Fig.  376).  He  first  indicates 
on  the  surface  the  longitudinal  fissure  and  the  horizontal  limb  of  the  fissure  of  Sylvius  fas  above). 
He  then  draws  two  perpendicular  lines  from  his  "base-line"  (that  is,  a  line  from  the  lowest 
part  of  the  infra-orbital  margin  through  the  middle  of  the  external  auditory  meatus  to  the  back 
of  the  head)  to  the  top  of  the  cranium,  one  (d  e,  Fig.  376)  from  the  depression  in  front  of  the 
external  auditory  meatus,  and  the  other  (f  g,  Fig.  376)  from  the  posterior  border  of  the  mastoid 
process  at  its  root.  He  has  thus  described  on  the  surface  of  the  head  a  four-sided  figure  (pdge, 
Fig.  376),  and  a  diagonal  line  from  the  posterior  superior  angle  to  the  anterior  perpendicular 
line  where  it  is  crossed  hy  the  fissure  of  Sylvius  will  represent  the  furrow. 

The  parieto-occipital  fissure  on  the  upper  surface  of  the  cerebrum  runs  outward  at  right 
angles  to  the  great  longitudinal  fissure  for  about  an  inch,  from  a  point  one-fifth  of  an  inch  in 
front  of  the  lambda  (posterior  fontanelle).  Reid  states  that  if  the  horizontal  limb  of  the  fissure 
of  Sylvius  be  continued  onward  to  the  sagittal  suture,  the  last  inch  of  this  line  will  indicate  the 
position  of  the  sulcus. 

The  precentral  sulcus  begins  four-fifths  of  an  inch  in  front  of  the  middle  of  the  fissure  of 
Rolando,  and  extends  nearly,  but  not  quite,  to  the  horizontal  limb  of  the  fissure  of  Sylvius. 

The  superior  frontal  fissure  runs  backward  from  the  supra-orbital  notch,  parallel  with  the 
line  of  the  longitudinal  fissure  to  two-fifths  of  an  inch  in  front  of  the  line  indicating  the  position 
of  the  fissure  of  Rolando. 

The  inferior  frontal  fissure  follows  the  course  of  the  superior  temporal  ridge  on  the  frontal 
bone. 

The  intraparietal  fissure  begins  on  a  level  with  the  junction  of  the  middle  and  lower  third 
of  the  fissure  of  Rolando,  on  a  line  carried  across  the  head  from  the  back  of  the  root  of  one 
auricle  to  that  of  the  other.  After  passing  upward  it  curves  backward,  lying  parallel  to  the 
longitudinal  fissure,  midway  between  it  and  the  parietal  eminence ;  it  then  curves  downward  to 
end  midway  between  the  posterior  fontanelle  and  the  parietal  eminence. 

THE  SPINAL  CORD  AND  ITS  MEMBRANES. 

Dissection. — To  dissect  the  cord  and  its  membranes  it  will  be  necessary  to  lay  open  the 
whole  length  of  the  spinal  canal.  For  this  purpose  the  muscles  must  be  separated  from  the 
vertebral  grooves,  so  as  to  expose  the  spinous  processes  and  laminae  of  the  vertebrae ;  and  the 
latter  must  be  sawn  through  on  each  side,  close  to  the  roots  of  the  transverse  processes,  from 
the  third  or  fourth  cervical  vertebra  above  to  the  sacrum  below.  The  vertebral  arches  having 
been  displaced  by  means  of  a  chisel  and  the  separate  fragments  removed,  the  dura  mater  will  be 
exposed,  covered  by  a  plexus  of  veins  and  a  quantity  of  loose  areolar  tissue,  often  infiltrated  with 
serous  fluid.  The  arches  of  the  upper  vertebrae  are  best  divided  by  means  of  a  strong  pair  of 
cutting  bone-forceps. 

MEMBRANES   OF    THE    CORD. 

The  membranes  which  envelop  the  spinal  cord  are  three  in  number.  The  most 
external  is  the  dura  mater,  a  strong  fibrous  membrane  which  forms  a  loose  sheath 
around  the  cord,  The  most  internal  is  the  pia  mater,  a  cellulo-vascular  membrane 
which  closely  invests  the  entire  surface  of  the  cord.  Between  the  two  is  the 
arachnoid  membrane,  a  non-vascular  membrane  which  envelops  the  cord  and  is 
connected  to  the  pia  mater  by  slender  filaments  of  connective  tissue. 

The  Dura  Mater  of  the  cord  represents  only  the  meningeal  or  supporting  layer 
of  the  cranial  dura  mater.  The  endocranial  or  endosteal  layer  ceases  at  the  foramen 
magnum  posteriorly,  but  reaches  as  low  as  the  third  cervical  vertebra  in  front ; 
below  these  levels  its  place  is  taken  by  the  periosteum.  It  forms  a  loose  sheath 
which  surrounds  the  cord,  and  is  separated  from  the  bony  walls  of  the  spinal  canal 
hy  a  quantity  of  loose  areolar  tissue  and  a  plexus  of  veins.  The  situation  of  the 
veins  between  the  dura  mater  of  the  cord  and  the  periosteum  of  the  vertebra? 
corresponds  therefore  to  that  of  the  cranial  sinuses  between  the  endocranial  and 
supporting  layers.  It  is  attached  to  the  circumference  of  the  foramen  magnum, 
and  to  the  axis  and  third  cervical  vertebra  ;  it  is  also  fixed  to  the  posterior  common 
ligament,  especially  near  the  lower  end  of  the  spinal  canal,  by  fibrous  slips:  it 
extends  below  as  far  as  the  second  or  third  piece  of  the  sacrum;  here  it  becomes 

1  Lancet,  1888,  vol.  i.,  p.  408. 


708 


THE   NERVOUS  SYSTEM. 


impervious,  and,  ensheathing  the  filum  terminale,  descends  to  the  back  of  the 
coccyx,  where  it  blends  with  the  periosteum.  The  dura  mater  is  much  larger  than 
is  necessary  for  its  contents,  and  its  size  is  greater  in  the  cervical  and  lumbar 
regions  than  in  the  dorsal.  Its  inner  surface  is  smooth.  On  each  side  may  be 
seen  the  double  openings  which  transmit  the  two  roots  of  the  corresponding  spinal 
nerve,  the  fibrous  layer  of  the  dura  mater  being  continued  in  the  form  of  a  tubular 
prolongation  on  them  as  they  pass  through  these  apertures.  These  prolongations 
of  the  dura  mater  are  short  in  the  upper  part  of  the  spine,  but  become  gradually 
longer  below,  forming  a  number  of  tubes  of  fibrous  membrane,  which  enclose  the 
sacral  nerves,  and  are  contained  in  the  spinal  canal. 

The  chief  peculiarities  of  the  dura  mater  of  the  cord,  as  compared  with  that 
investing  the  brain,  are  the  following : 

The  dura  mater  of  the  cord  is  not  adherent  to  the  bones  of  the  spinal  canal, 
which  have  an  independent  periosteum.  . 

It  does  not  send  partitions  into  the  fissures  of  the  cord,  as  in  the  brain. 
Its  fibrous  laminae  do  not  separate  to  form  venous  sinuses,  as  in  the  brain. 
Structure. — The  dura  mater  consists  of  white  fibrous  and  elastic  tissue  arranged 
in  bands  or  lamellae,  which,  for  the  most  part,  are  par- 
allel with  one  another  and  have  a  longitudinal  arrange- 
ment. Its  internal  surface  is  covered  by  a  layer  of 
endothelial  cells  which  gives  this  surface  its  smooth 
appearance.  It  is  sparingly  supplied  with  vessels,  and 
some  few  nerves  have  been  traced  into  it. 

The  Arachnoid  is  exposed  by  slitting  up  the  dura 
mater  and  reflecting  that  membrane  to  either  side  (Fig. 
377).  It  is  a  thin,  delicate,  tubular  membrane  which 
invests  the  surface  of  the  cord,  and  is  connected  to  the 
pia  mater  by  slender  filaments  of  connective  tissue. 
Above,  it  is  continuous  with  the  cerebral  arachnoid, 
on  each  side  it  is  continued  on  the  various  neives,  so 
as  to  form  a  sheath  for  them  as  they  pass  outward  to 
the  intervertebral  foramina.  The  outer  surface  of  the 
arachnoid  is  in  contact  with  the  inner  surface  of  the 
dura  mater,  and  the  two  are,  here  and  there,  joined 
together  by  isolated  connective-tissue  trabecule,  espe- 
cially on  the  posterior  surface  of  the  cord.  For  the 
most  part,  however,  the  membranes  are  not  connected 
together,  and  the  interval  between  them  is  named  the 
subdural  space.  The  inner  surface  of  the  arachnoid  is 
separated  from  the  pia  mater  by  a  considerable  interval, 
which  is  called  the  subarachwidean  space.  The  space 
is  the  largest  at  the  lower  part  of  the  spinal  canal,  and 
encloses  the  mass  of  nerves  which  form  the  cauda  equina.  Superiorly  it  is  con- 
tinuous with  the  cranial  subarachnoid  space,  and  communicates  with  the  general 
ventricular  cavity  of  the  brain  by  means  of  an  opening  in  the  pia  mater,  in  the 
roof  of  the  fourth  ventricle  {foramen  of  Majendie  and  foramina  of  Key  and 
Retzius).  It  contains  an  abundant  serous  secretion,  the  cerebrospinal  fluid.  This 
secretion  is  sufficient  in  amount  to  expand  the  arachnoid  membrane,  so  as  to  fill 
up  completely  the  whole  of  the  space  included  in  the  dura  mater.  The  subarach- 
noidean  space  is  occupied  by  trabecule  of  delicate  connective  tissue,  connecting 
the  pia  mater  on  the  one  hand  with  the  arachnoid  membrane  on  the  other.  This 
is  named  subarachnoid  tissue.  In  addition  to  this  it  is  partially  subdivided  by 
a  longitudinal  membranous  partition,  the  septum  posticum,  which  serves  to  con- 
nect the  arachnoid  with  the  pia  mater,  opposite  the  posterior  median  fissure  of  the 
spinal  cord,  a  partition  which  is  incomplete  and  cribriform  in  structure,  con- 
sisting of  bundles  of  white  fibrous  tissue  interlacing  with  each  other.  This 
space   is   to  be   regarded  as,   in   reality,  a  great  lymph   space,   from   which    the 


Bur 


Fig.  377.— The  spinal  cord  and 
its  membranes. 


THE   MEMBRANES    OF    THE    CORD. 


709 


Dura  mater 

Arachnoid 
Post,  root 

Ant.  root 


Dura  mater 

Plexus  venosus 


vertebralia 


Fig.  378.— Transverse  section  of  the  spinal 
cord  and  its  membranes.     (Gegenbaur.) 


lymph  carried   to   it   by  the  perivascular  lymphatics  is   conveyed  back   into  the 
circulation. 

Structure. — The  arachnoid  is  a  delicate  membrane  made  up  of  closely  arranged 
interlacing  bundles  of  connective  tissue  in  several  layers. 

The  Pia  Mater  of  the  cord  is  exposed 
on  the  removal  of  the  arachnoid  (Fig-  377). 
It  covers  the  entire  surface  of  the  cord,  to 
which  it  is  very  intimately  adherent,  form- 
ing its  neurilemma,  and  sending  a  process 
downward  into  its  anterior  fissure.  It  also 
forms  a  sheath  for  each  of  the  filaments  of 
the  spinal  nerves,  and  invests  the  nerves 
themselves.  A  longitudinal  fibrous  band 
extends  along  the  middle  line  on  its  anterior 
surface,  called  by  Haller  the  linea  splendens  ; 
and  a  somewhat  similar  band,  the  ligamentum 
denticulatum,  is  situated  on  each  side.  At 
the  point  where  the  cord  terminates  the  pia 
mater  becomes  contracted,  and  is  continued 
down  as  a  long,  slender  filament  (filum  ter- 
minals), which  descends  through  the  centre 
of  the  mass  of  nerves  forming  the  cauda  equina.  It  perforates  the  dura  about 
the  level  of  the  second  or  third  lumbar  vertebrse,  receiving  a  sheath  from  it,  and 
extends  downward  as  far  as  the  base  of  the  coccyx,  where  it  blends  with  the 
periosteum.  It  assists  in  maintaining  the  cord  in  its  position  during  the  movements 
of  the  trunk,  and  is  from  this  circumstance  called  the  central  ligament  of  the  spinal 
cord.  It  contains  a  little  gray  nervous  substance,  which  may  be  traced  for  some 
distance  into  its  upper  part,  and  is  accompanied  by  a  small  artery  and  vein. 
At  the  upper  part  of  the  cord  the  pia  mater  presents  a  grayish,  mottled  tint, 
which  is  owing  to  yellow  or  brown  pigment-cells  scattered  among  the  elastic 
fibres. 

Structure. — The  pia  mater  of  the  cord  is  less  vascular  in  structure,  but  thicker 
and  denser,  than  the  pia  mater  of  the  brain,  with  which  it  is  continuous.  It 
consists  of  two  layers :  an  outer  composed  of  bundles  of  connective-tissue  fibres, 
arranged  for  the  most  part  longitudinally ;  and  an  inner,  consisting  of  stiff 
bundles  of  the  same  tissue,  which  present  peculiar  angular  bends,  and  is  covered 
on  both  surfaces  by  a  layer  of  endothelium.  Between  the  two  layers  are  a 
number  of  cleftlike  lymphatic  spaces  which  communicate  with  the  subarachnoid 
cavity,  and  a  number  of  blood-vessels  which  are  enclosed  in  a  perivascular 
sheath,  derived  from  the  inner  layer  of  the  pia  mater,  into  which  the  lymphatic 
spaces  open.  It  is  also  supplied  with  nerves,  which  are  derived  from  the  sympa- 
thetic. 

The  Ligamentum  Denticulatum  (Fig.  377)  is  a  narrow  fibrous  band,  situated 
on  each  side  of  the  spinal  cord,  throughout  its  entire  length,  and  separating  the 
anterior  from  the  posterior  roots  of  the  spinal  nerves.  It  has  received  its  name 
from  the  serrated  appearance  which  it  presents.  Its  inner  border  is  continuous 
with  the  pia  mater  at  the  side  of  the  cord.  Its  outer  border  presents  a  series  of 
triangular,  dentated  serrations,  the  points  of  which  are  fixed  at  intervals  to  the 
dura  mater.  These  serrations  are  twenty-one  in  number  on  each  side,  the  first 
being  attached  to  the  dura  mater,  opposite  the  margin  of  the  foramen  magnum 
between  the  vertebral  artery  and  the  hypoglossal  nerve,  and  the  last  near  the 
lower  end  of  the  cord.  Its  use  is  to  support  the  cord  in  the  fluid  by  which  it  is 
surrounded. 

Surgical  Anatomy. — Evidence  of  great  value  in  the  diagnosis  of  meningitis  may  be  ob- 
tained by  puncturing  the  theca  of  the  cord  and  withdrawing  some  of  the  cerebrospinal  fluid, 
and  the  operation  is  regarded  by  some  as  curative,  under  the  supposition  that  the  draining  away 
of  the  cerebrospinal  fluid  relieves  the  patient  by  diminishing  the  intracranial  pressure.     The 


710 


THE   NERVOUS  SYSTEM. 


operation  is  performed  by  inserting  a  trocar,  of  the  smallest  size, 
between  the  lamina  of  the  third  and  fourth  or  the  fourth  and  fifth 
-Ik  lumbar  vertebrae  through  the  ligamenta  subflava.  The  spinal 
cord  even  of  a  child  at  birth  does  not  reach  below  the  third 
lumbar  vertebra,  and  therefore  the  canal  may  be  punctured  be- 
tween the  third  and  fourth  vertebra  without  any  risk  of  injuring 
its  contents.  The  point  of  puncture  is  indicated  by  laying  the 
child  on  its  side  and  dropping  a  perpendicular  line  from  the 
highest  point  of  the  crest  of  the  ilium  ;  this  will  cross  the  upper 
border  of  the  spine  of  the  fourth  lumbar  vertebra,  and  will  indi- 
cate the  level  at  which  the  trocar  should  be  inserted  a  little  to 
one  side  of  the-  median  line. 


h 


:.'--: 


THE    SPINAL    CORD    (Fig.  379). 

The  Spinal  Cord  (medulla  spinalis)  is  the  cylindrical, 
elongated  part  of  the  cerebro-spinal  axis  which  is  con- 
tained in  the  vertebral  canal.  Its  length  is  usually 
about  seventeen  or  eighteen  inches,  and  its  weight, 
when  divested  of  its  membranes  and  nerves,  about  one 
ounce  and  a  half,  its  proportion  to  the  encephalon  being 
about  1  to  33.  It  does  not  nearly  fill  the  canal  in 
Avhich  it  is  contained,  its  investing  membranes  being 
separated  from  the  surrounding  wTalls  by  areolar  tissue 
and  a  plexus  of  veins.  It  occupies,  in  the  adult,  the 
upper  two-thirds  of  the  vertebral  canal,  extending 
from  the  upper  border  of  the  atlas  to  the  lower  border 
of  the  body  of  the  first  lumbar  vertebra,  where  it  ter- 
minates in  a  slender  filament  of  gray  substance,  which 


Posterior 
— -Median  Fissure. 


Posterior 
Lateral  Fissure. 


Fig.  379. — Posterior  view  of  the 
spinal  cord  in  situ. 


Fig.  380.— Spinal  cord.  Side 
view.  Plan  of  the  .fissures  and 
columns. 

is  continued  for  so.me  distance  into  the  filum  terminate. 
In  the  foetus,  before  the  third  month,  it  extends  to  the 
bottom  of  the  sacral  canal,  but  after  this  period  it  grad- 
ually recedes  from  below,  as  the  growth  of  the  bones 
composing  the  canal  is  more  rapid  in  proportion  than 
that  of  the  cord,  so  that  in  the  child  at  birth  the  cord 
extends  as  far  as  the  third  lumbar  vertebra.  Its  position 
varies  also  according  to  the  degree  of  curvature  of  the 
spinal  column,  being  raised  somewhat  in  flexion  of  the 
spine.  On  examining  its  surface  it  presents  a  difference 
in  its  diameter  in  different  parts,  being  marked  by  two 
enlargements,  an  upper  or  cervical,  and  a  lower  or  lum- 
bar. The  cervical  enlargement  extends  from  about  the 
third  cervical  to  the  first  or  second  dorsal  vertebra :  its 
greatest  diameter  is  in  the  transverse  direction  (13 
mm.),  and  it  corresponds  with  the  origin  of  the  nerves 


THE   SPINAL    CORD. 


711 


which  supply  the  upper  extremities.  The  lumbar  enlargement  is  situated  opposite 
the  last  two  or  three  dorsal  vertebrae,  and  corresponds  with  the  origin  of  the  nerves 
which  supply  the  lower  extremities.  Below  the  lumbar  enlargement  the  cord 
gradually  tapers  to  form  a  cone,  the  eonus  medullaris,  the  apex  of  which  is  con- 
tinuous with  the  filuin  terminate.  In  form,  the  spinal  cord  is  a  cylinder,  flattened 
before  and  behind. 

Fissures. — It  presents  on  its  anterior  surface,  along  the  middle  line,  a  longi- 
tudinal fissure,  the  anterior  median  fissure,  and  on  its  posterior  surface  another 
fissure,  which  also  extends  along  the  entire  length  of  the  cord,  the  posterior  median 
fissure.  These  fissures  penetrate  through  the  greater  part  of  the  thickness  of  the 
cord,  and  incompletely  divide  the  cord  into  symmetrical  halves,  united  in  the 
middle  line  by  a  transverse  band  of  nervous  substance,  the  commissure. 

The  Anterior  Median  Fissure  is  wider,  but  of  less  depth,  than  the  posterior, 
extending  into  the  cord  for  about  one-third  of  its  thickness,  and  is  deepest  at  the 
lower  part  of  the  cord.  It  contains  a  prolongation  from  the  pia  mater,  and  its  floor 
is  formed  by  the  anterior  white  commissure,  which  is  perforated  by  numerous 
blood-vessels  passing  to  the  centre  of  the  cord. 

The  Posterior  Median  Fissure  is  not  an  actual  fissure,  as  the  space  between  the 
lateral  halves  of  the  posterior  part  of  the  cord  is  crossed  by  connective  tissue  and 
numerous  blood-vessels,  so  that  no  actual  hiatus  exists,  and  there  is  consequently 
no  prolongation  of  the  pia  mater  into  it.  It  extends  into  the  cord  to  about  one- 
half  its  depth,  and  its  floor  is  formed  by  the  posterior  gray  commissure. 


Opposite  middle  of  cervical  region. 


Opposite  middle  of  dorsal  region. 


Fig. 381 
cord. 


Opposite  lumbar  region.  ' 

Transverse  sections  of  the 


Fig.  382.— From  a  transverse  section  through  the  spinal 
cord  of  a  calf.  Magnified  about  180  diameters,  showing  part 
of  the  central  canal  and  the  tissue  immediately  around  it, 
viz.,  the  central  gray  matter.  (Klein  and  Noble  Smith.) 
The  canal  is  lined  with  epithelium,  composed  of  ciliated, 
more  or  less  conical,  cells  ;  in  most  instances  a  filamentous 
process  passes  from  the  cell  into  the  tissue  underneath. 
This  tissue  contains,  in  a  hyaline  matrix,  a  network  of 
fibrils ;  most  of  these  run  horizontally  ;  others  have  a  longi- 
tudinal course,  and  appear  therefore"  here  cut  transversely 
— i.  e.,  as  small  dots.  The  nuclei  correspond  to  the  cells  of 
the  neuroglia,  the  cell-substance  not  being  shown.  Both 
the  nuclei  of  the  neuroglia-cells  and  those  of  the  epithe- 
lium contain  three  or  more  large  disc-shaped  particles. 


Lateral  Fissures. — On  each  side  of  the  posterior  median  fissure,  along  the  line 
of  attachment  of  the  posterior  roots  of  the  nerves,  a  delicate  fissure  may  be  seen, 
leading  down  to  the  gray  matter  which  approaches  the  surface  in  this  situation ; 
this  is  called  the  postero-lateral  fissure  of  the  spinal  cord.  On  the  posterior  sur- 
face of  the  spinal  cord,  between  the  posterior  median  fissure  and  the  postero-lateral 
fissure  on  each  side,  is  a  slight  longitudinal  furrow  [posterior  intermediate  furrow), 
marking  off  two  slender  tracts,  the  poster o-median  and  postero-lateral  columns. 
These  are  most  distinct  in  the  cervical  region,  but  are  stated  by  Foville  to  exist 
throughout  the  whole  length  of  the  cord.  On  each  side  of  the  anterior  median 
fissure  the  anterior  roots  of  the  spinal  nerves  emerge  from  the  cord,  not  in  one 
vertical  line,  but  by  separate  bundles  which  occupy  an  area  of  some  width.  This 
is  called,  by  some  anatomists,  the  antero-lateral  fissure  of  the  cord,  although  no 
actual  fissure  exists  in  this  situation. 

Columns  of  the  Cord. — Each  half  of  the  spinal  cord  is  thus  divided  into  four 
columns  :  an  anterior  column,  a  lateral  column,  a  posterior  column,  and  a  postero- 
median column.     This  division,  however,  is  very  imperfect,  since  the  limit  between 


712  THE   NERVOUS   SYSTEM. 

the  so-called  anterior  and  lateral  columns  cannot  be  defined  on  account  of  the 
bundles  of  the  anterior  roots  being  spread  over  a  considerable  area.  It  is  there- 
fore customary  to  divide  each  half  of  the  spinal  cord  into  two  columns,  separated 
by  the  postero-lateral  groove :  (1)  a  small  posterior  column,  which  is  bounded  in- 
ternally by  the  posterior  median  fissure,  and  externally  by  the  postero-lateral  fissure, 
and  (2)  a  large  antero-lateral  column,  which  comprises  the  rest  of  the  cord.  The 
posterior  column  is  further  divided,  at  all  events  at  its  upper  part,  by  the  posterior 
intermediate  septum,  into  a  postero-median  column  and  a  postero-lateral  column. 

Structure  of  the  Cord. — If  a  transverse  section  of  the  spinal  cord  be  made,  it 
will  be  seen  to  consist  of  white  and  gray  nervous  substance.  The  white  matter  is 
situated  externally,  and  constitutes  the  greater  part.  The  gray  substance  occu- 
pies the  centre,  and  is  so  arranged  as  to  present  on  the  surface  of  the  section  two 
crescentic  masses,  placed  one  in  each  lateral  half  of  the  cord,  united  together  by  a 
transverse  band  of  gray  matter,  the  gray  commissure.  Each  crescentic  mass  has 
an  anterior  (ventral)  and  a  posterior  (dorsal)  horn.  The  posterior  horn  is  long  and 
narrow,  and  approaches  the  surface  of  the  postero-lateral  fissure,  near  which  it 
presents  a  slight  enlargement,  the  caput  comu :  from  this  it  tapers  to  form  the 
apex  comu,  which  at  the  surface  of  the  cord  becomes  continuous  with  some  of  the 
fibres  of  the  posterior  roots  of  the  spinal  nerves.  The  anterior  horn  is  short  and 
thick,  and  does  not  quite  reach  the  surface,  but  extends  toward  the  point  of  attach- 
ment of  the  anterior  roots  of  the  nerves.  Its  margin  presents  a  dentate  or  stellate 
appearance.  Owing  to  the  projections  toward  the  surface  of  the  anterior  and  poste- 
rior horns  of  the  gray  matter,  each  half  of  the  cord  is  divided,  more  or  less  com- 
pletely, into  three  columns,  anterior,  middle,  and  posterior,  the  anterior  and  middle 
being  joined  to  form  the  antero-lateral  column,  as  the  anterior  horn  does  not  quite 
reach  the  surface. 

The  commissure  of  the  spinal  cord  is  composed  of  white  and  gray  matter,  and 
is  therefore  divided  into  the  white  and  gray  commissures.  The  white  commissure 
is  situated  at  the  bottom  of  the  anterior  median  fissure,  and  is  formed  of  medullated 
nerve-fibres,  which  pass  between  the  gray  matter  of  the  anterior  horn  and  the 
anterior  white  column  of  the  one  side  into  similar  parts  on  the  other.  The  fibres 
are  oblique  in  dh-ection  ;  many  which  enter  at  the  posterior  part  of  the  commissure 
on  the  one  side  leave  it  at  the  anterior  part  of  the  commissure  on  the  other,  and 
vice  versd,  a  decussation  taking  place  in  the  middle  line. 

The  gray  commissure,  which  connects  the  two  crescentic  masses  of  gray  matter, 
is  separated  from  the  bottom  of  the  anterior  median  fissure  by  the  anterior  white 
commissure.  It  consists  of  transverse  medullated  nerve-fibres,  with  a  considerable 
quantity  of  neuroglia  between  them.  The  fibres  when  they  reach  the  lateral  cres- 
cents diverge :  some  pass  backward  to  the  posterior  roots  ;  others  spread  out,  at 
various  angles,  into  the  crescent. 

Running  through  the  gray  commissure  of  the  whole  length  of  the  cord  is  a 
minute  canal,  which  is  barely  visible  to  the  naked  eye  in  the  human  cord,  but  is 
proportionately  larger  in  some  of  the  lower  vertebrata.  It  is  called  the  central 
canal ;  it  opens  above  into  the  fourth  ventricle,  and  terminates  below  in  a  some- 
what dilated  extremity.  It  is  surrounded  by  an  area  of  neuroglia,  which,  in  the 
recent  state,  has  a  gelatinous  appearance,  and  in  which  there  are  no  nerve-fibres. 
This  is  sometimes  called  the  substantia  gelatinosa  centralis.  When  hardened  in 
alcohol  or  chromic  salts  it  has  a  finely  reticulated  appearance.  The  canal  is  lined 
in  the  foetus  by  columnar  ciliated  epithelium,  but  in  the  adult  the  cilia  have  disap- 
peared, and  the  canal  is  filled  with  their  remains. 

The  mode  of  arrangement  of  the  gray  matter,  and  its  amount  in  proportion  to 
the  white,  vary  in  different  parts  of  the  cord.  Thus,  the  posterior  horns  are  long 
and  narrow  in  the  cervical  region ;  short  and  narrower  in  the  dorsal ;  short,  but 
wider,  in  the  lumbar  region.  In  the  cervical  region  the  crescentic  portions  are 
small,  and  the  white  matter  more  abundant  than  in  any  other  region  of  the  cord. 
In  the  dorsal  region  the  gray  matter  is  least  developed,  the  white  matter  being 
also  small  in  quantity.     In  the  lumbar  region  the  gray  matter  is  more  abundant 


THE  SPINAL    CORD. 


713 


than  in  any  other  region  of  the  cord.  Toward  the  lower  end  of  the  cord  the  white 
matter  gradually  ceases.  The  crescentic  portions  of  the  gray  matter  soon  blend  into 
a  single  mass,  which  forms  the  only  constituent  of  the  extreme  point  of  the  cord. 

Minute  Anatomy  of  the  Cord. — The  cord  consists  of  an  outer  part,  composed 
of  medullated  nerve-fibres,  which  is  the  white  substance  ;  and  of  a  central  part,  the 
gray  matter,  both  supported  in  a  peculiar  kind  of  tissue,  called  neuroglia. 

The  neuroglia  consists  of  a  homogeneous  transparent  matrix,  of  a  network  of 
very  delicate  fibrillae,  and  of  small  stellate  or  branched  cells,  the  neuroglia-cells. 

In  addition  to  forming  a  ground  substance,  in  which  the  nerve-fibres,  nerve- 
cc]ls,  and  blood-vessels  are  imbedded,  a  considerable  accumulation  of  neuroglia 
takes  place  in  three  situations — (1)  on  the  surface  of  the  cord,  beneath  the  pia 
mater ;  (2)  around  the  central  canal,  the  substantia  gelatinosa  centralis ;  and 
(3)  as  a  cap  over  the  extremity  of  the  posterior  horn,  forming  the  substantia 
cinerea  gelatinosa. 

The  white  substance  of  the  cord  consists  of  medullated  nerve-fibres,  mostly 
disposed  longitudinally,  with  blood-vessels  and  neuroglia.  When  stained  with 
carmine  it  presents  a  very  striking  appearance  on  transverse  section.  It  is  seen 
to  be  studded  all  over  with  minute  dots,  surrounded  by  a  white  area  (Fig.  387). 
This  is  due  to  the  longitudinal  medullated  fibres  seen  on  section.  The  dot  is  the 
axis-cylinder,  the  white  area  the  substance  of  Schwann.  Externally,  the  neuroglia 
forms  a  sheath  closely  investing  the  outer  surface  of  the  cord  immediately  beneath 
the  pia  mater;  from  it  numerous  septa  pass  inward  and  separate  the  respective 
bundles  of  fibres  and  extend  between  the  individual  nerve-fibres,  acting  as  a 
supporting  medium,  in  which  they  are  imbedded. 

There  are,  however,  also  oblique  and  transverse  fibres  in  the  white  substance. 
These  principally  consist  of  (1)  the  fibres  of  the  white  commissure ;  (2)  horizontal 
or  oblique  fibres  passing  from  the  roots  of  the  nerves  into  the  gray  matter :  and 
(3)  fibres  leaving  the  gray  matter  and  pursuing  a  longer  or  shorter  horizontal  course. 

Conducting  Tracts. — It  is  impossible  to  trace  the  course  of  the  nerve-fibres  in 
their  passage  through  the  cord ; 
but  the  investigation  of  patho- 
logical lesions  has  shown  that 
the  white  matter  of  the  cord 
consists  of  certain  columns  or 
tracts  of  fibres ;  for  it  has  been 
found  that  certain  lesions  are 
strictly  limited  to  certain  well- 
determined  parts  of  the  cord 
without  involving  neighboring 
regions.  That  these  parts  or 
fasciculi  correspond  to  so  many 
distinct  anatomical  systems,  each 
endowed  with  special  functions, 
seems  abundantly  proved  by  the 
researches  of  Flechsig  and  others 
on  the  development  of  the  spinal 
cord  during  the  later  periods  of 
utero-gestation  and  in  the  newly 
born  infant.  By  these  researches 
several  tracts  can  be  traced 
along  the  greater  part  of  the 
cord  and  into  or  from  the  en- 
cephalon.  Thus  (1)  in  the  antero- 
lateral column  of  the  cord,  on 
either  side  of  the  anterior  median 
fissure,  a  portion  of  the  column 
may  be  divided  off  as  the  direct  pyramided  tract  (fasciculus  of  Tiirck).    This  tract 


Fig.  383.— Columns  of  the  cord. 


714 


THE   NERVOUS  SYSTEM. 


is  only  found  in  the  upper  part  of  the  cord ;  it  gradually  diminishes  as  it  is  traced 
downward,  and  disappears  about  the  middle  of  the  dorsal  region.  It  consists  of  cen- 
trifugal or  descending  fibres  which  can  be  traced  downward  from  the  pyramid  of  the 
medulla  of  the  same  side,  and  are  derived  from  the  motor  area  of  the  cerebral  cortex. 
The  fibres  of  this  tract  decussate  in  their  course  down  the  cord,  passing  across  the 
middle  line  through  the  anterior  white  commissure ;  this  explains  the  gradual  dimi- 
nution and  eventual  disappearance  of  the  tract.  (2)  In  the  hinder  part  of  the  antero- 
lateral column  is  a  somewhat  triangular  area,  larger  than  the  preceding,  which  is 
named  the  crossed  pyramidal  tract  This  also  consists  of  descending  fibres,  which 
are  derived  from  the  pyramid  of  the  medulla  of  the  opposite  side,  and  which  have 
crossed  in  the  decussation  of  the  pyramids.  The  fibres  are  derived  from  the  motor 
area  of  the  cerebral  cortex  of  the  opposite  side.  Thus  it  will  be  seen  that  all  the 
fibres  from  the  motor  area,  which  descend  through  the  internal  capsule,  the  crus 
cerebri,  and  the  pons  Varolii  to  the  pyramidal  body  of  the  medulla,  decussate ; 
some  at  the  upper  part  of  the  cord,  and  these  descend  through  it  as  the  crossed 
pyramidal  tract ;  and  others,  which  descend  as  the  direct  pyramidal  tract  and  cross 
through  the  anterior  commissure  of  the  cord  to  reach  the  crossed  pyramidal  tract 
of  the  opposite  side.  Although  this  is  the  usual  method  of  describing  the  crossing 
of  the  direct  pyramidal  tract  in  the  cord,  it  seems  probable  that  its  fibres  cross  in 
the  anterior  commissure  and  pass  directly  to  the  anterior  horn  of  gray  matter,  to 
end  by  forming  synapses  around  its  cells.  (3)  The  antero-lateral  ascending  tract 
(Gower's  tract)  is  an  extensive  crescent-shaped  strand  which  skirts  the  circumfer- 
ence of  the  anterior  three-quarters  of  the  antero-lateral  column  of  the  cord.  Behind, 
where  it  is  thickest,  it  lies  in  the  angle  formed  by  the  direct  cerebellar  and  crossed 
pyramidal  tracts,  becoming  narrower  as  it  passes  forward  toward  the  direct  pyrami- 
dal tract.  It  consists  of  centripetal  or  ascending  fibres,  which  arise  from  cells  situ- 
ated at  the  base  of  the  posterior  horn  and  which  cross  to  the  opposite  side  of  the 

cord  in  the  anterior  gray  commis- 
sure. They  can  be  traced  upward 
through  the  medulla  and  pons  to 
the  cerebellum,  reaching  the  latter 
through  its  superior  peduncles.  If 
the  spinal  cord  is  divided  in  the  cer- 
vical region,  some  scattered  fibres  in 
this  column  degenerate  in  a  down- 
ward direction.  This  would  seem 
to  prove  therefore  that  it  contains 
some  descending  fibres,  which  are 
believed  to  be  derived  from  the  same 
side  of  the  cerebellum.  (4)  The 
direct  cerebellar  tract  is  situated  at 
the  circumference  of  the  cord  behind 
the  preceding  and  external  to  the 
crossed  pyramidal  tract,  occupying 
a  narrow  area  which  extends  back- 
ward as  far  as  the  postero-lateral 
fissure  or  nearly  so.  It  commences  at  the  level  of  the  upper  lumbar  region,  and 
increases  in  size  as  it  ascends  and  passes  through  the  restiform  body  of  the  medulla 
to  the  cerebellum.  Its  fibres  are  derived  from  the  cells  of  the  posterior  vesicular 
column  cf  Clarke  in  the  gray  matter  of  the  cord.  (5)  Close  to  the  point  where 
the  posterior  roots  enter  the  cord,  in  the  antero-lateral  column,  is  a  small  collection 
of  fibres,  which  is  known  as  the  tract  of  Lissauer  ;  it  is  formed  by  some  of  the 
fibres  of  the  posterior  roots  which  run  upward  in  the  tract  for  a  short  distance,  and 
then  enter  the  posterior  horn  of  the  gray  matter.  (6)  The  rest  of  the  antero- 
lateral column  of  the  spinal  cord  is  occupied  by  the  antero-lateral  ground  bundle. 
It  surrounds  the  anterior  cornu  and  separates  the  antero-lateral  tract  and  the  crossed 
pyramidal  tract  from  the  gray  matter  of  the  cord.     It  consists  of  (a)  longitudinal 


Coruus ■*> 


Fig.  384.— Transverse  section  of  the  gray  substance  of  the 
spinal  cord,  near  the  middle  of  the  dorsal  region.  Magni- 
fied 13  diameters. 


THE   SPINAL    COBB. 


715 


commissural  fibres,  which  unite  the  groups  of  cells  in  the  gray  matter  with  one 
another ;  (b)  of  fibres  which  pass  across  the  anterior  commissure  from  the  gray 
matter  of  the  opposite  side  ;  and  (c)  horizontal  fibres  belonging  to  the  anterior  roots 
of  the  nerves,  which  pass  through  it  before  leaving  the  cord. 

In  the  posterior  column  of  the  cord  there  are  two  tracts.  They  are  marked 
off  from  each  other  by  the  posterior  intermediate  furrow  on  the  surface  of  the  cord. 
The  part  which  has  been  described  previously  as  the  posterior  median  column 
pretty  nearly  corresponds  to  the  one  tract,  the  tract  of  Goll,  and  the  remainder 
of  the  posterior  column  corresponds  to  the  other,  the  tract  of  Burdach.  (7)  The 
tract  of  Goll  increases  as  it  ascends,  and  consists  of  long,  but  small,  fibres  derived 
from  the  posterior  roots  of  the  spinal  nerves,  which  ascend  to  the  medulla  oblon- 
gata, where  they  end  in  the  nucleus  gracilis.  (8)  The  tract  of  Burdach  consists 
of  shorter,  but  larger,  fibres  than  the  preceding ;  they  are,  however,  derived  from 
the  same  source,  the  posterior  roots ;  some  ascend  only  for  a  short  distance  in  the 
tract  and  then  enter  the  gray  matter  and  come  into  close  relationship  with  the  cells 
of  the  posterior  vesicular  column  of  Clarke  ;  others  incline  toward  the  mesial  plane, 
and,  entering  Goll's  column,  can  be  traced  as  far  as  the  medulla.     In  the  cervical 


Fig.  385.— Transverse  section  of  the  gray  substance  of  the  spinal  cord  through  the  middle  of  the  lumbar 
enlargement.  On  the  left  side  of  the  figure  groups  of  large  cells  are  seen  ;  on  the  right  side,  the  course  of  the 
fibres  is  shown  without  the  cells.    Magnified  13  diameters. 

and  upper  dorsal  regions  there  is  contained  in  the  substance  of  Burdach 's  column  a 
small  strand  of  fibres,  called  the  descending  comma  tract.  It  presents,  on  trans- 
verse section,  the  appearance  of  a  comma,  the  blunt  extremity  of  which  is  directed 
forward.  The  fibres  forming  it  probably  represent  in  part  descending  portions  of 
the  dorsal  nerve-roots,  together  with  descending  commissural  fibres  within  the  cord 
itself.  A  small  strand  of  similar  descending  fibres  is  seen,  in  the  lower  part  of 
the  cord,  lying  in  the  inner  part  of  Goll's  column. 

The  gray  substance  of  the  cord  occupies  its  central  part  in  the  shape  of  two 
crescentic  horns,  joined  together  by  the  gray  commissure.  Each  of  these  crescents 
has  an  anterior  or  ventral  and  a  posterior  or  dorsal  cornu. 

The  posterior  horn  consists  of  a  slightly  narrowed  portion,  at  its  base,  where 
it  is  connected  with  the  rest  of  the  gray  substance — this  is  the  cervix  cornu  ;  from 
this  it  gradually  expands  into  the  main  part  of  the  horn,  the  caput  cornu ;  around 


716 


THE  NERVOUS  SYSTEM. 


its  extremity  is  a  lamina  or  layer  of  gelatinous  material,  which  covers  the  head 
like  a  cap,  and  from  this  it  tapers  almost  to  a  point,  which  approaches  the  surface 
of  the  cord  at  the  postero-lateral  groove. 

The  gelatinous  substance  is  a  peculiar  accumulation  of  neuroglia  (Klein) 
similar  to  that  found  around  the  central  canal  (page  713),  and  has  been  named 
by  Rolando  the  substantia  cinerea  gelatinosa.  It  probably  takes  its  origin  from 
the  columnar  cells  which  line  the  posterior  part  of  the  embryonic  spinal  canal. 

The  anterior  horn  of  the  gray  substance  in  the  cervical  and  lumbar  swellings, 
where  it  gives  origin  to  the  motor  nerves  of  the  extremities,  is  much  larger  than 
in  any  other  region,  and  contains  several  distinct  groups  of  large  and  variously 
shaped  cells. 

In  addition  to  this,  a  lateral  horn  is  found  projecting  outward  from  the 
lateral  region  of  the  gray  matter  on  a  level  with  the  gray  commissure  in  the  upper 
part  of  the  dorsal  region  of  the  cord ;  in  the  cervical  and  lumbar  regions  this 
lateral  horn  blends  with  the  anterior  horn,  which  thus  becomes  broad  and  ex- 
panded. From  the  concavity  of  the  crescent,  between  the  anterior  and  posterior 
horns,  processes  of  gray  matter  extend  into  the  white  substance,  where  they 
divide  and  anastomose  to  form  a  network,  termed  the  formatio  reticularis. 


Posterior  Boots. 


Posterior 
Column. 


Anterior 
Colvmn. 


Fig.  386.— Longitudinal  section  of  the 
white  and  gray  substance  of  the  spinal 
cord,  through  the  middle  of  the  lumbar 
enlargement.    Magnified  14  diameters. 


'''■-:'  -IBl 


Fig.  387.— Transverse  section  through  the 
white  matter  of  the  spinal  cord  of  a  calf. 
Magnified  about  300  diameters.  (Klein  and 
Noble  Smith.) 

In  the  upper  part  are  shown  two  isolated 
flattened  nucleated  cells  of  the  neuroglia, 
under  a  somewhat  higher  power  than  the 
rest.  In  the  bulk  of  the  figure  the  nerve- 
fibres  are  seen  in  transverse  section.  They 
are  of  different  sizes,  and  possess  a  laminated 
medullary  sheath  surrounding  the  axis- 
cylinder,  which  was  deeply  stained  in  the 
preparation,  and  is  here  represented  by  a 
black  dot.  The  nerve-fibres  are  embedded 
in  the  neuroglia.  Among  the  neuroglia  are 
also  seen  two  branched  connective-tissue 
cells— neuroglia-cells. 


The  gray  commissure  contains  the  central  canal,  and  is  situated  behind 
the  white  commissure,  which  separates  it  from  the  bottom  of  the  anterior  median 
fissure. 

The  gray  substance  of  the  cord  consists  of — (1)  nerve-fibres  of  variable  but 
smaller  average  diameter  than  those  of  the  white  columns  ;  (2)  nerve-cells  of 
various  shapes  and  sizes,  with  from  two  to  eight  processes ;  (3)  blood-vessels  and 
connective  tissue. 

The  nerve-fibres  of  the  gray  matter  of  the  posterior  horn  are  for  the  most  part 
composed  of  a  dense  interlacement  of   minute   fibrils,  intermingled  with   nerves 


THE   NERVE- TRACTS.  717 

of  a  larger  size.  This  interlacement  is  formed  partly  by  the  axons  and  dendrites 
of  the  cells  of  the  gray  matter,  and  partly  by  fibres  which  enter  the  gray  matter 
and  which  come  from  various  sources. 

The  nerve-cells  of  the  gray  matter  are  collected  into  groups  as  seen  on  trans- 
verse section,  but  they  really  form  columns  of  cells  placed  longitudinally ;  or  else 
they  are  found  scattered  throughout  the  whole  of  the  gray  matter. 

In  the  anterior  horn  the  cells  consist  of  two  chief  groups :  one  mesial,  the 
more  constant,  near  the  anterior  column ;  the  other  lateral,  near  the  lateral  column. 
A  second  lateral  group  is  present  in  the  cervical  and  lumbar  enlargements. 
At  the  base  of  the  posterior  horn  on  its  inner  side,  adjoining  the  gray  commissure, 
is  a  group  of  nerve-cells,  called  Clarke's  posterior  vesicular  column,  which  extends 
from  the  eighth  cervical  to  the  second  lumbar  nerve. 

At  the  junction  of  the  anterior  and  posterior  cornu,  in  the  outer  portion  of  the 
gray  matter,  is  a  third  group  of  cells,  the  lateral  cell  column  ;  this  is  best  seen  in 
the  dorsal  region.  In  certain  regions  of  the  cord  these  cells  extend  in  among  the 
fibres  of  the  white  matter  of  the  lateral  column,  and  give  rise  to  the  lateral  horn. 
In  addition  to  these  groups  a  few  large  scattered  cells  are  found  in  the  posterior 
horn  and  in  the  substantia  gelatinosa  of  Rolando. 

Origin  of  the  Spinal  Nerves. — The  roots  of  the  spinal  nerves  are  attached  to  the 
surface  of  the  cord,  opposite  the  horns  of  gray  matter. 

The  posterior  nerve-root  enters  the  cord  in  two  bundles,  mesial  and  lateral.  The 
mesial  strand  consists  of  coarse  fibres  which  enter  the  outer  part  of  the  column  of 
Burdach.  The  lateral  strand  is  sometimes  divided  into  a  middle  and  an  external 
bundle.  The  former  contains  large  fibres,  and  passes  through  the  gelatinous  sub- 
stance of  Rolando  into  the  posterior  horn.  The  external  bundle  consists  of  fine 
fibres  which  assume  a  longitudinal  direction  in  Lissauer's  tract.  All  the  posterior 
root-fibres  divide  into  ascending  and  descending  branches  on  entering  the  cord,  and 
these  in  their  turn  give  off  collaterals.  The  fibres  and  their  collaterals  terminate 
by  forming  arborescences,  some  around  the  cells  in  the  posterior  horn,  and  others 
around  the  cells  of  Clarke's  column,  while  the  long  ascending  branches  pass  up  in 
the  columns  of  Groll  and  Burdach,  and  end  by  arborizing  around  the  cells  in  the 
gracile  and  cuneate  nuclei.  Some  of  the  fibres,  however,  pass  to  the  gray  matter 
of  the  opposite  horn,  and  others  to  the  anterior  horn  of  the  same  side  of  the  cord. 

Anterior  Nerve-roots. — The  majority  of  the  fibres  of  the  anterior  nerve-roots  are 
the  continuations  outward  of  the  axons  of  the  large  or  small  multipolar  cells  in  the 
anterior  horn  of  gray  matter.  Some,  however,  appear  to  pass  across  in  the  anterior 
white  commissure  to  the  cells  in  the  anterior  horn  of  the  opposite  side,  while  others 
extend  backward  to  the  posterior  horn  and  outward  to  the  lateral  column  of  the 
same  side. 

The  Nerve-tracts. 

The  anatomy  of  the  various  parts  of  the  central  nervous  system  having  been 
described,  a  short  account  will  now  be  given  of  the  course  taken  by  its  more  impor- 
tant nerve-tracts,  and  of  the  direction  in  which  impulses  pass  along  them.  Before 
doing  so,  however,  it  is  necessary  to  refer  to  the  methods  employed  in  elucidating 
this  complex  subject.  All  nerve  fibres  may  be  regarded  as  outgrowths  from  nerve- 
cells,  and  it  is  found  that  if  a  nerve-fibre  be  cut,  the  portion  of  it  which  is  severed 
from  the  cell  undergoes  degeneration  and  becomes  atrophied.  Until  recent  years 
it  was  believed  that  the  cell  itself  showed  no  change  under  such  circumstances. 
This,  however,  is  not  the  case,  for  if  a  nerve,  the  sciatic  for  instance,  be  divided  in 
an  animal,  and  after  an  interval  of  some  weeks  the  animal  be  injected  with  mcthv- 
lene-blue  and  killed,  it  will  be  seen,  on  examining  sections  of  the  lumbar  region 
of  the  spinal  cord,  that  the  cells  are  stained  imperfectly  or  not  at  all,  owing  to  a 
diminution,  or,  it  may  be,  an  entire  disappearance  of  the  chromatin,  a  substance 
which,  in  a  normal  cell,  shows  marked  affinity  for  staining  reagents.  Further,  the 
body  of  the  cell  is  swollen,  the  nucleus  displaced  toward  the  periphery,  and  the 
part  of  the  axon  still  attached  to  the  altered  cell  is  diminished  in  size  and  some- 


718 


THE  NERVOUS  SYSTEM. 


what  atrophied.  Under  favorable  conditions  the  cell  is  capable  of  reassuming  its 
normal  appearance,  and  the  axon  may  commence  to  grow.  This  method  of  inject- 
ino-  methylene-blue  is  of  great  value  in  determining  the  origin  of  nerve-fibres  from 
their  cells.  Again,  stimulation  of  certain  localized  areas  of  the  brain  or  of  the 
tracts  arising  from  them  is  followed  by  the  contraction  of  the  muscles  of  the  body. 
These  cortical  centres  of  the  motor  tracts  are  situated  in  the  convolutions  adjacent 
to  the  fissure  of  Rolando.  When  the  stimulus  is  applied  to  one  part  the  muscles 
of  the  hind  limb  contract,  while  other  portions  control  the  movements  of  the  fore 
limb,  etc.  Destruction  of  these  parts  entails  loss  of  function,  paralysis  of  muscles, 
and  degeneration  of  the  tracts  below  the  seat  of  injury.  During  life  injury  and 
disease  may  give  rise  to  symptoms  resembling  either  the  effects  of  stimulation  or 
those  of  destruction ;  and  after  death  the  tracts,  or  the  centres  of  the  tracts,  are 
seen  to  be  degenerated  or  otherwise  altered.  Further,  by  observing  the  develop- 
ment of  the  nervous  system  during  the  growth  of  the  embryo,  the  fact  is  disclosed 
that  all  axis-cylinders  do  not  acquire  a  medullary  sheath  at  one  and  the  same  time. 
Speaking  generally,  it  may  be  said  that  afferent  fibres  become  medullated  before 
efferent,  and  that  in  the  case  of  the  latter  myelination  occurs  earlier  in  the  brain 
than  in  the  cord.  By  watching  the  effects  of  these  different  processes  the  func- 
tions of  a  considerable  part  of  the  brain  and  of  the  nerves  leading  from  or  to  it 
have  been  determined. 


The  Motor,  Efferent,  or  Descending  Tract. 

The  constituent  fibres  of  this  tract  are  the  axis-cylinder  processes  of  cells  situated 
in  the  cortex  of  the  convolutions  around  the  fissure  of  Rolando.  At  first  they  are 
somewhat  widely  diffused,   but  as  they  descend   through  the  corona  radiata  they 

gradually  approach  each  other  and 
pass  between  the  lenticular  nucleus 
and  optic  thalamus  in  the  genu  and 
anterior  two-thirds  of  the  posterior 
limb  of  the  internal  capsule.  Pro- 
ceeding downward  they  next  oc- 
cupy the  middle  of  the  pes  or 
crusta  of  the  crus  cerebri,  and 
enter  the  pons  Varolii,  where  the 
transverse  fibres  of  this  body  not 
only  conceal  them,  but  divide  them 
up  into  irregular  bundles.  Event- 
ually they  reach  the  medulla,  and 
here  the  motor  tracts  form  the 
anterior  pyramids  which  lie  one 
on  each  side  of  the  median  fissure. 
The  transit  of  the  fibres  from  the 
medulla  is  effected  by  two  paths. 
The  fibres  nearest  to  the  anterior 
median  fissure  cross  the  middle 
line,  forming  the  decussation  of  the 
pyramids,  and  descend  in  the  op- 
posite side  of  the  cord  as  the  indi- 
rect or  crossed  pyramidal  tract. 
Throughout  the  length  of  the 
spinal  cord  fibres  from  this  column 
pass  into  the  gray  matter,  to  ter- 
minate by  ramifying  around  the  cells  of  the  anterior  horn.  The  more  laterally 
placed  portion  of  the  motor  tract  does  not  decussate  in  the  medulla,  but  descends 
as  the  direct  or  uncrossed  pyramidal  tract ;  these  fibres,  however,  end  in  the  ante- 
rior gray  horn  of  the  opposite  side  of  the  spinal  cord  by  passing  across  in   the 


Fig.  388.— Dorsal  roots  entering  cord  and  dividing  into 
ascending  and  descending  branches.  (Van  Gehuchten.)  a, 
Stem-fibre ;  b,  b,  ascending  and  descending  limbs  of  bifurca- 
tion ;  c,  collateral  arising  from  stem-fibre. 


THE  NERVE    TRACTS.  719 

anterior  white  commissure.  Further,  it  must  he  rememhered  that  many  fibres 
which  descend  in  and  constitute  part  of  the  motor  tract  decussate  before  reaching 
the  medulla,  and  terminate  by  forming  synapses  with  the  nuclei  of  the  cranial 
nerves  situated  near  the  aqueduct  of  Sylvius,  in  the  pons  or  in  the  medulla  itself. 
There  is  considerable  variation  in  the  extent  to  which  decussation  takes  place  in 
the  medulla,  the  commonest  condition  being  that  in  which  about  three-fourths  of 
the  fibres  decussate  in  the  medulla  and  the  remainder  in  the  cord. 

Other  Descending  Tracts. 

1.  From  the  cortex  of  the  frontal  lobe,  anterior  to  the  Rolandic  area,  fibres 
arise  which  descend  through  the  anterior  limb  of  the  internal  capsule  and  enter 
the  crusta,  where  they  lie  to  the  inner  side  of  the  pyramidal  tract;  finally  they 
enter,  and  end  in,  the  pons. 

2.  Descending  fibres  also  take  origin  in  the  temporo-occipital  cortex  and  pass 
through  the  posterior  limb  of  the  internal  capsule  behind  the  fibres  from  the 
Rolandic  area.  They  pass  through  the  crusta,  where  they  lie  to  the  outer  side  of 
the  same  tract,  and  end  in  the  pons. 

3.  A  small  tract  arises  from  the  cells  of  the  caudate  nucleus  and  descends  to 
end  in  the  substantia  nigra  or  pons.  In  the  crus  cerebri  it  lies  immediately  above 
the  motor  tract,  which  is  on  its  ventral  aspect. 

The  Sensory,  Afferent,  Ascending  Tract. 

The  course  taken  by  those  fibres  of  the  posterior  nerve-roots  which  ascend  has 
been  arrived  at  by  dividing  the  nerve-roots  between  their  ganglia  and  their  entrance 
into  the  spinal  cord  and  subsequently  examining  the  degenerated  areas.  It  has 
been  found  that  the  fibres  pursue  an  oblique  course,  being  situated  at  first  in  the 
outer  part  of  Burdach's  column;  higher  up  they  occupy  the  middle  of  this  column, 
being  displaced  inward  by  the  accession  of  other  entering  fibres,  while  still  higher 
they  enter  and  are  continued  upward  in  the  column  of  Goll.  The  upper  cervical 
fibres  do  not  reach  the  column  of  Goll,  but  are  entirely  confined  to  that  of  Bur- 
dach.  The  degeneration  method  proves  that  the  localization  of  these  fibres  is  very 
precise  :  the  sacral  nerves  lying  to  the  inner  side  of  Goll's  column  and  near  its 
periphery ;  the  lumbar  nerves  to  their  outer  side ;  the  dorsal  nerves  still  more 
laterally :  while  the  cervical  nerves  are  confined  to  the  outer  part  of  Burdach's 
column. 

On  reaching  the  medulla  these  ascending  fibres  end  by  arborizing  around  the 
cells  in  the  gracile  and  cuneate  nuclei,  and  the  further  upward  course  of  the  tract 
is  effected  by  the  axis-cylinder  processes  of  these  cells.  These  new  fibres  decus- 
sate in  the  medulla,  dorsal  to  the  crossing  of  the  motor  tract,  in  what  is  termed 
the  superior  pyramidal  decussation,  the  sensory  decussation,  or  decussation  of  the 
fillet;  terms  which  are  synonymous.  Having  crossed  the  middle  line  they  ascend 
through  the  pons  and  tegmentum  of  the  crus  cerebri,  and,  reaching  the  ventral 
surface  of  the  optic  thalamus,  the  majority  end  either  in  the  subthalamic  region  or 
in  the  optic  thalamus,  but  a  small  proportion  is  continued  directly  into  the  brain 
cortex.  From  the  gray  matter  of  the  optic  thalamus  the  fibres  of  the  third  link 
in  the  chain  arise.  They  pass  through  the  internal  capsule  and  end  in  the  cere- 
bral cortex  :  those  which  go  to  the  fronto-parietal  cortex  being  situated  in  the 
extreme  front  part  of  the  anterior  limb  of  the  internal  capsule,  while  in  the  hinder 
extremity  of  the  posterior  limb  other  fibres  pass  to  their  distribution  in  the  tem- 
poral and  occipital  cortex. 

Other  Ascending  Tracts. 

The  direct  cerebellar  tract  begins  about  the  level  of  the  second  lumbar  vertebra, 
and  is  the  continuation  upward  of  the  axis-cylinders  of  Clarke's  column.  At  the 
upper  end  of  the  cord  it  passes  into  the  restiform  body  and  through  this  reaches 


720  THE   NERVOUS  SYSTEM. 

the  cerebellum.  This  tract  seems  to  lose  some  of  its  fibres  in  the  cord,  since  the 
area  of  its  degeneration  resulting  from  a  section  of  the  lower  part  of  the  cord 
diminishes  from  below  upward ;  only  some  of  its  fibres  therefore  pass  directly  to 
the  cerebellum.  On  the  other  hand,  the  tract  is  reinforced  by  an  accession  of  fibres 
from  the  cord  itself,  so  that  its  transverse  area  is  greater  above  than  below. 

The  antero-lateral  ascending  tract  of  Gower  arises  in  the  cord,  probably  as  the 
axis-cylinders  of  cells  situated  in  the  posterior  horn.  Passing  across  the  middle 
line  through  the  anterior  gray  commissure  the  fibres  ascend  in  the  antero-lateral 
column  of  the  cord,  and  ultimately  reach  the  cerebellum  through  its  superior 
peduncles.1 

THE    CRANIAL   NERVES. 

The  cranial  nerves  arise  from  some  part  of  the  cerebrospinal  centre,  and  are 
transmitted  through  foramina  in  the  base  of  the  cranium.  They  have  been  named 
numerically,  according  to  the  order  in  which  they  pass  through  the  dura  mater 
lining  the  base  of  the  skull.  Other  names  are  also  given  to  them,  derived  from 
the  parts  to  which  they  are  distributed  or  from  their  functions.  Taken  in  their 
order,  from  before  backward,  they  are  as  follows  : 

1st.  Olfactory.  7th.  Facial  (Portio  dura). 

2d.  Optic.  8th.  Auditory  (Portio  mollis). 

3d.  Motor  oculi.  9th.  Glosso-pharyngeal. 

4th.  Trochlear  (Pathetic).  10th.  Pneumogastric  (or  Vagus). 

5th.  Trifacial  (Trigeminus).  11th.  Spinal  accessory. 

6th.  Abducent.  12th.  Hypoglossal. 

All  the  cranial  nerves  are  connected  to  some  part  of  the  surface  of  the  brain. 
This  is  termed  their  superficial  or  apparent  origin.  But  their  fibres  may,  in  all 
cases,  be  traced  deeply  into  the  substance  of  the  brain  to  some  special  centre  of 
gray  matter,  termed  a  nucleus.  This  is  called  their  deep  or  real  origin.  The 
nerves,  after  emerging  from  the  brain  at  their  apparent  origin,  pass  through 
foramina  or  tubular  prolongations  in  the  dura  mater,  leave  the  skull  through 
foramina  in  its  base,   and  pass  to   their  final  distribution. 

The  First  Nerve  (Fig.  350,  page  654). 

The  First  cranial  or  the  Olfactory  nerves  (nn.  olfactorii),  the  special  nerves  of 
the  sense  of  smell,  are  about  twenty  in  number.  They  are  given  off'  from  the  under 
surface  of  the  olfactory  bulb,  an  oval  mass  of  a  grayish  color,  which  rests  on  the 
cribriform  plate  of  the  ethmoid  bone,  and  forms  the  anterior  expanded  extremity 
of  a  slender  process  of  brain-substance,  named  the  olfactory  tract.  The  olfactory 
tract  and  bulb  have  already  been  described  (page  654). 

Each  nerve  is  surrounded  by  a  tubular  prolongation  from  the  dura  mater  and 
pia  mater,  the  former  being  lost  on  the  periosteum  lining  the  nose,  the  latter  in 
the  neurilemma  of  the  nerve.  The  nerves,  as  they  enter  the  nares,  are  divisible 
into  two  groups :  an  inner  group,  larger  than  those  on  the  outer  wall,  spread  out 
over  the  upper  third  of  the  septum  ;  and  an  outer  set,  which  is  distributed  over 
the  superior  turbinated  bone,  and  the  surface  of  the  ethmoid  in  front  of  it.  As 
the  filaments  descend,  they  unite  in  a  plexiform  network,  and  are  believed  by  most 
observers  to  terminate  by  becoming  continuous  with  the  deep  extremities  of  the 
olfactory  cells. 

The  olfactory  differs  in  structure  from  other  nerves  in  being  composed 
exclusively  of  non-medullated  fibres.  They  are  deficient  in  the  white  substance 
of  Schwann,  and  consist  of  axis-cylinders,  with  a  distinct  nucleated  sheath,  in 
which  there  are,  however,  fewer  nuclei  than  in  ordinary  non-medullated  fibres. 
The  olfactory  centre  in  the  cortex  is  not  definitely  known.     It  is  generally  asso- 

1  Testut  describes  the  ascending  column  of  Gower  as  joining  with  the  fillet,  and  through  it  being 
carried  to  the  cerebral  cortex. 


THE  SECOND    OB    OPTIC  NERVE. 


721 


ciated  with  the  temporal  lobe,  where  it  probably  includes  the  gyrus  hippocampi, 
uncus,  and  hippocampus  major.  It  is  further  described  as  comprising  the  part 
of  the  callosal  convolution  which  lies  below  the  genu  and  rostrum  of  the  corpus 
callosum,  and  also  the  posterior  part  of  the  orbital  surface  of  the  frontal  lobe. 

Surgical  Anatomy. — In  severe  injuries  to  the  head  the  olfactory  bulb  may  become  sepa- 
rated from  the  olfactory  nerves,  thus  producing  loss  of  the  sense  of  smelling  [anosmia),  and  with 
this  a  considerable  loss  in  the  sense  of  taste,  as  much  of  the  perfection  of  the  sense  of 
taste  is  due  to  the  saj)id  substances  being  also  odorous  and  simultaneously  exciting  the  sense  of 
smell. 

The  Second  Nerve  (Fig.  389). 

The  Second  or  Optic  nerve  (n.  opticus),  the  special  nerve  of  the  sense  of  sight, 
is  distributed  exclusively  to  the  eyeball.      The  nerves  of  opposite  sides  are  connected 
together  at  the  commissure,  and  from  the  back 
of  the  commissure  they  may  be  traced  to  the 
brain,  under  the  name  of  the  optic  tracts. 

The  optic  tract,  at  its  connection  with  the 
brain,  is  divided  into  two  bands,  external  and 
internal.  The  external  band  is  the  larger ;  it 
arises  from  the  external  geniculate  body  and 
from  the  under  part  of  the  pulvinar  of  the  optic 
thalamus,  and  is  partly  continuous  Avith  the 
brachium  of  the  anterior  or  upper  quadrigeminal 
body.  The  internal  band  curves  round  the 
crusta,  and  passes  beneath  the  internal  genicu- 
late body,  with  which  it  is  connected,  and  then 
appears  to  lose  itself  in  the  brachium  of  the 
posterior  or  inferior  quadrigeminal  body.  The 
fibres  by  which  it  is  connected  to  the  internal 
geniculate  body  are  merely  commissural,  form- 
ing part  of  Gudden's  commissure.  From  this 
origin  the  tract  winds  obliquely  across  the  under 
surface  of  the   crus  cerebri,  in  the  form  of  a 

flattened  band,  and  is  attached  to  the  crus  by  its  anterior  margin.  It  then  assumes 
a  cylindrical  form,  and,  as  it  passes  forward,  is  connected  with  the  tuber  cinereum 
and  lamina  cinerea.  It  finally  joins  with  the  tract  of  the  opposite  side  to  form  the 
optic  commissure. 

The  commissure  or  chiasma,  somewhat  quadrilateral  in  form,  rests  upon  the 
olivary  eminence  and  on  the  anterior  part  of  the  diaphragma  sellse,  being  bounded, 
above,  by  the  lamina  cinerea ;  behind  by  the  tuber  cin- 
ereum ;  on  either  side  by  the  anterior  perforated  space. 
Within  the  commissure,  the  optic  nerves  of  the  two 
sides  undergo  a  partial  decussation.  The  fibres  which 
form  the  inner  margin  of  each  tract  and  posterior 
part  of  the  commissure  have  no  connection  with  the 
optic  nerves.  They  simply  pass  across  the  commissure 
from  one  hemisphere  of  the  brain  to  the  other,  and  con- 
nect the  internal  geniculate  bodies  of  the  two  sides. 
They  are  known  as  the  commissure  of  Gudden.  The  remainder  and  principal 
part  of  the  commisr;ire  consists  of  two  sets  of  fibres,  crossed  and  uncrossed.  The 
crossed,  which  are  the  more  numerous,  occupy  the  central  part  of  the  chiasma.  and 
pass  from  the  optic  tract  of  one  side  to  the  optic  nerve  of  the  other,  decussating  in 
the  commissure  with    sinvlar  fibres  of  the  opposite  tract.      The  uncrossed  fibres 

apy  the  oute)      trt  of  the  chiasma,  ai"'  •         from  the  tract  of  one  side  to   the 
e  of  the  sam  * 

1 A  specimen  of  ibsence  of  the  0]  ure  is  to  be  found  in  the  Museum  of  *the 

tminster  Hospit  >  Henle,  Nerverdi  d.  2. 

46 


Fig.  389.- 
tracts. 


The  left  optic  nerve  and  optic 


Fig.  390.— Course   of  the  fibres 
in  the  optic  commissure. 


722  THE  NERVOUS  SYSTEM. 

The  great  majority  of  the  fibres  of  the  optic  nerve  consist  of  the  afferent  axons 
of  nerve-cells  in  the  retina.  Some  few,  however,  are  efferent  fibres,  and  grow  out 
from  the  brain.  The  afferent  fibres  end  in  arborizations  around  the  cells  in  the 
external  geniculate  body,  pulvinar,  and  upper  quadrigeminal  body,  which  are  some- 
times termed  the  lower  visual  centres.  From  these  nuclei  other  fibres  are  prolonged 
to  the  cortical  visual  centre,  which,  according  to  most  observers,  is  situated  in  the 
cuneus,  and  probably  also  in  the  lingual  lobule  of  the  occipital  lobe. 

It  should  be  stated  that  some  fibres  are  detached  from  the  optic  tract,  and  pass 
through  the  crus  cerebri  to  the  nucleus  of  the  third  nerve.  These  fibres  are  small, 
and  may  be  regarded  as  afferent  branches  for  the  sphincter  pupillas  and  ciliary 
muscles.  Other  fibres  pass  to  the  cerebellum  through  its  superior  peduncles,  while 
others,  again,  are  lost  in  the  pons. 

The  optic  nerves  arise  from  the  fore  part  of  the  commissure,  and,  diverging 
from  one  another,  become  rounded  in  form  and  firm  in  texture,  and  are  enclosed  in 
a  sheath  derived  from  the  pia  mater  and  arachnoid.  As  each  nerve  passes  through 
the  corresponding  optic  foramen  it  receives  a  sheath  from  the  dura  mater ;  and  as 
it  enters  the  orbit  this  sheath  subdivides  into  two  layers,  one  of  which  becomes  con- 
tinuous with  the  periosteum  of  the  orbit ;  the  other  forms  the  proper  sheath  of  the 
nerve  and  surrounds  it  as  far  as  the  sclerotic.  The  nerve  passes  forward  and  out- 
ward through  the  cavity  of  the  orbit,  pierces  the  sclerotic  and  choroid  coats  at  the 
back  part  of  the  eyeball,  about  one-eighth  of  an  inch  to  the  nasal  side  of  its  centre, 
and  expands'  into  the  retina.  A  small  artery,  the  arteria  centralis  retinas,  perfo- 
rates the  optic  nerve  a  little  behind  the  globe,  and  runs  along  its  interior  in  a 
tubular  canal  of  fibrous  tissue.  It  supplies  the  inner  surface  of  the  retina,  and  is 
accompanied  by  corresponding  veins. 

Surgical  Anatomy. — The  optic  nerve  is  peculiarly  liable  to  become  the  seat  of  neuritis  or 
undergo  atrophy  in  affections  of  the  central  nervous  system,  and,  as  a  rule,  the  pathological 
relationship  between  the  two  affections  is  exceedingly  difficult  to  trace.  There  are,  however, 
certain  points  in  connection  with  the  anatomy  of  this  nerve  which  tend  to  throw  light  upon  the 
frequent  association  of  these  affections  with  intracranial  disease  :  (1 )  From  its  mode  of  develop- 
ment and  from  its  structure  the  optic  nerve  must  be  regarded  as  a  prolongation  of  the  brain-sub- 
stance, rather  than  as  an  ordinary  cerebrospinal  nerve.  (2)  As  it  passes  from  the  brain  it  receives 
sheaths  from  the  three  cerebral  membranes — a  perineural  sheath  from  the  pia  mater,  an  inter- 
mediate sheath  from  the  arachnoid,  and  an  outer  sheath  from  the  dura  mater,  which  is  also  con- 
nected with  the  periosteum  as  it  passes  through  the  optic  foramen.  These  sheaths  are  separated 
from  each  other  by  spaces  which  communicate  with  the  subdural  and  subarachnoid  spaces 
respectively.  The  innermost  or  perineural  sheath  sends  a  process  around  the  arteria  centralis 
retinae  into  the  interior  of  the  nerve,  and  enters  intimately  into  its  structure.  Thus  inflamma- 
tory affections  of  the  meninges  or  of  the  brain  may  readily  extend  themselves  along  these  spaces 
or  along  the  interstitial  connective  tissue  in  the  nerve. 

The  course  of  the  fibres  in  the  optic  commissure  has  an  important  pathological  bearing,  and 
has  been  the  subject  of  much  controversy.  Microscopic  examination,  experiments,  and  pathology 
all  seem  to  point  to  the  fact  that  there  is  a  partial  decussation  of  the  fibres,  each  tract  supplying 
the  corresponding  half  of  each  eye,  so  that  the  right  tract  supplies  the  right  half  of  each  eye, 
and  the  left  tract  the  left  half  of  each  eye.  At  the  same  time,  Charcot  believes — and  his  view 
has  met  with  general  acceptation — that  the  fibres  which  do  not  decussate  at  the  optic  commis- 
sure have  already  decussated  in  the  corpora  quadrigemina,  so  that  lesion  of  the  cerebral  centre 
of  one  side  causes  complete  blindness  of  the  opposite  eye,  because  both  sets  of  decussating  fibres 
are  destroyed.'  Whereas  should  one  tract — say  the  right — be  destroyed  by  disease,  there  will  be 
blindness  of  the  right  half  of  both  retinas. 

An  antero-posterior  section  through  the  commissure  would  divide  the  decussating  fibres, 
and  would  therefore  produce  blindness  of  the  inner  half  of  each  eye ;  while  a  section  at  the 
margin  of  the  side  of  the  optic  commissure  would  produce  blindness  of  the  external  half  of  the 
retina  of  the  same  side. 

The  optic  nerve  may  also  be  affected  in  injuries  or  diseases  involvi*  2  the  orbit,  in  fractures 
of  the  anterior  fossa  of  the  base  of  the  skull,  in  tumors  of  the  orbit  itself,  or  those  invading  this 
cavity  from  neighboring  parts. 

The  Third  Nerve  (Figs.  391,  392,  393). 

The  Third  or  Motor  oculi  nerve  (n.  qeulo-motorirts)  supplies  all  the  muscles 
of* the  orbit  except  the  Superior  oblique  and  Extern/al  rectus;  it  also  supplies, 
through  its  connection  with  the  ciliary  ganglion,  the  Sphincter  muscle  of  the  iris 


THE    THIRD    OR    MOTOR    OCULI  NERVE. 


723 


and  the  Ciliary  muscle.     It  is  rather  a  large  nerve,  of  rounded  form  and  firm 
texture.  ^ 

Its  aparent  origin  is  from  the  inner  surface  of  the  crus  cerebri,  immediately^ 
front  of  the  pons  Varolii.  The  deep  origin  may  be  traced  through  the  substantia 
nigra  and  tegmentum  of  the  crus  to  a  nucleus  situated  on  either  side  of  the  me- 
dian line  beneath  the  floor  of  the  aqueduct  of  Sylvius.  The  nucleus  of  the  third 
nerve  also  receives  fibres  from  the  sixth  nerve  of  the  opposite  side.  These  will 
be  referred  to  again  in  the  description  of  the  latter  nerve.  The  nucleus  of  the 
third  nerve,  considered  from  a  physiological  standpoint,  can  be  subdivided  into 
several  smaller  groups  of  cells,  each  group  controlling  a  particular  muscle.  The 
nerves  to  the  different  muscles  appear  to  take  their  origin  from  before  backward, 
as  follows :  Inferior  oblique,  Inferior  rectus,  Superior  rectus  and  Levator  palpe- 
brse,  Internal  rectus ;  while  from  the  anterior  end  of  the  nucleus  the  fibres  for 
accommodation  and  for  the  Sphincter  pupillae  take  their  origin. 


Tnfratrochlear 
nerve. 


4#N. 

Motor  root.   /  % — Recurrent  filament 
Sensory  root.  to  dura  mater. 

Fig.  391.— Nerves  of  the  orbit.    Seen  from  above. 

On  emerging  from  the  brain,  the  nerve  is  invested  with  a  sheath  of  pia  mater, 
and  enclosed  in  a  prolongation  from  the  arachnoid.  It  passes  between  the 
superior  cerebellar  and  posterior  cerebral  arteries,  and  then  pierces  the  dura 
mater  in  front  of  and  external  to  the  posterior  clinoid  process,  passing  between 
the  two  processes  from  the  free  and  attached  borders  of  the  tentorium,  which  are 
prolonged  forward  to  be  connect*  1  with  the  anterior  and  posterior  clinoid 
processes  of  the  sphenoid  bo  i  It  passes  along  the  outer  wall  of  the  cavernous 
sinus,  above  the  other  orbital  ■  receiving  in  its  course  one  or  two  filaments 

from  the  cavernous  plexus  of  the  sympathetic,  and  a  communicating  branch  from 
the  first  division  of  the  fifth,      tt  then  divides  into  two  branches,  which  enter  the 


724 


THE   NERVOUS  SYSTEM. 


orbit  through  the  sphenoidal  fissure,  between  the  two  heads  of  the  External  rectus 
muscle.  On  passing  through  the  fissure,  the  nerve  is  placed  below  the  fourth  and 
the  frontal  and  lachrymal  branches  of  the  ophthalmic  nerve,  and  has  passing  be- 
tween its  two  divisions  the  nasal  nerve. 

The  superior  division,  the  smaller,  passes  inward  over  the  optic  nerve,  and 
supplies  the  Superior  rectus  and  Levator  palpebrfe. 

The  inferior  division,  the  larger,  divides  into  three  branches.  One  passes 
beneath  the  optic  nerve  to  the  Internal  rectus ;  another,  to  the  Inferior  rectus 
and  the  third,  the  longest  of  the  three,  passes  forward  between  the  Inferior  and 
External  recti  to  the  Inferior  oblique.  From  this  latter  a  short,  thick  branch  is 
given  off  to  the  lower  part  of  the  lenticular  ganglion,  which  forms  its  inferior 
root.  It  also  gives  off  one  or  two  filaments  to  the  Inferior  rectus.  All  these 
branches  enter  the  muscles  on  their  ocular  surface,  except  that  to  the  Inferior 
oblique,  which  enters  its  posterior  border. 

Surgical  Anatomy. — Paralysis  of  the  third  nerve  maybe  the  result  of  many  causes :  as 
cerebral  disease ;  conditions  causing  pressure  on  the  cavernous  sinus ;  periostitis  of  the  bones 
entering  into  the  formation  of  the  sphenoidal  fissure.  It  results,  when  complete,  in  (1)  ptosis, 
or  drooping  of  the  upper  eyelid,  in  consequence  of  the  Levator  palpebrae  being  paralyzed ;  (2) 
external  strabismus,  on  account  of  the  unopposed  action  of  the  External  rectus  muscle,  which 
is  not  supplied  by  the  third  nerve,  and  is  not  therefore  paralyzed ;  (3)  dilatation  of  the  pupil, 
because  the  sphincter  fibres  of  the  iris  are  paralyzed ;  (4)  loss  of  power  of  accommodation,  as 
the  sphincter  pupillae,  the  ciliary  muscle,  and  the  Internal  rectus  are  paralyzed ;  (5)  slight 
prominence  of  the  eyeball,  owing  to  most  of  its  muscles  being  relaxed.  Occasionally  paralysis 
may  affect  only  a  part  of  the  nerve;  that  is  to  say,  there  may  be,  for  example,  a  dilated  and 
fixed  pupil,  with  ptosis,  but  no  other  signs.  Irritation  of  the  nerve  causes  spasm  of  one  or  other 
of  the  muscles  supplied  by  it ;  thus,  there  may  be  internal  strabismus  from  spasm  of  the  Internal 
rectus ;  accommodation  for  near  objects  only  from  spasm  of  the  ciliary  muscle,  or  myosis,  contrac- 
tion of  the  pupil,  from  irritation  of  the  sphincter  of  the  pupil. 

The  Fourth  Nerve  (Fig.  391). 

The  Fourth  or  Trochlear  nerve  (n.  trochlears),  the  smallest  of  the  cranial 
nerves,  supplies. the  Superior  oblique  muscle. 

Its  apparent  origin,  at  the  base  of  the  brain,  is  on  the  outer  side  of  the  crus 
cerebri,  just  in  front  of  the  pons  Varolii,  but  the  fibres  can  be  traced  backward 


LEVATOR    PALPEBRC. 


Fig.  392.— Plan  of  the  motor  oculi  nerve.    (After  Flower/ 


behind  the  corpora  quadrigemina  to  the  valve  of  Vieussens,  on  the  upper  surface 
of  which  the  two  nerves  decussate.  Its  deep  origin-may  be  traced  to  a  nucleus 
in  the  floor  of  the  aqueduct  of  Sylvius  immediately  below  that  of  the  third  nerve, 
Avith  which  it  is  continuous. 


THE   FIFTH   OR    TRIFACIAL    NERVE.  725 

Emerging  from  the  upper  end  of  the  valve  of  Vieussens,  the  nerve  is  directed 
outward  across  the  superior  peduncle  of  the  cerebellum,  and  then  winds  forward 
round  the  outer  side  of  the  crus  cerebri,  immediately  above  the  pons  Varolii, 
pierces  the  dura  mater  in  the  free  border  of  the  tentorium  cerebelli,  just  behind, 
and  external  to,  the  posterior  clinoid  process,  and  passes  forward  in  the  outer 
wall  of  the  cavernous  sinus,  between  the  third  nerve  flitd  the  ophthalmic  division 
of  the  fifth.  It  crosses  the  third  nerve  and  enters  the  orbit  through  the  sphe- 
noidal fissure.  It  now  becomes  the  highest  of  all  the  nerves,  lying  at  the  inner 
extremity  of  the  fissure  internal  to  the  frontal  nerve.  In  the  orbit  it  passes 
inward,  above  the  origin  of  the  Levator  palpebrse,  and  finally  enters  the  orbital 
surface  of  the  Superior  oblique  muscle.  In  the  outer  wall  of  the  cavernous 
sinus  this  nerve  is  not  infrequently  blended  with  the  ophthalmic  division  of  the 
fifth. 

Brandies  of  Communication. — In  the  outer  wall  of  the  cavernous  sinus  it 
receives  some  filaments  from  the  cavernous  plexus  of  the  sympathetic.  In  the 
sphenoidal  fissure  it  occasionally  gives  off  a  branch  to  assist  in  the  formation  of 
the  lachrymal  nerve. 

Brandies  of  Distribution. — It  gives  off  a  recurrent  branch,  which  passes  back- 
ward between  the  layers  of  the  tentorium,  dividing  into  two  or  three  filaments 
which  may  be  traced  as  far  back  as  the  wall  of  the  lateral  sinus. 

Surgical  Anatomy. — The  fourth  nerve  when  paralyzed  causes  loss  of  function  in  the 
Superior  oblique,  so  that  the  patient  is  unable  to  turn  his  eye  downward  and  outward.  Should 
the  patient  attempt  to  do  this,  the  eye  on  the  affected  side  is  twisted  inward,  producing-  diplopia 
or  double  vision.  Accordingly,  it  is  said  that  the  first  symptom  of  this  disease  which  presents 
itself  is  giddiness  when  going  down  hill  or  in  descending  stairs,  owing  to  the  double  vision 
induced  by  the  patient  looking  at  his  steps  while  descending. 

The  Fifth  Nerve. 

The  Fifth  or  Trifacial  Nerve  (n.  trigeminus)  is  the  largest  cranial  nerve.  It 
resembles  a  spinal  nerve  (1)  in  arising  by  two  roots ;  (2)  in  having  a  ganglion 
developed  on  its  posterior  root;  and  (3)  in  its  function,  since  it  is  a  compound 
nerve.  It  is  the  great  sensory  nerve  of  the  head  and  face  and  the  motor  nerve 
of  the  muscles  of  mastication.  Its  upper  two  divisions  are  entirely  sensory  ;  the 
third  division  is  partly  sensory  and  partly  motor.  It  arises  by  two  roots :  of  these 
the  anterior  is  the  smaller,  and  is  the  motor  root ;  the  posterior,  the  larger  and 
sensory.  Its  superficial  origin  is  from  the  side  of  the  pons  Varolii,  nearer  to  the 
upper  than  the  loAver  border.  The  smaller  root  consists  of  three  or  four  bundles; 
the  larger  root  consists  of  numerous  bundles  of  fibres,  varying  in  number  from 
seventy  to  a  hundred.  The  two  roots  are  separated  from  one  another  by  a  few  of 
the  transverse  rbres  of  the  pons.  The  deep  origin  of  the  larger  or  sensory  root 
is  chiefly  from  a ;  long  tract  in  the  medulla,  the  lower  sensory  nucleus,  which  is 
continuous  below  with  the  substantia  gelatinosa  of  Rolando.  The  fibres  from  this 
nucleus  form  the.  .V>-calied  ascending  root  of  the  fifth  ;  they  pass  upward  through 
the  pons  and  join  with  fibres  from  the  locus  cseruleus  or  upper  sensory  nucleus, 
which  is  situated  t  the  titer  side  of  the  nucleus,  from  which  the  lower  part  of 
the  motor  root  t,i  '<  H*11*  ^he  deep  origin  of  the  smaller  or  motor  root  is 
derived  partly  fr-  icleus  embedded  in  the  gray  matter  of  the  upper  part  of 

the  floor  of  the  p  "iitricle  and  partly  from  a  collection  of  nerve-cells  situated 

at  the  side  of  tbara  I  of  Sylvius,  from  which  the  fibres  pass  downward  under 

the  name  of  therti  /  root  of  the  fifth.      The  real  origin  of  the  sensory  root 

is  from  the  Gaswv  unglion,  which   corresponds  with  the  ganglion  on  a  spinal 

nerve  (see  Develo;  Spinal  Nerves  in  section  on  Embryology). 

The  two  roofc«  ,,.■—-   ~ass   forward  below  the  tentorium  cerebelli  as  it 

bridges  over  the  a  er   part   of  the  superior  border  of  the  petrous 

portion  of  the   t  |>ne :    they   then  run  between  the  bone  and  the  dura 

mater  to  the  ap  I  portion  of  the  temporal  bone,  where  the  fibres 

of  the  sensory  rcr«i  Blarir       emilunar  ganglion  (Gfasserian),  while  the  motor 


726  THE  NEBVOUS  SYSTEM. 

root  passes  beneath  the  ganglion  without  having  any  connection  with  it,  and  joins 
outside  the  cranium  with  one  of  the  trunks  derived  from  it. 

The  Gasserian  or  semilunar  ganglion1  is  lodged  in  an  osteo-fibrous  space,  the 
cavum  Meckelii,  near  the  apex  of  the  petrous  portion  of  the  temporal  bone.  It  is 
of  somewhat  crescentic  foitek.  with  its  convexity  turned  forward.  Its  upper  surface 
is  intimately  adherent  tof;TOe>'dura  mater.  Besides  the  small  or  motor  root,  the 
large  superficial  petrosal  nerve  lies  underneath  the  ganglion. 

Branches  of  Communication. — This  ganglion  receives,  on  its  inner  side,  fila- 
ments from  the  carotid  plexus  of  the  sympathetic.  Branches  of  Distribution. — It 
gives  off  minute  branches  to  the  tentorium  cerebelli  and  the  dura  mater  in  the 
middle  fossa  of  the  cranium.  From  its  anterior  border,  which  is  directed  for.vard 
and  outward,  three  large  branches  proceed — the  ophthalmic,  superior  maxillary, 
and  inferior  maxillary.  The  ophthalmic  and  superior  maxillary  consist  exclu- 
sively of  fibres  derived  from  the  larger  root  and  ganglion,  and  are  solely  nerves 
of  common  sensation.  The  third  division,  or  inferior  maxillary,  is  joined  outside 
the  cranium  by  the  motor  root.  This,  therefore,  strictly  speaking,  is  the  only 
portion  of  the  fifth  nerve  which  can  be  said  to  resemble  a  spinal  nerve. 

Ophthalmic  Nerve  (Figs.  391,  393,  394). 

The  Ophthalmic  (n.  ophthalmicus),  or  first  division  of  the  fifth,  is  a  sensory 
nerve.  It  supplies  the  eyeball,  the  lachrymal  gland,  the  mucous  lining  of  the  eye 
and  nasal  fossae,  and  the  integument  of  the  eyebrow,  forehead,  and  nose.  It  is 
the  smallest  of  the  three  divisions  of  the  fifth,  arising  from  the  upper  part  of  the 
Gasserian  ganglion.  It  is  a  short,  flattened  band,  about  an  inch  in  length,  which 
passes  forward  along  the  outer  wall  of  the  cavernous  sinus,  below  the  other  nerves, 
and  just  before  entering  the  orbit,  through  the  sphenoidal  fissure,  divides  into 
three  branches — lachrymal,  frontal,   and  nasal. 

Branches  of  Communication. — The  ophthalmic  nerve  is  joined  by  filaments 
from  the  cavernous  plexus  of  the  sympathetic,  communicates  with  the  third  and 
sixth  nerves,  and  is  not  infrequently  joined  with  the  foui 

Branches  of  Distribution. — It  gives  off  recurrent  filaments  which  pass  between 
the  layers  of  the  tentorium,  and  then  divides  into 

Lachrymal.  Frontal.  Nasal. 

The  lachrymal  is  the  smallest  of  the  three  branch  ?a  of  the  ophthalmic.  It 
sometimes  receives  a  filament  from  the  fourth    ler  e,  b    '  is  possibly  derived 

from  the  branch  of  communication  which  pc:se...  fror  th<;  ophthalmic  to  the  fourth. 
It  passes  forward  in  a  separate  tube  of  duri*  n  ater    ind  the  orbit  through 

the  narrowest  part  of  the  sphenoidal  fissure.      In  the  orbi  ie  along  the  upper 

border  of  the  External  rectus  muscle,  with  the  lachry;  ry,  and  communi- 

cates with  the  temporo-malar  branch   of  the   superior  It  enters   the 

lachrymal  gland  and  gives  off  several   filamerr^    which  g  the  gland  and  the 

conjunctiva.  Finally,  it  pierces  the  superior  palpebral  igagjsnt,  and  terminates 
in  the  integument  of  the  upper  eyelid,  joining  with  fi'  [  the  facial  nerve* 

The  lachrymal  nerve  is  occasionally  absent,  when  its  place  is  taken  by  the  temporal 
branch  of  the  superior  maxillary.      Sometimes  the  la  a  is  absent,  and  a 

continuation  of  the  lachrymal  is  substituted  for  it. 

The  frontal  is  the  largest  division  of  the  ophthalmi<  be  regarded,  both 

from  its  size  and  dix-ection,  as  the  continuation  of  the  nerve.  It  enters  the  orbit 
above  the  muscles,  through  the  sphenoidal   fissure,  anu  :)rward  along  the 

middle  line,  between  the  Levator  palpebrse  and  the  per;'  Midway  between 

1  A  Viennese  anatomist.  Raimund  Balthasar  Hirsch  (1765)5^  he  first  who  recognized  the 
ganglionic  nature  of  the  swelling  on  the  sensory  root  of  the  fifth  ae  f  *md  called  it,  in  honor  of  his 
otherwise  unknown  teacher,  Jon.  Laur.  Gasser,  the  "  GanglionfGal  |  Jt    'us  Casserius  whose 

name  is  given  to  the  musculo-cutaneous  nerve  of  the  arm,  was  prafea.^ff  at  P^dua,  1545-1605.  (See 
Hyrtl,  Lehrbuch  der  Anatomie,  p.  895  and  p.  55.) 


7  ;   BRANCHES    OF    THE   FIFTH  NERVE. 


727 


the  apex  and  the  1  ise  of  the  orbit  it  divides  into  two  branches,  supratrochlear  and 
supra-orbital. 

The  supratrochlear  branch,  the  smaller  of  the  two,  passes  inward,  above  the 
pulley  of  the  superior  oblique  muscle,  and  gives  off  a  descending  filament,  which 
joins  with  the  infratrochlear  branch  of  the  nasal  nerve.  It  then  escapes  from  the 
orbit  between  the  pulley  of  the  Superior  oblique  and  the  supra-orbital  foramen, 
curves  up  on  ta  the  forehead  close  to  the  bone,  ascends  beneath  the  Corrugator 
sur  jrcilii  and  Qccipito-frontalis  muscles,  and,  dividing  into  branches  which  pierce 
these  muscles,  it  supplies  the  integument  of  the  lower  part  of  the  forehead  on 
either  side  of  the  middle  line  and  sends  filaments  to  the  conjunctiva  and  skin  of 
the,  upper  lid. 


Internal  carotid  artery 
and  carotid  plexus, 


Motor  root: 


Fig.  393.— Nerves  of  theo&ruit  and  ophthalmic  ganglion.    Side  view. 

The   supra-orbital  branch  passes   forward  through  the   supra-orbital  foramen, 

and  gives  off,  in  this  situation,  palpebral  filaments  to  the  upper  eyelid.     It   then 

ascends  upon  the  forehead,  and  terimnartes  in  cutaneous  and  pericranial  branches. 

The    cutaneous    branches,  tv  i.   i.i    ;<)un}ber,  an    inner    and    an   outer,  su^V  t1-  ^ 

integument  of  the  cranium  -■"■  far^fja  ;1|[  as  the  occiput.     They  are  .--^fseparatelj. 

beneath  the  Occipito-fronta    t,  th*r  inner  branch  perforating  +^mumcation  from 

the  muscle,  the  outer  branch  its  f        'ions  aponeurosis.     "~        m,  -,  ■,. 

These  are  delicate 


mm 


nous  aponeurosis. 
:e  snort  -.  .  i      serves. 
~  al  ar 


are  distributed  to  the  pericrania" 

The  Nasal  nerve  is  intermectber'  whl.ch  arif  ir°mthe  fo™  Par+V °f,tlie  S\nSh°n 
more  deeply  placed  than  the  t^S!1Pe™r  ™d  inferior  angles ;  the  lower  bundle 
between  {he  two  heads  of  tfa  ^  .5  th. the  Clliar?  arteneS  m  a  ™vj  course  one 
the  optic  nerve,  beneath  the  *£?  °Ptlc  nerv?>  an(?  are  accompanied  by  the  long 
inner  wall  of  the  orbit,  wher  ThfT  Pierce  the  sclerotrlc  at  tlie,  back  part  of  the 
and,  entering  the  cavity  of  J  gloves  on  its  inner  surface  and  are  distributed  to 
the  cribriform  plate  of  the  .**?«*■  Tiedemann  has  described  e;^r>mall  branch 
side  of  the  crista  galli,  inu  '  '  lth  the  arteria  centralls  retin8e- 

nal  and  an  external.     The    .      _,     .„         __  /r?.      oac\ 

.i     f  ,     f,i  >nor  Maxillary  Nerve  (fig.  ol-»o). 

the  tore  part  of  the  septum  >  ■  \     »  / 

on  the  inner  surface  of  the  i#  maxUlaris),  or  second  division  of  the  fifth,  is  a  sensory 
brane  covering  the  iorc^,^  jn  p0Siti0n  and  size,  between  the  ophthalmic 
pongy  bono ;  it  then  le  mmenCes  at  the  middle  of  the  Gasserian  ganglion  as 
e  nasal  be  o  and  the  u,^  passing  horizontallv  forward,  it  leaves  the  skull 
ith  the  Compressor  nasi!   1?  ^here   it  becomes  "more  cylindrical  in  form  and 

nose,  joining  with  the  facial  m 


728 


THE  NERVOUS  SYSTEM. 


from  the  brani-;  §/ 

It  passes  forward  iw 

the  narrowest  part  of  th^ 

border  of  the  External  recti! >^„  .^acle,  with 

cates  with  the  temporo-malar  branch   of  the   sup 

lachrymal  gland  and  gives  off  several   filamen^    wi 

conjunctiva.     Finally,  it  pierces  the   superior  palpi 

in  the  integument  of  the  upper  eyelid,  joining  with 

The  lachrymal  nerve  is  occasionally  absent,  when  its  jn, 

branch  of  the  superior  maxillary.      Sometimes  the  r 

continuation  of  the  lachrymal  is  substituted  for  it. 

The  frontal  is  the  largest  division  of  the  ophthalmi 
from  its  size  and  direction,  as  the  continuation  of  the 
above  the  muscles,  through  the  sphenoidal  fissure,  a 
middle  line,  between  the  Levator  palpebrse  and  the  pi 


^  A  Viennese  anatomist,  Eaimund  Balthasar  Hirsch  (1765)."  s^^>- 

ganglionic  nature  of  the  swelling  on  the  sensory  root  of  the  fifth  :fter  Flower.) 

otherwise _  unknown  teacher,  Jon.  Laur.  Gasser,  the  "Ganglion 

name  is  given  to  the  musculo-cutaneous  nerve  of  the  arm,  was  p        7  •  •»  •  \     '   f  n 


Hyrtl,  Lehrbuch  der  Anatomic,  p.  895  and  p.  55.) 


THE  BRANCHES    OF   THE  FIFTH  NERVE.  729 

The  ganglionic  is  a  slender  branch,  about  half  an  inch  in  length,  which  usually 
arises  from  the  nasal,  between  the  two  heads  of  the  External  rectus.  It  passes 
forward  on  the  outer  side  of  the  optic  nerve,  and  enters  the  postero-superior 
angle  of  the  ciliary  ganglion,  forming  its  superior  or  long  root.  It  is  sometimes 
joined  by  a  filament  from  the  cavernous  plexus  of  the  sympathetic  or  from  the 
superior  division  of  the  third  nerve. 

The  long  ciliary  nerves,  two  or  three  in  number,  are  given  off  from  the  nasal 
as  it  crosses  the  optic  nerve.  They  join  the  short  ciliary  nerves  from  the  ciliary 
ganglion,  pierce  the  posterior  part  of  the  sclerotic,  and,  running  forward  between 
it  and  the  choroid,  are  distributed  to  the  ciliary  muscles,  iris,  and  cornea. 

The  infratrochlear  branch  is  given  off  just  before  the  nasal  nerve  passes 
through  the  anterior  ethmoidal  foramen.  It  runs  forward  along  the  upper  border 
of  the  Internal  rectus,  and  is  joined,  beneath  the  pulley  of  the  Superior  oblique, 
by  a  filament  from  the  supratrochlear  nerve.  It  then  passes  to  the  inner  angle 
of  the  eye,  and  supplies  the  integument  of  the  eyelids  and  side  of  the  nose,  the 
conjunctiva,  lachrymal  sac,  and  caruncula  lachrymalis. 

The  Ophthalmic  Ganglion  (Figs.  391,  394). 

Connected  with  the  three  divisions  of  the  fifth  nerve  are  four  small  ganglia. 
With  the  first  division  is  connected  the  ophthalmic  ganglion ;  with  the  second 
division,  the  sphenopalatine  or  Meckel s  ganglion;  and  with  the  third,  the  otic 
and  submaxillary  ganglia.  All  the  four  receive  sensory  filaments  from  the  fifth, 
and  motor  and  sympathetic  filaments  from  various  sources  ;  these  filaments  are 
called  the  roots  of  the  ganglia. 

The  Ophthalmic,  Lenticular,  or  Ciliary  Ganglion  is  a  small,  quadrangular, 
flattened  ganglion,  of  a  reddish-gray  color,  and  about  the  size  of  a  pin's  head, 
situated  at  the  back  part  of  the  orbit  between  the  optic  nerve  and  the  External 
rectus  muscle,  lying  generally  on  the  outer  side  of  the  ophthalmic  artery.  It  is 
enclosed  in  a  quantity  of  loose  fat,  which  makes  its  dissection  somewhat  difficult. 

Its  branches  of  communication,  or  roots,  are  three,  all  of  which  enter  its 
posterior  border.  One,  the  long  or  sensory  root,  is  derived  from  the  nasal  branch 
of  the  ophthalmic  and  joins  its  superior  angle.  The  second,  the  short  or  motor 
root,  is  a  short,  thick  nerve,  occasionally  divided  into  two  parts,  which  is  derived 
from  the  branch  of  the  third  nerve  to  the  Inferior  oblique  muscle,  and  is  connected 
with  the  inferior  angle  of  the  ganglion.  The  third,  the  sympathetic  root,  is  a 
slender  filament  from  the  cavernous  plexus  of  the  sympathetic.  This  is  frequently 
blended  with  the  long  root,  though  it  sometimes  passes  to  the  ganglion  separately. 
According  to  Tiedemann,  this  ganglion  receives  a  filament  of  communication  from 
the  spheno-palatine  ganglion. 

Its  branches  of  distribution  are  the  short  ciliary  nerves.  These  are  delicate 
filaments,  from  six  to  ten  in  number,  which  arise  from  the  fore  part  of  the  ganglion 
in  two  bundles,  connected  with  its  superior  and  inferior  angles ;  the  lower  bundle 
is  the  larger.  They  run  forward  >  th  the  ciliary  arteries  in  a  wavy  course,  one 
set  above  and  the  other  below  the  optic  nerve,  and  are  accompanied  by  the  long 
ciliary  nerves  from  the  nasal.  They  pierce  the  sclerotic  at  the  back  part  of  the 
globe,  pass  forward  in  delicate  grooves  on  its  inner  surface,  and  are  distributed  to 
the  Ciliary  muscle,  iris,  and  cornea.  Tiedemann  has  described  pj^Jpynall  branch 
as  penetrating  the  optic  nerve  ,  ith  the  arteria  centralis  retinae. 

The  Superb  *  Maxillary  Nerve  (Fig.  395). 

The  Superior  Maxillary  (n.  maxillaris),  or  second  division  of  the  fifth,  is  a  sensory 
nerve.  It  is  intermediate,  bo  n  in  position  and  size,  between  the  ophthalmic 
and  inferior  maxillary.  It  commences  at  the  middle  of  the  Gasserian  ganglion  as 
a  flattened  plexiform  band,  and,  passing  horizontally  forward,  it  leaves  the  skull 
through  the  foramen  rotundum,  where   it   becomes  more  cylindrical  in  form  and 


730  THE   NERVOUS  SYSTEM. 

firmer  in  texture.  It  then  crosses  the  spheno-maxillary  fossa,  enters  the  orbit 
through  the  spheno-maxillary  fissure,  traverses  the  infra-orbital  canal  in  the  floor 
of  the  orbit,  and  appears  upon  the  face  at  the  infra-orbital  foramen.1  At  its 
termination  the  nerve  lies  beneath  the  Levator  labii  superioris  muscle,  and  divides 
into  a  leash  of  branches,  which  spread  out  upon  the  side  of  the  nose,  the  lower 
eyelid,  and  upper  lip,  joining  with  filaments  of  the  facial  nerve. 

Branches  of  Distribution. — The  branches  of  this  nerve  may  be  divided  into  four 
groups:  1.  Those  given  off  in  the  cranium.  2.  Those  given  off  in  the  spheno- 
maxillary fossa.     3.  Those  in  the  infra-orbital  canal.     4.  Those  on  the  face. 

In  the  cranium     .    .    .  Meningeal. 

(  Orbital  or  temporo-malar. 

Spheno-maxillary  fossa  <^  Spheno-palatine. 

(  Posterior  superior  dental. 

T   „         ,  .    !  ,  f    Middle  superior  dental. 

Infra-orbital  canal  ■<     *         •  a     *.  i 

(_   Anterior  superior  dental. 

{Palpebral. 
Nasal. 
Labial. 

The  meningeal  branch  is  given  off  directly  after  its  origin  from  the  Gasserian 
ganglion ;  it  accompanies  the  middle  meningeal  artery  and  supplies  the  dura 
mater. 

The  orbital  or  temporo-malar  branch  arises  in  the  spheno-maxillary  fossa, 
enters  the  orbit  by  the  spheno-maxillary  fissure,  and  divides  at  the  back  of  that 
cavity  into  two  branches,   temporal  and  malar. 

The  temporal  branch  runs  in  a  groove  along  the  outer  wall  of  the  orbit  (in  the 
malar  bone),  receives  a  branch  of  communication  from  the  lachrymal,  and, 
passing  through  a  foramen  in  the  malar  bone,  enters  the  temporal  fossa.  It 
ascends  between  the  bone  and  substance  of  the  Temporal  muscle,  pierces  this 
muscle  and  the  temporal  fascia  about  an  inch  above  the  zygoma,  and  is  distributed 
to  the  integument  covering  the  temple  and  side  of  the  forehead,  communicating 
with  the  facial  and  auriculo-temporal  branch  of  the  inferior  maxillary  nerve.  As 
it  pierces  the  temporal  fascia  it  gives  off  a  slender  twig,  which  runs  between  the 
two  layers  of  the  fascia  to  the  outer  angle  of  the  orbit. 

The  malar  branch  passes  along  the  external  inferior  angle  of  the  orbit,  emerges 
upon  the  face  through  a  foramen  in  the  malar  bone,  and,  perforating  the  Orbicu- 
laris palpebrarum  muscle,  supplies  the  skin  on  the  prominence  of  the  cheek,  and 
is  named  subcutaneus  malm.  It  joins  with  the  facial  and  the  palpebral  branches 
of  the  superior  maxillary. 

The  spheno-palatine  branches,  two  in  number,  descend  to  the  spheno-palatine 
ganglion. 

The  posterior  superior  dental  branches  arise  from  the  trunk  of  the  nerve  just 
as  iHs  about  to  enter  the  infra-orbital  canal;  they  are  generally  two  in  number, 
but  sometimes  arise  by  a  single  trunk,  and  immediately  divide  and  pass  downward 
on  the  tuberosity  of  the  superior  maxillary  bone.  They  give  off  several  twigs  to 
the  gums  and  neighboring  parts  of  the  mucous  membrane  of  the  cheek  (superior 
gingival  branches).  They  then  enter  the  posterior  dental  canals  on  the  zygomatic 
surface  of  tlof  t&perior  maxillary  bone,  and,  passing  from  behind  forward  in  the 
substance  of  the  bone,  communicate  with  the  middle  dental  nerve,  and  give  off 
branches  to  the  lining  membrane  of  the  antrum  and  three  twigs  to  each  of  the 
molar  teeth.  These  twigs  enter  the  foramina  at  the  apices  of  the  fangs  and 
supply  the  pulp. 

The  middle  superior  dental  branch  is  given  off  from  the  superior  maxillary  nerve 

in  the  back   part  of  the  infra-orbital  canal,  and  runs  downward  and  forward  in  a 

special  canal  in  the  outer  wall  of  the  antrum  to  supply  the  two  bicuspid  teeth.     It 

communicates  with  the  posterior  and  anterior  dental  branches.     At  its  point  of 

1  After  it  enters  the  infra-orbital  canal,  the  nerve  is  frequently  called  the  infra-orbital. 


THE  BRANCHES   OF   THE  FIFTH  NERVE. 


731 


communication  with  the  posterior  branch  is  a  slight  thickening  which  has  received 
the  name  of  the  ganglion  of  Valentin  ;  and  at  its  point  of  communication  with  the 
anterior  branch  is  a  second  enlargement,  which  is  called  the  ganglion  of  Bochdalek. 
Neither  of  these  is  probably  a  true  ganglion. 

The  anterior  superior  dental  branch,  of  large  size,  is  given  off  from  the  supe- 
rior maxillary  nerve  just  before  its  exit  from  the  infra-orbital  foramen  ;  it  enters  a 
special  canal  in  the  anterior  wall  of  the  antrum,  and  divides  into  a  series  of 
branches  which  supply  the  incisor  and  canine  teeth.  It  communicates  with  the 
middle  dental  nerve,  and  gives  off  a  nasal  branch,  which  passes  through  a  minute 
canal  into  the  nasal  fossa,  and  supplies  the  mucous  membrane  of  the  fore  part  of 
the  inferior  meatus  and  the  floor  of  this  cavity,  communicating  with  the  nasal 
branches  from  Meckel's  ganglion. 


Sensory  root 
Motor  root. 


Auriculo-temporal 
nerve. 


Fig.  395.— Distribution  of  the  second  and  third  divisions  of  the  fifth  nerve  and  submaxillary  ganglion. 

The  palpebral  branches  pass  upward  beneath  the  Orbicularis  palpebrarum. 
They  supply  the  integument  and  conjunctiva  of  the  lo^ev  ^yelkl  with  sensation, 
joining  at  the  outer  angle  of  the  orbit  with  the  facial  nevvf  and  ui^ar  branch  of 
the  orbital. 

The  nasal  branches  pass  inward;  they  supply  t:  e  tegument  of  the  side  of 
the  nose  and  join  with  the  nasal  branch  of  the  opht'ui  'mic, 

The  labial  branches,  the  largest  and  mos.  numerous,  descend  beneath  the 
Levator  labii  superioris,  and  are  distributed  to  the  integument  of  the  upper  lip. 
the  mucous  membrane  of  the  mouth,  and  labiaj 

All  these  branches  are  joined,  immediaf''' y  |  the  oibit,  by  filaments  from 

the  facial  nerve,  forming  an  intricate  plexus    jjhe  infra-orbital. 

'      /  i 


732  THE  NERVOUS  SYSTEM. 

The  Spheno-palatine  Ganglion  (Fig.  396). 

The  spheno-palatine  ganglion  (Meckel's),  the  largest  of  the  cranial  ganglia,  is 
deeply  placed  in  the  spheno-maxillary  fossa,  close  to  the  spheno-palatine  foramen. 
It  is  triangular  or  heart-shaped,  of  a  reddish-gray  color,  and  is  situated  just  below 
the  superior  maxillary  nerve  as  it  crosses  the  fossa. 

Its  Branches  of  Communication. — Like  the  other  ganglia  of  the  fifth  nerve,  it 
possesses  a  motor,  a  sensory,  and  a  sympathetic  root.  Its  sensory  root  is  derived 
from  the  superior  maxillary  nerve  through  its  two  spheno-palatine  branches.  These 
branches  of  the  nerve,  given  off  in  the  spheno-maxillary  fossa,  descend  to  the 
ganglion.  Their  fibres,  for  the  most  part,  pass  in  front  of  the  ganglion,  as  they 
proceed  to  their  destination,  in  the  palate  and  nasal  fossa,  and  are  not  incorporated 
in  the  ganglionic  mass ;  some  few  of  the  fibres,  however,  enter  the  ganglion, 
constituting  its  sensory  root.  Its  motor  root  is  derived  from  the  facial  nerve 
through  the  large  superficial  petrosal  nerve,  and  its  sympathetic  root  from  the 
carotid  plexus,  through  the  large  deep  petrosal  nerve.  These  two  nerves  j  oin  together 
to  form  a  single  nerve,  the  Vidian,  before  their  entrance  into  the  ganglion. 


Termination  of 

naso-palatine 

nerve. 


Fig.  396.— The  spheno-palatine  ganglion  and  its  branches. 

The  large  superficial  petrosal  branch  {nervus  petrosus  superfieialis  major)  is 
given  off  from  the  geniculate  ganglion  of  the  facial  nerve  in  the  aqueductus  Fal- 
lopii ;  it  passes  through  the  hiatus  Fallopii ;  enters  the  cranial  cavity,  and  runs 
forward  contained  in  a  groove  on  the  anterior  surface  of  the  petrous  portion  of  the 
temporal  bone,  lying  beneath  the  dura  mater.  It  then  enters  the  cartilaginous 
substance  which  fills  in  the  foramen  lacerum  medium  basis  cranii,  and,  joining 
with  the  large  deep  petrosal  branch,  forms  the  Vidian  nerve. 

The  large  deep  petrosal  branch  [nervus  petrosus  profundus)  is  given  off  from 
the  carotid  plexus,  and  runs  through  the  carotid  canal  on  the  outer  side  of  the 
internal  carotid  artery.  It"  tneu  enters  the  cartilaginous  substance  which  fills  in 
the  foramen  lacerum.  nedium,  and  i^ns  w^tn  tne  large  superficial  petrosal  nerve  to 
form  the  Vidian. 

cartilaginous   substance  which   fills   in  the 
.ion   of  the   two   preceding  nerves,  passes 


The  Vidian  nerve,  formed  in 
middle  lacerated   foi^men   by  the' 


THE  BRANCHES    OF    THE   FIFTH  NERVE.  733 

forward,  through  the  Vidian  canal,  with  the  artery  of  the  same  name,  and  is 
joined  by  a  small  ascending  branch,  the  sphenoidal  branch,  from  the  otic  ganglion. 
Finally,  it  enters  the  spheno-maxillary  fossa,  and  joins  the  posterior  angle  of 
Meckel's  ganglion. 

Its  branches  of  distribution  are  divisible  into  four  groups  :  ascending,  which 
pass  to  the  orbit ;  descending,  to  the  palate  :  internal,  to  the  nose  ;  and  posterior 
branches,  to  the  pharynx  and  nasal  fossae. 

The  ascending  branches  are  two  or  three  delicate  filaments,  which  enter  the 
orbit  by  the  spheno-maxillary  fissure,  and  supply  the  periosteum.  According  to 
Luschka,  some  filaments  pass  through  foramina  in  the  suture  between  the  os 
planum  of  the  ethmoid  and  frontal  bones  to  supply  the  mucous  membrane  of  the 
posterior  ethmoidal  and  sphenoidal  sinuses. 

The  descending  or  palatine  branches  are  distributed  to  the  roof  of  the  mouth, 
the  soft  palate,  tonsil,  and  lining  membrane  of  the  nose.  They  are  almost  a  direct 
continuation  of  the  spheno-palatine  branches  of  the  superior  maxillary  nerve,  and 
are  three  in  number — anterior,  middle,  and  posterior. 

The  anterior  or  large  palatine  nerve  descends  through  the  posterior  palatine 
canal,  emerges  upon  the  hard  palate  at  the  posterior  palatine  foramen,  and  passes 
forward  through  a  groove  in  the  hard  palate  nearly  as  far  as  the  incisor  teeth.  It 
supplies  the  gums,  the  mucous  membrane  and  glands  of  the  hard  palate,  and 
communicates  in  front  with  the  termination  of  the  naso-palatine  nerve.  While  in 
the  posterior  palatine  canal  it  gives  off  inferior  nasal  branches,  which  enter  the 
nose  through  openings  in  the  palate  bone,  and  ramify  over  the  inferior  turbinated 
bone  and  middle  and  inferior  meatuses ;  and  at  its  exit  from  the  canal  a  palatine 
branch  is  distributed  to  both  surfaces  of  the  soft  palate. 

The  middle  or  external  palatine  nerve  descends  through  one  of  the  accessory 
palatine  canals,  distributing  branches  to  the  uvula,  tonsil,  and  soft  palate.  It  is 
occasionally  wanting. 

The  posterior  or  small  palatine  nerve  descends  with  a  minute  artery  through  the 
small  posterior  palatine  canal,  emerging  by  a  separate  opening  behind  the  posterior 
palatine  foramen.  It  supplies  the  Levator  palati  and  Azygos  uvuhe  muscles,1  the 
soft  palate,  tonsil,  and  uvula.  The  middle  and  posterior  palatine  join  with  the 
tonsillar  branches  of  the  glosso-pharyngeal  to  form  the  plexus  around  the  tonsil 
{cir  cuius  tonsillaris). 

The  internal  branches  are  distributed  to  the  septum  and  outer  wall  of  the  nasal 
fossge.     They  are  the  superior  nasal  (anterior)  and  the  naso-palatine. 

The  superior  nasal  branches  (anterior),  four  or  five  in  number,  enter 
the  back  part  of  the  nasal  fossa  by  the  spheno-palatine  foramen.  They 
supply  the  mucous  membrane  covering  the  superior  and  middle  spongy  bones, 
and  that  lining  the  posterior  ethmoidal  cells,  a  few  being  prolonged  to  the 
upper  and  back  part  of  the  septum. 

The  naso-palatine  nerve  (Coiunnius)  also  enters  the  nasal  fossa  through  the 
spheno-palatine  foramen,  and  passes  inward  across  the  roof  of  the  nose,  below 
the  orifice  of  the  sphenoidal  sinus,  to  reach  the  septum  ;  it  then  runs  obliquely 
downward  and  forward  along  the  lower  part  of  the  septum,  to  the  anterior  palatine 
foramen,  lying  between  the  periosteum  and  mucous  membrane.  It  descends  to  the 
roof  of  the  mouth  through  the  anterior  palatine  canal.  The  two  nerves  are  here 
contained  in  separate  and  distinct  canals,  situated  in  the  intermaxillary  suture, 
and  termed  the  foramina  of  Scarpa,  the  left  nerve  being  usually  anterior  to  the 
right  one.  In  the  mouth  they  become  united,  supply  the  mucous  membrane  behind 
the  incisor  teeth,  and  join  with  the  c  itevior  palatine  nerve.  The  naso-palatine 
nerve  furnishes  a  few  small  filaments  to  the  mucous  spembrane  of  the  septum. 

The  posterior  branches  are  the  phar  mjrea]  (pterygopalatine)  and  the  upper 
posterior  nasal  branches. 

The  pharyngeal  nerve  Q-^HM  iVi'l  is  a  small   branch   arising  from   the 

1  It  is  probable  that  this  is  not  th  Jm  tor  *ipply  to  these  muscles,  but  that  they  are  supplied 
by  the  spinal  accessory  through  the  phaityngea'  plexus. 


734  THE  NERVOUS  SYSTEM. 

back  part  of  the  ganglion,  being  generally  blended  with  the  Vidian  nerve.  It 
passes  through  the  pterygopalatine  canal  with  the  ptery go-palatine  artery,  and  is 
distributed  to  the  mucous  membrane  of  the  upper  part  of  the  pharynx,  behind  the 
Eustachian  tube. 

The  upper  posterior  nasal  branches  are  a  few  twigs  given  off  from  the  posterior 
part  of  the  ganglion,  which  run  backward  in  the  sheath  of  the  Vidian  nerve  to 
the  mucous  membrane  at  the  back  part  of  the  roof,  septum,  and  superior  meatus 
of  the  nose  and  that  covering  the  end  of  the  Eustachian  tube. 

The  Inferior  Maxillary  Nerve  (Fig.  395). 

The  Inferior  Maxillary  Nerve  (n.  mandibularis)  distributes  branches  to  the 
teeth  and  gums  of  the  lower  jaw,  the  integument  of  the  temple  and  external  ear, 
the  lower  part  of  the  face  and  lower  lip,  and  the  muscles  of  mastication ;  it  also 
supplies  the  tongue  with  a  large  branch.  It  is  the  largest  of  the  three  divisions 
of  the  fifth,  and  is  made  up  of  two  roots  :  a  large  or  sensory  root  proceeding  from 
the  inferior  angle  of  the  Gasserian  ganglion  ;  and  a  small  or  motor  root,  which 
passes  beneath  the  ganglion,  and  unites  with  the  sensory  root  just  after  its  exit 
from  the  skull  through  the  foramen  ovale.  Immediately  beneath  the  base  of  the 
skull  this  nerve  divides  into  two  trunks,  anterior  and  posterior.  Previous  to  its 
division  the  primary  trunk  gives  off  from  its  inner  side  a  recurrent  (meningeal) 
branch  and  the  nerve  to  the  Internal  pterygoid  muscle. 

The  recurrent  branch  is  given  off  directly  after  its  exit  from  the  foramen  ovale. 
It  passes  backward  into  the  skull  through  the  foramen  spinosum  with  the  middle 
meningeal  artery.  It  divides  into  two  branches,  anterior  and  posterior,  which 
accompany  the  main  divisions  of  the  artery  and  supply  the  dura  mater.  The 
posterior  branch  also  supplies  the  mucous  lining  of  the  mastoid  cells.  The  anterior 
branch  communicates  with  the  meningeal  branch  of  the  superior  maxillary  nerve. 

The  Internal  Pterygoid  Nerve,  given  off  from  the  inferior  maxillary  previous  to 
its  division,  is  intimately  connected  at  its  origin  with  the  otic  ganglion.  It  is  a 
long  and  slender  branch,  which  passes  inward  to  enter  the  deep  surface  of  the 
Internal  pterygoid  muscle. 

The  anterior  and  smaller  division,  which  receives  nearly  the  whole  of  the  motor 
root,  divides  into  branches  which  supply  the  muscles  of  mastication.  They  are 
the  masseteric,  deep  temporal,  buccal,  and  external  pterygoid. 

The  masseteric  branch  passes  outward,  above  the  External  pterygoid  muscle,  in 
front  of  the  temporo-mandibular  articulation  and  behind  the  tendon  of  the  tem- 
poral muscle ;  it  crosses  the  sigmoid  notch  with  the  masseteric  artery,  to  the  deep 
surface  of  the  Masseter  muscle,  in  which  it  ramifies  nearly  as  far  as  its  anterior 
border.  It  occasionally  gives  a  branch  to  the  Temporal  muscle,  and  a  filament 
to  the  articulation  of  the  jaw. 

The  deep  temporal  branches,  two  in  number,  anterior  and  posterior,  supply  the 
deep  surface  of  the  Temporal  muscle.  The  posterior  branch,  of  small  size,  is 
placed  at  the  back  of  the  temporal  fossa.  It  is  sometimes  joined  with  the  masse- 
teric branch.  The  anterior  branch  is  frequently  given  off  from  the  buccal  nerve ; 
it  is  reflected  upward,  at  the  pterygoid  ridge  of  the  sphenoid,  to  the  front  of  the  tem- 
poral fossa.  Sometimes  there  are  three  deep  temporal  branches  ;  the  third  branch 
(middle  deep  temporal)  passes  outward  above  the  External  pterygoid  muscle,  and 
runs  upward  on  the  bone  to  enter  the  deep  surface  of  the  Temporal  muscle. 

The  buccal  branch  passes  forward  between  the  two  heads  of  the  External 
pterygoid,  and  downward  beneath  the  inner  surface  of  the  coronoid  process  of  the 
lower  jaAv,  or  through  the  fibres  of  the  Temporal, muscle,  to  reach  the  surface  of 
the  Buccinator,  upon  which  it  divides  into  a  superior  and  an  inferior  branch.  It 
gives  a  branch  to  the  External  pterygoid  daring  its  passage  through  that  muscle, 
and  a  few  ascending  filaments  to  the  Temporal  muscle,  one  of  which  occasionally 
joins  with  the  anterior  branch  of  the  deep  temporal  nerve.  The  upper  branch 
supplies  the   integument  and  upper  part  of  the  Buccinator  muscle,  joining  with 


THE   BRANCHES    OF   THE   FIFTH  NERVE.  735 

the  facial  nerve  round  the  facial  vein.  The  loiver  branch  passes  forward  to  the 
angle  of  the  mouth  :  it  supplies  the  integument  and  Buccinator  muscle,  as  -well 
as  the  mucous  membrane  lining  the  inner  surface  of  that  muscle,  and  joins  the 
facial  nerve.1 

The  External  Pterygoid  Nerve  is  most  frequently  derived  from  the  buccal,  but 
it  may  be  given  off  separately  from  the  anterior  trunk  of  the  nerve.  It  enters 
the  muscle  on  its  inner  surface. 

The  posterior  and  larger  division  of  the  inferior  maxillary  nerve  is  for  the 
most  part  sensory,  but  receives  a  few  filaments  from  the  motor  root.  It  divides 
into  three  branches  :   auriculotemporal,  lingual  (gustatory),  and  inferior  dental. 

The  auriculotemporal  nerve  generally  arises  by  two  roots,  between  which  the 
middle  meningeal  artery  passes.  It  runs  backward  beneath  the  External  ptery- 
goid muscle  to  the  inner  side  of  the  neck  of  the  lower  jaw.  It  then  turns  upward 
with  the  temporal  artery,  between  the  external  ear  and  condyle  of  the  jaw,  under 
cover  of  the  parotid  gland,  and,  escaping  from  beneath  this  structure,  ascends 
over  the  zygoma  and  divides  into  two  temporal  branches. 

The  branches  of  communication  are  with  the  facial  and  with  the  otic  ganglion. 
The  branches  of  communication  with  the  facial,  usually  two  in  number,  pass  for- 
ward from  behind  the  neck  of  the  condyle  of  the  jaw,  to  join  this  nerve  at  the 
posterior  border  of  the  Masseter  muscle.  They  form  one  of  the  principal  branches 
of  communication  between  the  facial  and  the  fifth  nerve.  The  filaments  of  com- 
munication with  the  otic  ganglion  are  derived  from  the  commencement  of  the 
auriculotemporal  nerve. 

The  branches  of  distribution  are — 

Anterior  auricular.  Articular, 

Branches  to  the  meatus  auditorius.  Parotid- 

Superficial  temporal. 

The  anterior  auricular  branches  are  usually  two  in  number.     They  supply  the 
front  of  the  upper  part  of  the  pinna,  being  distributed  principally  to   the  I 
covering  the  front  of  the  helix  and  tragus. 

Branches  to  the  meatus  auditorius,  two  in  number,  enter  the  canal  bet 
bony  and  cartilaginous  portion  of  the  meatus.      They  supply  the  skin  lini'i 
meatus  ;  the  upper  one  sending  a  filament  to  the  membrana  tympairi. 

A  branch  to  the  temporo-mandibular  articulation  is  usually  derived  from  thfJ 
auriculo-temporal  nerve. 

The  parotid  branches  supply  the  parotid  gland. 

The  superficial  temporal  accompanies  the  temporal  artery  to  the  vertex  of  the 
skull,  and  supplies  the  integument  of  the   temporal  region,  communicating  wi 
the  facial  nerve,  and  the  temporal  branch  of  the  temporo-inalar,  from  the  superior 
maxillary. 

The  lingual  nerve  (gustatory)  supplies  the  papillae  and  mucous  membrane  of 
the  anterior  two-thirds  of  the  tongue.  It  is  deeply  placed  throughout  the  whole 
of  its  course.  It  lies  at  first  beneath  the  External  pterygoid  muscle,  together  with 
the  inferior  dental  nerve,  being  placed  to  the  inner  side  of  this  nerve,  and  is 
occasionally  joined  to  it  by  a  branch  which  may  cross  the  internal  maxillary 
artery.  The  chorda  tympani  also  joins  it  at  an  acute  angle  in  this  situation. 
The  nerve  then  passes  between  the  Internal  pterygoid  muscle  and  the  inner  side 
of  the  ramus  of  the  jaw,  and  crosses  obliquely  to  the  side  of  the  tongue  over  the 
Superior  constrictor  and  Stylo-glossus  muscles,  and  then  between  the  Hyo-glossus 
muscle  and  deep  part  of  the  submaxillary  gland ;  the  nerve  finally  runs  across 
Wharton's  duct,  and  along  the  side  of  the  tongue  to  its  apex,  lying  immediately 
beneath  the  mucous  membrane. 

The  branches  of  communication  are  with  the  facial  through  the  chorda  tvni- 
pahi,  the  inferior  dental  and  hypoglossal  nerves,  and  the  submaxillary  ganglion. 

1  There  seems  to  be  no  reason  to  doubt  that  the  branch  supplying  the  Buccinator  muscle  is  entirely 
a  nerve  of  ordinary  sensation,  and  that  the  true  motor  supply  of  this  muscle  is  from  the  facial. 


736  THE   NERVOUS  SYSTEM. 

The  branches  to  the  submaxillary  ganglion  are  two  or  three  in  number ;  those 
connected  with  the  hypoglossal  nerve  form  a  plexus  at  the  anterior  margin  of  the 
Hyo-glossus  muscle. 

The  branches  of  distribution  supply  the  mucous  membrane  of  the  mouth,  the 
gums,  the  sublingual  gland,  the  filiform  and  fungiform  papillae  and  mucous  mem- 
brane of  the  tongue  ;  the  terminal  filaments  communicate,  at  the  tip  of  the  tongue, 
with  the  hypoglossal  nerve. 

The  Inferior  Dental  is  the  largest  of  the  three  branches  of  the  inferior  max- 
illary nerve.  It  passes  downward  with  the  inferior  dental  artery,  at  first  beneath 
the  External  pterygoid  muscle,  and  then  between  the  internal  lateral  ligament 
and  the  ramus  of  the  jaAV  to  the  dental  foramen.  It  then  passes  forward  in  the 
dental  canal  of  the  inferior  maxillary  bone,  lying  beneath  the  teeth,  as  far  as  the 
mental  foramen,  where  it  divides  into  two  terminal  branches,  incisor  and  mental. 

The  branches  of  the  inferior  dental  are,  the  mylo-hyoid,  dental,  incisive,  and 
mental. 

The  mylo-hyoid  is  derived  from  the  inferior  dental  just  as  that  nerve  is  about 
to  enter  the  dental  foramen.  It  descends  in  a  groove  on  the  inner  surface  of  the 
ramus  of  the  jaw,  in  which  it  is  retained  by  a  process  of  fibrous  membrane.  It 
reaches  the  under  surface  of  the  Mylo-hyoid  muscle,  and  supplies  it  and  the 
anterior  belly  of  the  Digastric. 

The  dented  branches  supply  the  molar  and  bicuspid  teeth.  They  correspond 
in  number  to  the  fangs  of  those  teeth :  each  nerve  entering  the  orifice  at  the 
point  oi   the  fang  and  supplying  the  pulp  of  the  tooth. 

The  incisive  branch  is  continued  onward  within  the  bone  to  the  middle  line, 
tpplies  the  canine  and  incisor  teeth. 

nental  branch  emerges  from  the  bone  at  the  mental  foramen,  and  divides 
bene  b.  the  Depressor  anguli  oris  into  two  or  three  branches ;  one  descends  to 
supply  the  skin  of  the  chin,  and  another  (sometimes  two)  ascends  to  supply  the 
skin  and  mucous  membrane  of  the  lower  lip.  These  branches  communicate  freely 
with  the  facial  nerve. 

Two  small  ganglia  are  connected  with  the  inferior  maxillary  nerve — the  otic 
w    I    the  trunk  of  the  nerve,  and  the  submaxillary  with  its  lingual  branch. 

.     Otic  Ganglion  (Fig.  397). 

1.  Otic  Ganglion* (^Arnold's  ;<?  a  small,  oval-shaped,  flattened  ganglion  of  a 
/eddish-gray  color,  situated  inlmediately  below  the  foramen  ovale,  on  the  inner 
surface  oi  the  inferior  maxillary  nerve,  and  round  the  origin  of  the  internal  ptery- 
goid nerve.  It  is  in  relation,  e  eternally,  with  the  trunk  of  the  inferior  maxillary 
nerve,  at  the  point  where  the  motor  root  joins  the  sensory  portion ;  internally, 
with  the  cartilaginous  part  of  the  Eustachian  tube,  and  the  origin  of  the  Tensor 
palati  muscle;  behind  it  is  the  middle  meningeal  artery. 

Branches  of  Communication. — This  ganglion  is  connected  with  the  internal 
pterygoid  branch  of  the  inferior  maxillary  nerve  by  two  or  three  short,  delicate 
filaments.  From  this  it  may  obtain  a  motor  root,  and  possibly  also  a  sensory  root, 
as  these  filaments  from  the  nerve  to  the  Internal  pterygoid  may  contain  sensory 
fibres.  It  communicates  with  the  glosso-pharyngtil  and  facial  nerves  through  the 
small  superficial  petrosal  nerve  continued  frem  the  tympanic  plexus,  and  through 
.  this  communication  it  probably  receives  its  sens  'ry  ro<  t  from  the  glossopharyngeal 
and  its  motor  root  from  the  facial;  its  communication  Avith  the  sympathetic  is 
effected  by  a  filament  from  the  plexus    surrounding  the  !  meningeal  artery. 

The  ganglion  also  communicates  with  the   auriculo-te.  This  is  prob- 

ably a  branch  from  the  glosso-pharyngeal  which  passes  to  the  &  .  and  through 

it  and  the    auriculo-temporal  nerve   to    the  parotid  gland.  r   filament 

(sphenoidal)  ascends  from  it  to  the  Vidian  nerve. 

Its  branches  of  distribution  are  a  filament  to  the  Tensor  tv  li  and  one  to  the 

Tensor  palati.     The  former  passes  backward  on  the  outer  sid ;  of  the  Eustachian 


THE   BRANCHES    OF    THE  FIFTH  NERVE. 


I'dl 


tube ;  the  latter  arises  from  the  ganglion,  near  the  origin  of  the  internal  pterygoid 
nerve,  and  passes  forward.     The  fibres  of  these  nerves  are,  however,  mainly  derived 


Fig.  397. — The  otic  ganglion  and  its  branches. 


from  the  nerve  to  the  Internal  pterygoid  muscle, 
municating  branch  to  the  chorda  tympani. 


It  also  gives  oif  a  small  com- 


The  Submaxillary  Ganglion  (Fig.   395). 

The  submaxillary  ganglion  is  of  small  size,  fusiform  in  shape,  and  situated 
above  the  deep  portion  of  the  submaxillary  gland,  near  the  posterior  border  of  the 
Mylo-hyoid  muscle,  being  connected  by  filaments  with  the  lower  border  of  the 
lingual  (gustatory)  nerve. 

Branches  of  Communication. — This  ganglion  is  connected  with  the  lingual 
(gustatory)  nerve  by  a  few  filaments  which  join  it  separately  at  its  fore  and  back 
part.  It  also  receives  a  branch  from  the  chorda  tympani,  by  which  it  communicates 
with  the  facial,  and  communicates  with  the  sympathetic  by  filaments  from  the 
sympathetic  plexus  around  the  facial  artery. 

Branches  of  Distribution. — These  are  five  or  six  in  number:  they  arise  from 
the  lower  part  of  the  ganglion,  and  supply  the  mucous  membrane  of  the  mouth  and 
Wharton's  duct,  some  being  lost  in  the  submaxillary  gland.  The  branch  of  com- 
munication from  the  lingual  to  the  fore  part  of  the  ganglion  is  by  some  regarded 
as  a  branch  of  distribution,  by  which  filaments  of  the  chorda  tympani  pass  from 
the  ganglion  to  the  nerve,  and  by  it  are  conveyed  to  the  sublingual  gland  and  the 
tongue. 

Surface  Marking. — It  will  be  seen  from  the  above  description  that  the  three  terminal 
branches  of  the  three  divisions  of  the  fifth  nerve  emerge  from  foramina  in  the  bones  of  the  skull 
and  face  on  to  the  face :  the  terminal  branch  of  the  first  division  emerging  through  the  supra- 
orbital foramen  ;  that  of  the  second  through  the  infra-orbital  foramen  ;  and  the  third  through 
the  mental  foramen.  The  supra-orbital  foramen  is  situated  at  the  junction  of  the  internal 
and  middle  third  of  the  supra-orbital  arch.  If  a  straight  line  is  drawn  from  this  point  to  the 
lower  border  of  the  inferior  maxillary  bone,  so  that  it  passes  between  the  two  bicuspid  teeth  of 
the  lower  jaw,  it  will  pass  over  the  infra-orbital  and  mental  foramina,  the  former  being  situated 
about  one  centimetre  (two-fifths  of  an  inch)  below  the  margin  of  the  orbit,  and  the  latter  varying 
in  position  according  to  the  age  of  the  individual.  In  the  adult  it  is  midway  between  the  upper 
and  lower  borders  of  the  inferior  maxillary  bone  ;  in  the  child  it  is  nearer  the  lower  border :  and 
in  the  edentulous  jaw  of  old  age  it  is  close  to  the  upper  margin. 
47 


738  THE  NERVOUS  SYSTEM. 

Surgical  Anatomy  .—The  fifth  nerve  may  be  affected  in  its  entirety,  or  its  sensory  or  motor 
root  may  be  affected,  or  one  of  its  primary  main  divisions.  In  injury  to  the  sensory  root  there 
is  anaesthesia  of  the  half  of  the  face  on  the  side  of  the  lesion,  -with  the  exception  of  the  skin 
over  the  parotid  gland ;  insensibility  of  the  conjunctiva,  followed  by  destructive  inflammation 
of  the  cornea,  partly  from  loss  of  trophic  influence,  and  partly  from  the  irritation  produced  by 
the  presence  of  foreign  bodies  on  it,  which  are  not  perceived  by  the  patient,  and  therefore  not 
expelled  by  the  act  of  winking  ;  dryness  of  the  nose,  loss  to  a  considerable  extent  of  the  sense 
of  taste,  and  diminished  secretion  of  the  lachrymal  and  salivary  glands.  In  injury  to  the  motor 
root  there  is  impaired  action  of  the  lower  jaw  from  paralysis  of  the  muscles  of  mastication  on 
the  affected  side. 

The  fifth  nerve  is  often  the  seat  of  neuralgia,  and  each  of  the  three  divisions  has  been 
divided  or  a  portion  of  the  nerve  excised  for  this  affection.  The  supra-orbital  nerve  may  be 
exposed  by  making  an  incision  an  inch  and  a  half  in  length  along  the  supra-orbital  margin  below 
the  eyebrow,  which  is  to  be  drawn  upward,  the  centre  of  the  incision  corresponding  to  the  supra- 
orbital notch.  The  skin  and  Orbicularis  palpebrarum  having  been  divided,  the  nerve  can  be 
easily  found  emerging  from  the  notch  and  lying  in  some  loose  cellular  tissue.  It  should  be  drawn 
up  by  a  blunt  hook  and  divided,  or,  what  is-  better,  a  portion  of  it  removed.  The  infra-orbital 
nerve  has  been  divided  at  its  exit  by  an  incision  on  the  cheek  ;  or  the  floor  of  the  orbit  has  been 
exposed,  the  infra-orbital  canal  opened  up,  and  the  anterior  part  of  the  nerve  resected  ;  or  the 
whole  nerve,  together  with  Meckel's  ganglion  as  far  back  as  the  foramen  rotundum,  has  been 
removed.  This  latter  operation,  though  undoubtedly  a  severe  proceeding,  appears  to  have  been 
followed  by  the  best  results.  The  operation  is  performed  as  follows :  The  superior  maxillary 
bone  is  first  exposed  by  a  T-shaped  incision,  one  limb  passing  along  the  lower  margin  of  the  orbit, 
the  other  from  the  centre  of  this  vertically  down  the  cheek  to  the  angle  of  the  mouth.  The 
nerve  is  then  found,  divided,  and  a  piece  of  silk  tied  to  it  as  a  guide.  A  small  trephine  (one- 
half  inch)  is  then  applied  to  the  bone  below,  but  including,  the  infra-orbital  foramen,  and  the 
antrum  opened.  The  trephine  is  now  applied  to  the  posterior  wall  of  the  antrum,  and  the 
spheno-maxillary  fossa  exposed.  The  infra-orbital  canal  is  now  opened  up  from  below  by  fine 
cutting-pliers  or  a  chisel,  and  the  nerve  drawn  down  into  the  trephine  hole,  it  being  held  on  the 
stretch  by  means  of  the  piece  of  silk ;  it  is  severed  with  fine  curved  scissors  as  near  the  foramen 
rotundum  as  possible,  any  branches  coming  off  from  the  ganglion  being  also  divided.1  The 
mental  branch  of  the  inferior  dental  nerve  has  been  divided  at  its  exit  from  the  foramen  by  an 
incision  made  through  the  mucous  membrane  where  it  is  reflected  from  the  alveolar  process  on 
to  the  lower  lip  ;  or  a  portion  of  the  trunk  of  the  inferior  dental  nerve  has  been  resected  by  an 
incision  on  the  cheek  through  the  Masseter  muscle,  exposing  the  outer  surface  of  the  ramus  of 
the  jaw.  A  trephine  was  then  applied  over  the  position  of  the  inferior  dental  foramen  and  the 
outer  table  removed,  so  as  to  expose  the  inferior  dental  canal.  The  nerve  was  dissected  out  of 
the  portion  of  the  canal  exposed,  and,  having  been  divided  after  its  exit  from  the  mental  foramen, 
it  was  by  traction  on  the  end  exposed  in  the  trephine  hole,  drawn  out  entire,  and  cut  off  as  high 
up  as  possible.2  The  inferior  dental  nerve  has  also  been  divided  by  an  incision  within  the  mouth, 
the  bony  point  guarding  the  inferior  dental  foramen  forming  the  guide  to  the  nerve.  The  buc- 
cal nerve  may  be  divided  by  an  incision  through  the  mucous  membrane  of  the  mouth  and 
the  Buccinator  just  in  front  of  the  anterior  border  of  the  ramus  of  the  lower  jaw  (Stimson).  _ 

The  lingual  (gustatory)  nerve  is  occasionally  divided  with  the  view  of  relieving  the  pain  in 
cancerous  disease  of  the  tongue.  This  may  be  done  in  that  part  of  its  course  where  it  lies  below 
and  behind  the  last  molar  tooth.  If  a  line  is  drawn  from  the  middle  of  the  crown  of  the  last 
molar  tooth  to  the  angle  of  the  jaw,  it  will  cross  the  nerve,  which  lies  about  half  an  inch  behind 
the  tooth,  parallel  to  the  bulging  alveolar  ridge  on  the  inner  side  of  the  body  of  the  bone.  If 
the  knife  is  entered  three-quarters  of  an  inch  behind  and  below  the  last  molar  tooth  and  carried 
down  to  the  bone,  the  nerve  will  be  divided.  Hilton  divided  it  opposite  the  second  molar  tooth, 
where  it  is  covered  only  by  the  mucous  membrane,  and  Lucas  pulls  the  tongue  forward  and  over 
to  the  opposite  side,  when  the  nerve  can  be  seen  standing  out  as  a  firm  cord  under  the  mucous 
membrane  by  the  side  of  the  tongue  and  can  be  easily  seized  with  a  sharp  hook  and  divided  or 
a  portion  excised.  This  is  a  simple  enough  operation  on  the  cadaver,  but  when  the  disease  is 
extensive  and  has  extended  to  the  floor  of  the  mouth,  as  is  generally  the  case  when  division  of 
the  nerve  is  required,  the  operation  is  not  practicable. 

The  Sixth  Nerve  (Fig.  393). 

The  Sixth  or  Abducent  Nerve  supplies  the  External  rectus  muscle. 

Its  superficial  origin  is  by  several  filaments  from  the  constricted  part  of  the 
pyramid,  close  to  the  pons,  or  from  the  lower  border  of  the  pons  itself,  in  the 
groove  between  this  body  and  the  medulla.  Its  deep  origin  is  from  the  upper  part 
of  the  floor  of  the  fourth  ventricle,  close  to  the  median  line,  beneath  the  eminentia 
teres. 

From  the  nucleus  of  the  sixth  nerve  fibres  pass  through  the  posterior  longi- 

1  Camochan,  Amer.  Journ.  Med.  Science,  1858,  p.  136. 

2  Mears,  Trans.  Amer.  Surg.  Assoc,  vol.  ii.  p.  469. 


THE   BRANCHES    OF    THE   SIXTH  NERVE.  739 

tudinal  bundle  to  the  oculq^notor  nucleus  of  the  opposite  side  and  into  the  third 
nerve,  along  which  they' are  carried  to  the  Internal  rectus  muscle.  The  External 
rectus  of  one  eye  and  4he  Internal  rectus  of  the  other  may  therefore  be  said  to 
receive  their  nerves  from  the  same  nucleus — a  factor  of  great  importance  in  con- 
nection with  the  conjugate  movements  of  the  eyeball,  and  one  that  may  explain 
certain  paralytic  phenomena  of  the  Recti  muscles,  which  are  often  associated  with 
lesions  in  the  pons. 

The  nerve  pierces  the  dura  mater  on  the  basilar  surface  of  the  sphenoid  bone, 
runs  through  a  notch  immediately  below  the  posterior  clinoid  process,  and  enters 
the  cavernous  sinus.  It  passes  forward  through  the  sinus,  lying  on  the  outer  side 
of  the  internal  carotid  artery.  It  enters  the  orbit  through  the  sphenoidal  fissure, 
and  lies  above  the  .ophthalmic  vein,  from  which  it  is  separated  by  a  lamina  of  dura 
mater.  It  then  ,'pk>s*tes  between  the  two  heads  of  the  External  rectus,  and  is 
distributed  to  that  muscle  on/its  ocular  surface. 

Branches  of  Communication. — It  is  joined  by  several  filaments  from  the  carotid 
and  cavernous  plexus,  and  by  one  from  the  ophthalmic  nerve. 

The  above-mentioned  nerve,  as  well  as  the  third,  fourth,  and  the  ophthalmic 
division  of  the  fifth,  as  they  pass  to  the  orbit,  bear  a  certain  relation  to  each  other 
in  the  cavernous  sinus,  at  the  sphenoidal  fissure,  and  in  the  cavity  of  the  orbit, 
which  will  now  be  described. 

In  the  cavernous  sinus  (Fig.  327)  the  third,  fourth,  and  ophthalmic  division  of 
the  fifth^are  placed  on  the  outer  wall  of  the  sinus,  in  their  numerical  order  both 
from  above  downward  and  from  within  outward.  The  sixth  nerve  lies  at  the 
outer  side  of  the  internal  carotid  artery.  As  these  nerves  pass  forward  to  the 
sphenoidal  fissure,  the  third  and  fifth  nerves  become  divided  into  branches,  and 
the  sixth  approaches  the  rest,  so  that  their  relative  position  becomes  considerably 
changed. 

In  the  sphenoidal  fissure  (Fig.  398)  the  fourth  and  the  frontal  and  lachrymal 
divisions    of  the  ophthalmic   lie   upon   the  same  plane,  the  former    being  most 

Lachrymal. 
Frontal. 


Superior  division  of  3d. 
Vasal, 
"erior  division  of  3d. 

Ophthalmic  vein. 


Fig.  398.— Relations  of  structures  passing  through  the  sphenoidal  fissure. 


internal,  the  latter  external,  and  they  enter  the  cavity  of  the  orbit  above  the  mus- 
cles. The  remaining  nerves  enter  the  orbit  between  the  two  heads  of  the 
External  rectus.  The  superior  division  of  the  third  is  the  highest  of  these; 
beneath  this  lies  the  nasal  branch  of  the  ophthalmic  ;  then  the  inferior  division  of 
the  third ;  and  the  sixth  lowest  of  all. 

In  the  orbit  the  fourth  and  the  frontal  and  lachrymal  divisions  of  the  ophthal- 
mic lie  on  the  same  plane  immediately  beneath  the  periosteum,  the  fourth  nerve 
being  internal  and  resting  on  the  Superior  oblique,  the  frontal  resting  on  the 
Levator  palpebrae,  and  the  lachrymal  on  the  External  rectus.  Next  in  order 
comes  the  superior  division  of  the  third  nerve,  lying  immediately  beneath  the 
Superior  rectus,  and  then  the  nasal  branch  of  the  ophthalmic,  crossing  the  optic 
nerve  from  the  outer  to  the  inner  side  of  the  orbit.  Beneath  these  is  found  the 
optic  nerve,  surrounded  in  front  by  the  ciliary  nerves,  and  having  the  lenticular 


> 


740  THE  NERVOUS  8Y&FEM. 


1 

■'  SYthrjii 


\ 


ganglion  on  its  outer  side,  between  it  and  the  External  rectus.  Below  the  optic 
is  the  inferior  division  of  the  third  and  the  sixth,  which  'iies  on  the  outer  side  of 
the  orbit. 

Surgical  Anatomy. — The  sixth  nerve  is  more  frequently  involved  in  fractures  of  the  base 
of  the  skull  than  any  other  of  the  cranial  nerves.  The  result  of  paraiy&is  of  this  nerve  is  internal 
or  convergent  squint.  When  injured  so  that  its  function  is  destroyed,  there  is,  in  addition  to 
the  paralysis  of  the  External  rectus  muscle,  often  a  certain  amount  of  contraction  of  the  pupil, 
because  some  of  the  sympathetic  fibres  to  the  radiating  muscle  of  the  iris  pass  along  with  this 
nerve. 

The  Seventh  Nerve  (Figs.  399,  400,  401). 

The  Seventh  or  Facial  Nerve  (portio  dura)  is  the  motor  nerve  of  all  the  muscles 
of  expression  in  the  face,  and  of  the  Platysma  and  Buccinator ;  the  muscles  of 
the  External  ear ;  the  posterior  belly  of  the  Digastric,  and  the  Stylo-hyoid.  Its 
chorda  tympani  branch  is  the  nerve  of  taste  for  the  anterior  two-thirds  of  the 
tongue  and  the  vaso-dilator  nerve  of  the  submaxillary  and  sublingual  glands ;  its 
tympanic  branch  supplies  the  Stapedius. 

Its  superficial  origin  is  from  the  upper  end  of  the  medulla  oblongata,  in  the 
groove  between  the  olivary  and  restiform  bodies.      Its  deep  origin  is  from  a  nucleus 

situated  in  the  reticular  formation 
of  the  lower  part  of  the  pons,  a 
little   external   and  ventral   to   the 


Small W%Jgj^ggS  I    •^^WM       nUCleUS  °f  the  SiXth   DerVe'       Fl'°m 

Large  superficial  petrosal.  '  \   i':Jp        I  ,  \-;\     this    origin    the    fibres    pursue    a 

intumescentiagangiioformis.  ^^Jf^pj^^li  V%\    curved  course  in  the  substance  of 

the  pons.  They  first  pass  backward 
and  inward,  and  then  turn  upward 
and  forward  forming  the  funiculus 

Fig.  399.— The  course  and  connections  of  the  facial  nerve       ,  1  •   -i  j  _■«. „ 

in  the  temporal  bone.  teres,  which  produces  an  eminence 

(eminentia  teres)  on  the  floor  of  the 
fourth  ventricle,  and  finally  bend  sharply  downward  and  outward  round  the  upper 
end  of  the  nucleus  of  origin  of  the  sixth  nerve,  to  reach  their  superficial  origin 
between  the  olivary  and  restiform  bodies.  From  the  nucleus  of  the  third  nerve 
some  fibres  arise  which  descend  in  the  posterior  longitudinal  bundle  and  join  the 
facial  just  before  it  leaves  the  pons  ;  these  fibres  are  said  to  supply  the  anterior 
belly  of  the  Occipito-frontalis,  Orbicularis  palpebrarum,  and  the  Corrugator 
superc;Iii,  as  these  muscles  have  been  observed  to  escape  paralysis  in  lesions  of  the 
nucleus  of  the  facial  nerve. 

The  auditory  nerve  (portio  mollis)  lies  to  its  outer  side  ;  and  between  the  two 
is  a  small  fasciculus,  the  pars  intermedia  of  Wrisberg,  which  arises  from  the 
medulla  and  joins  the  facial  nerve  in  the  internal  auditory  meatus.  The  deep 
origin  of  the  pars  intermedia  is  from  the  upper  end  of  the  nucleus  of  the  glosso- 
pharyngeal nerve,  and  at  its  emergence  it  is  frequently  connected  with  both  nerves. 

The  pars  intermedia  may  be  regarded  as  the  sensory  root  of  the  facial  nerve, 
analogous  to  the  sensory  root  of  the  fifth,  and  its  real  nucleus  of  origin  would 
then  consist  of  the  geniculate  ganglion. 

The  facial  nerve,  firmer,  rounder,  and  smaller  than  the  auditory,  passes  forward 
and  outward  upon  the  middle  peduncle  of  the  cerebellum,  and  enters  the  internal 
auditory  meatus  with  the  auditory  nerve.  Within  the  meatus  the  facial  nerve  lies 
in  a  groove  along  the  upper  and  anterior  part  of  the  auditory  nerve,  and  the  pars 
intermedia  is  placed  between  the  two,  and  joins  the  inner  angle  of  the  geniculate 
ganglion.  Occasionally  a  few  of  its  fibres  pass  into  the  auditory  nerve.  Beyond 
the  ganglion  its  fibres  are  generally  regarded  as  forming  the  chorda  tympani. 

At  the  bottom  of  the  meatus,  the  facial  nerve  enters  the  aquseductus  Fallopii, 
and  follows  the  course  of  that  canal  through  the  petrous  portion  of  the  temporal 
bone,  from  its  commencement  at  the  internal  meatus,  to  its  ter  ^ination  at  the 
stylo-mastoid  foramen.  It  is  at  first  directed  outward  betwef  lie  cochlea  and 
vestibule  toward  the  inner  wall  of  the  tympanum;   it  then  r  nddenly  back- 

ward and  arches  downward  behind  the  tympanum  to  r  ,j,      «>id  foramen. 


/ 

THE   SEVENTH   OB   FACIAL    NERVE.  741 

| At  the  point  where  it  changes  itc  direction,  it  presents  a  reddish  gangliform  swell- 
ing (intumescentia  ganglioformis,  or  geniculate  ganglion).  On  emerging  from  the 
stylo-mastoid  foramen  it  runs  forward  in  the  substance  of  the  parotid  gland, 
crosses  the  external  carotid  artery,  and  divides  behind  the  ramus  of  the  lower  jaw 
into  two  primary  branches,  temporo-faeial  and  cervicofacial,  from  which  numerous 
offsets  are  distributed  over  the  side  of  the  head,  face,  and  upper  part  of  the  neck, 
supplying  the  superficial  muscles  in  these  regions.  As  the  primary  branches  and 
their  offsets  diverge  from  each  other,  they  present  somewhat  the  appearance  of  a 
bird's  claw  ;  hence  the  name  of  pes  anserinus  is  given  to  the  divisions  of  the  facial 
nerve  in  and  near  the  parotid  gland. 

The  communications  of  the  facial  nerve  may  be  thus  arranged : 
In  the  internal  auditory  meatus  .      With  the  auditory  nerve. 

With     Meckel's     ganglion     by    the   large 

superficial  petrosal  nerve. 
With    the    otic    ganglion    by    the    small 
From  the  geniculate  ganglion     .  {       superficial  petrosal  nerve. 

With  the  sympathetic  on  the  middle 
meningeal  by  the  external  superficial 
petrosal  nerve. 

T      ,     -^  „     .  -,  f  With  the  auricular  branch  of  the  pneumo- 

In  the  fallopian  aqueduct  .  <  ,  ■  r 

r  1  {      gastric. 

fWith  the  glossopharyngeal. 

At  its  exit  from  the  stylo-mastoid  J  With  the  pneumogastric. 

foramen        .  .  .  .    j  With  the  auricularis  magnus. 

I^With  the  auriculo-temporak—  t 

Behind  the  ear  ....      With  the  small  occipital. 

On  the  face        ....      With  the  three  divisions  of  the  fifth. 

In  the  neck        ....      With  the  superficial  cervical. 
•  In  the  internal  auditory  meatus  some  minute  filaments  pass  between  the  facial 
and  auditory  nerves. 

Opposite  the  hiatus  Fallopii,  the  gangliform  enlargement  on  the  facial  nerve 
communicates  with  Meckel's  ganglion  by  means  of  the  large  superficial  petrosal 
nerve,  which  forms  its  motor  root ;  with  the  otic  ganglion,  by  the  small  superficial 
petrosal  nerve ;  and  with  the  sympathetic  filaments  accompanying  the  middle  men- 
ingeal artery,  by  the  external  petrosal  (Bidder).  From  the  gangliform  enlarge- 
ment, according  to  Arnold,  a  twig  is  sent  back  to  the  auditory  nerve.  Just  before 
the  facial  nerve  emerges  from,  the  stylo-mastoid  foramen  it  generally  receives  a 
twig  of  communication  from  the  auricular  branch  of  the  pneumogastric. 

After  its  exit  from  the  stylo-mastoid  foramen,  it  sends  a  twig  to  the  glosso- 
pharyngeal, another  to  the  pneumogastric  nerve,  and  communicates  with  the  great 
'auricular  branch  of  the  cervical  plexus,  with  the  auriculotemporal  branch  of  the 
inferior  maxillary  nerve  in  the  parotid  gland,  with  the  small  occipital  behind  the 
ear,  on  the  face  with  the  terminal  branches  of  the  three  divisions  of  the  fifth,  and 
in  the  neck  with  the  transverse  cervical. 

Branches  of  Distribution. 

f  Tympanic,  to  t'i     ."• r  muscle. 


Within  the  aquaeductus  Fallopii  .  <'  ^    T 

^  1  Chorda  U  •■   pam. 

...  .,„         ,,        ,   ,  ,   . ,   f  Poster   >r  Auricular 

At  its  exit  from  the  stylo-mastoid  J   TV 


foramen 


"\  the  face 


£tylo-hyoid.  \ 

(Trni!    ral. 
e  "emporo-facial<  Malai 

(Infra-o 
j  (  Buccal /L 

^  Cervico-facial    <  Supvama:-  iilary. 

(inframaxill 


742 


/ 


THE   NERVOUS  SYSTEM. 


■ 


-).•"'■ 


The  tympanic  branch  arises  from  the  nerve  opposite  the  pyramid ;  it  pjassej 
through  a  small  canal  in  the  pyramid,  and  supplies  the  Stapedius  muscle. 

The  chorda  tympani  is  given  oft'  from  the  facial  as  it  passes  vertically  d&wi 
ward  at  the  back  of  the  tympanum,  about  a  quarter  of  an  inch  before  its  lejJ 
from  the  stylo-mastoid  foramen.     It  passes  from  below  upward  and  forward  ir( 


To  Auditory 


- — Vidiaif. 
Deep  Petrosal 


Digastric 
Stylo-hyoid 


Supramaxillari 
Infram  axillary 


Fig.  400.— Plan  of  the  facial  nerve. 


nal,  and  enters  the  cavity  of  the  tympanum  through  an  aperturd  (i 
dee  po  n  its  posterior  wall   between  the  opening  of  the  mastoid  c 

.;<-     umcut  of  the  membrana  tympani,  and  becomes  invested  with  mucou 

membrane.     It  passes  forward  through  the  cavity  of  the  tympanum,  between 
fibrous  and  mucous  layers  of  the  membrana  tympani,  and  over  the  handle  of  the 
malleus,  emerging  from  that  cavity  through  a  foramen  at  the  inner  end  jf  the 
Glaserian  fissure,  which  is  called   the  iter  chordce  anterius,  or  canal  of  Huyuier. 
It  then  descends  between  the  two    Pterygoid  muscles,   meets  the  lingual   ' 
at  an  acute    angle,   and   accompanies    it  to  the    submaxillary  gland ;   partlc 
then  joins  the  submaxillary  ganglion  ;   the  rest  is  continued  onward  throu|l 
muscular  substance  of  the  tongue  to  the   mucous  membrane  covering  its  aiit^ 
two-thirds.     A  few  of  its  fibres  probably   pass   through  the  submaxillary  ;g 
lion  to  the  sublingual  gland.      Before  joining  the  lingual  nerve  it  receives  a*' 
communicating  branch  from   the  otic  ganglion.     As  already   stated,   the  I 
tympani  nerve  is  by  many  regarded  as  the  continuation   of  the  pars  intern 
of  Wrisberg. 

The  Posterior  auricular  nerve  arises  close  to  the  stylo-mastoid  foramea, 
passes  upward  in  fr'ht  of  the  mastoid-process,  where  it  is  joined  by  a  filament*, 
the  auricular  b*   nch  of  the  pneumogu\>trie,  and  communicates  with  the  ljE* 
branch  of  the  great  auricular  and  with  the  small  occipital.     As  it  ascends  b# 
the  meatus  and  mastoid  process  it  divides  into  tw~o  branches.      The  auricula''" 
supples  the  Retrahens  auriculum  and  tbe  small  muscles  on  the  cranial  s*r" 
the  pinna.     The  occipital  branch,  the  larger,  passes  backward  along  th'  au 
curved  line  of  the  occipital  bone,  and  supplies  the  occipital  portion  of  tH  (- 
frontalis.  \ 


THE  SEVENTH   OB    FACIAL    NERVE. 


743 


The  digastric  branch  usually  arises  by  a  common  trunk  with  the  Stylo-hyoid 
branch  :  it  divides  into  several  filaments,  which  supply  the  posterior  belly  of  the 
Digastric ;  one  of  these  perforates  that  muscle  to  join  the  glosso-pharyngeal  nerve. 

The  stylo-hyoid  is  a  long,  slender  branch,  which  passes  inward,  entering  the 
Stylo-hyoid  muscle  about  its  middle. 

The  Temporo-facial,  the  larger  of  the  two  terminal  branches,  passes  upward 
and  forward  through  the  parotid  glands,  crosses  the  external  carotid  artery  and 
temporo-maxillary  vein,  and  passes  over  the  neck  of  the  condyle  of  the  jaw,  being 
connected  in  this  situation  with  the  auriculotemporal  branch  of  the  inferior 
maxillary  nerve,  and  divides  into  branches  which  are  distributed  over  the  temple 
and  upper  part  of  the  face ;  these  are  divided  into  three  sets — temporal,  malar,  and 
infra-orbital. 


Terminations 
T  of  supratrochlear. 

*    r\Of  infratrochlear 
i\  <A\      of  nasal. 


Fig.  401.— The  nerves  of  the  scalp,  face,  and  side  of  the  neck. 

The  temporal  branches  cross  the  zygoma  to  the  temporal  region,  supplying  the 
Attrahens  and  Attollens  auriculam  muscles,  and  join  with  the  temporal  branch  of 
the  temporo-malar,  a  branch  of  the  superior  maxillary,  and  with  the  auriculotem- 
poral branch  of  the  inferior  maxillary.  The  more  anterior  branches  supply  the 
frontal  portion  of  the  Occipito-frontalis,  the  Orbicularis  palpebrarum,  and  Corruga- 
tor  supercilii  muscles,  joining  with  the  supra-orbital  and  lachrymal  branches  of 
the  ophthalmic. 

The  malar  branches  pass  across  .-the  malar  bone  to  the  outer  angle  of  the  orbit, 


V 


I 

) 

744  THE   NERVOUS   SYSTEM. 


f\ 


where  they  supply  the  Orbicularis  palpebrarum  muscle,  joining  with  filaments  from 
the  lachrymal  nerve;  others  supply  the  lower  eyelid,  joining  with  filaments  of  the 
malar  branch  (subcutaneus  malce)  of  the  superior  maxillary  nerve. 

The  infra-orbital,  of  larger  size  than  the  rest,  pass  horizontally  forward  to  be 
distributed  between  the  lower  margin  of  the  orbit  and  the  mouth.  The  superficial 
brandies  run  beneath  the  skin  and  above  the  superficial  muscles  of  the  face,  which 
they  supply  :  some  branches  are  distributed  to  the  Pyramidalis  nasi,  joining  at  the 
inner  angle  of  the  orbit  with  the  infratrochlear  and  nasal  branches  of  the 
ophthalmic.  The  deep  branches  pass  beneath  the  Zygomatici  and  the  Levator  labii 
superioris,  supplying  them  and  the  Levator  anguli  oris,  and  form  a  plexus  (infra- 
orbital) by  joining  with  the  infra-orbital  branch  of  the  superior  maxillary  nerve 
and  the  buccal  branches  of  the  cervico-facial.  This  branch  also  supplies  the 
Levator  labii  superioris  alseque  nasi  and  the  small  muscles  of  the  nose. 

The  Cervico-facial  division  of  the  facial  nerve  passes  obliquely  downward  and 
forward  through  the  parotid  gland,  crossing  the  external  carotid  artery.  In  this 
situation  it  is  joined  by  branches  from  the  great  auricular  nerve.  Opposite  the 
angle  of  the  lower  jaw  it  divides  into  branches  which  are  distributed  on  the  lower 
half  of  the  face  and  upper  part  of  the  neck.  These  may  be  divided  into  three  sets 
— buccal,  supramaxillary,  and  inframaxillary. 

The  buccal  branches  cross  the  Masse^er  muscle.  They  supply  the  Buccinator 
and  Orbicularis  oris,  and  join  with  the  infra-orbital  branches  of  the  temporo-facial 
division  of  the  nerve,  and  with  filaments  of  the  buccal  branch  of  the  inferior 
maxillary  nerve. 

The  supramaxillary  or  mandibular  bran^^p&ss  forward  beneath  the  Platysma 
;ind  Depressor  anguli  oris,  supplying  the  lMrles  of  the  lower  lip  and  chin,  and 
communicating  with  the  mental  branch  of  |Jae^jiferior  dental  nerve. 

The  inframaxillary  or  cervical  bj-anches^^^^orwiwd  beneath  the  Platysma, 
and  form  a  series  of  arches  across  the  side^^Mie  neck  over  the  suprahyoid 
region.  One  of  these  branches  desauids  vertin^m  to  join  with  the  superficial 
cervical   nerve  from  the  cervical  plexim:   others  s^»ly  the  Platysma. 


Surgical  Anatomy. — The  facial  nerve  is  ri»e  frequenH^aaralyzed  than  any  of  the  othei 
of  the  cranial  nerves.  The  paralysis  may  depend  wither  upon  ^■central  causes — i.  e.  blood-clots 
or  intracranial  tumors  pressing  on  the  nerve  beforelits  entrance  imp  the  internal  auditory  meatus. 
It  is  also  one  of  the  nerves  involved  in  "  bulbar  paralysis."  Oil(2)  it  may  be  paralyzed  in  its 
passage  through  the  petrous  bone  by  damage  due  to  middle-ear  aisease  or  by  fractures  of  the 
base.  Or  (3)  it  maybe  affected  at  or  after  its  exjt  from  the  st3'lo-mastoid  foramen.  This  is 
commonly  known  as  "Bell's  paralysis."  It  may  be  due  to  exposure  to  cold  or  to  injury  of  the 
nerve,  either  from  accidental  wounds  of  the  face  or  during  some  surgical  operation,  as  removal 
of  parotid  tumors,  opening  of  abscesses,  or  operations  on  the  lower  jaw. 

When  the  cause  is  central,  the  sixth  nerve  is  usually  paralyzed  \as  well,  and  there  is  also 
hemiplegia  on  the  opposite  side.  In  these  cases  the  electrical  reactions  are  the  same  as  in 
health  ;  whereas,  when  the  paralysis  is  in  the  course  of  the  nerve,  the  reaction  is  usually  lost.  . 
When  the  nerve  is  paralyzed  in  the  petrous  bone,  in  addition  to  the  paralysis  of  the  muscles  of 
expression,  there  is  loss  of  taste  in  the  anterior  part  of  the  tongue,  and  the  patient  is  unable  to 
recognize  the  difference  between  bitters  and  sweets,  acids  and  salines,  from  involvement  of  the 
chorda  tympani.  The  mouth  is  dry,  because  the  salivary  glands  are  not  secreting ;  and  the 
sense  of  hearing  is  affected  from  paralysis  of  the  Stapedius.  When  the  cause  of  the  paralysis 
is  from  fracture  of  the  base  of  the  skull,  the  auditory  nerve  and  the  petrosal  nerves,  which  are 
connected  with  the  intumescentia  ganglioformis,  are  also  involved.  When  the  injury  to  the 
nerve  is  after  its  exit  from  the  stylo-mastoid  foramen,  all  the  muscles  of  expression,  except 
the  Levator  palpebrae,  together  with  the  posterior  belly  of  the  Digastric  and  Stylo-hyoid,  are 
paralyzed.  There  is  smoothness  of  the  forehead,  and  the  patient  is  unable  to  frown ;  the  eye- 
lids cannot  be  closed,  and  the  lower  lid  droops,  so  that  the  punctum  is  no  longer  in  contact  with 
the  globe,  and  the  tears  run  down  the  cheek ;  there  is  smoothness  of  the  cheek  and  loss  of  the 
naso-labial  furrow ;  the  nostril  cannot  be  dilated ;  the  mouth  is  drawn  to  the  sound  side,  and 
there  is  inability  to  whistle ;  food  collects  between  the  cheek  and  gum  from  paralysis  of  the 
Buccinator.  / 

The  facial  nerve  is  at  fault  in  cases  of  so-called  "histrionic  spasm,"  which  consists  in  an 
almost  constant  and  uncontrollable  twitching  of  the  muscles  of  the  face.  _  This  twitching  is 
sometimes  so  severe  as  to  cause  great  discomfort  and  annoyance  to  the  patient  and  to  interfere 
with  sleep,  and  for  its  relief  the  facial  nerve  has  been  stretched.  The  operation  is  performed 
by  making  an  incision  behind  the  ear  from  the  root  of  the  mastoid  process  to  the  angle  of  the 
jaw.     The  parotid  is  turned  forward,  and  the  disseetW  carried  along  the  anterior  border  of  the 


THE   EIGHTH   OR    AUDITORY  NERVE.  745 

Sterno-mastoid  muscle  and  mastoid  process  until  the  upper  border  of  the  posterior  belly  of  the 
Digastric  is  found.  The  nerve  is  parallel  to  this  on  about  a  level  of  the  middle  of  the  mastoid 
process.  When  found,  the  nerve  must  be  stretched  by  passing  a  blunt  hook  beneath  it  and 
pulling  it  forward  and  outward.  Too  great  force  must  not  be  used,  for  fear  of  permanent  injury 
to  the  nerve. 

Eighth  Nerve. 

The  Eighth  or  Auditory  Nerve  ( portio  mollis)  is  the  special  nerve  of  the  sense 
of  hearing,  being  distributed  exclusively  to  the  internal  ear. 

Origin  of  the  Eighth  Nerve. — The  eighth  nerve  consists  of  two  sets  of  fibres. 
Avhich,  although  differing  in  their  central  connections,  are  both  concerned  in  the 
transmission  of  afferent  impulses  from  the  internal  ear  to  the  medulla  and  pons, 
and  from  there,  by  means  of  new  fibres  which  arise  from  collections  of  gray 
matter  in  these  structures,  to  the  cerebrum  and  cerebellum.  One  set  of  fibres 
forms  the  vestibular  root  of  the  nerve,  and  arises  from  the  cells  in  the  ganglion 
of  Scarpa ;  the  other  set  constitutes  the  cochlear  root,  and  takes  origin  from  the 
cells  in  the  ganglion  spirale  or  ganglion  of  Corti.  At  its  connection  with  the 
brain  the  eighth  nerve  occupies  the  groove  between  the  pons  and  medulla,  where  it 
is  situated  between  the  restiform  body,  which  is  behind,  and  the  seventh  nerve, 
which  is  in  front. 

Vestibular  or  Ventral  Root. — The  fibres  of  this  root  enter  the  medulla  to  the 
inner  side  of  those  of  the  cochlear  root,  and  pass  between  the  restiform  body, 
which  is  to  their  outer  side,  and  the  inferior  root  of  the  fifth,  which  lies  to  their 
inner  side.  They  then  divide  into  an  ascending  and  a  descending  set.  The  fibres 
of  the  latter  end  by  arborizing  round  the  cells  of  the  internal  nucleus,  which  is 
situated  in  the  trigonum  acustici  in  the  floor  of  the  fourth  ventricle.  The  ascend- 
ing fibres  either  end  in  the  same  manner  or  in  the  external  nucleus,  which  is 
situated  to  the  outer  side  of  the  trigonum  acustici  and  farther  from  the  ventricular 
fl<i>or.  It  is  described  as  consisting  of  two  parts,  an  inner,  the  nucleus  of  Belters, 
and  an  outer,  the  nucleus  of  Bechteren.  Some  of  the  axons  of  the  cells  of  the 
external  nucleus,  and  possibly  also  of  the  internal  nucleus,  are  continued  upward 
through  the  restiform  body  to  the  roof  nuclei  of  the  opposite  side  of  the  cere- 
bellum, to  which  also  are  prolonged  other  fibres  of  the  vestibular  root  without 
undergoing  a  relay  in  the  nuclei  of  the  medulla.  A  second  set  of  fibres  from  the 
internal  and  external  nuclei  end  partly  in  the  tegmentum,  while  the  remainder 
ascend  in  the  posterior  longitudinal  bundle  to  arborize  around  the  nuclei  of  the 
oculo-motor  nerve. 

Cochlear  or  Dorsal  Root. — This  part  of  the  nerve  is  placed  externally  to  the 
vestibular  root.  Its  fibres  end  in  two  nuclei,  one  of  which,  the  accessory  nucleus, 
lies  immediately  in  front  of  the  restiform  body  ;  the  other,  the  tuherculum  acusti- 
cum,  somewhat  to  its  outer  side. 

The  striae  acusticse  or  medullary  striae  are  the  axons  of  the  cells  of  the  tuber- 
culum  acusticum.  They  pass  backward  and  inward  over  the  restiform  body,  and 
across  the  floor  of  the  fourth  ventricle  toward  the  middle  line.  Here  they  dip  into 
the  substance  of  the  pons,  to  end  around  the  cells  of  the  superior  olive  of  the  same  or 
opposite  side.  There  are,  however,  other  fibres,  and  these  are  both  direct  and 
crossed,  which  do  not  arborize  around  the  tegmental  nuclei,  but  pass  into  the  lateral 
fillet.  The  cells  of  the  accessory  nucleus  give  origin  to  fibres  which  pass  trans- 
versely in  the  pons  and  constitute  the  trapezium.  The  description  given  as  to  the 
mode  of  ending  of  the  striae  acusticse  is  applicable  to  that  of  the  trapezoid  fibres, 
viz.,  around  the  cells  of  the  superior  olive  or  of  the  trapezoid  nucleus  (which  lies 
ventral  to  the  olive)  of  the  same  or  opposite  side,  while  others,  crossed  or  uncrossed, 
pass  directly  into  the  lateral  fillet. 

If  the  further  connections  of  the  cochlear  nerve  of  one  side,  say  the  left,  are 
considered,  it  is  found  that  they  lie  to  the  outer  side  of  the  main  sensory  tract,  the 
fillet,  and  are  therefore  termed  the  lateral  fillet.  The  fibres  comprising  the  left 
lateral  fillet  arise  in  the  superior  olive  or  trapezoid  nucleus  of  the  same  or  opposite 
side,  while  others  are  the  uninterrupted  fibres  already  alluded  to,  and  these  are 


746  THE  NERVOUS  SYSTEM. 

either  crossed  or  uncrossed,  the  former  being  the  axons  of  the  cells  of  the  right 
accessory  nucleus  or  of  the  cells  of  the  right  tuberculum  acusticum,  while  the  latter 
are  derived  from  the  same  cells  of  the  left  side.  In  the  upper  part  of  the  fillet 
there  is  a  collection  of  nerve-cells,  the  nucleus  of  the  fillet,  around  the  cells  of 
which  some  of  the  fibres  arborize,  and  from  the  cells  of  which  axons  originate  to 
continue  upward  the  tract  of  the  lateral  fillet.  The  ultimate  ending  of  the  left  lat- 
eral fillet  is  partly  in  the  quadrigeminal  bodies  of  the  same  or  opposite  side,  while 
the  remainder  of  the  fibres  ascend  in  the  posterior  limb  of  the  internal  capsule  to 
reach  the  first  and  perhaps  the  second  left  temporal  convolution. 

The  auditory  nerve  contains  a  few  afferent  fibres  which  arise  in  the  quadrigemi- 
nal bodies,  the  nucleus  of  the  lateral  fillet,  trapezoid  nucleus,  and  superior  olive. 

The  auditory  nerve  after  leaving  the  medulla  passes  forward  across  the  poste- 
rior border  of  the  middle  peduncle  of  the  cerebellum,  in  company  with  the  facial 
nerve,  from  which  it  is  partially  separated  by  a  small  artery  (auditory).  It  then 
enters  the  internal  auditory  meatus  with  the  facial  nerve.  At  the  bottom  of  the 
meatus  it  receives  one  or  two  filaments  from  the  facial  nerve,  and  then  divides  into 
its  two  branches,  cochlear  and  vestibular.  The  auditory  nerve  is  soft  in  texture 
(hence  the  name,  portio  mollis),  and  is  destitute  of  neurilemma.  The  distribution 
of  the  auditory  nerve  in  the  internal  ear  will  be  found  described  along  with  the 
anatomy  of  that  organ  in  a  subsequent  page. 

Surgical  Anatomy. — The  auditory  nerve  is  frequently  injured,  together  with  the  facial 
nerve,  in  fractures  of  the  middle  fossa  of  the  base  of  the  skull  implicating  the  internal  auditory 
meatus.  The  nerve  may  be  either  torn  across,  producing  permanent  deafness,  or  it  may  be 
bruised  or  pressed  upon  by  extravasated  blood  or  inflammatory  exudation,  when  the  deafness 
will  in  all  probability  be  temporary.  The  nerve  may  also  be  injured  by  violent  blows  on  the 
head  without  fracture,  and  deafness  may  arise  from  loud  explosions  from  dynamite,  etc. ,  prob- 
ably from  some  lesion  of  this  nerve,  which  is  more  liable  to  be  injured  than  the  other  cranial 
nerves  on  account  of  its  structure.  The  test  that  the  nerve  is  destroyed  and  that  the  deafness  is 
not  due  to  some  lesion  of  the  auditory  apparatus  is  obtained  by  placing  a  vibrating  tuning-fork 
on  the  head.  The  vibrations  will  be  heard  in  cases  where  the  auditory  apparatus  is  at  fault,  but 
not  in  cases  of  destruction  of  the  auditory  nerve. 

.      The  Ninth  Pair  (Figs.  402,  403,  404). 

The  Ninth  or  Glosso-pharyngeal  Nerve  is  distributed,  as  its  name  implies,  to 
the  tongue  and  pharynx,  being  the  nerve  of  ordinary  sensation  to  the  mucous 
membrane  of  the  pharynx,  fauces,  and  tonsil ;  and  the  nerve  of  taste  to  all  parts 
of  the  tongue  to  which  it  is  distributed. 

Its  superficial  origin  is  by  three  or  four  filaments,  closely  connected  together, 
from  the  upper  part  of  the  medulla  oblongata,  in  the  groove  between  the  olivary 
and  restiform  body. 

Its  deep  origin  may  be  traced  through  the  fasciculi  of  the  lateral  tract,  to  three 
different  sources:  (1)  some  of  the  fibres  may  be  traced  to  a  nucleus  of  gray  matter 

at  the  lower  part  of  the  floor   of  the  fourth  ventricle 
juguiareangi.  beneath  the   inferior  fovea ;  (2)  others  may  be  traced 

pet™*  Gangt.  downward    into    the  funiculus    solitarius,   a    rounded 

Tympanic  r.       j^^g  0f  f[Dres  jn  the  lower  part  of  the  medulla,  com- 
.ctoaso-        mencing  immediately  above  the  decussation  of  the  pyr- 
amids (these   fibres  have  not  been  distinctly  traced  to 
cells)  ;  (3)  a  third  set  of  fibres  take  origin  from  the  cells 
of  the  nucleus  ambiguus.     This  nucleus  is  situated  some 
distance  from   the  floor  of  the  fourth  ventricle  and  lies 
^x*      slightly  internal  to  the  inferior  fovea.     It  gives  origin 
ftwgartri*         to   the  mQtor    branclies   0f  the  glosso-pharyngeal  and 

eommunicittonsigionf  gth£U&ilt8     vagus,  and  to  the  bulbar  part  of  the  spinal  accessory. 
neve's  and     eleventh     craniaI     The  real   origin    of  the   sensory   fibres  of  the  glosso- 
pharyngeal must  be  looked  for  in  the  jugular  and  pe- 
trosal ganglia  which  are  developed  from  the  neural  crest. 

From  its  superficial  origin  it  passes  outward  across  the  flocculus,  and  leaves  the 


THE   NINTH   OB    GLOSSOPHARYNGEAL    NEBVE. 


nd 


FIG-  403-Plan  of  the  glossopharyngeal,  pneumogastric,  and  spinal  accessory  nerves.    (After  PI  - " 

^tr^xtLSfM    Pf  °*  ^  JU/lLlar  f°ramen'  in  a  seParate  s^ath  -to  a  second 
matei,  external  to  and  m  front  of  the  pneumogastric  and  spinal  acce^  trunk  of 


748  THE  NERVOUS  SYSTEM. 

(Fig.  329).  In  its  passage  through  the  jugular  foramen  it  grooves  the  lower 
border  of  the  petrous  portion  of  the  temporal  bone,  and  at  its  exit  from  the  skull 
passes  forward  between  the  jugular  vein  and  internal  carotid  artery,  and  descends 
in  front  of  the  latter  vessel,  and  beneath  the  styloid  process  and  the  muscles  con- 
nected Avith  it,  to  the  lower  border  of  the  Stylo-pharyngeus.  The  nerve  now 
curves 'inward,  forming  an  arch  on  the  side  of  the  neck,  and  lying  upon  the  Stylo- 
pharyngeus  and  Middle  constrictor  of  the  pharynx.  It  then  passes  beneath  the 
Hyoglossus,  and  is  finally  distributed  to  the  mucous  membrane  of  the  fauces  and 
base  of  the  tongue,  and  the  mucous  glands  of  the  mouth  and  tonsil. 

In  passing  through  the  jugular  foramen  the  nerve  presents,  in  succession,  two 
gangliform  enlargements.  The  superior,  the  smaller,  is  called  the  jugular  gan- 
glion ;  the  inferior  and  larger,  the  petrous  ganglion,  or  the  ganglion  of  Andersch. 

The  superior  or  jugular  ganglion  is  situated  in  the  upper  part  of  the  groove  in 
which  the  nerve  is  lodged  during  its  passage  through  the  jugular  foramen.  It  is 
of  very  small  size,  and  involves  only  the"  lower  part  of  the  trunk  of  the  nerve. 
It  is  usually  regarded  as  a  segmentation  from  the  lower  ganglion. 

The  inferior,  or  petrous,  ganglion  is  situated  in  a  depression  in  the  lower  bor- 
der of  the  petrous  portion  of  the  temporal  bone ;  it  is  larger  than  the  former  and 
involves  the  whole  of  the  fibres  of  the  nerve.  From  this  ganglion  arise  those 
filaments  which  connect  the  glosso-pharyngeal  with  the  pneumogastric  and  sym- 
pathetic nerves. 

The  branches  of  communication  are  with  the  pneumogastric,  sympathetic,  and 
facial. 

The  branches  to  the  pneumogastric  are  two  filaments,  arising  from  the  petrous 
ganglion,  one  to  its  auricular  branch,  and  one  to  the  upper  ganglion  of  the 
pneumogastric. 

The  branch  to  the  sympathetic,  also  arising  from  the  petrous  ganglion,  is  con- 
nected with  the  superior  cervical  ganglion. 

The  branch  of  communication  with  the  facial  perforates  the  posterior  belly  of 
the  Digastric.  It  arises  from  the  trunk  of  the  nerve  below  the  petrous  ganglion, 
and  joins  the  facial  just  after  its  exit  from  the  stylo-mastoid  foramen. 

The  branches  of  distribution  are  the  tympanic,  carotid,  pharyngeal,  muscular, 
tonsillar,  and  lingual. 

The  tympanic  branch  (Jacobsons  nerve)  arises  from  the  petrous  ganglion,  and 
enters  a  small  bony  canal  in  the  lower  surface  of  the  petrous  portion  of  the  tem- 
poral bone,  the  lower  opening  of  which  is  situated  on  the  bony  ridge  which  sep- 
arates the  carotid  canal  from  the  jugular  fossa.  It  ascends  to  the  tympanum, 
enters  that  cavity  by  an  aperture  in  its  floor  close  to  the  inner  wall,  and  divides 
into  branches  which  are  contained  in  grooves  upon  the  surface  of  the  promontory, 
forming  the  tympanic  plexus.  This  plexus  gives  off  (1)  the  greater  part  of  the 
small  superficial  petrosal  nerve;  (2)  a  branch  to  join  the  great  superficial  petrosal 
nerve ;  and  (3)  branches  to  the  tympanic  cavity,  all  of  which  will  be  described  in 
connection  with  the  anatomy  of  the  ear. 

The  carotid  branches  descend  along  the  trunk  of  the  internal  carotid  artery  as 
far  as  its  commencement,  communicating  with  the  pharyngeal  branch  of  the  pneu- 
mogastric and  with  branches  of  the  sympathetic. 

The  pharyngeal  branches  are  three  or  four  filaments  which  unite  opposite  the  Mid- 
dle constrictor  of  the  pharynx  with  the  pharyngeal  branches  of  the  pneumogastric 
and  sympathetic  nerves  to  form  the  pharyngeal  plexus,  branches  from  which  perforate 
the  muscular  coat  of  the  pharynx  to  supply  the  muscles  and  mucous  membrane. 

The  muscular  branch  is  distributed  to  the  Stylo-pharyngeus. 

The  tonsillar  branches  supply  the  tonsil,  forming  a  plexus  (circulus  tonsillaris) 
around  this  body,  from  which  branches  are  distributed  to  the  soft  palate  and  fauces, 
n^.->r(j  they  communicate  with  the  palatine  nerves. 

*  lingual  branches  are  two  in  number  :   one  supplies  the  circumvallate  papillse 

sal  San.,cous  membrane  covering  the  surface  of  the  base  of  the  tongue  ;  the  other 
om  lls  substance,  and  supplies  the  mucous  membrane  and  follicular  glands  of 
half  of  the  tongue  and  communicates  with  the  lingual  nerv^. 


THE    TENTH    OR    PNEUMOGASTRIC 


749 


Glosso-pharyn  jeal.  >.     . 
Pneumogastr  ■  c.   Jf3| 
Spinal  accessor!/,  r" 


The  Tenth  Pair  (Figs.  403,  404). 

The  Tenth  or  Pneumogastric  Nerve  (nervus  van  en  or  }a,    valgum)  has  a  more 
extensive  distribution  than  any  of  the  other  crania  ;,  passing  through  the 

neck  and  thorax  to  the  upper  part 
of  the  abdomen.  It  is  composed 
of  both  motor  and  sensory  fibres. 
It  supplies  the  organs  of  voice 
and  respiration  with  motor  and 
sensory  fibres,  and  the  pharynx, 
oesophagus,  stomach,  and  heart 
with  motor  fibres.  Its  superficial 
origin  is  by  eight  or  ten  filaments 
from  the  groove  between  the  oli- 
vary and  the  restiform  body  below 
the  glosso-pharyngeal ;  its  deep 
origin  may  be  traced  through  the 
fasciculi  of  the  medulla  to  termi- 
nate in  a  nucleus  of  gray  matter, 
the  nucleus  vagi,  at  the  lower  part 
of  the  floor  of  the  fourth  ventricle 
beneath  the  ala  cinerea  below  and 
continuous  with  the  nucleus  of 
origin  of  the  glosso-pharyngeal. 
In  addition  to  this  a  few  fibres 
pass  into  the  funiculus  solitarius, 
and  others  into  the  nucleus  am- 
biguus  or  accessory  vagal  nucleus. 
The  real  origin  of  the  sensory 
fibres  of  the  vagus  is  to  be  found 
in  the  cells  of  the  ganglia  on  the 
nerve,  viz.,  the  ganglion  of  the 
root  and  the  ganglion  of  the  trunk. 
The  filaments  become  united  and 
form  a  flat  cord,  which  passes  out- 
ward beneath  the  flocculus  to  the 
jugular  foramen,  through  which 
it  emerges  from  the  cranium.  In 
passing  through  this  opening  the 
pneumogastric  accompanies  the 
spinal  accessory,  being  contained 
in  the  same  sheath  of  dura  mater 
with  it,  a  membranous  septum 
separating  them  from  the  glosso- 
pharyngeal, which  lies  in  front 
(Fig.  329).  The  nerve  in  this 
situation  presents  a  weR-marked 
ganglionic  enlargement,  which  is 
called  the  jugular  ganglion,  or  the 
ganglion  of  the  root  of  the  pneu- 
mogastric :  to  it  the  acces?  ory  part 
of  the  spinal   acce  rve  is 

connected  by  one  or  tw  filaments. 
After  the  exit  o.  th  >  necve  from 
the  jugular  fi.iai     n    ■!•■■■    n  srve  is 

joined  by  th<   ac  ry  portion  of  the  spinal  accessory,  and  enlarges  into  a  second 

gangliform  swell  in  3  the  ganglion  inferius,  or  the  ganglion  of  the  trunk  of 


Fig.  404.— Course  and  distribution  of  the  ninth,  tenth,  and 
eleventh  nerves. 


K  THE   NERVOUS  SYSTEM. 


the  nerve,  through  which  the  fibres  of  the  spinal  accessory  pass  unchanged,  being 
principally  distributed  to  the  pharyngeal  and  superior  laryngeal  branches  of  the 
vagus ;  but  some  of  fjhe  filaments  from  it  are  continued  into  the  trunk  of  the  vagus 
below  the  ganglion,-,  to  b'«*  distributed  with  the  recurrent  laryngeal  nerve,  and  prob- 
ably also  with  the  cardiac  new*  ;.  The  nerve  passes  vertically  down  the  neck 
within  the  sheath  of  the  caret  <\  vessels  lying  between  the  internal  carotid  artery 
and  internal  jugular  vein  as  far  as  the  thyroid  cartilage,  and  then  between  the  same 
vein  and  the  common  carotid  to  the  "spot  of  the  neck.  Here  the  course  of  the  nerve 
becomes  different  on  the  two  sides  oi*  the  body. 

On  the  right  side  the  nerve  passes  across  the  subclavian  artery  between  it  and 
the  right  innominate  vein,  and  desceiuu  by  the  side  of  the  trachea  to  the  back  part 
of  the  root  of  the  lung,  where  it  spreads  out  in  a  plexiform  network  (posterior  pul- 
monary), from  the  lower  part  of  which  two  cord?  descend  upon  the  oesophagus,  on 
which  they  divide,  forming,  with  branches  from  the  opposite  nerve,  the  oesophageal 
plexus  (plexus  gulce);  below,  these  branches  are  collected  into  a  single  cord,  which 
runs  along  the  back  part  of  the  oesophagus,  enters  the  abdomen,  and  is  distributed 
to  the  posterior  surface  of  the  stomach,  joining  the  left  side  of  the  solar  plexus,  and 
sending  filaments  to  the  splenic  plexus  and  a  considerable  branch  to  the  coeliac 
plexus. 

On  the  left  side  the  pneumogastric  nerve  enters  the  chest  between  the  left 
carotid  and  subclavian  arteries,  behind  the  left  innominate  vein.  It  crosses  the 
arch  of  the  aorta  and  descends  behind  the  root  of  the  left  lung,  forming  the  poste- 
rior pulmonary  plexus,  and  along  the  anterior  surface  of  the  oesophagus,  where  it 
unites  with  the  nerve  of  the  right  side  in  forming  the  plexus  guise,  to  the  stomach, 
distributing  branches  over  its  anterior  surface,  some  extending  over  the  great 
cul-de-sac,  and  others  along  the  lesser  curvature.  Filaments  from  these  branches 
enter  the  gastro-hepatic  omentum  and  join  the  hepatic  plexus. 

The  ganglion  of  the  root  is  of  a  grayish  color,  circular  in  form,  about 
two  lines  in  diameter,  and  resembles  the  ganglion  on  the  large  root  of  the  fifth 
nerve. 

Connecting  Branches. — To  this  ganglion  the  accessory  portion  of  the  spinal 
accessory  nerve  is  connected  by  several  delicate  filaments  ;  it  also  has  a  communi- 
cating twig  with  the  petrous  ganglion  of  the  glosso-pharyngeal,  with  the  facial 
nerve  by  means  of  its  (the  ganglion's)  auricular  branch,  and  with  sympathetic 
by  means  of  an  ascending  filament  from  the  superior  cervical  ganglion. 

The  ganglion  of  the  trunk  (inferior)  is  a  plexiform  cord,  cylindrical  in 
form,  of  a  reddish  color,  and  about  an  inch  in  length ;  it  involves  the  whole 
of  the  fibres  of  the  nerve,  and  passing  through  it  is  the  accessory  portion  of 
the  spinal  accessory  nerve,  which  blends  with  the  pneumogastric  below  the 
ganglion,  and  is  then  principally  continued  into  its  pharyngeal  and  superior 
laryngeal  branches. 

Connecting  Branches. — This  ganglion  is  connected  with  the  hypoglossal,  the 
superior  cervical  ganglion  of  the  sympathetic,  aoftd  the  loop  between  the  first  and 
second  cervical  nerves. 

The  branches  of  the  pneumogastric  are — 

t    J.-L    •       i      *  i  Meningeal. 

In  the  uigular  tossa     .  .  •     (    a      •     i 

J   &  )  Auricular, 

(  Pharyngeal. 

T     ,,  ,  Superior  laryngeal. 

In  the  neck         .         .         .         .    <  t>  *  i  i 

ttecurrent  laryngeal. 

[(''       ical  cardiac. 

f  Th   raijjc  cardiac. 

T    ,,     ,1'  Anterior1  ouftnonary. 

In  the  thorax      .         .         .         .    <  t>  */■ 

re  mo.nary. 

I^OE,  ophag*\al. 

In  the  abdomen  .  Gastric. 


THE    TENTH    OB    PNEUMOOASTBIC  NEBVE. 


751 


The  meningeal  branch  is  a  recurrent  filament  given  off  from  the  ganglion  of  the 
root  in  the  jugular  foramen.  It  passes  backward,  and  is  distributed  to  the  dura 
mater  covering  the  posterior  fossa  of  the  base  of  the  skull. 

The  auricular  branch  (Arnold's)  arises  from  the  ganglion  of  the  root,  and  is 
joined  soon  after  its  origin  by  a  filament  from  the  petrous  ganglion  of  the  glosso- 
pharyngeal; it  passes  outward  behind  the  jugular  vein,  and  enters  a  small  canal 
on  the  outer  wall  of  the  jugular  fossa.  Traversing  the  substance  of  the  temporal 
bone,  it  crosses  the  aqueductus  Fallopii  about  tAVO  lines  above  its  termination  at 
the  stylo-mastoid  foramen ;  here  it  gives  off  an  ascending  branch,  which  joins  the 
facial :  the  continuation  of  the  nerve  reaches  the  surface  by  passing  through  the 
auricular  fissure  between  the  mastoid  process  and  the  external  auditory  meatus,  and 
divides  into  two  branches,  one  of  which  communicates  with  the  posterior  auricular 
nerve,  while  the  other  supplies  V  e  integument  at  the  back  part  of  the  pinna  and 
the  posterior  part  of  the  external  auditory  meatus. 

The  pharyngeal  branch,  the  principal  motor  nerve  of  the  pharynx,  arises  from 
the  upper  part  of  the  inferior  ganglion  of  the  pneumogastric.  It  consists  principally 
of  filaments  from  the  accessory  portion  of  the  spinal  accessory :  it  passes  across 
the  internal  carotid  artery  to  the  upper  border  of  the  Middle  constrictor,  where  it 
divides  into  numerous  filaments  which  join  with  those  from  the  glosso-pharyngeal, 
superior  laryngeal  (its  external  branch),  and  sympathetic,  to  form  the  pharyngeal 
plexus,  from  which  branches  are  distributed  to  the  muscles  and  mucous  membrane 
of  the  pharynx  and  the  muscles  of  the  soft  palate.  From  the  pharyngeal  plexus 
a  minute  filament  is  given  off,  which  descends  and  joins  the  hypoglossal  nerve  as 
it  winds  round  the  occipital  artery. 

The  superior  laryngeal  is  the  nerve  of  sensation  to  the  larynx.  It  is  larger  than 
the  preceding,  and  arises  from  the  middle  of  the  inferior  ganglion  of  the  pneumo- 
gastric. It  consists  principally  of  filaments  from  the  accessory  portion  of  the  spinal 
accessory.  In  its  course  it  receives  a  branch  from  the  superior  cervical  ganglion 
of  the  sympathetic.  It  descends  by  the  side  of  the  pharynx  behind  the  internal 
carotid,  where  it   livicles  into  two  branches,  the  external  and  internal  laryngeal. 

The  external  laryngeal  branch,  the  smaller,  descends  by  the  side  of  the  larynx, 
beneath  the  Sterrw -thyroid,  to  supply  the  Crico-thyroid  muscle.  It  gives  branches 
to  the  pharyngeal  plexus  and  the  Inferior  constrictor,  and  communicates  with  the 
superior  cardiac  nerve,  behind  the  common  carotid. 

The  internal  laryngeal  branch  descends  to  the  opening  in  the  thyro-hyoid 
membrane,  through  -which  it  passes  with  the  superior  laryngeal  artery,  and  is 
distributed  to  the  mucous  membrane  of  the  larynx.  A  small  branch  communicates 
with  the  recurrent  laryngeal  nerve.  The  branches  to  the  mucous  membrane  are 
distributed,  some  in  front  to  the  epiglottis,  the  base  of  the  tongue,  and  the 
epiglottidean  glands  ;  while  others  pass  backward,  in  the  aryteno-epiglottidean 
fold,  to  supply  the  'mucous  membrane  surrounding  the  superior  orifice  of  the 
larynx,  as  well  a  the  membrane  which  lines  the  cavity  of  the  larynx  as  low  down 
as  the  vocal  cord  T"i>e  filament  which  joins  with  the  recurrent  laryngeal  descends 
beneath  the  mucous  membrane  on  the  inner  surface  of  the  thyroid  cartilage,  where 
the  two  nerves  become  united. 

The  inferior  or  recurrent  laryngeal,  so  called  from  its  reflected  course,  is  the 
motor  nerve  of  the  laiynx.  ;  It  arises  on  the  right  side,  in  front  of  the  subclavian 
artery;  winds  fr<  backward  round  that  vessel,  and  ascends  obliquely  to 

the  side  of  the  trac  r-hind  the  common  carotid  and  behind  or  in  front  of  the 


inferior  thyroid  artei 
aorta,  and  winds  f 
remains  of  the   duel 
side  of  the  trache ... 
trachea  and  oesop 
strictor  muscle,  er  1 1 
the  thyroid  cartil  <#• 
larynx  except  th<     0 


ti  the  left  side  it  arises  in  front  of  the  arch  of  the 
te   backward  round  the   aorta  at  the  point  where  the 

•iosus  are  connected  with  it,  and  then  ascends  to  the 
ferves  on  both  sides  ascend  in  the  groove  between  the 
It  passing  under  the  lower  border  of  the  Inferior  con- 
l-ynx  behind  the  articulation  of  the  inferior  cornu  of 
ge  cricoid,  being  distributed  to  all  the  muscles  of  the 
Iroid.      It  communicates  with  the  superior  laryngeal 


752  THE   NERVOUS  SYSTEM. 

nerve  and  gives  off  a  few  filaments  to  the  mucous  membrane  of  the  lower  part  of 
the  larynx. 

The  recurrent  laryngeal,  as  it  winds  round  the  subclavian  artery  and  aorta, 
gives  off  several  cardiac  filaments,  which  unite  with  the  cardiac  branches  from 
the  pneumogastric  and  sympathetic.  As  it  ascends  in  the  neck  it  gives  off  oesoph- 
ageal branches,  more  numerous  on  the  left  than  on  the  right  side,  which  supply 
the  mucous  membrane  and  muscular  coat  of  the  oesophagus  ;  tracheal  branches  to 
the  mucous  membrane  and  muscular  fibres  of  the  trachea  :  and  some  pharyngeal 
filaments  to  the  Inferior  constrictor  of  the  pharynx. 

The  cervical  cardiac  branches,  two  or  three  in  number,  arise  from  the  pneumo- 
gastric, at  the  upper  and  lower  part  of  the  neck. 

The  superior  branches  are  small,  and  communicate  with  the  cardiac  branches 
of  the  sympathetic.     They  can  be  traced  to  the  great  or  deep  cardiac  plexus. 

The  inferior  branches,  one  on  each  side,  arise  at  the  lower  part  of  the  neck, 
just  above  the  first  rib.  On  the  right  side  this  branch  passes  in  front  or  by  the 
side  of  the  arteria  innominata,  and  communicates  with  one  of  the  cardiac  nerves 
proceeding  to  the  great  or  deep  cardiac  plexus.  On  the  left  side  it  passes  in  front 
of  the  arch  of  the  aorta  and  joins  the  superficial  cardiac  plexus. 

The  thoracic  cardiac  branches,  on  the  right  side,  arise  from  the  trunk  of  the 
pneumogastric  as  it  lies  by  the  side  of  the  trachea,  and  from  its  recurrent  laryngeal 
branch,  but  on  the  left  side  from  the  recurrent  nerve  only ;  passing  inward,  they 
terminate  in  the  deep  cardiac  plexus. 

The  anterior  pulmonary  branches,  two  or  three  in  number,  and  of  small 
size,  are  distributed  on  the  anterior  aspect  of  the  root  of  the  lungs.  They  join 
with  filaments  from  the  sympathetic,  and  form  the  anterior  pulmonary  plexus. 

The  posterior  pulmonary  branches,  more  numerous  and  larger  than  the  anterior, 
are  distributed  on  the  posterior  aspect  of  the  root,  of  the  lung :  they  are  joined  by 
filaments  from  the  third  and  fourth  (sometimes  also  first  and  second)  thoracic 
ganglia  of  the  sympathetic,  and  form  the  posterior  pulmonary  plexus.  Branches 
from  both  plexuses  accompany  the  ramification  of  the  air-tubes  through  the  sub- 
stance of  the  lungs. 

The  oesophageal  branches  are  given  off  from  the  pneumogastric  both  above  and 
below  the  pulmonary  branches.  The  lower  are  more  numerous  and  larger 
than  the  upper.  They  form,  together  with  branches  from  the  opposite  nerve,  the 
oesophageal  plexus  or  plexus  gulce.  From  this  plexus  branches  are  distributed  to 
the  back  of  the  pei'icardium. 

The  gastric  branches  are  the  terminal  filaments  of  the  pneumogastric  nerve. 
The  nerve  on  the  right  side  is  distributed  to  the  posterior  surface  of  the  stomach, 
and  joins  the  left  side  of  the  coeliac  plexus  and  the  splenic  plexus.  The  nerve 
on  the  left  side  is  distributed  over  the  anterior  surface  of  the  stomach,  some 
filaments  passing  across  the  great  cul-de-sac,  and  others  along  the  lesser  curvature. 
They  unite  with  branches  of  the  right  nerve  and  with  the  sympathetic,  some  fila- 
ments passing  through  the  lesser  omentum  to  the  hepatic  plexus. 

Surgical  Anatomy. — The  laryngeal  nerves  are  of  considerable  importance  in  considering 
some  of  the  morbid  conditions  of  the  larynx.  When  the  peripheral  terminations  of  the  superior 
laryngeal  nerve  are  irritated  by  some  foreign  body  passing  over  them,  i-eflex  spasm  of  the  glottis 
is  the  result.  When  the  trunk  of  this  same  nerve  is  pressed  upon  by,  for  instance,  a  goitre  or 
an  aneurism  of  the  upper  part  of  the  carotid,  we  have  a  peculiar  dry^  brassy  cough.  When  the 
nerve  is  paralyzed,  we  have  anaesthesia  of  the  mucous  membrane  of  ^he  larynx,  so  that  foreign 
bodies  can  readily  enter  the  cavity,  and,  in  consequence  of  its  supplying  the  crico-thyroid  muscle, 
the  vocal  cords  cannot  be  made  tense,  and  the  voice  is  deep  and  hoarse.  Paralysis  of  the 
superior  laryngeal  nerves  may  be  the  result  of  bulbar  paralysis,  may  be  a  sequel  to  diphtheria, 
when  both  nerves  are  usually  involved,  or  it  may,  though  less  commonly,  be  caused  by  the 
pressure  of  tumors  or  aneurisms,  when  the  paralysis  is  generally  Unilateral.  Irritation  of  the 
inferior  laryngeal  nerves  produces  spasm  of  the  muscles  of  the'  larynx.  When  both  these 
recurrent  nerves  are  paralyzed,  the  vocal  cords  are  motionless,  in  the  so-called  "cadaveric  posi- 
tion " — that  is  to  say,  in  the  position  in  which  they  are  found  in  ordinary  tranquil  respiration — 
neither  closed  as  in  phonation,  nor  open  as  in  deep  inspiratory  efforts.  When  one  recurrent 
nerve  is  paralyzed,  the  cord  of  the  same  side  is  motionless,  w^3e  the  opposite  one  crosses  the 
middle  line  to  accommodate  itself  to  the  affected  one  ;  hence  phonation  is  present,  but  the  voice 


THE   ELEVENTH   OR    SPINAL    ACCESSORY  NERVE.  753 

is  altered  and  weak  in  timbre.  The  recurrent  laryngeal  nerves  may  be  paralyzed  in  bulbar 
paralysis  or  after  diphtheria,  when  it,  usually  affects  both  sides  ;  or  they  may  be  affected  by  the 
pressure  of  aneurisms  of  the  aorta,  innominate  or  subclavian  arteries ;  by  mediastinal  tumors ; 
by  bronchocele ;  or  by  cancer  of  the  upper  part  of  the  oesophagus,  when  the  paralysis  is  often 


unilateral. 


The  Eleventh  Pair  (Figs.  403,  404). 


The  Eleventh  or  Spinal  Accessory  Nerve  consists  of  two  parts  :  one,  the  acces- 
sory part  to  the  vagus,  and  the  other  the  spinal  portion. 

The  bulbar  or  accessory  part  is  the  smaller  of  the  two.  Its  superficial  origin 
is  by  four  or  five  delicate  filaments  from  the  side  of  the  medulla,  below  the  roots 
of  the  vagus.  Its  deep  origin  may  be  traced  to  a  nucleus  of  gray  matter  at  the 
back  of  the  medulla,  dorso-lateral  to  the  hypoglossal  nucleus,  and  extending  as  far 
down  as  the  intermedio-lateral  tract  of  the  spinal  cord.  It  passes  outward  to  the 
jugular  foramen,  where  it  interchanges  fibres  with  the  spinal  portion  or  becomes 
united  to  it  for  a  short  distance  ;  it  is  also  connected,  in  the  foramen,  with  the 
upper  ganglion  of  the  vagus  by  one  or  two  filaments.  It  then  passes  through  the 
foramen,  and  becoming  again  separated  from  the  spinal  portion  it  is  continued 
over  the  surface  of  the  ganglion  of  the  trunk  of  the  vagus,  being  adherent  to  its 
surface,  and  is  distributed  principally  to  the  pharyngeal  and  superior  laryngeal 
branches  of  the  pneumogastric.  Through  the  pharyngeal  branch  it  probably  sup- 
plies the  muscles  of  the  soft  palate  (see  page  331).  Some  few  filaments  from 
it  are  continued  into  the  trunk  of  the  vagus  below  the  ganglion,  to  be  dis- 
tributed with  the  recurrent  laryngeal  nerve,  and  probably  also  with  the  cardiac 
nerves. 

The  spinal  portion  is  firm  in  texture.  Its  superficial  origin  is  by  several  fila- 
ments from  the  lateral  tract  of  the  cord,  as  low  down  as  the  sixth  cervical  nerve. 
Its  deep  origin  may  be  traced  to  the  intermedio-lateral  tract  of  the  gray  matter  of 
the  cord.  This  portion  of  the  nerve  ascends  between  the  ligamentum  denticulatum 
and  the  posterior  roots  of  the  spinal  nerves,  enters  the  skull  through  the  foramen 
magnum,  and  is  then  directed  outward  to  the  jugular  foramen,  through  which  it 
passes,  lying  in  the  same  sheath  as  the  pneumogastric,  but  separated  from  it  by  a 
fold  of  the  arachnoid.  In  the  jugular  foramen  it  receives  one  or  two  filaments 
from  the  accessory  portion.  At  its  exit  from  the  jugular  foramen  it  passes  back- 
ward, either  in  front  of  or  behind  the  internal  jugular  vein,  and  descends  obliquely 
behind  the  Digastric  and  Stylo-hyoid  muscles  to  the  upper  part  of  the  Sterno- 
mastoid.  It  pierces  that  muscle,  and  passes  obliquely  across  the  posterior  triangle, 
to  terminate  in  the  deep  surface  of  the  Trapezius.  This  nerve  gives  several 
branches  to  the  Sterno-mastoid  during  its  passage  through  it,  and  joins  in  its  sub- 
stance with  branches  from  the  second  cervical,  which  supply  the  muscle.  In  the 
posterior 'triangle  it'joins  with  the  second  and  third  cervical  nerves,  while  beneath 
the  Trapezius  it  forms  a  sort  of  plexus  with  the  third  and  fourth  cervical  nerves, 
and  from  this  plexus  fibres  are  distributed  to  the  muscle. 

Surgical  Anatomy. — In  cases  of  spasmodic  torticollis  in  which  all  palliative  treatment  has 
failed,  division  or  excision  of  a  portion  of  the  spinal  accessory  nerve  has  been  resorted  to.  This 
may  be  done  either  along  the  anterior  or  posterior  border  of  the  Sterno-mastoid  muscle.  The 
former  operation  is  performed  by  making  an  incision  from  the  apex  of  the  mastoid  process, 
three  inches  in  length,  along  the  anterior  border  of  the  Sterno-mastoid  muscle.  The  anterior 
border  of  the  muscle  is  defined  and  pulled  backward,  so  as  to  stretch  the  nerve,  which  is  then  to 
be  sought  for  beneath  the  Digastric  muscle,  about  two  inches  below  the  apex  of  the  mastoid 
process.     T  i  operation  consists  in  making  an  incision  along  the  posterior  border  of  the 

muscle,  so  that  the  <  e  of  the  incision  corresponds  to  the  middle  of  this  border  of  the  mus- 
cle. The  superficid  structures  having  been  divided  and  the  border  of  the  muscle  defined,  the 
nerve  is  to  be  so  ■ .  as  it  emerges  from  the  muscle  to  cross  the  occipital  triangle.     When 

found,  it  is  to  b  \  upward  through  the  muscle,  and  a  portion  of  it  excised^  above  the  point 

where  it  givt  <  i  •  riches  to  the  Sterno-mastoid.     In  this  operation  one  of  the  descending 

branches  of  the  d  cervical  plexus  is  liable  to  be  mistaken  for  the  nerve. 

43 


754 


THE   NERVOUS 


The  Twelfth  Pair  (Fig-: 


06). 


The  Twelfth  or  Hypoglossal  Nerve  is  the  in  ;  of  the  tongue. 

Its  superficial  origin  is  by  several  filaments,  fro  ten  to  fifteen  in  number, 
from  the  groove  between  the  pyramidal  ai/  xlies  of  the  medulla,  in  a 

continuous  line  with  the  anterior  roots  of  th  rves.     Its  deep  origin  can 

be  traced  to   a  nucleus  of  gray  matter  (trigone  /lossi)   on  the  floor   of  the 

fourth  ventricle. 

The  filaments  of  this  nerve  are  collected  into  U  bundles,  which  perforate  the 
dura  mater  separately,  opposite  the  anterior  Jcondyl oid  foramen,  and  unite  together 
after  their  passage  through  it.  In  those  oases  in  which  the  anterior  condyloid 
foramen  in  the  occipital  bone  is  double,  these  two  portions  of  the  nerve  are  sepa- 
rated by  the  small  piece  of  bone  which  diviles  the  foramen.  The  nerve  descends 
almost  vertically  to  a  point  corresponding  with  the  angle  of  the  jaw.  It  is  at  first 
deeply  seated  beneath  the  internal  carotid  artery  and  internal  jugular  vein,  and 
intimately    connected   with    the    pneumogastric   nerve;    it   then    passes   forward 


To  Dura-mater 


•  To  Ganglion  on  Trunk  of  Vagus 


To  Anterior  Belly  of  Omo-hyoid 


To  Sterno-hyoid 


To  Sterno-thyroid 
{To  Posterior  Belly  of  Omo-hyoid 

Fig.  405.— Plan  of  the  hypoglossal  nerve. 

between  the  vein  and  artery,  and  lower  down  in  the  neck  becomes  superficial  below 
the  Digastric  muscle.  The  nerve  then  loops  round  the  occipital  artery,  and  crosses 
the  external  carotid  and  its  lingual  branch  below  the  tendon  of  tha  Digastric  mus- 
cle. It  passes  beneath  the  tendon  of  the  Digastric,  the  Stylo-hyoi  j,  and  the  Mylo- 
hyoid muscles,  lying  between  the  last-named  muscle  and  the  Hyo-glossus,  and  com- 
municates at  the  anterior  border  of  the  Hyo-glossus  with  the  lingual  (gustatory) 
nerve ;  it  is  then  continued  forward  in  the  fibres  of  the  Genio-hyo-glossus  muscle 
as  far  as  the  tip  of  the  tongue,  distributing  branches  to  its  muscular  substance. 


THE    TWELFTH   OR    HYPOGLOSSAL    NERVE. 


(ob 


The  branches  of  communication  are — with  the 


Pneumogastric. 
Sympathetic. 


First  and  Second  Cervical  Nerves. 
Lingual  (gustatory). 


The  first  mentioned  takes  place  close  to  the  exit  of  the  nerve  from  the  skull, 
numerous  filaments  passing  between  the  hypoglossal  and  lower  ganglion  of  the 
pneumogastric  through  the  mass  of  connective  tissue  which  here  unites  the  two 
nerves.  It  also  communicates  with  the  pharyngeal  plexus  by  a  minute  filament 
as  it  winds  round  the  occipital  artery. 

The  communication  with  the  sympathetic  takes  place  opposite  the  atlas  by 
branches  derived  from  the  superior  cervical  ganglion,  and  in  the  same  situation 
the  nerve  is  joined  by  filaments  derived  from  the  loop  connecting  the  first  two 
cervical  nerves. 

The  communication  with  the  lingual  (gustatory)  takes  place  near  "the  anterior 
border  of  the  Hyo-glossus  muscle  by  numerous  filaments  which  ascend  upon  it. 

The  branches  of  distribution  are — the 


Meningeal. 
Descendens  hypoglossi. 


Thyro-hyoid. 
Muscular. 


Meningeal  Branches. — As  the  hypoglossal  nerve  passes  through  the  anterior 


Fig.  406.— H]  e.  cervical  plexus,  and  their  branches. 

condyloid  foramen  it  giv  -    rding  to  Luschka,  several  filaments  to  the  dura 

mater  in  the  posterior  f!  5  base  of  the  skull ;   these  filaments  are  probably 


756  THE   NERVOUS  SYSTEM. 

derived  from  a  branch  which  passes  from  the  first  cervical  nerve  to  the  hypoglossal 
nerve. 

The  descendens  hypoglossi  is  a  long  slender  branch,  which  quits  the  hypoglossal 
where  it  turns  round  the  occipital  artery.  It  consists  mainly  of  fibres  which  pass 
to  the  hypoglossal  from  the  first  and  second  cervical  nerves  in  the  above-mentioned 
communication.  It  descends  in  front  of  or  within  the  sheath  of  the  carotid  vessels, 
o-ivino-  off  a  branch  to  the  anterior  belly  of  the  Omo-hyoid,  and  then  joins  the 
communicating  branches  from  the  second  and  third  cervical  nerves,  just  below  the 
middle  of  the  neck,  to  form  a  loop,  the  ansa  hypoglossi.  From  the  convexity  of 
this  loop  branches  pass  to  supply  the  Sterno-hyoid,  Sterno-thyroid,  and  the  pos- 
terior belly  of  the  Omo-hyoid.  According  to  Arnold,  another  filament  descends 
in  front  of  the  vessels  into  the  chest,  and  joins  the  cardiac  and  phrenic  nerves. 

The  thyro-hyoid  is  a  small  branch  arising  from  the  hypoglossal  near  the  poste- 
rior border  of  the  Hyo-glossus  ;  it  passes  obliquely  across  the  great  cornu  of  the 
hyoid  bone  and  supplies  the  Thyro-hyoid  muscle. 

The  muscular  branches  are  distributed  to  the  Stylo-glossus,  Hyoglossus,  Genio- 
hyoid, and  Grenio-hyo-glossus  muscles.  At  the  under  surface  of  the  tongue  numer- 
ous slender  branches  pass  upward  into  the  substance  of  the  organ  to  supply  its 
intrinsic  muscles. 

Surgical  Anatomy. — The  hypoglossal  nerve  is  an  important  guide  in  the  operation  of 
ligation  of  the  lingual  artery  (see  page  489).  It  runs  forward  on  the  Hyo-glossus  just  above 
the  great  cornu  of  the  hyoid  hone,  and  forms  the  upper  boundary  of  the  triangular  space  in 
which  the  artery  is  to  be  sought  for  by  cutting  through  the  fibres  of  the  Hyo-glossus. 

THE  SPINAL  NERVES. 

The  spinal  nerves  are  so  called  because  they  take  their  origin  from  the  spinal 
cord,  and  are  transmitted  through  the  intervertebral  foramina  on  either  side  of  the 
spinal  column.  There  are  thirty-one  pairs  of  spinal  nerves,  which  are  arranged 
into  the  following  groups,  corresponding  to  the  region  of  the  spine  through  which 
they  pass : 

Cervical 8  pairs. 

Dorsal 12      " 

Lumbar  . 5     " 

Sacral 5      " 

Coccygeal 1  pair. 

It  will  be  observed  that  each  group  of  nerves  corresponds  in  number  with  the 
vertebrae  in  that  region,  except  the  cervical  and  coccygeal. 

Each  spinal  nerve  arises  by  two  roots,  an  anterior  or  motor  root  and  a  pos- 
terior or  sensory  root,  the  latter  being  distinguished  by  a  ganglion,  termed  the 
spinal  ganglion.  , 

The  Roots  of  the  Spinal  Nerves. 

The  Anterior  Roots. — The  superficial  origin  is  from  the  antero-lateral  columns 
of  the  cord,  corresponding  to  the  situation  of  the  anterior  cornu  of  gray  matter. 
Each  root  is  composed  of  from  four  to  eight  filaments. 

The  deep  origin  can  be  traced  through  the  antero-lateral  column ;  the  roots, 
after  penetrating  horizontally  through  the  longitudinal  fibres  of  this  tract,  enter 
the  gray  substance,  where  their  fibrils  diverge  in  several  directions :  some  passing 
inward,  are  continued  across  the  anterior  commissure  in  front  of  the  central  canal, 
to  become  continuous  with  the  axis-cylinder  processes  of  the  large  cells  of  the 
anterior  cornu  of  the  opposite  side;  others  terminate  in  the  mesial  group  of  cells 
of  the  anterior  column  of  the  same  side  ;  other  fibrils  pass  outward,  to  become  con- 
tinuous with  the  axis-cylinder  processes  op  the  group  of  cells  in  the  lateral  part  of 
the  anterior  column. 

The  Posterior  Roots. — The  superficial  origin  is  from  the  posterolateral  fissure 
of  the  cord.     The  real  origin  of  these  fibres  is  from  the  nerve-cells  in  the  posterior 


THE   SPINAL    NERVE. 


757 


root  ganglion,  from  which  they  can  be  traced  into  the  cord  in  two  main  bundles, 
the  course  of  which  has  already  been  studied  (page  697). 

The  anterior  roots  are  smaller  than  the  posterior,  devoid  of  ganglionic  enlarge- 
ment, and  their  component  fibrils  are  collected  into  two  bundles  near  the  inter- 
vertebral foramina. 

The  posterior  roots  of  the  nerves  are  larger,  but  the  individual  filaments  are 
finer  and  more  delicate  than  those  of  the  anterior.  As  their  component  fibrils  pass 
outward  toward  the  aperture  in  the  dura  mater,  they  coalesce  into  two  bundles, 
receive  a  tubular  sheath  from  that  membrane,  and  enter  the  ganglion  which  is 
developed  upon  each  root. 

The  posterior  root  of  the  first  cervical  nerve  forms  an  exception  to  these 
characters.  It  is  smaller  than  the  anterior,  has  occasionally  no  ganglion 
developed  upon  it,  and  when  the  ganglion  exists,  it  is  often  situated  within  the 
dura  mater. 

The  Ganglia  of  the  Spinal  Nerves. 

A  ganglion  is  developed  upon  the  posterior  root  of  each  of  the  spinal  nerves. 
These  ganglia  are  of  an  oval  form  and  of  a  reddish  color  :  they  bear  a  proportion 
in  size  to  the  nerves  upon  which  they  are  formed,  and  are  placed  in  the  inter- 
vertebral foramina,  external  to  the  point  where  the  nerves  perforate  the  dura 


Neuraxis  of  Peripheral 
Sensory  Neurone 


Nerve  Trunk  ■ 


Spinal  Ganglion 


Dendrite  of 

Peripheral  Sensory 

Neurone 


Neuraxis  of 
Sympathetic  Nnn 


Anterior  Horn  of  Gray  Matter 
of  Spinal  Cord 

"Neuraxis  of  Peripheral  Motor  Neurone 
f Sympathetic  Ganglion 


Fig.  407.— Diagram  to  show  the  composition  of  a  peripheral  nerve-trunk.    (Bohm  and  Davidoff.) 

mater.  Each  ganglion  is  bifid  internally,  where  it  is  joined  by  the  two  bundles 
of  the  posterior  root,  the  two  portions  being  united  into  a  single  mass  externally. 
The  ganglion  upon  the  first  and  second  cervical  nerves  forms  an  exception  to  these 
characters,  being  placed  on  the  arches  of  the  vertebrae  over  which  the  nerves  pass. 
The  ganglia  of  the  sacral  nerves  are  placed  within  the  spinal  canal ;  and  that  on 
the  coccygeal  nerve,  also  in  the  canal,  is  situated  at  some  distance  from  the  origin 
of  the  posterior  root. 

Distribution  of  the  Spinal  Nerves. 

Immediately  beyond  the  ganglion  the  two  roots  coalesce,  their  fibres  inter- 
mingle, and  the  trunk  thus  formed  constitutes  the  spinal  nerve  ;  it  passes  out  of 
the  intervertebral  foramen,  and  divides  into  a  posterior  division  for  the  supply  of 
the  posterior  part  of  the  body,  and  an  anterior  division  for  the  supply  of  the 
anterior  part  of  the  body,  each  containing  fibres  from  both  roots. 

Before  dividing,  each  spinal  nerve  gives  off  a  small  recurrent  or  meningeal 
branch,  which  is  joined  by  a  filament  from  the  communicating  branch  of  the 
sympathetic,  which  connects  the  ganglion  with  the  anterior  division.  It  passes 
inward  through  the  intervertebral  foramen  and  supplies  the  dura  mater,  sending 
branches  to  the  bones  and  ligaments. 


758 


THE   NERVOUS  SYSTEM. 


The  posterior  divisions  of  the  spinal  nerves  are  generally  smaller  than  the 
anterior  ;  they  arise  from  the  trunk  resulting  from  the  union  of  the  roots,  in  the 
intervertebral  foramina  ;  and,  passing  backward,  divide  into  internal  and  external 
branches,  which  are  distributed  to  the  muscles  and  integument  behind  the  spine. 
The  first  cervical,  the  fourth  and  fifth  sacral,  and  the  coccygeal,  do  not  divide 
into  external  and  internal  branches. 

The  anterior  divisions  of  the  spinal  nerves  supply  the  parts  of  the  body  in 
front  of  the  spine,  including  the  limbs.  They  are  for  the  most  part  larger  than 
the  posterior  divisions.  Each  division  is  connected  by  a  slender  filament  with  the 
sympathetic.  In  the  dorsal  region  the  anterior  divisions  of  the  spinal  nerves  are 
quite  separate  from  each  other,  and  are  uniform  in  their  distribution  ;  but  in  the 
cervical,  lumbar,  and  sacral  regions  they  form  intricate  plexuses  previous  to  their 
distribution. 


Points  of  Emergence  of  the  Spinal  Nerves. 

The  roots  of  the  spinal  nerves  from  their  origin  in  the  cord  run  obliquely 
downward  to  their  point  of  exit  from  the  intervertebral  foramina,  the  amount  of 
obliquity  varying  in  different  regions  of  the  spine,  and  being  greater  in  the  lower 
than  the  upper  part.    The  level  of  their  emergence  from  the  cord  is  within  certain 


Level  of 

Level  of  tip 

Level  of 

Level  of  tip 

Body  of 

No.  of  Nerve. 

of  Spine  of 

Body  of 

No.  of  Nerve. 

of  Spine  of 

C.  1 

C.  1 

D.  8 

9 

7  d. 

2{ 

2 

_ . 

9 

10 

8d. 

3 

1  c. 

10 

11 

9d. 

3 

4 

2  c. 

— 

12 

10  d. 

4 

5 

3  c. 

11 

L.  1 

11  d. 

5 

6 

4  c. 

f 

2 

— 

6 

7 
8 

5  c. 

6  c. 

12i 

3 

4 

}  12  d. 

7 
D.  1 

D.  1 

2 

7  c. 
Id. 

f 

5 

S.  1 

}- 

2 

3 

— 

L.l-j 

2 

3 

4 

2d. 

1 

3 

4 

5 

3d. 

I 

4 

1L. 

5 

6 

4d. 

5 

6 

7 

5d. 

— 

C.  1 

7 

8 

6d. 

L.  2 

— 

— 

limits  variable,  and  of  course  does  not  correspond  to  the  point  of  emergence  of 
the  nerve  from  the  intervertebral  foramina.  The  preceding  table,  from  Mac- 
alister,  shows  as  accurately  as  can  be  shown  the  relation  of  these  points  of  origin 
from  the  spinal  cord  to  the  bodies  and  spinous  processes  of  the  vertebrae. 

THE  CERVICAL  NERVES. 

The  roots  of  the  cervical  nerves  increase  in  size  from  the  first  to  the  fifth,  and 
then  remain  the  same  size  to  the  eighth.  The  posterior  roots  bear  a  proportion 
to  the  anterior  as  3  to  1,  which  is  much  greater  than  in  any  other  region,  the 
individual  filaments  beins;  also  much  larger  than  those  of  the  anterior  roots.  The 
posterior  root  of  the  first  cervical  is  an  exception  to  this  rule :  it  is  smaller  than 
the  anterior  root.  In  direction  the  roots  of  the  cervical  are  less  oblique  than 
those  of  the  other  spinal  nerves.  The  first  cervical  nerve  is  directed  a  little  up- 
ward  and  outward ;  the  second  is  horizontal;  the  others  are  directed  obliquely 
downward  and  outward ,  the  lowest  being  the  most  oblique,  and  consequently 
longer  than  the  upper,  the  distance  betAveen  their  place  of  origin  and  their  point 
of  exit  from  the  spinal  canal  never  exceeding  the  depth  of  one  vertebra. 

The  trunk  of  the  first  cervical  nerve  (suboccijntal)  leaves  the  spinal  canal  betAveen 
the  occipital  bone  and  the  posterior  arch  of  the  atlas ;  the  second,  between  the 


THE    CERVICAL    NERVES. 


759 


posterior  arch  of  the  atlas  and  the  lamina  of  the  axis ;  and  the  eighth  (the  last), 
between  the  last  cervical  and  first  dorsal  vertebrae. 

Each  nerve,  at  its  exit  from  the  intervertebral  foramen,  divides  into  a  posterior 
and  an  anterior  division.  The  anterior  divisions  of  the  four  upper  cervical  nerves 
form  the  cervical  plexus.  The  anterior  divisions  of  the  four  lower  cervical  nerves, 
together  with  the  first  dorsal,  form  the  brachial  plexus. 


A0  SCe^. 


S&in.  aver* 


v&» 


$*> 


•F 


Fig.  408.— Posterior  divisions  of  the  upper  cervical  nerves. 


Posterior  Divisions  of  the  Cervical  Nerves  (Fig.  408). 

The  posterior  division  of  the  first  cervical  {suboccipital)  nerve  differs  from  the 
posterior  divisions  of  the  other  cervical  nerves  in  not  dividing  into  an  internal 
and  external  branch.  It  is  larger  than  the  anterior  division,  and  escapes  from  the 
spinal  canal  between  the  occipital  bone  and  the  posterior  arch  of  the  atlas,  lying 
beneath  the  vertebral  artery.  It  enters  the  suboccipital  triangle  formed  by  the 
Rectus  capitis  posticus  major,  the  Obliquus  superior,  and  Obliquus  inferior,  and 
supplies  the  Recti  and  Obliqui  muscles,  and  the  Complexus.  From  the  branch 
which  supplies  the  Inferior  oblique  a  filament  is  given  off  which  joins  the  second 
cervical  nerve.     This  nerve  also  occasionally  gives  off  a  cutaneous  filament,  which 


760  THE  NERVOUS  SYSTEM. 

accompanies  the  occipital  artery  and  communicates  with  the  occipitalis  major  and 
minor  nerves. 

The  posterior  division  of  the  second  cervical  nerve  is  three  or  four  times  greater 
than  the  anterior  division,  and  the  largest  of  all  the  posterior  cervical  divisions. 
It  emerges  from  the  spinal  canal  between  the  posterior  arch  of  the  atlas  and 
lamina  of  the  axis,  below  the  Inferior  oblique.  It  supplies  a  twig  to  this  muscle, 
and  receives  a  communicating  filament  from  the  first  cervical.  It  then  divides 
into  an  internal  and  an  external  branch. 

The  internal  branch,  called,  from  its  size  and  distribution,  the  occipitalis  major, 
ascends  obliquely  inward  between  the  Obliquus  inferior  and  Complexus,  and 
pierces  the  latter  muscle  and  the  Trapezius  near  their  attachments  to  the 
cranium.  It  is  now  joined  by  a  filament  from  the  posterior  division  of  the  third  cer- 
vical nerve,  and,  ascending  on  the  back  part  of  the  head  with  the  occipital  artery, 
divides  into  two  branches,  which  supply  the  integument  of  the  scalp  as  far  forward 
as  the  vertex,  communicating  with  the  occipitalis  minor.  It  gives  off  an  auricular 
branch  to  the  back  part  of  the  ear  and  muscular  branches  to  the  Complexus. 
The  external  branch  is  often  joined  by  the  external  branch  of  the  posterior 
division  of  the  third,  and  supplies  the  Splenius,  Trachelo-mastoid,  and  Complexus. 

The  posterior  division  of  the  third  cervical  is  smaller  than  the  preceding,  but 
larger  than  the  fourth  ;  it  differs  from  the  posterior  divisions  of  the  remaining 
cervical  nerves  in  its  supplying  an  additional  filament,  the  third  occipital  nerve, 
to  the  integument  of  the  occiput.  The  posterior  division  of  the  third  nerve,  like 
the  others,  divides  into  an  internal  and  external  branch.  The  internal  branch 
passes  between  the  Complexus  and  Semispinalis,  and,  piercing  the  Splenius  and 
Trapezius,  supplies  the  skin  over  the  latter  muscle  ;  the  external  branch  joins  with 
that  of  the  posterior  division  of  the  second  to  supply  the  Splenius,  Trachelo-mas- 
toid, and  Complexus. 

The  third  occipital  nerve  arises  from  the  internal  or  cutaneous  branch  beneath 
the  Trapezius ;  it  then  pierces  that  muscle,  and  supplies  the  skin  on  the  lower  and 
back  part  of  the  head.  It  lies  to  the  inner  side  of  the  occipitalis  major,  with 
which  it  is  connected. 

The  posterior  division  of  the  suboccipital  nerve  and  the  internal  branches  of 
the  posterior  divisions  of  the  second  and  third  cervical  nerves  are  occasionally 
joined  beneath  the  Complexus  by  communicating  branches.  This  communication 
is  described  by  Cruveilhier  as  the  posterior  cervical  plexus. 

The  posterior  divisions  of  the  fourth,  fifth,  sixth,  seventh,  and  eighth  cervical 
nerves  (Fig.  415)  pass  backward,  and  divide,  behind  the  Intertransversales 
muscles,  into  internal  and  external  branches.  The  internal  branches,  the  larger, 
are  distributed  differently  in  the  upper  and  lower  part  of  the  neck.  Those 
derived  from  the  fourth  and  fifth  nerves  pass  between  the  Complexus  and  Semi- 
spinalis muscles,  and,  having  reached  the  spinous  processes,  perforate  the 
aponeurosis  of  the  Splenius  and  Trapezius,  and  are  continued  outwrard  to  the 
integument  over  the  Trapezius,  whilst  those  derived  from  the  three  lowest'cervical 
nerves  are  the  smallest,  and  are  placed  beneath  the  Semispinalis  colli,  which  they 
supply,  and  then  pass  into  the  Interspinals,  Multifidus  spinse,  and  Complexus, 
and  send  twigs  through  this  latter  muscle  to  supply  the  integument  near  the 
spinous  processes  (Hirschfeld).  The  external  branches  supply  the  muscles  at  the 
side  of  the  neck — viz.  the  Cervicalis  ascendens,  Transversalis  colli,  and  Trachelo- 
mastoid. 

Anterior  Divisions  of  the  Cervical  Nerves. 

The  anterior  division  of  the  first  or  suboccipital  nerve  is  of  small  size.  It 
escapes  from  the  spinal  canal  through  a  groove  upon  the  posterior  arch  of  the 
atlas.  In  this  groove  it  lies  beneath  the  vertebral  artery,  to  the  inner  side  of 
the  Rectus  capitis  lateralis.     As  it  crosses  the  foramen  in  the  transverse  process 


THE    CERVICAL    NERVES.  761 

of  the  atlas  it  receives  a  filament  from  the  sympathetic.  It  then  descends  in  front 
of  this  process,  to  communicate  with  an  ascending  branch  from  the  second  cervi- 
cal nerve. 

Communicating  filaments  from  the  loop  between  this  nerve  and  the  second 
join  the  pneumogastric,  the  hypoglossal,  and  sympathetic  and  some  branches  are 
distributed  to  the  Rectus  lateralis  and  the  two  Anterior  recti.  The  fibres  which 
communicate  with  the  hypoglossal  simply  pass  through  the  latter  nerve  to  become 
for  the  most  part  the  descendens  hypoglossi.  According  to  Valentin,  the  anterior 
division  of  the  suboccipital  distributes  filaments  to  the  occipito-atlantal  articula- 
tion and  mastoid  process  of  the  temporal  bone. 

The  anterior  division  of  the  second  cervical  nerve  escapes  from  the  spinal  canal, 
between  the  posterior  arch  of  the  atlas  and  the  lamina  of  the  axis,  and,  passing 
forward  on  the  outer  side  of  the  vertebral  artery,  divides  in  front  of  the  Inter- 
transverse muscle  into  an  ascending  branch,  which  joins  the  first  cervical ;  and 
one  or  two  descending  branches,  which  join  the  third.  It  gives  off  the  small 
occipital ;  a  branch  to  assist  in  forming  the  great  auricular ;  another  to  assist  in 
forming  the  superficial  cervical ;  one  of  the  communicantes  hypoglossi,  and  a 
filament  to  the  Sterno-mastoid,  which  communicates  in  the  substance  of  the 
muscle  with  the  spinal  accessory. 

The  anterior  division  of  the  third  cervical  nerve  is  double  the  size  of  the  pre- 
ceding. At  its  exit  from  the  intervertebral  foramen  it  passes  downward  and  out- 
ward beneath  the  Sterno-mastoid,  and  divides  into  two  branches.  The  ascending 
branch  joins  the  anterior  division  of  the  second  cervical ;  the  descending  branch 
passes  down  in  front  of  the  Scalenus  anticus  and  communicates  with  the  fourth. 
It  gives  off  the  larger  part  of  the  great  auricular  and  superficial  cervical  nerves  ; 
one  of  the  communicantes  hypoglossi ;  a  branch  to  the  supraclavicular  nerves  ;  a 
filament  to  assist  in  forming  the  phrenic  ;  and  muscular  branches  to  the  Levator 
anguli  scapulse  and  Trapezius ;  this  latter  nerve  communicates  beneath  the 
muscle  with  the  spinal  accessory.  Sometimes  the  nerve  to  the  Scalenus  medius 
is  derived  from  this  source. 

The  anterior  division  of  the  fourth  cervical  is  of  the  same  size  as  the  preceding. 
It  receives  a  branch  from  the  third,  sends  a  communicating  branch  to  the  fifth 
cervical,  and,  passing  downward  and  outward,  divides  into  numerous  filaments, 
which  cross  the  posterior  triangle  of  the  neck,  forming  the  supraclavicular  nerves. 
It  gives  a  branch  to  the  phrenic  nerve,  wrhile  it  is  contained  in  the  intertransverse 
space,  and  sometimes  a  branch  to  the  Scalenus  medius  muscle.  It  also  gives  a 
branch  to  the  Levator  anguli  scapulae  and  to  the  Trapezius,  which  unites  with  the 
branch  given  off  from  the  third  nerve,  and  communicates  beneath  the  muscle  with 
the  spinal  accessory. 

The  anterior  divisions  of  the  fifth,  sixth,  seventh,  and  eighth  cervical  nerves  are 
remarkable  for  their  size.  They  are  much  larger  than  the  preceding  nerves,  and 
are  all  of  equal  dimensions.      They  assist  in  the  formation  of  the  brachial  plexus. 

The  Cervical   Plexus. 

The  cervical  plexus  (Fig.  409)  is  formed  by  the  anterior  divisions  of  the  four 
upper  cervical  nerves.  It  is  situated  opposite  the  four  upper  cervical  vertebne. 
resting  upon  the  Levator  anguli  scapulae  and  Scalenus  medius  muscles,  and 
covered  in  by  the  Sterno-mastoid. 

Its  branches  may  be  divided  into  two  groups,  superficial  and  deep,  which  may 
be  thus  arranged : 


Superficial    < 


(  Occipitalis  minor. 
Ascending    .  <  Auricularis  magnus. 
(  Superficialis  colli. 


f  Suprasternal. 
(^Descending  .       Supraclavicular    <  Supraclavicular. 

(  Supra-acromial. 


762  THE   NERVOUS  SYSTEM. 


(  Communicating. 
)  Muscular. 

J  Communicantes  hypoglossi. 
Deep  .   .  -.    -I  (^Phrenic. 


r 


Internal 


tt.  L        ,  f  Communicating. 

External  .    .  <  «         ,  & 

[  Muscular. 


Superficial  Branches  of  the  Cervical  Plexus. 

The  Occipitalis  minor  (Fig.  415)  arises  from  the  second  cervical  nerve,  some- 
times also  from  the  third ;  it  curves  round  the  posterior  border  of  the  Sterno- 
mastoid,  and  ascends,  running  parallel  to  the  posterior  border  of  the  muscle,  to 
the  back  part  of  the  side  of  the  head.  Near  the  cranium  it  perforates  the  deep 
fascia,  and  is  continued  upward  along  the  side  of  the  head  behind  the  ear,  supply- 
ing the  integument,  and  communicating  with  the  occipitalis  major,  the  auricularis 
magnus,  and  with  the  posterior  auricular  branch  of  the  facial. 

This  nerve  gives  oif  an  auricular  branch,  which  supplies  the  integument  of 
the  upper  and  back  part  of  the  auricle,  communicating  with  the  mastoid  branch 
of  the  auricularis  magnus.  This  branch  is  occasionally  derived  from  the  great 
occipital  nerve.      The  occipitalis  minor  varies  in  size ;  it  is  occasionally  double. 

The  Auricularis  Magnus  is  the  largest  of  the  ascending  branches.  It  arises 
from  the  second  and  third  cervical  nerves,  winds  round  the  posterior  border  of 
the  Sterno-mastoid,  and,  after  perforating  the  deep  fascia,  ascends  upon  that 
muscle  beneath  the  Platysma  to  the  parotid  gland,  where  it  divides  into  facial, 
auricular,  and  mastoid  branches. 

The  facial  branches  pass  across  the  parotid,  and  are  distributed  to  the  integ- 
ument of  the  face  over  the  parotid  gland ;  others  penetrate  the  substance  of  the 
gland  and  communicate  with  the  facial  nerve. 

The  auricular  branches  ascend  to  supply  the  integument  of  the  back  of 
the  pinna,  except  at  its  upper  part,  communicating  with  the  auricular  branches 
of  the  facial  and  pneumogastric  nerves.  A  filament  pierces  the  pinna  to  reach 
its  outer  surface,  where  it  is  distributed  to  the  lobule  and  lower  part  of  the 
concha. 

The  mastoid  branch  communicates  with  the  occipitalis  minor  and  the  posterior 
auricular  branch  of  the  facial,  and  is  distributed  to  the  integument  behind  the  ear. 

The  Superflcialis  Colli  arises  from  the  second  and  third  cervical  nerves,  turns 
round  the  posterior  border  of  the  Sterno-mastoid  about  its  middle,  and,  passing 
obliquely  forward  beneath  the  external  jugular  vein  to  the  anterior  border  of  the 
muscle,  perforates  the  deep  cervical  fascia,  and  divides  beneath  the  Platysma  into 
two  branches  which  are  distributed  to  the  antero-lateral  parts  of  the  neck. 

The  ascending  branch  gives  a  filament  which  accompanies  the  external  jugular 
vein ;  it  then  passes  upward  to  the  submaxillary  region,  and  divides  into  branches, 
some  of  which  form  a  plexus  with  the  cervical  branches  of  the  facial  nerve  beneath 
the  Platysma ;  others  pierce  that  muscle  and  are  distributed  to  the  integument  of 
the  upper  half  of  the  neck,  at  its  fore  part,  as  high  as  the  chin. 

The  descending  branch  (occasionally  represented  by  two  or  more  filaments) 
pierces  the  Platysma,  and  is  distributed  to  the  integument  of  the  side  and  front 
of  the  neck,  as  low  as  the  sternum. 

The  Descending  or  supraclavicular  branches  arise  from  the  third  and  fourth 
cervical  nerves :  emerging  beneath  the  posterior  border  of  the  Sterno-mastoid, 
they  descend  in  the  posterior  triangle  of  the  neck  beneath  the  Platysma  and  deep 
cervical  fascia.  Near  the  clavicle  they  perforate  the  fascia  and  Platysma  to  become 
cutaneous,  and  are  arranged,  according  to  their  position,  into  three  groups. 

The  inner  or  suprasternal  branches  cross  obliquely  over  the  external  jugular 
vein  and  the  clavicular  and  sternal  attachments  of  the  Sterno-mastoid,  and  supply 
the  integument  as  far  as  the  median  line.  They  furnish  one  or  two  filaments  to 
the  sterno-clavicular  joint. 


DEEP   BRANCHES    OF    THE    CERVICAL    PLEXUS. 


763 


The  middle  or  supraclavicular  v  branches  cross  the  clavicle,  and  supply  the 
integument  over  the  Pectoral  and  J)eltoid  muscles,  communicating  with  the 
cutaneous  branches  of  the  upper  intercostal  nerves. 

The  external  or  supra-acromial  branches  pass  obliquely  across  the  outer  surface 
of  the  Trapezius  and  the  acromion,  and  supply  the  integument  of  the  upper  and 
back  part  of  the  shoulder.  ' 


Beet.  Cap.  Lat 


iJRe.ct.  Ant.  Major 
)Rect.  Ant.  Minor 


'To  Sympathetic 

)  To-  Hypoglossal 
i To  Vagus 


To  Scalp,  and  Occipito  Frontalis 
To  Auricle 


Mastoid 


Auricular 
Facial 


Fig.  409.— Plan  of  the  cervical  plexus. 

Deep  Branches  of  the  Cervical  Plexus.    Internal  Series. 

The  communicating  branches  consist  of  "several  filaments,  which  pass  from 
the  loop  between  the  first  and  second  cervical  nerves  in  front  of  the  atlas  to  the 
pneumogastric,  hypoglossal,  and  sympathetic ;  of  branches  from  all  four  cervical 
nerves  to  the  superior  cervical  ganglion  of  the  sympathetic,  together  with  a  branch 
from  the  fourth  to  the  fifth  cervical. 

Muscular  branches  supply  the  Anterior  recti  and  Rectus  lateralis  muscles  ; 
they  proceed  from  the  first  cervical  nerve,  and  from  the  loop  formed  between  it 
and  the  second. 

The  Communicans  Hypoglossi  (Fig.  406)  consists  usually  of  two  filaments,  one 
being  derived  from  the  second,  and  the  other  from  the  third,  cervical.  These 
filaments  pass  downward  on  the  outer  side  of  the  internal  jugular  vein,  cross  in 
front  of  the  vein  a  little  below  the  middle  of  the  neck,  and  form  a  loop  with 
the  descendens  hypoglossi  in  front  of  the  sheath  of  the  carotid  vessels  (see 
page  756).  Occasionally,  the  junction  of  these  nerves  takes  place  within  the 
sheath. 

The  Phrenic  Nerve  (internal  respiratory  of  Bell)  arises  chiefly  from  the  fourth 


\ 

764  THE  NERVOUS  SYSTEM. 

cervical  nerve,  with  a  few  filaments  from  the  third  and  a  communicating  brancn 
from  the  fifth.  It  descends  to  the  root  of  the  neck,  running  obliquely  across  the 
front  of  the  Scalenus  anticus,  and  beneath  the  Sterno-mastoid,  the  posterior  belly 
of  the  Omo-hyoid,  and  the  Transversalis  colli  and  suprascapular  vessels.  It  next 
passes  over  the  first  part  of  the  subclavian  artery,  between  it  and  the  subclavian 
vein,  and,  as  it  enters  the  chest,  crosses  the  internal  mammary  artery  near  its  origin. 
Within  the  chest  it  descends  nearly  vertically  in  front  of  the  root  of  the  lung  and 
by  the  side  of  the  pericardium,  between  it  and  the  mediastinal  portion  of  the  pleura, 
to  the  Diaphragm,  where  it  divides  into  branches,  which  separately  pierce  that 
muscle  and  are  distributed  to  its  under  surface. 

The  two  phrenic  nerves  differ  in  their  length,  and  also  in  their  relations  at 
the  upper  part  of  the  thorax. 

The  right  nerve  is  situated  more  deeply,  and  is  shorter  and  more  vertical  in 
direction  than  the  left ;  it  lies  .on  the  outer  side  of  the  right  vena  innominata  and 
superior  vena  cava. 

The  left  nerve  is  rather  longer  than  the  right,  from  the  inclination  of  the  heart 
to  the  left  side,  and  from  the  Diaphragm  being  lower  on  this  than  on  the  opposite 
side.  It  enters  the  thorax  behind  the  left  innominate  vein,  and  crosses  in  front 
of  the  vagus  and  the  arch  of  the  aorta  and  the  root  of  the  lung.  In  the  thorax 
each  phrenic  nerve  is  accompanied  by  a  branch  of  the  internal  mammary  artery, 
the  comes  nervi  phrenici. 

Each  nerve  supplies  filaments  to  the  pericardium  and  pleura,  and  near  the 
chest  is  joined  by  a  filament  from  the  sympathetic,  and,  occasionally,  by  one  from 
the  union  of  the  descendens  hypoglossi  with  the  spinal  nerves :  this  filament  is 
found,  according  to  Swan,  only  on  the  left  side.  It  frequently  receives  a  filament 
from  the  nerve  to  the  Subclavius  muscle.  Branches  have  been  described  as 
passing  to  the  peritoneum. 

From  the  right  nerve  one  or  two  filaments  pass  to  join  in  a  small  ganglion  with 
phrenic  branches  of  the  solar  plexus  ;  and  branches  from  this  ganglion  are  dis- 
tributed to  the  hepatic  plexus,  the  suprarenal  capsule,  and  inferior  vena  cava. 
From  the  left  nerve  filaments  pass  to  join  the  phrenic  plexus  of  the  sympathetic, 
but  without  any  ganglionic  enlargement. 

Deep  Branches  of  the  Cervical  Plexus.    External  Series. 

Communicating  Branches. — The  deep  branches  of  the  external  series  of  the 
cervical  plexus  communicate  with  the  spinal  accessory  nerve,  in  the  substance 
of  the  Sterno-mastoid  muscle,  in  the  posterior  triangle,  and  beneath  the  Tra- 
pezius. 

Muscular  branches  are  distributed  to  the  Sterno-mastoid,  Trapezius,  Levator 
anguli  scapulae,  and  Scalenus  medius. 

The  branch  for  the  Sterno-mastoid  is  derived  from  the  second  cervical ;  the 
Trapezius  and  Levator  anguli  scapulae  receive  branches  from  the  third  and  fourth. 
The  Scalenus  medius  is  derived  sometimes  from  the  third,  sometimes  the  fourth, 
and  occasionally  from  both  nerves. 

The  Brachial  Plexus  (Fig.  410). 

The  Brachial  Plexus  is  formed  by  the  union  of  the<  anterior  divisions  of  the 
four  lower  cervical  and  the  greater  part  of  the  first  dorsal  nerves,  receiving  usually 
a  fasciculus  from  the  fourth  cervical  nerve,  and  frequently  one  from  the  second 
dorsal  nerve.  It  extends  from  the  lower  part  of  the  side  of  the  neck  to  the 
axilla.  It  is  very  broad,  and  presents  little  of  a  plexiform  arrangement  at  its 
commencement.  It  is  narrow  opposite  the  clavicle,  becomes  broad  and  forms 
a  more  dense  interlacement  in  the  axilla,  and  divides  opposite  the  coracoid 
process  into  numerous  branches  for  the  supply  of  the  upper  limb.  The  nerves 
which    form  the   plexus   are  all   similar   in  size,   and  their  mode  of  communica- 


THE   BRACHIAL    PLEXUS. 


765 


Hon  is  subject  to  considerable  variation,  so  that  no  one  plan  can  be  given 
as  applying  to  every  case.  The  following  appears,  however,  to  be  the  most  con- 
stant arrangement :  the  fifth  and  sixth  cervical  unite  together  soon  after  their 
exit  from  the  intervertebral  foramina  to  form  a  common  trunk.  The  eighth  cervi- 
cal and  first  dorsal  also  unite  to  form  one  trunk.  So  that  the  nerves  forming  the 
plexus,  as  they  lie  on  the  Scalenus  medius  external  to  the  outer  border  of  the 


V Cervical 


Rhomboid 

Subclavian 


C.  with  Phrenic 


Branches  to  Longus 
Colli  and  Scaleni 


Anterior  division 
of  Middle  Trunk 


I  Dorsal 


Suprascapular 

Upper  Trunk 

Middle  Trunk 

Anterior  division  of  Upper  Trunk 

External  Anterior  Thoracic 
Posterior  division  of  Upper  Trunk 
Upper  Sub-scapular 
Middle  and  Lower 
Sub-scapular 

Circumflex 


Lower  Trunk 


Posterior  division  of  Middle  Trunk 


Posterior  Thoracic 
Anterior  division  of  Lower  Trunk 

Posterior  division  of  Lower  Trunk 

Internal  Anterior  Thoracic 


Musculo-cutaneous 


Lesser  Internal  Cutaneous 

Internal  Cutaneous 

Ulnar  \ 

Musculo-spiral 

Fig.  410.— Plan  of  the  brachial  plexus. 


Scalenus  anticus,  are  blended  into  three  trunks — an  upper  one,  formed  by  the 
junction  of  the  fifth  and  sixth  cervical  nerves ;  a  middle  one,  consisting  of  the 
seventh  cervical  nerve ;  and  a  lower  one,  formed  by  the  junction  of  the  eighth 
cervical  and  first  dorsal  nerves.  As  they  pass  beneath  the  clavicle,  each  of  these 
three  trunks  divides  into  two  branches,  an  anterior  and  a  posterior.1  The  anterior 
divisions  of  the  upper  and  middle  trunks  then  unite  to  form  a  common  cord, 
which  is  situated  on  the  outer  side  of  the  middle  part  of  the  axillary  artery,  and 
is  called  the  outer  cord  of  the  brachial  plexus.  The  anterior  division  of  the 
Tower  trunk  passes  down  on  the  inner  side  of  the  axillary  artery  in  the  middle 
of  the  axilla,  and  forms  the  inner  cord  of  the  brachial  plexus.  The  posterior 
divisions  of  all  three  trunks  unite  to  form  the  posterior  cord  of  the  brachial 
plexus,  which  is  situated  behind  the  second  portion  of  the  axillary  artery.  From 
this  posterior  cord  are  given  oif  the  two  lower  subscapular  nerves,  the  upper  sub- 
scapular nerve  being  given  off  from  the  posterior  division  of  the  upper  trunk 
prior  to  its  junction  with  the  posterior  division  of  the  loAver  and  middle  trunks. 
The  posterior  cord  divides  into  the  circumflex  and  musculo-spiral  nerves. 

The  brachial  plexus  communicates  with  the  cervical  plexus  by  a  branch  from 
the  fourth  to  the  fifth  nerve,  and  with  the  phrenic  nerve  by  a  branch  from  the 

1  The  posterior  division  of  the  lower  trunk  is  very  much  smaller  than  the  others,  and  is  frequently 
derived  entirely  frjoni  the  eighth  cervical  nerve. 


766 


THE  NERVOUS  SYSTEM. 


•  i  i.-  -U  •  ,-^c  +W  nprvp  on  the  Anterior  scalenus  muscle:  the  fifth 
fifth  cemcal,  whic JJ°™  fa 0Seb;nfiZent8  to  the  middle  cervical  ganglion 
:fthe1^Xl  Z  -G  eighth  cervical  to  its  inferior  ganghon,  and 


t<# 


V 


r-4f 


■M 


Fig.  411.— Cutaneous  nerves  of  right  upper 
extremity.    Anterior  view. 


Fig.  412.— Cutaneous  nerves  of  right  upper 
extremity.    Posterior  view. 


the  first  dorsal  nerve  to  its  first  thoracic  ganglion,  close  to   then-  exit  from  the 


THE   BRACHIAL    PLEXUS. 


767 


anterior  thoracic. 
Internal  anterior  thoracic. 

'Musculo-cutaneous. 


Median. 


Musculo-spiral. 

Wk Posterior 

interosseous. 


Anterior 
interosseous, 


Fig.  413. — Nerves  of  the  left  upper  extremity. 


scaleni  muscles,  and  then  above  and  to  the  outer  side  of  the  subclavian  artery :  it 
npxt  passes  behind  the  clavicle  and  Subclavius  muscle,  lying  upon  the  first  serra- 


768  THE   NERVOUS  SYSTEM. 

tion  of  the  Serratus  inagnus,  and  the  Subscapularis  muscles.  In  the  axilla,  it  is 
placed  on  the  outer  side  of  the  first  portion  of  the  axillary  artery ;  it  surrounds 
the  artery  in  the  second  part  of  its  course,  one  cord  lying  upon  the  outer  side  of 
that  vessel,  one  on  the  inner  side,  and  one  behind  it,  and  at  the  lower  part  of  the 
axillary  space  gives  off  its  terminal  branches  to  the  upper  extremity. 

Branches. — The  branches  of  the  brachial  plexus  are  arranged  in  two  groups — 
viz.,  those  given  off  above,  the  clavicle,  and  those  below  that  bone. 

Branches  above  the  Clavicle. 

Communicating.  Posterior  thoracic. 

Muscular.  Suprascapular. 

The  communicating  branch  with  the  phrenic  is  derived  from  the  fifth  cervical 
nerve  or  from  the  loop  between  the  fifth  and  sixth  ;  it  joins  the  phrenic  on  the 
Anterior  scalenus  muscle.  The  communications  with  the  sympathetic  have  already 
been  referred  to. 

The  muscular  branches  supply  the  Longus  colli,  Scaleni,  Rhomboidei,  and  Sub- 
clavius  muscles.  Those  for  the  Longus  colli  and  Scaleni  arise  from  the  four  lower 
cervical  nerves  at  their  exit  from  the  intervertebral  foramina.  The  Rhomboid 
branch  arises  from  the  fifth  cervical,  pierces  the  Scalenus  medius,  and  passes 
beneath  the  Levator  anguli  scapulte,  which  it  occasionally  supplies,  to  the  Rhom- 
boid muscles.  The  nerve  to  the  Subclavius  is  a  small  filament  which  arises  from 
the  fifth  cervical  at  its  point  of  junction  with  the  sixth  nerve;  it  descends  in 
front  of  the  third  part  of  the  subclavian  artery  to  the  Subclavius  muscle,  and  is 
usually  connected  by  a  filament  with  the  phrenic  nerve. 

The  posterior  thoracic  nerve  {long  thoracic,  external  respiratory  of  Bell)  (Fig. 
413)  supplies  the  Serratus  magnus,  and  is  remarkable  for  the  length  of  its  course. 
It  sometimes  arises  by  two  roots  from  the  fifth  and  sixth  cervical  nerves  imme- 
diately after  their  exit  from  the  intervertebral  foramina,  but  generally  by  three 
roots  from  the  fifth,  sixth,  and  seventh  nerves.  These  unite  in  the  substance  of 
the  Middle  scalenus  muscle,  and,  after  emerging  from  it,  the  nerve  passes  down 
behind  the  brachial  plexus  and  the  axillary  vessels,  resting  on  the  outer  surface 
of  the  Serratus  magnus.  It  extends  along  the  side  of  the  chest  to  the  lower 
border  of  that  muscle,  supplying  filaments  to  each  of  its  digitations. 

The  suprascapular  nerve  (Fig.  414)  arises  from  the  cord  formed  by  the  fifth 
and  sixth  cervical  nerves;  passing  obliquely  outward  beneath  the  Trapezius  and 
the  Omo-hyoid,  it  enters  the  supraspinous  fossa  below  the  transverse  or  supra- 
scapular ligament,  and,  passing  beneath  the  Supraspinatus  muscle,  curves  round 
the  external  border  of  the  spine  of  the  scapula  to  the  infraspinous  fossa.  In  the 
supraspinous  fossa  it  gives  off  two  branches  to  the  Supraspinatus  muscle,  and  an 
articular  filament  to  the  shoulder-joint ;  and  in  the  infraspinous  fossa  it  gives  off 
two  branches  to  the  Infraspinatus  muscle,  besides  some  filaments  to  the  shoulder- 
joint  and  scapula, 

Branches  below  the  Clavicle. 

The  branches  given  off  below  the  clavicle  are  derived  from  the  three  cords  of 
the  brachial  plexus,  in  the  following  manner : 

From  the  outer  cord  arise' the  external  anterior  thoracic  nerve,  the  musculo- 
cutaneous, and  the  outer  head  of  the  median. 

From  the  inner  cord  arise  the  internal  anterior  thoracic  nerve,  the  internal 
cutaneous,  the  lesser  internal  cutaneous  (nerve  of  ■  Wrisberg),  the  ulnar,  and  inner 
head  of  the  median. 

From  the  posterior  cord  arise  two  of  the  three  subscapular  nerves,  the  third 
taking  origin  from  the  posterior  division  of  the  trunk  formed  by  the  fifth  and  sixth 
cervical  nerves;  the  cord  then  divides  into  the  musculo-spiral  and  circumflex 
nerves. 


THE   BRACHIAL    PLEXUS.  769 

These  may  be  arranged  according  to  the  parts  they  supply : 

•     To  the  chest         .         .         .         .         Anterior  thoracic. 
„      .       .      , ,  f  Subscapular. 

To  the  shoulder  ......      j  Circumflex. 

r  Musculo-cutaneous. 
Internal  cutaneous. 
_.     .  _  iii  I  Lesser  internal  cutaneous. 

To  the  arm,  forearm,  and  hand  .        \  Median 

Ulnar. 
Musculo-spiral. 

The  fasciculi  of  which  these  nerves  are  composed  may  be  traced  through  the 
plexus  to  the  spinal  nerves  from  which  they  originate.     They  are  as  follows : 

External  anterior  thoracic  from  5th,  6th,  and  7th  cervical. 
Internal  anterior  thoracic     "      8th  cervical  and  1st  dorsal. 
Subscapular  "      5th,  6th,  7th,  and  8th  cervical. 

Circumflex  "      5th  and  6th  cervical. 

Musculo-cutaneous  "       5th  and  6th'  cervical. 

Internal  cutaneous  "      8th  cervical  and  1st  dorsal. 

Lesser  internal  cutaneous     "      1st  dorsal. 

Median  "      6th,  7th,  and  8th  cervical,  and  1st  dorsal. 

Ulnar  "      8th  cervical  and  1st  dorsal. 

Musculo-spiral  "      6th,  7th,  and  8th  cervical,  sometimes  also 

from  the  5th. 

The  Anterior  Thoracic  Nerves  (Fig.  413),  two  in  number,  supply  the  Pectoral 
muscles. 

The  external  or  superficial  nerve,  the  larger  of  the  two,  arises  from  the  outer 
cord  of  the  brachial  plexus,  through  which  its  fibres  may  be  traced  to  the  fifth, 
sixth,  and  seventh  cervical  nerves.  It  passes  inward,  across  the  axillary  artery 
and  vein,  pierces  the  costo-coracoid  membrane,  and  is  distributed  to  the  under 
surface  of  the  Pectoralis  major.  It  sends  doAvn  a  communicating  filament  to  join 
the  internal  nerve,  which  forms  a  loop  round  the  inner  side  of  the  axillary  artery. 

The  internal  or  deep  nerve  arises  from  the  inner  cord,  and  through  it  from 
the  eighth  cervical  and  first  dorsal.  It  passes  behind  the  first  part  of  the  axillary 
artery,  then  curves  forward  between  the  axillary  artery  and  vein,  and  joins  with 
the  filament  from  the  anterior  nerve.  It  then  passes  to  the  under  surface  of  the 
Pectoralis  minor  muscle,  where  it  divides  into  a  number  of  branches,  which  supply 
the  muscle  on  its  under  surface.  Some  two  or  three  branches  pass  through  the 
muscle  to  supply  the  Pectoralis  major. 

The  Subscapular  Nerves,  three  in  number,  supply  the  Subscapulars,  Teres 
major,  and  Latissimus  dorsi  muscles.  The  fasciculi  of  which  they  are  composed 
may  be  traced  to  the  fifth,  sixth,  seventh,  and  eighth  cervical  nerves. 

The  upper  subscapular  nerve,  the  smallest,  enters  the  upper  part  of  the  Sub- 
scapulars muscle  ;  this  nerve  is  frequently  represented  by  two  branches. 

The  loiver  subscapular  nerve  enters  the  axillary  border  of  the  Subscapularis 
and  terminates  in  the  Teres  major.  The  latter  muscle  is  sometimes  supplied  by  a 
separate  branch. 

The  middle  or  long  subscapular,  the  largest  of  the  three,  follows  the  course  of 
the  subscapular  artery,  along  the  posterior  wall  of  the  axilla  to  the  Latissimus 
dorsi,  through  which  it  may  be  traced  as  far  as  its  lower  border. 

The  Circumflex  Nerve  (Fig.  414)  supplies  some  of  che  muscles  and  the  integu- 
ment of  the  shoulder  and  the  shoulder-joint.  It  arises  from  the  posterior  cord  of 
the  brachial  plexus,  in  common  with  the  musculo-spiral  nerve,  and  its  fibres  may 
be  traced  through  the  posterior  cord  to  tire  fifth  and  sixth  cervical  nerves.  It  is 
at  first  placed  behind  the  axillary  artery,  between  it  and  the  Subscapularis  muscle, 

49 


^ 


/ 
770  THE   NERVOUS   SYSTEM. 

and  passes  downward  and  outward  to  the  lower  border  of  that  muscle.  It  then 
winds  backward  in  company  with  the  posterior  circumflex  artery,  through  a 
quadrilateral  space  bounded  above  by  the  Teres  minor,  below  by  the  Teres  major, 
internally  by  the  long  head  of  the  Triceps,  and  externally  by  the  neck  of  the 
humerus,  and  divides  into  two  branches. 

The  upper  branch  winds  round  the  surgical  neck  of  the  humerus,  beneath  the 
Deltoid,  with  the  posterior  circumflex  vessels,  as  far  as  the  anterior  border  of  that 
muscle,  supplying  it,  and  giving  off  cutaneous  branches,  which  pierce  the  muscle 
and  ramify  in  the  integument  covering  its  lower  part. 

The  lower  branch,  at  its  origin,  distributes  filaments  to  the  Teres  minor  and 
back  part  of  the  Deltoid  muscles.  Upon  the  filament  to  the  former  muscle  an  oval 
enlargement  usually  exists.  The  nerve  then  pierces  the  deep  fascia,  and  supplies 
the  integument  over  the  lower  two-thirds  of  the  posterior  surface  of  the  Deltoid,  as 
well  as  that  covering  the  long  head  of  the  Triceps. 

The  circumflex  nerve,  before  its  division,  gives  off  an  articular  filament,  which 
enters  the  shoulder-joint  below  the  Subscapularis. 

The  Musculo-cutaneous  Nerve  (Fig.  413)  {external  cutaneous  or  perforans  Cas- 
serii ) l  supplies  some  of  the  muscles  of  the  arm  and  the  integument  of  the  fore- 
arm. It  arises  from  the  outer  cord  of  the  brachial  plexus,  opposite  the  lower  border 
of  the  Pectoralis  minor,  receiving  filaments  from  the  fifth,  sixth,  and  seventh 
cervical  nerves.  It  perforates  the  Coraco-brachialis  muscle,  passes  obliquely 
between  the  Biceps  and  Brachialis  anticus  to  the  outer  side  of  the  arm,  and,  a  little 
above  the  elbow,  winds  round  the  outer  border  of  the  tendon  of  the  Biceps,  and, 
perforating  the  deep  fascia,  becomes  cutaneous.  This  nerve,  in  its  course  through 
the  arm,  supplies  thes/ Coraco-brachialis,  VBiceps,  and  the  greater  part  of  the 
Brachialis  anticus  muscles.  The  branch  to  the  Coraco-brachialis  is  given  off 
from  the  nerve  close  to  its  origin,  and  in  some  instances,  especially  in  early  life, 
as  a  separate  filament  from  the  outer  cord  of  the  plexus.  The  branches  to  the 
Biceps  and  Brachialis  anticus  are  given  off  after  the  ner\Te  has  pierced  the  Coraco- 
bracliialis.  The  nerve  also  sends  a  small  branch  to  the  bone,  which  enters  the 
nutrient  foramen  with  the  accompanying  artery,  and  a  filament,  from  the  branch 
supplying  the  Brachialis  anticus,  to  the  elbow-joint. 

The  cutaneous  portion  of  the  nerve  passes  behind  the  median  cephalic  vein,  and 
divides,  opposite  the  elbow-joint,  into  an  anterior  and  a  posterior  branch. 

The  anterior  branch  descends  along  the  radial  border  of  the  forearm  to  the 
wrist,  and  supplies  the  integument  over  the  outer  half  of  the  anterior  surface.  At 
the  wrist-joint  it  is  placed  in  front  of  the  radial  artery,  and  some  filaments, 
piercing  the  deep  fascia,  accompany  th  t  vessel  to  the  back  of  the  wrist,  supplying 
the  carpus.  The  nerve  then  passes  downward  to  the  ball  of  the  thumb,  where  it 
terminates  in  cutaneous  filaments.  It  communicates  with  a  branch  from  the  radial 
nerve  and  the  palmar  cutaneous  branch  of  the  median. 

The  posterior  branch  passes  downward  along  the  back  part  of  the  radial  side 
of  the  forearm  to  the  wrist.  It  supplies  the  integument  of  the  lower  third  of  the 
forearm,  communicating;  with  the  radial  nerve  and  the  external  cutaneous  branch 
of  the  musculo-spiral. 

The  musculo-cutaneous  nerve  presents  frequent  irregularities.  It  may  adhere 
for  some  distance  to  the  median  and  then  pass  outward,  beneath  the  Biceps, 
instead  of  through  the  Coraco-brachialis.  Frequently  some  of  the  fibres  of  the 
median  run  for  some  distance  in  the  musculo-cutaneous  and  then  leave  it  to  join 
their  proper  trunk.  Less  frequently  the  reverse  is  the  case,  and  the  median  sends 
a  branch  to  join  the  musculo-cutaneous.  Instead  of  piercing  the  Coraco-brachialis, 
the  nerve  may  pass  under  it  or  through  the  Biceps.  Occasionally  it  gives  a  fila- 
ment to  the  Pronator  teres,  and  it  has  been  seen  to  supply  the  back  of  the  thumb 
when  the  radial  nerve  was  absent. 

The  Internal  Cutaneous  Nerve  (Fia;.  413)  is  one  of  the  smallest  branches  of  the 
brachial  plexus.     It  arises  from  the  inner  cord  in  common  with  the  ulnar  and 

1  See  foot-note,  page  726. 


THE   BRACHIAL    PLEXUS.  771 

internal  head  of  the  median,  and,  at  its  commencement,  is  placed  on  the  inner  side 
of  the  axillary,  and  afterward  of  the  brachial  artery.  It  derives  its  fibres  from 
the  eighth  cervical  and  first  dorsal  nerves.  It  passes  down  the  inner  side  of  the 
arm,  pierces  the  deep  fascia  with  the  basilic  vein,  about  the  middle  of  the  limb, 
and,  becoming  cutaneous,  divides  into  two  branches,  anterior  and  posterior. 

"jThis  nerve  gives  off,  near  the  axilla,  a  cutaneous  filament,  which  pierces  the 
fascia  and  supplies  the  integument  covering  the  Biceps  muscle  nearly  as  far  as 
the  elbow.  This  filament  lies  a  little  external  to  the  common  trunk,  from  which 
it  arises. 

The  anterior  branch,  the  larger  of  the  two,  passes  usually  in  front  of,  but 
occasionally  behind,  the  median  basilic  vein.  It  then  descends  on  the  anterior 
surface  of  the  ulnar  side  of  the  forearm,  distributing  filaments  to  the  integument 
as  far  as  the  wrist,  and  communicating  with  a  cutaneous  branch  of  the  ulnar 
nerve. 

The  posterior  branch  passes  obliquely  downward  on  the  inner  side  of  the 
basilic  vein,  passes  in  front  of,  or  over,  the  internal  condyle  of  the  humerus  to  the 
back  of  the  forearm,  and  descends  on  the  posterior  surface  of  its  ulnar  side  as  far 
as  the  wrist,  distributing  filaments  to  the  integument.  It  communicates,  above 
the  elbow,  with  the  lesser  internal  cutaneous,  and  above  the  wrist  with  the  dorsal 
cutaneous  branch  of  the  ulnar  nerve  (Swan). 

The  Lesser  Internal  Cutaneous  Nerve  {nerve  of  Wrisberg)  (Fig.  413)  is  distrib- 
uted to  the  integument  on  the  inner  side  of  the  arm.  It  is  the  smallest  of  the 
branches  of  the  brachial  plexus,  and,  arising  from  the  inner  cord  with  the  internal 
cutaneous  and  ulnar  nerves,  receives  its  fibres  from  the  first  dorsal  nerve.  It 
passes  through  the  axillary  space,  at  first  lying  behind,  and  then  on  the  inner  side 
of,  the  axillary  vein,  and  communicates  with  the  intercosto-humeral  nerve.  It 
descends  along  the  inner  side  of  the  brachial  artery  to  the  middle  of  the  arm., 
where  it  pierces  the  deep  fascia,  and  is  distributed  to  the  integument  of  the  back 
part  of  the  lower  third  of  the  arm,  extending  as  far  as  the  elbow,  where  some 
filaments  are  lost  in  the  integument  in  front  of  the  inner  condyle,  and  others 
over  the  olecranon.  It  communicates  with  the  posterior  branch  of  the  internal 
cutaneous  nerve. 

In  some  cases  the  nerve  of  Wrisberg  and  intercosto-humeral  are  connected  by 
two  or  three  filaments  which  form  a  plexus  at  the  back  part  of  the  axilla.  In 
other  cases  the  intercosto-humeral  is  of  large  size,  and  takes  the  place  of  the 
nerve  of  Wrisberg,  receiving  merely  a  filament  of  communication  from  the  brachial 
plexus,  which  represents  the  latter  nerve.  In  other  cases  this  filament  is  wanting, 
the  place  of  th,e  nerve  of  Wrisberg  being  supplied  entirely  from  the  intercosto- 
humeral. 

The  Median  Nerve  (Fig.  413)  has  received  its  name  from  the  course  it  takes 
along  the  middle  of  the  arm  and  forearm  to  the  hand,  lying  between  the  ulnar 
and  the  musculo-spiral  and  radial  nerves.  It  arises  by  two  roots,  one  from  the 
outer,  and  one  from  the  inner,  cord  of  the  brachial  plexus  ;  these  embrace  the  lower 
part  of  the  axillary  artery,  uniting  either  in  front  or  on  the  outer  side  of  that 
vessel.  It  receives  filaments  from  the  sixth,  seventh,  and  eighth  cervical  and  the 
first  dorsal.  As  it  descends  through  the  arm,  it  lies  at  first  on  the  outer  side  of 
the  brachial  artery,  crosses  that  vessel  in  the  middle  of  its  course,  usually  in 
front,  but  occasionally  behind  it,  and  lies  on  its  inner  side  to  the  bend  of  the 
elbow,  where  it  is  placed  beneath  the  bicipital  fascia,  and  is  separated  from  the 
elbow-joint  by  the  Brachialis  anticus.  In  the  forearm  it  passes  between  the  two 
heads  of  the  Pronator  radii  teres,  and  descends  beneath  the  Flexor  sublimis,  lying 
on  the  Flexor  profundus,  to  within  two  inches  above  the  annular  ligament,  where 
it  becomes  more  superficial,  lying  between  the  tendons  of  the  Flexor  sublimis 
and  Flexor  carpi  radialis,  beneath,  and  rather  ttf  the  radial  side  of,  the  tendon  of 
the  Palmaris  longus,  covered  by  the  integument  and  fascia.  It  then  passes 
beneath  the  annular  ligament  into  the  hand.  In  fits  course  through  the  forearm  it 
is  accompanied  by  a  branch  of  tie  anterior  interosseous  artery. 


772  THE  NERVOUS  SYSTEM. 

Branches. — With  the  exception  of  the  nerve  to  the  Pronator  teres,  which  some- 
times arises  above  the  elbow-joint,  the  median  nerve  gives  off  no  branches  in  the 
arm.  In  the  forearm  its  branches  are  muscular,  anterior  interosseous,  and  palmar 
cutaneous,  and,  according  to  Riidinger  and  Macalister,  two  articular  twigs  to  the 
elbow-joint. 

The  muscular  branches  supply  all  the  superficial  muscles  on  the  front  of  the 
forearm  except  the  Flexor  carpi  ulnaris.  These  branches  are  derived  from  the 
nerve  near  the  elbow.  4 

The  anterior  interosseous  supplies  the  deep  muscles  on  the  front  of  the  fore- 
arm, except  the  inner  half  of  the  Flexor  profundus  digitorum.  It  accompanies 
the  anterior  interosseous  artery  along  the  interosseous  membrane,  in  the  interval 
between  the  Flexor  longus  pollicis  and  Flexor  profundus  digitorum  muscles,  both 
of  which  it  supplies,  and  ternlinates  below  in  the  Pronator  quadratus  and  wrist- 
joint. 

The  palmar  cutaneous  branch  arises  from  the  median  nerve  at  the  lower  part? 
of  the  forearm.  It  pierces  the  fascia  above  the  annular  ligament,  and,  descending 
over  that  ligament,  divides  into  two  branches ;  of  which  the  outer  supplies  the 
skin  over  the  ball  of  the  thumb,  and  communicates  Avith  the  anterior  cutaneous 
branch  of  the  musculo-cutaneous  nerve  ;  and  the  inner  supplies  the  integument  of 
the  palm  of  the  hand,  communicating  with  the  cuta.neous  branch  of  the  ulnar. 

In  the  palm  of  the  hand  the  median  nerve  is  covered  by  the  integument  and 
palmar  fascia  and  crossed  by  the  superficial  palmar  arch.  It  rests  upon  the 
tendons  of  the  flexor  muscles.  In  this  situation  it  becomes  enlarged,  somewhat 
flattened,  of  a  reddish  color,  and  divides  into  tAvo  branches.  Of  these,  the 
external  supplies  a  muscular  branch  to  some  of  the  muscles  of  the  thumb  and 
digital  branches  to  the  thumb  and  index  finger ;  the  internal  supplies  digital 
branches  to  the  contiguous  sides  of  the  index  and  middle  and  of  the  middle  and 
ring  fingers. 

The  branch  to  the  muscles  of  the  thumb  is  a  short  nerve  which  divides  to 
supply  the  Abductor,  Opponens,  and  the  superficial  head  of  the  Flexor  brevis 
pollicis  muscles,  the  remaining  muscles  of  this  group  being  supplied  by  the  ulnar 
nerve. 

The  digital  branches  are  five  in  number.  The  first  and  second  pass  along  the 
borders  of  the  thumb,  the  external  branch  communicating  with  branches  of  the 
radial  nerve.  The  third  passes  along  the  radial  side  of  the  index  finger,  and 
supplies  the  First  lumbricalis  muscle.  The  fourth  subdivides  to  supply  the  adjacent 
sides  of  the  index  and  middle  fingers,  and  sends  a  branch  to  the  Second  lumbrical 
muscle.  The  fifth  supplies  the  adjacent  sides  of  the  middle  and  ring  fingers,  and 
communicates  with  a  branch  from  the  ulnar  nerve. 

Each  digital  nerve,  opposite  the  base  of  the  first  phalanx,  gives  off  a  dorsal 
branch,  which  joins  the  dorsal  digital  nerve  from  the  radial  and  runs  along  the 
side  of  the  dorsum  of  the  finger,  to  end  in  the  integument  over  the  last  phalanx. 
At  the  end  of  the  finger  the  digital  nerve  divides  into  a  palmar  and  a  dorsal 
branch,  the  former  of  which  supplies  the  extremity  of  the  finger,  and  the  latter 
ramifies  round  and  beneath  the  nail.  The  digital  nerves,  as  they  run  along  the 
fingers,  are  placed  superficial  to  the  digital  arteries. 

The  Ulnar  Nerve  (Fig.  413)  is  placed  along  the  inner  or  ulnar  side  of  the  upper 
limb,  and  is  distributed  to  the  muscles  and  integument  of  the  forearm  and  hand. 
It  is  smaller  than  the  median,  behind  which  it  is  placed,  diverging  from  it  in  its 
course  down  the  arm.  It  arises  from  the  inner  cord  of  the  brachial  plexus,  in 
common  with  the  inner  head  of  the  median  and  the  internal  cutaneous  nerve,  and 
derives  its  fibres  from  the  eighth  cervical  and  first  dorsal  nerves.  At  its  commence- 
ment it  lies  to  the  inner  side  of  the  axillary  artery,  and  holds  the  same  relation 
with  the  brachial  artery  to  the  middle  of  the  arm.  From  this  point  it  runs  obliquely 
across  the  internal  head  of  the  Triceps,  pierces  the  internal  intermuscular  septum, 
and  descends  to  the  groove  between  the  internal  condyle  and  the  olecranon,  accom- 
panied by  the  inferior  profunda  artery.      At  the  elbow  it  rests  upon  the  back  of  the 


THE   BRACHIAL    PLEXUS. 


773 


inner  condyle,  and  passes  into  the  forearm  between  the  two  heads  of  the  Flexor 
carpi  ulnaris.  In  the  forearm  it  descends  in  a  perfectly  straight  course  along  its 
ulnar  side,  lying  upon  the  Flexor  profundus  digitorurn,  its  upper  half  being  covered 
by  the  Fiexor  carpi  ulnaris,  its  lower  half  lying  on  the  outer  side  of  the  muscle, 
covered  by  the  integument  and  fascia.  The  ulnar  artery,  in  the  upper  third  of  its 
course,  is  separated  from  the  ulnaf  nerve  by  a  considerable  interval,  but  in  the 
rest  of  its  extent  the  nerve  lies  to  its'  inner  side.  At  the  wrist  the  ulnar  nerve 
crosses  the  annular  ligament  on  the  outer  side  of  the  pisiform  bone,  to  the  inner 
-side  of  and  a  little  behind  the  ulnar  artery,  and  immediately  beyond  this  bone 
divides  into  two  branches,  superficial  and  deep  palmar. 
The  branches  of  the  ulnar  nerve  are — 


♦ 


,- Articular  (elbow). 
Muscular. 
In  the  forearm  \  Cutaneous. 

I  Dorsal  cutaneous. 
^•Articular  (wrist). 


t    .a.    i       if  Superficial  palmar. 
In  the  hand  -<  -r\  i 

[  Deep  palmar. 


The  articular  branches  distributed  to  the  elbow-joint  consist  of  several  small 
filaments.  They  arise  from  the  nerve  as  it  lies  in  the  groove  between  the  inner 
condyle  and  olecranon. 

The  muscular  branches  are  two  in  number — one  supplying  the  Flexor  carpi 
ulnaris ;  the  other,  the  inner  half  of  the  Flexor  profundus  digitorurn.  They  arise 
from  the  trunk  Of  the  i.erve  near  the  elbow. 

The  cutaneous  br<  ?h  arises  from  the  ulnar  nerve  about  the  middle  of  the  fore- 
arm, and  divides  int'      wo  branches. 

3ntly  absent)  pierces  the  deep  fascia  near  the  wrist,  and  is 
itegument,   communicating    with  a  branch  of  the    internal 


One  branch  (fre 
distributed  to  the 
cutaneous   ner* 

The  seconc 
accompanies  tr 
the  integumer 

The  dor  si 
passes  backw 
and,  running 
branches ;    o 
supplies  the 
of  the  radia 
fingers,  and 
region  of  tr. 

On  t  e 
of  the  tr 


nch   (palmar  cutaneous)  lies  on  the  ulnar  artery,   which   it 
.    hand,  some  filaments  entwining  round  the  vessel ;  it  ends  in 
the  palm,  communicating  with  branches  of  the  median  nerve. 
:aneous   branch  arises   about    two  inches    above    the  wrist ;    it 
oeneath   the   Flexor  carpi    ulnaris,    perforates  the  deep  fascia,, 
lg  the  ulnar  side  of  the  back  of  the  wrist  and  hand,  divides  intr 
f   these  supplies   the   inner   side   of   the   little    finger ;   a  secom 
tcent  sides  of  the  little  and  ring  fingers ;  a  third  joins  the  branch 
rve  which  supplies  the   adjoining   sides  of  the   middle   and  ring 
ists  in  supplying  them  ;  a  fourth  is  distributed  to  the  metacarpal 
.ind,  communicating  with  a  branch  of  the  radial  nerve, 
le  finger  the  dorsal  digital  branches  extend  only  as  far  as  the  base 
i  phalanx,  and  on  the  ring  finger  as  far  as  the  base  of  the  second 
phalanx  :nore  distal   parts  of  these   digits  are  supplied  by  dorsal  branches 

derived  e  palmar  digital  branches  of  the  ulnar. 

The  'ial  palmar  branch  supplies  the  Palmaris  brevis  and  the  integument 

on  the  ide  of  the  hand,  and  terminates  in  two  digital  branches,  which  are 

distribuf  -,  to  the  ulnar  side  of  the  little  finger,  the  other  to  the  adjoining 

sides  of  le  and  ring  fingers,  the  latter  communicating  with  a  branch  from 

the   met  fhe    digital   branches   are  distributed   to  the  fingers   in   the   same 

manner  digital  branches  of  the  median. 

The  mlmar  branch,  accompanied  by  the  deep  branch  of  the  ulnar  artery, 

passes  b  n  the  Abductor  and   Flexor  brevis  minimi  digiti  muscles;    it  then 

perforate  Opponens  minimi  digiti  and  follows  the  course  of  the  deep  palmar 

arch  ben  the  flexor  tendons.      At  its  origin  it  supplies  the  muscles  of  the  little 

finger,      'i        t  crosses   the  deep  part  of  the  hand  it  sends  two  branches  to  each 
interosseo         iace,  one  for  the  Dorsal  and  one  for  the  Palmar  interosseous  muscle, 
the  branch      bo  the  Second  and  Third  palmar  interossei  supplying  filaments  to  the1 
two  inner  .     -rubrical  muscles.      At  its  termination  between  the  thumb  and  inde:Q\e 


774 


THE  NERVOUS  SYSTEM. 


finger,  it  supplies  the  Adductores  transversus  et  obliquus  pollicis  and  the  inner  head 
of  the  Flexor  brevis  pollicis.     It  also  sends  articular\filaments  to  the  wrist-joint. 

It  will  be  remembered  that  the  inner  part  o^  the  Flexor  profundus  digitorum 
is  supplied  by  the  ulnar  nerve ;  the  two  inner  Lumbricales,  which  are  connected 
with  the  tendons  of  this  part  of  the  muscle,  are  therefore  supplied  by  the  same 
nerve.  The  outer  part  of  the  Flexor  profundus  is  supplied  by  the  median  nerve ; 
the  two  outer  Lumbricales,  which  are  connected  with  the  tendons  of  this  part  of 

the  muscle,  are  therefore  sup- 
plied by  the  same  nerve. 
Brooks  states  that  in  twelve 
instances  out  of  twenty-one  he 
found  that  the  third  lumbrical 
received  a  twig  from  the  median 
nerve,  in  addition  to  its  branq 
from  the  ulnar. 

The    Musculo-spiral   Ner 
(Fig.  414),  the  largest  branc 
of  the  brachial  plexus,  supplies 
the  muscles  of  the  back  part 


Suprascapula 


an 

| 

cHT 


of  the 
the    int. 
parts,    a 
back   of 
from  th 
brachial 
may  be 
tinuation 
from    the 
eighth,  a: 
the  fifth   . 
its  comme 
behind  tht 
part  of  th> 
passing   do    . 
tendons  of  i 
and   Teres 
round  the  hr 
culo-spiral  g 
peri  or  pro  fur   * 
from  the  inn 
of  the  bone, 
nal  and  exte 
Triceps  muse 
external  intei 
and     descend 
Brachialis    an 
nator   longus 
the  external  c 
divides    into 
posterior  inter 
The  brarr 
culo-spiral  ne 
Muscu 
Cutane 
Radial. 
Posterii 
The   muscvlfir   branches  are   divided  into   internal,   pcsterioi 


id  forearm,  and 

mt    of   the    same 

1    as    that  of  the 

hand.     It    arises 

^rior  cord  of  the 

of   which    it 

1  as  the  con- 

•  iives  filaments 

seventh,    and 

mes  also  from 

nerves.     At 

it  is  placed 

and  upper 

tl    arteries, 

ont  of  the 

.    imus  dorsi 

It    winds 

l  the  mus- 

,h  the  su- 

r,  passing 

outer  side 

he  inter- 


Fig.  414.— The  suprascapular,  circumflex,  and  musculo-spiral 
nerves. 


s  of  the 

fees  the 

septum, 

n     the 

Supi- 

mt  of 

a ere  it 

1    and 

tares. 

\  mus- 


eous. 
ernal ; 


THE   BRACHIAL    PLEXUS.  7~7 

they  supply  the  Triceps,  Anconeus,  Supinator  longus,  Extensor  s  only  slightly 
longior,  and  Brachialis  anticus.  These  branches  are  derived  fron  length  from 
the  inner  side,  back  part,  and  outer  side  of  the  arm.  ;vn  in  contact 

The  internal  muscular  branches  supply  the  inner  and  middle  \ro  vertebrae, 
Triceps  muscle.  That  to  the  inner  head  of  the  Triceps  is  a  long,  sleitervertebral 
which  lies  close  to  the  ulnar  nerve,  as  far  as  the  lower  third  of  tlerior  (dorsal) 
therefore  frequently  spoken  of  as  the  ulnar  collateral. 

The  posterior  muscular  branch,  of  large  size,  arises  from  the  nervine  respects, 
between  the  Triceps  and  the  humerus.      It  divides  into  branches  w.x 
outer  and  inner  head  of  the  Triceps  and  Anconeus  muscles.      The  brancn  . 
latter  muscle  is  a  long,  slender   filament  which  descends  in   Ihe  substance  of  tx* 
Triceps  to  the  Anconeus. 

tThe  external  muscular  branches  supply  the  Supinator  longus,  Extensor  carpi 
■adia-lis  longior,  and  (usually)  the  outer  part  of  the  Brachialis  anticus. 
The  cutaneous  brandies  are  three  in  number,  one  internal  and  two  external. 

The  internal  cutaneous  branch  arises  in  the  axillary  space  with  the  inner  mus- 
cular branch.  It  is  of  small  size,  and  passes  through  the  axilla  to  the  inner  side 
of  the  arm,  supplying  the  integument  on  its  posterior  aspect  nearly  as  far  as  the 
olecranon.  In  its  course  it  crosses  beneath  the  intercosto-humeral,  with  which 
it  communicates. 

The  two  external  cutaneous  branches  perforate  the  outer  head  of  the  Triceps 
at  its  attachment  to  the  humerus.  The  upper  and  smaller  one  passes  to  the 
front  of  the  elbow,  lying  close  to  the  cephalic  vein,  and  supplies  the  integu- 
ment of  the  lower  half  of  the  arm  on  its  anterior  aspect.  The  lower  branch 
pierces  the  deep  fascia  below  the  insertion  of  the  Deltoid,  and  passes  down  along 
the  outer  side  of  the  arm  and  elbow,  and  then  along  the  back  part  of  the  radial 
side  of  the  forearm  to  the  wrist,  supplying  the  integument  in  its  course,  and  join- 
ing, near  its  termination,  with  the  posterior  cutaneous  branch  of  the  musculo- 
cutaneous nerve. 

The  radial  nerve  passes  along  the  front  of  the  radial  side  of  the  forearm  to 
the  commencement  of  its  lower  third.  It  lies  at  first  a  little  to  the  outer  side  of 
the  radial  artery,  concealed  beneath  the  Supinator  longus.  In  the  middle  third 
of  the  forearm  it  lies  beneath  the  same  muscle,  in  close  relation  with  the  outer 
side  of  the  artery.  It  quits  the  artery  about  three  inches  above  the  wrist,  passes 
beneath  the  tendon  of  the  Supinator  longus,  and,  piercing  the  deep  fascia  at  the 
outer  border  of  the  forearm,  divides  into  two  branches. 

The  external  branch,  the  smaller  of  the  two,  supplies  the  integument  of  the 
radial  side  and  ball  of  the  thumb,  joining  with  the  anterior  branch  of  the  musculo- 
cutaneous nerve. 

The  internal  branch  communicates,  above  the  wrist,  with  the  posterior  cuta- 
neous branch  from  the  musculo-cutaneous,  and  on  the  back  of  the  hand  forms  an 
arch  with  the  dorsal  cutaneous  branch  of  the  ulnar  nerve.  It  then  divides  into 
four  digital  nerves,  which  are  distributed  as  follows  :  The  first  supplies  the  ulnar 
side  of  the  thumb  ;  the  second,  the  radial  side  of  the  index  finger ;  the  third, 
the  adjoining  sides  of  the  index  and  middle  fingers  ;  and  the  fourth,  the  adjacent 
borders  of  the  middle  and  ring  fingers.1  The  latter  nerve  communicates  with  a 
filament  from  the  dorsal  branch  of  the  ulnar  nerve. 

The  Posterior  Interosseous  Nerve  winds  to  the  back  of  the  forearm  round  the 
outer  side  of  the  radius,  passes  between  the  two  planes  of  fibres  of  the  Supinator 
brevis,  and  is  prolonged  downward  between  the  superficial  and  deep  layer  of 
muscles,  to  the  middle  of  the  forearm.  Considerably  diminished  in  size,  it  de- 
scends on  the  interosseous  membrane,  beneath  the  Extensor  longus  pollicis,  to  the 
back  of  the  carpus,  where  it  presents  a  gangliform  enlargement  from  which  fila- 
ments are  distributed  to  the  ligaments  and  articulations  of  the  carpus.     It  supplies 

1  According  to  Hutchinson,  tae  digital  nerve  to  the  thumb  reaches  only  as  high  as  the  root  of 
the  nail  ;  the  one  to  the  forefinger  as  high  as  the  middle  of  the  second  phalanx  ,  and  the  one  to  the 
middle  and  ring  fingers  not  higher  than  the  first  phalangeal  joint  {London  Horn.  Gaz.,  vol.  iii.,  p.  31 9). 


THE   NERVOUS  SYSTEM. 

ft]   '  Fl       r  1  °^  ^e  rac^a^  anc^  posterior  brachial  regions,  excepting  the  Anco- 
-r      mi   i      c  longus,  and  Extensor  carpi  radialis  longior./ 

is  supplied  b^atomy. — The  brachial  plexus  may  be  ruptured  by  traction  on  the  limb,  leading 

with   the  ten  -a^7S's-    ^n  these  cases  the  lesion  would  appear  to  be  rather  a  tearing  away  of  the 

rp,       i  spinal  cord  than  a  solution  of  continuity  of  the  nerve-fibres  themselves.    In  the 

nerve.      ±ne  c  nerves  forming  the  brachial  plexus  may  be  injured  in  a  wound  of  this  part,  the 

the  two  outer  >e  one  which  is  most  frequently  damaged  from  its  exposed  position,  and  the 

n  account  of  its  sheltered  and  deep  position,  being  the  least  often  wounded. 

<.      v*us  in  the  axilla  is  often  damaged  from  the  pressure  of  a  crutch,  producing  the 

Suprascajjularr^i  as  "crutch  paralysis."     In  these  cases  the  musculo-spiral  appears  most  fre- 

„o  be  the  nerve  which  is  chiefly  implicated ;  the  ulnar  nerve  being  the  one  that  appears 

..arfer  next  in  frequency. 

The  circumflex  nervt  is  of  particular  surgical  interest.     On  account  of  its  course  round  the 
surgical  neck  of  the  humeius,  it  is  liable  to  be  torn  in  fractures  of  this  part  of  the  bone,  and 
in  dislocations  of  the  shouldc-joint,  leading  to  paralysis  of  the  deltoid,  and,  according  to  Erb,^ 
inflammation  of  the  shoulcler-jcint  is  liable  to  be  followed  by  a  neuritis  of  this  nerve  fromB 
extension  of  the  inflammation  to  it.  ™ 

Mr.  Hilton  takes  the  circumflex  nerve  as  an  illustration  of  a  law  which  he  lays  down,  that 
"  the  same  trunks  of  nerves  whose  branches  supply  the  groups  of  muscles  moving  a  joint  furnish 
also  a  distribution  of  nerves  to  the  skin  over  the  insertions  of  the  same  muscles,  and  the  interior 
of  the  joint  receives  its  nerves  from  the  same  source."  In  this  way  he  explains  the  fact  that  an 
inflamed  joint  becomes  rigid,  because  *he  same  nerves  which  supply  the  interior  of  the  joint 
supply  the  muscles  also  which  move  thai,  ioint. 

The  median  nerve  is  liable  to  injury  in  wounds  of  the  forearm.  When  paralyzed,  there  is 
loss  of  flexion  of  the  second  phalanges  of  all  the  fingers  and  of  the  terminal  phalanges  of  the 
index  and  middle  fingers.  Flexion  of  the  terminal  phalanges  of  the  ring  and  middle  fingers  is 
effected  by  that  portion  of  the  Flexor  profundus  digitorum  which  is  supplied  by  the  ulnar  nerve. 
There  is  power  to  flex  the  proximal  phalanges  through  the  Interossei.  The  thumb  cannot  be 
flexed  or  opposed,  and  is  maintained  in  a  position  of  extension  and  adduction.  All  power  of 
pronation  is  lost.  The  wrist  can  be  flexed,  if  the  hand  is  first  adducted,  by  the  action  of  the 
Flexor  carpi  ulnaris.  There  is  loss  or  impairment  of  sensation  on  the  palmar  surface  of  the 
thumb,  index,  middle,  and  outer  half  of  the  ring  fingers,  and  on  the  dorsal  surface  of  the  same 
fingers  over  the  last  two  phalanges  ;  except  in  the  thumb,  where  the  loss  of  sensation  would  be 
limited  to  the  back  of  the  last  phalanx.  In  order  to  expose  the  median  nerve  for  the  purpose 
of  stretching  an  incision  should  be  made  along  the  radial  side  of  the  tendon  of  the  Palmaris 
longus,  which  serves  as  a  guide  to  the  nerve. 

The  ulnar  nerve  is  also  liable  to  be  injured  in  wounds  of  the  forearm..  When  paralyzed, 
there  is  loss  of  power  of  flexion  in  the  ring  and  little  fingers  ;  there  is  impaired  power  of  ulnar 
flexion  and  adduction  ;  there  is  inability  to  spread  out  the  fingers  from  paralysis  of  the  Inter- 
ossei ;  and  there  is  inability  to  adduct  the  thumb.  Sensation  is  lost  or  impaired  in  the  skin  sup- 
plied by  the  nerve.  In  order  to  expose  the  nerve  in  the  lower  part  of  the  forearm,  an  incision 
should  be  made  along  the  outer  border  of  the  tendon  of  the  Flexor  carpi  ulnaris,  and  the  nerve 
will  be  found  lying  on  the  ulnar  side  of  the  ulnar  artery. 

The  musculo-spiral  nerve  is  probably  more  frequently  injured  than  any  other  nerve  of  the 
upper  extremity.  In  consequence  of  its  close  relationship  to  the  humerus  as  it  lies  in  the  mus- 
culo-spiral groove,  it  is  frequently  torn  or  injured  in  fractures  of  this  bone,  or  subsequently 
involved  in  the  callus  that  may  be  thrown  out  around  a  fracture,  and  thus  pressed  upon  and  its 
functions  interfered  with.  It  is  also  liable  to  be  contused  against  the  bone  by  kicks  or  blows  or 
to  be  divided  by  wounds  of  the  arm.  When  paralyzed,  the  hand  is  flexed  at  the  wrist  and  lies 
flaccid.  This  is  known  as  "  drop-wrist."  The  fingers  are  also  flexed,  and  on  an  attempt  being 
made  to  extend  them  the  last  two  phalanges  only  will  be  extended  through  the  action  of  the  Inter- 
ossei, the  first  phalanges  reniainin.se  flexed.  There  is  no  power  of  extending  the  wrist.  Supina- 
tion is  completely  lost  when  the  forearm  is  extended  on  the  arm,  but  it  is  possible  to  a  certain 
extent  il  the  forearm  is  flexed  so  as  to  allow  of  the  action  of  the  Biceps.  The  power  of  exten- 
sion of  the  forearm  is  lost  on  account  of  paralysis  of  the  Triceps.  The  best  position  in  which 
to  expose  the  nerve  for  the  purpose  of  stretching  is  to  make  an  incision  along  the  inner 
border  of  the  Supinator  longus,  just  above  the  level  of  the  elbow-joint.  The  skin  and  super- 
ficial structures  are  to  be  divided  and  the  deep  fascia  exposed.  The  white  line  in  this  struc- 
ture indicating  the  border  of  the  muscle  is  to  be  defined,  and  the  deep  fascia  divided  in  this 
line.  By  now  raising  the  Supinator  longus  the  nerve  will  be  found  lying  beneath  it,  on  the 
Brachialis  anticus. 

THE    DORSAL    NERVES  (Fig.  415). 

The  Dorsal  Nerves  are  twelve  in  number  on  each  side.  The  first  appears 
between  the  first  and  second  dorsal  vertebrae,  and  the  last  between  the  last  dorsal 
and  first  lumbar. 

The  roots  of  the  dorsal  nerves  are  of  small  size,  and  vary  but  slightly  from  the 


THE  DORSAL    NERVES.  777 

second  to  the  last.  Both  roots  are  very  slender,  the  posterior  roots  only  slightly 
exceeding  the  anterior  in  thickness.  They  gradually  increase  in  length  from 
above  downward,  and  in  the  lower  part  of  the  dorsal  region  pass  down  in  contact 
with  the  spinal  cord  for  a  distance  equal  to  the  height  of  at  least  two  vertebrae, 
before  they  emerge  from  the  spinal  canal.  They  then  join  in  the  intervertebral 
foramen,  and  at  their  exit  divide  into  two  primary  divisions,  a  posterior  (dorsal) 
and  an  anterior  (intercostal). 

The  first,  the  second,  and  the  last  dorsal  nerves  are  peculiar  in  some  respects. 

Posterior  Divisions  of  the  Dorsal  Nerves. 

The  posterior  divisions  of  the  dorsal  nerves,  which  are  smaller  than  the  ante- 
rior, pass  backward  between  the  transverse  processes,  and  divide  into  internal  and 
external  branches. 

i  The  internal  branches  of  the  six  upper  nerves  pass  inward  between  the  Semi- 
spinals dorsi  and  Multifidus  spinae  muscles,  which  they  supply,  and  then,  piercing 
the  origins  of  the  Rhomboidei  and  Trapezius  muscles,  become  cutaneous  by  the 
side  of  the  spinous  processes  and  ramify  in  the  integument.  The  internal  branches 
of  the  six  lower  nerves  are  distributed  to  the  Multifidus  spinae,  without  giving  off 
any  cutaneous  filaments. 

The  external  branches  increase  in  size  from  above  downward.  They  pass 
through  the  Longissimus  dorsi  to  the  cellular  interval  between  it  and  the  Ilio- 
costalis,  and  supply  those  muscles,  as  well  as  their  continuations  upward  to  the 
head,  and  the  Levatores  costarum ;  the  five  or  six  lower  nerves  also  give  off 
cutaneous  filaments,  which  pierce  the  Serratus  posticus  inferior  and  Latissimus  dorsi 
in  a  line  with  the  angles  of  the  ribs,  and  then  ramify  in  the  integument. 

The  cutaneous  branches  of  the  posterior  primary  divisions  of  the  dorsal  nerves 
are  twelve  in  number.  The  six  upper  cutaneous  nerves  are  derived  from  the  in- 
ternal branches  of  the  posterior  divisions  of  the  dorsal  nerves.  They  pierce  the 
origins  of  the  Rhomboidei  and  Trapezius  muscles,  and  become  cutaneous  by  the 
side  of  the  spinous  processes,  and  then  ramify  in  the  integument.  They  are  fre- 
quently furnished  with  gangliform  enlargements.  The  six  lower  cutaneous  nerves 
are  derived  from  the  external  branches  of  the  posterior  divisions  of  the  dorsal  nerves. 
They  pierce  the  Serratus  posticus  inferior  and  Latissimus  dorsi  in  a  line  with  the 
angles  of  the  ribs,  and  then  ramify  in  the  integument. 

Anterior  Divisions  of  the  Dorsal  Nerves. 

The  anterior  divisions  of  the  dorsal  nerves  (intercostal  nerves)  are  twelve  in 
number  on  each  side.  They  are,  for  the  most  part,  distributed  to  the  parietes  of 
the  thorax  and  abdomen,  separately  from  each  other,  without  being  joined  in  a 
plexus ;  in  which  respect  they  differ  from  the  other  spinal  nerves.  Each  nerve  is 
connected  with  the  adjoining  ganglia  of  the  sympathetic  by  one  or  two  filaments. 
The  intercostal  nerves  may  be  divided  into  two  sets,  from  the  difference  they 
present  in  their  distribution.  The  six  upper,  with  the  exception  of  the  first  and 
the  intercosto-humeral  branch  of  the  second,  are  limited  in  their  distribution  to  the 
parietes  of  the  chest.  The  six  lower  supply  the  parietes  of  the  chest  and  abdomen, 
the  last  one  sending  a  cutaneous  filament  to  the  buttock. 

The  First  Dorsal  Nerve. — The  anterior  division  of  the  first  dorsal  nerve  divides 
into  two  branches :  one,  the  larger,  leaves  the  thorax  in  front  of  the  neck  of  the 
first  rib,  and  enters  into  the  formation  of  the  brachial  plexus  ;  the  other  and 
smaller  branch  runs  along  the  first  intercostal  space,  forming  the  first  intercostal 
nerve,  and  terminates  on  the  front  of  the  chest  by  forming  the  first  anterior 
cutaneous  nerve  of  the  thorax.  Occasionally  this  anterior  cutaneous  branch  is 
wanting.  The  first  intercostal  nerve,  as  a  rule,  gives  off  no  lateral  cutaneous 
branch,  but  sometimes  a  small  branch  is  given  off  which  communicates  with  the 
intercosto-humeral.  It  frequently  receives  a  connecting  twig  from  the  second 
dorsal  nerve,  which  passes  upward  over  the  neck  of  the  second  rib. 


778 


THE   NERVOUS  SYSTEM. 


Fig.  415.— Superficial  and  deep  distribution  of  the  posterior  divisions  of  the  spinal  nerves  (after  Hirschfeld 
and  Leveill6).  On  the  left  side  the  cutaneous  branches  are  represented  lying  on  the  superficial  layer  of  mus- 
cles. On  the  right  side  the  superficial  muscles  have  been  removed,  the  Splenius  capitis  and  Complexus  divided 
in  the  neck,  and  the  Erector  spinse  divided  and  partly  removed  in  the  back,  so  as  to  expose  the  posterior  divis- 
ions of  the  spinal  nerves  near  their  origin,  a  a.  Lesser  occipital  nerve  from  the  cervical  plexus.  1.  External 
muscular  branches  of  the  first  cervical  nerve,  and  union  by  a  loop  with  the  second.  2,  placed  on  the  Rectus 
capitis  posticus  major  muscle,  marks  the  great  occipital  nerve,  passing  round  the  short  muscles  and  piercing 
the  Complexus  :  the  external  branch  is  seen  to  the  outside.  3.  External  branch  from  the  posterior  division  of 
the  third  nerve.  3'.  Its  internal  branch,  sometimes  called  the  third  occipital.  4' to  8'.  The  internal  branches 
of  the  several  corresponding  nerves  on  the  left  side.  The  external  branches  of  these  nerves,  proceeding  to 
muscles,  are  displayed  on  the  right  side,  d  1  to  d  6,  and  thence  to  d  12.  External  muscular  branches  of  the  pos- 
terior divisions  of  the  twelve  dorsal  nerves  on  the  right  side,  d  1'  to  d  6'.  The  internal  cutaneous  branches  of 
the  six  upper  dorsal  nerves  on  the  left  side,  d  7'  to  d  12'.  Cutaneous  twigs  from  the  external  branches  of  the 
six  lower  dorsal  nerves.  1 1.  External  branches  from  the  posterior  divisions  of  several  lumbar  nerves  on  the 
right  side,  piercing  the  muscles,  the  lower  descending  over  the  gluteal  region.  I'  V.  The  same,  more  super- 
ficially, on  the  left  side,  s  s.  The  issue  and  union  by  loops  of  the  posterior  divisions  of  four  sacral  nerves  on  the 
right  side,    s'  s'.  Some  of  those  distributed  to  the  skin  on  the  left  side. 

The  Upper  Dorsal  Nerves. — The  anterior  divisions  of  the  second,  third,  fourth, 
fifth,   and  sixth   dorsal  nerves  and  the  small  branch    from   the    first  dorsal  are 


THE   DORSAL    NERVES.  779 

confined  to  the  parietes  of  the  thorax,  and  are  named  upper  or  pectoral  intercostal 
nerves.  They  pass  forward  in  the  intercostal  spaces  with  the  intercostal  vessels, 
being  situated  below  them.  At  the  back  of  the  chest  they  lie  between  the  pleura 
and  the  External  intercostal  muscle,  but  are  soon  placed  between  the  two  planes 
of  Intercostal  muscles  as  far  as  the  middle  of  the  rib.  They  then  enter  the 
substance  of  the  Internal  intercostal  muscles,  and,  running  amidst  their  fibres  as  far 
as  the  costal  cartilages,  they  gain  the  inner  surface  of  the  muscles  and  lie  between 
them  and  the  pleura.  Near  the  sternum,  they  cross  in  front  of  the  internal  mam- 
mary artery  and  Triangularis  sterni  muscle,  pierce  the  Internal  intercostal  muscles, 
the  anterior  intercostal  membrane,  and  Pectoralis  major  muscle,  and  supply  the 
integument  of  the  front  of  the  chest  and  over  the  mammary  gland,  forming  the 
anterior  cutaneous  nerves  of  the  thorax ;  the  branch  from  the  second  nerve  is 
joined  with  the  supraclavicular  nerves  of  the  cervical  plexus. 

Branches. — Numerous  slender  muscular  filaments  supply  the  Intercostals,  the 
Infracostales,  the  Levatores  costarum,  Serratus  posticus  superior,  and  Triangularis 
sterni  muscles.  Some  of  these  branches,  at  the  front  of  the  chest,  cross  the  costal 
cartilages  from  one  to  another  intercostal  space. 

Lateral  Cutaneous  Nerves. — These  are  derived  from  the  intercostal  nerves, 
midway  between  the  vertebrae  and  sternum  ;  they  pierce  the  External  intercostal 
and  Serratus  magnus  muscles,  and  divide  into  two  branches,  anterior  and  posterior. 

The  anterior  branches  are  reflected  forward  to  the  side  and  the  fore  part  of  the 
chest,  supplying  the  integument  of  the  chest  and  mamma ;  those  of  the  fifth  and 
sixth  nerves  supply  the  upper  digitations  of  the  External  oblique. 

The  posterior  branches  are  reflected  backward  to  supply  the  integument  over 
the  scapula  and  over  the  Latissimus  dorsi. 

The  lateral  cutaneous  branch  of  the  second  intercostal  nerve  is  of  large  size, 
and  does  not  divide,  like  the  other  nerves,  into  an  anterior  and  posterior  branch. 
It  is  named,  from  its  origin  and  distribution,  the  inter costo-humeral  nerve  (Fig.  413). 
It  pierces  the  External  intercostal  muscle,  crosses  the  axilla  to  the  inner  side  of 
the  arm,  and  joins  with  a  filament  from  the  nerve  of  Wrisberg.  It  then  pierces 
the  fascia,  and  supplies  the  skin  of  the  upper  half  of  the  inner  and  back  part  of 
the  arm,  communicating  with  the  internal  cutaneous  branch  of  the  musculo-spiral 
nerve.  The  size  of  this  nerve  is  in  inverse  proportion  to  the  size  of  the  other 
cutaneous  nerves,  especially  the  nerve  of  Wrisberg.  A  second  intercosto-humeral 
nerve  is  frequently  given  off  from  the  third  intercostal.  It  supplies  filaments  to 
the  armpit  and  inner  side  of  the  arm. 

The  Lower  Dorsal  Nerves. — The  anterior  divisions  of  the  seventh,  eighth,  ninth, 
tenth,  and  eleventh  dorsal  nerves  are  continued  anteriorly  from  the  intercostal 
spaces  into  the  abdominal  wall,  and  the  twelfth  dorsal  is  continued  throughout  its 
whole  course  in  the  abdominal  wall,  since  it  is  placed  below  the  last  rib  ;  hence 
these  nerves  are  named  lower  or  abdominal  intercostal  nerves.  They  have  (with 
the  exception  of  the  last)  the  same  arrangement  as  the  upper  ones  as  far  as  the 
anterior  extremities  of  the  intercostal  spaces,  where  they  pass  behind  the  costal 
cartilages,  and  between  the  Internal  oblique  and  Transversalis  muscles,  to  the 
sheath  of  the  Rectus,  Avhich  they  perforate.  They  supply  the  Rectus  muscle,  and 
terminate  in  branches  which  become  subcutaneous  near  the  linea  alba.  These 
branches  are  named  the  anterior  cutaneous  nerves  of  the  abdomen.  They  are 
directed  outward  as  far  as  the  lateral  cutaneous  nerves,  supplying  the  integument 
of  the  front  of  the  belly.  The  lower  intercostal  nerves  supply  the  Intercostals, 
Serratus  posticus  inferior,  and  Abdominal  muscles,  and,  about  the  middle  of  their 
course,  give  off  lateral  cutaneous  branches  which  pierce  the  External  intercostal 
and  External  oblique  muscles,  in  the  same  line  as  the  lateral  cutaneous  nerves  of 
the  thorax,  and  divide  into  anterior  and  posterior  branches,  which  are  distributed 
to  the  integument  of  the  abdomen  and  back  ;  the  anterior  branches  supply  the 
digitations  of  the  External  oblique  muscle  and  extend  downward  and  forward 
nearly  as  far  as  the  margin  of  the  Rectus  ;  the  posterior  branches  pass  backward 
to  supply  the  skin  over  the  Latissimus  dorsi. 


780  THE  NERVOUS  SYSTEM. 

The  last  dorsal  is  larger  than  the  other  dorsal  nerves.  Its  anterior  division 
runs  along  the  lower  border  of  the  last  rib,  and  passes  under  the  external  arcuate 
ligament  of  the  Diaphragm.  It  then  runs  in  front  of  the  Quadratus  lumborum, 
perforates  the  Transversalis,  and  passes  forward  between  it  and  the  Internal 
oblique,  to  be  distributed  in  the  same  manner  as  the  lower  intercostal  nerves.  It 
communicates  with  the  ilio-hypogastric  branch  of  the  lumbar  plexus,  and  is  fre- 
quently connected  with  the  first  lumbar  nerve  by  a  slender  branch,  the  dorsi- 
lumbar  nerve,  which  descends  in  the  substance  of  the  Quadratus  lumborum.  It 
gives  a  branch  to  the  Pyramidalis  muscle. 

The  lateral  cutaneous  branch  of  the  last  dorsal  is  remarkable  for  its  large  size; 
it  perforates  the  Internal  and  External  oblique  muscles,  passes  downward  over  the 
crest  of  the  ilium  in  front  of  the  iliac  branch  of  the  ilio-hypogastric  (Fig.  422), 
and  is  distributed  to  the  integument  of  the  front  part  of  the  gluteal  region,  some  of 
its  filaments  extending  as  Ioav  down  as  the  trochanter  major.  It  does  not  divide 
into  an  anterior  and  a  posterior  branch,  like  the  other  lateral  cutaneous  branches 
of  the  intercostal  nerves. 

Surgical  Anatomy. — The  lower  seven  intercostal  nerves  and  the  ilio-hypogastric  from  the 
first  lumbar  nerve  supply  the  skin  of  the  abdominal  wall.  They  run  downward  and  inward 
fairly  equidistant  from  each  other.  The  sixth  and  seventh  supply  the  skin  over  the  "  pit  of  the 
stomach;"  the  eighth  corresponds  to  about  the  position  of  the  middle  linea  transversa;  the 
tenth  to  the  umbilicus  ;  and  the  ilio-hypogastric  supplies  the  skin  over  the  pubes  and  external 
abdominal  ring.  There  are  several  points  of  surgical  importance  about  the  distribution  of  these 
nerves,  and  it  is  important  to  remember  their  origin  and  course,  for  in  many 'diseases  affecting 
the  nerve-trunks  at  or  near  the  origin  the  pain  is  referred  to  their  peripheral  terminations. 
Thus  in  Pott's  disease  of  the  spine  children  will  often  be  brought  to  the  surgeon  suffering  from 
pain  in  the  belly.  This  is  due  to  the  fact  that  the  nerves  are  irritated  at  the  seat  of  disease  as 
they  issue  from  the  spinal  canal.  When  the  irritation  is  confined  to  a  single  pair  of  nerves,  the 
sensation  complained  of  is  often  a  feeling  of  constriction,  as  if  a  cord  were  tied  round  the  abdo- 
men ;  and  in  these  cases  the  situation  of  the  sense  of  constriction  may  serve  to  localize  the 
disease  in  the  spinal  column.  In  other  cases,  where  the  bone  disease  is  more  extensive  and  two 
or  more  nerves  are  involved,  a  more  general  diffused  pain  in  the  abdomen  is  complained  of.  A 
similar  condition  is  sometimes  present  in  affections  of  the  cord  itself,  as  in  tabes  dorsalis. 

Again,  it  must  be  borne  in  mind  that  the  same  nerves  which  supply  the  skin  of  the  abdomen 
supply  also  the  planes  of  muscle  which  constitute  the  greater  part  of  the  abdominal  wall.  Hence 
it  follows  that  any  irritation  applied  to  the  peripheral  terminations  of  the  cutaneous  branches  in 
the  skin  of  the  abdomen  is  immediately  followed  by  reflex  contraction  of  the  abdominal  muscles. 
A  good  practical  illustration  of  this  may  sometimes  be  seen  in  watching  two  surgeons  examine 
the  abdomen  of  the  same  patient.  One,  whose  hand  is  cold,  causes  the  muscles  of  the  abdominal 
wall  to  at  once  contract  and  the  belly  to  become  rigid,  and  thus  not  nearly  so  suitable  for  examina- 
tion; the  other,  who  has  taken  the  precaution  to  warm  his  hand,  examines  the  abdomen  with- 
out exciting  any  reflex  contraction.  The  supply  of  both  muscles  and  skin  from  the  same  source 
is  of  importance  in  protecting  the  abdominal  viscera  from  injury.  A  blow  on  the  abdomen, 
even  of  a  severe  character,  will  do  no  injury  to  the  viscera  if  the  muscles  are  in  a  condition  of 
firm  contraction ;  whereas  in  cases  where  the  muscles  have  been  taken  unawares,  and  the  blow 
has  been  struck  while  they  were  in  a  state  of  rest,  an  injury  insufficient  to  produce  any  lesion  of 
the  abdominal  wall  has  been  attended  with  rupture  of  some  of  the  abdominal  contents.  The 
importance,  therefore,  of  immediate  reflex  contraction  upon  the  receipt  of  an  injury  cannot  be 
overestimated,  and  the  intimate  association  of  the  cutaneous  and  muscular  fibres  in  the  same 
nerve  produces  a  much  more  immediate  response  on  the  part  of  the  muscles  to  any  peripheral 
stimulation  of  the  cutaneous  filaments  than  would  be  the  case  if  the  two  sets  of  fibres  were  derived 
from  independent  sources. 

Again,  the  nerves  supplying  the  abdominal  muscles  and  skin  derived  from  the  lower  inter- 
costal nerves  are  intimately  connected  with  the  sympathetic  supplying  the  abdominal  viscera 
through  the  lower  thoracic  ganglia  from  which  the  splanchnic  nerves  are  derived.  In  con- 
sequence of  this,  in  laceration  of  the  abdominal  viscera  and  in  acute  peritonitis  the  muscles  of  the 
belly-wall  become  firmly  contracted,  and  thus  as  far  as  possible  preserve  the  abdominal  contents 
in  a  condition  of  rest. 

THE  LUMBAR  NERVES. 

The  lumbar  nerves  are  five  in  number  on  each  side.  The  first  appears  between 
the  first  and  second  lumbar  vertebrae,  and  the  last  between  the  last  lumbar  and  the 
base  of  the  sacrum. 

The  roots  of  the  lumbar  nerves  are  the  largest,  and  their  filaments  the  most 
numerous,  of  all  the  spinal  nerves,  and  they  are  closely  aggregated  together  upon 
the  lower  end  of  the  cord.      The  anterior  roots  are  the  smaller,  but  there  is  not  the 


THE   LUMBAR    PLEXUS.  781 

I 
same  disproportion  between  them  and  the  posterior  roots  as  in  the  cervical  nerves. 
The  roots  of  these  nerves  have  a  vertical  direction,  and  are  of  considerable  length, 
more  especially  the  lower  ones,  since  the  spinal  cord  does  not  extend  beyond  the  first 
lumbar  vertebra.  The  roots  become  joined  in  the  intervertebral  foramina,  and  the 
nerves  so  formed  divide  at  their  exit  into  two  divisions,  posterior  and  anterior. 

The  Posterior  Divisions  of  the  Lumbar  Nerves. 

The  posterior  divisions  of  the  lumbar  nerves  (Fig.  415)  diminish  in  size  from 
above  downward  ;  they  pass  backward  between  the  transverse  processes,  and  divide 
into  internal  and  external  branches. 

The  internal  branches,  the  smaller,  pass  inward  close  to  the  articular  processes 
of  the  vertebrae,  and  supply  the  Multifidus  spinse  and  Interspinales  muscles. 

The  external  branches  supply  the  Erector  spinas  and  Intertransverse  muscles. 
From  the  three  upper  branches  cutaneous  nerves  are  derived  which  pierce  the 
aponeurosis  of  the  Latissimus  dorsi  muscle  and  descend  over  the  back  part  of  the 
crest  of  the  ilium,  to  be  distributed  to  the  integument  of  the  gluteal  region,  some 
of  the  filaments  passing  as  far  as  the  trochanter  major. 

The  Anterior  Divisions  of  the  Lumbar  Nerves. 

The  anterior  divisions  of  the  lumbar  nerves  increase  in  size  from  above  down- 
ward. At  their  origin  they  communicate  wdth  the  lumbar  ganglia  of  the  sympa- 
thetic by  long,  slender  filaments,  which  accompany  the  lumbar  arteries  round  the 
sides  of  the  bodies  of  the  vertebrae,  beneath  the  Psoas  muscle.  The  nerves  pass 
obliquely  outward  behind  the  Psoas  magnus  or  between  its  fasciculi,  distributing 
filaments  to  it  and  the  Quadratus  lumborum.  The  anterior  divisions  of  the  four 
upper  nerves  are  connected  together  in  this  situation  by  anastomotic  loops,  and  form 
the  lumbar  plexus.  The  anterior  division  of  the  fifth  lumbar,  joined  with  a  branch 
from  the  fourth,  descends  across  the  base  of  the  sacrum  to  join  the  anterior  division 
of  the  first  sacral  nerve  and  assist  in  the  formation  of  the  sacral  plexus.  The  cord 
resulting  from  the  union  of  the  fifth  lumbar  and  the  branch  from  the  fourth  is  called 
the  lumbosacral  cord. 

The  Lumbar  Plexus  (Fig.  416). 

The  lumbar  plexus  is  formed  by  the  loops  of  communication  between  the  anterior 
divisions  of  the  four  upper  lumbar  nerves.  The  plexus  is  narrow  above,  and  often 
connected  with  the  last  dorsal  by  a  slender  branch,  the  dorsi-lumbar  nerve;  it  is 
broad  belowT,  where  it  is  joined  to  the  sacral  plexus  by  the  lumbo-sacral  cord.  It 
is  situated  in  the  substance  of  the  Psoas  muscle  near  its  posterior  part,  in  front  of 
the  transverse  process  of  the  lumbar  vertebrae. 

The  mode  in  which  the  plexus  is  arranged  varies  in  different  subjects.  It  differs 
from  the  brachial  plexus  in  not  forming  an  intricate  interlacement,  but  the  several 
nerves  of  distribution  arise  from  one  or  more  of  the  spinal  nerves,  somewhat  in  the 
following  manner :  The  first  lumbar  nerve  receives  a  branch  from  the  last  dorsal, 
and  gives  off  a  larger  branch,  which  subdivides  into  the  ilio-hypogastric  and  ilio- 
inguinal ;  a  communicating  branch  which  passes  down  to  the  second  lumbar  nerve; 
and  a  third  branch  which  unites  with  a  branch  of  the  second  lumbar  to  form  the 
genito-crural  nerve.  The  second,  third,  and  fourth  lumbar  nerves  divide  into  an 
anterior  and  a  posterior  division.  The  anterior  division  of  the  second  divides  into 
two  branches,  one  of  which  joins  with  the  above-mentioned  branch  of  the  first  nerve 
to  form  the  genito-crural ;  the  other  unites  with  the  anterior  division  of  the  third 
nerve,  and  a  part  of  the  anterior  division  of  the  fourth  nerve  to  form  the  obturator 
nerve.  The  remainder  of  the  anterior  division  of  the  fourth  nerve  passes  down  to 
communicate  with  the  fifth  lumbar  nerve.  The  posterior  divisions  of  the  second 
and  third  nerves  divide  into  two  branches,  a  smaller  branch  from  each  uniting  to 
form  the  external  cutaneous  nerve,  and  a  larger  branch  from  each,  which  join  with 


782 


THE   NERVOUS  SYSTEIf. 


the  whole  of  the  posterior  division  of  the  fourth  lumbar  nerve  to  form  the  anterior 
crural.  The  accessory  obturator,  when  it  exists,  is  formed  by  the  union  of  two 
small  branches  given  off  from  the  third  and  fourth  nerves. 


IstL 


2dL 


3dL 


ithL 


5th  L 


Fig.  416.— Plan  of  the  lumbar  plexus. 

From  this  arrangement  it  follows  that  the  ilio-hypogastric  and  ilio-inguinal 
are  derived  entirely  from  the  first  lumbar  nerve ;  the  genito-crural  from  the  first 
and  second  nerves ;  the  external  cutaneous  from  the  second  and  third ;  the  ante- 
rior crural  and  obturator  by  fibres  derived  from  the  second,  third,  and  fourth ; 
and  the  accessory  obturator,  when  it  exists,  from  the  third  and  fourth. 

The  branches  of  the  lumbar  plexus  are — the 


Ilio-hypogastric. 
Ilio-inguinal. 
Genito-crural. 
External  cutaneous. 


Anterior  crural. 
Obturator. 
Accessory  obturatoi 


The  Ilio-hypogastric  Nerve  arises  from  the  first  lumbar  nerve.  It  emerges  from 
the  outer  border  of  the  Psoas  muscle  at  its  upper  part,  and  crosses  obliquely  in 
front  of  the  Quadratus  lumborum  to  .the  crest  of  the  ilium.  It  then  perforates  the 
Transversalis  muscle  at  its  posterior  part  near  the  crest  of  the  ilium,  and  divides 
between  it  and  the  Internal  oblique  into  two  branches,  iliac  and  hypogastric. 

The  iliac  branch  pierces  the  Internal  and  External  oblique  muscles  immediately 
above  the  crest  of  the  ilium,  and  is  distributed  to  the  integument  of  the  gluteal 
region,  behind  the  lateral  cutaneous  branch  of  the  last  dorsal  nerve  (Fig.  422). 
The  size  of  this  nerve  bears  an  inverse  proportion  to  that  of  the  cutaneous  branch 
of  the  last  dorsal  nerve. 

The  hypogastric  branch  (Fig.  418)  continues  onward  between  the  Internal 
oblique  and  Transversalis  muscles.  It  then  pierces  the  Internal  oblique,  and 
becomes  cutaneous  by  perforating  the  aponeurosis  of  the  External  oblique,  about 


. 


TJ{IE   LUMBAR    PLEXUS.  783 

an  inch  above  and  a  little  to  the  outer  side  of  the  external  abdominal  ring,  and  is 
distributed  to  the  integument  of  the  hypogastric  region. 

The  ilio-hypogastric  nerve  communicates  with  the  last  dorsal  and  ilio-inguinal 
nerves. 

The  Ilio-inguinal  Nerve,  smaller  than  the  preceding,  arises  with  it  from  the  first 
lumbar  nerve.  It  emerges  from  the  outer  border  of  the  Psoas  just  below  the  ilio- 
hypogastric, and,  passing  obliquely  across  the  Quadratus  lumborum  and  Iliacus 
muscles,  perforates  the  Transversalis  near  the  fore  part  of  the  crest  of  the  ilium, 
and  communicates  with  the  ilio-hypogastric  nerve  between  that  muscle  and  the 
Internal  oblique.  The  nerve  then  pierces  the  Internal  oblique,  distributing  fila- 
ments to*it ;  and,  accompanying  the  spermatic  cord  through  the  external  abdominal 
ring,  is  distributed  to  the  integument  of  the  upper  and  inner  part  of  the  thigh, 
and  to  the  scrotum  in  the  male  and  to  the  labium  majus  in  the  female.  The  size  of 
this  nerve  is  in  inverse  proportion  to  that  of  the  ilio-hypogastric.  Occasionally  it 
is  very  small,  and  ends  by  joining  the  ilio-hypogastric;  in  such  cases  a  branch 
from  the  ilio-hypogastric  takes  the  place  of  the  ilio-inguinal,  or  the  latter  nerve 
may  be  altogether  absent. 


Fig.  417.— The  lumbar  plexus  and  its  branches. 

The  Genito-crur?l  Ner^e  arises  from  the  first  and  second  lumbar  nerves.  It 
passes  obliquely  through  tie,  substance  of  the  Psoas,  and  emerges  from  its  inner 
border  at  a  level  c  ",ng  to  the  intervertebr  1  substance  between  the  third 

and  fourth  lumbar  vertdjrae  ;   it  then -descends  on  the  surface  of  the  Psoas  muscle, 
under  cover  of  the  peritonemin,  and  divides  into  a  genital  and  a  crural  branch. 


■'A 


784 


THE  NERVOUS  SYSTEM. 


External 
saphenous. 


External 
cutaneous. 


Anterior  crural. 


cutaneous. 


-Anterior  tibial. 


■  Anterior  division 
1         of  obturator. 
Internal 
•  »■     (i ;A  'GMiJhfXMffl     cutaneous. 

M      '  " 


Internal 
saphenous. 


treaty.  41|r^ntUy!e;°US  nerVGS  °f  l0Wer  ex" 


PiG.  419.~Nerves  o<~  the  lower  extremity.    Front  view. 


•^Stt6^*a=ate,-usas; 


THE   LUMBAR    PLEXUS.  785 

the  back  part  of  the  spermatic  cord  to  the  scrotum,  and  supplies,  in  the  male,  the 
Cremaster  muscle.  In  the  feuale,  it  accompanies  the  round  ligament,  and  is  lost 
upon  it. 

The  crural  branch  descends  on  the  external  iliac  artery,  sending  a  few  filaments 
round  it,  and,  passing  beneath  Poupart's  ligament  to  the  thigh,  enters  the  sheath 
of  the  femoral  vessels,  lying  superficial  and  a  little  external  to  the  femoral  artery. 
It  pierces  the  anterior  layer  of  the  sheath  of  the  vessels,  and,  becoming  superficial 
by  passing  through  the  fascia  lata,  it  supplies  the  skin  of  the  anterior  aspect  of  the 
thigh  as  far  as  midway  between  the  pelvis  and  knee.  On  the  front  of  the  thigh  it 
communicates  with  the  outer  branch  of  the  middle  cutaneous  nerve,  derived  from 
the  anterior  crural. 

A  few  filaments  from  this  nerve  may  be  traced  on  to  the  femoral  artery ;  they 
are  derived  from  the  nerve  as  it  passes  beneath  Poupart's  ligament. 

The  External  Cutaneous  Nerve  arises  from  the  second  and  third  lumbar  nerves. 
It  emerges  from  the  outer  border  of  the  Psoas  muscle  about  its  middle,  and  crosses 
the  Iliacus  muscle  obliquely,  toward  the  anterior  superior  spine  of  the  ilium.  It 
then  passes  under  Poupart's  ligament  and  over  the  Sartorius  muscle  into  the  thigh, 
where  it  divides  into  two  branches,  anterior  and  posterior. 

The  anterior  branch  descends  in  an  aponeurotic  canal  formed  in  the  fascia 
lata,  becomes  superficial  about  four  inches  below  Poupart's  ligament,  and  divides 
into  branches  which  are  distributed  to  the  integument  along  the  anterior  and 
outer  part  of  the  thigh,  as  far  down  as  the  knee.  This  nerve  occasionally  com- 
municates with  a  branch  of  the  long  saphenous  nerve  in  front  of  the  knee- 
joint. 

The  posterior  branch  pierces  the  fascia  lata,  and  subdivides  into  branches  Avhich 
pass  backward  across  the  outer  and  posterior  surface  of  the  thigh,  supplying  the 
integument  from  the  crest  of  the  ilium  as  far  as  the  middle  of  the  thigh. 

The  Obturator  Nerve  supplies  the  obturator  externus  and  Adductor  muscles  of 
the  thigh,  the  articulations  of  the  hip  and  knee,  and  occasionally  the  integument 
of  the  thigh  and  leg.  It  arises  by  three  branches — from  the  second,  the  third,  and 
the  fourth  lumbar  nerves.  Of  these,  the  branch  from  the  third  is  the  largest, 
while  that  from  the  second  is  often  very  small.  It  descends  through  the  inner 
fibres  of  the  Psoas  muscle,  and  emerges  from  its  inner  border  near  the  brim  of 
the  pelvis ;  it  then  runs  along  the  lateral  wall  of  the  pelvis,  above  the  obturator 
vessels,  to  the  upper  part  of  the  obturator  foramen,  where  it  enters  the  thigh,  and 
divides  into  an  anterior  and  a  posterior  branch,  separated  by  some  of  the  fibres  of 
the  Obturator  externus  (Fig.  257),  and  lower  down  by  the  Adductor  brevis  muscle. 

The  anterior  branch  (Fig.  419)  passes  down  in  front  of  the  Adductor  brevis, 
being  covered  by  the  Pectineus  and  Adductor  longus,  and  at  the  lower  border  of 
the  latter  muscle  communicates  with  the  internal  cutaneous  and  internal  saphenous 
nerves,  forming  a  kind  of  plexus.  It  then  descends  upon  the  femoral  artery,  upon 
which  it  is  finally  distributed-  The  nerve,  near  the  obturator  foramen,  gives  off  an 
articular  branch  to  the  hip-joint.  ,  Behind  the  Pectineus  it  distributes  muscular 
branches  to  the  Adductor  longus  and  Gracilis,  and  usually  to  the  Adductor  brevis, 
and  in  rare  cases  to  the  Pectineus,  and  receives  a  communicating  branch  from  the 
accessory  obturator  nerve. 

Occasionally  the  communicating  branch  to  the  internal  cutaneous  and  internal 
saphenous  nerves  is  continued  down,  as  a  cutaneous  branch,  to  the  thigh  and  leg. 
When  this  is  so,  this  occasional  cutaneous  branch  emerges  from  beneath  the  lower 
border  of  the  Adductor  longus,  descends  along  the  posterior  margin  of  the  Sartorius 
to  the  inner  side  of  the  knee,  where  it  pierces  the  deep  fascia,  communicates  with 
the  long  saphenous  nerve,  and  is  distributed  to  the  integument  of  the  inner  side 
of  the  leg  as  low  down  as  its  middle.  When  this  communicating  branch  is  small, 
its  place  is  supplied  by  the  internal  cutaneous  nerve. 

The  posterior  branch  of  the  obturator  nerve  pierces  the  Obturator  externus, 
sending  branches  to  supply  it,  and  passes  behind  the  Adductor  brevis  on  the  front 
of  the  Adductor  magnus,  where  it  divides  into  numerous  muscular  branches,  which 

50 


786 


THE   NERVOUS   SYSTEM. 


supply  the  Adductor  magnus,  and  the  Adductor  .,  revis  when  the  latter  does  not 
receive  a  branch  from  the  anterior  division  of  the  nerve.  One  of  the  branches 
gives  off  a  filament  to  the  knee-joint. 

The  articular  branch  for  the  knee-joint  is  sometimes  absent ;  it  perforates  the 
lower  part  of  the  Adductor  magnus,  and  enters  the  popliteal  space ;  it  then 
descends  upon  the  popliteal  artery,  as  far  as  the  back  part  of  the  knee-joint,  where 
it  perforates  the  posterior  ligament,  and  is  distributed  to  the  synovial  membrane. 
It  gives  filaments  to  the  artery  in  its  course. 

The  Accessory  Obturator  Nerve  (Fig.  417)  is  not  constantly  present.  It  is  of 
small  size,  and  arises  by  separate  filaments  from  the  third  and  fourth  lumbar  nerves. 
It  descends  along  the  inner  border  of  the  Psoas  muscle,  crosses  the  ascending  ramus 
of  the  os  pubis,  and  passes  under  the  outer  border  of  the  Pectineus  muscle,  where 
it  divides  into  numerous  branches.  One  of  these  supplies  the  Pectineus,  pene- 
trating its  under  surface ;  another  is  distributed  to  the  hip-joint ;  while  a  third 
communicates  with  the  anterior  branch  of  the  obturator  nerve.  "When  this  nerve 
is  absent  the  hip-joint  receives  two  branches  from  the  obturator  nerve.  Occasion- 
ally it  is  very  small,  and  becomes  lost  in  the  capsule  of  the  hip-joint. 

The  Anterior  Crural  Nerve  (Figs.  417,  419)  is  the  largest  branch  of  the  lumbar 
plexus.  It  supplies  muscular  branches  to  the  Iliacus,  Pectineus,  and  ail  the 
muscles  on  the  front  of  the  thigh,  excepting  the  Tensor  fasciae  femoris ;  cutaneous 
filaments  to  the  front  and  inner  side  of  the  thigh,  and  to  the  leg  and  foot ;  and 
articular  branches  to  the  hip  and  knee.  It  arises  from  the  second,  third,  and  fourth 
lumbar  nerves.  It  descends  through  the  fibres  of  the  Psoas  muscle,  emerging  from 
it  at  the  lower  part  of  its  outer  border,  and  passes  down  between  it  and  the  Iliacus, 
and  beneath  Poupart's  ligament,  into  the  thigh,  where  it  becomes  someAvhat  flat- 
tened, and  divides  into  an  anterior  and  a  posterior  part.  Under  Poupart's  liga- 
ment it  is  separated  from  the  femoral  artery  by  a  portion  of  the  Psoas  muscle,  and 
lies  beneath  the  iliac  fascia. 

Within  the  abdomen  the  anterior  crural  nerve  gives  off  from  its  outer  side  some 
small  branches  to  the  Iliacus,  and  a  branch  to  the  femoral  artery  which  is  distrib- 
uted upon  the  upper  part  of  that  vessel.  The  origin  of  this  branch  varies  :  it 
occasionally  arises  higher  than  usual,  or  it  may  arise  lower  down  in  the  thigh. 

External  to  the  pelvis  the  following  branches  are  given  off : 


From  the  Anterior  Division. 
Middle  cutaneous. 
Internal  cutaneous. 
Muscular. 


From  the  Posterior  Division. 

Long  saphenous. 

Muscular. 
Articular. 


The  middle  cutaneous  nerve  (Fig.  418)  pierces  the  fascia  lata  (generally  the 
Sartorius  also)  about  three  inches  below  Pouparts  ligament,  and  divides  into  two 
branches,  which  descend  in  immediate  proximity  along  the  fore  part  of  the  thigh, 
to  supply  the  integument  as  low  as  the  front  of  the  knee,  where  it  communicates 
with  the  internal  cutaneous  and  the  patellar  branch  of  the  internal  saphenous 
nerve,  to  form  the  patellar  plexus.  In  the  upper  part  of  the  thigh  the  outer 
division  of  the  middle  cutaneous  communicates  with  the  crural  branch  of  the 
genito-crural  nerve. 

The  internal  cutaneous  nerve  passes  obliquely  across  the  upper  part  of  the 
sheath  of  the  femoral  artery,  and  divides  in  front  or  at  the  inner  side  of  that  vessel 
into  two  branches,  anterior  and  posterior  or  internal. 

The  anterior  branch  runs  downward  on  the  Sartorius,  perforates  the  fascia  lata 
at  the  lower  third  of  the  thigh,  and  divides  into  two  branches,  one  of  which 
supplies  the  integument  as  low  down  as  the  inner  side  of  the  knee  ;  the  other 
crosses  to  the  outer  side  of  the  patella,  communicating  in  its  course  with  the 
nervus  cutaneus  patellae,  a  branch   of  the  internal  .saphenous  nerve. 

The  posterior  or  internal  branch  descends  along  the  inner  border  of  the 
Sartorius  muscle  to  the  knee,  where  it  pierces  the  fascia  lata,  communicates  with 


AC  THE   LUMBAR    PLEXUS.  787 

// 

the  long  saphenoaS  nerve,  and  gives  off  several  cutaneous  branches.  The  nerve 
then  passes  clown  the  inner  side  of  the  leg,  to  the  integument  of  which  it  is 
distributed.  This  nerve,  beneath  the  fascia  lata,  at  the  lower  border  of  the 
Adductor  lonJiS,  joins  in  a  plexiform  network  by  uniting  with  branches  of  the 
long  saphenrj  Is  and  obturator  nerves  (Fig.  419).  When  the  communicating  branch 
from  the  ol  :  irator  nerve  is  large  and  continued  to  the  integument  of  the  leg,  the 
inner  branch  of  the  internal  cutaneous  is  small  and  terminates  at  the  plexus, 
occasionally  giving  off  a  few  cutaneous  filaments. 

The  internal  cutaneous  nerve,  before  dividing,  gives  off  a  few  filaments,  which 
pierce  the  fascia  lata,  to  supply  the  integument  of  the  inner  side  of  the  thigh, 
accompanying  the  long  saphenous  vein.  One  of  these  filaments  passes  through 
the  saphenous  opening ;  a  second  becomes  subcutaneous  about  the  middle  of  the 
thigh ;  and  a  third  pierces  the  fascia  at  its  lower  third. 

Muscular  Branches  of  the  Anterior  Division. — The  nerve  to  the  Pectineus  is 
often  duplicated ;  it  arises  from  the  anterior  crural  immediately  below  Poupart's  liga- 
ment, and  passes  inward  behind  the  femoral  sheath  to  enter  the  anterior  surface  of 
the  muscle.     The  nerve  to  the  Sartorius  arises  in  common  with  the  middle  cutaneous. 

The  long  or  internal  saphenous  nerve  is  the  largest  of  the  cutaneous  branches 
of  the  anterior  crural.  It  approaches  the  femoral  artery  where  this  vessel  passes 
beneath  the  Sartorius,  and  lies  in  front  of  it,  beneath  the  aponeurotic  covering  of 
Hunter's  canal,  as  far  as  the  opening  in  the  lower  part  of  the  Adductor  magnus. 
It  then  quits  the  artery,  and  descends  vertically  along  the  inner  side  of  the  knee, 
beneath  the  Sartorius,  pierces  the  fascia  lata  opposite  the  interval  between  the 
tendons  of  the  Sartorius  and  Gracilis,  and  becomes  subcutaneous.  The  nerve 
then  passes  along  the  inner  side  of  the  leg,  accompanied  by  the  internal  saphenous 
vein,  descends  behind  the  internal  border  of  the  tibia,  and,  at  the  lower  third  of 
the  leg  divides  into  two  branches :  one  continues  its  course  along  the  margin  of 
the  tibia,  terminating  at  the  inner  ankle ;  the  other  passes  in  front  of  the  ankle, 
and  is  distributed  to  the  integument  along  the  inner  side  of  the  foot,  as  far  as  the 
great  toe,  communicating  with  the  internal  branch  of  the  musculocutaneous  nerve. 

Branches. — The  long  saphenous  nerve  about  the  middle  of  the  thigh  gives  off  a 
communicating  branch  which  joins  the  plexus  formed  by  the  obturator  and  internal 
cutaneous  nerves. 

At  the  inner  side  of  the  knee  it  gives  off  a  large  patellar  branch  (nefvus 
cutaneus  patellce)  which  pierces  the  Sartorius  and  fascia  lata,  and  is  distributed  to 
the  integument  in  front  of  the  patella.  This  nerve  communicates  above  the  knee 
with  the  anterior  branch  of  the  internal  cutaneous  and  with  the  middle  cutaneous  ; 
below  the  knee,  with  other  branches  of  the  long  saphenous  ;  and  on  the  outer  side 
of  the  joint,  with  branches  of  the  external  cutaneous  nerve,  forming  a  plexiform 
network,  the  plexus  patella?.  The  cutaneous  nerve  of  the  patella  is  occasionally 
small,  and  terminates  by  joining  the  internal  cutaneous,  which  supplies  its  place 
in  front  of  the  knee. 

Below  the  knee  the  branches  of  the  long  saphenous  nerve  are  distributed  to  the 
integument  of  the  front  and  inner  side  of  the  leg,  communicating  with  the  cutaneous 
branches  from  the  internal  cutaneous  or  from  the  obturator  nerve. 

The  muscular  branches  of  the  posterior  division  supply  the  four  parts  of  the 
Quadriceps  extensor  muscle. 

The  branch  to  the  Rectus  muscle  enters  its  under  surface  high  up,  sending  off 
a  small  filament  to  the  hip-joint. 

The  branch  to  the  Vastus  externus,  of  large  size,  follows  the  course  of  the 
descending  branch  of  the  external  circumflex  artery  to  the  lower  part  of  the  muscle. 
It  gives  off  an  articular  filament  to  the  knee-joint. 

The  branch  to  the  Vastus  internus    is   a  long  branch  which  runs  down  on  the 

© 

outer  side  of  the  femoral  vessels  in  company  with  the  internal  saphenous  nerve  for 
its  upper  part.  It  enters  the  muscle  about  its  middle,  and  gives  off  a  filament 
which  can  usually  be  traced  downward  on  the  surface  of  the  muscle  to  the  knee- 
joint. 


788 


THE  NERVOUS  SYSTEM. 


The  branch  to  the  Orureus  enters  the  muscle  on  its  an  W.'^r  surface  about 
the  middle  of  the  thigh,  and  sends  a  filament  through  the  mw|hle  to  the  Sub- 
crureus  and  the  knee-joint. 

The  articular  branch  to  the  hip-joint  is  derived  from  the  nervy  to  the  Rectus. 

The  articular  Ranches  to  the  knee-joint  are  three  in  number.,  '  hie,  a  long, 
slender  filament,  is  derived  from  the  nerve  to  the  Vastus  externum  i  penetrates 
the  capsular  ligament  of  the  joint  on  its  anterior  aspect.  Another  is  derived  from 
the  nerve  to  the  Vastus  internus.  It  can  usually  be  traced  downward'  on  the  sur- 
face of  this  muscle  to  near  the  joint;  it  then  penetrates  the  muscular  fibres,  and 
accompanies  the  deep  branch  of  the  anastomotica  magna  artery,  pierces  the  capsular 
lio-ament  of  the  joint  on  its  inner  side,  and  supplies  the  synovial  membrane.  The 
third  branch  is  derived  from  the  nerve  to  the  Crureus. 

THE    SACRAL    AND    COCCYGEAL    NERVES. 

The  sacral  nerves  are  five  in  number  on  each  side.  The  four  upper  ones  pass 
from  the  sacral  canal  through  the  sacral  foramina ;  the  fifth  through  the  foramen 
between  the  sacrum  and  coccyx. 

The  roots  of  the  upper  sacral  nerves  are  the  largest  of  all  the  spinal  nerves ; 
while  those  of  the  lowest  sacral  and  coccygeal  nerve  are  the  smallest.  They  are 
longer  than  those  of  any  of  the  other  spinal  nerves,  on  account  of  the  spinal  cord 
not  extending  beyond  the  first  lumbar  vertebra.  From  their  great  length,  and  the 
appearance  they  present  in  connection  with  their  attachment  to  the  spinal  cord, 
the  roots  of  origin  of  these  nerves   are  called  collectively  the  cauda  equina. 

Each  sacral  and  coccygeal  nerve  separates  into  two  divisions,  posterior  and 
anterior. 

The  posterior  divisions  of  the  sacral  nerves  (Fig.  420)  are  small,  diminish  in 


Fig.  420.— The  posterior  sacral  nerves. 

size  from  above   downward,  and  emerge,  except  the  last,  from  the  sacral  canal 
by  the  posterior  sacral  foramina. 


THE   SACRAL    AND    COCCYGEAL    NERVES. 


789 


The  three  upper  ones  are  covered,  at  their  exit  from  the  sacral  canal,  by  the 
Multifidus  spina,  and  divide  into  internal  and  external  branches. 

The  internal  branches  are  small,  and  supply  the  Multifidus  spinse. 

The  external  branches  join  with  one  another,  and  with  the  last  lumbar  and 
fourth  sacral  nerves,  in  the  form  of  loops  on  the  posterior  surface  of  the  sacrum. 
From  these  loops  branches  pass  to  the  outer  surface  of  the  great  sacro-sciatic 
ligament,  where  they  form  a  second  series  of  loops  beneath  the  Gluteus  maximus. 
Cutaneous  branches  from  this  second  series  of  loops,  usually  two  or  three  in 
number,  pierce  the  Gluteus  maximus  along  a  line  drawn  from  the  posterior 
superior  spine  of  the  ilium  to  the  tip  of  the  coccyx.  They  supply  the  integument 
over  the  posterior  part  of  the  gluteal  region. 

The  posterior  divisions  of  the  two  lower  sacral  nerves  are  situated  below  the 
Multifidus  spinse.  They  are  of  small  size,  and  do  not  divide  into  internal  and 
external  branches,  but  join  with  each  other,  and  with  the  coccygeal  nerve,  so  as 
to  form  loops  on  the  back  of  the  sacrum,  filaments  from  which  supply  the  Extensor 
coccygis  and  the  integument  over  the  coccyx. 

The  coccygeal  nerve  divides  into  its  anterior  and  posterior  divisions  in  the  spinal 
canal.  The  posterior  division  is  the  smaller.  It  does  not  divide,  but  receives,  as 
already  mentioned,  a  communicating  branch  from  the  last  sacral,  and  is  lost  in  the 
integument  over  the  back  of  the  coccyx. 

The  anterior  divisions  of  the  sacral  nerves  diminish  in  size  from  above  down- 


Femoral  ar 


Coccygeal. 
'Br.  to1  Br.  to 

LEVATOR  ANI.    SPHINCTER  ANI 

Fig.  421.— Side  view  of  pelvis,  showing  sacral  nerves. 

ward.  The  four  upper  ones  emerge  from  the  anterior  sacral  foramina :  the  ante- 
rior division  of  the  fifth,  after  emerging  from  the  spinal  canal  through  its  termi- 
nal opening,  curves  forward  between  the  sacrum  and  the  coccyx.  All  the  anterior 
sacral  nerves  communicate  Avith  the  sacral  ganglia  of  the  sympathetic  at  their 
exit  from  the  sacral  foramina.  The  first  nerve,  of  large  size,  unites  with  the 
lumbosacral  cord,  formed  by  the  fifth  lumbar,  and  a  branch  from  the  fourth  lum- 


790  THE  NERVOUS  SYSTEM. 

bar.  The  second,  equal  in  size  to  the  preceding,  and  the  third,  about  one-fourth 
the  size  of  the  second,  unite  with  this  trunk,  and  form,  with  a  small  fasciculus 
from  the  fourth,  the  sacral  plexus,  a  visceral  branch  being  given  off  from  the 
third  nerve  to  the  bladder. 

The  fourth  anterior  sacral  nerve  sends  a  branch  to  join  the  sacral  plexus.  The 
remaining  portion  of  the  nerve  divides  into  visceral  and  muscular  branches,  and 
a  communicating  filament  descends  to  join  the  fifth  sacral  nerve.  The  visceral 
branches  are  distributed  to  the  viscera  of  the  pelvis,  communicating  with  the 
sympathetic  nerve.  These  branches  ascend  upon  the  rectum  and  bladder,  and 
in  the  female  upon  the  vagina,  communicating  with  branches  of  the  sympathetic 
from  the  pelvic  plexus.  The  muscular  branches  are  distributed  to  the  Levator 
ani,  Coccygeus,  and  Sphincter  ani.  The  branch  to  the  Sphincter  ani  pierces  the 
Levator  ani,  so  as  to  reach  the  ischio-rectal  fossa,  where  it  is  found  lying  in  front 
of  the  coccyx.  Cutaneous  filaments  arise  from  the  latter  branch,  which  supply 
the  integument  between  the  anus  and  coccyx.  Another  cutaneous  branch  is  fre- 
quently given  off  from  this  nerve,  though  sometimes  from  the  pudic  (Schwalbe). 
It  perforates  the  great  sacro-sciatic  ligament,  and,  winding  round  the  lower  bor- 
der of  the  Gluteus  maximus,  supplies  the  skin  over  the  lower  and  inner  part  of 
this  muscle. 

The  fifth  anterior  sacral  nerve,  after  passing  from  the  lower  end  of  the  sacral 
canal,  curves  forward  through  the  fifth  sacral  foramen,  formed  between  the  lower 
part  of  the  sacrum  and  the  transverse  process  of  the  first  piece  of  the  coccyx.  It 
pierces  the  Coccygeus  muscle,  and  descends  upon  its  anterior  surface  to  near  the 
tip  of  the  coccyx,  where  it  again  perforate*s  the  muscle,  to  be  distributed  to  the 
integument  over  the  back  part  and  side  of  the  coccyx.  This  nerve  communicates 
above  with  the  fourth  sacral  and  below  with  the  coccygeal  nerve,  and  supplies  the 
Coccygeus  muscle. 

The  anterior  division  of  the  coccygeal  nerve  is  a  delicate  filament  which  escapes 
at  the  termination  of  the  sacral  canal ;  it  passes  downward  behind  the  rudiment- 
ary transverse  process  of  the  first  piece  of  the  coccyx,  and  curves  forward  through 
the  notch  between  the  first  and  second  pieces,  piercing  the  Coccygeus  muscle,  and 
descending  on  its  anterior  surface  to  near  the  tip  of  the  coccyx,  where  it  again 
pierces  the  muscle,  to  be  distributed  to  the  integument  over  the  back  part  and  side 
of  the  coccyx.  It  is  joined  by  a  branch  from  the  fifth  anterior  sacral  as  it 
descends  on  the  surface  of  the  Coccygeus  muscle. 


The  Sacral  Plexus  (Fig.  421). 

The  sacral  plexus  is  formed  by  the  lumbo-sacral  cord,  the  anterior  divisions  of 
the  three  upper  sacral  nerves,  and  part  of  that  of  the  fourth.  These  nerves  pro- 
ceed in  different  directions  :  the  upper  ones  obliquely  downward  and  outward,  the 
lower  ones  nearly  horizontally,  and  they  all  unite  into  two  cords :  an  upper  and 
larger,  which  is  formed  by  the  lumbo-sacral  cord  with  the  first,  second,  and  the 
greater  part  of  the  third  sacral  nerves ;  and  a  lower  and  smaller,  formed  by  the 
remainder  of  the  third,  with  a  portion  of  the  fourth  sacral  nerve.  The  upper 
cord  is  prolonged  into  the  great  sciatic  nerve  and  the  lower  into  the  pudic.  Fre- 
quently a  small  filament  is  given  off  from  the  second  sacral  nerve  to  "join  the 
lower  cord. 

The  sacral  plexus  is  triangular  in  form,  its  base  corresponding  with  the 
exit  of  the  nerves  from  the  sacrum,'  its  apex  with  the  lower  part  of  the  great 
sacro-sciatic  foramen.  It  rests  upon  the  anterior  surface  of  the  Pyriformis, 
and  is  covered  in  front  by  the  pelvic  fascia,  which  separates  it  from  the  sciatic 
and  pudic  branches  of  the  internal  iliac  artery  and  from  the  viscera  of  the 
pelvis. 

The  branches  of  the  sacral  plexus  are : 


Tj 


\E  SACRAL   PLEXUS.  793 

branches  {descending)  are  numerous  filaments,  derived 

p  it      ves,  which  are  distributed  to  the  back,  inner,  and  outer 

skin  covering  the  popliteal  space,  and  to  the  upper  part 

caneous  Nerve  usually  arises  from  the  second  and  third  sacral 
all  size.  It  is  continued  backward  through  the  great  sacro- 
ad,  winding  round  the  lower  border  of  the  Gluteus  maximus, 
The  Muscularjm(Jnt  coverjng  the  inner  and  lower  part  of  that  muscle. 
Gemelli,  and  th^rve>  -s  tne  direct  continuation  of  the  lower  cord  of  the  sacral 
the  upper  twoyes  itg  fiDres  from  the  third  and  fourth  sacral  nerves,  and  frequently 
Obturator  int^  ^o.  It  leaves  the  pelvis  through  the  great  sacro-sciatic  foramen, 
nerves  :  it  Priformis.  It  then  crosses  the  spine  of  the  ischium,  and  re-enters  the 
the  Pyrifog'  k  t^e  \essev  sacro-sciatic  foramen.  It  accompanies  the  pudic  vessels 
the  lesser  a  forwar{l  along  the  outer  wall  of  the  ischio-rectal  fossa,  being  contained 
the  branitll  0f  tne  obturator  fascia,  termed  AlcocJc's  canal,  and  divides  into  two 
rator  intkranches,  the  perineal  nerve  and  the  dorsal  nerve  of  the  penis  or  clitoris, 
small  br?  ^vision  it  gives  off  the  inferior  hemorrhoidal  nerve. 
uPPer  ^inferior  hemorrhoidal  nerve  is  occasionally  derived  separately  from  the 
the  Pyriexus.  It  passes  across  the  ischio-rectal  fossa,  with  its  accompanying 
tendon  cQwar(j  tne  jower  en(j  0f  the  rectum,  and  is  distributed  to  the  Sphincter 
rior  surlnus  an(j  to  the  integument  round  the  anus.  Branches  of  this  nerve  corn- 
branch  i  with  the  inferior  pudendal  and  superficial  perineal  nerves  at  the  fore  part 

Ine  rineuni. 
sacral  Perineal  nerve,  the  inferior  and  larger  of  the  two  terminal  branches  of  the 
pelvis  th  situated  below  the  pudic  artery.     It  accompanies  the  superficial  perineal 
paniedn  t^e  perineum,  dividing  into  cutaneous  and  muscular  branches. 

Tj.e  cutaneous  branches  (superficial  perineal)  are  two  in  number,  posterior  and 
suPIior.  The  posterior  or  external  branch  pierces  the  base  of  the  triangular 
.  ment  of  the  urethra,  and  passes  forward  along  the  outer  side  of  the  urethral 
d:ngle  in  company  with  the  superficial  perineal  artery;  it  is  distributed  to  the 
fen  of  the  scrotum.  It  communicates  with  the  inferior  hemorrhoidal,  the  inferior 
lendal,  and  the  other  superficial  perineal  nerve.  The  anterior  or  internal  branch 
sa>  pierces  the  base  of  the  triangular  ligament,  and  passes  forward  nearer  to  the 
It:.dle  line,  to  be  distributed  to  the  inner  and  back  part  of  the  scrotum.  Both 
mi<e  nerves  supply  the  labia  majora  in  the  female. 

muThe  muscular  branches  are  distributed  to  the  Transversa  perinsei,  Accelerator 
ae,  Erector  penis,  and  Compressor  urethras.  A  distinct  branch  is  given  off 
an(  the  nerve  to  the  Accelerator  urinse,  which  pierces  this  muscle,  and  supplies 
^corpus  spongiosum,  ending  in  the  mucous  membrane  of  the  urethra.  This 
issu,  nerve  to  the  bulb. 

mus,he  dorsal  nerve  of  the  penis  is  the  deepest  division  of  the  pudic  nerve ;  it 
low®ipanies  the  pudic  artery  along  the  ramus  of  the  ischium  ;  it  then  runs  forward 
fasci  the  inner  margin  0f  the  ramus  of  the  os  pubis,  between  the  superficial  and 
regiclayers  of  the  triangular  ligament.  Piercing  the  superficial  layer  it  gives  a 
tne  e  to  the  corpus  cavernosum,  and  passes,  forward,  in  company  with  the  dorsal 
commup  tne  penis,  between  the  layers  of  the  suspensory  ligament,  on  to  the  dorsum 
TllSnis,  along  which  it  is  carried  as  far  as  the  glans,  to  which  it  is  distributed, 
follows^  femaie  the  dorsal  nerve  is  very  small,  and  supplies  the  clitoris. 

Tn£lreat  sciatic  nerve  (Fig.  423)  supplies  nearly  the  whole  of  the  integument 
which  t^  the  muscies  of  the  back  of  the  thigh,  and  those  of  the  leg  and  foot.  It 
integum'gest  nervous  Cord  in  the  body,  measuring  three-quarters  of  an  inch  m 
Thetnd  is  the  continuation  of  the  upper  division  of  the  sacral  plexus.  It 
inner  si<t  of  tne  pelvis  tjSl,(  n  tne  great  sacro-sciatic  foramen,  below  the  Pyri- 
the  W\scle.  It  descends  .veen  the  trochanter  major  and  tuberosity  of  the 
lata,  an<jong  tne  Dack  part  ot  the  thigh,  to  about  its  lower  third,  where  it  divides 
tributecjargg  DraIlch  ernal  and  external  popliteal  nerves. 

commu  ^vision  may  e  at  any  point  between  the  sacral  plexus  and  the 


790  THE  NERVVUS  SYSTIM, 

bar.      The  second,  equal  in  size  to  the  preceding,  and 
the  size  of  the  second,  unite  with  this  trunk,  and  for. 
from  the  fourth,  the  sacral  'plexus,  a  visceral  branch 
third  nerve  to  the  bladder. 

The  fourth  anterior  sacral  nerve  sends  a  branch  to  join 
remaining  portion  of  the  nerve  divides  into  visceral  and  mii 
a  communicating  filament  descends  to  join  the  fifth  sacral 
branches  are  distributed  to  the  viscera  of  the  pelvis,  commu 
sympathetic  nerve.  These  branches  ascend  upon  the  rectum  Sll^r 
in  the  female  upon  the  vagina,  communicating  with  branches  of" 
from  the  pelvic  plexus.  The  muscular  branches  are  distributed  W 
ani,  Coccygeus,  and  Sphincter  ani.  The  branch  to  the  Sphincter  af<» 
Levator  ani,  so  as  to  reach  the  ischio-rectal  fossa,  where  it  is  found  ly^ 
of  the  coccyx.  Cutaneous  filaments  arise  from  the  latter  branch,  whi 
the  integument  between  the  anus  and  coccyx.  Another  cutaneous  braiJ| 
quently  given  off  from  this  nerve,  though  sometimes  from  the  pudic  (Sc 
It  perforates  the  great  sacro-sciatic  ligament,  and,  winding  round  the  lc 
der  of  the  Gluteus  maximus,  supplies  the  skin  over  the  lower  and  innei 
this  muscle. 

The  fifth  anterior  sacral  nerve,  after  passing  from  the  lower  end  of  ti 
canal,  curves  forward  through  the  fifth  sacral  foramen,  formed  between  t 
part  of  the  sacrum  and  the  transverse  process  of  the  first  piece  of  the  coc 
pierces  the  Coccygeus  muscle,  and  descends  upon  its  anterior  surface  to 
tip  of  the  coccyx,  where  it  again  perforates  the  muscle,  to  be  distribute 
integument  over  the  back  part  and  side  of  the  coccyx.  This  nerve  comn 
above  with  the  fourth  sacral  and  below  with  the  coccygeal  nerve,  and  sup 
Coccygeus  muscle. 

The  anterior  division  of  the  coccygeal  nerve  is  a  delicate  filament  which  esv 
at  the  termination  of  the  sacral  canal ;  it  passes  downward  behind  the  rudin 
ary  transverse  process  of  the  first  piece  of  the  coccyx,  and  curves  forward  throu 
the  notch  between  the  first  and  second  pieces,  piercing  the  Coccygeus  muscle,  s 
descending  on  its  anterior  surface  to  near  the  tip  of  the  coccyx,  where  it  ag* 
pierces  the  muscle,  to  be  distributed  to  the  integument  over  the  back  part  and  s 
of  the  coccyx.  It  is  joined  by  a  branch  from  the  fifth  anterior  sacral  as 
descends  on  the  surface  of  the  Coccygeus  muscle. 


The  Sacral  Plexus  (Fig.  421). 

The  sacral  plexus  is  formed  by  the  lumbo-sacral  cord,  the  anterior  division 
the  three  upper  sacral  nerves,  and  part  of  that  of  the  fourth.     These  nerves 
ceed  in  different  directions:  the  upper  ones  obliquely  downward  and  outwarc 
lower  ones  nearly  horizontally,  and  they  all  unite  into  two  cords  :  an  uppei 
larger,  which   is  formed  by  the  lumbo-sacral   cord  with  the  first,  second,  an 
greater  part  of  the  third  sacral  nerves ;   and   a  lower  and  smaller,  formed  * 
remainder  of  the   third,  with  a   portion  of  the  fourth   sacral  nerve.     Thr 
cord  is  prolonged  into  the  great  sciatic  nerve  and  the  lower  into  the  pudi< 
quently  a  small   filament  is  given  off  from    the  second  sacral  nerve  to  '; 
lower  cord. 

The    sacral   plexus    is    triangular    in    form,  its   base    corresponding 
exit  of  the  nerves  from  the  sacrum,'  its   apex  with  the  lower  part  of  ' 
sacro-sciatic  foramen.      It  rests  upon    the    anterior  surface    of   the    P; 
and  is  covered  in  front  by  the  pelvic  fascia,  which  separates  it  from  tl 
and   pudic   branches  of  the   internal   iliac   artery  and  from  the  viscer    . 

n    . r  J  ;enor 

pelvis. 

The  branches  of  the  sacral  plexus  are  :  L,   . 

1  Mieir  nor- 


THE  SACRAL   PLEXUS.  793 

The  femoral  cutaneous  branches  {descending)  are  numerous  filaments,  derived 
from  both  sides  of  the  nerves,  which  are  distributed  to  the  back,  inner,  and  outer 
sides  of  the  thigh,  to  the  skin  covering  the  popliteal  space,  and  to  the  upper  part 
of  the  leg. 

The  Perforating  Cutaneous  Nerve  usually  arises  from  the  second  and  third  sacral 
nerves,  and  is  of  small  size.  It  is  continued  backward  through  the  great  sacro- 
sciatic  ligament,  and,  winding  round  the  lower  border  of  the  Gluteus  maximus, 
supplies  the  integument  covering  the  inner  and  lower  part  of  that  muscle. 

The  Pudic  Nerve,  is  the  direct  continuation  of  the  lower  cord  of  the  sacral 
plexus,  and  derives  its  fibres  from  the  third  and  fourth  sacral  nerves,  and  frequently 
from  the  second  also.  It  leaves  the  pelvis  through  the  great  sacro-sciatic  foramen, 
below  the  Pvriformis.  It  then  crosses  the  spine  of  the  ischium,  and  re-enters  the 
pelvis  through  the  lesser  sacro-sciatic  foramen.  It  accompanies  the  pudic  vessels 
upward  and  forward  along  the  outer  Avail  of  the  ischio-rectal  fossa,  being  contained 
in  a  sheath  of  the  obturator  fascia,  termed  Alcock's  canal,  and  divides  into  two 
terminal  branches,  the  perineal  nerve  and  the  dorsal  nerve  of  the  penis  or  clitoris. 
Before  its  division  it  gives  off  the  inferior  hemorrhoidal  nerve. 

The  inferior  hemorrhoidal  nerve  is  occasionally  derived  separately  from  the 
sacral  plexus.  It  passes  across  the  ischio-rectal  fossa,  with  its  accompanying 
vessels,  toward  the  lower  end  of  the  rectum,  and  is  distributed  to  the  Sphincter 
ani  externus  and  to  the  integument  round  the  anus.  Branches  of  this  nerve  com- 
municate with  the  inferior  pudendal  and  superficial  perineal  nerves  at  the  fore  part 
of  the  perineum. 

The  perineal  nerve,  the  inferior  and  larger  of  the  two  terminal  branches  of  the 
pudic,  is  situated  below  the  pudic  artery.  It  accompanies  the  superficial  perineal 
artery  in  the  perineum,  dividing  into  cutaneous  and  muscular  branches. 

The  cutaneous  branches  (superficial  perineal)  are  two  in  number,  posterior  and 
anterior.  The  posterior  or  external  branch  pierces  the  base  of  the  triangular 
ligament  of  the  urethra,  and  passes  forward  along  the  outer  side  of  the  urethral 
triangle  in  company  with  the  superficial  perineal  artery  ;  it  is  distributed  to  the 
skin  of  the  scrotum.  It  communicates  with  the  inferior  hemorrhoidal,  the  inferior 
pudendal,  and  the  other  superficial  perineal  nerve.  The  anterior  or  internal  branch 
also  pierces  the  base  of  the  triangular  ligament,  and  passes  forward  nearer  to  the 
middle  line,  to  be  distributed  to  the  inner  and  back  part  of  the  scrotum.  Both 
these  nerves  supply  the  labia  majora  in  the  female. 

The  muscular  branches  are  distributed  to  the  Transversus  perinsei,  Accelerator 
urinse,  Erector  penis,. and  Compressor  urethras.  A  distinct  branch  is  given  off 
from  the  nerve  to  the  Accelerator  urinse,  which  pierces  this  muscle,  and  supplies 
the  corpus  spongiosum,  ending  in  the  mucous  membrane  of  the  urethra.  This 
is  the  nerve  to  the  bulb. 

The  dorsal  nerve  of  the  penis  is  the  deepest  division  of  the  pudic  nerve;  it 
accompanies  the  pudic  artery  along  the  ramus  of  the  ischium  ;  it  then  runs  forward 
along  the  inner  margin  of  the  ramus  of  the  os  pubis,  between  the  superficial  and 
deep  layers  of  the  triangular  ligament.  Piercing  the  superficial  layer  it  gives  a 
branch  to  the  corpus  cavernosum,  and  passes,  forward,  in  company  with  the  dorsal 
artery  of  the  penis,  between  the  layers  of  the  suspensory  ligament,  on  to  the  dorsum 
of  the  penis,  along  which  it  is  carried  as  far  as  the  glans,  to  which  it  is  distributed. 

In  the  female  the  dorsal  nerve  is  very  small,  and  supplies  the  clitoris. 

The  Great  sciatic  nerve  (Fig.  423)  supplies  nearly  the  whole  of  the  integument 
of  the  leg,  the  muscles  of  the  back  of  the  thigh,  and  those  of  the  leg  and  foot.  It 
is  the  largest  nervous  cord  in  the  body,  measuring  three-quarters  of  an  inch  in 
bi'eadth,  and  is  the  continuation  of  the  upper  division  of  the  sacral  plexus.  It 
passes  out  of  the  pelvis  tl  h  the  great  sacro-sciatic  foramen,  below  the  Pyri- 

formis  muscle.  It  descends  b  .veen  the  trochanter  major  and  tuberosity  of  the 
ischium,  along  the  back  part  ol  the  thigh,  to  about  its  lower  third,  where  it  divides 
into  two  large  branch       r      .     ernal  and  external  popliteal  nerves. 

This  division  may  rake  p      e  at  any  point  between  the  sacral  plexus  and  the 


794  THE   NERVOUS  SYSTEM. 

lower  third  of  the  thigh.  When  the  division  occurs  at  the  plexus,  the  two  nerves 
descend  together  side  by  side  ;  or  they  may  be  separated,  at  their  commencement, 
by  the  interposition  of  part  or  the  whole  of  the  Pyriformis  muscle.  As  the  nerve 
descends  along  the  back  of  the  thigh,  it  rests  upon  the  posterior  surface  of  the 
ischium,  the  nerve  to  the  Quadratus  femoris,  and  the  External  rotator  muscles,  in 
company  with  the  small  sciatic  nerve  and  artery,  being  covered  by  the  Gluteus 
maximus ;  lower  down,  it  lies  upon  the  Adductor  magnus,  and  is  covered  by  the 
long  head  of  the  Biceps. 

The  branches  of  the  nerve,  before  its  division,  are  articular  and  muscular. 

The  articular  branches  arise  from  the  upper  part  of  the  nerve  ;  they  supply  the 
hip-joint,  perforating  the  posterior  part  of  its  fibrous  capsule  posteriorly.  These 
branches'  are  sometimes  derived  from  the  sacral  plexus. 

The  muscular  branches  are  distributed  to  the  flexors  of  the  leg :  viz.,  the 
Biceps,  Semitendinosus,  and  Semimembranosus,  and  a  branch  to  the  Adductor 
magnus.      These  branches  are  given  off  beneath  the  Biceps  muscle. 

The  Internal  Popliteal  Nerve,  the  larger  of  the  two  terminal  branches  of  the 
great  sciatic,  descends  along  the  back  part  of  the  thigh,  through  the  middle  of  the 
popliteal  space,  to  the  lower  part  of  the  Popliteus  muscle,  where  it  passes  with  the 
artery  beneath  the  arch  of  the  Soleus  and  becomes  the  posterior  tibial.  It  is  over- 
lapped by  the  hamstring  muscles  above,  and  then  becomes  more  superficial,  and 
lies  to  the  outer  side  of,  and  some  distance  from,  the  popliteal  vessels ;  opposite 
the  knee-joint  it  is  in  close  relation  with  the  vessels,  and  crosses  to  the  inner  side  of 
the  artery.     Below,  it  is  overlapped  by  the  Gastrocnemius. 

The  branches  of  this  nerve  are — articular,  muscular,  and  a  cutaneous  branch, 
the  communicans  tibialis  nerve. 

The  articular  branches,  usually  three  in  number,  supply  the  knee-joint :  two  of 
these  branches  accompany  the  superior  and  inferior  internal  articular  arteries,  and 
a  third,  the  azygos  articular  artery. 

The  muscular  branches,  four  or  five  in  number,  arise  from  the  nerve  as  it  lies 
between  the  two  heads  of  the  Gastrocnemius  muscle ;  they  supply  that  muscle, 
the  Plantaris,  Soleus,  and  Popliteus.  The  filaments  which  supply  the  Popliteus 
turn  round  its  lower  border  and  are  distributed  to  its  deep  surface. 

The  communicayis  tibialis  descends  between  the  two  heads  of  the  Gastrocnemius 
muscle,  and  about  the  middle  of  the  back  of  the  leg  pierces  the  deep  fascia, 
and  joins  a  communicating  branch  {communicans  peronei)  from  the  external 
popliteal  nerve  to  form  the  external  or  short  saphenous  (Fig.  422).  The  exter- 
nal saphenous  nerve,  formed  by  the  communicating  branches  of  the  internal  and 
external  popliteal  nerves,  passes  downward  and  outward  near  the  outer  margin  of 
the  tendo  Achillis,  lying  close  to  the  external  saphenous  vein,  to  the  interval 
between  the  external  malleolus  and  the  os  calcis,  It  winds  round  the  outer  mal- 
leolus, and  is  distributed  to  the  integument  along  the  outer  side  of  th,e  foot  and 
little  toe,  communicating  on  the  dorsum  of  the  foot  with  the  musculo-cutaneous 
nerve.     In   the   leg  its   branches  communicate  with  those  of  the  small  sciatic. 

The  Posterior  Tibial  Nerve  (Fig.  423)  commences  at  the  lower  border  of  the 
Popliteus  muscle,  and  passes  along  the  back  part  of  the  leg  with  the  posterior 
tibial  vessels  to  the  interval  between  the  inner  malleolus  and  the  heel,  where  it 
divides  into  the  external  and  internal  plantar  nerves.  It  lies  upon  the  deep 
muscles  of  the  leg,  and  is  covered  in  the  upper  part  by  the  muscles  of  the  calf, 
lower  down  by  the  skin  and  fascia,  In  the  upper  part  of  its  course  it  lies  to  the 
inner  side  of  the  posterior  tibial  artery,  but  it  soon  crosses  that  vessel,  and  lies  to 
its  outer  side  as  far  as  the  ankle.  In  the  lower  third  of  the  leg  it  is  placed 
parallel  with  the  inner  margin  of  the  tendo  Achillis. 

The  branches  of  the  posterior  tibial  nerve  are  muscular,  calcaneo-plantar,  and 
articular. 

The  muscular  branches  arise  either  separately  or  by  a  common  trui  *  om  the 
upper  part  of  the  nerve.  They  supply  the  Soleus,  Tibialis  posticus,  Fie  r  longus 
digitorum,  and  Flexor  longus  hallv.cis  muscles  ;  the  branch  to  the  k         muscle 


THE   PLANTAR    NERVES. 


795 


Internal 
plantar.' 


External 
plantar. 


accompanying  the  peroneal  artery.  The  branch  to  the  Soleus  enters  its  deep 
surface,  while  the  branch  which  this  muscle  receives  from  the  internal  popliteal 
enters  its  superficial  aspect. 

The  calcaneo-plantar  (internal  calcanean)  branch  perforates  the  internal 
annular  ligament,  and  supplies  the  integument  of  the  heel  and  inner  side  of  the 
sole  of  the  foot. 

The  articular  branch  is  given  off  just  above  the  bifurcation  of  the  nerve  and 
supplies  the  ankle-joint. 

The  Internal  Plantar  Nerve  (Fig.  424),  the  larger  of  the  two  terminal  branches 
of  the  posterior  tibial,  accompanies  the  internal  plantar  artery  along  the  inner  side 
of  the  foot.  From  its  origin  at  the  inner  ankle  it  passes  beneath  the  Abductor 
hallucis,  and  then  forward  between  this  muscle  and  the  Flexor  brevis  digitorum, 
divides  opposite  the  bases  of  the  metatarsal  bones  into  four  digital  branches,  and 
communicates  with  the  external  plantar  nerve. 

Branches. — In  its  course  the  internal  plantar  nerve  gives  off  cutaneous 
branches,  which  pierce  the  plantar  fascia  and  supply  the  integument  of  the  sole 
of  the  foot ;  muscular  branches,  which  supply  the  Abductor  hallucis  and  Flexor 
brevis  digitorum ;  articular  branches,  to  the  articulations  of  the  tarsus  and  meta- 
tarsus ;  and  four  digital  branches.  The 
three  outer  branches  pass  between  the  divis- 
ions of  the  plantar  fascia  in  the  clefts  be- 
tween the  toes  :  the  first  (innermost)  branch 
becomes  cutaneous  farther  back  between  the 
Adductor  hallucis  and  Flexor  brevis  digi- 
torum. They  are  distributed  in  the  following 
manner :  The  first  supplies  the  inner  border 
of  the  great  toe,  and  sends  a  filament  to  the 
Flexor  brevis  hallucis  muscle  ;  the  second 
bifurcates,  to  supply  the  adjacent  sides  of 
the  great  and  second  toes,  sending  a  filament 
to  the  First  lumbrical  muscle ; 1  the  third 
digital  branch  supplies  the  adjacent  sides  of 
the  second  and  third  toes ;  the  fourth  sup- 
plies the  corresponding  sides  of  the  third  and 
fourth  toes,  and  receives  a  communicating 
branch  from  the  external  plantar  nerve. 
Each  digital  nerve  gives  off  cutaneous  and 
articular  filaments ;  and  opposite  the  last 
phalanx  sends  a  dorsal  branch,  which  sup- 
plies the  structures  around  the  nail,  the  con- 
tinuation of  the  nerve  being  distributed  to 
the  ball  of  the  toe.  It  will  be  observed  that 
the  distribution  of  these  branches  is  precisely 
similar  to  that  of  the  median  nerve  in  the 
hand. 

The  External  Plantar  Nerve,  the  smaller 
of  the  two,  completes  the  nervous  supply  to 

the  structures  of  the  sole  of  Sae  foot,  being  distributed  to  the  little  toe  and  one- 
half  of  the  fourth,  as  well  as  to  most  of  the  deep  muscles,  its  distribution  being 
similar  to  that  of  the  ulnar  in  the  hand.  It  passes  obliquely  forward  with  the  ex- 
ternal plantar  artery  to  the  outer  side  of  the  foot,  lying  between  the  Flexor  brevis 
digitorum  and  Flexor  accessorius,  and  in  the  interval  between  the  former  muscle 
and  Abductor  minimi  digiti  divides  into  a  superficial  and  a  deep  branch.  Before 
its  divisio^jj/t  supplies  the  Flexor  accessorius  and  Abductor  minimi  digiti. 

Tl  merficial  branch  separates  into  two  digital  nerves  :  one,  the  smaller  of 
the  tv>     applies  the  outer  side  of  the  little  toe,  the  Flexor  brevis  minimi  digiti, 

1  See  foot-note,  page  448. 


Deep 
branch. 


Fig.  424.— The  plantar  nerves. 


796  THE   NERVOUS  SYSTEM. 

and  the  two  Interosseous  muscles  of  the  fourth  metatarsal  space  ;  the  other  and 
larger  digital  branch  supplies  the  adjoining  sides  of  the  fourth  and  fifth  toes,  and 
communicates  with  the  internal  plantar  nerve. 

The  deep  or  muscular  branch  accompanies  the  external  plantar  artery  into  the 
deep  part  of  the  sole  of  the  foot,  beneath  the  tendons  of  the  Flexor  muscles  and 
Adductor  obliquus  hallucis,  and  supplies  all  the  Interossei  (except  those  in  the 
fourth  metatarsal  space),  the  three  outer  Lumbricales,  the  Adductor  obliquus  hal- 
lucis, and  the  Adductor  transversus  hallucis. 

The  External  Popliteal  or  Peroneal  Nerve  (Fig.  423),  about  one-half  the  size  of 
the  internal  popliteal,  descends  obliquely  along  the  outer  sides  of  the  popliteal 
space  to  the  head  of  the  fibula,  close  to  the  inner  margin  of  the  Biceps  muscle.  It 
is  easily  felt  beneath  the  skin  behind  the  head  of  the  fibula  at  the  inner  side  of  the 
tendon  of  the  Biceps.  It  passes  between  the  tendon  of  the  Biceps  and  outer  head 
of  the  Gastrocnemius  muscle,  winds  round  the  neck  of  the  fibula,  between  the 
Peroneus  longus  and  the  bone,  and  divides  beneath  the  muscle  into  the  anterior 
tibial  and  musculo-cutaneous  nerves. 

The  branches  of  the  peroneal  nerve,  previous  to  its  division,  are  articular  and 
cutaneous. 

The  articular  branches  are  three  in  number  ;  two  of  these  accompany  the 
superior  and  inferior  external  articular  arteries  to  the  outer  side  of  the  knee.  The 
upper  one  occasionally  arises  from  the  great  sciatic  nerve  before  its  bifurcation. 
The  third  (recurrent)  articular  nerve  is  given  off  at  the  point  of  division  of  the 
peroneal  nerve ;  it  ascends  with  the  anterior  recurrent  tibial  artery  through  the 
Tibialis  anticus  muscle  to  the  front  of  the  knee,  which  it  supplies. 

The  cutaneous  branches,  two  or  three  in  number,  supply  the  integument  along 
the  back  part  and  outer  side  of  the  leg ;  one  of  these,  larger  than  the  rest,  the 
communicans  peronei,  arises  near  the  head  of  the  fibula,  crosses  the  external  head 
of  the  Gastrocnemius  to  the  middle  of  the  leg,  and  joins  with  the  communicans 
tibialis  to  form  the  external  saphenous.  This  nerve  occasionally  exists  as  a  sepa- 
rate branch,  which  is  continued  as  far  down  as  the  heel. 

The  Anterior  Tibial  Nerve  (Fig.  419)  commences  at  the  bifurcation  of  the  pero- 
neal nerve,  between  the  fibula  and  upper  part  of  the  Peroneus  longus,  passes 
obliquely  forward  beneath  the  Extensor  longus  digitorum  to  the  fore  part  of  the 
interosseous  membrane,  and  gets  into  relation  with  the  anterior  tibial  artery 
above  the  middle  of  the  leg ;  it  then  descends  with  the  artery  to  the  front  of  the 
ankle-joint,  where  it  divides  into  an  external  and  an  internal  branch.  This  nerve 
lies  at  first  on  the  outer  side  of  the  anterior  tibial  artery,  then  in  front  of  it,  and 
again  at  its  outer  side  at  the  ankle-joint. 

The  branches  of  the  anterior  tibial  nerve  in  its  course  through  the  leg  are  the 
muscular  branches  to  the  Tibialis  anticus,  Extensor  longus  digitorum,  Peroneus 
tertius,  and  Extensor  proprius  hallucis  muscles,  and  an  articular  branch  to  the 
ankle-joint. 

The  external  or  tarsal  branch -of  the  anterior  tibial  passes  outward  across  the 
tarsus,  beneath  the  Extensor  brevis-  digitorum,  and,  having  become  enlarged, 
like  the  posterior  interosseous  nerve  at  the  wrist,  supplies  the  Extensor  brevis 
digitorum.  From  the  enlargement  three  minute  ini  °rosseous  branches  are  given  off 
which  supply  the  tarsal  joints  and  the  meta  rha^ngeal  joints  of  the  second, 

third,  and  fourth  toes.  The  first  of  the?^  sej  \  anient  to  the  second  dorsal 
interosseous  muscle. 

The  internal  branch,  the  continuation  ')  panies  the  dorsalis 

pedis  artery  along  the  inner  side  of  the  o^  ]  e  first  inter- 

osseous space  divides  into  two  branches,  whicli  )es  of  the 

great  and  second  toes,  communicating  with  thajinTerna]  brain.  musculo- 

cutaneous nerve.     Before  it  divides  it  gives  off  sseo'm  bram  first 

space,  which  supplies  the  metatarso-phalangeai  j<_>ii/.  of  the  great  to-jiiik  VeV.ls  a 
filament  to  the  First  dorsal  interosseous  muscle. 

The  Musculo-cutaneous  Nerve  (Fig.  419)  supplies  ihe  muscles  on  u'tter  nular 


THE  MUSCULO-CUTANEOVS   NERVES.  797 

side  of  the  leg  and  the  integument  of  the  dorsum  of  the  foot.  It  passes  forward 
between  the  Peronei  muscles  and  the  Extensor  longus  digitorum,  pierces  the  deep 
fascia  at  the  lower  third  of  the  leg  on  its  front  and  outer  side,  and  divides  into 
two  branches.  S  This  nerve  in  its  course  between  the  muscles  gives  off  muscular 
branches  to  the  Peroneus  longus  and  brevis,  and  cutaneous  filaments  to  the 
integument   of  the  lower  part  of  the  leg. 

The  internal  branch  of  the  musculo-cutaneous  nerve  passes  in  front  of  the 
ankle-joint,  and  divides  into  two  branches,  one  of  which  supplies  the  inner  side 
of  the  great  toe,  the  other,  the  adjacent  sides  of  the  second  and  third  toes.  It 
also  supplies  the  integument  of  the  inner  ankle  and  inner  side  of  the  foot, 
communicating  with  the  internal  saphenous  nerve,  and  joining  with  the  anterior 
tibial  nerve,  between  the  great  and  second  toes. 

The  external  branch,  the  smaller,  passes  along  the  outer  side  of  the  dorsum  of 
the  foot,  and  divides  into  two  branches,  the  inner  being  distributed  to  the  con- 
tiguous sides  of  the  third  and  fourth  toes,  the  outer  to  the  opposed  sides  of  the 
fourth  and  fifth  toes.  It  also  supplies  the  integument  of  the  outer  ankle  and 
outer  side  of  the  foot,  communicating  with  the  short  saphenous  nerve. 

The  branches  of  the  musculo-cutaneous  nerve  supply  all  the  toes  excepting 
the  outer  side  of  the  little  toe,  and  the  adjoining  sides  of  the  great  and  second 
toes,  the  former  being  supplied  by  the  external  saphenous,  and  the  latter  by  the 
internal  branch  of  the  anterior  tibial.  It  frequently  happens,  however,  that 
some  of  the  outer  branches  of  the  musculo-cutaneous  are  absent,  their  place 
being  then  taken  by  branches  of  the  external  saphenous  nerve. 

Surgical  Anatomy. — The  lumbar  plexus  passes  through  the  Psoas  muscle,  and,  therefore 
in  psoas  abscess  any  or  all  of  its  branches  may  be  irritated,  causing  severe  pain  in  the  part  to 
which  the  irritated  nerves  are  distributed.  The  genito-crural  nerve  is  the  one  which  is  most 
frequently  implicated.  This  nerve  is  also  of  importance,  as  it  is  concerned  in  one  of  the  princi- 
pal reflexes  employed  in  the  investigation  of  diseases  of  the  spine.  If  the  skin  over  the  inner 
side  of  the  thigh  just  below  Poupart's  ligament,  the  part  supplied  by  the  crural  branch  of  the 
genito-crural  nerve,  be  gently  tickled  in  a  male  child,  the  testicle  will  be  noticed  to  be  drawn 
upward  through  the  action  of  the  Cremaster  muscle,  supplied  by  the  genital  branch  of  the  same 
nerve.  The  same  result  may  sometimes  be  noticed  in  adults,  and  can  almost  always  be  produced 
by  severe  stimulation.  This  reflex,  when  present,  shows  that  the  portion  of  the  cord  from  which 
the  first  and  second  lumbar  nerves  are  derived  is  in  a  normal  condition. 

The  anterior  crural  nerve  is  in  danger  of  being  injured  in  fractures  of  the  true  pelvis,  since 
the  fracture  most  commonly  takes  place  through  the  ascending  ramus  of  the  os  pubis,  at  or 
near  the  point  where  this  nerve  crosses  the  bone.  It  is  also  liable  to  be  injured  in  fractures 
and  dislocations  of  the  femur,  and  is  likely  to  be  pressed  upon,  and  its  functions  impaired, 
in  some  tumors  growing  in  the  pelvis.  Moreover,  on  account  of  its  superficial  position,  it 
is  exposed  to  injury  in  wounds  and  stabs  in  the  groin.  When  this  nerve  is  paralyzed,  the 
patient  is  unable  to  flex  his  hip  completely,  on  account  of  the  loss  of  motion  in  the  Iliacus ; 
or  to  extend  the  knee  on  the  thigh,  on  account  of  paralysis  of  the  Quadriceps  extensor  cruris ; 
there  are  complete  paralysis  of  the  Sartorius  and  partial  paralysis  of  the  Pectineus.  There  is 
loss  of  sensation  down  the  front  and  inner  side  of  the  thigh,  except  in  that  part  supplied  by 
the  crural  branch  of  the  genito-crural,  and  by  the  ilio-inguinal.  There  is  also  loss  of  sensation 
down  the  inner  side  of  the  leg  and  foot  as  far  as  the  ball  of  the  great  toe. 

The  obturator  nerve  is  of  special  surgical  interest.  It  is  rarely  paralyzed  alone,  but  occa- 
sionally in  association  with  the  anterior  crural.  The  principal  interest  attached  to  it  is  in  con- 
nection with  its  supply  to  the  knee ;  pain  in  the  knee  being  symptomatic  of  many  diseases  in 
which  the  trunk  of  this  nerve,  or  one  of  its  branches,  is  irritated.  Thus  it  is  well  known  that 
in  the  earlier  stages  of  hip-joint  disease  the  patient  does  not  complain  of  pain  in  that  articu- 
lation, but  on  the  inner  side  of  the  knee,  or  in  the  knee-joint  itself,  both  these  articulations 
being  supplied  by  the  obturator  nerve,  the  final  distribution  of  the  nerve  being  to  the  knee- 
joint.  Again,  the  same  thing  occurs  in  sacro-iliac  disease :  pain  is  complained  of  in  the  knee- 
joint  or  on  its  inner  side.  The  obturator  nerve  is  in  close  relationship  with  the  sacro-iliac 
articulation,  passing  over  it,  and,  according  to  some  anatomists,  distributing  filaments  to  it. 
Again,  in  cancer  of  the  sigmoid  flexure,  and  even  in  cases  where  masses  of  hardened  faaces  are 
impacted  in  this  portion  of  the  gut,  pain  is  complained  of  in  the  knee.  The  left  obturator 
nerve  lies  beneath  the  sigmoid  flexure,  and  is  readily  pressed  upon  and  irritated  when  disease 
exists_  in  this  part  of  the  intestine.  Finally,  pain  in  the  knee  forms  an  important  diagnostic 
sign  in  »bturator  hernia.  The  hernial  protrusion  as  it  passes  out  through  the  opening  in  the 
obturror  membrane  presses  upon  the  nerve  and  causes  pain  in  the  parts  supplied  by  its  periph- 
eral filaments.  When  the  obturator  nerve  is  paralyzed,  the  patient  is  unable  to  press  his  knees 
together  or  to  cross  one  leg  over  the  other,  on  account  of  paralysis  of  the  Adductor  muscles. 


798  THE   NERVOUS  SYSTEM. 

Kotation  outward  of  the  thigh  is  impaired  from  paralysis  of  the  Obturator  externus.  Some- 
times there  is  loss  of  sensation  in  the  upper  half  of  the  inner  side  of  the  thigh. 

The  great  sciatic  nerve  is  liable  to  be  pressed  upon  by  various  forms  of  pelvic  tumors, 
giving  rise  to  pain  along  its  trunk,  to  which  the  term  sciatica  is  applied.  Tumors  growing  from 
the  pelvic  viscera,  or  bones,  aneurisms  of  some  of  the  branches  of  the  internal  iliac  artery, 
calculus  in  the  bladder  when  of  large  size,  accumulation  of  faeces  in  the  rectum,  may  all  cause 
pressure  on  the  nerve  inside  the  pelvis,  and  give  rise  to  sciatica.  Outside  the  pelvis  exposure  to 
cold,  violent  movements  of  the  hip-joint,  exostoses  or  other  tumors  growing  from  the  margin  of 
the  sacro-sciatic  foramen,  may  also  give  rise  to  the  same  condition.  When  paralyzed  there  is 
loss  of  motion  in  all  the  muscles  below  the  knee,  and  loss  of  sensation  in  the  same  situation, 
except  the  upper  half  of  the  back  of  the  leg,  supplied  by  the  small  sciatic  and  the  upper  half 
of  the  inner  side  of  the  leg,  when  the  communicating  branch  of  the  obturator  is  large  (see 
page  785). 

The  sciatic  nerve  has  been  frequently  cut  down  upon  and  stretched,  or  has  been  acupunct- 
ured for  the  relief  of  sciatica.  The  nerve  has  also  been  stretched  in  cases  of  locomotor  ataxy, 
the  anaesthesia  of  leprosy,  etc.  In  order  to  define  it  on  the  surface,  a  point  is  taken  at  the 
junction  of  the  middle  and  lower  third  of  a  line  stretching  from  the  posterior  superior  spine  of 
the  ilium  to  the  outer  part  of  the  tuber  ischii,  and  a  line  drawn  from  this  to  the  middle  of  the 
upper  part  of  the  popliteal  space.  The  line  must  be  slightly  curved  with  its  convexity  outward, 
and  as  it  passes  downward  to  the  lower  border  of  the  Gluteus  maximus  is  slightly  nearer  the 
tuber  ischii  than  the  great  trochanter,  as  it  crosses  a  line  drawn  between  these  two  points.  The 
operation  of  stretching  the  sciatic  nerve  is  performed  by  making  an  incision  over  the  course  of 
the  nerve  about  the  centre  of  the  thigh.  The  skin,  superficial  structures,  and  deep  fascia 
having  been  divided,  the  interval  between  the  inner  and  outer  hamstrings  is  to  be  defined,  and 
these  "muscles  pulled  inward  and  outward  with  retractors.  The  nerve  will  be  found  a  little  to 
the  inner  side  of  the  Biceps.  It  is  to  be  separated  from  the  surrounding  structures,  hooked  up 
with  the  finger,  and  stretched  by  steady  and  continuous  traction  for  two  or  three  minutes.  _  The 
sciatic  nerve  may  also  be  stretched  by  what  is  known  as  the  "  dry"  plan.  The  patient  is  laid 
on  his  back,  the  foot  is  extended,  the  leg  flexed  on  the  thigh,  and  the  thigh  strongly  flexed  on 
the  abdomen.  While  the  thigh  is  maintained  in  this  position  the  leg  is  forcibly  extended  to  its 
full  extent,  and  the  foot  as  fully  flexed  on  the  leg. 

The  position  of  the  external  popliteal,  close  behind  the  tendon  of  the  Biceps  on  the  outer 
side  of  the  ham,  should  be  remembered  in  subcutaneous  division  of  the  tendon.  After  it  is 
divided,  a  cord  often  rises  up  close  beside  it,  which  might  be  mistaken  for  a  small  undivided 
portion  of  the  tendon,  and  the  surgeon  might  be  tempted  to  reintroduce  his  knife  and  divide  it. 
This  must  never  be  done,  as  the  cord  is  the  external  popliteal  nerve,  which  becomes  prominent 
as  soon  as  the  tendon  is  divided. 

THE  SYMPATHETIC   NERVE. 

The  Sympathetic  Nervous  System  consists  of  (1)  a  series  of  ganglia,  connected 
together  by  intervening  cords,  extending  from  the  base  of  the  skull  to  the  coccyx, 
one  on  each  side  of  the  middle  line  of  the  body,  partly  in  front  and  partly  on  each 
side  of  the  vertebral  column  ;  (2)  of  three  great  gangliated  plexuses  or  aggregations 
of  nerves  and  ganglia,  situated  in  front  of  the  spine  in  the  thoracic,  abdominal,  and 
pelvic  cavities  respectively ;  (3)  of  smaller  ganglia,  situated  in  relation  with  the 
abdominal  viscera ;  and  (4)  of  numerous  nerve-fibres.  These  latter  are  of  two 
kinds :  communicating,  by  which  the  ganglia  communicate  with  each  other  and 
with  the  cerebro-spinnl  nerves ;  and  distributor?/,  supplying  the  internal  viscera 
and  the  coats  of  the  blood-vessels. 

Each  gangliated  cord  may  be  traced  upward  from  the  base  of  the  skull  into 
its  cavity  by  an  ascending  branch,  which  passes  through  the  carotid  canal,  forms 
a  plexus  on  the  internal  carotid  artery,  and  communicates  with  the  ganglia  on  the 
first  and  second  divisions  of  the  fifth  nerve.  According  to  some  anatomists,  the 
two  cords  are  joined,  at  their  cephalic  extremities,  by  these  ascending  branches 
communicating  in  a  small  ganglion  (the  ganglion  of  Ribes),  situated  upon  the 
anterior  communicating  artery.  The  ganglia  of  these  cords  are  distinguished  as 
cervical,  dorsal,  lumbar,  and  sacral,  and  except  in  the  neck  they  correspond  pretty 
nearly  in  number  to  the  vertebrae  against  Avhich  they  lie.  They  may  be  thus 
arranged : 

Cervical  portion         .  .  3  pairs  of  ganglia. 

Dorsal  "  .  .        12 

Lumbar       "  4  " 

Sacral          "  .  .4  or  5 


THE  SYMPATHETIC  NERVE.  799 

In  the  neck  they  are  situated  in  front  of  the  transverse  processes  of  the  verte- 
brae ;  in  the  dorsal  region,  in  front  of  the  heads  of  the  ribs  ;  in  the  lumbar  region, 
on  the  sides  of  the  bodies  of  the  vertebrae  ;  and  in  the  sacral  region,  in  front  of  the 
sacrum.  As  the  two  cords  pass  into  the  pelvis  they  converge  and  unite  together 
in  a  single  ganglion  [ganglion  impar)  placed  in  front  of  the  coccyx.  Each 
ganglion  may  be  regarded  as  a  distinct  centre,  and,  in  addition  to  its  branches  of 
distribution,  possesses  also  branches  of  communication  which  communicate  with 
other  ganglia  and  with  the  cerebro-spinal  nerves. 

The  branches  of  communication  between  the  ganglia  are  composed  of  gray 
and  white  nerve-fibres,  the  latter  being  continuous  with  those  fibres  of  the  spinal 
nerves  which  pass  to  the  ganglia. 

The  branches  of  communication  between  the  ganglia  and  the  cerebro-spinal 
nerves  also  consist  of  white  and  gray  nerve-fibres,  which  may  be  contained  in 
separate  filaments  or  united  in  a  single  branch  ;  the  former  proceeding  from  the 
spinal  nerve  to  the  ganglion,  the  latter  passing  from  the  ganglion  to  the  spinal 
nerve,  so  that  a  double  interchange  takes  place  between  the  two  systems.  While 
gray  communicating  fibres  pass  from  all  the  sympathetic  ganglia  to  all  the  spinal 
nerves,  it  would  appear  that  the  white  communicating  fibres  from  the  spinal  nerves 
to  the  sympathetic  only  exist  in  the  dorsal  and  upper  lumbar  regions. 

The  three  great  gangliated  plexuses  are  situated  in  front  of  the  spine  in  the 
thoracic,  abdominal,  and  pelvic  regions,  and  are  named,  respectively,  the  cardiac, 
the  solar  or  epigastric,  and  the  hypogastric  plexus.  They  consist  of  collections  of 
nerves  and  ganglia,  the  nerves  being  derived  from  the  gangliated  cords  and  from 
the  cerebro-spinal  nerves.     They  distribute  branches  to  the  viscera. 

Smaller  ganglia  are  also  found  lying  amidst  the  nerves,  some  of  them  of 
microscopic  size,  in  certain  viscera — as,  for  instance,  in  the  heart,  the  stomach,  and 
the  uterus.     They  serve  as  additional  centres  for  the  origin  of  nerve-fibres. 

The  branches  of  distribution  derived  from  the  gangliated  cords,  from  the 
prevertebral  plexuses,  and  also  from  the  smaller  ganglia,  are  principally  destined 
for  the  blood-vessels  and  thoracic  and  abdominal  viscera,  supplying  the  involuntary 
muscular  fibre  of  the  coats  of  the  vessels  and  the  hollow  viscera,  and  the  secreting 
cells,  as  well  as  the  muscular  coats  of  the  vessels  in  the  glandular  viscera. 

THE  GANGLIATED  CORD.. 
Cervical  Portion  of  the  Gang-hated  Cord. 

The  cervical  portion  of  the  gangliated  cord  consists  of  three  ganglia  on  each 
side,  which  are  distinguished,  according  to  their  position,  as  the  superior,  middle, 
and  inferior  cervical. 

The  Superior  Cervical  Ganglion,  the  largest  of  the  three,  is  placed  opposite  the 
second  and  third  cervical  vertebrae.  It  is  of  a  reddish-gray  color,  and  usually 
fusiform  in  shape,  sometimes  broad  and  flattened,  and  occasionally  constricted  at 
intervals,  so  as  to  give  rise  to  the  opinion  that  it  consists  of  the  coalescence  of 
several  smaller  ganglia ;  and  it  is  usually  believed  that  it  is  formed  by  the  coales- 
cence of  the  four  ganglia  corresponding  to  the  four  upper  cervical  nerves.  It  is 
in  relation,  in  front,  with  the  sheath  of  the  internal  carotid  artery  and  internal 
jugular  vein;  behind,  it  lies  on  the  Rectus  capitis  anticus  major  muscle. 

Its  branches  may  be  divided  into  superior,  inferior,  external,  internal,  and 
anterior. 

The  superior  branch  appears  to  be  a  direct  prolongation  of  the  ganglion.  It 
is  soft  in  texture  and  of  a  reddish  color.  It  ascends  by  the  side  of  the  internal 
carotid  artery,  and,  entering  the  carotid  canal  in  the  temporal  bone,  divides  into  two- 
branches,  which  lie,  one  on  the  outer,  and  the  other  on  the  inner,  side  of  that  vessel. 

The  outer  branch,  the  larger  of  the  two,  distributes  filaments  to  the  internal 
carotid  artery  and  forms  the  carotid  plexus. 

The  inner  branch  also  distributes  filaments  to  the  internal  carotid,  and,  con- 
tinuing onward,  forms  the  cavernous  plexus. 


800 


THE  NERVOUS  SYSTEM. 


Superior  cervical 

Middle  cervical  ganrjli 
Inferior  cervical  ganglion. 


Pharyngeal  branches. 
Cardiac  branches. 

Deep  cardiac  plexus. 

Superficial  cardiac  plexus. 


Sacral  ganglia. 


Ganglion  impar.  ^ 


Solar  plexus. 


Aortic  plexus. 


Hypogastric  plexus. 


Fig.  425.— The  sympathetic  nerve. 


THE    CAROTID    AND    CAVERNOUS   PLEXUSES.  801 

The  Carotid  Plexus. 

The  carotid  plexus  is  situated  on  the  outer  side  of  the  internal  carotid.  Fila- 
ments from  this  plexus  occasionally  form  a  small  gangliform  swelling  on  the  under 
surface  of  the  artery,  which  is  called  the  carotid  ganglion.  The  carotid  plexus 
communicates  with  the  Gasserian  ganglion,  with  the  sixth  nerve,  and  the  spheno- 
palatine ganglion,  and  distributes  filaments  to  the  wall  of  the  carotid  artery  and 
to  the  dura  mater  (Valentin),  while  in  the  carotid  canal  it  communicates  with 
Jacobson's  nerve,  the  tympanic  branch  of  the  glosso-pharyngeal. 

The  communicating  branches  with  the  sixth  nerve  consist  of  one  or  two  fila- 
ments which  join  that  nerve  as  it  lies  upon  the  outer  side  of  the  internal  carotid. 
Other  filaments  are  also  connected  with  the  Gasserian  ganglion.  The  communi- 
cation with  the  spheno-palatine  ganglion  is  effected  by  a  branch,  the  large  deep 
petrosal,  which  is  given  off  from  the  plexus  on  the  outer  side  of  the  artery,  and 
which  passes  through  the  cartilage  filling  up  the  foramen  lacerum  medium,  and 
joins  the  great  superficial  petrosal  to  form  the  Vidian  nerve.  The  Vidian  nerve 
then  proceeds  along  the  pterygoid  or  Vidian  canal  to  the  spheno-palatine  ganglion. 
The  communication  with  Jacobson's  nerve  is  effected  by  two  branches,  one  of 
which  is  called  the  small  deep  petrosal  nerve,  and  the  other  the  caroticotympanic  ; 
the  latter  may  consist  of  two  or  three  delicate  filaments. 

The  Cavernous  Plexus. 

The  cavernous  plexus  is  situated  below  and  internal  to  that  part  of  the  internal 
carotid  which  is  placed  by  the  side  of  the  sella  Turcica  in  the  cavernous  sinus, 
and  is  formed  chiefly  by  the  internal  division  of  the  ascending  branch  from  the 
superior  cervical  ganglion.  It  communicates  with  the  third,  the  fourth,  the 
ophthalmic  division  of  the  fifth,  and  the  sixth  nerves,  and  with  the  ophthalmic 
ganglion,  and  distributes  filaments  to  the  wall  of  the  internal  carotid.  The 
branch  of  communication  with  the  third  nerve  joins  it  at  its  point  of  division; 
the  branch  to  the  fourth  nerve  joins  it  as  it  lies  on  the  outer  wall  of  the  cavernous 
sinus ;  other  filaments  are  connected  with  the  under  surface  of  the  trunk  of  the 
ophthalmic  nerve;  and  a  second  filament  of  communication  joins  the  sixth  nerve. 

The  filament  of  connection  with  the  ophthalmic  ganglion  arises  from  the 
anterior  part  of  the  cavernous  plexus ;  it  accompanies  the  nasal  nerve  or  con- 
tinues forward  as  a  separate  branch. 

The  terminal  filaments  from  the  carotid  and  cavernous  plexuses  are  prolonged 
along  the  internal  carotid,  forming  plexuses  which  entwine  round  the  cerebral  and 
ophthalmic  arteries ;  along  the  former  vessels  they  may  be  traced  on  to  the  pia 
mater;  along  the  latter,  into  the  orbit,  where  they  accompany  each  of  the  sub- 
divisions of  the  vessel,  a  separate  plexus  passing,  with  the  arteria  centralis  retinae, 
into  the  interior  of  the  eyeball.  The  filaments  prolonged  on  to  the  anterior  com- 
municating artery  form  a  small  ganglion,  the  ganglion  of  Mibes,1  which  serves,  as 
mentioned  above,  to  connect  the  sympathetic  nerves'  of  the  right  and  left  sides. 

The  inferior  or  descending  branch  of  the  superior  cervical  ganglion'  communi- 
cates with  the  middle  cervical  ganglion. 

The  external  branches  are  numerous,  and  communicate  with  the  cranial  nerves 
and  with  the  four  upper  spinal  nerves.  Sometimes  the  branch  to  the  fourth 
spinal  nerve  may  come  from  the  cord  connecting  the  upper  and  middle  cervical 
ganglia.  The  branches  of  communication  with  the  cranial  nerves  consist  of 
delicate  filaments,  which  pass  from  the  superior  cervical  ganglion  to  the  ganglion 
of  the  trunk  of  the  pneumogastric  and  to  the  hypoglossal  nerve.  A  separate 
filament  from  the  cervical  ganglion  subdivides  and  joins  the  petrosal  ganglion  of 
the  glosso-pharyngeal  and  the  ganglion  of  the  root  of  the  pneumogastric  in  the 
jugular  foramen. 

The  internal  branches  are  three  in  number — the  pharyngeal,  laryngeal,  and 
superior  cardiac  nerve.     The  pharyngeal  branches  pass  inward  to  the  side  of  the 

1  The  existence  of  this  ganglion  is  doubted  by  some  observers. 
51 


802 


THE  NERVOUS  SYSTEM. 


Fig.  426.— Plan  of  the  cervical  portion  of  the  sympathetic.    (After  Flower.) 


THE  MIDDLE    CERVICAL    GANGLION.  803 

pharynx,  Avhere  they  join  with  branches  from  the  glosso-pharyngeal,  pneumogastric, 
and  external  laryngeal  nerves  to  form  the  pharyngeal  plexus.  The  laryngeal 
branches  unite  with  the  superior  laryngeal  nerve  and  its  branches. 

The  superior  cardiac  nerve  (nervus  superficialis  cordis)  arises  by  two  or  more 
branches  from  the  superior  cervical  ganglion,  and  occasionally  receives  a  filament 
from  the  cord  of  communication  between  the  first  and  second  cervical  ganglia.  It 
runs  down  the  neck  behind  the  common  carotid  artery,  lying  upon  the  Longus 
colli  muscle,  and  crosses  in  front  of  the  inferior  thyroid  artery  and  recurrent 
laryngeal  nerve. 

The  right  superior  cardiac  nerve,  at  the  root  of  the  neck,  passes  either  in  front 
of  or  behind  the  subclavian  artery,  and  along  the  arteria  innominata,  to  the  back 
part  of  the  arch  of  the  aorta,  where  it  joins  the  deep  cardiac  plexus.  This  nerve, 
in  its  course,  is  connected  with  other  branches  of  the  sympathetic  :  about  the 
middle  of  the  neck  it  receives  filaments  from  the  external  laryngeal  nerve ;  lower 
down,  one  or  two  twigs  from  the  pneumogastric  ;  and  as  it  enters  the  thorax  it  is 
joined  by  a  filament  from  the  recurrent  laryngeal.  Filaments  from  this  nerve 
communicate  with  the  thyroid  branches  from  the  middle  cervical  ganglion. 

The  left  superior  cardiac  nerve,  in  the  chest,  runs  by  the  side  of  the  left  com- 
mon carotid  artery  and  in  front  of  the  arch  of  the  aorta  to  the  superficial  cardiac 
plexus,  but  occasionally  it  passes  behind  the  aorta  and  terminates  in  the  deep 
cardiac  plexus. 

The  anterior  branches  ramify  upon  the  external  carotid  artery  and  its  branches, 
forming  round  each  a  delicate  plexus,  on  the  nerves  composing  which  small  ganglia 
are  occasionally  found.  The  plexuses  accompanying  some  of  these  arteries  have 
important  communications  with  other  nerves.  That  surrounding  the  external 
carotid  is  connected  with  the  branch  of  the  facial  nerve  to  the  Stylo-hyoid  muscle ; 
that  surrounding  the  facial  communicates  with  the  submaxillary  ganglion  by  one 
or  two  filaments  ;  and  that  accompanying  the  middle  meningeal  artery  sends  offsets 
which  pass  to  the  otic  ganglion  and  to  the  geniculate  ganglion  of  the  facial  nerve 
(external  petrosal). 

The  Middle  Cervical  Ganglion  [thyroid  ganglion)  is  the  smallest  of  the  three 
cervical  ganglia,  and  is  occasionally  altogether  wanting.  It  is  placed  opposite  the 
sixth  cervical  vertebra,  usually  upon,  or  close  to,  the  inferior  thyroid  artery ; 
hence  the  name,  "thyroid  ganglion,"  assigned  to  it  by  Haller.  It  is  probably 
formed  by  the  coalescence  of  two  ganglia  corresponding  to  the  fifth  and  sixth  cer- 
vical nerves. 

Its  superior  branches  ascend  to  communicate  with  the  superior  cervical  gan- 
glion. 

Its  inferior  branches  descend  to  communicate  with  the  inferior  cervical  ganglion. 

Its  external  branches  pass  outward  to  join  the  fifth  and  sixth  spinal  nerves. 
These  branches  are  not  constantly  found. 

Its  internal  branches  are  the  thyroid  and  the  middle  cardiac  nerve. 

The  thyroid  branches  are  small  filaments  which  accompany  the  inferior  thyroid 
artery  to  the  thyroid  gland ;  they  communicate,  on  the  artery,  with  the  superior 
cardiac  nerve,  and,  in  the  gland,  with  branches  from  the  recurrent  and  external 
laryngeal  nerves. 

The  middle  cardiac  nerve  (nervus  cardiacus  magnus),  the  largest  of  the  three 
cardiac  nerves,  arises  from  the  middle  cervical  ganglion  or  from  the  cord  between 
the  middle  and  inferior  ganglia.  On  the  right  side  it  descends  behind  the  common 
carotid  artery,  and  at  the  root  of  the  neck  passes  either  in  front  of  or  behind  the 
subclavian  artery ;  it  then  descends  on  the  trachea,  receives  a  few  filaments  from 
the  recurrent  laryngeal  nerve,  and  joins  the  right  side  of  the  deep  cardiac  plexus. 
In  the  neck  it  communicates  with  the  superior  cardiac  and  recurrent  laryngeal 
nerves.  On  the  left  side  the  middle  cardiac  nerve  enters  the  chest  between  the 
left  carotid  and  subclavian  arteries,  and  joins  the  left  side  of  the  deep  cardiac 
plexus. 

The  Inferior  Cervical  Ganglion  is  situated  between  the  base  of  the  transverse 


804  THE  NERVOUS   SYSTEM. 

process  of  the  last  cervical  vertebra  and  the  neck  of  the  first  rib  on  the  inner  side 
of  the  superior  intercostal  artery.  Its,  form  is  irregular;  it  is  larger  in  size  than 
the  preceding,  and  frequently  joined  with  the  first  thoracic  ganglion.  It  is  proba- 
blv  formed  by  the  coalescence  of  two  ganglia  which  correspond  to  the  two  last 
cervical  nerves. 

Its  superior  branches  communicate  with  the  middle  cervical  ganglion. 

Its  inferior  branches  descend,  some  in  front  of,  others  behind,  the  subclavian 
artery,  to  join  the  first  thoracic  ganglion. 

Its  internal  branch  is  the  inferior  cardiac  nerve. 

The  inferior  cardiac  nerve  {nervus  cardiacus  minor)  arises  from  the  inferior 
cervical  or  first  thoracic  ganglion.  It  passes  down  behind  the  subclavian  artery 
and  along  the  front  of  the  trachea  to  join  the  deep  cardiac  plexus.  It  communi- 
cates freely  behind  the  subclavian  artery  with  the  recurrent  laryngeal  and  middle 
cardiac  nerves. 

The  external  branches  consist  of  several  filaments,  some  of  which  communi- 
cate with  the  seventh  and  eighth  spinal  nerves ;  others  accompany  the  vertebral 
artery  along  the  vertebral  canal,  forming  a  plexus  round  the  vessel,  supplying  it 
with  filaments,  which  are  continued  up  the  vertebral  and  basilar  to  the  cerebral 
arteries.     The  branches  communicate  with  the  cervical  spinal  nerves. 

The  Thoracic  Portion  of  the  Gangliated  Cord. 

The  thoracic  portion  of  the  gangliated  cord  consists  of  a  series  of  ganglia 
which  usually  correspond  in  number  to  that  of  the  vertebrae,  but,  from  the  occa- 
sional coalescence  of  two,  their  number  is  uncertain.  These  ganglia  are  placed 
on  each  side  of  the  spine,  resting  against  the  heads  of  the  ribs  and  covered  by  the 
pleura  costalis ;  the  last  two  are,  however,  anterior  to  the  rest,  being  placed  on  the 
side  of  the  bodies  of  the  eleventh  and  twelfth  dorsal  vertebrae.  The  ganglia  are 
small  in  size  and  of  a  grayish  color.  The  first,  larger  than  the  rest,  is  of  an 
elongated  form  and  frequently  blended  with  the  last  cervical.  They  are  connected 
together  by  cord-like  prolongations  from  their  substance. 

The  external  branches  from  each  ganglion,  usually  two  in  number,  communi- 
cate with  each  of  the  dorsal  spinal  nerves. 

The  internal  branches  from  the  five  or  six  upper  ganglia  are  very  small ;  they 
supply  filaments  to  the  thoracic  aorta  and  its  branches,  besides  small  branches  to 
the  bodies  of  the  vertebrae  and  their  ligaments.  Branches  from  the  third  and 
fourth,  and  sometimes  also  from  the  first  and  second  ganglia,  form  part  of  the 
posterior  pulmonary  plexus. 

The  internal  branches  from  the  six  or  seven  lower  ganglia  are  large  and  white 
in  color ;  they  distribute  filaments  to  the  aorta,  and .  unite  to  form  the  three 
splanchnic  nerves.  These  are  named  the  great,  the  lesser,  and  the  smallest  or 
renal  splanchnic. 

The  great  splanchnic  nerve  is  of  a  white  color,  firm  in  texture,  and  bears  a 
marked  contrast  to  the  ganglionic  nerves.  It  is  formed  by  branches  from  the 
thoracic  ganglia  between  the  fifth  or  sixth  and  the  ninth  or  tenth,  but  the  fibres  in 
the  higher  roots  may  be  traced  upAvard  in  the  sympathetic  cord  as  far  as  the  first 
or  second  thoracic  ganglia.  These  roots  unite  to  form  a  large  round  cord  of 
considerable  size.  It  descends  obliquely  inward  in  front  of  the  bodies  of  the 
vertebrae  along  the  posterior  mediastinum,  perforates  the  crus  of  the  Diaphragm, 
and  terminates  in  the  semilunar  ganglion  of  the  solar  plexus,  distributing  filaments 
to  the  renal  and  suprarenal  plexus. 

The  lesser  splanchnic  nerve  is  formed  by  filaments  from  the  tenth  and  eleventh 
ganglia,  and  from  the  cord  between  them.  It  pierces  the  Diaphragm  with  the 
preceding  nerve,  and  joins  the  solar  plexus.  It  communicates  in  the  chest 
with  the  great  splanchnic  nerve,  and  occasionally  sends  filaments  to  the  renal 
plexus. 

The  smallest  or  renal  splanchnic  nerve  arises  from    the   last  ganglion,  and. 


THE    CARDIAC  PLEXUS.  805 

piercing  the   Diaphragm,  terminates  in  the  renal  plexus  and  lower  part  of  the 
solar  plexus.     It  occasionally  communicates  with  the  preceding  nerve. 

A  striking  analogy  appears  to  exist  between  the  splanchnic  and  the  cardiac 
nerves.  The  cardiac  nerves  are  three  in  number;  they  arise  from  the  three 
cervical  ganglia,  and  are  distributed  to  a  large  and  important  organ  in  the  thoracic 
cavity.  The  splanchnic  nerves,  also  three  in  number,  are  connected  probably  with 
all  the  dorsal  ganglia,  and  are  distributed  to  important  organs  in  the  abdominal 
cavity. 

The  Lumbar  Portion  of  the  Gangliated  Cord. 

The  lumbar  portion  of  the  gangliated  cord  is  situated  in  front  of  the  vertebral 
column  along  the  inner  margin  of  the  Psoas  muscle.  It  consists  usually  of  four 
ganglia,  connected  together  by  interganglionic  cords.  The  ganglia  are  of  small 
size,  of  a  grayish  color,  shaped  like  a  barleycorn,  and  placed  much  nearer  the 
median  line  than  the  thoracic  ganglia. 

The  superior  and  inferior  branches  of  the  lumbar  ganglia  serve  as  communi- 
cating branches  between  the  chain  of  ganglia  in  this  region.  They  are  usually 
single  and  of  a  white  color. 

The  external  branches  communicate  with  the  lumbar  spinal  nerves.  From  the 
situation  of  the  lumbar  ganglia  these  branches  are  longer  than  in  the  other  regions. 
They  are  usually  two  in  number  from  each  ganglion,  but  their  connection  with  the 
spinal  nerves  is  not  so  uniform  as  in  other  regions.  They  accompany  the  lumbar 
arteries  around  the  sides  of  the  bodies  of  the  vertebrae,  passing  beneath  the  fibrous 
arches  from  which  some  of  the  fibres  of  the  Psoas  muscle  arise. 

Of  the  internal  branches,  some  pass  inward,  in  front  of  the  aorta,  and  help  to 
form  the  aortic  plexus.  Other  branches  descend  in  front  of  the  common  iliac 
arteries,  and  join  over  the  promontory  of  the  sacrum,  helping  to  form  the  hypo- 
gastric plexus.  Numerous  delicate  filaments  are  also  distributed  to  the  bodies  of 
the  vertebras  and  the  ligaments  connecting  them. 

Pelvic  Portion  of  the  Gangliated  Cord. 

The  pelvic  portion  of  the  gangliated  cord  is  situated  in  front  of  the  sacrum 
along  the  inner  side  of  the  anterior  sacral  foramina.  It  consists  of  four  or  five 
small  ganglia  on  each  side,  connected  together  by  interganglionic  cords.  Below, 
these  cords  converge  and  unite  on  the  front  of  the  coccyx  by  means  of  a  small 
ganglion  (the  coccygeal  ganglion  or  ganglion   impar). 

The  superior  and  inferior  branches  are  the  cords  of  communication  between  the 
ganglia  above  and  below. 

The  external  branches,  exceedingly  short,  communicate  with  the  sacral  nerves. 
They  are  two  in  number  from  each  ganglion.  The  coccygeal  nerve  communicates 
either  with  the  last  sacral  or  coccygeal  ganglion. 

The  internal  branches  communicate,  on  the  front  of  the  sacrum,  with  the 
corresponding  branches  from  the  opposite  side ;  some,  from  the  first  two  ganglia, 
pass  to  join  the  pelvic  plexus,  and  others  form  a  plexus  which  accompanies  the 
middle  sacral  artery  and  sends  filaments  to  the  coccygeal  gland. 

THE   GREAT  PLEXUSES   OF  THE  SYMPATHETIC. 

The  great  plexuses  of  the  sympathetic  are  the  large  aggregations  of  nerve? 
and  ganglia,  above  alluded  to,  situated  in  the  thoracic,  abdominal,  and  pelvic- 
cavities  respectively.  From  them  are  derived  the  branches  which  supply  the 
viscera. 

The  Cardiac  Plexus. 

The  cardiac  plexus  is  situated  at  the  base  of  the  heart,  and  is  divided  into  a 
superficial  part,  which  lies  in  the  concavity  of  the   arch  of  the  aorta,  and  a  deep 


806  THE   NERVOUS  SYSTEM. 

part,  which  lies  between  the  trachea  and  aorta.     The  two  plexuses  are,  however, 
closely  connected. 

The  great  or  deep  cardiac  plexus  {plexus  magnus  profundus,  Scarpa)  is  situated 
in  front  of  the  trachea  at  its  bifm-cation,  above  the  point  of  division  of  the  pul- 
monary artery  and  behind  the  arch  of  the  aorta.  It  is  formed  by  the  cardiac  nerves 
derived  from  the  cervical  ganglia  of  the  sympathetic  and  the  cardiac  branches  of 
the  recurrent  laryngeal  and  pneumogastric.  The  only  cardiac  nerves  which  do  not 
enter  into  the  formation  of  this  plexus  are  the  left  superior  cardiac  nerve  and  the 
inferior  cervical  cardiac  branch  from  the  left  pneumogastric. 

The  branches  from  the  rigid  side  of  this  plexus  pass,  some  in  front  of,  and 
others  behind,  the  right  pulmonary  artery ;  the  former,  the  more  numerous, 
transmit  a  few  filaments  to  the  anterior  pulmonary  plexus,  and  are  then  continued 
onward  to  form  part  of  the  anterior  coronary  plexus  ;  those  behind  the  pulmonary 
artery  distribute  a  few  filaments  to  the  right  auricle,  and  are  then  continued 
onward  to  form  part  of  the  posterior  coronary  plexus. 

The  branches  from  the  left  side  of  the  deep  cardiac  plexus  distribute  a  few 
filaments  to  the  superficial  cardiac  plexus,  to  the  left  auricle  of  the  heart,  and  to 
the  anterior  pulmonary  plexus,  and  then  pass  on  to  form  the  greater  part  of  the 
posterior  coronary  plexus. 

The  superficial  (anterior)  cardiac  plexus  lies  beneath  the  arch  of  the  aorta,  in 
front  of  the  right  pulmonary  artery.  It  is  formed  by  the  left  superior  cardiac 
nerve,  the  left  (and  occasionally  the  right)  inferior  cervical  cardiac  branches  of  the 
pneumogastric,  and  filaments  from  the  deep  cardiac  plexus.  A  small  ganglion 
{cardiac  ganglion  of  Wrisberg)  is  occasionally  found  connected  with  these  nerves 
at  their  point  of  junction.  This  ganglion,  when  present,  is  situated  immediately 
beneath  the  arch  of  the  aorta,  on  the  right  side  of  the  ductus  arteriosus.  The 
superficial  cardiac  plexus  forms  the  chief  part  of  the  anterior  coronary  plexus,  and 
several  filaments  pass  along  the  pulmonary  artery  to  the  left  anterior  pulmonary 
plexus. 

The  posterior  or  right  coronary  plexus  is  chiefly  formed  by  filaments  prolonged 
from  the  left  side  of  the  deep  cardiac  plexus,  and  by  a  few  from  the  right  side.  It 
surrounds  the  branches  of  the  coronary  artery  at  the  back  of  the  heart,  and  its 
filaments  are  distributed  with  those  vessels  to  the  muscular  substance  of  the 
ventricles. 

The  anterior  or  left  coronary  plexus  is  formed  chiefly  from  the  superficial  cardiac 
plexus,  but  receives  filaments  from  the  deep  cardiac  plexus.  Passing  forward 
between  the  aorta  and  pulmonary  artery,  it  accompanies  the  left  coronary  artery 
on  the  anterior  surface  of  the  heart. 

Valentin  has  described  nervous  filaments  ramifying  under  the  endocardium  ; 
and  Remak  has  found,  in  several  mammalia,  numerous  small 'ganglia  dn  the  cardiac 
nerves,  both  o/n  the  surface  of  the  heart  and  in  its  muscular  substance. 

The  Epigastric  or  Solar  Plexus  (Figs.  425,  427).  .__. 

The  Epigastric  or  Solar  plexus  supplies  all  the  viscera  in  the  abdominal  cavity. 
It  consists  of  a  great  network  of  nerves  and  ganglia,  situated  behind  the  stomach 
and  hi  front  of  the  aorta  and  crura  of  the  Diaphragm.  It  surrounds  the  coeliac 
axis  and  root  of  the  superior  mesenteric  artery,  extending  downward  as  low  as  the 
pancreas  and  outward  to  the  suprarenal  capsules.  This  plexus,  and  the  ganglia 
connected  with  it,  receive  the  great  and  small  splanchnic  nerves  of  both  sides, 
and  some  filaments  from  the  right  pneumogastric.  It  distributes  filaments  which 
accompany,  under  the  name  of  plexuses,  all  the  branches  from  the  front  of  the 
abdominal  aorta. 

Of  the  ganglia  of  which  the  solar  plexus  is  partly  composed  the  principal  are 
the  two  semilunar  ganglia,  which  are  situated  one  on  each  side  of  the  plexus,  and 
are  the  largest  ganglia  in  the  body.  They  are  large  irregular  gangliform  masses 
formed  by  the  aggregation  of  smaller  ganglia,  having  interspaces  between  them. 

■r 


THE   EPIGASTRIC    OR    SOLAR    PLEXUS. 

Diaphragmatic  ganglion. 


807 


Hepatic 
artery.  \ 


Suprarenal  capsule 


Small  splanchnic  nerve 


Left  semilunar  ganglion. 
Superior  mesenteric  artery. 
Great  splanchnic  nerve. 
Small  splanchnic  nerve. 

Renal  ganglion. 


Renal  artery. 

Superior  mesenteric  ganglion. 


Branch  to  aortic  plexus. 


Gangliated  cord  of 
sympathetic. 


iferior  mesenteric  artery. 


Inferior  mesenteric  ganglion. 


Sacro-vertebral  angle. 
Coiiintou  iliac  vein. 
Common  iliac  artery. 


Fig.  427.-Lumbar  portion  of  the  gangliated  cord,  with  the  solar  and  hypogastric  plexuses.    (After  Henle.) 

They  are  situated  in  front  of  the  crura  of  the  Diaphragm,  close  to  the  suprarenal 
capsules:  the  one  on  the  right  side  lies  beneath  the  inferior  vena  cava  :  the  upper 
part  of  each  ganglion  is  joined  by  the  greater  splanchnic  nerve,  and  to  the  inner 
side  of  each  the  branches  of  the  solar  plexus  are  connected. 

\ 


808  THE   NERVOUS  SYSTEM. 

From  the  epigastric  or  solar  plexus  are  derived  the  following : 

Phrenic  or  Diaphragmatic  plexus.  (  Gastric  plexus. 

Suprarenal  plexus.  Coeliac  plexus  <  Splenic  plexus. 

Renal  plexus.  (  Hepatic  plexus. 

Spermatic  plexus.  Superior  mesenteric  plexus. 

Aortic  plexus. 

The  phrenic  plexus  accompanies  the  phrenic  artery  to  the  Diaphragm,  which 
it  supplies,  some  filaments  passing  to  the  suprarenal  capsule.  It  arises  from  the 
upper  part  of  the  semilunar  ganglion,  and  is  larger  on  the  right  than  on  the  left 
side.  It  receives  one  or  two  branches  from  the  phrenic  nerve.  In  connection 
with  this  plexus,  on  the  right  side,  at  its  point  of  junction  with  the  phrenic  nerve, 
is  a  small  ganglion  (ganglion  diaphragmaticum).  This  ganglion  is  placed  on  the 
under  surface  of  the  Diaphragm,  near  the  suprarenal  capsule.  Its  branches  are 
distributed  to  the  inferior  vena  cava,  suprarenal  capsule,  and  hepatic  plexus. 
There  is  no  ganglion  on  the  left  side. 

The  suprarenal  plexus  is  formed  by  branches  from  the  solar  plexus,  from  the 
semilunar  ganglion,  and  from  the  phrenic  and  great  splanchnic  nerves,  a  ganglion 
being  formed  at  the  point  of  junction  of  the  latter  nerve.  It  supplies  the  supra- 
renal capsule.  The  branches  of  this  plexus  are  remarkable  for  their  large  size  in 
comparison  with  the  size  of  the  organ  they  supply. 

The  renal  plexus  is  formed  by  filaments  from  the  solar  plexus,  the  outer  part 
of  the  semilunar  ganglion,  and  the  aortic  plexus.  It  is  also  joined  by  filaments 
from  the  lesser  and  smallest  splanchnic  nerves.  The  nerves  from  these  sources, 
fifteen  or  twenty  in  number,  have  numerous  ganglia  developed  upon  them.  They 
accompany  the  branches  of  the  renal  artery  into  the  kidney,  some  filaments  on 
the  right  side  being  distributed  to  the  inferior  vena  cava,  and  others  to  the  sper- 
matic plexus  on  both  sides. 

The  spermatic  plexus  is  derived  from  the  renal  plexus,  receiving  branches  from 
the  aortic  plexus.     It  accompanies  the  spermatic  vessels  to  the  testes. 

In  the  female  the  ovarian  plexus  is  distributed  to  the  ovaries  and  fundus  of  the 
uterus. 

The  cceliac  plexus,  of  large  size,  is  a  direct  continuation  from  the  solar  plexus : 
it  surrounds  the  coeliac  axis  and  subdivides  into  the  gastric,  hepatic,  and  splenic 
plexuses.  It  receives  branches  from  the  lesser  splanchnic  nerves,  and,  on  the  left 
side,  a  filament  from  the  right  pneumogastric. 

The  gastric  or  coronary  plexus  accompanies  the  gastric  artery  along  the  lesser 
curvature  of  the  stomach,  and  joins  with  branches  from  the  left  pneumogastric 
nerve.     It  is  distributed  to  the  stomach 

The  hepatic  plexus,  the  largest  offset  from  the  coeliac  plexus,  receives  filaments 
from  the  left  pneumogastric  and  right  phrenic  nerves.  It  accompanies  the  hepatic 
artery,  ramifying  in  the  substance  of  the  liver  upon  its  branches  and  upon  those 
of  the  vena  portae. 

Branches  from  this  plexus  accompany  all  the  divisions  of  the  hepatic  artery. 
Thus  there  is  a  pyloric  plexus  accompanying  the  pyloric  branch  of  the  hepatic, 
which  joins  with  the  gastric  plexus  and  pneumogastric  nerves.  There  is  also  a 
g astro-duodenal  plexus,  which  subdivides  into  the  pancreatico-duodenal  plexus, 
which  accompanies  the  pancreatico-duodenal  artery,  to  supply  the  pancreas  and 
duodenum,  joining  with  branches  from  the  mesenteric  plexus ;  and  a  gastroepi- 
ploic plexus,  which  accompanies  the  right  gastro-epiploic  artery  along  the  greater 
curvature  of  the  stomach  and  anastomoses  with  branches  from  the  splenic  plexus. 
A  cystic  plexus,  which  supplies  the  gall-bladder,  also  arises  from  the  hepatic  plexus 
near  the  liver. 

The  splenic  plexus  is  formed  by  branches  from  the  coeliac  plexus,  the  left  semi- 
lunar ganglia,  and  from  the  right  pneumogastric  nerve.  It  accompanies  the 
splenic  artery  and  its  branches  to  the  substance  of  the  spleen,  giving  off,  in  its 
course,  filaments  to  the  pancreas  (pancreatic  plexus}  and  the  left  gastro-epipjloic 


THE   PELVIC  PLEXUS.  809 

plexus,  which  accompanies  the  gastro-epiploica  sinistra  artery  along  the  convex 
border  of  the  stomach. 

The  superior  mesenteric  plexus  is  a  continuation  of  the  lower  part  of  the  great 
solar  plexus,  receiving  a  branch  from  the  junction  of  the  right  pneumogastric 
nerve  with  the  coeliac  plexus.  It  surrounds  the  superior  mesenteric  artery,  which  it 
accompanies  into  the  mesentery,  and  divides  into  a  number  of  secondary  plexuses, 
which  are  distributed  to  all  the  parts  supplied  by  the  artery — viz.  pancreatic  branches 
to  the  pancreas  ;  intestinal  branches,  which  supply  the  whole  of  the  small  intestine  ; 
and  ileo-colic,  right  colic,  and  middle  colic  branches,  which  supply  the  correspond- 
ing parts  of  the  great  intestine.  The  nerves  composing  this  plexus  are  white  in 
color  and  firm  in  texture,  and  have  numerous  ganglia  developed  upon  them  near 
their  origin. 

The  aortic  plexus  is  formed  by  branches  derived,  on  each  side,  from  the  solar 
plexus  and  the  semilunar  ganglia,  receiving  filaments  from  some  of  the  lumbar 
ganglia.  It  is  situated  upon  the  sides  and  front  of  the  aorta,  between  the  origins 
of  the  superior  and  inferior  mesenteric  arteries.  From  this  plexus  arise  part  of 
the  spermatic,  the  inferior  mesenteric,  and  the  hypogastric  plexuses ;  and  it  dis- 
tributes filaments  to  the  inferior  vena  cava. 

The  inferior  mesenteric  plexus  is  derived  chiefly  from  the  left  side  of  the  aortic 
plexus.  It  surrounds  the  inferior  mesenteric  artery,  and  divides  into  a  number  of 
secondary  plexuses,  which  are  distributed  to  all  the  parts  supplied  by  the  artery — 
viz.  the  left  colic  and  sigmoid  plexuses,  which  supply  the  descending  and  sigmoid 
flexure  of  the  colon  ;  and  the  superior  hemorrhoidal  plexus,  which  supplies  the 
upper  part  of  the  rectum  and  joins  in  the  pelvis  with  branches  from  the  pelvic 
plexus. 

The  Hypogastric  Plexus. 

The  Hypogastric  Plexus  supplies  the  viscera  of  the  pelvic  cavity.  It  is  situated 
in  front  of  the  promontory  of  the  sacrum,  between  the  two  common  iliac  arteries, 
and  is  formed  by  the  union  of  numerous  filaments,  which  descend  on  each  side 
from  the  aortic  plexus  and  from  the  lumbar  ganglia.  This  plexus  contains  no 
evident  ganglia ;  it  bifurcates,  below,  into  two  lateral  portions,  which  form  the 
pelvic  plexuses. 


The  Pelvic  Plexus. 


The  pelvic  plexus  (sometimes  called  inferior  hypogastric)  supplies  the  viscera 
of  the  pelvic  cavity,  is  situated  at  the  side  of  the  rectum  in  the  male,  and  at  the 
side  of  the  rectum  and  vagina  in  the  female.  It  is  formed  by  a  continuation  of  the 
hypogastric  plexus,  by  branches  from  the  second,  third,  and  fourth  sacral  nerves, 
and  by  a  few  filaments  from  the  first  two  sacral  ganglia.  At  the  point  of  junction 
of  these  nerves  small  ganglia  are  found.  From  this  plexus  numerous  branches  are 
distributed  to  all  the  viscera  of  the  pelvis.  They  accompany  the  branches  of  the 
internal  iliac  artery. 

The  inferior  hsemorrhoidal  plexus  arises  from  the  back  part  of  the  pelvic 
plexus.  It  supplies  the  rectum,  joining  with  branches  of  the  superior  hemor- 
rhoidal plexus. 

The  vesical  plexus  arises  from  the  fore  part  of  the  pelvic  plexus.  The  nerves 
composing  it  are  numerous,  and  contain  a  large  proportion  of  spinal  nerve-fibres. 
They  accompany  the  vesical  arteries,  and  are  distributed  at  the  side  and  base  of 
the  bladder.  Numerous  filaments  also  pass  to  the  vesiculse  seminales  and  vas 
deferens ;  those  accompanying  the  vas  deferens  join,  on  the  spermatic  cord,  with 
branches  from  the  spermatic  plexus. 

The  prostatic  plexus  is  continued  from  the  lower  part  of  the  pelvic  plexus. 
The  nerves  composing  it  are  of  large  size.  They  are  distributed  to  the  pros- 
tate gland,  vesiculse  seminales,  and  erectile  structure  of  the  penis.     The  nerves. 


810  THE   NERVOUS  SYSTEM. 

supplying  the  erectile  structure  of  the  penis  consist  of  two  sets,  the  small  and 
large  cavernous  nerves.  They  are  slender  filaments,  which  arise  from  the  fore 
part  of  the  prostatic  plexus,  and,  after  joining  with  branches  from  the  internal 
pudic  nerve,  pass  forward  beneath  the  pubic  arch. 

The  small  cavernous  nerves  perforate  the  fibrous  covering  of  the  penis  near  its 
roots. 

The  large  cavernous  nerve  passes  forward  along  the  dorsum  of  the  penis, 
joins  with  the  dorsal  branch  of  the  pudic  nerve,  and  is  distributed  to  the  corpus 
cavernosum  and  spongiosum. 

The  vaginal  plexus  arises  from  the  lower  part  of  the  pelvic  plexus.  It  is  lost 
on  the  walls  of  the  vagina,  being  distributed  to  the  erectile  tissue  at  its  anterior 
part  and  to  the  mucous  membrane.  The  nerves  composing  this  plexus  contain, 
like  the  vesical,  a  large  proportion  of  spinal  nerve-fibres. 

The  uterine  plexus  arises  from  the  upper  part  of  the  pelvic  plexus  above  the 
point  where  the  branches  from  the  sacral  nerves  join  the  plexus.  Its  branches 
accompany  the  uterine  arteries  to  the  side  of  the  organ  between  the  layers  of  the 
broad  ligament,  and  are  distributed  to  the  cervix  and  lower  part  of  the  body  of  the 
uterus,  penetrating  its  substance. 

Other  filaments  pass  separately  to  the  body  of  the  uterus  and  Fallopian  tube. 

Branches  from  the  plexus  accompany  the  uterine  arteries  into  the  substance 
of  the  uterus.      Upon  these  filaments  ganglionic  enlargements  are  found. 


THE  ORGANS  OF  SPECIAL  SENSE. 


THE  Organs  of  the  Senses  are  five  in  number,  viz.,  those  of  Touch,  of  Taste, 
of  Smell,  of  Hearing,  and  of  Sight.  The  skin,  which  is  the  principal  seat 
of  the  sense  of  touch,  will  be  described  in  the  section  on  General  Anatomy.  The 
remaining  four  are  the  Organs  of  Special  Sense. 


THE  TONGUE. 

The  Tongue  is  the  organ  of  the  special  sense  of  taste.  It  is  situated  in  the 
floor  of  the  mouth,  in  the  interval  between  the  two  lateral  portions  of  the  body  of 
the  lower  jaw. 

Its  base  or  root  is  directed  backward,  and  connected  with  the  os  hyoides  by 
the  Hyo-glossi  and  Genio-hyo-glossi  muscles  and  the  hyo-glossal  membrane ;  with 
the  epiglottis  by  three  folds  (glosso-epiglottic)  of  mucous  membrane ;  with  the  soft 
palate  by  means  of  the  anterior  pillars  of  the  fauces ;  and  with  the  pharynx  by 
the  Superior  constrictors  and  the  mucous  membrane.  Its  apex  or  tip,  thin  and 
narrow,  is  directed  forward  against  the  inner  surface  of  the  lower  incisor  teeth. 
The  under  surface  of  the  tongue  is  connected  with  the  lower  jaw  by  the  Genio-hyo- 
glossi  muscles ;  from  its  sides  the  mucous  membrane  is  reflected  to  the  inner  sur- 
face of  the  gums ;  and  from  its  under  surface  on  to  the  floor  of  the  mouth,  where, 
in  the  middle  line,  it  is  elevated  into  a  distinct  vertical  fold,  the  frcenum  lingual. 
To  the  outer  side  of  the  frsenum  is  a  slight  fold  of  the  mucous  membrane,  the 
plica  fimbriata,  the  free  edge  of  which  exhibits  a  series  of  fringe-like  processes. 

The  tip  of  the  tongue,  part  of  the  under  surface,  its  sides,  and  dorsum  are  free. 

The  dorsum  of  the  tongue  is  convex,  marked  along  the  middle  line  by  a  raphe\ 
which  divides  it  into  symmetrical  halves  ;  this  raphe  terminates  behind,  about  an 
inch  from  the  base  of  the  organ,  in  a  depression,  the  foramen  caecum,  from  which 
a  shallow  groove,  the  sulcus  terminalis  of  His,  runs  outward  and  forward  on  each 
side  to  the  lateral  margin  of  the  tongue.  The  part  of  the  dorsum  of  the  tongue  in 
front  of  this  groove,  forming  about  two-thirds  of  its  upper  surface,  is  rough  and 
covered  with  papillae ;  the  posterior  third  is  smoother,  and  contains  numerous 
muciparous  glands  and  lymphoid  follicles. 

Structure  of  the  Tongue. — The  tongue  is  partly  invested  by  mucous  membrane 
and  a  submucous  fibrous  layer.  It  consists  of  symmetrical  halves,  separated  from 
each  other,  in  the  middle  line,  by  a  fibrous  septum.  Each  half  is  composed  of 
muscular  fibres  arranged  in  various  directions  (page  325),  containing  much  inter- 
posed fat,  and  supplied  by  vessels  and  nerves. 

The  mucous  membrane  invests  the  entire  extent  of  the  free  surface  of  the 
tongue.  On  the  dorsum  it  is  thicker  behind  than  in  front,  and  is  continuous  with 
the  sheath  of  the  muscles  attached  to  it,  through  the  submucous  fibrous  layer.  On 
the  under  surface  of  the  organ,  where  it  is  thin  and  smooth,  it  can  be  traced  on 
each  side  of  the  fireenum  through  the  ducts  of  the  submaxillary  and  the  sublingual 
glands.  As  it  passes  over  the  borders  of  the  organ  it  gradually  assumes  its  papil- 
lary character. 

The  structure  of  the  mucous  membrane  of  the  tongue  differs  in  different  parts. 
That  covering  the  under  surface  of  the  organ  is  thin,  smooth,  and  identical  in 

811 


812 


THE    ORGANS   OF  SPECIAL   SENSE. 


structure  with  that  lining  the  rest  of  the  oral  cavity.  The  mucous  membrane 
covering  the  tongue  behind  the  foramen  caecum  and  sulcus  terminalis  is  thick  and 
freely  movable  over  the  subjacent  parts.  It  contains  a  large  number  of  lymphoid 
follicles,  which  together  constitute  what  is  sometimes  termed  the  lingual  tonsil. 
Each  follicle  forms  a  rounded  eminence,  the  centre  of  which  is  perforated  by  a 
minute  orifice  leading  into  a  funnel-shaped  cavity  or  recess ;  around  this  recess 
are  grouped  numerous  oval  or  rounded  nodules  of  lymphoid  tissue,  each  enveloped 
by  a  capsule  derived  from  the  submucosa,  while  opening  into  the  bottom  of  the 
recesses  are  also  seen  the  ducts  of  mucous  glands.  The  mucous  membrane  on  the 
anterior  part  of  the  dorsum  of  the  tongue  is  thin  and  intimately  adherent  to  the 


PHARYNX 


RCUM- 

VALLATE 

PAPILUE. 


Fig.  428.— Upper  surface  of  the  tongue. 


muscular  tissue,  and  covered  with  minute  eminences,  the  papilla  of  the  tongue. 
It  consists  of  a  layer  of  connective  tissue,  the  eorium  or  mucosa,  supporting 
numerous   papillae,  and  covered,  as  well  as  the  papillae,  with   epithelium. 

The  epithelium  is  of  the  scaly  variety,  like  that  of  the  epidermis.  It  covers  the 
free  surface  of  the  tongue,  as  may  be  easily  demonstrated  by  maceration  or  boiling, 
when  it  can  be  easily  detached  entire  :  it  is  much  thinner  than  on  the  skin :  the 
intervals  between  the  large  papillae  are  not  filled  up  by  it,  but  each  papilla  has 
a  separate  investment  from  root  to  summit.  The  deepest  cells  may  sometimes  be 
detached  as  a  separate  layer,  corresponding  to  the  rete  mucosum,  but  they  never 
contain  coloring  matter. 


THE    TONGUE. 


813 


The  corium  consists  of  a  dense  feltwork  of  fibrous  connective  tissue,  with, 
numerous  elastic  fibres,  firmly  connected  with  the  fibrous  tissue  forming  the  septa 
between  the  muscular  bundles  of  the  tongue.  It  contains  the  ramifications  of  the 
numerous  vessels  and  nerves  from  which  the  papillae  are  supplied,  large  plexuses 
of  lymphatic  vessels,  and  the  glands  of  the  tongue. 

The  Papillae  of  the  Tongue. — These  are  papillary  projections  of  the  corium. 
They  are  thickly  distributed  over  the  anterior  two-thirds  of  its  upper  surface,  giving 
to  it  its  characteristic  roughness.  The  varieties  of  papillae  met  with  are — the 
papillae  maximae  (circumvallatae),  papillae  mediae  (fungiformes),  papillae  minimae 
(conicae  or  fliformes),  and  papillae  simplices. 


Filiform. 


Fungiform. 


Secondary 

ffliV  (1/1 ; J M Wm~^7  papilla. 


Circumvallate. 


Artery,  ^a  f^Vein. 


Fig.  429. — The  three  kinds  of  papillse,  magnified. 


The  papillae  maximce  (circumvallatae)  are  of  large  size,  and  vary  from  eight  to 
twelve  in  number.  They  are  situated  at  the  back  part  of  the  dorsum  of  the  tongue, 
near  its  base,  forming  a  row  on  each  side,  which,  running  backward  and  inward, 
meet  in  the  middle  line,  like  the  two  lines  of  the  letter  V  inverted.  Each  papilla 
consists  of  a  projection  of  mucous  membrane  from  ^j  to  -^  of  an  inch  wide, 
attached  to  the  bottom  of  a  cup-shaped  depression  of  the  mucous  membrane ;  the 
papilla  is  in  shape  like  a  truncated  cone,  the  smaller  end  being  directed  down- 
ward and  attached  to  the  tongue,  the  broader  part  or  base  projecting  on  the  sur- 
face and  being  studded  with  numerous  small  secondary  papillae,  which,  however, 
are  covered  by  a  smooth  layer  of  the  epithelium.  The  cup-shaped  depression 
forms  a  kind  of  fossa  round  the  papilla,  having  a  circular  margin  of  about  the 
same  elevation  covered  with  smaller  papillae. 

Immediately  behind  the  apex  of  the  V  is  the  foramen  caecum,  mentioned  above. 
This,  according  to  His,  represents  the  remains  of  the  invagination  which  forms  the 
median  rudiment  of  the  thyroid  body,  and  for  a  time  opens  by  a  duct,  the  thyro- 
glossal  duct,  on  to  the  dorsum  of  the  tongue.  It  may  extend  downward  toward 
the  hyoid  bone.      Kanthack,  however,  disputes  this  view.1 

The  'papillae  mediae  (fungiformes),  more  numerous  than  the  preceding,  are 
scattered  irregularly  and  sparingly  over  the  dorsum  of  the  tongue,  but  are  found 
chiefly  at  its  sides  and  apex.  They  are  easily  recognized  among  the  other 
papillae,  by  their  large  size,  rounded  eminences,  and  deep-red  color.  They  are 
narrow  at  their  attachment  to  the  tongue,  but  broad  and  rounded  at  their  free 
extremities,  and  covered  with  secondary  papillae.  Their  epithelial  investment  is 
very  thin. 

The  papillae  minimae  (conicae  or  filiformes)  cover  the  anterior  two-thirds  of  the 
dorsum  of  the  tongue.  They  are  very  minute,  more  or  less  conical  or  filiform  in 
shape,  and  arranged  in  lines  corresponding  in  direction  with  the  two  rows  of  the 
papillae  circumvallatae,  excepting  at  the  apex  of  the  organ,  where  their  direction 


1  Journal  of  Anat.  and  Physiol.,  1891. 


814 


THE    ORGANS    OF  SPECIAL   SENSE. 


Fig.  430.— Circumvallate  papillce  of  tongue 
of  rabbit,  showing  position  of  taste-goblets. 
(Stohr.)  a.  Duct  of  gland,  d.  Serous  gland,  g. 
Taste-buds.  I.  Primary  septa,  and  V ,  second- 
ary septa,,  of  papillae,  n.  Medullated  nerve. 
M.  Muscular  fibres. 


is  transverse.     Projecting  from  their   apices   are  numerous  filiform  processes  or 
secondary  papillae  ;  these  are  of  a  whitish  tint,  owing  to  the  thickness  and  density 

of  the  epithelium  of  which  they  are  com- 
posed, and  which  has  here  undergone  a 
peculiar  modification,  the  cells  having  be- 
come cornified  and  elongated  into  dense, 
imbricated,  brush-like  processes.  They  con 
tain  also  a  number  of  elastic  fibres,  which 
render  them  firmer  and  more  elastic  than 
the  papillae  of  mucous  membrane  generally. 
Simple  papilla?,  similar  to  those  of  the 
skin,  cover  the  whole  of  the  mucous  mem- 
brane of  the  tongue,  as  well  as  the  larger 
papillae.  They  consist  of  closely  set,  micro- 
scopic elevations  of  the  corium,  containing 
a  papillary  loop,  covered  by  a  layer  of  epi- 
thelium. 

Structure  of  the  Papillce. — The  papillae 
apparently  resemble  in  structure  those  of 
the  cutis,  consisting  of  a  cone-shaped  pro- 
jection of  connective  tissue,  covered  with  a 
thick  layer  of  squamous  epithelium,  and 
contain  one  or  more  capillary  loops,  amongst 
which  nerves  are  distributed  in  great  abundance.  If  the  epithelium  is  removed, 
it  will  be  found  that  they  are  not  simple  elevations  like  the  papillae  of  the 
skin,  for  the  surface  of  each  is  studded  with  minute  conical  processes  of  the 
mucous  membrane,  which  form  secondary  papillae  (Todd  and  Bowman).  In 
the  papillae  circumvallatae  the  nerves  are  numerous  and  of  large  size;  in  the 
papillae  fungiformes  they  are  also  numerous,  and  terminate  in  a  plexiform  net- 
work, from  which  brush-like-  branches  proceed ;  in  the  papillae  filiformes  their 
mode  of  termination  is  uncertain.  Buried  in  the  epidermis  of  the  papillae  circum- 
vallatae, and  in  some  of  the  fungiformes,  are  certain  peculiar  bodies,  called  taste-buds.1 
They  are  flask-like  in  shape,  their  broad  base 
resting  on  the  corium,  and  their  neck  opening  by 
an  orifice,  the  gustatory  pore,  between  the  cells 
of  the  epithelium.  They  are  formed  by  two  kinds 
of  cells ;  supporting  cells  and  gustatory  cells. 
The  supporting  cells  are  mostly  arranged  like  the 
staves  of  a  cask,  and  form  an  outer  envelope  for 
the  bud.  Some,  however,  are  found  in  the  interior 
of  the  bud  between  the  gustatory  cells.  The 
gustatory  cells  occupy  the  central  portion  of  the 
bud ;  they  are  spindle-shaped,  and  each  possesses 
a  large  spherical  nucleus  near  the  middle  of  the 
cell.  The  peripheral  end  of  the  cell  terminates 
at  the  gustatory  pore  in  a  fine,  hair-like  filament, 

the  gustatory  hair.  The  central  process  passes  toward  the  deep  extremity  of  the 
bud,  and  there  ends  in  a  single  or  bifurcated  varicose  filament,  which  was  formerly 
supposed  to  be  continuous  with  the  terminal  fibril  of  a  nerve ;  the  investigations 
of  Lenhossek  and  others  would  seem  to  prove,  however,  that  this  is  not  so,  but 
that  the  nerve-fibrils  after  losing  their  medullary  sheaths  enter  the  taste-bud.  and 
terminate  in  a  fine  extremity  between  the  gustatory  cells.  Other  nerve-fibrils 
may  be  seen  ramifying  between  the  cortical  cells  and  terminating  in  fine 
extremities ;  these,  however,  are  believed  to  be  nerves  of  ordinary  sensation,  and 
not  gustatory. 

1  These  bodies  are  also  found  in  considerable  numbers  at  the  side  of  the  base  of  the  tongue,  just 
in  front  of  the  anterior  pillars  of  the  fauces,  and  also  on  the  posterior  surface  of  the  epiglottis  and 
anterior  surface  of  the  soft  palate. 


Fig.  431. — Taste-buds,   a,  Supporting 
cells.    6.  Gustatory  cell. 


THE    TONGUE. 


815 


Glands  of  the   Tongue. — The  tongue  is  provided  with  mucous  and  serous 

glands. 

The  mucous  glands  are  similar  in  structure  to  the  labial  and  buccal  glands. 
They  are  found  especially  at  the  back  part,  behind  the  circumvallate  papillae, 
but  are  also  present  at  the  apex  and  marginal  parts.  In  connection  with  these 
glands  a  special  one  has  been  described  by  Blandin  or  Nuhn.  It  is  situated  near 
the  apex  of  the  tongue  on  either  side  of  the  frsenum,  and  is  covered  over  by  a 


Bristles 
in  ducts 
of  glands. 

Glands  of 
Blandin 

i    or  Nuhn. 


Lingual  nerve.         Ranine  artery. 
Fig.  432.— Under  surface  of  tongue,  showing  position  and  relations  of  gland  of  Blandin  or  Nuhn.    (From  a 
preparation  in  the  Museum  of  the  Royal  College  of  Surgeons  of  England.) 

fasciculus  of  muscular  fibre  derived  from  the  Stylo-glossus  and  Inferior  lingualis. 
It  is  from  half  an  inch  to  nearly  an  inch  long  and  about  the  third  of  an  inch 
broad.  It  has  from  four  to  six  ducts,  which  open  on  the  under  surface  of  the 
apex. 

The  serous  glands  occur  only  at  the  back  of  the  tongue  in  the  neighborhood 
of  the  taste-buds,  their  ducts  opening  for  the  most  part  into  the  fossae  of  the  cir- 
cumvallate papillae.  These  glands  are  racemose,  the  duct  branching  into  several 
minute  ducts,  which  terminate  in  alveoli  lined  by  a  single  layer  of  more  or  less 
columnar  epithelium.  Their  secretion  is  of  a  watery  nature,  and  probably  assists 
in  the  distribution  of  the  substance  to  be  tasted  over  the  taste-area  (Ebner). 

The  fibrous  septum  consists  of  a  vertical  layer  of  .fibrous  tissue,  extending 
throughout  the  entire  length  of  the  middle  line  of  the  tongue,  from  the  base 
to  the  apex,  though  not  quite  reaching  the  dorsum.  It  is  thicker  behind  than 
in  front,  and  occasionally  contains  a  small  fibro-cartilage  about  a  quarter  of  an 
inch  in  length.  It  is  well  displayed  by  making  a  vertical  section  across  the 
organ. 

The  Hyo-glossal  membrane  is  a  strong  fibrous  lamina  which  connects  the  under 
surface  of  the  base  of  the  tongue  to  the  body  of  the  hyoid  bone.  This  membrane 
receives,  in  front,  some  of  the  fibres  of  the  Genio-hyo-glossi. 

Vessels  of  the  Tongue. — The  arteries  of  the  tongue  are  derived  from  the  lin- 
gual, the  facial,  and  ascending  pharyngeal.  The  veins  open  into  the  internal 
jugular. 

Muscles  of  the  Tongue. — The  muscular  fibres  of  the  tongue  run  in  various 
directions.  These  fibres  are  divided  into  two  sets,  Extrinsic  and  Intrinsic,  which 
have  already  been  described  (page  325). 

The  lymphatic  vessels  from  the  tongue  pass  to  one  or  two  small  glands  situated 


816 


THE    ORGANS    OF  SPECIAL    SENSE. 


on  the  Hyo-glossus  muscle  in  the  submaxillary  region,  and  thence  to  the  deep 
glands  of  the  neck. 

The  nerves  of  the  tongue  are  five  in  number  in  each  half :  the  lingual  branch 
of  the  fifth,  which  is  distributed  to  the  papillae  at  the  fore  part  and  sides  of 
the  tongue,  and  forms  the  nerve  of  ordinary  sensibility  for  its  anterior  two-thirds  ; 
the  chorda  tympani,  which  runs  in  the  sheath  of  the  lingual,  is  generally  regarded  as 


Submaxillary 
artery. 


i  nerve. 

Submaxillary 
lion. 

Hypo- glossal 


Glosso-jpharyn 
geal  nerve. 


Superior  laryn 
geal  nerve. 


Fig.  433.— Under  surface  of  tongue,  showing  the  distribution  of  nerves  to  this  organ.    (From  a  preparation 
in  the  Museum  of  the  Royal  College  of  Surgeons  of  England.) 

the  nerve  of  taste  for  the  same  area  ;  the  lingual  branch  of  the  glosso-pharyngeal, 
which  is  distributed  to  the  mucous  membrane  at  the  base  and  sides  of  the  tongue, 
and  to  the  papilla  circutuvallatae,  and  which  supplies  both  sensory  and  gustatory 
filaments  to  this  region ;  the  hypo-glossal  nerve,  which  is  the  motor  nerve  to  the 
muscular  substance  of  the  tongue  ;  and  the  superior  laryngeal,  which  sends  some 
fine  branches  to  the  root  near  to  the  epiglottis.  Sympathetic  filaments  also  pass 
to  the  tongue  from  the  nervi  molles  on  the  lingual  and  other  arteries  supplying  it. 

Surgical  Anatomy. — The  diseases  to  which  the  tongue  is  liable  are  numerous,  and  its 
surgical  anatomy  of  importance,  since  any  or  all  the  structures  of  which  it  is  composed — muscles, 
connective  tissue,  mucous  membrane,  glands,  vessels,  nerves,  and  lymphatics — may  be  the  seat 
of  morbid  changes.  It  is  not  often  the  seat  of  congenital  defects,  though  a  few  cases  of  vertical 
cleft  have  been  recorded,  and  it  is  occasionally,  though  much  more  rarely  than  is  commonly  sup- 
posed, the  seat  of  "tongue-tie,"  from  shortness  of  the  fhenum.     (See  page  489.) 

There  is,  however,  one  condition  which  must  be  regarded  as  congenital,  though  it  does  not 
sometimes  evidence  itself  until  a  year  or  two  after  birth,  which  is  not  uncommon.  This  is  an 
enlargement  of  the  tongue  which  is  due  primarily  to  a  dilatation  of  the  lymph-channels  and  a 
greatly  increased  development  of  the  lymphatic  tissue  throughout  the  tongue.     This  is  often 


THE    TONGUE.  817 

aggravated  by  inflammatory  changes  induced  by  injury  or  exposure,  and  the  tongue  may  assume 
enormous  dimensions  and  hang  out  of  the  mouth,  giving  the  child  an  imbecile  expression.  The 
treatment  consists  in  excising  a  V-shaped  portion  and  bringing  the  cut  surfaces  together  with 
deeply-placed  silver  sutures.  Compression  has  been  resorted  to  in  some  cases  and  with  success, 
but  it  is  difficult  to  apply.  Acute  inflammation  of  the  tongue,  which  may  be  caused  by  injury 
and  the  introduction  of  some  septic  or  irritating  matter,  is  attended  by  great  swelling  from 
infiltration  of  its  connective  tissue,  which  is  in  considerable  quantity.  This  renders  the  patient 
incapable  of  swallowing  or  speaking,  and  may  seriously  impede  respiration.  It  may  run  on  to 
suppuration  and  the  formation  of  an  acute  abscess.  Chronic  abscess,  which  has  been  mistaken 
for  cancer,  may  also  occur  in  the  substance  of  the  tongue. 

The  mucous  .membrane  of  the  tongue  may  become  chronically  inflamed,  and  presents 
different  appearances  in  different  stages  of  the  disease,  to  which  the  terms  leucoplakia,  psoriasis, 
and  ichthyosis  have  been  given. 

The  tongue,  being  very  vascular,  is  often  the  seat  of  naevoid  growths,  and  these  have  a  tend- 
ency to  grow  rapidly. 

The  tongue  is  frequently  the  seat  of  ulceration,  which  may  arise  from  many  causes,  as  from 
the  irritation  of  jagged  teeth,  dyspepsia,  tubercle,  syphilis,  and  cancer.  Of  these  the  cancerous 
ulcer  is  the  most  important,  and  probably  also  the  most  common.  The  variety  is  the  squamous 
epithelioma,  which  soon  develops  into  an  ulcer  with  an  indurated  base.  It  produces  great  pain, 
which  speedily  extends  to  all  parts  supplied  with  sensation  by  the  fifth  nerve,  especially  to  the 
region  of  the  ear.  The  pain  in  these  cases  is  conducted  to  the  ear  and  temporal  region  by  the 
lingual  nerve,  and  from  it  to  the  other  branches  of  the  inferior  maxillary  nerve,  especially  the 
auriculotemporal.  Possibly  pain  in  the  ear  itself  may  be  due  to  implication  of  the  fibres  of 
the  glosso-pharyngeal  nerve,  which  by  its  tympanic  branch  is  conducted  to  the  tympanic 
plexus. 

Cancer  of  the  tongue  may  necessitate  removal  of  a  part  or  the  whole  of  the  organ,  and 
many  different  methods  have  been  adopted  for  its  excision.  It  may  be  removed  from  the  mouth 
by  the  ecraseur  or  the  scissors.  Probably  the  better  method  is  by  the  scissors,  usually  known 
as  Whitehead's  method.  _  The  mouth  is  widely  opened  with  a  gag,  the  tongue  transfixed  with  a 
stout  silk  ligature,  by  which  to  hold  and  make  traction  on  it  and  the  reflection  of  mucous  mem- 
brane from  the  tongue  to  the  jaw,  and  the  insertion  of  the  Genio-hyo-glossus  first  divided  with 
a  pair  of  curved  blunt  scissors.  The  Palato-glossus  is  also  divided.  The  tongue  can  now  be 
pulled  well  out  of  the  mouth.  The  base  of  the  tongue  is  cut  through  by  a  series  of  short  snips, 
each  bleeding  vessel  being  dealt  with  as  soon  as  divided,  until  the  situation  of  the  ranine  artery 
is  reached.  The  remaining  undivided  portion  of  tissue  is  to  be  seized  with  a  pair  of  Wells's 
forceps,  the  tongue  removed,  and  the  vessel  secured.  In  the  event  of  the  ranine  artery  being 
accidentally  injured  haemorrhage  can  be  at  once  controlled  by  passing  two  fingers  over  the 
dorsum  of  the  tongue  as  far  as  the  epiglottis  and  dragging  the  root  of  the  tongue  forcibly 
forward. 

In  cases  where  the  disease  is  confined  to  one  side  of  the  tongue  this  operation  may  be 
modified  by  splitting  the  tongue  down  the  centre  and  removing  only  the  affected  half.  In 
cases  where  the  submaxillary  glands  are  involved  Kocher's  operation  should  be  performed. 
He  removes  the  tongue  from  the  neck,  having  performed  a  preliminary  tracheotomy,  by  an  incis- 
ion from  near  the  lobule  of  the  ear,  down  the  anterior  border  of  the  Sterno-mastoid  to  the  level 
of  the  great  cornu  of  the  hyoid  bone,  then  forward  to  the  body  of  the  hyoid  bone,  and  upward 
to  near  the  symphysis  of  the  jaw.  The  lingual  artery  is  now  secured,  and  by  a  careful  dissec- 
tion the  submaxillary  lymphatic  glands  and  the  tongue  removed.  Regnoli  advocated  the  removal 
of  the  tongue  by  a  semilunar  incision  in  the  submaxillary  triangle  along  the  line  of  the  lower 
jaw,  and  a  vertical  incision  from  the  centre  of  the  semilunar  one  backward  to  the  hyoid  bone. 
Care  must  be  taken  not  to  carry  the  first  incision  too  far  backward,  so  as  to  wound  the  facial 
arteries.  The  tongue  is  thus  reached  through  the  floor  of  the  mouth,  pulled  out  through  the 
external  incision,  and  removed  with  the  ecraseur  or  knife.  The  great  objection  to  this  operation 
is  that  all  the  muscles  which  raise  the  hyoid  bone  and  larynx  are  divided,  and  that  therefore  the 
movements  of  deglutition  and  respiration  are  interfered  with. 

Finally,  where  both  sides  of  the  floor  of  the  mouth  are  involved  in  the  disease,  or  where 
very  free  access  is  required  on  account  of  the  extension  backward  of  the  disease  to  the  pillars 
of  the  fauces  and  the  tonsil,  or  where  the  lower  jaw  is  involved,  the  operation  recommended  by 
Syme  must  be  performed.  This  is  done  by  an  incision  through  the  central  line  of  the  lip,  across 
the  chin,  and  down  as  far  as  the  hyoid  bone.  The  lower  jaw  is  sawn  through  at  the  symphysis, 
and  the  two  halves  of  the  bone  forcibly  separated  from  each  other.  The  mucous  membrane  is 
separated  from  the  bone,  and  the  Genio-hyo-glossi  detached  from  the  bone,  and  the  Hyo-glossi 
divided.  The  tongue  is  then  drawn  forward  and  removed  close  to  its  attachment  to  the  hyoid 
bone.  Any  glands  which  are  enlarged  can  be  removed,  and  if  the  bone  is  implicated  in  the 
disease,  it  can  also  be  removed  by  freeing  it  from  the  soft  parts  externally  and  internally,  and 
making  a  second  section  with  the  saw  beyond  the  diseased  part. 

Formerly  many  surgeons  before  removing  the  tongue  performed  a  preliminary  tracheotomy : 
(1)  to  prevent  blood  entering  the  air-passages  ;  and  (2)  to  allow  the  patient  to  breathe  through 
the  tube  and  not  inspire  air  which  had  passed  over  a  sloughy  wound,  and  which  was  loaded  with 
septic  organisms  and  likely  to  induce  septic  pneumonia.  By  the  judicious  use  of  iodoform  this 
secondary  evil  may  be  obviated,  and  the  preliminary  tracheotomy  is  now  usually  dispensed 
with. 

52 


818 


THE    ORGANS    OF  SPECIAL    SENSE. 
THE   NOSE. 


The  nose  is  the  peripheral  organ  of  the  sense  of  smell :  by  means  of  the  pecu- 
liar properties  of  its  nerves  it  protects  the  lungs  from  the  inhalation  of  delete- 
rious gases  and  assists  the  organ  of  taste  in  discriminating  the  properties  of  food. 


Seen  from  below. 


Side  view. 


Lower  lateral  cartilage. 


Sesamoid  cartilages 


Figs.  434,  435.— Cartilages  of  the  nose. 


The  organ  of  smell  consists  of  two  parts :  one  external,  the  outer  nose ;  the 
other  internal,  the  nasal  fossce. 

The  outer  nose  (nasus  externus)  is  the  more  anterior  and  prominent  part  of  the 
organ  of  smell.  Of  a  triangular  form,  it  is  directed  downward,  and  projects  from 
the  centre  of  the  face,  immediately  above  the  upper  lip.  Its  summit,  or  root,  is 
connected  directly  with  the  forehead.  Its  inferior  part,  or  base,  presents  two  ellip- 
tical orifices,  the  nostrils  or  anterior  nares,  separated  from  each  other  by  an  antero- 
posterior septum,  the  columna.  The  margins  of  these  orifices  are  provided  with 
a  number  of  stiff  hairs,  or  vibrissa?,  which  arrest  the  passage  of  foreign  substances 
carried  with  the  current  of  air  intended  for  respiration.  The  lateral  surfaces  of 
the  nose  form,  by  their  union  in  the  middle  line,  the  dorsum,  the  direction  of 
which  varies  considerably  in  different  individuals.  The  lateral  surface  terminates 
below  in  a  rounded  eminence,  the  ala  nasi. 

The  nose  is  composed  of  a  framework  of  bones  and  cartilages,  the  latter  being 
slightly  acted  upon  by  certain  muscles.  It  is  covered  externally  by  the  integument, 
internally  by  mucous  membrane,  and  supplied  with  vessels  and  nerves. 

The  bony  framework  occupies  the  upper  part  of  the  organ:  it  consists  of  the 
nasal  bones  and  the  nasal  processes  of  the  superior  maxillary. 

The  cartilaginous  framework  consists  of  five  pieces,  the  two  upper  and  the  two 
lower  lateral  cartilages  and  the  cartilage  of  the  septum. 

The  upper  lateral  cartilages  are  situated  below  the  free  margin  of  the  nasal 
bones  ;  each  cartilage  is  flattened  and  triangular  in  shape.  Its  anterior  margin  is 
thicker  than  the  posterior,  and  continuous  with  the  cartilage  of  the  septum.  Its 
posterior  margin  is  attached  to  the  nasal  process  of  the  superior  maxillary  and  nasal 
bones.  Its  inferior  margin  is  connected  by  fibrous  tissue  with  the  lower  lateral 
cartilage ;  one  surface  is  turned  outward,  the  other  inward  toward  the  nasal  cavity. 

The  lower  lateral  cartilages  are  two  thin,  flexible  plates  situated  immediately 
below  the  preceding,  and  bent  upon  themselves  in  such  a  manner  as  to  form  the 
inner  and  outer  walls  of  each  orifice  of  the  nostril.  The  portion  which  forms  the 
inner  wall,  thicker  than  the  rest,  is  loosely  connected  with  the  same  part  of  the 
opposite  cartilage,  and  forms  a  small  part  of  the  columna.  Its  inferior  border, 
free,  rounded,  and  projecting,  forms,  with  the  thickened  integument  and  subja- 
cent tissue  and  the  corresponding  parts  of  the  opposite  side,  the  septum  mobile 


THE   NOSE. 


819 


nasi.  The  part  which  forms  the  outer  wall  is  curved  to  correspond  with  the  ala  of 
the  nose ;  it  is  oval  and  flattened,  narrow  behind,  where  it  is  connected  with  the 
nasal  process  of  the  superior  maxilla  by  a  tough  fibrous  membrane,  in  which  are 
found  three  or  four  small  cartilaginous  plates  (sesamoid  cartilages — cartilagines 
minores).  Above,  it  is  connected  by  fibrous  tissue  to  the  upper  lateral  cartilage 
and  front  part  of  the  cartilage  of  the  septum  ;  below,  it  falls  short  of  the  margin 
of  the  nostril  ;  the  ala  being  formed  by  dense  cellular  tissue  covered  by  skin. 
In  front  the  lower  lateral  cartilages  are  separated  by  a  notch  which  corresponds 
with  the  point  of  the  nose. 

The  cartilage  of  the  septum  is  somewhat  quadrilateral  in  form,  thicker  at  its 
margins  than  at  its  centre,  and  completes  the  separation  between  the  nasal  fossae 
in  front.  Its  anterior  margin,  thickest 
above,  is  connected  with  the  nasal 
bones,  and  is  continuous  with  the  ante- 
rior margins  of  the  two  upper  lateral 
cartilages.  Below,  it  is  connected  to 
the  inner  portions  of  the  lower  lateral 
cartilages  by  fibrous  tissue.  Its  poste- 
rior margin  is  connected  with  the  per- 
pendicular lamella  of  the  ethmoid ;  its 
inferior  margin  with  the  vomer  and  the 
palate  processes  of  the  superior  maxil- 
lary bones. 

It  may  be  prolonged  backward  (es- 
pecially in  children)  for  some  distance 
between  the  vomer  and  perpendicular 
plate  of  the  ethmoid,  forming  what  is 
termed  the  processus  sphenoidalis.  The 
septal  cartilage  does  not  reach  as  far  as 
the  lowest  part  of  the  nasal  septum. 
This  is  formed  by  the  inner  portions  of  the  lower  lateral  cartilages  and  by  the 
skin ;  it  is  freely  movable,  and  hence  is  termed  the  septum  mobile  nasi. 

These  various  cartilages  are  connected  to  each  other  and  to  the  bones  by  a 
tough  fibrous  membrane,  which  allows  the  utmost  facility  of  movement  between 
them. 

The  muscles  of  the  nose  are  situated  beneath  the  integument :  they  are  (on 
each  side)  the  Pyramidalis  nasi,  the  Levator  labii  superioris  alaeque  nasi,  the 
Dilatator  naris,  anterior  and  posterior,  the  Compressor  nasi,  the  Compressor 
narium  minor,  and  the  depressor  alae  nasi.  They  have  been  described  above 
(page  306). 

The  integument  covering  the  dorsum  and  sides  of  the  nose  is  thin,  and  loosely 
connected  with  the  subjacent  parts  :  but  where  it  forms  the  tip  and  the  alae  of  the 
nose  it  is  thicker  and  more  firmly  adherent,  and  is  furnished  with  a  large  number 
of  sebaceous  follicles,  the  orifices  of  which  are  usually  very  distinct. 

The  mucous  membrane  lining  the  interior  of  the  nose  is  continuous  with  the 
skin  externally  and  with  that  which  lines  the  nasal  fossae  within. 

The  arteries  of  the  nose  are  the  lateralis  nasi  from  the  facial,  and  the  inferior 
artery  of  the  septum  from  the  superior  coronary,  which  supply  the  alae  and 
septum,  the  sides  and  dorsum  being  supplied  from  the  nasal  branch  of  the 
ophthalmic  and  the  infra-orbital. 

The  veins  of  the  nose  terminate  in  the  facial  and  ophthalmic. 

The  nerves  for  the  muscles  of  the  nose  are  derived  from  the  facial,  while  the 
skin  receives  its  branches  from  the  infra-orbital,  infratrochlear,  and  nasal  branches 
of  the  ophthalmic. 


Fig.  436. — Bones  and  cartilages  of  septum  of  nose. 
Right  side. 


820  THE    ORGANS    OF  SPECIAL    SENSE. 

Nasal  Fossae. 

The  nasal  fossae  are  two  irregular  cavities  situated  in  the  middle  of  the  face, 
and  extending  from  before  backward.  They  open  in  front  by  the  two  anterior 
nares,  and  terminate,  behind,  by  the  posterior  nares  in  the  naso-pharynx.  The 
anterior  nares  are  somewhat  pear-shaped  apertures,  each  measuring  about  one  inch 
antero-posteriorly  and  half  an  inch  transversely  at  their  widest  part.  The  posterior 
nares  are  two  oval  openings,  which  are  smaller  in  the  living  or  recent  subject  than 
in  the  skeleton,  because  they  are  narrowed  by  the  mucous  membrane.  Each 
measures  an  inch  in  the  vertical,  and  half  an  inch  in  the  transverse  direction  in  a 
well-developed  adult  skull. 

For  the  description  of  the  bony  boundaries  of  the  nasal  fossae  see  section  on 
Osteology. 

Inside  the  aperture  of  the  nostril  is  a  slight  dilatation,  the  vestibule,  which 
extends  as  a  small  pouch,  the  ventricle,  toward  the  point  of  the  nose.  The  fossa, 
above  and  behind  the  vestibule,  has  been  divided  into  two  parts :  an  olfactory 
portion,  consisting  of  the  upper  and  central  part  of  the  septum  and  probably  the 
superior  turbinated  bone,  and  a  respiratory  portion,  which  comprises  the  rest  of 
the  fossa. 

Outer  Wall. — The  sphenoidal  air  sinus  opens  into  the  spheno- ethmoidal  recess, , 
a  narrow  recess  above  the  superior  turbinated  bone.  The  posterior  ethmoidal 
cells  open  into  the  front  and  upper  part  of  the  superior  meatus.  On  raising  or 
cutting  away  the  middle  turbinated  bone  the  outer  wall  of  the  middle  meatus  is 
fully  exposed,  and  presents  (1)  a  rounded  elevation,  termed  the  bulla  ethmoidalis, 
opening  on  or  immediately  above  which  are  the  orifices  of  the  middle  ethmoidal 
cells ;  (2)  a  deep,  narrow,  curved  groove,  in  front  of  the  bulla  ethmoidalis,  termed 
the  hiatus  semilunaris,  into  which  the  anterior  ethmoidal  cells  and  the  antrum  of 
Highmore  open,  the  orifice  of  the  latter  being  placed  near  the  level  of  its  roof. 
The  middle  meatus  is  prolonged,  above  and  in  front,  into  the  infundibulum,  which 
leads  into  the  frontal  sinus.  The  anterior  extremity  of  the  meatus  is  continued 
into  a  depressed  area,  which  lies  above  the  vestibule  and  is  named  the  atrium. 
The  nasal  duct  opens  into  the  anterior  part  of  the  inferior  meatus,  the  opening 
being  frequently  overlapped  by  a  fold  of  mucous  membrane.  v 

The  inner  wall  or  septum  is  frequently  more  or  less  deflected  from  the  mesial 
plane,  thus  limiting  the  size  of  one  fossa  and  increasing  that  of  the  other.  Ridges 
or  spurs  of  bone  growing  outward  from  the  septum  are  also  sometimes  present.^ 
Immediately  over  the  incisive  foramen  at  the  lower  edge  of  the  cartilage  of  the 
septum  a  depression,  the  naso-palatine  recess,  may  be  seen.  In  the  septum  close 
to  this  recess  a  minute  orifice  may  be  discerned:  it  leads  into  a  blind  pouch,  the 
rudimentary  organ  of  Jacobson,  which  is  well  developed  in  some  of  the  lower  ani- 
mals, and  is  supported  by  a  plate  of  cartilage,  the  cartilage  of  Jacobson. 

The  mucous  membrane  lining  the  'nasal  fossae  is  called  the  pituitary,  from  the 
nature  of  its  secretion  ;  or  S c Jm eider ian,  from  Schneider,  the  first  anatomist  who 
showed  that  the  secretion  proceeded  from  the  mucous  membrane,  and  not,  as  was 
formerly  imagined,  from  the  brain.  It  is  intimately  adherent  to  the  periosteum 
or  perichondrium,  over  which  it  lies.  It  is  continuous  externally  with  the  skin 
through  the  anterior  nares.  and  with  the  mucous  membrane  of  the  naso-pharynx 
through  the  posterior  nares.  From  the  nasal  fossae  its  continuity  may  be  traced 
with  the  conjunctiva  through  the  nasal  duct  and  lachrymal  canals;  with  the 
lining  membrane  of  the  tympanum  and  mastoid  cells  through  the  Eustachian 
tube ;  and  with  the  frontal,  ethmoidal,  and  sphenoidal  sinuses,  and  the  antrum  of 
Highmore  through  the  several  openings  in  the  meatuses.  The  mucous  membrane 
is  thickest  and  most  vascular  over  the  turbinated  bones.  It  is  also  thick  over  the 
septum,  but  in  the  intervals  between  the  spongy  bones  and  on  the  floor  of  the 
nasal  fossae  it  is  very  thin.  Where  it  lines  the  various  sinuses  and  the  antrum  of 
Highmore  it  is  thin  and  pale. 

Owing  to  the  great  thickness  of   this  membrane,  the  nasal    fossae  are  much 


THE   NASAL    FOSSJE. 


821 


narrower,  and  the  turbinated  bones,  especially  the  lower  ones,  appear  larger  and 
more  prominent  than  in  the  skeleton.  From  the  same  circumstance  also  the 
various  apertures  communicating  with  the  meatuses  are  considerably  narrowed  or 
completely  closed. 

The  vestibule  is  lined  by  modified  skin,  and  contains  hairs  or  vibrissa  which 
guard  the  entrance  of  the  nostril. 

Structure  of  the  Mucous  Membrane. — The  epithelium  covering  the  mucous 
membrane  differs  in  its  character  according  to  the  functions  of  the  part  of  the  nose 
in  which  it  is  found.  In  the  respiratory  portion  of  the  nasal  cavity  the  epithelium 
is  columnar  and  ciliated.  Interspersed  among  the  columnar  ciliated  cells  are 
goblet  or  mucin  cells,  while  between  their  bases  are  found  smaller  pyramidal  cells. 
In  this  region,  beneath  the  epithelium  and  its  basement  membrane,  is  a  fibrous 


Hiatus  Ant.  ethm. 

semilunaris  cells 


Eye-ball 


Groove  (hiatus  semilunaris) 
leading  to  infundibulum 
Middle  turbinated  bone 

Middle  meatus 
Antrum  of  Highmore 
Inferior  meatus 


'Inferior  turbinated  bone 


f  Buccal  cavity 


Space  between  cheek  and  gum 
-Molar  tooth,  upper  jaw 


' —Moot  of  molar  tooth 


J^       III 

•"  >'  Tongue         Hard  palate 


Inferior  dental  nerve 


Septum 
nasi 

Fig.  437— Transverse  vertical  section  of  the  nasal  fossee.    The  section  is  made  anterior  to  the  superior 
turbinated  bones.    (Cryer.) 


layer  infiltrated  with  lymph-corpuscles,  so  as  to  form  in  many  parts  a  diffuse 
adenoid  tissue,  and  beneath  this  a  nearly  continuous  layer  of  smaller  and  larger 
glands,  some  mucous  and  some  serous,  the  ducts  of  which  open  upon  the  surface. 
In  the  olfactory  region  the  mucous  membrane  is  yellowish  in  color  and  the  epi- 
thelial cells  are  columnar  and  non-ciliated  ;  they  are  of  two  kinds,  supporting 
cells  and  olfactory  cells.  The  supporting  cells  contain  oval  nuclei,  situated  in  the 
deeper  parts  of  the  cells  :  the  free  surface  of  each  cell  presents  a  sharp  outline, 
and  its  deep  extremity  is  prolonged  into  a  process  which  runs  inward,  branching 
to  communicate  with  similar  processes  from  neighboring  cells,  so  as  to  form  a  net- 
work in  the  deep  part  of  the  mucous  membrane.  Lying  between  these  central 
processes  of  the  supporting  cells  are  a  large  number  of  spindle-shaped  cells,  the 
olfactory  cells,  which  consist  of  a  large  spherical  nucleus  surrounded  by  a  small 


822 


THE    ORGANS    OF  SPECIAL    SENSE. 


amount  of  granular  protoplasm,  and  possessing  two  processes,  of  which  one  runs 
outward  between  the  columnar  epithelial  cells,  and  projects  on  the  surface  of  the 


Fig.  438— Section  of  the  olfactory  mucous  membrane.    (Cadiat.)    a.  Epithelium,    b.  Glands  of  Bowman, 
c.  Nerve  bundles. 


mucous  membrane  as  a  fine,  hair-like  process,  the  olfactory  Mir ;  the  other  or 
deep  process  runs  inward,  is  frequently  beaded  like  a  nerve-fibre,  and  is  be- 
lieved by  most  observers  to  be  in  con- 
nection with  one  of  the  terminal  fila- 
ments of  the  olfactory  nerve.  Beneath 
the  epithelium,  extending  through  the 
thickness  of  the  mucous  membrane,  is  a 
layer  of  tubular,  often  .branched,  glands, 
the  glands  of  Boivman,  identical  in 
structure  with  serous  glands. 

The  arteries  of  thp  nasal  fossoe  are 
the    anterior    and    posterior   ethmoidal, 
from  the  ophthalmic,  which  supply  the 
ethmoidal     cells,    frontal    sinuses,    and 
roof  of  the  nose ;    the  spheno-palatine, 
from  the  internal  maxillary,  which  sup- 
plies   the    mucous    membrane    covering 
the  spongy  bones,  the  meatuses,  and  sep- 
tum ;    the   inferior    artery   of   the    sep^. 
turn,  from  the  superior  coronary  of  the 
facial ;  and  the  infraorbital  and  alveolar 
branches    of    the     internal    maxillary, 
which  supply  the  lining  membrane  of  the  antrum.      The  ramifications  of  these 
vessels  form   a   close,    plexiform   network,    beneath   and  in   the  substance  of  the 
mucous  membrane. 

The  veins  of  the  nasal  fossce  form  a  close,  cavernous-like  network  beneath  the 
mucous  membrane.  This  cavernous  appearance  is  especially  well  marked  over  the 
lower  part  of  the  septum  and  over  the  middle  and  inferior  turbinated  bones.  Some 
of  the  veins  pass,  with  those  accompanying  the  spheno-palatine  artery,  through  the 
spheno-palatine  foramen;  and  others,  through  the  alveolar  branch,  to  join  the 
facial  vein ;  some  accompany  the  ethmoidal  arteries,  and  terminate  in  the  ophthal- 
mic vein ;  and,  lastly,  a  few  communicate  with  the  veins  in  the  interior  of  the 


Fig.  439.— Nerves  of  septum  of  nose.    Right  side. 


THE  NASAL    FOSSJE.  823 

skull,  through  the  foramina  in  the  cribriform  plate  of  the  ethmoid  bone,  and  the 
foramen  caecum. 

The  lymphatics  can  be  injected  from  the  subdural  and  subarachnoid  spaces. 
and  form  a  plexus  in  the  superficial  portion  of  the  mucous  membrane.  The 
lymph  is  drained  partly  into  one  or  two  glands  which  lie  near  the  great  cornu  of 
the  hyoid  bone  and  partly  into  a  gland  situated  in  front  of  the  axis. 

The  nerves  are :  the  olfactory,  the  nasal  branch  of  the  ophthalmic,  filaments 
from  the  anterior  dental  branch  of  the  superior  maxillary,  the  Vidian,  the  naso- 
palatine, descending  anterior  palatine,  and  nasal  branches  of  Meckel's  ganglion. 

The  olfactory,  the  special  nerve  of  the  sense  of  smell,  is  distributed  to  the 
olfactory  region,  already  referred  to  (page  820). 

The  nasal  branch  of  the  ophthalmic  distributes  filaments  to  the  fore  part  of  the 
septum  and  outer  wall  of  the  nasal  fossae. 

Filaments  from  the  anterior  dental  branclt  of  the  superior  maxillary  .supply  the 
inferior  meatus  and  inferior  turbinated  bone. 

The  Vidian  nerve  supplies  the  upper  and  back  part  of  the  septum  and  superior 
spongy  bone,  and  the  upper  anterior  nasal  branches  from  the  spheno-palatine 
ganglion  have  a  similar  distribution. 

The  naso-palatine  nerve  supplies  the  middle  of  the  septum. 

The  larger  or  anterior  palatine  nerve  supplies  the  lower  nasal  branches  to  the 
middle  and  lower  spongy  bones. 

Surgical  Anatomy. — Instances  of  congenital  deformity  of  the  nose  are  occasionally  met 
with,  such  as  complete  absence  of  the  nose,  an  aperture  only  being  present ;  or  perfect  develop- 
ment on  one  side,  and  suppression  or  malformation  on  the  other ;  or  there  may  be  imperfect 
apposition  of  the  nasal  bones,  so  that  the  nose  presents  a  median  cleft  or  furrow.  Deformities 
which  have  been  acquired  are  much  more  common,  such  as  flattening  of  the  nose,  the  result  of 
syphilitic  necrosis,  or  imperfect  development  of  the  nasal  bones  in  cases  of  congenital  syphilis,  or 
a  lateral  deviation  of  the  nose  may  result  from  fracture. 

The  skin  over  the  alae  and  tip  of  the  nose  is  thick  and  closely  adherent  to  subjacent  parts. 
Inflammation  of  this  part  is  therefore  very  painful,  on  account  of  the  tension.  It  is  largely  sup- 
plied with  blood,  and,  the  circulation  here  being  terminal,  vascular  engorgement  is  liable  to  occur, 
especially  in  women  at  the  menopause  and  in  both  sexes  from  disorders  of  digestion,  exposure  to 
cold,  etc.  The  skin  of  the  nose  also  contains  a  large  number  of  sebaceous  follicles,  and  these,  as 
the  result  of  intemperance,  are  apt  to  become  affected  and  the  nose  reddened,  congested,  and 
irregularly  swollen.  To  this  the  term  ' '  grog-blossom  ' '  is  popularly  applied.  In  some  of  these  cases 
there  is  enormous  hypertrophy  of  the  skin  and  subcutaneous  tissues,  producing  pendulous  masses, 
termed  lipomata  nasi.  Epithelioma  and  rodent  ulcer  may  attack  the  nose,  the  latter  being  the 
more  common  of  the  two.  Lupus  and  syphilitic  ulceration  frequently  attack  the  nose,  and  may 
destroy  the  whole  of  the  cartilaginous  portion.  In  fact,  lupus  vulgaris  begins  more  frequently  on 
the  ala  of  the  nose  than  in  any  other  situation. 

Cases  of  congenital  occlusion  of  one  or  both  nostrils,  or  adhesion  between  the  ala  and  septum 
may  occur,  and  may  require  immediate  operation,  since  the  obstruction  much  interferes  with  suck- 
ing.    Bony  closure  of  the  posterior  nares  may  also  occur. 

To  examine  the  nasal  cavities,  the  head  should  be  thrown  back  and  the  nose  drawn  upward, 
the  parts  being  dilated  by  some  form  of  speculum.  It  can  also  be  examined  with  the  little  finger 
or  a  probe,  and  in  this  way  foreign  bodies  detected.  A  still  more  extensive  examination  can  be 
made  by  Rouge's  operation,  which  was  introduced  for  the  cure  of  ozama  by  the  removal  of  any 
dead  bone  which  may  be  present  in  this  disease.  The  whole  framework  of  the  nose  is  lifted  up 
by  an  incision  made  inside  the  mouth,  through  the  junction  of  the  upper  lip  with  the  bone  ;  the 
septum  nasi  and  the  lateral  cartilages  are  divided  with  strong  scissors  till  the  anterior  nares  are 
completely  exposed.  The  posterior  nares  can  be  explored  by  reflected  light  from  the  mouth,  by 
which  the  posterior  nares  can  be  illuminated.  The  examination  is  very  difficult  to  carry  out, 
and,  as  a  rule,  sufficient  information  regarding  the  presence  of  foreign  bodies  or  tumors  in  the 
naso-pharyux  can  be  obtained  by  the  introduction  of  the  finger  behind  the  soft  palate  through 
the  mouth.  The  septum  of  the  nose  may  be  displaced  or  deviate  from  the  middle  line :  this 
may  be  the  result  of  an  injury  or  from  some  congenital  defect  in  its  development ;  in  the  latter 
case  the  deviation  usually  occurs  along  the  line  of  union  of  the  vomer  and  mesethmoid,  and  rarely 
occurs  before  the  seventh  year.  Sometimes  the  deviation  may  be  so  great  that  the  septum  may 
come  in  contact  with  the  outer  wall  of  the  nasal  fossae,  and  may  even  become  adherent  to  it. 
thus  producing  complete  obstruction.  Perforation  of  the  septum  is  not  an  uncommon  affection 
and  may  arise  from  several  causes  :  syphilitic  or  tubercular  ulceration,  blood-tumor  or  abscess  of 
the  septum,  and  especially  in  workmen  exposed  to  the  vapor  of  bichromate  of  potash,  from  the 
irritating  and  corrosive  action  of  fumes.  When  small,  the  perforation  may  cause  a  peculiar 
whistling  sound  during  respiration.  When  large,  it  may  lead  to  the  falling  in  of  tho  bridge  of 
the  nose. 


824  THE    ORGANS    OF  SPECIAL    SENSE. 

Epistaxis  is  a  very  common  affection  in  children.  It  is  rarely  of  much  consequence,  and 
will  almost  always  subside,  but  in  the  more  violent  haemorrhages  of  later  life  it  may  be 
necessary  to  plug  the  posterior  nares.  In  performing  this  operation  it  is  desirable  to  remember 
the  size  of  the  posterior  nares.  A  ready  method  of  regulating  the  size  of  the  plug  to  fit 
the  opening  is  to  make  it  of  the  same  size  as  the  terminal  phalanx  of  the  thumb  of  the  patient 
to  be  operated  on. 

Nasal  polypus  is  a  very  common  disease,  and  presents  itself  in  three  forms :  the  gelatinous, 
the  fibrous,  and  the  malignant.  The  first  is  by  far  the  most  common.  It  grows  from  the 
mucous  membrane  of  the  outer  wall  of  the  nasal  fossa,  where  there  is  an  abundant  layer  of 
highly  vascular  submucous  tissue ;  rarely  from  the  septum,  where  the  mucous  membrane  is 
closely  adherent  to  the  cartilage  and  bone,  without  the  intervention  of  much,  if  any,  submucous 
tissue.  Their  most  common  seat  is  probably  the  middle  turbinated  bone.  The  fibrous  polypus 
generally  grows  from  the  base  of  the  skull  behind  the  posterior  nares  or  from  the  roof  of  the  nasal 
fossae.  The  malignant  polypi,  both  sarcomatous  or  carcinomatous,  may  arise  in  the  nasal  cavities 
and  the  naso-pharynx ;  or  they  may  originate  in  the  antrum,  and  protrude  through  its  inner  wall 
into  the  nasal  fossa. 

Rhinoliths,  or  nose-stones,  may  sometimes  be  found  in  the  nasal  cavities,  from  the  formation 
of  phosphate  of  lime  upon  either  a  foreign  body  or  a  piece  of  inspissated  secretion. 

THE  EYE. 

The  eyeball  is  contained  in  the  cavity  of  the  orbit.  In  this  situation  it  is 
securely  protected  from  injury,  whilst  its  position  is  such  as  to  ensure  the  most 
extensive  range  of  sight.  It  is  acted  upon  by  numerous  muscles,  by  which  it  is 
capable  of  being  directed  to  different  parts  ;  it  is  supplied  by  vessels  and  nerves, 
and  is  additionally  protected  in  front  by  several  appendages,  such  as  the  eyebrow, 
eyelids,  etc. 

The  eyeball  is  imbedded  in  the  fat  of  the  orbit,  but  is  surrounded  by  a  thin 
membranous  sac,  the  capsule  of  Tenon,  which  isolates  it,  so  as  to  allow  of  free 
movement. 

The  capsule  of  Tenon  consists  of  a  thin  membrane  which  envelops  the  eyeball 
from  the  optic  nerve  to  the  ciliary  region,  separating  it  from  the  orbital  fat  and 
forming  a  socket  in  which  it  plays.  Its  inner  surface  is  smooth,  and  is  in  contact 
with  the  outer  surface  of  the  sclerotic,  the  perisclerotic  lymph-space  only  interven- 
ing. This  lymph-space  is  continuous  with  the  subdural  and  subarachnoid  spaces, 
and  is  traversed  by  delicate  bands  of  connective  tissue  which  extend  between  the 
capsule  and  the  sclerotic.  The  capsule  is  perforated  behind  by  the  ciliary  vessels 
and  nerves  and  by  the  optic  nerve,  being  continuous  with  the  sheath  of  the  latter. 
In  front  it  blends  with  the  ocular  conjunctiva,  and  with  it  is  attached  to  the  ciliary 
region  of  the  eyeball.  It  is  perforated  by  the  muscles  which  move  the  eyeball  and 
on  each  it  sends  a  tubular  sheath.  The  sheath  of  the  Superior  oblique  is  carried 
as  far  as  the  fibrous  pulley  of  that  muscle ;  that  on  the  Inferior  oblique  reaches  as 
far  as  the  floor  of  the  orbit,  to  which  it  gives  off  a  slip.  The  sheaths  on  the  recti 
are  gradually  lost  in  the  perimysium,  but  they  give  off  important  expansions. 
The  expansion  from  the  Superior  rectus  blends  with  the  tendon  of  the  Levator 
palpebr?e  ;  that  of  the  Inferior  rectus  is  attached  to  the  inferior  tarsal  plate. 
These  two  recti,  therefore,  will  exercise  some  influence  on  the  movements  of  the 
eyelids.  The  expansions  from  the  sheaths  of  the  Internal  and  External  recti  are 
strong,  especially  the  one  from  the  latter  muscle,  and  are  attached  to  the  lachrymal 
and  malar  bones  respectively.  As  they  probably  check  the  action  of  these  two 
recti,  they  have  been  named  the  internal  and  external  check  ligaments. 

Lockwood  has  also  described  a  thickening  of  the  lower  part  of  the  capsule  of 
Tenon,  which  he  has  named  the  suspensory  ligament  of  the  eye.  It  is  slung  like  a 
hammock  below  the  eyeball,  being  expanded  in  the  centre  and  narrow  at  its 
extremities,  which  are  attached  to  the  malar  and  lachrymal  bones  respectively.1 

The  eyeball  is  composed  of  segments  of  two  spheres  of  different  sizes.  The 
anterior  segment  is  one  of  a  small  sphere,  and  forms  about  one-sixth  of  the  eyeball. 
It  is  more  prominent  than  the  posterior  segment,  which  is  one  of  a  much  larger 
sphere,  and  forms  about  five-sixths  of  the  globe.     The  segment  of  the  larger  sphere 

TSee  a  paper  by  C.  B.  Lockwood,  Journal  of  Anatomy  and  Physiology,  vol.  xz.,  part  i.,  p.  1. 


TUNICS    OF    THE   EYE.  825 

is  opaque,  and  formed  by  the  sclerotic,  the  tunic  of  protection  to  the  eyeball ;  the 
smaller  sphere  is  transparent,  and  formed  by  the  cornea-  The  term  anterior  pole  is 
applied  to  the  central  point  of  the  anterior  curvature  of  the  eyeball,  and  that  of 
posterior  pole  to  the  central  point  of  its  posterior  curvature;  a  line  joining  the  two 
poles  forms  its  sagittal  axis.  The  axes  of  the  eyeballs  are  nearly  parallel,  and 
therefore  do  not  correspond  to  the  axes  of  the  orbits,  which  are  directed  outward. 
The  optic  nerves  follow  the  direction  of  the  axes  of  the  orbits,  and  are  therefore 
not  parallel ;  each  enters  its  eyeball  about  1  mm.  below  and  3  mm.  to  the  inner  or 
nasal  side  of  the  posterior  pole.  The  eyeball  measures  rather  more  in  its  transverse 
and  antero-posterior  diameters  than  in  its  vertical  diameter,  the  former  amounting 
to  nearly  an  inch,  the  latter  to  about  nine-tenths  of  an  inch. 

The  eyeball  is  composed  of  three  investing  tunics  and  of  three  refracting  media. 

TUNICS  OF  THE  EYE. 

From  without  inward  the  three  tunics  are : 

1.  Sclerotic  and  Cornea. 

2.  Choroid,  Ciliary  Body,  and  Iris. 

3.  Retina. 

I.  The  Sclerotic  and  Cornea. 

The  sclerotic  and  cornea  (Fig.  440)  form  the  external  tunic  of  the  eyeball ;  they 
are  essentially  fibrous  in  structure,  the  sclerotic  being  opaque,  and  forming  the 
posterior  five-sixths  of  the  globe  ;  the  cornea,  which  forms  the  remaining  sixth, 
being  transparent. 

The  Sclerotic  (axkrjpoz,  hard)  has  received  its  name  from  its  extreme  density 
and  hardness  ;  it  is  a  firm,  unyielding,  fibrous  membrane,  serving  to  maintain  the 
form  of  the  globe.  It  is  much  thicker  behind  than  in  front.  Its  external  surface 
is  of  a  white  color,  and  is  in  contact  with  the  inner  surface  of  the  capsule  of  Tenon  ; 
it  is  quite  smooth,  except  at  the  points  where  the  Recti  and  Obliqui  muscles  are  in- 
serted into  it,  and  its  anterior  part  is  covered  by  the  conjunctival  membrane :  hence 
the  whiteness  and  brilliancy  of  the  front  of  the  eyeball.  Its  inner  surface  is 
stained  of  a  brown  color,  marked  by  grooves,  in  which  are  lodged  the  ciliary  nerves 
and  vessels ;  this  is  loosely  connected  by  an  exceedingly  fine  cellular  tissue  (lamina 
fused)  with  the  outer  surface  of  the  choroid,  an  extensive  lymph-space  [peri- 
choroidal) intervening  between  the  sclerotic  and  choroid.  Behind  it  is  pierced  by 
the  optic  nerve,  and  is  continuous  with  its  fibrous  sheath,  which  is  derived  from  the 
dura  mater.  At  the  point  where  the  optic  nerve  passes  through  the  sclerotic,  this 
tunic  forms  a  thin  cribriform  lamina  (the  lamina  cribrosa)  ;  the  minute  orifices  in 
this  region  serve  for  the  transmission  of  the  nervous  filaments,  and  the  fibrous 
septa  dividing  them  from  one  another  are  continuous  with  the  membranous  processes 
which  separate  the  bundles  of  nerve-fibres.  One  of  these  openings,  larger  than  the 
rest,  occupies  the  centre  of  the  lamella ;  it  transmits  the  arteria  centralis  retinae  to 
the  interior  of  the  eyeball.  Around  the  cribriform  lamella  are  numerous  small 
apertures  for  the  transmission  of  the  ciliary  vessels  and  nerves,  and  about  midway 
between  the  margin  of  the  cornea  and  the  entrance  of  the  optic  nerve  are  four  or 
five  large  apertures,  for  the  transmission  of  veins  (vena?  vorticosos).  In  front,  the 
fibrous  tissue  of  the  sclerotic  is  directly  continuous  with  that  of  the  cornea  by  direct 
continuity  of  tissue,  but  the  opaque  sclerotic  slightly  overlaps  the  outer  surface  of 
the  transparent  cornea. 

Structure. — The  sclerotic  is  formed  of  white  fibrous  tissue  intermixed  with  fine 
elastic  fibres,  and  of  flattened  connective-tissue  corpuscles,  some  of  which  are  pig- 
mented, contained  in  cell-spaces  betAveen  the  fibres.  These  fibres  are  aggregated 
into  bundles,  which  are  arranged  chiefly  in  a  longitudinal  direction.  It  yields 
gelatin  on  boiling.  Its  vessels  are  not  numerous,  the  capillaries  being  of  small 
size,  uniting  at  long  and  wide  intervals.  Its  nerves  are  derived  from  the  ciliary 
nerves,  but  their  exact  \node  of  ending  is  not  known. 


826 


THE    ORGANS    OF  SPECIAL    SENSE. 


The  Cornea  is  the  projecting  transparent  part  of  the  external  tunic  of  the 
eyeball,  and  forms  the  anterior  sixth  of  the  globe.  It  is  almost  circular  in  shape, 
occasionally  a  little  broader  in  the  transverse  than  in  the  vertical  direction.  It 
is  convex  anteriorly,  and  projects  forward  from  the  sclerotic  in  the  same  manner 
that  a  watch-glass  does  from  its  case.  Its  degree  of  curvature  varies  in  different 
individuals,  and  in  the  same  individual  at  different  periods  of  life,  it  being  more 
prominent  in  youth  than  in  advanced  life,  when  it  becomes  flattened.  The 
cornea  is  dense  and  of  uniform  thickness  throughout ;  its  posterior  surface  is 
perfectly  circular  in  outline,  and  exceeds  the  anterior  surface  slightly  in  extent, 
from  the  latter  being  overlapped  by  the  sclerotic. 

Structure. — The  cornea  consists  of  four  layers — namely,  (1)  several  strata 
of  epithelial  cells,  continuous  with  those  of  the  conjunctiva  ;  (2)  a  thick  central 


Canal  of  Schlemm. 


Posterior 
chamber. 

Ciliary 

body. 


Canal  of 
Petit. 


NTERNAL 
RECTUS 
MUSCLE. 


Retina 


Choroid  coat 


Canal  for 

artery. 


Optic  nerve. 


Fig.  440.— A  horizontal  section  of  the  eyeball.    (Allen.) 


fibrous  structure,  the  substantia  propria ;  (3)  a  homogeneous  elastic  lamina ;  and 
(4)  a  single  layer  of  endothelial  cells  forming  part  of  the  lining  membrane  of  the 
anterior  chamber  of  the  eyeball. 

The  conjunctival  epithelium,  which  covers  the  front  of  the  cornea  proper,  con- 
sists of  several  strata  of  epithelial  cells.  The  deepest  layers  are  columnar :  then 
follow  two  or  three  layers  of  polyhedral  cells,  the  majority  of  which  present  finger- 
like processes  (i.  e.,  prickle-cells),  similar  to  those  found  in  the  cuticle.  Lastly, 
there  are  three  or  four  layers  of  scaly  epithelium  with  flattened  nuclei. 

The  proper  substance  of  the  cornea  is  fibrous,  tough,  unyielding,  perfectly 
transparent,  and  continuous  with  the  sclerotic.  It  is  composed  of  about  sixty 
flattened  lamellae,  superimposed  one  on  another.  These  lamella?  are  made  up  of 
bundles  of  modified  connective  tissue,  the  fibres  of  which  are  directly  continuous 
with  the  fibres  of  the  sclerotic.  The  fibres  of  each  lamella  are  for  the  most  part 
parallel  with  each  other  ;  those  of  alternating  lamellae  at  right  angles  to  each  other. 
Fibres,  however,  frequently  pass  from  one  lamella  to  the  next. 

The  lamellse  are  connected  with  each  other  by  an  interstitial  cement-substance, 


THE    CORNEA.  827 

in  which  are  spaces,  the  corneal  spaces.  The  spaces  are  stellate  in  shape,  and  have 
numerous  offsets  by  which  they  communicate  with  each  other.  Each  contains  a 
cell,  the  corneal  corpuscle,  which  resembles  in  form  the  space  in  which  it  is  lodged, 
but  it  does  not  entirely  fill  it. 

Immediately  beneath  the  conjunctival  epithelium  the  cornea  proper  presents 
certain  characteristics  which  have  led  some  anatomists  to  regard  it  as  a  distinct 
membrane,  and  it  has  been  named  by  Bowman  the  anterior  elastic  lamina.  It 
differs,  however,  from  the  true  elastic  lamina  or  membrane  of  Descemet  in  many 
essential  particulars,  presenting  evidence  of  fibrillar  structure,  and  not  having  the 
same  tendency  to  curl  inward  or  to  undergo  fracture  when  detached  from  the  other 
layers  of  the  cornea.  It  consists  of  extremely  closely  interwoven  fibrils,  similar  to 
those  found  in  the  rest  of  the  cornea  proper,  but  contains  no  corneal  corpuscles. 
It  ought,  therefore,  to  be  regarded  as  a  part  of  the  proper  tissue  of  the  cornea.1 

The  posterior  elastic  lamina  [membrane  of  Descemet  or  Demours),  which  covers 
the  proper  structure  of  the  cornea  behind,  presents  no  structure  recognizable  under 
the  microscope.  It  consists  of  an  elastic,  and  perfectly  transparent  homogeneous 
membrane,  of  extreme  thinness,  which  is  not  rendered  opaque  by  either  water, 
alcohol,  or  acids.  It  is  very  brittle,  but  its  most  remarkable  property  is  its  extreme 
elasticity,  and  the  tendency  which  it  presents  to  curl  up,  or  roll  upon  itself,  with 
the  attached  surface  innermost,  when  separated  from  the  proper  substance  of  the 
cornea.  Its  use  appears  to  be  (as  suggested  by  Dr.  Jacob)  "to  preserve  the  requisite 
permanent  correct  curvature  of  the  flaccid  cornea  proper." 

At  the  margin  of  the  cornea  this  posterior  elastic  membrane  breaks  up  into  fibres 
to  form  a  reticular  structure  at  the  outer  angle  of  the  anterior  chamber,  the  intervals 
between  the  fibres  forming  small  cavernous  spaces,  the  spaces  of  Fontana.  These 
little  recesses  communicate  with  a  circular  canal  in  the  substance  of  the  sclerotic 
close  to  its  junction  with  the  cornea.  This  is  the  canal  of  Schlemm,  or  sinus 
venosus  scleras;  it  communicates  internally  with  the  anterior  chamber  through  the 
spaces  of  Fontana,  and  externally  with  the  scleral  veins.  Some  of  the  fibres  of  this 
reticulated  structure  are  continued  into  the  front  of  the  iris,  forming  the  ligamentum 
pectinatum  iridis ;  while  others  are  connected  with  the  fore  part  of  the  sclerotic 
and  choroid. 

The  endothelial  lining  of  the  aqueous  chamber  covers  the  posterior  surface  of 
the  elastic  lamina,  is  reflected  on  to  the  front  of  the  iris,  and  also  lines  the  spaces  of 
Fontana.  It  consists  of  a  single  layer  of  polygonal  flattened  transparent  nucleated 
cells,  similar  to  those  lining  other  serous  cavities. 

Arteries  and  Nerves. — The  cornea  is  a  non- vascular  structure,  the  capillary 
vessels  terminating  in  loops  at  its  circumference.  Lymphatic  vessels  have  not  as 
yet  been  demonstrated  in  it,  but  are  represented  by  the  channels  in  which  the 
bundles  of  nerves  run ;  these  are  lined  by  an  endothelium  and  are  continuous 
with  the  cell-spaces.  The  nerves  are  numerous,  twenty-four  to  thirty-six  in 
number  (Kolliker),  forty  to  forty-five  (Waldeyer  and  Siimisch) ;  they  are  derived 
from  the  ciliary  nerves  and  enter  the  laminated  tissue  of  the  cornea.  They 
ramify  throughout  its  substance  in  a  delicate  network,  and  their  terminal  fila- 
ments form  a  firm  and  closer  plexus  on  the  surface  of  the  cornea  proper  beneath 
the  epithelium.  This  is  termed  the  subepithelial  plexus,  and  from  it  fibrils  are 
given  off  which  ramify  between  the  epithelial  cells,  forming  a  network  which  is 
termed  the  intra-ejnthelial  plexus. 

Dissection. — In  order  to  separate  the  sclerotic  and  cornea,  so  as  to  expose  the  seeoud  tunic, 
the  eyeball  should  be  immersed  in  a  small  vessel  of  water  and  held  between  the  finger  and 
thumb.  The  sclerotic  is  then  carefully  incised,  in  the  equator  of  the  globe,  till  the  choroid  is 
exposed.  One  blade  of  a  pair  of  probe-pointed  scissors  is  now  introduced  through  the  opening 
thus  made,  and  the  sclerotic  divided  around  its  entire  circumference,  and  removed  in  separate 
portions.  The  front  segment  being  then  drawn  forward,  the  handle  of  the  scalpel  should  be 
pressed  gently  against  it  at  its  connection  with  the  iris,  and,  these  being  separated,  a  quantity 

1  This  layer  has  been  called  by  Keichert  the  "  anterior  limiting  layer  "—a  name  which  appears 
more  applicable  to  it  than  that  of  "  anterior  elastic  lamina." 


828 


THE    ORGANS    OF  SPECIAL    SENSE. 


of  perfectly  transparent  fluid  will  escape ;  this  is  the  aqueous  humor.  In  the  course  of  the 
dissection  the  ciliary  nerves  may  be  seen  lying  in  the  loose  cellular  tissue  between  the  choroid 
and  sclerotic  or  continued  in  delicate  grooves  on  the  inner  surface  of  the  latter  membrane. 

II.  The  Choroid,  Ciliary  Body,  and  Iris. 

The  Second  Tunic  of  the  Eye  {tunica  vaseulosa  oculi)  is  formed  from  behind 
forward  by  the  choroid,  the  ciliary  body,  and  the  iris. 

The  choroid  is  the  vascular  and  pigmentary  tunic  of  the  eyeball,  investing  the 
posterior  five-sixths  of  the  globe,  and  extending  as  far  forward  as  the  ora  serrata 
of  the  retina;  the  ciliary  body  connects  the  choroid  to  the  circumference  of  the 
iris.  The  iris  is  the  circular  muscular  septum,  which  hangs  vertically  behind  the 
cornea,  presenting  in  its  centre  a  large  rounded  aperture,  the  pupil. 

The  Choroid,  is  a  thin,  highly  vascular  membrane,  of  a  dark-brown  or  chocolate 
color,  which  invests  the  posterior  five-sixths  of  the  globe,  and  is  pierced  behind 
by  the  optic  nerve,  and  in  this  situation  is  firmly  adherent  to  the  sclerotic.  It  is 
thicker  behind  than  in  front.  Externally,  it  is  loosely  connected  by  the  lamina 
fusca  with  the  inner  surface  of  the  sclerotic.  Its  inner  surface  is  attached  to  the 
retina. 


Fig.  441.— The  choroid  and  iris.    (Enlarged.) 

Structure. — The  choroid  consists  mainly  of  a  dense  capillary  plexus  and  of 
small  arteries  and  veins,  carrying  the  blood  to  and  returning  it  from  this  plexus. 
On  its  external  surface — i.  e.,  the  surface  next  the  sclerotic — is  a  thin  membrane, 
the  lamina  superchoroidea,  composed  of  delicate  non-vascular  lamellae,  each  lamella 
consisting  of  a  network  of  fine  elastic  fibres,  among  which  are  branched  pigment- 
cells.  The  spaces  between  the  lamellae  are  lined  by  endothelium,  and  open  freely 
into  the  perichoroidal  lymph-space,  which,  in  its  turn,  communicates  with  the 
perisclerotic  space  by  the  perforations  in  the  sclerotic  through  which  tbe  vessels 
and  nerves  are  transmitted. 

Internal  to  this  is  the  choroid  proper,  and,  in  consequence  of  the  small  arteries 
and  veins  being  arranged  on  the  outer  surface  of  the  capillary  network,  it  is 
customary  to  describe  this  as  consisting  of  two  layers  :  the  outermost,  composed 
of  small  arteries  and  veins,  with  pigment-cells  interspersed  between  them,  and 
tbe  inner,  consisting  of  a  capillary  plexus.      The  external  layer  or  lamina  vaseulosa 


THE    EYE. 


829 


consists,  in  part,  of  the  larger  branches  of  the  short  ciliary  arteries  which  run 
forward  between  the  veins,  before  they  bend  inward  to  terminate  in  the  capillaries ; 
but  is  formed  principally  of  veins,  which  are  named,  from  their  arrangement,  vence 
vorticosa.  They  converge  to  four  or  five  equidistant  trunks,  which  pierce  the 
sclerotic  midway  between  the  margin  of  the  cornea  and  the  entrance  of  the  optic 
nerve.  Interspersed  between  the  vessels  are  dark  star-shaped  pigment-cells,  the 
offsets  from  which,  communicating  with  similar  branchings  from  neighboring  cells, 
form  a  delicate  network  or  stroma,  which  toward  the  inner  surface  of  the  choroid 
loses  its  pigmentary  character.  The  internal  layer  consists  of  an  exceedingly  fine 
capillary  plexus,  formed  by  the  short  ciliary  vessels,  and  is  known  as  the  lamina 
chorio-c axillaris  or  tunica  Ruyschiana.  The  network  is  close,  and  finer  at  the 
hinder  part  of  the  choroid  than  in  front.  About  half  an  inch  behind  the  cornea 
its  meshes  become  larger,  and  are  continuous  with  those  of  the  ciliary  processes. 


Fig.  442.— The  veins  of  the  choroid.    (Enlarged.) 

These  two  laminae  are  connected  by  an  intermediate  stratum,  which  is  destitute  of 
pigment-cells  and  consists  of  fine  elastic  fibres.  On  the  inner  surface  of  the  lamina 
chorio-capillaris  is  a  very  thin,  structureless,  or,  according  to  Kblliker,  faintly 
fibrous  membrane,  called  the  lamina  basalis  or  membrane  of  Bruch  ;  it  is  closely 
connected  with  the  stroma  of  the  choroid,  and  separates  it  from  the  pigmentary 
layer  of  the  retina. 

Tapetum. — This  name  is  applied  to  the  iridescent  appearance  which  is  seen  in 
the  outer  and  posterior  part  of  the  choroid  of  many  animals. 

The  ciliary  body  should  now  be  examined.  It  may  be  exposed,  either  by  detaching  the 
iris  from  its  connection  with  the  Ciliary  muscle,  or  by  making  a  transverse  section  of  the  globe, 
and  examining  it  from  behind. 

The  ciliary  body  comprises  the  orbiculus  ciliaris,  the  ciliary  processes,  and  the 
Ciliary  muscle. 

The  orbiculus  ciliaris  is  a  zone  of  about  one-sixth  of  an  inch  in  width,  directly 
continuous  with  the  anterior  part  of  the  choroid ;  it  presents  numerous  ridges 
arranged  in  a  radial  manner. 

The  ciliary  processes  are  formed  by  the  plaiting  and  folding  inward  of  the 
various  layers  of  the  choroid — i.  e.,  the  choroid  proper  and  the  lamina  basalis — at  its 
anterior  margin,  and  are  received  between  corresponding  foldings  of  the  suspensory 
ligament  of  the  lens,  thus  establishing  a  connection  between  the  choroid  and  inner 
tunic  of  the  eye.  They  are  arranged  in  a  circle,  and  form  a  sort  of  plaited  frill 
behind  the  iris,  round  the  margin  of  the  lens.  They  vary  between  sixty  and  eighty 
in  number,  lie  side  by  side,  and  may  be  divided  into  large  and  small ;  the  latter, 
consisting   of  about   one-third  of  the   entire  number,   are   situated  in  the  spaces 


830 


THE    ORGANS    OF  SPECIAL    SENSE. 


between  the  former,  but  without  regular  alternation.  The  larger  processes  are 
each  about  one-tenth  of  an  inch  in  length,  and  are  attached  by  their  periphery  to 
three  or  four  of  the  ridges  of  the  orbiculus  ciliaris,  and  are  continuous  with  the 
layers  of  the  choroid :  the  opposite  margin  is  free,  and  rests  upon  the  circumfer- 
ence of  the  lens.  Their  anterior  surface  is  turned  toward  the  back  of  the  iris, 
with  the  circumference  of  which  they  are  continuous.  The  posterior  surface  is 
connected  with  the  suspensory  ligament  of  the  lens. 

Structure. — The  ciliary  processes  are  similar  in  structure  to  the  choroid,  but 
the  vessels  are  larger,  and  have  chiefly  a  longitudinal  direction.  They  are  covered 
on  their  inner  surface  by  two  strata  of  black  pigment-cells,  which  are  continued 
forward  from  the  retina,  and  are  named  the  pars  ciliaris  retince.  In  the  stroma  of 
the  ciliary  processes  there  are  also  stellate  pigment-cells,  which,  however,  are  not 
so  numerous  as  in  the  choroid  itself. 


Anterior  ciliary  artery. 


Short  ciliary  arteries.  ^'- 


interior  ciliary  artery. 


Fig.  443.— The  arteries  of  the  choroid  and  iris.    The  sclerotic  has  been  mostly  removed.    (Enlarged.) 


The  Ciliary  muscle  (Bowman)  consists  of  unstriped  fibres :  it  forms  a  grayish, 
semi  transparent,  circular  band,  about  one-eighth  of  an  inch  broad,  on  the  outer 
surface  of  the  fore  part  of  the  choroid.  It  is  thickest  in  front,  and  gradually 
becomes  thinner  behind.  It  consists  of  two  sets  of  fibres,  radiating  and  circular. 
The  former,  much  the  more  numerous,  arise  at  the  point  of  junction  of  the  cornea 
and  sclerotic,  and  partly  also  from  the  ligamentum  pectinatum  iridis,  and,  passing 
backward,  are  attached  to  the  choroid  opposite  to  the  ciliary  processes.  One 
bundle,  according  to  Waldeyer,  is  continued  backward  to  be  inserted  into  the 
sclerotic.  The  circular  fibres  are  internal  to  the  radiating  ones  and  to  some  extent 
unconnected  with  them,  and  have  a  circular  course  around  the  attachment  of  the 
iris.  They  are  sometimes  called  the  "  ring  muscle  "  of  Miiller,  and  were  formerly 
described  as  the  ciliary  ligament.  They  are  well  developed  in  hypermetropic,  but 
are  rudimentary  or  absent  in  myopic  eyes.  The  Ciliary  muscle  is  admitted  to 
be  the  chief  agent  in  accommodation, — i.  e.,  in  adjusting  the  eye  to  the  vision  of 
near  objects.  Bowman  believed  that  this  was  effected  by  its  compressing  the 
vitreous  body,  and  so  causing  the  lens  to  advance ;  but  the  view  which  now  pre- 
vails is  that  the  contraction  of  the  muscle,  by  drawing  on  the  ciliary  processes, 
relaxes  the  suspensory  ligament  of  the  lens,  thus  allowing  the  anterior  surface  of 
the  lens  to  become  more  convex.  The  pupil  is  at  the  same  time  slightly  con- 
tracted.1 

The  Iris  (iris,  a  rainbow)  has  received  its  name  from  its  various  colors  in  dif- 
ferent individuals.     It  is  a  thin,  circular-shaped,  contractile  curtain,  suspended  in 

1  See  explanation  and  diagram  in  Power's  Illustrations  of  some  of  the  Principal  Diseases  of  the  Eye, 
p.  590. 


THE   EYE. 


831 


the  aqueous  humor  behind  the  cornea,  and  in  front  of  the  lens,  being  perforated  a 
little  to  the  nasal  side  of  its  centre  by  a  circular  aperture,  the  pupil,  for  the  trans- 
mission of  light.  By  its  circumference  it  is  continuous  with  the  ciliary  body,  and 
is  also  connected  with  the  posterior  elastic  lamina  of  the  cornea  by  means  of  the 
pectinate  ligament ;  its  inner  or  free  edge  forms  the  margin  of  the  pupil ;  its  sur- 
faces are  flattened,  and  look  forward  and  backward,  the  anterior  toward  the  cornea, 
the  posterior  toward  the  ciliary  processes  and  lens.  The  anterior  surface  of  the 
iris  is  variously  colored  in  different  individuals,  and  marked  by  lines  which  con- 
verge toward  the  pupil.  The  posterior  surface  is  of  a  deep  purple  tint,  from  being 
covered  by  two  layers  of  pigmented,  columnar  epithelium,  which  are  continuous 
posteriorly  with  the  pars  ciliaris  retinse.  This  pigmented  epithelium  is  termed  the 
pars  iridica  retinae,  though  it  is  sometimes  named  uvea,  from  its  resemblance  in 
color  to  a  ripe  grape. 


Circ.  fibres 
of  sclerotic. 


Circ. fibres   / 
of  Ciliary  muscle, 


Radiating 

fibres  of 

Ciliary  muscle. 


( Pars  ciliaris 
\     retinx. 


Fig.  444.— Section  of  the  eye,  showing  the  relations  of  the  cornea,  sclerotic,  and  iris,  together  with  the 
Ciliary  muscle  and  the  cavernous  spaces  near  the  angle  of  the  anterior  chamber.    (Waldeyer.) 


Structure. — The  iris  is  composed  of  the  following  structures : 

1.  In  front  is  a  layer  of  flattened  endothelial  cells  placed  on  a  delicate  hyaline 
basement-membrane.  This  layer  is  continuous  with  the  epithelial  layer  covering 
the  membrane  of  Descemet,  and  in  men  with  dark-colored  irides  the  cells  contain 
pigment-granules. 

2.  Stroma. — The  stroma  consists  of  fibres  and  cells.  The  former  are  made  of 
fine,  delicate  bundles  of  fibrous  tissue,  of  which  some  few  fibres  have  a  circular 
direction  at  the  circumference  of  the  iris,  but  the  chief  mass  consists  of  fibres 
radiating  toward  the  pupil.  They  form,  by  their  interlacement,  a  delicate  mesh, 
in  which  the  vessels  and  nerves  are  contained.  Interspersed  between  the  bundles 
of  connective  tissue  are  numerous  branched  cells  with  fine  processes.  Many  of 
them  in  dark  eyes  contain  pigment-granules,  but  in  blue  eyes  and  the  pink  eyes 
of  albinos  they  are  unpigmented. 

3.  The  muscular  fibre  is  involuntary,  and  consists  of  circular  and  radiating 
fibres.  The  circular  fibres  (sphincter  pupillre)  surround  the  margin  of  the  pupil 
on  the  posterior  surface  of  the  iris,  like  a  sphincter,  forming  a  narrow  band  about 
one-thirtieth  of  an  inch  in  width,  those  near  the  free  margin  being  closely  aggre- 


832  THE    ORGANS    OF  SPECIAL    SENSE. 

gated ;  those  more  external  somewhat  separated,  and  forming  less  complete  circles. 
The  radiating  fibres  (dilator  pupillse)  converge  from  the  circumference  toward  the 
centre,  and  blend  with  the  circular  fibres  near  the  margin  of  the  pupil.  These 
fibres  are  regarded  by  some  as  elastic,  not  muscular. 

4.  Pigment. — The  situation  of  the  pigment-cells  differs  in  different  irides.  In 
the  various  shades  of  blue  eyes  the  only  pigment-cells  are  several  layers  of  small 
round  or  polyhedral  cells  filled  with  dark  pigment,  situated  on  the  posterior  surface 
of  the  iris  and  continuous  with  the  pigmentary  lining  of  the  ciliary  processes.  The 
color  of  the  eye  in  these  individuals  is  due  to  this  coloring-matter  showing  more 
or  less  through  the  texture  of  the  iris.  In  the  albino  even  this  pigment  is  absent. 
In  the  gray,  brown,  and  black  eye  there  are,  as  mentioned  above,  pigment-granules 
to  be  found  in  the  cells  of  the  stroma  and  in  the  epithelial  layer  on  the  front  of  the 
iris ;  to  these  the  dark  color  of  the  eye  is  due. 

The  arteries  of  the  iris  are  derived  from  the  long  and  anterior  ciliary  and 
from  the  vessels  of  the  ciliary  processes  (see  page  509).  ■  The  long  ciliary  arteries, 
two  in  number,  having  reached  the  attached  margin  of  the  iris,  divide  into  an 
upper  and  a  lower  branch,  and,  encircling  the  iris,  anastomose  with  corresponding 
branches  from  the  opposite  side;  into  this  vascular  zone  (circulus  major)  the  ante- 
rior ciliary  pour  their  blood.  From  this  zone  vessels  converge  to  the  free  margin 
of  the  iris,  and  these  communicate  by  branches  from  one  to  another  and  thus  form 
a  second  zone  (circulus  minor)  in  this  situation. 

The  nerves  of  the  choroid  and  iris  are  derived  from  the  ciliary  branches 
of  the  lenticular  ganglion,  and  the  long  ciliary  from  the  nasal  branch  of  the 
ophthalmic  division  of  the  fifth.  They  pierce  the  sclerotic  around  the  entrance 
of  the  optic  nerve,  and  run  forward  in  the  perichoroidal  space,  and  supply 
the  blood-vessels  of  the  choroid.  After  reaching  the  iris  they  form  a  plexus 
around  its  attached  margin ;  from  this  are  derived  non-medullated  fibres 
which  terminate  in  the  circular  and  radiating  muscular  fibres.  Their  exact 
mode  of  termination  has  not  been  ascertained.  Other  fibres  from  the  plexus 
terminate  in  a  network  on  the  anterior  surface  of  the  iris.  The  fibres  derived 
from  the  motor  root  of  the  lenticular  ganglion  (third  nerve)  supply  the  circular 
fibres,  while  those  derived  from  the  sympathetic  supply  the  radiating  fibres. 

Membrana  Papillaris. — In  the  foetus  the  pupil  is  closed  by  a  delicate  transparent 
vascular  membrane,  the  membrana  pupillaris,  which  divides  the  space  into  which 
the  iris  is  suspended  into  two  distinct  chambers.  This  membrane  contains  numerous 
minute  vessels,  continued  from  the  margin  of  the  iris  to  those  on  the  front  part  of 
the  capsule  of  the  lens.  These  vessels  have  a  looped  arrangement,  and  converge 
toward  each  other  without  anastomosing.  Between  the  seventh  and  eighth  months 
the  membrane  begins  to  disappear,  by  its  gradual  absorption  from  the  centre 
toward  the  circumference,  and  at  birth  only  a  few  fragments  remain.  It  is  said 
sometimes  to  remain  permanent  and  produce  blindness. 

III.  The  Retina. 

The  Retina  is  a  delicate  nervous  membrane,  upon  the  surface  of  which  the 
images  of  external  objects  are  received.  Its  outer  surface  is  in  contact  with  the 
choroid  ;  its  inner  with  the  vitreous  body.  Behind,  it  is  continuous  with  the  optic 
nerve ;  it  gradually  diminishes  in  thickness  from  behind  forward ;  and,  in  front, 
extends  nearly  as  far  as  the  ciliary  body,  where  it  appears  to  terminate  in  a  jagged 
margin,  the  ora  serrata.  Here  the  nervous  tissues  of  the  retina  end,  but  a  thin 
prolongation  of  the  membrane  extends  forward  over  the  back  of  the  ciliary  proc- 
esses and  iris,  forming  the  pars  ciliaris  retinoe  and  pars  iridica  retinas,  already 
referred  to.  This  forward  prolongation  consists  of  the  pigmentary  layer  of  the 
retina  together  with  a  stratum  of  columnar  epithelium.  The  retina  is  soft,  semi- 
transparent,  and  of  a  purple  tint  in  the  fresh  state,  owing  to  the  presence  of  a 
coloring-material  named  rhodopsin  or  visual  purple  ;  but  it  soon  becomes  clouded, 
opaque,  and   bleached  when   exposed   to  sunlight.     Exactly  in  the  centre  of  the 


THE   EYE. 


833 


posterior  part  of  the  retina,  corresponding  to  the  axis  of  the  eye,  and  at  a  point 
in  which  the  sense  of  vision  is  most  perfect,  is  an  oval  yellowish  spot,  called,  after 
its  discoverer,  the  yellow  spot  or  macula  lutea  of  Sommerring,  having  a  central 
depression,  the  fovea  centralis.  The  retina  in  the  situation  of  the  fovea  centralis 
is  exceedingly  thin,  and  the  dark  color  of  the  choroid  is  distinctly  seen  through 
it ;  so  that  it  presents  more  the  appearance  of  a  foramen,  and  hence  the  name 
"foramen  of  Sommerring  "  at  first  given  to  it.  It  exists  only  in  man,  the  quad- 
rumana,  and  some  saurian  reptiles.  About  one-eighth  of  an  inch  (3  mm.)  to  the 
inner  side  of  the  yellow  spot  is  the  point  of  entrance  of  the  optic  nerve  (2)orus 
opticus) ;  here  the  nervous  substance  is  slightly  raised  so  as  to  form  an  eminence 
(colliculus  nervi  optici)  ;  the  arteria  centralis  retinae  pierces  its  centre.  This  is  the 
only  part  of  the  surface  of  the  retina  from  which  the  power  of  vision  is  absent, 
and  is  termed  the  "blind  spot." 

Structure. — The  retina  is  an  exceedingly  complex  structure,  and,  when  examined 
microscopically  by  means  of  sections  made  perpendicularly  to  its  surface,  is  found 
to  consist  of  ten  layers,  which  are  named  from  within  outward,  as  follows : 

1.  Membrana  limitans  interna. 

2.  Layer  of  nerve-fibres  (stratum  opticum). 

3.  Ganglionic  layer,  consisting  of  nerve-cells. 

4.  Inner  molecular,  or  plexiform,  layer. 

5.  Inner  nuclear  layer,  or  layer  of  inner  granules. 

6.  Outer  molecular,  or  plexiform,  layer. 

7.  Outer  nuclear  layer,  or  layer  of  outer  granules. 

8.  Membrana  limitans  externa. 

9.  Jacob's  membrane  (layer  of  rods  and  cones). 
10.  Pigmentary  layer  (tapetum  nigrum). 

1.  The  membrana  limitans  interna  is  the  most  internal  layer  of  the  retina,  and 
is  in  contact  with  the  hyaloid  membrane  of  the  vitreous  humor.  It  is  derived 
from  the  supporting  framework  of  the  retina,  with  which  tissue  it  will  be 
described. 

2.  The  layer  of  nerve-fibres  is  formed  by  the  expansion  of  the  optic  nerve. 
This  nerve  passes  through  all  the  other  layers  of  the  retina,  except  the  membrana 


Fig.  445.— The  arteria  centralis  retinae,  yellow  spot,  etc.,  the  anterior  half  of  the  eyeball  being  removed. 
(Enlarged.) 

limitans  interna,  to  reach  its  destination.  As  the  nerve  passes  through  the  lamina 
cribrosa  of  the  sclerotic  coat,  the  fibres  of  which  it  is  composed  lose  their  medullary 
sheaths  and  are  continued  onward,  through  the  choroid  and  retina,  as  simple  axis- 
cylinders.     When   these   non-medullated  fibres   reach  the  internal  surface  of  the 

53 


834 


THE    ORGANS    OF  SPECIAL    SENSE. 


retina,  they  radiate  from  their  point  of  entrance  over  the  surface  of  the  retina, 
grouped  in  bundles,  and  in  many  places,  according  to  Michel,  arranged  in  plexuses'. 
Most  of  the  fibres  in  this  layer  are  centripetal,  and  are  the  direct  continuations  of 
the  axis-cylinder  processes  of  the  cells  of  the  next  layer,  but  a  few  of  them 
(centrifugal  fibres)  pass  through  it  and  the  next  succeeding  layer  to  ramify  in  the 
inner  molecular  and  inner  nuclear  layers,  where  they  terminate  in  enlarged 
extremities  (Fig.  448,  1,  m).  The  layer  is  thickest  at  the  optic  nerve  entrance, 
and  gradually  diminishes  in  thickness  toward  the  ora  serrata. 

3.  The  ganglionic  layer  consists  of  a  single  layer  of  large  ganglion-cells; 
except  in  the  macula  lutea,  where  there  are  several  strata.  The  cells  are  some- 
what flask-shaped,  their  rounded  internal  margin   resting  on  the  preceding  layer 


i,j!i.y 


4  'J**9C 


Fig.  446  and  447.— Vertical  sections  of  the  human  retina.  Fig.  446,  half  an  inch  from  the  entrance  of  the 
optic  nerve.  Fig.  447,  close  to  the  latter.  1.  Layer  of  rods  and  cones,  Jacob's  membrane,  bounded  underneath 
by  the  membrana  limitans  externa.  2.  Outer  nuclear  layer.  3.  Outer  molecular  layer.  4.  Inner  nuclear  layer. 
5.  Inner  molecular  layer.  6.  Ganglionic  layer.  7.  Layer  of  nerve-fibres.  8.  Sustentacular  fibres  of  Muiler. 
9.  Their  attachment  to  the  membrana  limitans  interna. 

and  sending  off  an  axon  which  is  prolonged  as  a  nerve-fibre  into  the  fibrous  layer. 
From  the  opposite  extremity  numerous  thicker  processes  (dendrites)  extend 
into  the  inner  molecular  layer,  where  they  branch  out  into  flattened  arborizations 
at  different  levels  (Fig.  448,  vn).  The  ganglion-cells  vary  much  in  size,  and  the 
dendrites  of  the  smaller  ones  as  a  rule  arborize  in  the  inner  molecular  layer  as 
soon  as  they  enter  it ;  while  the  processes  of  the  larger  cells  ramify  close  to  the 
inner  nuclear  layer. 

4.  The  inner  molecular  layer  is  made  up  of  a  dense  reticulum  of  minute  fibrils, 
formed  by  the  interlacement  of  the  dendrites  of  the  ganglion-cells  with  those  of 
the  cells  contained  in  the  next  layer,  immediately  to  be  described.  Within  the 
reticulum  formed  by  these  fibrils  a  few  branched  spongioblasts  are  sometimes 
imbedded. 

5.  The  inner  nuclear  layer  is  made  up  of  a  number  of  closely  packed  cells,  of 
which  there  are  three  different  kinds.  (1)  A  large  number  of  oval  cells,  which  are 
commonly  regarded  as  bipolar  nerve-cells,  and  are  much  more  numerous  than  either 
of  the  other  kind.  They  each  consist  of  a  large  oval  body  placed  vertically  to  the 
surface,  and  containing  a  distinct  nucleus  :  they  are  surrounded  by  a  small  amount 
of  protoplasm,  which  is  prolonged  into  two  processes  :  one  of  these  passes  inward 
into  the  inner  molecular  layer,  is  varicose  in  appearance,  and  ends  in  a  terminal 
ramification,  which  is  often  in  close  proximity  to  the  ganglion-cells  (Fig.  448  1,  c). 


THE   EYE.  835 

The  outer  process  passes  outward  into  the  outer  molecular  layer,  and  there  breaks 
up  into  a  number  of  branches.  According  to  Cajal,  there  are  two  varieties  of  these 
bipolar  cells :  one  in  which  the  outer  process  arborizes  around  the  knobbed  ends  of 
the  rod-fibres,  and  the  inner  around  the  cells  of  the  ganglionic  layer ;  these  he 
calls  rod-bipolars  (Fig.  448,  1,  c,  d);  the  others  are  those  in  which  the  outer 
process  breaks  up  in  a  horizontal  ramification,  in  contact  with  the  end  of  a  cone- 
fibre  ;  these  are  the  cone-bipolars,  and  their  inner  process  breaks  up  into  its  terminal 
ramifications  in  the  inner  molecular  layer  (Fig.  448,  1,  e).  (2)  At  the  innermost 
part  of  this  inner  nuclear  layer  is  a  stratum  of  cells,  which  are  named  by  Cajal 
amacrine  cells,  from  the  fact  that  they  have  no  axis-cylinder  process,  but  they  give 
a  number  of  short  protoplasmic  processes  which  extend  into  the  inner  molecular 
layer  and  there  ramify  (Fig.  448,  1,  h).  There  are  also  at  the  outermost  part  of 
this  layer  some  cells,  the  processes  of  which  extend  into  and  ramify  in  the  outer 
molecular  layer.  These  are  the  horizontal  cells  of  Cajal.  (3)  Some  few  cells  are 
also  found  in  this  layer,  connected  with  the  fibres  of  Miiller,  and  will  be  described 
with  those  structures. 

6.  The  outer  molecular  layer  is  much  thinner  than  the  inner  molecular  layer ; 
but,  like  it,  consists  of  a  dense  network  of  minute  fibrils,  derived  from  the  proc- 
esses of  the  horizontal  cells  of  the  preceding  layer  and  the  outer  processes  of  the 
bipolar  cells,  which  ramify  in  it,  forming  arborizations  around  the  ends  of  the  rod- 
fibres  and  with  the  branched  foot-plates  of  the  cone-fibres. 

7.  The  Outer  Nuclear  Layer. — Like  the  inner  nuclear  layer,  this  layer  contains 
several  strata  of  clear  oval  nuclear  bodies  ;  they  are  of  two  kinds,  and  on  account 
of  their  being  respectively  connected  with  the  rods  and  cones  of  Jacob's  membrane 
are  named  rod-granules  and  cone-granules.  The  rod-granules  are  much  the  more 
numerous,  and  are  placed  at  different  levels  throughout  the  layer.  Their  nuclei 
present  a  peculiar  cross-striped  appearance,  and  prolonged  from  either  extremity 
of  the  granule  is  a  fine  process  :  the  outer  process  is  continuous  with  a  single  rod 
of  Jacob's  membrane ;  the  inner  passes  inward  toward  the  outer  molecular  layer 
and  terminates  in  an  enlarged  extremity,  and  is  embedded  in  the  tuft  into  which 
the  outer  process  of  the  rod-bipolars  break  up.  In  its  course  it  presents  numerous 
vaiucosities.  The  cone-granules,  fewer  in  number  than  the  rod-granules,  are  placed 
close  to  the  membrana  limitans  externa,  through  which  they  are  continuous  with 
the  cones  of  Jacob's  membrane.  They  do  not  present  any  cross-striping,  but  con- 
tain a  pyriform  nucleus  which  almost  completely  fills  the  cell.  From  their  inner 
extremity  a  thick  process  passes  inward  to  the  outer  molecular  layer,  upon  which  it 
rests  by  a  somewhat  pyramidal  enlargement,  from  which  are  given  off  numerous 
fine  fibrils,  which  enter  the  outer  molecular  layer,  where  they  come  in  contact  with 
the  outer  processes  of  the  cone-bipolars. 

8.  The,  Membrana  Limitans  Externa. — This  layer,  like  the  membrana  limitans 
interna,  is  derived  from  the  fibres  of  Miiller,  with  which  structures  it  will  be 
described. 

9.  Jacob's  Membrane  (Layer  of  Rods  and  Cones). — The  elements  which  com- 
pose this  layer  are  of  two  kinds,  rods  and  cones,  the  former  being  much  more 
numerous  than  the  latter.  The  rods  are  of  nearly  uniform  size,  and  arranged 
perpendicularly  to  the  surface.  Each  rod  consists  of  two  portions,  an  outer  and 
inner,  which  are  of  about  equal  length.  The  segments  differ  from  each  other  as 
regards  refraction  and  in  their  behavior  with  coloring  reagents,  the  inner  portion 
becoming  stained  by  carmine,  iodine,  etc.,  the  outer  portion  remaining  unstained 
with  these  reagents,  but  staining  yellowish  brown  with  osmic  acid.  The  outer  por- 
tion of  each  rod  is  marked  by  transverse  striae,  and  is  made  up  of  a  number  of  thin 
disks  superimposed  on  one  another.  It  also  exhibits  faint  longitudinal  markings. 
The  inner  portion  of  each  rod,  at  its  deeper  part  where  it  is  joined  to  the  outer 
process  of  the  rod-granule,  is  indistinctly  granular  ;  its  more  superficial  part  pre- 
sents a  longitudinal  striation,  being  composed  of  fine,  bright,  highly  refracting 
fibrils.  The  visual  purple  or  rhodopsin  is  found  only  in  the  outer  segments  of 
the  rods. 


836 


THE    ORGANS    OF  SPECIAL    SENSE. 


•    THE  EYE.  837 

The  cones  are  conical  or  flask-shaped,  their  broad  ends  resting  upon  the  mem- 
brana  limitans  externa,  the  narrow  pointed  extremity  being  turned  to  the  choroid. 
Like  the  rods,  they  are  made  up  of  two  portions,  outer  and  inner ;  the  outer  por- 
tion is  a  short  conical  process,  which,  like  the  outer  segment  of  the  rods,  presents 
transverse  striae.  The  inner  portion  resembles  the  inner  portion  of  the  rods  in 
structure,  presenting  a  superficial  striated  and  deeper  granular  part ;  but  differs 
from  it  in  size,  being  bulged  out  laterally  and  presenting  a  flask  shape.  The 
chemical  and  optical  characters  of  the  two  portions  are  identical  with  those  of 
the  rods. 

10.  The  Pigmentary  Layer,  or  Tapetum  Nigrum. — The  most  external  layer  of 
the  retina,  formerly  regarded  as  a  part  of  the  choroid,  consists  of  a  single  layer  of 
hexagonal  epithelial  cells,  loaded  with  pigment-granules.  They  are  smooth  exter- 
nally, where  they  are  in  contact  with  the  choroid,  but  internally  they  are  prolonged 
into  fine,  straight  processes,  which  extend  between  the  rods,  this  being  especially 
the  case  when  the  eye  is  exposed  to  light.  In  the  eyes  of  albinos,  the  cells  of  the 
pigmentary  layer  are  present,  but  they  contain  no  coloring-matter.  In  many  of 
the  mammals  also,  as  in  the  horse,  and  many  of  the  carnivora,  there  is  no  pigment 
in  the  cells  of  this  layer,  and  the  choroid  possesses  a  beautiful  iridescent  lustre, 
which  is  termed  the  tapetum  lucidum. 

Supporting  Frametvork  of  the  Retina. — Almost  all  these  layers  of  the  retina 
are  connected  together  by  a  supporting  framework,  formed  by  the  fibres  of  Midler, 
or  radiating  fibres,  from  which  the  membrana  limitans  interna  et  externa  are 
derived.  These  fibres  are  found  stretched  between  the  two  limiting  layers,  k,as 
columns  between  a  floor  and  a  ceiling,"  and  passing  through  all  the  nervous  layers 
except  Jacob's  membrane.  Each  commences  on  the  inner  surface  of  the  retina  by 
a  conical  hollow  base,  which  sometimes  contains  a  spheroidal  body,  stained  deeply 
with  hematoxylin,  the  edges  of  the  bases  of  adjoining  fibres  being  united  and 
thus  forming  a  boundary  line,  which  is  the  membrana  limitans  interna.  As  they 
pass  through  the  nerve-fibre  and  ganglionic  layers  they  give  off  few  lateral  branches  ; 
in  the  inner  nuclear  layer  they  give  off  numerous  lateral  processes  for  the  support 
of  the  inner  granules,  while  in  the  outer  nuclear  layer  they  form  a  network  around 
the  rod  and  cone-fibrils,  and  unite  to  form  the  external  limiting  membrane  at  the 
bases  of  the  rods  and  cones.  In  the  inner  nuclear  layer  each  fibre  of  Miiller  pre- 
sents a  clear  oval  nucleus,  which  is  sometimes  situated  at  the  side  of,  sometimes 
altogether  within,  the  fibre. 

DESCRIPTION  OF  FIG.  448. 

I.  Section  of  the  dog's  retina,  a,  Cone-fibre,  b,  Rod-fibre  and  nucleus,  e,  d,  Bipolar  cells  (inner  granules) 
with  vertical  ramification  of  outer  processes  destined  to  receive  the  enlarged  ends  of  rod-fibres. 
e,  Bipolars  with  flattened  ramification  for  ends  of  cone-fibres.  /,  Giant  bipolar  with  flattened  ramifica- 
tion, g,  Cell  sending  a  neuron  or  nerve-fibre  process  to  the  outer  molecular  layer,  h,  Amacrine  cell 
with  diffuse  arborization  in  inner  molecular  layer,  i,  Nerve-fibrils  passing  to  outer  molecular  layer. 
j,  Centrifugal  fibres  passing  from  nerve-fibre  layer  to  inner  molecular  layer,  m,  Nerve-fibril  passing 
into  inner  molecular  laver.  n.  Ganglionic  cells. 
II.  Horizontal  or  basal  cells  of  "the  outer  molecular  layer  of  the  dog's  retina,  a,  Small  cell  with  dense  arbori- 
zation, r,  Large  cell,  lying  in  inner  nuclear  layer,  but  with  its  processes  branching  in  the  outer 
molecular,    a,  Its  horizontal  neuron,     c,  Medium-sized  cell  of  the  same  character. 

III.  Cells  from  the  retina  of  the  ox.    a,  Rod-bipolars  with  vertical  arborizations.    b,  c.  d  e.  Cone-bipolars  with 

horizontal  ramification  of  outer  process,  h,  Cells  lying  on  the  outer  surface  of  the  outer  molecular 
layer,  and  ramifying  within  it.  i,j,  m,  Amacrine  cells  within  the  substance  of  the  inner  molecular 
layer. 

IV.  Neurons  or  axis-cylinder  processes  belonging  to  horizontal  cells  of  the  outer  molecular  layer,  one  of  them, 

b,  ending  in  a'close  ramification  at  a. 
V.  Nervous  elements  connected  with  the  inner  molecular  laver  of  the  ox's  retina,  a,  Amacrine  cell,  with 
long  processes  ramifying  in  the  outermost  stratum,  b.  Large  amacrine  with  thick  processes  ramifying 
in  second  stratum,  c,  Flattened  amacrine  with  long  and  fine  processes  ramifying  mainly  in  the  first 
and  fifth  strata,  d,  Amacrine  with  radiating  tuft  of  fibrils  destined  for  third  stratum.  E,  Large 
amacrine,  with  "processes  rarnifving  in  fifth  stratum,  f,  Small  amacrine.  branching  into  second 
stratum,  g,  h,  Other  amacrines  destined  for  fourth  stratum,  a,  Small  gangliorl-cell  sending  its  proc- 
esses to  fourth  stratum,  b.  A  small  ganglion-cell  with  ramifications  in  three  strata,  e,  A  small  cell 
ramifying  ultimately  in  first  stratum,  d,  A  medium-sized  ganglion-cell  ramifying  in  fourth  stratum. 
e,  Giant-cell,  branching  in  third  stratum.    /,  A  bistratified  cell  ramifying  in  second  and  fourth  strata. 

VI.  Amacrines  and  ganglion-cells  from  the  dog.  a",  Amacrine  with  radiating  tuft.  E.  Large  amacrine  passing 
to  third  stratum,  c  and  g,  Small  amacrines  with  radiations  in  second  stratum.  F,  Small  amacrine 
passing  to  third  stratum,  d,  Amacrine  with  diffuse  arborization.  E,  Amacrine  belonging  to  fourth 
stratum,  a,  d,  e,  g,  Small  ganglion-cells,  ramifying  in  various  strata.  &,/,  Large  ganglion-cells  show- 
ing two  different  characters  of  arborization,    i,  Bistratified  cell. 

VII.  Amacrines  and  ganglion-cells  from  the  dog.  a,  b,  c,  Small  amacrines  ramifying  in  middle  of  molecular 
layer,  b,  d,  g,  h,i.  Small  ganglion-cells  showing  various  kinds  of  arborization.  /,  A  larger  cell,  similar 
in"  character  to  g,  but  with  longer  branch.  a,c,e,  Giant-cells  with  thick  branches  ramifying  in  the 
first,  second,  and  third  layers,    l,  l,  Ends  of  bipolars  branching  over  ganglion-cells. 


838 


THE    ORGANS    OF  SPECIAL    SENSE. 


Macula  Lutea  and  Fovea  Centralis. — The  structure  of  the  retina  at  the  yellow 
spot  presents  some  modifications.     In  the  macula  lutea  (1)  the  nerve-fibres  are 


Pigmentary  layer. 


Jacob's  membrane. 


Membrana  limitans  externa. 


Outer  nuclear  layer. 


g  Outer  molecular  layer. 


Inner  nuclear  layer. 


Fibre  of  Mutter. -~ 


Inner  molecular  layer. 

Vesicular  layer. 

Fibrous  layer. 

Membrana  limitans  interna. 
Fig.  449.— The  layers  of  the  retina  (diagrammatic).     (After  Schultze.) 

wanting  as  a  continuous  layer  ;  (2)  the  ganglionic  layer  consists  of  several  strata 
of  cells,  instead  of  a  single  layer;  (3)  in  Jacob's  membrane  there  are  no  rods,  but 
only  cones,  and  these  are  longer  and  narrower  than  in  other  parts  ;  and  (4)  in  the 
outer  nuclear  layer  there  are  only  cone  fibres,  which  are  very  long  and  arranged 
in  curved  lines.  At  the  fovea  centralis  the  only  parts  which  exist  are  the  cones 
of  Jacob's  membrane,  the  outer  nuclear  layer,  the  cone-fibres  of  which  are  almost 
horizontal  in  direction,  and  an  exceedingly  thin  inner  granular  layer,  the  pigmentary 
layer,  which  is  thicker  and  its  pigment  more  pronouncod  than  elsewhere.  The 
color  of  the  macula  seems  to  imbue  all  the  layers  except  Jacob's  membrane;  it  is 
of  a  rich  yellow,  deepest  toward  the  centre,  and  does  not  appear  to  consist  of 
pigment-cells,  but  simply  a  staining  of  the  constituent  parts. 

At  the  ora  serrata  the  nervous  layers  of  the  retina  terminate  abruptly,  and  the 
retina  is  continued  onward  as  a  single  layer  of  elongated  columnar  cells  covered  by 
the  pigmentary  layer.  This  prolongation  is  known  as  the  pars  ciliaris  retina?,  and 
can  be  traced  forward  from  the  ciliary  processes  on  to  the  back  of  the  iris,  where 
it  is  termed  the  pars  iridiea  retince  or  uvea. 

From  the  description  given  of  the  nervous  elements  of  the  retina  it  will  be 
seen  that  there  is  no  direct  continuity  between  the  structures  which  form  its 
different  layers  except  between  the  ganglionic  and  nerve-fibre  layers,  the  majority 
of  the  nerve-fibres  being  formed  of  the  axons  of  the  ganglionic  cells.  In  the 
inner  molecular  layer  the  dendrites  of  the  ganglionic  layer  interlace  with  those 
of  the  cells  of  the  inner  nuclear  layer,  while  in  the  outer  molecular  layer  a  like 


THE    VITREOUS  BODY.  839 

synapsis  occurs  between  the  processes  of  the  inner  granules  and  the  rod  and  cone 
elements. 

The  arteria  centralis  retinae  and  its  accompanying  vein  pierce  the  optic  nerve, 
and  enter  the  globe  of  the  eye  through  the  porus  opticus.  It  immediately  bifur- 
cates into  an  upper  and  a  lower  branch,  and  each  of  these  again  divides  into  an 
inner,  or  nasal,  and  an  outer,  or  temporal,  branch,  which  at  first  run  between  the 
hyaloid  membrane  and  the  nervous  layer ;  but  they  soon  enter  the  latter,  and  pass 
forward,  dividing  dichotomously.  From  these  branches  a  minute  capillary  plexus 
is  given  off,  which  does  not  extend  beyond  the  inner  nuclear  layer.  The  macula 
receives  small  twigs  from  the  temporal  branches  and  others  directly  from  the  central 
artery  ;  these  do  not,  however,  reach  as  far  as  the  fovea  centralis,  which  has  no  blood- 
vessels. The  branches  of  the  arteria  centralis  retinae  do  not  anastomose  with  each 
other — in  other  words,  they  are  "  terminal  arteries."  In  the  foetus,  a  small  vessel 
passes  forward,  through  the  vitreous  humor,  to  the  posterior  surface  of  the  capsule 
of  the  lens. 

REFRACTING  MEDIA. 

The  Refracting  media  are  three,  viz.  : 

Aqueous  humor.  Vitreous  body.  Crystalline  lens. 

I.  Aqueous  Humor. 

The  aqueous  humor  completely  fills  the  anterior  and  posterior  chambers  of  the 
eyeball.  It  is  small  in  quantity  (scarcely  exceeding,  according  to  Petit,  four  or 
five  grains  in  weight),  has  an  alkaline  reaction,  in  composition  is  little  more  than 
water,  less  than  one-fiftieth  of  its  weight  being  solid  matter,  chiefly  chloride  of 
sodium. 

The  anterior  chamber  is  the  space  bounded  in  front  by  the  cornea ;  behind,  by 
the  front  of  the  iris.  The  posterior  chamber  is  a  narrow  chink  between  the 
peripheral  part  of  the  iris,  the  suspensory  ligament  of  the  lens,  and  the  ciliary 
processes. 

In  the  adult,  these  two  chambers  communicate  through  the  pupil ;  but  in  the 
foetus  of  the  seventh  month,  when  the  pupil  is  closed  by  the  membrana  pupillaris, 
the  two  chambers  are  quite  separate. 

II.  Vitreous  Body. 

The  vitreous  body  forms  about  four-fifths  of  the  entire  globe.  It  fills  the 
concavity  of  the  retina,  and  is  hollowed  in.  front,  forming  a  deep  concavity,  the 
fossa  patellaris,  for  the  reception  of  the  lens.  It  is  perfectly  transparent,  of  the 
consistence  of  thin  jelly,- and  is  composed  of  an  albuminous  fluid  enclosed  in  a 
delicate  transparent  membrane,  the  membrana  hyaloidea.  It  has  been  supposed 
by  Hannover,  that  from  its  inner  surface  numerous  thin  lamellae  are  prolonged 
inward  in  a  radiating  manner,  forming  spaces  in  which  the  fluid  is  contained.  In 
the  adult,  these  lamellae  cannot  be  detected  even  after  careful  microscopic  examina- 
tion in  the  fresh  state,  but  in  preparations  hardened  in  weak  chromic  acid  it  is 
possible  to  make  out  a  distinct  lamellation  at  the  periphery  of  the  body:  and  in 
the  foetus  a  peculiar  fibrous  texture  pervades  the  mass,  the  fibres  joining  at 
numerous  points,  and  presenting  minute  nuclear  granules  at  their  point  of  junction. 
In  the  centre  of  the  vitreous  humor,  running  from  the  entrance  of  the  optic  nerve 
to  the  posterior  surface  of  the  lens,  is  a  canal,  filled  with  fluid  and  lined  by  a 
prolongation  of  the  hyaloid  membrane.  This  is  the  canal  of  Stilling,  which  in 
the  embryonic  vitreous  humor  conveyed  the  minute  vessel  from  the  central  artery 
of  the  retina  to  the  back  of  the  lens.  The  fluid  from  the  vitreous  body  resembles 
nearly  pure  water  ;  it  contains,  however,  some  salts  and  a  little  albumin. 

The  hyaloid  membrane  encloses  the  whole  of  the  vitreous  humor.  In  front 
of  the  ora  serrata  it  is  thickened  bv  the  accession  of  radial  fibres  and  is  termed 


840  THE    ORGANS    OF  SPECIAL    SENSE. 

the  zonule  of  Zinn  or  zonula  ciliaris.  It  presents  a  series  of  radially  arranged 
furrows,  in  which  the  ciliary  processes  are  accommodated  and  to  which  they  are 
adherent,  as  evidenced  by  the  fact  that  when  removed  some  of  their  pigment 
remains  attached  to  the  zonule.  The  zonule  of  Zinn  splits  into  two  layers,  one 
of  which  is  thin  and  lines  the  fossa  patellaris;  the  other  is  named  the  suspensory 
ligament  of  the  lens  ;  it  is  thicker,  and  passes  over  the  ciliary  body  to  be  attached 
to  the  capsule  of  the  lens  a  short  distance  in  front  of  its  equator.  Scattered  and 
delicate  fibres  are  also  attached  to  the  region  of  the  equator  itself.  This  ligament 
retains  the  lens  in  position,  and  is  relaxed  by  the  contraction  of  the  radial  fibres 
of  the  Ciliary  muscle,  so  that  the  lens  is  allowed  to  become  more  convex.  Behind 
the  suspensory  ligament  there  is  a  sacculated  canal,  the  canal  of  Petit,  which 
encircles  the  equator  of  the  lens  and  which  can  be  easily  inflated  through  a  fine 
blow-pipe  inserted  through  the  suspensory  ligament. 

In  the  foetus,  the  centre  of  the  vitreous  humor  presents  the  canal  of  Stilling, 
already  referred  to,  which  transmits  a  minute  artery  to  the  capsule  of  the  lens. 
In  the  adult,  no  vessels  penetrate  its  substance ;  so  that  its  nutrition  must  be 
carried  on  by  the  vessels  of  the  retina  and  ciliary  processes,  situated  upon  its 
exterior. 

III.  Crystalline  Lens. 

The  crystalline  lens,  enclosed  in  its  capsule,  is  situated  immediately  behind 
the  pupil,  in  front  of  the  vitreous  body,  and  encircled  by  the  ciliary  processes, 
which  slightly  overlap  its  margin. 

The  capsule  of  the  lens  is  a  transparent,  highly  elastic,  and  brittle  membrane, 
which  closely  surrounds  the  lens.  It  rests,  behind,  in  the  fossa  patellaris  in  the 
fore  part  of  the  vitreous  body ;  in  front,  it  is  in  contact 
with  the  free  border  of  the  iris,  this  latter  receding  from 
it  at  the  circumference,  thus  forming  the  posterior  cham- 
ber of  the  eye ;  and  it  is  retained  in  its  position  chiefly 
by  the  suspensory  ligament  of  the  lens,  already  described. 
The  capsule  is  much  thicker  in  front  than  behind,  and 
structureless  in  texture  ;  when  ruptured,  the  edges  roll 
up  with  the  outer  surface  innermost,  like  the  elastic 
lamina  of  the  cornea. 

The  anterior  surface  of  the  lens  is  covered  by  a  single 
lens^harlfe^an^dfvide'dL  layer  of  transparent,  polygonal,  nucleated  cells.  At  the 
(Enlarged.)  circumference  of  the  lens,  these  cells  undergo  a  change  in 

form :  they  become  elongated,  and  Babucin  states  that  he 
can  trace  the  gradual  transition  of  the  cells  into  proper  lens-fibres,  with  which 
they  are  directly  continuous.  There  is  no  epithelium  on  the  posterior  surface. 
In  the  foetus,  a  small  branch  from  the  arteria  centralis  retinse  runs  forward, 
as  already  mentioned,  through  the  vitreous  humor  to  the  posterior  part  of  the 
capsule  of  the  lens,  where  its  branches  radiate  and  form  a  plexiform  network, 
which  covers  its  surface,  and  they  are  continuous  round  the  margin  of  the  capsule 
with  the  vessels  of  the  pupillary  membrane  and  with  those  of  the  iris.  In  the 
adult  no  vessels  enter  its  substance. 

The  lens  is  a  transparent,  biconvex  body,  the  convexity  being  greater  on  the 
posterior  than  on  the  anterior  surface.  The  central  points  of  its  anterior  and 
posterior  surfaces  are  known  as  its  anterior  and  posterior  poles.  It  measures 
from  9  to  10  mm.  in  the  transverse  diameter,  and  about  4  mm.  in  the  antero- 
posterior. It  consists  of  concentric  layers,  of  which  the  external  in  the  fresh  state 
are  soft  and  easily  detached  {substantia  corticalis) ;  those  beneath  are  firmer,  the 
central  ones  forming  a  hardened  nucleus  [nucleus  lentis).  These  laminae  are  best 
demonstrated  by  boiling  or  immersion  in  alcohol,  and  consist  of  minute  parallel 
fibres,  which  are  hexagonal  prisms,  the  edges  being  dentated,  and  the  dentations 
fitting  accurately  into  each  other ;  their  breadth  is  about  5*Q0  of  an  inch. 
Faint  lines  radiate  from  the  anterior  and  posterior  poles  to  the  circumference  of 


THE    CRYSTALLINE   LENS.  841 

the  lens.  In  the  adult  there  may  be  six  or  more  of  these,  but  in  the  foetus  they 
are  only  three  in  number  and  diverge  from  each  other  at  angles  of  120°  (Fig.  451). 
On  the  anterior  surface  one  line  ascends  vertically  and  the  other  two  diverge 
downward  and  outward.      On  the  posterior  surface  one   ray  descends  vertically 


Fig.  451.— Diagram  to  show  the  direction  and  arrangement  of  the  radiating  lines  on  the  front  and  back  of  the 
foetal  lens,    (a)  from  the  front,    (b)  from  the  back. 

and  the  other  two  diverge  upward.  They  correspond  with  the  free  edges  of  an 
equal  number  of  septa  in  the  lens,  along  which  the  ends  of  the  lens  fibres  come 
into  apposition  and  are  joined  by  transparent  amorphous  substance.  The  fibres 
run  in  a  curved  manner  from  the  septa  on  the  anterior  surface  to  those  on  the 
posterior  surface.  No  fibres  pass  from  pole  to  pole,  but  they  are  arranged  in  such 
a  way  that  fibres  which  commence  near  the  pole  on  the  one  aspect  of  the  lens 
terminate  near  the  peripheral  extremity  of  the  plane  on  the  other,  and  vice  versd. 
The  fibres  of  the  outer  layers  of  the  lens  each  contain  a  nucleus,  which  together 
form  a  layer  (nuclear  layer)  on  the  surface  of  the  lens,  most  distinct  toward  its 
circumference. 

The  changes  produced  in  the  lens  by  age  are  the  following  : 

In  the  foetus  its  form  is  nearly  spherical,  its  color  of  a  slightly  reddish  tint,  it 
is  not  perfectly  transparent,  and  is  so  soft  as  to  break  down  readily  on  the  slightest 
pressure. 

In  the  adult  the  posterior  surface  is  more  convex  than  the  anterior  ;  it  is  color- 
less, transparent,  and  firm  in  texture. 

In  old  age  it  becomes  flattened  on  both  surfaces,  slightly  opaque,  of  an  amber 
tint,  and  increases  in  density. 

The  arteries  of  the  globe  of  the  eye  are  the  short,  long,  and  anterior  ciliary 
arteries  and  the  arteria  centralis  retinae.  They  have  been  already  described  (see 
page  509). 

The  ciliary  veins  are  seen  on  the  outer  surface  of  the  choroid,  and  are  named, 
from  their  arrangement,  the  vence  vorticosos.  They  converge  to  four  or  five 
equidistant  trunks,  which  pierce  the  sclerotic  midway  between  the  margin  of  the 
cornea  and  the  entrance  of  the  optic  nerve.  Another  set  of  veins  accompany  the 
anterior  ciliary  arteries  and  open  into  the  ophthalmic  vein. 

The  ciliary  nerves  are  derived  from  the  nasal  branch  of  the  ophthalmic  and 
from  the  ciliary  or  ophthalmic  ganglion. 

Surgical  Anatomy.*— From  a  surgical  point  of  view  the  cornea  may  be  regarded  as  consist- 
ing of  three  layers  :  (1 )  of  an  external  epithelial  layer,  developed  from  the  epi  blast,  and  con- 
tinuous with  the  external  epithelial  covering  of  the  rest  of  the  body,  and  therefore  in  its  lesions 
resembling  those  of  the  epidermis  ;  (2)  of  the  cornea  proper,  derived  from  the  mesoblast,  and 
associated  in  its  diseases  with  the  fibro- vascular  structures  of  the  body  ;  and  (3)  the  posterior 
elastic  layer  with  its  endothelium,  also  derived  from  the  mesoblast  and  having  the  characters  vi' 
a  serous  membrane,  so  that  inflammation  of  it  resembles  inflammation  of  the  other  serous  and 
synovial  membranes  of  the  body. 

The  cornea  contains  no  blood-vessels,  except  at  its  periphery,  where  numerous  delicate 
loops,  derived  from  the  anterior  ciliary  arteries,  may  be  demonstrated  on  the  anterior  surface  oi 
the  cornea.  The  rest  of  the  cornea  is  nourished  by  lymph,  which  gains  access  to  the  proper  sub- 
stance of  the  cornea  and  the  posterior  layer  through  the  spaces  of  Fontana  I  his  lack  of  a 
direct  blood-supply  renders  the  cornea  very  apt  to  inflame  in  the  cachectic  and  ill-nourished,  in 
cases  of  granular  lids  there  is  a  peculiar  affection  of  the  cornea,  called  panmts,  m  which  the 
anterior  layers  of  the  cornea  become  vascularized,  and  a  rich  network  of  blood-vessels  may  be 
seen  on  the  cornea;  and  in  interstitial  keratitis  new  vessels  extend  into  the  cornea,  giving'  it  a 
pinkish  hue,  to  which  the  term  "  salmon  patch  "  is  applied.     The  cornea  is  richly  supplied  wit  a 


842  THE    ORGANS    OF  SPECIAL    SENSE. 

nerves,  derived  from  the  ciliary,  which  enter  the  cornea  through  the  fore  part  of  the  sclerotic 
and  form  plexuses  in  the  stroma,  terminating  between  the  epithelial  cells  by  free  ends  or  in  cor- 
puscles. In  cases  of  glaucoma  the  ciliary  nerves  may  be  pressed  upon  as  they  course  between 
the  choroid  and  sclerotic,  and  the  cornea  becomes  anaesthetic.  The  sclerotic  has  very  few  blood- 
vessels and  nerves.  The  blood-vessels  are  derived  from  the  anterior  ciliary,  and  form  an  open 
plexus  in  its  substance.  As  they  approach  the  corneal  margin  this  arrangement  is  peculiar. 
Some  branches  pass  through  the  sclerotic  to  the  ciliary  body ;  others  become  superficial  and  lie 
in  the  episcleral  tissue,  and  form  arches,  by  anastomosing  with  each  other,  some  little  distance 
behind  the  corneal  margin.  From  these  arches  numerous  straight  vessels  are  given  off",  which 
run  forward  to  the  cornea,  forming  its  marginal  plexus.  In  inflammation  of  the  sclerotic  and 
episcleral  tissue  these  vessels  become  conspicuous,  and  form  a  pinkish  zone  of  straight  vessels 
radiating  from  the  corneal  margin,  commonly  known  as  the  zone  of  ciliary  injection.  In  inflam- 
mation of  the  iris  and  ciliary  body  this  zone  is  present,  since  the  sclerotic  speedily  becomes 
involved  when  these  structures  are  inflamed.  But  in  inflammation  of  the  cornea  the  sclerotic  is 
seldom  much  affected,  though  the  cornea  and  sclerotic  are  structurally  continuous.  This  would 
appear  to  be  due  to  the  fact  that  the  nutrition  of  the  cornea  is  derived  from  a  different  source 
from  that  of  the  sclerotic.  The  sclerotic  may  be  ruptured  subcutaneously  without  any  laceration  of 
the  conjunctiva,  and  the  rupture  usually  occurs  near  the  corneal  margin,  where  the  tunic  is  thin- 
nest. It  may  be  complicated  with  lesions  of  adjacent  parts — laceration  of  the  choroid,  retina, 
iris,  or  suspensory  ligament  of  the  lens— and  is  then  often  attended  with  haemorrhage  into  the 
anterior  chamber,  which  masks  the  nature  of  the  injury.  In  some  cases  the  lens  has  escaped 
through  the  rent  in  the  sclerotic,  and  has  been  found  under  the  conjunctiva.  Wounds  of  the 
sclerotic  are  always  dangerous,  and  are  often  followed  by  inflammation,  suppuration,  and  by 
sympathetic  ophthalmia. 

One  of  the  functions  of  the  choroid  is  to  provide  nutrition  for  the  retina  and  to  convey  ves- 
sels and  nerves  to  the  ciliary  body  and  iris.  Inflammation  of  the  choroid  is  therefore  followed 
by  grave  disturbance  in  the  nutrition  of  the  retina,  and  is  attended  with  early  interference  with 
vision.  In  its  diseases  it  bears  a  considerable  analogy  to  those  which  affect  the  skin,  and,  like  it, 
is  one  of  the  places  from  which  melanotic  sarcomata  may  grow.  These  tumors  contain  a  large 
amount  of  pigment  in  their  cells,  and  grow  only  from  those  parts  where  pigment  is  naturally 
present.  The  choroid  may  be  ruptured  without  injury  to  the  other  tunics,  as  well  as  participa- 
ting in  general  injuries  of  the  eyeball.  In  cases  of  uncomplicated  rupture  the  injury  is  usually 
at  its  posterior  part,  and  is  the  result  of  a  blow  on  the  front  of  the  eye.  It  is  attended  by  con- 
siderable haemorrhage,  which  for  a  time  may  obscure  vision,  but  in  most  cases  this  is  restored  as 
soon  as  the  blood  is  absorbed. 

The  iris  is  the  seat  of  a  malformation,  termed  coloboma,  which  consists  in  a  deficiency  or 
cleft,  which  in  a  great  number  of  cases  is  clearly  due  to  an  arrest  in  development.  In  these  cases 
it  is  found  at  the  lower  aspect,  extending  directly  downward  from  the  pupil,  and  the  gap 
frequently  extends  through  the  choroid  to  the  entrance  of  the  optic  nerve.  In  some  rarer  cases 
the  gap  is  found  in  other  parts  of  the  iris,  and  is  then  not  associated  with  any  deficiency  of  the 
choroid.  The  iris  is  abundantly  supplied  with  blood-vessels  and  nerves,  and  is  therefore  very 
prone  to  become  inflamed.  And  when  inflamed,  in  consequence  of  the  intimate  relationship 
which  exists  between  the  vessels  of  the  iris  and  choroid  this  latter  tunic  is  very  apt  to  participate 
in  the  inflammation.  And,  in  addition,  inflammation  of  adjacent  structures,  the  cornea  and 
sclerotic,  is  apt  to  spread  into  the  iris.  The  iris  is  covered  with  epithelium,  and  partakes  of  the 
character  of  a  serous  membrane,  and,  like  these  structures,  is  liable  to  pour  out  a  plastic  exuda- 
tion when  inflamed,  and  contract  adhesions,  either  to  the  cornea  in  front  {synechia  anterior),  or 
to  the  capsule  of  the  lens  behind  (synechia  ]jnsterior).  In  iritis  the  lens  may  become  involved, 
and  the  condition  known  as  secondary  cataract  maybe  set  up.  Tumors  occasionally  commence  in 
the  iris ;  of  these,  cysts,  which  are  usually  congenital  and  sarcomatous  tumors,  are  the 
most  common  and  require  removal.  Grummata  are  not  unfrequently  found  in  this  situa- 
tion. In  some  forms  of  injury  of  the  eyeball,  as  the  impact  of  a  spent  shot,  the  rebound  of  a 
twig,  or  a  blow  with  a  whip,  the  iris  may  be  detached  from  the  Ciliary  muscle,  the  amount  of 
detachment  varying  from  the  slightest  degree  to  the  separation  of  the  whole  iris  from  its  ciliary 
connection. 

The  retina,  with  the  exception  of  its  pigment-layer  and  its  vessels,  is  perfectly  transparent, 
so  as  to  be  invisible  when  examined  by  the  ophthalmoscope,  so  that  its  diseased  conditions  are 
recognized  by  its  loss  of  transparency.  In  retinitis,  for  instance,  there  is  more  or  less  dense  and 
extensive  opacity  of  its  structure,  and  not  unfrequently  extravasations  of  blood  into  its  sub- 
stance. Haemorrhages  may  also  take  place  into  the  retina  from  rupture  of  a  blood-vessel  with- 
out inflammation. 

The  retina  may  become  displaced  from  effusion  of  serum  between  it  and  the  choroid  or  by 
blows  on  the  eyeball,  or  may  occur  without  appai-ent  cause  in  progressive  myopia,  and  in  this 
case  the  ophthalmoscope  shows  an  opaque,  tremulous  cloud.  Glioma,  a  form  of  sarcoma,  and 
essentially  a  disease  of  early  life,  is  occasionally  met  with  in  connection  with  the  retina. 

The  lens  has  no  blood-vessels,  nerves,  or  connective  tissue  in  its  structure,  and  therefore  is 
not  subject  to  those  morbid  changes  to  which  tissues  containing  these  structures  are  liable.  It 
does,  however,  present  certain  morbid  or  abnormal  conditions  of  various  kinds.  Thus,  variations 
in  shape,  absence  of  the  whole  or  a  part  of  the  lens,  and  displacements  are  amongst  its  congeni- 
tal defects.  Opacities  may  occur  from  injury,  senile  changes,  malnutrition,  or  errors  in  growth 
or  development.     Senile  changes  may  take  place  in  the  lens,  impairing  its  elasticity  and  render- 


THE   APPENDAGES    OF    THE   EYE.  843 

ing  it  harder  than  in  youth,  so  that  its  curvature  can  only  be  altered  to  a  limited  extent  by  the 
Ciliary  muscle.  And,  finally,  the  lens  may  be  dislocated  or  displaced  by  blows  upon  the  eyeball, 
and  its  relations  to  surrounding  structures  altered  by  adhesions  or  the  pressure  of  new  growths. 
There  are  two  particular  regions  of  the  eye  which  require  special  notice :  one  of  these  is 
known  as  the  "  filtration  area,"  and  the  other  as  the  "  dangerous  area."  The  filtration  area  is 
the  circumcorneal  zone  immediately  in  front  of  the  iris.  Here  are  situated  the  cavernous  spaces 
of  Fontana,  which  communicate  with  the  canal  of  Schlemm,  through  which  the  chief  transuda- 
tion of  fluid  from  the  eye  is  now  believed  to  take  place.  The  dangerous  area,  of  the  eye  is  the 
region  in  the  neighborhood  of  the  ciliary  body,  and  wounds  or  injuries  in  this  situation  are 
peculiarly  dangerous  ;  for  inflammation  of  the  ciliary  body  is  liable  to  spread  to  many  of  the 
other  structures  of  the  eye,  especially  to  the  iris  and  choroid,  which  are  intimately  connected  by 
nervous  and  vascular  supplies.  Moreover,  wounds  which  involve  the  ciliary  region  are  especially 
liable  to  be  followed  by  sympathetic  ophthalmia,  in  which  destructive  inflammation  of  one  eye 
is  excited  by  some  irritation  in  the  other. 

The  Appendages  of  the  Eye. 

The  appendages  of  the  eye  (tutamina  oculi)  include  the  eyebrows,  the  eyelids, 
the  conjunctiva,  and  the  lachrymal  apparatus — viz.  the  lachrymal  gland,  the 
lachrymal   sac,    and  the  nasal   duct. 

The  eyebrows  (supercilici)  are  two  arched  eminences  of  integument  which 
surmount  the  upper  circumference  of  the  orbit  on  each  side,  and  support  numer- 
ous short,  thick  hairs,  directed  obliquely  on  the  surface.  In  structure  the  eye- 
brows consist  of  thickened  integument,  connected  beneath  with  the  Orbicularis 
palpebrarum,  Corrugator  supercilii,  and  Occipito-frontalis  muscles.  These  mus- 
cles serve,  by  their  action  on  this  part,  to  control  to  a  certain  extent  the  amount 
of  light  admitted  into  the  eye. 

The  eyelids  (palpebrce)  are  two  thin,  movable  folds  placed  in  front  of  the 
eye,  protecting  it  from  injury  by  their  closure.  The  upper  lid  is  the  larger 
and  the  more  movable  of  the  two,  and  is  furnished  with  a  separate  elevator- 
muscle,  the  Levator  palpebral  superioris.  When  the  eyelids  are  opened  an 
elliptical  space  (fissura  palpebrarum)  is  left  between  their  margins,  the  angles 
of  which  correspond  to  the  junction  of  the  upper  and  lower  lids,  and  are 
called  eanthi. 

The  outer  canthus  is  more  acute  than  the  inner,  and  the  lids  here  lie  in  close 
contact  with  the  globe ;  but  the  inner  canthus  is  prolonged  for  a  short  distance 
inward  toward  the  nose,  and  the  two  lids  are  separated  by  a  triangular  space,  the 
lacus  lachrymalis.  At  the  commencement  of  the  lacus  lachrymalis,  on  the  margin 
of  each  eyelid,  is  a  small  conical  elevation,  the  lachrymal  papilla,  the  apex  of 
wThich  is  pierced  by  a  small  orifice,  the  punctum  lachrymale,  the  commencement  of 
the  lachrymal  canal. 

The  eyelashes  (cilia)  are  attached  to  the  free  edges  of  the  eyelids  ;  they  are 
short,  thick,  curved  hairs,  arranged  in  a  double  or  triple  row  at  the  margin  of  the 
lids :  those  of  the  upper  lid,  more  numerous  and  longer  than  the  lower,  curve 
upward ;  those  of  the  lower  lid  curve  downward,  so  that  they  do  not  interlace  in 
closing  the  lids.  Near  the  attachment  of  the  eyelashes  are  the  openings  of  a 
number  of  glands,  glands  of  Moll,  arranged  in  several  rowTs  close  to  the  free 
margin  of  the  lid.     They  are  regarded  as  enlarged  and  modified  sweat-glands. 

Structure  of  the  Eyelids. — The  eyelids  are  composed  of  the  following  structures, 
taken  in  their  order  from  Avithout  inward : 

Integument,  areolar  tissue,  fibres  of  the  Orbicularis  muscle,  tarsal  plate,  and 
its  ligament,  Meibomian  glands  and  conjunctiva.  The  upper  lid  has.  in  addition. 
the  aponeurosis  of  the  Levator  palpebrce. 

The  integument  is  extremely  thin,  and  continuous  at  the  margin  of  the  lids 
with  the  conjunctiva. 

The  subcutaneous  areolar  tissue  is  very  lax  and  delicate,  seldom  contains  any 
fat,  and  is  extremely  liable  to  serous  infiltration. 

The  fibres  of  the  Orbicularis  muscle,  where  they  cover  the  palpebnw  are  thin, 
pale  in  color,  and  possess  an  involuntary  action. 

The  tarsal  plates  are   two  thin   elongated  plates  of  dense   connective   tissue 


844 


THE    ORGANS    OF  SPECIAL   SENSE. 


about  an  inch  in  length.      They  are  placed  one  in  each  lid,  contributing  to  their 
form  and  support.  ,  .         . 

The  superior,  the  larger,  is  of  a  semilunar  form,  about  one-third  of  an  men  in 
breadth  at  the  centre,  and  becoming  gradually  narrowed  at  each  extremity.     To 

the  anterior  surface  of  this  plate  the 
aponeurosis  of  the  Levator  palpebrse  is 
attached. 

The  inferior  tarsal  'plate,  the  smaller, 
is  thinner  and  of  an  elliptical  form. 

The  free  or  ciliary  margin  of  these 
plates  is  thick,  and  presents  a  perfectly 
straight  edge.  The  attached  or  orbital 
margin  is  connected  to  the  circumference 
of  the  orbit  by  the  fibrous  membrane  of 
the  lids,  with  which  it  is  continuous.  The 
outer  angle  of  each  plate  is  attached  to 
the  malar  bone  by  the  external  tarsal 
ligament.  The  inner  angles  of  the  two 
plates  terminate  at  the  commencement 
of  the  lacus  lacrimalis  ;  they  are  attached 
to  the  nasal  process  of  the  superior  max- 
illa by  the  internal  tarsal  ligament  or 
ten  do  oculi. 

The  palpebral  ligaments  are  mem- 
branous expansions  situated  one  in  each 
lid,  and  are  attached  marginally  to  the 
edge  of  the  orbit,  where  they  are  con- 
tinuous with  the  periosteum.  The  supe- 
rior ligament  blends  with  the  tendon  of 
the  Levator  palpebrse,  the  inferior  with 
the  inferior  tarsal  plate.  Externally  the 
two  ligaments  fuse  to  form  the  external 
tarsal  ligament,  just  referred  to  ;  inter- 
nally they  are  much  thinner  and,  be- 
coming separated  from  the  internal  tarsal 
ligament,  are  fixed  to  the  lachrymal  bone 
immediately  behind  the  lachrymal  sac. 
Together,  the  ligaments  form  an  incom- 
plete septum,  the  septum  orbitale,  which 
is  perforated  by  the  vessels  and  nerves 
which  pass  from  the  orbital  cavity  to  the 
face  and  scalp. 

The  Meibomian  glands  (Fig.  453)  are  situated  upon  the  inner  surface  of  the 
eyelids  between  the  tarsal  plates  and  conjunctiva,  and  may  be  distinctly  seen 
through  the  mucous  membrane  on  everting  the  eyelids,  presenting  the  appear- 
ance of  parallel  strings  of  pearls.  They  are  about  thirty  in  number  in  the  upper 
eyelid,  and  somewhat  fewer  in  the  lower.  They  are  imbedded  in  grooves  in  the 
inner  surface  of  the  tarsal  plates,  and  correspond  in  length  with  the  breadth  of 
each  plate ;  they  are,  consequently,  longer  in  the  upper  than  in  the  lower  eyelid. 
Their  ducts  open  on  the  free  margin  of  the  lids  by  minute  foramina,  which  cor- 
respond in  number  to  the  follicles.  The  use  of  their  secretion  is  to  prevent  adhe- 
sions of  the  lids. 

Structure  of  the  Meibomian  Glands. — These  glands  are  a  variety  of  the  cuta- 
neous sebaceous  glands,  each  consisting  of  a  single  straight  tube  or  follicle,  having 
a  CEecal  termination,  and  with  numerous  small  secondary  follicles  opening  into  it. 
The  tubes  consist  of  basement-membrane,  lined  at  the  mouths  of  the  tubes  by 
stratified  epithelium  ;  the  deeper  parts  of  the  tubes  and  the  secondary  follicles  are 


"Fig.  452. — Vertical  section  through  the  upper  eye- 
lid. (After  Waldeyer.)  a.  Skin.  b.  Orbicularis  palpe- 
brarum, b'.  Marginal  fasciculus  of  orbicularis  (cil- 
iary bundle),  c.  Levator  palpebrae.  d.  Conjunctiva. 
e.  Tarsal  plate.  /.  Meibomian  gland,  g.  Sebaceous 
gland,  h.  Eyelashes,  i.  Small  hairs  of  skin.  j.  Sweat- 
glands,    k.  Posterior  tarsal  glands. 


THE   APPENDAGES    OF    THE   EYE. 


845 


lined  by  a  layer  of  polyhedral  cells.  They  are  thus  identical  in  structure  with  the 
sebaceous  glands. 

The  conjunctiva  is  the  mucous  membrane  of  the  eye.  It  lines  the  inner  sur- 
face of  the  eyelids,  and  is  reflected  over  the  fore  part  of  the  sclerotic  and  cornea. 
In  each  of  these  situations  its  structure  presents  some  peculiarities. 

The  palpebral  portion  of  the  conjunctiva  is  thick,  opaque,  highly  vascular,  and 
covered  with  numerous  papillae,  its  deeper  parts  presenting  a  considerable  amount 
of  lymphoid  tissue.  At  the  margin  of  the  lids  it  becomes  continuous  with  the 
lining  membrane  of  the  ducts  of  the  Meibomian  glands,  and,  through  the  lachry- 
mal canals,  with  the  lining  membrane  of  the  lachrymal  sac  and  nasal  duct.  At 
the  outer  angle  of  the  upper  lid  the  lachrymal  ducts  open  on  its  free  surface ;  and 
at  the  inner  angle  of  the  eye  it  forms  a  semilunar  fold,  the  plica  semilunaris.  The 
folds  formed  by  the  reflection  of  the  conjunctiva  from  the  lids  on  to  the  eve  are 
called  the  superior  and  inferior  palpebral  folds,  the  former  being  the  deeper  of  the 
two.  Upon  the  sclerotic  the  conjunctiva  is  loosely  connected  to  the  globe:  it  be- 
comes thinner,  loses  its  papillary  structure,  is  transparent,  and  only  slightly  vas- 
cular in  health.  Upon  the  cornea  the  conjunctiva  consists  only  of  epithelium, 
constituting  the  anterior  layer  of  the  cornea  (conjunctival  epithelium)  already 
described  (see  page  826).  Lymphatics  arise  in  the  conjunctiva  in  a  delicate  zone 
around  the  cornea,  from  which  the  vessels  run  to  the  ocular  conjunctiva. 

At  the  point  of  reflection  of  the  conjunctiva  from  the  lid  on  to  the  globe  of  the 
eye,  termed  the  fornix  conjunctiva?,  are  a  number  of  mucous  glands  which  are  much 
convoluted.     They  are  chiefly  found  in  the  upper  lid.     Other  glands,  analogous  to 


Puncta  lachrymalia 


Fig.  453.— The  Meibomian  glands,  etc.,  seen  from  the  inner  surface  of  the  eyelids. 


lymphoid  follicles,  and  called  by  Henle  trachoma  glands,  are  found  in  the  con- 
junctiva, and,  according  to  Strohmeyer,  are  chiefly  situated  near  the  inner  canthus 
of  the  eye.  They  were  first  described  by  Brush,  in  his  description  of  Peyer's 
patches  of  the  small  intestines,  as  "identical  structures  existing  in  the  under  eye- 
lid of  the  ox." 

The  nerves  in  the  conjunctiva  are  numerous  and  form  rich  plexuses.  According 
to  Krause,  they  terminate  in  a  peculiar  form  of  tactile  corpuscle,  which  he  terms 
the  "  terminal  bulb." 

The  caruncida  lachrymalis  is  a  small,  reddish,  conical-shaped  body,  situated  at 
the  inner  canthus  of  the  eye,  and  filling  up  the  small  triangular  space  in  this  situa- 
tion, the  lacus  lachrymalis.  It  consists  of  a  small  island  of  skin  contain- 
ing sebaceous  and  sweat  glands,  and  is  the  source  of  the  whitish  secretion 
which  constantly  collects  at  the  inner  angle  of  the  eye.  A  few  slender 
hairs  are  attached  to  its  surface.  On  the  outer  side  of  the  caruncula  is  a  slight 
semilunar  fold  of  mucous  membrane,  the  concavity  of  which  is  directed  toward  the 


846 


THE    ORGANS    OF  SPECIAL    SENSE. 


cornea  ;  it  is  called  the  plica  semilunaris.  Miiller  found  smooth  muscular  fibres 
in  this  fold,  and  in  some  of  the  domesticated  animals  a  thin  plate  of  cartilage  has 
been  discovered.  This  structure  is  considered  to  be  the  rudiment  of  the  third  eyelid 
in  birds,  the  membrana  nictitans. 

The  Lachrymal  Apparatus  (Fig.  454). 

The  lachrymal  apparatus  consists  of  the  lachrymal  gland,  which  secretes  the 
tears,  and  its  excretory  ducts,  which  convey  the  fluid  to  the  surface  of  the  eye. 
This  fluid  is  carried  away  by  the  lachrymal  canals  into  the  lachrymal  sac,  and  along 
the  nasal  duct  into  the  cavity  of  the  nose. 

The  lachrymal  gland  is  lodged  in  a  depression  at  the  outer  angle  of  the  orbit, 
on  the  inner  side, of  the  external  angular  process  of  the  frontal  bone.  It  is  of  an 
oval  form,  about  the  size  and  shape  of  an  almond.  Its  upper  convex  surface  is  in 
contact  with  the  periosteum  of  the  orbit,  to  which  it  is  connected  by  a  few  fibrous 
bands.  Its  under  concave  surface  rests  upon  the  convexity  of  the  eyeball  and 
upon  the  Superior  and  External  recti  muscles.  Its  vessels  and  nerves  enter  its 
posterior  border,  whilst  its  anterior  margin  is  closely  adherent  to  the  back  part  of 
the  upper  eyelid,  where  it  is  covered  to  a  slight  extent  by  the  reflection  of  the  con- 
junctiva. The  fore  part  of  the  gland  is  separated  from  the  rest  by  a  fibrous  septum  ; 
hence  it  is  sometimes  described  as  a  separate  lobe,  called  the  palpebral  portion  of 
the  gland  {accessory  gland  of  Rosenmuller).  Its  ducts,  from  six  to  twelve  in  number 
run  obliquely  beneath  the  mucous  membrane  for  a  short  distance,  and,  separating 
from  each  other,  open  by  a  series  of  minute  orifices  on  the  upper  and  outer  half 


Fig.  454.— The  lachrymal  apparatus.    Right  side. 

of  the  conjunctiva  near  its  reflection  on  to  the  globe.  These  orifices  are  arranged 
in  a  row,  so  as  to  disperse  the  secretion  over  the  surface  of  the  membrane. 

Structure  of  the  Lachrymal  Grland. — In  structure  and  general  appearance  the 
lachrymal  resembles  the  serous  salivary  glands  (page  885).  In  the  recent  state  the 
cells  are  so  crowded  with  granules  that  their  limits  can  hardly  be  defined.  They 
contain  an  oval  nucleus,  and  the  cell-protoplasm  is  finely  fibrillated. 

The  lachrymal  canals  commence  at  the  minute  orifices,  puncta  lachrymalia, 
on  the  summit  of  a  small  conical  elevation,  the  lachrymal  papilla,  seen  on  the 
margin  of  the  lids  at  the  outer  extremity  of  the  lacus  lachrymalis.  The  superior 
canal,  the  smaller  and  shorter  of  the  two,  at  first  ascends,  and  then  bends  at  an 
acute  angle,  and  passes  inward  and  downward  to  the  lachrymal  sac.  The 
inferior  canal  at  first  descends,  and  then,  abruptly  changing  its  course,  passes 
almost  horizontally  inward  to  the  lachrymal  sac.     These  canals  are  dense  and 


THE  LACHRYMAL    APPARATUS.  847 

elastic  in  structure  and  somewhat  dilated  at  their  angle.  The  mucous  membrane 
is  covered  with  scaly  epithelium. 

The  lachrymal  sac  is  the  upper  dilated  extremity  of  the  nasal  duct,  and  is 
lodged  in  a  deep  groove  formed  by  the  lachrymal  bone  and  nasal  process  of  the 
superior  maxillary.  It  is  oval  in  form,  its  upper  extremity  being  closed  in  and 
rounded,  whilst  below  it  is  continued  into  the  nasal  duct.  It  is  covered  by  a  fibrous 
expansion  derived  from  the  tendo  oculi,  and  on  its  deep  surface  it  is  crossed  bv  the 
Tensor  tarsi  muscle  (Horner's  muscle,  page  302),  which  is  attached  to  the  ridge  on 
the  lachrymal  bone. 

Structure. — It  consists  of  a  fibrous  elastic  coat,  lined  internally  by  mucous 
membrane,  the  latter  being  continuous,  through  the  lachrymal  canals,  with  the 
mucous  lining  of  the  conjunctiva,  and,  through  the  nasal  duct,  with  the  pituitarv 
membrane  of  the  nose. 

The  nasal  duct  is  a  membranous  canal,  about  three-quarters  of  an  inch  in 
length,  which  extends  from  the  lower  part  of  the  lachrymal  sac  to  the  inferior 
meatus  of  the  nose,  where  it  terminates  by  a  somewhat  expanded  orifice,  provided 
with  an  imperfect  valve,  the  valve  of  ITasner,  formed  by  the  mucous  membrane.  It 
is  contained  in  an  osseous  canal  formed  by  the  superior  maxillary,  the  lachrymal,  and 
the  inferior  turbinated  bones,  is  narrower  in  the  middle  than  at  each  extremity, 
and  takes  a  direction  downward,  backward,  and  a  little  outward.  It  is  lined 
by  mucous  membrane,  which  is  continuous  below  with  the  pituitary  lining  of  the 
nose.  This  membrane  in  the  lachrymal  sac  and  nasal  duct  is  covered  with  columnar 
epithelium,  as  in  the  nose.      This  epithelium  is  in  places  ciliated. 

Surface  Form. — The  palpebral  fissure,  or  opening  between  the  eyelids,  is  elliptical  in  shape, 
and  differs  in  size  in  different  individuals  and  in  different  races  of  mankind.  In  the  Mong'olian 
races,  for  instance,  the  opening  is  very  small,  merely  a  narrow  fissure,  and  this  makes  the  eye- 
ball appear  small  in  these  races,  whereas  the  size  of  the  eye  is  relatively  very  constant.  The 
normal  direction  of  the  fissure  is  slightly  oblique,  in  a  direction  upward  and  outward,  so  that  the 
outer  angle  is  on  a  slightly  higher  level  than  the  inner.  This  is  especially  noticeable  in  the  Mon- 
golian races,  in  whom,  owing  to  the  upward  projection  of  the  malar  bone  and  the  shortness  of 
the  external  angular  process  of  the  frontal  bone,  the  tarsal  plate  of  the  upper  lid  is  raised  at  its 
outer  part  and  gives  an  oblique  direction  to  the  palpebral  fissure. 

When  the  eyes  are  directed  forward,  as  in  ordinary  vision,  the  upper  part  of  the  cornea  is 
covered  by  the  upper  lid,  and  the  lower  margin  of  the  cornea  corresponds  to  the  level  of  the 
lower  lid,  so  that  about  the  lower  three-fourths  of  the  cornea  is  exposed  under  ordinary  circum- 
stances. On  the  margins  of  the  lids,  about  a  quarter  of  an  inch  from  the  inner  eanthus,  are  two 
small  openings,  the  puncta  lachrymalia,  the  commencement  of  the  lachrymal  canals.  They  are 
best  seen  by  everting  the  eyelids.  In  the  natural  condition  they  are  in  contact  with  the  con- 
junctiva of  the  eyeball,  and  are  maintained  in  this  position  by  the  Tensor  tarsi  muscle,  so  that 
the  tears  running  over  the  surface  of  the  globe  easily  find  their  way  into  the  lachrymal  canals. 
The  position  of  the  lachrymal  sac  into  which  the  canals  open  is  indicated  by  a  little  tubercle 
(page  119),  which  is  plainly  to  be  felt  on  the  lower  margin  of  the  orbit.  The  lachrymal  sac  lies 
immediately  above  and  to  the  inner  side  of  this  tubercle,  and  a  knife  passed  through  the  skin 
in  this  situation  would  open  the  cavity.  The  position  of  the  lachrymal  sac  may  also  be  indicated 
by  the  tendo  oculi  or  internal  tarsal  ligament.  If  both  lids  be  drawn  outward,  so  as  to  tense  the 
skin  at  the  inner  angle,  a  prominent  cord  will  be  seen  beneath  the  tightened  skin.  This  is  the 
tendo  oculi,  which  lies  immediately  over  the  lachrymal  sac,  bisecting  it,  and  thus  forming  a  use- 
ful guide  to  its  situation.  A  knife  entered  immediately  beneath  the  tense  cord  would  open  the 
lower  part  of  the  sac.  A  probe  introduced  through  this  opening  can  be  readily  passed  down- 
ward through  the  duct  into  the  inferior  meatus  of  the  nose.  The  direction  of  the  duct  is  down- 
ward, outward,  and  backward,  and  this  course  should  be  borne  in  mind  in  passing  the  probe, 
otherwise  the  point  may  be  driven  through  the  thin  bony  walls  of  the  canal.  A  convenient 
plan  is  to  direct  the  probe  in  such  a  manner  that  if  it  were  pushed  onward  it  would  strike  the 
first  molar  tooth  of  the  lower  jaw  on  the  same  side  of  the  body.  In  other  words,  the  surgeon 
standing  in  front  of  his  patient  should  carry  in  his  mind  the  position  of  the  first  molar  tooth, 
and  should  push  his  probe  onward  in  such  a  way  as  if  he  desired  to  reach  this  structure. 

Beneath  the  internal  angular  process  of  the  frontal  bone  the  pulley  of  the  Superior  oblique 
muscle  of  the  eye  can  be  plainly  felt  by  pushing  the  finger  backward  between  the  upper  and 
inner  angle  of  the  eye  and  the  roof  of  the  orbit ;  passing  backward  and  outward  from  this 
pulley,  the  tendon  can  be  felt  for  a  short  distance. 

Surgical  Anatomy. — The  eyelids  are  composed  of  various  tissues,  and  consequently  are 
liable  to  a  variety  of  diseases.  The  skin  which  covers  them  is  exceedingly  thin  and  delicate,  and 
is  supported  on  a  quantity  of  loose  and  lax  subcutaneous  tissue  which  contains  no  fat.  In  conse- 
quence of  this  it  is  very  freely  movable,  and  is  liable  to  be  drawn  down  by  the  contraction  of 
neighboring  cicatrices,  and  thus  produce  an  eversion  of  the  lid  known  as  ectropion.     Inversion 


848  THE    ORGANS    OF  SPECIAL    SENSE. 

of  the  lids  {entropion)  from  spasm  of  the  Orbicularis  palpebrarum  or  from  chronic  inflammation 
of  the  palpebral  conjunctiva  may  also  occur.  The  eyelids  are  richly  supplied  with  blood,  and  are 
often  the  seat  of  vascular  growths,  such  as  naevi.  Rodent  ulcer  also  frequently  commences  in 
this  situation.  The  loose  cellular  tissue  beneath  the  skin  is  liable  to  become  extensively  infil- 
trated either  with  blood  or  inflammatory  products,  producing  very  great  swelling.  Even  from 
very  slight  injuries  to  this  tissue  the  extravasation  of  blood  may  be  so  great  as  to  produce  consid- 
erable swelling  of  the  lids  and  complete  closure  of  the  eye,  and  the  same  is  the  case  when  inflam- 
matory products  are  poured  out.  The  follicles  of  the  eyelashes  or  the  sebaceous  glands  associated 
with  these  follicles  maybe  the  seat  of  inflammation,  constituting  the  ordinary  "sty."  The 
Meibomian  glands  are  affected  in  the  so-called  "  tarsal  tumor  ;  "  the  tumor,  according  to  some, 
being  caused  by  the  retained  secretion  of  these  glands ;  by  others  it  is  believed  to  be  a  neoplasm 
connected  with  the  gland.  The  ciliary  follicles  are  liable  to  become  inflamed,  constituting  the 
disease  known  as  blepharitis  ciliaris,  or  "blear-eye."  Irregular  or  disorderly  growth  of  the  eye- 
lashes not  unfrequently  occurs,  some  of  them  being  turned  toward  the  eyeball  and  producing 
inflammation  and  ulceration  of  the  cornea,  and  possibly  eventually  complete  destruction  of  the 
eye.  The  Orbicularis  palpebrarum  may  be  the  seat  of  spasm,  either  in  the  form  of  slight  quiv- 
ering of  the  lids  or  repeated  twitchings,  most  commonly  due  to  errors  of  refraction  in  children, 
or  more  continuous  spasm,  due  to  some  irritation  of.  the  fifth  or  seventh  cranial  nerve.  The 
Orbicularis  may  be  paralyzed,  generally  associated  with  paralysis  of  the  other  facial  muscles. 
Under  these  circumstances  the  patient  is  unable  to  close  the  lids,  and,  if  he  attempts  to  do  so, 
rolls  the  eyeball  upward  under  the  upper  lid.  The  tears  overflow  from  displacement  of  the 
lower  lid,  and  the  conjunctiva  and  cornea,  being  constantly  exposed  and  the  patient  being  unable 
to  wink,  become  irritated  from  dust  and  foreign  bodies.  In  paralysis  of  the  Levator  palpebrae 
superioris  there  is  drooping  of  the  upper  eyelid  and  other  symptoms  of  implication  of  the  third 
nerve.  The  eyelids  may  be  the  seat  of  bruises,  wounds,  or  burns.  In  these  latter  injuries  adhe- 
sions of  the  margins  of  the  lids  to  each  other  or  adhesion  of  the  lids  to  the  globe  may  take 
place.  The  eyelids  are  sometimes  the  seat  of  emphysema  after  fracture  of  some  of  the  thin 
bones  forming  the  inner  wall  of  the  orbit.  If  shortly  after  such  an  injury  the  patient  blows  his 
nose,  air  is  forced  from  the  nostril  through  the  lacerated  structures  into  the  connective  tissue  of 
the  eyelids,  which  suddenly  swell  up  and  present  the  peculiar  crackling  characteristic  of  this 
affection. 

Foreign  bodies  frequently  get  into  the  conjunctival  sac  and  cause  great  pain,  especially  if 
they  come  in  contact  with  the  corneal  surface,  during  the  movements  of  the  lid  and  the  eye  on 
each  other.  The  conjunctiva  is  frequently  involved  in  severe  injuries  of  the  eyeball,  but  is 
seldom  ruptured  alone  ;  the  most  common  form  of  injury  to  the  conjunctiva  alone  is  from  a 
burn,  either  from  fire,  strong  acids,  or  lime.  In  these  cases  union  is  liable  to  take  place  between 
the  eyelid  and  the  eyeball.  The  conjunctiva  is  often  the  seat  of  inflammation  arising  from  many 
different  causes,  and  the  arrangement  of  the  conjunctival  vessels  should  be  remembered  as 
affording  a  means  of  diagnosis  between  this  condition  and  injection  of  the  sclerotic,  which  is 
present  in  inflammation  of  the  deeper  structures  of  the  globe.  The  inflamed  conjunctiva  is 
bright  red  ;  the  vessels  are  large  and  tortuous,  and  greatest  at  the  circumference,  shading  off 
toward  the  corneal  margin ;  they  anastomose  freely  and  form  a  dense  network,  and  they  can  be 
emptied  or  displaced  by  gentle  pressure. 

The  lachrymal  gland  is  occasionally,  though  rarely,  the  seat  of  inflammation,  either  acute 
or  chronic ;  it  is  also  sometimes  the  seat  of  tumors,  benign  or  malignant,  and  for  these  may 
require  removal.  This  may  be  done  by  an  incision  through  the  skin  just  below  the  eyebrow  ; 
and  the  gland,  being  invested  with  a  special  capsule  of  its  own,  may  be  isolated  and  removed 
without  opening  the  general  cavity  of  the  orbit.  The  canaliculi  may  be  obstructed,  either  as  a 
congenital  defect  or  by  some  foreign  body,  as  an  eyelash  or  a  dacryolith,  causing  the  tears  to  run 
over  the  cheek.  The  canaliculi  may  also  become  occluded  as  the  result  of  burns  or  injury ;  over- 
flow of  the  tears  may  in  addition  result  from  deviation  of  the  puncta  or  from  chronic  inflamma- 
tion of  the  lachrymal  sac.  This  latter  condition  is  set  up  by  some  obstruction  to  the  nasal  duct 
frequently  occurring  in  tubercular  subjects.  In  consequence  of  this  the  tears  and  mucus  accumu- 
late in  the  lachrymal  sac,  distending  it.  Suppuration  in  the  lachrymal  sac  is  sometimes  met 
with  ;  this  may  be  the  sequel  of  a  chronic  inflammation  ;  or  may  occur  after  some  of  the  erup- 
tive fevers  in  cases  where  the  lachrymal  passages  were  previously  quite  healthy.  It  may  lead  to 
lachrymal  fistula. 

THE  EAR. 

The  organ  of  hearing  is  divisible  into  three  parts — the  external  ear.,  the  middle 
ear  or  tympanum,  and  the  internal  ear  or  labyrinth. 

The  External  Ear. 

The  external  ear  consists  of  an  expanded  portion  named  pinna  or  auricle,  and 
the  auditory  canal  or  meatus.  The  former  serves  to  collect  the  vibrations  of  the  air 
by  which  sound  is  produced  ;  the  latter  conducts  those  vibrations  to  the  tympanum. 

The  pinna,  or  auricle  (Fig.  455),  is  of  an  ovoid  form,  with  its  larger  end  directed 


THE  EAR.  849 

upward.  Its  outer  surface  is  irregularly  concave,  directed  slightly  forward,  and 
presents  numerous  eminences  arid  depressions  which  result  from  the  foldings  of  its 
fibrocartilaginous  element.  To  each  of  these,  names  have  been  assigned.  Thus 
the  external  prominent  rim  of  the  auricle  is  called  the  helix.  Another  curved 
prominence,  parallel  with  and  in  front  of  the  helix,  is  called  the  antihelix  ;  this 
bifurcates  above,  so  as  to  enclose  a  triangular  depression,  the  fossa  of  the  antihelix 
(fossa  triangularis).  The  narrow  curved  depression  between  the  helix  and  anti- 
helix is  called  the  fossa  of  the  helix  (Scapha);  the  antihelix  describes  a  curve 
round  a  deep,  capacious  cavity,  the  concha,  which  is  partially  divided  into  two 
parts  by  the  cms  helicis  or  the  commencement  of  the  helix  ;  the  upper  part  is 
termed  the  cymba  concha?,  the  lower  part  the  cavum  conchas.  In  front  of  the 
concha,  and  projecting  backward  over  the  meatus,  is  a  small  pointed  eminence,  the 
tragus,  so  called  from  its  being  generally  covered  on  its  under  surface  with  a  tuft 
of  hair  resembling  a  goat's  beard.  Opposite  the  tragus,  and  separated  from  it  by 
a  deep  notch  (incisura  intertragicd)  is  a  small  tubercle,  the  antitragus.  Below  this 
is  the  lobule,  composed  of  tough  areolar  and  adipose  tissue,  wanting  the  firmness 
and  elasticity  of  the  rest  of  the  pinna.  Where  the  helix  turns  downward  a  small 
tubercle,  the  tubercle  of  Darwin,  is  frequently  seen.  This  tubercle  is  very  evident 
about  the  sixth  month  of  foetal  life ;  at  this  stage  the  human  pinna  has  a  close 
resemblance  to  that  of  some  of  the  adult  monkeys. 

The  cranial  surface  of  the  pinna  presents  elevations  which  correspond  to  the 
depressions  on  its  outer  surface  and  after  which  they  are  named,  e.  g.,  eminentia 
conchas,  eminentia  triangularis,  etc. 

Structure  of  the  Pinna. — The  pinna  is  composed  of  a  thin  plate  of  yellow  fibro- 
cartilage,  covered  with  integument,  and  connected  to  the  surrounding  parts  by  the 
extrinsic  ligaments  and  muscles  ;  and  to  the  commencement  of  the  external  audi- 
tory canal  by  fibrous  tissue. 

The  integument  is  thin,  closely  adherent  to  the  cartilage,  and  covered  with 
hairs  furnished  with  sebaceous  glands,  which  are  most  numerous  in  the  concha 
and  scaphoid  fossa.  The  hairs  are  most  numerous  and  largest  on  the  tragus  and 
antitragus. 

The  cartilage  of  the  pinna  consists  of  one  single  piece  :  it  gives  form  to  this 
part  of  the  ear,  and  upon  its  surface  are  found  all  the  eminences  and  depressions 
above  described.  It  does  not  enter  into  the  construction  of  all  parts  of  the  auricle  : 
thus  it  does  not  form  a  constituent  part  of  the  lobule  ;  it  is  deficient  also  between 
the  tragus  and  beginning  of  the  helix,  the  notch  between  them  being  filled  up  by 
dense  fibrous  tissue.  At  the  front  part  of  the  pinna,  where  the  helix  bends  upward, 
is  a  small  projection  of  cartilage,  called  the  spina  helicis,  while  the  lower  part  of 
the  helix  is  prolonged  downward  as  a  tail-like  process,  the  cauda  helicis ;  this  is 
separated  from  the  antihelix  by  a  fissure,  the  fissura  antitragohelicina.  The  carti- 
lage of  the  pinna  presents  several  intervals  or  fissures  in  its  substance  which  par- 
tially separate  the  different  parts.  The  fissure  of  the  helix  is  a  short  vertical  slit, 
situated  at  the  fore  part  of  the  pinna.  Another  fissure,  the  fissure  of  the  tragus,  is 
seen  upon  the  anterior  surface  of  the  tragus.  The  cartilage  of  the  pinna  is  very 
pliable,  elastic,  of  a  yellowish  color,  and  belongs  to  that  form  of  cartilage  which  is 
known  under  the  name  of  yellow  fibro-cartilage. 

The  ligaments  of  the  pinna  consist  of  two  sets  :  1.  The  extrinsic  set,  or  those 
connecting  it  to  the  side  of  the  head.  2.  The  intrinsic  set,  or  those  connecting  the 
various  parts  of  its  cartilage  together. 

The  extrinsic  ligaments,  the  most  important,  are  two  in  number,  anterior  and 
posterior.  The  anterior  ligament  extends  from  the  spina  helicis  and  tragus  to 
the  root  of  the  zygoma.  The  posterior  ligament  passes  from  the  posterior  sur- 
face of  the  concha  to  the  outer  surface  of  the  mastoid  process  of  the  temporal 
bone. 

The  chief  intrinsic  ligaments  are :  (1)  a  strong  fibrous  band,  stretching  across 
from  the  tragus  to  the  commencement  of  the  helix,  completing  the  meatus  in  front, 
and  partly  encircling  the  boundary  of  the  concha  ;  and  ("2)  a  band  which   extends 

54 


850 


THE    ORGANS    OF  SPECIAL    SENSE. 


between   the  anti-helix   and  the  cauda  helicis.      Other  less  important   bands   are 
found  on  the  cranial  surface  of  the  pinna. 

The  muscles  of  the  pinna  (Fig.  456)  consist  of  two  sets :  1.  The  extrinsic, 
which  connect  it  with  the  side  of  the  head,  moving  the  pinna  as  a  whole — viz.,  the 
Attollens,  Attrahens,  and  Retrahens  auriculum  (page  301) ;  and  2.  The  intrinsic, 
which  extend  from  one  part  of  the  auricle  to  another,  viz. : 


Helicis  major. 
Helicis  minor. 
Tragicus. 


Antitragicus. 
Transversus  auriculae. 
Obliquus  auriculae. 


The  Musculus  helicis  major  is  a  narrow  vertical  band  of  muscular  fibres,  situated 
upon  the  anterior  margin  of  the 
helix.  It  arises,  below,  from  the 
cauda  helicis,  and  is  inserted  into 
the  anterior  border  of  the  helix, 
just  where  it  is  about  to  curve 
backward.  It  is  pretty  constant  in 
its  existence. 


Fig.  455.— The  pinna,  or  auricle. 
Outer  surfaces. 


Fig.  456.— The  muscles  of  the  pinna. 


The  Musculus  helicis  minor  is  an  oblique  fasciculus  which  covers  the  crus 
helicis. 

The  Tragicus  is  a  short,  flattened  band  of  muscular  fibres  situated  upon  the 
outer  surface  of  the  tragus,  the  direction  of  its  fibres  being  vertical. 

The  Antitragicus  arises  from  the  outer  part  of  the  antitragus :  its  fibres  are 
inserted  into  the  cauda  helicis  and  antihelix.      This  muscle  is  usually  very  distinct. 

The  Transversus  auricula?  is  placed  on  the  cranial  surface  of  the  pinna.  It 
consists  of  scattered  fibres,  partly  tendinous  and  partly  muscular,  extending  from 
the  convexity  of  the  concha  to  the  prominence  corresponding  with  the  groove  of  the 
helix. 

The  Obliquus  auriculce  (Tod)  consists  of  a  few  fibres  extending  from  the  upper 
and  back  part  of  the  concha  to  the  convexity  immediately  above  it. 

The  arteries  of  the  pinna  are  the  posterior  auricular  from  the  external  carotid, 
the  anterior  auricular  from  the  temporal,  and  an  auricular  branch  from  the 
occipital  artery. 

The  veins  accompany  the  corresponding  arteries. 

The.  nerves  are  :  the  auricularis  magnus,  from  the  cervical  plexus ;  the  auricu- 


THE   EAR. 


Sol 


lar  branch  of  the  pneumogastric ;  the  auriculo-temporal  branch  of  the  inferior 
maxillary  nerve ;  the  occipitalis  minor  from  the  cervical  plexus,  and  the  occipitalis 
major  or  internal  branch  of  the  posterior  division  of  the  second  cervical  nerve. 
The  muscles  of  the  pinna  are  supplied  by  the  facial  nerve. 

The  Auditory  Canal  [meatus  auditorium  externum)  extends  from  the  bottom  of 
the  concha  to  the  membrana  tympani  (Fig.  457).  It  is  about  an  inch  and  a  half 
in  length  if  measured  from  the  tragus ;  from  the  bottom  of  the  concha  its  length 
is  about  an  inch.  It  forms  a  sort  of  S-shaped  curve,  and  is  directed  at  first  inward 
forward,  and  slightly  upward  ( pars  externa) ;  it  then  passes  inward  and  backward 
{pars  media),  and  lastly  is  carried  inward,  forward,  and  slightly  downward  (pars 
interna).  It  forms  an  oval  cylindrical  canal,  the  greatest  diameter  being  in  the 
vertical  direction  at  the  external  orifice,  but  in  the  transverse  direction  at  the 
tympanic  end.  It  presents  two  constrictions,  one  near  the  inner  end  of  the  carti- 
laginous portion,  and  another,  the  isthmus,  in  the  osseous  portion,  about  three- 
quarters  of.  an  inch  from  the  bottom  of  the  concha.  The  membrana  tympani, 
which  occupies  the  termination  of  the  meatus,  is  obliquely  directed,  in  consequence 
of  which  the  floor  of  the  canal  is  longer  than  the  roof,  aad  thr  anterior  wall  longer 
than  the  posterior.  The  auditory  canal  is  formed  partly  bv  cartilage  and  mem- 
brane, and  partly  by  bone,  and  is  lined  by  skin. 


Promont. 


Fig.  457.— Transverse  sectioiif  0f  external  anditory  meatus  and  tympanum.    Left  side.    (Gegenbaur.) 

The  cartilaginous  portion  is  about  one-third  of  an  inch  (8  mm.)  in  length,  it  is 
formed  by  the  cartilage  of]  the  pinna,  prolonged  inward,  and  firmly  attached  to  the 
circumference  of  the  auditory  process  of  the  temporal  bone.  The  cartilage  is  deficient 
at  its  upper  and  back  parti  its  place  being  supplied  by  fibrous  membrane.  This 
part  of  the  canal  is  rendered  extremely  movable  by  two  or  three  deep  fissures 
(incisurce  Santorini),  which1  extend  through  the  cartilage  in  a  vertical  direction. 

The  osseous  portion  is  ilbout  two-thirds  of  an  inch  (16  mm.)  in  length,  and 
narrower  than  the  cartilaginc,us  portion.  It  is  directed  inward  and  a  little  forward, 
forming  a  slight  curve  in  its'  course,  the  convexity  of  which  is  upward  and  back- 
ward. Its  inner  end,  wBch  communicates,  in  the  dry  bone,  with  the  cavity  of  the 
tympanum,  is  smaller  than  the  outer  and  sloped,  the  anterior  wall  projecting  beyond 
the  posterior  about  two  lines;  itl  is  marked,  except  at  its  upper  part,  by  a  narrow 
groove,  the  sulcus  tympanici>,si  J0Y  the  insertion  of  the  membrana  tympani.  Its 
outer  end  is  dilated  and  roughj  jn  the  greater  part  of  its  circumference,  for  the 
attachment  of  the  cartilage  of  t  W  pinna.  Its  vertical  transverse  section  is  oval,  the 
greatest  diameter  being  from  -yDove  downward.  The  front  and  lower  parts  of  this 
canal  are  formed  by  a  curv^V/ plate  of  bone,  which,  in  the  foetus,  exists  as  a  separate 
ring  (annulus  tympanism /^incomplete  at  its  upper  part.      See  section  on  Osteology. 


852 


THE    ORGANS    OF  SPECIAL    SENSE. 


The  skin  lining  the  meatus  is  very  thin,  adheres  closely  to  the  cartilaginous 
and  osseous  portion  of  the  tube,  and  covers  the  surface  of  the  membrana  tympani, 
forming  its  outer  layer.  After  maceration  the  thin  pouch  of  epidermis,  when 
withdrawn,  preserves  the  form  of  the  meatus.  In  the  thick  subcutaneous  tissue 
of  the  cartilaginous  part  of  the  meatus  are  numerous  ceruminous  glands,  which 
secrete  the  ear-wax.  They  resemble  in  structure  sweat-glands,  and  their  ducts 
open  on  the  surface  of  the  skin. 

Relations  of  the  Meatus. — In  front  of  the  osseous  part  is  the  condyle  of  the 
mandible,  which,  however,  is  separated  from  the  cartilaginous  part  by  the  retro- 
mandibular part  of  the  parotid  gland.  The  movements  of  the  jaw  influence  to  some 
extent  the  lumen  of  this  latter  portion.  Behind  the  osseous  part  are  the  mastoid 
air-cells,  separated  from  it  by  a  thin  layer  of  bone. 

The  arteries  supplying  the  meatus  are  branches  from  the  posterior  auricular, 
internal  maxillary,  and  temporal. 

The  nerves  are  chiefly  derived  from  the  auriculo-temporal  branch  of  the  inferior 
maxillary  nerve  and  the  auricular  branch  of  the  pneumogastric. 

Surface  Form.— At  the  point  of  junction  of  the  osseous  and  cartilaginous  portions  the  tube 
forms  an  obtuse  angle,  which  projects  into  the  tube  at  its  anteroinferior  wall.  This  produces  a 
sort  of  constriction  in  this  .situation,  and  renders  it  the  narrowest  portion  of  the  canal— an  im- 
portant point  to  be  borne  in  lQ.'nd  in  connection  with  the  presence  of  foreign  bodies  in  the  ears. 
The  cartilaginous  is  connected  to  She  bony  part  by  fibrous  tissue,  which  renders  the  outer  part 
of  the  tube  very  movable,  and  therefore  by  drawing  the  pinna  upward  and  backward  the  canal 
is  rendered  almost  straight.  At  the  external  orifice  are  a  few  short,  crisp  hairs  which  serve  to 
prevent  the  entrance  of  small  particles  of  dust,  or  fiie:^  or  other  insects.  In  the  external  auditory 
meatus  the  secretion  of  the  ceruminous  glands  s^et  to  catch  any  small  particles  which  may 
find  their  way  into  the  canal,  and  prevent  their  .  the  membrana  tympani,  where  their 

presence  might  excite  irritation.     In  young  children    ho 
being  very  deficient,  and  consisting  merely  of  a  bony  ri 
the  membrana  tympani.     In  the  foetus  the  ossecns  pa  1 
canal  in  children  should  be  borne  in  mind  in  intrcdur  a 
pushed  in  too  far,  at  the  risk  of  injuring  the  membra  m 
speculum  should  never  be  introduced  beyond  the  co 
osseous  and  cartilaginous  portions.     In   using  this  in  t. 
should  be  drawn  upward,  backward,  and  a  little  outward,  „ 

possible,  and  thus  assist  the  operator  in  obtaining,  by  the  aid  o  '  J  -iected  light,  a  good  view  of 
the  membrana  tympani.  Just  in  front  of  the  membrane  is  a  ^-'U-marked  depression,  situated 
on  the  floor  of  the  canal  and  bounded  by  a  somewhat  promineli1  ridge  ;  in  this  foreign  bodies 
may  become  lodged.  By  aid  of  the  speculum,  combined  with  trac\;ion  of  the  auricle  upward  and 
backward,  the  whole  of  the  membrana  tympani  is  rendered  ,:s;!  Je-  Ifc  is  a  pearly-gray  mem- 
brane, slightly  glistening  in  the  adult,  placed  obliquely,  so  as  to  fori  i  Wltn  the  noor  of  tne  meatus 
a  very  acute  angle,  (about  55°)  while  with  the  roof  it  forms  an  obtt-se  angle.  At  birth  it  is  more 
horizontal,  situated  in  almost  the  same  plane  as  the  base  of  the  skv'n-  About  midway  between 
the  anterior  and  posterior  margins  of  the  membrane,  and  extendi!0?  from  the  centre  obliquely 
upward,  is  a  reddish-yellow  streak ;  this  is  the  handle  of  the  mallW  wPich  -is  inserted  into  the 
membrane.  At  the  upper  part  of  this  streak,  close  to  the  roof  (of  the  meatus  a  little  white 
rounded  prominence  is  plainly  to  be  seen  ;  this  is  the  processus  b,evls  °'  *he  malleus,  projecting 
against  the  membrane.  The  membrana  tympani  does  not  prese  nt  a  P*an?,  surl a?e  >  0I},  e  con^ 
trary,  its  centre  is  drawn  inward,  on  account  of  its  connection  mtf1  ^\e  handle  of  the  malleus,  and 
thus  the  external  surface  is  rendered  concave.  j 


us  is  very  short,  the  osseous  part 

ai'rfiir,  tympanicus),  which  supports 

absent.    The  shortness  of  the 

i  r  1  speculum,  so  that  it  be  not 

m\)am     indeed,  even  in  the  adult  the 

,ch  marks  the  junction  of  the 

is  advisable  that  the  pinna 

der  the  canal  as  straight  as 


The  Middle  Ear,  or  Tympana.-' 

The  middle  ear,  or  tympanum,  is  an  irregular  car  Hy,  compressed  from  without 
inward,  and  situated  within  the  petrous  bone.  It  is  tflaeed  above  the  jugular  fossa ; 
the  carotid  canal  lying  in  front,  the  mastoid  cell.-  behind,  the  meatus  auditorius 
externally,  and  the  labyrinth  internally.  It  is  ftfjed  with  air,  and  communicates 
with  the  naso-pharynx  by  the  Eustachian  tube.  *'Re  tympanum  is  traversed  by  a 
chain  of  movable  bones,  which  connect  the  membr^a  tympani  with  the  labyrinth, 

toV 


and  serve  to  convey  the  vibrations  communicated 
the  cavity  of  the  tympanum  to  the  internal  ear. 

The  tympanic  cavity  consists  of  two  parts :  the  atrii.' 
opposite  the  tympanic  membrane,  and  the  attic  pr  epr, 
level  of  the  upper  part  of  the  membrane ;  the  latter  cor 


the    aembrana  tympani  across 


or  tympanic,  cavity  proper, 

\npanic  recess,  above  the 

;ns  the  upper  half  of  the 


THE   MIDDLE   EAR. 


853 


malleus  and  the  greater  part  of  the  incus.  Its  diameter,  including  the  attic, 
measures  about  15  mm.  vertically  and  transversely.  From  without  inward  it 
measures  about  6  mm.  above  and  4  mm.  below  ;  opposite  the  centre  of  the  tympanic 
membrane  it  is  only  about  2  mm.  It  is  bounded  externally  by  the  membrana  tym- 
pani  and  meatus  ;  internally,  by  the  outer  surface  of  the  internal  ear  ;  and  commu- 
nicates, behind,  with  the  mastoid  antrum  and  through  it  with  the  mastoid  cells;  and 
in  front  with  the  Eustachian  tube  and  canal  for  the  Tensor  tympani.  Its  roof  and 
floor  are  formed  by  thin  osseous  laminae,  the  one  forming  the  roof  being  a  thin 
plate  situated  on  the  anterior  surface  of  the  petrous  portion  of  the  temporal  bone, 
close  to  its  angle  of  junction  with  the  squamous  portion  of  the  same  bone. 

The  roof  (paries  tegmentalis)  is  broad,  flattened,  and  formed  of  a  thin  plate  of 
bone  (tegmen  tympani),  which  separates  the  cranial  and  tympanic  cavities.  It  is 
prolonged  backward  so  as  to  roof  in  the  mastoid  antrum ;  it  is  also  carried  forward 
to  cover  in  the  canal  for  the  Tensor  tympani  muscle, 

The  floor  (paries  jugularis)  is  narrow,  and  is  separated  by  a  thin  plate  of  bone 
(fundus  tympani)  from  the  jugular  fossa.  It  presents,  near  the  inner  wall,  a  small 
aperture  for  the  passage  of  Jacobson's  nerve. 

The  outer  wall  is  formed  mainly  by  the  membrana  tympani,  partly  by  the  ring 
of  bone  into  which  this  membrane  is  inserted.  This  ring  of  bone  is  incomplete  at 
its  upper  part,  forming  a  notch  (incisura  Rivini).  Close  to  it  are  three  small  aper- 
tures; the  iter  chordae  posterius,  the  Glaserian  fissure,  and  the  iter  chordae  anterius. 


Chorda  tympa 


Fig.  458.— View  of  inner  wall  of  tympanum.    (Enlarged.) 

The  iter  chordce  posterius  is  in  the  angle  of  junction  between  the  posterior  and 
external  walls  of  the  tympanum,  immediately  behind  the  membrana  tympani  and 
on  a  level  with  the  upper  end  of  the  handle  of  the  malleus ;  it  leads  into  a  minute 
canal,  which  descends  in  front  of  the  aquaeductus  Fallopii,  and  terminates  in  that 
canal  near  the  stylo-mastoid  foramen.  Through  it  the  chorda  tympani  nerve  enters 
the  tympanum. 

The  Glaserian  fissure  opens  just  above  and  in  front  of  the  ring  of  bone  into 
which  the  membrana  tympani  is  inserted ;  in  this  situation  it  is  a  mere  slit  about  a 
line  in  length.  It  lodges  the  long  process  and  anterior  ligament  of  the  malleus. 
and  gives  passage  to  the  tympanic  branch  of  the  internal  maxillary  artery. 

The  iter  chorda',  anterius  is  seen  at  the  inner  end  of  the  preceding  fissure :  it 
leads  into  a  canal  (canal  of  Huguier),  which  runs  parallel  with  the  Glaserian  fissure. 
Through  it  the  chorda  tympani  nerve  leaves  the  tympanum. 

The  internal  wr11  of  lbs  tympanum  (paries  labyrinthiea)  (Fig.  458)  is  vertical 
in  direction,  and  k  .  Li]  dy  outward.  It  presents  for  examination  the  follow- 
ing parts  : 

Fenestra        .  :-      <  Promontory. 

Fenestn  Ridge  of  the  aquaeductus  Fallopii. 


854  THE    ORGANS   OF  SPECIAL   SENSE. 

The  fenestra  ovalis  is  a  reniform  opening  leading  from  the  tympanum  into  the 
vestibule ;  its  long  diameter  is  directed  horizontally,  and  its  convex  border  is 
upward.  The  opening  in  the  recent  state  is  occupied  by  the  base  of  the  stapes, 
which  is  connected  to  the  margin  of  the  foramen  by  an  annular  ligament. 

The  fenestra  rotunda  is  an  aperture  placed  at  the  bottom  of  a  funnel-shaped 
depression  leading  into  the  cochlea.  It  is  situated  below  and  rather  behind  the 
fenestra  ovalis,  from  which  it  is  separated  by  a  rounded  elevation,  the  promontory  ; 
it  is  closed  in  the  recent  state  by  a  membrane  (membrana  tympani  secundaria, 
Scarpa).  This  membrane  is  concave  toward  the  tympanum,  convex  toward  the 
cochlea.  It  consists  of  three  layers  :  the  external,  or  mucous,  derived  from  the 
mucous  lining  of  the  tympanum ;  the  internal,  from  the  lining  membrane  of  the 
cochlea ;  and  an  intermediate,  or  fibrous  layer. 

The  promontory  is  a  rounded  hollow  prominence,  formed  by  the  projection  out- 
ward of  the  first  turn  of  the  cochlea ;  it  is  placed  between  the  fenestrse,  and  is 
furrowed  on  its  surface  by  three  small  grooves,  which  lodge  branches  of  the  tym- 
panic plexus.  A  minute  spicule  of  bone  frequently  connects  the  promontory  to  the 
pyramid. 

The  rounded  eminence  of  the  aquceductus  Fallopii,  the  prominence  of  the  bony 
canal  in  which  the  facial  nerve  is  contained,  traverses  the  inner  wall  of  the  tympa- 
num above  the  fenestra  ovalis,  and  behind  that  opening  curves  nearly  vertically 
downward  along  the  posterior  wall. 

The  posterior  wall  of  the  tympanum  (paries  mastoidea)  is  wider  above  than 
below,  and  presents  for  examination  the 

Opening  of  the  antrum.  Pyramid. 

The  opening  of  the  antrum  is  a  large  irregular  aperture,  which  extends  back- 
ward from  the  epitympanic  recess  and  leads  into  a  considerable  air  space,  the  antrum 
mastoideum  (see  page  68).  The  antrum  communicates  with  large  irregular  cavities 
contained  in  the  interior  of  the  mastoid  process,  the  mastoid  air-cells.  These 
cavities  vary  considerably  in  number,  size,  and  form  ;  they  are  lined  by  mucous  mem- 
brane continuous  with  that  lining  the  cavity  of  the  tympanum. 

The  pyramid  is  a  conical  eminence  situated  immediately  behind  the  fenestra 
ovalis,  and  in  front  of  the  vertical  portion  of  the  eminence  above  described ;  it  is 
hollow  in  the  interior,  and  contains  the  Stapedius  muscle;  its  summit  projects 
forward  toward  the  fenestra  ovalis,  and  presents  a  small  aperture  which  transmits 
the  tendon  of  the  muscle.  The  cavity  in  the  pyramid  is  prolonged  into  a  minute 
canal,  which  communicates  with  the  aquse  ductus  Fallopii  and  transmits  the  nerve 
which  supplies  the  Stapedius. 

The  anterior  wall  of  the  tympanum  {paries  caroticd)  is  wider  above  than  below; 
it  corresponds  with  the  carotid  canal,  from  which  it  is  separated  by  a  thin  plate  of; 
bone,  perforated  by  the  tympanic  branch  of  the  internal  carotid  artery.     It  presents 
for  examination  the 

Canal  for  the  Tensor  tympani.  Orifice  of  the  Eustachian  tube. 

The  processus  cochleariformis. 

The  orifice  of  the  canal  for  the  Tensor  tympani  and  the  orifice  of  the  Eustachian 
tube  are  situated  at  the  upper  part  of  the  anterior  wall,  being  separated  from  each 
other  by  a  thin, -delicate,  horizontal  plate  of  bone,  the  processus  cochleariformis. 
These  canals  run  from  the  tympanum  forward,  inward,  and  a  little  downward,  to  the 
retiring  angle  between  the  squamous  and  petrous  portions  of  the  temporal  bone. 

The  canal  for  the  Tensor  tympani  is  the  superior  and  the  smaller  of  the  two  ;  it 
is  rounded  and  lies  beneath  the  forward  prolongation  of  the  tegmen  tympani.  It 
extends  on  to  the  inner  wall  of  the  tympanum  and  ends  immediately  above  the  fenestra 
ovalis.  The  processus  cochleariformis  passes  backward  below  this  part  of  the  canal, 
forming  its  outer  wall  and  floor ;  it  expands  above  the  anterior  extremity  of  the 
fenestra  ovalis  and  terminates  by  curving  outward  so  as  to  form  a  pulley  over  which 
the  tendon  passes. 


THE   MIDDLE   EAR.  855 

The  Eustachian  tube  is  the  channel  through  which  the  tympanum  communicates 
with  the  pharynx.  Its  length  is  an  inch  and  a  half  (36  mm.),  and  its  direction 
downward,  forward,  and  inward,  forming  an  angle  of  about  45°  with  the  sagittal 
plane  and  one  of  from  30°  to  40°  with  the  horizontal  plane.  It  is  formed  partly 
of  bone,  partly  of  cartilage  and  fibrous  tissue. 

The  osseous  portion  is  about  half  an  inch  in  length.  It  commences  in  the 
anterior  wall  of  the  tympanum,  below  the  processus  cochleariformis,  and,  gradually 
narrowing,  terminates  at  the  angle  of  junction  of  the  petrous  and  squamous  por- 
tions, its  extremity  presenting  a  jagged  margin  which  serves  for  the  attachment  of 
the  cartilaginous  portion. 

The  cartilaginous  portion,  about  an  inch  in  length,  is  formed  of  a  triangular  plate 
of  elastic  fibro-cartilage,  the  apex  of  which  is  attached  to  the  margin  of  the  inner 
extremity  of  the  osseous  canal,  while  its  base  lies  directly  under  the  mucous  mem- 
brane of  the  naso-pharynx,  where  it  forms  an  elevation  or  cushion  behind  the 
pharyngeal  orifice  of  the  tube.  The  upper  edge  of  the  cartilage  is  curled  upon 
itself,  being  bent  outward  so  as  to  present  on  transverse  section  the  appearance  of 
a  hook  ;  a  groove  or  furrow  is  thus  produced,  Avhich  opens  beloAv  and  externally, 
and  this  part  of  the  canal  is  completed  by  fibrous  membrane.  The  cartilage  is  fixed 
to  the  base  of  the  skull,  and  lies  in  a  groove  between  the  petrous-temporal  and  the 
greater  wing  of  the  sphenoid ;  this  groove  ends  opposite  the  middle  of  the  internal 
pterygoid  plate.  The  cartilaginous  and  bony  portions  of  the  tube  are  not  in  the 
same  plane,  the  former  inclining  downward  a  little  more  than  the  latter.  The 
diameter  of  the  canal  is  not  uniform  throughout,  being  greatest  at  the  pharyngeal 
orifice  and  least  at  the  junction  of  the  bony  and  cartilaginous  portions,  where  it  is 
named  the  isthmus ;  it  again  expands  somewhat  as  it  approaches  the  tympanic 
cavity.  The  position  and  relations  of  the  pharyngeal  orifice  are  described  with 
the  anatomy  of  the  naso-pharynx.  Through  this  canal  the  mucous  membrane  of 
the  pharynx  is  continuous  with  that  which  lines  the  tympanum.  The  mucous  mem- 
brane is  covered  with  ciliated  epithelium  and  is  thin  in  the  osseous  portion,  while 
in  the  cartilaginous  portion  it  contains  many  mucous  glands  and  near  the  pharyn- 
geal orifice  a  considerable  amount  of  adenoid  tissue,  which  has  been  named  by 
Gerlach  the  tube-tonsil.  The  tube  is  opened  during  deglutition  by  the  Salpingo- 
pharyngeus  and  'Dilator  tubse  muscles. 

The  membrana  tympani  separates  the  cavity  of  the  tympanum  from  the  bottom 
of  the  external  meatus.  It  is  a  thin,  semi-transparent  membrane,  nearly  oval  in 
form,  somewhat  broader  above  than  below,  and  directed  very  obliquely  downward 
and  inward  so  as  to  form  an  angle  of  about  55°  with  the  floor  of  the  meatus. 
The  greater  part  of  its  circumference  is  thickened  to  form  an  annular  ring  which 
is  fixed  in  a  groove,  the  sulcus  tympanicus,  at  the  inner  extremity  of  the  meatus. 
This  sulcus  is  deficient  superiorly  at  the  incisure  or  notch  of  Rivinus.  From  the 
extremities  of  this  notch  two  bands,  the  anterior  and  posterior  malleolar  folds,  are 
prolonged  to  the  short  process  of  the  malleus.  The  small,  somewhat  triangular 
part  of  the  membrane  situated  above  these  folds  is  lax  and  thin,  and  is  named  the 
membrana  Jlaccida  of  Shrapnell ;  in  it  a  small  orifice  is  sometimes  seen.  The 
handle  of  the  malleus  is  firmly  attached  to  the  inner  aspect  of  the  membrane  as 
far  as  its  centre,  which  it  draws  inward  toward  the  cavity  of  the  tympanum.  The 
outer  surface  of  the  membrane  is  thus  concave,  and  the  most  depressed  part  of 
this  concavity  is  named  the  umbo  or  navel. 

Structure. — This  membrane  is  composed  of  three  layers,  an  external  (cuticular), 
a  middle  (fibrous),  and  an  internal  (mucous).  The  cuticular  lining  is  derived 
from  the  integument  lining  the  meatus.  The  fibrous  layer  consists  of  two  strata, 
an  external,  of  radial  fibres,  which  diverge  from  the  handle  of  the  malleus,  and  an 
internal,  of  circular  fibres,  which  are  plentiful  around  the  circumference  but  sparse 
and  scattered  near  the  centre  of  the  membrane.  Branched  or  dendritic  fibres,  as 
pointed  out  by  Gruber,  are  also  present,  especially  in  the  posterior  half  of  the 
membrane. 

The  arteries  are  derived  from  the  deep  auricular  branch  of  the  internal  maxil- 


856  THE    ORGANS    OF  SPECIAL    SENSE. 

lary,  which  ramifies  beneath  the  cuticular  layer  and  from  the  stylo-mastoid  branch 
of  the  posterior  auricular  and  tympanic  branch  of  the  internal  maxillary,  which 
are  distributed  on  the  mucous  surface.  The  superficial  veins  open  into  the  exter- 
nal jugular;  those  on  the  mucous  surface  drain  themselves  partly  into  the  lateral 
sinus  and  veins  of  the  dura  mater  and  partly  into  a  plexus  on  the  Eustachian  tube. 
The  membrane  receives  its  nervous  supply  from  the  auriculo-temporal  branch  of 
the  inferior  maxillary,  the  auricular  branch  of  the  vagus,  and  the  tympanic  branch 
of  the  glossopharyngeal. 

Ossicles  of  the  Tympanum  (Fig.  459). 

The  tympanum  is  traversed  by  a  chain  of  movable  bones,  three  in  number,  the 
malleus,  incus,  and  stapes.  The  first  is  attached  to  the  membrana  tympani,  the 
last  to  the  fenestra  ovalis,  the  incus  being  placed  between  the  two,  and  is  con- 
nected to  both  by  delicate  articulations. 

The  Malleus,  so  named  from  its  fancied  resemblance  to  a  hammer,  consists  of  a 
head,  neck,  and  three  processes — the  handle  or  manubrium,  the  processus  gracilis, 
and  the  processus  brevis. 

The  head  is  the  large  upper  extremity  of  the  bone ;  it  is  oval  in  shape,  and 
articulates  posteriorly  with  the  incus,  being  free  in  the  rest  of  its  extent.  The 
facet  for  articulation  with  the  incus  is  constricted  near  the  middle,  and  is  divided 
by  a  ridge  into  an  upper,  larger,  and  lower,  lesser  part,  which  form  nearly  a  right 
angle  with  each  other.  Opposite  the  constriction  the  lower  margin  of  the  facet 
projects  in  the  form  of  a  process,  the  cog-tooth  or  spur  of  the  malleus. 

The  neck  is  the  narrow  contracted  part  just  beneath  the  head;  and  below  this 
is  a  prominence,  to  which  the  various  processes  are  attached. 

The  manubrium  is  a  vertical  process  of  bone,  which  is  connected  by  its  outer 
margin  with  the  membrana  tympani.  It  is  directed  downward,  inward,  and  back- 
ward ;  it  decreases  in  size  toward  its  extremity,  where  it  is  curved  slightly  forward, 
and  flattened  from  within  outward.  On,  the  inner  side,  near  its  upper  end,  is  a 
slight  projection,  into  which  the  tendon  of  the  Tensor  tympani  is  inserted. 

The  processus  gracilis  is  a  long  and  very  delicate  process,  which  passes  from 
the  eminence  below  the  neck  forward   and  outward   to  the   Glaserian  fissure,  to 

which  it  is  connected  by  ligamentous  fibres. 
In  the  foetus  this  is  the  longest  process  of  the 
malleus,  and  is  in  direct  continuity  with  the 
cartilage  of  Meckel. 

The  processus  brevis  is  a  slight  conical  pro- 

rocessus  brevis  -t        .  .  &  r      1 

jection,  which  springs  from  the  root  ot  the 
manubrium ;  it  is  directed  outward,  and  is 
attached  to  the   upper  part   of  the  tympanic 

Stapes^  ~^%$\  n        ~  membrane. 

"  "rblculare-  The  Incus  has  received  its  name  from  its 

supposed  resemblance  to  an  anvil,  but  it  is 
more   like  a   bicuspid   tooth,    with  two  roots. 

Fig.  459.— The  small   bones  of  the  ear,  i  •    i_   j-rr       •      i         Ii_  i  -j   1  a    J 

seen  from  the  outside.   (Enlarged.)  which  differ  in  length,  and  are  widely  separated 

from  each  other.  It  consists  of  a  body  and 
two  processes. 

The  body,  is  somewhat  quadrilateral  but  compressed  laterally.  On  its  anterior 
surface  is  a  deeply  concavo-convex  facet,  which  articulates  with  the  head  of  the 
malleus;  in  the  fresh  state  it  is  covered  with  cartilage  and  the  joint  lined  with 
synovial  membrane. 

The  two  processes  diverge  from  one  another  nearly  at  right  angles. 

The  short  process,  somewhat  conical  in  shape,  projects  nearly  horizontally 
backward,  and  articulates  with  a  depression,  the  fossa  incudis,  in  the  lower  and 
back  part  of  the  epitympanic  recess. 

The  long  process,  longer  and  more  slender  than  the  preceding,  descends  nearly 


THE   MIDDLE   EAR.  857 

vertically  behind  and  parallel  to  the  handle  of  the  malleus,  and,  bending  inward, 
terminates  in  a  rounded  globular  projection,  the  os  orbicular e  or  lenticular  process, 
which  is  tipped  with  cartilage,  and  articulates  with  the  head  of  the  stapes.  In  the 
foetus  the  os  orbiculare  exists  as  a  separate  bone. 

The  Stapes,  so  called  from  its  close  resemblance  to  a  stirrup,  consists  of  a  head, 
neck,  two  crura,  and  a  base. 

The  head  presents  a  depression,  tipped  with  cartilage,  which  articulates  with 
the  os  orbiculare. 

The  neck,  the  constricted  part  of  the  bone  succeeding  the  head,  receives  the 
insertion  of  the  Stapedius  muscle. 

The  two  crura  diverge  from  the  neck  and  are  connected  at  their  extremities  by 
a  flattened,  oval-shaped  plate  (the  base),  which  forms  the  foot-plate  of  the  stirrup 
and  is  fixed  to  the  margin  of  the  fenestra  ovalis  by  ligamentous  fibres.  Of  the 
two  crura,  the  anterior  is  shorter  and  less  curved  than  the  posterior. 

Ligaments  of  the  Ossicula. — These  small  bones  are  connected  with  each  other 
and  with  the  walls  of  the  tympanum  by  ligaments,  and  moved  by  small  muscles. 
The  articular  surfaces  of  the  malleus  and  incus  and  the  orbicular  process  of  the 
incus  and  head  of  the  stapes  are  covered  with  cartilage,  connected  together  by 
delicate  capsular  ligaments  and  lined  by  synovial  membrane.  The  ligaments  con- 
necting the  ossicula  with  the  walls  of  the  tympanum  are  five  in  number — three  for 
the  malleus,  one  for  the  incus,  and  one  for  the  stapes. 

The  anterior  ligament  of  the  malleus  was  formerly  described  by  Sb'mmerring  as 
a  muscle  (Laxator  tympani).  It  is  now,  however,  believed  by  most  observers  to 
consist  of  ligamentous  fibres  only.  It  is  attached  by  one  extremity  to  the  neck 
of  the  malleus,  just  above  the  processus  gracilis,  and  by  the  other  to  the  anterior 
wall  of  the  tympanum,  close  to  the  Glaserian  fissure,  some  of  its  fibres  being  pro- 
longed through  the  fissure  to  reach  the  spine  of  the  sphenoid. 

The  superior  ligament  of  the  malleus  is  a  delicate,  round  bundle  of  fibres 
which  descends  perpendicularly  from  the  roof  of  the  epitympanic  recess  to  the 
head  of  the  malleus. 

The  external  ligament  of  the  malleus  is  a  triangular  plane  of  fibres  passing 
from  the  posterior  part  of  the  notch  in  the  tympanic  ring  (incisura  Rivini)  to  the 
short  process  of  the  malleus. 

The  posterior  ligament  of  the  incus  is  a  short,  thick,  ligamentous  band  which 
connects  the  extremity  of  the  short  process  of  the  incus  to  the  posterior  and 
lower  part  of  the  epitympanic  recess,  near  the  margin  of  the  opening  of  the 
mastoid  cells. 

The  inner  surface  and  the  circumference  of  the  base  of  the  stapes  are  covered 
with  hyaline  cartilage,  and  the  annular  ligament  of  the  stapes  connects  the  cir- 
cumference of  the  base  to  the  margin  of  the  fenestra  ovalis. 

A  superior  ligament  of  the  incus  has  been  described  by  Arnold,  but  it  is  little 
more  than  a  fold  of  mucous  membrane. 

The  muscles  of  the  tympanum  are  two  : 

Tensor  tympani.  Stapedius. 

The  Tensor  tympani,  the  larger,  is  contained  in  the  bony  canal  above  the 
osseous  portion  of  the  Eustachian  tube,  from  which  it  is  separated  by  the  processus 
cochleariformis.  It  arises  from  the  under  surface  of  the  petrous  bone,  from  the 
cartilaginous  portion  of  the  Eustachian  tube,  and  from  the  osseous  canal  in  which 
it  is  contained.  Passing  backward  through  the  canal,  it  terminates  in  a  slender 
tendon  which  enters  the  tympanum  and  makes  a  sharp  bend  outward  round  the 
extremity  of  the  processus  cochleariformis,  and  is  inserted  into  the  handle  of  the 
malleus  near  its  root.     It  is  supplied  by  a  branch  from  the  otic  ganglion. 

The  Stapedius  arises  from  the  side  of  a  conical  cavity  hollowed  out  of  the  inte- 
rior of  the  pyramid ;  its  tendon  emerges  from  the  orifice  at  the  apex  of  the  pyra- 
mid, and,  passing  forward,  is  inserted  into  the  neck  of  the  stapes.  Its  surface  is 
aponeurotic,  its  interior  fleshy,  and  its  tendon  occasionally  contains  a  slender  bony 


858  THE   ORGANS    OF  SPECIAL   SENSE. 

spine,  which  is  constant  in  some  mammalia.  It  is  supplied  by  the  tympanic 
branch  of  the  facial  nerve. 

Actions. — The  Tensor  tympani  draws  the  membrana  tympani  inward  and  thus 
heightens  its  tension.  The  Stapedius  draws  the  head  of  the  stapes  backward,  and 
thus  causes  the  base  of  the  bone  to  rotate  on  a  vertical  axis  drawn  through  its  own 
centre :  in  doing  this  the  back  part  of  the  base  would  be  pressed  inward  toward 
the  vestibule,  while  the  fore  part  would  be  drawn  from  it.  It  probably  compresses 
the  contents  of  the  vestibule. 

The  mucous  membrane  of  the  tympanum  is  continuous  with  the  mucous  mem- 
brane of  the  pharynx  through  the  Eustachian  tube.  It  invests  the  ossicula,  and 
the  muscles  and  nerves  contained  in  the  tympanic  cavity ;  forms  the  internal 
layer  of  the  membrana  tympani,  and  the  outer  layer  of  the  membrana  tympani 
secundaria,  and  is  reflected  into  the  mastoid  antrum  and  cells,  which  it  lines 
throughout.  It  forms  several  vascular  folds,  which  extend  from  the  walls  of  the 
tympanum  to  the  ossicles ;  of  these,  one  descends  from  the  roof  of  the  tympanum 
to  the  head  of  the  malleus  and  upper  margin  of  the  body  of  the  incus,  a  second 
invests  the  Stapedius  muscle  :  other  folds  invest  the  chorda  tympani  nerve  and  the 
Tensor  tympani  muscle.  These  folds  separate  oif  pouch-like  cavities,  and  give 
the  interior  of  the  tympanum  a  somewhat  honey-comb  appearance.  One  of  these 
pouches  is  Avell  marked — viz.,  the  pouch  of  Prussak,  which  lies  between  the  neck 
of  the  malleus  and  the  membrana  flaccida.  In  the  tympanum  this  membrane  is 
pale,  thin,  slightly  vascular,  and  covered  for  the  most  part  with  columnar  ciliated 
epithelium,  but  that  covering  the  pyramid,  ossicula,  and  membrana  tympani  pos- 
sesses a  flattened  non-ciliated  epithelium.  In  the  antrum  and  mastoid  cells  its 
epithelium  is  also  non-ciliated.  In  the  osseous  portion  of  the  Eustachian  tube 
the  membrane  is  thin ;  but  in  the  cartilaginous  portion  it  is  very  thick,  highly 
vascular,  covered  with  ciliated  epithelium,  and  provided  with  numerous  mucous 
glands. 

The  arteries  supplying  the  tympanum  are  six  in  number.  Two  of  them  are 
larger  than  the  rest — viz.,  the  tympanic  branch  of  the  internal  maxillary,  which 
supplies  the  membrana  tympani ;  and  the  stylo-mastoid  branch  of  the  posterior 
auricular,  which  supplies  the  back  part  of  the  tympanum  and  mastoid  cells. 
The  smaller  branches  are — the  petrosal  branch  of  the  middle  meningeal,  which 
enters  through  the  hiatus  Fallopii ;  a  branch  from  the  ascending  pharyngeal  and 
another  from  the  Vidian,  which  accompany  the  Eustachian  tube  ;  and  the  tympanic 
branch  from  the  internal  carotid,  given  off  in  the  carotid  canal  and  perforating 
the  thin  anterior  wall  of  the  tympanum. 

The  veins  of  the  tympanum  terminate  in  the  pterygoid  plexus  and  in  the 
superior  petrosal  sinus. 

The  nerves  of  the  tympanum  constitute  the  tympanic  plexus,  which  ramifies 
upon  the  surface  of  the  promontory.  The  plexus  is  formed  by  (1)  the  tympanic 
branch  of  the  glossopharyngeal ;  (2)  the  small  deep  petrosal  nerve ;  (3)  the 
small  superficial  petrosal  nerve ;  and  (4)  a  branch  which  joins  the  great  super- 
ficial petrosal. 

The  tympanic  branch  of  the  glosso-pharyngeal  (Jacobson's  nerve)  enters  the 
tympanum  by  an  aperture  in  its  floor  close  to  the  inner  wall  and  divides  into 
branches,  which  ramify  on  the  promontory  and  enter  into  the  formation  of  the 
plexus.  The  small  deep  petrosal  nerve  from  the  carotid  plexus  of  the  sympathetic 
passes  through  the  wall  of  the  carotid  canal,  and  joins  the  branches  of  Jacobson's 
nerve.  The  branch  to  the  great  superficial  petrosal  passes  through  an  opening  on 
the  inner  wall  of  the  tympanum  in  front  of  the  fenestra  ovalis.  The  small  super- 
ficial petrosal  nerve,  derived  from  the  otic  ganglion,  passes  through  a  foramen  in 
the  middle  fossa  of  the  base  of  the  skull  (sometimes  the  foramen  ovale),  passes 
backward  and  enters  the  petrous  bone  through  a  small  aperture,  situated  external 
to  the  hiatus  Fallopii  on  the  anterior  surface  of  this  bone  ;  it  then  courses  downward 
through  the  bone,  and,  passing  by  the  gangliform  enlargement  of  the  facial  nerve, 
receives  a  connecting   filament   from  it  and   enters  the  tympanic  cavity,   where 


THE  INTERNAL    EAR. 


859 


it  communicates  with  Jacobson's  nerve,  and  assists  in  forming  the  tympanic 
plexus. 

The  branches  of  distribution  of  the  tympanic  plexus  are  distributed  to  the 
mucous  membrane  of  the  tympanum  ;  one  special  branch  passing  to  the  fenestra 
ovalis,  another  to  the  fenestra  rotunda,  and  a  third  to  the  Eustachian  tube.  The 
small  superficial  petrosal  may  be  looked  upon  as  a  branch  from  the  plexus  to  the 
otic  ganglion. 

In  addition  to  the  tympanic  plexus  there  are  the  nerves  supplying  the  muscles. 
The  Tensor  tympani  is  supplied  by  a  branch  from  the  third  division  of  the  fifth 
through  the  otic  ganglion,  and  the  Stapedius  by  the  tympanic  branch  of  the  facial. 

The  chorda  tympani  nerve  crosses  the  tympanic  cavity.  It  is  given  off  from 
the  facial  as  it  passes  vertically  downward  at  the  back  of  the  tympanum,  about 
a  quarter  of  an  inch  before  its  exit  from  the  stylo-mastoid  foramen.  It  passes 
from  below  upward  and  forward  in  a  distinct  canal,  and  enters  the  cavity  of  the 
tympanum  through  an  aperture,  iter  chordce  posterius,  already  described  (page 
853),  and  becomes  invested  with  mucous  membrane.  It  passes  forward,  through 
the  cavity  of  the  tympanum,  crossing  internal  to  the  membrana  tympani  and  over 
the  handle  of  the  malleus  to  the  anterior  inferior  angle  of  the  tympanum,  and 
emerges  from  that  cavity  through  the  iter  chordce  anterius,  or  canal  of  Huguier. 
It  is  invested  by  the  fold  of  mucous  membrane  already  mentioned,  and  therefore 
lies  between  the  mucous  and  fibrous  layers  of  the  membrana  tympani. 

The  Internal  Ear  or  Labyrinth. 

The  internal  ear  is  the  essential  part  of  the  organ  of  hearing,  receiving  the 
ultimate  distribution  of  the  auditory  nerve.  It  is  called  the  labyrinth,  from  the 
complexity  of  its  shape,  and  consists  of  two  parts  :  the  osseous  labyrinth,  a  series 
of  cavities  channelled  out  of  the  substance  of  the  petrous  bone,  and  the  membran- 
ous labyrinth,  the  latter  being  contained  within  the  former. 

The  Osseous  Labyrinth. 

The  osseous  labyrinth  consists  of  three  parts  :  the  vestibule,  semicircular  canals, 
and  cochlea.     These  are  cavities  hollowed  out  of  the  substance  of  the  bone,  and 


Opening  of  aqueductus  vestibuli 

Bristle  passed  through  foramen  rotundum. 

Opening  of  aqueductus  cochlese 
Fig.  460. — The  osseous  labyrinth  laid  open.    (Enlarged.) 

lined  by  periosteum  ;   they  contain  a  clear  fluid,  perilymph,  or  liquor  Cotunnii.  in 
which  the  membranous  labyrinth  is  situated. 

The   Vestibule   (Fig.    460)   is   the   common   central   cavity  of  communication 


860  THE    ORGANS    OF  SPECIAL    SENSE. 

between  the  parts  of  the  internal  ear.  It  is  situated  on  the  inner  side  of  the 
tympanum,  behind  the  cochlea,  and  in  front  of  the  semicircular  canals.  It  is 
somewhat  ovoidal  in  shape  from  before  backward,  flattened  from  within  outward, 
and  measures  about  one-fifth  of  an  inch  from  before  backward,  as  well  as  from 
above  downward,  and  about  one-eighth  of  an  inch  from  without  inward.  On  its 
outer  or  tympanic  wall  is  the  fenestra  ovalis,  closed,  in  the  recent  state,  by  the  base 
of  the  stapes,  and  its  annular  ligament.  On  its  inner  wall,  at  the  fore  part,  is  a 
small  circular  depression,  fovea  hemispheric  a  or  recessus  sphairicus,  which  is  per- 
forated, at  its  anterior  and  inferior  part,  by  several  minute  holes  (macula  cribrosa 
media)  for  the  passage  of  filaments  of  the  auditory  nerve  to  the  saccule ;  and 
behind  this  depression  is  a  vertical  ridge,  the  crista  vestihuli.  This  ridge  bifurcates 
below  to  enclose  a  small  depression,  the  fossa  cochlearis,  which  is  perforated  by  a 
number  of  holes  for  the  passage  of  filaments  of  the  auditory  nerve  which  supply 
the  posterior  end  of  the  ductus  cochlearis.  At  the  hinder  part  of  the  inner  wall  is 
the  orifice  of  the  aquceductus  vestihuli,  which  extends  to  the  posterior  surface  of 
the  petrous  portion  of  the  temporal  bone.  It  transmits  a  small  vein,  and  contains 
a  tubular  prolongation  of  the  lining  membrane  of  the  vestibule,  the  ductus  endo- 
lymphaticus,  which  ends  in  a  cul-de-sac  between  the  layers  of  the  dura  mater  within 
the  cranial  cavity.  On  the  upper  wall  or  roof  is  a  transversely  oval  depression, 
fovea  semi-ellipiica,  separated  from  the  fovea  hemisphaerica  by  the  crista  vestihuli 
already  mentioned.  Behind,  the  semicircular  canals  open  into  the  vestibule  by 
five  orifices.  In  front  is  an  elliptical  opening,  which  communicates  with  the  scala 
vestibuli  of  the  cochlea  by  an  orifice,  apertura  scaloz  vestihuli  cochlea?. 

The  Semicircular  canals  are  three,  bony  canals  situated  above  and  behind  the 
vestibule.  They  are  of  unequal  length,  compressed  from  side  to  side,  and  describe 
the  greater  part  of  a  circle.  They  measure  about  one-twentieth  of  an  inch  in 
diameter,  and  each  presents  a  dilatation  at  one  end,  called  the  ampulla,  which 
measures  more  than  twice  the  diameter  of  the  tube.  These  canals  open  into  the 
vestibule  by  five  orifices,  one  of  the  apertures  being  common  to  two  of  the  canals. 
The  superior  semicircular  canal  is  vertical  in  direction,  and  is  placed  trans- 
versely to  the  long  axis  of  the  petrous  portion  of  the  temporal  bone,  on  the  anterior 
surface  of  which  its  arch  forms  a  round  projection.  It  describes  about  two-thirds 
of  a  circle.  Its  outer  extremity,  which  is  ampullated,  communicates  by  a  distinct 
orifice  in  the  upper  part  of  the  vestibule ;  the  opposite  end  of  the  canal,  which  is 
not  dilated,  joins  with  the  corresponding  part  of  the  posterior  canal  to  form  the 
crus  commune,  which  opens  into  the  upper  and  inner  part  of  the  vestibule. 

The  posterior  semicircular  canal,  also  vertical  in  direction,  is  directed  backward, 
nearly  parallel  to  the  posterior  surface  of  the  petrous  bone ;  it  is  the  longest  of 
the  three;  its  ampullated  end  commences  at  the  lower  and  back  part  of  the 
vestibule,  its  opposite  end  joining  to  form  the  common  canal  already  mentioned. 

The  external  or  horizontal  canal  is  the  shortest  of  the  three,  its  arch  being 
directed  outward  and  backward;  thus  each  semicircular  canal  stands  at  right 
angles  to  the  other  two.  Its  ampullated  end  corresponds  to  the  upper  and  outer 
angle  of  the  vestibule,  just  above  the  fenestra  ovalis,  where  it  opens  close  to  the 
ampullary  end  of  the  superior  canal ;  its  opposite  end  opens  by  a  distinct  orifice  at 
the  upper  and  back  part  of  the  vestibule. 

The  Cochlea  bears  some  resemblance  to  a  common  snail-shell  r  it  forms  the 
anterior  part  of  the  labyrinth,  is  conical  in  form,  and  placed  almost  horizontally  in 
front  of  the  vestibule ;  its  apex  is  directed  forward  and  outward,  with  a  slight 
inclination  downward,  toward  the  upper  and  front  part  of  the  inner  wall  of  the 
tympanum ;  its  base  corresponds  with  the  anterior  depression  at  the  bottom  of  the 
internal  auditory  meatus,  and  is  perforated  by  numerous  apertures  for  the  passage 
of  the  cochlear  division  of  the  auditory  nerve.  It  measures  nearly  a  quarter  of  an 
inch  (5  mm.)  from  base  to  apex,  and  its  breadth  across  the  base  is  somewhat  greater 
(about  9  mm.).  It  consists  of  a  conical-shaped  central  axis,  the  modiolus  or 
columella;  of  a  canal,  the  inner  wall  of  which  is  formed  by  the  central  axis, 
wound  spirally  around  it  for  two  turns  and  three-quarters,  from  the  base  to  the 


THE   INTERNAL    EAR. 


861 


apex,  and  of  a  delicate  lamina  (the  lamina  spiralis  ossea)  which  projects  from  the 
modiolus,  and,  following  the  windings  of  the  canal,  partially  subdivides  into  two. 
In  the  recent  state  certain  membranous  layers  are  attached  to  the  free  border  of 
this  lamina,  which  project  into  the  canal  and  completely  separate  it  into  two 
passages,  which,  however,  communicate  with  each  other  at  the  apex  of  the  modiolus 
by  a  small  opening,  named  the  helicotrema. 

The  modiolus  or  columella  is  the  central  axis  or  pillar  of  the  cochlea.  It  is 
conical  in  form,  and  extends  from  the  base  to  the  apex  of  the  cochlea.  Its  base 
is  broad,  and  appears  at  the  bottom  of  the  internal  auditory  meatus,  where  it 
corresponds  with  the  area  cochleae  ;  it  is  perforated  by  numerous  orifices,  which 
transmit  filaments  of  the  cochlear  division  of  the  auditory  nerve,  the  nerves  for 
the  first  turn  and  a  half  being  transmitted  through  the  foramina  of  the  tractus 
spiralis  foraminosus ;  the  fibres  for  the  apical  turn  passing  up  through  the  foramen 
centrale.  The  foramina  of  the  tractus  spiralis  foraminosus  pass  up  through  the 
modiolus  and  successively  bend  outward  to  reach  the  attached  margin  of  the  lamina 
spiralis  ossea.  Here  they  become  enlarged,  and  by  their  apposition  form  a  spiral 
canal  {canalis  spiralis  modioli),  which  follows  the  course  of  the  attached  margin 
of  the  lamina  spiralis  ossea  and  lodges  the  ganglion  spirale.  The  foramen  centrale 
is  continued  as  a  canal  up  the  middle  of  the  modiolus  to  its  apex.  The  axis 
diminishes  rapidly  in  size  in  the  second  and  succeeding  coil. 

The  bony  canal  of  the  cochlea  (Fig.  461)  takes  two  turns  and  three-quarters 
round  the  modiolus.      It   is  a  little   over  an  inch   in  length  (about  30  mm.),  and 


Fig.  451.— The  cochlea  laid  open.    (Enlarged.) 

diminishes  gradually  in  size  from  the  base  to  the  summit,  where  it  terminates  in 
a  cul-de-sac,  the  cupola,  which  forms  the  apex  of  the  cochlea.  The  commence- 
ment of  this  canal  is  about  the  tenth  of  an  inch  in  diameter ;  it  diverges  from  the 
modiolus  toward  the  tympanum  and  vestibule,  and  presents  three  openings.  One, 
the  fenestra  rotunda,  communicates  with  the  tympanum  ;  in  the  recent  state  this 
aperture  is  closed  by  a  membrane,  the  membrana  tympani  secundaria.  Another 
aperture,  of  an  elliptical  form,  enters  the  vestibule.  The  third  is  the  aperture  of 
the  aqmeductus  cochleae,  leading  to  a  minute  funnel-shaped  canal,  which  opens  on 
the  basilar  surface  of  the  petrous  bone  and  transmits  a  small  vein,  and  also  forms 
a  communication  between  the  subarachnoidean  space  of  the  skull  and  the 
perilymph  contained  in  the  seal  a  tympani. 

The  lamina  spiralis  ossea  is  a  bony  shelf  or  ledge  which  projects  outward  from 
the  modiolus  into  the  interior  of  the  spiral  canal,  and,  like  the  canal,  takes  two 
and  three-quarter  turns  round  the  modiolus.  It  reaches  about  half-way  toward  the 
outer  wall  of  the  spiral  tube,  and  partially  divides  its  cavity  into  two  passages  or 
scalae,  of  which  the  upper  is  named  the  scala  vestibuli,  while  the  lower  is  termed 
the  scala  tympani.  Near  the  summit  of  the  cochlea  the  lamina  terminates  in  a 
hook-shaped  process,  the  hamulus,  which  assists  to  form  the  boundary  of  a  small 
opening,  the  helicotrema,  by  which  the  two  scalse  communicate  with  each  other. 
From  the  canalis  spiralis  modioli  numerous  foramina  pass  outward  through  the 
osseous  spiral  lamina  as  far  as  its  outer  or  free  edge.     In  the  lower  part  of  the  first 


M 


862 


THE    ORGANS    OF  SPECIAL    SENSE. 


turn  a  second  bony  lamina  {lamina  spiralis  secundaria)  projects  inward  from  the 
outer  wall  of  the  bony  tube  ;  it  does  not,  however,  reach  the  primary  osseous  spiral 
lamina,  so  that  if  viewed  from  the  vestibule  a  narrow  fissure,  the  fissura  vestibuli, 
is  seen  between  them. 

The  Membranous  Labyrinth  (Fig.  462). 

The  membranous  labyrinth  is  contained  within  the  bony  cavities  just  described, 
having  the  same  general  form  as  the  cavities  in  which  it  is  contained,  though 
considerably  smaller,  being  separated  from  the  bony  walls  by  a  quantity  of  fluid, 
the  perilymph.  It  does  not,  however,  float  loosely  in  this  fluid,  but  in  places  is 
fixed  to  the  walls  of  the  cavity.  The  membranous  sac  contains  fluid,  the 
endolymph.  and  on  it  the  ramifications  of  the  auditory  nerve  are  distributed. 

"Within  the  osseous  vestibule  the  membranous  labyrinth  does  not  quite  preserve 
the  form  of  the  bony  cavity,  but  presents  two  membranous  sacs,  the  utricle  and 
the  saccule.  The  utricle  is  the  larger  of  the  two,  of  an  oblong  form,  compressed 
laterally,  and  occupies  the  upper  and  back  part  of  the  vestibule,  lying  in  contact 
with  the  fovea  semi-elliptica  and  the  part  below  it.  That  portion  which  is  lodged 
in  the  fovea  forms  a  sort  of  pouch  or  cul-de-sac,  the  floor  and  anterior  wall  of  which 
are  much  thicker  than  elsewhere,  and  form  the  macula  acustica  utricularis,  which 
receives  the  utricular  filaments  of  the  auditory  nerve  and  has   attached   to  its 


Ductus 
Endolymphaticus 

Fig.  462.— The  membranous  labyrinth.    (Enlarged.) 

internal  surface  a  layer  of  calcareous  particles  (otoliths).  The  cavity  cf  the  utricle 
communicates  behind  with  the  membranous  semicircular  canals  by  five  orifices. 
From  its  anterior  wall  is  given  off  a  small  canal,  which  joins  with  a  canal  from  the 
saccule  to  form  the  ductus  endolymphaticus. 

The  saccule  is  the  smaller  of  the  two  vestibular  sacs ;  it  is  globular  in  form, 
lies  in  the  fovea  hemisphserica  near  the  opening  of  the  scala  vestibuli  of  the 
cochlea.  Its  anterior  part  exhibits  an  oval  thickening,  the  macula  saccularis.  to 
which  are  distributed  the  saccular  filaments  of  the  auditory  nerve.  Its  cavity 
does  not  directly  communicate  with  that  of  the  utricle.  From  the  posterior  wall 
is  given  off  a  canal,  which  joins  with  a  similar  canal  given  off  from  the  utricle  to 
form  the  ductus  endo-lymphaticus.  This  duct  passes  along  the  aquseductus  vesti- 
buli and  ends  in  a  blind  pouch  on  the  posterior  surface  of  the  petrous  portion  of 
the  temporal  bone,  where  it  is  in  contact  with  the  dura  mater.  From  the  lower 
part  of  the  saccule  a  short  tube,  the  canalis  reuniens  of  Hensen,  passes  down- 
ward and  outward  to  open  into  the  ductus  cochlearis  (Fig.  462). 

The  membranous  semicircular  canals  are  about  one-third  the  diameter  of  the 
osseous  canals,  but  in  number,  shape,  and  general  form  they  are  precisely  similar, 


THE   INTERNAL    EAR. 


863 


and  present  at  one  end  an  ampullary  enlargement.  They  open  by  five  orifices  into 
the  utricle,  one  opening  being  common  to  two  canals.  In  the  ampullae  the  wall 
is  thickened,  and  projects  into  the  cavity  as  a  fiddle-shaped,  transversely  placed 
elevation,  the  septum  transversum,  in  which  the  nerves  end. 

The  utricle,  saccule,  and  membranous  canals  are  held  in  position  by  numerous 
fibrous  bands  which  stretch  across  the  space  between  them  and  the  bony  Avails. 

Structure. — The  walls  of  the  utricle,  saccule,  and  semicircular  canals  consist 
of  three  layers.  The  outer  layer  is  a  loose  and  flocculent  structure,  apparently 
composed  of  ordinary  fibrous  tissue,  containing  blood-vessels  and  pigment-cells 
analogous  to  those  in  the  pigment  coat  of  the  retina.  The  middle  layer,  thicker 
and  more  transparent,  bears  some  resemblance  to  the  hyaloid  membrane,  but  it 
presents  on  its  internal  surface,  especially  in  the  semicircular  canals,  numerous 
papilliform  projections,  and,  on  the  addition  of  acetic  acid,  presents  an  appearance 
of  longitudinal  fibrillation  and  elongated  nuclei.  The  inner  layer  is  formed  of 
polygonal  nucleated  epithelial  cells.  In  the  maculae  of  the  utricle  and  saccule, 
and  in  the  transverse  septa  of  the  ampullae  of  the  canals,  the  middle  coat  is  thick- 
ened and  the  epithelium  is  columnar,  and  consists  of  supporting  cells  and  hair- 
cells,  the  free  ends  of  the  latter  being  surmounted  by  a  long,  tapering  filament 
(auditory  hair)  which  projects  into  the  cavity.  The  filaments  of  the  auditory 
nerve  enter  these  parts,  and,  having  pierced  the  outer  and  thickened  middle  layer, 
they  lose  their  medullary  sheath,  and  their  axis-cylinders  ramify  between  the  hair- 
cells. 

Two  small  rounded  bodies  termed  otoliths,  and  consisting  of  a  mass  of  minute 
crystalline  grains  of  carbonate  of  lime,  held  together  in  a  mesh  of  delicate  fibrous 


Fig.  463.— Floor  of  scala  media,  showing  the  organ  of  Corti,  etc. 

tissue,  are  contained  in  the  walls  of  the  utricle  and  saccule  opposite  the  distribution 
of  the  nerves.  A  calcareous  material  is  also,  according  to  Bowman,  sparingly 
scattered  in  the  cells  lining  the  ampullae  of  the  semicircular  canals. 

The  membranous  cochlea,  ductus  cochlearis,  or  scala  media  consists  of  a 
spirally  arranged  tube  enclosed  in  the  bony  canal  of  the  cochlea  and  lying  along 
its  outer  wall.     The  manner  in  which  it  is  foi'med  will  now  be  described. 

The  osseous  spiral  lamina,  as  above  stated,  extends  only  part  of  the  distance 
between  the  modiolus  and  the  outer  bony  wall  of  the  cochlea.  A  membrane,  the 
membrana  basilaris,  stretches  from  its  free  edge  to  the  outer  wall  of  the  cochlea, 
and  completes  the  roof  of  the  scala  tympani.  A  second  and  more  delicate  mem- 
brane, the  membrane  of  Reissner,  extends  from  the  thickened  periosteum  covering 
the  lamina  spiralis  ossea  to  the  outer  wall  of  the  cochlea,  to  which  it  is  attached 
at  some  little  distance  above  the  membrana  basilaris.  A  canal  is  thus  shut  off 
between  the  scala  tympani  below  and  the  scala  vestibuli  above ;  this  is  the  mem- 
branous canal  of  the  cochlea,  ductus  cochlearis,  or  scala  media.  It  is  triangular 
on  transverse  section,  its  roof  being  formed  by  the  membrane  of  Reissner,  its 
outer  wall  by  the  periosteum  which  lines  the  bony  canal,  and  its  floor  by  the 


864 


THE    ORGANS    OF  SPECIAL    SENSE. 


membrana  basilaris,  and  the  outer  part  of  the  lamina  spiralis  ossea,  on  the  former 
of  which  is  placed  the  organ  of  Corti.  Reissner's  membrane  is  thin  and  homoge- 
neous, and  is  covered  on  its  upper  and  under  surfaces  by  a  layer  of  epithelium. 
The  periosteum,  which  forms  the  outer  wall  of  the  ductus  cochlearis,  is  greatly 
thickened  and  altered  in  character,  forming  what  is  called  the  ligamentum  spirale. 
It  projects  inward  below  as  a  triangular  prominence,  the  crista  basilaris,  which 
gives  attachment  to  the  outer  edge  of  the  membrana  basilaris,  and  immediately 
above  which  .is  a  concavity,  the  sulcus  spiralis  externus.  The  upper  portion  of 
the  ligamentum  spirale  contains  numerous  capillary  loops  and  small  blood-vessels, 
and  forms  what  is  termed  the  stria  vascularis. 

The  lamina  spiralis  ossea  consists  of  two  plates  of  bone  extending  outward ; 
between  these  are  the  canals  for  the  transmission  of  the  filaments  of  the  auditory 
nerve.  On  the  upper  plate  of  that  part  of  the  osseous  spiral  lamina  which  is 
outside  Reissner's  membrane  the  periosteum  is  thickened  to  form  the  limbus 
lamifice  spiralis,  and  this  terminates  externally  in  a  concavity,  the  sulcus  spiralis 
internus,  which  presents,  on  section,  the  form  of  the  letter  C ;  the  upper  part  of 
the  letter,  formed  by  the  overhanging  extremity  of  the  limbus,  is  named  the 
labium  vestibulare ;  the  lower  part,  prolonged  and  tapering,  is  called  the  labium 
tympanicum,  and  is  perforated  by  numerous  foramina  [foramina  nervosa)  for  the 
passage  of  the  cochlear  nerves.  Externally,  the  labium  tympanicum  is  continuous 
with  the  membrana  basilaris.  The  upper  surface  of  the  labium  vestibulare  is 
intersected  at  right  angles  by  a  number  of  furrows,  between  Avhich  are  numerous 
elevations ;  these  present  the  appearance  of  teeth  along  the  free  margin  of  the 
labium,  and  have  been  named  by  Huschke  the  auditory  teeth.  The  basilar  mem- 
brane may  be  divided  into  two  areas,  inner  and  outer.  The  inner  is  thin,  and  is 
named  the  zona  arcuata:  it  supports  the  organ  of  Corti.  The  outer  is  thicker 
and  striated,  and  is  termed  the  zona  pectinata.  The  under  surface  of  the  mem- 
brane is  covered  by  a  layer  of  vascular  connective  tissue.  One  of  these  vessels  is 
somewhat  larger  than  the  rest,  and  is  named  the  vas  spirale  ;  it  lies  below  Corti's 
tunnel. 

Organ  of  Corti.1 — This  organ  (Fig.  464)  is  situated  upon  the  inner  part  of  the 
membrana    basilaris,   and    appears   at   first   sight  as   a  papilla,   winding   spirally 


Membrana  tectoria. 


Outer  hair  cells. 


Limbus. 


>0<5-*>o  (>o0  O  O  O   O 

x-*-°°°?ii°%0Q%  Oil 
Cells  of  Deiters. 

Outer  rod. 


Nerve  fibres 


Inner  rod. 

Basilar  membrane. 
Fig.  464.— Section  through  the  organ  of  Corti.    Magnified.    (G.  Retzius.) 


throughout  the  whole  length  of  the  ductus  cochlearis,  from  which  circumstance  it 
has  been  designated  the  papilla  spiralis.  More  accurately  viewed,  it  is  seen  to 
be  composed  of  a  remarkable  arrangement  of  cells,  which  may  be  likened  to  the 
keyboard  of  a  pianoforte.  Of  these  cells,  the  two  central  ones  are  rodlike  bodies 
1  Corti's  original  paper  is  in  the  Zeitschrift  f.  Wissen.  Zoo!.,  iii.,  109. 


THE  INTERNAL    EAR. 


865 


and  are  called  the  inner  and  outer  rods  of  Corti.  They  are  placed  on  the  basilar 
membrane,  at  some  little  distance  from  each  other,  but  are  inclined  toward  each 
other,  so  as  to  meet  at  their  opposite  extremities,  and  form  a  series  of  arches 
roofing  over  a  minute  tunnel,  the  tunnel  of  Corti,  between  them  and  the  basilar 
membrane,  which  ascends  spirally  through  the  whole  length  of  the  cochlea. 

The  inner  rods,  some  6000  in  number,  are  more  numerous  than  the  outer 
ones,  and  rest  on  the  basilar  membrane,  close  to  the  labium  tympanicum  ;  they 
project  obliquely  upward  and  outward,  and  terminate  above  in  expanded 
extremities  which  resemble  in  shape  the  upper  end  of  the  ulna,  with  its  sigmoid 
cavity,  coronoid  and  olecranon  processes.  On  the  outer  side  of  the  rod,  in 
the  angle  formed  between  it  and  the  basilar  membrane,  is  a  nucleated  mass  of 
protoplasm  ;  while  on  the  inner  side  is  a  row  of  epithelial  cells  {inner  hair-cells), 
surmounted  by  a  brush  of  fine,  stiff,  hairlike  processes.  On  the  inner  side  of  these 
cells  are  two  or  three  rows  of  columnar  supporting  cells,  which  are  continuous  with 
the  cubical  cells  lining  the  sulcus  spiralis  internus. 

The  outer  rods,  numbering  about  4000,  also  rest  by  a  broad  foot  on  the 
basilar  membrane ;  they  incline  upward  and  inward,  and  their  upper  extremity 
resembles  the  head  and  bill  of  a  swan :  the  back  of  the  head  fitting  into  the  con- 
cavity— the  analogue  of  the  sigmoid  cavity — of  one  or  more  of  the  internal  rods, 
and  the  bill  projecting  outward  as  a  phalangeal  process  of  the  membrana  reticu- 
laris, presently  to  be  described. 

In  the  head  of  these  outer  rods  is  an  oval  portion,  where  the  fibres  of  which 
the  rod  appears  to  be  composed  are  deficient,  and  which  stains  more  deeply  with 
carmine  than  the  rest  of  the  rod.  At  the  base  of  the  rod,  on  its  internal  side — 
that  is  to  say,  in  the  angle  formed  by  the  rod  with  the  basilar  membrane — is  a 
similar  protoplasmic  mass  to  that  found  on  the  outer  side  of  the  base  of  the  inner 
rod ;  these  masses  of  protoplasm  are  probably  the  undifferentiated  portions  of  the 
cells  from  which  the  rods  are  developed.     External  to  the  outer  rod  are  three  or 


Fig.465—  Longitudinal  section  of  the  cochlea,  showing  the  relations  of  the  scalae,  the  ganglion  spirale,  etc. 
S.  V.  Scala  vestibuli.  S.  T.  Scala  tympani.  S.  M.  Scala  media.  L.  S.  Ligamentum  spirale.  G.  S.  Ganglion 
spirale. 


four  successive  rows  of  epithelial  cells,  more  elongated  than  those  found  on  the 
internal  side  of  the  inner  rod.  but,  like  them,  furnished  with  minute  hairs  or  cilia. 
These  are  termed  the  outer  hair-cells,  in  contradistinction  to  the  inner  hair-cells 
above  referred  to.  There  are  about  12,000  outer  hair-cells,  and  about  8500  inner 
hair-cells. 

The  hair-cells  are  somewhat  oval  in  shape ;    their  free  extremities  are  on  a 
level   with   the  heads  of  Corti's   rods,  and  from   each   some  twenty  fine  hairlets 

55 


866  THE    ORGANS    OF  SPECIAL    SENSE. 

project  and  are  arranged  in  the  form  of  a  crescent,  the  concavity  of  which  opens 
inward.  The  deep  ends  of  the  cells  are  rounded  and  contain  large  nuclei :  they 
reach  only  as  far  as  the  middle  of  Corti's  rods,  and  are  in  contact  with  the 
ramifications  of  the  nervous  filaments.  Between  the  rows  of  the  outer  hair-cells 
are  rows  of  supporting  cells,  called  the  cells  of  Betters  ;  their  expanded  bases  are 
planted  on  the  basilar  membrane,  while  their  opposite  ends  present  a  clubbed 
extremity  or  phalangeal  process.  Immediately  to  the  outer  side  of  Deiters's  cells 
are  some  five  or  six  rows  of  columnar  cells,  the  supporting  cells  of  Hensen.  Their 
bases  are  narrow,  while  their  upper  parts  are  expanded  and  form  a  rounded 
elevation  on  the  floor  of  the  ductus  cochlearis.  The  columnar  cells  lying  outside 
Hensen's  cells  are  termed  the  cells  of  Claudius.  A  space  is  seen  between  the 
outer  rods  of  Corti  and  the  adjacent  hair-cells;  this  is  called  the  space  of 
Nuel. 

The  lamina  reticularis  or  membrane  of  Kb'lliker  is  a  delicate  framework 
perforated  by  rounded  holes.  It  extends  from  the  inner  rods  of  Corti  to  the 
external  row  of  the  outer  hair-cells,  and  is  formed  by  several  rows  of  "minute 
fiddle-shaped  cuticular  structures,"  called  phalanges,  between  which  are  circular 
apertures  containing  the  free  ends  of  the  hair-cells.  The  innermost  row  of 
phalanges  consists  of  the  phalangeal  processes  of  the  outer  rods  of  Corti ;  the 
outer  rows  are  formed  by  the  modified  free  ends  of  Deiters's  cells. 

Covering  over  these  structures,  but  not  touching  them,  is  the  membrana  tec- 
toria,  or  membrane  of*  Corti,  which  is  attached  to  the  vestibular  surface  of  the 
lamina  spiralis  close  to  the  attachment  of  the  membrane  of  Reissner.  It  is  thin 
near  its  inner  margin,  and  overlies  the  auditory  teeth  of  Buschke.  Its  outer  half 
is  thick,  and  along  its  lower  edge,  opposite  the  inner  hair-cells,  is  a  clear  band, 
named  Hensen's  stripe.  Externally,  the  membrane  becomes  much  thinner,  and  is 
attached  to  the  outer  row  of  Deiters's  cells  (Retzius). 

The  inner  surface  of  the  osseous  labyrinth  is  lined  by  an  exceedingly  thin 
fibro-serous  membrane,  analogous  to  a  periosteum,  from  its  close  adhesion  to  the 
inner  surfaces  of  these  cavities,  and  performing  the  office  of  a  serous  membrane  by 
its  free  surface.  It  lines  the  vestibule,  and  from  this  cavity  is  continued  into  the 
semicircular  canals  and  the  scala  vestibuli  of  the  cochlea,  and  through  the  helico- 
trema  into  the  scala  tympani.  A  delicate  tubular  process  is  prolonged  along  the 
aqueduct  of  the  vestibule  to  the  inner  surface  of  the  dura  mater.  This  membrane 
is  continued  across  the  fenestra  ovalis  and  rotunda,  and  consequently  has  no  com- 
munication with  the  lining  membrane  of  the  tympanum.  Its  attached  surface  is 
rough  and  fibrous,  and  closely  adherent  to  the  bone ;  its  free  surface  is  smooth  and 
pale,  covered  with  a  layer  of  epithelium,  and  secretes  a  thin,  limpid  fluid,  the  aqua 
labgrinthi,  liquor  Ootunnii,  or  perilymph  (Blainville). 

The  scala  media  is  closed  above  and  below.  The  upper  blind  extremity  is 
termed  the  lagena,  and  is  attached  to  the  cupola  at  the  upper  part  of  the  heli- 
cotrema ;  the  lower  end  is  lodged  in  the  recessus  cochlearis  of  the  vestibule.  Near 
this  blind  extremity,  the  scala  media  receives  the  canalis  reuniens  of  Hensen  (Fig. 
462),  a  very  delicate  canal,  by  which  the  ductus  cochlearis  is  brought  into  con- 
tinuity with  the  saccule. 

The  arteries  of  the  labyrinth  are  the  internal  auditory,  from  the  basilar,  and 
the  stylo-mastoid,  from  the  posterior  auricular.  The  internal  auditory  divides  at 
the  bottom  of  the  internal  meatus  into  two  branches :   cochlear  and  vestibular. 

The  cochlear  branch  subdivides  into  from  twelve  to  fourteen  twigs,  which 
traverse  the  canals  in  the  modiolus,  and  are  distributed,  in  the  form  of  a  capillary 
network,  in  the  substance  of  the  lamina  spiralis. 

The  vestibular  branches  accompany  the  nerves,  and  are  distributed,  in  the 
form  of  a  minute  capillary  network,  in  the  substance  of  the  membranous  labyrinth. 

The  veins  (auditory)  of  the  vestibule  and  semicircular  canals  accompany  the 
arteries,  and,  receiving  those  of  the  cochlea  at  the  base  of  the  modiolus,  terminate 
in  the  posterior  pai-t  of  the  superior  petrosal  sinus  or  in  the  lateral  sinus. 

The  auditory  nerve,  the  special  nerve  of  the  sense  of  hearing,  divides,  at  the 


SURGICAL    ANATOMY    OF    THE   EAR.  867 

bottom  of  the  internal  auditory  meatus,  into  two  branches,  the  cochlear  and 
vestibular. 

The  vestibular  ne?'ve,  the  posterior  of  the  two,  presents,  as  it  lies  in  the  internal 
auditory  meatus,  a  ganglion,  the  ganglion  of  /Scarpa;  it  divides  into  three 
branches  which  pass  through  minute  openings  at  the  upper  and  back  part  of  the 
bottom  of  the  meatus  (area  vestibular  superior),  and,  entering  the  vestibule,  are 
distributed  to  the  utricle  and  to  the  ampulla  of  the  external  and  superior  semicir- 
cular canals. 

The  nervous  filaments  enter  the  ampullary  enlargements  opposite  the  septum 
transversum,  and  arborize  around  the  hair-cells.  In  the  utricle  and  saccule  the 
nerve-fibres  pierce  the  membrana  propria  of  the  maculae,  and  end  in  arborizations 
round  the  hair-cells. 

The  cochlear  nerve  gives  off  the  branch  to  the  saccule,  the  filaments  of  which 
are  transmitted  from  the  internal  auditory  meatus  through  the  foramina  of  the 
area  vestibularis  inferior,  which  lies  at  the  lower  and  back  part  of  the  floor  of  the 
meatus.  It  also  gives  off  the  branch  for  the  ampulla  of  the  posterior  semicircular 
canal,  which  leaves  the  meatus  through  the  foramen  singulars. 

The  rest  of  the  cochlear  nerve  divides  into  numerous  filaments  at  the  base  of 
the  modiolus ;  those  for  the  basal  and  middle  coils  pass  through  the  foramina  in 
the  tractus  foraminosus,  those  for  the  apical  coil  through  the  canalis  centralis,  and 
the  nerves  bend  outward  to  pass  between  the  lamellge  of  the  osseous  spiral  lamina. 
Occupying  the  spiral  canal  of  the  modiolus  is  the  ganglion  spirale,  consisting  of 
bipolar  nerve-cells,  which  really  constitute  the  true  cells  of  origin  of  this  nerve, 
one  pole  being  prolonged  centrally  to  the  brain  and  the  other  peripherally  to  the 
hair-cells  of  Corti's  organ.  Reaching  the  outer  edge  of  the  osseous  spiral  lamina, 
they  pass  through  the  foramina  in  the  labium  tympanicum,  and  end,  some  by 
arborizing  around  the  bases  of  the  inner  hair^cells,  while  others  pass  between 
Corti's  rods  and  through  the  tunnel,  to  terminate  in  a  similar  manner  in  relation 
to  the  outer  hair-cells. 

Surgical  Anatomy. — Malformations,  such  as  imperfect  development  of  the  external  parts, 
absence  of  the  meatus,  or  supernumerary  auricles,  are  occasionally  met  with.  Or  the  pinna  may 
present  a  congenital  fistula  which  is  due  to  defective  closure  of  the  first  visceral  cleft,  or  rather 
of  that  portion  of  it  which  is  not  concerned  in  the  formation  of  the  Eustachian  tube,  tympanum, 
and  meatus.  The  skin  of  the  auricle  is  thin  and  richly  supplied  with  blood,  but  in  spite  of  this 
it  is  frequently  the  seat  of  frost-bite,  due  to  the  fact  that  it  is  much  exposed  to  cold,  and  lacks 
the  usual  underlying  subcutaneous  fat  found  in  most  other  parts  of  the  body.  A  collection  of 
blood  is  sometimes  found  between  the  cartilage  and  perichondrium  {hematoma  auris),  usually 
the  result  of  traumatism,  but  not  necessarily  due  to  this  cause.  It  is  said  to  occur  most  fre- 
quently in  the  ears  of  the  insane.  Keloid  sometimes  grows  in  the  auricle  around  the  puncture 
made  for  earrings,  and  epithelioma  occasionally  affects  this  part.  Deposits  of  urate  of  soda  are 
•often  met  with  in  the  pinna  in  gouty  subjects. 

The  external  auditory  meatus  can  be  most  satisfactorily  examined  by  light  reflected 
down  a  funnel-shaped  speculum ;  by  gently  moving  the  latter  in  different  directions  the 
whole  of  the  canal  and  membrana  tympani  can  be  brought  into  view.  The  points  to  be  noted 
lire,  the  presence  of  wax  or  foreign  bodies,  the  size  of  the  canal,  and  the  condition  of  the  mem- 
brana tympani.  The  accumulation  of  wax  is  often  the  cause  of  deafness,  and  may  give  rise  to 
very  serious  consequences,  causing  ulceration  of  the  membrane  and  even  absorption  of  the  bony 
wall  of  the  canal.  Foreign  bodies  are  not  infrequently  introduced  into  the  ear  by  children,  and. 
when  situated  in  the  first  portion  of  the  canal,  may  be  removed  with  tolerable  facility  by  means 
of  a  minute  hook  or  loop  of  fine  wire,  with  reflected  light;  but  when  they  have  slipped  beyond 
the  narrow  middle  part  of  the  meatus,  their  removal  is  in  no  wise  easy,  and  attempts  to  effect 
it,  in  inexperienced  hands,  may  be  followed  by  destruction  of  the  membrana  tympani  and  possi- 
bly the  contents  of  the  tympanum.  The  calibre  of  the  external  auditory  canal  maybe  narrowed 
by  inflammation  of  its  lining  membrane,  running  on  to  suppuration  ;  by  periostitis  ;  by  polypi, 
sebaceous  tumors,  and  exostoses.  The  membrana  tympani,  when  seen  in  a  healthy  ear.  "reflects 
light  strongly,  and,  owing  to  its  peculiar  curvature,  presents  a  bright  spot  of  triangular  shape  at 
its  lower  and  anterior  portion. ' '  From  the  apex  of  this,  proceeding  upward  and  slightly  forward, 
is  a  white  streak  formed  by  the  handle  of  the  malleus,  while  near  the  upper  part  of  the  mem- 
brane may  be  seen  a  slight  projection,  caused  by  the  short  process  of  the  malleus.  In  disease 
alterations  in  color,  lustre,  curvature  or  inclination,  and  perforation  must  be  noted.  Such  per- 
forations may  be  caused  by  a  blow,  a  loud  report,  a  wound,  or  as  the  result  of  suppuration  in 
the  middle  ear. 

The  upper  wall  of  the  meatus  is  separated  from  the  cranial  cavity  by  a  thin  plate  of  bone ; 


868  THE    ORGANS    OF  SPECIAL   SENSE. 

the  anterior  wall  is  separated  from  the  temporo-mandibular  joint  and  parotid  gland  by  the  bone 
forming  the  glenoid  fossa ;  and  the  posterior  wall  is  in  relation  with  the  mastoid  cells ;  hence 
inflammation  of  the  external  auditory  meatus  may  readily  extend  to  the  membranes  of  the 
brain,  to  the  temporo-mandibular  joint,  or  to  the  mastoid  cells ;  and,  in  addition  to  this,  blows 
on  the  chin  may  cause  fracture  of  the  wall  of  the  meatus. 

The  nerves  supplying  the  meatus  are  the  auricular  branch  of  the  pneumogastric,  the 
auriculo-temporal,  and  the  auricularis  magnus.  The  connections  of  these  nerves  explain  the 
fact  of  the  occurrence,  in  cases  of  any  irritation  of  the  meatus,  of  constant  coughing  and  sneez- 
ing from  implication  of  the  pneumogastric,  or  of  yawning  from  implication  of  the  auriculo- 
temporal.  No  doubt  also  the  association  of  earache  with  toothache  in  cancer  of  the  tongue  is 
due  to  implication  of  the  same  nerve,  a  branch  of  the  fifth,  which  supplies  also  the  teeth  and 
the  tongue.  The  vessels  of  the  meatus  and  membrana  tympani  are  derived  from  the  posterior 
auricular,  temporal,  and  internal  maxillary  arteries.  The  upper  half  of  the  membrana  tympani 
is  much  more  richly  supplied  with  blood  than  the  lower  half.  For  this  reason,  and  also  to  avoid 
the  chorda  tympani  nerve  and  ossicles,  incisions  through  the  membrane  should  be  made  at  the 
lower  and  posterior  part. 

The  principal  point  in  connection  with  the  surgical  anatomy  of  the  tympanum  is  its  relations 
to  other  parts.  Its  roof  is  formed  by  a  thin  plate  of  bone,  which,  with  the  dura  mater,  is  all  that 
separates  it  from  the  temporal  lobe  of  the  brain.  Its  floor  is  immediately  above  the  jugular 
fossa  behind  and  the  carotid  canal  in  front.  Its  posterior  wall  presents  the  openings  of  the 
mastoid  cells.  On  its  anterior  wall  is  the  opening  of  the  Eustachian  tube.  Thus  it  follows 
that  in  disease  of  the  middle  ear  we  may  get  subdural  abscess,  septic  meningitis,  or  abscess  of 
the  cerebrum  or  cerebellum  from  extension  of  the  inflammation  through  the  bony  roof:  throm- 
bosis of  the  lateral  sinus,  with  or  without  pyaemia,  by  extension  through  the  floor ;  or  mastoid 
abscess  by  extension  backward.  In  addition  to  this,  we  may  get  fatal  hemorrhage  from  the 
internal  carotid  in  destructive  changes  of  the  middle  ear ;  and  in  throat  disease  we  may  get  the 
inflammation  extending  up  the  Eustachian  tube  to  the  middle  ear.  The  Eustachian  tube  is  ac- 
cessible from  the  nose.  If  the  nose  and  mouth  be  closed  and  an  attempt  made  to  expire  air,  a 
sense  of  pressure  with  dulness  of  hearing  is  produced  in  both  ears,  from  the  air  finding  its  way 
up  the  Eustachian  tube  and  bulging  out  the  membrana  tympani.  During  the  act  of  swallowing, 
the  pharyngeal  orifice  of  the  tube,  which  is  normally  closed,  is  opened,  probably  by  the 
action  of  the  Dilator  tubea  muscle.  This  fact  was  employed  by  Politzer  in  devising  an  easy 
method  of  inflating  the  tube.  The  nozzle  of  an  india-rubber  syringe  is  inserted  into  the  nostril ; 
the  patient  takes  a  mouthful  of  water  and  holds  it  in  his  mouth  ;  both  nostrils  are  closed  with 
the  finger  and  thumb  to  prevent  the  escape  of  air,  and  the  patient  is  then  requested  to  swallow ; 
as  he  does  so  the  air  is  forced  out  of  the  syringe  into  his  nose,  and  is  driven  into  the  Eustachian 
tube,  which  is  now  open.  The  impact  of  the  air  against  the  membrana  tympani  can  be  heard,  if 
the  membrane  is  sound,  by  means  of  a  piece  of  india-rubber  tubing,  one  end  of  which  is  inserted 
into  the  meatus  of  the  patient's  ear,  the  other  into  that  of  the  surgeon.  The  direct  examination 
of  the  Eustachian  tube  is  made  by  the  Eustachian  catheter.  This  is  passed  along  the  floor  of 
the  nostril,  close  to  the  septum,  with  the  point  touching  the  floor,  to  the  posterior  wall  of  the 
pharynx.  When  this  is  felt,  the  catheter  is  to  be  withdrawn  about  half  an  inch,  and  the  point 
rotated  outward  through  a  quarter  of  a  circle,  and  pushed  again  slightly  backward,  when  it  will 
enter  the  orifice  of  the  tube,  and  will  be  found  to  be  caught,  and  air  forced  into  the  catheter 
will  be  heard  impinging  on  the  tympanic  membrane  if  the  ears  of  the  patient  and  surgeon  are 
connected  by  an  india-rubber  tube. 


ni 


THE  ORGANS  OF  DIGESTION. 


THE  Apparatus  for  the  Digestion  of  the  Food  consists  of  the  alimentary  canal 
and  of  certain  accessory  organs. 

The  alimentary  canal  is  a  musculo-membranous  tube,  about  thirty  feet  in 
length,  extending  from  the  mouth  to  the  anus,  and  lined  throughout  its  entire 
extent  by  mucous  membrane.  It  has  received  different  names  in  the  various  parts 
of  its  course  :  at  its  commencement,  the  mouth,  we  find  provision  made  for  the 
mechanical  division  of  the  food  {mastication),  and  for  its  admixture  with  a  fluid 
secreted  by  the  salivary  glands  {insalivation) ;  beyond  this  are  the  organs  of 
deglutition,  the  pharynx  and  the  oesophagus,  which  convey  the  food  into  that  part 
of  the  alimentary  canal  (the  stomach)  in  which  the  principal  chemical  changes 
occur,  and  in  which  the  reduction  and  solution  of  the  food  take  place  ;  in  the  small 
intestines  the  nutritive  principles  of  the  food  (the  chyle)  are  separated,  by  its 
admixture  with  the  bile,  pancreatic  and  intestinal  fluids,  from  that  portion  which 
passes  into  the  large  intestine,  most  of  which  is  expelled  from  the  system. 

Alimentary  Canal. 

{  Duodenum. 
Mouth.  Small  intestines  Jejunum. 

Pharynx.  ( Ileum. 

(Esophagus.  ( Caecum. 

Stomach.  Large  intestine^  Colon. 

(  Rectum. 
Accessory    Organs. 
Teeth. 

( Parotid.  Liver. 

Salivary  glands  -<  Submaxillary.  Pancreas. 

( Sublingual.  Spleen. 

THE  MOUTH. 

The  mouth  {oral  or  buccal  caviiy)  is  placed  at  the  commencement  of  the  ali- 
mentary canal ;  it  is  a  nearly  oval-shaped  cavity,  in  which  the  mastication  of  the 
food  takes  place  (Fig.  466).  It  consists  of  two  parts  ;  an  outer,  smaller  portion, 
the  vestibule  (vestibulum  oris),  and  an  inner,  larger  part,  the  cavity  proper  of  the 
mouth  (cavum  oris  proprium). 

The  vestibulum  oris  is  a  slit-like  aperture,  bounded  in  front  and  laterally  by 
the  lips  and  cheeks;  behind  and  internally  by  the  gums  and  teeth.  Above  and 
below  it  is  limited  by  the  reflection  of  the  mucous  membrane  from  the  lips  and 
cheeks  to  the  gum  covering  the  upper  and  lower  alveolar  arch  respectively.  It- 
receives  the  secretion  from  the  parotid  glands,  and  communicates,  when  the  jaws 
are  closed,  with  the  cavum  oris  by  an  aperture  on  each  side  behind  the  wisdom  teeth. 

The  cavum  oris  proprium  is  bounded  laterally  and  in  front  by  the  alveolar 
arches  with  their  contained  teeth  ;  behind  it  communicates  with  the  pharynx  by  a 
constricted  aperture  termed  the  isthmus  faucium.  It  is  roofed  in  by  the  hard  and 
soft  palate,  while  the  greater  part  of  the  floor  is  formed  by  the  tongue,  the  remainder 
being  completed  by  the  reflection  of  the  mucous  membrane  from  the  sides  and 
under  surface  of  the  tongue  to  the  gum  lining  the  inner  aspect  of  the  mandible. 
It  receives  the  secretion  from  the  submaxillary  and  sublingual  glands. 

The  mucous  membrane  lining  the  mouth  is  continuous  with  the  integument  at 
the  free  margin  of  the  lips  and  with  the  mucous  lining  of  the  pharynx  behind  ;■  it 
is  of  a  rose-pink  tinge  during  life,  and  very  thick  where  it  covers  the  hard  parts 
bounding  the  cavity.     It  is  covered  by  stratified  epithelium. 

The  lips  are  two  fleshy  folds  which  surround  the  orifice  of  the  mouth,  formed 

869 


870 


THE    OH  GAMS'    OF   DIGESTION. 


externally  by  integument  and  internally  by  mucous  membrane,  between  which  are 
found  the  Orbicularis  oris  muscle,  the  coronary  vessels,  some  nerves,  areolar  tissue, 
and  fat,  and  numerous  small  labial  glands.  The  inner  surface  of  each  lip  is  connected 
in  the  middle  line  to  the  gum  of  the  corresponding  jaw  by  a  fold  of  mucous  membrane, 
the  frcenum  labii  superioris  and  inferioris — the  former  being  the  larger  of  the  two. 

The  labial  glands  are  situated  between  the  mucous  membrane  and  the  Orbicu- 
laris oris  round  the  orifice  of  the  mouth.  They  are  rounded  in  form,  about  the 
size  of  small  peas,  their  ducts  opening  by  small  orifices  upon  the  mucous  mem- 
brane.    In  structure  they  resemble  the  salivary  glands. 

The  cheeks  form  the  sides  of  the  face  and  are  continuous  in  front  with  the  lips. 
They  are  composed  externally  of  integument,  internally  of  mucous  membrane, 
and  between  the  two  of  a  muscular  stratum,  besides  a  large  quantity  of  fat,  areolar 
tissue,  vessels,  nerves,  and  buccal  glands. 

The  mucous  membrane  lining  the  cheek  is  reflected  above  and  below  upon  the 
gums,  where  its  color  becomes  lighter ;  it  is  continuous  behind  with  the  lining  mem- 


Opening  of  nasal  duct. 


h-istle  passed  thivug 
Stenson'  s  duct. 


Fig.  466. — Sectional  view  of  the  nose,  mouth,  pharynx,  etc. 

gums,  and  it  is  continuous  behind  with  the  lining  membrane  of  the  soft  palate. 
Opposite  the  second  molar  tooth  of  the  upper  jaw  is  a  papilla,  the  summit  of  which 
presents  the  aperture  of  the  duct  of  the  parotid  gland.  The  principal  muscle  of 
the  cheek  is  the  Buccinator,  but  numerous  other  muscles  enter  into  its  formation 
— viz.,  the  Zygomatici,  Risorius  Santorini,  and  Platysma  myoides. 

The  buccal  glands  are  placed  between  the  mucous  membrane  and  Buccinator  mus- 
cle :  they  are  similar  in  structure  to  the  labial  glands,  but  smaller.  Two  or  three  of 
larger  size  than  the  rest  are  placed  between  the  Masseter  and  Buccinator  muscles ;  their 
ducts  open  into  the  mouth  opposite  the  last  molar  tooth.    They  are  called  molar  glands. 

The  gums  are  composed  of   a   dense   fibrous  tissue  closely  connected  to   the 


THE    TEETH. 


871 


periosteum  of  the  alveolar  processes  and  surrounding  the  necks  of  the  teeth.  They 
are  covered  by  smooth  and  vascular  mucous  membrane,  which  is  remarkable  for  its 
limited  sensibility.  Around  the  necks  of  the  teeth  this  membrane  presents  numer- 
ous fine  papillae  ;  and  from  this  point  it  is  reflected  into  the  alveolus,  where  it  is 
continuous  with  the  periosteal  membrane  lining  that  cavity. 


THE  TEETH. 

The  human  subject  is  provided  with  two  sets  of  teeth,  which  make  their  appear- 
ance at  different  periods  of  life.     The  first  set  appear  in  childhood,  and  are  called 

the  temporary,  deciduous,  or  milk  teeth.    The 
second  set  are  named  permanent. 

The  temporary  teeth  are  twenty  in  num- 
ber— four  incisors,  two  canine,  and  four 
molars,   in  each  jaw  (Fig.  467). 

The  permanent  teeth  are  thirty-two  in 
number — four  incisors  (two  central  and  two 
lateral),  two  canines,  four  bicuspids,  and  six 
molars  in  each  jaw  (Fig.  468). 

General  Characters. — Each  tooth  consists 
of  three  portions :  the  croion,  or  body,  pro- 
jecting above  the  gum;  the  root,  ox  fang, 
entirely  concealed  within  the  alveolus ;   and 
the  neck,  the  constricted  portion,  between  the 
root  and  crown. 
The  surfaces  of  a  tooth  are  named  thus :  that  which  looks  toward  the  lips  is 
the  labial;  that  toward  the  tongue  is  the  lingual;  that  toward  the  mesial  line, 
proximal;  that  away  from  the  same,  distal;  that  toward  the  cheek,  the  buccal 
surface.     This  applies  to  the  roots  as  well  as  to  the  crowns  of  teeth. 


Fig.  467.— Deciduous  teeth.    Left  side. 


Fig.  468.— Permanent  teeth.    Right  side  (Burchard). 

The  roots  of  the  teeth  are  firmly  implanted  within  the  alveoli  (Fig.  472) ;  these 
depressions  are  lined  with  periosteum  (the  pericementum)  which  is  reflected  on  to 
the  tooth  at  the  point  of  the  root  and  covers  it  as  far  as  the  neck.  At  the  margin 
of  the  alveolus  the  periosteum  becomes  continuous  with  the  fibrous  structure  of 
the  gums. 

Permanent  Teeth  (Figs.  469  and  470). 

The  incisors,  or  cutting  teeth,  are  so  named  from  their  presenting  a  sharp  cut- 
ting edge,  adapted  for  incising  the  food.  They  are  eight  in  number,  and  comprise 
the  four  front  teeth  in  each  jaw. 


872 


THE    ORGANS   OF  DIGESTION. 


Fig.  469.— Right  half  ol  upper 
jaw  (from  below),  with  the  cor- 
responding teeth.  The  letters 
and  numbers  point  to  the 
classes  of  teeth  and  the  num- 
bers in  classes. 


The  crown  is  directed  almost  vertically  and  is  spade-like  in  form  ;  it  has  the  form 
of  a  truncated  cone  whose  top  has  been  compressed  into  a  sharp  horizontal  cutting 
edge.  Before  being  subjected  to  attrition  this  edge  pre- 
sents three  small  elevations.  The  labial  surface  is  convex, 
and  marked  by  three  longitudinal  ridges  extending  from 
the  edge  tubercles  toward  the  neck  of  the  tooth.  The 
lingual  surface  is  concave,  and  is  marked  by  two  marginal 
ridges  extending  from  an  encircling  ridge  at  the  neck  to 
the  angles  of  the  cutting  edge  of  the  tooth.  The  ridge  at 
the  neck  is  termed  the  cingulum  or  basal  ridge. 

The  mesial  and  distal  surfaces  are  triangular,  the 
apex  of  the  triangle  at  the  cutting  edge. 
The  neck  of  the  tooth  is  constricted. 
The  root  is  long,  single,  and  has  the  form  of  a  trans- 
versely flattened  cone,  thicker  before  than  behind.     The 
root  may  be  curved. 

The  incisors  of  the  upper  jaiv  are  altogether  larger 
and  stronger  than  those  of  the  lower  jaw,  the  central 
incisors  being  larger  and  flatter  than  the  laterals.  They 
are  directed  obliquely  downward  and  forward. 

The  incisors  of  the  lower  jaw  are  smaller  and  flatter 
than  the  upper,  and  the  elevations  upon  their  lingual 
faces  are  not  marked.  The  two  central  are  smaller  than 
the  two  lateral  incisors,   being  the  smallest  of  all   the 

teeth.  The  roots  of  these  teeth  are  flattened  laterally. 
The  canine  teeth  (cuspidati)  are  four  in  number,  two 
in  the  upper,  two  in  the  lower  jaw — one  being  placed 
distal  to  each  lateral  incisor.  They  are  larger  and 
stronger  than  the  incisors,  especially  in  the  roots,  which 
are  deeply  implanted  and  cause  well-marked  prominence 
of  the  process  at  the  places  of  insertion. 

The  crown  is  large,  of  spear-head,  form  and  its  very 
convex  labial  surface  is  marked  by  three  longitudinal 
ridges.  The  concave  labial  surface  is  also  marked  by 
three  ridges  which  unite  at  a  basal  ridge.  The  point  or 
cusp  is  longer  than  in  the  other  teeth,  and  is  the  point  of 
division  between  a  short  mesial  and  a  long  distal  cutting 
edge. 

The  root  is  oval  or  elliptical  in  transverse  section,  and 
is  longer  and  more  prominent  than  the  roots  of  the 
incisors. 

The  upper  canines  or  cuspids  (vulgarly  called  the  eye 
teeth)  are  larger  and  longer  than  the  two  lower,  and 
in  occlusion  are  distal  to  them  to  the  extent  of  half  the 
width  of  the  crown. 

The  lower  canines  (vulgarly  called  the  stomach  teeth) 
have  the  general  form  of  the  upper  cuspids,  but  their  lin- 
gual surfaces  are  much  more  flattened1,  owing  to  the 
absence  of  the  elevations  marking  the  upper.  Their  roots  are  more  flattened  and 
may  be  bifid  at  their  apices. 

The  bicuspid  teeth  (premolars)  are  eight  in  number,  four  in  each  jaw  ;  they  are 
placed  distal  to  the  cuspid  teeth,  two  upon  each  side.  They  are  double  cuspids  in  form. 
The  crown  is  surmounted  by  two  cusps,  one  buccal  and  one  lingual,  separated 
by  a  groove,  the  buccal  being  more  prominent  and  larger  than  the  lingual.  The 
lower  bicuspids  are  not  truly  bicuspid,  the  first  having  but  a  primitive  lingual  cusp,  the 
second  having  the  lingual  cusp  divided  into  two  sections — i.  e.  it  is  usually  tricuspid. 
The  ?ie.cks  of  the  teeth  are  oval ;  the  roots  are  laterally  compressed,  that  of  the 


Fig.  470.— Right  half  of 
lower  jaw,  with  the  corre- 
sponding teeth.  The  letter 
and  numbers  point  to  the 
various  cusps  or  their  modifi- 
cations on  the  different  teeth 
(Burchard). 


THE    TEETH. 


873 


first  upper  bicuspid  being  frequently  bifid.  The  first  upper  bicuspid  is  usually  the 
largest  of  the  series. 

The  molar  teeth  (multicuspidati ;  or  grinders)  are  the  largest  teeth  of  the  den- 
ture. They  are  adapted  by  their  forms  for  the  crushing  and  grinding  of  the  food. 
They  are  twelve  in  number,  six  in  each  jaw,  three  being  placed  posterior  to  each 
second  bicuspid. 

The  crowns  are  cuboidal  in  form,  are  convex  buccally  and  lingually ;  they  are 
flattened  mesially  and  distally.  They  are  formed  by  the  fusion  of  three  primitive 
cuspids  in  the  upper  and  four  in  the  lower.  To  these  are  added  in  the  first  and 
second  upper  molars  a  disto-lingual  tubercle,  and  in  the  first  and  third  molars  of 
the  lower  jaw  a  disto-buccal  tubercle.  The  unions  of  the  primitive  forms  are 
marked  by  sulci.      The  necks  of  these  teeth  are  large  and  rhomboidal  in  form. 

The  roots  of  the  upper  molars  are  three  in  number — one  large  lingual  and  two 
smaller  buccal  roots.  In  the  lower,  two  roots  are  found,  a  mesial  and  a  distal,  each 
of  which  is  much  flattened  from  before  backward. 

The  first  molar  teeth  are  the  largest  of  the  dental  series  :  they  have  four  cusps 
on  the  upper  and  five  in  the  lower — three  buccal  and  two  lingual. 

The  second  molars  are  smaller ;  the  crown  of  the  upper  is  compressed  until  the 
disto-lingual  cusp  is  reduced.  The  crowns  of  the  lower  are  almost  rectangular,  with 
a  cusp  at  each  angle. 

The  third  molars  are  called  the  wisdom  teeth  (dentes  sajnentiaf)  from  their  late 
eruption  :  they  have  three  cusps  upon  the  upper  and  five  upon  the  lower.  The 
three  roots  of  the  upper  are  frequently  fused  together,  forming  a  grooved  cone, 
which  is  usually  curved  backward.  The  roots  of  the  lower,  two  in  number,  are 
compressed  together  and  curve  backward. 


Temporary  Teeth  (Figs.  467  and  471) 

The  temporary  or  milk  teeth  are  smaller,  but 
resemble  in  form  those  of  the  permanent  set.  The 
neck  is  more  marked,  owing  to  the  greater  degree 
of  convexity  of  the  labial  and  lingual  surfaces  of 
the  crown.  The  hinder  of  the  two  temporary  mo- 
lars is  the  largest  of  all  the  deciduous  teeth,  and  is 
succeeded  by  the  second  bicuspid.  The  first  upper 
molar  has  only  three  cusps — two  labial,  one  lin- 
gual ;  the  second  upper  molar  has  four  cusps.  The 
first  lower  molar  has  four  cusps ;  the  second  lower 
molar  has  five.  The  roots  of  the  temporary  molar 
teeth  are  smaller  and  more  divergincp  than  those 
of  the  permanent  set,  but  in  other  respects  bear  a 
strong  resemblance  to  them. 


Right  upper. 


Deciduous  teeth. 


Arrangement  of  the  Teeth.1 

The  human  teeth  are  arranged  in  two  parabolic  arches,  the  upper  arch  being 
larger,  its  teeth  overlapping  the  lower.  The  average  distance  between  the  centres 
of  the-  condyles  of  the  inferior  maxillary  bones  is  about  four  inches,  which  is  also 
the  distance  from  either  of  these  points  to  the  line  of  junction  between  the  lower 
incisor  teeth.  Whether  the  jaw  be  large  or  small,  the  equilateral  triangle  indicated 
is  included  in  it ;  the  range  of  size  is  between  %\"— ^\" ■ 

Owing  to  the  smaller  sizes  of  the  lower  incisors,  the  teeth  of  the  lower  jaw  are 
each  one  half  a  tooth  in  advance  of  its  upper  fellow,  so  that  each  tooth  of  the  dental 
series  has  two  antagonists,  with  the  exception  of  the  lower  central  incisors  and 
upper  third  molars  (Figs.  472,  473). 

The  grinding  faces  of  the  upper  bicuspids  and  molars  curve  progressively  up- 
ward and  point  outward,  the  first  molar  being  at  the  lowest  point  of  the  curve, 

1  After  Dr.  W.  G.  A.  Bonwill. 


874 


THE    ORGANS    OF  DIGESTION. 


the  third  molar  at  the  highest.  The  curve  of  the  lower  dental  arch  is  the  reverse, 
the  first  molar  at  its  deepest  part,  the  third  molar  at  its  extremity.  The  greater 
the  depth  to  which  the  upper  incisors  overlap  the  lower,  the  more  marked  this 
curve  and  the  more  pointed  are  the  cusps  of  the  grinding  teeth. 


Fig.  472.— View  of  teeth  in  situ,  with  the  external  plates  of  the  alveolar  processes  removed  (Cryer). 

The  movement  of  the  human  mandible  is  forward  and  downward,  the  resultant 
of  these  directions  being  an  oblique  line,  upon  an  average  35°  from  the  horizontal 

plane.1  When  the  lower 
jaw  is  advanced  until  the 
cutting  edges  of  the  in- 
cisors are  in  contact,  the 
jaws  are  separated,  but 
as  the  highest  point  of 
the  lower  arch,  its  third 
molar  advances,  it  meets 
and  rests  upon  a  high 
point,  second  molar  of  the 
upper  arch,  and  thus  un- 
due strain  of  the  incisors 
is  obviated. 

In  the  lateral  move- 
ments of  the  mandible  but 
one  side  is  in  effective  action 
at  one  time ;  the  oblique 
positions  of  the  cusps  of 
the  opposite  teeth  are  such 
that  when  either  side  is  in  action  the  other  is  balanced  at  two  or  more  points. 

1  W.  E.  Walker,  Denial  Cosmos,  1896. 


<. 


Fig.  473.— Front  and  side  views  of  the  teeth  and  jaws. 


STRUCTURE    OF    THE    TEETH. 


875 


There  is  an  anatomical  correspondence  between  the  forms  and  arrangement 
of  the  teeth,  the  form  of  the  condyle  of  the  inferior  maxilla,  and  the  mus- 
cular arrangement.  Individuals  who  have  teeth  with  long  cusps  have  the  head 
of  the  bone  much  rounded  from  before  behind,  and  have  a  preponderance  of 
the  direct  over  the  oblique  muscles  of  mastication,  and  vice  versd ;  teeth  with 
short  or  no  cusps  are  associated  with  a  flattened  condyle  and  strong  oblique 
muscles. 

Very  great  aberrations  in  the  dental  arrangement  are  frequently  followed  by 
accomodative  changes  in  the  heads  of  the  inferior  maxilla. 


Structure  of  the  Teeth. 

The  Dental  Pulp. — A  longitudinal  section  of  a  tooth  will  show  the  presence  of  a 
central  chamber  having  the  general  form  of  the  crown  of  the  tooth.  Processes  of 
the  chamber  pass  from  its  body,  one  for  each  root  and  down  each  root,  and  open  at 


Pulp 

cavity. 


Fig.  474. — Vertical  section  of  a  molar  tooth, 

the  apex  by  a  minute  orifice,  the  apical 
foramen.  This  cavity  is  known  as  the 
pulp-chamber,  the  minute  canals  the 
pulp-canals.  The  cavity  contains  a  soft, 
vascular,  and  sensitive  organ  called  the 
dental  pulp.  It  is  made  up  of  myxoma- 
tous tissues,  and  contains  numerous  blood- 
vessels and  nerves,  which  enter  by  way 
of  the  apical  foramina.  It  does  not  pos- 
sess lymphatics.  The  periphery  of  the 
pulp  is  bounded  by  a  layer  of  cells  ar- 
ranged like  columnar  epithelium,  each 
cell  sending  one  or  more  branched  pro- 
cesses through  the  basic  substance  of  the 
dentine.  These  are  the  dentine-forming 
cells,  the  odontoblasts  of  Waldeyer.  The 
blood-vessels  break  up  into  innumerable 
capillary  loops  which  lie  beneath  the 
layer  of  odontoblasts.  The  nerve-fibrils 
break  up  into  numberless  non-medullary 
filaments,  which  spread  out  beneath  the 
odontoblasts,  and  probably  send  terminal 
filaments  to  the  extreme  periphery  of  the 
pulp  outside  the  odontoblasts. 

The  matrix  cells  and  their  processes 
are  irregularly  arranged  in  the  body  of 
the  pulp,  but  in  the  canal  portion  the 
fibrillse  are  in  the  direction  of  the  axis 
of  the  root. 

The  section  will  exhibit  three  hard  tissues  in  a  tooth,  one  forming  the  greater 
mass  of  the  tooth ;  hence  its  name  dentine  (the  ivory).  The  dentine  upon  the 
crown  is  sheathed  by  a  layer  called  the  enamel ;  the  dentine  of  the  root  is  enclosed 


Fig.  475.— Vertical  section  of  a  tooth  in  situ  U5 
diameters),  c  is  placed  in  the  pulp-cavity,  opposite 
the  cervix  or  neck  of  the  tooth ;  the  part  above  is  the 
crown,  that  below  is  the  root  (fang).  1.  Enamel  with 
radial  and  concentric  markings.  2.  Dentine  with 
tubules  and  incremental  lines.  :5.  Cement  <>r  crusta 
petrosa,  with boi.  corpuscles.  4.  Dental  periosteum. 
5.  Bone  of  lower  jaw. 


876 


THE    0BQAN8    OF  DIGESTION. 


in  a  distinct  tissue,  the  cementum  or  crusta  petrosa ;  both  cementum  and  enamel  are 
thinnest  at  the  neck  and  thickest  upon  their  distal  portions. 

The  solid  portion  of  the  tooth  consists  of  three  distinct  structures — viz.  the 
proper  dental  substance,  which  forms  the  larger  portion  of  the  tooth,  the  ivory  or 

dentine;  a  layer  which  covers  the 
exposed  part  of  the  crown,  the 
enamel ;  and  a  thin  layer,  which  is 
disposed  on  the  surface  of  the  fang, 
the  cement  or  crusta  petrosa. 

The  ivory,  or  dentine  (Fig.  475), 
forms  the  principal  mass  of  a  tooth ; 
in  its  central  part  is  the  cavity  en- 
closing   the    pulp.     It   is    a    modi- 
j  fication    of    osseous     tissue,    from 

which  it  differs,  however,  in  struc- 
ture. On  microscopic  examination 
it  is  seen  to  consist  of  a  number 
of  minute  wavy  and  branching 
tubes  having  distinct  parietes. 
They  are  called  the  dentinal  tu- 
bulin and  are  imbedded  in  a  dense 
homogeneous  substance,  the  inter- 
tubular  tissue. 

The  dentinal  tubuli  (Fig-  476) 
are  placed  parallel  with  one  an- 
other, and  open  at  their  inner  ends 
into  the  pulp-cavity.  In  their 
course  to  the  periphery  they  present 
two  or  three  curves,  and  are  twisted 
on  themselves  in  a  spiral  direc- 
tion. The  direction  of  these  tubes 
varies :  they  are  vertical  in  the  up- 
per portion  of  the  crown,  oblique 
in  the  neck  and  upper  part  of  the  root,  and  toward  the  lower  part  of  the  root 
they  are  inclined  downward.  The  tubuli,  at  their  commencement,  are  about 
-j-fW  of  an  inch  in  diameter ;  in  their  course  thev  divide  and  subdivide  dichoto- 
mously,  so  as  to  give  to  the  cut  surface  of  the  dentine  a  striated  appearance. 
From  the  sides  of  the  tubes,  especially  in  the  root,  ramifications  of  extreme 
minuteness  are  given  off,  which  join  together  in  loops  in  the  intertubular  sub- 
stance, or  terminate  in  small  dilatations,  from  which  branches  are  given  off. 
Near  the  periphery  of  the  dentine  the  finer  ramifications  of  the  tubuli  terminate 
in  a  layer  of  irregular  branched  spaces  which  communicate  with  each  other. 
These  are  called  the  interglobular  spaces  of  Czermak,  or  the  granular  layer  of 
Tomes  (Fig.  476,  J).  The  dentinal  tubuli  have  comparatively  thick  walls,  and  con- 
tain slender  cylindrical  prolongations  from  the  processes  of  the  cells  of  the  pulp- 
tissue  already  mentioned,  and  first  described  by  Mr.  Tomes  and  named  Tomes's 
fibres  or  dentinal  fibres.  These  dentinal  fibres  are  analogous  to  the  soft  contents 
of  the  canaliculi  of  bone.  Between  Tomes's  fibres  and  the  ivory  around  the  canals 
there  is  a  tissue  which  is  markedly  resistant  to  the  action  of  acids — the  dentinal 
sheath  of  Neumann. 

The  intertubular  substance  or  tissue  is  translucent,  and  contains  the  chief  part 
of  the  earthy  matter  of  the  dentine.  After  the  earthy  matter  has  been  removed 
by  steeping  a  tooth  in  weak  acid  the  animal  basis  remaining  may  be  torn  into 
laminae  which  run  parallel  with  the  pulp-cavity  across  the  direction  of  the  tubules. 
These  laminae  show  the  method  of  growth  to  be  by  deposition  of  successive  strata 
of  dentine.  Fibrils  have  been  found  in  the  matrix  of  the  intertubular  substance, 
and  are  probably  continuous  with  the  dentinal  fibres  of  Tomes.     In  a  dry  tooth  a 


FIG.  476.— Ground  section  through  the  root  of  a  human 
premolar:  D,  dentine  ;  K,  cement  corpuscles  ;  O,  osteoblasts ; 
Ep.,  remains  of  Hertwig's  epithelial  sheath,  200  diameters; 
J,  interglobular  spaces  (Rose). 


STRUCTURE    OF   THE    TEETH. 


(I 


section  of  dentine  often  displays  a  series  of  lines — the  incremental  lines  of  Salter — 
which  are  parallel  with  the  laminae  above  mentioned.  These  lines  are  caused  by 
two  facts :  (1)  The  imperfect  calcification  of  the  dentinal  laminae  immediately 
adjacent  to  the  line;  (2)  The  drying  process,  which  reveals  these  defects  in  the 
calcification.  These  lines  are  wide  or  narrow  according  to  the  number  of  laminae 
involved,  and  along  their  course,  in  consequence  of  the  imperfection  in  the  calci- 
fying process,  little  irregular  cavities  are  left,  which  are  the  interglobular  spaces 
already  referred  to.  They  have  received  their  name  from  the  fact  that  they  are 
surrounded  by  minute  nodules  or  globules  of  dentine.  Other  curved  lines  may 
be  seen  parallel  to  the  surface.  These  are  the  lines  of  Schreger,  and  are  due  to 
the  optical  effect  of  simultaneous  curvature  of  the  dentinal  tubules. 

Chemical  Composition. — According  to  Berzelius  and  Bibra,  dentine  consists  of 
28  parts  of  animal  and  72  of  earthy  matter.  The  animal  matter  is  resolvable  by 
boiling  into  gelatin.  The  earthy  matter  consists  of  phosphate  and  carbonate  with 
calcium,  with  a  trace  of  fluoride  of  calcium,  phosphate  of  magnesia,  and  other 
salts. 

The  enamel  is  the  hardest  and  most  compact  part  of  a  tooth,  and  forms  a  thin 
crust  over  the  exposed  part  of  the  crown  as  far  as  the  commencement  of  the  root. 
It  is  thickest  on  the  grinding  surface  of  the  crown  until  worn  away  by  attrition, 
and  becomes  thinner  toAvard  the  neck.  It  consists  of  a  congeries  of  minute 
hexagonal  rods,  columns,  or  prisms.  They  lie  parallel  with  one  another,  resting 
by  one  extremity  upon  the  dentine,  which  presents  a  number  of  minute  depres- 
sions for  their  reception,  and  forming  the  free  surface  of  the  crown  by  the  other 
extremity.     These   fibres  are    directed  vertically  on  the  summit  of  the  crown, 


Fig.  477.— Enamel  prisms  (350  diameters).   A.  Fragments  and  single  fibres  of  the  enamel  isolated  by  the  action, 
of  hydrochloric  acid.    B.  Surface  of  a  small  fragment  of  enamel,  showing  the  hexagonal  ends  of  the  fibres. 

horizontally  at  the  sides ;  they  are  about  the  5-5V0  of  an  inch  in  diameter,  and 
pursue  a  more  or  less  wavy  course.  Each  enamel  rod  is  crossed  by  a  series  of 
dark  transverse  lines,  which  mark  the  mode  of  the  formation  of  the  rods  (Fig. 
477).  Another  series  of  lines,  having  a  brown  appearance,  and  denominated  the 
parallel  strice  of  Hetzius,  or  the  colored  lines,  are  seen  on  a  section  of  the  enamel. 
These  lines  are  concentric  and  cross  the  enamel  rods.  They  are  caused  by  the 
mode  of  enamel  deposition.  Inasmuch  as  the  enamel  columns,  when  near  the  den- 
tine, cross  each  other  and  only  become  parallel  farther  away,  a  series  of  radial 
markings,  light  and  dark   alternately,  is  obtained  (Fig.  475). 

Numerous  minute  interstices  intervene  between  the  enamel-fibres  near  their 
dentinal  surface.  It  is  noted  in  rare  cases  that  the  dentinal  fibres  penetrate 
a  certain  distance  between  the  rods  of  the  enamel.  No  nutritive  canals  exist 
in  the  enamel. 

Chemical  Composition. — According  to  Bibra,  enamel  consists  of  96.5  per  cent, 
of  earthy  matter  and  3.5  per  cent,  of  animal  matter.     The  earthy  matter  consists 


878  THE    ORGANS    OF  DIGESTION. 

of  the  phosphate  with  the  carbonate  of  calcium,  with  traces  of  fluoride  of  calcium, 
phosphate  of  magnesia,  and  other  salts. 

The  cortical  substance,  or  cementum  {crusta  petrosa),  is  disposed  as  a  thin  layer 
on  the  roots  of  the  teeth,  from  the  termination  of  the  enamel  as  far  as  the  apex  of 
the  root,  where  it  is  usually  very  thick.  In  structure  and  chemical  composition 
it  resembles  bone.  It  contains,  sparingly,  the  lacunae  and  canaliculi  which 
characterize  true  bone ;  the  lacunae  placed  near  the  surface  have  the  canaliculi 
radiating  from  the  side  of  the  lacunae  toward  the  periodontal  membrane,  dental 
periosteum,  and  those  more  deeply  placed  join  with  adjacent  dentinal  tubuli.  In 
the  thicker  portions  of  the  crusta  petrosa  the  lamellae  and  Haversian  canals  pecu- 
liar to  bone  are  also  occasionally  found. 

As  age  advances  the  cement  increases  in  thickness,  and  gives  rise  to  those  bony  growths,  or 
exostoses,  so  common  in  the  teeth  of  the  aged  ;  the  pulp-cavity  becomes  also  partially  filled  up 
by  a  hard  substance  intermediate  in  structure  between  dentine  and  bone  {osteo-dentine,  Owen  ; 
secondary  dentine,  Tomes).  It  is  formed  by  the  odontoblasts,  the  dental  pulp  lessening  in 
volume. 

Development  of  the  Teeth. 

The  teeth  are  an  evolution  from  the  dermoid  system,  and  not  of  the  bony  skele- 
ton :  they  are  developed  from  two  of  the  blastodermic  layers,  the  epiblast  and 
mesoblast.  From  the  former  the  enamel  is  developed,  from  the  latter  the  dental 
pulp,  dentine,  cementum,  and  pericementum.  It  is  customary  to  view  the  develop- 
ment of  the  permanent  and  temporary  teeth  as  separate  studies. 

The  earliest  evidence  of  tooth-formation  in  the  human  embryo  is  observed  in 
about  the  seventh  week.  The  mucous  membrane  covering  the  embryonic  jaws  is 
seen  to  rise  as  a  longitudinal  ridge  along  the  summit  of  each  jaw.1  A  transverse 
section  through  the  jaws  will  show  the  elevation  to  be  due  to  a  linear  and  outlined 
activity  of  the  germinal  epithelial  layer:  a  corresponding  epithelial  growth  is  seen 
to  sink  as  a  band  into  the  mesoblastic  tissue  beneath.  The  local  cell-activity  con- 
tinues, and  in  its  descent  the  band  appears  to  meet  with  a  resistance  which  causes  a 
flattening  of  its  extremity  into  a  continuous  lamina.  From  the  inner  (toward  the 
tongue)  edge  of  the  lamina  epithelial  cords  are  given  off,  ten  in  number,  one  for 
each  temporary  tooth. 

The  growth  of  each  cord  continues,  and  each  expands  into  a  flask -like  form,  the 
walls  covered  by  a  layer  of  germinal  cells,  its  interior  by  swollen  mature  cells. 
The  ingrowing  bulb  is  now  seen  to  flatten  upon  its  lower  surface,  as  though  it  had 
met  with  an  outlined  resistance  from  the  mesoblastic  tissue  beneath.  The  epithelial 
ingrowth  assumes  the  general  form  of  the  several  teeth  ;  it  is  the  enamel-organ  of 
the  tooth  (Fig.  478).  At  this  period  the  mesoblastic  tissue  around  each  enamel- 
organ  is  seen  to  become  differentiated  into  fibrous  tissue  surrounding  the  enamel- 
organs,  but  at  some  distance  from  them.  Islets  of  bone  are  also  seen  to  be  forming 
the  beginning  of  the  bony  maxillae. 

The  indentation  of  the  base  of  the  enamel-organ  continues  until  it  assumes 
the  form  of  the  future  teeth.  The  cells  bounding  the  organ  assume  a  cylin- 
drical form ;  the  cells  of  the  interior  become  much  expanded,  irregular  in  size 
and  form. 

The  mesoblastic  tissue  underlying  the  enamel-organ  is  much  condensed  ;  evi- 
dences of  cellular  differentiation  and  a  vascular  system  appear.  Bone  continues  to 
develop  until  all  of  the  tooth-follicles  are  embraced  in  a  gutter  of  bone.  From  the 
lingual  side  of  the  cords  of  the  temporary  teeth  epithelial  buds  are  given  off,  which 
sink  into  the  mesoblastic  tissue  and  form  the  enamel-organs  of  the  permanent  teeth. 
The  condensation  of  fibrous  tissue  continues  until  each  embryonic  tooth  is  enveloped 
in  a  sac,  the  dental  sac ;  this,  together  with  all  of  its  contents,  is  called  the  dental 
follicle. 

The  cells  of  the  enamel-organ  now  undergo  a  series  of  differentiations  :  the 
inner  layer  is  arranged  as  columnar  epithelium,  and  is  called  the  ameloblastic  or 

1  The  maxillary  rampart  of  Kolliker  Waldeyer. 


THE   DEVELOPMENT    OF    THE    TEETH. 


879 


enamel-forming  layer  (Figs.  479  and  480).      The  cells  of  the  outer  wall  remain 
cuboidal ;  the  cells  which  lie  between  become  much  distended,  and  on  account  of 


Fig.  478.— Diagram  of  method  of  development  of  the  teeth.  1.  Early  stage.  4.  Later  stage.  2,  3.  Interme- 
diate stages.  «.  Common  dental  germ.  o.  Special  dental  germ  (milk),  o'.  Special  dental  germ  (permanent). 
p.  Papilla,    e.  Dental  furrow.    (Gegenbaur.) 

their  appearance  when  seen  in  section  this  portion  of  the  organ  is  called  the  stellate 
reticulum  (the  enamel-jelly).  The  layer  of  cells  immediately  contiguous  to  the 
ameloblasts  form  a  layer  called  the  stratum  intermedium  (Fig.  480A — D). 

The  enclosed  mesoblastic  papilla  (the  future  dental  pulp)  has  its  peripheral  cells 
differentiated  into  columnar  bodies  disposed  as  a  layer,  each  cell  having  a  large 


Dental  furrow 


Remains  of  '-'neck"  of 
enamel  organ,  or  of  the~ 
common  dental  germ 


Permanent  special 

dental  germ 


Meckel's  cartilage 


Internal  enamel  layer, 
or  adamantoblusts 


Dental  sac 

Enamel  pulp 
External  enamel 
layer 
Papilla 


Lower  jaw. 


Fig.  479. — "Vertical  section  of  the  inferior  maxilla  of  an  early  human  fcetus.    (Magnified  25  diameters.) 

nucleus.  The  vascular  supply  of  the  pulp  is  now  well  marked.  A  section  of  a 
follicle  at  this  period  will  exhibit  the  follicular  wall  springing  from  the  base  of  the 
dental  papilla  and  having  a  well-marked  blood-supply.  The  bony  alveolar  walls 
are  well  outlined,   and  evidences  of  a  periosteum  appear  (Figs.  479  and  480). 

Development  of  Enamel. — In  point  of  time,  the  deposition  of  dentine  actually 
begins  before  that  of  enamel,  so  that  the  first-formed  layer  of  enamel  is  deposited 
against  a  layer  of  immature  dentine.  The  enamel  is  built  up  of  two  distinct  sub- 
stances— globules  of  uniform  size  which  are  formed  by  the  ameloblasts,  and  a 
cementing  substance,  probably  an  albuminate  of  calcium  (calco-globulin),  the  basis 
of  all  the  calcified  tissues.  At  the  ends  of  the  ameloblasts,  next  to  the  dentine, 
the  secretion  calco-globulin  is  deposited,  and  into  the  plastic  mass  the  enamel- 
globules  are  extruded,  each  globule  remaining  connected  with  the  ameloblasts  by 
plasmic  strings,  which  also  join  the  globules   laterally.1 

The  first  deposit  of  enamel  begins  in  the  tips  of  the  cusps,  and  is  quickly  fol- 
lowed by  a  disappearance  of  the  stellate  reticulum  at  that  point ;  the  stellate  retic- 
ulum now  appears  to  atrophy,  so  that  the  vascular  follicular  wall  is  brought  into 
direct  apposition  with  the  stratum  intermedium,  which  becomes  differentiated  into  a 
glandular  (secreting)  tissue  which  elaborates  the  calcic  albuminous  basis  of  the 
enamel.  The  secretion  passes  from  the  cells  of  the  stratum  intermedium  through  a 
membrane  into  the  ameloblasts,   where  it  is  in  part  combined  with  the  cellular 

1  J.  L.  Williams,  Dental  Cosmos,  1896. 


880 


THE    ORGANS    OF  DIGESTION. 


globules,  and  irregular  masses  of  it  extruded  as  cementing  substance.  The  deposi- 
tion continues  until  the  enamel-cap  has  its  typical  form.  The  deposition  of  the 
layers  of  globules  is  indicated  by  parallel  lines  transverse  to  the  axes  of  the  enamel- 


Fig.  480. — A.  Section  through  tooth-follicle — huniau  canine 7A months:  A,  follicular  wall ;  B,  outer  epithelial 
coat ;  G,  stellate  reticulum  ;  D,  stratum  intermedium ;  E,  ameloblasts  ;  F,  odontoblasts  ;  G,  pulp. 

B.  Diagram  after  Williams  (Dental  Cosmos,  1896),  mode  of  enamel  deposition  :  A,  blood  supply  to  B,  secreting 
papillte ;  C,  layer  of  ameloblasts  containing  enamel  globules  and  droplets  of  calcoglobulin  ;  D,  enamel-globules 
deposited ;  E,  formed  dentine ;  F,  forming  dentine ;  67,  layer  of  odontoblasts ;  if,  blood  supply  to  odonto- 
blastic layer. 

rods.     At  the  completion  of  amelification  the  ameloblasts  are  partially  calcified  and 
form  the  cuticula  dentis  or  Nasmyth's  membrane. 

Formation  of  Dentine. — The  layer  of  columnar  cells  bounding  the  periphery  of 
the  pulp  (the  odontoblasts)  are  in  apposition  "with 
a  plexus  of  capillary  vessels  (Fig.  480,  A).  Each 
cell  is  a  secreting  body  which  selects  the  mate- 
rial for  dentine-building.  Against  the  layer  of 
ameloblasts  covering  the  dental  papilla  the  odon- 
toblasts deposit  globules  of  the  calcium  albu- 
minate, and,  receding  as  the  deposits  are  made, 
leave  one  or  more  protoplasmic  processes  in 
the  calcic  deposit  (Tomes's  fibres).  The  process 
continues  until  the  normal  dentine  thickness  is 
formed.  The  deposit  is  laid  down  in  a  scaffold- 
ing of  finely  fibrillated  tissue.  The  layer  of 
formative  cells  remains  constant. 

Formation  of  Cementum. — Hertwig  asserts 
that  the  epithelial  edge  of  the  enamel-organ 
formed  by  the  inner  and  outer  epithelial  layers 
of  the  organ  grows  downward,  or  rather  the 
developing  tooth  grows  upward  until  the  future  root-form  of  the  tooth  is  outlined 
by  a  double  layer  of  epithelial  cells  (the  root-sheath  of  Hertwig).  The  growth  of 
alveolar  process  is  synchronous. 

Upon  the  pulp  side  of  the  sheath  a  layer  of  odontoblasts  is  developed  ;  upon 
the  outer  side  the  fibrous  encasement  becomes  closely  attached  to  the  sheath  and  a 
layer  of  osteogenetic  cells  (cementoblasts)  is  differentiated.  The  growth  of  the 
dentine  of  the  root  is  the  same  as  in  the  crown.  The  epithelial  sheath  undergoes 
atrophic  changes,  leaving  epithelial  whorls  which  remain  in  the  pericementum. 
The  cementum  is  developed  as  subperiosteal  bone.  The  cementum  over  the  apex 
of  the  root  is  not  formed  until  after  the  eruption  of  the  tooth. 

Formation  of  Alveoli. — By  the  time  the  crowns  of  the  teeth  have  formed,  each 


Fig.  481. — Part  of  section  of  developing 
tooth  of  young  rat,  showing  the  mode  of 
deposition  of  the  dentine  (highly  magni- 
fied), a.  Outer  layer  of  fully-calcified  den- 
tine. 6.  Uncaicified  matrix  with  si  few  nod- 
ules of  calcareous  matter,  c.  Odontoblasts- 
with  processes  extending  into  the  dentine. 
d.  Pulp.  The  section  is  stained  with  car- 
mine, which  colors  the  uncaicified  matrix, 
but  not  the  calcified  part. 


THE   DEVELOPMENT   OF    THE    TEETH  881 

is  enclosed  in  a  loculus  of  bone  which  has  developed  around  it  and  at  some  distance 
from  it;  the  loculus  is  open  at  the  top  toward  the  gums,  where  it  is  closed  by 
fibrous  tissue ;  the  developing  permanent  tooth  is  contained  in  the  same  loculus, 
but  is  later  separated  from  the  temporary  tooth  by  a  growth  of  bone.  The  alveolar 
process  is  not  completed  until  after  the  eruption  of  the  teeth.  During  eruption 
that  portion  of  the  process  overlying  the  crown  undergoes  absorption,  and  as  soon 
as. the  immature  tooth  has  erupted  the  alveolar  process  is  developed  about  the  root, 
whose  formation  is  also  completed  after  eruption. 

Development  of  the  Permanent  Teeth. — The  permanent  teeth  as  regards  their 
development  may  be  divided  into  two  sets :  (1)  those  which  replace  the  temporary 
teeth,  and  which,  like  them,  are  ten  in  number :  these  are  the  successional  per- 
manent teeth;  and  (2)  those  which  have  no  temporary  predecessors,  but  are 
superadded  at  the  back  of  the  dental  series.  These  are  three  in  number  on  either 
side  in  each  jaw,  and  are  termed  the  superadded  permanent  teeth.  They  are  the 
three  molars  of  the  permanent  set,  the  molars  of  the  temporary  set  being  replaced 
by  the  premolars  or  bicuspids  of  the  permanent  set. 

The  development  of  the  successional  permanent  teeth — the  ten  anterior  ones 
in  either  jaw — will  be  first  considered.  As  already  stated,  the  germ  of  each 
milk  tooth  is  a  special  thickening  of  the  "  free  "  edge  of  the  common  dental  germ 
or  dental  lamina.  In  like  manner  is  formed  the  special  dental  germ  of  each 
of  the  successional  permanent  teeth.  But  these  thickenings  are  not  at  the 
"free"  edge  of  the  dental  lamina,  but  occur  behind  and  lateral  to  each  of  the 
milk-tooth  germs  (Fig.  478).  There  are  ten  of  these,  and  they  appear  in  order, 
about  the  sixteenth  week,  on  each  side,  the  central  incisor  germs  being  the 
first. 

These  special  dental  germs  now  go  through  the  same  transformations  (and 
become  enamel-organs)  as  were  described  in  connection  Avith  those  of  the  milk 
teeth  ;  that  is,  they  recede  into  the  substance  of  the  gum  behind  the  germs  of  the 
temporary  teeth.  As  they  recede  they  become  flask-shaped,  form  an  expansion 
of  their  distal  extremity,  and  finally  meet  a  papilla,  which  has  been  formed  in 
the  mesoblast,  just  in  the  same  manner  as  was  the  case  in  the  temporary  teeth. 
The  apex  of  the  papilla  indentates  the  dental  germ,  which  encloses  it,  and  form- 
ing a  cap  for  it,  undergoes  analogous  changes  to  those  described  in  the  develop- 
ment of  the  milk  teeth,  and  becomes  converted  into  the  enamel,  whilst  the  papilla 
forms  the  dentine,  of  the  permanent  tooth.  In  its  development  it  becomes  en- 
closed in  a  dentinal  sac  which  adheres  to  the  bach  of  the  sac  of  the  temporary 
tooth.  The  sac  of  each  permanent  tooth  is  also  connected  with  the  fibrous  tissue 
of  the  gum  by  a  slender  band  or  gubernaculum,  which  passes  to  the  margin  of 
the  jaw  behind  the  corresponding  milk  tooth  (see  above). 

The  superadded  permanent  teeth — three  on  each  side  in  each  jaw — arise  from 
successive  extensions  backward — i.  e.  along  the  line  of  the  jaw — of  the  common 
dental  germ  from  the  back  part  of  the  special  dental  germ  of  the  immediately 
preceding  tooth.  During  the  fourth  month  or  seventeenth  week,  in  that  portion 
of  the  common  dental  germ  which  lies  behind — i.  e.  lateral  to  the  special  dental 
germ  of  the  last  temporary  molar  tooth,  and  which  has  hitherto  remained  unal- 
tered, there  is  developed  the  special  dental  germ  of  the  first  permanent  molar 
into  which  a  papilla  projects.  In  a  similar  manner,  about  the  fourth  month 
after  birth  the  second  molar  is  formed,  and  about  the  third  year  the  third 
molar. 

Eruption. — When  the  calcification  of  the  different  tissues  of  the  milk  tooth 
is  sufficiently  advanced  to  enable  it  to  bear  the  pressure  to  which  it  will  be  after- 
ward subjected,  its  eruption  takes  place,  the  tooth  making  its  way  through  the 
gum.  The  gum  is  absorbed  by  the  pressure  of  the  crown  of  the  tooth  against  it. 
which  is  itself  pressed  up  by  the  increasing  size  of  the  fang.  At  the  same  time 
the  septa  between  the  dentinal  sacs,  at  first  fibrous  in  structure,  ossify  and  thus 
form  the  loculi  or  alveoli ;  these  firmly  embrace  the  necks  of  the  teeth  and  afford 
them  a  solid  basis. 

56 


882 


THE    ORGANS    OF   DIGESTION. 


Previous  to  the  permanent  teeth  penetrating  the  gum,  the  bony  partitions 
which  separate  their  sacs  from  the  deciduous  teeth  are  absorbed,  the  roots  of 
the  temporary  teeth  disappear  by  absorption  through  the  agency  of  particular 
multinucleated  cells,  called  odontoclasts,  which  are  developed  at  the  time  in  the 
neighborhood  of  the  root,  and  the  permanent  teeth  become  placed  under  the 
loose  crown  of  the  deciduous  teeth ;  the  latter  finally  become  detached,  and  the 
permanent  teeth  take  their  place  in  the  mouth  (Fig.  482). 


Mi 


Fig.  482.— The  milk-teeth  in  a  child  of  about  four  years.    The  permanent  teeth  are  seen  in  their  alveoli. 

(Cryer.) 

Calcification  of  the  permanent  teeth  proceeds  in  the  following  order :  First 
molar,  soon  after  birth  ;  the  central  incisor,  lateral  incisor,  and  cuspid,  about  six 
months  after  birth  ;  the  bicuspids,  at  the  second  year  or  later ;  second  molar,  end 
of  second  year ;  third  molar,  about  the  twelfth  year. 

The  eruption  of  the  temporary  teeth  commences  at  the  seventh  month,  and  is 
complete  about  the  end  of  the  second  year. 

The  periods  for  the  eruption  of  the  temporary  set  are  (C.  S.  Tomes) — 

Lower  central  incisors 6  to    9  months. 

Upper  incisors 8  to  10 

Lower  lateral  incisors  and  first  molars  .        .       .        .  15  to  21 

Canines 16  to  20        " 

Second  molars ".       .       .  20  to  24 

The  eruption  of  the  permanent  teeth  takes  place  at  the  following  periods  the 
teeth  of  the  lower  jaw  preceding  those  of  the  upper  by  a  short  interval: 

6J  years,  first  molars.  10th  year,  second  bicuspid. 

7th  year,  two  middle  incisors.  11th  to  12th  year,  canine. 

8th  year,  two  lateral  incisors.  12th  to  13th  year,  second  molars. 

9th  year,  first  bicuspid.  17th  to  21st  year,  third  molars. 


THE   PALATE.  883 

THE  PALATE. 

The  palate  forms  thejoof  of  the  mouth  :  it  consists  of  two  portions,  the  hard 
palate  in  front,  the  soft  palate  behind. 

The  hard  palate  is  bounded  in  front  and  at  the  sides  by  the  alveolar  arches 
and  gums  ;  behind,  it  is  continuous  with  the  soft  palate.  It  is  covered  by  a  dense 
structure  formed  by  the  periosteum  and  mucous  membrane  of  the  mouth,  which 
are  intimately  adherent.  Along  the  middle  line  is  a  linear  ridge  or  raphe,  which 
terminates  anteriorly  in  a  small  papilla  corresponding  with  the  inferior  opening  of 
the  anterior  palatine  fossa.  This  papilla  receives  filaments  from  the  naso-palatine 
and  anterior  palatine  nerves.  On  either  side  and  in  front  of  the  raphe  the  mucous 
membrane  is  thick,  pale  in  color,  and  corrugated  ;  behind,  it  is  thin,  smooth,  and 
of  a  deeper  color :  it  is  covered  with  squamous  epithelium,  and  furnished  with 
numerous  glands  (palatal  glands),  which  lie  between  the  mucous  membrane  and 
the  surface  of  the  bone. 

The  soft  palate  {velum  pendulum  palati)  is  a  movable  fold  suspended  from  the 
posterior  border  of  the  hard  palate,  and  forming  an  incomplete  septum  between 
the  mouth  and  pharynx.  It  consists  of  a  fold  of  mucous  membrane  enclosing 
muscular  fibres,  an  aponeurosis,  vessels,  nerves,  adenoid  tissue,  and  mucous 
glands.  When  occupying  its  usual  position  (i.  e.  relaxed  and  pendent)  its  anterior 
surface  is  concave,  continuous  with  the  roof  of  the  mouth,  and  marked  by  a 
median  ridge  or  raphe,  which  indicates  its  original  separation  into  two  lateral 
halves.  Its  posterior  surface  is  convex,  and  continuous  with  the  mucous 
membrane  covering  the  floor  of  the  posterior  nares.  Its  upper  border  is  attached 
to  the  posterior  margin  of  the  hard  palate,  and  its  sides  are  blended  with  the 
pharynx.     Its  lower  border  is  free. 

Hanging  from  the  middle  of  its  lower  border  is  a  small,  conical-shaped 
pendulous  process,  the  uvula,  and  arching  outward  and  downward  from  the  base 
of  the  uvula  on  each  side  are  two  curved  folds  of  mucous  membrane,  containing 
muscular  fibres,  called  the  arches,  or  pillars  of  the  soft  palate,  or  pillars  of  the 
fauces. 

The  anterior  pillars  run  downward,  outward,  and  forward  to  the  sides  of  the 
base  of  the  tongue,  and  are  formed  by  the  projection  of  the  Palato-glossi  muscles, 
covered  by  mucous  membrane. 

The  posterior  pillars  are  nearer  to  each  other  and  larger  than  the  anterior ;  they 
run  downward,  outward,  and  backward  to  the  sides  of  the  pharynx,  and  are 
formed  by  the  projection  of  the  Palato-pharyngei  muscles,  covered  by  mucous 
membrane.  The  anterior  and  posterior  pillars  are  separated  below  by  a  triangular 
interval  in  which  the  tonsil  is  lodged. 

The  space  left  between  the  arches  of  the  palate  on  the  two  sides  is  called  the 
isthmus  of  the  fauces.  It  is  bounded,  above,  by  the  free  margin  of  the  soft  palate  ; 
below,  by  the  back  of  the  tongue  ;  and  on  each  side,  by  the  pillars  of  the  fauces 
and  the  tonsil. 

The  mucous  membrane  of  the  soft  palate  is  thin,  and  covered  with  squamous 
epithelium  on  both  surfaces,  excepting  near  the  orifice  of  the  Eustachian  tube, 
where  it  is  columnar  and  ciliated.1  Beneath  the  mucous  membrane  on  the  oral 
surface  of  the  soft  palate  is  a  considerable  amount  of  adenoid  tissue.  The  palatine 
glands  form  a  continuous  layer  on  its  posterior  surface  and  round  the  uvula. 

The  aponeurosis  of  the  soft  palate  is  a  thin  but  firm  fibrous  layer  attached  above 
to  the  posterior  border  of  the  hard  palate,  and  becoming  thinner  toward  the  free 
margin  of  the  velum.  Laterally,  it  is  continuous  with  the  pharyngeal  aponeurosis. 
It  forms  the  framework  of  the  soft  palate,  and  is  joined  by  the  tendon  of  the  Tensor 
palati  muscle. 

1  According  to  Klein,  the  mucous  membrane  on  the  nasal  surface  of  the  soft  palate  in  the  foetus 
is  covered  throughout  by  columnar  ciliated  epithelium,  which  subsequently  becomes  squamous;  and 
some  anatomists  state  that  it  is  covered  with  columnar  ciliated  epithelium,  except  at  its  free  margin, 
throughout  life. 


884  THE    ORGANS    OF  DIGESTION. 

The  muscles  of  the  soft  palate  are  five  on  each  side :  the  Levator  palati, 
Tensor  palati,  Azygos  uvulae,  Palato-glossus,  and  Palato-pharyngeus  (see  page  329). 
The  following  is  the  relative  position  of  these  structures  in  a  dissection  of  the  soft 
palate  from  the  posterior  or  nasal  to  the  anterior  or  oral  surface :  Immediately 
beneath  the  nasal  mucous  membrane  is  a  thin  stratum  of  muscular  fibres,  the 
posterior  fasciculus  of  the  Palato-pharyngeus  muscle,  joining  with  its  fellow  of 
the  opposite  side  in  the  middle  line.  Beneath  this  is  the  Azygos  uvulae,  consist- 
ing of  two  rounded  fleshy  fasciculi,  placed  side  by  side  in  the  median  line  of  the 
soft  palate.  Next  comes  the  aponeurosis  of  the  Levator  palati,  joining  with  the 
muscle  of  the  opposite  side  in  the  middle  line.  Fourthly,  the  anterior  fasciculus 
of  the  Palato-pharyngeus,  thicker  than  the  posterior,  and  separating  the  Levator 
palati  from  the  next  muscle,  the  Tensor  palati.  This  muscle  terminates  in  a  tendon 
which,  after  winding  round  the  hamular  process,  expands  into  a  broad  aponeurosis 
in  the  soft  palate,  anterior  to  the  other  muscles  which  have  been  enumerated. 
Finally,  we  have  a  thin  muscular  stratum,  the  Palato-glossus  muscle,  placed  in 
front  of  the  aponeurosis  of  the  Tensor  palati,  and  separated  from  the  oral  mucous 
membrane  by  adenoid  tissue. 

The  Tonsils  (amygdala?)  are  two  prominent  bodies  situated  one  on  each  side  of 
the  fauces,  between  the  anterior  and  posterior  pillars  of  the  soft  palate.  They  are 
of  a  rounded  form,  and  vary  considerably  in  size  in  different  individuals.  A 
recess,  the  fossa  supra-tonsillaris,  may  be  seen,  directed  upward  and  backward 
above  the  tonsil.  His  regards  this  as  the  remains  of  the  lower  part  of  the  second 
visceral  cleft.  It  is  covered  by  a  fold  of  mucous  membrane  termed  the  plica 
triangularis.  Externally  the  tonsil  is  in  relation  with  the  inner  surface  of  the 
Superior  constrictor,  to  the  outer  side  of  which  is  the  Internal  pterygoid  muscle. 
The  internal  carotid  artery  lies  behind  and  to  the  outer  side  of  the  tonsil,  and 
nearly  an  inch  (20  to  25  mm.)  distant  from  it.  It  corresponds  to  the  angle  of  the 
lower  jaw.  Its  inner  surface  presents  from  twelve  to  fifteen  orifices,  leading  into 
small  recesses,  from  which  numerous  follicles  branch  out  into  the  substance  of  the 
gland.  These  follicles  are  lined  by  a  continuation  of  the  mucous  membrane  of  the 
pharynx,  covered  with  epithelium  ;  around  each  follicle  is  a  layer  of  closed  cap- 
sules imbedded  in  the  submucous  tissue.  These  capsules  are  analogous  to  those  of 
Peyer's  glands,  consisting  of  adenoid  tissue.  No  openings  from  the  capsules  into 
the  follicles  can  be  recognized.  They  contain  a  thick  grayish  secretion.  Sur- 
rounding each  follicle  is  a  close  plexus  of  lymphatic  vessels.  From  these  plexuses 
the  lymphatic  vessels  pass  to  the  deep  cervical  glands  in  the  upper  part  of  the  neck, 
which  frequently  become  enlarged  in  affections  of  these  organs. 

The  arteries  supplying  the  tonsil  are  the  dorsalis  linguae  from  the  lingual,  the 
ascending  palatine  and  tonsillar  from  the  facial,  the  ascending  pharyngeal  from  the 
external  carotid,  the  descending  palatine  branch  of  the  internal  maxillary,  and  a 
twig  from  the  small  meningeal. 

The  veins  terminate  in  the  tonsillar  plexus,  on  the  outer  side  of  the 
tonsil. 

The  nerves  are  derived  from  Meckel's  ganglion  and  from  the  glosso-pharyngeal. 

THE  SALIVARY  GLANDS  (Fig.  483). 

The  principal  salivary  glands  communicating  with  the  mouth  and  pouring 
their  secretion  into  its  cavity  are  the  parotid,  submaxillary,  and  sublingual. 

The  parotid  gland,  so  called  from  being  placed  near  the  ear  (jtapd,  near ;  o5c, 
a»roc,  the  ear),  is  the  largest  of  the  three  salivary  glands,  varying  in  weight  from 
half  an  ounce  to  an  ounce.  It  lies  upon  the  side  of  the  face  immediately  below 
and  in  front  of  the  external  ear.  It  is  limited  above  by  the  zygoma ;  below,  by 
the  angle  of  the  jaw  and  by  a  line  drawn  between  it  and  the  mastoid  process: 
anteriorly,  it  extends  to  a  variable  extent  over  the  Masseter  muscle ;  posteriorly, 
it  is  bounded  by  the  external  meatus,  the  mastoid  process,  and  the  Sterno-mastoid 
and  Digastric  muscles,  slightly  overlapping  the  two  muscles. 


THE   SALIVARY    GLANDS. 


885 


Its  anterior  surface  is  grooved  to  embrace  the  posterior  margin  of  the  ramus  of 
the  lower  jaw,  and  advances  forward  beneath  the  ramus,  between  the  two  Pterygoid 
muscles  and  superficial  to  the  ramus  over  the  Masseter  muscle.  Its  outer  surface, 
slightly  lobulated,  is  covered  by  the  integument  and  parotid  fascia,  and  has  one  or 
two  lymphatic  glands  resting  on  it.  Its  inner  surface  extends  deeply  into  the  neck 
by  means  of  two  large  processes,  one  of  which  dips  behind  the  styloid  process  and 
projects  beneath  the  mastoid  process  and  the  Sterno-mastoid  muscle;  the  other  is 
situated  in  front  of  the  styloid  process,  and  passes  into  the  back  part  of  the  glenoid 
fossa,  behind  the  articulation  of  the  lower  jaw.  The  structures  passing  through 
the  parotid  gland  are — the  external  carotid  artery,  giving  off  its  three  terminal 
branches :  the  posterior  auricular  artery  emerges  from  the  gland  behind ;  the 
temporal  artery  above ;    the  transverse  facial,  a  branch  of  the  temporal,  in  front ; 


Fig.  483.— The  salivary  glands. 

and  the  internal  maxillary  winds  through  it  as  it  passes  inward,  behind  the  neck 
of  the  jaw.  Superficial  to  the  external  carotid  is  the  trunk  formed  by  the  union 
of  the  temporal  and  internal  maxillary  veins ;  a  branch,  connecting  this  trunk 
with  the  internal  jugular,  also  passes  through  the  gland.  It  is  also  traversed  by 
the  facial  nerve  and  its  branches,  which  emerge  at  its  anterior  border  ;  branches  of 
the  great  auricular  nerve  pierce  the  gland  to  join  the  facial,  and  the  auriculo- 
temporal branch  of  the  inferior  maxillary  nerve  emerges  from  the  upper  part  of  the 
gland.  The  internal  carotid  artery  and  internal  jugular  vein  lie  close  to  its  deep 
surface. 

The  duct  of  the  parotid  gland  (Stenson's)  is  about  two  inches  and  a  half  in 
length.  It  commences  by  numerous  branches  from  the  anterior  part  of  the  gland, 
crosses  the  Masseter  muscle,  and  at  its  anterior  border  dips  down  into  the  substance 
of  the  Buccinator  Tmis^le,  which  it  pierces;  it  then  runs  for  a  short  distance  obliquely 
forward  betwe  ,!'  .uccinator  and  mucous  membrane  of  the  mouth,  and  opens 
upon  the  innei  surface  of  the  cheek  by  a  small  orifice  opposite  the  second  molar 
tooth  of  the  upper  jaw.     While  crossing  the  Masseter  it  receives  the  duct  of  a  small 


886 


THE    ORGANS    OF  DIGESTION. 


detached  portion  of  the  gland,  socia  parotidis,  which  occasionally  exists  as  a  separate 
lobe,  just  beneath  the  zygomatic  arch.  In  this  position  it  has  the  transverse  facial 
artery  above  it  and  some  branches  of  the  facial  nerve  below  it. 

Structure. — The  parotid  duct  is  dense,  of  considerable  thickness,  and  its  canal 
about  the  size  of  a  crowquill,  but  at  its  orifice  on  the  inner  aspect  of  the  cheek  its 
lumen  is  greatly  reduced  in  size ;  it  consists  of  an  external  or  fibrous  coat,  of 
considerable  density,  containing  contractile  fibres,  and  of  an  internal  or  mucous 
coat  lined  with  short  columnar  epithelium. 

Surface  Form. — The  direction  of  the  duct  corresponds  to  a  line  drawn  across  the  face 
about  a  finger's  breadth  below  the  zygoma;  that  is,  from  the  lower  margin  of  the  concha  to 
midway  between  the  free  margin  of  the  upper  lip  and  the  ala  of  the  nose. 

Vessels  and  Nerves. — The  arteries  supplying  the  parotid  gland  are  derived  from 
the  external  carotid,  and  from  the  branches  given  off  by  that  vessel  in  or  near  its 
substance.  The  veins  empty  themselves  into  the  external  jugular  through  some 
of  its  tributaries.      The  lymphatics  terminate  in  the  superficial  and  deep   cervical 


Crescent  of  Gianuzzi. 

ir 

,1  r,/- 


i 

f*jB.Salivary  duct. 


Fig.  484.— A  highly  magnified  section  of  the  submaxillary  gland  of  the  dog,  stained  with  carmine.    (Kolliker.) 

glands,  passing  in  their  course  through  two  or  three  lymphatic  glands  placed  on 
the  surface  and  in  the  substance  of  the  parotid.  The  nerves  are  derived  from  the 
plexus  of  the  sympathetic  on  the  external  carotid  artery,  the  facial,  the  auriculo- 
temporal, and  great  auricular  nerves. 

It  is  probable  that  the  branch  from  the  auriculo-temporal  nerve  is  derived 
from  the  glosso-pharyngeal  through  the  otic  ganglion  (which  see).  At  all  events, 
in  some  of  the  lower  animals  this  has  been  proved  experimentally  to  be  the 
case. 

The  submaxillary  gland  is  situated  below  the  jaw,  in  the  anterior  part  of  the 
submaxillary  triangle  of  the  neck.  It  is  irregular  in  form  and  weighs  about  two 
drachms  (8-10  grammes).  It  is  covered  by  the  integument,  Platysma,  deep  cer- 
vical fascia,  and  the  body  of  the  lower  jaw,  corresponding  to  a  depression  on  the 
inner  surface  of  the  bone,  and  lies  upon  the  Mylo-hyoid,  Hyo-glossus,  and  Stylo- 
glossus muscles,  a  portion  of  the  gland  passing  beneath  the  posterior  border  of 
the  Mylo-hyoid.  In  front  of  it  is  the  anterior  belly  of  the  Digastric ;  behind,  it 
is  separated  from  the  parotid  gland  by  the  stylo-maxillary  ligament,  and  from  the 
sublingual  gland  in  front  by  the  Mylo-hyoid  muscle.  The  facial  artery  lies  im- 
bedded in  a  groove  in  its  posterior  and  upper  border. 

The  duct  of  the  submaxillary  gland  ( Wharton  s)  is  about  two  inches  in  length, 
and  its  walls  are  much  thinner  than  those  of  the  parotid  duct.  It  commences  by 
numerous  branches  from  the  deep  portion  of  the  gland  which  lies  on  the  upper 
surface  of  the  Mylo-hyoid  muscle,  and  passes  forward  and  inward  between  the 
Mylo-hyoid  and  the  Hyo-glossus  and  Genio-hyo-glossus  muscles,  then  between  the 
sublingual  gland  and  the  Grenio-hyo-glossus,  and  opens  by  a  narrow  orifice  on  the 


THE  SALIVARY   GLANDS.  887 

summit  of  a  small  papilla  at  the  side  of  the  frsenum  linguae.  On  the  Hyo-glossus 
muscle  it  lies  between  the  lingual  and  hypoglossal  nerves,  but  at  the  anterior  border 
of  the  muscle  it  crosses  under  the  lingual  nerve,  and  is  then  placed  above  it. 

Vessels  and  Nerves. — The  arteries  supplying  the  submaxillary  gland  are 
branches  of  the  facial  and  lingual.  Its  veins  follow  the  course  of  the  arteries. 
The  nerves  are  derived  from  the  submaxillary  ganglion,  through  which  it  receives 
filaments  from  the  chorda  tympani  of  the  facial  and  lingual  branch  of  the 
inferior  maxillai'y,  sometimes  from  the  mylo-hyoid  branch  of  the  inferior  dental, 
and  from  the  sympathetic. 

The  sublingual  gland  is  the  smallest  of  the  salivary  glands.  It  is  situated 
beneath  the  mucous  membrane  of  the  floor  of  the  mouth,  at  the  side  of  the  frsenum 
linguae,  in  contact  with  the  inner  surface  of  the  lower  jaw,  close  to  the  symphysis. 
It  is  narrow,  flattened,  in  shape  somewhat  like  an  almond,  and  weighs  about  a 
drachm.  It  is  in  relation,  above,  with  the  mucous  membrane  ;  beloiv,  with  the 
Mylo-hyoid  muscle;  in  front,  with  the  depression  on  the  side  of  the  symphysis  of 
the  lower  jaw,  and  with  its  fellow  of  the  opposite  side ;  behind,  with  the  deep 
part  of  the  submaxillary  gland ;  and  internally,  with  the  Genio-hyo-glossus, 
from  which  it  is  separated  by  the  lingual  nerve  and  Wharton's  duct.  Its 
exci'etory  ducts  {ducts  of  Rivinus),  from  eight  to  twenty  in  number;  some  join 
Wharton's  duct;  others  open  separately  into  the  mouth,  on  the  elevated  crest  of 
mucous  membrane  caused  by  the  projection  of  the  gland,  on  either  side  of  the 
fraenum  linguae.  One  or  more  join  to  form  a  tube  which  opens  into  the  Wharton- 
ian  duct ;  this  is  called  the  duct  of  BartJiolin. 

Vessels  and  Nerves. — The  sublingual  gland  is  supplied  with  blood  from  the 
sublingual  and  submental  arteries.     Its  nerves  are  derived  from  the  lingual. 

Structure  of  Salivary  (Hands. — The  salivary  are  compound  racemose  glands, 
consisting  of  numerous  lobes,  which  are  made  up  of  smaller  lobules  connected 
together  by  dense  areolar  tissue,  vessels,  and  ducts.  Each  lobule  consists  of  the 
ramifications  of  a  single  duct,  "branching  frequently  in  a  tree-like  manner,"  the 
branches  terminating  in  dilated  ends  or  alveoli,  on  which  the  capillaries  are 
distributed.  These  alveoli,  however,  as  Pfliiger  points  out,  are  not  necessarily 
spherical,  though  sometimes  they  assume  that  form ;  sometimes  they  are  perfectly 
cylindrical,  and  very  often  they  are  mutually  compressed.  The  alveoli  are  enclosed 
by  a  basement  membrane  which  is  continuous  with  the  membrana  propria  of  the 
duct.  It  presents  a  peculiar  reticulated  structure,  having  the  appearance  of  a 
basket  with  open  meshes,  and  consisting  of  a  network  of  branched  and  flattened 
nucleated  cells. 

The  alveoli  of  the  salivary  glands  are  of  two  kinds,  which  differ  both  in  the 
appearance  of  their  secreting  cells,  in  their  size,  and  in  the  nature  of  their 
secretion.  The  one  variety  secretes  a  ropy  fluid  which  contains  mucin,  and 
has  therefore  been  named  the  mucous,  whilst  the  other  secretes  a  thinner  and 
more  watery  fluid,  which  contains  serum-albumin,  and  has  been  named  serous 
or  albuminous.  The  sublingual  gland  may  be  regarded  as  an  example  of  the 
former  variety,  the  parotid  of  the  latter.  The  submaxillary  is  of  the  mixed 
variety,  containing  both  mucous  and  serous  alveoli,  the  latter,  however,  prepon- 
derating. 

Both  alveoli  are  lined  by  cells,  and  it  is  by  the  character  of  these  cells  that  the 
nature  of  the  gland  is  chiefly  to  be  determined.  In  addition,  howevei',  the  alveoli 
of  the  serous  glands  are  smaller  than  those  of  the  mucous  ones. 

The  cells  in  the  mucous  alveoli  are  spheroidal  in  shape,  glassy,  transparent,  and 
dimly  striated  in  appearance.  The  nucleus  is  usually  situated  in  the  part  of  the 
cell  Avhich  is  next  the  basement  membrane,  against  which  it  is  sometimes  flattened. 
The  most  remarkable  peculiarity  presented  by  these  cells  is,  thai  they  give  off  an 
extremely  fine  process,  which  is  curved  in  a  direction  parallel  to  the  surface  of  the 
alveolus,  lies  in  contact  with  the  membrana  propria,  and  overlaps  the  process  of 
neighboring  cells.  The  cells  contain  a  quantity  of  mucin,  to  which  their  clear, 
transparent  appearance  is  due. 


888  THE    ORGANS    OF  DIGESTION. 

Here  and  there  in  the  alveoli  are  seen  peculiar  half-moon-shaped  bodies  lying 
between  the  cells  and  the  membrana  propria  of  the  alveolus.  They  are  termed 
the  crescents  of  Gianuzzi  or  the  demilunes  of  Heidenhain  (Fig.  484),  and  are 
composed  of  polyhedral  granular  cells,  which  Heidenhain  regards  as  young  epi- 
thelial cells  destined  to  supply  the  place  of  those  salivary  cells  which  have  under- 
gone disintegration.     This  view,  however,  is  not  accepted  by  Klein. 

Serous  Alveoli. — In  the  serous  alveoli  the  cells  almost  completely  fill  the  cavity, 
so  that  there  is  hardly  any  lumen  perceptible.  Instead  of  presenting  the  clear, 
transparent  appearance  of  the  cells  of  the  mucous  alveoli,  they  present  a  granular 
appearance,  due  to  distinct  granules  of  an  albuminous  nature  imbedded  in  a  closely 
reticulated  protoplasm.  The  ducts  which  originate  out  of  the  alveoli  are  lined  at 
their  commencement  by  epithelium  which  differs  little  from  the  pavement  type. 
As  the  ducts  enlarge,  the  epithelial  cells  change  to  the  columnar  type,  and  the  part 
of  the  cell  next  the  basement-membrane  is  finely  striated.  The  lobules  of  the 
salivary  glands  are  richly  supplied  with  blood-vessels  which  form  a  dense  network 
in  the  interalveolar  spaces.  Fine  plexuses  of  nerves  are  also  found  in  the  inter- 
lobular tissue.  The  nerve-fibrils  pierce  the  basement-membrane  of  the  alveoli, 
and  end  in  branched  varicose  filaments  between  the  secreting  cells.  There  is  no 
doubt  that  ganglia  are  to  be  found  in  some  salivary  glands  in  connection  with  the 
nerve-plexuses  in  the  interlobular  tissue  ;  they  are  to  be  found  in  the  submaxillary, 
but  not  in  the  parotid. 

In  the  submaxillary  and  sublingual  glands  the  lobes  are  larger  and  more 
loosely  united  than  in  the  parotid. 

Mucous  Glands. — Besides  the  salivary  glands  proper,  numerous  other  glands 
are  found  in  the  mouth.  They  appear  to  secrete  mucus  only,  which  serves  to  keep 
the  mouth  moist  during  the  intervals  of  the  salivary  secretion,  and  Avhich  is  mixed 
with  that  secretion  in  swallowing.  Many  of  these  glands  are  found  at  the  posterior 
part  of  the  dorsum  of  the  tongue,  behind  the  circumvallate  papillae,  and  also  along 
its  margins  as  far  forward  as  the  apex.1  Others  lie  around  and  in  the  tonsil 
between  its  crypts,  and  a  large  number  are  present  in  the  soft  palate.  These 
glands  are  of  the  ordinary  compound  racemose  type. 

Surface  Form. — The  orifice  of  the  mouth  is  bounded  by  the  lips,  two  thick,  fleshy  folds 
covered  externally  by  integument  and  internally  by  mucous  membrane,  and  consisting  of 
muscles,  vessels,  nerves,  areolar  tissue,  and  numerous  small  glands.  The  size  of  the  orifice  of 
the  mouth  varies  considerably  in  different  individuals,  but  seems  to  bear  a  close  relation  to  the 
size  and  prominence  of  the  teeth.  Its  corners  correspond  pretty  accurately  to  the  outer  border 
of  the  canine  teeth.  In  the  Mongolian  tribes,  where  the  front  teeth  are  large  and  inclined  for- 
ward, the  mouth  is  large ;  and  this,  combined  with  the  thick  and  everted  lips  which  appear  to 
be  associated  with  prominent  teeth,  gives  to  the  negro's  face  much  of  the  peculiarity  by  which 
it  is  characterized.  The  smaller  teeth  and  the  slighter  prominence  of  the  alveolar  arch  of  the 
more  highly  civilized  races  render  the  orifice  of  the  mouth  much  smaller,  and  thus  a  small 
mouth  is  an  indication  of  intelligence,  and  is  regarded  as  an  evidence  of  the  higher  civilization 
of  the  individual. 

Upon  looking  into  the  mouth,  the  first  thing  we  may  note  is  the  tongue,  the  upper  surface 
of  which  will  be  seen  occupying  the  floor  of  the  cavity.  This  surface  is  convex,  and  is  marked 
along  the  middle  line  by  a  raphe  which  divides  it  into  two  symmetrical  portions.  The  anterior 
two-thirds  is  rough  and  studded  with  papillae  ;  the  posterior  third  smooth  and  tuberculated, 
covered  by  numerous  glands  which  project  from  the  surface.  Upon  raising  the  tongue  the 
mucous  membrane  which  invests  the  upper  surface  may  be  traced  covering  the  sides  of  the 
under  surface,  and  then  reflected  over  the  floor  of  the  mouth  on  to  the  inner  surface  of  the 
lower  jaw,  a  part  of  which  it  covers.  As  it  passes  over  the  borders  of  the  tongue  it  changes  its 
character,  becoming  thin  and  smooth  and  losing  the  papillae  which  are  to  be  seen  on  the  upper 
surface.  In  the  middle  line  the  mucous  membrane  on  the  under  surface  of  the  tip  of  the 
tongue  forms  a  distinct  fold,  the  frcenum  linguce,  by  which  this  organ  is  connected  to  the  sym- 
physis of  the  jaw.  Occasionally  it  is  found  that  this  fraenum  is  rather  shorter  than  natural, 
and,  acting  as  a  bridle,  prevents  the  complete  protrusion  of  the  tongue.  When  this  condition 
exists  and  an  attempt  is  made  to  protrude  the  organ,  the  tip  will  be  seen  to  remain  buried  in 
the  floor  of  the  mouth,  and  the  dorsum  of  the  tongue  is  rendered  very  convex,  and  more  or 

xIt  has  been  shown  by  Ebner  that  many  of  these  glands  open  into  the  trenches  around  the  cir- 
cumvallate papillae,  and  that  their  secretion  is  more  watery  than  that  of  ordinary  mucous  glands. 
He  supposes  that  they  assist  in  the  more  rapid  distribution  of  the  substance  to  be  tasted  over  the 
region  where  the  special  apparatus  of  the  sense  of  taste  is  situated. 


THE   PHARYNX.  889 

less  extruded  from  the  mouth ;  at  the  same  time  a  deep  furrow  will  be  noticed  to  appear  in  the 
middle  line  of  the  anterior  part  of  the  dorsum.  Sometimes,  a  little  external  to  the  frsenum, 
the  ranine  vein  may  be  seen  immediately  beneath  the  mucous  membrane.  The  corresponding 
artery,  being  more  deeply  placed,  does  not  come  into  view,  nor  can  its  pulsation  be  felt  with  the 
finger.  On  either  side  of  the  fraanum,  in  the  floor  of  the  mouth,  is  a  longitudinal  elevation  or 
ridge,  produced  by  the  projection  of  the  sublingual  gland,  which  lies  immediately  beneath  the 
mucous  membrane.  And  close  to  the  attachment  of  the  fraenum  to  the  tip  of  the  tongue  may 
be  seen  on  either  side  the  slit-like  orifices  of  Wharton's  ducts,  into  which  a  fine  probe  may  be 
passed  without  much  difficulty.  By  everting  the  lips  the  smooth  mucous  membrane  lining  them 
may  be  examined,  and  may  be  traced  from  them  on  to  the  outer  surface  of  the  alveolar  arch. 
In  the  middle  line,  both  of  the  upper  and  lower  lip,  a  small  fold  of  mucous  membrane  passes 
from  the  lip  to  the  bone,  constituting  the  frcena ;  these  are  not  so  large  as  the  frsenum  linguae. 
By  pulling  outward  the  angle  of  the  mouth,  the  mucous  membrane  lining  the  cheeks  can  be 
seen,  and  on  it  may  be  perceived  a  little  papilla  which  marks  the  position  of  the  orifice  of  Sten- 
son's  duct — the  duct  of  the  parotid  gland.  The  exact  position  of  the  orifice  of  the  duct  will  be 
found  to  be  opposite  the  second  molar  tooth  of  the  upper  jaw.  The  introduction  of  a  probe 
into  this  duct  is  attended  with  considerable  difficulty.  The  teeth  are  the  next  objects  which 
claim  our  attention  upon  looking  into  the  mouth.  There  are,  as  stated  above,  ten  in  either  jaw 
in  the  temporary  set,  and  sixteen  in  the  permanent  set.  The  gums,  in  which  they  are  implanted, 
are  dense,  firm,  and  vascular. 

At  the  back  of  the  mouth  is  seen  the  isthmus  of  the  fauces,  or,  as  it  is  popularly  called, 
"the  throat:"  this  is  the  space  between  the  pillars  of  the  fauces  on  either  side,  and  is  the 
means  by  which  the  mouth  communicates  with  the  pharynx.  Above,  it  is  bounded  by  the  soft 
palate,  the  anterior  surface  of  which  is  concave  and  covered  with  mucous  membrane,  which  is 
continuous  with  that  lining  the  roof  of  the  mouth.  Projecting  downward  from  the  middle  of 
its  lower  border  is  a  conical-shaped  projection,  the  uvula.  On  either  side  of  the  isthmus  of  the 
fauces  are  the  anterior  and  posterior  pillars,  formed  by  the  Palato-glossus  and  Palato-pharyngeus 
muscles  respectively,  covered  over  by  mucous  membrane.  Between  the  two  pillars  on  either 
side  is  situated  the  tonsil.  The  extirpation  of  this  body  is  not  unattended  with  danger  of 
hemorrhage.  Dr.  Weir  has  stated  that  he  believes  that  when  hemorrhage  occurs  after  their 
removal  it  arises  from  one  of  the  palatine  arteries  having  been  wounded.  These  vessels  are 
large  :  they  lie  in  the  muscular  tissue  of  the  palate,  and  when  wounded  are  constantly  exposed 
to  disturbance  from  the  contraction  of  the  palatine  muscles.  The  vessels  of  the  tonsil,  Dr.  Weir 
states,  are  small  and  lie  in  the  soft  tissue,  and  readily  contract  when  wounded. 

When  the  mouth  is  wide  open  a  prominent  tense  fold  of  mucous  membrane  may  be  seen 
and  felt,  extending  upward  and  backward  from  the  position  of  the  fang  of  the  last  molar  tooth 
to  the  posterior  part  of  the  hard  palate.  This  is  caused  by  the  Pterygo-maxillary  ligament, 
which  is  attached  by  one  extremity  to  the  apex  of  the  internal  pterygoid  plate,  and  by  the  other 
to  the  posterior  extremity  of  the  mylo-hyoid  ridge  of  the  lower  jaw.  It  connects  the  Buccina- 
tor with  the  Superior  constrictor  of  the  pharynx.  The  fang  of  the  last  molar  tooth  indicates 
the  position  of  the  lingual  (gustatory)  nerve,  where  it  is  easily  accessible,  and  can  with  readiness 
be  divided  in  cases  of  cancer  of  the  tongue  (see  page  735).  On  the  inner  side  of  the  last  molar 
tooth  we  can  feel  the  hamular  process  of  the  internal  pterygoid  plate  of  the  sphenoid  bone, 
around  which  the  tendon  of  the  Tensor  palati  plays.  The  exact  position  of  this  process  is  of 
importance  in  performing  the  operation  of  staphylorraphy.  About  one-third  of  an  inch  in 
front  of  the  hamular  process,  and  the  same  distance  directly  inward  from  the  last  molar  tooth, 
is  the  situation  of  the  opening  of  the  posterior  palatine  canal,  through  which  emerges  the  pos- 
terior or  descending  palatine  branch  of  the  internal  maxillary  artery  and  one  of  the  descending 
palatine  nerves  from  Meckel's  ganglion.  The  exact  position  of  the  opening  on  the  subject  may 
be  ascertained  by  driving  a  needle  through  the  tissues  of  the  palate  in  this  situation,  when  it 
will  be  at  once  felt  to  enter  the  canal.  The  artery  eme:*ging  from  the  opening  runs  forward  in  a 
groove  in  the  bone  just  internal  to  the  alveolar  border  of  the  hard  palate,  and  may  be  wounded 
in  the  operation  for  the  cure  of  cleft  palate.  Under  these  circumstances  the  palatine  canal  may 
require  plugging.  By  introducing  the  finger  into  the  mouth  the  anterior  border  of  the  coronoid 
process  of  the  jaw  can  be  felt,  and  is  especially  prominent  when  the  jaw  is  dislocated.  By 
throwing  the  head  well  back  a  considerable  portion  of  the  posterior  wall  of  the  pharynx  may  be 
seen  through  the  isthmus  faucium,  and  on  introducing  the  finger  the  anterior  surface  of  the 
bodies  of  the  upper  cervical  vertebrae  may  be  felt  immediately  beneath  the  thin  muscular  stra- 
tum forming  the  wall  of  the  pharynx.  The  finger  can  be  hooked  around  the  posterior  border 
of  the  soft  palate,  and  by  turning  it  forward  the  posterior  nares,  separated  by  the  septum,  can 
be  felt,  or  the  presence  of  any  adenoid  or  other  growths  in  the  naso-pharynx  ascertained. 

THE  PHARYNX. 
The  pharynx  is  that  part  of  the  alimentary  canal  which  is  placed  behind  the 
nose,  mouth,  and  larynx.  It  is  a  muscnlo-membranous  tube,  somewhat  conical  in 
form,  with  the  base  upward  and  the  apex  downward,  extending  from  the  under 
surface  of  the  skull  to  the  level  of  the  cricoid  cartilage  in  front  and  that  of  the  in- 
tervertebral disk  between  the  fifth  and  sixth  cervical  vertebrae  behind. 


890  THE    ORGANS    OF  DIGESTION. 

The  pharynx  is  about  four  inches  and  a  half  in  length,  and  broader  in  the 
transverse  than  in  the  antero-posterior  diameter.  Its  greatest  breadth  is  opposite 
the  cornua  of  the  In^oid  bone ;  its  narrowest  point,  at  its  termination  in  the 
oesophagus.  It  is  limited,  above,  by  the  body  of  the  sphenoid  and  basilar  process 
of  the  occipital  bone ;  below,  it  is  continuous  with  the  oesophagus ;  posteriorly,  it 
is  connected  by  loose  areolar  tissue  with  the  cervical  portion  of  the  vertebral 
column  and  the  Longi  colli  and  Recti  capitis  antici  muscles ;  anteriorly,  it  is 
incomplete,  and  is  attached  in  succession  to  the  internal  pterygoid  plate,  the 
pterygo-maxillary  ligament,  the  lower  jaw,  the  tongue,  hyoid  bone,  and  thyroid  and 
cricoid  cartilages ;  laterally,  it  is  connected  to  the  styloid  processes  and  their  mus- 
cles, and  is  in  contact  with  the  common  and  internal  carotid  arteries,  the  mternal 
jugular  veins,  and  the  glosso-pharyngeal,  pneumogastric,  hypoglossal,  and  sym- 
pathetic nerves,  and  above  with  a  small  part  of  the  Internal  pterygoid  muscles. 

It  has  seven  openings  communicating  with  it — the  two  posterior  nares,  the 
two  Eustachian  tubes,  the  mouth,  larynx,   and  oesophagus. 

The  pharynx  may  be  subdivided  from  above  downward  into  three  parts,  nasal, 
oral,  and  laryngeal.  The  nasal  part  of  the  pharynx  (pars  nasalis)  or  naso-pharynx 
lies  behind  the  nose  and  above  the  level  of  the  soft  palate  :  it  differs  from  the  two 
lower  parts  of  the  tube  in  that  its  cavity  always  remains  patent.  In  front  it  com- 
municates through  the  choanae  with  the  nasal  fossae.  On  its  lateral  wall  is  the 
pharyngeal  orifice  of  the  Eustachian  tube,  which  presents  the  appearance  of  a  ver- 
tical cleft  bounded  behind  by  a  firm  prominence,  the  cushion,  caused  by  the  inner 
extremity  of  the  cartilage  of  the  tube  impinging  on  the  deep  surface  of  the  mucous 
membrane.  A  vertical  fold  of  mucous  membrane,  the  plica  salpingo-pharyngea, 
stretches  from  the  lower  part  of  the  cushion  to  the  pharynx  ;  it  contains  the  Sal- 
pingo-pharyngeus  muscle.  A  second  and  smaller  mucous  fold  may  be  seen  stretch- 
ing from  the  upper  part  of  the  cushion  to  the  palate,  the  plica  salpingo-palatina. 
Behind  the  orifice  of  the  Eustachian  tube  is  a  deep  recess,  the  fossa  of  Hosenmuller, 
which  represents  the  remains  of  the  upper  part  of  the  second  branchial  cleft. 

The  oral  part  of  the  pharynx  (pars  oralis)  reaches  from  the  soft  palate  to  the 
level  of  the  hyoid  bone.  It  opens  anteriorly,  through  the  isthmus  faucium,  into 
the  mouth,  while  in  its  lateral  wall,  between  the  two  pillars  of  the  fauces,  is 
the  tonsil. 

The  laryngeal  part  of  the  pharynx  (pars  laryngea)  reaches  from  the  hyoid  bone 
to  the  lower  border  of  the  cricoid  cartilage,  where  it  is  continuous  with  the  oesoph- 
agus. In  front  it  presents  the  triangular  aperture  of  the  larynx,  the  base  of  which 
is  directed  forward  and  is  formed  by  the  epiglottis,  while  its  lateral  boundaries  are 
constituted  by  the  aryteno-epiglottidean  folds.  On  either  side  of  the  laryngeal 
orifice  is  a  recess,  termed  the  sinus  pyriformis  :  it  is  bounded  internally  by  the 
aryteno-epiglottidean  foJd,  externally  by  the  thyroid  cartilage  and  thyro-hyoid 
membrane.  * 

Structure. — The  pharynx  is  composed  of  three  coats — mucous,  fibrous,  and 
muscular. 

The  pharyngeal  aponeurosis,  or  fibrous  coat,  is  situated  between  the  mucous 
and  muscular  layers.  It  is  thick  above,  where  the  muscular  fibres  are  wanting,  and 
is  firmly  connected  to  the  basilar  process  of  the  occipital  and  petrous  portion  of  the 
temporal  bones.  As  it  descends  it  diminishes  in  thickness,  and  is  gradually  lost. 
It  is  strengthened  posteriorly  by  a  strong  fibrous  band  which  is  attached  above  to 
the  pharyngeal  spine  o'n  the  under  surface  of  the  basilar  portion  of  the  occipital 
bone,  and  passes  downward,  forming  a  median  raphe,  which  gives  attachment  to 
the  Constrictor  muscles  of  the  pharynx. 

The  mucous  coat  is  continuous  with  that  lining  the  Eustachian  tubes,  the  nares, 
the  mouth  and  the  larynx.  In  the  naso-pharynx  it  is  covered  by  columnar  ciliated 
epithelium  ;  in  the  buccal  and  laryngeal  portions  the  epithelium  is  of  the  squamous 
variety.  Beneath  the  mucous  membrane  are  found  racemose  mucous  glands;  they 
are  especially  numerous  at  the  upper  part  of  the  pharynx  around  the  orifices  of 
the  Eustachian    tubes.      Throughout  the  pharynx    are   also  numerous  crypts  or 


THE    (ESOPHAGUS'.  891 

recesses,  the  walls  of  which  are  surrounded  by  lymphoid  tissue  similar  to  what  is 
found  in  the  tonsils.  Across  the  back  part  of  the  pharyngeal  cavity,  between  the 
two  Eustachian  tubes,  a  considerable  mass  of  this  tissue  exists,  and  has  been  named 
the  pharyngeal  tonsil.  Above  this  in  the  middle  line  is  an  irregular,  flask-shaped 
depression  of  the  mucous  membrane,  extending  up  as  far  as  the  basilar  process  of 
the  occipital  bone.  It  is  known  as  the  bursa  pharyngea,  and  was  regarded  by 
Luschka  as  the  remains  of  the  diverticulum,  which  is  concerned  in  the  development 
of  the  anterior  lobe  of  the  pituitary  body.  Other  anatomists  believe  that  it  is 
connected  with  the  formation  of  the  pharyngeal  tonsils. 

The  muscular  coat  has  been  already  described  (page  328). 

Surgical  Anatomy.— The  internal  carotid  artery  is  in  close  relation  with  the  pharynx,  so 
that  its  pulsations  can  be  felt  through  the  mouth.  It  has  been  occasionally  wounded  by  sharp- 
pointed  instruments  introduced  into  the  mouth  and  thrust  through  the  wall  of  the  pharynx. 
In  aneurism  of  this  vessel  in  the  neck  the  tumor  necessarily  bulges  into  the  pharynx,  as  this  is 
the  direction  in  which  it  meets  with  the  least  resistance,  nothing  lying  between  the  vessel  and 
the  mucous  membrane  except  the  thin  Constrictor  muscle,  whereas  on  the  outer  side  there  is 
the  dense  cervical  fascia,  the  muscles  descending  from  the  styloid  process,  and  the  margin  of  the 
Sterno-mastoid.  . 

The  mucous  membrane  of  the  pharynx  is  very  vascular,  and  is  often  the  seat  of  inflamma- 
tion, frequently  of  a  septic  character,  and  dangerous  on  account  of  its  tendency  to  spread  to  the 
larynx.  On  account  of  the  tissue  which  surrounds  the  pharyngeal  wall  being  loose  and  lax,  the 
inflammation  is  liable  to  spread  through  it  far  and  wide,  extending  downward  into  the  posterior 
mediastinum  along  the  oesophagus.  Abscess  may  form  in  the  connective  tissue  behind  the 
pharynx,  between  it  and  the  vertebral  column,  constituting  what  is  known  as  retro-pharyngeal 
abscess.  This  is  most  commonly  due  to  caries  of  the  cervical  vertebrae,  but  may  also  be  caused 
by  suppuration  of  a  lymphatic  gland  which  is  situated  in  this  position  opposite  the  axis,  and 
which  receives  lymphatics  from"  the  nares,  or  by  a  gumma  or  by  acute  pharyngitis.  In  these 
cases  the  pus  may  be  easily  evacuated  by  an  incision,  with  a  guarded  bistoury,  through  the 
mouth,  but,  for  aseptic  reasons,  it  is  desirable  that  the  abscess  should  be  opened  from  the  neck. 
In  some  instances  this  is  perfectly  easy  ;  the  abscess  can  be  felt  bulging  at  the  side  of  the  neck 
and  merely  requires  an  incision  for  its  relief,  but  this  is  not  always  so,  and  then  an  incision 
should  be  made  along  the  posterior  border  of  the  Sterno-mastoid  and  the  deep  fascia  divided. 
A  director  is  now  to  be  inserted  into  the  wound,  the  forefinger  of  the  left  hand  being  introduced 
into  the  mouth  and  pressure  made  upon  the  swelling.  This  acts  as  a  guide,  and  the  director  is 
to  be  pushed  onward  until  pus  appears  in  the  groove.  A  pair  of  sinus  forceps  are  now  inserted 
along  the  director  and  the  opening  into  the  cavity  dilated. 

Foreign  bodies  not  infrequently  become  lodged  in  the  pharynx,  and  most  usually  at  its  termi- 
nation at  about  the  level  of  the  cricoid  cartilage,  just  beyond  the  reach  of  the  finger,  as  the  dis- 
tance from  the  arch  of  the  teeth  to  the  commencement  of  the  oesophagus  is  about  six  inches. 

THE    (ESOPHAGUS. 

The  (Esophagus,  or  gullet,  is  a  muscular  canal,  about  nine  inches  in  length,  ex- 
tending from  the  pharynx  to  the  stomach.  It  commences  at  the  upper  border  of 
the  cricoid  cartilage,  opposite  the  intervertebral  disk  between  the  fifth  and  sixth 
cervical  vertebrae,  descends  along  the  front  of  the  spine  through  the  posterior  medi- 
astinum, passes  through  the  Diaphragm,  and,  entering  the  abdomen,  terminates  at 
the  cardiac  orifice  of  the  stomach  opposite  the  tenth  dorsal  vertebra  or  the  inter- 
vertebral disk  between  the  tenth  and  eleventh  dorsal  vertebrae.  The  general  direc- 
tion of  the  oesophagus  is  vertical,  but  it  presents  two  or  three  slight  curves  in  its 
course.  At  its  commencement  it  is  placed  in  the  median  line,  but  it  inclines  to  the 
left  side  as  far  as  the  root  of  the  neck,  gradually  passes  to  the  middle  line  again, 
and  finally  again  deviates  to  the  left  as  it  passes  forward  to  the  oesophageal  open- 
ing of  the  Diaphragm.  The  oesophagus  also  presents  an  antero-posterior  flexure, 
corresponding  to  the  curvature  of  the  cervical  and  thoracic  portions  of  the  spine. 
It  is  the  narrowest  part  of  the  alimentary  canal,  being  most  contracted  at  its  com- 
mencement and  at  the  point  where  it  passes  through  the  Diaphragm. 

Eelations. — In  the  neck  the  oesophagus  is  in  relation,  in  front,  with  the  trachea, 
and  at  the  lower  part  of  the  neck,  where  it  projects  to  the  left  side,  with  the  thy- 
roid gland  and  thoracic  duct ;  behind,  it  rests  upon  the  vertebral  column  and  Longi 
colli  muscles  ;  on  each  side,  it  is  in  relation  with  the  common  carotid  artery  (espe- 
cially the  left,  as  it  inclines  to  that  side)  and  part  of  the  lateral  lobes  of  the  thy- 
roid gland ;  the  recurrent  laryngeal  nerves  ascend  between  it  and  the  trachea. 


892  THE    ORGANS   OF  DIGESTION. 

In  the  thorax,  it  is  at  first  situated  a  little  to  the  left  of  the  median  line ;  it 
then  passes  behind  the  aortic  arch,  separated  from  it  by  the  trachea,  and  descends 
in  the  posterior  mediastinum,  along  the  right  side  of  the  aorta,  nearly  to  the 
Diaphragm,  where  it  passes  in  front  and  a  little  to  the  left  of  the  artery,  previous 
to  entering  the  abdomen.  It  is  in  relation,  in  front,  with  the  trachea,  the  arch  of 
the  aorta,  the  left  carotid  and  left  subclavian  arteries,  which  incline  toward  its  left 
side,  the  left  bronchus,  the  pericardium,  and  the  Diaphragm  ;  behind,  it  rests  upon 
the  vertebral  column,  the  Longi  colli  muscles,  the  right  intercostal  arteries,  and  the 
vena  azygos  minor;  and  below,  near  the  Diaphragm,  upon  the  front  of  the  aorta  ; 
laterally,  it  comes  in  contact  with  both  pleurae,  especially  with  the  left  pleura  above 
and  the  right  pleura  below:  it  overlaps  the  vena  azygos  major,  which  lies  on  its 
right  side,  wnile  the  descending  aorta  is  placed  on  its  left  side.  The  pneumogastric 
nerves  descend  in  close  contact  with  it,  the  right  nerve  passing  down  behind,  and 
the  left  nerve  in  front  of  it ;  the  two  nerves  uniting  to  form  a  plexus  (the  'plexus 
gulm)  around  the  tube. 

In  the  lower  part  of  the  posterior  mediastinum  the  thoracic  duct  lies  to 
the  right  side  of  the  oesophagus ;  higher  up,  it  is  placed  behind  it,  and,  cross- 
ing about  the  level  of  the  fourth  dorsal  vertebra,  is  continued  upward  on  its 
left  side. 

Structure. — The  oesophagus  has  three  coats — an  external  or  muscular;  a 
middle  or  areolar  ;  and  an  internal  or  mucous  coat. 

The  muscular  coat  is  composed  of  two  planes  of  fibres  of  considerable  thickness, 
an  external  longitudinal  and  an  internal  circular. 

The  longitudinal  fibres  are  arranged,  at  the  commencement  of  the  tube,  in  three 
fasciculi :  one  in  front,  which  is  attached  to  the  vertical  ridge  on  the  posterior 
surface  of  the  cricoid  cartilage ;  and  one  at  each  side,  which  is  continuous  with 
the  fibres  of  the  Inferior  constrictor  :  as  they  descend  they  blend  together  and 
form  a  uniform  layer,  which  covers  the  outer  surface  of  the  tube. 

Accessory  slips  of  muscular  fibres  are  described  by  Cunningham  as  passing 
between  the  oesophagus  and  the  left  pleura,  where  it  covers  the  thoracic  aorta 
(almost  always),  or  the  root  of  the  left  bronchus  (usually),  or  the  back  of  the 
pericardium,  as  well  as  other  still  more  rare  accessory  fibres.  In  Fig.  485,  taken 
from  a  dissection  in  the  Museum  of  the  Royal  College  of  Surgeons  of  England, 
several  of  these  accessory  slips  may  be  seen  passing  from  the  oesophagus  to  the 
pleura,  and  two  slips  to  the  back  of  the  trachea  just  above  its  bifurcation. 

The  circular  fibres  are  continuous  above  with  the  Inferior  constrictor ;  their 
direction  is  transverse  at  the  upper  and  lower  parts  of  the  tube,  but  oblique  in  the 
central  part. 

The  muscular  fibres  in  the  upper  part  of  the  oesophagus  are  of  a  red  color,  and 
consist  chiefly  of  the  striped  variety,  but  below  they  consist  for  the  most  part  of 
involuntary  muscular  fibre. 

The  areolar  coat  connects  loosely  the  mucous  and  muscular  coats. 

The  mucous  coat  is  thick,  of  a  reddish  color  above  and  pale  below.  It  is 
disposed  in  longitudinal  folds,  which  disappear  on  distension  of  the  tube.  Its 
surface  is  studded  with  minute  papillae,  and  it  is  covered  throughout  with  a  thick 
layej  of  stratified  pavement  epithelium.  Beneath  the  mucous  membrane,  between 
it  and  the  areolar  coat,  is  a  layer  of  longitudinally  arranged  non-striped 
muscular  fibres.  This  is  the  muscularis  mucosas.  At  the  commencement  it  is 
absent,  or  only  represented  by  a  few  scattered  bundles ;  lower  down  it  forms  a 
considerable  stratum. 

The  oesophageal  glands  are  numerous  small  compound  racemose  glands 
scattered  throughout  the  tube ;  they  are  lodged  in  the  submucous  tissue,  and  open 
upon  the  surface  by  a  long  excretory  duct.  They  are  most  numerous  at  the  lower 
part  of  the  tube,  where  they  form  a  ring  round  the  cardiac  orifice. 

Vessels  of  the  (Esophagus. — The  arteries  supplying  the  oesophagus  are  de- 
rived from  the  inferior  thyroid  branch  of  the  thyroid  axis  of  the  subclavian, 
from  the  descending  thoracic  aorta,  and  from  the  gastric  branch  of  the  coeliac 


THE    (ESOPHAGUS. 


893 


axis,  and  from  the  left  inferior  phrenic  of  the  abdominal  aorta.  They  have  for  the 
most  part  a  longitudinal  direction. 

Nerves  of  the  (Esophagus. — The  nerves  are  derived  from  the  pneumogastric 
and  from  the  sympathetic ;  they  form  a  plexus  in  which,  are  groups  of  ganglion- 
cells  between  the  two  layers  of  the  muscular  coats,  and  also  a  second  plexus  in 
the  submucous  tissue. 

Surgical  Anatomy. — The  relations  of  the  oesophagus  are  of  considerable  practical  interest 
to  the  surgeon,  as  he  is  frequently  required,  in  cases  of  stricture  of  this  tube,  to  dilate  the  canal 
by  a  bougie,  when  it  is  of  importance  that  the  direction  of  the 
oesophagus  and  its  relations  to  surrounding  parts  should  be 
remembered.  In  cases  of  malignant  disease  of  the  oesophagus, 
where  its  tissues  have  become  softened  from  infiltration  of  the 
morbid  deposit,  the  greatest  care  is  requisite  in  directing  the 
bougie  through  the  structured  part,  as  a  false  passage  may 
easily  be  made,  and  the  instrument  may  pass  into  the  medi- 
astinum, or  into  one  or  the  other  pleural  cavity,  or  even  into 
the  pericardium. 

The  student  should  also  remember  that  obstruction  of  the 
oesophagus,  and  consequent  symptoms  of  stricture,  are  occa- 
sionally produced  by  an  aneurism  of  some  part  of  the  aorta 
pressing  upon  this  tube.  In  such  a  case  the  passage  of  a 
bougie  could  only  hasten  the  fatal  issue. 

In  passing  a  bougie  the  left  fore  finger  should  be  intro- 
duced into  the  mouth  and  the  epiglottis  felt  for,  care  being 
taken  not  to  throw- the  head  too  far  backward.  The  bougie  is 
theri  to  be  passed  beyond  the  finger  until  it  touches  the  pos- 
srior  wall  of  the  pharynx.  The  patient  is  now  asked  to  swal- 
low, and  at  the  moment  of  swallowing  the  bougie  is  passed 
gently  onward,  all  violence  being  carefully  avoided. 

It  occasionally  happens  that  a  foreign  body  becomes  im- 
pacted in  the  oesophagus  which  can  neither  be  brought  upward 
nor  moved  downward.  When  all  ordinary  means  for  its  re- 
moval have  failed,  excision  is  the  only  resource.  This,  of 
course,  can  only  be  performed  when  it  is  not  very  low  down. 
If  the  foreign  body  is  allowed  to  remain,  extensive  inflamma- 
tion and  ulceration  of  the  oesophagus  may  ensue.  In  one  case 
the  foreign  body  ultimately  penetrated  the  intervertebral  sub- 
stance, and  destroyed  life  by  inflammation  of  the  membranes 
and  substance  of  the  cord. 

The  operation  of  oesophagotomy  is  thus  performed  :  The 
patient  being  placed  upon  his  back,  with  the  head  and  shoul- 
ders slightly  elevated,  an  incision,  about  four  inches  in  length, 
should  be  made  on  the  left  side  of  the  trachea,  from  the  thy- 
roid cartilage  downward,  dividing  the  skin,  Platysma,  and 
deep  fascia.  The  edges  of  the  wound  being  separated,  the 
Omo-hyoid  muscle  should,  if  necessary,  be  divided,  and  the 
fibres  of  the  Sterno-hyoid  and  Sterno-thyroid  muscles  drawn 
inward ;  the  sheath  of  the  carotid  vessels,  being  exposed, 
must  be  drawn  outward,  and   retained   in  that    position  by 

retractors :  the  oesophagus  will  now  be  exposed,  and  should  be  divided  over  the  foreign  body, 
which  can  then  be  removed.  Great  care  is  necessary  to  avoid  wounding  the  thyroid  vessels,  the 
thyroid  gland,  and  the  laryngeal  nerves. 

The  oesophagus  may  be  obstructed  not  only  by  foreign  bodies,  but  also  by  changes  in 
its  coats,  producing  stricture,  or  by  pressure  on  it  from  without  of  new  growths  or  aneurism, 
etc. 

The  different  forms  of  stricture  are:  (1)  the  spasmodic,  usually  occurring  in  nervous 
women,  and  intermittent  in  character,  so  that  the  dysphagia  is  not  constant ;  (2)  fibrous,  due  to 
cicatrization  after  injuries,  such  as  swallowing  corrosive  fluids  or  boiling  water  ;  and  (3)  malig- 
nant, usually  epitheliomatous  in  its  nature.  This  is  situated  generally  either  at  the  upper  end 
of  the  tube,  opposite  to  the  cricoid  cartilage,  or  at  its  lower  end  at  the  cardiac  orifice,  but  is 
also  occasionally  found  at  that  part  of  the  tube  where  it  is  crossed  by  the  left  bronchus. 

The  operation  of  cesophagostomy  has  occasionally  been  performed  in  cases  where  the 
stricture  in  the  oesophagus  is  at  the  upper  part,  with  a  view  to  making  a  permanent  opening 
below  the  stricture  through  which  to  feed  the  patient,  but  the  operation  has  been  far  from  a 
successful  one,  and  the  risk  of  setting  up  diffuse  inflammation  in  the  loose  planes  of  con- 
nective tissue  deep  in  the  neck  is  so  great  that  it  would  appear  to  be  better,  if  any  operative 
interference  is  undertaken,  to  perform  gastrostomy.  The  operation  is  performed  in  the  same 
manner  as  oesophagotomy,  but  the  edges  of  the  opening  in  the  oesophagus  are  stitched  to  the 
skin  incision. 


Fig.  485. — Accessory  muscular  fi- 
bres between  the  oesophagus  and 
pleura,  and  oesophagus  and  trachea. 
(From  a  preparation  in  the  Museum 
of  the  Royal  College  of  Surgeons  of 
England.) 


894 


THE    ORGANS    OF  DIGESTION 


Fig.  486,-Topographv  of  thoracic  and  abdominal  vis 


THE   ABDOMEN.  895 

THE  ABDOMEN. 

The  Abdomen  is  the  largest  cavity  in  the  body.  It  is  of  an  oval  form,  the 
extremities  of  the  oval  being  directed  upward  and  downward  :  the  upper  one 
being  formed  by  the  under  surface  of  the  Diaphragm,  the  lower  by  the  upper 
concave  surface  of  the  Levatores  ani.  In  order  to  facilitate  description,  it  is 
artificially  divided  into  two  parts:  an  upper  and  larger  part,  the  abdomen  proper; 
and  a  lower  and  smaller  part,  the  pelvis.  These  two  cavities  are  not  separated 
from  each  other,  but  the  limit  between  them  is  marked  by  the  brim  of  the  true 
pelvis.  The  space  is  wider  above  than  below,  and  measures  more  in  the  vertical 
than  in  the  transverse  diameter. 

The  abdomen  proper  differs  from  the  other  great  cavities  of  the  body  in  being 
bounded  for  the  most  part  by  muscles  and  fasciae,  so  that  it  can  vary  in  capacity 
and  shape  according  to  the  condition  of  the  viscera  which  it  contains  ;  but,  in 
addition  to  this,  the  abdomen  varies  in  form  and  extent  with  age  and  sex.  In 
the  adult  male,  with  moderate  distention  of  the  viscera,  it  is  oval  or  barrel-shaped, 
but  at  the  same  time  flattened  from  before  backward.  In  the  adult  female,  with  a 
fully  developed  pelvis,  it  is  conical  with  the  apex  above,  and  in  young  children  it 
is  conical  with  the  apex  below. 

Boundaries. — The  boundary  between  the  thorax  and  abdomen  is  the  Diaphragm. 
This  muscle  forms  a  dome  over  the  abdomen,  and  the  cavity  extends  high  into  the 
bony  thorax,  reaching  to  the  level  of  the  junction  of  the  fourth  costal  cartilage 
with  the  sternum.  The  lower  end  of  the  abdomen  is  limited  by  the  structures 
which  clothe  the  inner  surface  of  the  bony  pelvis,  principally  the  Levatores  ani 
and  Coccygei  muscles  on  either  side.  These  muscles  are  sometimes  termed  the 
Diaphragm  of  the  pelvis.  The  abdomen  proper  is  bounded  in  front  and  at  the 
sides  by  the  lower  ribs,  the  abdominal  muscles,  and  the  venter  ilii ;  behind,  by  the 
vertebral  column  and  the  Psoas  and  Quadratus  lumborum  muscles ;  above,  by  the 
Diaphragm  ;  below,  by  the  brim  of  the  pelvis.  The  muscles  forming  the  boundaries 
of  the  cavity  are  lined  upon  their  inner  surface  by  a  layer  of  fascia,  differently 
named,  according  to  the  part  which  it  covers. 

The  abdomen  contains  the  greater  part  of  the  alimentary  canal;  some  of  the 
accessory  organs  to  digestion,  viz.,  the  liver  and  pancreas  ;  the  spleen,  the  kidneys, 
and  suprarenal  capsules.  Most  of  these  structures,  as  well  as  the  wall  of  the 
cavity  in  which  they  are  contained,  are  covered  by  an  extensive  and  complicated 
serous  membrane,  the  peritoneum. 

The  apertures  found  in  the  walls  of  the  abdomen,  for  the  transmission  of 
structures  to  or  from  it,  are,  the  umbilicus,  for  the  transmission  (in  the  foetus)  of 
the  umbilical  vessels  ;  the  caval  opening  in  the  Diaphragm,  for  the  transmission 
of  the  inferior  vena  cava ;  the  aortic  opening,  for  the  passage  of  the  aorta,  vena 
azygos  major,  and  thoracic  duct;  and  the  oesophageal  opening,  for  the  oesophagus 
and  pneumogastric  nerves.  Below,  there  are  two  apertures  on  each  side :  one  for 
the  passage  of  the  femoral  vessels,  and  the  other  for  the  transmission  of  th 
spermatic  cord  in  the  male,  and  the  round  ligament  in  the  female. 

Regions. — For  convenience  of  description  of  the  viscera,  as  well  as  of  re 

to  the  morbid  conditions  of  the  contained  parts,  the  abdomen  is  artificial^ 

into  nine  regions.     Thus,  if  two   circular  lines  are  drawn  round  the  bod'outiine.) 

through  the  extremities  of  the  ninth  ribs  where  they  join  their  costal  carl    ^^  ^ 

the  other  through  the  highest  point  of  the  crests  of  the  ilia    C  f~~?i° 
,..,,.        ".  °  r  .,,,  ,      ,        rignt  side, 

is  divided  into  three  zones— an  upper,  a  middle,  and^a  1^   abJominal  wall  and  0f 

are  drawn  perpendicularly  upward  from  the  cer^^  ig  lined  and  the  latter  more 

these  zones  is  subdivided  into  three  parts-^  ^  peritmeuvu 

1  Anatomists  are  far  from  agreed   as  to  the  be 
Cunningham  suggests  that  the  lower  line  should  en«oneum. 

of  the  iliac  crest    as  seen  from  the  front-a  point  brane   in  the    body    and    consists,  in 

outer  lip  of  the  iliac  crest  about  two  inches   behi  .  JJ>  . 

careful  analysis  of  the  abdominal  viscera  in  forty  s-.S  applied  against  the  abdominal  panetes. 
,  T        ,  ,  .    .  ,  D.    .  e  contained  viscera.      In  the  female  the 

1  Journal  of  Anatomy  and  Physi 


896 


THE    ORGANS    OF  DIGESTION. 


The  middle  region  of  the  upper  zone  is  called  the  epigastric  (inc,  over  ;  yaorrjp, 
the  stomach) ;  and  the  two  lateral  regions,  the  right  and  left  hypochondriac  (wro, 
under ;  %ov6f>ot,  the  cartilages).  The  central  region  of  the  middle  zone  is  the 
umbilical ;  and  the  two  lateral  regions,  the  right  and  left  lumbar.  The  middle 
region  of  the  lower  zone  is  the  hypogastric  ox  pubic  region  ;  and  the  lateral  regions 
are  the  right  and  left  inguinal  or  iliac.  The  viscera  contained  in  these  different 
regions  are  the  folloAving  (Fig.  487). 


Right  Hypochondriac. 

The  greater  part  of 
right  lobe  of  the  liver, 
the  hepatic  flexure  of  the 
colon,  and  part  of  the 
right  kidney. 


Right  Lumbar. 

Ascending  colon,  part 
of  the  right  kidney,  and 
some  convolutions  of  the 
small  intestines. 


Right  Inguinal  [Iliac). 

The  caecum  and  vermi- 
form appendix. 


Epigastric  Region. 

The  greater  part  of  the 
stomach,  including  both 
cardiac  and  pyloric  ori- 
fices, the  left  lobe  and 
part  of  the  right  lobe  of 
the  liver  and  the  gall- 
bladder, the  pancreas,  the 
duodenum,  the  suprarenal 
capsules,  and  parts  of  the 
kidneys. 

Umbilical  Region. 

The  transverse  colon, 
part  of  the  great  omentum 
and  mesentery,  transverse 
part  of  the  duodenum,  and 
some  convolutions  of  the 
jejunum  and  ileum,  and 
part  of  both  kidneys. 

Hypogastric  Region. 

Convolutions  of  the 
small  intestines,  the  blad- 
der in  children,  and  in 
adults  if  distended,  and  the 
uterus  during  pregnancy. 


Left  Hypochondriac. 

The  fundus  of  the 
stomach,  the  spleen  and 
extremity  of  the  pancreas, 
the  splenic  flexure  of  the 
colon,  and  part  of  the 
left  kidney. 


Left  Lumbar. 

Descending  colon,  part 
of  the  omentum,  part  of 
the  left  kidney,  and  some 
convolutions  of  the  small 
intestines. 


Left  Inguinal  {Iliac). 

Sigmoid  flexure  of  the 
colon. 


If  the  anterior  abdominal  wall  is  reflected  in  the  form  of  four  triangular  flaps 
by  means  of  vertical  and  transverse  incisions — the  former  from  the  ensiform  carti- 
lage to  the  symphysis  pubis,  the  latter  from  flank  to  flank  at  the  level  of  the 
umbilicus — the  abdominal  or  peritoneal  cavity  is  freely  opened  into  and  the 
contained  viscera  are  in  part  exposed.1 

Above  and  to  the  right  side  is  the   liver,  situated  chiefly  under  the  shelter  of 

Tht  ribs  and  their  cartilages,  but  extending  across  the  middle  line,  and  reach- 

'Ome  distance  below  the  level  of  the  ensiform  cartilage.     Below  and  to  the 

e  liver  is  the  stomach,  from  the  lower  border  of  which  an  apron-like  fold 

3um,  the  great  omentum,  descends  for  a  varying  distance,  and  obscures, 

er  extent,  the  other  viscera.      Below  it,  however,  some  of  the  coils 

r  o-enerally  be  seen,  while  in  the  right  and  left  iliac  regions 

'*****qmoid  flexure  of  the  colon  are  exposed.     The 

f  the  pelvis,  and,  if  distended,  will   project 


T|)  two  lateral  lines  drawn  vertically  through  a  point 
ip  and  the  symphysis  pubis ;   (3)  an  upper  transverse 
he  supra-sternal  notch  ;  and  (4)  a  lower  transverse 
Fig.  486.— Topography  of  thoraer  of  the  symphysis  pubis. 

he  term  abdominal  cavity  is  used,  there   is,  under 
ymph-space,  since  the  viscera  are  everywhere  in 


THE   PERITONEUM. 


897 


above  the  symphysis  pubis  ;  the  rectum  lies  in  the  concavity  of  the  sacrum,  but 
is  usually  obscured  by  the  coils  of  the  small  intestine. 

If  the  stomach  is  followed  from  left  to  right  it  will  be  found  to  be  continuous 
with  the  first  part  of  the  small  intestine,  or  duodenum,  the  point  of  continuity  beino- 
marked  by  a  thickened  ring  which  indicates  the  position  of  the  pyloric  valve. 
The  duodenum  passes  toward  the  under  surface  of  the  liver,  and  then  curving 
downward,  is  lost  to  sight.  If,  however,  the  great  omentum  be  thrown  upward 
over  the  chest,  the  terminal  part  of  the  duodenum  will  be  observed  passing  across 
the  spine  toward  the  left  side,  where  it  becomes  continuous  with  the  coils  of  the 
small  intestine.  These  measure  some  twenty  feet  in  length,  and  if  followed  down- 
ward Avill  be  seen  to  end  in  the  right  iliac  fossa  by  opening  into  the  coecum  or 
commencement  of  the  large  intestine.  From  the  crecum  the  large  intestine  takes 
an  arched  course,  passing  at  first  upward  on  the  right  side,  then  across  the  middle 
line  and  downward  on  the  left  side,  and  forming  respectively  the  ascending,  trans- 
verse, and  descending  parts  of  the  colon.  In  the  left  iliac  region  it  makes  still 
another  bend,  the  sigmoid  flexure,  and  then  follows  the  curve  of  the  sacrum  as 
the  rectum. 


Fig.  487.— The  regions  of  the  abdomen  and  their  contents.   (Edge  of  costal  cartilages  in  dotted  outline.) 

The  spleen  lies  behind  the  stomach  in  the  left  hypochondriac  region,  and  may 
be  in  part  exposed  by  pulling  the  stomach  over  toward  the  right  side. 

The  glistening  appearance  of  the  deep  surface  of  the  abdominal  wall  and  of 
the  exposed  viscera  is  due  to  the  fact  that  the  former  is  lined  and  the  latter  more 
or  less  completely  covered  by  a  serous  membrane,  the  peritoneum. 

The  Peritoneum. 
The  peritoneum  is  the  largest  serous  membrane  in  the  body,  and  consists,  in 
ie  male,  of  a  closed  sac,  a  part  of  which  is  applied  against  the  abdominal  parietes. 
hile  the  remainder  is  reflected  over  tbe  contained  viscera.     In  the  female  the 

57 


\ 


THE    ORGANS    OF   DIGESTION. 

peritoneum  is  not  a  closed  sac,  since  the  free  extremities  of  the  Fallopian  tubes 
open  directly  into  the  peritoneal  cavity.  The  former  constitutes  the  parietal, 
the  latter  the  visceral  part  of  the  peritoneum.  The  free  surface  of  the  membrane 
is  smooth,  covered  by  a  layer  of  flattened  endothelium,  and  lubricated  by  a  small 
quantity  of  serous  fluid.  Hence  the  viscera  can  glide  freely  against  the  Avail  of  the 
cavity  or  upon  one  another  with  the  least  possible  amount  of  friction.  Its  attached 
surface  is  rough,  being  connected  to  the  viscera  and  inner  surface  of  the  parietes 
by  means  of  areolar  tissue  termed  the  subserous  areolar  tissue.  The  parietal  por- 
tion is  loosely  connected  "with  the  fascia  lining  the  abdomen  and  pelvis,  but  more 
closely  to  the  under  surface  of  the  Diaphragm  and  also  in  the  middle  line  of  the 
abdomen. 

The  peritoneum  differs  from  the  other  serous  membranes  of  the  body  in 
presenting  a  much  more  complex  arrangement — an  arrangement  which  can  only 
be  clearly  understood  by  following  the  changes  which  take  place  in  the  alimentary 
canal  dui'ing  its  development;  and  therefore  the  student  is  advised  to  preface  his 
study  of  the  peritoneum  by  reviewing  the  chapter  dealing  with  this  subject  in  the 
section  on  Embryology. 

To  trace  the  continuity  of  the  membrane  from  one  viscus  to  another,  and  from 
the  viscera  to  the  parietes,  it  is  necessary  to  follow  its  reflections  in  the  vertical 
and  horizontal  directions,  and  in  doing  so  it  matters  little  where  a  start  is  made. 

If  the  stomach  is  drawn  downward,  a  fold  of  peritoneum  will  be  seen  stretching 
from  its  lesser  curvature  to  the  transverse  fissure  of  the  liver  (Fig.  488).  This  is 
the  g astro-hepatic  or  small  omentum,  and  consists  of  two  layers ;  these,  on  being 
traced  downward,  split  to  envelop  the  stomach,  covering  respectively  its  anterior 
and  posterior  surfaces.  At  the  greater  curvature  of  the  stomach  they  again  come 
into  contact  and  are  continued  downward  in  front  of  the  transverse  colon,  forming 
the  anterior  two  layers  of  the  great  or  gastro-colic  omentum.  Reaching  the  free 
edge  of  this  fold  they  are  reflected  upward  as  its  two  posterior  layers,  and  thus  the 
great  omentum  consists  of  four  layers  of  peritoneum.  Followed  upward  the  two 
posterior  layers  separate  so  as  to  enclose  the  transverse  colon,  above  which  they 
once  more  come  into  contact  and  pass  backward  to  the  abdominal  wall  as  the  trans- 
verse mesocolon.  Reaching  the  abdominal  wall  about  the  level  of  the  transverse 
part  of  the  duodenum,  the  two  layers  of  the  transverse  mesocolon  become  separated 
from  each  other  and  take  different  directions  ;  the  upper  or  anterior  layer  ascends 
(ascending  layer  of  transverse  mesocolon)  in  front  of  the  pancreas,  and  its  further 
course  will  be  followed  presently.  The  lower  or  posterior  layer  is  carried  down- 
ward, as  the  anterior  layer  of  the  mesentery,  by  the  superior  mesenteric  vessels  to 
the  small  intestine,  around  which  it  may  be  followed  and  subsequently  traced 
upward  as  the  posterior  layer  of  the  mesentery  to  the  abdominal  wall.  From  the 
posterior  abdominal  wall  it  sweeps  downward  over  the  aorta  into  the  pelvis,  where 
it  invests  the  first  part  of  the  rectum  and  attaches  it  to  the  front  of  the  sacrum  by 
a  fold  termed  the  mesorectum.  Leaving  first  the  sides  and  then  the  front  of  the 
second  part  of  the  rectum  it  is  reflected  on  to  the  back  of  the  bladder,  and,  after 
covering  the  posterior  and  upper  aspects  of  this  viscus,  is  carried  by  the  urachus 
and  obliterated  hypogastric  arteries  on  to  the  posterior  surface  of  the  anterior 
abdominal  wall.  Between  the  rectum  and  bladder  it  forms  a  pouch,  the  recto- 
vesical pouch,  bounded  on  each  side  by  a  crescentic  or  semilunar  fold  ;  the  bottom 
of  this  pouch  is  about  on  a  level  with  the  middle  of  the  vesiculpe  seminales — i.  e., 
three  inches  or  so  from  the  orifice  of  the  anus.  When  the  bladder  is  distended  the 
peritoneum  is  carried  up  with  the  expanded  viscus,  so  that  a  considerable  part  of 
the  anterior  surface  of  the  latter  lies  directly  against  the  abdominal  wall  without 
the  intervention  of  the  peritoneal  membrane. 

In  the  female  the  peritoneum  is  reflected  from  the  rectum  on  to  the  upper  part 
of  the  posterior  vaginal  wall,  forming  the  recto-vaginal  pouch  or  pouch  of  Douglas. 
It  is  then  carried  over  the  posterior  aspect  and  fundus  of  the  uterus  on  to  its 
anterior  surface,  which  it  covers  as  far  as  the  junction  of  the  body  and  cervix 
uteri,  forming  here  a  second  but  shallower  depression,  the  utero-vesical pouch.      It 


/ 


THE   PERITONEUM.  899 

is  also  reflected  from  the  sides  of  the  uterus  to  the  lateral  walls  of  the  pelvis  as  two 
expanded  folds,  the  broad  ligaments  of  the  uterus,  in  the  free  margin  of  each  of 
which  can  be  felt  a  thickened  cord-like  structure,  the  Fallopian  tube. 

On  following  the  parietal  peritoneum  upward  on  the  back  of  the  anterior 
abdominal  wall  it  is  seen  to  be  reflected  around  a  fibrous  band,  the  ligamentum 
teres  or  obliterated  umbilical  vein,  which  reaches  from  the  umbilicus  to  the  under 
surface  of  the  liver.  Here  the  membrane  forms  a  somewhat  triangular  fold,  the 
falciform  or  suspensory  ligament  of  the  liver,  which  attaches  the  upper  and  anterior 
surfaces  of  that  organ  to  the  Diaphragm  and  abdominal  wall.  With  the  exception 
of  the  line  of  attachment  of  this  ligament  the  peritoneum  covers  the  under  surface 
of  the  anterior  part  of  the  Diaphragm  and  is  reflected  from  it  on  to  the  upper 
surface  of  the  liver  as  the  anterior  or  superior  layer  of  the  coronary  ligament. 
Covering  the  upper  and  anterior  surfaces  of  the  liver  it  is  reflected  round  its  sharp 
margin  on  to  its  under  surface  as  far  as  the  transverse  fissure,  where  it  is  continuous 
with  the  anterior  layer  of  the  small  omentum  from  which  a  start  was  made.  The 
posterior  layer  of  this  omentum  is  carried  backward  from  the  transverse  fissure  over 
the  under  surface  and  Spigelian  lobe  of  the  liver,  and  is  then  reflected,  as  the  pos- 
terior or  inferior  layer  of  the  coronary  ligament,  on  to  the  Diaphragm  and  is  pro- 
longed downward  over  the  pancreas  to  become  continuous  with  the  ascending  layer 
of  the  transverse  mesocolon.  Between  the  two  layers  of  the  coronary  ligament 
there  is  a  triangular  surface  of  the  liver  which  is  devoid  of  peritoneum  ;  it  is 
named  the  bare  area  of  the  liver,  and  is  attached  to  the  Diaphragm  by  connective 
tissue.  If,  however,  the  two  layers  of  the  coronary  ligaments  are  traced  toward 
the  right  and  left  margins  of  the  liver,  they  approach  each  other,  and,  ultimately 
fusing,  they  form  the  right  and  left  lateral  ligaments  of  the  liver  and  attach  its 
right  and  left  lobes  respectively  to  the  Diaphragm. 

If  the  small  omentum  is  followed  toward  the  right  side  it  is  seen  to  form  a 
distinct  free  edge  around  Avhich  its  anterior  and  posterior  layers  are  continuous  with 
each  other  and  between  which  are  situated  the  portal  vein,  hepatic  artery,  and  bile- 
duct.  If  the  finger  is  introduced  behind  this  free  edge,  it  passes  through  a  some- 
what constricted  ring,  the  foramen  of  Winslow.  This  is  the  communication 
between  what  are  termed  the  greater  and  lesser  sacs  of  the  peritoneum  and  has  the 
following  boundaries :  in  front,  the  free  edge  of  the  gastro-hepatic  omentum  with 
the  portal  vein,  hepatic  artery,  and  bile-duct  bctwreen  its  two  layers ;  behind,  the 
vena  cava  inferior ;  above,  the  Spigelian  and  caudate  lobes  of  the  liver ;  below, 
the  duodenum  and  the  hepatic  artery,  as  the  latter  passes  forward  and  upward 
from  the  coeliac  axis. 

The  lesser  sac  of  the  peritoneum  therefore  lies  behind  the  small  omentum  and 
has  the  following  dimensions  :  above,  it  is  limited  by  the  portion  of  the  liver  which 
lies  behind  the  transverse  fissure  ;  below,  it  extends  downward  into  the  great  omen- 
tum, reaching,  in  the  foetus,  as  far  as  its  free  edge ;  in  the  adult,  however,  its  verti- 
cal extent  is  limited  by  adhesions  between  the  layers  of  the  omentum.  In  front,  it 
is  bounded  by  the  small  omentum,  stomach,  and  anterior  two  layers  of  the  great 
omentum  ;  behind,  by  the  tw7o  posterior  layers  of  the  great  omentum,  the  trans- 
verse colon,  and  ascending  layer  of  the  transverse  mesocolon  which  passes  upward 
in  front  of  the  pancreas  as  far  as  the  posterior  surface  of  the  liver.  Laterally  the 
lesser  sac  reaches  from  the  foramen  of  Winslow  on  the  right  side  as  far  as  the 
spleen  on  the  left,  where  it  is  limited  by  the  lieno-renal  ligament.  The  extent  of 
the  lesser  sac  and  its  relations  to  surrounding  parts  can  be  definitely  made  out  by 
tearing  through  the  small  omentum  and  inserting  the  hand  through  the  opening 
thus  made. 

It  should  be  stated  that  during  a  considerable  part  of  foetal  life  the  transverse 
colon  is  suspended  from  the  posterior  abdominal  wall  by  a  mesentery  of  its  own — 
the  two  posterior  layers  of  the  great  omentum  passing,  at  this  stage,  in  front  of 
the  colon.  This  condition  sometimes  persists  throughout  adult  life,  but  as  a  rule 
adhesion  occurs  between  the  mesentery  and  the  transverse  colon  and  the  posterior 
laver  of  the  great  omentum,   with  the  result  that  the  colon  appears   to  receive 


900 


THE    ORGANS    OF   DIGESTION. 


its  peritoneal  covering  by  the  splitting  of  the  two  posterior  layers  of  the  latter 
fold. 

In  addition  to  tracing  the  peritoneum  vertically,  it  is  necessary  to  trace  it  hori- 
zontally. If  this  is  done  below  the  transverse  colon,  the  circle  is  extremely  simple, 
as  it  includes  only  the  greater  sac  of  the  peritoneum  (Fig.  488).  Above  the  level 
of  the  transverse  colon  the  arrangement  is  more  complicated,  on  account  of  the 
existence  of  the  two  sacs. 

Starting  from  the  linea  alba,  below  the  level  of  the  transverse  colon,  and 
tracing  the  continuity  in  a  horizontal  direction  to  the  right,  the  peritoneum  covers 
the  internal  surface  of  the  abdominal  wall  almost  as  far  as  the  anterior  border  of 
the  Quadratus  lumborum  muscle ;  it  encloses  the  caecum,  and  is  reflected  over  the 
sides  and  anterior  surface  of  the  ascending  colon,  fixing  it  to  the  abdominal  wall, 
from  which  it  can  be  traced  over  the  kidney  to  the  front  of  the  bodies  of  the 
vertebras.     It  then  passes  along  the  mesenteric  vessels  to  invest  the  small  intes- 


Passes  through  foramen  of 
Window. 


^Lesser  omentum. 


.r-£^ 


Fig.  488. — The  reflections  of  the  peritoneum,  as  seen  in  a  vertical  section  of  the  abdomen. 

tine,  and  back  again  to  the  spine,  forming  the  mesentery,  between  the  layers  of 
which  are  contained  the  mesenteric  blood-vessels,  nerves,  lacteals,  and  glands. 
Lastly,  it  passes  over  the  left  kidney  to  the  sides  and  anterior  surface  of  the  descend- 
ing colon,  and,  reaching  the  abdominal  wall,  is  continued  along  it  to  the  middle 
line  of  the  abdomen. 

Above  the  transverse  colon  (Fig.  489)  the  peritoneum  can  be  traced,  forming 
the  greater  and  lesser  cavities,  and  their  communication  through  the  foramen  of 
Winslow  can  be  demonstrated.  Commencing  in  the  middle  line  of  the  abdomen, 
the  membrane  may  be  traced  lining  its  anterior  wall,  and  sending  a  process  back- 
ward to  encircle  the  obliterated  umbilical  vein  (the  round  ligament  of  the  liver), 
forming  the  falciform  or  longitudinal  ligament  of  the  liver.      Continuing  its  course 


THE   PERITONEUM. 


901 


to  the  right,  it  is  reflected  over  the  front  of  the  upper  part  of  the  right  kidney, 
across  the  vena  cava  inferior  and  aorta,  and  over  the  left  kidney  to  the  hiluru  of 
the  spleen,  forming  the  anterior  layer  of  the  lieno-renal  ligament,  the  posterior 
layer  being  formed  by  the  termination  of  the  cul-de-sac  of  the  greater  cavity  be- 
tween the  kidney  and  spleen.  From  the  hilum  of  the  spleen  it  is  reflected  to  the 
stomach,  forming  the  posterior  layer  of  the  g astro-splenic  omentum.  It  covers  the 
posterior  surface  of  the  stomach,  and  from  its  lesser  curvature  it  passes  around  the 
portal  vein,  hepatic  artery,  and  bile-duct,  and  back  again  to  the  stomach,  as  the 
lesser  omentum,  and  thus  it  forms  the  anterior  boundary  of  the  foramen  of  Wins- 
low.  It  now  covers  the  front  of  the  stomach,  and  upon  reaching  the  cardiac 
extremity  it  passes  to  the  hilum  of  the  spleen,  forming  the  anterior  layer  of  the 
gastro-splenic  omentum.  From  the  hilum  of  the  spleen  it  can  be  traced  over  the 
surface  of  this  organ,  to  which  it  gives  a  serous  covering  ;  it  is  then  reflected  from 
the  posterior  border  of  the  hilum  on  to  the  left  kidney,  forming  the  posterior  layer 
of  the  lieno-renal  ligament. 


Lesser  omentum. 


ROUND    LIGAMENT   OF    LIVER. 


Hepatic  artery,  portal 
(vein,  and  hepatic  duct. 


Gastro-splenic 
omentum, 


lieno-renal  ligament.     Abdominal  aorta.  Vena  cava. 

Fig.  489.— Transverse  section  of  peritoneum. 

Numerous  folds,  formed  by  the  peritoneum,  extend  between  the  various  organs 
or  connect  them  to  the  parietes.  These  serve  to  hold  them  in  position,  and  at  the 
same  time  enclose  the  vessels  and  nerves  proceeding  to  each  part.  Some  of  these 
folds  are  called  ligaments,  such  as  the  ligaments  of  the  liver  and  the  false  ligaments 
of  the  bladder.  Others,  which  connect  certain  parts  of  the  intestine  with  the 
abdominal  wall,  constitute  the  mesenteries ;  and  lastly,  those  which  proceed  from 
the  stomach  to  certain  viscera  in  its  neighborhood  are  called  omenta. 

The  Ligaments,  formed  by  folds  of  the  peritoneum,  include  those  of  the  liver, 
spleen,  bladder,  and  uterus.  They  will  be  found  described  with  their  respective 
organs. 

The  Omenta  are :  the  lesser  omentum,  the  great  omentum,  and  the  gastro-splenic 
omentum. 

The  lesser  omentum  {g astro-hepatic)  is  the  duplicature  which  extends  between 
the  transverse  fissure  of  the  liver  and  the  lesser  curvature  of  the  stomach.  It  is 
extremely  thin,  and  consists  of  two  layers  of  peritoneum  :   that  is,  the  two   lavers 


902  THE    ORGANS    OF   DIGESTION. 

covering  respectively  the  anterior  and  posterior  surfaces  of  the  stomach.  When 
these  two  layers  reach  the  lesser  curvature  of  the  stomach,  they  join  together  and 
ascend  as  the  double  fold  to  the  transverse  fissure  of  the  liver  ;  to  the  left  of  this 
fissure  the  double  fold  is  attached  to  the  fissure  of  the  ductus  venosus  as  far  as  the 
Diaphragm,  where  the  two  layers  separate  to  embrace  the  end  of  the  oesophagus. 
At  the  right  border  the  lesser  omentum  is  free,  and  the  two  layers  of  which  it  is 
composed  are  continuous.  The  anterior  layer,  which  belongs  to  the  greater  sac, 
turns  round  the  hepatic  vessels  to  become  continuous  with  the  posterior  layer  be- 
longing to  the  lesser  one.  They  here  form  a  free,  rounded  margin,  which  contains 
between  its  layers  the  hepatic  artery,  the  common  bile-duct,  the  portal  vein, 
lymphatics,  and  the  hepatic  plexus  of  nerves — all  these  structures  being  enclosed  in 
loose  areolar  tissue,  called  Glisson's  capsule.  Between  the  layers  where  they  are 
attached  to  the  stomach  lie  the  gastric  artery  and  the  pyloric  branch  of  the  hepatic, 
anastomosing  with  it. 

The  great  omentum  (cjastro-colic)  is  the  largest  peritoneal  fold.  It  consists  of 
four  layers  of  peritoneum,  two  of  which  descend  from  the  stomach,  one  from  its 
anterior,  the  other  from  its  posterior  surface,  and,  uniting  at  its  lower  border, 
descend  in  front  of  the  small  intestines,  sometimes  as  low  down  as  the  pelvis ; 
they  then  turn  upon  themselves,  and  ascend  again  as  far  as  the  transverse  colon, 
where  they  separate  and  enclose  that  part  of  the  intestine.  These  separate  layers 
may  be  easily  demonstrated  in  the  young  subject,  but  in  the  adult  they  are  more 
or  less  inseparably  blended.  The  left  border  of  the  great  omentum  is  continuous 
with  the  gastro-splenic  omentum :  its  right  border  extends  as  far  only  as  the 
duodenum.  The  great  omentum  is  usually  thin,  presents  a  cribriform  appearance, 
and  always  contains  some  adipose  tissue,  which  in  fat  subjects  accumulates  in 
considerable  quantity.  Its  use  appears  to  be  to  protect  the  intestines  from  the 
cold,  and  to  facilitate  their  movement  upon  each  other  during  their  vermicular 
action.  Between  its  two  anterior  layers  is  the  anastomosis  between  the  right  and 
left  gastro-epiploic  arteries. 

The  gastro-splenic  omentum  is  the  fold  which  connects  the  margins  of  the 
hilum  of  the  spleen  to  the  cul-de-sac  of  the  stomach,  being  continuous  by  its  lower 
border  with  the  great  omentum.      It  contains  the  vasa  brevia  vessels. 

The  Mesenteries  are :  the  mesentery  proper,  the  transverse  mesocolon,  the 
sigmoid  mesocolon,  and  the  mesorectum.  In  addition  to  these  there  are  some- 
times present  an  ascending  and  a  descending  mesocolon. 

The  mesentery  yfxsaov  ivrepov),  so  called  from  being  connected  to  the  middle 
of  the  cylinder  of  the  small  intestine,  is  the  broad  fold  of  peritoneum  which 
connects  the  convolutions  of  the  jejunum  and  ileum  with  the  posterior  wall  of 
the  abdomen.  Its  root,  the  part  connected  with  the  vertebral  column,  is  narrow, 
about  six  inches  in  length,  and  directed  obliquely  from  the  left  side  of  the  second 
lumbar  vertebra  to  the  right  sacro-iliac  symphysis  (Fig.  490).  Its  intestinal 
border  is  much  longer  ;  and  here  its  two  layers  separate  so  as  to  enclose  the 
intestine,  and  form  its  peritoneal  coat.  Its  breadth,  between  its  vertebral  and 
intestinal  border,  is  about  eight  inches.  Its  upper  border  is  continuous  with  the 
under  surface  of  the  transverse  mesocolon  :  its  lower  border,  with  the  peritoneum 
covering  the  caecum  and  ascending  colon.  It  serves  to  retain  the  small  intestines 
in  their  position,  and  contains  between  its  layers  the  mesenteric  vessels  and 
nerves,  the  lacteal  vessels,  and  mesenteric  glands. 

In  most  cases  the  peritoneum  covers  only  the  front  and  sides  of  the  ascending 
and  descending  parts  of  the  colon.  Sometimes,  however,  these  are  surrounded 
by  the  serous  membrane  and  attached  to  the  posterior  abdominal  wall  by  an 
ascending  and  a  descending  mesocolon  respectively.  At  the  place  where  the 
transverse  colon  turns  downwards  to  form  the  descending  colon,  a  fold  of  perito- 
neum is  continued  to  the  under  surface  of  the  Diaphragm  opposite  the  tenth  and 
eleventh  ribs.  This  is  the  phreno-colic  ligament ;  it  passes  below  the  spleen,  and 
serves  to  support  this  organ,  and  therefore  it  has  received  the  second  name  of 
sustentaculum  lienis. 


THE   PERITONEUM. 


903 


The  transverse  mesocolon  is  a  broad  fold,  which  connects  the  transverse  colon 
to  the  posterior  wall  of  the  abdomen.  It  is  formed  by  the  two  ascending  or 
posterior  layers  of  the  great  omentum,  which,  after  separating  to  surround  the 
transverse  colon,  join  behind  it,  and  are  continued  backward  to  the  spine,  where 
they  diverge  in  front  of  the  duodenum.  This  fold  contains  between  its  layers  the 
vessels  which  supply  the  transverse  colon. 


Right  lateral 
ligament  of  liver. 


Falciform  ligament  Left  lateral 

of  liver.  ligament  of  liver. 


Vena  cava  inferior 


(Esophagus.- 
Right  phrenic  artery.- 


Coronary  artery.- 
Hepatic  artery. 


Inf.  pane. -duo.  artery.- 

Colica  media.- 

Superior  mesenteric. 

Duodenum  (3rd  part). 

Aorta.  ■ 

Duodenum  (2nd part).' 

Right  and  left  kidneys. 

Superior  mesenteric. 

Aorta. 

Colica  sinistra. 

Colica  dextra. 

Yasa  intestini.  < 

Sigmoid  artery, 
t.  hemorrhoidal  artery. 

Gomrnan  iliac  artery. 


Internal  iliac  artery.— 

External  iliac  artery. '" 

Epigastric  artery.  "" 
Bladder.  " 


Peritoneum. 
Extra-peritoneal  tissue. 

C  Diaphragmatic  end  of 
I    gastro-hepatic  omentum, 
Gastro-phrenic  ligament. 


Gastro- splenic  omentum. 
Foramen  of  Winslow. 
Duodenum  (1st  part). 


Costo-colic  ligament. 
C  Dot  between  two  anterior 
I    layers  of  great  omentum. 
Transverse  meso-colon. 

<  Bare  surface  for  descend' 
i    ing  colon. 


The  two  layers  of  the 
mesentery  proper. 


\  Bare  surface  for  ascend' 
i    ing  colon. 


Sigmoid  meso-colon. 


Bare  surface  for  cecum. 
Meso- rectum. 

5  Bare  surface  for  2nd  part 
f    of  rectum. 
j  Left  lateral  false  liga- 
(    ment  of  bladder. 


Fig.  490.— Diagram  devised  by  Dr. 
of  the  abdomen  to  invest  the  viscera. 


Delepine  to  show  the  lines  along  which  the  peritoneum  leaves  the  wall 


The  sigmoid  mesocolon  is  the  fold  of  peritoneum  which  retains  the  sigmoid 
flexure  in  connection  with  the  left  iliac  fossa. 

The  mesorectum  is  the  narrow  fold  which  connects  the  upper  part  of  the 
rectum  with  the  front  of  the  sacrum.  It  contains  the  superior  hemorrhoidal 
vessels. 

The  appendices  epiploicce  are  small  pouches  of  the  peritoneum  filled  with  fat 
and  situated  along  the  colon  and  upper  part  of  the  rectum.  They  are  chiefly 
appended  to  the  transverse  colon. 

~  Retro-peritoneal  fossa?. — In  certain  parts  of  the  abdominal  cavity  there  are 
recesses  of  peritoneum  forming  culs-de-sac  or  pouches,  which  are  of  surgical  inter- 


904  THE    ORGANS    OF  DIGESTION. 

est  in  connection  with  the  possibility  of  the  occurrence  of  retro-peritoneal  hernia. 
One  of  these  is  the  lesser  sac  of  the  peritoneum,  which  may  be  regarded  as  a  recess 
of  peritoneum  through  the  foramen  of  Winslow,  in  which  a  hernia  may  take  place, 
but  there  are  several  others,  of  smaller  size,  which  require  mention. 

These  recesses  of  fossae  may  be  divided  into  three  groups,  viz. :  (1)  the  duodenal 
fossae ;  (2)  pericecal  fossae  ;  and  (3)  the  intersigmoid  fossa. 

1.  Duodenal  Fossce. — Moynihan  has  described  no  less  than  nine  fossae  as  occur- 
ring in  the  neighborhood  of  the  duodenum.  Three  of  these  are  fairly  constant,  and 
are  the  only  ones  which  require  mention,  (a)  The  inferior  duodenal  fossa  is  the 
most  constant  of  all  the  peritoneal  fossae  in  this  region,  being  present  in  from  70  to 
75  per  cent,  of  cases.  It  is  situated  opposite  the  third  lumbar  vertebra  on  the  left 
side  of  the  ascending  portion  of  the  duodenum.  The  opening  into  the  fossa  is 
directed  upward,  and  is  bounded  by  a  thin  sharp  fold  of  peritoneum  with  a  concave 
margin,  called  the  inferior  duodenal  fold.  The  tip  of  the  index  finger  introduced 
into  the  fossa  under  the  fold  passes  some  little  distance  up  behind  the  ascending  or 
fourth  portion  of  the  duodenum,  (b)  The  superior  duodenal  fossa  is  the  next  most 
constant  pouch  or  recess,  being  present  in  from  40  to  50  per  cent,  of  cases.  It 
often  coexists  with  the  inferior  one,  and  its  orifice  looks  downward,  in  the  opposite 
direction  to  the  preceding  fossa.  It  lies  to  the  left  of  the  ascending  portion  of  the 
duodenum.  It  is  bounded  by  the  free  edge  of  the  superior  duodenal  fold,  which 
presents  a  semilunar  margin  ;  to  the  right  it  is  blended  with  the  peritoneum  cover- 
ing the  ascending  duodenum,  and  to  the  left  with  the  peritoneum  covering  the  peri- 
renal tissues.  The  fossa  is  bounded  in  front  by  the  superior  duodenal  fold  ;  behind 
by  the  second  lumbar  vertebra  ;  to  the  right  by  the  duodenum.  Its  depth  is  2  cm., 
and  it  terminates  in  the  angle  formed  by  the  left  renal  vein  crossing  the  aorta.  This 
fossa  is  of  importance,  as  it  is  in  relation  with  the  inferior  mesenteric  vein  :  that  is 
to  say,  the  vein  almost  always  corresponds  to  the  line  of  union  of  the  superior 
duodenal  fold  with  the  posterior  parietal  peritoneum,  (c)  The  duodenojejunal  fossa 
can  be  seen  by  pulling  the  jejunum  downward  and  to  the  right,  after  the  transverse 
colon  has  been  pulled  upward.  It  will  appear  as  an  almost  circular  opening,  look- 
ing downward  and  to  the  right,  and  bounded  by  two  free  borders  or  folds  of  perito- 
neum, the  duodeno-inescocolic  ligaments.  The  opening  admits  the  little  finger  into 
the  fossa  to  the  depth  of  from  2  to  3  cm.  The  fossa  is  bounded  above  by  the 
pancreas,  to  the  right  by  the  aorta,  and  to  the  left  by  the  kidney  ;  beneath  is  the 
left  renal  vein.  The  fossa  exists  in  from  15  to  20  per  cent,  of  cases,  and  has  never 
yet  been  found  in  conjunction  with  any  other  form  of  duodenal  fossa. 

2.  Pericecal  Fossce. — There  are  at  least  three  pouches  or  recesses  to  be  found 
in  the  neighborhood  of  the  caecum,  which  are  termed  pericecal  fossce.  (1)  The 
ileo-colic  fossa  (superior  ileo-caecal)  is  formed  by  a  fold  of  peritoneum,  the  ileo-colic 
fold,  arching  over  a  branch  of  the  ileo-colic  artery,  which  supplies  the  ileo-colic 
junction,  and  appears  to  be  the  direct  continuation  of  the  artery.  The  fossa  is  a 
narrow  chink  situated  between  the  ileo-colic  fold  in  front,  and  the  mesentery  of  the 
small  intestine,  the  ileum,  and  a  small  portion  of  the  caecum  behind.  (2)  The 
ileo-coscal  fossa  (inferior  ileo-caecal)  is  situated  behind  the  angle  of  junction  of  the 
ileum  and  caecum.  It  is  formed  by  a  fold  of  peritoneum  (the  ileo-caecal  fold  or 
bloodless  fold  of  Treves),  the  upper  border  of  which  is  attached  to  the  ileum,  oppo- 
site its  mesenteric  attachment,  and  the  lower  border,  passing  over  the  ileo-caecal 
junction,  joins  the  mesentery  of  the  appendix,  and  sometimes  the  appendix  itself; 
hence  this  fold  is  sometimes  called  the  ileo-appendicular.  Between  this  fold  and 
the  mesentery  of  the  vermiform  appendix  is  the  ileo-caecal  fossa.  It  is  bounded 
above  by  the  posterior  surface  of  the  ileum  and  the  mesentery ;  in  front  and  below  by 
the  ileo-caecal  fold,  and  behind  by  the  upper  part  of  the  mesentery  of  the  appendix. 
(3)  The  subcecal  fossa  (retro-caecal)  is  situated  immediately  behind  the  caecum, 
which  has  to  be  raised  to  bring  it  into  view.  It  varies  much  in  size  and  extent.  In 
some  cases  it  is  sufficiently  large  to  admit  the  index  finger,  and  extends  upward 
behind  the  ascending  colon  in  the  direction  of  the  kidney  :  in  others  it  is  merely  a 
shallow  depression.     It  is  bounded  and  formed  by  two  folds:  one,  the parieto-colic, 


THE   STOMACH.  905 

which  is  attached  by  one  edge  to  the  abdominal  wall  from  the  lower  border  of  the 
kidney  to  the  iliac  fossa  and  by  the  other  to  the  postero-external  aspect  of  the  colon ; 
and  the  other,  mesenterico-parietal,  which  is  in  reality  the  insertion  of  the  mesen- 
tery into  the  iliac  fossa.     In  some  instances  the  subcaecal  fossa  is  double. 

3.  The  Intersigmoid  fossa  is  constant  in  the  foetus  and  during  infancy,  but 
disappears  in  a  certain  percentage  of  cases  as  age  advances.  Upon  drawing  the 
sigmoid  flexure  upward,  the  left  surface  of  the  sigmoid  mesocolon  is  exposed,  and 
on  it  will  be  seen  a  funnel-shaped  recess  of  the  peritoneum,  lying  on  the  external 
iliac  vessels,  in  the  interspace  between  the  Psoas  and  Iliacus  muscles.  This  is  the 
orifice  leading  to  the  fossa  intersigmoidea,  which  lies  behind  the  sigmoid  mesocolon, 
and  in  front  of  the  parietal  peritoneum.  The  fossa  varies  in  size  ;  in  some  instances 
it  is  a  mere  dimple,  whereas  in  others  it  will  admit  the  whole  of  the  index  finger. 

Any  of  these  fossae  may  be  the  site  of  a  retro-peritoneal  hernia.  The  periesecal 
fossae  are  of  especial  interest,  because  hernia  of  the  vermiform  appendix  frequently 
takes  place  into  one  of  them,  and  may  there  become  strangulated.  The  presence 
of  these  pouches  also  explains  the  course  which  pus  has  been  known  to  take  in 
cases  of  perforation  of  the  appendix,  where  it  travels  upward  behind  the  ascending 
colon  a3  far  as  the  Diaphragm.1 

THE  STOMACH. 

The  Stomach  is  the  principal  organ  of  digestion.  It  is  the  most  dilated  part  of 
the  alimentary  canal,  and  is  situated  between  the  termination  of  the  oesophagus  and 
the  commencement  of  the  small  intestine.  Its  form  is  somewhat  pyriform  with  the 
large  end  {fundus)  directed  upward  and  the  small  end  bent  to  the  right.  It  is 
situated  in  the  left  hypochondriac  and  epigastric  regions,  and  is  placed,  in  part, 
immediately  behind  the  anterior  wall  of  the  abdomen  and  beneath  the  Diaphragm. 
Viewing  the  stomach  from  in  front  it  appears  that  the  right  margin  of  the  oesopha- 
gus is  continued  downward  as  the  upper  two-thirds  of  the  lesser  curvature  of  the 
stomach,  the  remaining  third  of  this  border  bending  sharply  backward  and  to  the 
right,  to  complete  the  smaller  curvature  (Fig.  491).  The  greater  curvature  begins  at 
the  left  border  of  the  termination  of  the  oesoph- 
agus in  a  somewhat  acute  angle ;  it  then 
passes  upward  and  to  the  left  to  the  under  sur- 
face of  the  Diaphragm,  with  which  it  lies  in  Cardiac  orifice^ 
contact  for  some  distance,  and  then  sweeps 
downward  with  a  convexity  to  the  left,  and,  Lesser  curvature^ 
continued  across  the  middle  line  of  the  body, 
finally  turns  upward  and  backward,  to  termi- 
nate at  the  commencement  of  the  small  intes- 
tine. It  will  thus  be  seen  that  the  stomach  Pylorus^ 
may  be  divided  into  a  main  or  cardiac  portion, 
the  long  axis  of  which  is  directed  downward,  pylon 
with  a  little  inclination  forward  and  to  the  right,  Fig.  491.— Diagrammatic  outline  of  the 

and  a  smaller  or  pyloric  portion,  the  long  axis 

of  which  is  horizontal  with  an  inclination  backward.  Of  the  two  openings,  the 
cardiac  orifice,  by  which  it  communicates  with  the  oesophagus,  is  situated  slightly 
to  the  left  of  the  middle  line  of  the  body  to  the  right  of  the  fundus,  or  dilated 
upper  extremity  of  the  stomach,  and  is  directed  downward ;  the  other,  the  pyloric 
orifice,  by  which  it  communicates  with  the  small  intestine,  is  on  a  lower  plane,  close 
to  the  right  of  the  mid-line,  and  looks  directly  backward. 

The  stomach  has  two  surfaces,  called  anterior  and  posterior,  and  two  borders, 
termed  the  greater  and  lesser  curvatures. 

Surfaces. — With  regard  to  the  so-called  anterior  and  posterior  surfaces  of  the 
stomach,  it  must  be  borne  in  mind  that  these  names  are  not  strictly  correct,  as  the 
anterior  surface  has  a  certain  amount  of  inclination  upward  and  the  posterior 
downward. 

1  On  the  anatomy  of  these  fossae,  see  the  Arris  and  Gale  Lectures  by  Moynihan,  1899. 


906  THE    ORGANS    OF  DIGESTION. 

The  anterior  surface  has  a  somewhat  flattened  appearance  when  the  stomach  is 
empty,  but  when  it  is  full  the  surface  becomes  convex.  It  is  in  relation  with  the 
Diaphragm ;  the  thoracic  wall  formed  by  the  anterior  parts  of  the  seventh,  eighth, 
and  ninth  ribs  of  the  left  side;  the  left  lobe  of  the  liver;  and  the  anterior 
abdominal  wall.  Between  the  part  covered  by  the  liver  and  that  covered  by  the 
left  ribs  there  is  a  triangular  segment  of  the  anterior  wall  of  the  stomach,  which 
is  in  contact  with  the  abdominal  wall  and  is  the  only  part  of  the  stomach  which 
is  visible  when  the  abdominal  wall  is  removed  and  the  viscera  allowed  to  remain 
in  situ.  It  is  of  about  40  sq.  cm.  and  is  of  great  importance  to  the  surgeon,  as 
the  stomach  can  readily  be  reached  in  this  situation.  Occasionally  the  transverse 
colon  may  be  found  lying  in  front  of  the  loAver  part  of  the  anterior  surface  of  the 
stomach.     The  whole  of  this  surface  of  the  stomach  is  covered  by  peritoneum. 

The  posterior  surface  of  the  stomach  is  in  relation  with  the  Diaphragm,  the 
gastric  surface  of  the  spleen,  the  left  supra-renal  capsule,  the  upper  part  of  the  left 
kidney,  the  anterior  surface  of  the  pancreas,  the  splenic  flexure  of  the  colon,  and 
the  ascending  layer  of  the  transverse  mesocolon.  These  structures  form  a  shallow 
concavity  or  bed  on  which  this  surface  of  the  stomach  rests.  The  transverse 
mesocolon  intervenes  between  the  stomach  and  the  duodeno-jejunal  junction  and 
commencement  of  the  ileum.  Its  greater  curvature  is  in  relation  with  the  trans- 
verse colon  and  has  attached  to  it  the  anterior  two  layers  of  the  great  omentum. 
Almost  the  whole  of  this  surface  is  covered  with  peritoneum,  but  behind  the 
cardiac  orifice  there  is  a  small  portion  of  the  stomach  which  is  uncovered  by 
peritoneum  and  is  in  contact  with  the  Diaphragm  and  frequently  with  the  upper 
portion  of  the  left  supra-renal   capsule. 

The  lesser  curvature  of  the  stomach  extends  between  the  cardiac  and  pyloric 
orifices  along  the  right  border  of  the  organ.  It  descends  in  front  of  the  left  crus 
of  the  Diaphragm,  along  the  left  side  of  the  eleventh  and  twelfth  dorsal  vertebrae, 
and  then  turning-  to  the  right  it  crosses  the  first  lumbar  vertebra  and  ascends  to 
the  pylorus.  It  gives  attachment  to  the  two  layers  of  the  gastro-hepatic  omentum, 
between  which  blood-vessels  and  lymphatics  pass  to  reach  the  organ. 

The  greater  curvature  is  directed  to  the  left,  and  is  four  or  five  times  as  long 
as  the  lesser  curvature.  Starting  from  the  cardiac  orifice,  it  forms  an  arch  to  the 
left  with  its  convexity  upward,  the  highest  point  of  which  is  on  a  level  with  the 
costal  cartilage  of  the  sixth  rib  of  the  left  side.  It  then  passes  nearly  straight 
downward,  with  a  slight  convexity  to  the  left,  as  low  as  the  costal  cartilage  of 
the  ninth  rib  and  then  turns  to  the  right  to  end  at  the  pylorus.  As  it  crosses  the 
median  line  the  lowest  edge  of  the  greater  curvature  is  about  two  fingers'  breadth 
above  the  umbilicus.  The  lower  part  of  the  greater  curvature  gives  attachment  to 
the  two  anterior  layers  of  the  great  omentum,  between  which  layers,  vessels  and 
lymphatics  pass  to  the  organ. 

The  cardiac  orifice  is  the  opening  by  which  the  oesophagus  communicates  with 
the  stomach.  It  is  therefore  sometimes  termed  the  oesophageal  opening.  It  is 
the  most  fixed  part  of  the  stomach,  and  is  situated  about  two  inches  below  the 
highest  part  of  the  fundus  on  a  level  with  the  body  of  the  tenth  or  eleventh 
dorsal  vertebra  to  the  left  and  a  little  in  front  of  the  aorta.  This  would  correspond 
on  the  anterior  surface  of  the  body  to  the  articulation  of  the  seventh  left  costal 
cartilage  to  the  sternum. 

The  pyloric  orifice  communicates  with  the  duodenum,  the  aperture  being 
guarded  by  a  valve.  Its  position  varies  with  the  movements  of  the  stomach. 
When  the  stomach  is  empty  the  pylorus  is  situated  just  to  the  right  of  the  median 
line  of  the  body,  on  a  level  with  the  upper  border  of  the  first  lumbar  vertebra. 
On  the  anterior  surface  of  the  body  its  position  would  be  indicated  by  a  point  one 
inch  below  the  tip  of  the  ensiform  cartilage  and  a  little  to  the  right.  As  the 
stomach  becomes  distended  the  pylorus  moves  to  the  right,  and  in  a  fully  distended 
stomach  may  be  situated  two  or  three  inches  to  the  right  of  the  median  line. 
Near  the  pylorus  the  stomach  frequently  exhibits  a  slight  dilatation,  which  is 
named  the  antrum  pylorus. 


THE   STOMACH. 


907 


The  size  of  the  stomach  varies  considerably  in  different  subjects.  When  mod- 
erately distended  its  greatest  length,  from  the  top  of  the  fundus  to  the  lowest  part 
of  the  greater  curvature,  is  from  ten  to  twelve  inches ;  and  its  diameter  at  the 
widest  part  from  four  to  five  inches.  The  distance  between  the  two  orifices  is  three 
to  six  inches,  and  the  measurement  from  the  anterior  to  the  posterior  wall  three 
and  a  half  inches.  Its  weight,  according  to  Clendinning,  is  about  four  ounces  and 
a  half,  and  its  capacity  in  the  adult  male  is  five  to  eight  pints. 

Alterations  in  Position. — There  is  no  organ  in  the  body  the  position  and  connections  of  which 
present  such  frequent  alterations  as  the  stomach.  When  empty,  it  lies  at  the  back  part  of  the 
abdomen,  some  distance  from  the  surface.  Its  pyloric  end  is  situated  close  to  or  very  slightly  to 
the  right  of  the  middle  line,  covered  in  front  by  the  left  lobe  of  the  liver,  and  being  on  a  level 
with  the  first  lumbar  vertebra.  When  empty,  the  stomach  assumes  a  more  or  less  cylindrical 
form,  especially  noticeable  at  its  pyloric  end.  When  the  stomach  is  distended,  its  surfaces,  which 
are  flattened  when  the  organ  is  empty,  become  convex.  The  greater  curvature  is  elevated  and 
carried  forward,  so  that  the  anterior  surface  is  turned  more  or  less  upward  and  the  posterior 
surface  downward,  and  the  stomach  brought  well  against  the  anterior  wall  of  the  abdomen.  Its 
fundus  expands  and  rises  considerably  above  the  level  of  the  cardiac  orifice :  in  doing  this  the 


Cystic  duct. 


Fig.  492. — The  mucous  membrane  of  the  stomach  and  duodenum  with  the  bile-ducts. 

Diaphragm  is  forced  upward,  contracting  the  cavity  of  the  chest ;  hence  the  dyspnoea  complained 
of,  from  inspiration  being  impeded.  The  apex  of  the  heart  is  also  tilted  upward ;  hence  the 
oppression  in  this  region  and  the  palpitation  experienced  in  extreme  distention  of  the  stomach. 
The  left  lobe  of  the  liver  is  pushed  to  the  right  side.  When  the  stomach  becomes  distended 
the  change  in  the  position  of  the  pylorus  is  very  considerable;  it  is  shifted  to  the  right,  seme 
two  or  three  inches  from  the  median  line,  and  lies  under  cover  of  the  liver,  near  the  neck  of  the 
gall-bladder.  In  consequence  of  the  distention  of  the  stomach  the  lesser  ad-de-sac  bulges  over 
the  pylorus,  concealing  it  from  view,  and  causing  it  to  undergo  a  rotation,  so  that  its  orifice  is 
directed  backward.  During  inspiration  the  stomach  is  displaced  downward  by  the  descent  of 
the  Diaphragm,  and  elevated  by  the  pressure  of  the  abdominal  muscles  during  expiration. 
Pressure  from  without,  as  from  tight  lacing,  pushes  the  stomach  down  toward  the.  pelvis.  In 
disease,  also,  the  position  and  connection  of  the  organ  maybe  greatly  changed,  from  the  accumu- 
lation of  fluid  in  the  chest  or  abdomen,  or  from  alteration  in  size  of  any  of  the  surrounding 


908 


THE    ORGANS    OF  DIGESTION. 


viscera.  Variations  according  to  Age. — In  an  early  period  of  development  the  stomach  is  verti- 
cal, and  in  the  newborn  child  it  is  more  vertical  than  later  on  in  life,  as  owing  to  the  large  size 
of  the  liver  it  is  more  pushed  over  to  the  left  side  of  the  abdomen,  and  the  whole  of  the  anterior 
surface  is  covered  by  the  left  lobe  of  this  organ. 

On  looking  into  the  pyloric  end  of  the  stomach,  the  mucous  membrane  is 
found  projecting  inward  in  the  form  of  a  circular  fold,  the  'pyloric  valve,  leaving 
a  narrow  circular  aperture,  about  half  an  inch  in  diameter,  by  which  the  stomach 
communicates  with  the  duodenum. 

The  pyloric  valve,  is  formed  by  a  reduplication  of  the  mucous  membrane  of  the 
stomach,  containing  numerous  circular  fibres,  which  are  aggregated  into  a  thick 
circular  ring ;  the  longitudinal  fibres  and  serous  membrane  being  continued  over 
the  fold  Avithout  assisting  in  its  formation. 

Structure. — The  wall  of  the  stomach  consists  of  four  coats  :  serous,  muscular, 
areolar,  and  mucous,  together  with  vessels  and  nerves. 

The  serous  coat  is  derived  from  the  peritoneum,  and  covers  the  entire  surface 
of  the  organ,  excepting  along  the  greater  or  lesser  curvatures,  at  the  points  of 
attachment  of  the  greater  and  lesser  omenta ;  here  the  two  layers  of  peritoneum 
leave  a  small  triangular  space,  along  which  the  nutrient  vessels  and  nerves  pass. 
On  the  posterior  surface  of  the  stomach,  close  to  the  cardiac  orifice,  there  is  also  a 
small  area  uncovered  by  peritoneum,  where  the  organ  is  in  contact  with  the  under 
surfaces  of  the  Diaphragm. 

The  muscular  coat  (Fig.  493)  is  situated  immediately  beneath  the  serous  cover- 
ing, to  which  it  is  closely  connected.  It  consists  of  three  sets  of  fibres — longi- 
tudinal, circular,  and  oblique. 


'  vature. 
Fig.  493.— The  muscular  coat  of  the  stomach. 


The  longitudinal  fibres  are  most  superficial ;  they  are  continuous  with  the 
longitudinal  fibres  of  the  oesophagus,  radiating  in  a  stellate  manner  from  the  cardiac 
orifice.  They  are  most  distinct  along  the  curvatures,  especially  the  lesser,  but  are 
very  thinly  distributed  over  the  surfaces.  At  the  pyloric  end  they  are  more  thickly 
distributed,  and  continuous  with  the  longitudinal  fibres  of  the  small  intestine. 

The  circular  fibres  form  a  uniform  layer  over  the  whole  extent  of  the  stomach 
beneath  the  longitudinal  fibres.  At  the  pylorus  they  are  most  abundant,  and  are 
aggregated  into  a  circular  ring,  which  projects  into  the  cavity,  and  forms,  with  the 
fold  of  mucous  membrane  covering  its  surface,  the  pyloric  valve.  They  are  con- 
tinuous with  the  circular  fibres  of  the  oesophagus. 


THE   STOMACH. 


909 


The  oblique  fibres  are  limited  chiefly  to  the  cardiac  end  of  the  stomach,  where 
they  are  disposed  as  a  thick  uniform  layer,  covering  both  surfaces,  some  passing 
obliquely  from  left  to  right,  others  from  right  to  left,  round  the  cardiac  end. 

The  areolar  or  submucous  coat  consists  of  a  loose,  filamentous,  areolar  tissue, 
connecting  the  mucous  and  muscular  layers.  It  supports  the  blood-vessels  previous 
to  their  distribution  to  the  mucous  membrane :  hence  it  is  sometimes  called  the 
vascular  coat. 

The  mucous  membrane  is  thick  ; 
fresh  state  it  is  of  a  pinkish  tinge 
brown  color  over  the  rest  of  its 
vascular  redness  being  more 

thicker  toward  the  pylorus.  During  the  contracted  state  of  the  organ  it  is  thrown 
into  numerous  plaits  or  rugse,  which  for  the  most  part  have  a  longitudinal  direc- 
tion, and  are  most  marked  toward  the  lesser  end  of  the  stomach  and  along  the 
greater  curvature  (Fig.  492).  These  folds  are  entirely  obliterated  when  the  organ 
becomes  distended. 

Structure  of  the  Mucous  Membrane. — When  examined  with  a  lens  the  inner 
surface  of  the  mucous  membrane  presents  a  peculiar  honeycomb  appearance,  from 


its  surface  smooth,  soft,  and  velvety.     In  the 
at  the  pyloric  end,  and  of  a  red  or  reddish- 
surface.      In  infancy  it  is  of  a  brighter  hue,  the 
marked.     It  is  thin  at  the   cardiac  extremity,   but 


Fig.  4lJ4  —  Pyloric  gland. 


Fig.  495.— Peptic  gastric  gland. 


being  covered  with  small  shallow  depressions  or  alveoli  of  a  polygonal  or  hexagonal 
form  which  vary  from  ^  to  ^  of  an  inch  in  diameter,  and  are  separated  bv 
slightly  elevated  ridges.  In  the  bottom  of  the  alveola  are  seen  the  orifices  of 
minute  tubes,  the  gastric  glands,  which  are  situated  perpendicularlv  side  bv  side 
throughout  the  entire  substance  of  the  mucous  membrane.  The  surface  of  the 
mucous  membrane  of  the  stomach  is  covered  by  a  single  layer  of  columnar  epithe- 
lium ;  it  lines  the  alveoli,  and  also  for  a  certain  distance  the  mouths  of  the  gastric 
glands.  This  epithelium  commences  verv  abruptly  at  the  cardiac  orifice,  where  the 
cells  suddenly  change  in  character  from  the  stratified  epithelium  of  the  oesophagus. 
Ihe  cells  are  elongated,  and  consist  of  two  parts,  the  inner  or  attached  portions 
being  granular,  and  the  outer  or  free  parts  being  clear  and  occupied  by  a  muco- 
albuminous  substance. 


910  THE    ORGANS    OF  DIGESTION. 

The  gastric  glands  are  of  two  kinds,  which  differ  from  each  other  in  structure, 
and  it  is  believed  also  in  the  nature  of  their  secretion.  They  are  named  respectively 
pyloric' audi  cardiac  or  oxyntic  glands.  They  are  both  tubular  in  character,  and 
are  formed  of  a  delicate  basement-membrane,  lined  by  epithelium.  The  basement- 
membrane  consists  of  flattened  transparent  endothelial  cells,  with  processes  which 
extend  between  and  support  the  epithelium.  The  pyloric  glands  (Fig.  494)  are 
most  numerous  at  the  pyloric  end  of  the  stomach,  and  from  this  fact  have  received 
their  name.  They  consist  of  two  or  three  short,  closed  tubes  opening  into  a  con 
mon  duct,  the  external  orifice  of  which  is  situated  at  the  bottom  of  an  alveolus. 
The  caecal  tubes  are  wavy,  and  are  of  about  equal  length  with  the  duct.  The  tubes 
and  duct  are  lined  throughout  with  epithelium,  the  duct  being  lined  by  columnar 
cells  continuous  with  the  epithelium  lining  the  surface  of  the  mucous  membrane 
of  the  stomach,  the  tubes  with  shorter  and  more  cubical  cells  which  are  finely  gran- 
ular. The  cardiac  glands  (Fig.  495)  are  found  all  over  the  surface  of  the  stomach, 
but  occur  most  numerously  at  the  cardiac  end.  Like  the  pyloric  glands,  they  con- 
sist of  a  duct,  into  which  open  two  or  more  caecal  tubes.  The  duct,  however,  in 
these  glands  is  shorter  than  in  the  other  variety,  sometimes  not  amounting  to  more 
than  one-sixth  of  the  whole  length  of  the  gland  ;  it  is  lined  throughout  by  columnar 
epithelium.  At  the  point  where  the  terminal  tubes  open  into  the  duct,  and  which 
is  termed  the  neck,  the  epithelium  alters,  and  consists  of  short  columnar  or  polyhe- 
dral, granular  cells,  which  almost  fill  the  tube,  so  that  the  lumen  becomes  suddenly 
constricted,  and  is  continued  down  as  a  very  fine  channel.  They  are  known  as  the 
chief  or  the  central  cells  of  the  glands.  Between  these  cells  and  the  basement- 
membrane  are  found  otheivdarker  granular-looking  cells,  studded  throughout  the 
tube  at  intervals,  and  giving  it  a  beaded  or  varicose  appearance.  These  are  known 
as  the  parietal  or  oxyntic  ells.  Between  the  glands  the  mucous  membrane  con- 
sists of  a  connective-t^oe  framework  with  lymphoid  tissue.  In  places  this  latter 
tissue,  especially  in  early  life,  is  collected  into  little  masses,  which  to  a  certain 
extent  resemble  the  solitary  glands  of  the  intestine,  and  are  by  some  termed  the 
lenticular  glands  of  the  stomach.  They  are  not,  however,  so  distinctly  circum- 
scribed as  the  Solitary  glands.  Beneath  the  mucous  membrane,  and  between  it 
and  the  submucous  coat,  is  a  thin  stratum  of  involuntary  muscular  fibre  {muscu- 
lar is  mucosce),  which  in  some  parts  consists  only  of  a  single  longitudinal  layer;  in 
others,  of  two  layers,  an  inner  circular,  and  an  outer  longitudinal. 

Vessels  and  Nerves. — The  arteries  supplying  the  stomach  are — the  gastric,  the 
pyloric  and  right  gastro-epiploic  branches  of  the  hepatic,  the  left  gastro-epiploic 
and  vasa  brevia  from  the  splenic.  They  supply  the  muscular  coat,  ramify  in  the 
submucous  coat,  and  are  finally  distributed  to  the  mucous  membrane.  The 
arrangement  of  the  vessels  in  the  mucous  membrane  is  someAvhat  peculiar.  The 
arteries  break  up  at  the  base  of  the  gastric  tubules  into  a  plexus  of  fine  capillaries 
Avhich  run  upward  between  the  tubules,  anastomosing  with  each  other,  and  ending 
in  a  plexus  of  larger  capillaries,  Avhich  surround  the  mouths  of  the  tubes  and  also 
form  hexagonal  meshes  around  the  alveoli.  From  these  latter  the  veins  arise,  and 
pursue  a  straight  course  downward  betAveen  the  tubules,  to  the  submucous  tissue, 
and  terminate  either  in  the  splenic  and  superior  mesenteric  veins  or  directly  in 
the  portal  vein.  The  lymphatics  are  numerous ;  they  consist  of  a  superficial  and 
deep  set,  which  pass  through  the  lymphatic  glands  found  along  the  two  curvatures 
of  the  organ.  The  nerves  are  the  terminal  branches  of  the  right  and  left  pneumo- 
gastric,  the  former  being  distributed  upon  the  back,  and  the  latter  upon  the  front 
part  of  the  organ.  A  great  number  of  branches  from  the  sympathetic  also  supply 
the  organ. 

Surface  Form. — The  stomach  lies  for  the  most  part  in  the  left  hypochondriac  region,  but 
also  slightly  in  the  epigastric  region,  and  is  partly  in  contact  with  the  abdominal  wall,  partly 
under  C0ATer  of  the  lower  ribs  on  the  left  side,  and  partly  under  the  left  lobe  of  the  liver.  Its 
cardiac  orifice  corresponds  to  the  articulation  of  the  seventh  left  costal  cartilage  with  the  ster- 
num. The  pyloric  orifice  is  in  a  vertical  line  drawn  from  the  right  border  of  the  sternum,  two 
and  a  half  or  three  inches  below  the  level  of  the  sterno-xiphoid  articulation.  According  to 
Braune,  Avhen  the  stomach  is  distended,  the  pylorus  moves  considerably  to  the  right,  as  much 


THE   SMALL    INTESTINE.  911 

sometimes  as  three  inches.  The  fundus  of  the  stomach  reaches,  on  the  left  side,  as  high  as  the 
level  of  the  sixth  costal  cartilage  of  the  left  side,  being  a  little  below  and  behind  the  apex  of  the 
heart.  The  portion  of  the  stomach  which  is  in  contact  with  the  abdominal  walls,  and  is  therefore 
accessible  for  opening  in  the  operations  of  gastrotomy  and  gastrostomy,  is  represented  by  a  triangular 
space,  the  base  of  which  is  formed  by  a  line  drawn  from  the  tip  of  the  tenth  costal  cartilage  on 
the  left  side  to  the  tip  of  the  ninth  costal  cartilage  on  the  right,  and  the  sides  by  two  lines  drawn 
from  the  extremity  of  the  eighth  costal  cartilage  on  the  left  side  to  the  ends  of  the  base  line. 

Surgical  Anatomy. — Operations  on  the  stomach  are  frequently  performed.  By 
"gastrotomy  "  is  meant  an  incision  into  the  stomach  for  the  removal  of  a  foreign  body,  the 
opening  being  immediately  afterward  closed — in  contradistinction  to  "gastrostomy,"  the 
making  of  a  more  or  less  permanent  fistulous  opening.  Gastrotomy  is  probably  best  performed 
by  an  incision  in  the  linea  alba,  especially  if  the  foreign  body  is  large,  by  a  cut  from  the 
ensiform  cartilage  to  the  umbilicus,  but  may  be  performed  by  an  incision  over  the  body  itself, 
where  this  can  be  felt,  or  by  one  of  the  incisions  for  gastrostomy,  to  be  mentioned  immediately. 
The  peritoneal  cavity  is  opened,  and  the  point  at  which  the  stomach  is  to  be  incised  decided 
upon.  This  portion  is  then  brought  out  of  the  abdominal  wound  and  sponges  carefully 
packed  around.  The  stomach  is  now  opened  by  a  transverse  incision  and  the  foreign  body 
extracted.  The  wound  in  tbe  stomach  is  then  closed  by  Lembert's  sutures — i.  e.  by  sutures 
passed  through  the  peritoneal  and  muscular  coats  in  such  a  way  that  the  peritoneal  surfaces 
on  each  side  of  the  wound  are  brought  into  apposition,  and  in  this  way  the  wound  is  closed. 
Gastrostomy  was  formerly  done  in  two  stages  by  the  direct  method.  The  first  stage  consisted  in 
opening  the  abdomen,  drawing  up  the  stomach  into  the  external  wound,  and  fixing  it  there  ;  and 
the  second  stage,  performed  from  two  to  four  days  afterward,  consisted  in  opening  the  stomach. 
The  operation  is  now  done  by  a  valvular  method.  An  incision  is  commenced  opposite  the  eighth 
intercostal  space,  two  inches  from  the  median  line,  and  carried  downward  for  three  inches.  By 
this  incision  the  fibres  of  the  Rectus  muscle  are  exposed  and  these  are  separated  from  each 
other  in  the  same  line  with  a  steel  director.  The  posterior  layer  of  the  sheath,  the  transver- 
salis  fascia  and  the  peritoneum,  are  then  divided,  and  the  peritoneal  cavity  opened.  The  ante- 
rior wall  of  the  stomach  is  now  seized  and  drawn  out  of  the  wound  and  a  silk  suture  passed 
through  its  muscular  and  serous  coats  at  the  point  selected  for  opening  the  viscus.  This  is 
held  by  an  assistant  so  that  a  long  conical  diverticulum  of  the  stomach  protrudes  from  the  ex- 
ternal wound,  and  the  parietal  peritoneum  and  the  posterior  layer  of  the  sheath  of  the  rectus 
are  sutured  to  it.  A  second  incision  is  made  through  the  skin,  over  the  margin  of  the  costal 
cartilage,  above  and  a  little  to  the  outer  side  of  the  first  incision.  With  a  pair  of  dressing 
forceps  a  track  is  made  under  the  skin  through  the  subcutaneous  tissue  from  the  one  open- 
ing to  the  other  and  the  diverticulum  of  the  stomach  is  drawn  along  this  track  by  means  of 
the  suture  inserted  into  it ;  so  that  its  apex  appears  at  the  second  opening.  A  small  perforation 
is  now  made  into  the  stomach  through  this  protruding  apex  and  its  margins  carefully  and 
accurately  sutured  to  the  margin  of  the  external  wound.  The  remainder  of  this  incision  and 
the  whole  of  the  first  incision  are  then  closed  in  the  ordinary  way  and  the  wound  dressed. 

In  cases  of  gastric  ulcer  perforation  soinetimes  takes  place,  and  this  was  formerly  regarded 
as  an  almost  fatal  complication.  In  the  present  clay,  by  opening  the  abdomen  and  closing 
the  perforation,  which  is  generally  situated  on  the  anterior  surface  of  the  stomach,  a  considera- 
ble percentage  of  cases  are  cured,  provided  the  operation  is  undertaken  within  twelve  or  fifteen 
hours  after  the  perforation  has  taken  place.  The  opening  is  best  closed  by  bringing  the  peri- 
toneal surfaces  on  either  side  into  apposition  by  means  of  Lembert's  sutures. 

Excision  of  the  pylorus  has  occasionally  been  performed,  but  the  results  of  this  operation 
are  by  no  means  favorable,  and,  in  cases  of  cancer  of  the  pylorus,  before  operative  proceedings 
are  undertaken,  the  tumor  has  become  so  fixed  and  has  so  far  implicated  surrounding  parts  that 
removal  of  the  pylorus  is  impossible  and  gastroenterostomy  has  to  be  substituted.  The  object 
of  this  operation  is  to  make  a  fistulous  communication  between  the  stomach,  on  the  cardiac  side 
of  the  disease,  and  the  small  intestine,  as  high  up  as  is  possible. 

Digital  dilatation  of  the  pylorus  for  simple  stricture  was  first  performed  by  Loreta.  He 
exposed  the  stomach  and  opened  it  by  a  transverse  incision  near  the  pylorus.  He  then  inserted 
the  forefingers  of  both  hands  and  passed  these  through  the  pylorus  and  stretched  it  with  some 
degree  of  force.  The  operation  has  now,  however,  dropped  out  of  use  and  been  replaced  by 
pyloro-plasty.  This  consists  in  making  a  longitudinal  incision  from  the  stomach  through  the 
pylorus  into  the  duodenum,  and  converting  this  longitudinal  incision  into  a  transverse  one  by 
traction  at  the  centre  of  the  incision,  and  retaining  it  permanently  in  this  position  by  sutures. 

THE   SMALL  INTESTINE. 

The  small  intestine  is  a  convoluted  tube,  extending  from  the  pylorus  to  the 
ileo-cascal  valve,  where  it  terminates  in  the  large  intestine.  It  is  about  twenty 
feet   in  length,1  and  gradually  diminishes  in  size  from  its  commencement  to  its 

1  Treves  states  that,  in  one  hundred  cases,  the  average  length  of  the  small  intestine  in  the  adult 
male  was  22  feet  6  inches,  and  in  the  adult  female  23  feet  4  inches:  but  that  it  varies  very  much, 
the  extremes  in  the  male  being  31  feet  10  inches  in  one  case,  and  15  feet  6  inches  in  another,  a 
difference  of  over  15  feet.  He  states  that  he  has  convinced  himself  that  the  length  of  the  bowel  is 
independent,  in  the  adult,  of  age,  height,  and  weight. 


912  THE    ORGANS    OF  DIGESTION. 

termination.  It  is  contained  in  the  central  and  lower  part  of  the  abdominal.cavity, 
and  is  surrounded  above  and  at  the  sides  by  the  large  intestine ;  a  portion  of  it 
extends  below  the  brim  of  the  pelvis  and  lies  in  front  of  the  rectum  ;  it  is  in  relation, 
in  front,  with  the  great  omentum  and  abdominal  parietes ;  and  connected  to  the 
spine  by  a  fold  of  peritoneum,  the  mesentery.  The  small  intestine  is  divisible  into 
three  portions — the  duodenum,  the  jejunum,  and  ilium. 

The  duodenum  has  received  its  name  from  being  about  equal  in  length  to  the 
breadth  of  twelve  fingers  (ten  inches).  It  is  the  shortest,  the  widest,  and  the  most 
fixed  part  of  the  small  intestine.  Its  course  presents  a  remarkable  curve,  which 
in  the  adult,  as  regards  the  greater  part  of  its  extent,  is  U-shaped ;  though  some- 
times, in  consequence  of  the  transverse  portion  being  very  short  or  altogether 
wanting,  it  partakes  more  of  the  character  of  the  letter  V.  In  children,  up  to  the 
age  of  about  seven,  the  duodenum  is  annular ;  its  two  extremities  are  on  about  the 
same  level ;  and  between  them  it  describes  a  regular  curve  embracing  the  head  of 
the  pancreas,  the  neck  of  which  lies  between  the  two  extremities  of  the  ring. 

In  the  adult  the  course  of  the  duodenum  is  as  folloAvs  :  commencing  at  the 
pylorus  the  direction  of  the  first  portion  depends  upon  the  amount  of  distention 
of  the  stomach  and  therefore  upon  the  position  of  the  pylorus.  When  the  stomach 
is  empty  and  the  pylorus  situated  at  the  right  of  the  upper  border  of  the  first 
lumbar  vertebra,  it  is  nearly  horizontal  and  transverse ;  but  where  the  stomach  is 
distended,  in  consequence  of  the  alteration  of  the  position  of  the  pylorus  to  the 
right  the  proximal  end  of  the  duodenum  also  becomes  altered  in  position,  while  the 
distal  end  remains  fixed  and  the  direction  of  this  portion  of  the  bowel  is  now  antero- 
posterior. Whether  directed  transversely  or  antero-posteriorly,  it  reaches  the 
under  surface  of  the  liver,  where  it  takes  a  sharp  curve  and  descends  along  the 
right  side  of  the  vertebral  column,  for  a  variable  distance,  generally  to  the  body  of 
the  fourth  lumbar  vertebra.  It  now  takes  a  second  bend,  and  passes  across  the 
front  of  the  vertebral  column  from  right  to  left  and  finally  ascends  on  the  left  side 
of  the  vertebral  column  and  aorta  to  the  level  of  the  upper  border  of  the  second 
lumbar  vertebra  and  there  terminates  in  the  jejunum.  As  it  unites  with  the 
jejunum  it  often  turns  abruptly  forward,  forming  the  duodeno-jejunal  angle.  From 
the  above  description  it  will  be  seen  that  the  duodenum  may  be  divided  for  purposes 
of  description  into  four  portions — superior,  descending,  transverse,  and  ascending. 

The  first  or  superior  portion  (Fig.  496)  is  very  variable  in  length,  but  is  usually 
estimated  as  being  about  two  inches.  Beginning  at  the  pylorus,  it  ends  at  the 
neck  of  the  gall-bladder.  It  is  the  most  movable  of  the  four  portions.  It  is 
almost  completely  covered  by  peritoneum  derived  from  the  two  layers  of  the  lesser 
omentum,  but  a  small  part  of  its  posterior  surface  near  the  neck  of  the  gall-bladder 
and  the  inferior  vena  cava  is  uncovered.  It  is  in  such  close  relation  with  the  gall- 
bladder that  it  is  usually  found  to  be  stained  by  bile  after  death,  especially  on  its 
anterior  surface.  It  is  in  relation  above  and  in  front  with  the  quadrate  lobe  of  the 
liver  and  the  gall-bladder;  behind  with  the  gastro-duodenal  artery,  the  common 
bile-duct,  and  the  vena  porta;   and  below  with  the  head  of  the  pancreas. 

The  second  or  descending  portion  is  between  three  and  four  inches  in  length, 
and  extends  from  the  neck  of  the  gall-bladder  on  a  level  with  the  first  lumbar 
vertebra  along  the  right  side  of  the  vertebral  column  as  low  as  the  body  of  the 
fourth  lumbar  vertebra.  It  is  crossed  in  its  middle  third  by  the  transverse  colon, 
the  posterior  surface  of  which  is  uncovered  by  peritoneum  and  is  connectecTto  the 
duodenum  by  a  small  quantity  of  connective  tissue  (Fig.  490).  The  portions  of  the 
descending  part  of  the  duodenum  above  and  below  this  interspace  are  named  the 
supra-  and  infra-colic  portions,  and  are  covered  in  front  by  peritoneum.  The  right 
side  of  the  supra-colic  portion  is  covered  by  peritoneum  derived  from  the  anterior 
surface  of  the  right  kidney,  the  left  side  of  the  same  portion  being  covered  by  the 
peritoneum  forming  the  lesser  sac.  The  infra-colic  part  is  covered  by  the  right 
leaf  of  the  mesentery.  Posteriorly  the  descending  portion  of  the  duodenum  is 
uncovered  by  peritoneum.  It  is  in  relation,  in  front,  with  the  transverse  colon, 
and  above  this  with  the  liver ;  behind  with  the  front  of  the  right  kidney,  to  which 


THE  SMALL   INTESTINE.  9]0 

-ilSSSA  SMSaSrSSff  ^  *  ve„a  cava  inferior; 
-  »  outer  Slde  is  the  hepatic  Eft  jfli^-*.  £«-**«-£ 


Tributary  to  vena  cava. 


Jancreatic  duct  perforate  the  inner  c,M-  „f  «.: 

ome  three  or  four  inches  belowX  itlol      ^ "  ?/  the  h,teStine  »M"l"clv. 

ae  duodenun,  to  the  right  ^eylrtTooJ^^Z^  ""*  P°"  5 

' « ,he  subject  from  *"h  ,he  -  «  —  *• «  ^  - .o,re;than  noma, 


914  THE    ORGANS    OF  DIGESTION. 

The  third  or  transverse  portion  (pre-aortic  portion)  varies  much  in  length  ; 
when  the  duodenum  assumes  the  ordinary  U-shaped  form,  it  measures  from  two  to 
three  inches  :  but  when  it  presents  the  rarer  V-shaped  form,  it  is  practically  want- 
ino-  or  very  much  reduced  in  length.  It  commences  at  the  ri^ht  side  of  the  fourth 
lumbar  vertebra  and  passes  from  right  to  left,  with  a  slight  inclination  upward,  in 
front  of  the  great  vessels  and  crura  of  the  Diaphragm,  and  ends  in  the  fourth  por- 
tion just  to  the  left  of  the  abdominal  aorta.  It  is  crossed  by  the  superior  mesen- 
teric vessels  and  mesentery.  Its  front  surface  is  covered  by  the  anterior  layer  of 
the  mesentery,  but  near  the  middle  line  it  is  separated  from  this  layer  of  the 
mesentery  by  the  superior  mesenteric  vessels  as  they  cross  this  portion  of  the 
duodenum.  Its  posterior  surface  is  uncovered  by  peritoneum,  except  toward  its 
left  extremity,  where  the  posterior  layer  of  the  mesentery  may  sometimes  be  found 
covering  it  to  a  variable  extent.  This  surface  rests  upon  the  aorta,  the  vena  cava 
inferior,  and  the  crura  of  the  Diaphragm.  By  its  upper  surface  this  portion  of  the 
duodenum  is  in  relation  with  the  head  of  the  pancreas. 

The  fourth  or  ascending  portion  of  the  duodenum  is  about  two  inches  long. 
It  ascends  on  the  left  side  of  the  vertebral  column  and  aorta,  as  far  as  the  level 
of  the  upper  border  of  the  second  lumbar  vertebra,  where  it  turns  abruptly  forward 
to  become  the  jejunum,  forming  the  duodeno-jejunal  flexure.  It  is  covered 
entirely  in  front  and  partly  at  the  sides  by  peritoneum,  derived  from  the  left 
portion  of  the  mesentery.  It  touches  the  left  kidney,  slightly  overlapping  its 
inner  margin,  and  rests  upon  the  left  crus  of  the  Diaphragm. 

The  first  part  of  the  duodenum,  as  stated  above,  is  somewhat  movable,  but  the 
rest  is  practically  fixed  and  is  bound  down  to  neighboring  viscera  and  the  posterior 
abdominal  wall  by  the  peritoneum.  In  addition  to  this,  the  fourth  part  of  the 
duodenum  and  the  duodeno-jejunal  flexure  is  further  bound  down  and  fixed  by  a 
structure  to  which  the  name  of  inusculus  suspensorius  duodeni  has  been  given. 
This  structure  commences  in  the  connective  tissue  around  the  coeliac  axis  and  left 
crus  of  the  Diaphragm,  and  passes  downward  to  be  inserted  into  the  superior 
border  of  the  duodeno-jejunal  curve  and  a  part  of  the  ascending  duodenum,  and 
from  this  it  is  continued  into  the  mesentery.  It  possesses,  according  to  Treitz, 
plain  muscular  fibres  mixed  with  the  fibrous  tissue,  of  which  it  is  principally  made 
up.     It  is  of  little  importance  as  a  muscle,  but  acts  as  a  suspensory  ligament. 

Vessels  and  Nerves. — The  arteries  supplying  the  duodenum  are  the  pyloric 
and  pancreatico-duodenal  branches  of  the  hepatic,  and  the  inferior  pancreatico- 
duodenal branch  of  the  superior  mesenteric.  The  veins  terminate  in  the  splenic 
and  superior  mesenteric.     The  nerves  are  derived  from  the  solar  plexus. 

Jejunum  and  Ileum. — The  remainder  of  the  small  intestine  from  the  termination 
of  the  duodenum  is  named  jejunum  and  ileum;  the  former  term  being  given  to  the 
upper  two-fifths  and  the  latter  to  the  remaining  three-fifths.  There  is  no  morpho- 
logical line  of  distinction  between  the  two,  and  the  division  is  arbitrary ;  but  at 
the  same  time  it  must  be  noted  that  the  character  of 'the  intestine  gradually  under- 
goes a  change  from  the  commencement  of  the  jejunum  to  the  termination  of  the 
ileum,  so  that  a  portion  of  the  bowel  taken  from  these  two  situations  would  present 
characteristic  and  marked  differences.      These  are  briefly  as  follows : 

The  jejunum,  which  derives  its  name  from  the  Latin  word  jejunus  (empty), 
because  it  was  formerly  supposed  to  be  empty  after  death,  is  wider,  its  diameter 
being  about  one  inch  and  a  half,  and  is  thicker,  more  vascular,  and  of  a  deeper 
color  than  the  ileum,  so  that  a  given  length  weighs  more.  Its  valvular  conniventes 
are  large  and  thickly  set  and  its  villi  are  larger  than  in  the  ileum.  The  glands 
of  Peyer  are  almost  absent  in  the  upper  part  of  the  jejunum,  and  in  the  lower 
part  are  less  frequently  found  than  in  the  ileum,  and  are  smaller  and  tend  to 
assume  a  circular  form.  Brunner's  glands  are  only  found  in  the  upper  part  of 
the  jejunum.  By  grasping  the  jejunum  between  the  finger  and  thumb  the  val- 
vule conniventes  can  be  felt  through  the  walls  of  the  gut:  these  being  absent  in 
the  lower  part  of  the  ileum,  it  is  possible  in  this  way  to  distinguish  the  upper  from 
the  lower  part  of  the  small  intestine. 


THE  SHALL    INTESTINE.  915 

The  ileum,  so  called  from  the  Greek  word  eiXecv  (to  twist),  on  account  of  its 
numerous  coils  and  convolutions,  is  narrow,  its  diameter  being  one  inch  and  a 
quarter,  and  its  coats  thinner  and  less  vascular  than  those  of  the  jejunum.  It  pos- 
sesses but  few  valvuloe  conniventes,  and  they  are  small  and  disappear  entirely 
toward  its  lower  end,  but  Peyer's  patches  are  larger  and  more  numerous.  The 
jejunum  for  the  most  part  occupies  the  umbilical  and  left  iliac  regions,  while  the 
ileum  occupies  chiefly  the  umbilical,  hypogastric,  right  iliac,  and  pelvic  regions. 
and  terminates  in  the  right  iliac  fossa  by  opening  into  the  inner  side  of  the  com- 
mencement of  the  large  intestine.  The  jejunum  and  ileum  are  attached  to  the 
posterior  abdominal  wall  by  an  extensive  fold  of  peritoneum,  the  mesentery,  which 
allows  the  freest  motion,  so  that  each  coil  can  accommodate  itself  to  changes  ir 
form  and  position.  The  mesentery  is  fan-shaped;  its  posterior  border,  about  six 
inches  in  length,  is  attached  to  the  abdominal  wall  from  the  left  side  of  the  second 
lumbar  vertebra  to  the  right  iliac  fossa  (Fig.  490).  Its  length  is  about  eight 
inches  from  its  commencement  to  its  termination  at  the  intestine,  and  it  is  rather 
longer  about  its  centre  than  at  either  end  of  the  bowel.  According  to  Lockwood, 
it  tends  to  increase  in  length  as  age  advances.  Between  the  two  layers  of  which 
it  is  composed  are  contained  blood-vessels,  nerves,  lacteals,  and  lymphatic  glands, 
together  with  a  variable  amount  of  fat. 

Meckel's  Diverticulum. — Occasionally  there  may  be  found  connected  with  the 
lower  part  of  the  ileum,  on  an  average  of  about  three  and  a  half  feet  from  its  ter- 
mination, a  blind  diverticulum  or  tube,  varying  in  length.  It  is  attached  to  and 
communicates  with  the  lumen  of  the  bowel  by  one  extremity,  and  by  the  other  is 
unattached  or  may  be  connected  with  the  abdominal  wall  or  some  other  portion  of 
the  intestine  by  a  fibrous  band.  This  is  Meckel's  diverticulum,  and  represents  the 
remains  of  the  vitelline  or  omphalo-mesenteric  duct,  the  duct  of  communication 
between  the  umbilical  vesicle  and  the  alimentary  canal  in  early  foetal  life. 

Structure. — The  wall  of  the  small  intestine  is  composed  of  four  coats — serous, 
muscular,  areolar,  and  mucous. 

The  serous  coat  is  derived  from  the  peritoneum.  The  first  or  ascending 
portion  of  the  duodenum  is  almost  completely  surrounded  by  this  membrane  near 
its  pyloric  end,  but  only  in  front  at  the  other  extremity  ;  the  second  or  descending 
portion  is  covered  by  it  in  front,  except  where  it  is  carried  off  by  the  transverse 
colon ;  and  the  third  or  transverse  portion  lies  behind  the  peritoneum,  which 
passes  over  it,  without  being  closely  incorporated  with  the  other  coats  of  this  part 
of  the  intestine,  and  is  separated  from  it  in  the  middle  line  by  the  superior  mesen- 
teric artery.  The  remaining  portion  of  the  small  intestine  is  surrounded  by  the 
peritoneum,  excepting  along  its  attached  or  mesenteric  border ;  here  a  space  is 
left  for  the  vessels  and  nerves  to  pass  to  the  gut. 

The  muscular  coat  consists  of  two  layers  of  fibres,  an  external  or  longitudinal, 
and  an  internal  or  circular  layer.  The  longitudinal  fibres  are  thinly  scattered 
over  the  surface  of  the  intestine,  and  are  more  distinct  along  its  free  border. 
The  circular  fibres  form  a  thick,  uniform  layer;  they  surround  the  cylinder  of 
the  intestine  in  the  greater  part  of  its  circumference,  and  are  composed  of  plain 
muscle-cells  of  considerable  length.  The  muscular  coat  is  thicker  at  the  upper 
than  at  the  lower  part  of  the  small  intestine. 

The  areolar  or  submucous  coat  connects  together  the  mucous  and  muscular 
layers.  It  consists  of  loose,  filamentous  areolar  tissue,  which  forms  a  nidus  for 
the  subdivision  of  the  nutrient  vessels,  previous  to  their  distribution  to  the  mucous 
surface. 

The  mucous  membrane  is  thick  and  highly  vascular  at  the  upper  part  of  the 
small  intestine,  but  somewhat  paler  and  thinner  below.  It  consists  of  the 
following  structures  :  next  the  areolar  or  submucous  coat  is  a  layer  of  unstriped 
muscular  fibres,  the  muscularis  mucosa?  ;  internal  to  this  is  a  quantity  of  retiform 
tissue,  enclosing  in  its  meshes  lymph-corpuscles,  and  in  which  the  blood-vessels 
and  nerves  ramify.  Lastly,  a  basement-membrane,  supporting  a  single  layer  of 
epithelial  cells,  which  throughout  the  intestines  are  columnar  in  character.      They 


916 


THE    ORGANS    OF  DIGESTION. 


are  granular  in  appearance,  and  possess  a  clear,  oval  nucleus.  At  their  superficial 
or  unattached  end  they  present  a  distinct  layer  of  highly  refracting  material, 
marked  by  vertical  striae,  which  were  formerly  believed  to  be  minute  channels 
by  which  the  chyle  was  taken  up  into  the  interior  of  the  cell,  and  by  them 
transferred  to  the  lacteal  vessels  of  the  mucous  membrane. 

The  mucous  membrane  presents  for  examination  the  following  structures  con- 
tained Avithin  it  or  belonging  to  it : 

Valvule  conniventes.  f  Duodenal  glands. 

Villi.  Glands  <  Solitary  glands. 

Simple  follicles.  t  Peyer's  or  agminate  glands. 

The  valvulae  conniventes  (valves  of  Kerkring)  are  large  folds  or  valvular  flaps 
projecting  into  the  lumen  of  the  bowel.  They  are  composed  of  reduplications 
or  folds  of  the  mucous  membrane,  the  two  layers  of  the  fold  being  bound  together 
by  submucous  tissue ;  they  contain  no  muscular  fibres,  and,  unlike  the  folds  in 
the  stomach,  they  are  permanent,  and  are  not  obliterated  when  the  intestine  is 
distended.     The  majority  extend  transversely  across  the  cylinder  of  the  intestine 


Fig.  497.— Diagrammatic  section  of  a  villus.  (Watney.)  ep.  Epithelium  only  partially  shaded  in.  I.  Central 
chyle-vessel ;  the  cells  forming  the  vessel  have  been  less  shaded  to  distinguish  them  from  the  cells  of  the 
parenchyma  of  the  villus,  m,  Muscle-fibres  running  up  by  the  side  of  the  chyle-vessel.  It  will  be  noticed  that 
each  muscle-fibre  is  surrounded  by  the  reticulum,  and  by  this  reticulum  the  muscles  are  attached  to  the  cells 
forming  the  membrana  propria,  as" at  e',  or  to  the  reticulum  of  the  villus.  Ic.  Lymph-corpuscles,  marked  by  a 
spherical  nucleus  and  a  clear  zone  of  protoplasm.  I' .  Upper  limit  of  the  chyle-vessel,  e,  e,  e'.  Cells  forming 
the  membrana  propria.  It  will  be  seen  that  there  is  hardly  any  difference  between  the  cells  of  the  parenchyma, 
the  endothelium  of  the  upper  part  of  the  chyle-vessel,  and  "the  cells  of  the  membrana  propria.  V.  Blood-vessels. 
2.  Dark  line  at  base  of  the  epithelium  formed  by  the  reticulum.  It  will  be  seen  that  the  reticulum  penetrates 
between  all  the  other  elements  of  the  villus.  The  reticulum  contains  thickenings  or  "nodal  points."  The 
diagram  shows  that  the  cells  of  the  upper  part  of  the  villus  are  larger  and  contain  a  larger  zone  of  protoplasm 
than  those  of  the  lower  part.  The  cells  of  the  upper  part  of  the  chyle-vessel  differ  somewhat  from  those  of  the 
lower  part  iu  that  they  more  nearly  resemble  the  cells  of  the  parenchyma. 

for  about  one-half  or  two-thirds  of  its  circumference,  but  some  form  complete 
circles,  and  others  have  a  spiral  direction  ;  the  latter  usually  extend  a  little  more 
than  once  round  the  bowel,  but  occasionally  two  or  three  times.  The  spiral 
arrangement  is  the  characteristic  one  of  the  shark  family  of  fishes.  The  larger 
folds  are  about  one-third  of  an  inch  in  depth  at  their  broadest  part ;  but  the 
greater  number  are  of  smaller  size.  The  larger  and  smaller  folds  alternate  with 
each   other.     They  are  not  found  at  the  commencement  of  the  duodenum,   but 


THE   SMALL    INTESTINE. 


91' 


begin  to  appear  about  one  or  two  inches  beyond  the  pylorus.  In  the  lower  part 
of  the  descending  portion,  below  the  point  where  the  bile  and  pancreatic  ducts 
enter  the  intestine,  they  are  very  large  and  closely  approximated.  In  the  trans- 
verse portion  of  the  duodenum  and  upper  half  of  the  jejunum  they  are  large  and 
numerous  ;  and  from  this  point,  down  to  the  middle  of  the  ileum,  they  diminish 
considerably  in  size.  In  the  lower  part  of  the  ileum  they  almost  entirely  dis- 
appear ;  hence  the  comparative  thinness  of  this  portion  of  the  intestine  as  com- 
pared with  the  duodenum  and  jejunum.  The  valvulae  conniventes  retard  the 
passage  of  the  food  along  the  intestines,  and  afford  a  more  extensive  surface  for 
absorption. 

The  villi  are  minute,  highly  vascular  processes,  projecting  from  the  mucous 
membrane  of  the  small  intestine  throughout  its  whole  extent,  and  giving  to  its 
surface  a  velvety  appearance.  In  shape,  according  to  Rauber,  they  are  short  and 
leaf-shaped  in  the  duodenum,  tongue-shaped  in  the  jejunum,  and  filiform  in  the 
ileum.  They  are  largest  and  most  numerous  in  the  duodenum  and  jejunum,  and 
become  fewer  and  smaller  in  the  ileum.  Krause  estimates  their  number  in  the 
upper  part  of  the  small  intestine  at  from  fifty  to  ninety  in  a  square  line ;  and  in 
the  lower  part  from  forty  to  seventy,  the  total  number  for  the  whole  length  of 
the  intestine  being  about  four  millions. 

Structure  of  the  Villi  (Fig.  497). — The  structure  of  the  villi  has  been  studied 
by  many  eminent  anatomists.  We  shall  here  follow  the  description  of  Watney,1 
whose  researches  have  a  most  important  bearing  on  the  physiology  of  that  which 
is  the  peculiar  function  of  this  part  of  the  intestine,  the  absorption  of  fat. 


Capillaries. 
Lymph  trunk. 


-—Lymph  trunk. 


Capillaries. 


Small  artery.'    ~""  Lymphatic  plexus. 

Fig.  498.— Villi  of  small  intestine.    (Cadiat.) 

The  essential  parts  of  a  villus  are — the  lacteal  vessel,  the  blood-vessels,  the 
epithelium,  the  basement  membrane  and  muscular  tissue  of  the  mucosa,  these 
structures  being  supported  and  held   together  by  retiform  lymphoid  tissue. 

These  structures  are  arranged  in  the  following  manner:  situated  in  the  centre 
of  the  villus  is  the  lacteal,  terminating  near  the  summit  in  a  blind  extremity; 
running  along  this  vessel  areunstriped  muscular  fibres  :  surrounding  it  is  a  plexus 
of  capillary  vessels,  the  whole  being  enclosed  by  a  basement-membrane,  and  covered 
by  columnar  epithelium.  Those  structures  which  are  contained  within  the  base- 
ment-membrane— namely,  the  lacteal,  the  muscular  tissue,  and  the  blood-vessels — 

1  Phil.  Trans.,  vol.  clxv.,  pt.  ii. 


918 


THE    ORGANS    OF   DIGESTION. 


are  surrounded  and  enclosed  by  a  delicate  reticulum  which  forms  the  matrix  of 
the  villus,  and  in  the  meshes  of  which  are  found  large  flattened  cells  with  an  oval 
nucleus,  and,  in  smaller  numbers,  lymph-corpuscles.  These  latter  are  to  be 
distinguished  from  the  larger  cells  of  the  villus  by  their  behavior  with  reagents, 
by  their  size,  and  by  the  shape  of  their  nucleus,  which  is  spherical.  Transitional 
forms,  however,  of  all  kinds  are  met  with  between  the  lymph- corpuscles  and  the 
proper  cells  of  the  villus.  Nerve-fibres  are  contained  within  the  villi ;  they  form 
ramifications  throughout  the  reticulum. 

The  lacteals  are  in  some  cases  double,  and  in  some  animals  multiple.  Situated 
in  the  axis  of  the  villi,  they  commence  by  dilated  caecal  extremities  near  to,  but 
not  quite  at,  the  summit  of  the  villus.  The  walls  are  composed  of  a  single  layer 
of  endothelial  cells,  the  interstitial  substance  between  the  cells  being  continuous 
with  the  reticulum  of  the  matrix. 

The  muscular  fibres  are  derived  from  the  muscularis  mucosae,  and  are  arranged 
in  bundles  around  the  lacteal  vessel,  extending  from  the  base  to  the  summit  of  the 
villus,  and  giving  off  laterally,  individual  muscle-cells,  which  are  enclosed  by  the 
reticulum,  and  by  it  are  attached  to  the  basement  membrane. 

The  blood-vessels  form  a  plexus  between  the  lacteal  and  the  basement  mem- 
brane, and  are  enclosed  in  the  reticular  tissue ;  in  the  interstices  of  the  capillary 
plexus,  which  they  form,  are  contained  the  cells  of  the  villus. 

These  structures  are  surrounded  by  the  basement  membrane,  which  is  made 

up  of  a  stratum  of  endothelial  cells,  and  upon  which  is  placed  a  layer  of  columnar 

epithelium.     The  reticulum  of  the  matrix  is  continuous  through  the   basement 

membrane   (that  is,   through   the   interstitial   substance   between   the   individual 

endothelial  cells)  with  the  interstitial  cement  substance  of  the  columnar  cells  on 

the  surface  of  the  villus.    Thus  we  are  enabled  to  trace  a  direct  continuity  between 

the  interior  of  the  lacteal  and  the  surface  of  the  villus  by  means  of  the  reticular 

tissue,  and  it  is  along  this  path  that  the  chyle  passes  in  the 

oD  process  of  absorption  by  the  villi.     That  is  to  say,  it  passes 

.^sy^  first  of  all  into  the  columnar  epithelial  cells,  and,  escaping 

from  them,  is  carried  into  the  reticulum  of  the  villus,  and 

thence  into  the  central  lacteal. 

The  simple  follicles,  or  crypts  of  Lieberhuhn  (Figs.  499, 
500),  are  found  in  considerable  numbers  over  every  part 
of  the  mucous  membrane  of  the  small  intestine.  They 
consist  of  minute  tubular  depressions  of  the  mucous  mem- 
brane, arranged  perpendicularly  to  the  surface,  upon 
which  they  open  by  small  circular  apertures.  They  may 
be  seen  with  the  aid  of  a  lens,  their  orifices  appearing  as 
minute  dots  scattered  between  the  villi.  Their  walls  are 
thin,  consisting  of  a  basement-membrane  lined  by  columnar 
epithelium,  and  covered  on  their  exterior  by  capillary 
vessels. 

The  duodenal  or  Brunner's  glands  are  limited  to  the  duo- 
denum and  commencement  of  the 
jejunum.  They  are  small,  flat- 
tened,granular  bodies  embedded 
in  the  submucous  areolar  tissue, 
and  open  upon  the  surface  of 
the  mucous  membrane  by  mi- 
nute excretory  ducts.  They 
are  most  numerous  and  largest 
near  the  pylorus.  They  are 
small  compound  acino-tubular 
glands,  and  much  resemble  the 
small  glands  which  are  found 
in  the  mucous  membrane  of  the 


Fig.  499.— Longitudinal 
section  of  crypts  of  Lieber- 
kuhn.  Goblet  -  cells  seen 
among  the  columnar  epi- 
thelial cells.  (Klein  and 
Noble  Smith.) 


Fig.  500. — Transverse  section 
of  crypts  of  Lieberkuhn.  (Klein 
and  Noble  Smith.) 


THE   831 ALL    INTESTINE. 


919 


JU 


mouth.  They  are  believed  by  Watney  to  be  direct  continuations  of  the  pyloric 
glands  of  the  stomach.  They  consist  of  a  number  of  tubular  alveoli,  lined  by 
epithelium,  and  opening  by  a  single  duct  on  the  inner  surface  of  the  intestine. 

The  solitary  glands  (glandulce  solitarice)  are  found  scattered  throughout  the 
mucous  membrane  of  the  small  intestine,  but  are  most  numerous  in  the  lower  part 
of  the  ileum.  They  are  small,  round,  whitish  bodies,  from  half  a  line  to  a  line  in 
diameter.  Their  free  surface  is  covered  with  villi,  and  each  gland  is  surrounded 
by  the  openings  of  the  follicles  of  Lieberkuhn.  They  are  now  recognized  as 
lymph-follicles,  and  consist  of  a  dense 
interlacing  retiform  tissue  closely  packed 
with  lymph-corpuscles,  and  permeated 
with  an  abundant  capillary  network  (Fig. 
501).  The  interspaces  of  the  retiform 
tissue  are  continuous  with  larger  lymph- 
spaces  at  the  base  of.  the  gland,  through 
which  they  communicate  with  the  lacteal 
system.  They  are  situated  partly  in  the 
submucous  tissue,  partly  in  the  mucous 
membrane,  whence  they  form  slight  pro- 
jections of  its  epithelial  layer,  after  having 
penetrated  the  muscularis  mucosae.  The 
villi  which  are  .  situated  on  them  are 
generally  absent  from  the  very  summit 
(or  "cupola,"  as  Frey  calls  it)  of  the 
gland. 

Peyer's  glands  (agminated  glands) 
(Figs.  501  to  504)  may  be  regarded  as 
aggregations  of  solitary  glands,  forming 
circular  or  oval  patches  from  twenty  to 
thirty  in  number,  and  varying  in  length 
from  half  an  inch  to  four  inches.  They 
are  largest   and    most    numerous    in    the 

ileum.  In  the  lower  part  of  the  jejunum  they  are  small,  of  a  circular  form,  and 
few  in  number.  They  are  occasionally  seen  in  the  duodenum.  They  are  placed 
lengthwise    in    the    intestine,   and    are   sit-uated  in  the  portion  of  the  tube  most 


Fig.  501.— Transverse  section  through  the  equa- 
torial plane  of  three  of  Peyer's  follicles  from  the 
rabbit. 


Fig.  502.— Patch  of  Peyer's  srlands. 
From  the  lower  part  of  the  ileum. 


4 


'■">,'  v 


^ 


ji 


•Jtw„  \     ...  ^ 


M 


m.-x 


A;,  a 


Fig.  503.— A  portion  of  the  above 
magnified. 


distant  from  the  attachment  of  the  mesentery.  Each  patch  is  formed  of  a  group 
of  the  above-described  solitary  glands  covered  with  mucous  membrane,  and  in 
almost  every  respect  are  similar  in  structure  to  them.      They  do   not.  however,  as 


920 


THE    ORGANS    OF  DIGESTION, 


a  rule,  possess  villi  on  their  free  surface.  Each  patch  is  surrounded  by  a  circle 
of  the  crypts  of  Lieberkiihn.  They  are  best  marked  in  the  young  subject,  becoming 
indistinct  in  middle  age,  and  sometimes  altogether  disappearing  in  advanced  life. 


Fig.  504.— Vertical  section  of  one  of  Peyer's  patches  from  man,  injected  through  its  lymphatic  canals,  a. 
Villi  with  their  chyle-passages,  b.  Follicle's  of  Lieberkiihn.  c.  Muscularis  mucosae,  d.  Cupola  or  apex  of  soli- 
tary glands,  e.  Mesial  zone  of  glands.  /.  Base  of  glands,  g.  Points  of  exit  of  the  chyle-passages  from  the 
villi,  and  entrance  into  the  true  mucous 'membrane,  h.  Retiform  arrangement  of  the  lymphatics  in  the  mesial 
zone.  i.  Course  of  the  latter  at  the  base  of  the  glands,  k.  Confluence  of  the  lymphatics  opening  into  the 
vessels  of  the  submucous  tissue.    I.  Follicular  tissue  of  the  latter. 

They  are  largely  supplied  with  blood-vessels,  which  form  an  abundant  plexus 
around  each  follicle  and  give  off  fine  branches  which  permeate  the  lymphoid  tissue 
in  the  interior  of  the  follicle.     The  lacteal  plexuses  which  are  found  throughout 


Multipolar  ganglion-cells. 


Single  ganglion-cell. 


Fig.  505.— Meissner's  plexus.   (Klein  and  Noble  Smith. 


the  small  intestine  are  especially  abundant  around  these  patches ;  here  they  form 
rich  plexuses  with  sinuses  around  the  glands  (Fig.  504). 


THE   LARGE   INTESTINE. 


921 


Vessels  and  Nerves. — The  jejunum  and  ileum  are  supplied  by  the  superior 
mesenteric  artery,  the  branches  of  which,  having  reached  the  attached  border 
of  the  bowel,  run  between  the  serous  and  muscular  coats,  with  frequent  inoscu- 
lations to  the  free  border,  where  they  also  anastomose  with  other  branches 
running  round  the  opposite  surface  of  the  gut.  From  these  vessels  numerous 
branches  are  given  off,  which  pierce  the  muscular  coat,  supplying  it  and  forming 
an  intricate  plexus  in  the  submucous  tissue.  From  this  plexus  minute  vessels 
pass  to  the  glands  and  villi  of  the  mucous  membrane.  The  veins  have  a  similar 
course  and  arrangement  to  the  arteries.  The  lymphatics  of  the  small  intestines 
(lacteals)  are  arranged  in  two  sets,  those  of  the  mucous  membrane,  and  those  of  the 
muscular  coat.  The  lymphatics  of  the  villi  commence  in  these  structures  in  the 
manner  described  above,  and  form  an  intricate  plexus  in  the  mucous  and  submucous 
tissue,  being  joined  by  the  lymphatics  from  the  lymph-spaces  at  the  bases  of  the 
solitary  glands,  and  from  this  pass  to  larger  vessels  at  the  mesenteric  border  of  the 
gut.  The  lymphatics  of  the  muscular  coat  are  situated  to  a  great  extent  between 
the  two  layers  of  muscular  fibres,  wrhere  they  form  a  close  plexus,  and  throughout 
their  course  communicate  freely  with  the  lymphatics  from  the  mucous  membrane, 
and  empty  themselves  in  the  same  manner  into  the  commencement  of  the  lacteal 
vessels  at  the  attached  border  of  the  gut. 

The  nerves  of  the  small  intestines  are  derived  from  the  plexuses  of  sympathetic 
nerves  around  the  superior  mesenteric  artery.  From  this  source  they  run  to  a 
plexus  of  nerves  and  ganglia  situated  between  the  circular  and  longitudinal  muscu- 
lar fibres  (Auerbach 's  plexus),  from  which  the  nervous  branches  are  distributed  to 
the  muscular  coats  of  the  intestine.  From  this  plexus  a  secondary  plexus  is 
derived  (Meissner  s  plexus),  and  is  formed  by  branches  which  have  perforated  the 
circular  muscular  fibres  (Fig.  505).  This  plexus  lies  between  the  muscular  and 
mucous  coats  of  the  intestine.  It  is  also  gangliated,  and  from  it  the  ultimate  fibres 
pass  to  the  muscularis  mucosae  and  to  the  villi  and  mucous  membrane. 


It 


THE  LARGE  INTESTINE. 

The  large  intestine  extends  from  the  termination  of  the  ileum  to  the  anus, 
is  about  five  feet  in  length,  being  one- 
fifth  of  the  wdiole  extent  of  the  intestinal 
canal.  It  is  largest  at  its  commencement 
at  the  caecum,  and  gradually  diminishes 
as  far  as  the  rectum,  where  there  is  a  dilata- 
tion of  considerable  size  just  above  the 
anus.  It  differs  from  the  small  intestine 
in  its  greater  size,  its  more  fixed  position,  its 
sacculated  form,  and  in  possessing  certain 
appendages  to  its  external  coat,  the  appen- 
dices epiploicos.  Further,  its  longitudinal 
muscular  fibres  do  not  form  a  continuous 
layer  around  the  gut,  but  are  arranged  in 
three  longitudinal  bands  or  tosnice.  The  large 
intestine,  in  its  course,  describes  an  arch, 
which  surrounds  the  convolutions  of  the 
small  intestine.  It  commences  in  the  right 
inguinal  region,  in  a  dilated  part,  the 
coscum.  It  ascends  through  the  right  lum- 
bar and  hypochondriac  regions  to  the  under 
surface  of  the  liver ;  it  here  takes  a  bend 
(the  hepatic  flexure)  to  the  left,  and  passes 
transversely  across  the  abdomen  on  the  con- 
fines of  the  epigastric  and  umbilical  regions, 
to  the  left  hypochondriac  region;  it  then  bends  again  (the  splenic  flexure),  and 
descends  through  the  left  lumbar  region  to  the  left  iliac  fossa,  where  it  becomes  con- 


Fig.  506.—  The  caecum  and  colon  laid  open  to 
show  the  ileo-csecal  valve. 


922  THE    ORGANS    OF  DIGESTION. 

voluted,  and  forms  the  sigmoid  flexure  ;  finally  it  enters  the  pelvis,  and  descends 
along  its  posterior  wall  to  the  anus.  The  large  intestine  is  divided  into  the 
caecum,  colon,  and  rectum. 

The  Caecum  (csecus,  blind)  is  the  large  blind  pouch,  or  cul-de-sac,  situated  below 
the  ileo-caecal  valve,  in  which  the  large  intestine  commences  (Fig.  506).  Its  blind 
end  is  directed  downward,  and  its  open  end  upward,  communicating  directly  with 
the  colon,  of  which  this  blind  pouch  appears  to  be  the  beginning  or  head,  and  hence 
the  old  name  caput  coscum  coli  was  applied  to  it.  Its  size  is  variously  estimated 
by  different  authors,  but  on  an  average  it  may  be  said  to  be  two  and  a  half  inches 
in  length  and  three  in  breadth.  It  is  situated  in  the  right  iliac  fossa,  above  the 
outer  half  of  Poupart's  ligament :  it  rests  on  the  Ilio-psoas  muscle  and  lies  imme- 
diately behind  the  abdominal  wall.  As  a  rule,  it  is  entirely  enveloped  on  all  sides 
by  peritoneum,  but  in  a  certain  number  of  cases  (6  per  cent.,  Berry)  the  peritoneal 
covering  is  not  complete,  so  that  a  small  portion  of  the  upper  end  of  the  posterior 
surface  is  uncovered  and  connected  to  the  iliac  fascia  by  connective  tissue.  The 
caecum  lies  quite  free  in  the  abdominal  cavity  and  enjoys  a  considerable  amount  of 
movement,  so  that  it  often  becomes  herniated  down  the  right  inguinal  canal,  and 
has  occasionally  been  found  in  an  inguinal  hernia  on  the  left  side.  The  caecum 
varies  in  shape,  but,  according  to  Treves,  in  man  it  may  be  classified  under  one  of 
four  types.  In  early  foetal  life  it  is  short,  conical,  and  broad  at  the  base,  with  its 
apex  turned  upward  and  inward  toward  the  ileo-csecal  junction.  It  then  resembles 
the  caecum  of  some  of  the  monkey  tribe,  e.  g.<  Mangabey  monkey.  As  the  foetus 
grows  the  caecum  increases  in  length  more  than  in  breadth,  so  that  it  forms  a  longer 
tube  than  in  the  primitive  form  and  without  the  broad  base,  but  with  the  same 
inclination  inward  of  the  apex  toward  the  ileo-caecal  junction.  This  form  is  seen 
in  others  of  the  monkey  tribe,  e.  g.,  the  spider  monkey.  As  development  goes  on, 
the  lower  part  of  tube  ceases  to  grow  and  the  upper  part  becomes  greatly  increased, 
so  that  at  birth  there  is  a  narrow  tube,  the  vermiform  appendix,  hanging  from  a 
conical  projection,  the  caecum.  This  is  the  infantile  form,  and  as  it  may  persist 
throughout  life,  in  about  2  per  cent,  of  cases,  it  is  regarded  by  Treves  as  the  first 
of  his  four  types  of  human  caeca.  The  caecum  is  conical  and  the  appendix  rises 
from  its  apex.  The  three  longitudinal  bands  start  from  the  appendix  and  are 
equidistant  from  each  other.  In  the  second  type,  the  conical  caecum  has  become 
quadrate  by  the  growing  out  of  a  saccule  on  either  side  of  the  anterior  longitudinal 
band.  These  saccules  are  of  equal  size,  and  the  appendix  arises  from  between 
them,  instead  of  from  the  apex  of  a  cone.  This  type  is  found  in  about  3  per  cent, 
of  cases.  The  third  type  is  the  normal  type  of  man.  Here  the  two  saccules, 
which  in  the  second  type  were  uniform,  have  grown  at  unequal  rates :  the  right 
with  greater  rapidity  than  the  left.  In  consequence  of  this  an  apparently  new 
apex  has  been  formed  by  the  growing  downward  of  the  right  saccule,  and  the 
original  apex,  with  the  appendix  attached,  is  pushed  over  to  the  left  toward  the 
ileo-caecal  junction.  The  three  longitudinal  bands  still  start  from  the  base  of  the 
appendix,  but  they  are  now  no  longer  equidistant  from  each  other,  because  the  right 
saccule  has  grown  between  the  anterior  and  postero-external  bands,  pushing  them 
over  to  the  left.  This  type  occurs  in  about  90  per  cent,  of  cases.  The  fourth 
type  is  merely  an  exaggerated  condition  of  the  third ;  the  right  saccule  is  still 
larger,  and  at  the  same  time  the  left  saccule  has  been  atrophied,  so  that  the  original 
apex  of  the  caecum,  with  the  appendix,  is  close  to  the  ileo-caecal  junction,  and  the 
anterior  band  courses  inward  to  the  same  situation.  This  type  is  present  in  about 
4  per  c^nt.  of  cases. 

The  vermiform  appendix  is  a  long,  narrow,  worm-shaped  tube,  which  starts 
from  what  was  originally  the  apex  of  the  caecum,  and  may  pass  in  several  direc- 
tions:  upward  behind  the  caecum;  to  the  left  behind  the  ileum  and  mesentery; 
or  downward  and  inward  into  the  true  pelvis.  It  varies  from  one  to  nine  inches  in 
length,  its  average  being  about  three  inches.  It  is  retained  in  position  by  a  fold 
of  peritoneum  derived  from  the  left  leaf  of  the  mesentery,  which  forms  a  mesentery 
for  it.      This  is  triangular  in  shape,  but  does  not  extend  the  whole  length  of  the 


THE   LARGE   IX TESTIS E.  923 

tube,  hut  leaves  the  distal  third  free  and  completely  covered  by  peritoneum. 
Between  its  two  layers  lies  a  considerable  branch  of  the  ileo-colic  artery,  the  artery 
of  the  appendix.  Its  canal  is  small,  extends  throughout  the  whole  length  of  the 
tube,  and  communicates  with  the  caecum  by  an  orifice  which  is  placed  below  and 
behind  the  ileo-caecal  opening.  It  is  sometimes  guarded,  according  to  Gerlach, 
by  a  semilunar  valve  formed  by  a  fold  of  mucous  membrane,  but  this  is  by  no 
means  constant.  Its  coats  are  the  same  as  those  of  the  intestine :  serous,  muscu- 
lar, submucous,  and  mucous,  the  latter  containing  an  abundant  supply  of  retiform 
tissue,  especially  in  young  subjects. 

It  is  stated  that  the  vermiform  appendix  tends  to  undergo  obliteration  as  an 
involution  change  of  a  functionless  organ. 

The  Ileo-csecal  Valve  {Valvida  Bauldni). — The  lower  end  of  the  ileum  termi- 
nates by  opening  into  the  inner  and  back  part  of  the  large  intestine,  at  the  point 
of  junction  of  the  caecum  with  the  colon.  The  opening  is  guarded  by  a  valve, 
consisting  of  two  semilunar  segments,  an  upper  or  colic  and  lower  or  caecal,  which 
project  into  the  lumen  of  the  large  intestine.  The  upper  one,  nearly  horizontal  in 
direction,  is  attached  by  its  convex  border  to  the  point  of  junction  of  the  ileum 
with  the  colon  ;  the  lower  segment,  which  is  more  concave  and  longer,  is  attached 
to  the  point  of  junction  of  the  ileum  with  the  caecum.  At  each  end  of  the  aper- 
ture the  two  segments  of  the  valve  coalesce,  and  are  continued  as  a  narrow  mem- 
branous ridge  around  the  canal  for  a  short  distance,  forming  the  frcena  or  retinacula 
of  the  valve.  The  left  or  anterior  end  of  the  aperture  is  rounded ;  the  right  or 
posterior  is  narrow  and  pointed. 

Each  segment  of  the  valve  is  formed  by  a  reduplication  of  the  mucous  mem- 
brane and  of  the  circular  muscular  fibres  of  the  intestine,  the  longitudinal  fibres 
and  peritoneum  being  continued  uninterruptedly  across  from  one  portion  of  the 
intestine  to  the  other.  When  these  are  divided  or  removed,  the  ileum  may  be 
drawn  outward,  and  all  traces  of  the  valve  will  be  lost,  the  ileum  appearing  to 
open  into  the  large  intestine  by  a  funnel-shaped  orifice  of  large  size. 

The  surface  of  each  segment  of  the  valve  directed  toward  the  ileum  is  covered 
with  villi,  and  presents  the  characteristic  structure  of  the  mucous  membrane  of  the 
small  intestine ;  while  that  turned  toward  the  large  intestine  is  destitute  of  villi, 
and  marked  with  the  orifices  of  the  numerous  tubular  glands  peculiar  to  the  mucous 
membrane  of  the  large  intestine.  These  differences  in  structure  continue  as  far  as 
the  free  margin  of  the  valve. 

When  the  caecum  is  distended,  the  margins  of  the  opening  are  approximated  so 
as  to  prevent  any  reflux  into  the  ileum. 

The  colon  is  divided  into  four  parts — the  ascending,  transverse,  descending, 
and  the  sigmoid  flexure. 

The  ascending  colon  is  smaller  than  the  caecum,  with  which  it  is  continuous. 
It  passes  upward,  from  its  commencement  at  the  caecum,  opposite  the  ileo-caecal 
valve,  to  the  under  surface  of  the  right  lobe  of  the  liver,  on  the  right  of  the  gall- 
bladder, where  it  is  lodged  in  a  shallow  depression,  the  impressio  colica ;  here  it 
bends  abruptly  inward  to  the  left,  forming  the  hepatic  flexure.  It  is  retained  in 
contact  with  the  posterior  wall  of  the  abdomen  by  the  peritoneum,  which  covers  its 
anterior  surface  and  sides,  its  posterior  surface  being  connected  by  loose  areolar 
tissue  with  the  Quadratus  lumborum  and  Transversalis  muscles,  and  with  the  front 
of  the  lower  and  outer  part  of  the  right  kidney  (Figs.  507  and  508).  Sometimes 
the  peritoneum  almost  completely  invests  it,  and  forms  a  distinct  but  narrow  meso- 
colon.1 It  is  in  relation,  in  front,  with  the  convolutions  of  the  ileum  and  the 
abdominal  parietes. 

1  Treves  states  that,  after  a  careful  examination  of  one  hundred  subjects,  he  found  that  in  fifty- 
two  there  was  neither  an  ascending  nor  a  descending  mesocolon.  In  twenty-two  there  was  a  descend- 
ing mesocolon,  but  no  trace  of  a  corresponding  fold  on  the  other  side.  In  fourteen  subjects  there  was 
a  mesocolon  to  both  the  ascending  and  the  descending  segments  of  the  bowel  ;  while  in  the  remain- 
ing twelve  there  was  an  ascending  mesocolon,  but  no  corresponding  fold  on  the  left  side.  It  follows, 
therefore,  that  in  performing  lumbar  colotoniy  a  mesocolon  may  be  expected  on  the  left  side  in  36 
per  cent,  of  all  cases,  and  on  "the  right  in  26  per  cent.  {The  Anatomy  of  the  Intestinal  Canal  and  Peri- 
toneum in  Man,  1885,  p.  55.) 


924 


THE    ORGANS    OF  DIGESTION. 


fiom^MTTS8  C°l0n'ihe  l0.TSt  Part  °f  tLe  lar§e  intestl»e'  P««eB  transversely 
horn  nght  to  left  across  the  abdomen,  opposite  the  confines  of  the  epi^astri »n3 
umb.hcal  zones,  into  the   left  hypochondriac  region,  where  it  cur^s'dotnward 


Middle 
lamella  of 

Anterior  hJm^r 

lamella  of        fasfm' 
lumbar  fascia. 


Posterior 

lamella  of 

lumbar  fascia. 

h-  - 

/§-%.   :_:QUADRATUS    LUMBORUM. 


LATISSIMUS 
DORSI. 


Fig.  507.-Diagram  of  the  relations  of  the  Ian 


;e  intestine  and  kidney,  from  behind. 


column  and  a  Um^^^^^f^61^  back™*  toward  ^  vertebral 

is   the  most  movable   par  'of X  tl  nM?e'.frww?«^  ««*  ^  ^   «>&».      This 

part  of   the    colon,  being    almost    completely   invested   b* 


THE   LARGE  INTESTINE.  925 

peritoneum,  and  connected  to  the  spine  behind  by  a  large  and  wide  duplicative  of 
that  membrane,  the  transi^erse  mesocolon.  It  is  in  relation,  by  its  upper  surface, 
with  the  liver  and  gall-bladder,  the  great  curvature  of  the  stomach,  and  the  lower 
end  of  the  spleen  ;  by  its  under  surface,  with  the  small  intestines  ;  by  its  anterior 
surface,  with  the  anterior  layers  of  the  great  omentum  and  the  abdominal  parietes ; 
its  posterior  surface  on  the  right  side  is  in  relation  with  the  second  portion  of  the 
duodenum,  and  on  the  left  is  in  contact  with  some  of  the  convolutions  of  the 
jejunum  and  ileum. 

The  descending  colon  passes  downward  through  the  left  hypochondriac  and 
lumbar  regions  along  the  outer  border  of  the  left  kidney.  At  the  lower  end  of  the 
kidney  it  turns  inward  toward  the  outer  border  of  the  Psoas  muscle,  along  which 
it  descends  to  the  crest  of  the  ilium,  where  it  terminates  in  the  sigmoid  flexure. 
At  its  commencement  it  is  connected  with  the  Diaphragm  by  a  fold  of  peritoneum, 
the  plireno-colic  ligament  (see  page  902).  It  is  retained  in  position  by  the 
peritoneum,  which  covers  its  anterior  surface  and  sides,  its  posterior  surface  being 
connected  by  areolar  tissue  with  the  outer  border  of  the  left  kidney,  and  the 
Quadratus  lumborum  and  Transversalis  muscles  (Figs.  507,  508).  It  is  smaller  in 
calibre  and  more  deeply  placed  than  the  ascending  colon,  and  is  more  frequently 
covered  with  peritoneum  on  its  posterior  surface  than  the  ascending  colon  (Treves). 

The  sigmoid  flexure  is  the  narrowest  part  of  the  colon :  it  is  situated  in  the 
left  iliac  fossa,  commencing  from  the  termination  of  the  descending  colon,  at  the 
margin  of  the  crest  of  the  ilium,  and  ending  in  the  rectum  at  the  brim  of  the  true 
pelvis  opposite  the  left  sacro-iliac  symphysis.  It  curves  in  the  first  place  forward, 
downward,  and  inward  for  about  two  inches,  and  then  forms  a  loop,  which  varies  in 
length  and  position,  and  which  terminates  in  the  rectum.1  The  first  portion  is  in 
close  relation  with  the  iliac  fascia,  and  is  covered  by  peritoneum  on  its  sides  and 
anterior  surface  only.  The  loop  is  entirely  surrounded  by  peritoneum,  and  is 
retained  in  its  place  by  a  loose  fold  of  peritoneum,  the  sigmoid  mesocolon,  which 
connects  it  to  the  Psoas  muscle.  This  loop,  which  normally  hangs  downward, 
sometimes  into  the  true  pelvis,  is  very  movable,  and  may  be  displaced  upward  in 
cases  of  distention  of  the  pelvic  viscera.  The  sigmoid  flexure  is  in  relation  in 
front  with  the  small  intestines  and  abdominal  parietes.  The  sigmoid  mesocolon  is 
attached  to  a  line  running  downward  and  inward  from  the  crest  of  the  ilium, 
across  the  Psoas  muscle,  to  become  continuous  with  the  mesorectum  near  the 
bifurcation  of  the  common  iliac  artery  (Fig.  490).  In  its  left  layer  is  the  inter- 
sigmoid  fossa  (see  page  905). 

The  rectum  is  the  terminal  part  of  the  large  intestine,  and  extends  from  the 
sigmoid  flexure  to  the  anal  orifice.  The  superior  limit  cannot  be  determined 
precisely,  since  there  is  no  point  of  demarcation  between  the  sigmoid  flexure  and 
the  first  part  of  the  rectum  ;  but  the  brim  of  the  true  pelvis,  opposite  the  left 
sacro-iliac  joint,  is  arbitrarily  given  as  its  point  of  commencement.  From  this 
point  it  passes  downward,  backward,  and  to  the  right  to  the  level  of  the  third 
sacral  vertebra,  where  it  lies  in  the  middle  line.  This  is  the  Jirst  part  of  the 
rectum.  The  second  part  curves  forward  and  is  continued  downward  as  far  as  the 
apex  of  the  prostate  gland,  about  an  inch  in  front  of  the  tip  of  the  coccyx.  From 
this  point  the  bowel  is  directed  backward,  and,  passing  downward,  terminates  at 
the  anal  orifice.  This  is  the  third  portion  of  the  rectum,  or,  as  described  by 
Symington,  the  anal  canal.  It  will  be  seen,  therefore,  that  the  rectum  presents 
two  antero-posterior  curves:  the  first,  with  its  convexity  backward,  is  due  to  the 
conformation  of  the  sacro-coccygeal  column,  and  represents  the  arc  of  a  circle,  the 
centre  of  which  is  opposite  the  third  sacral  vertebra.  The  lower  one  has  its 
convexity  forward,  and  is  angular.  Its  centre  corresponds  to  a  line  drawn  between 
the  anterior  parts  of  the  ischial  tuberosities.      Two  lateral  curves  are  also  described  : 

1  Treves  describes  the  sigmoid  flexure  somewhat  differently.  He  includes  in  his  description  of 
this  portion  of  the  bowel  the  upper  part  of  the  rectum,  and  makes  it  terminate  opposite  the  third 
portion  of  the  sacrum.  Instead  of  forming  a  sigmoid  curve,  he  describes  it  as  a  large  loop  or  bend, 
more  like  the  Greek  letter  £2  (omega). 


926 


THE    ORGANS    OF   DIGESTION. 


the  one  to  the  right,  opposite  the  junction  of  the  third  and  fourth  sacral  vertebrae ; 
the  other  to  the  left,  opposite  the  sacro-coccygeal  articulation.  They  are  of  little 
importance. 


Semilunar 

ganglion. 


Great  splanchnic 

nerve  piercing 

cms. 

\ 

\ 


Receptaculum 
chyli. 


Great  splanchnic 

nerve  piercing 

crus. 

Semilunar 
ganaiion. 

/ 


Fig.  508.— The  relations  of  the  viscera  and  large  vessels  of  the  abdomen.    (Seen  from  behind,  the  last  dorsal 
vertebra  being  well  raised.) 

The  length  of  the  rectum  is  about  eight  inches.  The  first  part  is  four  inches, 
the  second  three,  and  the  third  one  to  one  and  a  half,  being  rather  longer  in  the 
male  than  in  the  female.     The  rectum  is  narrower  in  its  upper  part  than  the  sig- 


THE   LARGE   INTESTINE. 


moid  flexure,  but  is  capable  of  considerable  distention.     In  the  lowei 
second  portion   it  becomes  a  transverse  slit,  its  anterior  and  posterior 
close  together  when  the  tube  is  empty,  on  account  of  the  organs  in  the  i. 
of  the  pelvis  pushing  the  rectum  backward  on  the  sacrum  and  coccyx.      Ti. 
part  of  the   rectum,  the  anal  canal,  is  also  a  slit,  with,  however,  an  antero-p.. 
rior  direction,  so  that  its  lateral  walls  are  in  apposition  (Fig.  509). 

The  first  portion  of  the  rectum  is  almost  completely  surrounded  by  peritoneum, 
and  is  connected  to  the  anterior  surface  of  the  sacrum  by  a  double  fold,  called  the 
mesorectum,  which  is  continuous  above  with  the  sigmoid  mesocolon.  The  ineso- 
rectum  is  triangular  in  shape,  the  apex 
of  which  ends  below  at  the  third  sacral 
vertebra ;  between  its  two  layers  is 
the  superior  hemorrhoidal  artery.  The 
second  portion  has  no  mesorectum,  but 
is  covered  in  front  and  laterally  by 
peritoneum  at  its  upper  part ;  gradu- 
ally the  peritoneum  leaves  its  sides, 
and  about  an  inch  above  the  prostate 
is  reflected  from  the  anterior  surface  of 
the  bowel  on  to  the  posterior  wall  of  the 
bladder  in  the  male,  and  the  upperfifth 
of  the  posterior  wall  of  the  vagina  in 
the  female,  forming  the  recto-vesical 
and  recto-vaginal  pouches,  respectively. 
The  third  portion  of  the  rectum  has  no 
peritoneal  covering.  The  level  at  which 
the  peritoneum  leaves  the  anterior  Avail 
of  the  rectum  to  be  reflected  on  to  the 
viscus  in  front  of  it  is  of  considerable 
importance  from  a  surgical  point  of 
view,  in  connection  with  removal  of 
the  lower  part  of  the  rectum.  It  is 
higher  in  the  male  than  in  the  female. 
In  the  former  the  height  of  the  recto- 
vesical pouch  is  about  three  inches ;  that 
is  to  say,  the  height  to  which  an  ordinary  index  finger  can  reach  from  the  anus. 
In  the  female  the  height  of  the  recto- vaginal  pouch  is  about  2\  inches  from  the 
anal  orifice. 

The  first  portion  of  the  rectum  is  in  relation,  behind,  with  the  mesorectum  and 
the  superior  hemorrhoidal  artery,  the  left  Pyriformis  muscle,  and  left  sacral  plexus 
of  nerves,  which  separate  it  from  the  anterior  surface  of  the  upper  sacral  vertebrae ; 
to  its  left  side  are  the  branches  of  the  left  internal  iliac  artery  and  the  left  ureter ; 
in  front  it  is  separated,  in  the  male,  from  the  posterior  surface  of  the  bladder;  in 
the  female,  from  the  posterior  surface  of  the  uterus  and  its  appendages,  by  some 
convolutions  of  the  small  intestine,  and  frequently  by  the  sigmoid  flexure  of  the 
colon.  The  second  portion  of  the  rectum  is  in  relation,  in  front,  in  the  male,  with 
the  recto-vesical  pouch,  the  triangular  portion  of  the  base  of  the  bladder,  the  vesic- 
ulse  seminales,  and  vasa  deferentia,  and  more  anteriorly  with  the  under  surface  of 
the  prostate.  In  the  female,  with  the  posterior  wall  of  the  vagina  below,  and  the 
recto-vaginal  pouch  above,  in  which  are  some  convolutions  of  the  small  intestine. 
The  third  portion  or  anal  canal  is  invested  by  the  Internal  sphincter,  supported 
by  the  Levatores  ani  muscles,  and  surrounded  at  its  termination  by  the  External 
sphincter  ;  in  the  empty  condition  it  presents  the  appearance  of  a  longitudinal 
slit.  In  the  male  it  is  separated  from  the  membranous  portion  and  bulb  of  the 
urethra  by  a  triangular  space ;  and  in  the  female  it  is  separated  from  the  lower 
end  of  the  vagina  by  the  perineal  body.  Laterally  is  the  fat  in  the  ischio-rectal 
fossae. 


Fig.  509. — Coronal  section  through  the  anal  canal. 
(Symington.)  B.  Cavity  of  bladder.  VD.  Vas  deferens, 
sv.  Seminal  vesicle,  e.  Second  part  of  rectum,  ac. 
Anal  canal,  la.  Levator  ani.  is.  Internal  sphincter. 
es.   External  sphincter. 


THE    ORGANS    OF  DIGESTION. 
.cture. — The  large  intestine  has  four  coats — serous,  muscular,  areolar,  and 

.3. 

The  serous  coat  is  derived  from  the  peritoneum,  and  invests  the  different  por- 
tions of  the  large  intestine  to  a  variable  extent.  The  caecum  is  completely  covered 
by  the  serous  membrane,  except  in  a  small  percentage  of  cases  (5  or  6  per  cen^.), 
where  a  small  portion  of  the  upper  end  of  the  posterior  surface  is  uncovered.  The 
ascending  and  descending  colon  are  usually  covered  only  in  front  and  at  the  sides  ; 
a  variable  amount  of  the  posterior  surface  is  uncovered.1  The  transverse  colon  is 
almost  completely  invested,  the  parts  corresponding  to  the  attachment  of  the  great 
omentum  and  transverse  mesocolon  being  alone  excepted.  The  sigmoid  flexure 
is  completely  surrounded,  except  along  the  line  to  which  the  sigmoid  mesocolon  is 
attached.  The  upper  part  of  the  rectum  is  completely  invested  by  the  peritoneum, 
except  along  the  attachment  of  the  mesorectum  ;  the  middle  portion  is  covered 
only  on  its  anterior  surface,  and  part  of  its  sides  in  the  upper  portion ;  and  the 
lower  portion  is  entirely  devoid  of  any  serous  covering.  In  the  course  of  the  colon 
and  upper  part  of  the  rectum  the  peritoneal  coat  is  thrown  into  a  number  of  small 
pouches  filled  with  fat,  called  appendices  epiploicos.  They  are  chiefly  appended  to 
the  transverse  colon. 

The  muscular  coat  consists  of  an  external  longitudinal  and  an  internal  circular 
layer  of  muscular  fibres. 

The  longitudinal  fibres,  although  found  to  a  certain  extent  all  round  the  intes- 
tine, do  not  form  a  uniform  layer  over  the  whole  surface  of  the  large  intestine. 
In  the  caecum  and  colon  they  are  especially  collected  into  three  flat  longitudinal 
bands  or  taeniae,  each  being  about  half  an  inch  in  width.  These  bands  commence 
at  the  attachment  of  the  vermiform  appendix,  which  is  surrounded  by  a  uniform 
layer  of  longitudinal  muscular  fibres,  to  the  caecum  :  one,  the  posterior,  is  placed 
along  the  attached  border  of  the  intestine  ;  the  anterior,  the  largest,  corresponds 
along  the  arch  of  the  colon  to  the  attachment  of  the  great  omentum,  but  is  in  front 
in  the  ascending  and  descending  colon  and  sigmoid  flexure  ;  the  third,  or  lateral 
band,  is  found  on  the  inner  side  of  the  ascending  and  descending  colon,  and  on 
the  under  aspect  of  the  transverse  colon.  These  bands  are  nearly  one-half  shorter 
than  the  other  coats  of  the  intestine,  and  serve  to  produce  the  sacculi  which  are 
characteristic  of  the  caecum  and  colon  ;  accordingly,  when  they  are  dissected  off, 
the  tube  can  be  lengthened,  and  its  sacculated  character  becomes  lost.  In  the 
sigmoid  flexure  the  longitudinal  fibres  become  more  scattered;  but  upon  its  lower 
part,  and  round  the  rectum,  they  spread  out  and  form  a  layer  which  completely 
encircles  this  portion  of  the  gut,  but  is  thicker  on  the  anterior  and  posterior  sur- 
faces, where  it  forms  two  bands,  than  on  the  lateral  surfaces.  In  addition  to  the 
muscular  fibres  of  the  bowels,  two  bands  of  plain  muscular  tissue  arise  from  the 
second  and  third  coccygeal  vertebrae,  and  pass  downward  and  forward  to  blend  with 
the  longitudinal  muscular  fibres  on  the  posterior  wall  of  the  anal  canal.  These  are 
known  as  the  recto-coccygeal  muscles. 

The  circular  fibres  form  a  thin  layer  over  the  caecum  and  colon,  being  especially 
accumulated  in  the  intervals  between  the  sacculi ;  in  the  rectum  they  form  a 
thick  layer,  especially  at  its  lower  end,  where  they  become  numerous,  and  consti- 
tute the  Internal  sphincter. 

The  areolar  coat  connects  the  muscular  and  mucous  layers  closely  together. 

The  mucous  membrane,  in  the  caecum  and  colon,  is  pale,  smooth,  destitute  of 
villi,  and  raised  into  numerous  crescentic  folds  which  correspond  to  the  intervals 
between  the  sacculi.  In  the  rectum  it  is  thicker,  of  a  darker  color,  more  vascular, 
and  connected  loosely  to  the  muscular  coat,  as  in  the  oesophagus.  When  the  lower 
part  of  the  rectum  is  contracted,  its  mucous  membrane  is  thrown  into  a  number  of 
folds,  some  of  which,  near  the  anus,  are  longitudinal  in  direction,  and  are  effaced 
by  the  distention  of  the  gut.  Besides  these  there  are  certain  permanent  folds,  of  a 
semilunar  shape,  known  as  Houston's  valves.2  They  are  usually  three  in  number ; 
sometimes  a  fourth  is  found,  and  occasionally  only  two  are  present.  One  is  situated 
1  See  foot-note,  p.  924.  2  Dublin  Hosp.  Reports,  vol.  v.  p.  163. 


THE   LARGE   INTESTINE. 


929 


near  the  commencement  of  the  rectum,  on  the  right  side  ;  another  extends  inward 
from  the  left  side  of  the  tube,  opposite  the  middle  of  the  sacrum  ;  the  largest  and 
most  constant  one  projects  backward  from  the  fore  part  of  the  rectum,  opposite  the 
base  of  the  bladder.  When  a  fourth  is  present,  it  is  situated  about  an  inch  above 
the  anus  on  the  back  of  the  rectum.  These  folds  are  about  half  an  inch  in  width, 
and  contain  some  of  the  circular  fibres  of  the  gut.  In  the  empty  state  of  the  intes- 
tine they  overlap  each  other,  as  Houston  remarks,  so  effectually  as  to  require  con- 
siderable manceuvering  to  conduct  a  bougie  or  the  finger  along  the  canal  of  the 
intestine.  Their  use  seems  to  be  "  to  support  the  weight  of  fecal  matter,  and 
prevent  its  urging  toward  the  anus,  where  its  presence  always  excites  a  sensation 
demanding  its  discharge." 

As  in  the  small  intestine,  the  mucous  membrane  consists  of  a  muscular  layer, 
the  muscularis  mucosse  ;  of  a  quantity  of  retiform  tissue  in  which  the  vessels 
ramify  ;  of  a  basement-membrane  and  epithelium,  which  is  of  the  columnar  variety, 
and  exactly  resembles  the  epithelium  found  in  the  small  intestine.  The  mucous 
membrane  of  this  portion  of  the  bowel  presents  for  examination  simple  follicles  and 
solitary  glands. 

The  simple  follicles  are  minute  tubular  prolongations  of  the  mucous  membrane 
arranged  perpendicularly,  side  by  side,  over  its  entire  surface ;  they  are  longer, 
more  numerous,  and  placed  in  much  closer  apposition  than  those  of  the  small  intes- 
tine ;  and  they  open  by  minute  rounded  orifices  upon  the  surface,  giving  it  a  cribri- 
form appearance.. 

The  solitary  glands  (Fig.  510)  in  the  large  intestine  are  most  abundant  in  the 
ccecum  and  vermiform  appendix,  but  are  irregularly  scattered  also  over  the  rest  of 
the  intestine.     They  are  similar  to  those  of  the  small  intestine. 

Surface  of  mucous  membrane, 
uith  openings  of  Lifberkiihn't 
follicles. 


Lieberkuhris  follicle*. 


77,7^-1    Muscularis  mucosa;  (two  layer*). 
Submucous  connective  tissue. 


Solitary  gland 

Fig.  510. — Minute  structure  of  large  intestine. 


Vessels  and  Nerves. — The  arteries  supplying  the  large  intestine  give  off  large 
branches,  which  ramify  between  the  muscular  coats  supplying  them,  and,  after 
dividing  into  small  vessels  in  the  submucous  tissue,  pass  to  the  mucous  membrane 
The  rectum  is  supplied  mainly  by  the  superior  hemorrhoidal  branch  of  the  inferior 
mesenteric,  but  also  at  its  lower  end  by  the  middle  hemorrhoidal  from  the  internal 
iliac,  and  the  inferior  hemorrhoidal  from  the  pudic  artery.  The  superior  hemor- 
rhoidal, the  continuation  of  the  superior  mesenteric,  divides  into  two  branches,  which 
run  down  either  side  of  the  rectum  to  within  about  five  inches  of  the  anus ;  they 
here  split  up  into  about  six  branches,  which  pierce  the  muscular  coat  and  descend 
between  it  and  the  mucous  membrane  in  a  longitudinal  direction,  parallel  with 
each  other  as  far  as  the  Internal  sphincter,  where  they  anastomose  with  the  other 
hemorrhoidal  arteries  and  form  a  series  of  loops  around  the  anus.     The  veins  of 

59 


930  THE    ORGANS    OF  DIGESTION. 

the  rectum  commence  in  a  plexus  of  vessels  which  surrounds  the  lower  extremity  of 
the  intestinal  canal.  In  the  vessels  forming  this  plexus  are  small  saccular  dilata- 
tions just  within  the  margin  of  the  anus;  from  it  about  six  vessels  of  considerable 
size  are  given  off.  These  ascend  between  the  muscular  and  mucous  coats  for  about 
five  inches,  running  parallel  to  each  other  ;  they  then  pierce  the  muscular  coat, 
and,  by  their  union,  form  a  single  trunk,  the  superior  hemorrhoidal  vein.  This 
arrangement  is  termed  the  hemorrhoidal  plexus ;  it  communicates  with  the 
tributaries  of  the  middle  and  inferior  hemorrhoidal  veins  at  its  commencement,  and 
thus  a  communication  is  established  between  the  systemic  and  portal  circulations. 
The  nerves  are  derived  from  the  plexuses  of  the  sympathetic  nerve  around  the 
branches  of  the  superior  and  inferior  mesenteric  arteries  that  are  distributed  to  the 
large  intestine.  They  are  distributed  in  a  similar  way  to  those  in  the  small  intes- 
tine. The  lymphatic  vessels  of  the  large  intestine  are  found  in  the  submucosa, 
where  they  form  a  wide-meshed  network,  and  also,  more  deeply  seated,  beneath  the 
simple  follicles.  Those  from  the  colon  open  into  the  mesenteric  glands  ;  those  from 
the  sigmoid  flexure  into  the  lumbar  glands  ;  those  from  the  rectum  enter  the  glands 
which  are  situated  in  the  hollow  of  the  sacrum  ;  and  those  around  the  anus  open 
into  the  glands  in  the  groin. 

Surface  Form. — The  coils  of  the  small  intestine  occupy  the  front  of  the  abdomen  below  the 
transverse  colon,  and  are  covered  more  or  less  completely  by  the  great  omentum.  For  the  most 
part  the  coils  of  the  jejunum  occupy  the  left  side  of  the  abdominal  cavity — i.  e.  the  left  lumbar 
and  inguinal  regions  and  the  left  half  of  the  umbilical  region — whilst  the  coils  of  the  ileum  are 
situated  to  the  right,  in  the  right  lumbar  and  inguinal  regions,  in  the  right  half  of  the  umbilical 
region,  and  also  the  hypogastric.  The  caecum  is  situated  in  the  right  inguinal  region.  Its  posi- 
tion varies  slightly,  but  the  mid-point  of  a  line  drawn  from  the  anterior  superior  spinous  process 
of  the  ilium  to  the  symphysis  pubis  will  about  mark  the  middle  f  its  lower  border.  It  is  com- 
paratively superficial.  From  it  the  ascending  colon  passes  upward  through  the  right  lumbar 
and  hypochondriac  regions,  and  becomes  more  deeply  situated  as  it  ascends  to  the  hepatic  flexure, 
which  is  deeply  placed  under  cover  of  the  liver.  The  transverse  coion  crosses  the  belly  trans- 
versely on  the  confines  of  the  umbilical  and  epigastric  regions,  its  lower  border  being  on  a  level 
slightly  above  the  umbilicus,  its  upper  border  just  below  the  greater  curvature  of  the  stomach. 
The  splenic  flexure  of  the  colon  is  situated  behind  the  stomach  in  the  left  hypochondrium,  and 
is  on  a  higher  level  than  the  hepatic  flexure.  The  descending  colon  is  deeply  seated,  passing 
down  through  the  left  hypochondriac  and  lumbar  regions  to  the  sigmoid  flexure,  which  is  situ- 
ated in  the  left  inguinal  region,  and  which  can  be  felt  in  thin  persons,  with  relaxed  abdominal 
walls,  rolling  under  the  fingers  when  empty,  and  when  distended  forming  a  distinct  tumor.  I  he 
position  of  the  base  of  the  vermiform  appendix  is  indicated  by  a  point  two  inches  Irom  the 
anterior  superior  spinous  process  of  the  ilium,  in  a  line  drawn  irom  this  process  to  the  umbilicus. 
This  is  known  as  AlcBuinieys  spot.  Another  mode  of  defining  the  position  of  the  base  of  the 
appendix  is  to  draw  a  line  between  the  anterior  superior  spines  of  the  ilia  and  marking  the 
point  where  this  line  intersects  the  right  semilunar  line. 

Upon  introducing  the  finger  into  the  rectum,  the  membranous  portion  of  the  urethra  can 
be  felt,  if  an  instrument  has  been  introduced  into  the  bladder,  exactly  in  the  middle  line; 
behind  this  the  prostate  gland  can  be  recognized  by  its  shape  and  hardness  and  any  enlargement 
detected ;  behind  the  prostate  the  fluctuating  wall  of  the  bladder  when  lull  can  le  felt,  and  if 
thought  desirable  it  can  be  tapped  in  this  situation  ;  on  either  side  and  behind  the  prostate  the 
vesiculse  seminales  can  be  readily  felt,  especially  if  enlarged  by  tuberculous  disease.  Behind, 
the  coccyx  is  to  be  felt,  and  on  the  mucous  membrane  one  or  two  of  Houston's  folds-  rJ  he 
ischio-reetal  foss:e  can  be  explored  on  either  side,  with  a  view  to  ascertaining  the  presence  of 
deep-seated  collections  of  pus.  Finally,  it  will  be  noted  that  the  finger  is  firmly  gripped  by  the 
sphincter  for  about  an  inch  up  the  bowel.  By  gradual  dilatation  of  the  sphincter,  the  whole 
hand  can  be  introduced  into  the  rectum  so  as  to  reach  the  descending  colon.  This  method  of 
exploration  is  rarely,  however,  required  for  diagnostic  purposes. 

Surgical  Anatomy. — The  small  intestines  are  much  exposed  to  injury,  but,  in  consequence 
of  their  elasticity  and  the  ease  with  which  one  ibid  glides  over  another,  they  are  not  so  frequently 
ruptured  as  would  otherwise  be  the  case.  Any  part  of  the  small  intestine  may  be  ruptured,  but 
probably  the  most  common  situation  is  the  transverse  duodenum,  on  account  of  its  being  more 
fixed  than  other  portions  of  the  bowel,  and  because  it  is  situated  in  front  of  the  bodies  of  the 
vertebras,  so  that  if  this  portion  of  the  intestine  is  struck  by  a  sharp  blow,  as  irom  the  kick  of 
a  horse,  it  is  unable  to  glide  out  of  the  way,  but  is  compressed  against  the  bone  and  so  lacerated. 
Wounds  of  the  intestine  sometimes  occur.  If  the  wound  is  a  small  puncture,  under,  it  is  said, 
three  lines  in  length,  no  extravasation  of  the  contents  of  the  bowel  takes  place.  The  mucous 
membrane  becomes  everted  and  plugs  the  little  opening.  The  bowels,  therefore,  may  be  safely 
punctured  with  a  fine  capillary  trocar,  in  cases  of  excessive  distension  of  the  intestine  with  gas, 
without  fear  of  extravasation.     A  longitudinal  wound  gapes  more  than  a  transverse,  owing  to 


SURGICAL    ANATOMY    OF    THE   INTESTINAL    CANAL.         931 

the  greater  amount  of  circular  muscular  fibres.  The  small  intestine,  and  most  frequently  the 
ileum,  may  become  strangulated  by  internal  bands,  or  through  apertures,  normal  or  abnormal. 
The  bands  may  be  formed  in  several  different  ways :  they  may  be  old  peritoneal  adhesions  from 
previous  attacks  of  peritonitis ;  or  an  adherent  omentum  from  the  same  cause  ;  or  the  band 
may  be  formed  by  Meckel's  diverticulum,  which  has  contracted  adhesions  at  its  distal  extremity  : 
or  (he  band  may  be  the  result  of  the  abnormal  attachment  of  some  normal  structure,  as  the 
adhesion  of  two  appendices  epiploicae,  or  an  adherent  vermiform  appendix  or  Fallopian  tube. 
Intussusception  or  invagination  of  the  small  intestine  may  take  place  in  any  part  of  the  jejunum 
and  ileum,  but  the  most  frequent  situation  is  at  the  ileo-caecal  valve,  the  valve  forming  the  apex 
of  the  entering  tube.  This  form  may  attain  great  size,  and  it  is  not  uncommon  in  these  cases  to 
find  the  valve  projecting  from  the  anus.  Stricture,  the  impaction  of  foreign  bodies,  and  twist- 
ing of  the  gut  (volvulus)  may  lead  to  intestinal  obstruction. 

Resection  of  a  portion  of  the  intestine  may  be  required  in  cases  of  gangrenous  gut ;  in  cases 
of  intussusception  ;  for  the  removal  of  new  growth  in  the  bowel ;  in  dealing  with  artificial 
anus;  and  in  cases  of  rupture.  The  operation  is  termed  enter  ectomy,  and  is  performed  as 
follows :  the  abdomen  having  been  opened  and  the  amount  of  bowel  requiring  removal  having 
been  determined  upon,  the  gut  must  be  clamped  on  either  side  of  this  portion  in  order  to 
prevent  the  escape  of  any  of  the  contents  of  the  bowel  during  the  operation.  The  portion  of 
bowel  is  then  separated  above  and  below  by  means  of  scissors.  If  the  portion  removed  is 
small,  it  may  be  simply  removed  from  the  mesentery  at  its  attachment  and  the  bleeding  vessels 
tied ;  but  if  it  is  large,  it  will  be  necessary  to  remove  also  a  triangular  piece  of  the  mesentery, 
and,  having  secured  the  vessels,  suture  the  cut  edges  of  this  structure  together.  The  surgeon 
then  proceeds  to  unite  the  cut  ends  of  the  bowel  together  by  the  operation  of  what  is  termed 
end-to-end  anastomosis.  There  are  many  ways  of  doing  this,  which  may  be  divided  into  two 
classes :  one  where  the  anastomosis  is  made  by  means  of  some  mechanical  appliance,  such  as 
Murphy's  button,  or  one  of  the  forms  of  decalcified  bone  bobbins;  and  the  other,  where  the 
operation  is  performed  by  suturing  the  ends  of  the  bowel  in  such  a  manner  that  the  peritoneum 
covering  the  free  divided  ends  of  the  bowel  is  brought  into  contact,  so  that  speedy  union  may 
ensue. 

The  vermiform  appendix  is  very  liable  to  become  inflamed.  This  condition  may  be  set  up 
by  the  appendix  becoming  twisted,  owing  to  the  shortness  of  its  mesentery,  in  consequence  of 
distention  of  the  caecum.  As  the  result  of  this  its  blood-supply,  which  is  mainly  through  one 
large  artery  running  in  the  mesentery,  becomes  interfered  with.  Again,  in  rarer  cases,  the 
inflammation  is  set  up  by  the  impaction  of  a  solid  mass  of  feces  or  a  foreign  body  in  it.  The 
inflammation  may  result  in  ulceration  and  perforation,  or.  if  the  torsion  is  very  acute,  in  gangrene 
of  the  appendix.  These  conditions  may  require  operative  interference,  and  in  cases  of  recurrent 
attacks  of  appendicitis  it  is  generally  advisable  to  remove  this  diverticulum  of  the  bowel.  In 
external  hernia  the  ileum  is  the  portion  of  bowel  most  frequently  herniated.  When  a  part  of 
the  large  intestine  is  involved,  it  is  usually  the  caecum,  and  this  may  occur  even  on  the  left  side. 
In  some  few  cases  the  vermiform  appendix  has  been  the  part  implicated  in  cases  of  strangulated 
hernia,  and  has  given  rise  to  serious  symptoms  of  obstruction.  Occasionally  ulceration  of  the 
duodenal  glands  may  occur  in  cases  of  burns,  but  is  not  a  very  common  complication.  The 
ulcer  may  perforate  one  of  the  large  duodenal  vessels,  and  may  cause  death  from  hemorrhage, 
or  it  may  perforate  the  coats  of  the  intestine  and  produce  fatal  septic  peritonitis.  The  diameter  of 
the  large  intestine  gradually  diminishes  from  the  caecum,  which  has  the  greatest  diameter  of  any 
part  of  the  bowel,  to  the  point  of  junction  of  the  sigmoid  flexure  with  the  rectum,  at  or  a  little 
below  which  point  stricture  most  commonly  occurs  and  diminishes  in  frequency  as  one  proceeds 
upward  to  the  caecum.  When  distended  by  some  obstruction  lowr  down,  the  outline  of  the  large 
intestine  can  be  defined  throughout  nearly  the  whole  of  its  course — all,  in  fact,  except  the 
hepatic  and  splenic  flexures,  which  are  more  deeply  placed ;  the  distention  is  most  obvious  in 
the  two  flanks  and  on  the  front  of  the  abdomen  just  above  the  umbilicus.  The  caecum,  how- 
ever, is  that  portion  of  the  bowel  which  is,  of  all,  most  distended.  It  sometimes  assumes 
enormous  dimensions,  and  has  been  known  to  give  way  from  the  distention,  causing  fatal  peri- 
tonitis. The  hepatic  flexure  and  the  right  extremity  of  the  transverse  colon  are  in  close  rela- 
tionship with  the  liver,  and  abscess  of  this  viscus  sometimes  bursts  into  the  gut  in  this  situation. 
The  gall-bladder  may  become  adherent  to  the  colon,  and  gall-stones  may  find  their  way  through 
into  the  gut,  where  they  may  become  impacted  or  may  be  discharged  per  anum.  The  mobility 
of  the  sigmoid  flexure  renders  it  more  liable  to  become  the  seat  of  a  volvulus  or  twist  than  any 
other  part  of  the  intestine.  It  generally  occurs  in  patients  who  have  been  the  subjects  of 
habitual  constipation,  and  in  whom,  therefore,  the  meso-sigmoid  flexure  is  elongated.  The  gut 
at  this  part  being  loaded  with  feces,  from  its  weight  falls  over  the  gut  below,  and  so  gives  rise 
to  the  twist. 

The  surgical  anatomy  of  the  rectum  is  of  considerable  importance.  There  may  be  congeni- 
tal malformation  due  to  arrest  or  imperfect  development.  Thus,  there  may  be  no  inflection  of 
the  epiblast,  and  consequently  a  complete  absence  of  the  anus ;  or  the  hind-gut  may  be  imper- 
fectly developed,  and  there  may  be  an  absence  of  the  rectum,  though  the  anus  is  developed ; 
or  the  inflection  of  the  epiblast  may  not  communicate  with  the  termination  of  the  hind-gut 
from  want  of  solution  of  continuity  in  the  septum  which  in  early  feetal  life  exists  between  the 
two.  The  mucous  membrane  is  thick  and  but  loosely  connected  to  the  muscular  coat  beneath. 
and  thus  favors  prolapse,  especially  in  children.  The  vessels  of  the  rectum  are  arranged, 
as  mentioned  above,  longitudinally,  and  are  contained  in  the  loose  cellular  tissue  between  the 


932  THE    ORGANS    OF   DIGESTION. 

mucous  and  muscular  coats,  and  receive  no  support  from  surrounding  tissues,  and  this  favors 
varicosity.     Moreover,  the  veins,  after  running  upward  in  a  longitudinal  direction  for  about  five 
inches  in  the  submucous  tissue,  pierce  the  muscular  coats,  and  are  liable  to  become  constricted 
at  this  by  the  contraction  of  the  muscular  wall  of  the  gut.     In  addition  to  this  there  are  no 
valves  in  the  superior  hemorrhoidal  veins,  and  the  vessels  of  the  rectum  are  placed  in  a  depend- 
ent position,  and  are  liable  to  be  pressed  upon  and  obstructed  by  hardened  feces.     The  anatomi- 
cal arrangement,  therefore,  of  the  hemorrhoidal  vessels  explains   the   great  tendency  to  _  the 
occurrence  of  piles.     The  presence  of  the  Sphincter  ani  is  of  surgical  importance,  since  it  is 
the  constant  contraction  of  this  muscle  which  prevents  an  ischio-rectal  abscess  from  healing 
and  causes  it  to  become  a  fistula.     Also,  the  reflex  contraction  of  this  muscle  is  the  cause  of  the 
severe  pain  complained  of  in  fissure  of  the  anus.     The  relations  of  the  peritoneum  to  the  rectum 
are  of  importance  in  connection  with  the  operation  of  removal  of  the  lower  end  of  the  rectum 
for  malignant  disease.     This  membrane  gradually  leaves  the  rectum  as  it  descends  into  the 
pelvis ;  first  leaving  its  posterior  surface,  then  the  sides,  and  then  the  anterior  surface  to  become 
reflected  in  the  male  on  to  the  posterior  wall  of  the  bladder,  forming  the  recto-vesical  pouch,  and 
in  the  female  on  to  the  posterior  wall  of  the  vagina,  forming  Douglas's  pouch.   _  The  recto-vesical 
pouch  of  peritoneum  extends  to  within  three  inches  from  the  anus,  so  that  it  is  not  desirable 
to  remove  more  than  two  and  a  half  inches  of  the  entire   circumference  of  the  bowel,  for 
fear  of  the  risk  of  opening  the  peritoneum.     When,   however,  the  disease  is  confined  to  the 
posterior  surface  of  the  rectum,  or  extends  farther  in  this  direction,  a  greater  amount  of  the 
posterior  wall  of  the  gut  may  be  removed,  as  the  peritoneum  does  not  extend  on  this  surface  to 
a  lower  level  than  five  inches  from  the  margin  of  the  anus.     The  recto-vaginal  or  Douglas's 
pouch  in  the  female  extends  somewhat  lower  than  the  recto-vesical  pouch  of  the  male,  and 
therefore  it  is  necessary  to  remove  a  less  length  of  the  tube  in  this  sex.     Of  recent  years, 
however,  much  more  extensive  operations  have    been   done   for  the  removal  of  cancer  of 
the  rectum,   and  in  these  the  peritoneal  cavity   has  necessarily  been  opened.     If,  in  these 
cases,  the  opening  is  plugged  with  antiseptic  wool  until  the  operation  is  completed  and  then  the 
edges  of  the  wound  in  the  peritoneum  accurately  brought  together  with  sutures,  no  evil  result 
appears  to  follow.     For  cases  of  cancer  of  the   rectum  which  are  too_  low  to  be  reached  by 
abdominal  section,  and  too  high  to  be  removed  by  the  ordinary  operation  from  below,  Kraske 
has  devised  an  operation  which  goes  by  his  name.      The  patient  is  placed  on  his  right  side  and 
an  incision  is  made  from  the  second  sacral  spine  to  the  anus.     The  soft  parts  are  now  separated 
from  the  back  of  the  left  side  of  the  sacrum  as  far  as  its  left  margin,  and  the  greater  and  lesser 
sacro-sciatic  ligaments  are  divided.     A  portion  of  the  lateral  mass  of  the  sacrum,  commencing 
on  the  left  border  at  the  level  of  the  third  posterior  sacral  foramen,  and  running  downward  and 
inward  through  the  fourth  foramen  to  the  cornu,  is  now  cut  away  with  a  chisel.     The  left  side 
of  the  wound  being  now  forcibly  drawn  outward,  the  whole  of  the  rectum  is  brought  into  view, 
and  the  diseased  portion  can  be  removed,  leaving  the  anal  portion  of  the  gut,  if  healthy.     The 
two  divided  ends  of  the  gut  can  then  be  approximated  and  sutured  together  in  front,  the 
posterior  part  being  left  open  for  drainage. 

The  colon  frequently  requires  opening  in  cases  of  intestinal  obstruction,  and  by  some 
surgeons  this  operation  is  performed  in  cases  of  cancer  of  the  rectum,  as  soon  as  the  disease 
is  recognized,  in  the  hope  that  the  rate  of  growth  may  be  retarded  by  removing  the  irritation 
produced  by  the  passage  of  fecal  matter  over  the  diseased  surface.  The  operation  of  colotomy 
may  be  performed  either  in  the  inguinal  or  lumbar  region ;  but  inguinal  colotomy  has  in  the 
present  day  almost  superseded  the  lumbar  operation.  The  main  reason  for  preferring  this 
operation  is  that  a  spur-shaped  process  of  the  meso-colon  can  be  formed  which  prevents  any 
fecal  matter  finding  its  way  past  the  artificial  anus  and  becoming  lodged  on  the  diseased  struct- 
ures below.  The  sigmoid  flexure  being  almost  entirely  surrounded  by  peritoneum,  a  coil  can  be 
drawn  out  of  the  wound  and  the  greater  part  of  its  calibre  removed,  leaving  the  remainder 
attached  to  the  meso-colon,  which  forms  a  spur,  much  the  same  as  in  an  artificial  anus  caused 
by  sloughing  of  the  gut  after  a  strangulated  hernia,  and  this  prevents  any  fecal  matter  finding 
its  way  from  the  gut  above  the  opening  into  that  below.  The  operation  is  performed  by  making 
an  incision  two  or  three  inches  in  length  from  a  point  one  inch  internal  to  the  anterior  superior 
spinous  process  of  the  ilium,  parallel  to  Poupart's  ligament.  The  various  layers  of  abdominal 
muscles  are  cut  through,  and  the  peritoneum  opened  and  sewn  to  the  external  skin.  The 
sigmoid  flexure  is  now  sought  for,  and  pulled  out  of  the  wound  and  fixed  by  passing  a  needle 
threaded  with  carbolized  silk  through  the  meso-colon  close  to  the  gut  and  then  through  the 
abdominal  wall.  The  intestine  is  now  sewn  to  the  skin  all  round,  the  suture  passing  only 
through  the  serous  and  muscular  coats.  The  wound  is  dressed,  and  on  the  second  to  the  fourth 
day,  according  to  the  requirements  of  the  case,  the  protruded  coil  of  intestine  is  opened  and 
removed  with  scissors. 

Lumbar  colotomy  is  performed  by  placing  the  patient  on  the  side  opposite  to  the  one  to  be 
operated  on,  with  a  firm  pillow  under  the  loin.  A  line  is  then  drawn  from  the  anterior  superior 
to  the  posterior  superior  spine  of  the  ilium,  and  the  mid-point  of  this  line  (Heath)  or  half  an 
inch  behind  the  mid-point  (Allingham)  is  taken,  and  a  line  drawn  vertically  upward  from  it  to 
Jie  last  rib.  This  line  represents,  with  sufficient  correctness,  the  position  of  the  normal  colon. 
An  oblique  incision  four  inches  in  length  is  now  made  midway  between  the  last  rib  and  the  crest 
of  the  ilium,  so  that  its  centre  bisects  the  vertical  line,  and  the  following  parts  successively 
divided:  (1)  The  skin,  superficial  fascia,  with  cutaneous  vessels  and  nerves  and  deep  fascia. 
(2)  The  posterior  fibres  of  the  External  oblique  and  anterior  fibres  of  the  Latissimus  dorsi. 


THE   LIVER. 


933 


*(3)  The  Internal  oblique.  (4)  The  lumbar  fascia  and  the  external  border  of  the  Quadratus  luni- 
borum.  The  edges  of  the  wound  are  now  to  be  held  apart  with  retractors,  and  the  transversalis 
fascia  will  be  exposed.  This  is  to  be  opened  with  care,  commencing  at  the  posterior  angle  of 
the  incision.  If  the  bowel  is  distended,  it  will  bulge  into  the  wound,  and  no  difficulty  will  be 
found  in  dealing  with  it.  If,  however,  the  gut  is  empty,  this  bulging  will  not  take  place,  and 
the  colon  will  have  to  be  sought  for.  The  guides  to  it  are  the  lower  end  of  the  kidney,  which 
will  be  plainly  felt,  and  the  outer  edge  of  the  Quadratus  lumborum.  The  bowel  having  been 
found,  is  to  be  drawn  well  up  into  the  wound,  and  it  may  be  opened  at  once  and  the  margins 
of  the  openings  stitched  to  the  skin  at  the  edge  of  the  wound ;  or,  if  the  case  is  not  an  urgent 
one,  it  may  be  retained  in  this  position  by  two  harelip  pins  passed  through  the  muscular  coat, 
the  rest  of  the  wound  closed,  and  the  bowel  opened  in  three  or  four  days,  when  adhesion  of  the 
bowel  to  the  edges  of  the  wound  has  taken  place. 

THE  LIVER. 

The  Liver  is  the  largest  gland  in  the  body,  and  is  situated  in  the  upper  and 
right  part  of  the  abdominal  cavity,  occupying  almost  the  whole  of  the  right  hypo- 
chondrium,  the  greater  part  of  the  epigastrium,  and  extending  into  the  left  hvpo- 
•chondrium  as  far  as  the  mammary  line.  In  the  male  it  weighs  from  fifty  to  sixty 
ounces  ;  in  the  female,  from  forty  to  fifty.  It  is  relatively  much  larger  in  the  foetus 
than  in  the  adult,  constituting,  in  the  former,  about  one-eighteenth,  and  in  the 
latter,  about  one  thirty-sixth  of  the  entire  body-weight.  Its  greatest  transverse 
measurement  is  from  eight  to  nine  inches.  Vertically,  near  its  lateral  or  right 
surface,  it  measures  about  six  or  seven  inches,  while  its  greatest  antero-posterior 
diameter  is  on  a- level  with  the  upper  end  of  the  right  kidney  and  is  from  four  to 
five  inches.  Opposite  the  vertebral  column  its  measurement  from  before  backward 
is  reduced  to  about  three  inches.  Its  consistence  is  that  of  a  soft  solid ;  it  is, 
however,  friable  and  easily  lacerated  ;  its  color  is  a  dark  reddish-brown,  and  its 
specific  gravity  is  1.05. 

To  obtain  a  correct  idea  of  its  shape,  it  must  be  hardened  in  situ,  an'}  it  will 
then  be  seen  to  present  the  appearance  of  a  wedge,  the  base  of  which  ifc  directed 

Gall-bladder. 


LEFT    LATERAL 
LIGAMENT. 


RIGHT    LATERAL 
LIGAMENT. 


Fig.  511.— The  liver 


f>om  His's  models.) 


to  the  right  and  the  thin  edge  ie  left.      Svmington  describes  its  shape  as 

that  "of  a  right-angled  trian  with  the  right  angles  rounded  off."     It 

possesses  five  surfaces,  viz  inferior,  anterior,  posterior,  and  lateral. 

The  superior  ar.d  anterioi  are  separated  from  each  other  by  a  thick 

rounded  border,  and  are  atta<  ied  0  the  Diaphragm  and  anterior  abdominal  wall 
"by  a  triahgular  or  falciform  idd  f0f  per.toneum,  the  suspensory  or  falciform  liga- 
ment, wh/ich  divides  the  live*  in;{0  two  unequal  parts,  termed  the  right  and  left 


./ 


934  THE    ORGANS    OF  DIGESTION. 

lobes.     Except  along  the  line  of  attachment  of  this  ligament  to  the  liver,  the 
superior  and  anterior  surfaces  are  covered  by  peritoneum. 

The  superior  surface  (Fig.  511)  comprises  a  part  of  both  lobes,  and,  as  a  whole, 
is  convex,  and  fits  under  the  vault  of  the  Diaphragm  ;  its  central  part,  however, 
presents  a  shallow  depression,  which  corresponds  with  the  position  of  the  heart  on 
the  upper  surface  of  the  Diaphragm.  It  is  separated  from  the  anterior,  posterior, 
and  lateral  surfaces  by  thick,  rounded  borders.  Its  left  extremity  is  separated 
from  the  under  surface  by  a  prominent  sharp  margin. 

The  anterior  surface  is  large  and  triangular  in  shape,  comprising  also  a  part 
of  both  lobes.  It  is  directed  forward,  and  the  greater  part  of  it  is  in  contact  with 
the  Diaphragm,  which  separates  it  from  the  right  lower  ribs  and  their  cartilages. 
In  the  middle  line  it  lies  behind  the  ensiform  cartilage,  to  the  left  of  which  it  is- 
protected  by  the  seventh  and  eighth  left  costal  cartilages.  In  the  angle  between 
the  diverging  rib  cartilages  of  opposite  sides  the  anterior  surface  is  in  contact  with 
the  abdominal  wall.  It  is  separated  from  the  inferior  surface  by  a  sharp  margin, 
and  from  the  superior  and  lateral  surfaces  by  thick  rounded  borders. 

The  lateral  or  right  surface  is  convex   from  before  backward  and  slightly  so 

from  above  downward.      It  is  directed  toward  the  right  side,  forming  the  base  of 

the  wedge,  and  lies  against  the  lateral  portion  of  the  Diaphragm,  which  separates 

t  from  the  lower  part   of  the  left  pleura    and  lung,  outside  which  are  the  right 

costal  arches  from  the  seventh  to  the  eleventh  inclusive. 

Its  under  or  visceral  surface  (Figs.  512,  513)  is  uneven,  concave,  directed  down- 
and  backward  and  to  the  left,   and   is  in  relation  with  the  stomach  and 
"uum,  the  hepatic  flexure  of  the  colon,  and  the  right  kidney  and  suprarenal 
capsule.    The  surface  is  divided  by  a  longitudinal  fissure  into  a  right  and  a  left  lobe, 
and  : '  al  oost  completely  invested  by  peritoneum  ;  the  only_parts  where  this  cover- 
absent  are  whe_re  the  gall-bladder  is  attached  to  the^liyer  ana  at  the  trans- 
ure.  where  the  two  layers  of  the  lesser  omentum  are  separated  frohTeaeh. 
other  "by  t  e  blood-vessels  and  duct  of  the  viscus.      The  under  surface  of  the  left 
lobe  presents  behind  and  to  the  left  a  depression  where  it  is  moulded  over  the  car- 
diac port  of  the  stomach,  and  to  the  right  and  near  the  centre  a  rounded  eminence, 
the  tuber  omentale.  which  fits  into  the  concavity  of  the  lesser  curvature,  lying  in 
front  of  the  anterior  layer  of  the  lesser  omentum.      The  under  surface  of  the  rirrht 
lobe  is  divided  -into  two  unequal  portions  by  a  fossa,  which  lodges  the  gall-bladderp 
the  fossa  vcsiccHis ;  the-  portion  to  the  left,  the  smaller  of  the  two,  is  somewhat 
oblong  in  sh;.        its  antero-posterior  diameter  being  greater  than  its  transverse.     It 
is  known  as  th.      "         te  lobe,  and  is  in  relation  with  the  pyloric  end  of  the  stomach 
and  the  first  f  the  duodenum.      The  portion  of  the  under  surface  of  the- 

right  lobe  to  the  >f  the  fossa  vesicalis  presents  two  shallow"  concave  impres- 

sions, one  situat*  »ci  -1      tnd  the  other,  the  two  being  separated  by  a  ridge.     The 
anterior  of  these   t  ipressionf     he  impres.sio  colica,  is  produced  by  the  hepatic 

flexure  of  the  colon  ;  e  impressio  renalis,  is  occupied  by  the  upper 

end  of  the  right   kidnej  side  of  the  latter  impression  is  a  third  and 

slightly  marked    im]      -      u  veen   it  and   the  neck   of  the  gall-bladder. 

This  is  caused  I  ond   j      mm  of  the  duodenum,  and  is  known  as  the  im- 

pressio duodenalis.    Just  f&^fron.  of  the  vena  cava  is  a  narrow  strip  of  liver  tissue, 
the  caudate  lobe,  which  connects    th  inferior  angle  of  the  Spigelian  lobe  to 

the  under  surface  of  the  right  lobe.         pimediately   below   it  is  the  foramen  of 
Winslow. 

The  posterior  surface  is  roum  1  the  rirrht  lobe,  but  narrow 

on  the  left.      Over  a  large  part  ol  it  is  nol   ■■■<  by  peritoneum;  this 

uncovered  portion  is  about  three  inches    b'rc8af^  ar,d  is  in  di  intact  with  the 

Diaphragm.     It  is  marked  off  from  the  up  er\sur^ace  D>"  T^!(  reflection  of 

the   upper   or  anterior  layer  of  the  coroi  »ry  \igament.      It  i  ~ime  way 

marked  off  from  the  under  surface  of  th     liveV   Dv  tne  ^"'  of  the- 

lower  layer  of  the  coronary  ligament.      Tri        cen£re  tn^s  posterior  su  deeply 

notched  for  the  vertebral  column  a  of  t\tne  Diaphragm,  right 


THE   LIVER. 


935 


of  this  it  is  indented  for  the  inferior  vena  cava,  which  is  often  partly  imbedded  in 
its  substance.  Close  to  the  right  of  this  indentation  and  immediately  above  the 
renal  impression  is  a  small  triangular  depressed  area  (impressio  suprarenalis),  the 
greater  part  of  which  is  devoid  of  peritoneum ;  it  lodges  the  right  suprarenal 
capsule.  To  the  left  of  the  inferior  vena  cava  is  the  Spigelian  lobe,  which  lies 
between  the  fissure  for  the  vena  cava  and  the  fissure  for  the  ductus  venosus. 
Below  and  in  front  it  projects  and  forms  part  of  the  posterior  boundary  of  the 
transverse  fissure.  Here,  to  the  right,  it  is  connected  with  the  under  surface  of 
the  right  lobe  of  the  liver  by  the  caudate  lobe,  and  to  the  left  it  presents  a  tubercle, 
the  tuber  papillaire.  It  is  opposite  the  tenth  and  eleventh  dorsal  vertebrae,  and 
rests  upon  the  aorta  and  crura  of  the  Diaphragm,  being  covered  by  the  peritoneum 
of  the  lesser  sac.  The  lobe  is  nearly  vertical  in  position,  and  is  directed  back- 
ward :  it  is  longer  from  above  downward  than  from  side  to  side,  and  is  somewhat 
concave  in  the  transverse  direction.  On  the  posterior  surface  to  the  left  of  the 
Spigelian  lobe  is  a  groove  indicating  the  position  of  the  oesophageal  orifice  of  the 
stomach. 


Suprarenal 
impression 
(non- peritoneal). 

Suprarenal 
impression 
(peritoneal), 

Tuberculum 
caudatum. 


Tuber. 
papillare. 


Umbilical  fissure. 


Transverse  fissure. 


Fig.  512.— The  liver.    Posterior  and  inferior  surfaces.    (Drawn  from  His's  models.) 

The  inferior  border  is  thin  and  sharp,  and  marked  opposite  the  attachment  of 
the  falciform  ligament  by  a  deep  notch,  the  umbilical  notch,  and  opposite  the 
cartilage  of  the  ninth  rib  by  a  second  notch  for  the  fundus  of  the  gall-bladder.  In 
adult  males  this  border  usually  corresponds  with  the  margin  of  the  ribs  in  the 
right  nipple  line ;   but  in  women  and  children  it  usually  projects  below  the  ribs. 

The  left  extremity  of  the  liver  is  thin  and  flattened  from  above  downward. 

Fissures  (Fig.  512). — Five  fissures  are  seen  upon  the  under  and  posterior  sur- 
faces of  the  liver,  which  serve  to  divide  it  into  6  >bes.  They  are,  the  umbilical 
fissure,  the  fissure  of  tb    ductus  i    n<  su         ~  erse  fissure,  the  Assure  for  the 

tJ  e  inferior  vena  cava  They  are  arranged  in  the 
•  f  the  H  is  known  as  the  longitudinal  fissure. 
le  fissure  for  the  gall-bladdi ■>■ ,  and  behind 
by  the  fit  r  the  inferior  vena  cava ;   these  two  fissures  are  separated  from 

each  othe  ;  < ■  caudate  lobe.     The  connecting  bar  of  the  H  is  the  transverse  or 

portt  It  separates  the   quadrate  lobe  in  front   from   the  caudate  and 

Spi^  behind. 

Tlu  linal  fissure  is  a  deep  groove,  which  extends  from  the  notch  on  the 

anterior  ras  n  of  the  liver  to  t]  e  upper  border  of  the  posterior  surface  of  the 
organ.  I I  .separates  the  right  ami  left  lobes;  the  transverse  fissure  joins  it,  at 
right  angles,  and  divides  it  into  two  parts.  The  anterior  part  is  called  the 
umbilical  fissure  ;  it  is  deeper  than  the  posterior,  and  lodges  the  umbilical  vein  in 


gall-bladder,  and  th 
form  of  the  letter  H 
The  riglil 


936 


THE    ORGANS    OF  DIGESTION. 


the  foetus,  and  its  remains  (the  round  ligament)  in  the  adult ;  the  posterior  part 
contains  the  ductus  venosus,  and  is  known  as  the  fissure  of  the  ductus  venosus. 
This  fissure  lies  between  the  quadrate  lobe  and  the  left  lobe  of  the  liver,  and  is 
often  partially  bridged  over  by  a  prolongation  of  the  hepatic  substance,  the  pons 
hepatis. 

The  fissure  of  the  ductus  venosus  is  the  back  part  of  the  longitudinal  fissure, 
and  is  situated  mainly  on  the  posterior  surface  of  the  liver.  It  lies  between  the 
left  lobe  and  the  lobe  of  Spigelius.  It  lodges  in  the  foetus  the  ductus  venosus,  and 
in  the  adult  a  slender  fibrous  cord,  the  obliterated  remains  of  that  vessel. 

The  transverse  or  portal  fissure  is  a  short  but  deep  fissure,  about  two  inches  in 
length,  extending  transversely  across  the  under  surface  of  the  left  portion  of  the 
right  lobe,  nearer  to  its  posterior  surface  than  its  anterior  border.  It  joins,  nearly 
at  right  angles,  with  the  longitudinal  fissure,  and  separates  the  quadrate  lobe  in 
front  from  the  caudate  and  Spigelian  lobes  behind.  By  the  older  anatomists  this 
fissure  was  considered  the  gateway  (porta)  of  the  liver  ;  hence  the  large  vein  which 
enters  at  this  fissure  was  called  the  portal  vein.  Besides  this  vein,  the  fissure 
transmits  the  hepatic  artery  and  nerves,  and  the  hepatic  duct  and  lymphatics. 
At  their  entrance  into  the  fissure,  the  hepatic  duct  lies  in  front  and  to  the  right, 
the  hepatic  artery  to  the  left,  and  the  portal  vein  behind  and  between  the  duct 
and  artery. 


(Esophageal  groove.         Portal  vein.         Suprarenal  impression. 


LIGAMENTUM 
TERES. 


Hepatic  artery.       I 

Common  bile-duct. 

Fig.  513.— Posterior  and  under  surfaces  of  the  liver.    (From  Ellis.1* 


The  fissure  for  the  gall-bladder  (fossa  vesicjalis)  is  a  shallow,  oblong  fossa, 
placed  on  the  under  surface  of  thl9  right  h  parallel  with. the  longitudinal  fissure. 
It  extends  from  the  anterior  ^ee  margin  of  th  iver,  which  is  notched  for  its 
reception,  to  the  right  extremity  of  tl;  fissure. 

The  fissure  for  the  inferior  vena  cavu  .  I    deep  fissure,  ocea!  on  ally  a  com- 

plete canal,  in  consequence  of  the  substance  of  the  liver  surroundj  he  vena  cava. 
It  extends  obliquely  upward  from  the  lobus  caudatus,  which  scr  it  from   the 

transverse  fissure,  on  the  posterior  surface  of  the  liver,  and  separatee,  the  Spigelian 
from  the  right  lobe.  On  slitting  open  the  inferior  vena  cava  the  orifices  of  the 
hepatic  veins  will  be  seen  opening  into  this  vessel  at  its  upper  part,  after  perforat- 
ing the  floor  of  this  fissure. 

Lobes. — The  lobes  of  the  liver,  like  the  ligaments  and  fissures,  aie  five  in 
number — the  right  lobe,  the  left  lobe,  the  lobus  quadratus,  the  lobus  Spigelii,  and 
the  lobus  caudatus,  the  last  three  being  merely  parts  of  t.ie  right  lobe. 


THE   LIVER.  937 

The  right  lobe  is  much  larger  than  the  left;  the  proportion  between  them  being 
as  six  to  one.  It  occupies  the  right  hypochondrium,  and  is  separated  from  the  left 
lobe,  on  its  upper  and  anterior  surfaces  by  the  falciform  ligament ;  on  its  under  and 
posterior  surfaces  by  the  longitudinal  fissure;  and  in  front  by  the  umbilical  notch. 
It  is  of  a  somewhat  quadrilateral  form,  its  under  and  posterior  surfaces  being 
marked  by  three  fissures — the  transverse  fissure,  the  fissure  for  the  gall-bladder,  and 
the  fissure  for  the  inferior  vena  cava,  which  separate  its  left  part  into  three  smaller 
lobes — lobus  Spigelii,  lobus  quadratus,  and  lobus  caudatus.  On  it  are  seen  four 
shallow  impressions,  one  in  front  (impjressio  colicd),  for  the  hepatic  flexure  of  the 
colon ;  a  second  behind  (impressio  renalis),  for  the  right  kidney  ;  a  third  internal, 
between  the  last-named  and  the  gall-bladder  (impress™  duodenalis),  for  the  second 
part  of  the  duodenum ;  and  a  fourth  on  its  posterior  surface,  for  the  suprarenal 
capsule  (impressio  suprarenalis). 

The  lobus  quadratus,  or  square  lobe,  is  situated  on  the  under  surface  of  the 
right  lobe,  bounded  in  front  by  the  inferior  margin  of  the  liver  ;  behind  by  the 
transverse  fissure ;  on  the  right,  by  the  fissure  of  the  gall-bladder :  and  on  the  left 
by  the  umbilical  fissure. 

The  lobus  Spigelii  is  situated  upon  the  posterior  surface  of  the  right  lobe  of  the 
liver.  It  looks  directly  backward,  and  is  nearly  vertical  in  direction.  It  is 
bounded,  above,  by  the  upper  layer  of  the  coronary  ligament ;  below,  by  the 
transverse  fissure  ;  on  the  right,  by  the  fissure  for  the  vena  cava  ;  and,  on  the  left, 
by  the  fissure  for  the  ductus  venosus.  Its  left  upper  angle  forms  part  of  the  groove 
for  the  oesophagus. 

The  lobus  caudatus,  or  tailed  lobe,  is  a  small  elevation  of  the  hepatic  substance 
extending  obliquely  outward,  from  the  lower  extremity  of  the  lobus  Spigelii  to  the 
under  surface  of  the  right  lobe.  It  is  situated  behind  the  transverse  fissure,  and 
separates  the  fissure  for  the  gall-bladder  from  the  commencement  of  the  fissure  for 
the  inferior  vena  cava. 

The  left  lobe  is  smaller  and  more  flattened  than  the  right.  It  is  situated  in  the 
epigastric  and  left  hypochondriac  regions.  Its  upper  surface  is  slightly  convex  ; 
its  under  surface  is  concave,  and  presents  a  shallow  depression  for  the  stomach 
(gastric  impression).  This  is  situated  in  front  of  the  groove  for  the  oesophagus,  and 
is  separated  from  the  longitudinal  fissure  by  the  omental  tuberosity,  which  lies 
against  the  small  omentum  and  lesser  curvature  of  the  stomach. 

Ligaments. — The  liver  is  connected  to  the  under  surface  of  the  Diaphragm  and 
the  anterior  wall  of  the  abdomen  by  five  ligaments,  four  of  which  are  peritoneal 
folds ;  the  fifth  is  a  round,  fibrous  cord,  resulting  from  the  obliteration  of  the 
umbilical  vein.  These  ligaments  are  the  falciform,  two  lateral,  coronary,  and 
round.  It  is  also  attached  to  the  lesser  curvature  of  the  stomach  by  the  gastro- 
hepatic  or  small  omentum  (see  page  902). 

The  falciform  ligament  (broad  or  suspensory  ligament)  is  a  broad  and  thin 
antero-posterior  peritoneal  fold,  falciform  in  shape,  its  base  being  directed  down- 
ward and  backward,  its  apex  upward  and  backward.  It  is  attached  by  one  margin 
to  the  under  surface  of  the  Diaphragm,  and  the  posterior  surface  of  the  sheath  of 
the  right  Rectus  muscle  as  low  down  as  the  umbilicus  ;  by  its  hepatic  margin  it 
extends  from  the  notch  on  the  anterior  margin  of  the  liver,  as  far  back  as  its 
posterior  surface.  It  consists  of  two  layers  of  peritoneum  closely  united  together. 
Its  base  or  free  edge  contains  the  round  ligament  between  its  layers. 

The  lateral  ligaments  (Fig.  511),  two  in  number,  right  and  left,  are  triangular 
-in  shape.  They  are  formed  by  the  apposition  of  the  upper  and  lower  layers  of  the 
coronary  ligament,  and  extend  from  the  Diaphragm  to  the  liver — the  right  being 
attached  to  the  border  between  its  lateral  and  inferior  surfaces,  the  left,  the  longer 
of  the  two,  to  the  upper  surface  of  the  left  lobe,  where  it  lies  in  front  of  the 
oesophageal  opening  in  the  Diaphragm. 

The  coronary  ligament  connects  the  posterior  surface  of  the  liver  to  the  Dia- 
phragm. It  is  formed  by  the  reflection  of  the  peritoneum  from  the  Diaphragm  on 
to  the  upper  and  lower  margins  of  the  posterior  surface  of  the  organ.      The   coro- 


938  THE    ORGANS    OF  DIGESTION. 

nary  ligament  consists  of  two  layers,  which  are  continuous  on  each  side  with  the 
lateral  ligaments ;  and,  in  front,  with  the  falciform  ligament.  Between  the  layers 
a  large  triangular  area  is  left  uncovered  by  peritoneum,  and  is  connected  to  the 
Diaphragm  by  firm  areolar  tissue. 

The  round  ligament  (ligamentum  teres)  is  a  fibrous  cord  resulting  from  the 
obliteration  of  the  umbilical  vein.  It  ascends  from  the  umbilicus,  in  the  free 
margin  of  the  falciform  ligament,  to  the  notch  in  the  anterior  border  of  the  liver, 
from  which  it  may  be  traced  along  the  longitudinal  fissure  on  the  under  surface  of 
the  liver  ;  on  the  posterior  surface  it  is  continued  as  the  obliterated  ductus  venosus 
as  far  back  as  the  inferior  vena  cava. 

Vessels. — The  vessels  connected  with  the  liver  are  also  five  in  number  :  they 
are,  the  hepatic  artery,  the  portal  veins,  the  hepatic  vein,  the  hepatic  duct,  and 
the  lymphatics. 

The  hepatic  artery  and  portal  vein,  accompanied  by  numerous  lymphatics  and 

<        nerves,  ascend  to  the  transverse  fissure  between  the  layers  of  the  gastro-hepatic 

omentum.     The  hepatic  duct,  lying    in    company  with   them,  descends   from   the 

[  transverse  fissure  between  the  layers  of  the  same  omentum.     The  relative  position 

j)f  the  three  structures  is  as  follows  :   the  hepatic  duct  lies  to  the  right,  the  hepatic 

5?  Artery  to  the  left,  and  the  portal  vein  behind   and  between  the  other  two.      They 

are  enveloped  in  a  loose  areolar  tissue,  the  capsule  of  Glisson,  which  accompanies 

the  vessels  in  their  course  through  the  portal  canals  in  the  interior  of  the  organ. 

The  hepatic  veins  convey  the  blood  from  the  liver.  They  commence  in  the 
substance  of  the  liver,  in  the  capillary  terminations  of  the  portal  vein  and  hepatic 
artery ;  these  tributaries,  gradually  uniting,  usually  form  three  veins,  which,  con- 
verge toward  the  posterior  surface  of  the  liver  and  open  into  the  inferior  vena 
cava,  while  that  vessel  is  situated  in  the  groove  at  the  back  part  of  this  organ. 
Of  these  three  veins,  one  from  the  right  and  another  from  the  left  lobe  open 
obliquely  into  the  vena  cava  ;  that  from  the  middle  of  the  organ  and  lobus  Spigelii 
having  a  straight  course. 

The  hepatic  veins  have  very  little  cellular  investment ;  what  there  is  binds 
their  parietes  closely  to  the  walls  of  the  canals  through  which  they  run  ;  so  that, 
on  section  of  the  organ,  these  vein3  remain  widely  open  and  solitary,  and  may  be 
easily  distinguished  from  the  branches  of  the  portal  vein,  which  are  more  or  less 
collapsed,  and  always  accompanied  by  an  artery  and  duct.  The  hepatic  veins  are 
destitute  of  valves. 

Structure. — The  substance  of  the  liver  is  composed  of  lobules  held  together  by 
an  extremely  fine  areolar  tissue,  and  of  the  ramifications  of  the  portal  vein,  hepatic 
duct,  hepatic  artery,  hepatic  veins,  lymphatics,  and  nerves,  the  whole  being 
invested  by  a  serous  and  a  fibrous  coat. 

The  serous  coat  is  derived  from  the  peritoneum,  and  invests  the  greater  part 
of  the  surface  of  the  organ.     It  is  intimately  adherent  to  the  fibrous  coat. 

The  fibrous  coat  lies  beneath  the  serous  investment  and  covers  the  entire  sur- 
face of  the  organ.  It  is  difficult  of  demonstration,  excepting  where  the  serous 
coat  is  deficient.  At  the  transverse  fissure  it  is  continuous  with  the  capsule  of 
Glisson,  and  on  the  surface  of  the  organ  with  the  areolar  tissue  separating  the 
lobules. 

The  lobules  form  the  chief  mass  of  the  hepatic  substance;  they  may  be  seen 
either  on  the  surface  of  the  organ  or  by  making  a  section  through  the  gland. 
They  are  small  granular  bodies  about  the  size  of  a  millet-seed,  measuring  from 
one-twentieth  to  one-tenth  of  an  inch  in  diameter.  In  the  human  subject  their 
outline  is  very  irregular,  but  in  some  of  the  lower  animals  (for  example,  the  pig) 
they  are  well-defined,  and  when  divided  transversely  have  a  polygonal  outline. 
If  divided  longitudinally  they  are  more  or  less  foliated  or  oblong.  The  bases  of 
the  lobules  are  clustered  round  the  smallest  radicles  (sublobular)  of  the  hepatic 
veins,  to  which  each  is  connected  by  means  of  a  small  branch  which  issues  from 
the  centre  of  the, lobule  (intralobular).  The  remaining  part  of  the  surface  of  each 
lobule  is  imperfectly  isolated  from  the  surrounding  lobules  by  a  thin  stratum  of 


THE   LIVER. 


939 


areolar  tissue  in  which  is  contained  a  plexus  of  vessels  (the  interlobular  plexus) 
and  ducts.  In  some  animals,  as  the  pig,  the  lobules  are  completely  isolated  one 
from  another  by  this  interlobular  areolar  tissue. 

If  one  of  the  sublobular  veins  be  laid  open,  the  bases  of  the  lobules  may  be 
seen  through  the  thin  wall  of  the  vein  on  which  they  rest,  arranged  in  the  form 
of  a  tesselated  pavement,  the  centre  of  each  polygonal  space  presenting  a  minute 
aperture,  the  mouth  of  an  intralobular  vein  (Fig.  514). 

Microscopic  Appearance. — Each  lobule  is  composed  of  a  mass  of  cells  {hepatic 
cells)  surrounded  by  a  dense  capillary  plexus,  composed  of  vessels  which  penetrate 
from   the   circumference  to  the  centre  of  the  lobule,  and  terminate  in  a  single 


.  Hepatic 

auct.     artery. 


Portal  vein 


Orifices  of  intralobular  veins. 


Fig.  514.— Longitudinal  section  of  an  hepatic 
vein.    (After  Kiernan.) 


Fig.  515.— Longitudinal  section  of  a  small  portal 
vein  and  canal.    (After  Kiernan.; 


straight  vein,  which  runs  through  its  centre,  to  open  at  its  base  into  one  of 
the  radicles  of  the  hepatic  vein.  Between  the  cells  are  also  the  minute  com- 
mencements of  the  bile-ducts.  Therefore  in  the  lobule  we  have  all  the  essen- 
tials of  a  secreting  gland ;  that  is  to  say :  (1)  cells,  by  which  the  secretion  is 
formed ;  (2)  blood-vessels,  in  close  relation  with  the  cells,  containing  the  blood 
from  which  the  secretion  is  derived ;  and  (3)  ducts,  by  which  the  secretion, 
when  formed,  is  carried  away.  Each  of  these  structures  will  have  to  be  further 
considered. 

(1)  The  hepatic  cells  are  of  more  or  less  spheroidal  form,  but  may  be  rounded, 
flattened,  or  many-sided  from  mutual  compression.  They  vary  in  size  from  the 
■t  0\  0  to  the  2"oVo"  °f  an  incn  in  diameter.  They  consist  of  a  honeycomb  net- 
work (Klein)  without  any  cell-wall,  and  contain  one  or  sometimes  two  distinct 
nuclei.  In  the  nucleus  is  a  highly  refracting  nucleolus  with  granules.  Embedded 
in  the  honeycomb  network  are  numerous  yellow  particles,  the  coloring  matter  of 
the  bile,  and  oil-globules.  The  cells  adhere  together  by  their  surfaces  so  as  to 
form  rows,  which  radiate  from  the  centre  to  the  circumference  of  the  lobules.1  As 
stated  above,  they  are  the  chief  agents  in  the  secretion  of  the  bile. 

(2)  The  Blood-vessels.- — The  blood  in  the  capillary  plexus  around  the  liver- 
cells  is  brought  to  the  liver  principally  by  the  portal  vein,  but  also  to  a  certain 
extent  by  the  hepatic  artery.  For  the  sake  of  clearness  the  distribution  of  the 
blood  derived  from  the  hepatic  artery  may  be  considered  first. 

1Dele'pine  states  that  there  are  evidences  of  the  arrangement  of  these  cells  in  the  form  of  col- 
umns, which  form  tubes  witli  narrow  lumina  branching  from  terminal  bile-ducts.  This  branching  is 
evidenced  by  a  divergence  of  the  columns  from  lines  extending  between  adjacent  portal  vessels.  The 
columns  of  cells  group  round  terminal  bile-ducts,  and  not  round  the  so-called  intralobular  veins. 
{Lancet,  1895,  vol.  i.,  p.  1254.) 


940  THE    ORGANS    OF  DIGESTION. 

The  hepatic  artery,  entering  the  liver  at  the  transverse  fissure  with  the  portal 
vein  and  hepatic  duct,  ramifies  with  these  vessels  through  the  portal  canals.  It 
gives  off  vaginal  branches  which  ramify  in  the  capsule  of  Glisson,  and  appear  to 
be  destined  chiefly  for  the  nutrition  of  the  coats  of  the  large  vessels,  the  ducts, 
and  the  investing  membranes  of  the  liver.  It  also  gives  off  capsular  branches 
which  reach  the  surface  of  the  organ,  terminating  in  its  fibrous  coat  in  stellate 
plexuses.  Finally  it  gives  off  interlobular  branches  which  form  a  plexus  on  the 
outer  side  of  each  lobule,  to  supply  its  wall  and  the  accompanying  bile-ducts. 
From  this,  lobular  branches  enter  the  lobule  and  end  in  the  capillary  network 
between  the  cells.  Some  anatomists,  however,  doubt  whether  it  transmits  any 
blood  directly  to  the  capillary  network. 

The  portal  vein  also  enters  at  the  transverse  fissure  and  runs  through  the 
portal  canals,  enclosed  in  Glisson's  capsule,  dividing  into  branches  in  its  course, 
which  finally  break  up  into  a  plexus  (the  interlobular  plexus)  in  the  interlobular 
spaces.  In  their  course  these  branches  receive  the  vaginal  and  capsular  veins, 
corresponding  to  the  vaginal  and  capsular  branches  of  the  hepatic  artery  (Fig.  515). 
Thus  it  will  be  seen  that  all  the  blood  carried  to  the  liver  by  the  portal  vein  and 
hepatic  artery,  except  perhaps  that  derived  from  the  interlobular  branches  of  the 
hepatic  artery,  directly  or  indirectly  finds  its  way  into  the  interlobular  plexus. 
From  this  plexus  the  blood  is  carried  into  the  lobule  by  fine  branches  which  pierce 
its  wall  and  then  converge  from  the  circumference  to  the  centre  of  the  lobule, 
forming  a  number  of  converging  vessels  Avhich  are  connected  by  transverse  branches 
(Fig.  516).      In  the  interstices  of  the  network  of  vessels  thus  formed  are  situated, 


Trunk  of  intralobular 
vein. 


Intralobular  vein. 


Fig.  516.— Horizontal  section  of  liver  (dog). 


as  before  said,  the  liver-cells  :  and  here  it  is  that,  the  blood  being  brought  into 
intimate  connection  with  the  liver-cells,  the  bile  is  secreted.  Arrived  at  the  centre 
of  the  lobule,  all  these  minute  vessels  empty  themselves  into  one  vein,  of  consider- 
able size,  which  runs  down  the  centre  of  the  lobules  from  apex  to  base  and  is  called 
the  intralobular  vein.  At  the  base  of  the  lobule  this  vein  opens  directly  into  the 
sublobular  vein,  with  which  the  lobule  is  connected,  and  which,  as  before  men- 
tioned, is  a  radicle  of  the  hepatic  vein.  The  sublobular  veins,  uniting  into  larger 
and  larger  trunks,  end  at  last  in  the  hepatic  veins,  which  do  not  receive  any  intra- 
lobular veins.  Finally,  the  hepatic  veins,  as  mentioned  at  page  619,  converge  to 
form  three  large  trunks  which  open  into  the  inferior  vena  cava,  while  that  vessel 
is  situated  in  the  fissure  appropriated  to  it  at  the  back  of  the  liver. 

(3)  The  Ducts. — Having  shown  how  the  blood  is  brought  into  intimate  relation 
with  the  hepatic  cells  in  order  that  the  bile  may  be  secreted,  it  remains  now  only 
to  consider  the  way  in  which  the  secretion,  having  been  formed,  is  carried  away. 


THE   LIVER. 


941 


Several  views  have  prevailed  as  to  the  mode  of  origin  of  the  hepatic  ducts  ;  it 
seems,  however,  to  be  clear  that  they  commence  by  little  passages  which  are  formed 
between  the  cells,  and  which  have  been  termed  intercellular  biliary  passages  or 
bile-capillaries.     These  passages  are  merely  little  channels  or  spaces  left  between 

the  contiguous  surfaces  of  two  cells  or  in 
the  angle  where  three  or  more  liver-cells 
meet  (Fig.  517),  and  it  seems  doubtful 
whether  there  is  any  delicate  membrane 


*m& 


Hepatic 
cells. 


Capillary. 


Biliar 


Fig.  517.— Section  of  liver. 


Fig.  518.— A  transverse  section  of  a  small  portal 
canal  and  its  vessels.  (After  Kiernan.)  1.  Portal  vein. 
2.  Interlobular  branches.  3.  Vaginal  branches.  4. 
Hepatic  duct.    5.  Hepatic  artery. 


forming  the  wall  of  the  channel.  The  channels  thus  formed  radiate  to  the  circum- 
ference of  the  lobule,  and,  piercing  its  wall,  form  a  plexus  {interlobular)  between 
the  lobules.  From  this  plexus  ducts  are  derived  which  pass  into  the  portal  canals, 
become  enclosed  in  Glisson's  capsule,  and,  accompanying  the  portal  vein  and 
hepatic  artery  (Fig.  518),  join  with  other  ducts  to  form  two  main  trunks,  which 
leave  the  liver  at  the  transverse  fissure,  and  by  their  union  form  the  hepatic  duct. 

Structure. — The  coats  of  the  smallest  biliary  ducts,  which  lie  in  the  interlobular 
spaces,  are  a  connective- tissue  coat,  in  which  are  muscle-cells,  arranged  both  cir- 
cularly and  longitudinally,  and  an  epithelial  layer,  consisting  of  short  columnar 
cells.  In  the  larger  ducts,  which  lie  in  the  portal  canals,  there  are  a  number  of 
orifices  disposed  in  two  longitudinal  rows,  which  were  formerly  regarded  as  the 
openings  of  mucous  glands,  but  which  are  merely  the  orifices  of  tubular  recesses. 
They  occasionally  anastomose,  and  from  the  sides  of  them  saccular  dilatations  are 
given  off. 

Lymphatics  of  the  Liver. — The  lymphatics  in  the  substance  of  the  liver  com- 
mence in  lymphatic  spaces  around  the  capillaries  of  the  lobules  ;  they  accompany 
the  vessels  of  the  interlobular  plexus,  often  enclosing  and  surrounding  them.  These 
unite  and  form  larger  vessels,  which  run  in  the  portal  canals,  enclosed  in  Glisson's 
capsule,  and  emerge  at  the  portal  fissure  to  be  distributed  in  the  manner  described. 
Other  superficial  lymphatics  form  a  close  plexus,  under  the  peritoneum,  where  this 
membrane  covers  the  liver,  and  pass  in  various  directions  through  the  ligaments  of 
the  liver  (page  634). 

Nerves  of  the  Liver. — The  nerves  of  the  liver  derived  from  the  pneumogastric 
and  sympathetic  enter  the  liver  at  the  transverse  fissure  and  accompany  the  vessels 
and  ducts  to  the  interlobular  spaces.  Here,  according  to  Korolkow,  the  medul- 
lated  fibres  are  distributed  almost  exclusively  to  the  coats  of  the  blood-vessels ; 
while  the  non-medullated  enter  the  lobules  and  ramify  between  the  cells. 

The  Excretory  Apparatus  of  the  Liver. 

The  excretory  apparatus  of  the  liver  consists  of  (1)  the  hepatic  duct,  which, 
as  we  have  seen,  is  formed  by  the  junction  of  the  two  main  ducts,  which  pass  out 
of  the  liver  at  the  transverse  fissure,  and  are  formed  by  the  union  of  the  bile-capil- 


942  THE    ORGANS    OF  DIGESTION. 

laries  :  (2)  the  gall-bladder,  which  serves  as  a  reservoir  for  the  bile  ;  (3)  the  cystic 
duct,  which  is  the  duct  of  the  gall-bladder ;  and  (4)  the  common  bile-duct,  formed 
by  the  junction  of  the  hepatic  and  cystic  ducts. 

The  Hepatic  Duct. — Two  main  trunks  of  nearly  equal  size  issue  from  the  liver 
at  the  transverse  fissure,  one  from  the  right,  the  other  from  the  left  lobe ;  these 
unite  to  form  the  hepatic  duct,  which  then  passes  downward  and  to  the  right  for 
about  an  inch  and  a  half,  between  the  layers  of  the  lesser  omentum,  where  it  is 
joined  at  an  acute  angle  by  the  cystic  duct,  and  so  forms  the  ductus  communis 
choledochus.  The  hepatic  duct,  as  it  descends  from  the  transverse  fissure  of  the 
liver,  between  the  two  layers  of  the  lesser  omentum,  lies  in  company  with  the 
hepatic  artery  and  portal  vein. 

The  Gall-bladder  is  the  reservoir  for  the  bile ;  it  is  a  conical  or  pear-shaped 
musculo-membranous  sac,  lodged  in  a  fossa  on  the  under  surface  of  the  right  lobe 
of  the  liver,  and  extending  from  near  the  right  extremity  of  the  transverse  fissure 
to  the  anterior  border  of  the  organ.  It  is  about  four  inches  in  length,  one  inch  in 
breadth  at  its  widest  part,  and  holds  from  eight  to  ten  drachms.  It  is  divided  into 
a  fundus,  body,  and  neck.  The  fundus,  or  broad  extremity,  is  directed  downward, 
forward,  and  to  the  right,  and  projects  beyond  the  anterior  border  of  the  liver  ; 
the  body  and  neck  are  directed  upward  and  backward  to  the  left.  The  upper  sur- 
face of  the  gall-bladder  is  attached  to  the  liver  by  connective  tissue  and  vessels. 
The  under  surface  is  covered  by  peritoneum,  which  is  reflected  on  to  it  from  the 
surface  of  the  liver.  Occasionally  the  whole  of  the  organ  is  invested  by  the  serous 
membrane,  and  is  then  connected  to  the  liver  by  a  kind  of  mesentery. 

Relations. — The  body  of  the  gall-bladder  is  in  relation,  by  its  upper  surface, 
with  the  liver,  to  which  it  is  connected  by  areolar  tissue  and  vessels;  by^its  under 
surface,  with  the  commencement  of  the  transverse  colon  :  and  further  back,  with 
the  upper  end  of  the  descending  portion  of  the  duodenum  or  sometimes  with  the 
pyloric  end  of  the  stomach  or  first  portion  of  the  duodenum.  The  fundus  is  com- 
pletely invested  by  peritoneum;  it  is  in  relation,  in  front,  with  the  abdominal 
parietes,  immediately  below  the  ninth  costal  cartilage  ;  behind  with  the  transverse 
arch  of  the  colon.  The  neck  is  narrow,  and  curves  upon  itself  like  the  letter  S ; 
at  its  point  of  connection  with  the  cystic  duct  it  presents  a  well-marked  constriction. 

When  the  gall-bladcler  is  distended  with  bile  or  calculi,  the  fundus  may  be  felt  through  the 
abdominal  parietes,  especially  in  an  emaciated  subject  :  the  relations  of  this  sac  will  also  serve  to 
explain  the  occasional  occurrence  of  abdominal  biliary  fistulas,  through  which  biliary  calculi  may 
pass  out,  and  of  the  passage  of  calculi  from  the  gall-bladder  into  the  stomach,  duodenum,  or 
colon,  which  occasionally  happens. 

Structure. — The  gall-bladder  consists  of  three  coats — serous,  fibrous  and  mus- 
cular, and  mucous. 

The  external  or  serous  coat  is  derived  from  the  peritoneum  ;  it  completely  in- 
vests the  fundus,  but  covers  the  body  and  neck  only  on  their  under  surface. 

The  fibro-muscular  coat  is  a  thin  but  strong  layer  which  forms  the  framework 
of  the  sac,  consisting  of  dense  fibrous  tissue  which  interlaces  in  all  directions  and 
is  mixed  with  plain  muscular  fibres  which  are  disposed  chiefly  in  a  longitudinal 
direction,  a  few  running  transversely. 

The  internal  or  mucous  coat  is  loosely  connected  with  the  fibrous  layer.  It  is 
generally  tinged  with  a  yellowish-brown  color,  and  is  everywhere  elevated  into 
minute  rugse,  by  the  union  of  which  numerous  meshes  are  formed ;  the  depressed 
intervening  spaces  having  a  polygonal  outline.  The  meshes  are  smaller  at  the 
fundus  and  neck,  being  most  developed  about  the  centre  of  the  sac.  Opposite  the 
neck  of  the  gall-bladder  the  mucous  membrane  projects  inward  in  the  form  of 
oblique  ridges  or  folds,  forming  a  sort  of  screw-like  valve. 

The  mucous  membrane  is  covered  with  columnar  epithelium,  and  secretes  an 
abundance  of  thick  viscid  mucus ;  it  is  continuous  through  the  hepatic  duct  with 
the  mucous  membrane  lining  the  ducts  of  the  liver,  and  through  the  ductus  com- 
munis choledochus  with  the  mucous  membrane  of  the  alimentary  canal. 


THE   LIVER.  943 


5% 


The  Cystic  Duct,  the  smallest  of  the  three  biliary  ducts,  is  about  an  inch  and  a 
half  in  length.  It  passes  obliquely  downward  and  to  the  left  from  the  neck  of 
the  gall-bladder,  and  joins  the  hepatic  duct  to  form  the  common  bile-duct.  It  lies 
in  the  gastro-hepatic  omentum  in  front  of  the  vena  portse,  the  hepatic  artery  lying 
to  its  left  side.  The  mucous  membrane  lining  its  interior  is  thrown  into  a  series 
of  crescentic  folds,  from  five  to  twelve  in  number,  similar  to  those  found  in  the 
neck  of  the  gall-bladder.  They  project  into  the  duct  in  regular  succession,  and 
.are  directed  obliquely  round  the  tube,  presenting  much  the  appearance  of  a  con- 
tinuous spiral  valve.  When  the  duct  is  distended,  the  spaces  between  the  folds  are 
•dilated,  so  as  to  give  to  its  exterior  a  sacculated  appearance. 

The  Ductus  Communis  Choledochus,  or  common  bile-duct,  the  largest  of  the  three, 
is  the  common  excretory  duct  of  the  liver  and  gall-bladder.  It  is  about  three 
inches  in  length,  of  the  diameter  of  a  goose-quill,  and  formed  by  the  junction  of 
the  cystic  and  hepatic  ducts. 

It  descends  along  the  right  border  of  the  lesser  omentum  behind  the  first  por- 
tion of  the  duodenum,  in  front  of  the  vena  portse,  and  to  the  right  of  the  hepatic 
artery ;  it  then  passes  between  the  pancreas  and  descending  portion  of  the  duo- 
denum, and  running  for  a  short  distance  along  the  right  side  of  the  pancreatic 
duct,  near  its  termination,  passes  with  it  obliquely  between  the  mucous  and  mus- 
cular coats.  The  two  ducts  open  by  a  common  orifice  upon  the  summit  of  a  papilla, 
situated  at  the  inner  side  of  the  descending  portion  of  the  duodenum,  a  little  below 
its  middle  and  about  three  or  four  inches  below  the  pylorus. 

Structure. — The  coats  of  the  large  biliary  ducts  are  an  external  or  fibrous,  and 
.an  internal  or  mucous.  The  fibrous  coat  is  composed  of  strong  fibro-areolar  tissue, 
with  a  certain  amount  of  muscular  tissue  arranged,  for  the  most  part,  in  a  circu- 
lar manner  around  the  duct.  The  mucous  coat  is  continuous  with  the  lining  mem- 
brane of  the  hepatic  ducts  and  gall-bladder,  and  also  with  that  of  the  duodenum  ; 
and,  like  the  mucous  membrane  of  these  structures,  its  epithelium  is  of  the  col- 
umnar variety.  It  is  provided  Avith  numerous  mucous  glands,  which  are  lobulated 
and  open  by  minute  orifices  scattered  irregularly  in  the  larger  ducts.  The  coats 
•of  the  smallest  biliary  ducts,  which  lie  in  the  interlobular  spaces,  are  a  connective- 
tissue  coat,  in  which,  according  to  Heidenhain,  are  muscle-cells  arranged  loth  cir- 
cularly and  longitudinally,  and  an  epithelial  layer,  consisting  of  short  columnar 
cells. 

Surface  Relations. — The  liver  is  situated  in  the  right  hypochondriac  and  the  epigastric 
regions,  and  is  moulded  to  the  arch  of  the  Diaphragm.  In  the  greater  part  of  its  extent  it 
lies  under  cover  of  the  lower  ribs  and  their  cartilages,  but  in  the  epigastric  region  it  comes 
in  contact  with  the  abdominal  wall,  in  the  Sjjhcps,tal  -apfilp-  The  vpf.tr  limit  of  the  right 
lobe  of  the  liver  may  be  defined  in  the  middle  hneby  the  junction  of  the  mesoslernum  with  the 
ensiform  cartilage;  on  the  right  side  the  line  must  be  carried  upward  as  far  as  the  fiiih  rib  car- 
tilage in  the  line  of  the  nipple  and  then  downward  to  reach  the  seventh  rib  at  the  side  of  the  chest. 
The  upper  limit  of  the  left  lobe  maybe  defined  by  continuing  this  line  to  the  left  with  an  inclina- 
tion downward  to  a  point  about  two  inches  to  the  left  of  the  sternum  on  a  level  with  the  sixth 
left  costal  cartilage.  The  lower  limit  of  the  liver  may  be  indicated  by  a  line  drawn  half  an  inch 
below  the  lower  border  of  the  thorax  on  the  right  side  as  far  as  the  ninth  right  costal  cartilage, 
and  thence  obliquely  upward  across  the  subcostal  angle  to  the  eighth  left  costal  cartilage.  A 
slight  curved  line  with  its  convexity  to  the  left  from  this  point — i.  e.,  the  eighth  left  costal 
cartilage — to  the  termination  of  the  line  indicating  the  upper  limit  will  denote  the  left  margin 
of  the  liver.  The  fundus  of  the  gall-bladder  approaches  the  surface  behind  the  anterior 
extremity  of  the  ninth  costal  cartilage,  close  to  the  outer  margin  of  the  Right  rectus  muscle. 

It  must  be  remembered  that  the  liver  is  subject  to  considerable  alterations  in  position,  and 
the  student  should  make  himself  acquainted  with  the  different  circumstances  under  which  this 
-occurs,  as  they  are  of  importance  in  determining  the  existence  of  enlargement  or  other  diseases 
of  the  organ. 

Its  position  varies  according  to  the  posture  of  the  body.  In  the  erect  position  in  the  adult 
male  the  edge  of  the  liver  projects  about  half  an  inch  below  the  lower  edge  of  the  right  costal 
cartilages,  and  its  anterior  border  can  be  often  felt  in  this  situation  if  the  abdominal  wall  is  thin. 
In  the  supine  position  the  liver  gravitates  backward  and  recedes  above  the  lower  margin  of  the 
ribs,  and  cannot  then  be  detected  by  the  finger.  In  the  prone  position  it  falls  forward,  and  can 
then  generally  be  felt  in  a  patient  with  loose  and  lax  abdominal  walls.  Its  position  varies  also 
with  the  ascent  or  descent  of  the  Diaphragm.  In  a  deep  inspiration  the  liver  descends  below 
the  ribs;  in  expiration  it  is  raised  behind  them.     Again,  in  emphysema,  where  the  lungs  are 


944  THE    ORGANS    OF  DIGESTION.         . 

distended  and  the  Diaphragm  descends  very  low,  the  liver  is  pushed  down;  in  some  other 
diseases,  as  phthisis,  where  the  Diaphragm  is  much  arched,  the  liver  rises  very  high  up.  Pres- 
sure from  without,  as  in  tight-lacing,  by  compressing  the  lower  part  of  the  chest,  displaces  the 
liver  considerably,  its  anterior  edge  often  extending  as  low  as  the  crest  of  the  ileum  ;  and  its 
convex  surface  is  often  at  the  same  time  deeply  indented  from  the  pressure  of  the  ribs.  Again, 
its  position  varies  greatly  according  to  the  greater  or  less  distension  of  the  stomach  and  intestines. 
When  the  intestines  are  empty  the  liver  descends  in  the  abdomen,  but  when  they  are  distended 
it  is  pushed  upward.  Its  relations  to  surrounding  organs  may  also_  be  changed  by  the  growth  of 
tumors  or  by  collections  of  fluid  in  the  thoracic  or  abdominal  cavities. 

Surgical  Anatomy. — On  account  of  its  large  size,  its  fixed  position,  and  its  friability,  the 
liver  is  more  frequently  ruptured  than  any  of  the  abdominal  viscera.  The  rupture  may  vary 
considerably  in  extent,  from  a  slight  scratch  to  an  extensive  laceration  completely  through  its 
substance,  dividing  it  into  two  parts.  Sometimes  an  internal  rupture  without  laceration  of  the 
peritoneal  covering  takes  place,  and  such  injuries  are  most  susceptible  of  repair  ;  but  small  tears 
of  the  surface  may  also  heal ;  when,  however,  the  laceration  is  extensive,  death  usually  takes 
place  from  haemorrhage,  on  account  of  the  fact  that  the  hepatic  veins  are  contained  in  rigid 
canals  in  the  liver-substance  and  are  unable  to  contract,  and  are  moreover  unprovided  with 
valves.  The  liver  may  also  be  torn  by  the  end  of  a  broken  rib  perforating  the  Diaphragm. 
The  liver  may  be  injured  by  stabs  or  other  punctured  wounds,  and  when  these  are  inflicted 
through  the  chest-wall  both  pleural  and  peritoneal  cavities  may  be  opened  up  and  both  lung  and 
liver  be  wounded.  In  cases  of  wound  of  the  liver  from  the  front,  hernia  of  a  part  of  this  viscus 
may  take  place,  but  can  generally  easily  be  replaced.  In  cases  of  laceration  of  the  liver,  when 
there  is  evidence  that  bleeding  is  going  on,  the  abdomen  must  be  opened,  the  laceration  sought 
for,  and  the  bleeding  arrested.  This  may  be  done  temporarily  by  introducing  the  forefinger 
into  the  foramen  of  Winslow  and  placing  the  thumb  on  the  gastro-hepatic  omentum  and  com- 
pressing the  hepatic  artery  and  portal  vein  between  the  two.  Any  bleeding  points  can  then  be 
seen  and  tied  and  the  margins  of  the  laceration,  if  small,  brought  together  and  sutured  by 
means  of  a  blunt  curved  needle  passed  from  one  side  of  the  wound  to  the  other.  All  sutures 
must  be  passed  before  any  are  tied,  and  this  must  be  done  with  the  greatest  gentleness,  as  the 
liver  substance  is  very  friable.  When  the  laceration  is  extensive  it  must  be  packed  with  iodoform 
gauze,  the  end  of  which  is  allowed  to  hang  out  of  the  external  wound.  Abscess  of  the  liver 
is  of  not  infrequent  occurrence,  and  may  open  in  many  different  ways  on  account  of  the  relations 
of  this  viscus  to  other  organs.  Thus  it  has  been  known  to  burst  into  the  lungs  and  the  pus 
coughed  up,  or  into  the  stomach  and  the  pus  vomited  ;  it  may  burst  into  the  colon,  or  into  the 
duodenum ;  or,  by  perforating  the  diaphragm,  it  may  empty  itself  into  the  pleural  cavity. 
Frequently  it  makes  its  way  forward,  and  points  on  the  anterior  abdominal  wall,  and  finally  it 
may  burst  into  the  peritoneal  or  pericardiac  cavities.  Abscesses  of  the  liver  frequently  require 
opening,  and  this  must  be  done  by  an  incision  in  the  abdominal  wall,  in  the  thoracic  wall,  or  in 
the  lumbar  region,  according  to  the  direction  in  which  the  abscess  is  tracking.  The  incision 
through  the  abdominal  wall  is  to  be  preferred  when  possible.  The  abdominal  wall  is  incited 
over  the  swelling,  and  unless  the  peritoneum  is  adherent,  sponges  are  packed  all  around  the 
exposed  liver  surface  and  the  abscess  opened,  if  deeply  seated  preferably  by  the  thermo-cautery. 
Hydatid  cysts  are  more  often  found  in  the  liver  than  in  any  other  of  the  viscera.  The  reason 
of  this  is  not  far  to  seek.  The  embryo  of  the  egg  of  the  taenia  echinococcus  being  liberated 
in  the  stomach  by  the  disintegration  of  its  shell,  bores  its  way  through  the  gastric  walls  and 
usually  enters  a  blood-vessel,  and  is  carried  by  the  blood-stream  to  the  hepatic  capillaries,  where 
its  onward  course  is  arrested,  and  where  it  undergoes  development  into  the  fully  formed  hydatid. 
Tumors  of  the  liver  have  recently  been  subjected  to  surgical  treatment  by  removal  of  a  portion 
of  the  organ.  The  abdomen  is  opened  and  the  diseased  portion  of  liver  exposed  ;  the  circula- 
tion is  controlled  by  compressing  the  portal  vein  and  the  hepatic  artery  in  the  gastro-hepatic 
omentum  and  a  wedge-shaped  portion  of  liver  containing  the  tumor  removed ;  the  divided 
vessels  are  ligated  and  the  cut  surfaces  brought  together  and  sutured  in  the  manner  directed 
above. 

When  the  gall-hladder  or  one  of  its  main  ducts  is  ruptured,  which  may  occur  independently 
of  laceration  of  the  liver,  death  usually  occurs  from  peritonitis.  If  the  symptoms  have  led  to 
the  performance  of  a  laparotomy  and  a  rent  is  found,  it  should  be  sutured  if  small,  or  the  gall- 
bladder removed  if  it  is  extensive.  If  the  cystic  duct  is  torn,  its  intestinal  end  must  be  closed 
and  the  gall-bladder  removed.  In  rupture  of  either  of  the  other  ducts,  the  only  thing  which 
can  be  done  is  to  provide  for  free  drainage,  in  the  hope  that  a  biliary  fistula  may  form. 

The  gall-bladder  may  become  distended  with  bile  in  cases  of  obstruction  of  its  duct  or  the 
common  bile-duct,  or  from  a  collection  of  gall-stones  within  its  interior,  thus  forming  a  large 
tumor.  The  swelling  is  pear-shaped,  and  projects  downward  and  forward  to  the  umbilicus.  It 
moves  with  respiration,  since  it  is  attached  to  the  liver.  To  relieve  this  condition  the  gall-bladder 
must  be  opened  and  the  gall-stones  removed.  The  operation  is  performed  by  an  incision  two  or 
three  inches  long  in  the  right  semilunar  line,  commencing  at  the  costal  margin.  _  The  peritoneal 
cavity  is  opened,  and,  the  tumor  havinc  been  found,  sponges  are  packed  round  it  to  protect  the 
peritoneal  cavity,  and  it  is  aspirated.  When  the  contained  fluid  has  been  evacuated  the  flaccid 
bladder  is  drawn  out  of  the  abdominal  wound  and  its  wall  incised  to  the  extent  of  an  inch ;  any 
gall-stones  in  the  bladder  are  now  removed  and  the  interior  of  the  sac  sponged  dry.  If  the  case 
is  one  of  obstruction  of  the  duct,  an  attempt  must  be  made  to  dislodge  the  stone  by  manipulation 
through  the  wall  of  the  duct ;  or  it  may  be  crushed  from  without  by  the  fingers  or  carefully 


THE  PANCJIEAS. 


945 


padded  forceps.  If  this  does  not  succeed,  the  safest  plan  is  to  incise  the  duct,  extract  the  stone, 
and  close  the  incision  by  fine  sutures  in  two  layers.  After  all  obstruction  has  been  removed, 
four  courses  are  open  to  the  surgeon :  1.  The  wound  in  the  gall-bladder  may  be  at  once  sewn 
up,  the  organ  returned  into  the  abdominal  cavity,  and  the  external  incision  closed.  2.  The 
edges  of  the  incision  in  the  gall-bladder  may  be  sutured  to  the  external  wound,  and  a  fistulous 
communication  established  between  the  gall-bladder  and  the  exterior ;  this  fistulous  opening 
usually  closes  in  the  course  of  a  few  weeks.  3.  The  gall-bladder  may  be  connected  with  the 
intestinal  canal,  preferably  the  duodenum,  by  means  of  a  lateral  anastomosis ;  this  is  known  as 
cholecystenterostomy.     4.  The  gall-bladder  may  be  completely  removed. 

THE  PANCREAS. 

Dissection. — The  pancreas  maybe  exposed  for  dissection  in  three  different  ways :  1.  By 
raising  the  liver,  drawing  down  the  stomach,  and  tearing  through  the  gastro-hepatic  omentum 
and  the  ascending  layer  of  the  transverse  mesocolon.  2.  By  raising  the  stomach,  the  arch  of 
the  colon,  and  great  omentum,  and  then  dividing  the  inferior  layer  of  the  transverse  mesocolon 
and  raising  its  ascending  layer.  3.  By  dividing  the  two  layers  of  peritoneum,  which  descend 
from  the  great  curvature  of  the  stomach  to  form  the  great  omentum ;  turning  the  stomach 
upward,  and  then  cutting  through  the  ascending  layer  of  the  transverse  mesocolon  (see  Fig.  488, 
page  900). 

The  Pancreas  (itav-xpeas,  all  flesh)  is  a  compound  racemose  gland,  analogous  in 
its  structure  to  the  salivary  glands,  though  softer  and  less  compactly  arranged  than 
those  organs.  It  is  long  and  irregularly  prismatic  in  shape,  and  has  been  compared 
to  a  human  or  a  dog's  tongue  :  its  right  extremity  being  broad,  is  called  the  head — 
this  is  connected  to  the  main  portion  of  the  organ,  the  body,  by  a  slight  constriction, 
the  neck  ;  while  its  left  extremity  gradually  tapers  to  form  the  tail.     It  is  situated 


Fig.  519.— The  pancreas  and  its  relations. 

transversely  across  the  posterior  wall  of  the  abdomen   at  the  back  of  the  epigastric 
and  left   hypochondriac  regions.      Its  length    "   LneniS\im   fiv    ^'r?'^^ 
breadth  is  an  inch  and  a  half,  and  its  thick?  Jreas'  callepd  *«  P""*^  d»ct  or  ™™ l 
greater  at  its  right  extremity  and  along  inversely  from  left  to  right  through  the 
two  to  three  and  a  half  ounces,  but  it  m"0^8 V*'  the  superficial  portion  of  the 
The  right  extremity  or  head  of  the  ^es  b*v  th/  '    l,of  th^ma11  ducts  of  the 

of  a  hammer,  being  elongated  both  a^eas'  and'  [unn,n8  fro™  riSht  to  left  thl-°ufh 
backward,  and  conforms  to  the  whole  <  ducts  of  the  US  lobules  comPosing  the 

overlapped   by  it.      The  anterior   sund  Physiolgy,  .  1,  p.  102. 

60 


946 


THE    ORGANS    OF  DIGESTION. 


superior  mesenteric  vessels,  and  at  its  lower  end  it  is  crossed  by  the  transverse 
colon  and  its  mesocolon.  Behind,  the  head  of  the  pancreas  is  in  relation  with 
the  inferior  vena  cava,  the  left  renal  vein,  the  right  cr us  of  the  Diaphragm,  and 
the  aorta.  The  common  bile-duct  descends  b©kuia,  between  the  duodenum  and 
pancreas ;  and  the  pancreatico-duodenal  artery  descends  in  front  between  the 
same  parts. 

The  neck  of  the  pancreas  is  about  an  inch  long,  and  passes  upward  and  forward 
to  the  left,  having  the  first  part  of  the  duodenum  above  it,  and  the  termination  of 
the  fourth  portion  below.  It  lies  in  front  of  the  commencement  of  the  vena  portse, 
and  is  grooved  on  the  right  by  the  gastro-duodenal  and  superior  pancreatico-duodenal 
arteries.     The  pylorus  lies  just  above  it. 

The  body  and  tail  of  the  pancreas  are  somewhat  prismatic  in  shape,  and  have 
three  surfaces  :  anterior,  posterior,  and  inferior. 

The  anterior  surface  is  somewhat  concave,  and  is  covered  by  the  posterior 
surface  of  the  stomach  which  rests  upon  it,  the  two  organs  being  separated  by  the 
lesser  sac  of  the  peritoneum.  At  its  right  extremity  there  is  a  well-marked  promi- 
nence, called  by  His  the  omental  tuberosity. 


Gastric  artery 


Lower  end  of  oesophagus. 


Inferior  mesenteric 
artery. 


Superior  mesenteric 
artery. 


\  Spermatic  vessels 


Fig.  520.— The  duodenum  and  pancreas.  The  liver  has  been  lifted  up  and  the  greater  part  of  the  stomach 
removed.  (Testut.)  a:  Portal  vein  ;  b,  Hepatic  ducti;  c,  Cystic  duct ;  d,  Hepatic  artery  ;  e,  Right  suprarenal 
capsule  ;  /,  Pyloric  orifice ;  g,  Right  gastro-epiploic  artery ;  h,  Superior  mesenteric  vein  ;  i,  Left  crus  of  dia- 
phragm ;  j,  Left  suprarenal  capsult ;  fc,  Splenic  vein;  I,  Splenic  artery ;  m,  Duodenojejunal  junction  ;  A,  B,  C,  d, 
The  f<~  -,,.,.  portions  of  the  duodenum.    ,iUll 

tumor.     The  swelling  is  p.  .ped,  and  pi 

moves  with  respiration,  since  it  is  attached  to  ti.  from  the  vertebral  column  by  the  aorta,  the 

a^etllX^t^S:ZZi  Jljfr  *?  kft  s«F-nal  capsule,  the  pillars 

cavity  is  opened,  and,  the  tumor  havinc  been  founduPenor  mesenteric  artery. 

peritoneal  cavity,  and  it  is  aspirated.     When  the  cos  upon  the  duodeno-jejunal  flexure  and 

bladder  is  drawn  out  of  the  abdominal  wound  and  its.mity  rests  on  the  splenic  flexure  of  the 

gall-stones  in  the  bladder  are  now  removed  and  the  in 

is  one  of  obstruction  of  the  duct,  an  attempt  must  be  1      ,  n  ,       .   ,  ,    , 

through  the  wall  of  the  duct;  or  it  may  be  crushed  ind  flat  to  tne  nght  '>   narrow  and  sharp 


THE   PANCREAS. 


947 


to  the  left,  near  the  tail.  It  commences  to  the  right  in  the  omental  tuberosity,  and 
is  in  relation  with  the  cceliac  axis,  from  which  the  hepatic  artery  courses  to  the 
right  just  above  the  gland,  -while  the  splenic  branch  runs  in  a  groove  along  this 
border  to  the  left. 

The  anterior  border  is  the  position  where  the  two  layers  of  the  transverse  meso- 
colon separate :  the  one  passing  upward  in  front  of  the  anterior  surface,  the  other 
backward  below  the  inferior  surface. 

The  lesser  end  or  tail  of  the  pancreas  is  narrow  ;  it  extends  to  the  lett  as  far  as 
the  lower  part  of  the  inner  aspect  of  the  spleen. 

Birmingham  describes  the  body  of  the  pancreas  as  projecting  forward  as  a  promi- 
nent ridge  into  the  abdominal  cavity  and  forming  a  sort  of  shelf  on  which  the 
stomach  lies.  He  says  :  "  The  portion  of  the  pancreas  to  the  left  of  the  middle  line 
has  a  very  considerable  antero-posterior  thickness ;  as  a  result  the  anterior  surface 
is  of  considerable  extent,  it  looks  strongly  upward,  and  forms  a  large  and  important 
part  of  the  shelf.  As  the  pancreas  extends  to  the  left  toward  the  spleen  it  crosses 
the  upper  part  of  the  kidney,  and  is  so  moulded  on  to  it  that  the  top  of  the  kidney 
forms  an  extension  inward  and  backward  of  the  upper  surface  of  the  pancreas  and 
extends  the  bed  in  this  direction.     On  the  other  hand,  the  extremity  of  the  pan- 


HECTUS    MUSCLE 

A 


8th  Costal  Cartilage. 

7th  Costal  Cartilage. 


7th  Rib. 


■8th  Bib. 


i-4~- 9th  Rib. 


-10th  Rib. 


Abdominal  Aorta. 


12th  Rib.    nth  Rib. 


Fig.  521. — Transverse  section  through  the  middle  of  the  first  lumbar  vertebra,  showing  the  relations  of  the 
pancreas.    (Braune.) 


creas  comes  in  contact  with  the  spleen  in  such  a  way  that  the  plane  of  its  upper 
surface  runs  with  little  interruption  upward  and  backward  into  the  concave  gastric 
surface  of  the  spleen,  which  completes  the  bed  behind  and  to  the  left,  and  running 
upward,  forms  a  partial  cap  for  the  wide  end  of  the  stomach  "  1  (see  Fig.  496). 

The  principal  excretory  duct  of  the  pancreas,  called  the  pancreatic  duct  or  canal 
of  Wirsung,  from  its  discoverer,  extends  transversely  from  left  to  right  through  the 
substance  of  the  pancreas.  In  order  to  expose  it,  the  superficial  portion  of  the 
gland  must  be  removed.     It  commences  by  tli     '  i  of  the  small  ducts  of  the 

lobules  situated  in  the  tail  of  the  pancreas,  and,  running  from  right  to  left  through 
the  body,  it  constantly  receives  the  ducts  of  the    rarious  lobules  composing  the 


1  Journal  of  Anatomy  and  Physiolgy, 


1,  p.  102. 


948  THE    ORGANS    OF  DIGESTION. 

gland.  Considerably  augmented  in  size,  it  reaches  the  neck,  and  turning  obliquely 
downward,  backward",  and  to  the  right,  it  comes  into  relation  with  the  common  bile- 
duct,  lying  to  its  left  side ;  leaving  the  head  of  the  gland,  it  passes  very  obliquely 
through  the  mucous  and  muscular  coats  of  the  duodenum,  and  terminates  by  an  orifice 
common  to  it  and  the  ductus  communis  choledochus  upon  the  summit  of  an  elevated 
papilla,  situated  at  the  inner  side  of  the  descending  portion  of  the  duodenum,  three 
or  four  inches  below  the  pylorus. 

Sometimes  the  pancreatic  duct  and  ductus  communis  choledochus  open  separately 
into  the  duodenum.  Occasionally  there  is  an  accessory  duct,  which  is  given  off 
from  the  canal  of  Wirsung  in  the  neck  of  the  pancreas  and  passes  horizontally  to 
the  rio-ht  to  open  into  the  duodenum  about  an  inch  above  the  orifice  of  the  main 
duct.     This  is  known  as  the  ductus  pancreaticus  accessonus  or  ductus  bantorim. 

The  pancreatic  duct,  near  the  duodenum,  is  about  the  size  of  an  ordinary  quill : 
its  walls  are  thin,  consisting  of  two  coats,  an  external  fibrous  and  an  internal  mucous  ; 
the  latter  is  smooth,  and  furnished  near  its  termination  with  a  few  scattered  follicles. 

In  structure,  the  pancreas  resembles  the  salivary  glands.  It  differs  from  them, 
however,  in  certain  particulars,  and  is  looser  and  softer  in  its  texture.  It  is  not 
enclosed  in  a  distinct  capsule,  but  is  surrounded  by  areolar  tissue,  which  dips  into 
its  interior,  and  connects  together  the  various  lobules  of  which  it  is  composed.  Each 
lobule,  like  the  lobules  of  the  salivary  glands,  consists  of  one  of  the  ultimate  rami- 
fications of  the  main  duct,  terminating  in  a  number  of  csecal  pouches  or  alveoli, 
which  are  tubular  and  somewhat  convoluted.  The  minute  ducts  connected  with  the 
alveoli  are  narrow  and  lined  with  flattened  cells.  The  alveoli  are  almost  completely 
filled  with  secreting  cells,  so  that  scarcely  any  lumen  is  visible.  In  some  animals 
those  cells  which  occupy  the  centre  of  the  alveolus  are  spindle-shaped,  and  are 
known  as  the  centro-acinar  cells  of  Langerhans.  The  true  secreting  cells  which 
line  the  wall  of  the  alveolus  are  very  characteristic.  They  are  columnar  in  shape 
and  present  two  zones :  an  outer  one  clear  and  finely  striated  next  the  basement- 
membrane,  and  an  inner  granular  one  next  the  lumen.  During  activity  the  granular 
zone  occupies  the  greater  part  of  the  cell :  before  the  cells  are  called  into  action, 
while  in  a  condition  of  rest,  the  outer  or  clear  zone  is  the  larger.  In  some  secret- 
ing cells  of  the  pancreas  is  a  spherical  mass,  staining  more  easily  than  the  rest  of 
the  cells;  this  is  termed  the  paranucleus,  and  is  believed  to  be  an  extension  from 
the  nucleus.  The  connective  tissue  between  the  alveoli  presents  in  certain  parts 
collections  of  cells,  which  are  termed  inter -alveolar  cell-islets. 

Vessels  and  Nerves. — The  arteries  of  the  pancreas  are  derived  from  the  splenic 
and  the  pancreatico-duodenal  branches  of  the  hepatic  and  the  superior  mesenteric. 
Its  veins  open  into  the  splenic  and  superior  mesenteric  veins.  Its  lymphatics  termi- 
nate in  the  lumbar  glands.     Its  nerves  are  filaments  from  the  splenic  plexus. 

Surface  Form. — The  pancreas  lies  in  front  of  the  second  lumbar  vertebra,  and  can  some- 
times be  felt,  in  emaciated  subjects,  when  the  stomach  and  colon  are  empty,  by  making  deep 
pressure  in  the  middle  line  about  three  inches  above  the  umbilicus. 

Surgical  Anatomy. — The  pancreas  presents  but  little  of  surgical  importance.  It  is  occa- 
sionally the  seat  of  cancer,  which  usually  affects  the  head  or  duodenal  end,  and  therefore  often 
speedily  involves  the  common  bile-duct,  leading  to  persistent  jaundice.  Cysts  are  also  occasion- 
ally found  in  it,  which  may  present  in  the  epigastric  region,  above  and  to  the  right  of  the  umbil- 
icus, and  may  require  opening  and  drainage.  The  fluid  in  them  contains  some  of  the  elements 
of  the  pancreatic  secretion  and  is  very  irritating,  so  that,  if  allowed  to  come  in  contact  with  the 
skin  of  the  abdominal  wall,  it  is  likely  to  produce  intractable  eczema.  It  has  been  said  that  the 
pancreas  is  the  only  abdominal  viscus  which  has  never  been  found  in  a  hernial  protrusion  ;  but 
even  this  organ  has  been  found,  in  company  with  other  viscera,  in  rare  cases  of  diaphragmatic 
hernia.  The  pancreas  has  been  known  to  become  invaginated  into  the  intestine,  and  portions 
of  the  organ  have  sloughed  off.  In  cases  of  excision  of  the  pylorus  great  care  must  be  exer- 
cised to_  avoid  wounding  the  pancreas,  as  the  escape  of  the  pancreatic  fluid  may  be  attended 
with  serious  results.  .  According  to  Billroth,  it  is  likely,  in  consequence  of  its  peptonizing  quali- 
ties, to  dissolve  the  cicatrix  of  the  stomach. 


THE   SPLEEN. 


THE  SPLEEN. 


949 


\j 


The  Spleen  belongs  to  that  class  of  bodies  which  are  known  as  ductless  glands. 
It  is  probably  related  to  the  blood-vascular  system,  but  in  consequence  of  its 
anatomical  relationship  to  the  stomach  and  its  physiological  relationship  to  the 
liver  it  is  convenient  to  describe  it  in  this  place.  It  is  situated  principally  in  the 
left  hypochondriac  region,  its  upper  and  inner  extremity  extending  into  the  epigas- 
tric region  ;  lying  between  the  fundus  of  the  stomach  and  the  Diaphragm.  It  is 
the  largest  of  the  ductless  glands,  and  measures  some  five  or  six  inches  in  length. 
It  is  of  an  oblong,  flattened  form,  soft,  of  very  brittle  consistence,  highly  vascular, 
and  of  a  dark  purplish  color. 

Surfaces. — The  external  or  phrenic  surface  is  convex,  smooth,  and  is  directed 
upward,  backward,  and  to  the  left,  except  at  its  upper  end,  where  it  is  directed 
slightly  inward.  It  is  in  relation  with  the  under  surface  of  the  Diaphragm,  which 
separates  it  from  the  eighth,  ninth,  tenth, 
and  eleventh  ribs  of  the  left  side,  and  in 
part  from  the  lower  border  of  the  left  lung 
and  pleura. 

The  internal  surface  is  concave,  and 
divided  by  a  ridge  into  an  anterior  or 
larger,  and  a  posterior  or  smaller  portion. 

The  anterior  portion  of  the  internal 
surface  or  gastric  surface,  which  is  directed 
forward  and  inward,  is  broad  and  concave, 
and  is  in  contact  with  the  posterior  wall 
of  the  great  end  of  the  stomach ;  and 
below  this  with  the  tail  of  the  pancreas. 
It  presents  near  its  inner  border  a  long 
fissure,  termed  the  hilum.  This  is  pierced 
by  several  irregular  •  apertures,  for  the 
entrance  and  exit  of  vessels  and  nerves. 

The  posterior  portion  of  the  internal 
surface  or  renal  surface  is  directed  inward 
and  downward.  It  is  somewhat  flattened, 
does  not  reach  as  high  as  the  gastric  sur- 
face, is  considerably  narrower  than  the 
latter,  and  is  in  relation  with  the  upper 
part  of  the  outer  surface  of  the  left  kidney 
and  occasionally  with  the  left  suprarenal 
capsule. 

The  upper  end  is  directed  inward,  toward  the  vertebral  column,  where  it  lies 
on  a  level  with  the  eleventh  dorsal  vertebra.  The  lower  end,  sometimes  termed 
the  basal  surface,  is  flat,  triangular  in  shape,  and  rests  upon  the  splenic  flexure  of 
the  colon  and  the  phreno-colic  ligament,  and  is  generally  in  contact  with  the  tail 
of  the  pancreas.  The  anterior  border  is  free,  sharp,  and  thin,  and  is  often  notched, 
especially  below.  It  separates  the  phrenic  from  the  gastric  surface.  "The  posterior 
border  is  more  rounded  and  blunter  than  the  anterior.  It  separates  the  renal  por- 
tion of  the  internal  surface  from  the  phrenic  surface.  It  corresponds  to  the  lower 
border  of  the  eleventh  rib  and  lies  between  the  Diaphragm  and  left  kidney.  The 
internal  border  is  the  name  sometimes  given  to  the  ridge  which  separates  the  renal 
and  gastric  portions  of  the  internal  surface. 

The  spleen  is  almost  entirely  surrounded  by  peritoneum,  which  is  firmly  adher- 
ent to  :  capsule,  and  is  held  in  position  by  two  folds  of  this  membrane  :  one. 
the  li<  ■'■    ligament,  is  derived  from  the  layers  of  peritoneum  forming  the 

great*  er  sacs,  where  they  come  into  contact  between  the  left  kidney  and 

the  s       :in.    Between  its  two  layers  the  splenic  vessels  pass  (Fig.  489);  the  second, 
the  p  enic  omentum,  also  formed  of  two  layers,  derived  from  the  greater 


Fig.  522.— The  spleen,  showing 
renal  surfaces.     (Testut.) 


its  gastric  and 


950 


THE    ORGANS    OF  DIGESTION. 


and  lesser  sacs,  respectively,  where  they  meet  between  the  spleen  and  stomach 
(Fig.  489).  Between  these  two  layers  'run  the  vasa  brevia  of  the  splenic  artery 
and  vein.  It  is  also  supported  by  the  phreno-colic  ligament,  upon  which  its  lower 
end  rests  (see  page  902). 

The  size  and  Aveight  of  the  spleen  are  liable  to  very  extreme  variations  at  dif- 
ferent periods  of  life,  in  different  individuals,  and  in  the  same  individual  under 
different  conditions.  In  the  adult,  in  whom  it  attains  its  greatest  size,  it  is  usually 
about  five  inches  in  length,  three  inches  in  breadth,  and  an  inch  or  an  inch  and  a 
half  in  thickness,  and  weighs  about  seven  ounces.  At  birth,  its  weight,  in  propor- 
tion to  the  entire  body,  is  almost  equal  to  what  is  observed  in  the  adult,  being  as 
1  to  350 :  while  in  the  adult  it  varies  from  1  to  320  and  400.  In  old  age,  the 
organ  not  only  decreases  in  weight,  but  decreases  considerably  in  proportion  to 
the  entire  body,  being  as  1  to  700.    The  size  of  the  spleen"  is  increased  during  and 


Fig.  523.— Transverse  section  of  the  spleen,  showing  the  trabecular  tissue  and  the  splenic  vein  and  its  trib- 
utaries. 

after  digestion,  and  varies  considerably  according  to  the  state  of  nutrition  of  the 
body,  being  large  in  highly  fed,  and  small  in  starved  animals.  In  intermittent 
and  other  fevers  it  becomes  much  enlarged,  weighing  occasionally  from  18  to  20 
pounds. 

Frequently  in  the  neighborhood  of  the  spleen,  and  especially  in  the  gastro- 
splenic  and  great  omenta,  small  nodules  of  splenic  tissue  may  be  found,  either 
isolated  or  connected  to  the  spleen  by  thin  bands  of  splenic  tissue.  They  are 
known  as  supernumerary  or  accessory  spleens.  They  vary  in  size  from  that  of  a 
pea  to  that  of  a  plum. 

Structure. — The  spleen  is  invested  by  two  coats — an  external  serous,  and  an 
internal  fibro-elastic   coat. 

The  external  or  serous  coat  is  derived  from  the  peritoneum ;  it  is  thin,  smooth, 
and  in  the  human  subject  intimately  adherent  to  the  fibro-elastic  coat.  It  invests 
the  entire  organ,  except  at  the  places  of  its  reflection  on  to  the  stomach  and 
Diaphragm  and  at  the  hilum. 

The  fibro-elastic  coat  forms  the  framework  of  the  spleen.  It  invests  the  organ, 
and  at  the  hilum  is  reflected  inward  upon  the  vessels  in  the  form  of  sheaths. 
From  these  sheaths,  as  well  as  from  the  inner  surface  of  the  fibro-elastic  coat, 
numerous  small  fibrous  bands,  trabecular  (Fig.  524),  are  given  off  in  all  directions ; 
these  uniting,  constitute  the  framework  of  the  spleen.  This  resembles  a  sponge- 
like material,  consisting  of  a  number  of  small  spaces  or  areolce  formed  by  the  tra- 
beculse,  which  are  given  off  from  the  inner   surface  of  the  capsule,  or  from  the 


THE   SPLEEN. 


951 


sheaths  prolonged  inward  on  the  blood-vessels.     In  these  spaces  or  areolae  is  con- 
tained the  splenic  pulp. 

The  proper  coat,  the  sheaths  of  the  vessels  and  the  trabeculee,  consist  of  a, 
dense  mesh  of  white  and  yellow  elastic  fibrous  tissues,  the  latter  considerably  pre- 
dominating. It  is  owing  to  the  presence  of  this  tissue  that  the  spleen  possesses 
a  considerable  amount  of  elasticity,  which  allows  of  the  very  great  variations  in 
size  that  it  presents  under  certain  circumstances.  In  addition  to  these  con- 
stituents of  this  tunic,  there  is  found  in  man  a  small  amount  of  non-striped  muscu- 
lar fibre,  and  in  some  mammalia  (e.  g.  dog,  pig,  and  cat)  a  very  considerable 
amount,  so  that  the  trabecules  appear  to  consist  chiefly  of  muscular  tissue.  It  is 
probably  owing  to  this  structure  that  the  spleen  exhibits,  when  acted  upon  b}-  tL*.  \ 
galvanic  current,  faint  traces  of  contractility. 

The  proper  substance  of  the  spleen  or  spleen-pulp  is  a  soft  mass  of  a  dark 
reddish-brown  color,  resembling  grumous  blood.  When  examined,  by  means  of  a 
thin  section,  under  a  microscope,  it  is  found  to  consist  of  a  number  of  branching 
cells  and  an  intercellular  substance.  The  cells  are  connective-tissue  corpuscles, 
and  have  been  named  the  sustentacular  or  supporting  cells  of  the  pulp.  The 
processes  of  these  branching  cells  communicate  with  each  other,  thus  forming  a 
delicate  reticulated  tissue  in  the  interior  of  theareolae  formed  by  the  trabecule  of 
the  capsule ;  so  that  each  primary  space  may  be  considered  to  be  divided  into  a 
number  of  smaller  spaces  by  the  junction  of  these  processes  of  the  branching 
corpuscles.  These  secondary  spaces  contain  blood,  in  which,  however,  the  white 
corpuscles  are  found  to  be  in  larger  proportions  than  they  are  in  ordinary  blood. 
The  sustentacular  cells  are  either  small  uni-nucleated  or  larger  multi-nucleated 
cells ;  they  do  not  become  deeply  stained  with  carmine,  like  the  cells  of  the 
Malpighian  bodies,  presently  to  be  described  (W.  Miiller),  but  like  them  they  pos- 
sess amoeboid  movements  (Cohnheim).      In  manv  of  them  may  be  seen  deep  red 


Fig.  524— Transverse  section  of  the  human  spleen,  showing  the  distribution  of  the  splenic  artery  and  its 
branches. 

or  reddish-yellow  granules  of  various  sizes  which  present  the  characters  of  the 
haematin  of  the  blood.  Sometimes,  also,  unchanged  blood-disks  are  seen  included 
in  these  cells,  but  more  frequently  blood-disks  are  found  which  are  altered  both 
in  form  and  color.  In  fact,  blood-corpuscles  in  all  stages  of  disintegration  may 
be  noticed  to  occur  within  them.  Klein  has  recently  pointed  out  that  some- 
times these  cells  in  the  young  spleen  contain  a  proliferating  nucleus ;  that  is  to 
say,  the  nucleus  is  of  large  size,  and  presents  a  number  of  knob-like  projections, 
as  if  small  nuclei  were  budding  from  it  by  a  process  of  gemmation.  This  observa- 
tion is  of  importance,  as  it  may  explain  one  possible  source  of  the  colorless  blood- 
corpuscles. 

The  interspaces  or  areolae  formed  by  the  framework  of  the  spleen  are  thus  filled 


952 


THE    ORGANS    OF  DIGESTION. 


by  a  delicate  reticulum  of  branched  connective-tissue  corpuscles  the  interstices  of 
which  are  occupied  by  blood,  and  in  which  the  blood-vessels  terminate  in  the 
manner  now  to  be  described. 

Blood-vessels  of  the  Spleen. — The  splenic  artery  is  remarkable  for  its  large 
size  in  proportion  to  the  size  of  the  organ,  and  also  for  its  tortuous  course. 
It  divides  into  six  or  more  branches,  Avhich  enter  the  hilum  of  the  spleen  and 
ramify  throughout  its  substance  (Fig.  524),  receiving  sheaths  from  the  involution 
of  the  external  fibrous  tissue.      Similar  sheaths  also  invest  the  nerves  and  veins. 

Each  branch  runs  in  the  transverse  axis  of  the  organ  from  within  outward, 
diminishing  in  size  during  its  transit,  and  giving  off  in  its  passage  smaller 
n  .riches,  some  of  which  pass  to  the  anterior,  others  to  the  posterior  part.  These 
ultimately  leave  the  trabecular  sheaths,  and  terminate  in  the  proper  substance  of 
the  spleen  in  small  tufts  or  pencils  of  minute  arterioles,  which  open  into  the 
interstices  of  the  reticulum  formed  by  the  branched  sustentacular  cells.  Each  of 
the  larger  branches  of  the  artery  supplies  chiefly  that  region  of  the  organ  in 
which  the  branch  ramifies,  having  no  anastomosis  with  the  majority  of  the  other 
branches. 

The  arterioles,  supported  by  the  minute  trabecule,  traverse  the  pulp  in 
all  directions  in  bundles  or  penicilli  of  straight  vessels.  Their  external  coat,  on 
leaving  the  trabecular  sheaths,  consists  of  ordinary  connective  tissue,  but  it  gradu- 
ally undergoes  a  transformation,  becomes  much  thickened,  and  is  converted  into 
a  lymphoid  material.1  This  change  is  effected  by  the  conversion  of  the  con- 
nective tissue  into  a  lymphoid  tissue,  the  bundles  of  connective  tissue  becoming 
looser  and  laxer,  their  fibrils  more  delicate,  and  containing  in  their  interstices 
an  abundance  of  lymph-corpuscles  (W.  Miiller).  This  lymphoid  material  is 
supplied  with  blood  by  minute  vessels  derived  from  the  artery  with  which  they 
are  in  contact,  and  which  terminates  by  breaking  up  into  a  network  of  capillary 
vessels. 

The  altered  coat  of  the  arterioles,  consisting  of  lymphoid  tissue,  presents  here 
and  there  thickenings  of  a  spheroidal  shape,  the  Malpighian  bodies  of  the  spleen. 
These  bodies  vary  in  size  from  about  the  tJ-q-  of  an  inch  to  the  -^g-  of  an  inch  in 
diameter.  They  are  merely  local  expansions  or  hyperplasias  of  the  lymphoid 
tissue  of  which  the  external  coat  of  the  smaller  arteries  of  the  spleen  is  formed. 
They  are  most  frequently  found  surrounding  the  arteriole,  which  thus  seems  to 

tunnel  them,  but  occasionally  they  grow  from 
one  side  of  the  vessel  only,  and  present  the 
appearance  of  a  sessile  bud  growing  from  the 
arterial  wall.  Klein,  however,  denies  this,  and 
says  it  is  incorrect  to  describe  the  Malpighian 
bodies  as  isolated  masses  of  adenoid  tissue,  but 
that  they  are  always  formed  around  an  artery, 
though  there  is  generally  a  greater  amount  on 
one  side  than  the  other,  and  that,  therefore,  in 
transverse  sections  the  artery  in  the  majority  of 
cases  is  found  in  an  eccentric  position.  These 
bodies  are  visible  to  the  naked  eye  on  the  surface 
of  a  fresh  section  of  the  organ,  appearing  as 
minute  dots  of  semi-opaque  whitish  color  in  the 
dark  substance  of  the  pulp.  In  minute  structure 
they  resemble  the  adenoid  tissue  of  lymphatic 
glands,  consisting  of  a  delicate  reticulum  in  the 
meshes  of  which  lie  ordinary  lymphoid  cells. 
The  reticulum  of  the  tissue  is  made  up  of  extremely  delicate  fibrils,  and  is 
comparatively  open  in  the  centre  of  the  corpuscle,  becoming  closer  at  the  periphery 

1  According  to  Klein,  it  is  the  sheath  of  the  small  vessel  which  undergoes  this  transformation, 
and  forms  a  "  solid  mass  of  adenoid  tissue  which  surrounds  the  vessel  like  a  cylindrical  sheath  "  (Atlas 
•if  Histology,  p.  424). 


Fig.  525.— Part  of  a  Malpighian  capsule 
of  the  spleen  of  man.  (Klein  and  Noble 
Smith.)  o,  Arterial  branch  in  longitudinal 
section.  6,  Adenoid  tissue,  still  containing 
the  lymph-corpuscles ;  only  their  nuclei 
are  shown,  c,  Adenoid  reticulum,  the 
lymph-corpuscles  accidentally  removed. 


the  spleen: 


953 


of  the  body.  The  cells  which  it  encloses,  like  the  supporting  cells  of  the  pulp,  are 
possessed  of  amoeboid  movements,  but  when  treated  with  carmine  become  deeply 
stained,  and  can  thus  easily  be  recognized  from  those  of  the  pulp. 

The  arterioles  terminate  in  capillaries,  which  traverse  the  pulp  in  all  directions  ; 


Supporting  cell. 


Vessel  undergoing  lymphoid  change. 


Small 
artery.' 


Vessel  continuous 
ivith  processes  of 
supporting  cells. 


Supporting  cell. 


Fig.  526. — Section  of  spleen,  showing  the  termination  of  the  small  blood-vessels. 

their  walls  become  much  attenuated,  lose  their  tubular  character,  and  the  cells  of" 
the  lymphoid  tissue  of  which  they  are  composed  become  altered,  presenting  a 
branched  appearance  and  acquiring  processes  which  are  directly  connected  with 
the  processes  of  the  sustentacular  cells  of  the  pulp  (Fig.  526).  In  this  manner  the 
capillary  vessels  terminate,  and  the  blood  flowing  through  them  finds  its  way  into 
the  interstices  of  the  reticulated  tissue  formed  by  the  branched  connective-tissue 
corpuscles  of  the  splenic  pulp.  Thus  the  blood  passing  through  the  spleen  is 
brought  into  intimate  relation  with  the  elements  of  the  pulp,  and  no  doubt  under- 
goes important  changes. 

After  these  changes  have  taken  place  the  blood  is  collected  from  the  interstices 
of  the  tissue  by  the  rootlets  of  the  veins,  which  commence  much  in  the  same  way 
as  the  arteries  terminate.  Where  a  vein  is  about  to  commence  the  connective- 
tissue  corpuscles  of  the  pulp  arrange  themselves  in  rows  in  such  a  way  as  to  form 
an  elongated  space  or  sinus.  They  become  changed  in  shape,  being  elongated 
and  spindle-shaped,  and  overlap  each  other  at  their  extremities.  They  thus  form 
a  sort  of  endothelial  lining  of  the  path  or  sinus,  which  is  the  radicle  of  a  vein. 
On  the  outer  surface  of  these  cells  arc  seen  delicate  transverse  lines  or  markings 
which  are  due  to  minute  elastic  fibrillae  arranged  in  a  circular  manner  around  the 
sinus.  Thus  the  channel  obtains  a  continuous  external  investment,  and  gradually 
becomes  converted  into  a  small  vein,  which  after  a  time  presents  a  coat  of 
ordinary  connective  tissue,  lined  by  a  layer  of  fusiform  epithelial  cells  which  are 
continuous  with  the  supporting  cells  of  the  pulp.  The  smaller  veins  unite  to  form 
larger  ones  which  do  not  accompany  the  arteries,  but  soon  enter  the  trabecular 
sheaths  of  the  capsule,  and  by  their  junction  form  from  six  or  more  branches  which 
emerge  from  the  hilum  and,  uniting,  form  the  splenic  vein,  the  largest  radicle  of 
the  vena  porta. 

The  veins  are  remarkable  for  their  numerous  anastomoses,  while  the  arteries 
hardly  anastomose  at  all. 

The  lymphatics  originate  in  two  ways, — i.  e.,  from  the  sheaths  of  the  arteries 
and  in  the  trabeculse.  The  former  accompany  the  blood-vessels,  the  latter  pass  to 
the  superficial  lymphatic  plexus,  which  may  be  seen  on  the  surface  of  the  organ. 
The  two  sets  communicate  in  the  interior  of  the  organ.  They  pass  through  the 
lymphatic  glands  at  the  hilum,  and  terminate  in  the  thoracic  duct. 


954  THE    ORGANS    OF   DIGESTION. 

The  nerves  are  derived  from  branches  of  the  right  and  left  semilunar  ganglia, 
and  from  the  right  pneumogastric  nerve. 

Surface  Form.— The  spleen  is  situated  under  cover  of  the  ribs  of  the  left  side,  being 
separated  from  them  by  the  Diaphragm,  and  above  by  a  small  portion  of  the  lower  margin  of 
the  left  lung  and  pleura.  Its  position  corresponds  to  the  eighth,  ninth,  tenth,  and  eleventh 
ribs.  It  is  placed  very  obliquely.  "It  is  oblique  in  two  directions,  viz. ,  from  above  downward 
and  outward,  and  also  from  above  downward  and  forward"  (Cunningham).  "Its  highest  and 
lowest  points  are  on  a  level  respectively  with  the  ninth  dorsal  and  first  lumbar  spines ;  its  inner 
end  is  distant  about  an  inch  and  a  half  from  the  median  plane  of  the  body,  and  its  outer  end 
about  reaches  the  midaxillary  line  "  (Quain). 

Surgical  Anatomy. — Injury  of  the  spleen  is  less  common  than  that  of  the  liver,  on  account 
of  its  protected  situation  and  connections.  It  may  be  ruptured  by  direct  or  indirect  violence, 
torn  by  a  broken  rib,  or  injured  by  a  punctured  or  gunshot  wound.  When  the  organ  is  enlarged 
the  chance  of  rupture  is  increased.  The  great  risk  is  haemorrhage,  owing  to  the  great  vascu- 
larity of  the  organ,  and  the  absence  of  a  proper  system  of  capillaries.  The  injury  is  not,  how- 
ever, necessarily  fatal,  and  this  would  appear  to  be  due  in  a  great  measure  to  the  contractile 
power  of  its  capsule,  which  narrows  the  wound  and  prevents  the  escape  of  blood.  In  cases 
where  the  diagnosis  is  clear  and  the  symptoms  indicate  danger  to  life  laparotomy  must  be  per- 
formed ;  and  if  the  hsernorrhage  cannot  be  stayed  by  ordinary  surgical  methods  the  spleen  must 
be  removed.  The  spleen  may  become  displaced,  producing  great  pain  from  stretching  of  the 
vessels  and  nerves,  and  this  may  require  removal  of  the  organ.  The  spleen  may  become  enor- 
mously enlarged  in  certain  diseased  conditions,  such  as  ague,  leukaemia,  syphilis,  valvular  dis- 
ease of  the  heart,  or  without  any  obtainable  history  of  previous  disease.  It  may  also  become 
enlarged  in  lymphadenoma  as  a  part  of  a  general  blood- disease.  In  these  cases  the  tumor  may 
fill  the  abdomen  and  extend  into  the  pelvis,  and  may  be  mistaken  for  ovarian  or  uterine  disease. 

The  spleen  is  sometimes  the  seat  of  cystic  tumors,  especially  hydatids,  and  of  abscess. 
These  cases  require  treatment  by  incision  and  drainage  ;  and  in  abscess  great  care  must  be  taken 
if  there  are  no  adhesions  between  the  spleen  and  abdominal  cavity,  to  prevent  the  escape  of  any 
of  the  pus  into  the  peritoneal  cavity.  If  possible,  the  operation  should  be  performed  in  two 
stages.  Sarcoma  and  carcinoma  are  occasionally  found  in  the  spleen,  but  very  rarely  as  a 
primary  disease. 

Extirpation  of  the  spleen  has  been  performed  for  wounds  or  injuries,  in  floating  spleen,  in 
simple  hypertrophy,  and  in  leukaemic  enlargement ;  but  in  these  latter  cases  the  operation  is 
now  regarded  as  unjustifiable,  as  every  case  in  which  it  has  been  performed  has  terminated 
fatally.  The  incision  is  best  made  in  the  left  semilunar  line  :  the  spleen  is  isolated  from  its  sur- 
roundings, and  the  pedicle  transfixed  and  ligatured  in  two  portions,  before  the  tumor  is  turned 
out  of  the  abdominal  cavity,  if  this  is  possible,  so  as  to  avoid  any  traction  on  the  pedicle,  which 
may  cause  tearing  of  the  splenic  vein.  In  applying  the  ligature  care  must  be  taken  not  to 
include  the  tail  of  the  pancreas,  and  in  lifting  out  the  organ  to  avoid  rupturing  the  capsule. 


THE  ORGANS  OF  VOICE  AND  RESPIRATION. 


THE    LARYNX. 


THE  Larynx  is  the  organ  of  voice,  placed  at  the  upper  part  of  the  air-passage. 
It  is  situated  between  the  trachea  and  base  of  the  tongue,  at  the  upper  and 
fore  part  of  the  neck,  where  it  forms  a  considerable  projection  in  the  middle  line. 
On  either  side  of  it  lie  the  great  vessels  of  the  neck  ;  behind,  it  forms  part  of  the 
boundary  of  the  pharynx,  and  is  covered  by  the  mucous  membrane  lining  that 
cavity.  Its  vertical  extent  corresponds  to  the  fourth,  fifth,  and  sixth  cervical 
vertebrae,  but  it  is  placed  somewhat  higher  in  the  female  and  also  during  childhood. 
In  infants  between  six  and  twelve  months  of  age  Symington  found  that  the  tip  of 
the  epiglottis  was  a  little  above  the  level  of  the  cartilage,  between  the  odontoid 
process  and  body  of  the  axis,  and  that  between  infancy  and  adult  life  the  larynx 
descends  for  a  distance  equal  to  two  vertebral  bodies  and  two  intervertebral  disks. 
According  to  Sappey,  the  average  measurements  of  the  adult  larynx  are  as  follows  : 


In  males. 

In  females. 

Vertical  diameter 

44  mm. 

36  mm. 

Transverse  diameter    . 

.     43    " 

41     " 

Antero-posterior  diameter    . 

.     36    " 

26     " 

Circumference 

.  136    " 

112     " 

Until  puberty  there  is  no  marked  difference  between  the  larynx  of  the  male 
and  that  of  the  female.  In  the  latter  its  further  increase  in  size  is  only  slight, 
whereas  in  the  former  it  is  great;  all  the  cartilages  are  enlarged,  and  the  thyroid 
becomes  prominent  as  the  pomum  Adami  in  the  middle  line  of  the  neck,  while 
the  length  of  the  glottis  is  nearly  doubled. 

The  larynx  is  broad  above,  where  it  presents  the  form  of  a  triangular  box, 
flattened  behind  and  at  the  sides,  and  bounded  in  front  by  a  prominent  vertical 
ridge.  Below,  it  is  narrow  and  cylindrical.  It  is  composed  of  cartilages,  which 
are  connected  together  by  ligaments  and  moved  by  numerous  muscles.  It  is  lined 
by  mucous  membrane,  which  is  continuous  above  with  that  lining  the  pharynx  and 
below  with  that  of  the  trachea. 

The  Cartilages  of  the  Larynx  are  nine  in  number,  three  single,  and  three 
pairs : 

Thyroid.  Two  Arytenoid. 

Cricoid.  Two  Cornicula  Laryngis. 

Epiglottis.  Two  Cuneiform. 

The  thyroid  (dupsoz,  a  shield)  is  the  largest  cartilage  of  the  larynx.  It  con- 
sists of  two  lateral  lamellae  or  alae,  united  at  an  acute  angle  in  front,  forming  a 
vertical  projection  in  the  middle  line  which  is  prominent  above,  and  called  the 
pomum  Adami.  This  projection  is  subcutaneous,  more  distinct  in  the  male 
than  in  the  female,  and  occasionally  separated  from  the  integument  by  a  bursa 
mucosa. 

Each  lamella  is  quadrilateral  in  form.  Its  outer  surface  presents  an  oblique 
ridge,  which  passes  downward  and  forward  from  a  tubercle,  situated  near  the  root 
of  the  superior  cornu,  to  a  small  tubercle  near  the  anterior  part  of  the  lower 
border.      This   ridge    gives   attachment  to   the   Sterno-thyroid    and    Thyro-hyoid 

955 


956 


THE    ORGANS    OF    VOICE   AND    RESPIRATION. 


muscles,  and  the  portion  of  cartilage  included  between  it  and  the  posterior  border 
to  part  of  the  Inferior  constrictor  muscle. 

The  inner  surface  of  each  ala  is  smooth,  slightly  concave,  and  covered  by 
mucous  membrane  above  and  behind  ;  but  in  front,  in  the  receding  angle  formed  by 
their  junction,  are  attached  the  epiglottis,  the  true  and  false  vocal  cords,  the  Thyro- 
arytenoid and  Thyro-epiglottidean  muscles,  and  the  thyro-epiglottidean  ligament. 

The  upper  border  of  the  thyroid  cartilage  is  sinuously  curved,  being  concave 
at  its  posterior  part,  just  in  front  of  the  superior  cornu,  then  rising  into  a  convex 
outline,  which   dips  in  front  to  form  the  sides  of  a  notch,  the  thyroid  notch,  in 

the  middle  line,  immediately  above  the  pomum 
Adami.  This  border  gives  attachment  through- 
out its  whole  extent  to  the  thyro-hyoid  mem- 
brane. 

The  lower  border  is  nearly  straight  in  front, 
but  behind,  close  to  the  cornu,  is  concave.  It 
is  connected  to  the  cricoid  cartilage,  in  and  near 
the  median  line,  by  the  middle  portion  of  the 
crico-thyroid  membrane  ;  and,  on  each  side,  by 
the  Crico-thyroid  muscle. 

The  'posterior  borders,  thick  and  rounded, 
terminate,  above,  in  the  superior  cornua,  and 
below,  in  the  inferior  cornua.  The  two  superior 
cornua  are  long  and  narrow,  directed  upward, 
backward,  and  inward,  and  terminate  in  conical 
extremities,  which  give  attachment  to  the  lateral 
thyro-hyoid  ligament.  The  two  inferior  cornua 
are  short  and  thick  ;  they  pass  downward,  with 
a  slight  inclination  forward  and  inward,  and 
present,  on  their  inner  surfaces,  a  small  oval 
articular  facet  for  articulation  with  the  side  of 
the  cricoid  cartilage.  The  posterior  border 
receives  the  insertion  of  the  Stylo-pharyngeus 
and  Palato-pharyngeus  muscles  on  each  side. 
.During  infancy  the  alse  of  the  thyroid  carti- 
lage are  joined  to  each  other  by  a  narrow,  lozenge-shaped  strip,  named  the  intra- 
thyroid  cartilage.  This  strip  extends  from  the  upper  to  the  lower  border  of  the 
cartilage  in  the  middle  line,  and  is  distinguished  from  the  alse  by  being  more 
transparent  and  more  flexible. 

The  cricoid  cartilage  is  so  called  from  its  resemblance  to  a  signet  ring 
(xgtxo^,  a  ring).  It  is  smaller,  but  thicker  and  stronger  than  the  thyroid  carti- 
lage, and  forms  the  lower  and  back  part  of  the  cavity  of  the  larynx.  It  consists 
of  two  parts :  a  quadrate  portion,  situated  behind,  and  a  narrow  ring  or  arch,  one- 
fourth  or  one-fifth  the  depth  of  the  posterior  part,  situated  in  front.  The  posterior 
square  portion  rapidly  narrows  at  the  sides  of  the  cartilage,  at  the  expense  of  the 
upper  border,  into  the  anterior  portion. 

Its  posterior  portion  is  very  deep  and  broad,  and  measures  from  above  down- 
ward about  an  inch  (2-3  cm.) ;  it  presents,  on  its  posterior  surface,  in  the 
middle  line,  a  vertical  ridge  for  the  attachment  of  the  longitudinal  fibres  of  the 
oesophagus  ;  and  on  either  side  a  broad  depression  for  the  Crico-arytenoideus 
posticus  muscle. 

Its  anterior  portion  is  narrow  and  convex,  and  measures  vertically  about  one- 
fourth  or  one-fifth  of  an  inch  (5-7  cm.);  it  affords  attachment  externally  in 
front  and  at  the  sides  to  the  Crico-thyroid  muscles,  and  behind,  to  part  of  the 
Inferior  constrictor. 

At  the  point  of  junction  of  the  posterior  quadrate  portion  with  the  rest  of  the 
cartilage  is  a  small  round  elevation,  for  articulation  with  the  inferior  cornu  of  the 
thyroid  cartilage.  •  ,        ' 


Fig.  527. — Side  view  of  the  thyroid  and 
cricoid  cartilages. 


THE   LARYNX. 


957 


Epiglottis. 


The  lower  border  of  the  cricoid  cartilage  is  horizontal,  and  connected  to  the 
upper  ring  of  the  trachea  by  fibrous  membrane. 

Its  upper  border  is  directed  obliquely  upward  and  backward,  owing  to  the 
great  depth  of  the  posterior  surface.  It  gives  attachment,  in  front,  to  the  middle 
portion  of  the  crico-thyroid  mem- 
brane ;  at  the  sides,  to  the  lateral 
portion  of  the  same  membrane  and 
to  the  lateral  Crico-arytenoid  mus- 
cle ;  behind,  it  presents,  in  the 
middle,  a  shallow  notch,  and  on 
each  side  of  this  is  a  smooth,  oval 
surface,  directed  upward  and  out- 
ward, for  articulation  with  the 
arytenoid  cartilage. 

The  inner  surface  of  the  cricoid 
cartilage  is  smooth,  and  lined  by 
mucous  membrane. 

The  arytenoid  cartilages  are 
so  called  from  the  resemblance  they 
bear,  when  approximated,  to  the 
mouth  of  a  pitcher  (dpuzacva,  a 
pitcher).  They  are  two  in  number, 
and  situated  at  the  upper  border 
of  the  cricoid  cartilage,  at  the  back 
of  the  larynx.  Each  cartilage  is 
pyramidal  in  form,  and  presents 
for  examination  three  surfaces,  a 
base,  and  an  apex. 

The  posterior  surface  is  tri- 
angular, smooth,  concave,  and 
gives  attachment  to  the  Arytenoid 
muscle. 

The  anterior  or  external  surface 
is  somewhat  convex  and  rough. 
It  presents  rather  below  its  centre 
a  transverse  ridge,  to  the  inner  ex- 
tremity of  which  is  attached  the 
false  vocal  cord,  and  to  the  outer 
part,  as  well  as  the  surfaces  above 
and  below,  is  attached  the  Thyro- 
arytenoid muscle. 

The  internal  surface  is  narrow, 
smooth,  and  flattened,  covered  by 
mucous  membrane,  and  forms  the 
lateral  boundary  of  the  respiratory  part  of  the  glottis. 

The  base  of  each  cartilage  is  broad,  and  presents  a  concave  smooth  surface, 
for  articulation  with  the  cricoid  cartilage.  Two  of  its  angles  require  special 
mention :  the  external,  which  is  short,  rounded,  and  prominent,  projects  back- 
ward and  outward,  and  is  termed  the  muscular  pi'ocess,  from  receiving  the 
insertion  of  the  Posterior  and  Lateral  crico-arytenoid  muscles.  The  anterior  angle, 
also  prominent,  but  more  pointed,  projects  horizontally  forward,  and  gives  attach- 
ment to  the  true  vocal  cord.     This  angle  is  called  the  vocal  process. 

The  apex  of  each  cartilage  is  pointed,  curved  backward  and  inward,  and  sur- 
mounted by  a  small  conical,  cartilaginous  nodule,  the  corniculum  laryngis. 

The  cornicula  laryngis  [cartilages  of  Santorvni)  are  two  small  conical  nodules, 
consisting  of  white  fibro-cartilage,  which  articulate  with  the  summit  of  the  aryte- 
noid cartilages  and  serve  to  prolong  them  backward  and  inward.      To  them  are 


Cornicula  laryngis. 

o 


Posterior 
surface. 


Thyroid 


Cuneiform  cartilage. 


Arytenoid. 


Insertion  of 

CRICO-ARYTENOIDEUS 
POSTICUS  ET  LATERALIS 


Cricoid. 

Articular  facet  for 
arytenoid  cartilage. 

Articular  facet  for 
inferior  coma,  of 
thyroid  cartilage. 


Fig.  528. — The  cartilages  of  the  larynx.    Posterior  view. 


Arytenoid  cartilages,  base. 


958  THE    ORGANS    OF    VOICE   AND    RESPIRATION. 

attached  the  aryteno-epiglottidean  folds.     They  are  sometimes  united  to  the  aryte- 
noid cartilages. 

The  cuneiform  cartilages  [cartilages  of  Wrisberg)  are  two  small,  elongated,  car- 
tilaginous bodies,  placed  one  on  each  side,  in  the  fold  of  mucous  membrane  which 
extends  from  the  apex  of  the  arytenoid  cartilage  to  the  side  of  the  epiglottis 
{aryteno-epiglottidean  fold) ;  they  give  rise  to  small  whitish  elevations  on  the  inner 
surface  of  the  mucous  membrane,  just  in  front  of  the  arytenoid  cartilages. 

The  epiglottis  is  a  thin  lamella  of  fibro-cartilage,  of  a  yellowish  color,  shaped 
like  a  leaf,  and  placed  behind  the  tongue  in  front  of  the  superior  opening  of  the 
larynx.  Its  free  extremity  is  broad  and  rounded  ;  its  attached  part  is  long,  nar- 
row, and  connected  to  the  receding  angle  between  the  two  alse  of  the  thyroid  car- 
tilage, just  below  the  median  notch,  by  a  long,  narrow  ligamentous  band,  the 
thyroepiglottic  ligament.  It  is  also  connected  to  the  posterior  surface  of  the  body 
of  the  hyoid  bone  by  an  elastic  ligamentous  band,  the  hyo-ep>iglottic  ligament. 

Its  anterior  or  lingual  surface  is  curved  forward,  toward  the  tongue,  and 
covered  at  its  upper,  free  part  by  mucous  membrane,  which  is  reflected  on  to  the 
sides  and  base  of  the  organ,  forming  a  median  and  two  lateral  folds,  the  glosso- 
epiglottidean  folds.  The  depressions  between  the  epiglottis  and  the  base  of  the 
tongue,  on  either  side  of  the  median  fold,  are  named  the  valleculas.  The  lower  part 
of  its  anterior  surface  lies  behind  the  hyoid  bone,  the  thyro-hyoid  membrane,  and 
upper  part  of  the  thyroid  cartilage,  but  is  separated  from  these  structures  by  a 
mass  of  fatty  tissue. 

Its  posterior  or  laryngeal  surface  is  smooth,  concave  from  side  to  side,  concavo- 
convex  from  above  downward;  its  lower  part  projects  backward  as  an  elevation, 
the  tubercle  or  cushion  ;  when  the  mucous  membrane  is  removed,  the  surface  of 
the  cartilage  is  seen  to  be  studded  with  a  number  of  small  mucous  glands,  which 
are  lodged  in  little  pits  upon  its  surface.  To  its  sides  the  aryteno-epiglottidean 
folds  are  attached. 

Structure. — The  cuneiform  cartilages,  the  epiglottis,  and  the  apices  of  the  aryte- 
noids are  composed  of  yellow  fibro-cartilage,  which  shows  little  tendency  to  cal- 
cification; on  the  other  hand,  the  thyroid,  cricoid,  and  the  greater  part  of  the 
arytenoids  consist  of  hyaline  cartilage,  and  become  more  or  less  ossified  as  age 
advances.  Ossification  commences  about  the  twenty-fifth  year  in  the  thyroid  car- 
tilage, somewhat  later  in  the  cricoid  and  arytenoids ;  by  the  sixty-fifth  year  these 
cartilages  may  be  completely  converted  into  bone.  The  cornicula  laryngis  consist 
of  white  fibro-cartilage,  which  becomes  Osseous  about  the  seventieth  year. 

Ligaments. — The  ligaments  of  the  larynx  are  extrinsic — i.  e.,  those  connecting 
the  thyroid  cartilage  and  epiglottis  with  the  hyoid  bone,  and  the  cricoid  cartilage 
with  the  trachea ;  and  intrinsic,  those  which  connect  the  several  cartilages  of  the 
larynx  to  each  other. 

The  ligaments  connecting  the  thyroid  cartilage  with  the  hyoid  bone  are  three 
in  number — the  thyro-hyoid  membrane,  and  the  two  lateral  thyro-hyoid  liga- 
ments. 

The  thyro-hyoid  membrane,  or  middle  thyro-hyoid  ligament,  is  a  broad,  fibro- 
elastic,  membranous  layer,  attached  below  to  the  upper  border  of  the  thyroid 
cartilage,  and  above  to  the  posterior  border  of  the  body  and  greater  cornua  of  the 
hyoid  bone,  thus  passing  behind  the  postero-inferior  surface  of  the  hyoid,  and 
being  separated  from  it  by  a  synovial  bursa,  which  facilitates  the  upward  move- 
ment of  the  larynx  during  deglutition.  It  is  thicker  in  the  middle  line  than  at 
either  side,  and  is  pierced,  in  the  latter  situation,  by  the  superior  laryngeal  vessels 
and  the  internal  branch  of  the  superior  laryngeal  nerve.  Its  anterior  surface  is  in 
relation  with  the  Thyro-hyoid,  Sterno-hyoid,  and  Omo-hyoid  muscles,  and  with  the 
body  of  the  hyoid  bone. 

The  two  lateral  thyro-hyoid  ligaments  are  rounded,  elastic  cords,  which  pass 
between  the  superior  cornua  of  the  thyroid  cartilage  and  the  extremities  of  the 
greater  cornua  of  the  hyoid  bone.  A  small  cartilaginous  nodule  {cartilago  triticea), 
sometimes  bony,  is  frequently  found  in  each. 


THE   LARYNX.  959 

The  ligament  connecting  the  epiglottis  with  the  hyoid  bone  is  the  liyo-epiglottic. 
In  addition  to  this  extrinsic  ligament,  the  epiglottis  is  connected  to  the  tongue  by 
the  three  glosso-epiglottidean  folds  of  mucous  membrane,  which  may  also  be  con- 
sidered as  extrinsic  ligaments  of  the  epiglottis. 

The  hyo-epiglottic  ligament  is  an  elastic  band,  which  extends  from  the  anterior 
surface  of  the  epiglottis,  near  its  apex,  to  the  upper  border  of  the  body  of  the 
hyoid  bone. 

The  lio-aments  connecting  the  thyroid  cartilage  to  the  cricoid  are  also  three  in 
number — the  crico-thyroid  membrane,  and  the  capsular  ligaments. 

The  crico-thyroid  membrane  is  composed  mainly  of  yellow  elastic  tissue.  It  con- 
sists of  three  parts,  a  central,  triangular  portion  and  two  lateral  portions.  The 
central  part  is  thick  and  strong,  narrow  above  and  broadening  out  below.  It  con- 
nects together  the  contiguous  margins  of  the  thyroid  and  cricoid  cartilages.  It  is 
convex,  concealed  on  each  side  by  the  Crico-thyroid  muscle,  but  subcutaneous  in 
the  middle  line  ;  it  is  crossed  horizontally  by  a  small  anastomotic  arterial  arch, 
formed  by  the  junction  of  the  two  crico-thyroid  arteries.  The  lateral  portions  are 
thinner  and  lie  close  under  the  mucous  membrane  of  the  larynx.  They  extend  from 
the  superior  border  of  the  cricoid  cartilage  to  the  inferior  margin  of  the  true  vocal 
cords,  with  which  they  are  continuous. 

The  lateral  portions  are  lined  internally  by  mucous  membrane,  and  covered  by 
the  lateral  Crico-arytenoid  and  Thyro-arytenoid  muscles. 

A  capsular  ligament  encloses  the  articulation  of  the  inferior  cornu  of  the 
thyroid  with  the  cricoid  cartilage  on  each  side.  The  articulation  is  lined  by 
synovial  membrane. 

The  ligaments  connecting  the  arytenoid  cartilages  to  the  cricoid  are  two  capsu- 
lar ligaments  and  two  posterior  crico-arytenoid  ligaments.  The  capsular  ligaments 
are  thin  and  loose  capsules  attached  to  the  margin  of  the  articular  surfaces ;  they 
are  lined  internally  by  synovial  membrane.  The  posterior  crico-arytenoid  liga- 
ments extend  from  the  cricoid  to  the  inner  and  back  part  of  the  base  of  the  aryte- 
noid cartilage. 

The  ligament  connecting  the  epiglottis  with  the  thyroid  cartilage  is  the  thyro- 
epiglottic. 

The  thyro -epiglottic  ligament  is  a  long,  slender,  elastic  cord  which  connects 
the  apex  of  the  epiglottis  with  the  receding  angle  of  the  thyroid  cartilage, 
immediately  beneath  the  median  notch,  above  the  attachment  of  the  vocal  cords. 

The  eric o -tracheal  ligament  connects  the  cricoid  cartilage  with  the  first  ring  of 
the  trachea.  It  resembles  the  fibrous  membrane  which  connects  the  cartilaginous 
rings  of  the  trachea  to  each  other. 

Interior  of  the  Larynx. — The  cavity  of  the  larynx  extends  from  its  superior 
aperture  to  the  lower  border  of  the  cricoid  cartilage.  It  is  divided  into  two  parts 
by  the  projection  inward  of  the  true  vocal  cords,  between  which  is  a  narrow  triangu- 
lar fissure  or  chink,  the  rima  glottidis.  The  portion  of  the  cavity  of  the  larynx 
above  the  true  vocal  cords,  sometimes  called  the  vestibule,  is  broad  and  triangular 
in  shape,  and  corresponds  to  the  interval  between  the  alse  of  the  thyroid  cartilage ; 
it  contains  the  false  vocal  cords,  and  between  these  and  the  true  vocal  cords  are 
the  ventricles  of  the  larynx.  The  portion  below  the  true  vocal  cords  widens  out, 
and  is  at  first  of  an  elliptical  and  lower  down  of  a  circular  form,  and  is  continuous 
with  the  tube  of  the  trachea. 

The  superior  aperture  of  the  larynx  (Fig.  529)  is  a  triangular  or  cordiform 
opening,  Avide  in  front,  narrow  behind,  and  sloping  obliquely  downward  and  back- 
ward. It  is  bounded,  in  front,  by  the  epiglottis  ;  behind,  by  the  apices  of  the 
arytenoid  cartilages  and  the  cornicula  laryngis  ;  and  laterally,  by  a  fold  of  mucous 
membrane,  enclosing  ligamentous  and  muscular  fibres,  stretched  between  the  sides 
of  the  epiglottis  and  the  apices  of  the  arytenoid  cartilages  :  these  are  the  aryteno- 
epiglottidcan  folds,  on  the  margins  of  which  the  cuneiform  cartilages  form  more  or 
less  distinct  whitish  prominences. 

The  rima  glottidis  is  the  elongated  fissure  or  chink  between  the  inferior  or  true 


960 


THE    ORGANS    OF    VOICE   AND    RESPIRATION. 


vocal  cords  in  front,  and  between  the  bases  and  vocal  processes  of  the  arytenoid 
cartilages  behind.  It  is  therefore  frequently  subdivided  into  an  anterior  interliga- 
mentous  or  vocal  portion  {glottis  vocalis)  and  a  posterior  intercartilaginous  or 
respiratory  part  {glottis  respiratoria).  Posteriorly  it  is  limited  by  the  mucous 
membrane  passing  between  the  arytenoid  cartilages.  The  vocal  portion  averages 
about  three- fifths  of  the  length  of  the  entire  aperture.     It  is  the  narrowest  part  of 


Inferior  vocal 
cord. 


Superior 
vocal  cord 


Corniculum  laryngis. 

Apex  of  sup.  horn  of 

thyroid  cartilage. 

Cuneiform  cartilage. 

An/teno- epiglottic 
fold. 

Apex  of  great 
horn  of  hyoid. 


Tongin 

Middle  glosso-epiglottic  fold. 
Fig.  529.— Larynx,  viewed  from  above.    (Testut.) 

the  cavity  of  the  larynx,  and  its  level  corresponds  to  the  bases  of  the  arytenoid 
cartilages.  Its  length,  in  the  male,  measures  rather  less  than  an  inch  (20-25  mm.) ; 
in  the  female  it  is  shorter  by  5  or  6  mm.,  or  three  lines.  The  width  and  shape 
of  the  rima  glottidis  vary  with  the  movements  of  the  vocal  cords  and  arytenoid 
cartilages  during  respiration  and  phonation.  In  the  condition  of  rest — i.  e.,  when 
these  structures  are  uninfluenced  by  muscular  action,  as  in  quiet  respiration — the 
glottis  vocalis  is  triangular,  with  its  apex  in  front  and  its  base  behind,  the  latter 
being  represented  by  a  line  about  8  mm.  long,  connecting  the  anterior  extremities 
of  the  vocal  processes,  while  the  inner  surfaces  of  the  arytenoids  are  parallel  to 
each  other,  and  hence  the  glottis  respiratoria  is  rectangular.  During  extreme 
adduction  of  the  cords,  as  in  the  emission  of  a  high  note,  the  glottis  vocalis  is 
reduced  to  a  linear  slit  by  the  apposition  of  the  cords,  while  the  glottis  respiratoria 
is  triangular,  its  apex  corresponding  to  the  anterior  extremities  of  the  vocal 
processes  of  the  arytenoids,  which  are  approximated  by  the  inward  rotation  of  the 
cartilages.  Conversely  in  extreme  abduction  of  the  cords,  as  in  forced  inspiration, 
the  arytenoids  and  their  vocal  processes  are  rotated  outward,  and  the  glottis  respi- 
ratoria is  triangular  in  shape,  but  with  its  apex  directed  backward.  In  this  con- 
dition the  entire  glottis  is  somewhat  lozenge-shaped,  the  sides  of  the  glottis  vocalis 
diverging  from  before  backward,  those  of  the  glottis  respiratoria  diverging  from 
behind  forward,  the  widest  part  of  the  aperture  corresponding  with  the  attachment 
of  the  cords  to  the  vocal  processes.1 

The  superior  or  false  vocal  cords,  so  called  because  they  are  not  directly  con- 
cerned in  the  production  of  the  voice,  are  two  thick  folds  of  mucous  membrane, 
enclosing  a  narrow  band  of  fibrous  tissue,  the  superior  thyro-arytenoid  ligament, 
which  is  attached  in  front  to  the  angle  of  the  thyroid  cartilage  immediately  below 
the  attachment  of  the  epiglottis,  and  behind  to  the  anterior  surface  of  the  aryte- 
noid cartilage.  The  lower  border  of  this  ligament,  enclosed  in  mucous  membrane, 
forms  a  free  crescentic  margin,  which  constitutes  the  upper  boundary  of  the  ven- 
tricle of  the  larynx. 

1  On  the  shape  of  the  rima  glottidis,  in  the  various  conditions  of  breathing  and  speaking,  see 
Czermak,  On  the  Laryngoscope,  translated  for  the  New  Sydenham  Society. 


THE   LARYNX. 


961 


Glosso-epiglottic 
fold. 


Aryteno- 
•piglottic  fold. 


Arytenoid 
cartilage. 


RYTENCIDEU3 
MUSCLE. 


The  inferior  or  true  vocal  cords,  so  called  from  their  being  concerned  in  the 
production  of  sound,  are  two  strong  bands  (inferior  thyro-arytenoid  ligaments), 
covered  on  their  surface  by  a  thin  layer 
of  mucous  membrane.  Each  ligament 
consists  of  a  band  of  yellow  elastic  tis- 
sue, attached  in  front  to  the  depression 
between  the  two  aire  of  the  thyroid  carti- 
lage, and  behind  to  the  anterior  angle 
(vocal  process)  of  the  base  of  the  aryte- 
noid. Its  lower  border  is  continuous 
with  the  thin  lateral  part  of  the  crico- 
thyroid membrane.  Its  upper  border 
forms  the  lower  boundary  of  the  ven- 
tricle of  the  larynx.  Externally,  the 
Thyro-arytenoideus  muscle  lies  parallel 
with  it.  It  is  covered  internally  by 
mucous  membrane,  which  is  extremely 
thin,  and  closely  adherent  to  its  surface. 

The  ventricle  of  the  larynx  is  an 
oblong  fossa,  situated  between  the  supe- 
rior and  inferior  vocal  cords  on  each 
side,  and  extending  nearly  their  entire 
length.  This  fossa  is  bounded,  above, 
by  the  free  crescentic  edge  of  the  supe- 
rior vocal  cord ;  below,  by  the  straight 
margin  of  the  true  vocal  cord ;  exter- 
nally, by  the  mucous  membrane  cover- 
ing the  corresponding  Thyro-arytenoid- 
eus muscle.  The  anterior  part  of  the 
ventricle  leads  up  by  a  narrow  opening 
into  a  caecal  pouch  of  mucous  membrane  of  variable  size,  called  the  laryngeal 
pouch. 

The  saceulus  laryngis,  or  laryngeal  pouch,  is  a  membranous  sac,  placed  between 
the  superior  vocal  cord  and  the  inner  surface  of  the  thyroid  cartilage,  occasionally 
extending  as  far  as  its  upper  border  or  even  higher  :  it  is  conical  in  form,  and 
curved  slightly  backward.  On  the  surface  of  its  mucous  membrane  are  the  open- 
ings of  sixty  or  seventy  mucous  glands,  which  are  lodged  in  the  submucous  areolar 
tissue.  This  sac  is  enclosed  in  a  fibrous  capsule,  continuous  below  with  the  superior 
thyro-arytenoid  ligament :  its  laryngeal  surface  is  covered  by  the  Aryteno-epiglot- 
tideus  inferior  muscle  (Compressor  sacculi  laryngis,  Hilton) ;  while  its  exterior  is 
covered  by  the  Thyro-arytenoideus  and  Thyro-epiglottideus  muscles.  These  mus- 
cles compress  the  saceulus  laryngis,  and  discharge  the  secretion  it  contains  upon 
the  chordae  vocales,  the  surfaces  of  which  it  is  intended  to  lubricate. 

Muscles. — The  intrinsic  muscles  of  the  larynx  are  eight  in  number,  five  of 
which  are  the  muscles  of  the  vocal  cords  and  rima  glottidis,  and  three  are  con- 
nected with  the  epiglottis. 

The  five  muscles  of  the  vocal  cords  and  rima  glottidis  are  the — 


Fig.  530.— Vertical  section  of  the  larynx  and  upper 
part  of  the  trachea. 


Crico-thyroid.  Crico-arytenoideus  lateralis. 

Crico-arytenoideus  posticus.  Arytenoideus. 

Thyro-arytenoideus. 

The  Crico-thyroid  is  triangular  in  form,  and  situated  at  the  fore  part  and  side 
of  the  cricoid  cartilage.  It  arises  from  the  front  and  lateral  part  of  the  cricoid 
cartilage ;  its  fibres  diverge,  passing  obliquely  upward  and  outward  to  be  inserted 
into  the  lower  border  of  the  thyroid  cartilage  and  into  the  anterior  border  of  the 
lower  cornua. 


61 


962 


THE    ORGANS    OF    VOICE   AND    RESPIRATION 


The  inner  borders  of  these  two  muscles  are  separated  in  the  middle  line  by  a 
triangular  interval  occupied  by  the  central  part  of  the  crico-thyroid  membrane. 

The  Crico-arytenoideus  posticus  arises  from  the  broad  depression  occupying 
each  lateral  half  of  the  posterior  surface  of  the  cricoid  cartilage ;  its  fibres  pass 
upward  and  outward,  converging  to  be  inserted  into  the  outer  angle  (muscular  proc- 
ess) of  the  base  of  the  arytenoid  cartilage.  The  upper  fibres  are  nearly  hori- 
zontal, the  middle  oblique,  and  the  lower  almost  vertical.1 

The  Qrico-arytenoideus  lateralis  is  smaller  than  the  preceding,  and  of  an 
oblong  form.  It  arises  from  the  upper  border  of  the  side  of  the  cricoid  cartilage, 
and,  passing  obliquely  upward  and  backward,  is  inserted  into  the  muscular  process 
of  the  arytenoid  cartilage  in  front  of  the  preceding  muscle. 

The  Arytenoideus  is  a  single  muscle  filling  up  the  posterior  concave  surface 
of  the  arytenoid  cartilages.     It  arises  from  the  posterior  surface  and  outer  border 

of  one  arytenoid  cartilage,  and  is  in- 
serted into  the  corresponding  parts  of 
the  opposite  cartilage.  It  consists  of 
three  planes  of  fibres,  two  oblique  and 
one  transverse.  The  oblique  fibres, 
the  most  superficial,  form  two  fasciculi, 


Cornicul 


Articular  facet  ft 
inferior  cornu 
thyroid  cartilage 


Fig.  531.— Muscles  of  larynx, 
of  thyroid  cartilage  removed. 


Side  view.    Right  ala 


Fig. 532.— Interior  of  the  larynx,  seen  from  above. 
(Enlarged.) 


which  pass  from  the  base  of  one  cartilage  to  the  apex  of  the  opposite  one.  The 
transverse  fibres,  the  deepest  and  most  numerous,  pass  transversely  across  between 
the  two  cartilages ;  hence  the  Arytenoideus  was  formerly  considered  as  three  mus- 
cles, the  transverse  and  the  two  oblique.  A  few  of  the  oblique  fibres  are  occa- 
sionally continued  round  the  outer  margin  of  the  cartilage,  and  blend  with  the 
Thyro-arytenoid  or  the  Aryteno-epiglottideus  muscle. 

The  Thyro-arytenoideus  is  a  broad,  flat  muscle,  which  lies  parallel  with  the 
outer  side  of  the  true  vocal  cord.  It  arises  in  front  from  the  lower  half  of  the 
receding  angle  of  the  thyroid  cartilage,  and  from  the  crico-thyroid  membrane.     Its 

1  Merkel,  of  Leipsic,  has  described  a  muscular  slip  which  occasionally  extends  between  the  outer 
border  of  the  posterior  surface  of  the  cricoid  cartilage  and  the  posterior  margin  of  the  inferior  cornu 
of  the  thyroid  ;  this  he  calls  the  "Musculus  kerato-cricoideus."  It  is  not  found  in  every  larynx, 
and  when  present  exists  usually  only  on  one  side,  but  is  occasionally  found  on  both  sides.  Sir  Wil- 
liam Turner  {Edinburgh  Medical  Journal,  Feb.,  1860)  states  that  it  is  found  in  about  one  casein  five. 
Its  action  is  to  fix  the  lower  horn  of  the  thyroid  cartilage  backward  and  downward,  opposing  in  some 
measure  the  part  of  the  Crico-thyroid  muscle,  which  is  connected  to  the  anterior  margin  of  the  horn. 


THE   LARYNX.  963 

fibres  pass  backward  and  outward,  to  be  inserted  into  the  base  and  anterior  surface 
of  the  arytenoid  cartilage.  This  muscle  consists  of  two  fasciculi.1  The  inner  or 
inferior  portion,  the  thicker,  is  inserted  into  the  vocal  process  of  the  arytenoid 
cartilage,  and  into  the  adjacent  portion  of  its  anterior  surface;  it  lies  parallel  with 
the  true  vocal  cord,  to  Avhich  it  is  adherent.  The  outer  or  superior  fasciculus,  the 
thinner,  is  inserted  into  the  anterior  surface  and  outer  border  of  the  arytenoid 
cartilage  above  the  preceding  fibres ;  it  lies  on  the  outer  side  of  the  sacculus 
laryngis,  immediately  beneath  the  mucous  membrane.2 
The  muscles  of  the  epiglottis  are  the — 

Thyro-epiglottideus.  Aryteno-epiglottideus  superior. 

Aryteno-epiglottideus  inferior. 

The  Thyro-epiglottideus  is  a  delicate  fasciculus,  which  arises  from  the  inner 
surface  of  the  thyroid  cartilage,  just  external  to  the  origin  of  the  Thyro-arytenoid 
muscle,  of  which  it  is  sometimes  described  as  a  part,  and  spreads  over  the  outer 
surface  of  the  sacculus  laryngis ;  some  of  its  fibres  are  lost  in  the  aryteno-epiglot- 
tidean  fold,  while  the  others  are  continued  forward  to  the  margin  of  the  epiglottis 
{Depressor  epiglottidis). 

The  Aryteno-epiglottideus  superior  consists  of  a  few  delicate  muscular  fascic- 
uli, which  arise  from  the  apex  of  the  arytenoid  cartilages,  and  become  lost  in  the 
fold  of  mucous  membrane  extending  between  the  arytenoid  cartilage  and  the  side 
of  the  epiglottis  {aryteno-epiglottidean  fold). 

The  Aryteno-epiglottideus  inferior  (Compressor  sacculi  laryngis,  Hilton)  arises 
from  the  arytenoid  cartilage,  just  above  the  attachment  of  the  superior  vocal  cord  ; 
passing  forward  and  upward,  it  spreads  out  upon  the  anterior  surface  of  the  epi- 
glottis. This  muscle  is  separated  from  the  preceding  by  an  indistinct  areolar 
interval.3 

Actions. — In  considering  the  action  of  the  muscles  of  the  larynx,  they  may 
be  conveniently  divided  into  two  groups,  viz. :  1.  Those  which  open  and  close 
the  glottis.     2.  Those  which  regulate  the  degree  of  tension  of  the  vocal  cords. 

1.  The  muscles  which  open  the  glottis  are  the  Crico-arytenoidei  postici ;  and 
those  which  close  it  are  the  Arytenoideus  and  the  Crico-arytenoidei  laterales. 
2.  The  muscles  which  regulate  the  tension  of  the  vocal  cords  are  the  Crico- 
thyroidei,  which  tense  and  elongate  them  ;  and  the  Thyro-arytenoidei,  which  relax 
and  shorten  them.  The  Thyro-epiglottideus  is  a  depressor  of  the  epiglottis,  and 
the  Aryteno-epiglottidei  constrict  the  superior  aperture  of  the  larynx,  compress 
the  sacculi  laryngis,   and  empty  them  of  their  contents. 

The  Crico-arytenoidei  postici  separate  the  chordae  vocales,  and  consequently  open  the  glottis, 
by  rotating  the  arytenoid  cartilages  outward  around  a  vertical  axis  passing  through  the  crico- 
arytenoid joints,  so  that  their  vocal  processes  and  the  vocal  cords  attached  to  them  become  widely 
separated. 

The  Crico-arytenoidei  laterales  close  the  glottis  by  rotating  the  arytenoid  cartilages  inward 
so  as  to  approximate  their  vocal  processes. 

The  Arytenoideus  muscles  approximate  the  arytenoid  cartilages,  and  thus  close  the  opening 
of  the  glottis,  especially  at  its  back  part. 

The  Crico-tkyroid  muscles  produce  tension  and  elongation  of  the  vocal  cords.  This  is 
effected  as  follows :  the  thyroid  cartilage  is  fixed  by  its  extrinsic  muscles ;  then  the  Crico- 
thyroid muscles,  when  they  act,  draw  upward  the  front  of  the  cricoid  cartilage,  and  so  depress 

1  Henle  describes  these  two  portions  as  separate  muscles,  under  the  names  of  External  and 
Internal  thyro-arytenoid. 

2  Luschka  has  described  a  small  but  fairly  constant  muscle  as  the  Arytenoideus  rectus.  It  is 
attached  below  to  the  posterior  concave  surface  of  the  arytenoid  cartilage,  beneath  the  Arytenoideus 
muscle,  and,  passing  upward,  emerges  at  the  upper  border  of  this  muscle,  and  is  inserted  into  the 
posterior  surface  of  the  cartilage  of  Santorini  {Anatomy,  by  Hyrtl,  page  718). 

3  Museums  triticeo-«lossus.  Bochdalek,  jun.  (Prager  Vierteljahrsschrift,  2d  part,  1866), 
describes  a  muscle  hitherto  entirely  overlooked,  except  a  brief  statement  in  Henle's  Anatomy,  which 
arises  from  the  nodule  of  cartilage  (corpus  triticeum)  in  the  posterior  thyrohyoid  ligament,  and  passes 
forward  and  upward  to  enter  the  tongue  along  with  the  Hyo-glossus  muscle.  He  met  with  this 
muscle  eight  times  in  twenty-two  subjects.  It  occurred  in  both  sexes,  sometimes  on  both  sides,  at 
others  on  one  only. 


964  THE    ORGANS    OF    VOICE   AND    RESPIRATION. 

the  posterior  portion,  which  carries  with  it  the  arytenoid  cartilages,  and  thus  elongate  the  vocal 
cords. 

The  Thyro-arytenoidei  muscles,  consisting  of  two  parts  having  different  attachments  and 
different  directions,  are  rather  complicated  as  regards  their  action.  Their  main  use  is  to  draw 
the  arytenoid  cartilages  forward  toward  the  thyroid,  and  thus  shorten  and  relax  the  vocal  cords. 
But,  owing  to  the  connection  of  the  inner  portion  with  the  vocal  cord,  this  part,  if  acting  sep- 
arately, is  supposed  to  modify  its  elasticity  and  tension,  and  the  outer  portion,  being  inserted 
into  the  outer  part  of  the  anterior  surface  of  the  arytenoid  cartilage,  may  rotate  it  inward,  and 
thus  narrow  the  rima  glottidis  by  bringing  the  two  cords  together. 

The  Thyro-epiglottidei  may  depress  the  epiglottis ;  they  assist  in  compressing  the  sacculi 
laryngis.  The  Aryteno-epiglottideus  superior  constricts  the  superior  aperture  of  the  larynx, 
when  it  is  drawn  upward,  during  deglutition.  The  Aryteno-epiglottideus  inferior,  together  with 
some  fibres  of  the  Thyro-arytenoidei,  compress  the  sacculus  laryngis. 

The  Mucous  Membrane  of  the  Larynx  is  continuous  above  with  that  lining  the 
mouth  and  pharynx,  and  it  is  prolonged  through  the  trachea  and  bronchi  into  the 
lungs.  It  lines  the  posterior  surface  and  the  anterior  part  of  the  upper  surface  of 
the  epiglottis,  to  which  it  is  closely  adherent,  and  forms  the  aryteno-epiglottidean 
folds  which  form  the  laterial  boundaries  of  the  superior  aperture  of  the  larynx.  It 
lines  the  whole  of  the  cavity  of  the  larynx  ;  forms,  by  its  reduplication,  the  chief 
part  of  the  superior  or  false  vocal  cord ;  and,  from  the  ventricle,  is  continued  into 
the  sacculus  laryngis.  It  is  then  reflected  over  the  true  vocal  cords,  where  it  is 
thin  and  very  intimately  adherent ;  covers  the  inner  surface  of  the  crico-thyroid 
membrane  and  cricoid  cartilage ;  and  is  ultimately  continuous  with  the  lining 
membrane  of  the  trachea.  The  fore  part  of  the  anterior  surface  and  the  upper 
half  of  the  posterior  surface  of  the  epiglottis,  the  upper  part  of  the  aryteno- 
epiglottidean  folds,  and  the  true  vocal  cords  are  covered  by  stratified  squamous 
epithelium  ;  all  the  rest  of  the  laryngeal  mucous  membrane  is  covered  by  columnar 
ciliated  cells. 

Glands. — The  mucous  membrane  of  the  larynx  is  furnished  with  numerous 
muciparous  glands,  the  orifices  of  which  are  found  in  nearly  every  part ;  they 
are  very  numerous  upon  the  epiglottis,  being  lodged  in  little  pits  in  its  substance ; 
they  are  also  found  in  large  numbers  along  the  posterior  margin  of  the  aryteno- 
epiglottidean  fold,  in  front  of  the  arytenoid  cartilages,  where  they  are  termed  the 
arytenoid  glands.  They  exist  also  in  large  numbers  upon  the  inner  surface  of  the 
sacculus  laryngis.     None  are  found  on  the  free  edges  of  the  vocal  cords. 

Vessels  and  Nerves. — The  arteries  of  the  larynx  are  the  laryngeal  branches 
derived  from  the  superior  and  inferior  thyroid.  The  veins  accompany  the  arteries  : 
those  accompanying  the  superior  laryngeal  artery  join  the  superior  thyroid  vein 
which  opens  into  the  internal  jugular  vein  ;  while  those  accompanying  the  inferior 
laryngeal  artery  join  the  inferior  thyroid  vein  which  opens  into  the  innominate 
vein.  The  lymphatics  consist  of  two  sets,  superior  and  inferior.  The  former 
accompany  the  superior  laryngeal  artery  and  pierce  the  thyro-hyoid  membrane,  to 
terminate  in  the  glands  situated  near  the  bifurcation  of  the  common  carotid  artery. 
The  latter  pass  through  the  crico-thyroid  membrane,  and  open  into  one  or  two 
glands  lying  either  in  front  of  that  membrane  or  to  the  side  of  the  cricoid  cartilage. 
The  nerves  are  derived  from  the  internal  and  external  laryngeal  branches  of  the 
superior  lai-yngeal  nerve,  from  the  inferior  or  recurrent  laryngeal,  and  from  the 
sympathetic.  The  internal  laryngeal  nerve  is  almost  entirely  sensory,  but  some 
motor  filaments  are  said  to  be  carried  by  it  to  the  Arytenoideus  muscle.  It 
divides  into  a  branch  which  is  distributed  to  both  surfaces  of  the  epiglottis,  a 
second  to  the  aryteno-epiglottidean  folds,  and  a  third,  the  largest,  which  supplies 
the  mucous  membrane  over  the  back  of  the  larynx  and  communicates  with  the 
recurrent  laryngeal.  The  external  laryngeal  nerve  supplies  the  Crico-thyroid 
muscle.  The  recurrent  laryngeal  passes  upward  under  the  lower  border  of 
the  Inferior  constrictor,  and  enters  the  larynx  between  the  cricoid  and  thyroid 
cartilages.  It  supplies  all  the  muscles  of  the  larynx  except  the  Crico-thyroid  and 
part  of  the  Arytenoideus.  The  sensory  branches  of  the  laryngeal  nerves  form 
subepithelial  plexuses,  from  which  fibres  ascend  to  end  between  the  cells  covering 
the  mucous  membrane. 


THE    TRACHEA, 


965 


Over  the  posterior  surface  of  the  epiglottis,  in  the  aryteno-epiglottidean  folds, 
and  less  regularly  in  some  other  parts,  taste-buds,  similar  to  those  in  the  tongue, 
are  found. 

THE  TRACHEA  (Fig.   533). 

The  trachea,  or  windpipe,  is  a  cartilaginous  and  membranous  cylindrical  tube, 
flattened  posteriorly,  which  extends  from  the  lower  part  of  the  larynx,  on  a  level 
with  the  sixth  cervical  vertebra,  to  opposite  the  fourth,  or  sometimes   the  fifth. 


Superio) 
C'omu. 


Fig.  533.— Front  view  of  cartilages  of  larynx ;  the  trachea  and  bronchi. 

dorsal  vertebra,  where  it  divides  into  two  bronchi,  one  for  each  lung.  The  trachea 
measures  about  four  inches  and  a  half  in  length ;  its  diameter,  from  side  to  side, 
is  from  three-quarters  of  an  inch  to  an  inch,  being  always  greater  in  the  male 
than  in  the  female. 

Relations. — The  anterior      irface  of  the  trachea  is  convex,  and  covered  in  the 
neck,  from   above   downward,  isthmus  of  the  thyroid  gland,  the   inferior 

thyroid  veins,  the  arteria  thyi  a  ima  (when  that  vessel  exists),  the  Sterno-hyoid 
and   Sterno-thyroid   muscles,  cal   fascia,  and  more   superficially,  by  the 

anastomosing  branches  betw<  nterior  jugular  veins  :    in  the  thorax  it  is 


966  THE    ORGANS    OF    VOICE  AND   RESPIRATION. 

covered  from  before  backward  by  the  first  piece  of  the  sternum,  the  remains  of  the 
thymus  gland,  the  left  innominate  vein,  the  arch  of  the  aorta,  the  innominate  and 
left  common  carotid  arteries,  and  the  deep  cardiac  plexus.  Posteriorly,  it  is  in 
relation  with  the  oesophagus  ;  laterally,  in  the  neck,  it  is  in  relation  with  the  com- 
mon carotid  arteries,  the  lateral  lobes  of  the  thyroid  gland,  the  inferior  thyroid 
arteries,  and  recurrent  laryngeal  nerves ;  and,  in  the  thorax,  it  lies  in  the  upper 
part  of  the  interpleural  space  (superior  mediastinum),  and  is  in  relation  on  the 
right  to  the  pleura  and  right  vagus,  and  near  the  root  of  the  neck  to  the 
innominate  artery  ;  on  its  left  side  are  the  recurrent  laryngeal  nerve,  the  aortic 
arch,  the  left  common  carotid  and  subclavian  arteries. 

The  Right  Bronchus,  wider,  shorter,  and  more  vertical  in  direction  than  the 
left,  is  about  an  inch  in  length,  and  enters  the  right  lung  opposite  the  fifth  dorsal 
vertebra.  The  vena  azygos  major  arches  over  it  from  behind;  and  the  right 
pulmonary  artery  lies  below  and  then  in  front  of  it.  About  three-quarters  of  an 
inch  from  its  commencement  it  gives  off  a  branch  to  the  upper  lobe  of  the  right 
lung.  This  is  termed  the  eparterial  branch,  because  it  is  given  off  above  the 
right  pulmonary  artery.  The  bronchus  now  passes  below  the  artery,  and  is  known 
as  the  hyparterial  branch.  It  divides  into  two  branches  for  the  middle  and  lower 
lobes. 

The  Left  Bronchus  is  smaller  and  longer  than  the  right,  being  nearly  two  inches 
in  length.  It  enters  the  root  of  the  left  lung,  opposite  the  sixth  dorsal  vertebra, 
about  an  inch  lower  than  the  right  bronchus.  It  passes  beneath  the  arch  of  the 
aorta,  crosses  in  front  of  the  oesophagus,  the  thoracic  duct,  and  the  descending 
aorta,  and  has  the  left  pulmonary  artery  lying  at  first  above,  and  then  in  front  of 
it.  The  left  bronchus  has  no  branch  corresponding  to  the  eparterial  branch  of  the 
right  bronchus,  and  therefore  it  has  been  supposed  by  some  that  there  is  no  upper 
lobe  to  the  left  lung,  but  that  the  so-called  upper  lobe  corresponds  to  the  middle 
lobe  of  the  right  lung. 

When  the  bronchi  enter  the  lung  they  appear  to  divide  into  nearly  equal 
branches  at  the  root  of  the  lung,  but  a  somewhat  similar  arrangement  to  what  is 
found  in  many  animals  may  be  made  out  where  each  bronchus  passes  downward 
and  backward  toward  the  extremity  of  the  lower  lobe,  giving  off  four  branches  at 
intervals  in  two  directions,  dorsally  and  ventrally,  and,  in  addition,  accessory 
branches,  which  arise  from  the  front  of  the  bronchus  and  pass  mesially  and  dor- 
sally  into  the  inferior  lobe.  In  the  right  bronchus  the  first  ventral  branch  sup- 
plies the  middle  lobe,  the  other  three  and  all  the  dorsal  going  to  the  lower  lobe ;  in 
the  left  bronchus,  the  first  ventral  supplies  the  superior  lobe,  and  all  the  others, 
both  ventral  and  dorsal,  go  to  the  lower  lobe. 

If  a  transverse  section  of  the  trachea  is  made  a  short  distance  above  its 
point  of  bifurcation,  and  a  bird's-eye  view  taken  of  its  interior  (Fig.  534),  the 
septum  placed  at  the  bottom  of  the  trachea  and  separating  the  two  bronchi  will  be 
seen  to  occupy  the  left  of  the  median  line,  and  the  right  bronchus  appears  to  be  a 
more  direct  continuation  than  the  left,  so  that  any  solid  body  dropping  into  the 
trachea  would  naturally  be  directed  toward  the  right  bronchus.  This  tendency  is 
aided  by  the  larger  size  of  the  right  tube  as  compared  with  its  fellow.  This  fact 
serves  to  explain  why  a  foreign  body  in  the  trachea  more  frequently  falls  into  the 
right  bronchus.1 

Structure. — The  trachea  is  composed  of  imperfect  cartilaginous  rings,  fibrous 
membrane,  muscular  fibres,  mucous  membrane,   and  glands. 

The  cartilages  vary  from  sixteen  to  twenty  in  number :  each  forms  an  imper- 
fect ring,  which  surrounds  about  two-thirds  of  the  cylinder  of  the  trachea, 
being  imperfect  behind,  where  the  tube  is  completed  by  fibrous  membrane.  The 
cartilages  are  placed  horizontally  above  each  other,  separated  by  narrow  mem- 
branous intervals.  They  measure  about  two  lines  in  depth,  and  half  a  line  in 
thickness.      Their  outer  surfaces  are  flattened,   but   internally  they  are  convex, 

1  Reigel  asserts  that  the  entry  of  a  foreign  body  into  the  left  bronchus  is  by  no  means  so  infre- 
quent as  is  generally  supposed.     See  also  Med.-Chir.'  Trans.,  vol.  lxxi.,  p.  121. 


THE    TRACHEA.  967 

from  being  thicker  in  the  middle  than  at  the  margins.  Two  or  more  of  the  carti- 
lages often  unite,  partially  or  completely,  and  are  sometimes  bifurcated  at  their 
extremities.    They  are  highly  elastic,  but  Riht 

sometimes  become  calcified  in  advanced 
life.  In  the  right  bronchus  the  carti- 
lages vary  in  number  from  six  to  eight ; 
in  the  left,  from  nine  to  twelve.  They 
are  shorter  and  narrower  than  those  of 
the  trachea.  The  peculiar  cartilages  are 
the  first  and  the  last. 

The   first  cartilage   is   broader   than 

.1  j.  j  i-  j-    •  i     i       i  Fig.  534. — Transverse  section  of  the  trachea,  just 

tne    rest,    and    sometimes    divided    at    One       above  its  bifurcation,  with  a  bird's-eye  view  of  the 

end ;    it  is   connected   by   fibrous   mem-     mterior- 

brane  with  the  lower  border  of  the  cricoid  cartilage,  with  which  or  with  the  suc- 
ceeding cartilage  it  is  sometimes  blended. 

The  last  cartilage  is  thick  and  broad  in  the  middle,  in  consequence  of  its  lower 
border  being  prolonged  into  a  triangular  hook-shaped  process  which  curves  down- 
ward and  backward  between  the  two  bronchi.  It  terminates  on  each  side  in  an 
imperfect  ring  which  encloses  the  commencement  of  the  bronchi.  The  cartilage 
above  the  last  is  somewhat  broader  than  the  rest  at  its  centre. 

The  Fibrous  Membrane. — The  cartilages  are  enclosed  in  an  elastic  fibrous 
membrane  which  forms  a  double  layer,  one  layer,  the  thicker  of  the  two,  passing 
over  the  outer  surface  of  the  ring,  the  other  over  the  inner  surface ;  at  the  upper 
and  lower  margins  of  the  cartilages  these  two  layers  blend  together  to  form  a  single 
membrane,  which  connects  the  rings  one  with  another.  They  are  thus,  as  it  were, 
imbedded  in  the  membrane.  In  the  space  behind,  between  the  extremities  of  the 
rings,  the  membrane  forms  a  single  distinct  layer. 

The  muscular  fibres  are  disposed  in  two  layers,  longitudinal  and  transverse. 
The  longitudinal  fibres  are  the  most  external,  and  consist  merely  of  a  few  scattered 
longitudinal  bundles  of  fibres. 

The  transverse  fibres  (Trachealis  muscle,  Todd  and  Bowman"),  the  most  internal, 
form  a  thin  layer,  which  extends  transversely  between  the  ends  of  the  cartilages 
and  the  intervals  between  them  at  the  posterior  part  of  the  trachea.  The  muscular 
fibres  are  of  the  unstriped  variety. 

The  Mucous  membrane  is  continuous  above  with  that  of  the  larynx,  and  below 
with  that  of  the  bronchi.  Microscopically,  it  consists  of  areolar  and  lymphoid 
tissue,  and  presents  a  well-marked  basement-membrane,  supporting  a  layer  of 
columnar,  ciliated  epithelium,  between  the  deeper  ends  of  which  are  smaller  tri- 
angular cells,  the  bases  of  which,  often  branched,  are  attached  to  the  basement- 
membrane.  These  triangular  cells  are  mucus-secreting,  and  may  be  seen  as  goblet- 
or  chalice-cells  when  their  contents  have  been  discharged.  In  the  deepest  part  of 
the  mucous  membrane,  and  especially  between  the  mucous  and  submucous  layers, 
longitudinally  arranged  fibres  are  very  abundant  and  form  a  distinct  layer. 

The  Tracheal  glands  are  found  in  great  abundance  at  the  posterior  part  of  the 
trachea.  They  are  racemose  glands,  and  consist  of  a  basement-membrane  lined  by 
columnar  mucus-secreting  cells.  They  are  situated  at  the  back  of  the  trachea, 
outside  the  layer  of  muscular  tissue,  between  it  and  the  outer  fibrous  layer.  Their 
excretory  ducts  pierce  the  muscular  and  inner  fibrous  layers,  and  pass  through  the 
submucous  and  mucous  layers  to  open  on  the  surface  of  the  mucous  membrane. 
Some  glands  of  smaller  size  are  also  found  at  the  sides  of  the  trachea,  between  the 
layers  of  fibrous  tissue  connecting  the  rings,  and  others  immediately  beneath  the 
mucous  coat.  The  secretion  from  these  glands  serves  to  lubricate  the  inner  surface 
of  the  trachea. 

Vessels  and  Nerves. — The  trachea  is  supplied  with  blood  by  the  inferior 
thyroid  arteries.  The  veins  terminate  in  the  thyroid  venous  plexus.  The  nerves 
are  derived  from  the  pneumogastric  and  its  recurrent  branches  and  from  the 
sympathetic. 


968  THE    ORGANS    OF    VOICE  AND    RESPIRATION. 

Surface  Form. — In  the  middle  line  of  the  neck  some  of  the  cartilages  of  the  larynx  can  be 
readily  distinguished.-  In  the  receding  angle  below  the  chin  the  hyoid  bone  can  easily  be  made 
out  (see  page  126),  and  a  finger's  breadth  below  it  is  the  pomum  Adami,  the  prominence  between 
the  upper  borders  of  the  two  alae  of  the  thyroid  cartilage.  _  About  an  inch  below  this,  in  the 
middle  line,  is  a  depression  corresponding  to  the  crico-thyroid  space,  in  which  the  operation  of 
laryngotomy  is  performed.  This  depression  is  bounded  below  by  a  prominent  arch,  the  anterior 
ring  of  the  cricoid  cartilage,  below  which  the  trachea  can  be  felt,  though  it  is  only  in  the  emaci- 
ated adult  that  the  separate  rings  can  be  distinguished.  The  lower  part  of  the  trachea  is  not 
easily  made  out,  for  as  it  descends  in  the  neck  it  takes  a  deeper  position,  and  is  farther  removed 
from  the  surface.  The  level  of  the  vocal  cords  corresponds  to  the  middle  of  the  anterior  margin 
of  the  thyroid  cartilage. 

With  the  laryngoscope,  the  following  structures  can  be  seen :  The  base  of  the  tongue  and 
the  upper  surface  of  the  epiglottis,  with  the  glosso-epiglottic  ligaments ;  the  superior  aperture  of 
the  larynx,  bounded  on  either  side  by  the  aryteno-epiglottidean  folds,  in  which  may  be  seen  two 
rounded  eminences  corresponding  to  the  cornicula  and  cuneiform  cartilages.  Beneath  these,  the 
true  and  false  vocal  cords,  with  the  ventricle  between  them.  Still  deeper,  the  cricoid  cartilage 
and  some  of  the  anterior  parts  of  the  rings  of  the  trachea,  and  sometimes,  in  deep  inspiration, 
the  bifurcation  of  the  trachea. 

Surgical  Anatomy.— Foreign  bodies  often  find  their  way  into  the  air-passages.  These  may 
be  either  large  soft  substances,  as  a  piece  of  meat,  which  may  become  lodged  in  the  upper  aper- 
ture of  the  larynx  or  in  the  rima  glottidis,  and  cause  speedy  suffocation  unless  rapidly  got  rid  of, 
or  unless  an  opening  is  made  into  the  air-passages  below,  so  as  to  enable  the  patient  to  breathe. 
Smaller  bodies,  frequently  of  a  hard  nature,  such  as  cherry  or  plum  stones,  small  pieces  of  bone, 
buttons,  etc.,  may  find  their  way  through  the  rima  glottidis  into  the  trachea  or  bronchus,  or  may 
become  lodged  in  the  ventricle  of  the  larynx.  The  dangers  then  depend  not  so  much  upon  the 
mechanical  obstruction  as  upon  the  spasm  of  the  glottis  which  they  excite  from  reflex  irritation. 
When  lodged  in  the  ventricle  of  the  larynx,  they  may  produce  very  few  symptoms  beyond 
sudden  loss  of  voice  or  alteration  in  the  voice  sounds,  immediately  following  the  inhalation  of 
the  foreign  body.  When,  however,  they  are  situated  in  the  trachea,  they  are  constantly  striking 
against  the  vocal  cords  during  expiratory  efforts,  and  produce  attacks  of  dyspnoea  from  spasm 
of  the  glottis.  When  lodged  in  the  bronchus,  they  usually  become  fixed  there,  and,  occluding 
the  lumen  of  the  tube,  cause  a  loss  of  the  respiratory  murmur  on  the  affected  side,  which  is,  as 
stated  above,  more  often  the  right. 

Beneath  the  mucous  membrane  of  the  upper  part  of  the  air-passages  there  is  a  consider- 
able amount  of  submucous  tissue  which  is  liable  to  become  much  swollen  from  effusion  in 
inflammatory  affections,  constituting  the  disease  known  as  "oedema  of  the  glottis."  This 
effusion  does  not  extend  below  the  level  of  the  vocal  cords,  on  account  of  the  fact  that  the 
mucous  membrane  is  closely  adherent  to  these  structures,  without  the  intervention  of  any 
submucous  tissue.  So  that,  in  cases  of  this  disease  in  which  it  is  necessary  to  open  the  air- 
passages  to  prevent  suffocation,  the  operation  of  laryngotomy  is  sufficient. 

Chronic  laryngitis  is  an  inflammation  of  the  mucous  glands  of  the  larynx,  which  occurs  in 
those  who  speak  much  in  public,  and  is  known  as  "  clergyman's  sore  throat."  It  is  due  to  the 
dryness  induced  by  the  large  amount  of  cold  air  drawn  into  the  air-passages  during  prolonged 
speaking,  which  incites  increased  activity  in  the  mucous  glands  to  keep  the  parts  moist,  and 
this  eventually  terminates  in  inflammation  of  these  structures. 

Ulceration  of  the  larynx  may  occur  from  syphilis,  either  as  a  superficial  ulceration,  or  from 
the  softening  of  a  gumma ;  from  tuberculous  disease  (laryngeal  phthisis),  or  from  malignant 
disease  (epithelioma). 

The  air-passages  may  be  opened  in  two  different  situations:  through  the  crico-thyroid 
membrane  (laryngotomy),  or  in  some  part  of  the  trachea  [tracheotomy)]  and  to  these  some 
surgeons  have  added  a  third  method,  by  opening  the  crico-thyroid  membrane  and  dividing  the 
cricoid  cartilage  with  the  upper  ring  of  the  trachea  (laryn  go-tracheotomy). 

Laryngotomy  is  anatomically  the  more  simple  operation  :  it  can  readily  be  performed,  and 
should  be  employed  in  those  cases  where  the  air-passages  require  opening  in  an  emergency  for 
the  relief  of  some  sudden  obstruction  to  respiration.  The  crico-thyroid  membrane  is  very 
superficial,  being  covered  only  in  the  middle  line  by  the  skin,  superficial  fascia,  and  the  deep 
fascia.  On  each  side  of  the  middle  line  it  is  also  covered  by  the  Sterno-hyoid  and  Sterno- 
thyroid muscles,  which  diverge  from  each  other  at  their  upper  parts,  leaving  a  slight  interval 
between  them.  On  these  muscles  rest  the  anterior  jugular  veins.  The  only  vessel  of  any 
importance  in  connection  with  this  operation  is  the  crico-thyroid  artery,  which  crosses  the  crico- 
thyroid membrane,  and  which  may  be  wounded,  but  rarely  gives  rise  to  any  trouble.  The 
operation  is  performed  thus:  the  head  being  thrown  back  and  steadied  by  an  assistant,  the 
finger  is  passed  over  the  front  of  the  neck,  and  the  crico-thyroid  depression  felt  for.  A  vertical 
incision  is  then  made  through  \kiQ  skin,  in  the  middle  line  over  this  spot,  and  carried  down 
through  the  fascia  until  the  crico-thyroid  membrane  is  exposed.  A  cross  cut  is  then  made 
through  the  membrane,  close  to  the  upper  border  of  the  cricoid  cartilage,  so  as  to  avoid,  if 
possible,  the  crico-thyroid  artery,  and  a  tracheotomy  tube  introduced.  It  has  been  recommended, 
as  a  more  rapid  way  of  performing  the  operation,  to  make  a  transverse  instead  of  a  longitudinal 
cut,  through  the  superficial  structures,  and  thus  to  open  at  once  the  air-passages.  It  will  be 
seen,  however,  that  in  operating  in  this  way  the  anterior  jugular  veins  would  be  in  danger  of 
being  wounded. 


THE  PLEUBJE.  969 

Tracheotomy  may  be  performed  either  above  or  below  the  isthmus  of  the  thyroid  body,  or 
this  structure  may  be  divided  and  the  trachea  opened  behind  it. 

The  isthmus  of  the  thyroid  gland  usually  crosses  the  second  and  third  rings  of  the  trachea ; 
along  its  upper  border  is  frequently  to  be  found  a  large  transverse  communicating  branch  between 
the  superior  thyroid  veins  ;  and  the  isthmus  itself  is  covered  by  a  venous  plexus  formed  between 
the  thyroid  veins  of  the  opposite  sides.  Theoretically,  therefore,  it  is  advisable  to  avoid  dividing 
this  structure  in  opening  the  trachea. 

Above  the  isthmus  the  trachea  is  comparatively  superficial,  being  covered  by  the  skin,  super- 
ficial fascia,  deep  fascia,  Sterno-hyoid  and  Sterno-thyroid  muscles,  and  a  second  layer  of  the 
deep  fascia,  which,  attached  above  to  the  lower  border  of  the  hyoid  bone,  descends  beneath  the 
muscles  to  the  thyroid  body,  where  it  divides  into  two  layers  and  encloses  the  isthmus. 

Below  the  isthmus  the  trachea  lies  much  more  deeply,  and  is  covered  by  the  Sterno-hyoid 
and  the  Sterno-thyroid  muscles  and  a  quantity  of  loose  areolar  tissue  in  which  is  a  plexus  of 
veins,  some  of  them  of  large  size  ;  they  converge  to  two  trunks,  the  inferior  thyroid  veins,  which 
descend  on  either  side  of  the  median  line  on  the  front  of  the  trachea  and  open  into  the  innomi- 
nate veins.  In  the  infant  the  thymus  gland  ascends  a  variable  distance  along  the  front  of  the 
trachea,  and  opposite  the  episternal  notch  the  windpipe  is  crossed  by  the  left  innominate  vein. 
Occasionally  also,  in  young  subjects,  the  innominate  artery  crosses  the  tube  obliquely  above  the 
level  of  the  sternum.  The  thyroidea  ima  artery,  when  that  vessel  exists,  passes  from  below  up- 
ward along  the  front  of  the  trachea. 

From  these  observations  it  must  be  evident  that  the  trachea  can  be  more  readily  opened 
above  than  below  the  isthmus  of  the  thyroid  body. 

Tracheotomy  above  the  isthmus  is  performed  thus :  the  patient  should,  if  possible,  be  laid 
on  his  back  on  a  table  in  a  good  light.  A  pillow  is  to  be  placed  under  the  shoulders  and  the 
head  thrown  back  and  steadied  by  an  assistant.  The  surgeon  standing  on  the  right  side  of  his 
patient  makes  an  incision  from  an  inch  and  a  half  to  two  inches  in  length  in  the  median  line  of 
the  neck  from  the  top  of  the  cricoid  cartilage.  The  incision  must  be  made  exactly  in  the  middle 
line,  so  as  to  avoid  the  anterior  jugular  veins,  and  after  the  superficial  structures  have  been 
divided  the  interval  between  the  Sterno-hyoid  muscles  must  be  found,  the  raphe  divided,  and 
the  muscles  drawn  apart.  The  lower  border  of  the  cricoid  cartilage  must  now  be  felt  for,  and 
the  upper  part  of  the  trachea  exposed  from  this  point  downward  in  the  middle  line.  Bose  has 
recommended  that  the  layer  of  fascia  in  front  of  the  trachea  should  be  divided  transversely  at 
the  level  of  the  lower  border  of  the  cricoid  cartilage,  and,  having  been  seized  with  a  pair  of 
forceps  pressed  downward  with  the  handle  of  the  scalpel.  By  this  means  the  isthmus  of  the 
thyroid  gland  is  depressed,  and  is  saved  from  all  danger  of  being  wounded,  and  the  trachea 
cleanly  exposed.  The  trachea  is  now  transfixed  with  a  sharp  hook  and  drawn  forward  in  order 
to  steady  it,  and  is  then  opened  by  inserting  the  knife  into  it  and  dividing  the  two  or  three 
upper  rings  from  below  upward.  If  the  trachea  is  to  be  opened  below  the  isthmus,  the  incision 
must  be  made  from  a  little  below  the  cricoid  cartilage  to  the  top  of  the  sternum. 

In  the  child  the  trachea  is  smaller,  more  deeply  placed,  and  more  movable  than  in  the  adult. 
In  fat  or  short-necked  people,  or  in  those  in  whom  the  muscles  of  the  neck  are  prominently 
developed,  the  trachea  is  more  deeply  placed  than  in  the  opposite  conditions. 

A  portion  of  the  larynx  or  the  whole  of  it  has  been  removed  for  malignant  disease,  laryng- 
ectomy. The  results  which  have  been  obtained  from  the  removal  of  the  whole  of  it  have  not 
been  very  satisfactory,  and  the  cases  in  which  the  operation  is  justifiable  are  very  few.  It  may 
be  removed  by  a  median  incision  through  the  soft  parts,  freeing  the  cartilage  from  the  muscles 
and  other  structures  in  front,  separating  the  larynx  from  the  trachea  below,  and  dissecting  off 
the  deeper  structure  from  below  upward. 

THE  PLEURA. 

Each  lung  is  invested,  upon  its   external  surface,  by  an  exceedingly  delicate 
serous  membrane,  the  pleura,  which    encloses  the  organ  as  far  as  its  root,  and  is 
then  reflected  upon  the  inner  surface  of  the  thorax.      The  portion  of  the  serous 
membrane  investing  the  surface  of  the  lung  and  dipping  into  the  fissures  between  its 
lobes,  is  called  the  pleura  pulmonalis  (visceral  layer  of  pleura),  while  that  which 
lines  the  inner  surface  of  the  chest  is  called  the  pleura  costalis  (parietal  layer  of 
pleura).     The  space  between  these  two  layers  is  called  the  cavity  of  the  pleura, 
,t  it  must  be  borne  in  mind  that  in  the  healthy  condition  the  two  layers  are  in 
intact,  and  there  is  no  real  cavity  until  the  lung  becomes  collapsed  and  a  separa- 
on  of  it  from  the  wall  of  the  chest  takes  place.      Each  pleura  is  therefore  a  shut 
ac,  one  occupying  the  right,  the  other  the  left  half  of  the  thorax,  and  they  are 
perfectly  separate  from  each  other.      The  two  pleura?  do  not  meet  in  the  middle  line 
of  the  chest,  excepting  anteriorly  opposite  the  second  and  third  pieces  of  the  ster- 
num— a  space  being  left  between  them,  which  contains  all  the  viscera  of  the  thorax 
excepting  the  lungs:  this  is  the  mediastinum. 

Reflections  of  the  Pleura  (Fig.  535). — Commencing  at  the  sternum,  the  pleura 
passes    outAvaifd,  lines    the    costal    cartilages,   the    inner    surface  of  the  ribs   and 


970 


THE    ORGANS    OF    VOICE   AND    RESPIRATION 


Intercostal  muscles,  and  at  the  back  part  of  the  thorax  passes  over  the  thoracic 
ganglia  and  their  branches,  and  is  reflected  upon  the  sides  of  the  bodies  of  the 


TRIANGULARIS    STERIMI. 

Internal  Mammary  Vessels. 


Left  Phrenic  Nerve 


Pleura  Pulmonalis. 
Pleura  Costalis. 


Sympathetic  Nerve. 
Thoracic  Duct. 


Vena  Azygos  Major 
Pneumogastric  Nerves 


Fig.  535. — A  transverse  section  of  the  thorax,  showing  the  relative  position  of  the  viscera  and  the  reflections 
of  the  nleura?. 


vertebrae,  where  it  is  separated  by  a  narrow  interval,  the  posterior  mediastinum, 
from  the  opposite  pleura.  From  the  vertebral  column  the  pleura  passes  to  the  side 
of  the  pericardium,  which  it  covers  to  a  slight  extent ;  it  then  covers  the  back  part 
of  the  root  of  the  lung,  from  the  lower  border  of  which  a  triangular  fold  descends 
vertically  by  the  side  of  the  posterior  mediastinum  to  the  Diaphragm.  This  fold 
is  the  broad  ligament  of  the  lung,  the  lig amentum  latum  pulmonis,  and  serves  to 
retain  the  lower  part  of  that  organ  in  position.  From  the  root  the  pleura  may  be 
traced  over  the  convex  surface  of  the  lung,  the  summit  and  base,  and  also  over  the 
sides  of  the  fissures  between  the  lobes  on  to  its  inner  surface  and  the  front  part  of 
its  root ;  from  this  it  is  reflected  on  to  the  pericardium,  and  from  it  to  t"he  back  of 
the  sternum.  Below,  it  covers  the  upper  surface  of  the  Diaphragm,  and  extends  in 
front  as  low  as  the  costal  cartilage  of  the  seventh  rib  ;  at  the  side  of  the  chest,  to 
the  lower  border  of  the  tenth  rib  on  the  left  side,  and  to  the  upper  border  of  the 
same  r?b  on  the  right  side  ;  and  behind,  it  reaches  as  low  as  the  twelfth  rib,  and 
sometimes  even  as  low  as  the  transverse  process  of  the  first  lumbar  vertebra.  Above, 
its  apex  projects,  in  the  form  of  a  cul-de-sac,  through  the  superior  opening  of  the 
thorax  into  the  neck,  extending  from  one  to  two  inches  above  the  margin  of  the 
first  rib,  and  receives  the  summit  of  the  corresponding  lung ;  this  sac  is  strength- 
ened, according  to  Sibson,  by  a  dome-like  expansion  of  fascia,  attached  in  front 
to  the  posterior  border  of  the  first  rib,  and  behind  to  the  anterior  border  of  the 
transverse  process  of  the  seventh  cervical  vertebra.  This  is  covered  and  strength- 
ened by  a  few  spreading  muscular  fibres  derived  from  the  Scaleni  muscles. 

In  the  front  of  the  chest,  where  the  parietal  layer  of  the  pleura  is  reflected  back- 
ward to  the  pericardium,  the  two  pleural  sacs  are  in  contact  for  a  considerable  extent. 
At  the  upper  part  of  the  chest,  behind  the  manubrium,  they  are  not  in  contact ; 
the  point  of  reflection  being  represented  by  a  line  drawn  from  the  sterno-clavicular 
articulation  to  the  mid-point  of  the  junction  of  the  manubrium  to  the  body  of  the 
sternum.     From  this  point  the  two  pleurae  descend  in  close  contact  to  the  level  of 


THE   MEDIASTINUM.  971 

the  fourth  costal  cartilage.  Here  the  line  of  reflection  on  the  right  side  is  con- 
tinued onward  in  nearly  a  straight  line  to  the  lower  end  of  the  gladiolus  and  then 
turns  outward,  while  on  the  left  side  the  line  of  reflection  diverges  outward,  so  that 
opposite  the  seventh  cartilage  it  is  about  three-quarters  of  an  inch  from  the  left 
border  of  the  sternum.  It,  however,  always  extends  considerably  farther  over 
the  pericardium  than  the  corresponding  lung.  The  lower  limit  of  the  pleura  is  on 
a  considerably  lower  level  than  the  lower  limit  of  the  lung,  but  does  not  extend  to 
the  attachment  of  the  Diaphragm,  so  that  below  the  line  of  reflection  of  the  pleura 
from  the  chest  wall  on  to  the  Diaphragm  the  latter  is  in  direct  contact  with  the 
rib  cartilages  and  the  Internal  intercostal  muscles.  Moreover,  in  ordinary  inspira- 
tion the  thin  margin  of  the  base  of  the  lung  does  not  extend  as  low  as  the  line  of 
pleural  reflection,  with  the  result  that  the  costal  and  diaphragmatic  pleura  are  here 
in  contact,  the  narrow  slit  between  the  two  being  termed  the  phrenico-costal  sinus. 
A  similar  condition  exists  behind  the  sternum  and  rib  cartilages,  where  the  anterior 
thin  margin  of  the  lung  falls  short  of  the  line  of  pleural  reflection,  and  where  the 
slit-like  cavity  between  the  two  layers  of  pleura  forms  what  is  sometimes  called  the 
costo-mediastinal  sinus. 

The  inner  surface  of  the  pleura  is  smooth,  polished,  and  moistened  by  a  serous 
fluid ;  its  outer  surface  is  intimately  adherent  to  the  surface  of  the  lung,  and  to  the 
pulmonary  vessels  as  they  emerge  from  the  pericardium  ;  it  is  also  adherent  to  the 
upper  surface  of  the  Diaphragm  :  throughout  the  rest  of  its  extent  it  is  somewhat 
thicker,  and  may  be  separated  from  the  adjacent  parts  with  extreme  facility. 

The  right  pleural  sac  is  shorter,  wider,  and  reaches  higher  in  the  neck  than 
the  left. 

Vessels  and  Nerves. — The  arteries  of  the  pleura  are  derived  from  the  inter- 
costal, the  internal  mammary,  the  musculo-phrenic,  thymic,  pericardiac,  and 
bronchial.  The  veins  correspond  to  the  arteries.  The  lymphatics  are  very 
numerous.  The  nerves  are  derived  from  the  phrenic  and  sympathetic  (Luschka). 
Kolliker  states  that  nerves  accompany  the  ramification  of  the  bronchial  arteries 
in  the  pleura  pulmonalis. 

Surgical  Anatomy. — In  operations  upon  the  kidney  it  must  be  borne  in  mind  that  the 
pleura  may  sometimes  extend  below  the  level  of  the  last  rib,  and  may  therefore  be  opened  in 
these  operations,  especially  when  the  last  rib  is  removed  in  order  to  give  more  room. 

THE  MEDIASTINUM. 

The  Mediastinum  is  the  space  left  in  the  median  portion  of  the  chest  by  the  non- 
approximation  of  the  two  pleurae.  It  extends  from  the  sternum  in  front  to  the 
spine  behind,  and  contains  all  the  viscera  in  the  thorax  excepting  the  lungs.  The 
mediastinum  may  be  divided  for  pui'poses  of  description  into  two  parts — an 
upper  portion,  above,  the  upper  level  of  the  pericardium,  which  is  named  the 
Superior  mediastinum  (Struthers) ;  and  a  lower  portion,  below  the  upper  level  of 
the  pericardium.  This  lower  portion  is  again  subdivided  into  three — that  part 
which  contains  the  pericardium  and  its  contents,  the  middle  mediastinum  ;  that 
part  which  is  in  front  of  the  pericardium,  the  anterior  mediastinum  ;  and  that 
part  which  is   behind  the  pericardium,   the  posterior  mediastinum. 

The  superior  mediastinum  is  that  portion  of  the  interpleural  space  which  lies 

above  t^e  upper  level  of  the  pericardium,  between  the  manubrium  sterni  in  front  and 

tli a  upper  dorsal  vertebrae  behind.     It  is  bounded  below  by  a  plane  passing  baek- 

Voni  the  junction  of  the  manubrium  and  gladiolus  sterni   to  the  lower  part 

dy  of  the  fourth  dorsal  vertebra,  and  laterally  by  the  lungs  and  pleurae. 

ns  the  origins  of  the   Sternp-hyoid  and  Sterno-thyroid   muscles   and  the 

r  ends  of  the  Longi  colli  muscles  :  the  arch  of  the  aorta  ;  the  innominate,  the 

portion  of  the  left  carotid  and  subclavian  arteries  ;   the  upper  half  of  the 

>'■  vena  cava  and  the  innominate  veins,  and  the  left  superior  intercostal  vein  ; 

umagastric,    cardiac,    phrenic,    and   left   recurrent   laryngeal   nerves;    the 

oesophagus,  and  thoracic  duct ;  the  remains  of  the  thymus  gland  and  some 

tic  glands. 


972 


THE    ORGANS    OF    VOICE   AND    RESPIRATION 


The  anterior  mediastinum  is  bounded  in  front  by  the  sternum,  on  each  side  by 
the  pleura,  and  behind  by  the  pericardium.  It  is  narrow  above,  but  widens  out 
a  little  below,  and,  owing  to  the  oblique  course  taken  by  the  left  pleura,  it  is 
directed  from  above  obliquely  downward  and  to  the  left.  Its  anterior  wall  is 
formed  by  the  left  Triangularis  sterni  muscle  and  the  fifth,  sixth,  and  seventh  left 


Fig.  536. — The  posterior  mediastinum. 

costal  cartilages.  It  contains  a  quantity  of  loose  areolar  tissue,  some  lymphatic 
vessels  which  ascend  from  the  convex  surface  of  the  liver,  two  or  three  lymphatic 
glands  (anterior  mediastinal  glands),  and  the  small  mediastinal  branches  of  the  in- 
ternal mammary  artery. 

The  middle  mediastinum  is  the  broadest  part  of  the  interpleural  space.     It  con- 
tains the  heart  enclosed  in  the  pericardium,  the  ascending  aorta,  the  lower  half  of 


THE   LUNGS. 


973 


the  superior  vena  cava,  with  the  vena  azygos  major  opening  into  it,  the  bifurcation 
of  the  trachea  and  the  two  bronchi,  the  pulmonary  artery  dividing  into  its  two 
branches  and  the  right  and  left  pulmonary  veins,  the  phrenic  nerves,  and  some 
bronchial  lymphatic  glands. 


Left  Inom-     Left  Carotid      Thymus 
inate  Vein.  Artery.  Gland. 


Pneumogastric 

Nerve. 


Pneumogast 


Mammari 
Artery. 


Vertebral 
Artery.--— 
Left  Sublcavian, 
A  rtery. 

(Esophagus.-  - 


2nd  Rib. 


Fig.  537. — Transverse  section  through  the  upper  margin  of  the  third  dorsal  vertebra.    (Braune.) 

The  posterior  mediastinum  (Fig.  536)  is  an  irregular  triangular  space  running 
parallel  with  the  vertebral  column ;  it  is  bounded  in  front  by  the  pericardium  and 
roots  of  the  lungs,  behind  by  the  vertebral  column  from  the  lower  border  of  the 
fourth  dorsal  vertebra,  and  on  either  side  by  the  pleura.  It  contains  the  descend- 
ing thoracic  aorta,  the  greater  and  lesser  azygos  veins,  the  pneumogastric  and 
splanchnic  nerves,  the  oesophagus,  thoracic  duct,  and  some  lymphatic  glands\  A^. 


THE   LUNGS. 

The  Lungs  are  the  essential  organs  of  respiration ;  they  are  two  in  number, 
placed  one  on  each  side  of  the  chest,  separated  from  each  other  by  the  heart  and 
other  contents  of  the  mediastinum.  Each  lung  is  conical  in  shape,  and  presents 
for  examination  an  apex,  a  base,  two  borders,  and  two  surfaces  (Fig.  538). 

The  apex  forms  a  tapering  cone  which  extends  into  the  root  of  the  neck  about 
an  inch  to  an  inch  and  a  half  above  the  level  of  the  first  rib. 

The  base  is  broad,  concave,  and  rests  upon  the  convex  surface  of  the  Dia- 
phragm, which  separates  the  right  lung  from  the  upper  surface  of  the  right  lobe  of 
the  liver  and  the  left  lung  from  the  upper  surface  of  the  left  lobe  of  the  liver,  the 
stomach,  and  spleen;  its  circumference  is  thin,  and  projects  for  some  distance  into 
the  phrenico-costal  sinus  of  the  pleura,  between  the  lower  ribs  and  the  costal 
attachment  of  the  Diaphragm,  extending  lower  down  externally  and  behind  than  in 
front. 

The  external  or  thoracic  surface  :'s  smooth,  convex,  of  considerable  extent, 
and  corresponds  to  the  form  of  the  cavity  of  the.ebest.  being  deeper  behind  than 
in  front.  _,  dictations  become  n,.  . 

The  inner  surface  is  concave.      It  r**t  it  loses  its  cylindrical  charaette£8Dondinpr 


974 


THE    ORGANS    OF    VOICE   AND    RESPIRATION. 


to  the  convex  surface  of  the  pericardium,  and  behind  a  deep  fissure  (the  hilum 
pulmonis)  which  gives  attachment  to  the  root  of  the  lung. 

The  -posterior  border  is  rounded  and  broad,  and  is  received  into  the  deep  con- 
cavity on  either  side  of  the  spinal  column.  It  is  much  longer  than  the  anterior 
border,  and  projects,  below,  into  the  phrenico-costal  sinus. 

The  anterior  border  is  thin  and  sharp,  overlaps  the  front  of  the  pericardium, 
and  is    projected  into   the  costo-mediastinal  sinus  of   the    pleura.      The  anterior 


Fig.  538.— Front  view  of  the  heart  and  lungs. 


border  of  the  right  lung  is  almost  vertical ;  that  of  the  left  presents,  below,  an 
angular  notch,  the  ineisura  cardiaca,  into  which  the  heart  and  pericardium  are 
received. 

Each  lung  is  divided  into  two  lobes,  an  upper  and  a  lower,  by  a  long  and  deep 
fissure,  which  extends  from  the  upper  part  of  the  posterior  border  of  the  organ 
about  three  inches  from  its  apex,  downward  and  forward  to  the  lower  part  of  its 
anterior  border.  This  fissure  penetrates  nearly  to  the  root.  In  the  right  lung  the 
upper  lobe  is  partially  subdivided  by  a  second  and  shorter  fissure,  which  extends 
almost  horizontally  forward  from  the  middle  of  the  preceding  to  the  anterior  mar- 
gin of  the  organ,  marking  off  a  small  triangular  portion,  the  middle  lobe. 

The  right  lung  is  the  larger  and  heavier ;  it  is  broader  than  the  left,  owing  to 
the  inclination  of  the  heart  to  the  left  side  ;  it  is  also  shorter  by  an  inch,  in  conse- 
quence of  the  Diaphragm  rising  higher  on  the  right  side  to  accommodate  the  liver. 

The  Root  of  the  Lungs. — A  little  above  the  middle  of  the  inner  surface  of  each 

lung,  and  nearer  its  posterior   than  its  anvjrior  border,  is  its   root,  by  which  the 

lung  is  connected  to  the  heart  and  the  trachea.      The  root  is  formed  by  the  bronchial 

tube,  the  puln^^cliastinum  is  the  broa>vPDaiT  veins,  the  bronchial  arteries  and  veins, 

ttJ-hepulnii^art  enclosed  in  the  pericardium';^  bronchial  glands,  and  areolar  tissue,  all 

*wh"  deura.     The  root  of  the  right  lunar  lies 


y 


i ' 


THE   LUNGS.  975 

behind  the  superior  vena  cava  and  ascending  portion  of  the  aorta  and  below  the 
vena  azygos  major.  That  of  the  left  lung  passes  beneath  the  arch  of  the  aorta  and 
in  front  of  the  descending  aorta;  the  phrenic  nerve  and  the  anterior  pulmonary 
plexus  lie  in  front  of  each,  and  the  pneumogastric  and  posterior  pulmonary  plexus 
behind  each. 

The  chief  structures  composing  the  root  of  each  lung  are  arranged  in  a  similar 
manner  from  before  backward  on  both  sides — viz.,  the  two  pulmonary  veins  in 
front ;  the  pulmonary  artery  in  the  middle  ;  and  the  bronchus,  together  with  the 
bronchial  vessels,  behind.  From  above  downward,  on  the  two  sides,  their  arrange- 
ment differs,  thus : 

On  the  right  side  their  position  is — bronchus,  pulmonary  artery,  pulmonary 
veins ;  but  on  the  left  side  their  position  is — pulmonary  artery,  bronchus,  pulmo- 
nary veins.  It  should  be  noted  that  the  entire  right  bronchus  does  not  lie  above 
the  right  pulmonary  artery,  but  only  its  eparterial  branch  (see  page  966),  which 
passes  to  the  upper  lobe  of  the  right  lung  ;  the  divisions  of  the  bronchus  for  the 
middle  and  lower  lobes  lie  below  the  artery. 

The  weight  of  both  lungs  together  is  about  forty-two  ounces,  the  right  lung 
being  two  ounces  heavier  than  the  left ;  but  much  variation  is  met  with  according 
to  the  amount  of  blood  or  serous  fluid  they  may  contain.  The  lungs  are  heavier 
in  the  male  than  in  the  female,  their  proportion  to  the  body  being  in  the  former 
as  1  to  37,  in  the  latter  as  1  to  43.  The  specific  gravity  of  the  lung-tissue  varies 
from  0.345  to  0.746,  water  being  1000. 

The  color  of  the  lungs  at  birth  is  a  pinkish-white ;  in  adult  life  a  dark 
slate-color,  mottled  in  patches ;  and  as  age  advances  this  mottling  assumes  a 
black  color.  The  coloring  matter  consists  of  granules  of  a  carbonaceous  substance 
deposited  in  the  areolar  tissue  near  the  surface  of  the  organ.  It  increases  in 
quantity  as  age  advances,  and  is  more  abundant  in  males  than  in  females.  The 
posterior  border  of  the  lung  is  usually  darker  than  the  anterior. 

The  surface  of  the  lung  is  smooth,  shining,  and  marked  out  into  numerous 
polyhedral  spaces,  indicating  the  lobules  of  the  organ ;  the  area  of  each  of  these 
spaces  is  crossed  by  numerous  lighter  lines. 

The  substance  of  the  lung  is  of  a  light,  porous,  spongy  texture ;  it  floats  in 
water  and  crepitates  when  handled,  owing  to  the  presence  of  air  in  the  tissue ;  it 
is  also  highly  elastic ;  hence  the  collapsed  state  of  these  organs  when  they  are 
removed  from  the  closed  cavity  of  the  thorax. 

Structure. — The  lungs  are  composed  of  an  external  serous  coat,  a  subserous 
areolar  tissue,  and  the  pulmonary  substance  or  parenchyma. 

The  serous  coat  is  derived  from  the  pleura ;  it  is  thin,  transparent,  and  invests 
the  entire  organ  as  far  as  the  root. 

The  subserous  areolar  tissue  contains  a  large  proportion  of  elastic  fibres ;  it 
invests  the  entire  surface  of  the  lung,  and  extends  inward  between  the  lobules. 

The  parenchyma  is  composed  of  lobules  which,  although  closely  connected 
together  by  an  interlobular  areolar  tissue,  are  quite  distinct  from  one  another,  and 
may  be  teased  asunder  without  much  difficulty  in  the  foetus.  The  lobules  vary  in 
size ;  those  on  the  surface  are  large,  of  pyramidal  form,  the  base  turned  toward 
the  surface ;  those  in  the  interior,  smaller  and  of  various  forms.  Each  lobule  i- 
composed  of  one  of  the  ramifications  of  a  bronchial  tube  and  its  terminal  air-cells, 
and  of  the  ramifications  of  the  pulmonary  and  bronchial  vessels,  lymphatics,  and 
nerves,  all  of  these  structures  being  connected  together  by  areolar  tissue. 

The  bronchus,  upon  entei'ing  the  substance  of  the  lung,  divides  and  subdivides 
bipinnatcly,  throughout  the  entire  organ.  Sometimes  three  branches  arise  together, 
and  occasionally  small  lateral  branches  are  given  off  from  the  sides  of  a  main 
trunk.  Each  of  the  smaller  subdivisions  of  the  bronchi  enters  a  pulmonary  lobule, 
tand  is  termed  a  lobular  bronchial  tube  or  bronchiole.  Its  wall  now  begins  to  pre- 
sent irregular  dilatations,  air-cells  or  alveoli,  at  first  sparingly  and  on  one  side  of 
tube  only,  but  as  it  proceeds  onward  these  dilatations  become  more  numerous 
and  surround  the  tube  on  all  sides,  so  that  it  loses  its  cylindrical  character.      The 


976  THE   ORGANS  OF    VOICE  AND   RESPIRATION. 

bronchiole  now  becomes  enlarged,  and  is  termed  the  atrium  or  alveolar  passage  ; 
from  it  are  given  off,  on  all  sides,  ramifications,  called  infundibula,  which  are 
closely  beset  in  all  directions  by  alveoli  or  air-cells.  Within  the  lungs  the  bron- 
chial tubes  are  circular,  not  flattened,  and  present  certain  peculiarities  of  structure. 

Changes  in  the  Structure  of  the  Bronchi  in  the  Lungs. — 1.  In  the  Lobes  of  the 
Lungs. — In  the  lobes  of  the  lungs  the  following  changes  take  place.  The  cartilages 
are  not  imperfect  rings,  but  consist  of  thin  laminae,  of  varied  form  and  size,  scat- 
tered irregularly  along  the  sides  of  the  tube,  being  most  distinct  at  the  points  of 
division  of  the  bronchi.  They  may  be  traced  into  tubes,  the  diameter  of  which  is 
only  one-fourth  of  a  line.  Beyond  this  point  the  tubes  are  wholly  membranous. 
The  fibrous  coat  is  continued  into  the  smallest  ramifications  of  the  bronchi.  The 
muscular  coat  is  disposed  in  the  form  of  a  continuous  layer  of  annular  fibres, 
which  may  be  traced  upon  the  smallest  bronchial  tubes,  and  consists  of  the 
unstriped  variety  of  muscular  tissue.  The  mucous  membrane  lines  the  bronchi 
and  its  ramifications  throughout,  and  is  covered  with  columnar  ciliated  epithelium. 

In  the  Lobules  of  the  Lung. — In  the  lobular  bronchial  tubes  and  in  the 
infundibula  the  following  changes  take  place :  The  muscular  tissue  begins  to  dis- 
appear, so  that  in  the  infundibula  there  is  scarcely  a  trace  of  it.  The  fibrous  coat 
becomes  thinner,  and  degenerates  into  areolar  tissue.  The  epithelium  becomes 
non-ciliated  and  flattened.  This  occurs  gradually  ;  thus,  in  the  lobular  bronchioles 
patches  of  non-ciliated  flattened  epithelium  may  be  found  scattered  among  the 
columnar  ciliated  epithelium  ;  then  these  patches  of  non-ciliated  flattened  epithe- 
lium become  more  and  more  numerous,  until  in  the  infundibula  and  air-cells  all 
the  epithelium  is  of  the  non-ciliated  pavement  variety.  In  addition  to  these  flat- 
tened cells,  there  are  small  polygonal  granular  cells  in  the  air-sacs,  in  clusters  of 
two  or  three,  between  the  others. 

The  air-cells  are  small,  polyhedral  recesses  composed  of  a  fibrillated  connec- 
tive tissue  and  surrounded  by  a  few  involuntary  muscular  and  elastic  fibres.  Free 
in  their  cavity  are  to  be  seen  under  the  microscope  granular,  rounded,  amoeboid 
cells  (eosinophile  leucocytes),  often  containing  carbonaceous  particles.  The  air- 
cells  are  well  seen  on  the  surface  of  the  lung,  and  vary  from  -j-g-g-th  to  ^th  of  an 
inch  in  diameter,  being  largest  on  the  surface  at  the  thin  borders  and  at  the  apex, 
and  smallest  in  the  interior. 

The  pulmonary  artery  conveys  the  venous  blood  to  the  lungs ;  it  divides  into 
branches  which  accompany  the  bronchial  tubes,  and  terminates  in  a  dense  capillary 
network  upon  the  walls  of  the  intercellular  passages  and  air-cells.  In  the  lung  the 
branches  of  the  pulmonary  artery  are  usually  above  and  in  front  of  a  bronchial 
tube,  the  vein  below. 

The  pulmonary  capillaries  form  plexuses  which  lie  immediately  beneath  the 
mucous  membrane  in  the  walls  and  septa  of  the  air-cells  and  of  the  infundibula. 
In  the  septa  between  the  air-cells  the  capillary  network  forms  a  single  layer.  The 
capillaries  form  a  very  minute  network,  the  meshes  of  which  are  smaller  than  the 
vessels  themselves  ; 1  their  walls  are  also  exceedingly  thin.  The  arteries  of  neigh- 
boring lobules  are  independent  of  each  other,  but  the  veins  freely  anastomose 
together. 

The  pulmonary  veins  commence  in  the  pulmonary  capillaries,  the  radicles 
coalescing  into  larger  branches,  which  run  along  through  the  substance  of  the 
lung,  independently  from  the  minute  arteries  and  bronchi.  After  freely  com- 
municating with  other  branches  they  form  large  vessels,  which  ultimately  come 
into  relation  with  the  arteries  and  bronchial  tubes,  and  accompany  them  to  the 
hilum  of  the  organ.  Finally  they  open  into  the  left  auricle  of  the  heart,  con- 
veying oxygenated  blood  to  be  eventually  distributed  to  all  parts  of  the  body 
by  the  aorta. 

The  bronchial  arteries  supply  blood  for  the  nutrition  of  the  lung ;  they  are 
derived  from  the  thoracic  aorta  or  from  the  upper  aortic  intercostal  arteries,  and, 

/The  meshes  are  only  0.002///  to  0.008"' in  width,  while  the  vessels  are  0.003"'  to  0.005"' 
(Kolliker,  Human  Microscopic  Anatomy). 


THE   LUNGS.  977 

accompanying  the  bronchial  tubes,  are  distributed  to  the  bronchial  glands,  and 
upon  the  walls  of  the  larger  bronchial  tubes  and  pulmonary  vessels.  Those  sup- 
plying the  bronchial  tubes  form  a  capillary  plexus  in  the  muscular  coat,  from 
which  branches  are  given  off  to  form  a  second  plexus  in  the  mucous  coat.  This 
plexus  communicates  with  branches  of  the  pulmonary  artery,  and  empties  itself 
into  the  pulmonary  vein.  Others  are  distributed  in  the  interlobular  areolar  tissue, 
and  terminate  partly  in  the  deep,  partly  in  the  superficial,  bronchial  veins.  Lastly, 
some  ramify  upon  the  surface  of  the  lung  beneath  the  pleura,  where  they  form  a 
capillary  network. 

The  bronchial  vein  is  formed  at  the  root  of  the  lung,  receiving  superficial  and 
deep  veins  corresponding  to  branches  of  the  bronchial  artery.  It  does  not,  how- 
ever, receive  all  the  blood  supplied  by  the  artery,  as  some  of  it  passes  into  the 
pulmonary  vein.  It  terminates  on  the  right  side  in  the  vena  azygos  major,  and 
on  the  left  side  in  the  superior  intercostal  or  left  upper  azygos  vein. 

The  lymphatics  consist  of  a  superficial  and  deep  set :  they  terminate  at  the 
root  of  the  lung,  in  the  bronchial  glands. 

Nerves. — The  lungs  are  supplied  from  the  anterior  and  posterior  pulmonary 
plexuses,  formed  chiefly  by  branches  from  the  sympathetic  and  pneumogastric. 
The  filaments  from  these  plexuses  accompany  the  bronchial  tubes,  upon  which 
they  are  lost.      Small  ganglia  are  found  upon  these  nerves. 

Surface  Form. — The  apex  of  the  lung  is  situated  in  the  neck,  behind  the  interval  between 
the  two  heads  of  origin  of  the  Sterno-mastoid.  The  height  to  which  it  rises  above  the  clavicle 
varies  very  considerably,  but  is  generally  about  one  inch.  It  may,  however,  extend  as  much  as 
an  inch  and  a  half  or  an  inch  and  three-quarters,  or,  on  the  other  hand,  it  may  scarcely  project 
above  the  level  of  this  bone.  In  order  to  mark  out  the  anterior  margin  of  the  lung,  a  line  is 
to  be  drawn  from  the  apex-point,  one  inch  above  the  level  of  the  clavicle,  and  rather  nearer  the 
posterior  than  the  anterior  border  of  the  Sterno-mastoid  muscle,  downward  and  inward  across 
the  ster no- clavicular  articulation  and  first  piece  of  the  sternum  until  it  meets,  or  almost  meets, 
its  fellow  of  the  other  side  opposite  the  articulation  of  the  manubrium  and  gladiolus.  From  this 
point  the  two  lines  are  to  be  drawn  downward,  one  on  either  side  of  the  mesial  line  and  close  to 
it,  as  far  as  the  level  of  the  articulation  of  the  fourth  costal  cartilages  to  the  sternum.  From 
here  the  two  lines  diverge  ;  the  left  is  to  be  drawn  at  first  passing  outward  with  a  slight  inclina- 
tion downward,  and  then  taking  a  bend  downward  with  a  slight  inclination  outward  to  the  apex 
of  the  heart,  and  thence  to  the  sixth  costo-chondral  articulation.  The  direction  of  the  anterior 
border  of  this  part  of  the  left  lung  is  denoted  with  sufficient  accuracy  by  a  curved  line  with  its 
convexity  directed  upward  and  outward  from  the  articulation  of  the  fourth  right  costal  cartilage 
of  the  sternum  to  the  fifth  intercostal  space,  an  inch  and  a  half  below  and  three-quarters  of  an 
inch  internal  to  the  left  nipple.  The  continuation  of  the  anterior  border  of  the  right  lung  is 
marked  by  a  prolongation  of  its  line  from  the  level  of  the  fourth  costal  cartilages  vertically 
downward  as  far  as  the  sixth,  when  it  slopes  off  along  the  line  of  the  sixth  costal  cartilage  to  its 
articulation  with  the  rib. 

The  lower  border  of  the  lung  is  marked  out  by  a  slightly  curved  line  with  its  convexity  down- 
ward from  the  articulation  of  the  sixth  costal  cartilage  to  its  rib  to  the  spinous  process  of  the 
tenth  dorsal  vertebra.  If  vertical  lines  are  drawn  downward  from  the  nipple,  the  mid-axillary 
line,  and  the  apex  of  the  scapula,  while  the  arms  are  raised  from  the  sides,  they  should  intersect 
this  convex  line,  the  first  at  the  sixth,  the-  second  at  the  eighth,  and  the  third  at  the  tenth  rib. 
It  will  thus  be  seen  that  the  pleura  (see  page  971)  extends  farther  down  than  the  lung,  so  that 
it  may  be  wounded,  and  a  wound  pass  through  its  cavity  into  the  Diaphragm,  and  even  injure 
the  abdominal  viscera,  without  the  lung  being  involved. 

The  posterior  border  of  the  lung  is  indicated  by  a  line  drawn  from  the  level  of  the  spinous 
process. of  the  seventh  cervical  vertebra,  down  either  side  of  the  spine,  corresponding  to  the 
costo-vertebral  joints  as  low  as  the  spinous  process  of  the  tenth  dorsal  vertebra.  The  trachea 
bifurcates  opposite  the  spinous  process  of  the  fourth  dorsal  vertebra,  and  from  this  point  the  two 
bronchi  are  directed  outward. 

The  position  of  the  great  fissure  in  the  right  lung  may  be  indicated  by  a  line  drawn  from 
the  fourth  dorsal  vertebra  round  the  side  of  the  chest  to  the  anterior  margin  of  the  lung  opposite 
the  seventh  rib,  and  the  smaller  or  secondary  fissure  by  a  line  drawn  from  the  preceding  where 
it  bisects  the  mid-axillary  line  to  the  junction  of  the  fourth  costal  cartilage  to  the  sternum.  The 
i  ,f  fissure  in  the  left  lung  is  a  little  higher,  extending  from  the  third  dorsal  vertebra  round  the 
i  'best  to  reach  the  anterior  margin  of  the  lung  opposite  the  sixth  costal  cartilage. 

il  Anatomy. — The  lungs  may  be  wounded  or  torn  in  three  ways  :  (1)  By  compres- 
chest,  without  any  injury  to  the  ribs.  (2)  By  a  fractured  rib  penetrating  the  lung. 
is,  irunshot  wounds,  etc. 

rst  form,  where  the  lung  is  ruptured  by  external  compression  without  any  fracture 
ribs,  is  very  rare,  and  usually  occurs  in  young  children,  and  affects  the  root  of  the  lung — 


978 


THE    ORGANS    OF    VOICE   AND    RESPIRATION. 


i.e.,  the  most  fixed  part — and  thus,  implicating  the  great  vessels,  is  frequently  fatal.  It  would 
seem  a  priori  a  most  unusual  injury,  and  its  exact  mode  of  causation  is  difficult  to  interpret. 
The  probable  explanation  is  that  immediately  before  the  compression  is  applied  a  deep  inspira- 
tion is  taken  and  the  lungs  are  fully  inflated  ;   owing  then  to  spasm  of  the  glottis  at  the  moment 


Recur, 
lar.  nerve' 


\ 
Palm. " 


Great 
coron.  vein 


Epart. 

.bronchu 


Foramen  for 
oesophagus 

Fig.  539.— Thoracic  contents  seen  from  behind.    (Joessel.) 

of  compression,  the  air  is  unable  to  escape  from  the  lung,  which  is  not  able  to  recede,  and  con- 
sequently gives  way.  - 

In  the  second  variety,  when  the  wound  in  the  lung  is  produced  by  the  penetration  of  a 
broken  rib,  both  the  pleura  costalis  and  pulmonalis  must  necessarily  be  injured,  and  consequently 
the  air  taken  into  the  wounded  air-cells  may  find  its  way  through  these  wounds  into  the  cellular 


THE    THYROID    GLAND.  979 

tissue  of  the  parietes  of  the  chest.  This  it  may  do  without  collecting  in  the  pleural  cavity ; 
the  two  layers  of  the  pleura  are  so  intimately  in  contact  that  the  air  passes  straight  through 
from  the  wounded  lung  into  the  subcutaneous  tissue.  Emphysema  constitutes,  therefore,  the 
most  important  sign  of  injury  to  the  lung  in  cases  of  fracture  of  the  ribs.  Pneumothorax,  or 
air  in  the  pleural  cavity,  is  much  more  likely  to  occur  in  injuries  to  the  lung  of  the  third  variety  ; 
that  is  to  say,  from  external  wounds,  from  stabs,  gunshot  injuries,  and  such  like,  in  which  cases 
air  passes  either  from  the  wound  of  the  lung  or  from  an  external  wound  into  the  cavity  of  the 
pleura  during  the  respiratory  movements.  In  these  cases  there  is  generally  no  emphysema  of 
the  subcutaneous  tissue  unless  the  external  wound  is  small  and  valvular,  so  that  the  air  drawn 
into  the  wound  during  inspiration  is  then  forced  into  the  cellular  tissue  around  during  expiration 
because  it  cannot  escape  from  the  external  wound.  Occasionally  in  wounds  of  the  parietes  of 
the  chest  no  air  finds  its  way  into  the  cavity  of  the  pleura,  because  the  lung  at  the  time  of  the 
accident  protrudes  through  the  wound  and  blocks  the  opening.  This  occurs  where  the  wound 
is  large,  and  constitutes  one  form  of  hernia  of  the  lung.  Another  form  of  hernia  of  the  lung 
occurs,  though  very  rarely,  after  wounds  of  the  chest  wall,  when  the  wound  has  healed  and  the 
cicatrix  subsequently  yields  from  the  pressure  of  the  viscus  behind.  It  forms  a  globular,  elastic, 
crepitating  swelling,  which  enlarges  during  expiratory  efforts,  falls  in  during  inspiration,  and 
disappears  on  holding  the  breath. 

THE    THYROID    GLAND. 

The  thyroid  gland  is  classified  with  the  thymus,  suprarenal  capsules,  and  spleen, 
under  the  head  of  ductless  glands — i.  e.,  glands  which  do  not  possess  an  excretory 
duct.  From  its  situation  in  connection  with  the  trachea  and  larynx,  the  thyroid 
body  is  usually  described  with  those  organs,  although  it  takes  no  part  in  the  func- 
tion of  respiration.  It  is  situated  at  the  front  and  sides  of  the  neck,  and  consists 
of  two  lateral  lobes  connected  across  the  middle  line  by  a  narrow  transverse 
portion,  the  isthmus. 

The  weight  of  the  gland  is  somewhat  variable,  but  is  usually  about  one  ounce. 
It  is  somewhat  heavier  in  the  female,  in  whom  it  becomes  enlarged  during  men- 
struation and  pregnancy. 

The  lobes  are  conical  in  shape,  the  apex  of  each  being  directed  upward  and 
outward  as  far  as  the  junction  of  the  middle  with  the  lower  third  of  the  thyroid 
cartilage  ;  the  base  looks  downward,  and  is  on  a  level  with  the  fifth  or  sixth  tracheal 
ring. 

The  external  or  superficial  surface  is  convex,  and  covered  by  the  skin,  the 
superficial  and  deep  fascia,  the  Sterno-mastoid,  the  anterior  belly  of  the  Omo- 
hyoid, the  Sterno-hyoid  and  Sterno-thyroid  muscles,  and  beneath  the  last  muscle 
by  the  pre-tracheal  layer  of  the  deep  fascia,  which  forms  a  capsule  for  the  gland. 

The  deep  or  internal  surface  is  moulded  over  the  underlying  structures,  viz., 
the  thyroid  and  cricoid  cartilages,  the  trachea,  the  inferior  constrictor  and  posterior 
part  of  the  Crico-thyroid  muscles,  the  oesophagus  (particularly  on  the  left  side  of 
the  neck),  the  superior  and  inferior  thyroid  arteries,  and  the  recurrent  laryngeal 
nerves. 

Its  anterior  border  is  thin,  and  inclines  obliquely  from  above  downward  and 
inward  toward  the  middle  line  of  the  neck,  while  the  posterior  border  is  thick  and 
overlaps  the  common  carotid  artery.  Each  lobe  is  about  two  inches  in  length,  its 
greatest  width  is  about  one  inch  and  a  quarter,  and  its  thickness  about  three 
quartet's  of  an  inch. 

The  isthmus  connects  the  lower  third  of  the  two  lateral  lobes ;  it  measures 
about  half  an  inch  in  breadth  and  the  same  in  depth,  and  usually  covers  the 
second  and  third  rings  of  the  trachea.  Its  situation  presents,  however,  many 
variations,  a  point  of  importance  in  the  operation  of  tracheotomy.  In  the  middle 
line  of  the  neck  it  is  covered  by  the  skin  and  fascia,  and  close  to  the  middle  line, 
on  either  side,  by  the  Sterno-hyoid.  Across  its  upper  border  runs  a  branch  of 
the  superior  thyroid  artery ;  at  its  lower  border  are  the  inferior  thyroid  veins. 
Sometimes  the  isthmus  is  altogether  wanting. 

A  third  lobe,  of  conical  shape,  called  the  pyramid,  occasionally  arises  from  the 
upper  part  of  the  isthmus,  or  from  the  adjacent  portion  of  either  lobe,  but  most 
commonly  the  left,  and  ascends  as  high  as  the  hyoid  bone.  It  is  occasionally 
quite  detached,  or  divided  into  two  or  more  parts,  or  altogether  wanting. 


980 


THE    ORGANS    OF    VOICE  AND    RESPIRATION. 


A  few  muscular  bands  are  occasionally  found  attached,  above,  to  the  body  of 
the  hyoid  bone,  and  below  to  the  isthmus  of  the  gland  or  its  pyramidal  process. 
These  form  a  muscle,  which  was  named  by  Sommerring  the  Levator  glandulce 
thyroidal. 

Small  detached  portions  of  thyroid  tissue  {accessory  thyroid)  are  sometimes 
found  above  the  isthmus,  and  their  presence  is  readily  explained  by  a  reference  to 
the  manner  in  which  the  gland  is  developed.  They  represent  isolated  portions  of 
the  median  thyroid  rudiment.     (See  section  on  Embryology.) 

Structure. — The  thyroid  body  is  invested  by  a  thin  capsule  of  connective  tissue 
which  projects  into  its  substance  and  imperfectly  divides  it  into  masses  of  irregular 
form  and  size.  When  the  organ  is  cut  into,  it  is  of  a  brownish-red  color,  and  is 
seen  to  be  made  up  of  a  number  of  closed  vesicles  containing  a  yellow  glairy  fluid 
and  separated  from  each  other  by  intermediate  connective  tissue. 

According  to  Baber,  who  has  published  some  important  observations  on 
the  minute  structure  of  the  thyroid,1  the  vesicles  of  the  thyroid  of  the  adult 
animal  are  generally  closed  cavities ;   but   in  some  young  animals  (e.  g.,  young 


Vesicle. 


Lymphatic  vessel 


Wall  of  gland-vesicle 

Fig.  540. — Minute  structure  of  thyroid 
matic.)    (Baber.) 


From  a  transverse  section  of  the  thyroid  of  a  dog.    (Serni-diagram- 


dogs)  the  vesicles  are  more  or  less  tubular  -ancL  branched.  This  appearance  he 
supposes  to  be  due  to  the  mode  of  growth  of  the  gland,  and  merely  indicating  that 
an  increase  in  the  number  of  vesicles  is  taking  place.  Each  vesicle  is  lined  by  a 
single  layer  of  epithelium,  the  cells  of  which,  though  differing  somewhat  in  shape 
in  different  animals,  have  always  a  tendency  to  assume  a  columnar  form.  Between 
the  epithelial  cells  exists  a  delicate  reticulum.  The  vesicles  are  of  various  sizes 
and  shapes,  and  contain  as  a  normal  product  a  viscid,  homogeneous,  semi-fluid, 
slightly  yellowish  material  which  frequently  contains  blood,  the  red  corpuscles 
of  which  are  found  in  it  in  various  stages  of  disintegration  and  decolorization,  the 
yellow  tinge  being  probably  due  to  the  haemoglobin,  which  is  thus  set  free  from 
the  colored  corpuscles.  Baber  has  also  described  in  the  thyroid  gland  of  the 
dog  large  round  cells  ("  parenchymatous  cells  "),  each  provided  with  a  single  oval- 
shaped  nucleus,  which  migrate  into  the  interior  of  the  gland-vesicles. 

The  capillary  blood-vessels  form  a  dense  plexus  in  the  connective  tissue  around 
the  vesicles,  between  the  epithelium  of  the  vesicles  and  the  endothelium  of  the 
lymph-spaces,  which  latter  surround  a  greater  or  smaller  part  of  the  circumference 
of  the  vesicle.  These  lymph-spaces  empty  themselves  into  lymphatic  vessels 
which  run  in  the  interlobular  connective  tissue,  not  uncommonly  surrounding  the 
1  "Researches  on  the  Minute  Structure  of  the  Thyroid  Glands,"  Phil.  Trans.,  part  iii.,  1881. 


THE    THYMUS    GLAND.  981 

arteries  which  they  accompany,  and  communicates  with  a  network  in  the  capsule 
of  the  gland.  Baber  has  found  in  the  lymphatics  of  the  thyroid  a  viscid  material 
which  is  morphologically  identical  with  the  normal  constituent  of  the  vesicle. 

Vessels  and  Nerves. — The  arteries  supplying  the  thyroid  are  the  superior  and 
inferior  thyroid,  and  sometimes  an  additional  branch  (thyroidea  media  or  ima) 
from  the  innominate  artery  or  the  arch  of  the  aorta,  which  ascends  upon  the 
front  of  the  trachea.  The  arteries  are  remarkable  for  their  large  size  and  frequent 
anastomoses.  The  veins  form  a  plexus  on  the  surface  of  the  gland  and  on  the 
front  of  the  trachea,  from  which  arise  the  superior,  middle,  and  inferior  thyroid 
veins,  the  two  former  terminating  in  the  internal  jugular,  the  latter  in  the  innom- 
inate vein.  The  lymphatics  are  numerous,  of  large  size,  and  terminate  in  the 
thoracic  and  right  lymphatic  ducts.  The  nerves  are  derived  from  the  middle  and 
inferior  cervical  ganglia  of  the  sympathetic. 

Surgical  Anatomy. — The  thyroid  gland  is  subject  to  enlargement,  which  is  called  goitre. 
This  may  be  due  to  hypertrophy  of  any  of  the  constituents  of  the  gland.  The  simplest 
(parenchymatous  goitre)  is  due  to  an  enlargement  of  the  follicles.  The  fibroid  is  due  to  increase 
of  the  interstitial  connective  tissue.  The  cystic  is  that  form  in  which  one  or  more  large  cysts* 
are  formed  from  dilatation  and  possibly  coalescence  of  adjacent  follicles.  The  pulsating  goitre  is 
where  the  vascular  changes  predominate  over  the  parenchymatous,  and  the  vessels  of  the 
gland  are  especially  enlarged.  Finally,  there  is  exophthalmic  goitre  (Graves's  disease),  where 
there  is  great  vascularity  and  often  pulsation,  accompanied  by  exophthalmos,  palpitation,  and 
rapid  pulse. 

For  the  relief  of  these  growths  various  operations  have  been  resorted  to,  such  as  injection 
of  tincture  of  iodine  or  perchloride  of  iron,  especially  applicable  to  the  cystic  form  of  the  disease, 
ligature  of  the  thyroid  arteries,  excision  of  the  isthmus,  and  extirpation  of  the  whole  or  a  part 
of  the  gland.  This  latter  operation  is  one  of  difficulty,  and  when  the  entire  gland  has  been 
removed  the  operation  has  been  followed  by  a  condition  resembling  myxcedema.  In  removing 
the  organ  great  care  must  be  taken  to  avoid  tearing  the  capsule,  as  if  this  happens  the  gland- 
tissue  bleeds  profusely.  The  thyroid  arteries  should  be  ligatured  before  an  attempt  is  made  to 
remove  the  mass,  and  in  ligaturing  the  inferior  thyroids  the  position  of  the  recurrent  laryngeal 
nerve  must  be  borne  in  mind,  so  as  not  to  include  it  in  the  ligature.  A  large  number  of  cases 
of  what  were  formerly  supposed  to  be  goitre  are  now  known  to  be  cases  of  adenomatous  enlarge- 
ment, where  an  adenoma,  starting  in  one  part  of  the  gland,  gradually  spreads  and  involves  the 
whole  organ. 

Parathyroids. — These  are  small  rounded,  brownish-red  bodies,  with  an  average 
diameter  of  about  a  quarter  of  an  inch,  situated  in  or  near  the  thyroid  gland,  from 
which,  however,  they  differ  in  structure,  being  composed  of  masses  of  cells  arranged 
in  a  more  or  less  columnar  fashion  with  numerous  intervening  capillaries.  They 
are  divided  from  their  situation  into  external  and  internal.  The  former,  usually 
two  in  number,  are  situated,  one  on  each  side,  in  relation  to  the  postero-internal 
surface  of  the  lateral  lobe ;  sometimes  they  are  duplicated.  The  latter,  also 
usually  two  in  number,  are  placed  one  in  each  lateral  lobe,  generally  near  its  mesial 
surface. 

THE  THYMUS  GLANDS. 

The  thymus  gland  is  a  temporary  organ,  attaining  its  full  size  at  the  end  of  the 
second  year,  when  it  ceases  to  grow,  and  gradually  dwindles,  until  at  puberty  it 
has  almost  disappeared.  If  examined  when  its  growth  is  most  active,  it  will  be 
found  to  consist  of  two  lateral  lobes  placed  in  close  contact  along  the  middle  line, 
situated  partly  in  the  superior  mediastinum,  partly  in  the  neck,  and  extending 
from  the  fourth  costal  cartilage  upward  as  high  as  the  lower  border  of  the 
thyroid  gland.  It  is  covered  by  the  sternum  and  by  the  origins  of  the  Sterno- 
hyoid and  Sterno-thyroid  muscles.  Below,  it  rests  upon  the  pericardium,  being 
separated  from  the  arch  of  the  aorta  and  great  vessels  by  a  layer  of  fascia.  In 
the  neck  it  lies  on  the  front  and  sides  of  the  trachea,  behind  the  Sterno-hyoid 
and  Sterno-thyroid  muscles.  The  two  lobes  generally  differ  in  size;  they  are 
occasionally  united  so  as  to  form  a  single  mass,  and  sometimes  separated  by  an 
intermediate  lobe.  The  thymus  is  of  a  pinkish-gray  color,  soft,  and  lobulated  on  its 
surfaces.  It  is  about  two  inches  in  length,  one  and  a  half  in  breadth  below,  and 
about  three  or  four  lines  in  thickness.     At  birth  it  weighs  about  half  an  ounce. 


982 


THE    ORGANS    OF    VOICE   AND    RESPIRATION 


Structure. — Each  lateral  lobe  is  composed  of  numerous  lobules  held  together 
by  delicate  areolar  tissue,  the  entire  gland  being  enclosed  in  an  investing  capsule 
of  a  similar  but  denser  structure.  The  primary  lobules  vary  in  size  from  a  pin's 
head  to  a  small  pea,  and  are  made  up  of  a  number  of  small  nodules  or  follicles 
which  are  irregular  in  shape  and  are  more  or  less  fused  together,  especially 
toward  the  interior  of  the  gland.  Each  follicle  consists  of  a  medullary  and  corti- 
cal portion,  which  differ  in  many  essential  particulars  from  each  other.  The  corti- 
cal portion  is  mainly  composed  of  lymphoid  cells  supported  by  a  delicate  reticulum. 
In  addition  to  this  reticulum,  of  which  traces  only  are  found  in  the  medullary 
portion,  there  is  also  a  network  of  finely  branched  cells  which  is  continuous  with  a 
similar  network  in  the  medullary  portion.  This  network  forms  an  adventitia  to 
the  blood-vessels.  In  the  medullary  portion  there  are  but  few  lymphoid  cells,  but 
there  are,  especially  toward  the  centre,  granular  cells  and  concentric  corpuscles. 
The  granular  cells  are  rounded  or  flask-shaped  masses  attached  (often  by  fibril- 
lated  extremities)  to  blood-vessels  and  to  newly  formed  connective  tissue.  The 
concentric  corpuscles  are  composed  of  a  central  mass  consisting  of  one  or  more 
granular  cells,  and  of  a  capsule  which  is  formed  of  epithelioid  cells  which  are 
continuous  with  the  branched  cells  forming  the  network  mentioned  above. 

Each  follicle  is  surrounded  by  a  capillary  plexus  from  which  vessels  pass  into 
the  interior  and  radiate  from  the  periphery  toward  the  centre,  and  form  a  second 
zone  just  within  the  margin  of  the  medullary  portion.  In  the  centre  of  the 
medulla  there  are  very  few  vessels,  and  they  are  of  minute  size. 

Watney  has  recently  made  the  important  observation  that  haemoglobin  is 
found  in  the  thymus  either  in  cysts  or   in  cells  situated  near  to  or  forming  part 


Fig.  541.— Minute  structure  of  thymus  gland.  Upper  portion  of  the  thymus  of  a  fetal  pig  of  2"  in 
length,  showing  the  bud-like  lobuli  and  glandular  elements.  2.  Cells  of  the  thymus,  mostly  from  a  man. 
a.  Free  nuclei,  b.  Small  cells,  c.  Larger,  d.  Larger,  with  oil-globules,  from  the  ox.  e,  f.  Cells  completely 
filled  with  fat,  at/ without  a  nucleus,  g,  h.  Concentric  bodies,  g.  An  encapsulated  nucleated  cell.  h.  A  com- 
posite structure  of  a  similar  nature. 

of  the  concentric  corpuscles.  This  haemoglobin  varies  from  granules  to  masses 
exactly  resembling  colored  blood-corpuscles,  oval  in  the  bird,  reptile,  and  fish  ; 
circular  in  all  mammals  except  in  the  camel.  Dr.  Watney  has  also  discovered 
in  the  lymph  issuing  from  the  thymus  similar  cells  to  those  found  in  the  gland, 
and,  like  them,  containing  haemoglobin  either  in  the  form  of  granules  or  masses. 
From  these  facts  he  arrives  at  the  physiological  conclusion  that  the  thymus  is  one 
source  of  the  colored  blood-corpuscles. 

Vessels  and  Nerves. — The  arteries  supplying  the  thymus  are  derived  from 
the  internal  mammary  and  from  the  superior  and  inferior  thyroid.  The  veins 
terminate  in  the  left  innominate  vein  and  in  the  thyroid  veins.     The  lymphatics 


THE    THYMUS    GLAND. 


983 


are  of  large  size,  arise  in  the  substance  of  the  gland,  and  are  said  to  terminate  in 
the  internal  jugular  vein.      The  nerves  are  exceedingly  minute  ;  they  are  derived 


Artery. 


Artery 


Fig.  542. — Minute  structure  of  the  thymus  gland.  Follicle  of  injected  thymus  from  calf,  four  days  old, 
slightly  diagrammatic,  magnified  about  50  diameters.  The  large  vessels  are  disposed  in  two  rings,  one  of  which 
surrounds  the  follicle,  the  other  lies  just  within  the  margin  of  the  medulla.  (Watney.)  A  and  B.  From  thy- 
mus of  camel,  examined  without  addition  of  any  reagent.  Magnified  about  400  diameters.  A.  Large  colorless 
cell  containing  small  oval  masses  of  hsemoglobin.  Similar  cells  are  found  in  the  lymph-glands,  spleen,  and 
medulla  of  bone.    B.  Colored  blood-corpuscles. 

from  the  pneumogastric  and  sympathetic.  Branches  from  the  descendens  hypo- 
glossi  and  phrenic  reach  the  investing  capsule,  but  do  not  penetrate  into  the  sub- 
stance of  the  gland. 


THE  URINARY  ORGANS. 


THE    KIDNEYS. 


THE  Kidneys,  two  in  number,  are  situated  in  the  back  part  of  the  abdomen,  and 
are  for  the  purpose  of  separating  from  the  blood  certain  materials  which, 
when  dissolved  in  a  quantity  of  water,  also  separated  from  the  blood  by  the  kid- 
neys,  constitute  the  urine. 

They  are  placed  in  the  loins,  one  on  each  side  of  the  vertebral  column,  behind 
the  peritoneum,  and  surrounded  by  a  mass  of  fat  and  loose  areolar  tissue.  Their 
upper  extremity  is  on  a  level  with  the  upper  border  of  the  twelfth  dorsal  vertebra, 
their  lower  extremity  on  a  level  with  the  third  lumbar.  The  right  kidney  is 
usually  on  a  slightly  lower  level  than  the  left,  probably  on  account  of  the  vicinity 
of  the  liver. 

Each  kidney  is  about  four  inches  in  length,  two  to  two  and  a  half  in  breadth, 
and  rather  more  than  one  inch  in  thickness.  The  left  is  somewhat  longer,  though 
narrower,  than  the  right.  The  weight  of  the  kidney  in  the  adult  male  varies  from 
4^  ounces  to  6  ounces ;  in  the  adult  female,  from  4  ounces  to  5J  ounces.  The  com- 
bined weight  of  the  two  kidneys  in  proportion  to  the  body  is  about  1  in  240. 

The  kidney  has  a  characteristic  form.  It  is  flattened  on  its  sides  and  presents 
at  one  part  of  its  circumference  a  hollow.  It  is  larger  at  its  upper  than  its  lower 
extremity.  It  presents  for  examination  two  surfaces,  two  borders,  and  an  upper 
and  lower  extremity. 

Its  anterior  surface  is  convex,  looks  forward  and  outward,  and  is  partially 
covered  by  peritoneum.  The  right  kidney  in  its  upper  three-fourths  is  in  con- 
tact with  the  posterior  part  of  the  under  surface  of  the  right  lobe  of  the  liver,  on 
which  it  produces  a  concave  impression,  the  impressio  renalis  (page  918). 
Toward  its  inner  border  it  is  covered  by  the  second  part  of  the  duodenum,  while 
its  lower  and  outer  part  is  in  relation  with  the  hepatic  flexure  of  the  colon.  The 
relation  of  the  second  part  of  the  duodenum  to  the  front  of  the  right  kidney  is  a 
varying  one.  The  left  kidney  is  covered  above  by  the  posterior  surface  of  the 
stomach,  below  the  stomach  by  the  pancreas,  behind  which  are  the  splenic  vessels. 
Its  lower  half  is  in  contact  with  some  of  the  coils  of  the  small  intestine  and  some- 
times with  the  third  part  of  the  duodenum.  Near  its  outer  border  the  anterior  sur- 
face lies  behind  the  spleen  and  the  splenic  flexure  of  the  colon. 

The  kidneys  are  partly  covered  in  front  by  peritoneum  and  partly  uncovered. 
On  the  right  kidney,  the  hepatic  area,  that  is  to  say  that  portion  of  the  kidney 
which  produces  the  renal  impression  on  the  liver,  is  covered  by  peritoneum,  which 
therefore  separates  the  kidney  from  the  liver :  the  duodenal  and  colic  areas  are  not 
peritoneal,  and  these  structures  are  connected  to  the  kidney  by  loose  connective 
tissue;  at  the  lower  and  inner  extremity  is  a  small  area,  the  mesocolic  area,  which 
is  covered  by  a  layer  of  peritoneum  of  the  greater  sac  and  by  the  colic  vessels. 
On  the  left  kidney,  the  gastric  area  is  covered  by  the  peritoneum  of  the  lesser  sac  ; 
the  pancreatic  and  colic  areas  are  non-peritoneal :  while,  as  on  the  right  side,  at  the 
lower  and  inner  extremity,  is  an  area,  mesocolic,  which  is  covered  by  the  perito- 
neum of  the  greater  sac  and  by  the  colic  vessels. 

The  posterior  surface  of  the  kidney  is  flatter  than  the  anterior  and  is  directed 
backward  and  inward.  It  is  entirely  devoid  of  peritoneal  covering,  being  im- 
bedded in  areolar  and  fatty  tissue.  It  lies  upon  the  Diaphragm,  the  anterior  layer 
of  the  lumbar  aponeurosis,  the  external  and  internal  arcuate  ligaments,  the  Psoas 

985 


986 


THE    URINARY   ORGANS. 


and  Transversalis  muscles,  one  or  two  of  the  upper  lumbar  arteries,  the  last  dorsal, 
ilio-hypogastric,  and  ilio-inguinal  nerves.  The  right  kidney  rests  upon  the  twelfth 
rib,  the  left  usually  on  the  eleventh  and  twelfth.  The  Diaphragm  separates  the 
kidney  from  the  pleura  as  it  dips  down  to  form  the  phrenico-costal  sinus,  but  fre- 
quently the  muscular  fibres  of  the  Diaphragm  are  defective  or  absent  over  a  trian- 
gular area  immediately  above  the  external  arcuate  ligament,  and  when  this  is  the 
case  the  perirenal  areolar  tissue  is  in  immediate  apposition  with  the  diaphragmatic 
pleura. 

The  external  border  is  convex,  and  is  directed  outward  and  backward,  toward 
the  postero-lateral  wall  of  the  abdomen.  On  the  left  side  it  is  in  contact,  at  its 
upper  part,  with  the  spleen. 

The  internal  border  is  concave,  and  is  directed  forward  and  a  little  downward. 
It  presents  a  deep  longitudinal  fissure,  bounded  by  a  prominent  overhanging  ante- 
rior and  posterior  lip.  This  fissure  is  named  the  hilum,  and  allows  of  the  passage 
of  the  vessels,  nerves,  and  ureter  into  and  out  of  the  kidney. 

The  superior  extremity,  directly  slightly  inward  as  well  as  upward,  is  thick 
and  rounded,  and  is  surmounted  by  the  suprarenal  capsule,  which  covers  also  a 
small  portion  of  the  anterior  surface. 

The  inferior  extremity,  directed  a  little  outward  as  well  as  downward,  is 
smaller  and  thinner  than  the  superior.  It  extends  to  within  two  inches  of  the 
crest  of  the  ilium. 

At  the  hilum  of  the  kidney  the  relative  position  of  the  main  structures  passing 
into  and  out  of  the  kidney  is  as  follows  :  the  vein  is  in  front,  the  artery  in  the 
middle,  and  the  duct  or  ureter  behind  and  toward  the  lower  part.  By  a  knowledge 
of  these  relations  the  student  may  distinguish  between  the  right  and  left  kidney. 
The  kidney  is  to  be  laid  on  the  table  before  the  student  on  its  posterior  surface, 
with   its   lowrer  extremity  toward   the   observer — that  is  to  say,  with  the  ureter 

behind  and  below  the  other  vessels ;  the  hilum 
will  then  be  directed  to  the  side  to  which  the 
kidney  belongs. 

General  Structure  of  the  Kidney. — The  kidney 
is  surrounded  by  a  distinct  investment  of  fibrous 
tissue  which  forms  a  firm,  smooth  covering  to  the 
organ.  It  closely  invests  it,  but  can  be  easily 
stripped  off,  in  doing  which,  however,  numerous 
fine  processes  of  connective  tissue  and  small  blood- 
vessels are  torn  through.  Beneath  this  coat  a 
thin  Avide-meshed  network  of  unstriped  muscular 
fibre  forms  an  incomplete  covering  to  the  organ. 
When  the  fibrous  coat  is  stripped  off,  the  surface 
of  the  kidney  is  found  to  be  smooth  and  even 
and  of  a  deep-red  color. 

In  infants  fissures  extending  for  some  depth 
may  be  seen  on  the  surface  of  the  organ,  a  rem- 
nant of  the  lobular  construction  of  the  gland. 
The  kidney  is  dense  in  texture,  but  is  easily 
lacerable  by  mechanical  force.  In  order  to  ob- 
tain a  knowledge  of  the  structure  of  the  gland, 
a  vertical  section  must  be  made  from  its  convex 
to  its  concave  border,  and  the  loose  tissue  and 
fat  removed  around  the  vessels  and  the  excretory 
duct  (Fig.  543).  It  will  be  then  seen  that  the 
kidney  consists  of  a  central  cavity  surrounded  at 
all  parts  but  one  by  the  proper  kidney-substance. 
This  central  cavity  is  called  the  sinus,  and  is  lined  by  a  prolongation  of  the  fibrous 
coat  of  the  kidney,  which  enters  through  a  longitudinal  fissure,  the  hilum  (before 
mentioned),  which  is  situated  at  that  part  of  the   cavity  which  is  no+  surrounded 


Fig.  543.— Vertical  section  of  kidney. 


THE   KIDNEYS. 


V 


987 


by  kidney-structure.  Through  this  fissure  the  blood-vessels  of  the  kidney  and  its 
excretory  duct  pass,  and  therefore  these  structures,  upon  entering  the  kidney,  are 
contained  within  the  sinus.  The  excretory  duct,  or  ureter,  after  entering,  dilates 
into  a  wide,  funnel-shaped  sac  named  the  pelvis.  This  divides  into  two  or  three 
tubular  divisions,  which  subdivide  into  several  short,  truncated  branches  named 
calices  or  infundibula,  all  of  which  are  contained  in  the  central  cavity  of  the  kid- 
ney. The  blood-vessels  of  the  kidney,  after  passing  through  the  hilum,  are  con- 
tained in  the  sinus  or  central  cavity,  lying  between  its  lining  membrane  and  the 
excretory  apparatus,  before  entering  the  kidney-substance. 

This  central  cavity,  as  before  mentioned,  is  surrounded  on  all  sides  except  at 
the  hilum  by  the  substance  of  the  kidney,  which  is  at  once  seen  to  consist  of  two 
parts — viz.  of  an  external  granular  investing  part,  which  is  called  the  cortical 
portion  ;  and  of  an  internal  part,  the  medullary  portion,  made  up  of  a  number  of 
dark-colored  pyramidal  masses,  with  their  bases  resting  on  the  cortical  part  and 
their  apices  converging  toward  the  centre,  where  they  form  prominent  papillae 
which  project  into  the  interior  of  the  calices. 

The  cortical  substance  is  of  a  bright  reddish-brown  color,  soft,  granular,  and 
easily  lacerable.  It  is  found  everywhere  immediately  beneath  the  capsule,  and  is 
seen  to  extend  in  an  arched  form  over  the  base  of  each  medullary  pyramid.  The 
part  separating  the  sides  of  any  two  pyramids  through 

which  the  arteries  and  nerves  enter,  and  the  veins  and      ^ m — 

lymphatics  emerge,  from  the  kidney,  is  called  a  cortical 


lymphatics  emerge,  trom  the  kidney,  is  called  a  cortical  rvrvl'Ol  H 

column  or  column '  of  Bertin  (a,  a',  Fig.  543)  ;  while  ^CCxV  r~\  U>  fc^^l 
that  portion  which  stretches  from  one  cortical  column  to 
the  next,  and  intervenes  between  the  base  of  the  pyra- 
mid and  the  capsule  (marked  by  the  dotted  line  extend- 
ing from  A  to  a'  in  Fig.  543),  is  called  a  cortical  arch, 
the  depth  of  which  varies  from  a  third  to  half  an  inch. 

The  medullary  substance,  as  before  stated,  is  seen 
to  consist  of  red-colored,  striated,  conical  masses,  the 
pyramids  of  Malpighi,  the  number  of  which,  varying 
from  eight  to  eighteen,  corresponds  to  the  number  of 
lobes  of  which  the  organ  in  the  foetal  state  is  composed. 
The  base  of  each  pyramid  is  surrounded  by  a  cortical 
arch,  and  directed  toward  the  circumference  of  the  kid- 
ney ;  the  sides  are  contiguous  with  the  cortical  columns  ; 
while  the  apex,  known  as  the  papilla  or  mammilla  of 
the  kidney,  projects  into  one  of  the  calices  of  the  ureter, 
each  calyx  receiving  two  or  three  papillae. 

These  two  parts,  cortical  and  medullary,  so  dissimi- 
lar in  appearance,  are  very  similar  in  structure,  being 
made  up  of  urinary  tubes  and  blood-vessels  united  and 
bound  together  by  a  connecting  matrix  or  stroma. 

Minute  Anatomy. — The  tubuli  uriniferi,  of  which 
the  kidney  is  for  the  most  part  made  up,  Commence  in 
the  cortical  portion  of  the  kidney,  and,  after  pur- 
suing a  very  circuitous  course  through  the  cortical  and 
medullary  parts  of  the  kidney,  finally  terminate  at  the 
apices  of  the  Malpighian  pyramids  by  open  mouths 
(Fig.  544),  so  that  the  fluid  which  they  contain  is 
emptied  into  the  dilated  extremity  of  the  ureter  con- 
tained in  the  sinus  of  the  kidney.  If  the  surface  of 
one  of  the  papillae  is  examined  with  a  lens,  it  will  be  seen  to  be  studded  over  with 
a  number  of  small  depressions,  from  sixteen  to  twenty  in  number,  and  in  a  fresh 
kidney,  upon  pressure  being  made,  fluid  will  be  seen  to  exude  from  these  depres- 
sions. They  are  the  orifices  of  the  tubuli  uriniferi,  which  terminate  in  this  situa- 
tion.    They  commence   in   the   cortical   portion  of  the   kidney  as  the  Malpighian 


Fig.  5-14.— Plan  of  uriniferous 
tubes,  a,  a.  Malpighian  bodies. 
B,  B.  Margin  of  medullary  struc- 
ture, c,  c,  c.  Loops  ofHenle. 
d,  d,  d.  Straight  tubes  out  off. 
F..  Commencing  straight  tubes. 
F.  Termination  of  straight  tube. 


988 


THE    URINARY    ORGANS. 


bodies,  which  are  small  rounded  masses,  varying  in  size,  but  average  about  y^  of 
an  inch  in  diameter.  They  are  of  a  deep-red  color,  and  are  found  only  in  the  cor- 
tical portion  of  the  kidney.  Each  of  these  little  bodies  is  composed  of  two  parts — 
a  central  glomerulus  of  vessels,  called  a  Malpighian  tuft,  and  a  membranous  en- 
velope, the  Malpighian  capsule,  or  capsule  of  Boivman,  which  latter  is  a  small 
pouch-like  commencement  of  a  uriniferous  tubule. 

The  Malpighian  tuft,  or  vascular  glomerulus,  is  a  network  of  convoluted 
capillary  blood-vessels  held  together  by  scanty  connective  tissue  and  grouped  into 
from  two  to  five  lobules.  This  capillary  network  is  derived  from  a  small  arterial 
twig,  the  afferent  vessel,  which  pierces  the  wall  of  the  capsule,  generally  at  a  point 
opposite  that  at  which  the  latter  is  connected  with  the  tube  ;  and  the  resulting 
vein,  the  efferent  vessel,  emerges  from  the  capsule  at  the  same  point.  The  afferent 
vessel  is  usually  the  larger  of  the  two  (Fig.  545).  The  Malpighian  or  Bowman  s 
capsule,  which  surrounds  the  glomerulus,  is  formed  of  a  hyaline  membrane  sup- 
ported by  a  small  amount  of  connective  tissue  which  is  continuous  with  the  con- 
nective tissue  of  the  tube.  It  is  lined  on  its  inner  surface  by  a  layer  of  squa- 
mous epithelial  cells  which  are  reflected  from  the  lining  membrane  on  to  the 
glomerulus  at  the  point  of  entrance  or  exit  of  the  afferent  and  efferent  vessels. 
The  whole  surface  of  the  glomerulus  is  covered  with  a  continuous  layer  of  the 
same  cells  on  a  delicate  supporting  membrane,  which  with  the  cells  dips  in  between 
the  lobules  of  the  glomerulus,  closely  surrounding  them  (Kg.  546).  Thus,  between 
the  glomerulus  and  the  capsule  a  space  is  left,  forming  a  cavity  lined  by  a  COn- 


usan  b, 


Fig.  545. — Minute  structure  of  kidney. 


Fig.  546.— Malpighian  body. 


tinuous  layer  of  cells,  which  varies  in  size  according  to  the  state  of  secretion  and 
the  amount  of  fluid  present  in  it.  The  cells,  as  above  stated,  are  squamous  in  the 
adult,  but  in  the  foetus  and  young  subject  they  are  polyhedral  or  even  columnar. 

The  tubuli  uriniferi,  commencing  in  the  Malpighian  bodies,  in  their  course 
present  many  changes  in  shape  and  direction,  and  are  contained  partly  in  the 
medullary  and  partly  in  the  cortical  portions  of  the  organ.  At  their  junction  with 
the  Malpighian  capsule  they  present  a  somewhat  constricted  portion  which  is 
termed  the  neck.  Beyond  this  the  tube  becomes  convoluted,  and  pursues  a  con- 
siderable course  in  the  cortical  structure,  constituting  the  "proximal  convoluted 
tube.  After  a  time  the  convolutions  disappear,  and  the  tube  approaches  the 
medullary  portion  of  the  kidney  in  a  more  or  less  spiral  manner.  This  section  of 
the  tube  has  been  called  the  spiral  tube  of  Schachowa.  Throughout  this  portion 
of  their  course  the  tubuli  uriniferi  have  been  contained  entirely  in  the  cortical 
structure,  and  have  presented  a  pretty  uniform  calibre.  They  now  enter  the 
medullary  portion,  and  suddenly  become  much  smaller,  quite  straight  in  direction, 
and  dip  down  for  a  variable  depth  into  the  pyramids,  constituting  the  descending 
limb  of  BTenle's  loop.  Bending  on  themselves,  they  form  a  kind  of  loop,  the  loop 
of  Henle,  and,  reascending,  become  suddenly  enlarged  and  again  spiral  in 
direction,  forming  the   ascending  limb  of  Henle 's   loop,  and   re-enter  the   cortical 


THE   KIDNEYS. 


989 


structure.  This  portion  of  the  tube  does  not  present  a  uniform  calibre,  but 
becomes  narrower  as  it  ascends  and  irregular  in  outline.  As  a  narrow  tube  it  enters 
the  cortex  and  ascends  for  a  short  distance,  when  it  again  becomes  dilated,  irregular, 
and  angular.  This  section  is  termed  the  irregular  tubule ;  it  terminates  in  a 
convoluted  tube  which  exactly  resembles  the  proximal  convoluted  tubule ;  and  is 
called  the  distal  convoluted  tubule.  This  again  terminates  in  a  narrow  curved  tube, 
which  enters  the  straight  or  collecting  tube. 

Each  straight,  otherwise  called  a  collecting  or  receiving,  tube  commences  by  a 
small  orifice  on  the  summit  of  one  of  the  papillae,  thus  opening  and  discharging 
its  contents  into  the  interior  of  one  of  the  calices.  Traced  into  the  substance  of 
the  pyramid,  these  tubes  are  found  to  run  from  apex  to  base,  dividing  dichotomously 
in  their  course  and  slightly  diverging  from  each  other.  Thus  dividing  and  sub- 
dividing, they  reach  the  base  of  the  pyramid,  and  enter  the  cortical  structure 
greatly  increased  in  number.  Upon  entering  the  cortical  portion  they  continue  a 
straight  course  for  a  variable  distance,  and  are  arranged  in  groups  called  medullary 
rays,  several  of  these  groups  corresponding  to  a  single  pyramid.  The  tubes  in  the 
centre  of  the  group  are  the  longest,  and  reach  almost  to  the  surface  of  the  kidney, 
while  the  external  ones  are  shorter,  and  advance  only  a  short  distance  into  the 


Descending  limb  \ 
of  Henle's  loop.  J 


Fig.  547.— Uriniferous  tube.    For  the  sake  of  clearness  the  epithelial  cells  have  been  represented  more 
highly  magnified  than  the  tubes  in  which  they  are  contained. 

cortex.  In  consequence  of  this  arrangement  the  cortical  portion  presents  a  number 
of  conical  masses,  the  apices  of  which  reach  the  periphery  of  the  organ,  and  the 
bases  are  applied  to  the  medullary  portion.  These  are  termed  the  pyramids  of 
Ferrein.  As  they  run  through  the  cortical  portion  the  straight  tubes  receive  on 
either  side  the  curved  extremity  of  the  convoluted  tubes,  which,  as  stated  above, 
commence  at  the  Malpighian  bodies. 

It  will  be  seen  from  the  above  description  that  there  is  a  continuous  series 
of  tubes  from  their  commencement  in   the   Malpighian   bodies  to  their  termina- 


990 


THE    UBINABY   OBGANS. 


tion  at  the  orifices  on  the  apices  of  the  pyramids  of  Malpighi,  and  that  the 
urine,  the  secretion  of  which  commences  in  the  capsule,  finds  its  way  through 
these  tubes  into  the  calices  of  the  kidney,  and  so  into  the  ureter.  To  recapitulate : 
the  tube  first  presents  a  constricted  portion,  (1)  the  neck.  2.  It  forms  a  wide 
convoluted  tube,  the  proximal  convoluted  tube.  3.  It  becomes  spiral,  the  spiral 
tubule  of  Schachowa.  4.  It  enters  the  medullary  structure  as  a  narrow,  straight 
tube,  the  descending  limb  of  HenWs  loop.  5.  Forming  a  loop  and  becoming 
dilated,  it  ascends  somewhat  spirally,  and,  gradually  diminishing  in  calibre, 
ao-ain  enters  the  cortical  structure,  the  ascending  limb  of  Henle's  loop.  6.  It  now 
becomes  irregular  and  angular  in  outline,  the  irregidar  tubule.  7.  It  then  becomes 
convoluted,  the  distal  convoluted  tubide.  8.  Diminishing  in  size,  it  forms  a  curve, 
the  curved  tubide.  9.  Finally,  it  joins  a  straight  tube,  the  straight  collecting  tube, 
which  is  continued  downward  through  the  medullary  substance  to  open  at  the  apex 
of  a  pyramid. 

The  Tubuli  Uriniferi:  their  Structure. — The  tubuli  uriniferi  consist  of  base- 
ment membrane  lined  with  epithelium.  The  epithelium  varies  considerably  in 
different  sections  of  the  uriniferous  tubes.  In  the  neck  the  epithelium  is  con- 
tinuous with  that  lining  the  Malpighian  capsule,  and,  like  it,  consists  of  flattened 
cells  with  an  oval  nucleus  (Fig.  547  a).  The  cells  are,  however,  very  indistinct  and 
difficult  to  trace,  and  the  tube  has  here  the  appearance  of  a  simple  basement 
membrane  unlined  by  epithelium.  In  the  proximal  convoluted  tubule  and  the 
spiral  tubule  of  Schachowa  the  epithelium  is  polyhedral  in  shape,  the  sides  of  the 
cells  not  being  straight,  but  fitting  into  each  other,  and  in  some  animals  so  fused 


Fig.  548.1— Longitudinal  section  of  Henle's 
descending  limb.  a.  Membrana  propria.  6. 
Epithelium. 


Fig.  549.— Longitudinal  section  of  straight 
tube.  a.  Cylindrical  or  cubical  epithelium. 
6.  Membrana  propria. 


together  that  it  is  impossible  to  make  out  the  lines  of  junction.  In  the  human 
kidney  the  cells  often  present  an  angular  projection  of  the  surface  next  the  base- 
ment membrane.  These  cells  are  made  up  of  more  or  less  rod-like  fibres,  which 
rest  by  one  extremity  on  the  basement  membrane,  whilst  the  other  projects  toward 
the  lumen  of  the  tube.  This  gives  to  the  cells  the  appearance  of  distinct  striation 
(Heidenhain)  (Fig.  547,  b).  In  the  descending  limb  of  Henle's  loop  the  epithelium 
resembles  that  found  in  the  Malpighian  capsule  and  the  commencement  of  the  tube, 
consisting  of  flat  transparent  epithelial  plates  with  an  oval  nucleus  (Figs.  547,  A, 
518).  In  the  ascending  limb,  on  the  other  hand,  the  cells  partake  more  of  the 
character  of  those  described  as  existing  in  the  proximal  convoluted  tubule,  being 
polyhedral  in  shape  and  presenting  the  same  appearance  of  striation.  The  nucleus, 
however,  is  not  situated  in  the  centre  of  the  cell,  but  near  the  lumen  (Fig.  547,  c). 
After  the  ascending  limb  of  Henle's  loop  becomes  narrower  upon  entering  the 
cortical  structure,  the  striation  appears  to  be  confined  to  the  outer  part  of  the  cell : 
1  From  Handbook  for  the  Physiological  Laboratory. 


THE   KIDNEYS. 


991 


at  all  events,  it  is  much  more  distinct  in  this  situation,  the  nucleus,  which  appears 
flattened  and  angular,  being  still  situated  near  the  lumen  (Fig.  547,  d).  In  the 
irregular  tubule  the  cells  undergo  a  still  farther  change,  becoming  very  angular, 
and  presenting  thick  bright  rods  or  markings,  which  render  the  striation  much 
more  distinct  than  in  any  other  section  of  the  urinary  tubules  (Fig.  547,  h).      In 


Fig.  723. — Transverse  section  of  pyramidal  substance  of  kidney  of  pig,  the  blood-vessels  of  which  are  injected. 
a.  Large  collecting  tube  cut  across,  lined  with  cylindrical  epithelium.  6.  Branch  of  collecting  tube  cut  across, 
lined  with  epithelium  with  shorter  cylinders,  c  and  d.  Henle's  loops  cut  across,  e.  Blood-vessels  cut  across. 
d.  Connective-tissue  ground-substance. 

the  distal  convoluted  tubule  the  epithelium  appears  to  be  somewhat  similar  to  that 
which  has  been  described  as  existing  in  the  proximal  convoluted  tubule,  but 
presents  a  peculiar  refractive  appearance  (Fig.  547,  b).  In  the  curved  tubule,  just 
before  its  entrance  into  the  straight   collecting  tube,  the  epithelium  varies  greatly 


a  A 


Fig.  552.— A  portion  of  Fig.  551  enlarged, 
references  are  the  same.; 


(The 


Fig.  551.— Diagrammatical  sketch  of  the  blood- 
vessels of  kidney. 

A,  a.  Proper  renal  artery  and  vein,  the  former  giving  off  the  renal  afferents,  the  latter  receiving  the  renal 
efferents.  b,  b.  Interlobular  artery  and  vein,  the  latter  commencing  from  the  stellate  veins,  and  receiving 
branches  from  the  plexus  around  the  tubuli  contorti,  the  former  giving  off  renal  afferents.  c.  Straight  tube,  sur- 
rounded by  tubuli  contorti,  with  which  it  communicates,  as  more  fully  shown  in  Fig.  544.  d.  Margin  of  medul- 
lary substance,  e,  e,  e.  Receiving  tubes  cut  off.  f,/.  Arteriolse  et  venae  rectse,  the  latter  arising  from  (g)  the 
plexus  at  the  medullary  apex. 

as  regards  the  shape  of  the  cells,  some  being  angular  with  short  processes,  others 
spindle-shaped,  others  polyhedral  (Fig.  547,  e). 

In  the  straight  tubes  the  epithelium  is  more  or  less  columnar ;  in  its  papillary 
portion  the  cells  are  distinctly  columnar  and  transparent  (Figs.  549,  550),  but  as 
the  tube  approaches  the  cortex  the  cells  are  less  uniform  in  shape ;  some  are 
polyhedral,  and  others  angular  with  short  processes  (Fig.  547,  F  and  g). 


992 


THE    URINARY   ORGANS. 


The  Renal  Blood-vessels. — The  kidney  is  plentifully  supplied  with  blood  by 
the  renal  artery,  a  large  offset  of  the  abdominal  aorta.  Previously  to  entering 
the  kidney,  each  artery  divides  into  four  or  five  branches,  which  are  distributed 
to  its  substance.  At  the  hilum  these  branches  lie  between  the  renal  vein  and 
ureter,  the  vein  being  in  front,  the  ureter  behind.  Each  vessel  gives  off  some 
small  .  branches  to  the  suprarenal  capsules,  the  ureter,  and  the  surround- 
ing cellular  tissue  and  muscles.  Frequently  there  is  a  second  renal  artery, 
which  is  given  off  from  the  abdominal  aorta  at  a  lower  level,  and  supplies  the 
lower  portion  of  the  kidney.  It  is  -termed  the  inferior  renal  artery.  The 
branches  of  the  renal  artery  whilst  in  the  sinus  give  off  a  few  twigs  for  the 
nutrition  of  the  surrounding  tissues,  and  terminate  in  the  arteria?  propria?  renales, 
which  enter  the  kidney  proper  in  the  columns  of  Bertin.  Two  of  these  pass 
to  each  pyramid  of  Malpighi  and  run  along  its  sides  for  its  entire  length, 
giving  off  as  they  advance  the  afferent  vessels  of  the  Malpighian  bodies  in  the 
columns.  Having  arrived  at  the  bases  of  the  pyramids,  they  make  a  bend  in 
their  course,  so  as  to  lie  between  the  bases  of  the  pyramids  and  the  cortical  arches, 
where  they  break  up  into  two  distinct  sets  of  branches  devoted  to  the  supply  of  the 
remaining  portions  of  the  kidney. 

The  first  set,  the  interlobular  arteries  (Figs.  551,  552,  b),  are  given  off  at  right 

angles  from  the  side  of  the  arteriae  proprise 
renales  looking  toward  the  cortical  substance, 
and,  passing  directly  outward  between  the  pyra- 
mids of  Ferrein,  they  reach  the  capsule,  where 
they  terminate  in  the  capillary  network  of 
this  part.  In  their  outward  course  they  give 
off  lateral  branches  ;  these  are  the  afferent  ves- 
sels for  the  Malpighian  bodies  (see  page  988), 
and,  having  pierced  the  capsule,  end  in  the 
Malpighian  tufts.  From  each  tuft  the  corre- 
sponding renal  efferent  arises,  and,  having  made 
its  egress  from  the  capsule  near  to  the  point 
where  the  afferent  vessel  entered,  breaks  up 
into  a  number  of  branches  which  form  a  dense 
venous  plexus  around  the  adjacent  urinary 
tubes  (Fig.  553). 

The  second  set  of  branches  from  the  arteries 
proprise  renales  are  for  the  supply  of  the  medul- 
lary pyramids,  which  they  enter  at  their  bases ; 
and,  passing  straight  through  their  substance 
to  their  apices,  terminate  in  the  venous  plex- 
They  are   called   the  arterioles  rectce  (Figs.  551, 


Fig.  553.— Diagrammatic  representation 
of  the  blood-vessels  in  the  substance  of  the 
cortex  of  the  kidney,  m.  Region  of  the 
medullary  ray.  b.  Region  of  the  tortuous 
portion  of  the  tubules,  ai.  Arteria  inter- 
lobularis.  vi.  Vena  interlobularis.  va.  Vas 
afferens.  gl.  Glomerulus,  ve.  Vas  efferens. 
vz.  Venous  twig  of  the  interlobularis.  (From 
Ludwig,  in  Strieker's  Handbook.) 


uses   found   in    that   situation. 
552,  f). 

The  renal  veins  arise  from  three  sources — the  veins  beneath  the  capsule,  the 
plexuses  around  the  convoluted  tubules  in  the  cortical  arches,  and  the  plexuses 
situated  at  the  apices  of  the  pyramids  of  Malpighi.  The  veins  beneath  the  capsule 
are  stellate  in  arrangement,  and  are  derived  from  the  capillary  network  of  the 
capsule,  into  which  the  terminal  branches  of  the  interlobular  arteries  break  up. 
These  join  to  form  the  vence  interlobular es,  which  pass  inward  between  the  pyramids 
of  Ferrein,  receive  branches  from  the  plexuses  around  the  convoluted  tubules, 
and,  having  arrived  at  the  bases  of  the  Malpighian  pyramids,  join  with  the  venae 
rectce,  next  to  be  described  (Figs.  551,  552,  b). 

The  Vena}  Rectos  are  branches  from  the  plexuses  at  the  apices  of  the  medullary 
pyramids,  formed  by  the  terminations  of  the  arteriolse  rectse.  They  pass  outward 
in  a  straight  course  between  the  tubes  of  the  medullary  structure,  and  joining,  as 
above  stated,  the  venae  interlobulares,  form  the  proper  renal  veins  (Figs.  551,  552,/). 

These  vessels,  Vena?  Propria?  Renales,  accompany  the  arteries  of  the  same  name, 
running  along  the  entire  length  of  the  sides  of  the  pyramids ;  and,  having  received 


THE   KIDNEYS.  993 

in  their  course  the  efferent  vessels  from  the  Malpighian  bodies  in  the  cortical 
structure  adjacent,  quit  the  kidney  substance  to  enter  the  sinus.  In  this  cavity 
they  inosculate  with  the  corresponding  veins  from  the  other  pyramids  to  form  the 
renal  vein,  which  emerges  from  the  kidney  at  the  hilum  and  opens  into  the  inferior 
vena  cava,  the  left  being  longer  than  the  right,  from  having  to  cross  in  front  of 
the  abdominal  aorta. 

Nerves  of  the  Kidney. — The  nerves  of  the  kidney,  although  small,  are  about 
fifteen  in  number.  They  have  small  ganglia  developed  upon  them,  and  are  derived 
from  the  renal  plexus,  which  is  formed  by  branches  from  the  solar  plexus,  the 
lower  and  outer  part  of  the  semilunar  ganglion  and  aortic  plexus,  and  from  the 
lesser  and  smallest  splanchnic  nerves.  They  communicate  with  the  spermatic 
plexus,  a  circumstance  which  may  explain  the  occurrence  of  pain  in  the  testicle  in 
affections  of  the  kidney.  So  far  as  they  have  been  traced,  they  seem  to  accompany 
the  renal  artery  and  its  branches,  but  their  exact  mode  of  termination  is  not 
known.  * 

The  lymphatics  consist  of  a  superficial  and  deep  set  which  terminate  in  the 
lumbar  glands. 

Connective  Tissue,  or  Intertubular  Stroma. — Although  the  tubules  and  vessels 
are  closely  packed,  a  certain  small  amount  of  connective  tissue,  continuous  with 
the  capsule,  binds  them  firmly  together.  This  tissue  was  first  described  by  Goodsir, 
and  subsequently  by  Bowman.  Ludwig  and  Zawarykin  have  observed  distinct 
fibres  passing  around  the  Malpighian  bodies,  and  Henle  has  seen  them  between 
the  straight  tubes  composing  the  medullary  structure. 

Surface  Form. — The  kidneys,  being  situated  at  the  back  part  of  the  abdominal  cavity  and 
deeply  placed,  cannot  be  felt  unless  enlarged  or  misplaced.  They  are  situated  on  the  confines 
of  the  epigastric  and  umbilical  regions  internally,  with  the  hypochondriac  and  lumbar  regions 
externally.  The  left  is  somewhat  higher  than  the  right.  According  to  Morris,  the  position  of 
the  kidney  may  be  thus  defined:  Anteriorly:  "1.  A  horizontal  line  through  the  umbilicus  is 
below  the  lower  edge  of  each  kidney.  2.  A  vertical  line  carried  upward  to  the  costal  arch  from 
the  middle  of  Poupart's  ligament  has  one-third  of  the  kidney  to  its  outer  side  and  two-thirds  to 
its  inner  side — i.  e.  between  this  line  and  the  median  line  of  the  body."  In  adopting  these  lines 
it  must  be  borne  in  mind  that  the  axes  of  the  kidneys  are  not  vertical,  but  oblique,  and  if  con- 
tinued upward  would  meet  about  the  ninth  dorsal  vertebra.  Posteriorly  :  The  upper  end  of  the 
left  kidney  would  be  defined  by  a  line  drawn  horizontally  outward  from  the  spinous  process  of  the 
eleventh  dorsal  vertebra,  and  its  lower  end  by  a  point  two  inches  above  the  iliac  crest.  The  right 
kidney  would  be  half  to  three-quarters  of  an  inch  lower.  Morris  lays  down  the  following  rules 
for  indicating  the  position  of  the  kidney  on  the  posterior  surface  of  the  body  :  "1.  A  line  par- 
allel with,  and  one  inch  from,  the  spine,  between  the  lower  edge  of  the  tip  of  the  spinous  pro- 
cess of  the  eleventh  dorsal  vertebra  and  the  lower  edge  of  the  spinous  process  of  the  third 
lumbar  vertebra.  2.  A  line  from  the  top  of  this  first  line  outward  at  right  angles  to  it  for 
2|  inches.  3.  A  line  from  the  lower  end  of  the  first  transversely  outward  for  2f  inches.  4.  A 
line  parallel  to  the  first  and  connecting  the  outer  extremities  of  the  second  and  third  lines  just 
described." 

The  hilum  of  the  kidney  lies  about  two  inches  from  the  middle  line  of  the  back,  at  the  level 
of  the  spinous  process  of  the  first  lumbar  vertebra. 

Surgical  Anatomy. — Malformations  of  the  kidney  are  not  uncommon.  There  may  be  an 
entire  absence  of  one  kidney,  though,  according  to  Morris,  the  number  of  these  cases  is  "  exces- 
sively small  "  :  or  there  may  be  congenital  atrophy  of  one  kidney,  when  the  kidney  is  very  small, 
but  usually  healthy  in  structure.  These  cases  are  of  great  importance,  and  must  be  duly  taken 
into  account,  when  nephrectomy  is  contemplated.  A  more  common  malformation  is  where  the 
two  kidneys  are  fused  together.  They  may  be  only  joined  together  at  their  lower  ends  by  means 
of  a  thick  mass  of  renal  tissue,  so  as  to  form  a  horseshoe-shaped  body  or  they  may  be  completely 
united,  forming  a  disc-like  kidney,  from  which  two  ureters  descend  into  the  bladder.  These 
fused  kidneys  are  generally  situated  in  the  middle  line  of  the  abdomen,  but  may  be  misplaced 
as  well. 

One  or  both  kidneys  may  be  misplaced  as  a  congenital  condition,  and  remain  fixed  in  this 
abnormal  position.  They  are  then  very  often  misshapen.  They  may  be  situated  higher  or  lower 
than  normal  or  removed  farther  from  the  spine  than  usual  or  they  may  be  displaced  into  the 
iliac  fossa,  over  the  sacro-iliac  join!  j  the  promontory  of  the  sacrum,  or  into  the  pelvis 

between  the  rectum  and  bladder  or  by  ti  side  of  the  uterus.  In  these  latter  cases  they  may 
give  rise  to  very  serious  trouble.  The  kidney  may  also  be  misplaced  as  a  congenital  condition, 
but  may  not  be  fixed.  It  is  then  know;  ts  a  floating  kidney.  It  is  believed  to  be  due  to  the 
fact  that  the  kidney  is  complete  oped  by  peritoneum  which  then  passes  backward  to  the 

spine  as  a  double  layer,  forming  hron,  which  permits  of  movement  taking  place.    The 

kidney  may  also  be  misplaced  a  ed  condition  ;  in  these  cases  the  kidney  is  mobile  in 

63 


994  THE    URINARY   ORGANS. 

the  tissues  by  which  it  is  surrounded,  either  moving  in  its  capsule  or  else  moving  with  the  capsule 
in  the  perinephric  tissues.  This  condition  is  known  as  movable  kidney,  and  is  more  common 
in  the  female  than  the  male.  Other  malformations  are  the  persistence  of  the  foetal  lobulation  ; 
the  presence  of  two  pelves  or  two  ureters  to  the  one  kidney.  In  some  rare  instances  a  third 
kidney  may  be  present. 

The  kidney  is  imbedded  in  a  large  quantity  of  loose  fatty  tissue,  and  is  but  partially  covered 
by  peritoneum  ;  hence  rupture  of  this  organ  is  not  nearly  so  serious  an  accident  as  rupture  of 
the  liver  or  spleen,  since  the  extravasation  of  blood  and  urine  which  follows  is,  in  the  majority 
of  cases,  outside  the  peritoneal  cavity.  Occasionally  the  kidney  may  be  bruised  by  blows  in  the 
loin  or  by  being  compressed  between  the  lower  ribs  and  the  ilium  when  the  body  is  violently 
bent  forward.  "This  is  followed  by  a  little  transient  hematuria,  which,  however,  speedily  passes 
off.  Occasionally,  when  rupture  involves  the  pelvis  of  the  kidney  or  the  commencement  of  the 
ureter,  this  duct  may  become  blocked,  and  hydronephrosis  follow. 

The  loose  cellular  tissue  around  the  kidney  may  be  the  seat  of  suppuration,  constituting 
perinephritic  abscess.  This  may  be  due  to  injury,  to  disease  of  the  kidney  itself,  or  to  extension 
of  inflammation  from  neighboring  parts.  The  abscess  may  burst  into  the  pleura,  constituting 
empyema ;  into  the  colon  or  bladder  ;  or  may  point  externally  in  the  groin  or  loin.  Tumors  of  the 
kidney,  of  which,  perhaps,  sarcoma  in  children  is  the  most  common,  may  be  recognized  by  their 
position  and  fixity ;  by  the  resonant  colon  lying  in  front  of  it ;  by  their  not  moving  with  respira- 
tion ;  and  by  their  rounded  outline,  not  presenting  a  notched  anterior  margin  like  the  spleen,  with 
which  they  are  most  likely  to  be  confounded.  The  examination  of  the  kidney  should  be  biman- 
ual ;  that  is  to  say,  one  hand  should  be  placed  in  the  flank  and  firm  pressure  made  forward,  while 
the  other  hand  is  buried  in  the  abdominal  wall,  over  the  situation  of  the  organ.  Manipulation 
of  the  kidney  frequently  produces  a  peculiar  sickening  sensation,  with  sometimes  faintness. 

The  kidney  is  mainly  held  in  position  by  the  mass  of  fatty  matter  in  which  it  is  embedded. 
If  this  fatty  matter  is  loose  or  lax  or  is  absorbed,  the  kidney  may  become  movable  and  may  give 
rise  to  great  pain.  This  condition  occurs,  therefore,  in  badly  nourished  people  or  in  those  who 
have  become  emaciated  from  any  cause,  and  is  more  common  in  women  than  in  men.  It  must 
not  be  confounded  with  the  floating  kidney :  this  is  a  congenital  condition  due  to  the  develop- 
ment of  a  mesonephron,  which  permits  the  organ  to  move  more  or  less  freely.  _  The  two  con- 
ditions cannot,  however,  be  distinguished  until  the  abdomen  is  opened  or  the  kidney  explored 
from  the  loin. 

The  kidney  has,  of  late  years,  been  frequently  the  seat  of  surgical  interference.^  It  may  be 
exposed  for  exploration  or  the  evacuation  of  pus  (nephrotomy) ;  it  may  be  incised  for  the 
removal  of  stone  (nephrolithotomy) ;  it  may  be  sutured  when  movable  or  floating  (nephror- 
raphy) ;  or  it  may  be  removed  (nephrectomy). 

The  kidney  may  be  exposed  either  by  a  lumbar  or  abdominal  incision.  The  operation  is 
best  performed  by  a  lumbar  incision,  except  in  cases  of  very  large  tumors  or  of  wandering 
kidneys  with  a  loose  mesonephron,  on  account  of  the  advantages  which  it  possesses  of  not 
opening  the  peritoneum  and  of  affording  admirable  drainage.  It  may  be  performed  either  by 
an  oblique,  a  vertical,  or  a  transverse  incision.  Perhaps  the  preferable,  as  affording  the  best 
means  for  exploring  the  whole  surface  of  the  kidney,  is  an  incision  from  the  tip  of  the  last  rib 
backward  to  the  edge  of  the  Erector  spinse.  This  incision  must  not  be  quite  parallel  to  the  rib, 
but  its  posterior  end  must  be  at  least  three-quarters  of  an  inch  below  it,  lest  the  pleura  be 
wounded.  This  cut  is  quite  sufficient  for  an  exploration  of  the  organ.  Should  it  require  removal, 
a  vertical  incision  can  be  made  downward  to  the  crest  of  the  ilium,  along  the  outer  border  of  the 
Quadratus  lumborum.  The  structures  divided  are  the  skin,  the  superficial  fascia  with  the 
cutaneous  nerves,  the  deep  fascia,  the  posterior  border  of  the  External  oblique  muscle  of  the 
abdomen,  and  the  outer  border  of  the  Latissimus  dorsi ;  the  Internal  oblique  and  the  posterior 
aponeurosis  of  the  Transversalis  muscle ;  the  outer  border  of  the  Quadratus  lumborum.  and  the 
deep  layer  of  the  lumbar  fascia,  and  the  transversalis  fascia.  The  fatty  tissue  around  the  kidney 
is  now  exposed  to  view,  and  must  be  separated  by  the  fingers  or  a  director  in  order  to  reach  the 
kidney. 

The  abdominal  operation  is  best  performed  by  an  incision  in  the  linea  semilunaris  on  the 
side  of  the  kidney  to  be  removed,  as  recommended  by  Langenbuch  ;  the  kidney  is  then  reached 
from  the  outer  side  of  the  colon,  ascending  or  descending,  as  the  case  may  be,  and  the  vessels 
of  the  colon  are  not  interfered  with.  If  the  incision  is  made  in  the  linea  alba,  the  kidney  is 
reached  from  the  inner  side  of  the  colon,  and  the  vessels  running  to  supply  it  must  necessarily 
be  interfered  with.  The  incision  is  made  of  varying  length  according  to  the  size  of  the  kidney, 
commencing  just  below  the  costal  arch.  The  abdominal  cavity  is  opened.  The  intestines  are 
held  aside,  and  the  outer  layer  of  the  mesocolon  incised,  so  that  the  fingers  can  be  introduced 
behind  the  peritoneum  and  the  renal  vessels  sought  for.  These  are  then  to  be  ligatured  :  if  tied 
separately,  care  must  be  taken  to  ligature  the  artery  first.  The  kidney  must  now  be  enucleated, 
and  the  vessels  and  the  ureter  divided,  and  the  latter  tied,  or  if  thought  necessary,  stitched  to  the 
edge  of  the  wound. 

THE   URETERS. 

The  Ureters  are  the  two  tubes  which  conduct  the  urine  from  the  kidneys  into 
the  bladder.  They  commence  within  the  sinus  of  the  kidney  by  a  number  of 
short  truncated  branches,  the  calices  or  infundibula,  which  unite  either  directly 


THE    URETERS.  995 

or  indirectly  to  form  a  dilated  pouch,  the  pelvis,  from  which  the  ureter,  after 
passing  through  the  hilum  of  the  kidney,  descends  to  the  bladder.  The  calices  are 
•cup-like  tubes  encircling  the  apices  of  the  Malpighian  pyramids ;  but  inasmuch  as 
one  calyx  may  include  two  or  even  more  papillae,  their  number  is  generally  less 
than  the  pyramids  themselves,  the  former  being  from  seven  to  thirteen,  whilst  the 
latter  vary  from  eight  to  eighteen.  These  calices  converge  into  two  or  three 
tubular  divisions  which  by  their  junction  form  the  pelvis  or  dilated  portion  of  the 
ureter.  The  portion  last  mentioned,  where  the  pelvis  merges  into  the  ureter 
proper,  is  found  opposite  the  spinous  process  of  the  first  lumbar  vertebra,  in  which 
situation  it  is  accessible  behind  the  peritoneum  (see  Fig.  507,  page  924). 

The  ureter  proper  is  a  cylindrical  membranous  tube,  about  sixteen  inches  in 
length  and  of  the  diameter  of  a  goosequill,  extending  from  the  pelvis  of  the  kidney 
to  the  bladder.  Its  course  is  obliquely  downward  and  inward  through  the  lumbar 
region  into  the  cavity  of  the  pelvis  where  it  passes  downward,  forward,  and  inward 
across  that  cavity  to  the  base  of  the  bladder,  into  which  it  then  opens  by  a  con- 
stricted orifice,  after  having  passed  obliquely  for  nearly  an  inch  between  its  muscular 
and  mucous  coats. 

Relations. — In  its  course  it  rests  upon  the  Psoas  muscle,  being  covered  by  the 
peritoneum,  and  crossed  obliquely,  from  within  outward,  by  the  spermatic  vessels ; 
the  right  is  crossed  by  the  branches  of  the  mesenteric  arteries,  which  are  distributed 
to  the  ascending,  and  the  left  by  those  for  the  descending  colon ;  the  right  ureter 
lying  close  to  the  outer  side  of  the  inferior  vena  cava.  Opposite  the  first  piece  of 
the  sacrum  it  crosses  either  the  common  or  external  iliac  artery,  lying  behind  the 
ileum  on  the  right  side  and  the  sigmoid  flexure  of  the  colon  on  the  left.  In  the 
pelvis  it  enters  the  posterior  false  ligament  of  the  bladder,  below  the  obliterated 
hypogastric  artery,  the  vas  deferens  in  the  male  passing  between  it  and  the  bladder. 
In  the  female  the  ureter  passes  along  the  side  of  the  neck  of  the  uterus  and  upper 
part  of  the  vagina.  At  the  base  of  the  bladder  it  is  situated  about  two  inches 
from  its  fellow  :  lying,  in  the  male,  about  an  inch  and  a  half  from  the  vesical  orifice 
•of  the  urethra,  at  one  of  the  posterior  angles  of  the  trigone. 

Structure. — The  ureter  is  composed  of  three  coats — a  fibrous,  muscular,  and 
mucous. 

The  fibrous  coat  is  the  same  throughout  the  entire  length  of  the  duct,  being 
continuous  at  one  end  with  the  capsule  of  the  kidney  at  the  floor  of  the  sinus,  while 
at  the  other  it  is  lost  in  the  fibrous  structure  of  the  bladder. 

In  the  pelvis  of  the  kidney  the  muscular  coat  consists  of  two  layers,  longitudinal 
and  circular:  the  longitudinal  fibres  become  lost  upon  the  sides  of  the  papillae  at 
the  extremities  of  the  calices ;  the  circular  fibres  may  be  traced  surrounding  the 
medullary  structure  in  the  same  situation.  In  the  ureter  proper  the  muscular 
fibres  are  very  distinct,  and  are  arranged  in  three  layers — an  external  longitudinal, 
a  middle  circular,  and  an  internal  layer,  less  distinct  than  the  other  two,  but 
having  a  general  longitudinal  direction.  According  to  Kolliker,  this  internal  layer 
is  only  found  in  the  neighborhood  of  the  bladder. 

The  mucous  coat  is  smooth,  and  presents  a  few  longitudinal  folds  which 
become  effaced  by  distension.  It  is  continuous  with  the  mucous  membrane  of  the 
bladder  below,  whilst  it  is  prolonged  over  the  papillae  of  the  kidney  above.  Its 
epithelium  is  of  a  peculiar  character,  and  resembles  that  found  in  the  bladder.  It 
is  known  by  the  name  of  "  transitional  "  epithelium.  It  consists  of  several  layers 
of  cells,  of  which  the  innermost — that  is  to  say,  the  cells  in  contact  with  the 
urine — are  quadrilateral  in  shape,  with  a  concave  margin  on  their  outer  surface, 
into  which  fits  the  rounded  end  of  the  cells  of  the  second  layer.  These,  the  inter- 
mediate cells,  more  or  less  resemble  columnar  epithelium,  and  are  pear-shaped, 
with  a  rounded  internal  ex'  lich  fits  into  the  concavity  of  the  cells  of  the 

first  layer,  and  a  narrow  ei  tremity  which  is  Avedged  in  between  the  cells 

of  the  third  layer.  The  external  ( i  third  layer  consists  of  conical  or  oval  cells 
varying  in  number  in  diffe  ,  and  presenting  processes  which  extend  down 

into  the  basement  membra 


996 


THE    URINARY   ORG  AN 8. 


The  arteries  supplying  the  ureter  are  branches  from  the  renal,  spermatic,, 
internal  iliac,  and  inferior  vesical. 

The  nerves  are  derived  from  the  inferior  mesenteric,  spermatic,  and  pelvic 
plexuses. 

Surgical  Anatomy. — Subcutaneous  rupture  of  the  ureter  is  not  a  common  accident,  but 
occasionally  occurs  from  a  sharp,  direct  blow  on  the  abdomen,  as  from  the  kick  of  a  horse.  It 
may  be  either  torn  completely  across  or  only  partially  divided,  and,  as  a  rule,  the  peritoneum 
escapes  injury.  If  torn  completely  across,  the  urine  collects  in  the  retroperitoneal  tissues ;  if  it 
is  not  completely  divided,  the  lumen  of  the  tube  may  become  obstructed  and  hydro-nephrosis  or 
pyo-nephrosis  result.  The  ureter  may  be  accidentally  wounded  in  some  abdominal  operations ; 
if  this  should  happen,  the  divided  ends  must  be  sutured  together,  or,  failing  to  accomplish  this, 
the  upper  end  must  be  implanted  into  the  bladder  or  the  intestine. 


THE  SUPRARENAL  CAPSULES. 

The  Suprarenal  Capsules  belong  to  the  class  of  ductless  glands.  They  are  two 
small  flattened  bodies,  of  a  yellowish  color,  situated  at  the  back  part  of  the  abdo- 
men, behind  the  peritoneum,  and  immediately 
above  and  in  front  of  the  upper  end  of  each  kid- 
ney ;  hence  their  name.  The  right  one  is  some- 
what triangular  in  shape,  bearing  a  resemblance 
to  a  cocked  hat ;  the  left  is  more  semilunar, 
usually  larger  and  placed  at  a  higher  level  than 
the  right.  They  vary  in  size  in  different  individ- 
uals, being  sometimes  so  small  as  to  be  scarcely 

S^-Capsule.     ■- 

Zona 
glomerulosa. 


Zona 
fasciculata. 


Gland 
cylinders. 


Fig.  555.— Minute  structure  of  suprarenal: 
capsule. 


Framework. 


Nuclei. 


Zona  reticularis. 


Fig.  554.— Vertical  section  of  the  suprarenal 
capsule.    From  Elberth,  in  Strieker's  Manual. 


Capillary* 


Fig.  556. — Minute  structure  of  suprarenal 
capsule. 


detected :  their  usual  size  is  from  an  inch  and  a  quarter  to  nearly  two  inches  in 
length,  rather  less  in  width,  and  from  two  to  three  lines  in  thickness.  "  Their  average 
weight  is  from  one  to  one  and  a  half  drachms  each. 


THE  SUPRARENAL    CAPSULES.  997 

Relations. — The  relations  of  the  suprarenal  capsules  differ  on  the  two  sides  of 
the  body.  The  right  suprarenal  is  roughly  triangular  in  shape,  its  angles  pointing 
upward,  downward,  and  outward.  It  presents  two  surfaces  for  examination,  an 
anterior  and  a  posterior.  The  anterior  surface  presents  two  areas,  separated  by  a 
furrow,  the  hilum  :  one  area  occupying  about  one-third  of  the  whole  surface,  is 
situated  above  and  internally;  it  is  depressed,  uncovered  by  peritoneum,  and  is  in 
contact  in  front  with  the  posterior  surface  of  the  right  lobe  of  the  liver,  and  along 
its  inner  border  with  the  inferior  vena  cava;  the  remaining  area  is  elevated, 
and  is  divided  into  a  non-peritoneal  portion,  in  contact  with  the  hepatic  flex- 
ure of  the  duodenum,  and  a  portion  covered  by  peritoneum  forming  the  hepato- 
renal fold.  The  posterior  surface  is  slightly  convex,  and  rests  upon  the  Dia- 
phragm. The  base  is  concave,  and  is  in  contact  with  the  upper  end  and  the  adja- 
cent part  of  the  anterior  surface  of  the  kidney.  The  left  suprarenal  is  crescentic 
in  shape,  its  concavity  being  adapted  to  the  upper  end  of  the  left  kidney.  It 
presents  an  inner  border  which  is  convex,  and  an  outer  w7hich  is  concave ;  its 
upper  border  is  narrow,  and  its  lower  rounded.  Its  anterior  surface  presents  two 
areas  :  an  upper  one,  covered  by  the  peritoneum  forming  the  lesser  sac,  which 
separates  it  from  the  cardiac  end  of  the  stomach  and  to  a  small  extent  from  the 
superior  extremity  of  the  spleen  ;  and  a  lower  one,  which  is  in  contact  with  the 
pancreas  and  splenic  artery,  and  is  therefore  not  covered  by  the  peritoneum. 
Its  posterior  surface  presents  a  vertical  ridge,  which  divides  it  into  two  areas. 
The  ridge  lies  in  the  sulcus  between  the  kidney  and  crus  of  the  Diaphragm, 
while  the  area  on  either  side  of  it  lies  on  these  parts  respectively ;  the  outer 
area,  which  is  thin,  resting  on  the  kidney,  and  the  inner  and  smaller  area  rest- 
ing on  the  left  crus  of  the  Diaphragm.  The  surface  of  the  suprarenal  gland 
is  surrounded  by  areolar  tissue  containing  much  fat,  and  closely  invested  by  a 
thin  fibrous  coat,  wThich  is  difficult  to  remove,  on  account  of  numerous  fibrous 
processes  and  vessels  which  enter  the  organ  through  the  furrows  on  its  anterior 
surface  and  base. 

Small  accessory  suprarenals  are  often  to  be  found  in  the  connective  tissue 
around  the  suprarenals.  The  smaller  of  these,  on  section,  show  a  uniform  surface, 
but  in  some  of  the  larger  a  distinct  medulla  can  be  made  out. 

Structure. — On  making  a  perpendicular  section,  the  gland  is  seen  to  consist  of 
two  substances — external  or  cortical,  and  internal  or  medullary.  The  former, 
which  constitutes  the  chief  part  of  the  organ,  is  of  a  deep  yellow  color.  The 
medullary  substance  is  soft,  pulpy,  and  of  a  dark  brown  or  black  color,  whence 
the  name  atrabiliary  capsules  formerly  given  to  these  organs.  In  the  centre  is 
often  seen  a  space,  not  natural,  but  formed  by  breaking  down  after  death  of  the 
medullary  substance. 

The  cortical  portion  consists  chiefly  of  narrow  columnar  masses  placed  perpen- 
dicularly to  the  surface.  This  arrangement  is  due  to  the  disposition  of  the  cap- 
sule, which  sends  into  the  interior  of  the  gland  processes  passing  in  vertically  and 
communicating  with  each  other  by  transverse  bands  so  as  to  form  spaces  which 
open  into  each  other.  These  spaces  are  of  slight  depth  near  the  surface  of  the 
organ,  so  that  there  the  section  somewhat  resembles  a  net ;  this  is  termed  the 
zona  glomerulosa  ;  but  they  become  much  deeper  or  longer  farther  in,  so  as  to 
resemble  pipes  or  tubes  placed  endwise,  the  zona  fasciculata.  Still  deeper  down, 
near  the  medullary  part,  the  spaces  become  again  of  small  extent ;  this  is  named 
the  zona  reticularis.  These  processes  or  trabecule,  derived  from  the  capsule  and 
forming  the  framework  of  the  spaces,  are  composed  of  fibrous  connective  tissue 
with  longitudinal  bundles  of  unstriped  muscular  fibres.  Within  the  interior  of 
the  spaces  are  contained  groups  of  polyhedral  cells,  which  are  finely  granular  in 
appearance,  and  contain  a  spherical  nucleus,  and  not  infrequently  fat-globules. 
These  groups  of  cells  do  not  entirely  fill  the  spaces  in  which  they  are  contained, 
I>ut  between  them  and  the  trabecule  of  the  framework  is  a  channel  which 
is  believed  to  be  a  lymph-path  or  sinus,  and  which  communicates  with  certain 
passages  between  the  cells  composing  the  group.     The  lymph-path   is  supposed 


998  THE    URINARY  ORGANS. 

to  open  into  a  plexus  of  efferent  lymphatic  vessels  which  are  contained  in  the- 
capsule. 

In  the  medullary  portion  the  fibrous  stroma  seems  to  be  collected  together 
into  a  much  closer  arrangement,  and  forms  bundles  of  connective  tissue  which  are 
loosely  applied  to  the  large  plexus  of  veins  of  which  this  part  of  the  organ  mainly 
consists.  In  the  interstices  lie  a  number  of  cells  compared  by  Frey  to  those  of 
columnar  epithelium.  They  are  coarsely  granular,  do  not  contain  any  fat- 
molecules,  and  some  of  them  are  branched.  Luschka  has  affirmed  that  these 
branches  are  connected  with  the  nerve-fibres  of  a  very  intricate  plexus  which  is 
found  in  the  medulla :  this  statement  has  not  been  verified  by  other  observers, 
for  the  tissue  of  the  medullary  substance  is  less  easy  to  make  out  than  that  of  the- 
cortical,  owing  to  its  rapid  decomposition. 

The  numerous  arteries  which  enter  the  suprarenal  bodies  from  the  sources 
mentioned  below  penetrate  the  cortical  part  of  the  gland,  where  they  break  up 
into  capillaries  in  the  fibrous  septa,  and  these  converge  to  the  very  numerous  veins 
of,  the  medullary  portion,  which  are  collected  together  into  the  suprarenal  vein, 
which  usually  emerges  as  a  single  vessel  from  the  centre  of  the  gland. 

The  arteries  supplying  the  suprarenal  capsules  are  numerous  and  of  large- 
size  ;  they  are  derived  from  the  aorta,  the  phrenic,  and  the  renal ;  they  sub- 
divide into  numerous  minute  branches  previous  to  entering  the  substance  of  the 
gland. 

The  suprarenal  vein  returns  the  blood  from  the  medullary  venous  plexus,  and 
receives  several  branches  from  the  cortical  substance ;  it  opens  on  the  right  side 
into  the  inferior  vena  cava,  on  the  left  side  into  the  renal  vein. 

The  lymphatics  terminate  in  the  lumbar  glands. 

The  nerves  are  exceedingly  numerous,  and  are  derived  from  the  solar  and 
renal  plexuses,  and,  according  to  Bergmann,  form  the  phrenic  and  pneumogastric 
nerves.  They  enter  the  lower  and  inner  part  of  the  capsule,  traverse  the  cortex, 
and  terminate  round  the  cells  of  the  medulla.  They  have  numerous  small  ganglia 
developed  upon  them,  from  which  circumstance  the  organ  has  been  conjectured  to 
have  some  function  in  connection  with  the  sympathetic  nervous  system. 

THE  CAVITY  OF  THE  PELVIS. 

The  cavity  of  the  pelvis  is  that  part  of  the  general  abdominal  cavity  which  is 
below  the  level  of  the  linea  ilio-pectinea  and  the  promontory  of  the  sacrum. 

Boundaries. — It  is  bounded  behind  by  the  sacrum,  the  coccyx,  the  Pyriformis 
muscle,  and  the  great  sacro-sciatic  ligaments  ;  in  front  and  at  the  sides  by  theossa 
pubis  and  ischia,  covered  by  the  Obturator  muscles  ;  above,  it  communicates  with 
the  cavity  of  the  abdomen ;  and  below,  the  outlet  is  closed  by  the  triangular 
ligament,  the  Levatores  ani  and  Coccygei  muscles,  and  the  visceral  layer  of  the- 
pelvic  fascia,  which  is  reflected  from  the  wall  of  the  pelvis  on  to  the  viscera.' 

Contents. — The  viscera  contained  in  this  cavity  are — the  urinary  bladder,  the 
rectum,  and  some  of  the  generative  organs  peculiar  to  each  sex,  and  some  convo- 
lutions of  the  small  intestines  ;  they  are  partially  covered  by  the  peritoneum, 
and  supplied  with  blood-vessels,  lymphatics,  and  nerves. 

THE  BLADDER. 

The  bladder  is  the  reservoir  for  the  urine.  It  is  a  musculo-membranous  sac 
situated  in  the  pelvis,  behind  the  pubes,  and  in  front  of  the  rectum  in  the  male,, 
the  cervix  uteri  and  vagina  intervening  between  it  and  that  intestine  in  the  female. 
The  shape,  position,  and  relations  of  the  bladder  are  greatly  influenced  by  age, 
sex,  and  the  degree  of  distention  of  the  organ.  Duri?ig  infancy  it  is  conical  in 
shape,  and  projects  above  the  upper  border  of  the  ossa  pubis  into  the  hypogastric 
region.  In  the  adult,  when  quite  empty  and  contracted,  it  is  cup-shaped,  and  on 
vertical  median  section  its  cavity,  with  the  adjacent  portion  of  the  urethra,  pre- 
sents a  Y-shaped  cleft,  the  stem  of  the  Y  corresponding  to  the  urethra.     It  is- 


THE   BLADDER. 


999 


placed  deeply  in  the  pelvis,  flattened  from  before  backward,  and  reaches  as  high 
as  the  upper  border  of  the  symphysis  pubis.  When  slightly  distended,  it  has  a 
rounded  form,  and  is  still  contained  within  the  pelvic  cavity  ;  and  when  greatly 
distended  it  is  ovoid  in  shape,  rising  into  the  abdominal  cavity,  and  often  extend- 
ing nearly  as  high  as  the  umbilicus.  It  is  larger  in  its  vertical  diameter  than 
from  side  to  side,  and  its  long  axis  is  directed  from  above  obliquely  downward 
and  backward,  in  a  line  directed  from  some  point  between  the  symphysis  pubis 
and  umbilicus  (according  to  its  distention)  to  the  end  of  the  coccyx.  The  bladder, 
when  distended,  is  slightly  curved  forward  toward  the  anterior  Avail  of  the  abdo- 
men, so  as  to  be  more  convex  behind  than  in  front.  In  the  female  it  is  larger  in 
the  transverse  than  in  the  vertical  diameter,  and  its  capacity  is  said  to  be  greater 


\ Suspensory 

~^T     ligament. 


SPHINCTER    ANI. 


Fossa  na  vicularis.- 


Fig.  557.— Vertical  section  of  bladder,  penis,  and  urethra. 


than  in  the  male.1  When  moderately  distended,  it  measures  about  five  inches  in 
length,  and  three  inches  across,  and  the  ordinary  amount  which  it  contains  is 
about  a  pint. 

The  bladder  is  divided  for  purposes  of  description  into  a  superior,  an  antero- 
inferior, and  two  lateral  surfaces,  a  base  or  fundus  and  a  summit  or  apex. 

The  superior  or  abdominal  surface  is  entirely  free,  and  is  covered  throughout 
by  peritoneum.  It  looks  aim''  directly  upward  into  the  abdominal  cavity,  and 
extends  in  an  antero-posterior  direction  from  the  apex  to  the  base  of  the  bladder. 
It  is  in  relation  with  the  smaii  intestine  and  sometimes  with  the  sigmoid  flexure, 
and  in  the  female,  with   the  uterus.     On  each  side,  in  the  male,  a  portion  of  the 

1  According  to  Henle,  the  blad  erably  smaller  in  the  female  than  in  the  male. 


1000 


THE    URINARY   ORGANS. 


vas  deferens  is  in  contact  with  the  hinder  part  of  this  surface,  lying  beneath  the 
peritoneum. 

The  antero-inferior  or  pubic  surface  looks  downward  and  forward.  In  the 
undistended  condition  it  is  uncovered  by  peritoneum,  and  is  in  relation  with  the 
Obturator  internus  muscle  on  each  side,  with  the  recto-vesical  fascia,  and  anterior 
true  ligaments  of  the  bladder.  It  is  separated  from  the  body  of  the  pubis  by  a 
triangular  interval,  the  space  of  Retzius,  occupied  by  fatty  tissue.     As  the  bladder 


Prostate 
gland. 


Sphincter  ani. 


Fig.  558. — Vertical  median  section  of  the  male  pelvis.    (Henle.') 

ascends  into  the  abdominal  cavity  during  distention  the  distance  between  its  apex 
and  the  umbilicus  is  necessarily  diminished,  and  the  urachus  is  thus  relaxed;  so 
that,  instead  of  passing  directly  upward  to  the  umbilicus,  it  descends  first  on  the 
upper  part  of  the  anterior  surface  of  the  bladder,  and  then,  curving  upward, 
ascends  on  the  back  of  the  abdominal  wall.  The  peritoneum,  which  follows  the 
urachus,  thus  comes  to  form  a  pouch  of  varying  depth  between  the  anterior  surface 
of  the  viscus  and  the  abdominal  wall.  Thus,  when  the  bladder  is  distended,  the 
upper  part  of  its  anterior  surface  is  in  relation  to  the  urachus  and  is  covered  by 
peritoneum.  The  lower  part  of  its  anterior  surface,  a  distance  of  about  two 
inches  above  the  symphysis  pubis,  is  devoid  of  peritoneum,  and  is  in  contact  with 
the  abdominal  wall. 

The  lateral  surfaces  are  covered  behind  and  above  by  peritoneum,  which 
extends  as  low  as  the  level  of  the  obliterated  hypogastric  artery ;  below  and  in 
front  of  this,  these  surfaces  are  uncovered  by  peritoneum,  and  are  separated  from 


THE  BLADDER. 


1001 


the  Levatores  ani  muscles  and  walls  of  the  pelvis  by  a  quantity  of  loose  areolar 
tissue  containing  fat.  In  front  this  surface  is  connected  to  the  recto-vesical  fascia 
by  a  broad  expansion  on  either  side,  the  lateral  true  ligaments.  The  vas  deferens 
crosses  the  hinder  part  of  the  lateral  surface  obliquely,  and  passes  between  the 
ureter  and  the  bladder. 

The  fundus  or  base  is  directed  downward  and  backward,  and  is  partly  covered 
by  peritoneum  and  partly  uncovered.  In  the  male  the  upper  portion,  to  within 
about  an  inch  and  a  half  of  the  prostate,  is  covered  by  the  recto-vesical  pouch  of 
peritoneum.  The  lower  part  is  in  direct  contact  with  the  anterior  wall  of  the 
second  part  of  the  rectum  and  the  vesiculse  seminales  and  vasa  deferentia.  The 
ureters  enter  the  bladder  at  the  upper  part  of  its  base,  about  two  inches  above  the 
prostate  gland. 


Vermiform  appendix 


External  iliac         Anterior  crural        External  oblique 


artery. 


muscle. 


Profunda  vessels,    levator  ani 


Fig.  559.— Frontal  section  of  the  lower  part  of  the  abdomen.    Viewed  from  the  front.    (Braune.) 

The  portion  of  the  bladder  in  relation  with  the  rectum  corresponds  to  a 
triangular  space,  bounded,  below,  by  the  prostate  gland ;  above,  by  the  recto- 
vesical fold  of  the  peritoneum  ;  and  on  each  side,  by  the  vesicula  seminalis  and 
vas  deferens.  It  is  separated  from  direct  contact  with  the  rectum  by  the  recto- 
vesical fascia.  When  the  bladder  is  very  full,  the  peritoneal  fold  is  raised  with 
it,  and  the  distance  between  its  reflection  and  the  anus  is  about  four  inches ;  but 
this  distance  is  much  diminished  when  the  bladder  is  empty  and  contracted.  In 
the  female,  the  base  of  the  bladder  is  connected  to  the  anterior  aspect  of  the  cervix 
uteri  by  areolar  tissue,  and  is  adherent  to  the  anterior  wall  of  the  vagina.  Its 
upper  surface  is  separated  from  the  anterior  surface  of  the  body  of  the  uterus  by 
the  utero-vesical  pouch  of  peritoneum. 

The  so-called  neck  (cervix)  of  the  bladder  is  the  point  of  commencement  of  the 
urethra ;  there  is,  however,  no  tapering  part,  which  would  constitute  a  true  neck, 


1002  THE    URINARY   ORGANS. 

but  the  bladder  suddenly  contracts  to  the  opening  of  the  urethra.  In  the  male  its 
direction  is  oblique  in  the  erect  posture,  and  it  is  surrounded  by  the  prostate  gland. 
In  the  female  its  direction  is  obliquely  downward  and  forward. 

The  urachus  is  the  obliterated  remains  of  the  tubular  canal  of  the  allantois, 
which  exists  in  the  embryo,  and  a  portion  of  which  becomes  expanded  to  form  the 
bladder  (see  section  on  Embryology).  It  passes  upward,  from  the  apex  of  the 
bladder,  between  the  transversalis  fascia  and  peritoneum,  to  the  umbilicus,  becom- 
ing thinner  as  it  ascends.  It  is  composed  of  fibrous  tissue,  mixed  with  plain  mus- 
cular fibres.  On  each  side  of  it  is  placed  a  fibrous  cord,  the  obliterated  portion 
of  the  hypogastric  artery,  which,  passing  upward  from  the  side  of  the  bladder, 
approaches  the  urachus  above  its  summit.  In  the  infant,  at  birth,  it  is  occasion- 
ally found  pervious,  so  that  the  urine  escapes  at  the  umbilicus,  and  calculi  have 
been  found  in  its  canal. 

Ligaments. — The  bladder  is  retained  in  its  place  by  ligaments,  which  are  divided 
into  true  and  false.  The  true  ligaments  are  five  in  number :  two  anterior,  two 
lateral,  and  the  urachus.  The  false  ligaments,  also  five  in  number,  are  formed  by 
folds  of  the  peritoneum. 

The  anterior  true  ligaments  (p  lib  o-pro  static)  extend  from  the  back  of  the  ossa 
pubis,  one  on  each  side  of  the  symphysis,  to  the  front  of  the  neck  of  the  bladder, 
over  the  anterior  surface  of  the  prostate  gland.  These  ligaments  are  formed  by 
the  recto-vesical  fascia,  and  contain  a  few  muscular  fibres  prolonged  from  the 
bladder. 

The  lateral  true  ligaments,  also  formed  by  the  recto-vesical  fascia,  are  broader 
and  thinner  than  the  preceding.  They  are  attached  to  the  lateral  parts  of  the 
prostate  and  to  the  sides  of  the  base  of  the  bladder. 

The  urachus  is  the  fibro-muscular  cord  already  mentioned,  extending  between 
the  summit  of  the  bladder  and  the  umbilicus.  It  is  broad  below,  at  its  attachment 
to  the  bladder,  and  becomes  narrower  as  it  ascends. 

The  false  ligaments  of  the  bladder  are  two  posterior,  two  lateral,  and  one 
superior. 

The  two  posterior  pass  forward,  in  the  male,  from  the  sides  of  the  rectum ;  in 
the  female,  from  the  sides  of  the  uterus,  to  the  posterior  and  lateral  aspect  of  the 
bladder :  they  form  the  lateral  boundaries  of  the  recto-vesical  fold  of  the  perito- 
neum, and  contain  the  obliterated  hypogastric  arteries,  and  the  ureters,  together 
with  vessels  and  nerves. 

The  two  lateral  ligaments  are  reflections  of  the  peritoneum,  from  the  iliac  fossae 
and  lateral  walls  of  the  pelvis  to  the  sides  of  the  bladder. 

The  superior  ligament  (ligamentum  suspensorium)  is  the  prominent  fold  of 
peritoneum  extending  from  the  summit  of  the  bladder  to  the  umbilicus.  It  is 
carried  off  from  the  bladder  by  the  urachus  and  the  obliterated  hypogastric  arteries. 

Structure. — The  bladder  is  composed  of  four  coats — serous,  muscular,  sub- 
mucous, and  mucous. 

The  serous  coat  is  partial,  and  derived  from  the  peritoneum.  It  invests  the 
superior  surface  and  the  upper  part  of  the  lateral  surfaces  and  base,  and  is  reflected 
from  these  parts  on  to  the  abdominal  and  pelvic  walls. 

The  muscular  coat  consists  of  three  layers  of  unstriped  muscular  fibre :  an 
external  layer,  composed  of  fibres  having  for  the  most  part  a  longitudinal  arrange- 
ment ;  a  middle  layer,  in  which  the  fibres  are  arranged,  more  or  less,  in  a  circular 
manner ;  and  an  internal  layer,  in  which  the  fibres  have  a  general  longitudinal 
arrangement. 

The  fibres  of  the  external  longitudinal  lager  arise  from  the  posterior  surface  of 
the  body  of  the  os  pubis  in  both  sexes  (onusculi  pubo-vesicalis),  and  in  the  male  from 
the  adjacent  part  of  the  prostate  gland  and  its  capsule.  They  pass,  in  a  more  or 
less  longitudinal  manner,  up  the  anterior  surface  o^  the  bladder,  over  its  apex, 
and  then  descend  along  its  posterior  surfac"  to  its  base,  where  they  become 
attached  to  the  prostate  in  the  male  and  *o  the  front  of  the  vagina  in  the  female. 


THE   BLADDER.  1003 

At  the  sides  of  the  bladder  the  fibres  are  arranged  obliquely  and  intersect  one 
another.     This  layer  has  been  named  the  detrusor  urince  muscle. 

The  middle  circular  layers  are  very  thinly  and  irregularly  scattered  on  the  body 
of  the  organ,  and,  though  to  some  extent  placed  transversely  to  the  long  axis  of  the 
bladder,  are  for  the  most  part  arranged  obliquely.  Toward  the  lower  part  of  the 
bladder,  round  the  cervix  and  commencement  of  the  urethra,  they  are  disposed  in 
a  thick  circular  layer,  forming  the  sphincter  vesica?,  which  is  continuous  with  the 
muscular  fibres  of  the  prostate  gland. 

The  internal  longitudinal  layer  is  thin,  and  its  fasciculi  have  a  reticular 
arrangement,  but  with  a  tendency  to  assume  for  the  most  part  a  longitudinal 
direction. 

Two  bands  of  oblique  fibres,  originating  behind  the  orifices  of  the  ureters, 
converge  to  the  back  part  of  the  prostate  gland,  and  are  inserted,  by  means  of  a 
fibrous  process,  into  the  middle  lobe  of  that  organ.  They  are  the  muscles  of  the 
ureters,  described  by  Sir  C.  Bell,  who  supposed  that  during  the  contraction  of  the 
bladder  they  served  to  retain  the  oblique  direction  of  the  ureters,  and  so  prevent 
the  reflux  of  the  urine  into  them. 

The  submucous  coat  consists  of  a  layer  of  areolar  tissue  connecting  together  the 
muscular  and  mucous  coats,  and  intimately  united  to  the  latter. 

The  mucous  coat  is  thin,  smooth,  and  of  a  pale  rose  color.  It  is  continuous  above 
through  the  ureters  with  the  lining  membrane  of  the  uriniferous  tubes,  and  below 
with  that  of  the  urethra.  It  is  connected  loosely  to  the  muscular  coat  by  a  layer 
of  areolar  tissue,  and  is  therefore  thrown  into  folds  or  ruga?  when  the  bladder  is 
empty.  The  epithelium  covering  it  is  of  the  transitional  variety,  consisting  of  a 
superficial  layer  of  polyhedral  flattened  cells,  each  with  one,  two,  or  three  nuclei ; 
beneath  these,  a  stratum  of  large  club-shaped  cells  with  the  narrow  extremity  di- 
rected downward  and  wedged  in  between  smaller  spindle-shaped  cells,  containing 
an  oval  nucleus  (Figs.  560,  561).      There  are  no  true  glands  in  the  mucous  mem- 


Fig.  560.— Superficial  layer  of  the  epithelium  of  Fig.561.— Deep  layers  of  epithelium  of  bladder, 

the  bladder.    Composed  of  polyhedral  cells  of  vari-  showing    large   club-shaped   cells   above,  and 

ous    sizes,    each  with  one,  two,  or    three    nuclei.  smaller,  more  spindle-shaped  cells  below,  each 

(Kleiu  and  Noble  Smith.)  with  an  oval  nucleus.    (Klein  and  Noble  Smith,  i 

brane  of  the  bladder,  though  certain  mucous  follicles  which  exist,  especially  near 
the  neck  of  the  bladder,  have  been  regarded  as  such. 

Objects  seen  on  the  Inner  Surface. — Upon  the  inner  surface  of  the  bladder  are 
seen  the  orifices  of  the  ureters,  the  trigone,  and  the  commencement  of  the 
urethra. 

The  Orifices  of  the  Ureters. — These  are  situated  at  the  base  of  the  trigone, 
being  distant  from  each  other  about  two  inches  ;  they  are  about  an  inch  and  a  half 
from  the  base  of  the  prostate  and  the  commencement  of  the  urethra. 

The  trigonum  vesica?,  or  trigone  vesical,  is  a  triangular  smooth  surface,  with 
the  apex  directed  forward,  situated  at  the  base  of  the  bladder,  immediately  behind 
the  urethral  orifice.  It  is  paler  in  color  than  the  rest  of  the  interior,  and  never 
presents  any  rugae,  even  in  the  collapsed  condition  of  the  organ,  owing  to  the  inti- 
mate adhesion  of  its  mucous  membrane  to  the  subjacent  tissue.  It  is  bounded  at  each 
posterior  angle  by  the  orifice  of  the  ureter,  and  in  front  by  the  orifice  of  the  urethra. 


1004  THE    URINARY    ORGANS. 

Projecting  from  the  lower  and  anterior  part  of  the  bladder,  and  reaching  to  the 
orifice  of  the  urethra,  is  a  slight  elevation  of  mucous  membrane,  called  the  uvula 
vesica.     It  is  formed  by  a  thickening  of  the  submucous  tissue. 

The  arteries  supplying  the  bladder  are  the  superior,  middle,  and  inferior  vesi- 
cal in  the  male,  with  additional  branches  from  the  uterine  and  vaginal  in  the 
female.  They  are  all  derived  from  the  anterior  trunk  of  the  internal  iliac.  The 
obturator  and  sciatic  arteries  also  supply  small  visceral  branches  to  the  bladder. 

The  veins  form  a  complicated  plexus  round  the  neck,  sides,  and  base  of  the 
bladder,  and  terminate  in  the  internal  iliac  vein. 

The  lymphatics  form  two  plexuses,  one  in  the  muscular  and  another  in  the  sub- 
mucous coat ;  they  are  most  numerous  in  the  neighborhood  of  the  trigone.  They 
accompany  the  blood-vessels,  and  ultimately  terminate  in  the  internal  iliac  glands. 

The  nerves  are  derived  from  the  pelvic  plexus  of  the  sympathetic  and  from  the 
third  and  the  fourth  sacral  nerves  ;  the  former  supplying  the  upper  part  of  the 
organ,  the  latter  its  base  and  neck.  According  to  F.  Darwin,  the  sympathetic 
fibres  have  ganglia  connected  with  them,  which  send  branches  to  the  vessels  and 
muscular  coat. 

Surface  Form.— The  surface  form  of  the  bladder  varies  with  its  degree  of  distention  and 
under  other  circumstances.  In  the  young  child  it  is  represented  by  a  conical  figure,  the  apex 
of  which,  even  when  the  viscus  is  empty,  is  situated  in  the  hypogastric  region,  about  an  inch 
above  the  level  of  the  symphysis  pubis.  In  the  adult,  when  the  bladder  is  empty,  its  apex  does 
not  reach  above  the  level  of  the  upper  border  of  the  symphysis  pubis,  and  the  whole  organ  is  situ- 
ated in  the  pelvis ;  the  neck,  in  the  male,  corresponding  to  a  line  drawn  horizontally  backward 
through  the  symphysis  a  little  below  its  middle.  As  the  bladder  becomes  distended,  it  gradually 
rises  out  of  the  pelvis  into  the  abdomen,  and  forms  a  swelling  in  the  hypogastric  region  which  is 
perceptible  to  the  hand  as  well  as  to  percussion.  In  extreme  distention  it  reaches  into  the  um- 
bilical regiou  Under  these  circumstances  the  lower  part  of  its  anterior  surface,  for  a  distance 
of  about  two  inches  above  the  symphysis  pubis,  is  closely  applied  to  the  abdominal  wall,  without 
the  intervention  of  peritoneum,  so  that  it  can  be  tapped  by  an  opening  in  the  middle  line  just 
above  the  symphysis  pubis,  without  any  fear  of  wounding  the  serous  membrane.  When  the 
rectum  is  distended,  the  prostatic  portion  of  the  urethra  is  elongated  and  the  bladder  lifted  out 
of  the  pelvis  and  the  peritoneum  pushed  upward.  Advantage  is  taken  of  this  by  some  surgeons 
in  performing  the  operation  of  suprapubic  cystotomy.  The  rectum  is  distended  by  an  India- 
rubber  bag,  which  is  introduced  into  this  cavity  empty,  and  then  filled  with  ten  or  twelve  ounces 
of  water.  If  now  the  bladder  is  injected  with  about  half  a  pint  of  some  antiseptic  fluid,  it  will 
appear  above  the  pubes  plainly  perceptible  to  the  sight  and  touch.  The  peritoneum  will  be 
pushed  out  of  the  way,  and  an  incision  three  inches  long  may  be  made  in  the  linea  alba,  from 
the  symphysis  pubis  upward,  without  any  great  risk  of  wounding  the  peritoneum.  Other  sur- 
geons object  to  the  employment  of  this  bag,  as  its  use  is  not  unattended  with  risk,  and  because 
it  causes  pressure  on  the  prostatic  sinuses  and  produces  congestion  of  the  vessels  over  the 
bladder  and  a  good  deal  of  venous  hemorrhage. 

When  distended,  the  bladder  can  be  felt  in  the  male,  from  the  rectum,  behind  the  prostate, 
and  fluctuation  can  be  perceived  by  a  bimanual  examination,  one  finger  being  introduced  into  the 
rectum  and  the  distended  bladder  tapped  on  the  front  of  the  abdomen  with  the  finger  of  the 
other  hand.  This  portion  of  the  bladder — that  is,  the  portion  felt  in  the  rectum  by  the  finger — 
is  also_  uncovered  by  peritoneum,  and  the  bladder  may  here  be  punctured  from  the  rectum,  in 
the  middle  line,  without  risk  of  wounding  the  serous  membrane. 

Surgical  Anatomy. — A  defect  of  development  in  which  the  bladder  is  implicated  is  known 
under  the  name  of  extroversion  of  the  bladder.  In  this  condition  the  lower  part  of  the  abdomi- 
nal wall  and  the  anterior  wall  of  the  bladder  are  wanting,  so  that  the  posterior  surface  of  the 
bladder  presents  on  the  abdominal  surface,  and  is  pushed  forward  by  the  pressure  of  the  viscera 
within  the  abdomen,  forming  a  red,  vascular  tumor,  on  which  the  openings  of  the  ureters  are 
^uSl^}e'  ^ie  pen*s'  excePt  the  glans,  is  rudimentary  and  is  cleft  on  its  dorsal  surface,  exposing 
the  floor  of  the  urethra — a  condition  known  as  epispadias.  The  pelvic  bones  are  also  arrested 
in  development  (see  page  183). 

The  bladder  may  be  ruptured  by  violence  applied  to  the  abdominal  wall  when  the  viscus  is 
distended  without  any  injury  to  the  bony  pelvis,  or  it  may  be  torn  in  cases  of  fracture  of  the 
pelvis.  The  rupture  may  be  either  intraperitoneal  or  extraperitoneal — that  is,  may  implicate  the 
superior  surface  of  the  bladder  in  the  former  case,  or  one  of  the  other  surfaces  in  the  latter. 
Rupture  of  the  anteroinferior  surface  alone  is.  however,  very  rare.  Until  recently  intraperi- 
toneal rupture  was  uniformly  fatal,  but  now  abdominal  section  and  suturing  the  rent  with  Lem- 
bert  s  suture  are  resorted  to,  with  a  very  considerable  amount  of  success.  The  sutures  are  inserted 
only  through  the  peritoneal  and  muscular  coats  in  such  a  way  as  to  bring  the  serous  surfaces  at 
the  margins  of  the  wound  into  apposition,  and  one  is  inserted  just  beyond  each  end  of  the  wound. 
The  bladder  should  be  tested  as  to  whether  it  is  water-tight  before  closing  the  external  incision. 

The  muscular  coat  of  the  bladder  undergoes  hypertrophy  in  cases  in  which   there  is  any 


THE   MALE    URETHRA. 


1005 


\ 


obstruction  to  the  flow  of  urine.  Under  these  circumstances  the  bundles  of  which  the  muscular 
coat  consists  become  much  increased  in  size,  and,  interlacing  in  all  directions,  give  rise  to  what 
is  known  as  the  fasciculated  bladder.  Between  these  bundles  of  muscular  fibres  the  mucous 
membrane  may  bulge  out,  forming  sacculi,  constituting  the  sacculated  bladder,  and  in  these 
little  pouches  phosphatic  concretions  may  collect,  forming  encysted  calculi  The  mucous  mem- 
brane is  very  loose  and  las,  except  over  the  trigone,  to  allow  of  the  distention  of  the  viscus. 

Various  forms  of  tumors  have  been  found  springing  from  the  wall  of  the  bladder.  The 
innocent  tumors  are  the  papilloma  and  the  mucous  polypus,  arising  from  the  mucous  membrane ; 
the  fibrous,  from  the  submucous  tissue  ;  and  the  myoma,  originating  in  the  muscular  tissue ; 
and,  very  rarely,  dermoid  tumors,  the  exact  origin  of  which  it  is  difficult  to  explain.  Of  the 
malignant  tumors,  epithelioma  is  the  most  common,  but  sarcomata  are  occasionally  found  in  the 
bladder  of  children. 

Puncture  of  the  bladder  may  be  performed  either  above  the  pubes  or  through  the  rectum, 
in  both  cases  without  wounding  the  peritoneum.  The  former  plan  is  generally  to  be  preferred, 
since  in  puncture  by  the  rectum  a  permanent  fistula  may  be  left  from  abscess  forming  between 
the  rectum  and  the  bladder ;  or  pelvic  cellulitis  may  be  set  up ;  moreover,  it  is  exceedingly 
inconvenient  to  keep  a  cannula  in  the  rectum.  In  some  cases  in  performing  this  operation  the 
recto-vesical  pouch  of  peritoneum  has  been  wounded,  inducing  fatal  peritonitis.  The  operation, 
therefore,  has  been  almost  completely  abandoned. 


Verumon 
tanum. 


Prostate. 


THE    MALE    URETHRA. 

The  urethra  in  the  male  extends  from  the  neck  of  the  bladder  to  the  meatus 
urinarius  at  the  end  of  the  penis.  It  presents  a  double  curve  in  the  flaccid  state 
of  the  penis  (Fig.  557),  but  in  the  erect  state  of  this  organ  it  forms  only  a  single 
curve,  the  concavity  of  which  is  directed  up- 
ward. Its  length  varies  from  eight  to  nine 
inches ;  and  it  is  divided  into  three  portions, 
the  prostatic,  membranous,  and  spongy,  the 
structure  and  relations  of  which  are  essentially 
different.  Except  during  the  passage  of  the 
urine  or  semen,  the  urethra  is  a  more  trans-  Cowper's  giand.^ 
verse  cleft  or  slit,  with  its  upper  and  under 
surfaces  in  contact.  At  the  meatus  urinarius 
the  slit  is  vertical,  and  in  the  prostatic  portion 
somewhat  arched. 

The  Prostatic  Portion  is  the  widest  and 
most  dilatable  part  of  the  canal.  It  passes 
through  the  prostate  gland,  from  its  base  to 
the  apex,  lying  nearer  its  anterior  than  its 
posterior  surface.  It  is  about  an  inch  and  a 
quarter  in  length  ;  the  form  of  the  canal  is 
spindle-shaped,  being  wider  in  the  middle  than 
at  either  extremity,  and  narrowest  below,  where 
it  joins  the  membranous  portion.  A  transverse 
section  of  the  canal  as  it  lies  in  the  prostate 
is  horse-shoe  in  shape,  the  convexity  being 
directed  forward  (Fig.  563),  since  the  direction 
of  the  canal  is  nearly  vertical. 

Upon  the  floor  of  the  canal  is  a  narrow 
longitudinal  ridge,  the  verumontanum,  or  caput 
gallinaginis,  formed  by  an  elevation  of  the 
mucous  membrane  and  its  subjacent  tissue. 
It  is  eight  or  nine  lines  in  length,  and  a  line 
and  a  half  in  height ;  and  contains,  according 
to  Kobelt,  muscular  and  erectile  tissues.  When 
distended,  it  may  serve  to  prevent  the  passage 
of  the  semen  backward  into  the  bladder.  On 
each  side  of  the  verumontanum  is  a  slightly 
depressed  fossa,  the  prostatic  sinus,  the  floo 
of  which  is  perforated  by  numerous  apertures,  the  orifices  of  the  prostatic  ducts 
from  the  lateral  lobes  of  the  gland  ;   the  ducts  of  the  middle  lobe  open  behind  the 


Glans. 


Fossa 
navic. 


Meatus. 


Fig.  562.— The  male  urethra,  laid  open  on  its 
anterior  (upper)  surface.    (Testut.) 


1006  THE    URINARY   ORGANS. 

verumontanum.  At  the  fore  part  of  the  verumontanum,  in  the  middle  line,  is  a 
depression,  the  sinus  pocularis  (vesicula  prostatica) ;  and  upon  or  within  its  mar- 
gins are  the  slit-like  openings  of  the  ejaculatory  ducts.  The  sinus  pocularis  forms 
a  cul-de-sac  about  a  quarter  of  an  inch  in  length,  which  runs  upward  and  back- 
ward in  the  substance  of  the  prostate  behind  the  middle  lobe ;  its  prominent  ante- 
rior wall  partly  forms  the  verumontanum.  Its  walls  are  composed  of  fibrous  tissue, 
muscular  fibres,  and  mucous  membrane,  and  numerous  small  glands  open  on  its 
inner  surface.  It  has  been  called  by  Weber,  who  discovered  it,  the  uterus  mascu- 
linus,  from  its  being  developed  from  the  united  lower  ends  of  the  atrophied 
Mullerian  ducts,  and  therefore  homologous  with  the  uterus  and  vagina  in  the 
female. 

The  Membranous  Portion  of  the  Urethra  extends  between  the  apex  of  the  pros- 
tate and  the  bulb  of  the  corpus  spongiosum.  It  is  the  narrowest  part  of  the  canal 
(excepting  the  meatus),  and  measures  three-quarters  of  an  inch  along  its  upper, 
and  half  an  inch  along  its  lower,  surface,  in  consequence  of  the  bulb  projecting 
backward  beneath  it.  Its  anterior  concave  surface  is  placed  about  an  inch  below 
and  behind  the  pubic  arch,  from  which  it  is  separated  by  the  dorsal  vessels  and 
nerves  of  the  penis,  and  some  muscular  fibres.  Its  posterior  convex  surface  is 
separated  from  the  rectum  by  a  triangular  space,  which  constitutes  the  perineum. 
The  membranous  portion  of  the  urethra  lies  between  the  inferior  and  superior 
layers  of  the  triangular  ligament.  As  it  pierces  the  inferior  layer,  the  fibres 
around  the  opening  are  prolonged  over  the  tube.  It  is  also  surrounded  by  the 
Compressor  urethrse  muscle. 

The  Spongy  Portion  is  the  longest  part  of  the  urethra,  and  is  contained  in  the 
corpus  spongiosum.  It  is  about  six  inches  in  length,  and  extends  from  the  ter- 
mination of  the  membranous  portion  of  the  meatus  urinarius.  Commencing  just 
below  the  triangular  ligament,  it  inclines  downward  for  a  short  distance ;  it  next 
ascends  for  about  half  its  length,  end  then,  in  the  flaccid  condition  of  the  penis, 
it  bends  suddenly  downward.  It  is  narrow,  and  of  uniform  size  in  the  body  of 
the  penis,  measuring  about  a  quarter  of  an  inch  in  diameter  ;  being  dilated  behind, 
within  the  bulb ;  and  again  anteriorly  within  the  glans  penis,  where  it  forms  the 
fossa  navicularis. 

The  Bulbous  portion  is  a  name  given,. in  some  descriptions  of  the  urethra,  to 
the  posterior  part  of  the  spongy  portion  contained  within  the  bulb. 

The  meatus  urinarius  is  the  most  contracted  part  of  the  urethra  ;  it  is  a  vertical 
slit,  about  three  lines  in  length,  bounded  on  each  side  by  two  small  labia. 

The  inner  surface  of  the  lining  membrane  of  the  urethra,  especially  on  the  floor 
of  the  spongy  portion,  presents  the  orifices  of  numerous  mucous  glands  and  follicles 
situated  in  the  submucous  tissue,  and  named  the  glands  of  Littre.  They  vary  in 
size,  and  their  orifices  are  directed  forward,  so  that  they  may  easily  intercept  the 
point  of  a  catheter  in  its  passage  along  the  canal.  One  of  theselacunse,  larger  than 
the  rest,  is  situated  in  the  upper  surface  of  the  fossa  navicularis,  about  an  inch  and 
a  half  from  the  orifice ;  it  is  called  the  lacuna  magna.  Into  the  bulbous  portion 
are  found  opening  the  ducts  of  Cowper's  glands. 

Structure. — The  urethra  is  composed  of  a  continuous  mucous  membrane, 
supported  by  a  submucous  tissue  which  connects  it  with  the  various  structures 
through  which  it  passes. 

The  mucous  coat  forms  part  of  the  genito-urinary  mucous  membrane.  It  is 
continuous  with  the  mucous  membrane  of  the  bladder,  ureters,  and  kidneys ; 
externally  with  the  integument  covering  the  glans  penis  ;  and  is  prolonged  into 
the  ducts  of  the  glands  which  open  into  the  urethra — viz.  Cowper's  glands  and  the 
prostate  gland — and  into  the  vasa  deferentia  and  vesiculse  seminales  through  the 
ejaculatory  ducts.  In  the  spongy  and  membranous  portions  the  mucous  membrane 
is  arranged  in  longitudinal  folds  when  the  tube  is  empty.  Small  papillae  are  found 
upon  it  near  the  orifice,  and  its  epithelial  lining  is  of  the  columnar  variety,  except- 
ing near  the  meatus,  where  it  is  squamous. 

The  submucous  tissue  consists  of  a  vascular  erectile  layer,  outside  which  is  a 


THE  FEMALE   BLADDER    AND     URETHRA.  1007 

layer  of  unstriped  muscular  fibres,  arranged  in  a  circular  direction,  which  sepa- 
rates the  mucous  membrane  and  submucous  tissue  from  the  tissue  of  the  corpus 
spongiosum. 

Surgical  Anatomy. — The  urethra  maybe  ruptured  by  the  patient  falling  astride  of  any 
hard  substance  and  striking  his  perinaeum,  so  that  the  urethra  is  crushed  against  the  pubic  arch. 
Bleeding  will  at  once  take  place  from  the  urethra,  and  this,  together  with  the  bruising  in  the 
perinaeum  and  the  history  of  the  accident,  will  at  once  point  to  the  nature  of  the  injury. 

The  surgical  anatomy  of  the  urethra  is  of  considerable  importance  in  connection  with  the 
passage  of  instruments  into  the  bladder.  Otis  was  the  first  to  point  out  that  the  urethra  is 
capable  of  great  dilatability,  so  that,  excepting  through  the  externa^  meatus,  an  instrument  cor- 
responding to  18  English  gauge  (29  French)  can  usually  be  passed  without  damage.  The  orifice 
of  the  urethra  is  not  so  dilatable,  and  therefore  frequently  requires  slitting.  A  recognition  of 
this  dilatability  caused  Bigelow  to  very  considerably  modify  the  operation  of  lithotrity  and  intro- 
duce that  of  litholapaxy.  In  passing  catheters,  especially  fine  ones,  the  point  of  the  instrument 
should  be  kept  as  far  as  possible  along  the  upper  wall  of  the  canal,  as  the  point  is  otherwise  very 
liable  to  enter  one  of  the  lacunas.  Stricture  of  the  urethra  is  a  disease  of  very  common  occur- 
rence, and  is  generally  situated  in  the  spongy  portion  of  the  urethra,  most  commonly  in  the 
bulbous  portion,  just  in  front  of  the  membranous  urethra,  but  in  a  very  considerable  number  of 
eases  in  the  penile  or  ante-scrotal  part  of  the  canal. 

THE  FEMALE  BLADDER  AND  URETHRA. 

The  Bladder  is  situated  at  the  anterior  part  of  the  pelvis.  It  is  in  relation,  in 
front,  with  the  symphysis  pubis  ;  behind,  with  the  utero-vesical  pouch  of  peritoneum, 
which  separates  it  from  the  body  of  the  uterus  ;  its  base  lies  in  contact  with  the 
connective  tissue  in  front  of  the  cervix  and  upper  part  of  the  vagina.  Laterally, 
is  the  recto-vesical  fascia.  The  bladder  is  said  by  some  anatomists  to  be  larger  in 
the  female  than  in  the  male.  At  any  rate,  it  does  not  rise  above  the  symphysis 
pubis  till  more  distended  than  in  the  male,  but  this  is  perhaps  owing  to  the  more 
capacious  pelvis  rather  than  to  its  being  of  actually  larger  size. 

THE  URETHRA. 

The  Urethra  is  a  narrow  membranous  canal,  about  an  inch  and  a  half  in 
length,  extending  from  the  neck  of  the  bladder  to  the  meatus  urinarius.  It  is 
placed  beneath  the  symphysis  pubis,  imbedded  in  the  anterior  wall  of  the  vagina ; 
and  its  direction  is  obliquely  downward  and  forward,  its  course  being  slightly 
curved,  the  concavity  directed  forward  and  upward.  Its  diameter  when  undilated 
is  about  a  quarter  of  an  inch.  The  urethra  perforates  the  triangular  ligament, 
and  its  external  orifice  is  situated  directly  in  front  of  the  vaginal  opening  and 
about  an  inch  behind  the  glans  clitoridis. 

Structure. — The  urethra  consists  of  three  coats :  muscular,  erectile,  and  mucous. 

The  muscular  coat  is  continuous  with  that  of  the  bladder ;  it  extends  the  whole 
length  of  the  tube,  and  consists  of  a  circular  stratum  of  muscular  fibres.  In 
addition  to  this,  between  the  two  layers  of  the  triangular  ligament,  the  female 
urethra  is  surrounded  by  the  Compressor  urethrse,  as  in  the  male. 

A  thin  layer  of  spongy  erectile  tissue,  containing  a  plexus  of  large  veins  inter- 
mixed with  bundles  of  unstriped  muscular  fibre,  lies  immediately  beneath  the 
mucous  coat. 

The  mucous  coat  is  pale,  continuous  externally  with  that  of  the  vulva,  and 
internally  with  that  of  the  bladder.  It  is  thrown  into  longitudinal  folds,  one  of 
which,  placed  along  the  floor  of  the  canal,  resembles  the  verumontanum  in  the 
male  urethra.  It  is  lined  by  laminated  epithelium,  which  becomes  transitional 
near  the  bladder.     Its  external  orifice  is  surrounded  by  a  few  mucous  follicles. 

The  urethra,  from  not  being  surrounded  by  dense  resisting  structures,  as  in  the  male,  admits 
of  considerable  dilatation,  which  enables  the  surgeon  to  remove  with  considerable  facility  calculi 
or  other  foreign  bodies  from  the  cavity  of  the  bladder. 


THE  MALE  ORGANS  OF  GENERATION. 


THE  PROSTATE  GLAND. 

THE  Prostate  Gland  {npoiarrjfii,  to  stand  before)  is  a  pale,  firm,  partly  glandular 
and  partly  muscular  body,  "which  is  placed  immediately  below  the  neck  of  the 
bladder  and  around  the  commencement  of  the  urethra.  It  is  placed  in  the  pelvic 
cavity,  behind  the  lower  part  of  the  symphysis  pubis,  and  above  the  deep  layer  of 
the  triangular  ligament,  and  rests  upon  the  rectum,  through  which  it  may  be 
distinctly  felt,  especially  when  enlarged.      In  shape  and  size  it  resembles  a  chestnut. 


-r3  4->V  -  >. 


W 


Fig.  563. — Transverse  section  of  normal  prostate  through  the  middle  of  the  verumontanum,  from  a  subject 
aged  nineteen  years.  (Taylor.)  a.  Longitudinal  sections  of  ducts  leading  from  the  lobules  of  the  prostatic 
glands;  b,  verumontanum ;  c,  sinus  pocularis;  d,  urethra;  e,  ejaculatory  ducts; /,  arteries,  veins,  and  venous 
sinuses  in  capsule  of  prostate  ;  g,  nerve  trunks  in  capsule  ;  h,  point  of  origin  of  ribro-muscular  bands  encircling 
urethra;  i,  zone  of  striated  voluntary  muscle  on  superior  surface.   (Drawn  from  Erdinger  projection  apparatus.) 

Its  base  is  directed  upward,  and  is  situated  immediately  below  the  neck  of  the 
bladder. 

Its  apex  is  directed  downward  to  the  deep  layer  of  the  triangular  ligament, 
which  it  touches. 

Its  posterior  surface  is  flattened,  marked  by  a  slight  longitudinal  furrow,  and 
rests  on  the  second  part  of  the  rectum,  and  is  distant  about  one  inch  and  a  half 
from  the  anus. 

Its  anterior  surface  is  convex,  and  placed  about  three-quarters  of  an  inch 
behind  the  pubic  symphysis,  from  which  it  is  separated  by  a  plexus  of  veins  and  a 
quantity  of  loose  fat.  It  is  connected  to  the  pubic  bone  on  either  side  by  the 
pubo-prostatic  ligaments. 

The  lateral  surfaces  are  prominent,  and  are  covered  by  the  anterior  portions 
64  1009 


1010  THE   MALE    ORGANS    OF    GENERATION. 

of  the  Levatores  ani  muscles,  which  are,  however,  separated  from  the  gland  by  a 
plexus  of  veins. 

The  prostate  measures  about  an  inch  and  a  half  transversely  at  the  base,  an 
inch  in  its "  antero-posterior  diameter,  and  an  inch  and  a  quarter  in  its  vertical 
diameter.  Its  weight  is  about  four  and  a  half  drachms.  It  is  held  in  position 
by  the  anterior  ligaments  of  the  bladder  (pub o-pro static) ;  by  the  deep  layer  of 
the  triangular  ligament,  which  invests  the  commencement  of  the  membranous 
portion  of  the  urethra  and  prostate  gland ;  and  by  the  anterior  portions  of  the 
Levatores  ani  muscles,  which  pass  bacluvard  from  the  os  pubis  and  embrace  the 
sides  of  the  prostate.  These  portions  of  the  Levatores  ani,  from  the  support  they 
afford  to  the  prostate,  are  named  the  Levator  prostata?. 

The  prostate  consists  of  two  lateral  lobes  and  a  middle  lobe. 

The  two  lateral  lobes  are  of  equal  size,  separated  by  a  deep  notch  behind,  and 
by  a  slight  furrow  upon  the  anterior  and  posterior  surfaces  of  the  gland,  which 
indicates  the  bilobed  condition  of  the  organ  in  some  animals. 

The  third,  or  middle  lobe,  is  a  small  transverse  band,  occasionally  a  rounded  or 
triangular  prominence,  placed  between  the  two  lateral  lobes  at  the  posterior  part 
of  the  organ.  It  lies  immediately  beneath  the  neck  of  the  bladder,  behind  the 
commencement  of  the  urethra,  and  above  the  ejaculatory  ducts,  which  pass  through 
the  gland  between  its  middle  and  lateral  lobes.  Its  existence  is  not  constant,  but 
it  is  occasionally  found  at  an  early  period  of  life,  as  well  as  in  adults  and  in  old  age. 

The  prostate  gland  is  perforated  by  the  urethra  and  the  ejaculatory  ducts. 
The  urethra  usually  lies  along  the  junction  of  its  anterior  with  its  middle  third. 
The  ejaculatory  ducts  pass  obliquely  downward  and  forward  through  the  posterior 
part  of  the  prostate,  and  open  into  the  prostatic  portion  of  the  urethra. 

Structure. — The  prostate  is  immediately  enveloped  by  a  thin  but  firm  fibrous 
capsule,  distinct  from  that  derived  from  the  recto-vesical  fascia,  and  separated  from 
it  by  a  plexus  of  veins.  Its  substance  is  of  a  pale  reddish-gray  color,  of  great 
density  and  not  easily  torn.  It  consists  of  glandular  substance  and  muscular 
tissue. 

The  muscular  tissue,  according  to  Kolliker,  constitutes  the  proper  stroma  of 
the  prostate,  the  connective  tissue  being  very  scanty,  and  simply  forming  thin 
trabecule  between  the  muscular  fibres,  in  which  the  vessels  and  nerves  of  the 
gland  ramify.  The  muscular  tissue  is  arranged  as  follows :  immediately  beneath 
the  fibrous  capsule  is  a  dense  layer  which  forms  an  investing  sheath  for  the  gland ; 
secondly,  around  the  urethra  as  it  lies  in  the  prostate,  is  another  dense  layer  of 
circular  fibres,  continuous  above  with  the  internal  layer  of  the  muscular  coat  of 
the  bladder,  and  below  blending  with  the  fibres  surrounding  the  membranous 
portion  of  the  urethra.  Between  these  two  layers  strong  bands  of  muscular  tissue, 
which  decussate  freely,  form  meshes  in  which  the  glandular  structure  of  the  organ 
is  imbedded.  In  that  part  of  the  gland  which  is  situated  in  front  of  the  urethra 
the  muscular  tissue  is  especially  dense,  and  there  is  here  little  or  no  gland  tissue  ; 
while  in  that  part  which  is  behind  the  urethra  the  muscular  tissue  presents  a  wide- 
meshed  structure,  which  is  densest  at  the  base  of  the  gland — that  is,  near  the 
bladder — becoming  looser  and  more  sponge-like  toward  the  apex  of  the  organ. 

The  glandular  substance  is  composed  of  numerous  follicular  pouches,  opening 
into  elongated  canals,  which  join  to  form  from  twelve  to  twenty  small  excretory 
ducts.  The  follicles  are  connected  together  by  areolar  tissue,  supported  by 
prolongations  from  the  fibrous  capsule  and  muscular  stroma,  and  enclosed  in  a 
delicate  capillary  plexus.  The  epithelium  lining  of  both  the  canals  and  the 
terminal  vesicles  is  of  the  columnar  variety.  The  prostatic  ducts  open  into  the 
floor  of  the  prostatic  portion  of  the  urethra. 

Vessels  and  Nerves. — The  arteries  supplying  the  prostate  are  derived  from  the 
internal  pudic,  vesical,  and  hemorrhoidal.  Its  veins  form  a  plexus  around  the  sides 
and  base  of  the  gland ;  they  receive  in  front  the  dorsal  vein  of  the  penis,  and 
terminate  in  the  internal  iliac  vein.  The  nerves  are  derived  from  the  pelvic 
plexus. 


THE   PENIS.  1011 

Surgical  Anatomy. — The  relation  of  the  prostate  to  the  rectum  should  be  noted :  by  means 
of  the  finger  introduced  into  the  gut  the  surgeon  detects  enlargement  or  other  disease  of  this 
organ ;  he  can  feel  the  apex  of  the  gland,  which  is  the  guide  to  Cock's  operation  for  stricture  : 
he  is  enabled  also  by  the  same  means  to  direct  tbe  point  of  a  catheter  when  its  introduction  is 
attended  with  difficulty  either  from  injury  or  disease  of  the  membranous  or  prostatic  portions  of 
the  urethra.  When  the  finger  is  introduced  into  the  bowel  the  surgeon  may,  in  some  cases, 
especially  in  boys,  learn  the  position,  as  well  as  the  size  and  weight,  of  a  calculus  in  the  bladder ; 
and  in  the  operation  for  its  removal,  if,  as  is  not  unfrequently  the  case,  it  should  be  lodged  behind 
an  enlarged  prostate,  it  may  be  displaced  from  its  position  by  pressing  upward  the  base  of  the 
bladder  from  the  rectum.  The  prostate  gland  is  occasionally  the  seat  of  suppuration,  either  due  to 
injury,  gonorrhoea,  or  tuberculous  disease.  The  gland,  being  enveloped  in  a  dense  unyielding 
capsule,  determines  the  course  of  the  abscess,  and  also  explains  the  great  pain  which  is  present 
in  the  acute  form  of  the  disease.  The  abscess  most  frequently  bursts  into  the  urethra,  the 
direction  in  which  there  is  least  resistance,  but  may  occasionally  burst  into  the  rectum,  or  more 
rarely  in  the  perinaeum.  In  advanced  life  the  prostate  becomes  considerably  enlarged,  and  pro- 
jects into  the  bladder  so  as  to  impede  the  passage  of  the  urine.  According  to  Dr.  Messer's 
researches,  conducted  at  Greenwich  Hospital,  it  would  seem  that  such  obstruction  exists  in  20 
per  cent,  of  all  men  over  sixty  years  of  age.  In  some  cases  the  enlargement  affects  principally 
the  lateral  lobes,  which  may  undergo  considerable  enlargement  without  causing  much  incon- 
venience. In  other  cases  it  would  seem  that  the  middle  lobe  enlarges  most,  and  even  a  small 
enlargement  of  this  lobe  may  act  injuriously,  by  forming  a  sort  of  valve  over  the  urethral  orifice, 
preventing  the  passage  of  the  urine,  and  the  more  the  patient  strains,  the  more  completely  will 
it  block  the  opening  into  the  urethra.  In  consequence  of  the  enlargement  of  the  prostate  a 
pouch  is  formed  at  the  base  of  the  bladder  behind  the  projection,  in  which  water  collects  and 
cannot  entirely  be  expelled.  It  becomes  decomposed  and  ammoniacal,  and  leads  to  cystitis. 
For  this  condition  "prostatectomy"  is  sometimes  done.  The  bladder  is  opened  by  an  incision 
above  the  symphysis  pubis,  the  mucous  membrane  incised,  and  the  enlarged  and  projecting 
middle  lobe  enucleated. 

COWPER'S    GLANDS. 

Cowper's  Glands  are  two  small,  rounded,  and  somewhat  lobulated  bodies  of 
a  yellow  color,  about  the  size  of  peas,  placed  behind  the  fore  part  of  the  mem- 
branous portion  of  the  urethra,  between  the  two  layers  of  the  triangular  ligament. 
They  lie  close  above  the  bulb,  and  are  enclosed  by  the  transverse  fibres  of  the 
Compressor  urethrae  muscle.  Their  existence  is  said  to  be  constant :  they  gradually 
diminish  in  size  as  age  advances. 

Structure. — Each  gland  consists  of  several  lobules  held  together  by  a  fibrous 
investment.  Each  lobule  consists  of  a  number  of  acini  lined  by  columnar 
epithelial  cells,  opening  into  one  duct,  which,  joining  with  the  ducts  of  other 
lobules  outside  the  gland,  form  a  single  excretory  duct.  The  excretory  duct  of 
each  gland,  nearly  an  inch  in  length,  passes  obliquely  forward  beneath  the 
mucous  membrane,  and  opens  by  a  minute  orifice  on  the  floor  of  the  bulbous 
portion  of  the  urethra. 

THE    PENIS. 

The  Penis  consists  of  a  root,  body,  and  extremity  or  glans  penis. 

The  root  is  firmly  connected  to  the  rami  of  the  os  pubis  and  ischium  by  two 
strong  tapering,  fibrous  processes,  the  crura,  and  to  the  front  of  the  symphysis 
pubis  by  the  suspensory  ligament,  a  strong  band  of  fibrous  tissue  which  passes 
downward  from  the  front  of  the  symphysis  pubis  to  the  upper  surface  of  the  root 
of  the  penis,  where  it  splits  into  two  portions  and  blends  with  the  fascial  sheath 
of  the  organ. 

The  extremity  or  glans  penis,  presents  the  form  of  an  obtuse  cone,  flattened 
from  above  downward.  At  its  summit  is  a  vertical  fissure,  the  orifice  of  the 
urethra  (meatus  urinarius).  The  base  of  the  glans  forms  a  rounded  projecting 
border,  the  corona  glandis,  and  behind  the  corona  is  a  deep  constriction,  the 
cervix.  Upon  both  of  these  parts  numerous  small  sebaceous  glands  are  found, 
the  glandulce  Tysonii  odoriferce.  They  secrete  a  sebaceous  matter  of  very  peculiar 
odor,  which  probably  contains  caseine  and  becomes  easily  decomposed. 

1  Stieda  (Comptes  rendus  du  XII  Congres  International  de  Medecine,  Moscow,  1897)  asserts  that 
Tyson's  glands  are  never  found  on  the  corona  glandis,  and  that  what  have  hitherto  been  mistaken  for 
glands  are  really  large  papillse. 


1012  THE   MALE    ORGANS    OF    GENERATION. 

The  body  of  the  penis  is  the  part  between  the  root  and  extremity.  In  the 
flaccid  condition  of  the  organ  it  is  cylindrical,  but  when  erect  has  a  triangular 
prismatic  form  with  rounded  angles,  the  broadest  side  being  turned  upward,  and 
called  the  dorsum.  The  body  is  covered  by  integument,  and  contains  in  its  interior 
a  large  portion  of  the  urethra.  The  integument  covering  the  penis  is  remarkable 
for  its  thinness,  its  dark  color,  its  looseness  of  connection  with  the  deeper  parts 
of  the  organ,  and  its  containing  no  adipose  tissue.  At  the  root  of  the  penis  the 
integument  is  continuous  with  that  upon  the  pubes  and  scrotum,  and  at  the 
neck  of  the  glans  it  leaves  the  surface  and  becomes  folded  upon  itself  to  form  the 
prepuce. 

The  internal  laver  of  the  prepuce  is  attached  behind  to  the  cervix,  and 
approaches  in  character  to  a  mucous  membrane  ;  from  the  cervix  it  is  reflected 
over  the  glans  penis,  and  at  the  meatus  urinarius  is  continuous  with  the  mucous 
lining  of  the  urethra. 

The  integument  covering  the  glans  penis  contains  no  sebaceous  glands,  but 
projecting  from  its  free  surface  are  a  number  of  small,  highly  sensitive  papillae. 
At  the  back  part  of  the  meatus  urinarius  a  fold  of  mucous  membrane  passes 
backward  to  the  bottom  of  a  depressed  raphe",  where  it  is  continuous  with  the 
prepuce;  this  fold  is  termed  the  frcenum  prceputii. 

Structure  of  the  Penis. — The  penis  is  composed  of  a  mass  of  erectile  tissue 
enclosed  in  three  cylindrical  fibrous  compartments.  Of  these,  two,  the  corpora 
cavernosa,  are  placed  side  by  side  along  the  upper  part  of  the  organ ;  the  third,  or 
corpus  spongiosum,  encloses  the  urethra  and  is  placed  below. 

The  Corpora  Cavernosa  form  the  chief  part  of  the  body  of  the  penis.  They 
consist  of  two  fibrous  cylindrical  tubes,  placed  side  by  side,  and  intimately 
connected  along  the  median  line  for  their  anterior  three-fourths,  whilst  at  their 
back  part  they  separate  from  each  other  to  form  the  crura,  which  are  two  strong 
tapering  fibrous  processes  firmly  connected  to  the  rami  of  the  os  pubis  and 
ischium.  Each  crus  commences  by  a  blunt -pointed  process  in  front  of  the 
tuberosity  of  the  ischium,  and  before  its  junction  with  its  fellow  to  form  the 
body  of  the  penis  it  presents  a  slight  enlargement,  named  by  Kobelt  the  bulb 
of  the  corpus  cavernosum.  Just  beyond  this  point  they  become  constricted, 
and  retain  an  equal  diameter  to  their  anterior  extremity,  where  they  form  a 
single  rounded  end  which  is  received  into  a  fossa  in  the  base  of  the  glans  penis. 
A  median  groove  on  the  upper  surface  lodges  the  dorsal  vein  of  the  penis,  and  the 
groove  on  the  under  surface  receives  the  corpus  spongiosum.  The  root  of  the 
penis  is  connected  to  the  symphysis  pubis  by  the  suspensory  ligament. 

Structure. — The  corpora  cavernosa  are  surrounded  by  a  strong  fibrous  envelope, 
consisting  of  two  sets  of  fibres — the  one,  longitudinal  in  direction,  being  common 
to  the  two  corpora  cavernosa,  and  investing  them  in  a  common  covering ;  the 
other,  internal,  circular  in  direction,  and  being  proper  to  each  corpus  caverno- 
sum. The  internal  circular  fibres  of  the  two  corpora  cavernosa  form,  by  their 
junction  in  the  mesial  plane,  an  incomplete  partition  or  septum  between  the  two 
bodies. 

The  septum  between  the  two  corpora  cavernosa  is  thick  and  complete  behind, 
but  in  front  it  is  incomplete,  and  consists  of  a  number  of  vertical  bands,  which  are 
arranged  like  the  teeth  of  a  comb,  whence  the  name  which  it  has  received,  septum 
pectiniforme.  These  bands  extend  between  the  dorsal  and  the  urethral  surface 
of  the  corpora  cavernosa.  This  fibrous  investment  is  extremely  dense,  of  con- 
siderable thickness,  and  consists  of  bundles  of  shining  white  fibres,  with  an 
admixture  of  well-developed  elastic  fibre,  so  that  it  is  possessed  of  great 
elasticity. 

From  the  internal  surface  of  the  fibrous  envelope,  as  well  as  from  the  sides  of 
the  septum,  are  given  off  a  number  of  bands  or  cords  which  cross  the  interior  of 
the  corpora  cavernosa  in  all  directions,  subdividing  them  into  a  number  of 
separate  compartments,  and  giving  the  entire  structure  a  spongy  appearance. 
These  bands  and  cords  are  called  trabecular,  and  consist  of  white  fibrous  tissue, 


THE   PENIS. 


1013 


elastic  fibres,  and  plain  muscular  fibres.  In  them  are  contained  numerous 
arteries  and  nerves. 

The  component  fibres  of  which  the  trabecule  are  composed  are  larger  and 
stronger  round  the  circumference  than  at  the  centre  of  the  corpora  cavernosa ; 
they  are  also  thicker  behind  than  in  front.  The  interspaces,  on  the  contrary,  are 
larger  at  the  centre  than  at  the  circumference,  their  long  diameter  being  directed 
transversely  ;  they  are  largest  anteriorly.  They  are  occupied  by  venous  blood, 
and  are  lined  by  a  layer  of  flattened  cells  similar  to  the  endothelial  lining  of  veins. 

The  whole  of  the  structure  of  the  corpora  cavernosa  contained  within  the 
fibrous  sheath  consists,  therefore,  of  a  sponge-like  tissue  of  areolar  spaces  freely 
communicating  with  each  other  and  filled  with  venous  blood.  The  spaces  may 
therefore  be  regarded  as  large  cavernous  veins. 

The  arteries  bringing  the  blood  to  these  spaces  are  the  arteries  of  the  corpora 
cavernosa  and  branches  from  the  dorsal  artery  of  the  penis,  which  perforate  the 
fibrous  capsule,  along  the  upper  surface,  especially  near  the  fore  part  of  the 
organ. 

These  arteries  on  entering  the  cavernous  structure  divide  into  branches  which 
are  supported  and  enclosed  by  the  trabecule.  Some  of  these  terminate  in  a 
capillary  network,  the  branches  of  which  open  directly  into  the  cavernous  spaces ; 
others  assume  a  tendril-like  appearance,  and  form  convoluted  and  somewhat 
dilated  vessels,  which  were  named  by  Miiller  helicine  arteries.  They  project 
into  the  spaces,  and  from  them  are  given  off  small  capillary  branches  to  supply 
the  trabecular  structure.  They  are  bound  down  in  the  spaces  by  fine  fibrous 
processes,  and  are  more  abundant  in  the  back  part  of  the  corpora  cavernosa 
(Fig.   564). 

The  blood  from  the  cavernous  spaces  is  returned  by  a  series  of  vessels,  some 
of  which  emerge  in  considerable  numbers  from  the  base  of  the  glans  penis  and 


Fig.  564.—  From  the  peripheral  portion  of  the  corpus  cavernosum  penis  under  a  low  magnifying  power. 
(Copied  from  Langer.)  1.  a.  Capillary  network,  b.  Cavernous  spaces.  2.  Connection  of  the  arterial  twigs  (a) 
with  the  cavernous  spaces. 

converge  on  the  dorsum  of  the  organ  to  form  the  dorsal  vein ;  others  pass  out  on 
the  upper  surface  of  the  corpora  cavernosa  and  join  the  dorsal  vein  ;  some  emerge 
from  the  under  surface  of  the  corpora  cavernosa,  and,  receiving  branches  from  the 
corpus  spongiosum,  wind  round  the  sides  of  the  penis  to  terminate  in  the  dorsal 
vein;  but  the  greater  number  pass  out  at  the  root  of  the  penis  and  join  the 
prostatic  plexus. 

The  Corpus  Spongiosum  encloses  the  urethra,  and  is  situated  in  the  groove  on 
the  under  surface  of  the  corpora  cavernosa.  It  commences  posteriorly  below  the 
superficial  layer  of  the  triangular  ligament  of  the  urethra,  between  the  diverging 
crura  of  the  corpora  cavernosa,  where  it  forms  a  rounded  enlargement,  the  bulb, 
and  terminates  anteriorly  in  another  expansion,  the  glans  penis,  which  overlaps 
the  anterior  rounded  extremity  of  the  corpora  cavernosa.  The  central  portion, 
or  body  of  the  corpus  spongiosum,  is  cylindrical,  and  tapers  slightly  from  behind 
forward. 

The  bulb  varies  in  size  in  different  subjects  ;  it  receives  a  fibrous  investment 


1014  THE   MALE    ORGANS    OF    GENERATION. 

from  the  superficial  layer  of  the  triangular  ligament,  and  is  surrounded  by  the 
Accelerator  urinse  muscle.  The  urethra  enters  the  bulb  nearer  its  upper  than  its 
lower  surface,  being  surrounded  by  a  layer  of  erectile  tissue,  a  thin  prolongation 
of  which  is  continued  backward  round  the  membranous  and  prostatic  portions  of 
the  canal  to  the  neck  of  the  bladder,  lying  between  the  two  layers  of  muscular 
tissue.  The  portion  of  the  bulb  below  the  urethra  presents  a  partial  division  into 
two  lobes,  being  marked  externally  by  a  linear  raphe',  whilst  internally  there 
projects,  for  a  short  distance,  a  thin  fibrous  septum,  which  is  more  distinct  in  early 
life. 

Structure. — The  corpus  spongiosum  consists  of  a  strong  fibrous  envelope, 
enclosing  a  trabecular  structure,  which  contains  in  its  meshes  erectile  tissue.  The 
fibrous  envelope  is  thinner,  whiter  in  color,  and  more  elastic  than  that  of  the 
corpora  cavernosa.  The  trabecule  are  more  delicate,  nearly  uniform  in  size,  and 
the  meshes  between  them  smaller  than  in  the  corpora  cavernosa,  their  long 
diameter,  for  the  most  part,  corresponding  with  that  of  the  penis.  The  external 
envelope  or  outer  coat  of  the  corpus  spongiosum  is  formed  partly  of  unstriped 
muscular  fibre,  and  a  layer  of  the  same  tissue  immediately  surrounds  the  canal 
of  the  urethra. 

The  lymphatics  of  the  penis  consist  of  a  superficial  and  deep  set ;  the  former 
are  derived  from  a  dense  network  on  the  skin  of  the  glans  and  prepuce  and  from 
the  mucous  membrane  of  the  urethra,  and  terminate  in  the  superficial  inguinal 
glands ;  the  latter  emerge  from  the  corpora  cavernosa  and  corpus  spongiosum,  and, 
passing  beneath  the  pubic  arch,  join  the  deep  lymphatics  of  the  pelvis. 

The  nerves  are  derived  from  the  internal  pudic  nerve  and  the  pelvic  plexus.  On 
the  glans  and  bulb  some  filaments  of  the  cutaneous  nerves  have  Pacinian  bodies 
connected  with  them,  and,  according  to  Krause,  many  of  them  terminate  in  a 
peculiar  form  of  end-bulb. 

Surgical  Anatomy. — The  penis  occasionally  requires  removal  for  malignant  disease. 
Usually,  removal  of  the  ante-scrotal  portion  is  all  that  is  necessary,  but  sometimes  it  is  requisite 
to  remove  the  whole  organ  from  its  attachment  to  the  rami  of  the  ossa  pubis  and  ischia.  The 
former  operation  is  performed  either  by  cutting  off  the  whole  of  the  anterior  part  of  the  penis 
with  one  sweep  of  the  knife,  or,  what  is  better,  cutting  through  the  corpora  cavernosa  from  the 
dorsum,  and  then  separating  the  corpus  spongiosum  from  them,  dividing  it  at  a  level  nearer  the 
glans  penis.  The  mucous  membrane  of  the  urethra  is  then  slit  up,  and  the  edges  of  the  flap 
attached  to  the  external  skin,  in  order  to  prevent  contraction  of  the  orifice,  which  would  other- 
wise take  place.  The  vessels  which  require  ligature  are  the  two  dorsal  arteries  of  the  penis,  the 
arteries  of  the  corpora  cavernosa,  and  the  artery  of  the  septum.  When  the  entire  organ  requires 
removal  the  patient  is  placed  in  the  lithotomy  position,  and  an  incision  is  made  through  the 
skin  and  subcutaneous  tissue  round  the  root  of  the  penis,  and  carried  down  the  median  line  of 
the  scrotum  as  far  as  the  perineum.  The  two  halves  of  the  scrotum  aie  then  separated  from 
each  other,  and  a  catheter  having  been  introduced  into  the  bladder  as  a  guide,  the  spongy 
portion  of  the  urethra  below  the  triangular  ligament  is  separated  from  the  corpora  cavernosa 
and  divided,  the  catheter  having  been  withdrawn  just  behind  the  bulb.  The  suspensory  liga- 
ment is  now  severed,  and  the  crura  separated  from  the  bone  with  a  periosteum  scraper,  and  the 
whole  penis  removed.  The  membranous  portion  of  the  urethra,  which  has  not  been  removed, 
is  now  to  be  attached  to  the  skin  at  the  posterior  extremity  of  the  incision  in  the  perinaeum. 
The  remainder  of  the  wound  is  to  be  brought  together,  free  drainage  being  provided  for. 

THE    TESTES    AND    THEIR    COVERINGS    (Fig.  565). 

The  Testes  are  two  glandular  organs,  which  secrete  the  semen ;  they  are  sit- 
uated in  the  scrotum,  being  suspended  by  the  spermatic  cords.  At  an  early 
period  of  foetal  life  the  testes  are  contained  in  the  abdominal  cavity,  behind  the 
peritoneum.  Before  birth  they  descend  to  the  inguinal  canal,  along  which  they 
pass  with  the  spermatic  cord,  and,  emerging  at  the  external  abdominal  ring,  they 
descend  into  the  scrotum,  becoming  invested  in  their  course  by  numerous  coverings 
derived  from  the  serous,  muscular,  and  fibrous  layers  of  the  abdominal  parietes, 
as  well  as  by  the  scrotum.     The  coverings  of  the  testes  are — the 


THE    TESTES   AND    THEIR    COVERINGS. 


1015 


Skill         )      rj  , 

Dartos  J 

Intercolumnar,  or  External  spermatic  fascia. 

Cremasteric  fascia. 

Infimdibuliform,  or  Fascia  propria  (Internal  spermatic  fascia). 

Tunica  vaginalis. 

The  Scrotum  is  a  cutaneous  pouch  which  contains  the  testes  and  part  of  the 
spermatic  cords.  It  is  divided  on  its  surface  into  two  lateral  portions  by  a  median 
line,  or  raphe,  which  is  continued  forward  to  the  under  surface  of  the  penis  and 
backward  along  the  middle  line  of  the  perineum  to  the  anus.  Of  these  two  lateral 
portions,  the  left  is  longer  than  the  right,  and  corresponds  with  the  greater  length 
of  the  spermatic  cord  on  the  left  side.  Its  external  aspect  varies  under  different 
circumstances :  thus  under  the  influence  of  warmth  and  in  old  and  debilitated 
persons  it  becomes  elongated  and  flaccid,  but  under  the  influence  of  cold  and  in 
the  young  and  robust  it  is  short,  corrugated,  and  closely  applied  to  the  testes. 

The  scrotum  consists  of  two  layers,  the  integument  and  the  dartos. 

The  integument  is  very  thin,  of  a  brownish  color,  and  generally  thrown  into 
folds  or  rugae.  It  is  provided  with  sebaceous  follicles,  the  secretion  of  which  has 
a  peculiar  odor,  and  is  beset  with  thinly-scattered,  crisp  hairs,  the  roots  of  which 
are  seen  through  the  skin. 

The  dartos  is  a  thin  layer  of  loose  reddish  tissue,  endowed  with  contractility : 
it  forms  the  proper  tunic  of  the  scrotum,  is  continuous,  around  the  base  of  the 
scrotum,  with  the  two  layers  of  the  superficial  fascia  of  the  groin  and  peringeum, 

Skin. 

Dartos. 

External  spermatic  fascia. 

Cremasteric  fascia. — 

Infimdibuliform  fascia 

Parietal  tunica  vaginalis. 

Visceral  tunica  vaginalis 

Tunica  albuginea. ... 
A  lobule  of  the  testicle..^ 

A  septum — 

Mediastinum 

Digital  fossa 

Spermatic  vein._^_ 
Epididymis. .  _ 

Vas  deferens. 

Artery  to  vas.—- 

Spermatic  artery 

Internal  muscular 

tunic  of  Kolliker. 

Fig.  565.— Transverse  section  through  the  left  side  of  the  scrotum  and  the  left  testicle.    The  sac  of  the 
tunica  vaginalis  represented  in  a  distended  condition.    (Delepine.) 

and  sends  inward  a  distinct  septum,  septum  scroti,  which  divides  it  into  two 
cavities  for  the  two  testes,  the  septum  extending  betAveen  the  raphe  and  the  under 
surface  of  the  penis  as  far  as  its  root. 

The  dartos  is  closely  united  to  the  skin  externally,  but  connected  with  the 
subjacent  parts  by  delicate  areolar  tissue,  upon  which  it  glides  with  the  greatest 
facility.  The  dartos  is  very  vascular,  and  consists  of  a  loose  areolar  tissue  con- 
taining unstriped  muscular  fibre,  but  no  fat.  Its  contractility  is  slow,  and  excited 
by  cold  and  mechanical  stimuli,  but  not  by  electi'icity. 

The  intercolumnar  fascia  is  a  thin  membrane  derived  from  the  margin  of  the 


1016  THE   MALE    ORGANS    OF    GENERATION. 

pillars  of  the  external  abdominal  ring,  during  the  descent  of  the  testes  in  the 
foetus,  which  is  prolonged  downward  around  the  surface  of  the  cord  and  testis.  It 
is  separated  from  the  dartos  by  loose  areolar  tissue,  which  allows  of  considerable 
movement  of  the  latter  upon  it,  but  is  intimately  connected  with  the  succeeding 
layers. 

The  cremasteric  fascia  consists  of  scattered  bundles  of  muscular  fibres 
(Oremaster  muscle)  connected  together  into  a  continuous  covering  by  intermediate 
areolar  tissue.  The  muscular  fibres  are  continuous  with  the  lower  border  of  the 
Internal  oblique  muscle  (see  page  360). 

The  infundibuliform  fascia  is  a  thin  membranous  layer,  which  loosely  invests 
the  surface  of  the  cord.  It  is  a  continuation  downward  of  the  fascia  transversalis. 
Beneath  it  is  a  quantity  of  loose  connective  tissue  which  connects  this  layer  of 
fascia  with  the  spermatic  cord  and  posterior  part  of  the  testicle.  This  connective 
tissue  is  continuous  above  with  the  subserous  areolar  tissue  of  the  abdomen.  These 
two  layers,  the  infundibuliform  fascia  and  the  tissue  beneath  it,  are  known  collec- 
tively as  the  fascia  propria. 

The  tunica  vaginalis  is  described  with  the  testis. 

Vessels  and  Nerves. — The  arteries  supplying  the  coverings  of  the  testis  are  : 
the  superficial  and  deep  external  pudic,  from  the  femoral ;  the  superficial  perineal 
branch  of  the  internal  pudic  ;  and  the  cremasteric  branch  from  the  epigastric.  The 
veins  follow  the  course  of  the  corresponding  arteries.  The  lymphatics  terminate 
in  the  inguinal  glands.  The  nerves  are  :  the  ilio-inguinal  branch  of  the  lumbar 
plexus,  the  two  superficial  perineal  branches  of  the  internal  pudic  nerve,  the  inferior 
pudendal  branch  of  the  small  sciatic  nerve,  and  the  genital  branch  of  the  genito- 
crural  nerve. 

The  Spermatic  Cord  extends  from  the  internal  abdominal  ring,  where  the 
structures  of  which  it  is  composed  converge,  to  the  back  part  of  the  testicle.  In 
the  abdominal  wall  the  cord  passes  obliquely  along  the  inguinal  canal,  lying  at 
first  between  the  Internal  oblique  and  upon  the  fascia  transversalis  ;  but  nearer  the 
pubes  it  rests  upon  Poupart's  ligament,  having  the  aponeurosis  of  the  External 
oblique  in  front  of  it  and  the  conjoined  tendon  behind  it.  It  then  escapes  at  the 
external  ring,  and  descends  nearly  vertically  into  the  scrotum.  The  left  cord  is 
rather  longer  than  the  right,  consequently  the  left  testis  hangs  somewhat  lower 
than  its  fellow. 

Structure  of  the  Spermatic  Cord. — The  spermatic  cord  is  composed  of  arteries, 
veins,  lymphatics,  nerves,  and  the  excretory  duct  of  the  testicle.  These  structures 
are  connected  together  by  areolar  tissue,  and  invested  by  the  layers  brought  down 
by  the  testicle  in  its  descent. 

The  arteries  of  the  cord  are  :  the  spermatic,  from  the  aorta  ;  the  artery  of  the 
vas  deferens,  from  the  superior  vesical ;  the  cremasteric,  from  the  deep  epigastric. 

The  spermatic  artery,  a  branch  of  the  abdominal  aorta,  escapes  from  the 
abdomen  at  the  internal  or  deep  abdominal  ring,  and  accompanies  the  other  con- 
stituents of  the  spermatic  cord  along  the  inguinal  canal  and  through  the  external 
abdominal  ring  into  the  scrotum.  It  then  descends  to  the  testicle,  and,  becoming 
tortuous,  divides  into  several  branches,  two  or  three  of  which  accompany  the 
vas  deferens  and  supply  the  epididymis,  anastomosing  with  the  artery  of  the  vas 
deferens  ;  others  pierce  the  back  of  the  tunica  albuginea  and  supply  the  substance 
of  the  testis. 

The  cremasteric  artery  is  a  branch  of  the  deep  epigastric  artery.  It  accom- 
panies the  spermatic  cord  and  supplies  the  Cremaster  muscle  and  other  coverings 
of  the  cord,  anastomosing  with  the  spermatic  artery, 

The  artery  of  the  vas  deferens,  a  branch  of  the  superior  vesical,  is  a  long  slender 
vessel  which  accompanies  the  vas  deferens,  ramifying  upon  the  coats  of  that  duct, 
and  anastomosing  with  the  spermatic  artery  near  the  testis. 

The  spermatic  veins  emerge  from  the  back  of  the  testis  and  receive  tributaries 
from  the  epididymis  ;  they  unite  and  form  a  convoluted  plexus  {plexus  pampini- 
formis),  which  forms  the  chief  mass  of  the  cord  :  the  vessels  composing  this  plexus 


THE    TESTES.  1017 

are  very  numerous,  and  ascend  along  the  cord  in  front  of  the  vas  deferens ;  below 
the  external  or  superficial  abdominal  ring  they  unite  to  form  three  or  four  veins, 
which  pass  along  the  inguinal  canal,  and,  entering  the  abdomen  through  the 
internal  or  deep  abdominal  ring,  coalesce  to  form  two  veins.  These  again  unite  to 
form  a  single  vein,  which  opens  on  the  right  side  into  the  inferior  vena  cava  at  an 
acute  angle,  and  on  the  left  side  into  the  renal  vein  at  a  right  angle. 

The  lymphatic  vessels  terminate  in  the  lumbar  glands. 

The  nerves  are  the  spermatic  plexus  from  the  sympathetic,  joined  by  filaments 
from  the  pelvic  plexus  which  accompany  the  artery  of  the  vas  deferens. 

Surgical  Anatomy. — The  scrotum  forms  an  admirable  covering  for  the  protection  of  the 
testicle.  This  body,  lying  suspended  and  loose  in  the  cavity  of  the  scrotum  and  surrounded  by 
a  serous  membrane,  is  capable  of  great  mobility,  and  can  therefore  easily  slip  about  within  the 
scrotum,  and  thus  avoid  injuries  from  blows  or  squeezes.  The  skin  of  the  scrotum  is  very 
elastic  and  capable  of  great  distension,  and  on  account  of  the  looseness  and  amount  of  subcu- 
taneous tissue  the  scrotum  becomes  greatly  enlarged  in  cases  of  oedema,  to  which  this  part  is 
especially  liable  on  account  of  its  dependent  position.  The  scrotum  is  frequently  the  seat  of 
epithelioma ;  this  is  no  doubt  due  to  the  rugae  on  its  surface,  which  favor  the  lodgment  of  dirt, 
and  this,  causing  irritation,  is  the  exciting  cause  of  the  disease,  which  is  especially  common  in 
chimney-sweeps  from  the  lodgment  of  soot.  The  scrotum  is  also  the  part  most  frequently 
affected  by  elephantiasis. 

On  account  of  the  looseness  of  the  subcutaneous  tissue  considerable  extravasations  of  blood 
may  take  place  from  very  slight  injuries.  It  is  therefore  generally  recommended  never  to  apply 
leeches  to  the  scrotum,  since  they  may  lead  to  considerable  ecchymosis,  but  rather  to  puncture 
one  or  more  of  the  superficial  veins  of  the  scrotum  in  cases  where  local  bloodletting  from  this 
part  is  judged  to  be  desirable.  The  muscular  fibre  in  the  dartos  causes  contraction  and  consider- 
able diminution  in  the  size  of  a  wound  of  the  scrotum,  as  after  the  operation  of  castration,  and 
is  of  assistance  in  keeping  the  edges  together  and  covering  the  exposed  parts. 

THE  TESTES. 

The  Testes  are  suspended  in  the  scrotum  by  the  spermatic  cords.  As  the  left 
spermatic  cord  is  rather  longer  than  the  right  one,  the  left  testicle  hangs  somewhat 
lower  than  its  fellow.  Each  gland  is  of  an  oval  form,  compressed  laterally,  and 
having  an  oblique  position  in  the  scrotum,  the  upper  extremity  being  directed 
forward  and  a  little  outward,  the  lower,  backward  and  a  little  inward ;  the  anterior 
convex  border  looks  forward  and  downward ;  the  posterior  or  straight  border,  to 
which  the  cord  is  attached,  backward  and  upward. 

The  anterior  border  and  lateral  surfaces,  as  well  as  both  extremities  of  the 
organ,  are  convex,  free,  smooth,  and  invested  by  the  visceral  layer  of  the  tunica 
vaginalis.  The  posterior  border,  to  which  the  cord  is  attached,  receives  only  a 
partial  investment  from  that  membrane.  Lying  upon  the  outer  edge  of  this  poste- 
rior border  is  a  long,  narrow,  flattened  body,  named  from  its  relation  to  the  testis, 
the  epididymis  (dcdufios,  testis).  It  consists  of  a  central  portion,  or  body ;  an 
upper  enlarged  extremity,  the  head,  or  globus  major  ;  and  a  lower  pointed  extrem- 
ity, the  tail,  or  globus  minor.  The  globus  major  is  intimately  connected  with  the 
upper  end  of  the  testicle  by  means  of  its  efferent  ducts,  and  the  globus  minor  is 
connected  with  its  lower  end  by  cellular  tissue  and  a  reflection  of  the  tunica  vagi- 
nalis. The  outer  surface  and  upper  and  lower  ends  of  the  epididymis  are  free  and 
covered  by  serous  membrane  ;  the  body  is  also  completely  invested  by  it,  excepting 
along  its  posterior  border,  and  between  the  body  and  the  testicle  is  a  pouch  or  cul- 
de-sac,  named  the  digital  fossa.  The  epididymis  is  connected  to  the  back  of  the 
testis  by  a  fold  of  the  serous  membrane.  Attached  to  the  upper  end  of  the  testis, 
close  to  the  globus  major,  are  two  small  pedunculated  bodies.  One  of  them  is 
pear-shaped,  and  attached  by  its  narrow  stalk  ;  the  other  is  small  and  sessile ;  they 
are  believed  to  be  the  remains  of  the  upper  extremity  of  the  Mullerian  duct,  and 
are  termed  the  hydatids  of  Morgagni ;  some  observers,  however,  regard  the  stalked 
hydatid  as  being  a  rudiment  of  the  pronephros.  When  the  testiele  is  removed 
from  the  body,  the  position  of  the  vas  deferens,  on  the  posterior  surface  of  the 
testicle  and  inner  side  of  the  epididymis,  marks  the  side  to  which  the  gland  has 
belonged. 


1018 


THE   MALE    ORGANS    OF    GENERATION. 


Size  and  Weight. — The  average  dimensions  of  this  gland  are  from  one  and  a 
half  to  two  inches  in  length,  one  inch  in  breadth,  and  an  inch  and  a  quarter  in  the 
antero-posterior  diameter,  and  the  weight  varies  from  six  to  eight  drachms,  the 
left  testicle  being  a  little  the  larger. 

The  testis  is  invested  by  three  tunics — the  tunica  vaginalis,  tunica  albuginea, 
and  tunica  vasculosa. 

The  Tunica  Vaginalis  is  the  serous  covering  of  the  testis.  It  is  a  pouch  of 
serous  membrane,  derived  from  the  peritoneum  during  the  descent  of  the  testis  in 
the  foetus  from  the  abdomen  into  the  scrotum.  After  its  descent  that  portion  of 
the  pouch  which  extends  from  the  internal  ring  to  near  the  upper  part  of  the  gland 
becomes  obliterated,  the  lower  portion  remaining  as  a  shut  sac,  which  invests 
the  outer  surface  of  the  testis,  and  is  reflected  on  to  the  internal  surface  of  the 
scrotum ;  hence  it  may  be  described  as  consisting  of  a  visceral  and  parietal 
portion. 

The  visceral  portion  of  the  tunica  vaginalis  covers  the  outer  surface  of  the 
testis,  as  well  as  the  epididymis,  connecting  the  latter  to  the  testis  by  means  of  a 
distinct  fold.  From  the  posterior  border  of  the  gland  it  is  reflected  on  to  the 
internal  surface  of  the  scrotum. 

The  parietal  portion  of  the  tunica  vaginalis  is  far  more  extensive  than  the 
visceral  portion,  extending  upward  for  some  distance  in  front  and  on  the  inner  side 
of  the  cord,  and  reaching  below  the  testis.  The  inner  surface  of  the  tunica  vagi- 
nalis is  free,  smooth,  and  covered  by  a  layer  of  endothelial  cells.  The  interval 
between  the  visceral  and  parietal  layers  of  this  membrane  constitutes  the  cavity 
of  the  tunica  vaginalis. 

The  obliterated  portion  of  the  pouch  may  generally  be  seen  as  a  fibro-celklar 
thread  lying  in  the  loose  areolar  tissue  around  the  spermatic  cord ;  sometimes  this 
may  be  traced  as  a  distinct  band  from  the  upper  end  of  the  inguinal  canal,  where 
it  is  connected  with  the  peritoneum,  down  to  the  tunica  vaginalis ;  sometimes  it 

gradually  becomes  lost  on  the  spermatic  cord. 
Occasionally  no  trace  of  it  can  be  detected.  In 
some  cases  it  happens  that  the  pouch  of  peri- 
toneum does  not  become  obliterated,  but  the  sac 
of  the  peritoneum  communicates  with  the  tunica 
vaginalis.  This  may  give  rise  to  one  of  the 
varieties  of  oblique  inguinal  hernia  (page  1049). 
Or  in  other  cases  the  pouch  may  contract,  but 
not  become  entirely  obliterated ;  it  then  forms 
a  minute  canal  leading  from  the  peritoneum  to 
the  tunica  vaginalis.1 

The  Tunica  Albuginea  is  the  fibrous  cover- 
ing of  the  testis.  It  is  a  dense  fibrous  mem- 
brane, of  a  bluish-white  color,  composed  of 
bundles  of  white  fibrous  tissue,  which  interlace 
in  every  direction.  Its  outer  surface  is  covered 
by  the  tunica  vaginalis,  except  at  the  points  of 
attachment  of  the  epididymis  to  the  testicle,  and 
along  its  posterior  border,  where  the  spermatic- 
vessels  enter  the  gland.  This  membrane  sur- 
rounds the  glandular  structure  of  the  testicle, 
and  at  its  posterior  border  is  reflected  into  the 
interior  of  the  gland,  forming  an  incomplete  vertical  septum,  called  the  mediasti- 
num testis  (corpus  Highmorianum). 

The  mediastinum  testis  extends  from  the  upper,  nearly  to  the  lower,  extremity 

1  It  is  recorded  that  in  the  post-mortem  examination  of  Sir  Astley  Cooper  this  minute  canal  was 
found  on  both  sides  of  the  body.  Sir  Astley  Cooper  states  that  when  a  student  he  suffered  from 
inguinal  hernia  ;  probably  this  was  of  the  congenital  variety,  and  the  canal  found  after  death  was 
the  remains  of  the  one  down  which  the  hernia  travelled  (Lancet,  1824,  vol.  ii.,  p.  116). 


Spermatic  cord. 


rtery  of 
cord. 


Tunica  vaginalis, 
parietal  layer, 


Digital 
fossa 


Fig.  566.— The  testis  in  situ,  the  tunica 
vaginalis  having  been  laid  open. 


THE    TESTES.  1019 

of  the  gland,  and  is  wider  above  than  below.  From  the  front  and  sides  of  this 
septum  numerous  slender  fibrous  cords  and  imperfect  septa  (trabecular)  are  given 
off,  which  radiate  toward  the  surface  of  the  organ,  and  are  attached  to  the  inner 
surface  of  the  tunica  albuginea.  They  therefore  divide  the  anterior  of  the  organ 
into  a  number  of  incomplete  spaces,  which  are  somewhat  cone-shaped,  being  broad 
at  their  bases  at  the  surface  of  the  gland,  and  becoming  narrower  as  they  converge 
to  the  mediastinum.  The  mediastinum  supports  the  vessels  and  ducts  of  the  testis 
in  their  passage  to  and  from  the  substance  of  the  gland. 

The  Tunica  Vasculosa  is  the  vascular  layer  of  the  testis,  consisting  of  a  plexus 
of  blood-vessels  held  together  by  a  delicate  areolar  tissue.  It  covers  the  inner 
surface  of  the  tunica  albuginea  and  the  different  septa  in  the  interior  of  the  gland, 
and  therefore  forms  an  internal  investment  to  all  the  spaces  of  which  the  gland  is 
composed. 

Structure. — The  glandular  structure  of  the  testis  consists  of  numerous  lobules 
[lobuli  testis).  Their  number,  in  a  single  testis,  is  estimated  by  Berres  at  250,  and 
by  Krause  at  400.  They  differ  in  size  according  to  their  position,  those  in  the 
middle  of  the  gland  being  larger  and  longer.  The  lobules  are  conical  in  shape, 
the  base  being  directed  toward  the  circumference  of  the  organ,  the  apex  toward  the 
mediastinum.  Each  lobule  is  contained  in  one  of  the  intervals  between  the  fibrous 
cords  and  vascular  processes  which  extend  between  the  mediastinum  testis  and 
the  tunica  albuginea,  and  consists  of  from  one  to  three  or  more  minute  convoluted 
tubes,  the  tubuli  seminiferi.  The  tubes  may  be  separately  unravelled  by  careful 
dissection  under  Avater,  and  may  be  seen  to  commence  either  by  free  csecal  ends  or 
by  anastomotic  loops.  The  total  number  of  tubes  is  considered  by  Munro  to  be 
about  300,  and  the  length  of  each  about  sixteen  feet ;  by  Lauth  their  number  is 
estimated  at  840,  and  their  average  length  two  feet  and  a  quarter.  The  diameter 
varies  from  -^-^  to  y^-g-  of  an  inch.  The  tubuli  are  pale  in  color  in  early  life,  but 
in  old  age  they  acquire  a  deep  yellow  tinge  from  containing  much  fatty  matter. 
Each  tube  consists  of  a  basement  layer,  formed  of  epithelioid  cells  united  edge  to 
edge,  outside  which  are  other  layers  of  flattened  cells  arranged  in  interrupted 
laminae,  which  give  to  the  tube  an  appearance  of  striation  in  cross  section.  The 
cells  of  the  outer  layers  gradually  pass  into  the  interstitial  tissue.  Within  the 
basement-membrane  are  epithelial  cells  arranged  in  several  irregular  layers,  which 
ire  not  always  clearly  separated,  but  which  may  be  arranged  in  three  different 
groups.  Among  these  cells  may  be  seen  the  spermatozoa  in  different  stages  of 
development.  1.  Lining  the  basement-membrane  and  forming  the  outer  zone  is 
a  layer  of  cubical  cells,  with  small  nuclei  ;  these  are  known  as  the  lining  cells  or 
spermatogonia.  The  nucleus  of  some  of  them  may  be  seen  to  be  in  the  process 
of  indirect  division  (Jcaryokinesis),  and  in  consequence  of  this  daughter  cells  are 
formed,  which  constitute  the  second  zone.  2.  Within  this  first  layer  is  to  be  seen 
a  number  of  larger  cells  with  clear  nuclei,  arranged  in  two  or  three  layers;  these 
are  the  intermediate  cells  or  spermatocytes.  Most  of  these  cells  are  in  a  condition 
of  karyokinetic  division,  and  the  cells  which  result  from  this  division  form  those 
of  the  next  layer,  the  spermatoblasts  or  spermatids.  3.  The  third  layer  of  cells 
therefore  consists  of  the  spermatoblasts  or  spermatids,  and  each  of  these,  without 
further  subdivision,  becomes  a  spermatozoon.  They  are  ill-defined  granular  masses 
of  protoplasm,  of  an  elongated  form,  with  a  nucleus  which  becomes  the  head  of 
the  future  spermatozoon.  In  addition  to  these  three  layers  of  cells  others  are  seen, 
which  are  termed  the  supporting  cells,  or  cells  of  Sertoli.  They  are  elongated  and 
columnar,  and  project  inward  from  the  basement-membrane  toward  the  lumen  of 
the  tube.  They  give  off  numerous  lateral  branches,  which  form  a  reticulum  for 
the  support  of  the  three  groups  of  cells  just  described.  As  development  of  the 
spermatozoa  proceeds  the  latter  group  themselves  around  the  inner  extremities  of 
the  supporting  cells.  The  nuclear  part  of  the  spermatozoon,  which  is  partly 
imbedded  in  the  supporting  cell,  is  differentiated  to  form  the  head  of  the  spermato- 
zoon, while  the  cell  protoplasm  becomes  lengthened  out  to  form   the  middle  piece 


1020 


THE  MALE    ORGANS    OF    GENERATION. 


and  tail,  the  latter  projecting  into  the  lumen  of  the  tube.      Ultimately  the  heads 
are  separated  and  the  spermatozoa  are  set  free. 

Spermatogenesis. — The  stages  in  the  development  of  the  spermatozoa  are  as 
follows :  The  spermatogonia  become  enlarged  to  form  the  spermatocytes,  and 
each  spermatocyte  subdivides  into  two  cells,  and  each  of  these  again  divides  into 
two  spermatids  or  young  spermatozoa,  so  that  the  spermatocyte  gives  origin  to 
four  spermatozoa. 

The  process  of  spermatogenesis  bears  a  close  relation  to  that  of  maturation  of 
the  ovum.  The  spermatocyte  is  equivalent  to  the  immature  ovum.  It  undergoes 
subdivision,  and  ultimately  gives  origin  to  four  spermatozoa,  each  of  which  con- 
tains, therefore,  only  one- fourth  of  the  chromatin  elements  of  the  nucleus  of  the 
spermatocyte.  In  the  process  of  maturation  of  the  ovum  its  nucleus  divides,  one 
half  being  extended  as  the  first  polar  body.  The  remaining  half  of  the  nucleus 
again  subdivides,  one  half  being  extended  as  the  second  polar  body.  The  portion 
of  the  nucleus  which  is  retained  to  form  the  female  pronucleus  of  the  now 
matured  ovum  contains,  therefore,  only  one-fourth  of  the  chromatin  elements  of 
the  original  nucleus,  and  thus  the  spermatozoon  and  the  matured  ovum,  so  far  as 
their  nuclear  elements  are  concerned,  may  be  regarded  as  of  the  same  morpho- 
logical value. 

The  tubules  are  enclosed  in  a  delicate  plexus  of  capillary  vessels,  and  are  held 
together  by  anintertubular  connective  tissue,  which  presents  large  interstitial  spaces 
lined  by  endothelium,  which  are  believed  to  be  the  rootlets  of  lymphatic  vessels 
of  the  testis. 

In  the  apices  of  the  lobules  the  tubuli  become  less  convoluted,  assume  a  nearly 
straight  course,  and  unite  together  to  form  from  twenty  to  thirty  larger  ducts,  of 
about  -^g  of  an  inch  in  diameter,  and  these,  from  their  straight  course,  are  called 
vasa  recta. 

The  vasa  recta  enter  the  fibrous  tissue  of  the  mediastinum,  and  pass  upward 
and  backward,  forming,  in  their   ascent,  a  close   network  of  anastomosing  tubes, 

which  are  merely  channels  in  the  fibrous  stroma, 
lined  by  flattened  epithelium,  and  having  no 
proper  walls  ;  this  constitutes  the  rete  testis.  At 
the  upper  end  of  the  mediastinum  the  vessels  of 
the  rete  testis  terminate  in  from  twelve  to  fifteen 
or  twenty  ducts,  the  vasa  efferentia :  they  per- 
forate the  tunica  albuginea,  and  carry  the  sem- 
inal fluid  from  the  testis  to  the  epididymis.  Their 
course  is  at  first  straight ;  they  then  become  en- 
larged and  exceedingly  convoluted,  and  form  a 
series  of  conical  masses,  the  coni  vasculosis  which, 
together,  constitute  the  globus  major  of  the  epi- 
didymis. Each  cone  consists  of  a  single  con- 
voluted duct  from  six  to  eight  inches  in  length, 
the  diameter  of  which  gradually  decreases  from 
the  testis  to  the  epididymis.  Opposite  the  bases 
of  the  cones  the  efferent  vessels  open  at  narrow 
intervals  into  a  single  duct,  which  constitutes, 
by  its  complex  convolutions,  the  body  and  globus 
minor  of  the  epididymis.  When  the  convolutions 
of  this  tube  are  unravelled,  it  measures  upward 
of  twenty  feet  in  length,  and  it  increases  in  diam- 
eter and  thickness  as  it  approaches  the  vas  def- 
erens. The  convolutions  are  held  together  by  fine 
areolar  tissue  and  by  bands  of  fibrous  tissue. 
The  vasa  recta  are  of  smaller  diameter  than  the  seminal  tubes,  and  have  very 
thin  parietes.  They,  like  the  channels  of  the  rete  testis,  are  lined  by  a  single 
layer  of  flattened  epithelium.      The  vasa  efferentia  and  the  tube  of  the  epididymis 


Tunica  Vaginalis 


Tunica  Albugii 


Fig.  567.— Vertical  section  of  the  testi- 
cle, to  show  the  arrangement  of  the  ducts. 


THE    TESTES.  1021 

have  walls  of  considerable  thickness,  on  account  of  the  presence  in  them  of  mus- 
cular tissue,  which  is  principally  arranged  in  a  circular  manner.  These  tubes  are 
lined  by  columnar  ciliated  epithelium. 

The  Vas  Deferens,  the  excretory  duct  of  the  testis,  is  the  continuation  of  the 
epididymis.  Commencing  at  the  lower  part  of  the  globus  minor,  it  ascends  along 
the  posterior  border  of  the  testis  and  inner  side  of  the  epididymis,  and  along  the 
back  part  of  the  spermatic  cord,  through  the  inguinal  canal  to  the  internal  or 
deep  abdominal  ring.  From  the  ring  it  curves  round  the  outer  side  of  the  epi- 
gastric artery,  crosses  the  external  iliac  vessels,  and  descends  into  the  pelvis  at 
the  side  of  the  bladder ;  it  arches  backward  and  downward  to  its  base,  crossing 
over  the  obliterated  hypogastric  artery  and  to  the  inner  side  of  the  ureter.  At  the 
base  of  the  bladder  it  lies  between  that  viscus  and  the  rectum,  running  along  the 
inner  border  of  the  vesicula  seminalis.  In  this  situation  it  becomes  enlarged  and 
sacculated,  forming  the  ampulla,  and  then,  becoming  narrowed  at  the  base  of  the 
prostate,  unites  with  the  duct  of  the  vesicula  seminalis  to  form  the  ejaculatory 
duct.  The  vas  deferens  presents  a  hard  and  cord-like  sensation  to  the  ringers ;  it 
is  about  two  feet  in  length,  of  cylindrical  form,  and  about  a  line  and  a  quarter  in 
diameter.  Its  walls  are  dense,  measuring  one- third  of  a  line,  and  its  canal  is 
extremely  small,  measuring  about  half  a  line. 

Structure. — The  vas  deferens  consists  of  three  coats  :  1.  An  external  or  areolar 
coat.  2.  A  muscular  coat,  which  in  the  greater  part  of  the  tube  consists  of  two 
layers  of  unstriped  muscular  -fibre  :  an  outer,  longitudinal  in  direction,  and  an 
inner,  circular  ;  but  in  addition  to  these,  at  the  commencement  of  the  vas  deferens, 
there  is  a  third  layer,  consisting  of  longitudinal  fibres,  placed  internal  to  the  circular 
stratum,  between  it  and  the  mucous  membrane.  3.  An  internal  or  mucous  coat, 
which  is  pale,  and  arranged  in  longitudinal  folds  ;  its  epithelial  covering  is  of  the 
columnar  variety. 

A  long  narrow  tube,  the  vas  a.berrans  of  Holler,  is  occasionally  found  connected 
with  the  lower  part  of  the  canal  of  the  epididymis  or  with  the  commencement  of 
the  vas  deferens.  It  extends  up  into  the  cord  for  about  two  or  three  inches,  where 
it  terminates  by  a  blind  extremity,  which  is  occasionally  bifurcated.  Its  length 
varies  from  an  inch  and  a  half  to  fourteen  inches,  and  sometimes  it  becomes  dilated 
toward  its  extremity ;  more  commonly  it  retains  the  same  diameter  throughout. 
Its  structure  is  similar  to  that  of  the  vas  deferens.  Occasionally  it  is  found  uncon- 
nected with  the  epididymis. 

Organ  of  Giraldes. — This  term  is  applied  to  a  small  collection  of  convoluted 
tubules,  situated  in  front  of  the  lower  part  of  the  cord  or  above  the  globus  major 
of  the  epididymis.  These  tubes  are  lined  with  columnar  ciliated  epithelium,  and 
probably  represent  the  remains  of  a  part  of  the  Wolffian  body. 

Surgical  Anatomy. — The  testicle  frequently  requires  removal  for  malignant  disease ;  in 
tuberculous  disease ;  in  cystic  disease ;  in  cases  of  large  hernia  testis,  and  in  some  instances  of 
incompletely  descended  or  misplaced  testicles.  The  operation  of  castration  has  also  been,  during 
the  last  few  years,  performed  for  enlargement  of  the  prostate  ;  for  it  has  been  found  that  removal 
of  the  testicle  is  followed  by  very  rapid  and  often  considerable  diminution  in  the  size  of  the 
prostate.  The  operation  is,  however,  one  of  severity,  and  is  frequently  followed  by  death  in 
these  cases,  performed,  as  it  necessarily  is,  in  old  men.  Reginald  Harrison  has  proposed  to  sub- 
stitute for  it  excision  of  a  portion  of  the  vasa  deferentia.  The  operation  of  castration  is  a  com- 
paratively simple  one.  An  incision  is  made  into  the  tunica  vaginalis  from  the  external  ring  to 
the  bottom  of  the  scrotum.  The  coverings  are  shelled  off  the  organ,  and  the  mesorchium, 
stretching  between  the  back  of  the  testicle  and  the  scrotum,  divided.  The  cord  is  then  isolated, 
and  an  aneurism  needle,  armed  with  a  double  ligature,  passed  under  it,  as  high  as  is  thought 
necessary,  and  the  cord  tied  in  two  places,  and  divided  between  the  ligatures.  Sometimes,  in 
cases  of  malignant  disease,  it  is  desirable  to  open  the  inguinal  canal  and  tie  the  cord  as  near  the 
internal  abdominal  ring  as  possible. 

Spermatozoa. — The  spermatozoa  are  minute,  thread-like  bodies,  which  constitute 
the  essential  elements  of  the  semen.  Each  consists  of  a  head,  a  middle  piece  or 
body,  and  an  elongated  filament  or  tail.  The  head,  on  surface  view,  appears  oval  in 
shape,  but  if  seen  in  profile  it  is  narrow  and  pointed  at  its  free  end.     It  represents 


1022 


THE   MALE    ORGANS    OF    GENERATION. 


the  modified  nucleus  of  the  spermatid,  and  consists  chiefly  of  chromatin,  and  so 
stains  readily  with  nuclear  reagents  ;  it  is  covered  by  a  thin  cap  of  protoplasm. 
The  body  is  a  short  cylindrical  or  conical  piece,  intervening  between  the  head  and 
tail,  and  is  therefore  sometimes  spoken  of  as  the  intermediate  segment.  The  tail 
is  about  four  times  the  combined  lengths  of  the  head  and  body ;  its  terminal  part 
is  extremely  fine,  and  is  named  the  end-piece.  Contained  within  the  body  and  tail 
is  an  axial  filament,  surrounded,  except  in  the  end-piece,  by  a  thin  layer  of  proto- 
plasm ;  this  axial  filament  terminates  just  below  the  head  in  a  rounded  knob  or 
button.  In  virtue  of  their  tails,  which  act  as  propellers,  the  spermatozoa,  in  the 
fresh  condition,  are  capable  of  free  movement,  and  if  placed  in  favorable  surroundings 
(e.  g.,  in  the  female  passages)  may  retain  their  vitality  for  some  days  or  even  weeks. 

VESICULA    SEMINALES. 

The  Seminal  Vesicles  are  two  lobulated  membranous  pouches  placed  between  the 
base  of  the  bladder  and  the  rectum,  serving  as  reservoirs  for  the  semen,  and  secreting 
a  fluid  to  be  added  to  the  secretion  of  the  testicles.  Each  sac  is  somewhat  pyramidal 


Right  Ejaculatory 
duct. 


Fig.  568. — Base  of  the  bladder,  with  the  vasa  deferentia  and  vesiculse  seminales. 


in  form,  the  broad  end  being  directed  backward  and  the  narrow  end  forward  toward 
the  prostate.  They  measure  about  two  and  a  half  inches  in  length,  about  five  lines 
in  breadth,  and  two  or  three  lines  in  thickness.  They  vary,  however,  in  size, 
not  only  in  different  individuals,  but  also  in  the  same  individual  on  the  two  sides. 
Their  upper  surface  is  in  contact  with  the  base  of  the  bladder,  extending  from  near 
the  termination  of  the  ureters  to  the  base  of  the  prostate  gland.  Their  under  surface 
rests  upon  the  rectum,  from  which  they  are  separated  by  the  recto-vesical  fascia. 
Their  posterior  extremities  diverge  from  each  other.  Their  anterior  extremities  are 
pointed,  and  converge  toward  the  base  of  the  prostate  gland,  where  each  joins  with 
the  corresponding  vas  deferens  to  form  the  ejaculatory  duct.  Along  the  inner 
margin  of  each  vesicula  runs  the  enlarged  and  convoluted  vas  deferens.  The  inner 
border  of  the  vesiculse  and  the  corresponding  vas  deferens  form  the  lateral 
boundaries  of  a  triangular  space,  limited  behind  by  the  recto-vesical  peritoneal 
fold ;  the  portion  of  the  bladder  included  in  this  space  rests  on  the  rectum. 

Each  vesicula  consists  of  a  single  tube,  coiled  upon  itself  and  giving  off  several 
irregular  caecal  diverticula,  the  separate  coils,  as  well  as  the  diverticula,  being  con- 
nected together  by  fibrous  tissue.  When  uncoiled  this  tube  is  about  the  diameter 
of  a  quill,  and  varies  in  length  from  four  to  six  inches  ;  it  terminates  posteriorly  in 


\ 

THE    VESICUL^E  SEMINALES.  1023 

a  cul-de-sac  ;  its  anterior  extremity  becomes  constricted  into  a  narrow  straight  duct, 
which  joins  with  the  corresponding  vas  deferens,  and  forms  the  ejaculatory  duct. 

The  ejaculatory  ducts,  two  in  number,  one  on  each  side,  are  formed  by  the  junc- 
tion of  the  ducts  of  the  vesiculse  seminales  with  the  vasa  deferentia.  Each  duct  is 
about  three-quarters  of  an  inch  in  length  ;  it  commences  at  the  base  of  the  prostate, 
and  runs  forward  and  downward  between  its  middle  and  lateral  lobes,  and  along 
the  side  of  the  sinus  pocularis,  to  terminate  by  a  separate  slit-like  orifice  close  to 
or  just  within  the  margins  of  the  sinus.  The  ducts  diminish  in  size  and  also  con- 
verge toward  their  termination. 

Structure. — The  vesiculge  seminales  are  composed  of  three  coats  :  an  external  or 
areolar ;  a  middle  or  muscular  coat,  which  is  thinner  than  in  the  vas  deferens, 
arranged  in  two  layers,  an  outer,  longitudinal,  and  inner,  circular;  an  internal  or 
mucous  coat,  which  is  pale,  of  a  whitish-brown  color,  and  presents  a  delicate  retic- 
ular structure,  like  that  seen  in  the  gall-bladder,  but  the  meshes  are  finer.  The 
epithelium  is  columnar. 

The  coats  of  the  ejaculatory  ducts  are  extremely  thin.  They  are:  an  outer 
fibrous  layer,  which  is  almost  entirely  lost  after  their  entrance  into  the  prostate  ;  a 
layer  of  muscular  fibres,  consisting  of  an  outer  thin  circular  and  an  inner  longi- 
tudinal layer  ;  and  the  mucous  membrane. 

Vessels  and  Nerves. — The  arteries  supplying  the  vesiculse  seminales  are  derived 
from  the  middle  and  inferior  vesical  and  middle  hemorrhoidal.  The  veins  and 
lymphatics  accompany  the  arteries.  The  nerves  are  derived  from  the  pelvic 
plexus. 

Surgical  Anatomy. — The  vesiculae  seminales  are  often  the  seat  of  an  extension  of  the 
disease  in  cases  of  tuberculous  disease  of  the  testicle,  and  should  always  be  examined  from  the 
rectum  before  coming  to  a  decision  with  regard  to  castration  in  this  affection. 


1022 


THE   MALE    ORGANS    OF    GENERATION. 


the  modified  nucleus  of  the  spermatid,  and  consists  chiefly  of  chromatin,  and  so 
stains  readily  with  nuclear  reagents  ;  it  is  covered  by  a  thin  cap  of  protoplasm. 
The  body  is  a  short  cylindrical  or  conical  piece,  intervening  between  the  head  and 
tail,  and  is  therefore  sometimes  spoken  of  as  the  intermediate  segment.  The  tail 
is  about  four  times  the  combined  lengths  of  the  head  and  body  ;  its  terminal  part 
is  extremely  fine,  and  is  named  the  end-piece.  Contained  within  the  body  and  tail 
is  an  axialfilament,  surrounded,  except  in  the  end-piece,  by  a  thin  layer  of  proto- 
plasm ;  this  axial  filament  terminates  just  below  the  head  in  a  rounded  knob  or 
button.  In  virtue  of  their  tails,  which  act  as  propellers,  the  spermatozoa,  in  the 
fresh  condition,  are  capable  of  free  movement,  and  if  placed  in  favorable  surroundings 
(e.  g.,  in  the  female  passages)  may  retain  their  vitality  for  some  days  or  even  weeks. 

VESICULA    SEMINALES. 

The  Seminal  Vesicles  are  two  lobulated  membranous  pouches  placed  between  the 
base  of  the  bladder  and  the  rectum,  serving  as  reservoirs  for  the  semen,  and  secreting 
a  fluid  to  be  added  to  the  secretion  of  the  testicles.  Each  sac  is  somewhat  pyramidal 


Bight  Ejaculatory 
duct. 


Fig.  568.— Base  of  the  bladder,  with  the  vasa  deferentia  and  vesiculse  seminales. 


in  form,  the  broad  end  being  directed  backward  and  the  narrow  end  forward  toward 
the  prostate.  They  measure  about  two  and  a  half  inches  in  length,  about  five  lines 
in  breadth,  and  two  or  three  lines  in  thickness.  They  vary,  however,  in  size, 
not  only  in  different  individuals,  but  also  in  the  same  individual  on  the  two  sides. 
Their  upper  surface  is  in  contact  with  the  base  of  the  bladder,  extending  from  near 
the  termination  of  the  ureters  to  the  base  of  the  prostate  gland.  Their  under  surface 
rests  upon  the  rectum,  from  which  they  are  separated  by  the  recto-vesical  fascia. 
Their  posterior  extremities  diverge  from  each  other.  Their  anterior  extremities  are 
pointed,  and  converge  toward  the  base  of  the  prostate  gland,  where  each  joins  with 
the  corresponding  vas  deferens  to  form  the  ejaculatory  duct.  Along  the  inner 
margin  of  each  vesicula  runs  the  enlarged  and  convoluted  vas  deferens.  Ine  inner 
border  of  the  vesiculse  and  the  corresponding  vas  deferens  form  the  lateral 
boundaries  of  a  triangular  space,  limited  behind  by  the  recto-vesical  peritoneal 
fold ;  the  portion  of  the  bladder  included  in  this  space  rests  on  the  rectum. 

Each  vesicula  consists  of  a  single  tube,  coiled  upon  itself  and  giving  off  several 
irregular  cascal  diverticula,  the  separate  coils,  as  well  as  the  diverticula,  being  con- 
nected together  by  fibrous  tissue.  When  uncoiled  this  tube  is  about  the  diameter 
of  a  quill,  and  varies  in  length  from  four  to  six  inches ;  it  terminates  posteriorly  m 


THE    VESICULJE  SEMINALES.  1023 

a  cul-de-sac  ;  its  anterior  extremity  becomes  constricted  into  a  narrow  straight  duct, 
which  joins  with  the  corresponding  vas  deferens,  and  forms  the  ejaculatory  duct. 

The  ejaculatory  ducts,  two  in  number,  one  on  each  side,  are  formed  by  the  junc- 
tion of  the  ducts  of  the  vesiculas  seminales  with  the  vasa  deferentia.  Each  duct  is 
about  three-quarters  of  an  inch  in  length  ;  it  commences  at  the  base  of  the  prostate, 
and  runs  forward  and  downward  between  its  middle  and  lateral  lobes,  and  alone 
the  side  of  the  sinus  pocularis,  to  terminate  by  a  separate  slit-like  orifice  close  to 
or  just  within  the  margins  of  the  sinus.  The  ducts  diminish  in  size  and  also  con- 
verge toward  their  termination. 

Structure. — The  vesiculse  seminales  are  composed  of  three  coats  :  an  external  or 
areolar ;  a  middle  or  muscular  coat,  which  is  thinner  than  in  the  vas  deferens, 
arranged  in  two  layers,  an  outer,  longitudinal,  and  inner,  circular;  an  internal  or 
mucous  coat,  which  is  pale,  of  a  whitish-brown  color,  and  presents  a  delicate  retic- 
ular structure,  like  that  seen  in  the  gall-bladder,  but  the  meshes  are  finer.  The 
epithelium  is  columnar. 

The  coats  of  the  ejaculatory  ducts  are  extremely  thin.  They  are:  an  outer 
fibrous  layer,  which  is  almost  entirely  lost  after  their  entrance  into  the  prostate  ;  a 
layer  of  muscular  fibres,  consisting  of  an  outer  thin  circular  and  an  inner  longi- 
tudinal layer  ;  and  the  mucous  membrane. 

Vessels  and  Nerves. — The  arteries  supplying  the  vesiculse  seminales  are  derived 
from  the  middle  and  inferior  vesical  and  middle  hemorrhoidal.  The  veins  and 
lymphatics  accompany  the  arteries.  The  nerves  are  derived  from  the  pelvic 
plexus. 

Surgical  Anatomy.— The  vesiculae  seminales  are  often  the  seat  of  an  extension  of  the 
disease  in  cases  of  tuberculous  disease  of  the  testicle,  and  should  always  be  examined  from  the 
rectum  before  coming  to  a  decision  with  regard  to  castration  in  this  affection. 


1026 


THE   FEMALE    ORGANS    OF    GENERATION. 


enclosing  the  common  urino-sexual  opening.  Each  labium  has  two  surfaces,  an 
outer,  which  is  pigmented  and  covered  with  strong,  crisp  hairs  ;  and  an  inner,  which 
is  smooth  and  is  beset  with  large  sebaceous  follicles  and  is  continuous  with  the 
genito-urinary  mucous  tract ;  between  the  two  there  is  a  considerable  quantity  of 
areolar  tissue,  fat,  and  a  tissue  resembling  the  dartos  of  the  scrotum,  besides  vessels, 
nerves,  and  glands.  The  labia  are  thicker  in  front,  where  they  form  by  their 
meeting  the  anterior  commissure.  Posteriorly  they  are  not  really  joined,  but  appear 
to  become  lost  in  the  neighboring  integument,  terminating  close  to,  and  nearly 
parallel  with,  each  other.  Together  with  the  connecting  skin  between  them,  they 
form  the  posterior  commissure  or  posterior  boundary  of  the  vulval  orifice.     The 


,,,*/ 


cut 


Deep  transv^perinsei.  Unstriped  muscular 

PHi§lyi-='  fibre. 


^Vagina. 


Fig.  570.— Vertical  median  section  of  the  female  pel  ii. 


interval  between  the  posterior  commissure  and  the  anus,  abou?:  inch  to  an  inch 
and  a  quarter  in  length,  constitutes  the  perinoeum.          »  '(?/'< :  |  is  the  anterior 

edge  of  the  perineum,  and  between  it  and  the  hymen  is  a  < -p  ,--ion.  the  fossa 
navicularis.     The  labia  correspond  to  the  scrotum  in  the  inal  - 

The  Labia  Minora,  or  Nymphae,  are  two  small  cutaneous  fol  _  sii  xted  within  the 
labia  majora,  and  extending  from  the  clitoris  obliquely  downward  )ut  ward,  and  back- 
ward for  about  an  inch  and  a  half  on  each  side  of  the  orifice  ot  ;e  vagina,  between 
which  and  the  labia  majora  they  are  lost.  Anteriorly,  the  two  h  ia  minora  meet 
and  form  the  frcenum  of  the  clitoris.     The  prepuce  of  the  clito  ng  backward 

on  each  side,  is  inserted,  as  it  were,  into  the  labium  minora,  but  is  not^  actually  a 
part  of  them.  The  nymphae  are  really  modified  skin.  Their  internal  surfaces  have 
numerous  sebaceous  follicles. 

The  Clitoris  is  an  erectile  structure  analogous  to  the  corpora  cavernosa^  >f  the 
penis.  It  is  situated  beneath  the  anterior  commissure,  partialy  hidden  betwB  'he 
anterior  extremities  of  the  labia  minora.      It  is  connected  to  he  rami  of  the  ;s 


THE   INTERNAL    ORGANS.  1027 

and  ischium  on  each  side  by  a  crus  ;  the  body  is  short  and  concealed  beneath  the 
labia ;  the  free  extremity,  or  g 'Jans  clitoridis,  is  a  small  rounded  tubercle,  consisting 
of  spongy  erectile  tissue,  and  highly  sensitive.  It  is  provided,  like  the  penis,  "with 
a  suspensory  ligament,  and  with  two  small  muscles,  the  Erectores  clitoridis,  Avhich 
are  inserted  into  the  crura  of  the  clitoris.  The  clitoris  consists  of  two  corpora 
cavernosa,  composed  of  erectile  tissue  enclosed  in  a  dense  layer  of  fibrous 
membrane,  united  together  along  their  inner  surfaces  by  an  inconijilete  fibrous 
pectiniform  septum. 

Between  the  clitoris  and  the  entrance  of  the  vagina  is  a  triangular  smooth 
surface,  bounded  on  each  side  by  the  nymphas ;  this  is  the  vestibule. 

The  orifice  of  the  urethra  (meatus  urinarius)  is  situated  at  the  back  part  of  the 
vestibule,  about  an  inch  below  the  clitoris  and  near  the  margin  of  the  vagina, 
surrounded  by  a  prominent  elevation  of  the  mucous  membrane.  Below  the  meatus 
urinarius  is  the  orifice  of  the  vagina,  more  or  less  closed  in  the  virgin  by  a  mem- 
branous fold,  the  hymen. 

The  Hymen  varies  much  in  shape.  Its  commonest  form  is  that  of  a  ring, 
generally  broadest  posteriorly :  sometimes  it  is  represented  by  a  semilunar  fold, 
with  its  concave  margin  turned  toward  the  pubes.  A  complete  septum  stretched 
across  the  lower  part  of  the  vaginal  orifice  is  called  ''imperforate  hymen." 
Occasionally  it  is  cribriform,  or  its  free  margin  forms  a  membranous  fringe,  or  it 
may  be  entirely  absent.  It  may  persist  after  copulation,  so  that  it  cannot  be 
considered  as  a  test  of  virginity.  After  parturition  the  small  rounded  elevations 
known  as  the  carunculce  myrtiformes  are  found  as  the  remains  of  the  hymen. 

Glands  of  Bartholin. — On  each  side  of  the  commencement  of  the  vagina,  and 
behind  the  hymen,  is  a  round  or  oblong  body,  of  a  reddish-yellow  color,  and  of 
the  size  of  a  horse-bean,  analogous  to  Cowper's  gland  in  the  male.  It  is  called 
the  gland  of  Bartholin.  Each  gland  opens  by  means  of  a  long  single  duct 
immediately  external  to  the  hymen,  in  the  angle  or  groove  between  it  and  the 
nympha. 

Bulbi  Vestibuli. — Extending  from  the  clitoris,  along  either  side  of  the  vestibule, 
and  lying  a  little  behind  the  nymphae,  are  two  large  oblong  masses,  about  an  inch 
in  length,  consisting  of  a  plexus  of  veins  enclosed  in  a  thin  layer  of  fibrous 
membrane.  These  bodies  are  narrow  in  front,  rounded  below,  and  are  connected 
with  the  crura  of  the  clitoris  and  rami  of  the  pubes  :  they  are  termed  by  Kobelt  the 
bulbi  vestibuli,  and  he  considers  them  analogous  to  the  bulb  of  the  corpus 
spongiosum  in  the  male.  Immediately  in  front  of  these  bodies  is  a  smaller  venous 
plexus,  continuous  with  the  bulbi  vestibuli  behind  and  the  glans  clitoridis  in  front : 
it  is  called  by  Kobelt  the  pars  intermedia,  and  is  considered  by  him  as  analogous 
to  that  part  of  the  body  of  the  corpus  spongiosum  which  immediately  succeeds 
the  bulb. 

INTERNAL   ORGANS. 

The  Internal  Organs  of  Generation  are — the  vagina,  the  uterus  and  its  append- 
ages, the  Fallopian  tubes,  the  ovaries  and  their  ligaments. 

The  Vagina  extends  from  the  vulva  to  the  uterus.  It  is  situated  in  the  cavity 
of  the  pelvis,  behind  the  bladder  and  in  front  of  the  rectum.  Its  direction  is 
curved  upward  and  backward,  at  first  in  the  line  of  the  outlet,  and  afterward  in 
that  of  the  axis  of  the  cavity  of  the  pelvis.  Its  walls  are  ordinarily  in  contact, 
and  its  usual  shape  on  transverse  section  is  that  of  an  H,  the  transverse  limb 
being  slightly  curved  forward  or  backward,  whilst  the  lateral  limbs  are  somewhat 
convex  toward  the  median  line.  Its  length  is  about  two  and  a  half  inches  along 
its  anterior  wall,  and  three  and  a  half  inches  along  its  posterior  wall.  It  is  con- 
stricted at  its  commencement,  and  becomes  dilated  medially,  and  narrowed  near  its 
uterine  extremity ;  it  surrounds  the  vaginal  portion  of  the  cervix  uteri,  a  short 
distance  from  the  os,  its  attachment  extending  higher  up  on  the  posterior  than  on 
the  anterior  wall  of  the  uterus. 


1028  THE   FEMALE    ORGANS    OF    GENERATION. 

Relations. — Its  anterior  surface  is  in  relation  with  the  base  of  the  bladder  and 
with  the  urethra.  Its  posterior  surface  is  connected  for  the  lower  three-fourths  of 
its  extent  to  the  anterior  wall  of  the  rectum,  the  upper  fourth  being  separated  from 
that  tube  by  the  recto- vaginal  pouch  of  peritoneum,  or  pouch  of  Douglas,  between 
the  vagina  and  rectum.      Its  sides  are  enclosed  between  the  Levatores  ani  muscles. 

Structure. — The  vagina  consists  of  an  internal  mucous  lining,  of  a  muscular 
coat,  and  between  the  two  of  a  layer  of  erectile  tissue. 

The  mucous  membrane  is  continuous  above  with  that  lining  the  uterus.  Its 
inner  surface  presents,  along  the  anterior  and  posterior  walls,  a  longitudinal  ridge 
or  raphe,  called  the  columns  of  the  vagina,  and  numerous  transverse  ridges  or 
rugae,  extending  outward  from  the  raphe*  on  either  side.  These  rugae  are  divided 
by  furrows  of  variable  depth,  giving  to  the  mucous  membrane  the  appearance,  of 
being  studded  over  with  conical  projections  or  papillae;  they  are  most  numerous 
near  the  orifice  of  the  vagina,  especially  in  females  before  parturition.  The  epi- 
thelium covering  the  mucous  membrane  is  of  the  squamous  variety.  The  sub- 
mucous tissue  is  very  loose  and  contains  numerous  large  veins,  which  by  their 
anastomoses  form  a  plexus,  together  with  smooth  muscular  fibres  from  the  muscular 
coat ;  it  is  regarded  by  Gussenbauer  as  an  erectile  tissue.  It  contains  a  number 
of  mucous  crypts,  but  no  true  glands. 

The  muscular  coat  consists  of  two  layers :  an  external  longitudinal,  which  is 
far  the  stronger,  and  an  internal  circular  layer.  The  longitudinal  fibres  are 
continuous  with  the  superficial  muscular  fibres  of  the  uterus.  The  strongest 
fasciculi  are  those  attached  to  the  recto-vesical  fascia  on  each  side.  The  two  layers 
are  not  distinctly  separable  from  each  other,  but  are  connected  by  oblique  decus- 
sating fasciculi  which  pass  from  the  one  layer  to  the  other.  In  addition  to  this 
the  vagina  at  its  lower  end  is  surrounded  by  a  band  of  striped  muscular  fibres,  the 
sphincter  vagince  (see  page  375). 

External  to  the  muscular  coat  is  a  layer  of  connective  tissue  containing  a 
large  plexus  of  blood-vessels. 

The  erectile  tissue  'consists  of  a  layer  of  loose  connective  tissue  situated  between 
the  mucous  membrane  and  the  muscular  coat;  imbedded  in  it  is  a  plexus  of  large 
veins,  and  numerous  bundles  of  unstriped  muscular  fibres  derived  from  the  circular 
muscular  layer.  The  arrangement  of  the  veins  is  similar  to  that  found  in  other 
erectile  tissues. 

THE  UTERUS. 

The  Uterus  is  the  organ  of  gestation,  receiving  the  fecundated  ovum  in  its  cavity, 
retaining  and  supporting  it  during  the  development  of  the  foetus,  and  becoming 
the  principal  agent  in  its  expulsion  at  the  time  of  parturition. 

In  the  virgin  state  it  is  pear-shaped,  flattened  from  before  backward,  and 
situated  in  the  cavity  of  the  pelvis  between  the  bladder  and  the  rectum  ;  it  is 
retained  in  its  position  by  the  round  and  broad  ligaments  on  each  side,  and  projects 
into  the  upper  end  of  the  vagina  below.  Its  upper  end,  or  base,  is  directed 
upward  and  forward ;  its  lower  end,  or  apex,  downward  and  backward,  in  the 
line  of  the  axis  of  the  inlet  of  the  pelvis.  It  therefore  forms  an  angle  with  the 
vagina,  since  the  direction  of  the  vagina  corresponds  to  the  axis  of  the  cavity  and 
outlet  of  the  pelvis.  The  uterus  measures  about  three  inches  in  length,  two  in 
breadth  at  its  upper  part,  and  nearly  an  inch  in  thickness,  and  it  weighs  from  an 
ounce  to  an  ounce  and  a  half. 

It  consists  of  two  parts  :  (1)  the  body,  with  its  upper  broad  extremity,  the 
fundus ;  and  (2)  the- cervix,  or  neck,  which  is  partly  above  the  vagina  and  partly 
in  the  vagina.  The  fundus  is  placed  on  a  line  below  the  level  of  the  brim  of  the 
pelvis,  and  its  direction  varies  with  the  condition  of  the  bladder. 

The  division  between  the  body  and  cervix  is  indicated  externally  by  a  slight 
constriction,  and  by  the  reflection  of  the  peritoneum  from  the  anterior  surface  of 
the  uterus  on  to  the  bladder,  and  internally  by  a  narrowing  of  the  canal,  called 
the  internal  os. 


THE    UTERUS. 


1029 


The  body  gradually  narrows  from  the  fundus  to  the  neck.  Its  anterior  surface 
is  flattened,  covered  by  peritoneum,  which  becomes  separated  from  it  at  its  union 
with  the  cervix,  in  order  to  form  the  utero-vesical  pouch,  which  lies  between  the 
uterus  and  bladder.  Its  posterior  surface  is  convex  transversely,  covered  by 
peritoneum  throughout,  and  separated  from  the  rectum  by  some  convolutions  of 
the  intestine.  Its  lateral  margins  are  concave,  and  give  attachment  to  the  Fal- 
lopian tube  above,  the^round  ligament  below  and  in  front  of  this,  and  the  ligament 
of  the  ovary  behind  both  of  these  structures. 

The  cervix  is  the  lower  constricted  segment  of  the  uterus ;  around  its  circum- 
ference is  attached  the  upper  end  of  the  vagina,  which  extends  upward  a  greater 
distance  behind  than  in  front. 

The  supravaginal  portion  is  not  covered  by  peritoneum  in  front ;  a  pad  of 
cellular  tissue  is1  interposed  between  it  and  the  bladder.  Behind,  the  peritoneum  is 
extended  over  it.      The  vaginal  portion  is  the  rounded  lower  end  projecting  into 


ROUND 
'LIGAMENT. 


nal  iliac 
tery. 


artery. 

Fig.  571.  -Douglas's  pouch.    (From  a  preparation  in  the  Museum  of  the   Royal  College  of  Surgeons  of 
England.) 

the  vagina.  On  its  surface  is  a  small  aperture,  the  os  uteri,  generally  circular  in 
shape,  but  sometimes  oval  or  almost  linear.  The  margin  of  the  opening  is,  in  the 
absence  of  past  parturition  or  disease,  quite  smooth. 

Ligaments. — The  ligaments  of  the  uterus  are  eight  in  number:  one  anterior; 
one  posterior ;  two  lateral  or  broad  ;  two  sacro-uterine. — all  these  being  formed  of 
peritoneum — and,  lastly,  two  round  ligaments. 

The  anterior  ligament  (vesico-uterine)  is  reflected  on  to  the  bladder  from  the 
front  of  the  uterus,  at  the  junction  of  the  cervix -and  body. 

The  posterior  ligament  (recto-uterine)  passes  from  the  posterior  wall  of  the 
uterus  over  the  upper  fourth  of  the  vagina,  and  thence  on  to  the  rectum  and  sacrum. 
It  thus  forms  a  pouch  called  Douglas's  pouch  (Fig.  571),  the  boundaries  of  which  are, 


1030 


THE   FEMALE    ORGANS    OF    GENERATION. 


in  front,  the  posterior  wall  of  the  uterus,  the  supravaginal  cervix,  and  the  upper 
fourth  of  the  vagina;  behind,  the  rectum  and  sacrum  ;  above,  the  small  intestine; 
and,  laterally,  the  sacro-uterine  ligaments. 

The  two  lateral  or  broad  ligaments  pass  from  the  sides  of  the  uterus  to  the 
lateral  walls  of  the  pelvis,  forming  a  septum  across  the  pelvis,  which  divides  that 
cavity  into  two  portions.  In  the  anterior  part  are  contained  the  bladder,  urethra, 
and  vagina ;  in  the  posterior  part,  the  rectum.  Between  the  two  layers  of  each 
broad  ligament  are  contained — (1)  the  Fallopian  tubes  superiorly  ;  (2)  the  round 
ligament;    (3)  the  ovary  and    its   ligament;    (4)  the  parovarium,  or  organ   of 


Fig.  572.— Side  view  of  the  female  pelvic  organs. 
of  Surgeons  of  England.) 


(From  a  preparation  in  the  Museum  of  the  Royal  College 


Rosenmiiller  ;  (5)  connective  tissue  ;  (6)  unstriped  muscular  fibre  ;  and  (7)  blood- 
vessels and  nerves.  The  Fallopian  tube  is  contained  in  a  special  fold  of  the  broad 
ligament,  which  is  attached  to  the  part  of  the  ligament  near  the  ovary,  and  is 
known  by  the  name  of  the  mesosalpinx.  Between  the  fimbriated  extremity  of  the 
tube  and  the  lower  attachment  of  the  broad  ligament  is  a  concave  rounded  margin, 
called  the  infundibulo-pelvic  ligament  (Fig.  574). 

The  sacro-uterine  ligaments  pass  from  the  second  and  third  bones  of  the 
sacrum,  downward  and  forward  on  the  lateral  aspects  of  the  rectum  to  be  attached 
one  on  each  side  of  the  uterus  at  the  jui  on  of  the  supravaginal  cervix  and  the 
body,  this  point  corresponding  internally  to  the  position  of  the  os  internum. 

The  round  ligament  will  be  described  in  '"he  sequel. 

The  cavity  of  the  uterus  is  small   in  comparison  with  the  size  of  the  organ; 


THE    UTERUS.  1031 

that  portion  of  the  cavity  which  corresponds  to  the  body  is  triangular,  flattened 
from  before  backward,  so  that  its  walls  are  closely  approximated,  and  having  its 
base  directed  upward  toward  the  fundus.  At  each  superior  angle  is  a  funnel- 
shaped  cavity,  which  constitutes  the  remains  of  the  division  of  the  body  of  the 
uterus  into  two  cornua,  and  at  the  bottom  of  each  cavity  is  the  minute  orifice  of 
the  Fallopian  tube.  At  the  inferior  angle  of  the  uterine  cavity  is  a  small  con- 
stricted opening,  the  internal  orifice  (ostium  internum),  which  leads  into  the  cavity 
of  the  cervix. 

The  cavity  of  the  cervix  is  somewhat  fusiform,  flattened  from  before  backward, 
broader  at  the  middle  than  at  either  extremity,  and  communicates  below  with  the 
vagina.  The  wall  of  the  canal  presents,  anteriorly  and  posteriorly,  a  longitudinal 
column,  from  which  proceed  a  number  of  small  oblique  columns,  giving  the  appear- 
ance of  branches  from  the  stem  of  a  tree ;  and  hence  the  name  arbor  vitce  uterina 
applied  to  it.     These  folds  usually  become  very  indistinct  after  the  first  labor. 

Structure. — The  uterus  is  composed  of  three  coats :  an  external  serous  coat,  a 
middle  or  muscular,  and  an  internal  mucous  coat. 

The  serous  coat  is  derived  from  the  peritoneum  ;  it  invests  the  fundus  and  the 
whole  of  the  posterior  surface  of  the  uterus  ;  but  covers  the  anterior  surface  only 
as  far  as  the  junction  of  the  body  and  cervix.  In  the  lower  fourth  of  the  posterior 
surface  the  peritoneum,  though  covering  the  uterus,  is  not  closely  connected  with 
it,  being  separated  from  it  by  a  layer  of  loose  cellular  tissue  and  some  large 
veins. 

The  muscular  coat  forms  the  chief  bulk  of  the  substance  of  the  uterus.  In 
the  unimpregnated  state  it  is  dense,  firm,  of  a  grayish  color,  and  cuts  almost  like 
cartilage.  It  is  thick  opposite  the  middle  of  the  body  and  fundus,  and  thin  at 
the  orifices  of  the  Fallopian  tubes.  It  consists  of  bundles  of  unstriped  muscular 
fibres,  disposed  in  layers,  intermixed  with  areolar  tissue,  blood-vessels,  lymphatic 
vessels,  and  nerves.  In  the  impregnated  state  the  muscular  tissue  becomes  more 
prominently  developed,  and  is  disposed  in  three  layers — external,  middle,  and 
internal. 

The  external  layer  is  placed  beneath  the  peritoneum,  disposed  as  a  thin  plane 
on  the  anterior  and  posterior  surfaces.  It  consists  of  fibres  which  pass  trans- 
versely across  the  fundus,  and,  converging  at  each  superior  angle  of  the  uterus, 
are  continued  on  the  Fallopian  tube,  the  round  ligament,  the  ligament  of  the 
ovary :  some  passing  at  each  side  into  the  broad  ligament,  and  others  running 
backward  from  the  cervix  into  the  sacro-uterine  ligaments. 

The  middle  layer  of  fibres,  which  is  thickest,  presents  no  regularity  in  its 
arrangement,  being  disposed  longitudinally,  obliquely,  and  transversely.  It  con- 
tains most  blood-vessels. 

The  internal  or  deep  layer  consists  of  circular  fibres  arranged  in  the  form  of 
two  hollow  cones,  the  apices  of  which  surround  the  orifices  of  the  Fallopian  tubes, 
their  bases  intermingling  with  one  another  on  the  middle  of  the  body  of  the  uterus. 
At  the  internal  os  these  circular  fibres  form  a  distinct  sphincter. 

The  mucous  membrane  is  thin,  smooth,  and  closely  adherent  to  the  subjacent 
tissue.  It  is  continuous,  through  the  fimbriated  extremity  of  the  Fallopian  tubes, 
with  the  peritoneum,  and  through  the   os  uteri  with  the  lining  of  the  vagina. 

In  the  body  of  the  uterus  it  is  smooth,  soft,  of  a  pale  red  color  lined  by  colum- 
nar ciliated  epithelium,  and  presents,  when  viewed  with  a  lens,  the  orifices  of 
numerous  tubular  follicles  arranged  perpendicularly  to  the  surface.  It  is  unpro- 
vided with,  any  submucosa,  but  is  intimately  connected  with  the  innermost  layer 
of  the  muscular  coat,  which  is  regarded  as  the  muscularis  mucosae.  In  structure 
its  corium  differs  from  ordinary  mucous  membrane,  consisting  of  an  embryonic 
nucleated  and  highly  cellular  form  of  connective  tissue  in  which  run  numerous 
large  lymphatics.  In  it  are  the  tube-like  uterine  glands,  which  are  of  small  size 
in  the  unimpregnated  uterus,  but  shortly  after  impregnation  become  enlarged, 
elongated,  presenting  a  contorted  or  waved  appearance  toward  their  closed  extrem- 


1032 


THE  FEMALE    ORGANS    OF    GENERATION. 


ities,  which  reaches  into  the  muscularis,  and  may  be  single  or  bifid.  They  consist 
of  a  delicate  membrane,  lined  by  an  epithelium,  which  becomes  ciliated  toward 
the  orifices.  The  changes  which  take  place  in  the  mucous  membrane  of  the  im- 
pregnated uterus  are  more  fully  dealt  with  in  the  section  on  Embryology. 

In  the  cervix  the  mucous  membrane  is  sharply  differentiated  from  that  of  the 
uterine  cavity.  It  is  thrown  into  numerous  oblique  ridges,  which  diverge  from  an 
anterior  and  posterior  longitudinal  raphe",  presenting  an  appearance  which  has 
received  the  name  of  arbor  vitce.  In  the  upper  two-thirds  of  the  canal  the  mucous 
membrane  is  provided  with  numerous  deep  glandular  follicles,  which  secrete  a  clear 
viscid  alkaline  mucus  ;  and  in  addition,  extending  through  the  whole  length  of  the 
canal,  are  a  variable  number  of  little  cysts,  presumably  follicles,  which  have  be- 
come occluded  and  distended  with  retained  secretion.  They  are  called  the  ovula 
Nabothi.      The  mucous  membrane  covering  the  lower  half  of  the  cervical  canal 


Branches  to  tube. 


Branches  to  fundus. 


Vaginal  arteries. 
Pig.  573.— The  arteries  of  the  internal  organs  of  generation  of  the  female,  seen  from  behind.    (After  Hyrtl.) 


presents  numerous  papillae.  The  epithelium  of  the  upper  two-thirds  is  cylindrical 
and  ciliated,  but  below  this  it  loses  its  cilia,  and  gradually  changes  to  squamous 
epithelium  close  to  the  external  os. 

Vessels  and  Nerves. — The  arteries  of  the  uterus  are  the  uterine,  from  the  internal 
iliac,  and  the  ovarian,  from  the  aorta.  They  are  remarkable  for  their  tortuous 
course  in  the  substance  of  the  organ  and  for  their  frequent  anastomoses.  The 
termination  of  the  ovarian  artery  meets  the  termination  of  the  uterine  artery,  and 
forms  an  anastomotic  trunk  from  which  branches  are  given  off  to  supply  the  uterus, 
their  disposition  being,  as  shown  by  Sir  John  Williams,  circular.  The  veins  are  of 
large  size,  and  correspond  with  the  arteries.  In  the  impregnated  uterus  these  ves- 
sels form  the.  uterine  sinuses,  consisting  of  the  lining  membrane  of  the  veins  ad- 
hering to  the  walls  of  the  canal  channelled  through  the  substance  of  the  uterus. 
They  terminate  in  the  uterine  plexuses.  The  lymphatics  of  the  body  terminate  in 
the  lumbar  glands,  those  of  the  cervix  in  the  pelvic  glands.  The  nerves  are 
derived  from  the  inferior  hypogastric  and  ovarian  plexuses,  and  from  the  third  and 
fourth  sacral  nerves. 


THE    UTERUS.  1033 

The  form,  size,  and  situation  of  the  uterus  vary  at  different  periods  of  life  and  under  dif- 
ferent circumstances. 

In  the  foetus  the  uterus  is  contained  in  the  abdominal  cavity,  projecting  beyond  the  brim  of 
the  pelvis.     The  cervix  is  considerably  larger  than  the  body. 

At  puberty  the  uterus  is  pyriform  in  shape,  and  weighs  from  eight  to  ten  drachms.  It  has 
descended  into  the  pelvis,  the  fundus  being  just  below  the  level  of  the  brim  of  this  cavity.  The 
arbor  vitae  is  distinct,  and  extends  to  the  upper  part  of  the  cavity  of  the  organ. 

The  position  of  the  uterus  in  the  adult  is  liable  to  considerable  variation,  'depending  chiefly 
on  the  condition  of  the  bladder  and  rectum.  When  the  bladder  is  empty  the  entire  uterus  is 
directed  forward,  and  is  at  the  same  time  bent  on  itself  at  the  junction  of  the  body  and  cervix, 
so  that  the  body  lies  upon  the  bladder.  As  the  latter  fills  the  uterus  gradually  becomes  more 
and  more  erect,  until  with  a  fully  distended  bladder  the  fundus  may  be  directed  backward  toward 
the  sacrum. 

During  menstruation  the  organ  is  enlarged  and  more  vascular,  its  surfaces  rounder;  the 
os  externum  is  rounded,  its  labia  swollen,  and  the  lining  membrane  of  the  body  thickened,  softer, 
and  of  a  darker  color.  According  to  Sir  J.  Williams,  at  each  recurrence  of  menstruation  a 
molecular  disintegration  of  the  mucous  membrane  takes  place,  which  leads  to  its  complete 
removal,  only  the  bases  of  the  glands  imbedded  in  the  muscle  being  left.  At  the  cessation 
of  menstruation  by  a  proliferation  of  the  remaining  structures  a  fresh  mucous  membrane  is 
formed. 

During  pregnancy  the  uterus  becomes  enormously  enlarged,  and  in  the  ninth  month  reaches 
the  epigastric  region.  The  increase  in  size  is  partly  due  to  growth  of  pre-existing  muscle  and 
partly  to  development  of  new  fibres. 

After  parturition  the  uterus  nearly  regains  its  usual  size,  weighing  about  an  ounce  and  a 
half;  but  its  cavity  is  larger  than  in  the  virgin  state,  the  external  orifice  is  more  marked,  its 
edges  present  a  fissured  surface,  its  vessels  are  tortuous,  and  its  muscular  layers  are  more 
defined. 

In  old  age  the  uterus  becomes  atrophied,  and  paler  and  denser  in  texture :  a  more  distinct 
constriction  separates  the  body  and  cervix.  The  ostium  internum  and,  occasionally,  the  vaginal 
orifice  often  become  obliterated,  and  its  labia  almost  entirely  disappear. 

Surgical  Anatomy. — The  uterus  may  require  removal  in  cases  of  malignant  disease  or  for 
fibroid  tumors.  Carcinoma  is  the  most  common  form  of  malignant  disease  of  the  uterus, 
though  cases  of  sarcoma  do  occur.  It  may  show  itself  either  as  a  columnar  carcinoma  or  as 
a  squamous  carcinoma ;  the  former  commencing  either  in  the  cervix  or  body  of  the  uterus, 
the  latter  always  commencing  in  the  epithelial  cells  of  the  mucous  covering  of  the  vaginal 
surface  of  the  cervix.  The  columnar  form  may  be  treated  in  the  early  stage,  before  fixation 
has  taken  place,  by  removal  of  the  uterus,  either  through  the  vagina  or  by  means  of  abdom- 
inal section.  The  former  operation  is  the  better  of  the  two,  and  is  attended  by  a  much 
smaller  death-rate.  Vaginal  hysterectomy  is  performed  by  placing  the  patient  in  the  lithotomy 
position  and  introducing  a  large  duckbill  speculum.  The  cervix  is  then  seized  with  a  volsel- 
lum  and  pulled  down  as  far  as  possible  and  the  mucous  membrane  of  the  vagina  incised 
around  the  cervix  and  as  near  to  it  as  the  disease  will  allow,  especially  in  front,  where  the 
ureters  are  in  danger  of  being  wounded.  _  A  pair  of  dressing  forceps  are  then  pushed  through 
into  Douglas's  pouch  and  opened  sufficiently  to  allow  of  the  introduction  of  the  two  fore- 
fingers, by  means  of  which  the  opening  is  dilated  laterally  as  far  as  the  sacro-uterine  ligaments. 
A  somewhat  similar  proceeding  is  adopted  in  front,  but  here  the  bladder  has  to  be  separated 
from  the  anterior  wall  of  the  uterus  for  about  an  inch  before  the  vesico-uterine  fold  of 
peritoneum  can  be  reached.  This  is  done  by  carefully  burrowing  upward  with  a  director  and 
stripping  the  tissues  off  the  anterior  uterine  wall.  When  the  vesico-uterine  pouch  has  been 
opened  and  the  opening  dilated  laterally,  the  uterus  remains  attached  only  by  the  broad  liga- 
ments, in  which  are  contained  the  vessels  that  supply  the  uterus.  Before  division  of  the 
ligaments,  these  vessels  have  to  be  dealt  with.  The  forefinger  of  the  left  hand  is  introduced 
into  Douglas's  pouch  and  an  aneurism  needle,  armed  with  a  long  silk  ligature,  is  inserted 
into  the  vesico-uterine  pouch,  and  is  pushed  through  the  broad  ligament  about  an  inch  above 
its  lower  level  and  at  some  distance  from  the  uterus.  One  end  of  the  ligature  is  now  pulled 
through  the  anterior  opening,  and  in  this  way  we  have  the  lowest  inch  of  the  broad  ligament, 
in  which  is  contained  the  uterine  artery  (Fig.  573),  enclosed  in  a  ligature.  This  is  tied  tightly, 
and  the  operation  is  repeated  on  the  other  side.  The  broad  ligament  is  then  divided  on 
either  side,  between  the  ligature  and  the  uterus,  to  the  extent  to  which  it  has  been  con- 
stricted. By  traction  on  the  volsellum  which  grasps  the  cervix,  the  uterus  can  be  pulled 
considerably  further  down  in  the  vagina,  and  a  second  inch  of  the  broad  ligament  is  treated 
in  a  similar  way.  This  second  ligature  will  embrace  the  pampiniform  plexus  of  veins,  and, 
when  the  broad  ligament  has  been  divided  on  either  side,  it  will  be  found  that  a  third  liga- 
ture can  be  made  to  pass  over  the  Fallopian  tube  and  top  of  the  broad  ligament,  after  the 
uterus  has  been  dragged,  down  as  far  as  possible.  After  the  third  ligature  has  been  tied  and 
the  structures  between  it  and  the  uterus  divided,  this  organ  will  be  freed  from  all  its  connec- 
tions and  can  be  removed  from  the  vagina.  This  canal  is  then  sponged  out  and  lightly  dressed 
with  gauze  ;  no  sutures  being  used.  The  gauze  may  be  removed  at  the  end  of  the  second  day. 
In  squamous  epithelioma,  amputation  of  the  cervix  is  all  that  is  necessary  in  those  cases  where 
the  disease  is  recognized  beforeit  has  invaded  the  walls  of  the  vagina  or  the  neighboring  broad 
ligaments.     The  operation  consists  in  removing  a  wedge-shaped  piece  of  the  uterus,  including 


1034 


THE  FEMALE    ORGANS    OF    GENERATION. 


the  cervix,  through  the  vagina  and  attaching  the  cut  surfaces  of  the  stump  to  the  anterior  and 
posterior  vaginal  walls,  so  as  to  prevent  retraction.  In  the  treatment  of  uterine  fibroids  which 
require  operative  interference,  removal  of  the  whole  of  the  uterus  together  with  the  tumors 
through  an  abdominal  incision  gives  the  most  satisfactory  results ;  for,  if  the  tumor  is  large,  its 
size  acts  as  a  barrier  to  its  safe  delivery  through  the  pelvis  and  genital  passages.  _  After  the 
abdomen  has  been  opened  the  uterine  vessels  are  secured  and  the  broad  ligaments  divided  in  a 
similar  manner  to  that  employed  in  vaginal  hysterectomy,  except  that  the  proceeding  is  com- 
menced from  above.  When  the  twofirst  ligatures  have  been  tied,  and  the  broad  ligament 
divided,  it  will  be  found  that  the  uterus  can  be  raised  out  of  the  pelvis.  A  transverse  incision 
is  now  made  through  the  peritoneum,  where  it  is  reflected  from  the  anterior  surface  of  the 
uterus  on  to  the  back  of  the  bladder  and  the  serous  membrane  _  peeled  from  the  surface  of 
the  uterus  until  the  vagina  is  reached.  The  anterior  wall  of  this  canal  is  cut  across._  The 
uterus  is  now  turned  forward  and  the  peritoneum  at  the  bottom  of  Douglas's  pouch  incised 
transversely,  and  the  posterior  wall  of  the  vagina  cut  across  until  it  meets  the  incision  on  the 
anterior  wall.  The  uterus  is  now  almost  free,  and  is  held  only  by  the  lower  part  of  the  broad 
ligament  on  either  side,  containing  the  uterine  artery.  A  third  ligature  is  made  to  encircle  this, 
and,  after  having  been  tied,  the  structures  are  divided  between  the  ligature  and  the  uterus. 
The  organ  can  now  be  removed.  The  vagina  is  plugged  'with  gauze,  and  the  external  wound 
closed  in  the  usual  way.  The  vagina  acts  as  a  drain,  and  therefore  the  opening  into  it  is  not 
sutured. 

APPENDAGES  OF  THE  UTERUS. 

The  appendages  of  the  uterus  are  the  Fallopian  tubes,  the  ovaries  and  their 
ligaments,  and  the  round  ligaments.  They  are  placed  in  the  following  order :  in 
front  is  the  round  ligament ;  the  Fallopian  tube  occupies  the  upper  margin  of  the 
broad  ligament ;  the  ovary  and  its  ligament  are  behind  and  below  both. 

THE  FALLOPIAN  TUBES. 

The  Fallopian  Tubes,  or  Oviducts,  convey  the  ova  from  the  ovaries  to  the  cavity 
of  the  uterus.  They  are  two  in  number,  one  on  each  side,  situated  in  the  upper 
margin  of  the  broad  ligament,  extending  from  each  superior  angle  of  the  uterus  to 
the  sides  of  the  pelvis.  Each  tube  is  about  four  inches  in  length  ;  and  is  described 
as  consisting  of  three  portions  :  (1)  the  isthmus,  or  inner  constricted  third  ;  (2)  the 
ampulla,  or  outer  dilated    portion,  which    curves    over    the    ovary ;    and  (3)  the 


Fimbriated 


^        Pa  r  ovarium. 


**1 


■ 

■ 


UTERUS 


m*» 


Fimbria  ovarica. 

Fig.  574. — Uterine  appendages,  seen  from  behind.    (Henle.) 

infundibulum  with  its  ostium  abdominale,  surrounded  by  fimbriae,  one  of  which  is 
attached  to  the  ovary,  the  fimbria  ovarica.  The  general  direction  of  the  Fallopian 
tube  is  outward,  backward  and  doAvnward.  The  uterine  opening  is  minute,  and 
will  admit  only  a  fine  bristle ;  the  abdominal  opening  is  somewhat  larger.  In 
connection  with  the  fimbriae  of  the  Fallopian  tube  or  with  the  broad  ligament  close 


THE    OVARIES. 


1035 


to  them  there  is  frequently  one  or  more  small  vesicles  floating  on  a  long  stalk  of 
peritoneum.      These  are  termed  the  hydatids  of  Morgagni. 

Structure. — The  Fallopian  tube  consists  of  three  coats — serous,  muscular,  and 
mucous. 

The  external  or  serous  coat  is  peritoneal. 

The  middle  or  muscular  coat  consists  of  an  external  longitudinal  and  an  internal 
circular  layer  of  muscular  fibres  continuous  with  those  of  the  uterus. 

The  internal  or  mucous  coat  is  continuous  with  the  mucous  lining  of  the  uterus 
and,  at  the  free  extremity  of  the  tube,  with  the  peritoneum.  It  is  thrown  into 
longitudinal  folds,  which  in  the  outer,  larger  part  of  the  tube,  or  ampulla,  are  much 
more  extensive  than  in  the  narrow  canal  of  the  isthmus.  The  lining  epithelium 
is  columnar  ciliated.  This  form  of  epithelium  is  also  found  on  the  inner  surface 
of  the  fimbria?,  while  on  the  outer  or  serous  surfaces  of  these  processes  the 
epithelium  gradually  merges  into  the  endothelium  of  the  peritoneum. 


THE  OVARIES. 

The  ovaries  (testes  muliebres,  Galen)  are  analogous  to  the  testes  in  the  male. 
They  are  oval-shaped  bodies  of  an  elongated  form,  flattened  from  above  downward, 
situated  one  on  each  side  of  the  uterus,  in  the  posterior  layer  of  the  broad  liga- 
ment behind  and  below  the  Fallopian  tubes.  Each  ovary  is  connected  by  its 
anterior  straight  margin  to  the  broad  ligament ;  by  its  lower  extremity  to  the 
uterus  by  a  proper  ligament,  the  ligament  of  the  ovary ;  and  by  its  upper  end  to 
the  fimbriated  extremity  of  the  Fallopian  tube  by  the  ovarian  fimbria  ;  its  mesial 
and  lateral  surfaces  and  posterior  convex  border  are  free.  The  ovaries  are  of  a 
grayish-pink  color,  and  present  either  a  smooth  or  puckered,  uneven  surface.  They 
are  each  about  an  inch  and  a  half  in  length,  three-quarters  of  an  inch  in  width, 
and  about  a  third  of  an  inch  thick,  and  weigh  from  one  to  two  drachms. 


Fimbriated  extremity 
of  tube. 

!■»  Fallopian  tube 


\»v\ 


Broad  ligament,    / 
upper  part. 


Vagina,  anterior  wall. 


Fig.  575. — The  uterus  and  its  appendages.  Posterior  view.  The  parts  have  been  somewhat  displaced  from 
their  proper  position  in  the  preparation  of  the  specimen;  thus  the  right  ovary  has  been  raised  above  the 
Fallopian  tube,  and  the  fimbriated  extremities  of  the  tubes  have  been  turned  upward  and  outward.  (From  a 
preparation  in  the  Museum  of  the  Royal  College  of  Surgeons  of  England.) 

The  exact  position  of  the  ovary  has  been  the  subject  of  considerable  difference 
of  opinion,  and  writers  differ  much  as  to  what  is  to  be  regarded  as  the  normal  posi- 
tion. The  fact  appears  to  be  that  it  is  differently  placed  in  different  individuals. 
Hasse  has  described  it  as  being  situated  with  its  long  axis  transverse,  or  almost 
transverse,  to  the  pelvic  cavity.      Schultze,  on  the  other  hand,  believes  that  its 


1036  THE   FEMALE    ORGANS    OF    GENERATION. 

long  axis  is  anteroposterior.  Kolliker  asserts  that  the  truth  lies  between  these 
two  views,  and  that  the  ovary  is  placed  obliquely  in  the  pelvis,  its  long  axis  lying 
parallel  to  the  external  iliac  vessels,  with  its  surface  directed  inward  and  outward,  and 
its  convex  free  border  upward.  His  has  made  some  important  observations  on  this 
subject,  and  his  views  are  largely  accepted.  He  teaches  that  the  uterus  rarely  lies 
symmetrically  in  the  middle  of  the  pelvic  cavity,  but  is  generally  inclined  to  one 
or  other  side,  most  frequently  to  the  left,  in  the  proportion  of  three  to  two.  The 
position  of  the  two  ovaries  varies  according  to  the  inclination  of  the  uterus.  When 
the  uterus  is  inclined  to  the  left,  the  ovary  of  this  side  lies  with  its  long  axis 
vertical  and  with  one  side  closely  applied  to  the  outer  wall  of  the  pelvis,  while  the 
ovary  of  the  opposite  side,  being  dragged  upon  by  the  inclination  of  the  uterus, 
lies  obliquely,  its  outer  extremity  being  retained  in  close  apposition  to  the  side  of 
the  pelvis  by  the  infundibulo-pelvic  ligament  (page  1030).  When,  on  the  other 
hand,  the  uterus  is  inclined  to  the  right,  the  position  of  the  two  ovaries  is  exactly 
reversed,  the  right  being  vertical  and  the  left  oblique.  In  whichever  position  the 
ovary  is  placed,  the  Fallopian  tube  forms  a  loop  around  it,  the  uterine  half 
ascending  obliquely  over  it,  and  the  outer  half,  including  the  dilated  extremity, 
descending  and  bulging  freely  behind  it.  From  this  extremity  the  fimbriae  pass 
upward  on  to  the  ovary  and  closely  embrace  it. 

Waldever1  states,  as  the  result  of  the  examination  of  fifty  female  subjects, 
ranging  from  early  childhood  to  advanced  age,  that  the  ovary  "  lies  on  the  lateral 
pelvic  wall  and  vertically  when  the  woman  takes  the  erect  posture."  Its  tubal 
extremity  is  near  the  external  iliac  vein  ;  its  uterine  end  is  directed  downward, 
while  the  Fallopian  tube  overlies  it  so  as  to  cover  it  on  its  medial  face  entirely  or 
nearlv  so.  Its  convex  margin  looks  downward  and  backward  toward  the  pelvic 
cavity  and  rectum,  while  its  straight  margin  or  hilum  lies  laterally  on  the  pelvic 
wall  attached  to  the  mesosalpinx.  He  also  finds  that  it  lies  in  a  distinct  but 
shallow  groove  (fossa  ovarii)  limited  above  by  the  hypogastric  artery  and 
below  by  the  ureter,  in  such  a  manner  that  the  ureter  lies  along  the  convex 
margin  of  the  ovary,  and  the  hypogastric  artery  passes  near  the  hilum  or  straight 
margin. 

Structure. — The  ovary  consists  of  a  number  of  Graafian  vesicles  imbedded  in 
the  meshes  of  a  stroma  or  framework,  and  invested  by  a  serous  covering  derived 
from  the  peritoneum. 

Serous  Covering. — Though  the  investing  membrane  of  the  ovary  is  derived 
from  the  peritoneum,  it  differs  essentially  from  that  structure,  inasmuch  as  its 
epithelium  consists  of  a  single  layer  of  columnar  cells,  instead  of  the  flattened 
endothelial  cells  of  other  parts  of  the  membrane ;  this  has  been  termed  the  ger- 
minal epithelium  of  Waldeyer,  and  gives  to  the  surface  of  the  ovary  a  dull  gray 
aspect  instead  of  the  shining  smoothness  of  serous  membranes  generally. 

Stroma. — The  stroma  is  a  peculiar  soft  tissue,  abundantly  supplied  with  blood- 
vessels, consisting  for  the  most  part  of  spindle-shaped  cells,  with  a  small  amount 
of  ordinary  connective  tissue.  These  cells  have  been  regarded  by  some  anatomists 
as  unstriped  muscle-cells,  which,  indeed,  they  most  resemble  (His) ;  by  others  as 
connective-tissue  cells  (Waldeyer,  Henle,  and  Kolliker).  On  the  surface  of  the 
organ  this  tissue  is  much  condensed,  and  forms  a  layer  composed  of  short  connec- 
tive-tissue fibres,  with  fusiform  cells  between  them.  This  was  formerly  regarded 
as  a  distinct  fibrous  covering,  and  was  termed  the  tunica  albuginea,  but  is  nothing 
more  than  a  condensed  layer  of  the  stroma  of  the  ovary. 

Graafian  Vesicles. — Upon  making  a  section  of  an  ovary  numerous  round  trans- 
parent vesicles  of  various  sizes  are  to  be  seen  ;  they  are  the  Graafian  vesicles  or 
ovisacs  containing  the  ova.  Immediately  beneath  the  superficial  covering  is  a 
layer  of  stroma,  in  which  are  a  large  number  of  minute  vesicles  of  uniform  size, 
about  y^-jj  of  an  inch  in  diameter.  These  are  the  Graafian  vesicles  in  their  earliest 
condition,  and  the  layer  where  they  are  found  has  been  termed  the  cortical  layer. 
They  are  especially  numerous  in  the  ovary  of  the  young  child.     After  puberty 

1  Journal  of  Anatomy  and  Physiology,  vol.  xxxii. 


THE    OVARIES. 


1037 


and   during   the  whole  of  the   child-bearing 
mature,  Graafian  vesicles   are  also  found  in 


period  large  and  mature,  or  almost 
the  cortical  layer  in  small  numbers, 
and  also  "corpora  lutea,"  the  re- 
mains of  vesicles  which  have  burst 
and  are  undergoing  atrophy  and 
absorption.  Beneath  this  super- 
ficial stratum  other  large  and  more 
mature  Graafian  vesicles  are  found 
imbedded    in   the   ovarian    stroma. 


Granula    » 


Peritoneum 


Fig.  576.— Section  of  the  ovary.  (After  Schron.)  1. 
Outer  covering.  1'.  Attached  border.  2.  Central  stroma. 
3.  Peripheral  stroma.  4.  Blood-vessels.  5.  Graafian  fol- 
licles in  their  earliest  stage.  6,  7,  8.  More  advanced  folli- 
cles. 9.  An  almost  mature  follicle.  9'.  Follicle  from 
which  the  ovum  has  escaped.     10.  Corpus  luteum. 


y^  '■■      ]    1  Coats  of  the 

Stroma  of  the  ovary  \   Graafian  vesicle, 

withblood-vessels.    Membrana 
granulosa. 
Fig.  577.— Section  of  the  Graafian  ves- 
icle.   (After  Von  Baer.) 


These  increase  in  size  as  they  recede  from  the  surface  toward  a  highly  vascular 
stroma  in  the  centre  of  the  organ,  termed  the  medullary  substance  {zona  vasculosa, 
Waldeyer).  This  stroma  forms  the  tissue  of  the  hilum  by  which  the  ovary  is 
attached,  and  through  which  the  blood-vessels  enter ;  it  does  not  contain  any 
Graafian  vesicles. 

The  larger  Graafian  follicles  consist  of  an  external  fibro- vascular  coat  connected 
with  the  surrounding  stroma  of  the  ovary  by  a  network  of  blood-vessels ;  and  an 
internal  coat,  named  ovicapsule,  which  is  lined  by  a  layer  of  nucleated  cells,  called 
the  membrana  granulosa.  The  fluid  contained  in  the  interior  of  the  vesicles  is 
transparent  and  albuminous,  and  in  it  is  suspended  the  ovum.  In  that  part  of 
the  mature  Graafian  vesicle  which  is  nearest  the  surface  of  the  ovary  the  cells  of 
the  membrana  granulosa  are  collected  into  a  mass  which  projects  into  the  cavity 
of  the  vesicle.  This  is  termed  the  discus  proligerus,  and  in  this  the  ovum  is 
imbedded.1 

The  ova  are  formed  from  the  germinal  epithelium  on  the  surface  of  the  ovarv. 
This  becomes  thickened,  and  in  it  are  seen  some  cells  which  are  larger  and  more 
rounded  than  the  rest ;  these  are  termed  the  primordial  ova.  The  germinal 
epithelium  grows  downward  in  the  form  of  tubes  or  columns,  termed  the  egg  tubes 
of  Pfliiger,  into  the  ovarian  stroma,  which  grows  outward  between  the  tubes,  and 
ultimately  cuts  them  off  from  the  germinal  epithelium.  These  tubes  are  further 
subdivided  into  rounded  nests  or  groups,  each  containing  a  primordial  ovum  which 
undergoes  further  development  and  growth  while  the  surrounding  cells  of  the  nest 
form  the  epithelium  of  the  Graafian  follicle. 

The  development  and  maturation  of  the  Graafian  vesicles  and  ova  continue 
uninterruptedly  from  puberty  to  the  end  of  the  fruitful  period  of  woman's  life, 
while  their  formation  commences  before  birth.  Before  puberty  the  ovaries  are 
small,  the  Graafian  vessels  contained  in  them  are  disposed  in  a  comparatively  thick 
layer  in  the  cortical  substance  ;  here  they  present  the  appearance  of  a  large  number 
of  minute  closed  vesicles,  constituting  the  early  condition  of  the  Graafian  vesicle ; 
many,  however,  never  attain  full  development,  but  shrink  and  disappear.  At 
puberty  the  ovaries  enlarge,  and  become  more  vascular,  the  Graafian  vesicles  are 
developed  in  greater  abundance,  and  their  ova  are  capable  of  fecundation. 

Discharge  of  the  Ovum. — The  Graafian  vesicles,  after  gradually  approaching 
the  surface  of  the  ovary,  burst :   the  ovum  and  fluid  contents  of  the   vesicles  are 


1  For  a  description  of  the  ovum,  see  section  on  Embryology. 


1038  THE  FEMALE    ORGANS    OF    GENERATION. 

liberated,  and  escape  on  the  exterior  of  the  ovary,  passing  thence  into  the  Fallopian 
tube.1 

In  the  fcetus  the  ovaries  are  situated,  like  the  testes,  in  the  lumbar  region,  near 
the  kidneys.  They  may  be  distinguished  from  those  bodies  at  an  early  period  by 
their  elongated  and  flattened  form,  and  by  their  position,  which  is  at  first  oblique 
and  then  nearly  transverse.      They  gradually  descend  into  the  pelvis. 

Lying  above  the  ovary  in  the  broad  ligament  between  it  and  the  Fallopian 
tube  is  the  organ  of  Rosenmuller,  called  also  the  parovarium  or  epoophoron. 
This  is  the  remnant  of  a  foetal  structure,  the  development  of  which  is  described  in 
the  section  on  Embryology.  In  the  adult  it  consists  of  a  few  closed  convoluted 
tubes,  lined  with  epithelium,  which  converge  toward  the  ovary  at  one  end  and  at 
the  other  are  united  by  a  longitudinal  tube,  which  is  the  homologue  of  the  duct  of 
Gartner  in  the  cow.  This  duct  terminates  in  a  bulbous  enlargement.  The 
parovarium  is  connected  at  the  uterine  extremity  with  the  remains  of  the  Wolffian 
duct.  A  few  scattered  rudimentary  tubules,  best  seen  in  the  child,  are  situated  in 
the  broad  ligament  between  the  parovarium  and  the  uterus.  These  constitute  the 
paroophoron  of   Waldeyer. 

The  ligament  of  the  ovary  is  a  rounded  cord,  which  extends  from  each  superior 
angle  of  the  uterus  to  the  inner  extremity  of  the  ovary ;  it  consists  of  fibrous 
tissue  and  a  few  muscular  fibres  derived  from  the  uterus. 

The  Round  Ligaments  are  two  rounded  cords,  between  four  and  five  inches  in 
length,  situated  between  the  layers  of  the  broad  ligament  in  front  of  and  below  the 
Fallopian  tube.  Commencing  on  each  side  at  the  superior  angle  of  the  uterus,  this 
ligament  passes  forward,  upward,  and  outward  through  the  internal  abdominal 
ring,  along  the  inguinal  canal,  to  the  labia  majora,  in  which  it  becomes  lost.  The 
round  ligament  consists  principally  of  muscular  tissue  prolonged  from  the  uterus ; 
also  of  some  fibrous  and  areolar  tissue,  besides  blood-vessels  and  nerves,  enclosed 
in  a  duplicature  of  peritoneum,  wThich  in  the  foetus  is  prolonged  in  the  form  of  a 
tubular  process  for  a  short  distance  into  the  inguinal  canal.  This  process  is  called 
the  canal  of  Nuck.  It  is  generally  obliterated  in  the  adult,  but  sometimes  remains 
pervious  even  in  advanced  life.  It  is  analogous  to  the  peritoneal  pouch  which 
precedes  the  descent  of  the  testis. 

Vessels  and  Nerves. — The  arteries  of  the  ovaries  and  Fallopian  tubes  are  the 
ovarian  from  the  aorta.  They  enter  the  attached  border,  or  hilum,  of  the  ovary. 
The  veins  follow  the  course  of  the  arteries  ;  they  form  a  plexus  near  the  ovary,  the 
pampiniform  plexus.  The  nerves  are  derived  from  the  inferior  hypogastric  or 
pelvic  plexus,  and  from  the  ovarian  plexus,  the  Fallopian  tube  receiving  a  branch 
from  one  of  the  uterine  nerves. 


THE  MAMMARY  GLANDS. 

The  mammae,  or  breasts,  secrete  the  milk,  and  are  "  accessory  glands  of  the 
generative  system.  They  exist  in  the  male  as  well  as  in  the  female ;  but  in  the 
former  only  in  the  rudimentary  state,  unless  their  growth  is  excited  by  peculiar 
circumstances.  In  the  female  they  are  two  large  hemispherical  eminences  situated 
toward  the  lateral  aspect  of  the  pectoral  region,  corresponding  to  the  intervals 
between  the  third  and  sixth  or  seventh  ribs,  and  extending  from  the  side  of  the 
sternum  to  the  axilla.  Their  weight  and  dimensions  differ  at  different  periods 
of  life  and  in  different  individuals.  Before  puberty  they  are  of  small  size,  but 
enlarge  as  the  generative  organs  become  more  completely  developed.  They 
increase  during  pregnancy,  and  especially  after  delivery,  and  become  atrophied  in 
old  age.  The  left  mamma  is  generally  a  little  larger  than  the  right.  Their  base 
is  nearly  circular,  flattened  or  slightly  concave,  and  has  its  long  diameter  directed 
upward  and  outward   toward  the  axilla;    they  are    separated   from   the  Pectoral 

1  This  is  effected  either  by  application  of  the  tube  to  the  ovary,  or  by  a  curling  upward  of  the 
fimbriated  extremity,  so  that  the  ovum  is  caught  as  it  falls. 


THE   MAMMARY   GLANDS. 


1039 


muscles  by  a  layer  of  fascia.  The  outer  surface  of  the  mamma  is  convex,  and 
presents,  just  below  the  centre,  a  small  conical  prominence,  the  nipple  (mammilla). 
The  surface  of  the  nipple  is  dark-colored  and  surrounded  by  an  areola  having  a 
colored  tint.  In  the  virgin  the  areola  is  of  a  delicate  rosy  hue;  about  the  second 
month  after  impregnation  it  enlarges  and  acquires  a  darker  tinge,  which  increases 
as  pregnancy  advances,  becoming  in  some  cases  of  a  dark-brown  or  even  black 
color.  This  color  diminishes  as  soon  as  lactation  is  over,  but  is  never  entirely  lost 
throughout  life.  These  changes  in  the  color  of  the  areola  are  of  importance  in 
forming  a  conclusion  in  a  case  of  suspected  first  pregnancy. 


Fat 
Lobule  unravelled 


Lactiferous 
duct. 


Lobule 


Ampulla. 


Loculi  in  connective  tissue. 


Fig.  578.— Dissection  of  the  lower  half  of  the  female  breast  during  the  period  of  lactation.    (From  Luschka.) 

The  nipple  is  a  cylindrical  or  conical  eminence  capable  of  undergoing  a  sort 
of  erection  from  mechanical  excitement,  a  change  mainly  due  to  the  contraction 
of  its  muscular  fibres.  It  is  of  a  pink  or  brownish  hue,  its  surface  wrinkled  and 
provided  with  papillae,  and  it  is  perforated  by  numerous  orifices,  the  apertures  of 
the  lactiferous  ducts.  Near  the  base  of  the  nipple  and  upon  the  surface  of  the 
areoli  are  numerous  sebaceous  glands,  which  become  much  enlarged  during  lacta- 
tion, and  present  the  appearance  of  small  tubercles  beneath  the  skin.  These 
glands  secrete  a  peculiar  fatty  substance,  which  serves  as  a  protection  to  the  integu- 
ment of  the  nipple  during  the  act  of  sucking.  The  nipple  consists  of  numerous 
vessels,  intermixed  with  plain  muscular  fibres,  which  are  principally  arranged  in  a 
circular  manner  around  the  base,  some  few  fibres  radiating  from  base  to  apex. 

Structure. — The  mamma  consists  of  gland-tissue  ;  of  fibrous  tissue,  connecting  its 
lobes ;  and  of  fatty  tissue  in  the  intervals  between  the  lobes.  The  gland-tissue, 
when  freed  from  fibrous  tissue  and  fat,  is  of  a  pale  reddish  color,  firm  in  texture, 
circular  in  form,  flattened  from  before  backward,  thicker  in  the  centre  than  at  the 
circumference,  and  presenting  several  inequalities  on  its  surface,  especially  in  front. 
It  consists  of  numerous  lobes,  and  these  are  composed  of  lobules  connected  together 
by  areolar  tissue,  blood-vessels,  and  ducts.  The  smallest  lobules  consist  of  a  cluster 
of  rounded  alveoli,  which  open  into  the  smallest  branches  of  the  lactiferous  ducts  ; 
these  ducts,  uniting,  form  larger  ducts,  which  terminate  in  a  single  canal,  correspond- 
ing with  one  of  the  chief  subdivisions  of  the  gland.    The  number  of  excretory  ducts 


1040  THE   FEMALE    ORGANS    OF    GENERATION. 

varies  from  fifteen  to  twenty  :  they  are  termed  the  tubuli  lactiferi,  or  galactophori. 
They  converge  toward  the  areola,  beneath  which  they  form  dilatations,  or  ampullce, 
which  serve  as  reservoirs  for  the  milk,  and  at  the  base  of  the  nipple  become 
contracted  and  pursue  a  straight  course  to  its  summit,  perforating  it  by  separate 
orifices  considerably  narrower  than  the  ducts  themselves.  The  ducts  are  composed 
of  areolar  tissue,  with  longitudinal  and  transverse  elastic  fibres  ;  muscular  fibres  are 
entirelv  absent ;  their  mucous  lining  is  continuous,  at  the  point  of  the  nipple,  witli 
the  integument.  The  epithelium  of  the  mammary  gland  differs  according  to  the 
state  of  activity  of  the  organ.  In  the  gland  of  a  woman  who  is  not  pregnant  or 
suckling  the  alveoli  are  very  small  and  solid,  being  filled  with  a  mass  of  granular 
polyhedral  cells.  During  pregnancy  the  alveoli  enlarge  and  the  cells  undergo 
rapid  multiplication.  At  the  commencement  of  lactation  the  cells  in  the  centre 
of  the  alveolus  undergo  fatty  degeneration,  and  are  eliminated  in  the  first  milk 
as  colostrum-corpuscles.  The  peripheral  cells  of  the  alveolus  remain,  and  form 
a  single  layer  of  granular,  short  columnar  cells,  with  a  spherical  nucleus,  lining 
the  limiting  membrana  propria.  These  cells  during  the  state  of  activity  of  the  gland 
are  capable  of  forming,  in  their  interior,  oil-globules,  which  are  then  ejected  into 
the  lumen  of  the  alveolus  and  constitute  the  milk-globules. 

The  fibrous  tissue  invests  the  entire  surface  of  the  breast,  and  sends  down 
septa  between  its  lobes,  connecting  them  together. 

The  fatty  tissue  surrounds  the  surface  of  the  gland  and  occupies  the  interval 
between  its  lobes.  It  usually  exists  in  considerable  abundance,  and  determines 
the  form  and  size  of  the  gland.  There  is  no  fat  immediately  beneath  the  areola 
and  nipple. 

Vessels  and  Nerves, — The  arteries  supplying  the  mammae  are  derived  from  the 
thoracic  branches  of  the  axillary,  the  intercostals,  and  internal  mammary.  The 
veins  describe  an  anastomotic  circle  round  the  base  of  the  nipple,  called  by  Haller 
the  circulus  venosus.  From  this  large  branches  transmit  the  blood  to  the 
circumference  of  the  gland  and  end  in  the  axillary  and  internal  mammary  veins. 
The' lymphatics,  for  the  most  part,  run  along  the  lower  border  of  the  Pectoralis 
major  to  the  axillary  glands  ;  some  few,  from  the  inner  side  of  the  breast,  perforate 
the  intercostal  spaces  and  empty  themselves  into  the  anterior  mediastinal  glands. 
The  nerves  are  derived  from  the  anterior  and  lateral  cutaneous  nerves  of  the  thorax. 


THE  SURGICAL  ANATOMY  OF  HERNIA. 


Dissection  (Fig.  217). — For  dissection  of  the  parts  concerned  in  inguinal  hernia  a  male 
subject,  free  from  fat,  should  always  be  selected.  The  body  should  be  placed  in  the  supine  posi- 
tion, the  abdomen  and  pelvis  raised  by  means  of  blocks  placed  beneath  them,  and  the  lower 
extremities  rotated  outward,  so  as  to  make  the  parts  as  tense  as  possible.  If  the  abdominal  walls 
are  flaccid,  the  cavity  of  the  abdomen  should  be  inflated  through  an  aperture  made  at  the 
umbilicus.  An  incision  should  be  made  along  the  middle  line  from  a  little  below  the  umbilicus 
to  the  symphysis  pubis,  and  continued  along  the  front  of  the  scrotum,  and  a  second  incision  from 
the  anterior  superior  spine  of  the  ilium  to  just  below  the  umbilicus.  These  incisions  should 
divide  the  integument,  and  the  triangular-shaped  flap  included  between  them  should  be  reflected 
downward  and  outward,  when  the  superficial  fascia  will  be  exposed. 

The  Superficial  Fascia  of  the  Abdomen. — This,  over  the  greater  part  of  the 
abdominal  wall,  consists  of  a  single  layer  of  fascia,  which  contains  a  variable 
amount  of  fat ;  but  as  it  approaches  the  groin  it  is  easily  divisible  into  two  layers, 
between  which  are  found  the  superficial  vessels  and  nerves  and  the  superficial 
inguinal  lymphatic  glands. 

The  superficial  layer  {fascia  of  Camper),  is  thick,  areolar  in  texture,  contain- 
ing adipose  tissue  in  its  meshes,  the  quantity  of  which  varies  in  different  subjects. 
Below,  it  passes  over  Poupart's  ligament,  and  is  continuous  with  the  outer  layer  of 
the  superficial  fascia  of  the  thigh.  In  the  male  this  fascia  is  continued  over  the 
penis  and  over  the  outer  surface  of  the  cord  to  the  iscrotum,  where  it  helps  to  form 
the  dartos.  As  it  passes  to  the  penis  and  over  the  cord  to  the  scrotum  it  changes 
its  character,  becoming  thin,  destitute  of  adipose  tissue,  and  of  a  pale  reddish 
color;  and  in  the  scrotum  it  acquires  some  involuntary  muscular  fibres.  From  the 
scrotum  it  may  be  traced  backward,  to  be  continuous  with  the  superficial  fascia  of 
the  perinseuni.     In  the  female  this  fascia  is  continued  into  the  labia  majora. 

The  hypogastric  branch  of  the  ilio-hypogastric  nerve  perforates  the  aponeurosis 
of  the  External  oblique  muscle  about  an  inch  above  and  a  little  to  the  outer  side  of 
the  external  abdominal  ring,  and  is  distributed  to  the  integument  of  the  hypogastric 
region. 

The  ilio-inguinal  nerve  escapes  at  the  external  abdominal  ring,  and  is  distributed 
to  the  integument  of  the  upper  and  inner  part  of  the  thigh,  to  the  scrotum  in  the 
male  and  to  the  labium  in  the  female. 

The  superficial  epigastric  artery  arises  from  the  femoral  about  half  an  inch 
below  Poupart's  ligament,  and,  passing  through  the  saphenous  opening  in  the  fascia 
lata,  ascends  on  to  the  abdomen,  in  the  superficial  fascia  covering  the  External 
oblique  muscle,  nearly  as  high  as  the  umbilicus.  It  distributes  branches  to  the 
superficial  inguinal  lymphatic  glands,  the  superficial  fascia,  and  the  integument, 
anastomosing  with  branches  of  the  deep  epigastric  and  internal  mammary  arteries. 

The  superficial  circumflex  iliac  artery,  the  smallest  of  the  cutaneous  branches, 
arises  close  to  the  preceding,  and,  piercing  the  fascia  lata,  runs  outward,  parallel 
with  Poupart's  ligament,  as  far  as  the  crest  of  the  ilium,  dividing  into  branches 
which  supply  the  superficial  inguinal  lymphatic  glands,  the  superficial  fascia,  and 
the  integument,  anastomosing  with  the  deep  circumflex  iliac  and  with  the  gluteal 
and  external  circumflex  arteries. 

The  superficial  external  pudic  (superior)  artery  arises  from  the  inner  side  of 
the  femoral  artery  close  to  the  preceding  vessels,  and,  after  passing  through  the 
saphenous  opening,  courses  inward  across  the  spermatic  cord,  to  be  distributed  to 
the  integument  on  the  lower  part  of  the  abdomen,  the  penis  and  scrotum  in  the  male, 
and  the  labium  in  the  female,  anastomosing  with  branches  of  the  internal  pudic. 

The  Superficial  Veins. — The  veins  accompanying  these  superficial  vessels  are 

66  1041 


1042 


THE   SURGICAL    ANATOMY   OF  HERNIA. 


usually  much  larger  than  the  arteries ;  they  terminate  in  the  internal  saphenous 


vein. 


The  superficial  inguinal  lymphatic  glands  are  placed  immediately  beneath  the 
integument,  are  of  large  size,  and  vary  from  eight  to  ten  in  number.  They  are 
divisible  into  two  groups :  an  upper,  disposed  irregularly  along  Poupart's  liga- 
ment, which  receive  the  lymphatic  vessels  from  the  integument  of  the  scrotum, 
penis,  parietes  of  the  abdomen,  perineal  and  gluteal  regions,  and  the  mucous 
membrane  of  the  urethra ;  and  an  inferior  group,  which  surround  the  saphenous 
opening  in  the  fascia  lata,  a  few  being  sometimes  continued  along  the  saphenous 


Superficial 
circumflex 
iliac  vein. 


ipv 

External  abdominal 


Fig.  579.— Inguinal  hernia.    Superficial  dissection. 

vein  to  a  variable  extent.  This  latter  group  receive  the  superficial  lymphatic 
vessels  from  the  lower  extremity. 

The  deep  layer  of  the  superficial  fascia  (fascia  of  Scarpa)  is  thinner  and  more 
membranous  in  character  than  the  superficial  layer.  In  the  middle  line  it  is 
intimately  adherent  to  the  linea  alba ;  above,  it  is  continuous  with  the  superficial 
fascia  over  the  rest  of  the  trunk  ;  below,  it  blends  with  the  fascia  lata  of  the  thigh 
a  little  below  Poupart's  ligament ;  below  and  internally,  in  the  male,  it  is  continued 
over  the  penis  and  over  the  outer  surface  of  the  cord  to  the  scrotum,  where  it  helps 
to  form  the  dartos.  From  the  scrotum  it  may  be  traced  backward  to  be  continuous 
with  the  base  of  the  triangular  ligament  of  the  urethra.  In  the  female  it  is  con- 
tinuous with  the  labia  majora. 

The  scrotum  is  a  cutaneous  pouch  which  contains  the  testes  and  part  of  the 
spermatic  cords,  and  into  which  an  inguinal  hernia  frequentlv  descends  (see  page 
1014). 

The  Aponeurosis  of  the  External  Oblique  Muscle. — This  is  a  thin  but  strone 


THE  SUPERFICIAL   FASCIA.  1043 

membranous  aponeurosis,  the  fibres  of  which  are  directed  obliquely  downward 
and  inward.  That  portion  of  the  aponeurosis  which  extends  between  the  anterior 
superior  spine  of  the  ilium  and  the  spine  of  the  os  pubis  is  a  broad  band,  folded 
inward  and  continuous  below  with  the  fascia  lata ;  it  is  called  Poupart's  ligament. 
The  portion  which  is  reflected  from  Poupart's  ligament  at  the  spine  of  the  os  pubis, 
along  the  pectineal  line,  is  called  Grimbernaf  s  ligament.  From  the  point  of  attach- 
ment of  the  latter  to  the  pectineal  line  a  few  fibres  pass  upward  and  inward, 
behind  the  inner  pillar  of  the  ring,  to  the  linea  alba.  They  diverge  as  they  ascend, 
and  form  a  thin,  triangular,  fibrous  band,  which  is  called  the  triangular  fascia  of 
the  abdomen. 

The  External  or  Superficial  Abdominal  Ring. — Just  above  and  to  the  outer  side 
of  the  crest  of  the  os  pubis  an  interval  is  seen  in  the  aponeurosis  of  the  External 
oblique,  called  the  external  abdominal  ring.  This  aperture  is  oblique  in  direction, 
somewhat  triangular  in  form,  and  corresponds  with  the  course  of  the  fibres  of  the 
aponeurosis.  It  usually  measures  from  base  to  apex  about  an  inch,  and  trans- 
versely about  half  an  inch.  It  is  bounded  below  by  the  crest  of  the  os  pubis ; 
above,  by  a  series  of  curved  fibres,  the  inter  columnar,  which  pass  across  the  upper 
angle  of  the  ring,  so  as  to  increase  its  strength ;  and  on  either  side,  by  the  mar- 
gins of  the  opening  in  the  aponeurosis,  which  are  called  the  columns  or  pillars  of 
the  ring. 

The  external  pillar,  which  at  the  same  time  is  inferior  from  the  obliquity  of 
its  direction,  is  the  stronger ;  it  is  formed  by  that  portion  of  Poupart's  ligament 
which  is  inserted  into  the  spine  of  the  os  pubis ;  it  is  curved,  so  as  to  form  a  kind 
of  groove,  upon  which  the  spermatic  cord  rests. 

The  internal  or  superior  pillar  is  a  broad,  thin,  flat  band,  which  is  attached 
to  the  front  of  the  body  of  the  os  pubis,  interlacing  with  its  fellow  of  the  oppo- 
site side  in  front  of  the  symphysis  pubis,  that  of  the  right  side  being  superficial. 

The  external  abdominal  ring  gives  passage  to  the  spermatic  cord  in  the^nale 
and  round  ligament  in  the  female  ;  it  is  much  larger  in  men  than  in  women,  on 
account  of  the  large  size  of  the  spermatic  cord,  and  hence  the  great  frequency 
of  inguinal  hernia  in  men. 

The  intercolumnar  fibres  are  a  series  of  curved  tendinous  fibres  which  arch 
across  the  lower  part  of  the  aponeurosis  of  the  External  oblique.  They  have 
received  their  name  from  stretching  across  between  the  two  pillars  of  the  external 
ring ;  they  increase  the  strength  of  the  lower  part  of  the  aponeurosis  and  prevent 
the  divergence  of  the  pillars  from  one  another.  They  are  thickest  below,  where 
they  are  connected  to  the  outer  third  of  Poupart's  ligament,  and  are  inserted  into 
the  linea  alba,  describing  a  curve,  with  the  convexity  downward.  They  are  much 
thicker  and  stronger  at  the  outer  angle  of  the  external  ring  than  internally,  and 
are  more  strongly  developed  in  the  male  than  in  the  female.  These  intercolumnar 
fibres,  as  they  pass  across  the  external  abdominal  ring,  are  themselves  connected 
together  by  delicate  fibrous  tissue,  thus  forming  a  fascia  which,  as  it  is  attached 
to  the  pillars  of  the  ring,  covers  it  in,  and  is  called  the  intercolumnar  fascia.  This 
intercolumnar  fascia  is  continued  downward  as  a  tubular  prolongation  around  the 
outer  surface  of  the  cord  and  testis,  and  encloses  them  in  a  distinct  sheath ;  hence 
it  is  also  called  the  external  spermatic  fascia.  The  sac  of  an  inguinal  hernia  in 
passing  through  the  external  abdominal  ring  receives  an  investment  from  the 
intercolumnar  fascia. 

If  the  finger  is  introduced  a  short  distance  into  the  external  ring,  and  then,  if 
the  limb  is  extended  and  rotated  outward,  the  aponeurosis  of  the  External  oblique, 
together  with  the  iliac  portion  of  the  fascia  lata,  will  be  felt  to  become  tense  and 
the  external  ring  much  contracted  ;  if  the  limb  is,  on  the  contrary,  flexed  upon  the 
pelvis  and  rotated  inward,  this  aponeurosis  will  become  lax,  and  the  external  ring 
sufficiently  enlarged  to  admit  the  finger  with  comparative  ease  ;  hence  the  patient 
should  always  be  put  in  the  latter  position  when  the  taxis  is  applied  for  the  reduc- 
tion of  an  inguinal  hernia,  in  order  that  the  abdominal  walls  may  be  relaxed  as 
much  as  possible. 


1044 


THE   SURGICAL    ANATOMY   OF  HERNIA. 


The  aponeurosis  of  the  External  oblique  should  be  removed  by  dividing  it  across  in  the  same 
direction  as  the  external  incisions,  and  reflecting  it  downward  and  outward  :  great  care  is  requisite 
in  separating  it  from  the  aponeurosis  of  the  muscle  beneath.  The  lower  part  of  the  Internal 
oblique  and  the  Cremaster  are  then  exposed,  together  with  the  inguinal  canal,  which  contains 
the  spermatic  cord  (Fig.  580).  The  mode  of  insertion  of  Poupart's  and  Grimbernat's  ligaments 
into  the  os  pubis  should  also  be  examined. 

Poupart's  ligament,  or  the  crural  arch,  is  the  lower  border  of  the  aponeurosis 
of  the  External  oblique  muscle,  which  extends  from  the  anterior  superior  spine  of 
the  ilium  to  the  spine  of  the  os  pubis.  From  this  latter  point  it  is  reflected 
outward  to  be  attached  to  the  pectineal   line  for  about  half   an  inch,  forming 


Fig.  580.— Inguinal  hernia.    Dissection  showing  the  Internal  oblique  and  Cremaster. 

Gimbernat's  ligament.  Its  general  direction  is  curved  downward  toward  the  thigh, 
where  it  is  continuous  with  the  fascia  lata.  Its  outer  half  is  rounded  and  oblique 
in  direction ;  its  inner  half  gradually  widens  at  its  attachment  to  the  os  pubis,  is 
more  horizontal  in  direction,  and  lies  beneath  the  spermatic  cord. 

Grimbernat's  Ligament  (Fig.  588)  is  that  portion  of  the  aponeurosis  of  the  Ex- 
ternal oblique  muscle  which  is  reflected  upward  and  outward  from  the  spine  of  the 
os  pubis  to  be  inserted  into  the  pectineal  line.  It  is  about  half  an  inch  in  length, 
larger  in  the  male  than  in  the  female,  almost  horizontal  in  direction  in  the  erect 
posture,  and  of  a  triangular  form,  with  the  base  directed  outward.  Its  base  or 
outer  margin  is  concave,  thin,  and  sharp,  and  lies  in  contact  with  the  femoral  sheath, 
forming  the  inner  boundary  of  the  crural  ring  (see  Fig.  588).  Its  apex  corre- 
sponds to  the  spine  of  the  os  pubis.  Its  posterior  margin  is  attached  to  the  pecti- 
neal liue,  and  is  continuous  with  the  pubic  portion  of  the  fascia  lata.  Its  anterior 
margin  is  continuous  with  Poupart's  ligament. 

The  triangular  fascia  of  the  abdomen  is  a  band  of  tendinous  fibres,  of  a 
triangular  shape,  which  is  attached  by  its  apex  to  the  pectineal  line,  where  it  is 
continuous  with  Gimbernat's  ligament.  It  passes  inward  beneath  the  spermatic 
cord,  and  expands  into  a  somewhat  fan-shaped  fascia*  lying  behind  the  inner. pillar 


THE    TRANSVERSA  LIS  MUSCLE.  1045 

of  the  external  abdominal  ring  and  in  front  of  the  conjoined  tendon,  and  interlaces 
with  the  ligament  of  the  other  side  at  the  linea  alba. 

The  Internal  oblique  muscle  has  been  previously  described  (page  360).  The 
part  which  is  now  exposed  is  partly  muscular  and  partly  tendinous  in  structure. 
Those  fibres  which  arise  from  Poupart's  ligament,  few  in  number  and  paler  in 
color  than  the  rest,  arch  downward  and  inward  across  the  spermatic  cord,  and, 
becoming  tendinous,  are  inserted,  conjointly  with  those  of  the  Transversalis,  into  the 
crest  of  the  os  pubis  and  pectineal  line,  forming  Avhat  is  known  as  the  conjoined 
tendon  of  the  Internal  oblique  and  Transversalis,  This  tendon  is  inserted  imme- 
diately behind  the  inguinal  canal  and  external  abdominal  ring,  serving  to  protect 
what  would  otherwise  be  a  weak  point  in  the  abdominal  wall.  Sometimes  this 
tendon  is  insufficient  to  resist  the  pressure  from  within,  and  is  carried  forward  in 
front  of  the  protrusion  through  the  external  ring,  forming  one  of  the  coverings  of 
direct  inguinal  hernia,  or  the  hernia  forces  its  way  through  the  fibres  of  the  con- 
joined tendon. 

The  Cremaster  is  a  thin  muscular  layer  composed  of  a  number  of  fasciculi 
which  arise  from  the  middle  of  Poupart's  ligament  at  the  inner  side  of  the  Internal 
oblique,  being  connected  with  that  muscle  and  also  occasionally  with  the 
Transversalis.  It  passes  along  the  outer  side  of  the  spermatic  cord,  descends  with 
it  through  the  external  ring  upon  the  front  and  sides  of  the  cord,  and  forms  a 
series  of  loops  which  differ  in  thickness  and  length  in  different  subjects.  Those 
at  the  upper  part  of  the  cord  are  exceedingly  short,  but  they  become  in  succession 
longer  and  longer,  the  longest  reaching  down  as  low  as  the  testicle,  where  a  few 
are  inserted  into  the  tunica  vaginalis.  These  loops  are  united  together  by  areolar 
tissue,  and  form  a  thin  covering  over  the  cord  and  testis,  the  fascia  cremasteric  a. 
The  fibres  ascend  along  the  inner  side  of  the  cord,  and  are  inserted  by  a  small 
pointed  tendon  into  the  crest  of  the  os  pubis  and  front  of  the  sheath  of  the  Rectus 
muscle. 

It  will  be  observed  that  the  origin  and  insertion  of  the  Cremaster  is  precisely 
similar  to  that  of  the  lower  fibres  of  the  Internal  oblique.  This  fact  affords  an  easy 
explanation  of  the  manner  in  which  the  testicle  and  cord  are  invested  by  this  muscle. 
At  an  early  period  of  foetal  life  the  testis  is  placed  at  the  lower  and  back  part  of  the 
abdominal  cavity,  but  during  its  descent  toward  the  scrotum,  which  takes  place 
before  birth,  it  passes  beneath  the  arched  border  of  the  Internal  oblique.  In  its 
passage  beneath  this  muscle  some  fibres  are  derived  from  its  lower  part  which 
accompany  the  testicle  and  cord  into  the  scrotum. 

It  occasionally  happens  that  the  loops  of  the  Cremaster  surround  the  cord,  some 
lying  behind  as  well  as  in  front.  It  is  probable  that  under  these  circumstances 
the  testis  in  its  descent  passes  through,  instead  of  beneath,  the  fibres  of  the  Internal 
oblique. 

In  the  descent  of  an  oblique  inguinal  hernia,  which  takes  the  same  course  as 
the  spermatic  cord,  the  Cremaster  muscle  forms  one  of  its  coverings.  This  muscle 
becomes  largely  developed  in  cases  of  hydrocele  and  large  old  scrotal  hernise.  No 
such  muscle  exist  in  the  female,  but  an  analogous  structure  is  developed  in  those 
cases  where  an  oblique  inguinal  hernia  descends  beneath  the  margin  of  the  Internal 
oblique. 

The  Internal  oblique  should  be  detached  from  Poupart's  ligament,  separated  from  the 
Transversalis  to  the  same  extent  as  in  the  previous  incisions,  and  reflected  inward  on  to  the 
sheath  of  the  Rectus  (Fig.  581).  The  deep  circumflex  iliac  vessels,  which  lie  between  these  two 
muscles,  form  a  valuable  guide  to  their  separation. 

The  Transversalis  muscle  has  been  previously  described  (page  362).  The  part 
which  is  now  exposed  is  partly  muscular  and  partly  tendinous  in  structure ;  it 
arises  from  the  outer  third  of  Poupart's  ligament,  its  fibres  curve  downward  and 
inward,  and  are  inserted,  together  with  those  of  the  Internal  oblique,  into  the  lower 
part  of  the  linea  alba,  into  the  crest  of  the  os  pubis  and  the  pectineal  line,  form- 
ing what  is  known  as  the   conjoined  tendon  of  the   Internal  oblique  and  Trans- 


1046 


THE  SURGICAL   ANATOMY   OF  HERNIA. 


versalis.  Between  the  lower  border  of  this  muscle  and  Poupart's  ligament  a  space 
is  left  in  which  is  seen  the  transversalis  fascia. 

The  inguinal  or  spermatic  canal  contains  the  spermatic  cord  in  the  male  and 
the  round  ligament  in  the  female.  It  is  an  oblique  canal,  about  an  inch  and  a  half 
in  length,  directed  downward  and  inward  and  placed  parallel  with,  and  a  little 
above,  Poupart's  ligament.  It  commences  above  at  the  internal  or  deep  abdominal 
ring,  which  is  the  point  where  the  cord  enters  the  inguinal  canal,  and  terminates 
below  at  the  external  or  superficial  ring.  It  is  bounded,  inL-famit^aj  the  integu- 
ment and  superficial  fascia,  by  the  aponeurosis  of  the  External  oblique  throughout 
its  whole  length,  and  by  the  Internal  oblique  for  its  outer  third;  behind,,  by  the 
triangular  fascia,  the  conjoined  tendon  of  the  Internal  oblique  and  Transversalis, 
transversalis  fascia,  and  the  subperitoneal  fat  and  peritoneum;  above,  by  the 
arched  fibres  of  the  Internal  oblique  and  Trans  versalis  j^beloWy  by  the  union  of  the 
transversalis  fascia  with  Poupart's  ligament.  That  form  of  hernia  in  which  the 
intestine  follows  the  course  of  the  spermatic  cord  along  the  inguinal  canal  is  called 
oblique  inguinal  hernia. 

The  transversalis  fascia  is  a  thin   aponeurotic  membrane  which  lies  between 


Epigastric  artery 


Pig.  581. — Inguinal  hernia, 
internal  abdominal  ring. 


Dissection  showing  the  Transversalis  muscle,  the  transversalis  fascia,  and  the 


the  inner  surface  of  the  Transversalis  muscle  and  the  peritoneum.  It  forms  part 
of  the  general  layer  of  fascia  which  lines  the  interior  of  the  abdominal  and  pelvic 
cavities,  and  is  directly  continuous  with  the  iliac  and  pelvic  fasciae. 

In  the  inguinal  region  the  transversalis  fascia  is  thick  and  dense  in  structure, 
and  joined  by  fibres  from  the  aponeurosis  of  the  Transversalis  muscle ;  but  it 
becomes  thin  and  cellular  as  it  ascends  to  the  Diaphragm.  Below,  it  has  the 
following  attachments  :  external  to  the  femoral  vessels  it  is  connected  to  the 
posterior  margin  of  Poupart's  ligament,  and  is  there  continuous  with  the  iliac 
fascia.  Internal  to  the  vessels  it  is  thin,  and  attached  to  the  os  pubis  and  pectineal 
line  behind  the  conjoined  tendon,  with  which  it  is  united;  and,  corresponding  to 
the  points  where  the  femoral  vessels  pass  into  the  thigh,  this  fascia  descends  in 
front  of  them,  forming  the  anterior  wall  of  the  femoral  sheath.    The  spermatic  cord 


THE  PERITONEUM.  1047 

in  the  male  and  the  i*ound  ligament  in  the  female  pass  through  this  fascia  ;  the 
point  where  they  pass  through  is  called  the  internal  or  deep  abdominal  ring.  This 
opening  is  not  visible  externally,  owing  to  a  prolongation  of  the  transversalis  fascia 
on  the  structures  forming  the  infundibuliform  fascia. 

The  internal  or  deep  abdominal  ring  is  situated  in  the  transversalis  fascia,  mid- 
way between  the  anterior  superior  spine  of  the  ilium  and  symphysis  pubis,  and 
about  half  an  inch  above  Poupart's  ligament.  It  is  of  an  oval  form,  its  long 
diameter  being  directed  upward  and  downward  ;  it  varies  in  size  in  different  sub- 
jects, and  is  much  larger  in  the  male  than  in  the  female.  It  is  bounded  above  and 
externally  by  the  arched  fibres  of  the  Transversalis  muscle,  below  and  internally 
by  the  deep  epigastric  vessels.  It  transmits  the  spermatic  cord  in  the  male  and 
the  round  ligament  in  the  female.  From  its  circumference,  a  thin,  funnel-shaped 
membrane,  the  infundibuliform  fascia,  is  continued  round  the  cord  and  testis, 
enclosing  them  in  a  distinct  pouch.  When  the  sac  of  an  oblique  inguinal  hernia 
passes  through  the  internal  or  deep  abdominal  ring,  the  infundibuliform  fascia 
constitutes  one  of  its  coverings. 

The  Subperitoneal  Areolar  Tissue. — Between  the  transversalis  fascia  and  the 
peritoneum  is  a  quantity  of  loose  areolar  tissue.  In  some  subjects  it  is  of  consider- 
able thickness  and  loaded  with  adipose  tissue.  Opposite  the  internal  ring  it  is 
continued  round  the  surface  of  the  cord,  forming  a  loose  sheath  for  it. 

The  deep  epigastric  artery  arises  from  the  external  iliac  artery  a  few  lines  above 
Poupart's  ligament.  It  at  first  descends  to  reach  this  ligament,  and  then  ascends 
obliquely  along  the  inner  margin  of  the  internal  or  deep  abdominal  ring,  lying 
between  the  transversalis  fascia  and  the  peritoneum,  and  passing  upward  pierces 
the  transversalis  fascia  and  enters  the  sheath  of  the  Rectus  muscle  by  passing  over 
the  semilunar  fold  of  Douglas.  Consequently  the  deep  epigastric  artery  bears  a 
very  important  relation  to  the  internal  abdominal  ring  as  it  passes  obliquely  up- 
ward and  inward  from  its  origin  from  the  external  iliac.  In  this  part  of  its  course 
it  lies  along  the  lower  and  inner  margin  of  the  internal  ring  and  beneath  the  com- 
mencement of  the  spermatic  cord.  At  its  commencement  it  is  crossed  by  the  vas 
deferens  in  the  male  and  by  the  round  ligament  in  the  female. 

The  peritoneum,  corresponding  to  the  inner  surface  of  the  internal  ring,  presents 
a  well-marked  depression,  the  depth  of  which  varies  in  different  subjects.  A  thin 
fibrous  band  is  continued  from  it  along  the  front  of  the  cord  for  a  variable  distance, 
and  becomes  ultimately  lost.  This  is  the  remains  of  the  pouch  of  peritoneum  which, 
in  the  foetus,  precedes  the  cord  and  testis  into  the  scrotum,  the  obliteration  of 
which  commences  soon  after  birth.  In  some  cases  the  fibrous  band  can  only  be 
traced  a  short  distance,  but  occasionally  it  may  be  followed,  as  a  fine  cord,  as  far 
as  the  upper  end  of  the  tunica  vaginalis.  Sometimes  the  tube  of  peritoneum  is 
closed  only  at  intervals  and  presents  a  sacculated  appearance,  or  a  single  pouch 
may  extend  along  the  whole  length  of  the  cord,  which  may  be  closed  above,  or  the 
pouch  may  be  directly  continuous  with  the  peritoneum  by  an  opening  at  its  upper 
part. 

In  the  female  foetus  the  peritoneum  is  also  prolonged  in  the  form  of  a  tubular 
process  for  a  short  distance  into  the  inguinal  canal.  This  process  is  called  the 
canal  of  Nuck.  It  is  generally  obliterated  in  the  adult,  but  sometimes  it  remains 
pervious  even  in  advanced  life. 

In  order  to  understand  the  relation  of  the  peritoneum  to  inguinal  hernia,  it  is 
necessary  to  view  the  anterior  abdominal  wall  from  its  internal  aspect,  when  it  will 
be  seen  as  shown  in  Fig.  582.  Between  the  upper  margin  of  the  front  of  the 
pelvis  and  the  umbilicus,  the  peritoneum,  when  viewed  from  behind,  will  be  seen 
to  be  raised  into  five  vertical  folds,  with  intervening  depressions,  by  more  or  less 
prominent  bands  which  converge  to  the  umbilicus.  One  of  these  is  situated  in  the 
median  line,  and  is  caused  by  the  urachus,  the  remnant  of  the  allantois  :  it  extends 
from  the  summit  of  the  bladder  to  the  umbilicus.  The  fold  of  peritoneum  covering 
it  is  known  as  the  plica  urachi.  On  either  side  of  this  is  a  prominent  band,  caused 
by  the  obliterated  hypogastric  artery,  which  extends  from  the  side  of  the  bladder 


1048 


THE  SURGICAL    ANATOMY   OF  HERNIA. 


obliquely  upward  and  inward  to  the  umbilicus.  This  is  covered  by  a  fold  of  peri- 
toneum, which  is  known  as  the  plica  hypogastrica.  To  either  side  of  these  three 
cords  is  the  deep  epigastric  artery,  which  ascends  obliquely  upward  and  inward 
from  a  point  midway  between  the  symphysis  pubis  and  the  anterior  superior  spine 
of  the  ilium  to  the  semilunar  fold  of  Douglas,  in  front  of  which  it  disappears.  It 
is  covered  by  a  fold  of  peritoneum,  which  is  known  as  the  plica  epigastrica.  Be- 
tween these  raised  folds  are  depressions  of  the  peritoneum,  constituting  so-called 
fossae.  The  most  internal,  between  the  plica  urachi  and  the  plica  hypogastrica,  is 
known  as  the  internal  inguinal  fossa  (fovea  supravesicalis).  The  middle  one  is 
situated  between  the  plica  hypogastrica  and  the  plica  epigastrica,  and  is  termed  the 
middle  inguinal  fossa  (fovea  inguinalis  mesialis).     The  external  one  is  external  to 


M.  iliacus. 


External 
inguinal 
fossa. 


External 
iliac 
vein. 


Internal  ingwi/t 
fossa. 


Femoral 
fossa. 
Superior  vesical 

artery. 
Middle  inguinal 
fossa. 


Fig.  582.— Posterior  view  of  the  anterior  abdominal  wall  in  its  lower  half.    The  peritoneum  is  in  place,  and 
the  various  cords  are  shining  through.    (After  Joessel.) 

the  plica  epigastrica,  and  is  known  as  the  external  inguinal  fossa  (fovea  inguinalis 
lateralis).  Occasionally  the  deep  epigastric  artery  corresponds  in  position  to  the 
obliterated  hypogastric  artery,  and  then  there  is  but  one  fold  on  each  side  of  the 
middle  line,  and  the  two  external  fossae  are  merged  into  one.  In  the  usual  con- 
dition of  the  parts  the  floor  of  the  external  inguinal  fossa  corresponds  to  the 
internal  abdominal  ring,  and  into  this  fossa  an  oblique  inguinal  hernia  descends. 
To  the  inner  side  of  the  plica  epigastrica  are  the  two  internal  fossae,  and  through 
either  of  these  a  direct  hernia  may  descend,  as  will  be  explained  in  the  sequel 
(page  1052).  The  whole  of  this  space,  that  is  to  say,  the  space  between  the  deep 
epigastric  artery,  the  margin  of  the  Rectus  and  Poupart's  ligament,  is  commonly 
known  as  Hesselbacli  s  triangle.  These  three  depressions  or  fossae  are  situated 
above  the  level  of  Poupart's  ligament,  and  in  addition  to  them  is  another  below 
the  ligament,  corresponding  to  the  position  of  the  femoral  ring,  and  into  which  a 
femoral  hernia  descends. 


OBLIQUE   INGUINAL    HERNIA. 


1049 


INGUINAL  HERNIA. 

Inguinal  hernia  is  that  form  of  protrusion  which  makes  its  way  through  the 
abdomen  in  the  inguinal  region. 

There  are  two  principal  varieties  of  inguinal  hernia — external  or  oblique,  and 
internal  or  direct. 

External  or  oblique  inguinal  hernia,  the  more  frequent  of  the  two.  takes  the 
same  course  as  the  spermatic  cord.  It  is  called  external  from  the  neck  of  the  sac 
being  on  the  outer  or  iliac  side  of  the  deep  epigastric  artery. 

Internal  or  direct  inguinal  hernia  does  not  follow  the  same  course  as  the  cord, 
but  protrudes  through  the  abdominal  wall  on  the  inner  or  pubic  side  of  the  deep 
epigastric  artery. 

Oblique  Inguinal  Hernia. 

In  oblique  inguinal  hernia  the  intestine  escapes  from  the  abdominal  cavity  at 
the  internal  ring,  pushing  before  it  a  pouch  of  peritoneum,  which  forms  the  hernial 


Fig.  583— Oblique  inguinal  hernia,  showing  its  various  coverings.     (From  a  preparation  in  the  Museum  of 
the  Royal  College  of  Surgeons.) 


sac  (Fig.  584,  a).  As  it  enters  the  inguinal  canal  it  receives  an  investment  from 
the  subserous  areolar  tissue,  and  is  enclosed  in  the  infundibuliform  process  of  the 
transversalis  fascia.  In  passing  along  the  inguinal  canal  it  displaces  upward  the 
arched  fibres  of  the  Transversalis  and  Internal  oblique  muscles,  and  is  surrounded 
by  the  fibres  of  the  Cremaster.  It  then  passes  along  the  front  of  the  cord,  and 
escapes  from  the  inguinal  canal  at  the  external  ring,  receiving  an  investment  from 


1050 


THE  SURGICAL    ANATOMY   OF  HERNIA. 


the  intercolumnar  fascia.    Lastly,  it  descends  into  the  scrotum,  receiving  coverings 
from  the  superficial  fascia  and  the  integument. 


\ Sac  of  hernia. 


Tunica      J> 
vaginalis.-'' 

A.  Common  scrotal  hernia. 


Tunica 
aginalis. 


B.  Congenital  hernia. 


Sac  of__ 
hernia. 


-—4 Sac  of  hernia. 


Tunica  vaginalis.  H~l 


of  hernia. 


E.  Hernia  into  the  funicular  process. 
Fig.  58-4.— Varieties  of  oblique  inguinal  hernia. 


The  coverings  of  this  form  of  hernia,  after  it  has  passed  through  the  external 
*ing,  are,  from  Without  inward,  the  integument,  superficial  fascia,  mtei  columnar 


OBLIQUE   INGUINAL    HERNIA.  1051 

ascia,  Creruaster  muscle,  infundibuliform  fascia,  subserous  areolar  tissue,  and 
)eritoneum. 

This  form  of  hernia  lies  in  front  of  the  vessels  of  the  spermatic  cord  and 
leldom  extends  below  the  testis,  on  account  of  the  intimate  adhesion  of  the  cover- 
ngs  of  the  cord  to  the  tunica  vaginalis. 

The  seat  of  stricture  in  oblique  inguinal  hernia  is  either  at  the  external  ring, 
n  the  inguinal  canal,  caused  by  the  fibres  of  the  Internal  oblique  or  Trans- 
rersalis ;  or  at  the  internal  ring,  most  frequently  in  the  latter  situation.  If  it  is 
ituated  at  the  external  ring,  the  division  of  a  few  fibres  at  one  point  of  its 
drcumference  is  all  that  is  necessary  for  the  replacement  of  the  hernia.  If 
n  the  inguinal  canal  or  at  the  internal  ring,  it  may  be  necessary  to  divide  the 
iponeurosis  of  the  External  oblique  so  as  to  lay  open  the  inguinal  canal.  In 
lividing  the  stricture  the  direction  of  the  incision  should  be  upward. 

When  the  intestine  passes  along  the  inguinal  canal  and  escapes  from  the 
sxternal  ring  into  the  scrotum,  it  is  called  complete  oblique  inguinal  or  scrotal 
lernia.  If  the  intestine  does  not  escape  from  the  external  ring,  but  is  retained 
n  the  inguinal  canal,  it  is  called  incomplete  inguinal  hernia,  or  bubonocele.  In 
sach  of  these  cases  the  coverings  which  invest  it  will  depend  upon  the  extent  to 
vhich  it  descends  in  the  inguinal  canal. 

There  are  some  other  varieties  of  oblique  inguinal  hernia  depending  upon  con- 
genital defects  in  the  processus  vaginalis.  The  testicle  in  its  descent  from  the 
,bdomen  into  the  scrotum  is  preceded  by  a  pouch  of  peritoneum,  which  about 
he  period  of  birth  becomes  shut  off  from  the  general  peritoneal  cavity  by  a  closure 
f  that  portion  of  the  pouch  which  extends  from  the  internal  abdominal  ring  to 
lear  the  upper  part  of  the  testicle,  the  lower  portion  of  the  pouch  remaining  per- 
istent  as  the  tunica  vaginalis.  It  would  appear  that  this  closure  commences  at 
wo  points — viz.  at  the  internal  abdominal  ring  and  at  the  top  of  the  epididymis — 
,nd  gradually  extends  until,  in  the  normal  condition,  the  whole  of  the  inter- 
ening  portion  is  converted  into  a  fibrous  cord.  From  failure  in  the  completion 
•f  this  process  variations  in  the  relation  of  the  hernial  protrusion  to  the 
esticle  and  tunica  vaginalis  are  produced,  which  constitute  distinct  varieties 
if  inguinal  hernia,  and  which  have  received  separate  names  and  are  of  surgical 
mportance.  These  are  congenital,  infantile,  encysted,  and  hernia  of  the  funicu- 
ar  process. 

Congenital  Hernia  (Fig.  584,  B). — Where  the  pouch  of  peritoneum  which  pre- 
edes  the  cord  and  testis  in  its  descent  remains  patent  throughout  and  is  unclosed 
t  any  point,  the  cavity  of  the  tunica  vaginalis  communicates  directly  with  the 
ieritoneum.  The  intestine  descends  along  this  pouch  into  the  cavity  of  the  tunica 
aginalis,  which  constitutes  the  sac  of  the  hernia,  and  the  gut  lies  in  contact  with 
be  testicle. 

Infantile  and  Encysted  Hernia. — Where  the  pouch  of  peritoneum  is  occluded 
,t  the  internal  ring  only,  and  remains  patent  throughout  the  rest  of  its  extent, 
wo  varieties  of  oblique  inguinal  hernia  may  be  produced,  which  have  received 
he  names  of  infantile  and  encysted  hernia.  In  the  infantile  form  (Fig.  584,  c) 
he  bowel,  pressing  upon  the  septum  and  the  peritoneum  in  its  immediate 
leighborhood,  causes  it  to  yield  and  form  a  sac,  which  descends  behind  the 
unica  vaginalis,  so  that  in  front  of  the  bowel  there  are  three  layers  of  per- 
toneum,  the  two  layers  of  the  tunica  vaginalis  and  its  own  sac.  In  the  encysted 
brm  (Fig.  584,  d)  pressure  in  the  same  position — namely,  at  the  occluded  spot  in 
he  pouch — causes  the  septum  to  yield  and  form  a  sac  which  projects  into  and  not 
behind  the  tunica  vaginalis,  as  in  the  infantile  form,  and  thus  it  constitutes  a  sac 
vithin  a  sac,  so  that  in  front  of  the  bowel  there  are  two  layers  of  peritoneum — one 
ayer  of  the  tunica  vaginalis  and  its  own  sac. 

Hernia  into  the  Funicular  Process  (Fig.  584,  e). — Where  the  pouch  of  perito- 
leum  is  occluded  at  the  lower  point  only — that  is,  just  above  the  testicle — the 
ntestine  descends  into  the  pouch  of  peritoneum  as  far  as  the  testicle,  but  is  pre- 
sented from  entering  the  sac  of  the  tunica  vaginalis  by  the  septum  which  has 


1052  THE  SURGICAL    ANATOMY   OF  HERNIA. 

formed  between  it  and  the  pouch,  so  that  it  resembles  the  congenital  form  in  all 
respects,  except  that,  instead  of  enveloping  the  testicle,  that  body  can  be  felt 
below  the  rupture. 

Direct  Inguinal  Hernia. 

In  direct  inguinal  hernia  the  protrusion  makes  its  way  through  some  part  of 
the  abdominal  wall  internal  to  the  epigastric  artery. 

At  the  lower  part  of  the  abdominal  wall  is  a  triangular  space  (Hesselbach' s 
triangle),  bounded  externally  by  the  deep  epigastric  artery,  internally  by  the 
margin  of  the  Rectus  muscle,  below  by  Poupart's  ligament  (Fig.  582).  The  con- 
joined tendon  is  stretched  across  the  inner  two-thirds  of  this  space,  the  remaining 
portion  of  the  space  having  only  the  subperitoneal  areolar  tissue  and  the  trans- 
versalis  fascia  between  the  peritoneum  and  the  aponeurosis  of  the  External  oblique 
muscle. 

In  some  cases  the  hernial  protrusion  escapes  from  the  abdomen  on  the  outer 
side  of  the  conjoined  tendon,  pushing  before  it  the  peritoneum,  the  subserous 
areolar  tissue,  and  the  transversalis  fascia.  It  then  enters  the  inguinal  canal, 
passing  along  nearly  its  whole  length,  and  finally  emerges  from  the  external  ring, 
receiving  an  investment  from  the  intercolumnar  fascia.  The  coverings  of  this 
form  of  hernia  are  precisely  similar  to  those  investing  the  oblique  form,  with  the 
insignificant  difference  that  the  infundibuliform  fascia  is  replaced  by  a  portion 
derived  from  the  general  layer  of  the  transversalis  fascia. 

In  other  cases — and  this  is  the  more  frequent  variety — the  hernia  is  either  forced 
through  the  fibres  of  the  conjoined  tendon  or  the  tendon  is  gradually  distended  in 
front  of  it  so  as  to  form  a  complete  investment  for  it.  The  intestine  then  enters 
the  lower  end  of  the  inguinal  canal,  escapes  at  the  external  ring  lying  on  the 
inner  side  of  the  cord,  and  receives  additional  coverings  from  the  superficial  fascia 
and  the  integument.  This  form  of  hernia  has  the  same  coverings  as  the  oblique 
variety,  excepting  that  the  conjoined  tendon  is  substituted  for  the  Cremaster,  and 
the  infundibuliform  fascia  is  replaced  by  a  portion  derived  from  the  general  layer 
of  the  transversalis  fascia. 

The  difference  between  the  position  of  the  neck  of  the  sac  in  these  two  forms 
of  direct  inguinal  hernia  has  been  referred,  with  some  probability,  to  a  difference 
in  the  relative  positions  of  the  obliterated  hypogastric  artery  and  the  deep 
epigastric  artery.  When  the  course  of  the  obliterated  hypogastric  artery  cor- 
responds pretty  nearly  with  that  of  the  deep  epigastric  the  projection  of  these 
arteries  toward  the  cavity  of  the  abdomen  produces  two  fossae  in  the  peritoneum. 
The  bottom  of  the  external  fossa  of  the  peritoneum  corresponds  to  the  position  of 
the  internal  abdominal  ring,  and  a  hernia  which  distends  and  pushes  out  the  peri- 
toneum lining  this  fossa  is  an  oblique  hernia.  When,  on  the  other  hand,  the 
obliterated  hypogastric  artery  lies  considerably  to  the  inner  side  of  the  deep  epi- 
gastric artery,  corresponding  to  the  outer  margin  of  the  conjoined  tendon,  it  divides 
the  triangle  of  Hesselbach  into  two  parts,  so  that  three  depressions  will  be  seen  on 
the  inner  surface  of  the  lower  part  of  the  abdominal  wall,  viz.,  an  external  one,  on 
the  outer  side  of  the  deep  epigastric  artery ;  a  middle  one,  between  the  deep 
epigastric  and  the  obliterated  hypogastric  arteries ;  and  an  internal  one,  on  the 
inner  side  of  the  obliterated  hypogastric  artery  (see  page  1051).  In  such  a  case 
a  hernia  may  distend  and  push  out  the  peritoneum  forming  the  bottom  of  either 
fossa.  When  the  hernia  distends  and  pushes  out  the  peritoneum  forming  the 
bottom  of  the  external  fossa,  it  is  an  oblique  or  external  inguinal  hernia.  These 
fossa?  are  the  inguinal  fossa?. 

When  the  hernia  distends  and  pushes  out  the  peritoneum  forming  the  bottom 
of  either  the  middle  or  the  internal  fossa,  it  is  a  direct  or  internal  hernia. 

The  anatomical  difference  between  these  two  forms  of  direct  or  internal 
inguinal  hernia  is  that,  when  the  hernia  protrudes  through  the  middle  fossa — that 
is,  the  fossa  between  the  deep  epigastric  and  the  obliterated  hypogastric  arteries — 
it  will  enter  the  upper  part  of  the  inguinal  canal;  consequently  its  coverings  will  be 


FEMORAL    HERNIA.  1053 

the  same  as  those  of  an  oblique  hernia,  with  the  insignificant  difference  that  the 
infandibuliform  fascia  is  replaced  by  a  portion  derived  from  the  general  layer  of 
the  transversalis  fascia,  whereas  when  the  hernia  protrudes  through  the  internal 
fossa  it  is  either  forced  through  the  fibres  of  the  conjoined  tendon  or  the  tendon  is 
gradually  distended  in  front  of  it  so  as  to  form  a  complete  investment  for  it.  The 
intestine  then  enters  the  lower  part  of  the  inguinal  canal,  and  escapes  from  the 
external  abdominal  ring  lying  on  the  inner  side  of  the  cord. 

This  form  of  hernia  has  the  same  coverings  as  the  oblique  variety,  excepting 
that  the  conjoined  tendon  is  substituted  for  the  Cremaster,  and  the  infundibuii- 
form  fascia  is  replaced  by  a  portion  derived  from  the  general  layer  of  the  fascia 
transversalis. 

The  seat  of  stricture  in  both  varieties  of  direct  hernia  is  most  frequently  at  the 
neck  of  the  sac  or  at  the  external  ring.  In  that  form  of  hernia  which  perforates 
the  conjoined  tendon  it  not  unfrequently  occurs  at  the  edges  of  the  fissure  through 
which  the  gut  passes.  In  dividing  the  stricture  the  incision  should  in  all  cases  bo 
directed  upward.1 

If  the  hernial  protrusion  passes  into  the  inguinal  canal,  but  does  not  escape 
from  the  external  abdominal  ring,  it  forms  what  is  c&]\ed  incomplete  direct  hernia. 
This  form  of  hernia  is  usually  of  small  size,  and  in  corpulent  persons  very  difficult 
of  detection. 

Direct  inguinal  hernia  is  of  much  less  frequent  occurrence  than  the  oblique, 
their  comparative  frequency  being,  according  to  Cloquet,  as  one  to  five.  _  It  occurs 
far  more  frequently  in  men  than  in  women,  on  account  of  the  larger  size  of  the 
external  ring  in  the  former  sex.  It  differs  from  the  oblique  in  its  smaller  size  and 
globular  form,  dependent  most  probably  on  the  resistance  offered  to  its  progress  by 
the  transversalis  fascia  and  conjoined  tendon.  It  differs  also  in  its  position,  being- 
placed  over  the  os  pubis  and  not  in  the  course  of  the  inguinal  canal.  The  deep 
epigastric  artery  runs  on  the  outer  or  iliac  side  of  the  neck  of  the  sac,  and  the 
spermatic  cord  along  its  external  and  posterior  side,  not  directly  behind  it,  as  in 
oblique  inguinal  hernia. 

FEMORAL    HERNIA. 

The  dissection  of  the  parts  comprised  in  the  anatomy  of  femoral  hernia  should  be  per- 
formed, if  possible,  upon  a  female  subject  free  from  fat.  The  subject  should  he  upon  its  back  : 
a  block  is  first  placed  under  the  pelvis,  the  thigh  everted,  and  the  knee  slightly  bent  and 
retained  in  this  position.  .  An  incision  should  then  be  made  from  the  anterior  superior  spinous 
process  of  the  ilium  alone  Poupart's  ligament  to  the  symphysis  pubis ;  a  second  incision  should 
be  carried  transversely  across  the  thigh  about  six  inches  beneath  the  preceding ;  and  these  are 
to  be  connected  together  by  a  vertical  one  carried  along  the  inner  side  of  the  thigh,  lhese 
several  incisions  should  divide  merely  the  integument ;  this  is  to  be  reflected  outward,  when  the 
superficial  fascia  will  be  exposed. 

The  superficial  fascia  forms  a  continuous  layer  over  the  whole  of  the  thigh, 
consisting  of  areolar  tissue,  containing  in  its  meshes  much  fat,  and  capable  of 
being  separated  into  two  or  more  layers,  between  which  are  found  the  superficial 
vessels  and  nerves.  It  varies  in  thickness  in  different  parts  of  the  limb.  In  the 
groin  it  is  thick,  and  the  two  layers  are  separated  from  one  another  by  the  super- 
ficial inguinal  lymphatic  glands,  the  internal  saphenous  vein,  and  several  smaller 
vessels.  One  of  these  layers,  the  superficial,  is  continuous  with  the  superficial 
fascia  of  the  abdomen. 

The  superficial  layer  should  be  detached  by  dividing  it  across  in  the  same  direction  as  the 
external  incisions ;  its  removal  will  be  facilitated  by  commencing  at  the  lower  and  inner  angle  of 
the  space,  detaching  it  at  first  from  the  front  of  the  internal  saphenous  vein,  and  dissecting  it 
off  from  the  anterior  surface  of  that  vessel  and  its  tributaries ;  it  should  then  be  reflected  ont- 

1  In  all  cases  of  inguinal  hernia,  whether  oblique  or  direct,  it  is  proper  to  divide  the  stricture 

directly  upward  :  the  reason  of  this  is  obvious,  for  by  cutting  in  this  direction  the  incision  is  made 
parallel  to  the  deep  epigastric  artery— either  external  to  it  in  the  oblique  variety,  or  internal  to  it  in 
the  direct  form  of  hernia— and  thus  all  chance  of  wounding  the  vessel  is  avoided.  If  the  incision 
was  made  outward,  the  artery  might  be  divided  if  the  hernia  was  direct ;  and  if  made  inward,  it  would 
stand  an  equal  chance  of  injury  if  the  case  was  one  of  oblique  inguinal  hernia. 


1054 


THE  SURGICAL    ANATOMY   OF  HERNIA. 


ward  in  the  same  mariner  as  the  integument.  The  cutaneous  vessels  and  nerves  and  superficial 
inguinal  glands  are  then  exposed,  lying  upon  the  deep  layer  of  the  superficial  fascia.  These  are 
the  internal  saphenous  vein  and  the  superficial  epigastric,  superficial  circumflex  iliac,  and  super- 
ficial external  pudic  vessels,  as  well  as  numerous  lymphatics,  ascending  with  the  saphenous  vein 
to  the  inguinal  glands. 

The  internal  or  long  saphenous  vein  ascends  along  the  inner  side  of  the  thigh, 
and,  passing  through  the  saphenous  opening  in  the  fascia  lata,  terminates  in  the 
femoral  vein  about  an  inch  and  a  half  below  Poupart's  ligament.  This  vein 
receives  at  the  saphenous  opening  the  superficial  epigastric,  the  superficial 
circumflex    iliac,   and  the  superficial  external  pudic  veins. 

The  superficial  external  pudic  artery  (superior)  arises  from  the  inner  side  of 
the  femoral  artery,  and,  after  passing  through  the  saphenous  opening,  courses 
inward  across  the  spermatic  cord,  to  be  distributed  to  the  integument  on  the 
lower  part  of  the  abdomen,  the  penis  and  scrotum  in  the  male  and  the  labium  in 
the  female,  anastomosing  with  branches  of  the  internal  pudic. 

The  superficial  epigastric  artery  arises  from  the  femoral  about  half  an  inch 
below  Poupart's  ligament,  and,  passing  through  the  saphenous  opening  in  the 
fascia  lata,   ascends  on  to  the    abdomen,   in  the  superficial  fascia  covering  the 


Fig.  585.— Femoral  hernia.    Superficial  dissection. 

External  oblique  muscle,  nearly  as  high  as  the  umbilicus.  It  distributes  branches 
to  the  superficial  inguinal  lymphatic  glands,  the  superficial  fascia,  and  the  integu- 
ment, anastomosing  with  branches  of  the  deep  epigastric  and  internal  mammary 
arteries. 

The  superficial  circumflex  iliac  artery,  the  smallest  of  the  cutaneous  branches, 
arises  close  to  the  preceding,  and,  piercing  the  fascia  lata,  runs  outward,  parallel 


FEMORAL    HERNIA.  1055 

with  Poupart's  ligam  mt,  as  far  as  the  crest  of  the  ilium,  dividing  into  branches 
which  supply  the  srperficial  inguinal  lymphatic  glands,  the  superficial  fascia,  and 
the  integument  of  the  groin,  anastomosing  with  the  deep  circumflex  iliac,  and  with 
the  gluteal  and  external  circumflex  arteries. 

The  Superficial  Veins. — The  veins  accompanying  these  superficial  arteries  are 
usually  much  larger  than  the  arteries  :  they  terminate  in  the  internal  or  long 
saphenous  vein  at  the  saphenous  opening. 

The  superficial  inguinal  lymphatic  glands,  placed  immediately  beneath  the 
integument,  are  of  large  size  and  vary  from  eight  to  ten  in  number.  They  are 
divisible  into  two  groups  :  an  upper,  disposed  irregularly  along  Poupart's  ligament, 
which  receive  the  lymphatic  vessels  from  the  integument  of  the  scrotum,  penis, 
parietes  of  the  abdomen,  perineal  and  gluteal  regions,  and  the  mucous  membrane 
of  the  urethra  ;  and  an  inferior  group,  which  surround  the  saphenous  opening  in 
the  fascia  lata,  a  few  being  sometimes  continued  along  the  saphenous  vein  to  a 
variable  extent.  This  latter  group  receive  the  superficial  lymphatic  vessels  from 
the  lower  extremity. 

The  ilio-inguinal  nerve  arises  from  the  first  lumbar  nerve.  It  escapes  at  the 
external  abdominal  ring,  and  is  distributed  to  the  integument  of  the  upper  and 
inner  part  of  the  thigh — to  the  scrotum  in  the  male  and  to  the  labium  in  the 
female.  The  size  of  this  nerve  is  in  inverse  proportion  to  that  of  the  ilio-hypo- 
gastric.  Occasionally  it  is  very  small,  and  ends  by  joining  the  ilio-hypogastric  : 
in  such  cases  a  branch  of  the  ilio-hypogastric  takes  the  place  of  the  ilio-inguinal, 
or  the  latter  nerve  may  be  altogether  absent.  The  crural  branch  of  the  genito- 
crural  nerve  passes  along  the  inner  margin  of  the  Psoas  muscle,  beneath  Poupart's 
ligament,  into  the  thigh,  entering  the  sheath  of  the  femoral  vessels,  and  lying 
superficial  and  a  little  external  to  the  femoral  artery.  It  pierces  the  anterior  layer 
of  the  sheath  of  the  vessels,  and,  becoming  superficial  by  passing  through  the  fascia 
lata,  it  supplies  the  skin  of  the  anterior  aspect  of  the  thigh  as  far  as  midway 
between  the  pelvis  and  knee.  On  the  front  of  the  thigh  it  communicates  with 
the  outer  branch  of  the  middle  cutanetms  nerve,  derived  from  the  anterior  crural. 

The  deep  layer  of  the  superficial  fascia  is  a  very  thin  fibrous  layer,  best  marked 
on  the  inner  side  of  the  long  saphenous  vein  and  below  Poupart's  ligament.  It  is 
placed  beneath  the  subcutaneous  vessels  and  nerves,  and  upon  the  surface  of  the 
fascia  lata,  to  which  it  is  intimately  adherent  at  the  lower  margin  of  Poupart's 
ligament.  It  covers  the  saphenous  opening  in  the  fascia  lata,  is  closely  united  to 
its  circumference,  and  is  connected  to  the  sheath  of  the  femoral  vessels  corre- 
sponding to  its  under  surface.  The  portion  of  fascia  covering  this  aperture  is 
perforated  by  the  internal  saphenous  vein  and  by  numerous  blood-  and  lymphatic 
vessels ;  hence  it  has  been  termed  the  cribriform  fascia,  the  openings  for  these 
vessels  having  been  likened  to  the  holes  in  a  sieve.  The  cribriform  fascia  adheres 
closely  both  to  the  superficial  fascia  and  to  the  fascia  lata,  so  that  it  is  described 
by  some  anatomists  as  a  part  of  the  fascia  lata,  but  it  is  usually  considered  (as  in  this 
work)  as  belonging  to  the  superficial  fascia.  It  is  not  till  the  cribriform  fascia  has 
been  cleared  away  that  the  saphenous  opening  is  seen,  so  that  this  opening  does 
not  in  ordinary  cases  exist  naturally,  but  is  the  result  of  dissection.  A  femoral 
hernia  in  passing  through  the  saphenous  opening  receives  the  cribriform  fascia  as 
one  of  its  coverings. 

The  deep  layer  of  superficial  fascia,  together  with  the  cribriform  fascia,  having 
been  removed,  the  fascia  lata  is  exposed. 

The  Fascia  Lata  has  been  already  described  with  the  muscles  of  the  front  of 
the  thigh  (page  419).  At  the  upper  and  inner  part  of  the  thigh,  a  little  below 
Poupart's  ligament,  a  large  oval-shaped  aperture  is  observed  after  the  superficial 
fascia  has  been  cleared  away  ;  it  transmits  the  internal  saphenous  vein  and  other 
smaller  vessels,  and  is  called  the  saphenous  opening.  In  order  the  more  correctly 
to  consider  the  mode  of  formation  of  this  aperture,  the  fascia  lata  in  this  part  of  the 
thigh  is  described  as  consisting  of  two  portions,  an  iliac  portion  and  a  pubic  portion. 

The  iliac  portion  is  all  that  part  of  the  fascia  lata  on  the  outer  side  of  the 


1056 


THE   SURGICAL    ANATOMY   OF   HI  LNIA. 


saphenous  opening.  It  is  attached  externally  to  the  cr(  of  the  ilium  and  its 
anterior  superior  spine ;  to  the  whole  length  of  Poupnrt  ligament ;  and  to  the 
pectineal  line  in  conjunction  with  Gimbernat's  lif  menl  From  the  spine  of  the 
os  pubis  it  is  reflected  downward  and  outward,  forjning  an  rched  margin,  the  outer 
boundary  or  falciform  process  or  superior  cornu  (  henous  opening.      This 

margin  overlies  and  is  adherent  to  the  anterior  layer  of  the  sheath  of  the  femoral 
vessels ;  to  its  edge  is  attached  the  cribriform  fascia,  and  below  it  is  continuous 
with  the  pubic  portion  of  the  fascia  lata. 

The  pubic  portion  of  the  fascia  lata  is  situated  at  the  inner  side  of  the  saphenous 
opening  :  at  the  lower  margin  of  this  aperture  it  is  continuous  with  the  iliac 
portion  :  traced  upward,  it  covers  the  surface  of  the  Pectineus,  Adductor  longus, 
and  Gracilis  muscles ;  and,  passing  behind  the  sheath  of  the  femoral  vessels,  to 
which  it  is  closely  united,  is  continuous  with  the  sheath  of  the  Psoas  and  Hiacul 
muscles,  and  is  attached  above  to  the  ilio-pectineal  line,  where  it  becomes 
continuous  wTith  the  fascia  covering  the  Iliacus  muscle.  From  this  description  it 
may  be  observed  that  the  iliac  portion  of  the  fascia  lata  passes  in  front  of  the 
femoral  vessels  and  the  pubic  portion  behind  them,  so  that  an  apparent  aperture 


Fig.  586.— Femoral  hernia,  showing  fascia  lata  and  saphenous  opening. 


consequently  exists  between  the  two,  through  which  the  internal  saphenous  joins 
the  femoral  vein.  .1 

The  Saphenous  Opening  is  an  oval-shaped  aperture  measuring  about  an  inch 
and  a  half  in  length  and  half  an  inch  in  width.  It  is  situated  at  the  upper  and 
inner  part  of  the  front  of  the  thigh,  below  Poupart's  ligament,  and  is  directed 
obliquely  downward  and  outward. 

Its  outer  margin  is  of  a  semilunar  form,  thin,  strong,  sharply  defined,  and  lies 
on  a  plane  considerably  anterior  to  the   inner   margin.      If  this    edge  is  traced 


FEMORAL    HERNIA. 


1057 


upward,  it  will  be  seen  to  form  a  curved  elongated  process,  the  falciform  process 
or  superior  cornu,  which  ascends  in  front  of  the  femoral  vessels,  and,  curving 
inward,  is  attached  to  Poupart's  ligament  and  to  the  spine  of  the  os  pubis  and 
pectineal  line,  where  it  is  continuous  with  the  pubic  portion.  If  traced  down- 
ward, it  is  found  continuous  with  another  curved  margin,  the  concavity  of  which 
is  directed  upward  and  inward :  this  is  the  inferior  cornu  of  the  saphenous 
opening,  and  is  blended  with  the  pubic  portion  of  the  fascia  lata  covering  the 
Pectineus  muscle. 

The  inner  boundary  of  the  opening  is  on  a  plane  posterior  to  the  outer  margin 
and  behind  the  level  of  the  femoral  vessels  ;  it  is  much  less  prominent  and  defined 
than  the  outer,  from  being  stretched  over  the  subjacent  Pectineus  muscle.  It  is 
through  the  saphenous  opening  that  a  femoral  hernia  passes  after  descending  along 
the  crural  canal. 

If  the  finger  is  introduced  into  the  saphenous  opening  while  the  limb  is  moved 
in  dhTerent  directions,  the  aperture  will  be  found  to  be  greatly  constricted  on 
extending  the  limb  or  rotating  it  outward,  and  to  be  relaxed  on  flexing  the  limb 


Fig.  587.— Femoral  hernia.    Iliac  portion  of  fascia  lata  removed,  and  sheath  of  femoral  vessels  and  femoral 
canal  exposed. 

and  inverting  it :  hence  the  necessity  for  placing  the  limb  in  the  latter  position  in 
employing  the  taxis  for  the  reduction  of  a  femoral  hernia. 

The  iliac  portion  of  the  fascia  lata,  but  not  its  falciform  process,  should  now  be  removed  by 
detaching  it  from  the  lower  margin  of  Poupart's  ligament,  carefully  dissecting  it  from  the  sub- 
jacent structures,  and  turning  it  inward,  when  the  sheath  of  the  femoral  vessels  is  exposed, 
descending  beneath  Poupart's  ligament  (Fig.  587). 

Poupart's  Ligament,  or  the  Crural  Arch,  is  the  lower  border  of  the  aponeurosis 
of  the  External  oblique  muscle,  Avhich  extends  from  the  anterior  superior  spine  of 
67 


1058 


THE  SURGICAL    ANATOMY   OF  HERNIA. 


the  ilium  to  the  spine  of  the  os  pubis.  From  this  latter  point  it  is  reflected  outward, 
to  be  attached  to  the  pectineal  line  for  about  half  an  inch,  forming  Gimbernat's 
ligament.  Its  general  direction  is  curved  downward  toward  the  thigh,  where  it 
is  continuous  with  the  fascia  lata.  Its  outer  half  is  rounded  and  oblique  in 
direction.  Its  inner  half  gradually  widens  at  its  attachment  to  the  os  pubis,  is 
more  horizontal  in  direction,  and  lies  beneath  the  spermatic  cord.  Nearly  the 
whole  of  the  space  included  between  the  crural  arch  and  innominate  bone  is  filled 
in  by  the  parts  which  descend  from  the  abdomen  into  the  thigh  (Fig.  588).  The 
outer  half  of  the  space  is  occupied  by  the  Iliacus  and  Psoas  muscles,  together  with 
the  external  cutaneous  and  anterior  crural  nerves.  The  pubic  half  of  the  space  is 
occupied  by  the  femoral  vessels  included  in  their  sheath,  a  small  oval-shaped 
interval  existing  between  the  femoral  vein  and  the  inner  wall  of  the  sheath, 
which  is  occupied  merely  by  a  little  loose  areolar  tissue,  a  few  lymphatic  vessels, 


Crural 
Poupart's  ligament      bmnch     Anterk 


External 
cutaneous  nerve. 


Iliac  portion  of         Sheath  of 
fascia  lata.    \         vessels. 


Femoral  vein 
Femoral  ring. 

Gimbernat's 
ligament 


and  occasionally  by  a  small  lymphatic  gland  ;  this  is  the  femoral  ring,  through  which 
the  gut  descends  in  femoral  hernia. 

Gimbernat's  Ligament  (Figs.  588,  589)  is  that  part  of  the  aponeurosis  of  the 
External  oblique  muscle  which  is  reflected  backward  and  outward  from  the  spine 
of  the  os  pubis,  to  be  inserted  into  the  pectineal  line.  It  is  about  half  an  inch  in 
length,  larger  in  the  male  than  in  the  female,  almost  horizontal  in  direction  in  the 
erect  posture,  and  of  a  triangular  form,  with  the  base  directed  outward.  Its  base, 
or  outer  margin,  is  concave,  thin,  and  sharp,  and  lies  in  contact  with  the  femoral 
sheath.  Its  apex  corresponds  to  the  spine  of  the  os  pubis.  Its  posterior  margin 
is  attached  to  the  pectineal  line,  and  is  continuous  with  the  pubic  portion  of  the 
fascia  lata.     Its  anterior  margin  is  continuous  with  Poupart's  ligamenj. 


FEMORAL    HERNIA. 


1059 


Femoral  Sheath. — The  fomoral  or  crural  sheath  is  a  continuation  downward  of 
the  fascise  that  line  the  abdomen,  the  transversalis  fascia  passing  down  in  front  of 
the  femoral  vessels,  and  the  iliac  fascia  descending  behind  them  ;  these  fascise 
are  directly  continuous  on  the  iliac  side  of  the  femoral  artery,  but  a  small  space 
exists  between  the  femoral  vein  and  the  point  where  they  are  continuous  on  the 
pubic  side  of  that  vessel,  which  constitutes  the  femoral  or  crural  canal.  The 
femoral  sheath  is  closely  adherent  to  the  contained  vessels  about  an  inch  below 
the  saphenous  opening,  being  blended  with  the  areolar  sheath  of  the  vessels, 
but  opposite  Poupart's  ligament  it  is  much  larger  than  is  required  to  contain  them  ; 
hence  the  funnel-shaped  form  which  it  presents.  The  outer  border  of  the  sheath 
is  perforated  by  the  genito-crural  nerve.  Its  inner  border  is  pierced  by  the  internal 
saphenous  vein  and  numerous  lymphatic  vessels.  In  front  it  is  covered  by  the 
iliac  portion  of  the  fascia  lata ;  and  behind  it  is  the  pubic  portion  of  the  same 
fascia. 

If  the  anterior  wall  of  the  sheath  is  removed,  the  femoral  artery  and  vein  are 
seen  lying  side  by  side,  a  thin  septum  separating  the  two  vessels,  while  another 
septum  may  be  seen  lying  just  internal  to  the  vein,  and  cutting  off  a  small  space 
between  the  vein  and  the  inner  wall  of  the  sheath.  The  septa  are  stretched  between 
the  anterior  and  posterior  walls  of  the  sheath,  so  that  each  vessel  is  enclosed  in 
a  separate  compartment.  The  interval  left  between  the  vein  and  the  inner 
wall  of  the  sheath  is  "not  filled  up  by  any  structure,  excepting  a  little  loose 
areolar  tissue,  a  few  lymphatic  vessels,  and  occasionally  by  a  small  lymphatic 


Fig.  589.— Hernia.    The  relations  of  the  femoral  and  internal  abdominal  rinsrs,  seen  from  within  the  abdo- 
men.   Right  side. 


gland :  this  is  the  femoral  or  crural  canal,  through  which  the  intestine  descends  in 
femoral  hernia. 

Deep  Crural  Arch. — Passing  across  the  front  of  the  femoral  sheath  on  the 
abdominal  side  of  Poupart's  ligament,  and  closely  connected  with  it,  is  a  thickened 
band  of  fibres  called  the  deep  crural  arch.  It  is  apparently  a  thickening  of  the 
transversalis  fascia,  joining  externally  to  the  centre  of  Poupart's  ligament,  and 
arching  across  the  front  of  the  crural  sheath,  to  be  inserted  by  a  broad  attachment 
into  the  pectineal  line  b-ehind  the  conjoined  tendon.  In  some  subjects  this 
structure  is  not  very  prominently  marked,  and  not  infrequently  it  is  altogether 
wanting. 

The  crural  canal  is  the  narrow  interval  between  the  femoral  vein  and  the  inner 
wall  of  the  femoral  sheath.     It  exists  as  a  distinct  canal  only  when  the  sheath  has 


1060  THE  SURGICAL    ANATOMY    OF  HERNIA. 

been  separated  from  the  vein  by  dissection  or  by  the  pressure  of  a  hernia  or  tumor. 
Its  length  is  from  a  quarter  to  half  an  inch,  and  it  extends  from  Gimbernat's  liga- 
ment to  the  upper  part  of  the  saphenous  opening. 

Its  anterior  wall  is  very  narrow,  and  formed  by  a  continuation  downward  of 
the  transversalis  fascia,  under  Poupart's  ligament,  covered  by  the  falciform  process 
of  the  fascia  lata. 

Its  posterior  ivall  is  formed  by  a  continuation  downward  of  the  iliac  fascia 
covering  the  pubic  portion  of  the  fascia  lata. 

Its  outer  wall  is  formed  by  the  fibrous  septum  separating  it  from  the  inner 
side  of  the  femoral  vein. 

Its  inner  wall  is  formed  by  the  junction  of  the  processes  of  the  transversalis 
and  iliac  fasciae,  which  form  the  inner  side  of  the  femoral  sheath,  and  lies  in 
contact  at  its  commencement  with  the  outer  edge  of  Gimbernat's  ligament. 

This  canal  has  two  orifices — an  upper  one,  the  femoral  or  crural  ring,  closed 
by  the  septum  crurale ;  and  a  lower  one,  the  saphenous  opening,  closed  by  the 
cribriform  fascia. 

The  femoral  or  crural  ring  (Fig.  589)  is  the  upper  opening  of  the  femoral  canal, 
and  leads  into  the  cavity  of  the  abdomen.  It  is  bounded  in  front  by  Poupart's 
ligament  and  the  deep  crural  arch  ;  behind,  by  the  os  pubis,  covered  by  the  Pectineus 
muscle  and  the  pubic  portion  of  the  fascia  lata ;  internally,  by  the  base  of 
Gimbernat's  ligament,  the  conjoined  tendon,  the  transversalis  fascia,  and  the 
deep  crural  arch ;  externally,  by  the  fibrous  septum  lying  on  the  inner  side  of  the 
femoral  vein.  The  femoral  ring  is  of  an  oval  form ;  its  long  diameter,  directed 
transversely,  measures  about  half  an  inch,  and  it  is  larger  in  the  female  than  in 
the  male,  which  is  one  of  the  reasons  of  the  greater  frequency  of  femoral  hernia 
in  the  former  sex. 

Position  of  Parts  around  the  Ring. — The  spermatic  cord  in  the  male  and  round 
ligament  in  the  female  lie  immediately  above  the  anterior  margin  of  the  femoral 
ring,  and  may  be  divided  in  an  operation  for  femoral  hernia  if  the  incision  for  the 
relief  of  the  stricture  is  not  of  limited  extent.  In  the  female  this  is  of  little 
importance,  but  in  the  male  the  spermatic  artery  and  vas  deferens  may  be 
divided. 

The  femoral  vein  lies  on  the  outer  side  of  the  ring. 

The  deep  epigastric  artery  in  its  passage  upward  and  inward  from  the  external 
iliac  artery  passes  across  the  upper  and  outer  angle  of  the  crural  ring,  and  is 
consequently  in  danger  of  being  wounded  if  the  stricture  is  divided  in  a  direction 
upward  and  outward. 

The  communicating  branch  between  the  deep  epigastric  and  obturator  lies  in 
front  of  the  ring. 

The  circumference  of  the  ring  is  thus  seen  to  be  bounded  by  vessels  in  every 
part,  excepting  internally  and  behind.  It  is  in  the  former  position  that  the 
stricture  is  divided  in  cases  of  strangulated  femoral  hernia. 

The  obturator  artery,  when  it  arises  by  a  common  trunk  with  the  deep  epigastric, 
which  occurs  once  in  every  three  subjects  and  a  half,  bears  a  very  important 
relation  to  the  crural  ring.  In  most  cases  it  descends  on  the  inner  side  of  the 
external  iliac  vein  to  the  obturator  foramen,  and  will  consequently  lie  on  the  outer 
side  of  the  crural  ring,  where  there  is  no  danger  of  its  being  wounded  in  the 
operation  for  dividing  the  stricture  in  femoral  hernia  (see  Fig.  314,  page  565, 
fig.  a).  Occasionally,  however,  the  obturator  artery  curves  along  the  free  margin 
of  Gimbernat's  ligament  in  its  passage  to  the  obturator  foramen  :  it  would  conse- 
quently skirt  along  the  greater  part  of  the  circumference  of  the  crural  ring,  and 
oould  hardly  avoid  being  wounded  in  the  operation  (see  Fig.  314,  page  565,  fig.  b). 

Septum  Crurale. — The  femoral  ring  is  closed  by  a  layer  of  condensed  areolar 
tissue  called,  by  J.  Cloquet,  the  septum  crurale.  This  serves  as  a  barrier  to  the 
protrusion  of  a  hernia  through  this  part.  Its  upper  surface  is  slightly  concave, 
and  supports  a  small  lymphatic  gland  by  which  it  is  separated  from  the  subserous 
areolar  tissue  and  peritoneum.     Its  under  surface  is   turned  toward  the  femoral 


FEMORAL    HERNIA.  1061 

canal.  The  septum  crurale  is  perforated  by  numerous  apertures  for  the  passage  of 
lymphatic  vessels  connecting  the  deep  inguinal  lymphatic  glands  with  those  sur- 
rounding the  external  iliac  artery. 

The  size  of  the  femoral  canal,  the  degree  of  tension  of  its  orifices,  and  con- 
sequently the  degree  of  constriction  of  a  hernia,  vary  according  to  the  position  of 
the  limb.  If  the  leg  and  thigh  are  extended,  abducted,  or  everted,  the  femoral 
canal  and  its  orifices  are  rendered  tense  from  the  traction  on  these  parts  by 
Poupart's  ligament  and  the  fascia  lata,  as  may  be  ascertained  by  passing  the  finger 
along  the  canal.  If,  on  the  contrary,  the  thigh  is  flexed  upon  the  pelvis,  and  at 
the  same  time  adducted  and  rotated  inward,  the  femoral  canal  and  its  orifices 
become  considerably  relaxed ;  for  this  reason  the  limb  should  always  be  placed  in 
the  latter  position  when  the  application  of  the  taxis  is  made  in  attempting  the 
reduction  of  a  femoral  hernia. 

The  subperitoneal  areolar  tissue  is  continuous  with  the  subserous  areolar  tissue 
of  surrounding  parts.  It  is  usually  thickest  and  most  fibrous  where  the  iliac 
vessels  leave  the  abdominal  cavity.  It  covers  over  the  small  interval  (crural  ring) 
on  the  inner  side  of  the  femoral  vein.  In  some  subjects  it  contains  a  considerable 
amount  of  adipose  tissue.  In  such  cases,  where  it  is  protruded  forward  in  front 
of  the  sac  of  a  femoral  hernia,  it  may  be  mistaken  for  a  portion  of  omentum.  The 
peritoneum  lining  the  portion  of  the  abdominal  wall  between  Poupart's  ligament 
and  the  brim  of  the  pelvis  is  similar  to  that  lining  any  other  portion  of  the  abdominal 
wall,  being  very  thin.      It  has  here  no  natural  aperture  for  the  escape  of  intestine. 

Descent  of  the  Hernia. — From  the  preceding  description  it  follows  that  the 
femoral  ring  must  be  a  weak  point  in  the  abdominal  wall :  hence  it  is  that  Avhen 
violent  or  long-continued  pressure  is  made  upon  the  abdominal  viscera  a  portion 
of  intestine  may  be  forced  into  it,  constituting  a  femoral  hernia ;  and  the  changes 
in  the  tissues  of  the  abdomen  which  are  produced  by  pregnancy,  together  with  the 
larger  size  of  this  aperture  in  the  female,  serve  to  explain  the  frequency  of  this 
form  of  hernia  in  women. 

When  a  portion  of  the  intestine  is  forced  through  the  femoral  ring,  it  carries 
before  it  a  pouch  of  peritoneum,  which  forms  what  is  called  the  hernial  sac ;  it 
receives  an  investment  from  the  subserous  areolar  tissue  and  from  the  septum 
crurale,  and  descends  vertically  along  the  crural  canal  in  the  inner  compartment  of 
the  sheath  of  the  femoral  vessels  as  far  as  the  saphenous  opening  ;  at  this  point  it 
changes  its  course,  being  prevented  from  extending  farther  down  the  sheath  on 
account  of  the  narrowing  of  the  sheath  and  its  close  contact  with  the  vessels,  and 
also  from  the  close  attachment  of  the  superficial  fascia  and  crural  sheath  to  the 
lower  part  of  the  circumference  of  the  saphenous  opening  ;  the  tumor  is  conse- 
quently directed  forward,  pushing  before  it  the  cribriform  fascia,  and  then  curves 
upward  on  to  the  falciform  process  of  the  fascia  lata  and  lower  part  of  the  tendon 
of  the  External  oblique,  being  covered  by  the  superficial  fascia  and  integument. 
While  the  hernia  is  contained  in  the  femoral  canal  it  is  usually  of  small  size, 
owing  to  the  resisting  nature  of  the  surrounding  parts ;  but  when  it  has  escaped 
from  the  saphenous  opening  into  the  loose  areolar  tissue  of  the  groin,  it  becomes 
considerably  enlarged.  The  direction  taken  by  a  femoral  hernia  in  its  descent  is 
at  first  downward,  then  forward  and  upward  ;  this  should  be  borne  in  mind,  as 
in  the  application  of  the  taxis  for  the  reduction  of  a  femoral  hernia  pressure  should 
be  directed  in  the  reverse  order. 

Coverings  of  the  Hernia. — The  coverings  of  a  femoral  hernia,  from  within 
outward,  are — peritoneum,  subserous  areolar  tissue,  the  septum  crurale,  crural 
sheath,  cribriform  fascia,  superficial  fascia,  and  integument.1 

1  Sir  Astley  Cooper  has  described  an  investment  for  femoral  hernia,  under  the  name  of  "  fascia 
propria,"  lying  immediately  external  to  the  peritoneal  sac,  but  frequently  separated  from  it  by  more 
or  less  adipose  tissue.  Surgically,  it  is  important  to  remember  the  existence  (at  any  rate,  the  occa- 
sional existence)  of  this  layer,  on  account  of  the  ease  with  which  an  inexperienced  operator  may  mis- 
take the  fascia  for  the  peritoneal  sac  and  the  contained  fat  for  omentum.  Anatomically,  this  fascia 
appears  identical  with  what  is  called  in  the  text  "  subserous  areolar  tissue,"  the  areolar  tissue  being 
thickened  and  caused  to  assume  a  membranous  appearance  by  the  pressure  of  the  hernia. 


1062  THE  SURGICAL    ANATOMY   OF  HERNIA. 

Varieties  of  Femoral  Hernia. — If  the  intestine  descends  along  the  femoral  canal 
only  as  far  as  the  saphenous  opening,  and  does  not  escape  from  this  aperture,  it  is 
called  incomplete  femoral  hernia.  The  small  size  of  the  protrusion  in  this  form 
of  hernia,  on  account  of  the  firm  and  resisting  nature  of  the  canal  in  which  it  is 
contained,  renders  it  an  exceedingly  dangerous  variety  of  the  disease,  from  the 
extreme  difficulty  of  detecting  the  existence  of  the  swelling,  especially  in  corpulent 
subjects.  The  coverings  of  an  incomplete  femoral  hernia  would  be,  from  without 
inward,  integument,  superficial  fascia,  falciform  process  of  fascia  lata,  crural 
sheath,  septum  crurale,  subserous  areolar  tissue,  and  peritoneum.  When,  however, 
the  hernial  tumor  protrudes  through  the  saphenous  opening  and  directs  itself 
forward  and  upward,  it  forms  a  complete  femoral  hernia.  Occasionally  the  hernial 
sac  descends  on  the  iliac  side  of  the  femoral  vessels  or  in  front  of  these  vessels,  or 
even  sometimes  behind  them. 

The  seat  of  stricture  of  a  femoral  hernia  varies  :  it  may  be.  in  the  peritoneum 
at  the  neck  of  the  hernial  sac ;  in  the  greater  number  of  cases  it  would  appear  to 
be  at  the  point  of  junction  of  the  falciform  process  of  the  fascia  lata  with  the 
lunated  edge  of  Gimbernat's  ligament,  or  at  the  margin  of  the  saphenous  opening 
in  the  thigh.  The  stricture  should  in  every  case  be  divided  in  a  direction  upward 
and  inward,  and  the  extent  necessai*y  in  the  majority  of  cases  is  about  two  or 
three  lines.  By  these  means  all  vessels  or  other  structures  of  importance  in 
relation  with  the  neck  of  the  hernial  sac  will  be  avoided. 


SURGICAL  ANATOMY  OF  THE  PERINEUM. 


.  Dissection. — The  student  should  select  a  well-developed  muscular  subject,  free  from  fat, 
and  the  dissection  should  be  commenced  early,  in  order  that  the  parts  may  be  examined  in  as 
recent  a  state  as  possible.  A  staff  having  been  introduced  into  the  bladder  and  the  subject 
placed  in  the  position  shown  in  Fig.  590,  the  scrotum  should  be  raised  upward,  and  retained  in 
that  position,  and  the  rectum  moderately  distended  with  tow. 

The  Perinaeum  corresponds  to  the  inferior  aperture  or  outlet  of  the  pelvis. 
Its  deep  boundaries  are,  in  front,  the  pubic  arch  and  subpubic  ligament ;  behind, 
the  tip  of  the  coccyx  ;  and  on  each  side,  the  rami  of  the  os  pubis  and  ischium,  the 
tuberosities  of  the  ischium,  and  great  sacro-sciatic  ligaments.  The  space  included 
by  these  boundaries  is  somewhat  lozenge-shaped,  and  is  limited  on  the  surface  of 
the  body  by  the  scrotum  in  front,  by  the  buttocks  behind,  and  on  each  side  by  the 
inner  side  of  the  thighs.  A  line  drawn  transversely  between  the  anterior  part  of 
the  tuberosity  of  the  ischium,  on  each  side,  in  front  of  the  anus,  divides  this  space 
into  two  portions.  The  anterior  portion  contains  the  penis  and  urethra,  and  is 
called  the  perinceum  proper  or  genito-urinary  region.  The  posterior  portion  con- 
tains the  termination  of  the  rectum,  and  is  called  the  isehio-rectal  or  anal  region. 

ISCHIO-RECTAL   REGION. 

The  isehio-rectal  region  contains  the  termination  of  the  rectum  and  a  deep  fossa, 
filled  with  fat,  on  each  side  of  the  intestine,  between  it  and  the  tuberosity  of  the 
ischium:  this  is  called  the  isehio-rectal  fossa. 

The  isehio-rectal  region  presents  in  the  middle  line  the  aperture  of  the  anus : 
around  this  orifice  the  integument  is  thrown  into  numerous  folds,  which  are 
obliterated  on  distension  of  the  intestine.  The  integument  is  of  a  dark  color, 
continuous  with  the  mucous  membrane  of  the  rectum,  and  provided  wTith  numerous 
follicles,  which  occasionally  inflame  and  suppurate,  and  may  be  mistaken  for 
fistulse.  The  veins  around  the  margin  of  the  anus  are  occasionally  much  dilated, 
forming  a  number  of  hard  pendent  masses,  of  a  dark  bluish  color,  covered  partly 
by  mucous  membrane  and  partly  by  the  integument.  These  tumors  constitute  the 
disease  called  external  piles. 

Dissection  (Fig.  590). — Make  an  incision  through  the  integument,  along  the  median 
line,  from  the  base  of  the  scrotum  to  the  anterior  extremity  of  the  anus :  carry  it  round  the 
margins  of  this  aperture  to  its  posterior  extremity,  and  continue  it  backward  to  about  an  inch 
behind  the  tip  of  the  coccyx.  A  transverse  incision  should  now  be  carried  across  the  base  of 
the  scrotum,  joining  the  anterior  extremity  of  the  preceding  ;  a  second,  carried  in  the  same 
direction,  should  be  made  in  front  of  the  anus ;  and  a  third  at  the  posterior  extremity  of  the 
first  incision.  These  incisions  should  be  sufficiently  extensive  to  enable  the  dissector  to  raise  the 
integument  from  the  inner  side  of  the  thighs.  The  flaps  of  skin  corresponding  to  the  ischio- 
rectal region  should  now  be  removed.  In  dissecting  the  integument  from  this  region  great  care 
is  required,  otherwise  the  Corrugator  cutis  ani  and  External  sphincter  will  be  removed,  as  they 
are  intimately  adherent  to  the  skin. 

The  superficial  fascia  is  exposed  on  the  removal  of  the  skin :  it  is  very  thick, 
areolar  in  texture,  and  contains  much  fat  in  its  meshes.  In  it  are  found  ramifying 
two  or  three  branches  of  the  perforating  cutaneous  nerve ;  these  turn  round  the 
inferior  border  of  the  Gluteus  maximus  and  are  distributed  to  the  integument 
around  the  anus. 

In  this  region,   and  connected  with  the  lower  end  of  the  rectum,   are  four 

1063 


1064  SUBGICAL   ANATOMY  OF   THE  PERINEUM. 

muscles :  the  Corrugator  cutis  ani ;  the  two  Sphincters,  External  and  Internal ; 
and  the  Levator  ani. 

These  muscles  have  been  already  described  (see  page  368). 

The  ischio-rectal  fossa  is  situated  between  the  end  of  the  rectum  and  the 
tuberosity  of  the  ischium.  It  is  triangular  in  shape ;  its  base,  directed  to  the 
surface  of  the  body,  is  formed  by  the  integument  of  the  ischio-rectal  region ;  its 
apex,  directed  upward,  corresponds  to  the  point  of  division  of  the  obturator  fascia 
and  the  thin  membrane  given  off  from  it,  which  covers  the  outer  surface  of  the 
Levator  ani  (ischio-rectal  or  anal  fascia).  Its  dimensions  are  about  an  inch  in 
breadth  at  the  base  and  about  two  inches  in  depth,  being  deeper  behind  than  in 
front.  It  is  bounded,  internally,  by  the  Sphincter  ani,  Levator  ani,  and  Coc- 
cygeus  muscles ;  externally,  by  the  tuberosity  of  the  ischium  and  the  obturator 
fascia,  which  covers  the  inner  surface  of  the  Obturator  internus  muscle;  in  front, 
it  is  limited  by  the  line  of  junction  of  the  superficial  fascia  with  the  base  of  the 
triangular  ligament ;  and  behind,  by  the  margin  of  the  Gluteus  maximus  and  the 
great  sacro-sciatic  ligament.  This  space  is  filled  with  a  large  mass  of  adipose 
tissue,  which  explains  the  frequency  with  which  abscesses  in  the  neighborhood  of 
the  rectum  burrow  to  a  considerable  depth. 

If  the  subject  has  been  injected,  on  placing  the  finger  on  the  outer  wall  of  this 
fossa  the  internal  pudic  artery,  with  its  accompanying  veins  and  the  two  divisions 
of  the  nerve,  will  be  felt  about  an  inch  and  a  half  above  the  margin  of  the  ischiatic 
tuberosity,  but  approaching  nearer  the  surface  as  they  pass  forward  along  the  inner 
margin  of  the  pubic  arch.  These  structures  are  enclosed  in  a  sheath  (canal  of 
Alcock)  formed  by  the  obturator  fascia,  the  pudic  nerve  lying  below  the  artery 
and  the  dorsal  nerve  of  the  penis  above  it  (Fig.  315).  Crossing  the  space  trans- 
versely, about  its  centre  are  the  inferior  hemorrhoidal  vessels  and  nerves,  which 
are  distributed  to  the  integument  of  the  anus  and  to  the  muscles  of  the  lower  end 
of  the  rectum.  These  vessels  are  occasionally  of  large  size,  and  may  give  rise  to 
troublesome  hemorrhage  when  divided  in  the  operation  of  lithotomy  or  in  that  for 
fistula  in  ano.  At  the  back  part  of  this  space,  near  the  coccyx,  may  be  seen  a 
branch  of  the  fourth  sacral  nerve,  and  at  the  fore  part  of  the  space  the  superficial 
perineal  vessels  and  nerves  can  be  seen  for  a  short  distance. 

THE  PERINJEUM  PROPER  IN  THE  MALE. 

The  perineal  space  is  of  a  triangular  form ;  its  deep  boundaries  are  limited, 
laterally,  by  the  rami  of  the  pubic  bones  and  ischia,  meeting  in  front  at  the  pubic 
arch ;  behind,  by  an  imaginary  transverse  line  extending  between  the  anterior 
parts  of  the  tuberosities  of  the  ischia.  The  lateral  boundaries  are,  in  the  adult, 
from  three  inches  to  three  inches  and  a  half  in  length,  and  the  base  from  two  to 
three  inches  and  a  half  in  breadth,  the  average  extent  of  the  space  being  two 
inches  and  three-quarters. 

The  variations  in  the  diameter  of  this  space  are  of  extreme  interest  in  connection  with  the 
operation  of  lithotomy  and  the  extraction  of  a  stone  from  the  cavity  of  the  bladder.  In  those 
cases  where  the  tuberosities  of  the  ischia  are  near  together  it  would  be  necessary  to  make  the 
incisions  in  the  lateral  operation  of  lithotomy  less  oblique  than  if  the  tuberosities  were  widely 
separated,  and  the  perineal  space  consequently  wider.  The  perinaeurn  is  subdivided  by  the 
median  raphe  into  two  equal  parts.  Of  these,  the  left  is  the  one  in  which  the  operation  of 
lithotomy  is  performed. 

In  the  middle  line  the  perinseum  is  convex,  and  corresponds  to  the  bulb  of  the 
urethra.  The  skin  covering  it  is  of  a  dark  color,  thin,  freely  movable  upon  the 
subjacent  parts,  and  covered  with  sharp  crisp  hairs,  which  should  be  removed 
before  the  dissection  of  the  part  is  commenced.  In  front  of  the  anus  a  prominent 
line  commences,  the  raphe,  continuous  in  front  with  the  raphe  of  the  scrotum. 

Upon  removing  the  skin  and  superficial  structures  from  this  region,  in  the 
manner  shown  in  Fig.  590,  a  plane  of  fascia  will  be  exposed,  covering  in  the 
triangular  space  and  stretching  across  from  one  ischio-pubic  ramus  to  the  other. 
This  is  the  deep  layer  of  the  superficial  fascia  or  fascia  of  Colles.     It  has  already 


0    ^ 


THE   PERINEUM  PROPER    IN   THE   MALE. 


1065 


been  described  (page  370).  It  is  a  layer  of  considerable  strength,  and  encloses  and 
covers  a  space  in  which  are  contained  muscles,  vessels,  and  nerves.  It  is  continu- 
ous in  front  with  the  dartos  of  the  scrotum  ;  on  each  side  it  is  firmly  attached  to 
the  margin  of  the  ischio-pubic  ramus  and  to  the  tuberosity  of  the  ischium ;  and 
posteriorly  it  curves  down  behind  the  Trans  versus  perinaei  muscles  to  join  the  base 
of  the  triangular  ligament. 

It  is  between  this  layer  of  fascia  and  the  triangular  ligament  of  the  urethra  that  extravasa- 
tion of  urine  most  frequently  takes  place  in  cases  of  rupture  of  the  urethra.  The  triangular 
ligament  of  the  urethra  (see  page  373)  is  attached  to  the  ischio-pubic  rami,  and  in  front  to  the 
subpubic  ligament.  It  is  clear,  therefore,  that  when  extravasation  of  fluid  takes  place  between 
these  two  layers,  it  cannot  pass  backward,  because  the  two  layers  are  continuous  with  each  other 
around  the  Transversi  perinaai  muscles  :  it  cannot  extend  laterally,  ,on  account  of  the  connection 
of  both  these  layers  to  the  rami  of  the  os  pubis  and  ischium ;  it  cannot  find  its  way  into  the 
pelvis,  because  the  opening  into  this  cavity  is  closed  by  the  triangular  ligament,  and,  therefore, 
so  long  as  these  two  layers  remain  intact,  the  only  direction  in  which  the  fluid  can  make  its  way 
is  forward  into  the  areolar  tissue  of  the  scrotum  and  penis,  and  then  on  to  the  anterior  wall  of 
the  abdomen. 

When  the  deep  layer  of  the  superficial  fascia  is  removed,  a  space  is  exposed, 
between  this  fascia  and  the  triangular  ligament,  in  which  are  contained  the  super- 
ficial perineal  vessels  and  nerves  and  some  of  the  muscles  connected  with  the  penis 
and  urethra,  viz.,  in  the  middle  line,  the  Accelerator  urinae  ;  on  each  side,  the 
Erector  penis;  and  behind,  the  transversus  perinsei ;  together  with  the  crura  of 
the  corpora  cavernosa  and  the  bulb  of  the  corpus  spongiosum.  Here  also  is  seen 
the  central  tendinous  point  of  the  perineum.  This  is  a  fibrous  point  in  the  middle 
line  of  the  perineum  between  the  urethra  and  the  rectum,  being  about  half  an  inch 
in  front  of  the  anus.     At  this  point  four  muscles  converge  and  are  attached,  viz., 


Fig.  590.— Dissection  of  perinaeum  and  ischio-rectal  region. 


the  External  sphincter  ani,  the  Accelerator  urinae,  and  the  two  Transversi  perinsei 
muscles ;  so  that  by  the  contraction  of  these  muscles,  which  extend  in  opposite 
directions,  it  serves  as  a  fixed  point  of  support. 

The  Accelerator  urinae,  the  Erector  penis,  and  the  Transversus  perinaei  muscles 
have  been  already  described  (page  371).  They  form  a  triangular  space,  bounded, 
internally,  by  the  Accelerator  urinae ;  externally,  by  the  Erector  penis ;  and 
behind,  by  the  Transversus  perinaei.  The  floor  of  this  space  is  formed  by  the 
triangular  ligament  of  the  urethra ;  and  running  from  behind  forward  in  it  are  the 
superficial  perineal  vessels  and  nerves,  and  the  transverse  perineal  artery  coursing 
along  the  posterior  boundary  of  the  space,  on  the  Transversus  perinaei  muscle. 

The  Accelerator  urinae  and  Erector  penis  should  now  be  removed,  when  the  triangular  liga- 
ment of  the  urethra  will  be  exposed,  stretching  across  the  front  of  the  outlet  of  the  pelvis. 
The  urethra  is  seen  perforating  its  centre,  just  behind  the  bulb ;  and  on  each  side  is  the  crus 
penis,  connecting  the  corpus  cavernosum  with  the  rami  of  the  ischium  and  os  pubis. 

The  Triangular  Ligament,  which  has  already  been  described  (see  page  373), 
consists  of  two   layers,   the   inferior   superficial   layer  of  which   is  now   exposed. 


1066 


SURGICAL    ANATOMY   OF    THE   PEBINJEVM. 


It  is  united  to  the  superior  or  deep  layer  behind,  but  is  separated  in  front  by  a 
subfascial  space  in  which  are  contained  certain  structures. 

The  inferior  layer  of  the  triangular  ligament  consists  of  a  strong  fibrous  mem- 
brane, the  fibres  of  which  are  disposed  transversely,  which  stretches  across  from 
one  ischio-pubic  ramus  to  the  other  and  completely  fills  in  the  pubic  arch  ;  it  is 
attached  in  front  to  the  subpubic  ligament,  except  just  in  the  centre,  where  a  small 
interspace  is  left  for  the  dorsal  vein  of  the  penis.  In  the  erect  position  of  the  body 
it  is  almost  horizontal.  It  is  perforated  by  the  urethra  in  the  middle  line,  and  on 
each  side  of  the  urethral  opening  by  the  ducts  of  Cowper's  glands  and  by  the 
arteries  of  the  bulb  ;  in  front,  and  external  to  this,  by  the  artery  of  the  corpus 
cavernosum,  immediately  before  this  vessel  enters  the  crus  penis.  Near  its  apex 
the  ligament  is  perforated  by  the  termination  of  the  pudic  artery  and  by  the  dorsal 
nerve  of  the  penis.  The  crura  penis  are  exposed,  lying  superficial  to  this  liga- 
ment. They  will  be  seen  to  be  attached  by  blunt-pointed  processes  to  the  rami  of 
the  os  pubis  and  ischium,  in  front  of  the  tuberosities,  and  passing  forward  and 
inward,  joining  to  form  the  body  of  the  penis.  In  the  middle  line  the  bulb  and 
corpus  spongiosum  are  exposed  by  the  removal  of  the  Accelerator  urinae  muscle. 


GREAT   SACRO- 
SCIATIC    LIGAMENT. 


Superficial  perineal  artery. 
Superficial  perineal  nerve. 
Internal  pudic  nerve. 
Internal  pudic  artery. 


Fig.  591.— The  superficial  muscles  and  vessels  of  the  perinseum. 

If  the  superficial  layer  of  the  deep  perineal  fascia  is  detached  on  either  side, 
the  deep  perineal  interspace  will  be  exposed  and  the  following  parts  will  be  seen 
between  it  and  the  deep  layer  of  the  ligament :  the  subpubic  ligament  in  front, 
close  to  the  symphysis  pubis ;  the  dorsal  vein  of  the  penis ;  the  membranous 
portion  of  the  urethra  and  the  Compressor  urethrge  muscle ;  Cowper's  glands  and 
their  ducts ;  the  pudic  vessels  and  the  dorsal  nerve  of  the  penis ;  the  artery  and 
nerve  of  the  bulb  and  a  plexus  of  veins. 

The  superior  layer  of  tJie  triangular  ligament,  or  deep  perineal  fascia,  is  derived 
from  the  obturator  fascia,  and  is  continuous  with  it  along  the  pubic  arch.  Behind, 
it  joins  with  the  superficial  layer  of  the  triangular  ligament,  and  is  continuous 
with  the  anal  fascia.  Above  it  is  the  prostate  gland,  supported  by  the  anterior 
fibres  of  the  Levator  ani,  which  act  as  a  sling  for  the  gland  and  form  the  Levator 
prostata   muscle.     The  superior  layer  of  the  triangular  ligament   is   continuous 


THE   PERINJETJM  PROPER    IN    THE   MALE. 


1067 


round  the  anterior  free  edge  of  this  muscle  with  the  recto-vesical  layer  covering 
the  prostate  gland.  The  superior  layer  of  the  triangular  ligament  is  perforated 
by  the  urethra.  Between  the  two  layers  of  the  triangular  ligament  are  situated 
Ine  membranous  part  of  the  urethra,  enveloped  by  the  Compressor  urethrse  muscle ; 
the  ducts  of  Cowper's  glands  ;  the  arteries  to  the  bulb ;  the  pudic  vessels  and  the 
iorsal  nerve  of  the  penis.  The  membranous  part  of  the  urethra  is  about  three- 
quarters  of  an  inch  in  length,  and  passes  downward  and  forward  behind  the 
symphysis  pubis,  from  which  it  is  distant  about  an  inch.  It  is  the  narrowest  part 
)f  the  tube,  and  is  enveloped,  as  has  already  been  stated,  by  the  Compressor 
arethrse  muscle. 

The  Compressor  urethrse  has  already  been  described  (page  374).  In  addition  to 
;his  muscle  and  immediately  beneath  it  circular  muscular  fibres  surround  the  mem- 
branous portion  of  the  urethra  from  the  bulb  in  front  to  the  prostate  behind,  and  are 
jontinuous  with  the  muscular  fibres  of  the  bladder.     These  fibres  are  involuntary. 

Cowper's  glands  are  situated  immediately  below  the  membranous  portion  of 
;he  urethra,  close  behind  the  bulb,  and  below  the  artery  of  the  bulb. 


Anterior  layer  of 

deep  perineal  fascia  removed, 

showing 

^COMPRESSOR    URETHRiE. 

JLnternal  pudic  artery. 
-Artery  of  the  bidb. 
Cowper's  gland. 


Fig.  592.— Deep  perineal  fascia.    On  the  left  side  the  anterior  layer  has  been  removed. 

The  pudic  vessels  and  dorsal  nerve  of  the  penis  are  placed  along  the  inner  mar- 
gin of  the  pubic  arch  (pages  565  and  793). 

The  artery  of  the  bulb  passes  transversely  inward,  from  the  internal  pudic 
along  the  base  of  the  triangular  ligament,  between  its  two  layers,  accompanied  by 
a  branch  of  the  pudic  nerve  (page  567).  If  the  deep  layer  of  the  triangular 
ligament  is  removed  and  the  crus  penis  of  one  side  detached  from  the  bone,  the 
under  or  perineal  surface  of  the  Levator  ani  is  brought  fully  into  view.  This 
muscle,  with  the  triangular  ligament  in  front  and  the  Coccygeus  and  Pyriformis 
behind,  closes  the  outlet  of  the  pelvis. 

The  Levator  ani  and  Coccygeus  muscles  have  already  been  described  (page  369). 

Position  of  the  Viscera  at  the  Outlet  of  the  Pelvis.— Divide  the  central  tendinous  point 
of  the  perinaeum,  separate  the  rectum  from  its  connections  by  dividing  the  fibres  of  the  Levator 
ani,  which  descend  upon  the  sides  of  the  prostate  gland,  and  draw  the  gut  backward  toward  the 
coccyx,  when  the  under  surface  of  the  prostate  gland,  the  neck  and  base  of  the  bladder,  the 
vesiculas  seminales,  and  the  vasa  deferentia  will  be  exposed. 


1068 


SURGICAL    ANATOMY   OF    THE   PERINEUM. 


The  Prostate  Gland  is  a  pale,  firm,  glandular  body  which  is  placed  immediately 
below  the  neck  of  the  bladder,  around  the  commencement  of  the  urethra.  It  is 
placed  in  the  pelvic  cavity,  behind  the  lower  part  of  the  symphysis  pubis,  above 
the  deep  layer  of  the  triangular  ligament,  and  rests  upon  the  rectum,  through 
which  it  may  be  distinctly  felt,  especially  when  enlarged.  In  shape  and  size  it 
resembles  a  chestnut.  Its  base  is  directed  upward  toward  the  neck  of  the  bladder. 
Its  apex  is  directed  downward  to  the  deeper  layer  of  the  triangular  ligament, 
which  it  touches. 

Its  posterior  surface  is  smooth,  marked  by  a  slight  longitudinal  furrow,  and  rests 
on  the  second  part  of  the  rectum,  to  which  it  is  connected  by  areolar  tissue.  Its 
anterior  surface  is  flattened,  marked  by  a  slight  longitudinal  furrow,  and  placed 
about  three-quarters  of  an  inch  below  the  pubic  symphysis.  It  measures  about 
an  inch  and  a  half  in  its  transverse  diameter  at  the  base,  an  inch  in  its  antero- 
posterior diameter,  and  three-quarters  of  an  inch  in  depth.  Hence  the  greatest 
extent  of  incision  that  can  be  made  in  it  without  dividing  its  substance  completely 
across  is  obliquely  backward  and  outward.  This  is  the  direction  in  which  the 
incision  is  made  in  it  in  the  lateral  operation  of  lithotomy. 


Artery  of  corpus  cavernosum 
Dorsal  artery  of  penis 


Artery  of  bulb. 
Internal  pudic  artery. 


Cowper's  gland 


Fig.  593.— A  view  of  the  position  of  the  viscera  at  the  outlet  of  the  pelvis. 


Above  the  prostate  a  small  triangular  portion  of  the  bladder  is  seen,  bounded, 
in  front  and  below,  by  the  prostate  gland ;  above,  by  the  recto-vesical  fold  of  the 
peritoneum  ;  on  each  side,  by  the  vesicula  seminalis  and  the  vas  deferens.  It  is 
separated  from  direct  contact  with  the  rectum  by  the  recto-vesical  fascia.  The 
relation  of  this  portion  of  the  bladder  to  the  rectum  is  of  extreme  interest  to  the 
surgeon.  In  cases  of  retention  of  urine  this  portion  of  the  organ  is  found  pro- 
jecting into  the  rectum,  between  three  and  four  inches  from  the  margin  of  the 
anus,  and  may  be  easily  perforated  without  injury  to  any  important  parts:  this 
portion  of  the  bladder  is,  consequently,  occasionally  selected  for  the  performance 
of  the  operation  of  tapping  the  bladder. 

Surgical  Anatomy. — The  student  should  consider  the  position  of  the  various  parts  in  refer 
ence  to  the  lateral  operation  of  lithotomy.  This  operation  is  performed  on  the  left  side  of  the  peri 
naeum,  as  it  is  most  convenient  for  the  right  hand  of  the  operator.     A  grooved  staff  having  beer 


THE   FEMALE   PEBINJEUM.  1069 

introduced  into  the  bladder,  the  first  incision  is  commenced  midway  between  the  anus  and  the 
back  of  the  scrotum  {%.  e.  in  an  ordinary  adult  perinseum  about  an  inch  and  a  half  in  front  of 
the  anus)  a  little  on  the  left  side  of  the  raphe,  and  carried  obliquely  backward  and  outward  to 
midway  between  the  anus  and  tuberosity  of  the  ischium.  The  incision  divides  the  integument 
and  superficial  fascia,  the  inferior  hemorrhoidal  vessels  and  nerves,  and  the  superficial  and  trans- 
verse perineal  vessels.  If  the  forefinger  of  the  left  hand  is  thrust  upward  and  forward  into 
the  wound,  pressing  at  the  same  time  the  rectum  inward  and  backward,  the  staff  may  be  felt  in 
the  membranous  portion  of  the  urethra.  The  finger  is  fixed  upon  the  staff,  and  the  structures 
covering  it  are  divided  with  the  point  of  the  knife,  which  must  be  directed  along  the  groove  toward 
the  bladder,  the  edge  of  the  knife  being  turned  outward  and  backward,  dividing  in  its  course 
the  membranous  portion  of  the  urethra  and  part  of  the  left  lobe  of  the  prostate  gland  to  the 
extent  of  about  an  inch.  The  knife  is  then  withdrawn,  and  the  forefinger  of  the  left  hand 
passed  along  the  staff  into  the  bladder.  The  position  of  the  stone  having  been  ascertained,  the 
staff  is  to  be  withdrawn,  and  the  forceps  is  introduced  over  the  finger  into  the  bladder.  If  the 
stone  is  very  large, _  the  opposite  side  of  the  prostate  may  be  notched  before  the  forceps  is  intro- 
duced :  the  finger  is  now  withdrawn,  and  the  blades  of  the  forceps  opened  and  made  to  grasp 
the  stone,  which  must  be  extracted  \>y  slow  and  cautious  undulating  movements. 

Parts  Divided  in  the  Operation. — The  various  structures  divided  in  this  operation  are  as 
follows  :  the  integument,  superficial  fascia,  inferior  haemorrhoidal  vessels  and  nerves,  and  prob- 
ably the  superficial  perineal  vessels  and  nerves,  the  posterior  fibres  of  the  Accelerator  urinse,  the 
Transversus  perinaei  muscle  and  artery,  the  triangular  ligament,  the  anterior  fibres  of  the 
Levator  ani,  part  of  the  Compressor  urethras,  the  membranous  and  prostatic  portions  of  the 
urethra,  and  part  of  the  prostate  gland. 

Parts  to  be  Avoided  in  the  Operation. — In  making  the  necessary  incisions  in  the  peri- 
naeum  for  the  extraction  of  a  calculus  the  following  parts  should  be  avoided  :  The  primary  incis- 
ion should  not  be  made  too  near  the  middle  line,  for  fear  of  wounding  the  bulb  of  the  corpus 
spongiosum  or  the  rectum  ;  nor  too  far  externally,  otherwise  the  pudic  artery  may  be  implicated 
as  it  ascends  along  the  inner  border  of  the  pubic  arch.  If  the  incisions  are  carried  too  far 
forward,  the  artery  of  the  bulb  may  be  divided ;  if  carried  too  far  backward,  the  entire  breadth 
of  the  prostate  and  neck  of  the  bladder  may  be  cut  through,  which  allows  the  urine  to  become 
infiltrated  behind  the  pelvic  fascia  into  the  loose  areolar  tissue  between  the  bladder  and  rectum, 
instead  of  escaping  externally  ;  diffuse  inflammation  is  consequently  set  up,  and  peritonitis,  from 
the  close  proximity  of  the  recto-vesical  peritoneal  fold,  is  the  result.  If,  on  the  contrary,  only 
the  anterior  part  of  the  prostate  is  divided,  the  urine  makes  its  way  externally,  and  there  is 
less  danger  of  infiltration  taking  place. 

During  the  operation  it  is  of  great  importance  that  the  finger  should  be  passed  into  the 
bladder  before  the  staff  is  removed ;  if  this  is  neglected,  and  if  the  incision  made  in  the  prostate 
and  neck  of  the  bladder  is  too  small,  great  difficulty  may  be  experienced  in  introducing  the 
finger  afterward ;  and  in  the  child,  where  the  connections  of  the  bladder  to  the  surrounding 
parts  are  very  loose,  the  force  made  in  the  attempt  is  sufficient  to  displace  the  bladder  upward 
into  the  abdomen,  out  of  the  reach  of  the  operator.  Such  a  proceeding  has  not  unfrequently 
occurred,  producing  the  most  embarrassing  results  and  total  failure  of  the  operation. 

It  is  necessary  to  bear  in  mind  that  the  arteries  in  the  perinaeum  occasionally  take  an  abnor- 
mal course.  Thus  the  artery  of  the  bulb,  when  it  arises,  as  sometimes  happens,  from  the  pudic 
opposite  the  tuber  ischii,  is  liable  to  be  wounded  in  the  operation  for  lithotomy  in  its  passage 
forward  to  the  bulb.  The  accessory  pudic  may  be  divided  near  the  posterior  border  of  the  pros- 
tate gland,  if  this  is  completely  cut  across  ;  and  the  prostatic  veins,  especially  in  people  advanced 
in  life,  are  of  large  size,  and  give  rise,  when  divided,  to  troublesome  haemorrhage. 

THE    FEMALE    PERINEUM. 

The  female  perinaeum  presents  certain  differences  from  that  of  the  male,  in 
consequence  of  the  whole  of  the  structures  which  constitute  it  being  perforated 
in  the  middle  line  by  the  vulvo-vaginal  passage. 

The  superficial  fascia,  as  in  the  male,  consists  of  two  layers,  of  which  the 
superficial  one  is  continuous  with  the  superficial  fascia  over  the  rest  of  the  body. 
and  the  deep  layer,  corresponding  to  the  fascia  of  Colles  in  the  male,  is  like  it 
attached  to  the  ischio-pubic  ramus,  and  in  front  is  continued  forward  through 
the  labia  majora  to  the  inguinal  region.  It  is  of  less  extent  than  the  male,  in 
consequence  of  being  perforated  by  the  aperture  of  the  vulva. 

On  removing  this  fascia  the  muscles  of  the  female  perinasum,  which  have 
already  been  described  (page  374),  are  exposed.  The  Sphincter  vaginas,  corre- 
sponding to  the  Accelerator  urinas  in  the  male,  consists  of  an  attenuated  plane  of 
fibres,  forming  an  orbicular  muscle  around  the  orifice  of  the  vagina,  instead  of 
being  united  in  a  median  raphe,  as  in  the  male.  The  Erector  clitoridis  is  propor- 
tionately reduced  in  size,  but  differs  in  no  other  respect,  and  the  Transversus 
perinaei  is  similar  to  the  muscle  of  the  same  name  in  the  male. 


1070 


SURGICAL    ANATOMY    OF    THE   PEBINJEUM. 


The  triangular  ligament  of  the  urethra  is  not  strongly  marked  as  in  the  male. 
It  transmits  the  urethra  and  the  tube  of  the  vagina. 

The  Compressor  Urethrae  (Transversus  perincei  profundus)  corresponds  with 
the  Compressor  urethrae  in  the  male.  It  arises  from  the  ischio-pubic  ramus,  and, 
passing  inward,  its  anterior  fibres  blend  with  the  muscle  of  the  opposite  side,  in 
front  of  the  urethra ;  its  middle  fibres,  the  most  numerous,  are  inserted  into  the 
side  of  the  vagina,  and  the  posterior  fibres  join  the  central  point  of  the  perinaeum. 

The  distribution  of  the  internal  pudic  artery  is  the  same  as  in  the  male  (see 
page  567),  and  the  pudic  nerve  has  also  a  similar  arrangement,  the  dorsal  nerve 
being,  however,  very  small  and  supplying  the  clitoris. 

The  corpus  spongiosum  is  divided  into  two  lateral  halves,  which  are  represented 
by  the  bulbi  vestibuli  and  partes  intermediales  (see  page  1027). 

The  perineal  body  fills  up  the  interval  between  the  lower  part  of  the  vagina 
and  the   rectum.     Its  base  is  covered  by  the  skin  lying  between  the  anus  and 


Internal  pudic  vessels 
and  nerve. 


Tuberosity  of 
ischium. 

Fig.  594.— A  transverse  section  of  the  pelvis,  showing  the  pelvic  fascia  from  behind. 


vagina  on  what  is  called  the  "perinaeum."  Its  anterior  surface  lies  behind  the 
posterior  vaginal  wall,  and  its  posterior  surface  lies  in  front  of  the  anterior  rectal 
wall  and  the  anus.  It  measures  about  an  inch  and  a  quarter  from  before  backward, 
and  laterally  extends  from  one  tuberosity  of  the  ischium  to  the  other.  In  it  are 
situated  the  muscles  belonging  to  the  external  organs  of  generation.  Through  its 
centre  runs  the  transverse  perineal  septum,  which  is  of  great  strength  in  women, 
and  forms  on  either  side,  behind  the  posterior  commissure,  a  hard,  ill-defined  body, 
consisting  of  connective  tissue,  with  much  yellow  elastic  tissue  and  interlacing 
bundles  of  involuntary  muscular  fibres,  in  which  the  voluntary  muscles  of  the  peri- 
nseum  are  inserted. 

THE    PELVIC   FASCIA. 

The  Pelvic  fascia  (Fig.  595)  is  a  thin  membrane  which  lines  the  whole  of  the 
cavity  of  the  pelvis  and  is  continuous  over  the  back  part  of*  the  ilio-pectineal  line 
with  the   iliac  fossa.     It  is  attached  to  the   brim  of  the  pelvis,   for  a  short  dis- 


THE   PELVIC  FASCIA. 


1071 


tance,  at  the  side  of  the  cavity,  and  to  the  inner  surface  of  the  bone  round  the 
attachment  of  the  Obturator  internus.  At  the  posterior  border  of  this  muscle  it  is 
continued  backward  as  a  very  thin  membrane  in  front  of  the  Pyriformis  muscle 
and  sacral  nerves  to  the  front  of  the  sacrum.  In  front  it  follows  the  attachment 
of  the  Obturator  internus  to  the  bone,  arches  beneath  the  obturator  vessels,  com- 
pleting the  orifice  of  the  obturator  canal,  and  at  the  front  of  the  pelvis  is  attached 
to  the  lower  part  of  the  symphysis  pubis.  At  the  level  of  a  line  extending  from 
the  lower  part  of  the  symphysis  pubis  to  the  spine  of  the  ischium  is  a  thickened 
whitish  band,  termed  the  white  line ;  this  marks  the  attachment  of  the  Levator  ani 
muscle  to  the  pelvic  fascia,  and  corresponds  to  its  point  of  division  into  two  layers, 
the  obturator  and  recto-vesical. 

The  obturator  fascia  descends  and  covers  the  Obturator  internus  muscle.  It  is 
a  direct  continuation  of  the  parietal  pelvic  fascia  below  the  white  line  above  men- 
tioned, and  is  attached  to  the  pelvic  arch,  the  ischial  tuberosities,  and  to  the  mar- 
gin of  the  great  sacro-sciatic  ligaments.     This  fascia  forms  a  canal  for  the  pudic 


Fig.  595.— Side  view  of  the  pelvic  viscera  of  the  male  subject,  showing  the  pelvic  and  perineal  fasciae. 

vessels  and  nerve  in  their  passage  forward  to  the  perinaeum,  and  gives  off  a  thin 
membrane  which  covers  the  perineal  aspect  of  the  Levator  ani  muscle,  called  the 
ischio-rectal  {anal)  fossa.  From  its  attachment  to  the  rami  of  the  os  pubis  and 
ischium  a  process  is  given  off  which  is  continuous  with  a  similar  process  from  the 
opposite  side,  so  as  to  close  the  front  part  of  the  outlet  of  the  pelvis,  forming  the 
deep  layer  of  the  triangular  ligament. 

The  recto-vesical  fascia  {visceral  layer  of  the  pelvic  fascia)  descends  into  the 
pelvis  upon  the  upper  surface  of  the  Levator  ani  muscle,  and  invests  the  prostate, 
bladder,  and  rectum.  From  the  inner  surface  of  the  symphysis  pubis  a  short 
rounded  band  is  continued,  on  each  side  of  the  middle  line,  to  the  upper  surface  of 
the  prostate  and  neck  of  the  bladder,  forming  the  pubo-prostatic  or  anterior  true  lig- 
aments of  the  bladder.  At  the  side  this  fascia  is  connected  to  the  side  of  the  pros- 
tate, enclosing  this  gland  and  the  vesico-prostatic  plexus  of  veins,  and  is  continued 


1072  SURGICAL   ANATOMY    OF    THE  PERINEUM. 

on  to  the  side  of  the  bladder,  forming  the  lateral  true  ligaments  of  the  organ. 
Another  prolongation  invests  the  vesiculse  seminales,  and  passes  across  between 
the  bladder  and  rectum,  being  continuous  with  the  same  fascia  of  the  opposite  side. 
Another  thin  prolongation  is  reflected  round  the  surface  of  the  lower  end  of  the 
rectum.  The  Levator  ani  muscle  arises  from  the  point  of  division  of  the  pelvic 
fascia,  the  visceral  layer  of'the  fascia  descending  upon  and  being  intimately  adher- 
ent to  the  upper  surface  of  the  muscle,  while  the  under  surface  of  the  muscle  is 
covered  by  a  thin  layer  derived  from  the  obturator  fascia,  called  the  ischio-rectal  or 
anal  fascia.  In  the  female  the  vagina  perforates  the  recto-vesical  fascia,  and 
receives  a  prolongation  from  it. 


GENERAL  ANATOMY  OR  HISTOLOGY. 


THE  ANIMAL  CELL  (Fig.  596). 

ALL  the  tissues  and  organs  of  which  the  body  is  composed  were  originally 
developed  from  a  microscopic  body  (the  ovum),  consisting  of  a  soft  gelatinous 
granular  material  enclosed  in  a  membrane,  and  containing  a  vesicle,  or  small 
spherical  body,  inside  which  are  one  or  more  solid  spots.  This  may  be  regarded 
as  a  perfect  cell.  Moreover,  all  the  solid  tissues  can  be  shown  to  consist  largely 
of  similar  bodies  or  cells,  differing,  it  is  true,  in  external  form,  but  essentially 
similar  to  an  ovum. 

In  the  higher  organisms  all  such  cells  may  be  defined  as  "  nucleated  masses  of 
protoplasm   of  microscopic  size."     The   two  essentials,  therefore,   of  an  animal 


Cell  wall. 

Attraction  sphere  (centro- 

sphere)  enclosing  two 

centrosomes. 
■Nuclear  membrane. 

Nucleus. 

Chromatin  network. 

Net-knot  of  chromatin  form- 
ing a  pseudo-nucleus. 


Vacuoles. 


■Fat  granules. 


Fig.  596.— Diagram  of  a  cell.    (Modified  from  Wilson.) 


cell  in  the  higher  organisms  are,  the  presence  of  a  soft  gelatinous  granular 
material,  similar  to  that  found  in  the  ovum,  and  which  is  usually  styled  proto- 
plasm ;  and  a  small  spherical  body  imbedded  in  it,  and  termed  a  nucleus  ;l  the 
remaining  constituents  of  the  ovum — viz.,  its  limiting  membrane  and  the  solid 
spot  contained  in  the  nucleus,  called  the  nucleolus — are  not  considered  essential 
to  the  cell,  and  in  fact  many  cells  exist  without  them. 

Protoplasm  [cytoplasm)  is  a  material  probably  of  variable  constitution,  but 
yielding  to  the  chemist  on  its  disintegration  bodies  chiefly  of  proteid  nature. 
Lecithin  and  cholesterin  are  constantly  found  in  it,  as  well  as  inorganic  salts, 
chief  among  which  are  the  phosphates  and  chlorides  of  the  alkali  metals  and  cal- 
cium. It  is  of  a  semifluid,  viscid  consistence,  and  appears  either  as  a  hyaline  sub- 
stance, homogeneous  and  clear,  or  else  it  exhibits  a  granular  appearance.    This  gran- 

1  In  certain  lower  forms  of  life  masses  of  protoplasm  without  a  nucleus  have  been  described  by 
Huxlev  and  others  as  cells. 


6S 


1073 


1074  GENERAL    ANATOMY   OR    HISTOLOGY. 

ular  appearance,  under  a  high  power  of  the  microscope,  is  seen  to  be  due  to  the  fact 
that  protoplasm  consists  of  a  network  or  honeycombed  reticulum,  containing  in  its 
meshes  a  homogeneous  substance.  The  former  is  known  as  spongioplasm,  the 
latter  as  hyaloplasm.  The  granular  appearance  is  often  caused  by  the  knots  of 
the  network  being  mistaken  for  granules ;  but,  in  addition  to  this,  protoplasm 
often  contains  true  granules,  some  of  which  are  proteid  in  nature  and  probably 
essential  constituents ;  others  are  fat-  or  pigment-granules,  and  are  regarded 
as  adventitious  material  taken  in  from  without.  The  size  and  shape  of  the 
meshes  of  the  spongioplasm  vary  in  different  cells  and  in  different  parts  of  the 
same  cell.  In  many  fixed  cells,  e.  g.,  epithelial  cells,  the  external  layer  becomes 
denser  than  the  rest,  and  often  altered  by  the  deposition  in  it  of  some  chemical 
substance,  so  as  to  constitute  a  membrane  which  encloses  the  rest  of  the  proto- 
plasm and  forms  the  cell-wall.  The  relative  amount  of  spongioplasm  and  hyalo- 
plasm varies  in  different  cells ;  the  latter  preponderating  in  the  young  cell 
and  the  former  increasing  in  amount,  at  the  expense  of  the  hyaloplasm,  as  the 
cell  grows. 

The  most  striking  characteristics  of  protoplasm  are  its  vital  properties  of  motion 
and  nutrition.  By  motion  is  meant  the  property  which  protoplasm  has  of  changing 
its  shape  and  position  by  some  intrinsic  power,  which  enables  it  to  thrust  out  from 
its  main  body  an  irregular  process,  into  which  the  whole  of  the  protoplasmic  sub- 
stance is  gradually  drawn,  so  that  the  mass  comes  to  occupy  a  new  position.  This, 
on  account  of  its  resemblance  to  the  movements  observed  in  the  Amoeba  or  Proteus 
animalcule,  has  been  termed  "amoeboid  movement."  Ciliary  movement,  or  the 
vibration  of  hair-like  processes  from  the  surface  of  any  structure,  may  also  be 
regarded  as  a  variety  of  the  motion  with  which  protoplasm  is  endowed. 

Nutrition  is  the  power  which  protoplasm  has  of  attracting  to  itself  the  materials 
necessary  for  its  growth  and  maintenance  from  surrounding  matter.  When  any 
foreign  particle  comes  in  contact  with  the  protoplasmic  substance,  it  becomes  incor- 
porated in  it  by  being  enwrapped  by  one  or  more  processes  projected  from  the 
parent  mass  which  enclose  it.  When  thus  taken  up,  it  may  remain  in  the  sub- 
stance of  the  protoplasm  for  some  time  without  change,  or  may  be  again  extruded. 

The  nucleus  is  a  minute  body,  imbedded  in  the  protoplasm,  and  usually  of  a 
spherical  or  oval  form,  its  size  having  little  relation  to  the  size  of  the  cell.  It 
is  surrounded  by  a  well-defined  wall,  the  nuclear  membrane,  which  encloses  the 
nuclear  contents.  These  are  known  as  the  nuclear  substance  (nuclear  matrix), 
which  is  composed  of  a  homogeneous  material  and  a  stroma  or  network.  The 
former  is  probably  of  the  same  nature  as  the  hyaloplasm  of  the  cell,  but  the  latter, 
Avhich  forms  also  the  wall  of  the  nucleus,  differs  from  the  spongioplasm  of  the  cell- 
substance.  It  is  sometimes  known  as  the  chromoplasm  or  intranuclear  network, 
and  consists  of  a  network  of  fibres  or  filaments  arranged  in  a  reticular  manner. 
These  filaments  stain  very  readily  with  certain  dyes ;  they  are  therefore  namec 
chromatin  ;  while  the  interstitial  substance  does  not  stain  readily,  and  is  hence 
called  achromatin.  In  some  resting  nuclei,  i.  e.,  nuclei  which  are  not  undergoing 
subdivision,  the  nuclear  filaments  do  not  form  a  network,  but  present  the  appear- 
ance of  a  convoluted  skein,  similar  to  that  found  in  a  nucleus  about  to  undergo 
division,  and  which  will  be  immediately  described. 

Within  the  nuclear  matrix  are  one  or  more  highly  refracting  bodies,  termec 
nucleoli,  connected  with  the  nuclear  membrane  by  the  nuclear  filaments.  The) 
are  regarded  as  being  of  two  kinds.  Some  are  mere  local  condensations  of  th( 
chromoplasm ;  these  are  irregular  in  shape  and  are  termed  pseudo-nucleoli . 
others  are  distinct  bodies  differing  from  the  pseudo-nucleoli  both  in  nature  anc 
chemical  composition ;  they  may  be  termed  true  nucleoli,  and  are  usually  founc 
in  resting  cells. 

The  nuclear  substance  differs  chemically  from  ordinary  protoplasm  in  containing 
nuclein,  in  its  power  of  resisting  the  action  of  acids  and  alkalies,  in  its  imbibing 
more  intensely  the  stain  of  carmine,  hasmatoxylin,  etc.,  and  in  its  remaining 
unstained  by  some  reagents  which  color  ordinary  protoplasm. 


THE   ANIMAL    CELL.  1075 

Recent  investigations  tend  to  show  that  most  living  cells  contain,  in  addition 
to  their  protoplasm  and  nucleus,  a  minute  particle  which,  on  account  of  the  power 
it  appears  to  possess  of  attracting  the  surrounding  protoplasmic  granules,  is 
termed  the  attraction-particle  or  centrosome ;  it  usually  lies  near  the  nucleus. 
The  spherical  arrangement  of  fibrillar  rows  of  granules  surrounding  the  central 
particle  is  termed  the  attraction-sphere  or  centrosphere.  These  spheres  are 
usually  double,  and  are  connected  by  a  spindle-shaped  system  of  delicate  fibrils 
{achromatic  spindle).  They  are  best  seen  in  young  cells  Avhich  are  about  to  undergo 
the  process  of  division,  a  process  believed  to  commence  in  these  bodies. 

The  process  of  reproduction  of  cells  is  usually  described  as  being  brought 
about  by  indirect  or  by  direct  division.  Indirect  division  or  karyokinesis  (karyo- 
mitosis)  has  been  observed  in  all  the  tissues — generative  cells,  epithelial  tissue, 
connective  tissue,  muscular  tissue,  and  nerve-tissue — and  probably  it  will  ulti- 
mately be  shown  that  the  division  of  cells  always  takes  place  in  this  way,  and 
that  the  process  of  reproduction  of  cells  by  direct  division  is,  as  is  believed  by 
some  observers,  merely  a  sort  of  imperfect  or  abnormal  karyokinesis. 

The  process  of  indirect  cell-division  is  characterized  by  a  series  of  complex 
changes  in  the  nucleus,  leading  to  its  subdivision  ;  this  being  followed  by  cleavage 
of  the  cell-protoplasm.  Starting  with  the  nucleus  in  the  quiescent  or  resting 
stage,  these  changes  may  be  briefly  grouped  under  the  four  following  phases: 

1.  Prophase. — The  nuclear  network  of  chr  omatin-filaments  assumes  the  form  of 
a  twisted  skein  or  spirem,  while  the  nuclear  membrane  and  nucleolus  disappear. 
The  convoluted  skein  of  chromatin  divides  into  a  definite  number  of  V-shaped 
loops  or  chromosomes.  Coincident  with  or  preceding  these  changes  the  centro- 
some, or  attraction-particle,  which  usually  lies  by  the  side  of  the  nucleus, 
undergoes  subdivision,  and  the  two  resulting  centrosomes,  each  surrounded  by  a 
centrosphere,  are  seen  to  be  connected  by  a  spindle  of  delicate  achromatic  fibres, 
the  achromatic  spindle.  These  centrosomes  move  away  from  each  other — one 
toward  each  extremity  of  the  nucleus — and  the  fibrils  of  the  achromatic  spindle 
are  correspondingly  lengthened.  The  centrosomes  are  now  situated  one  at 
either  extremity  or  pole  of  the  elongated  spindle,  and  each  is  surrounded  by  a 
centrosphere,  from  which  fibrils  radiate  into  the  investing  protoplasm.  A  line 
encircling  the  spindle  midway  between  its  poles  is  named  the  equator,  and 
around  this  the  V-shaped  chromosomes  arrange  themselves  in  the  form  of  a  star, 
thus  constituting  the  mother  star  or   monaster. 

2.  Metaphase. — Each  V-shaped  chromosome  now  undergoes  longitudinal 
cleavage  into  two  equal  halves  or  daughter  chromosomes,  the  cleavage  commenc- 
ing at  the  apex  of  the  V  and  extending  along  its  divergent  limbs.  The  daughter 
chromosomes,  thus  separated,  travel  in  opposite  directions  along  the  fibrils  of 
the  achromatic  spindle  toward  the  centrosomes,  around  which  they  group  them- 
selves, and  thus  two  star-like  figures  are  formed,  one  at  either  pole  of  the 
achromatic  spindle.      This  is  termed   the   diaster. 

3.  Anaphase. — The  V-shaped  daughter  chromosomes  now  assume  the  form  of 
a  skein  or  spirem,  and  eventually  form  the  network  of  chromatin  which  is  char- 
acteristic of  the  resting  nucleus.  The  nuclear  membrane  and  nucleolus  are  also 
differentiated  during  this  phase.  The  cell-protoplasm  begins  to  appear  constricted 
around  the  equator  of  the  achromatic  spindle,  where  double  rows  of  granules  are 
also  sometimes  seen.  The  constriction  deepens  and  the  original  cell  gradually 
becomes  divided. 

4.  Telophase. — In  this  stage  the  cell  is  completely  divided  into  two  new  cells, 
each  with  its  own  nucleus,  centrosome,  and  centrosphere,  which  assume  the 
ordinary  positions  occupied  by  such  structures  in  the  resting  stage. 

In  the  case  of  prickle-cells  the  subdivision  of  the  cell  is  incomplete  ;  here  the 
achromatic  spindle-threads  appear  to  persist  and  bridge  across  the  intercellular 
spaces,   constituting  the  prickles. 

The  series  of  diagrams  (Fig.  597),  by  Professor  S.  Del^pine,  is  intended  to 
pxplain  the  formation  of  some  of  the  most  important  changes  observed  in  nuclei 


1076 


GENERAL    ANATOMY   OB    HISTOLOGY. 


^^SIJ-SftfBS-jftS 


o  ¥^|^§t.t|5 


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t  -^^3-^s):' 


SIDE  OR  EQUATORIAL 
VIEW 


END  OR  POLAR 
VIEW 


SIDE  OR  EQUATORIAL 
VIEW 


Fig.  597,-Karyokinesis;  or  indirect  cell-division,  a.  Resting  nucleus  b  bkem  or  spirem,  close  C 
Skein  or  spirem,  open.  d.  Mother  star,  monaster,  e.  Metaphase.  v.  Daughter  stars ;  o  faster •  -G-  ^ughte 
skeins  or  dispirern,  beginning  to  form.    h.  Daughter  skeins  or  dispirem,  formed.    I.  Resting  daughter  nuclei. 


THE  NUTRITIVE   FLUIDS.  1077 

of  cells  during  karyokinesis  (mitosis) ;  it  is  based  chiefly  on  the  work  of  Flem- 
ming,  Strasburger,  E.  van  Beneden,  Rabl,  O'Hertwig,  Henneguy,  etc.  a.  Resting 
nucleus.  Nucleolus  and  nuclear  membrane  visible.  A  centrosome  is  represented 
near  the  nucleus.  B  and  c.  Skein  or  spirem.  Chromatic  filaments  much  convo- 
luted. Evidence  of  longitudinal  splitting  begins  to  be  distinct  in  several  parts. 
The  centrosome  has  divided ;  the  nuclear  membrane  is  becoming  indistinct.  The 
two  centrosomes  are  widely  separated,  and  the  space  between  them  is  occupied  by 
the  achromatic  spindle.  (Two  arrows  indicate  the  position  which  the  centrosomes 
will  ultimately  occupy  ;  during  their  passage  to  these  points  the  achromatic  spindle 
seems  to  be  within  the  nucleus.)  The  nuclear  membrane  has  disappeared.  D. 
Mother  star,  monaster.  The  nuclear  segments  (chromosomes)  resulting  from  the 
breaking-up  of  the  chromatic  filament  into  fragments  of  nearly  equal  length  have 
moved  toward  the  equator  of  the  spindle,  where  they  now  form  an  equatorial  plate. 
These  segments  are  all  split  longitudinally,  e.  Metaphase.  One  half  of  each 
chromosome  moves  toward  one  pole  and  the  other  half  toward  the  other 
pole,  being  guided  toward  the  centrosomes  by  the  achromatic  filaments.  F. 
Daughter  stars  or  diaster.  G.  Daughter  skeins  or  dispirem,  beginning  to  form. 
Segments  in  the  form  of  thick  loops  not  closely  packed.  H.  Daughter  skeins  or 
dispirem,  formed.  Segments  more  closely  packed  and  less  distinct,  owing  to  the 
formation  of  anastomoses.  1.  Resting  daughter  nuclei.  Cell  completely  divided 
into  two,  but  bridges  remain  between  them  in  the  region  previously  occupied  by 
the  achromatic  filaments,  these  being  specially  distinct  in  certain  cells,  e.  g., 
prickle-cells.       The  nucleus  has  a  distinct   nuclear  membrane  and  a  nucleolus. 

In  the  reproduction  of  cells  by  direct  division  the  process  is  brought  about 
either  by  segmentation  or  by  gemmation.  In  reproduction  by  segmentation  or 
fission  the  nucleus  becomes  constricted  in  its  centre,  assuming  an  hour-glass  shape, 
and  then  divides  into  two.  This  leads  to  a  cleavage  or  division  of  the  whole 
protoplasmic  mass  of  the  cell ;  and  thus  two  daughter  cells  are  formed,  each  con- 
taining a  nucleus.  These  daughter  cells  are  at  first  smaller  than  the  original 
mother  cell ;  but  they  grow,  and  the  process  may  be  repeated  in  them,  so  that 
multiplication  may  take  place  rapidly.  In  reproduction  by  gemmation  &  budding- 
off  or  separation  of  a  portion  of  the  nucleus  and  parent-cell  takes  place,  and, 
becoming  sepai-ated,  forms  a  new  organism. 

The  cell-wall,  which  is  not  an  essential  constituent,  and  in  fact  is  often  absent, 
is  merely  the  external  layer  of  the  protoplasm,  firmer  than  the  rest  of  the  cell, 
and  often  thickened  by  the  deposit  in  it  of  certain  chemical  substances.  It  forms 
a  flexible,  transparent,  finely  striated  membrane,  sometimes  furnished  with  minute 
pores,  so  as  to  be  permeable  to  fluids. 

THE  NUTRITIVE  FLUIDS. 

The  circulating  fluids  of  the  body,  which  subserve  its  nutrition,  are  the  blood, 
the  lymph,  and  the  chyle. 

THE  BLOOD. 

The  blood  is  an  opaque,  rather  viscid  fluid,  of  a  bright-red  or  scarlet  color 
when  it  flows  from  the  arteries,  of  a  dark-red  or  purple  color  when  it  flows  from 
the  veins.  It  is  salt  to  the  taste,  and  has  a  peculiar  faint  odor  and  an  alkaline 
reaction.  Its  specific  gravity  is  about  1.060,  and  its  temperature  is  generally 
about  100°  F.,  though  varying  slightly  in  different  parts  of  the  body. 

General  Composition  of  the  Blood. — Blood  consists  of  a  faintly  yellow  fluid, 
the  plasma  or  liquor  sanguinis,  in  which  are  suspended  numerous  minute  particles, 
the  blood-corpuscles,  the  majority  of  which  are  colored  and  give  to  the  blood  its 
red  tint.  If  a  drop  of  blood  is  placed  in  a  thin  layer  on  a  glass  slide  and  examined 
under  the  microscope,  a  number  of  these  corpuscles  will  be  seen  immersed  in 
the  clear  fluid  plasma. 

The   Blood-corpuscles    are    chiefly   of   two    kinds :    (1)  colored  corpuscles  or 


1078 


GENERAL   ANATOMY   OB    HISTOLOGY. 


Fig.  598.— Human  red  blood-corpuscles.  Highly  magnified, 
o.  Seen  from  the  surface,  b.  Seen  in  profile  and  forming 
rouleaux,  c.  Rendered  spherical  by  water,  d.  Rendered 
crenate  by  salt  solution. 


erythrocytes,  (2)  colorless  corpuscles   or  leucocytes.     A  third  variety,  the  blood- 
platelets,  are  of  subsidiary  importance. 

1.  Colored  or  red  corpuscles  {erythrocytes),  when  examined  under  the  micro- 
scope, are  seen  to  be  circular  disks,  biconcave  in  profile.     They  have  no  nuclei, 

but  in  consequence  of  their  bicon- 
cave shape  present,  according  to 
the  alteration  of  focus  under  an 
ordinary  high  power,  a  central 
part,  sometimes  bright,  sometimes 
dark,  which  has  the  appearance 
of  a  nucleus  (Fig.  598,  a).  It  is 
to  their  aggregation  that  the  blood 
owes  its  red  hue,  although  when 
examined  by  transmitted  light 
their  color  appears  to  be  only  a 
faint  reddish  yellow.  Their  size 
varies  slightly  even  in  the  same 
drop  of  blood ;  but  it  may  be 
stated  that  their  ordinary  diameter 
is  about  32100  of  an  inch,  while 
their  thickness  is  about  12^0lj  of 
an  inch  or  nearly  one-quarter  of 
their  diameter.  Besides  these  there  are  found,  especially  in  disease  (e.  g.,  anaemic 
conditions),  certain  smaller  corpuscles  of  about  one-half  or  one-third  of  the  size  just 
indicated;  these  are  termed  microcytes,  and  are  very  scarce  in  human  blood. 
The  number  of  red  corpuscles  in  the  blood  is  enormous;  between  4,000,000  and 
5,000,000  are  contained  in  a  cubic  millimetre.  Power  states  that  the  red  cor- 
puscles of  an  adult  would  present  an  aggregate  surface  of  about  3000  square 
yards.  Each  corpuscle  consists  of  a  colorless  elastic  spongework  or  stroma,  con- 
densed at  the  periphery  to  form  an  investing  membrane,  and  uniformly  diffused 
throughout  this  are  the  colored  fluid  contents.  The  stroma  is  composed  mainly 
of  nucleo-proteid  and  of  the  fatty  substances,  lecithin  and  cholesterin,  while  the 
colored  material  consists  chiefly  of  the  respiratory  proteid,  hcemoglobin,  which 
contains  a  proportion  of  iron  in  addition  to  the  ordinary  proteid  elements.  This 
proteid  has  a  great  affinity  for  oxygen,  and  when  removed  from  the  body  crys- 
tallizes readily  under  certain  circumstances.  It  is  very  soluble  in  water,  the 
addition  of  which  to  a  drop  of  blood  speedily  dissolves  out  the  haemoglobin  from 
the  corpuscles. 

If  the  web  of  a  frog's  foot  is  spread  out  and  examined  under  the  microscope, 
the  blood  is  seen  to  flow  in  a  continuous  stream  through  the  vessels,  and  the 
corpuscles  show  no  tendency  to  adhere  to  each  other  or  to  the  wall  of  the  vessel. 
Doubtless  the  same  is  the  case  in  the  human  body ;  but  when  the  blood  is  drawn 
and  examined  on  a  slide  without  reagents,  the  corpuscles  often  collect  into  heaps 
like  rouleaux  of  coins  (Fig.  598,  b).  It  has  been  suggested  that  this  phenom- 
enon may  be  explained  by  alteration  in  surface  tension. 

During  life  the  red  corpuscles  may  be  seen  to  change  their  shape  under  press- 
ure so  as  to  adapt  themselves  to  some  extent  to  the  size  of  the  vessel.  They 
are,  however,  highly  elastic,  and  speedily  recover  their  shape  when  the  pressure 
is  removed.  They  are  soon  influenced  by  the  medium  in  which  they  are  placed, 
and  by  the  specific  gravity  of  the  medium.  In  water  they  swell  up,  lose  their 
shape,  and  become  globular  (Fig.  598,  c).  Subsequently  the  haemoglobin  becomes 
dissolved  out,  and  the  envelope  can  be  barely  distinguished  as  a  faint,  circular 
outline.  Solutions  of  salt  or  sugar,  denser  than  the  plasma,  give  them  a  stel- 
late or  crenated  appearance  (Fig.  598,  d) ;  but  the  usual  shape  may  be  restored  by 
diluting  the  solution  to  the  same  specific  gravity  as  the  plasma.  The  crenated 
outline  may  be  produced  as  the  first  effect  of  the  passage  of  an  electric  shock 
subsequently,  if  sufficiently  strong,  the  shock  ruptures  the  envelope.     A  solution 


THE  NUTRITIVE  FLUIDS.  1079 

of  salt  or  sugar  of  the  same  specific  gravity  as  the  plasma,  merely  separates  the 
blood-corpuscles  mechanically  without  changing  their  shape. 

The  colorless  corpuscles  (leucocytes)  are  of  various  sizes,  some  no  larger,  others 
even  smaller,  than  the  red  corpuscles.  In  human  blood,  however,  the  majority 
are  rather  larger  than  the  red  corpuscles,  and  measure  about  2(H)  o  ^°  2  5*0  0  °f  an 
inch  in  diameter.  On  the  average  from  .10,000  to  12,000  leucocytes  are  found  in 
each  cubic  millimetre  of  blood. 

They  consist  of  minute  masses  of  nucleated  protoplasm,  and  exhibit  several 
varieties,  which  are  differentiated  from  each  other  chiefly  by  the  occurrence  or  non- 
occurrence of  granules  in  their  protoplasm  and 
by  the  staining  reactions  of  these  granules  when 
present  (Fig.  599).  (1)  The  most  numerous 
and  important  are  spherical  in  shape,  and  are 
characterized  by  a  nucleus,  which  often  con- 
sists of  two  or  three  parts  (multipartite)  con- 
nected together  by  fine  threads  of  chromatin. 
The  protoplasm  is  clear,  and  contains  a  number 
of  very  fine  granules,  which  stain  with  acid 
dyes,  as  eosin  (Fig.  599,  3).  (2)  A  second 
variety  comprises  about  2.4  per  cent,  of  the 
leucocytes;  they  are  larger  than  the  previous  fig.  599.— varieties  of  leucocytes  found  in 
kind,  and  are  made  up  of  a  coarsely  granular  ^  gSti*1,  SffflSShSShSS 
protoplasm,  the  granules   being   highly   refrac-      ™g*  £gg* g§p. 4  3H™^f|f* 

tile  and  grouped  round  a  single  nucleus  of  showing  nucleus  with  chromatin  threads 
,  11  /ttv        cr\r\     -i\         mi  i  an(i  two  centrosomes  in  clear  protoplasm. 

horseshoe  Shape  (rig-  09y,    1).       lhese  granules       5.  Finely  granular  leucocyte;  the  nucleus 

stain  deeply  with  eosin,  and  the  cells  are  ?^^£a1fwwiSdn■,,TitIl?,,,sicdye,,, 
therefore  often  termed  eosinophil    corpuscles. 

(3)  A  leucocyte  characterized  by  the  presence  of  a  trilobed  nucleus,  and  having 
in  its  protoplasm  fine  granules  which  stain  Avith  basic  dyes,  such  as  methylene- 
blue,  is  found  in  small  numbers  (Fig.  599,  5).  (4)  The  fourth  variety  is  called 
the  hyaline  cell  (Fig.  599,  4).  This  is  usually  about  the  same  size  as  that  of  the 
eosinophile  cell,  and,  when  at  rest,  is  spherical  in  shape  and  contains  a  single 
round  or  oval  nucleus.  The  protoplasm  is  free  from  granules,  but  is  not  quite 
transparent,  having  the  appearance  of  ground  glass.  (5)  The  fifth  kind  of  color- 
less corpuscle  is  designated  the  lymphocyte  (Fig.  599,  2),  because  it  is  identical 
with  the  lymphoid  cell  derived  from  the  lymphatic  glands,  the  spleen,  tonsil,  and 
thymus.  It  is  the  smallest  of  the  leucocytes,  and  consists  chiefly  of  a  spheroidal 
nucleus  with  very  little  surrounding  protoplasm  of  a  homogeneous  nature ;  it  is 
regarded  as  the  immature  form  of  the  hyaline  cell.  The  fourth  and  fifth  varieties 
together  constitute  from  20  to  30  per  cent,  of  the  colorless  cells,  but  of  these  two 
varieties  the  lymphocytes  are  by  far  the  more  numerous. 

The  white  corpuscles  are  very  various  in  shape  in  living  blood  (Fig.  600), 
because  many  of  them  have  the  power  of  constantly  changing  their  form  by  pro- 
truding finger-shaped  or  filamentous  processes  of  their  own  substance,  by  which 


^l|« 611 


Fig.  600.— Human  colorless  blood-corpuscle,  showing  its  successive  changes  of  outline  withiu  ten  minutes 
when  kept  moist  on  a  warm  stage.    (Sehofleld.) 

they  move,  and  may  take  up  granules  from  the  surrounding  medium.  In  locomo- 
tion the  corpuscle  pushes  out  a  process  of  its  substance — a  pseudopodium.  as  it  is 
called — and  then  shifts  the  rest  of  the  body  into  it.  In  the  same  way  when  any 
granule  or  particle  comes  in  its  way  it  wraps  a  pseudopodium  round  it.  and  then 
withdrawing  it,  lodges  the  particle  in  its  own  substance.  By  means  of  these  amoeboid 
properties  the  cells  have  the  power  of  wandering  or  emigrating  from  the  blood- 


1080  GENERAL   ANATOMY   OB   HISTOLOGY. 

vessels  by  penetrating  their  walls  and  thus  finding  their  way  into  the  extra-vascular 
spaces.  A  chemical  investigation  of  the  protoplasm  of  the  leucocytes  shows  the 
presence  of  nucleo-proteid  and  of  a  globulin.  The  occurrence  of  small  amounts  of 
fat  and  glycogen  may  also  be  demonstrated. 

The  Blood-platelets  are  discoid  or  irregularly  shaped,  colorless,  refractile 
bodies,  much  smaller  than  the  red  cells.  Considerable  discussion  has  arisen  as  to 
their  significance.  In  spite  of  the  fact  that  they  have  been  observed  in  the  blood- 
vessels during  life,  there  is,  at  present,  a  tendency  to  regard  them  as  products  of 
disintegration  of  the  white  cells,  or  as  precipitates,  possibly  of  nucleo-proteid,  and 
not  as  living  elements  of  the  blood. 

Origin  of  the  Blood-corpuscles. — In  the  embryo  the  red  corpuscles  are  developed 
from  mesoblastic  cells  in  the  vascular  area  of  the  blastoderm.  These  cells  unite 
with  one  another  to  form  a  network,  their  nuclei  multiply  in  number,  and  around 
some  of  the  nuclei  an  aggregation  of  colored  protoplasm  takes  place.  After  a 
time  the  network  becomes  hollowed  out  by  an  accumulation  of  fluid,  and  forms 
capillary  blood-vessels,  and  in  the  fluid  those  nuclei  which  are  surrounded  by 
colored  protoplasm  float  as  the  first  red  blood-cells.1  The  embryonic  corpuscles 
are  thus  nucleated,  and,  further,  they  have  the  power  of  amoeboid  movement. 
These  cells  disappear  in  later  embryonic  life,  to  be  replaced  by  smaller  non- 
nucleated  corpuscles,  having  all  the  characters  of  the  adult  erythrocyte,  which, 
according  to  Schafer,  are  formed  Avithin  certain  cells  of  the  connective  tissue. 
Small  globules  of  reddish  coloring-matter  appear  in  the  protoplasm  of  these  cells, 
and  these  eventually  becoming  larger,  more  uniform  in  size  and  disk-shaped,  float 
in  a  cavity  which  results  from  the  coalescence  of  numerous  vacuoles.  The  cells 
becoming  more  hollowed  join  with  neighboring  cells  to  form  new  blood-vessels, 
and  these  become  connected  with  previously  existing  vessels.  In  post-embryonic 
life  the  important  source  of  the  red  corpuscles  is  the  red  marrow  in  the  ends  of 
the  long  bones  and  especially  in  the  ribs  and  sternum.  Here  are  found  special, 
nucleated,  colored  cells,  termed  erythroblasts,  which  are  probably  direct  descend- 
ants of  the  nucleated,  embryonic  red  cells.  These  erythroblasts  by  atrophy 
and  disappearance  of  their  nuclei  (or,  as  some  observers  maintain,  by  their 
extrusion)  and  by  assumption  of  the  biconcave  form  are  transformed  into  the 
adult  red  corpuscle.  Of  the  white  corpuscles  of  the  blood,  the  lymphocytes  are 
derived  from  lymphatic  tissue  generally,  and  from  the  lymphatic  glands  especially, 
and  enter  the  blood  by  way  of  the  lymph-stream ;  the  hyaline  cells  probably 
develop  from  the  lymphocytes,  while  the  eosinophile  cells  are  believed  to  originate 
mainly  in  the  bone-marrow  and  possibly  also  in  the  connective  tissues. 

The  Plasma  or  Liquor  Sanguinis,  the  fluid  portion  of  the  blood,  has  a  yellowish 
tint,  is  alkaline  in  reaction,  and  of  a  specific  gravity  of  1.028.  It  contains  in 
solution  about  10  per  cent,  of  solids,  of  which  four-fifths  are  proteid  in  nature ; 
the  remainder  being  salts,  chiefly  chlorides,  phosphates,  and  sulphates  of  the 
alkali  metals ;  carbohydrates,  chiefly  sugar ;  fats  and  soaps,  cholesterin,  urea,  and 
other  nitrogenous  extractives.  The  proteids  are  three  in  number,  serum  albumen, 
serum  globulin,  and  fibrinogen.  Fibrinogen  is  a  body  of  the  globulin  class,  but 
differs  from  serum  globulin  in  several  respects.  It  is  the  substance  from  which 
the  fibrin,  which  plays  so  important  a  part  in  the  clotting  of  the  blood,  is  derived. 

Coagulation  of  the  Blood. — When  blood  is  drawn  from  the  body  and  allowed 
to  stand,  it  solidifies  in  the  course  of  a  very  few  minutes  into  a  jelly-like  mass  or 
"clot,"  which  has  the  same  appearance  and  volume  as  the  fluid  blood  and,  like  it, 
looks  quite  uniform.  Soon,  hoAvever,  drops  of  a  transparent  yellowish  fluid,  the 
"serum,"  begin  to  ooze  from  the  surface  of  the  mass  and  to  collect  around  it. 
Coincidently  the  clot  begins  to  contract,  so  that  in  the  course  of  about  tAventy-four 
hours,  having  become  considerably  smaller  and  firmer  than  the  first  formed  jelly- 
like mass,  it  floats  in  a  quantity  of  yelloAvish  serum.  The  clotting  of  the  blood  is 
due  to  the  formation  of  a  fine  meshAvork  of  the  insoluble  material,  fibrin,  Avhich 

1  Recent  observations  tend  to  show  that  the  endothelial  lining  of  the  vessels  and  the  blood- 
corpuscles  are  of  hypoblastic  origin. 


THE   NUTRITIVE  FLUIDS. 


1081 


entangles  and  encloses  the  blood-corpuscles.  It  is  supposed  that  when  blood  is 
drawn  a  nucleo-proteid,  termed  prothrombin,  appears  in  the  plasma,  probably  as 
the  result  of  disintegration  of  some  of  the  white  cells  and  perhaps  also  the  blood- 
platelets.  This  substance  interacts  with  soluble  lime  salts  in  the  blood,  and  a 
fresh  body,  thrombin  or  fibrin-ferment,  is  the  result.  The  thrombin  then  acts  on 
the  fibrinogen  in  solution  in  the  plasma,  converting  it  into  insoluble  fibrin,  while 
at  the  same  time  a  very  small  amount  of  a  new  proteid  of  the  globulin  type  passes 
into  solution. 

Fibrin  may  be  obtained,  practically  free  from  corpuscles,  by  whipping  the 
blood,  after  it  has  been  withdrawn  from  the  body,  with  a  bundle  of  twigs,  to  which 
the  fibrin  adheres  as  it  is  formed.  By  various  means  the  clotting  of  the  blood 
may  be  retarded,  so  that  the  plasma  may  be  obtained  free  from  corpuscles ;  from 
this  plasma  there  may  be  derived  fibrin  and  serum,  without  the  cellular  elements. 
Fibrin  thus  obtained  is  a  white  or  buff-colored  stringy  substance,  and  when 
observed  in  the  course  of  formation,  under  the  microscope,  shows  a  meshwork 
of  fine  fibrils.  After  exposure  to  the  air  for  some  time  it  becomes  hard,  dry, 
brown,  and  brittle.  It  is  one  of  the  class  of  coagulated  proteids,  insoluble  in  hot 
or  cold  water,  saline  solution,  alcohol,  or  ether.  Under  the  action  of  dilute  hydro- 
chloric acid  it  swells  up  but  does  not  dissolve,  but  when  thus  swollen  is  readily 
dissolved  by  a  solution  of  pepsin. 


Fig.  601. — Blood-crystals  :   A.   Haemoglobin  crystals  from  human  blood.     B.   Haemin  crystals  from  blood 
treated  with  acetic  acid.     C.  Hsematoidin  crystals  from  an  old  apoplectic  clot. 

Serum,  with  the  exception  of  its  proteids,  has  a  composition  identical  with  that 
of  plasma.  The  fibrinogen  characteristic  of  plasma  has  disappeared,  and  the 
fibrin-ferment  or  thrombin  is  found  instead,  together  with  the  serum  albumen 
and  serum  globulin  which  are  not  involved  in  the  process  of  coagulation. 

The  relation  of  the  various  constituents  of  the  blood  to  each  other  may  be 
easily  understood  by  a  reference  to  the  subjoined  plan : 

f  Corpuscles  ^ 

Bloodj  (  Fibrin  j    °l0t 

^  Plasma      < 

(_  Serum 

Gases  of  the  Blood. — When  blood  is  exposed  to  the  vacuum  of  an  air-pump. 
100  volumes  are  found  to  yield  about  60  volumes  of  gas.  The  gases  present  are 
carbon  dioxide,  oxygen,  and  nitrogen,  and  they  occur  in  the  following  proportions 
in  arterial  and  venous  blood : 


Carbon  dioxide. 

Oxygen. 

Nitrogen. 

Arterial  blood     . 

.     40  vols. 

20  vols. 

1  to  2  vols. 

/enous  blood 

.     46  to  50  vols. 

10  to  12  vols. 

1  to  2  vols. 

The  greater  quantity  of  the  oxygen  is  in  loose  chemical  combination  with  the 
haemoglobin  of  the  red  corpuscles.  The  carbon  dioxide  exists  in  combination  for 
the  most  part  as  sodium  bicarbonate  and  carbonate.  The  nitrogen  is  in  simple 
solution  in  the  plasma. 

Blood-crystals. — Haemoglobin,    as   already    stated,    readily    crystallizes    when 


1082  GENEBAL    ANATOMY    OB    HISTOLOGY. 

separated  from  the  blood-corpuscles.  In  human  blood  the  crystals  are  elongated 
prisms  (Fig-  601,  A),  and  in  the  majority  of  animals  belong  to  the  rhombic  system, 
though  in  the  squirrel  hexagonal  plates  are  met  with.  Small  brown  prismatic 
crystals  of  hcemin  (Fig.  601,  B)  may  be  obtained  by  mixing  dried  blood  with  common 
salt  and  boiling  with  a  few  drops  of  glacial  acetic  acid.  A  drop  of  the  mixture 
on  a  slide  will  show  the  characteristic  crystals  on  cooling.  Hcamatoidin  crystals 
(Fig.  601,  C)  occur  sometimes  in  old  blood-clots. 

LYMPH  AND  CHYLE. 

Lymph  is  a  transparent,  colorless  or  slightly  yellow  fluid,  which  is  conveyed 
by  a  set  of  vessels  named  lymphatics  into  the  blood.  These  vessels  arise  in 
nearly  all  parts  of  the  body  as  lymph-capillaries.  They  take  up  the  blood-plasma 
which  has  exuded  from  the  blood-capillaries  into  the  tissue-spaces  where  it  has 
nourished  the  tissue-elements,  and  return  it  into  the  veins  close  to  the  heart,  there 
to  be  mixed  with  the  mass  of  blood.  The  greater  number  of  these  lymphatics 
empty  themselves  into  one  main  duct,  the  thoracic  duct,  which  passes  upward  along 
the  front  of  the  spine  and  opens  into  the  large  veins  on  the  left  side  of  the  root  of 
the  neck.  The  remainder  empty  themselves  into  a  smaller  duct  which  terminates 
in  the  corresponding  veins  on  the  right  side  of  the  neck. 

Lymph,  as  its  name  implies,  is  a  watery  fluid  of  sp.  gr.  about  1.015,  closely 
resembling  the  blood-plasma,  but  more  dilute  and  containing  only  about  5  per  cent, 
of  proteids  and  1  per  cent,  of  salts  and  extractives.  "When  examined  under  the 
microscope,  leucocytes  of  the  lymphocyte  class  are  found  floating  in  the  trans- 
parent fluid.  They  are  always  increased  in  number  after  the  passage  of  the 
lymph  through  lymphoid  tissue,  as  in  lymphatic  glands.  They  are  constantly 
furnishing  a  fresh  supply  of  colorless  corpuscles  to  the  blood. 

Chyle  is  an  opaque,  milky-white  fluid,  absorbed  by  the  villi  of  the  small 
intestine  from  the  food,  and  carried  by  a  set  of  vessels  similar  to  the  lymphatics, 
named  lacteals,  to  the  commencement  of  the  thoracic  duct,  where  it  is  inter- 
mingled with  the  lymph  and  poured  into  the  circulation  through  the  same  chan- 
nels. It  must  be  borne  in  mind  that  these  two  sets  of  vessels,  lymphatics  and 
lacteals,  though  differing  in  name,  are  identical  in  structure,  and  that  the  character 
of  the  fluid  they  convey  is  different  only  while  digestion  is  going  on.  At  other 
times  the  lacteals  convey  a  transparent,  nearly  colorless  lymph. 

Chyle  exactly  resembles  lymph  in  its  physical  and  chemical  properties,  except 
that  it  has,  in  addition  to  the  other  constituents  of  lymph,  a  quantity  of  finely 
divided  fatty  particles,  the  so-called  "molecular  basis  of  chyle,"  to  which  the 
milky  appearance  is  due.  It  contains  a  little  more  proteid  than  lymph,  but  the 
chief  difference  lies  in  the  large  quantity  of  fats,  soaps,  lecithin,  and  cholesterin 
present  in  the  former.  Lymph  and  chyle,  containing,  as  they  do,  fibrinogen  in 
solution  and  leucocytes,  clot  on  removal  from  the  body,  the  coagulum  being  free 
from  red  cells,  and  presenting  a  clear  or  whitish  jelly-like  appearance. 

EPITHELIUM. 

All  the  surfaces  of  the  body — the  external  surface  of  the  skin,  the  internal 
surface  of  the  digestive,  respiratory,  and  genito-urinary  tracts,  the  closed  serous 
cavities,  the  inner  coat  of  the  vessels,  and  the  acini  and  ducts  of  all  secreting  and 
excreting  glands,  the  ventricles  of  the  brain,  and  the  central  canal  of  the  spinal 
cord — are  covered  by  one  or  more  layers  of  simple  cells,  called  epithelium  or 
epithelial  cells.  These  cells  are  also  present  m  the  terminal  parts  of  the  organs 
of  special  sense,  and  in  some  other  structures,  as  the  pituitary  and  thyroid  bodies. 
They  serve  various  purposes,  forming  in  some  cases  a  protective  layer,  in  others 
acting  as  agents  in  secretion  and  excretion,  and  again  in  others  being  con- 
cerned in  the  elaboration  of  the  organs  of  special  sense.  Thus,  in  the  skin, 
the  main  purpose  served  by  the  epithelium  (here  called  the  epidermis)  is  that  of 
protection.     As  the  surface  is  worn  away  by  the  agency  of  friction  or  change  of 


THE   EPITHELIUM. 


1083 


temperature  new  cells  are  supplied,  and  thus  the  surface  of  the  true  skin  and  the 
vessels  and  nerves  which  it  contains  are  defended  from  damage.  In  the  gastro- 
intestinal mucous  membrane  and  in  the  glands  the  epithelial  cells  appear  to  be 
the  principal  agents  in  separating  the  secretion  from  the  blood  or  from  the  aliment- 
ary fluids.  In  other  situations  (as  the  nose,  fauces,  and  respiratory  passages)  the 
chief  office  of  the  epithelial  cells  appears  to  be  to  maintain  an  equable  tempera- 
ture by  the  moisture  with  which  they  keep  the  surface  always  slightly  lubricated. 
In  the  serous  cavities  they  also  keep  the  opposed  layers  moist,  and  thus  facilitate 
their  movements  on  each  other.  Finally,  in  all  internal  parts  they  insure  a 
perfectly  smooth  surface. 

Of  late  years  there  has  been  a  tendency  on  the  part  of  many  histologists  to 
divide  these  several  epithelial  structures  into  two  classes:  (1)  epithelium,  consist- 
ing of  nucleated  protoplasmic  cells,  which 
form  continuous  masses  on  the  skin  and 
mucous  surfaces  and  the  linings  of  the  ducts 
and  alveoli  of  secreting  and  excreting  glands ; 
and  (2)  endothelium,  which  is  composed  of  a 
single  layer  of  flattened  transparent  squam- 
ous cells,  joined  edge  to  edge  in  such  a 
manner  as  to  form  a  membrane  of  cells.  This 
is  found  on  the  free  surfaces  of  the  serous 
membranes,  as  the  lining  membrane  of  the 
heart,  blood-vessels,  and  lymphatics  ;  on  the 
surface  of  the  brain  and  spinal  cord,  and  in 
the  anterior  chamber  of  the  eye.  Endothelium  originates  from  the  embryonic 
mesoblast,  Avhile  epithelium  arises,  as  a  rule,  from  the  epiblast  or  hypoblast. 

Epithelium  consists  of  one  or  more  layers  of  cells  united  together  by  an  inter- 
stitial cement-substance,  supported  on  a  basement-membrane,  and  is  naturally 
grouped  into  two  classes,  according  as  to  whether  there  is  a  single  layer  of  cells 
[simple  epithelium)  or  more  than  one  {stratified  epithelium).  A  third  variety 
(transitional  epithelium)  is  that  in  which  cells  in  three  or  four  layers  are  so  fitted 
together  that  the  appearance  is  not  one  of  distinct  stratification.  The  different 
varieties  of  simple  epithelium  are  usually  spoken  of  as  squamous  or  pavement, 
columnar,  glandular  or  spheroidal,    and  ciliated. 

The  pavement  epithelium  (Fig.  602)  is  composed  of  flat  nucleated  scales  of 
various  shapes,  usually  polygonal,  and  varying  in  size.  These  cells  fit  together 
by  their  edges,  like  the  tiles  of  a  mosaic  pavement.  The  nucleus  is  generally 
flattened,  but  may  be  spheroidal.  The  flattening  depends  upon  the  thinness  of 
the  cell.     The  protoplasm  of  the  cell  presents  a  fine  reticulum  or  honeycombed 


Fig.  602. — Simple  pavement  epithelium. 


-Striated  free  bonier* 
of  cells. 


Fig.  603.— Columnar  epithelium  from  an  intestinal  villus. 


Fig.  604.— Goblet  cells.    (From 
Kirk's  Physiology.) 


network,  which  gives  to  the  cell  the  appearance  of  granulation.  This  kind  of 
epithelium  forms  the  lining  of  the  air-cells  of  the  lungs.  The  endothelium, 
which  coders  the  serous  membranes,  and  which  lines  the  heart,  bloodvessels, 
lymphatics,  and  the  anterior  chamber  of  the  eye,  is  also  of  the  pavement  type. 
The  columnar  or  cylindrical  epithelium  (Fig.  603)  is  formed  of  cylindrical  or 
rod-shaped  cells  set  together  so  as  to  form  a  complete  layer,  resembling,  when 
viewed  in  profile,  a  palisade.      The   cells   have  a  prismatic  figure,   more  or  less 


1084 


GENEBAL    ANATOMY   OB   HISTOLOGY. 


flattened  from  mutual  pressure,  and  are  set  upright  on  the  surface  on  ivhich  they 
are  supported.  Their  protoplasm  is  always  more  or  less  reticulated,  and  fine 
longitudinal  striae  may  be  seen  in  it.  They  possess  a  nucleus  which  is  oval  in 
shape  and  contains  an  intranuclear  network. 

This  form  of  epithelium  covers  the  mucous  membrane  of  nearly  the  whole 
gastro-intestinal    tract    and    the    glands  of  that  part,   the   greater    part  of   the 


Fig.  605.— Spheroidal  epithelium. 
Magnified  250  times. 


Fig.  606. — Ciliated  epithelium  from  the  human 
trachea.  Magnified  350  times,  a.  Innermost 
layers  of  the  elastic  longitudinal  fibres,  b. 
Homogeneous  innermost  layer  of  the  mucous 
membrane,  c.  Deepest  round  cells,  d.  Middle 
elongated  cells,  e.  Superficial  cells,  bearing  cilia. 


urethra,  the  vas  deferens,  the  prostate,  Cowper's  glands,  Bartholini's  glands,  and 
a  portion  of  the  uterine  mucous  membrane.  In  a  modified  form  it  also  covers 
the  ovary. 

Goblet-  or  cJialice-celh  are  a  modification  of  the  columnar  cell.  They  appear 
to  be  formed  by  an  alteration  in  shape  of  the  columnar  epithelium  (ciliated  or 
otherwise)  consequent  on  the  formation  of  granules  which  consist  of  a  substance 
called  mucigen  in  the  interior  of  the  cell.  This  distends  the  upper  part  of  the  cell, 
while  the  nucleus  is  pressed  down  toward  its  deep  part,  until  the  cell  bursts  and 
the  mucus  is  discharged  on  to  the  surface  of  the  mucous  membrane  as  shown  in 
Fig.  604,  the  cell  then  assuming  the  shape  of  an  open  cup  or  chalice. 

The  glandular  or  spheroidal  epithelium  (Fig.  605)  is  composed  of  spheroidal  or 
polyhedral  cells,  but  the  cells  may  be  columnar  or  cubical  in  shape  in  some  situ- 


Fig.  607.— Epithelial  cells  from  the  oral  cavity  of  man.    Magnified  350  times,    a.  Large,    b.  Middle  sized 
c.  The  same  with  two  nuclei. 


ations.  Like  other  forms  of  epithelial  cells,  the  protoplasm  is  a  fine  reticulum, 
which  gives  to  the  cell  the  appearance  of  granulation.  They  are  found  in  the 
terminal  recesses  of  secreting  glands,  and  the  protoplasm  of  the  cells  usually 
contains  the  materials  which  the  cells  secrete. 

Ciliated  epithelium  (Fig.  606)  may  be  of  any  of  the  preceding  forms,  but  usually 
inclines  to  the  columnar  shape.  It  is  distinguished  by  the  presence  of  minute 
processes,  which  are  direct  prolongations  of  the  cell-protoplasm,  like  hairs  or  eye- 


THE   EPITHELIUM. 


1085 


Stratum 
granulosum 


Prickle-cell 
of  stratum 
Malpighii 


lashes  (cilia),  standing  up  from  the  free  surface.  If  the  cells  are  examined  during 
life  or  immediately  on  removal  from  the  living  body  (for  which  in  the  human  sub- 
ject the  removal  of  a  nasal  polypus  offers  a  convenient  opportunity)  in  a  weak 
solution  of  salt,  the  cilia  will  be  seen  in  lashing  motion  ;  and  if  the  cells  are 
separate,  they  will  often  be  seen  to  be  moved  about  in  the  field  by  this  motion. 

The  situations  in  which  ciliated  epithelium  is  found  in  the  human  body  are : 
the  respiratory  tract  from  the  nose  downward  to  the  smallest  ramifications  of  the 
bronchial  tube  (except  a  part  of  the  pharynx  and  the  surface  of  the  vocal  cords), 
the  tympanum  and  Eustachian  tube,  the  Fallopian  tube  and  upper  portion  of  the 
uterus,  the  vasa  efferentia,  coni  vasculosi,  and  the  first  part  of  the  excretory 
duct  of  the  testicle,  and  the  ventricles  of  the  brain  and  central  canal  of  the 
spinal  cord. 

Stratified  epithelium  (Fig.  608)  consists  of  several  layers  of  cells  superimposed 
one  on  the  top  of  the  other  and  varying  greatly  in  shape.  The  cells  of  the  deepest 
layer  are  for  the  most  part  colum- 
nar in  form,  and  as  a  rule  form  a 
single  layer,  placed  vertically  on 
the  supporting  membrane  ;  above 
these  are  several  layers  of  sphe- 
roidal cells,  which  as  they  ap- 
proach the  surface  become  more 
and  more  compressed,  until  the 
superficial  layers  are  found  to 
consist  of  flattened  scales  (Fig. 
607),  the  margins  of  which  over- 
lap one  another,  so  as  to  present 
an  imbricated  appearance.  They 
here  undergo  a  chemical  change 
from  the  conversion  of  their  pro- 
toplasm into  a  horny  substance 
(keratin): 

Certain  cells  found  in  the 
deeper  layers  of  stratified  epi- 
thelium, and  termed  prickle-cells  (Fig.  608),  constitute  a  variety  of  squamous  epi- 
thelium. These  cells  possess  short  fine  fibrils  which  pass  from  their  margins  to 
those  of  neighboring  cells,  serving  to  connect  them  together.  They  are  not  closely 
connected  together  by  cement-substance,  but  are  separated  from  each  other  by 
intercellular  channels,  across  which  these  fine  fibrils  may  be  seen  bridging ;  this 
gives  to  the  cell,  when  isolated,  the  appearance  of  being  covered  over  with  a 
number  of  short  spines,  in  consequence  of  the  fibrils  being  broken  through.  They 
were  first  described  by  Max  Schultze  and  Virchow,  and  it  was  believed  by  them 
that  the  cells  were  dovetailed  together.  Subsequently  this  was  shown  not  to  be 
so  by  Martyn,  who  pointed  out  that  the  prickles  were  attached  to  each  other 
by  their  apices  ;  and  recently  Deldpine  has  stated  that  he  believes  the  prickles  of 
prickle-cells  are  parts  of  fibrils  forming 
internuclear  bundles  between  the  nuclei 
of  the  cells  of  an  epithelium  in  a  state 
of  active  growth  (see  Fig.  597). 

Transitional  epithelium  occurs  in  the 
ureters  and  urinary  bladder.  Here  the 
cells  of  the  most  superficial  layer  are 
cubical,  with  depressions  on  their  under 
surfaces,  which  fit  on  to  the  rounded  ends 
of  the  cells  of  the  second  layer,  which 
are  pear-shaped,  the  apices  touching  the  basement-membrane.  Between  their 
tapering  points  is  a  third  variety  of  cells,  filling  in  the  intervals  between  them, 
and  of  smaller  size  than  those  of  the  other  two  layers  (Fig.  609). 


Fig.  608. 
the  finger, 
tology.") 


-Portion  of  epidermis  from  a  section  of  the  skin  of 
(Ranvier.)     (From  Schafer's  "Essentials  of  His- 


Fig.  609—  Transitional  epithelium. 


1086 


GENERAL   ANATOMY   OB   HISTOLOGY. 


CONNECTIVE  TISSUES. 

The  term  connective  tissue  includes  a  number  of  tissues  which  possess  this 
feature  in  common,  viz.,  that  they  serve  the  general  purpose  in  the  animal  econ- 
omy of  supporting  and  connecting  the  tissues  of  the  body.  These  tissues  may 
differ  considerably  from  each  other  in  appearance,  but  they  present,  nevertheless, 
many  points  of  relationship,  and  are,  moreover,  developed  from  the  same  layer 
of  the  embryo,  the  mesoblast.  They  are  divided  into  three  great  groups :  (1) 
the  connective  tissues  proper,  (2)  cartilage,  and  (3)  bone.  Blood,  which  has 
already  been  described,  is,  strictly  speaking,  a  form  of  connective  tissue,  and  is  so 
dealt  with  by  many  histologists. 

The  Connective  Tissues  Proper. — Several  forms  or  varieties  of  connective  tissue 
are  recognized:  (1)  Areolar  tissue.  (2)  White  fibrous  tissue.  (3)  Yellow  elastic 
tissue.  (4)  Mucous  tissue.  (5)  Retiform  tissue.  They  are  all  composed  of  a  homo- 
geneous matrix,  in  which  are  imbedded  cells  and  fibres — the  latter  of  two 
kinds,  white  and  yellow  or  elastic.  The  distinction  between  the  different  forms 
of  tissue  depends  upon  the  relative  preponderance  of  one  or  other  kind  of  fibre,  of 
cells,  or  of  matrix. 

Areolar  tissue  (Fig.  610)  is  so  called  because  its  meshes  are  easily  distended,  and 
thus  separated  into  areolae  or  spaces,  which  open  freely  into  each  other,  and  are 

Plasma  cell. 


^.White  fibres. 


Lamellar  cell. 
Fig.  610.— Subcutaneous  tissue  from  a  young  rabbit.    Highly  magnified.    (Schafer.) 

consequently  easily  blown  up  with  air,  or  permeated  by  fluid  when  injected  into 
any  part  of  the  tissue.  Such  spaces,  however,  do  not  exist  in  the  natural  con- 
dition of  the  body,  but  the  whole  tissue  forms  one  unbroken  membrane  com- 
posed of  a  number  of  interlacing  fibres,  variously  superimposed.  Hence  the 
term  "the  cellular  membrane"  is  in  many  parts  of  the  body  more  appropriate 
than  its  more  modern  equivalent.  The  chief  use  of  the  areolar  tissue  is  to  bind 
parts  together,  while  by  the  laxity  of  its  fibres  and  the  permeability  of  its  areolae 
it  allows  them  to  move  on  each  other,  and  affords  a  ready  exit  for  inflammatory 
and  other  effused  fluids.  It  is  one  of  the  most  extensively  distributed  of  all  the 
tissues.  It  is  found  beneath  the  skin  in  a  continuous  layer  all  over  the  body, 
connecting  it  to  the  subjacent  parts.  In  the  same  way  it  is  situated  beneath  the 
mucous  and  serous  membranes.     It  is  also  found  between  muscles,  vessels,  and 


THE    CONNECTIVE    TISSUES. 


1087 


nerves,  forming  investing  sheaths  for  them,  and  connecting  them  with  surround- 
ing structures.  In  addition  to  this,  it  is  found  in  the  interior  of  organs,  binding 
together  the  various  lobes  and  lobules  of  the  compound  glands,  the  various  coats 
of  the  hollow  viscera,  and  the  fibres  of  muscles,  etc.,  and  thus  forms  one  of  the 
most  important  connecting  media  of  the  various  structures  or  organs  of  which 
the  body  is  made  up.  In  many  parts  the  areolae  or  interspaces  of  areolar 
tissue  are  occupied  by  fat-cells,  constituting  adipose  tissue,  which  will  presently 
be  described. 

Areolar  tissue  presents  to  the  naked  eye  a  flocculent  appearance,  somewhat 
like  spun  silk.  When  stretched  out,  it  is  seen  to  consist  of  delicate  soft  elastic 
threads  interlacing  with  each  other  in  every  direction  and  forming  a  network  of 
extreme  delicacy.  When  examined  under  the  microscope  (Fig.  610)  it  is  found 
to  be  composed  of  white  fibres  and  elastic  fibres  intercrossing  in  all  directions, 
and  united  together  by  a  homogeneous  cement  or  ground-substance,  the  matrix, 
showing  cell-spaces  wherein  lie  many  cellular  elements,  the  connective-tissue  cor- 
puscles ;  these  contain  the  protoplasm  out  of  which  the  whole  is  developed  and 
regenerated. 

The  white  fibres  are  arranged  in  waving  bands  or  bundles  of  minute  transpar- 
ent homogeneous  filaments  or  fibrillar.  The  bundles  have  a  tendency  to  split  up 
longitudinally  or  send  off  slips  to  join  neighboring  bundles  and  receive  others  in 
return,  but  the  individual  fibres  are  unbranched  and  never  join  other  fibres ;  the 
yellow  elastic  fibres  have  a  well-defined  outline  and  are  considerably  larger  in  size 
than  the  white  fibrillse.  They  vary  much,  being  from  the  2Tiro  o  *°  *ne  ToVo  °f 
an  inch  in  diameter.  The  fibres  form  bold  and  wide  curves,  branch,  and  freely 
anastomose  with  each  other.  They  are  homogeneous  in  appearance,  and  tend  to 
curl  up,  especially  at  their  broken  ends. 

Connective-tissue  Corpuscles. — The  cells  of  areolar  tissue  are  of  three  principal 
kinds  :  (1)  Flattened  lamellar  cells,  which  may  be  either  branched  or  unbranched. 
The  branched  lamellar  cells  are  composed  of  clear  cell-substance,  in  which  is  con- 
tained an  oval  nucleus.  The  processes  of  these  cells  unite  so  as  to  form  an  open 
network,  as  in  the  cornea.  The  unbranched  cells  are  joined  edge  to  edge  like  the 
cells  of  an  epithelium.  The  "tendon-cells,"  presently  to  be  described,  are  an 
example  of  this  variety.  (2)  Granule-cells,  which  are  ovoid  or  spheroidal  in  shape 
and  formed  of  a  soft  protoplasm,  containing  granules  which  are  albuminous  in 
character  and  stain  deeply  with  eosin.  (3)  Plasma-cells  of  Waldeyer,  varying 
greatly  in  size  and  form,  but  always  to  be  distinguished  from  the  other  two 
varieties  by  containing  a 
largely  vacuolated  proto- 
plasm. The  vacuoles  are 
filled  with  fluid,  and  the 
protoplasm  between  the  spaces 
is  clear,  with  occasionally  a 
few  scattered  granules. 

In  addition  to  these  three 
typical  forms  of  connective- 
tissue  corpuscles,  areolar 
tissue  may  be  seen  to  possess 
wandering  cells,  i.  e.,  leuco- 
cytes which  have  emigrated 
from  the  neighboring  vessels, 

and  in  some  instances,  as  in  the  choroid  coat  of  the  eye,  cells  filled  with  granules 
of  pigment  (pigment-cells). 

The  connective-tissue  corpuscles  lie  in  spaces  in  the  ground-substance  between 
the  bundles  of  fibres,  and  these  spaces  may  be  brought  into  view  by  treating  the 
tissue  with  nitrate  of  silver  and  exposing  it  to  the  light.  This  will  color  the 
ground-substance  and  leave  the  cell-spaces  unstained. 

The  white  fibrous  tissue  (Fig.  611)  is  a  true  connecting  structure,  and  serves 


Fig.  611. — White  fibrous  tissue.    High  power. 


1088 


GENERAL   ANATOMY   OB   HISTOLOGY. 


three  purposes  in  the  animal  economy.  In  the  form  of  ligaments  it  serves  to 
bind  bones  together  ;  in  the  form  of  tendons,  it  serves  to  connect  muscles  to  bones 
or  other  structures,  and  it  forms  an  investing  or  protecting  structure  to  various 
organs  in  the  form  of  membranes.  Examples  of  where  it  serves  this  latter  office 
are  to  be  found  in  the  muscular  fasciae  or  sheaths,  the  periosteum,  and  perichon- 
drium ;  the  investments  of  the  various  glands  (such  as  the  tunica  albuginea  testis, 
the  capsule  of  the  kidney,  etc.),  the  investing  sheath  of  the  nerves  (epineurium), 
and  of  various  organs,  as  the  penis  and  the  eye  (sheath  of  the  corpora  cavernosa 
and  corpus  spongiosum,  and  of  the  sclerotic).  In  white  fibrous  tissue,  as  its  name 
implies,  the  white  fibres  predominate,  the  matrix  being  apparent  only  as  a  cement- 
substance,  the  yellow  elastic  fibres  comparatively  few,  while  the  tissue-cells  are 
arranged  in  a  special  manner.  It  presents  to  the  naked  eye  the  appearance  of 
silvery-Avhite  glistening  fibres,  covered  over  with  a  quantity  of  loose,  flocculent 
tissue  which  binds  the  fibres  together  and  carries  the  blood-vessels  (Fig.  612). 
It  is  not  possessed  of  any  elasticity,  and  only  the  very  slightest  extensibility ; 
it    is    exceedingly  strong,   so    that    upon    the    application  of  any  external   vio- 


«  \\\\\, 


ff 


vt 


nu 


Hi 


mx 


Fig.  612.— Connective  tissue.  (Klein  and 
Noble  Smith.)  a.  The  white  fibrous  element — 
a  layer  of  more  or  less  sharply-outlined,  paral- 
lel, wavy  bundles  of  connective-tissue  fibrils. 
On  the  surface  of  this  layer  is  b,  a  network  of 
fine  elastic  fibres. 


Fig.  613.— Tendon  of  mouse's  tail,  stained 
with  haematoxylin,  showing  chains  of  cells 
between  the  tendon-bundles.  (From  Quain's 
Anatomy.    E.  A.  Schafer.) 


lence  the  bone  with  which  it  is  connected  will  fracture  before  the  fibrous  tissue 
will  give  way.  In  ligaments  and  tendons  the  bundles  run  parallel  with  each 
other ;  in  membranes  they  intersect  one  another  in  different  places.  The  cells 
occurring  in  white  fibrous  tissue  are  often  called  "  tendon  cells."  They  are 
situated  on  the  surface  of  groups  of  bundles  and  are  quadrangular  in  shape, 
arranged  in  rows  in  single  file,  each  cell  being  separated  from  its  neighbors  by  a 
narrow  line  of  cement-substance.  The  nucleus  is  generally  situated  at  one  end 
of  the  cell,  the  nucleus  of  the  adjoining  cell  being  in  close  proximity  to  it  (Fig. 
613).  Upon  the  addition  of  acetic  acid  to  white  fibrous  tissue  it  swells  up  into  a 
glassy-looking,  indistinguishable  mass.  When  boiled  in  water  it  is  converted 
almost  completely  into  gelatin.  The  white  fibres  being  composed  of  the  albu- 
minoid collagen,  which  is  often  regarded  as  the  anhydride  of  gelatin. 

Yellow  Elastic  Tissue. — In  certain  parts  of  the  body  a  tissue  is  found  which 
when  viewed  in  mass  is  of  a  yellowish  color,  and  is  possessed  of  great  elasticity,  so 
that  it  is  capable  of  considerable  extension,  and  when  the  extending  force  is  with- 
drawn returns  at  once  to  its  original  condition.  This  is  yellow  elastic  tissue, 
which  may  be  regarded   as  a  connective  tissue  in  which  the  yellow  elastic  fibres 


THE    CONNECTIVE    TISSUES. 


1089 


have  developed  to  the  practical  exclusion  of  the  other  elements.  It  is  found  in 
the  ligamenta  subflava,  in  the  vocal  cords,  in  the  longitudinal  coat  of  the  trachea 
and  bronchi,  in  the  inner  coats  of  the  blood-vessels,  especially  the  larger  arteriesr 
and  to  a  very  considerable  extent  in  the  thyro-hyoid,  crico-thyroid,  and  stylo-hyoid 
ligaments.  It  is  also  found  in  the  ligamentum  nuchge  of  the  lower  animals  (Fig. 
614).  In  some  parts,  where  the  fibres  are  broad  and  large  and  the  network  close, 
the  tissue  presents  the  appearance  of  a  membrane,  with  gaps  or  perforations  cor- 
responding to  the  intervening  space.  This  is  to  be  found  in  the  inner  coat  of  the 
arteries,  and  to  it  the  name  of  fenestrated  membrane  has  been  given  by  Henle. 
The  yellow  elastic  fibres  remain  unaltered  by  acetic  acid.  Chemically  they  are 
composed  of  the  albuminoid  body,  elastin. 

Vessels  and  Nerves  of  Connective  Tissue. — The  blood-vessels  of  connective  tissue 
are  very  few — that  is  to  say,  there  are  few  actually  destined  for  the  tissue  itself, 


Fig.  614. — Yellow  elastic  tissue.    High  power. 

although  many  vessels  may  permeate  one  of  its  forms,  the  areolar  tissue,  carrying 
blood  tc  other  structures.  In  Avhite  fibrous  tissue  the  blood-vessels  usually  run 
parallel  to  the  longitudinal  bundles  and  between  them,  sending  transverse  com- 
municating branches  across,  and  in  some  forms,  as  the  periosteum  and  dura  mater, 
they  are  fairly  numerous.  In  the  yellow  elastic  tissue  the  blood-vessels  also  run 
between  the  fibres,  and  do  not  penetrate  them.  Lymphatic  vessels  are  very  numer- 
ous in  most  forms  of  connective  tissue,  especially  in  the  areolar  tissue  beneath  the 
skin  and  the  mucous  and  the  serous  surfaces.  They  are  also  found  in  abundance 
in  the  sheaths  of  tendons,  as  well  as  in  the  tendons  themselves.  Nerves  are 
to  be  found  in  the  white  fibrous  tissue,  where  they  terminate  in  a  special  manner; 
but  it  is  doubtful  whether  any  nerves  terminate  in  areolar  tissue ;  at  all  events, 
they  have  not  yet  been  demonstrated,  and  the  tissue  is  possessed  of  very  little 
sensibility. 

69 


1090 


GENERAL    ANATOMY   OB    HISTOLOGY. 


Development  of  Connective  Tissue. — Connective  tissue  is  developed  from 
embryonic  connective-tissue  cells  derived  from  the  mesoblast.  These  cells,  at 
first  rounded,  become  fusiform  and  branched,  and  ultimately  become  the  con- 
nective-tissue corpuscles.  A  mucinous  intercellular  substance  or  matrix,  partly 
formed  from  the  cells  themselves  and  partly  from  the  lymph  exuded  by  the 
neighboring  blood-vessels,  gradually  separates  the  cells.       In   the   matrix    the 


Fig.  615. — Mucous  tissue. 

fibres  are  deposited,  probably  under  the  influence  of  the  cells,  but  not  by  any 
transformation  of  the  cell  protoplasm.  In  the  case  of  yellow  elastic  fibres,  rows 
of  granules  of  elastin  are  first  laid  down,  these  eventually  fusing  to  form  the  fully 
developed  fibre. 

1.  Mucous  tissue  exists  chiefly  in  the  "jelly  of  Wharton,"  which  forms  the  bulk 

of  the  umbilical  cord,  but  is  also  found 
in  other  situations  in  the  foetus,  chiefly 
as  a  stage  in  the  development  of  the  con- 
nective tissue.  It  consists  of  a  matrix, 
largely  made  up  of  mucin,  in  which  are 
nucleated  cells  with  branching  and  anasto- 
mosing processes  (Fig.  615).  Few  fibres 
are  seen  in  typical  mucous  tissue,  though, 
at  birth,  the  umbilical  cord  shows  consid- 
erable development  of  fibres.  In  the  adult 
the  vitreous  humor  of  the  eye  is  a  persis- 
tent form  of  mucous  tissue,  in  which  there 
are  no  fibres,  and  from  which  the  cells 
have  disappeared,  leaving  only  the  mucin- 
ous ground-substance. 

2.  Retiform  connective  tissue  is  found 
extensively  in  many  parts  of  the  body, 
forming  the  framework  of  some  organs 
and  entering  into  the  construction  of 
many  mucous  membranes.  It  is  a  form  of  connective  tissue,  in  which  the  inter- 
cellular or  ground-substance  has,  in  a  great  measure,  disappeared,  and  has  been 
replaced  by  fluid.  It  is  apparently  composed  almost  entirely  of  extremely  fine 
bundles  of  white  fibrous  tissue,  forming  an  intricate  network,  yet  chemically 
it  yields,  besides  gelatin,  a  fresh  substance,  reticulin.  The  fibres  are  covered 
and  concealed  by  flattened  branched  connective-tissue  cells,  and  these  must  be 


Fig.  616.— Retiform  connective  tissue,  from  a 
lymphatic  gland ;  most  of  the  Ivmph-corpuscles 
are  removed.  (From  Klein's  "Elements  of  His- 
tology.") a,  The  reticulum,  c,  A  capillary  blood- 
vessel. 


THE    CONNECTIVE    TISSUES. 


1091 


removed  or  brushed  away  before  the  fibres  become  visible.  In  many  situations 
the  interstices  of  the  network  are  filled  with  rounded  lymph-corpuscles,  and  the 
tissue  is  then  termed  lymphoid  or  adenoid  tissue  (Fig.  616). 

3.   Basement-membranes,  formerly  described  as  homogeneous  membranes,  are 
really  a  form  of  connective  tissue.     They  constitute  the  supporting  membrane, 


Fig.  617.— Adipose  tissue.    High  power,    a,  Star-like  appearance  from  crystallization  of  fatty  acids. 


or  membrana  propria,  on  which  is  placed  the  epithelium  of  mucous  membranes  or 
secreting  glands,  and  in  other  situations.  By  means  of  staining  with  nitrate  of 
silver  they  may  be  shown  to  consist  of  flattened  cells  in  close  opposition,  and 
joined  together  by  their  edges,  thus 
forming  an  example  of  an  epithelioid 
arrangement  of  connective-tissue  cells. 
In  some  situations  the  cells,  instead 
of  adhering  by  their  edges,  give  off 
branching  processes,  which  join  with 
similar  processes  of  other  cells,  and 
so  form  a  network  rather  than  a  con- 
tinuous membrane.  In  other  instances 
basement-membranes  are  composed  of 
elastic  tissue,  as  in  the  cornea,  or, 
again,  in  other  cases  of  condensed 
ground-substance. 

Adipose  Tissue. — In  almost  all 
parts  of  the  body  the  ordinary  areolar 
tissue  contains  a  variable  quantity  of 
fat.  The  principal  situations  where 
it  is  not  found  are  the  subcutaneous 
tissue  of  the  eyelids,  the  penis  and 
scrotum,  the  nymphse,  within  the 
cavity  of  the  cranium,  and  in  the 
lungs,  except  near  their  roots.  Nevertheless,  its  distribution  is  not  uniform  :  in 
some  parts  it  is  collected  in  great  abundance,  as  in  the  subcutaneous  tissue,  espe- 
cially of  the  abdomen  ;  around  the  kidneys;  on  the  surface  of  the  heart  between 
the  furrows ;  and  in  some  other  situations.  Lastly,  fat  enters  largely  into  the 
formation  of  the  marrow  of  bones.  A  distinction  must  be  made  between  fat  and 
adipose  tissue;  the  latter  being  a  distinct  issue,  the  former  an  oily  matter,  which 
in  addition  to  forming  adipose  tissue  is  also  widely  present  in  the  body,  as  in  the 
fat  of  the  brain  and  liver,  and  in  the  blood  and  chyle,  etc. 

Adipose  tissue  consists  of  small  vesicles,  fat-cells,  lodged  in  the  meshes  of 
areolar  tissue.       The  fat-cells  (Fig.  617)  vary  in  size,  but  of  about  the  average 


Fig.  618.— Development  of  fat.  (Klein  and  Noble 
Smith.)  a.  Minute  artery,  v,  Minute  vein,  c.  Capillary 
elood-vessls  in  the  course  of  formation :  they  are  not 
yet  completely  hollowed  out,  there  being  still  left  in 
them  protoplasmic  septa,  rf.  The  ground-substance,  con- 
taining numerous  nucleated  cells,  some  of  which  are 
more  distinctly  branched  and  flattened  than  others,  and 
appear  therefore  more  spindle-shaped. 


1092  GENERAL    ANATOMY   OR    HISTOLOGY. 

diameter  of  -g-j^j-  of  an  inch.  They  are  formed  of  an  exceedingly  delicate  proto- 
plasmic membrane,  filled  with  fatty  matter,  -which  is  liquid  during  life,  but 
becomes  solidified  after  death.  They  are  round  or  spherical  where  they  have 
not  been  subjected  to  pressure ;  otherwise  they  assume  a  more  or  less  angular 
outline.  A  nucleus  is  always  present,  and  can  be  easily  demonstrated  by  staining 
with  hematoxylin  ;  in  the  natural  condition  it  is  so  compressed  by  the  contained 
oily  matter  as  to  be  scarcely  recognizable.  These  fat-cells  are  contained  in  clus- 
ters in  the  areolae  of  fine  connective  tissue,  and  are  held  together  mainly  by  a 
network  of  capillary  blood-vessels,  which  are  distributed  to  them. 

Chemically  the  oily  material  in  the  cells  is  composed  of  the  fats,  olein, 
palmitin,  and  stearin,  which  are  glycerin  compounds  with  fatty  acids.  Some- 
times fat-crystals  form  in  the  cells  after  death  (Fig.  617,  a).  By  boiling  the  tissue 
in  ether  or  strong  alcohol,  the  fat  may  be  extracted  from  the  vesicle,  which  is  then 
seen  empty  and  shrunken. 

Fat  is  said  to  be  first  detected  in  the  human  embryo  about  the  fourteenth 
week.  The  fat-cells  are  formed  by  the  transformation  of  connective-tissue 
corpuscles,  in  which  small  droplets  of  oil  are  formed  ;  these  coalesce  to  produce  a 
larger  drop,  and  this  increases  until  it  distends  the  corpuscle,  the  remaining 
protoplasm  and  the  nucleus  being  crowded  to  the  periphery  of  the  cell  (Fig.  618). 

THE  PIGMENT. 

In  various  parts  of  the  body  pigment  is  found ;  most  frequently  in  epithelial 
cells  and  in  the  cells  of  connective  tissue.  Pigmented  epithelial  cells  are  found 
in   the   external   layer  of  the   retina   and    on    the   posterior   surface  of  the   iris. 

Pigment  is  also  found  in  the  epithelial  cells  of  the 
deeper  layers  of  the  cuticle  in  some  parts  of  the  body 
— such  as  the  areola  of  the  nipple  and  in  colored 
patches  of  skin,  and  especially  in  the  skin  of  the 
colored  races,  and  also  in  hair.  It  is  also  found  in 
the  epithelial  cells  of  the  olfactory  region  and  of  the 
membranous  labyrinth  of  the  ear. 

In  the  connective-tissue  cells  pigment  is  fre- 
quently met  with  in  the  lower  vertebrates.  In  man 
it  is  found  in  the  choroid  coat  of  the  eye  (Fig.  619) 
and  in  the  iris  of  all  but  the  light-blue  eyes  and  the 
albino.     It  is  also  occasionally  met  with  in  the  cells 

Fig.    619.  —  Pigment-cells    from         ?        ,-n  ,■  j    •       ,i  .■_  r  .ti- 

the choroid  coat  of  the  eyeball.          ot  retitorm  tissue  and  in  the  pia  mater  of  the  upper 

part  of  the  spinal  cord.     These  cells  are  characterized 

by  their  larger  size  and  branched  processes,  which,  as  well  as  the  body  of  the 

cells,   are  filled  with  granules.     The   pigment   consists  of   dark-brown  or  black 

granules  of  very  small  size,    closely  packed    together  within  the  cells,  but  not 

invading  the  nucleus.      Occasionally  the  pigment  is  yellow,  and  when  occurring 

in  the  cells  of  the  cuticle  constitutes  "freckles." 

THE  CARTILAGE. 

Cartilage  is  a  non-vascular  structure  which  is  found  in  various  parts  of  the 
body — in  adult  life  chiefly  in  the  joints,  in  the  parietes  of  the  thorax,  and  in 
various  tubes,  such  as  the  air-passages,  nostrils,  and  ears,  which  are  to  be  kept 
permanently  open.  In  the  foetus  at  an  early  period  the  greater  part  of  the  skele- 
ton is  cartilaginous.  As  this  cartilage  is  afterward  replaced  by  bone,  it  is  called 
temporary,  in  contradistinction  to  that  which  remains  unossified  during  the  whole 
of  life,  and  which  is  called  permanent. 

Cartilage  is  divided,  according  to  its  minute  structure,  into  hyaline  cartilage, 
fibro-cartilage,  and  yellow  or  elastic  white  fibro-cartilage.  Besides  these  varieties 
met  with  in  the  adult  human  subject,  there  is  a  variety  called  cellular  cartilage, 
which  consists  entirely,  or  almost  entirely,  of  cells,  united  in  some  cases  by  a 


THE    CARTILAGE. 


1093 


Fig.  620. — Human   cartilage-cells   from   the  cricoid 
cartilage.    X  350. 


network  of  very  fine  fibres,  in  other  cases  apparently  destitute  of  any  intercellular 
substance.  This  is  found  in  the  external  ear  of  rats,  mice,  and  some  other 
animals,  and  is  present  in  the  chorda  dorsalis  of  the  human  embryo,  but  is  not 
found  in  any  other  human  structure.  The  various  cartilages  in  the  body  are  also 
classified,  according  to  their  function  and  position,  into  articular,  interarticular, 
costal,  and  membraniform. 

Hyaline  cartilage,  which  may  be  taken  as  the  type  of  this  tissue,  consists  of  a 
gristly  mass  of  a  firm  consistence,  but  of  considerable  elasticity  and  of  a  pearly- 
bluish  color.  Except  where  it  coats  the  articular  ends  of  bones,  it  is  covered 
externally  by  a  fibrous  membrane,  the  perichondrium,  from  the  vessels  of  which  it 
imbibes  its  nutritive  fluids,  being  destitute  of  blood-vessels.  It  contains  no  nerves. 
Its  intimate  structure  is  very  simple. 
If  a  thin  slice  is  examined  under  the 
microscope,  it  will  be  found  to  consist 


of  a  rounded  or  bluntly  angular  form,       J|  ^r**  \      /dfy'  I 

lying  in  groups  of  two  or  more  in  a 
granular  or  almost  homogeneous  matrix 
(Fig.  620).  The  cells,  when  arranged 
in  groups  of  two  or  more,  have  gener- 
ally a  straight  outline  where  they  are 
in  contact  with  each  other,  and  in  the 
rest  of  their  circumference  are  rounded. 
The  cell-contents  consist  of  clear  trans- 
lucent protoplasm,  in  which  fine  inter- 
lacing filaments  and  minute  granules  may  sometimes  be  seen  ;  imbedded  in  this 
are  one  or  two  round  nuclei,  having  the  usual  intranuclear  network.  The  cells  are 
imbedded  in  cavities  in  the  matrix,  called  cartilage  lacunce ;  around  these  the 
matrix  is  arranged  in  concentric  lines,  as  if  it  had  been  formed  in  successive  por- 
tions around  the  cartilage-cells.  This  constitutes  the  so-called  capsule  of  the 
space.  Each  lacuna  is  generally  occupied  by  a  single  cell,  but  during  the  division 
of  the  cells  it  may  contain  two,  four,  or  eight  cartilage-cells.  By  exposure  to  the 
action  of  an  electric  shock  the  cell  assumes  a  jagged  outline  and  shrinks  away 
from  the  interior  of  the   capsule. 

The  matrix  is  transparent  and  apparently  without  structure,  or  else  presents 
a  dimly  granular  appearance,  like  ground  glass.  Some  observers  have  shown 
that  the  matrix  of  hyaline  cartilage,  and  especially  the  articular  variety,  after 
prolonged  maceration,  can  be  broken  up  into  fine  fibrils.  These  fibrils  are  proba- 
bly of  the  same  nature,  chemically,  as  the  white  fibres  of  connective  tissue.  It 
is  believed  by  some  histologists  that  the  matrix  is  permeated  by  a  number  of 
fine  channels,  which  connect  the  lacunae  with  each  other,  and  that  these  canals 
communicate  with  the  lymphatics  of  the  perichondrium,  and  thus  the  structure  is 
permeated  with  a  current  of  nutrient  fluid.      This,  however,  is  somewhat  doubtful. 

Articular  cartilage,  costal  cartilage,  and  temporary  cartilage  are  all  of  the 
hyaline  variety.  They  present  minute  differences  in  the  size  and  shape  of  their 
cells  and  in  the  arrangement  of  their  matrix.  In  articular  cartilage,  which  shows 
no  tendency  to  ossification,  the  matrix  is  finely  granular  under  a  high  power ;  the 
cells  and  nuclei  are  small,  and  are  disposed  parallel  to  the  surface  in  the  superficial 
part,  while  nearer  to  the  bone  they  become  vertical.  Articular  cartilages  have  a 
tendency  to  split  in  a  vertical  direction  ;  in  disease  this  tendency  becomes  very 
manifest.  Articular  cartilage  is  not  covered  by  perichondrium,  on  its  free  surface, 
where  it  is  exposed  to  friction,  though  a  layer  of  connective  tissue  can  be  traced 
in  the  adult  over  a  small  part  of  its  circumference  continuous  with  that  of  the 
synovial  membrane,  and  here  the  cartilage-cells  are  more  or  less  branched  and  pass 
insensibly  into  the  branched  connective-tissue  corpuscles  of  the  synovial  membrane. 

Articular  cartilage  forms  a  thin  incrustation  upon  the  joint-surfaces  of  the 
bones,  and  its  elasticity  enables  it  to  break  the  force  of  any  concussion,  while  its 
smoothness  affords  ease  and  freedom  of  movement.     It  varies  in  thickness  accord- 


1094 


GENERAL    ANATOMY   OB    HISTOLOGY. 


Fig.  621.— Costal  cartilage  from  a  man  seventy- 
six  years  of  age,  showing  the  development  of  fibrous 
structure  in  the  matrix.  In  several  portions  of  the 
specimen  two  or  three  generations  of  cells  are  seen 
enclosed  in  a  parent  cell-wall.    High  power. 


ing  to  the  shape  of  the  articular  surface  on  which  it  lies ;  where  this  is  convex  the 
cartilage  is  thickest  at  the  centre,  where  the  greatest  pressure  is  received  ;  and  the 
reverse  is  the  case  on  the  concave  articular  surfaces.  Articular  cartilage  appears 
to  derive  its  nutriment  partly  from  the  vessels  of  the  neighboring  synovial  mem- 
brane, partly  from  those  of  the  bone  upon  which  it  is  implanted.      Toynbee  has 

shown  that  the  minute  vessels  of  the  can- 
cellous tissue  as  they  approach  the  articu- 
lar lamella  dilate  and  form  arches,  and 
then  return  into  the  substance  of  the 
bone. 

In  costal  cartilage  the  cells  and  nuclei 
are  large,  and  the  matrix  has  a  tendency 
to  fibrous  striation,  especially  in  old  age 
(Fig.  621).  In  the  thickest  parts  of  the 
costal  cartilages  a  few  large  vascular 
channels  may  be  detected.  This  appears, 
at  first  sight,  to  be  an  exception  to  the 
statement  that  cartilage  is  a  non-vascular 
tissue,  but  is  not  so  really,  for  the  vessels 
give  no  branches  to  the  cartilage  sub- 
stance itself,  and  the  channels  may  rather 
be  looked  upon  as  involutions  of  the  peri- 
chondrium. The  ensiform  cartilage  may 
be  regarded  as  one  of  the  costal  cartilages, 
and  the  cartilages  of  the  nose  and  of  the 
larynx  and  trachea  (except  the  epiglottis  and  cornicula  laryngis,  which  are  com- 
posed of  elastic  fibro-cartilage)  resemble  them  in  microscopical  characters. 

Temporary  cartilage  and  the  process  of  its  ossification  will  be  described  with 
bone.  The  hyaline  cartilages,  especially  in  adult  and  advanced  life,  are  prone  to 
calcify — that  is  to  say,  to  have  their  matrix  permeated  by  the  salts  of  lime  without 
any  appearance  of  true  bone.  The  process  of  calcification  occurs  also  and  still 
more  frequently,  according  to  Rollett,  in  such  cartilages  as  those  of  the  trachea 
and  in  the  costal  cartilages,  which  are  prone  afterward  to  conversion  into  true 
bone. 

White  fibro-cartilage  consists  of  a  mixture  of  white  fibrous  tissue  and  cartilagi- 
nous tissue  in  various  propor- 
tions ;  it  is  to  the  first  of  these 
two  constituents  that  its  flexi- 
bility and  toughness  are  chiefly 
owing,  and  to  the  latter  its  elas- 
ticity. When  examined  under 
the  microscope  it  is  found  to  be 
made  up  of  fibrous  connective 
tissue  arranged  in  bundles,  with 
cartilage-cells  between  the  bun- 
dles ;  these  to  a  certain  extent 
resemble  tendon-cells,  but  may 
be  distinguished  from  them  by 
being  surrounded  by  a  concen- 
trically striated  area  of  cartilage 
matrix  and  by  their  being  less 
flattened  (Fig.  622).  The  fibro-cartilages  admit  of  arrangement  into  four  groups 
— interarticular,  connecting,  circumferential,  and  stratiform. 

1.  The  interarticular  fibro-cartilages  (menisci)  are  flattened  fibrocartilaginous 
plates,  of  a  round,  oval,  triangular,  or  sickle-like  form,  interposed  between  the  articu- 
lar cartilages  of  certain  joints.  They  are  free  on  both  surfaces,  thinner  toward  their 
centre  than  at  their  circumference,  and  held  in  position  by  the  attachment  of  their 


>m: 


Fig.  622.— White  fibro-cartilage  from  an  intervertebral  disc. 


THE  CARTILAGE. 


1095 


margins  and  extremities  to  the  surrounding  ligaments.  The  synovial  membrane 
of  the  joint  is  prolonged  over  them  a  short  distance  from  their  attached  margins. 
They  are  found  in  the  temporo-mandibular,  sterno-clavicular,  acromio-clavicular, 
wrist-  and  knee-joints.  These  cartilages  are  usually  found  in  those  joints  which  are 
most  exposed  to  violent  concussion  and  subject  to  frequent  movement.  Their  use 
is  to  maintain  the  apposition  of  the  opposed  surfaces  in  their  various  motions  ;  to 
increase  the  depth  of  the  articular  surfaces  and  give  ease  to  the  gliding  movement ; 
to  moderate  the  effects  of  great  pressure  and  deaden  the  intensity  of  the  shocks  to 
which  the  parts  may  be  subjected.  Humphry  has  pointed  out  that  these  inter- 
articular  fibro-cartilages  serve  an  important  purpose  in  increasing  the  variety  of 
movements  in  a  joint.  Thus,  in  the  knee-joint  there  are  two  kinds  of  motion, 
viz.,  angular  movement  and  rotation,  although  it  is  a  hinge  joint,  in  which,  as 
a  rule,  only  one  variety  of  motion  is  permitted ;  the  former  movement  takes  place 
between  the  condyles  of  the  femur  and  the  interarticular  cartilage,  the  latter  between 
the  cartilage  and  the  head  of  the  tibia.  So,  also,  in  the  temporo-mandibular  joint, 
the  upward  and  downward  movement  of  opening  and  shutting  the  mouth  takes  place 
between  the  fibro-cartilage  and  the  jaw-bone,  the  grinding  movement  between  the 
glenoid  cavity  and  the  fibro-cartilage,  the  latter  moving  with  the  jaw-bone. 

2.  The  connecting  fibro-cartilages  are  interposed  between  the  bony  surfaces  of 
those  joints  which  admit  of  only  slight  mobility,  as  between  the  bodies  of  the 
vertebne  and  between  the  pubic  bones.  They  form  disks,  which  adhere  closely  to 
both  of  the  opposed  surfaces,  and  are  composed  of  concentric  rings  of  fibrous  tissue, 
with  cartilaginous  laininge  interposed,  the  former  tissue  predominating  toward  the 
circumference,  the  latter  toward  the  centre. 

3.  The  circumferential  fibro-cartilages  consist  of  a  rim  of  fibro-cartilage,  which 
surrounds  the  margin  of  some  of  the  articular  cavities,  as  the  cotyloid  cavitv  of 
the  hip  and  the  glenoid  cavity  of  the  shoulder ;  they  serve  to  deepen  the  articular 
surface,  and  to  protect  its  edges. 

4.  The  stratiform  fibro-cartilages  are  those  which  form  a  thin  coating  to  osseous 
grooves  through  which  the  tendons  of  certain  muscles  glide.  Small  masses  of  fibro- 
cartilages  are  developed  also  in  the  tendons  of  some  muscles,  where  they  glide  over 
bones,  as  in  the  tendons  of  the  Peroneus  longus  and  the  Tibialis  posticus. 

Yellow  or  elastic  fibro-cartilage  is  found  in  the  human  body  in  the  auricle  of 
the  external  ear,  the  Eustachian  tubes,  the  cornicula  laryngis,  and  the  epiglottis. 
It  consists  of  cartilage-cells  and  a  matrix,  the  latter  being  pervaded  in  every  direc- 
tion,     except      immediately 

'&) 


around  each  cell,  where  there 
is  a  variable  amount  of  non- 
fibrillated  hyaline,  intercellu- 
lar substance,  by  a  network 
of  yellow  elastic  fibres, 
branching  and  anastomosing 
in  all  directions  (Fig.  623). 
The  fibres  resemble  those  of 
yellow  elastic  tissue,  both  in 
appearance  and  in  being  un- 
affected by  acetic  acid  ;  and 
according  to  Rollett  their  con- 
tinuity with  the  elastic  fibres 
of  the  neighboring;  tissue  ad- 
mits  of  being  demonstrated. 
The  distinguishing  feature 
of  cartilage  as  to  its  chemical  composition  is  that  it  yields  on  boilino*  a  substance 
called  chondrin,  very  similar  to  gelatin,  but  differing  from  it  in  several  of  its  reac- 
tions. •  It  is  now  believed  that  chondrin  is  not  a  simple  body,  but  a  mixture  of 
gelatin  with  mucinoid  substances,  chief  among  which,  perhaps,  is  a  compound 
termed  chondro-mucoid. 


Fig.  623.— Yellow  cartilage,  ear  of  horse.    High  power. 


1096  GENERAL   ANATOMY   OR   HISTOLOGY. 


THE    BONE. 

Structure  and  Physical  Properties  of  Bone. — Bone  is  one  of  the  hardest  struct- 
ures of  the  animal  body  ;  it  possesses  also  a  certain  degree  of  toughness  and 
elasticity.  Its  color,  in  a  fresh  state,  is  of  a  pinkish  white  externally,  and  a  deep 
red  within.  On  examining  a  section  of  any  bone,  it  is  seen  to  be  composed  of  two 
kinds  of  tissue,  one  of  which  is  dense  in  texture,  like  ivory,  and  is  termed  com- 
pact tissue;  the  other  consists  of  slender  fibres  and  lamellfe,  which  join  to  form 
a  reticular  structure  ;  this,  from  its  resemblance  to  lattice-work,  is  called  cancellous 
tissue.  The  compact  tissue  is  always  placed  on  the  exterior  of  the  bone  ;  the  can- 
cellous is  always  internal.  The  relative  quantity  of  these  two  kinds  of  tissue 
varies  in  different  bones,  and  in  different  parts  of  the  same  bone,  as  strength  or 
lightness  is  requisite.  Close  examination  of  the  compact  tissue  shows  it  to  be 
extremely  porous,  so  that  the  difference  in  structure  between  it  and  the  cancellous 
tissue  depends  merely  upon  the  different  amount  of  solid  matter,  and  the  size  and 
number  of  spaces  in  each  ;  the  cavities  being  small  in  the  compact  tissue  and  the 
solid  matter  between  them  abundant,  while  in  the  cancellous  tissue  the  spaces  are 
large  and  the  solid  matter  in  smaller  quantity. 

Bone  during  life  is  permeated  by  vessels  and  is  enclosed,  except  where  it  is 
coated  with  articular  cartilage,  in  a  fibrous  membrane,  the  periosteum,  by  means 
of  which  many  of  these  vessels  reach  the  hard  tissue.  If  the  periosteum  is 
stripped  from  the  surface  of  the  living  bone,  small  bleeding  points  are  seen, 
which  mark  the  entrance  of  the  periosteal  vessels  ;  and  on  section  during  life 
every  part  of  the  bone  will  be  seen  to  exude  blood  from  the  minute  vessels  which 
ramify  in  it.  The  interior  of  the  bones  of  the  limbs  'presents  a  cylindrical  cavity 
filled  with  marrow  and  lined  by  a  highly  vascular  areolar  structure,  called  the 
medullary  membrane  or  internal  periosteum,  which,  however,  is  rather  the  areolar 
envelope  of  the  cells  of  the  marrow  than  a  definite  membrane. 

The  periosteum  adheres  to  the  surface  of  the  bones  in  nearly  every  part, 
excepting  at  their  cartilaginous  extremities.  When  strong  tendons  or  ligaments 
are  attached  to  the  bone,  the  periosteum  is  incorporated  with  them.  It  con- 
sists of  two  layers  closely  united,  the  outer  one  formed  chiefly  of  connective 
tissue,  containing  occasionally  a  few  fat-cells  ;  the  inner  one,  of  elastic  fibres  of 
the  finer  kind,  forming  dense  membranous  networks,  which  can  again  be  separated 
into  several  layers.  In  young  bones  the  periosteum  is  thick  and  very  vascular, 
and  is  intimately  connected  at  either  end  of  the  bone  with  the  epiphyseal  cartilage, 
but  less  closely  with  the  shaft,  from  which  it  is  separated  by  a  layer  of  soft 
tissue,  containing  a  number  of  granular  corpuscles  or  "  osteoblasts,"  in  which 
ossification  proceeds  on  the  exterior  of  the  young  bone.  Later  in  life  the  peri- 
osteum is  thinner,  less  vascular,  and  the  osteoblasts  have  become  converted  into 
an  epithelioid  layer,  which  is  separated  from  the  rest  of  the  periosteum  in  many 
places  by  cleft-like  spaces,  which  are  supposed  to  serve  for  the  transmission  of 
lymph.  The  periosteum  serves  as  a  nidus  for  the  ramification  of  the  vessels 
previous  to  their  distribution  in  the  bone ;  hence  the  liability  of  bone  to  exfolia- 
tion or  necrosis,  when  denuded  of  this  membrane  by  injury  or  disease.  Fine 
nerves  and  lymphatics,  which  generally  accompany  the  arteries,  may  also  be 
demonstrated  in  the  periosteum. 

The  marrow  not  only  fills  up  the  cylindrical  cavity  in  the  shafts  of  the  long 
bones,  but  also  occupies  the  spaces  of  the  cancellous  tissue  and  extends  into  the 
larger  bony  canals  (Haversian  canals)  which  contain  the  blood-vessels.  It  differs 
in  composition  in  different  bones.  In  the  shafts  of  adult  long  bones  the  marrow 
is  of  a  yelloiv  color,  and  contains,  in  100  parts,  96  of  fat,  1  of  areolar  tissue  and 
vessels,  and  3  of  fluid,  with  extractive  matter,  and  consists  of  a  matrix  of  fibrous 
tissue,  supporting  numerous  blood-vessels  and  cells,  most  of  which  are  fat-cells,  but 
some  are  "marrow-cells,"  such  as  occur  in  the  red  marrow,  to  be  immediately 
described.  In  the  flat  and  short  bones,  in  the  articular  ends  of  the  long  bones, 
in  the  bodies  of  the  vertebrae,  in  the  cranial  diploe,  and  in  the  sternum  and  ribs, 


THE   BONE.  1097 

it  is  of  a  red  color,  and  contains,  in  100  parts,  75  of  water  and  25  of  solid  matter, 
consisting  of  cell-globulin,  nucleo-proteid,  extractives,  salts,  and  only  a  small  pro- 
portion of  fat.  The  red  marrow  consists  of  a  small  quantity  of  connective  tissue, 
blood-vessels,  and  numerous  cells  (Fig.  624),  some  few  of  which  are  fat-cells,  but 
the  great  majority  roundish  nucleated  cells,  the  true  "  marrow-cells  "  of  Kolliker. 
These  marrow-cells  proper  resemble  in  appearance  lymphoid  corpuscles,  and  like 
them  are  amoeboid.  Among  them  may  be  seen  smaller  cells,  which  possess  a  slightly 
pinkish  hue  ;  these  are  the  erythroblasts,  from  which,  as  we  have  seen,  the  red 
corpuscles  of  the  adult  are  derived,  and  which  may  be  regarded  as  descendants 
of  the  nucleated  colored  corpuscles  of  the  embryo. 


(SL 


m^^ 


D  0  «$  <®  Q 


Fig.  6^4 —Cells  of  red  marrow  of  the  guinea-pig.    (Schafer.)    a-d.  Myeloplaques.    e-i.  Marrow-cells  proper. 
j-t.  Erythroblasts — some  in  process  of  division. 

Q-iant-celh  (myelo-plaques,  osteoclasts),  large,  multinucleated,  protoplasmic 
masses,  are  also  to  be  found  in  both  sorts  of  adult  marrow,  but  more  particularly 
in  red  marrow.  They  were  believed  by  Kolliker  to  be  concerned  in  the  absorption 
of  bone  matrix,  and  hence  the  name  which  he  gave  to  them — osteoclasts.  They 
excavate  small  shallow  pits  or  cavities,  which  are  named  How  ship  s  lacunas,  in 
which  they  are  found  lying. 

Vessels  of  Bone. — The  blood-vessels  of  bone  are  very  numerous.  Those  of  the 
compact  tissue  are  derived  from  a  close  and  dense  network  of  vessels  ramifying  in 
the  periosteum.  From  this  membrane  vessels  pass  into  the  minute  orifices  in  the 
compact  tissue,  running  through  the  canals  which  traverse  its  substance.  The 
cancellous  tissue  is  supplied  in  a  similar  way,  but  by  a  less  numerous  set  of  larger 
vessels,  which,  perforating  the  outer  compact  tissue,  are  distributed  to  the  cavities 
of  the  spongy  portion  of  the  bone.  In  the  long  bones  numerous  apertures  may 
be  seen  at  the  ends  near  the  articular  surfaces,  some  of  which  give  passage  to  the 
arteries  of  the  larger  set  of  vessels  referred  to ;  but  the  most  numerous  and  largest 
apertures  are  for  the  veins  of  the  cancellous  tissue,  which  run  separately  from  the 
arteries.  The  medullary  canal  in  the  shafts  of  the  long  bones  is  supplied  by  one 
large  artery  (or  sometimes  more),  which  enters  the  bone  at  the  nutrient  foramen 
(situated  in  most  cases  near  the  centre  of  the  shaft),  and  perforates  obliquely  the 
compact  structure.  The  medullary  or  nutrient  artery,  usually  accompanied  by 
one  or  two  veins,  sends  branches  upward  and  downward  to  supply  the  medullary 
membrane,  which  lines  the  central  cavity  and  the  adjoining  canals.  The  ramifica- 
tions of  this  vessel  anastomose  with  the  arteries  both  of  the  cancellous  and  com- 
pact tissues.  In  most  of  the  flat,  and  in  many  of  the  short  spongy  bones,  one 
or  more  large  apertures  are  observed,  which  transmit,  to  the  central  parts  of  the 
bone,  vessels  corresponding  to  the  medullary  arteries  and  veins.  The  veins  emerge 
from  the  long  bones  in  three  places  (Kolliker) :  (1)  by  one  or  two  large   veins, 


1098 


GENERAL    ANATOMY   OR    HISTOLOGY. 


which  accompany  the  artery ;  (2)  by  numerous  large  and  small  veins  at  the  artic- 
ular extremities ;  (3)  by  many  small  veins  which  arise  in  the  compact  substance. 
In  the  flat  cranial  bones  the  veins  are  large,  very  numerous,  and  run  in  tortuous 
canals  in  the  diploic  tissue,  the  sides  of  the  canals  being  formed  by  a  thin  lamella 
of  bone,  perforated  here  and  there  for  the  passage  of  branches  from  the  adjacent 
cancelli.  The  same  condition  is  also  found  in  all  cancellous  tissue,  the  veins  being 
enclosed  and  supported  by  osseous  structure  and  having  exceedingly  thin  coats. 
When  the  bony  structure  is  divided,  the  vessels  remain  patulous,  and  do  not  con- 
tract in  the  canals  in  which  they  are  contained.  Hence  the  occurrence  of  puru- 
lent absorption  after  amputation  in  those  cases  where  the  stump  becomes  inflamed 
and  the  cancellous  tissue  is  infiltrated  and  bathed  in  pus. 

Lymphatic  vessels,  in  addition  to  those  found  in  the  periosteum,  have  been 
traced  by  Cruikshank,  into  the  substance  of  bone,  and  Klein  describes  them  as 
running  in  the  Haversian  canals. 

Nerves  are  distributed  freely  to  the  periosteum,  and  accompany  the  nutrient 
arteries  into  the  interior  of  the  bone.     They  are  said  by  Kolliker  to   be   most 

numerous  in  the  articular  extremities 
of  the  long  bones,  in  the  vertebrae  and 
the  larger  flat  bones. 

Minute  Anatomy. — The  intimate 
structure  of  bone,  which  in  all  essential 
particulars  is  identical  in  the  compact 
and  cancellous  tissue,  is  most  easily 
studied  in  a  transverse  section  from  the 
compact  wall  of  one  of  the  long  bones 
after  maceration,  such  as  is  shown  in 
Fig.  625. 

If  this  is  examined  with  a  rather 
low  power  the  bone  will  be  seen  to  be 
mapped  out  into  a  number  of  circular 
districts,  each  one  of  which  consists  of 
a  central  hole,  surrounded  by  a  number 
of  concentric  rings.  These  districts  are 
termed  Haversian  systems ;  the  central 
hole  is  an  Haversian  canal,  and  the 
rings  around  are  layers  of  bone-tissue 
arranged  concentrically  around  the  cen- 
tral canal,  and  termed  lamellee.  More- 
over, on  closer  examination,  it  will  be  found  that  between  these  lamellae,  and 
therefore  also  arranged  concentrically  around  the  central  canal,  are  a  number  of 
little  dark  specks,  the  lacunce,  and  that  these  lacunae  are  connected  with  each 
other  and  with  the  central  Haversian  canal  by  a  number  of  fine  dark  lines,  which 
radiate  like  the  spokes  of  a  wheel  and  are  called  canaliculi.  All  these  structures 
— the  concentric  lamellae,  the  lacunae,  and  the  canaliculi — may  be  seen  in  any 
single  Haversian  system,  forming  a  circular  district  round  a  central,  Haversian, 
canal.  Between  these  circular  systems,  filling  in  the  irregular  intervals  which  are 
left  between  them,  are  other  lamellae,  with  their  lacunae  and  canaliculi,  running  in 
various  directions,  but  more  or  less  curved  (Fig.  626).  These  are  termed  interstitial 
lamellae.  Again,  other  lamellae,  for  the  most  part  found  on  the  surface  of  the  bone, 
are  arranged  concentrically  to  the  circumference  of  bone,  constituting,  as  it  were, 
a  single  Haversian  system  of  the  whole  bone,  of  which  the  medullary  cavity  would 
represent  the  Haversian  canal.  These  latter  lamellae  are  termed  circumferential, 
or  by  some  authors  primary  or  fundamental  lamellae,  to  distinguish  them  from  those 
laid  down  around  the  axis  of  the  Haversian  canals,  which  are  then  termed  secondary 
or  special  lamellae. 

The  Haversian  canals,  seen  as  round  holes  in  a  transverse  section  of  bone  at 
or  about  the  centre  of  each  Haversian  system,  may  be  demonstrated  to  be  true 


Fig.  625. — Prom  a  transverse  section  of  the  shaft  of 
the  humerus.  Magnified  350  times,  a.  Haversian 
canals,  b.  Lacunae,  with  their  canaliculi  in  the  lamellae 
of  these  canals,  c.  Lacunae  of  the  interstitial  lamellae. 
d.  Others  at  the  surface  of  the  Haversian  systems,  with 
canaliculi  given  off  from  one  side. 


THE   BONE. 


1099 


canals  if  a  longitudinal  section  is  made,  as  in  Fig.  628.  It  will  then  be  seen  that 
these  round  holes  are  tubes  cut  across,  which  run  parallel  -with  the  longitudinal 
axis  of  the  bone  for  a  short  distance,  and  then  branch  and  communicate.  They 
vary  considerably  in  size,  some  being  as  large  as  -j^ro  of  an  inch  in  diameter ;  the 
average  size  being,  however,  about  -g-^-g-  of  an  inch.  Near  the  medullary  cavity 
the  canals  are  larger  than  those  near  the  surface  of  the  bone.  Each  canal  con- 
tains two  blood-vessels,  with  a  small  quantity  of  delicate  connective  tissue  and 
some  nerve-filaments.  In  the  larger  ones  there  are  also  lymphatic  spaces  and 
branched  cells,  the  processes  of  which  communicate,  through  the  canaliculi,  -with 
the  branched  processes  of  certain  bone-cells  in  the  substance  of  the  bone.  Those 
canals  near  the  surface  of  the  bone  open  upon  it  by  minute  orifices,  and  those 
near  the  medullary  cavity  open  in  the  same  way  into  this  space,  so  that  the  whole 
of  the  bone  is  permeated  by  a  system  of  blood-vessels  running  through  the  bony 
canals  in  the  centre  of  the  Haversian  systems. 

The  lamellae  are  thin  plates  of  bone-tissue  encircling  the  central  canal,  and 
may  be  compared,  for  the  sake  of  illustration,  to  a  number  of  sheets  of  paper 
pasted  one  over  another  around  a  central  hollow  cylinder.  After  macerating  a 
piece  of  bone  in  dilute  mineral  acid  these  lamellae  may  be  stripped  off  in  a  Ion- 


<<mm 


Fig.  626.— Transverse  section  of  compact  tissue  of  bone.     Magnified  about  150  diameters.     (Sharpey.) 

gitudinal  direction  as  thin  films.  If  one  of  these  is  examined  with  a  high  power 
under  the  microscope,  it  will  be  found  to  be  composed  of  a  finely  reticular  struct- 
ure, presenting  the  appearance  of  lattice-work  made  up  of  very  slender,  trans- 
parent fibres,  decussating  obliquely,  and  coalescing  at  the  points  of  intersection 
so  as  to  form  an  exceedingly  delicate  network.  These  fibres  are  composed  of  fine 
fibrils,  identical  with  those  of  white  connective  tissue.  The  intercellular  matrix 
between  the  fibres  has  been  replaced  by  calcareous  deposit,  which  the  acid  dissolves. 
In  many  places  the  various  lamellae  may  be  seen  to  be  held  together  by  tapering 
fibres,  which  run  obliquely  through  them,  pinning  or  bolting  them  together. 
These  fibres  were  first  described  by  Sharpey,  and  were  named  by  him  perforating 
fibres  (Fig.  630). 

The  lacunce  are  situated  between  the  lamellae,  and  consist  of  a  number  of  oblong 
spaces.  In  an  ordinary  microscopic  section,  viewed  by  transmitted  light,  they 
appear  as  dark,  oblong,  opaque  spots,  and  were  formerly  believed  to  be  solid  cells. 
Subsequently,  when  it  was  seen  that  the  Haversian  canals  were  channels  which 
lodge  the  vessels  of  the  part,  and  the  canaliculi,  minute  tubes  by  which  the  plasma 
of  the  blood  circulates  through  the  tissue,  the  theory  was  formulated  that  the 
lacunae  were  hollow  spaces  filled  during  life  with  the  same  fluid,  and  only  lined  (if 


1100 


GENERAL    ANATOMY   OR    HISTOLOGY. 


lined  at  all)  by  a  delicate  membrane.  But  this  view  was  subsequently  proved 
to  be  erroneous,  for  examination  of  the  structure  of  bone,  when  recent,  led 
Virchow  to  believe  that  the  lacunae  are  occupied  during  life  by  a  branched  cell, 
termed  a  bone-cell  or  bone-corpuscle,  the  processes  from  which  pass  down  the 
canaliculi — a  view  which  is  now  universally  received  (Fig.  627).  It  is  by  means  of 
these  cells  that  the  fluids  necessary  for  nutrition  are  brought  into  contact  with 
the  ultimate  tissue  of  bone. 

The  canaliculi  are  exceedingly  minute  channels,  which  pass  across  the  lamellae 
and  connect  the  lacunae  with  the  neighboring  lacunae  and  also  with  the  Haversian 
canal.  From  this  central  canal  a  number  of  the  canaliculi  are  given  off,  which 
radiate  from  it,  and  open  into  the  first  set  of 
lacunae,  arranged  around  the  Haversian  canal, 
between  the  first  and  second  lamellae.  From 
these  lacunae  a  second  set  of  canaliculi  are 
given  off,  which  pass  outward  to  the  next 
series  of  lacunae,  and  so  on  until  they  reach  the 
periphery  of  the  Haversian  system :  here  the 
canaliculi  given  off  from  the  last  series  of 
lacunae  do  not  communicate  with  the  lacunae 
of  neighboring  Haversian  systems,  but  after 
passing  outward  for  a  short  distance  form  loops 


Fig.  627. — Nucleated  bone-cells  and  their  processes,  con- 
tained in  the  bone-lacunae  and  their  canaliculi  respectively. 
From  a  section  through  the  vertebra  of  an  adult  mouse. 
(Klein  and  Noble  Smith.) 


Fig.  628.— Section  parallel  to  the  surface 
from  the  shaft  of  the  femur.  Magnified  100 
times,  a.  Haversian  canals.  6,  Lacunae  seen 
from  the  side,  c,  Others  seen  from  the  sur- 
face in  lamellae  which  are  cut  horizontally. 


and  return  to  their  own  lacuna.  Thus  every  part  of  the  Haversian  system  is 
supplied  with  nutrient  fluids  derived  from  the  vessels  in  the  Haversian  canals  and 
traversing  the  canaliculi  and  lacunae. 

The  bone-cells  are  contained  in  the  lacunae,  which,  however,  they  do  not  com- 
pletely fill.  They  are  flattened  nucleated  cells,  which  Virchow  has  shown  are 
homologous  with  those  of  connective  tissue.  The  cells  are  branched,  and  the 
branches,  especially  in  young  bones,  pass  into  the  canaliculi  from  the  lacunae. 

If  a  longitudinal  section  is  examined,  as  in  Fig.  628,  the  structure  is  seen  to  be 
the  same.  The  appearance  of  concentric  rings  is  replaced  by  that  of  lamellae  or 
rows  of  lacunae,  parallel  to  the  course  of  the  Haversian  canals,  and  these  canals 
appear  like  half-tubes  instead  of  circular  spaces.  The  tubes  are  seen  to  branch 
and  communicate,  so  that  each  separate  Haversian  canal  runs  only  a  short  distance. 
In  other  respects  the  structure  has  much  the  same  appearance  as  in  transverse 
sections. 

In  sections  of  thin  plates  of  bone  (as  in  the  walls  of  the  cells  which  form  the 
cancellous  tissue)  the  Haversian  canals  are  absent,  and  the  canaliculi  open  into  the 
spaces  of  the  cancellous  tissue  (medullary  spaces),  which  thus  have  the  same  func- 
tion as  the  Haversian  canals  in  the  more  compact  bone. 


THE   BONE. 


1101 


Chemical  Composition. — Bone  consists  of  an  animal  and  an  earthy  part  inti- 
mately combined  together. 

The  animal  part  may  be  obtained  by  immersing  the  bone  for  a  considerable 
time  in  dilute  mineral  acid,  after  which  process  the  bone  comes  out  exactly  the 
same  shape  as  before,  but  perfectly  flexible,  so  that  a  long  bone  (one  of  the  ribs,  for 
example)  can  easily  be  tied  in  a  knot.  If  now  a  transverse  section  is  made  (Fig. 
630),  the  same  general  arrangement  of  the  Haversian  canals,  lamellae,  lacunae,  and 
canaliculi  is  seen,  though  not  so  plainly,  as  in  the  ordinary  section. 

The  earthy  part  may  be  obtained  separate  by  calcination,  by  which  the  animal 
matter  is  completely  burned  out.      The  bone  will  still  retain  its  original  form,  but 


Perforating  fibres  of 
Sharpey. 


Apertures  from 
-z?=which  the  fibres  have 
been  withdrawn. 


Decussating  fibres 
in  lamelja. 


Fig.  629.— Lamellae  torn  from  a  decalcified  human  parietal  bone  to  show  the  perforating  fibres  of  Sharpey. 
(Copied  from  a  drawing  by  Allen  Thomson.) 

it  will  be  white  and  brittle,  will  have  lost  about  one-third  of  its  original  weight, 
and  will  crumble  down  with  the  slightest  force.  The  earthy  matfer  confers  on 
bone  its  hardness  and  rigidity,    and  the  animal  matter  its  tenacity. 

The  animal  basis  is  largely  composed  of  ossein,  which  is  identical  with  the 
collagen  of  white  fibrous  tissue,  so  that  when  boiled  with  water,  especially  under 
pressure,  it  is  almost  entirely  resolved  into  gelatin. 

The  organic  matter  of  bone  forms   about  one-third,   or  33.3  per  cent.;   the 
inorganic  matter,  two-thirds,  or  66.7  per  cent.      Of  the  earthy  matter,  five-sixths 
is  calcium  phosphate,  the  remainder   consisting   of  calcium   carbonate,   calcium 
fluoride,  calcium  chloride,   and  magnesium 
phosphate,  with  small  amounts  of  sodium 
chloride    and    sulphate.       Even    after    the 
removal  of  all  the  marrow  a  small  percent- 
age of  fat  is  still  found  in  bone. 

Some  of  the  diseases  to  which  bones  are 
liable  mainly  depend  on  the  disproportion 
between  the  two  constituents  of  bone. 
Thus  in  the  disease  called  rickets,  so  com- 
mon in  the  children  of  the  poor,  the  bones 
become  bent  and  curved,  either  from  the 
superincumbent  weight  of  the  body  or 
under  the  action  of  certain  muscles.  This 
depends  upon  some  defect  of  nutrition  by  which  bone  becomes  deprived  of  its 
normal  proportion  of  earthy  matter,  while  the  animal  matter  is  of  unhealthv 
quality.  In  the  vertebrae  of  a  rickety  subject  Bostock  found  in  100  parts  7-9.75 
animal  and  20.25  earthy  matter. 

Development  of  Bone. — In   the   foetal   skeleton  some  bones  are  preceded  by 


Fig.  630.— Section  of  bone  after  the  removal  of 
the  earthy  matter  by  the  action  of  acids. 


1102 


GUXEBAL    AXATOJIY    OR    HISTOLOGY 


membrane,  such  as  those  forming  the  roof  and  sides  of  the  skull :  others,  such  as 
the  bones  of  the  limbs,  are  preceded  by  rods  of  cartilage.  Hence  two  kinds  of 
ossification  are  described:  the  intramembranous  and  the  intracartilaginous. 

Intramembranous  Ossification. — In  the  case  of  bones  which  are  developed  in 
membrane  no  cartilaginous  mould  precedes  the  appearance  of  the  bone-tissue. 
The  membrane,  which  occupies  the  place  of  the  future  bone,  is  of  the  nature  of 
connective  tissue,  and  ultimately  forms  the  periosteum.  At  this  stage  it  is  seen 
to  be  composed  of  fibres  and  granitlar  cells  in  a  matrix.  The  outer  portion  is 
more  fibrous,  while  internally,  the  cells  or  osteoblasts  predominate :  the  whole 
tissue  is  richly  supplied  with  blood-vessels.  At  the  outset  of  the  process  of  bone 
formation  a  little  network  of  bony  spicula?  is  first  noticed  radiating  from  the  point 
or  centre  of  ossification.  When  these  rays  of  growing  bone  are  examined  with  a 
microscope,  they  are  found  to  consist  at  their  growing  point  of  a  network  of  fine 
clear  fibres  and  granular  corpuscles  with  an  intervening  ground  substance  (Fig. 
631).  The  fibres  are  termed  osteopi)it-ti<:  fibres,  and  are  made  up  of  fine  fibrils  dif- 
fering little  from  those  of  white  fibrous  tissue.  Like  them,  they  are  probably 
deposited  in  the  matrix  through  the  influence  of  the  cells — in  this  case  the  osteo- 


Union  of- 
adjacent 

spicules. 


Osteoblasts. <: 


--Osteogenetic 

fibres. 


Calcific  deposit 

between  the 
fibres. 


_  Bony 
■  <:.  spicules. 

Fig.  631. — Part  of  the  growing  edge  of  the  developing  parietal  bone  of  a  fo?tal  cat.    (After  J.  Lawrence.) 

blasts.  The  osteogenetic  fibres  soon  assume  a  dark  and  granular  appearance  from 
the  deposition  of  calcareous  granules  in  the  fibres  and  in  the  intervening  matrix, 
and  as  they  calcify  they  are  found  to  enclose  some  of  the  granular  corpuscles  or 
osteoblasts.  By  the  fusion  of  the  calcareous  granules  the  bony  tissue  again  assumes 
a  more  transparent  appearance,  but  the  fibres  are  no  longer  so  distinctly  seen. 
The  involved  osteoblasts  form  the  corpuscles  of  the  future  bone,  the  spaces  in 
which  thev  are  enclosed  constituting  the  lacuna?.  As  the  osteocrenetic  fibres  grow 
out  to  the  periphery  they  continue  to  calcify,  and  give  rise  to  fresh  bone  spicules. 
Thus  a  network  of  bone  is  formed,  the  meshes  of  which  contain  the  blood-vessels 
and  a  delicate  connective  tissue  crowded  with  osteoblasts.  The  bony  trabecule 
thicken  by  the  addition  of  fresh  layers  of  bone  formed  by  the  osteoblasts  on  their 
surface,  and  the  meshes  are  correspondingly  encroached  upon.  Subsequently 
successive  layers  of  bony  tissue  are  deposited  under  the  periosteum  and  round 
the  larger  vascular  channels,  which  become  the  Haversian  canals,  so  that  the  bone 
increases  much  in  thickness. 

Intracartilaginous  Ossification. — Just  before  ossification  begins  the  bone  is 
entirely  cartilaginous,  and  in  a  Ion;:  bone,  which  may  be  taken  as  an  example,  the 
process  commences  in  the  centre  and  proceeds  toward  the  extremities,  which  for 


THE   BONE. 


1103 


some  time  remain  cartilaginous.  Subsequently  a  similar  process  commences  in  one 
or  more  places  in  those  extremities  and  gradually  extends  through  them.  The 
extremities  do  not,  however,  become  joined  to  the  shaft  by  bony  tissue  until  growth 
has  ceased,  but  are  attached  to  it  by  a  layer  of  cartilaginous  tissue  termed  the 
epiphyseal  cartilage. 

The  first  step  in  the  ossification  of  the  cartilage  is  that  the  cartilage-cells,  at 
the  point  where  ossification  is  commencing  and  which  is  termed  a  centre  of  ossifica- 
tion, enlarge  and  arrange  themselves  in  rows  (Fig.  632).  The  matrix  in  which  they 
are  imbedded  increases  in  quantity,  so  that  the  cells  become  further  separated  from 
each  other.     A  deposit  of  calcareous  material    now  takes    place   in   this  matrix. 


bl 

Fig.  632.— Section  of  fcetal  bone  of  cat.  ir.  Irruption  of 
the  subperiosteal  tissue,  p.  Fibrous  layer  of  the  perios- 
teum, o.  Layer  of  osteoblasts,  im.  Subperiosteal  bony 
deposit.  (From  Quain's  Anatomy,  E.  A.  Schafer.) 


Fig.  G33  —  Part  of  a  longitudinal  section  of 

the  developing  femur  of  a  rabbit,  a.  Flat- 
tened cartilage-cells,  b.  Enlarged  cartilage- 
cells,  c.  d.  Newly-formed  bone.  e.  Osteo- 
blasts. /.  Giant-cells  or  osteoclasts,  g.  h. 
Shrunken  cartilage-cells.  (From  Atlas  of  His- 
tology, Klein  and  Noble  Smith.) 


between  the  rows  of  cells,  so  that  they  become  separated  from  each  other  by  longi- 
tudinal columns  of  calcified  matrix,  presenting  a  granular  and  opaque  appearance. 
Here  and  there  the  matrix  between  two  cells  of  the  same  row  also  becomes  calci- 
fied, and  transverse  bars  of  calcified  substance  stretch  across  from  one  calcareous 
column  to  another.  Thus  there  are  longitudinal  groups  of  the  cartilage-cells 
enclosed  in  oblong  cavities,  the  walls  of  which  are  formed  of  calcified  matrix, 
which  cuts  off  all  nutrition  from  the  cells,  and  they,  in  consequence,  waste, 
leaving  spaces  called  the  primary  areola;  (Sharpey). 

At  the  same  time  that  this  process  is  going  on  in  the  centre  of  the  solid  bar  of 
cartilage  of  which  the  foetal  bone  consists,  certain  changes  are  taking  place  on 


1104 


GENERAL    ANATOMY   OB    HISTOLOGY. 


its  surface.  This  is  covered  by  a  very  vascular  membrane,  the  perichondrium, 
entirely  similar  to  the  embryonic  connective  tissue  already  described  as  constituting 
the  basis  of  membrane-bone,  on  the  inner  surface  of  which,  that  is  to  say,  on  the 
surface  in  contact  with  the  cartilage,  are  gathered  the  formative  cells,  the  osteo- 
blasts. By  the  agency  of  these  cells  a  thin  layer  of  bony  tissue  is  being  formed 
between  the  perichondrium  and  the  cartilage,  by  the  intramembranous  mode  of 
ossification  just  described.  There  are  then,  in  this  first  stage  of  ossification,  two 
processes  going  on  simultaneously  :  in   the  centre  of  the  cartilage  the  formation 


of  a  number  of  oblong  spaces,  formed 
withered  cartilage-cells,  and  on  the 
surface  of  the  cartilage  the  formation 
of  a  layer  of  true  membrane-bone. 
The  second  stage  consists  in  the  pro- 
longation into  the  cartilage  of  proc- 
esses of  the  deeper  or  osteogenetic 
layer  of  the  perichondrium,  which  has 
now  become  periosteum  (Fig.  632,  ir). 
The  processes  consist  of  blood-vessels 
and  cells — osteoblasts  or  bone-formers, 
and    osteoclasts,    or    bone-destroyers. 


of   calcified  matrix  and  containing  the 


Fig.  634. — Transverse  section  from  the  femur  of  a 
human  embryo  about  eleven  weeks  old.  a.  A  med- 
ullary sinus  cut  transversely;  and  b,  another,  long- 
itudinally, c.  Osteoblasts,  d.  Newly-formed  osseous 
substance  of  a  lighter  color,  e.  That  of  greater  age. 
/.  Lacunar  with  their  cells,  g.  A  cell  still  united  to 
an  osteoblast. 


Fig.  635. — Vertical  section  from  the  edge  of  the 
ossifying  portion  of  the  diaphysis  of  a  metatar- 
sal bone  from  a  fcetal  calf.  (After  Muller.)  a. 
Ground-mass  of  the  cartilage,  b.  Of  the  bone.  c. 
Newly-formed  bone-cells  in  profile,  more  or  less 
imbedded  .in  intercellular  substance,  d.  Medul- 
lary canal  in  process  of  formation,  with  vessels 
and  medullary  cells,  e.  /.  Bone-cells  on  their 
broad  aspect,  g.  Cartilage-capsules  arranged  in 
rows,  and  partly  with  shrunken  cell-bodies. 


The  latter  are  similar  to  the  giant-cells  (myelo-plaques)  found  in  marrow,  and 
they  excavate  passages  through  the  new-formed  bony  layer  by  absorption,  and 
pass  through  it  into  the  calcified  matrix  (Fig.  632).  Wherever  these  processes 
come  in  contact  with  the  calcified  walls  of  the  primary  areolae  they  absorb  it, 
and  thus  cause  a  fusion  of  the  original  cavities  and  the  formation  of  larger  spaces, 
which  are  termed  the  secondary  areola?.  (Sharpey)  or  medullary  spaces  (Muller). 
In  these  secondary  spaces  the  original  cartilage-cells  having  disappeared,  become 
filled  with  embryonic  marrow,  consisting  of  osteoblasts  and  vessels,  and  derived 
in  the  manner  described  above,  from  the  osteogenetic  laver  of  the  periosteum 
(Fig.  633). 


THE   BONE. 


1105 


Thus  far  there  has  been  traced  the  formation  of  enlarged  spaces  (secondary 
areolae),  the  perforated  walls  of  which  are  still  formed  by  calcined  cartilage-matrix, 
containing  an  embryonic  marrow,  derived  from  the  processes  sent  in  from  the 
osteogenetic  layer  of  the  periosteum,  and  consisting  of  blood-vessels  and  round 
cells,  osteoblasts  (Fig.  633).  The  walls  of  these  secondary  areolae  are  at  this  time 
of  only  inconsiderable  thickness,  but  they  become  thickened  by  the  deposition 
of  layers  of  new  bone  on  their  interior.  This  process  takes  place  in  the  following 
manner:  Some  of  the  osteoblasts  of  the  embryonic  marrow,  after  undergoing 
rapid  division,  arrange  themselves  as  an  epithelioid  layer  on  the  surface  of  the 
wall  of  the  space  (Fig.  634). 
This  layer  of  osteoblasts  form  a 
bony  stratum,  and  thus  the  wall 
of  the  space  becomes  gradually 
covered  with  a  layer  of  true 
osseous  substance.  On  this  a 
second  layer  of  osteoblasts  ar- 
range themselves,  and  in  their 
turn  form  an  osseous  layer.  By 
the  repetition  of  this  process  the 
original  cavity  becomes  very 
much  reduced  in  size,  and  at 
last  only  remains  as  a  small  cir- 
cular hole  in  the  centre,  con- 
taining the  remains  of  the  em- 
bryonic marrow  —  that  is,  a 
blood-vessel  and  a  few  osteo- 
blasts. This  small  cavity  con- 
stitutes the  Haversian  canal  of 
the  perfectly  ossified  bone.  The 
successive  layers  of  osseous 
matter  which  have  been  laid  down  and  which  encircle  this  central  canal  con- 
stitute the  lamellae  of  which,  as  we  have  seen,  each  Haversian  system  is  made 
up.  As  the  successive  layers  of  osteoblasts  form  osseous  tissue,  certain  of 
the  osteoblastic  cells  remain  included  between  the  various  bony  layers.  These 
persist  as  the  corpuscles  of  the  future  bone,  the  spaces  enclosing  them  forming 
the  lacunae  (Figs.  634  and  636).  The  canaliculi,  at  first  extremely  short,  are 
supposed  to  be  extended  by  absorption,  so  as  to  meet  those  of  neighboring 
lacunae. 

Such  are  the  changes  which  may  be  observed  at  one  particular  point,  the  centre 
of  ossification.  While  they  have  been  going  on  here  a  similar  process  has  been 
set  up  in  the  surrounding  parts  and  has  been  gradually  proceeding  toward  the  end 
of  the  shaft,  so  that  in  the  ossifying  bone  all  the  changes  described  above  may  be 
seen  in  different  parts,  from  the  true  bone  in  the  centre  of  the  shaft  to  the  hyaline 
cartilage  at  the  extremities.  The  bone  thus  formed  differs  from  the  bone  of  the 
adult  in  being  more  spongy  and  less  regularly  lamellated. 

Thus  far,  then,  we  have  followed  the  steps  of  a  process  by  which  a  solid  bony 
mass  is  produced,  having  vessels  running  into  it  from  the  periosteum,  Haversian 
canals  in  which  those  vessels  run,  medullary  spaces  filled  with  foetal  marrow, 
lacunae  with  their  contained  bone-cells,  and  canaliculi  growing  out  of  these 
lacunae. 

This  process  of  ossification,  however,  is  not  the  origin  of  the  whole  of  the 
skeleton,  for  even  in  those  bones  in  which  the  ossification  proceeds  in  a  great 
measure  from  a  single  centre,  situated  in  the  cartilaginous  shaft  of  a  long  bone,  a 
considerable  part  of  the  original  bone  is  formed  by  intramembranous  ossification 
beneath  the  perichondrium  or  periosteum  ;  so  that  the  girth  of  the  bone  is  increased 
by  bony  deposit  from  the  deeper  layer  of  this  membrane.  The  shaft  of  the  bone 
70 


Fig.  636.— Osteoblasts  from  the  parietal  bone  of  a  human  em- 
bryo thirteen  weeks  old.  (After  Gegenbauer.;  a,  Bony  septa  with 
the  cells  of  the  lacunae.  6,  La yers  of  osteoblasts,  c,  The  latter  in 
transition  to  bone-corpuscles. 


1106  GENERAL    ANATOMY   OB    HISTOLOGY. 

is  at  first  solid,  but  a  tube  is  hollowed  out  in  it  by  absorption  around  the  vessels 
passing  into  it,  which  becomes  the  medullary  canal.  This  absorption  is  supposed 
to  be  brought  about  by  large  "giant-cells,"  the  so-called  osteoclasts  of  Kolliker 
(Fig.  638).  They  vary  in  shape  and  size,  and  are  known  by  containing  a  large 
number  of  clear  nuclei,  sometimes  as  many  as  twenty.  The  occurrence  of  similar 
cells  in  some  tumors  of  bones  has  led  to  such  tumors  being  denominated 
"  myeloid." 

As  more  and  more  bone  is  removed  by  this  process  of  absorption  from  the 
interior  of  the  bone  to  form  the  medullary  canal,  so  more  and  more  bone  is 
deposited  on  the  exterior  from  the  periosteum,  until  at  length  the  bone  has  attained 
the  shape  and  size  which  it  is  destined  to  retain  during  adult  life.  As  the  ossifi- 
cation of  the  cartilaginous  shaft  extends  toward  the  articular  ends  it  carries  with 
it,  as  it  were,  a  layer  of.  cartilage,  or  the  cartilage  grows  as  it  ossifies,  and  thus  the 
bone  is  increased  in  length.  During  this  period  of  growth  the  articular  end,  or 
epiphysis,  remains  for  some  time  entirely  cartilaginous ;  then  a  bony  centre  appears 
in  it,  and  it  commences  the  same  process  of  intracartilaginous  ossification ;  but 
this  process  never  extends  to  any  great  distance.  The  epiphyses  remain  separated 
from  the  shaft  by  a  narrow  cartilaginous  layer  for  a  definite  time.  This  layer 
ultimately  ossifies,  the  distinction  between  shaft  and  epiphysis  is  obliterated,  and 
the  bone  assumes  its  completed  form  and  shape.  The  same  remarks  also  apply  to 
the  processes  of  bone  which  are  separately  ossified,  such  as  the  trochanters  of  the 
femur.  The  bones,  having  been  formed,  continue  to  grow  until  the  body  has 
acquired  its  full  stature.  They  increase  in  length  by  ossification  continuing  to 
extend  in  the  epiphysial  cartilage,  which  goes  on  growing  in  advance  of  the  ossi- 
fying process.  They  increase  in  circumference  by  deposition  of  new  bone,  from 
the  deeper  layer  of  the  periosteum,  on  their  external  surface,  and  at  the  same 
time  an  absorption  takes  place  from  within,  by  which  the  medullary  cavity  is 
increased. 

The  medullary  spaces  which  characterize  the  cancellous  tissue  are  produced  by 
the  absorption  of  the  original  foetal  bone  in  the  same  way  as  the  original  medul- 
lary canal  is  formed.  The  distinction  between  the  cancellous  and  compact  tissue 
appears  to  depend  essentially  upon  the  extent  to  which  this  process  of  absorption 
has  been  carried ;  and  we  may  perhaps  remind  the  reader  that  in  morbid  states  of 
the  bone  inflammatory  absorption  produces  exactly  the  same  change,  and  converts 
portions  of  bone  naturally  compact  into  cancellous  tissue. 

The  number  of  ossific  centres  is  different  in  different  bones.  In  most  of  the 
short  bones  ossification  commences  by  a  single  point  in  the  centre,  and  proceeds 
toward  the  circumference.  In  the  long  bones  there  is  a  central  point  of  ossifica- 
tion for  the  shaft  or  diaphysis ;  and  one  or  more  for  each  extremity,  the  epiphysis. 
That  for  the  shaft  is  the  first  to  appear.  The  union  of  the  epiphyses  with  the 
shaft  takes  place  in  the  reverse  order  to  that  in  which  their  ossification  began,  with 
the  exception  of  the  fibula,  and  appears  to  be  regulated  by  direction  of  the 
nutrient  artery  of  the  bone.  Thus  the  nutrient  arteries  of  the  bones  of  the  arm 
and  forearm  are  directed  toward  the  elbow,  and  the  epiphyses  of  the  bones  form- 
ing this  joint  become  united  to  the  shaft  before  those  at  the  opposite  extremity. 
In  the  lower  limb,  on  the  other  hand,  the  nutrient  arteries  pass  in  a  direction  from 
the  knee :  that  is,  upward  in  the  femur,  downward  in  the  tibia  and  fibula ;  and  in 
them  it  is  observed  that  the  upper  epiphysis  of  the  femur,  and  the  lower  epiphysis 
of  the  tibia  and  fibula,  become  first  united  to  the  shaft. 

Where  there  is  only  one  epiphysis,  the  medullary  artery  is  directed  toward 
that  end  of  the  bone  where  there  is  no  additional  centre,  as  toward  the  acromial 
end  of  the  clavicle,  toward  the  distal  end  of  the  metacarpal  bone  of  the  thumb 
and  great  toe,  and  toward  the  proximal  end  of  the  other  metacarpal  and  meta- 
tarsal bones. 

Besides  these  epiphyses  for  the  articular  ends,  there  are  others  for  projecting 
parts  or  processes,  which  are  formed  separately  from  the  bulk  of  the  bone.     For 


THE  MUSCULAR    TISSUE.  1107 

an  account  of  these  the  reader  must  be  referred  to  the  description  of  the  individual 
bones  in  the  sequel. 

A  knowledge  of  the  exact  periods  when  the  epiphyses  become  joined  to  the 
shaft  is  often  of  great  importance  in  medico-legal  inquiries.  It  also  aids  the  sur- 
geon in  the  diagnosis  of  many  of  the  injuries  to  which  the  joints  are  liable ;  for  it 
not  infrequently  happens  that,  on  the  application  of  severe  force  to  a  joint,  the 
epiphysis  becomes  separated  from  the  shaft,  and  such  injuries  may  be  mistaken  for 
fracture  or  dislocation. 

THE  MUSCULAR  TISSUE. 

The  muscles  are  formed  of  bundles  of  reddish  fibres,  endowed  with  the  property 
of  contractility.  The  two  principal  kinds  of  muscular  tissue  found  in  the 
body  are  voluntary  and  involuntary.  The  former  of  these,  from  the  character- 
istic appearances  which  their  fibres  exhibit  under  the  microscope,  are  known  as 
the  "striped"  muscles,  and  from  the  fact  that  it  is  capable  of  being  put  into 
action  and  controlled  by  the  will,  as  "voluntary"  muscle.  The  fibres  of  the 
latter  do  not  present  any  cross-striped  appearance,  and  for  the  most  part  are 
not  under  the  control  of  the  will;  hence  they  are  known  as  the  "unstriped"  or 
"involuntary"  muscles.  The  muscular  fibres  of  the  heart  differ  in  certain  par- 
ticulars from  both  these  groups,  and  they  are  therefore  separately  described  as 
"  cardiac  "  muscular  fibres. 

Thus  it  will  be  seen  that  there  are  three  varieties  of  muscular  fibres  :  (1) 
Transversely  striated  muscular  fibres,  which  are  for  the  most  part  voluntary  and 
under  the  control  of  the  will,  but  some  of  which  are 
not  so,  such  as  the  muscles  of  the  pharynx  and  upper 
part  of  the  oesophagus.  This  variety  of  muscle  is 
sometimes  called  skeletal.  (2)  Transversely  striated 
muscular  fibres,  which  are  not  under  the  control  of 
the  will — i.  e.,  the  cardiac  muscle.  (3)  Plain  or  un- 
striped muscular  fibres,  which  are  involuntary  and 
controlled  by  a  different  part  of  the  nervous  system 
from  that  which  controls  the  activity  of  the  voluntary 
muscles.  Such  are  the  muscular  walls  of  the  stomach 
and  intestine,  of  the  uterus  and  bladder,  of  the  blood- 
vessels, etc. 

The  striped  or  voluntary  muscles  are  composed  of  Wr'r^h '       ^ 

bundles  of  fibres  enclosed  in  a  delicate  web  called  the  fig.  637.-Transverse  section  from 
"perimysium,"  in  contradistinction  to  the  sheath  of  ^Z^I^'peSs: 
areolar  tissue  which  invests  the  entire   muscle,   the     iuin-     b.-  Fasciculus,     c.  internal 

...  ...   /T-,.        nn-r\         mi  n       perimysium,    d.  Fibre. 

"  epimysium     (-big-  bSl).     The   bundles   are  termed 

"fasciculi";  they  are  prismatic  in  shape,  of  different  sizes  in  different  muscles, 
and  for  the  most  part  placed  parallel  to  one  another,  though  they  have  a  tendency 
to  converge  toAvard  their  tendinous  attachments.  Each  fasciculus  is  made  up  of 
a  bundle  of  fibres,  which  also  run  parallel  with  each  other,  and  which  are  sepa- 
rated from  one  another  by  a  delicate  connective  tissue  derived  from  the  perimys- 
ium, and  termed  endomysium.  This  does  not  form  the  sheath  of  the  fibres,  but 
serves  to  support  the  blood-vessels  and  nerves  ramifying  between  them.  The 
fibres  are  enclosed  in  a  separate  and  distinct  sheath  of  their  own,  but  it  is  not 
areolar  tissue,   and  is  therefore  not   derived  from  the  perimysium. 

A  muscular  fibre  may  be  said  to  consist  of  a  soft  contractile  substance  en- 
closed in  a  tubular  sheath,  named  by  Bowman  the  sarcolemma.  The  fibres  are 
cylindrical  or  prismatic  in  shape,  and  are  of  no  great  length,  not  exceeding,  it  is 
said,  an  inch  and  a  half.  They  end  either  by  blending  with  the  tendon  or 
aponeurosis,  or  else  by  rounded  or  tapering  extremities  which  are  connected  to  the 
neighboring  fibres  by  means  of  the  sarcolemma.  Their  breadth  varies  in  man 
from  y^u  to  -g-^j-  of  an  inch.  As  a  rule,  the  fibres  do  not  divide  or  anastomose ; 
but  occasionally,  especially  in  the  tongue  and  facial  muscles,  the  fibres  may  be 


1108 


GENERAL    ANAT03IY    OB    HISTOLOGY. 


seen  to  divide  into  several  branches.  The  precise  mode  in  which  the  muscular 
fibre  joins  the  tendon  has  been  variously  described  by  different  observers.  It 
may,  perhaps,  be  sufficient  to  say  that  the  sarcolemma,  or  membranous  investment 
of  the  muscular  fibre,  appears  to  become  blended  with  a  small  bundle  of  fibres, 
into  which  the  tendon  becomes  subdivided,  while  the  muscular  substance  terminates 
abruptly  and  can  readily  be  made  to  retract  from  the  point  of  junction.  The  are- 
olar tissue  between  the  fibres  appears  to  be  prolonged  more  or  less  into  the  tendon, 
so  as  to  form  a  kind  of  sheath  around  the  tendon  bundles  for  a  longer  or  shorter 
distance.  When  muscular  fibres  are  attached  to  the  skin  or  mucous  membranes, 
their  fibres  are  described  by  Hyde  Salter  as  becoming  continuous  with  those  of 
the    areolar  tissue. 

The  sarcolemma,  or  tubular  sheath  of  the  fibre,  is  a  transparent,  elastic,  and 
apparently  homogeneous  membrane  of  considerable  toughness,  so  that  it  will  some- 
times remain  entire  when  the  included  substance  is  ruptured  (see  Fig.  638).     On 


Fig.  638.— Two  human  muscular  fibres. 
Magnified  350  times.  In  the  one,  the  bundle  of 
fibrillffi  (6)  is  torn,  and  the  sarcolemma  (a)  is 
seen  as  an  empty  tube. 


Fig.  639.— Fragments  of  striped  muscular  fibres, 
showing  a  cleavage  in  opposite  directions.  Magnified 
300  diameters,  a.  Longitudinal  cleavage.  The  longi- 
tudinal and  transverse  lines  are  both  seen.  Some  lon- 
gitudinal lines  are  darker  and  wider  than  the  rest,  and 
are  not  continuous  from  end  to  end.  This  results  from 
partial  separation  of  the  nbrillse.  c.  Fibrillar  separated 
from  one  another  by  violence  at  the  broken  end  of  the 
fibre,  and  marked  by  transverse  lines  equal  in  width  to 
those  on  the  fibre,  c',  c"  represent  two  appearances  com- 
monly presented  by  the  separated  single  fibrillse  (more 
highly  magnified).  At  c'  the  borders  and  transverse  lines 
are  all  perfectly  rectilinear,  and  the  included  spaces  per- 
fectly rectangular.  At  c"  the  borders  are  scalloped  and 
the  spaces  bead-Kke.  When  most  distinct  and  definite 
the  fibrilla  presents  the  former  of  these  appearances. 
b.  Transverse  cleavage.  The  longitudinal  lines  are 
scarcely  visible,  a.  Incomplete  fracture  following  the 
opposite  surfaces  of  a  disk,  which  stretches  across  the 
interval,  and  retains  the  two  fragments  in  connection. 
The  edge  and  surfaces  of  this  disk  are  seen  to  be 
minutely  granular,  the  granules  corresponding  in  size 
to  the  thickness  of  the  disk  and  to  the  distance  between 
the  faint  longitudinal  lines,  b.  Another  disk  nearly 
detached,  b'.  Detached  disk,  more  highly  magnified, 
showing  the  sarcous  elements. 


the  internal  surface  of  the  sarcolemma  in  mammalia,  and  also  in  the  substance  of 
the  fibre  in  the  lower  animals,  elongated  nuclei  are  seen,  and  in  connection  with 
these  a  row  of  granules,  apparently  fatty,  is  sometimes  observed. 

Upon  examination  of  a  voluntary  muscular  fibre  by  transmitted  light,  it  is 
found  to  be  apparently  marked  by  alternate  light  and  dark  bands  or  striae,  which 
pass  transversely,  or  somewhat  obliquely,  round  the  fibre  (Fig.  638).  The  dark 
and  light  bands  are  of  nearly  equal  breadth,  and  alternate  with  great  regularity. 
They  vary  in  breadth  from  about  yyVrr  to  TyVo~  of  an  inch.  If  the  surface  is 
carefully  focussed,  rows  of  granules  will  be  detected  at  the  point  of  junction  of 
the  dark  and  light  bands,  and  very  fine  longitudinal  lines  may  be  seen  running 
through  the  dark  bands  and  joining  these  granules  together.  By  treating  the 
specimen  with  certain  reagents  (e.  g.,  chloride  of  gold)  fine  lines  may  be  seen 
running  transversely  between  the  granules,  uniting  them  together.  This  appear- 
ance is  believed  to  be  due  to  a  reticulum  or  network  of  interstitial  substance  lying 
between  the  contractile  portions  of  the  muscle.     The  longitudinal  striation  gives 


THE   MUSCULAR    TISSUE. 


1109 


the  fibre  the  appearance  of  being  made  up  of  a  bundle  of  fibrillse,  which  have  been 
termed  sarcostyles  or  muscle-columns;  and  if  the  fibre  is  hardened  in  alcohol,  it 
can  be  broken  up  longitudinally  and  the  sarcostyles  separated  from  each  other 
(Fig.  639,  a).  The  reticulum,  with  its  longitudinal  and  transverse  meshes,  is 
sarcoplasm. 

If  now  a  transverse  section  of  a  muscular  fibre  is  made,  it  is  seen  to  be  divided 
into  a  number  of  areas,  called  the  areas  of  Cohnheim,  more  or  less  polyhedral  in 
shape,  and  consisting  of  the  transversely  divided  sarcostyles,  surrounded  by  trans- 
parent series  of  sarcoplasm  (Fig.  639,  B,  b). 

Upon  closer  examination,  and  by  somewhat  altering  the  focus,  the  appearances 
become  more  complicated,  and  are  susceptible  of  various  interpretations.  The 
transverse  striation,  which  in  Figs.  638  and  639  appears  as  a  mere  alternation  of 
dark  and  light  bands, is  resolved  into  the  appearance  seen  in  Fig.  640,  which  shows 
a  series  of  broad  dark  bands,  separated  by  light  bands,  which  are  divided  into  two 
by  a  dark  dotted  line.  This  line  is  termed  Krauses  membrane  (Fig.  642,  k), 
because  it   was  believed  by  Krause  to  be  an   actual   membrane  continuous  with 


J 


Fig.  640.— Portion  of  a  medium-sized  human  muscular 
fibre.  Magnified  nearly  800  diameters.  B.  Separated  bun- 
dles of  fibrils,  equally  magnified,  a.  a.  Larger,  and  6.  b, 
smaller  collections,  c.  Still  smaller,  d.  d.  The  smallest 
which  could  be  detached. 


Fig.  641. — Part  of  a  striped  muscular  fibre 
of  the  water-beetle,  prepared  with  absolute 
alcohol.  Magnified  300  diameters.  (Klein 
and  Noble  Smith.)  a.  Sarcolemma.  b. 
Membrane  of  Krause ;  owing  to  contrac- 
tion during  hardening,  the  sarcolemma 
shows  regular  bulgings.  At  the  side  of 
Krause's  membrane  is  the  transparent  lat- 
eral disk.  Several  nuclei  of  muscle-cor- 
puscles are  shown,  and  in  them  a  minute 
network. 


the  sarcolemma,  and  dividing  the  light  band  into  two  compartments.  It  is  now 
more  usually  regarded  as  being  due  to  an  optical  phenomenon,  from  the  light 
being  reflected  between  disks  of  different  refrangibility.  In  addition  to  the  mem- 
brane of  Krause,  fine  clear  lines  may  be  made  out,  with  a  sufficiently  high  power, 
crossing  the  centre  of  the  dark  band;  these  are  known  as  the  lines  of  Sensen 
(Fig.  642,  h). 

Formerly  it  was  supposed  by  Bowman  that  a  muscular  fibre  was  made  up  of 
a  number  of  quadrangular  particles,  which  he  named  sarcous  elements,  joined 
together  like  so  many  bricks  forming  a  column,  and  he  came  to  this  conclusion 
because  he  found  that  under  the  influence  of  certain  reagents  the  fibre  could  be 
broken  up  transversely  into  disks,  as  well  as  longitudinally  into  fibrilla?  (Fig. 
639,  b).  But  it  is  now  believed  that  this  cross-cleavage  is  purely  artificial,  and 
that  a  muscular  fibre  is  built  up  of  fibrill?e  and  not  of  small  quadrangular 
particles. 

Assuming  that  this  is  so,  we  have  now  to  consider  a  little  more  in  detail  the 
minute  structure  of  these  longitudinal  fibrillre,  or  sarcostyles.  as  they  are  termed. 
Perhaps  there  are  few  subjects  in  histology  which  have  received  more  attention, 


1110 


GENERAL    ANATOMY   OB    HISTOLOGY. 


and  in  which  the  appearances  seen  under  the  microscrope  have  been  more  differ- 
ently interpreted,  than  the  minute  anatomy  of  muscular  fibre.  Schafer  has 
recently  worked  out  this  subject,  particularly  in  the  wing-muscles  of  insects, 
which  are  peculiarly  adapted  for  this  purpose  on  account  of  the  large  amount  of 
interstitial  sarcoplasm  which  separates  the  sarcostyles.  In  the  following  descrip- 
tion Ave  shall  closely  follow  that  given  by  Professor  Schafer  (Fig.  642). 

Each  sarcostyle  may  be  said  to  be  made  up  of  successive  portions,  each  of 
which  Schafer  terms  a  sarcomere.  This  is  the  portion,  situated  between  two 
membranes  of  Krause,  which  transversely  divides  the  light  band.  Each  sarcomere 
consists  of  a  central  dark  part,  which  forms  a  portion  of  the  dark  band  of  the 
whole  fibre,  and  is  named  by  Schafer  a  sareous  element.1  This  sarcous  element 
really  consists  of  two  parts,  superimposed  one  on  the  top  of  the  other,  and  when  the 
fibre  is  stretched,  these  two  parts  become  separated  from  each  other  at  the  line  of 
Hensen  (Fig.  642,  A).  On  either  side  of  this  central  dark  portion  is  a  clear  layer, 
most  visible  Avhen  the  fibre  is  extended ;  this  is  situated  between  the  dark  centre 
and  the  membrane  of  Krause,  and  when  the  sarcomeres  are  joined  together  to 
form  the  sarcostyle,  constitutes  the  light  band  of  the  striated  muscular  fibre. 

When  the  sarcostyle  is  extended,  the  clear  intervals  are  well  marked  and 
plainly  to  be  seen;  when,  on  the  other  hand,  the  sarcostyle  is  contracted, 
that  is  to  say,  the  muscle  is  in  a  state  of  contraction,  these  clear  portions 
are  very  small  or  they  may  have  disappeared  altogether  (Fig.  642,  b).     When  the 


S.E. 


S.E. 


Fig.  642. — Diagram  of  a  sarcomere.    (After  Schafer.)    A.  In  moderately  extended  condition.     B.  In  a  con- 
tracted condition,    k.k.  Membranes  of  Krause  ;  h.  Line  or  plane  of  Hensen  ;  s.e.  Poriferous  sarcous  element. 

sarcostyle  is  stretched  to  its  full  extent,  not  only  is  the  clear  portion  very  well 
marked,  but  the  dark  portion — the  sarcous  element — will  be  seen  to  be  separated 
into  its  two  constituents  along  the  line  of  Hensen. 

The  sarcous  element  does  not  lie  free  in  the  sarcomere,  for  when  the  sarcostyle 
is  stretched,  so  as  to  render  the  clear  portion  visible,  very  fine  lines,  which  are 
probably  septa,  may  be  seen  running  through  it  from  the  sarcous  element  to  the 
membrane  of  Krause. 

Schafer  explains  these  phenomena  in  the  following  way.  He  considers  that 
each  sarcous  element  is  made  up  of  a  number  of  longitudinal  channels,  which 
open  into  the  clear  part  toward  the  membrane  of  Krause,  but  are  closed  at  the  line 
of  Hensen.  When  the  muscular  fibre  is  contracted  the  clear  part  of  the  muscular 
substance  finds  its  way  into  these  channels  or  tubes,  and  is  therefore  hidden  from 
sight,  but  at  the  same  time  it  swells  up  the  sarcous  element  and  widens  and 
shortens  the  sarcomere.  When,  on  the  other  hand,  the  fibre  is  extended,  this 
clear  substance  finds  its  way  out  of  the  tubes  and  collects  between  the  sarcous 
element  and  the  membrane  of  Krause,  and  gives  the  appearance  of  the  light  part 
between  these  two  structures ;  by  this  means  it  elongates  and  narrows  the 
sarcomere. 

If  this  view  is  true,  it  is  a  matter  of  great  interest,  and,  as  Schafer  has 
shown,  harmonizes  the  contraction  of  muscle  with  the  amoeboid  action  of  proto- 
1This  must  not  be  confused  with  the  "sarcous  element  of  Bowman."     (See  above.) 


THE   MUSCULAR    TISSUE. 


1111 


plasm.  In  an  amoeboid  cell  there  is  a  framework  of  spongioplasm,  Avhich  stains 
with  hematoxylin  and  similar  reagents,  enclosing  in  its  meshes  a  clear  substance, 
hyaloplasm,  which  will  not  stain  with  these  reagents.  Under  stimulation  the 
hyaloplasm  passes  into  the  pores  of  the  spongioplasm  ;  without  stimulation  it  tends 
to  pass  out  as  in  the  formation  of  pseudopodia.  In  muscle  there  is  the  same  thing  : 
viz.,  a  framework  of  spongioplasm  staining  with  hematoxylin — the  substance 
of  the  sarcous  element — and  this  encloses  a  clear  hyaloplasm,  the  clear  substance 
of  the  sarcomere,  which  resists  staining  with  this  reagent.  During  contraction 
of  the  muscle — i.  e.,  stimulation — this  clear  substance  passes  into  the  pores  of 
the  spongioplasm  ;  while  during  extension  of  the  muscle — i.  e.,  when  there  is  no 
stimulation — it  tends  to  pass  out  of  the  spongioplasm. 

In  this  way  the  contraction  is  brought  about :  under  stimulation  the  proto- 
plasmic material  (the  clear  substance  of  the  sarcomere)  recedes  into  the  sarcous 
element,  causing  the  sarcomere  to  widen  out  and  shorten.  The  contraction  of 
the  muscle  is  merely  the  sum  total  of  this  widening  out  and  shortening  of  these 
bodies. 

The  capillaries  of  striped  muscle  are  very  abundant,  and  form  a  sort  of  rect- 
angular network,  the  branches  of  which  run  longitudinally  in  the  endomysium 


Fig.  643.— Non-striated  muscular  fibre.     (From  Kirke's  Physiology.) 

between  the  muscular  fibres,  and  are  joined  at  short  intervals  by  transverse 
anastomosing  branches.  The  larger  vascular  channels,  arteries  and  veins,  are 
found  only  in  the  perimysium,  between  the  muscular  fasciculi. 

Nerves  are  profusely  distributed  to  striped  muscle.  The  mode  of  their 
termination  will  be   described  on   a   subsequent  page. 

The  existence  of  lymphatic  vessels  in  striped  muscle  has  not  been  ascertained, 
though  they  have  been  found  in  tendons  and  in  the  sheath  of  the  muscle. 

The  unstriped  plain,  or  involuntary  muscle,  is  found  in  the  walls  of  the  hollow 
viscera — viz.,  the  loAver  half  of  the  oesophagus  and  the  whole  of  the  remainder 
of  the  gastro-intestinal  tube;  in  the  trachea  and  bronchi,  and  the  alveoli  and 
infundibula  of  the  lungs  ;  in  the  gall-bladder  and  ductus  communis  choledochus  ; 
in  the  large  ducts  of  the  salivary  and  pancreatic  glands ;  in  the  pelvis  and  calices 
of  the  kidney,  the  ureter,  bladder,  and  urethra ;  in  the  female  sexual  organs — 
viz.,  the  ovary,  the  Fallopian  tubes,  the  uterus  (enormously  developed  in  preg- 
nancy), the  vagina,  the  broad  ligaments,  and  the  erectile  tissue  of  the  clitoris :  in  the 
male  sexual  organs — viz.,  the  dartos  of  the  scrotum,  the  vas  deferens  and  epididymis, 
the  vesiculse  seminales,  the  prostate  gland,  and  the  corpora  cavernosa  and  corpus 
spongiosum;  in  the  ducts  of  certain  glands,  as  in  Wharton's  duct;  in  the  capsule 


1112  GENERAL    ANATOMY   OB    HISTOLOGY. 

and  trabecule  of  the  spleen  ;  in  the  mucous  membranes,  forming  the  nmscularis 
mucosas ;  in  the  skin,  forming  the  arrectores  pilorum,  and  also  in  the  sweat- 
glands  ;  in  the  arteries,  veins,  and  lymphatics :  in  the  iris  and  the  ciliary  muscle. 
Plain  or  unstriped  muscle  is  made  up  of  spindle-shaped  cells,  called  con- 
tractile fibre-cells,  collected  into  bundles  and  held  together  by  a  cement-substance 
(Fig.  613).  These  bundles  are  further  aggregated  into  larger  bundles  or' 
flattened  bands,  and  bound  together  by  ordinary  connective  tissue. 

The  contractile  fibre-cells  are  elongated,  spindle-shaped,  nucleated  cells  of 
various  lengths,  averaging  from  -^-^  to  3-^-  of  an  inch  in  length,  and  45100  to 
3-Jjjq-  of  an  inch  in  breadth.  On  transverse  section  they  are  more  or  less  poly- 
hedral in  shape,  from  mutual  pressure.  They  present  a  faintly  longitudinal 
striated  appearance,  and  consist  of  an  elastic  cell- "wall  containing  a  central  bundle 
of  fibrillae,  representing  the  contractile  substance,  and  an  oval  or  rod-like  nu- 
cleus, which  includes,  within  a  membrane,  a  fine  network  communicating  at  the 
poles  of  the  nucleus  with  the  contractile  fibres  (Klein).  The  adhesive  interstitial 
cement-substance,  wThich  connects  the  fibre-cells  together,  represents  the  endomy- 
sium,  or  delicate  connective  tissue  which  binds  the  fibres  of  striped  muscular 
tissue  into  fasciculi ;  while  the  tissue  connecting  the  individual  bundles  together 
represents  the  perimysium.  The  unstriped  muscle,  as  a  rule,  is  not  under  the 
control  of  the  will,  nor  is  the  contraction  rapid  and  involving  the  whole  muscle, 
as  is  the  case  with  the  voluntary  muscles.  The  membranes  which  are  composed 
of  the  unstriped  muscle  slowly  contract  in  a  part  of  their  extent,  generally  under 
the  influence  of  a  mechanical  stimulus,  as  that  of  distention  or  of  cold;  and  then 
the  contracted  part  slowly  relaxes  wmile  another  portion  of  the  membrane  takes 
up  the  contraction.  This  peculiarity  of  action  is  most  strongly  marked  in  the 
intestines,  constituting  their  vermicular  motion. 

Cardiac  Muscular  Tissue. — The  fibres  of  the  heart  differ  very  remarkably  from 
those  of  other  striped  muscles.  They  are  smaller  by  one-third,  and  their  trans- 
verse striae  are  by  no  means  so  distinct.  The  fibres 
are  made  up  of  distinct  quadrangular  cells  joined 
end  to  end  (Fig.  044).  Each  cell  contains  a  clear 
oval  nucleus,  situated  near  the  centre  of  the  cell. 
The  extremities  of  the  cells  have  a  tendency  to 
branch  or  divide,  the  subdivisions  uniting  with 
offsets  from  other  cells,  and  thus  producing  an  an- 
astomosis of  the  fibres.  The  connective  tissue 
=  j  ~<      !  between   the  bundles  of  fibres  is  much  less  than  in 

:  :'   __^  -\        _  ordinary  striped    muscle,   and    no    sarcolemma  has 

-      r  -  =     '        ("fin!  been  proved  to  exist. 

-^!  Development  of  Muscle-Fibres. — AToluntary  mus- 

'^^  ',         ;:'r  cular  fibres  are   developed  from  the  mesoblast,  the 

*«■-■■=- *?        \_    -'  embryonic  cells  of  which  elongate,  show  multiplica- 

l[|  1:   I  1      '^H  tion  of  nuclei,  and  eventually  become  striated;  the 

%  :■■  :*$  striation   is  first   obvious   at  the  side   of  the  fibre, 

t^  MA    a      »        •  spreads   around   the   circumference,   and  ultimately 

Fig.  644.— Anastomosing  muscu-         L  .  •> 

lar  fibres  of  the  heart,  seen  ina  longi-     extends  to  the  centre.      IJie  nuclei,  at  first  situated 

tuclinal   section.      On  the   right  the  ,       n  n       n  xi      ■       n       i 

limits  of  the  separate  ceils  with      centrally,   gradually  pass  out  to  assume  their  trial 
t^t^Mt^X^^^^'X^     position  immediately  beneath   the  sarcolemma.     In 

the  case  of  plain  muscle  the  mesoblastic  cells  assume 
a  pointed  shape  at  the  extremities  and  become  flattened,  the  nucleus  also  length- 
ening out  tn  its  permanent  rod-like  form. 

Chemical  Composition  of  Muscle.  —  In  chemical  composition  the  muscular 
fibres  may  be  said,  in  round  numbers,  to  consist  of  75  per  cent,  of  water,  about 
20  per  cent,  of  proteids,  2  per  cent,  of  fat,  1  per  cent,  of  nitrogenous  extractives 
and  carbohydrates,  and  2  per  cent,  of  salts,  which  are  mainly  potassium  phosphate 
and  carbonate. 


THE   NERVOUS    TISSUE. 


1113 


THE    NERVOUS    TISSUE. 

The  nervous  tissues  of  the  body  are  comprised  in  two  great  systems — the 
cerebrospinal  and  the  sympathetic ;  and  each  of  these  systems  consist  of  a  central 
organ,  or  series  of  central  organs,  and  of  nerves. 

The  cerebrospinal  system  comprises  the  brain  (including  the  medulla  oblongata), 
the  spinal  cord,  the  cranial  nerves,  the  spinal  nerves,  and  the  ganglia  connected 
with  both  these  classes  of  nerves.  The  sympathetic  system  consists  of  a  double 
chain  of  ganglia,  with  the  nerves  which  go  to  and  come  from  them.  It  is  not 
directly  connected  with  the  brain  or  spinal  cord,  though  it  is  so  indirectly  by 
means  of  its  numerous  communications  with  the  cranial  and  spinal  nerves. 

All  these  nervous  tissues  are  composed  chiefly  of  two  different  structures — 
the  gray  or  cineritious  and  the  white  or  fibrous.  It  is  in  the  former,  as  is 
generally  supposed,  that  nervous  impressions  and  impulses  originate,  and  by  the 
latter  that  they  are  conducted.  Hence  the  gray  matter  forms  the  essential 
constituent  of  all  the  ganglionic  centres,  both  those  in  the  isolated  ganglia  and 
those  aggregated  in  the  cerebro-spinal  axis;  while  the  white  matter  is  found  in  all 
the  commissural  portions  of  the  nerve-centres  and  in  all  the  cerebro-spinal  nerves. 
The  nerves  of  the  sympathetic  system  are  chiefly  composed  of  a  material  of  a  some- 
what different  structure,  which  is  named  gray  or  gelatinous  nerve-fibre.  This 
form  of  nerve-fibre  is  also  found  in  some  of  the  cerebro-spinal  nerves. 


Fig.  645.— Nenroglia-cells  of  brain  shown  by  Golgi's  method.    (After  Andriezen.)    (Copied  from  Schiifer's 
Essentials  of  Histology.)    a.  Cell  with  branched  processes,    b.  Spider-cell  with  unbranched  processes. 

The  gray  nervous  substance  is  distinguished  by  its  dark  reddish-gray  color  and 
soft  consistence.  It  is  found  in  the  brain,  spinal  cord,  and  various  ganglia  inter- 
mingled with  the  fibrous  nervous  substance,  and  also  in  some  of  the  nerves  of 
special  sense,  and  in  gangliform  enlargements  which  are  found  here  and  there  in 
the  course  of  certain  cerebro-spinal  nerves.  It  is  composed  of  cells,  commonly 
called  nerve-cells  or  ganglion- corpuscles,  containing  nuclei  and  nucleoli.  The  cells 
together  with  the  blood-vessels  in  the  gray  nerve-substance,  and  the  nerve-fibres 
and  vessels  in  the  white  nerve-substance,  are  imbedded  in  a  peculiar  ground  sub- 
stance, named  by  Virchow  neuroglia.  It  consists  of  fibres  and  cells.  Some  of 
the  cells  are  stellate  in  shape,  and  their  fine  processes  become  neuroglia-fibres, 
which  extend  radially  and  unbranched  (Fig.  645,  b)  among  the  nerve-cells  and 
fibres  which  they  aid  in  supporting.  Other  cells  give  off  fibres  which  branch 
repeatedly  (Fig.  645,  a).     In  addition  to  these  fibres  there  are  others  which  do 


1114 


GENERAL    ANATOMY   OB    HISTOLOGY. 


not  appear  to  be  connected  with  the  neuroglia- cells.  They  start  from  the  epithelial 
cells  lining  the  ventricles  of  the  brain  and  central  canal  of  the  spinal  cord,  and 
pass  through  the  nervous  tissue,  branching  repeatedly  to  terminate  in  slight 
enlargements  on  the  pia  mater.  Thus,  neuroglia  is  evidently  a  connective  tissue 
in  function,  but  is  not  so  in  development;  it  is  epiblastic  in  origin,  whereas  all 
connective  tissues  are  mesoblastic. 

Each  nerve-cell   consists  of   a  finely  fibrillated    protoplasmic   material,    of  a 
reddish  or  yellowish-brown  color,  which  occasionally  presents  patches  of  a  deeper 


Fig.  646.— Nerve-cells  from  the  Gasserian 
ganglion  of  the  human  subject,  a.  A  globu- 
lar one  with  defined  border.  6.  Its  nucleus, 
c.  Its  nucleolus,  d.  Caudate  cell.  e.  Elong- 
ated cell  with  two  groups  of  pigment-par- 
ticles. /.  Cell  surrounded  by  its  sheath  or 
capsule  of  nucleated  particles,  g.  The  same, 
the  sheath  only  being  in  focus.  Magnified 
300  diameters. 


"heath  of 
cell  body. 

Nucleus. 

Cell  protoplasm. 


Axon. 
Myelin  sheath. 


Fig.  648.— Bipolar  nerve-cell  from  the  spinal  gan- 
glion of  the  pike.     (After  Kolliker.) 


Fig.  647.— Nerve-cells  from  the  inner  part  of  the 
gray  matter  of  the  convolutions  of  the  human  brain. 
Magnified  350  times.  Nerve-cells  :  a.  Larger.  6.  Smaller, 
c.  Nerve-fibre  with  axis-cylinder. 


Fig.  649.— Motor  nerve-cell  from  ventral  horn 
of  spinal  cord  of  rabbit.  (After  Nissl.)  The 
angular  and  spindle-shaped  Nissl  bodies  are 
well  shown. 


tint,  caused  by  the  aggregation  of  pigment-granules  at  one  side  of  the  nucleus, 
as  in  the  substantia  nigra  and  locus  cceruleus.  The  protoplasm  also  sometimes 
contains  peculiar  angular  granules,  which  stain  deeply  with  basic  dyes,  such  as 
methylene-blue  ;  these  are  known  as  NissVs  granules  (Fig.  649).  The  nucleus  is, 
as  a  rule,  a  large,  well-defined,  round,  vesicular  body,  often  presenting  an  intra- 
nuclear   network,    and    containing    a    nucleolus    which    is    peculiarly    clear    and 


I 


THE   NERVOUS    TISSUE. 


11  lo 


brilliant.      The  nerve-cells  vary  in  shape  and  size,  and  have  one    r  moi  ;sses. 

They   may   be   divided   for  pur    wes   of   description  into  three  groups,   according 
to  the  number  of  processes    which  they  -s :     1     Unipolar  cells,  "which  are 

found  in  the  spinal  ganglia;  their  single  process,   after  a  short  course,   divides 
in  a  T-shaped  manner.   (2)  B:r  -.  also  found  in  the  spinal  ganglia  'Fig.  6 

when  the  cells  are  in  an  embryonic  condition.     They  are  best  demonstrated  in  the 

sympathetic  ganglion-celis  of  a  frog. 
Sometimes  the  process  -  le  off  from 
opposite  poles  of  the  cell,  and  tl. 
then  assumes  a  spindle-shape  ;  at  others 
both  emerge  a:  the  same  point.  In 
some  cases  where  two  fibres  are  appar- 
ently  connected   with  a  cell,  one  of  the 


eort, 


Axon. 


Fig.  6-5*').— Pyramidal   cell  from  the  cerebral 
ex  of  a  mouse.    (After  Ramon  y  CajaL) 


Fig.  651. — Cell  of  Purkinje  from  the  cerebellum  of 

2.  r:i.:       at:-.-:  JalA:.  y  liA'.-J 


fibres  is  really  derived  from  an  adjoin- 
ing nerve-cell  and  is  passing  to  end  in  a 
ramification  around  the  ganglion-cell, 
or.  again,  it  may  be  coiled  spirally 
round  the  nerve  process  which  is  issuing 
from    the  cell.       (o1      Multipolar    cells. 


which  are  caudate  or  stellate  in  shape, 
and  characterized  by  their  large  size  and  by  the  tail-like  processes  which  if 
from  them.  The  processes  are  of  two  kinds  :  one  of  them  is  termed  the  axis- 
cylinder  process  or  axon,  because  it  becomes  the  axis-cylinder  of  a  nerve-fibre 
(Figs.  649,  650,  651  .  The  others  are  termed  the  protoplasmic  processes  or 
dendrons ;  they  begin  to  divide  and  subdivide  as  soon  as  they  emerge  from  the 
cell,  and  finally  end  in  minute  twigs  and  become  lost  among:  the  other  elements  of 
the  nervous  tissue. 

The  white  or  fibrous  nerve-substance  or  nerve-fibre  is  found  universally  in  the 
nervous  cords,  and  also  constitutes  a  great  |  ar:  of  the  brain  and  spinal  cord.  The 
fibres  of  which  it  consists  are  of  two  kinds,  the  medullated  or  white  fibres,  and  the 
non-medullated  or  gray  fibres. 


1116 


GENERAL    ANATOMY   OB    HISTOLOGY. 


The  medullated  fibres  form  the  white  part  of  the  brain  and  spinal  cord,  and 
also  the  greater  part  of  the  cerebro-spinal  nerves,  and  gives  to  these  struct- 
ures their  opaque,  white  aspect.  When  perfectly  fresh  they  appear  to  be  homo- 
geneous;  but  soon  after  removal  from  the  body  they  present,  when  examined  by 
transmitted  light,  a  double  outline  or  contour,  as  if  consisting  of  two  parts 
(Fig.  652).  The  central  portion  is  named  the  axis-cylinder  of  Purkinje  ;  around 
this  is  a  sort  of  sheath  of  fatty  material,  staining  black  with  osmic  acid,  named 


Fibrils  of  axis- 
cylinder. 


Neurilemma. 


_ ^Segment  of 
Lantermann. 


Fig.  652.— Wuite  or  medullated  nerve- 
fibres  showing  the  sinuous  outline  and 
double  contours.    (After  Sehafer.) 


Fig.  653.— Longitudinal  section  through  a  nerve-fibre  from 
the  sciatic  nerve  of  a  frog.  X  830.  (After  Bohm  and 
Davidoff.) 


the  white  substance  of  Schivann,  which  gives  to  the  fibre  its  double  contour,  and 
the  whole  is  enclosed  in  a  delicate  membrane,  the  neurilemma,  primitive  sheath, 
or  nucleated  sheath  of  Schwann  (Fig.  652). 

The  axis-cylinder  is  the  essential  part  of  the  nerve-fibre,  and  is  always 
present ;  the  other  parts,  the  medullary  sheath  and  the  neurilemma,  being  occa- 
sionally absent,  especially  at  the  origin  and  termination  of  the  nerve-fibre.  It 
undergoes  no  interruption  from  its  origin  in  the  nerve-centre  to  its  peripheral 
termination,  and  must  be  regarded  as  a  direct  prolongation  of  a  nerve-cell.  It 
constitutes  about  one-half  or  one-third  of  the  nerve-tube,  the  whole  substance  being 

greater  in  proportion  in  the 
Derves  than  in  the  central  organs. 
It  is  perfectly  transparent,  and 
is  therefore  indistinguishable  in 
a  perfectly  fresh  and  natural 
state  of  the  nerve.  It  is  made 
up  of  exceedingly  fine  fibrils, 
which  stain  darkly  with  gold 
chloride  (Fig.  653).  At  its 
termination  the  axis-cylinder  of  a  nerve-fibre  may  be  seen  to  break  up  into  fibrillse, 
confirming  the  view  of  its  structure.  These  fibrillre  have  been  termed  the  primi- 
tive fibrillar  of  Schultze.  The  axis-cylinder  is  said  by  some  to  be  enveloped  in  a 
special,  reticular  sheath,  which  separates  it  from  the  white  matter  of  Schwann,  and 
is  composed  of  a  substance  called  neurokeratin.  The  more  common  opinion  is  that 
this  network  or  reticulum  is  contained  in  the  white  matter  of  Schwann,  and  by 
some  it  is  believed  to  be  produced  by  the  action  of  the  reagents  employed  to  show 
it.  The  medullary  sheath  or  white  matter  of  Schivann  (Fig.  653)  is  regarded  as 
being  a  fatty  matter  in  a  fluid  state,  which  insulates  and  protects  the  essential  part 
of  the  nerve — the  axis-cylinder.     The  white  matter  varies  in  thickness  to  a  very 


Fig.  654.— A  node  of  Ranvier  of  a  medullated  nerve-fibre, 
viewed  from  above,  magnified  about  750  diameters.  The  medul- 
lary sheath  is  discontinuous  at  the  node,  whereas  the  axis- 
cylinder  pass?s  from  one  segment  into  the  other.  At  the  node 
the  sheath  of  Schwann  appears  thickened.  (Klein  and  Noble 
Smith.) 


THE   NERVOUS    TISSUE. 


1117 


considerable  extent,  in  some  forming  a  layer  of  extreme  thinness,   so   as   to   be 
scarcely  distinguishable ;   in  others  forming  about  one-half  the  nerve-tube.      The 


size  of  the   nerve-fibres,    which    varies   from 


to 


of  an  inch,    depends 


2000     *"     1200 

mainly  upon  the  amount  of  the  white  substance,  though  the  axis-cylinder  also 
varies  in  size  within  certain  limits.  The  white  matter  of  Schwann  does  not  always 
form  a  continuous  sheath  to  the  axis-cylinder,  but  undergoes  interruptions  in  its 
continuity  at  regular  intervals,  giving  to  the  fibre  the  appearance  of  constriction 
at  these  points.  These  were  first  described  by  Ranvier,  and  are  known  as  the 
nodes  of  Ranvier  (Fig.  654).  The  portion  of  nerve-fibre  between  two  nodes  is 
called  an  internodal  segment.  The  neurilemma  or  primitive  sheath  is  not  inter- 
rupted at  the  nodes,  but  passes  over  them  as  a  continuous  membrane.  In  addition 
to  these  interruptions  oblique  clefts  may  be  seen  in  the  medullary  sheath,  sub- 
dividing it  into  irregular  portions,  which  are  termed  medullary  segments,  or  seg- 
ments of  Lantermann  (Fig.  653).  There  is  reason  to  believe  that  these  clefts  are 
artificially  produced  in  the  preparation  of  the  specimens.  Medullated  nerve-fibres, 
when  examined,  frequently  present  a  beaded  or  varicose  appearance  :  this  is  due 
to  manipulation  and  pressure  causing  the  oily  matter  to  collect  into  drops,  and  in 
consequence  of  the  extreme  delicacy  of  the  primitive  sheath,  even  slight  pressure 
will  cause  the  transudation  of  the  fatty  matter,  which  collects  as  drops  of  oil  outside 
the  membrane.     This  is,  of  course,  promoted  by  the  action  of  certain  reagents. 

The  neurilemma  or  primitive  sheath  (sometimes  called  the  tubular  membrane  or 
sheath  of  Schivann)  presents  the  appearance  of  a  delicate,  structureless  membrane. 
Here  and  there  beneath  it,  and  situated  in  depres- 
sions in  the  white  matter  of  Schwann,  are  nuclei 
surrounded  by  a  small  amount  of  protoplasm.  The 
nuclei  are  oval  and  somewhat  flattened,  and  bear  a 
definite  relation  to  the  nodes  of  Ranvier ;  one 
nucleus  generally  lying  in  the  centre  of  each  inter- 
node.  The  primitive  sheath  is  not  present  in  all 
medullated  nerve-fibres,  being  absent  in  those  fibres 
which  are  found  in  the  brain  and  spinal  cord. 

Non-medullated  Fibres. — Most  of  the  nerves  of 
the  sympathetic  system,  and  some  of  the  cerebro- 
spinal, consist  of  another  variety  of  nervous  fibres, 
which  are  called  the  gray  or  gelatinous  nerve-fibres 
— fibres  of  Remak  (Fig.  655).  These  consist  of  a 
central  core  or  axis-cylinder  enclosed  in  a  nucleated 
sheath,  which  tends  to  split  into  fibrillse,  and  is 
probably  of  the  nature  of  neurokeratin.  In  exter- 
nal appearance  the  gelatinous  nerves  are  semi- 
transparent  and  gray  or  yellowish-gray.  The 
individual  fibres  vary  in  size,  generally  averaging  about  half  the  size  of  the 
medullated  fibres. 

Development  of  Nerve-cells  and  Fibres. — The  nerve- cells  are  developed  from 
certain  of  the  cells  which  line  the  neural  canal  or  form  the  neural  crest  of  the 
embryo  (see  section  on  Development).  Some  of  these  cells  assume  a  rounded  form 
and  are  termed  neuroblasts,  and  from  each  neuroblast  there  grows  out  a  process, 
the  axis-cylinder  process  or  axon,  and  subsequently  the  branching  processes  or 
dendrons.  The  axis-cylinders,  at  first  naked,  acquire  their  medullary  sheath, 
possibly  by  some  metamorphosis  of  their  outer  layer.  The  neurilemma  is  thought 
to  be  derived  from  mesoblastic  cells  which  become  flattened  and  wrapped  round 
the  fibre,  the  cement-substance  at  their  apposed  ends  forming  the  material  which 
stains  with  silver  nitrate  at  the  nodes  of  Ranvier.  Nerve-cells  in  the  sympathetic 
and  peripheral  ganglia  take  their  origin  from  small  collections  of  neuroblasts, 
.rhich  are  split  off  from  the  rudimentary  spinal  ganglia.  Cells  which  are,  origi- 
nally, similar  to  neuroblasts  seem  to  give  rise  to  neuroglia-cells,  numerous  processes 
sprouting  from  the  cell  to  form  the  neuroglial  fibres. 


Fig.  655.— A  small  nervous  branch 
from  the  sympathetic  of  a  mammal. 
a.  Two  medullated  nerve-fibres  among 
a  number  of  gray  nerve-fibres,  b. 


1118 


GENERAL    ANATOMY   OB   HISTOLOGY. 


Chemical  Composition. — The  amount  of  water  in  nervous  tissue  varies  with  the 
situation.  Thus  in  the  gray  matter  of  the  cerebrum  it  constitutes  about  83  per 
cent.,  in  the  white  matter  from  the  same  region  about  70  per  cent.,  while  in  the 
peripheral  nerves,  such  as  the  sciatic,  it  may  fall  to  60  per  cent.  The  solids  con- 
sist of  proteids  (in  the  gray  matter  they  form  half  the  total  solids),  neurokeratin, 
nuclein,  protagon,  lecithin,  cerebrosides,  cholesterin,  nitrogenous  extractives,  and 
salts,  with  some  gelatin  and  fat  from  the  adherent  connective  tissue. 

The  nervous  structures  are  divided,  as  before  mentioned,  into  two  great  systems, 
viz.,  the  cerebrospinal,  comprising  the  brain  and  spinal  cord,  the  nerves  con- 
nected with  these  structures,  and  the  ganglia  situated  on  them  ;  and  the  sympa- 
thetic, consisting  of  a  double  chain  of  ganglia  and  the  nerves  connected  with  them. 
All  these  structures  require  separate  consideration  ;   they  are  composed  of  the  two 

kinds  of  nervous  tissue  above  described, 
intermingled  in  various  proportions,  and 
having,  in  some  parts,  a  very  intricate 
arrangement. 

The  brain  or  encephalon  is  that  part 
of  the  cerebro-spinal  system  which  is 
contained  in  the  cavity  of  the  skull.  It 
is  divided  into  several  parts,  which  will 
be  described  in  the  sequel.  In  these 
parts  the  gray  or  vesicular  nervous 
matter  is  found  partly  on  the  surface 
of  the  brain,  forming  the  convolutions 
of  the  cerebrum  and  the  laminse  of  the 
cerebellum.  Again,  gray  matter  is 
found  in  the  interior  of  the  brain,  col- 
lected into  large  and  distinct  masses  or 
ganglionic  bodies,  such  as  the  corpus 
striatum,  optic  thalamus,  and  corpora 
quadrigemina.  Finally,  gray  matter  is 
found  intermingled  intimately  with  the 
white,  but  without  definite  arrangement, 
as  in  the  gray  matter  in  the  pons 
Varolii  and  the  floor  of  the  fourth 
ventricle. 

The  white  matter  of  the   brain   is 

divisible   into   three   distinct  classes  of 

fibres :     (1)    Diverging    or    peduncular 

fibres,  which  connect  the  hemispheres  with  the  medulla  oblongata  and  the  spinal 

cord.     (2)  Commissural  fibres,  which   connect   together  the  two  hemispheres.      (3) 

Association  fibres,  which  connect  different  parts  of  the  same  hemisphere. 

The  manner  in  which  these  fibres  are  intermingled  with  each  other  and  with 
the  gray  matter  in  the  brain  and  spinal  cord  is  very  intricate,  and  can  be  fully  under- 
stood only  by  a  careful  study  of  the  details  of  its  descriptive  anatomy  in  the  sequel. 
The  further  consideration  of  this  subject  will  therefore  be  deferred  until  after  the 
description  of  the  various  divisions  of  which  the  cerebro-spinal  system  is  made  up. 
The  nerves  are  round  or  flattened  cords,  formed  of  the  nerve-fibres  already 
described.  They  are  connected  at  one  end  with  the  cerebro-spinal  centre  or  with 
the  ganglia,  and  are  distributed  at  the  other  end  to  the  various  textures  of  the 
body ;  they  are  subdivided  into  two  great  classes — the  cerebrospinal,  which  pro- 
ceed from  the  cerebro-spinal  axis,  and  the  sympathetic  or  ganglionic  nerves,  which 
proceed  from  the  ganglia  of  the  sympathetic.  The  cerebro-spinal  nerves  consist 
of  numerous  nerve-fibres  collected  together  and  enclosed  in  a  membranous  sheath 
(Fig.  656).  A  small  bundle  of  primitive  fibres,  enclosed  in  a  tubular  sheath,  is 
called  a  funiculus ;  if  the  nerve  is  of  small  size,  it  may  consist  only  of  a  single 
funiculus ;   but  if  large,  the  funiculi  are  collected  together  into  larger  bundles  or 


Fig.  656. — Transverse  section  through  a  microscopic 
ntrve,  representing  a  compound  nerve-bundle,  sur- 
rounded by  perineurium.  Magnified  120  diameters. 
The  medullated  fibres  are  seen  as  circles  with  a  cen- 
tral dot — viz.,  medullary  sheath  and  axis-cylinder — in 
transverse  section.  They  are  embedded  in'  endoneur- 
ium,  containing  numerous  nuclei,  which  belong  to  the 
connective-tissue  cells  of  the  latter.  (Klein  and  Noble 
Smiths  p.  Perineurium,  consisting  of  laminfe  of  fibrous 
connective-tissues,  alternating  with  flattened  nucleated 
connective-tissue  cells.  I.  Lymph-space  between  epi- 
neurium  and  surface  of  nerve-bundle. 


THE   NERVOUS    TISSUE.  1119 

fasciculi,   which   are   bound   together  in  a  common  membranous  investment,  and 
constitute  the  nerve. 

In  structure  the  common  membranous  investment,  or  sheath  of  the  "whole  nerve, 
which  is  called  the  epineurium,  as  well  as  the  septa  given  off  from  it,  and  which 
separate  the  fasciculi,  consists  of  connective  tissue,  composed  of  white  and  yellow 
elastic  fibres,  the  latter  existing  in  great  abundance.  The  tubular  sheath  of  the 
funiculi,  called  the  perineurium,  consists  of  a  fine,  smooth,  transparent  membrane, 
which  may  be  easily  separated,  in  the  form  of  a  tube,  from  the  fibres  it  encloses  ; 
in  structure  it  consists  of  connective  tissue,  which  has  a  distinctly  lamellar  arrange- 
ment, consisting  of  several  lamellae,  separated  from  each  other  by  spaces  containing 
lymph.  The  nerve-fibres  are  held  together  and  supported  within  the  funiculus  by 
delicate  connective  tissue  called  the  endoneurium.  It  is  continuous  with  septa 
which  pass  inward  from  the  innermost  layer  of  the  perineurium,  and  consists  of  a 
ground-substance  in  which  are  embedded  fine  bundles  of  fibrous  connective  tissue 
which  run  for  the  most  part  longitudinally.  It  serves  to  support  the  capillary 
vessels,  which  are  arranged  so  as  to  form  a  network  with  elongated  meshes.  The 
cerebro-spinal  nerves  consist  almost  exclusively  of  the  medullated  nerve-fibres, 
the  non-medullated  existing  in  very   small   proportions. 

The  blood-vessels  supplying  a  nerve  terminate  in  a  minute  capillary  plexu6, 
the  vessels  composing  which  pierce  the  perineurium  and  run,  for  the  most  part, 
parallel  with  the  fibres  ;  they  are  connected  together  by  short,  transverse  vessels, 
forming  narrow,  oblong  meshes,  similar  to  the  capillary  system  of  muscle.  Fine 
non-medullated  nerve-fibres  accompany  these  capillary  vessels,  vaso-motor  fibres, 
and  break  up  into  elementary  fibrils,  which  form  a  network  around  the  vessel. 
Horsley  has  also  demonstrated  certain  medullated  fibres  as  running  in  the  epineu- 
rium  and  terminating  in  small  spheroidal  tactile  corpuscles  or  end-bulbs  of  Krause. 
These  nerve-fibres,  which  Marshall  believes  to  be  sensory,  and  which  he  has  termed 
nervi  nervorum,  are  considered  by  him  to  have  an  important  bearing  upon  certain 
neuralgic  pains. 

The  nerve-fibres,  as  far  as  is  at  present  known,  do  not  coalesce,  but  pursue  an 
uninterrupted  course  from  the  centre  to  the  periphery.  In  separating  a  nerve, 
however,  into  its  component  funiculi,  it  may  be  seen  that  they  do  not  pursue  a 
perfectly  insulated  course,  but  occasionally  join  at  a  very  acute  angle  with  other 
funiculi  proceeding  in  the  same  direction  ;  from  this,  branches  are  given  off,  to 
join  again  in  like  manner  with  other  funiculi.  It  must  be  distinctly  understood, 
however,  that  in  these  communications  the  nerve-fibres  do  not  coalesce,  but  merely 
pass  into  the  sheath  of  the  adjacent  nerve,  become  intermixed  with  its  nerve-fibres, 
and  again  pass  on,  to  become  blended  with  the  nerve-fibres  in  some  adjoining 
funiculus. 

Nerves,  in  their  course,  subdivide  into  branches,  and  these  frequently  commu- 
nicate with  branches  of  a  neighboring  nerve. 

The  communications  which  take  place  between  two  or  more  nerves  form  what 
is  called  a  plexus.  Sometimes  a  plexus  is  formed  by  the  primary  branches  of  the 
trunks  of  the  nerves — as  the  cervical,  brachial,  lumbar,  and  sacral  plexuses — and 
occasionally  by  the  terminal  funiculi,  as  in  the  plexuses  formed  at  the  periphery 
of  the  body.  In  the  formation  of  a  plexus  the  component  nerves  divide,  theni 
join,  and  again  subdivide  in  such  a  complex  manner  that  the  individual  funiculi 
become  interlaced  most  intricately ;  so  that  each  branch  leaving  a  plexus  may 
contain  filaments  from  each  of  the  primary  nervous  trunks  which  form  it.  In  the 
formation  also  of  smaller  plexuses  at  the  periphery  of  the  body  there  is  a  free 
interchange  of  the  funiculi  and  primitive  fibres.  In  each  case,  however,  the 
individual  filaments  remain  separate  and  distinct,  and  do  not  inosculate  with  one 
another. 

It  is  probable  that  through  this  interchange  of  fibres  the  different  branches 
passing  off  from  a  plexus  have  a  more  extensive  connection  with  the  spinal  cord 
than  if  they  each  had  proceeded  to  be  distributed  without  such  connection  with 
other  nerves.      Consequently  the  parts  supplied  by  these  nerves  have  more  extended 


1120  GENERAL    ANATOMY    OB    HISTOLOGY. 

relations  with  the  nervous  centres ;  by  this  means,  also,  groups  of  muscles  may  be 
associated  for  combined  action. 

The  sympathetic  nerves  are  constructed  in  the  same  manner  as  the  cerebro- 
spinal nerves,  but  consist  mainly  of  non-meclullated  fibres,  collected  into  funiculi, 
and  enclosed  in  a  sheath  of  connective  tissue.  There  is,  however,  in  these  nerves 
a  certain  admixture  of  medullated  fibres,  and  the  amount  varies  in  different 
nerves,  and  may  be  known  by  their  color.  Those  branches  of  the  sympathetic 
which  present  a  well-marked  gray  color  are  composed  more  especially  of  gelatinous 
nerve-fibres,  intermixed  with  a  few  medullated  fibres;  while  those  of  a  white 
color  contain  more  of  the  latter  fibres  and  a  few  of  the  former.  Occasionally,  the 
gray  and  white  cords  run  together  in  a  single  nerve,  without  any  intermixture,  as 
in  the  branches  of  communication  between  the  sympathetic  ganglia  and  the  spinal 
nerves,  or  in  the  communicating  cords  between  the  ganglia. 

The  nerve-fibres,  both  of  the  cerebro-spinal  and  sympathetic  system,  convey 
impressions  of  a  twofold  kind.  The  sensory  nerves,  called  also  centripetal  or 
afferent  nerves,  transmit  to  the  nervous  centres  impressions  made  upon  the 
peripheral  extremities  of  the  nerves,  and  in  this  way  the  mind,  through  the 
medium  of  the  brain,  becomes  conscious  of  external  objects.  The  motor  nerves, 
called  also  centrifugal  or  efferent  nerves,  transmit  impressions  from  the  nervous 
centres  to  the  parts  to  which  the  nerves  are  distributed,  these  impressions  either 
exciting  muscular  contraction,  or  influencing  the  processes  of  nutrition,  growth, 
and  secretion. 

Origin  and  Termination  of  Nerves. — By  the  expression  "  the  termination  of 
nerve-fibres  "  is  signified  their  connection  with  the  nerve-centres,  and  with  the 
parts  they  supply.  The  former  are  sometimes  called  their  origin,  or  central 
termination  ;  the  latter  their  perip>heral  termination.  The  origin  in  some  cases  is 
single — that  is  to  say,  the  whole  nerve  emerges  from  the  nervous  centre  by  a  single 
root ;  in  other  instances  the  nerve  arises  by  two  or  more  roots,  which  come  off 
from  different  parts  of  the  nerve-centre,  sometimes  widely  apart  from  each  other, 
and  it  often  happens,  when  a  nerve  arises  in  this  way  by  two  roots,  that  the 
functions  of  these  two  roots  are  different ;  as,  for  example,  in  the  spinal  nerves, 
each  of  which  arises  by  two  roots,  the  anterior  of  Avhich  is  motor  and  the  posterior 
sensory.  The  point  where  the  nerve  root  or  roots  emerge  from  the  nervous  centre 
is  named  the  superficial  or  apparent  origin,  but  the  fibres  of  which  the  nerve 
consists  can  be  traced  for  a  certain  distance  into  the  nervous  centre  to  some  por- 
tion of  the  gray  substance,  which  constitutes  the  deep  or  real  origin  of  the  nerve. 

The  manner  in  which  these  fibres  arise  at  their  deep  origin  varies  with  their 
functions.  The  centrifugal  or  efferent  nerve-fibres  originate  in  the  nerve-cells  of 
the  gray  substance,  the  axis-cylinder  processes  of  these  cells  being  prolonged  to 
form  the  fibres.  In  the  case  of  the  centripetal  or  afferent  nerves  the  fibres  grow 
inward  either  from  nerve-cells  in  the  organs  of  special  sense  (e.  g.,  the  retina) 
or  from  nerve-cells  in  the  ganglia.  Having  entered  the  nerve-centre,  they  branch 
and  send  their  ultimate  twigs  among  the  cells,  without,  however,  uniting  with  them. 

Peripheral  Terminations  of  Nerves. — Nerve-fibres  terminate  peripherally  in 
various  ways,  and  these  may  be  conveniently  studied  in  the  sensory  and  motor 
nerves,  respectively.  Sensory  nerves  would  appear  to  terminate  either  in  minute 
primitive  fibrillar  or  networks  of  these ;  or  else  in  special  terminal  organs,  which 
have  been  termed  peripheral  end-organs,  and  of  which  there  are  several  principal 
varieties,  viz.,  the  end-bulbs  of  Krause,  the  tactile  corpuscles  of  Wagner,  the 
Pacinian  corpuscles,  and  the  neuro-tendinous  and  neuro-muscular  spindles. 

Termination  in  FibriUse. — When  a  medullated  nerve-fibre  approaches  its  termi- 
nation, the  white  matter  of  Schwann  suddenly  disappears,  leaving  only  the  axis- 
cylinder,  surrounded  by  the  neurilemma,  and  forming  a  non-medullated  fibre. 
This,  after  a  time,  loses  its  neurilemma,  and  consists  only  of  an  axis-cylinder, 
which  can  be  seen,  in  preparations  stained  with  chloride  of  gold,  to  be  made  up 
of  fine  varicose  fibrils.  Finally,  the  axis-cylinder  breaks  up  into  its  constituent 
primitive  nerve-fibrillge,  which  often  present  regular  varicosities  and  anastomose 


THE   NERVOUS    TISSUE. 


1121 


with  one  another,  thus  forming  a  network.  This  network  passes  between  the 
elements  of  the  tissue  to  which  the  nerves  are  distributed,  which  is  always 
epithelial,  the  nerve-fibrils  lying  in  the  interstitial  substance  between  the  epithelial 
cells,  and  there  terminating,  though  some  observers  maintain  that  the  actual  ter- 
minations are  within  the  cells.  In  this  way  nerve-fibres  have  been  found  to  ter- 
minate in  the  epithelium  of  the  skin  and  mucous  membranes,  and  in  the  anterior 
epithelium  of  the  cornea. 

The  end-bulbs  of  Krause  (Fig.  657)  are  minute  cylindrical  or  oval  bodies,  con- 
sisting of  a  capsule  formed  by  the  expansion  of  the  connective-tissue  sheath  of  a 
medullated  fibre,  and  containing  a  soft  semifluid  core  in  which  the  termination  of 
the  axis-cylinder  is  situated,  ending  either  as  a  bulbous  extremity,  or  in  a  coiled- 
up  plexiforni  mass.  End-bulbs  are  found  in  the  conjunctiva  of  the  eye,  where 
they  are  spheroidal  in  shape  in  man,  but  cylindrical  in  most  other  animals,  in  the 
mucous  membrane  of  the  lips  and  tongue,  and  in  the  epineurium  of  nerve-trunks. 
They  are  also  found  in  the  genital  organs  of  both  sexes,  the  penis  in  the  male, 
and  the  clitoris  in  the  female.  In  this  situation  they  have  a  mulberry-like 
appearance,  from  being  constricted  by  connective-tissue  septa  into  from  two  to 
six  knob-like  masses,  and  have  received  the  name  of  genital  corpuscles.  Very 
similar  corpuscles  are  found  in  the  epineurium  of  nerve-trunks.  In  the  synovial 
membrane  of  certainjoints  (e.g.,  those  of  the  fingers),  rounded  or  oval  end-bulbs 
have  been  found ;  these  are  designated  articular  end-bulbs. 

Tactile  corpuscles  have  been  described  by  Grandry  as  occurring  in  the  papillae 
of  the  beak  and  tongue  of  birds,  and  by  Merkel  as  occurring  in  the  papillee  and 
epithelium  of  the  skin  of  man  and  animals,  especially  in  those  parts  of  the  skin 
devoid  of  hair.  They  consist  of  a  capsule  composed  of  a  very  delicate,  nucleated 
membrane,  and  contain  two  or  more  granular,  somewhat  flattened  cells,  between 
which  the  medullated  nerve-fibre,  which  enters  the  capsule  by  piercing  its  investing 
membrane,  is  supposed  to  terminate. 


Fig.  657— End-bulb  of  Krause.  a.  Medul- 
lated nerve-fibre,  b.  Capsule  of  corpuscle. 
(From  Klein's  Elements  of  Histology.) 


Fig.  658.— Tactile  papilla  of  the  band  treated  with  acetic 
acid.  Magnified  3.",0  times,  a.  Side  view  of  a  papilla  of  the 
hand.  a.  Cortical  layer,  b.  Tactile  corpuscle, with  transverse 
nuclei,  c.  Small  nerve  of  the  papilla,  with  neurilemma,  d. 
Its  two  nervous  fibres  running  with  spiral  coils  around  the 
tactile  corpuscle,  e.  Apparent  termination  of  one  of  these 
fibres,  b.  A  tactile  papilla  seen  from  above,  so  as  to  show 
its  transverse  section,  a.  Cortical  layer,  b.  Nerve-fibre,  c. 
Outer  layer  of  the  tactile  body,  with  nuclei,  d.  Clear 
interior  substance. 


The  tactile  corpuscles  (Fig.  658),  described  by  Wagner  and  Meissner,  are  oval- 
shaped  bodies,  made  up  of  connective  tissue,  and  consisting  of  a  capsule,  and 
imperfect  membranous  septa,  derived  from  it,  which  penetrate  its  interior.  The 
axis-cylinder  of  the  medullated  fibres  passes  through  the  capsule,  and  having 
entered  the  corpuscle  terminates  in  a  small  globular  or  pyriform  enlargement,  near 
the  inner  surface  of  the  capsule.  These  tactile  corpuscles  have  "been  described  as 
occurring  in  the  papillae  of  the  corium  of  the  hand  and  foot,   the  front  of  the 

71 


1122 


GENERAL    ANATOMY   OB    HISTOLOGY 


forearm,  skin  of  the  lips,  and  the  mucous  membrane  of  the  tip  of  the  tongue,  the 
palpebral  conjunctiva,  and  the  skin  of  the  nipple.  They  are  not  found  in  all  the 
papillse ;  but  from  their  existence  in  those  parts  in  which  the  skin  is  highly  sensi- 


Nerve-fibres. 


Terminal  ramifications 
of  axis-cylinder. 


Fig.  659.— Nerve-ending  of  Ruffini.     (After  A.  Ruffini,  Arch.  ital.  de  Biol.,  Turin,  t.  xxi.  1894.) 

tive,  it  is  probable  that  they  are  specially  concerned  in  the  sense  of  touch,  though 
their  absence  from  the  papillae  of  other  tactile  parts  shows  that  they  are  not  essen- 
tial to  this  sense. 

Ruffini  has   described  a  special  variety  of  nerve-ending  in   the  subcutaneous 
tissue  of  the  human  finger   (Fig.    659).      These   are  usually  known  as  Ruffini  s 

endings.  They  are  principally  situated  at  the 
junction  of  the  corium  with  the  subcutaneous  tis- 
sue ;  they  are  oval  in  shape,  and  consist  of  a 
strong  connective- tissue  sheath,  inside  which  the 
nerve-fibre  divides  into  numerous  branches,  which 
show  varicosities  and  end  in  small  free  knobs. 
They  resemble  the  corpuscles  of  Golgi. 

The  Pacinian  corpuscles1  (Fig.  660)  are  found 
in  the  human  subject  chiefly  on  the  nerves  of 
the  palm  of  the  hand  and  sole  of  the  foot 
and  in  the  genital  organs  of  both  sexes,  lying 
in  the  subcutaneous  tissue ;  but  they  have  also 
been  described  as  connected  with  the  nerves  of 
the  joints,  and  in  some  other  situations,  as  the 
mesentery  of  the  cat  and  along  the  tibia  of  the 
rabbit.  Each  of  these  corpuscles  is  attached  to 
and  encloses  the  termination  of  a  single  nerve- 
fibre.  The  corpuscle,  which  is  perfectly  visible 
to  the  naked  eye  (and  which  can  be  most  easily 
demonstrated  in  the  mesentery  of  a  cat),  consists 
of  a  number  of  lamellae  or  capsules,  arranged  more 
or  less  concentrically  around  a  central  clear  space, 
in  which  the  nerve-fibre  is  contained.  Each  lamella 
is  composed  of  bundles  of  fine  connective-tissue 
fibres,  and  is  lined  on  its  inner  surface  by  a  single 
layer  of  cells.  The  central  clear  space,  which  is 
elongated  or  cylindrical  in  shape,  is  filled  with  a 
transparent  material,  in  the  middle  of  which  is  the 
single  medullated  fibre,  which  traverses  the  space 
to  near  its  distal  extremity.  Here  it  terminates 
in  a  rounded  knob  or  end,  sometimes  bifurcating 
previously,  in  which  case  each  branch  has  a  sim- 
ilar arrangement.  Todd  and  Bowman  have  de- 
scribed minute  arteries  as  entering  by  the  sides  of  the  nerves  and  forming  capil- 
lary loops  in  the  intercapsular  spaces,  and  even  penetrating  into  the  central  space. 
1  Often  called  in  German  anatomical  works  "  corpuscles  of  Vater." 


Fig.  660.— Pacinian  corpuscle,  with  its 
system  of  capsules  and  central  cavity. 
a.  Arterial  twig,  ending  in  capillaries, 
which  form  loops  in  some  of  the  inter- 
capsular spaces,  and  one  penetrates  to 
the  central  capsule.  6.  The  fibrous  tissue 
of  the  stalk  prolonged  from  the  perineu- 
rium, n.  Nerve-tube  advancing  to  the 
central  capsule,  there  losing  its  white 
matter,  and  stretching  along  the  axis  to 
the  opposite  end,  where  it  is  fixed  by  a 
tubercular  enlargement. 


THE   NERVOUS    TISSUE. 


1123 


Other  authors  describe  the  artery  as  entering  the  corpuscle  at  the  pole  opposite  to 
the  nerve-fibre. 

Herbst  has  described  a  somewhat  similar  "nerve-ending"'  to  the  Pacinian 
corpuscle,  as  being  found  in  the  mucous  membrane  of  the  tongue  of  the  duck  and 
in  some  other  situations.  It  differs,  however,  from  the  Pacinian  corpuscles,  in 
being  smaller,  its  capsules  thinner  and  more  closely  approximated,  and  especially 
in  the  fact  that  the  axis-cylinder  in  the  central  clear  space  is  coated  with  a  con- 
tinuous row  of  nuclei.     These  bodies  are  known  as  the  corpuscles  of  Herbst. 


-^■■Nerve-fibres. 


Organ  of  Golgi,  showing  Tendon  bundles, 

ramification  of  nerve-fibrils. 
Muscular  fibres. 

Fig.  661.— Organ  of  Golgi  (neuro-tendinous  spindle)  from  the  human  tendon  AchLlis.    (After  Ciaccio.) 

Neuro -tendinous  spindles. — The  nerves  supplying  tendons  have  a  special  modifi- 
cation of  the  terminal  fibres,  especially  numerous  at  the  point  where  the  tendon  is 
becoming  muscular.  The  tendon  bundles  become  enlarged,  and  the  nerve-fibres — 
one,  two,  or  more  in  number — penetrate  between  the  fasciculi  of  the  tendon  and 
spread  out  between  the  fibres  to  end  in  irregular  discs  or  varicosities.  A  spindle- 
shaped  body  is  thus  formed,  composed  of  tendon  bundles  and  nerve-fibres,  which 
is  known  as  the  organ  of  Golgi  (Fig.  661). 


Dendritic  branchings 


Spirals. , 
Fig.  662.—  Middle  third  of  a  terminal  plaque  in  the  muscle  spindle  of  an  adult  cat.    (After  Ruffini.) 

Neuro-muscular  spindles. — In  the  majority  of  voluntary  muscles  there  have 
been  found  special  end-organs  consisting  of  a  small  bundle  of  peculiar  muscular 
fibres  (intrafusal  fibres),  embryonic  in  type,  invented  by  a  capsule  within  which 


1124 


GENERAL    ANATOMY   OB    HISTOLOGY. 


nerve-fibres,  experimentally  shown  to  be  sensory  in  origin,  terminate.  These 
neuro-muscular  spindles  vary  in  length  from  -^  to  ^  of  an  inch  and  have  a  distinctly 
fusiform  appearance.  The  large  medullated  nerve-fibres  passing  to  the  end-organ 
are  from  one  to  three  or  four  in  number ;  entering  the  fibrous  capsule  they  divide 
several  times,  and,  losing  their  medulla,  ultimately  end  in  naked  axis-cylinders 
encircling  the  intrafusal  fibres  by  flattened  expansions,  or  irregular  ovoid  or  rounded 
discs  (Fig.  662).  Neuro-muscular  spindles  have  not  yet  been  demonstrated  in  the 
tongue  or  eye  muscles. 

In  the  organs  of  special  sense  the  nerves  appear  to  terminate  in  cells  which 
belong  to  the  epithelial  class,  and  have  received  the  name  of  sensory  or  nerve- 
epithelium  cells.  This  is  not,  however,  the  real  state  of  the  case;  the  nerve-fibre 
is  in  reality  a  process  from  the  epithelial  cell,  and  terminates  by  branching  around 
a  ganglion-cell.  The  stimulus  carried  by  it  is  continued  onward  by  an  axis- 
cylinder,  derived  from  the  ganglion,  to  the  brain.  These  nerve-epithelium  cells 
must  therefore  be  regarded  as  modified  forms  of  nerve-cells.  They  will  be 
more  particularly  described  in  the  sequel,  in  connection  with  the  description  of  the 
organs  of  special  sense. 


I     '  "     '  '       '   Mil, 


o_    raijsw :-'""< 


',;■.!-;:: 


|lSr'ffl'''"'"''""'i',"'"''"7::;:,;r;ii:"i-i;' 

a 

Fig.  6^3. —Muscular  fibres,  of  Lacerta  wridtis  with  the  terminations  of  nerves,  a.  Seen  in  profile,  p.p.  The  nerve 
end-plates,  s.s.  The  base  of  the  plate,  consisting  of  a  granular  mass  with  nuclei.  6.  The  same  as  seen  in  look- 
ing at  a  perfectly  fresh  fibre,  the  nervous  ends  being  probably  still  excitable.  (The  forms  of  the  variously- 
divided  plate  can  hardly  be  represent  'd  in  a  woodcut  by  sufficiently  delicate  and  pale  contours  to  reproduce 
correctly  what  is  seen  in  nature.)    c.  The  same  as  seen  two  hours  after  death  from  poisoning  by  curare. 

Motor  nerves  are  to  be  traced  either  into  unstriped  or  striped  muscular  fibres. 
In  the  unstriped  or  involuntary  muscles  the  nerves  are  derived  from  the  sympa- 
thetic, and  are  composed  mainly  of  the  non-medullated  fibres.  Near  their  termi- 
nation they  divide  into  a  number  of  branches,  which  communicate  and  form  an 
intimate  plexus.  At  the  junction  of  the  branches  small  triangular  nuclear  bodies 
(ganglion-cells)  are  situated.  From  these  plexuses  minute  branches  are  given  off, 
which  divide  and  break  up  into  the  ultimate  fibrillas  of  which  the  nerve  is  com- 
posed. These  fibrillse  course  between  the  involuntary  muscle-cells,  and,  according 
to  Elischer,  terminate  on  the  surface  of  the  cell,  opposite  the  nucleus,  in  a  minute 
swelling.  Arnold  and  Frankenhauser  believed  that  these  ultimate  fibriUse  pene- 
trated the  muscular  cell  and  ended  in  the  nucleus.  More  recent  observation, 
however,  has  tended  to  disprove  this. 

In  the  striped  or  voluntary  muscle,  the  nerves  supplying  the  muscular  fibres 
are  derived  from  the  cerebro-spinal  nerves,  jind  are  composed  mainly  of  medullated 
fibres.  The  nerve,  after  entering  the  sheath  of  the  muscle,  breaks  up  into  fibres, 
or  bundles  of  fibres,  which  form  plexuses,  and  gradually  divide  until,  as  a  rule, 
a  single  nerve-fibre  enters  a  single  muscular  fibre.  Sometimes,  however,  if 
the  muscular  fibre  is  long,  more  than  one  nerve-fibre  enters  it.  Within  the 
muscular  fibre  the  nerve  terminates  in  a  special  expansion,  called  by  Kuhne,  who 
first  accurately  described  them,  motorial  end-plates  (Fig.  663). 1     The  nerve-fibre, 

1  They  had,  however,  previously  been  noticed,  though  not  accurately  described,  by  Doyere,  who 
named  them  "nerve-hillocks." 


THE   NERVOUS    TISSUE. 


1125 


on  approaching  the  muscular  fibre,  suddenly  loses  its  white  matter  of  Schwann, 
which  abruptly  terminates ;  the  neurilemma  becomes  continuous  with  the  sarco- 
lemma  of  the  muscle;  and  only  the  axis-cylinder  enters  the  muscular  fibre,  where 
it  immediately  spreads  out,  ramifying  like  the  roots  of  a  tree,  immediately  beneath 
the  sarcolemma,  and  is  imbedded  in  a  layer  of  granular  matter,  containing  a 
number  of  clear,  oblong  nuclei,  the  whole  constituting  an  end-plate  from  which 
the  contractile  wave  of  the  muscular  fibre  is  said  to  start. 

.  The  Ganglia  may  be  regarded  as  separate  small  aggregations  of  nerve-cells, 
connected  with  each  other,  with  the  cerebro-spinal  axis,  and  with  the  nerves  in 
various  situations.  They  are  found  on  the  posterior  root  of  each  of  the  spinal 
nerves ;  on  the  posterior  or  sensory  root  of  the  fifth  cranial  nerve ;  on  the  facial 
and  auditory  nerves ;  and  on  the  glosso-pharyngeal  and  pneumogastric  nerves. 
They  are  also  found  in  a  connected  series 
along  each  side  of  the  vertebral  column, 
forming  the  trunk  of  the  sympathetic ;  and 
on  the  branches  of  that  nerve,  generally 
in  the  plexuses  or  at  the  point  of  junction 
of  two  or  more  nerves  with  each  other  or 
with  branches  of  the  cerebro-spinal  sys- 
tem. On  section  they  are  seen  to  consist 
of  a  reddish-gray  substance,  traversed  by 
numerous  white  nerve-fibres  ;  they  vary 
considerably  in  form  and  size  ;  the  largest 
are  found  in  the  cavity  of  the  abdomen  ; 
the  smallest,  not  visible  to  the  naked  eye, 
exist  in  considerable  numbers  upon  the 
nerves  distributed  to  the  different  viscera. 
The  ganglia  are  invested  by  a  smooth 
and  firm,  closely  adhering  membranous 
envelope,  consisting  of  dense  areolar 
tissue ;  this  sheath  is  continuous  with 
the  perineurium  of  the  nerves,  and  sends 
numerous  processes  into  the  interior  of 
the  ganglion,  which  support  the  blood- 
vessels supplying  its  substance. 

In  structure  all  ganglia  are  essen- 
tially similar  (Fig.  664),  consisting  of 
the  same  structural  elements  as  the  other 
nervous    centres,   viz.,    a    collection    of 

nerve-cells  and  nerve-fibres.  Each  nerve-cell  has  a  nucleated  sheath,  which  is 
continuous  with  the  sheath  of  the  nerve-fibre  with  which  the  cell  is  connected. 
The  nerve-cells  in  the  ganglia  of  the  spinal  nerves  are  pyriform  in  shape,  and 
have  only  one  process,  the  axis-cylinder  or  axon.  A  short  distance  from  the  cell, 
and  while  still  within  the  ganglion,  this  process  divides  in  a  T-shaped  manner,  one 
limb  of  the  cross-bar  passing  centrally  and  forming  the  central  portion  of  a  sen- 
sory nerve-fibre ;  the  other  limb  passing  peripherally  to  form  the  axis-cylinder 
process  of  the  peripheral  nerve-fibre.  In  the  sympathetic  ganglia  the  nerve-cells 
are  multipolar  and  have  one  axis-cylinder  process  or  axon  and  several  protoplasmic 
processes  or  dendrons.  The  former  of  these  emerges  from  the  ganglion  as  a  non- 
medullated  nerve-fibre.  Similar  cells  are  found  in  the  ganglia  connected  with  the 
fifth  cranial  nerve,  and  these  ganglia  are  therefore  regarded  by  some  as  the  cranial 
portions  of  the  sympathetic  system.  The  nerve-cells  are  disposed  in  the  ganglia 
in  groups  of  varying  size,  and  these  groups  are  separated  from  each  other  by 
bundles  of  nerve-fibres,  some  of  which  traverse  the  ganglia  without  being  con- 
nected with  the  cells. 


Fig.  6G4.— Section  through  a  microscopic  ganglion. 
Magnified  300 diameters.  (Klein and  Noble  Smith.)  e. 
Capsule  of  the  ganglion,  n.  Nerve-fibres  passing  out 
of  the  ganglion.  The  nerve-fibres  which  entered  the 
ganglion  are  not  represented.  The  nerve-fibres  are 
ordinary  medullated  fibres,  but  the  details  of  their 
structure  are  not  shown,  owing  to  the  low  magnifying 
power.  The  ganglion-cells  are  invested  by  special 
capsules,  lined  by  a  few  nuclei,  which  are  here  repre- 
sented as  if  contained  in  the  capsule. 


1126 


GENERAL    ANATOMY   OB    HISTOLOGY. 


THE   VASCULAR   SYSTEM. 

The  Vascular  System,  exclusive  of  its  central  organ,  the  heart,  is  divided  into 
four  classes  of  vessels :  the  arteries,  capillaries,  veins,  and  lymphatics ;  the  minute 
structure  of  these  vessels  will  be  briefly  described  here,  the  reader  being  referred 
to  the  body  of  the  work  for  the  details  of  their  ordinary  anatomy. 

Structure  of  Arteries  (Fig.  665). — The  arteries  are  composed  of  three  coats : 
internal  or  endothelial  coat  {tunica  intima   of  Kolliker) ;    middle  muscular  coat 

{tunica  media) ;  and  external  connective- 
tissue  coat  {tunica  adventitia). 

The  two  inner  coats  together  are  very 
easily  separated  from  the  external,  as  by 
the  ordinary  operation  of  tying  a  ligature 
on  an  artery.  If  a  fine  string  be  tied  for- 
cibly upon  an  artery  and  then  taken  off, 
the  external  coat  will  be  found  undivided, 
but  the  internal  coats  are  divided  in  the 
track  of  the  ligature  and  can  easily  be  fur- 
ther dissected  from  the  outer  coat.  The 
inner  coat  can  be  separated  from  the  middle 
by  a  little  maceration,  or  it  may  be  stripped 
off  in  small  pieces ;  but,  on  account  of  its 
friability,  it  cannot  be  separated  as  a  com- 
plete membrane.  It  is  a  fine,  transparent, 
colorless  structure  which  is  highly  elastic, 
and  is  commonly  corrugated  into  longitudi- 
nal wrinkles.      The  inner  coat  consists  of — 

1.  A  layer  of  pavement-endothelium,  the  cells 
of  which  are  polygonal,  oval,  or  fusiform, 
and  have  very  distinct  round  or  oval  nuclei. 
This  endothelium  is  brought  into  view  most 
distinctly  by  staining  with  nitrate  of  silver. 

2.  A  subendothelial  layer,  consisting  of 
delicate  connective  tissue  with  branched 
cells  lying  in  the  interspaces  of  the  tissue. 
In  arteries  of  less  than  a  line  in  diameter 
the  subendothelial  layer  consists  of  a  single 
stratum  of  stellate  cells,  and  the  connective 
tissue  is  only  largely  developed  in  vessels 
of  a  considerable  size.  8.  An  elastic  or 
fenestrated  layer,  which  consists  of  a  mem- 
brane containing  a  network  of  elastic  fibres,  having  principally  a  longitudinal 
direction  and  in  which,  under  the  microscope,  small,  elongated  apertures  or  per- 
forations may  be  seen,  giving  it  a  fenestrated  appearance.  It  was  therefore 
called  by  Henle  the  fenestrated  membrane.  This  membrane  forms  the. chief 
thickness  of  the  inner  coat,  and  can  be  separated  into  several  layers,  some  of 
which  present  the  appearance  of  a  network  of  longitudinal  elastic  fibres,  and 
others  present  a  more  membranous  character,  marked  by  pale  lines  having  a 
longitudinal  direction.  The  fenestrated  membrane  in  microscopic  arteries  is  a 
very  thin  layer,  but  in  the  larger  arteries,  and  especially  in  the  aorta,  it  has  a 
very  considerable  thickness. 

The  middle  coat  {tunica  media)  is  distinguished  from  the  inner  by  its  color  and 
by  the  transverse  arrangement  of  its  fibres,  in  contradistinction  to  the  longitudinal 
direction  of  those  of  the  inner  coat.  In  the  smaller  arteries  it  consists  principally 
of  muscular  tissue,  being  made  up  of  plain  muscle-fibres  in  fine  bundles,  arranged 
in  lamellae  and  disposed  circularly  around  the  vessel.  These  lamellae  vary  in 
number  according  to  the  size  of  the  vessel ;  the  very  small  arteries  having  only  a 


Fig.  665. — Transverse  section  through  a  small 
artery  and  vein  of  the  mucous  membrane  of  the 
epiglottis  of  a  child.  Magnified  about  350  diame- 
ters. (Klein  and  Noble  Smith.)  a.  Artery,  show- 
ing the  nucleated  endothelium,  e, which  lines  it: 
the  vessel  being  contracted,  the  endothelial  cells 
appear  very  thick.  Underneath  the  endothelium 
is  the  wavy  elastic  intima.  The  chief  part  of  the 
wall  of  the  vessel  is  occupied  by  the  circular  mus- 
cle-coat m ;  the  staff-shaped  nuclei  of  the  muscle- 
cells  are  well  seen.  Outside  this  is  a,  part  of  the 
adventitia.  This  is  composed  of  bundles  of  con- 
nective-tissue fibres,  shown  in  section,  with  the 
nuclei  of  the  connective-tissue  corpuscles. 
The  adventitia  gradually  merges  into  the  sur- 
rounding connective  tissue,  v.  Vein  showing 
a  thin  endothelial  membrane,  e,  raised  acciden- 
tally from  the  intima,  which  on  account  of  its 
delicacy  is  seen  as  a  mere  line  on  the  media  m. 
This  latter  is  composed  of  a  few  circular  un- 
striped  muscle-cells,  a.  The  adventitia,  similar 
in  structure  to  that  of  an  artery. 


THE    VASCULAR   SYSTEM. 


U2\ 


single  layer,  and  those  not  larger  than  one-tenth  of  a  line  in  diameter  three  or  four 
layers.     It  is  to  this  coat  that  the  great  thickness  of  the  walls  of  the  artery  is 


0 

/  "  8 


$ i 


Fig.  666. — Longitudinal  section  of  artery  and  vein.  a.  an  artery  from  the  mesentery  of  a  child,  .062"',  and  6, 
vein  .067'"  in  diameter,  treated  with  acetic  acid  and  magnified  350  times,  a.  Tunica  adventitia.  with  elongated 
nuclei.  0.  Nuclei  of  the  contractile  fibre-cells  of  the  tunica  media,  seen  partly  from  the  surface,  partly  appar- 
ent in  transverse  section,    y.  Nuclei  of  the  endothelial  cells.    5.  Elastic  longitudinal  fibrous  coat. 

mainly  due  (Fig.  665,  A,  m).     In  the  larger  vessels,   as  the  iliac,  femoral,  and 
carotid,  elastic  fibres  unite  to  form  lamellae,  which  alternate  with  the  layers  of 

Endothelial    and    sub- 
endothelial  layer  of 
"     inner  coat. 
'Elastic  layer. 

Innermost  layers  of 
middle  coat. 


_. Outermost  layers  of 

V*fL«  ~    ,.--w"^-i         middle  coat. 


s&~'-*,.'?&yS~i.:::-~- '-■?/■  -•;  ;-*-";■;--.  ---.'  ;•_-••;••-  [__  Innermost  part 
'■'-• '•'£'■ •'»""•"  --"„"  ■■'■'.".'.".. s:':':.  .. '';-'."•'-;"»  v"""'  :*   j  outer  coat. 


<S£,"/*  ^^^S^-^E^o^' — -^::r^fr$~-i-:'  V- .Outer  part  of  outer 

jgjpy"" 
Fig.  667.— Section  of  a  medium-sized  artery.    (After  Griinstein.) 

muscular  fibre  and  are  united  by  elastic  fibres  which  pass  between  the  muscular 
bundles,  and  are  connected  with  the  fenestrated  membrane  of  the  inner  coat  (Fig. 
667).     In  the  largest  arteries,  as  the  aorta  and  innominate,  the  amount  of  elastic 


1128  GENERAL    ANATOMY    OR    HISTOLOGY. 

tissue  is  very  considerable.  In  these  vessels  also  bundles  of  white  connective 
tissue  have  been  found  in  small  quantities  in  the  middle  coat.  The  muscle-fibre 
cells  of  which  the  middle  coat  is  made  up  are  about  -^^  of  an  inch  in  length,  and 
contain  well-marked,  rod-shaped  nuclei,  which  are  often  slightly  curved. 

The  external  coat  {tunica  adventitial)  consists  mainly  of  fine  and  closely  felted 
bundles  of  white  connective  tissue,  but  also  contains  elastic  fibres  in  all  but  the 
smallest  arteries.  The  elastic  tissue  is  much  more  abundant  next  the  tunica  media, 
and  is  sometimes  described  as  forming  here,  between  the  adventitia  and  media,  a 
special  layer,  the  tunica  elastica  externa  of  Henle.  This  layer  is  most  marked  in 
arteries  oi  medium  size.  In  the  largest  vessels  the  external  coat  is  relativelv 
thin ;  but  in  small  arteries  it  is  of  greater  proportionate  thickness.  In  the  smaller 
arteries  it  consists  of  a  single  layer  of  white  connective  tissue  and  elastic  fibres; 
while  in  the  smallest  arteries,  just  above  the  capillaries,  the  elastic  fibres  are  want- 
ing, a.nd  the  connective  tissue,  of  which  the  coat  is  composed,  becomes  more  homo- 
geneous the  nearer  it  approaches  the  capillaries,  and  is  gradually  reduced  to  a  thin 
membranous  envelope  which  finally  disappears. 

Some  arteries  have  extremely  thin  coats  in  proportion  to  their  size ;  this  is 
especially  the  case  in  those  situated  in  the  cavity  of  the  cranium  and  spinal 
canal,  the  difference  depending  on  the  greater  thinness  of  the  external  and 
middle  coats. 

The  arteries,  in  their  distribution  throughout  the  body,  are  included  in  a  thin 
fibro-areolar  investment,  which  forms  what  is  called  their  sheath.  In  the  limbs 
this  is  usually  formed  by  a  prolongation  of  the  deep  fascia ;  in  the  upper  part 
of  the  thigh  it  consists  of  a  continuation  downward  of  the  transversalis  and  iliac 
fasciae  of  the  abdomen ;  in  the  neck,  of  a  prolongation  of  the  deep  cervical  fascia. 
The  included  vessel  is  loosely  connected  with  its  sheath  by  a  delicate  areolar  tissue ; 
and  the  sheath  usually  encloses  the  accompanying  veins,  and  sometimes  a  nerve. 
Some  arteries,  as  those  in  the  cranium,   are  not  included  in  sheaths. 

All  the  larger  arteries  are  supplied  with  blood-vessels  like  the  other  organs  of 
the  body;  they  are  called  the  vasa  vasorum.  These  nutrient  vessels  arise  from  a 
branch  of  the  arterv  or  from  a  neighboring  vessel,  at  some  considerable  distance 
from  the  point  at  which  they  are  distributed ;  they  ramify  in  the  loose  areolar 
tissue  connecting  the  artery  with  its  sheath,  and  are  distributed  to  the  external 
coat,  but  do  not,  in  man,  penetrate  the  other  coats ;  though  in  some  of  the  larger 
mammals  some  few  vessels  have  been  traced  into  the  middle  coat.  Minute  veins 
serve  to  return  the  blood  from  these  vessels ;  they  empty  themselves  into  the  vein 
or  veins  accompanying  the  artery.  Lymphatic  vessels  and  lymphatic  spaces  are 
also  present  in  the  outer  coat. 

Arteries  are  also  supplied  with  nerves,  which  are  derived  chiefly  from  the  sym- 
pathetic, but  partly  from  the  cerebro-spinal  system.  They  form  intricate  plexuses 
upon  the  surfaces  of  the  larger  trunks,  and  run  along  the  smaller  arteries  as  single 
filaments  or  bundles  of  filaments,  which  twist  around  the  vessel  and  unite  with 
each  other  in  a  plexiform  manner.  The  branches  derived  from  these  plexuses 
penetrate  the  external  coat,  and  are  principally  distributed  to  the  muscular  tissue 
of  the  middle  coat,  and  thus  regulate,  by  causing  the  contraction  and  relaxation 
of  this  tissue,  the  amount  of  blood  sent  to  any  part. 

The  Capillaries. — The  smaller  arterial  branches  (excepting  those  of  the  cavern- 
ous structure  of  the  sexual  organs,  of  the  spleen,  and  in  the  uterine  placenta) 
terminate  in  a  network  of  vessels  which  pervade  nearly  every  tissue  of  the  body. 
These  vessels,  from  their  minute  size,  are  termed  capillaries  (capillus,  a  hair). 
They  are  interposed  between  the  smallest  branches  of  the  arteries  and  the  com- 
mencing veins,  constituting  a  network,  the  branches  of  which  maintain  the  same 
diameter  throughout;  the  meshes  of  the  network  being  more  uniform  in  shape 
and  size  than  those  formed  by  the  anastomoses  of  the  small  arteries  and 
veins. 

The  diameter  of  the  capillaries  varies  in  the  different  tissues  of  the  body,  their 
usual  size  being  about  -3^00"  °f  an  incn-     The  smallest  are  those  of  the  brain  and 


THE    VASCULAR    SYSTEM. 


1129 


the  mucous  membranes  of  the  intestines;  and  the  largest  those  of  the  skin  and 
the  marrow  of  bone,  where  they  are  stated  to  be  as  large  as  y^oT  of  an  inch 

The  form  of  the  capillary  net  varies  in  the  different  tissues,  the  meshes  being 
generally  rounded  or  elongated.  The  rounded  form  of  mesh  is  most  common,  and 
prevails  where  there  is  a  dense  network,  as  in  the  lungs,  in  most  glands  and 
mucous  membranes,  and  in  the  cutis ;  here  the  meshes  are  more  or  less  angular, 
sometimes  nearly  quadrangular  or  polygonal*;  or  more  often  irregular  and  not  of 
an  absolutely  circular  outline. 

Elongated  meshes  are  observed  in  the  muscles  and  nerves,  the  meshes  being 
usually  of  a  parallelogram  form,  the  long  axis  of  the  mesh  running  parallel  with 
the  long  axis  of  the  nerve  and  fibre.  Sometimes  the  capillaries  have  a  looped 
arrangement;  a  single  vessel  projecting  from  the  common  network  and  returning 
after  forming  one  or  more  loops,  as  in  the  papillae  of  the  tongue  and  skin.  The 
number  of  the  capillaries,  and  the  size  of  the  meshes,  determine  the  degree  of 
vascularity  of  a  part.  The  closest  network  and  the  smallest  interspaces  are  found 
in  the  lungs  and  in  the  choroid  coat  of  the  eye.     In  these  situations  the  inter- 


Fig.  668- Capillaries  from  the 
mesentery  of  a  guinea-pig  after  treat- 
ment with  solution  of  nitrate  of  sil- 
ver,   a.  Cells,   b.  Their  nuclei. 


Fi«.  669. — Finest  vessels  on  the  arterial  side.  From  the  human 
brain.  Magnified  300  times.  1.  Smallest  artery.  2.  Transition 
vessel.  3.  Coarser  capillaries.  4.  Finer  capillaries,  a.  Structure- 
less membrane  still  with  some  nuclei,  representative  of  the 
tunica  adventitia.  b.  Nuclei  of  the  muscular  fibre-cells,  c. 
nuclei  within  the  small  artery,  perhaps  appertaining  to  an 
endothelium,    d.  Nuclei  in  the  transition  vessels. 


spaces  are  smaller  than  the  capillary  vessels  themselves.  In  the  kidney,  in  the 
conjunctiva,  and  in  the  cutis  the  interspaces  are  from  three  to  four  times  as  large 
as  the  capillaries  which  form  them  ;  and  in  the  brain  from  eight  to  ten  times  as 
large  as  the  capillaries  in  their  long  diameter,  and  from  four  to  six  times  as  large 
in  their  transverse  diameter.  In  the  adventitia  of  arteries  the  width  of  the  meshes 
is  ten  times  that  of  the  capillary  vessels.  As  a  general  rule,  the  more  active  the 
function  of  the  organ,  the  closer  is  its  capillary  net  and  the  larger  its  supply  of 
blood;  the  meshes  of  the  network  being  very  narrow  in  all  growing  parts,  in  the 
glands,  and  in  the  mucous  membranes  ;  wider  in  bones  and  ligaments,  which  are 
comparatively  inactive ;  and  nearly  altogether  absent  in  tendons,  in  which  very 
little  organic  change  occurs  after  their  formation. 

Structure. — The  walls  of  the  capillaries  consist  of  a  fine,  transparent,  endothelial 


1130 


GENERAL    ANATOMY    OB    HISTOLOGY. 


laver,  composed  of  cells  joined  edge  to  edge  by  an  interstitial  cement-substance,, 
and  continuous  with  the  endothelial  cells  which  line  the  arteries  and  veins.  When 
stained  with  nitrate  of  silver  the  edges  which  bound  the  epithelial  cells  are  brought 
into  view  (Fig.  668).  These  cells  are  of  large  size  and  of  an  irregular  polygonal  or 
lanceolate  shape,  each  containing  an  oval  nucleus  which  may  be  brought  into  view 
by  carmine  or  hematoxylin.  Between  their  edges,  at  various  points  of  their 
meeting,  roundish  dark  spots  are  sometimes  seen,  which  have  been  described  as 
stomata,  though  they  are  closed  by  intercellular  substance.  They  have  been 
believed  to  be  the  situation  through  which  the  white  corpuscles  of  the  blood,  when 
migrating  from  the  blood-vessels,  emerge ;  but  this  view,  though  probable,  is  not 
universally  accepted. 

Kolossow,  a  Russian  observer,  describes  these  cells  as  having  a  rather  more 
complex  structure.  He  states  that  they  consist  of  two  parts  :  of  hyaline  ground- 
plates,  and  of  a  protoplasmic  granular  part,  in  which  is  imbedded  the  nucleus,  on 
the  outside  of  the  ground-plates.  The  hyaline  internal  coat  of  the  capillaries 
does  not  form  a  complete  membrane,  but  consists  of  "plates"  which  are  inelastic, 
and,  though  in  contact  with  each  other,  are  not  continuous;  when,  therefore,  the 
capillaries  are  subjected  to  intra-vascular  pressure,  the  plates  become  separated 
from  each  other ;  the  protoplasmic  portions  of  the  cells,  on  the  other  hand,  are 
united  together. 

In  many  situations  a  delicate  sheath  or  envelope  of  branched  nucleated  con- 
nective-tissue cells  is  found  around  the  simple  capillary  tube,  particularly  in  the 
larger  ones ;  and  in  other  places,  especially  in  the  glands,  the  capillaries  are 
invested  with  retiform   connective  tissue. 

In  the  largest  capillaries  (which  ought,  perhaps,  to  be  described  rather  as  the 
smallest  arteries  or  pre-capillaries)  there  is,  outside  the  epithelial  layer,  a  muscular 
layer,  consisting  of  contractile  fibre-cells,  arranged  transversely,  as  in  the  tunica 
media  of  the  larger  arteries  (Fig.  669). 

The  veins,  like  the  arteries,  are  composed  of  three  coats — internal,  middle,  and 
external ;  and  these  coats  are,  with  the  necessary  modifications,  analogous  to  the 
coats  of  the  arteries  ;  the  internal  being  the  endothelial,  the  middle  the  muscular, 
and  the  external  the  connective  or  areolar  (Fig.  670).     The  main  difference  be- 

Endothelial  and 
/  snbendothelial 

layers. 
"Elastic  layer. 

—Middle  coat. 


■Outer  coat. 
Fig.  670.— Transverse  section  of  part  of  the  wall  of  one  of  the  posterior  tibial  veins.    (After  Schiifer). 

tween  the  veins  and  the  arteries  is  the  comparative  weakness  of  the  middle  coat  of 
the  former,  and  to  this  is  due  the  fact  that  the  veins  do  not  stand  open  when 
divided,  as  the  arteries  do,  and  that  they  are  passive  rather  than  active  organs  of 
the  circulation. 

In  the  veins  immediately  above  the  capillaries  the  three  coats  are  hardly  to  be 
distinguished.  The  endothelium  is  supported  on  an  outer  membrane  separable  into 
two  layers,  the  outer  of  which  is  the  thicker,  and  consists  of  a  delicate,  nucleated 
membrane  (adventitia),  while  the  inner  is  composed  of  a  network  of  longitudinal 
elastic  fibres  (media).  In  the  veins  next  above  these  in  size  (one-fifth  of  a  line, 
according  to  Kolliker)  a  muscular  layer  and  a  layer  of  circular  fibres  can  be  traced, 
forming  the  middle  coat,  while  the  elastic  and  connective  elements  of  the  outer 
coat  become  more  distinctly  perceptible.  In  the  middle-sized  veins  the  typical 
structure  of  these  vessels  becomes  clear.     The  endothelium  is  of  the  same  character 


THE    VASCULAR    SYSTEM.  1131 

as  in  the  arteries,  but  its  cells  are  more  oval,  less  fusiform.  It  is  supported  by  a 
connective-tissue  layer,  consisting  of  a  delicate  network  of  branched  cells,  and 
external  to  this  is  a  layer  of  longitudinal  elastic  fibres,  but  seldom  any  appearance 
of  a  fenestrated  membrane.  This  constitutes  the  internal  coat.  The  middle  coat  is 
composed  of  a  thick  layer  of  connective  tissue  with  elastic  fibres,  intermixed,  in  some 
veins,  with  a  transverse  layer  of  muscular  fibres.  The  white  fibrous  element  is 
in  considerable  excess,  and  the  elastic  fibres  are  in  much  smaller  proportion  in  the 
veins  than  in  the  arteries.  The  outer  coat  consists  of  areolar  tissue,  as  in  the 
arteries,  with  longitudinal  elastic  fibres.  In  the  largest  veins  the  outer  coat  is  from 
two  to  five  times  thicker  than  the  middle  coat,  and  contains  a  large  number  of 
longitudinal  muscular  fibres.  This  is  most  distinct  in  the  inferior  vena  cava,  and 
at  the  termination  of  this  vein  in  the  heart,  in  the  trunks  of  the  hepatic  veins,  in 
all  the  large  trunks  of  the  vena  portae,  in  the  splenic,  superior  mesenteric,  external 
iliac,  renal,  and  azygos  veins.  In  the  renal  and  portal  veins  it  extends  through 
the  whole  thickness  of  the  outer  coat,  but  in  the  other  veins  mentioned  a  layer  of 
connective  and  elastic  tissue  is  found  external  to  the  muscular  fibres.  All  the  large 
veins  which  open  into  the  heart  are  covered  for  a  short  distance  with  a  layer  of 
striped  muscular  tissue  continued  on  to  them  from  the  heart.  Muscular  tissue  is 
wanting  in  the  veins — (1)  of  the  maternal  part  of  the  placenta ;  (2)  in  the  venous 
sinuses  of  the  dura  mater  and  the  veins  of  the  pia  mater  of  the  brain  and  spinal 
cord ;  (3)  in  the  veins  of  the  retina ;  (4)  in  the  veins  of  the  cancellous  tissue  of 
bones ;  (5)  in  the  venous  spaces  of  the  corpora  cavernosa.  The  veins  of  the  above- 
mentioned  parts  consist  of  an  internal  endothelial  lining  supported  on  one  or  more 
layers  of  areolar  tissue. 

Most  veins  are  provided  with  valves,  which  serve  to  prevent  the  reflux  of  the 
blood.  They  are  formed  by  a  reduplication  of  the  inner  coat,  strengthened  by 
connective  tissue  and  elastic  fibres,  and  are  covered  on  both  surfaces  with  endo- 
thelium, the  arrangement  of  which  differs  on  the  two  surfaces.  On  the  surface 
of  the  valve  next  the  wall  of  the  vein  the  cells  are  arranged  transversely ;  whilst 
on  the  other  surface,  over  which  the  current  of  blood  flows,  the  cells  are  arranged 
vertically  in  the  direction  of  the  current.  The  valves  are  semilunar.  They  are 
attached  by  their  convex  edge  to  the  wall  of  the  vein  ;  the  concave  margin  is  free, 
directed  in  the  course  of  the  venous  current,  and  lies  in  close  apposition  with  the 
wall  of  the  vein  as  long  as  the  current  of  blood  takes  its  natural  course ;  if,  how- 
ever, any  regurgitation  takes  place,  the  valves  become  distended,  their  opposed 
edges  are  brought  into  contact,  and  the  current  is  interrupted.  Most  commonly 
two  such  valves  are  found  placed  opposite  one  another,  more  especially  in  the 
smaller  veins  or  in  the  larger  trunks  at  the  point  where  they  are  joined  by  smaller 
branches ;  occasionally  there  are  three  and  sometimes  only  one.  The  wall  of  the 
vein  on  the  cardiac  side  of  the  point  of  attachment  of  each  segment  of  the  valve 
is  expanded  into  a  pouch  or  sinus,  which  gives  to  the  vessel,  when  injected  or  dis- 
tended with  blood,  a  knotted  appearance.  The  valves  are  very  numerous  in  the 
veins  of  the  extremities,  especially  of  the  lower  extremities,  these  vessels  having 
to  conduct  the  blood  against  the  force  of  gravity.  They  are  absent  in  the  very 
small  veins — i.  e.  those  less  than  -^  of  an  inch  in  diameter ;  also  in  the  venag 
cavse,  the  hepatic  veins,  portal  vein  and  most  of  its  branches,  the  renal,  uterine, 
and  ovarian  veins.  A  few  valves  are  found  in  the  spermatic  veins,  and  one  also 
at  their  point  of  junction  with  the  renal  vein  and  inferior  vena  cava,  respectively. 
The  cerebral  and  spinal  veins,  the  veins  of  the  cancellated  tissue  of  bone,  the 
pulmonary  veins,  and  the  umbilical  vein,  and  its  branches,  are  also  destitute  of 
valves.  They  are  occasionally  found,  few  in  number,  in  the  venae  azygos  and 
intercostal   veins. 

The  veins  are  supplied  with  nutrient  vessels,  vasa  vasorum,  like  the  arteries. 
Nerves  also  are  distributed  to  them  in  the  same  manner  as  to  the  arteries,  but  in 
much  less  abundance. 

The  lymphatic  vessels,  including  in  this  term  the  lacteal  vessels,  which  are 
identical  in  structure  with  them,  are  composed  of  three  coats.      The  internal  is  an 


1132 


GENERAL    ANATOMY    OB    HISTOLOGY. 


endothelial  and  elastic  coat.  It  is  thin,  transparent,  slightly  elastic,  and  ruptures 
sooner  than  the  other  coats.  It  is  composed  of  a  layer  of  elongated  endothelial 
cells  with  serrated  margins,  by  which  the  adjacent 
cells  are  dovetailed  into  one  another.  These  are 
supported  on  a  single  layer  of  longitudinal  elastic 
fibres.  The  middle  coat  is  composed  of  smooth 
muscular  and  fine  elastic  fibres,  disposed  in  a  trans- 
verse direction.  The  external,  or  fibro-areolar,  coat 
consists  of  filaments  of  connective  tissue,  inter- 
mixed with  smooth  muscular  fibres,  longitudinally 
or  obliquely  disposed.  It  forms  a  protective  cover- 
ing to  the  other  coats,  and  serves  to  connect  the 
vessel  with  the  neighboring  structures.  The  above 
description  applies  only  to  the  larger  lymphatics ; 
in  the  smaller  vessels  there  is  no  muscular  or  elas- 
tic coat,  and  their  structure  consists  only  of  a  con- 
nective-tissue coat,  lined  by  endothelium.  The 
thoracic  duct  (Fig.  671)  is  a  somewhat  more  com- 
plex structure  than  the  other  lymphatics  ;  it  pre- 
sents a  distinct  subendothelial  layer  of  branched 
corpuscles,  similar  to  that  found    in   the   arteries, 


Fig.  672.— Stroma  of  serous  mem- 
branes. 1.  Endothelium  from  the  un- 
der surface  of  the  centrum  tendineum 
of  the  rabbit,  a.  Stomata.  2.  Endo- 
thelium of  the  mediastinum  of  the 
dog.  a.  Stomata.  3.  Section  through 
the  pleura  of  the  same  animal.  6. 
Free  orifices  of  short  lateral  passages 
of  the  lymph-canals.  (Copied  from 
Ludwig,  Schweigger-Seydel,  and  Dyb- 
kowsky.l 


a  b  c 


Fig.  671.— -Transverse  section  through  the  coats  of  the  thoracic 
•duct  of  man.  Magnified  30  times,  a.  Endothelium,  striated  lamelke, 
and  inner  elastic  coat.  &.  Longitudinal  connective  tissue  of  the 
middle  coat.  c.  Transverse  muscles  of  the  same.  d.  Tunica  adven- 
titia.  with  e,  the  longitudinal  muscular  fibres. 


and  in  the  middle  coat  is  a  layer  of  connective  tissue  with  its  fibres  arranged 
longitudinally.  The  lymphatics  are  supplied  by  nutrient  vessels,  which  are  dis- 
tributed to  their  outer  and  middle  coats ;  and  here  also  have  been  traced  many 
non-medullated  nerve-fibres  in  the  form  of  a  fine  plexus  of  fibrils. 

The  lymphatics  are  very  generally  provided  with  valves,  which  assist  materi- 
ally in  effecting  the  circulation  of  the  fluid  they  contain.  These  valves  are  formed 
of  a  thin  layer  of  fibrous  tissue,  lined  on  both  surfaces  by  endothelium,  which 
presents  the  same  arrangement  upon  the  two  surfaces  as  was  described  in  connec- 
tion with  the  valves  of  veins.  Their  form  is  semilunar;  they  are  attached  by 
their  convex  edge  to  the  sides  of  the  vessel,  the  concave  edge  being  free  and 
directed  along  the  course  of  the  contained  current.  Usually  two  such  valves,  of 
equal  size,  are  found  opposite  one  another ;  but  occasionally  exceptions  occur, 
especially  at  or  near  the  anastomoses  of  lymphatic  vessels.  Thus,  one  valve  may 
be  of  very  rudimentary  size  and  the  other  increased  in  proportion. 

The  valves  in  the  lymphatic  vessels  are  placed  at  much  shorter  intervals  than 
in  the  veins.  They  are  most  numerous  near  the  lymphatic  glands,  and  they  are 
found  more  frequently  in  the  lymphatics  of  the  neck  and  upper  extremity  than  in 
the  lower.  The  wall  of  the  lymphatics  immediately  above  the  point  of  attach- 
ment of  each  segment  of  a  valve  is  expanded  into  a  pouch  or  sinus,  which  gives 
to  these  vessels,  when  distended,  the  knotted  or  beaded  appearance  which  they 
present.  Valves  are  wanting  in  the  vessels  composing  the  plexiform  network  in 
which  the  lymphatics  usually  originate  on  the  surface  of  the  body. 

Origin  of  Lymphatics. — The  finest  visible  lymphatic  vessels  (lymphatic  capil- 
laries') form  a  plexiform  network  in  the  tissues  and  organs,  and  they  consist  of  a 
single  layer  of  endothelial  plates,  with  more  or  less  sinuous  margins.      These  ves- 


THE    VASCULAR    SYSTEM.  1133 

sels  commence  in  an  intercommunicating  system  of  clefts  or  spaces  -which  Lave  no 
complete  endothelial  lining  in  the  connective  tissue  of  the  different  organs.  They 
have  been  named  the  rootlets  of  the  lymphatics,  and  are  identical  with  the  spaces 
in  which  the  connective-tissue  corpuscles  are  contained.  This  then  is  properly 
regarded  as  one  method  of  their  commencement,  when  the  lymphatic  vessels  are 
apparently  continuous  with  spaces  in  the  connective  tissue,  and  Klein  has  described 
and  figured  a  direct  communication  between  these  spaces  and  the  lymphatic  vessel.1 
But  the  lymphatics  have  also  other  modes  of  origin,  for  the  intestinal  lacteals 
commence  by  closed  extremities,  though  some  observers  believe  that  the  closed 
extremity  is  continuous  with  a  minute  network  contained  in  the  substance  of  the 
villus,  through  which  the  lacteal  is  connected  with  the  endothelial  cells  covering  it. 
Again,  it  seems  now  to  be  conclusively  proved  that  the  serous  membranes  present 
stomata  or  openings  between  the  endothelial  cells  (Fig.  672)  by  which  there  is  an 
open  communication  Avith  the  lymphatic  system,  and  through  which  the  lymph  is 
thought  to  be  pumped  by  the  alternate  dilatation  and  contraction  of  the  serous 
surface,  due  to  the  movements  of  respiration  and  circulation,2  so  that  the  serous 
and  synovial  sacs  may  be  regarded,  in  a  certain  sense,  as  large  lymph-cavities  or 
sinuses.  Von  Recklinghausen  was  the  first  to  observe  the  passage  of  milk  and 
other  colored  fluids  through  these  stomata  on  the  peritoneal  surface  of  the 
central  tendon  of  the  diaphragm.  Again,  in  most  glandular  structures  the 
lymphatic  capillaries  have  a  lacunar  origin.  Here  they  begin  in  irregular  clefts  or 
spaces  in  the  tissue  of  the  part ;  occupying  the  penetrating  connective  tissue  and 
surrounding  the  lacunse  or  tubules  of  the  gland,  and  in  many  places  separating  the 
capillary  network  from  the  alveolus  or  tubule,  so  that  the  interchange  between  the 
blood  and  the  secreting  cells  of  the  part  must  be  carried  on  through  this  lymph- 
space  or  lacuna.  Closely  allied  to  this  is  the  mode  of  origin  of  lymphatics  in 
perivascular  and  perineural  spaces.  Sometimes  a  minute  artery  may  be  seen  to  be 
ensheathed  for  a  certain  distance  by  a  lymphatic  capillary  vessel,  Avhich  is 
often  many  times  wider  than  a  blood-capillary.  These  are  known  as  perivascular 
lymphatics. 

Terminations  of  Lymphatics. — The  lymphatics,  including  the  lacteals,  discharge 
their  contents  into  the  veins  at  two  points  ;  namely,  at  the  angles  of  junction 
of  the  subclavian  and  internal  jugular  veins :  on  the  left  side  by  means  of  the 
thoracic  duct,  and  on  the  right  side  by  the  right  lymphatic  duct.  (See  description 
of  lymphatics  on  page  623.) 

Lymphatic  glands  {conglobate  glands)  are  small  oval  or  bean-shaped  bodies, 
situated  in  the  course  of  lymphatic  and  lacteal  vessels,  so  that  the  lymph  and  chyle 
pass  through  them  on  their  way  to  the  blood.  They  generally  present  on  one 
side  a  slight  depression — the  hilum — through  which  the  blood-vessels  enter  and 
leave  the  interior.  The  efferent  lymphatic  vessel  also  emerges  from  the  gland  at 
this  spot,  while  the  afferent  vessels  enter  the  organ  at  different  parts  of  the 
periphery.  On  section  (Fig.  673),  a  lymphatic  gland  displays  two  different  struc- 
tures: an  external,  of  lighter  color — the  cortical;  and  an  internal,  darker — the 
medullary.  The  cortical  structure  does  not  form  a  complete  investment,  but  is 
deficient  at  the  hilum,  where  the  medullary  portion  reaches  the  surface  of  the 
gland ;  so  that  the  efferent  vessel  is  derived  directly  from  the  medullary  structure, 
while  the  afferent  vessels  empty  themselves  into  the  cortical  substance. 

Lymphatic  glands  consist  of  (1)  a  fibrous  envelope,  or  capsule,  from  which  a 
framework  of  processes  (trabecidw)  proceed  inward,  dividing  the  gland  into  open 
spaces  (alveoli)  freely  communicating  with  each  other;  (2)  a  quantity  of  lymphoid 
tissue  occupying  these  spaces  without  completely  filling  them  ;  (3)  a  free  supply 
of  blood-vessels,  which  are  supported  on  the  trabeculae  ;  and  (4)  the  afferent  and 
efferent  vessels.  Little  is  known  of  the  nerves,  though  Kolliker  describes  some 
fine  nervous  filaments  passing  into  the  hilum. 

1  Atlas  of  Histology,  pi.  viii.  fig.  xiv. 

2  The  resemblance  between  lymph  and  serum  led  Hewson  long  ago  to  regard  the  serous  cavities 
as  sacs  into  which  the  lymphatics  open.  Recent  microscopic  discoveries  confirm  this  opinion  in  a 
very  interesting  manner. 


1134 


GENERAL    ANATOMY    OB    HISTOLOGY. 


-Afferent  vessel 

.Trabeculse 


Lymph  path 


The  capsule  is  composed  of  a  layer  of  connective  tissue,  and  from  its  internal 
surface  are  given  oiF  a  number  of  membranous  septa  or  lamellae,  consisting,  in  man, 
of  connective  tissue,  with  a  small  admixture  of  plain  muscle-fibres ;  but  in  many 
of  the  lower  animals  composed  almost  entirely  of  involuntary  muscle.      They  pass 

inward,  radiating  toward  the  cen- 
tre of  the  gland,  for  a  certain 
distance  ;  that  is  to  say,  for  about 
one-third  or  one-fourth  of  the 
space  between  the  circumference 
and  the  centre  of  the  gland.  They 
thus  divide  the  outer  part  of  its 
interior  into  a  number  of  oval 
compartments  or  alveoli  (Fig. 
673).  This  is  the  cortical  por- 
tion of  the  gland.  After  having 
penetrated  into  the  gland  for 
some  distance,  these  septa  break 
up  into  a  number  of  smaller  tra- 
becule, which  form  flattened 
bands  or  cords,  interlacing  with 
each  other  in  all  directions,  form- 
ing in  the  central  part  of  the  organ 
a  number  of  intercommunicating  spaces,  also  called  alveoli.  This  is  the  medullary 
portion  of  the  gland,  and  the  spaces  or  alveoli  in  it  not  only  freely  communicate 
with  each  other,  but  also  with  the  alveoli  of  the  cortical  portion.  In  these  alveoli 
or  spaces  (Fig.  674)  is  contained  the  proper  gland-substance  or  lymphoid  tissue. 


Lymphoid 
tissue 


Efferent  vessel 


Medullary 
portion 


Fig.  673. — Diagrammatic  section  of  lymphatic  gland,  show- 
ing the  course  of  the  lymph. 


Fig.  674. — Follicle  from  a  lymphatic  gland  of  the  dog, 
in  vertical  section,  a.  Reticular  sustentacular  substance 
of  the  more  external  portion,  b,  of  the  more  internal,  and 
c,  of  the  most  external  and  most  finely  webbed  part  on  the 
surface  of  the  follicle,  d.  Origin  of  "a  large  lymph-tube. 
e.  Of  a  smaller  one.  /.  Capsule,  g.  Septa,  h.  Vasafferens. 
i.  Investing  space  of  the  follicle,  with  its  retinacula.  k. 
One  of  the  divisions  of  the  septa.  1,1.  Attachment  of  the 
lymph-tubes  to  the  septa. 


- 


Fig.  675.—  From  the  medullary  substance  of  an 
inguinal  gland  of  the  ox.  (After  His.)  a.  Lymph- 
tube,  with  its  complicated  system  of  vessels,  b. 
Retinacula  stretched  between  the  tube  and  the 
septa,  c.  Portion  of  another  lymph-tube.  d. 
Septa. 


The  gland-pulp  does  not,  however,  completely  fill  the  alveolar  spaces,  but  leaves, 
between  its  outer  margin  and  the  trabecule  forming  the  alveoli  a  channel  or  space 
of  uniform  width  throughout.  This  is  termed  the  lymph-path  or  lymph-sinus  (Fig. 
676).  Running  across  it  are  a  number  of  trabecule  of  retiform  connective  tissue, 
the  fibres  of  which  are,  for  the  most  part,  covered  by  ramified  cells.     This  tissue 


THE  SKIN  AND    ITS   APPENDAGES. 


1135 


the 
the 


Fig.  676.— Section  of  lymphatic  gland  tissue,  a.  Trabecules,  b. 
Small  artery  in  substance  of  same.  c.  Lvmph-paths.  d.  Lvmph- 
corpuscles.    e.  Capillary  plexus. 


appears  to  serve  the  purpose  of  maintaining  the  gland-pulp  in  the  centre  of  the 
space  in  its  proper  position. 

On  account  of  the  peculiar  arrangement  of  the  framework  of  the  organ 
gland-pulp  in  the  cortical  portion  is  disposed  in  the  form  of  nodules,  and  in 
medullary  part  in  the  form  of 
rounded  cords.  It  consists  of 
ordinary  lymphoid  tissue,  be- 
ing made  up  of  a  delicate  re- 
ticulum of  retiform  tissue, 
which  is  continuous  with  that 
in  the  lymph-paths,  but  mark- 
ed off  from  it  by  a  closer  retic- 
ulation ;  in  its  meshes  are 
closely  packed  lymph-corpus- 
cles, traversed  by  a  dense 
plexus  of  capillary  blood-ves- 
sels. 

The  afferent  vessels,  as 
above  stated,  enter  at  all  parts 
of  the  periphery  of  the  gland, 
and  after  branching  and  form- 
ing a  dense  plexus  in  the  sub- 
stance   of    the    capsule,  open 

into  the  lymph-sinuses  of  the  cortical  part.  In  doing  this  they  lose  all  their 
coats  except  their  endothelial  lining,  which  is  continuous  with  a  layer  of  similar 
cells  lining  the  lymph-paths.  In  like  manner  the  efferent  vessel  commences 
from  the  lymph-sinuses  of  the  medullary  portion.  The  stream  of  lymph  carried 
to  the  gland  by  the  afferent  vessel  thus  passes  through  the  plexus  in  the  capsule 
to  the  lymph-paths  of  the  cortical  portion,  where  it  is  exposed  to  the  action  of  the 
gland-pulp;  flowing  through  these,  it  enters  the  paths  or  sinuses  of  the  medullary 
portion,  and  finally  emerges  from  the  hilum  by  means  of  the  efferent  vessel.  The 
stream  of  lymph  in  its  passage  through  the  lymph-sinuses  is  much  retarded  by 
the  presence  of  the  reticulum.  Hence  morphological  elements,  either  normal  or 
morbid,  are  easily  arrested  and  deposited  in  the  sinuses.  This  is  a  matter  of  con- 
siderable importance  in  connection  with  the  subject  of  poisoned  wounds  and  the 
absorption  of  the  poison  by  the  lymphatic  system,  since  by  this  means  septic 
organisms  carried  along  the  lymphatic  vessels  may  be  arrested  in  the  lymph-sinuses 
of  the  gland  tissue,  and  thus  be  prevented  from  entering  the  general  circulation. 
Many  lymph-corpuscles  pass  with  the  efferent  lymph-stream  to  join  the  general 
blood-stream.  The  arteries  of  the  gland  enter  at  the  hilum,  and  either  pass  at 
once  to  the  gland-pulp,  to  break  up  into  a  capillary  plexus,  or  else  run  along  the 
trabecule,  partly  to  supply  them  and  partly  running  across  the  lymph-paths  to 
assist  in  forming  the  capillary  plexus  of  the  gland-pulp.  This  plexus  traverses 
the  lymphoid  tissue,  but  does  not  pass  into  the  lymph-sinuses.  From  it  the  veins 
commence,  and  emerge  from  the  organ  at  the  same  place  as  that  at  which  the 
artery  enters. 


THE    SKIN    AND    ITS    APPENDAGES. 

The  skin  (Fig.  677)  is  the  principal  seat  of  the  sense  of  touch,  and  may  be 
regarded  as  a  covering  for  the  protection  of  the  deeper  tissues;  it  plays  an 
important  part  in  the  regulation  of  the  body  temperature,  and  is  also  an  excretory 
and  absorbing  organ.  It  consists  principally  of  a  layer  of  vascular  tissue,  named 
the  derma,  eorium,  or  cutis  vera,  and  an  external  covering  of  epithelium,  termed 
the  epidermis  or  cuticle.  On  the  surface  of  the  former  layer  are  the  sensitive 
papilla?;  and  within,  or  imbedded  beneath  it.  are  certain  organs  with  special 
functions,  namely,  the  sweat-glands,  hair-follicles,  and  sebaceous  glands. 


1136 


GENERAL    ANATOMY    OR    HISTOLOGY. 


The  epidermis  or  cuticle  (scarf-skin)  is  non-vascular,  and  consists  of  stratified 
epithelium  (Fig.  678).  It  is  accurately  moulded  on  the  papillary  layer  of  the 
derma.  It  forms  a  defensive  covering  to  the  surface  of  the  true  skin,  and  limits 
the  evaporation  of  watery  vapor  from  its  free  surface.  It  varies  in  thickness  in 
different  parts.  In  some  situations,  as  in  the  palms  of  the  hands  and  soles  of  the 
feet,  it  is  thick,  hard,  and  horny  in  texture.  This  may  be  partly  due  to  the  fact 
that  these  parts  are  exposed  to  intermittent  pressure,  but  that  this  is  not  the  only 
cause  is  proved  by  the  fact  that  the  condition  exists  to  a  very  considerable  extent 
at  birth.  The  more  superficial  layer  of  cells,  called  the  horny  layer  (stratum 
corneum),  may  be  separated  by  maceration  from  the  deeper  layers,  which  are  called 


H  1  Epidermis 


Fibrous 
tissue 


Sebaceous 
Glands 


Sweat-Olands 


Nutrient  Artery 


Fig.  677. — A  sectional  view  of  the  skin  (magnified). 


the  rete  mueosum  or  stratum  Malpighii,  and  which  consist  of  several  layers  of 
differently  shaped  cells.  The  free  surface  of  the  epidermis  is  marked  by  a  net- 
work of  linear  furrows  of  variable  size,  marking  out  the  surface  into  a  number  of 
spaces  of  polygonal  or  lozenge-shaped  form.  Some  of  these  furrows  are  large,  as 
opposite  the  flexures  of  the  joints,  and  correspond  to  the  folds  in  the  dermis 
produced  by  their  movements.  In  other  situations,  as  upon  the  back  of  the  hand, 
they  are  exceedingly  fine,  and  intersect  one  another  at  various  angles ;  upon  the 
palmar  surface  of  the  hand  and  fingers  and  upon  the  sole  of  the  foot  these  lines 
are  very  distinct  and  are  disposed  in  curves.  They  depend  upon  the  large  size 
and  peculiar  arrangement  of  the  papillae  upon  which  the  epidermis  is  placed.  The 
deep  surface  of  the  epidermis  is  accurately  moulded  upon  the  papillary  layer  of 
the  dermis,  each  papilla  being  invested  by  its  epidermic  sheath  ;  so  that  when  this 
layer  is  removed  by  maceration,  it  presents  on  its  under  surface  a  number  of  pits 
or  depressions  corresponding  to  the  elevations  in  the  papillae,  as  well  as  the  ridges 
left  in  the  intervals  between  them.  Fine  tubular  prolongations  are  continued  from 
this  layer  into  the  ducts  of  the  sudoriferous  and  sebaceous  glands. 


THE   SKIN  AND    ITS   APPENDAGES. 


1137 


In  structure  the  epidermis  consists  of  several  layers  of  epithelial  cells  agglutinated 
together  and  having  a  laminated  arrangement.  These  several  layers  may  be 
described  as  composed  of  four  different  strata  from  within  outward  :  (1)  The  stratum, 
Malpighii,  composed  of  several  layers  of  epithelial  cells,  of  which  the  deepest  layer 
is  columnar  in   shape  and  placed  perpendicularly  on  the  surface  of   the  corium. 


Stratum  corneum 


Stratum  granulosum.  f 


-Nerve-fibrils. 


Fig.  678.— Section  of  epidermis.    (Kanvier.) 


their  lower  ends  being  denticulate,  to  fit  into  corresponding  denticulations  of  the 
true  skin;  this  deepest  layer  is  sometimes  termed  the  basilar  layer  or  stratum 
germinativum  ;  the  succeeding  laminae  consist  of  cells  of  a  more  rounded  or  polyhe- 
dral form,  the  contents  of  which  are  soft,  opaque,  granular,  and  soluble  in  acetic  acid. 


Fig.  679. — Microscopic  section  of  skin,  showing  the  epidermis  and  derma  ;  a  hair  in  its  follicle  :  the  erector 
pili  muscle;  sebaceous  and  sudoriferous  glands. 

They  are  often  marked  on  their  surfaces  with  ridges  and  furrows,  and  are  covered 
with  numerous  fibrils,  which  connect  the  surfaces  of  the  cells  :  these  are  known  as 
prickle  cells.  (See  page  1075.)  They  contain  numerous  epidermic  fibrils,  which 
are  stained  violet  with  hematoxylin  and  red  by  carmine,  and  form  threads  of  union 

72       . 


1138  GENERAL    ANATOMY    OR    HISTOLOGY. 

connecting  adjacent  cells.  Between  the  cells  are  fine  intercellular  clefts,  which 
serve  for  the  passage  of  lymph  and  in  which  lymph-corpuscles  or  pigment  granules 
may  be  found.  (2)  Immediately  superficial  to  these  are  two  or  three  layers  of 
flattened,  spindle-shaped  cells,  the  stratum  granulosum,  which  contain  granules 
that  become  deeply  stained  in  hsematoxylin  ;  the  granules  consist  of  a  material 
named  eleidin,  an  intermediate  substance  in  the  formation  of  horn.  They  are 
supposed  to  be  cells  in  a  transitional  stage  between  the  protoplasmic  cells  of  the 
stratum  Malpighii  and  the  horny  cells  of  the  superficial  layers.  (3)  Above  this 
layer  the  cells  become  indistinct,  and  appear,  in  sections,  to  form  a  homogeneous 
or  dimly  striated  membrane,  composed  of  closely  packed  scales,  in  which  traces  of 
a  flattened  nucleus  may  be  found.  It  is  called  the  stratum  lucidum.  (4)  As  these 
cells  successively  approach  the  surface  by  the  development  of  fresh  layers  from 
beneath,  they  assume  a  flattened  form  from  the  evaporation  of  their  fluid  contents, 
and  consist  of  many  layers  of  horny  epithelial  scales  in  which  no  nucleus  is 
discernible,  forming  the  stratum  corneum.  These  cells  are  unaffected  by  acetic 
acid,  the  protoplasm  having  become  changed  into  horny  material  or  keratin.  Ac- 
cording to  Ranvier,  they  contain  granules  of  a  material  which  has  the  characters 
of  beeswax.  The  deepest  layer  of  the  stratum  Malpighii  is  separated  from  the 
papillae  by  an  apparently  homogeneous  basement  membrane,  which  is  most 
distinctly  brought  into  view,  in  specimens  prepared  with  chloride  of  gold.  This, 
according  to  Klein,  is  merely  the  deepest  portion  of  the  epithelium,  and  is  "  made 
up  of  the  basis  of  the  individual  cells,  which  have  undergone  a  chemical  anc« 
morphological  alteration."  The  black  color  of  the  skin  in  the  negro  and  the 
tawny  color  among  some  of  the  white  races  is  due  to  the  presence  of  pigment  in 
the  cells  of  the  cuticle.  This  pigment  is  more  especially  distinct  in  the  cells  of 
the  deeper  layer,  or  stratum  Malpighii,  and  is  similar  to  that  found  in  the  cells  of 
the  pigmentary  layer  of  the  retina.  As  the  cells  approach  the  surface  and  desic- 
cate, the  color  becomes  partially  lost ;  the  disappearance  of  the  pigment  from  the 
superficial  layers  of  the  epidermis  is,  however,  difficult  to  explain. 

The  derma,  corium,  or  cutis  vera,  is  tough,  flexible,  and  highly  elastic,  in  order 
to  defend  the  parts  beneath  from  violence. 

It  varies  in  thickness,  from  a  quarter  of  a  line  to  a  line  and  a  half,  in  different 
parts  of  the  body.  Thus  it  is  very  thick  in  the  palms  of  the  hands  and  soles  of 
the  feet ;  thicker  on  the  posterior  aspect  of  the  body  than  the  front,  and  on  the 
outer  than  the  inner  side  of  the  limbs.  In  the  eyelids,  scrotum,  and  penis  it  is 
exceedingly  thin  and  delicate.  The  skin  is  generally  thicker  in  the  male  than  in 
the  female,  and  in  the  adult  than  in  the  child. 

The  corium  consists  of  felted  connective  tissue,  with  a  varying  amount  of 
elastic  fibres  and  numerous  blood-vessels,  lymphatics,  and  nerves.  The  fibro- 
areolar  tissue  forms  the  framework  of  the  cutis,  and  is  differently  arranged  in 
different  parts,  so  that  it  is  usual  to  describe  it  as  consisting  of  two  layers :  the 
deeper  or  reticular  layer,  and  the  superficial  or  pajnllary  layer.  ITnstriped 
muscular  fibres  are  found  in  the  superficial  layers  of  the  corium,  wherever  hairs 
are  found ;  and  in  the  subcutaneous  areolar  tissue  of  the  scrotum,  penis,  labia 
majora  of  the  female,  and  the  nipples.  In  the  latter  situation  the  fibres  are 
arranged  in  bands,  closely  reticulated  and  disposed  in  superimposed  laminae. 

The  reticular  layer  consists  of  strong  interlacing  fibrous  bands,  composed 
chiefly  of  the  white  variety  of  fibrous  tissue,  but  containing,  also,  some  fibres  of 
the  yellow  elastic  tissue,  which  vary  in  amount  in  different  parts,  and  connective- 
tissue  corpuscles,  Avhich  are  often  to  be  found  flattened  against  the  white  fibrous 
tissue-bundles.  Toward  the  attached  surface  the  fasciculi  are  large  and  coarse, 
and  the  areolae  which  are  left  by  their  interlacement  are  large,  and  occupied  by 
adipose  tissue  and  sweat-glands.  Below  this  the  elements  of  the  skin  become 
gradually  blended  with  the  subcutaneous  areolar  tissue,  which,  except  in  a  few 
situations,  contains  fat.  Toward  the  free  surface  the  fasciculi  are  much  finer, 
and  their  mode  of  interlacing  close  and  intricate. 

The  p apillary layer  is  situated  upon  the  free  surface  of  the  reticular  layer  ;  it  con- 


THE   SKIN  AND    ITS   APPENDAGES. 


1139 


sists  of  numerous  small,  highly  sensitive,  or  vascular  eminences,  the  papillce,  which 
rise  perpendicularly  from  its  surface.  The  papillae  are  conical-shaped  eminences, 
having  a  round  or  blunted  extremity,  occasionally  divided  into  two  or  more  parts  and 
are  received  into  corresponding  pits  on  the  under  surface  of  the  cuticle.  Their 
average  length  is  about  T^  of  an  inch,  and  they  measure  at  their  base  -j^o  °^  an 
inch  in  diameter.  On  the  general  surface  of  the  body,  more  especially  in  those 
parts  which  are  endoAved  with  slight  sensibility,  they  are  few  in  number,  short, 
exceedingly  minute,  and  irregularly  scattered  over  the  surface ;  but  in  some  situa- 
tions, as  upon  the  palmar  surface  of  the  hands  and  fingers,  upon  the  plantar  surface 
of  the  feet  and  toes,  and  around  the  nipple,  they  are  long,  of  large  size,  closely 
aggregated  together,  and  arranged  in  parallel  curved  lines,  forming  the  elevated 
ridges  seen  on  the  free  surface  of  the  epidermis.  Each  ridge  contains  two  rows  of 
papillae,  and  between  the  two  rows  the  ducts  of  the  sweat-glands  pass  outward  to 
open  on  the  summit  of  the  ridges.  In  structure  the  papillae  consist  of  very  small 
and  closely  interlacing  bundles  of  finely  fibrillated  tissue,  with  a  few  elastic  fibres ; 
within  this  tissue  is  a  capillary  loop,  and  in  some,  especially  in  the  palms  of  the 
hands  and  fingers,  there  are  tactile  corpuscles. 

The  arteries  supplying  the  skin  form  a  network  in  the  subcutaneous  tissue,  from 
which  branches  are  given  off  to  supply  the  sweat-glands,  the  hair-follicles,  and  the 
fat.  Other  branches  are  given  off  which  form  a  plexus  immediately  beneath  the 
corium  ;  from  this  fine  capillary  vessels  pass  into  the  papillae,  forming,  in  the  smaller 
papillae,  a  single  capillary  loop,  but  in  the  larger  a  more  or  less  convoluted  vessel. 
There  are  numerous  lymphatics  supplied  to  the  skin  which  form  two  networks,  super- 
ficial and  deep,  communicating  with  each  other  and  with  those  of  the  subcutaneous 
tissue  by  oblique  branches.      They  originate  in  the  cell-spaces  of  the  tissue. 

The  nerves  of  the  skin  terminate  partly  in  the  epidermis  and  partly  in  the  cutis 
vera.     The  former  are  prolonged  into  the  epidermis  from  a  dense  plexus  in  the 


Eponychmm. 

Nail.j^ 

Stratum  fe; 

Malpighii."^. 

Stratum  comeum  gB 

of  the  nail      "fife 

groove.  k 


Stratum 
co  1  neum. 
WStratum 

granulosum. 

Corium. 


§jL  Blood-vets  >1. 


WES 

Fig.  G80. — Longitudinal   section   through  human  nail  and  its  nail   groove  (sulcus).    (From  Bohm  and 
Davidoff  s  Histology). 

superficial  layer  of  the  corium  and  terminate  between  the  cells  in  bulbous  extremi- 
ties ;  or,  according  to  some  observers,  in  the  deep  epithelial  cells  themselves.  The 
latter  terminate  in  end-bulbs,  touch-corpuscles,  or  Pacinian  bodies,  in  the  manner 
already  described ;  and,  in  addition  to  these,  a  considerable  number  of  fibrils  are 
distributed  to  the  hair-follicles,  which  are  said  to  entwine  the  follicle  in  a  circular 
manner.  Other  nerve-fibres  are  supplied  to  the  plain  muscular  fibres  of  the  hair- 
follicles  (arrectores  pili)  and  to  the  muscular  coat  of  the  blood-vessels.  These  are 
probably  non-medullated  fibres. 

The  appendages  of  the  skin  are  the  nails,  the  hairs,  the  sudoriferous  and  seba- 
ceous glands,  and  their  ducts. 

The  nails  and  hairs  are  peculiar  modifications  of  the  epidermis,  consisting 
essentially  of  the  same  cellular  structure  as  that  tissue. 

The  nails  (Figs.  680,  681)  are  flattened,  elastic  structures  of  a  horny  texture, 
placed  upon  the  dorsal  surface  of  the  terminal  phalanges  of  the  fingers  and  toes. 
Each  nail  is  convex  on  its  outer  surface,  concave  within,  and  is  implanted  by  a 
portion,  called  the  root,  into  a  groove  in  the  skin ;  the  exposed  portion  is  called  the 


1140  GENERAL    ANATOMY   OB    HISTOLOGY. 

body,  and  the  anterior  extremity  the  free  edge.  The  nail  has  a  very  firm  adhesion 
to  the  cutis,  being  accurately  moulded  upon  its  surface,  as  the  epidermis  is  in  other 
parts.  The  part  of  the  cutis  beneath  the  body  and  root  of  the  nail  is  called  the 
matrix,  because  it  is  the  part  from  which  the  nail  is  produced.  Corresponding  to 
the  body  of  the  nail,  the  matrix  is  thick,  and  raised  into  a  series  of  longitudinal 

Nail. 

Stratum  Malpighii. 

Nail  wail. 

Nail  groove. 


Fig.  681. — Transverse  section  through  human  nail  and  its  sulcus.     (From  Bohm  and  Davidoff's   His- 
tology.) 

ridges,  which  are  very  vascular,  and  the  color  is  seen  through  the  transparent  tissue. 
Behind  this,  near  the  root  of  the  nail,  the  papillse  are  small,  less  vascular,  and  have 
no  regular  arrangement,  and  here  the  tissue  of  the  nail  is  somewhat  more  opaque ; 
hence  this  portion  is  of  a  whiter  color,  and  is  called  the  lunula  on  account  of  its  shape. 

The  cuticle,  as  it  passes  forward  on  the  dorsal  surface  of  the  finger  or  toe,  is 
attached  to  the  surface  of  the  nail,  a  little  in  advance  of  its  root;  at  the  extremity 
of  the  finger  it  is  connected  with  the  under  surface  of  the  nail  a  little  behind  its  free 
edge.  The  cuticle  and  horny  substance  of  the  nail  (both  epidermic  structures)  are 
thus  directly  continuous  with  each  other.  The  nails  consist  of  a  greatly  thick- 
ened stratum  lucidum,  the  stratum  corneum  forming  merely  the  thin  cuticular 
fold  (eponychium)  which  overlaps  the  lunula.  The  cells  have  a  laminated  arrange- 
ment, and  are  essentially  similar  to  those  composing  the  epidermis.  The  deepest 
layer  of  cells,  which  lie  in  contact  with  the  papillae  of  the  matrix,  are  columnar  in 
form  and  arranged  perpendicularly  to  the  surface ;  those  which  succeed  them  are 
of  a  rounded  or  polygonal  form,  the  more  superficial  ones  becoming  broad,  thin, 
and  flattened,  and  so  closely  compacted  as  to  make  the  limits  of  each  cell  very 
indistinct.  It  is  by  the  successive  growth  of  new  cells  at  the  root  and  under  surface 
of  the  body  of  the  nail  that  it  advances  forward  and  maintains  a  due  thickness, 
while,  at  the  same  time,  the  growth  of  the  nail  in  the  proper  direction  is  secured. 
As  these  cells  in  their  turn  become  displaced  by  the  growth  of  new  ones,  they 
assume  a  flattened  form,  and  finally  become  closely  compacted  together  into  a  firm, 
dense,  horny  texture.  In  chemical  composition  the  nails  resemble  the  upper  layers 
of  the  epidermis.  According  to  Mulder,  they  contain  a  somewhat  larger  proportion 
of  carbon  and  sulphur. 

The  hairs  are  peculiar  modifications  of  the  epidermis,  and  consist  essentially 
of  the  same  structure  as  that  membrane.  They  are  found  on  nearly  every  part  of 
the  surface  of  the  body,  excepting  the  palms  of  the  hands,  soles  of  the  feet,  and 
the  glans  penis.  They  vary  much  in  length,  thickness,  and  color  in  different 
parts  of  the  body  and  in  different  races  of  mankind.  In  some  parts,  as  in  the 
skin  of  the  eyelids,  they  are  so  short  as  not  to  project  beyond  the  follicles  con- 
taining them  ;  in  others,  as  upon  the  scalp,  they  are  of  considerable  length  :  again, 
in  other  parts,  as  the  eyelashes,  the  hairs  of  the  pubic  region,  and  the  whiskers  and 
beard,  they  are  remarkable  for  their  thickness.  Straight  hairs  are  stronger  than 
curly  hairs,  and  present  on  transverse  section  a  cylindrical  or  oval  outline ;  curly 
hairs,  on  the  other  hand,  are  flattened. 

A  hair  consists  of  a  root,  the  part  implanted  in  the  skin;  the  shaft  or  stem,  the 
portion  projecting  from  its  surface;   and  the  point. 

The  root  of  the  hair  presents  at  its  extremity  a  bulbous  enlargement,  which  is 
whiter  in  color  and  softer  in  texture  than  the  shaft,  and  is  lodged  in  a  follicular 
involution  of  the  epidermis  called  the  hair-follicle  (Fig.  679).     When  the  hair  is 


THE   SKIN  AND    ITS   APPENDAGES. 


1141 


Pig.  682.— Transverse  section 
of  hair-follicle.  1.  Dermic  coat 
of  follicle.  2.  Epidermic  coat  or 
root-sheath,  a,  Outer  layer  of 
dermic  coat,  with  blood-vessels. 
b.  b.  Vessels  cut  across,  c.  Middle 
layer,  d.  Inner  or  hyaline  layer. 
e.  Outer  root-sheath.  /.  g.  Inner 
root-sheath,  h.  Cuticle  of  root- 
sheath,  i.  Hair.  (From  Quain's 
Anatomy,  Biesiadecki./ 


of  considerable  length  the  follicle  extends  into  the  subcutaneous  cellular  tissue. 
The  hair-follicle  commences  on  the  surface  of  the  skin  Avith  a  funnel-shaped  open- 
ing, and  passes  inward  in  an  oblique  or  curved  direction — the  latter  in  curly  hair — 
to  become  dilated  at  its  deep  extremity,  where  it  cor- 
responds with  the  bulbous  condition  of  the  hair  which 
it  contains.  It  has  opening  into  it,  near  its  free  ex- 
tremity, the  orifices  of  the  ducts  of  one  or  more  seba- 
ceous glands.  At  the  bottom  of  each  hair-follicle  is  a 
small  conical,  vascular  eminence  or  papilla,  similar  in 
every  respect  to  those  found  upon  the  surface  of  the 
skin;  it  is  continuous  with  the  dermic  layer  of  the  fol- 
licle, is  highly  vascular,  and  probably  supplied  with 
nervous  fibrils.  In  structure  the  hair-follicle  consists 
of  two  coats — an  outer  or  dermic,  and  an  inner  or 
epidermic. 

The  outer  or  dermic  coat  is  formed  mainly  of  fibrous 
tissue ;  it  is  continuous  with  the  corium,  is  highly 
vascular,  and  supplied  by  numerous  minute  nervous 
filaments.  It  consists  of  three  layers  (Fig.  682).  The 
most  internal,  next  the  cuticular  lining  of  the  follicle, 
consists  of  a  hyaline  basement-membrane,  having  a 
glassy,  transparent  appearance,  which  is  well  marked 
in  the  larger  hair-follicles,  but  is  not  very  distinct  in 
the  follicles  of  minute  hairs.  It  is  continuous  with  the 
basement-membrane  of  the  surface  of  the  corium. 
External  to  this  is  a  compact  layer  of  fibres  and 
spindle-shaped  cells  arranged  circularly  around  the  fol- 
licle. This  layer  extends  from  the  bottom  of  the  follicle  as  high  as  the  entrance 
of  the  ducts  of  the  sebaceous  glands.  Externally  is  a  thick  layer  of  connective 
tissue,  arranged  in  longitudinal  bundles,  forming  a  more  open  texture  and  cor- 
responding to  the  reticular  part  of  the  corium.  In  this  are  contained  the  blood- 
vessels and  nerves. 

The  inner  or  epidermic  layer  is  closely  adherent  to  the  root  of  the  hair,  so 
that  when  the  hair  is  plucked  from  its  follicle  this  layer  most  commonly  adheres 
to  it  and  forms  what  is  called  the  mot-sheath.  It  consists  of  two  strata,  named 
respectively  the  outer  and  inner  root-sheath  ;  the  former  of  these  corresponds  with 
the  Malpighian  layer  of  the  epidermis,  and  resembles  it  in  the  rounded  form  and 
soft  character  of  its  cells  ;  at  the  bottom  of  the  hair-follicle  these  cells  become  con- 
tinuous with  those  of  the  root  of  the  hair.  The  inner  root-sheath  consists  of  a 
delicate  cuticle  next  the  hair,  composed  of  a  thin  layer  of  imbricated  scales  having 
a  downward  direction,  so  that  they  fit  accurately  over  the  upwardly  directed  imbri- 
cated scales  of  the  hair  itself;  then  of  one  or  two  layers  of  horny,  flattened, 
nucleated  cells,  known  as  Huxley  s  layer  ;  and  finally  of  a  single  layer  of  horny 
oblong  cells  without  visible  nuclei,  called  Henles  layer. 

The  hair-follicle  contains  the  root  of  the  hair,  which  terminates  in  a  bulbous 
extremity,  and  is  excavated  so  as  to  exactly  fit  the  papilla  from  which  it  grows. 
The  bulb  is  composed  of  polyhedral  epithelial  cells,  which  as  they  pass  upward 
into  the  root  of  the  hair  become  elongated  and  spindle-shaped,  except  some  in  the 
centre  which  remain  polyhedral.  Some  of  these  latter  cells  contain  pigment- 
granules,  which  give  rise  to  the  color  of  the  hair.  It  occasionally  happens  that 
these  pigment-granules  completely  fill  the  cells  in  the  centre  of  the  bulb,  which 
gives  rise  to  the  dark  tract  of  pigment  often  found,  of  greater  or  less  length,  in 
the  axis  of  the  hair. 

The  shaft  of  the  hair  consists  of  a  central  pith  or  medulla,  the  fibrous  part  of 
the  hair,  and  the  cortex  externally.  The  medulla  occupies  the  centre  of  the  shaft 
and  ceases  toward  the  point  of  the  hair.  It  is  usually  wanting  in  the  fine  hairs 
covering  the  surface  of  the  body,  and  commonly  in  those  of  the  head.      It  is  more 


1142  GENERAL    ANATOMY   OB    HISTOLOGY. 

opaque  and  deeper  colored  when  viewed  by  transmitted  light  than  the  fibrous. part ■; 
but  when  viewed  by  reflected  light  it  is  white.  It  is  composed  of  rows  of  poly- 
hedral cells,  which  contain  granules  of  eleidin  and  frequently  air-bubbles.  The 
fibrous  portion  of  the  hair  constitutes  the  chief  part  of  the  shaft ;  its  cells  are 
elongated  and  unite  to  form  flattened  fusiform  fibres.  Between  the  fibres  are  found 
minute  spaces  which  contain  either  pigment-granules  in  dark  hair  or  minute  air- 
bubbles  in  white  hair.  In  addition  to  this  there  is  also  a  diffused  pigment  con- 
tained in  the  fibres.  The  cells  which  form  the  cortex  of  the  hair  consist  of  a 
single  layer  which  surrounds  those  of  the  fibrous  part ;  they  are  converted  into 
thin,  flat  scales,  having  an  imbricated  arrangement. 

Connected  with  the  hair-follicles  are  minute  bundles  of  involuntary  muscular 
fibres,  termed  arrectores  pili.  They  arise  from  the  superficial  layer  of  the  corium, 
and  are  inserted  into  the  outer  surface  of  the  hair-follicle,  below  the  entrance  of 
the  duct  of  the  sebaceous  gland.  They  are  placed  on  the  side  toward  which  the 
hair  slopes,  and  by  their  action  elevate  the  hair  (Fig.  679). l 

The  sebaceous  glands  are  small,  sacculated,  glandular  organs,  lodged  in  the  sub- 
stance of  the  corium.  They  are  found  in  most  parts  of  the  skin,  but  are  especially 
abundant  in  the  scalp  and  face  :  they  are  also  very  numerous  around  the  apertures 
of  the  anus,  nose,  mouth,  and  external  ear  ;  but  are  wanting  in  the  palms  of  the 
hands  and  soles  of  the  feet.  Bach  gland  consists  of  a  single  duct,  more  or  less 
capacious,  which  terminates  in  a  cluster  of  small  secreting  pouches  or  saccules. 
The  sacculi  connected  with  each  duct  vary,  as  a  rule,  in  number  from  two  to  five, 
but  in  some  instances  may  be  as  many  as  twenty.  They  are  composed  of  a 
transparent,  colorless  membrane,  enclosing  a  number  of  epithelial  cells.  Those 
of  the  outer  or  marginal  layer  are  small  and  polyhedral,  and  are  continuous  with 
the  lining  cells  of  the  duct.  The  remainder  of  the  sac  is  filled  with  larger  cells, 
containing  fat,  except  in  the  centre,  where  the  cells  have  become  broken  up,  leav- 
ing a  cavity  containing  their  debris  and  a  mass  of  fatty  matter,  which  constitutes 
the  sebaceous  secretion.  The  orifices  of  the  ducts  open  most  frequently  into  the 
hair-follicles,  but  occasionally  upon  the  general  surface,  as  in  the  labia  minora  and 
the  free  margin  of  the  lips.  On  the  nose  and  face  the  glands  are  of  large  size, 
distinctly  lobulated,  and  often  become  much  enlarged  from  the  accumulation  of 
pent-up  secretion.  The  largest  sebaceous  glands  are  those  found  in  the  eyelids — 
the  Meibomian  glands. 

The  sudoriferous  or  sweat-glands  are  the  organs  by  which  a  large  portion  of 
the  aqueous  and  gaseous  materials  is  excreted  by  the  skin.  They  are  found  in 
almost  every  part  of  this  structure,  and  are  situated  in  small  pits  on  the  under  sur- 
face of  the  corium,  or,  more  frequently,  in  the  subcutaneous  areolar  tissue,  sur- 
rounded by  a  quantity  of  adipose  tissue.  They  are  small,  lobular,  reddish  bodies, 
consisting  of  a  single  convoluted  tube,  from  which  the  efferent  duct  proceeds  upward 
through  the  corium  and  cuticle,  becomes  somewhat  dilated  at  its  extremity,  and 
opens  on  the  surface  of  the  cuticle  by  an  oblique  valve-like  aperture.  The  efferent 
duct,  as  it  passes  through  the  epidermis,  presents  a  spiral  arrangement,  being 
twisted  like  a  corkscrew,  in  those  parts  where  the  epidermis  is  thick ;  where,  how- 
ever, it  is  thin,  the  spiral  arrangement  does  not  exist.  In  the  superficial  layers 
of  the  corium  the  duct  is  straight,  but  in  the  deeper  layers  it  is  convoluted  or  even 
twisted.  The  spiral  course  of  these  ducts  is  especially  distinct  in  the  thick  cuticle 
of  the  palm  of  the  hand  and  sole  of  the  foot.  The  size  of  the  glands  varies. 
They  are  especially  large  in  those  regions  where  the  amount  of  perspiration  is 
great,  as  in  the  axillae,  where  they  form  a  thin,  mammillated  layer  of  a  reddish 
color,  which  corresponds  exactly  to  the  situation  of  the  hair  in  this  region ;  they 
are  large  also  in  the  groin.  Their  number  varies.  They  are  most  numerous  on 
the  palm  of  the  hand,  presenting,  according  to  Krause,  2800  orifices  on  a  square 

1  Arthur  Thomson  suggests  that  the  contraction  of  these  muscles  on  follicles  which  contain 
weak  flat  hairs  will  tend  to  produce  a  permanent  curve  in  the  follicle,  and  this  curve  will  be  im- 
pressed on  the  hair  which  is  moulded  within  it,  so  that  the  hair,  on  emerging  through  the  skin,  will 
be  curled.     Curved  hair-follicles  are  characteristic  of  the  scalp  of  the  Bushman. 


THE   SKIN  AND    ITS   APPENDAGES. 


1143 


inch  of  the  integument,  and  are  rather  less  numerous  on  the  sole  of  the  foot.  In 
both  of  these  situations  the  orifices  of  the  ducts  are  exceedingly  regular,  and  open 
on  the  curved  ridges.  In  other  situations  they  are  more  irregularly  scattered,  but 
the  number  in  a  given  extent  of  surface  presents  a  fairly  uniform  average.  In  the 
neck  and  back  they  are  least  numerous,  their  number  amounting  to  -417  on  the 
square  inch  (Krause).  Their  total  number  is  estimated  by  the  same  writer  at 
2,381,248,  and,  supposing  tbe  aperture  of  each  gland  to  represent  a  surface  of  J-g- 
of  a  line  in  diameter,  he  calculates  that  the  whole  of  these  glands  would  present 
an  evaporating  surface  of  about  eight  square  inches.  Each  gland  consists  of  a 
single  tube  intricately  convoluted,  terminating  at  one  end  by  a  blind  extremity, 
and  opening  at  the  other  end  upon  the  surface  of  the  skin.  In  the  larger  glands 
this  single  duct  usually  divides  and  subdivides  dichotomously ;  the  smaller  ducts 
ultimately  terminating  in  short  caecal  pouches,  rarely  anastomosing.  The  wall  of 
the  duct  is  thick,  the  width  of  the  canal  rarely  exceeding  one-third  of  its  diameter. 
The  tube,  both  in  the  gland  and  where  it 
forms  the  excretory  duct,  consists  of  two 
layers — an  outer,  formed  by  fine  areolar 
tissue,  and  an  inner  layer  of  epithelium 
(Fig.  683).  The  external  or  fibro-cellular 
coat  is  thin,  continuous  with  the  super- 
ficial layer  of  the  corium,  and  extends 
only  as  high  as  the  surface  of  the  true 
skin.  The  epithelial  lining  in  the  distal 
part  of  the  coiled  tube  of  the  gland  proper 
consists  of  a  single  layer  of  cubical  epi- 
thelium, supported  on  a  basement-mem- 
brane, and  beneath  it,  between  the  epithe- 
lium and  the  fibro-cellular  coat,  is  a  layer 
of  longitudinally  or  obliquely  arranged 
fibres,  which  are  usually  regarded  as  mus- 
cular, though  the  evidence  that  this  is  so 
is  not  conclusive.  In  the  duct  and  the 
proximal  part  of  the  coiled  tube  of  the 
gland  proper  there  are  two  or  more  layers  of  polyhedral  cells,  lined  on  their  inter- 
nal surface — i.  <?.,  next  the  lumen  of  the  tube — by  a  delicate  membrane  or  cuticle, 
and  on  their  outer  surface  by  a  limiting  membrana  propria,  but  there  are  no  mus- 
cular fibres.  The  epithelium  is  continuous  with  the  epidermis  and  with  the  delicate 
internal  cuticle  of  the  epidermic  portion  of  the  tube.  When  the  cuticle  is  carefully 
removed  from  the  surface  of  the  cutis,  these  convoluted  tubes  of  epithelium  may 
be  drawn  out  and  form  short,  thread-like  processes  on  its  under  surface. 

The  contents  of  the  smaller  sweat-glands  are  quite  fluid ;  but  in  the  larger 
glands  the  contents  are  semifluid  and  opaque,  and  contain  a  number  of  colored 
granules  and  cells  which  appear  analogous  to  endothelial  cells. 


Fig.  683.— Coiled  tube  of  a  sweat-gland  cut  in  vari- 
ous directions,  a.  Longitudinal  section  of  the  proxi- 
mal part  of  the  coiled  tube.  b.  Transverse  section  of 
the  same.  c.  Longitudinal  section  of  the  distal  part 
of  the  coiled  tube.  d.  Transverse  section  of  the  same. 
(From  Klein  and  Noble  Smith's  Atlas  of  Histology.) 


SEROUS  MEMBRANES. 

The  serous  membranes  form  shut  sacs,  and  may  be  regarded  as  lymph-sacs,  from 
which  lymphatic  vessels  arise  by  stomata  or  openings  between  the  endothelial  cells. 
(See  page  1133.)  The  sac  consists  of  one  portion  which  is  applied  to  the  walls  of 
the  cavity  which  it  lines — the  parietal  portion  ;  and  another  reflected  over  the  sur- 
face of  the  organ  or  organs  contained  in  the  cavity — the  visceral  portion.  Some- 
times the  sac  is  arranged  quite  simply,  as  the  tunica  vaginalis  testis  ;  at  others 
with  numerous  involutions  or  recesses,  as  the  peritoneum,  in  which,  nevertheless, 
the  membrane  can  always  be  traced  continuously  around  the  whole  circumference. 
The  sac  is  completely  closed,  so  that  no  communication  exists  between  the  serous 
cavity  and  the  parts  in  its  neighborhood.  An  apparent  exception  exists  in  the 
peritoneum  of  the  female ;  for  the  Fallopian  tube  opens  freely  into  the  peritoneal 
cavity  in  the  dead  subject,  so  that  a  bristle  can  be  passed  from  the  one  into  the  other. 


1144 


GENERAL   ANATOMY   OB    HISTOLOGY. 


But  this  communication  is  closed  during  life,  except  at  the  moment  of  the  passage 
of  the  ovum  out  of  the  ovary  into  the  tube,  as  is  proved  by  the  fact  that  no  inter- 
change of  fluids  ever  takes  place  between  the  two  cavities  in  dropsy  of  the  perito- 
neum or  in  accumulation  of  fluid  in  the  Fallopian  tubes.1  The  serous  membrane 
is  often  supported  by  a  firm,  fibrous  layer,  as  is  the  case  with  the  pericardium,  and 
such  membranes  are  sometimes  spoken  of  as  "  fibro-serous." 

The  various  serous  membranes  are  the  peritoneum,  lining  the  cavity  of  the 
abdomen  ;  the  two  pleurae  and  the  pericardium,  covering  the  lungs  and  heart  respec- 
tively ;  and  the  tunicse  vaginalis,  surrounding  each  testicle  in  the  scrotum.2 
Serous  membranes  are  thin,  transparent,  glistening  structures,  lined  on  their  inner 
surface  by  a  single  layer  of  polygonal  or  pavement  endothelial  cells,  supported  on 
a  matrix  of  fibrous  connective  tissue,  with  networks  of  fine  elastic  fibres,  in  which 
are  contained  numerous  capillaries  and  lymphatics.  On  the  surface  of  the  endo- 
thelium between  the  cells  numerous  apertures  or  interruptions  are  to  be  seen.  Some 
of  these  are  stomata,  surrounded  by  a  ring  of  cubical  endothelium  (see  Fig.  684), 


Fig.  684.— Part  of  peritoneal  surface  of  the  central  tendon  of  diaphragm  of  rabbit,  prepared  with  nitrate 
of  silver,  s.  Stomata.  I.  Lymph-channels,  t.  Tendon-bundles.  The  stomata  are  surrounded  by  germinating 
epithelial  cells.     (From  Handbook  for  the  Physiological  Laboratory,  Klein. ) 


and  communicating  with  a  lymphatic  capillary;  others  ( pseudostomata)  are  mere 
interruptions  in  the  endothelial  layer,  and  are  occupied  by  processes  of  the  branched 
connective-tissue  corpuscle  of  the  subjacent  tissue  or  by  accumulations  of  the  inter- 
cellular cement-substance. 

The  amount  of  fluid  contained  in  these  closed  sacs  is,  in  most  cases,  only  suffi- 
cient to  moisten  the  surface,  but  not  to  furnish  any  appreciable  quantity  of  fluid. 
When  a  small  quantity  can  be  collected,  it  is  found  to  resemble  lymph,  and  like 
that  fluid  coagulates  spontaneously ;  but  when  secreted  in  large  quantities,  as  in 
dropsy,  it  is  a  more  watery  fluid,  but  still  contains  a  considerable  amount  of  proteid 
which  is  coagulated  on  boiling. 

1  The  communication  between  the  uterine  cavity  and  the  peritoneal  sac  is  not  only  apparent  in 
the  dead  subject,  but  is  an  anatomical  fact,  which  is  established  by  the  continuity  of  its  epithelium 
with  that  covering  the  uterus,  Fallopian  tubes,  and  fimbriae. 

2  The  arachnoid  membrane,  lining  the  brain  and  spinal  cord,  was  formerly  regarded  as  a  serous 
membrane,  but  is  now  no  longer  classed  with  them,  as  it  differs  from  them  in  structure,  and  does  not 
form  a  shut  sac  as  do  the  other  serous  membranes. 


THE   MUCOUS  MEMBBANE. 


1145 


SYNOVIAL  MEMBRANES. 

Synovial  membranes,  like  serous  membranes,  are  connective-tissue  membranes 
placed  between  two  movable  tissues,  so 
as  to  diminish  friction,  as  in  movable 
joints;  or  between  a  tendon  and  a  bone, 
where  the  former  glides  over  the  latter ; 
and  between  the  skin  and  various  subcu- 
taneous bony  prominences. 

The  synovial  membranes  are  composed 
essentially  of  connective  tissue,  with  the  cells 
and  fibres  of  that  structure,  containing  numer- 
ous vessels  and  nerves.  It  was  formerly  sup- 
posed that  these  membranes  were  analogous 
in  structure  to  the  serous  membranes,  and 
consisted  of  a  layer  of  flattened  cells  on  a 
basement-membrane.  No  such  continuous 
layer,  however,  exists,  although  here  and 
there  are  patches  of  cells  probably  epithelial 
in  nature.  They  are  surrounded  and  held 
together  by  an  albuminous  ground-substance. 
Long  villus-like  processes  (Fig.  685)  are 
often  found  projecting  from  the  surface  of 
synovial  membranes  ;  they  are  covered  by 
small  rounded  cells,  and  are  supposed  to 
extend  the  surface  for  the  secretion  of  the 
Huid  which  moistens  the  membranes,  and 
which  is  named  synovia.  It  is  a  rich  lymph, 
plus  a  mucin-like  substance,  and  to  the  latter 
constituent  it  owes  its  viscidity.  A  further 
description  of  the  synovial  membranes  will  be  found  in  the  descriptive  anatomv 
of  the  joints. 


Fig.    685.— Villus  of  synovial    membrane. 
(After  Hammar). 


MUCOUS    MEMBRANE. 

Mucous  membranes  line  all  those  passages  by  which  the  internal  parts  com- 
municate with  the  exterior,  and  are  continuous  with  the  skin  at  the  various  orifices 
of  the  surface  of  the  body.  They  are  soft  and  velvety,  and  very  vascular,  and 
their  surface  is  coated  over  by  their  secretion,  mucus,  which  is  of  a  tenacious  con- 
sistence, and  serves  to  protect  them  from  the  foreign  substances  introduced  into 
the  body  with  which  they  are  brought  in  contact. 

They  are  described  as  lining  the  two  tracts — the  gastro-pulmonary  and  the 
genito-urinary ;  and  all,  or  almost  all,  mucous  membranes  may  be  classed  as 
belonging  to  and  continuous  with  the  one  or  the  other  of  these  tracts. 

The  deep  surfaces  of  these  membranes  are  attached  to  the  parts  which  they 
line  by  means  of  connective  tissue,  which  is  sometimes  very  abundant,  forming  a 
loose  and  lax  bed,  so  as  to  allow  considerable  movement  of  the  opposed  surfaces 
on  each  other.  It  is  then  termed  the  submucous  tissue.  At  other  times  it  is 
exceedingly  scanty,  and  the  membrane  is  closely  connected  to  the  tissue  beneath ; 
sometimes,  for  example,  to  muscle,  as  in  the  tongue ;  sometimes  to  cartilage,  as 
in  the  larynx ;  and  sometimes  to  bone,  as  in  the  nasal  fossse  and  sinuses  of  the 
skull. 

In  structure  a  mucous  membrane  is  composed  of  corium  and  epithelium:  The 
epithelium  is  of  various  forms,  including  the  squamous,  columnar,  and  ciliated, 
and  is  often  arranged  in  several  layers.  This  epithelial  layer  is  supported  by  the 
corium,  which  is  analogous  to  the  dermis  of  the  skin,  and  consists  of  connective 
tissue,  either  simply  areolar  or   containing  a  greater  or  less  quantity  of  lymphoid 


1146  GENERAL    ANATOMY   OB    HISTOLOGY. 

tissue.  This  tissue  is  usually  covered  on  its  external  surface  by  a  transparent 
basement-membrane  generally  composed  of  clear  flattened  cells,  placed  edge  to 
edge ;  on  this  the  epithelium  rests.  It  is  only  in  some  situations  that  the  base- 
ment-membrane can  be  demonstrated.  The  corium  is  an  exceedingly  vascular 
membrane,  containing  a  dense  network  of  capillaries,  which  lie  immediately  beneath 
the  epithelium,  and  are  derived  from  small  arteries  in  the  submucous  tissue. 

The  fibro-vascular  layer  of  the  corium  contains,  besides  the  areolar  tissue  and 
vessels,  unstriped  muscle-cells,  which  form  in  many  situations  a  definite  layer, 
called  the  muscularis  mucosce.  These  are  situated  in  the  deepest  part  of  the  mem- 
brane, and  are  plentifully  supplied  with  nerves.  Other  nerves  pass  to  the  epi- 
thelium and  terminate  between  the  cells.  Lymphatic  vessels  are  found  in  great 
abundance,  commencing  either  by  caecal  extremities  or  in  networks,  and  com- 
municating with  plexuses  in  the  submucous  tissue. 

Imbedded  in  the  mucous  membrane  are  found  numerous  glands,  and  project- 
ing from  it  are  processes  (villi  and  papillae)  analogous  to  the  papillae  of  the  skin. 
These  glands  and  processes,  however,  exist  only  at  certain  parts,  and  they  have 
been  described  for  the  sake  of  convenience,  and  with  the  parts  as  they  occurred. 

SECRETING  GLANDS. 

The  secreting  glands  are  organs  whose  cells  produce,  by  tne  metabolism  of  their 
protoplasm,  certain  substances,  called  ''secretions,''  of  a  more  or  less  definite  com- 
position ;  the  material  for  the  secretion  being  primarily  selected  from  the  blood. 
The  essential  parts,  therefore,  of  a  secreting  gland  are  cells,  which  have  the  power 
of  extracting  from  the  blood  cei'tain  matters,  and  in  some  cases  converting  them 
into  new  chemical  compounds ;  and  blood-vessels,  by  which  the  blood  is  brought 
into  close  relationship  with  these  cells.  The  general  arrangement  in  all  secreting 
structures — that  is  to  say,  not  only  in  secreting  glands,  but  also  in  secreting  mem- 
branes— is  that  the  cells  are  arranged  on  one  surface  of  an  extravascular  basement- 
membrane,  which  supports  them,  and  a  minute  plexus  of  capillary  vessels  ramifies 
on  the  other  surface  of  the  membrane.  The  cells  then  extract  from  the  blood 
certain  constituents  which  pass  through  the  membrane  into  the  cells,  where  they 
are  prepared  and  elaborated.  The  basement-membrane  does  not,  however,  always 
exist,  and  any  free  surface  would  appear  to  answer  the  same  purpose  in  some  cases. 

By  the  various  modifications  of  this  secreting  surface  the  different  glands  are 
formed.  This  is  generally  effected  by  an  invagination  of  the  membrane  in  different 
ways,  the  object  being  to  increase  the  extent  of  secreting  surface  within  a  given 
bulk. 

In  the  simplest  form  a  single  invagination  takes  place,  constituting  a  simple 
gland ;  this  may  be  either  in  the  form  of  an  open  tube  (Fig.  686,  a),  or  the  walls 
of  the  tube  may  be  dilated  so  as  to  form  a  saccule  (Fig.  686,  b).  These  are  named 
the  simple  tubular  or  saccular  glands.  Or,  instead  of  a  short  tube,  the  invagination 
may  be  lengthened  to  a  considerable  extent,  and  then  coiled  up  to  occupy  less 
space.  This  constitutes  the  simple  convoluted  tubular  gland,  an  example  of  which 
may  be  seen  in  the  sweat-glands  of  the  skin  (Fig.  686,  c). 

If,  instead  of  a  single  invagination,  secondary  invaginations  take  place  from 
the  primary  one,  as  in  Fig.  686,  D  and  E,  the  gland  is  then  termed  a  compound 
one.  These  secondary  invaginations  may  assume  either  a  saccular  or  tubular  form, 
and  so  constitute  the  two  subdivisions — the  compound  saccular  or  racemose  gland, 
and  the  compjound  tubular.  The  racemose  gland  in  its  simplest  form  consists  of  a 
primary  invagination  which  forms  a  sort  of  duct,  upon  the  extremity  of  which  are 
found  a  number  of  secondary  invaginations  called  saccules  or  alveoli,  as  in  Brun- 
ner's  glands  (Fig.  686,  d).  But,  again,  in  other  instances,  the  duct,  instead  of  being 
simple,  may  divide  into  branches,  and  these  again  into  other  branches,  and  so  on ; 
each  ultimate  ramification  terminating  in  a  dilated  cluster  of  saccules,  and  thus  we 
may  have  the  secreting  surface  almost  indefinitely  extended,  as  in  the  salivary 


SECRETING    GLANDS. 


1147 


glands  (Fig.  686,  e).  In  the  compound  tubular  glands  the  division  of  the  primary 
duct  takes  place  in  the  same  way  as  in  the  racemose  glands,  but  the  branches 
retain  their  tubular  form,  and  do  not  terminate  in  saccular  recesses,  but  become 
greatly  lengthened  out  (Fig.  686,  f).    The  best  example  of  this  form  of  gland  is  to 


Fig.  686.— Diagrammatic  plan  of  varieties  of  secreting  glands,    a.  Simple  gland,    b.  Sacculated  simple  gland. 
C  Simple  convoluted  tubular  gland,    d,  e.  Racemose  gland,    f.  Compound  tubular  gland. 

be  found  in  the  kidney.  All  these  varieties  of  glands  are  produced  by  a  more  or 
less  complicated  invagination  of  a  secreting  membrane,  and  they  are  all  identical 
in  structure ;  that  is  to  say,  the  saccules  or  tubes,  as  the  case  may  be,  are  lined 
with  cells,  generally  spheroidal  or  columnar  in  figure,  and  on  their  outer  surface 
is  an  intimate  plexus  of  capillary  vessels.  The  secretion,  whatever  it  may  be,  is 
eliminated  by  the  cells  from  the  blood,  and  is  poured  into  the  saccule  or  tube,  and 
so  finds  it  way  out  through  the  primary  invagination  on  to  the  free  surface  of  the 
secreting  membrane.  In  addition,  however,  to  these  glands,  which  are  formed  by 
an  invagination  of  the  secreting  membrane,  there  are  some  few  others  which  are 
formed  by  a  protrusion  of  the  same  structure,  as  in  the  vascular  fringes  of  synovial 
membranes.  This  form  of  secreting  structure  is  not  nearly  so  frequently  met 
with. 


EMBRYOLOGY. 


THE  OVUM. 

THE  whole  body  is  developed  out  of  the  ovum  or  female  element  (Figs.  687  and 
688)  after  it  has  been  fertilized  by  the  spermatozoon  or  male  element.  The 
ovum  is  a  simple  nucleated  cell,  and  all  the  complicated  changes  by  which  the 
various  intricate  organs  of  the  body  are  formed  from  it  may  be  reduced  to  two 
general  processes,  viz.,  the  segmentation  or  cleavage  of  cells,  and  their  differentia- 
tion. The  former  process  consists  in  the  division  of  the  nucleus  and  the  surround- 
ing cell-substance,  whereby  the  original  cell  is  represented  by  two.  The  differentia- 
tion of  cells  is  a  term  used  to  describe  that  unknown  power  or  tendency  impressed 
on  cells,  apparently  identical  in  structure,  whereby  they  grow  into  different  forms  ; 
bo  that  (to  take  one  of  the  first  phenomena  which  occurs  in  the 
growth  of  the  embryo)  the  indifferent  cells  of  the  vascular  area 
are  differentiated,  some  of  them  into  blood-globules,  others  into 
the  solid  tissue  which  forms  the  blood-vessels.  The  extreme 
complexity  of  the  process  of  development  renders  it  at  all  times 
difficult  to  describe  intelligibly,  and  still  more  so  in  a  work  like 
this,  where  adequate  space  and  illustration  can  hardly  be  afforded, 
having  respect  to  the  main  purpose  of  the  work,  and  therefore 
an  outline  of  the  principal  facts  only  will  be  given.  Many  of 
the  statements  which  are  accepted  in  human  embryology  are 
made  on  the  strength  of  what  has  been  observed  to  occur  in  the 
lower  animals,  and  their  existence  in  the  human  subject  is 
merely  a  matter  of  inference.  Within  recent  years,  however, 
much  has  been  added  to  our  knowledge  of  the  development  of 
the  human  embryo,  and  this  more  especially  by  the  important 
researches  of  Professor  His  and  others. 

The  ovum  is  a  small  spheroidal  body  situated  in  the  immature  Graafian  follicle 
near  its  centre,  but  in  the  mature  one  in  contact  with  the  membrana  granulosa,1 
at  that  part  of  the  follicle  which  projects  from  the  surface  of  the  ovary.  The  cells 
of  the  membrana  granulosa  are  accumulated  round  the  ovum  in  greater  number 
than  at  any  other  part  of  the  follicle,  forming  a  kind  of  granular  zone,  the  discus 
proligerus. 

The  human  ovum  (Fig.  687)  is  extremely  minute,  measuring  from  Ti^  to  T^j  of 
an  inch  in  diameter.  It  is  a  cell  consisting  externally  of  a  transparent  striated 
envelope,  the  zona  pellucida,  zona  radiata,  or  vitelline  membrane.  The  extra- 
nuclear  protoplasm  contained  within  the  zona  pellucida  is  known  as  the  cyto- 
plasm;  it  is  a  sponge-like  material,  containing  in  its  meshes  numerous  large 
fatty  and  albuminous  granules,  which  constitute  the  yolk  or  vitellus ;  in  the 
neighborhood  of  the  nucleus,  however,  these  granules  are  comparatively  few  in 
number.  The  nucleus  is  a  large  spherical  body,  which  is  known  by  the  name 
of  the  germinal  vesicle,  and  resembles  in  structure  the  nucleus  of  an  ordinary 
cell.  Within  it  there  is  generally  one  nucleolus,  which  is  large  and  well  marked, 
and  is  known  as  the  germinal  spot.  The  zona  pellucida  is  believed  to  be  pierced 
by  numerous  pores   which   are   probably  channels  of  nutrition   and  which   give  it 

1  See  the  description  of  the  ovary  at  a  future  page. 

1149 


Fig.  6S7. — Human 
ovum  from  a  middle- 
sized  follicle.  Magni- 
fied 350  times,  a.  Zona 
pellucida  or  zona 
radiata.  b.  External 
border  of  the  yolk  and 
internal  border  of  the 
vitelline  membrane, 
c.  Germinal  vesicle 
and  germinal  spot. 


1150 


EMBRYOLOGY. 


the  appearance  of  being  radially  striated,  while  in  some  animals  {e.g.,  insects)  it 
presents  a  small  perforation  or  hole,  which  is  known  by  the  name  of  the  micropyle, 
and  is  believed  to  be  the  means  by  which  the  spermatozoa  enter  the  ovum. 

The  phenomena  attending  the  discharge  of  the  ova  from  the  Graafian  follicles, 
since  they  belong  as  much  or  more  to  the  ordinary  function  of  the  ovary  than  to 
the  general  subject  of  the  development  of  the  body,  are  described  with  the 
anatomy  of  the  ovaries  on  a  subsequent  page. 


Germinal  spot.~_ 


t>'Q 


■OnhQ  °  -0UOi 


Follicular  cells 
adhering  to  zona 
pellucida. 

Germinal  vesicle. 


o96;&p4 

On  o-°0>W 


p;o.-o -c  ' 


I^^^^Oc^^^^O^-^Oltf^j- 


Q< 


>;^§£°°S°°?§$ 


„Zona  'pellucida 
or  radiata. 

-Yolk  granules. 


-?:Q',ok:n&o, 


6,o%yo  o 


^t>S§-o^ 


o- 


\  (")"•  --'Vh*  •  6*-°'  0°0  6  •   ° ■  •  A° '  °  Or?  °J?/ 


\*?^&ox06P£dPM 


P.'jO  i.r  O^Kri  °o    •  O  °nOoO/ 


-Qa-O',-0, 


Fig.  688.— Ovum  of  rabbit.    Highly  magnified.    (After  Waldeyer.) 


Maturation  of  the  Ovum  previous  to  Fertilization. — Either  before  or  immedi- 
ately after  its  escape  from  the  Graafian  follicle,  important  changes  take  place  in  the 
nucleus  of  the  ovum,  which  result  in  its  partial  disappearance  and  in  the  forma- 
tion and  extrusion  from  the  yolk  of  two  peculiar  bodies,  the  polar  bodies  or  polar 
globules  of  Robin.  These  changes  constitute  what  is  termed  the  maturation  of 
the  ovum,  and  are  preparatory  to  its  being  fertilized  by  the  male  element  or 
spermatozoon.  The  nucleus  approaches  the  periphery  of  the  ovum  and  undergoes 
the  changes  associated  with  karyokinesis  ;  it  then  divides  into  two,  and  the  upper 
daughter  nucleus,  with  a  thin  investment  of  protoplasm,  becomes  extruded  as  the 
first  polar  body  into  a  space  between  the  yolk  and  the  vitelline  membrane,  which 
has  been  formed  in  consequence  of  a  contraction  or  shrinking  of  the  yolk.  The 
lower  daughter  nucleus  undergoes  the  same  process  of  division,  and  forms  a  second 
polar  body,  which  is  in  like  manner  extruded  (Fig.  689).  The  greater  part  (three- 
fourths)  of  the  original  nucleus  is  therefore  expelled  from  the  yolk  in  the  form  of 
the  two  polar  bodies,  and  the  remaining  fourth,  which  is  now  called  the  female 
pronucleus,  recedes  toward  the  centre  of  the  ovum.  The  shrinking  of  the  vitellus 
still  continues,  and  a  fluid — the  perivitelline  fluid — collects  in  the  space  between  it 
and  the  zona  pellucida ;  in  it,  spermatozoa,  which  have  passed  through  the  zona 
pellucida,  may  sometimes  be  seen. 

Although  the  process  of  maturation  has  been  closely  followed  in  many  of  the 
lower  animals,  it  has  not  yet  been  successfully  demonstrated  in  mammals. 

It  is  interesting  to  note  that  a  similar  nuclear  reduction  occurs  in  connection 
with  the  development  of  spermatozoa.  In  the  germinal  ridge,  which  is  to  become 
the  future  testicle,  certain  cells,  identical  with  primitive  ova,  are  found.  These 
are  termed  spermatoblasts,  and  they  become  enlarged  to  form  what  are  called  sper- 
matocytes, while  each  spermatocyte  ultimately  divides  into  four  spermatids.  The 
spermatids  become  changed,   without  further  subdivision,  into  spermatozoa,  and 


THE    OVUM. 


1151 


hence  the  fully  developed  spermatozoon  contains  only  one-fourth  of  the  nucleus 
of  the  original  spermatocyte.  The  matured  ovum  and  the  spermatozoon  may 
therefore  be  looked  upon  as  of  the  same  morphological  value. 


Fig.  689. — Formation  of  polar  bodies  in  Asterias  glacialis.  (Hertwig.)  In  I.  the  polar  spindle  (sp)  has 
advanced  to  the  surface  of  the  egg.  In  n.  a  small  elevation  (rk)  is  formed  which  receives  a  half  of  the 
spindle.  In  in.  the  elevation  is  constricted  off,  forming  a  polar  body  [rk').  Out  of  the  remaining  half  of 
the  previous  spindle  a  second  complete  spindle  (sp)  has  arisen.  In  iv.  is  seen  a  second  elevation,  which  in 
v.  has  become  constricted  off  as  the  second  polar  body.  Out  of  the  remainder  of  the  spindle  (iv.)  is  developed 
the  female  pronucleus. 

FERTILIZATION    AND    SEGMENTATION    OF    THE    OVUM. 

The  first  changes  in  the  ovum  which  take  place  at  the  time  of  conception 
are  as  follows : 

1.  Impregnation. — One,  or  perhaps  more,  spermatozoa  penetrate  the  zona 
pellucida  and  are  contained  in  the  perivitelline  fluid.     A  single   spermatozoon, 


r^ m.  pr. 


f.pr 


f.pr. 


r    ^^m^- 


f.  Pi- 


Fig.  690.— Fertilization  of  the  ovum  of  an  echinoderm.  s.  Spermatozoon,  m.  pr.  Male  pronucleus,  f.pr. 
Female  pronucleus.  1.  Accession  of  a  spermatozoon  to  the  periphery  of  the  vitellus.  2.  Its  penetration.  3. 
Transformation  of  the  head  of  the  spermatozoon  into  the  male  pronucleus.  4,  5.  Blending  of  the  male  and 
female  pronuclei.    (From  Quain's  Anatomy,  Selenka.j 

more  advanced  than  the  rest,  becomes  buried  in  the  yolk,  the  tail  disappears, 
and  the  head  constitutes  the  male  pronucleus.  This  gradually  approaches  the 
female  pronucleus,  and  ultimately  the  two  pronuclei  come  into  contact  and  fuse 
to  form  a  new  nucleus,  containing  both  male  and  female  elements,  and  named 
the  segmentation  or  cleavage  nucleus,  and  the  whole  cell  thus  modified  is  called 
the  blastosphere  (Fig.  690).  It  seems  as  if  this  normally  occurs  in  the  Fallopian 
tube,1  but  it  is  possible  that  it  sometimes  takes  place  before  the  ovum  has  entered 

1  Many  physiologists,  as  Bischoff  and  Dr.  M.  Barry,  taught  that  the  ovum  is  fecundated  in  the 
ovary,  but  the  reasoning  of  Dr.  Allen  Thomson  appears  very  cogent  in  proving  that  the  usual  spot 
at  which  the  spermatozoa  meet  the  ovum  is  in  the  tube,  down  which  it  slowly  travels  to  the  uterus, 
in  its  course  becoming  surrounded  by  an  albuminous  envelope  derived  from  the  walls  of  the  tube. 


1152 


EMBRYOLOGY. 


the  tube,  or  even  after  it  has  passed  through  the  tube  and  reached  the  cavity  of 
the  uterus ;   abnormally  it  may  take  place  in  the  peritoneal  cavity. 

2.  Segmentation. — The  first  result  of  fertilization  is  a  cleavage  or  subdivision 
of  the  ovum,  which  is  first  cleft  into  two  masses,  the  segmentation  nucleus  having 


Fig.  691.— First  stages  of  segmentation  of  a  mammalian  ovum :  semi-diagrammatic.  (From  a  drawing  by- 
Allen  Thomson.)  z.p.  Zona  pellucida.  p.  gl.  Polar  globules,  u.  Epiblastic  cell.  I.  Hypoplastic  cell.  a. 
Division  into  two  spheres.  6.  Stage  of  four  spheres,  c.  Eight  spheres,  the  epiblastic  cells  partially  enclosing 
the  hypoplastic  cells,  d,  e.  Succeeding  stages  of  segmentation,  showing  the  more  rapid  division  of  the  epi- 
blastic cells  and  the  enclosure  of  the  hypoblastic  cells  by  them. 

previously  split  up  into  two ;  so  that  it  now  consists  of  two  separate  masses  of 
protoplasm,  each  containing  a  nucleus,  and  situated  within  the  original  zona 
pellucida,  which  takes  no  part  in   this  process  of  division.     Then,  each  of  these 


Fig.  692.— Ovum  of  the  rabbit  at  the  end  of  the  process  of  segmentation,  oc.  Primitive  epiblast.  ic.  Primi- 
tive hypoblast,  bp.  Place  where  the  epiblast  has  not  yet  grown  over  the  hypoblast.  (From  Balfour,  after  Ed- 
van  Beneden.) 


two  divides  in  like  manner,  and  thus  four  are  formed,  and  so  on,  until  at  length 
a  mulberry-like  agglomeration  of  nucleated  masses  of  protoplasm  results  (Fig. 
691).     These  masses  are  sometimes  termed  vitelline  spheres. 

The  manner  in  which  segmentation  occurs  is  somewhat  peculiar.  The  two 
cells  resulting  from  the  first  cleavage  are  of  unequal  size.  One,  which  for  the  sake 
of  distinction  may  be  called  the  upper,  is  slightly  larger  and  paler  than  the  other, 
or  lower.  After  they  have  subdivided  three  or  four  times  the  rate  of  cleavage  in 
the  cells  derived  from  the  upper  becomes  more  rapid  than  that  in  the  cells  derived 
from  the  lower.     In  addition,  the  upper  cells  have  a  tendency  to  spread  over  and 


THE    OVUM. 


1153 


enclose  the  lower  cells,  so  that  by  the  ninth  or  tenth  division  there  is  an  external 
layer  of  pale  cells  enclosing  a  mass  of  slightly  smaller,  more  opaque  cells,  which, 
in  consequence   of  their  diminished  rate  of  cleavage,  are   fewer  in   number  (Fig. 


Blastodermic  vesicle. 


Inner  mass  of  cells. 

;  Hypoblast. 


Bauber's  layer. 


Fig.  693. 


-Blastodermic  vesicle  of  Vespertilio  murinus.    (After  Van  .Beneden.)     (Reduced  from  a  drawing  in 
the  Anatomischer  Anzeiger,  xvi.  Band,  Sept.  8,  1899.) 


692).  Fluid  collects  between  the  two  sets  of  cells,  except  at  one  part,  termed 
the  embryonal  pole,  so  that  a  vesicle,  the  blastodermic  vesicle,  is  formed.  This 
vesicle  consists  of  an  outer  layer  of  cells,  termed  Rauber's  layer,  derived  from  the 


Commencing  amniotic  cavity. 

Bauber's  layer. 


Hypoblast. 


Epiblast. 


Fig.  694.— Section  through  embryonic  area  of  Vespertilio  murinus.     (After  Van  Beneden.)    (Reduced  from  a 
drawing  in  the  Anatomischer  Anzeiger,  xvi.  Band,  Sept.  8, 1899.) 

subdivision  of  the  primary  upper  cell,  enclosing  at  the  embryonal  area  an  inner 
mass  of  cells  (Fig.  698)  resulting  from  the  cleavage  of  the  primary  lower  cell. 
Rauber's  layer  takes  no  share  in  the  formation  of  the  embryo  proper,  which  is 
entirely  developed  from   the  inner  mass  of  cells.     The   deepest  cells  of  this  mass 


Amniotic  cavity. 


Bauber's 


.  j  Plasmodioblast 

l<fer  {      and  cytoblast. 
Epiblast. 


Epiblast.         Hypoblast. 

Fig.  695.— Section  through  embryonic  area  of  Vespertilio  murinus  (after  Van  Beneden),  to  show  the  forma- 
ion  of  the  amniotic  cavity.      (Reduced  from  a  drawing  in  the  Anastomischer  Anzeiger,  xvi.  Band,  Sept.  8,  1899.) 


tion 


become  differentiated  as  a  layer  of  flattened  cells,  termed  the  hypoblast,  which 
spreads  outward  beneath  Rauber's  layer.  The  latter,  by  subdivision  of  the  cells 
of  its  upper  hemisphere,  is  differentiated  into  two  strata,  the  outer  of  which 
becomes  rapidly  thickened  and  forms  a  plasmodioblast  (i.  e.,  a  mass  of  protoplasm 
containing  numerous  nuclei,  but  not  subdivided  into  individual  cells  by  means  of 
73 


1154 


EMBRYOLOGY. 


arg 


Fig.  696. — Embryo  of  a  rabbit  of 
eight  days.  (After  Kolliker.)  arg. 
Embryonic  area.  pr.  Primitive 
streak. 


cell-walls)  ;  the  inner  layer  assumes  the  form  of  a  prismatic  epithelium,  and  is 
named  the  cytoblast  (Fig.  695).  These  two  layers  form  the  ectoplacenta  or 
chorion,  and  entirely  replace  the  lining  epithelium  of  the  uterus  where  the  blasto- 
dermic vesicle  comes  into  contact  with  it.  According  to  Van  Beneden,  the  ceils 
of  the  inner  mass  partly  undergo  atrophy  (Fig.  694),  giving  rise  to  a  cavity, 
limited  above  by  the  cytoblast  and  below  by  a  layer  of  cells,  which  constitutes  the 
primitive  upper  layer  of  the  embryo,  the  epiblast  or  ectoderm,  and  which  is  con- 
tinuous peripherally  with  the  cytoblast.      The  cavity  thus  formed  is  the  primitive 

amniotic  cavity,  and  becomes  the  permanent  amniotic 
cavity  in  man  and  monkeys,  and  in  some  of  the  bats 
(Fig.  695).  It  will  thus  be  seen  that  from  the  inner 
mass  of  cells  two  layers  are  formed — an  outer  of  pris- 
matic cells,  the  epiblast  or  ectoderm,  and  an  inner  of 
flattened  cells,  the  hypoblast  or  entoderm — and  this 
double  layer  constitutes  the  blastodermic  membrane, 
which  at  this  stage  is  bilaminar.1 

3.  Formation  of  the  Mesoblast. — At  first  the  area 
of  the  blastodermic  membrane  assumes  the  form  of  a 
small  disk,  the  germinal  disk  or  germinal  area.  This 
disk  becomes  oval  in  shape,  with  its  more  pointed  end 
situated  posteriorly.  In  it  the  first  traces  of  the 
embryo  are  seen  as  a  faint  streak,  the  primitive 
streak  (Fig.  696),  which  makes  its  appearance  at 
the  posterior  or  narroAv  end  of  the  oval  disk  and 
from  there  gradually  extends  forward.  The  epiblast  covering  the  primitive  streak 
becomes  indented  by  a  groove,   the  primitive  groove,  the  anterior  end  of   which 

communicates  through  a  canal 
with  the  yolk-sac,  forming  what  is 
termed  the  blastopore.  The  prim- 
itive streak  results  from  a  multi- 
plication of  the  cells  of  the  epi- 
blast, so  that  it  becomes  thickened 
and  grows  downward  toward  the 
hypoblast,  which  also  undergoes 
proliferation.  Together  they  form 
a  thick  cellular  column,  in  which 
it  is  no  longer  possible  to  distin- 
guish the  epiblastic  from  the  hypo- 
blastic  cells.  From  the  sides  of 
this  column  a  layer  of  cells  grows 
out  between  the  epiblast  and  hypo- 
blast, having  been  derived  partly 
from  both ;  this  layer  constitutes 
the  mesoblast  or  mesoderm. 

In  this  way  the  blastodermic 
membrane  comes  to  consist  of  three 
layers,  and  is  now  known  as  the 
trilaminar  blastoderm.  Each  layer 
has  distinctive  characters,  the  outer 
and  inner  presenting  the  ap-i 
pearance  of  epithelial  cells,  while) 
the  middle  consists  of  a  mass  of 
branched  cells  without  any  definite  arrangement.  The  external  is  termed  the 
epiblast,  or  ectoderm  ;  the  internal  the  hypoblast,  or  entoderm ;  and  the  middle, 
the  mesoblast,  or  mesoderm  (Fig.  698). 

1  Consult,  in  this  connection,  articles  by  Van  Beneden   and  Kollmann,  Anatomischer  Anzeiqer, 
1899  and  1900. 


Fig.  697. — Embryonic  area  of  the  ovum  of  a  rabbit  at  the 
seventh  day.  ag.  Embryonic  area,  o  o.  Region  of  the  blas- 
todermic vesicle  immediately  surrounding  the  embryonic 
area.  pr.  Primitive  streak.  *  rf.  Medullary  groove.  (From 
Kolliker.) 


THE   EMBRYO. 


1155 


The  epiblast  consists  of  a  layer  of  columnar  epithelial  cells,  which,  however, 
are  somewhat  flattened  toward  the  circumference  of  the  germinal  disk.  It 
forms  the  whole  of  the  nervous  system  (central  and  peripheral),  the  epidermis  of 
the  skin,  the  hairs  and  nails,  the  lining  cells  of  the  sebaceous,  sweat,  and  mammary 
glands,,  the  enamel  of  the  teeth,  and  the  epithelial  lining  of  the  nasal  passage 
and  of  portions  of  the  mouth  and  pharynx. 

The  hypoblast  consists,  at  first,  of  flattened  epithelial  cells,  which  subsequently 
become  columnar  and  even  larger  than  those  of  the  epiblast.  It  forms  the  epithelial 
lining  of  the  whole  of  the  alimentary  canal  except  the  anus  and  part  of  the  mouth 
(which  are  developed  from  involutions  of  the  epiblast),  the  epithelial  lining  of  all 
the  glands  opening  into  the  alimentary  canal,  the  epithelium  of  the  Eustachian 
tube  and  tympanic  cavity,  and  of  the  trachea,  bronchial  tubes,  and  air-sacs  of  the 
lungs,  the  epithelium  of  the  bladder  and  urethra,  and  also  that  which  lines  the 
follicles  of  the  thyroid  and  thymus  glands.      The  endothelial  lining  of  the  heart, 


Fig.  698.— Section  across  the  anterior  part  of  the  medullary  groove  of  an  earlv  embrvo  of  the  guinea-pig. 
(By  Sehafer.  From  Quain's  Anatomy,  1890.)  Folds  of  epiblast  rising  up  on  either  side  of  the  middle  line,  and 
thus  bounding  the  medullary  groove,  mg.  Middle  of  medullary  groove,  hy.  Hypoblast,  which  is  in  contact 
with  the  medullary  epiblast  at  the  middle  of  the  groove,  but  is  elsewhere  separated  from  it  by  mesoblast,  m, 
which  has  burrowed  forward  between  the  two  primary  layers.  A  cleft  is  seen  in  the  mesoblast  on  either  side ; 
this  is  the  commencement  of  the  anterior  part  of  the  body-cavity. 

blood-vessels,  and  serous  cavities  is  also  of  hypoblastic  origin,  while  recent  obser- 
vations tend  to  show  that  the  primitive  red  blood-cells  are  derived  from  the  same 
source. 

The  mesoblast  consists  of  loosely  arranged  branched  cells,  which  are  sur- 
rounded by  a  considerable  amount  of  intercellular  fluid,  and  which  therefore 
may  be  considered  as  resembling  embryonic  connective  tissue.  All  the  other 
tissues  of  the  embryo  are  developed  from  it,  including  the  extra-endothelial 
portion  of  the  walls  of  the  blood-vessels,  the  skeleton  and  voluntary  muscles,  the 
connective  tissues,  the  spleen,  the  generative  and  urinary  organs  (except  the  epithe- 
lium of  the  bladder  and  urethra),  and  the  involuntary  muscles. 


FIRST  RUDIMENTS  OF  THE  EMBRYO. 

The  primitive  streak  alluded  to  above  is  a  very  transitory  structure,  which 
merely  marks  the  direction  of  the  embryonic  axis,  the  embryo  proper  being 
developed  immediately  in  front  of  it  in  the  following  manner  (Figs.  697  and 
701): 

First,  two  longitudinal  ridges,  caused  by  a  looping  or  folding  up  of  the  epiblast, 
appear,  one  on  either  side  of  the  middle  line.  These  commence  in  the  anterior  part 
of  the  area  germinativa,  where  they  are  united,  and  extend  backward,  one  on  either 
side  of  the  primitive  streak,  gradually  enclosing  it,  and  thus  converting  the 
blastopore  into  the  neurenteric  canal.  This  folding  up  of  the  epiblast  gives  rise 
to  a  longitudinal  groove,  the  medullar)/  or  neural  groove  (Figs.  697  and  698), 
in  consequence  of  the  manner  in  which'  the  cells  of  the  epiblast  are  heaped  up  into 
two  longitudinal  ridges,  with  a  furrow  between  them  so  that  the  sides  and  floor  of 
the  groove  are  formed  of  epiblastic  cells  (Fig.  698).  The  mesoblast  fills  up  the 
space  between  the  epiblast  and  hypoblast,  so  that  the  sides  of  the  groove  are  occu- 
pied by  a  longitudinal    thickening   of  mesoblast ;    the   two  longitudinal  thicken- 


1156 


EMBRYOLOGY. 


ings  of  mesoblast  being  at  first  separated  at  the  bottom  of  the  groove  by  the  junc- 
tion of  the  epiblast  and  hypoblast  (Fig.  698).  The  groove  becomes  deeper 
in  consequence    of  the    further   growing    up  of  the    cells   to  form    the   ridge  on 

either  side.  In  this  way  the  ridges  eventually  be- 
come two  plates,  the  lamince  dorsales  or  medullary 
plates,  which  finally  coalesce  and  form  a  closed  tube, 
the  neural  canal,  which  is  lined  and  covered  by 
epiblast  (Figs.  699  and  700).  These  lining  and 
covering  layers  of  epiblast  are  at  first  in  contact 
with  one  another,  but  eventually  become  separated 
by  mesoblast  which  grows  up  between  them.  The 
coalescence  of  the  medullary  plates  first  takes  place 
in  the  region  of  the  future  hind-brain  of  the  embryo, 
and  then  extends  toward  the  cephalic  and  caudal 
ends.  The  posterior  extremity  presents  a  rhom- 
boidal  appearance  before  the  laminse  close  ;  this  has 
been  termed  the  sinus  rhomboidalis  (Fig.  701). 
The  epiblast  which  lines  the  neural  canal  is  devel- 
oped into  the  nervous  centres,  that  which  covers  the 
canal  into  the  epidermis  of  the  back  and  head.  The 
cephalic  extremity  of  the  neural  canal  is  scon  seen 
to  be  more  dilated  than  the  rest,  and  to  present 
restrictions  dividing  it  imperfectly  into  three 
chambers  :  the  brain  is  developed  from  this  dilated 
portion  ;  the  spinal  cord  takes  its  origin  from  the 
remainder  of  the  tube.  Below  the  neural  canal,  in 
front  of  the  internal  opening  of  the  blastopore,  a 
longitudinal  groove  forms  in  the  hypoblast ;  this 
groove  becomes  closed  off  from  the  roof  of  the  future 
enteron  and  forms  a  rod  of  cells  which  lies  between 
the  hypoblast  and  the  neural  canal.  This  rod  of 
cells  is  known  as  the  notochord  or  chorda  dorsalis, 
and  when  fully  developed  is  composed  of  clear  epi- 
thelium-like cells  enclosed  in  a  homogeneous  sheath 
( Fig.  700 ).  It  is  essentially  an  embryonic  structure,  though  traces  of  it  remain  in  the 
centre  of  the  intervertebral  disks  throughout  life.  The  collection  of  mesoblastic  cells, 
which  forms  a  thick  longitudinal  column  on  either  side  of  the  neural  canal,  is  termed 
the  paraxial  mesoblast.  as  distinguished  from  the  outer  or  lateral  part  of  the  meso- 


Fig.  699.  —  Transverse  sections 
through  the  embryo  chick,  before  and 
some  time  after  the  closure  of  the 
medullary  canal,  to  show  the  upward 
and  downward  inflections  of  the 
blastoderm.  (After  Eemak.)  a.  At  the 
end  of  the  first  day.  l.  Notochord.  2. 
Primitive  groove  in  the  medullary 
canal.  3.  Edge  of  the  dorsal  lamina. 
4.  Corneous  layer  or  epiblast.  5.  Meso- 
blast divided"  in  its  inner  part.  6. 
Hypoblast  or  epithelial  layer.  7.  Sec- 
tion of  protovertebral  plate.  B.  On 
the  third  day  in  the  lumbar  region. 
1.  Notochord  in  its  sheath.  2.  Medul- 
lary canal  now  closed  in.  3.  Section 
of  "the  medullary  substance  of  the 
spinal  cord.  4.  Corneous  layer.  5. 
Somatopleure  of  the  mesoblast.  5'. 
Splanchnopleure(one  figure  is  placed  in 
the  pleuro-peritoneal  cavity).  6.  Layers 
of  hypoblast  in  the  intestines  spreading 
also" over  the  yolk.  4  <  5.  Part  of  the 
fold  of  the  amnion  formed  by  epiblast 
and  somatopleure. 


Neural  canal. 


Epiblast. 


Plev.ro- 
Proto-     Wolffian  peritoneal 
vertebra,    duct.       cavity. 


Hypoblast. 


Notochord.  Aorta.  Splanchnopleure. 

Fig.  700. — Section  across  the  dorsal  part  of  a  chick  embryo  of  forty-five  hours'  incubation.     (Balfour.) 

blastic  layer.  The  paraxial  mesoblast  undergoes  a  series  of  transverse  segmenta 
tions  and  becomes  converted  into  a  row  of  well-defined,  dark,  square  segments  or 
masses,  the  protovertebrce  or  mesoblastic  somites,  separated  by  clear,  transverse- 
intervals  (Figs.  700  and  701).  They  first  make  their  appearance  in  the  region 
which  afterward  becomes  the  neck,  and  from   there   extend  backward   along  the 


THE    EMBRYO. 


1157 


entire  length  of  the  trunk.  These  bodies,  as  will  be  explained  hereafter,  are  not 
the  representatives  of  the  permanent  vertebrae,  but  are  differentiated,  partly  into 
the  vertebrae  and  partly  into  the  muscles  and  true  skin.  On  either  side  of  the 
proto vertebrae  the  lateral  mesoblast  splits  into  two  layers;  the  upper  becomes 
applied  to  the  epiblast,  forming  with  it  the  somatopleure  or  body  wall,  while  the 
lower  becomes  attached  to  the  hypoblast  and  with  it  forms  the  splanchnopleure  or 
wall  of  the  alimentary  tube  (Fig.'  699).     The  space  between  them  is  the  cesium  or 


Head  fold  of  amnion. 

Forebrain. 

Optic  reside. 


Midbrain. 

Hindbrain 


Auditory  vesicle.  ---. 


Medullary  ridge. 


-Heart. 


Omphalo-mesenteric  rein. 

■■  1  Protovertebrse  or 

.  j      mesoblastic  somites. 


*,*  M    .,g;» >is  rhomboidalis. 


Remains  of  primitive 
streak. 


Fig.  701,-Chick  embryo  of  thirty-three  hours'  incubation,  viewed  from  the  dorsal  aspect :  X  30.    'From 

Duval's  Atlas  d' Embryologie.) 


pleuro-peritoneal  cavity  (Fig.  700).  While  the  panetes  of  the  body  are  still 
unclosed,  this  cavity  is  continuous  with  the  space  between  the  amnion  and  chorion. 
as  seen  in  Fio-.  705*  The  embrvo.  which  at  first  seems  to  be  a  mere  streak,  ex- 
tends loncritudinallv  and  laterally.      As  its  grows  forward  the  cephalic  end  becomes 


1158 


EMBRYOLOGY. 


remarkably  curved  on  itself  (cephalic  flexure),  and  a  smaller  but  similar  folding- 
over  takes  place  at  its  hinder  end  (caudal  flexure).  At  the  same  time  the  sides  of 
the  embryo,  formed  by  the  somatopleure,  grow  and  curve  ventrally  toward  each 
other,  so  that  the  embryo  at  this  stage  is  aptly  compared  to  a  canoe  turned  over, 
and  becomes  marked  off  from  the  general  blastoderm  by  a  limiting  sulcus.  In 
consequence  of  this  incurving  of  the  embryo,  both  in  an  antero-posterior  and  a. 
lateral  direction,  the  blastodermic  vesicle  becomes  nipped  by  the  somatopleure  and 
resembles  an  hour-glass  with  two  unequal  parts.  The  smaller  portion  is  enclosed 
within  the  body  of  the  embryo,  and  constitutes  the  enteron  or  primitive  alimentary 
canal,  while  the  larger  portion,  left  outside  the  embryo,  is  termed  the  yolk-sac  or 
umbilical  vesicle.  These  two  parts  of  the  original  blastodermic  vesicle  communicate 
through  the  constricted  portion,  which   is  the  site  of  the  future  umbilicus,  and,. 


Fig.  703.— Diagrammatic  action  through  the  ovum  of  a  mammal  in  the  long  axis  of  the  embryo,  e.  The 
cranio- vertebral  axis,  i,  i.  The  cephalic  and  caudal  portions  of  the  primitive  alimentary  canal,  a.  The  amnion. 
a'.  The  point  of  reflection  into  the  false  amnion,  v.  Yolk-sac,  commnnicating  with  the  middle  part  of  the 
intestine  by  v  i,  the  vitello-intestinal  duct.  u.  The  allantois.  The  ovum  is  surrounded  externally  by  the  vil- 
lous chorion. 


when  the  body  cavity  is  ultimately  closed  at  the  umbilicus,  the  constriction  is 
narrowed  to  form  a  small  duct,  the  omphalo-mesenteric  or  vitelline  duct  (Figs.  702, 
703,  and  705).  The  cephalic  part  of  the  primitive  alimentary  canal  is  named  the 
fore-gut,  the  caudal  portion  the  hind-gut,  while  the  intermediate  portion  which 
communicates  directly  with  the  yolk-sac,  is  termed  the  mid-gut.  The  yolk-sac  is 
of  small  importance  and  very  temporary  duration  in  the  human  subject.  It  is  for 
the  purpose  of  supplying  nutrition  to  the  embryo  during  the  very  earliest  period 
of  its  existence.  In  the  oviparous  animals,  however,  where  no  supply  of  nourish- 
ment can  be  obtained  from  the  mother,  since  the  egg  is  entirely  separated  from 
her,  the  yolk-sac  is  large  and  of  great  importance,  as  it  supplies  nutrition  to  the 
chick  during  the  whole  of  foetation.  Vessels  developed  in  the  mesoblast  soon 
cover  the  yolk-sac,  forming  the  vascular  area ;  these  are  named  the  omphalo- 
mesenteric vessels,  and  are  two  in  number  (Fig.  704).  They  appear  to  absorb  the 
fluid  of  the  yolk-sac  which,  when  the  fluid  has  disappeared,  dries  up  and  has  no 
further  function.  The  activity  of  the  yolk-sac  ceases  about  the  fifth  or  sixth  week, 
at  the  same  time  that  the  allantois,  which  is  the  great  bond  of  vascular  connection 
between  the  embryo  and  the  uterine  tissues,  is  formed.  The  yolk-sac  remains 
visible,  however,  up  to  the  fourth  or  fifth  month,  with  its  pedicle  and  the  omphalo- 


'•«/  h.af 

da 


at  f     m 


Fig.  702. — Diagrams    to    illustrate    the  .development    of  the 

embryo  with  its  yolk-sac,  amnion,  and  allantois. 

(From  Hertwig's  'Embryology.') 

a.  External  germinal  layer,  mw.  Medullary  groove.  N.  Neutral  canal,  af.  Amnion  fold.  oaf. 
Anterior,  haf.  Posterior,  saf.  Lateral  amniotic  folds.  A.  Amnion,  ah.  Amniotic  cavity.  S.  Serous 
covering,  hn.  Umbilicus,  sf.  Lateral  folds.  kf\kf-.  Head  fold.  a/6.  External,  ifb.  Internal  layers 
of  amnion,  ur.  Border  of  embryonic  area.  dr.  Intestinal  groove,  dg.  Vitelline  duct.  al.  Allantois. 
ds.  Vitellus.  dn.  Intestinal  portion  of  umbilicus,  mk.  Middle  germinal  layer.  ink1.  Parietal  leaf 
of  mesoderm,  mk".  Visceral  leaf  of  mesoderm,  sf,.  Sinus  terminal  is.  dm.  Dorsal,  vm.  Ventral  mes- 
enterium.  Ih.  Somatic  cavity.  lhl.  Embryonal  portion.  Hi".  Extra-embryonal  portion  of  somatic 
cavity.  Figs.  1,  2,  6,  8,  9,  and  10  transections.  Figs.  3,  4,  5,  7,  and  U  long-sections  of  embryo.  Figs. 
1,  2,  3,  4,  and  5  chick  embryo.     Fig.  6  fish  embryo.     Figs.  7  and  11  selachian  embryo. 


THE   EMBRYO. 


1159 


mesenteric  vessels.     The  latter  vessels  become  atrophied  as  the  functional  activity 
of  the  body  with  which  they  are  connected  ceases. 

So  far  we  have  traced :  (1)  the  segmentation  or  cleavage  of  the  ovum  and  the 
formation  of  a  blastodermic  vesicle,  consisting  of  (a)  an  external  envelope,  and 
(I))  an  internal  mass  of  cells  applied  to  it  at  the  embryonal  pole,  but  separated 
elsewhere  by  an  albuminous  fluid.  (2)  The  separation  of  the  hypoblast  from  the 
inner  surface  of  this  internal  mass  and  its  extension  as  a  lining  to  the  external 
envelope.  (3)  The  development  of  the  epiblast,  also  from  the  internal  mass  of 
cells,  absorption  taking  place  between  it  and  the  external  layer  to  form  a  cavity. 
the  primitive  amniotic  cavity.  (4)  The  formation  of  an  oval-shaped  disk,  the 
germinal  disk,  and  the  appearance  of  the  primitive  streak  at  its  posterior  end. 


Fig.  704.— Magnified  view  of  the  human  embryo  of  four  weeks,  with  the  membranes  opened.  (From  I.eish- 
man,  after  Coste.)  y.  The  umbilical  vesicle  with  the  omphalo-mesenteric  vessels,  v,  and  its  long  tubular  attach- 
ment to  the  intestine,  c.  The  villi  of  the  chorion,  m.  The  amnion  opened,  u.  O'ul-de-sne  of  the  allantois,  and  on 
each  side  of  this  the  umbilical  vessels  passing  out  to  the  chorion.  In  the  embryo:  a.  The  eye.  e.  The  ear- 
vesicle,  h.  The  heart.  I.  The  liver,  o.  The  upper  ;  p,  the  lower  limb,  w.  Wolffian  body,  in  front  of  which  are 
the  mesentery  and  fold  of  intestine.    The  Wolffian  duct  and  tubes  are  not  represented. 


(5)  The  development  of  the  mesoblast  from  the  primitive  streak  and  its  extension 
between  the  epiblast  and  mesoblast.  (6)  The  formation  of  the  "neural  groove" 
in  front  of  this  primitive  streak,  caused  by  the  growing-up  of  the  epiblast  on  either 
side  of  it,  so  as  to  form  two  longitudinal  ridges,  called  the  "laminae  dorsales." 
(7)  The  increase  and  incurvation  of  these  laminse  dorsales,  until  they  meet  dorsally 
and  enclose  the  "neural  canal,"  from  the  epiblastic  lining  of  which  the  nervous 
centres  are  developed.  (8)  The  formation,  from  the  hypoblast  immediately 
under  the  canal,  of  a  continuous  rod  of  cells,  the  "  cauda  dorsalis"  or  "  noto- 
chord."  (9)  The  formation,  from  the  paraxial  mesoblast,  on  either  side  of  the 
notochord,  of  a  number  of  square  segments,  the  "  pro  to  vertebras  "  or  "  meso- 
blastic   somites."       (10)  The   splitting   of  the  lateral   mesoblast  into   two  layers 


1160 


EMBRYOLOGY. 


to  form  the  "  somatopleure "  and  "  splanchnopleure,"  the  space  between  the 
two  constituting  the  "  ccelum  "  or  "  pleuro-peritoneal  cavity."  (11)  The  curving 
of  the  embryo  on  itself,  both  longitudinally  and  laterally,  so  as  to  be  comparable 
to  a  canoe,  part  of  the  blastodermic  vesicle  being  enclosed  within  the  embryo  to 
form  the  "primitive  alimentary  tube,"  part  being  left  outside  as  the  "yolk-sac," 
the  two  communicating  by  a  duct,  the  "  omphalo-mesenteric  "  duct.  The  yolk-sac 
provides  nutrition  to  the  embryo  through  the  omphalo-mesenteric  vessels  until  such 
time  as  the  placenta  is  formed. 

FORMATION    OF    MEMBRANES. 

In  order  to  have  a  clear  understanding  of  the  manner  in  which  the  embryo  is 
developed,  it  is  necessary  at  this  stage  to  describe  the  development  of  the  foetal 
membranes. 

The  membranes  investing  the  foetus  are  the  amnion,  the  chorion,  and  the 
decidua.  The  first  two  are  developed  from  foetal  structures,  and  are  proper  to 
the  foetus ;  the  last  is  formed  in  the  uterus,  and  is  derived  from  the  maternal 
structures. 

The  Amnion. — The  amnion  is  the  innermost  of  the  membranes  which  surround 
the  embryo.  It  is  at  first  of  small  size,  but  increases  considerably  toward  the 
middle  of  pregnancy,  as  the  foetus  acquires  the  power  of  independent  movement. 
It  exists  only  in  reptiles,  birds,  and  mammals,  which  are  hence  called  "  Amniota," 
but  is  absent  in  amphibia  and  fishes.  In  man,  monkeys,  and  some  of  the  bats, 
the  primitive  amniotic  cavity,  already  described  on  page  1154,  persists.  In  reptiles, 
birds,  and  certain  mammals  the  amnion  is  formed  in  the  following  manner.     At  or 


False  amnion  or  chorion 


Villi  of 
chorion 


Fig.  705. — Diagram  of  a  transverse  section  of  a  mammalian  embryo,  showing  the  mode  of  formation  of  the 
amnion.  The  amniotic  folds  have  nearly  united  in  the  middle  line.  (From  Quain's  Anatomy,  vol.  i.  pt.  i. 
1890.)    Epiblast, ;  mesoblast, ;  hypoblast  and  notochord,  continuous  line. 


near  the  extremities  of  the  incurved  foetus — that  is  to  say,  at  the  point  of  constric- 
tion of  the  blastodermic  vesicle  where  the  primitive  alimentary  caial  of  the  embryo 
joins  the  yolk-sac — a  reflection  or  folding  backward  of  the  somatopleure,  which 
has  become  separated  from  the  splanchnopleure  by  the  formation  of  the  pleuro- 
peritoneal  cavity,  takes  place  (Fig.  702,  2,  3).  This  fold  commences  first  at  the 
cephalic  extremity,  and  subsequently  at  the  caudal  end  and  sides,  and  deepens 
more  and  more,  in  consequence  of  the  sinking  of  the  embiyo  into  the  blasto- 
dermic vesicle,  until,  gradually  approaching,  the  different  parts  meet  on  the 
dorsal  aspect  of  the  embryo  (Figs.  702,  10,  and  705).     After  they  come  in  contact 


FORMATION   OF  MEMBRANES. 


1161 


they  fuse  together,  and  the  septum  between  them  disappears;  so  that  the 
inner  layer  of  the  cephalic  fold  becomes  continuous  with  the  inner  layer  of 
the  caudal  and  lateral  folds,  and  the  outer  with  the  outer.  Thus  we  have  two 
membranes,  one  formed  by  the  inner  layer  of  the  fold — the  true  amnion — which 
encloses  a  space  over  the  back  of  the  embryo  — the  amniotic  cavity  (Fig.  702,  4,  5) — 
containing  a  clear  fluid,  the  liquor  amnii.  The  other,  the  outer  layer  of  the  fold 
— the  false  amnion — lines  the  internal  surface  of  the  original  zona  pellucida. 
Between  the  two  is  an  interval,  which  of  course  communicates  with  the  pleuro- 
peritoneal  cavity  until  the  body-walls  of  the  embryo  have  coalesced  at  the  umbili- 
cus. Then  the  amniotic  fold  is  carried  downward,  and  encloses  the  umbilical 
cord,  by  which  the  foetus  is  attached  to  the  placenta.  The  true  amnion — 
or,  as  it  is  usually  called,  the  amnion — is  formed  of  two  layers,  inner  and  outer, 
derived  respectively  from  the  epiblast  and  from  the  parietal  layer  of  the  meso- 
blast. 

The  amnion  is  at  first  in  close  contact  with  the  surface  of  the  body  of  the 
embryo,  but  about  the  fourth  or  fifth  week  fluid  begins  to  accumulate,  and  thus 
separates  the  two.  The  quantity  of  fluid  steadily  increases  up  to  about  the  sixth 
month  of  pregnancy,  after  which  it  diminishes  somewhat.  The  use  of  the  liquor 
amnii  is  believed  to  be  chiefly  to  allow  of  the  movements  of  the  foetus  in  the  later 
stages  of  pregnancy,  though  it  no  doubt  serves  other  purposes.  It  contains  about 
1  per  cent,  of  solid  matter,  chiefly  albumen,  with  traces  of  urea,  the  latter  prob- 
ably derived  from  the  urinary  secretion  of  the  foetus. 


Fig.  706— Transverse  section  through  the  dorsal  region  of  an  embryo  chick,  end  of  third  day.  (From  I  oster 
and  Balfour.)  Am.  Amnion,  mp.  Muscle-plate,  cv.  Cardinal  vein.  Ao.  Dorsal  aorta,  at  the  point  where  its 
two  roots  begin  to  join.  Ch.  Notochord.  Wd.  Wolffian  duct.  Wb.  Commencement  of  formation  of  \\ollhau 
body.  ep.  Epiblast.  So.  Somatopleure.  Hy.  Hypoblast.  The  section  passes  through  the  place  where  the  ali- 
mentary canal  (hy)  communicates  with  the  yolk-sac.    Sp.  Splanchnopleure. 


The  Chorion. — The  chorion  takes  its  origin,  as  has  already  been  seen  (page  1154), 
from  the  external  covering  of  the  blastodermic,  vesicle  the  cells  of  the  decidua  or 
uterine  mucous  membrane  contributing  no  elements  to  it.  From  its  outer  surface 
numerous  finger-like  processes,  termed  the  villi  of  the  chorion,  project.  These 
increase  rapidly  in  size  and  at  the  same  time  undergo  great  ramification  :  hence 
they  were  likened  by  Dalton  to  tufts  of  seaweed  (Figs.  705  and  708). 


Thev 


mva 


do 


1162  EMBB  YOL  OGY. 

the  decidua  of  the  uterus  and  probably  absorb  from  it  nutritive  materials  for 
the  growth  of  the  embryo  :  they  can  be  forcibly  withdrawn  from  the  decidua 
until  the  third  month  of  pregnancy.  Until  about  the  end  of  the  second  month 
the  villi  cover  the  Avhole  surface  of  the  chorion  and  are  of  an  almost  uniform 
size,  but  after  this  they  develop  unequally.  On  that  part  which  invades  the 
decidua  serotina  they  increase  greatly  in  size  and  complexity,  and  constitute  the 
chorion  frqndg'sum,  which  becomes  the  foetal  part  of  the  placenta  (Fig.  708). 
Over  the  remainder  of  the  chorion  they  undergo  atrophy,  so  that  by  the  fourth 
month  hardly  any  trace  of  them  is  left,  and  hence  this  part  becomes  smooth, 
and  is  therefore  named  the  chorion  losve.  The  chorionic  villi  are  at  first  non- 
vascular, but  subsequently  they  become  vascularized  by  the  growth  into  them 
of  the  allantoic  mesoblast,  which  carries  to  them  the  branches  of  the  allantoic 
arteries. 

The  Allantois. — The  allantois  grows  outward  as  a  hollow  bud  from  the  hind 
gut,  and  is  therefore  lined  by  hypoblast  and  covered  by  mesoblast  (Figs.  702,  4,  5, 
and  703).  It  is  projected  into  the  space  between  the  amnion  and  the  chorion, 
and  in  its  mesoblast  are  carried  a  pair  of  arteries,  the  allantoic  or  umbilical  arteries, 
which  are  continued  from  the  two  primary  aortse.  The  allantoic  mesoblast 
gradually  spreads  out  on  the  inner  surface  of  the  chorion,  and,  invading  the 
chorionic  villi,  supplies  them  with  blood-vessels.  In  this  way  the  allantois 
becomes  the  chief  agent  of  the  foetal  circulation,  since  it  carries  the  vessels  which 
convey  the  blood  of  the  embryo  to  the  chorion,  where  it  is  exposed  to  the  influence 
of  the  maternal  blood  circulating  in  the  decidua ;  from  the  maternal  blood  it 
imbibes  the  materials  of  nutrition  and  to  it  it  gives  up  effete  materials,  the  removal 
of  which  is  necessary  for  the  purification  of  the  foetal  blood.  In  some  animals  the 
allantois  is  a  hollow  projection,  and  is  usually  styled  the  allantoic  vesicle  ;  but  in 
most  mammals,  and  especially  in  man,  the  external  or  mesoblastic  element  under- 
goes great  development,  while  the  internal  or  hypoblastic  element  undergoes  little 
increase  beyond  the  body  of  the  embryo,  so  that  it  is  very  doubtful  whether  any 
cavity  exists  in  the  allantois  beyond  the  limits  of  the  umbilicus,  or  whether  it  does 
not  rather  consist  of  a  solid  mass  of  material  derived  from  the  mesoblastic  tissue.1 
The  proximal  part  of  the  allantoic  vesicle  within  the  body-cavity  is  eventually 
destined  to  form  the  bladder,  while  the  remainder  forms  an  impervious  cord,  the 
urachus,  stretching  from  the  summit  of  the  bladder  to  the  umbilicus.  The  part 
of  the  allantois  external  to  the  foetus  forms  the  umbilical  cord,  by  which  the 
foetus  is  connected  with  the  placenta. 

The  Decidua. — The  growth  of  the  chorion  and  placenta  can  be  understood  only 
by  tracing  the  formation  of  the  decidua. 

The  decidua  is  formed  from  the  uterine  mucous  membrane  before  the  fertilized 
ovum  reaches  the  cavity  of  the  uterus.  The  mucous  membrane  becomes  vascular 
and  tumid,  its  glands  are  greatly  elongated,  and  their  deeper  portions  are  dilated 
and  tortuous,  while  the  interglandular  tissue  becomes  crowded  with  epithelial- 
like  cells  (decidual  cells).  The  mucous  membrane,  thus  altered,  is  named  the 
decidua  vera ;  it  lines  the  cavity  of  the  uterus  as  far  as  the  os  internum,  without, 
however,  occluding  the  orifices  of  the  Fallopian  tubes.  When  the  fertilized  ovum 
reaches  the  uterus,  which  is  thus  prepared  for  its  reception,  it  becomes  attached 
to  the  decidua,  in  most  cases  in  the  neighborhood  of  the  fundus  uteri.  The  decidua 
then  grows  up  around  the  ovum  and  ultimately  covers  it  in.  The  part  of  the 
decidua  which  grows  up  to  envelop  the  ovum  is  named  the  decidua  reflexa  ;  that 
portion  to  Avhich  the  ovum  originally  became  attached  is  termed  the  decidua 
serotina,  and  from  it  the  maternal  part  of  the  placenta  is  derived.  After  concep- 
tion the  cervix  uteri  is  closed  by  a  plug  of  mucus  (Fig.  708). 

By  the  fourth  month  the  decidua  vera  has  acquired  a  thickness  of  about  half 

1  Indeed,  it  would  appear,  from  the  researches  of  His,  that  in  the  human  embryo  the  allantois  is 
formed  unusually  early,  being  present  from  a  very  early  period  as  a  stalk  of  mesoblast  connecting  the 
posterior  extremity  of  the  embryo  with  the  chorion.  This  stalk  is  termed  the  abdominal  stalk 
(Bauchstiel). 


FORMATION   OF  MEMBRANES. 


1163 


Mucous  membrane. 


Muscular  fibres. -- 


Stratum  compactum. 


>0*& 


Stratum  spongiosum.  -J 


an  inch,  and  consists  of  the  following  strata:  (1)  Stratum  compactum,  next  the 
free  surface,  in  which  the  uterine  glands 
are  little  altered  and  where  they  preserve 
a  comparatively  narrow  lumen  lined  by 
columnar  epithelium  ;  between  the  glands 
are  large  numbers  of  decidual  cells.  (2) 
Stratum  spongiosum,  in  which  the  gland 
tubes  are  very  tortuous  and  greatly  di- 
lated, while  their  lining  cells  are  flattened 
or  cubical.  (3)  Basal  layer,  next  the 
uterine  muscular  wall,  in  which  the  glands 
are  not  dilated  and  where  they  retain 
their  columnar  epithelium.  It  is  through 
this  basal  layer  that  the  placenta  is  sepa- 
rated after  the  birth  of  the  child  (Fig. 
707). 

The  decidua  reflexa  is  gradually  ex- 
panded by  the  growing  ovum,  and  ulti- 
mately comes  into  contact  and  blends 
with  the  decidua  vera  so  as  completely  to 
obliterate  the  uterine  cavity.  This  oblit- 
eration is  followed  by  the  degeneration  of 
the  deciduse ;  the  glands  of  the  decidua 
reflexa  become  atrophied,  and  the  entire 
decidua  practically  disappears,  while  the 
decidua  vera  is  much  thinned  and  its 
glands  also  disappear,  except  their  deepest 
portions,  which  persist  in  the  basal  layer. 

In  this  manner  the  embryo  becomes 
surrounded  by  three  membranes  :  (1)  the 
amnion,  derived,  in  the  case  of  reptiles, 
birds,  and  some  mammals,  from  the  outer 
layer  of  the  mesoblast  and  the  epiblast ; 
(2)  the  chorion,  formed  by  the  allantois 
(which  is  derived  from  the  hypoblast  and 
inner  layer  of  the  mesoblast)  and  the  false 
amnion ;  and  (3)  the  decidua,  derived 
from  the  mucous  membrane  of  the  uterus. 

Much  additional  interest  has  been 
given   to   the  physiology  of   the  decidua 

by  the  fact,  which  seems  to  be  now  established  by  the  researches  of  Sir  John 
Williams,  that  every  discharge  of  an  ovum,  whether  impregnated  or  not,  is.  as  a 
rule,  accompanied  by  the  formation  of  a  decidua,  and  that  the  essence  of  menstrua- 
tion consists  in  the  separation  of  a  decidual  layer  of  the  mucous  membrane  from 
the  uterus ;  while  in  the  case  of  pregnancy  there  is  no  exfoliation  of  the  mem- 
brane, but,  on  the  contrary,  it  undergoes  further  development  in  the  manner 
described  above. 

Formation  of  the  Placenta. — The  placenta  is  developed  partly  from  maternal 
and  partly  from  foetal  tissues — the  maternal  portion  being  derived  from  the  decidua 
serotina,  the  foetal  from  the  villi  of  the  chorion  frondosum.  These  villi  penetrate 
the  decidua  serotina,  which  then  undergoes  a  series  of  complicated  and.  as  yet, 
imperfectly  understood  changes.  Decidual  cells  accumulate  between  the  uterine 
glands,  while  the  glands  with  their  epithelial  lining  undergo  degeneration — a 
degeneration  which  does  not,  however,  extend  as  deep  as  the  basal  layer,  where 
the  glands  persist,  and  retain  their  epithelial  lining  throughout  the  entire  period 
of  gestation.  Ultimately  the  superficial  portion  of  the  decidual  tissue  disappears, 
and  the  uterine  vessels  become  expanded  to  form  a  labyrinth  of  freely  communi- 


Basal  layer.- 


Muscular  fibres.. 


Fig.  707. — Diagrammatic  sections  of  the  uterine 
mucous  membrane  :  (a)  of  the  non-pregnant  uterus  ; 
(b)  of  the  pregnant  uterus,  showing  the  thickened 
mucous  membrane  and  the  altered  condition  of  the 
uterine  glands. 


1164 


EMBRYOLOGY. 


eating  blood-channels  or  sinuses,  which  are  filled  with  maternal  blood,  and  in 
which  are  suspended  the  now  greatly  ramified  tufts  of  the  chorionic  villi.  These 
uterine  sinuses  anastomose  freely  Avith  one  another,  and  form,  at  the  edge  of  the 
placenta,  a  venous  channel  with  an  irregular  calibre,  which  runs  round  the  whole 
circumference  of  the  placenta,  and  is  termed  the  marginal  sinus.  Some  of  the 
chorionic  villi  are  attached  by  fibrous  bands  to  the  basal  layer  of  the  decidua  and 
to  the  imperfect  septa  between  the  sinuses,  but  the  majority  of  them  hang  free. 
Circulation  through  the  Placenta. — The    maternal    blood    is    brought  to  the 

Placental  villi  of  chorion  frondosum. 

Decidua  serotina. 

Fallopian  tube. 


Alia 


ntois. — \ — hEX| 


Umbilical  cord, 
with  its  con- — 
tained  vessels. 


"-Cavity  of  uterus. 


[ I^Decidua  vera. 


Decidua  reflexa.' 


J  Plug  of  mucus  in  the 
~]       neck  of  uterus. 


Fig.  708.— Sectional  plan  of  the  gravid  uterus  in  the  third  and  fourth  months.    (Modified  from  Wagner.) 


uterine  sinuses  by  the  "curling  arteries"  of  the  uterus  and  drained  away  by  the 
uterine  veins,  while,  as  already  stated,  within  the  chorionic  villi  are  found  the 
ramifications  of  the  foetal  vessels  derived  from  the  allantoic  or  umbilical  arteries. 
Since  the  villi  are  suspended  in  the  sinuses,  they  are  necessarily  bathed  in  the 
maternal  blood,  and  hence  it  follows  that  the  maternal  and  foetal  blood-currents 
are  brought  into  close  relationship.  There  is,  however,  no  intermingling  of  the 
tjvo  currents,  or,  in  other  words,  no  direct  communication  between  the  vascular 
svstem  of  the  mother  and  that  of  the  foetus,  the  interchange  of  materials  neces- 
sary for  the  growth  of  the  foetus  and  for  the  purification  of  the  foetal  blood  taking 
place  through  the  walls  of  the  villi.  The  purified  blood  is  carried  back  to  the 
foetus  by  the  umbilical  vein.  From  what  has  been  said,  it  will  be  understood  that 
the  placenta  is  the  organ  by  which  the  connection  between  the  foetus  and  the 
mother  is  established,  and  which  subserves  the  purposes  of  nutrition,  respiration, 
and  excretion. 

Placenta. — At  the  end  of  the  gestation  period  the  placenta  presents  the  form 
of  a  disk  which  weighs  about  a  pound  and  has  a  diameter  of  from  six  to  eight 
inches.  Its  average  thickness  is  about  an  inch  and  a  quarter,  but  diminishes  rap- 
idly near  the  circumference  of  the  disk.  Its  outer  or  decidual  surface  blends  with 
the  uterine  wall,  but  if  examined  after  the  separation  of  the  placenta,  it  presents 
a  comparatively  smooth  surface,  which  on  inspection  is  seen  to  be  incompletely 
divided  into  a  number  of  masses  named  cotyledons.  Its  inner  or  chorionic  surface 
is  smooth,  being  closely  invested  by  the  amnion.  The  umbilical  cord  is  attached 
near  the  centre  of  this  surface,  and  from  this  attachment  the  larger  branches  of  the 
umbilical  vessels  are  seen  radiating  under  the  amnion.  On  section  the  placenta 
presents    a  soft,   spongy  appearance,   caused  by  its   freely  communicating  blood- 


THE   EMBRYO.  1165 

sinuses  with  their  contained  villi.  Owing  to  the  rapid  thinning  of  the  placenta  at 
the  periphery  of  the  disk,  the  decidual  and  chorionic  surfaces  come  into  contact. 

Separation  of  the  Placenta. — After  the  birth  of  the  child  the  placenta  and 
the  membranes  (i.  e.,  the  amnion  and  chorion)  are  expelled  as  the  after-birth,  the 
separation  of  the  placenta  from  the  uterine  wall  taking  place  through  the  basal 
layer  of  the  decidua  and  necessarily  causing  rupture  of  the  uterine  vessels.  The 
orifices  of  the  torn  vessels  are,  however,  closed  by  the  firm  contraction  of  the 
uterine  muscular  fibres,  and  this,  together  with  the  formation  of  a  blood- clot  over 
the  placental  site,  prevents  post-partum  hemorrhage.  The  epithelial  lining  of  the 
uterus  is  regenerated  from  the  epithelium  which  lines  the  persistent  portions  of  the 
uterine  glands  in  the  basal  layer  of  the  decidua. 

The  umbilical  cord  appears  about  the  end  of  the  fifth  week  after  conception. 
It  consists  of  the  coils  of  two  arteries  and  a  single  vein,  the  ximbilical  arteries  and 
vein,  united  together  by  a  gelatinous  tissue  {jelly  of  Wharton).  There  are  origi- 
nally two  umbilical  veins,  but  one  of  these  vessels  becomes  obliterated,  as  do  also 
the  two  omphalo-mesenteric  arteries  and  veins  and  the  duct  of  the  umbilical  vesi- 
cle, all  of  which  are  originally  contained  in  the  rudimentary  cord.  The  umbilical 
cord  also  contains  the  remains  of  the  allantois,  and  is  covered  externally  by  a  layer 
of  the  amnion,  reflected  over  it  from  the  umbilicus. 


DEVELOPMENT  OF  THE  EMBRYO. 

The  further  development  of  the  embryo  will,  perhaps,  be  better  understood  if 
we  follow  briefly  the  principal  facts  relating  to  the  development  of  the  chief  parts 
of  which  the  body  consists,  viz.,  the  spine,  the  cranium,  the  pharyngeal  cavity, 
mouth,  etc.,  the  nervous  centres,  the  organs  of  the  senses,  the  circulatory  system, 
the  alimentary  canal  and  its  appendages,  the  organs  of  respiration,  and  the  genito- 
urinary organs.  The  reader  is  also  referred  to  the  chronological  table  of  the  devel- 
opment of  the  foetus  at  the  end  of  this  section. 

Development  of  the  Spine. — The  first  steps  in  the  formation  of  the  spine  have 
already  been  traced,  viz.  :  (1)  The  looping  up  of  two  longitudinal  folds  from  the 
cells  of  the  epiblast  in  front  of  the  primitive  streak,  to  form  the  neural  groove,  and 
the  gradual  growing  together  of  the  laminai  dor  sales  so  as  to  convert  the  groove 
into  the  neural  canal.  (2)  The  formation  on  the  ventral  aspect  of  this  groove  of  a 
continuous  cellular  cord,  the  notochord  or  chorda  dorsalis  (Fig.  700),  which  ex- 
tends from  the  cephalic  to  the  caudal  extremity  of  the  embryo,  and  lies  in  the 
situation  which  is  afterward  occupied  by  the  bodies  of  the  vertebrse.  (3)  The 
segmentation  of  the  paraxial  mesoblast  on  either  side  of  the  neural  canal  into  a 
number  of  quadrilateral  masses,  the  protovertebrce  or  mesoblastic  somites  (Fig.  701). 
The  process  of  segmentation  commences  in  the  cervical  region  and  proceeds  suc- 
cessively through  the  other  regions  of  the  spine  until  a  number  of  segments  are 
formed,  which  correspond  very  closely  to  the  number  of  the  permanent  vertebrse. 
Subsequently  the  protovertebral  somites  divide  into  two  parts — a  ventral  and  a 
dorsal.  From  the  ventral  division  the  vertebrse  are  formed  ;  the  dorsal  is  termed 
the  muscle-plate,  and  from  it  the  muscles  of  the  back  are  developed.  From  the  ven- 
tral division  of  the  protovertebral  somites  masses  of  cells  are  budded  off,  which 
grow  inward  toward  the  middle  line,  those  from  opposite  sides  meeting  and 
enclosing  the  notochord  and  extending  dorsally  around  the  neural  canal,  which  they 
also  envelop.  Fusion  of  the  ventral  divisions  also  occurs  in  the  antero-posterior 
direction,  so  that  all  trace  of  their  originally  segmented  condition  is  lost  and 
the  notochord  and  spinal  cord  are  surrounded  by  a  continuous  investment  of 
mesoblast,  the  ?nembranous  vertebral  column.  This  investment  also  extends 
forward  and  envelops  the  primitive  brain,  forming  the  membranous  or 
primordial  cranium.  From  this  investment  the  base  of  the  skull,  the  ver- 
tebrse and  their  ligaments,  and  the  membranes  of  the  cerebro-spinal  nervous 
system  are  developed.  The  future  vertebrae  make  their  first  appearance  about  the 
beginning  of  the  second  month  in  the  form  of  two  small  masses  of  cartilage  which 


1166 


EMBRYOLOGY. 


are  seen  in  the  membranous  vertebral  column,  one  on  each  side  of  the  notochord. 
These  small  masses  lie  opposite  to  the  intervals  between  the  muscle-plates  and  so 


alternate  with  these  structures. 


Pig.  799.— Cervical  part  of  the  primitive 
vertebral  column  and  adjacent  parts  of  an 
embryo  of  the  sixth  day,  showing  the  divi- 
sion of  the  primitive  vertebral  segments. 
(From  Kolliker,  after  Remak.)  1,1  Chorda 
dorsalis  in  its  sheath,  pointed  at  its  upper 
end.  2  points  by  three  lines  to  the  original 
intervals  of  the"  primitive  vertebrae,  o,  in 
a  similar  manner,  indicates  the  places  of 
new  division  into  permanent  bodies  of  ver- 
tebra?, c  indicates  the  body  of  the  first  cer- 
vical vertebra  ;  in  this  and  the  next  the 
primitive  division  has  disappeared,  as  also 
in  the  two  lowest  represented,  viz.,  d  and 
the  one  above  ;  in  those  intermediate  the 
line  of  division  is  shown.  4  points  in  three 
places  to  the  vertebral  arches  ;  and  5,  simi- 
larly, to  three  commencing  ganglia  of  the 
spinal  nerves ;  the  dotted  segments  outside 
these  parts  are  the  muscular  plates. 


They  are  soon  joined  across  the  middle  line  on 
the  ventral  aspect  of  the  notochord  by  a  hypo- 
chordal  cartilaginous  bar,  which  ultimately  dis- 
appears, except  in  the  case  of  the  atlas  ver- 
tebra, where  it  forms  the  anterior  arch  of  that 
bone.  The  vertebral  bodies  are  formed  imme- 
diately to  the  dorsal  aspect  of  these  hypo- 
chordal  bars,  alternating  with  the  muscle-plates 
which  represent  the  original  mesoblastic 
somites.  The  notochord  contained  in  the  centre 
of  this  chondrifying  mass  does  not  continue 
to  grow,  but  becomes  in  the  human  subject 
relatively  smaller,  so  as,  at  last,  to  form  a 
mere  slender  thread,  except  opposite  the  in- 
tervals between  the  bodies  of  the  permanent 
vertebrae.       Here  it  presents  thickenings  and 


»1 


Vertebral  body. --mi 
Intervertebral  disc.--\~-^ 

Notochord. -t^.. 


Fig.  710. — Longitudinal  section  of  vertebral  column  of  an 
eight  weeks'  human  foetus.    (Kolliker.) 


forms  an  irregular  network,  the  remains  of  which  are  to  be  found  at  all  periods 
of  life  in  the  central  pulp  of  the  intervertebral  disks  (Figs.  709,  710,  and  711). 

Development  of  the  Ribs  and  Sternum. — The  ribs  are  formed  from  the  muscle- 
plates  of  the  protovertebral  somites,  from  which  also  the  muscles  of  the  back  and 
the  true  skin  of  the  body-wall  are  formed.  The  ribs  consist  of  extensions  of  this 
mesoblastic  material,  which  speedily  undergo  chondrification,  and  appear  as  carti- 
laginous bars,  which  become  separated  from  the  vertebrae  at  their  posterior  extremi- 
ties. At  their  anterior  ends  the  nine  upper  costal  bars  turn  upward  and  fuse 
together  so  as  to  form  a  cartilaginous  strip  bounding  a  central  median  fissure.  The 
strips  on  either  side  then  join  in  the  middle  line  from  before  backward,  and  so  give 
rise  to  a  longitudinal  piece  of  cartilage,  which  represents  the  manubrium  and  gladi- 
olus of  the  sternum.  In  the  process  of  development  the  sternal  attachment  of  the 
eighth  rib  disappears,  while  that  of  the  ninth  subdivides,  one  portion  remaining 
attached  to  the  inferior  extremity  of  the  cartilaginous  sternum  and  becoming 
developed  into  the  ensiform  cartilage,  the  other  portion  receding  from  the  sternum 
and  becoming  attached  to  the  cartilage  of  the  eighth  rib. 

The  further  development  of  the  vertebrae,  ribs,  and  sternum,  and  the  ossifica- 
tion of  their  cartilaginous  framework,  are  described  in  the  body  of  the  work. 

Development  of  the  Cranium  and  Face. — It  has  been  seen  that  the  first  trace  of 
the  embryo  consists  in  the  formation  of  a  longitudinal  fold  of  the  epi blast  on  either 
side  of  the  neural  groove,  and  that  these  folds  or  ridges  grow  backward  and  meet 
in  the  median  line,  thus  forming  the  neural  canal.  This  canal,  at  the  cephalic 
extremity  of  the  embryo,  is  dilated  and  forms  a  bulbous  enlargement.  The  bul- 
bous enlargement  soon  expands  into  three  vesicular  dilatations,  the  three  primary 


THE  EMBRYO. 


1167 


cerebral  vesicles,  from  which  all  the  different  parts  of  the  encephalon  are  developed. 
The  primary  cerebral  vesicles  at  this  time  freely  communicate  with  each  other  at 
the  points  of  constriction. 

The  three  cavities  are  lined  by  epiblast  and  covered  by  the  same  structure. 
Between  these  two  layers  of  epiblast  a  layer  of  mesoblast  spreads  over  the  whole 
surface  of  the  cerebral  vesicles  and  forms  the  membranous  cranium.  From  these 
structures  the  cranium  and  its  contents  are  developed.  The  external  layer  of  the 
epiblast  forms  the  epidermis  and  hairs  of  the  scalp.  The  mesoblastic  layer  forms 
the  true  skin,  the  blood-vessels  (all  but  their  endothelial  lining),  muscles,  connec- 
tive tissue,  bones  of  the  skull,  and  membranes  of  the  brain.  The  layer  of  epiblast 
lining  the  vesicles  forms  the  nervous  substance  of  the  encephalon,  while  the  vesicles 
themselves  constitute  the  ventricles. 


-POSTERIOR    COMMON 
LIGAMENT. 

.Cartilaginous  end 

of  vertebral  body. 

Enlargement  of  noto- 

chord  in  disc. 
■Intervertebral  disc. 


Enlargement  of  noto- 
chord  in  the  carti- 
laginous end. 


Fig.  711.— Sagittal  section  through  the  intervertebral  disk  and  adjacent  parts  of  two  vertebrae  of  an  advanced 
sheep's  embryo.    (Kolliker.) 


The  cephalic  end  of  the  notochord  terminates  in  a  pointed  extremity  which 
extends  as  far  forward  as  the  situation  of  the  future  basi-sphenoid,  and  is  imbedded 
in  a  mass  of  mesoblast,  the  "investing  mass  of  Rathke."  The  posterior  part  of 
this  mass,  which  corresponds  to  the  future  basi-occipital,  shows  a  subdivision  into 
four  segments,  the  three  roots  of  the  hypoglossal  nerve  indicating  their  lines  of 
separation.  Two  cartilaginous  bars,  the  parachordal  cartilages,  then  become  de- 
veloped in  this  investing  mass,  and  these  surround  the  notochord,  meeting  first  on 
its  ventral  and  next  on  its  dorsal  aspect  to  form  the  basilar  plate,  the  anterior 
margin  of  which  forms  the  future  dorsum  sellse.  From  this  plate  are  developed  the 
basi-occipital  and  basi-sphenoid,  and  by  lateral  expansions  from  it  the  ex-occipital3 
and  the  greater  wings  of  the  sphenoid.  On  either  side  of  the  parachordal  cartilage 
a  cartilaginous  capsule,  the  labyrinthine  or  periotic  cartilage,  surrounds  the  otic 
vesicle,  and  from  it  the  petrous  and  mastoid  portions  of  the  temporal  bone  are 
developed.  In  front  of  the  investing  mass  of  Rathke  two  lateral  bars  are  directed 
forward,  enclosing  between  them  a  space,  which  forms  the  pituitary  fossa,  in  which 
the  pituitary  body  is  eventually  developed.  These  bars  are  named  the  prechordal 
cartilages  or  trabecules  cranii,  and  extend  as  far  forward  as  the  anterior  extremity 
of  the  head,  where  they  coalesce  with  each  other  to  form  the  ethmoid  plate  (Fig. 
712).  This  encloses  the  olfactory  pits  forming  the  cartilaginous  nasal  capsule, 
from  which  the  ethmoid  and  turbinated  bones  are  developed.  A  portion  of  the 
ethmoid  plate  remains  unossified  and  constitutes  the  cartilaginous  part  of  the  nasal 
septum  and  the  cartilages  of  the  outer  nose.  From  the  trabeculse  cranii  the  pre- 
sphenoid  is   developed,  and  from  this  two   lateral   expansions  extend  to  form  its 


1168 


EMBRYOLOGY. 


lesser  -wings ;  each  of  these  arises  by  two  roots,  one  above  and  one  below  the  optic 
nerve,  and,  uniting  outside  the  nerve,  enclose  the  optic  foramen.  The  base  of  the 
primitive  cranium  therefore  consists  of  two  parts,  prechordal  and  parachordal :  the 
former  receives  the  organ  of  smell  and  is  indented  by  the  eyeball ;  the  latter  sur- 
rounds the  auditory  vesicle.     Thus  it  will  be  seen  that  the  bones  which  form  the 


Situation  of  olfactory  pit. 


Pituitary  fossa.* 


Trabecula 
cranii. 

Situation  of 
otic  vesicle. 
Parachordal- 
cartilage. 

Kotochord.  ■ 


Ethmoid  cartilage 
and  nasal  septum. 


Olfactory  organ. 


-^Extension  around 
■'       olfactory  organ. 

Foramen  for 

olfactory  nerves.. 


—Eyeball. 
-Pituitary  fossa.. 

Investing  mass, 
"of  Bathke. 
Otic  vesicle. 

Notochord- 


Fig.  712.— Diagrams  of  the  cartilaginous  crauium.    (Wiedersheim.) 


base  of  the  skull  are  preceded  by  masses  of  cartilage,  which  together  form  the 
chondro cranium.  Those  of  the  vault  of  the  skull,  on  the  other  hand,  are  of  mem- 
branous formation,  and  are  termed  dermal  or  covering  bones.  They  are  developed 
in  the  mesoblast  which  lies  superficial  to  the  primordial  cranium,  or  in  that  which 
lies  subjacent  to  the  epithelial  lining  of  the  foregut.  They  comprise  the  upper 
portion  of  the  tabular  part  of  the  occipital  (interparietal),  the  squamous-temporals 
and  tympanic  rings,  the  two  parietals,  the  frontal,  the  vomer,  the  internal  ptery- 
goid plates,  and  the  bones  of  the  face.  Some  of  them  remain  distinct  through- 
out life  (e.  g.,  parietal  and  frontal),  while  others  join  with  the  bones  of  the 
chondrocranium  (e.  g.,  interparietal,  squamous-temporal,  and  internal  pterygoid 
plates). 

The  head  at  first  consists  simply  of  a  cranial  cavity,  the  face  and  neck  being 
subsequently  developed  in  the  manner  now  to  be  described. 

In  all  vertebrate  animals  there  is  at  one  period  of  their  development  a  series 
of  grooves  in  the  upper  neck  region  of  the  embryo.  These  are  named  the  branchial 
or  visceral  clefts,  and  in  man  are  four  in  number  from  before  backward.  They 
take  origin  as  paired  grooves  or  pouches  from  the  side  of  the  pharynx,  and  over 
each  groove  a  corresponding  indentation  of  the  epiblast  occurs,  so  that  the  latter 
comes  into  contact  with  the  hypoblast  lining  the  pharynx,  and  these  two  layers 
unite  to  form  thin  septa,  along  the  bottom  of  the  grooves,  between  the  pharyngeal 
cavity  and  the  exterior.  In  gill-bearing  animals  these  septa  disappear  and  the 
(grooves  become  complete  clefts,  the  gill  clefts,  opening  from  the  pharynx  on  to  the 
exterior ;  perforation  does  not,  however,  occur  in  birds  and  mammals.  In  front 
and  behind  each  cleft  the  mesoblast  becomes  thickened  in  the  form  of  arches,  the 
branchial  arches  (Figs.  713,  750).  In  the  human  embryo  there  are  five  pairs  of 
these  arches,  one  in  front  of  the  first  cleft,  one  behind  the  last,  and  the  three 
remaining  ones  between  the  first  and  second,  the  second  and  third,  and  the  third 
and  fourth  clefts,  respectively.  The  first  arch  is  named  the  mandibular ;  the 
second  the  hyoid ;  the  third  the  thyro-hyoid,  while  the  fourth  and  fifth  have  no. 
distinctive  names.     In  each  arch  there  is  developed  a  cartilaginous  bar  which  gives 


THE   EMBRYO. 


1169 


it  firmness  and  stability,  and  in  each  there  is  also  found  one  of  the  primitive  aortic 
arches.  Continuous  with  the  dorsal  end  of  the  first  arch  and  growing  forward 
from  it  is  a  triangular  process,  the  maxillary  process  (Figs.  714,  710,  738).  Ven- 
trally  it  is  separated  from  the  mandibular  arch  by  a  V-shaped  notch  ;  the  first 
branchial  arch  may  therefore  be  said  to  divide  into  two,  viz.,  the  mandibular  arch 


Lena. 


Maxillary  process. 

Mandibular  arch. 


Olfactory 

pit, 


Ilyo-mandlbular  cleft. 
i 

l    Auditory  vesicle. 

Jfyoid  arch. 

Thyro-hyoid  arch. 

Sinus 
r"pnecervicalis 


Fig.  713.— Profile  view  of  the  head  of  a  human  embryo,  estimated  as  twenty-seven  days  old.    (After  His.) 


and  the  maxillary  process.  In  front  of  the  mandibular  arch  is  a  pentagonal 
depression,  termed  the  oral  sinus  or  stomodwum,  since  it  forms  the  future  mouth. 
It  is  bounded  anteriorly  by  a  median  process,  the  fronto-nasal  process,  and  laterally 
by  the  maxillary  processes  (Fig.  714),  and  will  be  referred  to  again. 

These  parts  must  now  be  considered  with  a  little  more  detail. 

The  fronto-nasal  process  covers  the  forebrain  and  contains  the  coalesced  portion 
of  the  trabecule  cranii ;  it  consists  of  a  central  or  mid-frontal  process  and  two 
lateral  parts.     By  the  invagination 

of    the    olfactory  pits,    which     COm-  Cerebral  hemisphere. 

municate  below  with  the  cavity  of 

the  mouth,  each  lateral  portion  is 

subdivided    into    an   outer  and    an 

inner     nasal    process — the     latter 

having    been    termed    by    His    the 

processus  globularis.     The   lateral 

nasal  process  is  separated  from  the 

maxillary  process  by  a  groove  which 

extends  from  the  eye  to  the  olfactory 

pit ;    this  is    the    rudiment   of  the 

lachrymal  duct  (Figs.  714,  715,  and 

716).      The  globular  processes   are 

prolonged  backward  as  plates,  termed  the  nasal  laminae  :  these  laminae  are  at  first 

some  distance  apart,  but,  gradually  approaching,  they  ultimately  fuse  and  form  the 

nasal  septum,  while  the  globular  processes  themselves  meet  in  the  middle  line  and  form 

the  prsemaxillse  and  central  part  of  the  upper  lip  (Fig.  717).     The  depressed  part  of 


Fronto-nasal-. 

process-. 


Stomodseum. 


Lateral  nasal  process. 

---Eye. 

■—  Processus  globularis. 
Maxillary  process. 

*S^  Mandibular  arch, 

y^  i[;/o-mandibular  cleft. 


Fig.  714.— Under  surface  of  the  head  of  a  human  embryo, 
about  twenty-nine  days  old.    (After  His.) 


1170 


EMBRYOLOGY. 


Eye. 


Hyo-mandibular 
cleft. 


.Cerebral  hemisphere. 


^Lateral  nasalprocess. 
^Olfactory  pit. 
^.Processus  globularis. 
-■Maxillary  process. 

-Mandibular  arch. 


the  midfrontal  process  between  the  globular  processes  forms  the  lower  part  of  the 

nasal  septum,  while  above  this  is 
seen  a  prominent  angle  which  be- 
comes the  future  point,  and  still 
higher,  a  flat  area,  the  future  bridge 
of  the  nose  (Figs.  717,  718).  The 
alse  of  the  nose  are  developed  from 
the  lateral  nasal  processes. 

The  maxillary  processes  de- 
scend for  a  short  distance,  forming 
the  outer  wall  of  the  orbit,  in  which 
the  malar  bone  is  developed;  they 
then  incline  inward,  and,  meeting 
the  lateral  nasal  process,  form  the 
floor  of  the  orbit,  and  shut  it  off 
from  the  rest  of  the  face ;  con- 
tinuing their  course  downward  and 
inward,  they  join  the  globular  proc- 
esses, and  with  them  complete  the  alveolar  arch  and  upper  lip.  Finally  a  pair 
of  palatal  processes  are  formed  by  inward  extensions  of  the  maxillary  processes ; 
these  coalesce  with  each  other  in  the  median  line,  thus  separating  the  cavity  of  the 
mouth  from  the  nasal  fossae,  and  completing  the  palate  (Fig.  717).  In  front  the 
palatal  processes  join  with  the  premaxillse,  except  in  the  middle  line,  where  a  cleft 
remains  which  constitutes  the  naso-palatine  canal. 

The  mandibular  arch,  by  its  junction  with  the  corresponding  process  on  the  other 
side,  forms  the  lower  jaw  or  mandible.  The  cartilaginous  rod  which  it  contains  has 
long  been  known  as  the  " cartilage  of  Meckel."  The  proximal  end  of  this  cartilage 
is  in  contact  with  the  periotic  capsule,  and  from  it  are  developed  two  of  the  ossicles 


Fig.  715. — Under  surfiice  of  the  head  of  a  human  embryo 
about  thirty  days  old.    (After  His.) 


Mouth  of  olfactory  pit 

{external  nostril). 

Median  part  of  frorito 

nasal  process. 


Processus  globularis. 

Pituitary  body. 
Hyomandibular  pouch. 

Sinus  prsecervicalis. 

Larynx. 

Lung. 


Eye. 

Maxillary  process. 

Mandibular  arch. 

Membrane   closing 
hyomandibular  cleft 
{tympanic  membrane). 

Hyoid  arch. 
Thyro-hyoid  arch. 

Fourth  post-oral  arch. 


Fig.  716.— The  head  and  neck  of  a  human  embryo  thirty-two  days  old,  seen  from  the  ventral  surface.    The 
floor  of  the  mouth  and  pharynx  have  been  removed.    (His.j    (From  Marshall's  Vertebrate  Embryology.) 


of  the  middle  ear,  the  malleus  and  incus 1  (Fig.  719).  The  remainder  of  the  rod 
is  associated  with  the  formation  of  the  lower  jaw,  though  the  greater  part  of  that 
bone  is  developed  from  membrane.  The  second  visceral  arch  is  named  the  hyoid 
arch :  from  it  are  formed  the  styloid  process,  the  stylo-hyoid  ligament,  and  the 
lesser  cornu  of  the  hyoid  bone.  The  third,  or  thyro-hyoid  arch,  gives  origin  to  the 
1  The  incus  is  by  some  regarded  as  arising  from  the  proximal  end  of  the  hyoid  bar. 


THE  EMBRYO. 


1171 


great  cornu  of  the  hyoid  bone,  while  the  body  of  this  bone  is  formed  between  the 
second  and  third  arches.      The  fourth  and  fifth  arches  are  rudimentary. 

Between  the  maxillary  processes  and  the  mandibular  arch  the  buccal  cavity  or 
mouth  is  formed.     As  has  already  been  stated  (page  1157)  the  cephalic  end  of  the 

Mouth  of  olfactory 
Processus  globularis.  pit,  or  nostril. 

Palatal  process  of  pro-        \< 
cessus  globularis.  ' 

Palatal  part  of  maxil 
lory  process. 

Maxillary 
process, 


Mouth 

carity. 


Fig  717.-The  ">of  of  the  mouth  of  a  human  embryo  of  about  two  and  a  half  months  old,  showing  the 
mode  of  formation  of  the  palate.    (His.)     (From  Marshall's  Vertebrate  Embryology.) 

embryo  becomes  remarkably  curved  on  itself,  the  fore-brain  and  mid-brain  bendino- 
downward  over  the  anterior  portion  of  the  original  blastodermic  vesicle,  Avhich  is 
thus  enclosed  within  the  body  of  the  embryo  and  con- 
stitutes the  fore-gut ;  the  fore-gut  terminates  in  a  blind 
extremity  beneath  the  head  (Figs.  720  and  759). 
Another  prominence,  the  rudimentary  heart,  appears  on 
the  ventral  surface  of  the  fore-gut.  Between  these  two 
prominences,  caused  by  the  projection  of  the  fore-brain 
and  the  heart,  an  involution  of  the  epiblast  takes 
place,  gradually  deepening  until  it  comes  in  contact 
with  the  blind  end  of  the  fore-gut.  This  is  the  oral 
pit  or  stomodceum,  already  referred  to ;  it  presents  the 
form  of  a  pentangular  opening,  bounded  in  front  by 
the  fronto-nasal  process,  behind  by  the  mandibular 
arch,  and  laterally  by  the  maxillary  processes.  From 
the  beginning  the  mesoblast  is  absent  in  the  region  of 
the  oral  pit,  and  hence  its  epi  Mastic  lining  meets  the 
hypoblastic  covering  of  the  blind  anterior  end  of  the 
fore-gut  and  forms  a  thin  septum,  the  'pharyngeal  septum 
(Fig.  759) ;  this  soon  breaks  down,  and  a  communica- 
tion is  established  between  the  mouth  and  the  future 
pharynx.  The  oral  pit  or  stomodaeum  is  not  equivalent 
in  extent  to  the  adult  mouth,  since  the  latter  includes  the  tongue,  which  is  devel- 
oped from  the  floor  of  the  pharynx  ;  in  fact,  as  His  has  pointed  out,  the  ante- 
rior pillars  of  the  fauces  are  developed  from  the  second  branchial  or  hyoid  arch. 

From  the  upper  part  of  the  stomodoeum  a  pocket-like  involution  of  the  epiblast, 
the  pouch  of  JRathke,  extends  upward  between  the  trabecular  cranii  toward  the 
thalamencephalon.  This  involution  ultimately  loses  its  connection  with  the  stomo- 
dgeum,  and,  becoming  applied  to  the  infundibulum,  forms  the  anterior  lobe  of  the 
pituitary  body  (Fig.  720). 

The  anterior  visceral  arches  grow  more  rapidly  than  the  posterior,  with  the 
result  that  the  latter  become  telescoped  within  the  former,  and  a  deep  depression, 
the  sinus  prcecervicalis,  is  produced.  This  sinus  is  bounded  in  front  by  the  hyoid 
arch,  and  ultimately  becomes  obliterated  by  the  fusion  of  its  anterior  and  posterior 
walls. 


Fig.  718.— Head  of  a  human  em- 
bryo of  about  eight  weeks,  in  which 
the  nose  and  mouth  are  formed. 
(His.) 


1172 


EMBRYOLOGY. 


Before  leaving  the  subject  of  the  visceral  arches  and  clefts  it  is  necessary  to 
mention  that  the  clefts  disappear  early  in  embryonic  life,  with  the  exception  of 
portions  of  the  first,  which  remain  permanent — the  inner  portion,  or  the  Eustachian 
tube  and  tympanum  ;  the  outer,  as  the  external  auditory  meatus,  while  the  septum 


Malleus 


Tympanic  ring. 
\^*Mandible. 

Meckel's  cartilage. 


Incus. 


Hyoid  bone. 


Fig.  719.— Head  and  neck  of  a  human  embryo  eighteen  weeks  old,  with  Meckel's  cartilage  and  hyoid  bar 
exposed.    (After  Kolliker.) 

between  the  two  portions  becomes  invaded  by  mesoblast  and  forms  the  membrana 
tympani. 

Development  of  the  Nervous  Centres  and  the  Nerves. — The  medullary  or  neural 
groove  already  described  (page  1155)  is  the  rudiment  of  the  cerebro-spinal  axis. 
As  has  been  seen,  this  groove  is  converted  into  a  canal  (the  neural  canal) :  its 
cephalic  end  becomes  dilated  into  a  sac,  from  which  the  brain  is  developed ;  the 
remainder  forms  the  spinal  cord.  The  cavity  of  the  canal  becomes  the  central 
canal  of  the  spinal  cord,  and  that  of  the  upper  dilated  portion  the  ventricles  of  the 
brain.  The  wall  of  the  canal,  formed  of  epiblastic  cells,  undergoes  great  changes, 
and  from  it  the  nervous  matter  and  neuroglia  are  developed.  It  consists  at  first 
of  a  layer  of  columnar  epithelium,  covered  on  its  exterior  by  a  basement-mem- 
brane. The  wall  becomes  thickened,  partly  by  the  elongation  of  the  columnar 
cells  and  partly  by  the  formation  of  new  cells.  The  elongation  of  the  columnar 
cells,  now  called  spongioblasts,  is  followed  by  the  breaking  up  of  their  outer  ends 
into  a  reticulum,  which  is  termed  the  myelo-spongium,  and  eventually  forms  the 
neuroglia.  The  new  cells  which  are  formed  appear  between  the  inner  ends  of 
the  columnar  cells  as  rounded  masses,  which  speedily  divide,  and  are  termed  neuro- 
blasts ;  they  become  pear-shaped,  and  projecting  from  each  of  them  is  a  tapering 
process  which  perforates  the  basement-membrane.  These  neuroblasts  are  the  primi- 
tive nerve-cells,  and  their  tapering  processes  the  rudimentary  axis-cylinders  of  the 
cells  (Figs.  721  and  722). 

It  will  be  convenient,  in  the  first  place,  to  trace  the  changes  which  take  place 
in  the  cavity  of  the  cerebro-spinal  axis,  ignoring  for  a  time  those  which  go  on 
in  the  enclosing  wall.  But  before  doing  so,  it  is  necessary  to  mention  that,  in 
consequence  of  the  curve  which  the  cephalic  portion  of  the  embryo  undergoes,  a 
marked  bend  forward  of  the  canal  takes  place,  so  that  the  plane  of  the  ventricles 
is  almost  at  right  angles  with  the  long  axis  of  the  central  canal  of  the  cord. 

The  early  stage  thus  consists  of  a  hollow  sac,  which  is  the  rudimentary  brain, 
and  a  hollow  canal,  which  is  the  rudimentary  cord  ;  the  sac  and  the  canal  freely 
communicate  with  each  other.  The  sac  first  of  all  becomes  elongated ;  then  two 
constrictions  appear  in  it,  which  partially  divide  it  into  three  ;  these  are  named 
anterior,  middle,  and  posterior  cerebral  vesicles,  or  the  fore-brain,  mid-brain,  and 


THE   EMBRYO. 


1173 


hind-brain  (Fig.  701).  Subsequently  the  anterior  and  posterior  vesicle.-'  each 
become  constricted  into  two,  while  the 'middle  one  remains  undivided.  It  will  thus 
be  seen  that  at  the  anterior  extremity  of  the  medullary  canal  there  are  five  dilata- 
tions, separated  from  each  other  by  constrictions,  through  which,  however,  they 
freely  communicate  with  each  other.  These  five  vesicles  are  the  five  fundamental 
divisions  of  the  adult  brain,  and  are  named  from  before  backward  :  prosencephalon, 
thalamencephalon,    mesencephalon,   epencephalon,  and  metencephalon  (Figs.  723 


en 


Fig.  720.— Vertical  section  of  the  head  in  early  embryos  of  the  rabbit.  Magnified.  (From  Mihalkovics.) 
A.  From  an  embryo  five  millimetres  long,  b  From  an  embryo  six  millimetres  long.  c.  Vertical  section 
of  the  anterior  end  of  the  notochord  and  pituitary  body,  etc.,  from  an  embryo  sixteen  millimetres  long.  In  A, 
the  faucial  opening  is  still  closed.  In  B,  it  is  formed,  c.  Anterior  cerebral  vesicle,  vie.  Wesocerebrum.  mo. 
Medulla  oblongata,  co.  Corneous  layer,  m.  Medullary  layer,  if.  Infundibulum.  am.  Amnion,  zpc.  Spheno- 
ethmoidal. 6c.  Central  (dorsum  sella;),  and  spo.  spheno-occipital  parts  of  the  basis-cranii.  ft.  Heart.  /. 
Anterior  extremity  of  primitive  alimentary  canal  and  opening  (later)  of  the  fauces,  i.  Cephalic  portion  of 
primitive  intestine,  tha.  Thalamus,  p'.  Closed  opening  or  the  involuted  part  of  the  pituitary  body  (py).  ch. 
Notochord.    ph.  Pharynx. 

and  725).  They  are  at  first  fairly  uniform  in  size  and  shape,  but  soon  begin  to 
grow  at  different  rates  and  assume  different  forms.  The  changes  are  most 
marked  in  the  first  vesicle. 

The  first  secondary  vessel  (prosencephalon)  sends  out  two  hollow  protrusions, 
one  on  either  side,  from  the  forepart  of  its  lateral  surface ;  these  grow  rapidly  and 
spread  out  and  extend  forward,  laterally,  and  backward  over  the  sides  of  the 
first  and  second  vesicles,  forming  large  cavities,  which  become  the  lateral 
ventricles  (Fig.  725,  g).  From  each,  three  prolongations  take  place:  one, 
forward  and  outward;  a  second,  backward  and  inward;  and  a  third,  at  first 
backward,  outward,  and  downward,  and  then  forward  and  inward ;  these  form 
the  horns  of  the  lateral  ventricles.  These  prolongations  far  exceed  in  size  the 
original  vesicle  from  which  they  sprung,  which  does  not  increase  to  any  great 
extent.     It  remains  as  the   anterior  part  of  the  third  ventricle  (Fig.  725,  a),  and 


1174 


EMBRYOLOGY. 


the  communication  between  it  and  the  future  lateral  ventricle  persists  as  the  fora- 
men of  Monro  (Fig.  725.  h). 


' 


-Germinal  cell. 


—Neuroblast. 


Nuclei  of 
spongioblasts. 


■   : 


-Myelosgongium 

network . 


Fig.  721.— Transverse  section  of  the  spinal  cord  of  a  human  embryo  at  the  beginning  of  the  fourth  week. 
(After  His.)    The  top  of  the  figure  corresponds  to  the  lining  of  the  central  canal. 

The  second  vesicle  (ihalamencephalon)  becomes  elongated  from  before   back- 
ward   and    compressed    laterally  so    as    to    form    the    greater   part  of  the    third 


*  ( ■    \  ~<&r>Posterior  nerve  root. 
Central  canal. 


Nuclei  of  spongio- 
blasts. 


-Neuroblasts. 


Processes  of  neuroblasts 

growing  out  to  form 

anterior  nerve  root. 

Anterior  column. 


Fig.  "22.— Section  of  spinal  cord  of  a  four  weeks'  embryo.    (His.) 

ventricle  (Fig.  725,  b).  From  each  side  of  that  part  of  the  forebrain  which 
ultimately  becomes  the  second  vesicle  is  budded  off  a  hollow  projection,  the 
primary  optic  vesicle,  which  is  developed  eventually  into  optic  nerve  and 
retina :  it  will  be  considered  later  on.  The  constriction  between  the  first  and 
second  vesicle  disappears,  so  as  to  throw  the  whole  of  the  cavity  (the  future  third 


THE  EMBRYO. 


1175 


1176 


EMBRYOLOGY. 


ventricle),  formed  by  the  remains  of  the  first  vesicle  and  the  whole  of  the  second 
vesicle,  into  one. 

The  third  vesicle  (mesencephalon)  is  converted  into  a  narrow  channel,  the  iter 
a  tertio  ad  quart um  ventriculum  (Fig.  725.  c). 

The  fourth  vesicle  (epencephalon)  becomes  widened  out,  and  assumes  a  trian- 
gular form,  with  its  apex  directed  forward,  and  situated  at  the  original  point  of 
constriction  where  the  third  vesicle  joins  the 
fourth.  It  is  at  the  same  time  flattened  from 
above  downward,  and  constitutes  the  anterior 
half  of  the  fourth  ventricle  (Fig.  725,  i>). 

The  fifth  vesicle  (metencephalon)  undergoes 
the  same  change  in  form  as  the  fourth,  becom- 
ing triangular  in  shape  and  flattened  from  above 
downward,  but  with  this  difference,  that  the  apex 
of  the  triangle  is  directed  backward,  and  is 
continuous  with  the    portion    of  the    medullary 


u 


Fig.  725.— Plan  showing  the  mode  of 
formation  of  the  ventricles  of  the  brain 
and  the  central  canal  of  the  spinal  cord 
(After  Gerrish.)  a.  Prosencephalon,  b 
Thalamencephalon.  c.  Mesencephalon 
D.  Epencephalon.  e.  Metencephalon.  F 
Central  canal  of  cord.  g.  Lateral  ventri 
cle.    h.  Foramen  of  Monro. 


Fig.  724. — Section  of  the  medulla  in  the  cervical  region,  at  six 
weeks.  Magnified  50  diameters.  1.  Central  canal.  2.  Its  epithe- 
lium. 3.  Anterior  gray  matter.  4.  Posterior  gray  matter.  5.  An- 
terior commissure.  6."  Posterior  portion  of  the  banal,  closed  by 
the  epithelium  only.  7.  Anterior  column.  8.  Lateral  column. 
9.  Posterior  column.    10.  Anterior  roots.    11.  Posterior  roots. 

canal  which  goes  to  form  the  central  canal  of 
the  spinal  cord  (Fig.  725,  e).  The  base  is 
directed  forward  and  is  continuous  with  the  base 
of  the  triangular  space  formed  by  the  fourth 
vesicle ;  the  constriction  between  the  two  ves- 
icles having  disappeared,  the  two  spaces  freely 
communicate,  and  together  form  a  rhomboidal 
cavity  which  is  the  fourth  ventricle. 

These  vesicles  do  not  remain  in  the  same 
plane,  but  certain  definite  flexures  take  place, 
which  result  in  an  alteration  of  the  position  of  the  vesicles  to  one  another. 
The  first  of  these  flexures  {cephalic)  is  opposite  the  base  of  the  middle  vesicle, 
which  becomes  sharply  bent  on  itself  over  the  end  of  the  notochord.  This 
has  the  effect  of  causing  the  mid-brain  to  become  the  most  prominent  part  of  the 
encephalon  on  the  convexity  of  the  curve  (Fig.  723).  A  second  flexure  (poyital), 
with  its  curve  in  the  opposite  direction,  takes  place  in  the  epencephalon,  and  is 
very  abrupt.  A  third  but  less  marked  flexure  (nuchal)  takes  place  in  the  meten- 
cephalon at  its  junction  with  the  cord.  The  first  of  these  curves  or  flexures 
remains  permanent,  but  the  second  and  third  almost  entirely  disappear  in  the 
further  development  of  the  brain. 

The  manner  in  which  the  different  parts  of  the  encephalon  and  cord  are 
formed  from  the  walls  of  this  greatly  altered  medullary  canal  must  now  be  consid- 
ered, and  it  will  be  convenient  first  of  all  to  study  the  development  of  the  spinal  cord. 


THE   EMBRYO. 


1177 


The  lateral  walls  of  the  medullary  canal  become  thickened  and  marked  off 
into  two  laminae :  a  dorsal,  or  alar  lamina,  and  a  ventral,  or  basal  lamina,  the 
portion  of  the  canal  in  the  mid-line  both  on  its  dorsal  and  ventral  surfaces 
remaining  thin,  and  form  the  roof  and  floor  plates  respectively  (Fig.  724).  In  the 
thickened  lateral  portion  the  neuroblasts  begin  to  collect  into  groups :  one 
especially  being  noticeable  in  the  basal  lamina  at  the  situation  of  the  future 
anterior  horn.  The  processes  of  this  group  of  cells  pass  out  of  the  cord  and  form 
the  anterior  nerve-roots :  outside  this  group  of  cells  is  the  reticulated  tissue  of 
the  myelospongium,  which  represents  the  white  matter  at  this  stage,  and  through 
which  these  processes  pass  obliquely  before  they  leave  the  cord  (Fig.  722).  The 
anterior  and  posterior  columns  make  their  appearance  soon  after,  and  as  the  cornua 


Optic  thalamus 
Foramen  of  Monro 


Posterior  commissure. 
Pineal  hody. 


Cms  cerebri. 

Iqueduct  of  Sylvius. 


Corpora  quadrigemina. 
Cerebellum. 


Ventricle. 


Cerebral  hemisphere.  ; 

Ehinencephalon.  |  j   \ 

Lamina  cinerea.  [    \ 

Optic  nerve.  \        '     j 
Optic  commissure'.      ; 

Pituitary  body.  '• 
Infundibulum. 


Corpus 

albicans. 


Spinal  cord. 


Fig.  726.— Median  section  of  brain  of  human  fetus  during  the  third  month.    (After  His.) 


of  gray  matter  grow  out  from  the  central  mass  the  fissures  begin  to  appear. 
The  anterior  fissure  is  a  cleft  left  between  the  lateral  halves  of  the  cord.  The 
mode  of  formation  of  the  posterior  fissure  is  uncertain  ;  many  believe  that  it 
is  a  portion  of  the  neural  canal,  which,  dividing  into  two,  forms  an  anterior  part, 
the  permanent  canal,  and  a  posterior  portion,  which  becomes  filled  with  a 
septum  of  connective  tissue  from  the  pia  mater,  and  forms  the  posterior  fissure  of 
the  cord.  Others  are  of  opinion  that  it  is  developed  independently  of  the  central 
canal,  as  a  cleft  formed  by  the  enlargement  of  the  lateral  halves  of  the  cord, 
into  which  an  ingrowth  of  connective  tissue  from  the  pia,  mater  takes  place. 

At  first  the  foetal  spinal  cord  occupies  the  whole  length  of  the  spinal  canal, 
but  after  the  fourth  month  the  spinal  column  begins  to  grow  in  length  more 
rapidly  than  the  cord,  so  that  the  latter  no  longer  occupies  the  lower  part  of  the 
canal. 

The  ventricles  of  the  encephalon  arc  developed  in  the  manner  above  described 
from  the  five  secondary  vesicles  into  which  the  primary  expansion  of  the  anterior 
extremity  of  the  medullary  tube  is  differentiated. 


1178  EMBRYOLOGY. 

The  first  vesicle  or  prosencephalon  sends  out  two  hollow  protrusions,  which 
spread  rapidly,  and  in  the  walls  of  these  nervous  matter  is  developed,  which  con- 
stitutes the  cerebral  hemispheres  (Fig.  723,  h),  the  cavities  remaining  as  the 
lateral  ventricles.  As  these  hemispheres  extend  they  grow  forward  in  front  of 
the  anterior  extremity  of  the  primitive  brain,  and  lie  side  by  side,  separated  by  the 
longitudinal  fissure ;  they  also  grow  upward,  and  again  lying  side  by  side  are 
separated  by  another  portion  of  the  same  fissure,  containing  a  thin  layer  of 
mesoblast,  which  forms  the  falx  cerebri ;  behind  and  laterally  they  overlap  the  roof 
and  sides  of  the  other  cerebral  vesicles,  so  that  by  the  seventh  month  they  project 
behind  them.  In  the  floor  of  each  of  these  hemispheres  there  occurs  a  local 
thickening,  which  forms  the  corpus  striatum,  which  is  continuous  behind  with  the 
optic  thalamus,  presently  to  be  described.  The  surface  of  the  hemisphere  is  at 
first  smooth,  but  about  the  fifth  month  a  sulcus  or  groove  appears  in  either 
hemisphere  just  external  to  the  corpus  striatum  ;  this  is  the  fissure  of  Sylvius : 
subsequently  other  fissures  appear  on  the  surface,  three  of  which  are  of  sufficient 
depth  to  cause  a  projection  into  the  lateral  ventricle.  These  are  the  hippocampal 
fissure,  corresponding  to  the  hippocampus  major  of  the  lateral  ventricle;  the 
parieto-occipital  fissure,  corresponding  with  the  bend  of  the  posterior  horn  of  the 
ventricle;  and  the  calcarine  fissure,  corresponding  with  the  projection  of  the  calcar 
avis. 

The  remainder  of  the  first  vesicle  and  the  second,  as  we  have  seen,  form 
the  third  ventricle ;  in  its  normal  walls  a  thickening  takes  place,  which  forms  the 
optic  thalamus.  From  the  floor  of  this  ventricle  a  hollow  protrusion  passes  down- 
ward, and  is  intimately  connected  with  a  diverticulum  from  the  stomodseum,  to 
form  the  pituitary  body  or  hypophysis  cerebri  (Figs.  720,  723,  and  726).  The 
greater  part  of  the  roof  of  the  third  ventricle  is  very  thin,  and  with  the  pia  mater 
forms  the  velum  interpositum  ;  from  its  posterior  part  an  outgrowth  of  cells  forms 
the  pineal  body  or  epiphysis  cerebri.  Where  the  cerebral  hemispheres  are  not 
separated  in  the  middle  line  by  the  falx,  in  front  and  for  some  distance  backward 
over  the  roof  of  the  third  ventricle  their  mesial  surfaces  come  in  contact,  and  to  a 
certain  extent  fuse  together,  leaving  however  a  small  portion  where  no  union 
takes  place,  and  thus  a  slit-like  cavity  is  left ;  this  is  termed  the  fifth  ventricle, 
though  it  will  be  at  once  seen  that  its  development  is  quite  different  from  that  of 
the  other  ventricles.  Its  lateral  walls  form  the  septum  lucidum.  The  roof  of 
this  cavity  becomes  thickened,  and  nerve-fibres  pass  across  from  the  one  hemisphere 
to  the  other  to  form  the  corpus  callosum,  while  in  its  floor  longitudinal  fibres  are 
developed  to  form  the  fornix. 

The  third  vesicle,  the  cavity  of  which  forms  the  iter  a  tertio  ad  quartum  ven- 
triculum,  develops  in  its  roof  four  well-marked  thickenings,  which  together  form 
the  corpora  quadrigemina,  while  its  lateral  regions  become  thickened  to  form 
the  crura  cerebri  (Fig.   726). 

The  dorsal  surface  of  the  fourth  vesicle,  or  epencephalon,  forms  the  covering 
of  the  fourth  ventricle,  and  in  it  a  thickening  occurs,  which  is  developed  into  the 
cerebellum  ;  its  ventral  and  lateral  regions  form  the  pons  (Fig.  726). 

In  the  fifth  vesicle  or  metencephalon  the  lateral  parts  increase  and  grow  down- 
ward on  each  side  toward  the  middle  line,  forming  the  medulla,  while  the  dorsal 
surface  assists  in  forming  the  roof  of  the  fourth  ventricle. 

On  making  a  transverse  section  of  the  lower  part  of  the  fourth  ventricle,  the 
alar  and  basal  laminse,  already  referred  to  as  being  present  in  the  cord,  are  readily 
recognized,  while  the  thin  roof-plate  is  seen  to  be  greatly  expanded  laterally. 
The  dorsal  part  of  the  alar  lamina  becomes  folded  outward  and  downward,  form- 
ing what  is  termed  the  rhomboid  lip  (Fig.  727).  This  is  at  first  separated  by  a 
groove  from  the  lateral  aspect  of  the  alar  lamina,  but  ultimately  fuses  with  it.  As 
the  central  canal  of  the  cord  opens  out  to  form  the  fourth  ventricle,  the  alar  and 
basal  laminae  come  to  occupy  the  floor  of  the  ventricle — the  basal  lamina  lying 
nearest  the  mesial  plane. 

The  Nerves. — The  nerves  are  developed,  like  the  rest  of  the  nervous  system, 


THE  EMBRYO. 


1179 


from  epiblast.  The  spinal  nerves  are  developed  as  follows  :  close  to  the  point  of 
involution  of  the  epiblast  in  the  median  line,  that  is  to  say,  in  the  angle  of  junc- 
tion of  the   neural  and  general   epiblast,    a   cellular   swelling,    the   neural  crest, 


%... Rhomboid 
lip. 

',';"','■  J.-  .Tractus 

solitarius. 


"f  -Vagus  nerve. 


■l'.'SjI.  Hypoglossal 

nerve. 

Fig.  727.— Transverse  section  of  medulla  oblongata  of  human  embryo.    (After  His.) 

appears  and  forms  a  continuous  ridge  of  epiblast  on  the  dorsal  aspect  of  the  neural 
canal  (Fig.  728).  On  this  crest  enlargements  occur  corresponding  with  the  middle 
of  each  protovertebral  segment.      These  enlargements  grow  downward  between 


Neural  canal. 
Neural  crest 


Pleuroperitoneal  cavity. 


Somatopleure. 


Splanchnopleure. 

Omphalo-mesenteric  vein. 


Fig.  728. — Transverse  section  of  a  portion  of  a  chick  embryo  of  twenty-nine  hours'  incubation.    (From 
Duval's  Atlas  d' Embryologie.) 

the  neural  canal  and  the  protovertebrse,  and  occupy  a  position  on  the  lateral  wall 
of  the  canal.  They  are  the  rudiments  of  the  ganglia  of  the  posterior  roots,  and 
at  first  are  attached  to  the  neural  crest  from  which  they  spring,  but  subsequently 
this  attachment  becomes  lost,  and  they  then  form  isolated  masses  on  either  side  of 
the  neural  canal.  They  consist  of  oval  cells,  from  either  end  of  which  a  process 
eventually  springs ;  one,  growing  centrally,  passes  into  the  embryonic  cord  and 
constitutes  the  posterior  root  of  the  nerve;  the  other,  growing  peripherally,  joins 
the  fibres  of  the  anterior  root  to  form  the  spinal  nerve. 

The  anterior  root  is,  according  to  the  researches  of  His,  a  direct  outgrowth  of 
the  neuroblasts  which  are  found  in  the  rudimentary  cord  (Fig.  722).  These  cells, 
at  first  rounded  or  oval,  become  pear-shaped,  with  their  tapering  prolongations 
directed  outward  toward  the  surface  of  the  cord.  These  prolongations  are  the 
future  axis-cylinders  of  the  anterior  nerve-roots ;  they  pass  out  of  the  cord 
in  bundles  and  penetrate  the  mesoblast  to  join  with  the  fibres  of  the  pos- 
terior root,  and  from  the  point  of  union  the  nerve  grows  toward  its  peripheral 
termination. 

Cranial  Nerves. — With  the  exception  of  the  olfactory  and  optic  nerves,  which 
will  be  specially  referred  to,  the  cranial  nerves  may  be  developmentally  considered 


1180 


EMBRYOLOGY. 


as  consisting  of  two  sets  :  (1)  those  which  arise  as  outgrowths  from  neuroblasts 
situated  in  the  brain,  similar  to  the  mode  of  origin  of  the  anterior  spinal  nerve- 
roots  ;  (2)  those  which  arise  from  ganglionic  rudiments  situated  outside  the  brain 
and  derived  from  the  neural  crest ;  from  the  neuroblasts  of  these  ganglionic  rudi- 
ments one  process  grows  into  the  brain  and  the  other  outward  toward  the  periph- 
ery, similar  to  the  arrangement  which  exists  regarding  the  posterior  spinal 
nerve-roots.  To  the  first  group  belong  the  third,  fourth,  sixth,  seventh,  eleventh, 
and  twelfth  nerves,  together  with  the  motor  roots  of  the  fifth,  ninth,  and  tenth. 
To  the  second  group  belong  the  eighth  and  the  sensory  roots  of  the  fifth,  ninth, 
and  tenth.  While,  however,  the  anterior  spinal  nerve-roots  arise  in  one  series 
from  the  ventral  part  of  the  cord,  the  cranial  motor  fibres  arise  by  two  sets  of 
roots,  ventral  and  lateral ;  the  former  include  the  roots  of  the  sixth  and  twelfth 
and  probably  those  of  the  third  and  fourth,  the  latter  embrace  the  spinal  accessory 
and  the  motor  roots  of  the  fifth,  seventh,  ninth,  and  tenth. 

The  olfactory  lobe,  or  rhinencephalon,  arises  toward  the  end  of  the  fourth 
week  as  a  protrusion  of  the  antero-ventral  part  of  each  cerebral  hemisphere 
(Fig.  726),  and  extends  forward  toward  the  thickened  epiblast  of  the  olfactory 
area  (see  page  1169).  It  is  subsequently  divided  by  a  transverse  constriction  into 
two  parts :  an  anterior,  which  gives  rise  to  the  olfactory  bulb  and  tract  together 
with  the  trigonum  olfactorium,  and  a  posterior,  which  becomes  the  peduncle  of 
the  corpus  callosum  and  the  greater  part  of  the  anterior  perforated  space.  Neuro- 
blastic  cells,  formed  within  the  olfactory  area,  pass  out  and  form  a  ganglion 
between  the  area  and  the  olfactory  bulb.  From  this  ganglion  cell-processes  grow 
centripetally  to  form  the  nerve-roots,  and  centrifugally  to  form  the  olfactory  nerves 
which  ramify  in  the  olfactory  mucous  membrane,  while  the  ganglion  itself  fuses 
with  the  olfactory  bulb. 

The  optic  nerve  arises  as  a  hollow  outgrowth  of  the  brain,  which  subsequently 
becomes  solid.     It  will  be  considered  in  connection  with  the  development  of  the  eye. 

The  sympathetic  nerves  are  developed  as  outgrowths  from  the  ganglia  on  the 
roots  of  the  spinal  and  cranial  nerves. 


Forebrain 


Invagination  of  epi- 
blast to  form  the 
lens  rudiment. 


ented  layer 
retina. 

^Epiblast. 


Nervous  part 

of  retina. 
Optic  stalk. 


Fig.  729.— Transverse  section  of  head  of  chick  embryo  of  forty-eight  hours'  incubation;  X  55.  (From  Duval's 
Atlas  d' Embryologie.) 


Development  of  the  Eye. — The  optic  nerve  and  retina  are  developed  as  an  out- 
growth from  the  rudimentary  brain,  which  extends  toward  the  side  of  the  head, 
and  is  there  met  by  an  ingrowth  from  the  epiblast,  out  of  which  the  lens  and  the 
epithelium  of  the  conjunctiva  and  cornea  are  developed. 

The  first  appearance  of  the  eye  consists  in  a  hollow  protrusion  of  the  fore- 
brain  ;  this  is  called  the  primitive  optic  vesicle.  It  is  at  first  an  open  cavity  com- 
municating by  a  hollow  stalk  with  that  of  the  cerebral  vesicle.  As  it  is  prolonged 
forward,  the  epiblast  lying  immediately  over  it  becomes  thickened,  and  then 
forms  a  depression  which  gradually  encroaches  on  the  most  prominent  part 
of  the  primitive  ocular  vesicle;  this  in  its  turn  appears  to  recede  before  it, 
so  as  to  become  at  first  depressed  and  then  inverted  in  the  manner  indicated 


THE   EMBRYO. 


1181 


of  the  vesicle  is   almost  obliterated 
and    the    original    vesicle   converted 


sForebrain. 


in  Figs.  729  and  730,  so  that  the  cavity 
by  the  folding  back  of  its  anterior  half, 
into  a  cup,  the  optic  cup,  in  which  the 
involuted  epiblastic  layer,  the  rudiment 
of  the  lens,  is  received  (Fig.  730) ;  at 
the  same  time  the  proximal  part  of  the 
vesicle  becomes  elongated  and  narrowed 
into  a  hollow  stalk,  the  optic  stalk. 
This  cup-shaped  cavity  consists  there- 
fore of  two  layers  :  one,  the  outer,  orig- 
inally the  posterior  half  of  the  primi- 
tive ocular  vesicle,  is  thin,  and  even- 
tually forms  the  pigmented  layer  of  the 
retina  ;x  the  other  layer,  the  inner,  orig- 
inally the  anterior  or  more  prominent 
half,  which  has  become  folded  back,  is 
much  thicker,  and  is  converted  into  the 
nervous  layers  of  the  retina  (Figs. 
730  and  732).  Between  the  two  is 
the  remnant  of  the  cavity  of  the  original  primary  optic  vesicle,  which  finally 
becomes  obliterated  by  the  union  of  its  two  layers.  When  the  retina  is  estab- 
lished, the  optic  nerve-fibres  originate  from  its  cells  and  grow  backward  toward 
the  brain,  along  the  optic  stalk,  and  thus  convert  it  into  a  solid  optic  nerve.  The 
nerve-fibres  become  ultimately  connected  with  the  mesencephalon,  a  relationship 


en  I  id  layer 
retina. 

Epiblast. 


Lens  rudiment. 
Nervous  part 
of  retina. 


Optic  stalk. 


Fig.  730.— Transverse  section  of  head  of  chick  embryo 
fifty-two  houis'    incubation.     (From   Duval's  Atlas 

d'  Embryologie.) 


of 


Fig.  731.— "Diagram  of  development  of  the  lens,  a, 
B,  c.  Different  stages  of  development.  1.  Epidermic 
layer.  2.  Thickening  of  this  layer.  3.  Crystalline 
depression.  4.  Primitive  ocular  vesicle,  its  anterior 
part  pushed  back  by  the  crystalline  depression.  5. 
Posterior  part  of  the  primitive  ocular  vesicle,  form- 
ing the  external  layer  of  the  secondary  ocular  vesi- 
cle. 6.  Point  of  separation  between  the  lens  and  the 
epidermic  layer.  7.  Cavity  of  the  secondary  ocular 
vesicle,  occupied  by  the  vitreous. 


Fig.  732.— Diagrammatic  sketch  of  a  vertical 
longitudinal  section  through  the  eyeball  of  a 
human  foetus  of  four  weeks.  (After  Kolliker.) 
Magnified  100  diameters.  The  section  is  a  little 
to  the  side,  so  as  to  avoid  passing  through  the 
ocular  cleft,  c.  The  cuticle,  where  it  becomes 
later  the  epithelium  of  the  cornea.  I.  The  lens. 
op.  Optic  nerve  formed  by  the  pedicle  of  the 
primary  optic  vesicle,  vp.  Primary  medullary 
cavity  of  the  optic  vesicle,  p.  The  pigment  layer 
of  the  retina,  r.  The  inner  wall  forming  the 
nervous  layers  of  the  retina,  as.  Secondary  optic 
vesicle  containing  rudiment  of  the  vitreous 
humor. 


which  is  permanently  maintained.  The  mouth  of  the  optic  cup  overlaps  the 
equator  of  the  lens  as  far  as  the  future  aperture  of  the  pupil.  In  this  region 
the  inner  or  retinal  layer  of  the  cup  does  not  become  differentiated  into  nervous 
elements,  but  remains  as  a  single  layer  of  columnar  cells,  which  becomes  applied 
to  the  cells  of  the  pigmented  layer,  and  the  conjoined  strata  form  the  pars  ciliaris 
pars  iridica  retinae  of  the  adult  (Fig.  734).  As  development  proceeds  the  optic 
cup  increases  in  size,  and  thus  a  space  is  formed  between  it  and  the  rudimentary 
lens  ;  this  is  the  secondary  optic  vesicle,  and  in  it  the  vitreous  humor  is  developed 
(Figs,  731,  c,  and  732).     The  folding  in  of  the  primary  optic  vesicle  to  produce 

1This  layer  was  formerly  described  as  belonging  to  the  choroid,  but  developmentally  it  is  seen 
to  be  a  part  of  the  retina. 


1182  EMBRYOLOGY. 

the  optic  cup  not  only  takes  place  in  front,  at  its  most  prominent  part,  opposite 
the  lens,  but  also  along  its  postero-inferior  aspect,  where  a  cleft  or  fissure  is 
formed,  the  choroidal  fissure,  through  which  the  mesoblast  extends  to  form  the 
vitreous  humor.  This  gap  or  cleft  is  continued  for  some  distance  into  the  stalk  of 
the  optic  vesicle,  and  thus  allows  a  process  of  the  mesoblast  to  extend  down  the 
stalk  to  form  the  arteria  centralis  retinae  and  its  accompanying  vein  (Fig.  733). 
After  a  time  the  gap  or  fissure  becomes  closed,  by  a  coalescence  of  its  margins,  but 
the  line  of  union  remains  apparent  for  a  considerable  period. 

The  lens  is  at  first  a  thickening  of  the  epiblast,  then  a  depression  or  involution 
takes   place,   thus   forming    an   open    follicle,    the    margins    of   which    gradually 


Thalamen- 
ecphalon. 


Optic  stalk. — -Ifi 


~/ 


,^-  Prosencephalon. 

^V          Margin  of 
optic  cup. 

\ 

T"™8^ 

\ 

•    if" 

.  J     Choroidal 

^^Hi       fissure. 

-   ^L 

) 

"x,. 

/__        Central  artery 

■  i£' 

pr    "              of  retina. 

Fig.  733.— Optic  cup  and  choroidal  fissure  seen  from  below,  from  a  human  embryo  of  about  four  weeks. 

(Kollmann.) 

approach  each  other  and  coalesce,  forming  a  cavity,  the  lens  vesicle,  enclosed  by 
epiblastic  cells  (Fig.  731,  B  c).  At  the  point  of  involution  the  external  layer  of 
epiblast  separates  from  the  lens  and  passes  freely  over  the  surface,  so  that  the  lens 
becomes  disconnected  from  the  general  epiblast,  and  recedes  into  the  ocular  cup, 
while  the  cuticular  layer  covering  it  is  developed  into  the  corneal  epithelium.  The 
cells  forming  the  posterior  or  inner  wall  of  the  lens  vesicle  rapidly  increase  in 
size,  becoming  elongated  and  developed  into  the  lens-fibres,  and,  filling  up  the 
cavity,  convert  it  into  a  solid  body.  The  cells  on  the  anterior  wall  retain  their 
cellular  character,  and  form  the  anterior  lens  epithelium  of  the  adult.  The 
secondary  optic  vesicle,  or  space  between  the  lens  and  the  hollow  of  the  optic  cup 
(Figs.  731,  7,  and  734),  contains  a  quantity  of  mesoblastic  tissue  continuous  with 
the  general  mesoblast  through  the  choroidal  fissure.  This  tissue  becomes  con- 
verted into  the  vitreous  humor,  and  surrounds  the  lens  with  a  vascular  membrane, 
the  vascular  capsule  of  the  lens.  From  the  central  artery  of  the  retina  several 
branches  are  prolonged  forward  through  the  vitreous  body  to  the  capsule  of  the 
lens,  but  by  the  sixth  month  these  have  all  undergone  atrophy  except  one,  which 
persists  till  the  ninth  month  as  the  arteria  hyaloidea.  It  disappears,  however, 
before  birth,  and  its  position  is  indicated  in  the  adult  by  the  canalis  hyaloideus  of 
Stilling.  The  front  part  of  the  vascular  capsule  of  the  crystalline  lens  forms  the 
rnembrana  pupillaris,  and  also  attaches  the  iris  to  the  capsule  of  the  lens.  It  dis- 
appears about  the  seventh  month.  The  sclera,  cornea,  and  choroid  are  developed 
from  the  mesoblast  surrounding  the  optic  vesicle. 

The  eyelids  are  formed  at  the  end  of  the  third  month,  as  small  cutaneous  folds 
(Fig.  734),  which  come  together  and  unite  in  front  of  the  globe  and  cornea.  This 
union  is  broken  up  and  the  eyelids  separate  before  the  end  of  foetal  life. 

The  lachrymal   sac  and  nasal   duct  appear  to  result  from  a  thickening  of  the 


THE   EMBRYO. 


1183 


epiblast  in  the  groove  between  the  lateral  nasal  and  maxillary  processes.      This 
thickening  becomes  hollowed  out  into  a  channel,  and  the  lips  of  the  groove  meet 


Rudiment  of  choroid 
Rectus  muscle. - 


Oplic  nerve. 


Retina. . 
Pigment  layer. 
Vitreous  body 
{shrunken). 


\  \i  -3  --Eyelid. 


-Lens. 


Cornea. 


Cavity  of  hind  brain. 


MemWrana 

papillaris. 

Eyelid. 


~-<f   Pars  ciliaris  and  pars  iridica  retinae. 
Fig.  734.— Horizontal  section  through  the  eye  of  an  eighteen  days'  embryo  rabbit ;  X  30.    (KSlliker.) 

over  it,  enclose  it,  and   convert  it  into  a  duct,  which  eventually  opens  into  the 
nasal  fossa. 

Development  of  the  Ear. — The  first  rudiment  of  the  ear  appears  shortly  after 
that  of  the  eye,  in  the  form  of  a  thickening  of  the  epiblast,  on  the  outside  of  that 
part  of  the  third  pi'imary  cerebral  vesicle  which 
eventually  forms  the  medulla  oblongata.  The 
thickening  is  then  followed  by  an  involution  of 
the  epiblast  (Fig.  735),  which  becomes  deeper 
and  deeper,  and  sinking  toward  the  base  of  the 
skull,  forms  a  flask-shaped  cavity ;  by  the  nar- 
rowing of  the  external  aperture  the  neck  of 
the  flask  constitutes  the  recessus  labyrinthi. 
The  mouth  of  the  flask  then  becomes  closed, 
and  thus  a  shut  sac  is  formed,  the  primitive 
auditory  or  otic  vesicle  (Fig.  T36),  which  by  its 
sinking  inward  comes  to  be  placed  between  the 
ali-sphenoid  and  basi-occipital  matrices.  From  it 
the  epithelial  lining  of  the  labyrinth  is  formed. 
The  primary  otic  vesicle  becomes  imbedded  in  a  mass  of  mesoblastic  tissue, 
which  rapidly  undergoes  chondrification  and  ossification.  The  vesicle  is  at  first 
flask-  or  pear-shaped  ;  the  neck  of  the  flask,  or  recessus  labyrinthi,  prolonged 
backward,  forms  the  aqu?eductus  vestibuli.  From  it  are  given  off"  certain  pro- 
longations or  diverticula,  from  which  the  various  parts  of  the  labyrinth  are  formed. 
One  from  the  anterior  end  gradually  elongates,  and,  forming  a  tube,  bends  on 
itself  and  becomes  the  cochlea.  Three  others,  which  appear  on  the  surface  of  the 
vesicle,  form  the  semicircular  canals,  of  which  the  external  canal  is  the  last  to  be 
developed  (Figs.  738  and  739).  Subsequently  a  constriction  takes  place  in  the 
original  vesicle,  which  nearly  divides  it  into  two,  and  from  these  are  formed  the 
utricle  and  saccule  (Fig.  739).     Finally,  the  auditory  nerve,  which  has  been  devel- 


Auditory  pit. 


Epiblast. 


Fig.  735. — Section  through  the  head  of 
a  human  embryo,  about  twelve  days  old, 
in  the  region  "of  the  hind-brain.  "(Koll- 
mann.) 


1184 


EMBRYOLOGY. 


oped  from  the  "  neural  crest  "  in  the  manner  above  described  (page  1180),  pierces 
the  auditory  capsule  in  two  main  divisions — one  for  the  vestibule,  the  other  for  the 
cochlea.  The  middle  ear  and  Eustachian  tube  are  the  remains  of  the  inner  part 
of  the  first  branchial  cleft  (hyomandibular),  and  are  closed  externally  by  the  mem- 
brana  tympani,  which  originally  consists  of  a  layer  of  epiblast  externally,  and  a 
layer  of  hypoblast  internally ;  between  these  two  layers  the  mesoblast  extends  to 
form  the  substantia  propria  of  the  membrane.     With  regard  to  the  exact  mode 


Recessus  labyrinth* 
(aquxductus  vestibuli). 


Hind-brain. 


Auditory  vesicle. 


-Otic  vesicle. 


Fig.  736. — Section  through  hind-brain 
and  otic  vesicle  of  an  embryo  more  ad-  Fig.  737. — Left  auditory  vesicle  of  a  human  embryo  of  four 

vanced  than  that  of  Fig.  735.   (After  His.)       weeks,  seen  from  the  outer  surface.     (W.  His,  Jr.) 

of  development  of  the  ossicles  of  the  middle  ear  there  is  considerable  difference 
of  opinion.  The  most  probable  view  is  that  the  incus  and  malleus  are  developed 
from  the  proximal  end  of  the  mandibular  (Meckel's)  cartilage  (Fig.  719):  that 
the  base  of  the  stapes  is  formed  by  the  ossification  of  the  cartilage  which  fills  in 
the  foramen  ovale  and  its  arch  from  the  ossified  proximal  end  of  the  hyoidean  arch. 
The    external   auditory  meatus    is    formed    from    the   outer  part  of  the  hyo- 


Becessus  labyrinthi. 


Superior  semicircular  canal 


Posterior  semi- 
/circular  canal. 
jb^    External  semi- 
>v/  circular  canal. 


Rudiment  of  cochlea. 
Fig.  738.— Left  auditory  vesicle  of  a  human  embryo  of  five  weeks,  seen  from  the  outer  surface.    (W.  His,  Jr.) 

mandibular  cleft,  while  the  pinna  is  developed  by  the  gradual  differentiation  of  a 
series  of  processes  which  appear  around  the  outer  margin  of  the  cleft  (Fig.  741). 
Development  of  the  Nose. — The  olfactory  fossae,  like  the  primary  auditory  vesi- 
cles, are  formed  in  the  first  instance  by  a  thickening  and  involution  of  the  epiblast, 
which  takes  place  about  the  fourth  week,  at  a  point  below  and  in  front  of  the  ocular 
vesicle  (Fig.  723).  The  borders  of  the  involuted  portion  very  soon  become  promi- 
nent, in  consequence  of  the  development  of  the  mesial  and  lateral  nasal  processes 
already  referred  to  (page  1169),  and  which  are  formed  on  either  side  of  the  rudi- 
mentary fossa  (Figs.  714,  715).     As  these  processes  increase,  the  fossa  deepens 


THE   EMBRYO. 


1185 


and  becomes  converted  into  a  channel,  which  eventually  forms  the  olfactory  region 
of  the  nose  ;  this  comprises  tne  portion  to  which  the  olfactory  nerves  are  distributed. 
At  this  time  the  nasal  cavity  is  continuous  with  the  buccal  cavity  ;  but  as  the  palatal 
septum  is  formed,  the  buccal  cavity  is  divided  into  two  parts,  the  upper  of  which 


Ganglion 
cochleare' 


•m — Vertical  semi- 
circular canal. 


SB —  Utricle. 

Saccule. 

W. .External  semi- 
circular canal. 


V-Ductus  cochlearis. 


Fig.    739.— Transverse   section   through    head   of  foetal    sheep,  in  the    region   of    the  labyrinth.    X  30. 
(After  Boettcher.) 

forms  the  lower  part  of  the  nasal  fossae,  while  the  remainder  forms  the  permanent 
mouth.  On  the  mesial  wall  of  the  nasal  fossa  a  small  blind  pit  of  epiblast  becomes 
invaginated  and  extends  backward  into  the  nasal  septum.  This  forms  the  rudi- 
ment of  Jacobsons  organ,  which  ultimately  becomes  partly  enclosed  in  a  curved 
cartilaginous  plate  derived  from  a  cartilage  of  the  nasal  septum. 


.^    Embryonic    con- 
's ~S      nective  tissue. 
3  -o 


|fe     Canal  of 
v<\     cochlea. 


Epithelium  of  Corti's  organ. 


Yr^f-0^*^  Ligamentum 
spircUe. 

Scala  tympani. 


Fig.  740.— Transverse  section  of  the  canal  of  the  cochlea  of  a  foetal  cat. 
(Fiom  Kollmann's  Entwickelungsgeschichte.) 


(After  Boettcher  and  Ayres.) 


The  development  of  the  external  nose  has  already  been  described.  It  is 
perceptible  about  the  end  of  the  second  month.  The  nostrils  are  at  first  closed 
by  epithelium,  but  this  disappears  about  the  fifth  month. 

The  olfactory  lobe  (rhinencephalon)  is  formed,  as  already  explained,  by  an 
evagination  of  the  anterior  cerebral  vesicle. 

75 


1186  EMBR  YOL  OGY. 

Development  of  the  Skin,  Glands,  and  Soft  Parts. — The  epidermis  and  its 
appendages,  consisting  of  the  hairs,  nails,  sebaceous  and  sweat  glands,  are  devel- 
oped from  the  epiblast,  while  the  corium  or  true  skin  is  of  mesoblastic  origin. 
About  the  fifth  week  the  epidermis  consists  of  two  layers  of  cells,  the  deeper  one 
corresponding  to  the  rete  mucosum.  The  subcutaneous  fat  forms  about  the  fourth 
month,  and  the  papillae  of  the  true  skin  about  the  sixth.  A  considerable  desqua- 
mation of  epidermis  takes  place  during  fetal  life,  and  this  desquamated  epidermis, 
mixed  with  a  sebaceous  secretion,  constitutes  the  vernix  caseosa,  with  which  the 

Helix. 

Helix. 

,  Helix. 
Antihelix. . 

Helix.*  jM  "\       h...    Antihelix 


Tragus.  - 


Mandible.'  ,S    \  Tragus 


Antitragus. 


Lobule     \ 

Antitragus  Mandible.  Lobule. 

Fig.  ?41.— Left  ears  of  human   embryos,  estimated  at  thirty-five   and  thirty-eight  days   respectively. 
(After  His.) 

skin  is  smeared  during  the  last  three  months  of  fetal  life.  The  nails  are  formed 
at  the  third  month,  and  begin  to  project  from  the  epidermis  about  the  sixth.  The 
hairs  appear  between  the  third  and  fourth  months  in  the  form  of  solid  downgrowths 
of  the  deeper  layer  of  the  epidermis,  which  then  become  inverted  by  papillary 
projections  from  the  corium.  About  the  fifth  month,  the  fetal  hairs  (lanugo) 
appear,  first  on  the  head  and  then  on  the  other  parts ;  they  drop  off  after  birth, 
and  give  place  to  the  permanent  hairs.  The  cellular  structure  of  the  sudoriferous 
and  sebaceous  glands  is  formed  from  the  epiblast,  while  the  connective  tissue  and 


Aortic  bulb.- 4. 


Forebrain,-—^—^  J^fe--.-  -t-Optic  vesicle. 

\ 

WF    '  f  / 


Vi 


Auricle.—*^ 


Ventricle. 


-Omphalo-mesen- 
teric  veins. 


Fig.  742.—  Head  of  chick  embryo  of  about  thirty-eight  hours'  incubation,  viewed  from  the  ventral  surface. 
(From  Duval's  Atlas  d' Embryologie.) 

blood-vessels  are  derived  from  the  mesoblast.  The  mammary  gland  is  also  formed 
partly  from  mesoblast  and  partly  from  epiblast — its  blood-vessels  and  connective 
tissue  being  derived  from  the  former,  its  cellular  elements  from  the  latter.  Its 
first  rudiment  is  seen  about  the  third  month,  in  the  form  of  a  small  projection 
inward  of  epithelial  elements,  which  invade  the  mesoblast;  from  this,  similar 
tracts  of  cellular  elements  radiate ;   these  subsequently  give  rise  to  the  glandular 


THE   EMBRYO. 


1187 


follicles  and  ducts.  The  development  of  the  former,  however,  remains  imperfect, 
except  in  the  adult  female. 

Development  of  the  Limbs. — The  upper  and  lower  limbs  begin  to  project,  as 
buds,  from  the  anterior  and  posterior  part  of  the  embryo  about  the  fourth  week. 
These  buds  are  formed  by  a  projection  of  the  somatopleure  from  the  point  where 
the  mesoblast  splits  into  its  parietal  and  visceral  layers,  just  external  to  the  verte- 
bral somites,  of  which  they  may  be  regarded  as  lateral  extensions.  The  division 
of  the  terminal  portion  of  the  bud  into  fingers  and  toes  is  early  indicated,  and  soon 
a  notch  or  constriction  marks  the  future  separation  of  the  hand  or  foot  from  the 
forearm  or  leg.  Next,  a  similar  groove  appears  at  the  site  of  the  elbow  or  knee. 
The  indifferent  tissue,  of  which  the  whole  projection  is  at  first  composed,  is  differ- 
entiated into  muscle  and  cartilage,  before  the  appearance  of  any  internal  clefts  for 
the  joints  between  the  chief  bones. 

The  muscles  become  visible  about  the  seventh  or  eighth  week.  The  voluntary 
muscles  are  developed  from  the  muscle-plates  of  the  protovertebral  somites,  which 
are  at  first  segmentally  arranged  on  either  side  of  the  rudimentary  spine.  Each 
muscle-plate  becomes  differentiated  into  two  parts,  superficial  and  deep.  The 
former  is  termed  the  cutis  plate,  and  from  it  the  corium  or  true  skin  is  developed, 
while  the  latter  becomes  developed  into  longitudinal  groups  of  muscle-fibres,  ex- 
tending forward  into  the  neck  and  head  region  of  the  embryo  and  laterally  to 
enclose  the  cavities  of  the  thorax  and  abdomen.     The  muscles  of  the  limbs  are  also 


Maxillary  process. 
Stomodseum. 
Mandibular  arch. 


Aortic  bulb,~ 


Ventricle. 
Vena  cava  superior. 


Umbilical  vein.-- 


Fig.  743.— Heart  of  human  embryo  of  about  fifteen  days.    (Reconstruction  by  His.) 


formed  from  the  same  source,  being  produced  by  outgrowths  from  the  protoverte- 
bral somites  in  those  situations  where  the  limb  buds  appear.  The  involuntary 
muscles  are  derived  from  the  splanchnopleure  mesoblast,  and  are  therefore  not 
connected  in  any  way  with  the  protovertebral  somites. 

Development  of  the  Blood-vascular  System. — There  are  three  distinct  stages  in 
the  development  of  the  circulatory  system,  each  in  accordance  with  the  manner  in 
which  nourishment  is  provided  for  at  different  periods  of  the  existence  of  the  in- 
dividual. In  the  first  stage  there  is  the  vitelline  circulation,  during  which  nutri- 
ment is  extracted  from  the  vitellus  or  contents  of  the  yolk-sac.  In  the  second 
stage  there  is  the  placental  circulation,  during  which  nutrition  is  obtained  by 
means  of  the  placenta  from  the  blood  of  the  mother.  In  the  third  stage  there  is 
the  complete  circulation  of  the  adult,  commencing  at  birth,  during  which  nutrition 
is  provided  for  by  the  organs  of  the  individual  itself. 

1.  The  vitelline  circulation  is  carried  on  partly  within  the  body  of  the  embryo, 
and  partly  external  to  it  in  the  vascular  area  of  the  yolk-sac.  It  consists  of  a 
median  tubular  heart,  from  which  two  vessels  (arteries)  project  anteriorly.  These 
carry  the  blood  to  a  plexus  of  capillaries  spread  over  the  vascular  area,  from  which 


1188 


EMBRYOLOGY. 


the  blood  is  returned  by  two  vessels  (veins)  which  enter  the  heart  posteriorly,  and 
thus  a  complete  circulation  is  formed  (Fig.  744). 

In  these  vessels  and  the  heart  a  fluid  (blood)  is  contained,  in  which  rudi- 
mentary corpuscles  are  found.  The  mode  of  formation  of  these  elementary  parts 
must  first  be  considered. 

In  mammalia  the  heart  is  formed  by  a  longitudinal  fold  of  the  splanchnopleure 
with  its  underlying  hypoblast  on  either  side  of  the  median  line  in  front  of  the 
anterior  extremity  of  the  rudimentary  pharynx,  at  about  the  level  of  the  posterior 
primary  cerebral  vesicle.  The  folds  become  tubes,  their  walls  thicken  and  present 
two  distinct  strata  of  cells :  the  inner  and  thinner  layer,  derived  from  the  hypo- 
blast, forms  the  endocardium ;  the  outer  and  thicker,  derived  from  the  visceral 
mesoblast,  forms  the  muscular  wall  of  the  heart.  In  its  primitive  condition,  the 
heart  consists  therefore  of  a  pair  of  tubes,  one  on  either  side  of  the  body.  These, 
however,  soon  coalesce  in  the  median  line,  and,  fusing  together,  form  a  single 
central  tube.1  Each  of  the  two  primary  tubes  receives  posteriorly  a  large  vein 
(the  omphalo-mesenteric  vein),  and  is  prolonged  anteriorly  into  an  artery  (the 
primitive  aorta).  So  that  after  fusion  of  the  heart-tubes  has  taken  place  there  is, 
in  the  primitive  vitelline  circulation,  as  above  mentioned,  a  single  tubular  heart, 


if' 

Primitive  jugular — "%-X&  *^t^# p, ' 
vein.  ^'^SZs&Bf^* 

V- 

Amnion- ~~~'s^3T$Zj^°^4    i   r  -       :| 

Cardinal  vein. f^/ff'  '  -^  '  .^O^  T  ■    '  -     ''  K 

Descending  aorta." V*;:-r;TPs^ik  '    ,  $        ~  *****%' .- 

^\i\  — X,/  ;-"• 

Abdominal  stalk, ^x~^-    -':  |    •  ,  .,  "*'  '-^v --:--^- - ' 

(Bauchstiel).  — — -_    --f: ;.. '.      -  -:Z^r^— - — 

Chorionic  villi. <J    (J  V  (J 

Fig.  744.— Human  embryo    of    about    fourteen   days,  with  yolk-sac.     (After  His.)     (From  Kollmann's 
Enl  wickel  un  gsgeschichte. ) 

with  two  arteries  proceeding  from  it  and  two  veins  emptying  themselves  into  it. 
The  first  blood-vessels  are  developed  as  follows :  The  nucleated  embryonic  cells  of 
the  mesoblast  send  out  processes  in  various  directions.  These  processes  fuse  to- 
gether, and  an  irregular  network  is  formed.  The  nuclei  of  the  cells  multiply,  and, 
accumulating  around  themselves  a  small  quantity  of  the  protoplasm  of  the  cell, 
they  acquire  a  tinge  of  color  and  form  the  first  red  blood-corpuscles.  The  proto- 
plasm of  the  cells  and  their  branched  network  become  hollowed  out  into  a  system 
of  canals  containing  fluid,  in  which  the  newly  formed  corpuscles  float  (Fig.  745).2 

The  earliest  blood-corpuscles  are  all  nucleated,  and  in  this  and  other  respects — 
that  is,  in  their  possession  of  amoeboid  movements  and  in  their  capability  of  under- 

1In  most  fishes  and  in  amphibia  the  heart  originates  as  a  single  median  tube. 

2  Recent  observers  incline  to  the  view  that  the  blood-corpuscles  are  of  hypoblastic  origin,  being 
developed  from  the  endothelium  of  the  vessels,  the  sequence  of  the  development  of  the  different 
structures  being:  first  the  heart,  then  the  blood-vessels,  and  lastly  the  blood-corpuscles.  (Consult 
Dr.  Ernest  Mehnert's  Biomeckanik,  Jena,  1898.) 


THE   EMBRYO. 


1189 


Fig.  745. — Various  forms  of  mother-cells  under- 
going development  into  blood-vessels,  from  the 
middle  layer  of  the  chick's  blastoderm.  (Klein.) 
a.  Large  mother-cell  vacuolated,  forming  the 
rudimentary  vessel,  b.  The  wall  of  this  cell 
formed  of  protoplasm,  with  nuclei  embedded,  and 
in  some  cases  more  or  less  detached  and  projecting, 
c.  Processes  connected  with  neighboring  cells, 
formed  of  the  common  cellular  substance  of  the 
germinal  area.  d.  Blood-corpuscles.  /.  Small 
mother-cells— vacuolation  commencing.  B. 
Mother-cell  in  which  only  obscure  granular  matter 
is  found. 


going  multiplication  by  division — resemble  the  white  corpuscles.  Soon,  however, 
true  white  corpuscles  make  their  appearance,  and  it  seems  that  they  are  derived 
from  the  rudiments  of  the  thymus  gland.1  The  nucleated  condition  of  the  red 
globules  ceases  before  birth.  The  vitelline  circulation  commences  about  the 
fifteenth  day  and  lasts  till  the  fifth  week.  When  fully  established,  it  is  carried  on 
as  follows  :  Proceeding  from  the  anterior  end  of  the  tubular  heart  are  two  arteries, 
the  primitive  aortae  ;  these  run  down  in 
front  of  the  primitive  vertebrae  and  behind 
the  walls  of  the  intestinal  cavity  into  the 
two  omphalo-mesenteric  arteries,  which 
ramify  in  the  vascular  area  of  the  yolk- 
sac.  Here  they  terminate  peripherally  in 
a  circular  vessel — the  terminal  sinus, 
which  surrounds  the  vascular  area.  The 
blood  is  collected  from  the  capillaries  of 
the  vascular  area  into  the  two  omphalo- 
mesenteric veins,  which  open  into  the  pos- 
terior extremity  of  the  heart. 

2.  The  Placental  Circulation. — As  the 
umbilical  vesicle  diminishes,   the  allantois 
and    the    placenta    are   developed   in   the 
manner    above    described     (page    1162). 
When  the  umbilical  vesicle   atrophies  the 
placenta  becomes  the  only  source  of  nutri- 
tion for  the  embryo.      The  allantois  carries 
with  it  two  arteries  [umbilical  or  allantoic). 
derived  from  the  primitive  aortas,  and  two 
veins ;    these  vessels    become    much    en- 
larged as  the  placental  circulation  is  established,  but  subsequently  one  of  the  veins 
disappears,  and  in  the  later  stages   of  uterine  life  the  circulation  is   carried  on 
between  the  foetus  and  the  placenta  by  two  umbilical  arteries  and  one  umbilical 
vein. 

During  the  occurrence  of  these  changes  great  alterations  take   place  in  the 
primitive  heart  and  blood-vessels,  and  now  require  description. 

Further  Development  of  the  Heart. — The  following  is  an  outline  of  the  changes 
which  take  place  during  the  further  development  of  the  heart. 

The  simple  tubular  heart, 
already  described,  becomes  elon- 
gated and  bent  on  itself,  so  as  to 
form  an  S-shaped  loop,  the  anterior 
part  bending  to  the  right  and  the 
posterior  part  to  the  left.  The 
intermediate  portion  arches  trans- 
versely from  right  to  left,  and  then 
turns  sharply  forward  into  the 
anterior  part  of  the  loop.  Slight 
constrictions  make  their  appearance 
in  the  tube  and  divide  it  into  four 
parts,  viz.  :  (1)  the  sinus  venosus 
(sinus  reuniens  of  His) ;  (2)  the 
common  auricle  ;  (3)  the  common 
ventricle  :  (4)  the  aortic  bulb.    The 

common   auricle  and  ventricle  communicate  by  a  short  canal,  the  auricular  canal 
(Figs.  742,  743,  and  746). 

The  sinus  venosus  is  situated  in  the  septum  transversum  (a  layer  of  mesoblast 
from  which  the  ventral  part  of  the  Diaphragm  is  developed)  behind  the  common 
1  Consult  an  article  by  J.  Beard.  Analomischer  Anzeiger,  December,  1900. 


Bight 

auricle 


._   Left 
auricle. 


lortic 
bulb. 


utricle. 


Fig.  746,— Heart  of  a  human  embryo  of  5  mm.  in  length,  seen 
from  the  front ;    >.  30.    (His.) 


1190 


EMBRYOLOGY. 


auricle,  and  is  formed  by  the  union  of  three  pairs  of  veins,  viz.,  (1)  the  veins  or 
ducts  of  Cuvier  from  the  body  of  the  embryo ;  (2)  the  omphalo-mesenteric  veins 
from  the  yolk-sac ;  (3)  the  umbilical  veins  from  the  placenta  (Fig.  747).  The 
sinus  is  at  first  placed  transversely,  and  opens  by  a  median  aperture  into  the 
common  auricle.  Soon,  however,  it  assumes  an  oblique  position,  and  its  right 
half  or  horn  becomes  larger  than  the  left,  while  the  opening  into  the  auricle  is 
found  to  be  in  the  right  portion  of  the  auricular  cavity.  The  right  horn  ultimately 
becomes  incorporated  with  and  forms  a  part  of  the  right  auricle,  the  line  of 
union  between  it  and  the  auricle  proper  being  indicated  in  the  interior  of  the 
adult  auricle  by  a  vertical  crest,  the  crista  terminalis  of  His.  The  left  horn, 
which  ultimately  receives  only  the  lefir  duct  of  Cuvier,  persists  as  the  coronary 
sinus  (Fig.  753).  The  omphalo-mesenteric  and  umbilical  veins  are  soon  replaced 
by  a  single  vessel,  the  inferior  vena  cava,  and  the  three  veins  (inferior  vena  cava 
and  right  and  left  Cuvierian  ducts)  open  into  the  dorsal  aspect  of  the  auricle  by  a 
common  slit-like  aperture.     The  upper  part  of  this  aperture  represents  the  opening 


Aortic 
Left  auricle 
Left  ventricle.' 


Eiqht  auricle. 


.Superior  vena  cava. 
■Septum  transversum. 

■Umbilical  vein. 


Vitelline  or  Omphalo-mesenteric  vein. 
Fig.  747.— Heart  of  a  human  embryo  4.2  mm.  in  length,  seen  from  behind.    (His.) 

of  the  permanent  superior  vena  cava,  the  lower  part  that  of  the  inferior  vena  cava, 
and  the  intermediate  part  the  orifice  of  the  coronary  sinus.  The  slit-like  aperture 
lies  obliquely,  and  is  bordered  on  its  mesial  and  lateral  aspects  by  a  fold  of  endo- 
cardium. The  mesial  part  of  the  fold  disappears,  while  from  the  lateral  part  the 
Eustachian  and  Thebesian  valves  are  developed.  At  the  lower  extremity  of  the 
slit  is  a  triangular  thickening,  the  spina  vestibuli  of  His,  which  partly  closes  the 
aperture  between  the  two  auricles,  and  which,  according  to  His,  takes  a  part  in  the 
formation  of  both  the  interauricular  and  interventricular  septum. 

The  common  auricle  becomes  gradually  subdivided  into  right  and  left  auricles 
by  a  septum,  the  septum  superius,  which  grows  from  its  dorsal  and  upper  wall  so 
that  the  two  auricles  communicate  with  each  other  only  below  the  margin  of  this 
septum.  This  communication  (ostium  primum  of  Born)  does  not,  however,  represent 
the  future  foramen  ovale,  for  the  septum  grows  downward  and  blends  with  the 
partition  which  comes  to  subdivide  the  auricular  canal.  The  foramen  ovale 
(ostium  secundum  of  Born)  results  from  a  perforation  of  the  upper  part  of  the 
septum  superius. 

The  auricular  canal  is  at  first  a  short  straight  tube  connecting  the  auricular  with 
the  ventricular  portion  of  the  heart,  but  it  becomes  overlapped  by  the  growing 
auricles  and  ventricles  so  that  its  position  on  the  surface  of  the  heart  is  indicated 
only  by  an  annular  constriction  (Fig.  746).  Its  lumen  is  reduced  to  a  trans- 
verse slit,  and  a  thickening  appears  on  its  dorsal  and  ventral  walls.  These  thick- 
enings, or  endocardial  cushions  as  they  are  termed,  project  into  the  canal,  and, 
meeting  in  the  middle  line,  divide  the  canal  into  two  channels,  the  future  right 
and  left  auriculo-ventricular  orifices. 

The  common  ventricle  becomes  divided  by  a  septum,  the  septum  inferius,  which 


THE   EMBRYO. 


1191 


grows  upward  from  the  lower  part  of  the  ventricle,  its  position  being  indicated  on 
the  surface  of  the  heart  by  a  furrow.  It  extends  upward  almost  as  far  as  the 
auricular  canal,  but  for  some  time  an  interventricular  foramen  exists  between  it  and 
the  septum  of  the  auricular  canal  (Fig.  748). 


Aortic  septum. 

Common  auriculo- 
ventricular  orifice. 


Pulmonary 

artery. 
Bight 

auriculo- 

ventricular 

orifice, 


Aortic  septum. 


Aorta. 


Right 

ventricle 


Septum         Left 
inferius.    ventricle. 


Right 

ventricle. 


Left 
Septum  inferius.    ventricle. 


Fig.  748.— Showing  the  development  of  the  septum  of  the  aortic  hulb  and  of  the  ventricles.    (Born.) 

The  aortic  bulb  is  divided  by  the  aortic  septum.  This  makes  its  appearance 
at  the  distal  end  of  the  bulb  as  two  ridge-like  thickenings  of  its  endothelial 
lining;  these  increase  in  size,  and,  projecting  into  the  lumen,  ultimately  fuse 
to  form  the  septum,  and  thus  the  aortic  bulb  is  divided  into  the  pulmonary  artery 
and  the  aorta.  The  aortic  septum  takes  a  spiral  course  toAvard  the  proximal  end 
of  the  bulb,  so  that  the  two  vessels  lie  side  by  side  above ;  but  near  the  heart  the 
pulmonary  artery  is  in  front  of  the  aorta  (Fig.  749).  The  septum  grows  down 
into  the  ventricle  as  an  oblique  partition,  which  ultimately  blends  with  the  septum 


Aorta. 


Aorta. 


rpulmo- 

Pulmonary  nary  artery.  Pulmonary 

artery.  artery. 

Fig.  749.— Transverse  sections  through  the  aortic  bulb  to  show  the  growth  of  the  aortic  septum.    The  lowest 
section  is  on  the  left,  the  highest  on  the  right,  of  the  figure.    (After  His.j 

inferius  of  the  ventricles  in  such  a  way  as  to  bring  the  left  ventricle  into  commu- 
nication with  the  aorta  and  the  right  with  the  pulmonary  artery. 

Peculiarities  of  the  Foetal  Heart. — In  early  foetal  life  the  heart  is  placed  directly 
under  the  head  and  is  relatively  of  large  size.  Later  it  assumes  its  position  in 
the  thorax  but  lies  at  first  in  the  middle  line ;  toward  the  end  of  pregnancy  it 
gradually  becomes  oblique.  Its  auricular  portion  is  at  first  larger  than  the  ven- 
tricular part,  and  the  two  auricles  communicate  freely  through  the  foramen  ovale. 
In  consequence  of  the  communication,  through  the  ductus  arteriosus,  between  the 
pulmonary  artery  and  the  aorta,  the  contents  of  the  right  ventricle  are  mainly 
carried  into  the  latter  vessel  instead  of  to  the  lungs,  and  hence  the  wall  of  the 
right  ventricle  is  as  thick  as  that  of  the  left.  At  the  end  of  foetal  life,  however, 
the  left  ventricle  is  thicker  than  the  right,  a  difference  which  becomes  more  and 
more  emphasized  after  birth. 

Further  Development  of  the  Arteries. — In  the  vitelline  circulation,  two  arteries 
were  described  as  coming  off  from  the  primitive  heart,  and  running  down  in  front 
of  the  developing  vertebrse.  The  first  change  consists  in  the  fusion  of  these  arteries 
into  one  vessel  at  some  distance  from  the  heart ;  this  vessel  is  the  descending 
thoracic  and  abdominal  aorta.  In  consequence  of  the  lengthening  of  the  neck  the 
heart  falls  backward  to  its  lower  part  and  then  into  the  thorax,  and  the  two 
original  arteries,  proceeding  from  the  heart  to  their  point  of  fusion  in  the  common 


1192 


EMBRYOLOGY. 


descending  aorta,  become  elongated  and  assume  an  arched  form,  curving  backward 
on  each  side,  from  the  front  of  the  body  toAvard  the  vertebral  column  (Fig.  751,  a). 
These  are  the  first  or  primitive  aortic  arches.  As  the  heart  recedes  into  the  thorax, 
and  these  arches,  which  correspond  in  position  to  the  mandibular  arch,  become 
elongated,  four  additional  pairs  of  arches  are  formed  behind  them  around  the 
pharynx,  one  in  each  branchial  arch  (Fig.  750).  The  arches,  five  in  number, 
remain  permanent  in  fishes,  giving  off  from  their  convex  borders  the  branchial 
arteries  to  supply  the  gills.  In  many  animals  the  five  pairs  do  not  exist  together, 
for  the  first  two  have  disappeared  before  the  others  are  formed  ;  but  this  is  not  so 
in  man,  where  all  five  arches  are  present  and  pervious  during  a  certain  period  of 
embryonic  existence  (Fig.  750).      Only  some  of  the  arches  in  mammalia  remain  as 


Second  aortic  arch. 
Third  aortic  arch. 


Auditor 


Primiti 
jugular 

Fourth  aortic  ar 

Fifth  aortic- 
arch. 

Dorsal  aorta. ' 


Cardinal  vein. 


Mid-gut.  —  fe 


Hind-gut 


First  aortic  arch. 


Olfactory  j)  it. 


-  - .  ""  Maxillary  process. 
-^  ' '  Hyo-mandibular  cleft. 
^"•Mandibular  arch. 

Aortic  bulb. 

Auricle. 

Duct  of  Cuvier. 

Ventricle. 


Allantois. 
Umbilical  (allantoic  artery). 


Umbilical  vein. 


Fig.  750.— Profile  view  of  a  human  embryo,  estimated  at  twenty  or  twenty-one  days  old.     (After  His.) 


permanent  structures  ;  the  others,  or  portions  of  them,  become  obliterated  or  dis- 
appear. The  first  two  arches  entirely  disappear.  The  third  remains  as  a  part  of 
the  internal  carotid  artery,  the  remainder  being  formed  by  the  upper  part  of  the 
posterior  aortic  root — i.  e.,  the  descending  part  of  the  original  vessel  which  pro- 
ceeded from  the  rudimentary  tubular  heart.  The  common  and  external  carotid 
arteries  are  formed  from  the  anterior  aortic  root — that  is,  the  ascending  portion  of 
the  same  primitive  vessel.  The  fourth  arch  on  the  left  side  becomes  developed  into 
the  permanent  arch  of  the  aorta  in  mammals ;  but  in  birds  it  is  the  fourth  arch  on 
the  right  side  which  forms  the  aortic  arch  ;  in  reptiles  the  fourth  arch  on  both  sides 
persists,  so  that  these  animals  possess  a  permanent  double  aortic  arch.  The  fourth 
arch  on  the  right  side  forms  the  subclavian  artery,  and  by  the  junction  of  its  com- 


THE  EMBRYO. 


1193 


menceinent  with  the  anterior  aortic  root,  from  which  the  common  carotid  is  de- 
veloped, it  forms  the  innominate  artery.1  The  fifth  arch  on  the  left  side  forms  the 
pulmonary  artery  and  the  ductus  arteriosus ;  that  on  the  right  side  becomes 
atrophied  and  disappears.  The  first  part  of  the  fifth  left  arch  remains  connected 
with  that  part  of  the  aortic  bulb  which  is  separated  as  the  pulmonary  stem,  and 
with  it  forms  the  common  pulmonary  artery.  From  about  the  middle  of  this 
arch  two  branches  are  given  off,  which  form  the  right  and  left  pulmonary  arteries, 


Fig.  751.—  Showing  the  formation  of  the  aortic  arches  and  the  large  arteries.  I.  II.  III.  IV.  V.  First,  second, 
third,  fourth,  and  fifth  aortic  arches.  A.  Common  trunk  from  which  the  first  pair  spring;  the  place  where  the 
succeeding  pairs  are  formed  is  indicated  by  dotted  lines.  B.  Common  trunk,  with  four  arches  and  a  trace  of  the 
fifth.  C.  Common  trunk,  with  the  three  last  pairs,  the  first  two  having  been  obliterated.  D.  The  persistent 
arteries,  those  which  have  disappeared  being  indicated  by  dotted  lines.  1.  Common  arterial  trunk.  2.  Thoracic 
aorta.  3.  Right  branch  of  the  common  trunk  which  is  only  temporary.  4.  Left  branch,  permanent.  5.  Axillary 
artery.  6.  Vertebral.  7,  8.  Subclavian.  9.  Common  carotid.  10.  External,  and  11.  Internal  carotid.  12.  Aorta. 
13.  Pulmonary  artery.    14, 15.  Right  and  left  pulmonary  arteries. 


respectively,  and  the  remaining  portion — that  is,  the  part  beyond  the  origin  of  the 
branches — communicates  with  the  left  fourth  arch,  and  constitutes  the  ductus 
arteriosus.  This  duct  remains  pervious  during  the  whole  of  foetal  life,  but  after 
birth  becomes  obliterated  (Fig.  752).  A  series  of  intersegmental  or  intervertebral 
arteries  arise  from  the  primitive  dorsal  aortae,  those  in  the  neck  alternating  with 
the  cervical  segments  of  the  spine.  The  intersegmental  artery  which  lies  between 
the  sixth  and  seventh  segments  forms  the  lower  part  of  the  vertebral  artery  ;  its 
upper  part  is  formed  by  an  antero-posterior  anastomosis  between  the  higher  inter- 
segmental vessels.  The  subclavian  artery  is  originally  a  branch  of  the  vertebral, 
but,  owing  to  the  subsequent  growth  of  the  upper  limb,  it  comes  to  exceed  in  size 
the  parent  trunk. 

The  development  of  the  arteries  in  the  lower  part  of  the  body  is  going  on 
during  the  same  time.  It  has  been  seen  that  originally  there  were  two  primitive 
aortse  coming  off  from  the  simple  tubular  heart.  These  two  vessels  course  down- 
ward, one  on  either  side  of  the  notochord,  and  supply  the  omphalo-mesenteric 
arteries  to  the  yolk-sac.  At  the  hinder  end  of  the  embryo  the  primitive  aortas 
give  off  the  two  umbilical  or  allantoic  arteries  which  run  in  the  walls  of  the 
allantois  to  the  umbilicus,  beyond  which  they  are  carried  in  the  umbilical  cord  to 
the  placenta.  The  two  primitive  aortse  soon  fuse  to  form  a  single  vessel,  the  future 
descending  aorta ;  the  fusion  begins  in  the  thoracic  region,  and  from  there  proceeds 
backward  and  forward,  and  the  umbilical  arteries  now  appear  as  if  resulting  from 
the  bifurcation  of  the  single  vessel ;  the  part  of  the  fused  vessels,  beyond  their 
origin,  is  indicated,  however,  by  the  middle  sacral  artery.  The  common  and  inter- 
nal iliac  arteries  represent  the  proximal  end  of  the  umbilical  artery  ;  the  remainder 
of  the  vessel,  with  the  exception  of  the  part  which  gives  off  the  superior  vesical 
artery,  becomes  obliterated  after  birth  ;  and  the  obliterated  portions  of  the  two 
umbilical  arteries,  together  with  the  urachus,  carry  oft"  the  peritoneum  from  the 
bladder  as  its  superior  false  ligament.  The  external  iliac  and  femoral  arteries  are 
developed  from  a  minute  branch  given  off  from  the  umbilical  artery  near  its  origin, 
and  are  at  first  of  comparatively  small  size. 

1  This  is  interesting  in  connection  with  the  position  of  the  recurrent  laryngeal  nerve,  which  is 
thus  seen  to  hook  round  the  same  primitive  fetal  structure,  which  becomes  on  the  right  side  the  sub- 
clavian artery,  on  the  left  the  arch  of  the  aorta. 


1194 


EMBRYOLOGY. 


Development  of  the  Veins. — The  formation  of  the  great  veins  of  the  embryo 
may  be  best  considered  under  two  groups,  visceral  and  parietal. 

The  visceral  veins  are  the  two  vitelline  or  omphalomesenteric  veins  bringing 
the  blood  from  the  yolk-sac,  and  the  two  umbilical  or  allantoic  veins  returning 
the  blood  from  the  placenta ;  these  four  veins  open  close  together  into  the  sinus 
venosus  (Fig.  747). 

The  vitelline  veins  run  upward  at  first  in  front,  and  subsequently  on  either 
side  of  the  intestinal  canal.  They  unite  on  the  ventral  aspect  of  the  canal 
before  they  reach  the  liver,  and  then  encircle  the  intestinal  tube  by  forming 
around  it  two  venous  rings,  the  first  on  its  dorsal,  the  second  on  its  ventral  aspect. 
The  portions  of  the  veins  above  the  upper  ring  become  invaded  by  the  developing 


vagus  nerve 


common 
carotid 
recurrent 
laryngeal 
nerve 


right. 

subclavian 


pulmonary 
trunk 


descending  aorta 


Fig.  752.— Showing  the  destination  of  the  arterial  arches  in  man  and  mammals.  (Modified  from  Rathker.) 
(From  Quain's  Anatomy,  1890,  vol.  i.,  pt.  1.)  The  truncus  arteriosus  and  the  five  arterial  arches  springing  from 
it  are  represented  in  outline  only ;  the  permanent  vessels  in  shade — those  belonging  to  the  aortic  system  in 
heavy  shaded  line,  to  the  pulmonary  system  in  light  shaded  line. 

liver  and  broken  up  by  it  into  a  network  of  smaller  vessels,  the  central  part 
of  the  network  consisting  of  a  capillary  plexus.  The  branches  which  convey 
the  blood  to  this  plexus  are  named  the  venae  advehentes,  and  become  the 
branches  of  the  portal  vein  ;  while  the  vessels  which  drain  the  plexus  into  the 
sinus  venosus  are  termed  the  vence  revehentes,  and  form  the  future  hepatic  veins 
(Figs.  753  and  754). 

The  lower  part  of  the  portal  vein  is  formed  from  the  fused  vitelline  veins 
which  receive  the  veins  from  the  alimentary  canal ;  its  upper  part  is  derived  from 
the  venous  rings  by  the  persistence  of  the  left  half  of  the  lower  and  the  right 
half  of  the  upper  ring,  so  that  the  vessel  forms  a  spiral  turn  round  the  duodenum 
(Fig.  754). 

The  two  umbilical  veins  fuse  early  to  form  a  single  trunk  in  the  allantois,  but 
remain  double  for  some  time  in  the  embryo  and  pass  forward  to  the  sinus  venosus 
in  the  side  walls  of  the  body.  Like  the  vitelline  veins,  their  direct  connection 
with  the  sinus  venosus  becomes  interrupted  by  the  invasion  of  the  liver,  and  thus 
at  this  stage  the  whole  of  the  blood  from  the  yolk-sac  and  placenta  passes  through 
the  substance  of  the  liver  before  it  reaches  the  heart.     The  right  umbilical  vein 


THE   EMBRYO. 


1195 


shrivels  up  and  almost  entirely  disappears ;  the  left,  on  the  other  hand,  becomes 
much  enlarged  after  the  establishment  of  the  placental  circulation,  and  opens  into 
the  upper  venous  ring.  Finally  a  direct  branch  is  established  between  this  ring 
and  the  right  hepatic  vein  ;  this  branch  is  the  ductus  venosus  or  vena  ascendens, 
and,  enlarging  rapidly,  it  forms  a  wide  channel  through  which  most  of  the  blood, 
returned  from  the  placenta,  is  carried  direct  to  the  heart  (Fig.  754). 

The  Parietal  Veins. — The  first  indication  of  a  parietal  system  consists  in  the 
appearance  of  two  short  transverse  veins  (the  ducts  of  Cuvier),  which  open,  one 
on  either  side,  into  the  auricular  portion  of  the  heart,  Each  of  these  ducts  is 
formed  by  an  ascending  and  a  descending  vein.  The  ascending  veins  return  the 
blood  from  the  parietes  of  the  trunk  and  from  the  Wolffian  bodies,  and  are 
called   cardinal  veins.     The   descending  veins  return   the   blood  from  the  head, 


Right  primitive  jugular  vein. 
Right  cardinal  vei 

Right  duct  of  Cuvier. - 

sinus  venosus. - 
Right  hepatic  vein 

Portal  v 


Portal 
jRight  umbilical 

Vmbilical  cord.- 


Left  primitive 
^'jugular  vein. 

Left  cardinal  vein. 


W    'Left  duct  of  Cuvier. 


1  -Left  hepatic  vein. 
•\~L.eft  umbilical  veins. 


Left  umbilical  vein. 


Fig.  753.— Human  embryo  with  heart  and  anterior  body  wall  removed  to  show  the  sinus  venosus  and  its 
tributaries.    (From  Kollmann's  Entwickelungsgeschichte.)    (After  His.) 


and  are  called  primitive  jugular  veins  (Fig.  750).  The  blood  from  the  lower 
limbs  is  collected  by  the  iliac  veins,  which  empty  themselves  into  the  cardinal 
veins.  In  the  earlier  stages  of  development  the  right  and  left  iliac  veins 
open  into  the  corresponding  right  and  left  cardinal  veins  (Fig.  756),  but  later  od 
a  transverse  branch  connects  the  lower  ends  of  the  two  cardinal  veins,  and  through 
this  the  blood  from  the  left  iliac  vein  is  carried  into  the  right  cardinal  vein. 
By  the  development  of  a  similar  transverse  branch  higher  up  the  blood  from  the 
left  kidney  is  also  carried  into  the  right  cardinal  vein  (Fig.  755,  2).  The  portion 
of  the  left  cardinal  vein  above  the  origin  of  the  lower  transverse  branch 
becomes  atrophied  as  high  as  the  level  of  the  renal  vein,  above  which  it  persists 
as  the  vena  azygos  minor.  The  right  cardinal  vein,  which  now  receives  the 
blood  from  both  lower  extremities,  forms  a  large  venous  trunk  along  the  posterior 


1196 


EMBRYOLOGY. 


abdominal  wall ;  it  receives  the  renal  veins  from  the  kidneys,  and  forms,  up  to 
this  level,  the  inferior  vena  cava.  Above  the  level  of  the  renal  veins  the  inferior 
vena  cava  first  makes  its  appearance  as  a  small  vein  lying  in  the  tissue  between 
the  two  kidneys.      Superiorly  it  opens  into  the  sinus  venosus,  while  below  it  com- 


Anterior  detached  portions 
of  umbilical  veins. 


Venae  revehentes. 


Stomach. 

Venae  advehentes.  - 
Pancreas 
Bile  duct.  - 


Obliterated  portions 
of  venous  rings. 

Eight  umbilical  vein. 


-Ductus  venosus. 


'^JLiver. 


Left  umbilical  vein. 


Duodenum.-' 


Vitelline.  \ 
veins.        ^Portal  vein. 


Fig.  754.— The  liver,  and  the  veins  in  connection  with  it,  of  a  human  embryo,  twenty-four  or  twenty-five 
days  old,  as  seen  from  the  ventral  surface.     (After  His.)    (Copied  from  Milnes  Marshall's  Embryology.) 

municates  with  the  right  cardinal  vein  near  the  level  of  the  renal  veins  (Fig.  755, 
1,  2).  This  small  vein  ultimately  becomes  enlarged,  and  carries  the  blood  upward 
from  the  right  cardinal  vein,  and  so  forms  the  upper  part  of  the  inferior  vena  cava. 
The  portion  of  the  right   cardinal  vein  above  the   renal  veins  persists  as  the   vena 


Fig.  755.— Illustrating  the  development  of  the  principal  systemic  veins.  (Hertwig.)  dc.  Duct  of  Cuvier. 
je,ji.  External  and  internal  jugular  veins,  s.  Subclavian,  vh.  Hepatic  veins.  U.  Umbilical,  ci,  ci-.  Vena 
cava  inferior,  ca  (ca^,  ca?,caz).  Cardinal  veins.  ilcd,ilcs.  Right  and  left  common  iliac  veins,  ad,  as.  Eight  and 
left  innominate  veins,  cs.  Vena  cava  superior,  ess.  Rudimentary  portion  of  left  superior  vena  cava.  cc.  Coro- 
nary sinus,    az.  Azygos  major,    hz,  hzl.  Azygos  minor.    He.  External  iliac.    Hi.  Internal  iliac,    r.  Renal  vein. 

azygos  major,  and  receives  the  right  intercostal  veins,  while  the  vena  azygos  minor 
is  brought  into  communication  with  it  by  the  development  of  transverse  branches 
in  front  of  the  spinal  column  (Fig.  755,  2,  3). 


THE   EMBRYO. 


1197 


In  consequence  of  the  atrophy  of  the  Wolffian  bodies  the  cardinal  veins 
diminish  in  size  ;  the  primitive  jugular  veins,  on  the  other  hand,  become  enlarged, 
owing  to  the  rapid  development  of  the  head  and  brain.  They  are  further  aug- 
mented by  receiving  the  vein  {subclavian)  from  the  upper  extremity,  and  so  come 
to  form  the  chief  veins  of  the  Cuvierian  ducts ;  these  ducts  gradually  assume  an 


Fig  756.— Diagrammatic  outline  of  a  longitudinal  vertical  section  of  the  chick  on  the  fourth  d&y.  fP- 
Epiblast,  sm.  Somatic  mesoblast  Ay.  Hypoblast,  vm.  Visceral  mesoblast.  af.  Cephalic  fold,  pf.  Caudal  rold. 
am.  Cavity  of  true  amnion,  ys.  Yolk-sac  i.  Intestine  s.  Foregut.  a.  Future  anus,  still  closed,  m.  ine 
mouth,  me.  The  mesentery,  at.  The  allantoic  vesicle,  pp.  Space  between  inner  and  outer  folds  of  amnion. 
(From  Quain's  Anatomy,  Allen  Thomson.) 

almost  vertical  position  in  consequence  of  the  descent  of  the  heart  into  the 
thorax.  The  right  and  left  Cuvierian  ducts  are  originally  of  the  same  diameter, 
and  are  frequently  termed  the  right  and  left  superior  vence  cava?.  By  the 
development  of  a  transverse  branch  (the  future  left  innominate  vein)  between  the 


Amnio  n 


Fore-gut  /  Heart 

Chorda  Dorsalis 


Fig.  757.— Diagram  of  a  longitudinal  section  of  a  mammalian  embryo.    Very  early.    (After  Quain.) 

two  ducts  the  blood  is  carried  from  the  left  duct  into  the  right,  which  thus 
becomes  much  enlarged  and  forms  the  permanent  superior  vena  cava,  and  into 
which  the  vena  azygos  major  opens.  The  left  duct  atrophies  ;  its  upper  part 
remains  pervious  as  a  small  vein,  which  receives  the  left  superior  intercostal  vein  ; 
its  intermediate  portion  is  represented  by  the  vestigial  fold  of  Marshall ;  its 
lower  part  persists  as  a  small  vein,  the  oblique  vein  of  Marshall,  which  runs 
downward  across  the  back  of   the   left  auricle  to  join   the   coronary  sinus  ;    this 


1198 


EMBRYOLOGY 


sinus,  as  has  been  indicated,  represents  the  persistent  left  horn  of  the  sinus 
venosus.  The  primitive  jugular  veins  become  the  internal  jugular  veins  of  the 
adult;  the  lower  part  of  the  right  primitive  jugular  vein  forms  also  the  right 
innominate  veins  (Figs.  755,  1,  2,  3). 

The  foetal  circulation  has  been  described  in  the  section  on  the  Blood- Vascular 
System. 

Development  of  the  Alimentary  Canal. — As  already  indicated  (page  1157),  the 
primitive  alimentary  canal  is  formed,  at  an  early  stage,  by  the  enclosure  within 
the  embryo  of  a  portion  of  the  blastodermic  vesicle,  and  is  seen  to  consist  of  three 
parts,  viz.  :  (1)  the  fore-gut,  within  the  cephalic  flexure  and  dorsal  to  the  heart ; 
(2)  the  mid-gut,   opening  freely  into  the  yolk-sac  ;  and  (3)  the  hind-gut,  within 

the  caudal  flexure.  The  fore- 
gut  and  hind-gut  end  blindly, 
there  being  at  first  neither 
mouth  nor  anus  (Figs.  756  and 
757).  The  formation  of  the 
mouth  or  stomodaeum,  and  the 
subsequent  communication  be- 
tween it  and  the  cephalic  end 
of  the  fore-gut,  have  already 
been  considered  ;  the  manner  in 
which  the  anus  is  formed  will 
presently  be  discussed. 

From  the  fore-gut  are  de- 
veloped the  pharynx,  oesopha- 
gus, stomach,  and  duodenum, 
and  further,  as  diverticula  from 
the  duodenum,  the  liver  and 
pancreas ;  from  the  hind-gut, 
the  greater  part  of  the  rectum, 
and  as  a  tubular  outgrowth 
from  it  the  hollow  stalk  of  the 
allantois  ;  the  mid-gut  gives 
origin  to  the  remainder,  or 
longest  section,  of  the  alimentary  tube — i.  e.,  the  portion  which  reaches  from  the 
duodenum  to  the  rectum. 

The  upper  part  of  the  fore-gut  becomes  dilated  to  form  the  pharynx,  in  relation 
to  which  the  branchial  arches  are  developed  (Figs.  716  and  759) ;   the  succeeding 
part  remains  tubular,  and  with  the  descent  of  the  stomach  is  elongated  to  form  the 
oesophagus.     Soon  a  fusiform  dilatation,  the  future  stomach,  makes  its  appearance, 
and  beyond  this  the  mid-gut  opens  freely  into  the  yolk-sac  (Figs.   759  and  760). 
This  opening  is  at  first  wide,  but,  as  the  body-walls  close  in  around  the  umbilicus, 
it  is  gradually  narrowed  into  a  tubular   stalk,    the  yolk-stalk  or  vitello-intestinal 
duct.     At  this   stage,    therefore,    the    alimentary    canal   forms   a    nearly    straight 
tube   in    front    of    the    notochord    and   primitive    aortse   (Fig.    757).     From   the 
stomach  to  the  rectum  it  is  attached  to   the   notochord   by  a   band  of  mesoblast, 
from  which  the  common  mesentery  of  the  gut  is  subsequently  developed.     The} 
stomach  undergoes  a  further  dilatation,  and  its  two  curvatures  can  be  recognized^ 
(Figs.  760  and  764),  the  greater  directed  toward  the  vertebral  column  and  thej 
lesser  toward  the  anterior  wall  of  the  abdomen,  while  of  its  two  surfaces  one  looks  i 
to  the  right  and  the  other  to  the  left.    The  mid-gut  also  undergoes  great  elongation, ' 
and  forms  a  V-shaped  loop  which  projects   downward    and   forward  ;    from    the 
bend  or  angle  of  the  loop  the  vitello-intestinal  duct  passes  to  the  umbilicus  (Fig. 
764).     For  a  time  a    part  of  the    loop    extends    beyond    the    abdominal    cavity 
into  the  umbilical  cord,  but  by  the  end  of  the  third  month  this  is  withdrawn. 
With  the  lengthening  of  the  tube,  the  mesoblast,  which  attaches  it  to  the  future 
vertebral  column  and  which  carries  the  blood-vessels  for  the  supply  of  the  gut,  is 


Fig.  758.— Early  form  of  the  alimentary  canal.  (From 
Kolliker,  after  Bischoff.)  In  A  a  front  view  and  in  B  an 
antero-posterior  section  are  represented,  a.  Four  pharyngeal 
or  visceral  plates,  b.  The  pharynx,  c,  c.  The  commencing 
lungs,  d.  The  stomach.  /,  /.  The  diverticula  connected 
Avith  the  formation  of  the  liver,  g.  The  yolk-sac  into  which 
the  middle  intestinal  groove  opens,  h.  The  posterior  part  of 
the  intestine. 


THE   EMBRYO. 


1199 


thinned  and  drawn  out  to  form  the  primitive  or  common  mesentery.  The  portion* 
of  this  mesentery  which  is  attached  to  the  greater  curvature  of  the  stomach  is 
named  the  mesogastrium,  and  the  parts  which  suspend  the  colon  and  rectum  are 
respectively  termed  the  mesocolon  and  mesorectum  (Fig.  764).  About  the  sixth 
week  a  lateral  diverticulum  makes  its  appearance  a  short  distance  beyond  the 
vitello-intestinal  duct,  and  indicates  the  future  caecum  or  boundary  between  the 
small  and  the  large  intestine.  This  ctecal  diverticulum  has  at  first  a  uniform 
calibre,  but  its   blind   extremity  remains  rudimentary  and  forms  the  vermiform 


Midbrain. 


Cerebellum.-^ 


Pharyngeal  septum. 

Pharynx. 

Auditory  pit 

Aortic  bulb. 
Stomach.- - 


esicle. 


Cloacal  dilatation- 
of  hind-gut. 


Allantoic  stall 
Umbilical  vei 


Liver. 


Mid-gut  and  yolk 
stalk. 


nd-gut. 


Fig.  759.— Human  embryo,  about  fifteen  days  old.    Brain  and  heart  represented  from  right  side ;  alimentary 
canal  and  yolk-sac  in  mesial  section.    (After  His.) 

appendix  (Figs.  764,  765).  Changes  also  take  place  in  the  position  and  direction 
of  the  stomach.  It  falls  over  on  to  its  right  surface,  which  henceforth  is  directed 
backward,  while  its  original  left  surface  looks  forward  ;  further,  its  greater  curva- 
ture is  drawn  downward  and  to  the  left,  away  from  the  vertebral  column,  while  its 
lesser  curvature  is  directed  upward,  and  the  commencement  of  the  duodenum  is 
pushed  over  to  the  right  side  of  the  middle  line.  The  mesogastrium,  being  attached 
to  the  greater  curvature,  must  necessarily  follow  its  movements,  and  hence  it 
becomes  greatly  elongated  and  drawn  outward  from  the  vertebral  column,  and,  like 
the  stomach,  what  was  originally  its  right  surface  is  now  directed  backward  and  its 
left  forward.  In  this  way  a  pouch,  the  bursa  omentalis,  is  formed  behind  the  stomach  ; 
this  pouch  is  the  future  lesser  sac  of  the  peritoneum,  and  it  increases  in  size  as 
the  alimentary  tube  undergoes  further  development ;  the  entrance  to  the  pouch 
constitutes  the  future  foramen  of  Winslow  (Figs.  761,  765,  and  768).  The  re- 
mainder of  the  canal  becomes  greatly  increased  in  length,  so  that  the  tube  is  coiled 
on  itself,  and  this  increase  in  length  demands  a  corresponding  increase  in  the  width 
of  the  intestinal  attachment  of  the  mesentery,  so  that  it  becomes  plaited  or  folded. 
At  this  stage  the  small  and  the  large  intestine  are  attached  to  the  vertebral  col- 
umn by  a  common  mesentery,  the  coils  of  the  small  intestine  falling  to  the  right 
of  the  middle  line,  while  the  large  intestine  lies  on  the  left  side.1 

1  Sometimes  this  condition  persists  throughout  life,  and  it  is  then  found  that  the  duodenum  does 
not  cross  from  the  right  to  the  left  side  of  the  vertebral  column,  but  lies  entirely  on  the  right  side  of 
the  mesial  plane,  where  it  is  continued  into  the  jejunum  ;  the  arteries  to  the  small  intestine  i  rami 
intestini  tenuis)  also  arise  from  the  right  instead  of  the  left  side  of  the  superior  mesenteric  artery. 


1200 


EMBRYOLOGY. 


The  gut  now  becomes  rotated  upon  itself,  so  that  the  large  intestine  is  carried 
over  in  front  of  the  small  intestine,  and  the  caecum  is  placed  immediately  below 

Rathke's  pouch 
Notochord.        {pituitary  involution). 


Lung  diver-. -f- 
ticulum. 
Stomach 
Liver 


Opening  into__ . 
yolk  sac. 


Allantois.-r- 


_  J^-Blind  portion  of 
hind-gut. 

'■-Wolffian  duct. 

A 


Lung  diverticulum 
(Esophagus.  ^ 


Omphalo- 
mesenteric 
duct. 

Allantois. 


Median  rudiment  of 
J  thyroid  gland. 
1       t  Mandibular  arch. 
t     'Notochord. 

Rathke's 
~~pouch 
(pituitary 
involution). 


Blind  portion  of 
hind-gut. 


Wolffian  duct. 


Fig.  760.— Sketches  in  profile  of  two  stages  in  the  development  of  the  human  alimentary  canal.    (His.) 
Fig.  A  X  30.    Fig.  B  X  20. 

the  liver ;  about  the  sixth  month  the  caecum  descends  into  the  right  iliac  fossa, 
and  the  large  intestine  now  forms  an  arch  consisting  of  the  ascending,  transverse, 
and  descending  portions  of  the  colon — the  transverse  portion   crossing  in  front 


THE   EMBRYO. 


1201 


of  the  duodenum  and   lying  just  below  the  greater  curvature  of  the  stomach  ; 
within  this  arch  the  coils  of  the  small  intestine  are  disposed  (Fig.  765).     Some- 


Trachea.-- 
(Esophagus.- 

Stomach. 
Bile  duct.. 


V 'shaped  loop_ 
of  mid-gut.' 

Vitello-intestinal  duct.-- 

Cloaca 


•Lung. 


Trachea. 


t-Pancreas. 


Lung. 
—  (Esophagus. 


-rot—Stomach. 


Fig.  761.— Front  view  of  two  successive  stages  in  the  development  of  the  alimentary  canal.    (His.) 


times  the  downward  progress  of  the  caecum  is  arrested,  so  that  in  the  adult  it 
may  be  found  lying  immediately  below  the  liver  instead  of  in  the  right  iliac 
region. 

Further  changes  take  place  in  the  bursa  omentalis  and  in  the  common  mesen- 
tery, and  give  rise  to  the  peritoneal  re- 
lations seen  in  the  adult.      The  bursa 
omentalis,  which  at  first  reaches  only 
as  far  as  the  greater  curvature  of  the 


suprarenal 
capsule 


Right 

suprarenal 

capsule 


Left 

suprarenal 

capsule 


Liver 


Fig.  762. — Schematic  and  enlarged  cross-section 
through  the  body  of  a  human  embryo  in  the  region 
of  the  mesogastrium.  Begiuningof  third  month. 
(Toldt.) 


Livt 


Lesser   ^^  .«teaa>. 
omentum 

1 
Stomach 


•/.  >r        Left 
fr-^T'suprurennl 
^sy       capsule 


Liver 

Fig.  763.— Same  section  as   in  Fig   762.  at  end 
of  third  month.    (Toldt.) 


stomach,  grows  downward  to  form  the  great  omentum,  and  this  downward  extension 
lies  in  front  of  the  transverse  colon  and  the  coils  of  the  small  intestine.  The 
anterior  layer  of  the  transverse  mesocolon  is  at  first  quite  distinct  from  the  posterior 
wall  of  the  bursa  omentalis,  but  ultimately  the  two  blend,  and  hence  the  great  omen- 
tum appears  as  if  attached  to  the  transverse  colon  (Figs.  768,  769,  and  770).     The 

76 


1202 


EMBRYOLOGY. 


mesentery  of  the  duodenum,  in  which  the  rudiment  of  the  pancreas  is  enclosed,  dis- 
appears, and  so  this  part  of  the  gut  becomes  fixed  to  the  posterior  abdominal  wall, 
and  the  pancreas  lies  entirely  behind  the  peritoneal  membrane.  The  mesenteries 
of  the  ascending  and  descending  parts  of  the  colon  disappear  in  the  majority 
of  cases,  while  that  of  the  small  intestine  assumes  the  oblique  attachment  charac- 
teristic of  its  adult  condition. 


•Aorta. 


Anterior  part  of  mesogastrium.-jr--'- 


Spleen. 

Mesogastrinm. 
Cceliac  axis. 


Superior  mesenteric 


__  /-^Inferior  mesenteric  artery. 

Hind-gut. 

Fig.  764.— Abdominal  part  of  alimentary  canal  and  its  attachment  to  the  primitive  or  common  mesentery. 
Human  embryo  of  six  weeks.    (After  Toldt.)    (From  Kollmann  s  Entwickelungsgeschichte.) 


Meso- 
gastrium. '- 


Bile-duct 


Duodenum. 


Small 
intestine. 

Yolk-stalk 


Rectum . 


Duodenum 


Mesocolon 


Csecum 
Vermiform 
appendix. 
Mesentery. 

Yolk-stalk 


Rectum. 


Fig.  765.— Illustrating  two  stages  in  the  development  of  the  human  alimentary  canal  and  its  mesentery. 
The  arrow  indicates  the  entrance  to  the  bursa  omentalis. 

The  small  omentum  is  formed  by  a  thinning  of  the  mesoblast  or  anterior 
primitive  mesentery,  which  attaches  the  lesser  curvature  of  the  stomach  to  the 
anterior  abdominal  wall.  By  the  subsequent  growth  of  the  liver  this  leaf  of 
mesoblast  is  divided  into  two  parts,  viz.,  the  small  omentum  between  the  stomach 
and  liver,  and  the  falciform  ligament  between  the  liver  and  the  abdominal  wall 
and  Diaphragm  (Fig.  767). 

The  anus  is  developed  as  a  slight  invagination  of  the  epiblast  a  short  distance 


THE   EMBRYO. 


1203 


in  front  of  the  posterior  end  of  the  hind-gut.      This  invagination  is  termed  the 
proctodeum;    the   rnesohlast  between  it  and  the  hypoblastic  lining  of  the  hind- 
gut  is  thinned,  and  ultimately  the  septum  breaks  down,  and  disappears,  and  the 
hind-gut  opens   on  the  surface ;    into  this  part  of  the 
hind-gut    the    urinary  and   generative  organs  open  for 
a  time,  and  so   it  constitutes    a    common  cloaca.     The 
small  portion  of  the  hind-gut  behind  the  orifice  of  the 
anus   is   named  the  caudal  or  post-anal  gut ;    it  com- 
municates with  the  neural  tube    by  means   of  a  canal, 
the  ncur enteric  canal,  already  referred  to.      Ultimately 
the  post-anal  gut   becomes  obliterated,  and  it,  together 
with  the  ncurenteric  canal,  finally  disappears. 

The  peritoneal  cavity  is  the  space  left  between  the 
visceral  and  parietal  layers  of  the  mesoblast,  and  the 
serous  membrane  is  developed  from  these  layers. 

The  tongue  originates  from  the  floor  of  the  pharynx. 
The  anterior  or  papillary  portion  first  appears  as  a 
rounded  elevation,  the  tubereulum  impar,  between  the 
ventral  ends  of  the  mandibular  and  hyoid  arches.  Be- 
tween the  third  and  fourth  arches  a  second  larger  ele- 
vation arises,  in  the  centre  of  which  is  a  median  groove 
or  furrow.  This  second  elevation  is  termed  the  fur- 
cula,  and  from  it  the  epiglottis  is  developed,  while  the 
median  furrow  becomes  the  entrance  to  the  larynx  (Fig. 
771).  The  tubereulum  impar  and  the  furcula  are  at 
first  in  apposition,  but  are  soon  separated  by  a  ridge 
produced  by  the  forward  growth  of  the  second  and  third 
arches.  This  ridge  gives  rise  to  the  posterior  part  of 
the  tongue  and  extends  forward  in  the  form  of  a  V,  so  as 
to  embrace  between  its  two  limbs  the  tubereulum  impar. 
At  the  apex  of  the  V  there  is  a  pit-like  invagination  to 

form  the  middle  thyroid  rudiment,  and  this  depression  persists   as  the   foramen 
caecum  of  the  adult.     The  union  of  the  two  parts  of  the  tongue  is  indicated  even 


Fig.  766. — Final  disposition 
of  the  intestines  and  their  vas- 
cular relations.  (Jonnesco.)  A. 
Aorta.  II.  Hepatic  artery.  S. 
Splenic  artery.  M.  Col.  Branches 
of  superior  mesenteric  artery. 
m ,  m'.  Branches  of  inferior 
mesenteric  artery. 


Septum  transversum. 
-k- Aorta. 


Liver. 


Mesogastriurn         J 
(anterior  part)  1       11 


Mesogastriurn 

(posterior  part). 

Stomach. 


Intestinal 

V -shaped  loop. 
Mesentery. 


Colon. 


Fig.  767.— The  primitive  mesentery  of  a  six  weeks'  human  embryo,  half  schematic.    (Kollmaun .) 

in  the  adult  by  a  V-shaped  depression,  the  apex  of  which  is  at  the  foramen  caecum, 
while  the  two  limbs  run  outward  and  forward  parallel  to  but  a  little  behind  the 
circum vallate  papillae,  which  are  therefore  developed  from  the  tubereulum  impar 
(Figs.  772,  773).  The  tonsils  are  developed  from  the  second  branchial  cleft,  and 
make  their  appearance  between  the  fourth  and  fifth  months. 


1204 


EMBRYOLOGY. 


The  liver  arises  in  the  form  of  two  diverticula  or  hollow  outgrowths  from  the 
ventral   surface   of   that  portion  of  the    fore-gut  which  afterward    becomes    ihe 


Mesogastrium^ 4 

anterius.        ,.  rV     / 


Umbilical  veil 


Border  of  the  anteri 
mesogastrium. 


/  — \&Wh" Bursa  omentalis. 


-Pancreas. 


a— Mesogastrium 
I        posterius. 
1 —  Duodenum. 


■-■'    il-  i 

- j — Great  omentum. 


-Transverse 
mesocolon. 

-Transverse  colon. 


Fig.  768.— Schematic  figure  of  the  hursa  omentalis,  etc.    Human  embryo  of  eight  weeks.    (Kollmann.) 

duodenum  (Figs.  759,  760).  The  outgrowths,  which  represent  the  right  and  the 
left  lobes,  respectively,  of  the  adult  liver,  give  off  solid  buds  of  cells,  which  grow 
into  columns  or  cylinders :  these  unite  with  one  another  in  every  direction  to  form 
a  close  network,  in  the  meshes  of  which  are  contained  the  capillary  blood-vessels. 
Some  of  these  columns  become  hollowed  out  and  form  the  bile-ducts,  while  the 


Diaphragm ' 


Liver 


Stomach 

Greater  curvature 
Anterior  lamella  of  greater  omentum 
Posterior  lamella  of  greater  omentum 

Transverse  colon 


Greater  omentum 


Lesser  omentum 


Pancreas 


Transverse  mesocolon 
Duodenum 


Mesentery 


Small  intestine 


Fig.  769.— Illustrating  the  development  of  the  bursa  omentalis,  cavity  of  the  great  omentum  or  lesser  sac, 
Fretal  stage.    *  Lesser  sac.    (Hertwig.) 


remainder  constitute  the  secreting  structure.  The  minute  ducts  thus  produced 
unite  to  form  the  right  and  left  hepatic  ducts ;  while  the  common  bile-duct  is 
developed  as  a  protrusion  from  the  duodenal  wall,  and  as  it  grows  the  liver  becomes 
shifted  away  from  the  duodenum.  The  gall-bladder  and  cystic  duct  are  formed  by 
a  hollow  evagination  from  the  wall  of  the  common  bile-duct.  About  the  third 
month  the  liver  almost  fills  the  abdominal  cavity.  From  this  period  the  relative 
development  of  the  liver  is  less  active,  more  especially  that  of  the  left  lobe,  which 


THE   EMBRYO. 


1205 


now  becomes  smaller  than  the  right ;  but  up  to  the  end  of  foetal  life  the  liver 
remains  relatively  larger  than  in  the  adult. 

The  pancreas  is   also  an  early  formation,  being  far  advanced  in  the  second 


Stomach- 

Greater  curvature 

Posterior  lamella  of  greater  omentum 

Transverse  colon 


Greater  omentun 


Diaphragm 
Liver 

Lesser  omentum 


Pancreas 

Part  of  omentum  enclosing  pancreat 

Transverse  mesocolon 
Duodenum 


Mesentery 


Small  intestine 


Fig.  770.— Development  of  bursa  omentalis.    Infantile  stage.    Great  omentum  covers  the  intestines  and  has 
fused  with  the  transverse  mesocolon.    Pancreas  is  free  from  peritoneum  posteriorly.    (Hertwig.) 

month.  It  originates  as  a  hollow  projection  from  the  hypoblast  of  the  dorsal  wall 
of  the  duodenum  (Figs.  760  and  761),  opposite  the  hepatic  diverticula,  which,  as 
we  have  already  seen,  spring  from  its  ventral  wall.     This  hollow  process  grows 

Mandibular  arch. 
Hyoid  arch. 


Fig.  771.— The  floor  of  the  pharynx  of  a  human  embryo  about  fifteen  days  old ;  X  50.    (From  His.) 

between  the  two  layers  of  the  dorsal  mesentery  and  sends  out  offshoots,  which 
branch  abundantly  and  form  a  complicated  tubular  gland.  As  torsion  of  the 
stomach  takes  place,  the  pancreas  assumes  a  transverse  position  and  becomes  fixed 


Tuberculum  hnpar 
{papillary  part  of  tongue). 


Posterior  part  of  tongue. 


Furcula. 


Entrance  to  larynx 


Mandibular  arch. 


-Hyoid  arch. 


Third  arch. 
^•Fourth  arch. 


T~-r~~ — Y-Lung. 


Fig.  772.— The  floor  of  the  pharynx  of  a  human  embryo  about  twenty-three  days  old;  X  30.    (From  His.) 

across  the  dorsal  wall  of  the  abdomen,  the  posterior  layer  of  its  mesentery  under- 
going absorption.  Its  duct  ultimately  opens  into  the  duodenum  together  with  the 
common  bile-duct. 

The  sjyleen,  on  the  other  hand,  is  of  mesoblastic  origin,  for  there  is  never  any 


1 206  EMBB  YOL  OGY. 

connection  between  the  intestinal  cavity  and  the  substance  of  this  organ.  It 
originates  in  the  mesenteric  fold  which  connects  the  stomach  to  the  vertebral 
column  (mesogastrium)  (Fig.  764). 

The  thyroid  body  is  developed  as  a  median  and  two  lateral  diverticula  from 
the  ventral  wall  of  the  pharynx.  The  median  diverticulum  appears  first ;  it  com- 
mences at  the  foramen  caecum,  between  the  anterior  and  posterior  rudiments  of  the 
tongue,  and  extends  backward  as  a  tubular  duct,  the  ductus  thyro-glossus.  The 
lateral  diverticula  arise  from  the  fourth  visceral  cleft  and  fuse  with  the  median 

Papillary  portion  of  tongue. 


r—j— Mandibular  arch. 


V:-.v-.:.T  ©:\i|^l_-eS^Srre>.';        ■  Zs'^Hyoid  arch. 

Foramen  csecam.     Posterior  part     Third  arch, 
of  tongue. 
Fig.  773. — Floor  of  mouth,  of  an  embryo  slightly  older  than  that  shown  in  Fig.  772.    X  16.  (From  His.) 

part  to  form  the  thyroid  body.  The  connection  of  the  lateral  diverticula  with  the 
pharynx  disappears  early,  but  the  remains  of  the  ductus  tbyro-glossus  may  persist 
as  a  tube  leading  from  the  foramen  caecum  toward  the  hyoid  bone,  the  pyramid 
of  the  thyroid  probably  representing  its  lower  part.1 

The  thymus  is  developed  from  bilateral  diverticula,  which  are  principally  derived 
from  the  third  visceral  cleft.  It  increases  in  size  until  the  second  year  of  life, 
after  which  it  undergoes  atrophy. 

Development  of  the  Eespiratory  Organs. — The  lungs  appear  somewhat  later 
than  the  liver.  They  are  developed  from  a  small  median  cul-de-sac  or  diverticu- 
lum from  the  upper  part  of  the  fore-gut,  immediately  behind  the  fourth  visceral 
cleft.  During  the  fourth  week  a  pouch  is  formed  on  either  side  of  the  central 
diverticulum,  and  opens  freely  through  it  into  the  fore-gut  (pharynx).  These 
lateral  pouches  soon  become  subdivided — the  right  into  three  and  the  left  into  two 
parts,  these  subdivisions  being  the  early  indications  of  the  lobes  of  the  lungs 
(Figs.  716  and  761).  The  two  primary  pouches  have  thus  a  common  tube  of  com- 
munication with  the  pharynx.  This  common  tube  becomes  the  larynx  and  trachea, 
the  latter  rapidly  elongating  as  development  proceeds.  The  larynx  first  becomes 
evident  as  a  dilatation  of  the  upper  part  of  the  trachea  about  the  end  of  the  fifth 
week.  The  epiglottis  is  developed  from  the  anterior  or  median  portion  of  the  fur- 
cula,  and  the  aryteno-epiglottidean  folds  from  its  lateral  ridges  (Fig.  772).  The 
vocal  cords  and  ventricles  of  the  larynx  are  formed  about  the  fourth  month. 

As  the  lungs  grow  backward  they  project  into  the  anterior  part  of  the  coelum, 
which  becomes  shut  off  from  the  rest  of  the  body-cavity  by  the  pericardium  and 
Diaphragm  to  form  the  pleural  cavities. 

The  Diaphragm  is  formed  in  two  parts  :  (a)  ventral,  (b)  dorsal.  The  ventral 
part  appears  first,  and  consists  of  a  thick  septum  of  mesoblast,  the  septum  trans- 
versum,  which  projects  from  the  anterior  and  lateral  walls  of  the  embryo,  and 
which  ends  behind  in  a  free  edge.  The  sinus  venosus,  which  receives  the  vitelline, 
umbilical,  and  Cuvierian  veins  is  placed  originally  in  this  septum,  and  into  the 
posterior  part  of  it  also  the  liver  diverticula  grow  from  the  duodenum.  The  sinus 
separates  itself  above  from  the  septum,  and  the  greater  part  of  it  is  incorporated 
with  the  right  auricle.  The  liver  also  becomes  separated  from  it  below,  except 
where   the  veins   pass   through   into   the   heart.      The  septum   transversum  shuts 

1  Kanthack  (Journal  of  Anat.  and  Physiol,  vol.  xxv.,  p.  155)  disputed  'this  view.  He  examined 
100  subjects,  60  of  which  were  fetuses  or  infants,  and  found  that  in  many  cases  there  was  no  trace  of 
foramen  cfecum  and  that,  when  it  was  present,  it  formed  a  short  canal  near  the  surface  and  was  lined 
with  stratified  squamous,  not  columnar,  epithelium.  Further,  after  careful  microscopical  examina- 
tion he  found  no  trace  of  a  tubular  lumen  in  the  pyramid  of  the  thvroid  body. 


THE   EMBRYO. 


1207 


off  the  greater  part  of  the  thoracic  from  the  abdominal  cavity,  but  posteriorly 
there  remain  two  channels  of  communication,  one  on  each  side  of  the  alimentary 
tube ;  these  channels  subsequently  become  the  pleural  cavities,  and  are  shut  off 
from  the  abdomen  by  folds  which  grow  from  the  lateral   and  posterior  parts  of 


^, Wolffian  duct. 

_.Miillerian  duct. 


(  Stroma 
Genital  j       of  ovary, 
ridge.  \  Primitive     J 
[      ova. 


Mesentery.-  - 


-Wolffian 

'""       tubules. 


-Body  wall. 


Fig.  774.— Section  of  the  urogenital  area  of  a  chick  embryo  of  the  fourth  day.    (Waldeyer.) 

the  trunk  and  which  fuse  with  the  posterior  edge  of  the  septum  trans versum. 
Sometimes  the  fusion  is  incomplete,  thus  leaving  a  permanent  communication 
between  the  abdominal  and  one  or  other  of  the  pleural  cavities,  and  through 
which  some  of  the  abdominal  contents  may  pass,  forming  what  is  termed  a 
diaphragmatic  hernia. 

Development  of  the  Urinary  and  Generative  Organs. — The  urinary  organs  are 


Fig.  775.— Enlarged  view  from  the  front  of  the  left  Wolffian  body  before  the  establishment  of  the  distinc- 
tion of  sex.  (From  Farre,  after  Kobelt.)  a,  a,  b,  d,  Tubular  structure  of  the  Wolffian  body ;  e,  Wolffian  duct ; 
/.Its  upper  extremity;  g,  Its  termination  in  .c,  the  urogenital  sinus  ;  h,  The  duct  of  Nuller;  £,Its  upper,  funnel- 
shaped  extremity  ;  k,  Its  lower  end,  terminating  in  the  urogenital  sinus;  /,  The  mass  of  blastema  for  the  repro- 
ductive organ,  ovary  or  testicle. 

developed  from  a  ridge  of  mesoblast  at  the  point  where  this  layer  separates  into 
somatopleure  and  splanchnopleure.  As  this  ridge  is  situated  close  to  the  epiblast, 
between  the  paraxial  mesoblast  and  the  common  pleuro-peritoneal  cavity,  it  has 
been  named  the  "  intermediate  cell-mass."  It  is  at  first  solid,  and  in  it  is  formed 
a  cord-like  arrangement  of  some  of  the  cells,  which  extends  longitudinally  from 
just  below  the  heart  to  the  pt  tremity  of  the  body-cavity.     In  this  cord- 

like structure  a  tube  is  hollow^  gradually  becomes  separated  from  the  rest 

of  the  intermediate  cell-mass,  'iru'  is  '  I  n  named  the  Wolffian  duct  (Fig.  700). 1  Its 
posterior  end  becomes  connect  id  eventually  opens  into  the  hind-gut.     Its 

anterior  end  becomes  connecteo.  ike  involutions  of  the  peritoneal  epithelium, 

and  in  the  mesoblastic  tissue  between  hese  invaginations  a  vascular  glomerulus  is 
formed  which  projects  into  th  sal  cavity.     It  is  known  as  the  head-kidney 

1  By  some  embryologists  the  W  is  regarded  as  being  of  epiblastic  origin  and  formed 

by  a  longitudinal  invagination  of  the       blast. 


1208 


EMBRYOLOGY. 


or  pronephros  (Lankester),  and  is  a  very  rudimentary  organ  which  speedily  disap- 
pears. Behind  this  body  and  to  the  inner  side  of  the  Wolffian  duct,  between  it 
and  the  body-cavity,  a  number  of  tubes  are  formed,  which  communicate  by  one 
extremity  with  the  Wolffian  duct,  and,  passing  transversely  toward  the  body-cavity, 
terminate  in  csecal  extremities.  These  tubes  are  called  segmental  tubes,  and  the 
whole  mass  is  known  as  the  mid-kidney,  Wolffian  body,  or  mesonephros  (Lankester) 
(Fig.  775).  After  a  time  the  caecal  extremities  become  dilated  and  enclose  a  tuft 
or  glomerulus  of  capillary  blood-vessels.  As  soon  as  the  permanent  kidneys  are 
formed,  the  Wolffian  body  for  the  most  part  disappears.  In  the  male,  however,  the 
vasa  efferentia  and  rete  testis  of  the  testicle  are  formed  as  outgrowths  from  it.  In 
the  female  traces  of  it  are  left  as  the  parovarium  and  epobplioron.  In  the  male 
the  Wolffian  duct  becomes  the  epididymis  and  vas  deferens  ;  in  the  female  it  under- 
goes atrophy,  and  is  represented  only  by  the  functionless  duct  of  Gartner. 

Finally,  in  that  portion  of  the  intermediate  cell-mass  which  lies  behind  the 
Wolffian  body,  a  differentiation  of  cells  takes  place  which  results  in  the  formation 
of  a  number  of  convoluted  tubes ;  into  this  a  hollow  protrusion  of  the  lower  end 
of  the  Wolffian  duct  grows  up,  and  thus  is  formed  the  hind-kidney  or  metanephros 
(Lankester).  This  is  the  permanent  kidney.  The  uriniferous  convoluted  tubes 
and  Malpighian  corpuscles  are  formed  from  the  intermediate  cell-mass,  and  the 
collecting  tubules  and  ureter  from  the  protrusion  from  the  posterior  end  of  the 
Wolffian  duct. 

Shortly  after  the  formation  of  the  Wolffian  body,  a  second  duct  becomes  devel- 
oped. It  arises  on  the  outer  side  of  this  body  as  a  slight  thickening  of  the  cells 
lining  the  pleuro-peritoneal  cavity.  This  thickening  then  becomes  invaginated 
into  the  mesoblast  and  extends  as  a  cord  along  the  outer  side  of  the  Wolffian 

body,  to  the  posterior  extremity  of  the  em- 
bryo. It  speedily  acquires  a  lumen,  and  is 
then  known  as  the  Mullerian  duct  (Fig.  774). 
In  its  passage  to  the  posterior  extremity  of  the 
embryo  it  comes  into  close  relation  with  the 
Wolffian  duct,  and  the  two  ducts  on  either  side 
become  connected  with  their  fellows  on  the 
opposite  side  by  their  cellular  substance  into 
a  single  cord,  the  genital  cord  (Fig.  776,  g,  c), 
in  which  the  Wolffian  ducts  lie  side  by  side  in 
front,  and  the  ducts  of  Miiller  behind.  These 
latter  tubes  in  the  substance  of  the  genital 
cord  become  fused  together,  and  open  by  a 
single  orifice  into  the  hind-gut  (cloaca).  At 
their  anterior  extremities  the  ducts  of  Miiller 
open  by  a  somewhat  funnel-shaped  orifice  into 
the  pleuro-peritoneal  cavity.  In  the  female 
the  greater  part  of  the  Mullerian  duct  is  de- 
veloped into  the  Fallopian  tube,  but  the  pos- 
terior fused  portion  of  the  two  ducts  is  con- 
verted into  the  uterus  and  vagina  (Fig.  777). 
In  the  male  the  greater  part  of  the  ducts  dis- 
appears ;  the  posterior  fused  portion  is  believed 
to  be  represented  by  the  si?ius  pocularis  (uterus 
masculinus)  of  the  urethra. 

It  has  been  seen  that  the  Wolffian  and 
Mullerian  diets  open  into  the  common  cloaca, 
Avhich  is  the  termination  of  the  intestinal 
cavity,  and  into  which  the  allantois  also  opens 
in  front  (Fig.  776).  As  the  allantois  expands 
into  the  urinary  bladder  this  common  cavity 
is  divided  into  two  by  a  septum,  to  form  the  urogenital  sinus  in  front  and  the 


Fig.  776.— Diagram  of  the  primitive  uro- 
genital organs  in  the  embryo  previous  to  sexual 
distinction.  The  parts  are  shown  chiefly  in 
profile,  but  the  Mullerian  and  Wolffian  ducts 
are  seen  from  the  front.  3.  Ureter.  4.  Urinary 
bladder.  5.  Urachus.  ot,  The  mass  of  blastema 
from  which  ovary  or  testicle  is  afterward 
formed;  W,  Left  Wolffian  body;  w,  w,  Right 
and  left  Wolffian  ducts;  m,  m,  Right  and  left 
Mullerian  ducts  uniting  together  and  with  the 
Wolffian  ducts  in  gc,  the  genital  cord  ;  ug,  Sinus 
urogenitalis ;  i,  Lower  part  of  the  intestine; 
cl,  Common  opening  of  the  intestine  and  uro- 
genital sinus;  cp,  Elevation  which  becomes 
clitoris  or  penis  ;  Is,  Ridge  from  which  the  labia 
majora  or  scrotum  are  formed. 


THE   EMBRYO. 


1209 


rectum  behind,  and  the  Wolffian  and  Miillerian  ducts  now  open  into  the  urogenital 
sinus. 

The  urinary  bladder,  as  before  stated,  is  formed  by  a  dilatation  of  a  part  of  the 
intra-embryonic  portion  of  the  allantois.  At  the  end  of  the  second  month  the 
middle  part  of  this  portion  of  the  allantois  becomes  dilated  into  a  spindle-shaped 
cavity,  which  persists  as  the  urinary  bladder.  Between  the  lower  extremity  of 
the  spindle-shaped  dilatation  and  the  intestine  is  the  urogenital  sums,  into  which 
the  Miillerian  and  Wolffian  ducts  now  open,  and  which  becomes  the  first  part  of 
the  urethra.  The  upper  part  of  the  intra-embryonic  portion  of  the  allantois, 
which  is  not  dilated,  forms  the  urachus  (Fig.  776)  ;  this  extends  into  the  umbilical 
cord,  and  at  an  early  period  of  embryonic  existence  forms  a  tube  of  communica- 
tion with  the  allantois.  It  is  obliterated  before  the  termination  of  foetal  life,  but 
the  cord  formed  by  its  obliteration  is  perceptible  throughout  life,  passing  from  the 
upper  part  of  the  bladder  to  the  umbilicus.  It  occasionally  remains  patent  after 
birth,  constituting  a  well-known  malformation. 

The  suprarenal  bodies  are  developed  from  two  different  sources.  The  medul- 
lary part  of  the  organ  is  of  epiblastic  origin,  and  is  derived  from  the  tissues  form- 
ing the  sympathetic  ganglia  of  the  abdomen,  while  the  cortical  portion  is  of 
mesoblastic  origin,  and  originates  as  an  outgrowth  from  the  upper  part  of  the 
Wolffian  body.  The  two  parts  are  at  first  quite  distinct,  but  become  combined  in 
the  process  of  development.  The  suprarenal  capsules  are  at  first  larger  than  the 
kidneys ;  about  the  tenth  week  they  equal  them  in  size,  and  from  that  time 
decrease  relatively  to  the  kidney,  though  they  remain,  throughout  foetal  life, 
proportionally  much  larger  than  in  the  adult. 


Fig.  777.— Female  genital  organs  of  the  embryo,  with  the  remains  of  the  Wolffian  bodies.    (After  J.  Miiller.) 

a.  From  a  foetal  sheep:  a.  The  kidneys,  b.  The  ureters,  c.  The  ovaries,  d.  Remains  of  the  Wolffian  bodies. 
e.  Fallopian  tubes.    /.  Their  abdominal  openings,    b.  More  advanced,  from  a  foetal  deer  :  o.  Body  of  the  uterus. 

b.  Cornea,  c.  Tubes,  d.  Ovaries,  e.  Remainsof  the  Wolffian  bodies,  c.  Still  more  advanced,  from  the  human 
fcetus  of  three  months  :  a.  The  body  of  the  uterus,  b.  The  round  ligament,  c.  The  Fallopian  tubes,  d.  The 
ovaries,    e.  Remains  of  the  Wolffian  bodies. 

Ovaries  and  Testicles. — The  first  appearance  of  the  reproductive  organs  is 
essentially  the  same  in  the  two  sexes,  and  consists  in  a  thickening  of  the  epithelial 
layer  which  lines  the  peritoneal  or  body-cavity  close  to  the  inner  side  of  the 
Wolffian  body.  Beneath  this  thickened  epithelium  an  increase  in  the  mesoblast 
takes  place,  forming  a  distinct  projection  or  ridge.  .  This  is  termed  the  genital 
ridge  (Fig.  774),  and  from  it  the  testicle  in  the  one  sex.  and  the  ovary  in  the  other, 
are  developed.  As  the  embryo  grows  the  genital  ridge  gradually  becomes  pinched 
off  from  the  Wolffian  body,  with  which  it  is  at  first  continuous,  though  it  still 
remains  connected  to  the  remnant  of  this  body  by  a  fold  of  peritoneum,  the 
mesorchium  or  mesovarium.  About  the  seventh  week  the  distinction  of  sex  begins 
to  be  perceptible. 


1210 


EMBRYOLOGY. 


The  ovary,  thus  formed  from  the  genital  ridge,  consists  of  a  central  part  of 
connective  tissue  covered  by  a  layer  or  layers  of  epithelium,  the  germinal 
epithelium.  Columns  of  this  epithelium,  termed  egg-tubes,  grow  down  into  the 
stroma,  and  simultaneously  with  this  an  upward  growth  of  the  connective  tissue 
takes  place  between  the  columns  of  epithelial  cells.  It  results  from  this  that  the 
columns  of  cells  become  enclosed  in  meshes  of  connective  tissue  (Fig.  784). 
Each  egg-tube  or  nest  represents  a  primitive  Graafian  follicle,  one  cell  of  which 
becomes  enlarged  to  form  the  ovum ;  the  remainder  form  the  epithelium  of  the 
follicle.  The  remains  of  the  germinal  epithelium  on  the  surface  of  the  ovary  form 
the  permanent  epithelial  covering  of  this  organ.  According  to  Beard,  the  primi- 
tive ova  are  early  set  apart  during  the  segmentation  of  the  ovum  and  migrate  into 
the  germinal  ridge. 

The  testicle  is  developed  in  a  very  similar  way  to  the  ovary,  but  the  processes 
are  not  so  well  marked.  Like  the  ovary,  in  its  earliest  stages  it  consists  of  a 
central  mass  of  connective  tissue  covered  by  germinal  epithelium.  A  downward 
growth  of  columns  of  this  epithelium  into  the  central  connective  tissue  takes 
place.  From  these  the  seminiferous  tubules  are  developed  and  become  connected 
with  outgrowths  from  the  Wolffian  body,  which,  as  before  mentioned,  form  the 
rete  testis  and  vasa  efferentia. 

With  regard  to  the  other  parts  of  the  internal  female  organs,  the  Fallopian 
tube,  as  has  been  mentioned,  is  developed  from  the  upper  part  of  the  duct  of 
Miiller,  while  the  lower  parts  of  the  two  ducts  approach  each  other,  and,  lying 


Fig.  778.— Adult  ovary,  parovarium,  and  Fallopian  tube.  (From  Farre,  after  Kobelt.)  a,  a.  Epoophoron 
formed  from  the  upper  part  of  the  Wolffian  body.  b.  Remains  of  the  uppermost  tubes  sometimes  forming 
hydatids,  c.  Middle  set  of  tubes,  d.  Some  lower  atrophied  tubes,  e.  Atrophied  remains  of  the  Wolffian  duct. 
/.  The  terminal  bulb  or  hydatid,  h.  The  Fallopian  tube,  originally  the  duct  of  Miiller.  i.  Hydatid  attached 
to  the  extremity.    I.  The  oVary. 

side  by  side,  finally  coalesce  to  form  the  cavity  of  the  uterus  and  vagina. —  This 
coalescence  commences  in  the  middle  of  the  genital  cord,  and  corresponds  to  the 
body  of  the  uterus.  With  regard  to  the  further  changes  in  the  female  organs,  the 
only  remains  of  the  Wolffian  body  in  the  complete  condition  are  two  rudimentary 
or  vestigial  structures,  which  can  be  found,  on  careful  search,  in  the  broad 
ligament  near  the  ovary:  the  parovarium  or  organ  of  Rosenmiiller  and  the 
epoophoron  (Fig.  778).  The  organ  of  Rosenmiiller  consists  of  a  number  of  tubes 
which  converge  to  a  transverse  portion,  the  epoophoron,  and  this  is  sometimes 
prolonged  into  a  distinct  duct,  running  transversely,  the  duct  of  Gartner,  which  is 
much  more  conspicuous  and  extends  further  in  some  of  the  lower  animals.  This, 
as  has  been  pointed  out,  is  the  remains  of  the  Wolffian  duct.  About  the  fifth 
month  an  annular  constriction  marks  the  position  of  the  neck  of  the  uterus,  and 
after  the  sixth  month  the  walls  of  the  uterus  begin  to  thicken.  The  round  liga- 
ment is  derived  from  a  band  containing  involuntary  muscular  fibres,  which  runs 
downward  from  the  lower  part  of  the  Wolffian  body  to  the  groin,  and  which  in 


THE   EMBRYO. 


1211 


the  male  forms  the  gubernaculum  testis ;  the  peritoneum  constitutes  the  broad 
ligament ;  the  superior  ligament  of  the  Wolffian  body,  which  serves  to  connect  it 
with  the  Diaphragm,  disappears  with  that  body. 

With  regard  to  the  other  parts  of  the  male  organs,  the  Miillerian  ducts  dis- 
appear, with  the  exception  of  their  lower  ends.  These  unite  in  the  middle  line,  and 
open  by  a  common  orifice  into  the  urogenital  sinus.  This  constitutes  the  utriculus 
hominis  or  sinus  prostatitis.  Frequently,  however,  the  upper  end  of  the  duct  of 
Miiller  remains  visible  in  the  male  as  a  little  pedunculated  body,  called  the  hydatid 
of  Morgagni,  in  the  neighborhood  of  the  epididymis,1  between  the  testis  and  globus 
maj  or. 

The  epididymis,  the  vas  deferens,  and  ejaculatory  duct  are  formed  from  the 
Wolffian  duct.  One  or  more  of  the  tubes  of  the  Wolffian  body  form  the  vaa 
aberrans  and  a  structure  described  by  Giraldes,  and  called,  after  him.  >k  the  organ 
of  Giraldes,"  which  bears  some  resemblance  to  the  organ  of  Rosenm uller  in  the 
other  sex.  It  consists  of  a  number  of  convoluted  tubules,  lying  in  the  cellular 
tissue  in  front  of  the  cord,  and  close  to  the  head  of  the  epididymis. 

Descent  of  the  Testes. — The  testes,  at  an  early  period  of  foetal  life,  are  placed 
at  the  back  part  of  the  abdominal  cavity,  behind  the  peritoneum  and  a  little  below 
the  kidneys.  The  anterior  surface  and  sides  are  invested  by  peritoneum.  At 
about  the  third  month  of  intra-uterine  life  a  peculiar  structure,  the  gubernacvlnin 
testis,  makes  its  appearance.      This  structure  is  at  first  a  slender  band,  extending 


Ovarian  tube  of  epithelium. 


Blood-vessel. 
Graafian  follicle. 


■-Germinal  epithelium. 

"Primitive  ova. 
-Cell  nest. 


Fig.  779.— Section  of  the  ovary  of  a,  newly  born  child.    iWaldeyer.) 

from  that  part  of  the  skin  of  the  groin  which  afterward  forms  the  scrotum  through 
the  inguinal  canal  to  the  body  and  epididymis  of  the  testicle,  and  is  then  continued 
upward  in  front  of  the  kidney  toward  the  Diaphragm.  As  development  advances 
the  peritoneum  covering  the  testicle  encloses  it  and  forms  a  mesentery,  the  mesoi'- 
chium,  which  also  encloses  the  gubernaculum  and  forms  two  folds,  one  above  the 
testicle  and  the  other  below  it.  The  one  above  the  testiele  i*  the  plica  vascularis, 
and  contains  ultimately  the  spermatic  vessels  ;  the  one  below,  the  plica  gubernatrix, 
containsthe  lower  part  of  the  gubernaculum,  which  has  now  grown  into  a  thick 
cord;  it  terminates  below  at  the  internal  ring  in  a  tube  of  peritoneum,  the  proces- 
sus vaginalis,  which  protrudes  itself  down  the  inguinal  canal.  The  lower  part  of 
the  gubernaculum  by  the  fifth  month  has  become  a  thick  cord,  while  the  upper 
part  has  disappeared.  The  lower  part  can  now  be  seen  to  consist  of  a  central  core 
of  unstriped  muscle-fibre,  and  outside  this  of  a  firm  layer  of  striped  elements, 
connected,   behind  the  peritoneum,    with    the  abdominal  wall.       As  the  scrotum 

1  Mr.  Osborn,  in  the  St.  Thomas's  Ebspifal  Hrpnrtx,  1ST.",,  has  written  an  interesting  paper  pointing 
out  the  probable  connection  between  this  foetal  structure  and  one  form  of  hydrocele. 


1212  EMBR  YOL  OGY. 

develops,  the  lower  end  of  the  gubernaculum  is  carried  with  the  skin  to  which  it 
is  attached  to  the  bottom  of  this  pouch.  The  fold  of  peritoneum,  constituting  the 
processus  vaginalis,  projects  itself  downward  into  the  inguinal  canal,  and  emerges 
at  the  external  abdominal  ring,  pushing  before  it  a  part  of  the  internal  oblique 
muscle  and  the  aponeurosis  of  the  external  oblique,  which  form,  respectively,  the 
cremaster  muscle  and  the  external  spermatic  fascia.  It  forms  a  gradually  elon- 
gating depression  or  cul-de-sac,  which  eventually  reaches  the  bottom  of  the  scrotum, 
and  into  this  the  testicle  is  drawn  by  the  growth  of  the  body  of  the  foetus,  for  the 
gubernaculum  does  not  grow  commensurately  with  the  growth  of  other  parts,  and 
therefore  the  testicle,  being  attached  by  the  gubernaculum  to  the  bottom  of  the 
scrotum,  is  prevented  from  rising  as  the  bottom  grows,  and  is  drawn  first  into  the 
inguinal  canal  and  eventually  into  the  scrotum.  It  seems  certain  also  that  the 
gubernacular  cord  becomes  shortened  as  development  proceeds,  and  this  assists  in 
causing  the  testicle  to  reach  the  bottom  of  the  scrotum.  By  the  eighth  month  the 
testicle  has  reached  the  scrotum,  preceded  by  the  lengthened  pouch  of  peritoneum, 
the  processus  vaginalis,  which  communicates  by  its  upper  extremity  with  the  peri- 
toneal cavity.  Just  before  birth  the  upper  part  of  the  pouch  usually  becomes 
closed,  and  this  obliteration  extends  gradually  downward  to  within  a  short  distance 
of  the  testis.  The  process  of  peritoneum  surrounding  the  testis,  which  is  now 
entirely  cut  off  from  the  general  peritoneal  cavity,  constitutes  the  tunica  vaginalis} 
In  the  female  there  is  also  a  gubernaculum,  which  effects  a  considerable  change 
in  the  position  of  the  ovary,  though  not  so  extensive  a  change  as  that  of  the  testicle 
in  the  male.  The  gubernaculum  in  the  female,  as  it  lies  on  either  side  in  contact 
with  the  fundus  of  the  uterus  formed  by  the  union  of  the  Miillerian  ducts,  con- 
tracts adhesions  to  this  organ,  and  thus  the  ovary  is  prevented  from  descending 
below  this  level.  The  remains  of  the  gubernaculum— that  is  to  say,  the  part 
below  the  attachment  of  the  cord  to  the  uterus  to  its  termination  in  the  labia 
majora — ultimately  forms  the  round  ligament  of  the  uterus.  A  pouch  of  peritoneum 
accompanies  it  along  the  inguinal  canal,  analogous  to  the  processus  vaginalis  in 
the  male;  it  is  called  the  canal  of  Nuclc.  In  rare  cases  the  gubernaculuru  may 
fail  to  contract  adhesions  to  the  uterus,  and  then  the  ovary  descends  through  the 
inguinal  canal  into  the  labia  majora,  extending  down  the  canal  of  Nuck,  and 
under  these  circumstances  resembles  in  position  the  testicles  in  the  male. 

Surgical  Anatomy. — Abnormalities  in  the  formation  and  in  the  descent  of  the  testicle 
may  occur.  The  testicle  may  fail  to  be  developed  ;  or  the  testicle  may  he  fully  develo])ed,  and 
the  vas  deferens  may  be  undeveloped  in  whole  or  part ;  or,  again,  both  testicle  and  vas  deferens 
may  be  fully  developed,  but  the  duct  may  not  become  connected  to  the  gland.  The  testicle 
may  fail  in  its  descent^  or  it  may  descend  into  some  abnormal  position.  Thus  it  may  be  retained 
in  the  position  where  it  was  primarily  developed,  below  the  kidney  ;  or  it  may  descend  to  the 
internal  abdominal  ring,  but  fail  to  pass  through  this  opening  ;  it  may  be  retained  in  the  inguinal 
canal,  which  is  perhaps  the  most  common  position  ;  or  it  may  pass  through  the  external  abdom- 
inal ring  and  remain  just  outside  it,  failing  to  pass  to  the  bottom  of  the  scrotum.  On  the  other 
hand,  it  may  get  into  some  abnormal  position :  it  may  pass  the  scrotum  and  reach  the  peri- 
neum, or  it  may  fail  to  enter  the  inguinal  canal,  and  may  find  its  way  through  the  femoral  ring 
into  the  crural  canal,  and  present  itself  on  the  thigh  at  the  saphenous  opening.  There  is  still  a 
third  class  of  cases  of  abnormality  of  the  testicle  :  where  the  organ  has  descended  in  due  course 
into  the  scrotum,  but  is  malplaced.  The  most  common  form  of  this  is  where  the  testicle  is 
inverted;  that  is  to  say,  the  organ  is  rotated  so  that  the  epididymis  is  connected  to  the  front  of 
the  scrotum,  and  the  body,  surrounded  by  the  tunica  vaginalis,  is  directed  backward.  In  these 
cases  the  vas  deferens  is  to  be  felt  in  the  front  of  the  cord.  The  condition  is  of  importance  in 
connection  with  hydrocele  and  haematocele,  and  the  position  of  the  testicle  should  always  be 
carefully  ascertained  before  performing  any  operation  for  these  affections.  Again,  more  rarely, 
the  testicle  may  be  reversed.  _  This  is  a  condition  in  which  the  top  of  the  testicle,  indicated  by 
the  globus  major  of  the  epididymis,  is  at  the  bottom  of  the  scrotum,  and  the  vas  deferens 
comes  off  from  the  summit  of  the  organ.  Cases  sometimes  occur,  generally  in  the  young  adult, 
in  which  the  spermatic  cord  becomes  twisted.  In  consequence  of  this  the  circulation  through  it 
is  partially  or  completely  arrested,;  if  the  latter,  the  testicle  becomes  gangrenous;  if  the  former, 
it  may  undergo  atrophy. 

The   external  organs  of  generation  (Fig.  780),  like  the  internal,  pass  through 

1  The  obliteration  of  the  process  of  peritoneum  which  accompanies  the  cord,  and  is  hence  called 
the  funicular  process,  is  often  incomplete.     See  section  on  Inguinal  Hernia. 


THE   EMBRYO. 


1211 


a  stage  in  which  there  is  no  distinction  of  sex.  It  is  therefore  necessary  to 
describe  this  stage,  and  then  follow  the  development  of  the  female  and  male 
organs  respectively. 

As  stated  above,  the  anal  depression,  or  proctodeum,  at  an  early  period  is 
formed  by  an  involution  of  the  epiblast,  and  the  intestine  is  still  closed  at  its  lower 
end.  When  the  septum  between  the  two  opens,  which  is  about  the  fourth  week, 
the   urachus  in  front  and  the  intestine  behind   both  communicate  with  the  anal 


Posterior 

\f        extremity. 
^ —  Cloaca. 


rein 


Genital  eminence. 
.Genital  ridge. 
■  Genital  fold. 

Genital  groove. 


Glans  penis. 

Genital  ridge. 
[_Gen  ital  groove. 
I  Genital  fold. 
~Perinseum. 
-Anus. 


Clitoris. 
Genital  ridge. 
Genital  fold. 
Entrance  to  vagina. 
Perinseum. 
Anus. 


Fig.  780. — Stages  in  the  development  of  the  external  sexual  organs  in  the  male  and  female. 
Ecker-Ziegler  wax  models.)    (From  Hertwig's  Entwickelungsgesckichte.) 


(After  the 


depression.  This,  which  is  now  called  the  cloaca,  is  afterward  divided  by  a  trans- 
verse septum,  the  perinceum,  which  appears  about  the  second  month.  Two  tubes 
are  thus  formed :  the  posterior  becomes  the  lower  part  of  the  rectum,  the  anterior 
is  the  urogenital  sinus.  In  the  sixth  week  a  tubercle,  the  genital  eminence,  is 
formed  in  front  of  the  cloaca,  and  this  is  soon  surrounded  by  two  folds  of  skin,  the 
genital  ridges.  Toward  the  end  of  the  second  month  the  genital  tubercle 
presents,  on  its  lower  aspect,  a  groove,  the  genital  groove,  which  extends  down- 
ward toward  the  cloaca.  This  groove  becomes  deeper,  and  is  bounded  laterally 
by  projecting  folds  of  skin,  the  genital  folds.  All  these  parts  are  well  developed 
by  the  second  month,  yet  no  distinction  of  sex  is  possible. 

Female  Organs. — The  female  organs  are  developed  by  an  easy  transition  from 
the  above.  The  urogenital  sinus  persists  as  the  vestibule  of  the  vagina  and  the 
urethra.  The  genital  eminence  forms  the  clitoris,  the  genital  ridges  the  labia 
majora,  and  the  lips  of  the  genital  groove  the  labia  minora,  which  remain  open. 
An  innovation  of  the  epithelium  takes  place  on  either  side  close  to  the  root  of  the 
genital  tubercle,  which  becomes  the  glands  of  Bartholin. 

Male  Organs. — In  the  male  the  changes  are  greater.  The  genital  eminence  is 
developed  into  the  penis,  the  glans  appearing  in  the  third  month,  the  prepuce  and 
corpora  cavernosa  in  the  fourth.  The  genital  groove- closes  and  thus  forms  a  canal, 
the  spongy  portion  of  the  urethra.  The  urogenital  sinus  becomes  elongated  and 
forms  the  membranous  urethra.  The  genital  ridges  unite  in  the  middle  line  to 
form    the    scrotum,   at    about   the   same  time   as   the  genital  groove  closes,  viz., 


1214  EMBRYOLOGY. 

between  the  third  and  fourth  month.  A  similar  involution  of  epithelium  to  that 
which  in  the  female  forms  the  glands  of  Bartholin  takes  place  in  the  male  and 
becomes  the  glands  of  Cowper. 

The  following  table  is  translated  from  the  work  of  Beaunis  and  Bouchard,  with 
some  alterations,  especially  in  the  earlier  weeks.  It  will  serve  to  present  a  rtsumt 
of  the  above  facts  in  an  easily  accessible  form.1 

i  It  will  be  noticed  that  the  time  assigned  in  this  table  for  the  appearance  of  the  first  rudiment 
of  some  of  the  bones  varies  in  some  cases  from  that  assigned  in  the  description  of  the  various  bones 
in  the  sequel    This  is  a  point  on  which  anatomists  differ,  and  which  probably  varies  m  different  cases. 


CHRONOLOGICAL  TABLE 

.       OF 

THE  DEVELOPMENT  OF  THE  FCETUS. 

(Feom  Beaunis  and  Bouchard.) 

First  Week. — During  this  period  the  ovum  is  in  the  Fallopian  tube.  Having  been  fertilized  in 
the  upper  part  of  the  tube,  it  slowly  passes  down,  undergoing  segmentation,  and  reaches 
the  uterus  probably  about  the  end  of  the  first  week.  During  this  time  it  does  not  undergo 
much  increase  in  size. 

Second  Week. — The  ovum  rapidly  increases  in  size  and  becomes  imbedded  in  the  decidua,  so 
that  it  is  completely  enclosed  in  the  decidua  reflexa  by  the  end  of  this  period.  An  ovum 
believed  to  be  of  the  thirteenth  day  after  conception  is  described  by  Reich  ert.  There  was 
no  appearance  of  any  embryonic  structure.  The  equatorial  margins  of  tbe  ovum  were  beset 
with  villi,  but  the  surface  in  contact  with  the  uterine  wall  and  the  one  opposite  to  it  were 
bare.  In  another  ovum,  described  by  His,  believed  to  be  of  about  the  fourteenth  day, 
there  was  a  distinct  indication  of  an  embiyo.  There  was  a  medullary  groove  bounded  by 
folds.  In  front  of  this  a  slightly  prominent  ridge,  the  rudimentary  heart.  The  amnion 
was  formed  and  the  embryo  was  attached  by  a  stalk,  the  allantois,  to  the  inner  surface  of 
the  chorion.  It  may  be  said,  therefore,  that  these  parts,  the  amnion,  and  the  allantois.  and 
the  first  rudiments  of  the  embryo,  the  medullary  groove,  and  the  heart,  are  formed  at  the 
end  of  the  second  week, 

Third  Week. — By  the  end  of  the  third  week  the  flexures  of  the  embryo  have  taken  place,  so 
that  it  is  strongly  curved.  The  protovertebral  disks,  which  begin  to  be  formed  early  in  the 
third  week,  present  their  full  complement.  In  the  nervous  system  the  primary  divisions 
of  the  brain  are  visible,  and  the  primitive  ocular  and  auditory  vesicles  are  already  formed. 
The  primary  circulation  is  established.  The  alimentary  canal  presents  a  straight  tube  com- 
municating with  the  yolk-sac.  The  branchial  arches  are  formed.  The  limbs  have  appeared 
as  short  buds.     The  Wolffian  bodies  are  visible. 

Fourth  Week. — The  umbilical  vesicle  has  attained  its  full  development.  The  caudal  extremity 
projects.  The  upper  and  the  lower  limbs  and  the  cloacal  aperture  appear.  The  heart  sep- 
arates into  a  right  and  left  heart.  The  special  ganglia  and  anterior  roots  of  the  spinal 
nerves,  the  olfactory  fossae,  the  lungs  and  the  pancreas  can  be  made  out. 

Fifth  Week. — The  allantois  is  vascular  in  its  whole  extent.  The  first  traces  of  the  hands  and 
feet  can  be  seen.  The  primitive  aorta  divides  into  aorta  and  pulmonary  artery.  The  duct 
of  Muller  and  genital  gland  are  visible.  The  ossification  of  the  clavicle  and  the  lower  jaw 
commences.     The  cartilage  of  Meckel  occupies  the  first  post-oral  arch. 

Sixth  Week,- — The  activity  of  the  umbilical  vesicle  ceases.  The  pharyngeal  clefts  disappear. 
The  vertebral  column,  primitive  cranium,  and  ribs  assume  the  cartilaginous  condition.  The 
posterior  roots  of  the  nerves,  the  membranes  of  the  nervous  centres,  the  bladder,  kidney, 
tongue,  larynx,  thyroid  body,  the  germs  of  teeth,  and  the  genital  tubercle  and  folds 
are  apparent, 

Seventh  Week. — The  muscles  begin  to  be  perceptible.  The  points  of  ossification  of  the  ribs, 
scapula,  shaft  of  humerus,  femur,  tibia,  palate,  and  upper  jaw  appear. 

Eighth  Week. — The  distinction  of  arm  and  forearm,  and  of  thigh  and  leg.  is  apparent,  as  well  as 
the  interdigital  clefts.  The  capsule  of  the  lens  and  pupillary  membrane,  the  interventricu- 
lar and  commencement  of  the  interauricular  septum,  the  salivary  glands,  the  spleen,  and 
suprarenal  capsules  are  distinguishable.  The  larynx  begins  to  become  cartilaginous.  All 
the  vertebral  bodies  are  cartilaginous.  The  points  of  ossification  for  the  ulna,  radius,  fibula, 
and  ilium  make  their  appearance.  The  two  halves  of  the  hard  palate  unite.  The 
sympathetic  nerves  are  now  for  the  first  time  to  be  discerned. 

1  [Eternod  (Anat.  Anzeiger,  Band  xv.,  1898)  described  an  ovum  which  he  reconstructed.  It 
had  a  precise  history,  from  which  he  concluded  that  it  must  have  belonged  to  the  end  of  the  second 
or  the  beginning  of  the  third  week.  Including  the  villi  it  measured  10X8.2X6  mm.  I'  was 
flattened  on  its  embryonal  side,  and  the  embryo  measured  1.3  mm.  The  amnion  was  completely 
formed  and  the  allantois  existed  as  a  long  canal.  The  vitelline  circulation  was  established  and  the 
villi  of  the  chorion  were  beginning  to  be  vascularized.  The  blastopore  still  opened  into  the  amniotic 
cavity,  with  the  primitive  groove  behind  it  and  the  rudimentary  groove  in  front.  The  notochord 
was  closing  in  and  all  three  layers  of  the  blastoderm  were  distinct,  except  around  tbe  blastopore,  where 
they  formed  an  undivided  mass. — Eds.] 

1215 


1216  THE   FCETUS. 

Ninth  Week. — The  corpus  striatum  and  the  pericardium  are  first  apparent.  The  ovary  and 
testicle  can  be  distinguished  from  each  other.  The  genital  furrow  appears.  The  osseous 
nuclei  of  the  bodies  and  arches  of  the  vertebrae,  of  the  frontal,  vomer,  and  malar  bones  of  the 
shafts  of  the  metacarpal  and  metatarsal  bones,  and  of  the  phalanges  appear.  The  union  of 
the  hard  palate  is  completed.     The  gall-bladder  is  seen. 

Third  Month. — The  formation  of  the  foetal  placenta  advances  rapidly.  The  projection  of  the 
caudal  extremity  disappears.  It  is  possible  to  distinguish  the  male  and  female  organs  from 
each  other.  The  cloacal  aperture  in  divided  into  two  parts.  The  cartilaginous  arches  on  the 
dorsal  region  of  the  spine  close.  The  points  of  ossification  for  the  occipital,  sphenoid, 
lachrymal,  nasal,  squamous  portion  of  temporal  and  ischium  appear,  as  well  as  the  orbital 
centre  of  the  superior  maxillary.  The  pons  Varolii  and  fissure  of  Sylvius  can  be  made  out. 
The  eyelids,  the  hair,  and  the  nails  begin  to  form.  The  mammary  gland,  the  epiglottis, 
and  prostate  are  beginning  to  develop.  The  union  of  the  testicle  with  the  canals  of  the 
Wolffian  body  takes  place. 

Fourth  Month. — The  closure  of  the  cartilaginous  arches  of  the  spine  is  complete.  Osseous 
points  for  the  first  sacral  vertebra  and  os  pubis  appear.  The  ossification  of  the  malleus  and 
incus  takes  place.  The  corpus  callosum,  the  membrana  lamina  spiralis,  the  cartilage  of 
the  Eustachian  tube,  and  the  tympanic  ring  are  seen.  Fat  is  first  developed  in  the  sub- 
cutaneous cellular  tissue.  The  tonsils  are  seen,  and  the  closure  of  the  genital  furrow  and 
the  formation  of  the  scrotum  and  prepuce  take  place. 

Fifth  Month. — The  two  layers  of  the  decidua  begin  to  coalesce.  Osseous  nuclei  of  the  axis  and 
odontoid  process,  of  the  lateral  points  of  the  first  sacral  vertebra,  of  the  median  points  of 
the  second,  and  of  the  lateral  masses  of  the  ethmoid  make  their  appearance.  Ossification 
of  the  stapes  and  the  petrous  bone  and  ossification  of  the  germs  of  the  teeth  take  place. 
The  germs  of  the  permanent  teeth  and  the  organ  of  Corti  appear.  The  eruption  of  hair  on 
the  head  commences.  The  sudoriferous  glands,  Brunner's  glands,  the  follicles  of  the  tonsil 
and  base  of  the  tongue,  and  the  lymphatic  glands  appear  at  this  period.  The  differentiation 
between  the  uterus  and  vagina  becomes  apparent. 

Sixth  Month. — The  points  of  ossification  for  the  anterior  root  of  the  transverse  process  of  the 
seventh  cervical  vertebra,  the  lateral  points  of  the  second  sacral  vertebra,  the  median  points 
of  the  third,  the  manubrium  sterni  and  the  os  calcis  appear.  The  sacro-vertebral  angle 
forms.  The  cerebral  hemispheres  cover  the  cerebellum.  The  papillae  of  the  skin,  the 
sebaceous  glands,  and  Peyer's  patches  make  their  appearance.  The  free  border  of  the 
nail  projects  from  the  corium  of  the  dermis.     The  walls  of  the  uterus  thicken. 

Seventh  Month. — The  additional  points  of  the  first  sacral  vertebra,  the  lateral  points  of  the 
third,  the  median  point  of  the  fourth,  the  first  osseous  point  of  the  body  of  the  sternum, 
and  the  osseous  point  for  the  astragalus  appeal-.  Meckel's  cartilage  disappears.  The 
cerebral  convolutions,  the  island  of  Reil,  and  the  tubercula  quadrigemina  are  apparent.  The 
pupillary  membrane  atrophies.  The  testicle  passes  into  the  vaginal  process  of  the 
peritoneum. 

Eighth  Month. — Additional  points  for  the  second  sacral  vertebra,  lateral  points  for  the  fourth 
and  median  points  for  the  fifth  sacral  vertebrae,  can  be  seen. 

Ninth  Month. — Additional  points  for  the  third  sacral  vertebra,  lateral  points  for  the  fifth, 
osseous  points  for  the  middle  turbinated  bone,  for  the  body  and  great  cornu  of  the  hyoid, 
for  the  second  and  third  pieces  of  the  body  of  the  sternum,  and  for  the  lower  end  of  the 
femur  appear.  Ossification  of  the  bony  lamina  spiralis  and  axis  of  the  cochlea  takes  place. 
The  eyelids  open,  and  the  testicles  are  in  the  scrotum. 


INDEX. 


A. 

Abdomen,  895 

apertures  found  in,  895 
boundaries  of,  895 
lymphatics  of,  632 
muscles  of,  356 
regions  of,  895 
viscera  of,  896 
Abdominal  aorta,  549 
branches  of,  550 
surface-marking  of,  550 
surgical  anatomy  of,  550 
muscles,  356 
ring,  external.  357,  1043 

interna],  366,  1047 
stalk,  note,  1162    . 
viscera,  position  of,  896 
Abdominothoracic  arch,  133 
Abducent  nerve,  738 

surgical  anatomy  of,  740 
Abductor  hallucis  muscle,  444 
indicis  muscle,  408 
minimi  digiti  muscle,  foot,  445 

hand,  406 
pollicis  muscle,  404 
Aberrant  duct  of  testis,  1021 
Absorbent  glands,  623 
Absorbents,  623 
Accelerator  urinse  muscle,  371 
Accessorius  ad  ilio-costalem  mus- 
cle, 343 
pedis,  446 
Accessory    descending    palatine 
canals,  91 
gland  of  Rosenmiiller,  845 
obturator  nerve,  786 
olivary  nuclei,  703 
processes,  42 
pudic  artery,  565 
thyroid  glands,  980 
Acer vulus  cerebri,  673 
Acetabulum,  177 
Achromatic  spindle,  1075 
Achromatin,  1074 
Acromial  end  of  clavicle,  fract- 
ure of,  412 
region,  muscles  of,  382 
thoracic  artery,  532 
Acromio-clavicular  joint,  248 
surface  form  of,  249 
surgical  anatomy  of,  249 
Acromion  process,  140 

fracture  of,  412 
Actions  of  muscles.      See  each 

group  of  muscles. 
Adamantoblasts,  879 
Adductor  brevis  muscle,  425 
longus  muscle,  424 
magnus  muscle,  425 
obliquus  hallucis,  447 
pollicis,  404 

77 


Adductor    transversus    hallucis, 
447 

pollicis,  405 

tubercle,  187 
Adenoid  connective  tissue,  1091 
Adipose  tissue,  1091 
Adminiculum  lines?  alba?,  360 
Afferent  nerves,  1120 

vessels  of  kidney,  992 
Air-cells,  976 
Ala  cinerea,  698,  702 

lobuli  centralis,  686 

nasi,  818 

artery  of,  491 
Ala?  of  sacrum,  48 

of  vomer,  95 
Alar  lamina,  1177 

ligaments,  230 
of  knee,  278 

thoracic  artery,  533 
Alcock,  canal  of,  565,  1064 
Alimentary  canal,  869 
development  of,  1198 
subdivisions  of,  869 
Allantoic  vesicle,  1162 

vessels,  1162 
Allantois,  1162 
Alveolar  artery,  499 

process,  86,  98 
Alveoli,  formation  of,  880 

of  lower  jaw,  98 

of  stomach,  910 

of  upper  jaw,  86 
Alveus,  666 

Amacrine  cells  of  retina,  835 
Amnion,  1160 

false,  1161 

true,  1161 
Amniotic  cavity,  1161 

primitive,  1154 
Amphiarthrosis,  219 
Ampulla?  of  semicircular  canals, 
860 

of  tubuli  lactiferi,  1040 
Amygdala?,  884 

of  cerebellum,  688 
Amygdaloid  nucleus,  662 
Anal  canal,  925 

fascia,  369,  1071 
Anaphase  of  karyokinesis,  1075 
Anastomosis  of  arteries,  474 
Anastomotica  magna  of  brachial, 
536 
of  femoral,  580 
Anatomical   neck   of    humerus, 
144 
fracture  of,  149 
Anconeus  muscle,  397 
Andersch,  ganglion  of,  748 
Aneurisms  of  abdominal  aorta, 
550 

of  arch  of  aorta,  479 


Aneurisms    of     thoracic    aorta, 

547 
Angle  of  jaw,  101 
of  Ludwig,  132 
of  os  pubis,  176 
of  rib,  129 
sacro-vertebral.  46 
Angular  artery,  492 
convolution,  651 
movement,  222 
process,  external,  62 

internal,  62 
vein,  595 
Animal  cell,  1073 

constituent  of  bone,  1102 
Ankle-joint,  283 

relations  of  tendons  and  ves- 
sels to,  285 
surface  form  of,  285 
surgical  anatomy  of,  285 
Annular  ligament  of  ankle,  ante- 
rior, 442 
external,  443 
internal,  442 
of  radius  and  ulna,  259 
of  stapes,  857 
of  wrist,  anterior,  401 
posterior,  402 
Annulus  ovalis,  462 

tympanicus,  851 
Ansa  hypoglossi,  756 

peduncularis,  672 
Anterior       annular      ligament, 
ankle,  442 
wrist,  401 
chamber  of  eye,  839 
crescentic  lobe,  686 
crural  nerve,  786 

surgical  anatomy  of,  797 
dental  canal,  83 
ethmoidal  cells,  79 
fontanelle,  81 
fossa  of  skull,  103 
and    internal    frontal    arterv 

510> 
nasal  spine,  88 
nerve-roots,  717 
palatine  canal.  87 

fossa,  87,  108 
perforated  space,  655 
region  of  skull,  112 
triangle  of  neck,  500 
Anterolateral    ascending    tract 
of  cord,  714 
ganglionic  arterv.  511 
ground  bundle,  714 
Antero-median     ganglionic    ar- 
terv, 510 
Antihelix.  849 
fossa  of,  849 
Antitragicus  muscle,  So0 
Antitragus,  849 

1217 


1218 


INDEX. 


Antrum  of  Highmore,  83 
mastoid,  68,  854 
pylori,  906 
Anus,  1063 

development  of,  1202 
muscles  of,  368 
Aorta,  475 

abdominal,  549 
branches  of,  550 
surgical  anatomy  of  arch  of, 
479 
arch  of,  478 

branches  of,  480 
peculiarities  of,  479 

branches  of,  480 
sinuses  of,  477 
surgical  anatomy  of,  479 
descending,  546 
development  of,  1191 
thoracic,  546 
branches  of,  547 
sinuses  of,  477 
surgical  anatomy  of,  547 
transverse,  478 
Aortic  isthmus,  478 

opening  of  diaphragm,  353 

of  heart,  466 
plexus,  809 
semilunar  valves,  467 
septum,  1191 
sinuses,  467 
spindle,  478 
vestibule,  468 
Apertura   scalae  vestibuli   coch- 
leae, 861 
Apex  cornu  of  cord,  712 
Aponeurosis,  296 
of  deltoid,  382 
of  external  oblique  in  inguinal 

region,  357 
of  occipito-frontalis,  300 
of  soft  palate,  883 
suprahyoid,  321 
Apophysis,  34 
Apparatus    ligamentosus      coli, 

230 
Appendages  of  eye,  843 

surgical  anatomy  of,  847 
of  skin,  1139 
of  uterus,  1034 
Appendices  epiploicae,  928 
Appendix  of  left  auricle,  465 
of  right  auricle,  461 
vermiformis,  922 
Aqua  labyrinthi,  866 
Aquaeductus  cochleae,  69,  861 
Fallopii,  69,  854 
Sylvius,  676 
vestibuli,  69,  860 
Aqueous  humor,  839 
Arachnoid  of  brain,  641 

of  cord,  707 
Arantii  corpora,  464 
Arbor  vitae  of  cerebellum,  689 

uterina,  1031,  1032 
Arch  of  aorta,  478 
branches  of,  480 
peculiarities  of,  479 
surgical  anatomy  of,  479 
crural,  1057 
deep,  539 
of  os  pubis,  182 
palmar  superficial,  544 
plantar,  592 
supraorbital,  61 


Arch  of  a  vertebra,  34 

zygomatic,  111 
Arches,  aortic,  foetal,  1292 

branchial,  1168 
Arciform    or    arcuate   fibres    of 

medulla  oblongata,  696,  701 
Arcuate  fibres  of  cerebellum,  691 
Area  of  Broca,  655 
of  Cohnheim,  1109 
cribrosa,  media,  69 

superior,  69 
germinal,  1154 
vestibularis,  inferior,  867 
superior,  867 
Areas  of  Cohnheim,  1109 
Areola  of  breast,  1039 
Areolae  of  bone,  primary,  1103 

secondary,  1105 
Areolar  tissue,  1086 
Arm,  arteries  of,  514 
back  of,  muscles  of,  388 
bones  of,  144 
fascia  of,  386 
front  of,  muscles  of,  386 
lymphatic  glands  of,  628 
lymphatics  of,  628 
nerves  of,  764 
superficial  fascia  of,  382 
veins  of,  607 
Arnold's  ganglion,  736 
nerve,  751 
canal,  70 
Arrectores  pili,  1142 
Arteria  centralis  retinae,  509 
hyaloidea,  1182 
magna,  475 
Arteriae  hallucis,  588 
propria?  renales,  992 
receptaculi,  505 
Arteries,  anastomoses  of,  474 
capillary,  1128 
development  of,  1191 
distribution  of,  474 
general  anatomy  of,  1126 
mode  of  division,  474 

of  origin  of  branches,  474 
nerves  of,  1128 
sheath  of,  1128 
structure  of,  1126 
subdivision  of,  474 
systemic,  474 
vessels  of,  1128 
Arteries  or  artery,  accessory  pu- 
dic,  566 
acromial,  tlioracic,  532 
alar  thoracic,  533 
alveolar,  499 

anastomotica    magna    of  bra- 
chial, 537 
of  femoral,  580 
angular,  492 
anterior  cerebral,  510 
choroid,  512 
ciliary,  509 
communicating,  511 
inferior  cerebellar,  522 
intercostal,  526 
internal  frontal,  510 
spinal,  521 
antero-lateral  ganglionic,  511 
antero-pedian  ganglionic,  510 
aorta,  475 

abdominal,  549 
arch  of,  478 
ascending  part,  476 


Arteries  or  artery,  aorta,  descend- 
ing part,  546 

thoracic,  546 
articular  knee,  583 
ascending  cervical,  523 

pharyngeal,  494 
auditory,  522 
auricular,  anterior,  495 

posterior,  494 
axillary,  529 
azygos  of  knee,  584 
basilar,  522 
brachial,  533 
bronchia],  547,  976 
buccal,  498 
of  bulb,  567 
bulbar,  522 
calcanean,  external,  591 

internal,  591 
carotid,  common,  482 

external,  486 

internal,  502 
carpal,  radial,  540 

ulnar,  544 
of  cavernous  body,  567 
centralis  retinae,  509 
cerebellar,  522 
cerebral,  509,  511,  522 

ascending  cervical,  523 

princeps,  493 

profunda,  527 

superficial  cervical,  524 
choroid,  anterior,  512 

posterior,  523 
ciliary,  509 

circle  of  Willis,  512,  523 
circumflex,  of  arm,  533 

of  iliac,  deep,  572 

superficial,  578 

of  thigh,  579 
coccygeal,  568 
cochlear,  866 
coeliac  axis,  551 
colica  dextra,  555 

media,  555 

sinistra,  555 
conies  nervi  ischiadici,  568 

phrenici,  526 
common  carotid,  482 

iliac,  559 
communicating,  anterior  cere- 
bri, 510 

branch  of  ulnar,  544 

posterior  cerebri,  511 
coronarv  of  heart,  477 

of  lip,  491 
cremasteric,   571 
crico-thyroid,  488 
cystic,  553 
deep  branch  of  ulnar,  545 

cervical,  527 

palmar  arch,  538 

temporal,  498 
deferent,  563 
dental,  anterior,  499 

inferior,  498 
descending  aorta,  546 

coronary,  478 

palatine,  499 
digital  plantar,  592 

of  ulnar,  545 
dorsal,  of  penis,  565 

of  scapula,  533 
dorsalis  hallucis,  587,  588 

feidicis,  541 


INDEX. 


1219 


Arteries  or  artery,  dorsalis  lin- 
guae, 489 

pedis,  587 

pollicis,  541 
epigastric,  deep,  571 

superficial,  578 

superior,  527 
ethmoidal,  506 
external  carotid,  486 

iliac,  570 

plantar,  591 
facial,  489 
femoral,  572 

deep,  578 

frontal,  508 
gastric,  551,  553 
gastro-duodenalis,  552 
gastro-epipioica  dextra,  553 

sinistra,  553 
gluteal,  569 

inferior,  568 
helicine,  1013 
hemorrhoidal  inferior,  567 
middle,  563 

superior,  555 
hepatic,  551 

hyoid  branch  of  lingual,  489 
of  superior  thyroid,  488 
hypogastric,  in  foetus,  473,  562 
ileo-colic,  555 
iliac,  common,  559 

external,  570 

internal,  561 
iliolumbar,  569 
inferior    cerebellar,    anterior, 
522 
posterior,  521 

dental,  498 

labial,  491 

laryngeal,  523 

mesenteric,  555 

profunda,  537 

thyroid,  523 
infraorbital,  499 
infundibular,  478 
innominate,  480 
intercostal,  547 

anterior,  526 

superior,  527 
internal  auditory,  866 

carotid,  502 

iliac,  561 

mammary,  526 

maxillary,  496 

plantar,  591 
interosseous,  of  foot,  588 

of  hand,  543 

ulnar,  543 
intestini  tenuis,  554 
labial  inferior,  491 
lachrymal,  506 
laryngeal,  inferior,  523 

superior,  488 
lateral  nasal,  491 

sacral,  569 

spinal,  521 
lingual,  488 
long  ciliary,  509 

thoracic,  532 
lumbar,  558 
malleolar,  587 
mammary,  internal,  528 
marginal,  477 
masseteric,  498 
maxillary,  internal,  496 


Arteries  or   artery,  median,  of 
forearm,  543 

of  spinal  cord,  522 
mediastinal,  526 

posterior,  547 
meningeal,  anterior,  505 

middle,  496 

small,  498 

from  occipital,  493 
from  pharyngeal,  495 
from  vertebral,  520 
mesenteric,  inferior,  555 

superior,  553 
metacarpal,  540 
metatarsal,  588 
middle  cerebral,  511 

sacral,  558 
musculo-phrenic,  527 
mylo-hyoid,  498 
nasal,  of  ophthalmic,  508 

of  septum,  491 
inferior,  491 
superior,  499 
nutrient,  of  femur,  579 

of  fibula,  590 

of  humerus,  526 

of  tibia,  590 
obturator,  564 
occipital,  493 
ce&ophageal,  547 
ophthalmic,  505 
ovarian,  557 
palatine,  ascending,  491 

descending,  499 

palmar  arch,  deep,  544 
superficial,  544 

of  pharyngeal,  494 
palmar  interossei,  541 
palpebral,  508 
pancreatic,  553 
pancreatico-duodenalis,  553 

inferior,  554 
perforating,  of  foot,  592 

of  hand,  541 

of  internal  mammary,  526 

of  thigh,  579 
pericardiac,  526,  547 
perineal,  superficial,  567 

transverse,  567 
peroneal,  590 

anterior,  590 
pharyngeal,  ascending,  494 
phrenic,  557 
plantar,  591 
popliteal,  582 
posterior  auricular,  494 

cerebral,  522 

communicating,  511 

meningeal,   from  vertebral, 
521 

tibial,  588 
princeps  cervicis,  493 

pollicis,  541 
profunda    of     arm,     inferior, 
537 
superior,  537 

cervicis,  527 

femoris,  578 
pterygoid,  498 
ptery go-palatine,  499 
pudic,  deep  external,  578 

internal,  in  female,  567 
in  male,  565 

superficial  external,  578 
pulmonary,  475,  976 


Arteries  or  arterv,  pyloric,  552 
radial.  538 
radialis  indicia,  541 

ranine,  489 

recurrent  interosseous,  544 

radial,  539 

tibial,  anterior,  586 
posterior,  586 

ulnar,  anterior,  543 
posterior,  543 
renal,  556 
sacrai,  lateral,  569 

middle,  558 
scapular,  posterior,  526 
sciatic,  567 
short  ciliary,  509 
sigmoid,  555 
spermatic,  557,  1016 
spheno-palatine,  499 
spinal,  anterior,  521 

lateral,  521 

median,  521 

posterior,  521 
splenic,  553 
sterno-mastoid,  493 
stylo-mastoid,  494 
subclavian,  502 
subcostal,  547 
sublingual,  489 
submaxillary,  491 
submental,  491 
subscapular,  533 
superficial  cervical,  524 

circumflex  iliac,  578 

palmar  arch,  544 

perineal,  567 

temporal,  495 
superficialis  volse,  540 
superior  cerebellar,  522 

epigastric,  527 

hemorrhoidal,  555 

intercostal,  527 

laryngeal,  488 

mesenteric,  553 

profunda,  537 

thoracic,  532 

thyroid,  489 
supra-acromial,  524 
supraorbital,  506 
suprarenal,  556 
suprascapular,  524 
suprasternal,  524 
sural,  583 
tarsal,  588 
temporal,  495 

anterior,  495 

deep.  498 

middle,  495 

posterior,  495 
thoracic,  acromial,  532 

alar,  533 

aorta,  546 

long,  532 

superior,  532 
thyroid  axis,  523 

inferior,  523 

superior,  487 
thyroidea  ima,  481 
tibial,  anterior,  585 

posterior,  588 

recurrent,   586 
tonsillar,  491 
transverse,  coronarv,  477 

facial,  495 
transversalis  colli,  524 


1220 


INDEX. 


Arteries  or  artery,  tympanic,  from 
internal  carotid,  505 

from    internal     maxillary, 
524 
ulnar,  542 

recurrent  anterior,  543 
posterior,  543 
umbilical,  in  foetus,  562,  473 
uterine,  563 
vaginal,  564 
vasa  aberrantia  of  arm,  535 

brevia,  553 

intestini  tenuis,  554 

of  vas  deferens,  563 
vertebral,  520 
vesical,  inferior,  563 

middle,  563 

superior,  563 
Vidian,  499 
Arteriolar  rectse,  992 
Arthrodia,  220 

Articular   arteries  (knee),  from 
popliteal,  584 
cartilage,  1093 
end-bulbs,  1121 
lamella  of  bone,  217 
processes  of  vertebrae,  36 
synovial  membranes,  217 
Articulations,     acromio-clavicu- 
lar,  248 
ankle,  283 
astragalo-calcanean,  287 

navicular,  288 
atlan to-axial,  227 
calcaneo-astragaloid,  287 

-cuboid,  287 

-navicular,  288 
carpal,  263 
carpo-metacarpal,  265 
chondro-sternal,  238 
classification  of,  218 
coccygeal,  244 
costo-central,  234 

-transverse,  234 

-vertebral,  234 
of  cuboid  witb  external  cunei- 
form, 290 
of  cuneiform  with  each  other, 

290 
different  kinds  of,  218 
elbow  of,  255 
femoro- tibial,  274 
in  general,  217 
hip,  268 

immovable,  218 
knee,  274 
metacarpal,  263 
metacarpophalangeal,  267 
metatarsal,  291 
metatarso-phalangeal,  292  • 
mixed,  219 
movable,  219 
movements  of,  220 
naviculo-cuboid,  289 

-cuneiform,  289 
occipito-atlantal,  229 

-axial,  230 
pelvis,  241 

with  spine,  242 
phalanges,  268 
pubic,  244 
radio-carpal,  262 

-ulnar,  inferior,  260 
middle,  259 
superior,  259 


Articulations,      sacro-coccygeal, 
244 
-iliac,  242 
-sciatic,  242 
-vertebral,  240 
scapulo-clavicular,  248 

-humeral,  250 
shoulder,  251 
sterno-clavicular,  246 
of  sternum,  239 
tarsal,  287 

tarso-metatarsal,  290 
temporo-mandibular,  231 
tibio-fibular,  inferior,  283 
middle,  283 
superior,  283 
of  tympanic  bones,  857 
vertebral  column,  223 
wrist,  262 
Arytseno-epiglottidean  folds,  959 
Arytseno-epiglottideus,   inferior, 
963 
superior,  963 
Arytenoid  cartilages,  957 
glands,  964 
muscle,  962 
Arytenoideus  rectus,  note,  963 
Ascending  colon,  923 
cutaneous  nerve,  791 
frontal  artery,  511 
nerve  tracts,  719 
oblique   muscle   of   abdomen, 

360 
palatine  artery,  491 
parietal  artery,  511 
pharyngeal  artery,  494 

surgical  anatomy  of,  495 
Association  fibres  of  hemispheres 

of  brain,  678 
Asterion,  1151 
Astragalus,  203 

development  of,  211 
Atlanto-axial  articulation,  227 
Atlas,  36 

development  of,  43 
Atlo-odontoid  joint,  227 
Atrabiliarv  capsules,  997 
Atrium,  819 

of  right  auricle,  461 
of  tympanic  cavity,  853 
Attic   of    epitympanic    process, 
853 
of  tympanum,  1109 
Attollens  auriculam  muscle,  301 
Attraction   particle,    or    centro- 
some,  1075 
sphere,  or  centrosphere,  1075 
Attrahens     auriculam     muscle, 

300 
Auditory  artery,  866 
internal,  523 
canal,  851 

meatus,  external,  69 
surface  form  of,  852 
internal,  69 
nerve,  745,  866 

surgical  anatomy  of,  746 
teeth,  864 
veins,  866 
Auerbach's  plexus,  921 
Auricle  of  ear,  848 
cartilage  of,  849 
ligaments  of,  849 
of  heart,  left,  465 
appendix  of,  465 


Auricle  of  heart,  left,  sinus  of, 
465 
right,  461 

openings  in,  462 
septum  of,  402 
sinus  of,  461 
valves  in,  462 
Auricular  artery,  anterior,  495 
posterior,  494 
fissure,  70,  107 
lymphatic  glands,  625 
nerve  of  vagus,  751 

posterior,  from  facial,  743 
surface  of  sacrum,  47 
veins,  anterior,  596 
posterior,  597 
Auricularis  anterior  muscle,  300 
magnus  nerve,  762 
posterior  muscle,  301 
superior  muscle,  301 
Auriculo-tem  poral  nerve,  735 
Auriculo-ventricular  groove    of 
heart,  460 
opening,  left,  466 
right,  462 
Axes  of  the  pelvis,  181 
Axilla,  527 

dissection  of,  376 
surgical  anatomy  of,  527 
Axillary  artery,  529 
branches  of,  532 
lymphatic  glands,  628 
peculiarities  of,  531 
space,  528 

surface-marking  of,  531 
surgical  anatomy  of,  531 
vein,  609 

surgical  anatomy  of,  609 
Axis,  cerebro-spinal,  639 
cceliac,  551 
development  of,  45 
or  second  vertebra,  37 
thvroid,  523 
Axis-cylinder     of    nerve-fibres,. 

1116 
Axon  of  nerve-cells,  1115 
Azygos  artery,  articular,  584 
of  vagina,  563,  564 
uvulae  muscle,  330 
veins,  611 

B. 

Back,  muscles  of,  fifth  layer,  346 
first  layer,  336 
fourth  layer,  343 
second  layer,  340 
third  layer,  341 
Ball-and-socket  joint.  See  Enar- 

ihrodia. 
Band  of  Bail  larger,  664 
of  Giacomini,  653 
of  Gennari,  678 
inner,  678 
outer,  678 
Bartholin,  duct  of,  887 

glands  of,  1027 
Basal  lamina,1177 

layer  of  decidua,  1163 
ridge,  872 
Base  of  brain,  655 
of  sacrum,  48 
of  skull,  103 

external  surface,  106 
internal  surface,  103 


INDEX. 


1221 


Basement  membranes,  1091 
Basi-hyal  of  hyoid  bone,  122 
Basilar  artery,  522 

groove,  58 

membrane  of  cocblea,  863 

plate,  1167 

process,  56 

suture,  102 
Basilic  vein,  608 
median,  608 
Basis  vertebrarum  veme,  612 
Basket  cells  of  cerebellum,  692 
Banhin,  valve  of,  923 
Beak  of  corpus  callosum,  659 
Beaunis  et  Bouchard,  Table  of 
Development    of    Foetus 
from,  1215 
Bechterew,  nucleus  of,  745 
Bend  of  elbow,  534 
Biceps  flexor  cruris,  432 

cubiti,  387 
Bicipital  fascia,  387 

groove,  144 

ridges,  146 

tuberosity,  155 
Bicuspid  teeth,  872 
Biliary  ducts,  942,  943 

structure,  943 
Bird's  nest  of  cerebellum,  688 
Bi venter  cervicis  muscle,  346 
Biventral  lobe,  689 
Bladder,  998 

development  of,  1208 

female,  1007 

ligaments  of,  1002 

surface  form  of,  1004 

surgical  anatomy  of,  1004 

trigone  of,  1003 

vessels  and  nerves  of,  1004 
Blastodermic  membrane,  1154 

vesicle,  1153 
Blastopore,  1154 
Blood,  circulation  of, in  adult,  460 
in  foetus,  471 

coagulation  of,  1080 

gases  of,  1081 

general  composition  of,  1077 

plasma  of,  1080 
Blood-corpuscles,  1077 
Blood-crystals,  1081 
Blood-disks,      development     of, 

1188 
Blood-globules,  1078 
Blood-plaques,  1080 
Blood-vascular  system,  develop- 
ment of,  1187 
Blood-vessels  of  brain,  512 
Bochdalek,  ganglion  of,  731 

on  musculus    triticeo-glossus, 
963,  note. 
Body  of  a  tooth,  871 

of  a  vertebra,  35 
Bone,  animal  constituent  of,  1101 

apophysis  of,  34 

articular  lamella  of,  217 

canaliculi  of,  1100 

cancellous  tissue  of,  1096 

cells,  1100 

chemical  composition  of,  1101 

compact  tissue  of,  1096 

development  of,  1101 

diploe  of,  34 

earthy  constituent  of,  1101 

•eminences  and  depressions  of, 
34 


Bone,  epiphysis  of,  34 

general  anatomv  of,  1096 

growth  of,  1106" 

Haversian  canals  of,  1098 
systems  of,  1098 

inorganic  constituent  of,  1101 

lacuna?  of,  1099 

lamella;  of,  1099 

lymphatics  of,  1098 

marrow  of,  1096 

medullary  canal  of,  33,  1096 

membrane  of,  1096 

minute  anatomy,  1098 

nerves  of,  1098 

organic  constituent  of,  1101 

ossific  centres,  number  of,  1106 

ossification  of,  1102 

periosteum  of,  1096 

spongy  tissue  of,  33 

vessels  of,  1007 
Bones,  forms  of,  viz.,  long,  flat, 
short,    mixed,    irregular, 
33 

number  of,  in  the  body,  33 
Bones  or  bone,  astragalus,  203 

atlas,  36 

axis,  37 

calcaneum,  199 

carpal,  158 

clavicle,  135 

coccyx,  50 

cranial,  55 

cuboid,  204 

cuneiform,  of  carpus,  163 
of  tarsus,  205 

descriptive  anatomy  of,  33 

ear,  856 

ethmoid,  77 

facial,  81 

femur,  183 

fibula,  196 

frontal,  61 

hand,  158 

humerus,  144 

hyoid,  122 

ilium,  171 

incus,  856 

inferior  maxillary,  96 
turbinated,  94 

innominate,  171 

ischium,  171,  174 

lachrymal,  88 

lesser  lachrymal,  88 

lingual,  122 

magnum,  164 

malar,  89 

malleus,  856 

maxillary,  inferior,  96 
superior,  83 

metacarpal,  165 

metatarsal,  208 

nasal,  81 

navicular,  205 

occipital,  55 

orbicular,  857 

palate,  91 

parietal,  59 

patella,  191 

pelvic,  179 

phalanges  of  foot,  210 
of  hand,  169 

pisiform,  162 

pubic,  176 

radius,  155 

ribs,  128 


Bones  or  bone,  sacrum,  45 
scaphoid,  161 
scapula,  138 
semilunar,  162 
sesamoid,  214 
sphenoid,  73 
sphenoidal,  spongy,  76 
stapes,  857 
sternum,  126 
superior  maxillarv,  81 
tarsal,  199 
temporal.  65 
tibia,  192 
trapezium,  163 
trapezoid,  163 
triquetral,  80 
turbinate,  inferior,  94 
middle,  79 
superior,  79 
tympanic,  71 
ulna,  150 
unciform,   165 
vertebra  prominens,  39 
vertebra?,  cervical,  35 
dorsal,  39 
lumbar,  41 
vomer,  95 
Wormian,  81 
Bowman,  glands  of,  822 

sarcous  elements  of,  1109 
Bowman's  capsule,  988 
Brachia     of     corpora     quadri- 

gemina,  675 
Brachial  artery,  533 
branches  of,  536 
peculiarities  of,  534 
surface  marking  of,  535 
surgical  anatomy  of,  535 
lymphatic  glands,  628 
plexus,  764 

surgical  anatomy  of,  776 
region,    anterior,   muscles   of, 
390,  392 
posterior,  muscles  of,  396 
veins,  609 
Brachials  anticus  muscle,  388 
Brachio-  cephalic     artery.      See 

Innominate. 
Brachio-radialis     muscle.      See 

Supinator  longus. 
Brain,  643 
base  of,  655 
convolutions  of,  644 
development  of,  1172 
dura  mater  of,  639 
general  anatomy  of,  1118 
hemispheres  of,  643 
interior  of,  659 
lobes  of,  648 

membranes  and  dissection,  639 
subdivision  into  parts,  643 
weight  of,  703 
Branchial  arches,  1168 

clefts,  1168 
Breasts,  1038 
Bregma,  103 
Brim  of  pelvis,  180 
Broad  ligament  of  uterus.  1030 

formation  of,  899 
Broca,  convolution  of,  649 
Bronchi,  right  and  left,  966 
septum  o\\  967 
in  lung,  975 
Bronchial  arteries.  547,  976 
branch  of  innominate,  481 


1222 


INDEX. 


Bronchial  lymphatic  glands,  636 

septum,  967 

tubes.     See  Bronchi. 

veins,  612,  977 
Brunner's  glands,  918 
Bubonocele,  1051 
Buccal  arteries,  498 

cavity,  869 
development  of,  1171 

glands,  625 

lymphatic  glands,  625 

nerve  of  facial,  744 

of  inferior  maxillary,  734 

veins,  596 
Buccinator  muscle,  309 
Bucco-pharyngeal  fascia,  316 
Bulb,  artery  of,  567 

of  corpus  cavernosum,  1012 
spongiosum,  1013 

of  internal  jugular  vein,  598 

olfactory,  654,  720 

posterior  horn,  662 
Bulbar  arteries,  522 

portion    of    spinal     accessory 
nerve,  753 
Bulbi  vestibuli,  1027 
Bulbo-cavernous  muscle,  371 
Bulbous  portion  of  the  urethra 

1006 
Bulla  ethmoidalis,  820 
Bundle  of  Vicq  d'  Azyr,  657,  665 
Burda cli's  tract,  715 
Bursa  omen  talis,  1199 

pharyngea,  891 
Bursa?  of  knee,  278 
\  mucosae,  218 

of  shoulder,  251 

sy  no  viae,  218 
Bursal  synovial  membranes,  218 

C. 

Caecum,  922 

Calamus  scriptorius,  697 

Calcanean  arteries,  external,  591 

internal,  591 
Calcaneo-astragaloid    ligaments, 

287 
Calcaneo-cuboid  ligaments,  287 
Calcaneonavicular      ligaments, 

288 
Calcaneo-plantar  nerve,  795 
Calcaneum,  199 
Calcar  avis,  662 
femorale,  189 
Calcarine  fissure,  647 
Calices  of  kidney,  987 
Callosal  fissure,  653 
Camper,  fascia  of,  356 
Camper's  ligament.     See  Trian- 
gular Ligament  of  Urethra. 
Canaliculi  of  bone,  1100 
Canalis  centralis  cochlea?,  69 
hyaloid  eus  of  Stilling,  1182 
membranous  cochlea,  863 
reuniens,  862 
spiralis  modioli,  861 
Canals  or  canal,  accessorv  pala- 
tine, 91 
alimentary,  869 
anterior,   for  Arnold's  nerve, 
70 
dental,  84 
palatine,  87 
auditory,  851 


Canals  or  canal,  carotid,  70 

for  chorda  tympani,  66,  853 
of  cochlea,  863 
crural,  1059 
dental,  posterior,  84 
ethmoidal,  64 
Haversian,  of  bone,  1098 
of  Huguier,  66 
inferior  dental,  98 
infraorbital,  84 
inguinal,  1046 
for      Jacobson's      (tympanic) 

nerve,  70 
lachrymal,  845 
naso-palatine,  87 
of  Nuck,  1038,  1047,  1212 
of  Petit,  840 
palatine,  anterior,  87 

posterior,  85 
pterygo-palatine,  74 
sacral,  47 
of  Schlemm,  827 
semicircular,  860 
spermatic,  1046 
of  spinal  cord,  712 
spiral,  of  cochlea,  860 
of  modiolus,  861 
of  Stilling,  839 
temporo-malar,  90 
for  tensor  tympani,  71,  854 
vertebral,  53 
Vidian,  75 
of  Wirsung,  947 
Cancellous  tissue  of  bone,  1096 
Canine  eminence,  83 
fossa,  83 
teeth,  872 
Canthi  of  evelids,  843 
Capillaries,"  1128 

structure  of,  1129 
Capitellum  of  humerus,  147 
Capsula  extrema,  664 
Capsular  ligament  of  hip,  268 
of  knee,  274 
of  shoulder,  251 
of  thumb,  265 
of  vertebra?,  225 
Capsule,  external,  of  brain,  664 
in  foetus,  1182 
of  Glisson,  938 
internal,  of  brain,  663 
of  kidnev,  986 
of  lens,  840 
of  Tenon,  824 
Capsules,  suprarenal,   996 
Caput  cornu  of  cord,  712,  715 

gallinaginis,  1005 
Cardiac  lymphatics,  637 
muscular  tissue,  1112 
nerves,  803 

from  pneumogastric,  752 
plexus  of  nerves,  deep,  806 

superficial,  806 
veins,  621 
Cardinal  veins,  foetal,  1196 
Carotid  artery,  common,  482 

branches    of  (occasional), 

485 
peculiarities  of,  484,  485 
surface-marking  of,  485 
surgical  anatomy  of,  485 
external,  486 
branches  of,  487 
surface-marking  of,  487 
surgical  anatomy  of,  487 


Carotid  artery,  internal,  502 
branches  of,  505 
peculiarities  of,  504 
surgical  anatomy  of,  505> 
tubercle,  36 

branch  of  Vidian,  732 

canal,  68 

ganglion,  801 

groove,  73 

plexus,  799 

triangle,  anterior,  500 
inferior,  500 
superior,  500 
Carpal  arch,  anterior,  540 
posterior,  540 

arteries,  from  radial,  540 
from  ulnar,  544 

ligaments,  263 
Carpo-metacarpal    articulations, 

265 
Carpus,  158 

articulations  of,  263 

development  of,  170 

surface  form  of,  169 

surgical  anatomy  of,  170 
Cartilage,   articular,  1093 

arytenoid,  957 

of  bronchi,  976 

cellular,  1092 

costal,  132,  1094 

cricoid,  956 

cuneiform,  958 

of  ear,  849 

ensiform,  124 

of  epiglottis,  958 

fibro-,  1095 

general  anatomv,  1092 

hyaline,  1093 

of  Jacobson,  820 

of  larynx,  955 

matrix  of,  1093 

of  the  nose,  818 

permanent,  1092 

of  the  pinna,  849 

of  Santorini,  957 

semilunar,  of  knee,  276 

of  septum  of  nose,  819 

temporary,  1094 

thyroid,  955 

of  trachea,  966 

white  fibro-,  1094 

of  Wrisberg,  958 

yellow  elastic,  1095 

xiphoid,  124 
Cartilage-cells,  1092 
Cartilage-lacuna?,  1093 
Cartilagines  minores,  819 
Cartilago  triticea,  958 
Caruncula  lachrymalis,  846 
Carunculae  myrtiformes,  1027 
Cauda  equina,  788 

helicis,  849 
Caudal  or  post-anal  gut,  1203 
Cava,  inferior,  617 

peculiarities  of,  618 

superior,  611 
Cavernous  body,  artery  of,  56? 

groove,  73 

nerves  of  penis,  810 

plexus,  799 

sinus,  603 

nerves  in,  739 

surgical  anatomy  of,  604 
Cavity,  cotyloid,  177 

glenoid,  141 


INDEX. 


1223 


Cavity  of  pelvis,  180 
sigmoid,  greater,  152 
lesser,  152 
Cavum  concha?,  849 
Meckelii,  726 
oris  proprium,  869 
Cells,  animal,  1073 
of  bone,  1100 
chalice-,  1084 
of  Claudius,  866 
column  lateral,  717 
definition  of,  1073 
division  of,  direct,  1077 

indirect,  1075 
ethmoidal,  78 
fat,  1092 
goblet-,  1084 
of  Golgi,  680 
of  Martinotti,  680 
mastoid,  67 
nucleus  of,  1074 
prickle,  1085 
reproduction  of,  1075 
of  Sertoli,  1019 
structure  of,  1073 
wall,  1077 
Cement  of  teeth,  880 
formation  of,  880 
Central  canal  of  cord,  713 
ganglionic  vessels  of  brain,  513 
ligament  of  cord,  709 
lobe  of  cerebrum,  652 
tendon  of  diaphragm,  353 
Centres  of  ossification,  1106 
Centrifugal  nerve-fibres,  1120 
Centripetal  nerve-fibres,  1120 
Centro-acinar   cells  of    Langer- 

hans,  948 
Centrosomes,  1075 
Centrosphere,  1075 
Centrum  ovale  majus,  659 
minus,  659 
vertebra,  35 
Cephalic  vein,  608 

flexure  of  embryonic  brain, 

1176 
median,  607 
Cerato-hyal  of  hyoid  bone,  123 
Cerebellar   arteries,  anterior-in- 
ferior, 522 
posterior-inferior,  522 
superior,  522 
column,  714 
notch,  anterior,  684 

posterior,  684 
veins,  601 
Cerebellum,  684 

corpus  dentatum  of,  689,  693 
hemispheres  of,  684 
lamina  of,  685 
lobes  of,  684 

median,  684 
peduncles,  689 
under  surface,  688 
upper  surface,  685 
weight  of,  693 
Cerebral  arteries,  510 
anterior,  510 
middle,  511 
posterior,  522 
convolutions,  644 
lymphatics,  626 
topography,  705 
veins,  600 
ventricles,  660,  666,  669,  697 


Cerebral  vesicles,  1172 
Cerebro-spinal  axis,  639 
fluid,  642 
nerves,  1118 
system,  1113 
Cerebrum,  643 
base  of,  655 

commissural  fibres  of,  677 
commissures  of,  665,  671 
convolutions  of,  644 
crura  of,  674 
fibres  of,  677 
fissures  of,  646 
general    arrangement    of     its 

parts,  643 
gray  matter  of,  678,  1118 
hemispheres  of,  643 
interior  of,  659 
labia  of,  659 
lobes  of,  646 
peduncles  of,  673 
structure  of,  677 
sulci,  644 
under  surface,  655 
ventricles  of,  660,  666,  669,  697 
Ceruminous  glands,  852 
i  Cervical  artery,  ascending,  523 
superficial,  524 
fascia,  314 

ganglion,  inferior,  803 
middle,  803 
superior,  799 
lymphatic  glands,  deep,  628 
superficial,  628 
surgical  anatomy  of,  628 
nerves,  758 

anterior  divisions  of,  760 
posterior  divisions  of,  759 
roots  of,  758 
plexus,  761 

deep  branches  of,  763 
posterior  branches  of,  759 
superficial  branches   of,  761 
rib,  39 

veins,  deep,  599 
vertebrae,  35 

surgical  anatomy  of,  231 
Cervicalis  ascendens  muscle,  345 
Cervico-facial  nerve,  744 
Cervix  cornu  of  cord,  715 

uteri,  1028 
Chalice-cells,  1085 
Chambers  of  the  eye,  839 
Chassaignac's  tubercle,  36 
Check  ligaments,  231 

of  eye,  824 
Cheek,  muscles  of,  308 
Cheeks,  structure  of,  870 
Chest,  muscles  of  front,  377 
of  side,  381 
surface  form  of,  132 
surgical  anatomy  of,  132 
Chiasma,   or   optic    commissure, 

721 
Choanse,  117 
Cholesterin,  1078 
Chondrin,  1095 
Chondro-glossus  muscle,  324 
Chondro-nuicoid,  1095 
Chondro-sternal  ligaments,  238 
Chondro-xiphoid  ligament,  238 
Chorda  dorsalis,  1156 

tympani  nerve,  741,  859 
Chorda'    tendinese,    of  left   ven- 
tricle, 466 


Chorda?  tendinea?  of  right  ven- 
tricle, 464 
vocales,  961 
Willisii,  602 
Chorion,  1161 
frondosum,  1162 
keve,  1162 
Choroid  arteries,  anterior,  512 
posterior,  523 
coat  of  eye,  828 
plexus  of  fourth  ventricle,  698 
of  lateral  ventricle,  666 
of  third  ventricle,  669 
veins  of  brain,  601 
Choroidal  fissure,  1182 
Chromatin,  1074 
Ch  rom  oplasm,  1 074 
Chromosomes,  1075 
Chyle,  1082 

Chyli  reeeptaculum,  624 
Cilia,  or  eyelashes,  643 
Ciliary  arteries,  509,  905 
ganglion,  728 
muscle,  832 
nerves,  long,  729 

short,  729 
processes  of  eye,  829 
Ciliated  epithelium,  1084 
Cineritious  nervous  tissue,  1113 
Cingulum,  653,  678 
Circle  of  Willis,  523 
Circular  sinus,  603 
Circulation  of  blood  in  adult, 460 

in  foetus,  471 
Circulus  of  iris,  major,  509 
minor,  509 
tonsillaris,  733 
Circumduction,  226 
Circumferential     fibro-cartilage, 

1095 
Circumflex  artery  of  arm,  ante- 
rior, 533 
posterior,  533 
of  thigh,  external,  579 
internal,  579 
iliac  artery,  deep,  572 

superficial,  578 
nerve,  769 

surgical  anatomy  of,  776 
vein,  deep,  618 
superficial,  614 
Circmflexus  palati  muscle,  329 
Circumvallate  papilla?  of  tongue, 

813 
Cistern  of  Pecquet,  624 
Cisterna  magna,  641 

pontis,  641 
Clarke's  vesicular  column,  717 
Claustrum,  662 

(Java  of  funiculus  gracilis,  696 
Clavicle,  135 

development  of,  137 
fracture  of,  411 
peculiarities  in  sexes,  137 
surface  form  of,  137 
surgical  anatomy  of,  137 
Cleft  palate,  332 
(  linking  fibres  of  cerebellum,  693 
Clinoid  processes,  anterior,  75 
middle,  73 
posterior,  73 
Clitoris,  1026 
frsenum  of,  1026 
lymphatics  of,  634 
muscles  of,  375,  1027 


1224 


INDEX. 


Clitoris,  prepuce  of,  1027 
Clivus,  73 

monticuli  of  cerebellum,  686 
Cloaca,  1213 
Coccygeal  artery,  568 

gland,  558 

nerves,  789 
Coccygeus  muscle,  369 
Coccyx,  50 

development  of,  51 
Cochlea,  860 

aqueduct  of,  69 

arteries  of,  866 

central  axis  of,  861 

cupola  of,  861 

lamina  spiralis  of,  861 

nerves  of,  866 

scalse  of,  861 

spiral  canal  of,  860 

veins  of,  866 
Cochlear  artery,  866 

nerve,  867 
Cochleariform  process,  71,  855 
Coeliac  axis,  551 

plexus,  808 
Ccelum,  1157 
Cohnheim,  areas  of,  1109 
Colica  dextra  artery,  555 

media,  555 

sinistra,  555 
Collagen,  1088 

Collateral  circulation.  See  Surg- 
ical Anatomy  of  each 
Artery. 

fibres  of  cerebrum,  677 

fissure,  647 

intercostal  artery,  549 
Collecting  tubes  of  kidney,  989 
Colles,  fascia  of,  370 
Colli  cuius  nervi  optici,  833 
Colon,  923 
Colored  line  of  Retzius,  877 

or  red  corpuscles,  1078 
Colorless  corpuscles,  1079 
Colostrum  corpuscles,  1040 
Columella  cochleae,  861 
Columna  nasi,  818 
Columnse  carnese  of  left  ventri- 
cle, 467 
of  right  ventricle,  464 

fornicis,  664 

papillares,  464,  467 
Columnar  epithelium,  1083 
Columns  of  abdominal  ring,  1043 

of  spinal  cord,  711 

of  vagina,  1028 
Comes   nervi   ischiadici    artery. 

568 .  . 
phrenici  artery,  526 

Comma  tract,  descending,  715 

Commissural  fibres  of  brain,  677 

Commissure  of  brain,   anterior, 

665 

middle  or  soft,  670 

posterior,  671 

of  Gudden,  721 

optic,  721 

of  spinal  cord,  gray,  712 

white,  712 

Common  cloaca,  1203 

ligaments  of  vertebrae,  223 

Coram uni cans  peronei,  794 

tibialis,  794 

Communicantes    hypoglossi 

nerve,  793 


Communicating  artery  oi  brain, 
anterior,  511 
posterior,  511 
from  dorsalis  pedis,  588 
ulnar,  544 
Compact  tissue  of  bone,  33, 1096 
Complexus  muscle,  345 
Compressor  narium  minor,  306 
nasi,  306 

sacculi  laryngis,  963 
urethra,  374 
in  female,  375 
Conarium,  672 
Concentric  corpuscles  of  thymus, 

982 
Conception,  where  effected,  1151 
Concha,  849 

Conducting  tracts  of  cord,  713 
Conductor,  sonorous,  699 
Condyles  of  bones.     See  Bones. 
Condyloid  articulations,  220 
foramina,  56 
process,  99 
veins,  posterior,  599 
Cone-bipolar  cells,  835 

-gradules  of  retina,  835 
Cones  of  retina,  835 
Congenital   fissures   in   cranium 
81 
hernia,  1051 
Conglobate  glands,  623,  1133 
Conjoined  tendon  of  internal  ob- 
lique   and    transversalis, 
360,  1045 
Conjunctiva,  844 
Connecting  fibro-cartilages,  1095 
Connective  tissue,  1086 
adenoid,  1091 
corpuscles,   1087 
development  of,  1090 
elastic,  1088 
fibrous,  1087 
lymphatics  of,  1089 
lymphoid,  1091 
mucous,  1090 
nerves  of,  1089 
retiform,  1090 
vessels  of,  1089 
yellow,  1088 
Conoid  ligament,  249 

tubercle,  135 
Constrictor  inferior  muscle,  327 
isthmi  faucium,   328 
medius  muscle,  328 
superior  muscle,  328 
urethra  in  female,  375 
in  male,  374 
Contractile  fibre-cells,  1112 
Conus  arteriosus,  463 

medullaris,  711 
Convoluted  tubular  gland,  1146 
Convolutions,  angular,  651 
of  Broca,  649 
of  cerebrum,  structure  of,  642 

topography  of,  705 
of  corpus  callosura,  653 
cuneate,  651 
dentate,  653 
frontal,  648 
hippocampal,  653 
marginal,  650 
occipital,  651 
occipito-temporal,  652 
orbital,  649 
parietal,  650 


Convolutions,  precuneus,  651 
quadrate,  651 
supramarginal,  651 
temporal,  652 
Cooper,  ligament  of,  359 
Coraco-acromial  ligament,  249 
Coraco-brachialis  muscle,  387 
Coraco-clavicular  ligament,  249 
Coraco-humeral  ligament,  251 
Coracoid  ligament,  250 
process,  141 
fracture  of,  412 
Cord,  spermatic,  1016 
spinal,  710 
umbilical,  1165 
Cordiform  tendon  of  diaphragm, 

353 
Corium   of  mucous    membrane, 
1145 
of  skin,  1135 
of  tongue,  813 
Cornea,  826 
Corneal  corpuscles,  827 

spaces,  827 
Cornu  Ammonis,  666 
Cornua  of  the  coccyx,  50 
of  hyoid  bone,  123 
of  sacrum,  47 
of  thyroid  cartilage,  955 
Corona  glandis,  1011 

radiata,  677 
Coronal  suture,  101 
Coronary  arteries  of  lip,  491 
of  heart,  477 
descending,  477 
marginal,  477 
peculiarities  of,  478 
transverse,  477 
artery  of  stomach,  551 
ligament  of  liver,  937 
ligaments  of  knee,  277 
plexus,  anterior,  806 

posterior,  806 
sinus,  621 

opening  of,  462 
Coronoid  depression,  147 
process  of  jaw,  99 
of  ulna,  152 
Corpora  albicantia,  656 
Arantii,  464 
bigemina,  675 
cavernosa  clitoridis,  1027 
penis,  1012 
crura  of,  1012 
geniculata,  676 
mamillaria,  656 
quadrigemina,  675 
striatum,  662 
veins  of,  601 
Corpus  callosum,  659 
convolutions  of,  653 
genu  of,  659 
peduncles  of,  659 
cavernosum,  artery  of,  567 
dentatum  of  cerebellum,  693 
fimbriatum,  665 
Highmorianum,  1019 
of  olivary  body,  702 
spongiosum,  10l3 
striatum,  662 
subthalamicum,  676 
trapezoides  of  pons,  683 
Corpuscles,  blood-,  1077 
colored,  1078 
colorless,  1079 


INDEX. 


1225 


Corpuscles,  colorless,  origin   cf, 
1080 
development  of,  1188 
of  Herbst,  1128 
Malpighian,  of  kidney,  988 
Pacinian,  1122 
of  Purkinje,  692 
of  spleen,  952 
tactile,  1121 
of  Vater,  1122,  note. 
Corrugator  cutis  ani,  368 
supercilii  muscle,  302 
Cortex  of  cerebellum,  691 

of  cerebrum,  678 
Corti,  membrane  of,  866 
organ  of,  864 
rods  of,  865 
tunnel  of,  865 
Cortical  arches,  987 
arteries  of  brain,  513 
columns,  987 
substance  of  brain,  644 
of  kidney,  987 
of  suprarenal  capsules,  997 
visual  centre,  722 
Costal  cartilages,  132,  1094 
connection  with  ribs,  239 
process,  36 
Costo-central  articulation,  234 
Costo-chrondral  articulation,  239 
Costo-chrondro-xiphoid      1  i  g  a- 

ments,  238 
Costo-clavicular  ligament,  246 
Costo-coracoid  ligament,  379 

membrane,  379 
Costo-mediastinal  sinus,  971 
Costo-transverse       articulations, 

336 
Costo- vertebral  articulations,  234 

ligaments,  234 
Cotunnius,  nerve  of,  733 
Cotyloid  cavity,  177 
ligament,  270 
notch,  177 
Coverings  of  direct  inguinal  her- 
nia, 1052 
of  femoral  hernia,  1061 
of  oblique  hernia,  1049 
of  testis,  1014 
Cowper's  glands,  1011,  1067 
Cranial  bones,  55 

articulations  of,  103 
fossae,  103 
nerves,  720 

development  of,  1179 
eighth,  745 
eleventh,  753 
fifth,  725 
first  pair,  720 
fourth,  724 
ninth,  746 
second,  721 
seventb,  740 
sixth,  738 
tenth,  749 
third,  722 
twelfth,  754 
sutures,  101 
Cranium,  55 

congenital  fissures  in,  81 
development  of,  80,  1166 
lymphatics  of,  626 
Cremaster  muscle,  361 

formation  of,  361,  1045 
Cremasteric  arterv,  571 


Cremasteric  fascia,  361 
Crescentic  lobe,  anterior,  686 

posterior,  686 
Crescents  of  Giannuzzi,  888 
Crest,  frontal,  61 
of  ilium,  171 
lachrymal,  88 
nasal,  82 
occipital,  55 

internal,  57 
of  spine  of  scapula,  140 
turbinated,  of  palate,  92 
of  os  pubis,  170 
of  the  superior   maxillary, 

85 
of  tibia,  193 
Cribriform  fascia,  418,  1055 

plate  of  ethmoid,  78 
Crico-arytenoideus   lateralis 
muscle,  962 
posticus  muscle,  962 
Crico-thyroid  artery,  488 
membrane,  959 
muscle,  961 
Cricoid  cartilage,  956 
Crista  basilaris,  864 
falciformis,  69 
galli,  78 
pubis,  176 

terminalis,  461,  1190 
vestibuli,  860 
Crossed  pyramidal  tract,  714 
Crown  of  a  tooth,  872 
Crucial  anastomosis,  568,  579 

ligaments  of  knee,  276 
Cruciform  ligament,  228 
Crura  cerebri,  673 
of  corpora  cavernosa,  1012 
of  clitoris,  1027 
of  diaphragm,  352 
of  fornicis,  664 
Crural  arch,  359,  1057 
deep,  366,  1059 
canal,"  1059 
nerve,  anterior,  786 

surgical  anatomy  of,  797 
ring,  1060 
sheath,  1059 
septum,  1060 
Crureus  muscle,  422 
Crus  commune,  860 
helicis,  849 
penis,  1012 
Crusta  of  crus  cerebri,  673,  677 

petrosa  of  teeth,  878 
Crypts  of  Lieberkuhn,  918 
Crystalline  lens,  840 
Crystals,  blood,   1081 
Cuboid  bone,  204 
Culmen,    monticuli   of   cerebel- 
lum, 686 
Cuneate  funiculus,  695 
lobe,  651 
tubercle,  696 
Cuneiform  bone,  foot,   external, 
207 
internal,  206 
middle,  206 
hand,  162' 
cartilages,  958 
Cuneus,  651 
Cupola  of  cochlea,  861 
Curvatures  of  the  spine,  52 
Cushion  of  epiglottis,  958 
Cuspidate  teeth,  872 


Cusps  of  tricuspid  valve,  464 
Cutaneous  branches  of  accessory 
obturator,   786 
of  anterior  tibial  nerve,  796 
of  arm,  musculocutaneous, 

770 
of  buttock  and  thigh,  793 
of  cervical  plexus,  763 
of  circumflex,  770 
of  dorsal  nerve  of  penis,  793 
of  dorsal  nerves,  780 
of  externa]  popliteal,  796 
of  ilio-hypogastric,  782 
of  ilio-inguinak  783 
of     inferior    hemorrhoidal 

nerve,  793 
of  inguinal  region,  1055 
of  intercostal  nerves,  779 
internal,  770 
lesser,  771 
of  internal  popliteal,  794 
of  iscliio-rectal  region,  1064 

from  obturator,  785 
of  lesser  sciatic  nerve,  791 
of  lumbar  nerves,  781 
of  median,  772 
of  musculo-spiral,  775 
of  patella,  787 
of  perineal  nerve,  791 
of  plantar  nerve,  795 
of  posterior  tibial,  795 
of  radial,  775 
of  sacral  nerves,  789 
of  thigh,  external,  785 
internal,  787 
middle,  788 
of  ulnar  nerve,  773 
Cuticle  of  skin,  1136 
Cuticula  dentis,  880 
Cutis  plate,  1187 

vera,  1138 
Cuvier,  ducts  of,  1195 
Cylindrical  epithelium,  1083 
Cymba  concha3,  849 
Cystic  artery,  553 
duct,  943 

valve  of,  943 
plexus  of  nerves,  808 
veins,  621 
Cvtoblast,  1154 
Cytoplasm,  1073,  1149 

r>. 

Dacrvon.  114 
Dartos,  i015 
Darwin's  tubercle,  849 
Decidua,  1102 

reflexa,  1102 

serotina.  1102 

vera,  1162 
Decidual  cells,  1162 
Deciduous  teeth,  871 
Decussation  of  fillet,  719 

of  optic  nerves,  721 

of  pyramids,  693 
Deep  crural  arch,  366,  1059 

palmar  arch.  539 

perineal  fascia,  373,  1066 

transverse    fascia  of  les,  434, 
438 
Deferent  artery,  563 
Deglutition,  actions  of,  332 
Deiter's  nucleus,  684,  745 
Deltoid  aponeurosis,  382 


1226 


INDEX. 


Deltoid  muscle,  382 

tubercle,  135 
Demilunes  of  Heidenhain,  888 
Demours,  membrane  of,  827 
Dendron  of  nerve-cell,  1115 
Dens  sapientiee,  873 
Dental  artery,  anterior,  499 
inferior,  498 
posterior,  499 
canal,  anterior,  84 
inferior,  98 
posterior,  84 
furrow,  876 
germ,  common,  887 

special,  888 
groove,  887 
lamina,  887 
nerves,  anterior,  731 
inferior,  736 
middle,  730 
posterior,  730 
pulp,  875 
ridges,  887 
sacs,  881 
tubuli,  876 
vein,  inferior,  597 
Dentate  convolutions,  653 

fissure,  653 
Dentinal  tubuli,  876 
Dentine,  875 

formation  of,  880 
Depressions      of      Pacchionian 

bodies,  60 
Depressor  alse  nasi,  306 
anguli  oris,  308 
epiglottidis,  1107 
labii  inferioris,  308 
Derma,  or  true  skin,  1138 
Dermic     coat    of     hair-follicle, 

1141 
Descemet,  membrane  of,  827 
Descendens,    hypoglossi    nerve, 

756 
Descending  aorta,  546 
colon,  925 
comma  tract,  715 
nerve  tracts,  718 
oblique   muscle   of    abdomen, 
356 
Descent  of  testicle,  1211 
Detrusor  urinse,  l0O3 
Development  of  alimentary  canal 
and  its  appendages,  1198 
arteries,  1191 
atlas,  44 
axis,  44 
bone,  1101 
carpus,  170 
clavicle,  138 
coccyx,  51 
cranium,  80,  1166 
ear,  1183 
ethmoid,  80 
eye,  1180 
face,  1166 
femur,  189 
fibula,  198 
foot,  211 
frontal  bone,  64 
genital  or°ans,  1213 
hand,  170^ 
heart,  1189 
humerus,  148 
hyoid  bone,  123 
inferior  turbinated  bone,  95 


Development  of  lachrymal  bone, 
89 

lens,  1182 

lower  jaw,  99 

lumbar  vertebra?,  43 

malar  bone,  90 

mammae,  1186 

metacarpus,  171 

metatarsus,  211 

muscle,  1187 

muscle  fibre,  1112 

nasal  bone,  82 

nervous  centres,  1172 

nose,  1184 

occipital  bone,  58 

os  innominatum,  177 

Organ's,   Chronological    Table 
of,  1215 

palate,  1170 
bone,  93 

parietal  bone,  61 

patella,  192 

permanent  teeth,  881 

phalanges  of  foot,  211 
of  hand,  171 

radius,  151 

ribs,  131 

sacrum,  49 

scapula,  142 

seventh  cervical,  45 

skin,  1186 

sphenoid,  76 

spine,  1165 

sternum,  128 

superior  maxillary  bone,  87 

tarsus,  210 

temporal  bone,  71 

temporary  teeth,  878 

tibia,  196 

ulna,  154 

veins,  1194 

vertebrae,  43 

vomer,  96 

Wormian,  81 
Diameters  of  pelvis,  179 
Diaphragm,  352 

development  of,  1206 

lymphatics  of,  636 

of  pelvis,  895 
Diaphragma  sellse,  641 
Diaphysis,  1106 
Diarthrosis,  219 
Digastric  fossa,  67 

lobe  of  cerebellum,  687 

muscle,  321 

nerve,  from  facial,  743 
Digestion,  organs  of,  869 
Digital     arteries     from    palmar 
arch,  545 
from  plantar,  592 

fossa,  185 

nerves,  of  foot,  795 
from  median,  772 
from  radial,  775 
from  ulnar,  773 
Dilatator  naris,  anterior,  306 

posterior,  306 
Diploe,  34 

veins  of,  599 
Direct  cerebellar  tract  of  cord, 
714 

inguinal  hernia,  1052 
course  of,  1052 
coverings  of,  1053 

pyramidal  tract,  713 


Discus  proligerus,  1037,  1149 
Dissection  of  abdominal  muscles, 
360 
arm,  386 

auricular  region,  300 
axilla,  376 
back,  336 

epicranial  region,  298 
eye,  827 
face,  301 

femoral  hernia,  1053 
foot,  442 
forearm,  389 
gluteal  region,  426 
hand,  401 

heart,  left  auricle,  465 

left  ventricle,  465 

right  auricle,  461 

right  ventricle,  463 

hernia,  femoral,  1053 

inguinal,  1041 
iliac  region,  415 
inferior  maxillary  region,  308 
infrahyoid  region,  319 
inguinal  hernia,  1041 
inter-maxillary  region,  308 
ischio-rectal  region,  1063 
leg,  434 

lingual  region,  323 
neck,  314 
orbit,  303 
palatal  region,  329 
palm  of  hand,  401 
palpebral  region,  301 
pancreas,  945 
pectoral  region,  376 
perineum,  1063 
pharynx,  327 
pterygoid  muscles,  312 
radial  region,  395 
scalp,  298 
sole  of  foot,  443 
spinal   cord   and  membranes, 

707 
suprahyoid  region,  321 
temporal  muscle,  31 1 
thigh,  back  of,  432 
front  of,  418 
inner  side  of,  423 
Diverticulum,  Meckel's,  915 
Division  of  cells,  1075 
direct,  1077 
indirect,  1075 
Dorsal  artery  of  penis,  565 
auditory  nucleus,  702 
nerve  of  penis,  793 
nerves,  776 

anterior  divisions  of,  777 
peculiar,  777 
of  penis,  793 
posterior  divisions  of,  777 
ro'ots  of,  776 
vein  of  penis,  617 
vertebrae,  39 
peculiar,  41 
Dorsales  pollicis  arteries,  541 
Dorsalis  hallucis  artery,  588 
indicis,  541 
lingnse,  489 
nasi  artery,  509 
pedis,  587 

branches  of,  588 
peculiarities  of,  587 
surface  marking  of,  587 
surgical  anatomy  of,  587 


INDEX. 


1227 


Dorsalis  scapulae,  533 

Dorsi-lumbur  nerve,  781 
Dorsi-spinal  veins,  612 
Dorsum  of  scapula,  140 
ephippii  or  selke,  73 
Douglas,  pouch  of,  898,  1029 

semilunar  fold  of,  364 
Ducts  or  duct  of  Bartholin,  887 
biliary,  940 

of  Cowper's  glands,  1006 
Cuvier,  1195 
cystic,  943 
ejaculatory,  1023 
galactophorous,  1040 
of  Gartner,  1038,  1210 
hepatic,  941 
of  kidney,  989 
lactiferous,  1040 
of  liver,  940 
lymphatic,  right,  625 
nasal,  847 
of  pancreas,  947 
parotid,  884 
Rivini,  887 
seminal,  1021 
Stenson's,  885 
thoracic,  624 
Wharton's,  886 
Ductless  glands  :  spleen,  949 
suprarenal  capsule,  996 
thyroid,  979 
thymus,  981 
Ductus  arteriosus,  471,  475 

how  obliterated  in  foetus, 473 
communis  choledochus,  943 
endolymphaticus,  69,  862 
pancreaticus  accessorius,  948 
Rivini,  887 
Santorini,  94S 
thyro-glossus,  1206 
venosus,  471,  1195 
how  obliterated,  473 
Duodenal  fold,  904 
fossae,  904 

superior,  904 
glands,  918 
Duodeno-jejunal  flexure,  914 
fossa,  904 

-mesocolic  ligament,  904 
Duodenum,  912 

vessels  and  nerves  of,  914 
Dura  mater  of  brain,  639 
arteries  of,  640 
endosteal  layer  of,  639 
meningeal  layer  of,  639 
nerves  of,  640 
processes  of,  640 
structure  of,  639 
veins  of,  640 
of  cord,  707 

peculiarities  of,  708 
Dyaster,  or  daughter  star,  1075 

E. 

Ear,  848 

arteries  of,  850,  858,  1066 
auditory  canal,  851 
cochlea,  860 
development  of,  1183 
internal,  or  labyrinth,  859 
membranous  labyrinth,  862 
muscles  of  auricle,  850 

of  tympanum,  857 
ossicula  of,  856 


Ear,  pinna,  or  auricle  of,  848 

semicircular  canals,  860 

surface  form  of,  852 

surgical  anatomy  of,  867 

tympanum,  852 

vestibule,  859 
Earthy  constituents  of  hone,  1101 
Ectoderm,  1154 
Ectoplacenta,  or  chorion,  1154 
Efferent  nerves,  1119 
Egg-tubes,  1037,  1210 
Eighth  nerve,  745 

surgical  anatomy  of,  745 
Ejaculator  seminis  muscle,  371 
Ejaculatory  ducts,  1023 
Elastic  cartilage,  1095 

connective  tissue,  1088 

lamina  of  cornea,  827 
Elbow,  anastomoses  around,  537 

bend  of,  534 

joint,  255 

surface  form  of,  258 
surgical  anatomy  of,  258 
vessels   and   nerves  of,  256, 
257 
Eleidin,  1138 
Eleventh  nerve,  753 

surgical  anatomy  of,  753 
Embryo,  development  of,  1165 

first  rudiments  of,  1155 
Eminence    of    aquaeductus   Fal- 
lopii,  854 

canine,  83 

frontal,  61 

genital,  1213 

ilio-pectineal,  177 

nasal,  61 

parietal,  60 
Eminences    and    depressions   of 

bones,   34 
Eminentia  articularis,  65 

cinerea,  698 

collateralis,  666 

teres,  699 
Emissary  veins,  605 
Enamel  cells,  878 

epithelium,  878 

germ,  878 

neck  of,  878 

organ,  878 

pulp,  880 

rods,  877 

of  teeth,  877 

formation  of,  878 
Enarthrosis,  221 
Encephalon,  643 
End-bulbs  of  Krause,  1121 
Endings  of  Ruffini,  1122 
Endocardial  cushions,  1190 
Endocardium,  468 
Endolymph,  862 
Endomysium,  1107 
Endoneurium,  1119 
Endosteal  layer  of  dura  mater, 

639 
Endothelium,  1083 
End-plates,  motor ial,  of  Kiihne, 

1124 
Ensiform  appendix,  124 
Enteron,  1158 
Entoderm,   1154 
Eosinophile  corpuscles,  1079 
Eparterial  division  of  bronchus, 

966 
Epencephalon,  643,  1176 


Ependyma,  661 

Epiblast,  1154 

Epicardium,  468 

Epicondyle,  148 

Epidermic  coat  of  hair  follicle, 

1141 
Epidermis,  development  of,  1186 

structure  of,  1082,  1135 
Epididymis.  1017 

development  of,  1211 
Epigastric:  artery,  deep,  571 
peculiarities,  572 
relation     to    femoral    ring, 
1060 
with  internal  ring,  1047 
superficial,  578 
superior.  527 
plexus,  806 
region,  895 
vein,  deep,  616 
superficial,  614 
Epiglottic  glands,  964 
Epiglottis,  958 
Epimysium,  1 107 
Epineurium,   1119 
Epiphysial  cartilage,  1103,  1106 
Epiphysis,  34,  1107 

cerebri,  672 
Epithelium,  1082.     See   Various 
Organs. 
ciliated,  1084 
columnar,  1083 
cylindrical,  1083 
enamel,  879 
external,  S79 
internal,  879 
pavement,  1083 
spheroidal  or  glandular,  1084 
stratified,  1085 
transitional,  1085 
Epitrochlea,  148 
Epitvmpanic  recess,  68 
Eponyclium,  1140,  1210 
Epoophoron,  1038 
Erectile  tissue  of  clitoris,  1026- 
of  penis,  1012 

its  structure,  1012 
Erector  clitoridis,  375,  1026 
penis,  372 
spinse,  343 
Eruption  of  the  teeth,  S81 
Erythroblasts,  1080,  1097 
Erythrocytes,  1078 
Ethmo-frontal  suture,  103 
Ethmo-sphenoidal  suture,  103 
Ethmoid  bone,  77 

articulations  of,  80 
cribriform  plate  of,  78 
development  of,  80 
lateral  masses  of,  78 
os  planum  of,  79 
perpendicular  plate  of,  78 
plate,  1167 

unciform  process  of,  79 
Ethmoidal  artery,  506 
canal,  anterior,  til 

posterior,  64 
cells,  78 
notch,  63 
process  of  inferior  turbinated, 

95 
spine,  73 
Eustachian  tube,  855 

surgical  anatomy  of,  867 
valve,  462 


1228 


INDEX. 


Eustachian  valve,  in  fcetal  heart, 

470 
Expiration,  muscles  of,  355 
Extensor  brevis  digitorum  mus- 
cle, 444 

carpi  radialis  brevior,  396 
longior,  396 
pollicis,  399 
ulnaris,  397 

coccygis,  347 

communis    digitorum  (hand), 
396 

indicis,  399 

longus  digitorum  (foot),  435 
pollicis,  399 

minimi  digiti,  397 

ossis  metacarpi  pollicis,  399 

primi  internodii  pollicis.    See 
Extensor  longus  pollicis. 

proprius  hallucis,  435 

secundi  internodii  pollicis.  See 
Extensor  brevis  pollicis. 
External   abdominal   ring,   366, 
1043 

annular  ligament,  443 

capsule,  662 

inguinal  hernia,  1049 

medullary  lamina,  672 

orbital  foramina,  75 

pterygoid  plate,  75 

spermatic  fascia,  1043 

sphincter  ani,  368 
Extrinsic  muscles  of  tongue,  325 
Eye,  824 

appendages  of,  843 

aqueous  humors  of,  839 

chambers  of,  839 

choroid,  828 

ciliary  muscle,  830 
processes  of,  829 

conjunctiva,  845 

cornea,  826 

crystalline  lens,  840 

development  of,  1180 

clastica  lamina  of  cornea,  827 

hyaloid  membrane,  820 

humors  of,  839 

iris,  830 

Jacob's  membrane,  835 

membrana  pupillaris,  832 

pupil  of,  831 

retina,  832 

sclerotic,  825 

surgical  anatomy  of,  841 

tunics  of,  825 

uvea  of,  831 

vessels  of  globe  of,  841 

vitreous  humors  of,  839 
Eyeball,  muscles  of,  303 

nerves,  841 

vessels  of,  841 
Eyebrows,  843 
Evelashes,  843 
Eyelids,  843 

cartilages  or  plates  of,  843 

development  of,  1182 

Meibomian  glands  of,  844 

muscles  of,  297 

tarsal  ligament  of,  844 
Eye-teeth,  871 

F. 

Face,  arteries  of,  489 
bones  of,  54,  80 
development  of,  1166 


Face,  lymphatics  of,  626 
muscles  of,  297 
nerves  of,  740 
veins  of,  594 
Facial  artery,  489 

peculiarities  of,  493 

surgical  anatomy  of,  493 

transverse,  495 
bones,  81 
nerve,  740 

surgical  anatomy  of,  744 
vein,  596 

surgical  anatomy  of,  596 
Falciform  ligament  of  liver,  937 

of  sacro-sciatic  articulation, 
243 
process  of  fascia  lata,  420 
Fallopian  tubes,  1034 

development  of,  1210 

fimbriated      extremity      of, 
1034 

lymphatics  of,  634 

nerves  of,  1038 

structure  of,  1035 

vessels  of,  1038 
False  ligaments  of  bladder,  1002 
pelvis,  179 
ribs,  128 
Falx  cerebelli,  641 

cerebri,  641 
Fangs  of  teeth,  871 
Fascia  or  fasciae,  anal,  1071 
of  arm,  386 
bucco-pharyngeal,  316 
of  Camper,  356 
cervical,  deep,  315 

superficial,  314 
clavi-pectoral,  529 
of  Colles,  370 
costo-coracoid,  378 
of  cranial  region,  298 
cremasteric,  361 
cribriform,  418, 1055 
deep,  297 
dentata,  653 
dorsal,  of  foot,  443 
fibro-areolar,  its  structure,  296 
.  general  description  of,  295 
iliac,  415 

infundibuliform,  1016,  1047 
intercolumnar,  359 
intercostal,  350 
.  intermuscular,  of  arm,  386 
of  foot,  443 
ischio-rectal,  1071 
lata,  419,  1055 

falciform  process  of,  1056 

iliac  portion  of,  420,  1055 

pubic  portion,  420,  1056 
of  leg,  434 

deep  transverse,  438 
lumborum,  342 
of  mamma,  375 
-  masseteric,  310 
of  neck,  313 
obturator,  1071 
palmar,  402 
parotid,  310 
pelvic,  1070 
perineal,  deep,  1066 

superficial,  1064 
plantar,  443 

of  foot,  443 

of  forearm,  390 

of  band,  402 


Fascia  or   fascia?,    prevertebral, 
315 
propria,    of   spermatic    cord, 

1015 
recto-vesical,  1071 
of  Scarpa,  356 
spermatic,  358,  1043 
superficial,  296 

of  inguinal  region,  1041 
of  ischio-rectal  region,  1064 
of  thigh,  418 
temporal,  310 

of  thigh,  deep,  418 

superficial,  418 
of  thorax,  350,  377 
transversalis,  1046 
triangular,  359 
visceral  layer  of  pelvic,  1071 
Fasciculus  teres,  684,  699 

of  Tiirck,  713 
Fasciola  cinerea,  653 
Fat,  1091 
Fat-cells,  1091 

development  of,  1092 
Fauces,  isthmus  of,  883 
Fecundation  of  ovum,  1151 
Female   organs   of   generation : 
bulbi  vestibuli,  1027 
earunculse  myrtiformes,  1027 
clitoris,  1026 

development  of,  1209,  1213 
fossa  navicularis,  1026 
glands  of  Bartholin,  1027 
hymen,  1027 
labia  majora,  1025 

minora,  1026 
nymphae,  1026 
uterus,  1028 
vagina,  1027 
vestibule,  1027 
Femoral  artery,  572 
branches  of,  578 
common,  573 
deep,  578 

peculiarities  of,  575 
superficial,  574 
surface  marking  of,  575 
surgical  anatomy  of,  575 
or  crural  canal,  1060 

variation  in  size  of,  accord- 
ing to  position   of  limb, 
1061 
cutaneous  nerve,  793 
hernia,  complete,  1061 
coverings  of,  1061 
descent  of,  1 061 
dissection  of,  1053 
incomplete,  1062 
seat  of  stricture,  1062 
surgical  anatomy  of,  1053 
region,    muscles    of,   anterior, 
418 
internal,  423 
posterior,  432 
ring,  1060 
position  of  surrounding  parts, 

1060 
sheath,  1059 
spur,  189 
vein,  616 

relation  of  femoral  ring,  1060 
Femur,  183 

articulations  of,  189 
attachment  of  muscles  to,  189 
condyles  of,  187,  188 


INDEX. 


1229 


Femur,  development  of,  189 

fracture  of,  above  condyles, 451 
below  trochanters,  451 

head  of,  184 

neck  of,  184 

structure  of,  188 

surface  form  of,  190 

surgical  anatomy  of,  190 

trochanters  of,  185 
Fenestra  ovalis,  854 

rotunda,  854,  861 
Fenestrated  membrane  of  Henle, 

1089,  1126 
Ferrein,  pyramids  of,  989 
Fertilization  of  ovum,  1151 
Fibraa  proprise  of  cerebellum,  691 
Fibre-cells,  contractile,  1112 
Fibres  of  Miiller,  837 

of  muscle,  1107 

of  nerves,  1115 

of  Remak,  1117 
Fibrin,  1080,  1081 

ferment,  1081 
Fibrinogen,  1080 
Fibro-cartilage,  1094 

circumferential,  1095 

connecting,  1095 

interarticular,  1094 

stratiform,  1095 

yellow,  1095 
Fibro-cartilages,  acromio-clavic- 
ular,  248 

intercoccygean,  245 

intervertebral,  224 
of  knee,  277 
of  lower  jaw,  233 

pubic,  245 

radio-ulnar,  260 

sacro-coccygean,  244 

sterno-clavicular,  246 
Fibro-serous  membranes,  1143 
Fibrous  cartilage,  1094 

connective  tissue,  1087 

nervous  matter,  1115 

rings  of  heart,  468 

tissue,  white,  1087 
vellow,  1088 
Fibula,  196 

articulations  of,  198 

attachment  of  muscles  to,  198 

development  of,  198 

fracture    of,    with   dislocation 
of  the  foot,  453 

surface  form  of,  198 
Fibular  region,  muscles  of,  440 
Fifth  nerve,  725 

surface  marking  of,  737 
surgical  anatomy  of,  738 
ventricle  of  brain,  665 
Filiform  papilla?  of  tongue,  813 
Fillet,  lower,  674 

mesial,  674 

upper,  674 
Filum  terminale  of  cord,  709 
Fimbriae  of  Fallopian  tube,  1034 
Fimbrio-dentate  fissure,  667 
First  nerve,  720 

surgical  anatomy  of,  721 
Fissura  palpebrarum,  843 

prima,  655 
Fissure   or    fissures,     antitrago- 
helicina,  849 

auricular,  70 

brain,  644 
calcarine,  646 


Fissure  or  fissures,  callosal,  653 
cerebellum,  686 
post-central,  686 
post-clival,  686 
post-nodular,   688 
post-pyramidal,  688 
pre-central,  686 
pre-clival,  686 
pre-pyramidal,  688 
collateral,  646 
congenital,  in  cranium,  81 
dentate,  647 
of  ductus  venosus,  936 
of  gall-bladder,  935 
Glaserian,  66,  853 
horizontal,  of  cerebellum,   685 
longitudinal,  of  cerebrum,  643, 
'  655 

of  liver,  935 
of  lung,  974 
median,  of  medulla  oblongata, 

694 
pari  eto-  occipital,  646 
post-limbic,  647 
pterygo-maxillary,  112 
of  Rolando,  646 
sphenoidal,  75 
spheno-maxillary,  112 
spinal  cord,  711 
of  Sylvius,  645,  658 
transverse,  of  cerebrum,  668 

of  liver,  935 
umbilical,  935 
Flat  bones,  33 

Flexor  accessorium  muscle,  446 
brevis  digitorum,  444 
hallucis,  446 
minimi  digiti  (foot),  447 

(hand),  406 
pollicis,  404 
carpi  radialis,  391 

ulnaris,  391 
digitorum  sublimis,  392 

profundus,  393 
longus  digitorum,  439 
hallucis,  438 
pollicis  (hand),  394 
ossi  metacarpi  pollicis,  406 
Flexures   of    embryonic    brain, 
cephalic,  1176 
nuchal,  1176 
pontal,  1176 
Floating  ribs,  128 
Floccular  fossa,  69  • 
Flocculus,  688 
Flood's  ligament,  251 
Fluids,  nutritive,  1077 
Foetus,  circulation  in,  471 
Eustachian  valve  in,  470 
foramen  ovale  in,  470,  1190 
liver   of,    distribution    of    its 

vessels,  471 
vascular  system  in,  peculiari- 
ties, 470 
Fold  of  Douglas,  364 
Folds,  arvteno-epiglottidean,  959 
genital",  1213 
recto-uterine,  1029 

-vesical,  1002 
vesi  co-uterine,  1029 
Folia  of  cerebellum,  659 
Folium  cacuminis,  686 
Follicle  of  hair,  1141 

of  intestine,  918 
Follicles,  sebaceous,  1142 


Fontana,  spaces  of,  827 
Fontanelles,  •" 
Foot,  arteries  of,  587,  591 
bones  of,  199 
development  of,  21 1 
dorsum,  muscles  of,  444 
fascia  of,  443 
ligaments  of,  442 
nerves  of,  795 
sole  of,  fascia  of,  443 

muscles  of,  443 
surface  form  of,  213 
surgical  anatomy  of,  213 
veins  of,  614 
Foramen  caecum,  of  frontal  bone, 
63,  103 

of  medulla  oblongata,  693 

of  Vicq  d'Azyr,  694 

of  tongue,  813 
carotid,  70 
condyloid,  56 
dental  inferior,  98 
ethmoidal,  104 
of  Huschke,  71 
infraorbital,  83 
intervertebral,  35 
jugular,  106 
lacerum  anterius,  105 

medium,  106 

posterius,  106 
magnum,  56 

of  Majendie,  641,  698,  708 
mastoid,  67 
mental,  97 
of  Monro,  664,  671 
obturator,  177 
optic,  75,  105 
ovale  of  heart,  470,  1190 
of  sphenoid,  74 
palatine,  anterior,  87,  106 

posterior,  92,  108 
parietal,  60 
pterygo-palatine,  74 
quadratuni  of  diaphragm,  354 
rotundum,  74,  105 
sacro-sciatic,  174,  242 
of  Scarpa,  87,  108 
singulare,  69,  867 
of  Sommerring,  833 
spheno-palatine,  93,  116 
spinosum,  74,  105 
of  Stenson,  87,  108 
sternal,  125 
stylo-mastoid,  70 
supraorbital,  62 
thyroid,  177 
Vesalii,  74,  105 
of  Winslow,  899 
Foramina  of  diaphragm,  354 
external  orbital,  74 
of  Key  and  Retzius,  642,  698 
malar,  89 
nervosa,  864 
olfactory,  77 
sacral,  47 
Thebesii,  462,  622 
Forceps,  major,  660 

minor,  660 
Forearm,  arteries  of,  538 
bones  of,  150 
fascia  of,  389 
lymphatics  of,  628 
muscles  of,  389 
nerves  of,  769 
veins  of,  607 


1230 


INDEX. 


Fore-brain,  643 
Fore-gut,  1158 

development  of,  1198 
Form  of  bones,  33 
Formatio  reticularis  of  medulla 
alba,  701 
grisea,  701 
of  cord,  716 
of  mid-brain,  674 
Fornix,  664 

conjunctivae,  845 

pillar,  664 
Fossa  acetabuli,  177 

of  antihelix,  849 
.  canine,  83 

cochlearis,  860 

condyloid,  56 

digastric,  67 

digital,  185 

glenoid,  65 

of  helix,  849 

iliac,  174 

incisive,  83,  97 

incudis,  856 

infra-  and  supraspinous,  140 

ingninalis  lateralis,  1048 
mesialis,  1048 
supra-vesiculus,  104S 

ischio-rectal,  1064 

jugular,  71 

lachrymal,  63 

myrtiform,  83 

naviculars  of  urethra,  1006 
of  vulva,  1026 

occipital,  56 

olfactory,  of  foetus,  1185 

ovalis,  462 

ovarii,  1036 

palatine,  anterior,  87 

patellaris,  839 

pituitary,  73 

pterygoid  of  lower  jaw,  99 

of  sphenoid,  75 

of  Rosenmiiller,  890 

scapha,  849 

scaphoid,  76 

sigmoidea,  67 

skull,  anterior,  103 
middle,  105 
posterior,  106 

spheno-maxillary,  112 

sublingual,  97 

submaxillary,  97 

subscapular,  139 

supra-tonsillaris,  884 

temporal,  110 

triangularis.  849 

trochanteric,  185 

vesical  is,  936 

zygomatic,  111 
Fossae,  nasal,  115,  820 

of  skull,  103 
Fourchette,  1026 
Fourth  nerve,  724 

surgical  anatomy  of,  725 

ventricle,  697 
Fovea  centralis  retinae,  833 

hemispherica,  860 

inferior,    of    fourth   ventricle, 
698 

inguinalis  lateralis,  1048 
mesialis,  1048 

semi-elliptica,  860 

superior,   of  fourth  ventricle, 
698 


Fovea  supra-vesicalis,  1048 
Fracture  of  acromial  end  of  clav- 
icle, 412 
acromion  process,  412 
centre  of  clavicle,  411 
coracoid  process,  412 
coronoid  process  of  ulna,  413 
femur  above  condyles,  451 

below  trochanters,  451 
fibula,    with    dislocation      of 

tibia,  453 
humerus,  anatomical  neck,  413 
shaft  of,  412 

non-union,  149 
surgical  neck,  412 
neck  of  femur,  451 
olecranon  process,  413 
patella,  452 
Pott's,  453 
radius,  413 

lower  end  of,  414 
neck  of,  413 
shaft  of,  414 
and  ulna,  414 
tibia,  shaft  of,  453 
ulna,  shaft  of,  414 
Fraena  of  ilio-caecal  valve,  923 
Fraenulum  cerebellum,  686 
Fraenum  clitoridis,  1026 

labii     superioris    et   inferioris, 

870 
linguae,  811 
praeputii,  1012 
Frontal  artery,  508 
bone,  61 

articulations  of,  64 
attachment   of   muscles    to, 

64 
development  of,  64 
structure  of,  64 
crest,  63 
eminence,  61 
lobe,  646 
nerve,  726 
process  of  malar,  90 
sinuses,  64 
suture,  61,  64 
vein,  595 
Frontalis  muscle,  300 
Fronto-nasal  process,  1169 
Fronto-sphenoidal    suture,    101, 

102 
Fundus  tvmpani,  853 

of  uterus,  1028 
Fungiform    papillae   of    tongue, 

813 
Funiculus  cuneatus,  695 
gracilis,  695 
of  nerve,  1118 
of  Rolando,  695 
solitarius,  701 
teres,  699 
Furcula,  1203 
Furrow,  sternal,  132 
Furrowed    band  of   cerebellum, 
688 

G. 

Galactophorous  ducts,  1040 
Galen,  veins  of,  601,  669 
Gall-bladder,  942 

development  of,  1205 

fissure  for,  935 

structure  of,  942 

surface  form  of,  943 


Gall-bladder,  valve  of,  942 
Ganglion  or  ganglia  of  Andersch, 
748 

Arnold's  736 

of  Bochdalek,  731 

cardiac,  805 

carotid,  801 

cephalic,  729 

of  cerebellum,  693 

cervical  inferior,  803 
middle,  803 
superior,  799 

ciliary,  729 

on  circumflex  nerve,  769 

corpuscles,  1125 

diaphragmatic,  808 

on  facial  nerve,  740 

of  fifth  nerve,  729 

Gasserian,  725 

general  anatomy  of,  1125 

of  glosso-pharyngeal,  748 

geniculate,  741 

of  habenula,  672 

impar,  799,  805 

inferus,  749 

intercarotid,  803 

interpedunculare,  672 

jugular,  748 

lateral  root  of  eighth  nerve, 
745 

lenticular,  729 

lumbar,  805 

Meckel's,  731 

mesenteric,  809 

ophthalmic,  729 

otic,  736 

petrous,  748 

pharyngeal,  801 

of  pneumogastric,  750 

of  portio  dura,  741 

on  posterior  interosseous  nerve, 
775 

radicis  cochlearis,  702 

of  Iiibes,  801 

of  root  of  vagus,  749 

sacral,  805 

of  Scarpa,  867 

semilunar,  of  abdomen,  806 
of  fifth  nerve,  726 

spheno-palatine,  732 

of  spinal  nerves,  757 

spirale,  867 

submaxillary,  737 

suprarenal,  808 

of  sympathetic  nerve,  798 

thoracic,  804 

of  trunk  of  vagus,  749 

of  Valentin,  731 

of  Wrisberg,  806 
Ganglionic  branch  of  nasal  nerve, 
729 
nerves,  1118 
Gartner,  duct  of,  1210 
Gases  of  the  blood,  1081 
Gasserian  ganglion,  725 

depression  for,  69 
Gastric    arteries    (vasa    brevia), 
553 

artery,  551 

glands,  909 

impression  of  liver,  937 

nerves  from  vagus.  752 

plexus,  808 

vein,  620 
Gastrocnemius  muscle,  436 


INDEX. 


1231 


Gastro-colic  omentum,  902 
Gastro-duodenal  artery,  552 

plexus,  808 
Gastroepiploic  plexus,  808 

veins,  620 
Gastro-epiploica   dextra   artery, 
553 

sinistra,  553 
Gastro-hepatic  omentum,  901 
Gastro-splenic  omentum, 902,  949 
Gemellus  inferior  muscle,  430 

superior  muscle,  430 
Generative  organs,  development 
of,  1207 
female,  1025 
male,  1009 
Genial  tubercles,  97 
Geniculate  bodies,  675 

ganglion,  741 
Genio-hyo-glossus  muscle,  323 
Genio-hyoid  muscle,  322 
Genital  cord,  1209 

corpuscles,  1121 

eminence,  1213 

folds,  1213 

groove,  1213 

ridge,  1213 
Genito-crural  nerve,  783 
Genu  of  the  corpus  callosutn,659 
Germ,  common  dental,  877 

special  dental,  877 
Germinal  area,  1154 

disk,  1154 

epithelium,  1210 

spot,  1149 

vesicle,  1149 
Giacomini,  band  of,  653 
Giant  cells,  1097 
Gianuzzi,  crescents  of,  888 
Gimbernat's  ligament,  357,  1044 
Gingival    branches     of     dental 

nerves,  730 
Ginglvmus,  220 
Giraldes,  organ  of,  1021,  1211 
Girdle,  pelvic,  134 

shoulder,  134 
Glabella  of  frontal  bone,  61,  112 
Gladiolus,  125 
Gland  or  glands,  arytenoid,  964 

of  Bartholin,  1027 

of  biliary  ducts,  943 

of  Bowman,  822 

Brunner's,  918 

buccal,  870 

ceruminous,  852 

coccygeal,  558 

Cowper's,  1011,  1067 

development  of,  1133 

ductless,  949 
spleen,  949 
suprarenal,  996 
thymus,  981 
thyroid,  979 

duodena],   918 

epiglottic,  963 

gastric,  909 

of  Havers,  218 

labial,  870 

lachrymal,  846 

of  larynx,  964 

lingual,  816 

of  Littre\  1006 

of  Luschka,  558 

lymphatic,  1133 

mammary,  1038 


Gland    or    glands,    Meibomian, 
844 

molar,  870 

of  Moll,  843 

mucilaginous,  of  Havers,  218 

odorifene,  101 1 

esophageal,  8U2 

of  Pacchioni,  602,  642 

palatal,  883,  888 

parotid,  884 

Fever's,  919 

pharyngeal,  890 

pineal,  672 

pituitary,  656 

prostate,   1009 

racemose  or  saccular,  1146 

of  Rosenmiiller,  accessory,  846 

salivary,  884 

sebaceous,  1142 

secreting,  1146 

simple,  1146 

solitary,  919 

sublingual,  887 

submaxillary,  886 

sudoriferous,  1142 

suprarenal,  996 

thymus,  981 

thyroid,  979 

tracheal,  967 

tubular,  1146 
compound,  1146 
convoluted,  1146 

of  Tyson,  1011 

uterine,  1031 

of  vulva,  1027 
Glandules  odorifera?,  1011 

Pacchioni,  602,  642 
Glandular  epithelium,  1084 
Glans  penis,  1011 

clitoridis,  1027 
Glaserian  fissure,  65,  66,  853 
Gleno-humeral  ligament,  251 
Glenoid  cavity,  141 

fossa,  65 

ligament  of  Cruveilhier,  267 
of  phalanges,  267 
of  shoulder,  251 
Gliding  movement,  222 
Glisson's  capsule,  902,  938,  940 
Globus    major    of     epididymis, 
1017 

minor,  1017 

pallidus,  663 
Glosso-epiglottic  ligaments,  811, 
959 

-pharyngeal  nerve,  746 
Glottis  respiratoria,  960 

rima  of,  959 

vocalis,  960 
Gluteal  aponeurosis,  427 

artery,  569 
inferior,  568 

lymphatic  glands,  681 

nerve,  inferior,  791 
superior,  791 

region,  lymphatics  of,  633 
muscles  of,  426 

ridge,  186 

veins,  616 
Gluteus  maximus  muscle,  426 

medius,  427 

minimus,  428 
Goblet-cells,  1084 
Golgi-cells  of  cerebellum,  693 

organs  of,  1123 


|  GolPs  column,  715 
I  Gomphosis,  219 
j  Gower's  tract,  714 
Graafian    membrana    granulosa 
of,  1037 
ovicapsule  of,  10.';, 
structure  of,  1037 
vesicles,  1036 
Gracilis  muscle,  423 
Grande  lobe  limbique,  652 
Grandv,    tactile    corpuscles    of, 

"1121 
Granule  cells,  1087 
Gray  matter  of  cerebellum,  691 
of  cerebrum.  678 
of  medulla  oblongata,  699 
of  spinal  cord,  715 
nervous  substance,  1113 
Great  occipital  nerve,  760 
omentum,  902 
sciatic  nerve,  793 

surgical  anatomy  of,  797 
sinus  of  aorta,  477 
Greater  wings  of  sphenoid,  74 
Groin,  1053 

cutaneous  vessels  and  nerves 

of,  1054 
superficial  fascia  of,  1053 
surgical  anatomy  of,  1 053 
Groove,        auriculo-ventricular, 
460 
bicipital,  144 
cavernous,  73 
infraorbital,  84 
lachrymal,  85 
mylo-hyoid,  97 
nasal,  82 
occipital,  67 
optic,  73 
subclavian,  130 
Grooves  in  the  radius,  156 

interventricular,  460 
Growth  of  bones,  1106 
Gubernaculum  dentis,  881 

testis,  1211 
Gums,  870 
Gustatory  hair,  814 
nerve,  735 
pore,  814 
(iyri  brevis,  652 

or    convolutions    of    brain, 
644 
Gyrus  cinguli,  653 
first  annectant,  651 
fornicatus,  653 
hippocampi,  653 
longus,  652 
marginal,  650 
paracentral,  650 
rectus,  650 

second  annectant,  651 
third  annectant,  651 

H. 

Hematoidin  crvstals,  1082 
Ha?min  crystals,  1082 
Haemoglobin,  1078 

crystals,  1081 
Hemorrhoidal    arterv,   inferior, 
567 
middle,  563 
superior,  555 
nerve,  inferior,  793 
plexus  of  nerves,  809 


1232 


IXDEX. 


Hsemorrhoidal     venous    rdexus, 
616 
surgical  anatomy  of,  616 
Hair-cells  of  internal  ear,  865 

outer,  865 
Hair-follicles,  1140 
Hairs,  1140 

root-sheath  of,  1140 

shaft  of,  1141 

structure  of,  1140 
Hani,  region  of,  581 
Hamstring      tendons,      surgical 

anatomy  of,  433 
Hamular    process    of    humerus, 
146,  note. 
of  lachrymal,  88 
of  sphenoid,  76 
Hamulus,  861 
Hand,  arteries  of,  542 

bones  of,  158 

fascia  of,  400 

ligaments  of,  262 

muscles  of,  400 

nerves  of,  from  median,  772 
from  radial,  775 
from  ulnar,  773 

surface  form  of,  169,  409 
•  veins  of,  607 
Hard  palate,  883 
Harmon  i  a,  219 
Hasner,  valve  of,  847 
Havers,  glands  of,  218 
Haversian  canals  of  bone,  1 098 

svstem  of  bone,  1098 
Head,  kidney,  1208 

lymphatics  of,  625 

muscles  of,  297 

of  scapula,  141 

of  ulna,  154 

veins  of,  594 
Heart,  640 

annular  fibres  of  auricles,  468 

arteries  of,  469,  480 

circular  fibres  of,  468 

component  parts  of,  460 

development  of,  11S9 

endocardium,  468 

fibres  of  the  auricles,  468 
of  the  ventricles,  468 

fibrous  rings  of,  468 

foetal  relics  in,  462 

infundibulum  of,  463 

left  auricle,  465 
ventricle,  465 

looped  fibres  of  auricles,  468 

lymphatics  of,  469,  636 

muscular  fibres  of,  468 
structure  of,  1112 

nerves  of,  469,  752,  803 

position  of,  460 

right  auricle,  461 
ventricle,  463 

septum  ventriculorum,  463 

size  and  weight,  460 

spiral  fibres  of,  468 

structure  of,  468 

subdivision  into  cavities,  460 

superficial  fibres   of   auricles, 
468 

surface-marking  of,  470 

veins  of,  621 

vortex  of,  469 
Heidenhain,  demilunes  of,  888 
Helicine  arteries,  1013 
Helicis  major  muscle,  550 


Helicis  minor,  S50 
Helicotrema  of  cochlea,  861 
Helix,  849 

fossa  of,  849 

muscles  of,  850 

spine  of,  849 
Hemispheres  of  brain,  643 
Henle,  ligaments  of,  361 

looped  tubes  of,  988 
Henle's    layer   of    hair-follicle, 

1141" 
Hensen,    canalis      reuniens    of, 
866 

lines  of,  1109 

supporting  cells  of,  866 
Hensen's  stripe,  866 
Hepatic  arterv,  551,  940 

cells,  939 

duct,  941 

plexus,  808 

veins,  619,  941 
Herbst,  corpuscles  of,  1123 
Hernia,  congenital,  1051 

direct  inguinal,  1052 
dissection  of,  1053 

encysted,  1051 

femoral,  coverings  of,  1061 
descent  of,  1061 

of  funicular  process,  1051 

infantile,  1051 

inguinal,  1049 
dissection  of,  1041 

oblique  inguinal,  1049 

scrotal,  1051 
Hesselbach's  ligament,  361 

triangle,  1048,  1052 
Hiatus  Fallopii,  69 

semilunaris,  820 
Highmore,  antrum  of,  85 
Hilton's  muscle,  963 
Hilum  of  kidney,  986 

of  spleen,  949 
Hind-gut,  1158 

development  of.  1203 
Hind-kidney,  1208 
Hinge-joint,  220 
Hip-joint,  268 

muscles  of,  426 

in  relation  with,  291 

surface  form  of,  272 

surgical  anatomy  of,  272 
Hippocampal    convolution,  653, 

666 
Hippocampus  major,  66o 

minor,  647,  662 
Horizontal  cells  of  retina,  835 

plate  of  ethmoid,  78 
of  palate,  91 
Horner's  muscle,  302 
Houston's  folds  of  rectum,  928 
Howship's  lacuna?,  1097 
Huguier,  canal  of,  66,  853 
Humerus,  144 

anatomical  neck,  fracture  of, 
413 

articulations  of,  148 

attachment  of  muscles  to,  149 

development  of,  148 

head  of,  144 

neck  of,  144 

nutrient  artery  of,  537 

shaft  of,  fracture  of,  412 

surface  form  of,  149 

surgical  anatomy  of,  149 
neck,  fracture  of,  412 


Humerus,  tuberosities  of,  greater 

and  lesser,  144 
Humors  of  the  eye,  839 
Hunter's  canal,  572 
Hnschke,  foramen  of,  71 
Huxlev's  layer  of  hair -follicles, 

1141 
Hyaline  cartilage,  1093 

cell,  1079 
Hyaloid  membrane  of  eye,  839 
Hyaloplasm,  1074 
Hydatid     of    Morgagni,    1017, 

1035,  1211 
Hymen,  1027 

Hyo-epiglottic  ligament,  959 
Hyo-glossal  membrane,  815 
Hyo-°;lossus  muscle,  324 
Hyoiclarch  (foetal),  1170 

artery  of  superior  thvroid,  487 
bone,  122 

attachment  of  muscles  to,  123 
cornua  of,  123 
development  of,  123 
branch  of  lingual  artery,  489 
region,  muscles  of,  infra-,  319 
supra-,  321 
Hyparterial  branch  of  bronchus, 

966 
Hypoblast,  1153,  1154 
Hypochondriac  regions,  896 
Hypogastric    arteries    in   foetus, 
471,  562 
how  obliterated,  473 
plexus,  809 

inferior,  809 
region,  896 
Hypoglossal  nerve,  754 

surgical  anatomy  of,  756 
Hypophysis  cerebri,  756 

I. 

Ileo-c«cal  fossa,  904 

valve,  923 
Ileo-colic  arterv,  555 

fossa,  904 
Ileum,  914 

Iliac  arteries,  common,  559 
peculiarities  of,  559 
surface-marking  of,  560 
surgical  anatomy  of,  560 
external,  570 

surface-marking  of,  570 
surgical  anatomy  of,  570 
internal,  561 
at  birth,  562 
peculiarities  in  the  foetus, 

562 
surgical  anatomy  of,  562 
fascia,  415 
fossa,  174 
furrow,  182 
lymphatic  glands,  633 
portion  of  fascia  lata,  416 
region,  muscles  of,  415 
veins,  common,  617 

peculiarities  of,  617 
externa],  616 
internal,  616 
Iliacus  muscle,  417 
Ilio-costalis  muscle,  343 
Ilio-femoral  ligament,  269 
Ilio-hypogastric  nerve,  782 
Ilio-inguinal  nerve,  783 
Ilio-lumbar  artery,  569 


INDEX. 


1233 


Iliolumbar  ligament,  241 

vein,  618 
Ilio-pectineal  eminence,  177 

ligament,  416 
Ilio-tibial  band,  419 
Ilio-trochanteric  ligament,  270 
Ilium,  172 
crest  of,  1 74 
dorsum  of,  172 
spines  of,  174 
venter  of,  174 
Impregnation,  1151 
Impressio  colica,  937 
duodenalis,  937 
renalis,  937 
suprarenalis,  937 
Incisive  fossa,  83 
Incisor  teeth,  871 
Incisura  cardiaca,  974 

cerebelli    anterior,    or    semi- 
lunaris, 684 
posterior,    or     marsupial  is, 
684 
intertragica,  849 
Eivini,  853 
Santorini,  851 
Incremental   lines    of    dentine, 

876 
Incus,  856 

development  of,  1184 
ligament  of,  857 
superior,  857 
Infantile  hernia,  1051 
Inferior  dental  artery,  498 
canal,  88 
external  frontal  artery,  511 
internal  frontal  artery,  510 
maxillary  bone,  96 

changes  produced  by  age  in, 
99 
meatus  of  nose,  116 
occipital  protuberance,  57 
posterior  lobe  of  cerebellum, 

689 
profunda  artery.  537 
turbinated  bones,  94 
articulations  of,  95 
development  of,  95 
ethmoidal  process  of,  95 
lachrymal  process  of,  95 
maxillary  process  of,  95 
vena  cava,  617 
Infracostal  muscles,  351 
Infraglenoid  tubercles,  141 
Inframaxillary  nerves  from  fa- 
cial, 744 
Infraorbital  artery,  499 

branches  of  facial  nerve,  744 
canal,  84 
foramen,  83 
groove,  84 
plexus  of  nerves,  730 
Infraspinatus  muscle,  384 
Infraspinous  f"~^ia,  384 

fossa,  140 
Infra-sternal  depression,  133 
Infratrochlear  nerve,  729 
Infundibula  of  kidney,  987 
Infundibular  artery,  477 
Infundibuliform      fascia,      366, 

1047 
Infundibulum  of  brain,  656 
of  ethmoid,  79 
of  heart,  463 
Ingi-assias,  processes  of,  75 


Inguinal  canal,  1046 
glands,  deep,  630 

superficial,  630,  1042 
hernia,  1041 

dissection  of,  1042 
region,  895 
Inlet  of  pelvis,  180 
Innominate  artery,  480 
peculiarities  of,  481 
surgical  anatomy  of,  481 
bone,  171 

articulations  of,  17.S 
attachment    of    muscles   to, 

178 
development  of,  177 
veins,  609 

peculiarities  of,  610 
Inorganic  constituents  of  bone, 

1101 
Insertion  of  muscles,  296 
Inspiration,  muscles  of,  355 
Interalveolar  cell  islets,  948 
Interarticular       fibro  -  cartilage, 
1094 
of  acromioclavicular  joint, 

248 
of  jaw,  233 
of  knee,  276 
of  radio-ulnar  joint,  260 
of   sterno-clavicular     joint, 
247 
ligament  of  ribs,  238 
Intercavernous  sinus,  604 
Intercellular     biliarv    passages, 

941 
Interchondral  ligaments,  239 
Interclavicular  ligaments,  246 
Intercolumnar  fascia,  357,  1043 

fibres,  358 
Intercondyloid  notch,  187 
Intercostal  arteries,  547 
anterior,  526 
superior,  527 
fascise,  350 

lymphatic  glands,  636 
lymphatics,  637 
muscles,  350 
nerves,  777 
spaces,  128 
veins,  superior,  611 
Intercosto-humeral   nerves,  771, 

779 
Interlobular  arteries  of  kidney, 
999 
biliary  plexus,  940 
spaces,  876 
Intermaxillary  suture,  113 
Intermediate  cell  mass,  1208 
Intermembranous       ossification, 

1102 
Internal  abdominal  ring,  1047 
annular  ligament,  442 
capsule,  662 
carotid  artery,  502 
cutaneous  nerve,  771 
inguinal  hernia,  1049 
mammary  artery.  526 

-in,  610 
maxillary  artery,  496 
brand  "s  of,  496 
peculiarities  of,  496 
surgical  ar-,omv  of,  49*8 
medullary  lamina,  672 
oblique  muscle,  360 
occipital  crest,  57 


Internal  pterygoid  plate,  75 

sphincter,  368 
Internasal  suture,  113 
Internodal    segment  of    nerves, 

1117 
Internodia  or  phalanges,  169 
Intemssei    muscles,    dorsal,    of 
foot,  448 
of  hand,  408 
palmar,  40> 
plantar,  448 
Interosseous  artery  of  foot,  588 
of  forearm,  54 1 
recurrent,  544 
fibro-cartilage,  219 
membrane  of  forearm,  2G0 

of  leg,  283 
nerve,  anterior,  772 

posterior,  775 
veins  of  forearm,  608 
Interpeduncular  space  of  brain, 

656 
Intersigmoid  fossa,  905 
Interspinals  muscles,  347 
Interspinous  ligaments,  226 
Intertransversales  laterales,   347 
medial es,  347 
muscles,  347 
Intertransverse  ligaments,  226 
Intertrochanteric   line,  anterior, 
185 
posterior,  185 
Intertubular  stroma  of  kidnev, 

993 
Intervertebral  foramina,  53 
notches,  35 
substance,  224 
Intestinal  lymphatic  trunk,  635 
Intestine,  coats  of,  915 
development  of,  1198 
large,  coats  of,  928 
lymphatics  of,  635 
small,  911 

surface  form  of,  930 
surgical  anatomy  of,  930 
Intracartilaginous      ossification, 

1102 
Intralobular  veins,  940 
Intramembranous       ossification, 

1102 
Intranuclear  network,  1074 
Intraparietal  sulcus,  650 
thyroid  cartilage,  956 
Intrinsic  muscle  of  tongue,  325 
Intumescentia  gangliformis,  741 
Investing  mass  of  Ratlike,  1167 
Involuntary  muscle,  1111 
Iris,  830 

Irregular  bones,  34 
Ischiatic  lymphatic  glands,  631 
Ischio-capsular  ligament,  269 
Ischio-rectal  fascia,  1071 
fossa,  1064 

position  of  vessels  and  ncrve9 
in,  1064 
region,    surgical   anatomv   of, 
1063 
Ischium,  174 
body  of,  174 
ramus  of,  176 
spine  of,  175 
tuberosity  of,  175 
Island  of  Reil,  65S 
Isthmus,  aortic,  I7S 
of  auditory  canal,  851 


1234 


INDEX. 


Isthmus  cerebri,  673 
of  the  fauces,  883 
faucium,  869 
of  thyroid  gland,  979 
Iter   a   tertio  ad  quartum  ven- 
triculum,  676 
chordae  anterius,  742 
posterius,  742 
Ivory  of  tooth,  874 

J. 

Jacob's  membrane,  835 
Jacobson's  cartilage,  820 
nerve,  748,  858 
canal  for,  70 
organ,  820 
Jaw,  lower,  95 

articulations  of,  99 
attachment   of    muscles   to, 

99 
changes  produced  in,  bv  age, 

99 
condyle  of,  99 
development  of,  99 
ligaments  of,  231,  232 
oblique  line  of,  97 
pterygoid  fossa  of,  99 
rami  of,  98 
sigmoid  notch  of,  99 
symphysis  of,  96 
upper.     See  Maxillary  Bone. 
Jejunum,  914 

Jelly  of  Wharton,  1090,  1165 
Joint.     See  Articulations. 
Jugular  foramen,  106 
fossa,  71 
ganglion,  748 
process,  56 
surface,  70 
vein,  anterior,  598 
external,  597 

surgical  anatomy  of,  597 
internal,  598 

sinus  or  gulf  of,  598 
surgical  anatomy  of,  599 
posterior,  external,  598 

K. 

Karyokinesis,  1075 
Karyomitosis,  1075 
Keratin,  1138 
Kerkering,  valves  of,  916 
Kidney,  985 

calices,  987 

cortical  substance  of,  987 

development  of,  1207 

ducts  of,  994 

hilum  of,  9S6 

infundibula  of,  987 

lymphatics  of,  634,  993 

Malpighian  bodies  of,  988 

maniillae  of,  987 

medullary  substance,  987 

nerves  of,  993 

papillae  of,  987 

pelvis  of,  987 

pyramids  of  Ferrein,  989 

renal  artery,  556,  992 

sinus  of,  986 

surface-marking  of,  993 

surgical  anatomy  of,  993 

tubuli  uriniferi,  988 

veins  of,  619,  992 


Kidney,  weight  and  dimensions, 

985 
Knee-joint,  274 

surface  form  of,  280 
surgical  anatomy  of,  280 
Krause,  end-bulbs  of,  1121 

membrane  of,  1109 
Kiischner    on  structure   of    the 
heart's  valves,  463 

:l. 

Labia  cerebri,  659 

pudendi  majora,  1025 
minora,  1026 

lymphatics  of,  634 
Labial  artery,  491 

glands,  870 

veins,  inferior,  596 
superior,  596 
Labio-dental  furrow,  877 

strand,  877 
Labium  tympanicum,  864 

vestibulare,  864 
Labyrinth,  859 

arteries  of,  866 

fibro-serous  membrane  of,  866 
Labyrinthine  cartilage,  1167 
!  Lachrymal  apparatus,  846 

artery,  506 

bone,  88 

articulations  of,  89 
attachment  of  muscles  to,  89 
development  of,  89 

canals,  846 

caruncula,  845 

crest,  88 

fossa,  63 

gland,  846 

groove,  85 

nerve,  726 

notch,  84 

papilla,  846 

process  of  inferior  turbinated 
bone,  95 

puncta,  846 

sac,  847 

tubercle,  86 
Lacteals,  623,  918,  1082 
Lactiferous  ducts,  1039 
Lacuna  magna,  1006 
Lacunae  of  bone,  1099 

Howship's,  1087 
Lacus  lachrymalis,  843,  846 
Lagema,  866 
Lambda,  103 
Lambdoid  suture,  101 
Lamella  of  bone,  articular,  217 

horizontal,  of  ethmoid,  78 

perpendicular,      of     ethmoid, 
78 
Lamellae  of  bone,  1099 
Lamina,  bursalis,  829 

of  cerebellum,  685 

chorio-capillaris,  829 

cinerea,  656 

of  cornea,  664 
elastic,  827 

cribrosa,  69 
of  sclerotic,  825 

dental,  877 

fftsca,  825 

spiralis  ossva  of  cochlea,  861 

suprachoroidea,  828 

vasculosa,  S28 


Lamina  of  the  vertebrae,  34 
Laminae  dorsal es,  1156,  1165 
Lancisi,  nerves  of,  659 
Lanugo  (foetal  hairs),  1186 
Large  intestine,  921 
areolar  coat,  928 
caecum,  922 
colon,  923 

ileo-caecal  valve,  923 
mucous  coat,  928 
muscular  coat,  928 
rectum,  925 
serous  coat,  928 
Laryngeal  artery,  inferior,  523 
superior,  488 
nerve,  external,  751 
internal,  751 
recurrent,  751 
superior,  751 
surgical  anatomy  of,  752 
from  sympathetic,  803 
pouch,  961 
veins,  610 
Laryngo-tracheotomy,  969 
Laryngotomy,  968 
Larynx,  955 

actions  of  muscles  of,  963 
arteries  of,  948 
cartilages  of,  955 
cavity  of,  959 
glands  of,  964 
interior  of,  959 
ligaments  of,  958 
lymphatics  of,  964 
mucous  membrane  of,  964 
muscles  of,  961 
nerves  of,  964 
rima  glottidis,  959 
superior  aperture  of,  959 
surface  form  of,  968 
surgical  anatomy  of,  968 
veins  of,  964 
ventricle  of,  961 
vocal  cords  of,  false,  960 
true,  961 
Lateral  acoustic  tubercle,  702 
cell  column,  717 
horn  of  spinal  cord,  716 
masses  of  ethmoid,  78 
patellar  ligaments,  274 
recess    of     fourth    ventricle, 

697 
region  of  skull,  110 
sinus  of  brain,  602 
tract    of   medulla    oblongata, 
695,  699 
Lateralis  nasi  artery,  491 
Latissimus  dorsi  muscle,  399 
Lecithin,  1078 
Leg,  arteries  of,  585 
bones  of,  191 
fascia  of,  434 

deep  transverse,  438 
ligaments  of,  268 
lymphatics  Ci,  w.  0 
muscles  of,  434 
back  of,  436 
front  of,  435 
nerves  of,  790 
veins  of,  614 
Lemniscus,  674,  701 
Lens,  840 

changes  produced  in,  by  age, 
841 
development  of,  1182 


INDEX. 


1235 


Lens,    suspensory   ligament    of, 
840 
vesicle,  1182 
Lenticular  ganglion,  729 
glands  of  stomach,  910 
Lesser  lachrymal  bone,  88 
omentum,  901 
sciatic  nerve,  791 
wings  of  sphenoid,  75 
Leucocytes,  1079 

development  of,  1079,  1188 
Levator  anguli  oris,  307 
scapulae,  340 
ani,  369 
labii  inferioris,  308 

superior  alseque  nasi,  307 
superioris,  307 
menti,  308 
palati,  329 
palpebral,  302 
prostatas,  369 
Levatores  costarum,  352 
Lieberkiihn,  crypts  of,  918 
Lieno-renal  ligament,  901,  949 
Ligament,  structure  of,  217 
acromio-clavicular,      inferior, 
248 
superior,  248 
alar,  of  knee,  278 
of  ankle,  anterior,  284 

lateral,  284 
annular,  of  ankle,  284 
external,  284 
internal,  2S4 
of  radius,  259 
of  stapes,  857 
of  wrist,  anterior,  262 

posterior,  262 
anterior,  of  knee,  274 
arcuate,  352 
aryteno-epiglottic,  958 
astragalo-navicular,  289 
atlan to-axial,  anterior,  227 

posterior,  227 
of  bladder,  false,  1002 

true,  1002 
broad,  of  liver,  937 
calcaneo-astragaloid,  external, 
287 
interosseous,  287 
posterior,  287 
calcaneo-cuboid,  internal,  287 
long,  287 
short,  288 
superior,  287 
calcaneonavicular,      inferior, 

288 
calcaneonavicular,     superior, 

288 
capsular.  See  Individual  Joints. 
carpo-metacarpal,  dorsal,  263 
interosseous,  263 
palmar,  263 
of  carpus,  263 
central,  of  spinal  cord,  709 
check,  230 
chondro-sternal,   anterior,  238 

posterior,  238 
common    vertebral,    anterior, 
223 
posterior,  223 
conoid,  249 
of  Cooper,  359 
coraco-acromial,  249 
coraco-clavicular,  249 


Ligament,  coraco-humeral,  251 
coracoid,  250 
coronary,  of  liver,  937 
costo-clavicular,  246 
costo-vertebral,  or  stellate,  234 
cotyloid,  270 
crico-arytenoid,  959 
crico-thyroid,  959 
crucial,  of  knee,  276 
cruciform,  228 
deltoid,  284 

dorsal.     See  Individual  Joints. 
of  elbow,  255 

anterior,  255 

external  lateral,  256 

internal  lateral,  256 

posterior,  256 
falciform,  of  liver,  937 

of  pelvis,  240 
Flood's,  251 

Gimbernat's,  357,  1044,  1058 
glenoid,  252 

glosso-epiglottidean,  811,  959 
of  Henle,  361 
of  Hesselbach,  361,  364 
of  hip,  268  _ 
hyo-epiglottic,  958 
iliofemoral,  269 
ilio-Iumbar,  241    ~ 
ilio-pectineal,  416 
ilio-trochanteric,  270 
of  incus,  857 

interarticular,  of  ribs,  235 
interchondral,  238 
interclavicular,  246 
interosseous.      See   Individual 

Joints. 
interspinous,  226 
intertransverse,  226 
intervertebral,  224 
ischio-capsular,  269 
of  jaw,  231 
of  knee,  274 
of  larynx,  958 

lateral.     See  Individual  Joints. 
patellar,  274 

longitudinal,  of  liver,  938 
long  plantar,  287 
lumbo-sacral,  240 
of  malleus,  857 
metacarpal,  267 
metacarpophalangeal,  267 
metatarsal,  291 
metatarso-phalangeal,  292 
mucosum.  of  knee,  274 
nucha?,  339 
oblique,  259 

sacro-iliac,  242 
obturator,  429 
occipito-atlantal,  anterior,  229 

lateral,  229 

posterior,  229 
occipito-axial,  230 
odontoid,  230 
orbicular,  259 
of  ossicula,  S57 
of  ovary,  ]  038 
palpebral  or  tarsal,  844 
of  patella,  274 
of  pelvis,  240 
of  the  phalanges,  (foot),  293 

(hand),   '268 
phreno-colic,  902 
of  the  pinna,  279 
plantar,  291 


Ligament,  posterior,  of  knee,  or 
posticum  Winslowii,  274 
Poupart's,  357,  1044,  1057 
ptervgo-maxillarv,  309 
pubic,  anterior,  245 

posterior,  245 

superior,  245 
pnbo-femoral,  269 
pubo-prostatic,  1002 
radio-carpal,  262 
radio-ulnar  joint,  inferior,  260 
middle,  259 
superior,  259 
recto-uterine,  1029 
rhomboid,  246 
round,  of  hip,  269 

of  liver,  936 

of  radius  and  ulna,  259 

of  litems,  1038 
sacro-coccygeal,  anterior,  244 

posterior,  244 
saero-iliac,  anterior,  242 

oblique.  242 

posterior,  24 2 
sacro-sciatic,  greater,  242 

lesser,  243  ' 
sacro-uterine,  1029 
sacro-vertebral,  240 
of  scapula,  249 
scapuloclavicular,  248 
of  shoulder,  251 
spring,  289 
stellate,  234 
sterno-clavicular,  anterior,  246 

posterior,  246 
sterno-pericardiac,  458 
of  sternum,  2H9 
stylo-mandibular,  232 
subpubic,  245 
supraspinous,  225 
suspensory,  of  incus,  857 

of  lens,  840 

of  liver,  937 

of  malleus,  857 

of  mamma,  377 

of  penis,  101 1 

spheno-mandibular,  232 

spino-glenoid,  250 
sutural,  217 
tarsal,  of  eyelids,  8-13 
tarso  metatarsal,  290 
of  tarsus,  287 
teres,  of  hip,  270 
of  thumb,  265 
thyro-arytenoid,  inferior,  961 

superior,  960 
thyro-epiglotlie,  959 
thyro-hyoiil,  958 
tibio-tarsal,  283 
transverse,  of  atlas,  227 

of  hip,  267 

humeral,  252 

of  knee,  277 

of  scapula,  250 
trapezoid,  2-1'.' 
triangular,  of  tvmpanic  bones, 

856 
of  urethra,  1065 
of  uterus,  1029 
of  vertebra\  224 
vesico-uterine,  1029 
of  Winslow,  274 
of  "Wrisberg,  277 
of  wrist,  anterior,  262 

lateral  external,  262 


1236 


INDEX. 


Ligament   of  wrist,    lateral   in- 
ternal, 262 
posterior,  262 
of  Zinn,  304  _ 
Ligamenta  alaria,  278 
sobflava,  225 

suspensoria,  of  mamma,  377 
Ligamentous  action  of  muscles, 

222 
Ligamentum    arcuatum     exter- 
num, 352 
internum,  352 
arteriosum,  475 
denticulatum,  709 
latum  pulmonalis,  970 
mucosum,  277 
nuchae,  339 
patellae,  274 
pectinatum  iridis,  830 
posticum  Winslowii,  274 
spirale,  864 
teres,  270 
Ligature  of  arteries.     See  each 

Artery. 
Ligula,  698 
Limbic  lobe,  652 
Limbs,  development  of,  1187 
Limbus  laminae  spiralis,  864 
Limiting  sulcus,  1158 
Linea  alba,  365 
aspera,  186 
ilio-pectinea,  174 
quadrati,  186 
splendens,  709 
supracondylar,  187 
suprema,  56 
Lineae  semilunares,  365 

transverse,  of  abdomen,  365 
Lines  of  Henson,  1109 
Lingual  artery,  488 

surgical  anatomy  of,  489 
bone,  122 
lobule,  652 
nerve,  735 
tonsils,  812 
veins,  598 
Lingualis  muscle,  inferior,  326 
superior,  326 
transverse,  326 
vertical,  326 
Lingula,  686 

of  inferior  maxilla,  98 
of  sphenoid,  73 
Lips,  869 

arteries  of,  491 
Liquor  amnii,  1161 
Cotunnii,  866 
sanguinis,  1080 
Lissauer,  tract  of,  714 
Lithotomy,  parts  avoided  in  op- 
eration, 1069 
concerned   in  operation  of, 

1068 
divided  in  operation,  1069 
Littre,  glands  of,  1006 
Liver,  933 

change  of  position  in,  943 
development  of,  1204 
distribution   of  vessels   to,  in 

foetus,  471 
ducts  of,  941 
fibrous  coat  of,  938 
fissures  of,  935 
hepatic  artery  940 
cells,  939 


Liver,  hepatic  duct,  941 
veins,  938 
ligaments  of,  937 
coronary,  937 
lateral,  937 
round,  938 
lobes  of,  936 
lobules  of,  938 
lymphatics  of,  634 
nerves  of,  808 
portal  vein,  621 
situation,    size,    and     weight, 

933 
structure  of,  938 
surface  form  of,  943 
surfaces  of,  934 
surgical  anatomy  of,  944 
vessels  of,  938 
Lobe  or  lobes,  central,  652 
of  cerebellum,  685 
of  cerebrum,  646 
cuneate,  651 
frontal,  648 
of  kidney,  986 
limbic,  652 
of  liver,  936 
of  lung,  974 
marginal,  650 
occipital,  651 
orbital,  649 
parietal,  650 
of  prostate,  1010 
quadrate,  651 
temporal,  652 
of  testis,  1019 
of  thymus,  9S1 
of  thyroid,  979 
Lobule  of  the  ear,  849 
Lobules  of  kidney,  986 
of  liver,  938 
of  lung,  975 
Lobuli  testes,  1019 
Lobulus  centralis,  686 
Lobus  caudatus,  934 
clivus  monticuli,  686 
culmen  monticuli,  686 
quadratus,  934 
Spigelii,  936 
Locus  cceruleus,  699 
Long  bones,  33 

saphenous  nerve,  787 
Longissimus  dorsi  muscle,  345 
Longitudinal  fasciculus,  inferior, 
678 
perpendicular,  678 
superior,  678 
fissure  of  brain,  643,  655 

of  liver,  935 
sinus  of  brain,  inferior,  602 
superior,  602 
Longus  colli  muscle,  333 
Looped  tubes  of  Henle,  988 
Lower    extremity,    arteries     of, 
572 
bones  of,  171 
fascia  of,  415 
ligaments  of,  268 
lymphatics  of,  631 
muscles  of,  415 
nerves  of,  780 
surface  form  of  muscles  of, 

449 
veins  of,  614 
visual  centre,  722 
Lower,  tubercle  of,  463 


Lumbar  arteries,  558 

fascia  or  aponeurosis,  342 
ganglia,  805 
glands,  632 
nerves,  780 

anterior  divisions  of,  781 
posterior  divisions  of,  781 
roots  of,  780 

surgical  anatomy  of,  797 
plexus  of  nerves,  781 
region,  896 
vein,  ascending,  618 
veins,  618 
vertebra?,  41 

development  of,  43 
Lumbo-iliac  ligament,  241 
Lumbo-sacral  ligament,  240 

nerve,  781 
Lumbricales    muscles    (of    the 
foot),  446 
(of  the  hand),  408 
Lungs,  973 

air-cells  of,  -976 
bronchial  arteries,  976 

veins,  976 
capillaries  of,  976 
development  of,  1206 
lobes  and  fissures  of,  974 
lobules  of,  975 
lymphatics  of,  637,  977 
nerves  of,  977 
pulmonary  artery,  976 

veins,  976 
roots  of,  974 
structure  of.  975 
surface-marking,  977 
surgical  anatomy  of,  977 
weight,  color,  etc,  975 
Lunula?  of  nails,  1140 
Luschka's  gland,  558 
Lymph,  1082 
capillaries,  1082 
path  or  sinus,  1134 
Lymphatic    or    lymphatics    of 
abdomen,  632 
of  arm,  630 
of  bladder,  634 
bone,  1098 

broad  ligaments,  634 
cardiac,  637 
cerebral,  626 
cervical,  superficial  and  deep, 

627,  628 
chest,  636 
of  clitoris,  633 
of  cranium,  626 
diaphragm,  636 
duct,  right,  625 
face,  deep,  626 

superficial,  626 
Fallopian  tubes,  633 
general  anatomy  of,  1131 
glands,    anterior   mediastinal, 
636 
auricular  posterior,  625 
axillary,  628 
brachial,  628 
bronchial,  636 
buccal,  625 
cervical,  deep,  628 

superficial,  628 
in  front  of  elbow,  625 
general  anatomy  of,  1133 
gluteal,  631 
of  head,  625 


INDEX. 


1237 


Lymphatic  or  lymphatics,glands, 
iliac,  external,  632 
internal,  631 

inguinal,  deep,  630 
superficial,  630 

intercostal,  636 

internal  mammary,  636 

ischiatic,  631 

of  large  intestine,  635 

of  lower  extremity,  631 

lumbar,  632 

of  neck,  628 

occipital,  625 

parotid,  625 

of  pelvis,  632 

popliteal,  631 

radial,  628 

sacral,  632 

of  small  intestines,  635 

of  spleen,  635 

of  stomach,  635 

submaxillary,  625 

of  thorax,  636 

tibial  anterior,  631 

ulnar,  638 

of  upper  extremity,  628 
gluteal  region,  633 
head,  superficial,  625 
heart,  636 
intercostal,  636 
internal  mammary,  636 
intestines,  635 
kidneys,  634 
labia,  634 
lacteals,  635 
large  intestine,  635 
leg,  631 
liver,  634 

lower  extremity,  631 
lung,  637 
lymphatic  duct,  625 

right,  625 
meningeal,  626 
mouth,  627 
neck,  625 
nose,  627 
nymphse,  634 
esophagus,  637 
origin  of,  1132 
ovaries,  634 
pancreas,  635 
pelvis,  632 
penis,  633 
perinaeum,  633 
pharynx,  628 
pia  mater,  626 
prostate,  634 
rectum,  634 
scrotum,  633 
small  intestine,  635 
spleen,  635 
stomach,  635 

subdivisions  into  deep  and  su- 
perficial, 623 
terminations  of,  1133 
testicle,  634 
thoracic  duct,  624 
thorax,  636 
thymic,  637 
tipper  extremity,  630 
deep,  630 
superficial,  630 
uterus,  634 
valves  of,  1132 
vagina,  634 


Lymphocyte,  1079 
Lymphoid     connective 

1091 
Lyra  of  fornix,  665 


M. 


tissue, 


Macula  acustica  ntricularis,  862 
cribrosa,  860 
lutea,  833 
saccularis,  862 
Magnum  of  carpus,  164 
Majendie,  foramen  of,  641,  708 
Malar  bone,  89 

articulations  of,  91 
attachment    of   muscles   to, 

91 
development  of,  90 
foramina,  89 
frontal  process  of,  90 
maxillary  process  of,  90 
orbital  process  of,  90 
zygojnatic  process  of,  90 
canals,  90 

nerves,  from  fascial,  743 
process  of  superior  maxillary, 
85 
Male  urethra,  1005 
Malleolar  arteries,  external  and 
internal,  587 
folds,   anterior   and   posterior, 
855 
Malleolus,  external,  197 

internal,  195 
Malleus,  855 

development  of,  1184 
superior  ligament  of,  857 
Malpighi,  pyramids  of,  987 
Malpighian    bodies    of   kidney, 
988 
of  spleen,  952 
capsules,  988 
tufts,  988 
Mamma,  areola  of,  1039 
lobules  of,  1039 
nerves  of,  1040 
nipple  or  mammilla  of,  1039 
vessels  of,  1039 
Mammae,  development  of,  1186 
Mammary      arterv,      internal, 
526 
glands,  1038 
lymphatic  glands,  625 
veins,  internal,  610 
Mammilla  of  breast,  1039 

of  kidney,  987 
Mammillary  processes,  42 
Mandibular  arch,  1170 

nerve,  744 
Manubrium  of  malleus,  856 

of  sternum,  124 
Marginal  artery,  477 
gyrus,  650 
lobe,  650 
sinus,  1164 
Marrow  of  bone,  1096 
Marshall,  vestigial  fold  of,  460, 

1197 
Masseter  muscle,  310 
Masseteric  arteries,  498 
fascia,  310 
nerve,  734 
veins,  596 
Mastoid  antrum,  68 


Mastoid  antrum,  opening  of,  854 
cells,  67 
foramen,  67 

portion  of  temporal  bone,  67 
process  67 
vein,  597 
Masto-occipital  suture,  102 
.Ma^to-parietal  suture,  102 
Matrix  of  nail,  1140 
Maturation  of  ovum,  1150 
Maxillary  artery,  internal,  496 
bone,  inferior,  96 
sujierior,  83 

development  of,  87 
nerve,  inferior,  734 

superior,  729 
process  of  inferior  turbinated, 
94 
of  malar  bone,  90 
processes,  foetal,  1169 
sinus,  85 
tuberosity,  84 
vein,  anterior  internal,  596 
internal,  596 
Meatus  auditorius  externus,  68, 
851 
internus,  69 
of  nose,  inferior,   117 
middle,  117 
superior,  116 
urinarius,  female,  1027 
male,  1006 
Meatuses  of  the  nose,  117,  820 
Meckel's  cartilage,  1170 
diverticulum,  915 
ganglion,  732 
Median  artery  of  forearm,  543 
of  spinal  cord,  522 
nerve,  771 

surgical  anatomy  of,  776 
vein,  607 
Mediastinal  arteries,  from  inter- 
nal mammary,  526 
posterior,  from  aorta,  548 
lymphatic  glands,  636 
subpleural  plexus,  526 
Mediastinum,  anterior,  972 
middle,  972 
posterior,  973 
superior.  971 
testis,  1018 
Medio-tarsal  joint,  285 
Medulla  oblongata,  693 
arcuate  fibres  of,  696 
back  of,  696 
fissures  of,  694 
formatio  reticularis  of,  700 
funiculus  cuneatus  of,  695 
gracilis  of.  695 
of  Rolando  of,  695 
gray  matter  of,  699 
lateral  column  of,  695 

tract  of.  699 
olivary  body  of,  695 
pyramids  of,  694 
restiform  bodies  of,  696 
raphe  of,  703 
structure  of,  699 
spinalis,  710 
Medullary  artery  of  bone,  1097 
canal  of  bone,  33,  1096 
formation  of.  1105 
groove,  1155 
laminse,  external,  672 
internal,  672 


1238 


INDEX. 


Medullary   membrane  of  bone, 
1096 
plates,  1156 

segments  of  nerves,  1117 
sheath  of  nerve-fibres,  1116 
spaces  of  bone,  1104 
of  kidney,  9S7 
of  suprarenal  capsules,  997 
velum,  inferior,  of  cerebellum, 
688,  697 
superior,  697 
Medullated  nerve-fibres,  1116 
Medulli-spinal  veins,  612 
Meibomian  glands,  844 
Meissner's  plexus,  921 

tactile  corpuscles,   1121 
Metnbrana  basilaris,  863 
fusca,  825 
flaccida,  855 
granulosa,  of  Graafian  vesicle, 

1036 
hyaloidea,  839 
limitans  of  retina,  833,  837 
nictitans,  846 
propria,  1091 
pupillaris,  832 
sacciformis,  266 
tectoria,  866 
tympani,  855 
secundaria,  854 
Membrane  of  aqueous  chamber, 
827 
arachnoid,  spinal,  707 
cerebral,  641 
choroid,  828 
of  Cord,  866 
costo-coracoid,  378 
crico-thyroid,  959 
of  Descemet,  827 
fenestrated,  1126 
hyaloid,  839 
Jacob's,  835 
of  Kolliker,  866 
of  Krause,  1109 
limiting,  833,  835 
pituitary,  820 
pupillary,  832 
of  Reissner,  863 
Schneiderian,  820 
thyro-hyoid,  958 
Membranes  of  brain,  639 
of  fetus,  1160 
of  spinal  cord,  707 
Membranous  cranium,  1165 
labyrinth,  862 
portion  of  urethra,  1005 
semicircular  canals,  862 
vertebral  column,  1165 
Meningeal  artery,  from  ascending 
pharyngeal,  494 
anterior,  from    internal   ca- 
rotid, 505 
middle,  from  internal  maxil- 
lary, 496 
from  occipital,  493 
posterior,  from  vertebral,  521 
small,  from  internal  maxil- 
lary. 498 
layer  of  dura  mater,  639 
lymphatics,  626 
veins,  596,  640 
Meninges.     See  Membranes. 
Menisci,  1094 
Menisco-femoral  joint,  280 
Menisco-tibial  joint,  280- 


Mental  foramen,  97,  113 

process,  97 

tubercles,  97 
Mesencephalon,  643,  1176 
Mesenteric  artery,  inferior,  555 
superior,  553 

glands,  635 

plexus  of  nerves,  inferior,  809 
superior,  809 

vein,  inferior,  619 
superior,  619 
Mesenterico-parietal  folds,  905 
Mesenteries,  902 

development  of,  1198 
Mesial  fillet  of  midbrain,  674 
Mesoblast,  1154,  1155 
Mesoblastic  somites,  1156 
Mesocolon,  1199 

ascending,  902 

descending,  902 

transverse,  903 
Mesoderm,  1154 
Mesogastrium,  1199 
Mesonephros,  1208 
Mesorchium,  1209,  1211 
Mesorectum,  1199 
Mesosalpinx,  1030 
Mesosternum,  125 
Mesovarium,  1209 
Metacarpal  artery,  540 

articulations,  267 
Metacarpo-phalangeal    articula- 
tions, 267 
Metacarpus,  165 

common  characters  of,  165 

development  of,  171 

peculiar  bones  of,  166 
Metanephros,  1208 
Metaphase  of  karyokinesis,  1075 
Metasternum,  125 
Metatarsal  artery,  588 

articulations,  291 

bones,  208 
Metatarso-phalangeal      articula- 
tions, 292 
Metatarsus,  208 

development  of,  208 
Metencephalon,  643,  1176 
Metopic  suture,  64 
Microcytes,  1078 
Micropyle,  1150 
Mid-carpal  joint,  265 
Mid-frontal  process,  foetal,  1169 
Mid-gut,  1158 

development  of,  1198 
Mid-kidney,  1208 
Middle  clinoid  processes,  73,  105 

ear,  or  tympanum,  582 

ethmoidal  cells,  79 

fossa  of  skull,  105 

internal  frontal  artery,  510 

meatus,  117 

of  nasal  fossse,  117 

odontoid  ligament,  231 
Milk  teeth,  874 
Mitral  cells,  681 

valve,  466 
Mixed  bones,  34 
Moderator  band,  464 
Modiolus  of  cochlea,  861 
Molar  glands,  870 

teeth,  872 
Moll,  glands  of,  843 
Monaster  or  mother  star,  1075 
Monro,  foramen  of,  671 


Mons  Veneris,  1025 
Morgagni,  hydatid  of,  1211 

sinus  of,  328 
Motor  nerves,  1124 

efferent  or  descending   nerve 

tract,  718 
oculi  nerve,  722 

surgical  anatomy  of,  724 
Motorial  end-plates,  1124 
Mouth,  869 

mucous  membrane  of,  870 
muscles  of,  307 
surface  form  of,  888 
Movement   admitted   in  joints, 

220 
Mucilaginous  glands,  218 
Mucous  glands  of  tongue,  815 
membrane,  1145 
tissue,  1090 
Miiller,  duct  of,  1208 

fibres  of,  837 
Multicuspidate  teeth,  872 
Multifidus  spinse  muscle,  346 
Muscle,     general     anatomy    of, 
1107 
arrangement     of     fibres     of, 

1107 
bipenniform,  295 
blood-vessels  of,  1111 
chemical  composition  of,  1112 
derivation  of  names,  295 
development  of,  1112 
fasciculi  of,  1107 
fibres  of,  1107 
form  of,  295 
fusiform,  295 
insertion  of,  296 
involuntary,  1111 
lymphatics  of,  1111 
meaning  of  the   terms    "ori- 
gin"    and     "insertion," 
296 
mode  of   connection  of,  with 
bone,  cartilage,  skin,  etc., 
296 
nerves  of,  1111,1123 
origin  of,  925 
penniform,  925 
plate,  1165 
quadrilateral,  295 
rhomboidal,  295 
sarcous  elements  of,  1110 
sheath  of,  1107 
size  of,  295 
skeletal,  1107 
striped,  1107 
structure  of,  1107 
tendons  of,  296 
triangular,  295 
unstriped,  1111 
voluntary,  1107 
Muscles   or  muscle,   descriptive 
anatomy : 
of  abdomen,  356 
abductor  hallucis,  444 
indicis,  408 
minimi  digiti  (foot),  445 

(hand),  406 
pollicis  (hand),  404 
accelerator  urinse,  371 
accessorii  orbicularis  oris,  308 
accessorius  pedis,  446 

ad  ilio-costalem,  343 
adductor  brevis,  425 
longus,  424 


INDEX. 


1239 


Muscles   or   muscle,  descriptive 
anatomy  : 
adductor  magnus,  42.5 
obliquus  hallucis,  447 
pollicis  (hand),  405 
tranaversus  hallucis,  447 
pollicis,  405 
anconeus,  397 
antitragicus,  850 
aryteno-epiglottideus,  inferior, 
963 
superior,  963 
arytenoideus,  962 
rectus,  note,,  963 
attollens  auriculatn,  301 
attrahens  auricnlam,  300 
azygos  uvulae,  330 
biceps  (arm),  387 

(thigh),  431 
biventer  cervicis,  346 
brachialis  anticus,  388 
buccinator,  309 
cervicalis  ascendens,  345 
chondro-glossus,  324 
ciliary,  of  eye,  830 
circumflex  us  palati,  329 
coccygeus,  369 
columns,  1109 
complexus,  345 
compressor  naris,  306 
narium  minor,  306 
sacculi  laryngis,  963 
urethra?,  375 
in  female,  375 
constrictor     isthmi     faucium, 
325,  331 
pharvngeus  inferior,  327 
medius,  328 
superior,  328 
eoraco-brachialis,  387 
corrugator  of  cranial   region, 
298 
cutis  ani,  368 
supercilii,  302 
cremaster,  361 

crico-arytenoideus       lateralis, 
962 
posticus,  962 
crico-thyroid,  961 
crureus,  422 
deltoid,  382 
depressor  alas  nasi,   306 
anguli  oris,  308 
epiglottidis,  963 
labii  inferioris,  308 
diaphragm,  352 
digastric,  321 
dilatator  naris,  anterior,  306 

posterior,  306 
erector  clitoridis,  375 
penis,  372 
spinae,  343 
extensor     brevis      digitorum, 
444 
pollicis,  399 
carpi  longior,  396 
radialis  brevior,  396 
ulnaris,  397 
coccygis,  347 

digitorum  communis,  396 
indicis,  399 
longus  digitorum,  435 

pollicis,  399 
minimi  digiti,  397 
ossi  metacarpi  pollicis,  399 


Muscles   or   muscle,  descriptive 
anatomy : 
primi  internodii  pollicis,399 
proprius  hallucis,  435 
of  external  ear,  301 

sphincter,  368 
of  face,  301 

femoral  region,  anterior,  418 
internal,  423 
posterior,  432 
fibular  region,  440 
flexor  accessorius,  446 
brevis  digitorum,  444 
hallucis,  446 
minimi  digiti    (foot),  447 

(hand),  406 
pollicis  (hand),  404 
carpi  radialis,  391 

ulnaris,  391 
digitorum  sublimis,  392 
longus  digitorum,  439 
hallucis,  438 
pollicis  (hand),  394 
ossis  metacarpi  pollicis,  404 
profundus  digitorum,  393 
frontalis,  299 
gastrocnemius,  436 
gemellus,  inferior,  430 

superior,  430 
genio-hyo-glossus,  323 
genio-hyoid,   322 
gluteus  maximus,  426 
medius,  427 
minimus,  428 
gracilis,  423 
of  hand,  404 
of  head  and  face,  297 
helicis,  major,  850 

minor,  850 
Hilton's,  963 
of  hip,  426 
Horner's,  302 
hyo-glossus,  324 
iliac  region,  415 
iliacus,  417 
ilio-costalis,  343 
infracostal,  351 
infraspinatus,  384 
intercostal,  350 
internal  sphincter,  368 
interossei  of  foot,  448 

of  hand,  408 
interspinales,  347 
intertransversales,  347 
labial,  308 
of  larynx,  961 
latissimus  dorsi,  339 

of  leg,  434 
levator  angnli  oris,  307 
scapulae,  340 
ani,  369 

glandulae  thyroideae,  980 
labii  inferioris,  308 
menti,  308 
superioris,  307 
alaeque  nasi,  306 
palati,  329 
palpebral  302 
prostata,  370 
levatores  costarum,  352 
i:'ngualis,  323 
longissimus  dorsi,  345 
longus  colli,  333 
lumbricales  (foot),  446 
(hand),  408 


Muscles   or  muscle,  descriptive 
anatomy  : 
masseter,  310 
multifidus  Bpinae,  346 
musculus  accessories  ad    ilio- 

costalem,  3 !:; 
mylo-hyoid,  322 
naso-labialis,  306 
of  neck,  313 

obliquus  abdominis    externus, 
356 
interims,  360 

auriculae,  850 

capitis  inferior,  348 
superior,  3-18 
obturator  externus,  430 

internus,  429 
occipitalis,  299 
occipito-frontalis,  298 
oculi,  inferior,  304 

superior,304 
omohyoid,  320 
opponens  minimi  digiti,  406 

pollicis,  404 
orbicularis  oris,  308 

palpebrarum,  301 
palate,  329 

palato-glossus,  325,  331 
palato-pharyngens,  331 
palmaris  brevis,  406 

longus,  391 
pectineus,  424 
pectoralis,  major,  378 

minor,  379 
of  perineum,  female,  375 

male,  370 
peroneus  brevis,  441 

longus,  440 

tertius,  435 
pharyngo-glossus,  325 
of  pharynx,  327 
plantaris,  437 
plates,  1165 
platysma  myoides,  314 
popliteus,  438 
pronator  quadratus,  394 

radii  teres,  390 
psoas  magnus,  416 

parvus,  417 
pterygoid,  external,  312 

internal,  312 
pyramidalis  abdominis,  364 

nasi,  306 
pyriformis,  428 
quadratus  femoris,  430 

lumborum,  307 

menti,  308 
quadriceps     extensor     cruris, 

421 
rectus  abdominis,  362 

capitis  anticis  major,  332 
minor,  332 
posticus  major,  347 
minor,  348 

lateralis,  333 

oculi,  externus,  superior,  in- 
ferior,  and  internus,   304 
retrahens  auriculam,  301 
rhomboides  major,  340 

minor,  34<> 
risorius,  310 
rotatores  spiiw,  347 
sacro-lumbalis,  343 
salpingo-pharyngeus,  331 
sartor i us,  421 


1240 


INDEX. 


Muscles   or   muscle,  descriptive 
anatomy : 
scalenus  anticus,  334 

medius,  335 

posticus,  335 
semimembranosus,  432 
semispinalis  colli,  346 

dorsi,  346 
semitendinosus,  432 
serratus  magnus,  381 

posticus,  inferior,  341 
superior,  341 
sole  of  foot,  442 
first  layer,  444 
fourth  layer,  448 
second  layer,  446 
third  layer,  446 
soleus,  436 
sphincter,  external,  368 

internal,  368 

vaginse,  375 
spinalis  colli,  345 

dorsi,  345 
splenitis,  342 

capitis,  342 

colli,  342 
stapedius,  837 
sterno-cleido-mastoid,  317 
sterno-hyoid,  319 
stern  o-thyroid,  319 
stylo-glossus,  324 
stylo-hyoid,  322 
stylo-pharyngeus,  329 
subanconeus,  389 
subclavius,  380 
subcrureus,  423 
subscapularis,  383 
supinator  brevis,  398 

longus,  395 
supraspinales,  347 
supraspinatus,  384 
temporal,  311 
tensor  fasciae  femoris,  420 

palati,  329 

tarsi,  302 

tympani,  857 
teres  major,  386 

minor,  385 
thyro-arytenoideus,  962 
thyro-epiglottideus,  963 
thyrohyoid,  320 
tibialis  anticus,  434 

posticus,  439 
of  tongue,  325 
trachelo-mastoid,  345 
tragicus,  850 
transversalis  abdominis,  362 

colli,  345 
transversus  auriculae,  850 

perinaei  (female),  375 
profundus,  1070 
trapezius,  337 
triangularis  stern i,  351 
triceps,  extensor  cubiti,  388 
of  tympanum,  857 
of  ureters,  1003 
vastus  externus,  422 

internus  and  crureus,  422 
zygomaticus  major,  307 

minor,  307 
Muscles  of  expression,  314 
of    inspiration     and     expira- 
tion, 355 
of  pelvic  outlet,  367 
Muscular  fibres  of  heart,  1112 


Muscular  process  of  arytenoid, 

957 
Muscularis  mucosae,  1146 
Musculi  papillares,  left  ventricle, 
467 
right  ventricle,  464 
pectin  ati  in  left  auricle,  465 

in  right  auricle,  461 
pulvo-vesicalis,  1002 
Musculo-cutaneous  nerve  of  arm, 
770 
from  peroneal,  796 
Musculophrenic  artery,  527 
Musculo-spiral  groove,  146 
nerve,  774 

surgical  anatomy  of,  776 
Musculus    accessorius    ad    ilio- 
costal em,  343 
incisivus,  inferior,  309 

superior,  309 
suspensorius  duodeni,  914 
Myelo-plaques,  1097 
Myelo-spongium,  1172 
Mylo-hyoid  artery,  498 
groove,  98 
muscle,  322 
nerve,  736 
ridge,  98 
Myocardium,  468 
Myrtiform  fossa,  83 

3ST. 

Nails,  1139 
lunula  of,  1140 
matrix  of,  1140 
Nares,  anterior,  117,  820 
posterior,  117,  820,  890 
septum  of,  116,  820 
Nasal  angle,  82 

artery,  of  internal  maxillary, 
499 
transverse,  508 
of  ophthalmic,  508 
of  septum,  491 
bones,  81 

articulations  of,  82 
development  of,  82 
cartilages,  818 
crest,  87 
duct,  847 
eminence,  61 
fossae,  115,  820 
arteries  of,  822 
mucous  membrane  of,  820 
nerves  of,  823 
surgical  anatomy  of,  823 
veins  of,  822 
groove,  82 
laminae,  1169 
nerve,  727 
nerves  from  Meckel's  ganglion, 

732 
notch,  62 
process,  86 
spine,  62 

anterior,  87,  113 
posterior,  89 
venous  arch,  595 
Nasi  dorsal  is  artery,  509 
Nasion,  112 

Nasmyth's  membrane,  879 
Naso-labialis  muscle,  309 
Naso-maxillary  suture,  113 
Naso-palatine  nerve,  733 


Naso-palatine,  recess,  820 
Nates  of  brain,  675 
Navicular  bone,  205 

articulations  of,  205 
attachment   of   muscles   to, 

205 
tuberosity  of,  205 
Neck,  glands  of,  627 
lymphatics  of,  625 
muscles  of,  313 
triangle  of,  anterior,  500 

posterior,  501 
veins  of,  597 
Nelaton's  line,  190 
Nerve-cells,    or    ganglion    cor- 
puscles, 1113 
Nerve-epithelium  cells,  1124 
Nerve-roots,  anterior,  717 

posterior,  717 
Nerve-tracts  of  cord,  717 
Nerves,  general  anatomy  of,  1118 
cerebro-spinal,  1118 
development  of,  1172,  1178 
endoneurium,  1119 
epineurium,  1119 
funiculi  of,  1118 
origin  of,  1120 
perineurium  of,  1119 
plexus  of,  1119 
sheath  of,  1119 
spinal  roots  of,  756 
sympathetic,  1120 
termination  of,  1120 
vessels  of,  1119 
Nerves     or    nerve,    descriptive 
anatomy : 
of  abducens,  738 
accessory  obturator,  786 
anterior  crural,  786 
auditory,  745 
auricular,  posterior,  743 

of  vagus,  751 
auricularis  magnus,  762 
of  auriculo-temporal,  735 
of  second  cervical,  762 
of  small  occipital,  761 
of  brachial  plexus,  764 
buccal,  734 

of  facial,  744 
calcaneo-plantar,  795 
cardiac,  803 
inferior,  804 
middle,  803 
plexus,  deep,  806 
superficial,  806 
of  pneumogastric,  752 
superior,  803 
cavernous,  of  penis,  810 
cervical,  anterior,  760 
posterior,  759 
superficial,  762 
cervico-facial,  744 
chorda  tympani,  741 
ciliarv,  long,  729,  859 

sho'rt,  729 
circumflex,  769  / 

coccygeal,  789 
cochlear,  746 
communicans  hypoglossi,  763 

peronei,  796 
of  Cotunnins,  733 
cranial,  720 
crural  anterior,  786 
cutaneous.     See  that  heading. 
deep  palmar,  773 


INDEX. 


1241 


Nerves     or    nerve,    descriptive 
anatomy : 
deep  temporal,  734 
dental,  anterior  superior,  731 
inferior,  736 

middle  superior,  731 

posterior  superior,  730 
descendens  hypoglossi,  756 
digastric,  from  facial,  743 
digital,  795 

foot,  795 
dorsal  (hand),  776 

peculiar,  777 

of  penis,  793 

spinal,  777 
dorsi-lumbar,  781 
of  dura  mater,  640 
eighth  pair,  745 
eleventh  pair,  753 
of  eyeball,  721 
facial,  740 

femoral  cutaneous,  793 
fifth,  725 
fourth,  724 
frontal,  726 
ganglionic   branch    of   nasal, 

729 
gastric  branches  of  vagus,  808 
genito-crural,  783 
glosso- pharyngeal,  746 
gluteal,  inferior,  791 

superior,  791 
great  petrosal,  732 

splanchnic,  804 
gustatory,  735 
hemorrhoidal  inferior,  793 

of  heart.     See  Cardiac. 
hepatic,  808 
hypoglossal,  754 
ilio-hypogastric,  782 
ilio-inguinal,  783 
incisive,  736 
inferior  maxillary,  734 
inframaxillary,  of  facial,  744 
infraorbital,  of  facial,  744 
infratrochlear,  729 
intercostal,  777 
intercosto-humeral,  779 
interosseous,  anterior,  772 

posterior,  775 
ischiadic,  great,  793 

small,  791 
Jacobson's,  748 
labial,  731 
of  labyrinth,  866 
lachrymal,  726 
of  Lancisi,  659 
large  cavernous,  810 
laryngeal,  external,  751 

internal,  751 

recurrent,  751 

superior,  751 
lesser  splanchnic,  804 
lingual,  of  fifth,  735 

of  glosso-pharyngeal,  748 
long  ciliary,  729 

saphenous,  787 

thoracic,  768 
lumbar,  780 
lumbo-sacral,  781 
malar  branch  of  facial,  743 

of  orbital,  730 
masseteric,  734 
maxillary,  inferior,  734 

superior,  729 


Nerves     or    nerve,    descriptive 
anatomy : 
median,  771 
mental,  736 
middle  cardiac,  803 
motor    of    the  eye,  common, 
722 
external,  739 
musculo-cutaneous,  of  arm,  770 

of  leg,  796 
musculo-spiral,  774 
mylo-hyoid,  736 
nasal,  from  Meckel's  ganglion, 
731 

from  ophthalmic,  726 

from  Vidian,  733 
naso-palatine,  733 
ninth,  746 
obturator,  785 
occipital,  of  facial,  742 

great,  760 

small,  762 

of  third  cervical,  760 
oesophageal,  752 
olfactory,  720 
ophthalmic,  726 
optic,  721 

orbital    nerves    in    cavernous 
sinus,  739 

in  orbit,  739 

their  relation,  739 

in  sphenoidal  fissure,  739 

of  superior  maxillary,  729 
palatine,  anterior  or  large,  733 

external,  733 

posterior  or  small,  733 
palmar,  cutaneous,  of  median, 
772 
ulnar,  773 
palpebral,  731 
par  vagum,  749 
pars  intermedia,  740 
perforans  Casserii,  770 
perforating  cutaneous,  793 
perineal,  793 

superficial,  793 
peroneal,  796 
petrosal,  deep  large,  732 
small,  858 
superficial,  858 

long,  748 

superficial,  external,  or  large, 
732 
small,  748 
pharyngeal,  of  external  laryn- 
geal, 751 

of  glosso-pharyngeal,  748 

of  Meckel's  ganglion,  733 

of  pneumogastric,  751 

of  sympathetic,  801 
phrenic,  763 
plantar,  cutaneous,  795 

external,  795 

internal,  705 
pneumogastric,  749 
popliteal,  external,  796 

internal,  794 
portia  dura,  740 

mollis,  740 
posterior  auricular,  742 
pterygoid,  734 
pterygopalatine,  733 
pudendal,  inferior,  791 
pudic,  793 
pulmonary,  from  vagus,  752 


Nerves     or    nerve,    descriptive 
anatomy : 
radial,  775 
recurrent  laryngeal,  751 

to  tentorium,  l'1'i 
renal  splanchnic,  804 
respiratory,  external,  768 

internal,  7<i:j 
sacral,  788 

plexus,  790 
saphenous,   long   or    internal, 
787 

short  or  external,  794 
sciatic,  great,  793 

'if  second  cervical,  760 

small,  791 
short  ciliarv,  729 
sixth,  738 

small  cavernous,  810 
spinal,  756 

accessory,  753 
splanchnic,  great,  804 

small,  804 

smallest,  804 
stylo-hyoid  of  facial,  743 
suboccipital,  758 

posterior  branch  of,  759 
subscapular,  769 
superficialis  colli,  762 
superior  cardiac,  803 

maxillary,  729 
supra-acromial,  763 
supraclavicular,  763 
supramaxillary  of  facial,  744 
supra  orbital,  727 
suprascapular,  76S 
suprasternal,  762 
supratrochlear,  727 
temporal,  of    auriculotempo- 
ral, 735 

deep,  734 

of  facial,  743 
temporo-facial,  743 
temporo-malar,  730 
tenth,  749 

third,  or  motor  oculi,  722 
thoracic,  anterior,  769 

posterior,  76S 
thyro-hyoid,  756 
tibial,  anterior,  796 

posterior,  794 
of  tongue,  816 
tonsillar,  74S 

trifacial  or  trigeminus,  725 
trochlear,   724 
twelfth,  754 
tympanic,  of  facial,  742 

of   glosso-pharvngeal,    748, 
858 
ulnar,  772 
uterine,  810 
vaginal,  810 
vagus,  749 
vestibular.  745 
Vidian,  732 
of  "Wrisberg,  771 
Nervi-nervorum,  1119 
Nervous     centres,     development 
of,  1172 
tissue,  general  anatomy  of.  1113 

fibrous,  nervous  matter,  1115 

ganglia,  1125 

gelatinous  fibres,  1117 

gray     or     cineritious     sub- 
stance, 1113 


1242 


INDEX. 


Nervous  tissue, sympathetic,  1120 
chemical  composition  of, 
1118 
white  or  fibrous  substance, 
1115 
Nervus  cardiacus  magnus,  803 
minor,  804 

petrosus  profundus,  732 

superficialis  cordis,  803 
Nest  of  egg-tubes,  1037 
Neumann,    dentinal    sheath    of, 

876 
Neural  arch,  34: 

canal,  1156 

crest,  1179 

groove,  1155 
Neurenteric  canal,  1155,  1203 
Neurilemma,  1116,  1117 

of  cord,  784 
Neuroblasts,  1117,  1172 
Neuroglia,   1113 

of  cord,  713 
Neurokeratin,  1116 
Neuro-muscular  spindles,  1123 
Neuro-tendinous  spindles,  1123 
Nidus  avis  of  cerebellum,  688 
Ninth  nerve,  746 
Nipple,  1039 
Nissl's  granules,  1114 
Nodes  of  Ranvier,  1117 
Nodules  of  cerebellum,  688 
Non  -  mednllated    nerve  -  fibres, 

1117 
Nose,  818 

arteries  of,  822 

bones  of,  81    — -- 

cartilage  of  septum  of,  819 

cartilages  of,  818 

development  of,  1184 

fossa;  of,  115,  820 

mucous  membrane  of,  820 

muscles  of,  305 

nerves  of,  823 

surgical  anatomy  of,  823 

veins  of,  822 
Notch,  cotyloid,  177 

ethmoidal,   64,  78 

intercondyloid,  187 

nasal,  62 

sacro-sciatic,  greater,  175 
lesser,  175 

sigmoid,  99 

spheno-palatine,  93 

supra-orbital,  62 

suprascapular,  141 

supra-sternal,  336 
Notochord,  1156,  1166 
Nuchal    flexure    of    embryonic 

brain.  1176 
Nuck,  canal  of,  1047,  1212 
Nuclear  membrane,  1074 

substance,  1074 
Nucleated  sheath  of    Schwann, 

1116 
Nuclei,  accessory  olivary,  703 

auditory,  702 

of  auditorv  nerve,  684 

of  fifth  nerve,  683 

of  glosso-pharyngeal  and  vagus 
nerves,  702 

independent,  702 

pontis,  684 
Nucleoli,  1074 

pseudo-,  1074 

true,  1074 


Nucleo-proteid,  1078 
Nucleus,  ambiguus,  702 

amygdale,  664 

of  Bechterew,  745 

of  Deiters,  745 

caudatus,  662 

of  a  cell,  1074 

emboliformis,  693 

of  facial  nerve,  683 

fastigii,  693 

globosus,  693 

hypoglossal  nerve,  702 

lentis,  840 

lenticularis,  662 

of  olivary  body,  702 

of  optic  thalamus,  inner,  671 
outer,  671 

sixth  nerve,  683 

spinal  accessory  nerve,  702 

superior  olivary,  683 

of  the  tegmentum,  674 

vagi,  749 
Nutrient  artery  of  bone,  1097 
Nutritive  fluid's,  1077 
Nymphse,  1026 

lymphatics  of,  634 

o. 

Obelion,  103 
Obex,  698 

Oblique  inguinal  hernia,  1049 
coverings  of,  1050 
ligament,  259 
line  of  the  clavicle,  135 

of  the  fibula,  197 

of  lower  jaw,  97 

of  radius,  156 
ridge  of  ulna,  154 
Obliquus  auriculae  muscle,  850 
externus  abdominis,  357 
inferior  capitis,  348 

oculi,  304 
internus  abdominis,  359 
superior  capitis,  348 

oculi,  304 
Obturator  artery,  564 

peculiarities  of,  565 

relation  of,  to  femoral  ring, 
1060 
externus  muscle,  430 
fascia,  1071 
foramen,  177 
internus  muscle,  429 
ligament  or  membrane,  429 
membrane,  429 
nerve,  785 

accessory,  786 

surgical  anatomy  of,  797 
veins,  617 
Occipital  artery,  493 
bone,  55 

articulations  of,  59 

attachment  of  muscles  to,  59 

development  of,  58 
crests,  56,  57 

protuberances,  56,  57 
fossae,  56 
lobe,  646 

lymphatic  glands,  625 
groove,  67 
sinus,  603 
triangle,  501 
vein,  597 
Occipitalis  muscle,  299 


Occipitalis  nerve,  major,  760 

minor,  762 
Occipito-atlantal        articulation, 

229 
Occipito-axial  articulation,  230 
Occipito-frontalis  muscle,  298 
Occiput,  arteries  of,  493 
Odontoblasts,  874 
Odontoclasts,  882 
Odontoid  ligaments,  230 
tubercle  for,  57 
process  of  axis,  38 
Oesophageal  arteries,  547 
branches  of  vagus  nerve,  752 
glands,  892 

opening  of  diaphragm,  354 
plexus,  752 
CEsophagus,  891 
lymphatics  of,  637 
structure  of,  892 
surgical  anatomy  of,  893 
Olecranon  fossa,  147 
process,  150 
fracture  of,  413 
Olfactorv  bulb,  654,  720 
cells,  821 
fasciculus,  665 
foramina,  79 
fossae,  foetal,  1184 
hair,  822 
lobe,  654 
lobule,  anterior,  654 

posterior,  654 
nerve,  720 

surgical  anatomy  of,  721 
sulcus,  649 
Olivary   bodies   of  medulla  ob- 
longata, 695,  699 
nuclei,  accessory,  703 
nucleus,  702 
peduncle,  703 
process,  73 
Omenta,  901 
Omental  tuberosity  of  liver,  934 

of  pancreas,  946 
Omentum,  gastro-colic,  902 
gastro-hepatic,  901 
gastro-splenic,  902 
great,  902 
lesser,  901 
Omo-hyoid  muscle,  320 
Omphalo-mesenteric  arteries,  foe- 
tal, 1189 
duct,  1158 
veins,  1189 
vessels,  1158 
Opening  of  aorta  in  left  ventricle, 
466 
aortic,  in  diaphragm,  353 
canal,  in  diaphragm,  353 
of  coronary  sinus,  462 
of  inferior  cava,  462 
left  auriculo-ventricular,  466 
oesophageal,  in  diaphragm, 354 
of  pulmonary  artery,  463 

veins,  465 
right      auriculo  -  ventricular, 

466 
saphenous,  419,  1056 
superior  cava,  464 
Operations :  amputations  of  foot, 
213 
of  penis,  1014 
arteries,  ligature  of,  abdominal 
aorta,  550 


INDEX. 


1243 


Operations :    arteries,    axillary, 
531 
brachial,  536 
carotid,  common,  485 
external.  487 
internal,  505 
femoral,  575 
iliac,  common,  560 
external,  570 
internal,  562 
innominate,  481 
lingual,  489 
popliteal,  582 
radial,  539 
subclavian,  518 
thyroid,  inferior,  524 
tibial,  anterior,  586 

posterior,  589 
ulnar,  542 
catheterism     of     Eustachian 

tube,  868 
cholecystotomy,  945 
for  cleft  palate,  332 
colotomy,  932 

division  of  nerves,  facial,  744 
infraorbital,  738 
lingual,  738 
sciatic,  great,  798 
spinal  accessory,  753 
supra-orbital,  738 
excision  of  ankle,  286 
elbow,  258 
hip,  273 
knee,  281 
of  shoulder,  254 
extirpation  of  spleen,  954 

of  thyroid,  981 
gastrostomy,  911 
gastrotomy,  91 1 
hamstring    tendons,    division 

of,  434 
laryngotomy,  968 
lithotomy,  1068 
nephrotomy  and  nephrectomy, 

994 
cesophagotomy,  893 
paracentesis   of   pericardium, 

460 
prostatectomy,  1011 
puncture  of  the  bladder,  1005 
removal  of  the  clavicle,  138 
lower  jaw,  122 
scapula,  143 
testis,  1021 
tongue,  327,  817 
upper  jaw,  122 
for  strabismus,  306 
tapping  chest,  134 
for  torticollis,  319 
tracheotomy,  968 
venesection,  608 
Opercula  of  the  insula,  652 
Ophthalmic  artery,  505 
ganglion,  729 
nerve,  726 
vein,  604 
inferior,  604 
Opponens  minimi  digiti  muscle, 
foot,  447 
hand,  406 
pollicis  muscle,  404 
Optic  commissure,  721 
cup,  1181 
foramen,  73,  105 
groove,  73,  105 


Optic  lobes,  675 
nerve,  721 

surgical  anatomy  of,  722 
radiations  or  posterior  stalk  of 

optic  thalamus,  672 
recess,  670 
thalamus,  671 

anterior  tubercle  of,  671 
inner  nucleus  of,  671 
outer  nucleus  of,  671 
posterior  tubercle  of,  671 
stalk  of,  672 
tract,  271 

vesicle,  primitive,  1180 
secondary,  1181 
Ora  serrata,  832 
Oral  cavity,  869 
pit,  1171 
sinus,  1169 
Orbicular  bone,  857 

ligament,  259 
Orbicularis  ciliaris,  301 
latus,  301 
oris  muscle,  308 
palpebrarum,  301 
Orbi cuius  ciliaris,  829 
Orbit,  113 

arteries  of,  506 
muscles  of,  303 
relation  of  nerves  in,  739 
Orbital  fascia,  305 
foramina,  75 
lobe,  649 
nerve,  730 
process  of  malar,  90 

of  palate,  93 
sulcus,  649 
Organic  constituent  of  bone,  1101 
Organs  of  Giraldes,  102,  1211 
of  Golgi,  1123 
of  Jacobson,  820 
of  Eosenmuller,  1038,  1210 
Orifice,  cardiac,  of  stomach,  906 

pyloric,  of  stomach,  906 
Origin  of  muscles,  296 
Os  acetabuli,  178 
calcis,  199 

development  of,  211 
cordis,  468 
hyoids,  123 
innominatum,  171 

development  of,  177 
magnum  of  carpus,  164 
orbiculare,  857 
planum,  79 
pubis,  176 
trigonum,  204 
uteri,  1029 
Ossa  triquetra,  81 

unguis,  88 
Ossicula  auditus,  856 
ligaments  of,  857 
Ossification  of  bone,  1102 
defects  in,  54 
intracartilaginous,  1102 
intramembranous,  1102 
of  spine,  progress  in,  45 
subperiosteal,  1106 
Osteoblasts,  1096,  1104 
Osteoclasts,  1097,  1104 
Osteogenetic  fibres,  1102 
Osteology,  33 

Ostium  abdominale  of  Fallopian 
tube,  1034 
internum  or  uterinum,  1031 


Ostium  primum,   1190 

secundum,  1 190 
Otic  ganglion,  736 

vesicle,  1183 
Otoliths,  863 
Outlet  of  pelvis,  180 
Ovarian  arteries,  557 
plexus  of  nerves,  808 
veins,  618 
Ovary,  1035 

development  of.  1209 
Graafian  vesicles  of,  1036 
ligament  of,  1038 
lymphatics  of,  634 
nerves  of,  1038 
ovicapsule  of,  1037 
shape,    position,    and    dimen- 
sions, 1035 
stroma  of,  1036 
tunica  albuginea,  1036 
vessels  of,  1038 
Ovicapsule  of  Graafian  follicles, 

1037 
Oviducts,  1034 
Ovisacs  of  ovary,  1036 
Ovula  of  Naboth,  1032 
Ovum,  1073,  1149 
discharge  of,  1028 
discus  proligerus  of,  1149 
early  changes  in,  1150 
fertilization  of,  1151 
germinal  spot  of,  1149 

vesicle  of,  1149 
vitelline  membrane  of,  1149 
yolk  of,  1149 
zona  pellucida  of,  1149 
Oxyntic  cells  of  peptic  glands, 
910 
glands,  cardiac,  910 
pyloric,  910 

P. 

Pacchionian  depressions,  60 

glands,  602,  639,  642 
Pacinian  corpuscles,  1122 
Pad  of  corpus  callosum,  759 
Palatal  glands,  883 
Palate,  arches  of,  883 
bone,  91 

articulations  of,  94 
attachment  of  muscles  to,  91 
development  of.  93 
horizontal  plate  of,  91 
orbital  process  of,  93 
process  of  superior  maxil- 
lary, 87 
sphenoidal  process  of,  93 
turbinated  crest  of,  92 
vertical  plate  of,  92 
development  of,  1170 
hard,  883 
muscles  of,  329 
soft.  883 
Palatine  aponeurosis,  330 
artery,  ascending,  491 

descending  or  posterior,  499 
canal,  accessory,  91 
anterior,  87 
posterior,  91 
fossa,  anterior,  87 
nerves,  773 
process  of  superior  maxil'arv, 

87 
veins,  inferior,  596 


1244 


INDEX. 


Palato-glossus  muscle,  325,  331 
Palato-pharyngeus,  33l 
Palmar  arch,  deep,  538 
superficial,  544 
surface-marking  of,  545 

cutaneous  nerve,  772,  773 

fascia,  402 

interossei  arteries,  541 

nerve,  deep,  of  ulnar,  773 
superficial,  of  ulnar,  773 

veins,  607 
Palmaris  brevis  muscle,  406 

longus  muscle,  391 
Palpebral,  843 
Palpebral  arteries,  508 
external,  506 

cartilages  or  plates,  844 

fissures,  843 

surface  form  of,  847 

folds  of  conjunctiva,  845 

ligaments,  844 

muscles,  301 

veins,  inferior,  596 
superior,  596 
Pampiniform    plexus   of  veins, 

618,  1016,  1038 
Pancreas,  945 

development  of,  1205 

lymphatics  of,  635 

structure  of,  948 

surface  form  of,  948 

surfaces  of,  948 

surgical  anatomy  of,  948 

vessels  and  nerves  of,  948 
Pancreatic  arteries,  554 

duct,  947 

plexus  of  nerves,  808 

veins,  619 
Pancreatica  magna  artery,  553 
Pancreatico-duodenal  artery,  in- 
ferior, 554 
superior,  553 

plexus  of  nerves,  808 

vein.  619 
Pap  I  'is,  846 

spiralis,  864 
Papi '.  *  filiformes,  813 

■  Use),  813 

of  kidney ,  987 

^laximse  (circumvallatse),  813 

of  skin,  1139 

of  teeth,  878,  880 

of  tongue,  813 
Papillary  layer  of  skin,  1138 
Paracentral  gyrus,  650 
Parachordal  cartilage,  1167 
Parallel  sulcus,  652 
Paramastoid  process,  56 
Paranucleus,  948 
Parathyroids,  981 
Paraxial  mesoblast,  1156 
Paries  carotica,  854 

jugularis,  853 

labyrinthica,  853 

mastoidea,  854 

tegmentalis,  853 
Parietal  bones,  59 

articulations  of,  61 
attachment  of  muscles  to,  61 
development  of,  61 

cells  of  gastric  glands,  910 

eminence,  60 

foramen,  60 

lobe,  646 

veins,  1195 


Parieto-colic  fold,  904 
Parieto-occipital  fissure,  646 
Parieto-temporal  artery,  512 
Paroophoron  of  Waldeyer,  1038 
Parotid  duct,  885 

fascia,  310,  315 

gland,  884 

accessory  portion  of,  886 
nerves  of,  886 
vessels  of,  886 

lymphatic  glands,  625 

veins,  596 
Parovarium,  1038,  1208 
Par  vagum,  749 
Pars  basalis,  649 

ciliaris  retinas,  832 

externa,   interna  et  media  of 
auditory  canal  851 

intermedia  of  Wrisberg,  740 

iridica  retinae,  831 

laryngea,  890 

nasalis,  890 

oralis,  890 

orbitalis,  649 

triangularis,  649 
Patella,  191 

articulations  of,  192 

attachment  of  muscles  to,  192 

development  of,  192 

fracture  of,  452 

surface  form  of,  192 

surgical  anatomy  of,  192 
Patellar  ligament,  274 
Pecquet,  reservoir  of,  624 
Pectineus  muscle,  424 
Pectiniform  septum,  1012 
Pectoral  region,  dissection  of,  376 
Pectoralis  major,  378 

minor,  379 
Peculiar  dorsal  vertebrae,  41 
Pedicles  of  a  vertebra,  34 
Peduncles  of  cerebellum,  689 

of  cerebrum,  658,  673 

of  corpus  callosum,  656 

of  pineal  gland,  673 
Peduncular  fibres  of  cerebellum, 
689 
of  cerebrum,  677 
Pedun  cuius  conarii,  672 
Pelvic  fascia,  1070 

parietal  or  obturator  layer, 

1071 
visceral  laver,  1071 

girdle,  134 

plexus,  809 
Pelvis,  179,  998 

arteries  of,  561 

articulations  of,  241 

axes  of,  181 

boundaries  of,  179 

brim  of,  179 

cavity  of,  180 

diameters  of,  181 

false,  179 

in  foetus,  182 

inlet  of,  180 

of  kidney,  986 

ligaments  of,  241 

lymphatics  of,  632 

male  and    female,  differences 
of,  181 

outlet  of,  1 80 

position  of,  181 

of  viscera,  at  outlet  of,  1067 

true,  179 


Pelvis,  surface  form  of,  182 

surgical  anatomy  of,  183 
Penis,  1011 

arteries  of,  1013 

body  of,  1012 

corpora  cavernosa,  1012 

corpus  spongiosum,  1013 

development  of,  1215 

dorsal  artery  of,  567 
nerve  of,  793 
vein  of,  617 

lymphatics  of,  633,  1014 

muscles  of,  372 

nerves  of,  1014 

prepuce  of,  1012 

root  of,  1011 

surgical  anatomy  of,  1014 

suspensory  ligament,  1011 
Penniform  muscle,  295 
Perforans  Casserii  nerve,  770 
Perforated  space,  anterior,  655 

posterior,  657 
Perforating  arteries  of  hand,  541 
from  mammary  artery,  526 
from  plantar,  591 
from  profunda,  579 

cutaneous  nerve,  793 
Pericecal  fossae,  904 
Pericardiac  arteries,  526,  547 
Pericardium,  diverticula  of,  458 

fibrous  layer  of,  459 

nerves  of,  459 

relations  of,  457 

serous  layer  of,  459 

structure  of,  458 

transverse  sinus  of,  459 

vessels  of,  459 

vestigial  fold  of,  459 
Perichondrium,  1093,  1104 
Perichoroidal  lymph-space,  825 
Perilymph,  866 
Perimysium,  1107    , 
Perineal  artery,  superficial,  567 
transverse,  567 

fascia,  deep,  373,  1066 
superficial,  370 

nerve,  793 
cutaneous,  791 
superficial,  793 
Perineum,  abnormal    course   of 
arteries  in,  1070 

deep  boundaries  of,  1064 

development  of,  1213 

in  the  female,  1069 

lymphatics  of,  633 

in  the  male,  1064 

muscles  of,  367 

surgical  anatomy  of,  1063 
Perineurium,  1119 
Periosteum,  1096 

internal,  1096 

of  teeth,  871 
Peri  otic  cartilage,  1167 
Peripheral  termination  of  nerves, 

1120 
Perisclerotic  lymph-spaces,  824 
Peritoneum,  lesser  sac  of,  899 

ligaments  of,  901 

mesenteries  of,  902 

omenta  of,  901 

reflections  traced,  900 
Perivascular     lymphatics,     601, 

1133 
Perivitelline  fluid,  1150 
Permanent  cartilage,  1092 


INDEX. 


1245 


Perm;  lent  teeth,  871 

Peron  »90 

an 

pe     Lia  ',  590 

nervi 
tuber 
veins, 
Peroneus  brevis  muscle,  441 
longus  muscle,  440 
tertius  muscle,  435 
#  Perpendicular  line  of  ulna,  154 

plate  of  ethmoid,  78 
Pes  accessorius,.662 
anserinus,  741 
of  crus  cerebri,  673 
hippocampi,  665 
Petit,  canal  of,  840 

triangle  of,  357 
Petro-mastoid    portion   of    tem- 
poral bone,  71 
Petro-occipital  suture,  102 
Petro-sphenoidal  suture,  102 
Petro-squamous  sinus,  603 
Petrosal  nerve,  deep  large,  from 
Vidian,  732 
small,  858 
small  superficial,  858 
superficial  large,  732 
process,  73 
sinus,  inferior,  605 
superior,  604 
Petrous  ganglion,  748 

portion  of  temporal  bone,  68 
Peyer's  glands,  919 
Phalanges  of  cochlea,  866 
of  hand,  169 

articulations  of,  169,  268 
development  of,  169 
of  foot,  210 

articulations  of,  211,  293 
development  of,  211 
Pharyngeal  aponeurosis,  890 
artery,  ascending,  494 
glands,  890 

nerve,    from   external    laryn- 
geal, 751 
from  glosso-pharyngeal,  748 
from     Meckel's     ganglion, 

733 
from  sympathetic,  801 
from  vagus,  751 
plexus  of  nerves,  751,  801 
septum,  1171     , 
spine,  57 
tonsil,  890 
vein,  598 
Pharyngo-glossus  muscle,  325 
Pharynx,  889 

aponeurosis  of,  890 
arteries  of,  494 
development  of,  1198 
mucous  membrane  of,  890 
muscles  of,  327 
surgical  anatomy  of,  891 
Phleboliths,  617 
Phrenic  arteries,  551 
nerve,  763 

plexus  of  nerves,  808 
veins,  619 
Phrenico-costal  sinus,  971 
Phreno-colic  ligament,  902 
Pia  mater  of  brain,  642 

of  cord,  709 
Pigment,  1092 
cells,  1087 


Pigment  of  iris,  832 

of  skin,  1138 
Pigmentary    layer     of     retin 

837 
Pillars  of  diaphragm,  352 

of  external   abdominal    rinj 
358,  1043 

of  fauces,  883 
Pineal  eye  of  lizards,  673 

glands*',  672 

peduncles  of,  673 

recess,  671 
Pinna  of  ear,  848 
ligaments  of,  849 
muscles  of,  850 
nerves  of,  850 
vessels  of,  850 
Pisiform  bone,  162 
Piso-m'etacarpal  ligament,  264 
Piso-uncinate  ligament,  264 
Pit  of  stomach,  133 
Pituitary  body,  656 

development  of,  1178 

fossa,  73 

membrane,  820 
Pivot-joint,  220 
Placenta,  1164 

circulation  through,  1164 

formation  of,  1163 

separation  of,  1165 
Placental  circulation,  1189 
Plain  muscle,  1112 
Plantar  arch,  591 

artery,  external,  591 
internal,  591 

fascia,  443 

ligaments,  288 

nerve,  external,  795 
internal,  795 

veins,  external,  615 
internal.  615 
Plantaris  muscle,  437 
Plasma,  1077,  1080 

cells,  1087 
Plasmodioblast,  1153 
Platelets  of  blood,  1080 
Plates,  tarsal,  843 
Platysma  myoides,  314 
Pleura,  969 

cavity  of,  969 

costalis,  969 

pulmonalis,  969 

reflections  of,  traced,  969 

surgical  anatomy  of,  971 

vessels  and  nerves  of,  971 
Pleuro-peritoneal  cavity,  1157 
Plexus  of  nerves,  1119 

aortic,  809 

brachial,  764 

cardiac,  deep,  806 
superficial,  806 

carotid,  801 
external,  801 

cavernous,  801 

cervical,  761 
posterior,  762 

cceliac,  808 

of  cornea,  intra-epitlu 
sub-epithelial,  827 

coronary,  anterior,  806 
posterior,  S06 

cystic,  808 

diaphragmatic,  808 

epigastric  or  solar,  80'  • 

facial,  801 


Plexus,  gastric,  808 
gastro-duodenal,  SOS 

gastro-epiploic,  808 
left,  808 

great  cardiac,  806 

hemorrhoidal,  inferior,  809 
superior,  809 

hepatic,  808 

hypogastric,  809 
inferior,  809 

ileo-colic,  809 

infraorbital,  731 

lumbar,  781 

magnus  profundus,  806 

mesenteric,  inferior,  809 
superior,  809 

oesophageal,  752 

ovarian,  808 

pancreatic,  808 

pancreatieo  duodenal,  808 

patella?,  787 

pharyngeal,  751,  801 

phrenic,  808 

prostatic,  809 

pulmonary,  anterior,  752 
posterior,  752 

pvloric,  808 

renal,  808 

sacral,  788 

sigmoid,  809 

solar,  806 

spermatic,  808 

splenic,  808 

superficial  cardiac,  S06 

suprarenal,  808 

tonsillar,  74S 

tympanic,  858 

uterine,  810 

vaginal,  810 

of  veins.     See  Veins. 

vertebral,  804 

vesical,  809 
Plica  epigastrica.  1048 

fimbriata,  81 1 

gubernatrix,  1211 

hypogastrica,  1048 

salpingo-palatina,  890 

salpino'o-pharvngea,  890 

semilunaris,   845 

triangularis,  884 

uracil  i,  1047 

vascularis,  1211 
Pneumogastric  nerve,  749 
Polar     bodies    or    globules    o 

Robin,  1150 
Pom um  Adami,  955 
Pons,  hepatis,  936 

Tarina,  657 

Varolii.  681 
Pontal     flexure    of    embryoni 
brain,  1176 

mticulus  of  Arnold,  694 
.    ipliteal  artery,  581 
branches  of,  583 
peculiarities  of,  582 
surface-marking  of,  582 
surgical  anatomy  of,  581 
unusual  branches,  582 

lymphatic  glands,  O.'il 

nerve,  external,  796 

Burgical  anatomy  of,  797 
internal,  794 

notch,  193 

space,  581 

surface  cf  femur,  186 


1246 


INDEX. 


Popliteal  vein,  615 
Popliteus  muscle,  438 
Pores  of  the  skin,  1142 
Portal  canals,  938 

fissure,  936 

vein,  621,  938,  940 
Portio  dura  of  seventh  nerve,  740 

mollis  or  auditory  nerve,  740 
Porus  opticus  of  sclerotic,  833 
Post-central  fissure,  686 
Post-central  sulcus,  650 
Post-clival  fissure,  686 
Posterior.     See  under  each  sepa- 
rate head. 

choroid  artery,  523 

crescentic  lobe,  685 

glenoid  process,  73 

inferior  lobe,  689 

internal  frontal  artery,  511 

nerve  roots,  717 

superior  lobe,  685 

vesicular  column,  717 
Postero-lateral    ganglionic  arte- 
ries, 523 
Postero-median    ganglionic    ar- 
teries, 523 
Post-glenoid  process,  65 
Post-gracile  fissure,  687 
Post-limbic  fissure,  647 
Post-nodular  fissure,  688 
Post-patellar  bursa,  423 
Post-pyramidal  fissure,  688 
Pott's  fracture,  453 
Pouch  of  Douglas,  1029 

of  Prussak,  858 

of  Rathke,  1171 
Pouches,  laryngeal,  961 
Poupart's  ligament,    359,   1044, 

1057 
Pre-central  fissure,  686 

sulcus,  648 
Prechordal  cartilages,  1167 
Pre-clival  fissure,  686 
Precuneus  of  lobe  of  brain,  651 
Prepatellar  bursa,  423 
Prepuce,  1012 

of  clitoris,  1026 
Pre-occipital  notch,  646 
Pre-pyramidal  fissure,  688 
Presternal  notch,  124 
Presternum,  124 
Prevertebral  fascia,  317 
Prickle  cells,  1085,  1137 
Primary  areolae  of  bone,  1103 

cerebral  vesicles,  1166 
Primitive  amniotic  cavity,  1154 

aorta,  1191 

aortic  arches,  1192 

fibrillae  of  Schultze,  1116 

groove,  1154 

jugular  veins,  1195 

optic  vesicle,  1180 

otic  vesicle,  1183 

sheath  of  nerve-fibre,  1116 

streak,  1154,  1155 
Primordial  cranium,  1165 

ova,  1037 
Princeps  cervicis  artery,  493 

pollicis  artery,  541 
Processes  or  process  :  acromion, 
140 

alveolar,  86 

angular,  external,  62 
internal,  62 

basilar,  56 


Process  or  process  :  ciliary,  829 
c.inoid,  anterior,  75 
middle,  73 
posterior,  73 
cochleariform,  71,  854 
condyloid,  of  lower  jaw,  99 
coracoid,  141 
coronoid,  of  lower  jaw,  99 

of  ulna,  150 
costal,  36 

ethmoidal,  of    inferior   turbi- 
nated, 95 
frontal,  of  malar,  90 
hamular,  of  lachrymal,  88 

of  sphenoid,  76 
of  Ingrassias,  75 
jugular,  56 

lachrymal,    of  inferior   turbi- 
nated bone,  95 
malar,  85 
of  malar  bone,  89 
mammillary,  42 
mastoid,  67 

maxillary,   of  inferior   turbi- 
nated, 95 
mental,  97 
nasal,  86 

odontoid,  of  axis,  38 
olecranon,  150 
olivary,  73 
orbital,  of  malar,  90 

of  palate,  93 
palate,  of  superior  maxillary, 

86 
post-glenoid,  65 
pterygoid,  of  palate  bone,  92 

of  sphenoid,  75 
sphenoidal,  of  palate,  93 
spinous,  of  ilium,  174 
of  sphenoid,  74 
of  tibia,  192 
styloid,  of  radius,  156 
of  temporal,  70 
of  ulna,  154 
unciform,  165 

of  ethmoid,  79 
vaginal,  of  sphenoid,  74 

of  temporal,  70 
vermiform,  of  cerebellum,  in- 
ferior, 686 
superior,  685 
zygomatic,  90 
Processus  brevis  of  malleus,  856 
cochleariformis,  71,  854 
globularis,  1169 
gracilis  of  malleus,  856 
sphenoidalis,   819 
Proctodeum,  1203 
Profunda  cervicis  artery,  527 
femoris  artery,  578 
inferior  artery  of  arm,  537 
superior  artery  of  arm,  537 
vein,  616 
Promontory  of  sacrum,  46 

of  tympanum,  854 
Pronator  quadratus  muscle,  394 
radii  teres  muscle,  390 
ridge,  154 
Pronephros,  1208 
Pronucleus,  female,  1150 

male,  1151 
Prophase  of  karyokinesis,  1075 
Prosencephalon,  643,  1173 
Prostate  gland,    1009 

levator  muscle  of,  369,  1010 


Prostate  gland,  lobes  of,  1010 
lymphatics  of,   634 
'  surgical  anatomy  of,  1011 
vessels  and  nerves  of,  1010 
Prostatic  plexus  of  nerves,  809 
of  veins,  617 
portion  of  urethra,  1005 
sinus,  1005 
Prothrombin,  1081 
Protoplasm,  1073 
Proto  vertebra?,  1156,  1165 
Protuberance,    occipital,   exter- 
nal, 56 
internal,  57 
Pseudo-nucleoli,  1074 
Pseudopodium,  1079 
Pseudostomata  of    serous  mem- 
branes, 1144 
Psoas  magnus  muscle,  416 

surgical  anatomy  of,  417 
parvus,  417 
Pterion  ossicle,  81 
Pterygoid  arteries,  498 
fossa  of  jaw,  99 

of  sphenoid,  75 
muscles,  312 
nerve,  735 
notch,  75 

plexus  of  veins,  596 
process  of  palate  bone,  92 
processes  of  sphenoid,  75 
ridge,  74 
tubercle,  76 
Pterygo-maxillary  fissure,  112 

ligament,  309 
Pterygopalatine  artery,  499 
canal,  74 
nerve,  733 
Pubic  arch,  180 

articulations  of,  244 
portion  of  fascia  lata,  420 
Pubis,  angle  of,  176 
crest  of,  176 
os,  176 
spine  of,  176 
symphysis  of,  176,  244 
Pubo-femoral  ligament,  269 
Pubo-prostatic  ligaments,  1002, 

1010 
Pudendum,  1025 
Pudic  artery,  accessory,  566 
deep,  external,  578 
internal,  565 
in  female,  567 
in  male,  565 

peculiarities  of,  506 
superficial  external,  578 
nerve,  793 
vein,  614 
internal,  616 
Pulmonary  artery,  475,  976 

opening  of,    in    right   ven- 
tricle, 463 
capillaries,  976 
nerve  from  vagus,  752 
sinuses,  465 
veins,  593,  594.  976 

openings    of,     left    auricle, 
465 
Pulp-cavity  of  tooth,  874 
enamel,  879 
formative,  880 
permanent,  880 
of  spleen,  951 
of  teeth,  development  of,  882 


INDEX. 


1247 


Pulvinar  of  optic  thalamus,  671 
Puncta  lachrymalia,  846 

vasculosa,  659 
Pupil  of  eye,  831 

membrane  of,  832 
Purkinje,  axis-cylinder  of,  1116 

corpuscles  of,  692 
Putamen,  663 
Pyloric  artery,  552 
inferior,  552 

glands,  910 

plexus,  808 
Pylorus,  906 
Pyramid  of  cerebellum,  689 

of  thyroid  gland,  979 

of  tympanum,  854 
Pyramidal  cell  of  cerebral   cor- 
tex, 679 

decussation,  superior,  719 
Pyramidalis  muscle,  364 

nasi,  307 
Pyramids  of  Ferrein,  989 

of  Malpighi,  987 

of  medulla,  694 
decussation  of,  695 

of  the  spine,  52 
Pyriformis  muscle,  428 

Q. 

Quadrate  lobe,  651 
Quadratus  femoris  muscle,  430 
lumborum,  367 

fascia  covering,  367 
menti,  308 
Quadriceps  extensor  cruris  mus- 
cle, 421 
•Quadrigeminal  bodies,  675 

R. 

Racemose  glands,  1146 
Radial  artery,  538 
branches  of,  539 
peculiarities  of,  539 
surface  marking  of,  539 
surgical  anatomy  of,  539 
fossa,  147 

lymphatic  glands,  628 
nerve,  775 
recurrent  artery,  539 
region,  muscles  of,  395 
vein,  607 
Radialis  indicis  artery,  541 
Radio-carpal  articulation,  262 
surface  form  of,  263 
surgical  anatomy  of,  263 
Radio-ulnar   articulations,    infe- 
rior, 260 
middle,  259 
superior,  259 
region,   muscles   of,   anterior, 
390 
posterior,  396 
Radius,  155 

articulations  of,  157 
development  of,  157 
fracture  of,  413 
grooves  in  lower  end  of,  157 
muscles  attached  to,  157 
oblique  line  of,  156° 
sigmoid  cavity  of,  156 
surface  form  of,  157 
surgical  anatomy  of,  157 
tuberosity  of,  155 


Radius  and  ulna,  fractti 

Rami  of  the  lower  jaw, 

Ramus  of  ischium,  176 

of  os  pubis,  176 

ascending,  176 

descending,  177 

Ranine  artery,  489 

vein,  598 
Ranvier,  nodes  of,  1117 
Raphe  of  corpus  callosum,  659 
of  medulla,  702 
of  palate,  883 
of  perineum,  1064 
of  scrotum,  1015 
of  tongue,  811 
Rathke,  investing  mass  of,  1167 

pouch  of,  1171 
Receiving  tubes  of  kidney,  989 
Receptaculi  arterke,  505 
Receptaculum  chyli.  624 
Recess,  optic,  670 

pineal,  671 
Recessus  labyrinthi,  1183 

sphericus,  860 
Reciprocal    reception,    articula- 
tion by,  220 
Recto-coccygeus  muscle,  928 
Recto-uterine  ligaments,  1029 
Recto-vesical  fascia,   1071 

fold,  peritoneal,  1002 
Rectum,  925 
development  of,  1200 
folds  of,  929 
lymphatics  of,  636 
relations  of,  female,  927 

male,  927 
surgical  anatomy  of,  930 
Rectus  abdominis,  362 
capitis  anticus  major,  332 
minor,  332 
lateralis,  333 
femoris  muscle,  421 

surgical  anatomy  of,  423 
oculi,  internus,  superior,  infe- 
rior, and  externus,  304 
posticus  major,  347 
minor,  348 
Recurrent    artery,    interosseous, 
544 
radial,  539 
tibial,  anterior,  586 

posterior,  586 
ulnar,  anterior,  543 
posterior,  543 
laryngeal  nerve,  751 
nerves  to  tentorium,  726 
Red  corpuscles,  1078 

nucleus,  675 
Region  of  abdomen,  895 
muscles  of,  356 
acromial,  muscles  of,  382 
auricular,  300 
of  back,  m  uscles  of,  336 
cervical    superficial,    muscles 

of,  314 
cranial,  298 
epigastric,  896 
femi  s  of,  anterior, 

irrtt  !."» 

■•  rior,  432 
fibu 
of  fo  it,  dorsum  of,  444   ■ 

si  1  ■  of,  444 
glu>  ;  of,  426 


'•'egion  of  groin,  1053 
of  hand,  muscles  of,  400 
humeral,  anterior,  386 

posterior,  388 
hypochondriac,  8% 
hypogastric,  896 
iliac,  muscles  of,  415 
infrahyoid,  319 
inguinal,  896,  1041 
intermaxillary,     muscles     of, 

308 
ischio-rectal,  1063 
laryngo-trac-heal, surgical  anat- 
omy of,  896 
lingual,  muscles  of,  323 
lumbar,  896 

maxillarv,  muscles  of,  inferior, 
308 
superior,  307 
nasal,  muscles  of,  306 
orbital,  muscles  of,  303 
palatal,  muscles  of,  329 
palmar,  400 
palpebral,  301 
perineum,  1056 
pharyngeal,  muscles  of,  327 
popliteal,  581 
pterygo-mandibular,     muscles 

of,  312 
radial,  muscles  of,  395 
radio-ulnar,  anterior,  muscles 
of,  390 
posterior,  muscles  of,  396 
scapular,  muscles  of,  anterior. 
383 
posterior,  384 
Scarpa's  triangle,  572 
suprahyoid,  muscles  of,  321 
temporo-mandibular,    muscles 

of,  310 
thoracic,  350 
anterior,  377 
lateral,  381 
tibio-fibular,  anterior,  434 

posterior,  436 
ulnar,  of  hand,  406 
umbilical,  896 

vertebral,  muscles  of,  anterior, 
332 
lateral,  334 
Reil,  island  of,  652 
Kemak,  fibres  of,  1117 
Penal  afferent  vessels,  988,  992 
artery,  556,  992 
efferent  vessels,  9S8,  992 
plexus,  808 
veins,  619,  992 
Reservoir  of  Pecquet,  624 
Respiration,  muscles  of,  355 

organs  of,  955 
Respiratory  nerves  of  Bell,  ex- 
ternal, 768 
internal,  763 
organs,  development  of,  1206 
Restiform  bodies  of  medulla  ob- 
longata, 696 
Rete  mucosum  of  skin,  1136 

testis,  1020 
Recticuhu  layer  of  skin,  1138 

lamina  of  Kolliker,  866 
Reticulin,  1090 

Retiform  connective  tissue,  1090 
Retina,  832 

arteria  centralis  of,  509,  S39 
fovea  centralis  of,  833 


1248 


INDEX. 


Retina,  membrana,  layers  of,  833, 
834,  835 
limitans  externa,  835 
interna,  833 

structure  of,  833 
Retinacula  of  capsular  ligament 
of  hip,  268 

of  ileo-caecal  valve,  923 
Retrahens  auriculam  muscle,  301 
Retro-peritoneal  fossae,  903 
Retro-pharyngeal  space,  316 
Rhinencephalon,  1180 
Rhodopsin,  or  visual  purple,  832 
Rhomboid  impression,  136 

ligament,  246 

lip,  1178 
Rhomboideus  major,  340 

minor,  340 
Ribes,  ganglion  of,  798 
Ribs,  128 

angle  of,  129 

articulations  of,  234 

attachment  of  muscles  to,  131 

development  of,  131,  1166 

false,  128 

floating,  128 

head  of,  129 

ligaments  of,  234,  235 

neck  of,  129 

peculiar,  131 

true,  128 

tuberosity  of,  129 
Ridge,  mylo-hyoidean,  97 

superciliary,  61 

temporal.  65,  111 

terminal  occipital,  57 
Rima  glottidis,  959 
Ring,  abdominal,  external,  357, 
1043 
internal,  1047 

femoral  or  crural,  1060 

fibrous,  of  heart,  468 

muscle,  830 
Risorius  muscle,  310 
Rivini,  ducts  of,  887 

incisura  of,  853,  855 
Robin,  polar  globules  of,  1150 
Rod-bipolar  cells,  835 
Rod-granules  of  retina,  835 
Rods  of  Corti,  865 

of  retina,  835 
Rolando,  fissure  of,  646 

funiculus  of,  695 

topography  of,  706 

tubercle  of,  695 
Roof  nuclei  of  Stilling,  693 
Root  of  lung,  974 

sheath  of  hair,  1141 

of  spinal  nerves,  717 

of  teeth,  873 

of  zygomatic  process,  65 
Rosenmuller,  accessory  gland  of. 
846 

organ  of,  1038,  1210 
Rostrum  of  corpus  callosum,  659 

of  sphenoid  bone,  74 
Rotation,  222 

Rotatores  spinae  muscles,  347 
Round  ligaments  of  liver,  938 
of  uterus,  1038 
relations    of,  to    femoral 
ring,  1060 
Ruffini's  endings,  1122 
Rugae  of  stomach,  909 

of  vagina,  1028 


Rupture  of  urethra,  course  taken 

by  urine  in,  1065 
Rust-colored  layer  of  cerebellar 

cortex,  692 

S. 

Sac,  lachrymal,  847 
Saccular  secretory  glands,  1146 
Saccule  of  vestibule,  862 
Sacculus  laryngis,  961 
Sacra-media  artery,  558 
Sacral  arteries,  lateral,  569 
canal,  48 
cornua,  47 
foramina,  46 
ganglia,  805 
groove,  47 

lymphatic  gland,  632 
nerves,  788 

anterior  divisions  of,  789 
posterior  divisions  of,  788 
roots  of,  788 
plexus,  790 
vein,  lateral,  617 
middle,  617 
peculiarities  of,  617 
Sacro-coccygeal  ligaments,  244 
Sacro-iliac  articulations,  242 
Sacro-lumbalis  muscle,  343 
Sacro-sciatic    foramen,    greater, 
175,  243 
lesser,  175,  243 
ligaments,  242 
notch,  greater,  175 
lesser,  175 
Sacro-uterine  ligament,  1030 
Sacro-vertebral  angle,  46 

ligament,  242 
Sacrum,  45 
ala  of,  48 
articulations  of,  50 
attachment  of  muscles  to,  50 
development  of,  49 
peculiarities  of,  49 
structure  of,  49 
Sacs,  dental,  879 
Saddle-joint,  220 
Sagittal  suture,  101 
Salivary  glands,  884 
structure  of,  887 
Salpingo-pharyngeus,  331 
Salter,  incremental  lines  of,  876 
Santorini,  cartilages  of,  957 
Saphena  veins,  surgical  anatomy 

of,  615 
Saphenous  nerve,  long  or  inter- 
nal, 787 
short,  791 
opening,  419,  1055 
vein,  external  or  short,  614 
internal  or  long,  614,  1054 
surgical  anatomy  of,  615 
Sarcolemma,  1108 
Sarcopl?sm,  1109 
Sarcost  les,  1109 
Sarc"  i  elements  of  muscle,  1110 
Sartorius  muscle,  421 
Seal  a  media,  863 

tympani  of  cochlea,  861 
vestibuli  of  cochlea,  861 
ScabSe  of  cochlea,  861 
Seal   nus  anticus,  334 
njj  lius,  335 
pw  iticus,  335 


Scalp,  skin  of,  298 
Scaphoid  bone  (foot),  205 
(hand),  161 

fossa  of  sphenoid,  76 
Scapula,  138 

articulations  of,  143 

attachment  of  muscles  to,  143 

development  of,  142 

dorsum  of,  140 

glenoid  cavity  of,  141 

head  of,  380 

ligaments  of,  249,  250 

muscles  of,  383,  384 

spine  of,  140 

surface  form  of,  143 

surgical  anatomy  of,  143 

venter  of,  138 
Scapular  artery,  posterior,  526 

notch,  great,  140 

region,    muscles   of,    anterior, 
383 
posterior,  384 
Scapuloclavicular    articulation, 

248 
Scarfskin,  1136 
Scarpa,  fascia  of,  356 

foramina  of,  87,  108 
Scarpa's  triangle,  572 
Schachowa,  spiral  tubes  of,  988 
Schindylesis,  219 
Schlemm,  canal  of,  827 

ligaments  of,  251 
Schneiderian  membrane,  820 
Schreger,  lines  of,  876 
Schultze,    primitive   fibrillae    of, 

1116 
Schwann,    white    substance    of, 

1116 
Sciatic  artery,  568 

nerve,  greater,  793 

surgical  anatomy  of,  797 
lesser,  791 

veins,  617 
Sclerotic,  825 
Scrobiculus  cordis,  1 33 
Scrotal  hernia,  1051 
Scrotum,  1015 

dartos  of,  1015 

development  of,  1215 

lymphatics  of,  633 

nerves  of,  1016 

septum  of,  1015 

surgical  anatomy  of,  1017 

vessels  of,  1016 
Sebaceous  glands,  1142 
Second  nerve,  721 

surgical  anatomy  of,  722 
Secondary  areolae  of  bone,  1104 

optic  vesicle,  1181 
Secreting  glands,  1146 
Segment,  internodal,  1117 
Segmentation  of  ovum,  1152 

medullary,  1117 

of  Lantermann,  1117 
Sella  Turcica,  73 
Semicircular  canals,  860 
Semilunar  bone,  161 

fascia,  387 

fibro-cartilages  of  knee,  276 

fold  of  Douglas,  364 

ganglion  of  abdomen,  806 
of  fifth  nerve,  725 

lobe,  inferior  of    cerebellum, 
688 

valves,  aortic,  467 


INDEX. 


1249 


Semilunar  valves,  pulmonic,  465 
Semimembranosus  muscle,  432 
Seminal  cells,  1019 
tubes,  1019 

vesicles,  1022 
Semispinalis  muscle,  346 
Semitendinosus  muscle,  432 
Senses,  organs  of  the  special,  811 
Sensory,    afferent,    or  ascending 
nerve  tracts,  719 

decussation,  719 

epithelium  cells,  1124 
Septum  auricularum,  466 

between  bronchi,  966 

crurale,  1060 

inferius,  1190 

lucidum,  660 

mobile  nasi,  819 

of  nose,  117 
artery  of,  491 
cartilage  of,  820 
orbital,  844 

pectiniforme,  1012 

scroti,  1015 

superius,  1190 

of  tongue,  815 

transversum,  1206 

of  semicircular  canals,  863 

ventriculorum,  467 
Serous  glands  of  tongue,  815 

membranes,  1143 
Serratus  magnus,  381 

posticus,  inferior,  341 
superior,  341 
Serum,  1081 

-albumen,  1080 

-globulin,  1080 
Sesamoid  bones,  214 

cartilages,  819 
Seventh  nerve,  740 

surgical  anatomy  of,  744 
Shaft  of  a  bone,  its  structure,  33 

of  a  hair,  1141 
Sheath  of  arteries,  1128 

of  femoral  or  crural,  1059 

of  muscles,  1107 

of  nerves,  1118 

of  rectus  muscle,  363 
Shin,  193 
Short  bones,  33 
Shoulder-girdle,  134 

-joint,  251 
actions  of,  252 
surface  form  of,  254 
surgical  anatomy  of,  254 

muscles  of,  377 

vessels  and  nerves  of,  252 
Sigmoid  artery,  555 

cavity,  greater  and    lesser,  of 
radius,  155 
of  ulna,  152 

flexure  of  colon,  925 
of  meso-colon,  903 

notch  of  lower  jaw,  99 
Sinus  of  external  jugular    vein, 
597 

great,  of  aorta,  476 

intercavernous,  604 

of  internal  jugular  vein,  598 

of  kidney,  986 

of  Morgagni,  328 

petro-squamous,  603 

pocularis,  1006,  1208 

pnecervicalis,  1171 

prostaticus,  1005 


Sinus  pyriformis,  890 
reuniens  of  His,  1189 
rhomboidales,  1156 
spheno-parietal,  603 

transverse  pericardial,  459 
vena?  porta-,  827 
venosus,  461,  1189 
Sinuses,  cavernous,  603 
circular,  604 

of  coronary  vein,  462,  622 
cranial,  61,  594,  602 
ethmoidal,  78 
frontal,  61 
of  heart,  of  left  auricle,  465 

of  right  auricle,  462 
lateral,  602 
longitudinal  inferior,  602 

superior,  602 
maxillary,  85 
of  nose,  61 
occipital,  603 
petrosal,  inferior,  605 

superior,  604 
sphenoidal,  74 
straight,  602 
transverse,  605 
of  Valsalva,  aortic,  467,  477 
pulmonary,  465 
Sixth  nerve,  738 

surgical  anatomy  of,  740 
Skeletal  muscles,  1107 
Skeleton,  33 

number  of  its  pieces,  33 
Skin,  appendages  of,  1139 
arteries  of.  1139 
corium  of,  1138 
cuticle  of,   1136 
derma,  or  true  skin,  1138 
development  of,  1186 
epidermis  of,  1136 
furrows  of,  1136 
general  anatomy  of,  1135 
hairs,  1140 

muscular  fibres  of,  1142 
naiis,  1139 
nerves  of,  1139 
papillary  layer  of,  1138 
rete  mucosum  of,  1136 
sebaceous  glands  of,   1142 
sudoriferous    or    sweat-glands 

of,  1142 
tactile  corpuscles  of,  1121 
vessels  of,  1139 
Skull,  54,  103 

anterior  region,  112 

base  of,  external  surface,  103 

internal  surface,  103 
fossa  of.  anterior,  103 
middle,  105 
posterior,  106 
lateral  region  of,  109 
surface-marking  of,  118 
surgical  anatomy  of,  119 
tables  of,  33 
vertex  of  103 
vitreous  table  of.  34 
Slender  loin-  of  cerebellum,  688 
itestine,  91 1 
>lar  coat  of.  915 
idenum,  912 
mi,  ;>14 
mum,  914 
inucors  coat.  915 
iscuiar  coat,  915 
•ons  coat,  915 


Small  inte-tine,  simple  follicles, 
918 
valvulae  conniventes,  916 

villi  of,   !»17 
Socia  parotides,  886 
Soft  palate. 

aponeurosis  of. 
arches  or  pillars  of,   383 
muscles  of,  884 
structure  of,  883 
Solar  plexus,  806 
Sole    of    foot,    muscles   of,   first 
layer,  1  1  I 
fourth  layer,  448 
second  layer,  446 
third  layer,  446 
Soleus  muscle,  436 
Solitary  glands,  919 
Somatopleure,  1157 
Sommerring,  yellow  spot  of,  833 
Space,  anterior  perforated,  656 
axillary,  527 
intercostal,  128 
of  Mull,  866 
popliteal,  581 
posterior  perforated,  657 
of  Ketzius,  1000 
Spaces  of  Fontana,  827 
Spermatic  artery,  557,   1016 
canal,  1046 
cord,  1016 

arteries  of,  1016 
course  of,  1016 
lymphatics  of,  1017 
nerves  of,  1017 
relation  to  femoral  ring,  1060 
of,  in  inguinal  canal,  1016 
fascia,  external,  359,  1043 
plexus  of  nerves,  808 

of  veins,  618 
veins,  618,  1016 

surgical  anatomv  of,  618 
Spermatids.  1019,  1150 
Spermatoblasts,  1019,  1150 
Spermatocytes,  1019,  1150 
Spermatogenesis,  1020 
Spermatogonia,  1019 
Spermatozoa,  1021 
Spheno-ethnioidal  recess,  117,820 
Sphenoid  bone,  72 

articulations  of,  77 
attachment  of  muscles  to,  77 
body  of,  72 
development  of,  76 
greater  wings  of  74 
lesser  win^s  of,  75 
pterygoid   processes  of,  75 
rostrum  of,  74 
spinous  processes  of,  74 
vaginal  processes  of,  74 
Sphenoidal  fissure,  75 
nerves  ii>.  7.">'.' 
process  of  palate,  93 
sinuses,  7  1 

spongy  or  turbinated  bones,  76 
Spheno-mandibular  ligament.  232 
Spheno-maxillary  fissure,  112 

fossa,  1 12 
Spheno-palatine  artery,  499 
foramen.   93 
ganglion. 
nerves,  7. 
notch,  93 
Spheno-pari 
Spheroidal 


1250 


INDEX. 


Sphincter     muscle    of    bladder, 
1003 
of  rectum,  external,  368 

internal,  368 
of  vagina,  375 
vesicae,  1003 
Spina  bifida,  53 
helicis,  849 
vestibuli,  1190 
Spinal  accessory  nerve,  753 

surgical  anatomy  of,  753 
arteries,  anterior,  521 
lateral,  521 
median,  521 
posterior,  521 
canal,  53 
cord,  710 

arachnoid  of,  708 
arrangement    of   gray    and 

white  matter  in,  712 
central  canal  of,  712 

ligament  of,  709 
columns  of,  711 
development  of,  1165 
dura  mater  of,  707 
fissures  of,  711 
foetal,  peculiarity  of,  710 
gray  commissure  of,  712 
ligamentum  denticulatum  of, 

709 
minute  structure  of,  713 
neuroglia  of,  713 
pia  mater  of,  709 
sections  of,  712 
surgical    anatomy  of  mem- 
branes of,  709 
white  commissure  of,  712 
white  matter  of,  713 
foramen,  35 
nerves,  756 

arrangement     into    groups, 

756 
development  of,  1178 
distribution  of,  757 
divisions  of,  anterior,  758 

posterior,  758 
ganglia  of,  757 
origin  of,  in  cord,  756 
of  roots,  anterior,  757 
posterior,  757 
points  of  emergence,  758 
veins,  612 

longitudinal,  anterior,  613 
posterior,  613 
Spinalis  colli  muscle,  345 

dorsi  muscle,  345 
Spindle,  achromatic,  1075 
poles  of,  1075 
aortic,  478 
Spine,  34 

articulations  of,  223 
development  of,  1165 
general  description  of,  51 
ossification  of,  45 
surface  form  of,  53 
surgical  anatomy  of,  53 
Spines  of  bones,  ethmoidal,  73 
of  ischium,  175 
nasal,  62 
anterior,  87 
posterior,  90 
of  os  pubis,  176 
pharyngeal,  57 
of  scapula,  140 
Spino-glenoid  ligament,  250 


Spinous  process  of  ilium,  174 
of  sphenoid,  74 
of  tibia,  192 
of  vertebrae,  35 
Spiral  canal  of  cochlea,  861 

line  of  femur,  185 
Spirem  or  skein,  1075 
Splanchnic  nerve,  greater,  804 
lesser,  804 

smallest  or  renal,  804 
Splanchnopleure,  1157 
Spleen,  949 
artery  of,  952 
capillaries  of,  953 
development  of,  1205 
fibro-elastic  coat  of,  950 
lymphatics  of,  635,  953 
Malpighian  bodies  of,  952 
nerves  of,  954 
proper  substance  of,  951 
relations  of,  949 
serous  coat  of,  950 
size  and  weight  of,  950 
structure  of,  950 
surface-marking  of,  954 
surgical  anatomy  of,  954 
trabecular  of,  950 
veins  of,  953 
Splenic  artery,  553 

distribution  of,  952 
corpuscles,  952 
plexus,  808 
pulp,  951  . 
vein,  619 
Splenium  of    corpus    callosum, 

659 
Splenius  muscle,  342 
Spongioblasts,  1172 
Spongioplasm,  1074 
Spongy  portion  of  urethra,  1006 

tissue  of  bone,  33 
Spring  ligament,  289 
Spur  of  malleus,  856 
Squamo-parietal  suture,  102 
Squamo-sphenoidal  suture,  102 
Squamo-zygomatic     portion    of 

temporal  bone,  71 
Squamous  portion   of  temporal 

bone,  65 
Stalk  of   optic  thalamus,   ante- 
rior, 672 
inferior,  672 
posterior,  672 
Stapedius  muscle,  857 
Stapes,  857 

annular  ligament,  857 
development  of,  1184 
Stellate  ligament,  234 

plexus  of  kidney,  992 
Stenson,  foramina  of,  87,  108 
Stenson's  duct,  885 
Stephanion,  109 

Sternal  end  of  clavicle,  fracture 
of,  411 
foramen,  127 
furrow,  132 
ligaments,  239 
Sterno-clavicular       articulation, 
246 
surface  form  of,  247 
surgical  anatomy  of,  247 
Sterno-hyoid  muscle,  319 
Sterno-mastoid  artery,  493 

muscle,  317 
Sterno-pericardiac  ligament,  458 


Sterno-thyroid  muscle,  319 
Sternum,  124 

articulations  of,  128 

attachment    of    muscles    to, 
128 

development  of,  125,  1166 

ligaments  of,  239 
Stilling,  canal  of,  839 
Stomach,  905 

alteration  in  position  of,  907 

alveoli  of,  909 

areolar  coat  of,  909 

cardiac  glands  of,  910 

curvatures  of,  906 

development  of,  1198 

fundus  of,  905 

gastric  follicles  of,  909 

lymphatics  of,  635 

mucous  membrane  of,  909 

muscular  coat  of,  908 

orifices  of,  905 

pyloric  end  of,  905 
glands  of,  905 

pylorus,  906 

serous  coat  of,  908 

structure  of,  908 

surface  marking  of,  910 

surfaces  of,  905 

surgical  anatomy  of,  911 

vessels  and  nerves  of,  910 
Stomodoeum,  1169,  1171 
Straight  sinus,  602 

tubes  of  kidney,  990 
Strand,  labio-dental,  877 
Stratified  epithelium,  1085 
Stratiform  fibro-cartilage,  1095 
Stratum  cinereum,  675 

compactum  of  decidua,  1163 

corneum,  1136 

dorsale,  676 

germinativum,  1137 

granulosum,  1138 

lemnisci,  675 

lucidum,  1138 

Malpighii,  1136 

opticum,  675, 1138 

spongiosum,  1163 

zonale,  675 
Striae  laterales,  659 

longitudinales,  659 

medullaris  vel  acusticse,  698 

pinealis,  670,  673 
Striped  muscle,  1107 
Stroma  of  ovary,  1036 
Stylo-glossus  muscle,  324 
Stylo-hyoid  ligament,  322 

muscle,  322 

nerve  from  facial,  743 
Stylo-mandibular  ligament,  232 
Stylo-mastoid  artery,  494 

foramen,  70 

vein,  597 
Stylo-pharyngeus  muscle,  329 
Styloid  process  of  fibula,  196 
of  radius,  156 
of  temporal  bone,  70 
of  ulna,  154 
Subanconeous  muscle,  389 
Subarachnoid  fluid,  642 

space  of  brain,  641 
anterior,  641 
posterior,  641 
of  cord,  708 
of  septum,  708 

tissue,  641 


INDEX. 


1251 


Subcecal  fossa,  904 
Subcalcarine  convolution,  652 
Subclavian  arteries,  514 
branches  of,  520 
first  part  of,  left,  516 
right,  514 
•         peculiarities  of,  517 
second  portion  of,  516 
surface  form  of,  518 
surgical  anatomy  of,  51S 
third  portion  of,  516 
groove,  130 
nerve,  768 
triangle,    502 
vein,  609 
Subclavius  muscle,  380 
Subcollateral  convolution,  652 
Subcostal  angle,  124 
artery,  547 
muscle,  351 
Subcrureus  muscle,  423 
Subcutaneous  malar  nerve,  731 
Subdural  space,  641,  708 
Sublingual  artery,  489 
fossa,  97 
gland,  887 

vessels  and  nerves  of,  887 
Sublobular  veins,  940 
Submaxillary  artery,   491 
fossa,  97 
ganglion,  737 
gland,  886 
nerves  of,  887 
vessels  of,  887 
lymphatic  gland,  627 
triangle,  501 
vein,   596 
Submental  artery,  491 

vein,  596 
Suboccipital  nerve,  758 

posterior  branch  of,  759 
triangle,  348,  520 
Subpleural  mediastinal    plexus, 

526 
Subpubic  ligament,  245 
Subscapular  angle,   139 
artery,  533 
fascia,  383 
fossa,  138,  139 
nerves,  768 
Subscapulars  muscle,  383 
Substantia     cinerea     gelatinosa, 
716 
corticalis,  S40 
ferruginea,  699 
gelatinosa  centralis,  712 
nigra,  673 
Subthalamic  region,  676 
Sudoriferous  glands,  1142 
Sulci  of  cerebrum,  644 
Sulcus  centralis,  652 
frontal  inferior,  648 
frontalis  medius,  649 
mesialis,  649 
superior,  648 
intraparietal,  650 
longitudinalis  medianus,  698 
occipital,  inferior,  • 
middle,  651 
superior,  651 
oculi  motorii,  673 
olfactorv,  649 
orbital, '649 
parallel,  652 
post-central,  650 


Sulcus  precentral,  648 

spiralis,  interims  et  externus, 

845 
temporal,  first,  652 
second,  652 
third,  652 
terminate  of  His,  811 
of  right  auricle.  461 
tri-radiate,  649 
tympanicus,  851,  855 
vallecutae,  688 
Supercilia,  843 
Superciliary  ridge,  <il 
Superficial  cervical  artery,  524 
circumflex  iliac  artery,  518 
epigastric  artery,  578 
external  pudic  artery,  578 
palmar  arch,  544 
perineal  artery,  567 
temporal  artery,  495 

surgical  anatomy  of,  496 
transverse  ligament  of  fingers, 
404 
Superficialis  colli  nerve,  762 

vohe  artery,  540 
Superior  maxillary  bone,  81 
articulations  of,  88 
attachment  of  muscles  to, 

88 
changes  in,  produced  by 

age,  88 
development  of,  87 
nerve,  729 
ligament  of  incus,  857 

of  malleus,  857 
meatus,  116 
mediastinum,  971 
medullary  velum,  697 
olivary  nucleus,  683 
profunda  artery,  537 
pyramidal  decussation,  719 
thyroid  artery,  487 

surgical  anatomy  of,  488 
turbinated  crest,  85 

of  palate,  92 
vena  cava,  611 
Supernumerary  spleens,  950 
Supinator  brevis  muscle,  398 

longus  muscle,  395 
Supporting  cells  of  Hensen,  866 
Supra-acromial  artery,  524 

nerves,  763 
Supra-clavicular  nerves,  763 
Supracondylar    ridge,   external, 
146 
internal,  146 
Supraglenoid  tubercle.  141 
Suprahyoid  aponeurosis,  321 
Supramarginal  convolution.  651 
Supramastoid  crest,  66 
Suprainaxillary  nerves  from  fa- 
cial, 744 
Supraorbital  arch,  61 
artery,  506 
foramen,  62,  113 
nerve,  7 "27 
notch,  0'J 
Suprarenal  arteries,  556 
capsules,  996 
development  of,  1209 
nerves  of,  998 
vessels  of,  998 
plexus,  808 
veins,  619 
Suprascapular  artery,  ~>24 


Suprascapular  ligament,  250 

nerve,  769 
notch,  111 
Supraspinal^  muscles,  347 
Supraspinal  muscle,  38  1 
Supraspinous  fas        !  - ! 
fossa,  140 
ligaments,  225 
Suprasternal  artery,  o24 
nerves,  762 
notch,  336 
Supratrochlear  foramen,  148 

nerve,  7^7 
Sural  arteries,  583 

vein6,  616 
Surface  form  or  marking  of  ab- 
dominal aorta,  550 
of  acromio-clavicular  joint, 

249 
of  ankle-joint.  285 
of  anterior  tibial  artery,  5  36 
of  axillary  artery,  531 
of  bladder,  1004" 
of  brachial  artery,  535 
of  branches  of  internal  iliac 

artery,  569 
of  carpus,  169 
of  cerebral  convolutions,  705 
of  clavicle,  137 
of  common   carotid    arterv, 
485 
iliac  arterv,  560 
of  cranium,  1 1 8 
of  dorsalis  pedis  artery,  587 
of  elbow .  . 

of  external  auditory  meatus, 
852 
carotid  artery,  487 
iliac  artery.  560 
of  femoral  artery,  575 
of  femur,  190 
of.  fibula,  198 
of  fifth  cranial  nerve,  737 
of  foot,  213 
of  heart,  470 
of  hip-joint,  293 
of  humerus,  149 
of  hvoid  bone,  123 
of  intestines.  930 
of  kidney,  993 
of  knee-joint.  280 
of  knuckles,  268 
of  larynx, 
of  liver.  943 
of  lungs,  977 
of  mouth,  888 
of  muscles  of  abdomen.  366 
of  back,  349 
of  head  and  face,  313 
of  lower  extremity,  449 
of  neck.  '■'>'■'>'< 
of  upper  extremity,  409 
of  palmar  arches,  5  !•"> 
of  palpebral  fissure,  847 
of  pancreas,  948 

of  patella,  192 

of  pelvis.  L83 

of  plantar  arch,  592 

of  popliteal  artery,  582 

of    posterior    tibial    arterv, 

589 
of  radial  artery,  539 
of    radio-ulnar    joint,    infe- 
rior, 261 
superior,  259 


i 


1252 


INDEX, 


Surface  form  of  radius,  157 
of  scapula,  143 
of  shoulder-joint,  254 
of  skull,  118 
of  spleen,  954 
of  spine,  53 

of  sterno-clavicular  j  oint,  247 
of  sterno-mastoid,  319 
of  stomach,  910 
of  subclavian  artery,  518 
of  tarsus  and  foot,  213 
of  temporo-m  andibular 

joint,  234 
of  thorax,  132 
of  tibia,  196 
of  ulna,  155 
of  ulnar  artery,  542 
of  vertebral  column,  53 
of  wrist  and  hand,  169 
of  wrist-joint,  263 
Surgical  anatomy  of  abdominal 
aorta,  550 
of  abducent  nerve,  740 
of  acromio-clavicular  joint, 

249 
of  adductor  longus  muscle, 

426 
of  ankle-joint,  285 
of  anterior  tibial  artery,  586 
of  arch  of  aorta,  479 
of  artery  of  the  bulb,  567 
of  ascending  pharyngeal  ar- 
tery, 495 
of  auditory  nerve,  746 
of  axilla,  529 
of  axillary  artery,  531 

glands,  628 

vein,  609 
of  azvgos  veins,  612 
of  base  of  bladder,  1068 
of  bend  of  elbow,  534 
of  bones  of  face,  119 
of  brachial  artery,  535 

plexus,  776 
of  branches  of  internal  iliac, 

570 
of  cavernous  sinus,  604 
of  cervical  glands,  628 

vertebrae,  231 
of  clavicle,  137 
of  club-foot,  441 
of  common  carotid,  485 

iliac,  560 
of  deep  epigastric,  572 
of  deltoid  muscle,  383 
of  descending  aorta,  547 
of  dorsalis  pedis  artery,  587 
of  elbow-joint,  258 
of  Eustachian  tube,  868 
of  extensor  muscles  of  thumb, 

400 
of  external  carotid    arterv, 

487 
\  ear,  847 
I  iliac  artery,  560 
gular  vein,  597 
^eye,  841 

facial  artery,  493 

ierve,  744 

'ein,  596 

femoral  artery,  575 

lernia,  1053 

femur,  190 

foot,  bones  of,  213 

forearm,  bones  of,  157 


Surgical  anatomy  of  gluteal  ar- 
tery, 570 

of  hsemorrhoidal  veins,  616 

of  hamstrings,  433 

of  hand,  bones  of,  170 

of  heart,  470 

of  hip-joint,  272 

of  humerus,  149 

of  hyoid  bone,  123 

of  hypoglossal  nerve,  756 

of  iliac  fascia,  417 

of  inferior   thvroid   artery, 
524 
vena  cava,  612 

of  inguinal  glands,  630 
hernia,  1041 

of  innominate  artery,  481 

of  intercostal  nerves,  780 

of  internal    carotid    arterv, 
505 
iliac  artery,  570 
jugular  vein,  599 
mammary    artery,  527 
pudic  artery,  566 

of  intestines,  930 

of  ischio-rectal  region,  1063 

of  joints   of  cervical  verte- 
brse,  231 

of  kidneys,  993 

of  knee-joint,  280 

of  lachrymal  apparatus,  847 

of  laryngeal  nerves,  752 

of  larvngo-tracheal   region, 
968 

of  larynx,  968 

of  leg,  bones  of,  198 

of  lingual  artery,  489 

of  liver,  944 

of  lumbar  plexus,  797 

of  lungs,  977 

of  middle  meningeal  artery, 
498 

of  motor  oculi  nerve,  724 

of  muscles  of  eye,  306 
of  lower  extremity,  451 
of  soft  palate,  332 
of  upper  extremity,  411 

of  musculo-spiral  nerve,  776 

of  nasal  fossae,  823 

of  nose,  823 

of  oesophagus,  893 

of  olfactory  nerve,  721 

of  optic  nerve,  721 

of  palmar  arch,  545 
fascia,  404 

of  pancreas,  948 

of  patella,  192 

of  pelvis,  bones  of,  182 

of  penis,   1014 

of  perinseum,  1063 

of  peroneal  or  external  pop- 
liteal nerve,  797 

of  pharynx,  891 

of  plantar  arch,  592 
ligaments.  288 

of  pleura,  971 

of  popliteal  artery,  582 

of  posterior  tibial,  589 

of  pronator  radii  teres  mus- 
cle, 391 

of  prostate  gland,  1011 

of  psoas  magnus,  417 

of  radial  arterv,  539 

of  radio-uinar  joint,    supe- 
rior, 259 


Surgical  anatomy  of  rectus  fem- 
oris  muscle,  423 
of  ribs,  133 
of  saphena  veins,  615 
of  scapula,  143 
of  Scarpa's  triangle,   572 
of  sciatic  artery,  570 
nerve  (great),  7*97 
of  scrotum,  1017 
of  serratus  magnus  muscle, 

382 
of  shoulder-joint,  254 
of  skull,  119 
of  spermatic  veins,  618 
of    spinal    accessory   nerve, 

753 
of  spleen,  954 
of    sterno-clavicular    joint, 

247 
of    sterno-mastoid    muscle, 

319 
of  sternum,  133 
of  stomach,  911 
of  subclavian  artery,  518 
of  superior  thyroid    artery, 

488 
of  synovial  sheaths   of  ten- 
dons of  wrist,  402 
of  talipes,  441 
of  tarsal  joints,  288,  290 
of  temporal  artery,  496 
of  temporo-mandibular  joint, 

234 
of  testis,  1021 
of  thoracic  aorta,  547 
of  thorax,  133 
of  thyroid  gland,  981 
of  tongue,  327,  816 
of  triangles  of  neck,  500 
of  triceps,  389 
of  trifacial  nerve,  738 
of  trochlear  nerve,  725 
of  ulnar  arlery,  542 
of  upper  extremity,  411 
of  urethra,  1007 
of  vertebral  artery,  522 
of    vesico-prostatic    plexus, 

617 
of  vesieulse  seminales,  1023 
of  wrist-joint,  263 
Suspensorv  ligament  of  eye,  824 
of  lens,  840 
of  liver,  937 
of  penis,  1011 
Snstentacular  cells  of  spleen,  951 
Sustentaculum  lienis,  902 

tali,  203 
Sutura,  219 
dentata,  219 
harmonia,  219 
limbosa,  219 
notha,  219 
serrata,  219 
squamosa,  219 
vera,  219 
Sutural  ligament,  101 
Suture,  basilar,  102 
coronal,  101 
cranial,  101 
fronto-parietal,  101 
fronto-sphenoidal,  101,  102 
intermaxillary,  113 
internasal,  113 
interparietal,  101 
lambdoid,  101 


INDEX. 


1 253 


Suture,  masto-occipital,  102 
masto-parietal,  102 
metopic,  G4 
occipito-parietal,  101 
petro-occipital,  102 
petro-sphenoidal,  102 
petrosquamous,  68 
sagittal,  101 
sphenoparietal,  102 
squamo-parietal,  102 
squamo-sphenoidal,  102 
transverse  facial,  102 
Sweat-glands,  1142 
Sylvius,  aqueduct  of,  676 
fissure  of,  645 
surface-marking  of,  706 
Sympathetic  nerve,  798,  1120 
cervical  portion,  799 
cranial  portion,  799 
lumbar  portion,  805 
pelvic  portion,  805 
thoracic  portion,  804 
plexuses,  805 
cardiac,  805 
epigastric,  806 
hypogastric,  809 
pelvic,  809 
solar,  806 
Symphysis,  219,  221 
of  jaw,  96 
pubis,  176,  244 
Synarthrosis,  218 
Synchondrosis,  219,  221 
Syndesmo-odontoid  joint,  227 
Syndesmosis,  219,  221 
Synovia,  218,  1145 
Synovial  ligaments,  218 
membrane,  217,  1145 
articular,  217 
bursal,  218 

vaginal,  218.       See  also  In- 
dividual joints. 
sheaths,  218 
System,  Haversian,  1098 
Systemic  arteries,  474 
veins,  593 

T. 

Tables  of  the  skull,  33 
Tactile   corpuscles    of    Grand  v, 
1121 
of  Wagner  and    Meissner, 
1121 
Tsenia  of  fourth  ventricle,  698 

hippocampi,  667 

semicircularis,  664 
Tamiee  of  muscular  coat  of  in- 
testine, 921 

tectse,  659 
Tapetum,  or  mat,  660 

of  choroid,  829 

lucidum,  837 

nigrum,  837 
Tarsal  artery,  588 

bones,  199 

ligament  of  eyelid,  843 

ligaments,  287 

plates  of  eyelid,  844 
Tarso-metatarsal     articulations, 

290 
Tarsus,  199 

articulations  of,  2S7 

surface  form  of,  213 

surgical  anatomy  of,  213 


Tarsus,  synovial  membranes  of, 
287 
development  of,  211 
Taste-buds,  814 
Teeth,  871 
bicuspid,  872 
body  of,  871 
canine,  872 
cement  of,  876 
cortical  substance  of,  877 
crown  of,  871 
crusta  petrosa  of,  877 
cuspidate,  872 
deciduous,  871 
dental  tubuli  of,  875 
dentine  of,  874 
development  of,  877 
enamel  of,  877 
eruption  of,  852 
eye,  871 

false  molars,  872 
fang  of,  872 

general  characters  of,  871 
growth  of,  881 
incisors,  871 

intertubular  substance  of,  876 
ivory  of,  874 
milk,  871,  874 
molar,  872 
multicuspidate,  872 
permanent,  871 
pulp-cavity  of,  874 
root  of,  871 
structure  of,  874 
temporary,  871,  874 
true  or  large  molars,  872 
wisdom,  874 
Tegmen  tympani,  68,  853 
Tegmentum  of  crus  cerebri,  673, 

677 
Tela  choroidea,  inferior,  643,  697 
Telophase  of  karvokinesis,  1075 
Temporal  artery,  495 
anterior,  495 
deep,  498 
middle,  495 
posterior,  495 
surgical  anatomy  of,  496 
bone,  65 

articulations  of,  72 
attachment  of  muscles  to,  72 
development  of,  71 
mastoid  portion,  67 
petrous  portion,  68 
squamous  portion,  65 
structure  of,  71 
fascia,  311 
fossse,  110 
lobe,  646,  652 
muscle,  311 

nerves   of    auriculo-temporal, 
735 
deep,  734 
of  facial,  743 
ridge,  62,  65,  111 
veins,  596 
Temporarv  cartilage,  1094 

teeth,  871,  874 
Temporo-facial  nerve,  743 
Temporo-malar  nerve,  730 
Temporo-mandibular     articula- 
tion, 231 
surface  form  of,  234 
surgical  anatomy  of,  '234 
Temporo-maxillary  vein,  597 


Tendo  Acbillis.  437 

palpebrarum  or  oculi,  302 
Tendon,  central  or  cordiform,  of 
diaphragm,  353 

conjoined,  of  internal,  oblique 
and  transversalis,  36], 
1045 

structure  of,  296 

of  wrist,  relation  of,  401 
Tendril  fibres  of  cerebellum,  693 
Tenon,  capsule  of,  824 
Tensor    fasciae  femoris  muscle, 
420 

palati  muscle.  329 

tarsi  muscle,  302 

tympani  muscl 

canal  for,  71,  854 
Tenth  nerve,  749 

surgical  anatomy  of,  752 
Teres  major  muscle.  386 

minor  muscle,  385 
Terminal  sinus,  1189 
Testes,  1017 

coni  vasculosi  of.  1020 

coverings  of,  1017 

development  of,  1210 

gubernaculurn  testis,  1211 

lobules  of,  1019 

lymphatics  of,  634 

mode  of  descent,  1211 

muliebres,  1035 

rete  testis,  1020 

size  and  weight  of,  1018 

structure  of,  1019 

surgical  anatomy  of,  1021 

tubuli  seminiferi  of,  1019 

tunica  albuginea,  1018 
vaginalis,  1018 
vasculosa,  1019 

vas  aberrans  of,  1021 

vas  deferens  of.  1021 

vas  recta  of,  1020 

vasa  efferentia  of.  1020 
Thalamencephalon,  643,  1173 
Tbalami  optici,  671 
Thebesii  foramina,  622 

vena-,  622 
Thigh,  deep  fascia,  fascia   lata, 
418,  419 

muscles  of  back  of,  430 
of  front  of,  419 

superficial  fascia  of,  418,  1053 
Third  nerve,  722 

surgical  anatomy  of,  724 

ventricle  of  the  brain,  669 
Thoracic  aorta.  546 

surgical  anatomy  of,  547 

artery,  acromial,  532 

alar.  533 

long,  532 

superior,  532 
duct.  624,  1082 
ganglia  of  sympathetic,  804 
nerves,  anterior.  769 

j>.  sterior,  or  long,  ! r 
region,  muscles  of  anterior,  377 
lateral,  381 
Thorax,  base  of,  456 
bones  of,  1 '-'  1 
boundaries  <>f,  456 
cavity  of,  456 

cutaneous  nerves  of,  anterior, 
779 


lateral.  779 
fascia;  of,  350 


i 


1254 


INDEX. 


Thorax,  general  description  of, 
456 
lower  opening  of,  124 
lymphatics  of,  636 
muscles  of,  350 
parts   passing  through    upper 

opening  of,  456 
surface  form  of,  132 
upper  opening  of,  124 
Thrombin  of  fibrin  ferment,  1081 
Thumb,    articulation     of,    with 
carpus,  265 
muscles  of,  404 
Thymic  artery,  481 

lymphatic  vessels,  637 
Thvmus  gland,  981 
"  lobes  of,  981 
lymphatics  of,  982 
structure  of,  982 
Thyro-arytenoid    ligament,    in- 
ferior, 961 
superior,  960 
Thyro-arytenoideus  muscle,  962 
Thyro-epiglottic  ligament,  959 
Thyro-epiglottideus  muscle,  963 
Thvro-glossal  duct,  813,  1206 
Thvro-hyal  of  hyoid  bone,  123 
Thyro-hyoid  arch  (foetal),  1170 
ligaments,  958 
membrane,  958 
muscle,  320 
nerve,  756 
Thyroid  artery,  inferior,  523 
superior,  487 

surgical  anatomy  of,  488 
axis,  523 

branches  of  sympathetic,  803 
cartilage,  955 
foramen,  177 
ganglion,  803 
gland,  979 

isthmus  of,  979 
veins,  inferior,  610 
middle,  599 
superior,  598 
Thvroidea  ima  artery,  481 
Tibia,  192 

articulations  of,  196 
attachment  of  muscles  to,  196 
crest  of,  193 
development  of,  196 
fracture  of  shaft  of,  453 
nutrient  artery  of,  590 
spinous  process  of,  192 
surface  form  of,  196 
surgical  anatomy  of,  198 
tubercle  of,  193 
tuberosities  of,  192 
Tibial  artery,  anterior,  585 
branches  of,  586 
peculiarities  of,  5S6 
surface-marking  of,  586 
surgical  anatomy  of,  585 
posterior,  588 
branches  of,  590 
peculiarities  of,  589 
surface  marking  of,  589 
surgical  anatomy  of,  589 
lymphatic  glands,  631 
nerve,  anterior,  796 

posterior,  794 
recurrent  artery,  586 
veins,  anterior,  615 
posterior,  615 
Tibialis  anticus  muscle,  434 


Tibialis  posticus  muscle,  439 
Tibio-fibular  articulations,  282 
region,    anterior,    muscles   of, 
434 
posterior,  muscles  of,  436 
Tongue,  811 
arteries  of,  815 
development  of,  1171 
fibrous  septum  of,  815 
frsenum  of,  811 
mucous  glands  of,  815 
membrane  of,  811 
muscles  of,  324 
nerves  of,  816 
papillae  of,  813 
serous  glands  of,  815 
surgical  anatomy  of,  816 
Tonsillar  artery,  491 

nerves,  748 
Tonsils,  884 

of  cerebellum,  688 
nerves  of,  884 
vessels  of,  884 
Torcular  Herophili,  58,  602 
Trabecular    of    corpus   eaverno- 
sum,  1012 
cranii,  1167 
of  foetal  skull,  1167 
of  spleen,  950 
of  testis,  1019 
Trachea,  965 
cartilages  of,  966 
glands  of,  967 
relations  of,  965 
structure  of,  966 
surgical  anatomy  of,  968 
vessels  and  nerves  of,  967 
Trachealis  muscle,  967 
Trachelo-mastoid  muscle,  345 
Tracheotomy,  968 
Trachoma  glands,  845 
Tract,  afferent  or  ascending,  719 
of  cord,  antero-lateral,  714 

ground-bundle,  714 
of  Burdach,  715 
crossed  pyramidal,  714 
efferent  or  descending,  718 
descending  comma,  715 
direct  cerebellar,  714 

pyramidal,  713 
of  Goll,  715 
of  Gowers,  714 
of  Lissauer,  714 
Tractus  spiralis  foramenulentus, 

69,  861 
Tragicus  muscle,  850 
Tragus,  849 

Transitional  epithelium,  1085 
Transversalis     cervicis    muscle, 
345 
colli  artery,  524 

muscle,  345 
fascia,  1046 
humeri  artery,  524 
muscle,  362 
Transverse   arteries   of  basilar, 
522 
colon,  924 
coronary  artery,  477 
facial  artery,  495 

vein,  596 
fissure  of  brain,  669 

of  liver,  935 
humeral  ligament,  252 
joint  of  foot,  285 


Transverse  ligament  of  atlas,  227 
of  hip,  270 
of  knee,  277 
metatarsal,  292 
of  scapula,  250 
of  shoulder,  252 
superficial,  of  fingers,  404 
tibio-fibular,  283 
mesocolon,  903 
nasal  artery,  508 
process  of  a  vertebra,  35 
sinus,  605 

of  pericardium,  459 
suture,  102 
Transversus  auricula?,  850 
perinei,  371 

(in  female),  325 
profundus,  1070 
Trapezium,  bone,  163 

of  pons,  683 
Trapezius  muscle,  337 
Trapezoid  bone,  163 
ligament,  249 
nucleus,  715 
Treitz,  muscle  of,  914 
Triangle  of  elbow,  534 
of  Hesselbach,  1048,  1052 
inferior  carotid,  500 
of  neck,  anterior,  500 

posterior,  501 
occipital,  501 
Scarpa's,  572 
subclavian,  502 
submaxillary,  501 
suboccipital,  520 
superior  carotid,  500 
Triangular   interarticular  fibro- 
cartilage,  261 
fascia  of  abdomen,  357,  1044 
of  nrethra,  373 
Triangularis  sterni  muscle,  351 

menti  muscle,  308 
Triceps  extensor  cubiti,  388 

surse,  note,  437 
Tricuspid  valves,  463 
Trifacial  or  trigeminus   nerves, 
725 
surface-marking  of,  737 
surgical  anatomy  of,  738 
Trigone  of  bladder,  1 003 
Trigonum  acustici,  699 
habenula?,  672 
hypoglossi,  699 
olfactorium,  655 
vagi,  698 
ventriculi,  662 
Trilaminar  blastoderm,  1154 
Tri-radiate  sulcus,  649 
Trochanter,  greater,  185 

lesser,  185 
Trochanteric  fossa,  185 
Trochlea  of  femur,  187 

of  humerus,  147 
Trochlear  fossa,  63 
nerve,  724 

surgical  anatomy  of,  725 
Trochoides,  220 

Trolard,  anastomotic  vein  of,  601 
True  liagments  of  bladder,  1002 
pelvis,  179 
nucleoli,  1074 
ribs,  128 
Trunk,  articulations  of,  223 

muscles  of,  336 
Tube,  Eustachian,  855 


INDEX. 


1255 


Tube,  Fallopian,  1034 

tonsil,  855 
Tuber  annulare,  681 

cinereum,  656 

ischii,  175 

omentale,  934 

papillare,  935 

valvuke   or   posticum  of  cere- 
bellum, 689 
Tubercle,  adductor,  187 

carotid  or  Chassaignac's,  36 

conoid,  135 

cuneate,  696 

of  Darwin,  849 

deltoid,  135 

of  epiglottis,  958 

of  tbe  femur,  185 

genial,  97 

of  hyoid  bone,  122 

lachrymal,  86 

of  Lower,  463 

mental,  97 

of  navicular  bone,  205 

for  odontoid  ligaments,  56 

of  the  quadratus,  186 

of  ribs,  129 

of  Rolando,  695 

of  scaphoid,  161 

of  tibia,  193 

of  ulna,  152 

of  zygoma,  66 
Tubercula  quadrigemina,  675 
Tuberculiun  acusticum,  699 
caudatum,  696 
impar,  1203 
Tuberosities  of  humerus,  greater 
and  lesser,  144 

of  tibia,  192 
Tuberosity,  cuboid,  204 

of  ischium,  174 

maxillary,  84 

of  navicular  bone,  205 

of  palate  bone,  93 

of  radius,  155 

of  ribs,  129 
Tubes,  bronchial,  966 

structure  of,  in  lung,  975 
Tubular  membrane   of    nerves, 
1117 

secreting  glands,  1146 

substance  of  kidney,  988 
Tubuli,  dental,  875 

lactiferi,  1040 

seminiferi,  1019 

uriniferi,  988 
Tuft,    vascular,    in    Malpighian 

bodies  of  kidney,  988 
Tunica  adventitia,  1126 

albuginea,  1018 
of  eye,  304 

elastica  externa,  1128 

intima,  of  arteries,  1126 

media,  1126 

of  ovary,  1036 

Euyschiana,  829 

vaginalis,  1018 

vasculosa  oculi,  828 
testis,  1019 
Tunnel  of  Corti,  865 
Turbinated  bone,  inferior,  94 
middle,  79 
superior,  79 

crest,  inferior,  85 
superior,  85 
Tiirck,  fasciculus  of,  A  13 


Tutamina  oculi.  713 
Twelfth  nerve,  754 

surgical  anatomy  of,  756 
Tympanic  artery,  from  internal 
carotid,  505 
maxillary,  496 
nerve,  748,  859 
of  facial,  742 
plate,  66 
Tympanum,  852 
arteries  of,  858 
cavity  of,  852 
membrane  of,  855 
mucous  membrane  of,  858 
muscles  of,  857 
nerves  of,  858 
ossicula  of,  856 
veins  of,  858 
Types  of  human  caeca,  1011 
Tyson's  glands,  1011 

u. 

Ulna,  150 

articulations  of,  155 
coronoid  process  of,  152 
development  of,  154 
fracture  of  coronoid  process  of, 

413 
muscles  attached  to,  155 
of  olecranon,  413 
process  of,  150 
of  shaft,  413  _ 
sigmoid  cavities  of,  152 
styloid  process  of,  154 
surface  form  of,  155 
surgical  anatomy  of,  157 
tubercle  of,  152 
Ulnar  artery,  542 
brandies  of,  543 
peculiarities  of,  542 
recurrent,  anterior,  543 

posterior,  543 
surface-marking  of,  542 
surgical  anatomy  of,  542 
collateral  branch  of  inusculo- 

spiral,  775 
lymphatic  glands,  628 
nerve,  772 

surgical  anatomy  of,  776 
vein,  anterior,  607 
posterior,  607 
Umbilical  arteries  in  foetus,  471, 
1162 
how  obliterated,  473 
cord,  1165 
fissure  of  liver,  935 
region,  contents  of,  896 
vein,  1194 
vesicle,  1158 
Umbilicus,  365 
Umbo,  855 
Unciform  bone,   165 
process  of,  165 
process  of  ethmoid,  79 
Uncinate  fasciculus,  678 
Uncus,  653 

Ungual  phalanges,  169 
Unstriped  muscle,  1111 
Upper  extremities,    arteries   of, 
514 
bones  of,  1 34 
fascia  of,  376 
ligaments  of,  245 
lymphatics  of,  628 


Upper  extremities,  muscles  of, 
376 
nerves  of,  768 

surface  form  of,  409 
surgical  anatomy  of,  411 

veins  of,  6<  '•' 

Urachus,  1002  1162,  1209 
Ureters,  994 

muscles  of,  1003 

nerves  of,  996 

Structure  of,  995 

vessels  of,  996 
Urethra,     bulbous     portion    of, 
1006 

caput  gallinaginis,  1005 

development  of,  1215 

female,  1007 

male,  1005 

membranous  portion,  1006 

prostatic  portion,  1005 

rupture  of,    course    taken    by 
urine  in,  1065 

sinus  pocularis  of,  1006 

spongy  portion  of,  1006 

structure  of,  1006 

surgical  anatomy  of,  1007 

verumontanum,  1006 
Urinary  organs,  985 

development  of,  1207 
Urogenital  sinus,  1209 
Uterine  arteries,  563 

plexus,  810 
of  veins,  617 
Uterus,  1028 

after  parturition,  1033 

appendages  of,  1034 

arbor  vita?  of,  1032 

broad  ligaments  of,  1030 

cavity  of,  1030 

development  of,  1210 

in  foetus,  1033 

fundus,  bodv,  and    cervix   of, 
1028 

ganglia  of,  810 
nerves  of,  810 

ligaments  of,  1029 

lymphatics  of,  634 

masculinus  or  utriculus  hom- 
inis,  100<;,  1208,  1211 

during  menstruation,  1033 

nerves  of,  10.">2 

in  old  age,  1033 

during  pregnancy,  1033 

at  puberty,    1033 

round  ligaments  of,  1038 

shape,    position,     dimensions, 
1028 

structure  of,  1031 

vessels  of,  1032 
Utricle  of  vestibule,  862 
Uvea,  831 
Uvula  of  cerebellum,  687 

of  throat.  883 

vesica^,  1004 

V. 

Vagina,  1027 

columns  of,  1028 
lymphatics  of,  634 
orifice  of,  1025 
Vaginal  arteries,  564 
plexus  of  nerves,  810 

of  veins.  617 
portal  plexus,  9*40 


1256 


INDEX. 


Vaginal  process  of  .temporal,  66, 
70 

processes  of  sphenoid,  74 

synovial  membranes,  217 
Vagus,  ganglion  of  root  of,  750 

nerve,  749 
trunk  of,  750 
Valentin,  ganglion  of,  731 
Vallecula  of  cerebellum,  684 

Sylvii,  645 
Vallecula  of  larynx,  958 
Valsalva,  sinuses  of, 465, 468,  476 
Valve,  of  Bauhin,  923 

coronary,  462 

of  cystic  duct,  943 

Eustachian,  462 

of  gall-bladder,  942 

of  Hasner,  847 

ileo-csecal,  923 

of  Kerkring,  916 

mitral,  466 

of  Vieussens,  697 
Valves  of  lymphatics,  1132 

pulmonic,  462 

in  right  auricle,  462 

semilunar  aortic,  467 
pulmonic,  464 

tricuspid,  464 

of  veins,  1131 
Valvulae  conniventes,  916 
Vasa  aberrantia,  from  brachial 
artery,  535 

afferentia  of  lymphatic  glands, 
624 

brevia  arteries,  553 
veins,  619 

efferentia  of  lymphatic  glands, 
624 
of  testis,  1020 

intestini  tenuis,  554 

recta,  1020 

vasoruni  of  arteries,  1128 
of  veins,  1131 
Vascular  area  of  yolk  sac,  1189 

capsule  of  yolk  sac,  1182 

system,  changes  in,  at  birth, 473 
general  anatomy  of,  1126 
peculiarities  in  the  foetus,  471 
Vas  aberrans,  1021 
deferens,  1021 
structure  of,  1021 
Vas  spirale,  864 
Vaso-motor  nerves,  1119 
Vastus  externus  muscle,  422 

internus  and  crureus,  422 
Vater,  corpuscles  of,  note,  1122 
Veins,  general  anatomy  of,  1130 

anastomoses  of,  593 

coats  of,  1130 

development  of,  1194 

muscular  tissue  of,  1131 

plexuses  of,  593 

size,  form,  etc,  593 

structure  of,  1131 

valves  of,  1131 

vessels-  and  nerves  of,  1131 
Veins  or  vein,  descriptive  anat- 
omy of,  593 

of  ala?  nasi,  596 

angular,  595 

articular,  of  knee,  615 

auditory,  866 

auricular,  anterior,  596 
posterior,  597 
1  axillary,  609 


Veins  or  vein,  azvgos,  left  lower, 
611 
upper,  612 

right,  611 
basilic,  608 
basi-vertebral,  613 
of  bone,  1097 
brachial,  609 

brachio-cephalic    or   innomi- 
nate, 609 
bronchial,  612 
buccal,  597 
cardiac,  621 

anterior,  621 

left,  621 

posterior,  621 

right,  621 
cardinal,  1196 
cava  inferior,  617 

superior,  611 
cephalic,  608 
cerebellar,  601 
cerebral,  600 
cervical,  ascending,  599 

deep,  599 
choroid,  of  brain,  601 
circumflex,  iliac,  616 

superficial,  614 
condyloid  posterior,  599,  603 
of  corpora  cavernosa,  1013 
of  corpus  spongiosum,  617 

striatum,  601 
cystic,  621 

deep,  or  vense  comites,  594 
dental  inferior,  597 
digital,  of  hand,  608 
of  diploe,  599 
dorsal,  of  penis,  617 
dorsalis  nasi,  596 

pedis,  614 
dorsi-spinal,  612 
emissary,  605 

surgical  anatomy  of,  606 
epigastric,  deep,  616 

superficial,  614 
of  eyeball,  841 
facial,  596 
femoral,  616 
frontal,  595 
of  Galen,  601 
gastric,  620 
gastro-epiploic,  619 
gluteal,  616 
hemorrhoidal,  616 
of  head,  594 
hepatic,  619 
iliac,  common,  617 

external,  616 

internal,  616 
ilio-lumbar,  618 
inferior  cava,  617 
innominate,  609 
intercostal,  superior,  611 
interlobular,  of  kidney,  992 

of  liver,  940 
interosseous,  of  forearm,  608 
intralobular,  of  liver,  940 
jugular,  anterior,  598 

external,  597 
posterior,  598 

internal,  598 
of  kidney,  992 
labial,  inferior,   596 

superior,  596 
laryngeal,  611 


Veins  or  vein,  lateral  sacral,  617 
lingual,  598 
of  liver,  940 

longitudinal  inferior,  602 
lumbar,  618 

ascending,  618 
mammary,  internal,  610 
masseteric,  596 
mastoid,  597 

maxillary,  internal,  596 
median  basilic,  608 

cephalic,  608 
medulli-spinal,  612 
meningeal,  597 
meningo-rachidian,  613 
mesenteric,  inferior,  619 

superior,  619 
nasal,  594 

oblique  cardiac,  622 
obturator,  616 
occipital,  597 
oesophageal,  611 
ophthalmic,  604 
ovarian,  618 

inferior,  604 
palatine,  inferior,  596 
palmar,  deep,  608 
palpebral,  inferior,  596 

superior,  596 
pancreatic,  619 
pancreatico-duodenal,  619 
parotid,  596 
peroneal,  615 
pharyngeal,  598 
phrenic,  619 
plantar,  external,  615 

internal,  615 
plexuses,  of  ovarian,  1038 

pampiniform,      618,     1016,. 
1038 

pharyngeal,  598 

pterygoid,  596 

spermatic,  618,  1016 

uterine,  617 

vaginal,  617 

vesico-prostatic,  599 
popliteal,  615 
portal,  593,  621,  940 
profunda  femoris,  616 
pterygoid  plexus,  596 
pubic,  external,  614 

interna],  616 
pulmonary,  594 
radial,  607 
ranine,  596,  598 
renal,  619,  992 
sacral,  lateral,  617 

middle,  617 
salvatella,  607 
saphenous,  external,  or  short,, 

614 
internal,  or  long,  614,  1054 
sciatic,  616 
spermatic,  618 
spheno-palatine,  599 
spinal,  612 
splenic,  619 
stylo-mastoid,  597 
subclavian,  609 
sublobular,  940 
submaxillary,  596 
submental,  598 
superficial,  593 
supraorbital,  595 
suprarenal,  619 


-^ 


Veins  or  vein,  suprascapular,  598 
sural,  616 
systemic,  593 
temporal,  596 
middle,  596 
temporo-maxillarv,  597 
thyroid,  inferior,  610 
middle,  599 
superior,  598 
tibial,  anterior,  615 

posterior,  615 
transverse  cervical,  597 

facial,  596 
ulnar,  anterior,  607 
common,  607 
deep,  608 
posterior,  607 
umbilical,  471 
vaginal,  of  liver,  940 
vasa  brevia,  619 
vertebral,  599 
Vidian,  598 
Velum  interpositum,  669 

pendulum  palati,  883 
Vena  ascendens,  1195 
cava,  fetal,  1198 
inferior,  617 

peculiarities  of,  617 
superior,  611 
magna  Galeni,  669 
Venre  basis  vertebrae,  35 
comites,  594 
hepaticre  advehentes,  1194 

revehentes,  1194 
interlobulares  of  kidney,  992 
rectie  of  kidney,  992 
salvatella,  607 
Thebesii,   or   minimae  cordis, 

462,  622 
vorticosse.  829 
Venesection,  608 
Venous    lacuna?   of  dura  mater, 

640 
Venter  of  ilium,  174 

of  scapula,  138 
Ventral  auditory  nucleus,  702 
Ventricle  of  brain,  fifth,  666 
fourth,  697 

lining  membrane  of,  699 
third,  670 
of  heart,  left,  465 

right,  463 
of  larynx,  961 
lateral,  660 
of  nasal  fossa1,  820 
Vermicular  motion,  1112 
Vermiform    process   of  cerebel- 
lum, inferior,  686 
superior,  685 
Vernix  caseosa,  1186 
Vertebra  prominens,  39 
development  of,  43 
Vertebr:>\  .'!  1 
cervical,  35 
development  of,  43 
dorsal,  39 

general  characters,  34 
ligaments  of,  223 
lumbar,  41 
sacral,  45 
structure  of,  43 
Vertebral  aponeurosis,  341 
artery,  520 
column,  51 

articulation  of,  223 


TNDEX. 

Vertebral  column,  ossification  of, 
43 
surface  form  of,  53 
Burgical  anatomy  <>f.  53 
ligaments,  223 

region,    muscles   of,   anterior, 
332 
lateral,  334 
vein,  •",'.1'.) 

Vertex  of  skull,  103 
Vertical  plate  of  palate  bom-,  92 
Verumontanum,  1005 
Vesical  artery,  inferior,  563 
middle,  563 
superior,  563 
pleXUS  "I"  nerves,   809 

Vesicle,  auditory,  1 183 

cerebral,  1 167 
germinal,  1149 
optic,  11. SO 
umbilical,   1158 
Vesicles,  Graafian,  1036 
Vesico-prostatic  plexus  of  veins, 

617 
Vesico-uterine  ligaments,  1029 
Yesicula  prostatic),  1006 
Vesiculae  seminales,  1022 

surgical  anatomy  of,  1023 
vessels  and  nerves  of,  1023 
Vesicular  column,    posterior,  of 

Clarke,  717 
Vestibular  artery,  866 

nerve,  S67 
Vestibule,  aortic,  466 
of  ear,  859 

aqueduct  of,  69 
of  nose,  820 
Vestibulumoris,  869 
Vestigial    fold    of   pericardium, 

459 
Vibrissa?,  818 

Vicq  d'Azvr,  bundle  of,  657 
Vidian  artery,  499 
canal,  76 
nerve,  732 
Vieussens,  valve  of,  697 
Villi,  917 

of  the  chorion,  1161 
Viscera,  pelvic,    position    of,    in 
abdominal  region,  896 
at  outlet  of  pelvis,  1067 
Visual  centres,  cortical,  722 

lower,   722 
Vitelline  circulation,  1187 
duct,  1158 
membrane,  1149 
spheres,  1152 
Vitello-intestinal  duct,  1198 
Vitellus,   1149 
Vitreous  humor  of  the  eye,  839 

table  of  the  Bkllll,  34 
Vocal    cords,    inferior    or    true, 
(till 
superior  or  false,  960 
process,    957 

Voice,  organs  of,  955 

Voluntary  muscles,  ]  Ki7 
Vomer,  9") 

al.-e  of,  96 

articulations  of,  96 

development  of,  96 
Vomerine  cartilage,  96 
Vortex  of  heart,  469 
Vulva,  1025 

development  of,  1213 


•r-7 


w. 


Wagner,   tactile    corpusc 
1121 

Wandering  cell 

Wainev    on    the    structure 
thymus,  ! 

\\  eight     of    organs.       Si  >■     /.<• 

victual  < ).  (j 
Wharton's  duct, 
White  nbro-cartilage,  1094 

fibrous  tissue,  1087 

substance  of  cord,  7 13 

nervous.  1115 

of  Schwann,  1116 

Willis,  circle  of,  512,  523 

Win-low.  foramen  of,  899 

ligament  of,  274 
Wisdom  tooth,  S74 
Wolffian  body,  1208 

duet,  1207" 
Womb.     See  Uterus. 
Worm.     See  Vermiform  process. 
Wormian  bones,  81 
Wrisberg,  cartilages  of,       - 

ganglion  ol 

ligament  of,    277 

nerve  of,  771 
Wrist-joint,  262 

surface  form  of,  169,  263 

surgical  anatomy  of,  263 
Wry-neck,  319 


X. 

Xiphoid  appendix,  125 


Y. 

Y-ligament,  270 

Y-shaped  centre  of  acetabulum, 

17S 
Yellow  cartilage,  1095 

elastic  fibrous  tissue.  1088 

sprit  of  retina,  833 
Yolk,  11-19 

cleavage  of,  1151 

sac.  1 1 58  ; 

stalk,  1198 


Z. 

Zinn,  ligament  of.  304 
Zona  arcuata,  86  I 

fasciculata,  997 

glomerulosa,  997 

ineerta,  676 

orbicularis,  269 

pectinata,    86  1 

pellucida,  1 147 

radiata,  1  1  17 

reticularis,  '.''.'7 

vasculosa,  1037 

Zonula  ciliaris,  >  10 
Zonule  of  Zinn,  840 
Zygoma,  ''■■") 

roots  of,  65 

tubercle  of,  66 
Zygomatic  arch,  1 1 1 

fossa^  111 

process  of  malar,  90 
Zygomaticiis  major  muscleigj 

minor,  307 


Vas  sj 

Vaso-i 

Vastus 
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Vater, 

Veins, 
anas, 
coats 
deve 
muse 
plexi 
size,  i 
struct 
valve 
vessel 

Veins  c 
o 
of  alee 
anguh 
articul 
audito 
auricu 
posti 

1  axillar 


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